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Electrogenicity of phosphate transport by renal brush-border membranes.
Béliveau, R; Ibnoul-Khatib, H
Phosphate uptake by rat renal brush-border membrane vesicles was studied under experimental conditions where transmembrane electrical potential (delta psi) could be manipulated. Experiments were performed under initial rate conditions to avoid complications associated with the dissipation of ion gradients. First, phosphate uptake was shown to be strongly affected by the nature of Na+ co-anions, the highest rates of uptake being observed with 100 mM-NaSCN (1.010 +/- 0.086 pmol/5 s per micrograms of protein) and the lowest with 50 mM-Na2SO4 (0.331 +/- 0.046 pmol/5 s per micrograms of protein). Anion substitution studies showed that potency of the effect of the co-anions was in the order thiocyanate greater than nitrate greater than chloride greater than isethionate greater than gluconate greater than sulphate, which correlates with the known permeability of the membrane to these anions and thus to the generation of transmembrane electrical potentials of decreasing magnitude (inside negative). The stimulation by ion-diffusion-induced potential was observed from pH 6.5 to 8.5, indicating that the transport of both monovalent and divalent phosphate was affected. In addition, inside-negative membrane potentials were generated by valinomycin-induced diffusion of K+ from K+-loaded vesicles and showed a 57% stimulation of phosphate uptake, at pH 7.5. Similar experiments with H+-loaded vesicles, in the presence of carbonyl cyanide m-chlorophenylhydrazone gave a 50% stimulation compared with controls. Inside-positive membrane potentials were also induced by reversal of the K+ gradient (outside greater than inside) in the presence of valinomycin and gave 58% inhibition of phosphate uptake. The membrane-potential dependency of phosphate uptake was finally analysed under thermodynamic equilibrium, and a stimulation by inside-negative potential was observed. The transport of phosphate was thus driven against a concentration gradient by a membrane potential, implicating the net
Binding of Escherichia coli heat-stable enterotoxin to rat intestinal cells and brush border membranes.
Frantz, J C; Jaso-Friedman, L; Robertson, D C
The association of heat-stable enterotoxin (STa) produced by enterotoxigenic Escherichia coli 431 with isolated rat intestinal epithelial cells and brush border membranes was characterized. Specific binding of strain 431 125I-STa to a single class of specific high-affinity receptors was saturable and temperature dependent and reached a maximum between 5 and 10 min. A 1,000-fold excess of unlabeled 431 STa competitively displaced 90 to 95% of radiolabeled enterotoxin bound to brush border membranes. In contrast, specific binding of 431 125I-STa to intestinal cells ranged from 40 to 65%. The number of STa-specific receptors on rat intestinal cells determined by Scatchard analysis was 47,520 +/- 14,352 (mean +/- standard error of the mean) per cell, with affinity constants (KaS) of 2.55 X 10(11)and 4.32 x 10(11) liters/mol determined for intestinal cells and brush border membranes, respectively. Villus intestinal cells appeared to possess about twice as many STa receptors as did crypt cells. Dissociation of specifically bound 431 125I-STa from intestinal cells and brush border membranes was minimal (2 to 5%). In addition, neither the rate nor the extent of dissociation was increased by a 1,000-fold excess of unlabeled homologous 431 Sta. Binding experiments with 431 125I-STa and brush border membranes showed that purified unlabeled STas from enterotoxigenic E. coli strains 667 (class 1 porcine enteropathogen), B-41 (bovine enteropathogen), and human strains 213C2 (Mexico) and 153961-2 (Dacca, Bangledesh) exhibited patterns of competitive inhibition similar to those of homologous unlabeled 431 STa (class 2 enteropathogen). A lipid extract which contained gangliosides and glycolipids exhibited dose-dependent competitive inhibition of heat-labile enterotoxin binding to brush border membranes but did not inhibit binding of 431 125I-STa. Purified heat-labile enterotoxin from strain 286C2 did not inhibit binding of 431 STa to brush border membranes. Pronase treatment of
Calcium uptake by intestinal brush border membrane vesicles. Comparison with in vivo calcium transport.
Schedl, H P; Wilson, H D
In prior studies, we examined kinetics of steady state in vivo transepithelial calcium transport in rat and hamster. The present studies related calcium uptake by the brush border to in vivo transport. We measured calcium uptake by brush border membrane vesicles from the two species. In the rat, our prior in vivo studies had shown that (a) calcium transport was mediated, (b) no nonmediated component was detectable, and (c) Vmax was 2.5 times greater in proximal than distal small intestine. In brush border membrane vesicles from the rat, Vmax for the saturable component of calcium uptake was again 2.5 times greater in proximal than distal intestine. Contrasting with in vivo studies, a major nonsaturable component was present in vesicles from proximal and distal small intestine. In the hamster, our previous in vivo studies had shown (1) both mediated and nonmediated components of calcium transport, (2) greater nonmediated transport in proximal than distal small intestines, and (3) Vmax for calcium transport twice as great in distal as in proximal small intestine. In the present study with brush border membrane vesicles from hamster, Vmax for saturable calcium transport was again twice as great in distal as in proximal small intestine. However, nonsaturable calcium transport rates relative to saturable rates were much greater with vesicles than in in vivo studies, and were greater in vesicles from distal than proximal small intestine. Since rates of saturable calcium uptake by brush border membrane vesicles parallel corresponding in vivo mediated transport rates, we conclude that the segmental rates of calcium transport in rat and hamster could be determined by brush border function. PMID:2997294
Reconstitution of the renal brush-border membrane sodium/phosphate co-transporter.
Vachon, V; Delisle, M C; Laprade, R; Béliveau, R
A simple and rapid procedure was developed for the reconstitution of Na(+)-dependent phosphate-transport activity from bovine kidney brush-border membranes. The phosphate transporter appears to be particularly sensitive to extraction conditions. To prevent its inactivation, the phosphate carrier was solubilized in a buffer containing its substrates, Na+ and phosphate, CHAPS, dithiothreitol, brush-border membrane lipids and glycerol. The uptake of phosphate by reconstituted vesicles was strongly stimulated by the presence of a transmembrane Na+ gradient. This stimulation was abolished when the Na+ gradient was dissipated by monensin. The affinity of the carrier for phosphate was similar in proteoliposomes and in brush-border membrane vesicles (apparent Kt = 40 microM). The transporter was also stimulated by the presence of a high concentration of phosphate on the trans side of the membrane. The reconstituted transport activity was inhibited by arsenate, a known inhibitor of phosphate transport. However, the bovine phosphate carrier, intact or reconstituted, was much less sensitive to inhibition by phosphonoformic and phosphonoacetic acids than were those of other species studied so far. SDS/PAGE revealed that only a small number of brush-border membrane proteins were incorporated into the proteoliposomes. This reconstitution procedure should be useful for the purification and identification of the carrier protein. Images Fig. 5. PMID:1832858
Calcium uptake by brush-border and basolateral membrane vesicles in chick duodenum
Takito, J.; Shinki, T.; Sasaki, T.; Suda, T. )
Calcium uptake was compared between duodenal brush-border membrane vesicles (BBMV) and basolateral membrane vesicles (BLMV) isolated from vitamin D-deficient chicks and those injected with 625 ng of 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25(OH)2D3). The uptake by BBMV in the 1 alpha,25-(OH)2D3-treated birds attained a maximum (280% of the control) at 12 h and was maintained at an elevated level (210%) at 24 h after the injection of the vitamin. In contrast, ATP-dependent calcium uptake by BLMV reached a maximum (185% of the control) at 6 h and decreased to the control level at 24 h. The kinetic analysis revealed that 1 alpha,25(OH)2D3 increased Vmax values without any changes in apparent Km values in both BBMV and BLMV. The activity of ATP-dependent calcium uptake was localized exclusively in the basolateral membrane, and the activity was inhibited by vanadate (IC50, 1 microM), but not by oligomycin, theophylline, calmodulin, trifluoperazine, or calbindin D28K. These results indicate that calcium transport through both the brush-border and basolateral membranes is involved in the 1 alpha,25(OH)2D3-dependent intestinal calcium absorption. The initiation of calcium absorption by 1 alpha,25(OH)2D3 appears to be due to an increase in the rate of calcium efflux at the basolateral membrane rather than the rate at the brush-border membrane.
Cimetidine transport in isolated brush border membrane vesicles from bovine choroid plexus
Whittico, M.T.; Gang, Y.A.; Giacomini, K.M. )
The purpose of this study was to elucidate the mechanisms involved in the transport of cimetidine across the brush border membrane of choroid plexus epithelium. Brush border membrane vesicles were prepared from bovine choroid plexus and the uptake of (3H)cimetidine was studied using the methods of rapid vacuum filtration and scintillation counting. Cimetidine accumulated in the vesicles with time reaching equilibrium within 2 hr. The amount of cimetidine taken up by the vesicles at equilibrium decreased with increasing extravesicular media osmolarity suggesting that cimetidine accumulates in an osmotically reactive intravesicular space. Binding of cimetidine to the membrane was estimated to be less than 18%. Michaelis-Menten studies demonstrated that cimetidine transport involved both a saturable and a nonsaturable component. The Vmax and Km (mean +/- S.E.) were 16.7 +/- 5.9 pmol/sec/mg protein and 58.1 +/- 3.1 microM, respectively, suggesting that cimetidine is transported across the choroid plexus brush border membrane with a lower affinity and a higher capacity than across the renal brush border membrane. The organic cation, quinidine (0.1 mM), and the amino acid, histidine (20 mM), both significantly reduced the initial, but not the equilibrium, uptake of cimetidine. However, high concentrations (5 mM) of more polar organic cations including tetraethylammonium, as well as of several organic anions including salicylate did not inhibit cimetidine transport. Studies with unlabeled cimetidine revealed a countertransport phenomenon. Attempts to drive the concentrative uptake of cimetidine with various ion gradients were unsuccessful. Of note was the fact that an outwardly directed proton gradient could significantly accelerate the uptake of cimetidine.
Lipid rafts in epithelial brush borders: atypical membrane microdomains with specialized functions.
Danielsen, E Michael; Hansen, Gert H
Epithelial cells that fulfil high-throughput digestive/absorptive functions, such as small intestinal enterocytes and kidney proximal tubule cells, are endowed with a dense apical brush border. It has long been recognized that the microvillar surface of the brush border is organized in cholesterol/sphingolipid-enriched membrane microdomains commonly known as lipid rafts. More recent studies indicate that microvillar rafts, in particular those of enterocytes, have some unusual properties in comparison with rafts present on the surface of other cell types. Thus, microvillar rafts are stable rather than transient/dynamic, and their core components include glycolipids and the divalent lectin galectin-4, which together can be isolated as "superrafts", i.e., membrane microdomains resisting solubilization with Triton X-100 at physiological temperature. These glycolipid/lectin-based rafts serve as platforms for recruitment of GPI-linked and transmembrane digestive enzymes, most likely as an economizing effort to secure and prolong their digestive capability at the microvillar surface. However, in addition to microvilli, the brush border surface also consists of membrane invaginations between adjacent microvilli, which are the only part of the apical surface sterically accessible for membrane fusion/budding events. Many of these invaginations appear as pleiomorphic, deep apical tubules that extend up to 0.5-1 microm into the underlying terminal web region. Their sensitivity to methyl-beta-cyclodextrin suggests them to contain cholesterol-dependent lipid rafts of a different type from the glycolipid-based rafts at the microvillar surface. The brush border is thus an example of a complex membrane system that harbours at least two different types of lipid raft microdomains, each suited to fulfil specialized functions. This conclusion is in line with an emerging, more varied view of lipid rafts being pluripotent microdomains capable of adapting in size, shape, and content to
Specific binding of lactoferrin to brush-border membrane: Ontogeny and effect of glycan chain
Davidson, L.A.; Loennerdal, B. )
Bioavailability of iron from human milk is exceptionally high. It has been suggested that lactoferrin, the major iron-binding protein in human milk, may participate in this high iron bioavailability from milk. The authors examined the interaction of lactoferrin with the intestinal brush-border membrane using the rhesus monkeys as a model. Brush-border membrane vesicles were prepared from monkeys of various ages. Binding studies with {sup 59}Fe-labeled human and monkey lactoferrin were performed to examine interaction of lactoferrin with the brush-border membrane. Specific saturable binding of lactoferrin was found at all ages studied. The dissociation constant for lactoferrin-receptor binding was 9 {times} 10{sup {minus}6} M. In contrast, no binding of serum transferrin or bovine lactoferrin occurred. Removal of fucose from the lactoferrin glycans resulted in a significant decrease in binding. It was concluded that lactoferrin in milk may function in the process of iron absorption through interaction with a small intestinal receptor and that fucosylated glycans on the carbohydrate chain of lactoferrin are necessary for receptor recognition.
"Nonclassical" secretion of annexin A2 to the lumenal side of the enterocyte brush border membrane.
Danielsen, E Michael; van Deurs, Bo; Hansen, Gert H
Annexin A2 is a member of the annexin family of Ca(2+)-dependent lipid binding proteins and believed to be engaged in membrane transport processes in a number of cell types. In small intestinal enterocytes, we localized annexin A2 to the brush border region, where it was found mainly on the lumenal side of the microvilli, showing an apical secretion by a "nonclassical" mechanism. In addition, annexin A2 was associated with surface-connected, deep apical tubules in the apical terminal web region and with an underlying pleiomorphic, tubulo-vesicular compartment (subapical compartment/multivesicular bodies). By subcellular fractionation, the 36 kDa full-length form of annexin A2 was approximately equally distributed between the Mg(2+)-precipitated fraction (containing intracellular and basolateral membranes) and the microvillar membrane fraction. In addition, a 33 kDa molecular form of annexin A2 was seen in the latter fraction that could be generated from the full-length annexin A2 by digestion with trypsin. Taken together, the results suggest that annexin A2 acts in exocytic apical membrane trafficking and is proteolytically cleaved in situ by pancreatic proteinases once it has become externalized to the lumenal side of the brush border membrane. On the basis of its well-known membrane fusogenic properties, we propose a model for the nonclassical membrane translocation of annexin A2.
Dietary fat effects on brush border membrane composition and enzyme activities in rat intestine.
Kaur, M; Kaur, J; Ojha, S; Mahmood, A
The effect of dietary fats on the chemical composition and enzyme activities has been studied in intestinal brush border membranes (BBM) or rats. Animals were given commercial rat pellet diet (RP) or semisynthetic diet rich in either saturated [coconut oil (CCO))] or polyunsaturated [n-6, corn oil (CO) or n-3, fish oil (FO)] fat at the 10% level for 5 weeks. The membrane cholesterol/phospholipid ratio was augmented in CO- or RP-fed rats. There was an increase in level of saturated fatty acids in BBM from CCO- or FO-fed animals. n-3 polyunsaturated fatty acid content was raised in FO-fed rats, while the proportion of linoleic acid and arachidonic acid was enhanced in animals given a CO diet. Membrane fluidity was in the order of CCO < RP = CO < FO. The membrane hexose content was high (p < 0.05) in the CCO group. Hexosamines were elevated (p < 0.05) in CCO- or FO-fed rat brush borders. Membrane fucose was unaltered, while sialic acid content was elevated in CO- (p < 0.05) and FO- (p < 0.01) fed vs. CCO-fed rats. Lectin binding to brush borders corroborated these findings. The activities of alkaline phosphatase, sucrase and lactase were augmented (p < 0.001) in CCO-fed animals. Leucine-aminopeptidase and sucrase activities were depressed by FO feeding. The activities of PNP-beta-glycosidases were the highest in FO-fed rats. These results indicate that dietary fat quality markedly affects microvillus membrane lipid composition, glycosylation and enzyme functions in rat intestine.
Classical and channel-like urate transporters in rabbit renal brush border membranes.
Knorr, B A; Beck, J C; Abramson, R G
The precise mechanism by which urate is transported across rabbit renal proximal tubule luminal membranes has not been defined. To determine whether urate flux across this membrane represents simple diffusion or transport on specific carriers, urate uptake was examined in brush border membrane vesicles that were prepared by a Mg+(+)-aggregation technique and then exposed to CuCl2. Na(+)-independent, voltage sensitive urate transport was demonstrated in these Cu+(+)-exposed vesicles. Transport was trans-stimulated by urate and cis inhibited by pyrazinoic acid and oxonate. A small fraction of transported urate and urate in the extravesicular fluid was oxidized to allantoin. Kinetic analysis revealed the presence of two kinetically distinct transporters; a channel-like carrier that was inhibited by pyrazinoic acid and oxonate, and a high-affinity, classical, saturable carrier that was inhibited by higher concentrations of oxonate. These studies provide the first direct evidence for carrier-mediated urate transport in rabbit renal brush-border membranes and demonstrate that the rabbit transporter(s) share a number of properties with the urate uniporter in rat proximal tubule cell membranes.
Proteomic analysis of brush-border membrane vesicles isolated from purified proximal convoluted tubules
Walmsley, Scott J.; Broeckling, Corey; Hess, Ann; Prenni, Jessica
The renal proximal convoluted tubule is the primary site of water, electrolyte and nutrient reabsorption and of active secretion of selected molecules. Proteins in the apical brush-border membrane facilitate these functions and initiate some of the cellular responses to altered renal physiology. The current study uses two-dimensional liquid chromatography/mass spectrometry to compare brush border membrane vesicles isolated from rat renal cortex (BBMVCTX) and from purified proximal convoluted tubules (BBMVPCT). Both proteomic data and Western blot analysis indicate that the BBMVCTX contain apical membrane proteins from cortical cells other than the proximal tubule. This heterogeneity was greatly reduced in the BBMVPCT. Proteomic analysis identified 193 proteins common to both samples, 21 proteins unique to BBMVCTX, and 57 proteins unique to BBMVPCT. Spectral counts were used to quantify relative differences in protein abundance. This analysis identified 42 and 50 proteins that are significantly enriched (p values ≤0.001) in the BBMVCTX and BBMVPCT, respectively. These data were validated by measurement of γ-glutamyltranspeptidase activity and by Western blot analysis. The combined results establish that BBMVPCT are primarily derived from the proximal convoluted tubule (S1 and S2 segments), whereas BBMVCTX include proteins from the proximal straight tubule (S3 segment). Analysis of functional annotations indicated that BBMVPCT are enriched in mitochondrial proteins and enzymes involved in glucose and organic acid metabolism. Thus the current study reports a detailed proteomic analysis of the brush-border membrane of the rat renal proximal convoluted tubule and provides a database for future hypothesis-driven research. PMID:20219825
Enzymatic and transport characteristics of isolated snake renal brush-border membranes
Benyajati, S.; Dantzler, W.H. )
Brush-border membranes (BBM) or proximal tubules were isolated from the kidney of the garter snake (Thamnophis sirtalis) by a procedure involving hypotonic lysis, Ca precipitation, and differential centrifugation. The isolated membranes were enriched 15-fold in brush-border enzyme activities (alkaline phosphatase, {gamma}-glutamyl transpeptidase) compared with whole kidney homogenates and were substantially free of other contaminating membranes. The yield of the BBM preparation was 40%. The BBM vesicular transport of several organic solutes was characterized by a rapid filtration technique at 25{degree}C. D-glucose, p-aminohippurate (PAH), and urate entered the same osmotically active space and binding was minimal. An uptake overshoot for 3-O-methyl-D-glucose by reptilian BBM was observed only in the presence of an inwardly directed NaCl gradient and was abolished by 0.1 mM phlorizin. Reptilian BBM exhibited Na-gradient-stimulated uptake of PAH (90 {mu}M) with an overshoot that was inhibited by other organic acids and by 4-acetamido-4{prime}-isothiocyanostilbene-2,2{prime}-disulfonic acid (SITS). In contrast, urate uptake appeared to be Na independent and not appreciably affected by other organic anions or SITS. The presence of specific transport systems for organic solutes in the isolated membrane preparation distinctly characterizes the BBM of reptilian kidney.
Thyroid hormones increase Na -H exchange activity in renal brush border membranes
Kinsella, J.; Sacktor, B.
Na -H exchange activity, i.e., amiloride-sensitive Na and H flux, in renal proximal tubule brush border (luminal) membrane vesicles was increased in the hyperthyroid rat and decreased in the hypothyroid rat, relative to the euthyroid animal. A positive correlation was found between Na -H exchange activity and serum concentrations of thyroxine (T4) and triiodothyronine (T3). The thyroid status of the animal did not alter amiloride-insensitive Na uptake. The rate of passive pH gradient dissipation was higher in membrane vesicles from hyperthyroid rats compared to the rate in vesicles from hypothyroid animals, a result which would tend to limit the increase in Na uptake in vesicles from hyperthyroid animals. Na -dependent phosphate uptake was increased in membrane vesicles from hyperthyroid rats; Na -dependent D-glucose and L-proline uptakes were not changed by the thyroid status of the animal. The effect of thyroid hormones in increasing the uptake of Na in the brush border membrane vesicle is consistent with the action of the hormones in enhancing renal Na reabsorption.
Lanthanide-stimulated glucose and proline transport across rabbit intestinal brush-border membranes.
Stevens, B R; Kneer, C
Trivalent cations of the lanthanide series (La3+----Yb3+) stimulated uptake of proline or glucose in rabbit small intestinal brush-border membrane vesicles. The lanthanides stimulated uptake to an extent greater than Al3+, choline, and in many cases, Na+. A time-course of Er3+-stimulated glucose uptake gave initial rates and overshoots greater than Na+ stimulation. The best activators were Sm3+, Eu3+ and Tm3+, which stimulated proline initial uptakes by 400-600%, and stimulated glucose uptake by 120-150%, compared to Na+. The best lanthanide cotransport activators possessed high third ionization potentials.
Chloride ion transport into pig jejunal brush-border membrane vesicles.
Forsyth, G W; Gabriel, S E
1. This study was carried out to determine the types and activities of carrier proteins which transport the chloride ion in pig jejunal brush-border membranes, with an emphasis on studying the properties of chloride conductance activity in vesicles prepared from these membranes. 2. Sodium-chloride co-transport activity was not detected in this tissue. A sodium-proton antiport with typical amiloride sensitivity was present. An anion exchanger linking chloride to hydroxyl or bicarbonate ions was also found in the pig jejunal brush-border membrane vesicles. 3. Chloride conductance activity in this system was specifically dependent on the buffering agents used for vesicle preparation. Conductance activity could not be demonstrated in vesicles prepared in imidazolium acetate or in HEPES-Tris buffers. HEPES-tetramethylammonium buffering of vesicles in the chloride uptake system produced a significant conductance response to a potassium gradient plus valinomycin. 4. Chloride conductance showed saturable kinetics with respect to substrate concentration, with a Michaelis-Menten constant (Km) of approximately 116 mM and a maximum velocity (Vmax) of 132 nmol (mg protein)-1 min-1. 5. Preliminary screening of potential inhibitors of chloride conductance showed only minimal inhibitor effects of SITS (4-acetamido-4'-isothiocyanostilbene-2,2'-sulphonic acid), anthracene-9-carboxylate, N-phenylanthranilate and piretanide. 6. The conductance activity in pig jejunal vesicles appears to have stringent buffer requirements, and to be relatively insensitive to the effects of reported conductance inhibitors. PMID:2466986
Aboral changes in D-glucose transport by human intestinal brush-border membrane vesicles.
Bluett, M K; Abumrad, N N; Arab, N; Ghishan, F K
D-Glucose transport was investigated in isolated brush-border membrane vesicles from human small intestine. Characteristics of D-glucose transport from the jejunum were compared with that in the mid and terminal ileum. Jejunal and mid-ileal D-glucose transport was Na+-dependent and electrogenic. The transient overshoot of jejunal D-glucose transport was significantly greater than corresponding values in mid-ileum. The terminal ileum did not exhibit Na+-dependent D-glucose transport, but did exhibit Na+-dependent taurocholate transport. Na+-glucose co-transport activity as measured by tracer-exchange experiments was greatest in the jejunum, and diminished aborally. We conclude that D-glucose transport in man is Na+-dependent and electrogenic in the proximal intestine and directly related to the activity of D-glucose-Na+ transporters present in the brush-border membranes. D-Glucose transport in the terminal ileum resembles colonic transport of D-glucose. PMID:3800877
Characterization of the chloride conductance in porcine renal brush-border membrane vesicles.
Krick, W; Dölle, A; Hagos, Y; Burckhardt, G
The chloride conductance in brush-border membrane vesicles prepared from pig kidney cortex was investigated using a light-scattering assay, anion-diffusion-potential-dependent Na+-D-glucose cotransport and 36Cl- influx. K+-diffusion-potential-driven salt exit from, or entry into, the vesicles was slow in the presence of gluconate, SO42- and F-, intermediate with Cl- and Br-, and fast with I-, NO3-, and SCN-. Stimulation of Na+-D-glucose uptake followed a similar anion sequence. Conductive Cl- flux had a low activation energy and was inhibited by suphhydryl reagents, the stilbene disulphonates 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulphonate (SITS) and 4, 4'-diisothiocyanato-2,2'-disulphonate (DIDS), and the arylaminobenzoates diphenylamine-2-carboxylic acid (DPC) and 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB). Intravesicular Ca2+ and extravesicular nucleotides were without effect on conductive Cl- flux. These characteristics tentatively exclude some known Cl- channels and leave members of the ClC family as possible candidates responsible for the Cl- conductance in brush-border membranes.
Effect of amino acid intake on brush-border membrane uptake of sulfur amino acids.
Chesney, R W; Gusowski, N; Padilla, M; Lippincott, S
Alterations in the intake of sulfur amino acids (SAA) changes the rat renal brush-border membrane uptake of the beta-amino acid, taurine. A low-SAA diet enhances and a high-taurine diet reduces uptake (Chesney et al., Kidney Int. 24: 588-594, 1983). Neither the low-SAA diet nor the high-taurine diet alters the time course or concentration-dependent accumulation of the sulfur amino acids methionine and cystine or of inorganic sulfate. By contrast the uptake of beta-alanine, another beta-amino acid that competes with taurine, is greater in animals on the low-SAA diet. The high-taurine diet does not change beta-alanine uptake. The plasma levels of taurine are altered by dietary change, but not the values for methionine and cystine. This study indicates that renal adaptation is expressed for beta-alanine, a nonsulfur-containing beta-amino acid. By contrast, methionine, cystine, and sulfate, which participate in a variety of synthetic and conjugative processes, are not conserved by the renal brush-border surface following ingestion of either a low-methionine and -cystine diet or high-taurine diet.
Truncated brush border myosin I affects membrane traffic in polarized epithelial cells.
Durrbach, A; Raposo, G; Tenza, D; Louvard, D; Coudrier, E
We investigate, in this study, the potential involvement of an acto-myosin-driven mechanism in endocytosis of polarized cells. We observed that depolymerization of actin filaments using latrunculin A decreases the rate of transferrin recycling to the basolateral plasma membrane of Caco-2 cells, and increases its delivery to the apical plasma membrane. To analyze whether a myosin was involved in endocytosis, we produced, in this polarized cell line, truncated, non-functional, brush border, myosin I proteins (BBMI) that we have previously demonstrated to have a dominant negative effect on endocytosis of unpolarized cells. These non-functional proteins affect the rate of transferrin recycling and the rate of transepithelial transport of dipeptidyl-peptidase IV from the basolateral plasma membrane to the apical plasma membrane. They modify the distribution of internalized endocytic tracers in apical multivesicular endosomes that are accessible to fluid phase tracers internalized from apical and basolateral plasma membrane domains. Altogether, these observations suggest that an acto-myosin-driven mechanism is involved in the trafficking of basolaterally internalized molecules to the apical plasma membrane.
L-canavanine inhibits L-arginine uptake by broiler chicken intestinal brush border membrane vesicles.
Rueda, E; Michelangeli, C; Gonzalez-Mujica, F
1. Intestinal brush border membrane vesicles (BBMV) were prepared from 3-week-old broiler chickens. 2. Electron microscopy of the BBMV fraction showed single membrane vesicles of different sizes with no electron dense material inside. No other organelles were observed. The sucrase and maltase activities were enriched by factors of 16 and 18, respectively, in the BBMV fraction in comparison with the homogenate. On the other hand, the Na+/K+-ATPase sensitivity to ouabain was increased by a factor of 0.8. 3. The BBMV showed a maximum L-[14C]-arginine uptake (944.9 +/- 22.9 pmoles/mg protein) at 45 s and thereafter it declined slowly. In the presence of 0.5 mM L-canavanine, the L-[14C]-arginine uptake by BBMV was reduced by 43.6% at 45 s. 4. It is concluded that L-canavanine inhibits L-arginine Na+-dependent transport across the enterocyte apical membrane in a highly purified intestinal BBMV from broiler chickens.
Taurocholate transport by brush-border membrane vesicles from the developing rabbit ileum: Structure/function relationships
Schwarz, S.M.; Watkins, J.B.; Ling, S.C. )
To examine the ontogenesis of bile acid transport in the rabbit ileum, brush-border membrane vesicles (12- to 20-fold purified) were prepared from 14- to 49-day-old animals. Taurocholate uptake was characterized by the emergence of secondary active, Na(+)-dependent transport at the start of weaning (21 days). Transient intravesicular accumulation (overshoot) of taurocholate occurred at 5-10 s of incubation, and the overshoot maximum increased significantly from 21 days (349.2 +/- 22.4 nmol/mg protein) to 35 days (569.0 +/- 84.3 nmol/mg protein; p less than 0.001), without further increase at maturity (49 days, not equal to 607.6 +/- 136.7 nmol/mg protein). No significant taurocholate active uptake component was noted at 14 days; however, ileal vesicles from sucklings showed carrier-mediated, Na+ D-glucose cotransport. In greater than or equal to 35-day-old rabbits, osmolarity studies at 20 s of incubation showed that only approximately 12% of (14C)taurocholate uptake was secondary to bile acid-to-membrane binding. Conversely, at 20 min, greater than 95% of radiolabel incorporation represented solute bound to the external and/or internal membrane surface. Arrhenius plots establish brush-border membrane taurocholate uptake as an intrinsic, lipid-dependent process, with a slope discontinuity between 24 and 28 degrees C, similar to the membrane lipid thermotropic transition region. Steady-state fluorescence polarization studies (1,6-diphenyl-1,3,5-hexatriene) demonstrate a temporal association between the maturation of taurocholate uptake and age-related decreases in ileal brush-border membrane fluidity. These data indicate that maturation of bile acid secondary active transport in the rabbit ileum may be regulated, at least in part, by changes in brush-border membrane lipid dynamics.
Heparin blocks /sup 125/I-calmodulin internalization by isolated rat renal brush border membrane vesicles
Meezan, E.; Elgavish, A.; Roden, L.; Wallace, R.W.
/sup 125/I-Calmodulin is internalized by isolated rat renal brush border membrane vesicles (BBV) in a time, temperature and calcium dependent manner. Internalization of /sup 125/I-calmodulin into the osmotically sensitive space of BBV was distinguished from binding of the ligand to the outer BBV surface by examining the interaction of ligand and BBV at different medium osmolarities (300-1100 mosm), uptake was inversely proportional to medium osmolarity. Internalized /sup 125/I-calmodulin was intact and Western blots of solubilized BBV with /sup 125/I-calmodulin demonstrated the presence of several calmodulin-binding proteins of 143, 118, 50, 47.5, 46.5 and 35 kilodaltons which could represent potential intravesicular binding sites for the ligand. Heparin and the related glycosaminoglycan heparin sulfate both showed a dose-dependent inhibition (0.5-50 ..mu..g/ml) of /sup 125/I-calmodulin uptake by BBV, but other sulfated and nonsulfated glycosaminoglycans including chondroitin sulfates, keratan sulfate and hyaluronic acid showed little or no inhibitory effect. Desulfation of heparin virtually abolished the inhibition of uptake while depolymerization reduced it. Heparin did not block the binding of /sup 125/I-calmodulin to BBV proteins as assessed by Western blotting technique suggesting its effect was on internalization of the ligand rather than on its association with internal membrane proteins.
Effect of alpha interferon on glucose and alanine transport by rat renal brush border membrane vesicles
Batuman, V.; Chadha, I. New Jersey Medical School, Newark )
To investigate the pathogenetic mechanisms of interferon nephrotoxicity, we studied the effect of recombinant interferon alfa-2b on the uptake of {sup 14}C-D-glucose and {sup 14}C-L-alanine by rat renal brush-border-membrane vesicles. Interferon significantly inhibited 20 sec. sodium-dependent and 5 and 10 min. equilibrium uptake of both glucose and alanine. The inhibitory effect was dose dependent with maximum effect achieved at interferon concentration of 5 {times} 10{sup {minus}8}M in the uptake media. The half-maximal inhibitory concentrations, IC{sub 50}, of interferon on glucose uptake was 1.8 {times} 10{sup {minus}8}M, and 5.4 {times} 10{sup {minus}9}M on alanine uptake. Dixon plot analysis of uptake data was consistent with pure non-competitive inhibition. The inhibition constants, K{sub i}, 1.5 {times} 10{sup {minus}8}M for glucose uptake, and 7.3 {times} 10{sup {minus}9}M for alanine uptake, derived from Dixon plots were in close agreement with the IC{sub 50}s calculated from the semilog dose response curves. These observations reveal that direct interactions at the proximal tubule cell membrane are involved in the pathogenesis of interferon nephrotoxicity, and that its mechanism of nephrotoxicity is similar to that of other low molecular weight proteins.
Sulfate uptake by crustacean hepatopancreatic brush border membrane vesicles. [Homarus americanus
Gerencser, G.A.; Cattey, M.A; Ahearn, G.A. Univ. of Hawaii, Honolulu )
Purified brush border membrane vesicles (BBMV) were prepared from Atlantic lobster (Homarus americanus) hepatopancreas using differential centrifugation and Mg{sup +2} precipitation techniques. Uptake of 0.1 mM {sup 35}SO{sub 4}{sup {minus}2} was stimulated by pre-loading vesicles with Cl{sup {minus}} leading to a transient accumulation of isotope more than twice that at equilibrium. Pre-loading with HCO{sub 3}{sup {minus}} or gluconate had no effect on sulfate uptake. No stimulation of {sup 35}SO{sub 4}{sup {minus}2} was observed in the presence of inwardly directed Na{sup +} or tetramethylammonium{sup +} gradients. Uptake of the divalent anion was strongly stimulated by inwardly directed proton gradients (pH{sub o} < pH{sub i}) and markedly inhibited by outwardly directed proton gradients (pH{sub o} > pH{sub i}). {sup 35}SO{sub 4}{sup {minus}2}/Cl{sup {minus}} exchange was enhanced by imposing a transmembrane inside positive K{sup +} diffusion potential and inhibited by a membrane potential of the opposite polarity (K{sup +}/valinomycin). Results suggest the presence of a proton-dependent, electrogenic anion antiport mechanism in BBMV isolated from the crustacean hepatopancreas.
Cimetidine transport in rabbit renal cortical brush-border membrane vesicles
McKinney, T.D.; Kunnemann, M.E.
Cimetidine is an organic cation and commonly prescribed drug that is eliminated primarily by proximal renal tubular secretion. The present studies evaluated cimetidine transport in rabbit renal cortical brush-border membrane vesicles (BBMV). (/sup 3/H)Cimetidine uptake varied inversely with media osmolarity and was stimulated with uphill transport above equilibrium values (overshoot) produced by an initial proton gradient directed from the vesicle interior outwardly. Uphill transport occurred earlier and was of greater magnitude at 25/sup 0/C than at 5/sup 0/C. pH-stimulated (/sup 3/H)cimetidine uptake was inhibited by excess nonradiolabeled cimetidine, quinidine, and procainamide but was affected little by probenecid. Tetraethylammonium inhibited cimetidine uptake in the presence and absence of an initial proton gradient, indicating that nonionic diffusion and simple diffusion cannot totally account for cimetidine transport in BBMV. Preloading BBMV with an excess of procainamide enhanced cimetidine uptake. These results are consistent with the hypothesis that cimetidine is transported across BBMV by organic cation-proton exchange.
Transport of citrate across renal brush border membrane: effects of dietary acid and alkali loading
Jenkins, A.D.; Dousa, T.P.; Smith, L.H.
Dietary acid or alkali loading was given to rats by providing 150 mM NH4Cl or 150 mM NaHCO3 in place of drinking water for 6 days; control animals received 150 mM NaCl. After 6 days, the citrate clearance was 0.04 +/- 0.01 ml/min (mean +/- SE) in the acid-loaded group, 0.9 +/- 0.1 ml/min in the control group, and 2.5 +/- 0.2 ml/min in the alkali-loaded group. At the end of the experiment, the rats were killed, and the Na gradient-dependent citrate uptake was measured in brush border membrane (BBM) vesicles prepared from each group. At 0.3 min, the ( UC)citrate uptake was 198 +/- 8 pmol/mg protein (mean +/- SE) in the acid-loaded group, 94 +/- 16 pmol/mg protein in the control group, and 94 +/- 13 pmol/mg protein in the alkali-loaded group. The rate of Na -independent (NaCl in medium replaced by KCl) ( UC)-citrate uptake by BBM vesicles was the same for acid-loaded, control, and alkali-loaded animals. Thus, the increased capacity of the proximal tubular BBM to transport citrate from the tubular lumen into the cell interior may be an important factor that contributes to decreased urinary citrate in the presence of metabolic acidosis induced by chronic dietary acid loading.
Possible degradative process of cholecystokinin analogs in rabbit jejunum brush-border membrane vesicles.
Su, Sheng-Fang; Amidon, Gordon L; Lee, Hye J
Our recent work on the intestinal metabolism and absorption of cholecystokinin analogs, sulfated C-terminal octapeptide (CCK8; Asp-Tyr(SO(3)H)-Met-Gly-Trp-Met-Asp-Phe(NH(2)) = DY(SO(3)H)MGWMDF(NH(2))) and tetrapeptide (CCK4; Trp-Met-Asp-Phe(NH(2)) = WMDF(NH(2))), was extended to investigate the degradative process of these analogs using rabbit jejunum brush-border membrane vesicles and to find a better enzyme-inhibitor system for intestinal absorption of peptide drugs. Various enzyme inhibitors and a lower pH buffer were applied to discover the major enzyme(s) involved in each process. Metabolic pathways showing degradative processes were proposed for both analogs. The major cleavage site occurs at the W(1)-M(2) for CCK4. At least three metabolic pathways occur independently for CCK8 and appear at peptides bonds between G(4)-W(5), M(6)-D(7), and D(7)-F(NH(2))(8). Many different enzymes of aminopeptidase, endopeptidase, angiotensin-converting enzyme, metalloenzyme, and others were involved in each process. Identification of more specific yet safe enzyme inhibitors and co-administration of various these inhibitors may lead to further enhancement in intestinal peptide absorption when administered orally.
Effect of chronic (4 weeks) ingestion of ethanol on transport of proline into intestinal brush border membrane vesicles
Beesley, R.C.; Jones, T.D.
Hamsters were separated into two groups and fed liquid diets ad lib. Controls were given a diet similar to that described by DeCarli and Lieber while alcoholics received the same diet containing 5% ethanol isocalorically substituted for sucrose. The volume of diet consumed daily and the gain in body weights of alcoholics were not significantly different from those of controls. After four weeks the animals were sacrificed and the upper third of the small intestine was used to prepare brush border membrane vesicles. In the presence of a Na/sup +/ gradient, uptake of proline into vesicles prepared from both groups was rapid, reaching a maximum accumulation in 1 to 2 min and then decreasing to the equilibrium level. To normalize the results, the amount of proline take up at each time point was divided by the amount present at equilibrium. From the normalized data it was concluded that both the rate of uptake and the maximum accumulation of proline into brush border membrane vesicles isolated from alcoholics were significantly less than those obtained with vesicles from controls. These results suggest that chronic ingestion of ethanol results in a reduction in Na/sup +/-dependent transport of proline across the brush border membrane and, thus, may contribute to the malnutrition which is frequently associated with chronic alcoholism.
Intestinal assimilation of a proline-containing tetrapeptide. Role of a brush border membrane postproline dipeptidyl aminopeptidase IV.
Morita, A; Chung, Y C; Freeman, H J; Erickson, R H; Sleisenger, M H; Kim, Y S
The mechanism of hydrolysis and absorption of a proline-containing tetrapeptide, Leu-Pro-Gly-Gly (10 mM) by rat intestine was examined in vivo by using jejunal perfusion methods. The peptide substrate and hydrolysis products were analyzed by use of an automated amino acid analyzer. Leucine, proline, and glycine were absorbed by the intestine at a significantly higher rate from the tetrapeptide than from an equivalent amino acid mixture. The analysis of the hydrolytic products in the lumen during in vivo perfusion of the tetrapeptide showed that two dipeptides, Leu-Pro and Gly-Gly, were the major products. These two dipeptides were also the major hydrolytic products when a purified rat intestinal brush border membrane preparation was incubated with Leu-Pro-Gly-Gly. The rate of hydrolysis of the tetrapeptide was much higher than that for several other proline-containing peptides (Leu-Pro, Pro-Leu, and Pro-Gly-Gly) that were tested. Studies using Gly-Pro-beta-naphthylamide, a specific substrate for postproline dipeptidyl aminopeptidase IV, showed that this enzyme is mainly localized to the brush border membrane and is responsible for the hydrolysis of the tetrapeptide into the two dipeptides Leu-Pro and Gly-Gly. Thus, brush border membrane dipeptidyl aminopeptidase IV very likely plays an important role at the intestinal mucosal cell surface in the final stages of digestion of proline-containing peptides. PMID:6135710
Ezetimibe Promotes Brush Border Membrane-to-Lumen Cholesterol Efflux in the Small Intestine
Nakano, Takanari; Inoue, Ikuo; Takenaka, Yasuhiro; Ono, Hiraku; Katayama, Shigehiro; Awata, Takuya; Murakoshi, Takayuki
Ezetimibe inhibits Niemann-Pick C1-like 1 (NPC1L1), an apical membrane cholesterol transporter of enterocytes, thereby reduces intestinal cholesterol absorption. This treatment also increases extrahepatic reverse cholesterol transport via an undefined mechanism. To explore this, we employed a trans-intestinal cholesterol efflux (TICE) assay, which directly detects circulation-to-intestinal lumen 3H-cholesterol transit in a cannulated jejunal segment, and found an increase of TICE by 45%. To examine whether such increase in efflux occurs at the intestinal brush border membrane(BBM)-level, we performed luminal perfusion assays, similar to TICE but the jejunal wall was labelled with orally-given 3H-cholesterol, and determined elevated BBM-to-lumen cholesterol efflux by 3.5-fold with ezetimibe. Such increased efflux probably promotes circulation-to-lumen cholesterol transit eventually; thus increases TICE. Next, we wondered how inhibition of NPC1L1, an influx transporter, resulted in increased efflux. When we traced orally-given 3H-cholesterol in mice, we found that lumen-to-BBM 3H-cholesterol transit was rapid and less sensitive to ezetimibe treatment. Comparison of the efflux and fractional cholesterol absorption revealed an inverse correlation, indicating the efflux as an opposite-regulatory factor for cholesterol absorption efficiency and counteracting to the naturally-occurring rapid cholesterol influx to the BBM. These suggest that the ezetimibe-stimulated increased efflux is crucial in reducing cholesterol absorption. Ezetimibe-induced increase in cholesterol efflux was approximately 2.5-fold greater in mice having endogenous ATP-binding cassette G5/G8 heterodimer, the major sterol efflux transporter of enterocytes, than the knockout counterparts, suggesting that the heterodimer confers additional rapid BBM-to-lumen cholesterol efflux in response to NPC1L1 inhibition. The observed framework for intestinal cholesterol fluxes may provide ways to modulate the flux
Sodium/proton antiport in brush-border-membrane vesicles isolated from rat small intestine and kidney.
Murer, H; Hopfer, U; Kinne, R
Studies on proton and Na+ transport by isolated intestinal and renal brush-border-membrane vesicles were carried out to test for the presence of an Na+/H+-exchange system. Proton transport was evaluated as proton transfer from the intravesicular space to the incubation medium by monitoring pH changes in the membrane suspension induced by sudden addition of cations. Na+ transport was determined as Na+ uptake into the vesicles by filtration technique. A sudden addition of sodium salts (but not choline) to the membrane suspension provokes an acidification of the incubation medium which is abolished by the addition of 0.5% Triton X-100. Pretreatment of the membranes with Triton X-100 prevents the acidification. The acidification is also not observed if the [K+] and proton conductance of the membranes have been increased by the simultaneous addition of valinomycin and carbonyl cyanide p-trifluoromethoxyphenylhydrazone to the K+-rich incubation medium. Either valinomycin or carbonyl cyanide p-trifluoromethoxyphenylhydrazone when added alone do not alter the response of the membranes to the addition of Na+. Na+ uptake by brush-border microvilli is enhanced in the presence of a proton gradient directed from the intravesicular space to the incubation medium. Under these conditions a transient accumulation of Na+ inside the vesicles is observed. It is concluded that intestinal and renal brush-border membranes contain a NA+/H+ antiport system which catalyses an electroneutral exchange of Na+ against protons and consequently can produce a proton gradient in the presence of a concentration difference for Na+. This system might be involved in the active proton secretion of the small intestine and the proximal tubule of the kidney.
Hypothyroidism increases osmotic water permeability (Pf) in the developing renal brush border membrane.
Mulder, Jaap; Haddad, Maha N; Vernon, Kimberly; Baum, Michel; Quigley, Raymond
The osmotic water permeability (Pf) of the rabbit proximal tubule brush border membrane vesicles (BBMV) increases during maturation and is mediated by an increase in aquaporin-1 (AQP1) protein expression. Serum thyroid hormone levels increase after birth and have been shown to play a role in the maturation of other renal transport functions. We examined the hypothesis that thyroid hormone plays a role in the maturational increase in osmotic water permeability. Hypothyroidism was induced by addition of 0.1% propylthiouracil (PTU) to the drinking water of pregnant rabbits (starting 9 d before delivery) and was continued until the rabbits were studied as adults (9-11 wk). Some animals received thyroid hormone replacement by daily injection with triiodothyronine (T3; 10 microg/100 g body weight) for three days before study. Pf was found to be higher in BBMV from hypothyroid (82.7 +/- 5.5 microm/s) than from euthyroid (60.6 +/- 4.0 microm/s) and T3-replacement rabbits (69.0 +/- 5.0 microm/s) (p < 0.05). The activation energy (Ea; in kcal/deg.mol) of Pf was not different among the three experimental groups (euthyroid 5.6 +/- 0.9, hypothyroid 4.9 +/- 0.8, T3-replacement 5.0 +/- 1.0; p = NS), nor was the percentage mercury inhibition of Pf (euthyroid 66.5 +/- 5.3, hypothyroid 74.2 +/- 3.2 and T3-replacement 73.1 +/- 4.3; p = NS). AQP1 expression, measured by immunoblotting, was highest in BBMV from hypothyroid rabbits (p < 0.05). Membrane fluidity, measured as steady-state generalized polarization (GP) of Laurdan, which is inversely related to membrane fluidity, was significantly different between the three groups (GP: euthyroid 0.307 +/- 0.004, hypothyroid 0.271 +/- 0.004 and T3-replacement 0.287 +/- 0.003; for all p < 0.05). These data demonstrate that the maturational increase in thyroid hormone levels is not responsible for the maturational increase in water transport. Surprisingly, congenital hypothyroidism in rabbits is associated with an increased Pf when rabbits
Proline transport by brush-border membrane vesicles of lobster antennal glands
Behnke, R.D.; Wong, R.K.; Huse, S.M.; Reshkin, S.J.; Ahearn, G.A. )
Purified brush-border membrane vesicles (BBMV) of lobster antennal gland labyrinth and bladder were separately formed by a magnesium precipitation technique. L-(3H)proline uptake was stimulated by a transmembrane NaCl gradient (outside (o) greater than inside (i)) to a greater extent in BBMV from labyrinth than those from the bladder. Detailed study of the labyrinth proline-transport processes revealed a specific dependence on NaCl, with negligible stimulatory effects by NaSCN, Na-gluconate, or KCl. A transmembrane proton gradient (o greater than i) was without stimulatory effect on proline transport. A transmembrane potential difference alone, in the presence of equilibrated NaCl and L-(3H)proline, led to net influx of the labeled amino acid, suggesting that the uptake process was electrogenic and capable of bringing about the net transfer of positive charge to the vesicle interior. Although a transmembrane Na gradient alone, in the presence of equilibrated Cl and L-(3H)proline, was able to bring about the net influx of the amino acid, a transmembrane Cl gradient alone under Na- and L-(3H)proline-equilibrated conditions was not, suggesting that only the Na gradient could energize the carrier process through cotransport, while the anion served an essential activating role. Proline influx by these vesicles occurred by the combination of at least one saturable Michaelis-Menten carrier system (apparent Kt = 0.37 mM; apparent JM = 1.19 nmol.mg protein-1.10 s-1) and apparent diffusion (P = 0.33 nmol.mg protein-1.10 s-1.mM-1). Static head analysis of the transport process suggested a cotransport stoichiometry of 2 Na:1 proline with essential activation by Cl ion.
Effects of uricosuric and antiuricosuric agents on urate transport in human brush-border membrane vesicles.
Roch-Ramel, F; Guisan, B; Diezi, J
Inhibition of [14C]-urate uptake by uricosuric and antiuricosuric agents was investigated in human brush-border membrane vesicles, urate being transported either by anion exchange mechanisms or by voltage sensitive pathway. The IC50 for drugs on [14C]-urate uptake in vesicles loaded with 1 mM cold urate or with 5 mM lactate was, respectively: 0.7 and 0.3 microM for benzbromarone; 6 and 4 microM for salicylate; 133 and 13 microM for losartan; 520 and 190 microM for sulfinpyrazone and 807 and 150 microM, for probenecid. The IC50 ratio for [14C]-urate uptake in exchange for cold urate or for lactate varied from about 1 for salicylate to 10 for losartan, supporting the hypothesis that two distinct anion exchangers are involved in urate transport. Application of Hill equation revealed that urate/anion exchangers have more than one binding site, possibly two binding sites with high cooperativity, for benzbromarone and sulfinpyrazone, but only one for probenecid, salicylate and losartan. The uricosuric diuretic, tienilic acid was 10 to 50 times more potent than hydrochlorothiazide, chlorothiazide and furosemide, for inhibiting [14C]-urate uptake in exchange for cold urate. This higher potency is the reason of its uricosuric properties. All uricosuric agents, as well as the antiuricosuric agents, pyrazinoate and ethambutol, had a much lower potency for inhibiting [14C]-urate uptake through the voltage sensitive pathway (apical secretory step) than through the urate/anion exchangers. This suggests that antiuricosuria, induced by pyrazinoate and ethambutol, as well as by low concentrations of uricosuric agents, does not result from an inhibition of the apical voltage sensitive pathway.
Effect of lipid peroxidation on membrane-bound Ca2+-ATPase activity of the intestinal brush-border membranes.
Ohta, A; Mohri, T; Ohyashiki, T
We have studied lipid peroxidation and Ca2+-ATPase activity of the porcine intestinal brush-border membranes using a oxygen-radical-generating system consisting of dithiothreitol (DTT)/Fe2+ and tert-butyl hydroperoxide (t-BuOOH). The rates of lipid peroxidation were measured by formation of thiobarbituric acid-reactive substances (TBAR) and conjugated diene. Incubation of the membranes with DTT/Fe2+ in the absence and presence of t-BuOOH resulted in a slight (about 20%) and a marked (about 50%) inhibition of Ca2+-ATPase activity, respectively. The degree of inhibition was dependent on the hydroperoxide concentration. Addition of thiourea effectively protected Ca2+-ATPase activity but catalase and superoxide dismutase showed a slight and no effect on protection of the ATPase activity, respectively. Results of kinetic studies on the ATPase activity with varying ATP and Ca2+ concentrations revealed that the decrease in the enzyme activity by treatment with these oxidizing agents is mainly due to decrease of the Vmax value. Modification of SH groups in the membrane proteins by thiol group reagents such as N-ethylmaleimide, monoiodoacetate and monoiodacetamide did not induce the inhibition of Ca2+-ATPase activity. From these results, it is suggested that inhibition of the ATPase activity of the membranes by treatment with DTT/Fe2+ in the presence and absence of t-BuOOH is dependent on lipid peroxidation and that oxidative modification of SH groups may not be directly involved to the loss of the ATPase activity. In addition, results of the fluorescence anisotropy measurements of pyrene-labeled membranes suggested that change in the Ca2+-ATPase activity is partly related to a decrease in the membrane lipid fluidity.
Microbial sphingomyelinase induces RhoA-mediated reorganization of the apical brush border membrane and is protective against invasion
Saslowsky, David E.; Thiagarajah, Jay R.; McCormick, Beth A.; Lee, Jean C.; Lencer, Wayne I.
The apical brush border membrane (BBM) of intestinal epithelial cells forms a highly structured and dynamic environmental interface that serves to regulate cellular physiology and block invasion by intestinal microbes and their products. How the BBM dynamically responds to pathogenic and commensal bacterial signals can define intestinal homeostasis and immune function. We previously found that in model intestinal epithelium, the conversion of apical membrane sphingomyelin to ceramide by exogenous bacterial sphingomyelinase (SMase) protected against the endocytosis and toxicity of cholera toxin. Here we elucidate a mechanism of action by showing that SMase induces a dramatic, reversible, RhoA-dependent alteration of the apical cortical F-actin network. Accumulation of apical membrane ceramide is necessary and sufficient to induce the actin phenotype, and this coincides with altered membrane structure and augmented innate immune function as evidenced by resistance to invasion by Salmonella. PMID:26864627
High affinity 3H-Phe uptake by brush border membrane vesicles from whole larvae of Aedes aegypti (AaBMVw)
Technology Transfer Automated Retrieval System (TEKTRAN)
Brush border membrane vesicles from whole Aedes aegypti larvae (AaBBMVw) are confirmed to be valid preparations for membrane transport studies. The Abdul-Rauf and Ellar method was used to isolate AaBBMVw that were frozen, stored for several months, transported to a distant site, thawed and used to s...
Diabetes increases facilitative glucose uptake and GLUT2 expression at the rat proximal tubule brush border membrane
Marks, Joanne; Carvou, Nicolas J C; Debnam, Edward S; Srai, Surjit K; Unwin, Robert J
The mechanism of renal glucose transport involves the reabsorption of filtered glucose from the proximal tubule lumen across the brush border membrane (BBM) via a sodium-dependent transporter, SGLT, and exit across the basolateral membrane via facilitative, GLUT-mediated, transport. The aim of the present study was to determine the effect of streptozotocin-induced diabetes on BBM glucose transport. We found that diabetes increased facilitative glucose transport at the BBM by 67.5 % (P < 0.05) – an effect that was abolished by overnight fasting. Western blotting and immunohistochemistry demonstrated GLUT2 expression at the BBM during diabetes, but the protein was undetectable at the BBM of control animals or diabetic animals that had been fasted overnight. Our findings indicate that streptozotocin-induced diabetes causes the insertion of GLUT2 into the BBM and this may provide a low affinity/high capacity route of entry into proximal tubule cells during hyperglycaemia. PMID:12963802
Diabetes increases facilitative glucose uptake and GLUT2 expression at the rat proximal tubule brush border membrane.
Marks, Joanne; Carvou, Nicolas J C; Debnam, Edward S; Srai, Surjit K; Unwin, Robert J
The mechanism of renal glucose transport involves the reabsorption of filtered glucose from the proximal tubule lumen across the brush border membrane (BBM) via a sodium-dependent transporter, SGLT, and exit across the basolateral membrane via facilitative, GLUT-mediated, transport. The aim of the present study was to determine the effect of streptozotocin-induced diabetes on BBM glucose transport. We found that diabetes increased facilitative glucose transport at the BBM by 67.5 % (P < 0.05)--an effect that was abolished by overnight fasting. Western blotting and immunohistochemistry demonstrated GLUT2 expression at the BBM during diabetes, but the protein was undetectable at the BBM of control animals or diabetic animals that had been fasted overnight. Our findings indicate that streptozotocin-induced diabetes causes the insertion of GLUT2 into the BBM and this may provide a low affinity/high capacity route of entry into proximal tubule cells during hyperglycaemia.
Phosphorylation of adenosine in renal brush-border membrane vesicles by an exchange reaction catalysed by adenosine kinase.
Sayós, J; Solsona, C; Mallol, J; Lluis, C; Franco, R
Uptake of [3H]adenosine in brush-border membrane (BBM) vesicles from either rat or pig kidney leads to an accumulation of intravesicular [3H]AMP. The lack of significant levels of ATP and the presence of AMP in BBM indicated that a phosphotransfer between [3H]adenosine and AMP occurs. The phosphotransfer activity is inhibited by iodotubercidin, which suggests that it is performed by adenosine kinase acting in an ATP-independent manner. The existence of a similar phosphotransferase activity was demonstrated in membrane-free extracts from pig kidney. From the compounds tested it was shown that a variety of mononucleotides could act as phosphate donors. The results suggest that phosphotransfer reactions may be physiologically relevant in kidney. PMID:8110185
Kinetics of Bacillus thuringiensis toxin binding with brush border membrane vesicles from susceptible and resistant larvae of Plutella xylostella.
Masson, L; Mazza, A; Brousseau, R; Tabashnik, B
An optical biosensor technology based on surface plasmon resonance was used to determine the kinetic rate constants for interactions between the CryIA(c) toxin from Bacillus thuringiensis and brush border membrane vesicles purified from susceptible and resistant larvae of diamondback moth (Plutella xylostella). CryIA(c) association and dissociation rate constants for vesicles from susceptible larvae were determined to be 4.5 x 10(3) M-1 s-1 and 3.2 x 10(-5) s-1, respectively, resulting in a calculated affinity constant of 7 nM. CryIE toxin did not kill susceptible or resistant larvae and did not bind to brush border vesicles. Contrary to expectations based on previous studies of binding in resistant P. xylostella, the binding kinetics for CryIA(c) did not differ significantly between susceptible larvae and those that were resistant to CryIA(c). Determination of the number of CryIA(c) receptors revealed an approximately 3-fold decrease in total CryIA(c) receptor numbers for resistant vesicles. These results suggest that factors other than binding may be altered in our resistant diamondback moth strain. They also support the view that binding is not sufficient for toxicity.
Radiation-inactivation studies on brush-border-membrane vesicles. General considerations, and application to the glucose and phosphate carriers.
Béliveau, R; Demeule, M; Ibnoul-Khatib, H; Bergeron, M; Beauregard, G; Potier, M
Radiation-inactivation studies were performed on brush-border-membrane vesicles purified from rat kidney cortex. No alteration of the structural integrity of the vesicles was apparent in electron micrographs of irradiated and unirradiated vesicles. The size distributions of the vesicles were also similar for both populations. The molecular sizes of two-brush-border-membrane enzymes, alkaline phosphatase and 5'-nucleotidase, estimated by the radiation-inactivation technique, were 104800 +/- 3500 and 89,400 +/- 1800 Da respectively. Polyacrylamide-gel-electrophoresis patterns of membrane proteins remained unaltered by the radiation treatment, except in the region of higher-molecular-mass proteins, where destruction of the proteins was visible. The molecular size of two of these proteins was estimated from their mobilities in polyacrylamide gels and was similar to the target size, estimated from densitometric scanning of the gel. Intravesicular volume, estimated by the uptake of D-glucose at equilibrium, was unaffected by irradiation. Uptake of Na+, D-glucose and phosphate were measured in initial-rate conditions to avoid artifacts arising from a decrease in the driving force caused by a modification of membrane permeability. Na+-independent D-glucose and phosphate uptakes were totally unaffected in the dose range used (0-9 Mrad). The Na+-dependent uptake of D-glucose was studied in irradiated vesicles, and the molecular size of the transporter was found to be 288,000 Da. The size of the Na+-dependent phosphate carrier was also estimated, and a value of 234,000 Da was obtained. Images Fig. 1. Fig. 4. PMID:3421923
K⁺-dependent ³H-D-glucose transport by hepatopancreatic brush border membrane vesicles of a marine shrimp.
Obi, Ijeoma E; Sterling, Kenneth M; Ahearn, Gregory A
The effects of sodium, potassium, sugar inhibitors, and membrane potential on ³H-D-glucose uptake by hepatopancreatic epithelial brush border membrane vesicles (BBMV) of the Atlantic marine shrimp, Litopenaeus setiferus, were investigated. Brush border membrane vesicles were prepared using a MgCl₂/EGTA precipitation method and uptake experiments were conducted using a high speed filtration technique. ³H-D-Glucose uptake was stimulated by both sodium and potassium and these transport rates were almost doubled in the presence of an inside-negative-induced membrane potential. Kinetics of ³H-D-glucose influx were hyperbolic functions of both external Na⁺ or K⁺, and an induced membrane potential increased influx J(max) and lowered K(m) in both salts. ³H-D-Glucose influx versus [glucose] in both Na⁺ or K⁺ media also displayed Michaelis-Menten properties that were only slightly affected by induced membrane potential. Phloridzin was a poor inhibitor of 0.5 mM ³H-D-glucose influx, requiring at least 5 mM in NaCl and 10 mM in KCl to significantly reduce hexose transport. Several sugars (D-galactose, α-methyl-D-gluco-pyranoside, unlabeled D-glucose, D-fructose, and D-mannose) were used at 75 mM as potential inhibitors of 0.1 mM ³H-D-glucose influx. Only unlabeled D-glucose, D-fructose, and D-mannose significantly (p < 0.05) reduced labeled glucose transport. An additional experiment using increasing concentrations of D-mannose (0, 10, 25, 75, and 100 mM) showed this hexose to be an effective inhibitor of 0.1 mM ³H-D-glucose uptake at concentrations of 75 mM and higher. As a whole these results suggest that ³H-D-glucose transport by hepatopancreatic BBMV occurs by a carrier system that is able to use both Na⁺ and K⁺ as drivers, is enhanced by membrane potential, is relatively refractory to phloridzin, and is only inhibited by itself, D-fructose, and D-mannose. These properties are similar to those exhibited by the mammalian SLC5A9/SGLT4 transporter
Molecular size of the Na+-H+ antiport in renal brush border membranes, as estimated by radiation inactivation
Beliveau, R.; Demeule, M.; Potier, M.
The radiation inactivation method was applied to brush border membrane vesicles from rat kidney, in order to estimate the molecular size of the Na+-H+ antiporter. Sodium influx (1mM) driven by an acid intravesicular pH was unaffected by the high osmolarity of the cryoprotective solution. Initial rate of influx was estimated by linear regression performed on the first 10 seconds of transport: 0.512 pmol/micrograms protein/s. There was no binding component involved. Incubation performed in the presence of 1 mM amiloride, an inhibitor of the Na+-H+ antiport gave an initial rate of only 0.071 pmol/microgram/s, an 82% inhibition. Membrane vesicles were irradiated at -78 degrees C in a Gammacel Model 220. Sodium influx was reduced, as the dose of radiation increased, but the influx remained linear for the period of time (10s) during which the initial rate was estimated, indicating no alteration of the proton driving force during this time period. Amiloride-insensitive flux remained totally unaffected by the radiation dose, indicating that the passive permeability of the membrane towards sodium was unaffected. The amiloride-sensitive pathway presented a monoexponential profile of inactivation, allowing the molecular size to be estimated at 321 kDa. Based on DCCD-binding studies suggesting the molecular size of the monomer to be around 65 kDa for rat kidney, our results suggest that the functional transporter in the membrane to be a multimer.
Binding and degradation of /sup 125/I-insulin by isolated rat renal brush border membranes: evidence for low affinity, high capacity insulin recognition sites
Meezan, E.; Pillion, D.J.; Elgavish, A.
The kidney plays a major role in the handling of circulating insulin in the blood, primarily via reuptake of filtered insulin at the luminal brush border membrane. 125I-insulin associated with rat renal brush border membrane vesicles (BBV) in a time- and temperature-dependent manner accompanied by degradation of the hormone to trichloroacetic acid (TCA)-soluble fragments. Both association and degradation of 125I-insulin were linearly proportional to membrane protein concentration with virtually all of the degradative activity being membrane associated. Insulin, proinsulin and desoctapeptide insulin all inhibited the association and degradation of 125I-insulin by BBV, but these processes were not appreciably affected by the insulin-like growth factors IGF-I and IGF-II or by cytochrome c and lysozyme, low molecular weight, filterable, proteins, which are known to be reabsorbed in the renal tubules by luminal endocytosis. When the interaction of 125I-insulin with BBV was studied at various medium osmolarities (300-1100 mosM) to alter intravesicular space, association of the ligand with the vesicles was unaffected, but degradation of the ligand by the vesicles decreased progressively with increasing medium osmolarity. Therefore, association of 125I-insulin to BBV represented binding of the ligand to the membrane surface and not uptake of the hormone or its degradation products into the vesicles. Attempts to crosslink 125I-insulin to a high-affinity insulin receptor using the bifunctional reagent disuccinimidyl suberate revealed only trace amounts of an 125I-insulin-receptor complex in brush border membrane vesicles in contrast to intact renal tubules where this complex was readily observed. Both binding and degradation of 125I-insulin by brush border membranes did not reach saturation even at concentrations of insulin approaching 10(-5) M.
Binding of Bacillus thuringiensis Cry1 Toxins to the Midgut Brush Border Membrane Vesicles of Chilo suppressalis (Lepidoptera: Pyralidae): Evidence of Shared Binding Sites
Fiuza, L.; Nielsen-Leroux, C.; Goze, E.; Frutos, R.; Charles, J.
Binding and competition among Cry1Aa, Cry1Ac, and Cry1Ba toxins were analyzed quantitatively in vitro by using (sup125)I-labeled activated toxins and brush border membrane vesicles isolated from Chilo suppressalis larval midguts. The three toxins bound specifically to the midgut brush border membrane vesicles. Direct binding experiments showed that Cry1Aa and Cry1Ba recognized a single class of binding sites with different affinities, whereas Cry1Aa recognized two classes of binding sites, one with a high affinity and a low concentration and the other with a lower affinity but higher concentration. Competition experiments showed that toxins Cry1Ac and Cry1Ba shared a binding site in the C. suppressalis midgut membranes and that this site was also the low-affinity binding site for Cry1Aa. PMID:16535306
Uptake and binding of /sup 125/I-calmodulin by isolated rat renal brush border membrane vesicles
Meezan, E.; Elgavish, A.; Wallace, R.W.
The authors have investigated the interaction of /sup 125/I-calmodulin with isolated rat renal brush border membrane vesicles (BBV) using an experimental protocol which allows us to distinguish between ligand binding to the outside of the vesicles vs. uptake and possible binding to the vesicle interior. By examining the association of /sup 125/I-calmodulin with BBV as a function of medium osmolarity (300-1100 mosm) to alter intravesicular space, virtually all ligand interaction with BBV was found to represent uptake of intact /sup 125/I-calmodulin into the intravesicular space. Uptake appeared specific by the following criteria: (1) it was largely calcium dependent (2) it was inhibited in a dose dependent fashion by calmodulin and the homologous protein troponin C, but not by unrelated proteins (lysozyme, cytochrome C, insulin) (3) it was inhibited by known calmodulin antagonists (calmidazolium, mellitin, trifluoperazine). Calmodulin uptake may be followed by binding of /sup 125/I-calmodulin to intravesicular BBV proteins; calmodulin-binding proteins in BBV with molecular weights of 143K, 118K, 50K, 47.5K, 46.5K and 35K were identified by Western blotting techniques. The specific association of /sup 125/I-calmodulin with isolated BBV is of interest in regard to the possible role of this calcium regulatory protein in the protein reabsorptive and ion transport functions of this renal tubular membrane fraction.
Indirect coupling of urate and p-aminohippurate transport to sodium in human brush-border membrane vesicles.
Roch-Ramel, F; Guisan, B; Schild, L
[14C]urate and p-[14C]aminohippurate (PAH) uptake by human brush-border membrane vesicles (BBMV) were measured in the presence of an inwardly oriented sodium gradient. No direct sodium cotransport was observed. Indirect [14C]urate coupling to sodium transport was demonstrated by cis-stimulation of [14C]urate with nicotinate or pyrazinoate (PZA) in the extravesicular medium but not by adding lactate, alpha-ketoglutarate, or beta-hydroxybutyrate. Indirect sodium coupling of [14C]PAH uptake was observed only when alpha-ketoglutarate was added to the extravesicular medium, a mechanism similar to that of basolateral membranes. The ability for PZA (and nicotinate) to cis-stimulate urate uptake was correlated with a high apparent affinity for the urate/anion exchanger. In urate-loaded vesicles, for identical medium concentrations, [14C]PZA uptake via the urateanion exchanger was 10 times higher than [14C]lactate uptake. Such high PZA affinity for the urate exchanger, working in parallel with PZA sodium cotransport can account for the stimulation of urate reabsorption by PZA in vivo.
Brush border membrane binding properties of Bacillus thuringiensis Vip3A toxin to Heliothis virescens and Helicoverpa zea midguts.
Lee, Mi Kyong; Miles, Paul; Chen, Jeng-Shong
The binding properties of Vip3A, a new family of Bacillus thuringiensis insecticidal toxins, have been examined in the major cotton pests, Heliothis virescens and Helicoverpa zea. Vip3A bound specifically to brush border membrane vesicles (BBMV) prepared from both insect larval midguts. In order to examine the cross-resistance potential of Vip3A to the commercially available Cry1Ac and Cry2Ab2 toxins, the membrane binding site relationship among these toxins was investigated. Competition binding assays demonstrated that Vip3A does not inhibit the binding of either Cry1Ac or Cry2Ab2 and vice versa. BBMV protein blotting experiments showed that Vip3A does not bind to the known Cry1Ac receptors. These distinct binding properties and the unique protein sequence of Vip3A support its use as a novel insecticidal agent. This study indicates a very low cross-resistance potential between Vip3A and currently deployed Cry toxins and hence supports its use in an effective resistance management strategy in cotton.
Restoring effect of selenium on the molecular content, structure and fluidity of diabetic rat kidney brush border cell membrane.
Gurbanov, Rafig; Bilgin, Mehmet; Severcan, Feride
Diabetic kidney disease (DKD) is a dominant factor standing for kidney impairments during diabetes. In this study, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was used to disclose the diabetes-induced structural changes in the kidney and evaluate the effects of selenium on diabetes. The increase in the area of the olefinic band indicated increased amount of lipid peroxidation end products in diabetic kidney brush border cell membrane. Moreover, saturated lipid content of this cell membrane considerably diminished. DKD was found to disrupt lipid order and cause a decrease in membrane dynamics. However, the administration of selenium at low and medium doses was shown to improve these conditions by changing the lipid contents toward control values, restoring the ordered structure of the lipids and membrane dynamics. Curve-fitting and artificial neural network (ANN) analyses of secondary structures of proteins demonstrated a relative increase in α-helix and reduction in the β-sheet during diabetes in comparison to the control group, which were ameliorated following selenium treatment at low and medium doses. These findings were further confirmed by applying hierarchical cluster analysis (HCA) and principal component analysis (PCA). A clear separation of the experimental groups was obtained with high heterogeneity in the lipid and protein regions. These chemometric analyses showed that the low and medium doses of selenium-treated diabetic groups are successfully segregated from the diabetic group and clustered closer to the control. The study suggests that medium and, more predominantly, low-dose selenium treatment can be efficient in eliminating diabetes-induced structural alterations.
Phosphohydrolase activity of the isolated, brush-border membrane of Hymenolepis diminuta (Cestoda) following sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis.
Pappas, P W
Following electrophoresis of isolated, brush-border membranes of Hymenolepis diminuta on SDS-polyacrylamide gels, three distinct areas of alpha-naphthyl phosphate (NP) hydrolysis were detected; these corresponded to proteins with molecular weights of 106,800, 172,700, and greater than 340,000 Daltons. Hydrolysis of NP was inhibited by adenosine triphosphate, adenosine;5'-monophosphate, p-nitrophenyl-phosphate, glucose-1-phosphate, glucose-6-phosphate, fructose-6-phosphate, fructose-1,6-diphosphate, molybdate, ethylenediaminetetraacetate (EDTA), and ethyleneglycol-bis-(beta-amino-ethyl)-N,N'-tetraacetate (EGTA), but not by fluoride. Inhibition of NP hydrolysis by EDTA was relieved in the presence of Mg++ or Ca++. Heating the isolated, brush-border membrane in the presence of SDS for 5 min at 95 C destroyed all enzymatic activity. These characteristics indicated that the enzyme(s) responsible for NP hydrolysis (following separation of membrane proteins by SDS-polyacrylamide gel electrophoresis) were the same enzymes responsible for the phosphohydrolase activity associated with intact and solubilized, brush-border membrane preparations of H. diminuta.
Exploring the midgut transcriptome and brush border membrane vesicle proteome of the rice stem borer, Chilo suppressalis (Walker).
Ma, Weihua; Zhang, Zan; Peng, Chuanhua; Wang, Xiaoping; Li, Fei; Lin, Yongjun
The rice stem borer, Chilo suppressalis (Walker) (Lepidoptera: Pyralidae), is one of the most detrimental pests affecting rice crops. The use of Bacillus thuringiensis (Bt) toxins has been explored as a means to control this pest, but the potential for C. suppressalis to develop resistance to Bt toxins makes this approach problematic. Few C. suppressalis gene sequences are known, which makes in-depth study of gene function difficult. Herein, we sequenced the midgut transcriptome of the rice stem borer. In total, 37,040 contigs were obtained, with a mean size of 497 bp. As expected, the transcripts of C. suppressalis shared high similarity with arthropod genes. Gene ontology and KEGG analysis were used to classify the gene functions in C. suppressalis. Using the midgut transcriptome data, we conducted a proteome analysis to identify proteins expressed abundantly in the brush border membrane vesicles (BBMV). Of the 100 top abundant proteins that were excised and subjected to mass spectrometry analysis, 74 share high similarity with known proteins. Among these proteins, Western blot analysis showed that Aminopeptidase N and EH domain-containing protein have the binding activities with Bt-toxin Cry1Ac. These data provide invaluable information about the gene sequences of C. suppressalis and the proteins that bind with Cry1Ac.
Specific binding of activated Vip3Aa10 to Helicoverpa armigera brush border membrane vesicles results in pore formation.
Liu, Jing-Guo; Yang, Ai-Zhen; Shen, Xiao-Hong; Hua, Bao-Guang; Shi, Guang-Lu
Helicoverpa armigera is one of the most harmful pests in China. Although it had been successfully controlled by Cry1A toxins, some H. armigera populations are building up resistance to Cry1A toxins in the laboratory. Vip3A, secreted by Bacillus thuringiensis, is another potential toxin against H. armigera. Previous reports showed that activated Vip3A performs its function by inserting into the midgut brush border membrane vesicles (BBMV) of susceptible insects. To further investigate the binding of Vip3A to BBMV of H. armigera, the full-length Vip3Aa10 toxin expressed in Escherichia coli was digested by trypsin or midgut juice extract, respectively. Among the fragments of digested Vip3Aa10, only a 62kDa fragment (Vip3Aa10-T) exhibited binding to BBMV of H. armigera and has insecticidal activity. Moreover, this interaction was specific and was not affected by the presence of Cry1Ab toxin. Binding of Vip3Aa10-T to BBMV resulted in the formation of an ion channel. Unlike Cry1A toxins, Vip3Aa10-T was just slightly associated with lipid rafts of BBMV. These data suggest that although activated Vip3Aa10 specifically interacts with BBMV of H. armigera and forms an ion channel, the mode of action of it may be different from that of Cry1A toxins.
Exploring the Midgut Transcriptome and Brush Border Membrane Vesicle Proteome of the Rice Stem Borer, Chilo suppressalis (Walker)
Peng, Chuanhua; Wang, Xiaoping; Li, Fei; Lin, Yongjun
The rice stem borer, Chilo suppressalis (Walker) (Lepidoptera: Pyralidae), is one of the most detrimental pests affecting rice crops. The use of Bacillus thuringiensis (Bt) toxins has been explored as a means to control this pest, but the potential for C. suppressalis to develop resistance to Bt toxins makes this approach problematic. Few C. suppressalis gene sequences are known, which makes in-depth study of gene function difficult. Herein, we sequenced the midgut transcriptome of the rice stem borer. In total, 37,040 contigs were obtained, with a mean size of 497 bp. As expected, the transcripts of C. suppressalis shared high similarity with arthropod genes. Gene ontology and KEGG analysis were used to classify the gene functions in C. suppressalis. Using the midgut transcriptome data, we conducted a proteome analysis to identify proteins expressed abundantly in the brush border membrane vesicles (BBMV). Of the 100 top abundant proteins that were excised and subjected to mass spectrometry analysis, 74 share high similarity with known proteins. Among these proteins, Western blot analysis showed that Aminopeptidase N and EH domain-containing protein have the binding activities with Bt-toxin Cry1Ac. These data provide invaluable information about the gene sequences of C. suppressalis and the proteins that bind with Cry1Ac. PMID:22666467
Binding of Escherichia coli heat-stable toxin and rise of guanylyl cyclase activity in the brush-border membranes of rabbit intestinal epithelial cells.
Bhattacharya, J; Chakrabarti, M K
The study examines the age-related differences in the density of Escherichia coli heat-stable enterotoxin (STa) receptors in the small intestine of rabbits. The number of STa receptors was found to be 1.7 x 10(12) in 14-day old rabbits compared to 2.4 x 10(9) in 14-week old rabbits per milligram brush-border membrane protein. The STa-induced guanylyl cyclase activity in the intestinal brush-border membranes was found to be stimulated by 6.2 folds over the basal enzyme activity in 14-day old rabbits, whereas in the 14-week old rabbits, it was 4 folds over the basal activity. Moreover, the enzyme activity remained lower in the adult rabbits compared to the younger ones. Autoradiographic analysis of sodium dodecyl sulphate polyacrylamide gel electrophoresis showed two STa-binding proteins of apparent molecular weights of 140 and 38 kDa in the intestinal brush-border membranes of rabbits.
Angiotensin 2 directly increases rabbit renal brush-border membrane sodium transport: Presence of local signal transduction system
Morduchowicz, G.A.; Sheikh-Hamad, D.; Dwyer, B.E.; Stern, N.; Jo, O.D.; Yanagawa, N. )
In the present study, the authors have examined the direct actions of angiotensin II (AII) in rabbit renal brush border membrane (BBM) where binding sites for AII exist. Addition of AII (10(-11)-10(-7) M) was found to stimulate 22Na+ uptake by the isolated BBM vesicles directly. All did not affect the Na(+)-dependent BBM glucose uptake, and the effect of AII on BBM 22Na+ uptake was inhibited by amiloride, suggesting the involvement of Na+/H+ exchange mechanism. BBM proton permeability as assessed by acridine orange quenching was not affected by AII, indicating the direct effect of AII on Na+/H+ antiport system. In search of the signal transduction mechanism, it was found that AII activated BBM phospholipase A2 (PLA) and that BBM contains a 42-kDa guanine nucleotide-binding regulatory protein (G-protein) that underwent pertussis toxin (PTX)-catalyzed ADP-ribosylation. Addition of GTP potentiated, while GDP-beta S or PTX abolished, the effects of AII on BBM PLA and 22Na+ uptake, suggesting the involvement of G-protein in AII's actions. On the other hand, inhibition of PLA by mepacrine prevented AII's effect on BBM 22Na+ uptake, and activation of PLA by mellitin or addition of arachidonic acid similarly enhanced BBM 22Na+ uptake, suggesting the role of PLA activation in mediating AII's effect on BBM 22Na+ uptake. In summary, results of the present study show a direct stimulatory effect of AII on BBM Na+/H+ antiport system, and suggest the presence of a local signal transduction system involving G-protein mediated PLA activation.
Effect of dietary fatty acids on jejunal and ileal oleic acid uptake by rat brush border membrane vesicles.
Prieto, R M; Stremmel, W; Sales, C; Tur, J A
To test the effect of dietary fatty acids on fatty acid uptake, the influx kinetics of a representative long-chain fatty acid, 3H-oleic acid, in both the jejunum and ileum of rats has been studied using brush border membrane vesicles (BBMV). Animals were fed with semipurified diets containing 5 g fat/100 g diet, as corn oil (control group), safflower oil (unsaturated group) and coconut oil hydrogenated (saturated group). With increasing unbound oleate concentration in the medium, the three dietary groups showed saturable kinetics in both jejunal and ileal BBMV (controls: Vmax = 0.15 +/- 0.01 nmol x mg protein-1 x 5 min-1 and Km = 136 +/- 29.1 nmol for jejunum, and Vmax = 0.23 +/- 0.03 nmol x mg protein-1 x 5 min-1 and Km = 196 +/- 50.3 nmol for ileum; unsaturated: Vmax = 0.28 +/- 0.05 nmol x mg protein-1 x 5 min-1 and Km = 242.7 +/- 91.8 nmol for jejunum, and Vmax = 1.29 +/- 0.06 nmol x mg protein-1 x 5 min-1 and Km = 509.8 +/- 97.5 nmol for ileum; saturated: Vmax = 0.03 +/- 0.01 nmol x mg protein-1 x 5 min-1 and Km = 124.5 +/- 72.6 nmol for jejunum, and Vmax = 0.04 +/- 0.01 nmol x mg protein -1.5 min-1 and Km = 205.6 +/- 85.3 nmol for ileum). These results support the theory that feeding an isocaloric diet containing only unsaturated fatty acids enhanced oleic acid uptake, and feeding an isocaloric diet containing only saturated fatty acids decreased oleic acid uptake. The results obtained in the present work also show the adaptative ability of jejunum and ileum to the type of dietary fat.
Effect of fluoride on the intestinal epithelial cell brush border membrane
Rastogi, R.; Upreti, R.K.; Kidwai, A.M.
Fluoride consumed by man and animals is chiefly absorbed in the intestine. Chronic fluoride exposure causes mottled teeth and osteosclerosis. Over-fluoridation (126 mM) of drinking water have been reported to cause nausea, vomiting and diarrhea. Furthermore, the effect of acute and low concentrations of fluoride on gastric secretion, ion transport and other disorders have also been studied. Fluoride also causes alterations in the permeability of membranes and membrane bound enzymes. The intestinal cell lining plays an important role in digestion and absorption. It automatically becomes the most exposed site of contact to fluoride following ingestion. Earlier study have shown significant alterations in the formation of lipid peroxides in rat intestine following oral administration of fluoride. The present study was undertaken to investigate the damage of rat intestinal epithelium in situ caused by relatively high and low fluoride concentrations.
Isolation and characterization of rabbit kidney brush borders
Quirk, S. J.; Robinson, G. B.
1. Brush borders were isolated from rabbit kidney-cortex homogenates by rate-zonal centrifugation through a sucrose density gradient in a B-XIV zonal rotor, followed by differential centrifugation. 2. The method of preparation gave brush borders of high purity with a reasonable yield. The morphological appearance supported the evidence from enzymic and chemical investigations, that the brush borders were only slightly contaminated with endoplasmic reticulum, mitochondria, lysosomes and nuclei. 3. The molar ratio of cholesterol to phospholipid lay within the range found in other plasma membranes, but the carbohydrate content was double that found in liver plasma membranes. 4. Alkaline phosphatase, maltase, trehalase and aminopeptidase were major enzymic constituents of the brush borders, and had an approximately equal yield and enrichment, but none of these enzymes fulfilled the criteria for marker enzymes. 5. Mg2+-dependent and Na+,K+-dependent adenosine triphosphatases, although found in brush borders, had low yields and low enrichments. ImagesPLATE 2PLATE 1 PMID:4264701
Heterogeneity of L-alanine transport systems in brush-border membrane vesicles from rat placenta during late gestation.
Alonso-Torre, S R; Serrano, M A; Medina, J M; Alvarado, F
The placental uptake of L-alanine was studied by using purified brush-border membrane vesicles from rat trophoblasts. Saturation curves were carried out at 37 degrees C in buffers containing 100 mM (zero-trans)-NaSCN, -NaCl, -KSCN, -KCl, or -N-methyl-D-glucamine gluconate. The uncorrected uptake results were fitted by non-linear regression analysis to an equation involving one diffusional component either one or two saturable Michaelian transport terms. In the presence of NaCl, two distinct L-alanine transport systems were distinguished, named respectively System 1 (S-1; Vm1 about 760 pmol/s per mg of protein; KT1 = 0.5 mM) and System 2 (S-2; Vm2 about 1700 pmol/s per mg; KT2 = 9 mM). In contrast, in the presence of K+ (KCl = KSCN) or in the absence of any alkali-metal ions (N-methyl-D-glucamine gluconate), only one saturable system was apparent, which we identify as S-2. When Na+ is present, S-1, but not S-2, appears to be rheogenic, since its maximal transport capacity significantly increases in the presence of an inside-negative membrane potential, created either by replacing Cl- with the permeant anion thiocyanate (NaSCN > NaCl) or by applying an appropriate K+ gradient and valinomycin. alpha-(Methylamino)isobutyrate (methyl-AIB) appears to be a substrate of S-1, but not of S-2. For reasons that remain to be explained, however, methyl-AIB inhibits S-2. We conclude that S-1 represents a truly Na(+)-dependent mechanism, where Na+ behaves as an obligatory activator, whereas S-2 cannot discriminate between Na+ and K+, although its activity is higher in the presence of alkali-metal ions than in their absence (Na+ = K+ > N-methyl-D-glucammonium ion). S-2 appears to be fully developed 2 days before birth, whereas S-1 undergoes a capacity-type activation between days 19.5 and 21.5 of gestation, i.e. its apparent Vmax. nearly doubles, whereas its KT remains constant. PMID:1445280
Hepatocyte growth factor activates phosphoinositide 3-kinase C2 beta in renal brush-border plasma membranes.
Crljen, Vladiana; Volinia, Stefano; Banfic, Hrvoje
Upon stimulation of renal cortical slices with hepatocyte growth factor (HGF), inositol lipid metabolism was studied in basal-lateral plasma membranes (BLM) and brush-border plasma membranes (BBM). Whereas in BLM rapid increases in 1,2-diacylglycerol, PtdIns(3,4,5)P(3) and PtdIns(3,4)P(2) were observed, suggesting that in BLM HGF activates both phospholipase C (PLC) and phosphoinositide 3-kinase (PI3K), in BBM only HGF-induced transient accumulation of PtdIns3P was seen, which was temporarily delayed from signalling events in BLM and could be blocked by the PtdIns-specific-PLC inhibitor ET-18-OCH(3) and the calpain inhibitor calpeptin, suggesting that 3-kinase activation in BBM lies downstream of PLC activation in BLM and is a calpain-mediated event. Moreover, the increase in immunoprecipitable PI3K-C2 beta activity, which is sensitive to wortmannin (10 nM) and shows strong preference for PtdIns over PtdIns4P as a substrate, was observed only in BBM upon stimulation of renal cortical slices with HGF and could be mimicked by the Ca(2+) ionophore A23187 and blocked by the cell-penetrant Ca(2+) chelator BAPTA-AM [1,2-bis-(2-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid tetrakis(acetoxymethyl ester)]. On Western blots PI3K-C2 beta revealed a single immunoreactive band of 180 kDa in BLM and BBM, while after stimulation with HGF a gel shift of 18 kDa was noticed only in BBM, suggesting that the observed enzyme activation is achieved by proteolysis. When BBM were subjected to short-term (15 min) exposure to mu-calpain, a similar gel shift together with an increase in PI3K-C2 beta activity was observed, when compared with the BBM harvested after HGF stimulation. The above-mentioned gel shift and increase in PI3K-C2 beta activity could be prevented by the calpain inhibitor calpeptin. The data presented in this report show that in renal cells there is a spatial separation of the inositol lipid signalling system between BLM and BBM, and that HGF causes activation of PLC and
Modulatory effect of thyroid hormones on uptake of phosphate and other solutes across luminal brush border membrane of kidney cortex
Yusufi, A.N.; Murayama, N.; Keller, M.J.; Dousa, T.P.
The mechanism whereby thyroid hormones modulate the transport properties of luminal brush border membrane (BBM) of renal proximal tubules was studied in thyroparathyroidectomized rats. Administration of both T4 and T3 increased BBM capacity for Na/sup +/ gradient-dependent uptake of phosphate (P /sub i/) by BBM vesicles (BBMV). This effect of thyroid hormones was present in thyroparathyroidectomized and hypophysectomized rats, and it was not blocked by a saturating dose of propranolol. The stimulatory effect of T3 and T4 on BBM transport of P /sub i/ was dose dependent in the range of 5.2-520 nmol/100 g BW. Pretreatment of rats with inhibitors of 5'-monodeiodinase (5'-DI), iopanoic acid or ipodate, prevented the increase in serum T3 in rats injected with T4, but it did not diminish the increase in BBM transport of P /sub i/. Administration of iopanoic acid and ipodate also prevented a 5-fold increase in 5'-DI activity in renal cortical tissue elicited by T4 administration. Treatment with T3 resulted in an increase of Pi transport across BBM from kidneys of rats subjected to dietary P /sub i/ deprivation due either to total fasting or to feeding of a low P /sub i/ diet. Further, T3 administration enhanced amiloride-sensitive Na+-H+ countertransport across BBM, but the uptake of /sup 22/Na+ by BBMV in the absence of pH gradient was not changed. The Na+ gradient-dependent uptake of L-(/sup 3/H)proline by BBMV was slightly decreased, but the uptake of (/sup 14/C)citrate was not changed in response to T3. Administration of T3 increased P /sub i/ transport in BBMV prepared from juxtamedullary cortex, but not in BBMV from superficial cortex. Conversely, the rate of Na+-H+ countertransport was enhanced, and the enzymatic activity of alkaline phosphatase was decreased in BBMV from superficial cortex; no changes in these parameters were found in BBMV from juxtamedullary cortex.
[Effect of natural or synthetic detergents on the transport of D-glucose in the membranes of vesicles of the brush border of the intestine of the rabbit].
Favilli, F; Iantomasi, T; Stio, M; Treves, C; Vanni, P; Vincenzini, M T
We describe here the effects of natural and synthetic detergents on the D-glucose transport into brush-border membranes of vesicles of rabbit's intestine. Two synthetic detergents: Triton X-100 and dodecyltrimethylammonium bromide have been found very strong inhibitors (more than 50 p. 100 of inhibition of maximal D-glucose uptake). Kinetic studies showed that these detergents behaved as mixed type inhibitors. The Na+-dependent transport of amino acids (aspartic acid, lysine, phenylalanine) is only poorly affected by dodecyltrimethylammonium bromide, while Triton X-100 inhibits unspecifically all the transport studied.
Staphylococcus aureus enterotoxins A- and B: binding to the enterocyte brush border and uptake by perturbation of the apical endocytic membrane traffic.
Danielsen, E Michael; Hansen, Gert H; Karlsdóttir, Edda
Enterotoxins of Staphylococcus aureus are among the most common causes of food poisoning. Acting as superantigens they intoxicate the organism by causing a massive uncontrolled T cell activation that ultimately may lead to toxic shock and death. In contrast to our detailed knowledge regarding their interaction with the immune system, little is known about how they penetrate the epithelial barrier to gain access to their targets. We therefore studied the uptake of two staphylococcal enterotoxins (SEs), SEA and SEB, using organ cultured porcine jejunal explants as model system. Attachment of both toxins to the villus surface was scarce and patchy compared with that of cholera toxin B (CTB). SEA and SEB also bound to microvillus membrane vesicles in vitro, but less efficiently than CTB, and the binding was sensitive to treatment with endoglycoceramidase II, indicating that a glycolipid, possibly digalactosylceramide, acts as cell surface receptor at the brush border. Both SEs partitioned poorly with detergent resistant membranes (DRMs) of the microvillus, suggesting a weak association with lipid raft microdomains. Where attachment occurred, cellular uptake of SEA and SEB was also observed. In enterocytes, constitutive apical endocytosis normally proceeds only to subapical early endosomes present in the actomyosin-rich "terminal web" region. But, like CTB, both SEA and SEB penetrated deep into the cytoplasm. In conclusion, the data show that after binding to the enterocyte brush border SEA and SEB perturb the apical membrane trafficking, enabling them to engage in transcytosis to reach their target cells in the subepithelial lamina propria.
The transmembrane pH gradient drives uphill folate transport in rabbit jejunum. Direct evidence for folate/hydroxyl exchange in brush border membrane vesicles.
Schron, C M; Washington, C; Blitzer, B L
In rabbit jejunal, but not ileal brush border membrane vesicles, an outwardly directed OH- gradient (pH 7.7 inside, pH 5.5 outside) markedly stimulated the initial velocity of folate (0.1 microM) uptake compared with uptake in the absence of a pH gradient. Under pH gradient conditions, folate was transiently accumulated at a concentration four times that found at equilibrium (over-shoot), implying uphill transport of the vitamin. Equilibrium folate uptake was inversely proportional to medium osmolality, suggesting uptake into an osmotically sensitive space. pH gradient-stimulated folate uptake was markedly reduced by inhibitors of anion exchange (4,4'-diisothiocyano-2,2'-disulfonic acid stilbene; 4-acetamido-4-isothiocyanostilbene-2,2'-disulfonic acid; furosemide), and was saturable (folate Km = 0.19 +/- 0.02 microM; Vmax = 12.8 +/- 0.4 pmol X mg protein-1 X min-1). Imposition of an inside-positive electrical potential did not stimulate folate uptake, suggesting that stimulation by a pH gradient was not due to an induced electrical potential. In contrast, an inwardly directed Na+ or K+ gradient did not stimulate folate uptake. These findings provide evidence for a carrier on the jejunal brush border membrane that mediates folate/OH- exchange (or H+/folate co-transport), and are consonant with the known presence of an outwardly directed OH- gradient in vivo (brush border acid microclimate), an acidic pH optimum for intestinal folate uptake, and the primary role of the jejunum in folate absorption. PMID:4056063
Osmotic water permeability of rat intestinal brush border membrane vesicles: involvement of aquaporin-7 and aquaporin-8 and effect of metal ions.
Tritto, Simona; Gastaldi, Giulia; Zelenin, Sergey; Grazioli, Monica; Orsenigo, Maria Novella; Ventura, Ulderico; Laforenza, Umberto; Zelenina, Marina
Water channels AQP7 and AQP8 may be involved in transcellular water movement in the small intestine. We show that both AQP7 and AQP8 mRNA are expressed in rat small intestine. Immunoblot and immunohistochemistry experiments demonstrate that AQP7 and AQP8 proteins are present in the apical brush border membrane of intestinal epithelial cells. We investigated the effect of several metals and pH on the osmotic water permeability (Pf) of brush border membrane vesicles (BBMVs) and of AQP7 and AQP8 expressed in a cell line. Hg2+, Cu2+, and Zn2+ caused a significant decrease in the BBMV Pf, whereas Ni2+ and Li+ had no effect. AQP8-transfected cells showed a reduction in Pf in the presence of Hg2+ and Cu2+, whereas AQP7-transfected cells were insensitive to all tested metals. The Pf of both BBMVs and cells transfected with AQP7 and AQP8 was not affected by pH changes within the physiological range, and the Pf of BBMVs alone was not affected by phlorizin or amiloride. Our results indicate that AQP7 and AQP8 may play a role in water movement via the apical domain of small intestine epithelial cells. AQP8 may contribute to the water-imbalance-related clinical symptoms apparent after ingestion of high doses of Hg2+ and Cu2+.
Specificity of Bacillus thuringiensis endotoxins is correlated with the presence of high-affinity binding sites in the brush border membrane of target insect midguts
Hofmann, C.; Vanderbruggen, H.; Hoefte, H.; Van Rie, J.; Jansens, S.; Van Mellaert, H. )
Binding studies were performed with two {sup 125}I-labeled Bacillus thuringiensis {delta}-endotoxins on brush border membrane vesicles prepared from the larval midgut of the tobacco hornworm Manduca sexta or the cabbage butterfly Pieris brassicae. One {delta}-endotoxin, Bt2-protoxin, is a 130-kDa recombinant crystalline protein from B. thuringiensis subsp. berliner. It kills larvae of both insect species. The active Bt2-toxin is a 60-kDa proteolytic fragment of the Bt2-protoxin. It binds saturably and with high affinity to brush border membrane vesicles from the midgut of both species. The other {delta}-endotoxin, Bt4412-protoxin, is a 136-kDa crystalline protein from B. thuringiensis subsp. thuringiensis, which is highly toxic for P. brassicae, but not for M. sexta larvae. Bt4412-toxin, obtained after proteolytic activation of Bt4412-protoxin, shows high-affinity saturable binding to P. brassicae vesicles but not to M. sexta vesicles. The correlation between toxicity and specific binding is further strengthened by competition studies. Other B. thuringiensis {delta}-endotoxins active against M. sexta compete for binding of {sup 125}I-labeled Bt2-toxin to M. sexta vesicles, whereas toxins active against dipteran or coleopteran larvae do not compete. Bt2-toxin and Bt4412-toxin bind to different sites on P. brassicae vesicles.
Design of a Photoreactive Analogue of the Escherichia coli Heat-Stable Enterotoxin STIb: Use in Identifying Its Receptor on Rat Brush Border Membranes
NASA Astrophysics Data System (ADS)
Gariepy, Jean; Schoolnik, Gary K.
The Escherichia coli heat-stable enterotoxin, STIb was prepared by solid-phase peptide synthesis and purified to homogeneity by high-pressure liquid chromatography. This analogue was iodinated and shown to bind specifically to rat intestinal membranes. The radiolabeled peptide was derivatized at the amino terminus with the photoreactive heterobifunctional crosslinking agent N-hydroxysuccinimidyl p-benzoylbenzoate. This photoreactive probe also exhibited binding specificity. It was mixed with rat intestinal brush border membranes and photolyzed in the presence or absence of excess unlabeled STIb. Polyacrylamide gel electrophoresis performed in the presence of sodium dodecyl sulfate and 2-mercaptoethanol indicated that the peptide probe was cross-linked specifically to two molecular species of 57 and 75 kDa. One or both of these molecules appear to constitute the enterotoxin receptor or to be in close proximity to it.
Calcium and glucose uptake in rat small intestinal brush-border membrane vesicles. Modulation by exogenous hypercortisolism and 1,25-dihydroxyvitamin D-3.
Braun, H J; Birkenhäger, J C; De Jonge, H R
The effect of exogenous hypercortisolism and 1,25-dihydroxyvitamin D-3 on small-intestinal calcium and glucose transport in the rat was studied at the level of brush-border membrane vesicles generated from isolated villous cells by a freeze-thaw procedure. At 5 X 10(-5) M extravesicular calcium, initial uptake rates in vesicles prepared from triamcinolone-treated adult rats were decreased by 30% after 5 days. Since calcium ionophore A23187 virtually abolished the difference in calcium uptake, triamcinolone appeared to affect calcium channel density or activity rather than intravesicular binding capacity. Kinetic analysis showed that a decrease in Vmax of a saturable calcium transport system could entirely account for the diminished rate of vesicular calcium uptake. Calcium transport rates could be partially restored by in vivo administration of 1,25-dihydroxyvitamin D-3 at a dosage which did not affect vesicular calcium uptake in control animals. Conversely, sodium-driven glucose accumulation in brush-border vesicles from triamcinolone-treated rats was stimulated by 50-70% after 36 h and appeared insensitive to vitamin D. A specific triamcinolone action on the glucose carrier itself rather than on the driving force of the sodium gradient was indicated by (i) a similar stimulation of glucose transport under equilibrium exchange conditions and (ii) an opposite effect of triamcinolone on sodium-driven alanine transport. The triamcinolone-induced changes in calcium and glucose uptake were not accompanied by a gross alteration of membrane integrity in vitro or by major alterations in vesicular protein composition, intravesicular glucose space and sucrase or alkaline phosphatase activity. The modification of vesicular transport properties is discussed in relation to the vitamin D-antagonized inhibition of intestinal calcium uptake and the stimulation of glucose absorption in response to supraphysiologic amounts of glucocorticoids observed in intact epithelium.
Intestinal brush border assembly driven by protocadherin-based intermicrovillar adhesion
Crawley, Scott W.; Shifrin, David A.; Grega-Larson, Nathan E.; McConnell, Russell E.; Benesh, Andrew E.; Mao, Suli; Zheng, Yuxi; Zheng, Qing Yin; Nam, Ki Taek; Millis, Bryan A.; Kachar, Bechara; Tyska, Matthew J.
Transporting epithelial cells build apical microvilli to increase membrane surface area and enhance absorptive capacity. The intestinal brush border provides an elaborate example, with tightly packed microvilli that function in nutrient absorption and host defense. Although the brush border is essential for physiological homeostasis, its assembly is poorly understood. We found that brush border assembly is driven by the formation of Ca2+-dependent adhesion links between adjacent microvilli. Intermicrovillar links are composed of protocadherin-24 and mucin-like protocadherin, which target to microvillar tips and interact to form a trans heterophilic complex. The cytoplasmic domains of microvillar protocadherins interact with the scaffolding protein, harmonin, and myosin-7b, which promote localization to microvillar tips. Finally, a mouse model of Usher syndrome lacking harmonin exhibits microvillar protocadherin mislocalization and severe defects in brush border morphology. These data reveal an adhesion-based mechanism for brush border assembly and illuminate the basis of intestinal pathology in Usher syndrome patients. PMID:24725409
Contraction of isolated brush borders from the intestinal epithelium
Brush borders isolated from epithelial cells from the small intestine of neonatal rats are able to contract in the presence of ATP and Mg2+; Ca2+ is not required. Contraction is characterized by a pinching-in of the plasma membrane in the region of the zonula adherens and a subsequent rounding of the brush borders. No movement or consistent shortening of the microvilli is observed. The contraction appears to involve the 5- to 7-nm diameter microfilaments in the terminal web which associate with the zonula adherens. These filaments bind heavy meromyosin as do the actin core filaments of the microvilli. A model for contraction is presented in which, in the intact cell, terminal web filaments and core filaments interact to produce shortening of the microvilli. PMID:783170
Leucine transport is affected by Bacillus thuringiensis Cry1 toxins in brush border membrane vesicles from Ostrinia nubilalis Hb (Lepidoptera: Pyralidae) and Sesamia nonagrioides Lefebvre (Lepidoptera: Noctuidae) midgut.
Leonardi, M Giovanna; Caccia, Silvia; González-Cabrera, Joel; Ferré, Juan; Giordana, Barbara
The pore-forming activity of Cry1Ab, Cry1Fa and Cry1Ca toxins and their interaction with leucine transport mediated by the K(+)/leucine cotransporter were studied in brush border membrane vesicles (BBMVs) isolated from the midgut of Ostrinia nubilalis and Sesamia nonagrioides. In both species, as in other Lepidoptera, leucine uptake by BBMVs can take place in the absence of cations, but it can also be driven by a K(+) gradient. Experiments with the voltage-sensitive fluorescent dye 3,3'-diethylthiacarbocyanine iodide proved that Cry1Ab, a Bacillus thuringiensis toxin active in vivo, enhanced the membrane permeability to potassium in O. nubilalis BBMVs. This result is in agreement with similar effects observed in S. nonagrioides BBMV incubated with various Cry1 toxins active in vivo. The effect of the above toxins was tested on the initial rate of 0.1 mM: leucine influx. Instead of an increase in leucine influx, a reduction was observed with the Cry1 toxins active in vivo. Cry1Ab and Cry1Fa, but not the inactive toxin Cry1Da, inhibited in a dose-dependent manner leucine uptake both in the absence and in the presence of a K(+) gradient, a clear indication that their effect is independent of the channel formed by the toxins and that this effect is exerted directly on the amino acid transport system.
L-Carnitine transport in human placental brush-border membranes is mediated by the sodium-dependent organic cation transporter OCTN2.
Lahjouji, Karim; Elimrani, Ihsan; Lafond, Julie; Leduc, Line; Qureshi, Ijaz A; Mitchell, Grant A
Maternofetal transport of l-carnitine, a molecule that shuttles long-chain fatty acids to the mitochondria for oxidation, is thought to be important in preparing the fetus for its lipid-rich postnatal milk diet. Using brush-border membrane (BBM) vesicles from human term placentas, we showed that l-carnitine uptake was sodium and temperature dependent, showed high affinity for carnitine (apparent K(m) = 11.09 +/- 1.32 microM; V(max) = 41.75 +/- 0.94 pmol.mg protein(-1).min(-1)), and was unchanged over the pH range from 5.5 to 8.5. l-Carnitine uptake was inhibited in BBM vesicles by valproate, verapamil, tetraethylammonium, and pyrilamine and by structural analogs of l-carnitine, including d-carnitine, acetyl-d,l-carnitine, and propionyl-, butyryl-, octanoyl-, isovaleryl-, and palmitoyl-l-carnitine. Western blot analysis revealed that OCTN2, a high-affinity, Na(+)-dependent carnitine transporter, was present in placental BBM but not in isolated basal plasma membrane vesicles. The reported properties of OCTN2 resemble those observed for l-carnitine uptake in placental BBM vesicles, suggesting that OCTN2 may mediate most maternofetal carnitine transport in humans.
Polymer Brushes for Membrane Separations: A Review.
Keating, John Joseph; Imbrogno, Joseph; Belfort, Georges
The fundamentals and applications of polymer brush modified membranes are reviewed. This new class of synthetic membranes is explored with an emphasis on tuning the membrane performance through polymer brush grafting. This work highlights the intriguing performance characteristics of polymer brush modified membranes in a variety of separations. Polymer brushes are a versatile and effective means in designing membranes for applications in protein adsorption and purification, colloid stabilization, sensors, water purification, pervaporation of organic compounds, gas separations, and as stimuli responsive materials.
Influence of Ramadan-type fasting on carbohydrate metabolism, brush border membrane enzymes and phosphate transport in rat kidney used as a model.
Salim, Samina; Farooq, Neelam; Priyamvada, Shubha; Asghar, Mohammad; Khundmiri, Syed Jalal; Khan, Samia; Khan, Farah; Yusufi, Ahad Noor Khan
Ramadan fasting is a unique model of fasting in which Muslims the world over abstain from food and water from dawn to sunset for 1 month. We hypothesized that this model of prolonged intermittent fasting would result in specific adaptive alterations in rat kidney to keep a positive balance of metabolites and inorganic phosphate (Pi). The effect of Ramadan-type fasting was studied on enzymes of carbohydrate metabolism and brush border membrane (BBM) and BBM uptake of 32Pi in different renal tissue zones in the rat model. Rats were fasted (12 h) and then re-fed (12 h) daily for 30 d similar to human Ramadan fasting. Ramadan-type fasting resulted in increased serum Pi and phospholipids, whereas Pi clearance decreased. Serum creatinine and its clearance were not affected. Fasting caused a significant decrease in the activities of lactate and malate dehydrogenases, glucose-6-phosphatase and fructose-1,6-bisphosphatase, both in the renal cortex and medulla. However, the activity of glucose-6-phosphate dehydrogenase profoundly increased but that of malic enzyme decreased. The activities of alkaline phosphatase and gamma-glutamyl transpeptidase in BBM decreased, whereas transport of 32Pi significantly increased. The decrease in enzyme activities and increase in 32Pi transport were due to alterations of both maximal velocities and relative affinities. The results indicate that Ramadan-type fasting caused specific metabolic alterations with enhanced Pi conservation in different kidney tissues in a rat model used for Ramadan fasting in man.
Domain III of the Bacillus thuringiensis delta-endotoxin Cry1Ac is involved in binding to Manduca sexta brush border membranes and to its purified aminopeptidase N.
de Maagd, R A; Bakker, P L; Masson, L; Adang, M J; Sangadala, S; Stiekema, W; Bosch, D
Three types of binding assays were used to study the binding of Bacillus thuringiensis delta-endotoxin Cry1Ac to brush border membrane vesicle (BBMV) membranes and a purified putative receptor of the target insect Manduca sexta. Using hybrid proteins consisting of Cry1Ac and the related Cry1C protein, it was shown that domain III of Cry1Ac is involved in specificity of binding as observed by all three techniques. In ligand blotting experiments using SDS-PAGE-separated BBMV proteins as well as the purified putative receptor aminopeptidase N (APN), the presence of domain III of Cry1Ac in a hybrid with Cry1C was necessary and sufficient for specific binding to APN. Using the surface plasmon resonance (SPR) technique with immobilized APN, it was shown that the presence of domain III of Cry1Ac in a hybrid is sufficient for binding to one of the two previously identified Cry1Ac binding sites, whereas the second site requires the full Cry1Ac toxin for binding. In addition, the role of domain III in the very specific inhibition of Cry1Ac binding by the amino sugar N-acetylgalactosamine (GalNac) was determined. Both in ligand blotting and in surface plasmon resonance experiments, as well as in binding assays using intact BBMVs, it was shown that the presence of domain III of Cry1Ac in a toxin molecule is sufficient for the inhibition of binding by GalNAc. These and other results strongly suggest that domain III of delta-endotoxins play a role in insect specificity through their involvement in specific binding to insect gut epithelial receptors.
Aminopeptidase N purified from gypsy moth brush border membrane vesicles is a specific receptor for Bacillus thuringiensis CryIAc toxin.
Lee, M K; You, T H; Young, B A; Cotrill, J A; Valaitis, A P; Dean, D H
We have evaluated the binding of Bacillus thuringiensis Cry toxins to aminopeptidase N (APN) purified from Lymantria dispar (gypsy moth) brush border membrane vesicle (BBMV). CryIAc toxin bound strongly to APN, while either the structurally related CryIAa and CryIAb toxins or CryIC, CryIIA, and CryIIIA toxins showed weak binding to APN. An in vitro competition binding study demonstrated that the binding of CryIAc to L. dispar BBMV was inhibited by APN. Inhibition of short circuit current for CryIAc, measured by voltage clamping of whole L. dispar midgut, was substantially reduced by addition of phosphatidylinositol-specific phospholipase C, which is known to release APN from the midgut membrane. In contrast, addition of phosphatidylinositol-specific phospholipase C had only a marginal effect on the inhibition of short circuit current for CryIAa. These data suggest that APN is the major functional receptor for CryIAc in L. dispar BBMV. A ligand blotting experiment demonstrated that CryIAc recognized a 120-kDa peptide (APN), while CryIAa and CryIAb recognized a 210-kDa molecule in L. dispar BBMV. In contrast, CryIAa and CryIAb bound to both the 120- and 210-kDa molecules in Manduca sexta BBMV, while CryIAc recognized only the 120-kDa peptide. The 120-kDa peptide (APN) in L. dispar BBMV reacted with soybean agglutinin, indicating that N-acetylgalactosamine is a component of this glycoprotein. PMID:8702277
Correction of enhanced Na(+)-H+ exchange of rat small intestinal brush-border membranes in streptozotocin-induced diabetes by insulin or 1,25-dihydroxycholecalciferol
Dudeja, P.K.; Wali, R.K.; Klitzke, A.; Sitrin, M.D.; Brasitus, T.A. )
Diabetes was induced in rats by administration of a single i.p. injection of streptozotocin (50 mg/kg body wt). After 7 d, diabetic rats were further treated with insulin or 1,25-dihydroxycholecalciferol (1,25(OH)2D3) for an additional 5-7 d. Control, diabetic, diabetic + insulin, and diabetic + 1,25(OH)2D3 rats were then killed, their proximal small intestines were removed, and villus-tip epithelial cells were isolated and used to prepare brush-border membrane vesicles. Preparations from each of these groups were then analyzed and compared with respect to their amiloride-sensitive, electroneutral Na(+)-H+ exchange activity, using {sup 22}Na uptake as well as acridine orange techniques. The results of these experiments demonstrated that (a) H+ gradient-dependent {sup 22}Na uptake as well as Na+ gradient-dependent transmembrane H+ fluxes were significantly increased in diabetic vesicles compared to their control counterparts, (b) kinetic studies demonstrated that this enhanced {sup 22}Na uptake in diabetes was a result of increased maximal velocity (Vmax) of this exchanger with no change in apparent affinity (Km) for Na+, (c) serum levels of 1,25(OH)2D3 were significantly lower in diabetic animals compared with their control counterparts; and (d) insulin or 1,25(OH)2D3 treatment restored the Vmax alterations to control values, without any significant changes in Km, concomitant with significantly increasing the serum levels of 1,25(OH)2D3 in diabetic animals. These results indicate that Na(+)-H+ activity is significantly increased in proximal small intestinal luminal membranes of streptozotocin-induced diabetic rats. Moreover, alterations in the serum levels of 1,25(OH)2D3 may, at least in part, explain this enhanced antiporter activity and its correction by insulin.
Functional regulation of sugar assimilation by N-glycan-specific interaction of pancreatic α-amylase with glycoproteins of duodenal brush border membrane.
Asanuma-Date, Kimie; Hirano, Yuki; Le, Na; Sano, Kotone; Kawasaki, Nana; Hashii, Noritaka; Hiruta, Yoko; Nakayama, Ken-ichi; Umemura, Mariko; Ishikawa, Kazuhiko; Sakagami, Hiromi; Ogawa, Haruko
Porcine pancreatic α-amylase (PPA) binds to N-linked glycans of glycoproteins (Matsushita, H., Takenaka, M., and Ogawa, H. (2002) J. Biol Chem., 277, 4680-4686). Immunostaining revealed that PPA is located at the brush-border membrane (BBM) of enterocytes in the duodenum and that the binding is inhibited by mannan but not galactan, indicating that PPA binds carbohydrate-specifically to BBM. The ligands for PPA in BBM were identified as glycoprotein N-glycans that are significantly involved in the assimilation of glucose, including sucrase-isomaltase (SI) and Na(+)/Glc cotransporter 1 (SGLT1). Binding of SI and SGLT1 in BBM to PPA was dose-dependent and inhibited by mannan. Using BBM vesicles, we found functional changes in PPA and its ligands in BBM due to the N-glycan-specific interaction. The starch-degrading activity of PPA and maltose-degrading activity of SI were enhanced to 240 and 175%, respectively, while Glc uptake by SGLT1 was markedly inhibited by PPA at high but physiologically possible concentrations, and the binding was attenuated by the addition of mannose-specific lectins, especially from Galanthus nivalis. Additionally, recombinant human pancreatic α-amylases expressed in yeast and purified by single-step affinity chromatography exhibited the same carbohydrate binding specificity as PPA in binding assays with sugar-biotinyl polymer probes. The results indicate that mammalian pancreatic α-amylases share a common carbohydrate binding activity and specifically bind to the intestinal BBM. Interaction with N-glycans in the BBM activated PPA and SI to produce much Glc on the one hand and to inhibit Glc absorption by enterocytes via SGLT1 in order to prevent a rapid increase in blood sugar on the other.
Molecular Model of the Microvillar Cytoskeleton and Organization of the Brush Border
Brown, Jeffrey W.; McKnight, C. James
Background Brush border microvilli are ∼1-µm long finger-like projections emanating from the apical surfaces of certain, specialized absorptive epithelial cells. A highly symmetric hexagonal array of thousands of these uniformly sized structures form the brush border, which in addition to aiding in nutrient absorption also defends the large surface area against pathogens. Here, we present a molecular model of the protein cytoskeleton responsible for this dramatic cellular morphology. Methodology/Principal Findings The model is constructed from published crystallographic and microscopic structures reported by several groups over the last 30+ years. Our efforts resulted in a single, unique, self-consistent arrangement of actin, fimbrin, villin, brush border myosin (Myo1A), calmodulin, and brush border spectrin. The central actin core bundle that supports the microvillus is nearly saturated with fimbrin and villin cross-linkers and has a density similar to that found in protein crystals. The proposed model accounts for all major proteinaceous components, reproduces the experimentally determined stoichiometry, and is consistent with the size and morphology of the biological brush border membrane. Conclusions/Significance The model presented here will serve as a structural framework to explain many of the dynamic cellular processes occurring over several time scales, such as protein diffusion, association, and turnover, lipid raft sorting, membrane deformation, cytoskeletal-membrane interactions, and even effacement of the brush border by invading pathogens. In addition, this model provides a structural basis for evaluating the equilibrium processes that result in the uniform size and structure of the highly dynamic microvilli. PMID:20195380
Interaction between Cry9Ca and two Cry1A delta-endotoxins from Bacillus thuringiensis in larval toxicity and binding to brush border membrane vesicles of the spruce budworm, Choristoneura fumiferana Clemens.
Pang, Anthony S D; Gringorten, J Lawrence; van Frankenhuyzen, Kees
A genetically altered variant of Cry9Ca from Bacillus thuringiensis shows high potency against the spruce budworm, Choristoneura fumiferana Clemens. Its activity, as measured by feeding inhibition in frass-failure assays, is estimated to be four to seven times greater than B. thuringiensis subsp. kurstaki HD-1, the strain currently used in commercial products to control this insect. Bioassays against budworm of mixtures of the modified Cry9Ca and two of the Cry1A endotoxin proteins produced by HD-1 show neither synergism nor antagonism. Experiments with brush border membrane vesicles from budworm midgut revealed that Cry9Ca and the Cry1A toxins share a common binding site and that bound Cry9Ca can be displaced from the membrane to some extent by the Cry1A toxins. However, it is uncertain whether the binding site is actually the receptor molecule or a membrane protein associated with pore formation.
Brush-border calmodulin. A major component of the isolated microvillus core
Calmodulin is present in brush borders isolated from intestinal epithelial cells and is one of the major components of the microvillar filament bundle. Calmodulin was purified from either demembranated brush borders or microvilli by a simple boiling procedure. The boiled supernate derived from the microvillus cores contained one major polypeptide of 20,000 daltons.The supernate from the brush-border preparation contained the 20,000-dalton subunit and a second protein of 30,000 daltons. The 20,000-dalton subunit has been identified as calmodulin by several criteria: (a) heat resistance, (b) comigration with brain calmodulin on alkaline urea gels and SDS gels, both cases in which the 20,000-dalton protein, like calmodulin, exhibits a shift in electrophoretic mobility in the presence of Ca++, and (c) 4--5-fold activation of 3',5'-cyclic nucleotide phosphodiesterase in the presence but not the absence of Ca++. With a cosedimentation assay it was determined that brush-border calmodulin does not bind directly to actin. In the presence of Ca++ (greater than 5 x 10(-7) M) there was a partial release of calmodulin from the microvillus core, along with a substantial conversion of microvillus actin into a nonpelletable from. The dissociation of calmodulin was reversed by removal of Ca++. If microvillus cores were pretreated with phalloidin, the Ca++-induced solubilization of actin was prevented, but the partial dissociation of calmodulin still occurred. The molar ratio of calmodulin:actin is 1:10 in the demembranated brush border and 1:2-3 in the microvillus core. No calmodulin was detected in the detergent-solubilized brush-border membrane fraction. PMID:6893051
Comparison of intestinal brush-border 95-Kdalton polypeptide and alpha- actinins
To explore the suggestion that alpha-actinin cross-links actin filaments to the microvillar membrane (Mooseker and Tilney, 1975, J. Cell Biol. 67:725--743; Mooseker, 1976, J. Cell Biol. 71-417--433), we have assessed the possible relatedness of alpha-actinin and the brush- border 95-kdalton protein by four independent criteria: antigenicity, mobility on SDS gels, extractability in nonionic detergents, and peptide maps. We have found that anti-chicken gizzard alpha-actinin stains the junctional complex region of intact cells (Craig and Pardo, 1979, J. Cell Biol. 80:203--210) but does not stain isolated brush borders even though these structures contain a 95-kdalton polypeptide. Lack of staining is not caused by failure of the antibody to penetrate, as antiactin stains both the terminal web and the microvilli of isolated brush borders. By the antibody SDS gel overlay technique, we have established that anti-gizzard alpha-actinin recognizes homologous molecules in chicken skeletal and cardiac muscles, as well as in intestinal epithelial cells, but fails to recognize the brush-border 95- kdalton polypeptide. Conversely, anti-95-kdalton polypeptide does not recognize gizzard alpha-actinin. On high-resolution SDS polyacrylamide gel electrophoresis, alpha-actinin and brush-border 95-kdalton protein exhibit distinct mobilities. The two proteins also differ in their ability to be extracted in nonionic mobilities. The two proteins also differ in their ability to be extracted in nonionic detergent: epithelial cell immunoreactive alpha-actinin is soluble in NP-40, whereas 95-kdalton protein is insoluble. Finally, two-dimensional peptide mapping of iodinated tryptic peptides, as well as one- dimensional fingerprinting of partial tryptic, chymotryptic, papain, and S. aureus V8 protease digests, have revealed less than 5% homology between gizzard alpha-actinin and brush-border 95-kdalton polypeptide. The data suggest that there is no major structural homology between gizzard
Deep-apical tubules: dynamic lipid-raft microdomains in the brush-border region of enterocytes.
Hansen, Gert H; Pedersen, Jens; Niels-Christiansen, Lise-Lotte; Immerdal, Lissi; Danielsen, E Michael
The brush border of small intestinal enterocytes is highly enriched in cholesterol- and glycosphingolipid-containing membrane microdomains, commonly termed as lipid 'rafts'. Functionally, transcytosis of IgA and exocytosis of newly made brush-border proteins in enterocytes occur through apical lipid raft-containing compartments, but little is otherwise known about these raft microdomains. We therefore studied in closer detail apical lipid-raft compartments in enterocytes by immunogold electron microscopy and biochemical analyses. Novel membrane structures, deep-apical tubules, were visualized by the non-permeable surface marker Ruthenium Red in the brush-border region of the cells. The surface-connected tubules were labelled by antibodies to caveolin-1 and the glycolipid asialo G(M1), and they were sensitive to cholesterol depletion by methyl-beta-cyclodextrin, indicating the presence of raft microdomains. Deep-apical tubules were positioned close to the actin rootlets of adjacent microvilli in the terminal web region, which had a diameter of 50-100 nm, and penetrated up to 1 microm into the cytoplasm. Markers for transcytosis, IgA and the polymeric immunoglobulin receptor, as well as the resident brush-border enzyme aminopeptidase N, were present in these deep-apical tubules. We propose that deep-apical tubules are a specialized lipid-raft microdomain in the brush-border region functioning as a hub in membrane trafficking at the brush border. In addition, the sensitivity to cholesterol depletion suggests that deep-apical tubules function as a cell-surface membrane reservoir for cholesterol and for rapid adaptive changes in the size of microvilli at the brush border.
MYO1A (brush border myosin I) dynamics in the brush border of LLC-PK1-CL4 cells.
Tyska, M J; Mooseker, M S
The kidney epithelial cell line, LLC-PK1-CL4 (CL4), forms a well ordered brush border (BB) on its apical surface. CL4 cells were used to examine the dynamics of MYO1A (M1A; formerly BB myosin I) within the BB using GFP-tagged MIA (GFP-M1A), MIA motor domain (GFP-MDIQ), and tail domain (GFP-Tail). GFP-beta-actin (GFP-Actin) was used to assess actin dynamics within the BB. GFP-M1A, GFP-Tail, but not GFP-MDIQ localized to the BB, indicating that the tail is sufficient for apical targeting of M1A. GFP-Actin targeted to all the actin domains of the cell including the BB. Fluorescence recovery after photobleaching analysis revealed that GFP-M1A and GFP-Tail turnover in the BB is rapid, approximately 80% complete in <1 min. As expected for an actin-based motor, ATP depletion resulted in significant inhibition of GFP-M1A turnover yet had little effect on GFP-Tail exchange. Rapid turnover of GFP-M1A and GFP-Tail was not due to actin turnover as GFP-Actin turnover in the BB was much slower. These results indicate that the BB population of M1A turns over rapidly, while its head and tail domains interact transiently with the core actin and plasma membrane, respectively. This rapidly exchanging pool of M1A envelops an actin core bundle that, by comparison, is static in structure. PMID:11916846
The Secretion and Action of Brush Border Enzymes in the Mammalian Small Intestine.
Hooton, Diane; Lentle, Roger; Monro, John; Wickham, Martin; Simpson, Robert
Microvilli are conventionally regarded as an extension of the small intestinal absorptive surface, but they are also, as latterly discovered, a launching pad for brush border digestive enzymes. Recent work has demonstrated that motor elements of the microvillus cytoskeleton operate to displace the apical membrane toward the apex of the microvillus, where it vesiculates and is shed into the periapical space. Catalytically active brush border digestive enzymes remain incorporated within the membranes of these vesicles, which shifts the site of BB digestion from the surface of the enterocyte to the periapical space. This process enables nutrient hydrolysis to occur adjacent to the membrane in a pre-absorptive step. The characterization of BB digestive enzymes is influenced by the way in which these enzymes are anchored to the apical membranes of microvilli, their subsequent shedding in membrane vesicles, and their differing susceptibilities to cleavage from the component membranes. In addition, the presence of active intracellular components of these enzymes complicates their quantitative assay and the elucidation of their dynamics. This review summarizes the ontogeny and regulation of BB digestive enzymes and what is known of their kinetics and their action in the peripheral and axial regions of the small intestinal lumen.
Screening of the Bacillus thuringiensis Cry1Ac delta-endotoxin on the artificial phospholipid monolayer incorporated with brush border membrane vesicles of Plutella xylostella by optical biosensor technology.
Okumura, S; Akao, T; Mizuki, E; Ohba, M; Inouye, K
The binding of Cry1Ac, an insecticidal protein of Bacillus thuringiensis, to a brush border membrane (BBM) isolated from midguts of the diamondback moth Plutella xylostella was examined by surface plasmon resonance (SPR)-based biosensor. BBM was mixed with 1,3-ditetradecylglycero-2-phosphocholine (PC14), a neutral charged artificial lipid, and was reconstructed to a monolayer on a hydrophobic chip for the biosensor. The binding of Cry1Ac to the reconstructed monolayer was analyzed by a two-state binding model, and it was shown that Cry1Ac bound to the monolayer in the first step with an affinity constant (K(1)) of 508 nM, followed by the second uni-molecular step with an equilibrium constant (K(2)) of 0.472. The overall affinity constant K(d) was determined to be 240 nM. The binding was markedly inhibited by N-acetyl-D-galactosamine (K(i)=8 mM). The monolayer was shown to retain a high affinity to Cry1Ac, providing an insect-free system for rapid and large-scale screening of B. thuringiensis insecticidal proteins by the SPR-based biosensor technology.
Binding sites for Bacillus thuringiensis Cry2Ae toxin on heliothine brush border membrane vesicles are not shared with Cry1A, Cry1F, or Vip3A toxin.
Gouffon, C; Van Vliet, A; Van Rie, J; Jansens, S; Jurat-Fuentes, J L
The use of combinations of Bacillus thuringiensis (Bt) toxins with diverse modes of action for insect pest control has been proposed as the most efficient strategy to increase target range and delay the onset of insect resistance. Considering that most cases of cross-resistance to Bt toxins in laboratory-selected insect colonies are due to alteration of common toxin binding sites, independent modes of action can be defined as toxins sharing limited or no binding sites in brush border membrane vesicles (BBMV) prepared from the target insect larvae. In this paper, we report on the specific binding of Cry2Ae toxin to binding sites on BBMV from larvae of the three most commercially relevant heliothine species, Heliothis virescens, Helicoverpa zea, and Helicoverpa armigera. Using chromatographic purification under reducing conditions before labeling, we detected specific binding of radiolabeled Cry2Ae, which allowed us to perform competition assays using Cry1Ab, Cry1Ac, Cry1Fa, Vip3A, Cry2Ae, and Cry2Ab toxins as competitors. In these assays, Cry2Ae binding sites were shared with Cry2Ab but not with the tested Cry1 or Vip3A toxins. Our data support the use of Cry2Ae toxin in combination with Cry1 or Vip3A toxins in strategies to increase target range and delay the onset of heliothine resistance.
Binding Sites for Bacillus thuringiensis Cry2Ae Toxin on Heliothine Brush Border Membrane Vesicles Are Not Shared with Cry1A, Cry1F, or Vip3A Toxin ▿
Gouffon, C.; Van Vliet, A.; Van Rie, J.; Jansens, S.; Jurat-Fuentes, J. L.
The use of combinations of Bacillus thuringiensis (Bt) toxins with diverse modes of action for insect pest control has been proposed as the most efficient strategy to increase target range and delay the onset of insect resistance. Considering that most cases of cross-resistance to Bt toxins in laboratory-selected insect colonies are due to alteration of common toxin binding sites, independent modes of action can be defined as toxins sharing limited or no binding sites in brush border membrane vesicles (BBMV) prepared from the target insect larvae. In this paper, we report on the specific binding of Cry2Ae toxin to binding sites on BBMV from larvae of the three most commercially relevant heliothine species, Heliothis virescens, Helicoverpa zea, and Helicoverpa armigera. Using chromatographic purification under reducing conditions before labeling, we detected specific binding of radiolabeled Cry2Ae, which allowed us to perform competition assays using Cry1Ab, Cry1Ac, Cry1Fa, Vip3A, Cry2Ae, and Cry2Ab toxins as competitors. In these assays, Cry2Ae binding sites were shared with Cry2Ab but not with the tested Cry1 or Vip3A toxins. Our data support the use of Cry2Ae toxin in combination with Cry1 or Vip3A toxins in strategies to increase target range and delay the onset of heliothine resistance. PMID:21441333
Binding of diarrheagenic Escherichia coli to 32- to 33-kilodalton human intestinal brush border proteins.
Manjarrez-Hernandez, A; Gavilanes-Parra, S; Chavez-Berrocal, M E; Molina-Lopez, J; Cravioto, A
We have detected human intestinal brush border proteins to which Escherichia coli strains adhere by means of a blotting-nitrocellulose method in which the binding of radiolabeled bacteria to sodium dodecyl sulfate-polyacrylamide gel electrophoresis-separated intestinal cell membranes was evaluated. The brush border fraction contained several polypeptides that bound only adherent E. coli strains. The most prominent and consistent of these proteins had apparent molecular masses of 32 to 33 kDa. Additional polypeptides ranging from 50 to 70, from 105 to 130, and from 180 to 200 kDa were also recognized by adherent E. coli strains, although with less intensity (in accordance with the number of bound bacteria to these polypeptides). Independently of the pattern of adherence (localized [LA], diffuse [DA], or aggregative [AggA]) all HEp-2-adhering strains recognized, with different intensities, the 32- to 33-kDa brush border proteins, whereas nonadhesive strains did not. The relative avidity of an LA strain to bind to the 32- to 33-kDa proteins was approximately seven- and sixfold higher than the binding of strains with aggregative and diffuse adherence, respectively. Thus, it is reasonable to think that LA, DA, and AggA strains have a common adhesin that mediates binding to the 32- to 33-kDa bands. Inhibition experiments using HEp-2 cells demonstrated that isolated 32- to 33-kDa proteins or specific antiserum blocked preferentially bacterial adherence of the LA pattern. Delipidization and protein digestion of the human brush borders confirmed that E. coli bound to structures of a proteinaceous nature. Deglycosylation studies and sodium meta-periodate oxidation of the intestinal cell membranes decreased bacterial binding activity significantly, indicating that E. coli bound to carbohydrate moieties in the glycoproteins. These results suggest that binding of E. coli strains, mainly of the LA phenotype, to the 32- to 33-kDa proteins could play a role in colonization through
Cloning of cDNAs encoding a rabbit renal brush border membrane protein immunologically related to band 3. Sequence similarity with microsomal dipeptidase.
Igarashi, P; Karniski, L P
Distinct anion transport processes have been identified in the mammalian renal proximal tubule, but none of the responsible proteins or genes have been isolated. A 43 kDa rabbit microvillus membrane protein that is immunologically related to the erythroid anion exchanger (band 3) was a candidate for a renal anion transporter. To examine the structural relationship with band 3, we cloned cDNAs encoding the 43 kDa protein. The 43 kDa band-3-like protein was purified, and a novel sequence of 24 amino acids was obtained from the N-terminus. Degenerate oligonucleotides were synthesized based on this sequence, and the polymerase chain reaction with single-sided specificity was used to amplify and clone a 1330 bp cDNA from rabbit renal cortex. Additional overlapping 272 bp and 1123 bp cDNAs were obtained by synthesizing and screening a rabbit renal cortical cDNA library. The composite sequence was 1483 bp, terminated with (A)16, and was similar in size to the principal transcript expressed in rabbit renal cortex. The single long open reading frame was predicted to encode a protein composed of 410 amino acids with a molecular mass of 45,193 Da; 15 amino acids predicted to reside at the N-terminus were absent in the mature protein and may constitute a signal peptide. There was only limited sequence similarity with human erythroid band 3. Rather, the sequence was highly similar to microsomal dipeptidase, including the presence of a signal peptide and a consensus sequence for covalent linkage to glycosylphosphatidylinositol. In summary, the 43 kDa protein from rabbit renal cortex that is recognized by a monospecific antibody to erythroid band 3 is most likely a microvillus membrane dipeptidase. Images Fig. 1. Fig. 5. Fig. 6. PMID:1741759
Location of a protein of the fodrin-spectrin-TW260/240 family in the mouse intestinal brush border.
Hirokawa, N; Cheney, R E; Willard, M
We have determined that a protein of the fodrin-spectrin-TW260/240 (FST) family is a component of the thin fibrils (approximately 5 nm wide, 100-200 nm long) that cross-link bundles of actin filaments to adjacent actin bundles and to the plasma membrane in the terminal web of the brush border of the intestinal epithelium. When isolated brush borders were incubated with anti-fodrin antibodies and prepared for electron microscopy by the quick-freeze, deep-etch technique, these approximately 5 nm fibrils were specifically decorated with the antibody. In addition, these cross-linking fibrils disappeared when the anti-fodrin-reactive proteins were extracted from the brush border. We conclude that FST is a component of a cross-linking system composed of approximately 5 nm fibrils that are morphologically distinct from the approximately 8 nm myosin-containing fibrils which were identified by anti-myosin decoration. In addition to linking actin bundles to adjacent actin bundles and to the plasma membrane, these FST fibrils may mediate actin-vesicle, actin-intermediate filament and vesicle-plasma membrane linkages.
Phosphatase activities of rat intestinal enterocytes and their relation to diverse luminal pH, with special references to the possible localization of phytase along the brush border membrane.
Nakano, Y; Kawamoto, T; Takano, Y
Phosphatase activities associated with the intestinal brush border membrane (BBM) of the rat were examined histochemically in relation to the characteristic environment of the intestine, where luminal pH fluctuates drastically between alkaline and acid pH ranges. Special attention was given to intestinal alkaline phosphatase (IALP) and phytase on the BBM. Whole body fresh-frozen sections of young rats and their rapidly frozen and freeze-substituted small intestines, embedded in Technovit 7100, were processed for the histochemical demonstration of phosphatase activity at three different pH values (9.2, 7.3, and 5.2), representing the deviation of luminal pH in vivo. Either an azo-dye method or lead-salt method was employed using naphthol AS-MX phosphate and ATP as substrate, respectively. With the azo-dye method, intense phosphatase reactions were demonstrated along the BBM at all three pH ranges. Phosphatase reactions of the BBM at pH 9.2 and 7.3 were abolished by L(+)-phenylalanine, heat pre-treatment, and EDTA chelation although some reaction remained at pH 7.3 after the treatment with EDTA or L(+)-phenylalanine. Phosphatase reactions of the BBM at pH 5.2 were resistant to L(+)-phenylalanine, L(+)-tartrate, PCMB and EDTA chelation, implying that the characteristics of the enzyme responsible for phosphohydrolysis at acid pH values differed from those at higher pH values. The lead-salt method in which ATP was used as substrate revealed intense reactions--which were dependent on Mg++ and stimulated by Ca++ and resistant to L(+)phenylalanine--to be localized along the BBM at alkaline and neutral pH values, but not at acid pH values. In vitro experiments showed progressive hydrolysis of naphthol AS-MX phosphate by purified phytase at pH 5.2, in a dose-dependent manner, and suggested the possible involvement of phytase in the phosphatase reactions of the BBM at acid pH. These data indicate that the phosphatase reactions at alkaline and neutral pH values, associated
Binding of Cyt1Aa and Cry11Aa toxins of Bacillus thuringiensis serovar israelensis to brush border membrane vesicles of Tipula paludosa (Diptera: Nematocera) and subsequent pore formation.
Oestergaard, Jesko; Ehlers, Ralf-Udo; Martínez-Ramírez, Amparo C; Real, Maria Dolores
Bacillus thuringiensis serovar israelensis (B. thuringiensis subsp. israelensis) produces four insecticidal crystal proteins (ICPs) (Cry4A, Cry4B, Cry11A, and Cyt1A). Toxicity of recombinant B. thuringiensis subsp. israelensis strains expressing only one of the toxins was determined with first instars of Tipula paludosa (Diptera: Nematocera). Cyt1A was the most toxic protein, whereas Cry4A, Cry4B, and Cry11A were virtually nontoxic. Synergistic effects were recorded when Cry4A and/or Cry4B was combined with Cyt1A but not with Cry11A. The binding and pore formation are key steps in the mode of action of B. thuringiensis subsp. israelensis ICPs. Binding and pore-forming activity of Cry11Aa, which is the most toxic protein against mosquitoes, and Cyt1Aa to brush border membrane vesicles (BBMVs) of T. paludosa were analyzed. Solubilization of Cry11Aa resulted in two fragments, with apparent molecular masses of 32 and 36 kDa. No binding of the 36-kDa fragment to T. paludosa BBMVs was detected, whereas the 32-kDa fragment bound to T. paludosa BBMVs. Only a partial reduction of binding of this fragment was observed in competition experiments, indicating a low specificity of the binding. In contrast to results for mosquitoes, the Cyt1Aa protein bound specifically to the BBMVs of T. paludosa, suggesting an insecticidal mechanism based on a receptor-mediated action, as described for Cry proteins. Cry11Aa and Cyt1Aa toxins were both able to produce pores in T. paludosa BBMVs. Protease treatment with trypsin and proteinase K, previously reported to activate Cry11Aa and Cyt1Aa toxins, respectively, had the opposite effect. A higher efficiency in pore formation was observed when Cyt1A was proteinase K treated, while the activity of trypsin-treated Cry11Aa was reduced. Results on binding and pore formation are consistent with results on ICP toxicity and synergistic effect with Cyt1Aa in T. paludosa.
Protein patterns of brush-border fragments in congenital lactose malabsorption and in specific hypolactasia of the adult.
Freiburghaus, A U; Schmitz, J; Schindler, M; Rotthauwe, H W; Kuitunen, P; Launiala, K; Hadorn, B
Brush-border membrane proteins of the small-bowel mucosa were separated on polyacrylamide gels from intestinal biopsy specimens obtained from four children with congenital lactose malabsorption and from two adults with specific hypolactasia. In three patients with the congenital type of lactase deficiency the protein band corresponding to brush-border lactase was reduced in intensity, but was never completely absent. No difference in gel patterns was detected when this pattern in congenital deficiency was compared to that obtained from the two patients with adult-type selective hypolactasia. In one patient with congenital lactose malabsorption the protein band corresponding to lactase activity was not detectable. The findings suggest that the mechanisms leading to low lactase activity in the congenital and adult forms of lactose intolerance are similar.
Studies on the enzymology of purified preparations of brush border from rabbit kidney
George, S. G.; Kenny, A. J.
1. A method for the preparation of brush border from rabbit kidneys is described. Contamination by other organelles was checked by electron microscopy and by the assay of marker enzymes and was low. 2. Seven enzymes, all hydrolases, were substantially enriched in the brush-border preparation and are considered to be primarily located in this structure. They are: alkaline phosphatase, maltase, trehalase, aminopeptidase A, aminopeptidase M, γ-glutamyl transpeptidase and a neutral peptidase assayed by its ability to hydrolyse [125I]iodoinsulin B chain. 3. Adenosine triphosphatases were also present in the preparation, but showed lower enrichments. 4. Alkaline phosphatase was the most active phosphatase present in the preparation. The weak hydrolysis of AMP may well have been due to this enzyme rather than a specific 5′-nucleotidase. 5. The two disaccharidases in brush border were distinguished by the relative heat-stability of trehalase compared with that of maltase. 6. The individuality of the four peptidases was established by several means. The neutral peptidase and aminopeptidase M, both of which can attack insulin B chain, differed not only in response to inhibitors and activators but also in the inhibitory effect of a guinea-pig antiserum raised to rabbit aminopeptidase M. This antiserum inhibited both the purified and the brush-border activities of aminopeptidase M. The neutral peptidase and γ-glutamyl transpeptidase were unaffected but aminopeptidase A was weakly inhibited. The characteristic responses to Ca2+ and serine with borate served to distinguish aminopeptidase A and γ-glutamyl transpeptidase from other peptidases. 7. No dipeptidases, tripeptidases or carboxypeptidases were identified as brush-border enzymes. 8. Incubation of brush border with papain released almost all the aminopeptidase M activity but only about half the activities of maltase, γ-glutamyl transpeptidase and aminopeptidase A. No release of alkaline phosphatase, trehalase or the
Intra Amniotic Administration of Raffinose and Stachyose Affects the Intestinal Brush Border Functionality and Alters Gut Microflora Populations
Pacifici, Sarina; Song, Jaehong; Zhang, Cathy; Wang, Qiaoye; Glahn, Raymond P.; Kolba, Nikolai; Tako, Elad
This study investigates the effectiveness of two types of prebiotics—stachyose and raffinose—which are present in staple food crops that are widely consumed in regions where dietary Fe deficiency is a health concern. The hypothesis is that these prebiotics will improve Fe status, intestinal functionality, and increase health-promoting bacterial populations in vivo (Gallus gallus). By using the intra-amniotic administration procedure, prebiotic treatment solutions were injected in ovo (day 17 of embryonic incubation) with varying concentrations of a 1.0 mL pure raffinose or stachyose in 18 MΩ H2O. Four treatment groups (50, 100 mg·mL−1 raffinose or stachyose) and two controls (18 MΩ H2O and non-injected) were utilized. At hatch the cecum, small intestine, liver, and blood were collected for assessment of the relative abundance of the gut microflora, relative expression of Fe-related genes and brush border membrane functional genes, hepatic ferritin levels, and hemoglobin levels, respectively. The prebiotic treatments increased the relative expression of brush border membrane functionality proteins (p < 0.05), decreased the relative expression of Fe-related proteins (p < 0.05), and increased villus surface area. Raffinose and stachyose increased the relative abundance of probiotics (p < 0.05), and decreased that of pathogenic bacteria. Raffinose and stachyose beneficially affected the gut microflora, Fe bioavailability, and brush border membrane functionality. Our investigations have led to a greater understanding of these prebiotics' effects on intestinal health and mineral metabolism. PMID:28335485
Renal brush-border Na/sup +/-H/sup +/ exchange activity in the aging rat
Kinsella, J.L.; Sacktor, B.
Amiloride-sensitive Na/sup +/-H/sup +/ exchange activity in brush-border membrane vesicles isolated from male rat proximal tubules was decreased in the senescent rat (24 mo) compared with the young adult (6 mo). There was no significant loss in Na/sup +/-H/sup +/ exchange activity in the kidneys of animals between 6 and 18 mo of age. Amiloride-insensitive /sup 22/Na/sup +/ uptake and the rate of pH gradient dissipation were not altered during aging. The decrease in sodium-dependent (/sup 32/P) phosphate transport preceded the decline in Na/sup +/-H/sup +/ exchange activity by at least 6 mo. Sodium-dependent D-(/sup 3/H) glucose transport was not significantly altered during aging. Thus various renal plasma membrane transport functions were affected differently in the aging rat. The decrease in Na/sup +/-H/sup +/ exchange activity during aging contrasted with the increase in exchange activity reported previously in acute ablation models of chronic renal failure.
Radiation inactivation studies of renal brush border water and urea transport
Verkman, A.S.; Dix, J.A.; Seifter, J.L.; Skorecki, K.L.; Jung, C.Y.; Ausiello, D.A.
Radiation inactivation was used to determine the nature and molecular weight of water and urea transport pathways in brush border membrane vesicles (BBMV) isolated from rabbit renal cortex. BBMV were frozen to -50 degrees C, irradiated with 1.5 MeV electrons, thawed, and assayed for transport or enzyme activity. The freezing process had no effect on enzyme or transport kinetics. BBMV alkaline phosphatase activity gave linear ln(activity) vs. radiation dose plots with a target size of 68 +/- 3 kDa, similar to previously reported values. Water and solute transport were measured using the stopped-flow light-scattering technique. The rates of acetamide and osmotic water transport did not depend on radiation dose (0-7 Mrad), suggesting that transport of these substances does not require a protein carrier. In contrast, urea and thiourea transport gave linear ln(activity) vs. dose curves with a target size of 125-150 kDa; 400 mM urea inhibited thiourea flux by -50% at 0 and 4.7 Mrad, showing that radiation does not affect inhibitor binding to surviving transporters. These studies suggest that BBMV urea transport requires a membrane protein, whereas osmotic water transport does not.
In Vivo, Villin Is Required for Ca2+-Dependent F-Actin Disruption in Intestinal Brush Borders
Ferrary, Evelyne; Cohen-Tannoudji, Michel; Pehau-Arnaudet, Gérard; Lapillonne, Alexandre; Athman, Rafika; Ruiz, Tereza; Boulouha, Lilia; El Marjou, Fatima; Doye, Anne; Fontaine, Jean-Jacques; Antony, Claude; Babinet, Charles; Louvard, Daniel; Jaisser, Frédéric; Robine, Sylvie
Villin is an actin-binding protein localized in intestinal and kidney brush borders. In vitro, villin has been demonstrated to bundle and sever F-actin in a Ca2+-dependent manner. We generated knockout mice to study the role of villin in vivo. In villin-null mice, no noticeable changes were observed in the ultrastructure of the microvilli or in the localization and expression of the actin-binding and membrane proteins of the intestine. Interestingly, the response to elevated intracellular Ca2+ differed significantly between mutant and normal mice. In wild-type animals, isolated brush borders were disrupted by the addition of Ca2+, whereas Ca2+ had no effect in villin-null isolates. Moreover, increase in intracellular Ca2+ by serosal carbachol or mucosal Ca2+ ionophore A23187 application abolished the F-actin labeling only in the brush border of wild-type animals. This F-actin disruption was also observed in physiological fasting/refeeding experiments. Oral administration of dextran sulfate sodium, an agent that causes colonic epithelial injury, induced large mucosal lesions resulting in a higher death probability in mice lacking villin, 36 ± 9.6%, compared with wild-type mice, 70 ± 8.8%, at day 13. These results suggest that in vivo, villin is not necessary for the bundling of F-actin microfilaments, whereas it is necessary for the reorganization elicited by various signals. We postulate that this property might be involved in cellular plasticity related to cell injury. PMID:10459016
Exposure to Engineered Nanomaterial Results in Disruption of Brush Borders in Epithelia Models in vitro
NASA Astrophysics Data System (ADS)
Faust, James J.
Engineered nanoparticles (NP; 10-9 m) have found use in a variety of consumer goods and medical devices because of the unique changes in material properties that occur when synthesized on the nanoscale. Although many definitions for nanoparticle exist, from the perspective of size, nanoparticle is defined as particles with diameters less than 100 nm in any external dimension. Examples of their use include titanium dioxide added as a pigment in products intended to be ingested by humans, silicon dioxide NPs are used in foods as an anticaking agent, and gold or iron oxide NPs can be used as vectors for drug delivery or contrast agents for specialized medical imaging. Although the intended use of these NPs is often to improve human health, it has come to the attention of investigators that NPs can have unintended or even detrimental effects on the organism. This work describes one such unintended effect of NP exposure from the perspective of exposure via the oral route. First, this Dissertation will explain an event referred to as brush border disruption that occurred after nanoparticles interacted with an in vitro model of the human intestinal epithelium. Second, this Dissertation will identify and characterize several consumer goods that were shown to contain titanium dioxide that are intended to be ingested. Third, this Dissertation shows that sedimentation due to gravity does not artifactually result in disruption of brush borders as a consequence of exposure to food grade titanium dioxide in vitro. Finally, this Dissertation will demonstrate that iron oxide nanoparticles elicited similar effects after exposure to an in vitro brush border expressing model of the human placenta. Together, these data suggest that brush border disruption is not an artifact of the material/cell culture model, but instead represents a bona fide biological response as a result of exposure to nanomaterial.
The cell adhesion molecule Fasciclin2 regulates brush border length and organization in Drosophila renal tubules
Halberg, Kenneth A.; Rainey, Stephanie M.; Veland, Iben R.; Neuert, Helen; Dornan, Anthony J.; Klämbt, Christian; Davies, Shireen-Anne; Dow, Julian A. T.
Multicellular organisms rely on cell adhesion molecules to coordinate cell–cell interactions, and to provide navigational cues during tissue formation. In Drosophila, Fasciclin 2 (Fas2) has been intensively studied due to its role in nervous system development and maintenance; yet, Fas2 is most abundantly expressed in the adult renal (Malpighian) tubule rather than in neuronal tissues. The role Fas2 serves in this epithelium is unknown. Here we show that Fas2 is essential to brush border maintenance in renal tubules of Drosophila. Fas2 is dynamically expressed during tubule morphogenesis, localizing to the brush border whenever the tissue is transport competent. Genetic manipulations of Fas2 expression levels impact on both microvilli length and organization, which in turn dramatically affect stimulated rates of fluid secretion by the tissue. Consequently, we demonstrate a radically different role for this well-known cell adhesion molecule, and propose that Fas2-mediated intermicrovillar homophilic adhesion complexes help stabilize the brush border. PMID:27072072
Hormone induced expression of brush border lactase in suckling rat intestine.
Chaudhry, Kamaljit Kaur; Mahmood, Safrun; Mahmood, Akhtar
The postnatal development of intestine is associated with a decline in brush border lactase activity in rodents. This is similar to adulthood hypolactasia, a phenomenon prevalent in humans worldwide. In the present study, the effect of luminal proteases from adult rat intestine was studied in vitro on intestinal lactase activity in saline control, thyroxine, insulin and cortisone treated rat pups. Lactase levels were determined by enzyme analysis and Western blotting. mRNA levels encoding lactase were determined by Northern blotting. Administration of thyroxine for 4 days reduced (P<0.05) lactase activity, but insulin treatment had no effect in 8-day-old rat intestine. However, cortisone administration augmented (P<0.01) lactase activity, under these conditions. Western blot analysis showed decreased lactase signal corresponding to 220-kDa protein band in thyroxine treated animals. However, the intensity of lactase signal was high in cortisone treated animals compared to controls. mRNA levels encoding lactase showed a 6.8-kb mRNA transcript in saline and hormone treated rats. mRNA levels encoding lactase were increased in cortisone treated animals but were reduced in thyroxine injected pups compared to controls. Microvillus membranes from saline (P<0.01) and thyroxine (P<0.05) or insulin (P<0.01) treated rats upon incubation with luminal wash from adult rat intestine showed a significant decline in lactase activity. These findings suggest that thyroxine, insulin or cortisone induced changes in lactase expression in suckling rat intestine make it susceptible to luminal proteases, which may in part be responsible for observed maturational decline in lactase activity in adult rat intestine.
IgG trafficking in the adult pig small intestine: one- or bidirectional transfer across the enterocyte brush border?
Möller, Rebecca; Hansen, Gert H; Danielsen, E Michael
Immunoglobulin G (IgG) transfer in opposite directions across the small intestinal brush border serves different purposes in early life and in adulthood. In the neonate, maternal IgG is taken up from the gut lumen into the blood, conferring passive immunity to the offspring, whereas in the adult immunoglobulins, including IgG made by plasma cells in the lamina propria, are secreted via the brush border to the lumen as part of the mucosal defense. Here, IgG has been proposed to perform a luminal immune surveillance which eventually includes a reuptake through the brush border as pathogen-containing immune complexes. In the present work, we studied luminal uptake of FITC-conjugated and gold-conjugated IgG in cultured pig jejunal mucosal explants. After 1 h, binding to the brush border was seen in upper crypts and lower parts of the villi. However, no endocytotic uptake into EEA-1-positive compartments was detected, neither at neutral nor acidic pH, despite an ongoing constitutive endocytosis from the brush border, visualized by the polar tracer CF594. The 40-kDa neonatal Fc receptor, FcRn, was present in the microvillus fraction, but noteworthy, a 37 kDa band, most likely a proteolytic cleavage product, bound IgG in a pH-dependent manner more efficiently than did the full-length FcRn. In conclusion, our work does not support the theory that bidirectional transfer of IgG across the intestinal brush border is part of the luminal immune surveillance in the adult.
Beneficial influence of dietary spices on the ultrastructure and fluidity of the intestinal brush border in rats.
Prakash, Usha N S; Srinivasan, Krishnapura
The beneficial influence of three common spices was examined in experimental rats on: (i) the membrane fluidity of intestinal brush-border membranes (BBM), (ii) the activity of intestinal membrane-bound enzymes, and (iii) ultrastructural alterations in the intestinal epithelium. Groups of male Wistar rats were maintained on dietary black pepper (0.5 %), red pepper (3.0 %), ginger (0.05 %) and spice bioactive compounds piperine (0.02 %) and capsaicin (0.01 %) for 8 weeks. A membrane fluidity study using an apolar fluorescent probe showed increased BBM fluidity in all the spice-fed animals. This was corroborated by a decreased cholesterol:phospholipid ratio in the jejunal and ileal regions of the intestine. These dietary spices stimulated the activities of BBM enzymes (glycyl-glycine dipeptidase, leucine amino peptidase and gamma-glutamyl transpeptidase) in the jejunal mucosa, suggesting a modulation in membrane dynamics due to the apolar spice bioactive compounds interacting with surrounding lipids and hydrophobic portions in the protein vicinity, which may decrease the tendency of membrane lipids to act as steric constraints to enzyme proteins and thus modify enzyme conformation. Scanning electronic microscopy of the intestinal villi in these spice treatments revealed alterations in the ultrastructure, especially an increase in microvilli length and perimeter which would mean a beneficial increase in the absorptive surface of the small intestine, providing for an increased bioavailability of micronutrients. Thus, dietary spices (black pepper, red pepper and ginger) were evidenced to induce alterations in BBM fluidity and passive permeability property, associated with the induction of an increased microvilli length and perimeter, resulting in an increased absorptive surface of the small intestine.
Carbachol- and elevated Ca(2+)-induced translocation of functionally active protein kinase C to the brush border of rabbit ileal Na+ absorbing cells.
Cohen, M E; Wesolek, J; McCullen, J; Rys-Sikora, K; Pandol, S; Rood, R P; Sharp, G W; Donowitz, M
Protein kinase C is involved in mediating the effects of elevated Ca2+ in ileal villus Na+ absorbing cells to inhibit NaCl absorption. The present studies were undertaken to understand the mechanism by which this occurs. The effects of carbachol and the calcium ionophore A23187, agents which elevate intracellular Ca2+ and inhibit NaCl absorption in ileal villus cells, were studied. Carbachol treatment of villus cells caused a rapid decrease in protein kinase C activity in cytosol, with an accompanying increase in microvillus membrane C kinase. Exposure of the villus cells to calcium ionophore also caused a quantitatively similar decrease in cytosol C kinase and increase in C kinase activity in the microvillus membrane. This increase caused by carbachol and Ca2+ ionophore was specific for the microvillus membrane. In fact, 30 s and 10 min after exposure of the cells to carbachol, basolateral membrane protein kinase C decreased, in a time-dependent manner; whereas 10 min of Ca2+ ionophore exposure did not alter basolateral C kinase. Exposure of villus cells to Ca2+ ionophore or carbachol caused similar increases in microvillus membrane diacylglycerol content. As judged by the ability to inhibit Na+/H+ exchange measured in ileal villus cell brush border membrane vesicles, the protein kinase C which translocated to the microvillus membrane was functionally significant. Inhibition of Na+/H+ exchange required ATP and was reversed by the protein kinase C antagonist H-7. In conclusion, the effect of carbachol and Ca2+ ionophore in regulation of ileal NaCl absorption is associated with an increase in microvillus membrane diacylglycerol content and functionally active protein kinase C. The effects of both carbachol and Ca2+ ionophore are different on brush border and basolateral membrane distribution of protein kinase C. Images PMID:1885773
Brush border Myosin Ia has tumor suppressor activity in the intestine
Mazzolini, Rocco; Dopeso, Higinio; Mateo-Lozano, Silvia; Chang, Wakam; Rodrigues, Paulo; Bazzocco, Sarah; Alazzouzi, Hafid; Landolfi, Stefania; Hernández-Losa, Javier; Andretta, Elena; Alhopuro, Pia; Espín, Eloy; Armengol, Manel; Tabernero, Josep; Ramón y Cajal, Santiago; Kloor, Matthias; Gebert, Johannes; Mariadason, John M.; Schwartz, Simo; Aaltonen, Lauri A.; Mooseker, Mark S.; Arango, Diego
The loss of the epithelial architecture and cell polarity/differentiation is known to be important during the tumorigenic process. Here we demonstrate that the brush border protein Myosin Ia (MYO1A) is important for polarization and differentiation of colon cancer cells and is frequently inactivated in colorectal tumors by genetic and epigenetic mechanisms. MYO1A frame-shift mutations were observed in 32% (37 of 116) of the colorectal tumors with microsatellite instability analyzed, and evidence of promoter methylation was observed in a significant proportion of colon cancer cell lines and primary colorectal tumors. The loss of polarization/differentiation resulting from MYO1A inactivation is associated with higher tumor growth in soft agar and in a xenograft model. In addition, the progression of genetically and carcinogen-initiated intestinal tumors was significantly accelerated in Myo1a knockout mice compared with Myo1a wild-type animals. Moreover, MYO1A tumor expression was found to be an independent prognostic factor for colorectal cancer patients. Patients with low MYO1A tumor protein levels had significantly shorter disease-free and overall survival compared with patients with high tumoral MYO1A (logrank test P = 0.004 and P = 0.009, respectively). The median time-to-disease recurrence in patients with low MYO1A was 1 y, compared with >9 y in the group of patients with high MYO1A. These results identify MYO1A as a unique tumor-suppressor gene in colorectal cancer and demonstrate that the loss of structural brush border proteins involved in cell polarity are important for tumor development. PMID:22307608
Natural Selection at the Brush-Border: Adaptations to Carbohydrate Diets in Humans and Other Mammals
Pontremoli, Chiara; Mozzi, Alessandra; Forni, Diego; Cagliani, Rachele; Pozzoli, Uberto; Menozzi, Giorgia; Vertemara, Jacopo; Bresolin, Nereo; Clerici, Mario; Sironi, Manuela
Dietary shifts can drive molecular evolution in mammals and a major transition in human history, the agricultural revolution, favored carbohydrate consumption. We investigated the evolutionary history of nine genes encoding brush-border proteins involved in carbohydrate digestion/absorption. Results indicated widespread adaptive evolution in mammals, with several branches experiencing episodic selection, particularly strong in bats. Many positively selected sites map to functional protein regions (e.g., within glucosidase catalytic crevices), with parallel evolution at SI (sucrase-isomaltase) and MGAM (maltase-glucoamylase). In human populations, five genes were targeted by positive selection acting on noncoding variants within regulatory elements. Analysis of ancient DNA samples indicated that most derived alleles were already present in the Paleolithic. Positively selected variants at SLC2A5 (fructose transporter) were an exception and possibly spread following the domestication of specific fruit crops. We conclude that agriculture determined no major selective event at carbohydrate metabolism genes in humans, with implications for susceptibility to metabolic disorders. PMID:26319403
Food grade titanium dioxide disrupts intestinal brush border microvilli in vitro independent of sedimentation.
Faust, James J; Doudrick, Kyle; Yang, Yu; Westerhoff, Paul; Capco, David G
Bulk- and nano-scale titanium dioxide (TiO2) has found use in human food products for controlling color, texture, and moisture. Once ingested, and because of their small size, nano-scale TiO2 can interact with a number of epithelia that line the human gastrointestinal tract. One such epithelium responsible for nutrient absorption is the small intestine, whose constituent cells contain microvilli to increase the total surface area of the gut. Using a combination of scanning and transmission electron microscopy it was found that food grade TiO2 (E171 food additive coded) included ∼25% of the TiO2 as nanoparticles (NPs; <100 nm), and disrupted the normal organization of the microvilli as a consequence of TiO2 sedimentation. It was found that TiO2 isolated from the candy coating of chewing gum and a commercially available TiO2 food grade additive samples were of the anatase crystal structure. Exposure to food grade TiO2 additives, containing nanoparticles, at the lowest concentration tested within this experimental paradigm to date at 350 ng/mL (i.e., 100 ng/cm(2) cell surface area) resulted in disruption of the brush border. Through the use of two independent techniques to remove the effects of gravity, and subsequent TiO2 sedimentation, it was found that disruption of the microvilli was independent of sedimentation. These data indicate that food grade TiO2 exposure resulted in the loss of microvilli from the Caco-2BBe1 cell system due to a biological response, and not simply a physical artifact of in vitro exposure.
The Responses of Rat Intestinal Brush Border and Cytosol Peptide Hydrolase Activities to Variation in Dietary Protein Content DIETARY REGULATION OF INTESTINAL PEPTIDE HYDROLASES
Nicholson, J. Alex; McCarthy, Denis M.; Kim, Young S.
The effects of variation in dietary protein content on small intestinal brush border and cytosol peptide hydrolase activities have been investigated. One group of rats was fed a high protein diet (55% casein) and another group was fed a low protein diet (10% casein). After 1 wk, brush border peptide hydrolase activity (L-leucyl-β-naphthylamide as substrate) and cytosol peptide hydrolase activity (L-prolyl-L-leucine as substrate) were determined in mucosae taken from the proximal, middle, and distal small intestine. As judged by several parameters, brush border peptide hydrolase activity was significantly greater in rats fed the high protein diet when data for corresponding segments were compared. In contrast, no significant difference was seen in cytosol peptide hydrolase activity. In a second study, brush border and cytosol peptide hydrolase activities were determined in the proximal intestine by utilizing an additional three peptide substrates: L-leucyl-L-alanine, L-phenylalanylglycine, and glycyl-L-phenylalanine. Sucrase, maltase, and alkaline phosphatase activities were also determined. As before, brush border peptide hydrolase activities were significantly greater in rats fed the high protein diet. However, activities of the nonproteolytic brush border enzymes did not vary significantly with diet. In contrast to the results obtained with L-prolyl-L-leucine as substrate for the cytosol enzymes, cytosol activity against the three additional peptide substrates was greater in rats fed the high protein diet. It is suggested that the brush border peptide hydrolase response to variation in dietary protein content represents a functional adaptation analogous to the regulation of intestinal disaccharidases by dietary carbohydrates. The implication of the differential responses of the cytosol peptide hydrolases is uncertain, since little is known of the functional role of these nonorgan-specific enzymes. PMID:4430719
Apolipoprotein A-1 (apoA-1) deposition in, and release from, the enterocyte brush border: a possible role in transintestinal cholesterol efflux (TICE)?
Danielsen, E Michael; Hansen, Gert H; Rasmussen, Karina; Niels-Christiansen, Lise-Lotte; Frenzel, Franz
Transintestinal cholesterol efflux (TICE) has been proposed to represent a non-hepatobiliary route of cholesterol secretion directly "from blood to gut" and to play a physiologically significant role in excretion of neutral sterols, but so far little is known about the proteins involved in the process. We have previously observed that apolipoprotein A-1 (apoA-1) synthesized by enterocytes of the small intestine is mainly secreted apically into the gut lumen during fasting where its assembly into chylomicrons and basolateral discharge is at a minimal level. In the present work we showed, both by immunomicroscopy and subcellular fractionation, that a fraction of the apically secreted apoA-1 in porcine small intestine was not released from the cell surface but instead deposited in the brush border. Cholesterol was detected in immunoisolated microvillar apoA-1, and it was partially associated with detergent resistant membranes (DRMs), indicative of localization in lipid raft microdomains. The apolipoprotein was not readily released from microvillar vesicles by high salt or by incubation with phosphatidylcholine-specific phospholipase C or trypsin, indicating a relatively firm attachment to the membrane bilayer. However, whole bile or taurocholate efficiently released apoA-1 at low concentrations that did not solubilize the transmembrane microvillar protein aminopeptidase N. Based on these findings and the well known role played by apoA-1 in extrahepatic cellular cholesterol removal and reverse cholesterol transport (RCT), we propose that brush border-deposited apoA-1 in the small intestine acts in TICE by mediating cholesterol efflux into the gut lumen.
Antifouling Thin-Film Composite Membranes by Controlled Architecture of Zwitterionic Polymer Brush Layer.
Liu, Caihong; Lee, Jongho; Ma, Jun; Elimelech, Menachem
In this study, we demonstrate a highly antifouling thin-film composite (TFC) membrane by grafting a zwitterionic polymer brush via atom-transfer radical-polymerization (ATRP), a controlled, environmentally benign chemical process. Initiator molecules for polymerization were immobilized on the membrane surface by bioinspired catechol chemistry, leading to the grafting of a dense zwitterionic polymer brush layer. Surface characterization revealed that the modified membrane exhibits reduced surface roughness, enhanced hydrophilicity, and lower surface charge. Chemical force microscopy demonstrated that the modified membrane displayed foulant-membrane interaction forces that were 1 order of magnitude smaller than those of the pristine TFC membrane. The excellent fouling resistance imparted by the zwitterionic brush layer was further demonstrated by significantly reduced adsorption of proteins and bacteria. In addition, forward osmosis fouling experiments with a feed solution containing a mixture of organic foulants (bovine-serum albumin, alginate, and natural organic matter) indicated that the modified membrane exhibited significantly lower water flux decline compared to the pristine TFC membrane. The controlled architecture of the zwitterionic polymer brush via ATRP has the potential for a facile antifouling modification of a wide range of water treatment membranes without compromising intrinsic transport properties.
Ion induced changes in the structure of bordered pit membranes.
Lee, Jinkee; Holbrook, N Michele; Zwieniecki, Maciej A
Ion-mediated changes in xylem hydraulic resistance are hypothesized to result from hydrogel like properties of pectins located in the bordered pit membranes separating adjacent xylem vessels. Although the kinetics of the ion-mediated changes in hydraulic resistance are consistent with the swelling/deswelling behavior of pectins, there is no direct evidence of this activity. In this report we use atomic force microscopy (AFM) to investigate structural changes in bordered pit membranes associated with changes in the ionic concentration of the surrounding solution. When submerged in de-ionized water, AFM revealed bordered pit membranes as relatively smooth, soft, and lacking any sharp edges surface, in contrast to pictures from scanning electron microscope (SEM) or AFM performed on air-dry material. Exposure of the bordered pit membranes to 50 mM KCl solution resulted in significant changes in both surface physical properties and elevation features. Specifically, bordered pit membranes became harder and the fiber edges were clearly visible. In addition, the membrane contracted and appeared much rougher due to exposed microfibers. In neither solution was there any evidence of discrete pores through the membrane whose dimensions were altered in response to the ionic composition of the surrounding solution. Instead the variable hydraulic resistance appears to involve changes in the both the permeability and the thickness of the pit membrane.
Protein purification with polymeric affinity membranes containing functionalized poly(acid) brushes.
Jain, Parul; Vyas, Mukesh Kumar; Geiger, James H; Baker, Gregory L; Bruening, Merlin L
Porous nylon membranes modified with poly(acid) brushes and their derivatives can rapidly purify proteins via ion-exchange and metal-ion affinity interactions. Membranes containing poly(2-(methacryloyloxy)ethyl succinate) (poly(MES)) brushes bind 118 +/- 8 mg of lysozyme per cm(3) of membrane and facilitate purification of lysozyme from chicken egg white. Moreover, functionalization of the poly(MES) brushes with nitrilotriacetate (NTA)-Ni(2+) complexes yields membranes that bind poly(histidine)-tagged (His-tagged) ubiquitin with a capacity of 85 +/- 2 mg of protein per cm(3) of membrane. Most importantly, the membranes modified with poly(MES)-NTA-Ni(2+) allow isolation of His-tagged cellular retinaldehyde-binding protein directly from a cell extract in <10 min, and the protein purity is comparable to that achieved with commercial affinity columns. Therefore, porous nylon membranes containing functionalized poly(MES) brushes are attractive candidates for rapid, high-capacity purification of His-tagged proteins from cell extracts.
Improving protein resistance of α-Al 2O 3 membranes by modification with POEGMA brushes
NASA Astrophysics Data System (ADS)
He, Huating; Jing, Wenheng; Xing, Weihong; Fan, Yiqun
A kind of protein-resistant ceramic membrane is prepared by grafting poly(oligo (ethylene glycol) methyl ether methacrylate) (POEGMA) brushes onto the surfaces and pore walls of α-Al2O3 membrane (AM) by surface-initiated atom-transfer radical polymerization (SI-ATRP). Contact-angle, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and field-emission scanning electron microscopy (FESEM) were measured to confirm that the surfaces and pore walls of the ceramic porous membranes have been modified by the brushes with this method successfully. The protein interaction behavior with the POEGMA modified membranes (AM-POEGMA) was studied by the model protein of bovine serum albumin (BSA). A protein-resistant mechanism of AM-POEGMA was proposed to describe an interesting phenomenon discovered in the filtration experiment, in which the initial flux filtrating BSA solution is higher than the pure water flux. The fouling of AM-POEGMA was easier to remove than AM for the action of POEGMA brushes, indicated that the ceramic porous membranes modified with POEGMA brushes exhibit excellent protein resistance.
Genetic evidence of an accessory activity required specifically for cubilin brush-border expression and intrinsic factor-cobalamin absorption.
Xu, D; Kozyraki, R; Newman, T C; Fyfe, J C
Cubilin is a high molecular weight multiligand receptor that mediates intestinal absorption of intrinsic factor-cobalamin and selective protein reabsorption in renal tubules. The genetic basis of selective intestinal cobalamin malabsorption with proteinuria was investigated in a canine model closely resembling human Imerslund-Gräsbeck syndrome caused by cubilin mutations. Canine CUBN cDNA was cloned and sequenced, showing high identity with human and rat CUBN cDNAs. An intragenic CUBN marker was identified in the canine family and used to test the hypothesis of genetic linkage of the disease and CUBN loci. Linkage was rejected, indicating that the canine disorder resembling Imerslund-Gräsbeck syndrome is caused by defect of a gene product other than cubilin. These results imply that there may be locus heterogeneity among human kindreds with selective intestinal cobalamin malabsorption and proteinuria and that normal brush-border expression of cubilin requires the activity of an accessory protein.
Roles for Drosophila melanogaster Myosin IB in Maintenance of Enterocyte Brush-Border Structure and Resistance to the Bacterial Pathogen Pseudomonas entomophila
Mermall, Valerie; Tilney, Lewis G.; Mooseker, Mark S.
Drosophila myosin IB (Myo1B) is one of two class I myosins in the Drosophila genome. In the larval and adult midgut enterocyte, Myo1B is present within the microvillus (MV) of the apical brush border (BB) where it forms lateral tethers between the MV membrane and underlying actin filament core. Expression of green fluorescent protein-Myo1B tail domain in the larval gut showed that the tail domain is sufficient for localization of Myo1B to the BB. A Myo1B deletion mutation exhibited normal larval gut physiology with respect to food uptake, clearance, and pH regulation. However, there is a threefold increase in terminal deoxynucleotidyl transferase dUTP nick-end labeling-positive enterocyte nuclei in the Myo1B mutant. Ultrastructural analysis of mutant midgut revealed many perturbations in the BB, including membrane tethering defects, MV vesiculation, and membrane shedding. The apical localization of both singed (fascin) and Dmoesin is impaired. BBs isolated from mutant and control midgut revealed that the loss of Myo1B causes the BB membrane and underlying cytoskeleton to become destabilized. Myo1B mutant larvae also exhibit enhanced sensitivity to oral infection by the bacterial pathogen Pseudomonas entomophila, and severe cytoskeletal defects are observed in the BB of proximal midgut epithelial cells soon after infection. Resistance to P. entomophila infection is restored in Myo1B mutant larvae expressing a Myo1B transgene. These results indicate that Myo1B may play a role in the local midgut response pathway of the Imd innate immune response to Gram-negative bacterial infection. PMID:17855510
In vitro adhesion of K88ac+ Escherichia coli to Peyer's patch and peripheral blood lymphocytes, buccal and rectal epithelial cells or intestinal epithelial brush borders of weaned pigs.
Valpotić, I; Runnels, P L; Moon, H W
Escherichia coli adhesion assays were conducted using isolated porcine peripheral blood lymphocytes, Peyer's patch lymphocytes, rectal epithelial cells or brush borders, buccal epithelial cells and brush borders from small intestinal epithelial cells. The cells and brush borders were tested for their ability to bind K88-piliated enterotoxigenic E. coli Strain M1823B (K88ac) and E. coli Strain 1476 (K-12, K88ac). Comparison of adhesive phenotypes of 37 weaned pigs as determined by the adhesion assay with small intestinal brush borders and the adherence of K88ac+ enterotoxigenic E. coli to peripheral blood lymphocytes, Peyer's patch lymphocytes and rectal epithelial cells or brush borders, revealed no correlation. In vitro adhesion of K88ac-bearing E. coli was always negative with buccal epithelial cells. K88ac strains varied in their ability to adhere to lymphocytes and rectal epithelial cells or brush borders, indicating that the mechanism of adherence is unrelated to K88-mediated adhesion observed in animals that had the receptors on small-intestinal epithelial-cell brush borders. The non-piliated control E. coli Strain 123 adhered to fresh peripheral blood lymphocytes, and less intensively to frozen-thawed peripheral blood lymphocytes or Peyer's patch lymphocytes. It was concluded that none of the cell types or brush borders, except small-intestinal epithelial-cell brush borders, could be used as targets for phenotyping pigs for the presence of the K88 receptors that have been associated with adhesion and colonization of K88+ enterotoxigenic E. coli in the porcine small intestine.
Borders as membranes :metaphors and models for improved policy in border regions.
Malczynski, Leonard A.; Passell, Howard David; Forster, Craig B.; Cockerill, Kristan
Political borders are controversial and contested spaces. In an attempt to better understand movement along and through political borders, this project applied the metaphor of a membrane to look at how people, ideas, and things ''move'' through a border. More specifically, the research team employed this metaphor in a system dynamics framework to construct a computer model to assess legal and illegal migration on the US-Mexico border. Employing a metaphor can be helpful, as it was in this project, to gain different perspectives on a complex system. In addition to the metaphor, the multidisciplinary team utilized an array of methods to gather data including traditional literature searches, an experts workshop, a focus group, interviews, and culling expertise from the individuals on the research team. Results from the qualitative efforts revealed strong social as well as economic drivers that motivate individuals to cross the border legally. Based on the information gathered, the team concluded that legal migration dynamics were of a scope we did not want to consider hence, available demographic models sufficiently capture migration at the local level. Results from both the quantitative and qualitative data searches were used to modify a 1977 border model to demonstrate the dynamic nature of illegal migration. Model runs reveal that current US-policies based on neo-classic economic theory have proven ineffective in curbing illegal migration, and that proposed enforcement policies are also likely to be ineffective. We suggest, based on model results, that improvement in economic conditions within Mexico may have the biggest impact on illegal migration to the U.S. The modeling also supports the views expressed in the current literature suggesting that demographic and economic changes within Mexico are likely to slow illegal migration by 2060 with no special interventions made by either government.
An all-aqueous route to polymer brush-modified membranes with remarkable permeabilites and protein capture rates
Anuraj, Nishotha; Bhattacharjee, Somnath; Geiger, James H.; Baker, Gregory L.; Bruening, Merlin L.
Microporous membranes are attractive for protein purification because convection rapidly brings proteins to binding sites. However, the low binding capacity of such membranes limits their applications. This work reports a rapid, aqueous procedure to create highly permeable, polymer brush-modified membranes that bind large amounts of protein. The synthetic method includes a 10-min adsorption of a macroinitiator in a hydroxylated nylon membrane and a subsequent 5-min aqueous atom transfer radical polymerization of 2-(methacryloyloxy)ethyl succinate from the immobilized initiator to form poly(acid) brushes. This procedure likely leads to more swollen, less dense brushes than polymerization from silane initiators, and thus requires less polymer to achieve the same binding capacity. The hydraulic permeability of the poly(acid) membranes is 4-fold higher than that of similar membranes prepared by growing brushes from immobilized silane initiators. These brush-containing nylon membranes bind 120 mg/cm3 of lysozyme using solution residence times as short as 35 ms, and when functionalized with nitrilotriacetate (NTA)-Ni2+ complexes, they capture 85 mg/cm3 of histidine6-tagged (His-tagged) Ubiquitin. Additionally the NTA-Ni2+-functionalized membranes isolate His-tagged myo-inositol-1-phosphate synthase directly from cell extracts and show >90% recovery of His-tagged proteins. PMID:22287817
Regulation of the rabbit ileal brush-border Na+/H+ exchanger by an ATP-requiring Ca++/calmodulin-mediated process.
Rood, R P; Emmer, E; Wesolek, J; McCullen, J; Husain, Z; Cohen, M E; Braithwaite, R S; Murer, H; Sharp, G W; Donowitz, M
Brush-border vesicles purified from rabbit ileal villus cells were used to evaluate how Ca++/calmodulin (CaM) regulates the neutral linked NaCl absorptive process, part of which is a Na+/H+ exchanger. After freezing and thawing to allow incorporation of macromolecules into the vesicles, the effect of Ca++/CaM on brush-border Na+ uptake with an acid inside pH gradient, and on Na+/H+ exchange was determined. Freezing and thawing vesicles with 0.85 microM free Ca++ plus 5 microM exogenous CaM failed to alter Na+/H+ exchange as did the addition of exogenous ATP plus an ATP regenerating system, which was sufficient to elevate intravesicular ATP to 47 microM from a basal level of 0.4 microM. However, the combination of Ca++/CaM plus ATP inhibited Na+ uptake in the presence of an acid inside pH gradient and inhibited Na+/H+ exchange, while Na+ uptake in the absence of a pH gradient was not altered. This effect required a hydrolyzable form of ATP, and did not occur when the nonhydrolyzable ATP analogue, AMP-PNP, replaced ATP. Under the identical intravesicular conditions used for the transport studies, Ca++ (0.85 microM) plus exogenous CaM (5 microM), in the presence of magnesium plus ATP, increased phosphorylation of five brush-border peptides. These data are consistent with Ca++/CaM acting via phosphorylation to regulate the ileal brush-border Na+/H+ exchanger. PMID:2843567
Intestinal morphology, brush border and digesta enzyme activities of broilers fed on a diet containing Cu2+-loaded montmorillonite.
Ma, Y L; Guo, T
1. A total of 320 1-d-old Arbor Acres broiler chicks were used to investigate the effect of Cu(2+)-loaded montmorillonite (CM) on the growth performance, intestinal morphology and activities of brush border enzyme in the intestinal mucosa and digestive enzyme in the intestinal digesta of broilers. 2. The chicks were assigned randomly into 4 groups with 80 chicks per treatment. The 4 dietary treatments were: basal diet only (control group), basal diet + 2 g montmorillonite/kg, basal diet + 1 g CM/kg, and basal diet + 2 g CM/kg. The chicks were raised in cages and feed and water were provided ad libitum for a period of 42 d. 3. The addition of CM to the diet of broilers significantly increased body weight and feed efficiency. Similarly, birds receiving montmorillonite had higher feed efficiency than the control after 42 d of feeding. 4. Data on villus height and crypt depth for duodenum, jejunum and ileum indicated that treating the diet of broilers with either CM or montmorillonite improved the mucosal morphology of the small intestine. 5. The presence of CM in the diet of broilers significantly increased the activities of maltase, aminopeptidase N and alkaline phosphatase in small intestinal mucosa. However, the activities of protease, trypsin, chymotrypsin, amylase and lipase in small intestinal digesta of broilers fed on the CM-supplemented diet were slightly higher than control values.
Ultrathin, freestanding, stimuli-responsive, porous membranes from polymer hydrogel-brushes
NASA Astrophysics Data System (ADS)
Kang, Chengjun; Ramakrishna, Shivaprakash N.; Nelson, Adrienne; Cremmel, Clement V. M.; Vom Stein, Helena; Spencer, Nicholas D.; Isa, Lucio; Benetti, Edmondo M.
The fabrication of freestanding, sub-100 nm-thick, pH-responsive hydrogel membranes with controlled nano-morphology, based on modified poly(hydroxyethyl methacrylate) (PHEMA) is presented. Polymer hydrogel-brush films were first synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP) and subsequently detached from silicon substrates by UV-induced photo-cleavage of a specially designed linker within the initiator groups. The detachment was also assisted by pH-induced osmotic forces generated within the films in the swollen state. The mechanical properties and morphology of the freestanding films were studied by atomic force microscopy (AFM). Inclusion of nanopores of controlled diameter was accomplished by performing SI-ATRP from initiator-coated surfaces that had previously been patterned with polystyrene nanoparticles. Assembly parameters and particle sizes could be varied, in order to fabricate nanoporous hydrogel-brush membranes with tunable pore coverage and characteristics. Additionally, due to the presence of weak polyacid functions within the hydrogel, the membranes exhibited pH-dependent thickness in water and reversible opening/closing of the pores.The fabrication of freestanding, sub-100 nm-thick, pH-responsive hydrogel membranes with controlled nano-morphology, based on modified poly(hydroxyethyl methacrylate) (PHEMA) is presented. Polymer hydrogel-brush films were first synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP) and subsequently detached from silicon substrates by UV-induced photo-cleavage of a specially designed linker within the initiator groups. The detachment was also assisted by pH-induced osmotic forces generated within the films in the swollen state. The mechanical properties and morphology of the freestanding films were studied by atomic force microscopy (AFM). Inclusion of nanopores of controlled diameter was accomplished by performing SI-ATRP from initiator-coated surfaces that had
Smart polymer brush nanostructures guide the self-assembly of pore-spanning lipid bilayers with integrated membrane proteins
NASA Astrophysics Data System (ADS)
Wilhelmina de Groot, G.; Demarche, Sophie; Santonicola, M. Gabriella; Tiefenauer, Louis; Vancso, G. Julius
Nanopores in arrays on silicon chips are functionalized with pH-responsive poly(methacrylic acid) (PMAA) brushes and used as supports for pore-spanning lipid bilayers with integrated membrane proteins. Robust platforms are created by the covalent grafting of polymer brushes using surface-initiated atom transfer radical polymerization (ATRP), resulting in sensor chips that can be successfully reused over several assays. His-tagged proteins are selectively and reversibly bound to the nitrilotriacetic acid (NTA) functionalization of the PMAA brush, and consequently lipid bilayer membranes are formed. The enhanced membrane resistance as determined by electrochemical impedance spectroscopy and free diffusion of dyed lipids observed as fluorescence recovery after photobleaching confirmed the presence of lipid bilayers. Immobilization of the His-tagged membrane proteins on the NTA-modified PMAA brush near the pore edges is characterized by fluorescence microscopy. This system allows us to adjust the protein density in free-standing bilayers, which are stabilized by the polymer brush underneath. The potential application of the integrated platform for ion channel protein assays is demonstrated.
Fabrication of cell outer membrane mimetic polymer brush on polysulfone surface via RAFT technique
NASA Astrophysics Data System (ADS)
Ma, Qian; Zhang, Hui; Zhao, Jiang; Gong, Yong-Kuan
Cell membrane mimetic antifouling polymer brush was grown on polysulfone (PSF) membrane by surface-induced reversible addition-fragmentation chain transfer (RAFT) polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC). The RAFT agent immobilized PSF substrate was prepared by successive chloromethylation, amination with ethylenediamine (EDA) and amidation of the amine group of grafted EDA with the carboxylic group of 4-cyanopentanoic acid dithiobenzoate (CPAD). The surface RAFT polymerization of MPC was initiated in aqueous solution by 4,4‧-azobis-4-cyanopentanoic acid (ACPA). The formation of PMPC brush coating is evidenced by X-ray photoelectron spectroscopy and water contact angle measurements. The degree of polymerization of PMPC and the polymer grafting density were calculated from the high resolution XPS spectra. The platelet adhesion and protein adsorption results showed that the PMPC-grafted PSF surface has excellent antifouling ability to resist platelet adhesion completely and suppress protein adsorption significantly. This biomimetic and bio-friendly surface RAFT polymerization strategy could be promising for a variety of biomedical applications.
Constructing proton-conductive highways within an ionomer membrane by embedding sulfonated polymer brush modified graphene oxide
NASA Astrophysics Data System (ADS)
Zhao, Liping; Li, Yifan; Zhang, Haoqin; Wu, Wenjia; Liu, Jindun; Wang, Jingtao
Sulfonated polymer brush modified graphene oxide (SP-GO) fillers with controllable brush length are synthesized via the facile distillation-precipitation polymerization, and then incorporated into sulfonated poly(ether ether ketone) (SPEEK) matrix to fabricate composite membranes. The influences of SP-GO upon the microstructures, including thermal and mechanical properties, water uptake/swelling, proton conduction, H2 permeability and single PEMFC performances of composite membranes are intensively investigated. It is found that the SP-GO fillers are uniformly dispersed and tend to lie perpendicularly to the cross-section surface of the whole membrane, which allow SP-GO fillers creating inter-connected and broad ionic pathways through the sulfonic acid groups in polymer brushes. Meanwhile, the SP-GO fillers connect the ionic clusters in SPEEK matrix via interfacial interactions. In such a way, proton-transfer highways are constructed along the SPEEK/SP-GO interface, which lower the proton transfer activation energy and enhance the proton conductivities of the composite membranes under both hydrated and anhydrous conditions. Furthermore, elevating the brush length on SP-GO could further enhance the proton conductivity. Compared to SPEEK control membrane, a 95.5% increase in hydrated conductivity, an 178% increase in anhydrous conductivity and a 37% increase in maximum power density are obtained for the optimal composite membrane.
Structural and functional lesions in brush border of human polarized intestinal Caco-2/TC7 cells infected by members of the Afa/Dr diffusely adhering family of Escherichia coli.
Peiffer, I; Guignot, J; Barbat, A; Carnoy, C; Moseley, S L; Nowicki, B J; Servin, A L; Bernet-Camard, M F
Diffusely adhering Escherichia coli (DAEC) strains expressing F1845 fimbrial adhesin or Dr hemagglutinin belonging to the Afa/Dr family of adhesins infect cultured polarized human intestinal cells through recognition of the brush border-associated decay-accelerating factor (DAF; CD55) as a receptor. The wild-type Afa/Dr DAEC strain C1845 has been shown to induce brush border lesions by an adhesin-dependent mechanism triggering apical F-actin rearrangements. In the present study, we undertook to further characterize cell injuries following the interaction of wild-type Afa/Dr DAEC strains C1845 and IH11128 expressing fimbrial F1845 adhesin and Dr hemagglutinin, respectively, with polarized, fully differentiated Caco-2/TC7 cells. In both cases, bacterium-cell interaction was followed by rearrangement of the major brush border-associated cytoskeletal proteins F-actin, villin, and fimbrin, proteins which play a pivotal role in brush border assembly. In contrast, distribution of G-actin, actin-depolymerizing factor, and tubulin was not modified. Using draE mutants, we found that a mutant in which cysteine replaces aspartic acid at position 54 conserved binding capacity but failed to induce F-actin disassembly. Accompanying the cytoskeleton injuries, we found that the distribution of brush border-associated functional proteins sucrase-isomaltase (SI), dipeptidylpeptidase IV (DPPIV), glucose transporter SGLT1, and fructose transporter GLUT5 was dramatically altered. In parallel, SI and DPPIV enzyme activity decreased.
Affinity Separation of Lectins Using Porous Membranes Immobilized with Glycopolymer Brushes Containing Mannose or N-Acetyl-d-Glucosamine
Ogata, Yutaro; Seto, Hirokazu; Murakami, Tatsuya; Hoshino, Yu; Miura, Yoshiko
Porous membranes with glycopolymer brushes were prepared as biomaterials for affinity separation. Glycopolymer brushes contained acrylic acid and D-mannose or N-acetyl-D-glucosamine, and were formed on substrates by surface-initiated atom transfer radical polymerization. The presence of glycopolymer brush was confirmed by X-ray photoelectron spectroscopy, contact angle, and ellipsometry measurements. The interaction between lectin and the glycopolymer immobilized on glass slides was confirmed using fluorescent-labeled proteins. Glycopolymer-immobilized surfaces exhibited specific adsorption of the corresponding lectin, compared with bovine serum albumin. Lectins were continuously rejected by the glycopolymer-immobilized membranes. When the protein solution was permeated through the glycopolymer-immobilized membrane, bovine serum albumin was not adsorbed on the membrane surface. In contrast, concanavalin A and wheat germ agglutinin were rejected by membranes incorporating D-mannose or N-acetyl-D-glucosamine, respectively. The amounts of adsorbed concanavalin A and wheat germ agglutinin was increased five- and two-fold that of adsorbed bovine serum albumin, respectively. PMID:24956944
D-Glucose Acts via SGLTI to Increase NHE3 in Mouse Jejunal Brush Border by a NHERF2-Dependent Process
Lin, Rong; Murtazina, Rakhilya; Cha, Boyoung; Chakraborty, Molee; Sarker, Rafiquel; Chen, Tian-e; Lin, Zhihong; Hogema, Boris M.; de Jonge, Hugo R.; Seidler, Ursula; Turner, Jerrold R.; Li, Xuhang; Kovbasnjuk, Olga; Donowitz, Mark
Background & Aims Oral rehydration solutions (ORS) reduce diarrhea-associated mortality by unclear mechanisms. Sodium absorption is mediated by the Na+/H+ hydrogen exchanger NHE3 and is increased by Na+-glucose co-transport in vitro, but the mechanisms of this process are only partially understood and its in vivo relevance has not been determined. Methods Intracellular pH was measured in jejunal enterocytes of wild-type mice and mice with disrupted Na+/H+ exchange regulatory co-factor 2 (NHERF2−/− mice) by multi-photon microscopy. Diarrhea was induced by cholera toxin. Caco-2BBe cells that express NHE3 and the sodium/glucose cotransporter (SGLT)1 were studied by fluorometery, before and after siRNA-mediated knockdown of NHERF1 or NHERF2. NHE3 distribution was assessed by cell-surface biotinylation and confocal microscopy. Brush border mobility was determined by fluorescence recovery after photobleaching and confocal microscopy. Results The non-metabolized SGLT1 substrate α-methyl-D-Glu (α-MD-G) activated jejunal NHE3; this process required Akt and NHERF2. α-MD-G normalized NHE3 activity after cholera toxin-induced diarrhea. α-MD-G–stimulated jejunal NHE3 activity was: defective in NHERF2−/− mice and cells with NHERF2 knockdown, but occurred normally with NHERF1 knockdown; associated with increased NHE3 surface expression in Caco-2 cells, which was also NHERF2-dependent; associated with dissociation of NHE3 from NHERF2 and an increase in the NHE3 mobile fraction from the brush border; and accompanied by a NHERF2 ezrin-radixin-moesin–binding domain-dependent increase in co-precipitation of ezrin with NHE3. Conclusions SGLT1-mediated Na-glucose co-transport stimulates NHE3 activity in vivo by an Akt- and NHERF2-dependent signaling pathway. It is associated with increased brush border NHE3 and association between ezrin and NHE3. Activation of NHE3 corrects cholera toxin-induced defects in Na absorption and might mediate efficacy of ORS. PMID:20977906
Grafting of carboxybetaine brush onto cellulose membranes via surface-initiated ARGET-ATRP for improving blood compatibility.
Wang, Miao; Yuan, Jiang; Huang, Xiaobo; Cai, Xianmei; Li, Li; Shen, Jian
Grafting-from has proven to be a very effective way to create high grafting densities and well-controlled polymer chains on different kinds of surfaces. In this work, we aim to graft zwitterionic brush from cellulose membrane (CM) via ARGET-ATRP (Activator Regenerated by Electron Transfer ATRP) method indirectly for blood compatibility improvement. Characterization of the CM substrates before and after modification was carried out by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), water contact angle measurements, X-ray photoelectron spectroscopy analysis, and atomic force microscopy, respectively. The results demonstrated zwitterionic brushes were successfully grafted on the CM surfaces, and the content of the grafted layer increased gradually with the polymerization time. The platelet adhesion, hemolytic test and plasma protein adsorption results indicated the cellulose membrane had significantly excellent blood compatibility featured on lower platelet adhesion and protein adsorption without causing hemolysis. The functionalized cellulose substrate could have a great potential usage for biomedical applications.
High flux, positively charged loose nanofiltration membrane by blending with poly (ionic liquid) brushes grafted silica spheres.
Yu, Liang; Zhang, Yatao; Wang, Yuanming; Zhang, Haoqin; Liu, Jindun
Silica spheres modified by poly (ionic liquid) brushes, a novel positively charged nanomaterial is prepared by atom transfer radical polymerization (ATRP). A high flux positively charged loose nanofiltration membrane is fabricated via "blending-phase inversion" method. The morphology structures, hydrophilicity, thermal and mechanical properties, permeation performance of these membranes are investigated in detail. The results reveal that the hybrid membranes have enhanced surface hydrophilicity, water permeability, thermal stability, and mechanical properties. Characterization of membrane separation properties shows that the hybrid membranes possess higher salt permeability and relatively higher rejection for reactive dyes, which may open opportunities for the recycling of reactive dyes wastewater. Moreover, such hybrid membranes have an outstanding operational stability and salts concentration showed little effect on the separation properties.
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...
Thiolation of polycarbophil enhances its inhibition of intestinal brush border membrane bound aminopeptidase N.
Bernkop-Schnürch, A; Zarti, H; Walker, G F
The purpose of this study was to evaluate the potential of polycarbophil-cysteine conjugates (PCP-Cys) as an oral excipient to protect leucine enkephalin (leu-enkp) from enzymatic degradation by the intestinal mucosa. Cysteine was covalently linked to polycarbophil by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDAC). Inhibitory activity was tested towards isolated aminopeptidase N and excised intact pig intestinal mucosa, with native mucus. Aminopeptidase N activity was assayed spectrophotometrically using L-leucine p-nitroanilide (leu-pNA) as a synthetic substrate and against the model peptide drug leu-enkp, by high-performance liquid chromatography (HPLC). Free cysteine at 6.3 and 63 microM (pH 6) significantly (p < 0.05) inhibited aminopeptidase N activity, and PCP-Cys (0.25% w/v, pH 6) had a significantly (p < 0.05) greater inhibitory effect than PCP on the aminopeptidase N activity towards both substrates. PCP-Cys completely protected leu-enkp against aminopeptidase N activity over a 2-h incubation period, whereas 83 +/- 4 and 60 +/- 7% remained stable in the presence of PCP and buffer only, respectively. Leu-enkp in the absence and presence of PCP (0.25% w/v) at pH 6 was completely digested by the intact intestinal mucosa at the 60- and 90-min incubation time points, respectively, whereas in the presence of PCP-Cys (0.25% w/v, pH 6) 11 +/- 3.5% of leu-enkp remained at the 120-min time point. Thiolation of PCP increased the stability of leu-enkp against the enzymatic degradation by aminopeptidase N and the intact intestinal mucosa, identifying a promising new excipient for peroral delivery of peptides.
Dose-dependence of the effects of corticosterone and the non-glucocorticoid, 18-hydroxycorticosterone, on the brush-border Na+/K+ exchanger.
Igarreta, P; Lantos, C P; Calvo, J C; Paladini, A A; Damasco, M C
Up to now, only glucocorticoids were thought to act on the renal proximal Na+/H+ exchanger. Using fluorimetric techniques we studied the kinetics of Na+/H+ exchange in brush border vesicles from ADX rats treated with increasing doses of corticosterone (B) and 18-hydroxycorticosterone (18OHB). Significant linear correlations were obtained when the Vmax of each treatment were plotted against log doses. 18OHB exhibits a slightly higher sensitivity than B and log-dose responses were steeper for 18OHB than for B treated rats. Differences between both treatments were highly significant at the 4.8 microg/100 g level, corresponding to the physiological blood level of 18OHB. Physiological doses of both steroids elicited equal Na+/H+ exchange-responses. 18OHB is not a glucocorticoid since even 88 microg/100 g did not promote hepatic glycogen deposition while the same dose of B increases glycogen deposits 3.5-fold. These results demonstrate the importance of the Na+/H+ exchanger as a mediator between corticoid action and H+ transport and that of the non-glucocorticoid 18OHB in this process.
Border control--a membrane-linked interactome of Arabidopsis.
Jones, Alexander M; Xuan, Yuanhu; Xu, Meng; Wang, Rui-Sheng; Ho, Cheng-Hsun; Lalonde, Sylvie; You, Chang Hun; Sardi, Maria I; Parsa, Saman A; Smith-Valle, Erika; Su, Tianying; Frazer, Keith A; Pilot, Guillaume; Pratelli, Réjane; Grossmann, Guido; Acharya, Biswa R; Hu, Heng-Cheng; Engineer, Cawas; Villiers, Florent; Ju, Chuanli; Takeda, Kouji; Su, Zhao; Dong, Qunfeng; Assmann, Sarah M; Chen, Jin; Kwak, June M; Schroeder, Julian I; Albert, Reka; Rhee, Seung Y; Frommer, Wolf B
Cellular membranes act as signaling platforms and control solute transport. Membrane receptors, transporters, and enzymes communicate with intracellular processes through protein-protein interactions. Using a split-ubiquitin yeast two-hybrid screen that covers a test-space of 6.4 × 10(6) pairs, we identified 12,102 membrane/signaling protein interactions from Arabidopsis. Besides confirmation of expected interactions such as heterotrimeric G protein subunit interactions and aquaporin oligomerization, >99% of the interactions were previously unknown. Interactions were confirmed at a rate of 32% in orthogonal in planta split-green flourescent protein interaction assays, which was statistically indistinguishable from the confirmation rate for known interactions collected from literature (38%). Regulatory associations in membrane protein trafficking, turnover, and phosphorylation include regulation of potassium channel activity through abscisic acid signaling, transporter activity by a WNK kinase, and a brassinolide receptor kinase by trafficking-related proteins. These examples underscore the utility of the membrane/signaling protein interaction network for gene discovery and hypothesis generation in plants and other organisms.
Humic acid removal and easy-cleanability using temperature-responsive ZrO2 tubular membranes grafted with poly(N-isopropylacrylamide) brush chains.
Zhao, Yijiang; Zhou, Shouyong; Li, Meisheng; Xue, Ailian; Zhang, Yan; Wang, Jingang; Xing, Weihong
New poly(N-isopropylacrylamide) brushes grafted with ZrO2 (PNIPAAm-g-ZrO2) composite membranes, which had been prepared in our laboratory, were used for humic acid (HA) removal. We found that the fluxes associated with such membranes, when compared to those obtained from unmodified ZrO2 membranes, declined slightly at both 25 °C and 35 °C. The PNIPAAm-g-ZrO2 membrane achieved a high rejection, of 98.0%, at a suitable steady flux of 111.9 L m(-2) h(-1) at 25 °C. This membrane exhibited good anti-fouling properties as well as improved membrane performance during filtration of HA. The important role of pH and Ca(2+) concentration in HA removal was also investigated. Lower adsorption fouling and a higher rejection were obtained at higher pH levels. The Ca(2+) ions reduced the electrostatic exclusion and played a cross-linking role between HA and the PNIPAAm-g-ZrO2 membrane surface. Fouling was severe in the presence of Ca(2+). These tests led to the development of an environment-friendly membrane cleaning method, by means of temperature-change water elution around LCST of PNIPAAm-brushes. After the alternate temperature-change (25 °C/35 °C) cleaning, a flux recovery of 98.2% was obtained for the PNIPAAm-g-ZrO2 membrane. Moreover, after four repeated experiments, the anti-fouling and easy-cleaning properties were still maintained. It is implied that PNIPAAm-brushes were firmly "stuck" to the membrane surface, and could not easily be removed by water cleaning or HA filtration. The PNIPAAm-g-ZrO2 membranes exhibited good stability and great potential for HA removal.
Temperature-controlled flow switching in nanocapillary array membranes mediated by poly(N-isopropylacrylamide) polymer brushes grafted by atom transfer radical polymerization.
Lokuge, Ishika; Wang, Xuejun; Bohn, Paul W
We report actively controlled transport that is thermally switchable and size-selective in a nanocapillary array membrane (NCAM) prepared by grafting poly(N-isopropylacrylamide) (PNIPAAm) brushes onto the exterior surface of a Au-coated polycarbonate track-etched membrane. A smooth Au layer on the membrane surface, which is key to obtaining a uniform polymer film, was prepared by thermal evaporation of approximately 50 nm Au on both exterior surfaces. After evaporation, the inner diameter of the pore is reduced slightly, but the NCAM retains a narrow pore size distribution. PNIPPAm brushes with 10-30 nm (dry film) thickness were grafted onto the Au surface through surface-initiated atom transfer radical polymerization (ATRP) using a disulfide initiator, (BrC(CH3)2COO(CH2)11S)2. Molecular transport through the PNIPAAm polymer brush-modified NCAMs was investigated by real-time fluorescence measurements using fluorescein isothiocyanate (FITC)-labeled dextrans ranging from 4.4 to 282 kDa in membranes with variable initial pore diameters (80, 100, and 200 nm) and different PNIPAAm thicknesses. Manipulating the temperature of the NCAM through the PNIPAAm lower critical solution temperature (LCST) causes large, size-dependent changes in the transport rates. Over specific ranges of probe size, transport is completely blocked below the LCST but strongly allowed above the LCST. The combination of the highly uniform PNIPAAm brush and the monodisperse pore size distribution is critical in producing highly reproducible switching behavior. Furthermore, the reversible nature of the switching raises the possibility of using them as actively controlled filtration devices.
Organization of an actin filament-membrane complex. Filament polarity and membrane attachment in the microvilli of intestinal epithelial cells
The association of actin filaments with membranes is now recognized as an important parameter in the motility of nonmuscle cells. We have investigated the organization of one of the most extensive and highly ordered actin filament-membrane complexes in nature, the brush border of intestinal epithelial cells. Through the analysis of isolated, demembranated brush borders decorated with the myosin subfragment, S1, we have determined that all the microvillar actin filaments have the same polarity. The S1 arrowhead complexes point away from the site of attachment of actin filaments at the apical tip of the microvillar membrane. In addition to the end-on attachment of actin filaments at the tip of the microvillus, these filaments are also connected to the plasma membrane all along their lengths by periodic (33 nm) cross bridges. These bridges were best observed in isolated brush borders incubated in high concentrations of Mg++. Their visibility is attributed to the induction of actin paracrystals in the filament bundles of the microvilli. Finally, we present evidence for the presence of myosinlike filaments in the terminal web region of the brush border. A model for the functional organization of actin and myosin in the brush border is presented. PMID:1202021
Hemocompatibility of poly(vinylidene fluoride) membrane grafted with network-like and brush-like antifouling layer controlled via plasma-induced surface PEGylation.
Chang, Yung; Shih, Yu-Ju; Ko, Chao-Yin; Jhong, Jheng-Fong; Liu, Ying-Ling; Wei, Ta-Chin
In this work, the hemocompatibility of PEGylated poly(vinylidene fluoride) (PVDF) microporous membranes with varying grafting coverage and structures via plasma-induced surface PEGylation was studied. Network-like and brush-like PEGylated layers on PVDF membrane surfaces were achieved by low-pressure and atmospheric plasma treatment. The chemical composition, physical morphology, grafting structure, surface hydrophilicity, and hydration capability of prepared membranes were determined to illustrate the correlations between grafting qualities and hemocompatibility of PEGylated PVDF membranes in contact with human blood. Plasma protein adsorption onto different PEGylated PVDF membranes from single-protein solutions and the complex medium of 100% human plasma were measured by enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies. Hemocompatibility of the PEGylated membranes was evaluated by the antifouling property of platelet adhesion observed by scanning electron microscopy (SEM) and the anticoagulant activity of the blood coagulant determined by testing plasma-clotting time. The control of grafting structures of PEGylated layers highly regulates the PVDF membrane to resist the adsorption of plasma proteins, the adhesion of platelets, and the coagulation of human plasma. It was found that PVDF membranes grafted with brush-like PEGylated layers presented higher hydration capability with binding water molecules than with network-like PEGylated layers to improve the hemocompatible character of plasma protein and blood platelet resistance in human blood. This work suggests that the hemocompatible nature of grafted PEGylated polymers by controlling grafting structures gives them great potential in the molecular design of antithrombogenic membranes for use in human blood.
Impairments in enzyme activity and biosynthesis of brush border-associated hydrolases in human intestinal Caco-2/TC7 cells infected by members of the Afa/Dr family of diffusely adhering Escherichia coli.
Peiffer, I; Bernet-Camard, M F; Rousset, M; Servin, A L
Wild-type diffusely adhering Escherichia coli (DAEC) harbouring afimbrial adhesin (Afa) or fimbrial Dr and F1845 adhesins (Afa/Dr DAEC) apically infecting the human intestinal epithelial cells promote injuries in the brush border of the cells. We report here that infection by Afa/Dr DAEC wild-type strains C1845 and IH11128 in polarized human fully differentiated Caco-2/TC7 cells dramatically impaired the enzyme activity of functional brush border-associated proteins sucrase-isomaltase (SI) and dipeptidylpeptidase IV (DPP IV). Blockers of the transduction signal molecules, previously found to be active against the Afa/Dr DAEC-induced cytoskeleton injury, were inactive against the Afa/Dr-induced decrease in sucrase enzyme activity. In parallel, Afa/Dr DAEC infection promotes the blockade of the biosynthesis of SI and DPP IV without affection enzyme stability. The observation that no changes occurred in mRNA levels of SI and DPP IV upon infection suggested that the decrease in biosynthesis probably resulted from a decrease in the translation rate. When the cells were infected with recombinant E. coli strains expressing homologous adhesins of the wild-type strains, neither a decrease in sucrase and DPP IV enzyme activities nor an inhibition of enzyme biosynthesis were observed. In conclusion, taken together, these data give new insights into the mechanisms by which the wild-type Afa/Dr DAEC strains induce functional injuries in polarized fully differentiated human intestinal cells. Moreover, the results revealed that other pathogenic factor(s) distinct from the Afa/Dr adhesins may play(s) a crucial role in this mechanism of pathogenicity.
Binding of Bacillus thuringiensis Cry1A toxins with brush border membrane vesicles of maize stem borer (Chilo partellus Swinhoe).
Sharma, Priyanka; Nain, Vikrant; Lakhanpaul, Suman; Kumar, P A
Maize stem borer (Chilo partellus) is a major insect pest of maize and sorghum in Asia and Africa. Bacillus thuringiensis (Bt) δ-endotoxins have been found effective against C. partellus, both in diet-overlay assay and in transgenic plants. Gene stacking as one of the resistance management strategies in Bt maize requires an understanding of receptor sharing and binding affinity of δ-endotoxins. In the present study, binding affinity of three fluorescein isothiocyanate labeled Cry1A toxins showed high correlation with the toxicity of respective δ-endotoxins. Competitive binding studies showed that Cry1Ab toxins share some of the binding sites with Cry1Aa and Cry1Ac with low affinity and that Cry1Ab may have additional binding sites that are unavailable to the other two toxins tested.
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...
Impact of electroviscosity on the hydraulic conductance of the bordered pit membrane: a theoretical investigation.
Santiago, Michael; Pagay, Vinay; Stroock, Abraham D
In perfusion experiments, the hydraulic conductance of stem segments ( ) responds to changes in the properties of the perfusate, such as the ionic strength ( ), pH, and cationic identity. We review the experimental and theoretical work on this phenomenon. We then proceed to explore the hypothesis that electrokinetic effects in the bordered pit membrane (BPM) contribute to this response. In particular, we develop a model based on electroviscosity in which hydraulic conductance of an electrically charged porous membrane varies with the properties of the electrolyte. We use standard electrokinetic theory, coupled with measurements of electrokinetic properties of plant materials from the literature, to determine how the conductance of BPMs, and therefore , may change due to electroviscosity. We predict a nonmonotonic variation of with with a maximum reduction of 18%. We explore how this reduction depends on the characteristics of the sap and features of the BPM, such as pore size, density of chargeable sites, and their dissociation constant. Our predictions are consistent with changes in observed for physiological values of sap and pH. We conclude that electroviscosity is likely responsible, at least partially, for the electrolyte dependence of conductance through pits and that electroviscosity may be strong enough to play an important role in other transport processes in xylem. We conclude by proposing experiments to differentiate the impact of electroviscosity on from that of other proposed mechanisms.
Recruitment of CD55 and CD66e brush border-associated glycosylphosphatidylinositol-anchored proteins by members of the Afa/Dr diffusely adhering family of Escherichia coli that infect the human polarized intestinal Caco-2/TC7 cells.
Guignot, J; Peiffer, I; Bernet-Camard, M F; Lublin, D M; Carnoy, C; Moseley, S L; Servin, A L
The Afa/Dr family of diffusely adhering Escherichia coli (Afa/Dr DAEC) includes bacteria expressing afimbrial adhesins (AFA), Dr hemagglutinin, and fimbrial F1845 adhesin. We show that infection of human intestinal Caco-2/TC7 cells by the Afa/Dr DAEC strains C1845 and IH11128 is followed by clustering of CD55 around adhering bacteria. Mapping of CD55 epitopes involved in CD55 clustering by Afa/Dr DAEC was conducted using CD55 deletion mutants expressed by stable transfection in CHO cells. Deletion in the short consensus repeat 1 (SCR1) domain abolished Afa/Dr DAEC-induced CD55 clustering. In contrast, deletion in the SCR4 domain does not modify Afa/Dr DAEC-induced CD55 clustering. We show that the brush border-associated glycosylphosphatidylinositol (GPI)-anchored protein CD66e (carcinoembryonic antigen) is recruited by the Afa/Dr DAEC strains C1845 and IH11128. This conclusion is based on the observations that (i) infection of Caco-2/TC7 cells by Afa/Dr DAEC strains is followed by clustering of CD66e around adhering bacteria and (ii) Afa/Dr DAEC strains bound efficiently to stably transfected HeLa cells expressing CD66e, accompanied by CD66e clustering around adhering bacteria. Inhibition assay using monoclonal antibodies directed against CD55 SCR domains, and polyclonal anti-CD55 and anti-CD66e antibodies demonstrate that CD55 and CD66e function as a receptors for the C1845 and IH11128 bacteria. Moreover, using structural draE gene mutants, we found that a mutant in which cysteine replaced aspartic acid at position 54 displayed conserved binding capacity but failed to induce CD55 and CD66e clustering. Taken together, these data give new insights into the mechanisms by which Afa/Dr DAEC induces adhesin-dependent cross talk in the human polarized intestinal epithelial cells by mobilizing brush border-associated GPI-anchored proteins known to function as transducing molecules.
... bristles along the gumline at a 45-degree angle. Bristles should contact both the tooth surface and the gumline. Gently ... A rolling motion is when the brush makes contact with the gumline and ... a 45-degree angle with bristles contacting the tooth surface and gumline. ...
Bacterial biodegradation of extractives and patterns of bordered pit membrane attack in pine wood.
Burnes, T A; Blanchette, R A; Farrell, R L
Wood extractives, commonly referred to as pitch, cause major problems in the manufacturing of pulp and paper. Treatment of nonsterile southern yellow pine chips for 14 days with Pseudomonas fluorescens, Pseudomonas sp., Xanthomonas campestris, and Serratia marcescens reduced wood extractives by as much as 40%. Control treatments receiving only water lost 11% of extractives due to the growth of naturally occurring microorganisms. Control treatments were visually discolored after the 14-day incubation, whereas bacterium-treated wood chips were free of dark staining. Investigations using P. fluorescens NRRL B21432 showed that all individual resin and fatty acid components of the pine wood extractives were substantially reduced. Micromorphological observations showed that bacteria were able to colonize resin canals, ray parenchyma cells, and tracheids. Tracheid pit membranes within bordered pit chambers were degraded after treatment with P. fluorescens NRRL B21432. P. fluorescens and the other bacteria tested appear to have the potential for biological processing to substantially reduce wood extractives in pine wood chips prior to the paper making process so that problems associated with pitch in pulp mills can be controlled.
Secreted maltase-glucoamylase is upregulated in membrane maltase-glucoamylase null mice
Technology Transfer Automated Retrieval System (TEKTRAN)
The known mammalian brush-border glucohydrolases are membrane-bound, small intestine lumenal enzymes that digest dietary starches and sugars into monosaccharides for absorption. The phenotype of maltase-glucoamylase deficiency is not understood. To address this, we ablated membrane-bound maltase-gl...
Electrospun regenerated cellulose nanofibrous membranes surface-grafted with polymer chains/brushes via the atom transfer radical polymerization method for catalase immobilization.
Feng, Quan; Hou, Dayin; Zhao, Yong; Xu, Tao; Menkhaus, Todd J; Fong, Hao
In this study, an electrospun regenerated cellulose (RC) nanofibrous membrane with fiber diameters of ∼200-400 nm was prepared first; subsequently, 2-hydroxyethyl methacrylate (HEMA), 2-dimethylaminoethyl methacrylate (DMAEMA), and acrylic acid (AA) were selected as the monomers for surface grafting of polymer chains/brushes via the atom transfer radical polymerization (ATRP) method. Thereafter, four nanofibrous membranes (i.e., RC, RC-poly(HEMA), RC-poly(DMAEMA), and RC-poly(AA)) were explored as innovative supports for immobilization of an enzyme of bovine liver catalase (CAT). The amount/capacity, activity, stability, and reusability of immobilized catalase were evaluated, and the kinetic parameters (Vmax and Km) for immobilized and free catalase were determined. The results indicated that the respective amounts/capacities of immobilized catalase on RC-poly(HEMA) and RC-poly(DMAEMA) nanofibrous membranes reached 78 ± 3.5 and 67 ± 2.7 mg g(-1), which were considerably higher than the previously reported values. Meanwhile, compared to that of free CAT (i.e., 18 days), the half-life periods of RC-CAT, RC-poly(HEMA)-CAT, RC-poly(DMAEMA)-CAT, and RC-poly(AA)-CAT were 49, 58, 56, and 60 days, respectively, indicating that the storage stability of immobilized catalase was also significantly improved. Furthermore, the immobilized catalase exhibited substantially higher resistance to temperature variation (tested from 5 to 70 °C) and lower degree of sensitivity to pH value (tested from 4.0 and 10.0) than the free catalase. In particular, according to the kinetic parameters of Vmax and Km, the nanofibrous membranes of RC-poly(HEMA) (i.e., 5102 μmol mg(-1) min(-1) and 44.89 mM) and RC-poly(DMAEMA) (i.e., 4651 μmol mg(-1) min(-1) and 46.98 mM) had the most satisfactory biocompatibility with immobilized catalase. It was therefore concluded that the electrospun RC nanofibrous membranes surface-grafted with 3-dimensional nanolayers of polymer chains/brushes would be
Effects of Protease, Phytase and a Bacillus sp. Direct-Fed Microbial on Nutrient and Energy Digestibility, Ileal Brush Border Digestive Enzyme Activity and Cecal Short-Chain Fatty Acid Concentration in Broiler Chickens
Murugesan, Ganapathi R.; Romero, Luis F.; Persia, Michael E.
Two experiments were conducted to determine the effects of protease and phytase (PP) and a Bacillus sp. direct-fed microbial (DFM) on dietary energy and nutrient utilization in broiler chickens. In the first experiment, Ross 308 broiler chicks were fed diets supplemented with PP and DFM in a 2×2 factorial arrangement. The 4 diets (control (CON), CON + PP, CON + DFM, and CON + PP + DFM) were fed from 15–21 days of age. In Experiment 1, significant interaction (P≤0.01) between PP and DFM on the apparent ileal digestibility coefficient for starch, crude protein, and amino acid indicated that both additives increased the digestibility. Both additives increased the nitrogen retention coefficient with a significant interaction (P≤0.01). Although no interaction was observed, significant main effects (P≤0.01) for nitrogen-corrected apparent ME (AMEn) for PP or DFM indicated an additive response. In a follow-up experiment, Ross 308 broiler chicks were fed the same experimental diets from 1–21 days of age. Activities of ileal brush border maltase, sucrase, and L-alanine aminopeptidase were increased (P≤0.01) by PP addition, while a trend (P = 0.07) for increased sucrase activity was observed in chickens fed DFM, in Experiment 2. The proportion of cecal butyrate was increased (P≤0.01) by DFM addition. Increased nutrient utilization and nitrogen retention appear to involve separate but complementary mechanisms for PP and DFM, however AMEn responses appear to have separate and additive mechanisms. PMID:25013936
Amnionless function is required for cubilin brush-border expression and intrinsic factor-cobalamin (vitamin B12) absorption in vivo.
He, Qianchuan; Madsen, Mette; Kilkenney, Adam; Gregory, Brittany; Christensen, Erik I; Vorum, Henrik; Højrup, Peter; Schäffer, Alejandro A; Kirkness, Ewen F; Tanner, Stephan M; de la Chapelle, Albert; Giger, Urs; Moestrup, Søren K; Fyfe, John C
Amnionless (AMN) and cubilin gene products appear to be essential functional subunits of an endocytic receptor called cubam. Mutation of either gene causes autosomal recessive Imerslund-Gräsbeck syndrome (I-GS, OMIM no. 261100) in humans, a disorder characterized by selective intestinal malabsorption of cobalamin (vitamin B12) and urinary loss of several specific low-molecular-weight proteins. Vital insight into the molecular pathology of I-GS has been obtained from studies of dogs with a similar syndrome. In this work, we show that I-GS segregates in a large canine kindred due to an in-frame deletion of 33 nucleotides in exon 10 of AMN. In a second, unrelated I-GS kindred, affected dogs exhibit a homozygous substitution in the AMN translation initiation codon. Studies in vivo demonstrated that both mutations abrogate AMN expression and block cubilin processing and targeting to the apical membrane. The essential features of AMN dysfunction observed in vivo are recapitulated in a heterologous cell-transfection system, thus validating the system for analysis of AMN-cubilin interactions. Characterization of canine AMN mutations that cause I-GS establishes the canine model as an ortholog of the human disorder well suited to studies of AMN function and coevolution with cubilin.
Life at the border: Adaptation of proteins to anisotropic membrane environment
Pogozheva, Irina D; Mosberg, Henry I; Lomize, Andrei L
This review discusses main features of transmembrane (TM) proteins which distinguish them from water-soluble proteins and allow their adaptation to the anisotropic membrane environment. We overview the structural limitations on membrane protein architecture, spatial arrangement of proteins in membranes and their intrinsic hydrophobic thickness, co-translational and post-translational folding and insertion into lipid bilayers, topogenesis, high propensity to form oligomers, and large-scale conformational transitions during membrane insertion and transport function. Special attention is paid to the polarity of TM protein surfaces described by profiles of dipolarity/polarizability and hydrogen-bonding capacity parameters that match polarity of the lipid environment. Analysis of distributions of Trp resides on surfaces of TM proteins from different biological membranes indicates that interfacial membrane regions with preferential accumulation of Trp indole rings correspond to the outer part of the lipid acyl chain region—between double bonds and carbonyl groups of lipids. These "midpolar" regions are not always symmetric in proteins from natural membranes. We also examined the hydrophobic effect that drives insertion of proteins into lipid bilayer and different free energy contributions to TM protein stability, including attractive van der Waals forces and hydrogen bonds, side-chain conformational entropy, the hydrophobic mismatch, membrane deformations, and specific protein–lipid binding. PMID:24947665
... gov/ency/patientinstructions/000769.htm Brushing Your Child's Teeth To use the sharing features on this page, ... how to brush their teeth on their own. Tooth and Gum Care for Young Children You should ...
Impact of Electroviscosity on the Hydraulic Conductance of the Bordered Pit Membrane: A Theoretical Investigation1[C
Santiago, Michael; Pagay, Vinay; Stroock, Abraham D.
In perfusion experiments, the hydraulic conductance of stem segments () responds to changes in the properties of the perfusate, such as the ionic strength (), pH, and cationic identity. We review the experimental and theoretical work on this phenomenon. We then proceed to explore the hypothesis that electrokinetic effects in the bordered pit membrane (BPM) contribute to this response. In particular, we develop a model based on electroviscosity in which hydraulic conductance of an electrically charged porous membrane varies with the properties of the electrolyte. We use standard electrokinetic theory, coupled with measurements of electrokinetic properties of plant materials from the literature, to determine how the conductance of BPMs, and therefore , may change due to electroviscosity. We predict a nonmonotonic variation of with with a maximum reduction of 18%. We explore how this reduction depends on the characteristics of the sap and features of the BPM, such as pore size, density of chargeable sites, and their dissociation constant. Our predictions are consistent with changes in observed for physiological values of sap and pH. We conclude that electroviscosity is likely responsible, at least partially, for the electrolyte dependence of conductance through pits and that electroviscosity may be strong enough to play an important role in other transport processes in xylem. We conclude by proposing experiments to differentiate the impact of electroviscosity on from that of other proposed mechanisms. PMID:24014573
An insulated-strand fiber brush is provided for a DC motor /generator. The brush is comprised of a plurality of fiber segments which are insulated from one another near the contact surface of a rotor bar. In one embodiment, insulating spacers are fixed to a brush assembly and wear with the fibers, and in another embodiment insulation is provided by a separate shell. (Author)
Correlative light and scanning electron microscopy of the same sections gives new insights into the effects of pectin lyase on bordered pit membranes in Pinus radiata wood.
West, Mark; Vaidya, Alankar; Singh, Adya P
Bordered pits are structures in the cell walls of softwood tracheids which permit the movement of water between adjacent cells. These structures contain a central pit membrane composed of an outer porous ring (margo) and an inner dense and pectin-rich disc (torus). The membrane is overarched on each side by pit borders. Pits may be aspirated, a condition where the torus seals against the pit border, effectively blocking the pathway between cells. In living trees this maintains overall continuity of water conduction in xylem by sealing off tracheids containing air. Drying of timber results in further pit aspiration, which reduces wood permeability to liquid treatment agents such as antifungal chemicals. One possible way to increase permeability is by treating wood with pectin lyase to modify or remove the torus. The effectiveness of this treatment was initially evaluated using light microscopy (LM) of toluidine blue stained wood. Pectic material is coloured pink-magenta with this stain, and loss of this colour after treatment has been interpreted as indicating destruction of the torus. However, correlative light (LM) and scanning electron (SEM) microscopic observations of identical areas of toluidine blue stained sections revealed that many unstained pits had intact but modified tori when viewed with SEM. These observations indicate that LM alone is not sufficient to evaluate the effects of pectin lyase on pit membranes in wood. Combining LM and SEM gives more complete information.
Genetic diversity of the Plasmodium falciparum apical membrane antigen I gene in parasite population from the China-Myanmar border area.
Zhu, Xiaotong; Zhao, Zhenjun; Feng, Yonghui; Li, Peipei; Liu, Fei; Liu, Jun; Yang, Zhaoqing; Yan, Guiyun; Fan, Qi; Cao, Yaming; Cui, Liwang
To investigate the genetic diversity of the Plasmodium falciparum apical membrane antigen 1 (PfAMA1) gene in Southeast Asia, we determined PfAMA1 sequences from 135 field isolates collected from the China-Myanmar border area and compared them with 956 publically available PfAMA1 sequences from seven global P. falciparum populations. This analysis revealed high genetic diversity of PfAMA1 in global P. falciparum populations with a total of 229 haplotypes identified. The genetic diversity of PfAMA1 gene from the China-Myanmar border is not evenly distributed in the different domains of this gene. Sequence diversity in PfAMA1 from the China-Myanmar border is lower than that observed in Thai, African and Oceanian populations, but higher than that in the South American population. This appeared to correlate well with the levels of endemicity of different malaria-endemic regions, where hyperendemic regions favor genetic cross of the parasite isolates and generation of higher genetic diversity. Neutrality tests show significant departure from neutrality in the entire ectodomain and Domain I of PfAMA1 in the China-Myanmar border parasite population. We found evidence supporting a substantial continent-wise genetic structure among P. falciparum populations, with the highest genetic differentiation detected between the China-Myanmar border and the South American populations. Whereas no alleles were unique to a specific region, there were considerable geographical differences in major alleles and their frequencies, highlighting further necessity to include more PfAMA1 alleles in vaccine designs.
Zohns, M.A.; Jenkins, B.M.; Mehlschau, J.J.; Morrison, D.
This paper addresses the design, construction, and evaluation of an almond brush module cutter. The module cutter is one link in a system which processes tree prunings for fuel and fiber. This system includes a modified cotton module builder, a module mover, the cutter, and a tub grinder. An economic analysis of the cutter is presented along with the problems involved in cutting brush modules.
Cavitation during wire brushing
NASA Astrophysics Data System (ADS)
Li, Bo; Zou, Jun; Ji, Chen
In our daily life, brush is often used to scrub the surface of objects, for example, teeth, pots, shoes, pool, etc. And cleaning rust and stripping paint are accomplished using wire brush. Wire brushes also can be used to clean the teeth for large animals, such as horses, crocodiles. By observing brushing process in water, we capture the cavitation phenomenon on the track of moving brush wire. It shows that the cavitation also can affect the surface. In order to take clear and entire pictures of cavity, a simplified model of one stainless steel wire brushing a boss is adopted in our experiment. A transparent organic tank filled with deionized water is used as a view box. And a high speed video camera is used to record the sequences. In experiment, ambient pressure is atmospheric pressure and deionized water temperature is kept at home temperature. An obvious beautiful flabellate cavity zone appears behind the moving steel wire. The fluctuation of pressure near cavity is recorded by a hydrophone. More movies and pictures are used to show the behaviors of cavitation bubble following a restoring wire. Beautiful tracking cavitation bubble cluster is captured and recorded to show.
NASA Technical Reports Server (NTRS)
Hendricks, Robert C.; Wilson, Jack; Wu, Tom; Flower, Ralph
Presented is a study of the use of a set of I.D./O.D. bidirectional press seals to reduce the leakage losses in a wave rotor. Relative to the baseline configuration, data indicate the use of brush seals enhanced wave rotor efficiency from 36 to 45 percent at low leakages (small rotor endwall gap spacings) and from 15 to 33 percent at high leakages (larger endwall gap spacings). These brush seals are capable of sealing positive or negative pressure drops with respect to the axial direction. Surface tribology for these tests suggested little evidence of grooving although the bristles appeared polished.
[Involvement of tissue interaction between cranial neural crest cells, their pathways lateral to the midbrain hindbrain border and the buccopharyngeal membrane in Meckel's cartilage formation in avian embryos].
Imai, Hajime
Cranial neural crest cells migrate to the craniofacial primordia and differentiate into skeletal tissues of the jaw such as Meckel's cartilage. It has not been clearly demonstrated how neural crest cells are committed to differentiate into these tissues. In this study, the conditions that are required for the formation of Meckel's cartilage were investigated. In situ hybridization in chick embryos indicated that Fgf8 and Shh involved in the pattern formation of limb cartilages were expressed in the neural tube of the midbrain-hindbrain border, the buccopharyngeal membrane and the oro-proximal site of the 1st branchial arch (oro-proximal BA1). Cell-tracing with DiI confirmed that the neural crest cells derived from both the posterior midbrain and rhombomere 1 migrated to the buccopharyngeal membrane, which subsequently forms oro-proximal BA1, by passing through the mesenchyme lateral to the midbrain-hindbrain boundary. Based on the above results, we carried out two types of ectopic transplantation experiments by chick-quail chimera The graft of oro-proximal BA1, the complex of epithelium and mesenchyme, formed a Meckel's cartilage-like structure in a self-differentiation manner, whereas neither epithelium only nor mesenchyme formed any elongated cartilage. The ectopic transplant of the buccopharyngeal membrane into the mesenchyme lateral to the neural tube of the mid-hindbrain border in which neural crest cells were migrating formed a Meckel's cartilage-like structure. These results suggest that the cranial neural crest cells derived from the mid-hindbrain region are committed to the cell fate during migration, and receive further signaling to differentiate into Meckel's cartilage in their destination.
NASA Astrophysics Data System (ADS)
Morozov, Oleg G.; Kuznetsov, Artem A.; Morozov, Gennady A.; Nureev, Ilnur I.; Sakhabutdinov, Airat Z.; Faskhutdinov, Lenar M.; Artemev, Vadim I.
Aspects of the paper relate to a wear monitoring system for smart photonic carbon brush. There are many applications in which regular inspection is not feasible because of a number of factors including, for example, time, labor, cost and disruptions due to down time. Thus, there is a need for a system that can monitor the wear of a component while the component is in operation or without having to remove the component from its operational position. We propose a new smart photonic method for characterization of carbon brush wear. It is based on the usage of advantages of the multiplicative response of FBG and LPFG sensors and its double-frequency probing. Additional measuring parameters are the wear rate, the brush temperature, the engine rotation speed, the hangs control, and rotor speed. Sensor is embedded in brush. Firstly the change of sensor length is used to measure wear value and its central wavelength shift for temperature ones. The results of modeling and experiments are presented.
Finch, H.A.
A device for analyzing commutating characteristics of a motor or generator includes a holder for supporting a plurality of probes adjacent a brush of the motor or generator. Measurements of electrical current characteristics of the probes provides information useful in analyzing operation of the machine. Methods for employing a device in accordance with the invention are also disclosed.
Meigs, Richard A.
A fastening device is provided which is a variation on the conventional nut and bolt. The bolt has a longitudinal axis and threading helically affixed thereon along the longitudinal axis. A nut having a bore extending therethrough is provided. The bore of the nut has a greater diameter than the diameter of the bolt so the bolt can extend through the bore. An array of wire bristles are affixed within the bore so as to form a brush. The wire bristles extend inwardly from the bore and are constructed and arranged of the correct size, length and stiffness to guide the bolt within the bore and to restrain the bolt within the bore as required. A variety of applications of the wire brush nut are disclosed, including a bolt capture device and a test rig apparatus.
Meigs, R.A.
A fastening device is provided which is a variation on the conventional nut and bolt. The bolt has a longitudinal axis and threading helically affixed thereon along the longitudinal axis. A nut having a bore extending therethrough is provided. The bore of the nut has a greater diameter than the diameter of the bolt so the bolt can extend through the bore. An array of wire bristles are affixed within the bore so as to form a brush. The wire bristles extend inwardly from the bore and are constructed and arranged of the correct size, length and stiffness to guide the bolt within the bore and to restrain the bolt within the bore as required. A variety of applications of the wire brush nut are disclosed, including a bolt capture device and a test rig apparatus. 13 figs.
Biomolecule-functionalized polymer brushes.
Jiang, Hui; Xu, Fu-Jian
Functional polymer brushes have been utilized extensively for the immobilization of biomolecules, which is of crucial importance for the development of biosensors and biotechnology. Recent progress in polymerization methods, in particular surface-initiated atom transfer radical polymerization (ATRP), has provided a unique means for the design and synthesis of new biomolecule-functionalized polymer brushes. This current review summarizes such recent research activities. The different preparation strategies for biomolecule immobilization through polymer brush spacers are described in detail. The functional groups of the polymer brushes used for biomolecule immobilization include epoxide, carboxylic acid, hydroxyl, aldehyde, and amine groups. The recent research activities indicate that functional polymer brushes become versatile and powerful spacers for immobilization of various biomolecules to maximize their functionalities. This review also demonstrates that surface-initiated ATRP is used more frequently than other polymerization methods in the designs of new biomolecule-functionalized polymer brushes.
Trans-Membrane Area Asymmetry Controls the Shape of Cellular Organelles
Beznoussenko, Galina V.; Pilyugin, Sergei S.; Geerts, Willie J. C.; Kozlov, Michael M.; Burger, Koert N. J.; Luini, Alberto; Derganc, Jure; Mironov, Alexander A.
Membrane organelles often have complicated shapes and differ in their volume, surface area and membrane curvature. The ratio between the surface area of the cytosolic and luminal leaflets (trans-membrane area asymmetry (TAA)) determines the membrane curvature within different sites of the organelle. Thus, the shape of the organelle could be critically dependent on TAA. Here, using mathematical modeling and stereological measurements of TAA during fast transformation of organelle shapes, we present evidence that suggests that when organelle volume and surface area are constant, TAA can regulate transformation of the shape of the Golgi apparatus, endosomal multivesicular bodies, and microvilli of brush borders of kidney epithelial cells. Extraction of membrane curvature by small spheres, such as COPI-dependent vesicles within the Golgi (extraction of positive curvature), or by intraluminal vesicles within endosomes (extraction of negative curvature) controls the shape of these organelles. For instance, Golgi tubulation is critically dependent on the fusion of COPI vesicles with Golgi cisternae, and vice versa, for the extraction of membrane curvature into 50–60 nm vesicles, to induce transformation of Golgi tubules into cisternae. Also, formation of intraluminal ultra-small vesicles after fusion of endosomes allows equilibration of their TAA, volume and surface area. Finally, when microvilli of the brush border are broken into vesicles and microvilli fragments, TAA of these membranes remains the same as TAA of the microvilli. Thus, TAA has a significant role in transformation of organelle shape when other factors remain constant. PMID:25761238
Role of intracellular membranes in transcellular calcium transport
Coleman, J.R.; Young, L.B.; Wade, P.C.
Models can be tested through the use of various agents that affect different portions of the overall mechanism. The calcium ionophore A23187 can be used to increase the rate of calcium entry through the brush border, effectively removing diffusion through the brush border as a rate-limiting step. It would be expected that treatment with A23187 would thus increase the overall rate of calcium transcellular transport. In contrast, chlorpromazine has been shown to inhibit in vitro calcium uptake by Golgi membranes. Consequently if the model is correct, treatment with A23187 and chlorpromazine would tend to raise the cytoplasmic calcium concentration, since the Golgi membrane uptake mechanism would be inhibited, and calcium would accumulate in mitochondria with little or no increase in transcellular transport. Finally, Golgi membranes have been shown to release calcium in response to ATP. Sodium azide inhibits ATP generation and calcium uptake by mitochondria. Thus, treatment with A23187 and soidum azide should cause accumulation of calcium in the Golgi membranes, if the proposed model is correct. The purpose of this investigation was to use coordinated electron probe x-ray microanalysis and transmission electron microscopy to test the response of the intestinal absorptive cells to the agents mentioned.
Developmental organization of the intestinal brush-border cytoskeleton.
Takemura, R; Masaki, T; Hirokawa, N
At the terminal web of chicken intestinal epithelial cell, the actin bundles are cross-linked by a fine filamentous network of actin-associated cross-linkers. Myosin, fodrin, and TW 260/240 have been identified as major components of the cross-linkers. We studied the development of the cross-linkers by quick-freeze, deep-etch electron microscopy, and the expression of cross-linker proteins (myosin, fodrin 240, and TW 260) by immunofluorescence and immunoblotting analysis during the embryogenesis. Microvilli start to form at 5-7 days, and the rootlets begin to elongate at 10 days. At an early stage of the development of the terminal web (13 days), fodrin 240 and a small amount of myosin are expressed, and a few actin-associated cross-linkers are present between the rootlets. However, TW 260 is not expressed at this stage. At an intermediate stage (19 days), the amount of myosin increases, and TW 260 begins to be expressed. The number of cross-linkers associated with the unit length of the rootlets is 24/microns. At the final stage of the terminal web formation (2 days after hatching), the amount of fodrin 240, myosin, and TW 260 is similar to the adult level, and the number of the actin-associated cross-linkers per unit length of the rootlet is 27/microns (approximately 85% of the adult). These results suggest that the synthesis of cross-linker proteins may be intricately regulated to achieve the desired density of cross-linkages at each developmental stage: at early and intermediate stages, sufficient and not an excess of cross-linkages are formed; and at a final stage, a higher complexity of cross-linkages is achieved. In addition, there is a differential expression of the components of the actin-associated cross-linkers: myosin and fodrin could be early components of the cross-linkers involved in the basic stabilization of the terminal web structure, whereas TW 260/240 becomes incorporated later, possibly involved in the stabilization preparatory to the rapid elongation of microvilli, which occurs after the formation of the terminal web.
NASA Technical Reports Server (NTRS)
2006-01-01[figure removed for brevity, see original site] Annotated Version This mosaic was made from frames acquired by the microscopic imager on NASA's Mars Exploration Rover Spirit during Spirit's 1,031 Martian day, or sol, on the red planet (Nov. 27, 2006). It shows a rock target called 'King George Island' after the target was brushed by the rover's rock abrasion tool. The mosaic covers approximately 6 centimeters (2.4 inches) across and shows the granular nature of the rock exposure. The grains are typically about 1 millimeter (.04 inches) wide. Data from the rover's Moessbauer spectrometer provides evidence that they have an enhanced amount of the mineral hematite relative to surrounding soils.
Current developments in brush seals
NASA Technical Reports Server (NTRS)
Loewenthal, Bob
The objective of the brush seal development program is to develop a comprehensive design methodology for brush seals using application requirements from engine manufacturers and experimental characterization of seal design and tribological pairs. The goals are to substantially lower leakage compared to labyrinth seals, seal life consistent with man-rated mission requirements, to investigate single and multiple staged brush seals, temperature up to 1200 F and surface speed up to 900 fps, and pressure drop across the seal of 50 psid. Test results are presented in viewgraph format.
Distribution of Chains in Polymer Brushes Produced by a "Grafting From" Mechanism
Martinez, Andre P.; Carrillo, Jan-Michael Y.; Dobrynin, Andrey V.; ...
The molecular weight and polydispersity of the chains in a polymer brush are critical parameters determining the brush properties. However, the characterization of polymer brushes is hindered by the vanishingly small mass of polymer present in brush layers. In this study, in order to obtain sufficient quantities of polymer for analysis, polymer brushes were grown from high surface area fibrous nylon membranes by ATRP. We synthesized the brushes with varying surface initiator densities, polymerization times, and amounts of sacrificial initiator, then cleaved from the substrate, and analyzed by GPC and NMR. Characterization showed that the surface-grown polymer chains were moremore » polydisperse and had lower average molecular weight compared to solution-grown polymers synthesized concurrently. Furthermore, the molecular weight distribution of the polymer brushes was observed to be bimodal, with a low molecular weight population of chains representing a significant mass fraction of the polymer chains at high surface initiator densities. Moreover, the origin of this low MW polymer fraction is proposed to be the termination of growing chains by recombination during the early stages of polymerization, a mechanism confirmed by molecular dynamics simulations of brush polymerization.« less
Distribution of Chains in Polymer Brushes Produced by a "Grafting From" Mechanism
Martinez, Andre P.; Carrillo, Jan-Michael Y.; Dobrynin, Andrey V.; Adamson, Douglas H.
The molecular weight and polydispersity of the chains in a polymer brush are critical parameters determining the brush properties. However, the characterization of polymer brushes is hindered by the vanishingly small mass of polymer present in brush layers. In this study, in order to obtain sufficient quantities of polymer for analysis, polymer brushes were grown from high surface area fibrous nylon membranes by ATRP. We synthesized the brushes with varying surface initiator densities, polymerization times, and amounts of sacrificial initiator, then cleaved from the substrate, and analyzed by GPC and NMR. Characterization showed that the surface-grown polymer chains were more polydisperse and had lower average molecular weight compared to solution-grown polymers synthesized concurrently. Furthermore, the molecular weight distribution of the polymer brushes was observed to be bimodal, with a low molecular weight population of chains representing a significant mass fraction of the polymer chains at high surface initiator densities. Moreover, the origin of this low MW polymer fraction is proposed to be the termination of growing chains by recombination during the early stages of polymerization, a mechanism confirmed by molecular dynamics simulations of brush polymerization.
NASA Technical Reports Server (NTRS)
In an area north of the city of Al-Basrah, Iraq, which borders Iran, a former wetland has been drained and walled off. Now littered with minefields and gun emplacments, it is a staging area for military exercises. This image was acquired by Landsat 7's Enhanced Thematic Mapper plus (ETM+) sensor on January 24, 2001. This is a false-color composite image made using near-infrared, red, and green wavelengths. The image has also been sharpened using the sensor's panchromatic band. Image provided by the USGS EROS Data Center Satellite Systems Branch
Cryogenic Brush Seal Test Results
NASA Technical Reports Server (NTRS)
Proctor, Margaret P.; Walker, James F.
Brush seals are compliant, contact seals that have long-life, low-leakage characteristics desirable for use in rocket engine turbopumps. 50.8-mm (2.0 inch) diameter brush seals with a nominal initial radial interference of 0.127-mm (0.005 inch) were tested in liquid nitrogen at shaft speeds up to 35,000 rpm and differential pressure loads up to 1.21 MPa (175 psi) per brush. The measured leakage rate of a single brush was 2-3 times less than that measured for a 12-tooth, 0.127-mm (0.005 inch) radial clearance labyrinth seal used as a baseline. Stage effects were studied and it was found that two brush seals with a large separation distance leaked less than two brushes tightly packed together. The maximum measured groove depth on the Inconel 718 rotor was 25.4 (mu)m (0.001 inch) after 4.31 hours of shaft rotation. The Haynes-25 bristles wore approximately 25.4-76.2 (mu)m (0.001-0.003 inch) under the same conditions. Three seal runner coatings, chromium carbide, Teflon impregnated chromium, and zirconium oxide, were tested in liquid hydrogen at 35,000 and 65,000 rpm with separate 50.8 mm diameter brush seals made of Haynes-25 bristles and having a nominal initial radial interference of 129 rpm. Two bare Inconel-718 rotors were also tested as a baseline. The test results revealed significant differences between the wear characteristics of the uncoated and coated seal runners. At both speeds the brush seal with the bare Inconel-718 seal runner exhibited significant bristle wear with excessive material transferring to the runner surface. In contrast, the coated seal runners inhibited the transfer and deposit of bristle material. The chromium carbide coating showed only small quantities of bristle material transferring to its surface. The Teflon impregnated chromium coating also inhibited material transfer and provided some lubrication. This coating, however, is self-sacrificing. The Teflon remained present on the low speed runner, but it was completely removed from the
Effect of mechanical stimulation by tooth brushing on oxygen tension in dog gingiva.
Tanaka, M; Hanioka, T; Ojima, M; Hori, T; Shizukuishi, S
To determine oxygen tension (pO2) in gingival tissue, an oxygen micro-electrode with a membrane-coated Pt needle was inserted into the gingiva of 12 dogs. Teeth were brushed using a modified Bass technique for 10 s under 200 g pressure. pO2 increased and reached a maximum 15 min after brushing, then gradually returned to the baseline. A significant increase in pO2 persisted for approx. 1 h. These findings suggest that short-term stimulation by tooth brushing increases oxygen tension in the gingiva.
Mesoscale modeling of polyelectrolyte brushes with salt.
Ibergay, Cyrille; Malfreyt, Patrice; Tildesley, Dominic J
We report dissipative particle dynamics (DPD) simulations of a polyelectrolyte brush under athermal solvent conditions. The electrostatic interactions are calculated using the particle-particle particle-mesh (PPPM) method with charges distributed over the particles. The polymer beads, counterions, co-ions, and solvent particles are modeled explicitly. The DPD simulations show a dependence of the brush height on the grafting density and the charge fraction that is typical of the nonlinear osmotic brush regime. We report the effect of the addition of salt on the structural properties of the brush. In the case of a polyelectrolyte brush with a high surface coverage, the simulations reproduce the transition between the nonlinear osmotic brush regime where the thickness of the brush is independent of the salt concentration and the salted regime where the brush height decreases weakly with the salt concentration.
Charge transferred in brush discharges
NASA Astrophysics Data System (ADS)
Talarek, M.; Kacprzyk, R.
Electrostatic discharges from surfaces of plastic materials can be a source of ignition, when appear in explosive atmospheres. Incendivity of electrostatic discharges can be estimated using the transferred charge test. In the case of brush discharges not all the energy stored at the tested sample is released and the effective surface charge density (or surface potential) crater is observed after the discharge. Simplified model, enabling calculation of a charge transferred during electrostatic brush discharge, was presented. Comparison of the results obtained from the simplified model and from direct measurements of transferred charge are presented in the paper.
Macroion Interaction at Polyelectrolyte Brush Interfaces
NASA Astrophysics Data System (ADS)
Qu, Chen
The effect of macroions, including synthetic polyelectrolytes, DNA and proteins, on the structure and surface properties of charged polymer thin films remains inadequately understood partially due to the complexity involving the hydrophobic effect and the conformational change of polymeric macroions. In this work, we explore a group of inorganic nanocluster based macroions, hydrophilic polyoxometalates (POMs) of robust nanocluster structure and carrying high surface charges (~ 2-42 negative charges) to investigate their interaction with surface tethered poly-2-vinylpyridine (P2VP) brush-like thin films immersed in aqueous solution. We observe the collapse of swollen P2VP chains by adding POM macroions of increased concentration by AFM, QCM and contact goniometer measurements, in sharp contrast to the increased chain stretching by adding monovalent salts. A careful comparison is made between distinct POMs based on their charge, size and chemical nature. These findings serve as a good reference for theoretical model modification and design of new mesoporous composite membranes.
Fabrication of protein-resistant blend based on PVDF-HFP and amphiphilic brush copolymer made from PMMA and PEGMA
NASA Astrophysics Data System (ADS)
Hwangbo, Kyung-Hee; Kim, Yu-Jeong; Cho, Kuk Young
Polymeric blends provide a facile route to obtaining materials with various synergistic properties arising from the individual components. Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), a hydrophobic polymer, is finding new applications in polymer electrolytes, membranes, and heat-resistant structural materials owing to its high thermal stability, mechanical strength, and weatherability. In this report, blends of PVDF-HFP and polymer brush were prepared with enhanced water uptake and protein resistance, which are important requirements for membranes used in food and biological applications. Polymer brush is composed of poly(methyl methacrylate) main chains, which are miscible with PVDF-HFP, and hydrophilic poly(ethylene glycol) (PEG) brush chains. Incorporation of PEG chains through the polymer brush structure not only enhanced water uptake and protein adsorption resistance but also produced a well-distributed morphology of the blending components through the matrix as evidenced by observation of the morphology after selective extraction of polymer brush from the matrix.
75 FR 13489 - Natural Bristle Paint Brushes and Brush Heads from the People's Republic of China: Final Results...
Federal Register 2010, 2011, 2012, 2013, 2014
... International Trade Administration (A-570-501) Natural Bristle Paint Brushes and Brush Heads from the People's... order on natural bristle paint brushes and brush heads from the People's Republic of China (``PRC...; Natural Bristle Paint Brushes and Brush Heads From the People's Republic of China, 51 FR 5580 (February...
75 FR 44939 - Natural Bristle Paint Brushes and Brush Heads from the People's Republic of China: Final Results...
Federal Register 2010, 2011, 2012, 2013, 2014
... Bristle Paint Brushes and Brush Heads from the People's Republic of China: Final Results of Changed... duty order on natural bristle paint brushes and brush heads from the People's Republic of China (``PRC... antidumping duty order on natural paint brushes and brush head in March 1986. See Antidumping Duty...
Turbine-Driven Pipe-Cleaning Brush
NASA Technical Reports Server (NTRS)
Werlink, Rudy J.; Rowell, David E.
Simple pipe-cleaning device includes small turbine wheel axially connected, by standoff, to circular brush. Turbine wheel turns on hub bearing attached to end of upstream cable. Turbine-and-brush assembly inserted in pipe with cable trailing upstream and brush facing downstream. Water or cleaning solution pumped through pipe. Cable held at upstream end, so it holds turbine and brush in pipe at location to be cleaned. Flow in pipe turns turbine, which turns wheel, producing desired cleaning action. In addition to brushing action, device provides even mixing of cleaning solution in pipe.
Brush Seals for Improved Steam Turbine Performance
NASA Technical Reports Server (NTRS)
Turnquist, Norman; Chupp, Ray; Baily, Fred; Burnett, Mark; Rivas, Flor; Bowsher, Aaron; Crudgington, Peter
GE Energy has retrofitted brush seals into more than 19 operating steam turbines. Brush seals offer superior leakage control compared to labyrinth seals, owing to their compliant nature and ability to maintain very tight clearances to the rotating shaft. Seal designs have been established for steam turbines ranging in size from 12 MW to over 1200 MW, including fossil, nuclear, combined-cycle and industrial applications. Steam turbines present unique design challenges that must be addressed to ensure that the potential performance benefits of brush seals are realized. Brush seals can have important effects on the overall turbine system that must be taken into account to assure reliable operation. Subscale rig tests are instrumental to understanding seal behavior under simulated steam-turbine operating conditions, prior to installing brush seals in the field. This presentation discusses the technical challenges of designing brush seals for steam turbines; subscale testing; performance benefits of brush seals; overall system effects; and field applications.
Planar dipolar polymer brush: field theoretical investigations
NASA Astrophysics Data System (ADS)
Mahalik, Jyoti; Kumar, Rajeev; Sumpter, Bobby
Physical properties of polymer brushes bearing monomers with permanent dipole moments and immersed in a polar solvent are investigated using self-consistent field theory (SCFT). It is found that mismatch between the permanent dipole moments of the monomer and the solvent plays a significant role in determining the height of the polymer brush. Sign as well as magnitude of the mismatch determines the extent of collapse of the polymer brush. The mismatch in the dipole moments also affects the force-distance relations and interpenetration of polymers in opposing planar brushes. In particular, an attractive force between the opposing dipolar brushes is predicted for stronger mismatch parameter. Furthermore, effects of added monovalent salt on the structure of dipolar brushes will also be presented. This investigation highlights the significance of dipolar interactions in affecting the physical properties of polymer brushes. Csmd division, Oak Ridge National Laboratory, 1 Bethel Valley Rd, Oak Ridge, TN 37831, USA.
Nanotribology of charged polymer brushes
NASA Astrophysics Data System (ADS)
Klein, Jacob
Polymers at surfaces, whose modern understanding may be traced back to early work by Sam Edwards1, have become a paradigm for modification of surface properties, both as steric stabilizers and as remarkable boundary lubricants2. Charged polymer brushes are of particular interest, with both technological implications and especially biological relevance where most macromolecules are charged. In the context of biolubrication, relevant in areas from dry eye syndrome to osteoarthritis, charged polymer surface phases and their complexes with other macromolecules may play a central role. The hydration lubrication paradigm, where tenaciously-held yet fluid hydration shells surrounding ions or zwitterions serve as highly-efficient friction-reducing elements, has been invoked to understand the excellent lubrication provided both by ionized3 and by zwitterionic4 brushes. In this talk we describe recent advances in our understanding of the nanotribology of such charged brush systems. We consider interactions between charged end-grafted polymers, and how one may disentangle the steric from the electrostatic surface forces5. We examine the limits of lubrication by ionized brushes, both synthetic and of biological origins, and how highly-hydrated zwitterionic chains may provide extremely effective boundary lubrication6. Finally we describe how the lubrication of articular cartilage in the major joints, a tribosystem presenting some of the greatest challenges and opportunities, may be understood in terms of a supramolecular synergy between charged surface-attached polymers and zwitterionic groups7. Work supported by European Research Council (HydrationLube), Israel Science Foundation (ISF), Petroleum Research Fund of the American Chemical Society, ISF-NSF China Joint Program.
Stimuli-sensitive intrinsically disordered protein brushes
NASA Astrophysics Data System (ADS)
Srinivasan, Nithya; Bhagawati, Maniraj; Ananthanarayanan, Badriprasad; Kumar, Sanjay
Grafting polymers onto surfaces at high density to yield polymer brush coatings is a widely employed strategy to reduce biofouling and interfacial friction. These brushes almost universally feature synthetic polymers, which are often heterogeneous and do not readily allow incorporation of chemical functionalities at precise sites along the constituent chains. To complement these synthetic systems, we introduce a biomimetic, recombinant intrinsically disordered protein that can assemble into an environment-sensitive brush. This macromolecule adopts an extended conformation and can be grafted to solid supports to form oriented protein brushes that swell and collapse dramatically with changes in solution pH and ionic strength. We illustrate the value of sequence specificity by using proteases with mutually orthogonal recognition sites to modulate brush height in situ to predictable values. This study demonstrates that stimuli-responsive brushes can be fabricated from proteins and introduces them as a new class of smart biomaterial building blocks.
Resisting protein adsorption on biodegradable polyester brushes.
Hu, Xinfang; Gorman, Christopher B
The protein adsorption and degradation behaviors of poly(lactic acid), poly(glycolic acid) (PGA) and poly(ε-caprolactone) (PCL) brushes and their co-polymer brushes with oligo(ethylene glycol) (OEG) were studied. Both brush structure and relative amount of OEG and polyester were found to be important to the protein resistance of the brushes. A protein-resisting surface can be fabricated either by using OEG as the top layer of a copolymer brush or by increasing the amount of OEG relative to polyester when using a hydroxyl terminated OEG (OEG-OH) and a methoxy terminated OEG (OEG-OMe) mixture as the substrate layer. The degradation of single polyester brushes and their co-polymer brushes using OEG-OH as a substrate layer or using OEG as a top layer was hindered. This phenomenon was rationalized by the inhibition of the proposed back-biting process as the hydroxy end groups of polyester were blocked by OEG molecules. Among these brushes tested, PGA co-polymer brushes using the methoxy/hydroxyl OEG mixture as the substrate layer proved to be both protein-resistant and degradable due to the relatively large amount of OEG moieties and the good biodegradability of PGA.
Tooth brushing inhibits oral bacteria in dogs.
Watanabe, Kazuhiro; Hayashi, Kotaro; Kijima, Saku; Nonaka, Chie; Yamazoe, Kazuaki
In this study, scaling, polishing and daily tooth brushing were performed in 20 beagle dogs, and the number of oral bacteria was determined using a bacterial counter. The dogs were randomized into the scaling (S), scaling + polishing (SP), scaling + tooth daily brushing (SB) and scaling + polishing + tooth daily brushing (SPB) groups. Samples were collected from the buccal surface of the maxillary fourth premolars of the dogs immediately after scaling and every week thereafter from weeks 1 to 8. Throughout the study, the number of bacteria was significantly lower in the SB and SPB groups compared with the S group. The findings suggest that daily tooth brushing inhibited oral bacterial growth in the dogs.
Nanopatterned polymer brushes: conformation, fabrication and applications
NASA Astrophysics Data System (ADS)
Yu, Qian; Ista, Linnea K.; Gu, Renpeng; Zauscher, Stefan; López, Gabriel P.
Surfaces with end-grafted, nanopatterned polymer brushes that exhibit well-defined feature dimensions and controlled chemical and physical properties provide versatile platforms not only for investigation of nanoscale phenomena at biointerfaces, but also for the development of advanced devices relevant to biotechnology and electronics applications. In this review, we first give a brief introduction of scaling behavior of nanopatterned polymer brushes and then summarize recent progress in fabrication and application of nanopatterned polymer brushes. Specifically, we highlight applications of nanopatterned stimuli-responsive polymer brushes in the areas of biomedicine and biotechnology.
Development of a Brush Seals Program Leading to Ceramic Brush Seals
NASA Technical Reports Server (NTRS)
Hendricks, Robert C.; Flower, Ralph; Howe, Harold
Some events of a U.S. Army/NASA Lewis Research Center brush seals program are reviewed, and the development of ceramic brush seals is described. Some preliminary room-temperature flow data are given, and the results of testing metallic brushes in cryogenic nitrogen are discussed.
Myosin 1b Regulates Amino Acid Transport by Associating Transporters with the Apical Plasma Membrane of Kidney Cells.
Komaba, Shigeru; Coluccio, Lynne M
Amino acid transporters (AATers) in the brush border of the apical plasma membrane (APM) of renal proximal tubule (PT) cells mediate amino acid transport (AAT). We found that the membrane-associated class I myosin myosin 1b (Myo1b) localized at the apical brush border membrane of PTs. In opossum kidney (OK) 3B/2 epithelial cells, which are derived from PTs, expressed rat Myo1b-GFP colocalized in patched microvilli with expressed mouse V5-tagged SIT1 (SIT1-V5), which mediates neutral amino acid transport in OK cells. Lentivirus-mediated delivery of opossum Myo1b-specific shRNA resulted in knockdown (kd) of Myo1b expression, less SIT1-V5 at the APM as determined by localization studies, and a decrease in neutral AAT as determined by radioactive uptake assays. Myo1b kd had no effect on Pi transport or noticeable change in microvilli structure as determined by rhodamine phalloidin staining. The studies are the first to define a physiological role for Myo1b, that of regulating renal AAT by modulating the association of AATers with the APM.
Brush seal numerical simulation: Concepts and advances
NASA Technical Reports Server (NTRS)
Braun, M. J.; Kudriavtsev, V. V.
The development of the brush seal is considered to be most promising among the advanced type seals that are presently in use in the high speed turbomachinery. The brush is usually mounted on the stationary portions of the engine and has direct contact with the rotating element, in the process of limiting the 'unwanted' leakage flows between stages, or various engine cavities. This type of sealing technology is providing high (in comparison with conventional seals) pressure drops due mainly to the high packing density (around 100 bristles/sq mm), and brush compliance with the rotor motions. In the design of modern aerospace turbomachinery leakage flows between the stages must be minimal, thus contributing to the higher efficiency of the engine. Use of the brush seal instead of the labyrinth seal reduces the leakage flow by one order of magnitude. Brush seals also have been found to enhance dynamic performance, cost less, and are lighter than labyrinth seals. Even though industrial brush seals have been successfully developed through extensive experimentation, there is no comprehensive numerical methodology for the design or prediction of their performance. The existing analytical/numerical approaches are based on bulk flow models and do not allow the investigation of the effects of brush morphology (bristle arrangement), or brushes arrangement (number of brushes, spacing between them), on the pressure drops and flow leakage. An increase in the brush seal efficiency is clearly a complex problem that is closely related to the brush geometry and arrangement, and can be solved most likely only by means of a numerically distributed model.
Stratified polymer brushes from microcontact printing of polydopamine initiator on polymer brush surfaces.
Wei, Qiangbing; Yu, Bo; Wang, Xiaolong; Zhou, Feng
Stratified polymer brushes are fabricated using microcontact printing (μCP) of initiator integrated polydopamine (PDOPBr) on polymer brush surfaces and the following surface initiated atom transfer radical polymerization (SI-ATRP). It is found that the surface energy, chemically active groups, and the antifouling ability of the polymer brushes affect transfer efficiency and adhesive stability of the polydopamine film. The stickiness of the PDOPBr pattern on polymer brush surfaces is stable enough to perform continuous μCP and SI-ATRP to prepare stratified polymer brushes with a 3D topography, which have broad applications in cell and protein patterning, biosensors, and hybrid surfaces.
Brush-Wheel Samplers for Planetary Exploration
NASA Technical Reports Server (NTRS)
Rivellini, Tommaso
A report proposes brush-wheel mechanisms for acquiring samples of soils from remote planets. In simplest terms, such a mechanism would contain brush wheels that would be counter-rotated at relatively high speed. The mechanism would be lowered to the ground from a spacecraft or other exploratory vehicle. Upon contact with the ground, the counter-rotating brush wheels would kick soil up into a collection chamber. Thus, in form and function, the mechanism would partly resemble traditional street and carpet sweepers. The main advantage of using of brush wheels (in contradistinction to cutting wheels or other, more complex mechanisms) is that upon encountering soil harder than expected, the brushes could simply deflect and the motor(s) could continue to turn. That is, sufficiently flexible brushes would afford resistance to jamming and to overloading of the motors used to rotate the brushes, and so the motors could be made correspondingly lighter and less power hungry. Of course, one could select the brush stiffnesses and motor torques and speeds for greatest effectiveness in sampling soil of a specific anticipated degree of hardness.
Dual wound dc brush motor gearhead
NASA Technical Reports Server (NTRS)
Henson, Barrie W.
The design requirements, the design, development tests and problems, the qualification and life test and the findings of the strip examination of a dual wound DC brushed motor gearhead are described. It is the only space qualified dual wound dc brushed motor gearhead in Europe.
A Brush Seals Program Modeling and Developments
NASA Technical Reports Server (NTRS)
Hendricks, Robert C.; Flower, Ralph; Howe, Harold
Some events of a U.S. Army/NASA Lewis Research Center brush seals program are reviewed, and the development of ceramic brush seals is described. Some preliminary room-temperature flow data are modeled and compare favorably to the results of Ergun.
Chemopreventive effects of nonsteroidal anti-inflammatory drugs in the membrane lipid composition and fluidity parameters of the 1,2-dimethylhydrazine-induced colon carcinogenesis in rats.
Kanwar, Shailender Singh; Vaiphei, Kim; Nehru, Bimla; Sanyal, Sankar N
Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, celecoxib, and etoricoxib are reported to act as chemopreventive agents in experimental colon cancer induced by 1,2-dimethylhydrazine (DMH) as they are known cyclooxygenase (COX) enzyme inhibitors. To determine whether NSAIDs can also effectively modulate the membrane lipid compositions and the fluidity parameters of colonic brush border membrane, rats were injected subcutaneously (s.c.) with DMH 30 mg/kg body weight per week for 6 weeks. The animals were simultaneously treated with NSAIDs orally at the dose of aspirin, 60 mg/kg body weight; celecoxib, 6 mg/kg body weight; and etoricoxib, 0.6 mg/kg body weight. The animals were sacrificed after 6 weeks of treatments. Brush border membrane was isolated from proximal and distal portions of the colon. Membrane lipids were extracted and analyzed while the fluidity parameters were assessed by steady-state fluorescence polarization technique using the membrane extrinsic fluorophore 1,6-diphenyl-1,3,5-hexatriene (DPH). The translational diffusion was measured by using the excimer formation of pyrene incorporated in the membrane. Colonic mucosal changes in DMH alone and DMH+NSAID treated animals were assessed histologically. The results demonstrate that (a) there is a distinct occurrence of premalignant alterations in DMH-induced colon in the form of multiple plaque lesions (MPLs), which were greatly reduced by the NSAIDs used, (b) the membrane lipid changes in DMH-induced colon were completely restored back, (c) the alterations in membrane fluorescence polarization and the fluidity parameters are partially recovered, particularly with etoricoxib, and (d) the pyrene excimer formation process was completely restored. It may be concluded that the NSAIDs, particularly the coxib group of the drugs (COX-2 selective), are effective in chemoprevention in the DMH-induced colon carcinogenesis and membrane alterations.
Brush cells of rodent gallbladder and stomach epithelia express neurofilaments.
Luciano, Liliana; Groos, Stephanie; Reale, Enrico
It has been suggested that brush cells (BCs), a distinct type of cell occurring in various epithelia of the respiratory and gastrointestinal tracts, may function as receptor cells. The major characteristics of BCs are a prominent brush border and an unusually highly ordered arrangement of cytoskeletal elements (F-actin, microtubules, and intermediate filaments). In this study we aimed to characterize the nature of the intermediate filaments in BCs by light and electron microscopic immunostaining. Gallbladder and stomach specimens from mice and rats, respectively, were fixed in various solutions, embedded either in paraffin or epoxy resin, and processed for immunodetection. Commercially available, well-characterized antibodies against neurofilaments, peripherin, and cytokeratin peptide 18 were used. The polyclonal antiserum cocktail to neurofilaments was applied as a supplement in a double-labeling procedure with anti-actin and anti-cytokeratin 18 antibodies. The results demonstrate that the BCs of both organs express two types of intermediate filaments, i.e., neurofilaments and cytokeratin 18 filaments, and that these have a compartmentalized distribution in the cytoplasm. BCs do not express peripherin. The immunodetection of intermediate filaments distinctive for mature neurons in BCs supports their putative receptor function. The co-expression of neurofilaments and cytokeratins is shown for the first time in healthy tissues.
Liquid Crystalline Phases of Polymer Brushes
NASA Astrophysics Data System (ADS)
Amini, Kiana; Abukhdeir, Nasser; Matsen, Mark
The phase behavior of liquid-crystal polymeric brushes in solvent are investigated using self-consistent field theory. The polymers are modeled as freely-jointed chain consisting of N rigid segments. The isotropic interactions between the polymer and the solvent are treated using the standard Flory-Huggins theory, while the anisotropic liquid-crystalline (LC) interactions between rigid segments are taken into account using the Mayer-Saupe theory. For weak LC interactions, the brush exhibits the conventional parabolic-like profile, while for strong LC interactions, the polymers crystallize into a dense brush with a step-like profile. At intermediate interaction strengths, we find the microphase-segregated phase observed previously for lattice-model calculations. In this phase, the brush exhibits a crystalline layer next to the grafting surface with an external layer similar to the conventional brush. This work was supported by NSERC of Canada.
Construction of 3D micropatterned surfaces with wormlike and superhydrophilic PEG brushes to detect dysfunctional cells.
Hou, Jianwen; Shi, Qiang; Ye, Wei; Fan, Qunfu; Shi, Hengchong; Wong, Shing-Chung; Xu, Xiaodong; Yin, Jinghua
Detection of dysfunctional and apoptotic cells plays an important role in clinical diagnosis and therapy. To develop a portable and user-friendly platform for dysfunctional and aging cell detection, we present a facile method to construct 3D patterns on the surface of styrene-b-(ethylene-co-butylene)-b-styrene elastomer (SEBS) with poly(ethylene glycol) brushes. Normal red blood cells (RBCs) and lysed RBCs (dysfunctional cells) are used as model cells. The strategy is based on the fact that poly(ethylene glycol) brushes tend to interact with phosphatidylserine, which is in the inner leaflet of normal cell membranes but becomes exposed in abnormal or apoptotic cell membranes. We demonstrate that varied patterned surfaces can be obtained by selectively patterning atom transfer radical polymerization (ATRP) initiators on the SEBS surface via an aqueous-based method and growing PEG brushes through surface-initiated atom transfer radical polymerization. The relatively high initiator density and polymerization temperature facilitate formation of PEG brushes in high density, which gives brushes worm-like morphology and superhydrophilic property; the tendency of dysfunctional cells adhered on the patterned surfaces is completely different from well-defined arrays of normal cells on the patterned surfaces, providing a facile method to detect dysfunctional cells effectively. The PEG-patterned surfaces are also applicable to detect apoptotic HeLa cells. The simplicity and easy handling of the described technique shows the potential application in microdiagnostic devices.
Resistance to the Bacillus thuringiensis bioinsecticide in a field population of Plutella xylostella is due to a change in a midgut membrane receptor.
Ferré, J; Real, M D; Van Rie, J; Jansens, S; Peferoen, M
The biochemical mechanism for resistance to Bacillus thuringiensis crystal proteins was studied in a field population of diamondback moths (Plutella xylostella) with a reduced susceptibility to the bioinsecticidal spray. The toxicity and binding characteristics of three crystal proteins [CryIA(b), CryIB, and CryIC] were compared between the field population and a laboratory strain. The field population proved resistant (greater than 200-fold compared with the laboratory strain) to CryIA(b), one of the crystal proteins in the insecticidal formulation. Binding studies showed that the two strains differ in a membrane receptor that recognizes CryIA(b). This crystal protein did not bind to the brush-border membrane of the midgut epithelial cells of the field population, either because of strongly reduced binding affinity or because of the complete absence of the receptor molecule. Both strains proved fully susceptible to the CryIB and CryIC crystal proteins, which were not present in the B. thuringiensis formulation used in the field. Characteristics of CryIB and CryIC binding to brush-border membranes of midgut epithelial cells were virtually identical in the laboratory and the field population.
Binary Polymer Brushes of Strongly Immiscible Polymers.
Chu, Elza; Babar, Tashnia; Bruist, Michael F; Sidorenko, Alexander
The phenomenon of microphase separation is an example of self-assembly in soft matter and has been observed in block copolymers (BCPs) and similar materials (i.e., supramolecular assemblies (SMAs) and homo/block copolymer blends (HBCs)). In this study, we use microphase separation to construct responsive polymer brushes that collapse to generate periodic surfaces. This is achieved by a chemical reaction between the minor block (10%, poly(4-vinylpyridine)) of the block copolymer and a substrate. The major block of polystyrene (PS) forms mosaic-like arrays of grafted patches that are 10-20 nm in size. Depending on the nature of the assembly (SMA, HBC, or neat BCP) and annealing method (exposure to vapors of different solvents or heating above the glass transition temperature), a range of "mosaic" brushes with different parameters can be obtained. Successive grafting of a secondary polymer (polyacrylamide, PAAm) results in the fabrication of binary polymer brushes (BPBs). Upon being exposed to specific selective solvents, BPBs may adopt different conformations. The surface tension and adhesion of the binary brush are governed by the polymer occupying the top stratum. The "mosaic" brush approach allows for a combination of strongly immiscible polymers in one brush. This facilitates substantial contrast in the surface properties upon switching, previously only possible for substrates composed of predetermined nanostructures. We also demonstrate a possible application of such PS/PAAm brushes in a tunable bioadhesion-bioadhesive (PS on top) or nonbioadhesive (PAAm on top) surface as revealed by Escherichia coli bacterial seeding.
BSA adsorption on bimodal PEO brushes.
Bosker, W T E; Iakovlev, P A; Norde, W; Cohen Stuart, M A
BSA adsorption onto bimodal PEO brushes at a solid surface was measured using optical reflectometry. Bimodal brushes consist of long (N=770) and short (N=48) PEO chains and were prepared on PS surfaces, applying mixtures of PS(29)-PEO(48) and PS(37)-PEO(770) block copolymers and using the Langmuir-Blodgett technique. Pi-A isotherms of (mixtures of) the block copolymers were measured to establish the brush regime. The isotherms of PS(29)-PEO(48) show hysteresis between compression and expansion cycles, indicating aggregation of the PS(29)-PEO(48) upon compression. Mixtures of PS(29)-PEO(48) and PS(37)-PEO(770) demonstrate a similar hysteresis effect, which eventually vanishes when the ratio of PS(37)-PEO(770) to PS(29)-PEO(48) is increased. The adsorption of BSA was determined at brushes for which the grafting density of the long PEO chains was varied, while the total grafting density was kept constant. BSA adsorption onto monomodal PEO(48) and PEO(770) brushes was determined for comparison. The BSA adsorption behavior of the bimodal brushes is similar to the adsorption of BSA at PEO(770) monomodal brushes. The maximum of BSA adsorption at low grafting density of PEO(770) can be explained by ternary adsorption, implying an attraction between BSA and PEO. The contribution of primary adsorption to the total adsorbed amount is negligible.
Zwitterionic Poly(amino acid methacrylate) Brushes
A new cysteine-based methacrylic monomer (CysMA) was conveniently synthesized via selective thia-Michael addition of a commercially available methacrylate-acrylate precursor in aqueous solution without recourse to protecting group chemistry. Poly(cysteine methacrylate) (PCysMA) brushes were grown from the surface of silicon wafers by atom-transfer radical polymerization. Brush thicknesses of ca. 27 nm were achieved within 270 min at 20 °C. Each CysMA residue comprises a primary amine and a carboxylic acid. Surface zeta potential and atomic force microscopy (AFM) studies of the pH-responsive PCysMA brushes confirm that they are highly extended either below pH 2 or above pH 9.5, since they possess either cationic or anionic character, respectively. At intermediate pH, PCysMA brushes are zwitterionic. At physiological pH, they exhibit excellent resistance to biofouling and negligible cytotoxicity. PCysMA brushes undergo photodegradation: AFM topographical imaging indicates significant mass loss from the brush layer, while XPS studies confirm that exposure to UV radiation produces surface aldehyde sites that can be subsequently derivatized with amines. UV exposure using a photomask yielded sharp, well-defined micropatterned PCysMA brushes functionalized with aldehyde groups that enable conjugation to green fluorescent protein (GFP). Nanopatterned PCysMA brushes were obtained using interference lithography, and confocal microscopy again confirmed the selective conjugation of GFP. Finally, PCysMA undergoes complex base-catalyzed degradation in alkaline solution, leading to the elimination of several small molecules. However, good long-term chemical stability was observed when PCysMA brushes were immersed in aqueous solution at physiological pH. PMID:24884533
21 CFR 868.5795 - Tracheal tube cleaning brush.
Code of Federal Regulations, 2010 CFR
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Tracheal tube cleaning brush. 868.5795 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5795 Tracheal tube cleaning brush. (a) Identification. A tracheal tube cleaning brush is a device consisting of a brush with plastic bristles...
21 CFR 868.5795 - Tracheal tube cleaning brush.
Code of Federal Regulations, 2011 CFR
... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Tracheal tube cleaning brush. 868.5795 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5795 Tracheal tube cleaning brush. (a) Identification. A tracheal tube cleaning brush is a device consisting of a brush with plastic bristles...
21 CFR 868.5795 - Tracheal tube cleaning brush.
Code of Federal Regulations, 2012 CFR
... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Tracheal tube cleaning brush. 868.5795 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5795 Tracheal tube cleaning brush. (a) Identification. A tracheal tube cleaning brush is a device consisting of a brush with plastic bristles...
21 CFR 868.5795 - Tracheal tube cleaning brush.
Code of Federal Regulations, 2014 CFR
... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Tracheal tube cleaning brush. 868.5795 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5795 Tracheal tube cleaning brush. (a) Identification. A tracheal tube cleaning brush is a device consisting of a brush with plastic bristles...
21 CFR 868.5795 - Tracheal tube cleaning brush.
Code of Federal Regulations, 2013 CFR
... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Tracheal tube cleaning brush. 868.5795 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5795 Tracheal tube cleaning brush. (a) Identification. A tracheal tube cleaning brush is a device consisting of a brush with plastic bristles...
Effectiveness of oscillatory gutter brushes in removing street sweeping waste.
Vanegas-Useche, Libardo V; Abdel-Wahab, Magd M; Parker, Graham A
In this paper, the novel concept of oscillatory gutter brushes of road sweepers is studied experimentally. Their effectiveness in removing different debris types is studied by means of a brushing test rig. The debris types dealt with are medium-size gravel, small and fine particles, wet thin debris, and compacted debris. The performance of two types of brushes, cutting and F128, under diverse operating conditions is investigated. The purpose of the tests is to ascertain whether brush oscillations superimposed onto brush rotation improve sweeping effectiveness. According to the results, brush oscillations seem to be useful for increasing brushing effectiveness in the case of bonded particles and wet thin debris, especially for bonded debris, but they seem to be of no value for other loosed debris. Also, appropriate values of brush penetration, sweeper speed, brush angle of attack, rotational speed, and frequency of brush speed oscillations, for the debris types studied are provided.
75 FR 34097 - Natural Bristle Paint Brushes and Brush Heads From the People's Republic of China: Notice of...
Federal Register 2010, 2011, 2012, 2013, 2014
... International Trade Administration Natural Bristle Paint Brushes and Brush Heads From the People's Republic of... circumstances review to revoke the antidumping duty order on natural bristle paint brushes and brush heads from the People's Republic of China (``PRC''). See generally, Antidumping Duty Order: Natural Bristle...
Plaque removing effect of a convex-shaped brush compared with a conventional flat brush.
Thevissen, E; Quirynen, M; van Steenberghe, D
The plaque-removing effect of a convex-shaped multitufted brush was compared with that of a conventional flat multitufted brush. Two group (five and seven dental students, respectively), well instructed in the modified Bass technique, participated in a blind, splitmouth, crossover study during two consecutive experimental periods of 96 hours of undisturbed plaque growth. After each of these periods, a supervised brushing session was performed, followed by toothpick utilization. Plaque removal was evaluated using the modified Navy Plaque Index (MNPI) and planimetry. A 4% erythrosin solution was used as a disclosing agent. Planimetrically, the flat Oral B brush appeared significantly more effective than the convex shaped Ph brush (P less than 0.001). This superiority was even enhanced after the use of toothpicks (P less than 0.0005). The differences between the brushes, however, were too small to be detected by the less discriminating MNPI. Although it has been claimed that the convex brush could assure approximal plaque control, the results indicate that for the convex-shaped, as well as for the flat brush, an approximal aid is essential for good plaque control. The hypothesis that the design of the convex-shaped brush could facilitate the modified Bass technique for the average patient could not be proven in this study.
Flow visualization in a simulated brush seal
NASA Technical Reports Server (NTRS)
Braun, M. J.; Canacci, V.; Hendricks, R. C.
A method to visualize and characterize the complex flow fields in simulated brush seals is presented. The brush seal configuration was tested in a water and then in an oil tunnel. The visualization procedure revealed typical regions that are rivering, jetting, vortical or lateral flows and exist upstream, downstream or within the seal. Such flows are engendered by variations in fiber void that are spatial and temporal and affect changes in seal leakage and stability. While the effects of interface motion for linear or cylindrical configurations have not been considered herein, it is believed that the observed flow fields characterize flow phenomenology in both circular and linear brush seals. The axial pressure profiles upstream, across and downstream of the brush in the oil tunnel have been measured under a variety of inlet pressure conditions and the ensuing pressure maps are presented and discussed.
Three-Wheel Brush-Wheel Sampler
NASA Technical Reports Server (NTRS)
Duckworth, Geoffrey A.; Liu, Jun; Brown, Mark G.
A new sampler is similar to a common snow blower, but is robust and effective in sample collection. The brush wheels are arranged in a triangle shape, each driven by a brushless DC motor and planetary gearhead embedded in the wheel shaft. Its speed can be varied from 800 - 2,000 rpm, depending on the surface regolith resistance. The sample-collecting flow path, and internal features, are designed based on flow dynamics, and the sample-collecting rates have consistently exceeded the requirement under various conditions that span the range of expected surface properties. The brush-wheel sampler (BWS) is designed so that the flow channel is the main body of the apparatus, and links the brush-wheel assembly to the sample canister. The combination of the three brush wheels, the sample flow path, and the canister location make sample collection, storage, and transfer an easier task.
Tooth brushing inhibits oral bacteria in dogs
WATANABE, Kazuhiro; HAYASHI, Kotaro; KIJIMA, Saku; NONAKA, Chie; YAMAZOE, Kazuaki
In this study, scaling, polishing and daily tooth brushing were performed in 20 beagle dogs, and the number of oral bacteria was determined using a bacterial counter. The dogs were randomized into the scaling (S), scaling + polishing (SP), scaling + tooth daily brushing (SB) and scaling + polishing + tooth daily brushing (SPB) groups. Samples were collected from the buccal surface of the maxillary fourth premolars of the dogs immediately after scaling and every week thereafter from weeks 1 to 8. Throughout the study, the number of bacteria was significantly lower in the SB and SPB groups compared with the S group. The findings suggest that daily tooth brushing inhibited oral bacterial growth in the dogs. PMID:25994486
Preparation of gradient polyacrylate brushes in microchannels.
Lee, Seongyeol; Youm, Sang Gil; Song, Yeari; Yi, Whikum; Sohn, Daewon
Gradient poly(2-hydroxyethyl methacrylate) brushes were synthesized by surface-initiated atom transfer radical polymerization (ATRP) confined within a microfluidic system on a silicon wafer. For ATRP, surface initiator, 11-((2-bromo, 2-methyl) propionyloxy) undecyltrichlorosilane (BUC), was synthesized, and allowed to self-assemble in a monolayer on the Si wafer, as analyzed by XPS to confirm the presence of an ester group of BUC. A solution containing 2-hydroxyethylmethacrylate, Cu catalyst, and bipyridin was allowed to flow in a microchannel and polymerize, resulting in the brushes with a gradient of thickness on the Si wafer. Using ellipsometry and ATR-IR, we verified the gradients of well established brushes on the Si wafer. AFM and contact angle data showed that wettability of the brushes did not exhibit a linear relationship with hydrophilicity.
21 CFR 886.1090 - Haidinger brush.
Code of Federal Regulations, 2012 CFR
... brush is an AC-powered device that provides two conical brushlike images with apexes touching which are... component for measuring macular integrity. (b) Classification. Class I (general controls). The device...
21 CFR 886.1090 - Haidinger brush.
Code of Federal Regulations, 2014 CFR
... brush is an AC-powered device that provides two conical brushlike images with apexes touching which are... component for measuring macular integrity. (b) Classification. Class I (general controls). The device...
21 CFR 886.1090 - Haidinger brush.
Code of Federal Regulations, 2010 CFR
... brush is an AC-powered device that provides two conical brushlike images with apexes touching which are... component for measuring macular integrity. (b) Classification. Class I (general controls). The device...
21 CFR 886.1090 - Haidinger brush.
Code of Federal Regulations, 2011 CFR
... brush is an AC-powered device that provides two conical brushlike images with apexes touching which are... component for measuring macular integrity. (b) Classification. Class I (general controls). The device...
21 CFR 886.1090 - Haidinger brush.
Code of Federal Regulations, 2013 CFR
... brush is an AC-powered device that provides two conical brushlike images with apexes touching which are... component for measuring macular integrity. (b) Classification. Class I (general controls). The device...
Designing of dynamic polyethyleneimine (PEI) brushes on polyurethane (PU) ureteral stents to prevent infections.
Gultekinoglu, Merve; Tunc Sarisozen, Yeliz; Erdogdu, Ceren; Sagiroglu, Meral; Aksoy, Eda Ayse; Oh, Yoo Jin; Hinterdorfer, Peter; Ulubayram, Kezban
Permanent antibacterial coatings have been developed by brush-like polyethyleneimine (PEI) on polyurethane (PU) ureteral stents since bacterial adhesion and biofilm formation with the following encrustation on stent surface limit their long term usage. In order to control or prevent bacterial infections; PEI chains with two different molecular weights (Mn: 1800 or 60,000 Da) were covalently attached on the polyurethane (PU) surface by "grafting to" approach to obtain a brush-like structure. Then, PEI brushes were alkylated with bromohexane to enhance the disruption of bacterial membranes with increasing polycationic character. X-ray Photoelectron and Infrared Spectroscopy investigations confirmed that PEI grafting and alkylation steps were performed successfully. Surface roughness in dry state increased dramatically from 65.8 nm to 277.7 nm and 145.2 nm for short chain PEI and long chain PEI grafted samples, respectively. Both low and high molecular weight PEI grafts exhibited a brush-like structure and potent antibacterial activity by lowering the adherence of Klebsiella pneumonia, Escherichia coli and Proteus mirabilis species up to two orders of magnitude without any cytotoxic effect on L929 and G/G cells. Thus, permanent bactericidal activity was achieved by the contact-active strategy of dynamic PEI brush-like structures on polyurethane ureteral stent.
Water driven turbine/brush pipe cleaner
NASA Technical Reports Server (NTRS)
Werlink, Rudy J. (Inventor)
Assemblies are disclosed for cleaning the inside walls of pipes and tubes. A first embodiment includes a small turbine with angled blades axially mounted on one end of a standoff support. An O-ring for stabilizing the assembly within the pipe is mounted in a groove within the outer ring. A replaceable circular brush is fixedly mounted on the opposite end of the standoff support and can be used for cleaning tubes and pipes of various diameters, lengths and configurations. The turbine, standoff support, and brush spin in unison relative to a hub bearing that is fixedly attached to a wire upstream of the assembly. The nonrotating wire is for retaining the assembly in tension and enabling return of the assembly to the pipe entrance. The assembly is initially placed in the pipe or tube to be cleaned. A pressurized water or solution source is provided at a required flow-rate to propel the assembly through the pipe or tube. The upstream water pressure propels and spins the turbine, standoff support and brush. The rotating brush combined with the solution cleans the inside of the pipe. The solution flows out of the other end of the pipe with the brush rotation controlled by the flow-rate. A second embodiment is similar to the first embodiment but instead includes a circular shaped brush with ring backing mounted in the groove of the exterior ring of the turbine, and also reduces the size of the standoff support or eliminates the standoff support.
Cytohistological discordance on gastrointestinal brushings: Facts unfolded
Tyagi, Ruchita; Kaur, Jagpal; Kaur, Gursheen; Selhi, Pavneet Kaur; Puri, Harpreet Kaur; Sood, Neena
Introduction: Brush cytology is a rapid, cost-effective, and reliable tool to diagnose gastrointestinal tract (GIT) lesions in low-resource settings. Most of the studies on GIT brushings have focused on upper GI lesions. We have studied the diagnostic accuracy of brush cytology in the entire length of GIT and correlated the cytological diagnosis with histopathology. The aim of this study is to study diagnostic utility of brush cytology of GIT lesions in the context of correlation with biopsy and study the factors responsible for cytohistological discordance. Materials and Methods: A retrospective analysis of 101 cases of prebiopsy brush cytology samples of GIT lesions was done over a period of 1 year (June 2014 to May 2015). The cytological diagnosis was compared with histopathological diagnosis and percentage of correlation was calculated. The reasons for discordance were noted and studied. Results: The cytological diagnosis of 79 (78.2%) correlated with histopathological diagnosis. There was discordance in cytological and histological diagnosis in 22 cases (21.8%). Inadequacy of cytological sample and overlap of nuclear atypia caused by regenerative changes and malignancy were significant factors for cytohistological discordance. Conclusion: The diagnostic accuracy of brush cytology can be improved by taking appropriate measures to eliminate factors responsible for fallacies in cytological diagnosis. PMID:27833250
Carrier-mediated concentrative urate transport in rat renal membrane vesicles.
Abramson, R G; Lipkowitz, M S
[2-14C]Urate uptake and efflux were studied in brush border and basolateral membrane vesicles of rat renal cortex that were exposed to 20 microM copper chloride. In the presence of inwardly directed NaCl gradients urate uptake was maintained at levels in excess of chemical equilibrium. Comparison of glucose and chloride uptakes revealed that equilibrium glucose uptake was not affected by copper, but chloride failed to reach equilibrium in copper-exposed vesicles. It is suggested that the persistence of an electrolyte gradient could provide a driving force to raise the concentration of free intravesicular urate above that in the media. Preincubation of vesicles with unlabeled urate failed to diminish uptake of added urate; rather, urate uptake was trans stimulated. Uptake of labeled urate was also significantly accelerated when an outward gradient for unlabeled urate was created. Pyrazinoic and oxonic acids also trans stimulated urate uptake. The demonstration of accelerated homeo- and heteroexchange diffusion indicates that transport is carrier mediated in both brush border and basolateral vesicles. Outwardly directed hydroxyl gradients failed to influence urate uptake in either the presence or absence of copper or NaCl. Thus, this carrier, which is active only in the presence of trace amounts of copper, is distinct from a urate/anion exchanger.
Cold plasma brush generated at atmospheric pressure
Duan Yixiang; Huang, C.; Yu, Q. S.
A cold plasma brush is generated at atmospheric pressure with low power consumption in the level of several watts (as low as 4 W) up to tens of watts (up to 45 W). The plasma can be ignited and sustained in both continuous and pulsed modes with different plasma gases such as argon or helium, but argon was selected as a primary gas for use in this work. The brush-shaped plasma is formed and extended outside of the discharge chamber with typical dimension of 10-15 mm in width and less than 1.0 mm in thickness, which are adjustable by changing the discharge chamber design and operating conditions. The brush-shaped plasma provides some unique features and distinct nonequilibrium plasma characteristics. Temperature measurements using a thermocouple thermometer showed that the gas phase temperatures of the plasma brush are close to room temperature (as low as 42 deg. C) when running with a relatively high gas flow rate of about 3500 ml/min. For an argon plasma brush, the operating voltage from less than 500 V to about 2500 V was tested, with an argon gas flow rate varied from less than 1000 to 3500 ml/min. The cold plasma brush can most efficiently use the discharge power as well as the plasma gas for material and surface treatment. The very low power consumption of such an atmospheric argon plasma brush provides many unique advantages in practical applications including battery-powered operation and use in large-scale applications. Several polymer film samples were tested for surface treatment with the newly developed device, and successful changes of the wettability property from hydrophobic to hydrophilic were achieved within a few seconds.
ERIC Educational Resources Information Center
Kazanjian, Christopher John
Border pedagogy is a multicultural educational approach utilized in multicultural settings to help students understand their histories and experiences and how it affects their identities and cultures. The approach seeks to produce intellectuals that transcend physical and metaphysical boundaries. The goal of border pedagogy is to remove cultural…
Why Border Enforcement Backfired
Massey, Douglas S.; Durand, Jorge; Pren, Karen A.
In this article we undertake a systematic analysis of why border enforcement backfired as a strategy of immigration control in the United States. We argue theoretically that border enforcement emerged as a policy response to a moral panic about the perceived threat of Latino immigration to the United States propounded by self-interested bureaucrats, politicians, and pundits who sought to mobilize political and material resources for their own benefit. The end result was a self-perpetuating cycle of rising enforcement and increased apprehensions that resulted in the militarization of the border in a way that was disconnected from the actual size of the undocumented flow. Using an instrumental variable approach, we show how border militarization affected the behavior of unauthorized migrants and border outcomes to transform undocumented Mexican migration from a circular flow of male workers going to three states into an eleven-million person population of settled families living in 50 states. PMID:27721512
Bidirectional Brush Seals: Post-Test Analysis
NASA Technical Reports Server (NTRS)
Hendricks, Robert C.; Wilson, Jack; Wu, Tom Y.; Flower, Ralph; Mullen, Robert L.
A post-test analysis of a set of inside-diameter/outside-diameter (ID/OD) bidirectional brush seals used in three-port wave rotor tests was undertaken to determine brush bristle and configuration wear, pullout, and rotor coating wear. The results suggest that sharp changes in the pressure profiles were not well reflected in bristle tip configuration patterns or wear. Also, positive-to-negative changes in axial pressure gradients appeared to have little effect on the backing plates. Although the brushes had similar porosities, they had very different unpacked arrays. This difference could explain the departure of experimental data from computational fluid dynamics flow predictions for well-packed arrays at higher pressure drops. The rotor wear led to "car-track" scars (upper and lower wear bands) with a whipped surface between the bands. Those bands may have resulted from bristle stiffening at the fence and gap plates during alternate portions of the rotor cycle. Within the bristle response range the wear surface reflected the pressure distribution effect on bristle motion. No sacrificial metallurgical data were taken. The bristles did wear, with correspondingly more wear on the ID brush configurations than on the OD configurations; the complexity in constructing the ID brush was a factor.
Two-stage eutectic metal brushes
Hsu, John S [Oak Ridge, TN
A two-stage eutectic metal brush assembly having a slip ring rigidly coupled to a shaft, the slip ring being electrically coupled to first voltage polarity. At least one brush is rigidly coupled to a second ring and slidingly engaged to the slip ring. Eutectic metal at least partially fills an annulus between the second ring and a stationary ring. At least one conductor is rigidly coupled to the stationary ring and electrically coupled to a second voltage polarity. Electrical continuity is maintained between the first voltage polarity and the second voltage polarity. Periodic rotational motion is present between the stationary ring and the second ring. Periodic rotational motion is also present between the brush and the slip ring.
Improved molybdenum disulfide-silver motor brushes have extended life
NASA Technical Reports Server (NTRS)
Horton, J. C.; King, H. M.
Motor brushes of proper quantities of molybdenum disulfide and copper or silver are manufactured by sintering techniques. Graphite molds are used. These brushes operate satisfactorily for long periods in normal atmosphere or in a high-vacuum environment.
Design and Testing of High Performance Brushes.
contact drop of anode silver brush during current decrease . Three graphite brush during current decrease contact spota assumed...urn~ aici~ ~'IL~ 'Till lAst' GA.D cTIss lI~ II 1310 295 ~ ~O~IIMI 19-52 ~95* COA~~U 913•IM~ ~~~~~~ 29 ~~ 3.5 ~ lUI oi~~AT,. 10 .c .~~ ~0LT S 9313 ," I
Conductive Nanowires Templated by Molecular Brushes.
Raguzin, Ivan; Stamm, Manfred; Ionov, Leonid
In this paper, we report the fabrication of conductive nanowires using polymer bottle brushes as templates. In our approach, we synthesized poly(2-dimethylamino)ethyl methacrylate methyl iodide quaternary salt brushes by two-step atom transfer radical polymerization, loaded them with palladium salt, and reduced them in order to form metallic nanowires with average lengths and widths of 300 and 20 nm, respectively. The obtained nanowires were deposited between conductive gold pads and were connected to them by sputtering of additional pads to form an electric circuit. We connected the nanowires in an electric circuit and demonstrated that the conductivity of these nanowires is around 100 S·m(-1).
Angiotensin-converting enzyme of the human small intestine. Subunit and quaternary structure, biosynthesis and membrane association.
Naim, H Y
Angiotensin-converting enzyme (ACE) was isolated from detergent-derived extracts of human intestinal brush-border membranes (BBMs) by immunoprecipitation using a monoclonal antibody. Analysis of the immunoprecipitates by SDS/PAGE revealed a polypeptide of apparent M(r) 184,000 under reducing and non-reducing conditions, indicating that ACE does not contain intermolecular disulphide bridges. The quaternary structure of ACE was examined using cross-linking experiments with dithiobis[succinimidylpropionate] (DSP) and density gradient centrifugation on sucrose gradients. Both approaches demonstrated that ACE is assembled in the membrane as a monomer. By contrast, the control glycoprotein aminopeptidase N (ApN) exists as a dimer. Biosynthetic labelling experiments in intestinal tissue explants demonstrated that the 184,000-M(r) protein is generated from a single-polypeptide, mannose-rich precursor of ACE (M(r) 175,000) by modification of the carbohydrate side-chains in the Golgi apparatus. The mode of association of the mature form of the enzyme with BBMs was investigated by hydrophobic labelling of right-side-out brush-border vesicles with the photoactivatable carbene-generating reagent 125I-labelled 3-(trifluoromethyl)-3-(m[formylamino]phenyl)diazirine (125I-labelled TID), followed by treatment with trypsin at dilutions that do not cause substantial degradation of ACE. These studies demonstrated that ACE is associated with the membrane via a hydrophobic segment. Furthermore, treatment of 35S-labelled inside-out membrane vesicles with trypsin revealed that ACE possesses a cytoplasmic tail, and therefore has a transmembraneous orientation. Images Fig. 1. Fig. 2. Fig. 3. Fig. 4. Fig. 5. Fig. 6. PMID:1326943
Bordering on environmental disaster.
Schmidt, C W
Millions of people live on the U.S.-Mexico border, drawn by employment opportunities from industry and agriculture, and booming growth is expected to continue in the coming decades. But the influx of people has long outstripped the capacity of border towns and cities to provide for their citizens, and a large percentage of the population lives in sprawling, underserviced shantytowns. Although investment in environmental infrastructure on both sides has led to improvements, shortages among necessities such as drinking water, wastewater treatment, and solid waste disposal are at crisis levels. In addition, a host of diseases including gastrointestinal infections, asthma, tuberculosis, multiple myeloma, systemic lupus erythematosus, hepatitis A, neural tube defects, and lead poisoning have been linked to environmental conditions on the border. Ongoing binational studies are attempting to define the breadth of the public and environmental health crisis and find ways to help make the border a healthier place. PMID:10903625
Bordering on environmental disaster.
Schmidt, C W
Millions of people live on the U.S.-Mexico border, drawn by employment opportunities from industry and agriculture, and booming growth is expected to continue in the coming decades. But the influx of people has long outstripped the capacity of border towns and cities to provide for their citizens, and a large percentage of the population lives in sprawling, underserviced shantytowns. Although investment in environmental infrastructure on both sides has led to improvements, shortages among necessities such as drinking water, wastewater treatment, and solid waste disposal are at crisis levels. In addition, a host of diseases including gastrointestinal infections, asthma, tuberculosis, multiple myeloma, systemic lupus erythematosus, hepatitis A, neural tube defects, and lead poisoning have been linked to environmental conditions on the border. Ongoing binational studies are attempting to define the breadth of the public and environmental health crisis and find ways to help make the border a healthier place.
75 FR 21347 - Natural Bristle Paint Brushes From China
Federal Register 2010, 2011, 2012, 2013, 2014
... COMMISSION Natural Bristle Paint Brushes From China AGENCY: United States International Trade Commission... paint brushes from China. SUMMARY: The Commission hereby gives notice of the scheduling of a full review... whether revocation of the antidumping duty order on natural bristle paint brushes from China would...
75 FR 18237 - Natural Bristle Paint Brushes From China
Federal Register 2010, 2011, 2012, 2013, 2014
... COMMISSION Natural Bristle Paint Brushes From China AGENCY: United States International Trade Commission... duty order on natural bristle paint brushes from China. SUMMARY: The Commission hereby gives notice... paint brushes from China would be likely to lead to ] continuation or recurrence of material...
21 CFR 884.1100 - Endometrial brush.
Code of Federal Regulations, 2010 CFR
... endometrium (the mucosal lining of the uterus) by brushing its surface. This device is used to study...'s: (i) "Use of International Standard ISO 10993 'Biological Evaluation of Medical Devices—Part I: Evaluation and Testing,' " and (ii) "510(k) Sterility Review Guidance of 2/12/90 (K90-1)," (2) Labeling:...
Charge Transport Properties in Polymer Brushes
NASA Astrophysics Data System (ADS)
Moog, Mark; Tsui, Frank; Vonwald, Ian; You, Wei
Electrical transport properties in poly(3-methyl)thiophene (P3MT) brushes have been studied. The P3MT brushes correspond to a new type of surface-tethered, vertically oriented conjugated molecular wires, sandwiched between two metallic electrodes to form the electrode-molecule-electrode (EME) devices. P3MT is a highly conjugated polymer, a ''workhorse'' material for organic electronics and photonics. The P3MT brushes were grown on ITO surfaces with controlled length (between 2 and 100 nm). The top electrodes were transfer-printed Au films with lateral dimensions between 200 nm and 50 μm. I-V and differential conductance measurements were performed using conductive AFM and 4-terminal techniques. Tunneling and field-emission measurements in EME devices with molecular lengths < 5 nm show HOMO mediated direct hole tunneling with energy barriers of 0.3 and 0.5 eV at the respective interfaces with ITO and Au. The transport properties in longer brushes are indicative of the two quasi-Ohmic interfaces with a characteristic offset in the conductance minimum of 0.12 V biased toward the ITO. Temperature dependent parameters have been examined at various molecular lengths. The drift mobility and the interplay between intra- and intermolecular transport have been investigated.
Multifunctional brushes made from carbon nanotubes
NASA Astrophysics Data System (ADS)
Cao, Anyuan; Veedu, Vinod P.; Li, Xuesong; Yao, Zhaoling; Ghasemi-Nejhad, Mehrdad N.; Ajayan, Pulickel M.
Brushes are common tools for use in industry and our daily life, performing a variety of tasks such as cleaning, scraping, applying and electrical contacts. Typical materials for constructing brush bristles include animal hairs, synthetic polymer fibres and metal wires (see, for example, ref. 1). The performance of these bristles has been limited by the oxidation and degradation of metal wires, poor strength of natural hairs, and low thermal stability of synthetic fibres. Carbon nanotubes, having a typical one-dimensional nanostructure, have excellent mechanical properties, such as high modulus and strength, high elasticity and resilience, thermal conductivity and large surface area (50-200 m2 g-1). Here we construct multifunctional, conductive brushes with carbon nanotube bristles grafted on fibre handles, and demonstrate their several unique tasks such as cleaning of nanoparticles from narrow spaces, coating of the inside of holes, selective chemical adsorption, and as movable electromechanical brush contacts and switches. The nanotube bristles can also be chemically functionalized for selective removal of heavy metal ions.
Chinese Brush Calligraphy Character Retrieval and Learning
ERIC Educational Resources Information Center
Zhuang, Yueting; Zhang, Xiafen; Lu, Weiming; Wu, Fei
Chinese brush calligraphy is a valuable civilization legacy and a high art of scholarship. It is still popular in Chinese banners, newspaper mastheads, university names, and celebration gifts. There are Web sites that try to help people enjoy and learn Chinese calligraphy. However, there lacks advanced services such as content-based retrieval or…
Solvent response of mixed polymer brushes
NASA Astrophysics Data System (ADS)
Gong, Kai; Chapman, Walter G.
We have performed classical density functional theory calculations to study the behavior of mixed polymer brushes tethered to a planar surface. We assume no lateral segregation of the polymer at the grafting density studied and consider an implicit solvent. For a binary mixture of short and long athermal polymer chains, the short chain is compressed while the long chain is stretched compared with corresponding pure polymer chains at the same grafting density, which is consistent with simulation. This results from configurational entropy effects. Furthermore, we add a mean-field interaction for each polymer brush to simulate their different response towards a solvent. The long chain is forced to dislike the solvent more than the short chain. Through the interplay between the solvent effects and configurational entropy effects, a switch of the polymer brush surface (or outer) layer is found with increasing chain length of the long chain. The transition chain length (long chain) increases with increasing the solvent selectivity, and decreases with increasing the grafting density of the long chain. These results can provide guidance for the design of smart materials based on mixed polymer brushes.
Degrafting of polymer brushes from substrates enables insight about the brush structure and facilitates surface patterning
NASA Astrophysics Data System (ADS)
Patil, Rohan; Turgman-Cohen, Salomon; Srogl, Jiri; Kiserow, Douglas; Genzer, Jan
Polymers end-grafted to surfaces or interfaces, commonly referred to as polymer brushes, enable tailoring physico-chemical properties of material surfaces. Many applications of polymer brushes require information about the molecular weight (MW) and grafting density (GD) of polymer brushes. For brushes synthesized by surface initiated polymerization (SIP) determining these attributes was always a challenge. We have developed a simple method of measuring MW and GD of these systems by degrafting SIP from silica-based surfaces by using tetrabutyl ammonium fluoride (TBAF), which attacks selectively Si-O bonds and enables complete degrafting of poly(methyl methacrylate) (PMMA) brushes from silica based substrates without damaging the backbone. The rate of PMMA degrafting decreases with reaction time and depends on the concentration of TBAF, temperature, and the initial GD of the system. The molecular weight distribution of the degrafted PMMA was measured using size exclusion chromatography. The GD was calculated from known MW and dry thickness of the PMMA brush. Spatial patterns of degrafted regions on the substrate can be prepared by either localizing the TBAF to certain regions or by gradually immersing homogeneous samples into TBAF solution.
Measurements of experimental plasma brush behavior in hybrid armatures
NASA Astrophysics Data System (ADS)
Hawke, R. S.; Morrison, J. J.; Susoeff, A. R.
Hybrid armatures used in railguns, consist of a conducting link which is commutated to the rails by plasma brushes. The formation, properties and stability of plasma brushes is important to the performance of the armature. This paper describes a set of experiments in which the effects of varying plasma brush parameters including the initial mass of metal foil used to form the plasma as well as the current were studied. The evolution of the plasma brush from a solid metal foil through its melt, vapor and plasma phase were observed. The resulting brush length and voltage drop were measured. The results of these tests are presented, discussed and compared to numerical simulations.
Sugar uptake by intestinal basolateral membrane vesicles.
Wright, E M; van Os, C H; Mircheff, A K
A high yield of membrane vesicles was prepared from the basolateral surface of rat intestinal cells using an N2 cavitation bomb and density gradient centrifugation. The membranes were enriched 10-fold and were free of significatn contamination by brush border membranes and mitochondria. The rate of D-E114C]glucose and L-E13H]glucose uptake into the vesicle was measured using a rapid filtration technique. D-Glucose equilibrated within the vesicles with a half-time 1/25th that for L-glucose. The stereospecific uptake exhibited saturation kinetics with a Km of approx. 44 mM and a V of approx. 110 nmol . mg-1 min-1 at 10 degrees C. The activation energy for the process was 14 kcal . mol-1 below 15 degrees C and it approached 3 kcal . mol-1 above 22 degrees C. Carrier-mediated uptake was eliminated in the presence of 1 mM HgCl2 and 0.5 mM phloretin. The rate of transport was unaffected by the absence or presence of sodium concentration gradients. Competition studies demonstrated that all sugars with the D-glucose pyranose ring chair conformation shared the transport system, and that, with the possible exception of the -OH group at carbon No. 1, there were no specific requirements for an equatorial -OH group at any position in the pyranose ring. In the case of alpha-methyl-D-glucoside its inability to share the D-glucose transport system may be due to steric hindrance posed by the -OCH3 group rather than by a specific requirement for a free hydroxyl group at the position in the ring. It is concluded that sugars are transported across the basolateral membrane of the intestinal epithelium by a facilitated diffusion system reminiscent of that in human red blood cells.
Toward Infection-Resistant Surfaces: Achieving High Antimicrobial Peptide Potency by Modulating the Functionality of Polymer Brush and Peptide.
Yu, Kai; Lo, Joey C Y; Mei, Yan; Haney, Evan F; Siren, Erika; Kalathottukaren, Manu Thomas; Hancock, Robert E W; Lange, Dirk; Kizhakkedathu, Jayachandran N
Bacterial infection associated with indwelling medical devices and implants is a major clinical issue, and the prevention or treatment of such infections is challenging. Antimicrobial coatings offer a significant step toward addressing this important clinical problem. Antimicrobial coatings based on tethered antimicrobial peptides (AMPs) on hydrophilic polymer brushes have been shown to be one of the most promising strategies to avoid bacterial colonization and have demonstrated broad spectrum activity. Optimal combinations of the functionality of the polymer-brush-tethered AMPs are essential to maintaining long-term AMP activity on the surface. However, there is limited knowledge currently available on this topic. Here we report the development of potent antimicrobial coatings on implant surfaces by elucidating the roles of polymer brush chemistry and peptide structure on the overall antimicrobial activity of the coatings. We screened several combinations of polymer brush coatings and AMPs constructed on nanoparticles, titanium surfaces, and quartz slides on their antimicrobial activity and bacterial adhesion against Gram-positive and Gram-negative bacteria. Highly efficient killing of planktonic bacteria by the antimicrobial coatings on nanoparticle surfaces, as well as potent killing of adhered bacteria in the case of coatings on titanium surfaces, was observed. Remarkably, the antimicrobial activity of AMP-conjugated brush coatings demonstrated a clear dependence on the polymer brush chemistry and peptide structure, and optimization of these parameters is critical to achieving infection-resistant surfaces. By analyzing the interaction of polymer-brush-tethered AMPs with model lipid membranes using circular dichroism spectroscopy, we determined that the polymer brush chemistry has an influence on the extent of secondary structure change of tethered peptides before and after interaction with biomembranes. The peptide structure also has an influence on the density
Lubrication at physiological pressures by polyzwitterionic brushes.
Chen, Meng; Briscoe, Wuge H; Armes, Steven P; Klein, Jacob
The very low sliding friction at natural synovial joints, which have friction coefficients of mu < 0.002 at pressures up to 5 megapascals or more, has to date not been attained in any human-made joints or between model surfaces in aqueous environments. We found that surfaces in water bearing polyzwitterionic brushes that were polymerized directly from the surface can have mu values as low as 0.0004 at pressures as high as 7.5 megapascals. This extreme lubrication is attributed primarily to the strong hydration of the phosphorylcholine-like monomers that make up the robustly attached brushes, and may have relevance to a wide range of human-made aqueous lubrication situations.
Lubrication at Physiological Pressures by Polyzwitterionic Brushes
NASA Astrophysics Data System (ADS)
Chen, Meng; Briscoe, Wuge H.; Armes, Steven P.; Klein, Jacob
The very low sliding friction at natural synovial joints, which have friction coefficients of μ < 0.002 at pressures up to 5 megapascals or more, has to date not been attained in any human-made joints or between model surfaces in aqueous environments. We found that surfaces in water bearing polyzwitterionic brushes that were polymerized directly from the surface can have μ values as low as 0.0004 at pressures as high as 7.5 megapascals. This extreme lubrication is attributed primarily to the strong hydration of the phosphorylcholine-like monomers that make up the robustly attached brushes, and may have relevance to a wide range of human-made aqueous lubrication situations.
Vision, healing brush, and fiber bundles
NASA Astrophysics Data System (ADS)
Georgiev, Todor
The Healing Brush is a tool introduced for the first time in Adobe Photoshop (2002) that removes defects in images by seamless cloning (gradient domain fusion). The Healing Brush algorithms are built on a new mathematical approach that uses Fibre Bundles and Connections to model the representation of images in the visual system. Our mathematical results are derived from first principles of human vision, related to adaptation transforms of von Kries type and Retinex theory. In this paper we present the new result of Healing in arbitrary color space. In addition to supporting image repair and seamless cloning, our approach also produces the exact solution to the problem of high dynamic range compression of17 and can be applied to other image processing algorithms.
Dynamic Polymer Brush at Polymer/Water Interface
NASA Astrophysics Data System (ADS)
Yokoyama, Hideaki; Inoue, Kazuma; Ito, Kohzo; Inutsuka, Manabu; Tanaka, Keiji; Yamada, Norifumi
A layer of polymer chains tethered by one end to a surface is called polymer brush and known to show various unique properties such as anti-fouling. The surface segregation phenomena of copolymers with surface-active blocks should be useful for preparing such a brush layer in spontaneous process. We report hydrophilic polymer brushes formed at the interface between water and polymer by the segregation of amphiphilic diblock copolymers blended in a crosslinked rubbery matrix and call it ``dynamic polymer brush.'' In this system, the hydrophilic block with high surface energy avoids air surface, but segregates to cover the interface between hydrophobic elastomer and water. The structures of the brush layers at D2O/polymer interfaces were measured by neutron reflectivity. The dynamic polymer brush layer surprisingly reached 75% of the contour length of the chain and 2.7 chains/nm2. The brush density was surprisingly comparable to the polymer brush fabricated by the ``grafting-from'' method. We will discuss the dependence of the brush structure on molecular weight and block fraction of amphiphilic block copolymers. Such a surprisingly thick and dense polymer brush were induced by the large enthalpy gain of hydration of hydrophilic block.
Mechanisms for nano particle removal in brush scrubber cleaning
NASA Astrophysics Data System (ADS)
Huang, Yating; Guo, Dan; Lu, Xinchun; Luo, Jianbin
A model describing the nano particle (<100 nm) removal behavior in brush scrubber cleaning is presented based on experiment results and theoretical analysis. The forces on the particles in different situations are analyzed and discussed. The adhesion forces of the van der Waals force, the electrostatic force, the brush load and the static friction between the particle and the wafer are calculated. The contact elastic force, hydrodynamic drag force and friction between the brush and the particle are considered as removal forces and are evaluated. The porous structure and roughness surface of brush material are considered in the hydrodynamic model to describe the brush deformation and the flow field in the cleaning process. The porous structure will result in decrease of hydrodynamic drag force. There are four situations of the particles relative to the brush roughness asperities for which the forces on the particle are different. When the particle is in contact with a brush asperity or on the wafer surface and in a semi-infinite fluid flow field, the particle may be removed by hydrodynamic force and elastic force in the presence of surfactant. When the particle is embedded in the brush asperity, the remove will realized when the friction caused by adhesion between the brush and the particle overcome the adhesion force between particle and wafer surface. The removed particles will be in the flow field or adhered on the brush surface and may redeposit on the wafer surface.
Nuclear pore complex protein sequences determine overall copolymer brush structure and function.
Ando, David; Zandi, Roya; Kim, Yong Woon; Colvin, Michael; Rexach, Michael; Gopinathan, Ajay
The transport of cargo across the nuclear membrane is highly selective and accomplished by a poorly understood mechanism involving hundreds of nucleoporins lining the inside of the nuclear pore complex (NPC). Currently, there is no clear picture of the overall structure formed by this collection of proteins within the pore, primarily due to their disordered nature. We perform coarse-grained simulations of both individual nucleoporins and grafted rings of nups mimicking the in vivo geometry of the NPC and supplement this with polymer brush modeling. Our results indicate that different regions or blocks of an individual NPC protein can have distinctly different forms of disorder and that this property appears to be a conserved functional feature. Furthermore, this block structure at the individual protein level is critical to the formation of a unique higher-order polymer brush architecture that can exist in distinct morphologies depending on the effective interaction energy between the phenylalanine glycine (FG) domains of different nups. Because the interactions between FG domains may be modulated by certain forms of transport factors, our results indicate that transitions between brush morphologies could play an important role in regulating transport across the NPC, suggesting novel forms of gated transport across membrane pores with wide biomimetic applicability.
Steric interactions between two grafted polymer brushes
NASA Astrophysics Data System (ADS)
Ruckenstein, Eli; Li, Buqiang
A lattice model and a generator-matrix method are employed to calculate the interaction force profile between two grafted polymer brushes. The correlation between neighboring bonds and the interdigitation between the two brushes are taken into account. The calculations show that the effect of incorporating the bond correlations is equivalent to an increase in the value of the polymer-solvent interaction parameter when the bond correlations are ignored. The interdigitation between the two brushes decreases the free energy of the system and consequently results in a smaller steric repulsion. A complete interdigitation occurs at a separation close to half the separation between the two plates for which the interaction force is zero. The model is compared with the experimental interaction force profiles for ten systems which involve poly(2-vinylpyridine)-polyisoprene (PVP-PI), poly(2-vinylpyridine)-polystyrene (PVP-PS) block copolymers as well as end-functionalized polystyrenes (PS-X). For most of the systems, the theoretical predictions are in good agreement with experiment. In addition, the present results are compared with the equations proposed by de Gennes, based on the assumption of a step distribution function for the segment density, and by Milner et al., based on the parabolic distribution of the segment density. Both equations neglected interdigitation. It is shown in this paper that the interdigitation is not negligible and that it can decrease by an order of magnitude the repulsive force.
Optical brush: Imaging through permuted probes
Heshmat, Barmak; Lee, Ik Hyun; Raskar, Ramesh
The combination of computational techniques and ultrafast imaging have enabled sensing through unconventional settings such as around corners, and through diffusive media. We exploit time of flight (ToF) measurements to enable a flexible interface for imaging through permuted set of fibers. The fibers are randomly distributed in the scene and are packed on the camera end, thus making a brush-like structure. The scene is illuminated by two off-axis optical pulses. Temporal signatures of fiber tips in the scene are used to localize each fiber. Finally, by combining the position and measured intensity of each fiber, the original input is reconstructed. Unlike conventional fiber bundles with packed set of fibers that are limited by a narrow field of view (FOV), lack of flexibility, and extended coaxial precalibration, the proposed optical brush is flexible and uses off-axis calibration method based on ToF. The enabled brush form can couple to other types of ToF imaging systems. This can impact probe-based applications such as, endoscopy, tomography, and industrial imaging and sensing. PMID:26868954
NASA Astrophysics Data System (ADS)
Ferriere, D.; Rucinski, A.; Jankowski, T.
Establishing a Virtual Sea Border by performing a real-time, satellite-accessible Internet-based bio-metric supported threat assessment of arriving foreign-flagged cargo ships, their management and ownership, their arrival terminal operator and owner, and rewarding proven legitimate operators with an economic incentive for their transparency will simultaneously improve port security and maritime transportation efficiencies.
ERIC Educational Resources Information Center
Langston, Diane
Describes the Hands across the Border Cultural Exchange Program between the communities of Palominas, Arizona, and Arizpe, Sonora, Mexico. An Arizona fifth/sixth grader studies Mexico prior to hosting a visitor from Mexico and enjoying a reciprocal visit to the Arizpe student's home. Highlights the program's unique features and benefits. (DMM)
"Border Sexualities, Border Families in Schools": Queering Education
ERIC Educational Resources Information Center
Ryan, John
This essay reviews Maria Pallotta-Chiarolli's (2010) Lambda Award-winning monograph "Border Sexualities, Border Families in Schools", in which queer and mestizage pedagogies frame a groundbreaking and highly accessible exploration of the issues that sexual border dwellers experience. Her particular focus areas are bisexual "sexually fluid"…
Healthy Border 2020 Embassy Launch
The U.S.-Mexico Border Health Commission launched the Healthy Border 2020 at the Mexican Embassy in the United States on June 24, 2015. This new initiative aims to strengthening what was accomplished on the previous plan of action entitled Healthy Border 2010.
Rotordynamic and Leakage Characteristics of a 4-Stage Brush Seal
AD-A266 012 WL-TR-92-2125 .AP ROTORDYNAMIC AND LEAKAGE CHARACTERISTICS OF A 4-STAGE BRUSH SEAL K. J. CONNER D. W. CHILDS TURBOMACHINERY LABORATORIES...pre-rotation, and seal spacing. Direct damping is shown to increase with running speed; otherwise, the rotordynamic coefficients are relatively...test results for the 4-stage brush seal with an 8-cavity labyrinth showed superior rotordynamics performance for the brush seal; viz., larger values for
Morphological transformations in polymer brushes in binary mixtures: DPD study.
Cheng, Jianli; Vishnyakov, Aleksey; Neimark, Alexander V
Morphological transformations in polymer brushes in a binary mixture of good and bad solvents are studied using dissipative particle dynamics simulations drawing on a characteristic example of polyisoprene natural rubber in an acetone-benzene mixture. A coarse-grained DPD model of this system is built based on the experimental data in the literature. We focus on the transformation of dense, collapsed brush in bad solvent (acetone) to expanded brush solvated in good solvent (benzene) as the concentration of benzene increases. Compared to a sharp globule-to-coil transition observed in individual tethered chains, the collapsed-to-expanded transformation in brushes is found to be gradual without a prominent transition point. The transformation becomes more leveled as the brush density increases. At low densities, the collapsed brush is highly inhomogeneous and patterned into bunches composed of neighboring chains due to favorable polymer-polymer interaction. At high densities, the brush is expanded even in bad solvent due to steric restrictions. In addition, we considered a model system similar to the PINR-acetone-benzene system, but with the interactions between the solvent components worsened to the limit of miscibility. Enhanced contrast between good and bad solvents facilitates absorption of the good solvent by the brush, shifting the collapsed-to-expanded transformation to lower concentrations of good solvent. This effect is especially pronounced for higher brush densities.
Carbazole functionalized isocyanide brushes in heterojunction photovoltaic devices.
Lim, Eunhee; Gao, Feng; Schwartz, Erik; Cornelissen, Jeroen J L M; Nolte, Roeland J M; Rowan, Alan E; Greenham, Neil C; Do, Lee-Mi
In this work, carbazole-containing polyisocyanide (PIACz) brushes were used for photovoltaic devices. A photovoltaic device was fabricated on top of the brushes by spin-coating a suitable acceptor and evaporating an Al cathode. Devices with a poly(N-vinylcarbazole) (PVK) bulk polymer were also prepared for comparison. Interestingly, the brushes showed better photovoltaic characteristics as compared to the blended PVK system. This is attributed to the specific morphologies of the polyisocyanide brushes, which provide a large interfacial area between the donor and acceptor for efficient photogeneration. It was found that the device performance varied according to the molecular size of the incorporated acceptors.
Magnetically Activated Self-Cleaning Membranes
available nanofiltration membranes were modified by growing polymer brushes from the surface of the membrane. Two different polymerization methods have been...dimethylaminopyridine DMF: n,n-dimethylformamide EDC: 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide HEMA: 2-hydroxyethylmethacrylate NF: Nanofiltration NHS... nanofiltration , oily wastewaters, rejection, superparamagnetic nanoparticles Acknowledgements The financial support of the Strategic Environmental Research
Alterations in gut microflora populations and brush border functionality following intra-amniotic daidzein administration
Technology Transfer Automated Retrieval System (TEKTRAN)
Daidzein is an isoflavone found primarily in soybean and various soy-based products such as tofu. In the intestines, daidzein is reductively transformed to its constituent metabolites equol and O-desmethylangolensin. Although the ingestion of daidzein has been associated with marked physiological im...
Angiotensin I Converting Enzyme (Kininase II) of the Brush Border of Human and Swine Intestine.
C-0807, and the American Heart Association Texas Affiliate. LEGENDS Fig. 1. Transmission electron micrograph of final pellet of purified human...Investigator of the American Heart Association . +Presented in part at the 1978 Fall Meeting of the American Heart Association in Dallas, Texas. REFERENCES 1
NASA Astrophysics Data System (ADS)
Simmons, Mike
``Astronomers Without Borders'' is a new global organisational dedicated to furthering understanding and goodwill across national and cultural boundaries using the universal appeal of astronomy and space science. A growing network of affiliate organisations brings together clubs, magazines and other organizations involved in astronomy and space science. Forums, galleries, video conferences and other interactive technologies are used to connect participants around the world. Sharing of resources and direct connections through travel programs are also planned. One project, ``The World at Night'' (TWAN), has become an Special Project of IYA2009. TWAN creates wide-angle images of the night sky in important natural and historic settings around the world, dramatically demonstrating the universal nature and appeal of the night sky. ``Astronomers Without Borders'' is also a leader of the 100 Hours of Astronomy IYA2009 Global Cornerstone Project.
Metrics for border management systems.
Duggan, Ruth Ann
There are as many unique and disparate manifestations of border systems as there are borders to protect. Border Security is a highly complex system analysis problem with global, regional, national, sector, and border element dimensions for land, water, and air domains. The complexity increases with the multiple, and sometimes conflicting, missions for regulating the flow of people and goods across borders, while securing them for national security. These systems include frontier border surveillance, immigration management and customs functions that must operate in a variety of weather, terrain, operational conditions, cultural constraints, and geopolitical contexts. As part of a Laboratory Directed Research and Development Project 08-684 (Year 1), the team developed a reference framework to decompose this complex system into international/regional, national, and border elements levels covering customs, immigration, and border policing functions. This generalized architecture is relevant to both domestic and international borders. As part of year two of this project (09-1204), the team determined relevant relative measures to better understand border management performance. This paper describes those relative metrics and how they can be used to improve border management systems.
Effect of Frequency of Brushing Teeth on Plaque and Calculus Accumulation, and Gingivitis in Dogs.
Harvey, Colin; Serfilippi, Laurie; Barnvos, Donald
The efficacy of brushing the teeth of beagle dogs in a randomized, controlled, blinded study design using a clearly-defined brushing technique was evaluated for 4 brushing frequencies: brushing daily, brushing every other day, brushing weekly and brushing every other week, compared with no brushing in a control group of dogs. All dogs were fed a standard dry kibble diet during the study. Standard plaque, calculus, and gingivitis indices were used to score the teeth. A 'clean tooth' model was used. No gingival or non-gingival lacerations or other signs of injury to oral tissues were found at the end of the 28 day trial period. Brushing more frequently had greater effectiveness in retarding accumulation of plaque and calculus, and reducing the severity of pre-existing gingivitis. Brushing daily or every other day produced statistically significant improved results compared with brushing weekly or every other week. Based on the results of this study, daily brushing is recommended.
Domain III substitution in Bacillus thuringiensis delta-endotoxin CryIA(b) results in superior toxicity for Spodoptera exigua and altered membrane protein recognition.
de Maagd, R A; Kwa, M S; van der Klei, H; Yamamoto, T; Schipper, B; Vlak, J M; Stiekema, W J; Bosch, D
To test our hypothesis that substitution of domain III of Bacillus thuringiensis delta-endotoxin (Cry) proteins might improve toxicity to pest insects, e.g., Spodoptera exigua, in vivo recombination was used to produce a number of cryIA(b)-cryIC hybrid genes. A rapid screening assay was subsequently exploited to select hybrid genes encoding soluble protoxins. Screening of 120 recombinants yielded two different hybrid genes encoding soluble proteins with domains I and II of CryIA(b) and domain III of CryIC. These proteins differed by only one amino acid residue. Both hybrid protoxins gave a protease-resistant toxin upon in vitro activation by trypsin. Bioassays showed that one of these CryIA(b)-CryIC hybrid proteins (H04) was highly toxic to S. exigua compared with the parental CryIA(b) protein and significantly more toxic than CryIC. In semiquantitative binding studies with biotin-labelled toxins and intact brush border membrane vesicles of S. exigua, this domain III substitution appeared not to affect binding-site specificity. However, binding to a 200-kDa protein by CryIA(b) in preparations of solubilized and blotted brush border membrane vesicle proteins was completely abolished by the domain III substitution. A reciprocal hybrid containing domains I and II of CryIC and domain III of CryIA(b) did bind to the 200-kDa protein, confirming that domain III of CryIA(b) was essential for this reaction. These results show that domain III of CryIC protein plays an important role in the level of toxicity to S. exigua, that substitution of domain III may be a powerful tool to increase the repertoire of available active toxins for pest insects, and that domain III is involved in binding to gut epithelium membrane proteins of S. exigua. PMID:8633853
Nuclear Pore Complex Protein Sequences Determine Overall Copolymer Brush Structure and Function?
NASA Astrophysics Data System (ADS)
Ando, David; Kim, Yongwoon; Zandi, Roya; Colvin, Michael; Rexach, Michael; Gopinathan, Ajay
Disordered proteins are an interesting class of unfolded protein biopolymers which are functionally versatile. Their sequences are unconstrained by a sequence-structure relationship, and allow for a wide range of chemical and physical polymer properties. The Nuclear Pore Complex (NPC) contains over one hundred of such proteins (FG nups), which collectively function to regulate the exchange of all materials between the nucleus and cytoplasm. We perform coarse grained simulations of both individual FG nups and grafted rings of nups mimicking the in vivo geometry of the NPC, supplemented with polymer brush modeling. Our results indicate that different regions or ``blocks'' of an individual FG nup can have distinctly different forms of disorder, and that this property appears to be a conserved feature across eukarya. Furthermore, this block structure at the individual protein level is critical to the formation of a unique higher-order polymer brush architecture. Because the interactions between FG nups may be modulated by certain forms of transport factors, our results indicate that transitions between brush morphologies could play an important role in regulating transport across the NPC, suggesting novel forms of gated transport across membrane pores with wide biomimetic applicability.
75 FR 39706 - Natural Bristle Paint Brushes From China
Federal Register 2010, 2011, 2012, 2013, 2014
... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION Natural Bristle Paint Brushes From China AGENCY: United States International Trade Commission... the antidumping duty order on natural bristle paint brushes from China (75 FR 21347, April 23,...
A Critique of the Brushing for Life Programme
ERIC Educational Resources Information Center
Downer, Martin C.; Drugan, Caroline S.; Blinkhorn, Anthony S.
Background and objective: Brushing for Life is intended to promote regular brushing of children's teeth with fluoride toothpaste. The programme is delivered by health visitors who provide toothbrushes, toothpaste and dental health education material at children's 8, 18 and 36 month development checks. The purpose of the present paper was to…
The Effects of a Brushing Procedure on Stereotypical Behavior
ERIC Educational Resources Information Center
Davis, Tonya N.; Durand, Shannon; Chan, Jeffrey M.
In this study we analyzed the effects of a brushing protocol on stereotyped behavior of a young boy with autism. First, a functional analysis was conducted which showed that the participant's stereotypy was maintained by automatic reinforcement. Next, the Wilbarger Protocol, a brushing intervention, was implemented. An ABA design was implemented…
Shear and normal forces in charged polymer brushes
NASA Astrophysics Data System (ADS)
Liao, Qi; Rubinstein, Michael
We present the results of molecular dynamics simulations of steady shear between a pair of opposing charged polymer brushes in the osmotic-brush regime and compare the results with predictions of scaling models. Using the monomer and counterion density profiles, we have verified different regimes in the diagram of states of compressed polyelectrolyte brushes predicted by the scaling model of Zhulina et al[Macromolecules, 2014]. Our simulation results for the normal forces of compressed polyelectrolyte brushes are in excellent agreement with predictions of the scaling model. However, our results for the dependence of the shear forces on the separation between brushes are only in qualitative agreement with the predictions of the scaling model. The dependence of the interpenetration length on the separation of polyelectrolyte brushes exhibits a maximum instead of the plateau predicted by the scaling model for the partially interpenetrated brushes. Our simulation results confirm that our implicit solvent simulations of polyelectrolyte brushes that ignore hydrodynamics interaction are in agreement with the scaling predictions that include hydrodynamic interaction because of screening of hydrodynamic interaction and long range electrostatic interactions on the correlation length scale.
16 CFR Figure 9 to Part 1610 - Brushing Device Template
Code of Federal Regulations, 2012 CFR
... 16 Commercial Practices 2 2012-01-01 2012-01-01 false Brushing Device Template 9 Figure 9 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 9 Figure 9 to Part 1610—Brushing...
16 CFR Figure 7 to Part 1610 - Brushing Device
Code of Federal Regulations, 2013 CFR
... 16 Commercial Practices 2 2013-01-01 2013-01-01 false Brushing Device 7 Figure 7 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt. 1610, Fig. 7 Figure 7 to Part 1610—Brushing Device ER25MR08.006...
16 CFR Figure 7 to Part 1610 - Brushing Device
Code of Federal Regulations, 2010 CFR
... 16 Commercial Practices 2 2010-01-01 2010-01-01 false Brushing Device 7 Figure 7 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 7 Figure 7 to Part 1610—Brushing Device ER25MR08.006...
16 CFR Figure 7 to Part 1610 - Brushing Device
Code of Federal Regulations, 2012 CFR
... 16 Commercial Practices 2 2012-01-01 2012-01-01 false Brushing Device 7 Figure 7 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 7 Figure 7 to Part 1610—Brushing Device ER25MR08.006...
16 CFR Figure 9 to Part 1610 - Brushing Device Template
Code of Federal Regulations, 2010 CFR
... 16 Commercial Practices 2 2010-01-01 2010-01-01 false Brushing Device Template 9 Figure 9 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 9 Figure 9 to Part 1610—Brushing...
16 CFR Figure 7 to Part 1610 - Brushing Device
Code of Federal Regulations, 2014 CFR
... 16 Commercial Practices 2 2014-01-01 2014-01-01 false Brushing Device 7 Figure 7 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt. 1610, Fig. 7 Figure 7 to Part 1610—Brushing Device ER25MR08.006...
16 CFR Figure 8 to Part 1610 - Brush
Code of Federal Regulations, 2011 CFR
... 16 Commercial Practices 2 2011-01-01 2011-01-01 false Brush 8 Figure 8 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 8 Figure 8 to Part 1610—Brush ER25MR08.007...
16 CFR Figure 9 to Part 1610 - Brushing Device Template
Code of Federal Regulations, 2014 CFR
... 16 Commercial Practices 2 2014-01-01 2014-01-01 false Brushing Device Template 9 Figure 9 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt. 1610, Fig. 9 Figure 9 to Part 1610—Brushing...
16 CFR Figure 9 to Part 1610 - Brushing Device Template
Code of Federal Regulations, 2013 CFR
... 16 Commercial Practices 2 2013-01-01 2013-01-01 false Brushing Device Template 9 Figure 9 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt. 1610, Fig. 9 Figure 9 to Part 1610—Brushing...
16 CFR Figure 8 to Part 1610 - Brush
Code of Federal Regulations, 2012 CFR
... 16 Commercial Practices 2 2012-01-01 2012-01-01 false Brush 8 Figure 8 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 8 Figure 8 to Part 1610—Brush ER25MR08.007...
16 CFR Figure 8 to Part 1610 - Brush
Code of Federal Regulations, 2014 CFR
... 16 Commercial Practices 2 2014-01-01 2014-01-01 false Brush 8 Figure 8 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt. 1610, Fig. 8 Figure 8 to Part 1610—Brush ER25MR08.007...
16 CFR Figure 8 to Part 1610 - Brush
Code of Federal Regulations, 2013 CFR
... 16 Commercial Practices 2 2013-01-01 2013-01-01 false Brush 8 Figure 8 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt. 1610, Fig. 8 Figure 8 to Part 1610—Brush ER25MR08.007...
16 CFR Figure 9 to Part 1610 - Brushing Device Template
Code of Federal Regulations, 2011 CFR
... 16 Commercial Practices 2 2011-01-01 2011-01-01 false Brushing Device Template 9 Figure 9 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 9 Figure 9 to Part 1610—Brushing...
16 CFR Figure 7 to Part 1610 - Brushing Device
Code of Federal Regulations, 2011 CFR
... 16 Commercial Practices 2 2011-01-01 2011-01-01 false Brushing Device 7 Figure 7 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 7 Figure 7 to Part 1610—Brushing Device ER25MR08.006...
16 CFR Figure 8 to Part 1610 - Brush
Code of Federal Regulations, 2010 CFR
... 16 Commercial Practices 2 2010-01-01 2010-01-01 false Brush 8 Figure 8 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 8 Figure 8 to Part 1610—Brush ER25MR08.007...
JTAGG II Brush Seal Test Results
NASA Technical Reports Server (NTRS)
Arora, Gul K.; Proctor, Margaret P.
The Tri-services JTAGG 2 engine uses two identical brush seals, in tandem, located aft of the high pressure compressor. The engine operating conditions, at intermediate rated power (IRP), for this seal are estimated to be 50,000 rpm (899 ft/sec) speed, 175 psid air to air pressure differential and 1200 F air temperature. The testing was comprised of static air leakage, performance, seal offset, rotor run out tests and a 50 hr endurance test in the NASA Lewis seal rig. Based on the test results, it is concluded that the brush seal design should be able to meet the air leakage flow factor goal of less than 0.004 for the engine IRP operating conditions. For the 4.12 in. i.d. labyrinth seal, 0.005 in. typical radial clearance, at the JTAGG 2 operating conditions, the leakage flow factor is 0.007. The long term seal life can not be predicted accurately due to the limited endurance testing of 50 hr. However, based on the excellent condition of the test seal and rotor after 50 hr of testing, it is anticipated that the seals should easily meet the JTAGG 2 engine test requirement.
The hydration properties of carboxybetaine zwitterion brushes.
Du, Hongbo; Qian, Xianghong
Combined quantum mechanical calculations and classical molecular dynamics simulations were conducted to investigate the hydration properties of carboxybetaine zwitterion brushes with varying separation distances between the quaternary ammonium cation and carboxylic anion. The brushes consist of zwitterion trimers and are investigated to mimic interacting zwitterion chains grafted on a substrate as well as polymers with interacting zwitterion side chains. Our results show that the values of both positive and negative charges, their separation distances as well as chain interactions appear to play a critical role in the hydration properties of the zwitterions. The overall hydration property of these zwitterions is dictated by the competition between the strong hydration of the charged groups and the dehydration of the hydrocarbon chains. The strongest hydration occurs when the -CH2- unit in the hydrocarbon chain reaches 6-8 for these trimers. Further increase in the hydrocarbon chain length to 10-14 leads to significant and sudden dehydration of the trimers. The water structure and the water residence time surrounding the zwitterions also demonstrate substantial alteration at this length scale. This hydrophilic-to-hydrophobic transition is induced by the hydrophobic interactions of the trimer chains. Our hydration results could explain the observed trend of the superiority of the methylated carbohydrates and poly(ethylene glycol) as antifouling materials compared to corresponding hydroxyl-terminated compounds.
Atmospheric Science Without Borders
NASA Astrophysics Data System (ADS)
Panday, Arnico; Praveen, Ps; Adhikary, Bhupesh; Bhave, Prakash; Surapipith, Vanisa; Pradhan, Bidya; Karki, Anita; Ghimire, Shreta; Thapa, Alpha; Shrestha, Sujan
The Indo-Gangetic Plains (IGP) in northern South Asia are among the most polluted and most densely populated places in the world, and they are upwind of vulnerable ecosystems in the Himalaya mountains. They are also fragmented across 5 countries between which movement of people, data, instruments and scientific understanding have been very limited. ICIMOD's Atmosphere Initiative has for the past three years been working on filling data gaps in the region, while facilitating collaborations across borders. It has established several atmospheric observatories at low and mid elevations in Bhutan and Nepal that provide new data on the inflow of pollutants from the IGP towards the mountains, as well as quantify the effects of local emissions on air quality in mountain cities. EGU will be the first international conference where these data will be presented. ICIMOD is in the process of setting up data servers through which data from the region will be shared with scientists and the general public across borders. Meanwhile, to promote cross-border collaboration among scientists in the region, while addressing an atmospheric phenomenon that affects the lives of the several hundred million people, ICIMOD' Atmosphere Initiative has been coordinating an interdisciplinary multi-year study of persistent winter fog over the Indo-Gangetic Plains, with participation by researchers from Pakistan, India, China, Nepal, Bhutan and Bangladesh. Using a combination of in-situ measurements and sample collection, remote sensing, modeling and community based research, the researchers are studying how changing moisture availability and air pollution have led to increases in fog frequency and duration, as well as the fog's impacts on local communities and energy demand that may affect air pollution emissions. Preliminary results of the Winter 2015-2016 field campaign will be shown.
Simple effective thickness model for circular brush seals
NASA Astrophysics Data System (ADS)
Dowler, Constance A.; Chupp, Raymond E.; Holle, Glenn F.
Brush seals are being investigated as replacements for some of the labyrinth seals in gas turbine engines. A relatively simple flow model approach has been presented to generalize brush seal leakage throughout the range of test and application environments. The model uses a single parameter, effective brush thickness, to correlate flow through the seal. A revision to the flow model is presented in this paper to account for seal curvature, which is especially important for smaller diameter brush seals. The revised model has been applied to leakage flow data from five sources. The results demonstrate the utility of the flow model approach in correlating the performance of brush seals having different design geometries. The revised model is shown to effectively account for the effect of seal curvature.
NASA Astrophysics Data System (ADS)
Flatten, Amy
Physicists transcend national boundaries, ethnic differences, and scientific disciplines to address globally shared problems and questions. This talk will highlight how scientists have collaborated across borders - both geographic and scientific - to achieve ground-breaking discoveries through international scientific cooperation. The speaker also will address how international collaborations will be even more crucial for addressing future challenges faced by the physics community, such as building large-scale research facilities, strengthening scientific capacity in developing countries, fostering ''science for diplomacy'' in times of political tensions and other critical issues.
Computer Simulations of Bottle Brushes: From Melts to Soft Networks
Cao, Zhen; Carrillo, Jan-Michael Y.; Sheiko, Sergei S.; ...
We use a combination of Molecular dynamics simulations and analytical calculations, and study dens bottle-brush systems in a melt and network State. Analysis of our simulation results shows that bottle-brush macromolecules in melt behave as ideal chains with effective Kuhn length bK. Simulations show that the bottle-brush-induced bending rigidity is due to an entropy decrease caused by redistribution of the side chains upon backbone bending. The Kuhn length of the bottle:brushes increases with increasing the side-chain degree of polymerization nsc as bK proportional to nsc0.46. Moreover, this model of bottle brush macromolecules is extended to describe mechanical properties of bottlemore » brush networks in linear and nonlinear deformation regimes. In the linear deformation regime, the network shear modulus scales with the degree of polymerization of the side chains as G0 proportional to (nsc + 1)-1 as long as the ratio of the Kuhn length, bK, to the size of the fully extended bottle-brush backbone between cross-links, R-max, is smaller than unity, bK/Rmax << 1. Bottle-brush networks With bK/Rmax proportional to 1 demonstrate behavior similar to that of networks Of semiflexible chains with G0 proportional to nsc-0.5. Finally, in the nonlinear network deformation regime, the deformation-dependent shear modulus is a universal function of the first strain invariant I1 and bottle-brush backbone deformation ratio beta describing stretching ability of the bottle-brush backbone between cross-links.« less
Computer Simulations of Bottle Brushes: From Melts to Soft Networks
Cao, Zhen; Carrillo, Jan-Michael Y.; Sheiko, Sergei S.; Dobrynin, Andrey V.
We use a combination of Molecular dynamics simulations and analytical calculations, and study dens bottle-brush systems in a melt and network State. Analysis of our simulation results shows that bottle-brush macromolecules in melt behave as ideal chains with effective Kuhn length bK. Simulations show that the bottle-brush-induced bending rigidity is due to an entropy decrease caused by redistribution of the side chains upon backbone bending. The Kuhn length of the bottle:brushes increases with increasing the side-chain degree of polymerization nsc as bK proportional to nsc0.46. Moreover, this model of bottle brush macromolecules is extended to describe mechanical properties of bottle brush networks in linear and nonlinear deformation regimes. In the linear deformation regime, the network shear modulus scales with the degree of polymerization of the side chains as G0 proportional to (nsc + 1)-1 as long as the ratio of the Kuhn length, bK, to the size of the fully extended bottle-brush backbone between cross-links, R-max, is smaller than unity, bK/Rmax << 1. Bottle-brush networks With bK/Rmax proportional to 1 demonstrate behavior similar to that of networks Of semiflexible chains with G0 proportional to nsc-0.5. Finally, in the nonlinear network deformation regime, the deformation-dependent shear modulus is a universal function of the first strain invariant I1 and bottle-brush backbone deformation ratio beta describing stretching ability of the bottle-brush backbone between cross-links.
Potential applications of oral brush cytology with liquid-based technology: results from a cohort of normal oral mucosa.
Kujan, Omar; Desai, Mina; Sargent, Alexandra; Bailey, Andrew; Turner, Andrew; Sloan, Philip
Fifty healthy volunteers were studied to assess the potential applications of oral brush sampling using liquid-based cytology. Three specimens from the buccal mucosa and lateral border of tongue were collected from each subject by using cervical brushes and brooms. The brush was immersed in a preservative fluid. The sample in the preservative fluid was processed according to the manufacturer's directions (SurePath, UK). Slides were stained by the Papanicolaou method and assessed for squamous cell adequacy by the same criteria used for cervical cytology screening. Immunocytochemical staining for FHIT (Fragile Histidine Triad) was applied in liquid-based preparations following the streptavidin-biotin-peroxidase method. Human papillomavirus (HPV) detection was performed using the Hybrid Capture 2 assay (Digene) and the PCR-based Roche AMPLICOR HPV Test. LBC preparation slides showed good sample preservation, specimen adequacy and visualization of cell morphology. Interestingly, nine cases showed borderline cytological abnormalities from apparently normal oral mucosa. All cases showed good quality positive FHIT immunoreactivity staining. All studied cases were high-risk HPV negative using HC2 assay method. However, the AMPLICOR Roche Test detected four samples with positive results for high-risk HPVs. Liquid-based cytology has potential as a screening tool for oral cancer and precancer. The method may also have applications for research and practice in the field of oral cancer and precancer. However a special custom-designed oral cytobrush is required.
EUV mask black border evolution
NASA Astrophysics Data System (ADS)
Turley, Christina; Bonam, Ravi; Gallagher, Emily; Grohs, Jonathan; Kagawa, Masayuki; Kindt, Louis; Narita, Eisuke; Nash, Steven; Sakamoto, Yoshifumi
The black border is a frame created by removing all the multilayers on the EUV mask in the region around the chip. It is created to prevent exposure of adjacent fields when printing an EUV mask on a wafer. Papers have documented its effectiveness. As the technology transitions into manufacturing, the black border must be optimized from the initial mask making process through its life. In this work, the black border is evaluated in three stages: the black border during fabrication, the final sidewall profile, and extended lifetime studies. This work evaluates the black border through simulations and physical experiments. The simulations address concerns for defects and sidewall profiles. The physical experiments test the current black border process. Three masks are used: one mask to test how black border affects the image placement of features on mask and two masks to test how the multilayers change through extended cleans. Data incorporated in this study includes: registration, reflectivity, multilayer structure images and simulated wafer effects. By evaluating the black border from both a mask making perspective and a lifetime perspective, we are able to characterize how the structure evolves. The mask data and simulations together predict the performance of the black border and its ability to maintain critical dimensions on wafer. In this paper we explore what mask changes occur and how they will affect mask use.
Sterilization effects of atmospheric cold plasma brush
NASA Astrophysics Data System (ADS)
Yu, Q. S.; Huang, C.; Hsieh, F.-H.; Huff, H.; Duan, Yixiang
This study investigated the sterilization effects of a brush-shaped plasma created at one atmospheric pressure. A population of 1.0×104-1.0×105 Escherichia coli or Micrococcus luteus bacteria was seeded in filter paper media and then subjected to Ar and/or Ar +O2 plasmas. A complete kill of the Micrococcus luteus required about 3 min argon plasma exposures. With oxygen addition into the argon plasma gas streams, a complete kill of the bacteria needed only less than 1 min plasma exposure for Micrococcus luteus and about 2 min exposure for Escherichia coli. The plasma treatment effects on the different bacteria cell structures were examined using scanning electron microscopy.
Dispersing brush mice prefer habitat like home
Mabry, Karen E; Stamps, Judy A
During natal dispersal, young animals leave their natal area and search for a new area to live. In species in which individuals inhabit different types of habitat, experience with a natal habitat may increase the probability that a disperser will select the same type of habitat post-dispersal (natal habitat preference induction or NHPI). Despite considerable interest in the ecological and the evolutionary implications of NHPI, we lack empirical evidence that it occurs in nature. Here we show that dispersing brush mice (Peromyscus boylii) are more likely to search and settle within their natal habitat type than expected based on habitat availability. These results document the occurrence of NHPI in nature and highlight the relevance of experience-generated habitat preferences for ecological and evolutionary processes. PMID:18077253
Sterilization effects of atmospheric cold plasma brush
Yu, Q.S.; Huang, C.; Hsieh, F.-H.; Huff, H.; Duan Yixiang
This study investigated the sterilization effects of a brush-shaped plasma created at one atmospheric pressure. A population of 1.0x10{sup 4}-1.0x10{sup 5} Escherichia coli or Micrococcus luteus bacteria was seeded in filter paper media and then subjected to Ar and/or Ar+O{sub 2} plasmas. A complete kill of the Micrococcus luteus required about 3 min argon plasma exposures. With oxygen addition into the argon plasma gas streams, a complete kill of the bacteria needed only less than 1 min plasma exposure for Micrococcus luteus and about 2 min exposure for Escherichia coli. The plasma treatment effects on the different bacteria cell structures were examined using scanning electron microscopy.
CO₂-lased enamel microhardness after brushing and cariogenic challenge.
Corrêa-Afonso, Alessandra Marques; Bachmann, Luciano; de Almeida, Cíntia Guimarães; Dibb, Regina Guenka Palma; Corona, Silmara Aparecida Milori; Borsatto, Maria Cristina
This study aimed to assess how the wear that brushing promotes affects CO₂ laser-irradiated enamel microhardness after cariogenic challenge in vitro. Forty fragments measuring 4 × 4 mm were randomly assigned to four groups according to the enamel surface treatment: G1-control, G2-CO₂-laser irradiation, G3-brushing, and G4-CO₂ laser irradiation + brushing. A laser device emitting at 10.6 μm was used (power=0.5 W, energy per pulse=0.05 mJ, and frequency=10 kHz). Specimens belonging to groups G3 and G4 were brushed (80,000 strokes) with a brushing simulator using toothpaste. Next, the samples were challenged with acid: the specimens were immersed in demineralizing and remineralizing solutions for 8 days. The acid resistance of enamel was evaluated by cross-sectional microhardness tests. The area under the curve (KHN × μm) was calculated. Analysis of variance (ANOVA) one-away and Fisher's test were performed for the statistical analysis (p<0.05). Group G2 specimens (31,185 ± 4706) were statistically different from specimens belonging to groups G1 (26,723 ± 2446), G3 (28,194 ± 1376), and G4 (28,207 ± 2234), which were statistically similar. The brushing time used in the present study probably wore the CO₂-lased enamel, so demineralization could not be prevented in the brushed group.
Brushing abrasion of luting cements under neutral and acidic conditions.
Buchalla, W; Attin, T; Hellwig, E
Four resin based materials (Compolute Aplicap, ESPE; Variolink Ultra, Vivadent; C&B Metabond, Parkell and Panavia 21, Kuraray), two carboxylate cements (Poly-F Plus, Dentsply DeTrey and Durelon Maxicap, ESPE), two glass-ionomer cements (Fuji I, GC and Ketac-Cem Aplicap, ESPE), one resin-modified glass ionomer cement (Vitremer, 3M) one polyacid-modified resin composite (Dyract Cem, Dentsply DeTrey) and one zinc phosphate cement (Harvard, Richter & Hoffmann) were investigated according to their brushing resistance after storage in neutral and acidic buffer solutions. For this purpose 24 cylindrical acrylic molds were each filled with the materials. After hardening, the samples were stored for seven days in 100% relative humidity and at 37 degrees C. Subsequently, they were ground flat and polished. Then each specimen was covered with an adhesive tape leaving a 4 mm wide window on the cement surface. Twelve samples of each material were stored for 24 hours in a buffer solution with a pH of 6.8. The remaining 12 samples were placed in a buffer with a pH of 3.0. All specimens were then subjected to a three media brushing abrasion (2,000 strokes) in an automatic brushing machine. Storage and brushing were performed three times. After 6,000 brushing strokes per specimen, the tape was removed. Brushing abrasion was measured with a computerized laser profilometer and statistically analyzed with ANOVA and Tukey's Standardized Range Test (p < or = 0.05). The highest brushing abrasion was found for the two carboxylate cements. The lowest brushing abrasion was found for one resin based material, Compolute Aplicap. With the exception of three resin-based materials, a lower pH led to a higher brushing abrasion.
Brush Lettering II; Commercial and Advertising Art--Intermediate: 9185.01.
ERIC Educational Resources Information Center
Dade County Public Schools, Miami, FL.
This course outline has been prepared as a guide to help the student gain mastery in the proper brush techniques required for proficiency in brush lettering. The skills of Brush Lettering 1 are a prerequisite. Consisting of 135 clock hours, the course prepares the student to understand brush lettering for poster production and advertising layout.…
ERIC Educational Resources Information Center
Miller, Bruce Granville
The many Coast Salish groups distributed on both sides of the United States-Canada border on the Pacific coast today face significant obstacles to cross the international border, and in some cases are denied passage or intimidated into not attempting to cross. The current situation regarding travel by Aboriginal people reflects the…
Flow visualization in a single simulated brush seal
NASA Technical Reports Server (NTRS)
Braun, M. J.; Canacci, V. A.; Kazmierchak, M.; Hendricks, R. C.
A method to visualize and characterize the complex flow fields in brush seals is presented. A configuration characteristic of the brush seal confined in a two-dimensional tunnel with water as the working fluid was studied. Visualization of the flow field revealed regions that are characteristically jetting, vortical, and crossflow and exist upstream, downstream or within the seal. Such flows are engendered by variations in fiber void that are spatial and temporal and affect changes in seal leakage and stability. While the effects of interface motion and cylindrical configuration have not been considered herein, it is believed that the observed flow fields characterize flow phenomenology in brush seals.
Brush/gold nanoparticle hybrids: effect of grafting density on the particle uptake and distribution within weak polyelectrolyte brushes.
Christau, Stephanie; Möller, Tim; Yenice, Zuleyha; Genzer, Jan; von Klitzing, Regine
The effect of the brush grafting density on the loading of 13 nm gold nanoparticles (AuNPs) into stimuli-responsive poly(N,N-(dimethylamino ethyl) methacrylate) (PDMAEMA) brushes anchored to flat impenetrable substrates is reported. Atom-transfer radical polymerization (ATRP) is used to grow polymer brushes via a "grafting from" approach from a 2-bromo-2-methyl-N-(3-(triethoxysilyl) propyl) propanamide (BTPAm)-covered silicon substrate. The grafting density is varied by using mixtures of initiator and a "dummy" molecule that is not able to initiate polymerization. A systematic study is carried out by varying the brush grafting density while keeping all of the other parameters constant. X-ray reflectivity is a suitable tool for investigating the spatial structure of the hybrid, and it is combined with scanning electron microscopy and UV/vis spectroscopy to study the particle loading and interpenetration of the particles within the polymer brush matrix. The particle uptake increases with decreasing grafting density and is highest for an intermediate grafting density because more space between the polymer chains is available. For very low grafting densities of PDMAEMA brushes, the particle uptake decreases because of a lack of the polymer matrix for the attachment of particles. The structure of the surface-grafted polymer chains changes after particle attachment. More water is incorporated into the brush matrix after particle immobilization, which leads to a swelling of the polymer chains in the hybrid material. Water can be removed from the brush by decreasing the relative humidity, which leads to brush shrinking and forces the AuNPs to get closer to each other.
[Vesicular intracellular transport in the digestive organs. Membrane vesicle--the universal mechanism of the functional transport].
Morozov, I A
On the basis of long-term research of the morpho-functional characteristics of the cells of the stomach, small intestine and gallbladder the mechanism and function of membrane vesicles in the implementation of the main functions of these organs sets out in this article: the secretion of hydrochloric acid by parietal cells, the absorption of nutrients in the small intestine and the fluid at a concentration of bile epitheliocytes of gallbladder. Proofs of the intracellular formation of hydrochloric acid in tubulovesicles of the parietal cells and turnover of its secretory membranes in the process of secretory cycle, that has ensured the re-use and explained the extraordinary life of these unique cells are presented. The credible mechanism of HCl output oppression by H(+)-K(+)-ATPase activity blockers has set out on this basis. The article provides detailed endocytosis mechanism of the ions and nutrients absorption by enterocytes. The mechanism of participation of the apical contractile complex of brush border of epithelial cells in the initiation of endocytosis and cytoplasmic microtubules in transport of membrane vesicles in the cytoplasm was analyzed. Based on our research and numerous of the world scientific proceedings the conclusion was done about the existence of two energy dependent types of transport in the absorptive epithelium of the digestive--transmembrane (ionic and nutritive) homeostatic type which is realized by the ATP-system of the basal plasmalemma, and vesicular (endocytosis) type which is impltmented by apical contractile complex of brush border and cytoplasmic microtubules. Both types of transport are interrelated and are under constant cellular control. This observation is relevant to the majority of cells, including those involved in the secretion of various substances: hydrochloric acid by parietal cells, enzymes by main cells of the gastric glands and exocrinocytes of the pancreas, hormone by endocrine cells of the APUD system and, finally
Membrane fluidity and surface changes during initiation of 1,2 dimethylhydrazine-induced colon carcinogenesis: protection by zinc.
Chadha, Vijayta Dani; Dhawan, D K
The present study evaluated the modulatory effects of zinc on colonic membrane fluidity and surface abnormalities following 1,2 dimethylhydrazine (DMH)-induced colon carcinogenesis. Rats were segregated into four groups: normal control, DMH treated, zinc treated, DMH + zinc treated. Colon carcinogenesis was initiated through weekly subcutaneous injections of DMH (30 mg/kg body weight) for 8 weeks. Zinc (in the form of zinc sulphate) was supplemented to rats at a dose level of 227 mg/L in drinking water, ad libitum, for the entire duration of the study. Brush border membranes (BBM) were isolated from the colon of rats and the fluidity parameters were assessed by steady-state fluorescence polarization technique using the membrane extrinsic fluorophore 1,6-diphenyl-1,3,5-hexatriene (DPH). The translational diffusion was measured by using the excimer formation of pyrene incorporated in the membrane. The results demonstrated a significant increase in the polarization and anisotropy, accompanied by an increase in order parameter in the membrane preparations from the colon of DMH-injected rats. Further, studies with pyrene fluorophore indicated a marked decrease in membrane microviscosity following DMH treatment. However, the alterations in membrane fluorescence polarization and the fluidity parameters were completely restored following zinc treatment. Drastic alterations in colon surface were noticed after 8 weeks of DMH treatment. However, zinc treatment to DMH-treated rats greatly restored normalcy in the colonic surface. The study concludes that zinc has a strong membrane stabilizing effect and thus has a positive beneficial effect against chemically induced colonic preneoplastic progression in rats.
Dendron brushes and dendronized polymers: a theoretical outlook.
Borisov, O V; Polotsky, A A; Rud, O V; Zhulina, E B; Leermakers, F A M; Birshtein, T M
Dendron brushes are molecular structures built up of treelike macromolecules, with multiple generations of branches, grafted with a root segment to a surface (particle) or to a backbone chain (dendronized polymer) with a sufficiently high grafting density so that the dendrons interact laterally. Recent advances in the theory of dendron brushes are highlighted and complemented by insights from numerical self-consistent field modelling. Our focus is on controversial issues, which are still under debate, such as, the strain distribution in individual dendrons and the appearance of distinct populations with a different extent of stretching for dendrons in planar brushes. We anticipate that dendritic brushes (i) show a strong resistance against bending, which may manifest in a high apparent persistence length of dendronized polymers, and (ii) have an unusually large beneficial effect on the colloidal stability due to the sharp steric repulsive interaction observed when these surface layers are pushed towards the overlap.
Dense brushes of stiff polymers or filaments in fluid flow
NASA Astrophysics Data System (ADS)
Römer, F.; Fedosov, D. A.
Dense filamentous brush-like structures are present in many biological interfacial systems (e.g., glycocalyx layer in blood vessels) to control their surface properties. Such structures can regulate the softness of a surface and modify fluid flow. In this letter, we propose a theoretical model which predicts quantitatively flow-induced deformation of a dense brush of stiff polymers or filaments, whose persistence length is larger or comparable to their contour length. The model is validated by detailed mesoscopic simulations and characterizes different contributions to brush deformation including hydrodynamic friction due to flow and steric excluded-volume interactions between grafted filaments. This theoretical model can be used to describe the effect of a stiff-polymer brush on fluid flow and to aid in the quantification of experiments.
Astronauts Culbertson and Bursch brush their teeth on Discovery's middeck
NASA Technical Reports Server (NTRS)
Astronauts Frank L. Culbertson (right), mission commander, and Daniel W. Bursch, mission specialist, brush their teeth on Discovery's middeck. Two sleep restraints form part of the backdrop for the photograph.
Oral Health: Brush Up on Dental Care Basics
Healthy Lifestyle Adult health Think you know everything about proper brushing and flossing techniques? Understand the basics and ... 03, 2016 Original article: http://www.mayoclinic.org/healthy-lifestyle/adult-health/in-depth/dental/art-20045536 . Mayo ...
Surface wave excitations and backflow effect over dense polymer brushes
Biagi, Sofia; Rovigatti, Lorenzo; Sciortino, Francesco; Misbah, Chaouqi
Polymer brushes are being increasingly used to tailor surface physicochemistry for diverse applications such as wetting, adhesion of biological objects, implantable devices and much more. Here we perform Dissipative Particle Dynamics simulations to study the behaviour of dense polymer brushes under flow in a slit-pore channel. We discover that the system displays flow inversion at the brush interface for several disconnected ranges of the imposed flow. We associate such phenomenon to collective polymer dynamics: a wave propagating on the brush surface. The relation between the wavelength, the amplitude and the propagation speed of the flow-generated wave is consistent with the solution of the Stokes equations when an imposed traveling wave is assumed as the boundary condition (the famous Taylor's swimmer). PMID:26975329
Unique Tuft Test Facility Dramatically Reduces Brush Seal Development Costs
NASA Technical Reports Server (NTRS)
Fellenstein, James A.
Brush seals have been incorporated in the latest turbine engines to reduce leakage and improve efficiency. However, the life of these seals is limited by wear. Studies have shown that optimal sealing characteristics for a brush seal occur before the interference fit between the brush and shaft is excessively worn. Research to develop improved tribopairs (brush and coating) with reduced wear and lower friction has been hindered by the lack of an accurate, low-cost, efficient test methodology. Estimated costs for evaluating a new material combination in an engine company seal test program are on the order of $100,000. To address this need, the NASA Lewis Research Center designed, built, and validated a unique, innovative brush seal tuft tester that slides a single tuft of brush seal wire against a rotating shaft under controlled loads, speeds, and temperatures comparable to those in turbine engines. As an initial screening tool, the brush seal tuft tester can tribologicaly evaluate candidate seal materials for 1/10th the cost of full-scale seal tests. Previous to the development of the brush seal tuft tester facility, most relevant tribological data had been obtained from full-scale seal tests conducted primarily to determine seal leakage characteristics. However, from a tribological point of view, these tests included the confounding effects of varying contact pressures, bristle flaring, high-temperature oxidation, and varying bristle contact angles. These confounding effects are overcome in tuft testing. The interface contact pressures can be either constant or varying depending on the tuft mounting device, and bristle wear can be measured optically with inscribed witness marks. In a recent cooperative program with a U.S. turbine engine manufacturer, five metallic wire candidates were tested against a plasma-sprayed Nichrome-bonded chrome carbide. The wire materials used during this collaboration were either nickel-chrome- or cobaltchrome-based superalloys. These
High temperature, flexible pressure-actuated, brush seal
NASA Technical Reports Server (NTRS)
Steinetz, Bruce M. (Inventor); Sirocky, Paul J. (Inventor)
A high temperature, flexible brush seal comprises a bundle of fibers or bristles held tightly together and secured at one end with a backing plate. The assembly includes a secondary spring-clip having one end anchored to the brush seal backing plate. An alternate embodiment of the seal utilizes a metal bellows containing coolant holes. Another embodiment of the seal uses non-circular cross-sectional fibers which may be square, rectangular or hexagonal in cross section.
Solid Phase Synthesis of Polymacromer and Copolymacromer Brushes
Starting from an azide functional substrate, ?-azido,?-protected-alkyne macromonomers are added sequentially by thermally initiated click reactions to...initiated click reactions to form poly-macromer brushes wherein macromonomers are linked via triazole groups. After each addition step, the terminal...substrate, α- azido, ω-protected-alkyne macromonomers are added sequen- tially by thermally initiated click reactions to form poly- macromer brushes
Fibre evaluation for spacecraft cleaning. [vacuum brush materials
NASA Technical Reports Server (NTRS)
Jensen, W. M.
The employment of vacuum brushes utilizing sable tail hair for the physical removal of particulates from spacecraft surfaces has become problematical in connection with a lack of compatibility of the bristle with sterilization and biological decontamination procedures required for spacecraft cleaning. An investigation was, therefore, conducted to find a suitable fiber which can replace sable bristle. Felor fiber was found to have the best properties for use in a motorized cleaning brush.
Dispersion of Mixed Brush Gold Nanorods in Polymer Matrices
NASA Astrophysics Data System (ADS)
Ferrier, Robert; Koski, Jason; Riggleman, Robert; Composto, Russell
In this work we investigate, both experimentally and through hybrid particle/self-consistent field theoretic (hSCFT) calculations, the dispersion state of gold nanorods (AuNRs) grafted with homopolymer, bidispersed, or mixed polymer brushes. AuNRs are grafted with 11.5 kg/mol PS (HNRs), 11.5 kg/mol PS and 5.3 kg/mol PS (BNRs), or 11.5 kg/mol PS and 5 kg/mol poly(methyl methacrylate) (PMMA) (MBNRs) and cast in PS or PMMA films consisting of short to very long chains compared to the grafted brush. We further investigated the MBNR systems by varying the length of the PS brush. Overall, we find that the MBNRs dispersed markedly better than the other brush types (HNRs or BNRs) in PS matrices. We utilize hSCFT calculations, in particular potential of mean force (PMF) and brush profile calculations, to elucidate the thermodynamics of these systems. The PMFs and brush profiles exhibit similar trends for the BNRs and MBNRs where the short grafted chain forces the longer grafted chain away from the AuNR surface and promotes wetting by the matrix chains. The hSCFT calculations demonstrated qualitative trends consistent with the aggregation observed for AuNRs in PMMA matrices. Therefore, we have demonstrated that MBNR dispersion in polymer matrices is enhanced compared to the HNR and BNR cases, which extends the dispersion window for new combinations of nanorods and polymers.
Rotordynamic and leakage characteristics of a 4-stage brush seal
NASA Astrophysics Data System (ADS)
Conner, K. J.; Childs, D. W.
Experimental results are presented for the direct and cross-coupled stiffness and damping coefficients as well as the leakage performance for a 4-stage brush seal. Variable test parameters include the inlet pressure, pressure ratio, shaft speed, fluid prerotation, and seal spacing. Direct damping is shown to increase with running speed; otherwise, the rotordynamic coefficients are relatively insensitive to changes in the test parameters. Cross-coupled stiffness is generally unchanged by increasing the inlet tangential velocity to the seals, suggesting that the brush seal is not affected by inlet swirl. Direct stiffness is shown to increase with frequency; however, the magnitudes of direct stiffness are always positive. Cross-coupled stiffness increases slightly with frequency; yet not as drastically as direct stiffness. Comparisons of test results for the 4-stage brush seal with an 8-cavity labyrinth showed superior rotordynamics performance for the brush seal; viz., large values for direct stiffness and lower values for the (destabilizing) cross-coupled stiffness coefficient. The damping for brush seals is smaller, but comparable to labyrinth seals. The whirl-frequency ratio is always smaller for the brush seal.
Cues to Action as Motivators for Children's Brushing.
Walker, Kimberly K; Steinfort, Erin L; Keyler, Maria J
Dental caries is the most common chronic childhood disease. Home self-care procedures are the most important strategies to prevent tooth decay. Brushing is the most important single intervention for the prevention of tooth decay, yet compliance is not practiced and there is limited understanding of children's behavioral decisions. Guided by the Health Belief Model, this study consisted of eight focus groups with children in the second through fifth grades at three different socioeconomic-level school districts to determine the cues to action that are motivating or can motivate their brushing behavior. Results indicated children are primarily motivated to brush for aesthetic reasons, mainly due to viewed media pictures of "perfect" teeth. Other less commonly expressed motivations for brushing stemmed from interpersonal connections, such as relatives with dentures. Social media, on the other hand, played a key role in some children's understanding of more advanced oral health connections such as links between cardiovascular and oral disease, and smoking and oral cancer. These links were viewed as threatening to children to motivate better brushing. Additionally, the study found that home computers can be used as an external motivator to deliver tailored messages to encourage better brushing.
Brush development for underwater ship hull coating maintenance
NASA Astrophysics Data System (ADS)
Tribou, Melissa Eileen
Ship hull grooming has been proposed as an environmentally friendly method of maintaining ship hull coatings in a fouling-free condition. It is defined as the frequent and gentle cleaning of a ship hull coating to prevent the establishment of fouling. This research investigated the grooming tool properties and operational requirements needed to implement the method. The grooming tool needs to provide sufficient force to remove incipient fouling without damaging the surface and consume minimal energy. Research showed that a vertical rotating brush design containing brushes filled with angled polypropylene bristles provided an effective method. This brush system was able to successfully prevent incipient fouling from becoming established on a copper ablative and two silicone fouling release coatings when groomed on a weekly basis; however, biofilm was not completely controlled. Brush design and operational parameters in relation to brush normal forces were investigated and models were developed to understand the relationship between bristle stiffness, dimensions, and angular velocity. A preliminary look at wear found that bristle stiffness has an effect on the degree of marring of the surface of a silicone fouling release coating. The knowledge gained by this research may be used to optimize grooming brush design and operational parameters that can be applied to the design and deployment of low power autonomous underwater vehicles that will groom the ship while in port.
Polyelectrolyte brushes in mixed ionic medium studied via intermolecular forces
NASA Astrophysics Data System (ADS)
Farina, Robert; Laugel, Nicolas; Pincus, Philip; Tirrell, Matthew
The vast uses and applications of polyelectrolyte brushes make them an attractive field of research especially with the growing interest in responsive materials. Polymers which respond via changes in temperature, pH, and ionic strength are increasingly being used for applications in drug delivery, chemical gating, etc. When polyelectrolyte brushes are found in either nature (e.g., surfaces of cartilage and mammalian lung interiors) or commercially (e.g., skin care products, shampoo, and surfaces of medical devices) they are always surrounded by mixed ionic medium. This makes the study of these brushes in varying ionic environments extremely relevant for both current and future potential applications. The polyelectrolyte brushes in this work are diblock co-polymers of poly-styrene sulfonate (N=420) and poly-t-butyl styrene (N=20) which tethers to a hydrophobic surface allowing for a purely thermodynamic study of the polyelectrolyte chains. Intermolecular forces between two brushes are measured using the SFA. As multi-valent concentrations are increased, the brushes collapse internally and form strong adhesion between one another after contact (properties not seen in a purely mono-valent environment).
Controlling the swelling and wettability of weak polyelectrolyte brushes
NASA Astrophysics Data System (ADS)
Gurtowski, Richard; Jing, Benxin; Zhu, Elaine
Weak polyelectrolytes (PE) of tunable ionization shows great potential as ``smart'' polymer materials for diverse applications from drug delivery to energy storage. However, the conformational dynamics of surfaced-tethered weak PE chains remain inadequately understood due to the complexity of their dynamic charge states in response to solvation and surface immobilization conditions. In this work, we investigate the wetting and swelling characteristics of poly(2-vinyl pyridine) (P2VP) brushes grafted to a gold substrate by AFM and water contact angle measurements. We observe the collapse of P2VP brushes, accompanied with increased surface hydrophobicity, as increasing solution pH across a critical transition pH, which is considerably lower than the pKa of free P2VP chains in bulk solution. Surprisingly, the broadness of the transition pH range shows a strong dependence with brush thickness, but not grafting density, suggesting a distribution of chain ionization along grafted P2VP brushes. We further manipulate P2VP brush structures by applying ac-electric fields across the brushes to make tunable and switchable polymer surfaces.
The Unusual Conformational Behavior of Polyzwitterionic Brushes in Aqueous Solutions
NASA Astrophysics Data System (ADS)
Mao, Jun; Chen, Wei; Yuan, Guangcui; Yu, Jing; Tirrell, Matthew
Polyzwitterions constitute a peculiar class of polyelectrolytes, which are electrically neutral polymers containing both a positive and a negative charge on each repeating unit. Surfaces coated with polyzwitterionic brushes are resistant to the nonspecific accumulation of proteins and microorganisms, making them excellent candidates for a wide range of antifouling applications, from biocompatible medical devices to marine coatings. The surrounding environment can dramatically influence the conformational behavior of polyzwitterionic brushes. High-density polyzwitterionic brushes poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) were synthesized using surface initiated atom-transfer radical polymerization, and neutron reflectivity (NR) measurements were performed to investigate the ionic strength dependence of the conformational behaviors of PMPC brushes in monovalent salt solutions. Despite the numerous observations of normal pure polyelectrolyte brushes, NR results showed that both the densely concentrated layer near the substrate surface and the relatively swollen layer into the solution have been observed in different q range in a single neutron reflectivity profile. These results will definitely help us to better understand the relationship between the solution behaviors of zwitterionic polymer brushes and their antifouling properties.
Tension amplification in tethered layers of bottle-brush polymers
Leuty, Gary M.; Tsige, Mesfin; Grest, Gary S.; ...
In this paper, molecular dynamics simulations of a coarse-grained bead–spring model have been used to study the effects of molecular crowding on the accumulation of tension in the backbone of bottle-brush polymers tethered to a flat substrate. The number of bottle-brushes per unit surface area, Σ, as well as the lengths of the bottle-brush backbones Nbb (50 ≤ Nbb ≤ 200) and side chains Nsc (50 ≤ Nsc ≤ 200) were varied to determine how the dimensions and degree of crowding of bottle-brushes give rise to bond tension amplification along the backbone, especially near the substrate. From these simulations, wemore » have identified three separate regimes of tension. For low Σ, the tension is due solely to intramolecular interactions and is dominated by the side chain repulsion that governs the lateral brush dimensions. With increasing Σ, the interactions between bottle-brush polymers induce compression of the side chains, transmitting increasing tension to the backbone. For large Σ, intermolecular side chain repulsion increases, forcing side chain extension and reorientation in the direction normal to the surface and transmitting considerable tension to the backbone.« less
Tension amplification in tethered layers of bottle-brush polymers
Leuty, Gary M.; Tsige, Mesfin; Grest, Gary S.; Rubinstein, Michael
In this paper, molecular dynamics simulations of a coarse-grained bead–spring model have been used to study the effects of molecular crowding on the accumulation of tension in the backbone of bottle-brush polymers tethered to a flat substrate. The number of bottle-brushes per unit surface area, Σ, as well as the lengths of the bottle-brush backbones Nbb (50 ≤ Nbb ≤ 200) and side chains Nsc (50 ≤ Nsc ≤ 200) were varied to determine how the dimensions and degree of crowding of bottle-brushes give rise to bond tension amplification along the backbone, especially near the substrate. From these simulations, we have identified three separate regimes of tension. For low Σ, the tension is due solely to intramolecular interactions and is dominated by the side chain repulsion that governs the lateral brush dimensions. With increasing Σ, the interactions between bottle-brush polymers induce compression of the side chains, transmitting increasing tension to the backbone. For large Σ, intermolecular side chain repulsion increases, forcing side chain extension and reorientation in the direction normal to the surface and transmitting considerable tension to the backbone.
Border Security: Barriers Along the U.S. International Border
stretches of fencing along the southern border, totaling 850 miles.7 This requirement was modified by provisions in Division E of H.R. 2764, the...certain safety features be incorporated into the design of the fence, and authorized a total appropriation not to exceed $12 million to carry out...stretches of two-layered reinforced fencing, totaling roughly 850 miles, along the southwest border.23 IIRIRA § 102(b) was again amended by the
Border Security: Barriers Along the U.S. International Border
separate stretches of fencing along the southern border totaling 850 miles. In addition to border fencing, the USBP deploys both permanent and temporary...incorporated into the design of the fence, and authorized a total appropriation not to exceed $12 million to carry out the section.21 Section 102(c...species. The U.S. Fish and Wildlife Service, for example, reported that a total of 18 federally protected species have the potential to be found along
Endogenous peroxidase activity in brush cell-like cells in the large intestine of the bullfrog tadpole, Rana catesbeiana.
Sugimoto, K; Ichikawa, Y; Nakamura, I
A special cell type was identified in the mucosal epithelium of the large intestine of the tadpole of the bullfrog, Rana catesbeiana. It is a slender, columnar cell, with a dark, basally situated nucleus. By electron microscopy the cell displays prominent bundles of filaments emerging from each microvillus and extending deep into the cytoplasm without ending in the terminal web. It has longer and more crowded microvilli than the absorptive cell. The specialized cell is also characterized by the presence of many apical vesicles and numerous subapical dense bodies. These cytological features suggest that it may be a brush cell (Rhodin and Dalhamn 1956). These cells displayed endogenous peroxidase activity in smooth and rough endoplasmic reticulum, in the well-developed Golgi apparatus and in apical vesicles. Furthermore, peroxidase reaction product was frequently observed on their luminal surface membrane. These findings suggest that the brush cell in the large intestine of the bullfrog tadpole may be a secretory cell.
Border Sovereignty and Protection Act
Rep. Hunter, Duncan D. [R-CA-52
05/26/2009 Referred to the Subcommittee on Immigration, Citizenship, Refugees, Border Security, and International Law. (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:
Bacillus thuringiensis Cry1Ac toxin interaction with Manduca sexta aminopeptidase N in a model membrane environment.
Cooper, M A; Carroll, J; Travis, E R; Williams, D H; Ellar, D J
The Bacillus thuringiensis Cry1Ac delta-endotoxin was shown to bind in a biphasic manner to Manduca sexta aminopeptidase N (APN) present in a novel model membrane. Surface plasmon resonance analysis allowed the quantification of toxin binding to M. sexta APN in a supported lipid monolayer. The initial binding was rapid and reversible, with an affinity constant of 110 nM. The second phase was slower and resulted in an overall affinity constant of 3.0 nM. Reagents used to disrupt protein-protein interactions did not dissociate the toxin after high-affinity binding was attained. The initial association between Cry1Ac and APN was inhibited by the sugar GalNAc, but the higher-affinity state was resistant to GalNAc-induced dissociation. The results suggest that after binding to M. sexta APN, the Cry1Ac toxin undergoes a rate-limiting step leading to a high-affinity state. A site-directed Cry1Ac mutant, N135Q, exhibited a similar initial binding affinity for APN but did not show the second slower phase. This inability to form an irreversible association with the APN-lipid monolayer helps explain the lack of toxicity of this protein towards M. sexta larvae and its deficient membrane-permeabilizing activity on M. sexta midgut brush border membrane vesicles. PMID:9677328
Protein adsorption in polyelectrolyte brush type cation-exchangers.
Khalaf, Rushd; Coquebert de Neuville, Bertrand; Morbidelli, Massimo
Ion exchange chromatography materials functionalized with polyelectrolyte brushes (PEB) are becoming an integral part of many protein purification steps. Adsorption onto these materials is different than that onto traditional materials, due to the 3D partitioning of proteins into the polyelectrolyte brushes. Despite this mechanistic difference, many works have described the chromatographic behavior of proteins on polyelectrolyte brush type ion exchangers with much of the same methods as used for traditional materials. In this work, unconventional chromatographic behavior on polyelectrolyte brush type materials is observed for several proteins: the peaks shapes reveal first anti-Langmuirian and then Langmuirian types of interactions, with increasing injection volumes. An experimental and model based description of these materials is carried out in order to explain this behavior. The reason for this behavior is shown to be the 3D partitioning of proteins into the polyelectrolyte brushes: proteins that fully and readily utilize the 3D structure of the PEB phase during adsorption show this behavior, whereas those that do not show traditional ion exchange behavior.
Supporting awareness through collaborative brushing and linking of tabular data.
Hajizadeh, Amir Hossein; Tory, Melanie; Leung, Rock
Maintaining an awareness of collaborators' actions is critical during collaborative work, including during collaborative visualization activities. Particularly when collaborators are located at a distance, it is important to know what everyone is working on in order to avoid duplication of effort, share relevant results in a timely manner and build upon each other's results. Can a person's brushing actions provide an indication of their queries and interests in a data set? Can these actions be revealed to a collaborator without substantially disrupting their own independent work? We designed a study to answer these questions in the context of distributed collaborative visualization of tabular data. Participants in our study worked independently to answer questions about a tabular data set, while simultaneously viewing brushing actions of a fictitious collaborator, shown directly within a shared workspace. We compared three methods of presenting the collaborator's actions: brushing & linking (i.e. highlighting exactly what the collaborator would see), selection (i.e. showing only a selected item), and persistent selection (i.e. showing only selected items but having them persist for some time). Our results demonstrated that persistent selection enabled some awareness of the collaborator's activities while causing minimal interference with independent work. Other techniques were less effective at providing awareness, and brushing & linking caused substantial interference. These findings suggest promise for the idea of exploiting natural brushing actions to provide awareness in collaborative work.
Modeling bristle lift-off in idealized brush seal configurations
NASA Technical Reports Server (NTRS)
Modi, Vijay
We attempt in this paper to develop a model for the flow through brush seals and determine their elastic behavior in order to predict the dependence of brush/journal clearance on geometry and operating conditions. Several idealizations regarding brush seal configuration, flow conditions, and elastic behavior are made in the analysis in order to determine closed form parametric dependence. This formulation assumes that there is no initial interference between the bristle tip and the rotor. Also, interbristle, bristle-backing plate, and bristle-rotor friction is neglected. The bristle bundle or the brush seal as it is alternately called is assumed homogeneous and isotropic on a macroscopic scale so that a physical property like permeability is uniform. The fluid is assumed to be homogeneous, incompressible, viscous, and flowing under steady conditions. A schematic of a brush seal is shown. If the nominal bristle-shaft interference is absent then under static conditions the bristles may deflect axially due to the imposed pressure differential. This axial deflection may create a clearance permitting leakage flow in excess of that which occurs through the porous matrix formed by the bristle bundles. Under dynamic conditions the Couette flow created by shaft motion could be strong enough to cause bristle deflection and once again a clearance may develop. The paper proposes a means to determine this clearance (or at least describe its parametric dependence on geometry and operating conditions) under static as well as dynamic conditions.
What information can frictional properties of polymer brushes tell us?
NASA Astrophysics Data System (ADS)
Zhang, Zhenyu; Moxey, Mark; Morse, Andrew; Armes, Steven; Lewis, Andrew; Geoghegan, Mark; Leggett, Graham
We have used friction force microscopy (FFM) to quantitatively examine surface grown zwitterionic polymer brushes: poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC), and to establish the correlation between its frictional behaviour to other intrinsic properties. In a good solvent, it was found that the coefficient of friction (μ) decreased with increasing film thickness. We conclude that the amount of bound solvent increases as the brush length increases, causing the osmotic pressure to increase and yielding a reduced tendency for the brush layer to deform under applied load. When measured in a series of alcohol/water mixtures, a significant increase in μ was observed for ethanol/water mixtures at a volume fraction of 90%. This is attributed to brush collapse due to co-nonsolvency, leading to loss of hydration of the brush chains and hence substantially reduced lubrication. We show that single asperity contact mechanics is strongly dependent on solvent quality. Friction-load relationship was found linear in methanol (good solvent), but sub-linear in water and ethanol (moderate solvent).
Synthetic gene brushes: a structure–function relationship
Buxboim, Amnon; Daube, Shirley S; Bar-Ziv, Roy
We present the assembly of gene brushes by means of a photolithographic approach that allows us to control the density of end-immobilized linear double-stranded DNA polymers coding for entire genes. For 2 kbp DNAs, the mean distance varies from 300 nm, where DNAs are dilute and assume relaxed conformations, down to 30 nm, where steric repulsion at dense packing forces stretching out. We investigated the gene-to-protein relationship of firefly luciferase under the T7/E.Coli-extract expression system, as well as transcription-only reactions with T7 RNA polymerase, and found both systems to be highly sensitive to brush density, conformation, and orientation. A 'structure–function' picture emerges in which extension of genes induced by moderate packing exposes coding sequences and improves their interaction with the transcription/translation machinery. However, tighter packing impairs the penetration of the machinery into the brush. The response of expression to two-dimensional gene crowding at the nanoscale identifies gene brushes as basic controllable units en route to multicomponent synthetic systems. In turn, these brushes could deepen our understanding of biochemical reactions taking place under confinement and molecular crowding in living cells. PMID:18414482
Responsive behavior of polyampholyte brushes in electric fields
NASA Astrophysics Data System (ADS)
Cao, Qianqian; Li, Lujuan; Zuo, Chuncheng; Huang, Fengli; Hu, Dongmei
We conducted coarse-grained molecular dynamics simulations to study the responsive behaviors of polyampholyte brushes (PABs) under external electric fields. The effects of charge sequence, chain rigidity and electric field strength on the conformational transition and local structures of grafted chains were addressed systematically. Without electric field, the calculations indicate that the thickness of the PABs is smaller compared to polyelectrolyte brushes (PEBs). The presence of electric field leads to inconsistency of densities between negatively and positively charged monomers except for the alternating brush. Counterions from the PABs can diffuse inside or outside the brush. Unlike the PABs, to separate the polyelectrolytes and their counterions the electric field needs to overcome the osmotic pressure of counterions. The critical field which induces the extension of the flexible PABs is much larger than the PEBs. Meanwhile, it was also found that the critical field which induces the collapse of the PABs decreases as the block length increases. In the limit of strong field studied, the chains with longer blocks are in a local extended state. For diblock brushes, once oppositely charged blocks in a single chain are separated, the chain will become straighter due to strong electrostatic repulsion in intrablock.
Excluded volume effects in compressed polymer brushes: A density functional theory
Chen, Cangyi; Tang, Ping E-mail: email@example.com; Qiu, Feng E-mail: firstname.lastname@example.com; Shi, An-Chang
A classical density functional theory (DFT) is applied to investigate the behavior of compressed polymer brushes composed of hard-sphere chains. The excluded volume interactions among the chain segments are explicitly treated. Two compression systems are used to study the behavior of brush-wall and brush-brush interactions. For the brush-brush systems, an obvious interpenetration zone has been observed. The extent of the interpenetration depends strongly on the grafting density. Furthermore, the repulsive force between the brush and wall or between the two brushes has been obtained as a function of the compression distance. Compared to the prediction of the analytic self-consistent field theory, such force increases more rapidly in the brush-wall compression with high polymer grafting densities or at higher compressions. In the brush-brush compression system, the interpenetration between the two compressed brushes creates a "softer" interaction. The influence of hard-sphere solvents on the behavior of compressed brushes is also discussed.
A bulk flow model of a brush seal system
NASA Technical Reports Server (NTRS)
Hendricks, R. C.; Schlumberger, S.; Braun, M. J.; Choy, F.; Mullen, R. L.
Fibers can be readily fabricated into a variety of seal configurations that are compliant and responsive to high speed or lightly loaded systems. A linear, circular, or contoured brush seal system is a contact seal consisting of the bristle pattern and hardened interface. When compared to a labyrinth seal, the brush seal system is superior and features low leakage, dynamic stability, and permits compliant structures. But in turn, the system usually requires a hardened smooth interface and permits only limited pressure drops. Wear life and wear debris for operations with static or dynamic excitation are largely undetermined. A seal system involves control of fluid within specific boundaries. The brush and rub ring (or rub surface) form a seal system. Design similitudes, a bulk flow model, and rub ring (interface) coatings are discussed. The bulk flow model calculations are based on flows in porous media and filters. The coatings work is based on experience and expanded to include current practice.
An Overview of Non-Metallic Brush Seal Technology
NASA Technical Reports Server (NTRS)
Ruggiero, Eric J.
Non-metallic brush seals are ultra-low flow sealing elements ideal for low pressure differentials (<30 psid) and low temperature (typically <300 degF) applications. The compliant bristle pack of a non-metallic brush seal is advantageous in terms of sealing capability during transients. However, if not designed properly, the bristle pack compliance can be detrimental to the performance of the seal. GE GLobal Research has investigated the stiffness and heat generation properties of non-metallic brush seals made from Kevlar and Carbon Fiber. The presentation will review the progress made on the design points of the seals, as well as highlight some current commercial applications of the technology.
A New Tribological Test for Candidate Brush Seal Materials Evaluation
NASA Technical Reports Server (NTRS)
Fellenstein, James A.; Dellacorte, Christopher
A new tribological test for candidate brush seal materials evaluation has been developed. The sliding contact between the brush seal wires and their mating counterface journal is simulated by testing a small tuft of wire against the outside diameter of a high speed rotating shaft. The test configuration is similar to a standard block on ring geometry. The new tester provides the capability to measure both the friction and wear of candidate wire and counterface materials under controlled loading conditions in the gram to kilogram range. A wide test condition latitude of speeds (1 to 27 m/s), temperatures (25 to 700 C), and loads (0.5 to 10 N) enables the simulation of many of the important tribological parameters found in turbine engine brush seals. This paper describes the new test rig and specimen configuration and presents initial data for candidate seal materials comparing tuft test results and wear surface morphology to field tested seal components.
A new tribological test for candidate brush seal materials evaluation
Fellenstein, J.A.; DellaCorte, C.
A new tribological test for candidate brush seal materials evaluation has been developed. The sliding contact between the brush seal wires and their mating counterface journal is simulated by testing a small tuft of wire against the outside diameter of a high speed rotating shaft. The test configuration is similar to a standard block on ring geometry. The new tester provides the capability to measure both the friction and wear of candidate wire and counterface materials under controlled loading conditions in the gram to kilogram range. A wide test condition latitude of speeds (1 to 27 m/s), temperatures (25 to 700C), and loads (0.5 to 10 N) enables the simulation of many of the important tribological parameters found in turbine engine brush seals. This paper describes the new test rig and specimen configuration and presents initial data for candidate seal materials comparing tuft test results and wear surface morphology to field tested seal components.
Controlling the motion and placement of micrometer-sized metal particles using patterned polymer brush surfaces.
Dunderdale, Gary J; Howse, Jonathan R; Fairclough, J Patrick A
In this paper, we show that silicon surfaces patterned with poly(methacrylic acid) brushes are able to control the Brownian motion of 2-3 μm iron particles, which sediment onto the surface in aqueous solution and experience differences in repulsive force depending upon their position. Differences in repulsion lead to different gravitational potential energies across the surface, which gives bias to the Brownian motion taking place. Three regimes have been identified depending upon the brush height: (i) no control of Brownian motion when the brush height is small, (ii) Brownian motion that is influenced by the polymer brush when the brush 17 height is intermediate, (iii) Brownian motion that is confined by polymer brush barriers when the brush height is greatest. The height of brush found necessary to significantly influence iron particle motion was small at 39 nm or 2% of the particle diameter.
Thermal design and development of actively cooled brushes for compact homopolar generators
NASA Astrophysics Data System (ADS)
Makel, D. B.
The thermal and hydraulic design of actively cooled current transfer brushes for compact homopolar generators (HPG) is described. The development of high-energy-density HPG's at the Center for Electromechanics at the University of Texas at Austin requires brushgear capable of handling high current densities and large thermal loads. Platelet technology has been applied in the design of actively cooled brushes with coolant injection directly from the brush contact face into the brush-rotor interface. Coolant channels a few thousandths of an inch in diameter have been designed in brushes constructed of photoetched platelets of copper (0.020 to 0.005 in. thick) and then bonded to form the cooled brush. Platelet construction of brushes also permits the incorporation of internal instrumentation for temperature measurement. The brushes have been designed to provide data on the effects of rotor speed, current level, coolant flow rate, and coolant injection pattern.
Nonstate Actors and the Open Border Policy: The Border Security Case Study of Nepal and India
addressing political and social issues.10 Due to the current environment and the ability to move freely along the Nepalese- Indian border, the Nepalese...NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS Approved for public release; distribution is unlimited NONSTATE ACTORS...border, 15. NUMBER OF resti-icted border, border patJ·ol, ct-ime, economy, U.S.-Mexican border relations, border secm-ity force, PAGES Nepalese- Indian
Brush cytology: an adjunct to diagnostic upper GI endoscopy.
Patwari, A K; Anand, V K; Malhotra, V; Balani, B; Gangil, A; Jain, A; Kapoor, G
Endoscopic brush cytology (EBC) was performed in antral and duodenal brushings of children subjected to upper GI endoscopy for the detection of H. pylori (Hp) and trophozoites of Giardia lamblia (Glt) in addition to routine endoscopic grasp biopsy (EGB). It was hospital based prospective study. EBC was performed in children subjected to upper GI endoscopy with a sheathed cytology brush. Mucosal brushings were collected from antrum, body of the stomach and second or third part of duodenum by gently rubbing the surface of the brush with the mucosal wall in all the directions, brush withdrawn and brushings performed on a glass slide. The smears were placed in 95% ethyl alcohol and later examined for Glt and Hp using Giemsa and Hematoxylin & Eosin stain. EGB was taken from antrum, body of the stomach and duodenum from sites other than those used for brushings. One hundred and seventy children between 1-13 years (median age = 5 years) were subjected to upper GI endoscopy for malabsorption (n = 94), recurrent abdominal pain (n = 49), failure to thrive (n = 16) and recurrent vomiting/regurgitation (n = 11) and EBC was performed in addition to routine EGB. Thirty five children (20.4%) were colonized by Hp, 14 (8.2%) were detected to have Glt and in 6 cases (3.5%) both Hp as well as Glt were detected. Out of 41 cases colonized by Hp, 24 cases (58.5%) were detected by EGB and 27 cases (65.8%) were detected by EBC. Out of 20 children in whom Glt were detected from their duodenum, the detection was by EBG in 12 cases (60%) and by EBC in as many as 19 cases (95%). Comparison of EGB and EBC suggested that detection rates with EBC were higher than EGB. Detection by EBC was significantly higher for Glt than Hp. There were no complications attributed to EBC and procedure time for endoscopy was not significantly prolonged. On the contrary, detection of Hp and particularly Glt in higher proportion of cases with the help of EBC was helpful in their appropriate management. Our results
Hybrid Instruction Method of Brush Strokes with Haptic Device.
Nomura, Yoshihiko; Kato, Hirotsugu; Sakamoto, Ryota
This paper proposes an instruction method of brush strokes utilizing haptic devices. Focusing attention to the magnitude difference between the horizontal and the vertical in brush strokes, we introduced a position/force hybrid scheme for determining traction forces to be fed back to users: the horizontal component of the force was given to reduce the horizontal position deviation of a learner from an expert, and the vertical component was given as reaction forces of the expert-exerted forces. As an example, a bush stroke experiment was conducted for some Brahmi characters.
A comparative study of stain removal with two electric toothbrushes and a manual brush.
Moran, J M; Addy, M; Newcombe, R G
Recent studies have suggested that a sonic electric toothbrush is more effective than a manual brush at removing extrinsic dental stain. There have been few studies of the comparative stain removal properties of different electric brushes. The study reported here was conducted to compare the efficacy of the sonic toothbrush (Sonicare) with an oscillating/rotating brush (Braun Oral-B Plaque Remover) and a conventional manual brush (Crest Complete). The study was a single-blind, randomized, cross-over design, balanced for residual effects and employing 24 subjects. Stain was enhanced over a 21-day period by twice-daily rinses with chlorhexidine and frequent intakes of tea and/or coffee. At the end of each period, tooth stain intensity and area, tongue stain intensity and area, lower lingual calculus and subjective tooth sensitivity were recorded together with preference for the brushes determined at the study's completion. Similar levels of tongue staining were recorded for the three periods, with no significant differences between the three groups. Tooth stain intensity, for most sites, was not significantly different between the three groups. For mean total stain area and for lingual and lingual interproximal sites, a significant reduction in stain was seen following use of the oscillating/rotating brush compared to the manual brush. The reductions in stain with the sonic brush were not significantly different from the manual brush. With the exception of maximum stain intensity, there were no significant differences between the oscillating/rotating and sonic brushes. Significantly less tooth sensitivity was found following use of the oscillating/rotating brush compared to both the manual and sonic brushes. All three brushes were found to be safe, but volunteer preference significantly and predominantly favored the oscillating/rotating brush. The results suggest that the oscillating/rotating brush is superior to a manual brush for stain removal.
46 CFR 108.187 - Ventilation for brush type electric motors in classified spaces.
Code of Federal Regulations, 2014 CFR
...-MOBILE OFFSHORE DRILLING UNITS DESIGN AND EQUIPMENT Construction and Arrangement Ventilation § 108.187 Ventilation for brush type electric motors in classified spaces. Ventilation for brush type electric motors in... 46 Shipping 4 2014-10-01 2014-10-01 false Ventilation for brush type electric motors in...
46 CFR 108.187 - Ventilation for brush type electric motors in classified spaces.
Code of Federal Regulations, 2013 CFR
...-MOBILE OFFSHORE DRILLING UNITS DESIGN AND EQUIPMENT Construction and Arrangement Ventilation § 108.187 Ventilation for brush type electric motors in classified spaces. Ventilation for brush type electric motors in... 46 Shipping 4 2013-10-01 2013-10-01 false Ventilation for brush type electric motors in...
46 CFR 108.187 - Ventilation for brush type electric motors in classified spaces.
Code of Federal Regulations, 2012 CFR
...-MOBILE OFFSHORE DRILLING UNITS DESIGN AND EQUIPMENT Construction and Arrangement Ventilation § 108.187 Ventilation for brush type electric motors in classified spaces. Ventilation for brush type electric motors in... 46 Shipping 4 2012-10-01 2012-10-01 false Ventilation for brush type electric motors in...
Tooth brushing habits in uninstructed adults--frequency, technique, duration and force.
Ganss, C; Schlueter, N; Preiss, S; Klimek, J
Professional recommendations for individual oral hygiene mostly include tooth brushing at least twice daily for 2-3 min with gentle force using the Bass technique or modifications of it. This study evaluated whether habitual tooth brushing actually meets these standards. Uninstructed adults (n = 103; mean age 31 +/- 6 years; 61 female, 42 male) with habitual manual tooth brushing were given a self-administered questionnaire about the frequency of brushing and a computer system recorded their brushing technique, duration and force. The majority (79.6%) of participants brushed twice daily. The mean brushing duration was 96.6 +/- 36.0 s, the mean brushing force was 2.3 +/- 0.7 N (max. 4.1 N), and no significant differences were found for quadrants. Most subjects (73.8%) brushed with circling, 8.7% with horizontal/scrubbing, 13.6% with horizontal/circling and 3.9% with vertical/sweeping movements. Modified Bass technique was not observed. When appropriate brushing habits were defined as brushing at least twice daily for 120 s with a brushing force of less than 3 N and with circling or vertical sweeping movements, only 25.2% of the participants fulfilled all criteria, emphasising the ongoing need for oral hygiene education.
46 CFR 108.187 - Ventilation for brush type electric motors in classified spaces.
Code of Federal Regulations, 2010 CFR
... 46 Shipping 4 2010-10-01 2010-10-01 false Ventilation for brush type electric motors in classified... Ventilation for brush type electric motors in classified spaces. Ventilation for brush type electric motors in... Electrical Equipment in Hazardous Locations", except audible and visual alarms may be used if shutting...
da Silva, Cláudia Helena Lovato; Paranhos, Helena de Freitas Oliveira
Objective: This report evaluated the efficacy of three brushes and one biofilm disclosing agent in complete denture cleansing. Methods: Twenty-seven wearers of maxillary dentures were distributed into three groups and received different brushes: Oral B40, conventional toothbrush (Oral B); Denture, denture-specific brush (Condor); Johnson & Johnson, denture-specific brush (Johnson & Johnson). The 60-day experimental period was divided into two techniques: I - brushing (brush associated with a paste - Dentu Creme, Dentco) three times a day; II - brushing and daily application of 1% neutral red on the denture internal surface. Biofilm quantification was carried out weekly and the areas with dye biofilm were obtained by means of Image Tool 2.02 software. Results: Biofilm removal was more effective during Technique II (Wilcoxon test: p=0.01) for the three groups of brushes. When the brushes were compared in Technique I, the Kruskal Wallis test indicated statistical difference between Denture X Johnson & Johnson and Denture X Oral B40, in which the Denture was more efficient. For Technique II, there was no statistical difference between brushes (p>0.05). Conclusion: The disclosed application promoted more efficacy on biofilm removal, regardless of the brush used. Denture (Condor) was more efficient than the other brushes during Technique I. PMID:19089247
Brush Lettering I; Commercial and Advertising Art--Basic: 9183.05.
ERIC Educational Resources Information Center
Dade County Public Schools, Miami, FL.
The course outline has been prepared as a guide to help the students gain mastery in the proper brush techniques required for efficiency in brush lettering. The student is first given an orientation to the materials and equipment used, and the preparation of tempera paints for brush lettering. After this introduction, the student is guided through…
Keep Kids' Mouths Healthy: Brush 2min2X
... your kids brush for 2 minutes, twice a day. En Español facebook twitter Kids' Healthy Mouths ... about dental visits Floss Every Day Floss Every Day As soon as two teeth touch each other ( ...
An analytical methodology utilizing models from three disciplines is developed to assess the viability of brush control for wate yield in the Frio River Basin, TX. Ecological, hydrologic, and economic models are used to portray changes in forage production and water supply result...
Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey
10. VIEW OF BRUSH ALONG KINGS CANYON ROAD WHICH WILL BE REMOVED FOR 10 FEET ON THE RIGHT SIDE OF THE ROADWAY FOR A DISTANCE OF 50 FEET. LOCATED AT MILEPOST 1.45, FACING NORTH 100 EAST (10ø). - Kings Canyon Road, Carson City, Carson City, NV
Charge regulation and local dielectric function in planar polyelectrolyte brushes.
Kumar, Rajeev; Sumpter, Bobby G; Kilbey, S Michael
Understanding the effect of inhomogeneity on the charge regulation and dielectric properties, and how it depends on the conformational characteristics of the macromolecules is a long-standing problem. In order to address this problem, we have developed a field-theory to study charge regulation and local dielectric function in planar polyelectrolyte brushes. The theory is used to study a polyacid brush, which is comprised of chains end-grafted at the solid-fluid interface, in equilibrium with a bulk solution containing monovalent salt ions, solvent molecules, and pH controlling acid. In particular, we focus on the effects of the concentration of added salt and pH of the bulk in determining the local charge and dielectric function. Our theoretical investigations reveal that the dipole moment of the ion-pairs formed as a result of counterion adsorption on the chain backbones play a key role in affecting the local dielectric function. For polyelectrolytes made of monomers having dipole moments lower than the solvent molecules, dielectric decrement is predicted inside the brush region. However, the formation of ion-pairs (due to adsorption of counterions coming from the dissociation of added salt) more polar than the solvent molecules is shown to increase the magnitude of the dielectric function with respect to its bulk value. Furthermore, an increase in the bulk salt concentration is shown to increase the local charge inside the brush region.
Northern Border Pipeline Company NPDES Permit
Under NPDES permit MT-0030791, the Northern Border Pipeline Company is authorized to discharge from locations along the Northern Border Gas Transmission Pipeline located within the exterior boundaries of the Fort Peck Indian Reservation, Montana.
Controlled Synthesis of Polymer Brushes via Polymer Single Crystal Templates
NASA Astrophysics Data System (ADS)
Zhou, Tian
A novel synthetic method of polymer brushes using polymer single crystals (PSCs) as solid-state templates is introduced in this study. PSC has a quasi-2D lamellae structure with polymer chains fold back-and-forth perpendicular to the lamellae surfaces. During crystallization, the chain ends are excluded from the unit cell onto the lamellae surfaces, which makes the material extremely versatile in its functionality. Such structure holds the unique capability to harvest nanoparticles, or being immobilized onto macroscopic flat surfaces. After dissolving PSCs in good solvent, polymer brushes are chemically tethered on either nanoparticles or flat macroscopic surfaces. Because the chain-folding structure can be conveniently tailored by changing the molecular weight of polymer and the crystallization temperature, the thickness, grafting density and morphology of resulted polymer brushes can be precisely controlled. As a model system, poly(?-caprolactone) with thiol or alkoxysilane terminal groups was used, and polymer brushes were successfully prepared on both nanoparticles and glass/Au flat surfaces. The structure-property relationships of the as-prepared polymer brushes were studied in detail using multiple characterization techniques. First of all, when functionalizing nanoparticles, by engineering the chain-folding structure of the PSCs, interesting complex nanostructures can be formed by nanoparticles including Janus nanoparticles and nanoparticle dimers. These unique structures render hybrid nanoparticles very interesting responsive behavior which have been studied in detail in this dissertation. When grafted onto a flat surface on the other hand, not only the molecular weight and grafting density can be precisely controlled, the tethering points of a single polymer chain can also be conveniently tailored, resulting polymer brushes with either tail or loop structures. Such difference in brush structure can significantly alter the properties of functional surface
Hydrologic Effects of Brush Management in Central Texas
NASA Astrophysics Data System (ADS)
Banta, J. R.; Slattery, R.
Encroachment of woody vegetation into traditional savanna grassland ecosystems in central Texas has largely been attributed to land use practices of settlers, most notably overgrazing and fire suppression. Implementing brush management practices (removing the woody vegetation and allowing native grasses to reestablish in the area), could potentially change the hydrology in a watershed. The U.S. Geological Survey, in cooperation with several local, State, and Federal cooperators, studied the hydrologic effects of ashe juniper (Juniperus ashei) removal as a brush management conservation practice in the Honey Creek State Natural Area in Comal County, Tex. Two adjacent watersheds of 104 and 159 hectares were used in a paired study. Rainfall, streamflow, evapotranspiration (Bowen ratio method), and water quality data were collected in both watersheds. Using a hydrologic mass balance approach, rainfall was allocated to surface-water runoff, evapotranspiration, and groundwater recharge. Groundwater recharge was not directly measured, but estimated as the residual of the hydrologic mass balance. After hydrologic data were collected in both watersheds for 3 years, approximately 80 percent of the woody vegetation (ashe juniper) was selectively removed from the 159 hectare watershed (treatment watershed). Brush management was not implemented in the other (reference) watershed. Hydrologic data were collected in both watersheds for six years after brush management implementation. The resulting data were examined for differences in the hydrologic budget between the reference and treatment watersheds as well as between pre- and post-brush management periods to assess effects of the treatment. Preliminary results indicate there are differences in the hydrologic budget as well as water quality between the watersheds during pre- and post-treatment periods.
Brush-eating device promises reforestation, wood energy aid
Blackman, T.
An invention which began as a low-ground-pressure skidder developed into a machine which clears brush, thins plantations, and can harvest wood for energy. First came the notion of an extra-low-ground-pressure log skidder. A swinging chopper was added to the front to clear the skid roads. Working in manzanita brush 10 to 12 foot tall, and with stems up to 18 inches in diameter, the Shar 20 can clear one to two and a half acres an hour. The 30 will be able to clear two to five acres an hour. The big machine will have two chopper heads rotating in opposite directions to force the chopped wood into a chipper built into the machine. Chips will be blown to a van following the harvester so they can be used for hog fuel or as feedstock for methanol production. The head spins at a relatively slow 450 rpm - a safety factor. Surrounding brush catches most of the cut material, but an occasional chunk of wood does fly several yards. Companies are paying more attention to reforestation. Clearing the land will leave a mulch-like debris on the ground. This offers some shade and helps retain soil moisture. Even when brush is harvested for energy, about 10% of the material is left on the ground. California's Department of Forestry wants to start a five-year clearing cycle for the chaparral stands, ''mowing'' a million acres a year and returning every fifth year to reclear the brush. California alone has 27 million acres of brushland not suitable for timber. A brushy acre averages from 30 to 200 tons of wood at 10% moisture content. The machines are designed to run at up to 12 mph when moving.
Clickable Antifouling Polymer Brushes for Polymer Pen Lithography.
Bog, Uwe; de Los Santos Pereira, Andres; Mueller, Summer L; Havenridge, Shana; Parrillo, Viviana; Bruns, Michael; Holmes, Andrea E; Rodriguez-Emmenegger, Cesar; Fuchs, Harald; Hirtz, Michael
Protein-repellent reactive surfaces that promote localized specific binding are highly desirable for applications in the biomedical field. Nonspecific adhesion will compromise the function of bioactive surfaces, leading to ambiguous results of binding assays and negating the binding specificity of patterned cell-adhesive motives. Localized specific binding is often achieved by attaching a linker to the surface, and the other side of the linker is used to bind specifically to a desired functional agent, as e.g. proteins, antibodies, and fluorophores, depending on the function required by the application. We present a protein-repellent polymer brush enabling highly specific covalent surface immobilization of biorecognition elements by strain-promoted alkyne-azide cycloaddition click chemistry for selective protein adhesion. The protein-repellent polymer brush is functionalized by highly localized molecular binding sites in the low micrometer range using polymer pen lithography (PPL). Because of the massive parallelization of writing pens, the tunable PPL printed patterns can span over square centimeter areas. The selective binding of the protein streptavidin to these surface sites is demonstrated while the remaining polymer brush surface is resisting nonspecific adsorption without any prior blocking by bovine serum albumin (BSA). In contrast to the widely used BSA blocking, the reactive polymer brushes are able to significantly reduce nonspecific protein adsorption, which is the cause of biofouling. This was achieved for solutions of single proteins as well as complex biological fluids. The remarkable fouling resistance of the polymer brushes has the potential to improve the multiplexing capabilities of protein probes and therefore impact biomedical research and applications.
Design optimization of a brush turbine with a cleaner/water based solution
NASA Technical Reports Server (NTRS)
Kim, Rhyn H.
Recently, a turbine-brush was analyzed based on the energy conservation and the force momentum equation with an empirical relationship of the drag coefficient. An equation was derived to predict the rotational speed of the turbine-brush in terms of the blade angle, number of blades, rest of geometries of the turbine-brush and the incoming velocity. Using the observed flow conditions, drag coefficients were determined. Based on the experimental values as boundary conditions, the turbine-brush flows were numerically simulated to understand first the nature of the flows, and to extend the observed drag coefficient to a flow without holding the turbine-brush.
Border Security: Barriers Along the U.S. International Border
of necessary easements, required certain safety features be incorporated into the design of the fence, and authorized a total appropriation not to...Construction Account( total ) Tactical Infrastructure Construction 2007 (request) 256 106 2006 298 93 2005 92 15 2004 89 14 2003 235 23 2002 128 6 2001...spokesman reportedly noted that the total 123 mile length of the project "will form the largest continuous physical barrier along the border in the
The impact of Border policy effect on cross-border ethnic areas
NASA Astrophysics Data System (ADS)
Bie, Q. L.; Zhou, S. Y.; Li, C. S.
Boundary effect analysis is related to border policy making in the cross-border ethnic area. The border effect literatures show that geographic boundaries have obvious impacts on economic, social and cultural relations in both sides of a nation border. Particularly in cross-border ethnic areas, each ethnic group has strong internal spatial structure relevance, and the boundary effect is more obvious. However, most of China's border areas are cross-border ethnic areas, each of border issues is unique. Under this perspective, we analyze the border effects of various boundaries can provide basis for formulating border management policies. For small scale of cross-border ethnic minority areas, how to formulate the boundary management policy is a good question to explore. This paper is demonstrated by a study of the impact of border management policies in Dehong Dai and Jingpo Autonomous Prefecture in Yunnan Province at the border area to Burma. The comparative method is used to analysis the border management policies in past 50 decades for the border area of Yunnan Province .This research aims to define trends within border policy and its influences to national security. This paper also examines Wendy Brown's liberal theory of border management policy. We found that it is not suitable for Sino-Burma border area. The conclusion is that the changes or instability of international economic and political situation has more influence to this cross-border ethnic area, and only innovative policy will be effective in cross-border ethnic area. So the border management policies should reflect the change of international context.
Adsorption and desorption behavior of asphaltene on polymer-brush-immobilized surfaces.
Higaki, Yuji; Hatae, Kaoru; Ishikawa, Tatsuya; Takanohashi, Toshimasa; Hayashi, Jun-ichiro; Takahara, Atsushi
The adsorption behavior of a model compound for surface-active component of asphaltenes, N-(1-hexylheptyl)-N'-(12-carboxylicdodecyl) perylene-3,4,9,10-tetracarboxylic bisimide (C5Pe), and detachment behavior of asphaltene deposit films for high-density polymer brushes were investigated. Zwitterionic poly(3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropanesulfonate (PMAPS) brushes and hydrophobic poly(n-hexyl methacrylate) (PHMA) brushes exhibit less C5Pe adsorption than poly(methyl methacrylate) (PMMA). The asphaltene deposit films on the PHMA brush detached in a model oil (toluene/n-heptane=1/4 (v/v)), and the asphaltene films on the PMAPS brush detached in water. The antifouling character was explained by the interface free energy for the polymer-brush/asphaltenes (γSA) and polymer-brush/toluene (γSO).
Impact of self-tongue brushing on taste perception in Thai older adults: A pilot study.
Madiloggovit, Jirakate; Chotechuang, Nattida; Trachootham, Dunyaporn
Oral hygiene influences taste, affecting appetite and nutrition in older adults. However, the impact of self-administered tongue brushing on their taste perceptions was unclear. This pilot study (N = 44) was aimed to observe the changes in taste thresholds using Filter Paper Disc after tongue brushing in Thai older adults. Based on the results, continuous tongue brushing for 3 months reduced tongue coat (p < 0.01) and improved subjective taste in 74% of participants. Sweet and salty recognition thresholds were reduced in both anterior and posterior tongue, while sour and bitter thresholds were reduced only in posterior tongue. No changes in umami (savory) were observed. Daily brushing was more effective than weekly brushing in improving the sweet and bitter tastes. The data suggested that tongue brushing could improve perception of multiple tastes and daily tongue brushing was recommended as routine personal care for older adults. This study supports further investigation in a randomized-controlled setting.
Border Hunter Research Technical Report
full duration of the course. Teams 1 and 2 comprised Border Patrol Agents. Teams 3 and 4 comprised Soldiers, and Team 5's composition was mixed... durations of lost spoor they experienced since terrain difficulty in- creased markedly over the course of training. Indeed, there were few instances of...with terrain levels of 3–5 being common, lost spoor increased in frequency and duration . The key skill development here is 1) the confidence that
Border preserving skin lesion segmentation
NASA Astrophysics Data System (ADS)
Kamali, Mostafa; Samei, Golnoosh
Melanoma is a fatal cancer with a growing incident rate. However it could be cured if diagnosed in early stages. The first step in detecting melanoma is the separation of skin lesion from healthy skin. There are particular features associated with a malignant lesion whose successful detection relies upon accurately extracted borders. We propose a two step approach. First, we apply K-means clustering method (to 3D RGB space) that extracts relatively accurate borders. In the second step we perform an extra refining step for detecting the fading area around some lesions as accurately as possible. Our method has a number of novelties. Firstly as the clustering method is directly applied to the 3D color space, we do not overlook the dependencies between different color channels. In addition, it is capable of extracting fine lesion borders up to pixel level in spite of the difficulties associated with fading areas around the lesion. Performing clustering in different color spaces reveals that 3D RGB color space is preferred. The application of the proposed algorithm to an extensive data-base of skin lesions shows that its performance is superior to that of existing methods both in terms of accuracy and computational complexity.
A Test for Creutzfeldt–Jakob Disease Using Nasal Brushings
Orrú, Christina D.; Bongianni, Matilde; Tonoli, Giovanni; Ferrari, Sergio; Hughson, Andrew G.; Groveman, Bradley R.; Fiorini, Michele; Pocchiari, Maurizio; Monaco, Salvatore; Caughey, Byron; Zanusso, Gianluigi
BACKGROUND Definite diagnosis of sporadic Creutzfeldt–Jakob disease in living patients remains a challenge. A test that detects the specific marker for Creutzfeldt–Jakob disease, the prion protein (PrPCJD), by means of real-time quaking-induced conversion (RT-QuIC) testing of cerebrospinal fluid has a sensitivity of 80 to 90% for the diagnosis of sporadic Creutzfeldt–Jakob disease. We have assessed the accuracy of RT-QuIC analysis of nasal brushings from olfactory epithelium in diagnosing sporadic Creutzfeldt– Jakob disease in living patients. METHODS We collected olfactory epithelium brushings and cerebrospinal fluid samples from patients with and patients without sporadic Creutzfeldt–Jakob disease and tested them using RT-QuIC, an ultrasensitive, multiwell plate–based fluorescence assay involving PrPCJD-seeded polymerization of recombinant PrP into amyloid fibrils. RESULTS The RT-QuIC assays seeded with nasal brushings were positive in 30 of 31 patients with Creutzfeldt–Jakob disease (15 of 15 with definite sporadic Creutzfeldt–Jakob disease, 13 of 14 with probable sporadic Creutzfeldt–Jakob disease, and 2 of 2 with inherited Creutzfeldt–Jakob disease) but were negative in 43 of 43 patients without Creutzfeldt–Jakob disease, indicating a sensitivity of 97% (95% confidence interval [CI], 82 to 100) and specificity of 100% (95% CI, 90 to 100) for the detection of Creutzfeldt–Jakob disease. By comparison, testing of cerebrospinal fluid samples from the same group of patients had a sensitivity of 77% (95% CI, 57 to 89) and a specificity of 100% (95% CI, 90 to 100). Nasal brushings elicited stronger and faster RT-QuIC responses than cerebrospinal fluid (P<0.001 for the between-group comparison of strength of response). Individual brushings contained approximately 105 to 107 prion seeds, at concentrations several logs10 greater than in cerebrospinal fluid. CONCLUSIONS In this preliminary study, RT-QuIC testing of olfactory epithelium samples
Selenium as a modulator of membrane stability parameters and surface changes during the initiation phase of 1,2-dimethylhydrazine induced colorectal carcinogenesis.
Ghadi, Fereshteh Ezzati; Malhotra, Anshoo; Ghara, Abdollah Ramzani; Dhawan, D K
The present study evaluated the modulatory potential of selenium on colonic surface abnormalities and membrane fluidity changes following 1,2-dimethylhydrazine (DMH) induced colon carcinogenesis. Rats were segregated into four groups viz., normal control, DMH treated, selenium treated, and DMH + selenium treated. Initiation of molecular events leading to colon carcinogenesis was started following weekly subcutaneous injections of DMH (30 mg/Kg body weight) for 10 weeks. Selenium in the form of sodium selenite was supplemented to rats at a dose level of 1 PPM in drinking water, ad libitum for the entire duration of the study. Brush border membranes were isolated from the colon of rats and the viscosity as well as fluidity parameters were assessed using the membrane extrinsic fluorophore pyrene. DMH treatment resulted in a significant increase in lipid peroxidation. Reduced glutathione levels (GSH) and the activities of glutathione reductase (GR), glutathione transferase (GST), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were found to be significantly decreased following DMH treatment. On the other hand, supplementation with selenium to DMH treated rats resulted in a significant decrease in the levels of lipid peroxidation but caused a significant increase in the levels of GSH as well in the activities of GR, GST, SOD, CAT, and GPx. The results further, demonstrated a marked decrease in membrane microviscosity following DMH treatment. On the other hand, a significant increase was observed in the excimer/monomer ratio and fluidity parameter of DMH treated rats when compared to normal control rats. However, the alterations in membrane microviscosity and the fluidity parameters were significantly restored following selenium treatment. Further, histological as well as colon surface alterations were also observed following DMH treatment, which however were greatly prevented upon selenium co-administration. The study, therefore, concludes
Gelation threshold of cross-linked polymer brushes.
Hoffmann, Max; Lang, Michael; Sommer, Jens-Uwe
The cross-linking of polymer brushes is studied using the bond-fluctuation model. By mapping the cross-linking process into a two-dimensional (2D) percolation problem within the lattice of grafting points, we investigate the gelation transition in detail. We show that the particular properties of cross-linked polymer brushes can be reduced to the distribution of bonds which are formed between the grafted chains, and we propose scaling arguments to relate the gelation threshold to the chain length and the grafting density. The gelation threshold is lower than the percolation threshold for 2D bond percolation because of the longer range and broad distribution of bonds formed by the cross-linking process. We term this type of percolation problem star percolation. We observe a broad crossover from mean-field to critical percolation behavior by analyzing the cluster size distribution near the gelation threshold.
Adhesion between a polydisperse polymer brush and an elastomer
Aubouy, M.; Leger, L.; Marciano, Y.; Raphaeel, E.; Brown, H.R.
The interface between a flat solid surface and a cross-linked elastomer can be considerably strengthened by the addition of chains (chemically identical to the elastomer) that are tethered by one end to the solid surface. At high grafting densities these coupling chains may, however, segregate from the elastomer and the adhesion may drop considerably. This important problem has been recently considered by de Gennes {ital et} {ital al}. in the case of a monodisperse {open_quote}brush{close_quote}. In this article we analyse the adhesion between a polydisperse brush and an elastomer, having in mind some very recent experiments by Marciano {ital et} {ital al}. {copyright} {ital 1996 American Institute of Physics.}
Toxicological study of ''Aralhex Brush'' and its two components
London, J.E.; Smith, D.M.
The acute oral LD/sub 50/ values for the adhesive ''Aralhex Brush'' for mice and rats are greater than 5g/kg. According to classified guidelines, the mixture would be considered only slightly toxic or practically nontoxic in both species. Skin application studies in the rabbit with the adhesive demonstrated that it was cutaneously mildly irritating; however, based on the primary irritation index, the adhesive's two precursor components were nonirritating. The adhesive and components I were mildly irritating in the rabbit eye application studies and component II was non-irritating. The sensitization study in the guinea pig did not show ''Aralhex Brush'' or its two components to be sensitizers. 5 refs., 3 tabs.
Local chemical composition of nanophase-separated polymer brushes.
Filimon, M; Kopf, I; Schmidt, D A; Bründermann, E; Rühe, J; Santer, S; Havenith, M
Using scattering scanning nearfield infrared microscopy (s-SNIM), we have imaged the nanoscale phase separation of mixed polystyrene-poly(methyl methacrylate) (PS-PMMA) brushes and investigated changes in the top layer as a function of solvent exposure. We deduce that the top-layer of the mixed brushes is composed primarily of PMMA after exposure to acetone, while after exposure to toluene this changes to PS. Access to simultaneously measured topographic and chemical information allows direct correlation of the chemical morphology of the sample with topographic information. Our results demonstrate the potential of s-SNIM for chemical mapping based on distinct infrared absorption properties of polymers with a high spatial resolution of 80 nm × 80 nm.
Electrocatalysis of CO2 Reduction in Brush Polymer Ion Gels.
McNicholas, Brendon J; Blakemore, James D; Chang, Alice B; Bates, Christopher M; Kramer, Wesley W; Grubbs, Robert H; Gray, Harry B
The electrochemical characterization of brush polymer ion gels containing embedded small-molecule redox-active species is reported. Gels comprising PS-PEO-PS triblock brush polymer, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIm-TFSI), and some combination of ferrocene (Fc), cobaltocenium (CoCp2(+)), and Re(bpy)(CO)3Cl (1) exhibit diffusion-controlled redox processes with diffusion coefficients approximately one-fifth of those observed in neat BMIm-TFSI. Notably, 1 dissolves homogeneously in the interpenetrating matrix domain of the ion gel and displays electrocatalytic CO2 reduction to CO in the gel. The catalytic wave exhibits a positive shift versus Fc(+/0) compared with analogous nonaqueous solvents with a reduction potential 450 mV positive of onset and 90% Faradaic efficiency for CO production. These materials provide a promising and alternative approach to immobilized electrocatalysis, creating numerous opportunities for application in solid-state devices.
Brushed Target on Rock 'Champagne' in Gusev Crater
NASA Technical Reports Server (NTRS)
2005-01-01NASA's Mars Exploration Rover Spirit took this microscopic image of a target called 'Bubbles' on a rock called 'Champagne' after using its rock abrasion tool to brush away a coating of dust. The circular brushed area is about 5 centimeters (2 inches) across. This rock is different from rocks out on the plains of Gusev Crater but is similar to other rocks in this area of the 'Columbia Hills' in that it has higher levels of phosphorus. Plagioclase, a mineral commonly found in igneous rocks, is also present in these rocks, according to analysis with the minature thermal emission spectrometer. By using the alpha particle X-ray spectrometer to collect data over multiple martian days, or sols, scientists are also beginning to get measurements of trace elements in these rocks. Spirit took the images that are combined into this mosaic on sol 354 (Dec. 30, 2004).
Computer simulations of the mechanical response of brushes on the surface of cancerous epithelial cells
NASA Astrophysics Data System (ADS)
Goicochea, A. Gama; Guardado, S. J. Alas
We report a model for atomic force microscopy by means of computer simulations of molecular brushes on surfaces of biological interest such as normal and cancerous cervical epithelial cells. Our model predicts that the force needed to produce a given indentation on brushes that can move on the surface of the cell (called "liquid" brushes) is the same as that required for brushes whose ends are fixed on the cell's surface (called "solid" brushes), as long as the tip of the microscope covers the entire area of the brush. Additionally, we find that cancerous cells are softer than normal ones, in agreement with various experiments. Moreover, soft brushes are found to display larger resistance to compression than stiff ones. This phenomenon is the consequence of the larger equilibrium length of the soft brushes and the cooperative association of solvent molecules trapped within the brushes, which leads to an increase in the osmotic pressure. Our results show that a careful characterization of the brushes on epithelial cells is indispensable when determining the mechanical response of cancerous cells.
pH-Responsive Behavior of Poly(acrylic acid) Brushes of Varying Thickness
NASA Astrophysics Data System (ADS)
Yadav, Vivek; Robertson, Megan; Conrad, Jacinta
We have investigated the pH-dependent response of polyelectrolyte brushes of varying thickness. Our model system consists of poly(acrylic acid) brushes, which change from hydrophobic and neutral at low pH to hydrophilic and negatively charged at high pH, synthesized using a grafting-from approach at constant grafting density. As the polymer brush thickness increased, the brushes exhibited greater hysteresis in static water contact angle as a function of pH. We extracted the pKa of the polymer brushes from contact angle measurements. The relationship between the pKa and brush thickness depended on the order in which the brushes were exposed to solutions of varying pH: pKa decreased on increasing brush thickness when going from basic to acidic medium whereas pKa increased on increasing brush thickness when going from acidic to basic medium. We speculate that the origin of hysteresis can be explained by pH-dependent conformational changes in these polyelectrolyte brushes.
Experimental gingivitis and frequency of tooth brushing in the beagle dog model. Clinical findings.
Tromp, J A; van Rijn, L J; Jansen, J
The aim of this experiment was to study clinical parameters when 3 different frequencies of tooth brushing were applied to sites of experimental gingivitis in beagle dogs. 12 beagle dogs, at the start of the experiment 2 years of age, were used. After a thorough cleaning, the maxillary left and right first, second and third premolars were brushed daily for a period of 8 weeks. Subsequently, for 4 weeks, all brushing was omitted in order to establish an experimental gingivitis. After this pre-experimental period, the dogs were distributed into 3 groups of 4 dogs each: one group was brushed 7 times a week, a second was brushed 3 times a week and the third group was brushed only once a week. Brushing was carried out for 24 weeks, only on the right sides of the upper jaws, the left upper jaws serving as controls. At regular intervals, plaque index, gingival index and probing depths were assessed. A brushing effect was calculated for each dog, to include information on all within-dog and between-dog variations. The present study demonstrated that only by brushing every day can clinically healthy gingivae be obtained in the beagle dog model with experimental gingivitis at baseline. The state of gingival health at baseline may be used to determined the frequency of brushing necessary to create or maintain healthy gingivae.
Computer simulations of the mechanical response of brushes on the surface of cancerous epithelial cells
Goicochea, A. Gama; Guardado, S. J. Alas
We report a model for atomic force microscopy by means of computer simulations of molecular brushes on surfaces of biological interest such as normal and cancerous cervical epithelial cells. Our model predicts that the force needed to produce a given indentation on brushes that can move on the surface of the cell (called "liquid" brushes) is the same as that required for brushes whose ends are fixed on the cell's surface (called "solid" brushes), as long as the tip of the microscope covers the entire area of the brush. Additionally, we find that cancerous cells are softer than normal ones, in agreement with various experiments. Moreover, soft brushes are found to display larger resistance to compression than stiff ones. This phenomenon is the consequence of the larger equilibrium length of the soft brushes and the cooperative association of solvent molecules trapped within the brushes, which leads to an increase in the osmotic pressure. Our results show that a careful characterization of the brushes on epithelial cells is indispensable when determining the mechanical response of cancerous cells. PMID:26315877
Stability against brushing abrasion and the erosion-protective effect of different fluoride compounds.
Wiegand, A; Schneider, S; Sener, B; Roos, M; Attin, T
This study aimed to analyse the impact of brushing on the protective effect of different fluoride solutions on enamel and dentin erosion. Bovine enamel and dentin specimens were rinsed once with TiF4, AmF, SnF2 (0.5 M F, 2 min) or water (control). Specimens were either left unbrushed or brushed with 10, 20, 50, 100 or 500 brushing strokes in an automatic brushing machine (2 N, non-fluoridated toothpaste slurry). Ten specimens per group were eroded with hydrochloric acid (HCl) (pH 2.3) for 60 s, and calcium release into the acid was determined by atomic absorption spectroscopy. Additionally, enamel and dentin surfaces were analysed by X-ray energy-dispersive spectroscopy (EDS) (n = 6/group) and scanning electron microscopy (SEM) (n = 2/group) before brushing and after 500 brushing strokes. Statistical analysis (p < 0.05) was performed by three- and one-way ANOVA (calcium release) or repeated measures ANOVA (EDS). TiF4, AmF and SnF2 reduced the erosive calcium loss in unbrushed specimens to 58-67% (enamel) and 23-31% (dentin) of control. Calcium release increased with increasing brushing strokes prior to erosion and amounted to 70-88% (enamel) and 45-78% (dentin) of control after 500 brushing strokes. Brushing reduced the surface concentration of fluoride (AmF), tin (SnF2) and titanium (TiF4). SEM revealed that surface precipitates were affected by long-term brushing. Brushing reduced the protective potential of TiF4, AmF and SnF2 solutions. However, considering a small number of brushing strokes, the protective effect of fluoride solutions is only slightly affected by brushing abrasion.
Identification of Escherichia coli F4ac-binding proteins in porcine milk fat globule membrane.
Novakovic, Predrag; Huang, Yanyun Y; Lockerbie, Betty; Shahriar, Farshid; Kelly, John; Gordon, John R; Middleton, Dorothy M; Loewen, Matthew E; Kidney, Beverly A; Simko, Elemir
F4ac-positive enterotoxigenic Escherichia coli (ETEC) must attach to the intestinal mucosa to cause diarrhea in piglets. Prevention of bacterial attachment to the intestinal mucosa is the most effective defense against ETEC-induced diarrhea. Porcine milk fat globule membranes (MFGM) were shown to be able to inhibit attachment of ETEC to the intestinal brush border; however, the specific components of porcine MFGM that inhibited attachment of ETEC to enterocytes were not identified. Accordingly, the purpose of this study was to identify F4ac-binding MFGM proteins by overlay Western blot and affinity chromatography. The proteome of porcine MFGM was characterized and the following F4ac-binding proteins were detected by overlay Western blot and affinity chromatography: lactadherin, butyrophilin, adipophilin, acyl-CoA synthetase 3, and fatty acid-binding protein 3. The biological function of these proteins was not investigated but it is possible that their interaction with F4ac fimbria interferes with bacterial attachment and colonization.
Role of human placental apical membrane transporters in the efflux of glyburide, rosiglitazone, and metformin
HEMAUER, Sarah J.; PATRIKEEVA, Svetlana L.; NANOVSKAYA, Tatiana N.; HANKINS, Gary D.V.; AHMED, Mahmoud S.
Objective Substrates of placental efflux transporters could compete for a single transporter, which could result in an increase in the transfer of each substrate to the fetal circulation. Our aim was to determine the role of placental transporters in the biodisposition of oral hypoglycemic drugs that could be used as monotherapy or in combination therapy for gestational diabetes. Study design Inside-out brush border membrane vesicles from term placentas were used to determine the efflux of glyburide, rosiglitazone, and metformin by P-gp, Breast Cancer Resistance Protein (BCRP), and Multidrug Resistance Protein (MRP1). Results Glyburide was transported by MRP1 (43 ± 4%); BCRP (25 ± 5%); and P-gp (9 ± 5%). Rosiglitazone was transported predominantly by P-gp (71 ± 26%). Metformin was transported by P-gp (58 ± 20%) and BCRP (25 ± 14%). Conclusion Multiple placental transporters contribute to efflux of glyburide, rosiglitazone, and metformin. Administration of drug combinations could lead to their competition for efflux transporters. PMID:20350646
Cholinergic urethral brush cells are widespread throughout placental mammals.
Deckmann, Klaus; Krasteva-Christ, Gabriela; Rafiq, Amir; Herden, Christine; Wichmann, Judy; Knauf, Sascha; Nassenstein, Christina; Grevelding, Christoph G; Dorresteijn, Adriaan; Chubanov, Vladimir; Gudermann, Thomas; Bschleipfer, Thomas; Kummer, Wolfgang
We previously identified a population of cholinergic epithelial cells in murine, human and rat urethrae that exhibits a structural marker of brush cells (villin) and expresses components of the canonical taste transduction signaling cascade (α-gustducin, phospholipase Cβ2 (PLCβ2), transient receptor potential cation channel melanostatin 5 (TRPM5)). These cells serve as sentinels, monitoring the chemical composition of the luminal content for potentially hazardous compounds such as bacteria, and initiate protective reflexes counteracting further ingression. In order to elucidate cross-species conservation of the urethral chemosensory pathway we investigated the occurrence and molecular make-up of urethral brush cells in placental mammals. We screened 11 additional species, at least one in each of the five mammalian taxonomic units primates, carnivora, perissodactyla, artiodactyla and rodentia, for immunohistochemical labeling of the acetylcholine synthesizing enzyme, choline acetyltransferase (ChAT), villin, and taste cascade components (α-gustducin, PLCβ2, TRPM5). Corresponding to findings in previously investigated species, urethral epithelial cells with brush cell shape were immunolabeled in all 11 mammals. In 8 species, immunoreactivities against all marker proteins and ChAT were observed, and double-labeling immunofluorescence confirmed the cholinergic nature of villin-positive and chemosensory (TRPM5-positive) cells. In cat and horse, these cells were not labeled by the ChAT antiserum used in this study, and unspecific reactions of the secondary antiserum precluded conclusions about ChAT-expression in the bovine epithelium. These data indicate that urethral brush cells are widespread throughout the mammalian kingdom and evolved not later than about 64.5millionyears ago.
Characterization of Small DC Brushed and Brushless Motors
motors, the stator portion might have shunt, series , or compound coil wound stators. However, in small brushed motors permanent magnets are used...of the magnets over the coils also creates a back electromotive force (EMF) on the unenergized stator, which is sensed by the speed controller to...17 DC voltage into three-phase power for the motor. To do this, the speed controller uses a series of Metal-Oxide-Semiconductor Field-Effect
A Nanosecond Pulsed Plasma Brush for Surface Decontamination
NASA Astrophysics Data System (ADS)
Neuber, Johanna; Malik, Muhammad; Song, Shutong; Jiang, Chunqi
This work optimizes a non-thermal, atmospheric pressure plasma brush for surface decontamination. The generated plasma plumes with a maximum length of 2 cm are arranged in a 5 cm long, brush-like array. The plasma was generated in ambient air with <= 10 kV, 200 ns pulses at a repetition rate of 1.5 kHz. The energy per pulse and average power are in the range of 1-3 mJ and 0.5-1.5 W, respectively. Helium containing varying concentrations of water vapor was evaluated as the carrier gas and was fed into the plasma chamber at a rate varying between 1 to 7 SLPM. Optimization of the cold plasma brush for surface decontamination was tested in a study of the plasma inactivation of two common pathogens, Staphylococcus aureus and Acinetobacter baumannii. Laminate surfaces inoculated with over-night cultured bacteria were subject to the plasma treatment for varying water concentrations in He, flow rates and discharge voltages. It was found that increasing the water content of the feed gas greatly enhanced the bactericidal effect. Emission spectroscopy was performed to identify the reactive plasma species that contribute to this variation. Additional affiliation: Frank Reidy Research Center for Bioelectrics
Structural analysis of paintings based on brush strokes
NASA Astrophysics Data System (ADS)
Sablatnig, Robert; Kammerer, Paul; Zolda, Ernestine
The origin of works of art can often not be attributed to a certain artist. Likewise it is difficult to say whether paintings or drawings are originals or forgeries. In various fields of art new technical methods are used to examine the age, the state of preservation and the origin of the materials used. For the examination of paintings, radiological methods like X-ray and infra-red diagnosis, digital radiography, computer-tomography, etc. and color analyzes are employed to authenticate art. But all these methods do not relate certain characteristics in art work to a specific artist -- the artist's personal style. In order to study this personal style of a painter, experts in art history and image processing try to examine the 'structural signature' based on brush strokes within paintings, in particular in portrait miniatures. A computer-aided classification and recognition system for portrait miniatures is developed, which enables a semi- automatic classification and forgery detection based on content, color, and brush strokes. A hierarchically structured classification scheme is introduced which separates the classification into three different levels of information: color, shape of region, and structure of brush strokes.
Male brush-turkeys attempt sexual coercion in unusual circumstances.
Wells, David A; Jones, Darryl N; Bulger, David; Brown, Culum
Sexual coercion by males is generally understood to have three forms: forced copulation, harassment and intimidation. We studied Australian brush-turkeys, Alectura lathami, to determine whether some male behaviours towards females at incubation mounds could be classified as aggressive, whether males were attempting sexual coercion and, if so, whether the coercion was successful. We found that some male behaviours towards females were significantly more likely to be followed by the cessation of female mound activity, and hence could be classified as aggressive, while others were significantly more likely to be followed by the commencement of female mound activity, and hence could be classified as enticing. Copulation was preceded by higher rates of male enticement and by higher rates of certain types of male aggression. It therefore seemed that males were attempting sexual coercion. There was little evidence, however, that this combination of coercion and enticement was successful in obtaining copulations. While forced copulation did occur, it was infrequent, and no evidence could be found for intimidation. We conclude that harassment is the primary form of sexual coercion by male brush-turkeys. Although sexual coercion is understood to be a sub-optimal tactic, brush-turkey sexual coercion was employed as a primary tactic by dominant males who owned incubation mounds. One possible explanation for this apparent paradox is that aggression is the default solution for social conflicts in this species, and hence can be interpreted as a behavioural syndrome.
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Insulin uptake across the luminal membrane of the rat proximal tubule in vivo and in vitro
Kolman, Pavel; Pica, Angelo; Carvou, Nicolas; Boyde, Alan; Cockcroft, Shamshad; Loesch, Andrew; Pizzey, Arnold; Simeoni, Mariadelina; Capasso, Giovambattista; Unwin, Robert J.
We visualized insulin uptake in vivo across the apical membrane of the rat proximal tubule (PT) by confocal microscopy; we compared it with in vitro findings in a rat PT cell line (WKPT) using fluorescence microscopy and flow cytometry. Surface tubules were observed in vivo with a 633-nm single laser-illuminated real-time video-rate confocal scanning microscope in upright configuration for optical sectioning below the renal capsule. Fields were selected containing proximal and distal tubules; Cy5-labeled insulin was injected twice (the second time after ∼140 min) into the right jugular vein, and the fluorescence signal (at 650–670 nm) was recorded. Fluorescence was detected almost immediately at the brush-border membrane (BBM) of PT cells only, moving inside cells within 30–40 min. As a measure of insulin uptake, the ratio of the fluorescence signal after the second injection to the first doubled (ratio: 2.11 ± 0.26, mean ± SE, n = 10), indicating a "priming," or stimulating, effect of insulin on its uptake mechanism at the BBM. This effect did not occur after pretreatment with intravenous lysine (ratio: 1.03 ± 0.07, n = 6; P < 0.01). Cy2- or Cy3-labeled insulin uptake in a PT cell line in vitro was monitored by 488-nm excitation fluorescence microscopy using an inverted microscope. Insulin localized toward the apical membrane of these cells. Semiquantitative analysis of insulin uptake by flow cytometry also demonstrated a priming effect (upregulation) on insulin internalization in the presence of increasing amounts of insulin, as was observed in vivo; moreover, this effect was not seen with, or affected by, the similarly endocytosed ligand β2-glycoprotein. PMID:19261743
Insulin uptake across the luminal membrane of the rat proximal tubule in vivo and in vitro.
Kolman, Pavel; Pica, Angelo; Carvou, Nicolas; Boyde, Alan; Cockcroft, Shamshad; Loesch, Andrew; Pizzey, Arnold; Simeoni, Mariadelina; Capasso, Giovambattista; Unwin, Robert J
We visualized insulin uptake in vivo across the apical membrane of the rat proximal tubule (PT) by confocal microscopy; we compared it with in vitro findings in a rat PT cell line (WKPT) using fluorescence microscopy and flow cytometry. Surface tubules were observed in vivo with a 633-nm single laser-illuminated real-time video-rate confocal scanning microscope in upright configuration for optical sectioning below the renal capsule. Fields were selected containing proximal and distal tubules; Cy5-labeled insulin was injected twice (the second time after approximately 140 min) into the right jugular vein, and the fluorescence signal (at 650-670 nm) was recorded. Fluorescence was detected almost immediately at the brush-border membrane (BBM) of PT cells only, moving inside cells within 30-40 min. As a measure of insulin uptake, the ratio of the fluorescence signal after the second injection to the first doubled (ratio: 2.11 +/- 0.26, mean +/- SE, n = 10), indicating a "priming," or stimulating, effect of insulin on its uptake mechanism at the BBM. This effect did not occur after pretreatment with intravenous lysine (ratio: 1.03 +/- 0.07, n = 6; P < 0.01). Cy2- or Cy3-labeled insulin uptake in a PT cell line in vitro was monitored by 488-nm excitation fluorescence microscopy using an inverted microscope. Insulin localized toward the apical membrane of these cells. Semiquantitative analysis of insulin uptake by flow cytometry also demonstrated a priming effect (upregulation) on insulin internalization in the presence of increasing amounts of insulin, as was observed in vivo; moreover, this effect was not seen with, or affected by, the similarly endocytosed ligand beta2-glycoprotein.
SGLT2 inhibitors act from the extracellular surface of the cell membrane.
Ghezzi, Chiara; Hirayama, Bruce A; Gorraitz, Edurne; Loo, Donald D F; Liang, Yin; Wright, Ernest M
SGLT2 inhibitors are a new class of drugs that have been recently developed to treat type II diabetes. They lower glucose levels by inhibiting the renal Na(+)/glucose cotransporter SGLT2, thereby increasing the amount of glucose excreted in the urine. Pharmacodynamics studies have raised questions about how these inhibitors reach SGLT2 in the brush border membrane of the S1 and S2 segments of the renal proximal tubule: are these drugs filtered by the glomerulus and act extracellularly, or do they enter the cell and act intracellularly? To address this question we expressed hSGLT2 in HEK-293T cells and determined the affinity of a specific hSGLT2 inhibitor, TA-3404 (also known as JNJ-30980924), from the extra- and intracellular side of the plasma membrane. Inhibition of SGLT2 activity (Na(+)/glucose currents) by TA-3404 was determined using the whole-cell patch clamp that allows controlling the composition of both the extracellular and intracellular solutions. We compared the results to those obtained using the nonselective SGLT inhibitor phlorizin, and to the effect of TA-3404 on hSGLT1. Our results showed that TA-3404 is a potent extracellular inhibitor of glucose inward SGLT2 transport (IC50 2 nmol/L) but it was ineffective from the intracellular compartment at both low (5 mmol/L) and high (150 mmol/L) intracellular NaCl concentrations. We conclude that TA-3404 only inhibits SGLT2 from the extracellular side of the plasma membrane, suggesting that it is filtered from the blood through the glomerulus and acts from within the tubule lumen.
pH gradient effects on chloride transport across basolateral membrane vesicles from guinea-pig jejunum.
Touzani, K; Alvarado, F; Vasseur, M
1. The effects of alkaline-inside pH gradients on 36Cl- uptake were quantified by using brush-border membrane (BBM) and basolateral membrane (BLM) vesicles from guinea-pig jejunum. 2. With BBM vesicles, a pHo/pHi gradient of 5.0/7.5 yielded fast overshoots involving a random, non-obligatory Cl(-)-H+ symport, strongly inhibited by CCCP. In contrast, BLM vesicles responded to similar pH gradients with much smaller, delayed overshoots, unaffected by CCCP. 3. The initial Cl- entry rates into BLM vesicles were a function of each pHo, pHi and delta pH value. They were stimulated by valinomycin in the presence of inward-directed K+ gradients. Short-circuiting the membrane potential with equilibrated K+ and valinomycin inhibited pH gradient-dependent Cl- uptake, but only partially. 4. Taken together, these results indicate that guinea-pig jejunal BLM vesicles possess both Cl- conductance and Cl(-)-H+ symport activities. 5. Even when different, the BBM and the BLM symporters are mechanistically similar. Neither of them involves a Cl(-)-OH- antiport, nor a simultaneous Cl(-)-anion exchange mechanism. Rather, for each membrane, all of these activities (symport, anion exchange) can be explained in terms of a single mobile carrier acting as a random, non-obligatory Cl(-)-H+ symporter where exchange occurs simply by counterflow. Net Cl- translocation via either the ternary (Cl(-)-C-H+) or the binary (Cl(-)-C) complexes accounts, respectively, for the existence of two, operationally distinct, electroneutral and rheogenic components. 6. The BBM symporter appears to involve an AE2 protein, but the molecular identity of the BLM one remains to be established. PMID:9147326
Proteomic profiling of the effect of metabolic acidosis on the apical membrane of the proximal convoluted tubule
Walmsley, Scott J.; Freund, Dana M.
The physiological response to the onset of metabolic acidosis requires pronounced changes in renal gene expression. Adaptations within the proximal convoluted tubule support the increased extraction of plasma glutamine and the increased synthesis and transport of glucose and of NH4+ and HCO3− ions. Many of these adaptations involve proteins associated with the apical membrane. To quantify the temporal changes in these proteins, proteomic profiling was performed using brush-border membrane vesicles isolated from proximal convoluted tubules (BBMVPCT) that were purified from normal and acidotic rats. This preparation is essentially free of contaminating apical membranes from other renal cortical cells. The analysis identified 298 proteins, 26% of which contained one or more transmembrane domains. Spectral counts were used to assess changes in protein abundance. The onset of acidosis produced a twofold, but transient, increase in the Na+-dependent glucose transporter and a more gradual, but sustained, increase (3-fold) in the Na+-dependent lactate transporter. These changes were associated with the loss of glycolytic and gluconeogenic enzymes that are contained in the BBMVPCT isolated from normal rats. In addition, the levels of γ-glutamyltranspeptidase increased twofold, while transporters that participate in the uptake of neutral amino acids, including glutamine, were decreased. These changes could facilitate the deamidation of glutamine within the tubular lumen. Finally, pronounced increases were also observed in the levels of DAB2 (3-fold) and myosin 9 (7-fold), proteins that may participate in endocytosis of apical membrane proteins. Western blot analysis and accurate mass and time analyses were used to validate the spectral counting. PMID:22357915
Electrokinetic Transport in Nanochannels Grafted with Polyelectrolyte Brushes with End-Charging
NASA Astrophysics Data System (ADS)
Das, Siddhartha; Chen, Guang
Electrokinetic transport in nanochannels grafted with polyelectrolyte (PE) brushes is important for applications such as ion transport, ion manipulation, flow valving, etc. We discuss here a semi-analytical mean field theory approach to study electrokinetic transport in nanochannels grafted with polyelectrolyte brushes with end-charging. The model first probes the thermodynamics and the electrostatics of the PE brushes by appropriately accounting for the entropic (elastic), excluded volume, and electrostatic effects. The resulting knowledge on the electrostatic potential and the PE configuration is next used to obtain the electroosmotic transport. Results demonstrate the role of surface charges (at the end of the PE brushes) in modifying (shrinking or swelling) the brush height. This, in turn, alters the electroosmotic body force and the PE brush layer induced drag force on the fluid flow; therefore, the flow field eventually evolves from a non-trivial interplay of the PE electrostatic, entropic, and excluded volume effects.
Modeling helical polymer brushes using self-consistent field theory (SCFT)
NASA Astrophysics Data System (ADS)
Mahalik, Jyoti; Sumpter, Bobby; Kumar, Rajeev
We investigate structure of helical polymer brushes in terms of segment density distribution and local helical ordering using SCFT. A flexible chain model with vector potential was used to model liquid crystalline-like ordering in the brushes. The effects of surface grafting density, polymer molecular weight and the solvent quality on the brush structure were investigated. For densely grafted polymer brushes or the brushes made up of high molecular weight polymers, immersed in good quality solvent, stronger orientational ordering was found near the edge of the brushes (i.e., far from the grafting surface). Furthermore, an increase in the orientational ordering near the grafted end was found with decrease in solvent quality or decrease in molecular weight and decrease in surface grafting density. Computer Science and Mathematics Division, Oak Ridge National Laboratory.
Discriminatory bio-adhesion over nano-patterned polymer brushes
NASA Astrophysics Data System (ADS)
Gon, Saugata
Surfaces functionalized with bio-molecular targeting agents are conventionally used for highly-specific protein and cell adhesion. This thesis explores an alternative approach: Small non-biological adhesive elements are placed on a surface randomly, with the rest of the surface rendered repulsive towards biomolecules and cells. While the adhesive elements themselves, for instance in solution, typically exhibit no selectivity for various compounds within an analyte suspension, selective adhesion of targeted objects or molecules results from their placement on the repulsive surface. The mechanism of selectivity relies on recognition of length scales of the surface distribution of adhesive elements relative to species in the analyte solution, along with the competition between attractions and repulsions between various species in the suspension and different parts of the collecting surface. The resulting binding selectivity can be exquisitely sharp; however, complex mixtures generally require the use of multiple surfaces to isolate the various species: Different components will be adhered, sharply, with changes in collector composition. The key feature of these surface designs is their lack of reliance on biomolecular fragments for specificity, focusing entirely on physicochemical principles at the lengthscales from 1 - 100 nm. This, along with a lack of formal patterning, provides the advantages of simplicity and cost effectiveness. This PhD thesis demonstrates these principles using a system in which cationic poly-L-lysine (PLL) patches (10 nm) are deposited randomly on a silica substrate and the remaining surface is passivated with a bio-compatible PEG brush. TIRF microscopy revealed that the patches were randomly arranged, not clustered. By precisely controlling the number of patches per unit area, the interfaces provide sharp selectivity for adhesion of proteins and bacterial cells. For instance, it was found that a critical density of patches (on the order of
Improving Nigerian Border Security -- A Comprehensive Approach
U.S. Joint Chiefs of Staff, Homeland Defense, Joint Publication (JP) 3- 27 (Washington, D.C.: CJCS, 12 July 2007), viii. 2. Rafiu A. Akindele and Bola ...http://www.voiceofnigeria.org/Bordersecub.htm 6. Bola A. Akinterinwa and Bassey E. Ate, eds., Cross Border Armed Banditry in the Northeast: Issues in...Border Security, Cooperation and Integration, 69. 22. Adeola and Fayomi, Implications of Cross Border Migration, 6-7. 23. Ibid., 7. 24. Aluko Ola
A model for international border management systems.
Duggan, Ruth Ann
To effectively manage the security or control of its borders, a country must understand its border management activities as a system. Using its systems engineering and security foundations as a Department of Energy National Security Laboratory, Sandia National Laboratories has developed such an approach to modeling and analyzing border management systems. This paper describes the basic model and its elements developed under Laboratory Directed Research and Development project 08-684.
An effective technique for denture border evaluation.
Phoenix, R D; DeFreest, C F
Proper extension and adjustment of denture borders is a critical component in successful removable prosthodontic treatment. Unfortunately, commonly marketed disclosing media may not provide appropriate viscosities for the accurate assessment of denture border extensions. This article provides a technique for the mixing, unit-dose packaging, and utilization of a disclosing medium that is extremely well-suited for denture border applications. The technique employs commonly available materials and compiles with current "unit-dose" guidelines.
Grafting-Density Effects, Optoelectrical Properties and Nano-Patterning of Poly(para-Phenylene) Brushes
for studying conjugated polymer brushes because of the low -polydispersity (PDI < 1.1), high molecular weight (Mn ¼ 4k–19k), and the predominant 1,4...systematically control the grafting density of high molecular weight conjugated polymer brushes that would otherwise be insoluble. This allows us to examine how...convenient way to make and systematically control the grafting density of high molecular weight conjugated polymer brushes that would otherwise be
Comparison of Three types of Tooth Brushes on Plaque and Gingival Indices: A Randomized Clinical Trial
Moeintaghavi, Amir; Sargolzaie, Naser; Rostampour, Mehrnoosh; Sarvari, Sara; Kargozar, Sanaz; Gharaei, Shideh
Objective: To compare clinical results of three types of manual tooth brushes on plaque removal efficacy and gingivitis. Method: This study is a single blind randomized trial with crossover design which involved 30 periodontaly healthy individuals. Professional plaque removal and oral hygiene instruction were performed for all the participants in the first step of our study followed by asking them to avoid brushing for 2 days. Thereafter plaque and gingivitis scores were measured using plaque and gingival indices (PI and GI). Then subjects were instructed to use Pulsar tooth brush for a two-week period and then, GI and PI indices were assessed again. After passing one-week period for wash out, subjects didn't brush for 2 days and indices were recorded again. The same procedure was done for CrossAction, and Butler 411 tooth brushes respectively and at the end of the study these variables were analyzed using SPSS software ver.16. Repeated measurement ANOVA test was used to compare the scores between different brushes. Result: Finding of this study reveals that using all three types of tooth brushes resulted in significant plaque and gingivitis reduction compared to baseline levels. Pulsar tooth brush was significantly more effective in diminishing PI and GI than Butler tooth brush (p=0.044 and 0.031 respectively). Conclusion: According to our findings all 3 types of tooth brushes are effective in reduction of plaque and gingivitis and this reduction is significantly greater for Pulsar tooth brush compared to Butler and CrossAction tooth brushes. PMID:28357006
Tooth brushing, tongue cleaning and snacking behaviour of dental technology and therapist students
Azodo, Clement C.; Ehizele, Adebola O.; Umoh, Agnes; Ojehanon, Patrick I.; Akhionbare, Osagie; Okechukwu, Robinson; Igbinosa, Lawrence
Objective To determine the tooth brushing, tongue cleaning and snacking behaviour of dental technology and therapist students. Methods A descriptive cross-sectional study of students of Federal School of Dental Therapy and Technology Enugu, Nigeria. Self-administered questionnaire was used to obtain information on demography, frequency, duration and technique of tooth brushing and tongue cleaning as well as information on consumption of snacks. Results A total of 242 students responded. Dental technology students made up 52.5% of the respondents and dental therapist in training made up 47.5%. Majority (63.2%) of the respondents considered the strength of tooth brush when purchasing a tooth brush and 78.9% use tooth brushes with medium strength. Seven-tenth (71.9%) of the respondents brush their teeth twice daily and 52.1% brush for 3–5 minutes. About one-third (30.2%) brush their teeth in front of a mirror. Chewing stick was used by 51.7% of respondents in addition to the use of tooth brush. Tongue cleaning was done by 94.2% with only 9.5% using a tongue cleaner. Only 20.2% reported regular snacks consumption. Nine-tenth (90.4%) of respondents were previously involved in educating others, apart from their colleagues, on tooth brushing. Conclusion This survey revealed that most of the dental therapy and technology students had satisfactory tooth-brushing behaviour. The zeal to educate others about proper tooth brushing revealed in this study suggests that the students may be helpful in oral health promotion. PMID:21483575
Synthesis and characterization of polymer brushes for controlled adsorption of proteins
NASA Astrophysics Data System (ADS)
Hoy, Olha
Performance of biomedical devices to a large extent depends on the interactions between the device surface and the biological liquids/protein molecules. To achieve controllable interactions between the device and biomolecules and still retain the required mechanical strength on the whole, modification of the surface is often done. In the present study surface properties were modified through a polymer brush approach. After the modification, surfaces gain tunability toward protein adsorption. Mixed polymer brushes consisting of protein repelling and protein attractive components were used, with a "grafting to" method employed for the synthesis of polymer layers. First, poly(ethylene glycol), the protein repelling component of the mixed polymer brush, was tethered to the surface. Then, polyacrylic acid-b-polystyrene (the protein attractive component) was grafted on top of the previous layer. As one part of this study, the temperature dependence of grafting of the mixed brush components was studied. Surface morphology and surface properties of the mixed polymer brush were altered by treating the brush with different organic solvents. Changes in surface morphology and properties resulting from the solvent treatment were studied in dry conditions and in aqueous media. Hydrophobic interactions of the mixed polymer brush in different pH environments were also estimated. Synthesized mixed polymer brushes demonstrated a clear dependency between the external stimuli applied to the brush and the amount of the protein adsorbed onto the brush surface, allowing an effective control of protein adsorption. Attraction forces between the protein molecules and surface of he mixed polymer brush were measured using AFM and these supported the findings from the protein adsorption studies. 2-D molecular imprinting of the polymer brush approach was used to synthesize a surface with controlled positioning of the protein molecules on the surface. Protein adsorption onto the surface of the
Improved surface property of PVDF membrane with amphiphilic zwitterionic copolymer as membrane additive
NASA Astrophysics Data System (ADS)
Li, Jian-Hua; Li, Mi-Zi; Miao, Jing; Wang, Jia-Bin; Shao, Xi-Sheng; Zhang, Qi-Qing
An attempt to improve hydrophilicity and anti-fouling properties of PVDF membranes, a novel amphiphilic zwitterionic copolymer poly(vinylidene fluoride)-graft-poly(sulfobetaine methacrylate) (PVDF-g-PSBMA) was firstly synthesized by atom transfer radical polymerization (ATRP) and used as amphiphilic copolymer additive in the preparation of PVDF membranes. The PVDF-g-PSBMA/PVDF blend membranes were prepared by immersion precipitation process. Fourier transform infrared attenuated reflection spectroscopy (FTIR-ATR) and X-ray photoelectronic spectroscopy (XPS) measurements confirmed that PSBMA brushes from amphiphilic additives were preferentially segregated to membrane-coagulant interface during membrane formation. The morphology of membranes was characterized by scanning electron microscopy (SEM). Water contact angle measurements showed that the surface hydrophilicity of PVDF membranes was improved significantly with the increasing of amphiphilic copolymer PVDF-g-PSBMA in cast solution. Protein static adsorption experiment and dynamic fouling resistance experiment revealed that the surface enrichment of PSBMA brush endowed PVDF blend membrane great improvement of surface anti-fouling ability.
An Experimental-Theoretical Analysis of Protein Adsorption on Peptidomimetic Polymer Brushes
Lau, K.H. Aaron; Ren, Chunlai; Park, Sung Hyun; Szleifer, Igal; Messersmith, Phillip B.
Surface-grafted water soluble polymer brushes are being intensely investigated for preventing protein adsorption to improve biomedical device function, prevent marine fouling, and enable applications in biosensing and tissue engineering. In this contribution, we present an experimental-theoretical analysis of a peptidomimetic polymer brush system with regard to the critical brush density required for preventing protein adsorption at varying chain lengths. A mussel adhesive-inspired DOPA-Lys pentapeptide surface grafting motif enabled aqueous deposition of our peptidomimetic polypeptoid brushes over a wide range of chain densities. Critical densities of 0.88 nm−2 for a relatively short polypeptoid 10-mer to 0.42 nm−2 for a 50-mer were identified from measurements of protein adsorption. The experiments were also compared with the protein adsorption isotherms predicted by a molecular theory. Excellent agreements in terms of both the polymer brush structure and the critical chain density were obtained. Furthermore, atomic force microscopy (AFM) imaging is shown to be useful in verifying the critical brush density for preventing protein adsorption. The present co-analysis of experimental and theoretical results demonstrates the significance of characterizing the critical brush density in evaluating the performance of an anti-fouling polymer brush system. The high fidelity of the agreement between the experiments and molecular theory also indicate that the theoretical approach presented can aid in the practical design of antifouling polymer brush systems. PMID:22107438
The role of tooth-brushing and diet in the maintenance of periodontal health in dogs.
Gorrel, C; Rawlings, J M
Tooth-brushing every other day did not maintain clinically healthy gingivae in dogs. The daily addition of a dental hygiene chew to a regimen of tooth brushing every other day reduced the gingivitis scores and reduced the accumulation of dental deposits (plaque, calculus and stain). Daily tooth-brushing should be the recommendation to the dog owner irrespective of dietary regimen. Providing a dental hygiene chew daily seems to give an added health benefit when tooth-brushing is less frequent, and provides the pet owner with a useful adjunct for homecare.
Scaling Laws for liquid and ion transport in nanochannels grafted with polyelectrolyte brushes
NASA Astrophysics Data System (ADS)
Chen, Guang; Sinha, Shayandev; Das, Siddhartha; Soft Matter, Interfaces,; Energy Laboratory (Smiel) Team
Grafting nanochannels with polyelectrolyte (PE) brushes renders tremendous functionality to the nanochannels, making them capable of applications such as ion manipulation, ion sensing, current rectification, nanofluidic diode fabrication, and flow control. PE brush is a special case of polymers at interfaces; such brush-like structure is possible only when the grafting density (σ) is beyond a critical value. In this study, we shall propose scaling laws that identify σ-N(N is the size of the PE molecule) combination that simultaneously ensure that the grafted PE molecules adopt ''brush''-like configuration and the height of the PE brushes are smaller than the nanochannel half height. Secondly, we pinpoint the scaling conditions where the electrostatic effects associated with the PE brushes can be decoupled from the corresponding PE excluded volume and elastic effects; such de-coupling has tremendous connotation in context of modeling of electrostatics and transport at PE-brush-covered interfaces. Thirdly, we provide scaling arguments to quantify the dependence of the flow penetration depth into the PE brush as a function of the σ-N combination. Finally, our scaling estimates pinpoint the conditions where the flow or electric field induced deformation of the grafted nanochannel PE brushes can be neglected while modeling the pressure-driven or electroosmotic transport or ionic current in such nanochannels.
Friction, wear, and noise of slip ring and brush contacts for synchronous satellite use.
NASA Technical Reports Server (NTRS)
Lewis, N. E.; Cole, S. R.; Glossbrenner, E. W.; Vest, C. E.
A program is being conducted for testing of slip rings for synchronous orbit application. Instrumentation systems necessary for monitoring electrical noise, friction, and brush wear at atmospheric pressure and at less than 50 nanotorr have been developed. A multiplex scheme necessary for the simultaneous recording of brush displacement, friction, and electrical noise has also been developed. Composite brushes consisting of silver-molybdenum disulfide-graphite and silver-niobium diselenide-graphite have been employed on rings of coin silver and rhodium plate. Brush property measurements made included measurement of density, electrical resistivity, shear strength, and microstructure.
People Crossing Borders: An Analysis of U.S. Border Protection Policies
increased levels of inspection against hard-to-measure threats requires a calculus that systematically weighs security against commercial interests...While border agencies constantly strive to achieve a balance that mitigates these dilemmas, these fundamental problems lie at the heart of many border...contentious element in the border security framework. International Partnerships The United States has sought to expand its borders by harmonizing its
Nanostructure of a poly(acrylic acid) brush and its transition in the amphiphilic diblock copolymer monolayer on the water surface.
Matsuoka, Hideki; Suetomi, Yoshiko; Kaewsaiha, Ploysai; Matsumoto, Kozo
The nanostructure and its transition of in a poly(acrylic acid) (PAA) brush in the water surface monolayers of poly(hydrogenated isoprene)-b-poly(acrylic acid) with different block lengths and block ratios were investigated by X-ray reflectivity as a function of surface pressure (brush density) and salt concentration in the subphase. The PAA brush showed the same behavior after salt addition as did the poly(methacrylic acid) (PMAA) brush, which was investigated previously. The brush chains expanded and then shrunk after passing the maximum with increasing added salt concentration. This behavior could be explained by the change in electric charges on the PAA brush chains as was observed on the PMAA brush. The PAA brush chains showed a critical brush density, where there was a transition between the carpet layer only and carpet + brush layer structures, as did the PMAA and poly(styrene sulfonic acid) (PSS) brushes. The critical brush density was about 0.4 chains nm(-2), which was higher than that of the PSS brush, a strong acid brush, and was close to that of the PMAA brush, a weak acid brush. However, the critical brush density of the PAA brush was independent of the hydrophilic chain length whereas that of the PMAA brush decreased with increasing PMAA chain length. In addition, the PAA brush had a thicker carpet layer than the PSS and PMAA brushes. Hence, the mechanism of PAA brush formation was predicted to be different from that of not only the PSS brush (strong acid brush) but also the PMAA brush.
Aging and weathering of cool roofing membranes
Akbari, Hashem; Berhe, Asmeret A.; Levinson, Ronnen; Graveline,Stanley; Foley, Kevin; Delgado, Ana H.; Paroli, Ralph M.
Aging and weathering can reduce the solar reflectance of cool roofing materials. This paper summarizes laboratory measurements of the solar spectral reflectance of unweathered, weathered, and cleaned samples collected from single-ply roofing membranes at various sites across the United States. Fifteen samples were examined in each of the following six conditions: unweathered; weathered; weathered and brushed; weathered, brushed and then rinsed with water; weathered, brushed, rinsed with water, and then washed with soap and water; and weathered, brushed, rinsed with water, washed with soap and water, and then washed with an algaecide. Another 25 samples from 25 roofs across the United States and Canada were measured in their unweathered state, weathered, and weathered and wiped. We document reduction in reflectivity resulted from various soiling mechanisms and provide data on the effectiveness of various cleaning approaches. Results indicate that although the majority of samples after being washed with detergent could be brought to within 90% of their unweathered reflectivity, in some instances an algaecide was required to restore this level of reflectivity.
The Armchair at the Borders: The "Messy" Ideas of Borders and Border Epistemologies within Multicultural Science Education Scholarship
ERIC Educational Resources Information Center
Carter, Lyn
This paper aims to further articulate multicultural science education scholarship. In particular, it explores the notions of borders and border epistemologies as intellectual resources to think again about the challenges of science education in the global world that demand more sophisticated concepts to unravel some of its complexities. It…
Border Security: The Role of the U.S. Border Patrol
features are vast mountain ranges such as the Rockies, the Great Lakes, many different river systems, and in the winter heavy snow and bitter cold...Andrea Almond , "How Best to Count Border Deaths?" The Associated Press, November 7, 2004. Border Security: The Role of the U.S. Border Patrol
Border Security: The Role of the U.S. Border Patrol
Lakes, many different river systems, and in the winter heavy snow and bitter cold temperatures. Conversely, the southwestern border with Mexico touches...www.uh.edu/cir/Deaths_during_migration.pdf. 66 Andrea Almond , "How Best to Count Border Deaths?" The Associated Press, November 7, 2004. Border
The Intersectionality of Border Pedagogy and Latino/a Youth: Enacting Border Pedagogy in Multiple Spaces
ERIC Educational Resources Information Center
Ramirez, Pablo C.; Ross, Lydia; Jimenez-Silva, Margarita
In this one-year qualitative study, the authors examined how border pedagogy is enacted by two Latino/a high school teachers in a border community in Southern California. Through classroom observations, the authors documented powerful student discussions that named complex borders (Giroux, 1992) that existed in their daily lives. We drew from…
22 CFR 41.32 - Nonresident alien Mexican border crossing identification cards; combined border crossing...
Code of Federal Regulations, 2010 CFR
... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Nonresident alien Mexican border crossing... IMMIGRATION AND NATIONALITY ACT, AS AMENDED Temporary Visitors § 41.32 Nonresident alien Mexican border... Mexico on Form I-186, Nonresident Alien Mexican Border Crossing Card, or Form I-586, Nonresident...
22 CFR 41.32 - Nonresident alien Mexican border crossing identification cards; combined border crossing...
Code of Federal Regulations, 2014 CFR
... 22 Foreign Relations 1 2014-04-01 2014-04-01 false Nonresident alien Mexican border crossing... IMMIGRATION AND NATIONALITY ACT, AS AMENDED Temporary Visitors § 41.32 Nonresident alien Mexican border... Mexico on Form I-186, Nonresident Alien Mexican Border Crossing Card, or Form I-586, Nonresident...
22 CFR 41.32 - Nonresident alien Mexican border crossing identification cards; combined border crossing...
Code of Federal Regulations, 2012 CFR
... 22 Foreign Relations 1 2012-04-01 2012-04-01 false Nonresident alien Mexican border crossing... IMMIGRATION AND NATIONALITY ACT, AS AMENDED Temporary Visitors § 41.32 Nonresident alien Mexican border... Mexico on Form I-186, Nonresident Alien Mexican Border Crossing Card, or Form I-586, Nonresident...
22 CFR 41.32 - Nonresident alien Mexican border crossing identification cards; combined border crossing...
Code of Federal Regulations, 2013 CFR
... 22 Foreign Relations 1 2013-04-01 2013-04-01 false Nonresident alien Mexican border crossing... IMMIGRATION AND NATIONALITY ACT, AS AMENDED Temporary Visitors § 41.32 Nonresident alien Mexican border... Mexico on Form I-186, Nonresident Alien Mexican Border Crossing Card, or Form I-586, Nonresident...
22 CFR 41.32 - Nonresident alien Mexican border crossing identification cards; combined border crossing...
Code of Federal Regulations, 2011 CFR
... 22 Foreign Relations 1 2011-04-01 2011-04-01 false Nonresident alien Mexican border crossing... IMMIGRATION AND NATIONALITY ACT, AS AMENDED Temporary Visitors § 41.32 Nonresident alien Mexican border... Mexico on Form I-186, Nonresident Alien Mexican Border Crossing Card, or Form I-586, Nonresident...
International Issues, High-Stakes Testing, and Border Pedagogy: Social Studies at Border High School
ERIC Educational Resources Information Center
Cashman, Timothy G.; McDermott, Benjamin R.
A recently constructed border wall stands within walking distance of Border High School (BHS) and was created to impede the flow of people, goods, fauna, and contraband from Mexico into the United States (U.S.). The reality, however, is that this geopolitical border is fluid, allowing connections between sociopolitical zones. The researchers…
Semipermeable membrane devices (SPMDs) were deployed in indoor areas in approximately 50 residences along the border between Arizona and Mexico to measure airborne contaminants. The results of the primary analyses and gas chromatographic/mass spectrometric confirmation for org...
The effect of brushing time and dentifrice quantity on fluoride delivery in vivo and enamel surface microhardness in situ.
Zero, D T; Creeth, J E; Bosma, M L; Butler, A; Guibert, R G; Karwal, R; Lynch, R J M; Martinez-Mier, E A; González-Cabezas, C; Kelly, S A
While the clinical anticaries efficacy of fluoride toothpaste is now without question, our understanding of the relation of fluoride efficacy to brushing time and dentifrice quantity is limited. The aim of this in situ study was to determine how differences in brushing time and dentifrice quantity influence (i) fluoride distribution immediately after brushing, (ii) clearance of fluoride in saliva, (iii) enamel fluoride uptake (EFU) and (iv) enamel strengthening, via the increase in surface microhardness. The study compared brushing times of 30, 45, 60, 120 and 180 s with 1.5 g of dentifrice containing 1,100 microg/g fluoride as sodium fluoride. In addition, 60 s of brushing with 0.5 g dentifrice was evaluated. A longer brushing time progressively reduced retention of dentifrice in the brush, thereby increasing the amount delivered into the mouth. A longer brushing time also increased fluoride concentrations in saliva for at least 2 h after the conclusion of brushing, showing that increased contact time promoted fluoride retention in the oral cavity. There was a statistically significant positive linear relationship between brushing time and both enamel strengthening and EFU. Compared to 0.5 g dentifrice, brushing with 1.5 g dentifrice more than doubled the fluoride recovered in saliva after brushing and increased EFU. In conclusion, the results of this preliminary, short-term usage study suggest for the first time that both brushing time and dentifrice quantity may be important determinants both of fluoride retention in the oral cavity and consequent enamel remineralization.
Researching Transfronterizo Literacies in Texas Border Colonias
ERIC Educational Resources Information Center
Smith, Patrick H.; Murillo, Luz A.
This study examines literacies practiced in bilingual households located in emerging communities along the Texas-Mexico border known as border colonias. Drawing on theoretical notions of space as geographic and temporal, the simultaneity of global and local forces at work in colonias, and expressions of agency that are "in between"…
Border Pedagogy Cafes: Grassroots Conversations that Matter
ERIC Educational Resources Information Center
Necochea, Juan; Cline, Zulmara
This exploratory study uses qualitative methods to analyze the impact of conversations in the Border Pedagogy "Cafes" on more than 500 binational educators from the Tijuana/San Diego area on the U.S.-Mexico border. Four important themes emerged from the analysis that describe the impact of the cafes and offer a strong foundation on which…
Binational Border Collaboration in Teacher Education.
ERIC Educational Resources Information Center
Hampton, Elaine; Liguori, Olga; Rippberger, Susan
Describes an educational collaboration at the University of Texas El Paso designed to increase the U.S. border community's understanding of their Mexican school counterparts. This small teacher border exchange program grew into a laboratory for learning and teaching multicultural education through binational community-based experience. Research…
Computing border bases using mutant strategies
NASA Astrophysics Data System (ADS)
Ullah, E.; Abbas Khan, S.
Border bases, a generalization of Gröbner bases, have actively been addressed during recent years due to their applicability to industrial problems. In cryptography and coding theory a useful application of border based is to solve zero-dimensional systems of polynomial equations over finite fields, which motivates us for developing optimizations of the algorithms that compute border bases. In 2006, Kehrein and Kreuzer formulated the Border Basis Algorithm (BBA), an algorithm which allows the computation of border bases that relate to a degree compatible term ordering. In 2007, J. Ding et al. introduced mutant strategies bases on finding special lower degree polynomials in the ideal. The mutant strategies aim to distinguish special lower degree polynomials (mutants) from the other polynomials and give them priority in the process of generating new polynomials in the ideal. In this paper we develop hybrid algorithms that use the ideas of J. Ding et al. involving the concept of mutants to optimize the Border Basis Algorithm for solving systems of polynomial equations over finite fields. In particular, we recall a version of the Border Basis Algorithm which is actually called the Improved Border Basis Algorithm and propose two hybrid algorithms, called MBBA and IMBBA. The new mutants variants provide us space efficiency as well as time efficiency. The efficiency of these newly developed hybrid algorithms is discussed using standard cryptographic examples.
Teaching Orthodox Religious Education on the Border
ERIC Educational Resources Information Center
Berglund, Jenny
In geographical areas bordering those of other states, the function of educational systems, as the means for states to foster their citizens, is challenged by ambiguities and tensions connected to intercultural experiences. In this article, I illustrate some of the findings from a project that studies religious education in four border areas…
Reproductive functional anatomy and oestrous cycle pattern of the female brush-tailed porcupine (Atherurus africanus, Gray 1842) from Gabon.
Mayor, P; López-Béjar, M; Jori, F; Fenech, M; López-Gatius, F
In the present study, we examined certain features of the functional anatomy of the female genital tract of the wild brush-tailed porcupine (Atherurus africanus) to obtain data on the reproductive biology of this African forest rodent. Two consecutive experiments were performed. The aim of the first was to establish macroscopic and microscopic features of the genital organs, and to explore correlations between predominant ovarian structures and vaginal contents in 20 wild, mature females. In the second experiment, we inspected the external genitalia and vaginal smears of a further 10 females in captivity on a daily basis for 90 days. The uterus of the brush-tailed porcupine is bicornuate and composed of two separated uterine horns, a uterine body and cervix. The genital tract does not present a vaginal vestibule. Thus, there is no portion common to genital and urinary tracts. Females in the follicular phase of the oestrous cycle showed increased cornification of the vaginal epithelium and a high density of eosinophilic cells in vaginal smears. The vulva and vaginal opening were open, reddish and tumefacted. In luteal phase or in pregnancy, epithelial cornification and eosinophilic features were notably reduced and the vagina presented a pale, non-tumefacted vulva and a vaginal closure membrane. Females in captivity showed spontaneous cycles, a polyoestrous reproduction pattern and, based on features of the external genitalia and vaginal smears, their oestrous cycle length was 27.1+/-6.4 days (n=12).
Molecular interaction forces generated during protein adsorption to well-defined polymer brush surfaces.
Sakata, Sho; Inoue, Yuuki; Ishihara, Kazuhiko
The molecular interaction forces generated during the adsorption of proteins to surfaces were examined by the force-versus-distance (f-d) curve measurements of atomic force microscopy using probes modified with appropriate molecules. Various substrates with polymer brush layers bearing zwitterionic, cationic, anionic, and hydrophobic groups were systematically prepared by surface-initiated atom transfer radical polymerization. Surface interaction forces on these substrates were analyzed by the f-d curve measurements using probes with the same polymer brush layer as the substrate. Repulsive forces, which decreased depending on the ionic strength, were generated between cationic or anionic polyelectrolyte brush layers; these were considered to be electrostatic interaction forces. A strong adhesive force was detected between hydrophobic polymer brush layers during retraction; this corresponded to the hydrophobic interaction between two hydrophobic polymer layers. In contrast, no significant interaction forces were detected between zwitterionic polymer brush layers. Direct interaction forces between proteins and polymer brush layers were then quantitatively evaluated by the f-d curve measurements using protein-immobilized probes consisting of negatively charged albumin and positively charged lysozyme under physiological conditions. In addition, the amount of protein adsorbed on the polymer brush layer was quantified by surface plasmon resonance measurements. Relatively large amounts of protein adsorbed to the polyelectrolyte brush layers with opposite charges. It was considered that the detachment of the protein after contact with the polymer brush layer hardly occurred due to salt formation at the interface. Both proteins adsorbed significantly on the hydrophobic polymer brush layer, which was due to hydrophobic interactions at the interface. In contrast, the zwitterionic polymer brush layer exhibited no significant interaction force with proteins and suppressed
Polymer brushes in cylindrical pores: Simulation versus scaling theory
NASA Astrophysics Data System (ADS)
Dimitrov, D. I.; Milchev, A.; Binder, K.
The structure of flexible polymers endgrafted in cylindrical pores of diameter D is studied as a function of chain length N and grafting density σ, assuming good solvent conditions. A phenomenological scaling theory, describing the variation of the linear dimensions of the chains with σ, is developed and tested by molecular dynamics simulations of a bead-spring model. Different regimes are identified, depending on the ratio of D to the size of a free polymer N3/5. For D >N3/5 a crossover occurs for σ =σ*=N-6/5 from the "mushroom" behavior (Rgx=Rgy=Rgz=N3/5) to the behavior of a flat brush (Rgz=σ1/3N,Rgx=Rgy=σ-1/12N1/2), until at σ**=(D /N)3 a crossover to a compressed state of the brush, [Rgz=D,Rgx=Rgy=(N3D /4σ)1/8
Brush/Slip Ring Selection for High Power Satellite Loads.
046-45 80% MoS2 4 Cylindrical D=4.77 mm Lab/Renton 15% Mo L=3.18 mm 2. Boeing Met. 101 52.94% WS2 4 Cylindrical D=4.77 mm Lab/Renton 35.0% Ag L-3.18...Research has proven the inferiority of graphite as a lubricant.( 2 ,3 4 5) Consequently, future tests will consist of materials that contain MoS2 ...contamination, outgassing of insulation, paint, lubricants, oilcc S vapors, and humidity are also factors that influence brush wear rates. Excessive Z
Infrared radiation emerging from smoke produced by brush fires
NASA Technical Reports Server (NTRS)
Weinman, J. A.; Olson, W. S.; Harshvardhan, M.
The IR radiative transport properties of brush fire smoke clouds, computed for a model with finite horizontal dimensions as well as the more common plane-parallel model, are presented. The finite model is a three-dimensional version of the two-stream approximation applied to cubic clouds of steam, carbon, and silicates. Assumptions are made with regard to the shape and size distributions of the smoke particles. It is shown that 11.5-micron radiometry can detect fires beneath smoke clouds if the path integrated mass density of the smoke is less than or equal to 3 g/sq m.
A Modified Tactile Brush Algorithm for Complex Touch Gestures
Ragan, Eric
Several researchers have investigated phantom tactile sensation (i.e., the perception of a nonexistent actuator between two real actuators) and apparent tactile motion (i.e., the perception of a moving actuator due to time delays between onsets of multiple actuations). Prior work has focused primarily on determining appropriate Durations of Stimulation (DOS) and Stimulus Onset Asynchronies (SOA) for simple touch gestures, such as a single finger stroke. To expand upon this knowledge, we investigated complex touch gestures involving multiple, simultaneous points of contact, such as a whole hand touching the arm. To implement complex touch gestures, we modified the Tactile Brush algorithm to support rectangular areas of tactile stimulation.
Molecular cloning and expression of a cDNA encoding the rabbit ileal villus cell basolateral membrane Na+/H+ exchanger.
Tse, C M; Ma, A I; Yang, V W; Watson, A J; Levine, S; Montrose, M H; Potter, J; Sardet, C; Pouyssegur, J; Donowitz, M
A cDNA clone encoding a rabbit ileal villus cell Na+/H+ exchanger was isolated and its complete nucleotide sequence was determined. The cDNA is 4 kb long and contains 322 bp of 5'-untranslated region, 2451 bp of open reading frame and 1163 bp of 3'-untranslated area, with 70%, 91% and 40% identity to the human sequence, respectively. Amino acid sequence deduced from the longest open reading frame indicated a protein of 816 residues (predicted Mr 90,716) which exhibits 95% amino acid identity to the human Na+/H+ exchanger. The two putative glycosylation sites in the human Na+/H+ exchanger are conserved in this protein, suggesting that it is a glycoprotein. Stable transfection of the cDNA into an Na+/H+ exchanger deficient fibroblast cell line, established Na+/H+ exchange. The Na+/H+ exchanger was stimulated by serum and a phorbol ester but not by 8-Br-cAMP. In Northern blot analysis, the cDNA hybridized to a 4.8 kb message in rabbit ileal villus cells, kidney cortex, kidney medulla, adrenal gland, brain and descending colon and to a 5.2 kb message in cultured human colonic cancer cell lines, HT29-18 and Caco-2. In immunoblotting, a polyclonal antibody raised against a fusion protein of beta-galactosidase and the C-terminal 158 amino acids of the human Na+/H+ exchanger identified a rabbit ileal basolateral membrane protein of 94 kd and only weakly interacted with the ileal brush border membrane. In immunocytochemical studies using ileal villus and crypt epithelial cells, the same antibody identified basolateral and not brush border epitopes. Restriction analysis of genomic DNA with a 462 bp PstI-AccI fragment of the rabbit Na+/H+ exchanger strongly suggests the existence of closely related Na+/H+ exchanger genes. The near identity of the basolateral Na+/H+ exchanger and the human Na+/H+ exchanger plus the ubiquitous expression of this message suggests that the ileal basolateral Na+/H+ exchanger is the 'housekeeping' Na+/H+ exchanger. Images PMID:1712287
Scaling features of the tribology of polymer brushes of increasing grafting density around the mushroom-to-brush transition
NASA Astrophysics Data System (ADS)
Mayoral, E.; Klapp, J.; Gama Goicochea, A.
Nonequilibrium coarse-grained, dissipative particle dynamics simulations of complex fluids, made up of polymer brushes tethered to planar surfaces immersed in a solvent yield nonmonotonic behavior of the friction coefficient as a function of the polymer grating density on the substrates, Γ , while the viscosity shows a monotonically increasing dependence on Γ . This effect is shown to be independent of the degree of polymerization, N , and the size of the system. It arises from the composition and the structure of the first particle layer adjacent to each surface that results from the confinement of the fluid. Whenever such layers are made up of as close a proportion of polymer beads to solvent particles as there are in the fluid, the friction coefficient shows a minimum, while for disparate proportions the friction coefficient grows. At the mushroom-to-brush transition (MBT) the viscosity scales with an exponent that depends on the characteristic exponent of the MBT (6/5) and the solvent quality exponent (ν =0.5 , for θsolvent), but it is independent of the polymerization degree (N ). On the other hand, the friction coefficient at the MBT scales as μ ˜N6 /5 , while the grafting density at the MBT scales as Γ ˜N-6 /5 when friction is minimal, in agreement with previous scaling theories. We argue these aspects are the result of cooperative phenomena that have important implications for the understanding of biological brushes and the design of microfluidics devices, among other applications of current academic and industrial interest.
Scaling features of the tribology of polymer brushes of increasing grafting density around the mushroom-to-brush transition.
Mayoral, E; Klapp, J; Gama Goicochea, A
Nonequilibrium coarse-grained, dissipative particle dynamics simulations of complex fluids, made up of polymer brushes tethered to planar surfaces immersed in a solvent yield nonmonotonic behavior of the friction coefficient as a function of the polymer grating density on the substrates, Γ, while the viscosity shows a monotonically increasing dependence on Γ. This effect is shown to be independent of the degree of polymerization, N, and the size of the system. It arises from the composition and the structure of the first particle layer adjacent to each surface that results from the confinement of the fluid. Whenever such layers are made up of as close a proportion of polymer beads to solvent particles as there are in the fluid, the friction coefficient shows a minimum, while for disparate proportions the friction coefficient grows. At the mushroom-to-brush transition (MBT) the viscosity scales with an exponent that depends on the characteristic exponent of the MBT (6/5) and the solvent quality exponent (ν=0.5, for θsolvent), but it is independent of the polymerization degree (N). On the other hand, the friction coefficient at the MBT scales as μ∼N^{6/5}, while the grafting density at the MBT scales as Γ∼N^{-6/5} when friction is minimal, in agreement with previous scaling theories. We argue these aspects are the result of cooperative phenomena that have important implications for the understanding of biological brushes and the design of microfluidics devices, among other applications of current academic and industrial interest.
Alcohol abuse and dependence among U.S.-Mexico border and non-border Mexican Americans
Caetano, Raul; Caetano Vaeth, Patrice A.; Mills, Britain A.; Rodriguez, Lori A.
BACKGROUND This paper examines the prevalence, the symptom profile, and the drinking and sociodemographic predictors of current (past 12 month) DSM-IV alcohol abuse and dependence among Mexican Americans living along the U.S.-Mexico border and those living in metropolitan areas away from the border. METHODS Respondents in the non-border areas (primarily Houston and Los Angeles) constitute a multistage probability sample (N=1,288) of these areas, interviewed as part of the 2006 Hispanic Americans Baseline Alcohol Survey (HABLAS). Respondents in the border area (N=1,307) constitute a household probability sample of Mexican Americans living on the border. In both surveys, data were collected during computer assisted interviews conducted in respondents' homes. The HABLAS and the border sample response rates were 76% and 67%, respectively. RESULTS Although bivariate analyses revealed no overall differences between border and non-border locations, (negative) age trends were more pronounced on the border for male abuse and for dependence among both genders. Among females aged 18–29, border residence was linked to significantly higher rates of dependence. In multivariable analyses, the prevalence of male abuse declined more rapidly with age on the border than off the border. Other unique predictors of male abuse were Jewish/other religion and weekly volume of alcohol consumption. Being married or out of the workforce, attaining a higher education, no religious preference, and weekly volume uniquely predicted female dependence. Age and weekly volume uniquely predicted male dependence. CONCLUSIONS The prevalence of alcohol use disorders among Mexican Americans on and off the U.S.-Mexico border largely mirrors previously documented patterns of alcohol consumption in these areas. For young Mexican-American women in particular, border residence is linked to heightened vulnerability to alcohol dependence. PMID:23278433
A Colorimetric Interdental Probe as a Standard Method to Evaluate Interdental Efficiency of Interdental Brush
Bourgeois, D.; Carrouel, F.; Llodra, J.C.; Bravo, M.; Viennot, S.
The aim of this study is to evaluate the concordance between the empirical choice of interdental brushes of different diameters compared to the gold standard, the IAP CURAPROX© calibrating colorimetric probe. It is carried out with the aim of facilitating the consensus development of best practices. All the subjects' interproximal spaces were evaluated using the reference technique (colorimetric probe), then after a time lapse of 1.2 ± 0.2 hours, using the empirical clinical technique (brushes) by the same examiner. Each examiner explored 3 subjects. The order the patients were examined with the colorimetric interdental probe (CIP) was random. 446 sites were selected in the study out of 468 potential sites. The correspondence of scores between interdental bushes vs. colorimetric probe is 43.0% [95%-CI: 38.5-47.6]. In 33.41% of the 446 sites, the brush is inferior to the probe; in 23.54% of cases, the brush is superior to the probe. Among the discrepancies there is thus a tendency for the subjects to use brushes with smaller diameter than that recommended by the colorimetric probe. This review has found very high-quality evidence that colorimetric probes plus interdental brushing is more beneficial than interdental brushing alone for increase the concordance between the empirical choice of interdental brushes of different diameters compared to the gold standard. Uncertainties remain and further research is required to provide detailed data on user satisfaction. PMID:26966470
Friendship Network and Dental Brushing Behavior among Middle School Students: An Agent Based Modeling Approach
Sadeghipour, Maryam; Khoshnevisan, Mohammad Hossein; Jafari, Afshin; Shariatpanahi, Seyed Peyman
By using a standard questionnaire, the level of dental brushing frequency was assessed among 201 adolescent female middle school students in Tehran. The initial assessment was repeated after 5 months, in order to observe the dynamics in dental health behavior level. Logistic Regression model was used to evaluate the correlation among individuals' dental health behavior in their social network. A significant correlation on dental brushing habits was detected among groups of friends. This correlation was further spread over the network within the 5 months period. Moreover, it was identified that the average brushing level was improved within the 5 months period. Given that there was a significant correlation between social network's nodes' in-degree value, and brushing level, it was suggested that the observed improvement was partially due to more popularity of individuals with better tooth brushing habit. Agent Based Modeling (ABM) was used to demonstrate the dynamics of dental brushing frequency within a sample of friendship network. Two models with static and dynamic assumptions for the network structure were proposed. The model with dynamic network structure successfully described the dynamics of dental health behavior. Based on this model, on average, every 43 weeks a student changes her brushing habit due to learning from her friends. Finally, three training scenarios were tested by these models in order to evaluate their effectiveness. When training more popular students, considerable improvement in total students' brushing frequency was demonstrated by simulation results. PMID:28103260
Oligonucleotide Immobilization and Hybridization on Aldehyde-Functionalized Poly(2-hydroxyethyl methacrylate) Brushes.
Bilgic, Tugba; Klok, Harm-Anton
DNA biosensing requires high oligonucleotide binding capacity interface chemistries that can be tuned to maximize probe presentation as well as hybridization efficiency. This contribution investigates the feasibility of aldehyde-functionalized poly(2-hydroxyethyl methacrylate) (PHEMA) brush-based interfaces for oligonucleotide binding and hybridization. These polymer brushes, which allow covalent immobilization of oligonucleotides, are prepared by surface-initiated atom transfer radical polymerization (SI-ATRP) of HEMA followed by a postpolymerization oxidation step to generate side chain aldehyde groups. A series of polymer brushes covering a range of film thicknesses and grafting densities was investigated with regard to their oligonucleotide binding capacity as well as their ability to support oligonucleotide hybridization. Densely grafted brushes were found to have probe oligonucleotide binding capacities of up to ∼30 pmol/cm(2). Increasing the thickness of these densely grafted brush films, however, resulted in a decrease in the oligonucleotide binding capacity. Less densely grafted brushes possess binding capacities of ∼10 pmol/cm(2), which did not significantly depend on film thickness. The oligonucleotide hybridization efficiencies, however, were highest (93%) on those brushes that present the lowest surface concentration of the probe oligonucleotide. These results highlight the importance of optimizing the probe oligonucleotide surface concentration and binding interface chemistry. The versatility and tunability of the PHEMA-based brushes presented herein makes these films a very attractive platform for the immobilization and hybridization of oligonucleotides.
Towards controlled polymer brushes via a self-assembly-assisted-grafting-to approach
Zhou, Tian; Qi, Hao; Han, Lin; Barbash, Dmitri; Li, Christopher Y.
Precise synthesis of polymer brushes to modify the surface of nanoparticles and nanodevices for targeted applications has been one of the major focuses in the community for decades. Here we report a self-assembly-assisted-grafting-to approach to synthesize polymer brushes on flat substrates. In this method, polymers are pre-assembled into two-dimensional polymer single crystals (PSCs) with functional groups on the surface. Chemically coupling the PSCs onto solid substrates leads to the formation of polymer brushes. Exquisite control of the chain folding in PSCs allows us to obtain polymer brushes with well-defined grafting density, tethering points and brush conformation. Extremely high grafting density (2.12 chains per nm2) has been achieved in the synthesized single-tethered polymer brushes. Moreover, polymer loop brushes have been successfully obtained using oddly folded PSCs from telechelic chains. Our approach combines some of the important advantages of conventional 'grafting-to' and 'grafting-from' methods, and is promising for tailored synthesis of polymer brushes. PMID:27009369
STIR: A Pilot Study on the Bulk Properties and Morphology of Polypeptide-Grafted Brush Polymers
the average separation distance between individual brush polymers. Therefore, we cannot assert the extent of interdigitation between the brush...density of grafted chains (e.g., in PN20-g-PBLGn) made it more difficulty for the polypeptides to facilitate interdigitation effectively. As the
Gingival health and frequency of tooth brushing in the beagle dog model. Clinical findings.
Tromp, J A; Jansen, J; Pilot, T
The aim of this experiment was to study clinical parameters when 3 different frequencies of plaque removal were applied to healthy gingivae in the beagle dog model. The maxillary first, second and third premolars of 12 beagle dogs, at the start of the experiment 2 years of age, were, after a thorough cleaning, submitted to daily plaque removal during a pre-experimental period of 8 weeks. At the start of the experiment, the dogs were distributed into 3 groups of 4 dogs each: one group was brushed 7 times a week, a second group was brushed 3 times a week and another group was brushed only once a week. Brushing was executed over a period of 24 weeks, on the right sides of the upper jaws. The left upper jaws served as controls. At regular intervals, the plaque index, the gingival index and probing depths were assessed. A "brushing effect" was calculated for each dog, to include information on all within-dog and between dog variations. Comparison of brushing effects revealed that in this experimental model, plaque removal with a frequency of 3 times a week was sufficient to preserve gingival health, whereas tooth brushing once a week resulted in gingival inflammation. Therefore it can be concluded that 3 times a week is the critical brushing frequency in the beagle dog model with healthy gingiva at baseline.
Friendship Network and Dental Brushing Behavior among Middle School Students: An Agent Based Modeling Approach.
Sadeghipour, Maryam; Khoshnevisan, Mohammad Hossein; Jafari, Afshin; Shariatpanahi, Seyed Peyman
By using a standard questionnaire, the level of dental brushing frequency was assessed among 201 adolescent female middle school students in Tehran. The initial assessment was repeated after 5 months, in order to observe the dynamics in dental health behavior level. Logistic Regression model was used to evaluate the correlation among individuals' dental health behavior in their social network. A significant correlation on dental brushing habits was detected among groups of friends. This correlation was further spread over the network within the 5 months period. Moreover, it was identified that the average brushing level was improved within the 5 months period. Given that there was a significant correlation between social network's nodes' in-degree value, and brushing level, it was suggested that the observed improvement was partially due to more popularity of individuals with better tooth brushing habit. Agent Based Modeling (ABM) was used to demonstrate the dynamics of dental brushing frequency within a sample of friendship network. Two models with static and dynamic assumptions for the network structure were proposed. The model with dynamic network structure successfully described the dynamics of dental health behavior. Based on this model, on average, every 43 weeks a student changes her brushing habit due to learning from her friends. Finally, three training scenarios were tested by these models in order to evaluate their effectiveness. When training more popular students, considerable improvement in total students' brushing frequency was demonstrated by simulation results.
Synthesis and characterization of poly(3-sulfopropylmethacrylate) brushes for potential antibacterial applications.
Ramstedt, Madeleine; Cheng, Nan; Azzaroni, Omar; Mossialos, Dimitris; Mathieu, Hans Jörg; Huck, Wilhelm T S
This article describes the aqueous atom transfer radical polymerization synthesis of poly(3-sulfopropylmethacrylate) brushes onto gold and Si/SiO2 surfaces in a controlled manner. The effect of Cu(I)/Cu(II) ratio was examined, and a quartz crystal microbalance was used to study the kinetics of the brush synthesis. The synthesized brushes displayed a thickness from a few nanometers to several hundred nanometers and were characterized using atomic force microscopy, ellipsometry, Fourier transform infrared spectroscopy (FTIR), contact angle measurements, and X-ray photoelectron spectroscopy (XPS). The as-synthesized sulfonate brushes had very good ion-exchange properties for the ions tested in this study, i.e., Na+, K+, Cu2+, and Ag+. FTIR and XPS show that the metal ions are coordinating to sulfonate moieties inside the brushes. The brushes were easily loaded with silver ions, and the effect of silver ion concentration on silver loading of the brush was examined. The silver-loaded brushes were shown to be antibacterial toward both gram negative and gram positive bacteria. The silver leaching was studied through leaching experiments into water, NaNO3, and NaCl (physiological medium). The results from these leaching experiments are compared and discussed in the article.
Synthesis and characterization of polystyrene brushes for organic thin film transistors.
Hwang, Do-Hoon; Nomura, Akihiro; Kim, Jeongsik; Kim, Ji-Hoon; Cho, Hyunduck; Lee, Changhee; Ohno, Kohji; Tsujii, Yoshinobu
We synthesized and characterized polystyrene brushes on a silicon wafer using surface-initiated atom transfer radical polymerization. The thickness of the polymer brush was controlled by adjusting the reaction time. We investigated monomer conversion as well as the molecular weight and density of the polymer brushes. When the monomer conversion reached 100%, the number-average molecular weight and film thickness reached 135,000 and 113 nm, respectively. The estimated densities of the synthesized polystyrene brushes were in the range 0.34-0.54 chains/nm2, high enough to be categorized in the "concentrated brush" regime. The synthesized polymer brush was used as an insulating layer in an organic thin-film transistor. Organic thin-film transistors were fabricated using pentacene as an active p-type organic semiconductor and a polystyrene brush on a SiO2 layer as a gate dielectric. The pentacene based organic thin-film transistor with the polystyrene brush exhibited a field-effect mobility microFET of 0.099 cm2/(V x s).
Motion of integrated CdS nanoparticles by phase separation of block copolymer brushes.
Yu, Kai; Wang, Hanfu; Han, Yanchun
A new method of reversibly moving CdS nanoparticles in the perpendicular direction was developed on the basis of the phase separation of block copolymer brushes. Polystyrene-b-(poly(methyl methacrylate)-co-poly(cadmium dimethacrylate)) (PS-b-(PMMA-co-PCdMA)) brushes were grafted from the silicon wafer by surface-initiated atom transfer radical polymerization (ATRP). By exposing the polymer brushes to H2S gas, PS-b-(PMMA-co-PCdMA) brushes were converted to polystyrene-b-(poly(methyl methacrylate)-co-poly(methacrylic acid)(CdS)) (PS-b-(PMMA-co-PMAA(CdS))) brushes, in which CdS nanoparticles were chemically bonded by the carboxylic groups of PMAA segment. Alternating treatment of the PS-b-(PMMA-co-PMAA(CdS)) brushes by selective solvents for the outer block (a mixed solvent of acetone and ethanol) and the inner PS block (toluene) induced perpendicular phase separation of polymer brushes, which resulted in the reversible lifting and lowering of CdS nanoparticles in the perpendicular direction. The extent of movement can be adjusted by the relative thickness of two blocks of the polymer brushes.
Mixed brush of chemically and physically adsorbed polymers under shear: inverse transport of the physisorbed species.
Pastorino, C; Müller, M
We study mixed brushes under shear flow by molecular dynamics simulation with an explicit solvent. The primary brush is formed by chemically grafting polymers to a solid substrate, the secondary brush is comprised of shorter, physically end-adsorbed molecules that can laterally diffuse. By virtue of the immobility of the grafted end-points of the primary brush, its individual macromolecules perform a cyclic motion. If there is a well defined solvent-brush interface, this cyclic motion of the primary brush molecules will collectively result in the reversal of the flow inside of the primary brush. This backflow, linear in the shear rate, gives rise to the transport of the shorter, physically end-adsorbed molecules in the opposite direction of the solvent flow. We discuss which conditions are necessary to observe this counter-intuitive phenomenon. Comparing Poiseuille and Couette flow we demonstrate that the magnitude of the local shear rate at the brush-liquid interface dictates the cyclic motion and concomitant inversion of transport but that these universal effects are independent of the type of driving the flow.
Supramolecular Magnetic Brushes: The Impact of Dipolar Interactions on the Equilibrium Structure
The equilibrium structure of supramolecular magnetic filament brushes is analyzed at two different scales. First, we study the density and height distributions for brushes with various grafting densities and chain lengths. We use Langevin dynamics simulations with a bead–spring model that takes into account the cross-links between the surface of the ferromagnetic particles, whose magnetization is characterized by a point dipole. Magnetic filament brushes are shown to be more compact near the substrate than nonmagnetic ones, with a bimodal height distribution for large grafting densities. This latter feature makes them also different from brushes with electric dipoles. Next, in order to explain the observed behavior at the filament scale, we introduce a graph theory analysis to elucidate for the first time the structure of the brush at the scale of individual beads. It turns out that, in contrast to nonmagnetic brushes, in which the internal structure is determined by random density fluctuations, magnetic forces introduce a certain order in the system. Because of their highly directional nature, magnetic dipolar interactions prevent some of the random connections to be formed. On the other hand, they favor a higher connectivity of the chains' free and grafted ends. We show that this complex dipolar brush microstructure has a strong impact on the magnetic response of the brush, as any weak applied field has to compete with the dipole–dipole interactions within the crowded environment. PMID:26538768
Analytic models of regularly branched polymer brushes using the self-consistent mean field theory
NASA Astrophysics Data System (ADS)
LeSher, Daniel
Polymer brushes consist of multiple monomers connected together with one of the polymer chain's ends attached to a surface. Polymer brushes have shown great promise for a wide variety of applications including drug delivery dendrimer systems and as tunable brushes that can change their shape and physical properties in response to changes in their environment. Regularly branched polymer brushes which are structured as a function of their chemical indices are investigated here using the self-consistent mean field theory for electrically neutral polymers. The brushes were described using weighting functions, f(n), were n was the fewest number of monomers from a specified location to a free end. Brushes with weighting functions of the form f(n)=nb, f(n)=ebn, as well as f(n)=dan when d 2 and alpha > 2 were found to match the parabolic free chain end profile expected, while it was determined that polymer brushes described using f(n)=n b must be very small in order to remain in equilibrium. However, brushes described by f(n)=2G(N-n) N and f(n)2n were found to be unstable for real, positive values of the potential of the system.
Process Of Bonding A Metal Brush Structure To A Planar Surface Of A Metal Substrate
Slattery, Kevin T.; Driemeyer, Daniel E.; Wille; Gerald W.
Process for bonding a metal brush structure to a planar surface of a metal substrate in which an array of metal rods are retained and immobilized at their tips by a common retention layer formed of metal, and the brush structure is then joined to a planar surface of a metal substrate via the retention layer.
Brush Seal Arrangement for the RS-68 Turbopump Set
NASA Technical Reports Server (NTRS)
Nunez, D.; Ransom, D.; Prueger, G.
The nature of the RS-68 turbopumps requires that the hydrogen seals separating the pump from the turbine must have extremely low levels of leakage and be contained in small packages. Conventional seal technologies are not able to reasonably satisfy such design requirements. A review of experimental measurements and analysis publications suggests that brush seals are well suited for the design requirements. Brush seals are shown to have less leakage than conventional labyrinth and damper seals and have no adverse effects on the rotordynamics of the machine. The bulk-flow analysis presented by Hendricks et al. is used as a guideline to create a spreadsheet that provides mass flow through the seal and heat generated by the rubbing contact of the bristles on the shaft. The analysis is anchored to published data for LN2 and LH2 leakage tests. Finally, the analysis is used to design seals for both applications. It is observed that the most important analysis parameter is the thickness of the bristle pack and its relationship to seal clearance, lay angle and pressure drop.
Brush seal bristle flexure and hard-rub characteristics
NASA Technical Reports Server (NTRS)
Hendricks, Robert C.; Carlile, Julie A.; Liang, Anita D.
The bristles of a 38.1-mm (1.5-in.) diameter brush seal were flexed by a tapered, 40-tooth rotor operating at 2600 rpm that provided sharp leading-edge impact of the bristles with hard rubbing of the rotor lands. Three separate tests were run with the same brush accumulating over 1.3 x 10(exp 9) flexure cycles while deteriorating 0.2 mm (0.008 in.) radially. In each, the test bristle incursion depth varied from 0.130 to 0.025 mm (0.005 to 0.001 in.) or less (start to stop), and in the third test the rotor was set 0.25 mm (0.010 in.) eccentric. Runout varied from 0.025 to 0.076 mm (0.001 to 0.003 in.) radially. The bristles wore but did not pull out, fracture, or fragment. Bristle and rotor wear debris were deposited as very fine, nearly amorphous, highly porous materials at the rotor groove leading edges and within the rotor grooves. The land leading edges showed irregular wear and the beginning of a convergent groove that exhibited sharp, detailed wear at the land trailing edges. Surface grooving, burnishing, 'whipping', and hot spots and streaks were found. With a smooth-plug rotor, post-test leakage increased 30 percent over pretest leakage.
Brush seal bristle flexure and hard-rub characteristics
NASA Astrophysics Data System (ADS)
Hendricks, Robert C.; Carlile, Julie A.; Liang, Anita D.
The bristles of a 38.1-mm (1.5-in.) diameter brush seal were flexed by a tapered, 40-tooth rotor operating at 2600 rpm that provided sharp leading-edge impact of the bristles with hard rubbing of the rotor lands. Three separate tests were run with the same brush accumulating over 1.3 x 10(exp 9) flexure cycles while deteriorating 0.2 mm (0.008 in.) radially. In each, the test bristle incursion depth varied from 0.130 to 0.025 mm (0.005 to 0.001 in.) or less (start to stop), and in the third test the rotor was set 0.25 mm (0.010 in.) eccentric. Runout varied from 0.025 to 0.076 mm (0.001 to 0.003 in.) radially. The bristles wore but did not pull out, fracture, or fragment. Bristle and rotor wear debris were deposited as very fine, nearly amorphous, highly porous materials at the rotor groove leading edges and within the rotor grooves. The land leading edges showed irregular wear and the beginning of a convergent groove that exhibited sharp, detailed wear at the land trailing edges. Surface grooving, burnishing, 'whipping', and hot spots and streaks were found. With a smooth-plug rotor, post-test leakage increased 30 percent over pretest leakage.
Anomalous Shrinking-Swelling of Nanoconfined End-Charged Polyelectrolyte Brushes: Interplay of Confinement and Electrostatic Effects.
Chen, Guang; Das, Siddhartha
In this article, we model the structure and configuration of the end-charged polyelectrolyte (PE) brushes grafted on the inner walls of a nanochannel. When the confinement effect is weak, that is, d0 < h/2 (d0 is the PE brush height without electrostatic effects and h is the nanochannel half-height), d < d0 (d is the brush height with the electrostatic effects), that is, the brushes shrink due to the electrostatic effects. Furthermore, for this case, an increase in salt concentration increases d. On the contrary, for the case in which the confinement effect is strong (i.e., d0 > h/2), d > d0 (i.e., the electrostatic effects swell the brushes), and an increase in salt concentration decreases the brush height. These findings reveal that the behavior of the end-charged brushes shows three unique differences when compared to that of the standard PE brushes with charges along their entire backbone. These differences are (a) the presence of a distinct role of the confinement in dictating how the electrostatic effects mediated by the electric double layer govern the height of end-charged brushes, (b) electrostatic-effect-driven shrinking of end-charged brushes for d0 < h/2 (for backbone-charged brushes, the electrostatic effects always swell the brushes), and (c) swelling of end-charged brushes with an increase in salt concentration for d0 < h/2 (backbone-charged brushes always shrink with an increase in salt concentration). Such unique effects of confinement and electrostatics on PE brushes have not been reported previously, and we anticipate that these findings will shed new light on the structure and properties of PE-brush-functionalized nanochannels with implications in applications such as fabrication of functionalized-nanochannel-based nanofluidic diodes, valves, biosensors, current rectifiers, and so forth.
In Situ Infrared Ellipsometry for Protein Adsorption Studies on Ultrathin Smart Polymer Brushes in Aqueous Environment
Kroning, Annika; Furchner, Andreas; Aulich, Dennis; Bittrich, Eva; Rauch, Sebastian; Uhlmann, Petra; Eichhorn, Klaus-Jochen; Seeber, Michael; Luzinov, Igor; Kilbey, S. Michael; Lokitz, Bradley S.; Minko, Sergiy; Hinrichs, Karsten
The protein-adsorbing and -repelling properties of various smart nanometer-thin polymer brushes with high potential for biosensing and biomedical applications are studied by in-situ infrared-spectroscopic ellipsometry (IRSE). IRSE as a highly sensitive non-destructive technique allows us to investigate protein adsorption on polymer brushes in aqueous environment in dependence of external stimuli like temperature and pH. These stimuli are, for instance, relevant in switchable mixed brushes containing poly(N-isopropyl acrylamide) and poly(acrylic acid), respectively. We use such brushes as model surfaces for controlling protein adsorption of human serum albumin and human fibrinogen. IRSE can distinguish between polymer-specific vibrational bands, which yield insights into the hydration state of the brushes, and changes in the protein-specific amide bands, which are related to changes of the protein secondary structure.
In Situ Infrared Ellipsometry for Protein Adsorption Studies on Ultrathin Smart Polymer Brushes in Aqueous Environment
Kroning, Annika; Furchner, Andreas; Aulich, Dennis; ...
The protein-adsorbing and -repelling properties of various smart nanometer-thin polymer brushes with high potential for biosensing and biomedical applications are studied by in-situ infrared-spectroscopic ellipsometry (IRSE). IRSE as a highly sensitive non-destructive technique allows us to investigate protein adsorption on polymer brushes in aqueous environment in dependence of external stimuli like temperature and pH. These stimuli are, for instance, relevant in switchable mixed brushes containing poly(N-isopropyl acrylamide) and poly(acrylic acid), respectively. We use such brushes as model surfaces for controlling protein adsorption of human serum albumin and human fibrinogen. IRSE can distinguish between polymer-specific vibrational bands, which yield insights intomore » the hydration state of the brushes, and changes in the protein-specific amide bands, which are related to changes of the protein secondary structure.« less
Brushes of flexible, semiflexible, and rodlike diblock polyampholytes: Molecular dynamics simulation and scaling analysis.
Baratlo, Majid; Fazli, Hossein
Planar brushes of flexible, semiflexible, and rodlike diblock polyampholytes are studied using molecular dynamics simulations in a wide range of the grafting density. Simulations show linear dependence of the average thickness on the grafting density in all cases regardless of different flexibility of anchored chains and the brushes' different equilibrium conformations. Slopes of fitted lines to the average thickness of the brushes of semiflexible and rodlike polyampholytes versus the grafting density are approximately the same and differ considerably from that of the brushes of flexible chains. The average thickness of the brush of flexible diblock polyampholytes as a function of the grafting density is also obtained using a simple scaling analysis, which is in good agreement with our simulations.
Characterization of swollen structure of high-density polyelectrolyte brushes in salt solution by neutron reflectivity
NASA Astrophysics Data System (ADS)
Kobayashi, Motoyasu; Terayama, Yuki; Hino, Masahiro; Ishihara, Kazuhiko; Takahara, Atsushi
Zwitterionic and cationic polyelectrolyte brushes on quartz substrate were prepared by surface-initiated atom transfer radical polymerization of 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) and 2-(methacryloyloxy)ethyltrimethylammonium chloride (METAC), respectively. The effects of ionic strength on brush structure and surface properties of densely grafted polyelectrolyte brushes were analysed by neutron reflectivity (NR) measurements. NR at poly(METAC)/D2O and poly(MPC)/D2O interface revealed that the grafted polymer chains were fairly extended from the substrate surface, while the thickness reduction of poly(METAC) brush was observed in 5.6 M NaCl/D2O solution due to the screening of the repulsive interaction between polycations by hydrated salt ions. Interestingly, no structural change was observed in poly(MPC) brush even in a salt solution probably due to the unique interaction properties of phosphorylcholine units.
Observation of slow down of polystyrene nanogels diffusivities in contact with swollen polystyrene brushes.
Michailidou, V N; Loppinet, B; Vo, C D; Rühe, J; Tauer, K; Fytas, G
The diffusion of dilute colloids in contact with swollen polymer brushes has been studied by evanescent wave dynamic light scattering. Two polystyrene nanogels with 16 nm and 42 nm radius were put into contact with three polystyrene brushes with varying grafting densities. Partial penetration of the nanogels within the brushes was revealed by the evanescent wave penetration depth-dependent scattering intensities. The experimental short-time diffusion coefficients of the penetrating particles were measured and found to strongly slow down as the nanoparticles get deeper into the brushes. The slow down is much more marked for the smaller (16 nm) nanogels, suggesting a size exclusion type of mechanism and the existence of a characteristic length scale present in the outer part of the brush.
Development and Application of a Brush-Spray Derived from a Calligraphy-Brush-Style Synthetic Hair Pen for Use in ESI/MS
Liu, Jen-Ying; Chen, Pei-Chun; Liou, Yea-Wenn; Chang, Kai-Yin; Lin, Cheng-Huang
The development of a novel type of a sampling/ionization kit for use in electrospray ionization/mass spectrometry is reported. Using a small calligraphy-brush-style synthetic hair pen (nylon-brush), and analogous to paper-spray mass spectrometry, the analytes can be collected, elution/desorption and then ionized from the surface of the nylon-brush. The body of the kit was produced by means of a commercial 3D-printer, in which ABS (acrylonitrile butadiene styrene) was used as the starting material. Meanwhile, a small nylon-brush was embedded inside a 3D-printed plastic cell, in which a solvent was supplied to rinse the brush by means of capillary action. The size and weight of the kit were 1 g and 4 cm, respectively. The kit is disposable and it has various functions, including non-invasive sampling, sample-evaporation and ionization. As a result, when a type of pesticide was selected as the test sample (dimethoate; C5H12NO3PS2), the limit of detection was determined to be 0.1 μg/mL. Collecting the pesticide from a leaf-surface (lettuce) was also successful. The process for fabricating the nylon-brush kit and the optimized experimental conditions are reported herein. PMID:28337397
Development and Application of a Brush-Spray Derived from a Calligraphy-Brush-Style Synthetic Hair Pen for Use in ESI/MS.
Liu, Jen-Ying; Chen, Pei-Chun; Liou, Yea-Wenn; Chang, Kai-Yin; Lin, Cheng-Huang
The development of a novel type of a sampling/ionization kit for use in electrospray ionization/mass spectrometry is reported. Using a small calligraphy-brush-style synthetic hair pen (nylon-brush), and analogous to paper-spray mass spectrometry, the analytes can be collected, elution/desorption and then ionized from the surface of the nylon-brush. The body of the kit was produced by means of a commercial 3D-printer, in which ABS (acrylonitrile butadiene styrene) was used as the starting material. Meanwhile, a small nylon-brush was embedded inside a 3D-printed plastic cell, in which a solvent was supplied to rinse the brush by means of capillary action. The size and weight of the kit were 1 g and 4 cm, respectively. The kit is disposable and it has various functions, including non-invasive sampling, sample-evaporation and ionization. As a result, when a type of pesticide was selected as the test sample (dimethoate; C5H12NO3PS2), the limit of detection was determined to be 0.1 μg/mL. Collecting the pesticide from a leaf-surface (lettuce) was also successful. The process for fabricating the nylon-brush kit and the optimized experimental conditions are reported herein.
Intrinsic disorder of the bacterial cell division protein ZipA: coil-to-brush conformational transition.
López-Montero, Iván; López-Navajas, Pilar; Mingorance, Jesús; Rivas, Germán; Vélez, Marisela; Vicente, Miguel; Monroy, Francisco
The full-length ZipA protein from Escherichia coli, one of the essential elements of the cell division machinery, was studied in a surface model built as adsorbed monolayers. The interplay between lateral packing and molecular conformation was probed using a combined methodology based on the scaling analysis of the surface pressure isotherms and ellipsometry measurements of the monolayer thickness. The observed behavior is compatible with the one expected for an intrinsically disordered and highly flexible protein that is preferentially structured in a random coil conformation. At low grafting densities, ZipA coils organize in a mushroom-like regime, whereas a coil-to-brush transition occurs on increasing lateral packing. The structural results suggest a functional scenario in which ZipA acts as a flexible tether anchoring bacterial proto-ring elements to the membrane during the earlier stages of division.
The effects of dietary phosphorus deficiency on surface pH and membrane composition of the mucosa epithelium in caprine jejunum.
Busche, R; Schröder, B; Huber, K; Sallmann, H P; Breves, G
In ruminants, the uptake of inorganic phosphate (P(i)) across the intestinal mucosa epithelium by Na-dependent and Na-independent mechanisms is a main regulatory factor in P homeostasis. The aim of the study was to elucidate to which extent Na-independent mechanisms, including pH effects or composition of mucosal brush-border membranes, could be involved in positive stimulation of P(i) absorptive processes seen under the P deficient condition. Therefore, luminal, surface and intracellular pH of the jejunal epithelial cells in control and P depleted goats were compared and biochemical analyses of membrane phospholipids in the apical membrane of the jejunal epithelium were performed. Dietary P depletion resulted in decreased plasma P(i) levels. While pH in jejunal ingesta was not significantly changed, P depletion resulted in a significantly lower surface pH in the crypt region compared to control animals (7.62 +/- 0.02 vs. 7.77 +/- 0.04, n = 4, P < 0.01). Inhibition of apical Na(+)/H(+)-exchange resulted in an increase of the jejunal surface pH in P depleted animals by 0.07 +/- 0.01 (n = 6, P < 0.01) and 0.05 +/- 0.01 (n = 6, P < 0.01) for the villus and the crypt region, respectively. This increase were inversely correlated with the initial surface pH prior to inhibition. In contrast to surface pH, intracellular pH of the jejunal epithelium and the phospholipid composition of the apical jejunal membrane were not affected by P depletion. Although the data suggest the existence of a Na(+)/H(+)-exchange mechanism at the luminal surface of goat jejunum they do not support the hypothesis that adaptational processes of active P(i) absorption from goat jejunum in response to low dietary P could be based on "non P(i) transporter events".
ESCRTs breach the nuclear border.
Webster, Brant M; Lusk, C Patrick
The endosomal sorting complexes required for transport (ESCRT) are best known for their role in sorting ubiquitylated membrane proteins into endosomes. The most ancient component of the ESCRT machinery is ESCRT-III, which is capable of oligomerizing into a helical filament that drives the invagination and scission of membranes aided by the AAA ATPase, Vps4, in several additional subcellular contexts. Our recent study broadens the work of ESCRT-III by identifying its role in a quality control pathway at the nuclear envelope (NE) that ensures the normal biogenesis of nuclear pore complexes (NPCs). Here, we will elaborate on how we envision this mechanism to progress and incorporate ESCRT-III into an emerging model of nuclear pore formation. Moreover, we speculate there are additional roles for the ESCRT-III machinery at the NE that broadly function to ensure its integrity and the maintenance of the nuclear compartment.
Semantic Borders and Incomplete Understanding.
Silva-Filho, Waldomiro J; Dazzani, Maria Virgínia
In this article, we explore a fundamental issue of Cultural Psychology, that is our "capacity to make meaning", by investigating a thesis from contemporary philosophical semantics, namely, that there is a decisive relationship between language and rationality. Many philosophers think that for a person to be described as a rational agent he must understand the semantic content and meaning of the words he uses to express his intentional mental states, e.g., his beliefs and thoughts. Our argument seeks to investigate the thesis developed by Tyler Burge, according to which our mastery or understanding of the semantic content of the terms which form our beliefs and thoughts is an "incomplete understanding". To do this, we discuss, on the one hand, the general lines of anti-individualism or semantic externalism and, on the other, criticisms of the Burgean notion of incomplete understanding - one radical and the other moderate. We defend our understanding that the content of our beliefs must be described in the light of the limits and natural contingencies of our cognitive capacities and the normative nature of our rationality. At heart, anti-individualism leads us to think about the fact that we are social creatures, living in contingent situations, with important, but limited, cognitive capacities, and that we receive the main, and most important, portion of our knowledge simply from what others tell us. Finally, we conclude that this discussion may contribute to the current debate about the notion of borders.
Electrophysiological, morphological and topological properties of two histochemically distinct subpopulations of cerebellar unipolar brush cells
Kim, Jin-Ah; Sekerková, Gabriella; Mugnaini, Enrico; Martina, Marco
Unipolar brush cells (UBCs) are excitatory cerebellar granular layer interneurons whose brush-like dendrites receive one-to-one mossy fiber inputs. Subclasses of UBCs differ primarily by expressing metabotropic glutamate receptor (mGluR) 1α or calretinin. We used GENSAT Tg(Grp-EGFP) BAC-transgenic mice, which selectively express EGFP in mGluR1α-positive UBCs to compare the functional properties of the two subclasses. Compared to EGFP-negative UBCs, which include the calretinin-positive cells, EGFP-positive UBCs had smaller somata (diameter 18 vs. 21 μm), lower specific membrane resistance (6.4 vs.13.7 KΩ*cm2), were less prone to intrinsic firing and showed more irregular firing (in cell-attached ~49% were firing vs. ~88%, and the CV was 0.53 vs. 0.32 for EGFP-negative cells). Some of these differences are attributable to higher density of background K+ currents in EGFP-positive cells (at −120 mV the barium-sensitive current was 94 pA, vs 37 pA in EGFP-negative cells); Ih, on the contrary, was more abundantly expressed in EGFP-negative cells (at −140 mV it was −122 pA vs. −54 pA in EGFP-positive neurons); furthermore, while group II mGluR modulation of the background potassium current in EGFP-negative UBCs was maintained after intracellular dialysis, mGluR modulation in EGFP-positive UBCs was lost in whole cell recordings. Finally, cell-attached firing was reversibly abolished by the GABAB activation in EGFP-positive, but not in EGFP-negative UBCs. Immunohistochemistry showed that EGFP-negative UBCs express GIRK2 at high density, while mGluR1 UBCs are GIRK2-negative, suggesting that GIRK2 mediates the mGluR-sensitive current in EGFP-negative UBCs. These data suggest that the two subclasses perform different functions in the cerebellar microcircuits. PMID:22528965
Dynamics of an unconstrained oscillatory flicking brush for road sweeping
NASA Astrophysics Data System (ADS)
Vanegas Useche, L. V.; Abdel Wahab, M. M.; Parker, G. A.
This article studies the dynamics of a freely rotating flicking brush by means of a mathematical model. The bristles are treated as cantilever prismatic beams subjected to small deflections. A solution of the equation of motion for their forced transverse vibration is obtained through the normal-mode method. A novel oscillatory motion is superimposed onto the rotary motion of the brush. Two functions of oscillation are investigated: a sinusoidal angular velocity and a novel function, named after the authors 'VAP' (Vanegas Useche, Abdel Wahab, Parker), developed to provide small shaft accelerations. The VAP function may be a square wave, a triangle wave, or a smooth wave between them, depending on the value of a smoothness parameter, b. The results indicate that the maximum bending moment, stress, and deflection are independent of the mean angular velocity, are proportional to its alternating component, and increase linearly with the mount radius and the sine of the mount angle. In addition, the behaviour of the brush is strongly affected by the frequency of oscillation, the type of function, the value of b, and bristle wear, amongst other parameters. For the sinusoidal and VAP function, resonance occurs at the bristle natural frequencies. Moreover, the VAP function tends to produce a condition similar to resonance also at odd fractions of the natural frequencies. This phenomenon may be accentuated or reduced, by adjusting the value of b, and be expedited or impeded, by the selection of the frequency. The results of this work may also be applied to the case of a small-deflection cantilever beam, when the transverse external force is a sinusoidal, square, or triangle wave or when it is given by the new VAP function. Finally, the VAP wave may enable to excite a condition similar to resonance not only at the natural frequencies of the beam, but also at odd fractions of them. Small frequencies may be required to achieve a resonant behaviour of a high-frequency mode
Tooth brushing and utilization of dental services in Fiji (1998).
King, Temalesi
Utilization of services is considered the presence or absence of care received. The most common measure of utilization is the annual number of dental visits per person. This study aims to determine oral health practices, which were a measure of their oral hygiene status and the use of health care facilities. It also aims to investigate the major problems that exist within the health care system in 1998, which may explain the lack of use of dental services. Fijians and Indo-Fijians were two ethnic groups in the sample, selected by stratified multi-stage cluster sampling. Only two age categories, 15-19 and 35-44 year-olds were selected being the index age for World Health Organization in Oral Health Surveys. A total of 1,000 questionaires were distributed and the completed questionnaires (n = 619) were collected immediately. Thirty one percent of the respondents indicated that they learnt to care for their teeth from dental personnel. Of the individuals who brushed their teeth twice a day, 41% visited the dentist within the last 12 months. Majority of the individuals (65%) who brushed their teeth twice or more daily indicated that they needed dental treatment. Individuals who visited the dentist within the last 12 months reported having a tooth extracted (53%), check-up (29%), filling (8.9%), polishing of teeth (3.7%), gum problem (3.2%) and false teeth (1.8%). Individuals who brushed twice daily did not visit the dentist within the last 12 months because nothing was wrong (63.2%), too busy (9%) and afraid of the dentist (7%). More than 80% of the respondents were satisfied with the current services, but indicated improvement on the waiting time (31.2%), availability of more treatment options in dental clinics (27.5%), dental fees (15.4%), improvement on the facilities for dental care (10.1%), a customer-friendly dental personnel (9.4%) and considerations for infection control (6.4%).
The U.S.-Mexico Border Infectious Disease Surveillance Project: Establishing Binational Border Surveillance
Waterman, Stephen; Lucas, Carlos Alvarez; Falcon, Veronica Carrion; Morales, Pablo Kuri; Lopez, Luis Anaya; Peter, Chris; Gutiérrez, Alejandro Escobar; Gonzalez, Ernesto Ramirez; Flisser, Ana; Bryan, Ralph; Valle, Enrique Navarro; Rodriguez, Alfonso; Hernandez, Gerardo Alvarez; Rosales, Cecilia; Ortiz, Javier Arias; Landen, Michael; Vilchis, Hugo; Rawlings, Julie; Leal, Francisco Lopez; Ortega, Luis; Flagg, Elaine; Conyer, Roberto Tapia; Cetron, Martin
In 1997, the Centers for Disease Control and Prevention, the Mexican Secretariat of Health, and border health officials began the development of the Border Infectious Disease Surveillance (BIDS) project, a surveillance system for infectious diseases along the U.S.-Mexico border. During a 3-year period, a binational team implemented an active, sentinel surveillance system for hepatitis and febrile exanthems at 13 clinical sites. The network developed surveillance protocols, trained nine surveillance coordinators, established serologic testing at four Mexican border laboratories, and created agreements for data sharing and notification of selected diseases and outbreaks. BIDS facilitated investigations of dengue fever in Texas-Tamaulipas and measles in California–Baja California. BIDS demonstrates that a binational effort with local, state, and federal participation can create a regional surveillance system that crosses an international border. Reducing administrative, infrastructure, and political barriers to cross-border public health collaboration will enhance the effectiveness of disease prevention projects such as BIDS. PMID:12533288
Altered binding of the Cry1Ac toxin to larval membranes but not to the toxin-binding protein in Plodia interpunctella selected for resistance to different Bacillus thuringiensis isolates.
Mohammed, S I; Johnson, D E; Aronson, A I
Immunoblotting and cytochemical procedures were used to determine whether toxin binding was altered in strains of the Indianmeal moth, Plodia interpunctella, selected for resistance to various strains of Bacillus thuringiensis. Each of these B. thuringiensis subspecies produces a mixture of protoxins, primarily Cry1 types, and the greatest insect resistance is to the Cry1A protoxins. In several cases, however, there was also resistance to toxins not present in the B. thuringiensis strains used for selection. The Cry1Ab and Cry1Ac toxins bound equally well over a range of toxin concentrations and times of incubation to a single protein of ca. 80-kDa in immunoblots of larval membrane extracts from all of the colonies. This binding protein is essential for toxicity since a mutant Cry1Ac toxin known to be defective in binding and thus less toxic bound poorly to the 80-kDa protein. This binding protein differed in size from the major aminopeptidase N antigens implicated in toxin binding in other insects. Binding of fluorescently labeled Cry1Ac or Cry1Ab toxin to larval sections was found at the tips of the brush border membrane prepared from the susceptible but not from any of the resistant P. interpunctella. Accessibility of a major Cry1A-binding protein appears to be altered in resistant larvae and could account for their broad resistance to several B. thuringiensis toxins. PMID:8900008
Rep. Myrick, Sue Wilkins [R-NC-9
03/16/2009 Referred to the Subcommittee on Immigration, Citizenship, Refugees, Border Security, and International Law. (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:
Training mentally retarded adolescents to brush their teeth.
Horner, R D; Keilitz, I
The need for self-care by retarded individuals in behaviors such as brushing teeth led to the development and evaluation of a comprehensive toothbrushing program that included a task analysis and training procedure specific to each component of the task analysis. Eight mentally retarded adolescents, in two groups, individually received acquisition training that included scheduled opportunities for independent performances, verbal instruction, modelling, demonstration, and physical assistance. The first group of four subjects received token plus social reinforcement; the second received only social reinforcement. All eight subjects showed improved toothbrushing behaviors when compared to baseline. Six of the eight subjects correctly performed all toothbrushing steps in two of three consecutive sessions. The study emphasizes the need for systematic program development and evaluation. PMID:1184494
Design optimization of a brush turbine with a cleaner/water based solution
NASA Technical Reports Server (NTRS)
Kim, Rhyn H.
Recently, a fluid turbine which has a brush attached to it has been designed and tested with water as fluid. The purpose of the turbine-brush is to clean up fouling in a tube. The Montreal Protocol prohibits the use of CFC products from refrigeration industry or from industry in general as a cleanser in 1996. Alternatives for the cleansers, devices or a combination of alternative devices with a cleanser should be found. One of the methods is to develop a device which cleans fouling with a cleaning medium. In this paper, we describe a turbine connected with a brush. However, the turbine with the brush should be simple and easy to install. This device is a combined small liquid turbine with a brush. The turbine is activated by the liquid flowing through the tube. Then the turbine turns the brush cleaning fouling along the tube. Based on the energy conservation and the Bernoulli equation along with an empirical relationship of drag force obtained from an experimental apparatus, a relationship of the rotational speed, the number of blades, and geometric variables of the turbine-brush was obtained. The predicted rotational speeds were compared with the experimental observations. Further work was recommended for improvements.
pH-dependent control of particle motion through surface interactions with patterned polymer brush surfaces.
Dunderdale, Gary; Howse, Jonathan; Fairclough, Patrick
In this Article, we show that inclined silicon surfaces patterned with poly(methacrylic acid) brushes are able to control the position and movement of 20 μm silica particles, which are propelled across the patterned surface by sedimentation forces. Three different types of behavior were observed depending on the angle between the direction in which a particle sedimented and the orientation of the polymer-brush silicon interface. At small angles, particles were found to sediment to the brush interface and then sediment following the direction of the brush interface. At larger angles, particles sedimented to the interface and then followed the direction of the brush interface, but then after a certain distance changed direction to pass over the interface. At the largest angles where the brush interface was approximately perpendicular to the motion of the particle, particles were found to travel over the interface unperturbed. This behavior was also found to be pH dependent, allowing the formation of pH responsive "gates", which allow particles to pass at low pH but not at high pH. It was also found that if patterned polymer brush surfaces were oriented in the correct way, they were able to control the number of particles present at specific locations.
Synthesis and Biomedical Applications of Poly((meth)acrylic acid) Brushes.
Qu, Zhenyuan; Xu, Hong; Gu, Hongchen
Poly((meth)acrylic acid) (P(M)AA) brushes possess a number of distinctive properties that are particularly attractive for biomedical applications. This minireview summarizes recent advances in the synthesis and biomedical applications of P(M)AA brushes and brushes containing P(M)AA segments. First, we review different surface-initiated polymerization (SIP) methods, with a focus on recent progress in the surface-initiated controlled/living radical polymerization (SI-CLRP) techniques used to generate P(M)AA brushes with a tailored structure. Next, we discuss biomolecule immobilization methods for P(M)AA brushes, including physical adsorption, covalent binding, and affinity interactions. Finally, typical biomedical applications of P(M)AA brushes are reviewed, and their performance is discussed based on their unique properties. We conclude that P(M)AA brushes are promising biomaterials, and more potential biomedical applications are expected to emerge with the further development of synthetic techniques and increased understanding of their interactions with biological systems.
Nanocomposites Consisting of Nanoparticles with Multidentate PS Brushes Mixed with PS Matrices
NASA Astrophysics Data System (ADS)
Lee, Hyemin; Wooh, Sanghyuk; Lim, Jaehoon; Zorn, Matthias; Zentel, Rudolf; Char, Kookheon
In order to prevent massive phase separation of nanoparticles (NP) in a polymer matrix, the relevant hybridization of NPs with polymer matrices has proven to be an effective method for the high performance of nanocomposites in applications. The surface of inorganic (gold or QD) NPs of various size was modified with polystyrene (PS) polymer brushes, poly(styrene)-block-poly(cysteamine methyl disulfide), by the ligand exchange procedure. The disulfide groups in the PS brushes act as anchoring blocks for NPs. Different PS brushes were prepared with different total molecular weights and mole fractions of disulfide moieties. Compared with NPs dispersed in PS without disulfide anchoring groups, NPs anchored with PS brushes through disulfide groups were uniformly distributed within PS matrices. The dispersion of NPs within a polymer matrix was found to be influenced by the total molecular weight of PS brushes as well as the number of anchoring disulfide groups. Furthermore, the effect of the ratio between relative size of NP and the radius of gyration of a polymer brush as well as the grafting density of PS brushes anchored onto NPs on the NP distribution within a polymer matrix is discussed.
Modeling lower critical solution temperature behavior of associating polymer brushes with classical density functional theory.
Gong, Kai; Marshall, Bennett D; Chapman, Walter G
We study the lower critical solution temperature (LCST) behavior of associating polymer brushes (i.e., poly(N-isopropylacrylamide)) using classical density functional theory. Without using any empirical or temperature-dependent parameters, we find the phase transition of polymer brushes from extended to collapsed structure with increasing temperature, indicating the LCST behavior of polymer brushes. The LCST behavior of associating polymer brushes is attributed to the interplay of hydrogen bonding interactions and Lennard-Jones attractions in the system. The effect of grafting density and molecular weight on the phase behavior of associating polymer brushes has been also investigated. We find no LCST behavior at low grafting density or molecular weight. Moreover, increasing grafting density decreases the LCST and swelling ratio of polymer brushes. Similarly, increasing molecular weight decreases the LCST but increases the swelling ratio. At very high grafting density, a partial collapsed structure appears near the LCST. Qualitatively consistent with experiments, our results provide insight into the molecular mechanism of LCST behavior of associating polymer brushes.
Oxidation and Volatilization from Tungsten Brush High Heat Flux Armor During High Temperature Steam Exposure
Smolik, Galen Richard; Pawelko, Robert James; Anderl, Robert Andrew; Petti, David Andrew
Tungsten brush accommodates thermal stresses and high heat flux in fusion reactor components such as plasma facing surfaces or armor. However, inherently higher surface areas are introduced with the brush design. We have tested a specific design of tungsten brush in steam between 500 and 1100°C. Hydrogen generation and tungsten volatilization rates were determined to address fusion safety issues. The brush prepared from 3.2-mm diameter welding rods had a packing density of 85 percent. We found that both hydrogen generation and tungsten volatilization from brush, fixtured to represent a unit within a larger component, were less than projections based upon the total integrated surface area (TSA). Steam access and the escape of hydrogen and volatile oxide from void spaces within the brush are restricted compared to specimens with more direct diffusion pathways to the test environment. Hydrogen generation rates from restrained specimens based on normal surface area (NSA) remain about five times higher than rates based on total surface areas from specimens with direct steam access. Volatilization rates from restrained specimens based upon normal surface area (NSA) were only 50 percent higher than our historic cumulative maximum flux plot (CMFP) for tungsten. This study has shown that hydrogen generation and tungsten volatilization from brush do not scale according to predictions with previously determined rates, but in fact, with higher packing density could approach those from flat surfaces.
Brushing abrasion of eroded bovine enamel pretreated with topical fluorides.
Vieira, A; Lugtenborg, M; Ruben, J L; Huysmans, M C D N J M
Topical fluorides have been proposed for the prevention of erosive dental wear. This study evaluated the in vitro effect of a single professional application of 4% titanium tetrafluoride (TiF4), 1% amine fluoride (AmF) and 0.1% difluorosilane varnish (FV) in preventing wear due to combined erosion and brushing abrasion. One hundred and eight bovine enamel samples were used. Control groups were not pretreated with any product (C), pretreated with a fluoride-free varnish (FV-bl) or pretreated with fluoride varnish and subsequently submitted to varnish removal (FV-r). Wear was modeled by submitting the fluoride-treated and control groups to 3 cycles of the following regimens: erosion/remineralization (er/remin), abrasion/remineralization (abr/remin) or erosion/abrasion/remineralization (er/abr/remin). Erosion was simulated by immersion of the samples for 10 min in citric acid 50 mM (pH 3). Abrasion was carried out for 1 min (200 strokes, load 150 g) in a wear device. Remineralization (2 h artificial saliva) took place between the cycles. Two-way ANOVA showed that there was a significant interaction (p
Surface adsorption of colloidal brushes at good solvents conditions.
Striolo, Alberto
Monte Carlo simulations are presented for a minimal model of one spherical colloidal particle as it interacts with one attractive flat substrate. The colloidal particle is decorated by either 6 or 14 grafted polymer chains. The chains are always rather short, with their radius of gyration, estimated at infinite dilution in good solvent conditions, never larger than the spherical colloid diameter. Although all simulations are conducted under "good-solvent" conditions for the grafted polymer chains, we find that small changes in the polymer segment-polymer segment energetic interaction parameter can lead to significantly different scenarios. When the Lennard-Jones attraction is weak, 0.12 k(B)T, increasing the polymer length decreases the likelihood of colloidal adsorption, as expected. On the contrary, when the attraction is 0.18 k(B)T, increasing the length of the grafted polymer chains promotes the adsorption of the colloidal brush onto the surface. When the Lennard-Jones energetic parameter that describes polymer segment-polymer segment interactions is 0.15 k(B)T, as the length of the grafted polymer chains increases the probability of colloidal adsorption decreases to a minimum, and then increases. The results, explained in terms of a competition between entropic (due to the reduction in degrees of freedom available to the grafted polymer chains upon colloidal brush adsorption) and enthalpic driving forces (due to favorable colloid-surface and polymer segment-surface interactions), could be useful for controlling the circulation lifetime of liposomes within the blood stream, and optimizing solar energy harvesting by depositing colloidal particles on solid surfaces.
Compression induced phase transition of nematic brush: A mean-field theory study
Tang, Jiuzhou; Zhang, Xinghua; Yan, Dadong
Responsive behavior of polymer brush to the external compression is one of the most important characters for its application. For the flexible polymer brush, in the case of low grafting density, which is widely studied by the Gaussian chain model based theory, the compression leads to a uniform deformation of the chain. However, in the case of high grafting density, the brush becomes anisotropic and the nematic phase will be formed. The normal compression tends to destroy the nematic order, which leads to a complex responsive behaviors. Under weak compression, chains in the nematic brush are buckled, and the bending energy and Onsager interaction give rise to the elasticity. Under deep compression, the responsive behaviors of the nematic polymer brush depend on the chain rigidity. For the compressed rigid polymer brush, the chains incline to re-orientate randomly to maximize the orientational entropy and its nematic order is destroyed. For the compressed flexible polymer brush, the chains incline to fold back to keep the nematic order. A buckling-folding transition takes place during the compressing process. For the compressed semiflexible brush, the chains are collectively tilted to a certain direction, which leads to the breaking of the rotational symmetry in the lateral plane. These responsive behaviors of nematic brush relate to the properties of highly frustrated worm-like chain, which is hard to be studied by the traditional self-consistent field theory due to the difficulty to solve the modified diffusion equation. To overcome this difficulty, a single chain in mean-field theory incorporating Monte Carlo simulation and mean-field theory for the worm-like chain model is developed in present work. This method shows high performance for entire region of chain rigidity in the confined condition.
Compression induced phase transition of nematic brush: A mean-field theory study
NASA Astrophysics Data System (ADS)
Tang, Jiuzhou; Zhang, Xinghua; Yan, Dadong
Responsive behavior of polymer brush to the external compression is one of the most important characters for its application. For the flexible polymer brush, in the case of low grafting density, which is widely studied by the Gaussian chain model based theory, the compression leads to a uniform deformation of the chain. However, in the case of high grafting density, the brush becomes anisotropic and the nematic phase will be formed. The normal compression tends to destroy the nematic order, which leads to a complex responsive behaviors. Under weak compression, chains in the nematic brush are buckled, and the bending energy and Onsager interaction give rise to the elasticity. Under deep compression, the responsive behaviors of the nematic polymer brush depend on the chain rigidity. For the compressed rigid polymer brush, the chains incline to re-orientate randomly to maximize the orientational entropy and its nematic order is destroyed. For the compressed flexible polymer brush, the chains incline to fold back to keep the nematic order. A buckling-folding transition takes place during the compressing process. For the compressed semiflexible brush, the chains are collectively tilted to a certain direction, which leads to the breaking of the rotational symmetry in the lateral plane. These responsive behaviors of nematic brush relate to the properties of highly frustrated worm-like chain, which is hard to be studied by the traditional self-consistent field theory due to the difficulty to solve the modified diffusion equation. To overcome this difficulty, a single chain in mean-field theory incorporating Monte Carlo simulation and mean-field theory for the worm-like chain model is developed in present work. This method shows high performance for entire region of chain rigidity in the confined condition.
Temperature Dependence of the Surface and Volume Hydrophilicity of Hydrophilic Polymer Brushes.
Zhuang, Pengyu; Dirani, Ali; Glinel, Karine; Jonas, Alain M
The temperature-dependence of the volume and surface hydrophilicity of a series of water-swollen dense polymer brushes is measured by contact angle measurements in the captive bubble configuration, by ellipsometry, and by quartz crystal microbalance with dissipation monitoring (QCM-D). Thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) and poly(di(methoxyethoxy)ethyl methacrylate) (PMEO2MA), strongly hydrophilic poly(N,N-dimethylacrylamide) (PDMA) and poly(oligo(ethylene glycol) methacrylate) (POEGMA), and weakly hydrophilic poly(2-hydroxyethyl methacrylate) (PHEMA) brushes were synthesized by surface-initiated atom-transfer radical polymerization (SI-ATRP). Conditions leading to reproducible measurements of the contact angle are first provided, giving access to the surface hydrophilicity. Volume hydrophilicity is quantified by measuring the swelling of the brushes, either by QCM-D or by ellipsometry. A model-free methodology is proposed to analyze the QCM-D data. Comparison between the acoustic and optical swelling coefficients shows that QCM-D is sensitive to the maximal thickness of swollen brushes, while ellipsometry provides an integral thickness. Diagrams of surface versus volume hydrophilicity of the brushes finally lead to identify two types of behavior: strongly water-swollen brushes exhibit a progressive decrease of volume hydrophilicity with temperature, while surface hydrophilicity changes moderately; weakly water-swollen brushes have a close-to-constant volume hydrophilicity, while surface hydrophilicity decreases with temperature. Thermoresponsive brushes abruptly switch from one behavior to the other, and do not exhibit an abrupt change of surface hydrophilicity across their collapse transition contrarily to a common erroneous belief. In general, there is no direct correlation between surface and volume hydrophilicity, because surface properties are dependent on the details of conformation and composition at the surface, whereas volume properties
Coming apart at the seams: morphological evidence for pregnathal head capsule borders in adult Tribolium castaneum.
Haas, Merrilee Susan; Beeman, Richard W
Cephalization and seamless fusion of the anterior body segments during development obscure the segmental boundaries of the insect head. Most of the visible seams are thought to reflect cuticular infolding for structural reinforcement rather than a merger of cuticular plate borders. Incomplete fusions and other modifications of the adult head found in eight Tribolium mutations indicate that the frontal and gular sutures likely are true sutures that mark borders between adjacent cuticular plates, and suggest that the anterior facial shelf is a composite of three independent cuticular surfaces: ocular, antennal, and clypeo-labral. Additionally, midline splits of the clypeo-labrum and gula, and membranous lesions on the lateral head capsule reveal probable borders of adjacent cuticular plates where visible sutures are normally absent. The anterior lateral lesions seen in the Lucifer mutation mark a border between ocular and antennal plates and appear to identify part of the postfrontal sutures. While revealing or clarifying possible intersegmental borders between ocular, antennal, and clypeo-labral plates, the various modified or unfused surfaces of the head neither reveal an additional acronal plate nor support the view that the clypeo-labrum is segmentally associated with ocular cuticle.
Comparison between observed children's tooth brushing habits and those reported by mothers
Background Information bias can occur in epidemiological studies and compromise scientific outcomes, especially when evaluating information given by a patient regarding their own health. The oral habits of children reported by their mothers are commonly used to evaluate tooth brushing practices and to estimate fluoride intake by children. The aim of the present study was to compare observed tooth-brushing habits of young children using fluoridated toothpaste with those reported by mothers. Methods A sample of 201 mothers and their children (aged 24-48 months) from Montes Claros, Brazil, took part in a cross-sectional study. At day-care centres, the mothers answered a self-administered questionnaire on their child's tooth-brushing habits. The structured questionnaire had six items with two to three possible answers. An appointment was then made with each mother/child pair at day-care centres. The participants were asked to demonstrate the tooth-brushing practice as usually performed at home. A trained examiner observed and documented the procedure. Observed tooth brushing and that reported by mothers were compared for overall agreement using Cohen's Kappa coefficient and the McNemar test. Results Cohen's Kappa values comparing mothers' reports and tooth brushing observed by the examiner ranged from poor-to-good (0.00-0.75). There were statistically significant differences between observed tooth brushing habits and those reported by mothers (p < 0.001). When observed by the examiner, the frequencies of dentifrice dispersed on all bristles (35.9%), children who brushed their teeth alone (33.8%) and those who did not rinse their mouths during brushing (42.0%) were higher than those reported by the mothers (12.1%, 18.9% and 6.5%, respectively; p < 0.001). Conclusions In general, there was low agreement between observed tooth brushing and mothers' reports. Moreover, the different methods of estimation resulted in differences in the frequencies of tooth brushing habits
Complex polymer brush gradients based on nanolithography and surface-initiated polymerization.
Lin, Xiankun; He, Qiang; Li, Junbai
Confined surface gradients consisting of polymer brushes have great potential in various applications such as microfluidic devices, sensors, and biophysical research. Among the available fabrication approaches, nanolithographies combined with self-assembled monolayers and surface-initiated polymerization have became powerful tools to engineer confined gradients or predefined complex gradients on the nanometre size. In this tutorial review, we mainly highlight the research progress of the fabrication of confined polymer brush gradients by using electron beam, laser, and probe-based nanolithographies and the physical base for these approaches. The application of these polymer brush gradients in biomedical research is also addressed.
A sequence of calculation of the modes of dimensional combined processing by an electrode brush
NASA Astrophysics Data System (ADS)
Ryazantsev, A. Yu; Kirillov, O. N.; Smolentsev, V. P.; Totay, A. V.
In the article the way of calculation of the modes of dimensional processing by an electrode brush is considered. The choice of a liquid working environment is presented. A calculation of tension in electrodes and forces of the technological current realized during processing is given. A choice of a clip of wire bunches in a processing zone, feeding an electrode brush to a non-rigid work piece. The recommended technological indicators of the process of the finishing combined treatment by an electrode brush are presented.
Development of the Upgraded DC Brush Gear Motor for Spacebus Platforms
NASA Technical Reports Server (NTRS)
Berning, Robert H.; Viout, Olivier
The obsolescence of materials and processes used in the manufacture of traditional DC brush gear motors has necessitated the development of an upgraded DC brush gear motor (UBGM). The current traditional DC brush gear motor (BGM) design was evaluated using Six-Sigma process to identify potential design and production process improvements. The development effort resulted in a qualified UBGM design which improved manufacturability and reduced production costs. Using Six-Sigma processes and incorporating lessons learned during the development process also improved motor performance for UBGM making it a more viable option for future use as a deployment mechanism in space flight applications.
Border Security: The Role of the U.S. Border Patrol
Lakes, many different river systems, and in the winter heavy snow and bitter cold temperatures. Conversely, the southwestern border with Mexico...http://www.uh.edu/cir/Deaths_during_migration.pdf. 68 Andrea Almond , "How Best to Count Border Deaths?" The Associated Press, November 7, 2004