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What is the mIU unit as used in hCG hormone levels?
My girlfriend is in her very early pregnancy, and has provided several blood samples by now where the doctors measure her hCG levels.
The hCG hormone level is measure in a unit called mIU/ml which I figure is milli-something per milliliter blood. But what is that something? What is the IU?

IU stands for "International Units" and it is an arbitrarily chosen unit of measure used mostly to quantify hormones, vitamins or various substances found in the blood.
The idea is well explained by the Wikipedia article on international units)

Many biological agents exist in different forms or preparations (e.g. vitamin A in the form of retinol or beta-carotene). The goal of the IU is to be able to compare these, so that different forms or preparations with the same biological effect will contain the same number of IUs. To do so, the WHO Expert Committee on Biological Standardization provides a reference preparation of the agent, arbitrarily sets the number of IUs contained in that preparation, and specifies a biological procedure to compare other preparations of the same agent to the reference preparation. Since the number of IUs contained in a new substance is arbitrarily set, there is no equivalence between IU measurements of different biological agents. For instance, one IU of vitamin E cannot be equated with one IU of vitamin A in any way, including mass or efficacy.

For hCG, in the 55th report for of the WHO Expert Commitee on Biological Standardization, you could find:

The Expert Committee on Biological Standardization, after consideration of this issue (11), concluded that the choice of unit should be made on a case-by-case basis and reflect, and be based on, the biological and medical as well as the physicochemical information available.
  Many biologicals exist in both active and inactive states, and the clinically relevant form of the analyte may depend on the diagnostic aim. For example, the active state of the placental hormone chorionic gonadotrophin (hCG) is the relevant molecule to measure in the diagnosis of pregnancy, whereas the biologically inactive free beta subunit (hCG-beta) is measured to diagnose choriocarcinoma. Generally, a measurement of biological activity is expressed in IU, whereas measurement of the amount of a protein or of a specific protein structure is expressed in SI. In this case there would be a compelling reason to relate the measurement of hCG to a unit of biological activity, and the measurement of hCG-beta to an SI unit of quantity. Accordingly WHO has established a reference preparation for hCG (currently the fourth International Standard, with an assigned content of 650 IU/ampoule) (7) and a reference preparation for hCG-beta (currently the first WHO Reference Reagent for immunoassay of hCG beta subunit, with an assigned content of 0.88nmol/ampoule) (18). The former preparation was assigned a value based on bioassay, whereas the latter preparation had been extensively characterized by physicochemical and
  immunological methods and calibrated in nanomol by amino acid analysis. Applying these considerations of the properties of biological analytes, and their measurement in the clinical situation allowed the WHO biological reference standard for hepatitis B surface antigen, assigned a value in arbitrary IU rather than in SI units, to be adopted by the medical devices sector of the European Commission as the standard required for the fulfilment of the so-called Common Technical Specifications (CTS) for in vitro diagnostic devices. The Common Technical Specification document supporting the European (IVD) Medical Devices Directive 98/79 EC is a legally binding document within the 25 countries of the European Union.
  Where it is appropriate for a WHO biological reference standard to be calibrated in SI units, the principles outlined in ISO 17511 (8) should be followed. This will necessitate the existence and use of an appropriate single reference method and an assignment of uncertainty, derived from calibration data. Such a reference method should not be a biological assay because the factors that affect the results of such assays are not fully understood. Where they are used, SI units assigned to biological reference standards should be derived from, and traceable to, physicochemical procedures.

Note that IU are not the same as enzyme units (U) which is a measure of enzymatic activity


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Why do the two hemispheres of the brain control the opposite sides of the body?
Why does the left hemisphere control the right and the right hemisphere control the left? I googled it but didn't find a good answer regarding this. Could someone explain?
Does this adaptation help in the speed of transmission of nerve impulses?

I'd bet it's non-adaptive.

You seem to accept that we have two brain hemispheres that each control one half of the body without questionning this fact and then ask why does the left part control the right part and vice-versa. If we do so, as @NoahSnyder, I would tend to think that such thing is not adaptive because I think there were two possible solutions (cross wiring or no same-side wiring) that are equally fit and one was randomly chosen!

See also: http://cogsci.stackexchange.com/q/5771/301

Just to get the ball rolling here.  This particular aspect of brain evolution is very old. The cross wiring of the hemispheres of the brain seems to be as old as the right and left hemispheres itself.  It predates lizards - i.e. hundreds of millions of years ago. It  possibly predates right/left dominance and the organ asymmetry which puts the heart on the left side of the body.
Digging back deeper, we can see that worms have bilateral brain structure, but as noted in the comments below, the nervous systems do not cross.  I would guess that this means that the phenomenon appears sometime before lizards - putting the development having been done by the early Carboniferous period when the first animals came to the land and the first reptiles appears, which is the perhaps 350 million years ago.
Echinoderms (like starfish) are 'missing links' in bilateral symmetry as their larval stage has bilateral symmetry even though the adult has radial symmetry.  Such wiring may be so embedded in the way most animal body plans develop that it hasn't changed in evolutionary history. If that is related to other animals trait, it could be a billion years ago. Some argue this is not the case.
One might guess that the cross over of neurons in brain control is good for integrating the signals from both sides of the organism. There are quite a few theories.

layperson, here... just a theory, but if it goes far back enough, I could imagine that a small enough organism had some advantage to having fewer kinks/bends in the nerve fibers when going through a "neck", so the left half of the body being connected to the right half of the nerve... clump(?) allowed a straighter path... just a thought, unless we can find something REALLY small that seems to demonstrate this...

this is how the evolutionary biology game is played.  we try to understand the dynamics of selection by looking for examples that illustrate a point about the relative advantage of some configuration in living things.  If we don't see what we're looking for, then we have to re-think our logic.

Question, if there is an answer (?): how do the nerves go from one side of the brain to the other side of the body? Are they intermingled/intermeshed, or do the left hemisphere nerves typically go on front of the right hemisphere nerves? Or typically behind? If there's a significant correlation in dorsal/ventral or anterior/posterior based on hemisphere of origin, that could indicate some amount of "twisting" that occurred at some point way back in evolutionary time, where the head/brain bucket used to "point" the other way ..

symmetry in biology is inherited v. early in and is the result of genes that maintain the bilateral symmetry in our class of animals.  (radial symmetry and assymmetry exist too).  Those same factors that generate these symmetry are probably playing a part in the crossing from one side to another if they are symmetric crossings... just a guess.

This answer is very old, but I just came across it...Contralateral motor control is, as far as I am aware, a vertebrate phenomenon. Yes, worms have a lateralized nervous system, but they do not have contralateral control, so I think it is quite misleading to mention them in this context. There is not evidence that contralateral control is as old as bilateral symmetry. Mollusks and arthropods also have fairly advanced nervous systems but do not show a primary contralateral control.

thanks for the above - i was really just taking a stab. i corrected this however. i think the point about the starfish is still interesting but it could have been an independent development.  It doesn't seem to have cropped up too often though.

When I was in school it was discussed as an evolutionary survival advantage... If you are attacked from the right side, the left side of the brain is less likely to be damaged and can use the right sided limbs to fend off the attack as opposed to the right side being damaged and less responsive..

I've also head this repeated at undergraduate level

There's a good answer to this on https://www.quora.com/Why-does-our-left-hemisphere-of-brain-control-our-right-side-of-our-body-and-the-right-our-left.
In summary, a biopsychologist states that vertebrates and invertebrates have the digestive system and the nervous system in reverse locations. He also points out that the hearts are in the dorsal area for invertebrates and in the ventral area of an invertebrates. The evolutionary theory of these observations is that the body of an early vertebrate must have been turned upside down, and the easiest explanation is that a vertebrate ancestor swiveled its head 180°. In conclusion, it's believed that one vertebrate had its head turned around and that contralateral arrangement was conserved because it decreased chance of error in nervous system wiring (compared vs simpler same-sided wiring schemes).

Certainly an interesting idea.

Being a keen student of game theory and behavioural sciences one reason that comes to my mind is for the opposite wiring of brain hemispheres might be that

if right hemisphere controlled the right side and left hemisphere controlled the left side than cross hemisphere links and activity would be hard to achieve so the most efficient way of increasing cross hemisphere communication, links and activity with the least stress on physical resources is the opposite hemisphere wiring.
The second view that also compliments this cross arrangement might be the underlying law of increase in complexity and entropy (second law of thermodynamics), which is embedded in the universe from its births, dictates an increase in complexity hence cross wiring also achieves this underlying goal of increasing complexity because if you think about it straight wiring would have been too simple for such a complex structure as the brain.

It seems a bit voodoo indeed! I don't think the second law of thermodynamic can bring any insight into the general tendency observed in living things to increase in complexity through evolution. But the discussion might be interesting. But if your answer was an real explanation, you could use it to explain so many different weird phenotypes on earth. That makes me think that it is not really a satisfying explanation. But it's good to try such voodoo-like suggestions ;-)

It is simple.  The brain through evolution split into two hemispheres when binocular vision was evolving.  If you follow the neurons from the eye, the lateral neurons travel to the ipsilateral hemisphere.  The medial neurons cross to the contralateral hemisphere.  I would bet the protopathic pathways were around in evolutionary terms before binocular vision and the epicritic pathways developed after binary vision.  Vision drove the hemispheres into two compartments. I could draw the diagram but unable to do so on this response

Welcome to Biology SE. This answer could do with some references - see the guidelines on how to write a good answer http://biology.stackexchange.com/help/how-to-answer

It's for control, coordination and balance. From a mathematical point of view, parallel lines won't intersect and thus line A won't affect line B unless they intersect and thus would hardly influence the other unless and an external force is applied to any of the lines.
This is also why corpus callosum connects the left and the right side of the brain.

Could you please add references to this response!

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bi-directional transcription experiment
We suspect a bi-directional transcription event is happening at a locus in our organism where two genes are directly adjacent to each other. The annotation data is not well established. The intergenic distance is probably less than 200 base pairs.
The two genes are expressed in opposite directions towards each other. Base on the preliminary transcriptomics data, it seems like one gene is over transcribing (3' UTR perhaps?) into the adjacent gene, possibly resulting in some kind of transcriptional regulation of the adjacent gene.
Here is a rough diagram of what we think might be happening:
------------------------==========gene A================>----------------------

----------------------------------------<====gene B=====-----------------------

Of course we need to first confirm this by designing primers to see if this over transcription is actually happening.
If this is happening, we intend to do some knock down experiments. We have no transgenesis available in our organism, only RNAi by dsRNA. It is possible to specifically knock down geneA by introducing dsRNA to the 5' region of geneA that does not overlap with geneB. Perhaps this will lead to ectopic/over expression of geneB.
Is there anyway to knock down geneB specifically without knocking down geneA? It looks like designing dsRNA for geneB would knock down both A and B.

What organism is it? And how big the genes A and B are?

Both geneA and geneB have multiple exons. Transcript length-wise, both are around 2kb. Both have long introns resulting in a 4-5 kb total gene length.

If gene B makes a protein product, you can try designing a morpholino against the 5'-UTR of gene B. This can prevent translation initiation at the ribosome as the morpholino occludes mRNA entry into the ribosome. You can detect this by western blotting.
If gene B makes some sort of regulator RNA, you will need to target expression of gene B at the DNA level. If gene B has well established splice sites, a morpholino can interfere with splicing enhancers and silencers, and therefore, should produce a non-functional or impaired RNA product. You can detect splice variants by amplifying gene B from cDNA.
Theoretically, the advantage of using a morpholino is due to it's single stranded nature. Morpholinos designed against gene B should have no effect on gene A due to non–complemenetarity.

How well is gene A annotated? Do you have the gene A sequence (after post-transcriptional modifications)? If you do, you can order it from a company like DNA2.0 and they will synthesize it for you for like $0.35/base. Then you can transform the cells with this plasmid and do a knockout of gene B by inserting some sequence at the ~200bases overlap.
Also, I guess you can transform the immediate transcript (without modifications). It will also be modified once it is in the cell. But it will be longer and more expensive to synthesize, but there are a few methods you can use to do that.
Let me know if this idea appeals to you. I can give you more info if you are interested.

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Why is DNA replication  performed in the 5' to 3' direction?
DNA replication goes in the 5' to 3' direction because DNA polymerase acts on the 3'-OH of the existing strand for adding free nucleotides. Is there any biochemical reason why all organisms evolved to go from 5' to 3'?
Are there any energetic/resource advantages to using 5' to 3'? Is using the 3'-OH of the existing strand to attach the phosphate of the free nucleotide more energetically favorable than using the 3'-OH of the free nucleotide to attach the phosphate of the existing strand? Does it take more resources to create a 3' to 5' polymerase?

Prof. Allen Gathman has a great 10-minutes video on Youtube, explaining the reaction of adding nucleotide in the 5' to 3' direction, and why it doesn't work the other way.
Briefly, the energy for the formation of the phosphodiester bond comes from the dNTP, which has to be added. dNTP is a nucleotide which has two additional phosphates attached to its 5' end. In order to join the 3'OH group with the phosphate of the next nucleotide, one oxygen has to be removed from this phosphate group. This oxygen is also attached to two extra phosphates, which are also attached to a Mg++. Mg++ pulls up the electrons of the oxygen, which weakens this bond and the so called nucleophilic attack of the oxygen from the 3'OH succeeds, thus forming the phospodiester bond.
If you try to join the dNTP's 3'OH group to the 5' phosphate of the next nucleotide, there won't be enough energy to weaken the bond between the oxygen connected to the 5' phosphorous (the other two phosphates of the dNTP are on the 5' end, not on the 3' end), which makes the nucleophilic attack harder.
Watch the video, it is better explained there.

While the video explains the basics nicely, it ignores the possibility of adding a triphosphate to the primer (through another enzyme or a secondary polymerase functionality). The spontaneous hydrolysis of the triphosphate puts the 3'-5' variant at a disadvantage, but the idea is not as impossible as Prof. Gathman claims in the video.

DNA replications needs a source of energy to proceed, this energy is gained by cleaving the 5'-triphosphate of the nucleotide that is added to the existing DNA chain. Any alternative polymerase mechanism needs to account for the source of the energy required for adding a nucleotide.
The simplest way one can imagine to perform reverse 3'-5' polymerization would be to use nucleotide-3'-triphosphate instead of the nucleotide-5'-triphosphate every existing polymerase uses. This would allow for a practically identical mechanism as existing polymerases, just with different nucleotides as substrates. The problem with this model is that ribonucleotide-3'-triphosphates are less stable under acidic conditions due to the neighbouring 2'-OH (though this obviously only applies for RNA, not for DNA).
So any 3'-5' polymerase would likely need to use the same nucleotide-5'-triphosphates as the 5'-3' polymerase. This would mean that the triphosphate providing the energy for addition of a new nucleotide would be on the DNA strand that is extended, and not on the newly added nucleotide.
One disadvantage of this approach is that nucleotide triphosphates spontaneously hydrolyze under aqeuous conditions. This is no significant problem for the 5'-3' polymerase, as the triphosphate is on the new nucleotide and the polymerase just has to find a new nucleotide. For the 3'-5' polymerase spontaneous hydrolysis is a problem because the triphosphate is on the growing chain. If that one gets hydrolyzed, the whole polymerization needs to be either aborted or the triphosphate need to be readded by some mechanism.
You can take a look at the article "A Model for the Evolution of Nucleotide Polymerase Directionality" by Joshua Ballanco and, Marc L. Mansfield for more information about this. They created a model on early polymerase evolution, though they don't reach any final conclusion.

In my opinion, Prof. Allen Gathman's "great 10-minutes video on Youtube" is a pretty waste of time if you already know how hydrolysis happens. In fact, he has not considered the 3'->5' route in an unbiased manner; he doesn't seem to look at the possibility of a triphosphate appearing at the growing 5' tip of the strand in the 3'->5' case.
Actually, the only difference between the two routes (5'->3' and 3'->5') is that the reacting triphosphate appears in different places. In the usual case, the triphosphate which is hydrolysed belongs to the added nucleotide, while in the latter case, the triphosphate which is hydrolysed belongs to the nucleotide on the growing strand. Both are feasible.
In fact, it is known that RNA polymerase has dual activity, but you see, RNA polymerase doesn't have proofreading activity!.  Proofreading requires removal of the mismatched base, but in the 3'->5 direction the base's attachment had consumed the triphosphate at the 5' tip of the strand, so it is no longer available to add the replacement base. 3'->5' activity readily destroys  proofreading capability of a polymerase  So, basically, it is the need for proofreading that restricts the synthesis of DNA strands to 5'->3'. Why it is so, would need a lot more explanation (if in words) but I think a picture has far better explanatory power than a thousand words. I've added a picture from Essential Cell Biology that shows the answer to the 'WHY' question:
The other important consideration is repair. If one or more nucleotide is missing in one strand, repair of the missing nucleotide would be impossible for 3' to 5' synthesis, because no 5'-triphosphate is present. On the other hand, 5' to 3' synthesis does not require a 3'-triphosphate present at the repair site. This is important. That is 3' to 5' synthesis does not allow nucleotide repair.

This should be the accepted answer.

Actually there is a polymerase that catalyzes 3' - 5' elongation.  See for example the Thg1 superfamily.  "Doing it in reverse: 3'-to-5' polymerization by the Thg1 superfamily." Jackman, et al.

No reference, no use.


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What are good resources for self-learning modern molecular biology concepts?
My learning of molecular biology ended in the early 90's (and with early 90's era information). While I don't aspire to be a molecular biologist, I do aspire to better understand modern approaches better.
Short of going back to school and taking classes, what are good resources for learning on my own? I'd like to get to the point of being able to understand Nature, Science, Cell, etc. Is this even a feasible goal?

I've voted to close because this (the title much more-so than the rest) is very subjective so doesn't have a "right" answer. If you can narrow the scope to a particular issue it would be much improved.

I think this is going to come up often, so I raised an issue on meta: http://meta.biology.stackexchange.com/questions/24/should-questions-without-definitive-answers-be-closed

Just convert to a wiki.

@Poshpaws community wiki is not a crutch for extremely subjective questions.

@Nick T I wasn't suggesting it was. However, rather than chucking it out as "too subjective" if you change it to CM people can freely give their experience and suggestions which might turn into a useful resource.

Questions rarely, if ever, need community wiki. If the question needs this level of collaboration and discussion, it's probably not a good for for the site.  If calls for community wiki seem to somehow "fix" that, it's probably not a good fit for the site. http://blog.stackoverflow.com/2011/08/the-future-of-community-wiki/

Sure it's feasible! Of course, there are lots of papers that I can't read even with a recent education, but you should be able to make a good dent by:

Getting a good modern textbook like Molecular Biology of the Cell by Alberts et al. This is becoming a standard text and gives pretty good coverage of the field. I find that it doesn't always get as detailed as I would like, but such is the nature of textbooks I think. Another textbook that some people like is Molecular Cell Biology by Lodish et al, although I don't have experience with it myself.
Watch online lectures. MIT OpenCourseWare has a pretty good molecular biology course. It may get basic for you at times, but the lecturers are well-respected molecular biologists and geneticists.
Read reviews in things like Nature Reviews to get a 30,000-foot view. Review authors often touch on concepts that primary literature assume you know. Armed with a good text, you should be able to get a good idea of what people are talking about. On a similar note, the "News and Views" commentary articles that accompany "high-impact" papers are great for giving people unfamiliar with the field a taste of why a certain paper deserves attention.
Come back here and ask!

By far the best resource mentioned here is the first textbook, Molecular Biology of the Cell published by Garland Science. It's one of a few truly great modern textbooks, with some high-school biology and that book you can learn modern molecular biology to a high level.

You can watch the iBioSeminars, which are given by some of the best cell and molecular biologists out there.

Drop by the diybio.org mailing list, which is home to a bunch of autodidactic free thinkers like yourself.  They always can suggest fun projects and learning resources.
Also check out Nature's Scitable education resource ("A collaborative learning space for science")

conflict of interest: I helped start diybio.org

Sorry, I just couldn't help but point out the following book:

Joking aside, every book from this series I read was fantastic. I didn't read this particular one, but I would nonetheless recommend to give it a try.


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What does "rapamycin-sensitive oncogenic transformation" mean?
Can someone explain exactly what "rapamycin-sensitive oncogenic transformation" is? I get that it's a drug that suppresses the immune system but what does it have to do with oncogenic transformation?
Here's the article where they talk about it:
http://www.pnas.org/content/104/13/5569.full

i am not particularly sure but it could be related to dysregulation of the mTOR pathway.. mTOR pathway is involved in survival in stress..

The mammalian target of rapamycin (mTOR) is a Ser/Thr protein kinase that functions as an ATP and amino acid sensor to balance nutrient availability and cell growth. When sufficient nutrients are available, mTOR responds to a phosphatidic acid-mediated signal to transmit a positive signal to p70 S6 kinase and participate in the inactivation of the eIF4E inhibitor, 4E-BP1. These events result in the translation of specific mRNA subpopulations. mTOR is phosphorylated via the PI3 kinase/Akt signaling pathway and also autophosphorylates under translationally repressive conditions. mTOR plays a key role in cell growth and homeostasis and may be abnormally regulated in tumors. It is currently under investigation as a potential target for anti-cancer therapy.
The mTOR signaling pathway shows how mTOR is involved in numerous cell processes that can be dysregulated in cancer, including cell growth, proliferation, angiogenesis, autophagy, and various kinds of metabolism. "Rapamycin-sensitive oncogenic transformation" therefore means that the transformed cells still have intact "wild-type" mTOR complexes that can be down-regulated by the tumor-specific administration of rapamycin analogues, hence inhibiting the above-mentioned processes and arresting or killing the cells.


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Analysing the results of real-time PCR
I want to evaluate the level of gene expression by real-time PCR.  I have five controls that are "clinically" the same. I calculated the "fold change" of the target gene regarding each control.
What if the result of "fold change" for my target gene is different for each control? I mean it is up regulated according to three of them and down-regulated according to the rest two.
Is the intervention biased? Or should I consider the average?

I have no experience with RT-PCR in particular, but I'd say that the variations in your controls add to your error. And if they vary too much, you'll have a hard time to measure a significant difference in gene expression. The gene you selected might be influenced by a lot of other processes, leading to those variations.

Please provide more information: fold-change relative to what?
If you did what I think you did (single control gene that you calculated fold change to of your gene of interest) I'd say this is the wrong approach. What you need is a set of genes which have similar expression levels across all your samples (controls and cases) to be able to compare your gene of interest to some common baseline. Selection of such genes should be the first step in the project, and it might be a good idea to use one of the established approaches - I recommend Jo Vandensompele's GeNorm (link to the paper) method. It goes like this: from a panel of potential control genes you select two or three that are most stably expressed across your experimental conditions, and then use these two-three control genes along with your gene of interest in a qRT-PCR. You then normalize the signal from your gene to a mean of the control genes.
It has been repeatedly shown that using a single control gene, even a so-called 'housekeeping gene' is misleading, because those genes do change their expression levels in some conditions. Also, using several control genes protects you against potential problems due to unequal amplification efficiency in different samples/groups. However, if you have multiple gene of interest, they all must have comparable amplification efficiency.

You also probobably need to check if your samples haven't been contaminated with PCR reaction inhibitors, which is very common if you first extract your mRNA, digest remaining DNA and then run a PCR with a less then 10-fold dilution. You need at least a 200 times dilution to get rid of all the artifacts.
Once you've diluted your samples, place a repeats of successive dilutions of your target and baseline mRNA (200xdilution, 1000x dilution, 5000x dilution). Normally you will see a nice regular spacing between curves on your rtPCR plot. If you don't, something went wrong with the reaction.
More generally rtPCR is a pretty tricky experience, and if you want it to be 100% reliable, you've got a certain number of controls to perform. You can find a good and comprehensive guideline over here.


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What Proteins Are Universal To All Life Forms?
According to National Geographic, there are 23 proteins that are common to all life forms:

All species in all three domains share 23 universal proteins, though the proteins' DNA sequences—instructions written in the As, Cs, Gs, and Ts of DNA bases—differ slightly among the three domains

According to NCBI there are 324 proteins common to all life forms.
How many proteins are common to all life forms, and what are their names?

It must be 23 amino acids. Amino acids are structural units of proteins. Can you cite the material that said 23 proteins are common to all life forms?

what do you mean by common.. there are homologous proteins.. would you consider them as common?

There are 324 proteins in M. jannaschii, with at least one homologue present in some species from both the other two domains, Bacteria and Eukarya ..... I don't think the NCBI article you cited is talking about proteins common to all life forms.

I am skeptical about 324 as well because an organism named Tremblaya princeps apparently has only 120 protein coding genes. http://www.nytimes.com/2013/07/04/science/how-simple-can-life-get-its-complicated.html?_r=0

This question is based upon a wrong inference about the work that forms the basis of the National Geographic article, which includes this statement:

All species in all three domains share 23 universal proteins, though the proteins' DNA sequences—instructions written in the As, Cs, Gs, and Ts of DNA bases—differ slightly among the three domains (quick genetics overview).
  The 23 universal proteins perform fundamental cellular activities, such as DNA replication and the translation of DNA into proteins, and are crucial to the survival of all known life-forms—from the smallest microbes to blue whales.

The article is referring to a paper published in Nature in 2010.
http://www.ncbi.nlm.nih.gov/pubmed/20463738
This paper uses a set of 23 proteins to test the idea that certain genes arose only once.

The data set consists of a subset of the protein alignment data from ref. 27, containing 23 universally conserved proteins for 12 taxa from all three domains of life, including nine proteins thought to have been horizontally transferred early in evolution27. The conserved proteins in this data set were identified based on significant sequence similarity using BLAST searches, and they have consequently been postulated to be orthologues.

There is no suggestion that there are only 23 such proteins, it's just that the author chose this subset to test his ideas.
And here they are:

alanyl-tRNA synthetase, aspartyl-tRNA synthetase, glutamyl-tRNA synthetase, histidyl-tRNA synthetase, isoleucyl-tRNA synthetase, leucyl-tRNA synthetase, methionyl-tRNA synthetase, phenylalanyl-tRNA synthetase β subunit, threonyl-tRNA synthetase, valyl-tRNA synthetase, initiation factor 2, elongation factor G, elongation factor Tu, ribosomal protein L2, ribosomal protein S5, ribosomal protein S8, ribosomal protein S11, aminopeptidase P, DNA-directed RNA polymerase β chain, DNA topoisomerase I, DNA polymerase III γ subunit, signal recognition particle protein and rRNA dimethylase

This answer was downvoted - I'd be really interested to hear why.


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Defining paper(s) in epigenetics
For someone who is interested in learning about the discovery of epigenetics, which are the foundational defining papers in the area?

For epigenetics in humans, for me it's the Överkalix study on descendants of people who lived through the Dutch famine of the 1940s.

Disappointingly, the papers so far all highlight the heritability of epigenetics whose usefulness is rather limited, rather than epigenetics itself.

I understand that Robin Holliday was the first to discuss the possible role of DNA methylation
in the control of Gene expression. In his paper "The inheritance of epigenetic defects"
he presents what is one of the first modern formulations of what we now regard as epigenetics. The term "epigenetics" itself was coined by Conrad Waddington although this predated our modern understanding of heredity.
Holliday, R., The inheritance of epigenetic defects, 1987, Science, 238, 4824

There are few single papers that really drive the field by themselves, epigenetics has been a long slow progression (although more recently the definition has been muddied and started to include non-epigenetic modes of gene regulation).  A pretty good review of a lot of research, including a more circumspect discussion about what epigenetics is can be found in Youngson and Whitelaw's Annual Review (http://www.ncbi.nlm.nih.gov/pubmed/18767965).

I found two nice review papers focused of epigenetics and human disease, one from 2004, and one from 2006. But perhaps you are looking more for something like this?
I also found this article in the BBC news: The Ghost in Your Genes

They have shown that a famine at critical times in the lives of the grandparents can affect the life expectancy of the grandchildren. This is the first evidence that an environmental effect can be inherited in humans.

References:

 Jiang Y-H, Bressler J, Beaudet AL. 2004. Epigenetics and human disease. Annual review of genomics and human genetics 5: 479–510.
 Rodenhiser D, Mann M. 2006. Epigenetics and human disease: translating basic biology into clinical applications. CMAJ : Canadian Medical Association journal = journal de l’Association medicale canadienne 174: 341–8.
 Haig D. 2004. The (dual) origin of epigenetics. Cold Spring Harbor symposia on quantitative biology 69: 67–70. [pdf]

@Lisa: In the BBC article they discuss the Överkalix study.


text:
Is Webmedcentral a reputable scientific publisher?
I am a student, and I have written a paper (in drug discovery) which I want to publish. While searching for possible journals I came across Webmedcentral.
Is Webmedcentral a reputable scientific publisher?
What is the impact factor for this journal?

I checked this site and its journals in Scopus.com based on its "ISSN 2046-1690" but nothing was there. they are fast in submitting and publishing but it is not some thing great by it self. I think maybe its better to find some where better to publish your article(s).


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What's the state of the art in designing and creating your own life forms?
What's the state of the art for solving the following problem. You imagine a set of features that you want a life-form to have. Just to take an arbitrary example, say you want your life-form to have a) a strong sense of smell, b) the ability to fly and c) a comfortable couch shaped saddle on its back. What's the sequence of steps you need to take so that you can create this life-form in the lab?
I realize that we are probably far away from solving this very general problem. But perhaps there are some smaller subproblems that we do know how to solve.
For example, as far as I gather, you can probably make any living being fluorescent green in color by inserting into its genome the gene responsible for expressing the Green Fluorescent Protein. So may be if we limit the set of features one is allowed to choose from, the above problem can be solved. So my first question of the set of questions is:
1)  What features can be easily inserted into almost any organism easily?
Next, I imagine that to design and create an artificial life-form will consist of three steps:

Figure out which proteins will give rise to those feaures,
Design a genome that will express those proteins in the right quantities and
Implant that genome into a cell and actually let the being grow.

2)  Is the above sequence of steps correct, or am I missing something?
3)  What is the state of the art for each of these steps?
Finally, in light of the recent spur in the open source biology groups and DIYbio enthusiasts, I feel that there might be some very simple but really cool things related to my question that you can already do in your garage. For example, may be there is some very simple single-cell life-form that's so well understood that you can add or subtract tons of features from it with a budget of a few hundred dollars. So my final question is:
4) What is the cheapest experiment you can perform at your own home without access to a biology lab which involves changing the genome of a living organism in a way that's functionally visible? (An arbitrary example: Can you create an apple that's blue in color with a budget of $500? By create, I mean you should be able to hold the blue apple in your hand.)

You may want to try splitting this into multiple questions (along the delineations you've already set up).  It will keep the answers better organized.

This would seem to be far too localised: the situation will inevitably change every year. And you've asked several questions in one, which is very strongly discouraged.

@EnergyNumbers: I doubt that the situation of creating your transgenic life form in your garage with $500 will change anytime soon...

Addressing what you can do in your garage: Infusing E.coli (one of the best-undestood bacteria out there) with GFP requires: a) E.coli with appropriate medium obviously, b) antibiotic-medium to select for the transformed strains, c) a pGLO plasmid or equivalent, which contains GFP in an operon E.coli normally uses to digest arabinose (ara operon), d) calcium chloride for heatshocking them, e) UV light to see them glow; plus utensils for transferring the bacteria. Might be doable with $500 actually; but this only regards bacteria, which take up and integrate DNA happily.

@Armatus: hmmm... even just the competent cells + medium would probably be ~$500.

@nico huh? E. coli can be considered free, and media is about $20/kg dry (e.g. malt extract)

@David: hmmmm... and what is the transfection efficiency of naturally found E. Coli (I don't really want to know where you would find it :P)? I was specifically speaking about competent cells. As for the media, LB goes at around 100-120 euros/kg (powder). Again, even if that was almost free, the cheapest Taq would also be at least 50 euros (not a big amount), he would need restriction enzymes, ligases, a spectrophotometer, a thermocycler, micropipettes etc etc.

@nico: Can't all E.coli be induced competent under heat shock? Just need calcium chloride additionally. Also I thought you can buy the pGLO plasmid pre-prepared.

To put GFP into E.coli you would also need an autoclave or some other way to sterilize your medium and IPTG for induction in most cases. Naturally found E. coli would probably not be suitable, not even speaking on the difficulty of isolating them specifically (and the dangers if you accidentally isolate one of the dangerous strains). You probably would need to get some E. coli K12 and the plasmid from a friendly academic lab to be able to do this on a budget.

State of the art questions have the obvious defect that they are temporal. The answers to this question are now six years old — hardly 'state of the art'. Time to retire this question.

The problem is of course very complex so take my answers as simplifications.
Most transgenesis so far has been done on unicellular beings (bacteria, yeast), which we can change as much as we want fairly "easily", plants, insects and some mammals. Notably, for the latter case, mice are the species which has been used the most for transgenesis, as they are cheap (compared to, say, using pigs), do not take lots of space, have big litters and a quick reproductive cycle (~20 days). Aside from mice we've seen GFP rats, pigs, dogs, cats, sheep and probably there is more, but I will mostly restrict my answers to mice (as far as I know there are big technical difficulties in applying transgenics procedures to something bigger than a mouse, but to be honest I could not explain you the details on this as I have never done it).

What features can be easily inserted into almost any organism easily?

Well, essentially, it is easy to give rise to monogenic traits (i.e. traits that depend on a single gene). Generally speaking, when you want to have more traits, or need more than 1 gene to have the trait you create single transgenics and then breed them together.
So, if your phenotype depends on the presence of gene A and B you will generate a (mouse) line expressing A, one expressing B, you breed them together and, if you are lucky, a part of the pups will be expressing both.

Next, I imagine that to design and create an artificial life-form will consist of three steps: 1. Figure out which proteins will give rise to those feaures, 2. Design a genome that will express those proteins in the right quantities and 3. Implant that genome into a cell and actually let the being grow.
Is the above sequence of steps correct, or am I missing something?

No, that is not how it is done!
There has been, to my knowledge, only one (very impressive) attempt to do that, a project led by Craig Venter at Celera Genomics. The project resulted in the creation of the first synthetic life form, named Mycoplasma laboratorium (see also the original paper on Science). Doing this for a multicellular being is, presently, science-fiction.
What normally you would do is to insert or remove just the piece of DNA you need in the genome.
There are different approaches to do that: for instance, you can start from embryonic stem cells, from fertilized oocytes or from spermatozoa.
This is the general process for making a transgenic mouse:

Source: https://web.archive.org/web/20161212170103/http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/TransgenicAnimals.html
Now, depending on how you inject your gene you can distinguish between transgenics and knock-in mice. In a transgenic mouse you insert the gene somewhere in the genome and, although there are method to understand where it ended up you generally do not know.
Knock-in animals, instead, target a specific region of the genome. This is usually used in order to change an existing gene, to improve its function or to remove its function (knock-out animals). This process, called gene targeting relies on the biological process called homologous recombination.
So, why don't we just synthesize a new genome each time?
Aside from Venter's dream, the process would:

have incredibly high cost
be extremely complicated technically
be extremely long (mostly for reason 2)
suffer from the problem that there is so much we do not know about genome regulation in a bacteria, let alone in a mouse! You have to think that the genome is not just a series of genes one after another: there is a big part of regulatory regions that define things like the 3D form of the genome, which determines when and how much genes are accessible for transcription, when and where they are activated and so on. Also, more and more attention is now drawn to something called epigenetics marks, modifications of the DNA, or its associated proteins that can also modulate its transcription.

What is the cheapest experiment you can perform at your own home without access to a biology lab which involves changing the genome of a living organism in a way that's functionally visible? (An arbitrary example: Can you create an apple that's blue in color with a budget of $500? By create, I mean you should be able to hold the blue apple in your hand.)

Quick answer: no you cannot.

Health authorities will be not very happy if you start to produce transgenic organisms in your garage
The sole cost of the reagents which you will need to create the transgene will be >$500. You would then need various machines (e.g. a thermocycler, probably a spectrophotometer, a hood, etc etc.).
I personally don't have a clue how one creates a transgenic plant, but I suspect it is not much easier than an animal. And definitely you don't want a mouse colony in your garage, do you?

An easy experiment you can do is extracting (fairly unpurified) DNA with stuff you have at home. More than that it gets really complicated.

In principle a very good answer, but I think there are some points where science can actually do a bit more than you describe - I'll try to write up an additional answer with these points later :)

This answer is mostly meant to be an addition to nico's answer, which while  correct and on the point, does not completely cover what we can do nowadays.

1) What features can be easily inserted into almost any organism
  easily?

The short version of nico's answer here is 'any monogenic trait', which is basically the GFP example.
I would however say that - with additional, sometimes years of work of course - synthetic biology is at a point, where we can make a single cell perform pretty much any non too complicated task (ballpark something you can describe in one simple sentence): the creation of regulatory networks that react to a certain extra-cellular signal is totally possible, as is the generation of multiple proteins (genes) as output. (These two video's might give an idea, I couldn't find a good source right now that isn't overly specific.)
However, this is still very far away from things like sense of smell, flying or making certain body parts, all of which require the coordinated interplay of many different cells.

2)
  Next, I imagine that to design and create an artificial life-form will
  consist of three steps:

Figure out which proteins will give rise to those feaures
Design a genome that will express those proteins in the right quantities and
Implant that genome into a cell and actually let the being grow.

nico mostly focused on the problem with the second and third point: we don't make genomes - we change them. For adding or changing single genes this has only recently become relatively easy (this is what CRISPR is for), and even adding multiple things in one big block is doable. But at some point you need to start doing this iteratively, which comes with its own set of further complications.
However even with the first point there can be a problem: what if there is no single one protein that makes the function you want? Often you'll need multiple proteins interacting or you need to start combining multiple functions into one protein (which opens the box of protein design - I'm just not gonna go into that though)

4) What is the cheapest experiment you can perform at your own home
  without access to a biology lab which involves changing the genome of
  a living organism in a way that's functionally visible? (An arbitrary
  example: Can you create an apple that's blue in color with a budget of
  $500? By create, I mean you should be able to hold the blue apple in
  your hand.)

This may actually be the only point, where I think nico's answer is not really spot on.
He's right that there are considerable safety, legal and equipment barriers, but still 'open bio science' is a thing: from (mostly local) open wetlab spaces to 3D-printable laboratory equipment there is a lot of possibility out there. That being said, its is very illegal in most countries to make GMOs (which the blue apple would likely be) without the corresponding licenses etc.

Very good points Nicolai, and I definitely agree with you! Indeed it's incredible how fast things have changed since I wrote my original answer... thank you for improving on it!


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Evolution of Upside Down Catfish (Synodontis nigriventris)
My Biology teacher asked us to write 3 texts, explaining the evolution of the Upside Down Catfish Synodontis nigriventris, each one according to Lamarckism, Darwinism and Neodawrinism theories. She asked the same thing for other species but I'm having trouble with this one, since the other ones are simple to explain (like giraffes' necks or flamingo's legs).
She gave us a sheet in which there is some information:
They swim upside down, and their colors are inverted, because their backs are light and their bellies are dark (unlike the general fish). Their predators usually swim below them and it is harder for predators to find fish if their belly is light, because of the sun rays.
Well, all of this suggests that this fish swims upside down so that he can avoid predators, but how could he do this according to Lamarckism and Darwinism?
Also, how does he have inverted colors, and did he get them because of evolution?
I believe that the things which cause the evolution are the predators and the environment, but which characteristic is the first one and which is the one who appears because of the evolution? Also, both of them could be a product of evolution, right?
So how can I really explain this according to the theories of evolution?

Well, I haven't managed to find many studies that explores this but I suspect that their coloring was a result of their upside down swimming rather than the other way around.
They evolved from benthic (bottom-living) creatures that ate off the ground and would have had mouthparts evolved for that. So in order to feed at the surface they would have to turn themselves around. The areas that they lived in may have changed to have poorer benthic food quality making surface feeding more advantageous. They also do this for aquatic surface respiration in hypoxic (low oxygen) waters.
Check out "Chapman, L. J., Kaufman, L. and Chapman, C. A. (1994). Why swim upside down? A comparative study of two mochokid catfishes. Copeia" for more information.


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True or False: Vaccines are designed to protect against invaders that are encountered rarely, not all the time
I read the following statement in this article:

Vaccines are designed to protect against invaders that are encountered
  rarely - not all the time

Is it true? If yes, why?

I think the idea behind this is not the frequency of the pathogen itself, but the frequency of exposure. If I am exposed to a pathogen frequently anyway, I have a chance to naturally develop immunity. If I never am exposed to it, one single exposure might be dangerous, if I am not vaccinated (exposed artificially). (Just to add, this is not necessarily true, but I tried to imagine what the author might have wanted to say.)

This analogy is not completely true. A lot of diseases were relatively common before the wide introduction of vaccinations. Measles, Diphteria, Smallpox and others where pretty dangerous although they were common.

Not true. Vaccines were initially made for the highly contagious diseases that used to cause epidemics (which obviously means they were not rare).
The efficacy of a vaccine depends on multiple factors which includes adaptability of the pathogen.
The all-the-time encountered pathogen that the article is talking about is HIV; the reason for why no effective vaccine exists for it is because it has high mutation rate.

The source article had several major errors in it. I wouldn't trust any of it.

Vaccines are designed to protect against invaders that are encountered rarely - not all the time.

This is one of the major errors. There is a vaccine for chicken pox now - an infection which affected approximately 4,000,000 cases per year in the US before the vaccine. That is a very high number of children.
The overall HPV prevalence was 26.8% among US females aged 14 to 59 years before the vaccine. (This vaccine refutes two major errors in the paper.)
Measles, mumps, German Measles, Influenza, Haemophilus influenzae, and Pneumoccocal pneumonia were all common before vaccines for them were developed. Those are just the ones I can think of off the top of my head.
Factors that influence the ability to make a vaccine against a pathogen include the mechanism of pathogenicity, the ability to render the vaccine less harmful than the wild-type illness (such as polio), the ability to mass produce easily, reliably, etc.

False.
Theoretically, a vaccine could be constructed for any pathogen, but the value of doing so if different. In business, this is called 'Return on Investment'. So, vaccines against serious common diseases are more valuable than ones against minor rare ones.
Polio, smallpox, whooping cough, rubella and typhoid are not rare. They are rare now.

A vaccine is not made because a pathogen is rare. It's made because a pathogen is so vicious that you're body does not have enough time to counteract it. Your body is always attacked by invaders, even now.
But usually the Innate immune responses are enough to rid you of the threat. And, when it isn't, it acts as a barrier until the adaptive responses fire up. This time gap is crucial, because the adaptive system needs antigenic presentation from the dendritic cells to differentiate B-cells into plasma and memory cells, then create antibodies and finally these antibodies will opsonize the pathogenic agent and then let the complement system or the CTLs take over.
This is where vaccines come in, Vaccines generally but not always stimulate the Adaptive responses, allowing the creation of Plasma B cells and memory cells. So next time when an invader arrives, the Adaptive response responds as soon as an antigen is encountered. Which is why, the diseases mentioned above have become such a rarity, but rest assured that if individuals choose not vaccinate then these diseases will re-emerge once again as they are doing now in the US.
I cannot post more than 2 links, so if you're interested read up. and If you're even more interested, pick up a copy of Kuby's Immunology, it helped me when I was in college and I'm sure it will help you out too.
http:// en.wikipedia.org/wiki/Antigen_presentation
  http:// en.wikipedia.org/wiki/Dendritic_cell
  http:// en.wikipedia.org/wiki/B_cell
  http:// en.wikipedia.org/wiki/Opsonin


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Pre-linnaean names, where can I ask about current IDs?
I run a large website with lots of historical herb books. For the older ones, finding out current botanical names is very difficult.
Can I ask here? If not, does anybody know where I could ask what any given plant is, with or without images, usually with descriptions and pre-Linnaean names?

Where are you located geographically? Your best bet might be to get in touch with local botanists who are likely familiar with the local flora mentioned in the herb books. If you’re in the US, an organization like the Smithsonian Transcription Centre might be able to help you out: https://en.wikipedia.org/wiki/Smithsonian_Transcription_Center

I'm in Northern Europe. The old books are from Europe or the US, variously. I'll try the Smithsonian, thanks!

Ooo, nice! There’s a ton of biodiversity resources in Europe. I’m not sure who’d be best to approach first here (and I hope someone who does posts an answer to your question!), but this might be a good place to start: https://www.kew.org/blogs/kew-science/celebrating-50-years-of-library-collaboration

Kew isn't interested in pre-Linnaean, I've asked them. Or at least, I asked their "current botanical name database" people.

The Smithsonian botany set is complete, looks to be mostly herbarium specimens, with current botanical names. I don't think they do pre-Linnaean. (I do have Linné's works, of course, which helps a little.)

In case you're not aware, a late 19th century edition of Culpeper's complete herbal gives binomial names for many of the entries, and is freely available at archive.org

Culpeper is easy: http://medherb.com/culpeper_names.html
Salmon's Botanologia 1710 is difficult, here, for instance:
"Of Water Agrimony the Male Kind"
In Latin, Eupatorium aquaticum mas, Eupatorium Cannabinum mas, Agrimonia aquatica mas
It is ... the Genus to three other Kinds:

Our English Male Water Agrimony.
The New-England, or Hemp-like Agrimony.
The Virginian Kind.

I think #1 is Eupatorium cannabinum, #2 Eupatorium maculatum, and #3 could be Acnida cannabina or Amaranthus cannabinus.
Alas, Salmon has hundreds of such entries. Other old herbals can be as cryptic.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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Making penicillin using animals - specifically, a goat
In the scifi novel Lucifer's Hammer, one of the characters (a biologist, if I remember correctly) finds himself in a post-apocalyptic world and tries to make penicillin to save his own life. To do this, he repeatedly states that he needs "a goat" - for some reason which is never explained.
I know that penicillin (in its various forms) is a byproduct of some types of fungi (see Wikipedia), but I can't make sense of the statement "I need a goat to make it". Assuming you don't have a chemical lab at your disposal (think "post-apocalyptic world"), does this requirement make any sense to any of you (apart from "I need to eat the goat to stay alive long enough to find a deserted biochemical lab" :-) )?
If not, how would you go about finding or making penicillin in such an environment?

Here is a link to a survivalist blog with a protocol for making penicillin. (I'm not recommending this by the way.)
Is it possible that the reference to the goat in Lucifer's Hammer is for the extraction of insulin (from the pancreas)? Have a look at the Wikipedia entry for Eva Saxl - in Shanghai during WWII her husband kept her alive with insulin extracted from water buffalo pancreas.

I'm kind of lost... what does insulin have to do with penicillin?

I gather from my research that the post-apocalyptic manufacture of insulin is a plot element in the novel - just thought the questioner might have mixed things up a little.

ahhh... OK, now it makes sense! :)

Absolutely. I read the novel years ago and I did indeed mix up insulin and penicillin. Thank you for this hint, I feel a little stupid now but at least I got two correct answers for one question. :-)

By the way, it would not necessarily need to be a goat, insulin has for many years been extracted from the pancreas of pigs.

True. (Now that I know what to search for, it was rather easy to dig out new sources ...) btw, wouldn't it make sense to change the question now? I tried yesterday but it seems my edit wasn't saved. PS: Thank you!

So - anyone who has read the novel - why is it a goat that is specified?


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Does the speed of electrical impulses through neurones decrease with age?
From what I read on the NatGeo app, it stated that the speed of the electrical impulses that are sent by a neurone will be approximately 332 kilometers per hour.
Will the speed of this electrical impulse decreases over the years as we age?

I'm too busy right now to write a properly referenced answer... but you may want to have a look at this paper A theory of the effects of fibre size in medullated nerve - Rushton, J. Physiol. 1951, which gives very good explications (on a side note, look at the amazing aknowledgments at the end of the paper... precious!). Also, have a look at http://en.wikipedia.org/wiki/Action_potential#Propagation and http://en.wikipedia.org/wiki/Conduction_velocity

Myelination of neurons decreases with age, and that should reduce the speed of conduction.

As @Armatus notes, it is now generally understood that age-related cognitive decline is related to loss of myelination and axon damage (see, for example, Kohama et al, 2012). Myelin degeneration is also likely the cause of some age-related peripheral neuropathies. Loss of myelination (due to inflammation) is also the mechanism behind multiple sclerosis.
Myelin allows for fast and reliable transmission of action potentials by a mechanism known as saltatory conduction. This is necessary to compensate for axons which have small diameters (unlike the squid giant axon) and travel long distances. Degraded myelin will reduce conduction velocity and can result in propogation failures. The links @nico provided in his comment above are useful references.

Kohama, S.G., Rosene, D.L., Sherman, L.S., 2012. Age-related changes in human and non-human primate white matter: from myelination disturbances to cognitive decline. Age (Dordr) 34, 1093–1110.


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What is this critter
I found this "thing" crawling across my drive way. Never seen anything like it and no one I know can identify it.
Was about 4 to 5 inches long and 1/4 wide. It move some what like a worm in that segments of it's body seemed to move to propel itself forward very slowly.
I have a video as well if that would help but it is one my cell phone. I live near Gettysburg PA.

Upload your video on ezgif.com, convert it to a gif < 2mb in size, and add it to your post :)


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Are high sounds worse for your hearing than low sounds?
From about 80 dB it is possible to suffer loss hearing after a couple of hours. But does it make a difference what frequencies those sound waves are or is it just the volume of the sound in dB that matters?
In your ear the first sounds you lose in case of hearing loss are the high sounds because they are at the beginning of your ear. So are high sounds also more dangerous?

Loudness is a very subjective measure. What is loud to you may be very quiet to someone else who has had much more exposure to it. Decibels are the main measure of sound, measuring the intensity or level of the sound. Anything over 85 decibels can start causing hearing loss after some exposure, so it really does not matter how "loud" you think what you are hearing is. It only matters how "intense" the sound waves are.

Yes.  http://american-hearing.org/disorders/noise-induced-hearing-loss/#causes  Most of the discussion of noise-induced hearing loss talks about the loudness of the noise, only rarely mentioning that higher-pitched noise is more damaging.  Probably because it is much easier to measure the amount than the frequency.

Measuring the frequency of a noise is fairly trivial these days, so I don't think that's the whole story.


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What is this insect, the bite of which is causing deaths?
This insect is currently found in Kolkata, and in many parts of West Bengal, India. Its bite results in a fever, and if not treated immediately, the victim dies. This is the insect:

It seems that the insect belongs to the family of spiders due to its eight feet. But I can't conclude any more. Does someone know what this insect is, and how to be safe from it?

Howdy, is this really your picture?  I found it on this website.  Just mite want to attribute it.  :)

@rotaredom it came out on the newspapers, and it's bite is actually brutal.

This is a plant-feeding insect. It is of no danger to humans. Your article sounds a bit sensationalized. There are some small creatures that can kill you, but they are few and far between.

I am sorry that my question is partially incorrect. It is true that this insect is spreading the disease, but it is not the only one. The disease is this.

Well, you have your answer at least! Please note the disease may result in death if left untreated. No one dies immediately.

You were right to suspect arachnid. Its a red clover mite. But they normally don't bite humans or cause diseases. Could you post some links to news articles talking about the disease?

I could have gladly given the site, but it's in bengali and I couldn't find an English one.

Its ok, can I have the bengali site?

I am sorry that my question is partially incorrect. It is true that this insect is spreading the disease, but it is not the only one. The disease is this.

ah that makes more sense now. Thanks for the link


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Why is the Km of an enzyme half of Vmax?
Why is the Km of an enzyme half of Vmax?

We welcome new users to SE Biology, but we expect them to read the help on asking questions before posting, and to look at examples of well-presented questions. Your question, I am afraid does not come up to the mark. You have put half your question in the title, and the rest as a single line. The premise is incorrect in actual fact —  Km is the substrate concentration at Vmax/2, and I have no idea what you mean by "any other specific reason". This is why your question has been downvoted.

$K_M$ is a constant and is not $V_{\mathrm{max}}/2$ as they have different dimensions. But by the Michaelis Menten equation, $V=\frac{V_{\mathrm{max}}[S]}{K_M+[S]}$. So, when $[S]=K_M$, we have $V=\frac{V_{\mathrm{max}}[S]}{[S]+[S]}=\frac{V_{\mathrm{max}}}{2}$. Hence, $K_M$ is the substrate concentration, at which we would have $V=V_{\mathrm{max}}/2$.
Reference: Worthington Biochemical Corporation

We can also see that $K_M$ can't be identically $V_{\mathrm{max}}/2$ since $V_{\mathrm{max}}$ is dependent on the initial enzyme concentration while $K_M$ isnt.

Km is never Vmax/2. It is the substrate concentration at Vmax/2. I would sort out the question before giving an answer. In this case I would not answer the question because it is so badly presented and shows so little effort on the poster's part. See "Answer well-asked questions" in the Help on answering questions. And the suggestion that a naive user reads a "credible textbook on enzyme kinetics" is, well, incredible. Again, point him to a page online. And if you answer take the trouble to set it out in a readable manner.

[Edited] I believe your comment and my answer say the exact same thing. I've told the OP that what they've said is false. In my opinion, even if it's a low effort question, the OP deserves to know that they're wrong. If you would like the OP's question to be deleted, then please vote for that. If you take any particular issue with my formatting that suggests my answer isn't readable, please point it out.


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Do all mammals have a Ventricular system?
I am familiar with the human Ventricular system that circulates Cerebrospinal fluid. This is needed among other reasons, to suspend the heavy human brain, and for injury protection. Do all mammals have a need a Ventricular system?
Maybe some did not have as strong of an evolutionary need for cerebrospinal fluid?

Are you asking Do all animals... as in your title or do all mammals... as in your post. Note that after asking do all mammals... in your post you are asking For example don't woodpeckers..., while woodpeckers are obviously not mammals. Note that many animals don't have a circulatory system nor a brain (such as jellyfish for example) and so the answer to the question in the title is no.

Of course not. For the human primates, nearly most of them have the ventrcular system, but for the non-human primates, seldom of them get.

Just mammals then. I forgot about jellyfish. Which are such a great exception to so many attempts at generalizing the kingdom of animals.

A reiteration of the initial question based on the exclusion of jellyfish as invertebrates: How might the evolutionary development of the ventricular system coincide with a functional separation of the central and peripheral nervous systems?

The ventricular system is common to vertebrates. It's also necessary for brain nutrition, assists in preventing under/over perfusion by exerting/releasing pressure, and forms part of the brain's glymphatic clearance pathway.
See also:
Totally Tubular: The Mystery behind Function and Origin of the Brain Ventricular System


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Do other young mammals turn their backs to their parent when upset?
I have noticed that upset toddlers turn their back to someone who wronged them and huff. Most adults don't do this, so I don't know how this could be a learned behaviour. Do other animals express this behaviour? I do not see how this could be specific to culture.

Other Primates
Sulking is the behavior you are refering to and it is seen in orangutan, Chimp and Bonobo. Likely in other primates but I am not aware of any published works. I have heard about it in baboons but have not read the papers myself.
Source
Source2
Source3
Source4
Also adult humans DO do this on occasion, it is just often more subtle.
It is amazing how many identical social behaviors are seen in our close relatives, especially the ones about conflict and conflict resolution.

could you provide the citations for these papers directly in your post in case the links die? Also, a quick note/summary about what each states would be beneficial (not even entire abstracts but perhaps even a 1 line summary so people know what they're clicking on). thanks!


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Why are trichomes important for both the roots and shoots of plants?
In what ways are trichomes vital to the plant?
Why have them on the plant shoots as well?

This question would be better with more context. Trichome is a generic term for diverse, often microscopic, structures with a wide variety of functions. The question "but how does that work" should be addressed separately.

Ok let me fix it.

Plant leaf hairs, or trichomes are vital for many reasons.
Interestingly in 1975 researchers were correct when they stated:

"It can be argued that essentially the same genetic system should be required for both root hairs and trichomes." [1](Pay-wall)

For example:

C. salvifolius, there are more adaxial trichomes present to avoid UV light from injuring the abaxial surface.[2](Pay-wall)
Increased transpiration [3](Pay-wall)
Protecting against insect herbivores [4](Pay-wall)
Increasing tolerance to freezing [5](Pay-wall)


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How to set up a slow cooling on an AB Veriti thermal cycler?
I want to incubate my sample at 50ºC and then slowly cool it down to 4ºC at a rate of 0.1ºC/s. I am using  AB Veriti thermal cycler. Does anyone know how to set up the rate of cooling? It has to do something with the ramp rate, which is given in % but I don't know how to convert this into a real rate.

If I recall correctly (from when I interned at ABI), you can't directly set this in the Veriti interface.  However, (again, I'm not 100% certain -- I couldn't find anything to confirm this after 30 minutes of googling,) the ramp rate percent refers to the percent of maximum ramp rate for the heating block.
According to the product website, the max heating block ramp rate is 5 °C/s while the max sample ramp rate is 4.25 °C/s, so you need a ramp rate between 2% and 2.4%.

As a side note, the people at ABI are very proud of their instruments. If you'd like, (if the web contact forms aren't very helpful), I can put you in touch with someone from the Foster City office to help you squeeze the most out of your machine.  (I'm not sure how to say that without sounding like an advertisement — I'm just trying to be helpful.)

It would be great if you give me a contact. Can you email it to me please? Thanks a lot.

You've successfully hidden your email address from the internet, and I wouldn't want to ruin that for you, so if you'd like, you could email me with your address.  My email's in my profile.

apparently they are hidden to the world!

As Thomas pointed out, there is a maximum ramp rate which you can set up on the thermocycler. Its value can go from 0% to 100%. I can then assume that a 100% ramp rate will corespond to the maximum ramp rate of 4.25°C/s for the heating block or 5°C/s for the sample. which means that a ramp rate of ~2.4%. Subsequently, I set up my reaction at a 2% ramp rate, as I started a timer at the time the ramp cycle started. To my surprise, the temperature was cooling down too slowly. Thus, I empirically found out that a ramp rate of 5% corresponds to ~0.1°C/s cooling speed.
I wished there was more precise way to calculate it. Perhaps the slope of the line changed at different temperature intervals. It would be great if I can talk to the AB people so that they could justify my finding.

The maximum rates change with the product version, by the way.  The Veriti "Fast", 96-well has a ramp rate of 5 °C/s while the Veriti "normal", 96-well's max. sample ramp rate is 3.35 °C/s.  But still, this would be a 3% ramp rate, not 5% like you found.


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Efficiency of plasmid DNA isolation from frozen E. coli cell cultures
Has anyone isolated plasmid DNA from frozen (at -20degrees) E. coli cell cultures (not pellets)? Has that worked and if so, with what yields? What would be the quality of the isolated plasmid DNA if run on a gel? Would most of it be degraded or intact?

I have done that and it works without any problems. We harvested the cultures at the optimal timepoint (density) and then froze them to do maxipreps later on. Therefore we simply thawed the culture, made sure it didn't got too warm (meaning we worked on ice) and then simply followed the maxiprep protocol. No problems with yield or quality of the plasmide.
What I will do next time is to spin down the culture and take it up in max. 50 ml of medium before freezing. This way freezing will be faster as well as thawing. I have also done minipreps from stock cultures (glycerol stocks of plasmids in E.coli) which accidentally stayed out of the freezer for two days. Here the yields where not so great (but the density of the culture was also much lower), but the quality after standard miniprep was good and the plasmids worked both for subsequent cloning as well as for retransformation to make new stocks.

Thanks Chris. I tried it with 25ml cultures and I got great yields! I did not run them on a gel to check the quality of the DNA, but the sequencing results looked good!

Great to hear. In my experience plasmids are incredible stable given how complex this macromolecule is.


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What effect does vortexing have on a fluid sample that simple mechanical shaking does not?
Some protocols call for fluid samples to be mixed with a "vortexer" on the high setting.  What effect does the vortexing have on fluid samples that mechanical shaking does not?  Does it shear long molecules like DNA, for instance?
A friend is setting up a new lab and asked if vortexers were strictly necessary.  I am aware they are often called for in various protocols, but I actually don't know what specific effect the vortexing has that makes it better than manual shaking.  What do you think?

In my experience, shaking and mixing have different "dead spaces". Supposed you had an eppendorf tube and you stirred it around with a pipet tip for thirty minutes. You would have great convective mixing in the radial direction but virtually no mixing in the Z-direction. Supposed you had a very viscous fluid like PEG. If you set the tube on a shaker for an hour it will virtually not mix. The vortexer provides a very different profile of mixing.
Instances where I wouldn't use the vortexer would be for sensitive objects like DNA and cells.
(update)
We had some interesting suggestions from the FDA (since the FDA pays attention to these type of discussions). To get proper mixing, it is often not considered enough to merely swirl a tube a bunch. Their actual recommendation is to train technicians to perform a 90 degree angle arc with their forearm to generate proper force in mixing.

Vortexing is called for when one or more of the fluid samples is more viscous than water?  For instance (as you suggest), 100% glycerol is 1000x more dynamically viscous than water, hence the need for a vortexer to mix water and glycerol well (http://www.wolframalpha.com/input/?i=viscosity%20of%20glycerol%20%2F%20viscosity%20of%20water).

Besides mixing fluids of different viscosities, are vortexers necessary for any other lab operations?

@Maccowell, doesn't mixing liquids of different viscosities describe most lab operation? I would also include suspending non-soluble mixtures.

what specific effect the vortexing has that makes it better than manual shaking

In addition to @bobthejoe's answer about viscous fluids, (manual) mechanical shaking is also less consistent and more tiresome than vortexing.
If the vortexer is always at the same speed and each sample is vortexed for the same amount of time, then the shaking step will be less variable among samples. For example, the vigor of mixing an aqueous soil suspension could potentially affect the amount of aggregate decomposition and release of molecules into the suspension (I don't have a reference for this, but it is good practice to treat replicates the same to minimize any non-treatment effect).
Manual shaking is not only less consistent, it is also tiresome - especially with larger volumes (>=10ml) and large sample sizes.


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Why does a worm's skin need to be wet for oxygen to diffuse across it?
Pages I've read about worms' respiratory systems says that the skin needs to be wet (covered in mucus) or oxygen won't diffuse across the skin. Why? If there is more oxygen outside the worm's skin than inside, what prevents it from diffusing across the skin, even if the skin is dried out?

The quick answer: When the skin dries, the lipids in the cell membranes of the skin tissue undergo a phase transition which makes the membranes less permeable for oxygen.
Explanation: The lipids of the cell membrane can exist in different phase states. In the liquid disordered phase the lipids are relatively flexible and mobile, making this phase more oxygen permeable compared to the liquid ordered phase, in which the lipids are more rigidly packed.
The phase transition temperature of lipids increases upon dehydration (another reference), meaning that at the same ambient temperature, a dry lipid membrane is in the liquid ordered state and a wet lipid membrane is in the liquid disordered state.
Therefore, a dry cell membrane is less oxygen permeable than a wet one.

Because you are talking about diffusion, thus there needs to be a continuous pathway of gas or liquid for the molecule to move through. Membranes stop behaving like liquid when you dehydrate them.  Oxygen cannot diffuse through extracellular solids (not at a meaningful rate anyway), which is all that is left why the skin dries out, so there needs to be a liquid path for it to follow. The water around a cell membrane helps weaken the binding energy allowing materal to pass between the lipid molecules, without the water is becomes a functional solid.
Skin does not replace water with air when it dries out, it collapses in on itself losing volume so all you have is solids (or things close enough to solid to act as a barrier), those no path for the oxygen. It is the same reason CO2 cannot diffuse through a coke can, it can't diffuse through a solid.
Edit, there is some gas exchange but it is very minor especially compared to what happens normally, and occurs because there is an occasional gas path. Cell membranes can be diffused across, but they slow it down, layer upon layer of them packed tightly as you have in dehydrated skin produce much the same effect as a solid, reducing the diffusion rate the point it can barely be measured and is nowhere near what the organism needs.
Animals that do not need ot gas exchange across the skin add layers of waxes to the skin making it an even better barrier and thus making it even more water tight.

Isn't the worm's skin still solid underneath the mucus?

@MarkEichenlaub  No, like most other biological tissue it is a gel, a liquid held together by a matrix of solids. That is why the mucus evolved, to prevent the skin from dehydrating. There are air tight skins in other organisms, (by creating waxy barriers), generally they experience minimal gas exchange.

Respiration in aquatic organisms involves diffusion of dissolved gases present in the aquatic medium across their permeable cell membrane . In worms which lives in moist environment the skin functions as a respiratory surface and requires the surface to be moist to enable exchange of gases.

Thank you, but I don't see this an answer to the question. "to permit exchange of gasses across moist skin" why does the skin have to be moist? "which is stable when moist." What does it mean to be "stable"? Why is moisture important to that?

Hi Mala. When directly quoting a source, it's required that the words be in blockquotes with the source listed (just listing the source isn't enough), or the material is considered to be plagiarized. It's kind to answer the question, but this is not the correct way to do it.

Dear  Mark Eicheniiaub  Thanks . Stable relates to the functional status . To enable exchange of dissolved gases present in their. ( for worms which inhabit moist places) aquatic  environment requires wet surface .

Yes, but why does the surface have to be wet?

The dissolved oxygen in water needs moist surface to get diffused in to the cutaneous blood vessels located in the skin of worms . - basically to ensure that oxygen can be dissolved and absorbed by the circulatory system to fulfill the requirements of the organisms  to reach to the deeper parts of the body. Required amount of oxygen  can not be delivered directly in its gaseous form.

But why does it need moisture to diffuse?

Dear Mark Eichenlaub -Thanks .The rate of diffusion  varies with the area of diffusion, Concentration gradient and the thickness of the surface area as per Fick's law . A molecule of water which is at higher concentration inside the body than outside - diffuses out and makes the diffusion surface moist.  Gas exchanging surface in land animals are internal  to prevent  much loss of water from the body.


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Why do earthworms surface after a rain?
Googling, I find two different explanations for why earthworms tend to surface after a rain.
This page from UCSB, for example, gives both answers, contradicting itself:
The first explanation is that worms can breathe fine when it's wet underground, but surface after rain because it's their only chance to surface without drying out:

Worms, like all other animals need to breathe, but since worms do not have mouths, they have a different way they breathe. Worms breathe directly through their skin, but they can only do so if their skin remains moist. Deep down in the soil, where worms typically live, it is normally moister than the surface. For this reason, worms prefer to live underground. After it rains, the surface becomes wet enough to support worm life, so they can come above ground to explore new areas more quickly. Fun fact: worms actually don’t come above ground after it rains to avoid drowning. Earthworms can live underwater for approximately two weeks. Thank you very much for your question!

The second answer is that worms drown if they stay under ground after a rain

Worms are animals and, like you and me, they require oxygen to live. Instead of breathing air though their mouth into lungs, worms absorb oxygen from the air across their skin. Worms eat dirt. They burrow into the soil and normally live underground, where they are protected from the sun and so won't dry out. If you've ever played in the dirt by digging holes, you probably noticed that there are small holes or tiny pockets of air. The worms use that air, and the air that enters through their burrow holes, to breathe. When it rains and the dirt absorbs a lot of water, those air holes disappear, and the worms' burrows fill with water. If the worms do not come to the surface during a heavy rain, they will suffocate. Likewise, if they do not return to the soil after the sun comes out, they will dry out and die.

Which of these two is correct?

It looks like certain species of earthworms need to surface because they have higher oxygen consumption, while other species do not need to surface because of their lower consumption.
In particular, specimens of Amynthas gracilis were found to have low water tolerance, hence they

crawl out of the waterlogged soil, especially at night when their oxygen consumption increases

while Pontoscolex corethrurus

survived longer under water and was never observed to crawl out of the
  soil after heavy rain

Role of diurnal rhythm of oxygen consumption in emergence from soil at night after heavy rain by earthworms

Indeed annelids breathe through their skin, which needs to remain moist, but not immersed underwater. A thin layer of moisture is required for oxygen, CO2 to exchange. If totally immersed there is typically not enough oxygen in the water to support the rate of respiration required and they will literally drown.
The reason they surface after a rain is because the soil becomes saturated with water, again they will drown.

This answer needs authoritative references.


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What gaseous substances do humans emit?
Other than CO₂ and Methane what other gases do humans produce or emit?
For example, does  skin decomposition, or aerobic respiration emit any special gases that people don't normally realize or know about.
I ask because of a discovery I made during research is that while being poisonous to the central nervous system, methanol is a natural endogenous compound found in normal, healthy human individuals.
One study found a mean of 4.5 ppm in the exhaled breath of the subjects. https://iopscience.iop.org/article/10.1088/0967-3334/27/7/007

The probably origin of exhaled methane is anaerobic gut bacteria and archaea (yes there are always a few archaea in the gut).

There are 100+ gas phase compounds that come from humans.

Find other information about most of these families of compounds from wiki.
Full list of compounds is here
Methods and findings are here

A few spontaneous comments: 1-octen-3-ol and similar compounds are fungal products from lipid breakdown (probably on the skin) so not directly human metabolites. Also, cymene (and others, I didn't look up the full list) are plant secondary metabolites, i.e. essential oil components presumably from eating plant food with subsequent exhaling and/or pooping. Humans cannot make these themselves.

Oh golly that's interesting. Perhaps that would be a comment for the OP, i.e. that methane is not actually made by the cells of the human body. There are perhaps symbiont funghi on humans according to current research on microbiology.

Yes human skin fungi are mainly from genus Malassezia.

The gases NO, H₂S, CO even have a function in the human body!
Nitric oxide is produced in endothel and neurons as messenger, and in macrophages as cause of nitrosative stress for imprisoned bacteria. Hydrogen sulfide is produced in cysteine catabolism and functions as messenger (only recently discovered). Carbon monoxide appears to act as messenger, too.
http://en.wikipedia.org/wiki/Biological_functions_of_nitric_oxide
http://en.wikipedia.org/wiki/Hydrogen_sulfide#Function_in_the_body
Wu, L; Wang, R (December 2005). "Carbon Monoxide: Endogenous Production, Physiological Functions, and Pharmacological Applications". Pharmacol Rev 57 (4): 585–630. doi:10.1124/pr.57.4.3. PMID 16382109

I always understood that NO, when used as a neurotransmitter / second messenger, is in solution, i.e. not gaseous.

Would these gases be extreated from the body in gasous form?

H₂O is emitted through respiration and perspiration.

A key component of body odour is the volatile thioalcohol, 3-methyl-3-sulfanylhexan-1-ol (3M3SH).  The structure may be visualized as hexan-1-ol  "substituted by a methyl group and a thiol group at position 3 " (pubchem)
A major contributor to the formation of 3M3SH is the  commensal bacterium, Staphylococcus hominis,  which produces it  as a by-product of the metabolism of  (odourless)  Cys-Gly-3M3SH.
Cys-Gly-3M3SH, "an L-cysteinylglycine dipeptide-conjugated alcohol that is secreted onto the surface of the skin by apocrine  glands" (Ref 2), is itself produced as a by-product of human metabolism in sweat glands.
The key enzyme is a cysteine-thiol lyase (C-T lyase), which (among many other interesting attributes), contains pyridoxal phosphate.
References
Ref 1: Structural basis of malodour precursor transport in the human axilla (Minhas et al., 2018)
Ref 2: The molecular basis of thioalcohol production in human body odour  (Rudden et al., 2020; Nature (Scientific Reports))
Ref 3: Know sweat: scientists solve mystery behind body odour (The Guardian, July 2020)
Ref 4: Structure of 3M3SH at pubchem.


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What are the differences between mammal and insect digestion of cellulose?
I know that digestion of cellulose is difficult in mammals and requires a lot of steps. But I am fascinated by the idea of one day achieving human digestion of cellulose.
Which got me thinking about how insects digest cellulose much faster than mammals, how is this possible?

What precisely do you think you "know" about human digestion of cellulose. The reference you quote says that the limited and variable ability of humans to digest cellulose depends on gut bacteria and not their own enzymes. It also says nothing about the number of steps. You cite no sources for your statement about insects but it appears that, apart from termites and the like, most insects depend on bacteria  for their ability to digest cellulose too. So are you asking about the differences in human and insect microbiota? I won't speculate on the answer in a comment, but what do you think?

So from your comment and the answer below, its seems like there is little difference between the ways cellulose is metabolized. This has helped me update my understanding. Thank you.

…except the bacteria might well be different, especially as they are symbiotic. The intestinal system of insects have some similarities to higher animals, but…

What attempts to answer this question have you already taken? We ask that all question posters here attempt to search for an answer to their own question and explicitly indicate what research they've already done, what they learned, and what is still confusing or unknown to them. Our goal is not to simply be an answer site, but rather a site that promotes self-learning with some expert help along the way :). Please take a moment to edit your post with this additional detail, and it will likely be received more positively by our community. Thanks!

Update 2 (interpreting "faster" in terms of efficiency because it seems easier to measure)
The question has been updated but I still don't see a reference for insects being more efficient than mammals. Therefore I investigated this and did not find convincing evidence that it is the case.
Granted, the means of measuring efficiency are not necessarily comparable, but nonetheless it appears that ruminant cellulose digestion efficiency is comparable to overall distribution of cellulose-digesting bacteria.
(Overall, in both clades, the vast majority of species do not appreciably digest cellulose, so I focus on those that do.)
This paper suggests that while termites have remarkable ("nearly 99%") efficiencies they are a dramatic outlier among insects. In different groupings efficiencies range from 12-68%, 40-90%, and 11-50%.
This paper suggests that the "digestibility" of cellulose by cattle is in the range 0.7-0.8 (that is, 70%-80%). It is observed that the rate is higher in sheep (and goats?), though comparable figures are not provided. Other figures in the paper are in terms of animal body weight gain, which is unfortunately a poor measure due to the high energy cost of just living for warm-blooded animals.
If I interpret these numbers correctly, this means that ruminants in fact compare favorably to most celullolytic insects in their cellulose digestion efficiency. The very high efficiency of termites specifically is likely a facet of their being little microbial factories with legs; they are definitely an outlier among insects.
In conclusion, I don't think that there is any particular intrinsic advantage for insects in cellulose digestion.
Update
I went back and read the linked post and realized that much of my answer was covered there and thus somewhat duplicative.
What is not covered is the insect/animal comparison. I do not see the source material for the assertion that insects are more efficient at cellulose digestion, it might be true or be somewhat trivially true but I would need to see where you got this information to assess it.
I would suggest doing a little initial research to maybe get closer to an answer. For example, here is a review on cellulose digestion in insects, and here is a resource for mammals, here is a comparison between the two.
Original
Neither insects nor mammals (as far as I know) have the appropriate digestive enzymes to digest cellulose efficiently on their own. However, some special animals like termites and ruminants have assemblages of microbes in their gut that can break down cellulose. These enzymes are called cellulases.
However using these assemblages efficiently requires an extremely specialized gut system such as the rumen.
So you might get humans to digest cellulose by making transgenic humans with cellulases in their digestive system or completely redesigning the human digestive system. Possibly there would be a way to supplement with cellulase the way some people do with lactase.
A different concern might be that human physiology isn't set up to support that style of nutrition. For example I imagine that diabetes incidence would increase. But it's hard to predict.
If the idea is to feed a growing population of earth in a less carbon-intensive way, there are likely less complicated ways to do that by altering diet to e.g. less meat, popularization of sea vegetables, etc. But that's just my opinion, maybe you had something else in mind.
Hope that helps.

wow, you have worked so hard to answer my question. I know very little about human digestion of cellulose, but when I mentioned that cellulose being difficult in ruminant mammals, I was considering how much time it takes for grass to make its way though a cow's 'four stomachs', and the need for additional mechanical action, 'cud' chewing in order to make use of the cellulose. Where as locust, and snails seem (to my neophyte understanding) to have much less complicated digestion system. The locust digestive system having only 3 parts like humans.

ah, ok. Sorry to have gone down some unrelated rabbit holes. I agree that the stuff going through stomachs is probably faster purely in terms of having less tubes to go through in insects. However, that seems difficult to measure, particularly with regard to how it effects the animal's ability to actually digest cellulose, so I wasn't sure how to make a good investigation of it and did what I could. Hope it had some benefit!