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How is bad garlic breath eliminated by swalllowing a bit of raw garlic?
Please bear with me, as I am just a poor physicist.
I have learned how to make traditional pastourma  from a recipe given by my late aunt Dora, which is like pastrami except with a very strong garlic contribution and a lot of other spices. This leads, after eating, to strong garlic breath. My daughter complained of the "stink" when she was near me.
I somewhere heard that if one swallows a bit of raw garlic before eating food with strong garlic content, the breath stays fresh. I have tried it several times, and it works (my daughter the detector). It seems magical, or homoeopathic!
As a physicist, I would like to know how is this possible?

Searching the net for "how to avoid garlic breath" some references come up.

Enter Ohio State University to help. Researchers there have evidence suggesting that we can neutralize bad breath naturally before it offends those around us. According to science, here are three ways to do it.

Recommended: raw apples, lemon juice, green tea.

Green tea is very high in antioxidants called polyphenols. As with the enzymes in the apple, polyphenols cover up the odor-causing chemicals in garlic.
Sheryl Barringer, one of the study's lead researchers, said that it’s best to use the bad breath cures at the same time you’re eating garlic. So we’d recommend adding some apples to that salad with garlicky dressing or using some lemon juice in your next garlic dip. Unless you want to squeeze the citrus straight into your mouth, that is.

And in a link found there, the chemical explanation is:

According to the researchers, foods deodorize garlic breath through two mechanisms. First, enzymes in the raw foods help to destroy the odors, and then, phenolic compounds in both the raw and cooked foods destroy the volatiles. This is why raw foods were generally more effective because they contain both the enzymes and the phenolic compounds.

It must be that raw garlic taken just before eating garlicky stuff works the same way. No magic. Maybe the researchers will see this and do a proper experiment :).


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Why shouldn't I clean microscope slides with a paper towel?
I've recently bought a microscope and been looking at a lot of bacteria and such, and have quickly run out of clean slides. I've seen videos and articles saying how you shouldn't clean microscope slides with a paper towel and to use an ultrasonic cleaner instead. I don't have access to an ultrasonic cleaner, so I am wondering what is wrong with cleaning them with a paper towel?
Also if anyone knows of any good liquid solutions for cleaning slides that information would much be appreciated.

The main reason to avoid paper towels, tissues, and etc. is that they shed lint (paper fibers) which will be left behind on your slide and eventually interfere with your prep. They look small to the naked eye, but they are not small compared to the prep on your slide.
The other issue with paper towels and etc. is that there might be some particulate matter in the paper that's hard enough to scratch glass or optical coatings. This is more of an issue for optics - especially coated ones - than for cheap microscope slides, but it's something to consider.
If you're not mounting permanent preps then ultrasonic cleaning is probably a bit of overkill - although I have a surplus sonicator and it does a great job on a lot of tasks. It's generally sufficient to rinse the slide with distilled or deionized water and then follow up with (clean) alcohol. Optical purists will say spectroscopy grade methanol, but for home use any reasonably pure MeOH, EtOH or iPrOH will probably do. The main concern, again, is leaving behind particulates or residues. You can allow the slides to air dry if you're using pure alcohol, or use a piece of lens tissue (lint free paper tissue) to help them dry faster. I've also used Kimwipes in a pinch, but they're not truly lint free so not ideal. They're still much better than a tissue or paper towel.

+1. Distilled water, a wipe with Kimwipes if needed, then EtOH is all I use in the lab. Keep your slides in the box they came with, don't expose them.

For reference, a 280-pack of 1-ply kimwipes on fishersci.com is 9 dollars plus shipping. Other purists will still say buy lens wipes, which are like 1200 for $95 on fisher, but I find kimwipes do the job.

Kimwipes do this job quite well, but generic lens paper is quite cheap too - I think I got ~400 sheets on amazon for ~$10 and it's decent quality. Doesn't matter for this kind of cleaning, but for actual optics (if you're even wiping) it can be very hepful.

Methanol is toxic and very volatile, so you shouldn't advise its use without also advising to use it under a chemical hood.

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Why are Excavata called "Excavata"?
The explanation given in my textbook is:

Some members of this diverse group also have an “excavated” feeding
  groove on one side of the cell body. (Campbell Biology)

This still isn't clear, though. What does it mean that this groove is "excavated"? Is it hidden inside the organism and then dug out?? Several websites just say the same thing.

This is just a reference to the feeding groove - a morphological feature that groups these organisms. The presence of the term in quotes as "excavated" is an indication that the word is not meant to be taken literally. Quotation marks used like this are referred to as scare quotes - they are meant to alert the reader that the phrase in quotes is not to be interpreted by its standard meaning.
Instead, you could read the sentence as meaning:

Some members of this diverse group also have a feeding groove on one side of the cell body, as if part of the cell was excavated.

One should not take the etymology of species names too literally - they are really just names. This is also true of common names of organisms.

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Orangish-coloured insect living in wood chips
Can anyone Identify this organism?
I dug it up in a pile of 5 year old wood chips in Cleveland, Tennessee, United States. It is about 4 inches long.

That is the pupa of a unicorn beetle, Dynastes tityus. https://arthurevans.wordpress.com/2010/09/15/453/


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Calculating PCR Cycles
I have a problem understanding a PCR exercise, it says to calculate the number of cycles to get 1µg of the DNA fragment, starting from 10ng and then from 500ng, I know about 2^n, and the exercise even gave the answers:
For 10ng, we need 29 cycles
and for 500ng, we need 24 cycles
But I don't know how they did it, I tried with 2^n and ended up with something totally different. I would be grateful if someone explained it to me. Thank you.

With every round of PCR, your sample doubles (ideally) and you are right when using $2^n$ for calculating the amount of DNA produced.
The formula would basically be like this:
$$X_{n} = X_0 2^n \\[1em] n=\log_2(X_n/X_0)$$
Just substitute the values of $X_0$ and $X_n$ — 10ng and 1000ng. The answer would be ~6.64 cycles.
The 500ng case is easier to imagine. The amount is doubled between 1µg and 500ng. So it is just one cycle of PCR.
If this was your answer then you are right. If book says otherwise then it is wrong or you could have read the question wrong.

Thank you, i got exactly that, 6,64 and 1 cycle, but i was so confused.... there probably was a mistake in the book, thank you again, i appreciate it ^^


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Tools to find miRNA ID
How can I get accession numbers of bread wheat miRNAs by their sequences? What are the tools or website that can be used?

Somewhat out of character, I have given a (short) answer to your (even shorter) question, but you really should read the help on asking questions. You are expected to do some research before posting and show in your question what attempts you have made to help yourself. I do not work on wheat (or any plants, for that matter) but I know how to use the Google search engine. Did you search for "microRNAs and Triticum aestivum"? There are quite a few papers that come up that presumably could provide leads.

If you have a sequence, run a nucleotide BLAST search at NCBI, specifying Triticum aestivum (taxid:4565) as the organism.
The miRBase page for Triticum aestivum has details of wheat microRNAs, and a page where you can do a sequence search with either BLAST or SSEARCH (as @WYSIWYG kindly pointed out).
Perhaps the Triticum aestivum page at PlantGDB may help.

Reg. point#2: miRBase has BLAST and SSEARCH (Smith-Waterman) for searching by sequence.

Thanks @WYSIWYG. I had thought that there must be, but presumably I didn't scroll down far enough. Have modified my answer. miRBase seems to be the place the poster should go.


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What is Meriva Phytosome Curcumin?
What is Meriva Phytosome Curcumin other than being a food supplement?
Is it a plant? A type of plant extract?
I googled it but still couldn't figure out exactly what it is.
The reason I'm asking is because I came across the following list in a site selling vitamins and other food supplements:
Meriva Phytosome Curcumin
Turmeric (Curcumin)
Turmeric Formulas

It wasn't clear to me if Meriva Phytosome Curcumin is a specific kind of curcumin since it seems to be sold under a few different brands.

Well, http://meriva.org states that

Meriva® is a patented formulation of curcumin, a dietary phenolic, with soy lecithin (non-GMO)(1). The two compounds form a non-covalent adduct in a 1:2 weight ratio, and two parts of microcrystalline cellulose are then added to improve formulation, with an overall contents of curcumin of 20%

A phytosome is

[...]  a complex of a natural active ingredient and a phospholipid.
It is claimed that phytosome increases absorption of "conventional herbal extracts" or isolated active principles both topically as well as orally.
The complexation with phospholipid has been applied to many popular herbal extract or active molecules including [...] curcumin isolated from turmeric [...].

And Curcumin is

[...] is a diarylheptanoid. It is the principal curcuminoid of turmeric, which is a member of the ginger family (Zingiberaceae). Turmeric's other two curcuminoids are desmethoxycurcumin and bis-desmethoxycurcumin. The curcuminoids are natural phenols that are responsible for the yellow color of turmeric. Curcumin can exist in several tautomeric forms, including a 1,3-diketo form and two equivalent enol forms. The enol form is more energetically stable in the solid phase and in solution.

So, Meriva Phytosome Curcumin is a phytosome of curcumin developed by Meriva.

When I googled it I didn't reach any of those (except curcumin), perhaps because Google results are personalized...

@traveh It's not that it's personalised, it's that you have to know how to look for the answer. Adding things like "NCBI" or "PLOS ONE" to the end will help you find scholarly articles (same with using google scholar). Also, it might help to break things down into different parts, like searching for Miriva, phytosome and curcumin sepeartely. If you add quotations around a part of the search, that part is prioritised by google.

To summarize terdon's excellent answer:
curcumin is a chemical found in the plant turmeric (Curcuma longa)

I know what curcumin is, I was wonder what is "Meriva Phytosome Curcumin" specifically. :)

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Why lab technicians use indirect (antibody reaction) method for diagnosing?
In microbiology we have two types of microbial diagnosis. The direct method is where we detect the invader's DNA, Antigens or culture to see the exact pathogen while the second, indirect, method is the reacting the antibodies of patient's serum with different reagents.
If we use the indirect method (antibody reaction) and find that they are producing antibodies against a specific disease (let's say streptococcus A) what is the benefit of having found that they are fighting Strep A since the body is already clearly fighting it and putting up the best defence to fight the disease?
Would a doctor really prescribe antibiotics even though here is already an immune reaction against the infection?
If diagnosis and treatment are useless then why do we waste the time to do it?

Short answer: Antibiotic treatment is important because the body can't always keep up with the infection even if it has launched a response.
Background:
First, let's look at what the antibody reaction method is actually doing.

Taking a sample of blood or body fluid
Testing the sample with known pathogens - viruses, bacteria, fungi, etc.
Identifying which infection causes a reaction.

This allows us to determine which infection we are dealing with. This can be especially useful when the infection is hidden in a place we are unable to easily swab - the stomach, heart, a small wound that has already healed. Sometimes this test is just used to monitor how well you are fighting the infection, but it also allows them to evaluate what the best course of treatment is for you. (Reference 1)
Just because the body has an immune reaction doesn't mean that the body's immune system can actually finish the battle against a disease. In the example case of Strep A, you may be able to get over the infection yourself but it will take longer than if you are prescribed antibiotics against it.
See this question on the CDC:

Q: How common is invasive group A streptococcal disease?
A: Approximately 9,000-11,500 cases of invasive GAS (Group A Streptococcus) disease occur each
  year in the United States, resulting in 1,000-1,800 deaths annually.

Note that invasive Strep A usually infects children, elderly, and  immunocompromised people (anyone with a weaker immune system typically).

Unless you have absolutely no immune system at all, there will be an antibody response put out by your body. The NHS goes into detail about different parts of your immune system.
Recall also that Strep A (our example) could divide faster than the body can keep up with. So we would need antibiotic help to fight the disease. Using the "indirect" method we can find a hidden infection.
According to the NHS the antibiotics put a stop to growth and spread which allows the body to come in and finally finish them all off, or they disrupt a process the bacteria needs to survive and kill the infection for the body. Thereby helping the immune system (the body's best line of defence) finish off the infection when it couldn't do it on its own.

It is also worth pointing out that the premise of the question is wrong.  Assaying for an antibody response is rarely used to diagnose an ongoing disease, because the antibody response takes several days to develop; the exceptions are for chronic diseases (hepatitis B or C, HIV) where the pathogens have evolved defenses against the immune system and aren't cleared by it.

@iayork aren't antibodies tested for various diseases? Lepto, dengue, typhoid just to name a few....

They're used to test whether you had the disease, sure. For acute diseases like typhoid and Dengue, they're less useful because they're not detectable for a week or so after the disease starts.

One use of indirect testing is used to test for *exposure** to organisms that we wouldn't just naturally recover from as well. One example off the top of my head is HIV. The first line of testing for this infections is simply to look for antibody responses, but because it is not effectively resolved by the patient's immune response, it is important to know about this infection.
*Also note that because we are looking at antibodies, we only know that the patient has been exposed to the organism, not that they are actively infected. The antibody test is quick and easy though, so it saves money (and probably time) to do this first.
(originally, I included TB in this answer, however it is actually a skin test - not assayed ex vivo via ELISA, so I removed it.)

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How do t-lymphocytes become mature if thymus has lost its function?
The development of t-lymphocytes are done by thymus and we also know that the thymus degenerates before puberty and we also know the maximum lifespan of WBC's is 15 days. So, how do t-lymphocytes become mature if thymus has lost his function?

A few points, I'll expand on this later and add references if I have time:

The thymus starts degenerating at puberty but continues to function in thymocyte maturation for decades, albeit at a lower level
Many mature T cells can live for years
Through homeostatic proliferation, peripheral T cells maintain their population size
Immune surveillance generally decreases with age

Note that extended lifespans and homeostatic proliferation (points 2 and 3) don't contribute to TCR diversity but only maintain the existing repertoire.

The key thing is this: yes, the thymus involutes at puberty but that doesn't halt  thymopoiesis. The thymus continues to produce naive T lymphocytes throughout our lives (even up to 70 years of age-see references) albeit at a very reduced rate. This mechanism is very important for example in HIV-infected individuals who are still able to repopulate their immune cells through a combination of peripheral T cell division and thymic production of naive T cells.
References: Reference_1, Reference_2, Reference_3


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Halophiles' food habit
We know that some halophiles are heterotrophic, but in those highly saline environment what do these organisms eat as there might be very little chance of survival of any other organism?

When we look at the definition, Halophiles are just archaebacteria that require salt in their environment to live. Wikipedia states that they live in salt concentrations of 0.3 to 0.8 M (1.7 to 4.8% — seawater is 0.6 M or 3.5%).
According to The Saltwater Wetland bacteria in estuaries will get their food from dissolved organic mater in the water. An estuary can have a salt concentration of 0.5 to 35 ppt (according to google). This would be 0.05 - 3.5% salinity depending on the estuary, so obviously there are some estuaries would not be able to host Halophiles, but the concept is still the same. They would get their food from dissolved organic matter in the water.

Of course @KritikaWaghmare if it's what you were looking for click the check next to this answer to accept it. If you're looking for more you can wait to see if there are other answers :)


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Can someone die from pain?
I'm a CNA and I just got home from a very long day at work. I just started this job and I got hurt at work last night which made me wonder can enough pain cause death (without suicide)?
I think the answer is yes, but I'd like to know how/why.

Yes, you can go into shock from bleeding, emotional disturbance, a heart disorder, and/or a blood infection. It causes not enough oxygenated blood to get to important organs in your body and if it isn't treated it's normally fatal.
I would think that enough pain could cause a large emotional disturbance which could result in shock.

Please give some solid references. I do think this would be possible though, especially if one has a weak heart; as an increased heart rate from pain could stress it.

Pain and shock are completely different things. Your answer needs references and clarification.


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What causes head hair to be different than body and face hair?
If you feel your head hair, it typically feels a lot softer and is easier to manage (comb, brush, fix) than a lot of other hair on your body - specifically I'm thinking about beard hair and pubic hair, which typically are a lot coarser than the hair on your head.
Why are these hairs thicker?
What causes them to grow differently than the hair on our head?

Have a look at this post.

I have previously looked at that post @WYSIWYG, but I don't understand what makes the hair coarse on the body but fine on the head.

Is it so?? I don't think that is true.

Well, pull out a piece of hair from your head, and pull out a pubic or beard hair and compare them, the beard and pubic hair are thicker. Also, if you look at hair closely under a microscope, scientists can tell if it is a "head hair" or a "body hair" @WYSIWYG

Yes, of course body hair is different from head hair based on texture and thickness but I just said that the former may not be necessarily "coarser". It also varies from person to person.

What kind of answer are you looking for? Hair coverings are affected by follicle structure,and eyelashes and eyebrows and so on are also different. An evolutionary reason why these hairs would be different is one thing, and a complete description of all the weird follicles on your body is another.

A little of both, but more the description of the follicle. Although why it got there in evolution would be interesting to know, too. @Resonating


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What is the purpose of THC for a Cannabis plant?
Why does a Cannabis plant produce THC? This question is brought up drawing an analogy to nicotine in tobacco, where nicotine is developed by tobacco plants as a pesticide. Is THC a pesticide as well? I'm imagining that marijuana plants don't have rheumatoid arthritis.

It may also act as an insulation barrier for the plant to protect it from the cold.

Phytocannabinoids are found in an exceedingly wide range of plants, if that matters.

Apparently it is used by Cannabis sativa as a type of sunscreen as it absorbs UV light
https://www.reddit.com/r/trees/comments/2v79dv/science_sunday_13_wait_why_does_cannabis_have_thc/
https://en.wikipedia.org/wiki/Tetrahydrocannabinol


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How long can a naked human survive on Mars?
How long can a naked human survive at the surface of the Mars planet?
For instance, let's say a worker's base takes fire while he sleeps, the building is totally ablaze and he can do nothing but run to the emergency building 200 meters away without any respiratory equipment, pressure suit, UV protections or anything.
Maybe a human could survive for a rather long time, and apnea time is the real limiting factor?
Climate:

Temperature: 27 °C to −50 °C (base is at a rather warm location, on Equator)
Pressure: 0.006 bar (Earth: 1 bar)

I think two things might be the issue: 1) lack of atmospheric oxygen and 2) the dust.

@dd3: Don't hesitate to propose an answer around this :-)

"You should only ask practical, answerable questions based on actual problems that you face" - I'd take care if you're planning to test this ;-)

@RoryM: It is actually a problem that might be faced: http://mars-one.com Of course, more serious research must be performed eventually :-)

I did wonder if it was related to Mars One :L

One other important event that can kill the person is that the atmospheric pressure on Mars surface is less than one percent that of earth at ground level. Suddden exposure to extremely low atmospheric pressure will immediately release dissloved gases within blood and and other body fluids as bubbles and the individual is likely to get a very severe form of Decompression sickness as in divers coming up too fast. The person is likely to lose conciousness and die within a couple of meters after leaving the shelter.

That sounds like the fastest factor so far, thanks! Is there any reference or research on the topic? Accepting this answer.

The pressure difference human normal atmosphere - near vaccuum is about 1bar or the same as 10m of water. Are you sure this is enough to cause divers sickness?

@mart When ascending from 10m, divers will usually do a stop at 5m, then 3m to avoid any issues. That said, an emergency swimming ascent from 10m without stopping is part of the training (but obv not recommended). One thing to consider is that short (air) dives often don't last long enough for nitrogen levels to reach saturation levels in tissue, so presumably the situation on Mars would be worse.

Less then a minute breathing in the atmosphere (and a very painful death). Mars' atmosphere is >95% CO2 with only trivial O2. These are atmospheric conditions similar to those used to euthanize laboratory animals. He probably wouldn't even make it 200 meters before suffocating.

Certainly humans can hold their breath longer than a minute, but can they run 200 m while holding their breath given the elevated heart rate and blood pressure resulting from general sympathetic response resulting from their sleeping quarters being on fire? They won't freeze at 27 C.

the time to death after being submerged in ice water is not that short.  I'd say asphyxiation (< 5 minutes) would do it first.  This is kinda a bar-bet conversation... but still interesting.

@kmm: "These are atmospheric conditions similar to those used to euthanize laboratory animals" ← Very interesting! That should give us a pretty good idea of the time, right? Has this euthanisia method ever been used on a big monkey for instance? How long is usually necessary?

If the atmospheric conditions are similar to those used to euthanize animals, why is it such a painful death?

the article you link also mentions that mars' atmosphere has 0.6% the pressure of earth' atmosphere, so you only get 0.6% of the CO2 per lungful as the lab animals on earth - I doubt that you get enough to die of poisoning before freezing.


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Can someone identify this plant?

Can someone identify this plant? It was growing under my 2 year old's climbing wall / play house thing. I live in West Virginia, USA and it's currently June 3rd (if that helps from a climate standpoint).
I know there are some potentially dangerous invasive plants like the giant hogweed. I hope someone here can help me identify this and give me any tips on what to do about it if it is in fact hogweed.

My guess, some kind of wild lettuce.

Looks similar to spiny leaved sow thistle, but I'm no expert on plants.

Your question is fine but I would request that you clearly explain your geographical location instead of using the US state codes. We have users from all over the globe and not everyone would be aware of these codes. Also, it is good to describe the climate and other geological details especially if the place you are referring to is not likely to be known by many (in any case, it is generally a good practice and your post becomes more useful to others).

As @dd3 stated, it's a spiny (or prickly) sow thistle. It's an annual common in most of the US.
The leaf itself does not have a stem, and if you break the central stalk, it should be hollow and there should be a milky exudate. The plant spreads by fluffy seeds produced from a small dandelion-like flower.
If you pick it while young, it won't hurt (as much); if you prevent it from flowering, it should not spread, although unsprouted seeds can sprout still for a few years (it can come in on the wind as well.)

Prickly Sowthistle


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Do all transmembrane proteins contain channels or tunnels?
In my book, there is written something like this.
The integral proteins pass into the lipid bilayer to different depths and establish hydrophobic bonds with lipid molecules. Some of the integral proteins run throughout the lipid bilayer. They are called tunnel proteins OR transmembrane proteins.
My question is do all the transmembrane proteins have to have channel or tunnel for transport of materials?

https://www.ncbi.nlm.nih.gov/books/NBK26878/ Might help dude. Anyway it is quite easy to find something about it and if you dont do a little searching about it nobody will have attempt to answer it.

You know idk what you mean by the material stuff but i think the right answer is just no !

The substances .

What could it be other than this?

I was asking if all the transmembrane proteins have to be tunnel proteins as it was written in my book . And I think that's not right .

When you search Pubmed for "transmembrane proteins" you get 78328 hits.  "Tunnel protein" gets 2312.

@swbarnes2 that doesn't mean that they aren't interchangeable terms. For example, polytopic proteins and multi-pass proteins might return different numbers but mean the same thing. There is a lot of redundant jargon in this field!

It doesn't mean that they are.  When I checked a few of the abstracts in the pubmed search, they were mostly about the "exit tunnel" of the bacterial ribosome.  None were about transmembrane proteins.

@swbarnes2 I must say, I haven't read anything that suggests tunnel proteins and transmembrane proteins are interchangeable terms.

Transmembrane proteins don't all have tunnels.

Do all the transmembrane proteins have to have channel or tunnel for transport of materials?

Calling transmembrane proteins tunnel proteins is very misleading. There are a wide range of functions carried out by transmembrane proteins. I'd say the most famous example that don't include a tunnel are the GPCRs that have 7 transmembrane segments. These are used for passing information across a membrane by acting as a receptor to a molecule on one side causing a conformational change which causes an action on the other side of the membrane.
How many transmembrane proteins do have tunnels?
Here is a link to all the GO annotation held by UniProt on transmembrane proteins. There are 10s of millions of results including, but certainly not limited to tunnels and channels.
In the human proteome, there are 831 transmembrane proteins tagged with G-PCR (7TM proteins without a tunnel).
The "Transport" keyword, which probably has some sort of tunnel, is present in 1106 transmembrane proteins.
In total there are around 5200 human transmembrane proteins in the human proteome.


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How much vitamin C has a noticeable effect on E.coli k12
I am doing a research on effects of different concentrations of vitamin C on serial dilutions of E.coli k12. I am looking for literature that has already shown effects of vitamin C on E.coli, but there is a vast amount out there (26 thousand Scholar hits).
What might be the main effect of Vitamin C on E.coli? Is 1000mg vitamin C enough to have noticeable effects on the bacteria?

Can you please clarify what is 'noticeable effects' and give us some background of your research?

Aren't you doing the research to answer this exact question?

I don't think you should be doing research if you ask questions like "Is 1000mg vitamin C enough to have noticeable effects on the bacteria?". To how many bacteria in what volume under what conditions. I think it best to close this question.

@canadianer are you suggesting that you shouldn't do a literature review before running a series of experiments?

@DanHall Did I say that? My comment was on the initial revision of the question and perhaps makes more sense in that context. Perhaps.

@canadianer I see! And I see this is an old question by an inactive user. I suppose my heartfelt advice will just echo in the cyberspace, then.

You have @arberg's answer showing a report of an inhibitory effect of vitamin C on E. coli. Here's a PLoS One paper, in different conditions. It shows vitamin C rescues cultures that had no growth the previous night.

As the comments suggested, expect to see different results in different conditions.
Literature reviews before an experiment are important. When you're new to an area they are VERY HARD. Do them anyway. Give yourself a set amount of time, sit down at your computer, and start chugging away. Then do it again. And again. And again.
If you have a large number of possible articles, try narrowing your search. I often do this by tweaking my search terms or by limiting my search to a particular subset of journals that are more likely to give me what I'm looking for. Set up a hierarchy for how you read. Start by scanning the abstracts. If it looks helpful, pull the article and look at the figures. Note the article, your conclusion, and the authors' conclusions in a file somewhere that you can find later. If there is something interesting or useful in the introduction, follow the references.
Again, this is VERY HARD, but VERY IMPORTANT. Don't skimp on this step by just asking people.

I found a 'short communication' paper by Akira Murata et.al where they did In Vitro testing of Vitamin C on L. casei showing no inhibition of growth, and also tested on E.coli and B. subtilis and found that Vitamin C inhibited the growth. Also I believe Suzanne Humpries stated the same thing somewhere in this 1.5 hour long video, indicating she may posses more knowledge as to studies.

Ascorbic acid did not inhibit the growth of L. casei even at high
  concentrations, and rather stimulated the growth at certain
  concentrations (2~3 X 10- 2 M). This observation indicates that
  ascorbic acid can be used as an antiviral agent.
In E. coli and B. subtilis, unlike L. casei, a high concentration
  of ascorbic acid acted so as to lessen their growth rates (Fig. 3).
  Particularly, in B. subtilis W23, cell lysis was observed about 100
  min after the contact with ascorbic acid and, moreover, when a drop of
  the lysate was placed on a plate seeded with B. subtilis 168 and
  incubated overnight at 30oC, there appeared a clear zone around the
  placed lysate. Since B. subtilis W23 is known to possess an inducible
  defective phage PBSZ able to kill B. subtilis 168,3 ' 41 the observed
  result maybe ascribed to the induction of the defective prophage from
  B. subtilis W23 by action of ascorbic acid. Lwoff and Siminovitch51
  reported once that the lysogenic phage in B. megaterium was induced by
  treatment with ascorbic acid.

Maybe you have to think about vitamin C from another point of view. You start from the postulate that Vitamin C could destroy E. Coli. Maybe the action of vitamin C, rather then destroying E.coli is destroying the endotoxins generated by the bacteria, leaving the body immunity healthy and boosting the phagocytes that can therefore destroy E. Coli way more easily.
About the dosis of vitamin C to use, I would just use it to bowel tolerance. Body will take what is needed and just flush what's in excess. testing Lyposomal vitamin C would maybe also a good idea.
Many years ago , I had a monstrous and painful "tourista". It usually take a few days to cure. Well, I felt so bad that I took 2-3gr of vitamin C orally and, to my great surprise (and relief), Tourista symptoms were gone within 2 hours and I felt good.

Could you add sources to your answer to allow others to background read on your material?

It’s proven quite hard to find research on the effects of vitamin C on gram-negative bacteria.
http://www.sciencedirect.com/science/article/pii/S1089860301903714
This paper suggests that vitamin C (sometimes also referred to as ascorbic acid) can help inhibit the growth of E. coli when in the presence of mildly acidified urine with added nitrite. Keep in mind that this paper is quite old, and inside the first few paragraphs it states:

despite numerous studies the mechanism of any antibacterial action of
  vitamin C still remains unclear.

It later states

we have recently shown that large amounts of NO gas are released from
  nitrite-containing urine after mild acidification and this release is
  greatly potentiated in the presence of ascorbic acid.

So it seems this first paper doesn’t offer us much in terms of toxic effects of vitamin C on bacteria in isolation.
http://jb.asm.org/content/98/3/949.short
I found another paper that suggests that vitamin C can kill gram-negative bacteria, but again not in isolation, but in combination with other agents as well.
Perhaps your research is among the first to offer any insight on the effects of vitamin C on E. coli. I’ll be interested to know if anyone else finds a publication on this specific topic (I only searched for about 30 mins on the subject).


text:
Why are we (humans) more likely to help people genetically related to us than people who are not?

Question. Why are we (humans) more likely to help people genetically related to us than people who are not?

My understanding of this question as follows:
Because the reproduction of people genetically related to us can help us spread our genes. People genetically related to us are also more likely to help ourselves to reproduce.
Is this correct? What am I missing?
I was wondering if anybody had anything, especially intuition or some finer nuances, to add to what I have to say.

Do you have any sources to back up your claim?

Is it a homework question?

Why was this question closed? The idea that humans tend to be altruistic toward genetically related individuals is not outlandish.

This question seems to fall under the field of sociobiology, and more specifically I think kin selection. It's a controversial topic.  If sociobiology is a subfield of biology then it shouldn't have been closed. On the other hand if sociobiology is more of a social science, then I guess it should be asked somewhere else.  Still, it's a very interesting question.

I heard something like this before. E.g. it's important that children look like their parents because if they don't the mother probably cheated on the father. Promiscuous partners increase the chance of catching a disease, and so evolution made monogamous couples more prone to procreating which also helps to root the behaviour. Furthermore humans are social beings and like other primates, we strive together, so our relationships are very important. So much so that we even developed language.

I don't have time to search articles and I was just summing up related anthropological information I came across at some point. But I find your thesis very plausible. Like I said primates are social beings and of course we'll spend more time with family through out our lives, thereby building stronger bonds with genetically related individuals that help us survive as a group. Lots of other species of mammals do that too to some extent: lions and wolves.

It's also a no-brainer that the parents of any living offspring that take better care of their offspring will end up delivering offspring that will survive and succeed more often which is pretty much what you said. More advantages can be drawn from extending this model to less genetically related individuals such as cousins, the culmination of it all being an Italian mafia. :P


text:
Do the enzymes and compounds in saliva help with stain removal?
Does spitting on stains help with removal?
Saliva is high in amylase that should help with the breakdown of protein rich stains like blood and semen. It also contains antimicrobial enzymes and antibacterial compounds. Does semen contain any kind of surfactant agents?
So, my questions are:
Does spitting on a semen stain aid in or add to the cleanup?
On which stains are saliva beneficial and how long does it have to sit?

Why spit when you could just use soap and water?

Amylase doesn't break down proteins. It breaks down amylopectin -- a type of starch (sugar) molecule. Proteins are broken down by proteases (not found in saliva or semen), and many available stain removers use proteases.

@MCM Why don't you make this into a real answer?

As a chemist, I understand the amylase enzyme comment. Amylase in our mouth does help break down sugar compounds. However, there are other components in our saliva such as acids that could help in the removal of stains as well as water or sodium. I found that saliva helps with grease stains due to the sodium component within saliva, as saliva contains more than just the enzyme amylase.

It would depend on the stain - and more specifically the material and staining agent. Saliva contains blood clotting agents so I doubt it would help with removing blood stains. The enzymes in saliva are unlikely to help with the stain removal.
The water in saliva would be more likely to help, dissolving the stain. So your probably better off with water.

I've been spitting on anything red (
of biological origin (blood, wine, ketchup) for decades and seeing the stains dissolve and disappear like magic.
Spit on it generously, let it soak for a few seconds, rub it in with your fingernails; see it disappear.

do you have any biological explanation for your observation? Can you add any credible sources to back up what you're saying?

@Chris Observation is senior to theory. Not the other way around. You can easily perform the test and reproduce the results.
Having a somewhat bad case of psoriasis, I regularly deal with dried blood stains in bed sheets (the plaques break during the night, smearing blood on the sheets, which then dries by the morning). The saliva trick does work to a remarkable extent, pure water doesn't. The phenomenon is easy to observe and replicate.
I always assumed this was a well understood issue, but if not, it could be one of those "oh, that's funny..." observations that science thrives on.

Just did this and it worked. On a fresh curry stain which is notoriously difficult to remove. The guys acting like experts in the previous posts are just wrong. Not sure if it's the enzymes, the water or some other substance contained in our saliva, but it works like magic. Apply generous amount of saliva, let it soak for a couple mins and scrap vigorously with your fingernail. Stain disappears like magic.

Do you have any biological explanation for your observation? Can you add any credible sources to back up what you're saying?


text:
Do any terrestrial herbivores use auditory crypsis for predator avoidance?
Some terrestrial predators "stalk" their prey: they sneak up on it slowly, maintaining a low profile, while keeping as close to silent as possible.  This makes sense from an evolutionary perspective: silent predators catch more prey.
However, the prey near where I live are hopelessly noisy.  Deer will freeze if they suspect the presence of a predator, then bolt when they see one for sure.  Squirrels and other small mammals run around at top speed all the time - you can hear them dozens of feet away, rustling the dead leaves around.  Hedgehogs just wander, making a similar noise.  It seems like the only "stealth" option they have, as far as sound is concerned, is to remain still.
Are there any examples of terrestrial herbivores evolving to move more quietly in order to avoid predation? I'm not looking for a comprehensive list, but rather simply individual examples.

Why do you think it is really necessary for the herbivores to move silently? There are many strategies to stay alive.

Right - I don't know that it is necessary.  The thought hadn't really occurred to me until recently.  It struck me that I'd never seen one before, so I figured I'd ask if I was missing one.  "Freeze or bolt" seems like it's a pretty viable strategy, at least for the deer.

Whoops, botched the meaning of that word.  Was going for "non-human".  Will fix title.

in a sort-of-related way - have you heard about the crickets in Hawaii that evolved to court in silence when predatory flies were using the courtship song as a locator signal

That's pretty cool!  It's like the long-timescale version of this question.

Great question, by the way!

Thanks!  Yeah I'd originally been curious about vertebrate behavior, but your answer sparks new trains of thought.  I'll leave it open for a few days to see if it garners more answers.

Sloths: the ultimate steal herbivore. They are capable of moving quickly, noisily, violently, and slashing with big dagger-like claws, but unless they've "been had", they remain quiet, near motionless, and are almost undetectable.

@MarkBailey, that's probably worth an answer of its own right.

One point from your question: as you say, deer freeze when they suspect a predator, and bolt when they see one; if they can see a predator, it can see them, and by that point becoming completely silent probably isn't much help.

Could the voters-to-close elaborate a bit? It doesn't sound to me like all possible answers to this would have to be opinion-based.

As the question is closed :-( I'll have to answer in a short comment: I think animals in open landscape don't have to gain much from being quiet. They will be seen anyway. Looking for animals MOVING quietly, one should think about forest animals instead. I think Elk (Am: Moose) can be a good example. They move quietly and considering their size surprisingly secret and quiet.

@RHA There is something to gain from stealth. Predatory animals "stalk prey" in these open environments. They remain unseen and this is a big advantage. Lions in the open Savannah are nigh-on invisible if they choose to be. Why would their prey avoid stealthy grazing? They could potentially remain unseen.

@arboviral I voted to close based on the breadth of the question. It requires analysis of many prey animals to build a case. No one answer could cover this question absolutely. I did attempt to provide an answer on this limiting my scope to the example animals & why each may or may not need to avoid stealth. But that is nowhere near enough to answer the question. I see the point of subjectivity though; to you most prey animals are not stealthy but the overwhelming majority of prey animals probably engage on some level in avoiding predation encounters by hiding, camouflage, or stealth.

@James I can certainly see a stronger case for 'too broad' (although as with any question containing the phrase "are there any examples of" you only need one example to be able to answer "yes"). I'm less convinced by 'opinion-based', which is the reason showing at the moment.

@James I agree with arboviral that 'opinion-based' is unconvincing. And that it takes only one example to answer the question. The question would be too broad if it were asking for all possible strategies to remain unheard, which is the direction the answers have taken it.  (freezing, stealth etc.). However the question specifically asks for examples of MOVING animals that try to be quiet. These are relatively rare (sharp observation from OP!), and I think there must an evolutionary reason for this. Pity that this interesting question is closed.

I've edited the question specifying that only a single exception would answer the question. It is no longer opinion based, and no longer broad. I've initiated a reopen vote.

Does soundproofing count?
Most predators locate prey using visual or olfactory cues; the only predators I can think of that use auditory cues are nocturnal ones - owls and bats. Bats, of course, use echolocation, so even completely silent prey are still detectable. It has been suggested that the soft, fur-like body coverings of some owlet moths (Noctuidae) and tiger moths (within the Arctiinae) help hide them from echolocating predators by passively absorbing sound, although subsequent studies have suggested that they may instead be mimicking the acoustic signature of unpalatable prey.

(public domain image: source)
I have a suspicion this isn't what you meant by 'land-dwelling herbivore', but insects are people too...
Edit: just discovered this paper from May that provides evidence supporting the hypothesis that the twisted tails of luna moths (Actias luna) disrupt tracking by echolocating bats.

Image owned by Shawn Hanrahan, licensed under CC BY-SA 2.5

Lucky for you, the question is not about vertebrates. Great answer! ;)

I think that there are too many examples of animals being deliberately quiet when grazing to count. I'll discuss specifically the exceptions you raise and how they are exceptional. Hopefully you'll see my point: A lot of grazers are quiet and cautious or failing that have other adaptive strategies for not being eaten.
Deer are incredibly quiet and cautious when grazing, and fast and agile once they decide it's not safe. Squirrels use trees as an defense - not many predators of theirs can even climb trees let alone keep up with a squirrel darting through them, (related question about bushy tails of squirrels being counter intuitive). And hedgehogs... well... how do you eat one without getting a mouthful of pain? On a bigger scale, here is a related video of a juvenile lion trying to attack a porcupine. Being unsubtle helps them.

Why do you close a question that you give an answer to. If a question is answerable, it shouldn't be closed...

@RHA I agree. I got the end of this answer, realized my answer doesn't and can't really answer the question fully. Why? The question requires a massively broad answer. Do note I don't think that this question is necessarily opinion based, it's just too broad.Feel free to down vote. I'm considering deleting it if the question remains available.

To be honest, I was just looking for one counter-example.  It seems like you've provided one - deer while grazing.  Thus, a comprehensive survey of animals is not necessary, merely a single example.


text:
What happens when we eat excess fat?
The fats in our body are stored in fat cells. When we over eat fats does the size of our fat cells increase, are more fat cells generated, or do we "throw out" excess fat?

This is a really broad question, are you interested in fat storage? Fat metabolism? Lipocite creation and apoptosis? Fat apsortion?

The question is about fat cycle versus sugar cycle. Doing a research about low fat diets versus high fat diets

The number of fat cells, or adipocytes, in adult bodies remains constant. Therefore, consuming more fat only increases the size of the fat cells not the number. After reaching the age of about 20 years the average number of fat cells is closely related to body mass index.
On the other hand, the adipocytes in children increase in number as more fat is consumed. This explains why people who became fat as children have a harder time shifting their weight as adults.
A study on obese adults who went through surgery to decrease the amount of food intake showed a reduction in their body weight by 18%. While the average size of the fat cells decreased, the number of fat cells remained the same.
This doesn't mean that the same fat cells are active throughout your lifetime. Adipocytes normally die off and are replaced by new cells. One study shows that fat obtained from liposuction of people who were exposed to radioactive materials from atomic bombs in the Cold War showed a decrease in radioactive material stored in the cells which indicates replenishment of fat cells over the years.
So when adults intake excess fat, their fat cells increase in size. The average number of their fat cells is correlated with body mass index. However, when children eat excess fats they exhibit an increase in the number of fat cells.
For more information see: http://www.nature.com/news/2008/080505/full/news.2008.800.html


text:
Can estimating the likelihood of protein sequences adopting functional enzyme folds show life is too complex for evolutionary timescales?
An acquaintance provided me with this article1. I can't understand for sure what it is about.
My acquaintance said that it proves that time for generation of even the simplest proteins is on a larger timescale than evolution history (billions of years).
I'm asking you, is that a valid conclusion to be made from this paper? What is in this article that might drive someone to that conclusion?

Axe,D.D. (2004) Estimating the prevalence of protein sequences adopting functional enzyme folds. J. Mol. Biol., 341, 1295–315. http://www.ncbi.nlm.nih.gov/pubmed/15321723

In addition. As i understand, this man considered linear exhaustive search of nucleotides. As i understand it is wrong, because genetics and evolution algorithms are optimized exhaustive search.

I appreciate the way you phrased your question in terms of appropriateness, and the good will of the person that gave you an answer, but this is really not an appropriate question. The main reason is that it is not comprehensible as it stands. First one is required to go elsewhere to read a paper (which happens to be behind a paywall), and second the paper (at least the summary) makes no reference to evolutionary time. Thus, we do not know what argument your acquaintance is making. So, with reluctance, I am voting to close the question unless you can edit it to make it fully self-contained.

@James — I have no objection to Elsevier charging for what is there's. Your language is another matter. Even if the article were not behind a paywall the question is unsuitable for SE Biology as it requires one to read a paper and then imagine a third party's attitude to it. If you ask similar types of questions they too should be closed. The guidelines on writing questions are quite clear.

@David I've asked similar questions about skeptically analyzing conclusions drawn from articles. It certainly shouldn't be closed because of Elseviers shameless paywalls. Often abstracts don't include some observations, particularly long technical papers with advanced and nuanced methods like this. +1 good question.

@David The guidelines on questions aren't entirely clear in this case. This could be seen as a give me teh codes question, however I think the complex methods are indeed exceptional and asking whether they can have conclusion X drawn from them is a valid question. We disagree on Elsevier's right to ownership (they legally own it, but I'm an open access idealist), but you're right; you've lost when you start swearing!

You might find some useful analysis of the paper here: http://pandasthumb.org/archives/2007/01/92-second-st-fa.html

I think your acquaintance is trying to fit real science to some of his personal beliefs (that are obviously wrong).
If you read the article you'll see that it's not about evolution at all, but about protein folding and what proportion of possible sequences gives a working protein. It turns out random sequences are not that likely to fold, which leads to some conclusions about the probable mutational pathways to folded proteins.
The argument of your friend is sort of analogous to the infinite random monkey theorem. If you put a monkey behind a typewriter and wait long enough, eventually he'll write the complete works of Shakespeare. This doesn't mean we waited billions of years for this monkey to type it up, because the world doesn't work like that. There was just a guy with a brain.
In case of the proteins, evolution doesn't work by generating newly (random) 300 residue proteins that work 1 time in a billion. Probably in one generation a copy of the protein is made with the same function, and during many generations the function of this protein drifts towards a new function, while all the intermediate proteins stay folded because they're not that different.

For some background on the author of the paper (Douglas Axe) see for example http://rationalwiki.org/wiki/Douglas_Axe. My personal opinion is that the paper looks interesting from a quick scan, but there may be some agenda behind it.

Also from the wiki: Axe himself says his work does not support intelligent design. So there might be a conflict of interest, but the data in the paper doesn't prove anything regarding evolution anyway.

Conclusions from the paper.
The finally line in the article should actually be read first as it clearly spells out where the paper fits in the scientific literature.

So, if re-creating a fold by ordered assembly of sections of sequences
  that already adopt that fold is not a simple matter, generating new
  folds from parts of old ones may be much less feasible than has been
  supposed.

A popular hypothesis at the time was that some folds emerged at some point or another from substantially different folds.
This paper used advanced statistical analysis (well, they're convoluted, not particularly advanced...) using a very simplified and uncertain model to show that the chimera theory of fold genesis is unlikely. It is a critique of that model at the time, and does not seek to show how long it took for evolution to come up with the fold.
This is an incredibly important question to answer. This paper was probably accepted because it shows a genuine attempt to quantify the probability of a general hypothesis. However, almost every step of their method introduces over-simplification, arbitrary thresholds, and convolution of the biology. As I see it, the only thing the paper can say for certain is "that in a small subset of simple folds, with a tonne of caveats and conditions, it might be less likely than other people think that the fold formed that way".
What your friend is drawing from this.
It would be incredibly difficult, many philosophers would argue impossible, to prove how folds were formed. But to build up lots of different scientific hypothesis and disprove them as much as possible is more achievable. That, broadly speaking, is the scientific method and this paper generally adheres to that line of thought.
This paper is saying "The current hypothesis surely can't be the right method! Look how improbable it is." and your friend has drawn from it "A scientist said more time would be needed, which proves evolution needed longer than it had". A simple misunderstanding; a scientist said a model had problems, a layman thought this meant the problems were the truth. The paper is not aiming to prove anything (The author may be especially careful about doing this given his close ties to intelligent design movements), but I think your friend might be incorrectly using the paper to prove something!

The study by Axe (a creationist) is fatally flawed. See these comments on it by Arthur Kent, a biologist at the University of Kentucky. To summarize: Axe did not study the native form of the protein he was looking at (TEM-1 penicillinase), but specifically, a variant that both had lower activity and was especially temperature-sensitive. His results, then, can't be generalized to even the native form of the enzyme under investigation, let alone any other enzyme. As Kent points out, more recent techniques suggest a substantially larger proportion of functional variants than Axe's method suggested. In any case, experimental and observational evolution has settled this debate: we see proteins with novel functions constantly evolving from pre-existing proteins all around us (how do you think new bacteria are constantly emerging which can digest all sort of novel artificial synthetic plastics never before seen in nature? how do you think viruses switch hosts?), and so it is 'out of question' as to whether there is sufficient time for new proteins to emerge. We can see it happening ... all the time!


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Exclusive microtubule minus-end labeling
Like the title explains I am looking for a way to exclusively label microtubule minus end in vivo. Looking through the literature I could not find any techniques yet. Do you have an idea?

γ-Tubulin is specifically localized to the minus end of microtubules. GFP labeled γ-Tubulin can be used to label the minus ends in-vivo and without the requirement of staining. Fan et al have developed a phage display antibody specific to α-Tubulin that can be used to visualize minus ends. See the figure below.

The image is an electron-micrograph but it is certainly possible to do a fluorescent microscopy after IHC staining.


text:
A molecular marker for global protein synthesis
I know that protein synthesis is governed by a lot of factors (I'm mostly studying the mTOR pathway), but I'm looking for some kind of marker that will indicate the global protein synthesis rates.
I know there are tissue-specific markers (like actin/myosin in muscle) but I'd like something more that is ubiquitous and is proportional to global protein production (maybe a muscle can make more or less myosin depending on whether there are some factors).
I assume protein synthesis factors (like mTOR, S6K1 etc.) are quickly regulated, so they cannot be used as markers.
So, what would serve as the best molecular marker?

Witness is a wrong term. "Marker" is a right term for what you mean. I edited the question. See if this matches with what you intend to ask.

You could measure the fractional synthesis rate in vivo in humans if that's what you're after, e.g. http://ajpendo.physiology.org/content/273/1/E99.short describes it extensively.

The answer will not satisfy you. The truth is no protein marker will do.
On one hand you seem to be looking at some individual, representative protein, which you could measure by immunoblot. But most proteins are in scant concentrations, just as many as required for their job, and go up and down depending on their specific roles, rather than on general metabolic trends. Even if some general control mechanism increases protein synthesis across the board, in a cell proteins are 20% actin, 20% tubulin, 0.0001% 4E-BP and 0.0001% p70-S6K (made-up numbers for the sake of example), any 1% total protein increase you'd like to measure would be 200,000 easier to detect in tubulin than in p70-R6K. In order to be a marker of general control of protein synthesis, the marker protein you'd want to measure should be a plentiful protein, with little to no specific control.
On the other hand, those are the characteristics of a house-keeping gene. So you won't be able to normalize such a "representative" blot! Normalizing house-keeping by house-keeping, you will have pretty much no change.
Embrace labeling experiments. Even there, the right normalization is debatable. If anything, the fact that everyone does those, rather than looking at protein X, should be an indication of how much you will struggle to prove points about protein synthesis rate using anything else.

That's a really interesting answer, and you make points. You are right about labeling experiments, but I cannot do that in my current project.


text:
Pooling for qPCR
I am comparing miRNA expression levels in 3 different groups but I am low on money and time. I have to get some preliminary results to get the actual research going so I decided to pool my samples and get the results for 372 miRNAs and then if any of them shows prominent differential expression, I will investigate the expression levels of those candidate miRNAs in larger groups. But I can't decide how to group my samples for pooling. Should I pick 3 individual samples for each of the 3 groups (9 samples in total) or should I extract the total RNA for each sample for each group, make 3 pools of RNA and then just perform triplicates for each pool? The time and money spent in both situations is going to be the same. I think the second method is more appropriate yet I fear it might produce some deflated p-values, resulting in false discovery.

Should I pick 3 individual samples for each of the 3 groups (9 samples
  in total) or should I extract the total RNA for each sample for each
  group, make 3 pools of RNA and then just perform triplicates for each
  pool?

Depends on the nature of your samples. In general, pooling would average out the expression of different individuals. Pooling is generally done when you have low RNA yield per individual sample. If that is not the case then you should sample multiple individuals per group (three should be fine; more is better). This will let you know inter-individual/sample variation within a group. You can in turn set up three technical replicates for the qPCR to measure technical variation. So, in total, you would have 27 PCR reactions. This would not be very costly (unless you are using TaqMan like assay. Even then, sometimes working with more number of samples allows you to save the amount of reagent used per sample.


text:
Why is exclusive breastfeeding recommended for 6 months only?
The WHO recommends exclusive breastfeeding for the first 6 months of a child's life.

Review of evidence has shown that, on a population basis, exclusive breastfeeding for 6 months is the optimal way of feeding infants. Thereafter infants should receive complementary foods with continued breastfeeding up to 2 years of age or beyond.

Their website mentions "review of evidence", but what is that evidence? Why 6 months and not 4 or 5 or 7 or 8 or 9 or anything like that?
Can anyone give which review is WHO talking about?

I guess this is the review (ISBN: 92 4 156211 0) that they are referring to.

We found no objective evidence of a “weanling’s dilemma.” Infants who
  are exclusively breastfed for 6 months experience less morbidity from
  gastrointestinal infection than those who are mixed breastfed as of 3
  or 4 months, and no deficits have been demonstrated in growth among
  infants from either developing or developed countries who are
  exclusively breastfed for 6 months. Moreover, the mothers of such
  infants have more prolonged lactational amenorrhea. Although infants
  should still be managed individually so that insufficient growth or
  other adverse outcomes are not ignored and appropriate interventions
  are provided, the available evidence demonstrates no apparent risks in
  recommending, as public health policy, exclusive breastfeeding for the
  first6 months of life in both developing and developed country
  settings. Large randomized trials are recommended in both types of
  setting to rule out small adverse effects on growth and to confirm the
  reported health benefits of exclusive breastfeeding for 6 months.

However, another report suggests that exclusive breastfeeding for a long time may lead to deficiency of some nutrients which cannot be supplemented via maternal diet.

The dual dependency on exogenous dietary sources and endogenous stores
  to meet requirements needs to be borne in mind particularly when
  assessing the adequacy of iron and zinc in human milk. Human milk,
  which is a poor source of iron and zinc, cannot be altered by maternal
  supplementation with these two nutrients. It is clear that the
  estimated iron requirements of infants cannot be met by human milk
  alone at any stage of infancy. The iron endowment at birth meets the
  iron needs of the breastfed infant in the first half of infancy,i.e. 0
  to 6 months. If an exogenous source of iron is not provided,
  exclusively breastfed infants are at risk of becoming iron deficient
  during the second half of infancy. Net zinc absorption from human milk
  falls short of zinc needs, which appear to be subsidized by prenatal
  stores.

Both these reviews are from WHO website; you can search for different WHO research materials on the site.
Note: WHO does not say that breastfeeding should not be continued till a later stage. As noted in the review, exclusive breastfeeding for more than six months can cause some nutritional deficiencies. However, reducing exclusive breastfeeding to 3-4 months can reduce the immunity of the infant.

So basically they found the optimal time for exclusive breast feeding was between 4-6 months. I wonder what reason they listed 6 instead of the range?.

@John In such studies it is difficult to make fine measurements. Perhaps they just tried with 4 & 6 and didn't check other durations.

I liked the answer, but now I really want it to change, WHO should not make vague guidelines without sufficient data.

@AnubhavGoel WHO is trying to do best with whatever data they have. Note that whatever they say is a recommendation and general guideline. It is always better to consult a doctor for specific cases.

I am a medical student myself, and the part is doctor here dont see it as guidelines but as sacred stone line.

@AnubhavGoel exactly


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How does Celiac's Disease cause people to stop growing?
In all of the sites I've looked on, one of the symptoms of Celiac's Disease is the failure to grow in children. Why would an immune attack against gluten cause stunted growth?
Celiac.org states:

When people with celiac disease eat gluten (a protein found in wheat,
  rye and barley), their body mounts an immune response that attacks the
  small intestine. These attacks lead to damage on the villi, small
  fingerlike projections that line the small intestine, that promote
  nutrient absorption. When the villi get damaged, nutrients cannot be
  absorbed properly into the body

Journal of Pediatric Gastroenterology & Nutrition published a study on catch-up growth in children diagnosed with Celiac's before the age of nine.
Is the lack of nutrients what causes the impaired growth, or is there more to it than that?

The "proper" term to use in a case of growth retardation in children is "failure to thrive", abbreviated as FTT.
Celiac disease is one of the most common Organic endogenous (genetically based) FTT syndromes.
The main cause of FTT in pediatric celiac patients is malabsorption. In a case of insufficient vitamins and nutrients absorption the child will (have) FTT.


text:
How does this headless fish still move?
There is a (VIDEO) on Facebook where the fish starts to flail around despite no heart or internal organs.
What causes the fish to flail around the way it does?
My theories:

It is because of pressure causing the muscles to contract - much like when you leave your own hand loose and squeeze up your arm making your fingers curl.
It is because the nerves are still alive - much like how you can rub the fish heart the right way and cause it to beat again even though the fish is very much dead. (I watched my fifth-grade teacher do this in class)

I had actually heard a research talk related to this. It happens because of spinal reflex.

It is a widely known spinal reflex arc which causes decapitated animals (even soldier without head) to move over some period of time after decapitation.
One of the arc representations:

see also The life after decapitation
additional video


text:
Are dogs affected by dwarfism?
My husband and I noticed a dog today that looked like a smaller version of a purebred Border Collie, although it didn't appear to be a puppy. It made us wonder if other animal species experience dwarfism.
Are dogs known to display a dwarfism gene?

What is a dwarfism gene? Just a gene that influence body size? Is the question "Do we know in other species (than dogs) genes (loci) that affect the body size?". If this is the question, the answer is yes. Dwarfism exist in humans for example. A lot of species are under directional of balance selection for body size. In general, insular population tend to be of smaller size (in response to selection, there is therefore a gene coding for body size), a phenomenon called insular dwarfism.

Canines can have pituitary problems just like people, but it's rare, just like in people.

The short answer is yes, other animals can experience dwarfism, including dogs, although it may not be what you are expecting.  Dogs are apparently particularly susceptible but they often are a special case.  We've so heavily bred dogs for whatever traits we desire, so now entire breeds are affected by dwarfism, such as dachshunds and corgis.
The reality is that dwarfism is a mosaic, with many types, and shouldn't be classified under one umbrella.  You're probably mainly thinking of Achondroplasia, which is just one of many causes.  You may also be aware of Hypothyroidism.  Not every case looks like others, so in animals it may not be what you except.  Other animals are susceptible, such as the sheep mentioned in the above articles, and horses, which are also a long-time target of selected breeding.


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Species Identification: Spider
I usually would search for myself, but I need to be super sure about the identification because I need to know if I need to get an exterminator in here or not. (I think it might be a giant house spider, but don't let me influence your analysis.)
So I live in the northern part of Ireland (About 40 minutes from Derry Northern Ireland over in County Donegal) and I went to my bathroom to a VERY fun surprise this morning. It was this wonderful spider in my bathroom. For reference, the lip of the glasses it is depicted in are 8 - 8.5 cm in diameter.
The missing leg was not my fault either, I was very gentle with the spider and released it outside post photo-shoot. (Warning: these are macro shots of the said spider)

More high resolution photos available on my Flickr (SolarLunix).

"I live in the northern part of Ireland and I went to my bathroom" - assuming the bathroom is within walking distance of the house, its the northern region of Ireland ;P

An image from the top in good light would help, maybe a wolf spider

@rg255 That was the best I could do given the circumstances and the need to get it outside before my hubby woke up and freaked out.

The images in the question are of a giant house spider, as hypothesized in the question. (Eratigena duellica/atrica/saeva). These (along with the hobo spider, Eratigena agrestis) do not have any banding or annulations in their legs (dark/light stripes/rings).
The spider in the other answer of Tegenaria domestica do (always) exhibit leg banding. So, it is not the spider in question.
Both Eratigena and Tegenaria are in the funnel weaver family.

Looks like a house spider (Tegenaria domestica)

I just love these to-the-point answers +1

This is close, but not quite correct


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Evolution of blood types
What are the popular theories regarding how our blood divided into 4 groups. Particularly I'm interested in whether this was originally linked to disease.
Thanks for your answers, useful articles and further reading would also appreciated.

Hi and welcome. Your question is very interesting, however, the general expectation of SE is that you demonstrate that you have researched the topic of your question and have hit a wall in that search, or you are looking for expert advice to explain an advanced topic that you have found that you are having a difficult time explaining. Review How Do I Ask a Good Question for tips and general expectations for the site. Though I personally hope someone can provide an answer as I would be interested in this as well.

Possible duplicate of http://biology.stackexchange.com/q/31920/3340

yep, sorry for duplicating and thanks for your answers!


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Why would a venus fly traps mouth that's still "chewing" die?
A venus fly trap produces leaves that act like traps for insects. A trapped insect is digested over several days. The trap then opens again to catch another insect.
These traps regularly die off. They turn black. They are replaced with new ones. I'm not sure why that happens. As far as I know this is a swamp plant, which makes it unlikely that the traps die off due to being in contact with water. I read that a trap can only be reused 7 times. So I guess the traps are replaced by the plant in some interval.
As the dead traps start to rot in the pot, I pick them up from time to time and throw them away. Recently, during that process, I found this:

and it made me wonder why this mouth would die off. It looks like it caught something. As the mouth is still closed, I think the digestion process is not finished yet. But why would the plant give up this valuable resource?
Is it because the trap could not close entirely? There are signs of rot on the insect, but I don't know if that happened after or during the digestion process. Would rotten prey be a problem chemically? A human can dissolve quite a few things in its stomach, so I guess this could work similarly.
What are the reasons for the traps to die off in general?

A friend once figured that if his trap caught big ants, the traps often would blacken and die off. We guessed this could be related to the ants acid. My own trap that I had long ago used to "choke" on too big food and also have traps die off if they caught comparatively big insects. But all of this is just based on personal experience.

I remember reading somewhere that cultivated flytraps are much weaker than venus flytraps found in the wild, and they can't digest food that is too big. so this might be why they would fall off mid meal.

There are many things that could affect the rotting of your venus fly trap while digesting including: size of the bug, age of the trap, and temperature.
Sometimes a venus fly trap will turn black and fall off while it's digesting a bug when the trap is very old. As the trap ages, the digestive juices are recycled and as a result form a weaker mixture which slows the digestion process.
The bug it was digesting was also probably very large or had a hard shell inhibiting the trap from properly closing. This allowed bacteria and mold into the trap to digest the insect also proliferating the rotting of the fly trap itself in the process.
Temperature also has an effect on the trap's digestion where higher temperatures speeds up the enzymatic process of digestion. However, this is probably not a factor in your case.
It's not so much that your venus fly trap decided to give up on the valuable resource, it was either too old to properly digest the bug or it couldn't close properly because the bug was too large that bacteria infested the bug and the trap speeding up the process of the trap falling off the plant.
For more detailed explanation see: http://science.howstuffworks.com/life/botany/venus-flytrap4.htm


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What is the difference between a polysaccharide and a macromolecule?
I'm having trouble understanding the difference between "Polysaccharide"
and "Macromolecule".
I know that polysaccharides are made of chains of monosaccharides.  In addition, I know that macromolecules are made of monomers.
But what is the difference?

A macromolecule is a class of biomolecules that are made of monomers. These include polysaccharides (i.e. sugars) polypeptides (i.e. proteins) nucleic acids (like DNA and RNA) and lipids (fats ans phospholipids).
A polysaccharide is one type of macromolecule made up of monosaccharides like glucose and fructose. An example of a polysaccharide is starch or cellulose.

So they can both make up each other?

@intboolstring Well a polysaccharide is a macromolecule while not all macromolecules are polysaccharide. Just like how squares  are rectangles but not rectangles are squares.

@intboolstring macromolecules is a class of molecules in which polysaccharides are included.

A polysaccharide is a long chain sugar, formed by the polymerisation of many smaller sugar molecules (monomeric units which are the monosaccharides) They have a general formula of Cx(H2O)y where x is usually a large number between 200 and 2500. For example, starch, a long chain polymer of glucose.
Defined by wikipedia:

A macromolecule is a very large molecule commonly created by polymerization of smaller subunits (monomers). They are typically composed of thousands or more atoms. The most common macromolecules in biochemistry are biopolymers (nucleic acids, proteins, carbohydrates and polyphenols) and large non-polymeric molecules (such as lipids and macrocycles)
  An example of a macromolecule is DNA, which has deoxyribose sugar, phosphate groups and many nitrogenous bases.

So, to sum up, polysaccharides are macromolecules, but macromolecules may not all be polysaccharaides
More info
https://en.wikipedia.org/wiki/Macromolecule

When you say "polysaccharides may be macromolecules," do you mean they can make up macromolecules?

No, polysaccharides may be classified as macromolecules. That means that starch can be called a macromolecule as well as a polysaccharide.


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Why don't we have two hearts?
The human body is amazing. But there seems to be some evolutionary changes that appear to not make sense regarding redundancy.
While not necessarily the primary reason for their existence, the human body has a great deal of redundancy.

Two eyes.
Two arms.
Two legs
Two ears
Two nostrils
Two lungs
Two kidneys
Two sets of teeth
A very large liver that can work in part.
Two brain hemispheres that can (to some degree) do the work of the other.
An appendix that is not critical.

But why do we not have two hearts? It would seem like a good idea to have two smaller hearts, together they work above optimally, but survival would be possible with one.

Having two of almost all of those body parts is absolutely better than one i.e there is no redundancy. Even if a smaller liver can sustain a human, a bigger one is more tolerant to potentially harmful toxins. The brain can reassign parts of the brain to an incredible degree after a hemispherectomy, but not completely depending on age and type of trauma. It also looks like our appendixes are important for our digestion system too.

Two atria and Two ventricles....

One esophagus, one trachea, one stomach, one spleen, one thymus, one small intestine, one large intestine, one thyroid, one spinal cord, one diaphragm, one penis (apologies to those with Diphalia), one tongue, one vagina, one clitoris, one cervix, one uterus, one urethra, one umbilicus, one rectum, one anus... what's your point?

@AMR If you're referring to my comment re: two is better, I should have prefaced it with the ancestral symmetry answer. This question is flawed in my opinion because it assumes symetrical anatomy has absolute redundancy. These symmetrical body parts work together to perform optimally with their partner and are not redundant. The question requires a fairly speculative answer based on false assumptions that we may never be able to scientifically test.

@GoodGravy oh heaven's no... I was not commenting about your comment... It was an observation about the question...

@AMR I see now! Still, I should have given my first comment more context.

OP. How would you coordinate two pumps in order to maintain proper fluid pressure? Or get them to respond in unison to fight or flight hormones? Imbalances would likely create eddies in the blood vessels that could lead to air embolisms or clots. Even for normal function, you would need the timing to be exactly correct. How would you propagate that impulse between the separated organs? All of the examples of duplicates are capable of working independently, though, as @GoodGravy said to perform optimally, they work together. The two hearts would need to work together perfectly to work at all.

@AMR there are other animals that have more then one heart. Worms for example have 5 hearts. I agree a worm is simple in comparison but it has obviously found a way to work with more than one heart.

@AMR also while we do have 1 of lots of other things there is normally a very good reason why there is only 1. Such as the space needed to have it, or the energy required to keep it working.   In the case of a heart it would be possible to have two smaller hearts and maintain a fully working system that could cope with some damage. Also two smaller hearts may work better as they don't need to be as powerful as they are only pumping blood "halfway" around.

Two arms working together is clearly better, And is probably the reason we have two. But four would be even better! but we don't have four. We don't have four as it would be too bulky and too expensive to maintain. Thats a good answer for arms.     But that douse not explain a single heart.

And clearly one heart is good as that's why we have one heart. But there must have been a good reason to stick with one and not develop two. The point is not to say evolution is wrong. its to answer why it chose what it chose.

It is not about redundancy. There are evolutionary and developmental  reasons why we have two eyes or two legs and one heart. However just to give you short examples, two eyes are better than one because of our binocular vision while we have two legs because of its locomotor energetics.


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How do we know if the folding@home project results are right?
Some of us are involved in the folding@home project, spending time, money, and resources.
I would like to know the answer to two main questions:

How do we know we fold it right? I mean, these models used in folding calculations. Is it probable that in a decade we will find that all these results are nil and void?
Do we have any example that these calculations were practically applied anywhere?

https://en.wikipedia.org/wiki/Folding@home, also http://www.reddit.com/r/askscience/comments/r93i6/has_foldinghome_really_accomplished_anything/

the reddit link is quite interesting. Apparently there is someone that used F@H results for real drug development

in silico modelling of anything in biology is an active field of research. It's very useful for making predictions and developing hypotheses, but any findings need to be confirmed experimentally.
From the Folding@Home website:

Folding@home has been a success. In 2000-2001, we folded several small and fast folding proteins with experimental validation of our method. We are now working to further develop our method, and to apply it to more complex and interesting proteins and protein folding and misfolding questions. Since then (2002-2006), Folding@home has studied more complex proteins, reporting on the folding of many proteins on the microsecond timescale, including BBA5, the villin headpiece, Trp Cage, among others. In 2007, we crossed the millisecond milestone by simulating a protein called NTL9, and the 10 millisecond barrier in 2010 with ACBP.
More recently (2006-present), we have been putting a great deal of effort into studying proteins relevant for diseases, such as Alzheimer’s and Hunntington’s Disease. You can learn more about our results and peer-reviewed scientific achievements on our Papers Page.

As they say, you should check out their research contributions for how it's being practically applied.
You may also be interest in this article for the science behind and prospects of protein folding prediction: Bowman GR, Voelz VA, Pande VS. 2011. Taming the complexity of protein folding. Curr Opin Struct Biol 21(1):4-11. At least try reading the conclusion for a less technical overview.

In the coming years, making quantitative comparisons between theory and experiment should further deepen our understanding of processes like folding and allow us to refine simulation methodologies and parameterizations.

Looking to the future, it will perhaps be in the application of this knowledge to numerous related problems, such as protein misfolding (relevant for numerous diseases [2]) and protein dynamics associated with function (such as enzymatic activity [74]), where advances in protein folding will continue to yield insight and impact for many years to come.

It is from the Taming the complexity of protein folding.  first quote talks about refining MD simulation, does it mean the folding we do now will be rejected because of more precise methods?

Second quote - that's what I asked in my original question, where the knowledge was applied? I would like to see a research of treatment for any disease which was based on folding data and then verified by other means

Research contributions - I didn't read all 118 items but looks like it contributed mostly to modeling. something like "lets fold to make folding better", this is not the outcome I expect from project of this scale

I will try answer your question directly.

How do we know if we fold it right?
A. If you're interested in only the end product pf folding -- the 3D structure, then this is the subset of the folding problem called the structure prediction (from sequence alone).
a. We can verify the structure experimentally by determining the 3D structures by NMR or crystallography. In fact, the CASP competition withholds newly solved structures and see which algorithm comes out the closest to the experimental structure.
b. Based on Anfinsen's hypothesis, we can calculate the free energy of folding, and the structure that has the lowest energy among the assembles is probably (but not necessarily) the folded state.
B. If you're also interested in how exactly the protein folds, including its folding rate, plausible intermediates etc.:
a. You can experimentally determine the folding rate although the computed folding rate is often off by several order of magnitude.
b. Some interactions, esp non-native interactions (aka. interactions between amino acids that are only observed during folding but not in the final folded structure) can be verified by carefully designed NMR experiment.

1b. Yes it is possible. Adjusting the force constants and force field in molecular dynamics (MD) (the core engine of Folding@Home) so that the calculations converge to consistent and sensible results is not trivial.

If you mean the method of calculation, then yes, MD has a wide range of application outside the field of protein folding. Besides the improvement in MD algorithm and necessary approximation, it also facilitates some advances on calculation on more specialized hardwares e.g. GPU and programmable array.

2b. If you mean the end of product of computation model, then probably no, but one example came close. A model determined purely computationally (aka. ab initio), although still not as useful as an experimental structure, was close enough to facilitate the experimental determination of that structure (by a method called molecular replacement in X-ray crystallography)

A certain fold of a peptide string can be validated or ruled out if other experimental data is available. Some other techniques to infer protein structure are X-ray crystallography (requires pure protein that will crystallize) and single particle analysis.

As I understand crystallography is quite complex and expensive how  much of simulations were verified with crystallography to prove it right?

It's not really my field, but there are databases of protein structures, with annotations for each structure how it was obtained.


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What's the difference between blood value units 'mE/l', 'mU/l', 'mIU/l' and 'mEq/l'?
Wikipedia suggests 'mE/l' is the dutch or german translation (using 'eenheid'/'einheit' for 'unit') for 'mU/l', which can also be written as 'mIU/l'.
The article mentions The IU should not be confused with the enzyme unit, also known as the International unit of enzyme activity and abbreviated as U.. Is it safe to assume that in case of the unit 'mU/l' one never means the enzyme unit? I figure this is because the enzyme unit specifies a rate of conversion, which is not a blood value and would be meaningless to specify 'per liter'.
I have also encountered 'mEq/l', of which I am pretty sure it is different from 'mU/l', going by the wikipedia article.

did you read wiki article? there seems to be definitions on how units converted in mg. equivalents are essentially moles multiplied by charge of chemical. please read those pages and then articulate exact questions here

I was looking for confirmation that 'mE/l', 'mU/l' and 'mIU/l' are the same, but all different from 'mEq/l'. 'Is there a difference' is a yes/no question, which seems less appropriate to ask on stackexchange than a 'what's the difference' question. Since it's hard to google these units and they are easily confused I hope to establish a single reference here.


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What stops messenger RNA from binding to itself?
Since mRNA is single-stranded, and (mostly) floats freely within the cytosol, what stops it from folding onto itself (like DNA) and preventing transcription?

The premise of this question, that mRNA "(mostly) floats freely", is false. I don't have specific references (hence a comment, not an answer) but recent research on RNA interactions shows that mRNA is in fact rarely unbound. Under physiological conditions it's almost universally in a complex with proteins or (other) RNAs.

Yes @KonradRudolph is right. Approximately 60% of a eukaryotic mRNA is expected to be bound by protein http://biology.stackexchange.com/a/21898/3340.

It does fold on to itself. There are secondary structures in RNA and some of these secondary structures also have regulatory functions (for example, riboswitches). Some of these structures can also inhibit translation (by different mechanisms such as the masking of the ribosome binding site or analogous eukaryotic sequences, or stalling of ribosome etc). Other non-coding RNAs like tRNAs and rRNAs fold into specific structures that are essential for their function.
Many assays have been developed to study RNA secondary structure in vivo. SHAPE and DMS-seq are some examples.
The translation initiation factor eIF4A has a helicase activity that helps in resolving some secondary structures and facilitate translation (despite this, some structures can impede translation).
Also check out ribosome profiling experiments.

Due respects to everything given here so far (protein associations etc) in reply here as being accurate and part of your answer.  There is however the fundamental distinction between RNA and DNA yet to examine: that whole "deoxy-" matter right there in the 'D' of DNA.  That's the main key to why DNA more readily attains a double helix than does RNA.
There are at least two known physico-chemical reasons starting from the presence or absence of that 2' hydroxyl for this:  (1) DNA can more readily inhabit either an A- or B- form, (whereas RNA is more limited to the A-form).  So DNA has more entropic options as a helix former  (2) RNA's 2'-hydroxyl can become deprotonated and thus hydrolyzed more easily.  So less stability in the long run, not as good an information storage form, less likely to form complementary structures.  Not unlikely, just less likely.  Here's a good reference about this.


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ECG wave names origin
Why do electrocardiogram waves go  P, Q, R, S, T and not like A, B, C, D? Is there any specific reason behind this?

Interesting question! I searched briefly and came up with an answer from this short paper.
I won't repeat all the details of the paper, but to be not a completely link-only answer I will give a brief summary:
The technology used at the time was a lot different than modern ECG leads: it used a Lippman capillary electrometer that used moving mercury to detect brief current changes.
With this relatively primitive device, there were 4 apparent features in the trace, which were named A B C D (earlier, a different physiologist saw only two ventricular features that he logically named V1 and V2).
However, it was known that this primitive measurement was not showing the actual electrical signal, but rather a filtered version due to the physics of the mercury in the tube, which was subject to inertia and friction. When a physiologist used mathematics to essentially "deconvolve" the filtered signal to get the original signal back, he plotted both curves next to each other: one labeled A B C D, the other labeled P Q R S T (note that in this deconvolved version of the trace, there were 5 components rather than 4).
As for the choice of P Q R S T, the source I reference notes that these were the letters commonly used by Descartes, and since then have been commonly used to refer to series of variables when one needs to distinguish between ABCD, XYZ, etc.
Later measurements that directly displayed the 5-component PQRST wave continued to use that terminology.

Original: Einthoven W. Ueber die Form des menschlichen electrocardiogramms. Arch Gesamte Physiol.. 1895;60:101–123.
Reproduced in: Hurst, 1998

References:
Hurst, J. W. (1998). Naming of the waves in the ECG, with a brief account of their genesis. Circulation, 98(18), 1937-1942.

According to this site: http://www.ecglibrary.com/ecghist.html
Originally the waves were designated as A,B,C& D but after correction they were termed as P,QRS,  T.

Why PQRST and not ABCDE? The four deflections prior to the correction formula were labelled ABCD and the 5 derived deflections were labelled PQRST. The choice of P is a mathematical convention dating from Descartes (as used also by Du Bois-Reymond in his galvanometer's 'disturbance curve' 50 years previously) by using letters from the second half of the alphabet. N has other meanings in mathematics and O is used for the origin of the Cartesian coordinates. In fact Einthoven used O ..... X to mark the timeline on his diagrams. P is simply the next letter. A lot of work had been undertaken to reveal the true electrical waveform of the ECG by eliminating the damping effect of the moving parts in the amplifiers and using correction formulae. If you look at the diagram in Einthoven's 1895 paper you will see how close it is to the string galvanometer recordings and the electrocardiograms we see today. The image of the PQRST diagram may have been striking enough to have been adopted by the researchers as a true representation of the underlying form. It would have then been logical to continue the same naming convention when the more advanced string galvanometer started creating electrocardiograms a few years later. (For more on Descartes see Henson JR. Descartes and the ECG lettering series. J Hist Med Allied Sci. April 1971;181–186)


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Can a protein falling below a threshold trigger another response?
Is it possible that the falling of the concentration of a protein below a threshold triggers the release or production of another protein?

Welcome to SE Biology. Your question is very broad. You need to provide some context — is this a homework question or do you have a specific system in mind? Why are you asking this question and what attempts have you made to solve it yourself. See "How do I ask a good question". Oh, and please spell-check your titles at least. I'll correct this one.

A: Yes. There are too many examples to list.

Of course, that is possible. I'll give a simple example. If your protein (X) is an inhibitor of the other protein (Y), then when X falls, Y will rise. This would not really be "thresholded".
There are many mechanisms that can lead to thresholding which include co-operativity (in the action of X) and positive feedbacks. How these mechanisms work would be a different question altogether. (A quick read would be this wikipedia article).

Thank you very much. I'm a physicist and I'm interested in how axons can regulate its length. In a model I'm dealing with, the concrentration of a protein falls below a threshold when the axon reaches a distinct length. The question is if this falling below the threshold can stop the axon from growing.

@Peter123 As I mentioned above, it is possible. If you are asking an example of what those proteins X and Y may be in case of axon growth then I think you should do that literature mining yourself. There may be several examples. Check out a review on this topic.