qid int64 2 112k | question stringlengths 61 6.7k | positives listlengths 1 1 | negatives listlengths 1 10 |
|---|---|---|---|
5,647 | <p>What depth penetration can one typically get with <a href="http://en.wikipedia.org/wiki/Atomic_force_microscopy" rel="nofollow">atomic force microscopes</a>? (i.e. how far into the tissue can one image?). I have found numbers on acquisition times (minutes) and spatial resolutions (~nm), but what about depth? </p>
<p>Also, what is the sensitivity of AFM? (e.g. in moles)</p>
| [
{
"answer_id": 5648,
"pm_score": 3,
"text": "<p>Taken right from the Wiki page you linked to:</p>\n\n<p>AFM only images the surface of a specimen, to a maximum depth of 10-20 µm and a maximum scan area of 150 µm x 150 µm. Compared with scanning electron microscopy, SEM has a much large... | [
{
"answer_id": 78942,
"pm_score": 2,
"text": "<p>AFM is a surface technique, it has no depth. Spatial resolution can be far in excess of nm - there are publications wherein bonds -ewven hydrogen bonds- are shown. \nHere is a popularized article which is not behind a paywall\n<a href=\"https://www.chemis... |
5,649 | <p>I've read somewhere that after a person has a heart transplant, it is possible that his/her attitude, action or behavior would change slightly or significantly, as though he/she possesses some aspects of the organ donor's personality because he/she is using the donor's heart. </p>
<p>Anything to support this phenomenon? Does it suggest that there are actually memories 'stored' in the heart and these memories may be retrieved by the person that owns the heart even if he/she is not the original owner?</p>
| [
{
"answer_id": 5650,
"pm_score": 3,
"text": "<p>Although there is clearly no feasible mechanism for such a phenomenon, there is good evidence that transplant patients can <strong>believe</strong> in some sort of transference of qualities from the donor. See for example (my emphasis):</p>\n<blockquote>\n... | [
{
"answer_id": 13701,
"pm_score": 0,
"text": "<p>There are neurons all over the body, not just in the brain. The area with the most neurons, beside the brain, is the heart. It's been theorized that some memory could reside in these cells. I'm a big believer that if you keep an open mind people will t... |
5,676 | <p>Many people can grow extremely long head hair and facial hair. Are there evolutionary theories as to why this is the case? It seems like having long hair could be a disadvantage, and extremely long hair seems to be rare in other mammals.</p>
| [
{
"answer_id": 13572,
"pm_score": 5,
"text": "<p>How humans evolved to have head / beard hair that continues to grow longer than other animals is a topic that many anthropologists & biologists are still not sure about & there is no general consensus as to \"why\" yet.</p>\n\n<p>The three main vi... | [
{
"answer_id": 7100,
"pm_score": 3,
"text": "<p>The hair doesn't keep growing!</p>\n<p>It's important to notice that there isn't a set point for the actual hair length. The hair doesn't know that it's been cut for example. Rather, there's a set point for time. A single strand of hair, in humans, on the ... |
5,696 | <p>I've <a href="http://en.wikipedia.org/wiki/Cephalopod_eye" rel="nofollow noreferrer">read</a> that unlike humans, octopuses have eyes "designed" the "right way", i.e. with the nerve fibers behind the retina, thus getting rid of the blind spot we humans have as well as theoretically improving eyesight. </p>
<p>Have there been tests to compare octopus sight with that of humans, and do they indeed have better vision than us?</p>
| [
{
"answer_id": 5701,
"pm_score": 4,
"text": "<p>There are a couple of advantages and disadvantages of possessing the eyes of octopuses. </p>\n\n<ul>\n<li><p>The first <strong>advantage</strong> of the octopus eye is that it has no blind spot. This means that octopuses can see everything that is going on... | [
{
"answer_id": 76159,
"pm_score": 2,
"text": "<p>Adding to the answer above, another advantage of cephalopod eyes is the lower risk of retina detachment. (<a href=\"https://thehumanevolutionblog.com/2015/01/12/the-poor-design-of-the-human-eye/\" rel=\"nofollow noreferrer\">HumanEvolution</a>)</p>\n\n<p>... |
5,699 | <p>Can the combination of $+ve$ and $-ve$ blood groups of a couple be a cause of miscarriage in pregnancy? </p>
| [
{
"answer_id": 5700,
"pm_score": 4,
"text": "<blockquote>\n <p>I want to know can +ve and -ve blood group of a couple could be a cause of miscarriage in pregnancy?</p>\n</blockquote>\n\n<p><strong>Yes.</strong> In extreme cases, it can. You are talking about <strong>Rh Incompatibility</strong>, and can... | [
{
"answer_id": 5705,
"pm_score": 2,
"text": "<p>To add a more concise answer:</p>\n\n<p>Yes, the conflict between positive and negative Rh (Rhesus) blood groups can cause miscarriage.</p>\n\n<p>The genetic makeup decides whether red blood cells (RBC) carry a specific surface protein known as Rhesus fact... |
5,732 | <p>I know that ingesting testosterone and other hormonal drugs may stimulate libido and increase sexual desire.</p>
<p>But I wonder, if a man ingests female hormones such as estrogen, will he experience sexual desire towards other men or not? </p>
<p>Similarly, the other way around, whether a female ingesting male sexual hormones will experience desire towards other women?</p>
<p>The question is motivated by the interest to know whether transgender people, particularly, the MtF transsexuals engaged in prostitution experience genuine attraction to males.</p>
| [
{
"answer_id": 7564,
"pm_score": 4,
"text": "<p>There is no evidence that postnatal hormone exposure can change the sexual sexual preference of an individual. However atypical hormonal stimulation of the fetus can induce homosexuality.</p>\n\n<p>Homosexuality does not develop without a variety of social... | [
{
"answer_id": 5736,
"pm_score": 2,
"text": "<p>People suspect that hormones for have an effect, but there are also genetic and biological factors. Hormones have caused some animals, such as frogs, to change sexes. Also, both genders have testosterone and estrogen in their bodies. Men just have more tes... |
5,761 | <p>I am well aware of the phenomenon of neurogenesis induced by exercise, as well as the dopamine release that results from exercise. I am really interested in neuropsychology and the effects of exercise on personality. What are some other biological processes that are stimulated by exercise, does it activate our parasympathetic nervous system? Is there any cool research out there for me to read? I am grateful for any input. Any information about exercise and its effects on human biology is appreciated. </p>
<p><em>UPDATE</em> <br>
While this answer was appreciated, i'm interested in other biological processes... What happens to stress and anxiety? Do our adrenal glands stop secreting as much corticosteroids? What effect does exercise have on circadian rhythms? With exercise, can you circumvent the problem of not getting enough light in the winter? What effect does exercise have on memory? It should probably help, since it would lead to decreased damage to the hippocampus. How does exercise effect sleep, learning, memory, metabolic processes??? I'm searching for the comprehensive list of different primary and secondary effects of exercise from a biological standpoint. I'm really interested in what the short term and long term effects of exercise are on the brain.</p>
| [
{
"answer_id": 5789,
"pm_score": 2,
"text": "<p>Although current research has little to say about the effects of exercise on personality, there has been recent correlations demonstrated between personality and the \"drive\" to exercise--specifically, aggression as a personality trait has been linked to ... | [
{
"answer_id": 5776,
"pm_score": 0,
"text": "<p>Exercise stimulates various hormones which have impact on brain as well as other parts of the body. In psychological perspective, endorphins and serotonin released during exercise, are responsible to feel good feeling or act as antidepressants. Endorphins ... |
5,792 | <p>Assume that we planted floating solar cells on the ocean surfaces. Assume a 100km² solar cell field in the middle of the Pacific Ocean. All of the sunlight will be blocked by them. How would that affect the life in oceans?</p>
| [
{
"answer_id": 5789,
"pm_score": 2,
"text": "<p>Although current research has little to say about the effects of exercise on personality, there has been recent correlations demonstrated between personality and the \"drive\" to exercise--specifically, aggression as a personality trait has been linked to ... | [
{
"answer_id": 5776,
"pm_score": 0,
"text": "<p>Exercise stimulates various hormones which have impact on brain as well as other parts of the body. In psychological perspective, endorphins and serotonin released during exercise, are responsible to feel good feeling or act as antidepressants. Endorphins ... |
6,804 | <p>Antibodies or immunoglobulins are proteins made by the immune system in response to alien(!) molecules. Each antibody binds to its specific antigen. This great diversity and specificity is cause of diversity in Antigen Binding Site of heavy chain and light chain of antibody. Although other sections of Antibody are highly stable, Binding sites are very mutant. What is the reason for this difference in mutation rates in different parts of antibodies?</p>
| [
{
"answer_id": 6824,
"pm_score": 3,
"text": "<p>The processes are called gene rearrangement and <a href=\"http://en.wikipedia.org/wiki/Somatic_hypermutation\" rel=\"nofollow noreferrer\">somatic hypermutation</a>, and are used by maturing B-cells to generate very (<strong>very</strong>) large amounts of... | [
{
"answer_id": 6823,
"pm_score": 1,
"text": "<p>Antibody molecules or immunoglobulins (Ig) consist of heavy and light chains (e.g. two of each in IgG). Both heavy and light chains have variable domains at their N termini.</p>\n\n<p>During development of the immune system the pro-B cells in the bone marr... |
6,805 | <p>Quantitative analysis of microscope images is essential for many types of studies, but the techniques used most often are very labor-intensive. I have been able to find some literature about using computers to perform the analysis, but do not have a good picture of the state of the art.</p>
<ul>
<li><p>Is there a good literature review on the topic?</p></li>
<li><p>Is there much use in practice which I have not yet seen?</p></li>
</ul>
| [
{
"answer_id": 6809,
"pm_score": 3,
"text": "<p>Nature Methods seems to publish quite a few methods that facilitate this kind of analysis. E.g.\n<a href=\"http://www.nature.com/nmeth/journal/v8/n3/full/nmeth.1558.html\" rel=\"nofollow\">http://www.nature.com/nmeth/journal/v8/n3/full/nmeth.1558.html</a><... | [
{
"answer_id": 6808,
"pm_score": 2,
"text": "<p>The word to look for is 'Image segmentation'. But also here, it very much depends on what you're looking at. Segmentation and quantification of simple fluorescence images is relatively easy and widely used. It can get very complex depending on how complex ... |
6,816 | <p>When a person's glucose and glycogen stores are depleted, which can occur due to fasting or due to a diet consisting largely of fat (like eskimo diets), the body produces its energy by breaking down triglycerides into fatty acids. Fatty acids can be then converted to Acetyl-CoA, which can consequently enter the citric acid cycle, generating ATP.* </p>
<p>Now normally when a cell does not receive sufficient oxygen to undergo its natural processes, it usually breaks down glucose anaerobically to generate ATP and lactic acid. However, in the case where the body is running off fatty acids (e.g. fast, or fat/protein only diet), how does the body respond to such anaerobic situations? </p>
<p>*<em>(Note: In this situation many fatty acids are first taken up into the liver and converted to ketone bodies, which are subsequently converted to Acetyl-CoA after being taken up in the required tissues, hence causing "ketosis" as in the title)</em></p>
| [
{
"answer_id": 6817,
"pm_score": 4,
"text": "<p>You are correct in thinking that fatty acids cannot be metabolised anaerobically. However, in the type of metabolic state that you are describing, blood glucose will be maintained by the liver to support tissues or cells which are more or less dependent up... | [
{
"answer_id": 78765,
"pm_score": 0,
"text": "<p>In reality, a cell will die almost immediately in such anaerobic conditions. The question itself can be taken another way. That is, how does the body fuel anaerobic metabolism in the relative absence of glucose. It is important to understand that store... |
6,820 | <p>How does the digestive acid (HCl) not burn the surrounding membrane of our stomach? It digests the majority of raw food we eat but how does it stay safely in our stomach? </p>
<p>Also, how does the stomach maintain the ability for a human body to retain HCl for all lifetime?</p>
| [
{
"answer_id": 6821,
"pm_score": 5,
"text": "<p>Mucous-producing cells at the neck of the gastric pits create a layer of protective mucous covering the stomach lining. This mucous layer includes bicarbonate ions which act as a chemical barrier against the protons in gastric juice. See <a href=\"http://... | [
{
"answer_id": 6825,
"pm_score": 3,
"text": "<p>Cause of this secret are tight junctions and mucous.\nAs Wikipedia explains:</p>\n\n<blockquote>\n <p>Tight junctions, or zonula occludens, are the closely associated areas of two cells whose membranes join together forming a virtually impermeable barrier... |
6,839 | <p>I know that neurons communicate between each other by filling the junction between dendrites with neurotransmitters.</p>
<p><strong>What interests me is if a single neuron only works with one type of neurotransmitter(ex: serotonin), or if it can secrete/receive all of them (serotonin, dopamine, etc).</strong></p>
<p>If a neuron can secrete all, then can all dendrites secrete and respond to all neurotransmitters, or is it one per dendrite (one branch only works with dopamine, another one with serotonin, etc)? </p>
| [
{
"answer_id": 6842,
"pm_score": 3,
"text": "<p>I've googled this for a biology class I taught, and the quick answer is that both possibilities happen in different instances. Some specialized neurons secrete more than one type, even though the ruling concept used to be one neurotransmitter for one neur... | [
{
"answer_id": 13754,
"pm_score": 1,
"text": "<p>Check <a href=\"http://www.ncbi.nlm.nih.gov/books/NBK10818/\" rel=\"nofollow\">this</a> link out, It's a little simplistic but hopefully, will give the info you want so you can search elsewhere. </p>\n"
}
] |
6,851 | <p>If you had an isolate bacteria sample how would you determine if they were nitrogen fixing?</p>
| [
{
"answer_id": 6853,
"pm_score": 3,
"text": "<p>Never mind found the answer myself you can use the <a href=\"http://www.ncbi.nlm.nih.gov/pmc/articles/PMC223907/\" rel=\"nofollow\">acetylene reduction assay</a>.</p>\n"
}
] | [
{
"answer_id": 6856,
"pm_score": 0,
"text": "<p>I'd suggest doing a bioinformatic search of the bacterial genomes first before doing the experiments. You should be able to find homologues of the \"nif\" (nitrogen fixation) genes there.</p>\n"
}
] |
6,869 | <p>When I yawn I can't hear anything happening around me. I also feel some kind of muscles inside my head contract and hear a faint hum, but it is not loud enough to explain not hearing other sounds. I can force those muscles to contract even without yawning and it produces the same effect of humming and no other sound, so I suppose they cause this effect, but how?</p>
<p>What really happens? What muscles do I feel?</p>
| [
{
"answer_id": 6872,
"pm_score": 4,
"text": "<p>It is related to Eustachian tube. It links the back of throat and the middle ear and allows air pressure to equalize in the middle ear. When you yawn air pressure goes up in this and it bends the ear drum and causes impair hearing (notice, just impair and ... | [
{
"answer_id": 30755,
"pm_score": 0,
"text": "<p>Yawning increases pressure in eustachian tube because it takes place during inspiratory phase of respiration, so pushes Ear drum on the outer side</p>\n"
}
] |
6,899 | <p>I am trying to find information on Prostaglandin F2-alpha, specificaly production in men. Could somebody explain how this prostaglandin is produced? What types of cells are producing it, production signaling? Any books on this subject?</p>
| [
{
"answer_id": 6903,
"pm_score": 3,
"text": "<p>As I know:</p>\n\n<p>One of the most important chemical mediators are prostaglandins that in vivo act on different cell receptors and have different effects on the body. Prostaglandins are twenty-carbon lipid molecules and structurally similar to cholester... | [
{
"answer_id": 6901,
"pm_score": 1,
"text": "<p>PubChem is a good resource for finding out more about compounds of pharmaceutical interest:</p>\n\n<p><a href=\"http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=5280363\" rel=\"nofollow\">http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=52803... |
6,947 | <p>What effect do SSRIs have on the expression of the ligand-gated ion channel, the 5-HT<sub>3</sub> receptor?</p>
| [
{
"answer_id": 54056,
"pm_score": 3,
"text": "<p>There are five subunits to this receptor (5-HT3), which are encoded by the genes HTR3(A-D) and differentially expressed depending on cell location in the (human) body. In contrast to the information in the previous answer, my first source actually has sho... | [
{
"answer_id": 23556,
"pm_score": 0,
"text": "<p>SSRI's theoretically increase Serotonin levels. Serotonin is an agonist to the 5HT-3 receptors. The 5HT-3a primarily associated with the upper gut and the 5HT-3b with the lower gut. I would guess that theoretically again, SSRI's would tend to increase n... |
6,961 | <p>Inspired by <a href="https://biology.stackexchange.com/questions/653/why-20-amino-acids-instead-of-64">this question</a> among others.</p>
<p>It's widely suggested that the current 3-base codon system of encoding protein sequences in DNA evolved from an earlier 2-base codon system. This makes sense if you look at the coding sequences themselves but I fail to understand how it can evolve? Wouldn't any shift wreck the coding of all existing proteins?</p>
<p>Perhaps they could overlap, but wouldn't even that produce nonsense and how would it shift to non-overlapping codons? Perhaps both systems could run in parallel, but how would anything useful come from that in the short term? What selective of advantage of 3-base coding could be strong enough to overcome any disruption?</p>
<p>Has anyone developed a coherent model of what intermediate stages might look like?</p>
| [
{
"answer_id": 6963,
"pm_score": 4,
"text": "<p>It is not suggesting a 2-base->3-base code in the way you are thinking, but of a non-coding, two-coding triplet pattern occurring first.</p>\n\n<p>This means you would have 16 different coding sequences with 4 possible spacing bases in between.</p>\n\n<p>L... | [
{
"answer_id": 6973,
"pm_score": 1,
"text": "<p>Erives' paper is interesting:</p>\n\n<p><a href=\"http://www.ncbi.nlm.nih.gov/pubmed/21779963\" rel=\"nofollow\">A model of proto-anti-codon RNA enzymes requiring L-amino acid homochirality.</a></p>\n"
}
] |
6,988 | <p>QSAR modelling in pharmacology basically hangs on using mathematical modelling to approximate the effects different molecules will have on various pharmacological targets. I would like to know what software is available to assist me in doing these studies. </p>
| [
{
"answer_id": 7056,
"pm_score": 3,
"text": "<p>On the G6G Directory of OMICS and Intelligent software, I searched for \"QSAR Analysis, and received two product abstracts:</p>\n\n<p>1) SYBYL®-X Suite which contained:</p>\n\n<ul>\n<li>3D QSAR: use the power of industry leading CoMFA in a new way to\ngene... | [
{
"answer_id": 7058,
"pm_score": 0,
"text": "<p>Click2drug is a good ressource for in silico studies.</p>\n\n<p><a href=\"http://www.click2drug.org/index.html#QSAR\" rel=\"nofollow\">See this link.</a></p>\n"
}
] |
7,016 | <p>There's a <a href="http://greenspaces.in/blog/ted09/" rel="nofollow">claim</a> that <em>Sansevieria trifasciata</em> (Mother-in-law’s Tongue) generates oxygen from carbon dioxide during the night.</p>
<p>This seems surprising to me: that process requires energy; plants generate <strong>O₂</strong> from <strong>CO₂</strong> through photosynthesis, requiring light. So not photosynthesis, and no <strong>CO₂</strong> absorption, at night.</p>
<p>Am I missing something, or is this claim false?</p>
| [
{
"answer_id": 7021,
"pm_score": 5,
"text": "<p>This is an interesting topic! </p>\n\n<p><a href=\"http://en.wikipedia.org/wiki/Crassulacean_acid_metabolism\" rel=\"noreferrer\">Crassulacean acid metabolism</a> is a second CO₂ fixation pathway where <a href=\"http://en.wikipedia.org/wiki/Carbon_fixatio... | [
{
"answer_id": 7022,
"pm_score": 3,
"text": "<p>Shigeta submitted his answer as I was writing this!</p>\n\n<p>Sanseveria is one of a wide group of plants (mainly succulents) that adopt a photosynthetic strategy referred to as <a href=\"http://en.wikipedia.org/wiki/CAM_photosynthesis\">crassulacean acid ... |
7,074 | <p>I had a hard climb a week ago. I got so tired then any time I closed my eyes I saw these lights inside my head. I see these lights almost every time that I run fast or some thing like that. What are they and where do they come from?</p>
<p><img src="https://i.stack.imgur.com/eN5bc.jpg" alt="schematic representation"></p>
<p>Here is a picture I drew using Photoshop ;)</p>
| [
{
"answer_id": 10818,
"pm_score": 5,
"text": "<p>This is a common phenomena which most of us come across. Seeing flashes of light, stars and other shapes in the eyes occur when the body goes through stressful activities. For example while you are climbing the blood flow will be more to other prominent p... | [
{
"answer_id": 34942,
"pm_score": 2,
"text": "<p>It could be <a href=\"http://www.vision-and-eye-health.com/vitreous-detachment.html\" rel=\"nofollow\">posterior detachment of the vitreous humor</a>. Stress on the optic nerve caused by motion of the vitreous humor inside the eye can lead to the sensatio... |
7,075 | <p>I've started teaching myself about next-generation sequencing in preparation for a new job, and I'm wondering what the main differences are between the 454, SOLiD, and Illumina/Solexa machines, in terms of sample/library preparation and chemistry. How difficult is it for a protein veteran but next-gen newbie to get high-quality useful reads? I'm mainly going to be looking at antibody diversity, but consider this in general terms for any next-gen project.</p>
<p>I understand the basic theory of fluorescent chain-termination sequencing, but it's been a number of years since I last did it, and my career is now taking me back into the DNA realm.</p>
| [
{
"answer_id": 7101,
"pm_score": 5,
"text": "<p>Here is a short summary of the sequencing technologies you listed. Illumina is the most frequently used one.</p>\n\n<p>Roche/454 FLX Pyrosequencer technology is based on pyrosequencing method, which utilizes the use of the enzymes ATP sulfurylase and lucif... | [
{
"answer_id": 7098,
"pm_score": -1,
"text": "<p>It's not easy to write down a comprehensive answer to your question, I would suggest you read this paper <a href=\"http://onlinelibrary.wiley.com/doi/10.1111/j.1755-0998.2011.03024.x/pdf\" rel=\"nofollow\">Field guide to next-generation DNA sequencers</a>... |
7,084 | <p>I am tasked with designing an in vivo experiment in humans that requires manipulating the gut flora in one sample group to gauge its effect. Please suggest ways of doing this besides administering antibiotics.</p>
<p>I am of the view that antibiotics may have unintended consequences and may be unethical; explain any opposing view.</p>
| [
{
"answer_id": 7099,
"pm_score": 2,
"text": "<p>I can't think of any way to start with an intestinal \"blank slate\", so to speak, except with antibiotics.</p>\n\n<p>Perhaps it's possible to at least partially homogenize/standardize a sample group's biota with probiotics?</p>\n\n<p>If it's ethics you're... | [
{
"answer_id": 7086,
"pm_score": 0,
"text": "<p>I'm no expert, but I read this, and I found it very intresting:</p>\n\n<blockquote>\n <p>In its study, Henry Ford treated patients between May 2010 and June\n 2012 with a therapy called intestinal microbiota transplantation\n (IMT), using donated stool ... |
7,087 | <p>Every now and then I got a glimpse of this bird which I'm pretty sure is not native to Northern Germany where I live. There are at least three of these birds around but I usually only see something quick and green somewhere in the trees. I finally managed to get some decent pictures so I'm hoping someone can tell me what kind of bird this is. I'm curious what biological niche this bird is likely to fill and which native species it might compete with.</p>
<p><img src="https://i.stack.imgur.com/9ggwr.jpg" alt="photo of strange bird">
<img src="https://i.stack.imgur.com/y4Pfn.jpg" alt="detail of its head"></p>
| [
{
"answer_id": 7091,
"pm_score": 6,
"text": "<p>Almost definitely (I'm not a regular birder) <a href=\"http://en.wikipedia.org/wiki/European_Green_Woodpecker\"><strong>European Green Woodpecker</strong></a> (latin name: <em><a href=\"http://woodpeckersofeurope.info/?q=green_woodpecker\">Picus viridis</a... | [
{
"answer_id": 17173,
"pm_score": 4,
"text": "<p>I confirm rg255's answer: it is a <em>Picus viridis</em>. </p>\n\n<p>Additionally we can see it is a young male (immature). </p>\n\n<p>Young because the spots; picture of an adult <a href=\"http://fabrice.henon.oiseaux.net/european.green.woodpecker.32.htm... |
7,103 | <p>My biology book says, that the equilibrium potential for an ion with a charge of +1 is: $$E_{ion}= 62mV \biggl(\log\frac{[ion]_{outside}}{[ion]_{inside}}\biggr)$$</p>
<p>Where does the 62 mV come from? How was this value derived? I understand that it's the equilibrium voltage of $\ce{Na+}$.</p>
| [
{
"answer_id": 7107,
"pm_score": 4,
"text": "<p>The System intracellular/membrane/extracellular space is well described by the model of a Concentration cell (see more on <a href=\"http://en.wikipedia.org/wiki/Concentration_cell\" rel=\"nofollow noreferrer\">Wikipedia</a>). The equation you mentioned is ... | [
{
"answer_id": 7111,
"pm_score": 3,
"text": "<p>That quasi-travesty is the <em>Nernst equation</em> in $\\log_{10}$ for a positive monovalent ion at physiological temperatures (37 degrees celsius), but they've hidden all that from you. Shame on them.</p>\n\n<p>The canonical form of the Nernst equation, ... |
7,115 | <p>How do bats distinguish between day and night? Do they hunt at night - if yes, how they know that?</p>
<p>Are they afraid of sunlight?</p>
| [
{
"answer_id": 7116,
"pm_score": 3,
"text": "<p>Bats distinguish day and night the same way that other animals do, with an internal circadian clock and by environmental cues (dawn and dusk). </p>\n\n<p>Most bats (over 1000 different species total) are nocturnal, meaning that they are out of their roost ... | [
{
"answer_id": 17734,
"pm_score": 1,
"text": "<p>Mammals have what are called intrinsically photosensitive retinal ganglion cells (ipRGCs) (<a href=\"http://en.wikipedia.org/wiki/Intrinsically_photosensitive_retinal_ganglion_cells\" rel=\"nofollow\">Wikipedia</a>), including bats (<a href=\"http://a465g... |
7,118 | <p>I've just finished a course of double antibiotics for <em>Helicobacter pylori</em> in my stomach. I looked up <em>H. pylori</em> and found that it was a gram-negative bacterium. I looked up gram-negative and didn't understand the definition. I assume that if there are gram-negative bacteria then there are also gram-positive ones. Can someone explain the terms gram-negative and gram-positive in basic, layman's terms?</p>
<p>Thanks,</p>
<p>Sachin</p>
| [
{
"answer_id": 7116,
"pm_score": 3,
"text": "<p>Bats distinguish day and night the same way that other animals do, with an internal circadian clock and by environmental cues (dawn and dusk). </p>\n\n<p>Most bats (over 1000 different species total) are nocturnal, meaning that they are out of their roost ... | [
{
"answer_id": 17734,
"pm_score": 1,
"text": "<p>Mammals have what are called intrinsically photosensitive retinal ganglion cells (ipRGCs) (<a href=\"http://en.wikipedia.org/wiki/Intrinsically_photosensitive_retinal_ganglion_cells\" rel=\"nofollow\">Wikipedia</a>), including bats (<a href=\"http://a465g... |
7,124 | <p>I have been measuring my protein solutions' concentrations by diluting them in water 20 fold with a final volume of 100 uL and then measuring the absorbances of these solutions in 96 well plates with plate reader. I don't remember having any problem up until today.</p>
<p>I used 20 mM phosphate buffer instead of water to dilute them today and measured the absorbances at 280 nm repeatedly three times and the absorbance for one of the solutions went up from 0.043 to 0.068 (absorbance of 20 mM phosphate buffer is 0.030 at 280 nM with same volume); I stopped measuring after third one but it would probably go higher as I measured until I hit a plateau.</p>
<p>I measured absorbances of two proteins and only one of them went up that much, other one went up from 0.071 to 0.088; if this were to be concentration dependent I would expect the second solution go even higher but it didn't happen.</p>
<p>I know there may be differences in UV absorbances if protein is folded or unfolded; would it be that dramatic? What is the reason for that increase? I will be grateful for an explanation and a practical solution to the problem.</p>
<p>NOTE: I increased the total volume to 200 uL by simply adding 100 uL of 20 mM phosphate buffer into all wells and the signal increase slowed down a lot; there is still some increase though with 0.001-0.003 increments in each measurement.</p>
| [
{
"answer_id": 7125,
"pm_score": 3,
"text": "<p>It looks like your protein concentrations are right on the limit of detection of the spectrophotometer, and changing the diluent buffer changed their concentrations. The samples may not have been thoroughly mixed after dilution and before measurement, so t... | [
{
"answer_id": 7130,
"pm_score": 0,
"text": "<p>Could be protein unfolding or changes in conformation. Absorbance at 280 nm is mainly due to the tryptophan residues, and can change substantially as these residues move from a more hydrophobic (buried inside the protein) to a more hydrophilic (exposed to ... |
7,128 | <p>It's a pretty elementary concept, and when I first learned of it I don't think I had the foundations to even think of such a question, but I found myself the other day thinking about the amphipathic nature of the phospholipids in the plasma membrane and why it might be that lipid-soluble molecules don't stay in between the layers (of the bilayer). </p>
<p>I know that simple diffusion is a response to a concentration gradient, but consider a case where equilibrium is being restored and lipid-soluble molecules are diffusing from whatever extracellular matrix through the membrane and into the cytosol. Towards the end of this process, when equilibrium is nearly restored and the last few molecules are making their way into the cell, the rate of diffusion for these last couple molecules will be slower than those that diffused when the concentration difference was greater. Since the polar heads on the outside and inside of the bilayer are hydrophilic but the inner part, where the fatty acid tails are, is hydrophobic, what drives a molecule to leave the cozy, accepting, lipophilic environment of the middle (of the bilayer) to cross through the cytosolic-side rejecting polar heads and enter the cytosol?</p>
<p>I understand that initially these molecules were moving into the cell in response to a difference in intracellular vs extracellular concentration, but I'm asking whether we would ever see a case where the gradient is nearly zero and a molecule in transit simply decides to reside in between the layers instead of crossing all the way into the cell; as if moving through the cytosolic polar head side is not worth the effort to reduce a nearly-zero gradient to zero.</p>
<p>Please ask me if I can clarify my question in any way -- I'm finding it difficult to phrase. I asked my professor (who has her doctorate in toxicology & pharmacology) and she understood what I was asking but didn't have an answer. </p>
| [
{
"answer_id": 7135,
"pm_score": 3,
"text": "<p>I think, given Alan's answer the question you might be asking is something like \n'do compounds become concentrated in the lipid bilayer', as opposed to achieving high concentration inside the cell after diffusing through the membrane as he describes. </p>... | [
{
"answer_id": 7134,
"pm_score": 2,
"text": "<p>I interpret your question to refer to the movement of a lipid-soluble molecule that is therefore able to diffuse into cells down a concentration gradient. I think that you are asking whether as the gradient collapses, some of these molecules would \"stay i... |
7,170 | <p>First of all let me say that I'm not into Biology myself... but I have a question for those of you who are.</p>
<p>From what I've read, cancer is caused by <a href="http://www.foundationmedicine.com/patients-dna-cancer.php" rel="nofollow">'faulty' DNA that behaves abnormally</a>. <a href="http://learn.genetics.utah.edu/archive/sloozeworm/mutationbg.html" rel="nofollow">Mutations</a> can occur for various reasons, ranging from simple 'copying errors' to <a href="http://www.cancerresearchuk.org/cancer-info/cancerandresearch/all-about-cancer/what-is-cancer/what-causes-cancer/what-causes-cancer2" rel="nofollow">environmental factors</a>.</p>
<p>I was just wondering whether current research has dealt with storing DNA of people or animals (e.g. rodents) and observing how it changed, especially for cases where it eventually resulted in cancer. Something along the lines of <a href="http://www.bbc.co.uk/news/health-20663090" rel="nofollow">this</a>, but I'd like to know what research has actually been done so far.</p>
| [
{
"answer_id": 7171,
"pm_score": 3,
"text": "<p>I tried to comment but what I wrote is too long, so here it is as an answer of sorts.</p>\n\n<p>If I understand the question, you are asking: has anyone done a prospective study where they store the DNA of individuals and then later, when some of these ind... | [
{
"answer_id": 7172,
"pm_score": 1,
"text": "<p>There is a tremendous amount of information relating to mutations of genes and how they produce cancer. In fact, this is multi-billion area of research.</p>\n\n<p>What is even more interesting, is the aneuploidy hypothesis of cancer, in which it is chromo... |
7,214 | <p>I would like to be able to identify genera of fungi based on the shape, size, and colour of spores. So the requirements are:</p>
<ul>
<li>Must be able to view a 5 micrometre object clearly with reasonable resolution</li>
<li>Must be true colour</li>
<li>Must facilitate the measurement of an object within reasonable accuracy (500 nanometres would be nice)</li>
<li>Should be inexpensive (\$100-\$400) <sup><em>fingers crossed</em></sup></li>
<li>Bonus: Be able to take photos</li>
</ul>
<p>What type of microscope do I need? What magnification/resolution? Is there a good rule of thumb relating size of object with magnification?</p>
<p>How do I find and purchase a decent microscope after defining my requirements? Any tips?</p>
<p>Blue light is ~450 nm, so does that mean I will not get very good resolution?</p>
<p>(For the sake of context: I have absolutely no formal experience in biology, but I have recently taken an amateur interest in mycology and might enrol in an undergraduate course as part of my degree at some point.)</p>
| [
{
"answer_id": 7232,
"pm_score": 3,
"text": "<p>I think you have a good question, but if you want to get a good understanding of the issues you raise with it, then you really ought to consider spending some time reading this <a href=\"http://micro.magnet.fsu.edu/primer/\" rel=\"nofollow\">optical micros... | [
{
"answer_id": 7233,
"pm_score": 2,
"text": "<p>I agree with Kevin F, if I was you, I'd take a bit of training before buying something or even trying. Biology teachers or staff from the university are usually happy to provide you with a microscope to test something, so just ask. If you want a resolution... |
7,221 | <p>I've gotten conflicting advice on this: some people believe one can remove RNase contamination simply by spraying the bench, pipettes, gloves, etc. with ethanol. Others think ethanol does not destroy RNase and special reagents are needed to prevent RNase contamination. </p>
<p>So does ethanol remove RNase contamination? If not, what reagent does?</p>
| [
{
"answer_id": 7222,
"pm_score": 4,
"text": "<p>I think the protocols to clean glassware take no chances and just care about RNA degradation rather than targeting one class of enzymes. </p>\n\n<p>EtOH is supposed to denature RNAse and any other proteins on the surface. </p>\n\n<p>Other chemicals such ... | [
{
"answer_id": 7224,
"pm_score": 2,
"text": "<p>You don't want to only inhibit or temporarily denature RNAses, if you work with RNA you have to permanently inactivate the RNAses. I work with RNA, and I haven't seen anyone use ethanol to remove RNAses, I would not trust it to work reliably. RNAses are re... |
7,237 | <p>I see some popular science articles on the plastic eating bacteria and fungi appearing on the web since 2009. Most of the articles praise discoveries, because such organisms promise to break down plastics which were previously thought to be indestructible. However, from the articles it is hard to understand the total number/names of promising organisms that can biodegrade plastic. </p>
<p>Additionally, it's hard to gather from the dated articles if these plastic eating organisms have passed safety testing - for example that they don't break down plastic into something volatile and toxic.</p>
<p>My question is - <strong>which organisms as of 2013 are seriously considered for solving the plastic in landfills problem?</strong></p>
| [
{
"answer_id": 7241,
"pm_score": 4,
"text": "<p>I remember this link - about <a href=\"http://www.mnn.com/green-tech/research-innovations/blogs/boy-discovers-microbe-that-eats-plastic\" rel=\"nofollow\">a high school student who's science fair project</a> was a basic but effective selection experiment. ... | [
{
"answer_id": 67437,
"pm_score": 1,
"text": "<p>I know this is an old question however when it was posted there was not as much information as there is today. I have heard about two insects that have bacteria in their gut that degrade polimers. One of them is <em>Tenebrio molitor</em> which was reporte... |
7,245 | <p>My understanding, that may be wrong, is that cellulose/fibre has little nutritional value to many animals because it's hard to break down thus making consumption inefficient. However, <a href="http://en.wikipedia.org/wiki/Ruminant">Ruminating mammals</a>, other mammals such as <a href="http://www.cwf-fcf.org/en/resources/magazines/wild/wild-classes/grade-3/all-about-black-bears.html">black bears</a>, and many insects such as <a href="http://en.wikipedia.org/wiki/Grasshopper#Diet_and_digestion">grasshoppers</a> digest grasses.</p>
<p>Are there any birds with the gut flora to break down fibre? Or even some that eat grass but digest it in another way? </p>
| [
{
"answer_id": 7246,
"pm_score": 5,
"text": "<p>The <a href=\"http://en.wikipedia.org/wiki/Hoatzin#Feeding\">hoatzin</a> has a digestive system that makes use of bacterial fermentation. Many other birds also consume grass, e.g. <a href=\"http://en.wikipedia.org/wiki/Ostrich#Feeding\">ostriches</a>, <a h... | [
{
"answer_id": 30153,
"pm_score": 1,
"text": "<p>My society finch love to eat moist grass particularly orchard grass. Nibbling the whole strand they have chosen back and forth until they are satisfied with the texture and then proceeds to swallow it. They brake most grass into no bigger than an inch in ... |
7,263 | <p>It is said that human eye can see light with wavelength approximately between 400nm and 700nm.</p>
<p>Are these upper and lower bounds same for every human? If not, what are the means and standard deviations of these upper and lower wavelength values for human eyes?</p>
| [
{
"answer_id": 7266,
"pm_score": 4,
"text": "<p>Basically every human sees the same spectrum as we all have the same four types of photoreceptors: rods and a cone for green, red, and one for blue light.</p>\n\n<p>In very rare cases there are women who have a duplication of one of their cone genes (usual... | [
{
"answer_id": 7264,
"pm_score": 3,
"text": "<p>Human eyes all use the same optical pigment <a href=\"http://en.wikipedia.org/wiki/Photopsin\">photopsin</a>, so they all have the same basic frequency response.</p>\n\n<p>There are differences. For example cataracts will change the sensitivity of the eye ... |
7,269 | <p>I'm reading the papers linked below and all three of them mention a 20% cut-off for buried/exposed residues, by calculating a relative solvent accessibility (RSA) value.</p>
<p>I understand how the RSA is calculated, by dividing the calculated solvent accessibility against its total solvent accessibility values from paper 4 table 2.</p>
<p>RSA = calculated/total</p>
<p>e.g. if arginine is calculated to have a solvent accessibility of 55.43 and its total solvent accessibility is 241 then the RSA = 55.43/241 = 23%, so this arginine is considered exposed (see statement 1 below). </p>
<p>What leaves me confused is the definition or lack of the 20% method for defining an exposed or buried residue.</p>
<p>I am assuming it means one of the following:</p>
<ol>
<li><p>If an amino acids RSA is below 20% it is buried and above 20% it is exposed. So for an amino acid with an RSA of 21% is considered exposed, this value seems a little low for me. I think statement 2 would make for sense.</p></li>
<li><p>If an amino acids RSA is below 20% it is buried and above 80% it is exposed. </p></li>
</ol>
<p>Which statement if any is correct?</p>
<p><a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1142490/">Paper 1</a> - see methods section first paragraph</p>
<p><a href="http://biomine.ece.ualberta.ca/papers/PROTEINS-FlexibilitySolventAccessibility.pdf">Paper 2</a> - see figure 5 and table 3</p>
<p><a href="http://crpit.com/abstracts/CRPITV29Chen.html">Paper 3</a> - see abstract and dataset</p>
<p><a href="http://www.sciencedirect.com/science/article/pii/0022283687900386">Paper 4</a> - see table 2 for total values</p>
| [
{
"answer_id": 7272,
"pm_score": 4,
"text": "<p>Its 1. Below cutoff, <em>buried</em>, above cutoff <em>accessible</em>. </p>\n\n<p>Paper 1: \"A cutoff of 20% was used to define the two states, buried or exposed. With this definition, the dataset was, roughly, evenly split between the <em>two states</em... | [
{
"answer_id": 34124,
"pm_score": 0,
"text": "<p>Are you sure that the RSA formula is right?\nI have found a different description：Relative solvent accessibility classes are usually derived from the DSSP program by normalizing it at the maximum value of exposed surface area obtainable for each residue.D... |
7,302 | <p>Plants and animals have the following distinct properties: </p>
<ul>
<li>Plants live from solar energy by <a href="http://en.wikipedia.org/wiki/Photosynthesis" rel="noreferrer">photosynthesis</a>, they use solar energy to make sugar and oxygen out of carbon dioxide, which gives them energy. Animals live from the sugar and oxygen plants created and produce carbon dioxide for their energy.</li>
<li>Animals can move across the planet while plants are tied to the ground.</li>
</ul>
<p><em>Clearly, animals have a harder time to survive with no plants within their reach than plants have without animals coming close. This is logical because solar energy is always there while plants are not.</em></p>
<p>So my question is: <strong>Are there animals that can do photosynthesis?</strong> It's obvious that an animal with plant-like stateliness would be non-beneficial since it relies on eating other plants for it's energy and there may not always be plants within reach from it's spot.</p>
<p>But <em>animals using the sun and carbon dioxide for energy production does not sound so stupid.</em></p>
<ul>
<li>Night animals could also gather energy in their sleep.</li>
<li>Much easier than plants, animals could make sure nothing blocks their sunlight.</li>
<li>Many animals go through periods of hunger because food is scarce, for some of them this period is paired with high sunlight levels. (the dry season f.e.) (EDIT: This is just an idea, of course photosynthesis requires water, which is absent in the <em>dry season</em>. But still, in warm period with enough water, there's sometimes too much animals to feed from the available vegeation.)</li>
</ul>
<p>Some things I already took into consideration:</p>
<ul>
<li>I know that plants, because they are small in mass (compared to the area with which they can collect sunlight) and static, don't need nearly as much energy as animals do. Is this the main reason?</li>
<li>I know that f.e. reptiles, but in fact all cold-blooded animals, already use the sun's energy. But they only use the heat from the sun to warm their bodies, they don't photosynthesize.</li>
</ul>
| [
{
"answer_id": 7303,
"pm_score": 6,
"text": "<p>There are 5 answers, all "yes" (though the first one is disputable).</p>\n<ol>\n<li><p>First: there exists at least one <strong>animal which <a href=\"http://www.livescience.com/6030-surprising-sea-slug-plant-animal.html\" rel=\"noreferrer\">can ... | [
{
"answer_id": 9131,
"pm_score": 3,
"text": "<p>I was all set to answer anothervquestion which has now been marked as a duplicate of this one. My answer adds new information relevant to the accepted answer here, so I have decided to post it here..</p>\n\n<p>One longstanding candidate for something appro... |
7,336 | <p>Is gas produced by bacteria always mainly methane? Or, are there bacteria out there that produce some biogas composed mainly of hydrogen, natural gas, propane, butane? </p>
| [
{
"answer_id": 7351,
"pm_score": 4,
"text": "<p>Microbes can produce several gasses other than methane. </p>\n\n<ul>\n<li>All microbes produce $CO_2$ through the oxidation of reduced carbon</li>\n</ul>\n\n<p>Additionally some metabolic pathways produce other gases.</p>\n\n<ul>\n<li><p>Photosynthetic mi... | [
{
"answer_id": 7338,
"pm_score": 2,
"text": "<p>Well, some bacteria can produce Hydrogen Sulfide gas. For example, Proteus and Salmonella. The presence of $H_2S$ producing bacteria is actually clinically significant and we have a way to test for this, which is via the use of TSI (Triple Sugar Iron) medi... |
7,337 | <p>Puffer fish is known for having a anti-predation defense mechanism of having toxin-exuding spikes.</p>
<p>Are there predators which evolved specifically to prey on puffer fish? (presumably, by evolving immunity to the toxin)?</p>
<p>I know that sharks eat them, but I doubt sharks evolved to be immune specifically to puffer fish toxin, since their evolutionary development preceded puffer fish's.</p>
| [
{
"answer_id": 7349,
"pm_score": 3,
"text": "<p><a href=\"http://en.wikipedia.org/wiki/Tetraodontidae#Natural_defenses\" rel=\"nofollow\">Wikipedia</a> has some revealing information here: </p>\n\n<blockquote>\n <p>Not all puffers are necessarily poisonous; Takifugu oblongus, for example, is a fugu puf... | [
{
"answer_id": 105473,
"pm_score": -1,
"text": "<p>I know there are species of sea snakes that actually aren't bothered by the puffer fish's toxins! So they will eat them easily because puffer fish are extremely slow swimmers. Besides that sharks are the only other species, in specific Tiger Sharks don'... |
7,341 | <p>What nutrition is given to infants who are lactose intolerant? I understand, in today's day and that age we have non-lactose formula milk, but what happened, before lactose-free milk was created, to those who suffered from lactose intolerance (Native Americans, Asians, etc.)?</p>
| [
{
"answer_id": 7342,
"pm_score": 3,
"text": "<p>The <a href=\"http://en.wikipedia.org/wiki/Lactose_intolerance\" rel=\"nofollow\">lactose intolerance</a> Wikipedia page explains the problem fairly well, so I'll refer you to that for a more detailed explanation.</p>\n\n<p>Briefly, the most common cause o... | [
{
"answer_id": 7361,
"pm_score": 3,
"text": "<p>In fact, being lactose <em>tolerant</em> is the mutation. Adult mammals are normally not lactose tolerant, only the still milk drinking babies have the lactose gene activated. Humans developed this mutation earliest in the Neolithic.</p>\n\n<blockquote>\n ... |
7,364 | <p>Spent a half hour googling this and the best I could find was this: </p>
<blockquote>
<p>Now for some rhymes: Arginine = R. R we having fun yet?
Asparagine = N The kNights of Ne say "Ne".
<strong><em>Glutamine is a cute amine = Q</em></strong>
I say "glutamate"/a former vice president says "glutEmate" = E
ditto with AsparDic acid = D
Fenylalanine makes tasty italien sausage = F
Theres are two rings in tryptophan, and there are two v's in W = W
Tyrosine = Y, Y? Because we love biochemistry. Source: <a href="http://wwwchem.csustan.edu/chem4400/code.htm" rel="nofollow">One letter codes, rhyme and reason</a></p>
</blockquote>
| [
{
"answer_id": 7369,
"pm_score": 3,
"text": "<p><a href=\"http://www.biology.arizona.edu/biochemistry/problem_sets/aa/Dayhoff.html\" rel=\"nofollow\">The Biology Project</a> from the University of Arizona provides the best explanation of Dr. Margaret Oakley Dayhoff's logic for the non-obvious single let... | [
{
"answer_id": 7366,
"pm_score": 3,
"text": "<blockquote>\n <p>Initial letters of the names of the amino acids were chosen where\n there was no ambiguity. There are six such cases: cysteine, histidine.\n isoleucine, methionine, serine and valine. All the other amino acids\n share the initial letters... |
7,368 | <p>I want to stock up on autoclaved disposables, such as Eppendorf tubes, pasteur pipettes etc., and some buffers. </p>
<p>If I don't open the container after autoclaving, how long can I store autoclaved materials and consider them still sterile? Does it make a difference if the material is dry or if it is a liquid?</p>
| [
{
"answer_id": 7699,
"pm_score": 3,
"text": "<p>Not really an answer I know, but too long for the comments...</p>\n\n<p>This is still too broad a question. a well sealed, sterile plastic usually has a use by date, but can probably be used more than a year after you receive it. But these cases are not ... | [
{
"answer_id": 7373,
"pm_score": -1,
"text": "<p>If you work in a lab, there must be a SOP(Standard Operating Procedure) and you can (You should...) follow that. Each lab will have different standard so providing a single definitive answer here may not be beneficial. </p>\n"
}
] |
7,374 | <p>We are looking for an enzyme that appears in C. elegans but isn't common for: human, Drosophila or mouse.
We need it for a little research project, thanks for your help!</p>
| [
{
"answer_id": 7699,
"pm_score": 3,
"text": "<p>Not really an answer I know, but too long for the comments...</p>\n\n<p>This is still too broad a question. a well sealed, sterile plastic usually has a use by date, but can probably be used more than a year after you receive it. But these cases are not ... | [
{
"answer_id": 7373,
"pm_score": -1,
"text": "<p>If you work in a lab, there must be a SOP(Standard Operating Procedure) and you can (You should...) follow that. Each lab will have different standard so providing a single definitive answer here may not be beneficial. </p>\n"
}
] |
7,377 | <p>Do invertebrates (like <em>Drosophila</em> and <em>C.elegans</em>) have a urea cycle?</p>
| [
{
"answer_id": 7382,
"pm_score": 2,
"text": "<p><a href=\"http://www.genome.jp/kegg-bin/show_pathway?org_name=cel&mapno=00330&mapscale=&show_description=hide\" rel=\"nofollow\"><em>C. elegans</em> is missing all</a> of the urea cycle enzymes. <a href=\"http://www.genome.jp/kegg-bin/show_path... | [
{
"answer_id": 7390,
"pm_score": 2,
"text": "<p>Perhaps worth adding that the role of the urea cycle in terrestrial vertebrates is the disposal of excess N derived from protein metabolism. Such animals are ureotelic. Arthropods, in contrast, are uricotelic, using uric acid for N disposal, so it would ma... |
7,393 | <p>I am in an embryology course right now and we've just started covering cell-cell communication in development. We were talking about the roles of the various cadherins and their discoveries but we got to cell signaling pathways and in reading my textbook I'm finding myself confused by these pathways-- some of those that are mentioned include Notch, Wnt, FGF, TGF-beta, RTK, Jak-Stat, SMAD, integrins, PTHrP, Hedgehog, Discoidin domain receptors 1&2, and the unfolded protein response (UPR). </p>
<p>I know the RTK pathway and I know the SMAD pathway, but the others just seem to be specific ligands that are using these pathways -- is this correct?</p>
| [
{
"answer_id": 7398,
"pm_score": 3,
"text": "<p>@Alexandria Jak/Stat are two families of proteins which mediate signals through phosphotyrosines. </p>\n\n<p>JAK is a tyrosine kinase which binds to cell receptors and STAT is dimerized by JAK action. JAK specificity seems to be your question. A specifi... | [
{
"answer_id": 7395,
"pm_score": 0,
"text": "<p>With the exception of Jak/Stat, all of the proteins you mentioned are ligands and/or receptors. When a <em>ligand</em> binds to a <em>receptor</em>, it induces one or more cell signaling <em>pathways</em>, which are dependent on intracellular proteins bein... |
7,417 | <p>There are three mechanisms:</p>
<blockquote>
<ol>
<li>prevention of the interaction between antibiotic and the target PBP;</li>
<li>modification of the binding of the antibiotic to the PBP;</li>
<li>hydrolysis of the antibiotic by a beta-lactamase.</li>
</ol>
<p><em>Medical Microbiology</em>, 6e, p. 200, Murray</p>
</blockquote>
<p><sub>PBP: penicillin-binding protein</sub></p>
<p>It may be the case that the most common mechanism is not known.
It is just one of these three depending on the situation.</p>
<p><strong>What is the most common mechanism by which penicillin resistance develops in <em>S. pneumoniae?</em></strong></p>
| [
{
"answer_id": 7420,
"pm_score": 3,
"text": "<p>I think your guess is quite spot-on. According to this <a href=\"http://genomebiology.com/2011/12/11/R115\" rel=\"nofollow\">scientific article</a> I found online, They did a whole genome sequencing on penicillin-resistant <em>Streptococcus pneumoniae</em>... | [
{
"answer_id": 7443,
"pm_score": 0,
"text": "<p>Maybe you are asking where these genes came from and how they became so common? </p>\n\n<p>It turns out that antibiotics are very common - many free living plants and microorganisms make antibiotics. <a href=\"http://en.wikipedia.org/wiki/Penicillin\" re... |
7,436 | <p>There's a <a href="http://www.bloomberg.com/news/2013-03-03/hiv-infected-infant-cured-with-early-use-of-virus-blocking-drugs.html" rel="nofollow">story going round</a> the news about a baby that was, apparently, cured of HIV using a cocktail of drugs at an early age. The story piqued my interest, but details seem scarce. One of the main things I've seen being refuted about it is the difficulty in proving that (a) the child actually had HIV in the first place, and (b) that the child is really fully cured.</p>
<p>I've seen the following arguments:</p>
<ul>
<li>Western Blot tests on young children are practically useless, since they test for antibodies. The child will likely have antibodies passed down by the HIV+ mother, regardless of whether the child has HIV. The test will show the antibodies, which may be mistaken for an active immune response from the child. As such, there will be a high false-positive rate on such tests.</li>
<li>Using PCR to attempt to identify a lack of HIV is flawed, since it may lay dormant in a small colony of T-cells until a secondary immune response is triggered, causing a new outbreak. As such, it is very difficult to show that a patient is "cured".</li>
</ul>
<p>Are these arguments valid? Are there any other reasons to be sceptical about the claims? Any other information that might be useful in understanding the case?</p>
| [
{
"answer_id": 7439,
"pm_score": 4,
"text": "<blockquote>\n <p>Western Blot tests on young children are practically useless, since they test for antibodies. The child will likely have antibodies passed down by the HIV+ mother, regardless of whether the child has HIV. The test will show the antibodies, ... | [
{
"answer_id": 7438,
"pm_score": 2,
"text": "<p>The one that actually makes me skeptical of the <em>use</em> of this is that this \"cure\" was primarily a massive dose of antiretrovirals used as catchup therapy because the infant's mother didn't have access to prophylactic treatments while she was pregn... |
7,447 | <p><a href="http://en.wikipedia.org/wiki/Agar">Agar</a> is a relatively cheap substance from red algae. And it contains a saccharide agarose as well as a small amount of pectin. </p>
<p>Agar is used for culture plates as is, but for DNA gels a grade of agarose, I guess with the pectin removed. What happens when a gel is run in agar? i.e. why remove the pectin?</p>
<p>If you can guess, how is the pectin removed? I know there are <a href="http://en.wikipedia.org/wiki/Pectin_lyase">enzymes</a> that might do it, but not sure what's really used.</p>
| [
{
"answer_id": 7449,
"pm_score": 5,
"text": "<p>The answer to the first part of your question can be found on <a href=\"http://en.wikipedia.org/wiki/Agar\" rel=\"noreferrer\">Wikipedia</a>:</p>\n\n<blockquote>\n <p>Agar is a heterogeneous mixture of two classes of polysaccharide:\n agaropectin and aga... | [
{
"answer_id": 8961,
"pm_score": 1,
"text": "<p>Using DMSO (dimethyl sulfoxide), agarose can be separated. After heating and stirring around 2 hrs you will get a yellow stiff gel of agarose by filtering.</p>\n"
}
] |
7,472 | <p>I currently have two sets of gene expression data. The first is a dataframe of genes identified by Annotation id CG numbers (for example "CG10005") in one column and a numerical variable of interest associated with each of those genes in the other (the important part is that the genes are identified by the CG number). The second dataset is <a href="http://www.ncbi.nlm.nih.gov/pubmed/17994089" rel="nofollow">this study</a> from multiple species where genes are identified by "GLEANR" ID's like this one: "dsim_GLEANR_10060". </p>
<p>I would like to extract all of the values from this study for the D.melanogaster and D.simulans data, then link that to the Annotation ID's in the first dataset (to connect my variable of interest to the sex bias in expression for each species). The trouble I am having is connecting the orthologous genes within the second study to each other, and then connecting them to the CG identifiers in the first study.</p>
<p>Does anyone have any suggestions on resources which can be used to get this all to link up?</p>
| [
{
"answer_id": 7473,
"pm_score": 3,
"text": "<p>This is the FlyBase page for the example gene: <a href=\"http://flybase.org/reports/FBgn0181870.html\" rel=\"nofollow\">Dsim\\GD10095</a>. There, you have a section \"orthologs\", linking to <a href=\"http://cegg.unige.ch/OrthoDB6/results?searchtext=EOG65H... | [
{
"answer_id": 7475,
"pm_score": 0,
"text": "<p>You could also use <a href=\"http://central.biomart.org\" rel=\"nofollow\">biomart</a> for this purposes.</p>\n\n<p>Click on the \"ID Converter\" tab in the \"Tools\" section (on the left).</p>\n"
}
] |
7,480 | <p>I would appreciate an answer specifically in the form of an exothermic chemical reaction. Namely, the one primarily responsible for generating heat in warm blooded animals that does not take place in cold blooded animals.</p>
| [
{
"answer_id": 7482,
"pm_score": 3,
"text": "<p><a href=\"http://en.wikipedia.org/wiki/Brown_adipose_tissue\" rel=\"nofollow noreferrer\">Brown adipose tissue</a> or brown fat is one of the primary ways of generating body heat, and it is only found in warm-blooded animals. It is brown due to the high nu... | [
{
"answer_id": 7481,
"pm_score": 0,
"text": "<p>While all animals and even plants generate heat from chemical reactions or mechanical motion of their tissues (like muscle tissues), warm blooded animals have brown fat which has the unusual ability to generate heat directly from metabolic energy. </p>\n\... |
7,490 | <p>I'd like to do chemical structure prediction using a known molecule formulas. I'm familiar with <em>de novo</em> protein structure prediction, but are there any programs which will go from formula to structure with optimal geometry of random small chemicals (say 30 atoms)? I found <a href="http://cccbdb.nist.gov/mdlmol1.asp" rel="nofollow">http://cccbdb.nist.gov/mdlmol1.asp</a> but it selects mol files from a limited database. I need a command line UNIX program which computes mols from formulas. </p>
<hr>
<p>Concise structural formulas popular during past ages are unable to describe every type of chemical structure like morphine. I found no software that supports csf (Smiles and inchi are popular but are encoded and not human readable). When the bonds of the structure are known geometric minimization (DG-AMMOS) orients the structure to a stable native like direction.
<a href="http://www.mti.univ-paris-diderot.fr/fr/downloads.html" rel="nofollow">http://www.mti.univ-paris-diderot.fr/fr/downloads.html</a></p>
| [
{
"answer_id": 7497,
"pm_score": 3,
"text": "<p>Did you try to use <a href=\"http://www.bioclipse.net/bioclipse-features\" rel=\"nofollow\">Bioclipse</a>:</p>\n\n<blockquote>\n <p>Bioclipse is mainly based on the Chemistry Development Kit (CDK), and contains a framework for managing and analyzing chemi... | [
{
"answer_id": 64835,
"pm_score": 1,
"text": "<p>For the reference, there is also <a href=\"http://uspex-team.org/en/\" rel=\"nofollow noreferrer\">USPEX</a>, which works for a wide variety of molecular and continuous structures (mostly inorganic, though). </p>\n\n<blockquote>\n <p>USPEX can be used to... |
7,491 | <p>Speciation can occur by polyploidy. My understanding of the process is as follows:</p>
<p>'polyploidy is when the number of chromosomes in an organism's cell doubles. This means that the organism has more chromosomes than other individuals of the same species, meaning it cannot mate with other individuals. The polyploidy organism then evolves, eventually leading to it becoming a separate species'. </p>
<p>I realise this may not be exactly correct. Is someone able to provide a better description of speciation by polyploidy?</p>
| [
{
"answer_id": 7519,
"pm_score": 4,
"text": "<p>By definition, polyploidy just means that a cell or organism contains more than 2 pairs of homologous chromosomes (or is more than 2n). This is more common in plants than it is in animals. The plant, as shown below, undergoes failed meiosis, which means th... | [
{
"answer_id": 37110,
"pm_score": 1,
"text": "<p>In the genus Rhododendron polyploid species are common especially in deciduous azaleas and lepidotes. Yet complete reproductive isolation of the poylpoid species from the closely related diploid species is the exception rather than the rule.</p>\n\n<p>Clo... |
7,568 | <p>I have a very raw understanding of sexual selection:</p>
<p>Say a group of females of a certain species "like" some feature of a certain groups of males; by "like" I mean some behaviour that makes this group of females tend to mate with males having this feature, then the females are selecting their genes which make them feel appealed to males with the feature, and then this process becomes exponent since the group of females becomes bigger and forces the population of males to have this feauture, until an equilibrium is reached. I know this also happens with the roles interchanged.</p>
<p>My first question is, why do females tend to like males that have high amounts of these features, more than the average in the population?</p>
<p>My second question is, why do the end products of these selections are such beautiful features? Perhaps this may sound a little arrogant but I don't understand how an animal can appreciate this beauty, I suppose this is to make some sort of selection of healthy males.</p>
<p>Thanks </p>
| [
{
"answer_id": 9451,
"pm_score": 5,
"text": "<p>I think I can expand on the answer by @boo2060.</p>\n\n<p>The evolution of female mate choice depends on females achieving higher fitness by choosing certain males over others. At the broadest scale, there are two mechanisms by which this can occur, direct... | [
{
"answer_id": 7607,
"pm_score": 1,
"text": "<p><em>I'm not completely certain about the vocabulary used in this context so let me know if you wish clarification</em></p>\n\n<p>There are a few hypothesis why females care about the sexual features of males, the two most prominent are:</p>\n\n<ul>\n<li>Th... |
7,609 | <p>When I saw a DNA molecule for the first time, it kinda reminded me of a hard drive. It consists of <em>slots</em> and there are some possible combinations for each slot; in the hard drive these possible combinations would be 0's and 1's. In DNA, these <em>slots</em> would be G's, A's, T's, C's.</p>
<p>So, is there a way to measure the amount of bytes that are encoded in a DNA molecule? </p>
<p>I've made this <a href="http://www.scienceforums.net/topic/62128-dna-storage-capacity/#entry643821" rel="nofollow">question before</a> in another forum, but the answerer provided me only with Shannon's theorem, which is $K=L-\frac{(1-q^L)^n}{q^L}$ and told me a little about genetic redundancy. I could only search for the ammount of <em>slots</em> which are present in the DNA, but this genetic redundancy thing got me stuck.</p>
| [
{
"answer_id": 7611,
"pm_score": 3,
"text": "<p>Unfortunately the answer is highly dependent on what you mean. In the simplest terms, comparing it directly to how we measure data storage in digital media, the number of different states of a DNA string of length $n$ can have is simply $4^n$. A byte holds... | [
{
"answer_id": 7610,
"pm_score": 2,
"text": "<p>You might also be interested in this paper from EMBL-EBI about storing data on DNA.</p>\n\n<p><a href=\"http://www.nature.com/nature/journal/v494/n7435/full/nature11875.html\" rel=\"nofollow\">Towards practical, high-capacity, low-maintenance information s... |
7,619 | <p>Many papers I have seen describing transgenic rodent models (and presumably applicable to other model organisms) involve the knock-in, or modification to, a single gene, possibly two genes. With respect to recombineering techniques, what prevents targeting multiple genes in a single organism? For instance, if I wanted to simultaneously knock-in some genes and knock-out others within the same mouse, would I be forced to generate individually modified transgenic lines and then do some "fancy" breeding to generate the multiple-modified mice?</p>
| [
{
"answer_id": 7620,
"pm_score": 3,
"text": "<p>One reason is the low likelihood of success. Modifying a gene almost always involves a recombination event of plasmid DNA with a target site in the genome (and I say almost just because there may be some method that I don't know about, but all the ones I'm... | [
{
"answer_id": 37328,
"pm_score": 1,
"text": "<p>You could introduce multiple transgenes into your embryonic cell line before injecting into the blastocyst. That way you don't have to do it individually one by one and then breed them all together, which can take a lot of resources. This is especially ne... |
7,629 | <p>I am not a biology student, just a curious person. To be specific, I'm talking about female humans. I know that it might apply to other mammals.</p>
<p>What controls the size of breasts?</p>
<p>I have heard about progesterone hormone.</p>
<ul>
<li><p>Is it just progesterone?</p>
</li>
<li><p>Are there any other factors?</p>
</li>
<li><p>I have seen <a href="http://www.imdb.com/title/tt0315327" rel="nofollow noreferrer">a movie</a> in which couple talks about breast size increases after sex. Is it true?</p>
</li>
</ul>
<p>Can somebody give more info on this?</p>
| [
{
"answer_id": 7632,
"pm_score": 4,
"text": "<p>The known factors seem to be mainly oestrogen and genetic (although I haven't been able whatsoever to find detail on <em>what</em> genes):</p>\n<p>Manning et al (1997): <a href=\"https://doi.org/10.1016/S0162-3095(97)00002-0\" rel=\"nofollow noreferrer\">B... | [
{
"answer_id": 106730,
"pm_score": -1,
"text": "<p>The first signs of breast growth begin as a girl reaches her teens. The fat in the connective tissues starts to accumulate when the ovaries begin to secrete (express) estrogen. The breasts will then grow. Also, the duct system begins to grow. These brea... |
7,633 | <p>I understand that organ function varies with the stages of development. Does a fetal liver EVER perform lipogenesis, gluconeogenesis, make bile, etc? Or does it only begin performing these actions postnatally? </p>
<p>I have heard that a fetus delivered between 24-26 weeks can potentially be "okay" with proper care and monitoring in a hospital. I would assume (please correct me if I'm wrong) that this implies the fetus's liver has developed at this time. So in the case of a fetus that was not delivered at 24-26 weeks, does it spend the remainder of the pregnancy in a fully functioning state? Or at least, which functions does it begin to perform?</p>
<p>I've been trying to find an answer on Google, but one walks a fine line when searching for human development information -- either the results are oversimplified "expecting mothers" websites, or journal articles speculating about the effect of X on the development of Y in the mouse/chick/zebrafish/giraffe/et cetera other nonhuman model.</p>
| [
{
"answer_id": 7714,
"pm_score": 3,
"text": "<p>It's old and I can't get access to <a href=\"http://onlinelibrary.wiley.com/doi/10.1111/nyas.1963.111.issue-1/issuetoc\" rel=\"nofollow\">this</a> issue of the Annals of the New York Academy of Science, but it looks like it has some relevant information. S... | [
{
"answer_id": 7663,
"pm_score": 2,
"text": "<p>I found that a search through Google Books was helpful...</p>\n\n<p>While without the excretion of feces, it might seem as if the liver would not be active, but the liver tissue is not only active in development and tissue generation but serves direct phys... |
7,652 | <p>I have noticed that some of my sporadic gray hairs are gray at the tip side but oddly, not near the roots. Some are even only gray in the middle. I find all of this very counter intuitive, and I assure you nobody is secretly dying my hair.</p>
<p>How does the graying process work, and how is it that this can be happening?</p>
| [
{
"answer_id": 14665,
"pm_score": 3,
"text": "<p>Interesting question, I am not sure if I have a definite answer, but at least some ideas:\nThe pigment in the hair is made by specialized cells, the melanocytes. The make the pigment (eumelanin=dark and pheomelanin=red/yellowish) which is then deposited i... | [
{
"answer_id": 7653,
"pm_score": 1,
"text": "<p>Your hair grows out from the roots, and typically as you age, the pigments (melanin) that would normally keep your hair a certain colour are not produced anymore because the pigment producing cells (melanocytes) start to die. </p>\n\n<p>They're likely diff... |
7,654 | <p>My coach says that I need to eat 1.2 - 1.5 grams of proteins per kilogram when I have a common cold and flu.
I normally eat one gram of proteins per kilogram, while double it when doing my exercise training.</p>
<p>He explained that the reason why you need to get more good proteins when you are sick is that the body is building antibodies by the adaptive immune system and later for innate immunity.</p>
<p>I think he can be right based only on my own experiences getting better from common cold with low protein diet - it just takes a lot of time, while under high protein diet, you get better faster.
I also think his explanation makes complete sense to me, since antibodies and antigens are proteins.</p>
<p><strong>Why do you need more proteins when you are sick?</strong></p>
| [
{
"answer_id": 7655,
"pm_score": 3,
"text": "<p>Your body needs more energy when you are ill to facilitate the recovery process which includes the production of white blood cells to help fight the infection. This shouldn't be limited to proteins though, carbs are also very important as they are provide ... | [
{
"answer_id": 8074,
"pm_score": 1,
"text": "<p>Remember that your coach shouldn't give dietary advice unless he's trained as a dietician. Protein isn't as important as glucose really, that's the thing you burn the most. However you use everything: vitamins to tell the immune cells where to go, proteins... |
7,721 | <p>First off, I don't know if this is a normal healthy thing to occur. There have been many times where I have an itch on say my arm and I scratch it, only to feel the scratching elsewhere on my body. I assume somewhere along the transit of the touch signals to my brain the signal gets mixed up and is processed incorrectly.</p>
<p>So my questions are:</p>
<ul>
<li>Why does this mixup happen? <em>(chemical imbalance, damaged nerves, etc..)</em></li>
<li>How does my brain correspond the touch to somewhere else? <em>(what is the process behind it)</em></li>
</ul>
| [
{
"answer_id": 10588,
"pm_score": 3,
"text": "<p>Well nerve crossing or misinterpretation of nerve signal by the brain does not happen all the time. In case it happens frequently then I guess it would be Multiple Sclerosis or might be <a href=\"http://www.ehwidaho.com/fsp.html\" rel=\"nofollow noreferre... | [
{
"answer_id": 80136,
"pm_score": 0,
"text": "<p>This is part of a neuro issue...like seeing numbers in color, or touching something but feeling it in another part of your body. The sensations are processed in the brains communication area and ifeas/sensations get mixed or crossed. 4% of the population ... |
7,739 | <p>I am conducting a mutagenesis on a gene in vivo of which I need to ligate into an expression vector. The primers I have designed overlap restriction sites of which I plan to use to ligate into the expression vector. The parts between the primers I will try to create mutants with error prone PCR.</p>
<p>My concern is the 3' A overhangs that are created from Taq polymerase. How prevalent is this? If it is highly common, what is the best way to account for these additions when trying to ligate my PCR product into the vector?</p>
| [
{
"answer_id": 7740,
"pm_score": 3,
"text": "<p>I am not sure of a case where Taq <em>doesn't</em> add 3' A overhangs. </p>\n\n<p>You could use TA cloning to clone your PCR product. The basic principle is to use a vector with 3' T overhangs. If you have a vector without these overhangs, you can use a... | [
{
"answer_id": 7745,
"pm_score": 1,
"text": "<p>Use <a href=\"http://www.promega.com/~/media/Files/Resources/Protocols/Technical%20Manuals/0/pGEM-T%20and%20pGEM-T%20Easy%20Vector%20Systems%20Protocol.pdf\" rel=\"nofollow\">pGemT</a> to clone your PCR product into. It is exactly designed to take products... |
7,742 | <p>Parthenogenesis is defined as:</p>
<p>"A type of asexual reproduction in which egg develops without fertilization to form a new individual."</p>
<p>If parthenogenesis takes place in bees, a drone or male bee is produced.</p>
<p>My question is that parthenogenesis is the development of EGG into new individual so, how can egg be developed into male because egg won't have that "Y" chromosome required for male offspring?</p>
| [
{
"answer_id": 7743,
"pm_score": 4,
"text": "<p>Because the \"Y chromosome\" has nothing to do with sex determination in bees. Instead, the number of X chromosomes determines the sex. With only one X chromosome, the egg will develop into a male. This is called a <a href=\"http://en.wikipedia.org/wiki... | [
{
"answer_id": 55882,
"pm_score": 0,
"text": "<p>The Cape honey bee in South Africa can create female offspring without the queen being mated. Female stick insects can also produce female offspring without males, all daughters will however be clones of the mother. I guess this is a last resort to ensure... |
7,748 | <p>It's not a particularly sad or painful thing to pluck a few nose hairs, but it's common for the tear ducts to wet up when doing this. </p>
<p>I would like to know the physiological reason for the correlation, how/why are the tear ducts and nose hairs related in the human body?</p>
| [
{
"answer_id": 8148,
"pm_score": 3,
"text": "<p>Although I'm not sure, here's a working theory. The tear collection ducts feed into the nose. That's why when you cry you have a runny nose. When you pluck nose hairs you irritate the nasal mucosa, so that causes a reflex which attempts to flush out whatev... | [
{
"answer_id": 17176,
"pm_score": 2,
"text": "<p>Also, tears are an intrinsic pain response and considering the dermal-derivative nature of hair, there are loose nerve endings ensnaring the follicular area, so the sensory neurons detect pain and tears are a physical manifestation of the pain, cuing the ... |
7,807 | <p>I wonder if it's possible to pet a domestic crow, or an owl. Do birds respond to grooming as cats or dogs, for example? If so, then how does one pet a bird?</p>
| [
{
"answer_id": 7839,
"pm_score": 4,
"text": "<p>Birds do groom, but not like mammals do. People tend to call their grooming behavior <em>preening</em>. Preening removes dirt and parasites, arranges the feathers nicely, and distributes oils over the feather (very important for waterfowl.) </p>\n\n<p>To a... | [
{
"answer_id": 37267,
"pm_score": 0,
"text": "<p>I know first hand that Diamond, a tame <em>Pionus chalcopterus</em>, will sometimes respond to having his head and neck scratched in an interesting manner: he may make \"panting\" or \"huffing\" noises unique to this activity, lean his forehead or beak ag... |
7,829 | <p>In my classes and on the internet, brittle nails and dry hair (or hair loss) are described as symptoms of iron deficiency anemia, but none explains the cause of such symptoms.</p>
<p>Does anyone have any clues or explanation of such symptoms?</p>
<ul>
<li><a href="http://en.wikipedia.org/wiki/Iron_deficiency_anemia#Signs_and_symptoms" rel="nofollow">http://en.wikipedia.org/wiki/Iron_deficiency_anemia#Signs_and_symptoms</a></li>
</ul>
| [
{
"answer_id": 7830,
"pm_score": 4,
"text": "<p><a href=\"http://dx.doi.org/10.1016/S1471-4914%2801%2901920-7\" rel=\"nofollow\">The molecular basis of copper-transport diseases</a> in <em>Trends in Molecular Medicine</em>, Volume 7, Issue 2, 1 February 2001, Pages 64–69, has a link to a 1973 paper by J... | [
{
"answer_id": 7837,
"pm_score": 1,
"text": "<p>I did some searches on the relationship between iron deficiency anemia (IDA) and hair loss. Surprising, there are lots of debates about this and I don't think anyone has a solid reason.</p>\n\n<p>If iron deficiency is related to hair loss then taking iron ... |
7,861 | <p>I found it in Russia.</p>
<p><img src="https://i.stack.imgur.com/ZeCKJ.jpg" alt="Insect in question"></p>
<p>Where do they usually live? What do they eat?</p>
<p>Full length is approximately 2 cm.</p>
| [
{
"answer_id": 7865,
"pm_score": 3,
"text": "<p>Seems to be it's a Woodlouse!</p>\n\n<p><a href=\"http://en.wikipedia.org/wiki/Woodlouse\" rel=\"nofollow\">http://en.wikipedia.org/wiki/Woodlouse</a></p>\n"
}
] | [
{
"answer_id": 61210,
"pm_score": 3,
"text": "<p>This is a terrestrial <a href=\"https://en.wikipedia.org/wiki/Isopoda\" rel=\"nofollow noreferrer\">isopod</a> <a href=\"https://en.wikipedia.org/wiki/Crustacean\" rel=\"nofollow noreferrer\">crustacean</a> called a woodlouse (<a href=\"https://en.wikiped... |
7,881 | <p>Bacteria produce something called a biofilm. </p>
<p>I have found a few definitions; some say it is a complex of live and dead bacteria and others say it is a layer on cell wall.</p>
<ol>
<li>What is it made of?</li>
<li>What is its purpose?</li>
<li>How do we combat biofilms when we encounter them?</li>
</ol>
| [
{
"answer_id": 7892,
"pm_score": 4,
"text": "<p>Aside from the actual microbial cells themselves, biofilms are a slime matrix made of a variety of substances, including DNA, lipids, proteins, and other signaling molecules, but the major component is something called extracellular polymeric substance (EP... | [
{
"answer_id": 7883,
"pm_score": 2,
"text": "<p><a href=\"https://en.wikipedia.org/wiki/Biofilm\" rel=\"nofollow\">Bacterial biofilms</a> are a bunch of bacteria that have attached themselves to a surface or to each other as a floating mat to form a solid phase community. Its not seen in the lab so muc... |
7,894 | <p>Put another way if the muscle is given everything it needs to contract and do work will it ever get tired or have a reduction in energy efficiency? </p>
<p>As far as I understand muscles depend upon a blood supply delivering oxygen and nutrients (e.g. glucose and calcium) to effectively contract at its best level of performance. With the ability to work under anaerobic conditions if need be but producing lactic acid as a by-product which reduces the muscles ability to contract and therefore producing fatigue.</p>
<p>I also know that muscles are dependent upon temperature to work efficiently like the rest of the body. So, if the muscles temperature was able to be regulated well enough to maintain efficiency and aerobic conditions are met could fatigue be negated?</p>
| [
{
"answer_id": 7896,
"pm_score": 4,
"text": "<p>It seems that you are asking about activity significantly above basal metabolic rate. If aerobic conditions are maintained (and with appropriate training), muscles can operate more or less continuously for very long durations, days to weeks. In non-humans:... | [
{
"answer_id": 9569,
"pm_score": 2,
"text": "<p>If the muscle is provided with adequate food and oxygen, the muscle can theoretically work indefinitely. However, microtearing when a muscle is stressed more than usual can over time damage the muscle. This is the mechanism by which you get larger, stronge... |
7,905 | <p>People often claim, in a colloquial sense, that they are "allergic to everything". </p>
<p>Is it possible to have a full-fledged IgE mediated allergic response to very small molecules? I was always under the impression that the smallest antigen was a oligopeptide, but is it possible for someone to be allergic to something like isopropanol, glucose, or another small organic molecule? </p>
<p>How about allergies to metals, as I know those are fairly common, would they be mediated through a similar mechanism?</p>
| [
{
"answer_id": 7910,
"pm_score": 5,
"text": "<p>At one of my previous companies that raised antibodies to proteins and post-translational modifications, we found that 6-8 amino acids was generally the smallest peptide length required for an epitope. Anything much smaller than that won't induce the cross... | [
{
"answer_id": 7906,
"pm_score": 4,
"text": "<p>Small molecules do not have antigenic properties but they can elicit immune response by binding to a \"carrier\" protein. The small molecule is called a Hapten. An epitope forms at the protein-hapten binding interface. </p>\n\n<p><a href=\"http://www.ncbi.... |
7,909 | <p>How does your body know when it is infected with a virus or bacteria so it can invoke a fever or ramp up the immune system?</p>
| [
{
"answer_id": 7917,
"pm_score": 3,
"text": "<p>During infection certain macromolecules present in the pathogens (pathogen associated molecular patterns) such as lipopolysaccharide launch the <a href=\"http://en.wikipedia.org/wiki/Innate_immune_system\" rel=\"nofollow\">innate immune response</a>, throu... | [
{
"answer_id": 7963,
"pm_score": -1,
"text": "<p>An opinion by non-technical observer.</p>\n\n<p>If you know the function of a hive, you know that bees communicate with each other, touching and rubbing chemical information. In a few minutes the information reaches the center of the hive and returns to i... |
7,916 | <p>I am trying to recognize a deer by its antlers or any other means.
Elaborating:
I was hoping to use their antlers to recognize them but I have heard that most deers shed their antlers every year so it would be difficult to recognize it from the last year's photo unless these antlers retain the same pattern every year. </p>
<p>If not the antlers, what other characteristics should I be looking for?</p>
<p>Is there any software that can help me in recognizing a deer?</p>
<p><img src="https://i.stack.imgur.com/Ge3dA.jpg" alt="enter image description here"></p>
| [
{
"answer_id": 7942,
"pm_score": 3,
"text": "<p>There is a lot of variation in how and when deer shed their antlers. In most arctic and temperate-zone species, antler growth and shedding is annual, and is controlled by the length of daylight. In tropical species, antlers may be shed at any time of year,... | [
{
"answer_id": 7918,
"pm_score": 1,
"text": "<p>The Open Source Computer Vision library <a href=\"http://opencv.org/\" rel=\"nofollow\">OpenCV</a> is pretty popular. I'm a Python guy, but it also has C, C++, and Java interfaces. The O'Reilly book <a href=\"http://shop.oreilly.com/product/0636920022923.d... |
7,924 | <p>I am not a biologist, but I know there exist three variants of photosynthesis, namely C3, C4 and CAM.</p>
<p>I would like to know what type is used by the ocean's phytoplankton? It might also be that different photosynthetic mechanisms are used by the bacteria vs. algae. I have searched the web, but the information I find is too broad.</p>
| [
{
"answer_id": 7925,
"pm_score": 3,
"text": "<p>I'm not sure that all phytoplankton perform the same type of photosynthesis. </p>\n\n<p>Originally, people thought that they all performed C4, on the basis of genome sequencing, which revealed the presence of genes important for C4 photosynthesis. However... | [
{
"answer_id": 9364,
"pm_score": 2,
"text": "<p>Some wires crossed here. Most algae are C3, in other words they use the Calvin cycle to fix CO₂. Another way of saying it is that RUBISCO (Ribulose bisphosphate carboxylase) is dorectly responsible for CO₂ fixation. There is some evidence (disputed) that... |
7,943 | <p>Fungi and insects contain <a href="http://en.wikipedia.org/wiki/Chitin" rel="nofollow">chitin</a>, which is about 6% nitrogen.
Can an animal - like me - make use of this as a nitrogen source to build proteins?</p>
<p>Are there any animals that can do this?</p>
<p>Are there other uses an animal can put Nitrogen from this specific source to?</p>
| [
{
"answer_id": 7944,
"pm_score": 2,
"text": "<p><a href=\"http://en.wikipedia.org/wiki/Dietary_fiber\" rel=\"nofollow\">The first answer is that humans cannot.</a>\nChitin is a major component of the exoskeleton of insects and other arthropods, the cell wall of fungi and bacteria, the perisarco of hydro... | [
{
"answer_id": 62591,
"pm_score": 2,
"text": "<p>This article suggests a certain amount of chitin digestion is possible. </p>\n\n<p><a href=\"http://www.bio.unipd.it/agroecology/download/pdf/papers/2009/Chitin-Chitinases-Paoletti-From-Binomium-Chitnchitinase-Recent-Issues-Fp-Version.pdf\" rel=\"nofollow... |
8,026 | <p>In a neuroscience class I'm taking, it was explained that myelin covers axons in sections, the uncovered sections are called nodes of Ranvier, and signals propagate much faster in the covered sections.</p>
<p>But if it is faster for signals to propagate along myelinated regions of the axon, why doesn't the entire axon get covered by myelin? Wouldn't that make it faster?</p>
| [
{
"answer_id": 8029,
"pm_score": 4,
"text": "<p>Every signal rapidly fades out with distance if it is not amplified. So if the whole axon were covered with myelin, action potentials wouldn't reach their target. Each Ranvier node can be seen as an active signal repeater.</p>\n"
}
] | [
{
"answer_id": 8027,
"pm_score": 2,
"text": "<p>Action potentials arise and propagate by membrane depolarization. </p>\n\n<p>A myelin sheath is present in most neurons and is responsible for insulating the membrane against ions. The function of the myelin sheath is to prevent leakage of charge, by effec... |
8,028 | <p>How to know if a human female is fertile (can give birth to child in future) without making her pregnant? Any signs, tests?</p>
| [
{
"answer_id": 8039,
"pm_score": 3,
"text": "<p>If you are talking potential for fertility. There are a few... </p>\n\n<ul>\n<li>Having regular periods</li>\n<li>Healthy weight. Extremely thin women tend to stop ovulating. Obesity also impairs fertility by altering hormone levels.</li>\n<li>Whether she ... | [
{
"answer_id": 8032,
"pm_score": 3,
"text": "<p>Of course. There's several <a href=\"http://en.wikipedia.org/wiki/Fertility_testing#Diagnosis_of_infertility\" rel=\"noreferrer\">fertility tests available</a> to determine the quality and quantity of egg reserve, and whether or not the there are abnormali... |
8,072 | <p>Where would I find an up to date (last 6-7 years max) review on B cells? I've tried searching through pubmed with filters, cochrane library, medline and various other resources including searching old questions. A textbook would be fine too, but I'm not sure which one would give me detailed information. I'm a BSc student studying immunology. I'm not trying to create a war of "best" answers, any answer that fits these criteria I will accept. </p>
| [
{
"answer_id": 8078,
"pm_score": 3,
"text": "<p><a href=\"http://rads.stackoverflow.com/amzn/click/1437715281\" rel=\"nofollow\">Cellular and Molecular Immunology</a> by Abul Abbas et al. is pretty good, and you can't beat Charlie Janeway's <a href=\"http://rads.stackoverflow.com/amzn/click/0815342438\"... | [
{
"answer_id": 9690,
"pm_score": 1,
"text": "<p>I agree entirely with Matt, <a href=\"http://www.ncbi.nlm.nih.gov/books/NBK27142/\" rel=\"nofollow\">Abbas and Janeway</a>'s books are the standard for even graduate-level introductory Immunology. Both are easy to read and well organized. Definitely start ... |
8,081 | <p>I heard that some monkeys can be homosexual? a friend of mine was saying that he saw a male monkey having sex with another male monkey in the zoo, I honestly didn't believe him, I think he just got confused or he made it up. </p>
<p><strong>Could this be true? can monkeys become homosexuals? does homosexuality (other than human) exist in the animal kingdom?</strong></p>
| [
{
"answer_id": 8082,
"pm_score": 3,
"text": "<p>Cases of homosexuality have been described in numerous species, including primates, and the <a href=\"http://en.wikipedia.org/wiki/Homosexual_behavior_in_animals\" rel=\"nofollow noreferrer\">wikipedia link</a> posted by @shigeta lists and describes some o... | [
{
"answer_id": 8125,
"pm_score": 1,
"text": "<p><a href=\"http://www.ted.com/talks/kees_moeliker_how_a_dead_duck_changed_my_life.html\" rel=\"nofollow\">Here's a Ted talk about a case of homosexual necrophilia in mallard duck</a>. The speaker lists a few other examples of weird animal mating (frog with ... |
8,084 | <p>I read on <a href="https://en.wikipedia.org/wiki/Dog#Smell">Wikipedia</a> that:</p>
<blockquote>
<p>The wet nose, or rhinarium, is essential for determining the direction of the air current containing the smell. Cold receptors in the skin are sensitive to the cooling of the skin by evaporation of the moisture by air currents.</p>
</blockquote>
<p>That explains why their noses are wet. Why they're slightly moving them when smelling, like on <a href="http://youtu.be/bJ2DgCCUstA">this video</a> (see the close-up in the second part)? Could this very little movement create enough air currents around the nose to determine what smells are coming from what directions? Or is there another reason?</p>
| [
{
"answer_id": 8085,
"pm_score": 4,
"text": "<p>The dog's ability to smell the world around him and to interpret these odors <em>depends on a complicated chemical sensory system</em>. First of all, it possesses <strong>mobile nostrils</strong>, <em>that help to determine the direction of the smell</em>.... | [
{
"answer_id": 39607,
"pm_score": 2,
"text": "<p>Animals smell in stereo. Just the way you need 2 ears to know the direction of sound, you need 2 nostrils to know the direction of odor source. Sniffing around helps in doing exactly that as you sample from different locations; there is inter-nostril conc... |
8,133 | <p>Is it possible to use a biologically active Telemorease Elongation Reverse Transcriptase (TERT) in the place of the Reverse Transcriptase (RT) for quantitative Reverse Transcriptase pcr (qRT-pcr)? Yes I do know that it would seemingly have no advantages. What kind of reverse transcriptase is used in qRT-pcr is there a standard like taq dna pol is used for qpcr?</p>
| [
{
"answer_id": 8135,
"pm_score": -1,
"text": "<blockquote>\n <p>What kind of reverse transcriptase is used in qRT-pcr is there a standard like taq dna pol is used for qPCR</p>\n</blockquote>\n\n<p>M-MuLV (Monoley murine leukemia virus) reverse transcriptase</p>\n\n<p>Some RT enzymes are engineered to r... | [
{
"answer_id": 109291,
"pm_score": 1,
"text": "<p>hTERT is incapable of replacing common reverse transcriptases like MuLV or SuperScript.</p>\n<p>hTERT is specialized to bind with its own RNA (hTR aka TERC), and not any given RNA. hTERT uses hTR as a template to extend a DNA strand with the same repeats... |
8,153 | <p>I'm reading <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC509173/pdf/10111227.pdf" rel="nofollow">this fantastic article on estimating body time: Molecular-timetable methods for detection of body
time and rhythm disorders from single-time-point
genome-wide expression profiles</a> and one of the things that is not very clear to me is how the researchers estimated which genes are expressed and which ones are not:</p>
<blockquote>
<p>Total RNA was prepared by using Trizol reagent (GIBCOBRL). cDNA
synthesis and cRNA labeling reactions were performed as described (5).
Affymetrix high- density oligonucleotide arrays (Murine Genome Array
U74A, Version 1.0, measuring 9,977 independent transcripts) were
hybridized, stained, and washed according to the Technical Manual
(Affymetrix). Affymetrix software was used to deter- mine the average
difference (AD) between perfectly matched probes and
single-base-pair-mismatched probes. The AD of each probe was then
scaled globally so that the total AD of each microarray was equal. <strong>The
resulting AD values reflect the abundance of a given mRNA relative to
the total RNA popu- lation and were used in all subsequent analyses</strong></p>
</blockquote>
<p>I'm not sure if I'm reading this correctly - did the researchers look at all RNA available in the cells and calculated the levels of messenger RNA produced by expressed genes? if not, how can the level of expression of a gene be estimated?</p>
| [
{
"answer_id": 8157,
"pm_score": 4,
"text": "<p>The technique described here is called microarray. Your question has given me an opportunity to put forth one of my opinions about certain problems of gene expression studies.</p>\n\n<p>Gene expression is a measure of the activity of any gene. If the gene ... | [
{
"answer_id": 8164,
"pm_score": 2,
"text": "<p>Supplementary information from the Comments from the first answer: </p>\n\n<p>I have perhaps found @terdon's reference? Not sure if this is it, but by measuring transcription events in individual cells, <a href=\"http://www.sciencemag.org/content/329/5991... |
8,160 | <p>I have been trying to learn some basic DNA sequencing techniques and have been using <a href="http://blast.ncbi.nlm.nih.gov/" rel="nofollow noreferrer">BLAST</a> as a reference. I thought that I was starting to get it, but then I cam across this:</p>
<p><img src="https://i.stack.imgur.com/ebhyr.png" alt="enter image description here"></p>
<p>It looks like it's saying that the match starts at 10835 and ends at a smaller index (10714).
I tried clicking the link to view the full sequence, and I couldn't find the highlighted portion anywhere (not at 10835 or at 10776).</p>
<p>My question is: Where (in <a href="http://www.ncbi.nlm.nih.gov/nucleotide/374429547?report=genbank&log$=nuclalign&blast_rank=1&RID=RZH41XEJ01R" rel="nofollow noreferrer">NR_046235.1</a>) can I find the highlighted sequence?
And what does it mean to say that the <code>Sbjct</code> starts at 10835 and ends at a lower index?</p>
<p>I can post my query if necessary.
Thanks.</p>
| [
{
"answer_id": 8162,
"pm_score": 4,
"text": "<p>Just to flesh out Daniel Standage's answer a bit, remember that a genome is double stranded with one strand being complementary to the other. Genes can be found on either strand, the two are equivalent biologically. However, sequencing projects choose one ... | [
{
"answer_id": 8161,
"pm_score": 3,
"text": "<p>Note that the query sequence you have provided matches the minus strand of your target sequence. That means not only that the target sequence will be reversed (as you have noted), but it will also be complemented as well. So in the GenBank record, you shou... |
8,182 | <p>I'm reading a text (<a href="http://dx.doi.org/10.1534/genetics.107.074732" rel="nofollow noreferrer">Wagner, 2007</a>) on identifying positive selection. In the paper, the author says that low complexity regions are known to be associated with the relaxed selection. I'm trying to understand why this is true. I get that if the region is under relaxed selection then most mutations would be tolerated but why would that lead to low complexity (other than something like slippage during DNA replication)</p>
<p>It's in the section: "Little overlap between variation clusters and low complexity regions"</p>
<p>Wagner A. 2007. Rapid Detection of Positive Selection in Genes and Genomes Through Variation Clusters. <em>Genetics</em> 176(4): 2451–2463.</p>
| [
{
"answer_id": 86398,
"pm_score": 3,
"text": "<h1>What is complexity?</h1>\n<p>"Complexity" in this case is derived from the <a href=\"https://www.sciencedirect.com/science/article/pii/S0076687996660352\" rel=\"nofollow noreferrer\">SEG algorithm</a>, which is based on <a href=\"https://en.wik... | [
{
"answer_id": 8192,
"pm_score": 3,
"text": "<p>Low complexity regions <a href=\"http://www.broadinstitute.org/science/projects/fungal-genome-initiative/frequently-asked-questions#blast_lowcomplex\" rel=\"noreferrer\">have repeats in nucleotides</a> ( or amino acids ). E.g. PPCDPPPPPKDKKKKDDGPP or AAA... |
8,183 | <p>How many species did Carl Linnaeus (senior) classify?</p>
| [
{
"answer_id": 14375,
"pm_score": 4,
"text": "<p><strong>More than 13,000.</strong></p>\n\n<p><strong>Plants: >9,000 names</strong>.\nIn Systema Naturae 10th edition, commonly taken as the starting point of modern taxonomy, Linnaeus is reported to have published around 6,000 plant names (I haven't count... | [
{
"answer_id": 8191,
"pm_score": 2,
"text": "<p>Indeed this is a bit of interesting history. <a href=\"http://www.nhm.ac.uk/nature-online/science-of-natural-history/taxonomy-systematics/history-taxonomy/session1/\" rel=\"nofollow\">Linnaeus was not a modest man, but he was also a prodigious contributor... |
8,197 | <p>When sun rays shoot through my house from a window, sometimes if the lighting is correct, it will reveal a huge amount of floating particles and dust.</p>
<p>Are these particles dangerous to humans if you live with them constantly? </p>
| [
{
"answer_id": 8198,
"pm_score": 3,
"text": "<p>You asked the single most difficult questions ever, so be proud of yourself! I've spent some time in the lab with a post doctorate trying to answer that particular question. It all is based on something called the hygiene hypothesis: the belief that as we ... | [
{
"answer_id": 8218,
"pm_score": 0,
"text": "<p>Our basic defenses such as nasal hairs and mucus help in trapping the dust particles and other Suspended Particulate Matters (such as smoke etc). </p>\n\n<p>However, if there is too much of dust inhalation then, as you suspect, it will be harmful. This can... |
8,204 | <p>I know that when RNA is transcribed from the original strand of DNA it contains introns and exons, and that the introns are spliced out of the strand to provide genetic diversity. However, what I don't understand is, how does whatever is doing this splicing know whether the section it is reading is an intron or an exon? Are there start and stop codes like there are for polypeptides, or is it determined by epigenetic factors like methyl markers? Or is it neither?</p>
| [
{
"answer_id": 8221,
"pm_score": 3,
"text": "<p>Quick answer: we don't really know.</p>\n<p>As WYSIWYG said, splice sites <em>do</em> have a sequence signature. The image below (taken from <a href=\"http://dx.doi.org/10.1016/j.sbi.2004.05.007\" rel=\"nofollow noreferrer\">[1]</a>) shows the consensus fo... | [
{
"answer_id": 8216,
"pm_score": 2,
"text": "<p>There are some signature sequence which mark intron-exon boundaries. Usually introns start with a <code>GU</code> and end with an <code>AG</code>. But this feature per-se is not sufficient for splicing; there are other cis-elements such as <code>exon/intro... |
8,207 | <p>A neurotropic virus is a virus which capable of infecting nerve cells. </p>
<p>Herpes simplex virus (HSV) has low neuroinvasivesess and high neurovirulence. HSV is transmitted in vesicle fluid, saliva and vaginal secretions. So the site of infection determines the disease - "mixing and matching of mucous membranes". </p>
<p>Source: Murray 2013, Medical Microbiology.</p>
<p><strong>Why is herpes virus neurotropic?</strong></p>
| [
{
"answer_id": 62892,
"pm_score": 2,
"text": "<p>1/How Herpes does it:</p>\n\n<p>Quote: << HSV... can enter the <em>Peripheral Nervous System</em> by binding to receptors on axon termini of sensory and autonomic neurons, which respectively convey sensory and visceral information. Most alpha herpes... | [
{
"answer_id": 8258,
"pm_score": 3,
"text": "<p>Simply because it has neurotropic receptors. Why did acquiring these receptors seem evolutionarily advantageous? Well the immune system doesn't target nerve cells for destruction as well. There are few if any white blood cells in the CSF within which the n... |
8,285 | <p>Is this due to pressure differentials in the surrounding tissue? (Is it possible to have a pinched nerve without compression of the surrounding tissues, and does this cause pain?)</p>
<p>What are the molecules/cell types involved in this process? Is the pain dependent on the compression of axons from mechanosensitive or nociceptive neurons?</p>
| [
{
"answer_id": 8290,
"pm_score": 4,
"text": "<p>Typically nerve compression or a \"pinched\" nerve is due to inflammation in the tissue through which a nerve passes. The gap is already quite narrow so any inflammation is quite potent. Inflammation causes you to feel things as more painful (hyperalgesia)... | [
{
"answer_id": 8350,
"pm_score": 2,
"text": "<p>As AndroidPenguin described the nociceptive pathways are activated by inflammation or noxious chemicals. </p>\n\n<p>Sometimes pain can arise independent of active nociceptive pathways. Most evident in cases of <a href=\"http://en.wikipedia.org/wiki/Neuralg... |
8,289 | <p>An interesting tidbit floating around the internet these days is that <a href="http://en.wikipedia.org/wiki/Duncan_MacDougall_%28doctor%29">Dr. Duncan MacDougall</a> apparently weighed people shortly before and after death, and found an average of a 21 gram discrepancy, to which he attributed to be the soul departing. As we all know, this certainly can't be the right explanation. </p>
<p>Putting aside likely extreme bias and instrumental/experimental error, <strong>is there any bodily process at death that could potentially explain a small decrease in observed mass?</strong></p>
| [
{
"answer_id": 8291,
"pm_score": 5,
"text": "<p>Snopes.com gives a <a href=\"http://www.snopes.com/religion/soulweight.asp\" rel=\"noreferrer\">discussion of possible issues with the original experiment</a>. Evaporation or bowel or body movements for instance. I think the biggest complaint about the e... | [
{
"answer_id": 60367,
"pm_score": 0,
"text": "<p>There will be a quantifiable change in mass in any living object dies and then more with decomposition. The loss of energy from the living organisms changes the kinetic mass of the original subject. When death occurs other the process of decomposition now... |
8,295 | <p>By what mechanism does an obstructed bile duct (for example gallstones) cause steatorrhoea (excess fat in the stool)?</p>
| [
{
"answer_id": 8296,
"pm_score": 4,
"text": "<p>The function of bile produced by the liver and concentrated in the gall bladder is to aid in fat digestion. Bile acts as an emulsifier to allow the fat to be packaged into small droplets, micelles. The breakdown of fats into small micelles greatly increa... | [
{
"answer_id": 35348,
"pm_score": 2,
"text": "<p>Gallstones 'block' the plumbing system (i.e. the biliary tree) that drains bile produced in the liver from flowing into the duodenum through the ampulla of Vater. Since bile is a dietary detergent for fats (cholesterol, triglycerides, free fatty acids), t... |
8,297 | <p>Stress echocardiography means a pair of cardiac ultrasound imaging examinations, before and after exercise. I assume that coronary blood flow is increased after exercise. Is cardiac ultrasound technology capable of showing this blood flow difference?
<hr/>
Update: I emphasize that my question concerns <a href="https://en.wikipedia.org/wiki/Stress_echocardiography#Stress_echocardiography" rel="nofollow">stress echocardiography</a>, i.e. two echocardiography sessions before and after exercise (or pharmacological stress test) - not simply echocardiography.</p>
| [
{
"answer_id": 8296,
"pm_score": 4,
"text": "<p>The function of bile produced by the liver and concentrated in the gall bladder is to aid in fat digestion. Bile acts as an emulsifier to allow the fat to be packaged into small droplets, micelles. The breakdown of fats into small micelles greatly increa... | [
{
"answer_id": 35348,
"pm_score": 2,
"text": "<p>Gallstones 'block' the plumbing system (i.e. the biliary tree) that drains bile produced in the liver from flowing into the duodenum through the ampulla of Vater. Since bile is a dietary detergent for fats (cholesterol, triglycerides, free fatty acids), t... |
8,305 | <p>I understand multiple origin bubbles; DNA polymerase only synthesizes DNA from 5' to 3' and all that. But what I don't understand is why it has to be in fragments. Yes, DNA is anti parallel, and so the DNA elongates in opposite directions, since DNA polymerase can only go one way. But why not go on just like the leading strand? Why not continue happily along the DNA template continuously but in fragments? </p>
| [
{
"answer_id": 8321,
"pm_score": 3,
"text": "<p>I think you may have been misled by graphic representations of the process: The actual replication fork is very small as, like Rex Kerr mentions, it costs a lot of energy to keep DNA single stranded. </p>\n\n<p>Have a watch of <a href=\"https://www.youtube... | [
{
"answer_id": 8314,
"pm_score": 1,
"text": "<p>It's in fragments for efficiency. Single-stranded DNA is not very stable without <a href=\"http://en.wikipedia.org/wiki/Single-strand_binding_protein\" rel=\"nofollow\">proteins to stabilize it</a>. If you tried to replicate the entire strand in one go, ... |
8,307 | <p>According to this <a href="http://www.foxnews.com/science/2013/02/06/3d-printed-human-embryonic-stem-cells/" rel="nofollow">news</a>, scientists can use stem cells to print objects. So say theoretically, is there any possibility to print human beings? </p>
| [
{
"answer_id": 8311,
"pm_score": 4,
"text": "<p>The easiest answer to this question is NO. We will not be able to print humans any time soon, if ever. Despite the potential of the technology, it will likely still make more sense to use stem cells to fight genetic diseases, create limited cellular masses... | [
{
"answer_id": 8313,
"pm_score": 2,
"text": "<p>No.</p>\n\n<p>The reason is that development is extremely important for getting tissue organized on the appropriate scale. We can place groups of cells or a scaffold somewhere, but we can't assemble a working cell from component bits, much less make one t... |
8,356 | <p><a href="https://en.wikipedia.org/wiki/Slow_worm">Slow worms</a> are considered lizards as opposed to snakes, both are <a href="https://en.wikipedia.org/wiki/Reptile">reptiles</a>. Now I get that there are traits that distinguish them (eye lids, ears ...). But snake species themselves vary already quite a lot.</p>
<p>The <a href="https://en.wikipedia.org/w/index.php?title=Snake&oldid=552637116#Evolution">Wikipedia article on snakes</a> states:</p>
<blockquote>
<p>Based on comparative anatomy, there is consensus that snakes descended from lizards.</p>
</blockquote>
<p>But how comes slow worms are considered lizards despite the loss of their limbs during evolution, whereas the same evidently has happened to snakes?</p>
<p>What's the defining factor here? The time frame when it happened, that it happened independently (like the evolution of, say, an eye)?</p>
<p><strong>Note:</strong> I couldn't find any detailed descriptions about the alleged evolution of slow worms, whereas for snakes it is easy to find material.</p>
| [
{
"answer_id": 8377,
"pm_score": 5,
"text": "<p>You are correct that the reason is similar to that of convergent evolution of the eye.</p>\n\n<p>Both snakes and legless lizards are lizards (<a href=\"http://en.wikipedia.org/wiki/Squamata\" rel=\"noreferrer\">Squamata</a>) that have lost their legs. <str... | [
{
"answer_id": 8478,
"pm_score": 2,
"text": "<p>Slow worms share many characteristics with other lizards, such as the presence of eyelids, which no snake has. Leglessness in slow worms evolved separately than in snakes, as can be seen by the fact that other lizards in the same family, <a href=\"https://... |
8,401 | <p>We can cure many diseases nowadays, and thus the natural selection is very limited.
Plus, mankind spent the whole beginning of its existence in almost the same hostile environment, and that's where he evolved the most, whereas our environment is changing very quickly. So, can we say that mankind froze, if not stopped, its own evolution ?</p>
| [
{
"answer_id": 8402,
"pm_score": 3,
"text": "<p>Not at all. </p>\n\n<ul>\n<li>Mutations accumulate independent of medical progress. In fact harmful mutations which would otherwise cause an individual to die can now be \"cured\" thus if anything increasing the gene pool. </li>\n<li>Typically medical prog... | [
{
"answer_id": 8494,
"pm_score": 1,
"text": "<p>Keep in mind that most people live in environments where antibiotics are of limited availability and hygiene is not as rigorous as in the \"western\" world. Combine this with high population densities and you get, if anything, more natural selection due to... |
8,422 | <p>Recombinant technologies in micro-organisms being used to produce commercial and medically useful proteins like insulin are fairly common. </p>
<p>However some proteins are still produced commercially in genetically modified animals. Why are animals a better choice than microorganisms, and which are the most common proteins produced this way?</p>
| [
{
"answer_id": 8508,
"pm_score": 4,
"text": "<p><strong>The rationale</strong> for the choice of higher organisms as the producing source is based on costs and biological activity.</p>\n\n<ul>\n<li><em>Biological activity</em>. In their active forms, various proteins have\npost-translational modificatio... | [
{
"answer_id": 8424,
"pm_score": 3,
"text": "<p><a href=\"https://en.wikipedia.org/wiki/ATryn\">ATryn</a> is a human antithrombin produced in the milk of transgenic goats by GTC Biotherapeutics. It has FDA approval and I believe that it is available for prescription in the USA.</p>\n\n<p><strong>Added l... |
8,433 | <p>I am trying to learn about basic cell biology, and have what is probably an extremely simple question.</p>
<p>So this is how I understand it so far:
Proteins are made from amino acids. This process is called protein biosynthesis, which is carried out by the ribosomes. So proteins are made by the ribosomes in every single cell.</p>
<p>So are the proteins made by the ribosomes to stay in the cell? Or can a protein move to other cells, and if so, what's the reason behind it?</p>
| [
{
"answer_id": 8435,
"pm_score": 5,
"text": "<p>Yes. All proteins actually begin to get synthesized on cytoplasmic ribosomes but if they are going to be used for extracellular purposes, they are tagged and whole ribosome is taken to ER where protein synthesis is completed. The proteins are exocytosed wi... | [
{
"answer_id": 8710,
"pm_score": 1,
"text": "<p>I would like to complement dd3's answer a bit. It is about bacteria</p>\n\n<ol>\n<li><p>Bacteria secret enzymes outside. The bacterial membrane has import size limits and it is necessary for them to chop the big molecule into smaller pieces before import. ... |
8,469 | <p>Therapeutic antibodies, for example Rituximab which recognises CD20 on B lymphoma cells, can cause adverse effects (e.g. <a href="http://www.ncbi.nlm.nih.gov/pubmed/19399690" rel="nofollow">http://www.ncbi.nlm.nih.gov/pubmed/19399690</a>)</p>
<p>One reason behind these adverse effects could of course be an over-response of immune cells stimulated by the Fc region of antibodies attached to lymphona cells.</p>
<p>However, it could also be thinkable that the immune system launches a response against the antibody itself, recognising it as foreign. Does this occur? If so, what part of the injected antibody acts as the epitope recognised by immune cells as foreign?</p>
| [
{
"answer_id": 8474,
"pm_score": 3,
"text": "<p>The short answer is that antibodies are proteins like any other, and if an antibody from a foreign source is injected it can result in an immune response. This is, of course, exploited in the production of secondary antibodies for use in research (e.g. goa... | [
{
"answer_id": 8481,
"pm_score": 1,
"text": "<p>It is unlikely that an antibody would bind another antibody within just the human species. Human antibodies which bind to the human Fc portion cannot exist as they would be filtered by self tolerance mechanisms (as these B cells would be chronically activa... |
8,531 | <p>I've gathered that a centromere is a a region* where the DNA is bundles up even tighter (around <a href="http://en.wikipedia.org/wiki/Centromere#Structure" rel="nofollow">protein</a> different to Histone) and chromatids are 'joined'. However I'm still mostly in the dark regarding its physical structure and functioning.</p>
<p>At what point during DNA replication is the centromere created, and how is it created? How does it hold the chromatids together (what are its components)?</p>
<p>Specifically:</p>
<p>When it is being created (presumably during cell division) how is the positioning of the centromere controlled? Which flags are used by the enzymes in the process of making the centromere to tell them that it is the right spot: a section of DNA that 'says' "<em>Right part of centromere, to be attached to left part</em>"?</p>
<p>Secondly, after their condensation into chromosomes (e.g. during prophase), are the sister chromatids physically intertwined around each other** for the purpose of joining, or are they simply adjacent?</p>
<ul>
<li>Is there a 'loop' in the centromere slung over the adjacent chromatids to join them?</li>
<li>If they are intertwined, how is this achieved during DNA replication, whilst the non-centromere parts of the sister chromatids are not intertwined?</li>
</ul>
<p>How does the centromere break down to allow the chromatids to separate (e.g. during meoisis 2 and anaphase)?</p>
<p>On a somewhat unrelated note, what in the centromeres do the spindle fibres attach to, and how do the tips of the growing fibres notice it to head it its general direction?</p>
<hr>
<p>*(i.e. there is not a separate physical object dubbed 'the centromere', rather it is a collection of objects in a region)</p>
<p>**(That is, considering no other molecules than the chromatids, if you were to pinch the top and bottom ends of the left and right chromatids and pull them apart, could you separate them without them locking together (basically, do they intersect <a href="http://en.wikipedia.org/wiki/Knot_%28mathematics%29" rel="nofollow">knot</a>-theoretically)?)</p>
| [
{
"answer_id": 8542,
"pm_score": 3,
"text": "<p>There are many questions in your <em>question</em>. I'll try to answer each question pointwise.</p>\n\n<blockquote>\n <p>Which flags are used by the enzymes in the process of making the\n centromere to tell them that it is the right spot</p>\n</blockquot... | [
{
"answer_id": 54423,
"pm_score": 0,
"text": "<p>Supplemental </p>\n\n<blockquote>\n <p>When it is being created (presumably during cell division) how is the\n positioning of the centromere controlled?</p>\n</blockquote>\n\n<p>The marks of \"centromere\" is added the G1 (CENPA) and S phase (all other ... |
8,533 | <p>I've found it in my kitchen. It seems to be that he flew through the window from the street.</p>
<p>The country is Russia.</p>
<p><img src="https://i.stack.imgur.com/TVGP5.jpg" alt="Unknown flyting beetle. Top side">
<img src="https://i.stack.imgur.com/1lKu8.jpg" alt="Unknown flyting beetle. Bottom side"></p>
| [
{
"answer_id": 8551,
"pm_score": 4,
"text": "<p>This is <strong>Mealworm beetle</strong>, <em>Tenebrio molitor</em>, a species of darkling beetle.</p>\n\n<p><a href=\"http://en.wikipedia.org/wiki/Mealworm\" rel=\"nofollow noreferrer\">http://en.wikipedia.org/wiki/Mealworm</a></p>\n\n<p><img src=\"https:... | [
{
"answer_id": 8534,
"pm_score": 2,
"text": "<p>I am not an entomologist, I just happen to have worked on the genome of the red flour beetle, <em>Tribolium castaneum</em> and this looks very similar. A quick <a href=\"http://en.wikipedia.org/wiki/Confused_flour_beetle\" rel=\"nofollow noreferrer\">wikip... |
8,565 | <p>The wikipedia article on the <a href="http://en.wikipedia.org/wiki/Dopamine_transporter" rel="nofollow">dopamine transporter</a> gives examples of some drugs whose effects are mediated by the inhibition of the dopamine transporter, such as cocaine and amphetamines. Are there any drugs or substances whose mechanism of action involves increasing the activity of the dopamine transporter, i.e., a "DAT releaser?"</p>
| [
{
"answer_id": 8592,
"pm_score": 3,
"text": "<p>It's important to note the difference in mechanism between cocaine and meth. While cocaine blocks reuptake, meth makes VMAT - vesicular monoamine transport - leaky and actually reverses the transportation of dopamine, so that instead of transporting dopami... | [
{
"answer_id": 10226,
"pm_score": 0,
"text": "<p>Amphetamine isn't a DAT inhibitor. It actually causes exocytosis of dopamine vesicles. That is why cocaine is activity dependent as it's mechanism depends on presynaptic activity whereas amphetamine is activity independent.</p>\n"
}
] |
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