human biology - Why would taking antibiotics increase stamina and energy?

"There are antibiotics which contain carbohydrates, such as Gentamycin and Streptomycin (the aminoglycosides). These must be the antibiotics that could account for this phenomenon."

My conjecture that the carbohydrate moities contained within aminoglycosides account for the high energy is incorrect. Aminoglycosides are NEVER metabolized by the body, they are excreted out into the urine UNCHANGED. See here: http://www.ebmedicine.net/topics.php?paction=showTopicSeg&topic_id=43&seg_id=839

And even if it were possible to metabolize the carbohydrate molecules within them, the energy released would be far less than the energy consumed to break their linkages in the first place, thus placing a negative energy balance on the body, and thus, not providing the burst of energy that is apparently observed after taking antibiotics.

neuroscience - What is the full name of E. G. Gray?

Edward George Gray went by the first name of George, which isn't evident from his initials (he was born Edward George), but I happened to stumble upon the Wikipedia article below. From there, I found his obituary.

From his obituary:

GEORGE GRAY was a pioneer in the study of brain ultrastructure. He was Professor of Cytology in the anatomy department at University College London from 1967 to 1977 and then headed the Laboratory of Biological Ultrastructure at the National Institute for Medical Research.

From the Wikipedia article for synaptosome:

In a collaborative study with the electron microscopist George Gray from University College London, Victor P. Whittaker eventually showed that the acetylcholine-rich particles derived from guinea-pig cerebral cortex were synaptic vesicle-rich pinched-off nerve terminals. Whittaker coined the term synaptosome to describe these fractionation-derived particles and shortly thereafter synaptic vesicles could be isolated from lysed synaptosomes

sex - Can animals, like monkeys, be homosexual?

Cases of homosexuality have been described in numerous species, including primates, and the wikipedia link posted by @shigeta lists and describes some of them.

It could be difficult to untangle the difference between an animal not being able to identify sexes very well, or, deliberately mating to anyone and those actively making a choice to engage in intercourse with a same sex individual.

I there are some species where sexes are very difficult to tell apart so they may just go around having sex with anything that looks like the right species because the mating is relatively low cost so doesn't matter if the partner was male or female. This is one such example in sea snails:

"In a laboratory mate-choice experiment, male N. radiata preferred to
mate with females, indicating precopulatory sex identification. They
copulated with males, however, at the frequency of 37%, perhaps
because of sex misidentification."

Other likely candidates are those with little sexual dimorphism and those with sneaker males that mimic females.

I have also heard theoretical discussions (oh the joys of lunchtime in an evolutionary biology department!) which suggest it may be a way of individuals (particularly males) practising or keeping up fitness relating to sex or stimulating better sperm production etc.

Once you decide what constitutes "a homosexual animal" then it is perhaps easier to examine. I would say a homosexual animal is one that mates exclusively (or highly preferentially) with same sex individuals when given the choice.

Models of genetic and epigenetic inheritance have been used to suggest just how homosexuality could evolve and you can read more about it in this Biology.Stackexchange post.

So it seems that monkeys, and other animals, have been documented to exhibit homosexuality, reasons for them to do so could exist, and it could be a heritable trait which persists despite seemingly strong negative selection.

human biology - Distribution of nutrients throuought a drink made of plants?

In an attempts to eat my veggies for the day in one shot, I blended together a bag of salad with some water. The mixture separated by density, a thick top layer containing the bits of leaves, and a bottom layer of just juice. My question is: how many vitamins and nutrients are actually found in the top layer compared to the bottom, and how efficiently would the body process them?

biochemistry - Finding a easy and cheap method for dyeing dNTP

There may be such a dye, but I'm not aware of it. The standard way to measure dNTPs, and nucleic acids in general is by absorbance at 260 nm. This article has a table of molar extinction coefficients for dNTPs (Table 10.2). They are

        wavelength      molar extinction coefficient
dATP    259 nm          15,200
dCTP    280 nm          13,100
dGTP    253 nm          13,700
dTTP    267 nm           9,600

In practice for routine work with DNA you can use 260 nm and assume that an absorbance of 1 corresponds to [DNA] = 50 µg ml^-1. Using an average of the values in the Table, and disregarding the fact that these are actually at different wavelengths, and using an approximate average dNTP MW of 500, I calculate an absorbance for a 50 µg ml^-1 solution of all 4 dNTPs as 1.3, so that's a reasonable agreement given all of the assumptions I've made.

There are fluorescent dyes that can be used to measure DNA, but these rely upon the presence of stacked bases, so are not useful for free dNTPs.

So, bad news if you don't have a UV spectrophotometer. There are plans available for construction of simple spectrophotometers using Lego and a few optoelectronic components. These tend to use LEDs as a light source, but I don't know if UV LEDs are available.

genetics - Are there eukaryotes without introns?

I don't believe so. I have never come across a eukaryote that does not have introns although there are some genes that do not contain introns. Some eukaryotes like ciliates actually contain other non-intronic intergenetic regions that seem to be nonfunctional. These are called Internally Existed Sequences and are removed from the germ-line active micronucleus before going to form the transcriptionally active micronucleus. Interestingly, introns are also present in these organisms and are present in both the micro and macronucleus. These introns are spliced out in textbook fashion. I believe one of the organisms where introns was discovered was in Tetrahymena thermophila with the intron in the rDNA sequence.

eyes - Eyelids interconnected? - Biology

I cannot obviously speak for the specific case you mention (and, anyway, I am not a medical doctor so I would not make a diagnosis in any case), but one thing that comes to mind is that eyes are part of the immunologically privileged sites of the body. This means that an inflammatory response is not elicited in case of the introduction of an antigen.

I quote from Immunobiology by Charles Janeway

Some body sites are immunologically privileged. Tissue grafts placed in these sites often last indefinitely, and antigens placed in these sites do not elicit destructive immune responses.
Paradoxically, the antigens sequestered in immunologically privileged sites are often the targets of autoimmune attack; for example, brain autoantigens such as myelin basic protein are targeted in multiple sclerosis. It is therefore clear that this antigen does not induce tolerance due to clonal deletion of the self-reactive T cells. Mice only become diseased when they are deliberately immunized with myelin basic protein, in which case they become acutely sick, show severe infiltration of the brain with specific TH1 cells, and often die.
Thus, at least some antigens expressed in immunologically privileged sites induce neither tolerance nor activation, but if activation is induced elsewhere they can become targets for autoimmune attack (see Section 13-25). It seems plausible that T cells specific for antigens sequestered in immunologically privileged sites are more likely to remain in a state of immunological ignorance. Further evidence for this comes from the eye disease sympathetic ophthalmia (Fig. 13.36). If one eye is ruptured by a blow or other trauma, an autoimmune response to eye proteins can occur, although this happens only rarely. Once the response is induced, it often attacks both eyes. Immuno-suppression and removal of the damaged eye, the source of antigen, is frequently required to preserve vision in the undamaged eye.

evolution - Why does the apex of the human heart usually point to the left?

From a quick look at the paper @ChinmayKanchi links to (Palmer, 2004) it seems that:

All living vertebrates possess a heart that is conspicuously asymmetrical and normally displaced toward the left (Fishman & Chien, 1997).

So the heart orientation seems to be evolutionary conserved in vertebrates (as are many fundamental traits), and no specific explanation is needed for humans.

This is said with the reservation that human anatomy is not my subject field, and the refered paper also digs deeper into the molecular basis for the orientation/symmetry of organisms. For instance, it also says that:

Second, the molecular pathway directing hearts leftward—the nodal cascade—varies considerably among vertebrates (homology of form does not require homology of development) and was possibly co-opted from a preexisting asymmetrical chordate organ system.

so the molecular mechanisms governing this seems to differ between species. This could indicate that there is a selective pressure molding species into the same heart orientation. This is pure speculation on my part though.

I also want to mention that evolutionary outcomes doesn't have to have a "reason" (i.e. a selective advantage). Much depends on chance events and evolution can only act on what is present at the moment (i.e. is restricted by earlier evolutionary history).

human biology - Why do we yawn?

In an abstract, Brainerd at al. (2004) report the presence of yawn-like behaviors in "cartilaginous and ray-finned fishes, a lungfish, salamanders, caecilians, mammals, turtles, lizards, an alligator and birds".

So clearly the motor patterns necessary for this behavior evolved before air breathing and apparently have been conserved for ~400 million years. They reject the increased oxygen delivery hypothesis and associate yawning with stretching:

Yawning also has been thought to serve a similar physiological
function to stretching. We measured the stretching movements of fins
and limbs in association with yawns, and found that they follow the
same movement pattern as jaw opening and closing. This lends support
to the existing hypothesis that yawning and stretching serve a similar
function, but the detailed nature of this function remains unclear.

biochemistry - Amino acid characteristics that determine their chemical properties?

Sounds seriously like your homework, so it'd be better if you researched. However as a starting point amino acids can be polar and non-polar. These properties cause varying forces of attraction between amino acids and their surrounding environment. The location changes the way they can interact. Ask if you are unsure about something :)

molecular biology - Manipulation of gene expression using VP16 fusion and engrailed fusion to a transcription factor?

Today, a presenter briefly mentioned that gene expression in sea urchins during development might be manipulated using VP16 and engrailed fusions.

On a slide, it said that expression might be increased by mRNA injection or "VP16 fusion to binding domain of TF" and decreased by antisense morpholinos or "engrailed fusion to binding domain of TF".

I understand mRNA injection and antisense morpholinos, but I am unclear about the roles of VP16 and engrailed in this context. Can anyone clarify?

biochemistry - Diet of free-range herbivores

One key nutrient worth thinking about in the context of this question is vitamin B₁₂. Herbivores such as cows and sheep will derive this directly from the bacteria in their rumen. Rabbits produce two types of feces - soft and hard - and they eat the soft variety, rich in gut bacteria, as a source of nutrients like vitamin B₁₂. Gorillas are primarily herbivores, but are thought to derive their vitamin B₁₂ from insects, eaten purposefully or inadvertently.

So yes, herbivores derive this particular nutrient from non-plant sources.

cell biology - Can in the case of multiple sclerosis (MS), a too high osmotic pressure in the nerve, lead to a high intracellular concentration of potassium?

Can in the case of multiple sclerosis (MS),
a too high osmotic pressure in the nerve,
lead to a high intracellular concentration of potassium,
and also lead to 'pumping up' of nerve cells,
which then due to the strongly increased internal pressure,
the insulating myelin sheath can be pressed broken,
resulting in a lesion,
or a strong reduced transmission of stimuli ?

If that were to happen,
one can expect in cerebrospinal fluid,
cytokines, which are normally also a component of the nerve cell contents,
and that it wrongly can be interpreted,
as inflammatory reaction to a potential autoimmune disease.

Is there research of this ?

human biology - Is sperm contagious?

I'm unsure about the use of the word "contagious" here. If you would describe it as an organism "catching something" from another only once, this answer applies (vaguely perhaps).

One example of "contagious" sperm: sea urchins spray their sperm (called milt) into the surrounding water, so that it can hopefully fertilize roe, which are fish eggs. The eggs are also expulsed for some species, but for others they stay on the surface of the female sea urchin, as this Wikipedia article explains.

The gonads are lined with muscles underneath the peritoneum, and these allow the animal to squeeze its gametes through the duct and into the surrounding sea water where fertilization takes place.
...

In most cases, the eggs float freely in the sea, but some species hold onto them with their spines, affording them a greater degree of protection.

Thus, it's entirely possible for a female sea urchin to be bombarded by free-floating sperm, to ultimately fertilize the eggs on its surface. I don't know if one would strictly consider this a contagion, but it's what I initially thought of after reading the question.

---

When referring to sexually transmitted disease however, sperm in itself is not contagious, as it would require the pathogen to "tag along with it" in whichever environment (whether it be airborne or aquatic). Also, if considering impregnation as "contagious", physical contact would certainly be required.

In short: For humans, no. For sea urchins (and likely other aquatic animals), sort of.

genetics - Detecting Introns and Exons

Quick answer: we don't really know.

As WYSIWYG said, splice sites do have a sequence signature. The image below (taken from [1]) shows the consensus for human acceptor and donor sites:

In the images above, the size of a nucleotide represents its frequency at that location. As you can see, there is a clear signal around the splice sites and this signal is used by various programs that do splice site prediction. What is not quite clear yet is how the cell recognizes these signals. Sometimes a "perfect" (identical to the consensus) splice site is ignored by the cell in preference to one that we would consider "worse". This is further complicated by the presence of various downstream and upstream signals such as splicing enhancers, silencers and structural elements (loops, hairpins etc) in the mRNA molecule.

So, to answer your question yes there are start/end markers for introns/exons but they are far more complex than the simple START and STOP codons of transcription. We know know a lot about it but we still don't fully understand the details of splicing.

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References

Brent MR, Guigó R., Recent advances in gene structure prediction, Curr Opin Struct Biol. 2004 Jun;14(3):264-72.

How much energy does a cell expend maintaining its contents?

I'm going to take a stab at this. Its a difficult question to get right, just to put is in the right mood here.

Lets leave energy out of this as the proper term is structure. The cell is designed to compartmentalize itself to differentiate its own living tissue from other cells.

In this regard Alan Kay's analogy is pretty good. In multicellular organisms, individual cells (mostly) each maintain their own DNA and energy storage, though they get their nutrients and energy from outside. They create the organism as a whole by differentiation; each cell changes to take on a specialized role and depends on other cells to support it. E.g. in animals some cells/organs digest the food and distribute nutrients to the rest, others form the lung and help distribute oxygen and others scrub the blood of waste.

This is somewhat like good code design where functions are partitioned out into specialized parts of the software for the sake of maintainability and organization.

Somewhere after this point I think the analogy breaks down since after all the point of good coding practice is to organize the code for understanding within reasonable human conceptual limits. The cells and how they organize themselves are still plenty mysterious to us as they have their own definition of roles and function much of which is still being discovered today. For instance the many kinds of neurons in the brain and the sorts of structures they form are extremely diverse. We have few organizing principles for predicting how many cell types would exist in a system and these only create partial answers.

After all its just an analogy...

getting close to an answer?

evolution - Female preference for males who are already in a relationship

This is a widely researched topic in the overlap between social sciences and evolutionary biology. Evolution has become very influential in understanding human interaction and preferences.

This chapter from "The Adapted Mind : Evolutionary Psychology and the Generation of Culture" will give you an idea of how all this plays out in the big picture - its a fairly comprehensive review of many factors considered in human mate choice. The study may be psychological, but the logic is derived from biology these days. (stackexchange won't let me link to google books - you can search for the title and look at chapter 6).

Evolutionary tendencies will favor more successful offspring. But for people it includes not only the genetic qualities of the mate (appearance, height, disease resistance, health) but also social qualities (how reliable or willing a mate is to support offspring).

First off you can see that there are many many factors which women take into consideration in their preferences. Its commonly said they are more complex than men, but that's another question. You have to take a range of factors holistically including the social environment.

I can't find this particular issue addressed in the literature, but I think that it might be attractive to women in some social settings. If there is a lot competition for 'quality' mates or resources for instance - if you have very few secure males or pessimistic females might create pressure which would cause females to prefer males which were successful.

Its pretty easy to feel good about hypotheses like this. I couldn't find a specific study, but perhaps someone else will. There's a lot of such papers out there.

I should say that men are as easily led to do things by 'mate choice' psychology that aren't totally healthy or socially acceptable. That's biology.

pharmacology - How do Opioids Stimulate a Histamine Release?

Histamine is a neurotransmitter that also has peripheral functions such as the regulation of gastric acid secretions, allergic responses, etc. I know that opioids stimulate a release of histamine but I want to know how?

What exactly I would like answered is:

• Which of the opioid receptors are involved in the histamine release that opioids stimulate and to what extent are they?




• How does the activation of the opioid receptors in question lead to a release of histamine?




• Are there any ways of suppressing the histamine release stimulated by opioids without compromising the analgesia they elicit?

I would like an answer, not just links. However I would like you to cite journal articles, although a formal reference list is not required so long as I can easily find the link to the abstract/full article.