Human hibernation is not possible. Nothing new there.

I promised to get back to the article that Saikishan pointed me to. It occurs to me given the debate that was going on that Saikishan must have simply typed in “is human hibernation possible?” into google and sent us the first scholarly article link that popped up! Regardless, the research is interesting, even if the title has more hype than necessary. The article is from the Annual Review of Medicine, and has been written by Cheng Chi Lee from the U. Texas.

ResearchBlogging.org Some mammals like bears are known to hibernate over winter, while others like hamsters or mice are known to go into a circadian state of  torpor (circadian meaning ‘daily’; they showed this by ablating the suprachiasmatic nucleus which is known to control the circadian clock and finding that the torpor state is correspondingly disrupted). The difference between torpor and hibernation seems to be one of degree, says the author. The present article deals with the chemistry behind this transition from activity to torpor. Two compounds, 2-deoxyglucose and hydrogen sulphide are already known to induce a state of torpor in animals. The article finds that a third compound called 5′-adenosine monophosphate (if you know what ATP is, you get to AMP by taking away two ‘P’s – phosphate groups) can also be used. 5’-AMP is – or was, the article was written in 2008 and I haven’t checked for newer research – the only naturally occurring compound that can do this that we know of (or, as appropriate, knew of).

The first of the three compounds, 2-deoxygenase induces torpor by inhibiting glycolysis – stopping glucose from being utilised. Under administration, hamsters readily go into torpor even when they are in proper light. The second compound, H2S, was found to bring the body temperature of mice down to 15 C and a state of suspended animation for up to six hours. The precise mechanisms behind the effects these compounds have on mice and hamsters are as yet unknown. However, they both work by stopping production of ATP – 2-deoxygenase does this by stopping glucose from being oxidised to ATP and NADH (outside mitochondria, if that means anything to you), whereas H2S disrupts the oxidation inside mitochondria (by inhitibing cytochrome C, again if that means anything to you). Decreased ATP production and consumption are observed in all hibernating behaviour.

If this can happen with mice and hamsters, could other mammals too have retained similar biochemistry? We know that organs can be stored for several hours on ice, be transplanted into patients, and return to normal functioning. There are also cases of where people have been stuck in extreme cold and gone into hypothermia without dying, and even recovering full bodily function. The author deduces from this that non-hibernators’ organs are capable of withstanding extreme hypoxic stress if their metabolic demands are reduced. I should point out that both mice and hamsters do have natural torpor states. So, given that the difference between hibernation and torpor is one of degree, calling mice ‘non-hibernating mammals’ seems like stretching it.

Hibernation necessarily requires a dark environment. The author reports that using a gene analysis, a link was discovered between the circadian light-dark cycle and something called procolipase (‘lip-ase’ means something along the lines of ‘breakdown lipids’) which is only expressed in the liver and the pancreas, that procolipase was activated in peripheral organs in mice that were kept in the dark, and that the expression of procolipase was shut down in various organs when the animals were exposed to light. The only way a whole-body response like that could take place is if the circulatory system is involved, and if the molecule behind all this were a circulatory molecule with a circadian profile. The researchers found the 5′-AMP molecule to fit the bill, as it were.

5′-AMP works by inducing the procolipase gene expression, but with a time-lag, suggesting that this is an indirect process. 5′-AMP causes severe hypothermia in mice (body temperature of 25 C as opposed to 37C normally), and a severe reduction in heart-rate. 5′-AMP must, suggests the author, inhibit the natural thermoregulation of the body, causing core body temperature to drop and metabolism to slow down. It has been shown to also play a role in the regular torpor states of mice. However, what core temperature can be reached safely depends on what animal we’re talking about. Usually, the larger the animal, the smaller the reduction in temperature from 37C.

I will say nothing more here of the mechanism the author proposes for the effect of 5′-AMP; I don’t understand much of it. What is clear, however, is that this research has found a natural molecule that plays a role in torpor induction, and if it is true that other mammals have similar biochemical pathways as the mice, this molecule could be used to induce hypothermia and save lives in clinical applications (trauma, heart attacks, strokes, and other major surgeries). What this must tell you, however, is that none of this is a reason to go ‘oh, wow, human hibernation!’. We can already induce hypothermia in patients to save their organs. This is now done by literally putting the patient on ice, which is an inefficient way of doing it. A chemical hypothermia-inducing agent would be better.

Lee, C. (2008). Is Human Hibernation Possible? Annual Review of Medicine, 59 (1), 177-186 DOI: 10.1146/annurev.med.59.061506.110403

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Of irrationality and compartmentalisation

Forgive the sesquipedalian title. A surprising email-debate erupted in the EMU recently. This mail-a-thon started with something RR shared about the ‘you will get 72 virgins in heaven if you follow the quran‘ belief of Islam, from wikiislam – the online resource on Islam (yes, such a thing apparently exists).

Which led to some of us arguing that this stupidity of Islam is only symptomatic of what is wrong with religion in general. I commented that even somebody as seemingly moderate in his religion as Gandhi believed in the power of semen. This observation, which I naively assumed would clinch the argument, was only confirmed when RR volunteered that he believed in the power of semen too, and commented that I shouldn’t simply oppose the idea for the sake of opposition. RR also volunteered that he believed that people could survive without food, and that he personally knew somebody who has done it.

Lots of sarcasm and satire followed.

Which was all fun until ‘I-am-a-professional-centrist’ SS came along and started to defend the idea that human beings can live without food as being plausible. He even brought along references from medical literature. (Oh, never fret: while the research is perfectly fine, even the authors themselves dismiss the idea of human hibernation… right in the abstract. More about this research article here. [Update(12/4/2012): link added])

Now, both RR and SS are entirely sensible people… most of the time. But, in this case, they both took positions which – to put it gently – required serious mental gymnastics on their part.

Which brings me to the title. It has been my experience that otherwise competent and intelligent people can be irrational when it comes to some ideas. This cognitive dissonance requires that people compartmentalise – keep our rational minds from analysing some ideas we’ve invested in, and we do it very well indeed. This accounts for why, even among scientists, a significant majority are theists (this statistic changes if you ask only scientists from the very top of their fields, but never mind that).

Cue Jesus and Mo!

What we do this for is a complicated question to answer. It seems to me that social pressures are a factor. The ideas which one wants to keep out of reach of rationality are a function of one’s social milieu. The renowned biologist Ken Miller is known to believe in the literal trans-substantiation of bread and wine into the flesh and blood of Christ. Why could this be? It isn’t a stretch to argue that this is precisely because Miller was brought up Catholic. Francis Collins, the director of the human genome project, is known to be a kook when it comes to the positions he will take (on when in the process of evolution human beings attained the ‘image of god’, for example). It isn’t hard to see that this is because his faith in the belief that ‘man is made in the image of god’ is important to him.

I would even argue that people can defend a position even when it is patently irrational, simply because others in their peer-group hold the position. There are experiments which show that people ‘fell in line’ with an obviously wrong answer because other people (who were planted in the experiment by the experimenters) before them gave that wrong answer. But I think this phenomenon can be even more subtle. It seems to me that putting up a defence of one’s friends is important to people. Some of us do it overtly, some not so overtly. It seems to me to be important to us that our friends are right.

I’d like to end with a caveat. They say the worst thing you can do in a debate is to psycho-analyse your opponent, which seems to me a reasonable thing to keep in mind. Also, it is important to me that one doesn’t have to be on guard about what they say among friends – people deserve friends who will try and not judge everything that is said. So, if you don’t already know who RR and SS are, their identities are none of your business.

[Update (April 9, 12pm): The last two sentences in the last paragraph strike me as being hypocritical, given what this post is about. By all means, discount them. Lesson learnt.]