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April 2013 Archives

 OK, you could argue that you can't have a 'false' fact :) But that aside - I was recently introduced to this little gem of a video, True Facts About The Chameleon. Nice little sound-bites of information, rather lovely images - and the narrator's voice-over had me in stitches. (But he'll never replace Sir David Attenborough!)

Enjoy! (I'm going to sit & see what else he has to say about praying mantids: I've already heard the bits about having puppydog eyes and complex mouthparts that include "a moustache beneath [its] mouth - made of fingers" - a novel take on the animal's lower 'jaw'.)

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The other day one of my friends sent me a link to this discussion of a recently published paper. ('Published' in the sense that it's available through archiv, which I gather means it hasn't been through peer review.) The actual paper is available here. Basically, the authors claim that life has increased in complexity - they've used genome size as their measure - as it's evolved, and that extrapolating that trend backwards suggests that life evolved prior to the formation of the solar system.

But is genome size a particularly good proxy for complexity? Here's the graph that underpins the conclusions reached by Sharov & Gordon:complexity vs time.jpg

Do you see what they've done there? 'Worms' - which worms? For after all, there are a lot of them: at least 10,000 species of flatworms, more than 80,000 species of roundworms (aka nematodes), and another 10,000 or so annelids (including the familiar earthworm), not to mention the less familiar taxa such as velvet worms & the priapulids. As for the arthropods - well, good old Daphnia has more functional genes than we do. (The poetical Cuttlefish has a nice take on this story here.)

And I see that plants & protists have been left out altogether - unless they've been lumped in under the general heading 'eukaryotes'. Which is strange, because the overall genome size varies by 5 orders of magnitude** across the eukaryotes so far studied, so using a whole bunch of data points instead of the collective average, would make more sense. Unless that would spoil the nice straight line? (**Having said that, much of that variation is due to the number of introns & the quantity of non-coding DNA; however, the various regulatory sequence regions must surely come under the authors' heading of 'functional non-redundant genome'?)

I had also thought, on reading the review, that we were probably looking at an argument for panspermia. And I was right. This and other conclusions are presented in the abstract, & I note a certain amount of hubris in the assumption that humanity represents the only possibility of intelligent life in our universe (my emphasis).

(1) life took a long time (ca. 5 billion years) to reach the complexity of bacteria; (2) the environments in which life originated and evolved to the prokaryote stage may have been quite different from those envisaged on Earth; (3) there was no intelligent life in our universe prior to the origin of Earth, thus Earth could not have been deliberately seeded with life by intelligent aliens; (4) Earth was seeded by panspermia; (5) experimental replication of the origin of life from scratch may have to emulate many cumulative rare events; and (6) the Drake equation for guesstimating the number of civilizations in the universe is likely wrong, as intelligent life has just begun appearing in our universe.

A.A.Sharov & R.Gordon (2013) Life Before Earth arXiv:1304.3381v1  

PS Strangely, in a paper supposedly about biological evolution, the latter part of the article goes on to discuss technological (ie cultural) evolutionary change - I'm not convinced that it's appropriate to segue between a claimed link for genetic complexity & time, into the undoubted complexity and rapid 'evolution' of technology; apples & oranges, guys.

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As I've said previously, I find Facebook good for keeping up with friends & family, & profoundly irritating in its practice of 'targeting' ads to the user. Mind you, that offers endless opportunities for blogging (when one can find the time). And today I shall make use of that opportunity, for today FB offers me a link to "New Zealand's #1 way to lose weight" - and no, it's not a combination of exercise & eating sensibly!

First up, although the purported writer claims to be a New Zealander looking at use of a particular 'miracle' combination in NZ & documenting her own results, I couldn't help but notice that a) 'New Zealand' is mentioned but a single time in the blurb; b) she looks nothing like any of the women in her supposed 'before & after' photos (nor does she share a name with any of them - such sloppy editing, lol); & c) none of the women are from NZ.

Anyway, what's she raving about? There seems to be a new 'miracle weight loss/elixir of health' offered every week (there've been ads pushing reservatrol in the papers recently, for example). This particular wonder is the fruit of Garcina cambogia (aka Gambooge), native to Indonesia but grown through South-east Asia and parts of India & Africa, where it's widely used in cooking. However, it's also been claimed to have significant health benefits: the page FB promotes says

It is known to contain the highest antioxidant concentration [not according to this study]  of any known food, and is reported by many to have unprecented weight loss and health benefits. By combining Garcinia Cambogia [sic] supplements with a natural colon cleanse..., many people claim that their bodies have literally become "fat burning machines".

Ah, the wonders of pseudoscience - oxidation is required to 'burn' fat, so promoting an antioxidant to help lose fat sounds somewhat contradictory :) And colon 'cleanses' - money down the loo.

As for that claimed weight loss (the promotional web page claims 13 kgs!), well, the value of G.cambogia in achieving this has been put under the microscope. This approach is rather more reliable than relying on testimonials, even celebrity endorsements: like green coffee beans, gambooge has been promoted on Dr Oz's TV show as a "revolutionary" new fat buster.

Yet it isn't even new - its use has been studied for over 15 years. A study examining its potential as an anti-obesity agent, published back in 1998, concluded that

Garcinia cambogia failed to produce significant weight loss and fat mass loss beyond that observed with placebo.

And this meta-analysis of randomised clinical trials - published in 2011 - found that Garcinia extract (hydroxycitric acid) might cause short-term weight loss. However, they noted that in one trial those using the extract were more likely to suffer gastrointestinal upsets than people on a placebo, and went on to conclude that

The magnitude of the effect is small, and the clinical relevance is uncertain. Future trials should be more rigorous and better reported [my emphasis].

I'll stick to the exercise/sensible eating combo - it'll probably save me money too :)

 

S.B.Heymsfield, D.B.Allison, J.R. Vasselli, A.Pietrobelli, D.Greenfield & C.Nunez (1998) Garcinia cambogia (Hydroxycitric acid) as a potential antiobesity agent: a randomised controlled trial. JAMA 280 (18): 1596-1600. doi: 10.1001/jama.280.18.1596

I.Onakpoya, S.K.Hung, R.Perry, B.Wider & E.Ernst (2011) The use of Garcinia extract (hydroxycitric acid) as a weight-loss supplement: a systematic review and meta-analysis of randomised clinical trials. Journal of Obesity 2011. doi: 10.1155/2011/509038

 

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Many moons ago I used to do the occasional talk for Parents Centre ante-natal classes, on what to expect during a caesarian delivery. (I'd experienced an emergency C-section, so was happy to let others know what was involved.) So it was to be expected that this op.ed piece in today's NZ Herald (in the "Life & Style" section) would catch my eye. Initial interest turned to a thought that perhaps I was reading a spoof (check the date), but the paper described in this article does exist.

In January 2012 we brought together eleven researchers (midwives, scientists, epidemiologists, geneticists and epigeneticists) at the University of Hawaii and developed the EPIIC Hypothesis, which has just been published in Medical Hypothesis.

I did wonder in passing why epidemiologists & geneticists weren't counted as scientists, but what stood out is the fact the paper was published in Medical Hypotheses. (Being charitable, I'll assume the mis-spelling occurred in the editorial process.) In other words, there's no requirement to present any data in support of the hypothesis under discussion.

We have known for a while now that caesarean section is linked to longer-term health implications for the child...

As one of the commenters on the Herald piece points out, correlation is not the same as causation. Surely the researchers are aware of this?

We hypothesise that events during labour and birth - specifically the use of the synthetic hormone oxytocin, along with antibiotic use and caesarean sections - affect the epigenetic remodelling processes and the subsequent health of the mother and child.

Oxytocin is produced in large quantities during a normal labour; what would be the impact of that on epigenetic changes around the time of birth? In fact, the authors point the finger at more than (synthetic) oxytocin & C-sections, including forceps & vacuum-assisted deliveries as those potentially exerting a harmful effect. In describing this hypothesis, the op.ed. writer seems to be ignoring the fact that in at least some cases not using those interventions could result in the considerably more harmful outcome of death for mother &/or child. (To be fair, things are narrowed down somewhat in the MH paper.)

In the EPIIC hypothesis, we propose that physiological labour and birth have evolved to exert eustress (a healthy, positive form of stress) on the fetus, and that this process has an epigenomic effect on particular genes, particularly those that programme immune responses, genes responsible for weight regulation, and specific tumour-suppressor genes.

This is an interesting use of the term 'eustress', since its definitions suggest that whether or not stress is 'healthy' depends on how the individual perceives that stress, & whether they are left with a 'feeling of fulfilment' after experiencing it. At what point would a 'normal' labour cease to be so, & start generating 'non-healthy, negative' forms of stress? 

And how would this hypothesis be tested? The Medical Hypotheses paper (sorry; it's behind a paywall) does suggest a possible research program: essentially a long-term project tracking outcomes in individuals who birth experiences range from 

home births in the most familiar environment to the woman and without medical interventions ... to those born after elective caesarean section for breech presentation where there are no underlying medical complications...

and including

various ethnic groups, gestational ages, maternal ages and socioeconomic backgrounds.

With so many variables listed, proper data collection & analysis would be an extremely complex task. There is no mention of how this might be properly blinded. And - as that same Herald commenter says - why not go for an animal model first? And publish the results in a mainstream journal?

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