Nature 2006/10/12

Hmm. Lot’s of cool stuff in the Nature issue of 2006/10/12.

There’s the article on the use of ketamine to treat depression, and how its mechanism of action has got researchers rethinking what depression really is. Ketamine is a drug primarily used (legitimately) as an anesthetic agent in animals and young humans, and recreationally by adult humans as a psychedelic. Two-thirds of a study group of depressed people scored 50% on a quantitative assessment of depression, some of them finding themselves less depressed within two hours of treatment with ketamine. Ketamine’s target, unlike most anti-depressants currently prescribed that influence serotonin re-uptake, are receptors for glutamate in the brain. The resulting hypothesis is that in some patients, depression is the outcome of a brain that is over-producing glutamate, possibly as an abnormal response to stress. And there’s at least part of the rub. Depression may be a grab-bag of similar symptoms that patients may come to in a variety of different ways. It is certainly the case that patients with clinical depression may have to try several different anti-depressants before finding one that works well for their particular case; diagnostics do not yet make it easy to test a patient and determine the drug treatment of choice directly. Of interest was the sidebar item on John Lilly, the dolphin researcher with a thing for mind-altering drugs. My advisor, Bill Evans, had some anecdotes to tell about Lilly.

On the cosmological front, research reports that the transition from a quark-gluon plasma to hadronic matter was smooth rather than an abrupt phase transition, based upon high-performance computational analysis of the usual quantum chromo-dynamics (QCD) equations.

An article on the eyes of flies discusses how dipterans achieve higher visual resolution by subdividing their rhabdoms. Beyond the structure of the compound eye, it turns out that the rhabdom split plus some neural wiring leads to better visual acuity for dipteran flies.

Another item on vision concerns the co-option of plant photosynthetic chemistry by vertebrate species to transduce red light. This apparently happens in the wild in some fish. The brief communication shows that adding chlorin e_6, a chlorophyll derivative, to salamanders also boosted red light receptivity in vision. The article concludes that these results “highlight a potential for spectral enhancement by accessory chromophores in all opsin-based photoreception systems.”

While under the heading of ‘Developmental Biology’, a report on how signalling changes can lead to the growth of a two-chambered heart in the normally single-chambered tunicate Ciona intestinalis. This obviously has application to evolutionary questions about how changes in organs involving discrete numbers of sub-parts may come about. Evo-devo apparently comes up trumps for explaining such things as increasing the number of chambers in hearts.

A report on populations of pike in a lake with two almost completely separated basins shows that the populations match the “ideal free distribution” very well indeed. In animal populations, there are density-dependent effects, so high densities reduce overall fitness for members of the population. Different environments, such as different basins of a lake, can have their own and separate effect on fitness. The result is that there is an ideal free distribution such that members of a population cannot improve their fitness by changing from one environment to the other, and it turns out the the real-world pike populations match the ideal free distribution in the lake under study. This included a three-year period where human intervention changed the usual relationship in fitness between the two basins to make the one that generally had less fitness normally had higher fitness during that period. The pike population levels changed accordingly.

Of course, there is a clinker, the news item titled, “Intelligent design gets political”. Nature is years late with that assessment. ID always was political as socio-political movements can be. That it continues to be pushed politically hasn’t surprised those of us watching the antievolution movment.

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Wesley R. Elsberry

Falconer. Interdisciplinary researcher: biology and computer science. Photographer. Husband. Christian. Activist.