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Wednesday, 17 September 2008

News on genetics and evolution

Today:

  1. Gene Variation May Raise Risk of H.I.V., Study Finds
  2. Counting monkeys tick off yet another 'human' ability
  3. Frozen embryos give bouncier babies

Gene Variation May Raise Risk of H.I.V., Study Finds

Published: July 17, 2008

A genetic variation that once protected people in sub-Saharan Africa from a now extinct form of malaria may have left them somewhat more vulnerable to infection by H.I.V., the virus that causes AIDS. The gene could account for 11 percent of the H.I.V. infections in Africa, explaining why the disease is more common there than expected, researchers based in Texas and London say. The researchers said their finding had no immediate public health consequences. But if confirmed, it would offer an important insight into the biology of the virus.

The genetic variation has been studied in United States Air Force personnel, whose H.I.V. infections have been followed for 25 years. African-Americans who carried the variation were 50 percent more likely to acquire H.I.V. than African-Americans who did not, although their disease progressed more slowly, say researchers led by Sunil K. Ahuja, director of the Veterans Administration H.I.V./AIDS Center, San Antonio, and Matthew J. Dolan of the Uniformed Services University in Bethesda, Md. Their results were reported Wednesday in the journal Cell Host & Microbe.

David B. Goldstein, geneticist who studies H.I.V. at Duke University, said that the new result “would be pretty exciting if it holds up” and that many other researchers would now test it. “If the results are confirmed, it would mean that selection for resistance to malaria has created a vulnerability to infection with HIV-1,” he said, referring to the principal form of the virus.

The genetic variation, called a SNP, or snip, involves a change in one unit of DNA. This particular snip has a far-reaching consequence. It prevents red blood cells from inserting a certain protein on their surface. The protein is called a receptor because it receives signals from a hormone known as CCL5, which is part of the immune system’s regulatory system.

The receptor is also used by a malarial parasite called Plasmodium vivax to gain entry to the red blood cells it feeds on. About 10,000 years ago, people in Africa who possessed the SNP variation gained a powerful survival advantage from not being vulnerable to the ancestor of Plasmodium vivax. The SNP eventually swept through the population and the vivax parasite died out in Africa, to be replaced by its current successor, Plasmodium falciparum.

More than 90 percent of people in Africa now lack the receptor on their red blood cells, as do about 60 percent of African-Americans.

The possibility that the receptor has a bearing on H.I.V. infection first occurred to Robin Weiss, a biologist at University College, London, after he noticed that the virus seemed to be hitchhiking on red blood cells. Dr. Weiss, who wrote the new report with Dr. Ahuja and Dr. Dolan, showed in laboratory tests that H.I.V. latches onto the receptor in place of its intended guest, the CCL5 hormone.

The Texas-London research team is not certain how lack of the receptor promotes H.I.V. infection, but Dr. Ahuja said the red blood cells acted like a sponge for CCL5. Because CCL5 is known to obstruct multiplication of the virus, having lots of the hormone in the bloodstream may prevent infection. Conversely, people whose blood cannot soak up the hormone could be more vulnerable.

Dr. Weiss said the red blood cell receptor was similar to another receptor, CCR5, which occurs on the surface of the white blood cells that are H.I.V.’s major target. A small percentage of Europeans have a mutation that prevents the CCR5 receptor from being displayed on the surface of white blood cells, and they are protected against H.I.V.

It is somewhat puzzling that the absence of the two receptors has the opposite effect — vulnerability to H.I.V. when the red cell receptor is missing, protection from it when the white cell receptor is withdrawn. The researchers offer an explanation that they concede is far from straightforward.

Dr. Carl Dieffenbach, director of the AIDS division of the National Institute of Allergy and Infectious Diseases, said the new finding, if confirmed, would be intriguing because it pointed to the many ways in which pathogens have shaped the body’s receptors.

Although H.I.V. is too recent an infection to have left an evolutionary mark on the genome, human ancestors would have been exposed to malarial parasites and to S.I.V., which infects monkeys, and the genome still bears the marks of these challenges to survival. Better knowledge of these adaptations will help understand the biology of H.I.V. infection, he said. source

My comment: I have no idea if I didn't post this already since it's very very familiar to me. Probably I did. Sorry for those of you that find it annoying. Anyway, let's comment it from the point of view of evolution. Frequent argument against evolution is that we never saw it in action. Well, what better proof of its action. And the irony of life-how one thing that once made us strong, now makes us weak. As for HIV itself, I hope this research leads to a vaccination one day, since HIV is very unpleasant thing. Although I'm not sure if I would vaccinate me or my kids. When protection is as easy as using a condom always. I mean, you have to use it to keep syphilis away, anyway. Not to mention unwanted babies. So, why bothering torturing our immune system with one more vaccine. Though, on the evolutionary scale, I'm not sure if a vaccine trains a body response into our DNA or it just do it on the short scale. Because if it is on the long scale, it's not so bad, after all.

Counting monkeys tick off yet another 'human' ability

  • 11:03 01 July 2008
  • Ewen Callaway

At this rate a monkey might prove the Riemann hypothesis. Rhesus macaques have been shown to possess yet another numerical talent once thought unique to humans – they can simultaneously count audible beeps and dots on a computer screen.

Their ability to comprehend numbers not as just discrete images or sounds, but as abstract representations that can be combined suggests that such maths skills aren't unique to humans, says Kerry Jordan, a psychologist at Utah State University, Logan, US, who led the new study.

This sort of evidence "shows that [animals] have these precursors to math very early on in the evolutionary line and early on in development," she says.

Jordan and colleague Elizabeth Brannon, of Duke University in Durham, North Carolina, US, trained two eight-year-old female macaques to equate beeps to dots on a computer screen. So if a monkey heard seven beeps, it knew to tap a square on the screen displaying seven dots.

Next, the researchers tested the monkeys’ training in adding dots and beeps together.

The animals were presented dots of different sizes flash onto a screen. At the same time they heard a series of short tones.

To determine if the monkeys could combine the two, Jordan and Brannon showed the animals a screen with two numerical choices, represented as dots – one the correct sum, one incorrect.

Both monkeys did better than 50:50 – one added the sights and sounds correctly 72% of the time, the other 66% of the time.

Both monkeys tended to make mistakes when the right and wrong answers were numerically similar. For instance, if the choices were one and eight, the animals rarely got it wrong. But they found it harder to choose between, say, five and six.

People make the same kind of errors when making snap numerical judgements, such counting the number of people in a crowd, says Jordan, which is further evidence that our abstract maths skills aren't unique.

The monkey's ability to add numbers seen and heard together makes sense in the wild, says Jordan.

Irene Pepperberg, a psychologist at Harvard University in Cambridge, Massachusetts, who trained a parrot named Alex to add small sums, says the paper confirms observations in the wild.

Flycatchers, for instance, seem to communicate their mood to other birds using a numerical combination of song and wing motions. The more wing flicks and songs, the more likely it is to attack another bird, she says.

Journal reference: Cognition, DOI: 10.1016/j.cognition.2008.05.006 source

My comment:Animals learn abstract math! Because it is abstract for them to count beeps and dots. Again, an argument for evolution. I mean, given time and patience, you can practically teach a monkey to work with computer. At least, if you think carefully, that's what a computer is for. You tap things into it, it taps things into your brain via the eyes/ears. Isn't it great to live in such an intelligent universe?

Frozen embryos give bouncier babies

  • 09 July 2008

FROZEN embryos do better than fresh. That's the surprising conclusion of a study of children conceived by IVF which set out to address concerns that freezing might harm embryos.

Anja Pinborg of Copenhagen University Hospital in Denmark studied more than 1200 children born in the country between 1995 and 2006 as a result of IVF using frozen embryos and compared them with almost 18,000 children born after conventional IVF using fresh embryos.

The frozen embryos produced babies of roughly normal birth weight, while those from conventional IVF were on average about 200 grams lighter, Pinborg told the European Society of Human Reproduction and Embryology meeting in Barcelona, Spain, on 8 July.

Freezing an embryo shortly after fertilisation is unlikely to improve its viability, though. An alternative explanation, Pinborg argues, is that embryos able to survive the freezing and thawing process are likely to be healthier. "There's selection," she suggests.

What's more, women who have eggs frozen for later use tend to be younger and in better physical shape. And unlike women given conventional IVF, they will not be trying to establish a pregnancy immediately after being given hormone treatment to harvest their eggs - which it is thought could impair the process of implantation.

Pinborg's team also found that babies from frozen embryos were no more likely to suffer birth defects or neurological problems than conventional IVF babies.

From issue 2664 of New Scientist magazine, 09 July 2008, page 19 source
My comment: No comment, really. I just found it interesting and also, it's another argument for natural selection. Obviously it works in so many levels.

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