Histocompatibility Complex

Odour and mating preferences in humans

Two studies found MHC-associated odour preferences, and one study found MHC-dependent mating preferences. First, Wedekind et al. [7] found that women prefer the odour of MHC-dissimilar men. Forty-nine female and 44 male students were typed for their HLA-A, -B and -DR. The men wore a T-shirt for two nights. On the following day, the women were asked to judge the odours of six T-shirts each, and the shirts’ odours were judged as more ‘pleasant’ when they had been worn by men whose MHC genotype was different from that of the judging woman. In contrast, the odours were judged less pleasant when the MHC genotype of the odour-producing males and that of the judging women were similar. This difference in odour assessment was reversed when the women were taking oral contraceptives. Furthermore, the odours of MHC-dissimilar men more frequently reminded the women of their own present or former partners than did the odours of MHC-similar men. Although this is no direct evidence that odour influences mating preferences in humans (but see [16]), this study suggests that the MHC or linked genes influence human mate choice.

Second, Wedekind and Füri [17] tested whether odour preferences are aimed at producing offspring with certain MHC allele combinations (since certain combinations may offer increased resistance against pathogens) or simply increased heterozygosity. The former (but not the latter) possibility would specifically support the parasite hypotheses, since a preference for specific allele combinations that are beneficial under given environmental conditions would not be expected by the inbreeding avoidance hypothesis. The study was also designed to test for gender effects, and to get a first estimate of the amount of variance in pleasantness scorings that is correlated to the MHC. This time, 58 women and 63 men, all typed for their HLA-A, -B and -DR, were asked to score the odours of six T-shirts, worn always by the same two women and four men. The pleasantness scorings correlated again negatively with the degree of MHC similarity between smeller and T-shirt wearer in men and in women who were not using the contraceptive pill (but not in pill users). Depending on the T-shirt wearer, the amount of variance in the scorings of odour pleasantness that was explained by the degree of MHC similarity (=r²) varied between nearly 0 and 23%. The six T-shirt-wearers differed significantly from each other in the degree to which pleasantness scorings correlated to the MHC. There was no significant effect of gender in the correlation between pleasantness and MHC similarity: the highest r² was actually reached with one of the male odours sniffed by male smellers. Men and women who were reminded of their own mate/ex-mate when sniffing a T-shirt had significantly fewer MHC-alleles in common with this T-shirt wearer than expected by chance. This suggests again that the MHC or linked genes influence human mate choice. This study found no significant influence of the MHC on odour preferences when the degree of similarity between T-shirt wearer and smeller was statistically controlled. This negative finding suggests that body odour preferences are mainly influenced by the degree of similarity or dissimilarity at the MHC in the Swiss study population. The observed preferences would increase heterozygosity in the progeny, without producing specific combinations at the MHC. As mentioned above, a more specific choice of particular alleles would have provided strong evidence in favour of the parasite hypothesis, as opposed to the inbreeding avoidance hypothesis. However, this second study did not provide such evidence.

Third, Ober et al. [8] conducted a large study on American Hutterites, a reproductively isolated community of Austrian-German ancestry, and found direct evidence for MHC-disassortative mating preferences. Married couples were less likely to share MHC loci than expected by chance, even after inbreeding taboos were statistically controlled. However, Hedrick and Black [18] did not find such an effect in South Amerindians. Although the latter study had a lower statistical power (the sample size in their field study was much smaller than in the study by Ober et al. [8] while the heterogeneity on the MHC seemed to be larger, and fewer alleles had been analysed), the possibility remains that there might be population differences with respect to mating preferences. A study by Paterson and Pemberton [19] tested for MHC-dependent mate preferences in another mammal, the Soay sheep (Ovis aries). In contrast to the many studies in mice and the studies on humans mentioned above, they could not find any indication of such mate preferences in an unmanaged population on a Scottish island. Their analysis was conservative with respect to their conclusion, and their sample size was large, which strongly suggests that MHC-dependent mate choice is not universal among mammals.

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Too Much Sitting = Health Hazard

TOO MUCH SITTING CREATES A HEALTH HAZARD

Don't get too comfortable in that chair. Staying in your seat too long, too often could kill you.

Wed Jan 20, 2010 02:45 PM ET | content provided by Maria Cheng, Associated Press

Even if you also exercise regularly, prolonged periods of sitting could be a health risk.
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THE GIST:

• Prolonged sitting regularly could lead to obesity, heart disease and more.
• Even those who exercise regularly are at risk.

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Here's a new warning from health experts: Sitting is deadly.

Scientists are increasingly warning that sitting for prolonged periods -- even if you also exercise regularly -- could be bad for your health. And it doesn't matter where the sitting takes place -- at the office, at school, in the car or before a computer or TV -- just the overall number of hours it occurs.

Research is preliminary, but several studies suggest people who spend most of their days sitting are more likely to be fat, have a heart attack or even die.

In an editorial published this week in the British Journal of Sports Medicine, Elin Ekblom-Bak of the Swedish School of Sport and Health Sciences suggested that authorities rethink how they define physical activity to highlight the dangers of sitting.

While health officials have issued guidelines recommending minimum amounts of physical activity, they haven't suggested people try to limit how much time they spend in a seated position.

"After four hours of sitting, the body starts to send harmful signals," Ekblom-Bak said. She explained that genes regulating the amount of glucose and fat in the body start to shut down.

Even for people who exercise, spending long stretches of time sitting at a desk is still harmful. Tim Armstrong, a physical activity expert at the World Health Organization, said people who exercise every day -- but still spend a lot of time sitting -- might get more benefit if that exercise were spread across the day, rather than in a single bout.

Full Article: http://news.discovery.com/human/sitting-health-hazard.html

Where is the Chinese Food Truck?

I pose to you a question on this cold, snowy winter's day: Wherefore art the Chinese Food truck formerly of 36th and Market street? It appears to have been replaced with a mega-truck peddling greasy sandwiches. In spite of the new array lunch-time options, including the Irie cart with its raw chicken and Powelton pizza's offshoot proffering slices for less than $2 (has anyone given that a go yet?), I want my hot and sour soup today.

Mary, with your insider's ability to get brown rice served with meals, have you any idea where the kind man with mediocre-but-inexpensive meals has gone?

I could really go for an eggroll right now.

The Americanization of Mental Illness.......

By ETHAN WATTERS

Published: January 8, 2010

AMERICANS, particularly if they are of a certain leftward-leaning, college-educated type, worry about our country’s blunders into other cultures. In some circles, it is easy to make friends with a rousing rant about the McDonald’s near Tiananmen Square, the Nike factory in Malaysia or the latest blowback from our political or military interventions abroad. For all our self-recrimination, however, we may have yet to face one of the most remarkable effects of American-led globalization. We have for many years been busily engaged in a grand project of Americanizing the world’s understanding of mental health and illness. We may indeed be far along in homogenizing the way the world goes mad.

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Alex Trochut

This unnerving possibility springs from recent research by a loose group of anthropologists and cross-cultural psychiatrists. Swimming against the biomedical currents of the time, they have argued that mental illnesses are not discrete entities like the polio virus with their own natural histories. These researchers have amassed an impressive body of evidence suggesting that mental illnesses have never been the same the world over (either in prevalence or in form) but are inevitably sparked and shaped by the ethos of particular times and places. In some Southeast Asian cultures, men have been known to experience what is called amok, an episode of murderous rage followed by amnesia; men in the region also suffer from koro, which is characterized by the debilitating certainty that their genitals are retracting into their bodies. Across the fertile crescent of the Middle East there is zar, a condition related to spirit-possession beliefs that brings forth dissociative episodes of laughing, shouting and singing.

The diversity that can be found across cultures can be seen across time as well. In his book “Mad Travelers,” the philosopher Ian Hacking documents the fleeting appearance in the 1890s of a fugue state in which European men would walk in a trance for hundreds of miles with no knowledge of their identities. The hysterical-leg paralysis that afflicted thousands of middle-class women in the late 19th century not only gives us a visceral understanding of the restrictions set on women’s social roles at the time but can also be seen from this distance as a social role itself — the troubled unconscious minds of a certain class of women speaking the idiom of distress of their time.

“We might think of the culture as possessing a ‘symptom repertoire’ — a range of physical symptoms available to the unconscious mind for the physical expression of psychological conflict,” Edward Shorter, a medical historian at the University of Toronto, wrote in his book “Paralysis: The Rise and Fall of a ‘Hysterical’ Symptom.” “In some epochs, convulsions, the sudden inability to speak or terrible leg pain may loom prominently in the repertoire. In other epochs patients may draw chiefly upon such symptoms as abdominal pain, false estimates of body weight and enervating weakness as metaphors for conveying psychic stress.”

In any given era, those who minister to the mentally ill — doctors or shamans or priests — inadvertently help to select which symptoms will be recognized as legitimate. Because the troubled mind has been influenced by healers of diverse religious and scientific persuasions, the forms of madness from one place and time often look remarkably different from the forms of madness in another.

That is until recently.

For more than a generation now, we in the West have aggressively spread our modern knowledge of mental illness around the world. We have done this in the name of science, believing that our approaches reveal the biological basis of psychic suffering and dispel prescientific myths and harmful stigma. There is now good evidence to suggest that in the process of teaching the rest of the world to think like us, we’ve been exporting our Western “symptom repertoire” as well. That is, we’ve been changing not only the treatments but also the expression of mental illness in other cultures. Indeed, a handful of mental-health disorders — depression, post-traumatic stress disorder and anorexia among them — now appear to be spreading across cultures with the speed of contagious diseases. These symptom clusters are becoming the lingua franca of human suffering, replacing indigenous forms of mental illness.

DR. SING LEE, a psychiatrist and researcher at the Chinese University of Hong Kong, watched the Westernization of a mental illness firsthand. In the late 1980s and early 1990s, he was busy documenting a rare and culturally specific form of anorexia nervosa in Hong Kong. Unlike American anorexics, most of his patients did not intentionally diet nor did they express a fear of becoming fat. The complaints of Lee’s patients were typically somatic — they complained most frequently of having bloated stomachs. Lee was trying to understand this indigenous form of anorexia and, at the same time, figure out why the.........................

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