Archive for the ‘Darwin’ Category

Nearly 150 years ago, Charles Darwin recognized that facial expressions not only communicate the emotions we feel but intensify them, by sending cues back to the brain. In the ensuing decades, researchers proved again and again that we can influence the way we feel by the visage we project. Smiling can help us feel happier. Frowning can make us feel angrier.

But it was only in the past few years that a dermatologist from Chevy Chase, Md., noticed that some of the patients whose brows he temporarily paralyzed with Botox, to remove wrinkles, began to feel relief from depression. That physician, Eric Finzi, took his idea to psychiatrist, Norman Rosenthal, who teaches at Georgetown Medical School and had spent many years studying how light and odors, transmitted to the brain through the nerves that connect it with the eyes and nose, affect our moods.

Now there have been three small studies that show that Botox injections can help with depression. In the latest, published in the current issue of the Journal of Psychiatric Research, Finzi and Rosenthal showed that 17 of 33 patients experienced better than 50 percent reductions in their depression symptoms after a single Botox injection, and 27 percent of the group saw their depression go into remission. The study confirms a similar one reported in 2012 by German researchers Tillmann Kroger and Axel Wollmer, who spoke of their findings at a meeting of the American Psychiatric Association in New York this past weekend.

“There are several nerves, about 12 of them, that go straight into the brain through the skull,” Rosenthal told me Tuesday. “…We’re used to thinking of them in terms of their outbound messages or signals. We’re not used to thinking of them in terms of their inbound messages.”

The idea holds promise as a supplement or alternative to anti-depressants and psychotherapy for treating depression, according to Rosenthal. Minuscule amounts of Botox — which is made from the lethal botulinum toxin — are injected into the facial muscles and don’t even enter the bloodstream. The procedure has shown no side-effects.

If the whole idea seems almost too outlandish to believe — as it did for me — Rosenthal was quick to point out that he was laughed at 30 years ago, when he proposed the idea of “seasonal affective disorder” and the notion that exposing people to bright light in the depths of winter could help with that kind of depression. “Now, it’s ubiquitous,” he said. “Then, they thought it was ridiculous.”

The treatment isn’t perfect. Botox is expensive, at about $400 per dose, wears off in about three months and isn’t covered by insurance. And as the studies showed, it doesn’t work for everyone.

But the botulinum toxin already is used to treat a wide variety of medical conditions. Perhaps depression is next.

http://www.washingtonpost.com/news/to-your-health/wp/2014/05/07/using-botox-to-treat-depression-seriously/

sn-homosexuality

 

From a strictly Darwinian viewpoint, homosexuality shouldn’t still be around. It isn’t the best way to pass along one’s genes, and to complicate the picture further, no “gay genes” have even been identified. According to a newly released hypothesis, the explanation may not lie in DNA itself. Instead, as an embryo develops, sex-related genes are turned on and off in response to fluctuating levels of hormones in the womb, produced by both mother and child. This tug of war benefits the unborn child, keeping male or female development on a steady course even amid spikes in hormones. But if these so-called epigenetic changes persist once the child is born and has children of its own, some of those offspring may be homosexual, the study proposes.

Evolutionary geneticist William Rice of the University of California, Santa Barbara, felt there had to be a reason why homosexuality didn’t just fade away down the generations. Research estimates that about 8% of the population is gay, and homosexuality is known to run in families. If one of a set of identical twins is gay, there’s a 20% probability that the other will be, too.

Furthermore, Rice notes, “homosexuality isn’t just a human thing.” Among California gulls, which he watches from his office window, about 14% of pairs are female-female. In Australian black swans, some 6% of pairs are male-male, and 8% of male sheep are attracted exclusively to male partners.

But many genetic screens have failed to turn up genes that are responsible for sexual orientation. So to find out what makes homosexuality persist, Rice and colleagues began a comprehensive survey of the literature.

According to conventional wisdom, an embryo becomes a boy when a gene on the Y chromosome triggers the development of testes, which then begin to produce male sex hormones, including testosterone, at about the 8th week of gestation. With no Y chromosome and hence no testosterone, the embryo becomes a girl.

But testosterone doesn’t explain everything, the researchers found. For one thing, female fetuses are exposed to small amounts of the hormone from their adrenal glands, the placenta, and the mother’s endocrine system. At many key points of gestation, male and female fetuses are often exposed to similar amounts of testosterone. Levels of the hormone can even be higher than normal in females and lower than normal in males without any effect on genital or brain structure.

Rice and his co-workers were more intrigued by studies showing that male and female fetuses respond differently to the hormones that surround them, even when one hormone is temporarily higher. In their study, published online today in The Quarterly Review of Biology, the authors propose that differences in sensitivity to sex hormones result from “epigenetic” changes. These are changes that affect not the structure of a gene but when, if, and how much of it is activated—by chemically altering a gene’s promoter region or “on” switch, for example. Epigenetic changes at key points in the pathway through which testosterone exerts its effects on the fetus could blunt or enhance the hormone’s activity as needed, the authors suggest.

Although epigenetic changes are usually temporary, they involve alterations in the proteins that bind together the long strands of DNA. Thus, they can sometimes be handed down to offspring. According to the hypothesis, homosexuality may be a carry-over from one’s parents’ own prenatal resistance to the hormones of the opposite sex. The “epi-marks” that adjusted parental genes to resist excess testosterone, for example, may alter gene activation in areas of the child’s brain involved in sexual attraction and preference. “These epigenetic changes protect mom and dad during their own early development,” Rice says. The initial benefit to the parents may explain why the trait of homosexuality persists throughout evolution, he says.

“The authors have done a terrific job providing a mechanism for genetic variation, especially a variation that might not be expected to persist because it’s so tightly bound to reproduction,” says evolutionary biologist Marlene Zuk of the University of Minnesota, Twin Cities. But she adds that to go from changes in gene expression to why someone is attracted to a person of the same sex is a question for which science may never fill in all the blanks.

http://news.sciencemag.org/sciencenow/2012/12/homosexuality-may-start-in-the-w.html?ref=hp