Chapter 8. Hormones and Sex

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By Daisy Yuhas, When the shy, dark-haired boy met with clinicians for a full psychiatric evaluation two years ago, almost everything about him pointed to autism. W. had not spoken his first words until age 2. He was at least 4 before he could form sentences. As he got older, he was unable to make friends. He struggled to accept changes to his routine and maintain eye contact. And despite having an average intelligence quotient, he was unusually attached to objects; at age 11, he still lugged a bag of stuffed animals with him everywhere he went. But something else was clearly at work, too. “He had these things that he would call day dreams,” recalls Jennifer Foss-Feig, assistant professor of psychiatry at the Icahn School of Medicine at Mount Sinai in New York. When she evaluated W., she noticed that he would often gaze into an empty corner of the room—particularly when he seemed to suspect that she wasn’t paying attention to him. (For privacy reasons, Foss-Feig declined to reveal anything but the child’s first initial.) Occasionally, he would speak to that space, as though someone else were there. His parents, she recalls, were worried. They explained to Foss-Feig that their son had what he called an “imaginary family.” But W.’s invisible playmates weren’t of the usual harmless variety that many children have; they seemed to be a dangerous distraction both at home and at school. On one occasion, he wandered through a busy parking lot, seemingly oblivious to the oncoming traffic. © 2017 Scientific America

Keyword: Autism; Schizophrenia
Link ID: 23874 - Posted: 07.25.2017

By JANE E. BRODY Problems with estrogen and testosterone, the body’s main sex hormones, tend to attract widespread public interest. But we might all be better off paying more attention to a far more common endocrine disorder: abnormal levels of thyroid hormone. Thyroid disorders can affect a wide range of bodily functions and cause an array of confusing and often misdiagnosed symptoms. Because the thyroid, a small gland in the neck behind the larynx, regulates energy production and metabolism throughout the body, including the heart, brain, skin, bowels and body temperature, too much or too little of its hormones can have a major impact on health and well-being. Yet in a significant number of people with thyroid deficiencies, routine blood tests fail to detect insufficient thyroid hormone, leaving patients without an accurate explanation for their symptoms. These can include excessive fatigue, depression, hair loss, unexplained weight gain, constipation, sleep problems, mental fogginess and anxiety. Women of childbearing age may have difficulty getting pregnant or staying pregnant. Although thyroid disorders are more common in adults, children, whose cognitive and physical development depend on normal thyroid function, are not necessarily spared. In a review article published last year in JAMA Pediatrics, doctors from the Children’s Hospital of Philadelphia pressed primary care doctors to recognize childhood thyroid disease and begin treatment as early as the second week of life to ensure normal development. Hypothyroidism — low hormone levels — in particular is often misdiagnosed, its symptoms resembling those of other diseases or mistaken for “normal” effects of aging. Indeed, the risk of hypothyroidism rises with age. Twenty percent of people over 75, most of them women, lack sufficient levels of thyroid hormone that, among other problems, can cause symptoms of confusion commonly mistaken for dementia. © 2017 The New York Times Company

Keyword: Hormones & Behavior
Link ID: 23866 - Posted: 07.24.2017

Jon Hamilton Professional fighter Gina Mazany practices during a training session at Xtreme Couture Mixed Martial Arts in Las Vegas. She well remembers her first concussion — which came in her first fight. "I was throwing up that night, Mazany says. Bridget Bennett for NPR Gina Mazany grew up in Anchorage, Alaska. And that's where she had her first fight. "It was right after I turned 18," she recalls. A local bar had a boxing ring, and Mazany decided to give it a shot. Her opponent was an older woman with a "mom haircut." "She beat the crap out of me," Mazany says. "Like she didn't knock me out, she didn't finish me. But she just knocked me around for three rounds. And I remember, later that night I was very, very nauseous. I was throwing up that night." It was her first concussion. Concussions are just part of her sport, Mazany figures, but says she tries to protect herself, and to not give anyone else a head injury--at least in training. Bridget Bennett for NPR Thanks to research on boxers and football players, both athletes and the public are becoming more aware of the dangers of sports-related head injuries. Yet there is little data on participants like Mazany. That's because, unlike the vast majority of athletes studied, she is a woman. "We classically have always known the male response to brain injury," says Mark Burns, at Georgetown University. But there have been remarkably few studies of females. The bias runs throughout the scientific literature, even in studies of mice. © 2017 npr

Keyword: Brain Injury/Concussion
Link ID: 23865 - Posted: 07.24.2017

by Laurel Hamers The tempo of a male elephant seal’s call broadcasts his identity to rival males, a new study finds. Every male elephant seal has a distinct vocalization that sounds something like a sputtering lawnmower — pulses of sound in a pattern and at a pace that stays the same over time. At a California state park where elephant seals breed each year, researchers played different variations of an alpha male’s threat call to subordinate males who knew him. The seals weren’t as responsive when the tempo of that call was modified substantially, suggesting they didn’t recognize it as a threat. Modifying the call’s timbre — the acoustic quality of the sound — had the same effect, researchers report August 7 in Current Biology. Unlike dolphins and songbirds, elephant seals don’t seem to vary pitch to communicate. Those vocal name tags serve a purpose. During breeding season, male elephant seals spend three months on land without food or water, competing with rivals for social status and mating rights. Fights between two blubbery car-sized animals can be brutal. “We’ve seen males lose their noses,” says Caroline Casey, a biologist at the University of California, Santa Cruz. For lower-ranking males, identifying an alpha male by his call and then backing off might prevent a beach brawl. |© Society for Science & the Public 2000 - 2017

Keyword: Animal Communication; Sexual Behavior
Link ID: 23859 - Posted: 07.21.2017

Xiaomeng (Mona) Xu, assistant professor of experimental psychology, and Ariana Tart-Zelvin, If you have experienced the evolution from having a crush to falling in love, it may seem like the transition happens naturally. But have you ever wondered how we make such a huge emotional leap? In other words, what changes take place in our brains that allow us to fall deeply in love? Stephanie Cacioppo, a psychologist at the University of Chicago who has studied the neuroscience of romantic love for the past decade, explains that the process involves several complex changes, particularly in the brain’s reward system. More specifically, in a 2012 review of the love research literature Lisa Diamond and Janna Dickenson, psychologists at the University of Utah, found romantic love is most consistently associated with activity in two brain regions—the ventral tegmental area (VTA) and the caudate nucleus. These areas play an essential role in our reward pathway and regulate the “feel good” neurotransmitter dopamine. In other words, during the early stages of love you crave the person because he or she makes you feel so good. And over time these feelings persist. Our neuroimaging research and that of others suggests that once you are in love—as long as the relationship remains satisfying—simply thinking about your partner not only makes you feel good but can also buffer against pain, stress and other negative feelings. © 2017 Scientific American,

Keyword: Emotions; Sexual Behavior
Link ID: 23852 - Posted: 07.20.2017

Hannah Devlin Science correspondent Brash, brawny and keen to impose their will on anyone who enters their sphere of existence: the alpha male in action is unmistakable. Now scientists claim to have pinpointed the biological root of domineering behaviour. New research has located a brain circuit that, when activated in mice, transformed timid individuals into bold alpha mice that almost always prevailed in aggressive social encounters. In some cases, the social ranking of the subordinate mice soared after the scientists’ intervention, hinting that it might be possible to acquire “alphaness” simply by adopting the appropriate mental attitude. Or as Donald Trump might put it: “My whole life is about winning. I almost never lose.” Prof Hailan Hu, a neuroscientist at Zhejiang University in Hangzhou, China, who led the work said: “We stimulate this brain region and we can make lower ranked mice move up the social ladder.” The brain region, called the dorsal medial prefrontal cortex (dmPFC), was already known to light up during social interactions involving decisions about whether to be assertive or submissive with others. But brain imaging alone could not determine whether the circuit was ultimately controlling how people behave. The latest findings answer the question, showing that when the circuit was artificially switched on, low-ranking mice were immediately emboldened. “It’s not aggressiveness per se,” Hu said. “It increases their perseverance, motivational drive, grit.” © 2017 Guardian News and Media Limited

Keyword: Aggression; Sexual Behavior
Link ID: 23836 - Posted: 07.14.2017

By PAM BELLUCK How we look at other people’s faces is strongly influenced by our genes, scientists have found in new research that may be especially important for understanding autism because it suggests that people are born with neurological differences that affect how they develop socially. The study, published on Wednesday in the journal Nature, adds new pieces to the nature-versus-nurture puzzle, suggesting that genetics underlie how children seek out formative social experiences like making eye contact or observing facial expressions. Experts said the study may also provide a road map for scientists searching for genes linked to autism. “These are very convincing findings, novel findings,” said Charles A. Nelson III, a professor of pediatrics and neuroscience at Harvard Medical School and Boston Children’s Hospital, who was not involved in the research. “They seem to suggest that there’s a genetic underpinning that leads to different patterns of brain development, that leads some kids to develop autism.” Dr. Nelson, an expert in child development and autism who was an independent reviewer of the study for Nature, said that while autism is known to have a genetic basis, how specific genes influence autism’s development remains undetermined. The study provides detailed data on how children look at faces, including which features they focus on and when they move their eyes from one place to another. The information, Dr. Nelson said, could help scientists “work out the circuitry that controls these eye movements, and then we ought to be able to work out which genes are being expressed in that circuit.” “That would be a big advance in autism,” he said. In the study, scientists tracked the eye movements of 338 toddlers while they watched videos of motherly women as well as of children playing in a day care center. The toddlers, 18 months to 24 months old, included 250 children who were developing normally (41 pairs of identical twins, 42 pairs of nonidentical twins and 84 children unrelated to each other). There were also 88 children with autism. © 2017 The New York Times Company

Keyword: Autism; Vision
Link ID: 23832 - Posted: 07.13.2017

By Giorgia Guglielmi Semen has something in common with the brains of Alzheimer’s sufferers: Both contain bundles of protein filaments called amyloid fibrils. But although amyloid accumulation appears to damage brain cells, these fibrils may be critical for reproduction. A new study suggests that semen fibrils immobilize subpar sperm, ensuring that only the fittest ones make it to the egg. “I’m sure that from the very first time scientists described semen fibrils, they must have been speculating what their natural function was,” says Daniel Otzen, an expert in protein aggregates at Aarhus University in Denmark, who did not participate in the research. “This seems to be the smoking gun.” Researchers discovered semen fibrils in 2007. At first, they seemed like mostly bad news. Scientists showed that the fibrils, found in the seminal fluid together with sperm cells and other components, can bind to HIV, helping it get inside cells. But the fibrils are found in most primates, notes Nadia Roan, a mucosal biologist at the University of California, San Francisco. “If fibrils didn’t serve some beneficial purpose, they would have been eliminated over evolutionary time.” Because the way HIV fuses to cells is reminiscent of the way a sperm fuses to the egg, she wondered whether the fibrils facilitated fertilization. © 2017 American Association for the Advancement of Science.

Keyword: Alzheimers; Sexual Behavior
Link ID: 23828 - Posted: 07.12.2017

By Jessica Wright, Spectrum on July 11, 2017 Treatment with the hormone oxytocin improves social skills in some children with autism, suggest results from a small clinical trial. The results appeared today in the Proceedings of the National Academy of Sciences1. Oxytocin, dubbed the ‘love hormone,’ enhances social behavior in animals. This effect makes it attractive as a potential autism treatment. But studies in people have been inconsistent: Some small trials have shown that the hormone improves social skills in people with autism, and others have shown no benefit. This may be because only a subset of people with autism respond to the treatment. In the new study, researchers tried to identify this subset. The same team showed in 2014 that children with relatively high blood levels of oxytocin have better social skills than do those with low levels2. In their new work, the researchers examined whether oxytocin levels in children with autism alter the children’s response to treatment with the hormone. They found that low levels of the hormone prior to treatment are associated with the most improvement in social skills. “We need to be thinking about a precision-medicine approach for autism,” says Karen Parker, associate professor of psychiatry at Stanford University in California, who co-led the study. “There’s been a reasonable number of failed [oxytocin] trials, and the question is: Could they have failed because all of the kids, by blind, dumb luck, had really high baseline oxytocin levels?” The study marks the first successful attempt to find a biological marker that predicts response to the therapy. © 2017 Scientific American,

Keyword: Autism; Hormones & Behavior
Link ID: 23826 - Posted: 07.12.2017

By Abby Olena For more than 50 years, scientists have taken for granted that all snakes share a ZW sex determination system, in which males have two Z chromosomes and females have one Z and one W. But a study, published today (July 6) in Current Biology, reveals that the Central American boa (Boa imperator) and the Burmese python (Python bivittatus) use an XY sex determination system, which evolved independently in the two species. “This work is a culmination of a lot of questions that we’ve had about pythons and boas for a long time,” says Jenny Marshall Graves, a geneticist at La Trobe Univeristy in Melbourne, Australia, who did not participate in the study. Some of these questions came up for Warren Booth, a geneticist and ecologist at the University of Tulsa, as he studied parthenogenesis—the growth and development of offspring in the absence of fertilization. He noticed a pattern for organisms undergoing parthenogenesis: animal species that use a ZW system have only male (ZZ) offspring, and the organisms that use an XY system have only female (XX) offspring. Except this pattern doesn’t hold true for boas and pythons, who consistently produce female offspring by parthenogenesis. Booth contacted Tony Gamble, a geneticist at Marquette University in Milwaukee, Wisconsin, who studies sex chromosomes, to begin a collaboration to investigate whether boas and pythons might actually have X and Y chromosomes. Spurred by Booth’s questions, “I went back and reread some of the early papers” on snake sex chromosomes, says Gamble. “What became clear is that they didn’t show that boas and pythons had a ZW sex chromosome system. They just said it without any evidence.” © 1986-2017 The Scientist

Keyword: Sexual Behavior; Evolution
Link ID: 23815 - Posted: 07.09.2017

By Michael Price Male baboons that harass and assault females are more likely to mate with them, according to a new study, adding evidence that sexual intimidation may be a common mating strategy among promiscuous mammals. The study’s authors even argue that the findings could shed light on the evolutionary origins of our own species’ behavior, although others aren’t convinced the results imply anything about people. “I think the data and analyses in this study are first-rate,” says Susan Alberts, a biologist who studies primate behavior at Duke University in Durham, North Carolina. “[But] I also think it’s a big stretch to infer something about the origins of human male aggression towards women.” To conduct the research, Elise Huchard, a zoologist at the National Center for Scientific Research in Montpellier, France, and colleagues examined a group of chacma baboons (Papio ursinus) living in Tsaobis Nature Park in Namibia over a 9-year period. These brownish, dog-sized primates live in troops of dozens of males and females. Females will mate with multiple males throughout the year. The male chacma are about twice the size of females and aggressively fight one another and engage in howling competitions to establish dominance. The more dominant a male is, the more likely he is both to succeed in finding a mate and to sire offspring. Males rarely force females to mate, but after years spent observing the animals in the wild, Huchard noticed that a subtler form of sexual coercion appeared to be going on. “Males often chase and attack some females of their own group when meeting another group, and they generally target sexually receptive females on such occasions,” she says. “I spent a great deal of time studying female mate choice, and my main impression … was that females don't have much room to express any preference.” © 2017 American Association for the Advancement of Science

Keyword: Sexual Behavior; Aggression
Link ID: 23813 - Posted: 07.07.2017

By Nicholette Zeliadt Researchers have known that genes contribute to autism since the 1970s, when a team found that identical twins often share the condition. Since then, scientists have been racking up potential genetic culprits in autism, a process that DNA-decoding technologies have accelerated in the past decade. As this work has progressed, scientists have unearthed a variety of types of genetic changes that can underlie autism. The more scientists dig into DNA, the more intricate its contribution to autism seems to be. How do researchers know genes contribute to autism? Since the first autism twin study in 1977, several teams have compared autism rates in twins and shown that autism is highly heritable. When one identical twin has autism, there is about an 80 percent chance that the other twin has it, too. The corresponding rate for fraternal twins is around 40 percent. However, genetics clearly does not account for all autism risk. Environmental factors also contribute to the condition, although researchers disagree on the relative contributions of genes and environment. Some environmental risk factors for autism, such as exposure to a maternal immune response in the womb or complications during birth, may work with genetic factors to produce autism or intensify its features. Is there such a thing as an autism gene? Not really. There are several conditions associated with autism that stem from mutations in a single gene, including fragile X and Rett syndromes. But less than 1 percent of non-syndromic cases of autism stem from mutations in any single gene. © 1996-2017 The Washington Post

Keyword: Autism; Genes & Behavior
Link ID: 23794 - Posted: 07.01.2017

By STEPH YIN Whales and songbirds produce sounds resembling human music, and chimpanzees and crows use tools. But only one nonhuman animal is known to marry these two skills. Palm cockatoos from northern Australia modify sticks and pods and use them to drum regular rhythms, according to new research published in Science Advances on Wednesday. In most cases, males drop beats in the presence of females, suggesting they perform the skill to show off to mates. The birds even have their own signature cadences, not unlike human musicians. This example is “the closest we have so far to musical instrument use and rhythm in humans,” said Robert Heinsohn, a professor of evolutionary and conservation biology at the Australian National University and an author of the paper. A palm cockatoo drumming performance starts with instrument fashioning — an opportunity to show off beak strength and cleverness (the birds are incredibly intelligent). Often, as a female is watching, a male will ostentatiously break a hefty stick off a tree and trim it to about the length of a pencil. Holding the stick, or occasionally a hard seedpod, with his left foot (parrots are typically left-footed), the male taps a beat on his tree perch. Occasionally he mixes in a whistle or other sounds from an impressive repertoire of around 20 syllables. As he grows more aroused, the crest feathers on his head become erect. Spreading his wings, he pirouettes and bobs his head deeply, like an expressive pianist. He uncovers his red cheek patches — the only swaths of color on his otherwise black body — and they fill with blood, brightening like a blush. Over seven years, Dr. Heinsohn and his collaborators collected audio and video recordings of 18 male palm cockatoos exhibiting such behaviors in Australia’s Cape York Peninsula, where the birds are considered vulnerable because of aluminum ore mining. © 2017 The New York Times Company

Keyword: Animal Communication; Sexual Behavior
Link ID: 23790 - Posted: 06.29.2017

By Debra W. Soh If there was a way of telling who in our society is sexually attracted to children, are we entitled to know? A recent study from Georg-August-University Göttingen in Germany suggests that we may need to grapple with this question. Phallometric testing, also known as penile plethysmography, is considered the gold standard in measuring male sexual arousal, and particularly, deviant sexual interests such as pedophilia, which is the sexual interest in prepubescent children, roughly aged 3 to 10. The test involves measuring the volume of blood in the test-taker’s penis using an airtight glass tube (or conversely, measuring penile circumference with a mercury strain gauge) while he is presented with a series of images of children and adults, and audio stories describing a corresponding sexual encounter. Phallometry is commonly used in forensic settings to assess the sexual interests of sex offenders, in order to determine their risk of re-offending. As one can imagine, sex offenders tend not to be forthright about their sexual preferences, which makes phallometry all the more important. It has, however, been criticized because the test can become easier for individuals to fool with each successive assessment. Brain scanning using fMRI holds much promise as a diagnostic tool in evaluating sexual interests, as research has documented a reliable network of brain regions involved in sexual arousal. The current study took this another step by testing whether brain functional activation could be used to infer what someone finds sexually interesting without them knowing. © 2017 Scientific American,

Keyword: Sexual Behavior; Brain imaging
Link ID: 23783 - Posted: 06.28.2017

By Alice Klein Women are missing out on optimum medical treatment because most pre-clinical drug research is done in male animals, a new study suggests. New drugs must be evaluated in animals before being considered for human trials. Over three-quarters of these studies use only male animals because of concerns that female hormone cycles will affect experiments. It is also widely assumed that what works for males will work for females. However, research by Natasha Karp at the Wellcome Trust Sanger Institute in Cambridge and her colleagues casts doubt on this assumption. They compared 234 physical traits in 14,000 male and female lab mice. Sex differences were identified for 57 per cent of quantifiable traits – like cholesterol level and bone mass – and for 10 per cent of qualitative traits, like head shape. In another 40,000 mice, they found that when they switched off specific genes, the effects varied according to sex. This suggests that genetic diseases may manifest themselves differently in males and females and require different treatments, says Karp. These sex nuances mean that drugs optimised for male animals may be less effective in females, or even cause harm, says Karp. Between 1997 and 2001, 8 of the 10 drugs that were pulled from the market in the US posed greater health risks for women – possibly as a result of male-biased animal research, she says. © Copyright New Scientist Ltd.

Keyword: Sexual Behavior
Link ID: 23780 - Posted: 06.27.2017

By THERESE HUSTON “Does being over 40 make you feel like half the man you used to be?” Ads like that have led to a surge in the number of men seeking to boost their testosterone. The Food and Drug Administration reports that prescriptions for testosterone supplements have risen to 2.3 million from 1.3 million in just four years. There is such a condition as “low-T,” or hypogonadism, which can cause fatigue and diminished sex drive, and it becomes more common as men age. But according to a study published in JAMA Internal Medicine, half of the men taking prescription testosterone don’t have a deficiency. Many are just tired and want a lift. But they may not be doing themselves any favors. It turns out that the supplement isn’t entirely harmless: Neuroscientists are uncovering evidence suggesting that when men take testosterone, they make more impulsive — and often faulty — decisions. Researchers have shown for years that men tend to be more confident about their intelligence and judgments than women, believing that solutions they’ve generated are better than they actually are. This hubris could be tied to testosterone levels, and new research by Gideon Nave, a cognitive neuroscientist at the University of Pennsylvania, along with Amos Nadler at Western University in Ontario, reveals that high testosterone can make it harder to see the flaws in one’s reasoning. How might heightened testosterone lead to overconfidence? One possible explanation lies in the orbitofrontal cortex, a region just behind the eyes that’s essential for self-evaluation, decision making and impulse control. The neuroscientists Pranjal Mehta at the University of Oregon and Jennifer Beer at the University of Texas, Austin, have found that people with higher levels of testosterone have less activity in their orbitofrontal cortex. Studies show that when that part of the brain is less active, people tend to be overconfident in their reasoning abilities. It’s as though the orbitofrontal cortex is your internal editor, speaking up when there’s a potential problem with your work. Boost your testosterone and your editor goes reassuringly (but misleadingly) silent. © 2017 The New York Times Company

Keyword: Hormones & Behavior; Attention
Link ID: 23776 - Posted: 06.26.2017

Cassie Martin Long typecast as the strong silent type, bones are speaking up. In addition to providing structural support, the skeleton is a versatile conversationalist. Bones make hormones that chat with other organs and tissues, including the brain, kidneys and pancreas, experiments in mice have shown. “The bone, which was considered a dead organ, has really become a gland almost,” says Beate Lanske, a bone and mineral researcher at Harvard School of Dental Medicine. “There’s so much going on between bone and brain and all the other organs, it has become one of the most prominent tissues being studied at the moment.” At least four bone hormones moonlight as couriers, recent studies show, and there could be more. Scientists have only just begun to decipher what this messaging means for health. But cataloging and investigating the hormones should offer a more nuanced understanding of how the body regulates sugar, energy and fat, among other things. Of the hormones on the list of bones’ messengers — osteocalcin, sclerostin, fibroblast growth factor 23 and lipocalin 2 — the last is the latest to attract attention. Lipocalin 2, which bones unleash to stem bacterial infections, also works in the brain to control appetite, physiologist Stavroula Kousteni of Columbia University Medical Center and colleagues reported in the March 16 Nature. After mice eat, their bone-forming cells absorb nutrients and release a hormone called lipocalin 2 (LCN2) into the blood. LCN2 travels to the brain, where it gloms on to appetite-regulating nerve cells, which tell the brain to stop eating, a recent study suggests. © Society for Science & the Public 2000 - 2017.

Keyword: Hormones & Behavior
Link ID: 23762 - Posted: 06.22.2017

By Karl Gruber Birds, fish, and even humans have shattered barriers when it comes to mating rituals, from which partner initiates the courting to which one picks up the check at a fancy restaurant. But things are a bit simpler for frogs, as males and females stick to clearly defined roles: Males serenade the females, and females pick their favorite males to mate. Now, a new study suggests that the smooth guardian frog of Borneo (Limnonectes palavanensis) is an exception to that rule. During the mating season, the female frogs sing to the males in an attempt to win them over—a reversal of the normal process. In fact, if you see a single frog surrounded by a bunch of serenading croakers, called a “lek,” it’s most likely a lucky male being courted by a chorus of females. Males occasionally belt out “advertisement calls” to let females know that they are available. After mating, it’s the males who stay behind to care for the eggs, even taking tadpoles to small ponds after they hatch. This is the first known example of role reversal in singing frogs, scientists write in a recent issue of Behavioral Ecology and Sociobiology. It may even represent the first case of full-blown sex role reversal, which would also require that males do the mate choosing. Researchers are working on that now, but they say that—judging by the high rate of female serenading—males may be the picky ones. © 2017 American Association for the Advancement of Science.

Keyword: Sexual Behavior
Link ID: 23755 - Posted: 06.21.2017

Laurel Hamers When things get hot, embryonic bearded dragon lizards turn female — and now scientists might know why. New analyses, reported online June 14 in Science Advances, reveal that temperature-induced changes in RNA’s protein-making instructions might set off this sex switch. The findings might also apply to other reptile species whose sex is influenced by temperature. Unlike most mammals, many species of reptiles and fish don’t have sex chromosomes. Instead, they develop into males at certain temperatures and females at others. Bearded dragon lizards are an unusual case because chromosome combinations and temperature are known to influence sex determination, says ecologist Clare Holleley of the Commonwealth Scientific and Industrial Research Organisation in Canberra, Australia (SN: 7/25/15, p.7). When eggs are incubated below 32° Celsius, embryonic bearded dragons with two Z chromosomes develop as male, while dragons with a Z and a W chromosome develop as female. But as temperatures creep above 32°, chromosomally male ZZ dragons will reverse course and develop as females instead. “They have two sex chromosomes, but they also have this temperature override,” Holleley says. By comparing bearded dragons that are female because of their chromosomes and those that are female because of environmental influences, Holleley and her colleagues hoped to sort out genetic differences that might point to how the lizards make the switch. The team collected RNA from the brain, reproductive organs and other tissues of normal female, normal male and sex-reversed female Australian central bearded dragons (Pogona vitticeps). Then, the researchers compared that RNA, looking for differences in the ways the lizards were turning on genes. |© Society for Science & the Public 2000 - 2017.

Keyword: Sexual Behavior
Link ID: 23745 - Posted: 06.15.2017

By Lenny Bernstein A mother’s fever during pregnancy, especially in the second trimester, is associated with a higher risk that her child will be diagnosed with autism spectrum disorder, researchers reported Tuesday. Three or more fevers after 12 weeks of gestation may be linked to an even greater risk of the condition. The study by researchers at Columbia University’s Mailman School of Public Health adds support for the theory that infectious agents that trigger a pregnant woman’s immune response may disrupt a fetus’s brain development and lead to disorders such as autism. “Fever seems to be the driving force here,” not the infection itself, said Mady Hornig, director of translational research at the school’s Center for Infection and Immunity. Fever can be part of the body’s immune response to an infection, and molecules produced by a mother’s immune system may be crossing into the baby’s neurological system at a critical time, she said. The research, published in the journal Molecular Psychiatry, comes at a time when the scientifically discredited theory that some childhood vaccines cause autism has gained new attention. President Trump has promoted this myth, energizing some anti-vaccine groups. Some families say that their children developed autism after vaccinations. The timing is a coincidence, however; symptoms of autism typically become clear at around two years of age, which happens to be the age when children get certain vaccines. © 1996-2017 The Washington Post

Keyword: Autism
Link ID: 23737 - Posted: 06.13.2017