Chapter 8. Hormones and Sex
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Moheb Costandi Different immune cells regulate pain sensitization in male and female mice, according to research published on 29 June in Nature Neuroscience1. The surprising biological divide may explain why some clinical trials of pain drugs have failed, and highlights shortcomings in the way that many researchers design their experiments. The immune system has important roles in chronic pain, with cells called microglia being key players. Microglia express a protein called brain-derived neurotrophic factor (BDNF) to signal to spinal-cord neurons. When injury or inflammation occurs, this signal sensitizes the body to pain, so that even light touch hurts. Robert Sorge, a psychologist at the University of Alabama in Birmingham, and his colleagues induced persistent pain and inflammation in healthy male and female mice by severing two of the three sciatic nerve branches in their hind paws. Seven days later, they injected the animals with one of three drugs that inhibit microglial function. They found that all three drugs reversed pain sensitization in the male animals, as had been previously reported. But the treatments had no effect on the females, even though the animals had displayed equivalent levels of pain. The researchers also genetically engineered mice in which the BDNF gene could be deleted in microglia at any time during the animals' lives. At first, these animals exhibited normal responses to a nerve injury. Killing the microglia one week later extinguished that hypersensitivity in the male animals, but not in the females. This confirmed that in males, hypersensitivity to pain depends on BDNF signals from microglia, but that in females it is mediated by some other mechanism. © 2015 Nature Publishing Group,
By Christopher Intagliata Two decades ago, Swiss researchers had women smell the tee shirts that various men had slept in for two nights. Turned out that if women liked the aroma of a particular shirt, the guy who’d worn it was likely to have genetically coded immunity that was unlike the woman’s. Well the effect isn't just limited to sweaty shirts. Turns out we all smell things a little differently—you pick up a note of cloves, say, where I smell something more soapy—and that too gives clues to our degree of genetic similarity. Researchers tried that test with 89 people—having them sniff a couple dozen samples, and label each one using terms like lemony, coconut, fishy and floral. And each volunteer classified the scents differently enough that the researchers could single them out in subsequent tests, based on what they called each subject’s "olfactory fingerprint." Researchers then repeated that sniff test on another 130 subjects. But this time they did a blood test, too, to figure out each person's HLA type—an immune factor that determines whether you'll reject someone's organ, for example. They found that people who perceived smells similarly also had similar HLA types. Study author Lavi Secundo, a neuroscientist at the Weizmann Institute of Science in Israel, says the smell test could have real-world applications. "For organ donation you can think of this method as a quick, maybe a quick and dirty, method to sift between the best and the rest." He and his colleagues say it might even eliminate the need for 30 percent of the HLA tests done today. The work appears in the Proceedings of the National Academy of Sciences. [Lavi Secundo et al, Individual olfactory perception reveals meaningful nonolfactory genetic information] © 2015 Scientific American
Helen Shen In April 2011, Robert Froemke and his team were reprogramming the brains of virgin mice with a single hormone injection. Before the treatment, the female mice were largely indifferent to the cries of a distressed baby, and were even known to trample over them. But after an injection of oxytocin, the mice started to respond more like mothers, picking up the mewling pup in their mouths. Froemke, a neuroscientist at New York University's Langone Medical Center in New York City, was monitoring the animals' brains to find out why that happened. At first, the mice showed an irregular smattering of neural impulses when they heard the baby's cries. Then, as the oxytocin kicked in, the signal evolved into a more orderly pattern typical of a maternal brain. The study showed in unusual detail how the hormone changed the behaviour of neurons1. “Oxytocin is helping to transform the brain, to make it respond to those pup calls,” Froemke says. Oxytocin has been of keen interest to neuroscientists since the 1970s, when studies started to show that it could drive maternal behaviour and social attachment in various species. Its involvement in a range of social behaviours2, including monogamy in voles, mother–infant bonding in sheep, and even trust between humans, has earned it a reputation as the 'hug hormone'. “People just concluded it was a bonding molecule, a cuddling hormone, and that's the pervasive view in the popular press,” says Larry Young, a neuroscientist at Emory University in Atlanta, Georgia, who has been studying the molecule since the 1990s. “What we need to start thinking about is the more fundamental role that oxytocin has in the brain.” © 2015 Nature Publishing Group,
by Curtis Abraham A step forward for equal LGBT rights in Africa. Last week, the influential Academy of Science of South Africa (ASSAf) published a study on the science of human sexual diversity. A comprehensive review of recent scientific papers on the subject, it concluded that sexual behaviour is naturally varied, and discrimination unjustified. It stated that there is no evidence that orientation can be altered by therapy or that being gay is contagious. The report also sets straight the idea that homosexuality is a Western malaise: "There is no basis for the view that homosexuality is 'un-African' either in the sense of it being a 'colonial import', or on the basis that prevalence of people with same-sex or bisexual orientations is any different in African countries compared to countries on any other continent." Going further, the report asserted not only that tolerance of sexual diversity benefits communities but it positively affects public health, civil society and long-term economic growth. Zero tolerance Launched at the Seventh South African AIDS Conference in Durban, the study comes a year after the Ugandan government passed a law imposing a life sentence on anyone who has sexual relations with someone of the same sex. Other countries, including Burundi, Cameroon and Nigeria, then passed similar anti-gay laws. © Copyright Reed Business Information Ltd.
Keyword: Sexual Behavior
Link ID: 21071 - Posted: 06.18.2015
Tom Bawden The mystery behind the nightingale’s beautiful song has been revealed, with scientists finding that male birds sing complex notes to prove to females that they would be a good father to their children. Nightingales use their songs to advertise their family values, according to new research which discovers that the better the singer, the more support they are likely to offer their young family by feeding and defending them from predators. But while the beauty comes from the complexity of the song, the effect it has on the females is based on something far more mundane – the amount of effort the singer has put into his performance. Researchers at the Freie Universitat Berlin found that complicated choral arrangements are much harder to sing, especially when they include frequent appearances of long buzzing sounds and require the bird to be in good physical condition. “We don’t think the female is concerned with the beauty of the song but rather the information encoded in the song that tells her about the singer’s characteristics – his age, where he was raised, the strength of his immune system and how motivated he is to contribute to bringing up the young,” Professor Silke Kipper, one of the report’s authors, told The Independent. “The songs can also be a good indication of the bird’s ability to learn, which is another important characteristic of a good parent.” © independent.co.uk
by Michael Sean Pepper and Beverley Kramer People who are attracted to others of the same sex develop their orientation before they are born. This is not a choice. And scientific evidence shows their parents cannot be blamed. Research proving that there is biological evidence for sexual orientation has been available since the 1980s. The links have been emphasised by new scientific research. In 2014, researchers confirmed the association between same-sex orientation in men and a specific chromosomal region. This is similar to findings originally published in the 1990s, which, at that time, gave rise to the idea that a “gay gene” must exist. But this argument has never been substantiated, despite the fact that studies have shown that homosexuality is a heritable trait. Evidence points towards the existence of a complex interaction between genes and environment, which are responsible for the heritable nature of sexual orientation. These findings are part of a report released by the Academy of Science South Africa. The report is the outcome of work conducted by a panel put together in 2014 to evaluate all research on the subject of sexual orientation done over the last 50 years. It did this against the backdrop of a growing number of new laws in Africa which discriminate against people attracted to others of the same sex. The work was conducted in conjunction with the Ugandan Academy of Science.
Keyword: Sexual Behavior
Link ID: 21049 - Posted: 06.15.2015
By Brian Handwerk When it comes to mating, female mice must follow their noses. For the first time, scientists have shown that hormones in mice hijack smell receptors in the nose to drive behavior, while leaving the brain completely out of the loop. According to the study, appearing this week in Cell, female mice can smell attractant male pheromones during their reproductive periods. But during periods of diestrus, when the animals are unable to reproduce, the hormone progesterone prompts nasal sensory cells to block male pheromone signals so that they don't reach a female's brain. During this time, female mice display indifference or even hostility toward males. The same sensors functioned normally with regard to other smells, like cat urine, showing they are selective for male pheromones. When ovulation begins, progesterone levels drop, enabling the females to once more smell male pheromones. In short, the system "blinds" female mice to potential mates when the animals are not in estrus. The finding that the olfactory system usurped the brain's role shocked the research team, says lead author Lisa Stowers of the Scripps Research Institute. “The sensory systems are just supposed to sort of suck up everything they can in the environment and pass it all on to the brain. The result just seems wacky to us,” Stowers says. “Imagine this occurring in your visual system," she adds. "If you just ate a big hamburger and then saw a buffet, you might see things like the table and some people and maybe some fruit—but you simply wouldn't see the hamburgers anymore. That's kind of what happens here. Based on this female's internal-state change, she's missing an entire subset of the cues being passed on to her brain.”
by Clare Wilson The first drug for treating low sexual desire in women looks set to go on sale in the US next year Flibanserin, sometimes called the female Viagra, was approved by 18 votes to 6 by a US Food and Drug Administration advisory panel yesterday, although some of the committee members had doubts about the drug's risks and benefits. They required that certain "risk-management options" be put in place, on top of the usual list of side effects listed in the medicine's patient information leaflet. We have yet to hear what this means, but options include doctors having to verbally warn women not to drink alcohol or use various other medicines when taking the drug. The FDA's final say is due by August, but it usually follows the decision of its advisory panel. Assuming it gets the go-ahead, manufacturer Sprout Pharmaceuticals of Raleigh, North Carolina, plans to give the drug the brand-name Addyi, and has promised not to advertise the product directly to patients – which is normally allowed in the US – for the first 18 months it goes on sale. Addyi is no Viagra though – women would have to take it every day, whether or not they want sex. And, while the famous little blue pill works by increasing blood flow to the genitals, this new drug instead alters brain chemistry, affecting receptors for various signalling chemicals including serotonin and dopamine. © Copyright Reed Business Information Ltd.
Keyword: Sexual Behavior
Link ID: 21020 - Posted: 06.06.2015
By Elahe Izadi Researchers classified two new species of Dusky Antechinus, mouse-like creatures that engage in suicidal reproduction, and published their findings last week in the peer-reviewed journal Memoirs of the Queensland Museum -- Nature. The Mainland Dusky Antechinus, found in southeastern Australia, has been elevated from sub-species to a distinct species. And the newly discovered Tasman Peninsula Dusky Antechinus, found in southeastern Tasmania, already faces the threat of extinction due in part to loss of habitat and feral pests, researchers said. Their proclivity for ferocious, suicidal sex frenzies aren't helping them any. "The breeding period is basically two to three weeks of speed-mating, with testosterone-fueled males coupling with as many females as possible, for up to 14 hours at a time," lead author Andrew Baker of the Queensland University of Technology said in a release. All of that testosterone "triggers a malfunction in the stress hormone shut-off switch" for the males, Baker said. The males then get so stressed out that their immune systems fail, and they die before the females actually give birth. Suicidal reproduction -- or semelparity-- is rare in mammals, and has so far just been documented in these kinds of marsupials.
Allie Wilkinson For many species, reproduction is a duet between male and female. Now, for the first time, scientists report evidence of 'virgin birth' in a wild vertebrate, the smalltooth sawfish. The fish (Pristis pectinata) normally reproduces sexually, requiring contributions from both sexes. But the latest analysis estimates that nearly 4% of sawfish in a Florida estuary were born without any genetic contribution from a male, in a phenomenon known as parthenogenesis. This asexual reproduction is rare in vertebrates, and had previously been observed only in a handful of species in captivity, including snakes collected from the wild1 and Komodo dragons2. The latest findings appear in the 1 June issue of Current Biology3. Smalltooth sawfish are one of five large ray species that have chainsaw-like appendages protruding from their faces, and are in the same subclass as sharks. The smalltooth sawfish was once abundant along the US eastern and southern coastlines from North Carolina to Texas, but overfishing and coastal development have drastically reduced its numbers. The critically endangered fish are now found only off the coast of southwest Florida. Researchers discovered evidence of 'virgin births' among the sawfish while conducting a routine genetic analysis to determine whether they were inbreeding. Some of the 190 sawfish sampled in a Florida estuary showed unusually high levels of relatedness to other fish in the same population. © 2015 Nature Publishing Group
By ANDREW SOLOMON At the beginning of spring in 2013, Mary Guest, a lively, accomplished 37-year-old woman, fell in love, became pregnant and married after a short courtship. At the time, Mary taught children with behavioral problems in Portland, Ore., where she grew up. Her supervisor said that he had rarely seen a teacher with Mary’s gift for intuiting students’ needs. “Mary was a powerful person,” he wrote to her mother, Kristin. “Around Mary, one felt compassion, drive, calmness and support.” Mary had struggled with depression for much of her life. Starting in her 20s, she would sometimes say to Kristin that she just wanted to die. “She would always follow up by saying, ‘But you don’t need to worry, Mama,’ ” Kristin told me. “ ‘I don’t have a plan, and I don’t intend to do anything.’ ” In recent years, Mary and her mother went for a walk once a week, and Mary would describe the difficulties she was having. She was helped somewhat by therapy and by antidepressant and antianxiety medications, which blunted her symptoms. Mary’s friends appreciated her wacky sense of humor and her engaging wit. Colleagues said that her moods never impinged on her work; in fact, few of them knew what she was dealing with. Yet for years Mary worried that she would never be in a stable relationship and experience love or a family of her own. She said plaintively to Kristin, “I think I would be a really good mother.” So when she discovered that she was pregnant, she was delighted, and she expected the experience to be blissful. She decided to discontinue her antidepressants, having read about their potential danger for a growing fetus. Given her history of severe depression, she was monitored closely by a psychiatric nurse practitioner, who told her that she could call anytime for an immediate prescription. But Mary elected to stay off medication.
By ANDREW POLLACK Is sexual desire a human right? And are women entitled to a little pink pill to help them feel it? Those questions are being raised in a campaign that is pressing the Food and Drug Administration to approve a pill aimed at restoring lost libido in women. The campaign, backed by the drug’s developer and some women’s groups, accuses the F.D.A. of gender bias for approving Viagra and 25 other drugs to help men have sex, but none for women. “Women have waited long enough,” the effort, known as Even the Score, says in an online petition that has gathered more than 40,000 signatures. “In 2015, gender equality should be the standard when it comes to access to treatments for sexual dysfunction.” The drug, flibanserin, has been rejected twice by the F.D.A. on the grounds that its very modest effectiveness was outweighed by side effects like sleepiness, dizziness and nausea. The first rejection, in 2010, followed a decision by a committee of outside advisers to the agency who unanimously opposed approval. On Thursday, F.D.A. advisers will once again consider whether flibanserin should be approved. Sprout Pharmaceuticals, which now owns the drug, has submitted new data, including a study to demonstrate that the pill does not impair driving. Still, approval might hinge on whether the F.D.A. agrees to interpret the old data in a new way and whether the politics of such drugs has changed. © 2015 The New York Times Company
Keyword: Sexual Behavior
Link ID: 21002 - Posted: 06.01.2015
By Sarah C. P. Williams Here’s an easy way to tell if a female warbler is a year-round resident of the tropics or just a visiting snowbird: Females from species that spend their lives near the equator tend to have brighter plumage more typical of male birds. In contrast, females who fly north for the summer appear drab compared with their male counterparts. In the past, researchers thought the difference was due to the shorter breeding season in the north, hypothesizing that migrating males evolved bright colors to better compete for mates. But a new study hints that northern-breeding females may have evolved to be less colorful than males in order to be less conspicuous to predators during their long migrations. Researchers at Trinity University in San Antonio, Texas, studied the coloring, migration patterns, breeding locales, and ancestry of 109 warbler species. Migration distance, not the length of the breeding season, was the best predictor of color contrasts between male and female birds, they report online today in the Proceedings of the Royal Society B. Female bay-breasted warblers (Setophaga castanea), for instance, which migrate about 7000 kilometers between their breeding grounds in North America and their wintering grounds in the Caribbean, are a dull gray and white, whereas males boast more showy yellows and browns. But both male and female slate-throated redstarts (Myioborus miniatus), like the one shown above, flaunt bright colors in their year-round tropical homes in Mexico and Central America. For migrating warblers, the researchers hypothesize that the breeding benefits of brighter male colors outweigh the threat of being spotted by a hungry predator. © 2015 American Association for the Advancement of Science.
Steve Connor Having children can permanently affect the brain of women because the surge in female sex hormones during pregnancy can influence the development of key parts of the central nervous system, a series of studies has shown. The findings suggest that childbirth can affect the female brain, but they could also shed light on the controversy over whether hormone replacement therapy in menopausal women affects the risk of developing Alzheimer’s disease in later life, scientists said. The research looked at two of the oestrogen hormones used to treat the symptoms of menopausal women and found that they could have a complex effect depending on the age of the women and whether or not they had previously given birth. Although the work was mostly carried out on laboratory rats, the scientists said that the findings are more widely applicable to humans because the same hormones and brain cells are involved. The scientists found that the surge in oestrogen hormones during pregnancy, where levels can soar to several hundred times normal levels, can alter “neuroplasticity” or the re-growth of nerve cells in a part of the brain called the hippocampus, which is responsible for aspects of memory and spatial awareness. “Our most recent research show that previous motherhood alters cognition and neuroplasticity in response to hormone therapy, demonstrating that motherhood permanently alters the brain,” said Liisa Galea of the University of British Columbia in Vancouver, Canada.
By John Horgan The New York Times "Sunday Review" section has anointed Richard Friedman its go-to guy for touting behavioral genetics--or "gene-whiz science," as I prefer to call it. In March, Friedman, professor of clinical psychiatry at Weill Cornell Medical College, proclaimed that researchers had discovered a "feel-good gene," which "makes some people inherently less anxious, and more able to forget fearful and unpleasant experiences." As I pointed out on this blog, Friedman's claim—like virtually all reported linkages of complex human traits and disorders to specific genes (see Further Reading)--is based on flimsy, contradictory evidence. I'm so naïve, or arrogant, that I actually thought my critique might dissuade the Times from further hype of gene-whiz science. Times editors must care more about traffic than accuracy, because they devoted almost the entire front page of yesterday’s "Sunday Review" to Friedman's latest travesty, "Infidelity Lurks in Your Genes." The core of Friedman's essay is his assertion that some women are "biologically inclined to wander." More specifically, women who carry variants of the gene AVPR1A—which encodes the receptor for the hormone arginine vasopressin--are "much more likely to engage in 'extra-pair bonding,' the scientific euphemism for sexual infidelity." In support of this claim, Friedman cites a study of Finnish twins and non-twin siblings by a team led by Australian psychologist Brendan Zietsch. The team surveyed the Finnish subjects and found that 9.8 percent of the men and 6.4 percent of the women reported engaging in at least one "extra-pair mating." The researchers found an association between five AVPR1A markers and extra-pair mating in women but not in men.
By BENEDICT CAREY and PAM BELLUCK He was a graduate student who seemingly had it all: drive, a big idea and the financial backing to pay for a sprawling study to test it. In 2012, as same-sex marriage advocates were working to build support in California, Michael LaCour, a political science researcher at the University of California, Los Angeles, asked a critical question: Can canvassers with a personal stake in an issue — in this case, gay men and women — actually sway voters’ opinions in a lasting way? He would need an influential partner to help frame, interpret and place into context his findings — to produce an authoritative scientific answer. And he went to one of the giants in the field, Donald P. Green, a Columbia University professor and co-author of a widely used text on field experiments. “I thought it was a very ambitious idea, so ambitious that it might not be suitable for a graduate student,” said Dr. Green, who signed on as a co-author of Mr. LaCour’s study in 2013. “But it’s such an important question, and he was very passionate about it.” Last week, their finding that gay canvassers were in fact powerfully persuasive with people who had voted against same-sex marriage — published in December in Science, one of the world’s leading scientific journals — collapsed amid accusations that Mr. LaCour had misrepresented his study methods and lacked the evidence to back up his findings. On Tuesday, Dr. Green asked the journal to retract the study because of Mr. LaCour’s failure to produce his original data. Mr. LaCour declined to be interviewed, but has said in statements that he stands by the findings. © 2015 The New York Times Company
Keyword: Sexual Behavior
Link ID: 20979 - Posted: 05.26.2015
Richard A. Friedman AMERICANS disapprove of marital infidelity. Ninety-one percent of them find it morally wrong, more than the number that reject polygamy, human cloning or suicide, according to a 2013 Gallup poll. Yet the number of Americans who actually cheat on their partners is rather substantial: Over the past two decades, the rate of infidelity among married men has been pretty constant at around 21 percent, while the percentage of married women who admitted to cheating has mostly hovered between 10 and 15 percent, according to the General Social Survey at the University of Chicago’s independent research organization, NORC. We are accustomed to thinking of sexual infidelity as a symptom of an unhappy relationship, a moral flaw or a sign of deteriorating social values. When I was trained as a psychiatrist we were told to look for various emotional and developmental factors — like a history of unstable relationships or a philandering parent — to explain infidelity. But during my career, many of the questions we asked patients were found to be insufficient because for so much behavior, it turns out that genes, gene expression and hormones matter a lot. Now that even appears to be the case for infidelity. We have long known that men have a genetic, evolutionary impulse to cheat, because that increases the odds of having more of their offspring in the world. But now there is intriguing new research showing that some women, too, are biologically inclined to wander, although not for clear evolutionary benefits. Women who carry certain variants of the vasopressin receptor gene are much more likely to engage in “extra pair bonding,” the scientific euphemism for sexual infidelity. © 2015 The New York Times Company
By SINDYA N. BHANOO Male Java sparrows are songbirds — and, scientists reported on Wednesday, natural percussionists. The sparrows click their bills against a hard surface while singing. That clicking is done in coordination with the song, much as a percussion instrument accompanies a melody. Researchers at Hokkaido University in Japan observed the birds producing clicks frequently toward the beginning of their songs and around specific notes. Birds that were related produced similar percussive patterns, but whether this behavior is learned or innate is unclear. Next the scientists, who described their findings on Wednesday in the journal PLOS One, would like to know whether male sparrows use bill clicks during courtship communication. © 2015 The New York Times Company
by Karl Gruber "As clever as a guppy" is not a huge compliment. But intelligence does matter to these tropical fish: big-brained guppies are more likely to outwit predators and live longer than their dim-witted peers. Alexander Kotrschal at Stockholm University, Sweden, and his colleagues bred guppies (Poecilia reticulata) to have brains that were bigger or smaller than average. His team previously showed that bigger brains meant smarter fish. When put in an experimental stream with predators, big-brained females were eaten about 13 per cent less often than small-brained ones. There was no such link in males, and the researchers suspect that their bright colours may counter any benefits of higher intelligence. They did find, Kotrschal says , that large-brained males were faster swimmers and better at learning and remembering the location of a female. "This is exciting because it confirms a critical mechanism for brain size evolution," says Kotrschal. It shows, he adds, that interactions between predator and prey can affect brain size. It might seem obvious that bigger brains would help survival. Yet previous research simply found a correlation between the two, leaving the possibility open that some third factor may have been driving the effect. Now, direct brain size manipulation allowed Kotrschal's team to pin it down as a cause of better survival. "This is the first time anyone has tested whether a larger brain confers a survival benefit," says Kotrschal. "The fact that large-brained females survived better in a naturalistic setting is the first experimental proof that a larger brain is beneficial for the fitness of its bearer. This is like watching evolution happen and shows how brain size evolves." © Copyright Reed Business Information Ltd.
Alexandra Sifferlin Autism, already a mysterious disorder, is even more puzzling when it comes to gender differences. For every girl diagnosed with autism, four boys are diagnosed, a disparity researchers don’t yet fully understand. In a new study published in the journal Molecular Autism, researchers from the UC Davis MIND Institute tried to figure out a reason why. They looked at 112 boys and 27 girls with autism between ages 3 and 5 years old, as well as a control sample of 53 boys and 29 girls without autism. Using a process called diffusion-tensor imaging, the researchers looked at the corpus callosum — the largest neural fiber bundle in the brain — in the young kids. Prior research has shown differences in that area of the brain among people with autism. They found that the organization of these fibers was different in boys compared with girls, especially in the frontal lobes, which play a role in executive functions. “The sample size is still limited, but this work adds to growing body of work suggesting boys and girls with autism have different underlying neuroanatomical differences,” said study author Christine Wu Nordahl, an assistant professor in the UC Davis Department of Psychiatry and Behavioral Sciences, in an email. In other preliminary research presented at the International Meeting for Autism Research, or IMFAR, in Salt Lake City, the study authors showed that when girls and boys with autism are compared with typically developing boys and girls, the behavioral differences between girls with autism and the female controls are greater than the differences among the boys. Nordahl says this suggests that girls can be more severely affected than boys.