Chapter 8. Hormones and Sex
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by Bethany Brookshire Premenstrual syndrome, or PMS, can be a miserable experience. Women report over 200 symptoms in the days before menstruation occurs. The complaints run the gamut from irritable mood to bloating. PMS can be so slight you don’t even notice, or it can be so severe it has its own category — premenstrual dysphoric disorder. But to some, PMS is just a punchline, a joke featured in pop culture from Buffy the Vampire Slayer to Saturday Night Live. Michael Gillings, who studies molecular evolution at Macquarie University in Sydney, thinks that PMS could have a purpose. In a perspective piece published August 11 in Evolutionary Adaptations, Gillings proposes that PMS confers an evolutionary advantage, increasing the likelihood that a woman will leave an infertile mate. He hopes that his idea could lead to more research and less stigma about the condition. But while his hypothesis certainly sparked a lot of discussion, whether it is likely, or even necessary, is in doubt. Gillings first began to think about PMS when he found out that premenstrual dysphoric disorder was being added to the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders. “I started to think that we have a normal distribution of PMS responses, where some people don’t get any symptoms, the majority gets mild symptoms, and some get severe symptoms,” he explains. Including PMDD in DSM-5 made a statement, he says, that “we were going to take one end of this normal curve, the extreme far right end, and we were going to draw a line and say, those people there have a disease we’re going to label in our book. But if 80 percent of women get some kind of premenstrual symptoms, then it’s normal. And I wondered, if it’s so normal, what could be the reason for it?” © Society for Science & the Public 2000 - 2014.
By NICHOLAS BAKALAR Childhood treatment with human growth hormone is strongly associated with an increased risk for stroke in early adulthood, a new study has found. The study adds evidence to previous reports suggesting an increased cardiac and cerebrovascular risk in children treated with growth hormone. Researchers studied 6,874 children, average age 11, who were small for their age but otherwise generally healthy and were treated with growth hormone from 1985 to 1996. They followed them to an average age of 28. There were 11 strokes in the group, four of them fatal. The analysis found that this was more than twice as many strokes as would be expected in a population this size, a statistically significant difference. The results, published online in the journal Neurology, were particularly striking for hemorrhagic stroke, the type caused by a ruptured blood vessel — there were more than seven times as many as would be expected. The authors acknowledged that they were unable to take into account some risk factors for stroke, such as family history and smoking. “Subjects on growth hormones should not panic on reading these results,” said the senior author, Dr. Joël Coste, a professor of biostatistics and epidemiology at the Hôtel Dieu hospital in Paris. “The doctor prescribing the hormone or the family doctor should be consulted and will be able to inform and advise patients.” © 2014 The New York Times Company
By James Gallagher Health editor, BBC News website Breastfeeding can halve the risk of post-natal depression, according to a large study of 14,000 new mothers. However, there is a large increase in the risk of depression in women planning to breastfeed who are then unable to do so. The study, published in the journal Maternal and Child Health, called for more support for women unable to breastfeed. A parenting charity said mental health was a "huge issue" for many mothers. The health benefits of breastfeeding to the baby are clear-cut and the World Health Organization recommends feeding a child nothing but breast milk for the first six months. However, researchers at the University of Cambridge said the impact on the mother was not as clearly understood. 'Highest risk' One in 10 women will develop depression after the birth of their child. The researchers analysed data from 13,998 births in the south-west of England. It showed that, out of women who were planning to breastfeed, there was a 50% reduction in the risk of post-natal depression if they started breastfeeding. But the risk of depression more than doubled among women who wanted to, but were not able to, breastfeed. Dr Maria Iacovou, one of the researchers, told the BBC: "Breastfeeding does appear to have a protective effect, but there's the other side of the coin as well. "Those who wanted to and didn't end up breastfeeding had the highest risk of all the groups." BBC © 2014
By Kate Yandell Researchers have accumulated detailed knowledge of the neurons that drive male fruit flies’ mating behaviors. But the neurons that prompt females to respond—or not—to male overtures have been less-studied. Three papers published today (July 2) in Neuron and Current Biology begin to change that. They identify sets of neurons in female fruit flies that help process mating signals, modulate the insects’ receptivity to male courtship, and drive mating behavior. “These three groups independently identified important neuronal groups [that] are positioned in different points in the neuronal circuitry for regulating female receptivity,” said Daisuke Yamamoto, a behavioral geneticist at Tohoku University in Japan who was not involved in any of the studies. “We’ve had access to the male circuitry for a while now, and that’s turning out to be a really interesting way to study how behavior works,” said Jennifer Bussell, whose work as a PhD student at Rockefeller University contributed to the Current Biology paper. “Having that complementary circuit in the female can only provide more fodder for interesting experiments.” Female fruit flies’ mating behaviors depend on their reproductive state. They become receptive to mating as they mature, but become less receptive to males’ advances immediately after mating. If a female fruit fly is receptive to mating, she responds to male pheromones and courtship songs by engaging in a behavior called pausing, where she stops in her tracks near males so they can mount her and she opens her vaginal plates—hard coverings that protect her reproductive tract. © 1986-2014 The Scientist
Keyword: Sexual Behavior
Link ID: 19962 - Posted: 08.16.2014
by Laura Sanders In their first year, babies grow and change in all sorts of obvious and astonishing ways. As their bodies become longer, heavier and stronger, so do their brains. Between birth and a child’s first birthday, her brain nearly triples in size as torrents of newborn nerve cells create neural pathways. This incredible growth can be influenced by a baby’s early life environment, scientists have found. Tragic cases of severe neglect or abuse can throw brain development off course, resulting in lifelong impairments. But in happier circumstances, warm caregivers influence a baby’s brain, too. A new study in rats provides a glimpse of how motherly actions influence a pup’s brain. Scientists recorded electrical activity in the brains of rat pups as their mamas nursed, licked and cared for their offspring. The results, published in the July 21 Current Biology, offer a fascinating minute-to-minute look at the effects of parenting. Researchers led by Emma Sarro of New York University’s medical school implanted electrodes near six pups’ brains to record neural activity. Video cameras captured mother-pup interactions, allowing the scientists to link specific maternal behaviors to certain sorts of brain activity. Two types of brain patterns emerged: a highly alert state and a sleepier, zoned-out state, Sarro and colleagues found. Pups’ brains were alert while they were drinking milk and getting groomed by mom. Pups’ brains’ were similarly aroused when the pups were separated from their mom and siblings. Some scientists think that these bursts of brain activity help young brains form the right connections between regions. © Society for Science & the Public 2000 - 2013.
Older people who have a severe vitamin D deficiency have an increased risk of developing dementia, a study has suggested. UK researchers, writing in Neurology, looked at about 1,650 people aged over 65. This is not the first study to suggest a link - but its authors say it is the largest and most robust. However, experts say it is still too early to say elderly people should take vitamin D as a preventative treatment. There are 800,000 people with dementia in the UK with numbers set to rise to more than one million by 2021. Vitamin D comes from foods - such as oily fish, supplements and exposing skin to sunlight. However older people's skin can be less efficient at converting sunlight into Vitamin D, making them more likely to be deficient and reliant on other sources. The international team of researchers, led by Dr David Llewellyn at the University of Exeter Medical School, followed people for six years. All were free from dementia, cardiovascular disease and stroke at the start of the study. At the end of the study they found the 1,169 with good levels of vitamin D had a one in 10 chance of developing dementia. Seventy were severely deficient - and they had around a one in five risk of dementia. 'Delay or even prevent' Dr Llewellyn said: "We expected to find an association between low vitamin D levels and the risk of dementia and Alzheimer's disease, but the results were surprising - we actually found that the association was twice as strong as we anticipated." He said further research was needed to establish if eating vitamin D rich foods such as oily fish - or taking vitamin D supplements - could "delay or even prevent" the onset of Alzheimer's disease and dementia. But Dr Llewellyn added: "We need to be cautious at this early stage and our latest results do not demonstrate that low vitamin D levels cause dementia. BBC © 2014
By Darryl Fears At first she was surprised. Then she was disturbed. Now she’s a little alarmed. Each time a different batch of male fish with eggs in their testes shows up in the Chesapeake Bay watershed, Vicki Blazer’s eyebrows arch a bit higher. In the latest study, smallmouth bass and white sucker fish captured at 16 sites in the Delaware, Ohio and Susquehanna rivers in Pennsylvania had crossed over into a category called intersex, an organism with two genders. “I did not expect to find it quite as widespread,” said Blazer, a U.S. Geological Survey biologist who studies fish. Since 2003, USGS scientists have discovered male smallmouth and largemouth bass with immature eggs in several areas of the Potomac River, including near the Blue Plains Advanced Wastewater Treatment Plant in the District. The previous studies detected abnormal levels of compounds from chemicals such as herbicides and veterinary pharmaceuticals from farms, and from sewage system overflows near smallmouth-bass nesting areas in the Potomac. Those endocrine-disrupting chemicals throw off functions that regulate hormones and the reproductive system. In the newest findings, at one polluted site in the Susquehanna near Hershey, Pa., 100 percent of male smallmouth bass that were sampled had eggs, Blazer said. With the mutant bass, she said, “we keep seeing . . . a correlation with the percent of agriculture in the watershed where we conduct a study.”
by Bethany Brookshire The deep ocean has spawned a new record: the longest egg-brooding period. In April 2007, Bruce Robison of the Monterey Bay Aquarium Research Institute in Moss Landing, Calif., and colleagues sent a remote-operated vehicle down 1,397 meters (4,583 feet) into the Monterey Submarine Canyon. There they saw a deep-sea octopus (Graneledone boreopacifica) making its way toward a stony outcrop. One month later, the scientists spotted the same octopus, which they dubbed ‘Octomom,’ on the rock with a clutch of 155 to 165 eggs. The researchers returned to the site 18 times in total. Each time, there she was with her developing eggs. Most female octopuses lay only one clutch of eggs, staying with the eggs constantly and slowly starving to death while protecting them from predators and keeping them clean. When the eggs hatch, the female dies. The scientists report July 30 in PLOS ONE that the octopus was observed on her eggs for 53 months, until September 2011, the longest brooding period of any known animal. B. Robison et al. Deep-sea octopus (Graneledone boreopacifica) conducts the longest-known egg-brooding period of any animal. PLOS ONE. Published online July 30, 2014. doi: 10.1371/journal.pone.0103437 © Society for Science & the Public 2000 - 2013.
Keyword: Sexual Behavior
Link ID: 19904 - Posted: 07.31.2014
Posted by Celeste Biever | The four females and one male are onboard a satellite as part of an experiment to investigate sexual activity and reproduction in microgravity carried out by Russia’s space agency. Roscosmos launched the lizards using a six-tonne Foton-M4 rocket on 19 July. But the fate of the tiny cosmonauts became uncertain when their satellite briefly lost contact with ground control on Thursday 24 July. Luckily, technicians managed to restore control on Saturday, and Roscosmos announced on its website that since then it has communicated with the satellite 17 times.”Contact is established, the prescribed commands have been conducted according to plan,” said Roscosmos chief Oleg Ostapenko. Keeping the geckos company are Drosophila fruit flies, as well as mushrooms, plant seeds and various microorganisms that are also being studied. There is also a special vacuum furnace on board, which is being used to analyse the melting and solidification of metal alloys in microgravity. Foton-M4 is set to carry out experiments over two months, and involves a “study of the effect of microgravity on sexual behaviour, the body of adult animals and embryonic development”, according to the website of the Institute of Medico-Biological Problems of the Russian Academy of Sciences, which has developed the project along with Roscosmos. Specific aims of the Gecko-F4 mission include: Create the conditions for sexual activity, copulation and reproduction of geckos in orbit Film the geckos’ sex acts and potential egg-laying and maximise the likelihood that any eggs survive Detect possible structural and metabolic changes in the animals, as well as any eggs and foetuses © 2014 Macmillan Publishers Limited.
Keyword: Sexual Behavior
Link ID: 19896 - Posted: 07.30.2014
By PAUL VITELLO The conventional wisdom among animal scientists in the 1950s was that birds were genetically programmed to sing, that monkeys made noise to vent their emotions, and that animal communication, in general, was less like human conversation than like a bodily function. Then Peter Marler, a British-born animal behaviorist, showed that certain songbirds not only learned their songs, but also learned to sing in a dialect peculiar to the region in which they were born. And that a vervet monkey made one noise to warn its troop of an approaching leopard, another to report the sighting of an eagle, and a third to alert the group to a python on the forest floor. These and other discoveries by Dr. Marler, who died July 5 in Winters, Calif., at 86, heralded a sea change in the study of animal intelligence. At a time when animal behavior was seen as a set of instinctive, almost robotic responses to environmental stimuli, he was one of the first scientists to embrace the possibility that some animals, like humans, were capable of learning and transmitting their knowledge to other members of their species. His hypothesis attracted a legion of new researchers in ethology, as animal behavior research is also known, and continues to influence thinking about cognition. Dr. Marler, who made his most enduring contributions in the field of birdsong, wrote more than a hundred papers during a long career that began at Cambridge University, where he received his Ph.D. in zoology in 1954 (the second of his two Ph.D.s.), and that took him around the world conducting field research while teaching at a succession of American universities. Dr. Marler taught at the University of California, Berkeley, from 1957 to 1966; at Rockefeller University in New York from 1966 to 1989; and at the University of California, Davis, where he led animal behavior research, from 1989 to 1994. He was an emeritus professor there at his death. © 2014 The New York Times Company
By Michael Brooks Occasionally, scientific research comes up with banal findings that should nonetheless stop us in our tracks. For example, researchers recently published a study showing that a father’s brain will change its hormonal outputs and neural activity depending on his parenting duties. The conclusion of the research is, in essence, that men make good parents, too. Surely this is not news. Yet it does provide evidence that is sadly still useful. Those involved with issues of adoption, fathers’ rights, gay rights, child custody, and religion-fuelled bigotry will all benefit from understanding what we now know about what makes a good parent. The biggest enemy of progress has been the natural world, or at least our view of it. Females are the primary caregivers in 95 percent of mammal species. That is mainly because of lactation. Infants are nourished by their mothers’ milk, so it makes sense for most early caring to be done by females. Human beings, however, have developed more sophisticated means of nourishing and raising our offspring. Should the circumstances require a different set-up, we have ways to cope. It turns out that this is not just in terms of formula milk, nannies or day care: We also have a flexible brain. The new study, published in Proceedings of the National Academy of Sciences, scanned the brains of parents while they watched videos of their interactions with their children. The researchers found that this stimulated activity in two systems of the brain. One is an emotional network that deals with social bonding, ensures vigilance and coordinates responses to distress, providing chemical rewards for behaviours that maintain the child’s well-being. The other network is concerned with mental processing. It monitors the child’s likely state of mind, emotional condition, and future needs, allowing for planning. 2014 © The New Republic.
Keyword: Sexual Behavior
Link ID: 19883 - Posted: 07.26.2014
By Helen Briggs Health editor, BBC News website The timing of when a girl reaches puberty is controlled by hundreds of genes, say scientists. And age at first period may vary in daughters from the same family because of genetic factors, research shows. The findings, published in Nature, could give clues to why early puberty may be linked to an increased risk of health conditions. Scientists at 166 institutions analysed the DNA of more than 180,000 women in one of the largest studies of its kind. They found that hundreds of genes were involved in the timing of puberty. Unusually, a girl's first period was also influenced by imprinted genes - a rare event where genes from either the mother of father are silenced. "Our findings imply that in a family, one parent may more profoundly affect puberty timing in their daughters than the other parent," said lead researcher Dr John Perry of the University of Cambridge. He said the biological complexity revealed in the study was "amazing". "We identified more than 100 regions of the genome associated with puberty timing, but our analysis suggests there are likely to be thousands," he told BBC News. Lifestyle BBC © 2014
By Katherine Harmon Courage Octopuses do the darndest things. Like kill their mate during mating—by strangling him with three arms, according to new observations from the wild. Enterprising scientists Christine Huffard and Mike Bartick watched wild octopuses in action. They found that, for males, mating can be a dangerous game. Especially when your lady has long limbs. Some of the more dicey encounters are detailed in a new paper, published online July 11 in Molluscan Research. Hold on a second, you say. Strangling octopuses? Octopuses don’t even have necks—or inhale air. So how, exactly, does that work? The strangulation seems to happen when “an octopus wraps at least one arm around the base of the mantle of the competitor” (or mate), Huffard wrote in 2010. This constriction then keeps the octopus from taking in fresh water to run past its gills—starving the animal of its oxygen source. Octopuses are not known to get cuddly with one another on a day-to-day basis. In fact, “octopuses touch each other with their arms primarily in the context of mating and aggression,” the researchers write. And in this case it seems to have been both. Huffard came across a pair of mating day octopuses (Octopus cyanea) near Fiabacet Island in Indonesia. The female, as is often the case in this species, was larger—with a body about seven-and-a-half inches long; the male was closer to six inches long. They were positioned on a reef, outside the female’s den, the male’s mating arm (hectocotylus) inserted into the female’s mantle from a (presumably) safe distance. © 2014 Scientific American
Keyword: Sexual Behavior
Link ID: 19869 - Posted: 07.23.2014
By JAN HOFFMAN As it has for decades, the Centers for Disease Control and Prevention last week released its annual National Health Interview Survey on the health of Americans. But this year, there was a difference: For the first time, the respondents were asked about their sexual orientation. Of 34,557 adults ages 18 and older, the survey reported, 1.6 percent said they were gay or lesbian. Some critics say the numbers are low, but they fall in the range of other surveys. In the new survey, however, only 0.7 percent of respondents described themselves as bisexual; other studies have reported higher numbers. Adults who identified themselves as gay, lesbian or bisexual reported some different behaviors and concerns — for example, more alcohol consumption and cigarette smoking — than those who said they were straight. But it can be difficult to elicit information that many people consider private. The New York Times spoke about such challenges with Gary J. Gates, a demographer at the Williams Institute at the U.C.L.A. School of Law, which focuses on law and policy issues related to sexual orientation and gender identity. Some of Dr. Gates’s findings were echoed in the new survey. This interview was edited and condensed. Q.How was this survey conducted? A.Survey takers had a computer that guided them through questions which they asked the respondent in person, and they used flash cards to show them potential answers. Q.Why do you think the figure for bisexuality was lower than in other surveys? A.There is evidence that bisexuals perceive more stigma and discrimination than gay and lesbian people. They are much less likely to tell important people around them that they are bisexual. © 2014 The New York Times Company
Keyword: Sexual Behavior
Link ID: 19862 - Posted: 07.22.2014
By Joel Achenbach Friends often look alike. The tendency of people to forge friendships with people of a similar appearance has been noted since the time of Plato. But now there is research suggesting that, to a striking degree, we tend to pick friends who are genetically similar to us in ways that go beyond superficial features. For example, you and your friends are likely to share certain genes associated with the sense of smell. Our friends are as similar to us genetically as you’d expect fourth cousins to be, according to the study published Monday in the Proceedings of the National Academy of Sciences. This means that the number of genetic markers shared by two friends is akin to what would be expected if they had the same great-great-great-grandparents. “Your friends don’t just resemble you superficially, they resemble you genetically,” said Nicholas A. Christakis, a physician and social scientist at Yale University and a co-author of the study. The resemblance is slight, just about 1 percent of the genetic markers, but that has huge implications for evolutionary theory, said James Fowler, a professor of medical genetics and political science at the University of California at San Diego. “We can do better than chance at predicting if two people are going to be friends if all we have is their genetic data,” Fowler said. This is a data-driven study that covers hundreds of friendship pairs and stranger pairs, plus hundreds of thousands of genetic markers. There’s no single “friendship” gene driving people together. There’s no way to say that a person befriended someone else because of any one genetic trait.
By ALEX STONE Last summer, in a failed attempt at humor, Clorox ran an online ad that declared, “Like dogs or other house pets, new dads are filled with good intentions but lacking the judgment and fine motor skills to execute well.” Although the company pulled the ad amid a flurry of scorn from the online commentariat, it nevertheless played to a remarkably widespread stereotype — that fathers are somehow unfit to raise children. In “Do Fathers Matter?” — spoiler alert: they do — the veteran science writer Paul Raeburn jumps to Dad’s defense, drawing on several decades of research and his own experience as a five-time father. What emerges is a thought-provoking field piece on the science of fatherhood, studded with insights on how to apply it in the real world. Historically, developmental psychologists have largely dismissed fathers as irrelevant. Nearly half the articles on child and adolescent psychology published in leading journals from 1997 to 2005, for example, make no mention of fathers; before 1970, when fathers weren’t even allowed in delivery rooms, less than a fifth of the research on parental bonding took them into account. This bias reflects a deeply ingrained assumption that fathers play a marginal role in how their children turn out, a belief enshrined in the theory of infant attachment, which grew out of the work of the British psychiatrist John Bowlby in the second half of the 20th century. “It focused exclusively on mothers,” Mr. Raeburn writes. “The role of the father, Bowlby believed, was to provide support for the mother. In the drama of childhood, he was merely a supporting actor.” This was more or less the established view until a few decades ago, when psychologists, motivated in part by the growing number of women entering the work force, finally started paying attention to fathers. © 2014 The New York Times Company
|By William Skaggs Jet lag is a pain. Besides the inconvenience and frustration of traveling more than a few time zones, jet lag likely causes billions of dollars in economic losses. The most effective treatment, according to much research, is structured exposure to light, although the drug melatonin may also sometimes be helpful at bedtime. Both approaches have been used for more than 20 years, and during that time no viable new interventions have appeared. Recently, however, research into the molecular biology of circadian rhythms has raised the prospect of developing new drugs that might produce better results. Jet lag occurs when the “biological clock” in the brain becomes misaligned with the local rhythm of daily activity. The ultimate goal of circadian medicine is a treatment that instantly resets the brain's clock. Failing that, it would be helpful to have treatments that speed the rate of adjustment. Four recent discoveries suggest new possibilities. The first involves vasopressin, which is the main chemical signal used to synchronize cellular rhythms of activity in the brain area that is responsible for our biological clock. Blocking vasopressin makes it much easier to reset this clock. Potentially, a drug that interferes with vasopressin could work as a fast-acting treatment for jet lag. The second and third possibilities involve a pair of brain chemicals called salt-inducible kinase 1 (SIK1) and casein kinase 1ε (CK1ε), both of which limit the ability of light to reset the brain's clock. Drugs already exist that interfere with their action and greatly increase the effectiveness of light exposure. The existing drugs are not viable jet-lag treatments, because they are hard to administer and have unpleasant side effects, but researchers hope better drugs can be developed that work in a similar way. © 2014 Scientific American,
By Virginia Morell Many moth species sing courtship songs, and until now, scientists knew of only two types of such melodies. Some species imitate attacking bats, causing a female to freeze in place, whereas others croon tunes that directly woo the ladies. But the male yellow peach moth (Conogethes punctiferalis, pictured) belts out a combination song, scientists report online today in the Proceedings of the Royal Society B. These tiny troubadours, which are found throughout Asia, emit ultrasonic refrains composed of short and long pulses by contracting their abdominal tymbals, sound-producing membranes. (Listen to a male’s courtship song above.) The short pulses, the scientists say, are similar to the hunting calls of insectivorous horseshoe bats. However, unlike other moth species, these males aren’t directing the batlike tunes at females, but rather at rival males. Using playback experiments, the scientists showed that a male drives away competitors with the short pulses of his ditty, while inducing a female to mate with the long note. Indeed, a receptive virgin female moth (1 to 3 days old) typically raises her wings after hearing this part of the male’s song—a sign that she accepts the male, the scientists say. It is thus the first moth species known to have a dual-purpose melody. © 2014 American Association for the Advancement of Science
By LISA SANDERS, M.D. On Wednesday, we challenged Well readers to solve the case of a middle-aged woman who suddenly began to have episodes of confusion caused by low blood sugars. Her endocrinologist thought she might have an insulinoma, an insulin-producing tumor of the pancreas, but the testing he did seemed to rule out that diagnosis. Nearly 200 of you took on the challenge of trying to figure out what was causing her life-threatening drops in blood sugar level. The correct diagnosis is… Insulinoma The first respondent to make the diagnosis was Karen Unkel of Kinder, La. She is not a doctor but has a longstanding interest in hypoglycemia that allowed her to recognize the disease even in the face of an apparently negative work-up. Well done, Ms. Unkel. An insulinoma is a rare tumor of pancreatic tissue that makes and secretes insulin independently of blood glucose levels. This results in episodes of hypoglycemia that can be quite severe, even life-threatening. The diagnosis is suspected when a patient fulfills what is known as Whipple’s triad: 1) symptoms of hypoglycemia 2) associated with low measured blood sugar and 3) which improve when blood sugar is raised to the normal range. The diagnosis is made when doctors show that the patient is making too much insulin given his or her blood sugar level. Measuring insulin levels is not always accurate because insulin is processed rapidly in the body and because it is difficult to distinguish between insulin made naturally in the pancreas and any insulin that the patient might be injecting. What is measured instead is something known as C-peptide. Insulin is first made as a larger molecule known as proinsulin. When blood sugar rises, an extra bit is shaved off the molecule; that extra bit is C-peptide, and both the resulting insulin and C-peptide are released into the bloodstream. © 2014 The New York Times Company
Karen Ravn To the west, the skies belong to the carrion crow. To the east, the hooded crow rules the roost. In between, in a narrow strip running roughly north to south through central Europe, the twain have met, and mated, for perhaps as long as 10,000 years. But although the crows still look very different — carrion crows are solid black, whereas hooded crows are grey — researchers have found that they are almost identical genetically. The taxonomic status of carrion crows (Corvus corone) and hooded crows (Corvus cornix) has been debated ever since Carl Linnaeus, the founding father of taxonomy, declared them to be separate species in 1758. A century later, Darwin called any such classification impossible until the term 'species' had been defined in a generally accepted way. But the definition is still contentious, and many believe it always will be. The crows are known to cross-breed and produce viable offspring, so lack the reproductive barriers that some biologists consider essential to the distinction of a species, leading to proposals that they are two subspecies of carrion crow. In fact, evolutionary biologist Jochen Wolf from Uppsala University in Sweden and his collaborators have now found that the populations living in the cross-breeding zone are so similar genetically that the carrion crows there are more closely related to hooded crows than to the carrion crows farther west1. Only a small part of the genome — less than 0.28% — differs between the populations, the team reports in this week's Science1. This section is located on chromosome 18, in an area associated with pigmentation, visual perception and hormonal regulation. It is no coincidence, the researchers suggest, that the main differences between carrion and hooded crows are in colouring, mating preferences (both choose mates whose colouring matches theirs), and hormone-influenced social behaviours (carrion crows lord it over hooded ones). © 2014 Nature Publishing Group,