C-section and induced births dipped or spiked on
Halloween and Valentine’s Day…but so, intriguingly, did natural births.
With the rise of cesarean sections and scheduled births, it’s no surprise that expectant mothers might favor some dates over others for their children’s births. But a recent study drawing on US birth certificates from a ten-year period suggests that even with natural, spontaneous births, the mother may be able exert some kind of control over when she goes into labor. The team found that there were about 5% fewer births on Halloween and about 4% more on Valentine’s Day than there were on any day in the surrounding two weeks.
The researchers think that the frightening connotations of Halloween—skeletons, zombies, and so on—as experienced by the mother might be enough to affect the hormones that control labor, putting the birth off (and vice versa when it comes to the positive connotations of Valentine’s Day). But the specific biological connection between a mother’s holiday-influenced emotional state and labor is still an open question.
In cultures that don’t celebrate Halloween and Valentine’s Day but consider other days particularly auspicious or inauspicious, does this effect also happen? Inquiring minds want to know.
[via New Scientist]
That handsome young studmuffin at the other end of the bar may not look as good as a reliable, if boring, man once you’re taking a daily dose of hormones. That’s one of the conclusions drawn by a team of scientists, who’ve previously shown that where women are in their monthly cycle affects what kinds of men they select as potential mates from a series of photographs, after they took their work out of the lab and interviewed more than 2500 women to see what effect the pill has on their real-life decisions.
In lab studies, women who are in fertile stages of their cycle are more likely to go for men who look healthy, self-confident, and masculine, which tend to be markers for good genes, but also for infidelity. The pill mimics pregnancy, though, when the die has already been cast and being a good provider is more attractive than sexy. In the lab, women on the pill do indeed select men who look like they will be more reliable and steady.
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Hormones are major mood-regulators, as anyone who has been cranky before a period or had their reproductive organs removed for medical reasons can tell you. In fact, depression is a common side effect of such surgeries in humans. But does that extend to some of the most regularly de-hormoned animals out there—our pets? That’s the thought-provoking thesis of a recent Slate piece, and while there’s been no systematic research on how such surgeries affect cats and dogs, a smattering of research has suggested that having your supply of hormones eliminated does affect the mood of mice and primates, free of the confounding influences one finds in humans. (more…)
Researchers at Wake Forest University in North Carolina have now learned that Nazca boobies perpetuate a “cycle of violence”: bullied chicks tend to become bullies and pass on the pain. When parent birds leave their nests to eat, baby boobies are often visited by sexually and physically abusive non-breeding adults; the chicks, when grown, are more likely to abuse unrelated chicks. “The link we found indicates that nestling experience, and not genetics, influences adult behaviour,” lead researcher David Anderson told BBC.
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You’ve probably heard oxytocin referred to as the “love hormone,” but a new study in the Proceedings of the National Academy of Sciences reminds us that there’s much more to it than that. Jennifer Bartz and colleagues treated men either with nasal sprays that included oxytocin or placebo sprays that didn’t, with peculiar results.
From Ed Yong:
Before all of this, the men completed a series of widely used questionnaires to measure the state of their social ties. The questions assessed the nature of their bonds with their families and friends, how sensitive they are to rejection, how comfortable they are at being close to other people, how much they desire that closeness, and more. Shortly after using both sprays, the recruits also answered questions about their mother’s parenting style.
Bartz found that when she averaged out the volunteers’ results, the sniffs of oxytocin hadn’t seemed to colour their memories of their mothers. But things changed when she looked at them individually. Those who felt more anxious about their relationships took a dimmer view of their mother’s parenting styles when they sniffed oxytocin, compared to the placebo. Those who were more secure in their relationships reacted in the opposite way – they remembered mum as being closer and more caring when they took the oxytocin.
For the rest of this post, check out DISCOVER blog Not Exactly Rocket Science.
Related Content:
Not Exactly Rocket Science: Can a sniff of oxytocin improve the social skills of autistic people?
80beats: The “Love Hormone” Oxytocin Helps People Recognize Faces They’ve Seen Before
DISCOVER: A Dose of Human Kindness, Now in Chemical Form examines oxytocin’s effects on generosity
Image: iStockphoto
A little stress can do a mouse good, a new cancer study suggests.
Matthew During wanted to see whether stressing out mice by messing with their environment would affect the rate of tumor growth. So, for a study that now appears in Cell, he and his team divided up their mice into two groups. Some mice lived quiet, peaceful lives in cages shared between five mouse roommates, while the other group lived in a stressful cluttered cacophony, where the cages held 18 to 20 animals plus numerous distractions and challenges like toys, mazes, and wheels.
Mice were then injected with tumor cells, which led to malignancies in all of the control animals within 15 days… The rate of tumor formation in animals living in the enriched environment was significantly delayed, and 15 percent had not developed tumors after nearly three weeks; when tumors were visible, they were 43 percent smaller than the lesions on control animals [Scientific American].
Because the “enriched environment” gave those mice so much more to do, an obvious conclusion would be that it’s the uptick in physical activity—not the effect of added stress—that kept tumors at bay. So During’s team tested the mice to see if just giving them more time on the running wheel, independent of the other factors, was enough to see the effect. It wasn’t.
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It feels good to win. And it feels even better to win at home.
For a new study in the Proceedings of the National Academy of Sciences, Matthew Fuxjager and his colleagues investigated the winner effect, wherein animals (and perhaps humans) build up testosterone in advance of a confrontation, and the fight’s winner maintains that elevated level. By studying male mice fighting one another, Fuxjager was able to see what happens in the brains of winners. Not only did victorious mice experience the “winner effect,” but those who won at home—in their own cages—saw the most activity, and wanted to keep on fighting.
To get these results, Fuxjager’s team essentially created a tournament of mouse fights.
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After years of denial, Floyd Landis–the cyclist who was stripped of his winning title to the 2006 Tour de France after failing a drug test–admitted last week that he did take performance enhancing drugs. And his confession is causing a stir, partly because he also implicated former teammate Lance Armstrong, seven-time-winner of the Tour de France (Armstrong denies the accusation), and partly because of the particular drugs he fessed up to taking:
Mr. Landis said in [several emails to cycling officials] that during his career, he and other American riders learned how to conduct blood transfusions, take the synthetic blood booster Erythropoietin, or EPO, and use steroids. All these practices are banned in cycling. Mr. Landis said he started using testosterone patches, then progressed to blood transfusions, EPO, and a liquid steroid taken orally. [Wall Street Journal]
EPO shook the cycling community in the 1990s, when police raids during the 1998 Tour de France (dubbed the “Tour de Dopage“) found that several riders were using EPO. It looks like the drug, believed to be thwarted by drug tests, has returned.
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All it takes for some people to be a little less trusting of their fellow humans is a little more testosterone, according to a new study in the Proceedings of the National Academy of Sciences.
Researchers led by Jack van Honk of the Netherlands used a sample of 24 women in their study. The team showed photos of 150 strangers’ faces to the women and asked them to rate the faces for trustworthiness, using a scale from -100 to +100. The scores women gave after receiving a placebo became their “baseline” score. The women also completed a trustworthiness survey after being given an increase in testosterone instead of placebo (they weren’t told when they received which).
Scientists found that women were not so easily taken in by a stranger’s face after receiving a dose of the hormone…. Women who appeared the most trusting after receiving the “dummy” placebo reduced their scores by an average of 10 points when their testosterone was boosted [Press Association].
Why? The researchers point to the social advantages testosterone can confer:
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As we slowly slide out of the steroid era in baseball, human growth hormone (HGH) lingers as the next doping trend in major sports. Players like the New York Yankees’ Andy Pettitte have been implicated as HGH users already, and teammate Alex Rodriguez in currently one of many players being questioned in a federal investigation into the substance. However, until now there was no hard evidence that athletes gained a competitive edge by taking it. Researchers say a new study changes that.
“This is the first demonstration that growth hormone improves performance and justifies its ban in sport,” said Dr. Ken Ho, who led the study [AP].
The new research shows that the gains for athletes cheating with HGH could be staggering—but uneven and fraught with side effects. In the study published in the Annals of Internal Medicine, researchers divided 96 athletes into groups that received either placebo, HGH, testosterone, or a testosterone/HGH mix:
After eight weeks, researchers found that growth hormone improved sprint capacity in men and women by an average of 3.9% over the placebo group — which would trim 0.4 of a second from a 10-second time in the 100-meter dash, said study lead author Dr. Kenneth Ho at St. Vincent’s Hospital in Sydney, Australia. In the 2008 Olympics, the top three male finishers had times of 9.69, 9.89 and 9.91 seconds.
That same 3.9% improvement could cut 1.2 seconds from a 30-second time in a 50-meter swim, Ho said [Los Angeles Times].
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The technical way to explain this odd-looking fowl is that it’s “gynandromorphous.” But if you just want to call it “one seriously confused chicken,” that works, too.
For a new study in Nature, Michael Clinton and colleagues investigated a few of these half-male, half-female chickens they obtained from chicken farms. Gynandropmorphs show up now and then not just in chickens, but also in parrots, pigeons, and some other kinds of animals. But scientists weren’t sure how the mix-up happens, since the standard idea for sex differentiation is that the sex hormones released by the gonads either masculinize or feminize the embryo. Clinton’s team discovered that bird cells don’t need to be programmed by hormones. Instead they are inherently male or female, and remain so even if they end up mixed together in the same chicken [BBC News].
The researchers had first assumed that the half-and-half chickens followed the hormone pattern, and that they were females with some sort of chromosomal problem on the male side (the lighter half of the bird in the image, which also sports a large wattle, sturdy breast musculature, and a leg spur on its male side). Instead, they found the chickens to be almost perfectly split between male and female. The hen half was, for the most part, made up of normal female cells with female chromosomes, whereas the cockerel side contained mostly normal male cells with male chromosomes [Nature News].
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Atrazine, one of the world’s most widely used herbicides, is wreaking havoc on the sex lives of male frogs. In a new experiment, exposure to the chemical emasculated more than half of the male African claw frogs in the study, and made one in ten turn into females. The results, which were published in the Proceedings of the National Academy of Sciences, have raised concerns that the herbicide found in waterways is altering amphibians’ hormones, and could potentially have similar effects on other animals, including humans.
Biologist Tyrone Hayes studied 40 male control tadpoles along with 40 male tadpoles reared in water tainted with atrazine. The levels of the chemical matched the levels the frogs would encounter in their natural settings, and was also within the drinking water standards set by the Environmental Protection Agency. The results showed that 75 percent of male tadpoles reared in atrazine-contaminated water developed into frogs that had low testosterone levels, decreased breeding gland size, feminized laryngeal development, suppressed mating behavior, reduced sperm production and decreased fertility, while the control group showed features typically found in male frogs [AFP]. Most of these “chemically castrated” frogs were unable to reproduce.
The rest of the results were even more dramatic. Ten percent of tadpoles raised in the chemically tainted water developed into frogs with male genetics but female anatomy, and some of these were actually able to breed and produce eggs. The offspring, researchers found, were all male because both parents contributed male genes. Scientists worry that the sex-reversed males and the subsequent production of all-male offspring is skewing the sex ratio of wild frog populations, and may be contributing to the decline of frog populations worldwide.
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For the first time, researchers have found that oxytocin–the hormone at work when breastfeeding mothers bond with their babies and when couples cuddle–can help autistic patients with social interactions. The small but pioneering study showed that when autistic adults inhaled the “love hormone” oxytocin though a nasal spray, they paid more attention to expressions when looking at pictures of faces and were more likely to understand social cues in a game simulation [Reuters].
The findings will be published this week in the journal Proceedings of the National Academy of Sciences. Although more research is needed to confirm and explore the findings, the results are the latest in a growing body of evidence indicating that the hormone could lead to ways to help people with the often devastating brain disorder function better [Washington Post].
People with autism or with high-functioning autism spectrum disorders like Asperger’s syndrome have difficulty engaging in social situations [Scientific American]. They normally have trouble making eye contact and are awkward around other people. They also suffer from low levels of oxytocin–a hormone that is found naturally in humans and animals and helps humans understand emotions and social cues better.
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As 80beats reported back in March, the World Anti-Doping Agency (WADA) has been experimenting with so-called biological passports to curb cheating in sports. Biological passports are electronic records for individual athletes that provide baseline measurements of substances in their blood and urine that officials can track to catch juiced athletes, since a sudden deviation from the baseline would suggest funny business.
Now, the WADA has released a new set of guidelines to monitor athletes’ blood profiles for evidence of performance enhancing substances. The guidelines take effect immediately and provide advice to antidoping agencies on how to put programs in place to collect and store athletes’ blood samples and monitor them for any variations that could indicate doping—without an actual positive test [The New York Times]. The new guidelines are necessary to keep pace with increasingly sophisticated cheating techniques, such as hormone injections, self-blood transfusions, and potentially gene doping.
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Two researchers have reviewed the body of research on the effects of birth control pills on both women and men’s perceptions of attractiveness, and have come to some provocative conclusions. Women on the pill are less attracted to hyper-masculine men, they found, and don’t show the typical propensity towards men who are genetically dissimilar from themselves. In addition, women on the pill may lack the attractiveness edge that’s associated with ovulation, the study found.
An alarmist, tabloid-esque summary of the findings might read like this: Pill-taking women aren’t hotties, and they pick girlie men who are likely to give them ugly babies. But of course, there’s a lot more complexity to the findings. The contraceptive pill alters monthly fluctuations in hormones associated with the menstrual cycle, mimicking the more stable hormonal conditions associated with pregnancy [New Scientist]. While mounting evidence suggests that having one’s hormonal levels smoothed out in this way alters some of the laws of attraction between men and women, scientists hasten to add that hormones aren’t everything.
The new study (pdf), published in Trends in Ecology and Evolution, looked first at research that’s been conducted on women’s preferences for men. Women who aren’t on the pill have shown a preference for certain types of men while they’re ovulating: they prefer men with more traditionally masculine facial features, and have also been shown to prefer the smell of men who are genetically dissimilar (which in humanity’s earlier days, when inbreeding was a danger, would have been an advantage). Women on the pill don’t show these same preferences. But many would argue that personality is a far better way to choose a life partner than what they smell like. One recent study involving speed-dating experiments suggested that although women might say they prefer the scent of men with dissimilar immune systems, this doesn’t correspond with the men they actually chose to go out with [New Scientist].
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