When it comes to a sperm fertilizing an egg, it all comes down to speed and timing. If the sperm starts swimming at top speed too soon, it will die before it reaches the egg. But if it swims too slowly then it won’t get to its destination in time. Now, scientists have discovered a system in the sperm that acts like a gas pedal, causing the sperm to swim faster as it gets closer to the egg. The findings were published in the February issue of Cell.
Researchers already knew that the speed of a sperm depends on its pH, or its internal acidity levels. The less acidic and more alkline it is, the faster it swims. They also knew that a sperm doesn’t sprint at top speed for its entire trip through a woman’s reproductive tract. It travels relatively slowly for the first part of its journey, and then gets lodged in the sticky folds of the fallopian tubes, resting until another, still unknown signal raises their pH again. This initiates their final race to the egg. “It’s a tough job for a sperm — when it’s deposited it has to travel a long distance to the egg sites,” [said Dejian Ren, who was not involved in the new study]. “This process has been known for many decades, but how it actually happens remained a mystery” [The Scientist].
(more…)
There’s been lots of gloating, arguing, and tossing around of cliches like “game-changing” in the wake of a new study on abstinence education and its potential to reduce sexual activity in teens. But the study isn’t exactly what the political forces trumpeting its arrival would like you to believe.
The study appears in the journal Archives of Pediatrics & Adolescent Medicine. In its introduction, study leader John B. Jemmott III concludes that “Theory-based abstinence-only interventions may have an important role in preventing adolescent sexual involvement.”
So what’s actually in the study? Between 2001 and 2004, Jemmott’s team studied 662 African-American middle schoolers in the northeastern United States, who were each paid $20 a session to attend sex-education classes. The kids were randomly assigned to one of several different programs: One program emphasized only abstinence, one both safe sex and abstinence, one just safe sex, and the last was a control group that simply taught healthy living—eating well, exercise, and the like.
(more…)
Biologists are a step closer to figuring out the bizarre animals known as bdelloid rotifers, thanks to a new study in Science.
This group of near-microscopic aquatic organisms has lived for tens of millions of years without sex, can withstand blasts of gamma radiation, and if their habitat dries up they can survive for years in a dessicated state. Two years ago, DISCOVER covered the findings that determined how these all-female invertebrates manage to diversify their genes without sex: Their genome breaks apart when they dry up, and as they reassemble when water returns, they pull in new DNA from a host of other beings. Now, the new study says, drying up is also the key to how rotifers avoid parasites that would normally take advantage of their asexual ways.
(more…)
As if soccer, wars of incredible length, and the relative worth of wine vs. beer didn’t account for enough disagreements between Britain and France, add another spat to the pile: whether or not the G-spot really exists.
A few weeks ago, a team of scientists from King’s College London joined the ongoing scientific fray by publishing a new study on the much-debated female erogenous zone. It was the biggest to date, involving 1,800 women – all of whom were pairs of identical or non-identical twins. If the G-spot did exist, it said, then genetically identical twins would have been expected to both report having one. However, no such pattern emerged [The Telegraph]. As a result of the study, coauthor Tim Spector said, the study “shows fairly conclusively that the idea of a G-spot is subjective.”
(more…)
Researchers from the Imperial College London have a new strategy to combat malaria. The species of mosquito responsible for the spread of malaria in Africa, Anopheles gambiae, only mates once during its life. Putting a stop to their one shot at reproduction should slow down malaria transmission. Anopheles males deploy a glob of proteins and fluids known as a “mating plug” that is essential for ensuring sperm is correctly retained in the female’s sperm storage organ, from where she can fertilise eggs over the course of her lifetime [BBC News]. Without a mating plug, the sperm is not stored and the mosquitoes can’t reproduce. Simply put, the researchers want to prevent male mosquitoes from plugging in the wild.
Anopheles gambiae is the only known species of mosquito to use a mating plug. (However, mating plugs are found in other animals where they prevent multiple males from reproducing with a female. Plug checking mice in research laboratories is a right of passage for many graduate students.) In their research, written up in the journal PLoS Biology, scientists were able to alter the mosquitoes’ genes so that they could no longer form a plug, and thus were unable to reproduce. If this process could be developed for use in the field, perhaps in a spray form like an insecticide, it could “effectively induce sterility in female mosquitoes in the wild,” [study author Flaminia] Catteruccia wrote, offering potential as “one more weapon in the arsenal against malaria” [Reuters]. The WHO is optimistic that their increased funding efforts will produce more technologies similar to this one and that, hopefully, one of them will prove effective.
Related Content:
80beats: Potential Mosquito Repellent Keeps Them From Smelling Victims’ Breath
80beats: DEET Is Harmful to Cells in Lab Settings. What’s the Significance?
80beats: The Ultimate Source of Malaria Is Found in Chimps
Convicted sex offenders living in New York can say goodbye to their social-networking privileges. The state has just booted 3,533 convicted sex offenders off MySpace and Facebook in an attempt to fight online sexual predators.
The purge was the first sweep of registered sex offenders under the Electronic Security and Targeting of Online Predators Act (e-STOP), a 2008 law Attorney General Andrew Cuomo aggressively pushed [New York Daily News]. Those removed from Facebook and MySpace will be referred to their parole officers to determine if anyone violated the terms of their release by being on a social networking site. The e-STOP law bans those sex offenders whose victims were minors from joining social networking sites.
(more…)
Scientists have argued before that controlling the earth’s burgeoning population would be one of the most effective ways to slow global warming, since keeping millions of little consumers from being born would reduce the amount of fossil fuel that would have to be burned to keep them warm and fed and happy. Now, an advocacy group that focuses on overpopulation is taking the argument the next step, suggesting that people or companies looking to offset their carbon dioxide emissions should buy contraception that would be distributed in poor countries.
Optimum Population Trust (Opt) stresses that birth control will be provided only to those who have no access to it, and only unwanted births would be avoided. Opt estimates that 80 million pregnancies each year are unwanted. The cost-benefit analysis commissioned by the trust claims that family planning is the cheapest way to reduce carbon emissions [The Guardian].
(more…)
Researchers have long sought an answer to burning question of why women live longer on average then men (you know, other than the fact that, as Harry Belafonte puts it, “man smart, woman smarter“). Now a new study in Human Reproduction by Japanese researchers reinforces the argument that the fault lies in men’s genes, a conclusion they reached by taking males completely out of the picture.
They studied mice created with genetic material from two mothers, but no father. This was achieved by manipulating DNA in mouse eggs so the genes behaved like those in sperm [BBC News]. The scientists then implanted those sperm-behaving eggs into female mice, creating 13 “bimaternal” mice. On average, these fatherless mice lived a third longer than those conceived in the usual manner, according to study leader Tomohiro Kono.
(more…)
A chemical commonly found in plastics that has recently fallen under intense scrutiny by public health officials has now been linked to impotence. During a five year study, scientists followed 634 male Chinese factory workers who were exposed to high levels of the chemical bisphenol A (BPA) on the job and compared their sexual health with that of similar Chinese factory workers not exposed to BPA. The men handling BPA were four times as likely to suffer from erectile dysfunction and seven times as likely to have difficulty with ejaculation [Washington Post]. The study (PDF), published in the journal Human Reproduction, marks the first time sexual dysfunction has been linked to BPA exposure.
To be fair, the workers were exposed to BPA levels that are 50 times greater than the average U.S. man faces, so scientists can’t say how smaller amounts of the chemical will affect sexual health. However, the chemical resembles the hormone estrogen and that’s fueled worries that even very small amounts of BPA can cause harm [NPR News]. The feds are determined to get to the bottom of the issue and have pledged $30 million to researchers over the next two years in an effort to finally settle the question of whether BPA is safe.
(more…)
Our long national nightmare is over: At last, scientists can make rabbit penis spare parts.
In the Proceedings of the National Academy of Sciences, researchers led by Anthony Atala published the results of their successful attempt to engineer new corpora cavernosas, the column of tissue that engorges with blood during male arousal, for male rabbits. Other procedures can partially restore function to a damaged phallus, and Atala’s team has previously shown they could replace a small portion of the tissue (they had up to a 50 percent success rate in rabbits) [Scientific American]. This, however, was the first time they totally replaced corpora cavernosas.
Atala is best known for developing a technique in which cells are taken from an organ and sprayed onto a frame made of collagen, the primary structural protein in animal tissue. The structure is then bathed with growth-stimulating compounds and kept in an oven that duplicates the body’s temperature and chemical composition. Given these starting conditions, natural biology does the rest [Wired.com].
In this experiment, the team surgically removed the corpora cavernosas of 12 rabbits, and replaced them with new “scaffolds” built through this technique. The tissue took hold, and copulation ensued at stereotypical rabbit pace. Every one of the revitalized dozen attempted to mate within a minute of being introduced to females; four became fathers.
The Wake Forest research contains the standard caveat: No, the technique isn’t ready for humans yet. But when it is, look out. Such methods could potentially aid men who just want to enhance their normal penises, rather than repairing any damage. “Our intent and the goal of our work is to provide a solution for men who need penile erectile tissue for medical reasons…. Of course, you cannot control how the technology is used in terms of what patients want” [LiveScience], says Atala.
Related Content:
80beats: To Mend a Broken Heart, Scientists Start in the Stomach
80beats: Scientists Transform Diabetics’ Skin Cells Into Insulin-Producing Cells
80beats: Adult Mouse Gets a New Tooth, Grown From Embryonic Cells
Discoblog: Need a New Pancreas? It May Come from a Sheep.
Image: flickr/Gidzy
Before one species of jumping spider, known as Evarcha culicivora, goes trolling for a mate, it firsts look to feast on blood-fattened mosquitoes. What happens next seems like something out of a bad video game: The delicacy gives the spider a special power–a sweet smell that the opposite sex finds irresistible.
In a new study, which will be published in the Proceedings of the National Academy of Sciences, researchers exposed E. culicivora specimens to the odors of others raised on blood-fed female mosquitoes and on three other diets: sugar-fed females, males and lake flies…. [The] tested spiders of both sexes were most strongly attracted to the odor of spiders reared on blood-fed female mosquitoes. But the attraction was only for spiders of the opposite sex [The New York Times]. Spiders would hang around blood-fattened spiders of the opposite sex four times longer than they would linger around those fed on another diet. The blood perfume effect might only be triggered by a gender specific hormone, the researchers suggest.
(more…)
British doctors claim to have made an important step toward completing the first womb transplant. They say they have solved the problem of keeping the blood flowing to the transplanted uterus so that a pregnancy can be carried to term in the recipient. Womb transplants, if proven successful in humans, would offer an alternative to surrogacy or adoption for women whose own wombs have been damaged by diseases such as cervical cancer. Around 15,000 women of childbearing age are currently living with a womb that does not work or were born without one [Guardian]. The research was presented at the American Society for Reproductive Medicine (ASRM) conference in Atlanta.
However, the technique has only been demonstrated in rabbits, a far cry from successfully completing a womb transplant in humans. Using a “vascular patch technique” major blood vessels including the aorta were connected. Two of the five rabbits lived to 10 months and dissection after death showed the womb had stayed healthy [BBC News]. The research team has yet to show that the new wombs can actually support a pregnancy, which leaves some scientists skeptical that the procedure is actually an advancement.
Ethicists, medics and feminists have long argued as to whether infertility is a disease or a cultural phenomenon born of a society where women feel they have no value if they cannot reproduce. But illness or otherwise, it is not a fatal disease, and the suggestion that women could undergo major transplant surgery to fulfill their desire for a child may prompt unease [BBC News]. A woman who received the transplant would have to take drugs to suppress her immune system to prevent her body from rejecting the foreign organ. To avoid taking the drugs for life, the uterus would likely be removed again after the desired babies had been born.
Related Content:
80beats: Are Birth Control Pills Changing the Mating Game?
80beats: The Woman of Tomorrow: Shorter, Plumper, & More Fertile
80beats: Is It Ethical to Pay Women to Donate Eggs for Medical Research?
Image: iStockphoto
Look into the future and see the women of tomorrow! A new study predicts that future women will be a tad shorter, heavier, and more fertile—that is, if the women who are currently most successful at producing children are any indication. The team studied 2238 women who had passed menopause and so completed their reproductive lives…[and] tested whether a woman’s height, weight, blood pressure, cholesterol or other traits correlated with the number of children she had borne. They controlled for changes due to social and cultural factors to calculate how strongly natural selection is shaping these traits [New Scientist].
Their results show that shorter, heavier women tend to have more children, as do women with lower blood pressure and cholesterol. If the mothers pass on these traits for 10 generations, the average woman in 2409 will be 2 centimetres shorter and 1 kilogram [about 2 pounds] heavier than she is today. She will bear her first child about 5 months earlier and enter menopause 10 months later [New Scientist]. A two-centimeter decrease over 400 years may be a modest change, but the researchers say it’s evolution in action. The study will be published in Proceedings of the National Academy of Sciences.
(more…)
By altering a female fruit fly’s pheromones, researchers have created an insect with so much sex appeal that it even attracts males of other species. But in a surprising twist, they didn’t boost the levels of some courtship chemical–instead they created flies that lacked all pheromones, which were then besieged suitors. The discovery suggests pheromones can be back-off rather than come-hither signals. The finding could lead to a better understanding of the chemical signals that help flies and other animals interpret the world, including how to select a mate and how to distinguish other species [Science News].
The study, published in Nature, also found that males who lacked all pheromones attracted unwelcome attention from other males, who attempted to copulate with their heads. Says lead researcher Joel Levine: “It’s amazing what you see…. There are some pretty crude movies” [Nature News].
To conduct their experiments, the researchers identified the cells on the inside of the fly’s exoskeleton (pictured in glowing green) that produce the pheromones, and inserted a gene into the fly genome to kill all these cells. The manipulated flies provided a sort of blank canvas to allow the scientists to test the role played by each chemical – and how the chemical signals interacted. “We found that one compound – one that males transfer on to females when they copulate – kept other males away,” said Dr Levine. “It’s the male’s way of sort of protecting his investment” [BBC News].
Related Content:
80beats: Fake Love Pheromone Lures Invasive Vampire Fish to Their Doom
80beats: Do Humans Communicate Via Pheromones? The Jury is Still Out
80beats: Ants That Illegally Procreate Are Revealed By Their Guilty Smell
Image: Jean-Christophe Billeter
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].
(more…)
