 |
||
 |
|
|
 |
 |
 |
 |
 |
 |
 |
 |
The Yale Alumni Magazine is owned and operated by Yale Alumni Publications, Inc., a nonprofit corporation independent of Yale University. The content of the magazine and its website is the responsibility of the editors and does not necessarily reflect the views of Yale or its officers. |
|
In the animal kingdom, no masculine creature is better endowed than certain male ducks. Only three percent of all bird species possess what biologists call a phallus (defined as an “intromittent organ” that has no internal urinary plumbing and so is quite different anatomically from a penis). Among ducks such as the mallard, the Pekin, and the long-tailed, the phallus can reach surprising length: 4 to 5 inches is common. The Argentine river duck, the champion in this department, has a phallus up to 16 inches long—longer than the bird itself. In all these duck species, the organ, which shrinks to the size of a rice grain after the mating season and grows again the following year, is elaborately coiled. But although this phallus was first described in detail more than 100 years ago, no scientist ever bothered to investigate what seems the obvious corollary. That is, until Patricia Brennan, a post-doctoral researcher in ecology and evolutionary biology, entered the field. “What kind of structure,” Brennan wondered, “did he put it into?” Brennan says the answer, described in the May issue of the journal PL0S One, was “definitely not what I expected.” Unlike mammals, birds are equipped with only one opening, the cloaca, for reproductive and excretory functions. The phallus, when not in use, is tucked out of sight inside the cloaca. In most birds, which don’t possess a phallus at all, the transfer of sperm from male to female is accomplished by bringing the cloacas together, a fairly gymnastic move often called a “cloacal kiss.” Sperm then enter a small vagina-like tube and travel to the oviduct to fertilize the eggs. Given the size of the duck phallus, Brennan guessed that she'd find “an enlarged but simple sack” when she dissected female ducks. Instead, she uncovered a coiled organ bristling with detours, roadblocks, and dead ends. Upstream, it coils in the opposite direction from the phallus. “If you think of genitalia as locks and keys, then what we have here is an anti-lock-and-key situation,” says Richard Prum, the William Robertson Coe Professor of Ornithology and one of Brennan’s co-authors. “It seems designed to exclude males rather than let them in.” Brennan, Prum, and their colleagues analyzed the genital morphology of 16 duck species. They discovered that both the size of the phallus and the complexity of the female structures increased in relative lockstep with one variable in duck ''>But she believes that these female ducks must have also evolved “various ways to make it easy for her chosen mate to pass the barriers.” To investigate the mechanics of what Brennan terms “female cryptic choice,” she and Prum have designed an anatomically accurate model of a female duck. “Robo-hen” is equipped with a high-speed video camera. If all goes well, the model will supply clues as to just how the female duck helps her mate over the hurdles. But Robo-hen failed its initial test last month. Brennan blames bad timing, not the model. “The males were just not in the mood, since they wouldn’t mate with a real female either,” she says. Next, researchers plan to test Robo-hen with domesticated ducks less subject to seasonal fluctuations in hormones. Perhaps they should also provide a whiff of Eau de Pekin and the soundtrack from Duck Tales.
Gatekeepers of the Mind Working memory is a mysterious kind of inward eye that allows us to maintain brain-based models of our surroundings. Amy Arnsten, a medical school neurobiologist, has for the first time isolated its molecular lock-and-key mechanism, gaining insight into one possible cause of the cognitive deterioration associated with mental illness and old age. Arnsten’s breakthrough arose out of her curiosity about a drug she'd studied called guanfacine, occasionally used to treat attention deficit hyperactivity disorder (ADHD). The drug improved cognitive functioning, and it also inhibited a brain messenger called cyclic AMP. Arnsten figured out how the two were connected. She and her research team found that cells in the prefrontal cortex—the brain region responsible for high-level abstract thought—contain gatekeepers called HCN channels, which control the electrical flow of information through each cell’s membrane. Cyclic AMP locks and unlocks these channels. When cyclic AMP floods into the area near an HCN channel, the channel pops open—short-circuiting the membrane’s ability to transmit electrical signals and so cutting off the transmission of new information. When cyclic AMP is not present, however, the channels squeeze shut again, allowing information transmission to continue. Drugs like guanfacine work by stopping production of cyclic AMP, thus allowing the cortical network to remain connected and critical working-memory functions to proceed unchecked. Arnsten next plans to investigate whether conditions like ADHD, schizophrenia, and age-related cognitive decline might be touched off by the opening of too many HCN channels, leading to mental lapses.
Not-So-Lonesome George
When Lonesome George, the giant Galapagos tortoise that Guinness World Records calls the “rarest living creature,” was discovered in 1971 on the isolated island of Pinta, he was thought to be the last member of Geochelone abingdoni. But a recent DNA analysis suggests that other abingdoni tortoises might still be living on Isabela, an island nearby. Yale biologists Gisella Caccone and Jeff Powell and their colleagues tested DNA from a diverse community of tortoise species. In the May 1 issue of Current Biology, they report finding a male hybrid tortoise whose father was a pureblood member of George’s species. Since Isabela supports a large tortoise population, Caccone and Powell, when they can get funding for a return trip, expect to find other animals with Pinta genes—maybe even a pureblood abingdoni, so the two could breed. (George, who in captivity has failed to mate with females of closely related tortoise species, would have to show a little more enthusiasm.) If they find a female, Caccone already has a name. “We should call her ‘Esperanza,’” she says. “Hope.”
Breath and Birth Air pollution poses well-documented health dangers for everyone, but recent research by a team of Yale scientists offers conclusive evidence that mothers-to-be have particular reason for concern. “We found that the higher the air pollution exposure to the mother during pregnancy, the lower the birth weight,” says Michelle Bell, an assistant professor in the environment school. Bell and her team found that maternal exposure to air pollution increased the risk that infants would weigh under 2,500 grams (about 5.5 pounds), the medical definition of low birth weight. Infant mortality is strongly linked to low birth weight, and studies have demonstrated a correlation between it and subsequent health problems in adulthood, including diabetes and cardiovascular disease. In an article published online on April 11 in Environmental Health Perspectives, Bell and her colleagues compared levels of common pollutants—nitrogen dioxide, carbon monoxide, sulfur dioxide, and two kinds of minute airborne particles—against birth-weight records for more than 350,000 infants born in Connecticut and Massachusetts. Pollution levels observed in the study were relatively low. Of the 15 counties in the study, only two, New Haven and Hartford, failed to meet air pollution health standards. The researchers found that with the exception of sulfur dioxide, exposure to these pollutants lowered birth weights. For African American mothers, exposure to small airborne particles, commonly found in vehicle exhaust, was particularly high. The effect of air pollution on birth weight is relatively small in comparison with other influences on fetal health, like maternal smoking. But Bell cautions that “infants of black or African American mothers are already at higher risk for low birth weight. An additional risk could make the effect much higher.”
Noted Neural stem cells may help repair brains ravaged by Parkinson’s disease. Medical school neurobiologist D. Eugene Redmond Jr. and colleagues injected human neural stem cells into 29 monkeys with the disorder. All tolerated the treatment, and several experienced significant improvements in their ability to move, the team reported in Proceedings of the National Academy of Sciences online in June. But it will be years before the procedure is ready to test on humans. Adult resistance to evolution and to other scientific explanations, write psychologists Paul Bloom and Deena Skolnick Weisberg, may have roots in childhood. In a review of scientific literature for Science (May 18), they note that when scientific claims clash with a child’s intuitive understanding, science often loses. Resistance can persist, particularly if trusted authorities reinforce the non-scientific intuitions. The 2003 adoption of rules limiting hospital resident physicians to 80 hours per week did not lead to health care declines. In fact, write Leora Horwitz, a medical school postdoc, and her colleagues in Annals of Internal Medicine online (June 5), Yale–New Haven Hospital saw improvements: for instance, fewer patient transfers to intensive care and fewer interventions by pharmacists to prevent medication errors. If you enjoy cooling down with ice cream or iced tea,
thank your TRPM8. Pharmacology professor Sven-Eric Jordt and colleagues have
found that this protein helps trigger the cellular mechanism by which the body
detects cold temperatures (as well as the chill of menthol). In experiments, mice unable to produce this critical protein were less sensitive to the cold
than normal mice. The work appeared in the May 30 online edition of Nature. |
|
|
|
|
|
|
|
|
|
||
|
||
©1992–2012, Yale Alumni Publications, Inc. All rights reserved. Yale Alumni Magazine, P.O. Box 1905, New Haven, CT 06509-1905, USA. yam@yale.edu |
||