For many laboratories, monkey business is no laughing matter. The rise in bioterrorism research after the Sept. 11 tragedy puts an increased demand on the already limited supply of rhesus monkeys for research ("Monkey deficit crimps laboratories as scientists scramble for alternatives," The Wall Street Journal, May 14, 2002). The genetic similarity between humans and rhesus monkeys has helped establish the species as the preferred nonhuman primate model for medical research, making the monkeys essential for researching diseases such as AIDS. Once available from India for $80 (US), a healthy female rhesus monkey can now fetch as much as $14,000. "It's classic economics," says Andrew Lackner, director of the Tulane National Primate Research Center in Covington, La. "Bioterrorism research has placed increased demands on the system, outstripping the supply." Tulane has a breeding program, as do all eight of the National Institutes of Health primate research centers, but a female rhesus monkey can produce only one offspring each year. Although alternative nonhuman primates are available, many researchers hesitate to use them because of their extensive knowledge of the rhesus immune system. "If you change your species, all the history you've accumulated goes out the window," says Ron Desrosiers, director of the New England Primate Research Center, Southborough, Mass. Michael Friedman, chief medical officer for biomedical preparedness at the Pharmaceutical Research and Manufacturers of America Foundation (PhRMA), says many researchers have advance requests for rhesus monkeys; they are hoping to avoid time-consuming searches for test subjects in the future.
A Chink in the Armor of Soy's Healthy Reputation?
Soy, typically regarded as a vanguard of health and nutrition, may weaken an infant's immune system by shrinking the thymus gland and hindering other immune system functions. Researchers say the culprit, genistein, is an isoflavone found in soy milk and can mimic the immunosuppressing characteristics of estrogen (S. Yellayi et al., "The phytoestrogen genistein induces thymic and immune changes: A human health concern," Proceedings of the National Academy of Sciences, 99:7616-21, May 28, 2002). In genistein-fed mice whose blood levels were similar to those of infants fed soy-based formula, the weight of the thymus gland, where immune cells mature, was decreased by as much as 20%. Thymocyte levels decreased as much as 86%, and apoptosis doubled. Soy-based formula is used to feed 15% of infants in the United States. Paul Cooke, veterinary biosciences professor at the University of Illinois in Urbana-Champaign, says large-scale studies of these infants' immune systems are needed to conclusively verify the murine-based results, but he emphasizes that the study is still grounds for concern. Other studies, he says, have indicated that low doses of genistein can stimulate immune systems. "If you have no need to use soy formula, I wouldn't use it. Breastfeeding is flat-out the best way," says Cooke. "It's difficult to come up with an accurate blanket statement, but clearly these things have effects."
Out of, and Into, Africa
|Courtesy of NOAA |
A multicenter team has reported the largest analysis of DNA sequences unique to the Y chromosome in African populations, superimposed on geographical data for a peek at the past (F. Cruciani et al., "A back migration from Asia to Sub-Saharan Africa is supported by high-resolution analysis of Y-chromosome haplotypes," American Journal of Human Genetics, 70:1197-1214, May 2002). In 608 men from 22 African populations, researchers examined 77 Y-chromosome sites, each with two variants, which form 37 haplotypes or combinations of DNA sequences on one chromosome. The extensive results reveal that the Khoisan people, who today live south of the Sahara, actually originated in eastern Africa. Perhaps a long-ago migration contributed to their unique combination of traits, which includes skeletal distinctions, light skin color, large buttocks, and the clicking sounds in their language—as well as characteristic differences in DNA sequences. The evidence also indicates that the ancestors of modern males living near Lake Chad in central western Africa detoured to Asia before returning to Africa. "This finding does not alter the 'out-of-Africa' theory. There was an initial out-of-Africa migration and a later Asia-to-Africa back migration," explains Fulvio Cruciani, a research geneticist at the University La Sapienza in Rome.
Take Five? Researchers Say Grab an Hour
|Courtesy of Fragtopia Main Event|
A workday snooze may be more than the stuff of dreams—the brain may require the time out. Human performance on a visual-shape discrimination test deteriorated after subjects took repetitive tests during a day without resting. But researchers found that the subjects' optimum performance levels returned after the scientists repositioned the test objects and after the subjects took hour-long naps (S. Mednick et al., "The restorative effects of naps on perceptual deterioration," Nature Neuroscience, published online May 28, 2002, doi: 10.1038/nn864). During repetitive testing, the neurons of the early visual cortex became fatigued and experienced information overload. Psychology graduate student Sara Medwick of Harvard University says that an unvaried activity, such as typing, may become more inaccurate throughout the day. Besides a nap, she says, people also should switch tasks to avoid overtaxing any one part of the brain. "A nap allows you to go back to your optimal performance level or switch whatever part of the brain you are using," explains Medwick. "A half hour will stabilize performance, but there is much greater benefit from an hour." Medwick hopes to determine the neurological mechanisms that are responsible for sleep-dependent learning as well as those that induce learning during sleep.
Fly Research Bears Fruit
|Erica P. Johnson|
Already a powerful tool for studying genetic variation, Drosophila may provide insight into biodiversity and evolution in humans as well. The Human Genome Sequencing Center (HGSC) at Baylor College of Medicine in Houston recently received a $5 million grant from the National Human Genome Research Institute to sequence the genome of the fruit fly Drosophila pseudoobscura. Richard Gibbs, HGSC director, says the decision to sequence D. pseudoobscura is based on a likely sequence homology to D. melanogaster. "You want an organism that is distant enough to feature some divergence, but close enough to show some conservation, ... a lot like the relationship between mice and humans," Gibbs says. He attributes the grant to his institution's capabilities with the 'whole-shotgun' sequencing technique used in previous projects. Over the past three years, HGSC has collaborated with other institutions—public and private—to sequence D. melanogaster, rat, and slime mold. Gibbs maintains that while the Drosophila research community will be involved with annotation and data distribution, sequencing will remain an in-house project. The project is slated for completion by 2003, but Gibbs is optimistic it will be completed before the end of the year. "This would have been a big project a few years ago, but now an organism of this size can be comfortably done in one center," Gibbs says.
Getting Microfluidics Flowing
|Courtesy of Dave Beebe Lab, University of Wisconsin-Madison|
A new technique developed by university engineers can make microfluidic devices, such as the lab on a chip, in less than one-hundredth of the time now needed, according to one of the developers. "We can make devices in one or two minutes," says David Beebe, associate professor of biomedical engineering at the University of Wisconsin in Madison. This is an improvement on the reigning cheapest way, elastomeric micromolding, which requires a minimum of several hours. Reduced fabricating time can translate into cost savings, says Beebe, who developed the process with research scientist Glennys Mensing. The technique relies on liquid-phase photopolymerization to create the microfluidic channels directly from a liquid, Beebe says. Current processes involve using solids to make the channels, and then etching them away. The new process also circumvents the need for a clean room and other specialized equipment. Beebe also notes some limitations to the new technique—namely resolution. "In two minutes we can make low-resolution microfluidic devices on the order of 50- to 100-micron channels. If we want to go below that, the cost starts to creep back up, because you have to have high-resolution lithography, which implies more expense," Beebe says. The emergence of nanofluidics lays out a tougher task for the researchers as new technologies require devices with higher resolutions. "We're trying to get this process down to that scale," he states.