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 GENETICS: Receptors Discovered that Direct Rod Cell Development
HMS researchers have identified a new and surprising mechanism by which rod photoreceptors--the specialized light-gathering cells that line the retina--develop from a pool of undifferentiated precursors. Tracy Young (on left) and Connie Cepko show in a March 25 Neuron study that a pair of neurotransmitter receptors relay cues that tell the immature cells to develop into rods. The findings provide information that could lead to new methods of restoring or replacing these delicate cells, which are lost in retinitis pigmentosa and other blinding diseases.
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 SPECIAL REPORT: Visa Woes Threaten Conduct of Science
Visa delays caused by lengthy anti-terrorist screening procedures are taking a toll on the personal and professional lives of foreign students, research fellows, and faculty in the Harvard Medical community, report Sharon Ladd and others involved with the international community. Long waits to enter or reenter this country have interrupted research, discouraged international travel to scientific meetings, created uncertainty about visiting family members overseas, and may have begun to erode the ability of U.S. universities to attract the best minds from around the world. The trend is worrisome to those who believe science and technology advance best in an open society with a free exchange of information.
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 NEUROLOGY: Mutation Suggests Novel Signaling Mechanism in Brain Development
The cerebral cortex is the seat of many of the thought processes that make us human, including language, cognition, and problem-solving. It is no wonder then that the cortex in primates is so much bigger than it is in other animals. But what makes it so large? In the March 26 Science, Christopher A. Walsh and colleagues report that one little protein may play a big role. They reveal that mutations in GPR56, a G protein-coupled receptor, are responsible for the human disease bilateral frontoparietal polymicrogyria (BFPP). In this condition, the cerebral cortex is misfolded and much thinner than usual. The findings uncover a novel role for G protein receptors in human brain development and suggest how simple point mutations could have contributed to the evolution of the primate cortex.
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 METABOLISM: Kinase Pathway Seen to Regulate Urge to Eat
The search for obesity treatments has focused attention on neural pathways in the brain that control eating and metabolism. The enzyme AMP-dependent kinase (AMPK) has emerged as an important regulator of food intake in research by Barbara Kahn (left), Yasuhiko Minokoshi, and their colleagues at Beth Israel Deaconess Medical Center. AMPK activity in the hypothalamus was raised in mice whose food was withheld, and it declined in response to feeding, insulin, and leptin. Decreasing the activity of AMPK using a dominant negative kinase mutant caused the mice to eat less. The discovery, appearing online in Nature on March 17, reveals a new target for development of anti-obesity drugs.
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Copyright 2004 by the President and Fellows of Harvard College
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