Stories of modern science ... from UPI

SHARK PROTEIN PROMOTES WEIGHT LOSS

A substance derived from dogfish sharks suppresses appetite and decreases body weight in rodents, making it a potential new, safe anti-obesity treatment, researchers at Georgetown University and the University of Pennsylvania report. The researchers tested MSI-1436 -- a natural cholesterol-related compound derived from dogfish shark livers -- on normal and obese mice and rats. The findings were "striking," the researchers said. "The mice receiving the MSI-1436 ate less and lost weight. But the really remarkable thing was that they lost fat instead of muscle, and they experienced no decrease in their metabolism." In previous studies, MSI-1436 also was shown to correct Type II diabetes in animals with both the genetic and dietary forms of obesity. Small clinical human trials of the substance are expected to begin sometime next year.

WILD PLANTS OR FOOD?

Tiny, glassy structures called phytoliths in soil and plant remains are helping archaeologists to determine which plants were domesticated by early humans and when. Plant remains at archaeological sites usually are not well preserved, but the remains often contain the phytoliths, tiny silica dioxide deposits from plant tissues. The microfossils are considered smoking guns of plant domestication because they can distinguish a number of different crop plants clearly from their wild progenitors. For example, scientists at the Smithsonian Tropical Research Institute studied the rinds of 148 fruits from wild and cultivated species of squash. They found phytoliths formed in places in the rinds that can be used to identify when the plants grew and whether they were cultivated.

UNRAVELING WHY CELLS DIVIDE

Rockefeller University researchers have found a small but important error in understanding how and why cells divide. Studying cell division in yeast, they report in the British journal Nature that previous studies may have focused on the wrong protein -- a cyclin protein called Clb5. Cyclins help control when DNA in the nuclei of cells should rip itself into two halves, each of which grows into a new whole strand. Clb5 was thought to shut down cell division -- a crucial bit of knowledge in the quest to understand how the process becomes uncontrolled and sparks cancerous tumor growth. The researchers found cells do divide in the presence of Clb5, but Clb2 arrests the process. "Yeast and human cells share many of the same cell cycle mechanisms," researchers said. "Because of this and because they are easier to work with, yeast organisms are ideal models for studying how the cell cycle may normally work in humans, as well as how it might malfunction in cancer."

NEW CLUES TO EYE DEVELOPMENT

Researchers at the Salk Institute for Biological Studies have learned more about how the intricate process by which the eyes become wired to the brain. The researchers studied how a class of proteins called Eph receptors and ephrin ligands -- which cause cells either to repel or attract one another -- guide optical nerve cells to form delicate fibers connecting to the brain's visual centers. Studying eye development in mice, the researchers found different classes of the proteins helped guide axon growth from the top, bottom, right and left parts of the retina to their proper termination points within the brain. The researchers also found that in mice genetically altered to lack the proteins, optic nerves grew into incorrect areas of the brain. They concluded the proteins are needed to repel axons from areas where they do not belong. Although the findings do not have immediate clinical applications, the researchers said, they represent another page in the "manual for the wiring of the nervous system."

(Editors: For more information on SHARKS, contact Beth Porter at 202-687-4699 or bap2@georgetown.edu. For PLANTS, Dolores Piperno in Panama at +150-721-28101 or pipernod@tivoli.si.edu. For YEAST CELLS, Whitney Clavin at 212-327-7250 or clavinw@rockefeller.edu. For EYES, Wayne Carter at 214-648-3404 or Wayne.Carter@UTSouthwestern.edu)