In the third planet find, Sun Hong Rhie and David Bennett of the University of Notre Dame and their colleagues have located the smallest one yet, about the size of Neptune. Orbiting 300 million kilometers from its star, the planet was found through microlensing, which measures how the light from a star is gravitationally bent by a fainter star passing in front of it. A planet around the fainter star alters the light intensity in a distinct way. In another discovery that is changing the fundamental understanding of neurons, Jonas Frisen of the Karolinska Institute in Stockholm has located the stem cells of rat brains. Reporting in the January 8 issue of Cell, Frisen's team found that the rodent ependymal cells, which line the cavities of the brain's ventricles and the spinal cord, actually slowly divide, creating stem cells that can rapidly form into either neurons or support structures called glial cells.
Humans are likely to have neural stem cells in a similar location.
The identification of such cells could form the basis for treatment of spinal cord injuries or neural disorders such as Parkinson's. Overturning conventional wisdom, a collaboration supported by the National Institute of Allergy and Infectious Diseases has found that the thymus remains active into old age, albeit at a reduced level. The gland, located in the chest, produces the immune system's T cells and was thought to function only through childhood. It was, though, all in the name of science. James Levine and his Mayo Clinic colleagues were investigating why some people put on weight seemingly at the sight of food, whereas others can gorge themselves and stay svelte.