Science News, Feb. 3, 2007 LONDON - Mad cow disease and other brain disorders stemming from prion proteins have long resisted cure. Now, in a test in mice, a prion disease caught early has been reversed.  Prions-misfolded versions of a natural protein called PrP-trigger normal PrP to misfold in the same way. Over time, prion infection kills so many neurons that the brain becomes riddled with holes.  In the new study, neurologist Giovanna R. Mallucci of the Institute of Neurology in London and her colleagues tested whether shutting off the prions' supply of PrP could alter the course of disease.  "They are seeing alterations before there is massive damage in the brain," says neuroscientist Claudio A. Soto of the University of Texas Medical Branch in Galveston. "This is very important because that's when these changes are still reversible."