GALVESTON, Texas, April 21 (UPI) -- U.S. scientists said they have found strong evidence that proves the controversial theory that proteins cause mad cow disease and similar brain disorders.
Claudio Soto, of the University of Texas Medical Branch, said his findings, which appear in the April 21 issue of the journal Cell, offer "the best and final proof for the prion hypothesis."
The prevailing theory is mad cow and similar disorders are caused by an infectious protein called a prion, but this has remained controversial because prions have never been shown to be capable of causing disease.
In the study, Soto's team isolated prions from the brains of hamsters experimentally infected with scrapie, a mad cow-like illness that occurs in sheep. They amplified the prions and injected them back into healthy hamsters, which subsequently came down with scrapie symptoms.
Some experts said, however, the study still leaves open the possibility other pathogens may be the cause of these diseases.
Pierluigi Gambetti of the National Prion Disease Pathology Surveillance Center in Cleveland, wrote in an editorial accompanying the Cell article that Soto's experiment had not ruled out the possibility of other infectious agents contaminating the original sample.
