Prion

A Red Flag for a Neurodegenerative Disease That May Be Transmissible  Animal experiments show how a just-discovered prion triggers a rare Parkinson’s-like disease ----------------------------- Much evidence now supports the idea that many neurodegenerative diseases share this core mechanism of self-propagating proteins that accumulate and ultimately kill cells. Similar findings have been reported for amyloid beta, the protein that accumulates in Alzheimer's disease, although typically in terms of increasing damage, rather than transmission. “I think Prusiner's concept is valid—it's just important to be a bit careful about what you call a prion,” says Lary Walker, a neuroscientist at Emory University who was not involved with the study. “All these other diseases arise spontaneously within the brain; there's no evidence they're infectious by any standard definition of the word.” Walker and colleagues argue for changing the definition to proteinaceous nucleating particle. But the number of cases of prion disease from transmission, in humans, is actually tiny as a proportion. “The vast majority are sporadic, then genetic, then a tiny minority from infections,” Giles says. “A big difference is there aren't equivalents of Alzheimer's, Parkinson's and MSA in animals, and we don't generally eat humans.”