Prusiner, Stanley Ben (1942-…), is an American physician and medical researcher who discovered a previously unsuspected infectious particle called the prion << PREE on >>(see Prion). Scientists think prions cause a number of brain diseases, including scrapie in sheep and goats, mad cow disease in cattle, and Creutzfeldt-Jakob disease in human beings. For his discovery, Prusiner received the 1997 Nobel Prize in physiology or medicine.
Prusiner was born in Des Moines, Iowa. He graduated from the University of Pennsylvania in 1964 and earned an M.D. degree there in 1968.
Prusiner has spent his entire career at the Medical Center of the University of California at San Francisco. He served his internship and residency there from 1968 to 1974, specializing in neurology (the study of the nervous system). He joined the faculty of the Medical Center in 1974.
After one of Prusiner’s patients died of Creutzfeldt-Jakob disease in 1972, Prusiner set out to find the cause of the disorder. Ten years later, he identified the infectious particles and named them prions after isolating them in diseased hamster brains. 
Prusiner’s theory met great resistance among scientists after it was published in 1982. Prions seem to lack nucleic acid, the genetic material that occurs in all other infectious agents, such as bacteria and viruses. Scientists did not believe prions could reproduce without nucleic acid. Prusiner theorized that prions develop from normal proteins called prion proteins that exist harmlessly in the brains of all animals. According to his theory, prion proteins can be changed into disease-causing prions by contact with a prion from outside the body or by a mutation (genetic change). The prions then gradually multiply and destroy brain cells.
In 1996, British scientists confirmed that prions were involved in mad cow disease. Some scientists still doubt Prusiner’s theory, however.
