1. The Longtine Center for Molecular Biology and Genetics and W. H. Civin Laboratory of Neuropathology, Sun Health Research Institute, Sun City, Arizona 85351, Department of Microbiology, Midwestern University, Glendale, Arizona 85308, Pathology Section, Sun Health Boswell Hospital, Sun City, Arizona 85851, Centre for Research in Neurodegenerative Diseases, University of Toronto, Ontario M5S 3H2, Canada, and Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287