1. From the Departments of Medicine (S.P.B., L.S.L., Z.L.), Comparative Medicine (B.E.O.), and Pathology (C.L.C.), Oregon Health and Science University and Portland VA Medical Center, Portland, Ore, and the Department of Veterinary and Comparative Anatomy, Pharmacology and Physiology (R.C.S.), College of Veterinary Medicine, Washington State University, Pullman.