1. From the Department of Clinical Sciences, School of Veterinary Medicine, Purdue University, West Lafayette, IN 47907-1240 (Parnell) and the Departments of Medicine (Powell, Hohenhaus) and Pathology (Patnaik), and the Caspary Research Institute (Peterson), The Animal Medical Center and Bobst Animal Hospital, 510 East 62nd St, New York, NY 10021-8302.