1. From the Clinic for Small Animal Internal Medicine and Forensic Affairs (N.B., H.N., E.-G.G.), Faculty of Veterinary Medicine, Justus-Liebig-University Giessen; Department of Internal Medicine III (J.M.-E., N.H., C.Z., R.H.G.S.), University of Cologne, Germany; Department of Internal Medicine (U.K.), University of Tübingen; Institute of Biochemistry and Endocrinology (U.K., W.S.), Faculty of Veterinary Medicine, Justus-Liebig-University Giessen, Giessen, Federal Republic of Germany.