1. Departments of Chemistry and Biochemistry, College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5C9 Canada, Department of Pharmacology, University of Alberta, Edmonton, Alberta, T6G 2H7 Canada, Rega Institute for Medical Research, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium, and Department of Medicine, Wayne State University, Detroit, Michigan 48201-1908