1. Department of Biochemistry and Molecular Biology, and Department of Pharmacology, University of Nevada, Reno, NV 89557, U.S.A.
2. Section of Endocrinology and Metabolism, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520, U.S.A.
3. Department of Applied Mathematics, School of Mathematics and Statistics, University of New South Wales, Sydney 2052, Australia