1. Department of Internal Medicine III (M.E.-B.), University of Leipzig, 04103 Leipzig, Germany;
2. Department of Biochemistry (J.P.H., G.P.V.), Queen Mary and Westfield College, London E14NS, England;
3. National Institute of Child Health and Human Development (S.R.B.), National Institutes of Health, Bethesda, Maryland 20892;
4. Diabetes Research Institute at the Heinrich Heine University (W.A.S.), 40225 Düsseldorf, Germany