1. From the Department of Medicine, Mayo Clinic, Rochester, Minn. (S.D., R.R.), and the Department of Biochemistry, Whittier Institute for Diabetes and Endocrinology, La Jolla, Calif. (J.G.). Address reprint requests to Dr. Rizza at the Endocrine Research Unit, Rm. 5–164, W. Joseph Bldg., Mayo Clinic, Rochester, MN 55905.