1. From the Departments of Cell Biology (A.H.B., P.E.S.), Medicine (P.E.S.), Division of Endocrinology, and Diabetes Research and Training Center (P.E.S.), Albert Einstein College of Medicine, Bronx, NY. A.H. Berg’s present address: Department of Pathology, Brigham and Women’s Hospital, 75 Francis St, Boston, MA 02115.