1. Department of Internal Medicine, Gifford Laboratories, Center for Diabetes Research, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd., Dallas, TX 75235-9135, U.S.A.
2. Evans Department of Medicine and Department of Biochemistry, Boston University School of Medicine, Boston, MA 02118-2393, U.S.A.
3. Department of Biochemistry, Gifford Laboratories, Center for Diabetes Research, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd., Dallas, TX 75235-9135, U.S.A.