1. From the Departments of Internal Medicine, Divisions of Hypertension and Cardiology (W.Z., R.C.K., R.G.V.), and Molecular Biology and Oncology (R.C.K., E.N.O.), University of Texas Southwestern Medical Center, Dallas, Tex; and the Section of Hematology Research and the Department of Biochemistry and Molecular Biology (F.R., R.A.S.), Mayo Clinic and Foundation, Rochester, Minn.