1. From the Section of Experimental Physiology and Pharmacology, Cardiology Branch (D.F.L., M.S., M.S., E.H., M.A.S.R., J.A.S., S.E.E., E.F.U.), the Biostatistics Research Branch (S.H.), and the Pathology Branch (R.C.), National Heart, Lung, and Blood Institute, and the National Eye Institute (W.G.R.), National Institutes of Health, Bethesda, Md.