1. From the Department of Physiology, Loyola University Medical Center, Maywood, Ill (M.T.Z., L.S.M., J.B., D.M.B.), and the Cardiovascular Research Group, Department of Physiology, Temple University School of Medicine, Philadelphia, Pa (V.P., S.R.H.). Dr Maier is now at the Department of Cardiology, Georg-August-University, Goettingen, Germany.