1. From the Division of Cardiovascular Medicine (Y.-P.X., B.C., P.S., A.G., Y.L., R.M.W., I.M.G., M.E.A., L.-S.S.), Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA; Department of Physiology (Y.-P.X., L.-C.W.), Anhui Medical University, Anhui, China; Department of Veterans Affairs Medical Center (K.Z., I.M.G.), Iowa City, IA.