1. From the Departments of Medicine (A.M.P., D.W.N., O.M.K., W.L., H.L., F.Y.S., M.A.J., W.K., R.M.W., C.D.S., M.E.A., K.G.L., I.M.G.), Molecular Physiology and Biophysics (C.D.S., M.E.A.), and Pharmacology (P.K., C.D.S., K.G.L.), University of Iowa Carver College of Medicine, Iowa City, IA; and Iowa City VA Healthcare System, Iowa City, IA (K.G.L., I.M.G.).