1. From the Biomedical Engineering Program (H.Y.S.C., C.M.S., G.G., S.K.W., J.B.H.) and Physiological Sciences Program (B.R.S., S.K.W., J.B.H.), Vascular Research Group, University of Arizona, Tucson. B.R.S. is currently at the Boyer Center for Molecular Medicine, Yale School of Medicine, New Haven, Conn.