1. From the Departments of Neurology (R.F.M., D.K.C.) and Surgery (L.A.K.) and the Geriatrics Research Education and Clinical Center (R.F.M.), Baltimore Department of Veterans Affairs Medical Center, University of Maryland School of Medicine, Baltimore,, and the Departments of Molecular and Experimental Medicine and Vascular Biology (J.A.F., A.G., J.H.G.), The Scripps Research Institute, La Jolla, Calif.