Department of Pathology (Neuropathology Division), Brown University, Rhode Island Hospital, 593 Eddy Street, Providence, RI 02903; Department of Neuroscience, Brown University, Providence, RI 02912; Regeneron Pharmaceuticals, Inc., 777 Old Saw Mill River Road, Tarrytown, NY 10591; and Human Brain Tissue Resource Center, McLean Hospital/Harvard Medical School, Belmont, MA 02178 (At 1999-05-25)