1. From the Department of Cellular and Integrative Physiology (M.C.Z.), University of Nebraska Medical Center, Omaha, NE; Departments of Anatomy and Cell Biology (D.K.J., B.B., R.C.B., F.J.M.) and Internal Medicine (B.S., F.J.M.) and Free Radical and Radiation Biology Program (F.J.M.), University of Iowa, Iowa City, IA; Veterans Affairs Medical Center (M.T., F.J.M.), Iowa City, IA.