1. From the Departments of Pharmacology & Toxicology (B.T.L., D.D.G., W.B.C.) and Medicine (D.D.G., A.S., K.T., H.M.), Medical College of Wisconsin, Milwaukee; and Veterans Administration Medical Center (D.D.G.), Milwaukee, Wis; National Institute of Environmental Health Sciences (D.C.Z.), Research Triangle Park, NC; and Department of Biochemistry (V.L.M., J.R.F.), University of Texas Southwestern, Dallas.