1. From Missouri Breaks Industries Research Inc (L.G.B.), Timber Lake, SD; Medstar Research Institute (M.D., B.V.H.), Washington, DC; University of North Carolina (K.E.N.), Chapel Hill, NC; Southwest Foundation for Biomedical Research (J.W.M.), San Antonio, Tex; University of Oklahoma Health Sciences Center (Y.Z., E.T.L.), Oklahoma City, Okla; and University of Pittsburgh (S.D., R.E.F.), Pittsburgh, Pa.