1. From St Louis University Health Sciences Center (F.V.A., L.T.Y., B.R.C., M.J.K.), St Louis, Mo; Maryland Medical Research Institute (R.P.M., G.K.), Baltimore, Md; Mayo Clinic (P.B.B.), Rochester, Minn; University of Alabama (W.J.R.) (Birmingham); George Washington University (A.M.R.), Washington, DC; National Heart, Lung, and Blood Institute (G.S.), Bethesda, Md; Duke University (L.S.), Durham, NC, and Harvard Medical School (E.B.), Boston, Mass.