1. From the Department of Biology (A.B., B.L.T., J.M.E., R.D.R., M.K.) and Division of Comparative Medicine (M. Schrenzel), Massachusetts Institute of Technology, Cambridge, Mass; and Angiogenesis Research Center (M.J.P., K.S., M. Simons), Department of Medicine, Harvard Medical School and Beth Israel Deaconess Medical Center, Boston, Mass. Present address for B.L.T. is the Department of Biochemistry, McMaster University, Hamilton, Canada; for J.M.E., the Department of Medicine, Weill Medical College...