1. Pharmaceutical Research and Development Division, Bristol Myers Co., Wallingford, CIT 06492.
2. Department of Pharmacology, University of Pittsburgh, School of Medicine, Pittsburgh, PA 15261.
3. Department of Pathology, Harvard University, and Dana-Farber Cancer Center, Boston, MA 02115.
4. Department of Pharmacology, University of Vermont, Burlington, VT 05401.
5. Laboratory of Biochemistry, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.