1. Clinical Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892.
2. Departments of Medicine and Cell Biology, Vanderbilt University, Nashville, TN 37232.
3. Laboratory of Cell Biology, National Cancer Institute. Division of Cancer Biology and Diagnosis, National Institutes of Health, Bethesda, MD 20892.
4. Laboratory of Molecular Biology, National Cancer Institute, Division of Cancer Biology and Diagnosis, National Institutes of Health, Bethesda, MD 20892.