1. Department of Cell Biology, Advanced BioScience Laboratories, Inc., Kensington, MD.
2. Laboratory of Tumor Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
3. Laboratory of Molecular Virology and Carcinogenesis, Advanced BioScience Laboratories-Basic Research Program, National Cancer Institute-Frederick Cancer Research and Development Center, Frederick, MD 21702.