Abstract
The mouse sarcoma virus isolate MSV-M (MLV) induces a morphological conversion in monolayers of mouse cells. Although the mechanism of this phenomenon is not clear, it is known that it requires simultaneous infection of each cell by MSV and its helper virus, the MOLONEY leukaemia virus (MLV: Hartley & Rowe, 1966). In order to investigate the dependence of cell conversion on virus multiplication, 5-fluorouracil was used to block this multiplication.
MSV-M (MLV) stocks were prepared from BALB/c mouse tumour extracts (Chenaille et al. 1967). These stocks contained defective MSV and MLV with competent MSV (O'Connor & Fischinger, 1968; Guillemain et al. 1968) in a ratio 3/150,000/1 (Bernard et al. 1968). Cell line 8828 derived from mouse embryonic lung was kindly supplied by Dr Freeman (Microbiological Associates, Bethesda, U.S.A.) and was used in all experiments: this supports virus growth as well as mouse-embryo fibroblasts but cell conversion is more readily detectable.