A temperature-sensitive hamster cell mutant with altered morphology

A hamster cell mutant, ts-542, was isolated after nitrosoguanidine treatment. The mutant grows well at 33 °C and displays a normal, fibroblast-like morphology. It ceases cell division and becomes web-like in morphology after 4 days at 39 °C. No major lesion occurs in nucleic acid or protein synthesis during the first 3 days following transfer to 39 °C, but by the 4th day at this temperature there is a four-fold increase in acid phosphatase activity, an increase in nucleolar number, nuclear blebbing, and frequency of binucleate cells as well as increase in lysosomes. Cell death at 39 °C is independent of the cell density in the dishes or time of subculture. The mutation appears to be stable with a reversion frequency on the order of 10 −6.