Reproductive Capacity and Viability at Higher Temperatures of Various Trans- formed Hamster Cell Lines!. 2

SUMMARY-Hamster cells transformed to malignancy in vitro by the polyoma virus or simian virus 40 (SY 40) possess a reproductive capacity (ret) at 41.6° ( (rct/41.6°(+) that is not exhibited by cells transformed in vitro by X irradiation, dimethylnitrosamine, untreated hamster.embryo cultures, or by cell cultures derived from tumors initially produced in vivo by the polyoma virus and SY 40. Temperatures (t) that inhibited multiplica-tion did not kill the cells. However, cell cultures derived from serially transplanted SY 40 and polyoma virus tumors produced in vivo exhibited a distinctly lower viability ranging from 41.3-41.6° ( (t/41.3-41.6°(-) than those derived from a serially transplanted, sodium cholate tumor produced in vivo, or cultures transformed in vitro by these viruses, X irradiation, dimethylnitrosamine, or untreated hamster-embryo cultures. Uncloned or cloned rct/41.6°(+, t/41.6°(+ cultures of cells transformed in vitro by SY 40 or polyoma virus, transplanted one or more times in weanling hamsters, produced tumors that yielded rct/41.6°(-, t/41.6°(