The Chromosomes of Forty-Two Primary Rous Sarcomas of the Chinese Hamster

The present paper is the first collective publication of the results in primary tumors of the Chinese hamster; another aspect of the present work, the chromosomal response of Chinese hamster cells in vitro to RSV-SR and to RSV-Mill Hill, was reported recently (KATO, 1967). MATERIALS AND METHODS The animalsThe Chinese hamsters used in the present experiments were kindly provided by Dr. G. YERCANIAN from his colony at the Children's Cancer Research Foundation, Boston, Mass.His scheme for breeding procedures was followed including n reversed-lighting system (YERGANIAN, 1958).The breeding nucleus of the colony, which in 1962 consisted of 7 female and 5 male animals, was developed in two years into some 500 animals, which is the number normally kept in our colony.Breeding by brother-sister mating carried out €or five years, has now reached the 8th generation. The virusThe RSV-SR was kindly provided by Professor AHLSTROM.Material obtained from chicken sarcomas induced by the virus was finely minced and suspended in Hank's saline, 4 nil to each g of the tumor.This cell suspension was used directly for inoculation.In some cases, cell free virus suspensions were used.They were prepared from homogenized chicken sarcoma by one standard centrifugation followed by repeated ultracentrifugations. Unless the preparations were intended for immediate use, they were pooled and preserved in the deep freeze at -65' C. All preparative procedures were carried out aseptically and at Oo C . Induction and transplantation of tumorsMost of the present tumors were induced in new-born young.Each young was inoculated subcutaneously in the back with 0.05 ml of fresh cell or virus suspension, equivalent to 10 mg of the original chicken sarcoma.In addition, adult animals were used as hosts, both unconditioned and injected with two doses each of 0.25 mg hydrocortisone, one 16015223, 1968, 1,