Continuous irradiation of a murine lymphosarcoma in vivo.

Cells of an ascites tumour LS/BL growing in the peritoneal cavity of C57BL mice were continuously irradiated in vivo at a low exposure rate of 3.58 X 10(-7) C.kg-1.s-1 (5R/h) for several years. The total volume of the ascites tumour evaluated by counting cells in the peritoneal cavity declined with increasing time of irradiation. However, the viability of tumour cells was fully retained so that upon an intravenous injection of the same amount of cells they killed their hosts as rapidly as the unirradiated cells. Longer survival was noted in the hosts given the irradiated LS/BL cells subcutaneously. In the hosts of irradiated cells, the spleen weight was greater around day 8 after transfer and the 3H-thymidine incorporation into DNA was increased.