Behaviour of the Bp8 mouse ascites sarcoma after partial body irradiation

Mice bearing the Bp8 mouse ascites sarcoma were 4 days after inoculation irradiated with 2.5, 5 and 8 Gy. By shielding the head and the upper part of the thorax the mice survival, compared with whole body irradiation, was markedly prolonged and the behaviour of the ascites tumour could be evaluated up to 30 days after inoculation. While about 10 days after irradiation the total number of tumour cells started to decrease and amounted to only 4 per cent 20 days later, the ascites volume increased up to 30 ml. Using flow-cytometric cellular DNA analysis, the proportions of cells in the various parts of the cell cycle were determined. After an initial G2 blockage, a partial blockage with an increase proportion of G2 cells was found up to 20 days after inoculation. While the total number of G1, S-phase and mitotic cells started to decrease on day 10, the total number of G2 cells was independent of the dose and was constant up to day 18. This behaviour may indicate specific regulating processes linked to G2 cells.