V. Comparative impulse cytophotometric investigations for redistribution of lymphoma cells in vivo after treatment with 60Co-gamma-rays and fast neutrons
Ehm, I.; Magdon, E.; Regel, K.
Archiv für Geschwulstforschung 45(8): 753-766
1975
ISSN/ISBN: 0003-911X PMID: 1230123 Document Number: 85225
The synchronizing effect of 60Co-.gamma.-irradiation and fast neutrons on cell populations was compared using impulse cytophotometry. L5178Y-R lymphoma cells in ascitic form were used in the studies. The in vivo growing cells were removed from the mice at intervals from 4-70 h following irradiation with varying doses and fixed. Shortly before the measurements the cells were fluorochromated with ethidium bromide. 60Co-.gamma.-irradiation and fast neutrons produce a block of the (G2 + M) phase. In the low dose range a maximum (G2 + M) phase block is reached within 24 h postirradiation. At that time, 44.1%, 53.0%, 52.5% and 70.0% of the cells are found in this phase of the cell cycle after 300 rad (60Co-.gamma.), 500 rad (60Co-.gamma.), 100 rad (fast neutrons) and 200 rad (fast neutrons), respectively. This block is removed after 24 h. In the higher dose range a maximal block is reached in the (G2 + M) phase within 48 h postirradiation. The fact that maximal block is reached only 24 h later than with lower doses can probably be explained by prolongation of the cell cycle. After this period 79.2%, 76.2%, 86.8% and 86.4% of the cells are in the (G2 + M) phase after 700 rad (60Co-.gamma.), 1000 rad (60Co-.gamma.), 2300 rad (60Co-.gamma.) and 700 rad (fast neutrons), respectively. It is possible to calculate from these results RBE values for fast neutrons with respect to the cells in (G2 + M) phase 24 h after irradiation in the range from 3.3-5.0. The RBE decreases with increasing dose.