Characterization of radiation resistant XXXX cell subpopulations in @entity242 . (I). Centrifugal elutriation.

@entity242 @entity5 @entity19 @entity26 @entity519
Studies were performed to determine the location, with respect to cell cycle phase, of the radiobiologically @entity519 cells in @entity242 . Cells dispersed from solid KHT @entity5 were separated into subpopulations at different stages of the cell cycle by centrifugal elutriation. Flow cytometric analysis of the DNA content of these subpopulations indicated that the degree of synchrony that could be achieved was greater than or equal to 95% for G1 cells, 70-75% for S cells and 70-75% for G2M cells. The approach to locate and characterize @entity519 cells was based on the premise that due to their lack of @entity26 such cells would preferentially survive radiation treatment. Consequently @entity242 were irradiated in situ either in dead animals or in animals breathing air. Following treatment, the @entity5 were dissociated, the cells elutriated into the various phases of the cell cycle and clonogenic cell survival was determined. Complete dose-response curves were determined for cells in the G1, S and G2M cell cycle phases. The various cell cycle subpopulations obtained from @entity5 irradiated while @entity19 breathed air, all demonstrated survival curves with a break and final slope which paralleled that of the corresponding anoxic cell survival curve. From these curves the proportion of @entity5 cells in the G1 phase was calculated to be 10.1 +/- 1.7%. Because the elutriated S and G2M enriched cell fractions were to some extent contaminated by cells from other phases of the cell cycle, the percentage of @entity519 S and G2M @entity5 cells was estimated to range from 0-7% and 0-5% respectively. However, since G1 cells comprised the majority of all the neoplastic cells in these @entity5 , the data suggest that @entity519 cells in @entity242 are found primarily in this cell cycle stage.
