THE EFFECT OF X-IRRADIATION ON MITOSIS AND DNA SYNTHESIS IN EHRLICH ASCITES TUMOR CELLS. Thesis
Effects of x irradiation (300 r, 500 r, and 1,000 r) on mitosis and DNA synthesis of Ehrlich ascites tumor cells were studied. Dose-effect relations and time sequence on effects on the 2 processes were compared. The normal mitotic cycle of Ehrlich ascites tumor cells was determined by the method of tritiated thymidine labeling. The period of mitosis, M, was found to be 1 hr. This was followed by a period, G/sub 1/, of about 6 hr. The next period synthesis, S, lasted about 8 hr. The final stage, G/sub 2/, was 4 hr in duration. Various doses of x irradiation to tumor cells in vivo produced an immediate block in the G/sub 2/ period, resulting in the mitotic index dropping within an hour to a minimal value. The duration of mitotic inhibition was dependent upon radiation dose. There was a temporary increase in mitotic index above normal after release of the mitotic inhibition. The rate of DNA synthesis after various doses was reduced, as indicated by an increase in percentage of cells labeled in irradiated cells and by a decrease in mean grain count. The effect of irradiation on DNA synthesis was not as apparent as that on the mitotic index, There was no appreciable reduction in the rate of entry of irradiated cells from G/sub 1/ into S periods as studied by continuous in vivo labeling of DNA with H/sup 3/thymidine. It was concluded that x irradiation affected processes in 2 stages of the cell cycle, G/sub 2/ and DNA synthesis. (M.P.G.)
- Research Organization:
- Originating Research Org. not identified
- NSA Number:
- NSA-18-011800
- OSTI ID:
- 4121085
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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