EFFECT OF IRRADIATION ON CELL DIVISION AND NUCLEIC ACID SYNTHESIS IN STRAIN U-12 FIBROBLASTS
The sequence of events following an irradiation of 500 r was investigated in strain U-12 fibroblasts. The irradiation caused a rapid and almost complete inhibition of cell multiplication, as measured by nuclear counts. the mitotic index, and the number of colonies produced from single cells. Although mitotic figures reappeared and increased in frequency to abnormally high levels 13 to 20 hours after irradiation, a recovery in cell multiplication did not occur. Time-lapse cinematography showed that the increased incidence in mitotic figures was very probably caused by the increased time spent by these cells in abortive mitoses. In contrast to the immediate inhibition of mitosis, DNA synthesis was reduced at a later time, falling to less than 50% of the control 18-24 hours after irradiation. In this system, therefore, the immediate inhibition of mitosis camnot be the result of a deficiency in DNA synthesis, as measured by the number of individual cells incorporating H/sup 3/thymidine or by the specific activity of DNA after incorporation of P/sup 32/. On the other hand, it is possible that the reduction in the number of cells synthesizing DNA results entirely from the inhibition of mitosis and subsequent failure of the orderly progression of cells through the mitotic cycle. (auth)
- Research Organization:
- Western Reserve Univ., Cleveland. Atomic Energy Medical Research Project
- NSA Number:
- NSA-14-014656
- OSTI ID:
- 4140754
- Report Number(s):
- NYO-2907
- Country of Publication:
- United States
- Language:
- English
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