ANALYSIS OF X-RAY-INCUDED MITOTIC DELAY IN SEA URCHIN EGGS. (thesis)
X-ray-induced reversible mitotic delay in sea urchin eggs was studied. Detailed cytological analysis showed that sublethal doses of x rays affected the process of chromosome condensation in these eggs. The delay in chromosome condensation corresponded directly to the delay in cell division. Rate and time course of DNA synthesis in these cells were studied over two division cycles by following the incorporation of tritium-labeled thymidine. The study of radiosensitivity of DNA synthesis showed that x-ray doses that caused reversible mitotic delay had no effect on the time or rate of DNA synthesis in these cells. Furthermore, the experiments showed that delay of DNA synthesis in the second division was a result of interference with mitosis. An equation to determine the S period was derived and used to compute the S period in these cells. Variation of mitotic delay with dose and time of irradiation was studied. There existed in prophase a critical point. If cells were irradiated before this point, there was a delay in the first cleavage. Cells irradiated after this point did not show any delay in the first cleavage, but the second cleavage was delayed. Shortly before the onset of the visible prophase, there was a stage in which the delay produced by a given dose was maximum. Some experiments showing the effect of halogenated pyrimidines on cell division and the modification of this effect by radiation were described. (auth)
- Research Organization:
- California. Univ., Berkeley. Lawrence Radiation Lab.
- DOE Contract Number:
- W-7405-ENG-48
- NSA Number:
- NSA-18-009835
- OSTI ID:
- 4086092
- Report Number(s):
- UCRL-10979
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-64
- Country of Publication:
- United States
- Language:
- English
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