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Deficient DNA Synthesis and Mitotic Death in X-Irradiated HeLa Cells

L. E. Hopwood and L. J. Tolmach
Radiation Research
Vol. 46, No. 1 (Apr., 1971), pp. 70-84
DOI: 10.2307/3573103
Stable URL: http://www.jstor.org/stable/3573103
Page Count: 15
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Deficient DNA Synthesis and Mitotic Death in X-Irradiated HeLa Cells
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Abstract

DNA synthesis was measured in the generation (Generation 1) following the one in which synchronous HeLa S3 cells were irradiated during G1 with 220 kV x-rays. The rate of thymidine incorporation throughout the S phase is reduced in a dose-dependent fashion such that about 2/3 of the normal amount is incorporated after a dose of 500 rads. Chemical determination of the DNA content in G1 and G2 of Generation 1 confirms that the incorporation values are valid measures of DNA synthesis. Autoradiographic analysis shows that most of the cells synthesize a reduced amount of DNA, but that the reduction is much greater in some cells than in others. It had been shown previously that virtually the entire cell population completes Generation 1, but that about 25% of the cells are permanently arrested in mitosis at the end of that generation. The arrested cells were separated from those that divide and examined for the amount of DNA they had synthesized in Generation 1. On the average, only about 30% of the normal amount is replicated in those cells. The cells that divide, in contrast, replicate on the average about 80% of the normal amount. It is postulated that severely deficient DNA synthesis is closely related to permanent mitotic arrest.

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