Post-Irradiation Properties of Cultured Chinese Hamster Cells Exposed to Ultraviolet Light

Todd, Paul; Coohill, Thomas P.; Hellewell, Andrew B.; Mahoney, Judith A.

doi:10.2307/3572775

Cited by 29 publications

(4 citation statements)

References 34 publications

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“…In the interval between 10 hours to 24 hours, split-dose survivals reached a plateau level. In contrast to our findings, earlier papers on far-UV split-dose experiments reported negative or inconclusive results (Han et al, 1964;Todd et al, 1969). Later Humphrey et al (1970) demonstrated that there was an enhancement in cell survival for CHO asynchronous cells that were given a fractionated fluence of far-UV radiation with a recovery period of 2-4 hours.…”

Section: Fidelity Of 6-tg Ouabain and Dt Mutantscontrasting

confidence: 56%

“…The S-phase delay induced by far-UV is dosedependent, a more pronounced delay at a larger dose. After the delay, survivors resume growth at a nearly normal rate as measured by total cell numbers per dish or by average number of cells per colony (Cleaver, 1965;Bootsma and Humphrey, 1968;Damon and Rauth, 1968;Todd et al, 1969).…”

Section: Post Photoradiation Effectsmentioning

confidence: 99%

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Cell killing and mutation induction on Chinese hamster cells by photoradiations

Lam¹

1982

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Section: Fidelity Of 6-tg Ouabain and Dt Mutantscontrasting

confidence: 56%

Section: Post Photoradiation Effectsmentioning

confidence: 99%

Cell killing and mutation induction on Chinese hamster cells by photoradiations

Lam¹

1982

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“…Furthermore, Rauth (1967) found that incubation of UV-irradiated cells in caffeine synergistically reduced colonyforming ability and the kinetics of this action of caffeine have been interpreted as indicating that UV-damaged sites are altered during the passage of the cell through Sphase (Domon and Rauth, 1969). These findings coupled with the demonstrations that mammalian cells can recover colony-forming ability between fractionated doses of UV (Todd et al, 1969;Humphrey et al, 1970;Domon and Rauth, 1973) have led to the postulation that mammalian cells possess an S-phase specific system for recovery from UV-damage. Although many details of the molecular mechanisms are still obscure, it appears that mammalian cells may bypass UV-induced photoproducts during DNA replication in a manner similar to that proposed for bacterial cells by Rupp and Howard-Flanders (1968).…”

Section: Introductionmentioning

confidence: 95%

Effects of ultraviolet irradiation on the rate and sequence of DNA replication in synchronized Chinese hamster cells

Meyn¹,

Hewitt²,

Thomas³

et al. 1976

Biophysical Journal

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The effects of ultraviolet light (UV) irradiation on the rate of DNA replication in synchronized Chinese hamster ovary (CHO) cells were investigated. A technique for measuring semiconservative DNA replication was employed that involved growing the cells in medium containing 5-bromodeoxyuridine and subsequently determining the amount of DNA that acquired hybrid buoyant density in CsCl density gradients. One of the advantages of this technique was that it allowed a characterization of the extent of DNA replication as well as rate after irradiation. It was found that while there was a dose-dependent reduction in the rate of DNA replication following UV-irradiation, doses of up to 10 J/m2 (which produce many dimers per replication) did not prevent the ultimate replication of the entire genome. Hence, we conclude that dimers cannot be absolute blocks to DNA replication. In order to account for the total genome replication observed, a mechanism must exist that allows genome replication between dimers. The degree of reduction in the rate of replication by UV was the same whether the cells were irradiated at the G1-S boundary or 1 h into S-phase. Previous work had shown that cells in early S-phase are considerably more sensitive to UV than cells at the G1-S boundary. Experiments specifically designed to test for reiterative replication showed that UV does not induce a second round of DNA replication within the same S-phase.

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“…In general, the effect of caffeine on survival is particularly important at low doses which do not induce a long growth delay (Todd, Coohill, Hellewell and Mahoney 1969) ; in the E. coli lambda system, recombination repair (rec and red genes) is only efficient at low doses, for which DNA replication is not inhibited (Radman, Cordone, Krsmanovic-Simic and Errera 1970) ; this suggests that caffeine could specifically inhibit a repair mechanism of this type ; in Schizzosaccharomyces, Fabre (1970Fabre ( , 1971 has also observed partial elimination by caffeine, of the shoulder which characterizes, at low doses, the survival of strains with a recombination-like repair, the final slope of the curve remaining the same .…”

Section: 2 Survival Curves Of 2n and 4n Hc Cellsmentioning

confidence: 99%