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Proceedings: Chromium carcinogenesis and glycidal formation.

British Journal of Cancer
Nature Publishing Group
Publication Date
  • Research Article
  • Biology


250 B.A.C.R. 16TH ANNUAL GENERAL MEETING exponentially growing cultures (Hahn and Little, Curr. Top radiat. Res., 1972, 8, 39). The following results were obtained wvvith Chinese Hamster V79-379A cells grown in suspension to limiting cell density; cells remaining viable for 48 h in a post-mitotic state. Response to treatment with e.g. methyl methane sulphonate was compared with the response of similar, exponentially growing cells. The survival curves have similar slopes but the shoulder is much reduced with stationary cells. Non-semi-conservative syn- thesis occurs in both cases but the recovery of template-DNA size is slower and less com- plete in the case of stationary cells. This is consistent with the hypothesis that ligation of DNA is a deficient aspect of repair in these non-dividing cells. DECREASE IN THE ACCURACY OF DNA POLYMERASE FOLLOWING TREATMENT WITH y-RAYS AND METHYLNITROSOUREA. R. SAFHILL, Paterson Laboratories, Manchester. DNA synthesis in vivo must be a very accurate proce3s in order that the integrity of the base sequence of the genome be main- tained. When using in vitro systems, DNA polymerases from both bacterial and mam- malian sources have been found to incorporate only one wrong base in several hundred thousand, whilst in vivo their accuracy could result in only one wrong base in 101 0. We have been investigating the effect of ionizing radiation and various carcinogenic agents upon DNA polymerases and have found that y-rays or methylnitrosourea will decrease both the activity and accuracy of E. coli DNA polymerase I, as well as the proteolytically cleaved form of the enzyme, by up to 2 orders of magnitude. An error- prone DNA polymerase has recently been observed in human leukaemic cells and several recent reports further indicate that there may be a connection between the accuracy of DNA synthesis and carcino- genesis (Loeb, Springgate and Battula, Cancer Res., 1974, 34, 2311). UNSCHEDULED DNA SYNTHESIS STUDIED IN THE INTACT ANIMAL. V. M. CRADDOCK, MRC Laboratories

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