STUDIES ON THE FACTORS AFFECTING THE REJOINING OF CHROMOSOME BREAKS PRODUCED BY X-RAYS

Abstract

The influence of mitomycin C, chloramphenicol, ATP and various nucleosides on the yield of X-ray-induced chromosome aberrations was examined with the ovular tissue cells of Trillium kamtschaticum.Mitomycin C and chloramphenicol both brought about a significant increase of chromosome aberrations. ATP efficaciously reduced the aberration yield, thus indicating that the healing of chromosome lesions involves metabolic processes requiring energy supply. Simultaneous application of one, two or three kinds of nucleosides did not bring about any significant decrease in aberration frequency. Application of the nucleoside mixture containing the base components of DNA significantly decreased the aberration yield, but in the case of simultaneous application of four nucleosides of RNA components the frequency of aberrations in total did not reduce with a statistical significance, though there was seen a tendency that the aberration yield is reduced by the treatment. When the mixture of four nucleosides (adenosine, guanosine, cytidine, thymidine) or ATP were simultaneously administered with mitomycin C or chloramphenicol, the favorable action of the nucleoside mixture and ATP on the rejoining of chromosome breaks was completely arrested by these metabolic inhibitors.The experimental results suggested that both the syntheses of DNA and proteins are involved in the rejoining of X-ray-induced chromosome breaks, but do not necessarily give the clear-cut evidence as to which of them is more directly participated in the rejoining process.