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Abstract

A hybrid cell line was formed by fusing cells from two established vertebrate tissue culture cell lines (V79B1 hamster and A84 Xenopus), which were known to differ substantially in resistance to some radiation-induced lesions and in associated repair potential. Ultraviolet and gamma ray dose-survival relations were then determined and analyzed for the three cell lines, primarily to compare the radiosensitivity (Do dose) of the hybrid line with that of each parental line for each radiation. Further experimentation was conducted to determine the extent to which observed differences in these Do doses could be attributed to interactions of the combined parental repair potentials in the hybrid. The hybrid line proved to be more resistant to ultraviolet light-induced lethal damage than either parental line. Supporting experiments involving post ultraviolet irradiation treatments with caffeine and photoreactivating light suggested that this higher resistance resulted, at least in part, from complementation of the combined V79B1 and A84 dark radiation repair potentials. Because of these observed responses to ultraviolet light plus the observations that A84 cells were far more resistant to lethal gamma ray damage and exhibited a higher level of associated split-dose repair than V79B1 cells, it was anticipated that the hybrid cell would approach (or perhaps exceed) A84 cells in resistance to and repair of lethal gamma ray damage. However the gamma ray kinetics indicated that the hybrid cells differed little from V79B1 cells in both resistance to and repair of such damage. These kinetics also suggested that the gamma ray repair mechanisms possessed by the two parental lines differed significantly and, when combined in the hybrid, mutually interfered, resulting in marked inhibition of the A84 mechanism.

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