On the possibility that DNA repair is related to age in non-dividing cells.

Possible age-related deterioration in the efficacy of DNA repair was investigated in a complement of non-dividing mammalian cells which is not replenished during the lifetime of the animal. Internal granular-layer neurons were extracted from the cerebella of beagle dogs, aged from 7 weeks to 13 years, following exposure in situ to 4700 rads of collimated (60)Co gamma rays. The alkaline sucrose-gradient sedimentation profiles obtained from the DNA of those neurons after various post-irradiation periods in situ can be interpreted: (a) that there is not an age-associated decrease in the ability of the cells to rejoin the single-strand breaks induced by radiation, but (b) that there may be an age-associated decline in the size of the DNA-containing species which can be extracted from unirradiated cells. The latter effect may reflect normal aging of the cerebellum.