STUDIES ON THE SYNTHESIS AND DEGRADATION OF DNA IN DEVELOPING AND OLD CHICK CEREBELLUM

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Abstract
The levels of DNA, RNA, protein and acid and alkaline DNase were studied in developing and old chick cerebellum. The in vitro synthesis of DNA, by both chick cerebrum and cerebellum was also studied, by following the incorporation of [3H]thymidine into DNA. The increase in DNA content of chick cerebellum continued well beyond adult stages of life span. Maximal DNA synthesis, as judged by the [3H]thymidine incorporation, was noticed during the early embryonic development but decreased with advancement of age. There was another peak of activity, although smaller, about 9 mo. of age. Both cerebrum and cerebellum showed similar patterns. The highest specific activity of acid DNase was also found during the early period of cerebellar development, that is at a time when rapid cellular proliferation was occurring. The activity steadily declined with the aging and in 2 yr old cerebellum very little activity could be detected. Alkaline DNase, on the other hand, not only exhibited high activity during the early development but also remained at a significant level even in old cerebellum. Acid DNase apparently shows a positive correlation to the early embryonic DNA synthesis but not to the cell increase occurring in old age.