The Synthesis of Dna and Nuclear Protein by Gonocytes in the Testes of Normal and X-Irradiated Ratr

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Abstract
It had previous-ly been found that treatment of the testes of rats at 4 days of age with X-rays (300 r) suppressed mitotic activity in gonocytes and between 5 and 8 days of age these cells, together with their nuclei and nucleoli, became markedly increased in size. The present investigations showed that the nuclear hypertrophy in irradiated gonocytes was associated with the synthesis of both DNA and nuclear protein. Although DNA content and nuclear surface area were strongly correlated, it was found that DNA gradually became diluted as nuclei enlarged. The concentration of nuclear protein, however, remained constant, and production of this substance was regarded as being responsible for the nuclear hypertrophy. Hypertrophy of gonocyte nuclei in the testes of normal rats from 5 to 8 days of age was also found to be due to nuclear synthetic activity. At 5 days of age, enlargement, being associated with the pre-mitotic synthetic phase of gonocytes, could be regarded as a normal process. Excessive hypertrophy of some gonocyte nuclei which took place in the 5-8 day period, however, was regarded as being abnormal. This hypertrophy was due to the accumulation of DNA and protein synthesized by nuclei which had failed to complete the division process.