Résumé
The content of DNA, RNA and protein in cerebellum at different stages of the life span of rat as well as the ratios of protein to DNA, showed-that in this region extensive cell proliferation occurs between the 1st and 7th day after birth and once again between the ages of 225 and 750 days. The putative DNA degrading enzymes, acid and alkaline DNases, showed a positive correlation with the rapid DNA accretion noticed during developmental stages as well as during old age. From these results, it could be presumed that there was a second bout of glial cell multiplication in aging cerebellum and that DNases must be playing some important role in the process.
Résumé
The activities of acid and alkaline deoxyribonucleases in the white and grey matter areas of growing and old chick cerebrum were measured. Two marker enzymes for glial cells, butyrylcholinesterase and carbonic anhydrase were also measured in these regions. Higher specific activities of both butyrylcholinesterase and carbonic anhydrase were found in the white matter region at all the stages studied. Acid and alkaline deoxyribonuclease activities were observed in both white and grey matter. The decrease in the specific activity of acid deoxyribonuclease with advancement of age was more pronounced as compared to the alkaline deoxyribonuclease Marked reduction in total acid deoxyribonuclease activity in white matter, beyond the age of 130 days, was observed. On the other hand, total alkaline deoxyribonuclease activity in both white and grey matter continued to increase with age Further, the activity per mg of DNA also increased in white matter of the old brain. These results indirectly suggest a continued role for alkaline deoxyribonuclease in glial cells formed at a later age.