Alterations in the numerical density of perichromatin granules in different tissues during ageing and cell differentiation.

Perichromatin granules (PG) were counted on electron micrographs of different tissues taken from young and old female Wistar rats as well as in the basal and spinous layers of adult human epidermis. A significant age-dependent decrease was observed in the following cell types: large brain cortical cells, cerebellar granular cells, hepatocytes, parotid gland cells. No significant decrease was found in the heart muscle nuclei and in the erythroblasts of identical maturation level. The number of PG decreased during the erythroblast maturation almost to zero, and increased in the cells of spinous layer of human epidermis as compared to the basal cells. There is a very wide variation in the number of PG per nucleus between the different tissues. The correlation between the transcriptional activity, the protein synthesis, ageing and cell differentiation is discussed.