Nuclear events in B-cells of young and senescent rat islets in organ culture.

In vitro, B-cells maintain their capacity to multiply. However, the number of mitotic figures observed in cultured rat Langerhans islets is far larger for young donnor animals than for old ones. The same observation is true for the number of nuclei incorporating tritiated thymidine in vitro. These data are in agreement with the principal observation resulting from the study of senescence on different in vitro cellular models: the decrease of the replication potential with increasing age. The stimulation of DNA synthesis by glucose, however, does not seem to be altered with aging.