[Action of 8-azaguanine on cellular division of Chlorella pyrenoidosa : I. Selective inhibition of nuclear DNA synthesis].

Synchronized Chlorella cell cultures were supplemented with 8-azaguanine at different times in their life-cycle. The number of cells obtained after one cycle depended on the time at which the analogue was added to the cultures. The results suggest that, during one cycle, the successive cellular divisions are controlled by a specific "stimulus".When supplied to the cultures during at least one entire cycle, 8-azaguanine inhibited the replication of the nuclear DNA, whereas satellite DNAs continued to replicate. The possibility of a reversal of the phenomenon by guanosine has been studied.