INDUCTION OF CELL REPLICATION

C3H2K cells in the stationary phase divided synchronously after renewal of the culture medium. The maximum DNA synthesis was at about 20 h after medium change and mitosis 10 h later than DNA synthesis. At the peak of the DNA synthesis, approx. 50 per cent of the cells were in S phase. There were, at least, two peaks of RNA synthesis, just after the medium change and before the DNA synthesis. The factor inducing the cell division was contained in calf serum. The contact with fresh medium for 2.5 h induced the division of 50 per cent of the cells. The factor inducing the cell division was rapidly consumed in contact with the cell monolayer: it was lost almost completely within 24 h. © 1968.