Stimulierung von Kulturen embryonaler Rattenzellen durch Kälberserum, III / Stimulation of Embryonic Rat Cells in Culture by Calf Serum, III
Zeitschrift für Naturforschung. B, A journal of chemical sciences
Embryonic rat cells which have been stopped in G1-phase of their cell cycle by incubation in serum-free medium can be triggered by the addition of calf serum. Expamination of uridine uptake and RNA synthesis after stimulation gave the following results: 1) Uridine uptake into the acid soluble pool is increased within a few minutes. 2) 2 hours after the addition of serum cells incorporate twice as much 3H-uridine into the acid insoluble material as do cells in serum-free medium; this is not the
... m; this is not the result of a higher rate of RNA synthesis but is due to an increased uridine uptake. As demonstrated by isolation of RNA and electrophoresis in polyacrylamide gels a significant de novo synthesis can be detected 4 hours after stimulation. Sedimentation coefficients of these RNA species are between 28S and 18S, and 18S and 4/5S, resp.; they turn over quite rapidly as was demonstrated by chase experiments. 3) When cells are grown for 2 hours in medium containing 3H-uridine, little label can be detected in the ribosomal 18S- and 28S-RNA. Radioaktivity in these species is, however, strongly increased after another incubation period of 2 hours in culture medium without 3H-uridine. This indicates that precursor molecules ars synthetized and subsequently degrated into 28S- and 18S-rRNA.