RNA Metabolism in Primary Cultures of Xenopus laevis Kidney Cells. I. Characterization of Growth Phases and Changes in Number and Size of Nucleoli

Abstract

Cells from Xenopus kidneys were cultured. Incorporations of ³H-uridine, ³H-thymidine and ¹⁴C-protein hydrolyzate were examined, and synthesized RNA was electrophoretically analyzed. The synthesis of RNA, DNA and protein was found to take place at different rates at different phases and the synthesis of ribosomal RNA, as well as other macromolecules, was quite active during the early logarithmic phase. The number and size of nucleoli varied markedly during culture, and these changes were correlated with the activity of cellular RNA synthesis.