Incorporation of uridine in cleavage stage eggs of the sea urchin Paracentrotus lividus.

Incorporation of uridine in cleavage stage eggs of the sea urchin Paracentrotus lividus was investigated. It was shown by ion exchange and thin layer chromatography that most of the uridine taken up during the 16-cell stage was converted into UTP with some incorporation into UDP and UMP. Conversion of uridine to these phosphorylated nucleosides occurred throughout early cleavage stages. A very small amount of uridine taken up by cleavage stage eggs is incorporated into RNA heterogeneous in size. This RNA was examined by Polyacrylamide gel electrophoresis.