Quantitative aspects of RNA synthesis in normal and lithium-treated embryos ofXenopus laevis

The treatment ofXenopus early embryos with lithium chloride produces exogastruale - embryos which fail to gastrulate normally and in which the rates of cell division are reduced. In the present study estimations of incorporations of (5-³H) uridine and the specific activities of the 5'-ribonucleotide precursor pools showed that exogastrulae have higher rates of RNA synthesis per cell than control neurulae. Sub-cellular fractionations showed that a greater proportion of labelled RNA was retained in the nuclei of exogastrulae than of neurulae, while neurulae showed a greater incorporation into polysomes.