Cellular commitment for post-gastrular increase in alkaline phosphatase activity in Xenopus laevis development.

Xenopus embryos were dissociated into cells and cultured in Ca2+-free medium to study the relationship between the cell-to-cell interaction and macromolecular synthesis. Under the conditions, cells did not aggregate at all, and remained isolated even while they were dividing actively. Synthesis of DNA and protein as studied by the incorporation of (3H) thymidine and (3H) leucin proceeded as in the aggregating cells. Also, the activity to synthesize rRNA, 5S RNA, and heterogeneous RNA as determined by the incorporation of (3H) uridine was not impaired. Such as increase in the activity of alkaline phosphatase, as occurs in embryos after the gastrula stage, was found to be inhibited greatly when early-blastula cells were cultured in the non-aggregating conditions. However, we found here that the inhibition was not observed with cells isolated from late-blastulae. Therefore, it appears that the increase in the activity of alkaline phosphatase during post-gastrular stages is dependent on some cellular commitment which may be established by cell-to-cell contact during the blastula stage.