A ribonucleoprotein from amphibian gastrulae.

Abstract

DISAGGREGATION of amphibian embryos by agents which chelate calcium is succeeded by re-aggregation if the cells are returned to a medium containing calcium1. It is customary to consider that the removal of calcium from the environment of the cells is responsible for the loss of adhesion displayed in disaggregation. An attempt has been made to find out whether any organic material is removed from the embryos during disaggregation. Such organic material might lie on the cell surfaces or between the cells and assist in their adhesion, or it might be removed from within the cells during disaggregation. Batches of 250–260 late gastrulæ of Xenopus laevis were disaggregated in 0.001 M ethylene diamine tetraacetate at pH 8.03 in tris-hydrochloric acid buffer (0.001 M in tris) made up in calcium-free Holtfreter solution. The embryos were gently agitated on a rocker for 40 min. at 19–21° C., and at the end of this period the cells of the completely disaggregated embryos were allowed to settle. No evidence of cytolysis of the cells could be found. The supernatant was removed and centrifuged at 300–400 g for 10 min. A small number of intact cells, and a few yolk platelets probably of extracellular origin, formed the residue. The clear supernatant from this centrifugation was examined spectrophotometrically, and the absorption curve suggested the presence of nucleic acids. The preparation was frozen-dried.