Passage of Phosphorus-32 from Dried Yeast into Amphibian Gastrula Ectoderm

Abstract

BRACHET¹ has suggested that an important part is played by ribonucleoproteins or their breakdown products in the evocation of neural tissue in the Amphibian gastrula both by the natural organiser and by dead or cytolysing tissues. An experiment has therefore been made in which nucleoprotein incorporating phosphorus-32 was placed in contact with gastrula ectoderm, and a determination made to see whether the radioactive isotope passed across into the ectodermal cells. In the preliminary experiment, baker's yeast was grown in a medium containing phosphorus-32; the yeast was removed by filtration, washed with water, dried at 140° C., washed again with water, and implanted into the blastocœls of Triturus alpestris gastrulæ either as a dry powder or after incorporation into a jelly of coagulated egg albumen. After two days, or longer, the ectoderm overlying the implant was dissected off, carefully washed free of adhering particles, and placed in a Geiger counter; the implant was treated similarly. The number of ionizations produced by single ectoderms was in some, though not all, cases clearly above that of the background; when several fragments of ectoderm were combined, the results were always positive, as shown in the accompanying table.