[Early activation of ribosomal RNA synthesis in axolotl embryos]

The incorporation of labeled precursors (3H- and 14C-uridine) into the fractions of salt-insoluble RNAs and or rRNA was studied in the axolotl embryos at different stages of early development (from the end of synchronous cleavage divisions until the end of gastrulation). RNA preparations isolated from the embryos at all stages studied contained incorporated radioactivity. The radioactivity of salt-insoluble RNAs markedly increased at the beginning of blastulation and continued to grow, but less steeply, at the subsequent developmental stages. The sedimentation analysis has shown that the label is incorporated into the precursors and mature molecules of rRNA, beginning at least from the blastulation.