||Abstract: "[Investigators] studied here the change in the amount of ammonia within the embryo and its inhibitory action on the commencement of rRNA synthesis which normally occurs at the blastula stage of development. Ammonia exists at ca. 50 ng/egg (or ca. 3.0 mM at an intra-egg concentration) in the unfertilized egg." P.380 right column 3rd paragraph: "In the present study, [investigators] have examined ninhydrin-positive materials in the acid-soluble fraction of embryos at various stages, searching for ammonia and/or amines. [They] report that ammonia, but not amines, does exist in embryos at an intra-egg concentration of about 3 mM, the level that was found previously to be inhibitory to rRNA synthesis (Shiokawa et al., 1985a,b). Then, [they] followed the amount of ammonia during development on one hand, and tested the effects of ammonium salts on the commencement of rRNA synthesis in blastula cells in details on the other."