Regional differences in yolk platelet degradation activity and in types of yolk platelets degraded during early amphibian embryogenesis.

We compared the various regions of amphibian embryos before and during gastrulation to look for differences in activity and character in the degradation of yolk platelets (YPs). Cationic ferritin was used to examine YP degradation activity, the number of cationic-ferritin-containing endosomes and degrading YPs being compared among the various embryonic regions. In addition, we looked for differences in the types of degrading YPs among the various embryonic regions during early development. YP degradation activity was greatest in the animal and dorsal regions, and while large YPs (major axis more than 7 micro m) were degraded preferentially in the animal region, small YPs (major axis less than 2 micro m) were degraded preferentially in the dorsal region. These results suggest the possibility of different levels of YP degradation activity in different regions of the embryo, and also of regional differences in the types of YPs degraded during amphibian embryogenesis.