Activin-treated urodele animal caps: I. Mesoderm and endoderm differentiation of salamander animal caps

Abstract

The differentiation patterns of animal cap explants from the Japanese salamanders Hynobius lichenatus and Hynobius nigrescens were examined after exposure to various concentrations of activin A. A wide range of concentrations of activin A (0.5-100 ng/ml) induced various mesodermal tissues such as ventral mesoderm, somitic muscle, and notochord. At concentrations higher than 50 ng/ml, yolk-rich endodermal tissue was induced in many of the explants. Activin A is also known to have mesoderm-and/or endoderm-inducing activity on the animal caps of Xenopus laevis and Cynops pyrrhogaster, but their response patterns are slightly different. The mode of differentiation of activin-treated Hynobius animal caps was compared with that of Xenopus and Cynops in relation to the structure of the animal caps.