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.

Activin-treated Urodele Animal Caps: II. Inductive Interactions in Newt Animal Caps After Treatment with Activin A

“…Mesodermal tissues are subsequently induced in the outer layer cells as a result of the secondary inductive interaction with the activin-induced blastocoelic cells. The latter possibility is also supported by the results of our present study (series II) and of a study with salamander animal caps, which also consists of heterogeneous cell layers (Ariizumi et al, 1998).…”

“…However, when Cynops animal caps are treated with a high concentration of activin A they preferentially form a mass of yolk-laden cells. Based on their inductive properties, these cells are thought to be fated to form the anterior endoderm (Ariizumi and Asashima, 1995b;Ninomiya et al, 1998). Takata and Yamada (1960) reported an observation that well-organized endodermal organs develop from Cynops animal caps under the influence of a mesoderm-inducing agent, guinea pig bone marrow.…”