title: Development of the ectoderm in Xenopus: tissue specification and the role of cell association and division.
abstract: When do ectodermal cells become specified to form epidermis, that is, become committed to form epidermis when isolated? Animal pole explants of Xenopus cultured in saline from the 8-cell stage onwards express a specific epidermal antigen, whereas vegetal explants do not. The isolated outer layer of ectoderm formed by stage 7 is almost completely specified, the inner layer is only partially so. When are cell associations and cell divisions necessary for epidermal differentiation? Embryos that were either disaggregated or incubated in cytochalasin B after the midblastula stage do not require cell interactions, Ca2+, or cell divisions for epidermal differentiation to occur. Inhibition of mRNA transcription with actinomycin D shows that the epidermal antigen is certainly transcribed by the late gastrula stage (stage 12).
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D002448:Cell Adhesion; D002449:Cell Aggregation; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division; D003609:Dactinomycin / Q000494:pharmacology; D004475:Ectoderm / Q000166:cytology*; D004477:Ectogenesis; D000078404:Epidermal Cells; D014982:Xenopus laevis / Q000196:embryology*
chemical_list: D000911:Antibodies, Monoclonal; D003609:Dactinomycin