A demonstration of cellular interactions during the formation of mesoderm and primordial germ cells in Pleurodeles waltlii.
Animal, vegetal, dorsal and ventral blastomeres of eight-cell embryos of the urodele Pleurodeles waltlii were isolated and cultured for 15 days. The four animal blastomeres produced vesicles delimited by an irregularly shaped epidermis. In all other explants, the formation of mesodermal structures occurred, which can be interpreted as the result of inductive interaction, occurring during segmentation, between the ectodermal animal cap and vegetal yolk mass. Primordial germ cells (PGCs), which formed in 78% of cases when the presumptive ventral half to the embryo was cultured, occurred in only 48% of cases when the two ventral vegetal blastomeres were cultured alone. The absence of PGCs in the explants emanating from the four vegetal blastomeres is thought to have been due to inhibition of differentiation by notochord. This hypothesis has been confirmed by culture experiments in which the addition of presumptive chordomesoderm of young gastrulae prevented the differentiation of PGCs under conditions in which they are normally formed. These observations suggest that, in urodeles, PGCs do not arise from cells segregated as early as the eight-cell stage, but are the product of later inductive interaction between ectoderm and endoderm.
D000818:Animals; D001757:Blastomeres / Q000166:cytology / Q000502:physiology; D004625:Embryo, Nonmammalian / Q000166:cytology; D008648:Mesoderm / Q000166:cytology / Q000502:physiology; D009924:Organ Culture Techniques; D010999:Pleurodeles / Q000196:embryology*; D012455:Salamandridae / Q000196:embryology*