Communication between primary endoderm and mesoderm for erythroblast differentiation in early chick blastoderm.

Blood islands are mesodermal cells which, in close association with the underlying endoderm, form blood cells and endothelium in the early embryo. The primary hypoblast (primary endoderm), separated from the epiblast of chick blastoderm at the full hypoblast stage, was labeled with 14C-protein hydrolysate. The labeled hypoblast was recombined with its denuded unlabeled epiblast. Radioautographs and uptake and incorporation measurements in the blood islands show that there is transport of label from the primary hypoblast to the erythroblasts or to some progenitor cell(s) of the erythroblasts in the epiblast. The observed cell communication between mesoderm and the endoderm is in concert with the description of the blood island cytoarchitecture in which mesodermal cells are making direct contact with the adjacent endodermal cells during erythroblast differentiation.