Inhibitory and stimulatory influences on mesodermal erythropoiesis in the early chick blastoderm.

We use a standing-drop culturing method to investigate the effect on mesodermal erythropoiesis of ectoderm and endoderm from the area opaca vasculosa (AOV) and area pellucida (AP) of stage-4 chick blastoderms. We find that ectoderm from the AOV and ectoderm and endoderm from the AP exert an inhibitory influence on mesodermal erythropoiesis. This inhibitory influence is coupled with the tendency of the explants to spread out and become flattened in culture. In contrast, endoderm from the AOV is found to be stimulatory, in agreement with previous studies. We correlate these in vitro inhibitory and stimulatory influences with the morphogenetic patterns that occur during normal development.