Proliferation in the epiblast-hypoblast layers of the primitive-streak chick embryoblast in response to epidermal growth factor

The reaction of twenty four hour old primitive streak chick embryoblasts exposed to epidermal growth factor was compared with non-exposed controls. After 24-36 hours incubation, proliferation up to 5-6 cell layers in thickness of the epiblast-hypoblast layers was evident in the EGF exposed embryo blasts. This compared with the normally expected one cell layer in thickness at this stage of development.