Observations on chick-embryo lens histogenesis in vivo and in vitro.

Abstract

The 6-day chick-embryo lens anterior epithelium will undergo histogenesis in vitro. A 'normal' epithelial curvature in vitro is required for extensive fiber-cell elongation; a reversed curvature, or flat epithelial conformation, results in considerably reduced cell extension. With a 'normal' epithelial curvature, cell elongation in vitro progresses rapidly for about 3 days, and changes in cytoplasmic organization (ultrastructure) take place that are similar to those associated with fiber-cell differentiation in vivo. However, these cells do not achieve as full a cytoplasmic differentiation as was observed in the most differentiated cells of the normal embryonic lens. Epithelia explanted with a reversed curvature, while evidencing reduced cell elongation, had, after 3 days in vitro, differentiated (according to criteria of ultrastructure and relative proportions of soluble proteins) in a manner similar to those epithelia explanted with a 'normal' curvature and in which extensive cell elongation had been demonstrated.