A tissue-specific inhibitor of the cell proliferation of the retinal pigment epithelium in chick embryos

The salt extract of the nuclear fraction of a homogenate of the retinal pigment epithelium from 12-15 day old chick embryos inhibits selectively the proliferative activity in the retinal pigment epithelium of 3-5 day old embryos. The inhibiting effect of the nuclear factor is found within 20 h after its introduction into the egg. The nuclear extract from the pigment epithelium does not affect the level of proliferation in retina and lens anterior epithelium.