Temporal changes in embryonal cell surface recognition.

Plasma membranes have been prepared from optic tectum and neural retina of chick embryos. These membranes specifically inhibit the aggregation of homotypic cells. Plasma membranes prepared from each of these regions obtained from chick embryos at 7,8, and 9 days of development show specificity for homotypic cells of the same age and cross-react weakly with homotypic cells of different ages. Thus cell-surface recognition changes with age of development, and most of the cells in each region have a common cell-surface recognition specificity. Tectal cells react weakly with retinal cell membranes, but no inhibition of retinal cell aggregation by tectal cells has been noted.