Changes in cell proliferation kinetics during organogenesis and differentiation of the brain and optic cup in the...

The kinetics of cell proliferation on during early ontogenesis of the brain and formation of the eye was studied in the chick embryo. Kinetic parameters--the mitotic index (MI), proliferative activity (P), the duration of mitosis (tm) and the generation time (T)--were measured in various regions of the brain and eye cup, using colchicine as a stathmokinetic agent. It was found that MI could be taken as an indicator of P during early development. In stage 11 it is also clear that the shortest T occurs in areas of rapid proliferation. By stage 12, although the generation time in the various regions studied differs, P and MI are approximately the same. A short tm is not always restricted to areas with a high P. P is affected by variation of T rather than by tm or time of any other parameter of the cycle. With increasing age, tm values decrease and T increase, probably owing to the progress of differentiation during embryonic development.