TEMPORAL CHANGES IN INTRACELLULAR FREE CALCIUM LEVELS IN THE DEVELOPING NEUROEPITHELIUM DURING NEURULATION IN THE CHICK

Intracellular free calcium ion (Ca2+) levels of the developing chick n euroepithelium during neural tube closure (Hamburger and Hamilton stag es 3-11 of embryonic development) were determined using the hydrophobi c acetoxymethyl ester of the fluorescent dye fura-2 (fura-2/AM). Tempo ral changes in the free Ca2+ level in neuroepithelial cells are correl ated with the degree of folding of the neuroepithelium. The concentrat ion of intracellular Ca2+ in the neuroepithelium reaches its highest l evel when apposing neural folds are actively making contact.