Oscillation Of Intracellular Free Calcium In Cleaving And Cleavage-Arrested Embryos Of Xenopus-Laevis

Changes in the intracellular free calcium levels in the cortical region of cleaving Xenopus eggs were examined using semi-synthetic aequorin. We detected periodic oscillations in the free calcium levels accompanying the cleavage cycle as early as the first cleavage onward, The calcium levels began to increase at early interphase and were maximal during metaphase of mitosis. Eggs injected with colchicine to inhibit cleavage showed periodic oscillations in the calcium levels similar to those of normal eggs. This fact indicates that the furrowing process is not necessary for the periodic changes in the intracellular free calcium levels, but the changes are associated with the autonomous periodic cytoplasmic activity which controls cell cycle events.