CALCIUM BUFFER INJECTIONS INHIBIT OOPLASMIC SEGREGATION IN MEDAKA EGGS

Injection of the weak (K-D = 1.5 mu M) calcium buffer 5,5'-dibromo-BAPTA into fertilized medaka eggs inhibited the formation of the blastodisc at the animal pole, the movement of oil droplets toward the vegetal pole, and cytokinesis. These inhibitory actions were dependent upon the concentration of the buffer but were independent of free [Ca2+] in the injectate. Because this buffer has previously been shown to substantially suppress zones of elevated calcium at the animal and vegetal poles of the medaka egg, the results of the present study suggest that these zones are necessary for normal segregation of the ooplasm and its inclusions in the medaka egg.