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Sperm entry was monitored in voltage-clamped sea urchin eggs following insemination in a variety of artificial seawaters. In regular seawater, maintaining the membrane potential at increasingly negative values progressively inhibits sperm entry. Reducing [Ca2+]o relieves the inhibition, shifting the sperm entry vs voltage relationship toward more negative potentials. Raising [Ca2+]o shifts the relationship...
The mechanism of the elevation of intracellular free Ca 2+ ([Ca 2+ ] i ) induced by a single sperm in eggs of the sea urchinLytechinus variegatuswas investigated. Simultaneous measurements of [Ca 2+ ] i , and of the activation current, were carried out on eggs microinjected with Ca Green-1 or Ca Green dextran, and voltage clamped at -20 mV. The...