Electrophoretic introduction of calcium ions into the cortex of Xenopus laevis oocytes triggers meiosis neinitiation.

Meiosis reinitiation has been triggered via electrophoretic driving of Ca++ into the cortex of Xenopus laevis oocytes freed from functional follicle cells by collagenase treatment. Mg++ could not be substituted for Ca++. Ca++ induced maturation resembles progesterone induced maturation in so far both are inhibited by cycloheximide, give rise to amplifiable MPF in the cytoplasm of treated oocytes and allow chromosome condensation and the formation of a normal meiotic spindle.