Abstract
The optimum voltage for inducing activation by electrostimulation of porcine oocytes matured in vitro was determined.Oocytes matured for 42 h were exposed to a single squared pulse for 100, μ sec at 100 to 3, 000 V/cm DC and examined 12 h later. More than 90%of eggs pulsed at 250 to 1, 250 V/cm were activated, and the highest rate (98%) was obtained at 750 V/cm. Oocytes matured for 36 to 54 h were subjected to the stimulation at 750 V/cm. The rates of activation in oocytes cultured for 36 and 38 h (47 and 44%, respectively) were significantly lower than in those cultured longer than 42 h (94 to 99%; P<0.01). Succeeding events were examined.Oocytes matured for 42 h were pulsed at 750 V/cm, and anaphase II (32%) and telophase II (32%) were observed 10 min and 30 min after stimulation, respectively. Nuclear formation was completed 4 h after stimulation in 95%of the eggs.Meiotic resumption induced by electrostimulation is thus quite synchronous. Extrusion of the second polar body and formation of a nucleus was observed in 92%of activated eggs. These eggs when further cultured developed beyond the 4-cell stage.
