Effects of various electric fields on the fusion and in vitro development of mouse two-cell embryos

This study was undertaken to examine the effects of various electric fields such as alternating current (a.c.) voltage, fusion pulse strength, pulse duration, pulse number and electrode geometry on blastomere fusion and developmental rates of mouse two-cell embryos. The a.c. voltages (6 and 12 V/mm) did not affect the fusion and developmental rates. High fusion and developmental rates were obtained when pulse strengths of 1.0 to 2.5 kV/cm, pulse durations of 30 to 90 mu sec and pulse numbers of 1 to 6 were applied using a wire chamber. Comparison of electrode geometries showed that fusion rates were similarly high (93 to 98%) when pulse strengths of 1.0 to 2.5 kV/cm were applied, regardless of the electrode geometry. However, significantly lower developmental rates were observed in a rectangular chamber compared with those in a wire chamber, except when the pulse strength was 1.0 kV/cm. It was further observed that in a rectangular chamber, the developmental rate decreased with increasing pulse strength from 1.0 to 2.0 and 2.5 kV/cm. The results of this study indicate that by using a wire chamber, electric fields can be successfully applied across a relatively wide range of pulse strength, duration and number to provide sufficiently high fusion and subsequent developmental rates. The fusion conditions did, however, vary with chambers of different electrode geometries.