FACTORS AFFECTING ELECTROFUSION OF 2-CELL MOUSE EMBRYOS

Parameters of electrofusion of 2-cell mouse embryos were optimized for application as a model. for nuclear transplantation. There was consid erable lysis of embryos with M, as the medium for fusion; however, 100 % fusion (n=58) was obtained with a single 0.31-kv / cm, 1280-mu sec p ulse. With mannitol and sucrose solutions as the medium, a wide range of field strengths (0.31-1.41 kv / cm for 0.26 M sucrose solution and 0.31 to 2.04 kv / cm for 0.3 M mannitol solution) and durations of the electrical pulse (10-1280 mu sec) resulted in high rates of fusion (o ften 100%). Likewise, osmolarity of sucrose and mannitol solutions did not affect the rate of fusion using a 0.47-kv / cm pulse. With a fiel d strength of 2.04 kv / cm, the proportion of embryos that fused in ma nnitol solution increased (P <0.05) and the proportion that were lysed decreased (P < 0.05) as osmolarity increased. Both fused (162 / 642, 25%) and control embryos (32 / 72, 44%) continued to develop in cultur e for 48 h, after which they began to compact. Fused embryos were only at the 4-cell stage by this time, while control embryos were at the 8 -cell stage. Optimal pulse durations are plotted for field strengths b etween 0.31 and 1.41 kv / cm with 0.26 M sucrose as fusion medium.