Comparison of methods for activating mouse oocytes for spermatid nucleus transfer

In the mouse, mature oocytes injected with prespermatozoal cell nuclei remain unactivated. Additional stimulation is needed to trigger oocyte activation leading to embryo development. We compared various electrical stimulations, treatment with cycloheximide alone or in combination with electrical stimulation, and injection of sperm-borne oocyte-activating factor (oscillogen) in terms of their oocyte activation and embryo development rates. Of all the treatments tested, a single electrical pulse (1.0 kV/cm, 128 mu s) was the simplest, yet very effective, in allowing the development of the oocytes injected with spermatid nuclei.