Tubal cumulus-free oocytes recovered from C57BL/6J and BALB/c mice 16 to 24 h after hCG injection were parthenogenetically activated by a single DC-pulse of different voltage. The efficiency of activation was assessed 2, 4 and 24 h after electric stimulation according to the proportion of oocytes with second polar bodies, presence of pronuclei and development of parthenogenetic 2-cell embryos. The best results, 99% and 100% of oocytes with second polar body (2 h) or with second polar body and one pronucleus (4 h), were recorded when oocytes of both strains were activated by a single 60 V DC-pulse (30 microseconds) 20 h after hCG injection. Aging of oocytes or higher voltage of DC-pulse (120 V and 240 V) resulted in both strains in an increase of abnormal oocytes and oocytes with two pronuclei. While a large proportion of activated C57BL/6J oocytes were totally fragmented within 24 h and only 23% reached 2-cell stage, 78% of the activated BALB/c oocytes developed to parthenogenetic 2-cell embryos. It was shown that pronuclear oocytes and parthenogenetic 2-cell embryos for preparation of different types of cytoplasts could be effectively prepared by electric stimulation of tubal oocytes.

Institute of Molecular Genetics Czechoslovak Academy of Sciences Praha