Transplantation of Porcine Blastomere Nuclei into Oocytes Collected from Prepubertal Gilts.

Feasibility of utilizing follicular oocytes derived from gonadotropin treated prepubertal gilts and matured in vitro in nuclear transplantation of porcine embryos as the recipient cytoplasts was examined. After culture of 806 oocytes collected from gilts which had received an injection of 1500 i.u. PMSG followed by 750 i.u. hCG 72 h later, 488 (60.5%) matured normally, whilst fewer oocytes matured (144/308, 46.8%, P<0.05) when gilts were treated with 2000 i.u. PMSG. The proportion of oocytes activated after electric stimulation by double pulses of 150 V/mm D.C. for 30 or 60, usec were 62.9% (22/35) and 73.2% (30/41), respectively. Of 433 matured oocytes 342 (79.0%) were successfully manipulated to remove about 1/3 of cytoplasm adjacent to the polar body, with 68 of 77 (88.3%) being confirmed after acridine orange staining to be successfully enucleated. Attempts of electrofusion of the enucleated oocytes with 6 to 8 cell stage blastomeres resulted in 82.5% (66/80) successful fusion. Sixteen (45.7%) of the 35 nuclear transplanted embryos cleaved to 2 to 4 cell stage in culture with modified Kreb's Ringer Bicarbonate solution supplemented with 10% sheep serum.