Nuclear transplantation of rat embryos

The nuclei from one‐, two‐, four‐, and eight‐cell rat embryos were transferred into enucleated zygotes and development to term of the reconstituted embryos, after transfer to recipients, was examined. The rate of electrofusion of enucleated zygotes with karyoplasts was quite high (81–92%), but the fusion rate was only 8% when Sendai virus (HVJ) was used. A large percentage of the enucleated zygotes that received pronuclear karyoplasts developed to the two‐cell stage in vitro (89%) and to term (22%) after transfer to recipient rats. Although 67%, 57%, and 67% of enucleated zygotes receiving nuclei from two‐, four‐ and eight‐cell embryos, respectively, developed to the two‐cell stage, they failed to develop to term after transfer.