This study was conducted to examine the possibility of performing nuclear transplantation using parthenogenetically derived embryos as donor nuclei (karyoplasts) to support embryonic development after nuclear transplantation. The recipient oocytes (cytoplasts) were enucleated and then activated after maturation, and the donor blastomeres were obtained from 8to 16-cell stage embryos of parthenogenetically activated and fertilized embryos. The fusion, cleavage and blastocyst rates of

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... embryos that received fresh parthenogenetic blastomeres were 90%, 96% and 13%, respectively. The in vitro development of these reconstructed embryos was not significantly different (P>0.05) from the reconstructed embryos, which received IVF-derived blastomeres (94%, 95% and 21%, for fusion, cleavage and blastocyst rates, respectively). In contrast, these values decreased, when the reconstructed embryos received frozen-thawed parthenogenetic blastomeres (74%, 93% and 0%, for fusion, cleavage and blastocyst rates, respectively). Moreover, the development of reconstructed embryos that received parthenogenetic blastomeres showed some fragmentation at the compaction stage, unincorporation of blastomeres and multiple cavities (blastocoeles) in the blastocyst stage. This preliminary study has demonstrated the developmental potency of parthenogenetic bovine embryo nuclei, which could develop to the blastocyst stage when transplanted into enucleated oocytes.