| Abstract: | The objective of this research was to investigate the developmental capacity in vivo and in vitro of embryos produced by the transfer of nuclei from early morulae to enucleated oocytes from mammals of varying genetic distance from the nuclear donor. Nuclei of domestic bovine morulae were transferred to the bisected oocytes of bison, goats, sheep, and hamsters. Seventy-two reconstituted embryos were produced by the transfer of domestic bovine nuclei to bisected bison oocytes. Of 53 embryos recovered 7 days following transfer to the oviducts of intermediate host ewes. 1 ( 1.9%) had developed to the blastocyst stage. Of 112 bovine-caprine reconstituted embryos produced. 59 were recovered and I ( 1.7%) was a blastocyst. None of 1 10 bovineovine embryos recovered had developed to the blastocyst stage, and no cleavage was noted in 72 bovine-hamster embryos recovered. Control bovine intraspecific nuclear transfer resulted in the development of 44 blastocysts (17.2%) from 256 reconstituted embryos. When caprine nuclei were transferred to bisected bovine oocytes. 5 ( 1.8%) of 273 embryos recovered had developed to blastocysts. Development to blastocysts was not observed in 102 recovered embryos following the transfer of ovine nuclei to bisected bovine oocytes. Reconstituted embryos were also produced by the transfer of caprine morula nuclei to bovine oocytes enucleated using fluorescence microscopy. This enucleation technique eliminated the transfer of nucleated demi-oocytes to intermediate hosts, precluding the possibility of parthenogenesis. Development to blastocysts was not observed following the transfer of 160 of these reconstituted embryos to intermediate host oviducts, and of 271 to co-culture with bovine oviductal cells. However. 41 (9.86%) embryos cultured in-vivo or in-vitro dem onstrated one to three nuclear cleavage divisions as identified by fluorescence microsopy. Ultrastructure of interspecific caprine-bovine reconstituted embryos was compared to that of intraspecfic bovine reconstituted embryos 2 and 22 hours posttransfer. Abnormalities such as multinucleation were noted in both inter- and intraspecific embryos. Furthermore, there was evidence of inappropriate mitosis in the interspecific embryo. These results suggest that, in the species represented, reconstituted embryos produced by intergeneric nuclear transplantation may undergo one to three nuclear divisions, but do not complete normal preimplantation development. |
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