| Recently nuclear transfer technology has acquired many great achievements, butnulear transfer efficiency is still very low. It may be related to the abnormal changes inthe ultrastructure of reconstructed embryos. In this investigation, goat ear firbroblast cellswere used as donors, enucleated bovine and goat oocytes matured in vitro as recipients.The goat-goat reconstructed embryos (GG embryos) and goat-cattle reconstructedembryos (GC embryos) were produced by nuclear transfer. The aim was to study theultrastructure changes of two kinds of embryos in the process of development (2-cell,4-cell, 8-cell and 16-cell embryos), and to find the differences with fertilization embryosin vivo (FIV embryos), in order to provide basis for improving the methods of nucleartransfer. As shown by transmission electron microscopy, the hooded mitochondriasproportions of three types of embryos decreased unexceptionally, but GC embryos hadsignificantly lower hooded mitochondrias proportion than GG embryos and GIVembryos (P<0.05), but had significantly higher mature mitochondrias proportion than theothers at all embryo development stages (P<0.05). The proportions of differentmorphologic mitochondrias of GG embryos were similar to FIV embryos (P>0.05). Theresults indicated that different cytoplast may affect the mitochondria proportion. GCembryos at 8-cell and 16-cell stages showed significantly higher proportions of abnormalmitochondrias than in 2-cell and 4-cell (51.5% and 42.9%, 31.0% and 38.1%, P<0.05).GG embryos at 4-cell, 8-cell and 16-cell stages showed significantly higher proportionsof abnormal mitochondrias than 2-cell embryos (47.1%, 48% and 48.3%, 20.6%,P<0.05). In contrast, the abnormal mitochondrias proportions of FIV embryos had nosignificant change at any stages (P>0.05). At all different development stages, theproportions of abnormal mitochondrias of GG embryos were significantly higher thanFIV embryos (P<0.05). This proportion in 4-cell, 8-cell and 16-cell GG embryos wassignificantly higher than FIV embryos at the same stages (P<0.05). The proportion in2-cell GC embryos was higher than that in GG embryos (P<0.05), but there were nosignificant differences at other three stages. The results indicated that the mitochondriasin two reconstructed embryos had been destroyed in development. Before 8-cell stage, the blastmeres of GC embryos had junctions through enchasedmicrovilli, and the gap junction appeared at 16-cell stage. There were gap junctions at2-cell GG embryos, but these junctions became looser after 4-cell. GG and GC embryoshad bigger perivitelline and intercellular space than FIV embryos. In contrast, the gapjunction became tight without intercellular space since 8-cell FIV embryos. These resultsindicated that the information transmission in reconstructed embryos was normal atearlier stages, but became weaker in later stages. Zona pellucida (ZP) of three kinds ofembryos become thinner. The pores in ZP of both GC and GG embryos increased indevelopoment, especially in GC embryos, while FIV embryos had smooth ZP. The Golgiapparatus (Gi) and rough endoplasmic reticulum (RER) of two reconstructed embryosappeared until 8-cell stage, same as FIV embryos. The results showed that the excretionof reconstructed embryos was activated on time. Lipid drops of GC and GG embryosbecame bigger, and congregated. GIV embryos lipid drops changed little in volume anddispersed gradually from 4-cell period. From 4-cell, the vesicles and lysosomes increasedin GG embryos. In GC embryos, the lysosomes increased from 4-cell stage, and thevesicles increased from 16-cell, distributing around nucleus, while the other organellesdecreased. The nucleolus of GC and GG embryos changed from electron dense tomeshwork at 16-cell, showing that the nucleus function of the reconstructed embryos wasactivated. The broken nuclear envelope and multiple nucleolus in one blastmereilluminated that the nucleus function of reconstructed embryos was partly destroyed.Besides, at later stage of GC embryos, the nuclear envelope infolding, chromatin wasconcentrated, imp...
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