Nucleolar ultrastructure in bovine nuclear transfer embryos.

摘要: Nuclear transfer experiments in mammals have attempted to reprogram a donor nucleus state equivalent the zygotic one. Reprogramming of is, among other features, indicated by synthesis ribosomal RNA (rRNA). The initiation rRNA is simultaneously reflected nuclear morphology as transformation nucleolus precursor body into functional synthesising with characteristic ultrastructure. We examined nucleolar ultrastructure bovine vitro produced (control) embryos and reconstructed from MII phase (nonactivated) or S (activated) cytoplasts. Control were fixed at two-, four-, early eight- late eight-cell stages; 1 3 hr post fusion stages. possessed throughout all three cell cycles. In stage embryo, primary vacuole appeared an electron lucid area originating centre body. nonactivated cytoplasts, envelope was fragmented completely broken down after and, fusion, it restored again. At this time, reticulated fibrillo-granular had almost round shape. seen two-cell consisted intermingled filamentous components secondary vacuoles. A typical for control never observed. None group reached stage. activated contrast, exhibited complete time intervals fusion. originally blastomere changed consisting homogeneous fibrillar structure. four-cell embryos, which one cycle earlier than embryos. Only cytoplasts underwent remodelling nucleolus. reorganisation architecture functionally active observed embryo. These ultrastructural observations correlated our autoradiographic data on Mol. Reprod. Dev. 52:253–263, 1999. © 1999 Wiley-Liss, Inc.