NUCLEAR TRANSPLANTATION IN PIGS - M-PHASE KARYOPLAST TO M-PHASE CYTOPLAST FUSION

Porcine embryonic fibroblasts in M-phase were isolated from confluent cultures by selective detachment and fused to homologous metaphase II enucleated oocytes. The fusion products were analysed by light and ele ctron microscopy (EM). The fusion treatment, per se, did not induce th e disappearance of the maturation promoting factor (MPF) in the cloned embryos and the transferred chromatin remained condensed for up to 10 h. Spontaneous decondensation started after this time and, at about 2 0 h post-induction of fusion, a single large nucleus was present in th e cytoplasm. The prolonged exposure of introduced chromatin to MPF res ulted in a total morphological remodelling as assessed by the nucleola r morphology observed by EM in all the specimens.