• Proceedings of the KSAR Conference
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• 2001.03a
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• pp.11-11
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• 2001

In this study, we examined the developmental potential of reconstructed bovine embryos and the fate of donor mitochondria during their preimplantation development after nuclear transfer. Isolated cumulus cells were used as donor cells in nuclear transfer. Cumulus cells labelled with MitoTracker Green FM fluorochrome were injected into enucleated bovine MII oocytes and cultured in vitro. MitoTracker labelling on donor cells did not have a detrimental effect on blastocyst formation following nuclear transfer. Cleavage rate was about 69%(56/81) and blastocyst formation rate was 6.2% (5/81) at 7 days after nuclear transfer. The labelled mitochondria dispersed to the cytoplasm and became distributed among blastomeres and could be identified up to the 8- to 15-cell stages. Small patches of mitochondria were detected in some 8- to 15-cell stage embryos (5/20). However, donor mitochondria were not detected in embryos at the 16-cell stage and subsequent developmental stages. In the control group, mitochondria could be identified in arrested 1-cell embryos up to 7 days after nuclear transfer These results suggest that donor mitochondria disappear from recipient cytoplasm before 16-cell stage following nuclear transfer in reconstructed bovine embryos.

• Asian-Australasian Journal of Animal Sciences
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• v.16 no.1
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• pp.15-22
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• 2003

Experiments were conducted to evaluate the effect of blastomere diameters and cell cycle stages on the subsequent development of nuclear transplant rabbit embryos (NT-embryos) using nuclei derived from the 16- or 32-cell stage embryos. All blastomeres and NT-embryos were cultured individually in modified Ham's F-10 medium supplemented with 10% rabbit serum (RS) at $38^{\circ}C$ and 5% $CO_2$ in air. The diameter of blastomeres from 16-cell stage embryos was found twice of those from 32-cell stage (51 vs 27 ${\mu}m$). Significant differences were observed in cleavage rates ($\geq$3 divisions) in the isolated single blastomeres (54 vs 48 for 16-cell; 28 vs 14 for 32-cell, p<0.05), but the fusion rates of oocytes with transferred nuclei were similar between small and large single blastomeres derived from either 16-cell or 32-cell stage embryos. When 16-cell stage blastomeres were used as nuclear donors, cleavage rates ($\geq$3 divisions) of the NT-embryos were greater in the small nuclear donors than in the large donors (73 vs 55%, p<0.05). On the contrary, significantly higher cleavage (43 vs 6%, p<0.05) and developmental rates (14 vs 0%, p<0.05) were observed in the large blastomere nuclear donor group of the 32-cell stage embryos. When the cell cycle stages were controlled by a microtubule polymerization inhibitor (Demicolcine, DEM) or the combined treatment of DEM and Aphidicolin (APH), a DNA polymerase inhibitor, fusion rates were 88-96% for the 16-cell donor group (without DEM treatment), which were greater than the 32-cell donor group (54-58%). Cleavage rates were also greater in the transplants derived from G1 nuclear donor group (93-95%) than those from the DEM and APH combined treatment (73%) for the 16-cell donor group (p<0.05). No significant difference was detected in the morula/blastocyst rates in either donor cell stage (p>0.05). In conclusion, it appeared that no difference in the developmental competence between large and small isolated blastomeres was observed. When smaller 16-cell stage blastomeres were used as nuclear donor, the cleavage rate or development of NT-embryos was improved and was compromised when 32-cell stage blastomeres were used. Therefore, control nuclear stage of the donor cell at $G_1$ phase in preactivated nuclear recipients seemed to be beneficial for the cleavage rate of the reconstructed embryo in the 16-cell transplant, but not for subsequent morula or blastocyst development.

• Korean Journal of Animal Reproduction
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• v.20 no.2
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• pp.143-153
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• 1996

To improve the efficiency of nuclear transplantation in the rabbit, this study were evaluated the influence of celly cycle of donor nuclei on the in vitro developmental potential in the nuclear transplant embryos. The embryos of 16-cell stage were collected from the mated does at 48h post-hCG injection and they were synchronized to G1 phase of 32-cell stage. Synchronization of the cell cylce of blastomeres were induced, first, using an microtubules polymerization inhibitor, 0.5$\mu\textrm{g}$/ml colcemid for 10h to arrest blastomeres in metaphase, and secondly, using a DNA synthesis inhibitor, 0.1$\mu\textrm{g}$/ml aphidicolin for 1.5 to 2h to cleave to 32-cell stage and arrest them in G1 phase. The separated G1 phase blastomeres of 32-cell stage were injectied into enucleated recipient cytoplasms by micromanipulation. After culture until 20h post-hCG injection, the nuclear transplant oocytes were electrofused and activated by electrical stimulation. The nuclear transplant embryos were co-cultured for 120h. In vitro cultured embryos were monitored every 24h to assess for development rate. After in vitro cultue for 120h, the nuclear transplant embryos developed to blastocyst stage were stained with Hoechst 33342 dye for counting the number of blastomeres under a fluorescence microscopy. The cleavage rate of blastomeres from 16-cell stage stage rabbit embryos treated with colcemid for 10h or aphidicolin for 6h following colcemid for 10h were not significantly different. The electrofusion rate was similar by high in S and G1 phase donor nuclei as 80.6 and 79.1%, respectively. However, the nuclear transplant embryos using G1 phase donor nuclei were developed to blastocyst at high rate(60.3%) than those using S phase donor nuclei(26.0%). Moreover, the mean blastocyst stage were increased significantly(P<0.05) with the G1 phase donor nuclei(176.6 cells and 1.50 cycles), as compared with the S phase donor nuclei(136.6 cells and 1.42 cycles). These results show that the blastomeres of G1 phase were more successful as donor nuclei in the nuclear transplant procedure, compared with S phase.

• Journal of Veterinary Clinics
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• v.13 no.2
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• pp.149-152
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• 1996

This study was carried out to evaluate the efficiency of production of cloned embryos by nuclear translatation (NT) when using 4-cell to compact morula stage embryos as nuclear donor. In micromanitulation and electrofusion of blastomeres from 4-cell to morula stage embryos, the successful injection rate was higher with late stage blastomeres, on the contrary the fusion rate was lower. The in vitro developmental rate of NT embryos was not significantly different between cell-stages of donor blastomeres. Although the overall rate of production of cloned embryos with 4-cell. 8-cell, early and late morula stage embryos was 14.0, 18.0, 15.3 and 14.1%, respectively, the mean number of blastocysts produced with a donor embryo was the most (4.51) with the compact morulae. Therefore, it can be suggested that the embryos at thelate stage is more beneficial for the mulciple production of cloned embryos, If the late stage blastomeres have maintained their totipotency to produce intact offspring.

• Journal of Embryo Transfer
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• v.27 no.4
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• pp.193-203
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• 2012

The development of embryos reconstructed by nuclear transfer is dependent upon numerous factors including the type of recipient cell, method of enucleation, the type of donor cell, method of reconstruction, activation, the cell cycle stage of both the donor nucleus and the recipient cytoplasm and the method of culture of the reconstructed embryos. Many of these points which have been reviewed extensively elsewhere (Sun and Moor, 1995; Colman, 1999; Oback and Wells, 2002; Renard et al., 2002; Galli et al., 2003b), here we will concentrate on main area, the production of suitable cytoplast and nuclear donor, nuclear-cytoplasmic coordination, oocyte activation, culture of reconstructed embryos, and the effects that this may have on development.

• Asian-Australasian Journal of Animal Sciences
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• v.22 no.2
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• pp.194-200
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• 2009

The aim of this study was to investigate the effects of donor cell passage, size and type on the development of nuclear transfer embryos. Porcine cumulus cells, fetal fibroblasts and oviductal epithelial cells from 1-2, 3-6 and 7-10 passages were used for the nuclear transfer. In the oocytes with the cumulus donor cells, fusion and cleavage rates of oocytes and cell numbers per blastocyst among the three different passage groups did not show any differences, but the rates of blastocyst formation from 1-2 and 3-6 passage groups were higher than those from 7-10 passage group. The rates of fusion, cleavage and blastocyst formation, and the cell numbers per blastocyst were higher in the embryos with the sizes of <20 and 20 ${\mu}m$ cumulus donor cells compared to the >20 ${\mu}m$ cumulus donor cell. In the oocytes with the fetal fibroblast donor cells, the rate of blastocyst formation from the 3-6 passage group was higher than from 1-2 and 7-10 passage groups. The embryos with the size of 20 $\mu{m}$ fetal fibroblast donor cell showed higher rate of blastocyst formation compared to those with <20 and >20 ${\mu}m$ donor cells. In the oocytes with the oviductal epithelial cells, the rates of blastocyst formation from 1-2 and 3-6 passage groups were higher compared to those from 7-10 passage group. The embryos with the sizes of <20 and 20 ${\mu}m$ oviductal epithelial donor cells had a higher rate of blastocyst formation compared to those with >20 ${\mu}m$ donor cell. Fusion and cleavage rates of oocytes, and cell numbers per blastocyst among the three different donor cell types from the 3-6 passage did not show any differences. However, the rate of blastocyst formation of somatic cell nuclear transfer (SCNT) embryos with the fetal fibroblast donor cell was higher than that of blastocyst formation of SCNT embryos with the cumulus and oviductal epithelial donor cells.

• Korean Journal of Veterinary Research
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• v.33 no.1
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• pp.151-169
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• 1993

The present study was carried out to investigate the best condition for nuclear-cytoplasm fusion and in vitro culture of nuclear transplanted embryos and to investigate the production of nuclear transplanted offsprings. The nuclei from 2-, 4- and 8-cell mouse embryos were transferred into enucleated 2-cell embryos, and the reconstituted embryos were submitted to direct current(DC) pulses at output voltage of 1.0, 1.5 and 2.0 kV/cm for 100, 150 and $200{\mu}$ sec to induce cell fusion. 1. The culture of intact or zona cut 2-cell embryos in the medium supplemented with cytochalasin B($5{\mu}g/m{\ell}$) and colcemide($0.1{\mu}g/m{\ell}$)for 30 and 60 minutes did not affect the development to later stage. 2. The in vitro developmental rates of group A(a nucleus from one of the blastomeres was removed) and B(electrofusion of group A) were significantly lower than that of control group(p<0.01). 3. When nuclear transplanted embryos were submitted to electrofusion, the significantly higher fusion rates of 2-cell donor nuclei were achieved at the electric field strength of DC 1.5kV/cm for 100 and $150{\mu}$ sec, DC 2.0 kV/cm for $100{\sim}200{\mu}$ sec than DC 1.0 kV/cm for 100 and $150{\mu}$ sec(p<0.01). The significantly higher fusion rates of 4-cell donor nuclei were achieved at DC 2.0 kV/cm for 100 and $150{\mu}$ sec than DC 1.0kV/cm for $100{\sim}200{\mu}$ sec(p<0.01). These fusion rates in 8-cell donor nuclei were 88.7~99.3%. 4. The developmental potency to blastocyst in 2- and 4-cell donor nuclei was significantly higher in DC 1.0 and 2.0 kV/cm for $100{\sim}200{\mu}$ sec treated group and DC 2.0 kV/cm for 150 and $200{\mu}$ sec treated group (p<0.01). The developmental potency to blastocyst in 8-cell donor nuclei was significantly higher in DC 2.0 kV/cm for $100{\mu}$ sec treated group than in DC 1.0 kV/cm for $100{\mu}$ sec treated group and DC 2.0 kV/cm for 150 and $200{\mu}$ sec treated group(p<001). 5. The developmental potency to blastocyst after nuclear transplantation was significantly higher in 2-cell donor nuclei than in 8-cell donor nuclei(p<0.01). 6. The success rate of nuclear injection into enucleated 2-cell embryos was significantly higher in 2-cell donor nuclei than in 4- or 8-cell donor nuclei(p<0.01). 7. The culture time taken for the nuclear transplanted 2-cell embryos to blastocyst stage was significantly longer in 2-cell donor nuclei than in 8-cell donor nuclei(p<0.01). 8. There was no significant difference in the developmental potency of nuclear transplanted embryos within the concentration of EGF at 0 to 15 ng per $m{\ell}$ of BMOC-3 solution. 9. The production rates of offspring after transfer of nuclear transplanted embryos to recipient mouse were significantly higher in 2-cell donor nuclei than in 8-cell donor nuclei(p<0.01).

• Journal of Embryo Transfer
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• v.14 no.2
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• pp.93-97
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• 1999

The development potential of bovine somatic cells was evaluated using nuclear transfer. A single donor cell derived from fetus of HanWoo(Korean Native Cattle) was selected and deposited into perivitelline space of each enucleated oocyte before electrical fusion and activation. Nuclei of donor cells starved for 7 days (37%) tended to support the development of reconstitute embryo the blastocyst stage better than those of donor cells starved 3, 14 and 30 days. The cleavage rate was significantly lower(P<0.05) in reconstitute embryos derived from large size donor cells(51.2%), than those from small medium size donor cells(76.6 and 73.5, respectively). The developmental rate to blastocyst of reconstructed embryos from medium size donor cells was higher than those from small and medium size donor cells. This study demonstrates that an appropriate culture period for induction into quiescent stage and the size of donor cells effect on the efficiency of nuclear transfer using cultured bovine cells.

• Korean Journal of Veterinary Research
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• v.33 no.3
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• pp.547-554
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• 1993

This study was carried out to investigate the best condition for in vitro and in vivo culture after freezing and thawing of nuclear transplant 2 cell embryos. When nuclear transplant embryos were submitted to electrofusion, the significantly higher fusion rates of 2 cell donor nuclei were achieved at the electric field strength of DC 1.5 kV/cm for 100 and $150{\mu}sec$, DC 2.0 kV/cm for 100 and $150{\mu}sec$ than DC 1.0 kV/cm for 100 and $150{\mu}sec$(p<0.01). The significantly higher fusion rates of 4 cell donor nuclei were achievecl at DC 2.0 kV/cm for 100 and $150{\mu}sec$ than DC 1.0 kV/cm for 100 and $150{\mu}sec$(p<0.01). The fusion rates in 8 cell donor nuclei were 94.2~99.3%. The developmental potency to blastocyst in 2 cell donor nuclei was significantly higher in DC 2.0 kV/cm for $150{\mu}sec$ treated group(p<0.01). The significantly higher developmental potency to blastocyst in 4 cell donor nuclei were achieved at the electric field strength of DC 2.0 kV/cm for $150{\mu}sec$ than DC 1.5 kV/cm for 100 and $150{\mu}sec$, DC 2.0 kV/cm for $100{\mu}sec$ treated group(p<0.01). The develop mental potency to blastocyst in 8 cell donor nuclei was significantly higher in DC 2.0 kV/cm for $100{\mu}sec$ treated group(p<0.01). The developmental potency to blastocyst after nuclear transplantation was significantly higher in 2 cell donor nuclei than in 8 cell donor nuclei(p<0.01). When the recovered embryos in normal morphology were cultured in vitro, there were no significant differences in the developmental potency to blastocyst between the freezing methods and the concentrations of cryoprotectant(p<0.01). The production rates of offspring after transfer of nuclear transplant embryos to recipient mouse were no significant difference in 2, 4 and 8 cell donor nuclei.

• Journal of Embryo Transfer
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• v.12 no.1
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• pp.11-20
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• 1997

The influence of cryopreservation of donor embryos on the in vitro developmental potential in the nuclear transplant rabbit embryos was evaluated. The embryos of 16-cell stage were collected and cryopreserved with EFS solution by vitrification method. The frozen embryos were thawed and synchronized to S and G$_1$ phase of 32-cell stage. The recipient/ cytoplasms were obtained by removing the first polar body and chromosome mass from the oocytes collected by non-disruptive microsurgery procedure. The separated S and G$_1$ phase blastomeres of 32-cell stage were injected into enucleated recipient cytoplasms by micromanipulation. After culture until 20 hrs post-hCG injection, the nuclear transplant oocytes were electrofused and activated by electrical stimulation. The fused nuclear transplant embryos were co-cultured with rabbit oviduct epithelial cells. After in vitro culture for 120 hrs, the nuclear transplant embryos developed to blastocyst stage were stained with Hoechst 33342 dye and their blastomeres were counted. The electrofusion rate was significantly (P<0.05) reduced in the frozen nuclear donor,compared with fresh donor nuclei as 80.0 vs 62.8% in S phase and 81.7 vs 64.8% in G$_1$phase, respectivley. The in vitro developmental rate to blastocyst stage with the S and G$_1$phase of fresh embryos(26.3 and 61.1%, respectively) was found significantly (P<0.05) higher, compared to the S and G]phase of frozen embryos(11.9 and 34.6%, respectively). When frozen as well as fresh donor embryos were synchronized to G$_1$ phase, the in vitro developmental rate to blastocyst stage was significantly (P<0.05) higher, compared with S phase donor nuclei. The cell counts of nuclear transplant embryos developed to blastosyst stage were significantly (P<0.05) more in G$_1$ phase of fresh or frozen embryos (180.1 and 125.7 cells, respectively), compared with S phase nuclear donor (145.1 and 103.7 cells, respectively). From the above results it was concluded that the rabbit embryos cryo- preserved by vitrification might be available as nuclear donor, though the developmentalpotential and cell counts of nuclear transplant rabbit embryos were decreased significantly.