• Proceedings of the KSAR Conference
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• 2002.06a
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• pp.9-9
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• 2002

This study was to evaluate the in vitro survival of vitrified-thawed bovine MII enucleated (MIIe) oocytes according to activation timing and minimun volume cooling (MVC) method and their in vitro development after somatic cell nuclear transfer (SONT). Bovine oocytes were recovered from slaughtered bovine ovary and matured in TCM-199 supplemented with 10% FBS. (omitted)

• Korean Journal of Animal Reproduction
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• v.18 no.2
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• pp.121-126
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• 1994

This study was conducted to examine the condition of activation of the nuclear transplant bovine embryos. In vitro fertilized(IVF) and nuclear transplant embryos(NTs) were co-cultured with bovine oviduct epithelial tissue(BOET). NTs were treated with cycloheximide(CHXM) for 0 to 6 h after electrofusion to investigate the activation conditin of recipient ooplast. Then, the infljence of the CHXM treatment timing on the cleavage and development of NTs were investigated in relation to the nuclear transplant time. The cleavage rates of NTs were increased with the increasing time of the CHXM treatment from 0 to 6 h (54.7 to 91.3%, P<0.01). Similar trend was shown in the development into the morula or blastocyst stage, but very limitted. Activation of enucleated oocytes prior to fusion enhanced development of NTs compared with that post fustion. This result suggests that the frequency of activation of NTs can be greatly enhanced by treating with CHXM for 6 h. The result also suggests that if blastomeres of unknown cell cycle stage are used, activation of enucleated oocytes prior to fusion enhances development of NTs.

• Asian-Australasian Journal of Animal Sciences
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• v.8 no.6
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• pp.641-645
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• 1995

This study was conducted to develop a method for production of nuclear transplant bovine embryos using in vitro-matured (IVM) oocytes and to examine the effect of different conditions of electrofusion on fusion rate and developmental capacity of donor nucleus transplanted to enucleated oocytes. Eight- to sixteen-cell embryos derived from oocytes matured and fertilized in vitro used as donor blastomeres and IVM oocytes were used as recipient oocytes. Oocytes were enucleated immediately after 23-24 h IVM and then reconstituted with a donor blastomere in two different micromanipulation media. Fusion rate and subsequent development of the reconstituted oocytes was compared under the different electric stimuli and recipient oocyte ages. Success rate of enucleation was significantly higher in TCM-199 medium containing FCS than in DPBS. The high fusion rate(75-94%) and development (6.4-14.8%) to morulae and blastocyst (M + B) were obtained from 0.6-0.75 kV/cm DC voltage, although total cleavage was not different among the electric pulses. Most optimal condition of electric stimulation for fusion and development was 1 DC voltage of 0.75 kV/cm, in which 80.5% of oocytes were fused, 80.0% and 31.7% of which was cleaved and developed to M + B, respectively. No M + B was obtained from 1.2 kV/cm DC voltage regardless of pulse frequency. Recipint oocyte age at electrofusion greatly affected the cleavage and subsequent development to M + B, showing high rate at 40-41 h oocyte maturation. These results suggest that a suitable condition of electrofusion for donor nuclei derived from IVF may be 1-2 DC pulses of 0.7 kV/cm for $70{\mu}sec$ and that processing of a transplanted nucleus in IVM oocytes may be affected by maturation age of recipient oocytes.

• Korean Journal of Animal Reproduction
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• v.24 no.1
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• pp.59-67
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• 2000

This study was investigated the developmental potential of bovine embryos following nuclear transfer with bovine fetal fibroblasts (BFF). BFF were isolated from a male 45-day-old-fetus. Non-starved BFF labeled with MitoTracker were transferred into perivitelline space of enucleated oocytes. BFF-oocyte units were fused by electric pulse, and then fused oocytes were activated with calcium ionophore A23187 and subsequently 6-dimethylaminopurine (6-DMAP). The resulting zygotes were placed into CRlaa bovine embryo culture medium. Transfer of the nucleus into enucleated oocyte led to premature chromosome condensation, swelling and pronucleus formation. Remodeled oocytes were developed to the mitotic and 2-cell stage at 18 to 26 h after nuclear transfer. The incidence of in vitro development to the blastocyst stages was 21% of fused oocytes. Mitochondria of BFF eliminated rapidly and were not detected at 8 h after fusion. These results suggest that BFF can be successfully reprogrammed in enucleated bovine oocytes, and that reconstructed embryos can develop to the blastocyst stage.

• Proceedings of the KSAR Conference
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• 2001.03a
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• pp.18-18
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• 2001

Despite of importance of integrated events of nucleus and microtubule remodeling in nuclear transferred embryos with somatic cells, little information is available on this subject. In this study we configured chromatin and microtubule organization following somatic cell nuclear transfer in pre- and non-activated bovine oocytes in order to clearify nuclear remodeling process and to demonstrate centrosome inheritance during nuclear transfer. The cumulus-oocyte complexes were collected from slaughterhouse and were matured in vitro for 20 h in TCM 199 supplemented hormone. Matured bovine oocytes were enucleated by aspirating the frist polar body and metaphase chromatin using a beveled pipette. Bovine fibroblast cells were fused into enucleated oocyte by electrical stimulation. Reconstructed oocytes were activated with ionomycine and 6-dimethylaminopurin, and then cultured in CRlaa medium. The organization of nuclear and microtubules were observed using laser-scanning confocal microscopy. At 1 hour after fusion, microtubule aster was seen near the transferred nucleus in most oocytes regardless activation condition. While most of fibroblast nuclei remodeled to premature chromosome condensation (PCC) and to the two masses of chromosome in non-activated oocytes, a few number of fibloblasts went to PCC and multiple pronuclear like structures in activated oocytes. Microtubular spindle was seen around condensed chromosome. Gamma-tubulin was detected in the vicinity of condensed chromosome, suggesting this is a transient spindle. The spindle seperated nucleus into two masses of chromatin which developed to the pronuclear like structures. Two pronuclear like structures were than apposed by microtubular aster and formed one syngamy like nuclear structure at 15 h following nuclear transfer. At 17 to 18 h after fusion, two centrosomes were seen near the nucleus, which nucleates micrtubules for two cell cleavage. While 31% of reconstructed oocytes in non-activated condition developed to morulae and blastocysts, a few reconstructed oocytes in pre-activated condition developed to the blastocyst. These results suggested introduction of foreign centrosome during nuclear transfer, which appeared to give an important role for somatic cell nuclear reprogramming.

• Korean Journal of Animal Reproduction
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• v.20 no.3
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• pp.307-313
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• 1996

This study was conducted to investigate the effect of S-phase synthronized nuclear transfer on the development of nuclear transplant bovine embryos. A blastomere derived from the 16~32 cell stage bovine embryos was transferred into an enucleated metaphase II(MII) oocytes or activated S-phase eggs. From the MII-phase and S-phase nuclear transfer, 6.3%(4/63) and 13.8%(9/65) of nuclear transplant embryos developed to the blastocyst stage, respectively. In the S-phase nuclear transfer, maximal proportion of embryos developed to the blastocyst stage(16.6%) was obtained after the recipient cell was activated 8 h prior to receving a donor nucleus. MII-phase nuclear transplant embryos showed the PCC state of their nuclear at 1.5~2 h after fusion, whereas, S-phase nuclear transplant embryos did not undergo PCC. The result of this study suggests that if blastomeres of unknown cell-cycle-stage are used, S-phase nuclear transplantation through the activation of enucleated oocytes prior to fusion enhances development of nuclear transplant embryos. This result also suggests that the interval time from oocyte activation to cell fusion may affect the development of nuclear transplant embryos.

• Korean Journal of Animal Reproduction
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• v.22 no.2
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• pp.153-161
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• 1998

This study was conducted to examine the viability of nuclear transfer bovine embryos following embryo transfer. Donor embryos were treated with nocodazole to arrest their cell-cycle-stage at mitotic(M) phase. After releasing from nocodazole blastomeres were separated and transferred into the enucleated oocytes(BC), or cultured in medium with aphidicolin. Freshly cleaved blastomeres within 1.5h after cleavage(AC) and non-cleaved ones up to 3h after releasing from nocodazole(NC) were transferred into the enucleated oocytes. Blastocysts derived from nuclear transfer were transferred to Day 7~8 recipient cows. Some blastocysts were vitrified and thawed before embryo transfer. Developmental rates to the blastocyst stage were higher in AC(18.1%, P<0.05) than BC(8.6%) and NC(5.1%). Blastocyst development slightly enhanced with aphidicolin(1~2$\mu\textrm{g}$/ml) treatment(16.9~22.6%) compared to non treated control(11.1%). Survival rate fo vitrified nuclear transfer embryos after thawing was 75%(24/32). Twnety-three vitrified nuclear transfer embryos and 3 fresh ones were transferred to 23 recipients, 6 heads were pregnant and 1 male calf(24 kg) was born from a recipient cow recevied one vitrifiedthawed nuclear transfer embryo at 277 days after embryo transfer. This result suggests that the nuclear transfer embryos can developed to term after vitrification andembryo transfer.

• Korean Journal of Animal Reproduction
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• v.26 no.3
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• pp.245-252
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• 2002

This study was to evaluate the in vitro survival of bovine enucleated MII (eMII) oocytes according to minimum volume cooling (MVC) freezing method and activation timing, and their in vitro development after somatic cell nuclear transfer (SONT). in vitro matured bovine oocytes for 20 h were stained with 5 $\mu\textrm{g}$/$m\ell$ Hoechst, and their 1st polar body and MII plate were removed by enucleation micropipette under UV filter. Also, eMII oocytes were subjected to activation after (group II) and before (group III) vitrification in 5 ${\mu}{\textrm}{m}$ ionomycin added CRlaa medium for 5 min. For vitrification, eMll oocytes were pretreated with EG10 for 5 min, exposed to EG30 for 30 sec and then directly plunged into L$N_2$. Thawing was taken by 4-step procedures at 37$^{\circ}C$. Survived eMII oocytes were subjected to SONT with cultured adult bovine ear cells. Reconstructed oocytes were cultured in 10 $\mu\textrm{g}$/$m\ell$ of cycloheximide and 2.5 $\mu\textrm{g}$/$m\ell$ of cytochalasin D added CRlaa medium for 1 h, and then in 10 $\mu\textrm{g}$/$m\ell$ of cycloheximide added CRlaa medium for 4 h. Subsequently, the reconstructed oocytes were incubated for 2 days and cleaved embryos were further cultured on cumulus-cell monolayer drop in CRlaa medium for 6 days. Survival rates of bovine vitrified-thawed eMII oocytes in group II (activation after vitrification and thawing) and III (activation before vitrification) were 81.0% and 84.9%, respectively. Fusion rates of cytoplasts and oocytes in group II and III were 69.0% and 70.0%, respectively, and their results were not different with non-frozen NT group (control, 75.2%). Although their cleaved rates (53.4% and 58.4%) were not different, cytoplasmic fragment rate in group II (32.8%) was significantly higher than that in group III (15.6%)(P<0.05). Also, subsequent development rate into >morula in group II (8.6%) was low than that in group III(15.6%). However, in vitro development rate in group III was not different with that in control (24.8%). This result suggested that MVC method was appropriate freezing method for the bovine eMII oocytes and vitrified eMII oocytes after pre-activation could support in vitro embryonic development after SONT as equally well as fresh oocytes.

• Reproductive and Developmental Biology
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• v.36 no.1
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• pp.49-53
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• 2012

The present study was conducted to examine the generation of reactive oxygen species (ROS) during micromanipulation procedures in bovine somatic cell nuclear transfer (SCNT) embryos. Bovine enucleated oocytes were electrofused with donor cells, activated by a combination of Ca-ionophore and 6-dimethylaminopurine culture. Oocytes and embryos were stained in dichlorodihydrofluorescein diacetate or 3'-(p-hydroxyphenyl) fluorescein dye and the $H_2O_2$ or $^.OH$ radical levels were measured. $In$ $vitro$ fertilization (IVF) was performed for controls. The samples were examined with a fluorescent microscope, and fluorescence intensity was analyzed in each oocyte and embryo. The $H_2O_2$ and $^.OH$ radical levels of reconstituted oocytes were increased during manipulation (37.2~49.7 and 51.0~55.2 pixels, respectively) as compared to those of mature oocytes ($p$<0.05). During early $In$ $vitro$ culture, the ROS levels of SCNT embryos were significantly higher than those of IVF embryos ($p$<0.05). These results suggest that the cellular stress during micromanipulation procedures can generate the ROS in bovine SCNT embryos.

• Korean Journal of Animal Reproduction
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• v.27 no.3
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• pp.233-240
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• 2003

This study was conducted to examine the effects of oocyte maturation period, phytohemagglutinin-P (PHA-P) treatment and activation agent on the enucleation, fusion, activation or in vitro development of bovine nuclear transfer embryos. Bovine oocytes were enucleated at 16∼24 h of in vitro maturation (IVM). Adult ear skin cells treated or non-treated with PHA-P were transferred into enucleated oocytes. Reconstituted oocytes treated or non-treated with PHA-P were fused by a pulse of 1.5 kV/cm for 30 $\mu$sec. Fused oocytes were activated with a combination of calcium ionophore (A23187) and cycloheximide (CHXM) or dimethylaminopurine (DMAP), and cultured in vitro for 7∼9 days. Enucleation rate was significantly increased when oocytes were matured for 16∼18 h (70.2∼92.3%, P<0.05) compared to that of oocytes were matured for 20∼24 h (44.3∼53.4%). The location of metaphase-II plate was far off from the 1st polar body as maturation time was increased. PHA-P treatment of donor cells or reconstituted oocytes significantly improved fusion rate (P<0.05). Cleavage and blastocyst formation rates were significantly increased after activation with a combination of A23187 and DMAP (78.6% and 32.9%, respectively) compared to those of embryos activated with a combination of A23l87 and CHXM (48.5 and 15.2%, respectively). From the present result, it is suggested that high enucleation efficiency can obtained by using oocytes matured for 18 h. It also shows that PHA-P treatment can improve the fusion rate, and activation with a combination of A23187 and DMAP can enhance the embryo development.