• Journal of Embryo Transfer
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• v.24 no.2
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• pp.89-95
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• 2009

Successful in vitro embryo production heavily relies on the normal maturation and fertilisation of oocytes. We examined the normal and abnormal fertilisation of zebu cattle oocytes matured in vitro. Immature cumulus oocyte complexes (COCs) from zebu cattle ovaries at slaughter were matured in vitro (IVM) for 24 h. The oocytes were either fixed, stained and examined for nuclear changes or fertilised in vitro (IVF) with Percoll-separated, heparintreated spermatozoa (1.0 ${\times}$ $10^6$/mL) of zebu (n = 7) and crossbred bulls (n = 7). After 18 h of sperm-COCs co-incubation at $39^{\circ}$C with 5% $CO_2$ in humidified air, the presumptive zygotes were fixed, stained and examined for pronuclei. The number of oocytes retrieved per ovary was 5.4 ${\pm}$ 0.7. The percentage of matured oocytes was 73.0. The difference in motility of spermatozoa before and after Percoll seperation was significant (p<0.001). The percentages of normal and abnormal fertilisation (polyspermia and oocytes with one pronucleus) varied significantly depending on individual bulls (p<0.05). A protocol for IVF of IVM oocytes in Bangladeshi zebu cattle is developed. A future study may elucidate the capacity of such IVM-IVF oocytes to develop to the blastocyst stage for transfer to surrogate mother.

• Journal of Embryo Transfer
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• v.27 no.3
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• pp.149-154
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• 2012

This study was carried out to investigate effective condition for producing somatic cell nuclear transfer (SCNT) embryos of Jeju native cattle. As donor cells for SCNT, ear skin cells from Jeju native cattle were used. In experiment 1, the effect of recipient oocyte sources on the development of Jeju native cattle SCNT embryos were examined. Fusion rate of recipient oocyte and donor cell was not different between the Hanwoo and Holstein recipient oocytes (86.0% vs 89.9%). The rate of embryos developing to the blastocyst stage was significantly (p<0.05) higher in Hanwoo recipient oocytes than in Holstein recipient ones (28.2% vs 14.7%). Blastocysts derived from Hanwoo recipient oocytes contained higher numbers of total cells than those derived from Holstein ones ($115.1{\pm}40.8$ vs $101.4{\pm}33.3$), although there were no significant difference. The mean proportion of apoptotic cells in blastocyst was not different between the sources of recipient oocytes. In experiment 2, the development of Jeju native cattle and Hanwoo SCNT embryos were compared. Hanwoo oocytes were used as the recipient oocytes. Fusion rate was not different between the Jeju native cattle and Hanwoo SCNT embryos (92.1% vs 92.9%). The blastocyst rate of SCNT embryos was significantly (p<0.05) lower in Jeju native cattle than in Hanwoo (16.9% vs 31.0%). Blastocysts derived from Jeju native cattle SCNT embryos contained smaller numbers of total cells than those derived from Hanwoo ones ($136.6{\pm}33.7$ vs $149.9{\pm}39.7$), but there were no significant difference. The mean proportion of apoptotic cells in blastocyst was not different between the Jeju native cattle and Hanwoo SCNT embryos. The present study demonstrated that Hanwoo recipient oocytes were more effective in supporting production of Jeju native cattle SCNT embryos, although Jeju native cattle SCNT embryos showed reduced developmental capacity when compared to Hanwoo SCNT embryos.

• Korean Journal of Agricultural Science
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• v.45 no.3
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• pp.493-498
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• 2018

There has been widespread warming and a general increase in summer temperatures over the Korean peninsula ($0.5^{\circ}C$/10 years from 2001 to 2010). South Korea is transforming into a subtropical region, and the productivity of livestock is affected by the climatic changes. In this study, we investigated whether the summer heat waves affect the developmental competency of Korean native cattle (Hanwoo), a taurine type of cattle with a small portion of indicine varieties. We collected oocytes during the summer (heat stress, HS) and autumn (non-HS condition) and examined the developmental competencies including in vitro maturation and preimplantation embryo development. No significant differences were observed between the HS and non-HS oocytes in nuclear maturation (extrusion of the polar body); however, the cleavage and blastocyst rates were significantly lower in the HS group than those in the non-HS group. The lower developmental competence of the HS oocytes compared to the non-HS is, in part, due to insufficient cytoplasmic maturation because of a higher production of Reactive oxygen species (ROS) levels as well as peri/cortical distributed mitochondria in the HS oocytes after in vitro maturation. Next, we examined the ROS and mitochondria distribution and found a significant increase in the levels of ROS in the HS oocytes and a polarized distribution (pericortical cytoplasm) of mitochondria in the HS oocytes. In summary, impaired cytoplasmic maturation of oocytes from exposure to HS affects the preimplantation embryo development by dysfunction of mitochondria. To improve reproductive performance, embryo transfer using cryopreserved embryos/oocytes is recommended in the hot summer season of South Korea.

• Journal of Embryo Transfer
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• v.11 no.3
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• pp.259-269
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• 1996

The present study was undertaken to examine the critical effect of $Ca^2$+ concentration on electrostimulation and post-electrostimulation media for electric activation of in vitro matured oocytes of Korean Native Cattle. Oocytes collected from slaughterhouse ovaries were matured in TCM 199 containing FSH, estradiol-17$\beta$ and FBS with granulosa cell monolayer for 24 hours and denuded with hyaluronidase. And then cumulus-free oocytes were submitted to a DC field of 1.0 kV/cm for 60 $\mu$sec in electroporation media(0.28 M mannito' and PBS) with different $Ca^2$+ concentations (0.00, 0.05, 0.10 and 0.15 mM). Stimulated oocytes were stained and examined for pronuclear formation after incuhation in SOF for 12 hours. The rates of pronuclear formation in hovine oocytes electrically stimulated in 0.28 M mannitol with 0.05, 0.10 and 0.15 mM $Ca^2$+(60.3, 82.2 and 75.0%) were significantly higher than without $Ca^2$+(6.3%) at 12 hours after an electric pulse(p<0.005). The activation rates of Korean Native Cattle oocytes stimulated in PBS supplemented with 0.05, 0.10 and 0.15 mM $Ca^2$+(71.0, 75.8 and 75.4%) were significantly higher than without $Ca^2$+(23.5%) after post-stimulation incubation(p<0.005). After incubation of oocytes in SOF with and without $Ca^2$+ following electric stimulation in 0.28 M mannitol with 0.10 mM $Ca^2$+, the rates of pronuclear formation of bovine oocytes in $Ca^2$+-free SOF(85.7%) was significantly higher than in SOF with 1.71 mM $Ca^2$+(62.5%, p<0.05). When oocytes were stimulated in two electrostimulation media supplemented with $Ca^2$+ and incubated in $Ca^2$+-free SOF, there were no significant differences in the rates of pronuclear formation hetween 0.28 M mannitol and PBS. These results indicate that a single electric pulse could induce activation of Korea Native Cattle oocytes in 0.28 M mannitol and PBS supplemented with $Ca^2$+. Furthermore, to improve the activation rates, it was hetter that stimulated oocytes were incubated in $Ca^2$+-free SOF after electric stimulation than in SOF with $Ca^2$+.

• Korean Journal of Animal Reproduction
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• v.14 no.4
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• pp.263-271
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• 1990

This study was carried out to investigate the factors affecting maturation in vitro of follicular oocytes in Korean Native Cattle. The bovine ovaries were obtained at a slaughter house and the follicular oocytes were recovered by aspirating the follicular fluid from the visible follicles of 3~6mm. The bovine oocytes were matured in vitro in TCM-199 containing FCS and hormones. The effects of TCM-199 salt type, number of oocytes per drop, incubation time and co-culture with granulosa cells on maturation of oocytes, were investigated. The results obtained are summarized as follows. 1. The maturation rates of follicular oocytes cultured for 22, 25 and 28 hours in Hank's TCM-199 or Earle's TCM-199 were 59.3, 59.6, 80% and 80.0, 90.0, 93.7%, respectively. The maturation rate of follicular oocytes in Earle's TCM-199 was faster and higher than in Hank's TCM-199(P<0.05). 2. The maturation rates of oocytes were 54.5, 62.5 and 62.0% when cultured the oocytes number 10, 20 and 40 per 200${mu}ell$ drop for 18 hours. 3. The maturation of follicular oocytes in the Korean Native Cattle was induced at 14 hours culture, by giving the maturation rate of 90.0% after 20 hours. 4. The maturation rates were 63.3% and 66.7%, respectigely when the oocytes were co-cultured with granulosa cells from medium-size follicles used immediately after recovery in the presence or absence of hormones added(0.02AU/ml FSH, 10$\mu\textrm{g}$/ml LH and 1$\mu\textrm{g}$/ml estradiol 17-$\beta$). When the oocytes were co-cultured with granulosa cells from medium-size follicles cultured for 3 days, the maturation rates were 20.8% and 76.2%, respectively(P<0.05). 5. The maturation rate were 88.0% and 70.0%, respectively when the oocytes were co-cultured with granulosa cells from large-size follicles used immediately after recovery in the presence or absence of hormones added(0.02AU/ml FSH, 10$\mu\textrm{g}$/ml LH and 1$\mu\textrm{g}$/ml estradiol 17-$\beta$)(P<0.05). When the hormones added(0.02AU/ml FSH, 10$\mu\textrm{g}$/ml LH and 1$\mu\textrm{g}$/ml estradiol 17-$\beta$)(P<0.05). When the oocytes were co-cultred with granulosa cells from large-size follicles cultured for 3 days, the maturation rates were 41.2% and 73.3%, respectively(P<0.05).

• Korean Journal of Animal Reproduction
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• v.11 no.1
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• pp.73-84
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• 1987

This experiment was carried out to investigate the effects of hormone addition(FSH, HCG, estrogen and progesterone) and composition (BSA and FCS) of mKRB on the in vitro maturation and fertilizability of follicular oocytes of the Korean native cattle. The ovaries were removed at a slaughterhouse, returned to laboratory in a thermostat (30-35$^{\circ}C$) within 4 hr, and collected by aspirating normal follicles which had diameters of 1 to 6 mm. The oocytes with cumulus cells were cultured for 8, 16, 24 and 30 hr in a modified KRB solution containing BSA or FCS and hormones. The in vitro matured oocytes in mKRB containing FCS, FSH and steroids were transferred in the rabbit uterus for examination of their in vivo fertilizability with bovine sperm preincubated 4 to 6 hr in the rabbit uterus. 1. The mean number of oocytes collected per cattle was 6.5 from 1-3mm follicles, 1.3 from 4-6mm follicles, and total was 7.7. 2. The meiotic division at 16hr-cuture in the oocytes from 1-3mm follicles was slightly stimulated by the addition of FSH in mKRB + BSA solution compared with the control. At 30hr-culture, their maturation rates(%Met II) were also increased by FSH of 1 $\mu\textrm{g}$/ml(38.4%) and 5$\mu\textrm{g}$/ml(35.7%) as compared with the control (21.4%). The maturation rate at 30hr-culture in the oocytes from 4-6mm follicles was 53.8% and 57.1% by the FSH addition of 1$\mu\textrm{g}$/ml and 5$\mu\textrm{g}$/ml, respectively. These rates were similar with the control(57.1%), but higher than those of oocytes from 1-3mm follicles. 3. The meiotic division at 16hr-culture in the oocytes from 1-3mm follicles was stimulated by the HCG addition of 1IU/ml and 5IU/ml. However, the maturation rate at 30hr-culture was greatly decreased by the HCG addtion (26.6% and 13.3%) compared with the control(53.3%) and these rates (30.8%) in the oocytes from 4-6mm follicles were also lower than that fo the control(58.3%). 4. Low maturation rate (37.5%) of the oocytes cultured in mKRB containing BSA and 5IU/ml HCG was increased (55.0%) when 15% FCS with HCG was added to mKRB instead of BSA. 5. When 16hr-cultured oocytes in mKRB containing BSA and gonadotropins (5$\mu\textrm{g}$/ml FSH and 5IU/ml HCG) were transferred in the medium without gonadotropins and recultured for 16hr, the maturation rate of HCG-treated oocytes was greatly improved. 6. The maturation rates of oocytes were greatly affected by steroids. The combined addition of FCS+FSH+estrogen or +progesterone to mKRB increased the maturation rate compared with the combination of BSA+FSH or FCS+FSH in mKRB. 7. The fertilization rate, presence of pronuclei, was increased by the combination of FCS+FSH+p in mKRB as compared with that (5.6%) of BSA+FSH and the rates of FCS+FSH+steroids ranged from 12.5 to 17.6%.

• Journal of Embryo Transfer
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• v.15 no.1
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• pp.1-8
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• 2000

The ultrasound-guided oocytes cllection (ovum pick-up ; OPU) has become a substitution for superovlation in cattle. The objective of this study was to examine the effect of OPU frequency on the in vitro production of embryos in Hanwoo cattle. Six cycling Hanwoo cows were distributed into two groups for either once or twice weekly OPU sessions. Oocytes were collected by ultrasound-guided follicle aspiration(SA600) using a 6.5HMz transducer and attached with 18 gauge needle, with vacuum pressure of 40 mmHg. The cumulus-oocyte complexes (COCs) collected from each donor were matured in TCM 199 supplemented with 10% fetal bovine serum at 5% CO2 in air at 38.5$^{\circ}C$ for 22h and in vitro matured oocytes were co-incubated with sperm(separated by Percoll gradient) for 6h. The zygotes were co-cultured on cumulus cell monolayer in 10ul droplets in the same culture medium and conditions used for IVM for 7 days. On Day 7 of culture, development to blastocysts was examined. Although the number of oocytes collected was variable depending on individuals, overall embryo production in the twice per week OPU sessions was better that in the once per week sessions(6~21 vs 2~7 blastocysts produced, respectively). Two cows(E, A) were good oocyte donors and embryo production was superior in cow C ; however, cow F was a poor donor as compared to the others. In conclusion, these results suggest that for embryo production, twice weekly OPU sessions were better than once per week for producing embryos in vitro from Hanwoo cattle.

• Korean Journal of Animal Reproduction
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• v.14 no.4
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• pp.253-261
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• 1990

This study was carried out to investigate the factors affecting development in vitro of follicular oocytes fertilized in vitro in Korean Native Cattle. The bovine ovaries were obtained at a slaughter house and the follicular oocytes were recovered by aspirating the follicular fluid from the visible follciles of 3~6mm. The bovine oocytes were matured in vitro for 20~24 hours in TCM0-199 containing 10% FCS and hormones (0.02AU/ml FSH, 10$\mu\textrm{g}$/ml LH, 1$\mu\textrm{g}$/ml estradiol-17$\beta$). The matured oocytes were fertilized in vitro using Percoll-separated frozen-thawed spermatozoa in BO solution containing caffeine(5mM) and heparin(10$\mu\textrm{g}$/ml). Twenty-four hours after insemination, the oocytes were cultured in vitro and then the effects of cumulus cell layer, co-culture with cumulus cells, bovine oviduct epithelial cells from ampulla or isthmus on development of ova, were studied. The results obtained are summarized as follows : 1. The in vitro development degree of oocytes attached with compact and dense layered cumulus cells was higher than that with 3~4 layered cumulus cells to be 9~16cells(P<0.01). 2. When the in vitro fertilized oocytes were co-cultured with bovine oviduct epithelial cells or cumulus cells, the development rate to be morula was 20.2% and 12.7%, respectively and the rates were higher than that of control, 2.1%(P<0.05). 3. The development rate to be morula was 15.8% and 23.8%, respectively when the in vitro fertilized oocytes were co-cultured with bovine oviduct epithelial cells from ampulla or isthmus, and the rates were higher than that of control, 0%(P<0.05%).

• Journal of Embryo Transfer
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• v.10 no.3
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• pp.243-250
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• 1995

Frozen storage of the oocytes has been used in a few mammalian species including mouse, hamster, human and cattle. However, frozen4hawed oocvtes show different sperm penetration on the levels of the zona pellucida and the plasma memhrane when compared with fresh oocytes. To elucidate biological changes occurring during freezing and thawing, we examined the kinetics of sperm penetration into frozen-thawed hamster oocytes. Oocytes obtained from superovulated female golden hamsters were frozen-thawed in an autofreezer according to an established method. Fresh and frozen4hawed oocytes were fertilized in vitro with capacitated hamster spermatozoa after removing the zona pellucida. The oocytes were examined at 1, 2, 3 and 6 h postinsemination. Sperm penetration found to be 1 h delayed in frozen-thawed oocytes. Other parameters such as degree of polyspermy and decondensing sperm heads were not affected by freezing and thawing. The results suggest that freezing and thawing may cause changes in the egg membrane surface and subsequently which leads to delay in the sperm-egg fusion.

• Journal of Embryo Transfer
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• v.8 no.2
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• pp.143-149
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• 1993

The objective of this study was to produce calves derived from in vitro fertilization of in vitro matured follicular oocytes. Oocytes aspirated from small antral folicles of ovaries obtained at a local slaughter house were matured and fertilized in vitro. At l8hrs after insemination with Korean native cattle semen, oocytes were co-cultured for 6~7 days by utilizing co-culture system with bovine oviduct epithelial cell. After co-culture, good or excellent quality late morulae or early blastocysts were selected by morphological criteria under stereo microscope. Selected embryos were transferred to recipients on day 6 or 7 (estrus = day 0). Recipients were monitored by observation for estrus and rectal palpation after 60 days from embryo transfer. One of them went to term with the birth of a calf. This case is the first production of calf derived from in vitro fertilization in Korea.