• Korean Journal of Animal Reproduction
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• v.18 no.2
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• pp.113-119
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• 1994

To improve nuclear transplantation(NT) efficiency and to produce a large scale genetically identical cloned calves, examined the in vitro development capacity after co-culture of bovine oviductal epithelial cells (BOEC) and granulosa cells in TCM-199 supplemented with 10% fetal calf serum (FCS) with early bovine embryos derived from in vitro matured fertilized(IVM-IVF) oocyte. In addition, the age dependence of IVM oocyte on electro-stimulation and the effective electric voltage on in ivtro development of bovine NT embryos were examined. The results obtained were summerized as follows; 1. The cleavage rates of IVM-IVF bovine embryos in co-culture with bovine oviductal epithelial cells and granulosa cells were not significantly different(P<0.05), but the developmental rate into morula and blastocyst stage were different showing 38.3 and 20.2%, respectively. 2. The activation (82.5%) and development in vitro(8.6%) into later embryo stages of the aging oocytes of 32 hours post-maturation (hpm) were significantly higher than those of 24 hpm at direct current (DC) voltage of 1.5kV/cm, 60$\mu$sec pulse duration and 1 pulse time. 3. The fusion rates of NT eggs of 32 hpm following to different DC voltages from range 0.75 to 1.5kV/cm were not differ, but the developmental rate into morula and blastocyst stages at DC voltages of 0.75 and 1.0kV/cm were higher(11.4 and 12.6%, respectively) than those of 1.5kV/cm(0%). From these results, it can be suggested the optimal culture system for in vitro culture of IVM-IVF bovine embryos is a co-culture system with BOEC in TCM-199 supplemented 10% FCS. The effective time and the DC voltage for activation, electrofusion and in vitro development of NT embryos derived from IVM-IVF bovine embryo are 32hpm and 0.75~1.0kV/cm. But to improve NT efficiency, the advanced research (cell cycle synchronization, micromanipulation, culture system, etc.) is needed.

• The Korean Journal of Physiology and Pharmacology
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• v.6 no.2
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• pp.101-107
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• 2002

In the present study, the postnatal developmental changes in the expressional levels of cardiac sarcoplasmic reticulum (SR) $Ca^{2+}$ regulatory proteins, i.e. $Ca^{2+}-ATPase,$ phospholamban, and $Ca^{2+}$ release channel, were investigated. Both SR $Ca^{2+}-ATPase$ and phospholamban mRNA levels were about 35% of adult levels at birth and gradually increased to adult levels. Protein levels of both SR $Ca^{2+}-ATPase$ and phospholamban, which were measured by quantitative immunoblotting, were closely correlated with the mRNA levels. The initial rates of $Ca^{2+}$ uptake at birth were about 40% of adult rates and also increased gradually during the myocardial development. Consequently, the relative phospholamban/$Ca^{2+}-ATPase$ ratio was 1 in developmental hearts. $Ca^{2+}$ release channel (ryanodine receptor) mRNA was about $50{\sim}60%$ at birth and increased gradually to adult level throughout the postnatal rat heart development. $^3[H]ryanodine$ binding increased gradually during postnatal myocardial development, which was closely correlated with ryanodine mRNA expression levels during the development except the ryanodine mRNA level at birth. These findings indicate that cardiac SR $Ca^{2+}-ATPase,$ phospholamban, and $Ca^{2+}$ release channel are expressed coordinately, which may be necessary for intracellular $Ca^{2+}$ regulation during the rat heart development.

• Proceedings of the Korean Society of Developmental Biology Conference
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• 1998.07a
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• pp.12-18
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• 1998

Tremendous progress has been made over the past quarter-century studying the genetics of gametogenesis and the resulting gametes and embryos. Studies merging molecular techniques and conventional cytogenetics are now beginning to bridge the gap between what we have learned about the meiotic process in males and females and what we know of the mitotic chromosomes of zygotes. Numerical abnormalities in sperm, oocytes and embryo can now diagnosed by fluorescence in situ hybridization (FISH). "At risk" couples can, therefore, have only unaffected embryos replaced in the sterus and avoid the possibility of terminating a pregnancy that might only be diagnosed as affected later gestation. Single-cell genetic analysis has also provided powerful tools for studying genetic defects arising during early human development. Recent studies of sperms, oocytes and cleavage-stage human embryos have revealed an unexpectedly high incidence. These genetic abnormalities are likely to contribute to early pregnancy loss and have important implications for improving pregnancy rates in infertile couples by assisted reproduction. The widespread use of preimplantation genetic diagnosis (PGD) awaits further documentatio of safety and accuracy. Other issues also must be addressed. First, the ethical issues regarding germ cell and embryo screening must be addressed including what diseases are serious enough to warrant the procedure. Another concern is the use of this technology for non-genetic disorders such as gender selection. Finally, the experimental nature of these procedure must continually be discussed with patients, and long-term follow-up studies must be undertaken. Development of more accurate and less expensive assays coupled with improved assisted reproductive technology success rates may make PGD a more widely use clinical tool. The future awaits these development.velopment.

• Reproductive and Developmental Biology
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• v.41 no.1
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• pp.17-23
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• 2017

The oocyte undergoes various events during in vitro maturation (IVM) and subsequence development. One of the events is production of reactive oxygen species (ROS) that is a normal process of cell metabolism. But imbalances between ROS production and antioxidant systems induce oxidative stress that negatively affect to mammalian reproductive process. In vitro environments, in vitro matured oocytes have many problems, such as excessive production of ROS and imperfect cytoplasmic maturation. Therefore, in vitro matured oocytes still have lower maturation rates and developmental competence than in vivo matured oocytes. In order to improve the IVM and in vitro culture (IVC) system, antioxidants, vitamins were added to the IVM, IVC medium. Antioxidant supplementation was effective in controlling the production of ROS and it continues to be explored as a potential strategy to overcome mammalian reproductive disorders. Based on these studies, we expect that the use of antioxidants in porcine oocytes could improved maturation and development rates.

• Reproductive and Developmental Biology
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• v.28 no.4
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• pp.241-245
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• 2004

This study was conducted to investigate nuclear remodeling and developmental rate following nuclear transfer of fetal fibroblast cells, ear skin cells and oviduct epithelial cells into porcine recipient oocytes. To test par-thenogenetic activation, oocytes were treated with a 6-dimethylaminopurine (6-DMAP), a single DC-pulse (DC), calcium ionomycin (ionomycin), DC+6-DMAP and ionomycin + 6-DMAP after in vitro maturation. For nuclear transfer, in vitro matured oocytes were enucleated, and donor cells were transferred into oocytes. Cloned embryos were fused and stimulated with 6-DMAP for 4 h and cultured in vitro for 6 days. Among treatments for parthenogenesis, the activation rate of DC +6-DMAP treatment was significantly higher than that of single treatment roups (p<0.01), except for DC treatment group. However, the difference was not significant in activation rate compared to other complex treatment groups. Nuclear swelling of the cloned embryos was initiated at 60 min after stimulation and increased afterwards. Fusion rates were not different among different donor cells. Cleavage rates of DC treatment groups were significantly higher than those of DC+6-DMAP treatment groups (p<0.05) in case that fetal fibroblast and ear cells were used for nuclear donor. The cloned embryos from developed to blastocysts in oviduct epithelial cell nuclear transfer with DC+6-DMAP treatment was significantly higher compared to those with DC only treatment (p<0.05). However, no blastocyst was developed from nuclear transfer of fetal fibroblast and ear cells regardless of activation treatments. Based on these results, a proper activation stimulation may be necessary to increase the activation rate and the development to blastocyst in cloned porcine embryos.

• Clinical and Experimental Reproductive Medicine
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• v.22 no.2
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• pp.163-170
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• 1995

Growth factors (GFs) produced by the embryo or by the maternal reproductive tract have been reported to regulate the embryonic development and differentiation. Among GFs, EGF as a mitogen plays a role in mitosis and functional differentiation of trophectoderm cells in mouse. The present study was carried out to investigate the effect of EGF on development of mouse embryos and to localize EGF in the mouse oocytes and embryos, which has been reported to be detected in the reproductive tract in mammals. To investigate the effect of EGF on the development of the embryo, mouse 2-cell embryos were cultured to blastocysts stage in Ham's F10 medium, treated with EGF(10-50 ng/ml) for 72 hrs. Immunocytochemistry was performed from oocyte to blastocyst stage with anti-EGF and anti-Mouse IgG, in order to determine the stage which EGF would be expressed in mouse. Exogenous EGF (more than 10 ng/ml) in the culture medium improved the developmental and hatching rates in the mouse embryos. As a result of immunocytochemistry, the embryonic EGF was expressed after the late 4-cell stage. EGF is thought to enhance preimplantation embryonic development and hatching. Exogenous EGF in the culture medium is thought to activate EGF receptor in the late 4-cell embryos and to enhance blastulation and hatching in mouse embryos. It is concluded that EGF enhances the developmental and hatching rates in the mouse embryos.

• Korean Journal of Veterinary Research
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• v.35 no.3
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• pp.635-641
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• 1995

The purpose of this study was to investigate the effects of developmental stage and equilibration time on survival of rabbit embryos following freezing by vitrification. Adult New Zealand White female rabbits were superovulated with PMSG and hCG. The 8-cell stage embryos were collected from 40 to 45 hours after hCG injection by flushing oviducts with Dulbecco's phosphated buffered saline and in vitro cultured in TCM-199 containing 10% fetal calf serum(FCS). Each embryos developed in vitro to 16-cell, compact morula and blastocyst was cryopreserved and cultured following thawing to examine their developmental potential to expanded blastocyst stage in vitro. The frozen-thawed-cultured embryos were stained with Hoechst 33342, and their nuclei were counted using a fluorescence microscope. On the toxicity test of EFS solution as cryopreservation, the survival rates of 8-cell stage embryos was decreased in reverse to increasing of exposure time over 5 minutes. The post-thaw survival rates of embryos on equilibration times was significantly(P<0.05) higher for 2 min. than for 5 or 10 minutes. From morula to blastocyst of rabbit embryos was more suitable than 8-cell stage for cryopreservation by vitrification. The higher post-thaw survival rate of embryos can be achieved by keeping the cryoprotectant at $4^{\circ}C$ than at $20^{\circ}C$. The mean number of nuclei per embryo following freezing by vitrification and in vitro culture to expanded blastocyst at compacted morula and blastcyst was not significantly differ from fresh blastocyst.

• Clinical and Experimental Reproductive Medicine
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• v.51 no.1
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• pp.57-62
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• 2024

Objective: The purpose of this study was to use a mouse model to investigate the blastocyst formation rate in vitrified-warmed embryos derived from vitrified-warmed oocytes. Methods: Metaphase II oocytes obtained from BDF1 mice were vitrified and warmed, followed by fertilization with epididymal sperm. On day 3, a total of 176 embryos, at either the eight-cell or the morula stage, were vitrified-warmed (representing group 1). For group 2, 155 embryos at the same developmental stages were not vitrified, but rather were directly cultured until day 5. Finally, group 3 included day-5 blastocysts derived from fresh oocytes, which served as fresh controls. The primary outcome measured was the rate of blastocyst formation per day-3 embryo at the eight-cell or morula stage. Results: The rates of blastocyst formation per day-3 embryo were comparable between groups 1 and 2, at 64.5% and 69.7%, respectively (p>0.05). The formation rates of good-quality blastocysts (expanded, hatching, or hatched) were also similar for groups 1 and 2, at 35.5% and 43.2%, respectively (p>0.05). For the fresh oocytes (group 3), the blastocyst formation rate was 75.5%, which was similar to groups 1 and 2. However, the rate of good-quality blastocyst formation in group 3 was 57.3%, significantly exceeding those of group 1 (p=0.001) and group 2 (p=0.023). Conclusion: Regarding developmental potential to the blastocyst stage, vitrified-warmed day-3 embryos originating from vitrified-warmed oocytes demonstrated comparable results to non-vitrified embryos from similar oocytes. These findings indicate that day-3 embryos derived from vitrified-warmed oocytes can be effectively cryopreserved without incurring cellular damage.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.7
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• pp.956-965
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• 2019

Objective: The main goal of this study was to provide a morphological indicator that could be used to select high-quality oocytes of appropriate meiotic and developmental capabilities in pig. The higher quality of immature oocytes, the higher success rates of in vitro maturation (IVM) and in vitro fertilization (IVF). Thus, prior to the IVM culture, it is important to characterize oocytes morphologically and biochemically in order to assess their quality. Two of the largest indicators of oocyte quality are the presence of cumulus cells and status of chromatin. To investigate the effects of porcine oocyte chromatin configurations on the developmental capacity of blastocysts, we assessed oocyte chromatin status according to follicle size and measured the developmental potency of blastocysts. Methods: To sort by follicle size, we divided the oocytes into three groups (less than 1 mm, 1 to 3 mm, and more than 3 mm in diameter). To assess chromatin configuration, the oocytes were assessed for their stages (surrounded nucleolus [SN] germinal vesicle [GV], non-surrounded nucleolus [NSN] GV, GV breakdown, metaphase I [MI], pro-metaphase II [proMII], and metaphase II [MII]) at different maturation times (22, 44, and 66 h). To assess the development rate, oocytes of each follicle size were subjected to parthenogenetic activation for further development. Finally, GV oocytes were grouped by their chromatin configuration (SN, SN/NSN, and NSN) and their global transcriptional levels were measured. Results: SN GV oocytes were more suitable for IVF than NSN GV oocytes. Moreover, oocytes collected from the larger follicles had a greater distribution of SN GV oocytes and a higher developmental capacity during IVM, reaching MII more quickly and developing more often to blastocysts. Conclusion: Porcine oocytes with high-level meiotic and developmental capacity were identified by analyzing the relationship between follicle size and chromatin configuration. The porcine oocytes from large follicles had a significantly higher SN status in which the transcription level was low and could be better in the degree of meiotic progression and developmental capacity.

• Journal of Family Resource Management and Policy Review
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• v.25 no.3
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• pp.103-120
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• 2021

Recently, the importance of the fathers role in the care of young children has been emphasized in Korea for the balance of childcare responsibilities between mothers and fathers. This study investigates the trends in paternal childcare in Korea over the last 15 years. Childcare is divided into primary and developmental care and fathers's Childcare time and participation rates are inverstigated for dual- and single-income households. Data are collected from the four waves of the five-yearly Statistics of Korea Life Time Surveys between 2004(t₁) and 2019(t₄) including the workday time diaries of fathers with preschool children(n₁=2,264, n₂=1,242, n₃=959, n₄=952). Three major results are identified. First, paternal childcare time and participation rates have increased with dual-income fathers spending 24 more minutes a day with their young child(ren) in 2019 than in 2004, which is nearly double. Second, in the analysis of fathers' childcare time use and participation rates comparing primary and developmental care, primary care is found to have increased more than developmental care, especially among dual income fathers: this further exhibits a reversed relation between primary and developmental care over time. Third, the determinants of paternal childcare time are fathers' age, market labor time, commuting time, gender equality consciousness, and education. In particular, market labor time was significant in all four waves, while gender equality consciousness is only significant for single-income fathers. Based on these results, a specific agenda is provided for family-friendly policies to improve the balance of childcare roles between fathers and mothers, especially encouraging increased(significant and sufficient) participation of fathers in primary care activities.