• Clinical and Experimental Reproductive Medicine
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• v.21 no.1
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• pp.99-110
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• 1994

One consequence of fertilization in mammals is an increased resistance of the zona pellucida (ZP) to proteases and various chemical reagents. This phenomenon has been called 'zona pellucida hardening' (ZPH), and it is generally accepted that it is caused by the secretory products of cortical granules released by the egg at fertilization. ZP of mouse oocytes maturing in vitro in a chemically defined medium becomes progressively more resistant to solubilization by chymotrypsin ("Spontaneous" ZP hardening). In the present study, it was aimed to find the specificity of spontaneous ZPH in relation to its possible relevance to the cortical reaction and the physiological block to polyspermy. When a maturation inhibitors, cAMP analog(dbcAMP) and phosphodiesterase inhibitor (IBMX) was added to culture medium, it prevent spontaneous ZPH of mouse oocyte during in vitro culture. Thus spontaneous ZPH requires GVBD, since it is prevented by those agents, which inhibit GVBD in vitro. However, culture for 3 hours in the presence of PMA(lOng/ml), a protein kinase C activator, resulted in ZPH without GVBD, thus suggesting that ZPH may be regulated independently apart from the event of GVBD. Pretreatment of mouse oocyte with FBS result in partially inhibitory effect on subsequent spontaneous ZPH. Induction of GVBD in vivo had a inhibitory effect on the spontaneous ZPH, but subsequent spontaneous ZPH. Induction of GVBD in vivo had a inhinbitory effect on the spontaneous ZPII, but had no inhibitory effect on PMA-induced ZPH. Treatment with a microfilament formation blocker(cytochalasin-B) at 1${\mu}g$/ml concentration, resulted in the excellent inhibitory effect on spontaneous ZPH. However cytochalasin-B did not inhibit PMA-induced ZPH. Thus this suggesting that spontaneuse ZPH had a different mechanism from PMA-induced ZPH.

• Korean Journal of Animal Reproduction
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• v.27 no.1
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• pp.35-44
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• 2003

The present study was performed to investigate the first polar body(PB) extrusion during in-vitro maturation(IVM) and to examine the effect of different maturation time on the embryo development of Korean Native Cows(KNC) with regard to blastocyst(BL) cell numbers and pregnancy rates. PB extrusion did not take place for the first 12 hours(hr) of IVM, and most of KNC oocytes extruded PB from 14 to 20 hr after the onset of maturation. There was no significant difference in cleavage and 8-cell stage rates among the treatment groups, but BL and BL/8-cell rates were significantly higher(P<0.05) in 18 hr maturation group(31.0$\pm$5.7 and 82.0$\pm$5.1%) than 22 and 24 hr maturation group. The proportion of BL formed on day 7 and 8 was significantly higher(P<0.05) in 18 hr maturation group(85%) than in 24 hr maturation group(55%). There was a significant difference(P<0.05) in inner cell mass, trophectoderm and total cell number between day 7 BL produced by in-vivo and IVM 18 hr and day 8 BL produced by IVM 18 hr and 24 hr. Pregnancy rates are also significantly higher(P<0.05) in in-vivo(56.3%) and IVM 18 hr day 7(50.0%) group than day 8 treatment groups(18 hr: 16.7%, 24 hr: 10.5%). These results suggest that KNC oocytes achieve developmental competency within 20 hr of IVM, and "short" IVM (18 hr) is more effective than "long" IVM(24 hr) in embryo development rates, BL cell numbers and pregnancy rates.

• Journal of Embryo Transfer
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• v.21 no.2
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• pp.137-146
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• 2006

The objective of this study was to examine the effect of donor cell types, the source of recipient oocytes and estrous synchronization on pregnancy and delivery rates of somatic cell nuclear transfer (SCNT) embryos in Korean native goats. Recipient oocytes were surgically collected after superovulation. Ear cells and fetal fibroblasts were collected and cultured in serum-starvation condition (TCM-199 + 0.5% FBS) for cell confluence. The zonae pellucidae of in vivo- and in vitro-matured oocytes were partially drilled using a laser system. Single somatic cell was transferred into the enucleated oocyte. The reconstructed oocytes were electrically fused with 0.3 M mannitol. After the fusion, embryos were activated by Ionomycin+6-DMAP. NT embryos were cultured in mSOF medium supplemented with 0.8% BSA at $39^{\circ}C$ in an atmosphere of 5% $CO_2$, 5% $O_2$, 90% $N_2$ for 12 to 20 hr. One hundred and two SCNT embryos were transferred into 20 recipients and pregnancy rate at days 30 was 20.0%. Of them, one developed to term and delivered 1 kid. Ear cells showed significantly higher fusion (63.8 vs. 26.5%) and pregnancy rates (20.0 vs. 0.0%) than those of fetal fibroblast (p<0.05). The recipients synchronized by CIDR showed significantly lower pregnancy rates compared to that of recipient in natural estrus ($0.0{\sim}25.0%$ vs. 100%) (p<0.05). Cloned kid was born from the recipient in natural estrus. For the synchronization of estrus between recipient and donor, there was no difference between treatments (${\pm}0$ vs. +12 hr) in pregnancy rate. The first healthy cloned kid (Jinsoonny) was produced by transfer of SCNT embryos derived from in vivo oocytes and ear cells into a recipient goat whose estrus was synchronized with the donor. These results imply that donor cells for nuclear transfer may affect the success rate, and the estrus synchronization between donor and recipient animals can also be important.

• Journal of Embryo Transfer
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• v.28 no.3
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• pp.237-241
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• 2013

It is generally accepted that chronic stress impairs female reproduction. It negatively affects ovarian function and the number of ovulated oocytes. Chronic stress lowers the number of retrieved oocytes. Ovarian follicular development is regulated by both pituitary-derived gonadotropins and intraovarian regulatory factors. The main corticosteroids are cortisol, cortisone, 11-deoxycortisol and corticosterone, cortisol being one of the most commonly used welfare and stress physiological indicator. In this study, we investigated the effect of cortisol level on progesterone patterns and ovulation in the dog. Cortisol and progesterone level of serum were analyzed by radioimmunoassay. The day of ovulation was considered as the day when serum progesterone concentration was 6.0~8.0 ng/ml. In vivo dog oocytes were collected by flushing oviducts of mixed-breed bitches at three days after ovulation. We classified dogs as having group 1 (cortisol level, 0 ${\leq}$ or < $2{\mu}g/dl$), group 2 (corisol level, 2 ${\leq}$ or < $4{\mu}g/dl$), group 3 (cortisol level, 4 ${\leq}$ or < $6{\mu}g/dl$) and group 4 (cortisol level, $6{\mu}g/dl$ ${\leq}$). The patterns of progesterone were not different in four cortisol groups. The average numbers of retrieved oocytes was not different in four cortisol groups. These results suggest that different cortisol levels on estrus dogs do not affect ovulation, number of ovulated oocytes and progesterone changes.

• Clinical and Experimental Reproductive Medicine
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• v.41 no.2
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• pp.41-46
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• 2014

IVM refers to the maturation of immature oocytes in culture after their recovery from small antral follicles at the stage prior to selection and dominance. IVM requires little or no FSH in vivo and has been proposed as an alternative to conventional IVF, since it reduces the primary adverse effects caused by controlled ovarian stimulation, including the ovarian hyperstimulation syndrome. Moreover, IVM is a promising option for cases for which no standard protocol is suitable, such as FSH resistance, contraindications for ovarian stimulatory drugs, and the need for urgent fertility preservation. Recently, IVM has been used in women with regular cycles and normal ovaries. However, the pregnancy rate following IVM is suboptimal compared with that of conventional IVF, indicating that further studies to optimize the protocol and the culture conditions are warranted.

• Reproductive and Developmental Biology
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• v.31 no.2
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• pp.109-113
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• 2007

This study was conducted to evaluate the effect of cytochalasin B (CB) treatment in the activation medium on the development of somatic cell nuclear transfer (SCNT) rat embryos. Fetal fibroblast cells were isolated from a Day 14.5 fetus, and the oocytes for recipient cytoplasm were recovered from 4-week old Sprague Dawley rats. After enucleation and nuclear injection, the reconstructed oocytes were immediately exposed to activation medium consisting of 10 mM $SrCl_2$ with or without CB for 4 hr, and formation of pseudo-pronucleus (PPN) was checked at 18 hr after activation. Then, they were transferred into day 1 pseudopregnant recipients (Hooded Wistar) or cultured for 5 days to check their developmental competence in vivo or in vitro. The number of PPN was not affected by CB treatment during the activation. However, CB treatment supported pre-implantation development of rat SCNT embryos. Embryos generated by the procedures of SCNT were also capable of implanting, with 1 implantation scar found from a recipient following the transfer of 87 SCNT embryos to four foster mothers. The result of the present study shows that rat SCNT embryo can develop to post-implantation stage following treatment with CB.

• Asian-Australasian Journal of Animal Sciences
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• v.17 no.5
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• pp.617-620
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• 2004

The present study compares development of rabbit embryos generated using different oocyte activation protocols and reconstructed with embryonic or cumulus cells as nuclear donor. In vivo matured oocytes were collected from New Zealand White rabbits at 16 h after ovulation treatment and were activated at18 h of post-ovulation treatment. The following schemes of oocytes activation were tested: 1) single electric pulse (EP, 3.2 kV/cm, 3${\times}$20 $\mu$s, 0.3 M mannitol)+5 min culture in the presence of 5 mM Ionomycin, 2) single electric pulse (EP, 3.2 kV/cm, (${\times}$20 $\mu$s, 0.3 M mannitol)+1 h culture in the presence of 2 mM 6-DMAP, and 3) three electric pulses 30 min apart. Cleavage rate, percentage of expanded and hatched blastocysts as well as total cell number of blastomeres of parthenogenetic embryos were significantly higher using either EP+6-DMAP or 3${\times}$EP schemes, comparing with EP+Ionomycin. Development rate up to hatched blastocyst stage of cloned rabbit embryos using the EP+6-DMAP for activation of nuclei were 19% for embryonic cell nuclei and 36% for cumulus cell nuclei. The best activation protocol optimalized in this study was the combined treatment "P+6-DMAP" which may be potentially used for nuclear transfer protocol.

• Asian-Australasian Journal of Animal Sciences
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• v.22 no.3
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• pp.319-327
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• 2009

Follicular fluid meiosis-activating sterol (FF-MAS) has been suggested as a positive factor which could improve the oocyte quality and subsequent embryo development after in vitro fertilization. However, FF-MAS is a highly lipophilic substance and is hard to detect in studying the relationship between MAS and quality of oocyte maturation. The present study focused on the expression of lanosterol 14${\alpha}$-demethylase (LDM), a key enzyme that converts lanosterol to FF-MAS, on mouse oocyte maturation and its potency on development. LDM expression was strong in gonadotropin-primed germinal vesicle stage oocytes, weak after germinal vesicle breakdown (GVBD), and then strong in MII stage oocytes. The LDM-specific inhibitor azalanstat significantly inhibited oocyte fertilization (from 79.4% to 68.3%, p<0.05). Also, azalanstat (5 to 50 ${\mu}M$) decreased the percentage of blastocyst development dosedependently (from 78.7% to 23.4%, p<0.05). The specific inhibition of sterol ${\Delta}14$-reductase and ${\Delta}7$-reductase by AY9944 accumulates FF-MAS and could increase blastocyst development rates. Additionally, in the AY9944 group, the rate of inner cell mass (ICM)/ total cells was similar to that of in vivo development, but the rate was significantly decreased in azalanstat treatment. In conclusion, LDM, the key enzyme of FF-MAS production, may play an important role in fertilization and early development of the mouse embryo, especially in vitro.

• Reproductive and Developmental Biology
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• v.31 no.2
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• pp.127-131
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• 2007

Embryonic germ (EG) cells are undifferentiated stern cells isolated from cultured primordial germ cells (PGC). These cells share many characteristics with embryonic stem cells including morphology and pluripotency. Undifferentiated porcine EG cell lines demonstrating capacities of differentiation both in vitro and in vivo have been established. Since EG cells can be cultured indefinitely in an undifferentiated state, whereas somatic cells in primary culture are often unstable and have limited lifespan, EG cells may provide inexhaustible source of karyoplasts in nuclear transfer (NT). In this study the efficiencies of NT using porcine EG and fetal fibroblast cells were compared. Two different techniques were used to perform NT. With conventional NT procedure (Roslin method) involving fusion of donor cells with enucleated oocytes, the rates of development to the blastocyst stage in EG and somatic cell NT were 16.8% (59/351) and 14.5% (98/677), respectively. In piezo-driven microinjection (Honolulu method) of donor nuclei into enucleated oocytes, the rates of blastocyst formation in EG and somatic cell NT were 11.9% (15/126) and 9.4% (9/96), respectively. Regardless of NT methods used in this study, EG cell NT gave rise to comparable rate of blastocyst development to somatic cell NT. Overall, EG cells can be used as karyoplast donor in NT procedure, and embryos can be produced by EG cell NT that may be used as an alternative to conventional somatic cell NT.

• Journal of Animal Reproduction and Biotechnology
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• v.34 no.2
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• pp.75-85
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• 2019

Omega-3 α-linolenic acid and omega-6 linoleic acid are essential fatty acids for health maintenance of human and animals because they are not synthesized in vivo. The purpose of this study was to evaluate the effect of α-linolenic acid and linoleic acid supplementation on in vitro maturation and developmental potential of porcine oocytes. Various concentrations of α-linolenic acid and linoleic acid were added into in vitro maturation medium, and we evaluated the degree of cumulus expansion, oocyte nuclear-maturation rate, blastocyst rate, blastocyst quality, and levels of prostaglandin E₂, 17β-estradiol, and progesterone in the spent medium. High doses (100 μM) of α-linolenic acid and linoleic acid supplementation significantly inhibited cumulus expansion and oocyte nuclear maturation, and prostaglandin E₂ synthesis also significantly decreased compared with other groups (p < 0.05). Supplementation of 50 μM α-linolenic acid and 10 μM linoleic acid showed higher quality blastocysts in terms of high cell numbers and low apoptosis when compared with other groups (p < 0.05), and synthesis ratio of 17β-estradiol / progesterone also significantly increased compared with control group (3.59 ± 0.22 vs. 2.97 ± 0.22, 3.4 ± 0.28 vs. 2.81 ± 0.19, respectively; p < 0.05). Our results indicated that supplementation with appropriate levels of α-linolenic acid and linoleic acid beneficially affects the change of hormone synthesis (in particular, an appropriate increase in the 17β-estradiol / progesterone synthesis ratio) for controlling oocyte maturation, leading to improved embryo quality. However, high doses of α-linolenic acid and linoleic acid treatment results in detrimental effects.