• 한국동물생명공학회지
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• 제35권1호
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• pp.2-11
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• 2020

Assisted reproductive technologies (ART) merely depend on improving the oocyte maturation and their developmental competence to produce good quality embryos. Oocyte maturation passes through long and complex molecular steps starts from the early embryonic life and ends with sperm fertilization. Oocyte developmental competence can be attained by improving the nuclear and cytoplasmic mechanisms together with some epigenetic maturation. In this review, we highlight the cornerstones of oocyte maturation on both nuclear and cytoplasmic levels. Interfering or supporting these molecular mechanisms would help in the development of novel regulating agents for reproductive performance of humans and livestock species.

• Reproductive and Developmental Biology
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• 제30권2호
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• pp.115-118
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• 2006

Cyclin B1 is known to reflect the M-phase promoting factor (MPF), a universal regulator of G2/M-phase transition, activity during the process of oocytes maturation. To investigate whether culture condition affects the maturation rate and the expression of cyclin B1 protein, bovine immature oocytes are stimulated and cultured according to the following protocols: Experiment 1: denuded oocytes (denude) only, COC only, denuded oocytes+granulosa cells (denude+GCs) and COC+GCs; Experiment 2: no-activation (control), 7% ethanol for 5 min and $10{\mu}l/ml$ ionomycin for 5 min at immediately before maturation. The maturation rates of denude and no-activation group were significantly lower in both experiments (P<0.05), respectively. Co-culture or stimulation method in bovine immature oocytes culture increases the cyclin B1 expression significantly in both experiments (P<0.05). Based on these results, culture condition affects the maturation rate and the expression of cyclin B1 protein during the first meiotic maturation in bovine immature oocytes.

• Reproductive and Developmental Biology
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• 제39권2호
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• pp.37-41
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• 2015

The oocyte undergoes various events during maturation and requires many substances for the maturation process. Various intracellular organelles are also involved in maturation of the oocyte. During the process glucose is essential for nuclear and cytoplasmic maturation, and adenosine triphosphate is needed for reorganization of the organelles and cytoskeleton. If mitochondrial function is lost, several developmental defects in meiotic chromosome segregation and maturation cause fertilization failure. The endoplasmic reticulum, a store for $Ca^{2+}$, releases $Ca^{2+}$ into the cytoplasm in response to various cellular signaling molecules. This event stimulates secretion of hormones, growth factors and antioxidants in oocyte during maturation. Also, oocyte nuclear maturation is stimulated by growth factors such as epidermal growth factor. This review summarizes roles of organelles with focus on the Golgi apparatus during maturation in oocyte.

• 한국가축번식학회지
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• 제22권3호
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• pp.253-264
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• 1998

Porcine follicular oocyte, collected from antral follicles (2~5 mm in diameter) of gilt ovaries were matured in vitro porcine follicular fluid (pFF) with PMSG (pFF-PMSG) buffer with at 37$^{\circ}C$ under 5% CO2 in air their ability of maturation promoting factor (MPF), of GV and GVBD formation was examined followed during time after in vitro culture. Formation of second metaphase was observed in 57.6% and 71.2% of matured in with pFF-PMSG buffer to 45 and 50 hours after invitro. Porcine oocytes cultured in pFF-PMSG for various periods of up to 30 hours were stained with Hoechst-33342 and classified according to maturation before assaying. Histone H1 kinase (H1K) activity was assayed during meiotic maturation in porcine oocytes matured in pFF-PMSG buffer in vitro. In oocytes matured in pFF-PMSG, H1K activity was at the 30 hours after culture and increased about 15 fold than at the germinal vesicle stage with before at the cultured in vitro. This pattern is similar to those reported in non-mammalian species and su, pp.rts the concepts that H1K is ubiquitous in eukaryotes and controls the meiotic cell cycle in mammals. These results suggest that the maturation pFF-PMSG buffer used influences the fluctuation pattern of H1K activity and biological characteristics of porcine oocytes cultured in vitro.

• Animal cells and systems
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• 제5권1호
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• pp.45-50
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• 2001

Rana ovarian follicles consist of oocyte, vitelline envelope, granulosa cells, and theca/epithelial layer. Using scanning electron microscopy, the surface structure of each follicular component was investigated. Changes in oocyte surface during oocyte maturation were also examined. Theca/epithelial layer was almost transparent and some blood vessels and granulosa cells were observed underneath in intact follicle. The number of granulosa cells was estimated to be 6700-7200 per oocyte. The granulosa cells partially overlapped each other and their microvilli penetrated the vitelline membrane via holes present in the vitelline envelope and seemed to be linked to oocyte microvilli. After removal of the vitelline envelope by microforcep, oocyte microvilli were observed on the surface of the devitellined oocyte. The oocyte microvilli formed partial clusters on the surface of white spot area which appears iust before germinal vesicle breakdown (GVBD), whereas they were evenly distributed in other areas. The microvilli became shorter and less dense with oocyte maturation. The lengths of oocyte microvilli in the immature and mature oocyte were 1.5 $\mu$m and 0.6 $\mu$m, respectively. The present study suggests a fundamental structural change occurring on the oocyte surface during maturation.

• Clinical and Experimental Reproductive Medicine
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• 제39권2호
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• pp.58-67
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• 2012

Objective: Previously, we identified that transketolase (Tkt), an important enzyme in the pentose phosphate pathway, is highly expressed at 2 hours of spontaneous maturation in oocytes. Therefore, this study was performed to determine the function of Tkt in meiotic cell cycle regulation, especially at the point of germinal vesicle breakdown (GVBD). Methods: We evaluated the loss-of-function of Tkt by microinjecting Tkt double-stranded RNAs (dsRNAs) into germinal vesicle-stage oocytes, and the oocytes were cultured in vitro to evaluate phenotypic changes during oocyte maturation. In addition to maturation rates, meiotic spindle and chromosome rearrangements, and changes in expression of other enzymes in the pentose phosphate pathway were determined after Tkt RNA interference (RNAi). Results: Despite the complete and specific knockdown of Tkt expression, GVBD occurred and meiosis was arrested at the metaphase I (MI) stage. The arrested oocytes exhibited spindle loss, chromosomal aggregation, and declined maturation promoting factor and mitogen-activated protein kinase activities. The modified expression of two enzymes in the pentose phosphate pathway, Prps1 and Rbks, after Tkt RNAi and decreased maturation rates were amended when ribose-5-phosphate was supplemented in the culture medium, suggesting that the Tkt and pentose phosphate pathway are important for the maturation process. Conclusion: We concluded that Tkt and its associated pentose phosphate pathway play an important role in the MI-MII transition of the oocytes' meiotic cell cycle, but not in the process of GVBD.

• Asian-Australasian Journal of Animal Sciences
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• 제21권7호
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• pp.972-979
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• 2008

It has been recently shown that expression of the LH receptor (LHR) in cumulus cells is related with FSH-induced meiotic resumption of mouse cumulus enclosed oocytes (CEOs). However, to date, it is still unclear whether LHR expression in cumulus cells plays a key role during FSH-induced oocyte maturation. The purpose of this study was to characterize the functional role of LHRs in cumulus cells. CEOs were isolated from eCG-primed preovulatory follicles and cultured in hypoxanthine (HX) arrested medium. LHR protein expression in cumulus cells was time-dependent increasing during the process of FSH-induced oocyte maturation. While the sense oligodeoxynucleotide (ODN) had no effect, antisense ODN inhibited FSH-induced LHR expression and meiotic resumption. Moreover, this antisense ODN against LHR could inhibit FSH-induced mitogen-activated protein kinase (MAPK) phosphorylation. This study suggested that LHR expression in cumulus cells is involved in FSH-induced oocyte meiotic resumption, which process is possibly regulated by MAPK cascade.

• 한국수정란이식학회지
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• 제11권2호
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• pp.179-191
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• 1996

In-vitro culture has provided new inforrnation on mechanisms of oocytes rnaturation and results obtained in vitro have led to new questions. In porcine, follicular and oocyte size have the crucial importance for the oocytes maturation. The addition of hormones to the culture medium was found to accelerate and facilitate meiotic maturation. The presence of some factors in serum trigger the resumption of meiosis and support the maturation of oocytes in vitro. The maturation rate of porcine oocytes was also increased by supplementation of porcine follicular fluid to the culture medium. The growth factors can stimulate nuclear maturation and enhances cytoplasnic maturation of oocytes by interaction with gonadotropins. The maturation-promoting factor brings about GVBD and the subsequent maturational events in oocytes. However, cAMP can block the spontaneous meiotic maturation of oocytes in culture. The understanding of these influences is a prerequisite to enhancing in vitro maturation of porcine oocytes.

• BMB Reports
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• 제44권3호
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• pp.147-157
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• 2011

The meiotic process from the primordial stage to zygote in female germ cells is mainly adjusted by post-transcriptional regulation of pre-existing maternal mRNA and post-translational modification of proteins. Several key proteins such as the cell cycle regulator, Cdk1/cyclin B, are post-translationally modified for precise control of meiotic progression. The second messenger (cAMP), kinases (PKA, Akt, MAPK, Aurora A, CaMK II, etc), phosphatases (Cdc25, Cdc14), and other proteins (G-protein coupled receptor, phosphodiesterase) are directly or indirectly involved in this process. Many proteins, such as CPEB, maskin, eIF4E, eIF4G, 4E-BP, and 4E-T, post-transcriptionally regulate mRNA via binding to the cap structure at the 5' end of mRNA or its 3' untranslated region (UTR) to generate a closed-loop structure. The 3' UTR of the transcript is also implicated in post-transcriptional regulation through an association with proteins such as CPEB, CPSF, GLD-2, PARN, and Dazl to modulate poly(A) tail length. RNA interfering is a new regulatory mechanism of the amount of mRNA in the mouse oocyte. This review summarizes information about post-transcriptional and post-translational regulation during mouse oocyte meiotic maturation.

• Animal cells and systems
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• 제2권1호
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• pp.87-91
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• 1998

The present study investigated the involvement of the phospholipase C (PLC) and protein kinase C (PKC) signaling pathways during progesteroneinduced meiotic maturation in amphibian (Rana dybowskii) oocytes. Prosesterone-induced germinal vesicle breakdown (GVBD) of oocytes was significantly inhibited by a PKC inhibitor, staurosporine and a PLC inhibitor, U73122, in a dose-dependent manner. In contrast, U73343, an inactive analogue of U73122, was ineffective in suppressing GVBD. PKC activity in oocytes reached a maximum level at 30 min after progesterone stimulation and this elevated PKC activity was effectively suppressed by U73122 or staurosporine, suggesting that the activation of PKC enzyme is closely linked to PLC signaling during oocyte maturation. In addition, these inhib itors blocked the maturation promoting factor (MPF) activity which appeared in oocytes in response to progesterone, suggesting that PKC activation is an important signal for MPF activity. Therefore, this study demonstrates that the activation of PKC via PLC signaling is directly linked to an intracellular protein kinase cascade related to the appearance of MPF activity during meiotic maturation in amphibian (Rana dybowskii) oocytes.