• Korean Journal of Veterinary Research
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• v.34 no.4
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• pp.735-744
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• 1994

Catheters were placed into the external jugular veins of immature female rats. On the following day (day 28 of age), the animals were injected subcutaneously with pregnant mare serm gonadotropin(PMSG): 4IU(control) or 20IU(superovulation). Each animal was sequentially bled at Ohr and 12hr and subsequently at 6hr intervals until sacrifice at 72hr after PMSG. The superovulatory dose of PMSG significantly(P<0.05) increased the ovulatory response by 4.0 fold above controls. On the other hand, superovulated oocytes displayed considerably different stages of meiotic maturation: prophase I (14.7%), anaphase I (36.2%), telophase I (10.3%), metaphase I/II (32.4%), while in control rats a majority of the oocytes examined(94.0%) consistently showed a metaphase II configuration. Serum luteinizing hormone(LH) levels were determined by RIA. Both groups exhibited a similar time relationship with two distinct peaks: an initial slight rise at 0-18hr and a second sharp rise at 54-60hr. However, there was a marked change in the magnitude of LH levels between the two groups. In superovulated animals, prior to the second peak, overall LH levels were significantly(P<0.001) higher than controls. In contrast, at the peak occurring at 60hr, LH concentrations were significantly(P<0.001) reduced by 54% below that of control. Additionally, a maximum increase of mean ${\Delta}LH$ between two peaks was much less in superovulated as compared to control rats. The initial prolonged elevation of serum LH before 54hr in superovulated rats was found to result from actual cross-reaction of the injected PMSG with LH antibody in the assay, while a precipitous second elevation between 54hr and 60hr resulted primarily from an endogenous LH surge. This study clearly defines time-course features of serum LH in PMSG-treated rats. The overall results indicate that, following superovulatory treatment with PMSG, the increased ovulatory response is primarily associated with PMSG-derived intrinsic gonadotropin, and that the recovery of immature or asynchronously mature oocytes at ovulation may reult from the circulatory alteration of LH activity characterized by an initial prolonged elevation of serum LH and its subsequent attenuation.

• Clinical and Experimental Reproductive Medicine
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• v.31 no.4
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• pp.225-234
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• 2004

Objectives: To evaluate the efficacy of GnRH antagonist cetrorelix in women undergoing controlled ovarian hyperstimulation (COH) for in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) and to determine changes in serum hormone concentrations during cetrorelix administration. Methods: We performed a clinical trial on 30 patients undergoing COH with highly purified follicular stimulating hormone (HP-FSH) and gonadotropin releasing hormone antagonist (GnRHant), cetrorelix. FSH was administrated from day 2 or 3 of cycle with fixed dose and adjusted according to individual response. 0.25 mg of cetrorelix was injected daily subcutaneously from stimulation day 5 until the day of hCG administration. Daily ultrasound monitoring was performed for growing follicles and serum levels of luteinizing hormone (LH), estradiol ($E_2$) and progesterone were measured daily during cetrorelix administration. Up to 4 embryos were transferred. Results: Mean age of enrolled patients was $32.0{\pm}3.4$ years (mean $\pm$ S.D.). All of 30 patients underwent oocyte pick-up, and embryo transfer was done in 28 patients. The total and mean numbers of received oocytes were 196 and $6.5{\pm}4.7$, the number of fertilized eggs was 111, and the fertilization rate was 56.6%. Total duration of FSH administration was $9.2{\pm}2.2$ days and mean of $24.3{\pm}7.7$ ampules of HP-FSH was administered. Total duration of cetrorelix administration was $5.7{\pm}1.9$ days. Serum LH and progesterone levels were maintained in the range of $1.4{\sim}2.9\;mIU/mL$ and $0.3{\sim}0.6\;ng/mL$, which respectively reflected effective prevention of premature LH surge. Clinical pregnancies were achieved in 9 patients, and overall clinical pregnancy rate was 30.0% per oocyte retrieval, and 32.1% per embryo transfer. Conclusion: GnRH antagonist is safe and convenient for COH for IVF-ET and effective with optimal pregnancy rate.

• Clinical and Experimental Reproductive Medicine
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• v.49 no.1
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• pp.16-25
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• 2022

In mammalian species, females are born with a number of oocytes exceeding what they release via ovulation. In humans, an average girl is born with over a thousand times more oocytes than she will ovulate in her lifetime. The reason for having such an excessive number of oocytes in a neonatal female ovary is currently unknown. However, it is well established that the oocyte number decreases throughout the entire lifetime until the ovary loses them all. In this review, data published in the past 80 years were used to assess the current knowledge regarding the changing number of oocytes in humans and mice, as well as the reported factors that contribute to the decline of oocyte numbers. Briefly, a collective estimation indicates that an average girl is born with approximately 600,000 oocytes, which is 2,000 times more than the number of oocytes that she will ovulate in her lifetime. The oocyte number begins to decrease immediately after birth and is reduced to half of the initial number by puberty and almost zero by age 50 years. Multiple factors that are either intrinsic or extrinsic to the ovary contribute to the decline of the oocyte number. The inflammation caused by the ovulatory luteinizing hormone surge is discussed as a potential contributing factor to the decline of the oocyte pool during the reproductive lifespan.

• Korean Journal of Animal Reproduction
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• v.19 no.4
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• pp.307-322
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• 1996

The corpus luteum (CL) is formed by the action of a surge of luteinizing hormone (LH) on the pre-ovulatory follicle. Luteal cells derived from granulosa and theca interna cells continue to secrete progesterone for about two weeks. LH in domestic animals is essential for the normal secretion of progesterone at all stages of the luteal phase. For this process in the rodents, 20$\alpha$-hydroxysteroid dehydrogenase (20$\alpha$-HSD) is indispensable. 20$\alpha$-HSD is an enzyme to be a biologically inactive steroid. This enzyme plays a critical role in the regulation of the rat luteal function and reported to be present in steroid-producing tissues such as the testis and adrenal gland. We have purified 20$\alpha$-HSD and found two distinct 20$\alpha$-HSD molecules (HSD-1 and HSD-2). Their molecular weights are both estimated to be 33kd.The amino acid compositions of HSD-1 and HSD-2 are mostly similar, but there is a slight difference in the content of lysine. We demonstrated that 1) CL of previous generations contribute more to whole ovarian 20$\alpha$-HSD activity, 2) newly formed corpora lutea contain only 20$\alpha$-HSD-1 activity, and 3) old CL express activities of each HSD isozyme as shown in the luteal tissue of cycling rats on the day of diestrus where only degenerating old CL exist. The increase in 20$\alpha$-HSD activity identified seems to be related to the increase in the numbers of 20$\alpha$-HSD-positive cells. Interestingly, 20$\alpha$-HSD-1 activities were strongly found in the follicle fluids and theca interna cells by immunohistochemical study. Thus, the activity of 20$\alpha$-HSD may be related to a survival mechanism of those luteal cells and follicles remaining in the ovaries. Luteal cells arise from two sources. The small luteal cells are all of theca cell origin, while the large luteal cells are mainly of granulosa cell origin. CL of Korean Native Cattle, as those of other animal species, contains two morphologycally and functionally distinct luteal cell populations, such as small and large luteal cells as well as nonluteal cells. In all reproductive states except in the late luteal phase, the bovine CL also contained more small luteal cells than large luteal cells. Luteal tissue secretes a variety of growth factors (proteins) and the pattern of secretion changes during all stages of the luteal phase. These growth factors could be important in regulating the function of the bovine corpus luteum and may act in a potential endocrine autocrine and paracrine mechanisms. Therefore, further work has to be done to elucidate the role of growth factors in the ovary, especially in the corpus luterum. Interest should be focussed on interaction of these growth factors in the regulation of luteal cell and the localization of cytokine synthesis in differnet luteal cells.