• Fisheries and Aquatic Sciences
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• v.3 no.1
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• pp.37-43
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• 2000

We used a mammalian GnRH antagonist, $[Ac-3,4-dehydro-Pro^1,\;D-p-F-Phe^2,\;D-Trp^{3.6}]$-GnRH, to examine the details of the salmon type gonadotropin-releasing hormone (sGnRH) and GnRH agonist analog $(Des-Gly^{10}$[d-Ala^6]-ethylamide GnRH; GnRHa) functions in the control of maturational gonadotropin (GTH II) secretion, in precocious male rainbow trout, in both in vivo and in vitro experiments. In the in vivo study, plasma GTH II levels increased by sGnRH or GnRHa treatment, but the response was more rapid and stronger in the GnRHa treatment group. The increase in GTH II was significantly suppressed by the GnRH antagonist, while the antagonist had no effect on basal GTH II levels in both groups. The GnRH antagonist showed stronger suppression of GTH II levels in the sGnRH treatment fish than in the GnRHa treatment fish. In addition, plasma androgenic steroid hormones (testosterone and 11-ketotestosterone) increased by the sGnRH or GnRHa treatment. The GnRH antagonist significantly inhibited the increases in plasma androgenic steroid hormone levels stimulated by the sGnRH or GnRHa, while the antagonist had no effect on basal androgenic steroid hormone levels in both groups. In the in vitro study, treatment with sGnRH or GnRHa increased GTH II release from the cultured dispersed pituitary cells, but the response was stronger in the GnRHa treatment group. The increase in GTH II release by GnRH was suppressed by adding the GnRH antagonist, dose­dependently. On the other hand, basal release of GTH II did not decrease by the GnRH antagonist treatment in both groups. These results suggest that the GnRH antagonist, $[Ac-3,4-dehydro-Pro^1,\;D-p-F-Phe^2,\;D-Trp^{3.6}]-GnRH$, used in this study is effective in blocking the action of GnRH-induced GTH II release from the pituitary gland both in vivo and in vitro.

• Journal of Veterinary Clinics
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• v.21 no.4
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• pp.384-394
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• 2004

This study was carried out to monitor the response of ovaries and cyst according to treatment with GnRH or combination of GnRH and $PGF_2{\alpha}$ in dairy cows with ovarian follicular cysts. Thirty cows were diagnosed as having follicular cysts by rectal palpation, ultrasonography and progesterone (P4) assays. Ten cows were treated with GnRH (control), and the other twenty were treated with $PGF_2{\alpha}$ at 10 days after GnRH treatment. All the animals were re-examined by ultrasonography and blood was collected for the measurement of plasma P4 concentration at day 0 (the day of treatment), day 7, day 10, day 13, day 24 and day 34, respectively. In 30 cows that were diagnosed with follicular cysts, mean plasma P 4 concentrations on day -II and day -I were 0.3 ng/ml and 0.4 ng/ml. On day 10 increased as 2.7$\pm$0.2 ng/ml. Mean cystic wall thickness by ultrasonography on day -11 and day -I were 2.1 mm and 2.2 mm. In 9 cows responded on luteinization of cystic wall, cystic wall thickness was 3.9$\pm$0.5 mm at day 10 after GnRH treatment. The responses of ovaries until day 10 after GnRH treatment included development of corpus luteum in the ovary bearing the cyst or in the contralateral ovary (12 cows), luteinization of cystic wall (6 cows) and clouding of the anechoic antrum of cysts (2 cows). The ovarian responses according to the combination of GnRH and $PGF_2{\alpha}$ included regression of the corpus luteum (12 cows), increase (1 cow) and no change (1 cow) of cyst size until last examination, and complete disappearance on day 13 (6 cows), 23 (6 cows) and 34 (4 cows). Combination treatment group of GnRH and $PGF_2{\alpha}$ showed a higher pregnancy rate within 100 days after initial treatment (40.0 vs 65.0%) and shorter intervals from the treatment to conception (45.4$\pm$25.8 vs 53.5$\pm$31.4 days) compared with control. It was concluded that the administration of $PGF_2{\alpha}$ following GnRH treatment is effective in shortening the interval from treatment to conception in cows with follicular cyst. Also, this study suggested that the response of the cyst according to treatment revealed various types. Therefore, veterinarians should pay attention to monitor of the response of cystic ovaries after treatment, specially no change, slowly decrease or increasement of cyst size after treatment.

• Journal of Veterinary Clinics
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• v.3 no.1
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• pp.227-233
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• 1986

A total of 600 Holstein cows in Chonnam province was examined to make a diagnosis on the ovarian follicular cyst. By clinical signs and rectal examination, 57 cows were found to have ovarian follicular cyst. Attempts were made to treat the cows which had ovarian follicular cyst with GnRH, HCG respectively. The results obtained were summarized as follows : 1. The rates of estreous induction with GnRH or HCG were 91.4%, 77.2%, respectively. The GnRH treated group was showed significantly higher than HCG treated group. The mean days from the GnRH or HCG treated to estrum were 25.1 and 23.5 days, respectively. 2. The Conception rates with GnRH or HCG treatment were 78.2% and 76.5％, respectively. 3. Services per conception with GnRH or HCG treatment were 1.5 and 2.1 respectively. 4, Days from GnRH or HCG treatment to concept were 38.2 and 45.8 days, respectively. 5. Intramuscular injection with GnRH and intraovarian injection with HCG were revealed the most effective routes in all the other routes.

• Korean Journal of Animal Reproduction
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• v.27 no.3
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• pp.207-213
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• 2003

This objective of this experiment were to evaluate the effect of various estrus synchronization programs on estrus detection rate and pregnancy rate in Hanwoo. After Postpartum 60 Days, a total of 150 cows divided into 2 groups. Cows Group 1 were treated with one luteolytic dosage of PGF$_2$$\alpha$(25 mg, im; lutalyse. USA) on Day 0, and with a second dosage 14 d later; cows in Group 2 were treated with GnRH(l00 $\mu\textrm{g}$, im; Conceral. Korea) on Day 0, PGF$_2$$\alpha$ 7 d later, GnRH 2 d later, and then time-inseminated approximately 16 h after this second treatment with GnRH. Ovarian morphology was monitored cows by trans-rectal ultrasonography from 24 hr to 32 hrs after second GnRH injection. The result obtained summarized as follows: 1. Cows synchronization of estrus with GnRH+PGF$_2$$\alpha$+GnRH(Ov-synch) and PGF$_2$$\alpha$ were 91.3 and 40.0%, respectively. 2. Induced ovulation were 24 to 32hr after the second GnRH injection, but high induced ovulation was 28hr. 3. High conception rate were 24hr insemination after the second GnRH injection. 4. Conception rate with PGF$_2$$\alpha$, CIDR and GnRH treatment were 50.0, 36.0 and 76.9%, respectively.

• Animal cells and systems
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• v.13 no.4
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• pp.429-437
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• 2009

The control mechanism of gonadotropin-releasing hormone (GnRH) on gonadotropin (GTH) release was studied using cultured pituitary cell or cultured whole pituitary obtained from Testosterone (T) treated and control immature rainbow trout. The release of FSH was not changed by salmon type GnRH (sGnRH), chiken-II type (cGnRH-II), GnRH analogue ([des-$Gly^{10}D-Ala^6$] GnRH ethylamide) and GnRH antagonist ([Ac-3, 4-dehydro-$Pro^1$, D-p-F-$Phe^2$, D-$Trp^{3,6}$] GnRH) in cultured pituitary cells of T-treated and control fish. Indeed, FSH release was not also altered by sGnRH in cultured whole pituitary. All tested drugs had no effect on the release of LH in both culture systems of control fish. The levels of LH, in contrast, such as the pituitary content, basal release and responsiveness to GnRH were increased by T administration in both culture systems. In addition, the release of LH in response to sGnRH or cGnRH-II induced in a dose-dependent manner from cultured pituitary cells of T-treated fish, but which is not significantly different between in both GnRH at the concentration examined. Indeed, LH release was also increased by sGnRH in cultured whole pituitary of T-treated fish. GnRH antagonist suppressed the release of LH by sGnRH ($10^{-8}\;M$) and GnRH analogue ($10^{-8}\;M$) stimulation in a dose-dependent manner from cultured pituitary cells of T-treated fish, and which were totally inhibited by $10^{-7}\;M$ GnRH antagonist. These results indicate that the sensitivity of pituitary cells to GnRH is elevated probably through the T treatment, and that GnRH is involved in the regulation of LH release. GnRH-stimulated LH release is inhibited by GnRH antagonist in a dose-dependent manner. The effects of gonadal steroids on FSH levels are less clear.

• Journal of Embryo Transfer
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• v.23 no.2
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• pp.109-114
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• 2008

This study examined pregnancy and fetal loss rates according to different estrus synchronization protocols and injection of gonadotropin releasing hormone (GnRH) after transfer of Korean Native Cattle embryos to Holstein recipients. In Experiment 1, recipients received no treatment (Control, n = 119); two injections of prostaglandin$F_{2{\alpha}}$ ($PGF_{2{\alpha}}$ ) 11 days apart (PGF group, n = 120); GnRH (day 0)-$PGF_{2{\alpha}}$ (day 7)-GnRH (day 9) (Ovsynch group, n = 120); and CIDR (day 0)-$PGF_{2{\alpha}}$ and CIDR removal (day 7)-GnRH (day 9) (CIDR group, n = 110). In Experiment 2, the control group was received no treatment of GnRH. The treatment groups were received GnRH at embryo transfer (ET) (day 0), 7 days later, 14 days later, ET and 7 days later, 7 and 14 days later, or ET, 7 and 14 days later. Recipients were assigned to treatment randomly and received two in vitro produced blastocysts. Pregnancy was diagnosed at day 60 by palpation per rectum. Fetal loss to term was determined by palpation every 90 days thereafter. In Experiment 1, the pregnancy rate in the CIDR group (59.1%) were higher than in the Control group (42.0%) (p<0.01); fetal loss rates were similar for all groups (12.0 to 18.5%). In Experiment 2, the pregnancy rate in Day 0+7+14 group was higher (60.2%) than the control (40.2%) (p<0.01) and resulted in a lower fetal loss (p<0.05) than the control (4.6 vs. 11.4%). There were no significant difference between other treatment and the control (p>0.05). These results show that pregnancy rates of bovine embryos can be enhanced by CIDR insertion or GnRH $3{\times}$ treatment. Additionally, fetal loss may be reduced with GnRH treatment after ET.

• Korean Journal of Animal Reproduction
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• v.13 no.2
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• pp.79-84
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• 1989

This study was carried out to investigate the effect of LH-RH and Gn-RH treatment in Holstein cows with ovarian quiescence and follicular cystic ovaries. The cows with ovarian quiescence and follicular cystic ovaries injected intramuscularly with 100$\mu\textrm{g}$, 200$\mu\textrm{g}$ and 400$\mu\textrm{g}$ of LH-RH and 200$\mu\textrm{g}$ and 400$\mu\textrm{g}$ of Gn-RH respectively. The cows was diagnosed by repeated rectal palpation. The plasma progesterone and estradiol-17$\beta$ concentrations were assayed by radioimmunoassay methods. The resutls of this study were summarized as follows : 1. Ovulations were induced after treatment of LH-RH and Gn-RH. The concentrations of progesterone reached small peak level at luteal phase and estradiol-17$\beta$ reached obvious peak level with the development and maturation of the follicle during the periods of degeneration of the corpus luteum, and normal ovarian cycle activity started subsequently. 2. The cows with ovarian quiescence and follicular cystic ovaries were induced ovulation at 38.9$\pm$5.3 hrs. after treatment of LH-RH in 66.7% cows and at 52.7$\pm$7.9 hrs after treatment of Gn-RH in 60.0% cows respectively. 3. The good ovarian responses were indicated in treatment with 200$\mu\textrm{g}$ to 400$\mu\textrm{g}$ of LH-RH than those treated with 100$\mu\textrm{g}$ in cows with ovarian quiescence, and did not show difference of ovarian responses between treatments with 200$\mu\textrm{g}$ to 400$\mu\textrm{g}$ of Gn-RH in cows with follicular cystic ovaries.

• Korean Journal of Veterinary Research
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• v.39 no.2
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• pp.276-286
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• 1999

In the present study, to understand how gonadotropin-releasing hormone (GnRH) affects ovarian functions in superovulated rats, we examined the effects of GnRH agonist on the ovulatory response, the morphological normality and nuclear maturation of ovulated oocytes, the ovarian weight, the ovarian histology, and the circulating steroid hormone ($17{\beta}$-estradiol, progesterone and testosterone) levels in immature rats pretreated with 30IU pregnant mare serum gonadotropin (PMSG) and supplemented with 10IU human chorionic gonadotropin(hCG). GnRH agonist was intravenously injected via jugular vein catheter every 20min for 4hrs in early follicular phase (from 6hr after PMSG) of superovulated rats. In addition, GnRH antagonist, Antide, was intravenously injected in combination with GnRH agonist to verify the effects of GnRH agonist on ovarian functions. All animals were sacrificed at 72hr after PMSG administration. The administration with GnRH agonist in early follicular phase of superovulated rats caused inhibition of ovulatory response, increased the proportion of abnormal appearing oocytes(especially, in the rats of the group treated with 500ng GnRH agonist), decreased ovarian weight and promote follicular atresia, compared to those from the rats of control regimen that were not treated with GnRH agonist. In addition, the treatment with GnRH agonist in the superovulated rat distinctly decreased serum steroid hormone ($17{\beta}$-estradiol, progesterone and testosterone) levels in preovulatory phase. On the other hand, the inhibitory effects of GnRH agonist treatment in superovulation-pretreated rats on ovarian functions were totally reversed by the combination with GnRH antagonist, Antide. The nuclear maturation of oocytes recovered from the oviducts in immature rats treated with GnRH agonist and/or GnRH antagonist was characterized by prematurity and asynchronization in early follicular phase, which was similar to control group. The overall results of this study indicate that GnRH agonist disturbs directly ovarian function in early follicular phase of superovulated immature rats in terms of ovulatory response and morphological normality of ovulated oocytes. This concept has been further evidenced by the findings of a great decrease in ovarian weight, a marked increase in follicular and a distinct decrease circulating steroid hormone ($17{\beta}$-estradiol, progesterone and testosterone) levels in GnRH agonist treatment regimen in early follicular phase.

• Animal cells and systems
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• v.5 no.3
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• pp.217-224
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• 2001

The present study examines the expression and regulation of gonadotropin-releasing hormone (GnRH) and its receptor (GnRH-R) mRNA levels during mouse ovarian development. A fully processed, mature GnRH mRNA together with intron-containing primary transcripts was expressed in the immature mouse ovary as determined by Northern blot analysis and reverse transcription-polymerase chain reaction (RT-PCR). The size of ovarian GnRH mRNA was similar to that of hypothalamus, but its amount was much lower than that in the hypothalamus. Quantitative RT-PCR procedure also revealed the expression of GnRH-R mRNA in the ovary, but the estimated amount was a thousand-fold lower than that in the pituitary gland. We also examined the regulation of ovarian GnRH and GnRH-R mRNA levels during the follicular development induced by pregnant mare's serum gonadotropin (PMSG) and/or human chorionic gonadotropin (hCG). Ovarian luteinizing hormone receptor (LH-R) mRNA was abruptly increased st 48 h after the PMSG administration and rapidly decreased to the basal level thereafter. Ovarian GnRH mRNA level was slightly decreased at 48 h after the PMSG administration, and then returned to the basal value. GnRH-R mRNA level began to increase at 24 h after the PMSG treatment, decreased below the uninduced basal level at 48 h, and gradually increased thereafter. HCG administration did not alter ovarian GnRH mRNA level, while it blocked the PMSG-induced increase in GnRH mRNA level. Taken together, the present study demonstrates that the expression of GnRH and GnRH-R mRNA are regulated by gonadotropin during follicular development, suggesting possible intragonadal paracrine roles of GnRH and GnRH-R in the mouse ovarian development.

• Animal cells and systems
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• v.2 no.4
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• pp.483-488
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• 1998

We previously found that a potent gonadotropin-releasing hormone (GnRH) agonist, buserelin, decreases GnRH promoter activity together with GnRH mRNA level, providing evidence for an autoregulatory mechanism operating at the level of GnRH gene transcription in immortalized GT1-1 neuronal cells. To examine whether agonist-induced decrease in GnRH mRNA level requires the continuous presence of buserelin, we performed a pulse-chase experiment of buserelin treatment. Short-term exposure (15 min) of GT1-1 neuronal cells to buserelin ($10{\mu}M$) was able to decrease GnRH mRNA levels when determined 24 h later. When GT1-1 cells were treated with buserelin ( $10{\mu}M$) for 30 min and then incubated for 1, 3, 6, 12, 24, and 48 h after buserelin removal, a significant decrease in GnRH mRNA levels was observed after the 12 h incubation period. These data indicate that inhibitory signaling upon buserelin treatment may occur rapidly, but requires a long time (at least 12 h) to significantly decrease the GnRH mRNA level. To examine the possible involvement of de novo synthesis and/or mRNA stability in buserelin-induced decrease in GnRH gene expression, actinomycin D ($5{\mu}m/ml$), a potent RNA synthesis blocker, was co-treated with buserelin. Actinomycin D alone failed to alter basal GnRH mRNA Revel, but blocked the buserelin-induced decrease in GnRH mRNA level at 12 h of post-treatment. These data suggest that buserelin may exert its inhibitory action by altering the stability of GnRH mRNA. Moreover, a polvsomal RNA separation by sucrose gradient centrifugation demonstrated that buserelin decreased the translational efficiency of the transcribed GnRH mRNA. Taken together, these results clearly indicate that GnRH agonist buserelin acts as an inhibitory signal at multiple levels such as transcription mRNA stability, and translation.