Short-term mode of secretion of equine chorionic gonadotrop in and the effect of GNRH

Thompson, Donald L.; Reville, S. I.; Derrick, D. J.

doi:10.1016/0093-691x(82)90190-x

Cited by 13 publications

(12 citation statements)

References 14 publications

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“…Unlike the original study (Hobson & Wide, 1986), the present study used anti-eCG in an eCG-based RIA (Thompson et al, 1982). Preference for use of anti-eCG was based on the high degree of immunoreactivity between anti-eCG and eLH (344% cross-reactivity; Thompson et al, 1982), homology of the amino acid sequences of eLH a-and b-subunits (83 to 87% and 81 to 85% combined across several equine species) with dolphin LH/CG a-and b-subunits (Watanabe et al, 2007), and homology of eCG a-and b-subunits (78 and 80%, respectively) with hCG a-and b-subunits (Ward et al, 1982;Sugino et al, 1987). In addition, dolphin LH/CG also appears structurally related to the aand b-subunits of LH in other species (cattle, 92 and 84%;pigs, 97 and 94%;sheep, 92 and 84%;dogs, 94 and 91%;Watanabe et al, 2007) in which the eCG RIA used herein has been applied (cattle Table 1.…”

Section: Discussionmentioning

confidence: 91%

“…Analysis of the supernatants of respective placental tissue homogenates was done using an in-house validated radioimmunoassay (RIA) for eCG (Thompson et al, 1982). Main components of the assay included equine LH (eLH) as the 125 I-labeled ligand (40,000 cpm/tube), polyclonal rabbit anti-eCG as the primary antibody (working dilution, 1:4000/tube), goat anti-rabbit immune gamma globulin (IgG, working dilution, 1:20) as the secondary antibody, and eCG as the reference standard (0.1125, 0.225, 0.45, 0.9, 1.8, 3.6, 7.2, and 14.4 IU/mL).…”

Section: Methodsmentioning

confidence: 99%

“…Month of pregnancy was determined retrospectively from month of parturition (Month 0). cross-reactivity between eCG and eLH (Thompson et al, 1982). Apart from methodology, the preliminary nature of the previous studies involved one dolphin or placenta per study (Hobson & Wide, 1986;Watanabe et al, 2007) compared to four dolphins and six full-term placentas in the present study.…”

Section: Dolphin Placentamentioning

confidence: 95%

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Investigation of an Immunoreactive Chorionic Gonadotropin-Like Substance in the Placenta, Serum, and Urine of Pregnant Bottlenose Dolphins (Tursiops truncatus)

Bergfelt¹

2012

Aquat Mamm

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This study was designed to test the hypothesis that an immunoreactive chorionic gonadotropin (CG)-like substance is present in full-term dolphin placentas and to determine if CG immunoreactivity can be detected in corresponding serum and urine samples for potential application to diagnose pregnancy. Six placentas were collected immediately after parturition from four captive bottlenose dolphins in 2003, 2007 (Experiment 1), and 2011 (Experiment 2). Serum and urine were collected during early, middle, and late pregnancy from the same dolphins. In Experiment 1, an eCG radioimmunoassay (RIA) was used to analyze dilutions of supernatants from the homogenates of each placenta for eCG immunoreactivity, and a commercial hCG Enzyme-Linked Immunosorbent Assay (ELISA) was used to analyze individual serum samples and dilutions of pools of serum and urine for hCG immunoreactivity. Specific CG immunoreactivity was not detected above assay sensitivities in any of the supernatants of respective placental homogenates, including the highest concentrate (100 mg/mL), nor in any of the individual samples and pools of serum and urine. In Experiment 2, the highest placental homogenate was increased five-fold (500 mg/mL), sensitivity of the eCG RIA was increased six-fold, and a different combination of hCG antibodies was used in an alternative commercial "sandwich"-type ELISA. Despite the optimization, specific CG immunoreactivity in placental tissue and individual serum and urine samples was not detected above assay sensitivities.In conclusion, the hypothesis that an immunoreactive CG-like substance is present in full-term dolphin placentas was not supported. In addition, non-immunoreactivity of a CG-like substance in serum and urine samples collected during various stages of pregnancy precluded the development and application of a CG-based immunoassay for diagnosing pregnancy status in dolphins.

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Section: Discussionmentioning

confidence: 91%

Section: Methodsmentioning

confidence: 99%

Section: Dolphin Placentamentioning

confidence: 95%

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Investigation of an Immunoreactive Chorionic Gonadotropin-Like Substance in the Placenta, Serum, and Urine of Pregnant Bottlenose Dolphins (Tursiops truncatus)

Bergfelt¹

2012

Aquat Mamm

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“…The CG concentrations were not affected by naloxone. Because eCG release is not regulated via GnRH (Thompson et al 1982), a GnRH-mediated effect of naloxone was not to be expected. In addition, there is no direct opioidergic regulation of CG release from the endometrial cups.…”

Section: Discussionmentioning

confidence: 99%

Opioidergic inhibition of luteinising hormone and prolactin release changes during pregnancy in pony mares

Aurich

Aurich²,

Parvizi³

2001

Journal of Endocrinology

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In equine species, luteinising hormone (LH) and prolactin (PRL) release are reduced throughout pregnancy but increase at foaling. The present experiments were designed to study a possible opioidergic regulation of LH and PRL release in pregnant Shetland mares (n=6). At various stages of pregnancy (days 26·4 0·6, 75·4 5·4, 171·8 2·4, 226·2 4·8, 282·7 3·4 and 319·8 2·1), mares were injected with the opioid antagonist naloxone (0·5 mg/kg body weight) and saline. The two treatments were always separated by 2 days, and mares served as their own controls. Two hours after being given naloxone and saline, mares were given the gonadotrophin-releasing hormone (GnRH) analogue buserelin (5 µg per animal). The naloxone experiment was repeated at 2 days after foaling. Blood for the determination of LH and PRL was withdrawn at 15 min intervals for 240 min, and naloxone or saline was injected after 60 min. Naloxone induced significant (P<0·05) LH release on days 172, 226 and 283 of pregnancy but not on days 26, 76 and 320 and 2 days after foaling. Buserelin caused a significant (P<0·05) increase in plasma LH concentrations on days 172, 226, 282 and 320 of pregnancy. The experiments indicate that endogenous opioids are involved in the inhibition of LH release during the second half of pregnancy in equine species. The deactivation of opioid effects on LH release might be a prerequisite for the onset of ovarian activity postpartum. Plasma PRL concentrations increased significantly (P<0·05) after naloxone administration on days 226, 282 and 320 of pregnancy. The naloxone-induced PRL release was most pronounced towards term, indicating an increase in the naloxone-releasable pool and/or the absence of other PRL-release inhibitory mechanisms.

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“…1954). Peak plasma CG concentrations vary tremendously between individual mares, and appear to be proportional to the amount of mature cup tissue (Allen 1975;Ginther 1979; Thompson et al 1982b). The biological role of CG is not entirely clear, but it is thought to function as a hormone with luteotrophic activity to induce hormonal activity of primary and secondary corpora lutea (Allen 1984;Ginther 1992).…”

Section: Introductionmentioning

confidence: 99%

Effect of surgical removal of endometrial cups on concentrations of chorionic gonadotrophin and subsequent fertility in the mare

Huber

Roser

Riebold

et al. 1993

Equine Veterinary Journal

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Summary Seven pregnant mares underwent general anaesthesia, laparotomy, hysterotomy and removal of a 50‐day conceptus. Eversion of the uterine horn through the hysterotomy site allowed direct visualisation and electrosurgical removal of endometrial cup tissue from 5 randomly selected mares (Nos 1–5), while cup tissue in 2 mares (Nos 6 and 7) was left intact. Two pregnant mares served as unoperated controls (Nos 8 and 9). Efforts to re‐establish pregnancy were initiated 20 days after surgery. Serum samples collected before surgery and during the post‐operative period were analysed for concentration of horse chorionic gonadotrophin (CG) by radioimmunoassay. Mean (± sd) weight and area of removed tissue was 9.91 ± 4.6 g and 22.4 ± 5.9 cm2, respectively. Concentrations of CG ranging from 3440 to 21,220 ng/ml were highest at the time of cup removal (50 days) and declined thereafter. Peak concentrations of CG at the time of surgery were not linearly correlated (r=−0.59) with mass of excised cup tissue. Individual CG half‐life values for Mares 1–5 ranged from 5.4 to 8.8 days (mean 7.1 ± 1.2 days). Peak CG concentrations occurred 68 days after conception with a rate of disappearance (half‐time) of 13.4 ± 0.4 days in Mares 6 and 7 and at 74 and 78 days after conception with a half‐time of 14.0 ± 5.7 days in Mares 8 and 9. Mares 1–5 exhibited behavioural oestrus and ovulation 30–44 days after surgery. Pregnancy occurred in 3 mares within 41 days after surgery and was associated with concentrations of CG below 200 ng/ml. Pregnancies developed normally until 120 days when the study was terminated. Sham‐operated control mares failed to exhibit normal oestrous behaviour and ovulation during the 100‐day postoperative period. Uterine tissues from 3 mares examined at necropsy lacked significant gross and microscopic pathology associated with the surgery.

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Short-term mode of secretion of equine chorionic gonadotrop in and the effect of GNRH

Cited by 13 publications

References 14 publications

Investigation of an Immunoreactive Chorionic Gonadotropin-Like Substance in the Placenta, Serum, and Urine of Pregnant Bottlenose Dolphins (Tursiops truncatus)

Investigation of an Immunoreactive Chorionic Gonadotropin-Like Substance in the Placenta, Serum, and Urine of Pregnant Bottlenose Dolphins (Tursiops truncatus)

Opioidergic inhibition of luteinising hormone and prolactin release changes during pregnancy in pony mares

Effect of surgical removal of endometrial cups on concentrations of chorionic gonadotrophin and subsequent fertility in the mare

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