Gonadotrophin-Releasing Hormone Agonist Stimulates Milt Fluidity and Plasma Concentrations of 17,20β-Dihydroxylated and 5β-Reduced, 3α-Hydroxylated C21Steroids in Male Plaice (Pleuronectes platessa)

1998 ◽  
Vol 112 (2) ◽  
pp. 163-177 ◽  
Author(s):  
Etiënne L.M. Vermeirssen ◽  
Alexander P. Scott ◽  
Costadinos C. Mylonas ◽  
Yonathan Zohar
Keyword(s):  
Plasma Concentrations ◽  
Releasing Hormone ◽  
Pleuronectes Platessa ◽  
Gonadotrophin Releasing Hormone

Plasma LH and testosterone responses to gonadotrophin-releasing hormone in adult red deer (Cervus elaphus) stags during the annual antler cycle

1988 ◽  
Vol 117 (1) ◽  
pp. 35-41 ◽  
Author(s):  
P. F. Fennessy ◽  
J. M. Suttie ◽  
S. F. Crosbie ◽  
I. D. Corson ◽  
H. J. Elgar ◽  
...  
Keyword(s):  
Red Deer ◽  
Plasma Concentrations ◽  
Reproductive Hormones ◽  
Sexual Cycle ◽  
Late Winter ◽  
Releasing Hormone ◽  
Antler Growth ◽  
Velvet Antler ◽  
Antler Cycle ◽  
Gonadotrophin Releasing Hormone

ABSTRACT Eight adult red deer stags were given an i.v. injection of synthetic gonadotrophin-releasing hormone (GnRH) on seven occasions at various stages of the antler cycle, namely hard antler in late winter, casting, mid-velvet growth, full velvet growth, antler cleaning and hard antler both during the rut and in mid-winter. The stags were allocated at random on each occasion to one of four doses, i.e. 1, 3, 10 or 95 μg GnRH. Blood samples were taken before GnRH injection and for up to 2 h after injection. Pituitary and testicular responses were recorded in terms of plasma LH and testosterone concentrations. There was an increase in plasma concentration of LH after the GnRH injection in all stags at all stages of the antler cycle. Dose-dependent responses of LH to GnRH in terms of area under the curve were apparent at all stages of the antler cycle. The lowest responses were recorded at casting, during velvet antler growth and at the rut sampling. The pattern of testosterone response reflected the inter-relationship of the antler and sexual cycles with very low testosterone responses occurring at casting and during velvet antler growth. The responses were higher at antler cleaning and then increased to a maximum at the rut before declining to reach their nadir at casting. The results are consistent with a hypothesis that the antler cycle, as a male secondary sexual characteristic, is closely linked to the sexual cycle and its timing is controlled by reproductive hormones. Low plasma concentrations of testosterone, even after LH stimulation, are consistent with the hypothesis that testosterone is unnecessary as an antler growth stimulant during growth. J. Endocr. (1988) 117, 35–41

Anti-fertility effects of oral medroxyprogesterone acetate in rabbits

1996 ◽  
Vol 8 (8) ◽  
pp. 1185 ◽  
Author(s):  
NO Oguge ◽  
GK Barrell
Keyword(s):  
Single Dose ◽  
Luteinizing Hormone ◽  
Medroxyprogesterone Acetate ◽  
Plasma Concentrations ◽  
Inhibitory Effect ◽  
Multiple Dosing ◽  
Releasing Hormone ◽  
Single Meal ◽  
Gonadotrophin Releasing Hormone ◽  
Hypothalamic Level

Studies on the anti-fertility effects of medroxyprogesterone acetate (MPA) were conducted in rabbits. The bioavailability of MPA and plasma concentrations of progesterone and luteinizing hormone (LH) after mating were monitored following a single meal containing MPA (1000 mg) in entire does (n = 4); the response to gonadotrophin-releasing hormone (GnRH; 250 ng) was also observed in MPA-treated, ovariectomized does (n = 6). The reproductive tracts of rabbits mated following MPA treatment were examined 28-30 h after mating. Another group of rabbits (n = 4) received a single dose of MPA on Days 1, 10 or 19 after mating or daily for five days from Day 24. After dosage with 1000 mg MPA, plasma concentrations of MPA were detectable for eight days. However, following multiple dosing (10 mg, 5 days) MPA was detectable in the plasma for two days. MPA reduced the rate of ovulation and suppressed the increase in plasma concentrations of progesterone and LH observed after mating for four days, but had no effect on the response to GnRH. When administered late in gestation, MPA caused the death of fetuses. These results demonstrate an inhibitory effect of MPA on ovulation, probably at the hypothalamic level, and impairment of gestation or parturition.

Effects of pituitary-gonadal suppression with a gonadotrophin-releasing hormone agonist on fetal gonadotrophin secretion, fetal gonadal development and maternal steroid secretion in the sheep

1994 ◽  
Vol 141 (2) ◽  
pp. 317-324 ◽  
Author(s):  
G B Thomas ◽  
A S McNeilly ◽  
F Gibson ◽  
A N Brooks
Keyword(s):  
Gnrh Agonist ◽  
Fetal Development ◽  
Plasma Concentrations ◽  
Gonadal Development ◽  
Maternal Circulation ◽  
Biodegradable Implant ◽  
Steroid Secretion ◽  
Releasing Hormone ◽  
Pituitary Glands ◽  
Gonadotrophin Releasing Hormone

Abstract In order to investigate the regulation of the hypothalamo-pituitary-gonadal axis during fetal development, sheep fetuses at day 70 of gestation were implanted subcutaneously with a biodegradable implant containing the longacting gonadotrophin-releasing hormone (GnRH) agonist, buserelin. The treatment of fetuses with a GnRH agonist throughout the last half of gestation (term=145 days) abolished the increase in plasma LH concentrations that was seen in 2-day-old control lambs in response to an injection of GnRH. This attenuated response was associated with corresponding reductions in the pituitary content of LH and FSH. Immunolocalization studies revealed that pituitary glands from newborn lambs implanted with a GnRH agonist during fetal development were devoid of immunopositive LH- and FSH-containing cells. At birth the testicular weights of GnRH agonist-treated ram lambs were significantly decreased by 40% when compared with controls. This was associated with a 45% reduction in the total number of Sertoli cells per testis. In newborn ewe lambs GnRH agonist treatment had no effect on ovarian weight or on the morphological appearance of the ovaries. GnRH agonist treatment had no effect on the plasma concentrations of progesterone and oestrone in the maternal circulation or on the length of gestation. These results show (1) that GnRH positively regulates the synthesis and secretion of gonadotrophins in the fetus, (2) that reduced fetal gonadotrophic support during the last half of gestation results in a reduction in testicular growth, and (3) that fetal gonadotrophins do not affect maternal steroid secretion. Journal of Endocrinology (1994) 141, 317–324

Use of a new drug delivery formulation of the gonadotrophin-releasing hormone analogue Deslorelin for reversible long-term contraception in male dogs

2003 ◽  
Vol 15 (6) ◽  
pp. 317 ◽  
Author(s):  
A. Junaidi ◽  
P. E. Williamson ◽  
J. M. Cummins ◽  
G. B. Martin ◽  
M. A. Blackberry ◽  
...  
Keyword(s):  
Slow Release ◽  
Semen Quality ◽  
Animal Health ◽  
Plasma Concentrations ◽  
Testicular Volume ◽  
Releasing Hormone ◽  
Detectable Range ◽  
Effect Of Treatment ◽  
Gonadotrophin Releasing Hormone

In the present study, we tested the effect of treatment with a slow-release implant containing the gonadotrophin-releasing hormone agonist DeslorelinTM (Peptech Animal Health Australia, North Ryde, NSW, Australia) on pituitary and testicular function in mature male dogs. Four dogs were treated with Deslorelin (6-mg implant) and four were used as controls (blank implant). In control dogs, there were no significant changes over the 12 months of the study in plasma concentrations of luteinising hormone (LH) or testosterone, or in testicular volume, semen output or semen quality. In Deslorelin-treated dogs, plasma concentrations of LH and testosterone were undetectable after 21 and 27 days, testicular volume fell to 35% of pretreatment values after 14 weeks and no ejaculates could be obtained after 6 weeks. Concentrations returned to the detectable range for testosterone after 44 weeks and for LH after 51 weeks and both were within the normal range after 52 weeks. Semen characteristics had recovered completely by 60 weeks after implantation. At this time, the testes and prostate glands were similar histologically to those of control dogs. We conclude that a single slow-release implant containing 6 mg Deslorelin has potential as a long-term, reversible antifertility agent for male dogs.

Pituitary and testicular endocrine responses to exogenous gonadotrophin-releasing hormone (GnRH) and luteinising hormone in male dogs treated with GnRH agonist implants

2007 ◽  
Vol 19 (8) ◽  
pp. 891 ◽  
Author(s):  
A. Junaidi ◽  
P. E. Williamson ◽  
G. B. Martin ◽  
P. G. Stanton ◽  
M. A. Blackberry ◽  
...  
Keyword(s):  
Leydig Cells ◽  
Luteinising Hormone ◽  
Plasma Concentrations ◽  
Control Group ◽  
Release Formulation ◽  
Male Adult ◽  
Releasing Hormone ◽  
Slow Release Formulation ◽  
Gonadotrophin Releasing Hormone ◽  
Lh Releasing Hormone

The present study tested whether exogenous gonadotrophin-releasing hormone (GnRH) and luteinising hormone (LH) can stimulate LH and testosterone secretion in dogs chronically treated with a GnRH superagonist. Twenty male adult dogs were assigned to a completely randomised design comprising five groups of four animals. Each dog in the control group received a blank implant (placebo) and each dog in the other four groups received a 6-mg implant containing a slow-release formulation of deslorelin (d-Trp6-Pro9-des-Gly10–LH-releasing hormone ethylamide). The same four control dogs were used for all hormonal challenges, whereas a different deslorelin-implanted group was used for each challenge. Native GnRH (5 μg kg–1 bodyweight, i.v.) was injected on Days 15, 25, 40 and 100 after implantation, whereas bovine LH (0.5 μg kg–1 bodyweight, i.v.) was injected on Days 16, 26, 41 and 101. On all occasions after Day 25–26 postimplantation, exogenous GnRH and LH elicited higher plasma concentrations of LH and testosterone in control than deslorelin-treated animals (P < 0.05). It was concluded that, in male dogs, implantation of a GnRH superagonist desensitised the pituitary gonadotrophs to GnRH and also led to a desensitisation of the Leydig cells to LH. This explains, at least in part, the profound reduction in the production of androgen and spermatozoa in deslorelin-treated male dogs.

Suppression of LH response to gonadotrophin-releasing hormone or oestradiol by ACTH(1–24) treatment in anoestrous ewes

1988 ◽  
Vol 118 (2) ◽  
pp. 193-197 ◽  
Author(s):  
H. Dobson ◽  
S. A. Essawy ◽  
M. G. S. Alam
Keyword(s):  
Plasma Concentrations ◽  
Suppressive Effect ◽  
Reproductive Efficiency ◽  
Adrenocorticotrophic Hormone ◽  
Releasing Hormone ◽  
Oestradiol Benzoate ◽  
Lh Release ◽  
Gonadotrophin Releasing Hormone ◽  
Baseline Values ◽  
Lh Secretion

ABSTRACT Stress is known to result in lowered female reproductive efficiency. The objective of this study was to examine how increased pituitary-adrenal activity may influence gonadotrophin release in anoestrous ewes. Various doses (0·06–1·0 mg) of a synthetic adrenocorticotrophic hormone (ACTH(1–24)) preparation were injected into ewes 30 min or 3 h before an i.v. injection of 500 ng gonadotrophin-releasing hormone (GnRH). The LH response to GnRH given 30 min after ACTH(1–24) was similar to that after GnRH alone, whereas the response 3 h after ACTH(1–24) was significantly lower, irrespective of the dose of ACTH(1–24). At 30 min and 3 h after ACTH(1–24) the concentrations of cortisol exceeded 50 nmol/l compared with baseline values of < 10 nmol/l. The effect of ACTH(1–24) on oestradiol-induced LH release was also examined. Those ewes receiving 0·8 mg ACTH(1–24) depot and 50 μg oestradiol benzoate simultaneously had a preovulatory-type increase in LH 14–20 h later, similar to when oestradiol benzoate was given alone. None of the ewes receiving an additional 0·8 mg ACTH(1–24) depot 10 h after oestradiol benzoate had increases in LH concentration. The cortisol concentrations in all ewes receiving either one or two injections of ACTH(1–24) were > 35 nmol/l at 10 h after the oestradiol injection. However, concentrations of progesterone increased from 0·9 ± 0·3 (s.e.m.) nmol/l at the time of the second ACTH(1–24) injection to 2·1 ±0·3 nmol/l after 2 h. In summary, it would appear that the suppressive effect of ACTH(1–24) on LH secretion induced by GnRH or oestradiol in the anoestrous ewe is not dependent on increased plasma concentrations of cortisol. J. Endocr. (1988) 118, 193–197

162 Detection of ovulation disorders and normal ovulation using wireless sensors of ventral tail surface temperature and neck acceleration data in Japanese Black cows

2020 ◽  
Vol 32 (2) ◽  
pp. 207
Author(s):  
S. Matoba ◽  
M. Saito ◽  
K. Abe ◽  
S. Higaki ◽  
K. Yoshioka
Keyword(s):  
Surface Temperature ◽  
Wireless Sensors ◽  
Plasma Concentrations ◽  
The Body ◽  
Ovarian Cysts ◽  
Acceleration Sensor ◽  
Releasing Hormone ◽  
Acceleration Data ◽  
Gonadotrophin Releasing Hormone ◽  
The Mean

The present study aimed to clarify the possibility of detection of ovulation disorders and normal ovulation in Japanese Black cows using wearable wireless sensors based on continuous measurements of body surface temperature (ST) and neck acceleration data. For cows with normal ovulation (n=19, 8.5 years old, 476.2kg), controlled internal drug release (CIDR) and gonadotrophin-releasing hormone were administered on arbitrary days of the oestrous cycle (Day −10), and oestrus was induced by CIDR removal and prostaglandin F2α administration (Day −3). Ovulation (Day 0) was induced by gonadotrophin-releasing hormone administration on estimated oestrus day (Day −1) and was detected based on the disappearance of ≥8mm follicles using ultrasonography at 1- to 2-h intervals. For cows with spontaneous ovarian cysts (n=11, 8.6 years old, 471.2kg), oestrus and the next day were defined as Days −1 and 0, respectively. Plasma concentrations of progesterone (P4) and oestradiol-17β (E2) were measured on Days −9, −6, −2, −1, 0, 1, 5, and 8. The body ST sensor was attached to the ventral tail base (Day −16), and ST was measured every 10min for 24 days. For analysis of ST, after extracting hourly maximum ST values, the values were expressed as residual ST (RST; ST − mean ST for the same hour on the previous 3 days) for removal of circadian rhythm (Miura et al. 2017 Anim. Reprod. Sci. 180, 50-57; https://doi.org/10.1016/j.anireprosci.2017.03). The acceleration sensor (Farmnote Color, Farmnote Inc.) was attached to the neck (Day −16). Hourly oestrus level (amount of oestrus activity) was obtained from the amount of activity; the difference between the residual oestrus level (REL; same calculation as RST) and measured values of each day was used. To identify RST and REL of cows with normal ovulation and cows with ovarian cysts, the mean values and standard deviations for the same hours for 3-7 days before oestrus were calculated. Mean RST and REL for 3-7 days before oestrus were assumed according to the normal distribution. The 95% confidence range was determined using×1 standard deviation of all hours. Values over the 95% confidence range for ≥5h were considered to be different from the mean 4 days and the 5% level. For RST, no difference was found in both groups due to the large influence of environment, particularly low temperature. However, for REL, a difference was indicated for oestrus in all cows (P&lt;0.05). A large peak of REL appeared once on oestrus (&gt;14.4 REL for 20h) in normal cows, and three peaks occurred in &lt;21 days (&gt;16.2 REL for 21, 15, and 15h) in cows with ovulation disorders (P&lt;0.05). The REL rapidly increased following peaking E2 and decreasing P4 to oestrus (Day −1) in normal cows. In cows with an ovulation disorder, REL increased on oestrus; however, E2 and P4 remained high and low stable to oestrus, respectively. In conclusion, oestrus activity and the characteristics of normal cows and those with an ovulation disorder can be detected by the neck acceleration sensor using the correction value. This research was supported by The Research Project for the Future Agriculture Production Utilising Artificial Intelligence.

Effects of luteolysis during late pregnancy on pituitary responsiveness to gonadotrophin-releasing hormone in the rat

1991 ◽  
Vol 128 (3) ◽  
pp. 411-418
Author(s):  
T. R. Koiter ◽  
G. C. J. van der Schaaf-Verdonk ◽  
G. A. Schuiling
Keyword(s):  
Plasma Concentrations ◽  
Control Level ◽  
Late Pregnancy ◽  
Ovariectomized Rats ◽  
Normal Delivery ◽  
Releasing Hormone ◽  
Oestradiol Treatment ◽  
Progesterone Treatment ◽  
Gonadotrophin Releasing Hormone ◽  
Series Of Experiments

ABSTRACT We investigated whether the increase in the gonadotrophin response to gonadotrophin-releasing hormone (GnRH) during the last days of pregnancy and the occurrence of parturition on day 22 of pregnancy in rats are due to the increase in the plasma concentrations of oestradiol-17β after luteolysis, which occurs around day 20. In a first series of experiments we studied the effects of s.c. implantation of two capsules containing oestradiol on basal and GnRH-stimulated secretion of LH and FSH before and after luteolysis. Before luteolysis, ovariectomy increased basal LH and FSH; oestradiol treatment prevented this increase partly (FSH) or completely (LH). Ovariectomy also lowered the LH response to the infusion of GnRH (100 ng/h). Oestradiol treatment, on the other hand, increased the LH and FSH responses of both intact and ovariectomized rats above the level in intact non-treated control rats. After luteolysis, ovariectomy increased basal FSH only. Treatment with oestradiol did not prevent the increase in basal FSH and ovariectomy diminished the LH response to GnRH infusion. Oestradiol treatment maintained the LH response in ovariectomized rats at the control level and increased the FSH responses of both intact and ovariectomized rats to a higher level than in control rats. Furthermore, the LH and FSH responses of the oestradiol-treated groups of intact and ovariectomized rats were higher after luteolysis than before. In a second series of experiments two capsules containing progesterone were s.c. implanted before or after luteolysis. Progesterone treatment suppressed the plasma concentration of oestradiol and the gonadotrophin responses to infusion of GnRH on the expected day of parturition in both groups of rats. Parturition was delayed only in the rats in which progesterone treatment had started before luteolysis. It was concluded that throughout pregnancy ovarian factors suppress basal FSH and that the increase in responsiveness to GnRH after luteolysis is due partly to an increase in oestradiol production and partly to an ovarian factor which augments the action of oestradiol. Furthermore, normal delivery does not require high plasma concentrations of oestradiol during the last day of pregnancy. Journal of Endocrinology (1991) 128, 411–418

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