INFUSION OF ESTRADIOL DURING THE LUTEAL PHASE OF THE ESTROUS CYCLE IN THE EWE COMPLETELY ELIMINATES LH PULSES

1990 ◽  
Vol 70 (4) ◽  
pp. 1147-1150 ◽  
Author(s):  
I. B. J. K. JOSEPH ◽  
N. C. RAWLINGS
Keyword(s):  
Key Words ◽  
Estrous Cycle ◽  
Luteal Phase ◽  
Serum Estradiol ◽  
Lh Surge ◽  
Lh Secretion

Elevation of serum estradiol (E2) levels to ≈ 23 pg mL−1 on day 12 of the estrous cycle of the ewe eliminated LH pulses, but did not induce luteolysis and a preovulatory surge release of gonadotropins. The E2 treatment appeared to exert a functional luteotropic effect. The results indicate a strong synergism between E2 and progesterone (P4) in the control of tonic LH secretion during the luteal phase and that P4 blocks the preovulatory LH surge mechanism at high, but physiological levels of E2. Key words: Estradiol, LH pulses, luteal phase, ewe, luteotropic

Comparison of bovine uterine horns for progesterone and oxytocin levels with bilateral corpus luteum

1996 ◽  
Vol 76 (3) ◽  
pp. 463-464 ◽  
Author(s):  
W. A. Cerbito ◽  
M. P. B. Wijayagunawardane ◽  
M. Takagi ◽  
K. Sato ◽  
A. Miyamoto ◽  
...  
Keyword(s):  
Key Words ◽  
Corpus Luteum ◽  
Estrous Cycle ◽  
Luteal Phase ◽  
Uterine Horn ◽  
Corpora Lutea ◽  
Uterine Tissue ◽  
Tissue Samples ◽  
Significant Difference ◽  
The Right

Bovine uterine horns with both ovaries containing a corpus luteum (CL) were compared for progesterone (P4) and oxytocin (OT) concentrations during the luteal phase of the estrous cycle. Uterine tissue samples from five Holstein cows with bilateral CL obtained from the slaughterhouse were used for this study. No significant difference was observed in P4 and OT levels in the right and left horns with corpora lutea in both ovaries. The data clearly indicate that both sides of the uterine horn having a functional CL are exposed to similar levels of P4 and OT, supporting the hypothesis that luteal products are delivered locally to the uterus. Key words: Progesterone, oxytocin, uterine horn, bilateral, corpus luteum, cow

BLOOD HORMONE CHANGES ASSOCIATED WITH PUBERTY IN THE FEMALE PIG

1984 ◽  
Vol 64 (1) ◽  
pp. 177-181
Author(s):  
K.-H. PONZILIUS ◽  
L. M. SANFORD ◽  
G. D. PHILLIPS ◽  
W. M. PALMER
Keyword(s):  
Key Words ◽  
Estrous Cycle ◽  
Reproductive Hormones ◽  
Serum Concentrations ◽  
Lh Surge ◽  
Key Words Blood

Serum concentrations of reproductive hormones were determined in gilts around puberty. LH levels were low prior to pubertal estrus. FSH concentrations were high on day −5, decreased by day −1, then peaked simultaneously with the presumed preovulatory LH surge; a further increase was observed on day 3 of the first estrous cycle. Progesterone levels were consistently low prior to pubertal estrus and rose dramatically following ovulation. Peak levels of estrogen occurred between day −1 and day +1 of pubertal estrus. Key words: Blood hormone changes, puberty, female pig

Influence of PMSG antiserum on serum progesterone and estrous cycles of PMSG-treated gilts

1992 ◽  
Vol 72 (1) ◽  
pp. 173-176 ◽  
Author(s):  
R. N. Kirkwood ◽  
P. A. Thacker
Keyword(s):  
Key Words ◽  
Luteal Phase ◽  
Ovarian Activity ◽  
Serum Estradiol ◽  
Serum Progesterone ◽  
Estrous Cycles ◽  
Blood Samples ◽  
Effect Of Treatment

Forty-seven prepubertal gilts (88.4 ± 0.9 kg) received an injection of 750 IU PMSG to stimulate ovarian activity. After 96 h, 23 gilts received an injection of an anti-PMSG serum. Blood samples were obtained at the time of PMSG injection (day 0) and at 2, 4, 6, 11, 18, 25 and 32 d. There was no effect of treatment on serum estradiol concentrations or on the occurrence of normal estrous cycles. However, luteal phase serum progesterone concentrations were higher (P < 0.01) in gilts receiving the anti-PMSG. Key words: PMSG, antiserum, gilts, ovulation

Evidence that the switch from negative to positive feedback at the level of the pituitary gland is an important timing event for the onset of the preovulatory surge in LH in the ewe

1995 ◽  
Vol 145 (2) ◽  
pp. 271-282 ◽  
Author(s):  
I J Clarke
Keyword(s):  
Pituitary Gland ◽  
Negative Feedback ◽  
Luteal Phase ◽  
Bolus Injection ◽  
Pulse Frequency ◽  
Follicular Phase ◽  
Oestrous Cycle ◽  
Lh Surge ◽  
Small Rise ◽  
Lh Secretion

Abstract Experiments were performed to test the hypothesis that there is a negative feedback 'clamp' of ovarian hormones on the hypothalamus and pituitary gland during the follicular phase of the oestrous cycle that limits the secretion of GnRH and LH. GnRH secretion was monitored by sampling the hypophysial portal blood of ewes during the luteal phase of the oestrous cycle and either 24 h or 48 h after the induction of luteolysis by the injection of cloprostenol, a prostaglandin analogue. There was an increase in GnRH pulse frequency in the transition from the luteal to the follicular phase of the cycle. A reduction in the amplitude of GnRH pulses did not occur until 48 h after cloprostenol, suggestive of negative feedback at the level of the hypothalamus that is more profound in the latter part of the follicular phase. The responsivity of the pituitary gland to GnRH was monitored in ewes during the luteal phase of the oestrous cycle and 24 h or 48 h after cloprostenol. Injections of 250 ng or 1000 ng GnRH were given (i.v.) to ewes that had been anaesthetised to suppress endogenous secretion of GnRH and LH. Using the lower dose, the responses 48 h after cloprostenol were not significantly different from those in the luteal phase. With the higher dose of GnRH, a significant (P<0·05) increase in mean responsivity was seen 48 h after cloprostenol. There was, however, a marked variation in response, with some ewes showing profound increases in LH secretion in response to GnRH and others showing responses that were similar to those obtained during the luteal phase of the cycle. These data are interpreted to mean that the secretion of LH is 'clamped' during the follicular phase of the oestrous cycle and the 'clamp' is only released near the time of the preovulatory LH surge. To test whether or not a rise in GnRH input to the pituitary gland could over-ride the 'clamp' on the pituitary secretion of LH in the late follicular phase of the cycle, sheep were treated 40 h after cloprostenol with either a bolus injection of 500 ng GnRH or four pulses of 125 ng GnRH given at 10-min intervals. These treatments caused small elevations in LH secretion but did not always cause preovulatory LH surges. In some cases, a small rise in LH secretion was induced by GnRH treatments and levels of LH in plasma returned to baseline with the preovulatory LH surge occurring a few hours later. In one clear case, a bolus injection of GnRH induced an LH surge. The overall data from the GnRH-treated groups, however, indicated a significant delay in the onset of the LH surge which may have been due to perturbation of the subcellular mechanisms in the gonadotrophs. These data were interpreted to mean that the secretion of LH from the pituitary gland is inhibited up to very soon before the onset of the LH surge. The inhibitory factor could be oestrogen but could also be some other pituitary feedback hormone such as gonadotrophin surge-attenuating factor. It is concluded that the increase in the secretion of GnRH at the time of the onset of the LH surge is closely linked to an increase in the responsivity of the gonadotrophs to GnRH. The latter is not caused by the increase in the secretion of GnRH. Journal of Endocrinology (1995) 145, 271–282

Regulations of gonadotropin secretion by circulating inhibin, estradiol, and progesterone in cyclic hamsters

1999 ◽  
Vol 277 (5) ◽  
pp. E876-E882 ◽  
Author(s):  
Hisashi Kishi ◽  
Mariko Itoh ◽  
Ken-Ichi Ohshima ◽  
Ming-Wei Wang ◽  
Gen Watanabe ◽  
...  
Keyword(s):  
Estrous Cycle ◽  
Follicle Stimulating Hormone ◽  
Gonadal Hormones ◽  
Serum Estradiol ◽  
Elevated Plasma ◽  
Gonadotropin Secretion ◽  
Physiological Importance ◽  
Drastic Increase ◽  
Lh Secretion ◽  
Estradiol 17Β

The physiological importance of gonadal hormones in feedback control of gonadotropin secretion during the estrous cycle in golden hamsters was investigated with immunoneutralization methods. Anti-inhibin serum (inhibin-AS) treatment always induced a drastic increase in follicle-stimulating hormone (FSH) secretion and occasionally raised luteinizing hormone (LH) secretion. Anti-estradiol-17β serum (estradiol-AS) treatment increased LH secretion typically. Although estradiol-AS elevated FSH secretion occasionally, the elevation was much less than that by inhibin-AS. Plasma FSH reached ovariectomized levels by a synergistic effect of both antisera. Elevated plasma LH with both antisera was much less pronounced than in ovariectomized animals. Plasma LH increased dramatically to the levels in the ovariectomized group when antibody against progesterone (progesterone-AB) was given together with inhibin-AS and estradiol-AS, although progesterone-monoclonal antibody alone did not alter plasma gonadotropin levels. These results indicate that in hamsters FSH secretion is mainly regulated by inhibin and LH secretion is regulated by estradiol-17β and progesterone during the estrous cycle.

Ovarian responses of anestrous ewes to the "ram effect"

2002 ◽  
Vol 82 (4) ◽  
pp. 599-602 ◽  
Author(s):  
R. Ungerfeld ◽  
A. Pinczak ◽  
M. Forsberg ◽  
E. Rubianes
Keyword(s):  
Luteinizing Hormone ◽  
Key Words ◽  
Luteal Phase ◽  
Follicle Stimulating Hormone ◽  
Lh Surge ◽  
Follicular Cyst ◽  
Ram Effect ◽  
Ovulatory Follicles ◽  
Follicular Dynamics ◽  
Stimulating Hormone

Ovarian responses to the "ram effect" were characterized in 11 anestrous Corriedale ewes. In seven ewes, there was a luteinizing hormone (LH) surge 36.7 ± 12.3 h (mean ± SEM) after ram introduction and a concurrent increase (P < 0.05) in serum follicle stimulating hormone (FSH). Ovarian responses (monitored ultrasonographically) were highly variable. One ewe had two luteal phases (short and normal, respectively), three had delayed ovulation (days 5–7), two had luteinization of non-ovulatory follicles, one developed a luteinized follicular cyst, and four had no luteal phase. Key words: Ram effect, ovarian follicular dynamics, seasonal anestrus, ultrasonography, gonadotropin

Effect of mid-luteal phase progesterone levels on the first wave dominant follicle in cattle

1994 ◽  
Vol 74 (2) ◽  
pp. 281-285 ◽  
Author(s):  
C. Taylor ◽  
R. Rajamahendran
Keyword(s):  
Key Words ◽  
Estrous Cycle ◽  
Luteal Phase ◽  
Follicular Growth ◽  
Dominant Follicle ◽  
Prostaglandin F ◽  
Follicular Dynamics

A wave-like-pattern of follicular growth and regression during the luteal phase has been described in the bovine. The factors responsible for inducing the onset of regression of nonovulatory dominant follicles are unknown. The present study was designed to examine the effect of progesterone (P4) administration early in the estrous cycle on the first wave dominant follicle. Nine heifers were administered P4 on day 3 (200 mg), day 4 (100 mg) and day 5 (50 mg) of the estrous cycle (Day 0 = day of estrus) and seven heifers received vehicle to serve as controls. All heifers received a luteolytic dose of prostaglandin F2α (PGF2α) on day 7. Follicular dynamics were monitored by daily ultrasonography. All seven control heifers ovulated the first wave dominant follicle. In four P4 treated heifers, the first wave dominant follicle regressed prior to PGF2α administration and a dominant follicle from the second pool of follicles ovulated. The remaining five P4 treated heifers ovulated the first wave dominant follicle. However, in these heifers the growth of the first wave dominant follicle was slower (0.65 ± 0.13 mm day−1 between days 3 to 7 for treated vs 1.46 ± 0.23 mm day−1 for control; P < 0.05) and estrus and ovulation were delayed compared to controls (3.8 ± 0.3 vs 2.4 ± 0.2 and 5.2 ± 0.4 vs 3.9 ± 0.2 days after PGF2α, respectively; P < 0.05). The results indicate that P4 administered early in the estrous cycle to mimic the mid luteal phase levels alters follicular dynamics and is capable of inducing premature regression of the first wave dominant follicle. Key words: Progesterone, dominant follicle, cattle, atresia, ovulation

scholarly journals Melanocortins May Stimulate Reproduction by Activating Orexin Neurons in the Dorsomedial Hypothalamus and Kisspeptin Neurons in the Preoptic Area of the Ewe

Endocrinology ◽  
2009 ◽  
Vol 150 (12) ◽  
pp. 5488-5497 ◽  
Author(s):  
Kathryn Backholer ◽  
Jeremy Smith ◽  
Iain J. Clarke
Keyword(s):  
Estrous Cycle ◽  
Luteal Phase ◽  
Arcuate Nucleus ◽  
Preoptic Area ◽  
Neuronal Tracing ◽  
Dorsomedial Hypothalamus ◽  
Acute Response ◽  
Reproductive Axis ◽  
Positive Regulators ◽  
Lh Secretion

Abstract To further test the hypothesis that melanocortins stimulate the reproductive axis, we treated ewes with melanocortin agonist (MTII) in the luteal phase of the estrous cycle and during seasonal anestrus. Lateral ventricular infusion of MTII (10 μg/h) during the luteal phase increased LH secretion. Retrograde neuronal tracing in the brain showed few proopiomelanocortin or kisspeptin cells in the arcuate nucleus, but more than 70% of kisspeptin cells in the dorsolateral preoptic area (POA), projecting to the ventromedial POA in which GnRH cells are located. MTII infusion (20 h) was repeated in luteal phase ewes and brains were harvested to measure gene expression of preproorexin and kisspeptin. Expression of orexin in the dorsomedial hypothalamus and kisspeptin in the POA was up-regulated by MTII treatment and Kiss1 in the arcuate nucleus was down-regulated. Seasonally anestrous ewes were progesterone primed and then treated (lateral ventricular) with MTII (10 μg/h) or vehicle for 30 h, and blood samples were collected every 2 h from 4 h before infusion until 6 h afterward to monitor acute response in terms of LH levels. A rise in basal LH levels was seen, but samples collected around the time of the predicted LH surge did not indicate that an ovulatory event occurred. We conclude that melanocortins are positive regulators of the reproductive neuroendocrine system, but treatment with melanocortins does not fully overcome seasonal acyclicity. The stimulatory effect of melanocortin in the luteal phase of the estrous cycle may be via the activation of kisspeptin cells in the POA and/or orexin cells in the dorsomedial hypothalamus.

Reanalysis of the rat proestrous LH surge by deconvolution analysis

1993 ◽  
Vol 265 (5) ◽  
pp. R1222-R1222
Author(s):  
J. D. Veldhuis ◽  
M. L. Johnson ◽  
R. V. Gallo
Keyword(s):  
Estrous Cycle ◽  
Reference List ◽  
Deconvolution Analysis ◽  
Lh Surge ◽  
Low Level ◽  
Lh Release ◽  
Lh Secretion

Pages R240–R245: J. D. Veldhuis, M. L. Johnson, and R. V. Gallo. “Reanalysis of the rat proestrous LH surge by deconvolution analysis.” Page R244: Reference 7 was inadvertently dropped from the reference list by the printer. It should read: 7. Gallo, R. V. Pulsatile LH release during periods of low level LH secretion in the rat estrous cycle. Biol. Reprod. 24: 771–777, 1981.

The effects of acclimation to confinement on gonadotrophin and cortisol secretion during the estrous cycle of the ewe

1991 ◽  
Vol 71 (2) ◽  
pp. 327-332 ◽  
Author(s):  
N. C. Rawlings ◽  
S. J. Cook
Keyword(s):  
Key Words ◽  
Estrous Cycle ◽  
Pulse Amplitude ◽  
Pulse Frequency ◽  
Cortisol Secretion ◽  
Serum Concentrations ◽  
Blood Samples ◽  
Progesterone Secretion ◽  
Serum Lh ◽  
Lh Secretion

The purpose of the study was to examine the effects of acclimation to confined housing on tonic gonadotrophin, cortisol and progesterone secretion in ewes at different stages of the estrous cycle. On days 4, 12 and 16 of the estrous cycle separate groups of eight ewes were blood sampled every 5 min for 6 h. Of the eight ewes bled at each stage of the cycle four were moved from outside drylots to small pens in a building 2 d prior to blood sampling and four were moved 4 d prior to sampling. All blood samples were analyzed for concentrations of LH and FSH and one sample for each hour of intensive bleeding, for each ewe, was analyzed for cortisol and progesterone. All hormone concentrations were obtained by radioimmunoassay. On day 4 of the estrous cycle LH pulse frequency and mean serum concentrations of LH were higher, but mean FSH concentrations were lower, in ewes confined for 4 d, compared to those confined for 2 d (P < 0.05). On day 12 of the cycle, mean serum LH concentrations only were higher in ewes confined for 4 d (P < 0.05). At day 16 no differences were seen between ewes confined for 2 or 4 d. Serum concentrations of progesterone, cortisol and LH pulse amplitude did not vary significantly between ewes confined for 2 or 4 d. However, in ewes confined for 4 d, serum concentrations of cortisol fell from day 4 to day 16 of the estrous cycle (P < 0.05). We conclude that acclimation to confined housing in the intact cyclic ewe is reflected in changes in tonic LH secretion at stages of the estrous cycle when serum concentrations of cortisol are high. Key words: LH, FSH, cortisol, confinement, cyclic ewe

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