Effect of intrauterine saline infusion during the late luteal phase on the estrous cycle and luteal function of the mare

The intrauterine infusion of 500 ml of warm sterile saline solution into mares on days 12, 13, or 14 after ovulation failed to alter the ovulatory interval, although intervals were shorter for days 12 and 13 (20.6 days) when compared with those in control mares (21.6 days). The IU fusion shortened luteal-life-span on days 12 (12.0 vs 13.8 days) and 13 (13.0 vs 14.4 days) (P is less than 0.05), but not day 14 (14.0 vs 13.5 days), when comparing the effects of IU infusion with an average of before and after base-line data. There was no effect on the interval from corpus luteum regression to ovulation, ie, the final follicular phases. The treatment average for days 12 and 13 combined was 7.7 days vs 7.3 days for controls. Also, no significant effect was observed for the duration of estrus in that the treatment average for days 12 and 13 was 5.1 days, and for controls, 6.0 days. The infusion of saline solution caused an immediate release of prostaglandin F(2alpha) within 5 minutes, with additional large releases occurring over the next 24 hours. Progestin concentrations decreased rapidly in relation to this prostaglandin release.     

The effects of dexamethasone and prednisolone on pituitary and ovarian function in the mare

Reasons for performing study: Persistent mating induced endometritis is among the most common causes of infertility in the mare. Recently, improved pregnancy rates have been reported when corticosteroids were administered to ‘problem mares’ specifically, to modulate the post mating inflammatory response; however, the effect of treatment on pituitary and ovarian function requires further study. Objectives: To evaluate the effects of prolonged treatment with glucocorticoids on pituitary and ovarian function. Methods: Eighteen cycling Quarter Horse mares in early oestrus were assigned randomly to one of 3 treatment groups: dexamethasone 0.05 mg/kg bwt i.v. twice a day, prednisolone 0.5 mg/kg per os twice a day, or placebo for 5 days. Mares were examined by ultrasound daily to evaluate reproductive function. Blood samples were collected daily to measure luteinising hormone (LH), progesterone and cortisol levels. Results: Dexamethasone treatment caused greater (P<0.05) suppression of endogenous cortisol concentration (9.4 ± 1.1 ng/ml) compared to prednisolone‐ (41.9 ± 4.0 ng/ml) or placebo‐treated mares (32.4 ± 3.8 ng/ml). After 24 h, mares treated with dexamethasone exhibited lower uterine oedema scores than prednisolone‐ or placebo‐treated mares. An ovulation rate of 40% was observed in dexamethasone‐treated mares (2/5) compared to 83% for prednisolone (5/6) and 100% for placebo‐treated (6/6) mares. An absence of a LH surge was noted in 3 of 5 dexamethasone‐treated mares and one of 6 prednisolone‐treated mares. Conclusions: Repeated administration of dexamethasone to mares in oestrus is associated with decreased uterine oedema, suppression of LH and a high rate of ovulation failure. It is recommended that dexamethasone treatment is limited to only 1 or 2 days and that a lower dose is considered in the management of persistent mating induced endometritis to avoid potential adverse affects on reproductive function.     

Influence of experimental intrauterine infusion of Arcanobacterium pyogenes solution on ovarian activity in cycling cows

To examine the ovarian response to Arcanobacterium pyogenes (A. pyogenes) in uterus, bacterial solution was infused into the uteri of cows, and the follicle and corpus luteum (CL) development were monitored with a real-time ultrasound instrument. In addition, the plasma concentrations of progesterone (P(4)) and 13, 14-dihydro-15-keto-PGF(2alpha) (PGFM) were determined. A 10 ml bacterial solution that contained A. pyogenes (8 to 15 x 10(8) CFU/ml) was infused into the uterus of eight cows transcervically three days after natural ovulation. As a control, sterile physiological saline was infused into 4 other cows. The dominant follicle developed normally in 8 cows after bacteria inoculation. In 4 of these 8 cows, the developing CL regressed, and the first wave dominant follicles, which normally become atretic, ovulated after the inoculation. In the remaining 4 cows, the CL did not regress. The PGFM concentration increased transiently in all 8 cows after the infusion. The mean PGFM concentration of the cows with a regressed CL was significantly lower (P<0.01) than that of the cows whose CLs did not regress. In the control cows, there was no regression of developing CLs, no ovulation of first wave dominant follicles and no transient increase in PGFM after the infusion of sterile physiological saline. These results show that infusion of A. pyogenes into the uterus did not affect folliculogenesis and might have induced PGF(2alpha) production from the uterus.     

First luteal tissue in ewe lambs: influence on subsequent ovarian activity and response to hysterectomy

Two experiments were conducted in peripuberal ewe lambs to determine (a) the influence of the first luteal structure [most frequently a transient (i.e., 1 to 4 d) structure] on subsequent ovarian activity and (b) a role for the uterus in its demise. In Exp. 1, 21 lambs were assigned randomly on the day of the first rise in progesterone in the plasma to (1) sham-operation, (2) removal of the nonluteal ovary, (3) removal of the luteal ovary and (4) removal of the luteal ovary plus progesterone replacement (5 mg given three times 12 h apart, initiated at surgery). No effect of treatment on subsequent ovarian activity was observed. In Exp. 2, four of 14 lambs were assigned randomly to be hysterectomized before their first rise in progesterone. The remaining 10 lambs, (five each) were sham-operated or hysterectomized on the day of the first rise in progesterone. All hysterectomized lambs (N = 9) exhibited a rise in progesterone and maintained elevated concentrations of progesterone, whereas sham-operated lambs initiated estrous cycles. Oviducts and uteri collected from lambs hysterectomized on the day of the first rise in progesterone in Exp. 2 were flushed for presence of oocytes and none were found. Similarly, no retained oocytes were found in histological preparations of first luteal structures obtained from eight lambs ovariectomized in Exp. 1. Concentrations of luteinizing hormone (LH) and prolactin were determined in daily samples collected from 19 lambs in Exp. 1. Luteinizing hormone increased and became more variable as lambs matured, whereas prolactin decreased with no detectable change in variability. It is concluded that the transient luteal structure is not required for sexual maturation and that its lifespan is uterine dependent.     

The effects of prolactin and gonadotropin on luteal function and morphology in the cyclic golden hamster

The present study was conducted to evaluate the endocrinological effects of the pituitary on luteal maintenance and regression in the cyclic golden hamster (Mesocritus auratus). After hypophysectomy (Hypox) at 0900 h on day 1 of the estrous cycle (the day of ovulation), the animals received injection of prolactin (PRL) or PRL plus equine chorionic gonadotropin (eCG). They were decapitated at 1500 h on day 3 of the cycle, and trunk blood was collected for measurement of progesterone (P4). Corpora lutea (CLs) were dissected from one ovary for DNA ladder detection by electrophoresis, determination of DNA fragmentation ratio by fluorometric measurement method and measurement of P4. The other ovary was used for histological observation. After the Hypox, the daily injection of 1 mg ovine PRL restrained the DNA fragmentation ratio and number of apoptotic cell in the CLs. The PRL treatment maintained the luteal morphology and increased the luteal P4 concentration, but not in the plasma P4 concentration. In addition to PRL, injection of 2 IU eCG after the Hypox also restrained the DNA fragmentation ratio and number of apoptotic cells in the CLs to the level of a pregnant animal. The PRL plus eCG treatment maintained the luteal morphology in the same manner as the PRL only treatment and increased not only the luteal but also the plasma P4 concentration. These results suggest that PRL restrains luteal apoptosis and maintains luteal morphology and that the combination of PRL and eCG restrains not only structural but also functional luteal regression in the cyclic hamster.     

Follicular growth and estradiol influence on luteal function in mares

Follicular growth, circulating estradiol concentrations and endometrial prostaglandin F2 alpha (PGF2 alpha) production were measured to determine whether there is an interrelationship among these factors associated with luteolysis. Follicular growth was monitored by rectal palpation every other day during diestrus in 16 mares. Plasma estradiol was determined for daily samples during all estrous cycles. Endometrial tissue was removed for PGF2 alpha analysis by radioimmunoassay on d 10, 12, 14 or 16 during several normal cycles and after d 30 during spontaneously prolonged cycles. Circulating estradiol concentrations were highly correlated with follicular diameter. Follicular growth was initiated before d 14 in normal cycles, thus estradiol was significantly elevated during the portion of diestrus prior to luteolysis. This was not the case during spontaneously prolonged cycles in which a) there was no correlation between follicular size and circulating estradiol, b) follicular growth was initiated an average of 19 d postovulation, and c) estradiol concentrations did not increase. Diestrous estradiol concentrations, during normal cycles, were significantly elevated immediately (72 to 24 h) prior to the time at which peak endometrial PGF2 alpha production occurred (d 12 and 14). During spontaneously prolonged cycles, estradiol concentrations did not rise at the time of expected luteolysis, and endometrial PGF2 alpha production was minimal in d 30 biopsies. Results suggest that diestrus follicular growth and its consequent estradiol production may play a role in initiating luteolysis through endometrial PGF2 alpha production and that delay or failure of this process may result in spontaneously prolonged corpora luteal function.     

Effect of teasing, mechanical stimulation and the intrauterine infusion of saline on uterine contractions in mares

Uterine motility may have significance for the transportation of spermatozoa and the elimination of the ejaculate and inflammatory products after mares have been covered. The effect of some of the component stimuli of coitus on uterine contractions was investigated by using M-mode ultrasound. The number, amplitude and duration of the uterine contractions of each uterine horn and of the uterine body were measured in oestrous mares for four minutes before and four minutes after teasing by a stallion, mechanical stimulation of the vagina and cervix, the intrauterine infusion of 80 ml of sterile saline, the intrauterine infusion of 10 ml of sterile saline, the intrauterine infusion of 150 ml of sterile saline, and the transcervical passage of a uterine catheter. Teasing by a stallion did not affect the total number, mean amplitude or mean duration of the uterine contractions. Mechanical stimulation of the vagina and cervix increased the total number of uterine contractions, but did not affect the amplitude or duration of the contractions. The intrauterine infusion of 80 ml of sterile saline resulted in an increase in the total number of contractions and a significant increase in the mean amplitude and the mean duration of the contractions in the uterine horns but not the uterine body. The intrauterine infusion of 10 ml of sterile saline caused a significant decrease in the number of uterine contractions in the uterine horns, but had no effect on the contractions of the uterine body. The infusion of 150 ml of sterile saline reduced the number of contractions in the uterine horns but not the uterine body, and did not affect the mean amplitude and mean duration of the contractions. The transcervical insertion of a catheter reduced the number of contractions in the uterine horns, but did not affect the amplitude or duration of the uterine contractions.     

Unusual ovarian activity in a mare preceding the development of an ovarian granulosa cell tumour

An 8-year-old mare, with a foal at foot, was inseminated on foal heat with frozen semen, with the resultant pregnancy lost between days 34 and 41. The right ovary developed a large anovulatory follicle that was non-responsive to multiple doses of ovulating agents. The follicle eventually appeared to luteinise, although plasma progesterone concentrations did not reflect this. Another follicle developed, responded to GnRH and resulted in a pregnancy from frozen semen that went to term with a healthy foal. When the mare was examined after foaling, the structure on the right ovary appeared to be a granulosa cell tumour; the left ovary was smaller than normal and non-functional. Surgical removal of the right ovary before increasing photoperiod resulted in a return to function of the left ovary and a pregnancy to frozen semen on the second cycle following removal. Figures showing concentrations of inhibin, progesterone, androstenedione, oestradiol and testosterone are presented for this entire period. Unusual ovarian activity in the mare might be a prelude to the development of a granulosa cell tumour.     

Unusual ovarian activity in a mare preceding the development of an ovarian granulosa cell tumour

An 8-year-old mare, with a foal at foot, was inseminated on foal heat with frozen semen, with the resultant pregnancy lost between days 34 and 41. The right ovary developed a large anovulatory follicle that was non-responsive to multiple doses of ovulating agents. The follicle eventually appeared to luteinise, although plasma progesterone concentrations did not reflect this. Another follicle developed, responded to GnRH and resulted in a pregnancy from frozen semen that went to term with a healthy foal. When the mare was examined after foaling, the structure on the right ovary appeared to be a granulosa cell tumour; the left ovary was smaller than normal and non-functional. Surgical removal of the right ovary before increasing photoperiod resulted in a return to function of the left ovary and a pregnancy to frozen semen on the second cycle following removal. Figures showing concentrations of inhibin, progesterone, androstenedione, oestradiol and testosterone are presented for this entire period. Unusual ovarian activity in the mare might be a prelude to the development of a granulosa cell tumour.     

Energy balance and body condition influence luteal function in Holstein heifers

A factorial experiment was conducted to determine influence of energy balance (EB) and body condition (BC) on luteal function in heifers. Heifers with moderate (MBC) or fat (FBC) BC were fed individually to sustain positive EB (PEB) or to cause negative EB (NEB). Intake of feed was measured daily and body weight weekly. Progesterone was quantified daily in serum for 3.5 estrous cycles. On days 9, 10, or 11 after fourth estrus, blood was sampled every 15 min for 12 hr to quantify luteinizing hormone (LH), growth hormone (GH), insulin and non-esterified fatty acids (NEFA). The next day, luteal cells were incubated and proportions of small to large cells were determined. After fourth estrus, area of progesterone profiles in serum for 10 days postestrus was reduced in all heifers relative to MBC-PEB heifers. But, luteal weight from FBC-PEB and MBC-NEB heifers was less than MBC-PEB heifers and FBC-NEB heifers were intermediate. Secretion of progesterone in vitro was increased by LH for PEB but not NEB heifers. MBC-NEB heifers had increased ratios of small to large luteal cells. Independent of BC, NEB decreased concentrations of insulin and increased GH and NEFA. Secretion of progesterone was not associated with LH, GH or insulin, but was correlated negatively with NEFA. We conclude that reduced concentrations of progesterone in serum of FBC-PEB and MBC-NEB heifers is due to impaired luteal development. But, reduced concentrations of progesterone in serum of NEB heifers is due also to reduced basal (MBC) and LH-induced (MBC and FBC) secretion of progesterone by luteal cells. Body condition at onset of NEB may determine when effects of NEB on progesterone are detected.     

Inhibin activity in the mare and stallion

An overnight double antibody RIA, employing a rabbit antiserum raised to bovine 31 kDa inhibin (rAs-#1989, NICHD) and purified bovine 31 kDa inhibin (bINH-I-90/1, NICHD) as trace and standard, was validated to measure immunoreactive inhibin (iINH) concentrations in equine peripheral plasma, follicular fluid (FF), ovarian vein (OV) plasma, testicular tissue extracts (TTE) and testicular vein (TV) plasma. The dynamic relationship of iINH and follicle stimulating hormone (FSH) was investigated during the estrous cycle of the mare and the annual reproductive cycle of the stallion.In the RIA, parallel dose-response curves were observed between the bovine inhibin standard and serial dilutions of equine FF, OV, TTE, TV and plasma. The average recovery of a known amount of purified bovine inhibin added to gelding plasma was approximately 100%. In the inhibin bioassay, serial dilution of equine FF and TTE were observed to be parallel to the bovine inhibin standard. A five-fold difference (p<0.05) between jugular and gonadal vein plasma iINH concentrations was observed in the mare and an eight-fold difference (p<0.05) was observed in the stallion. Plasma levels of iINH in ovariectomized mares or geldings were undetectable in the RIA.Concentrations of FSH, estradiol and iINH changed significantly in the mare during the estrous cycle (p<0.05). Immunoreactive inhibin levels were highest (0.54 ± 0.06 ng/ml) on the day of ovulation, declined rapidly following ovulation and reached a nadir (0.21 ± 0.03 ng/ml) on day 7 post-ovulation. Plasma iINH and estradiol concentrations followed a similar profile and were found to be positively correlated (r=0.7064; p<0.01), whereas iINH and FSH levels demonstrated an inverse relationship (r=−0.7359, p<0.01) throughout the estrous cycle. Concentrations of FSH were also inversely related (−0.8498, p<0.01) with estradiol during the cycle. In the stallion, plasma iINH and FSH levels changed significantly during the year (p<0.05). The iINH profile reflected seasonal changes in testicular activity, with highest concentrations in late spring (3.37 ± 0.44 ng/ml) and lowest concentrations in the fall (2.21 ± 0.33 ng/ml). Plasma concentrations of iINH were positively correlated (r=0.7691, p<0.01) with FSH concentrations throughout the year.In conclusion, a specific and sensitive RIA for iINH has been validated for plasma and biological fluids in the horse. Furthermore, the gonads appear to be the source of bioactive and immunoreactive inhibin as observed in other species. The dynamic relationship between iINH and FSH that is present in both the mare and stallion suggests that iINH may be a useful marker of gonadal activity in this species.     

Local effect of progesterone infusion into ovarian artery on activin A and inhibin alpha-subunit secretion during the middle luteal phase in gilts

The present study was undertaken to elucidate whether an increased, but physiological, amount of progesterone (P4) supplied to the porcine corpus luteum affects luteal secretion of activin A and inhibin alpha-subunit (Inhalpha) in freely moving gilts. On day 9 of the estrous cycle (EC), both ovarian arteries and both ovarian veins of gilts (n = 5) were cannulated. Progesterone was infused into the right ovarian arteries in gilts on days 10, 11 and 12 of the EC at a rate adequate to its physiological retrograde transfer found during the middle luteal phase of the EC. The P4 infusion rate was 0.62 microg/min (day 10), 2 x 0.62 microg/min (day 11) and 3 x 0.62 microg/min (day 12). The left ovarian arteries were infused with saline (control). Blood samples were collected from both ovarian veins on days 10-12 of the EC before and after P4 or saline infusion. The mean plasma activin A level in the ovarian vein ipsilateral to the P4-infused ovary was higher (P < 0.0001) on days 10-12 of the EC than this found in the contralateral ovarian vein. The level of activin A in the ovarian vein ipsilataral to the infusion of P4 was higher on days 11 (P < 0.01) and 12 (P < 0.0001) and tended to be higher (P < 0.07) on day 10 of the EC than this in contralateral ovarian vein. The level of Inhalpha in the ovarian vein ipsilateral to the P4-infused ovary on days 10-12 of the EC was not significantly different (P > 0.05) than this found in the contralateral ovarian vein. The results of the present study indicate that a local elevation of P4 concentration in blood supplying the ovary during the middle luteal phase of the porcine EC affects ovarian secretion of activin A. The effect of P4 on the secretion of activin A suggested the existence of a short regulatory loop of a positive feedback between P4 being retrogradely transferred into the ovary and the secretion of this peptide.     

Melatonin and CIDR improved the follicular and luteal haemodynamics,uterine and ovarian arteries vascular perfusion,ovarian hormones and nitric oxide in cyclic cows

This study hypothesizes that melatonin with exogenous progesterone (CIDR) can improve follicular, luteal, ovarian and uterine haemodynamic of heat-stressed cows. Holstein cows (N = 12) studied for two spontaneous oestrous cycles during winter then divided equally during summer into the CIDR group received CIDR for 7 days and the melatonin group (Mel) received three injections of melatonin (75 mg/head) at the CIDR insertion, removal and ovulation days. Blood samples were collected to assay oestradiol (E2), progesterone (P4) and nitric oxide (NO). On day 0 (Ovulation), Mel had more small follicles (p < .05), higher ipsilateral and contralateral ovarian arteries (Ov.A.) peak systolic velocity (PSV), higher ipsilateral uterine artery (Ut.A.) PSV (p = .031) and blood flow volume (BFV), also Mel elevated contralateral Ut.A. PSV and BFV (p < .0001) but lowered contra Ut.A. pulsatility index (PI, p < .0001), E2 (p < .01) and NO (p < .0001). Mel increased the corpus luteum diameter (CL, p < .001), coloured area (p < .007) and P4 (p < .0001) on day 5 and reduced them (p < .05; p < .01) on Day 14. On day 10, Mel obtained CL diameter (p < .03) and coloured area (p < .002) of spontaneous that was higher than CIDR and decreased P4 (p < .003). Mel increased CL diameter, area and coloured area and decreased them thereafter. Mel increased the ipsilateral ovarian and uterine arteries PSV and BFV before ovulation and until day 8. Mel increased P4 and decreased NO until days 6 and 14. In conclusion, the improvement in follicular, luteal, ovarian and uterine haemodynamic and the decrease of NO production proved our hypothesis Melatonin doses higher than 75 mg/head is recommended to improve the heat-stressed cow's fertility.     

Effect of ovarian follicles on luteal regression in heifers

Our objectives were to determine whether or not ovarian follicles contribute to spontaneous luteal regression in heifers and, if so, when during diestrus do follicles exert their effect. Thirty-one Holstein heifers having displayed at least one estrous cycle (19 to 21 d) were assigned, as available, to randomized blocks for a factorial experiment. Reproductive organs were exposed through a midventral incision on d 9, 12 or 15 postestrus (estrus = d 0). Visible follicles were electrocauterized and both ovaries were x-irradiated (1,500 rads) in treated heifers, whereas ovaries of controls were exteriorized but follicles were not destroyed and ovaries were not x-irradiated. In two additional heifers, the ovary containing the corpus luteum was exteriorized and x-irradiated on d 15 postestrus, but follicles were not electrocauterized. Jugular blood was collected before and every 8 h after surgery until d 24 postestrus. All heifers were ovariectomized on d 24 postestrus to inventory follicles and to weigh corpora lutea. No follicles (greater than or equal to 1 mm diameter) were observed in ovaries from treated animals and concentrations of estradiol-17 beta did not change over time, whereas different numbers of follicles were observed in ovaries from controls and concentrations of estradiol-17 beta increased (P less than .05) during proestrus. Hence, treatment destroyed follicles and prevented follicular development. On d 24 postestrus, corpora lutea from treated heifers (5.5 +/- .5 g) were heavier (P less than .001) than corpora lutea from controls (1.1 +/- .1 g), independent of day when follicles were destroyed.(ABSTRACT TRUNCATED AT 250 WORDS)