Pituitary and ovarian luteinizing hormone releasing hormone receptors during the estrous cycle, pregnancy and lactation in the rat

Female Sprague-Dawley rats were decapitated at various stages of the estrous cycle, pregnancy, lactation and following ovariectomy. Anterior pituitary and ovarian tissues were collected and assayed to quantify luteinizing hormone releasing hormone (LHRH) receptors. No changes were noted in receptor affinity either between tissues or physiological stages studied. Pituitary LHRH receptor concentrations and content were greater (P less than 0.05) during diestrus II and proestrus than during estrus. Pituitary LHRH receptor concentrations and content during pregnancy were not different from those during estrus, however, a significant decrease was noted in pituitary LHRH receptor content and concentrations during lactation compared to estrus. Ovarian LHRH receptor content did not change with stage of reproduction (P less than 0.05). There was, however, a decrease (P less than 0.05) in ovarian LHRH receptor concentrations at Week 3 of pregnancy and Week 1 of lactation which was possibly due to the increase ovarian weight noted at both these physiological stages. There was no correlation (P less than 0.1) between ovarian and pituitary LHRH receptor numbers (r = 0.096). These findings suggest that the internal mechanisms which control changes in pituitary LHRH receptor numbers do not control ovarian LHRH receptor numbers.     

Prostaglandins F in uterine and ovarian venous plasma from nonpregnant and pregnant ewes collected by cannulation.

Periodic collections of uterine venous blood were obtained from three nonmated, three pregnant and two mated but nonpregnant ewes in which uterine veins were cannulated with polyvinyl tubing on day 11 postestrus. Frequent sampling was achieved in three of these ewes with additional cannulae in the ovarian veins. Blood samples were collected at 3-hr intervals from 0600 on day 12 to 1800 on day 13 and then 6-hr intervals through day 15. On day 13, three additional samples at 30-min intervals were collected between 1400 and 1530. Prostaglandins F (PGF) in plasma were quantified by radioimmunoassay. On day 12, one ewe in each group had at least one measurement which suggested an increased rate of release of PGF into the uterine vein. Seven of eight ewes on day 13 appeared to have increased rates of release of PGF from the uterus between 0900 and 1500. The highest level measured in each ewe during this period ranged from 2.7 to 11 ng per milliliter. Concentrations of PGF in ovarian venous plasma in two of three ewes were positively correlated (P less than .05) with concentrations of PGF in uterine venous plasma (r equals .64 in each ewe). No evidence was obtained that pregnant and nonpregnant ewes differ in rate or pattern of release of PGF from the uterus into the uterine vein on days 12 and 13. Comparisons could not be made with confidence concerning PGF either in uterine veins on days 14 and 15 or in ovarian veins on all days due to limited number of observations.     

Postpartum uterine flora following normal and abnormal puerperium in cows

Uterine swabs were taken from the uteri of three groups of cows (n = 5 each) on Days 1 and 2 and then at 3-d intervals up to 32 d post partum. Group I cows had a normal delivery, Group II cows had dexamethasone-induced parturition, and Group III cows were subjected to a Caesarian section. All cows in Group III and two cows in Group II retained their fetal membranes. A total of 230 bacterial isolates were made, and the most frequently isolated bacteria were Escherichia coli , streptococci, Proteus spp. , and clostridia. The highest number of bacterial isolates and the longest mean time to complete uterine involution were in the Group III cows.     

Prostaglandins F in uterine and ovarian venous plasma from nonpregnant and pregnant ewes collected by cannulation

Periodic collections of uterine venous blood were obtained from three nonmated, three pregnant and two mated but nonpregnant ewes in which uterine veins were cannulated with polyvinyl tubing on day 11 postestrus. Frequent sampling was achieved in three of these ewes with additional cannulae in the ovarian veins. Blood samples were collected at 3-hr intervals from 0600 on day 12 to 1800 on day 13 and then at 6-hr intervals through day 15. On day 13, three additional samples at 30-min intervals were collected between 1400 and 1530. Prostaglandins F (PGF) in plasma were quantified by radioimmunoassay.     

Effect of season, month of parturition and lactation on estrus behavior and ovarian activity in Barki x Rahmani crossbred ewes under subtropical conditions

The correlations between some meteorological parameters and fertility data were evaluated in Barki x Rahmani crossbred ewes using the records of five consecutive years (2003-2007). Additionally, estrus detection and ultrasonic evaluation were applied on eighteen mature dry ewes during breeding and non-breeding seasons. The effect of lactation was evaluated by monitoring estrus behavior in ninety four lactating ewes from 40 to 120 d after parturition. Moreover, ultrasonography was used to identify ovarian activity in six cyclic and six acyclic non-lactating ewes. Results revealed that relative estrus occurrence and fertile mating were positively correlated (P <0.05) with high temperature and long photoperiod (conditions of summer season), and were negatively correlated (P < 0.01) with rainfall (condition of winter season). During breeding season, estrus rate, serum progesterone concentration, and diameter of largest follicle were significantly (P < 0.05) higher than those observed during the non-breeding season. Furthermore, month of parturition had a significant effect (P < 0.05) on estrus rate of lactating ewes where ewes that lambed in August, September, and October recorded higher estrus rate than those lambed in November and December. However, the lactational strength did not exert any deleterious effect on the reproductive performance of lactating ewes.In conclusion, in Egypt under subtropical conditions, Barki x Rahmani crossbred ewes exerted optimum estrus behavior and fertile mating during summer season. The reduction in estrus activity during lactation was due to the seasonal effect rather than lactational stress.     

Follicle stimulating hormone secretion and compensatory ovarian hypertrophy in prepubertal ewes

A study was conducted to determine the effect of unilateral ovariectomy (ULO) on follicle stimulating hormone (FSH) secretion and compensatory ovarian hypertrophy in prepubertal ewes. Thirty-three ewe lambs were allotted according to age and weight to a control (C) or ULO group. In the C group, a sham ovariectomy was performed on day 0 and both ovaries were removed on day 7. In the ULO group, one ovary was removed on day 0 and the remaining ovary was removed on day 7. Blood samples were collected from the jugular vein via venipuncture at 0, 6, 12 and 24 hours after the time of sham surgery or ULO (day 0). Subsequent samples were collected daily until day 7, and all samples were assayed for FSH and LH. Unilateral ovariectomy increased (P<0.01) ovarian weight and follicular fluid weight; however, lyophilized ovarian weight was similar for both groups. Within the ULO group, removal of the ovary having the largest follicle(s) did not prevent an increase in ovarian weight or follicular fluid weight of the remaining ovary. Unilateral ovariectomy had no effect on the total number of follicles (1 to 6 mm) per ovary; however, the number of large (5 to 6 mm) follicles per ovary was increased (P<0.05) following ULO. By 12 hours after ULO there was a transient increase (P<0.05) in the circulating concentrations of FSH. Circulating concentrations of luteinizing hormone (LH) were either low or undetectable in these prepubertal ewes and no LH response was observed following ULO. These results indicate that compensatory ovarian hypertrophy in ULO prepubertal ewes is accompanied by a transient rise in circulating FSH concentrations.     

Seasonal changes in LH secretion in normal ewes and ewes which grazed oestrogenic clover

Plasma luteinizing hormone (LH) concentrations were measured in normal (control) Corriedale X Merino (comeback) ewes and in clover-infertile comeback ewes which had grazed oestrogenic Yarloop clover (Trifolium subterraneum L. cv. Yarloop) for more than 4 years. Plasma LH concentrations were measured in samples taken at 20-min intervals for 6 h during the dioestrous stage of the oestrous cycle in the breeding season (BS) and during the anoestrous season (AS). In the control ewes during BS, transitory elevation in plasma LH concentration (pulses) occurred, reflecting secretory episodes, with a frequency of one per 5.2 h. This frequency fell to one per 16.5 h during the anoestrous season. In clover-infertile ewes, LH pulses occurred with a frequency of one per 4.5 h during BS and one per 4.9 h during AS (difference not significant). In the controls, plasma LH levels were higher (P less than 0.05) during BS (mean +/- s.d. = 1.2 +/- 0.4 ng/ml, n = 9) than in AS (0.7 +/- 0.3 ng/ml, n = 5). In the clover-infertile ewes, plasma LH levels in BS (1.3 +/- 0.6 ng/ml, n = 12) were similar to those of controls. During AS, plasma LH levels in the clover-infertile ewes (1.0 +/- 0.6 ng/ml, n = 10) remained similar to their BS levels, being significantly (P less than 0.05) higher than LH levels in the controls at this time. These studies indicate that the higher plasma concentrations of LH which have been reported in clover-infertile ewes arise from more frequent LH pulses. Furthermore, in contrast to normal ewes, average plasma LH, reflecting pulse frequency, is not reduced in AS. This supports the view that ingestion of phytooestrogens affects neural centres involved in regulating LH secretion.     

Sex behavior and hormone responses in ewes administered testosterone propionate

Two ewes were administered testosterone propionate and subsequent plasma testosterone concentrations determined and male sex behavior recorded. Initially ewes were administered 50 mg of testosterone propionate every other day for 20 days. Within 6 days following the first injection, concentrations of testosterone in plasma increased to 8.0 to 10.0 ng/ml. A 50 mg injection of testosterone propionate administered every 10 days thereafter maintained concentrations of plasma testosterone at 1.0 to 3.0 ng/ml. Sex behavior tests conducted with non-estrus and estrus ewes showed that both testosterone treated ewes developed male sex behavior similar to a ram. Ewes in estrus were mounted by testosterone treated ewes an average of 6.7 ± 1.2 times during a 10 minute test whereas none of the non-estrus ewes were ever mounted. Silastic implants containing testosterone propionate placed in the ewes 83 days following the first injection maintained concentrations of plasma testosterone at 6.0 to 8.0 ng/ml for a 20 day period. Therefore, administration of testosterone propionate to ewes effectively stimulates male sex behavior and would obviate the necessity for vasectomized rams for estrus detection.     

IgA in uterine tissue: effect of estrous cycle, hormone treatment and intrauterine immunization

In order to determine whether uteri synthesize and store IgA, rats were sacrificed and uterine tissues placed in organ culture for 24 h under the following conditions: (i) at various stages of the estrous cycle, (ii) following ovariectomy and treatment with estradiol, and (iii) after intrauterine immunization with sheep red blood cells (SRBC). When IgA was analyzed in tissues both prior to and following organ culture and in incubation media, no significant increases in total IgA were observed, nor was IgA release into media reduced when cycloheximide, a potent inhibitor of protein synthesis, was present. Analysis of uterine tissues indicated that IgA levels remained relatively constant throughout the estrous cycle and was not markedly increased when ovariectomized rats were treated with estradiol (2 micrograms/day) for 3 days. These results indicate that tissue IgA levels remain relatively constant even during estradiol treatment, when uterine luminal IgA levels are known to increase markedly. Analysis of ovariectomized rats that received intrauterine immunizations with SRBC indicated tenfold greater amounts of IgA in immunized tissues than did uteri from intact or ovariectomized animals. Despite this, no evidence of protein synthesis was obtained, based on measurements of total IgA content before and after organ culture or inhibition of IgA synthesis by cycloheximide. These results indicate that IgA synthesis under the conditions examined is not occurring, but that uterine tissue may serve as a significant storage depot for IgA synthesized either distal to or within uterine tissues at times other than those analyzed in the present study.     

The relationship among ovarian condition, steroid hormones, and estrous behavior in Anolis carolinensis

The lizard Anolis carolinensis ovulates a single egg alternately from each ovary every 14 days. The ovulated egg enters the ipsilateral oviduct, acquires a shell, and is oviposited 18 or 19 days later. Thus, there is only a single egg in one of the oviducts (one-egg condition) during most of the estrous cycle, but there is a 4-5 day period when a mature, shelled egg is in one oviduct while a recently ovulated egg is in the contralateral oviduct (two-egg condition). Analysis of ovarian follicular diameters indicates that the largest follicle in a single ovary exhibits a growth spurt about halfway through its 28-day vitellogenic growth phase. The corpus luteum, once formed from the ovulated follicle, exhibits a linear decrease in weight, becoming fully regressed just before oviposition of the egg in the ipsilateral oviduct. Plasma concentrations of estradiol-17 beta and progesterone are high in two-egg animals. After oviposition, plasma concentrations of progesterone are still high in one-egg animals whereas those of estradiol-17 beta are much lower. These ovarian and hormonal changes during the estrous cycle are discussed in relation to the probable sources of estradiol-17 beta and progesterone, the control of the alternating pattern of ovulation and oviposition, and the role of steroid hormones in female sexual receptivity in this species.     

Daily rhythms of serum leptin in ewes: effects of feeding, pregnancy and lactation

The aim of the present study was to test whether serum concentrations of leptin in ewes vary with a daily rhythm. For this purpose, we examined 24 h serum leptin profiles of ewes exposed to natural photoperiodic conditions and subjected to two different feeding schedules (regular feeding and fasting). The results show for the first time the existence of daily rhythm of plasma leptin in regularly fed ewes, with a minimum during the light phase and a peak during the dark phase. Daily rhythms of serum leptin persisted after 50 h of fasting, although fasting shifted the peak of the rhythm to the beginning of the light phase and significantly reduced daily leptin production. To gain a better understanding of the role of leptin in the temporal organization of physiological events related to pregnancy and lactation, we measured serum leptin profiles throughout 24 h in ewes either during pregnancy or lactation. Daily leptin rhythms were found to persist during pregnancy and lactation, but both physiological conditions altered leptin concentrations. Maternal serum leptin concentration rose between early and mid pregnancy, then decreased in the late pregnancy and during lactation. Daily serum leptin concentration was significantly lower in nonpregnant, nonlactating ewes, compared either to lactating or to early pregnant ewes.     

Abattoir evidence on association between uterine and ovarian abnormalities in Ethiopian highland ewes

A study was conducted on 3275 non-pregnant Ethiopian highland ewes slaughtered at the Addis Ababa municipal abattoir to determine whether uterine and ovarian abnormalities were associated. Each reproductive tract was examined for the presence of ovarian cysts, ovarobursal adhesions and gross uterine abnormalities. The percentage of ewes with ovarian cysts, ovarobursal adhesions and combination of both on the same ovary was 4.3%, 7.6% and 1.7%, respectively. The percentage of uterine abnormalities in tracts with ovarian cysts, ovarobursal adhesions, combined ovarian cysts and ovarobursal adhesions and those with normal ovaries was 46.1%, 31.9%, 46.3% and 4.3%, respectively. The prevalence of uterine abnormalities including hydro/mucometra, endometritis and pyometra was significantly higher (P<0.001) in ewes with abnormal ovarian conditions than in those with normal ovaries. Also, the prevalence of uterine abnormalities was higher (P<0.01) in ewes with ovarian cysts than in those with ovarobursal adhesions alone while in those ewes with co-existing ovarian cysts and ovarobursal adhesions it did not differ (P>0.05) from those with either of these ovarian conditions. Among uterine abnormalities hydro/mucometra was higher (P<0.01) in ewes with abnormal ovaries. In both groups of ewes with and without ovarian abnormalities pyometra was the least prevalent uterine disorder. These results indicate a direct strong association between uterine and ovarian abnormalities in the Ethiopian highland ewes.     

Patterns of estrous cycles, estrous behavior, and circulating prolactin in spring and summer in ewes selected for autumn lambing and exposed to ambient or long-day photoperiods

Estrous behavior in response to ambient and long-day photoperiods was evaluated in ewes developed by 10 years of selection for ability to lamb in autumn. Following October lambing, 67 ewes were moved indoors and exposed to long-day (16L:8D) or ambient photoperiods from February 2 until July 6. Two vasectomized rams with marking harnesses were housed with each group. Estrous behavior was monitored twice weekly. Ewes from the selection line were unresponsive to long days, with no effects on estrous behavior, frequency of ovulation, or circulating prolactin. Adult ewes were anestrus for only 34±3 d, but 2- and 3-years-old ewes were anestrus for 72±7 and 57±10 d, respectively. Frequencies of ovulation based on circulating progesterone concentrations in March, May, and June were 97%, 95% and 52%, respectively, indicating that many ewes that did not exhibit estrus still ovulated. Prolactin concentrations increased from 10 ng/ml in February to 27 ng/ml in March and 173 ng/ml in June but were not affected by light treatment. Ten ewes that failed to exhibit estrus behavior for at most 24 d during the main study were then monitored for 74 additional long days. Nine of 10 ewes did not exhibit estrus for periods similar to 1 or 2 estrus cycles during this period, but eight ewes re-initiated cycles by the end of the study on September 18. Selection for ability to lamb in autumn thus resulted in ewes with an abbreviated seasonal anestrus and reduced sensitivity to long days.     

Circulating concentrations of ovarian steroids and follicle-stimulating hormone (FSH) in ewes with 3 or 4 waves of antral follicle emergence per estrous cycle

The mechanism governing the number of follicle-stimulating hormone (FSH) peaks and emerging follicular waves in ruminants remains unknown. The main purpose of the present study was to examine the relationships between progesterone (P(4)) levels, circulating concentrations of FSH and antral follicular development throughout the interovulatory interval in sheep. We retrospectively analyzed and compared daily serum concentrations of (P4), FSH and estradiol (E2) obtained in cyclic (November-December) Western White Face ewes (Columbia×Rambouillet) that had 3 (n=10) or 4 (n=19) follicular waves per estrous cycle. Follicular growth was monitored in all animals by daily transrectal ultrasonography. Mean P(4) concentrations were greater (p<0.05) in sheep with 4 waves per cycle compared to their counterparts with 3 waves of follicular growth. The ewes with 3 waves exceeded (p<0.05) animals with 4 follicular waves in mean serum FSH concentrations on days 0-2, 6, 7, 9-11, 14 and 15 post-ovulation. Animals with 4 follicular waves exceeded (p<0.05) the ewes with 3 waves in mean serum E(2)> concentrations on days - 1, 2 and 10 of the estrous cycle studied (day 0=ovulation). The present results are supportive of the notion that luteal P(4) is an important endocrine signal, which controls the periodicity of FSH peaks and the number of emerging follicular waves in cyclic ewes.     

Effects of different sexual stimuli on oxytocin release,uterine activity and receptive behavior in estrous sows

This study was designed to assess effects of exogenous oxytocin (OT) on uterine activity, and to compare three different sexual stimuli in their effects on OT release, uterine activity and receptive behavior in estrous sows. Uterine activity was recorded nonsurgically, by transcervical insertion of an open-end catheter into the caudal part of the uterine lumen. After recording spontaneous uterine activity, exogenous OT was administered (Experiment 1), or one of the following stimuli was applied to the sow (Experiment 2): tactile stimuli, i.e. manual stimulation of the sow's back and flanks, tactile stimulation in combination with boar pheromone spray (5alpha-androstenon), or tactile stimuli in the presence of a boar. Both exogenous OT and endogenously released OT increased uterine activity. The effect depended on the uterine activity before treatment, with the effect being greater in those sows with lower uterine activity before treatment. In Experiment 2, boar presence was the only stimulus that elicited a clear, surge-like release of OT, and also clearly increased uterine activity. Release of OT was not necessary for induction of receptive behavior: tactile stimulation alone and in combination with pheromone spray elicited a standing response in one third of the sows, but had no effect on OT release.     

Interaction between lactation, photoperiodism and male effect in German Merino ewes

A study with 93 German Merino ewes was performed from January until the end of March to clarify the relative importance of lactation, photoperiodism and ram effect on cyclic activity and lambing data. Ovarian activity was registered by progesterone concentrations in blood plasma three times weekly. Half of the ewes were kept under supplemental light (20 h/day) for the last 6 weeks of lactation and additionally 3 weeks post-weaning, the other half were kept under natural photoperiod but were weaned simultaneously. Thereafter, light was reduced to natural photoperiod and rams were introduced to half of the ewes, of both light reduced and photoperiod group. Ewes entered cyclicity during lactation gradually, but at weaning 56% of photoperiod ewes and 53% of supplemental light ewes were still acyclic. After weaning, resumption of cyclic activity before ram introduction was more pronounced (P<0.05) in the photoperiod group (75% cyclic) than in the supplemental light group (51% cyclic). Ram introduction led to cyclicity in all ewes. Light reduction without ram slightly increased cyclicity but 57% were still acyclic. In the photoperiod group without ram no ewe entered cyclicity and two ewes even ceased cycling again. Data show that German Merinos still have a remarkable lactational anoestrus but are extremely sensitive to ram. Light reduction has no direct effect on cyclicity but is likely to contribute to the elevated ovulation rate so that a combination with the ram effect led to a higher lambing rate (1.94) compared to photoperiod and ram (1.55).     

Plasma follicle stimulating hormone,ovulation rate and fertility in Merino ewes treated with bovine follicular fluid

Charcoal-treated bovine follicular fluid (bFF) given as four 5-ml subcutaneous injections to 13 Merino-Border Leicester ewes around the time of natural luteolysis suppressed (P<0.01) plasma levels of follicle stimulating hormone (FSH) [from 1.08 ± 0.05 to 0.41 ± 0.03, mean ± s.e.m. of log_e (ng+ 1) /mlplasma]. This was followed (P < 0.01) by hypersecretion or a rebound of FSH (to 1.46 ± 0.11) lasting 32 h in 10 of the treated ewes, and then by a further fall (to 0.73 ± 0.03, P < 0.05) before the surge (1.21 ± 0.07, P < 0.05) associated with the preovulatory surge of luteinizing hormone (LH).Plasma FSH at 56–72 h before the LH surge (i.e., at the time of the FSH rebound) was correlated with the subsequent ovulation rate (n=13, r= + 0.73, P < 0.01). Fewer ewes treated with four injections of 2 or 5 ml of bFF than control ewes (injected with bovine plasma) became pregnant (28 of 41 vs. 38 of 41, χ² = 4.05, P < 0.05), although plasma progesterone was similar at Day 11 in treated and control ewes. It is concluded that plasma FSH during such a rebound influences the subsequent ovulation rate in sheep.