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1.
The amount of β‐endorphin‐like immunoreactivity (β‐END‐LI) in porcine corpora lutea from several stages of the oestrous cycle and the effects of progesterone, oxytocin, and prolactin on β‐END‐LI secretion in vitro by luteal cells were studied. Porcine corpora lutea obtained on days 1–5, 6–10, 11–13, 14–18, and 19–21 of the cycle were used to prepare extracts for β‐END‐LI determination. Additionally, corpora lutea from days 11–13 and 14–18 were enzymatically dissociated and isolated luteal cells were used for further study of β‐endorphin secretion in vitro. Cells were cultured in serum‐free defined M 199 medium (106 cells/ml) at 37°C under 5% CO2 in air, for 12 h. The influences of the following factors on β‐END‐LI secretion by luteal cells were tested: progesterone (10–9, 10–7 and 10–5M ), oxytocin (0.01, 0.1, 1 and 10 ng/ml), and prolactin (0.1, 1, 10 and 100 ng/ml). The β‐END‐LI contents in extracts and media were measured by radioimmunoassay. The tissue concentration of β‐END‐LI was lowest on days 1–5 of the cycle (0.35 ± 0.03 ng/g wet tissue). Subsequently, it constantly increased to the highest value on days 14–18 (16.58 ± 0.52 ng/g wet tissue) and on days 19–21 it declined (11.10 ± 0.52 ng/g wet tissue). Progesterone at a low dose (10–9 M ) resulted in significant (p < 0.05) increases and decreases in β‐END‐LI secretion by luteal cells from days 11–13 and 14–18, respectively. Higher doses of progesterone (10–7 and 10–5 M ) had no effect on β‐END‐LI release, compared with the control group. All dose‐levels of oxytocin used decreased β‐END‐LI secretion by luteal cells on days 11–13 and 14–18 of the cycle. Prolactin at doses of 0.1 and 1 ng/ml on days 11–13, and all doses tested on days 14–18 resulted in decreases in β‐END‐LI release from luteal cells. These results document evident changes in β‐END‐LI content in the pig corpus luteum during its development and indicate the potential roles of progesterone, oxytocin, and prolactin in luteal cell secretion of β‐END‐LI.  相似文献   

2.
Luteolysis has been shown to be correlated with apoptosis in rats, sheep, and cows. In pigs, apoptosis has already been demonstrated as regards atretic follicles. The present study has been conducted to evaluate whether apoptosis occurs during corpora lutea regression in the pregnant pig and to investigate the temporal relationship between apoptosis and functional luteolysis. The apoptotic process has been studied through the research of oligonucleosome fragmentation by means of classical electrophoresis methods and by in situ detection on histological luteal sections. The latter method allows the identification of apoptosis and the localization of apoptotic cells. Pregnant sows were cloprostenol (PGF2α analog) treated and ovariectomized 0, 6, 12, 24, 48, and 72 hr after treatment. Corpora lutea were utilized for progesterone and DNA extraction and in situ evaluation of apoptosis. Clear evidence of apoptosis was seen earlier with the in situ technique (6 hr for stromal tissue, 12 hr for luteal cells) than with the classical method (24 hr). Apoptosis was, however, apparent after plasma and tissue progesterone had reached basal levels. In conclusion, these results are consistent with the hypothesis that apoptosis occurs during luteolysis in pigs. Moreover, the data obtained with the in situ technique made it possible to identify signs of structural regression in stromal tissue first than in parenchymal cells. A two-stage activation of apoptosis has been discussed to explain structural changes that occur during luteolysis after cloprostenol treatment in swine corpora lutea.  相似文献   

3.
Fifty Holstein dairy cows with palpable corpora lutea were divided into two groups. Twenty-five cows were given 500 micrograms of cloprostenol followed by 8 micrograms (2 mL) of buserelin, an analogue of gonadotropin-releasing hormone, and 25 were given cloprostenol followed by saline. Milk was collected for progesterone assay at the time of treatment and two days later. Differences in median progesterone concentrations before and following treatment were not significantly different between the saline and buserelin treated cows (p greater than 0.23).  相似文献   

4.
In mid-September, 1 month before the insertion of intravaginal pessaries to induce sexual activity, blood samples were collected every 4 days from 16 ewe lambs aged 7 months, in order to determine the incidence of ovulations by measurement of plasma progesterone concentrations. It has been studied whether the response to a progestagen treatment of ewe lambs apparently close to puberty could be modified by the onset of the ovarian events preceding puberty. The effect of the presence or absence of ovulations prior to progestagen treatment on the potential reproductive performance (fertility, litter size and fecundity), embryo development [embryo quality and interferon-tau (IFNτ) secretion], luteal function (progesterone secretion in vitro ) and endometrial progesterone content was studied in seven ovulating (Ov+) and nine nonovulating ewe lambs (Ov−) on day 14 after mating. The best potential reproductive results were obtained with Ov+ animals, although these differences could not be initially attributed to either different progesterone secretion in vitro or concentration of endometrial progesterone. Irrespective of the experimental groups, secretion of progesterone by luteal tissue from ewe lambs with normal embryos was significantly greater (p<0.05) than that of animals with abnormal embryos or with no embryos. Normal embryos secreted a higher amount of IFN-τ than those embryos classified as abnormal (p<0.07). In conclusion, ewe lambs which exhibit luteal activity before puberty have the highest levels of reproductive performances after a progestagen treatment. Corpora lutea from ewe lambs with normal embryos had higher rates of progesterone secretion in vitro and their embryos had a higher IFN-τ production by the embryos, indicating greater capacity for subsequent development.  相似文献   

5.
The expression and concentration of follistatin and activin change during oestrous cycle suggesting their involvement in the regulation of follicular development. The aim of this study was to determine the level, source and potential role of follistatin in the sheep ovary. Follistatin in ovarian venous blood, measured by radioimmunoassay, remained at its low level from follicular phase (day ?1 and 0) to mid‐luteal phase (days 11–13) phase but were significantly elevated during the late luteal phase (days 14 and 15) when corpora lutea underwent regression. Western blot analyses of follicular fluid at day 15 of the cycle showed two strong bands at 42 and 45 kDa and weakly stained bands at 39 and 31 kDa. At day 0, these bands became weaker and the 39 kDa band became undetectable. However, there were no differences in follistatin concentrations between ovaries with and without functional corpus luteum (CL) during the whole luteal phase. In addition, although the ovaries of Booroola ewes normally contain more corpora lutea than those of normal merino ewes, follistatin concentrations in both jugular and ovarian venous blood were similar in Booroola and normal merino ewes. It is concluded that the secretion of follistatin from the ovary is not related to the formation of CL or high ovulation rate of Booroola ewes. The elevation in follistatin concentration in follicular fluid and ovarian blood during late luteal phase may indicate a dual role of follistatin in the luteolysis of existing CL and development of new follicle cohort.  相似文献   

6.
The current study aimed to compare luteal function, as measured by corpora lutea dynamics and progesterone secretion, in 10 sows with obesity/leptin resistance genotype (Iberian pig) and 10 females of lean commercial crosses (Large White × Landrace). In all the animals, the oestrous cycle was synchronized with progestagens, and ovulation was induced by exogenous gonadotrophins. Thereafter, number and size of follicles and plasma oestradiol concentration were determined at oestrus detection, and number and size of corpora lutea and progesterone concentration were evaluated from Day 4 to 12 of the cycle. There were no differences between genotypes in follicle population and oestradiol concentration, and ovulation rate (15.2±1.3 in Iberian vs 12.7±1.8 in LWxL sows); however, there was a higher percentage of Iberian than control sows showing luteal cysts (66.7% vs 30%, respectively; p<0.05). In both breeds, both total luteal area and plasma progesterone concentration grew linearly from Day 4 to 8 (p<0.01) and remained more stable between Days 8 and 12, without significant differences between genotypes. In conclusion, current study supports that ovulatory processes and luteal functionality are not the main limiting factors for prolificacy in a pig model of leptin resistance and obesity.  相似文献   

7.
Two hundred and fifty-one cows fresh at least 37 days with normal reproductive tracts and palpable ovarian structures which clinicians believed to be corpora lutea and which were presumed to be producing progesterone were treated with 500 micrograms of cloprostenol. The cows were stratified into three groups based on milk progesterone concentrations in whole milk samples taken at the time of examination. The low group had milk progesterone concentrations less than or equal to 1 ng/ml, the intermediate group had milk progesterone concentrations between 1 and 3 ng/ml, and the high group had milk progesterone concentrations greater than or equal to 3 ng/ml. The proportion of cows in each group inseminated within 5 days of treatment and the fertility at that breeding were compared. There were no significant differences among the groups with respect to the proportion of cows that came into estrus within 5 days. However, the conception rate of the high group (54%) was significantly greater than that of the intermediate group (26%). To study the relationship between practitioner experience and diagnostic accuracy the proportion of cows with low, intermediate and high concentrations of progesterone selected by clinicians with more than 3 years experience was compared to that for clinicians with 3 years of experience or less. Less experienced clinicians were significantly more likely to make a false positive diagnosis of functional luteal tissue in cows with palpable ovarian structures than were more experienced clinicians.  相似文献   

8.
This study was designed to verify whether fasting influences vascular endothelial growth factor (VEGF) production and VEGF, VEGF receptor-2 (VEGFR-2) as well as endothelin (ET) system members (endothelin converting enzyme-1, ECE-1; ET-1; endothelin receptor type A, ET-A) mRNA expression in pig corpora lutea; furthermore, we wanted to assess whether fasting affects steroidogenesis in luteal cells. Eight prepubertal gilts were induced to ovulate and were randomly assigned to two groups: (A) n = 4, normally fed; and (B) n = 4, fasted for 72 h starting 3 days after ovulation. At the end of fasting, ovaries were removed from all the animals and corpora lutea (CLs) were collected. VEGF and steroid levels in luteal tissue were determined by ELISA and RIA, respectively; VEGF, VEGFR-2, ET-1, ET-A and ECE-1 mRNAs expression was measured by real-time PCR. VEGF protein levels were similar in the two groups, while all steroid (progesterone, testosterone, estradiol 17beta) concentrations were significantly (P < 0.001) higher in CLs collected from fasted animals compared with those from normally fed gilts. VEGF, VEGFR-2, ET-1 and ECE-1 (but not ET-A) mRNA expression was significantly lower (P < 0.05) in fasted versus normally fed animals. The overall conclusion is that all the parameters studied are affected by feed restriction, but the mechanisms activated at luteal level are possibly not fully adequate to compensate for nutrient shortage.  相似文献   

9.
The ability of ovine placental lactogen (oPL) to stimulate progesterone secretion of porcine luteal cells isolated from ovaries in different stages of the oestrous cycle and to support the luteotropic action of PGE2 or to protect the corpus luteum (CL) against the luteolytic action of PGF2 alpha was investigated. oPL in all doses used had no effect on progesterone production of cells isolated from early developing corpora lutea while in doses of 1 and 10 ng/ml it increased oestradiol secretion by this type of cells. In doses of 1, 10 and 100 ng/ml it also increased progesterone secretion of cells isolated from mature corpora lutea in a dose-dependent manner. No influence on progesterone production of cells isolated from regressing corpora lutea was observed. oPL added to the culture media had no effect on PGE2-stimulated progesterone production by cells isolated from mature corpora lutea. However, it exerted a protective effect against the luteolytic action of PGF2 alpha observed in cultures treated with PGF2 alpha alone or in combination with PGE2 in a ratio of 4:1. These studies provide evidence that oPL is luteotropic and supports progesterone production in swine. The fact that oPL acted directly on ovarian steroidogenesis suggests that it may also play some role under non-pregnant physiological conditions. Future studies of structural and functional proteins secreted by the porcine conceptus will help resolve this uncertainty.  相似文献   

10.
The aim of this study was to evaluate luteal dynamics in the Santa Inês ewes using colour Doppler (CD) ultrasonography. Oestrus was synchronized in nulliparous females (n = 18), and subsequently, they were only teased (n = 6) or teased and mated (n = 12). Blood samples were collected daily for plasma progesterone (P4) concentrations. Ultrasonographic images of corpora lutea (CL) in CD mode were obtained for further analysis in its largest diameter. The CD mode allowed an early sequential monitoring of CL that was visualized by the first time 0.77 ± 0.62 days after ovulation, with luteal area 29.68 ± 13.21 mm2. During the luteogenesis, a progressive increase was observed, followed by a plateau of luteal area, vascularization area and plasma concentrations of P4 reaching maximum values in D11 (124.0 ± 38.0 mm2, 52.78 ± 24.08 mm2 and 11.23 ± 4.89 ng/ml, respectively). In the luteolysis, the plasma concentrations of P4 decreased sharply, whereas luteal and vascularization area gradually. The vascularization area was positively correlated with plasma concentrations of P4 during the luteogenesis (r = 0.22) and luteolysis (r = 0.48). The luteal dynamics of Santa Inês ewes showed patterns similar to those observed in other sheep breeds studied. The CD ultrasonography has the potential to be used as a tool to assess luteal function in sheep.  相似文献   

11.
The objective of this study was to assess the efficacy of two reduced doses vs a high/luteolytic dose of cloprostenol on luteolytic activity and synchronization of oestrus in cyclic goats. Experiment 1, included 24 goats randomly allocated to three groups: control group (group H) received a single high dose of cloprostenol (87.5 μg; 1.0 ml; i.m.) and M and L groups, which received half (43.75 μg; 0.5 ml) and a third (26.25 μg; 0.3 ml) of the highest dose, respectively. Experiment 2, included 24 goats randomly assigned to the same experimental groups. Each group was treated using two injections of cloprostenol administered 10 days apart to synchronize oestrus. Transrectal ultrasonographic scanning (US) was performed to detect the presence, size and development of corpora lutea and ovarian follicles. Furthermore, detection of oestrus was performed every 12 h between 24 and 72 h after the second injection of cloprostenol, and the luteolytic effect was verified by US. In Experiment 1, all goats that had corpora lutea at timing of treatment regressed their corpora lutea. In Experiment 2, the occurrence of oestrus and the interval between treatment to onset of oestrus were: 100%, 49.5 ± 3.0 h; 100%, 51.0 ± 3.0 h; and 75%, 56.0 ± 3.5 h for H, M and L groups, respectively. The development of preovulatory follicles and occurrence of subsequent corpora lutea were similar among groups. In summary, the use of 26.25 μg of cloprostenol is effective for the synchronization of oestrus in cyclic goats.  相似文献   

12.
Twelve Hereford cross Friesian cows received subcutaneous implants containing 6 mg norgestomet and intramuscular injections of 5 mg oestradiol valerate and 3 mg norgestomet. Six of the cows also received 0.5 mg cloprostenol eight days later and all implants were removed on day 9. When treatment was commenced between days 3 and 5 of the ovarian cycle, luteal function was not prevented although the luteal phase was shortened in some cases. When treatment was commenced between days 8 and 14 of the cycle progesterone concentrations remained above basal levels for five to seven days. Cows with corpora lutea that were given cloprostenol underwent rapid luteolysis. It is concluded that oestradiol valerate does not control luteal function adequately, particularly if administered early in the cycle, and this may explain failure of oestrus synchronisation in some cases. Administration of prostaglandin 24 hours before norgestomet implant removal may improve the degree of oestrus synchronisation in groups of cyclic cows.  相似文献   

13.
Seven hundred and six bovine corpora lutea in various luteal stages were examined morphologically and endocrinologically to discover whether there is a relationship between the presence of a central cavity in the corpus luteum and infertility in cows. A central cavity was found in 42.1 per cent (80/190) of developing corpora lutea, 33.7 per cent (126/374) of fully developed corpora lutea, 11.1 per cent (7/63) of corpora lutea in regression and in 5.1 per cent (4/79) of corpora lutea in pregnancy. There was no significant difference between the rates of appearance of midcycle follicles in corpora lutea either with or without a central cavity. The proportion of luteal cell type 1 was higher in fully developed corpora lutea with a central cavity than without, but the reverse was found with luteal cell type 2. In fully developed corpora lutea the concentration of progesterone in the luteal tissue was significantly higher in corpora lutea with a central cavity. These results suggest that there are some differences in luteal function between corpora lutea with and without a central cavity, but that the presence of a central cavity in a corpus luteum cannot be described as a pathological condition.  相似文献   

14.
The aim of this study was to document the expression and localization of VEGF system comprising of VEGF isoforms (VEGF 120, VEGF 164 and VEGF 188) and their receptors (VEGFR1 and VEGFR2) in buffalo corpus luteum (CL) obtained from different stages of the oestrous cycle. Real‐time RT‐PCR (qPCR), Western blot and immunohistochemistry were applied to investigate mRNA expression, protein expression and localization of examined factors. In general, all the components of VEGF system (the VEGF isoforms and their receptors) were found in the water buffalo CL during the oestrous cycle. The mRNA as well as protein expression of VEGF system was highest during the early and mid‐luteal phase, which later steadily decreased (p < 0.05) after day 10 to reach the lowest level in regressed CL. As demonstrated by immunohistochemistry, VEGF protein was localized predominantly in luteal cells; however, VEGFR1 and VEGFR2 were localized in luteal cells as well as in endothelial cells. In conclusion, the dynamics of expression and localization of VEGF system in buffalo corpora lutea during the luteal phase were demonstrated in this study, indicating the possible role of VEGF system in the regulation of luteal angiogenesis and proliferation of luteal as well as endothelial cells through their non‐angiogenic function.  相似文献   

15.
This study describes the localization of progesterone receptors (PR) in the bovine ovary. Ovaries were obtained from 11 non‐pregnant and two pregnant cows. Progesterone receptors were visualized by immunohistochemistry on paraffin sections. Nuclear staining for PR was observed in cells of the follicles, corpora lutea, theca layers, surface epithelium, tunica albuginea, and in superficial and deep stroma cells. No staining was noticed in apoptotic bodies of atretic follicles. Expression of PR in follicle cells indicates an intrafollicular role of progesterone. The higher expression in thecal cells compared with follicle cells indicates that thecal cells mediate some effects of progesterone on the follicular development. Superficial stroma cells showing high expression might have a similar influence on primordial and primary follicles. In general, luteal cells had a lower expression than follicle cells, which may be explained by the down‐regulatory effect of locally produced progesterone. The lower expression in luteal cells during pregnancy can be due to the longer life span of this corpus luteum and concomitant degeneration of its PR. The high and rather constant expression of PR in cells of the surface epithelium remains to be elucidated.  相似文献   

16.
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17.
Experiments were conducted to determine the effect of additional gonadotropic support on induced corpora lutea of anestrous ewes. In one series of experiments, ewes were superovulated and half the ewes received an i.v. injection of 500 IU human chorionic gonadotropin (hCG) on day 5 after ovulation. Corpora lutea were collected from both groups on day 10 after ovulation. Dissociated corpora lutea collected from ewes which received additional hCG contained proportionately more large luteal cells than did those from control ewes (P<.05). In neither cell type was content of receptors for luteinizing hormone (LH) or secretion of progesterone in response to LH affected by an additional injection of hCG. Large cells from anestrous ewes produced more progesterone in response to LH (P<.05) than did large cells from similarly treated ewes during the breeding season. Small cells collected during either season responded similarly to LH. In another series of experiments, anestrous ewes were induced to ovulate and were exposed to fertile rams. Half the ewes received an i.v. injection of 500 IU hCG on day 5 after ovulation. Serum content of progesterone was higher on day 10 in ewes which received hCG 5 days earlier than in control ewes, although progesterone levels declined to generally nondetectable levels in nonpregnant ewes of both groups by day 16. Pregnancy rates in the two groups were not different. We concluded that additional gonadotropic support affects the morphology and function of corpora lutea from anestrous ewes and may be useful for enhancing fertility during the nonbreeding season.  相似文献   

18.
The aim of the present study was to evaluate the effects of cholesterol on progesterone production during long‐term culturing of luteal cell subpopulations at early and late luteal stages of the goat corpora lutea. Corpora lutea were collected from Angora goats on days 5 and 15 of the oestrous cycle. Luteal cells were isolated by collagenase digestion. The cells were separated into two distinct subpopulations by Percoll density‐gradient centrifugation. Both subpopulations of luteal cells staining positively for 3β‐HSD activities (5 × 104 cell/well) were cultured with or without 22(R)‐hydroxycholesterol (22R‐HC) in serum‐free culture medium for periods of up to 7 days. Cells were incubated with serum (10%) for the first 18 h of incubation followed by serum‐free medium. Cell treatment (10 and 20 μg/ml) was performed on days 1, 3 and 5. Treatment of cells with both concentrations of 22R‐HC resulted in significant (p < 0.01) and dose‐dependent stimulation (p > 0.05) on progesterone production in both fractions of cells throughout 7 days of incubation. Treatment of the cells with cholesterol resulted in 2.5‐ and 9.0‐fold increases in progesterone accumulation on day 3 of incubation. Steroid production was maintained throughout the incubations when cells are incubated in serum‐free media treated with cholesterol and ITS premix. Cells collected from higher density of percoll layers produced 2.82 and 2.32 times more progesterone, in comparison to the lover density percoll layer, on days 5 and 15 of the oestrous cycle in untreated cell groups, respectively. Progesterone accumulation was decreased as incubation time advanced in all groups of untreated cells. These results demonstrated that goat luteal cell subpopulations secrete substantial amounts of progesterone in response to cholesterol treatment at least for 7 days, and cholesterol is required as progesterone precursor for maintaining a high‐level steroidogenesis during long‐life culturing of both cell subpopulations.  相似文献   

19.
Luteolytic capacity is defined as the ability of corpora lutea (CL) to undergo luteolysis after prostaglandin (PG) F2alpha treatment. The mechanisms causing acquisition of luteolytic capacity are not yet identified but CL without luteolytic capacity have PGF2alpha receptors and respond to PGF2alpha with some changes in gene expression. Inhibition of progesterone biosynthesis is a key feature of luteolysis and therefore we postulated that genes involved in progesterone biosynthesis would be regulated by PGF2alpha differently in CL with or without luteolytic capacity. Gilts on day 9 after estrus (lack luteolytic capacity) or day 17 of pseudopregnancy (with luteolytic capacity) were treated with saline or a PGF2alpha analog (cloprostenol) and CL were collected 0.5 (Experiment I) or 10 h (Experiment II) later. In Experiment III, large luteal cells from CL on day 9 or 17 were cultured for 1, 12 and 24h with or without PGF2alpha. PGF2alpha decreased LDL receptor mRNA (27%), steroidogenic acute regulatory protein (StAR) mRNA (41%), StAR protein (75%), LH receptor mRNA (55%), and LH receptor protein (45%) at 10 h after treatment in day 17 but not day 9 CL. PGF2alpha increased DAX-1 mRNA at 0.5 h (43%) and 10 h (46%) after PGF2alpha in day 17 but not day 9 CL but decreased 3betaHSD mRNA ( approximately 20% at 10 h) in both days 9 and 17 CL. In vitro, PGF2alpha decreased StAR mRNA at 12 h only in day 17 luteal cells; however, continuous treatment with PGF2alpha for 24 h decreased StAR mRNA in both days 9 and 17 luteal cells. Thus, luteolytic capacity involves a critical change in responsiveness of DAX-1, StAR, and LH receptor to PGF2alpha that results in inhibition of luteal progesterone biosynthesis.  相似文献   

20.
Erratum     
This study describes the localization of progesterone receptors (PR) in the bovine ovary. Ovaries were obtained from 11 non‐pregnant and two pregnant cows. Progesterone receptors were visualized by immunohistochemistry on paraffin sections. Nuclear staining for PR was observed in cells of the follicles, corpora lutea, theca layers, surface epithelium, tunica albuginea, and in superficial and deep stroma cells. No staining was noticed in apoptotic bodies of atretic follicles. Expression of PR in follicle cells indicates an intrafollicular role of progesterone. The higher expression in thecal cells compared with follicle cells indicates that thecal cells mediate some effects of progesterone on the follicular development. Superficial stroma cells showing high expression might have a similar influence on primordial and primary follicles. In general, luteal cells had a lower expression than follicle cells, which may be explained by the down‐regulatory effect of locally produced progesterone. The lower expression in luteal cells during pregnancy can be due to the longer life span of this corpus luteum and concomitant degeneration of its PR. The high and rather constant expression of PR in cells of the surface epithelium remains to be elucidated.  相似文献   

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