Antioxidant enzymatic defence systems in sheep corpus luteum throughout pregnancy.
(2004)
Journal - Reproduction (Cambridge, England) (England )
Abstract :
The activities of copper, zinc-superoxide dismutase (SOD1), manganese SOD (SOD2), glutathione peroxidase (GPX), glutathione reductase (GSSG-R) and glutathione S-transferase (GST) were studied in sheep corpora lutea (CL) obtained on days 15, 40, 60, 80 and 128 of pregnancy. Maintained enzymatic activity of SOD1, SOD2, GPX, GSSG-R and GST were found in the sheep CL throughout pregnancy. Enzymatic activity of SOD1, GPX and GST increased significantly from day 15 to day 40 of pregnancy, and thereafter remained constant until day 128. SOD2 and GSSG-R activities were not different between any days of pregnancy examined. Apoptotic luteal cells identified by the terminal deoxynucleotidyl transferase-mediated fluorescein-dUTP nick-end labelling were very rarely observed, and their incidence (less than 0.5%) was not different between days of pregnancy. These results showed that the activities of antioxidant enzymes in the sheep CL are subject to major changes during early pregnancy, suggesting that the CL of early pregnancy may be rescued from luteolysis through increasing activities of key antioxidant enzymes and inhibition of apoptosis. Maintained levels of antioxidant enzymes in the CL throughout pregnancy may be linked to reactive oxygen species continuously generated in the steroidogenically active luteal cells, and may be involved in the maintenance of luteal steroidogenic activity and cellular integrity.
| ISSN : | 1470-1626 |
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| Mesh Heading : | Animals Antioxidants Apoptosis Corpus Luteum Corpus Luteum Maintenance Female Gestational Age Glutathione Peroxidase Glutathione Reductase Glutathione Transferase In Situ Nick-End Labeling Pregnancy Pregnancy, Animal Progesterone Sheep Superoxide Dismutase metabolism cytology analysis metabolism analysis metabolism analysis metabolism blood analysis metabolism |
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| Mesh Heading Relevant : | analysis enzymology metabolism |
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Corpus luteum derived copper, zinc-superoxide dismutase serves as a luteinizing hormone-release inhibiting factor in sheep.
(2003)
Journal - Molecular and cellular endocrinology (Ireland )
Abstract :
In the present study, we report the purification and characterization of a polypeptide from the sheep corpus luteum of pregnancy with a potent luteinizing hormone-release inhibiting factor (LH-RIF) bioactivity that stained as a single band in SDS-PAGE with an apparent molecular mass of 16000 Da. The amino acid sequences obtained after sequence analysis of peptides derived from the trypsin digestion of LH-RIF were subjected to a protein data bank search and were found to be identical with regions of sheep copper, zinc-superoxide dismutase (Cu,Zn-SOD). The measured mass of LH-RIF (15604.2+/-1.9 Da) was found to be similar to the theoretical mass of sheep Cu,Zn-SOD (15603.5 Da), with a disulfide bond and N acetylated alanine at the N-terminus. The inhibitory action of Cu,Zn-SOD on pulsatile LH secretion would suggest that this antioxidant may play an important role, either independently or in concert with some neurotransmitters, in the neuroendocrine regulation of sheep female reproductive function.
| ISSN : | 0303-7207 |
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| Mesh Heading : | Animals Corpus Luteum Electrophoresis, Polyacrylamide Gel Female Luteinizing Hormone Molecular Weight Pregnancy Sequence Analysis, Protein Sequence Homology, Amino Acid Sheep Superoxide Dismutase secretion chemistry isolation & purification |
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| Mesh Heading Relevant : | enzymology antagonists & inhibitors physiology |
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Effects of pregnancy on pulsatile secretion of LH and gonadotrophin-releasing hormone-induced LH release in sheep: a longitudinal study.
(2003)
Journal - Reproduction (Cambridge, England) (England )
Abstract :
Pulsatile LH secretion and its control throughout pregnancy have not been fully determined in sheep. Expt 1 determined the patterns of LH secretion in five ewes on days 10, 20, 60 and 120 of pregnancy and on day 10 postpartum, compared with those on day 10 of the oestrous cycle. Mean (+/- SEM) concentrations of LH declined steadily throughout pregnancy (ANOVA, P < 0.01) and were lower (P < 0.01) on day 60 (0.19 +/- 0.3 ng ml(-1)) and on day 120 (0.18 +/- 0.4 ng ml(-1)) of pregnancy than on day 10 of the oestrous cycle (0.55 +/- 0.04 ng ml(-1)). This decrease was due to a significant reduction in the number and the amplitude of LH pulses. Only on day 120 of pregnancy were progesterone concentrations higher (P < 0.01) than on day 10 of the oestrous cycle. Although concentrations of progesterone on day 10 postpartum were barely detectable, mean LH concentration (0.45 +/- 0.09 ng ml(-1)) was not different from that on day 10 of the oestrous cycle. Expt 2 examined the LH responses in a separate group of four ewes to a physiological dose of GnRH (0.2 microg) on days 10, 20, 60 and 120 of pregnancy and on day 10 postpartum, compared with those on day 10 of the oestrous cycle. The area under the LH response curve and the maximum LH concentrations induced by GnRH declined steadily throughout pregnancy (ANOVA, P < 0.01) and were lower (P < 0.01) on days 60 and 120 of pregnancy than on day 10 of the oestrous cycle, but these parameters were not different between day 10 postpartum and day 10 of the oestrous cycle. Expt 3 examined the LH responses in a separate group of four ewes to a potent GnRH agonist, buserelin (0.5 microg), on days 10, 60 and 120 of pregnancy. The area under the LH response curve and the maximum LH concentrations induced by GnRH were lower (P < 0.01) on days 60 and 120 than on day 10 of pregnancy, but were not different between days 60 and 120. This longitudinal study demonstrates that the pulsatile LH release and pituitary responsiveness to GnRH decreases progressively as pregnancy advances, but does not support the hypothesis that high concentrations of progesterone are solely responsible for the inhibition of pulsatile LH secretion and GnRH-induced LH release during pregnancy in sheep.
| ISSN : | 1470-1626 |
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| Mesh Heading : | Animals Area Under Curve Buserelin Dose-Response Relationship, Drug Female Gestational Age Gonadotropin-Releasing Hormone Luteal Phase Luteinizing Hormone Pituitary Gland Postpartum Period Pregnancy Pregnancy, Animal Progesterone Secretory Rate Sheep pharmacology blood blood blood blood |
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| Mesh Heading Relevant : | pharmacology secretion drug effects blood physiology |
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Effects of luteectomy on the maintenance of pregnancy, circulating progesterone concentrations and lambing performance in sheep.
(2000)
Journal - Reproduction, fertility, and development (AUSTRALIA )
Abstract :
In sheep, there have been few and conflicting data regarding the necessity of the corpus luteum (CL) for the maintenance of pregnancy. The aims of the present study were to examine the effect of luteectomy on and after Day 50 of pregnancy on maternal plasma progesterone concentrations and the progression of pregnancy, to determine the minimum placental progesterone support required for the maintenance of pregnancy, and to evaluate the effect of luteectomy on lambing performance. In Experiment 1, four ewes luteectomized on Day 50 of pregnancy aborted 2-7 days after surgery, whereas pregnancy progressed and parturition occurred between Days 143 and 149, with live lambs, in three of four ewes and in four ewes luteectomized on Days 60 and 70 of pregnancy respectively. The mean (+/- SEM) progesterone concentrations on the day before and one day after luteectomy decreased from 4.87+/-0.85 to 0.42+/-0.06 ng mL(-1) (P<0.01), from 4.57+/-0.51 to 0.80+/-0.12 ng mL(-1) (P<0.02) and from 6.05+/-0.52 to 1.67+/-0.11 ng mL(-1) (P<0.01), respectively, for the ewes luteectomized on Days 50, 60 and 70 of pregnancy. The fall in progesterone concentrations was 90%, 80% and 71%, respectively, for the ewes luteectomized on Days 50, 60 and 70 of pregnancy. In Experiment 2, pregnancy progressed in four ewes luteectomized on Day 70 and parturition occurred between Days 146 and 149, with live lambs. The mean progesterone concentrations declined (P<0.01) from 6.9+/-0.7 ng mL(-1) on the day before luteectomy to 2.1 = 0.3 ng mL(-1) the day after surgery. The concentrations of progesterone in blood collected every 3 h during a 24-h period were stable on Days 60 and 80 of pregnancy, but they were lower (P<0.03) on Day 80 than on Day 60 of pregnancy, for each time period examined. In Experiment 3, the gestation length and birthweights of single, twin and triplet lambs were not different between the control intact ewes (n = 111) and the ewes luteectomized on Days 70-80 of pregnancy (n = 71). Lamb mortality was not different between the two groups (7.2% v. 8.4%, control v. luteectomized). In conclusion, these results showed that (1) the sheep CL is necessary to maintain pregnancy until at least Day 60, (2) progesterone withdrawal induced by luteectomy on and after Day 50 of pregnancy must be of a critical magnitude to provoke abortion, (3) after Day 60 of pregnancy, the CL and the placenta together secrete more progesterone than required for pregnancy maintenance, (4) there is no apparent 24-hour rhythm in maternal plasma progesterone concentrations before and after luteectomy, and (5) luteectomy at mid pregnancy has no apparent effect on gestation length, lamb birthweight or lamb mortality.
| ISSN : | 1031-3613 |
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| Mesh Heading : | Animals Birth Weight Corpus Luteum Female Fetal Death Gestational Age Litter Size Male Pregnancy Pregnancy Outcome Pregnancy, Animal Progesterone Sheep surgery |
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| Mesh Heading Relevant : | physiology physiology blood physiology |
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The secretory patterns of growth hormone in pregnant and hysterectomized ewes.
(1999)
Journal - European journal of endocrinology / European Federation of Endocrine Societies (ENGLAND )
Abstract :
This work was undertaken to determine the secretory patterns of GH during pregnancy, and to evaluate the effect, if any, of hysterectomy during early pregnancy on subsequent secretion of GH in ewes. The concentrations of GH were determined in the plasma of jugular blood samples collected at 15-min intervals during a 6-h period on days 20, 40, 60, 80, 100 and 120 post-mating, and three times per week between days 29 and 120 post-mating from 5 pregnant ewes and from 5 ewes from which the gravid uterus was removed on day 30 post-mating. A pulse analysis program (Pulsar) was used to analyse the secretory patterns of GH in individual profiles of the serial sampling period. In the two groups of ewes, peripheral concentrations of GH fluctuated in an episodic manner during the frequent blood sampling of any stage of the post-mating period examined. The overall GH concentrations, the basal GH concentrations, the frequency and the amplitude of GH pulses remained fairly stable between days 20 and 120 post-mating in the two groups of ewes. The parameters of GH secretion were not different between the two groups of ewes. The secretory patterns of GH, as determined in plasma of blood collected three times per week between days 29 and 120 post-mating were also not different between the two groups of ewes. In conclusion, results of this study show that (i) the pulsatile secretion of GH does not change as pregnancy advances, and (ii) hysterectomy performed during early pregnancy does not subsequently affect the secretory patterns of GH. These findings suggest that the gravid uterus and/or the feto-placental unit secretory products are unlikely to be involved in the control of GH secretion during pregnancy in the ewe.
| ISSN : | 0804-4643 |
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| Mesh Heading : | Animals Female Growth Hormone Periodicity Pregnancy Pregnancy, Animal Sheep |
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| Mesh Heading Relevant : | Hysterectomy secretion physiology physiology |
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The secretion of prolactin in intact and lutectomized pregnant ewes. Effect of the anti-progesterone steroid RU 486.
(1999)
Journal - Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie (FRANCE )
Abstract :
To study the role, if any, of luteal factors in the control of prolactin secretion during the last two thirds of pregnancy in the ewe, we examined: a) the effect of RU 486 administration on prolactin secretion on days 97, 112 and 131 of pregnancy in five intact ewes and in five ewes from which the corpus luteum (CL) was removed on day 78 of pregnancy; and b) the secretory patterns of prolactin on days 60, 80, 100 and 120 of pregnancy in five intact ewes and in five ewes from which the CL was removed on day 70 of pregnancy. In a pilot experiment, we showed that daily i.v. injections (from day 91 to day 105 of pregnancy) of RU 486 at a dose of 50 mg caused a marked release of prolactin, without any effect on the secretion of progesterone and progression of pregnancy. In experiment 1, a single i.v. injection of 50 mg of RU 486 resulted in a significant (P < 0.01) increase in plasma prolactin concentrations on any day of pregnancy examined in the intact and lutectomized ewes. The prolactin responses (the maximum concentrations, the time to maximum concentrations and the area under the response curves) were not different between the two groups in any stage of pregnancy examined. In the two groups, spontaneous parturition occurred at term with alive lambs. There was no difference between the two groups in gestation length and lamb birth weight. In experiment 2, we showed that plasma concentrations of prolactin fluctuated in a pulsatile manner during the last two-thirds of pregnancy. The mean prolactin concentrations, the frequency and the amplitude of prolactin pulses were not significantly different between the intact and the lutectomized ewes in any stage of pregnancy examined. In conclusion, these experiments demonstrated that the ovine CL of pregnancy is not involved in the control of prolactin secretion in the ewe. The stimulation of prolactin secretion by the RU 486 is probably due to its anti-progesterone action exerted at the level of the receptor. The placental progesterone plays a central role in the control of prolactin secretion during the last two-thirds of pregnancy.
| ISSN : | 0764-4469 |
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| Mesh Heading : | Animals Corpus Luteum Female Mifepristone Pregnancy Pregnancy, Animal Prolactin Sheep Time Factors surgery drug effects blood |
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| Mesh Heading Relevant : | physiology pharmacology physiology secretion |
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Intracerebroventricular administration of copper-zinc superoxide dismutase inhibits pulsatile luteinizing hormone secretion in ovariectomized ewes.
(1999)
Journal - Neuroscience letters (IRELAND )
Abstract :
Intracerebroventricular (i.c.v.) injection of an inhibitor of nitric oxide synthase (NOS) abolishes pulsatile luteinizing hormone (LH) secretion. It has been demonstrated that structural and functional analogs of copper-zinc superoxide dismutase (Cu,Zn-SOD) inhibit neuronal NOS. The present study examined the ability of Cu,Zn-SOD to affect pulsatile LH release in the ewe. Bovine Cu,Zn-SOD was administrated into the third cerebral ventricle of unanesthetized, freely moving, ovariectomized (OVX) ewes. Jugular blood samples were taken every 15 min for 5 h before and 8 h after i.c.v. injections. In a pilot trial using three OVX ewes, i.c.v. injection of Cu,Zn-SOD at a dose of 0.5, 1.0 or 2.0 microg in 100 microl saline decreased plasma LH levels and abolished LH pulses, without affecting FSH secretion. In the main experiment, i.c.v. injection of 100 microl saline had no effect on mean LH levels and LH pulse frequency, whereas i.c.v. injection of Cu,Zn-SOD at a dose of 1 microg/100 microl saline significantly (P < 0.01) decreased mean LH levels and LH pulse frequency. In conclusion, this study provides the first evidence for the role of Cn,Zn-SOD in the control of LH secretion at the level of the brain in female mammals.
| ISSN : | 0304-3940 |
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| Mesh Heading : | Animals Depression, Chemical Female Follicle Stimulating Hormone Injections, Intraventricular Luteinizing Hormone Mice Sheep Superoxide Dismutase blood administration & dosage |
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| Mesh Heading Relevant : | Ovariectomy secretion pharmacology |
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Absence of regular pulsatile LH secretion during pre- and post-implantation periods in sheep.
(1999)
Journal - European journal of endocrinology / European Federation of Endocrine Societies (ENGLAND )
Abstract :
Two experiments were conducted to determine the patterns of LH secretion and to evaluate the LH responses to pulsatile administration of GnRH during early pregnancy in ewes. In experiment 1, pregnant ewes (n=16) were used to determine the concentration of LH in plasma of jugular blood samples collected every 15 min for 6h before (day 10 post-mating) and after (days 20 and 30 post-mating) implantation. In experiment 2, the pituitary LH responses to exogenous pulsatile administration of GnRH were examined on day 10 post-mating in 4 pregnant ewes. A small dose of GnRH (200 ng/ml saline) was injected (i.v.) every 3h and jugular blood samples were collected every 15 min for 12h beginning at the onset of GnRH administration and continuing through the 4th GnRH pulse. During the frequent-sample bleeding at any of the stages of pregnancy examined, LH concentrations oscillated in a pulsatile manner. However, pulsatile LH release occurred irregularly and infrequently. Overall mean LH concentrations, frequency and amplitude of LH pulses were not significantly different between any of the stages of pregnancy examined. Pulsatile administration of GnRH on day 10 post-mating induced regular pulses of LH. In conclusion, these data demonstrate that: (i) pulsatile LH secretion occurs irregularly during early pregnancy, and (ii) the absence of regular pulsatile LH release during early pregnancy is not attributed to a lack of pituitary responsiveness to GnRH.
| ISSN : | 0804-4643 |
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| Mesh Heading : | Animals Embryonic Development Estrus Synchronization Female Gonadotropin-Releasing Hormone Injections, Intravenous Luteinizing Hormone Male Pituitary Gland Pregnancy Pregnancy Outcome Pulsatile Flow Radioimmunoassay Sheep physiology blood physiology physiology secretion |
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| Mesh Heading Relevant : | physiology administration & dosage secretion physiology |
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