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PubMed1984

The effect of experimental induced hypocalcaemia on uterine activity in the sow during parturition and post-partum.

Uterine activity was measured by monitoring intrauterine pressure changes using ballon-tipped catheters placed in the lumen. An infusion rate of Na(2)EDTA of 35 mg/Kg/h gave a chelation rate equivalent to the rate of calcium mobilisation, and when infused at a level greater than this, resulted in a reduction in plasma calcium concentrations and a concomitant reduction in uterine activity. In three of the four sows infused intrapartum, there was complete cessation of uterine activity; however, plasma calcium concentrations of less than 6 mg 100 ml resulted in a reduction in uterine activity at this stage of parturition. The uterus of the sow post-partum appeared to be more sensitive to the effects of hypocalcaemia with reduced uterine activity when plasma calcium concentrations fell below 8.2 mg 100 ml and complete cessation of activity between 6 and 7 mg 100 ml . Although there was evidence of a delay in the expulsion of piglets in the hypocalcaemic sows, there was no evidence of an increased number of stillborn piglets compared with the two control sows.

Journal Article↗
PubMed1985

Induction of parturition in water buffaloes (Bubalus bubalis ).

Parturition was induced in ten buffaloes by combining treatments of dexamethasone and vetoestrol, so that they calved about one month before the expected term. Either dexamethasone alone (Group B) or dexamethasone and vetoestrol (Group C) was used. Another five animals served as controls (Group A). Calving was induced in four animals in group B and three animals in group C after two injections of the compounds four days apart. The average time from first injection to calving for these animals was 117.22 hr and 117.66 hr for groups B and C respectively. Induced calves weighed less at birth (P < 0.05) averaging 24.4 and 26.2 kg for groups B and C respectively, than controls (Group A; 30.20 kg). The body weight gain/week among calves was not significantly different (P > 0.05). The service period, number of services/conception and the milk yield of the buffaloes induced to calve was not significantly different (P > 0.05) from their previous records.

Journal Article↗
PubMed1985

Parturition control in sows with a prostaglandin analogue (alfaprostol).

The objective of this study was to determine the dose of alfaprostol (18, 19, 20-trinor-17-cyclohexyl-13, 14 didehydro-PGF(2)alpha-methylester) and the day of administration most effective in inducing sows to farrow during normal working hours (0700 to 1700). One-hundred forty multiparous crossbred sows, taken from a herd whose mean gestation length was 114.3 days, were assigned to one of five treatment groups: 1) control vehicle-propylene glycol, 2) 0.5 mg alfaprostol (AP). 3) 1 mg AP, 4) 2 mg AP and 5) 3 mg AP. Sows received an intramuscular injection of AP between 0800 and 0830 on either day 111, 112 or 113 of gestation. Parameters studied included interval from injection to birth of first pig, farrowing interval, total number of pigs born, number born alive, average birth weight, percent stillborn, interval from weaning to next estrus and number born alive next litter. The mean intervals from injection to the birth of the first pig were 55.2 +/- 7.1; 41.1 +/- 5.1; 29.6 +/- 4.0; 24.3 +/- 1.1; 24.8 +/- 0.9 h for groups 1, 2, 3, 4 and 5, respectively (P<0.05). The percentage of sows that farrowed during normal working hours (23 to 33 h after injection) for groups 1, 2, 3, 4 and 5 were 15, 53, 60, 77 and 70%, respectively. Average birth weights (kg) for treatment groups 1, 2, 3, 4 and 5 were 1.54 +/- 0.05; 1.65 +/- 0.05; 1.59 +/- 0.05; 1.54 +/- 0.05 and 1.42 +/- 0.05, respectively (P<0.05). Mean differences in total number of pigs born and number born alive were also statistically significant (P<0.05) but stillbirth rate was not different (P>0.05) among treatment groups. These results indicate that a single injection of 1, 2 or 3 mg of alfaprostol will successfully induce parturition the following day in a majority of the treated sows.

Journal Article↗
PubMed1989

Prostaglandin F in reproductive tissues collected during the luteal phase of the estrous cycle and at parturition in Virginia opossums (Didelphis virginiana ).

Prostaglandin F(2alpha) (PGF(2alpha)) plays a role in the regression of the corpus luteum (CL) in a number of placental mammals. However, the mechanism of luteal regression has not been extensively studied in marsupials. The objectives of this study were to characterize changes in concentrations of PGF(2alpha) within utero-ovarian (UO) tissue/venous plasma during the luteal phase of the estrous cycle in Virginia opossums, to correlate these changes with those of plasma progesterone (P(4)), and to characterize the peripheral pattern of 13,14-dihydro-15-keto-PGF(2alpha) (PGFM) in parturient opossums. Ovaries, uteri, UO venous plasma and peripheral plasma were collected on Days 5, 9 and 12 after induced ovulation (n = 3 to 4 opossums/group). In addition, concentrations of PGFM were measured in peripheral plasma collected from two opossums during late gestation (Days 7,9,11 and 12) and at parturition (Day 13). Concentrations of P(4), PGFM and PGF(2alpha) in tissue homogenates and plasma samples were estimated by radioimmunoassay. In nonpregnant opossums, peripheral P(4) levels were highest on Day 5 (38.8 +/- 11.1 ng/ml, x +/- SEM) declined on Day 9 (22.6 +/- 7.4 ng/ml), and were at basal levels by Day 12 (2.4 +/- 0.7 ng/ml). Endometrial concentrations of PGF(2alpha) increased (P = 0.056) from Day 5 (15.7 +/- 4.1 ng/g) to Day 9 (92.1 +/- 61.0 ng/g) and were maintained to Day 12 (97.2 +/- 25.7 ng/g). Prostaglandin F(2alpha) concentrations in UO plasma increased (P < 0.01) from Day 5 (143.1 +/- 32.7 pg/ml) to Day 12 (333.0 +/- 32.4 pg/ml). Prostaglandin F(2alpha) concentrations in ovarian tissue followed a similar pattern and were correlated with UO concentrations (r = 0.708, P < 0.05). In pregnant opossums, the highest levels of peripheral PGFM were recorded in the peripartum period, when luteal regression would also be expected to occur. The negative temporal relationship between peripheral concentrations of P(4) and concentrations of PGF(2alpha) in UO tissue/venous plasma observed in this preliminary study is consistent with the notion that PGF(2alpha) from the ovary and/or uterus may play a role in CL regression in the opossum.

Journal Article↗
PubMed1992

Circulating PgF2alpha and nutritional parameters at parturition in dairy cows with and without retained placenta: Relation to prepartum diet.

Reproductive and biochemical parameters were studied at parturition in multiparous single-carrying Holstein cows. These were compared in animals with (n=14) and without (n=40) a retained placenta and then according to 2 prepartum diets (corn silage/concentrate, n=44; grass silage/concentrate, n=10) in cows with and without retained placentas. Cows with retained placentas had a 4-day shorter gestation period and gave birth to 5 kg-lighter calves than cows without retained placentas. Furthermore, their plasma PGFM -PgF2alpha main metabolite- (3325 vs 5675 pg/ml; P<0.01) and glucose (79.2 vs 95.2 mg/100ml; P<0.05) levels were lower and their protein concentration was higher (85.7 vs 76.5 g/l; P<0.05) than those of cows without retained placentas. Retained placenta incidence in cows fed grass-silage was higher than in cows fed corn-silage (60% vs 18.2%; P<0.05). Cows with retained placentas and fed corn silage had shorter gestation lengths, gave birth to lighter calves, and had less circulating glucose at calving (77.6 vs 96.5 mg/100ml; P<0.05) than cows without retained placentas and fed the same forage. Cows with retained placentas and fed grass silage had less PGFM (2172 vs 4530 pg/ml; P<0.05) than cows without retained placentas and fed the same forage. Calving number, sex ratio and preceeding milk yield were not different between the two groups of cows whatever their prepartum diet. In the dairy cow, retained placenta could be due to a PgF2alpha or an energy deficiency at calving. Roles of the dietary polyunsaturated fatty acids toward the Pg synthesis and of the energy supply before calving in relation to retained placenta are discussed here.

Journal Article↗
PubMed1995

Secretion of unconjugated estrone during pregnancy and around parturition in goats.

The secretion of unconjugated estrone and its production site in pregnant goats were investigated in vivo. The mean estrone concentration (n = 15) in the peripheral plasma increased gradually, being 83 pg/ml on Day 40 and 483 pg/ml on Day 140 after mating. The estrone concentration increased rapidly after Day 2 before partum, reaching a peak at parturition (2370 pg/ml), and falling to 171 pg/ml at Day 1 post partum. The concentrations of estrone from the umbilical vein and umbilical artery did not differ from that found in the maternal jugular vein, suggesting that the fetus does not take part in estrogen production. The estrone concentration from the uterine vein after the fetus was removed was higher than the concentrations found in the maternal jugular vein and umbilical artery. In the placental tissue, a high concentration of estrone (18157 pg per gram of wet tissue) was detected. These findings suggest that the main production site of unconjugated estrone is the placenta.

Journal Article↗
PubMed1992

Choriodecidual production of interleukin-8 and mechanism of parturition.

Both prostaglandins and antiprogestagens can induce labour and ripen the cervix, but the mechanisms are unclear. The collagenases that bring about cervical ripening are neutrophil derived. We examined the potential of uterine tissues to control neutrophil attraction by measuring interleukin-8 production. Choriodecidual cells in culture produced substantial amounts of interleukin-8; release was inhibited by progesterone and stimulated by the antiprogestagen mifepristone. Interleukin-8 production was similar in cells from spontaneously delivered placentas and from those obtained at caesarean section. Since prostaglandin E and interleukin-8 have synergistic effects, we suggest that interleukin-8 activity is the final common step of prostaglandin and antiprogestagen action in parturition.

Cells, Cultured↗
PubMedDate not supplied

Syncytiotrophoblast membrane protein glycosylation patterns in normal human pregnancy and changes with gestational age and parturition.

The fetally derived syncytiotrophoblast in the placenta form the major interface with the maternal circulation. Cell surface N-linked oligosaccharides are known to influence cell-cell interactions in a variety of ways. The N-linked oligosaccharide component of the human syncytiotrophoblast membrane has been purified from term placentae, and its biochemical structure analysed. Ninety-five per cent of structures were complex N-linked oligosaccharides, with the remaining 5 per cent being of the oligomannose type. Seventy-two per cent of oligosaccharides were sialylated; 50 per cent having two or more sialic acid residues. Such a population of N-linked oligosaccharides would be expected to provide a surface which inhibits interactions between trophoblast and maternal leukocytes. The temporal changes in syncytiotrophoblast N-linked oligosaccharides from the end of the second, and through the third trimester (25-41 weeks) were analysed, as were the changes which occur during parturition. There was no change in the degree of sialylation of these structures. The only significant change was a 37 per cent decrease in core fucosylation of complex N-linked sugars during gestation (P less than 0.005). Women delivered by caesarean section at term, had significantly higher levels of fucosylation (equivalent to women with a gestational age of 31-36 weeks), than those who laboured at term. Present knowledge of core fucosylation of N-linked oligosaccharides is discussed in relation to trophoblast functioning.

Carbohydrate Sequence↗
PubMedDate not supplied

Human placental choline acetyltransferase activity at parturition.

Choline acetyltransferase (ChAT) activity measured in human placentae obtained during labour, or after labour of spontaneous onset, was significantly lower than that measured in placentae obtained before the onset of labour. The reduction in ChAT activity may partly account for the reduction in placental acetylcholine (ACh) content and release into maternal vessels at this time. When cycloheximide (10 micrograms/ml) was infused for 3 h into both fetal and maternal vessels of the perfused placental lobule, it did not significantly alter placental ChAT activity or ACh output from the fetal vessels, though it significantly reduced placental beta HCG release from the maternal side of the perfused lobule. These results suggest that regulation of placental ChAT activity at the time of human parturition may be due to endogenous modulators of its activity, rather than to acute changes in the synthesis of this enzyme.

Acetylcholine↗
PubMed1995

Corticotrophin releasing factor mRNA expression in the sheep brain during pregnancy, parturition and lactation and following exogenous progesterone and oestrogen treatment.

In the multiparous ewe, intracerebroventricular (i.c.v.) infusions of corticotrophin releasing factor (CRF) act centrally to facilitate the induction of maternal behaviour if administered with vaginocervical stimulation. Changes in CRF mRNA expression in the brains of multiparous ewes were therefore examined as a function of late pregnancy, parturition and lactation using in situ hybridisation histochemistry. As the induction of maternal behaviour in sheep is steroid dependent, a comparable analysis was undertaken in ovariectomised ewes treated with the sex steroids oestrogen and progesterone. Changes in CRF mRNA were quantified in the paraventricular nucleus (PVN) and in the bed nucleus of the stria terminalis (BNST). Expression levels in both the PVN and BNST were unaltered during pregnancy and lactation, but were significantly increased immediately post partum. CRF expression in the BNST, but not in the PVN, was significantly increased in response to treatments with progesterone and oestrogen alone or in combination, although there were no significant differences between treatments. These results indicate that CRF mRNA expression is increased in neuroanatomical locations relevant to the control of maternal behaviour when this behaviour is induced or, in the case of steroid influences on the BNST, is inducible by vaginocervical stimulation. They also indicate, that CRF mRNA expression in the BNST and PVN is differentially influenced by sex steroids.

Amygdala↗
PubMed1981

Premature parturition in ewes inoculated with Sarcocystis ovicanis.

A dose of 6 X 10(4) Sarcocystis ovicanis sporocysts produced premature parturition in ewes and eventually proved fatal. The main pathological findings were myositis, myocarditis and encephalitis. Dose rates over the range of 2.5 X 10(3) to 6 X 10(4) depressed the haematocrit levels of pregnant ewes during the period 5-9 weeks after inoculation. Previous infection with S. gigantia did not protect from subsequent challenge with S. ovicanis.

Animals↗
PubMed1993

Oxytocin neuron activation and Fos expression: a quantitative immunocytochemical analysis of the effect of lactation, parturition, osmotic and cardiovascular stimulation.

As c-fos expression is generally thought to be linked to neuronal activation, we compared Fos immunoreactivity in identified oxytocinergic and vasopressinergic neurons of female rats under various conditions known to elicit particular patterns of electrophysiological and secretory activity in these neurons. In suckled lactating animals, Fos immunoreactivity was visible only in rare oxytocinergic and vasopressinergic neurons of the paraventricular and supraoptic nuclei, even after interruption of suckling for 18-72 h. On the other hand, many Fos-positive cells were visible in the nuclei of parturient rats; they involved about 25% of supraoptic oxytocinergic elements. Even more Fos-positive elements were visible in the nuclei of lactating rats that had also undergone 24 h water deprivation or haemorrhage. This involved about 75% vasopressinergic neurons and 25% oxytocinergic neurons of the supraoptic nucleus. Fos immunoreactivity was particularly conspicuous in oxytocin neurons of the anterior commissural nucleus after haemorrhage. After water deprivation or haemorrhage, Fos-positive oxytocinergic neurons in the supraoptic nucleus were significantly more numerous in virgin rats than in lactating rats. Our observations show that suckling, although a most potent stimulus for oxytocin neuron activation and oxytocin release, is inefficient in inducing Fos synthesis in magnocellular neurons, even after a period of interruption. On the other hand, parturition, water deprivation and haemorrhage were more potent stimuli for both neurosecretory systems. However, under each type of stimulation, only part of the neuronal populations within each nucleus were Fos-positive, suggesting that different stimulus-specific pathways are involved in these regulations. In so far as electrical activity is one possible mechanism for c-fos expression, comparison of the patterns of c-fos activation with the known electrophysiological behaviour of hypothalamic magnocellular neurons suggests that Fos synthesis in these neurons is linked to the number of action potentials generated over a period of time, more than to the pattern of electrical activity, whatever the physiological impact of this pattern. Furthermore, within a group of neurons, the heterogeneity of the response in terms of Fos synthesis may be correlated to the variability of the electrophysiological response within this group.

Animals↗
PubMed1979

Immunogenicity, parturition and the prostaglandins.

Immunologists have long suspected that maintenance of pregnancy (viable placentation) is contingent upon the suppressed maternal immune response. Curiously, it has never been suggested that the termination of pregnancy at term might in some way be triggered by the un-blocking of this maternal immune suppression. It is the hypothesis of this paper that maintenance and termination of pregnancy are contravening expressions of a maternal-fetal immunologic regulatory response. The role of the prostaglandins in parturition, and the immune response, is discussed.

Abortifacient Agents↗
PubMed1978

Nexus formation in the myometrium during parturition and induced by estrogen.

The occurence of nexuses (gap junctions) in mouse uterine smooth muscle was found to depend on the hormonal state. As revealed by freeze-fracture electron microscopy, nexuses are virtually absent in virginal and pregnant mice. Abundant, large-sized nexuses were observed in the myometrium during parturition. Estrogen application to virginal mice also induced an increase in number and size of nexuses. Our observations indicate that a new formation of nexuses occurs in differentiated cells. New nexuses may be formed by the confluence of nexus subunits preexisting in the cell membrane or by newly biosynthesized components.

Animals↗
PubMed1982

Magnocellular neuropeptidergic terminals in neurohypophysis: rapid glial release of enclosed axons during parturition.

The ultrastructure of pituicytes as well as their relationship with neurosecretory axons were measured from the following groups of adult rats: virgin females; immediately pre-partum; post-partum; and following 14 days of lactation. Both parturition and lactation brought about a significant decrease in the number of pituicytes with neurosecretory axons completely surrounded by their cytoplasm. Since these two physiological states are each characterized by increased neurohypophysial hormone release, the data suggest that pituicyte enclosure of neurosecretory axons occurs mainly during conditions of low hormone release. Examination of pituicyte size and number of lipid inclusions, and the number of synaptoid contacts from neurosecretory axons onto pituicytes showed no differences among groups.

Animals↗
PubMed1991

Cerebrospinal fluid and plasma concentrations of oxytocin and vasopressin during parturition and vaginocervical stimulation in the sheep.

Simultaneous blood and cerebrospinal fluid (CSF) samples were taken from conscious sheep before, during and after parturition. Concentrations of plasma and CSF oxytocin were significantly elevated during contractions and particularly at birth. Mean prepartum CSF concentrations of oxytocin were around 55% of those found in plasma but postpartum they were up to 2-fold higher than those in plasma. Plasma concentrations of oxytocin were only significantly elevated, compared to prepartum levels, for 15 min postpartum whereas those in CSF were increased for the whole of the 120 min postpartum sampling period. Plasma, but not CSF, concentrations of arginine-vasopressin (AVP) were significantly raised during contractions and birth, and for 15 min postpartum. During the prepartum period CSF AVP concentrations were 67% of those found in plasma whereas at birth plasma levels were 10-fold higher than in CSF. In a separate experiment it was shown that 5 min of mechanical vaginocervical stimulation also stimulated significant increases in CSF and plasma oxytocin concentrations and in plasma vasopressin. Results support previous work suggesting an important role for central oxytocin release in the postpartum induction of maternal behavior and demonstrate that elevated concentrations of oxytocin in the CSF are present for a greater period than in blood. Elevated plasma AVP concentrations during contractions, birth or vaginocervical stimulation may be stimulated by stress associated with these stimuli.

Animals↗
PubMed1983

Delay in the onset of parturition in the rat following prenatal administration of developmental toxicants.

The duration of gestation was determined in Sprague-Dawley albino rats exposed during days 6-18 of pregnancy to diethylstilbestrol (DES) or 3,4,3',4'-tetrachlorobiphenyl (4CB). Each compound produced a delay in the onset of parturition compared to corn-oil-treated controls. The incidence of perinatal mortality was significantly elevated in animals born after 22 days of gestation in both control and treated litters.

Animals↗
PubMed1989

Plasma prolactin concentrations in mares and their neonates after oxytocin induction of parturition.

Studies were undertaken to investigate the effects of oxytocin induction on prolactin release in term (Group II) and preterm (Group III) mares and to compare these effects to spontaneously foaling mares (Group I). Since physiological concentrations of prolactin in blood have not been measured in the neonatal foal, experiments were designed to monitor prolactin in the cord artery and jugular blood of the foals from all groups of mares. Although prolactin levels varied in term mares (Group I and II) during the last 11 days of pregnancy, an increase was observed between Day -6 and Day 0 (2.7 and 11.9 ng/ml respectively; P less than 0.1). The average concentration of prolactin over the last 4 days (Days -3 to 0) had increased by 40% when compared to the average concentration on Days -6, -5, and -4. These findings indicate a rising trend which appears to occur concomitantly with changes in concentrations of 2 mammary components tested, sodium and potassium. Prolactin concentrations did not significantly increase in term mares after oxytocin treatment or in spontaneously foaling mares. However, the preterm induced mares had higher prolactin concentrations during the first stage of labor (19.3 +/- 7.2 ng/ml) than prior to treatment with oxytocin (4.7 +/- 2.0 ng/ml; P less than 0.01). Levels of prolactin in all groups significantly declined by 20-min post-placental expulsion. For the first 30 min after birth, prolactin concentrations in foals from oxytocin-induced mares appeared to be 2-fold higher than those from spontaneously foaling mares. Thereafter, prolactin values declined to baseline values by 48 hrs. When comparing cord arterial plasma with cord venous plasma in each group, prolactin concentrations were similar. However, the average prolactin levels in both the cord artery and vein appeared higher (ave: 1.1 ng/ml) in Group II and III than in Group I (less than 0.5 ng/ml). From these results, the authors suggest that 1) prolactin may have a role in regulating mammary secretory products in mares just prior to parturition; 2) oxytocin may increase prolactin secretion in preterm induced mares; 3) oxytocin induction may have a short term effect to increase circulatory prolactin concentrations in neonates in utero regardless whether their dams were treated preterm or term.

Animals↗