Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Parturition”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 595 records · Page 33Linked to original sources
PubMed1997

Evidence for the involvement of histaminergic neurones in the regulation of the rat oxytocinergic system during pregnancy and parturition.

1. Previous studies have shown that histaminergic neurones of the tuberomammillary nucleus project directly to hypothalamic magnocellular nuclei and that intracerebroventricular administration of histamine increases the synthetic activity of magnocellular oxytocin neurones. 2. Histaminergic neurones of the dorsomedial tuberomammillary nucleus that project to the magnocellular region of the paraventricular nucleus are activated during late pregnancy and lactation, as measured by an increase in mRNA for the synthetic enzyme histidine decarboxylase. 3. There is a concomitant increase in oxytocin mRNA in magnocellular neurones of the paraventricular nucleus. This increase in mRNA contributes to an accumulation of oxytocin before birth and to continued oxytocin synthesis during lactation. 4. Intracerebroventricular administration of mepyramine, a specific antagonist of the H1 histamine receptor, causes a delay in the birth of subsequent pups if given to the mother during parturition. Vehicle or the H2 receptor antagonist cimetidine has no effect. Thus, histamine acts centrally, via H1 receptors, during parturition and may have an excitatory effect on oxytocin release. 5. These results suggest that afferent histaminergic neurones show increased activity during pregnancy and may be responsible for the increase of synthesis in magnocellular oxytocin neurones at this time. If, as previously reported, these histamine neurones can reduce the electrical activity of oxytocin neurones via H2 receptors, then they may have a dual effect, increasing the synthesis of oxytocin while inhibiting its premature release. At term, any inhibitory effects of histamine are overcome to allow oxytocin secretion.

Afferent Pathways↗
PubMed1984

Endocrinology of human parturition: a review.

The existing data on the hormonal factors involved in human parturition indicate that the steroid hormones, progesterone and the oestrogens, play only a facilitatory role in the initiation of labour. A definite role for fetal adrenal steroids in this process has yet to be established, and they too may serve only a facilitating function. The stimulation of the uterine muscle during labour results from an interaction of oxytocin and prostaglandin (PG) F2 alpha. Recent evidence suggests that oxytocin is most important for the initial phase of labour, whereas increased synthesis of PGF2 alpha is essential for the progression of labour. The role of PGE2 remains unclear, but this PG may play an important role in the ripening of the cervix which in turn is essential for successful parturition. The finding of maximal oxytocin receptor concentrations in the myometrium in labour adds strong support to the notion that oxytocin is the trigger for uterine contractions. The factors which control oxytocin receptor formation are therefore important; this may be one of the processes where the steroids play a crucial role. Oxytocin is also one of the stimuli that increase uterine PG synthesis; the coupling of oxytocin receptor occupancy and PG synthetase activity in uterine tissues may be another crucial factor in the mechanism of labour. The formation of gap junctions between the myometrial cells also seems essential for the synchronization and progression of myometrial activity. We propose, therefore, that the co-ordinating of oxytocin receptor formation, PG synthesis and gap junction formation is a key to the initiation and maintenance of human labour. The fetus may fulfil such a co-ordinating role through its influence on placental oestrogen production, through mechanical distention of the uterus, and through its secretion of neuro-hypophysial hormones and other stimulators of PG synthesis.

Adrenal Cortex Hormones↗
PubMed1984

Maternal plasma inhibition of prostaglandin synthase during human pregnancy, parturition and the puerperium.

To study the possibility that circulating endogenous inhibitor(s) of prostaglandin synthesis (EIPS) represent a control mechanism for prostaglandin production during human pregnancy and parturition, we have measured maternal plasma EIPS levels serially during pregnancy, labour and the puerperium, and cross-sectionally during the course of labour. No significant trends were detected in relation to pregnancy or parturition. These results do not support a role for maternal plasma EIPS in the control of prostaglandin production during human pregnancy or labour.

Cyclooxygenase Inhibitors↗
PubMed1985

Maternal plasma prostaglandin E2 metabolite levels during human pregnancy and parturition.

Because of methodological problems associated with the measurement in biological fluids of both prostaglandin E2 (PGE2) and its unstable principal circulating metabolite 13,14-dihydro-15-keto-PGE2 (PGEM), there is little reliable information on these prostaglandins in human pregnancy and parturition. The recent discovery of a stable PGEM degradation product 11-deoxy-13,14-dihydro-15-keto-11 beta, 16 epsilon-cyclo-PGE2 (bicyclo-PGEM) has provided a means of studying endogenous plasma levels of PGEM which circumvents the problems encountered with direct measurements of PGE2 and PGEM. Using a radioimmunoassay for bicyclo-PGEM we have therefore determined maternal peripheral plasma PGE2 metabolite levels during human gestation. PGE2 metabolite levels did not alter significantly during the second or third trimesters nor during labour. This contrasts with maternal peripheral plasma levels of the principal circulating metabolite of PGF2 alpha 13,14-dihydro-15-keto-PGF2 alpha (PGFM) which increases several fold during labour. Compared to PGE2 therefore, PGF2 alpha may be quantitatively the more significant prostaglandin associated with human parturition.

Dinoprostone↗
PubMed1974

Plasma kinin and kininogen levels in the female rat during the oestrous cycle, pregnancy, parturition and the puerperium.

1 Plasma kininogen concentration of the female rat did not change during the oestrous cycle but increased two-fold during gestation. Plasma kininogen did not change during parturition, rose in the first puerperal day and then rapidly declined to non-pregnant levels.2 Free kinin levels in the blood of non-pregnant female rats were low and inconstant. Free kinin was undetectable in the blood of pregnant rats, but was found in four out of ten parturient rats.3 After administration of the kininase inhibitor dimercaprol (30 mg/kg i.p.), free kinin was present in the blood of six parturient rats. Dimercaprol caused appearance of free kinin in the blood of only one out of six non-pregnant rats.4 It appears that the plasma kinin system is activated to a small degree during parturition.

Animals↗
PubMed1988

Studies of the effects of subacute treatment with N-(cyclopropylmethyl)-19-isopentylnororvinol (M320) on timing of parturition in the rat.

1. Administration of 10 micrograms kg-1 of the long lasting potent kappa- and weaker mu-opioid agonist N-(cyclopropylmethyl)-19-isopentylnororvinol (M320) twice daily from day 20 of gestation prolonged the internal gestation period of the rat and retarded the development of the offspring in the perinatal period. 2. The capacities of myometrial, placental and cervical tissues to produce prostaglandin E2 (PGE2) were not affected by M320 treatment. 3. During the period in which parturition normally occurred in saline-treated rats, foetal pituitary levels of immunoreactive oxytocin (ir-OXY) but not immunoreactive arginine-vasopressin (ir-AVP) were greater in M320-compared to saline-treated animals. Following the completion of parturition, foetal pituitary ir-OXY and ir-AVP levels continued to rise in saline-treated rats, but fell dramatically in rats treated subacutely with M320. 4. These data indicate that subacute treatment with M320 may inhibit foetal oxytocin release at term. This foetal OXY release may be a stimulus for the initiation of labour.

Animals↗
PubMed1997

Lactation stage-dependent changes of lymphocyte subpopulations in mammary secretions: inversion of CD4+/CD8+ T cell ratios at parturition.

PROBLEM: Determination of lactation stage-dependent changes in levels of lymphocyte subpopulations in milk. METHOD: Flow cytometric assay was used to identify and assay lymphocyte subpopulations in bovine milk at different stages of lactation. RESULTS: Lymphocyte subpopulations in mammary secretions of dairy cows change during the lactation cycle. In involuting glands (dry gland), approximately 80-90% of lymphocytes were CD2+ T cells. The proportion of CD2+ T cells, however, decreased to approximately 50% at the colostral stage an fluctuated between 50 to 60% in normal (mature) milk. Throughout the lactation stages, less than 5% were B cells as identified by the monoclonal antibodies against CD21 and MHC class II antigens. Subset analysis showed, however, that the proportion of CD5+ T cells decreased from 90% in involuting gland secretions to 75% in colostrum (peripartum stage), and to approximately 40-50% in the normal (mature) milk, CD4+ T cells constituted between 45 to 55% of lymphocytes in the dry gland secretion but decreased drastically at parturition and maintained at the level below 20% throughout normal lactation. In contrast, the proportion of CD8+ T cells in the dry gland secretion was low, between 30 to 40%, but increased steadily, in an inversely-related manner with that of CD4+ T cells, to approximately 40-50% at parturition and maintained at approximately 30-40% during the normal lactation stage thereafter. Two-color immunofluorescence study revealed further that practically all of the CD8+ cells in dry gland secretions were CD2+, and approximately 40% of them were CD5-. Throughout the lactation cycle, WC1+ gamma delta T cells comprised only 2 to 5% of lymphocytes in mammary secretions. CONCLUSIONS: T lymphocyte subpopulations change dynamically during stages of the lactation cycle. The selective migration of T lymphocyte subpopulations to and from the mammary gland, and their functional roles in the immune competence and regulation of the dam and sucklings remain to be elucidated.

Animals↗
PubMed1985

Zinc, pregnancy and parturition.

The role of zinc in the nutrition of pregnant women and its relations to prenatal growth and parturition are reviewed. Zinc deficiency (ZD) affects fetal growth and development both in experimental animals and in man. The teratogenicity of zinc deficiency was widely demonstrated in animals and is also evident in humans. Alcohol intoxication potentiates the effects of ZD in animals. Plasma zinc levels decrease during pregnancy and apparently an adequate and continuous intake of zinc is required for a normal embryonic development. The zinc content of amniotic fluid seems to be related with fetal growth but its value as an indicator of embryonic development is controversial. Zinc deficiency also affects adversely parturition. Mild zinc deficiency may affect a large number of pregnant women, being potentially harmful to the mother and the fetus. This situation requires the screening of high-risk groups, the definition of adequate dietary intakes for each population, and the supplementation with zinc when deficits are detected.

Amniotic Fluid↗
PubMed1976

The induction of parturition using dexamethasone.

Premature parturition was successfully induced with a preparation containing 2 dexamethasone esters in 709 out of 716 cows and heifers of gestational periods ranging from 3 to 8 months. A mortality rate of 38.5% was experienced among calves produced by induced cows, while only a 2.7% mortality rate occurred among 4,330 calves from normal parturitions. Approximately 50% of all treated cattle retained foetal membranes, but with apparently no ill-effect. The treatment apparently did not affect milk production, post-calving fertility, and the overall incidence of dystocias in cows and post-calving diseases. Three deaths occurred among induced cattle, but they could not be attributed to the treatment. It was concluded that the technique may prove to be of great value in dairy cattle, in seasonal milking areas.

Animals↗
PubMed1995

The effects of induced parturition on the incidence of clinical disease and mortality in dairy cows from commercial herds in south-western Victoria.

The effects of induced parturition on clinical disease and mortality of cows were studied in 51 winter-calving, pasture-fed, dairy herds in south-western Victoria. Parturition was induced when most cows were between 27 and 35 weeks of pregnancy. Control groups were selected from herdmates that were not induced to calve. The incidence of retained placenta was much greater among induced cows of all ages. The proportion of cows affected by any clinical disease other than retained placenta, and the incidence of mortality were much greater after induction among cows aged over 6 years but not among cows aged 3 to 6 years.

Age Factors↗
PubMed1995

The effects of induced parturition in dairy cows on the incidence of mortality in calves from commercial herds in south-western Victoria.

The effects of induced parturition on calf mortality rates were studied in 24 winter-calving, pasture-fed, dairy herds in south-western Victoria. Parturition was induced when most cows were between 27 and 35 weeks of pregnancy. Control groups were selected from cows in the same herds in which calving was not induced. The incidence of mortality within 7 days of birth was much higher among calves from cows in induced groups relative to those in control groups (estimated median herd mortality incidence 72% and 7%, respectively). The incidence of calf mortality was high among groups induced at all stages of pregnancy that were investigated. However, differences in calf mortality incidence, relative to controls, were increased among groups induced at earlier stages of pregnancy.

Animals↗
PubMed1972

The composition of foetal and maternal blood during parturition in the ewe.

1. Changes in the composition of foetal and maternal blood have been followed during the last 5-10 days of gestation and throughout parturition in the conscious sheep.2. Catheters were placed in the foetal inferior vena cava through a tarsal vein and in a maternal uterine vein in ten ewes under sodium pentobarbitone anaesthesia. In four of the foetuses blood pressure and heart rates were recorded before and during parturition from an arterial catheter.3. Foetal blood gas tensions, pH and PCV remained stable during the latter part of gestation and throughout labour until 15 min before delivery, when P(O) (2) and pH fell while PCV and P(CO) (2) rose in about 50% of the foetuses examined.4. Metabolite levels were also relatively stable at the end of gestation. Plasma glucose in both maternal and foetal blood rose during the hour before birth, while foetal plasma lactate was elevated as early as 4 hr before birth and was unrelated to any maternal changes. Foetal fructose levels were maintained until after delivery.5. Rises in foetal blood pressure before birth were associated with uterine contractions. Foetal heart rate changes during labour varied in different individuals. The heart rate either fell gradually before birth or there was little change until a sudden drop at delivery.6. The most striking changes in the lamb occurred at, or a few minutes after, birth; pH and P(O) (2) fell, P(CO) (2) and PCV rose, and bradycardia at delivery was succeeded by prolonged tachycardia. There were marked increases in plasma glucose and lactic acid at this time.7. P(O) (2) rose rapidly once respiration was established, while pH and P(CO) (2) levels were restored within (1/2)-1 hr. Plasma FFA levels rose rapidly in the lambs 10-30 min after birth and remained high, while plasma glucose, lactate and fructose concentrations declined slowly in the 1-2 hr after birth, although suckling raised the plasma glucose levels. Considerable individual variation in the metabolite levels was found in both ewes and lambs.8. In the majority of ewes delivery was associated with an abrupt maternal hyperglycaemia, with a much smaller rise in lactate and virtually no change in maternal blood gases or pH.9. These findings are discussed in relation to existing information on new-born lambs and the human infant during birth.

Animals↗
PubMed1994

Pulsatile secretion of oxytocin during parturition in the pig: temporal relationship with fetal expulsion.

1. To assess changes in oxytocin release as they occur in relation to the rapid progress of events at fetal expulsion, continuous automated blood withdrawals (3 ml min-1) from an indwelling jugular catheter and intramammary pressure recordings were obtained from nine primiparous pigs (190-220 kg). Data were acquired over 16 h of normal parturition, during which thirty-five piglets were born. 2. Oxytocin secretion during parturition, when measured by radioimmunoassay (RIA) in blood collected and pooled every minute, showed a baseline secretion (19.8-88.37 pg ml-1) that was raised relative to preterm values. Analysis of individual secretion profiles revealed significant fluctuations or peaks of concentration superimposed on this baseline, with a slow periodicity of 4-12 min. These substantial peaks in secretion were not temporally related to fetal expulsion or visible abdominal contractions. 3. A small (13%) but significant increase in plasma oxytocin was also seen when assay data from the minutes coinciding with a birth were meaned and compared with the following minutes. This rise did not persist into further minutes. 4. Intramammary pressure recordings revealed a highly repeatable and characteristic phenomenon in that fetal expulsion was followed after 33.74 +/- 1.31 s (mean +/- S.E.M. time from emergence of fetus to peak pressure rise) in thirty-three of thirty-five instances by a distinctive and rapid bolus release of oxytocin. These 'postpartum oxytocin pulses' could be closely mimicked by injections of exogenous oxytocin (0.03-1.0 ng kg-1; lag time from jugular injection to peak pressure rise, 20.44 +/- 0.99 s). The timing of this event coincided with the small postpartum pulse measurable by radioimmunoassay.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1969

Fibrin degradation products in normal and abnormal pregnancy and parturition.

The levels of fibrin, fibrinogen degradation products (F.D.P.) in the serum were investigated in normal pregnancy and parturition, after caesarean section, and in patients with abruptio placentae, eclampsia, intrauterine death, and post-partum haemorrhage. No significant change occurred during normal pregnancy, but a highly significant increase was found during labour and again during the first week after normal delivery. After caesarean section the levels of F.D.P. were increased two to four hours after operation, and substantially higher levels were found three to eight days after operation than after normal delivery. High levels of F.D.P. were associated with abruptio placentae and eclampsia, and increased levels after intrauterine death and post-partum haemorrhage.An excess of F.D.P. with diminished or normal systemic fibrinolytic activity suggests that local intravascular fibrin deposition and fibrinolysis occur in normal parturition and in these complications of pregnancy. The very high levels of F.D.P. found in abruptio placentae will be important in the pathogenesis of the defective haemostasis that may accompany this complication.

Abruptio Placentae↗
PubMed1985

Attempt to control parturition in the sow using an oral progestogen.

Analogues of prostaglandin F2 alpha are widely used in the United Kingdom to induce parturition in sows. A disadvantage is that sows are induced to farrow in advance of expected delivery dates. An alternative might be to maintain gestation by the application of a progestogen. Farrowing might then be initiated on the withdrawal of the progestogen. The use of an orally active progestogen (allyl-trenbolone) in an attempt to control the time of parturition in sows is described. In experiment 1, 20 large white cross landrace sows were allocated at random to one of two treatments. Treated sows were fed 16 mg/day of allyl-trenbolone from day 111 of gestation to day 118 of gestation. The farrowing performance of these sows was compared with that of control sows which farrowed naturally. Treated sows farrowed significantly (P less than 0.01) later than the control sows (118.2 and 116.1 days respectively). For treated sows the interval from progestogen withdrawal to farrowing was 29.6 +/- 4.8 hours. The number of stillbirths for treated and control sows respectively was 2.1 and 0.4 per litter. Treatment had no effect either on the birth weight of piglets or on their weaning weight at six weeks old. There was a tendency for more treated sows to show subsequent reproductive malfunction. In a second experiment, under commercial conditions, 81 sows and 12 gilts were allocated to one of four treatments. Treatment A animals were untreated controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Effect of prostaglandin F2 alpha on hormone concentrations in dairy cows after parturition.

This study was designed to evaluate the effects of exogenous prostaglandin F2 alpha (PGF2 alpha) on hormone secretion in cows without a corpus luteum. Blood samples were taken from 10 Friesian dairy cows at frequent intervals from a jugular vein and the caudal vena cava starting between nine and 20 days after parturition. PGF2 alpha (25 mg dinoprost) was injected intramuscularly into five cows after the first eight hours of sampling. Plasma concentrations of 13,14-dihydro 15-keto PGF2 alpha (PGFM) increased rapidly but had returned to baseline by 14 hours after injection. There was no significant effect of the treatment on the time taken by the cows to resume ovarian cycles, and it had no consistent effect on plasma luteinising hormone (LH) patterns; however the amplitude of pulses of LH was temporarily suppressed in two cows and the frequency of pulses of LH was immediately increased in one cow. Treatment with PGF2 alpha had no significant effect on the concentration of oestradiol in blood from the vena cava. It is concluded that any enhancement of the reproductive performance of cows treated with PGF2 alpha after parturition is not due to a direct effect on pituitary-ovarian function.

Animals↗
PubMed1978

Possible role of gap junctions in activation of myometrium during parturition.

Gap junctions between smooth muscle cells of the myometrium of pregnant rats were found only immediately prior to, during and immediately after parturition by quantitative thin-section and freeze-fracture microscopy. Ovariectomy of 16- to 17-days-pregnant rats resulted in premature termination of pregnancy and the appearance of gap junctions. Methods that prolonged normal pregnancy in rats or maintained pregnancy in ovariectomized animals (progesterone treatment) prevented the appearance of gap junctions. Gap junctions formed in tissues incubated for 24--96 h in vitro without any hormonal influence. We propose that gap junctions are essential for normal labor and delivery for synchronous contraction of the muscle of the uterus. We present a model for control of parturition that may apply to other animals including humans. The model proposes: 1) the possible roles progesterone, prostaglandins, or estrogens may play in initiating gap-junction formation; 2) that the formation of gap junctions is a necessary step in activation of the myometrium leading to labor; and 3) that agents used to stimulate or inhibit labor may do so by affecting gap junctions.

Animals↗
PubMed1990

PGF2 alpha and PGE2 binding to rat myometrium during gestation, parturition, and postpartum.

The specific binding of prostaglandins (PG) F2 alpha and E2 was studied in a rat myometrial membrane-enriched fraction during the latter part of gestation and parturition, as well as in the postpartal period. Tritiated PGE2 and PGF2 alpha binding was specific, saturable, time dependent, and directly proportional to the amount of membrane protein. Scatchard analysis indicated the presence of high-affinity (Kd2) and low-affinity (Kd2) binding sites for both PGs. The affinity of both binding sites for PGF2 alpha and the apparent Kd2 for PGE2 remained essentially the same throughout gestation and post-partially and were similar to nonpregnant rats. The apparent Kd1 of PGE2, however, increased by 10-fold from day 21 of gestation to 1 day postpartum. Although the maximal binding capacity of the high-affinity (Bmax1) and low-affinity (Bmax2) binding sites of PGF2 alpha showed a nonsignificant increase compared with prepartum values, reaching maximal values 12-24 h postpartum, those of PGE2 showed a significant increase on the third day after delivery. The concentration of prostanoids in uterine venous plasma and amniotic fluid increased significantly with approaching parturition, whereas plasma progesterone decreased, raising the estradiol-progesterone ratio 25-fold. After unilateral fetectomy, the binding sites for PGF2 alpha and PGE2 increased significantly compared with the contralateral pregnant horns. Administration of the PG synthetase inhibitor, indomethacin, also increased two- to threefold both PGF2 alpha and PGE2 binding compared with the placebo group, whereas intrauterine administration of PGF2 alpha and PGE2 significantly reduced it.(ABSTRACT TRUNCATED AT 250 WORDS)

Abortion, Spontaneous↗