- [Show abstract] [Hide abstract] ABSTRACT: Background: Preterm birth before 37 weeks' gestation is the most common and costly complication of pregnancy and remains the leading cause of neonatal morbidity, mortality and reduced achievement in surviving infants. Magnesium sulfate is one class of tocolytics for threatened preterm labor however its clinical efficacy has been questioned. Twin pregnancies are at increased risk of preterm delivery compared to singleton gestations, suggesting there is twin-specific risk to preterm delivery in twins. The prevention strategies applied to singleton pregnancies however have not been shown to be effective in twin pregnancies. Objective(s): To compare the relaxant effect of magnesium sulfate (MgSO4) on spontaneous and oxytocin-augmented contractions of human myometrium from singleton and twin pregnancies and examine whether the effect of oxytocin on MgSO4's potency could be reversed using the oxytocin receptor antagonist, atosiban. Study design: Myometrium was obtained at the time of pre-labor cesarean section (36-40 weeks gestation) from women with singleton (n=23) or twin (n=12) pregnancy. Isometric tension recordings were made on myometrial strips mounted in organ baths superfused with physiological saline. Strips were exposed to rising concentrations of MgSO4 and the effect on spontaneous contractions or stimulated with oxytocin (0.5nmol/L) and in the presence or absence of atosiban (100nmol/L) was recorded. The contractile characteristics after each application of MgSO4, including amplitude of contraction and activity integral, were measured. Concentration-response curves were fitted using non-linear regression and comparison of the -logIC50 values. Results: MgSO4 exerted an equal concentration-dependent inhibitory effect on spontaneous myometrial contractions from both singleton and twin myometrium (P>0.05). The application of oxytocin produced a significant rightward shift in the concentration-response curves (P<0.001) but no differences were found between pregnancy groups (P>0.05). The addition of atosiban shifted concentration-response curves significantly back to the left for amplitude of contraction and activity integral in singletons (P<0.001). However, only activity integral was significantly reversed in twins (P<0.0001). Conclusion(s): MgSO4 is equipotent in suppressing contractions in singleton and twin myometrium. Oxytocin (0.5nmol/L) significantly reduces the tocolytic potency of MgSO4 which may explain in part, MgSO4's poor efficacy in vivo but this can be partially reversed using an oxytocin receptor antagonist. Combination tocolysis involving oxytocin receptor antagonists requires further investigation.
- [Show abstract] [Hide abstract] ABSTRACT: Ethnopharmacological relevance: People living in the tropical rain forest of South-Western Nigeria use Rinorea dentata (P. Beauv.) Kuntze (Violaceae) in ethno-veterinary medicine to facilitate parturition. There are no evidence-based pharmacological investigations for the uterotonic activity of this plant. Aims of study (i) Collection of data about the ethnopharmacological uses of R. dentata and evaluation of its uses and applications in health care; (ii) determining potential uterotonic effects in vitro, and (iii) chemical characterization of R. dentata, which is a member of the Violaceae family known to express circular cystine-knot peptides, called cyclotides. Materials and Methods The ethnopharmacological use of R. dentata in settlement camps within the area J4 of Omo forest has been investigated by semi-structured questionnaires and open interviews. Use index analysis has been performed by seven quantitative statistical models. Respondents' claim on the beneficial ethno-veterinary application of the plant to aid parturition has been investigated in vitro by myometrial contractility organ bath assays. The bioactive plant extract was screened by chemical derivatization and mass spectrometry-based peptidomics using reversed-phase HPLC fractionation and MALDI-TOF/TOF analysis. Results Based on the survey analysis, medicinal preparations of R. dentata have been used for anti-microbial and anti-malaria purpose in humans, and for aiding parturition in farm animals. The latter application was mentioned by one out of six respondents who claimed to use this plant for any medicinal purpose. The plant extract exhibited a weak uterotonic effect using organ bath studies. The plant contains cyclotides and the peptide riden A has been identified by de novo amino acid sequencing using mass spectrometry. Conclusion Few dwellers around the settlement camps of the tropical forest of Omo (Nigeria) use R. dentata for various health problems in traditional veterinary and human medicine. The weak uterotonic effect of the cyclotide-rich extract is in agreement with the low use value index obtained for this plant. Cyclotides have been reported in the genus Rinorea confirming the ubiquitous expression of these stable bioactive plant peptides within the family of Violaceae.
Dataset: Supplementary appendix
- [Show abstract] [Hide abstract] ABSTRACT: Aim: Magnesium sulphate (MgSO4) is currently used in obstetrics for treatment of seizures in women with preeclampsia. It is also used for neonatal protection and given to women who are anticipated to deliver before 32 weeks of gestation. The use of MgSO4 as a tocolytic is however questioned. The aim of this study was to assess in vitro the inhibitory effects of MgSO4 in term pregnant and non-pregnant mice myometrium. Methods: Myometrial strips obtained from term pregnant (18 days) and non-pregnant mice were superfused in physiological saline solution at pH 7.4 and 37 °C. After steady contractions were achieved, the effect of different concentrations of MgSO4 (2 –12 mM) was examined on spontaneous and oxytocin induced (0.5 nM) myometrial contractions. Results: MgSO4 had an inhibitory effect on mouse myometrium. Compared with controls (100%),10mM MgSO4 produced a significant (P <0.001) decrease in force integral of spontaneous (6.14 ± 3.18%, n=9) and oxytocin-induced (50.5 ± 3.93%, n=11) contracting pregnant myometrium, mean ± SEM. 50% reduction of force integral was achieved in spontaneous and oxytocin induced contractions at 4mM and 10mM respectively. In non-pregnant myometrium, the effect of MgSO4 was less than that observed in pregnant, 50% reduction was seen at 8 and 10mM of spontaneous and oxytocin induced contractions respectively and further decreased with increased concentrations. Conclusion: Our in vitro data demonstrated that MgSO4 had a dose dependent inhibitory effect on pregnant and non-pregnant mouse myometrial contractility. Oxytocin decreases its effectiveness which may affect its tocolytic ability in vivo.
- [Show abstract] [Hide abstract] ABSTRACT: Advances in molecular, genetic and "omic" technologies are fuelling the thirst to better understand the uterus, and then apply this information to problems in pregnancy and labour. Progress has, however, been limited while we still have an incomplete understanding of some of the basic physiology of uterine smooth muscle (myometrium). In this review and opinion piece I will explore some of the fascinating findings from selected recent studies and see how these may provide new avenues for physiological and clinical research. It is also the case however that there is still limited mechanistic understanding about physiological and pathophysiological processes in the myometrium. This lack of understanding limits the usefulness of some finding from genomic and allied studies. By focussing on some key recent findings and relating these to two important clinical problems in childbirth that involve myometrial activity; preterm delivery and difficult labours, the interplay between our physiological knowledge and information provided by newer technologies will be explored. My opinion is that physiology has provided much more new mechanistic insight into difficult births and that the newer technologies may lead to breakthroughs in preterm birth research, but that this has not happened yet. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
- [Show abstract] [Hide abstract] ABSTRACT: We compared the relaxant effect of 2 known tocolytics; indomethacin and atosiban and progesterone, on pregnant human myometrial spontaneous and oxytocin-induced contractions from singleton and twin pregnancies. All agents exerted a concentration-dependent relaxant effect on myometrial contractions. There was no significant difference in the concentration-response curves between singletons and twins for progesterone or indomethacin on spontaneous contractions or atosiban on oxytocin-induced contraction. Under oxytocin however, the concentration-response curves for indomethacin and progesterone were significantly shifted to the right for both amplitude of contraction (P < .01) and activity integral (P < .01). When compared to singleton myometrium however, the concentration-response curves were significantly shifted to the right in the twin myometrium group (P < .05 progesterone and P < .001 indomethacin). We conclude that a greater concentration of progesterone and indomethacin is required to inhibit oxytocin-induced myometrial contractions in twins compared to singletons in vitro. The differences noted in the tissue pharmacologies may have implications for the successful prevention or inhibition of preterm labor in twin pregnancy. © The Author(s) 2015.
- [Show abstract] [Hide abstract] ABSTRACT: Lactate is increased in myometrial capillary blood from women in slow or non-progressive labour (dystocia), suggesting that it is detrimental to uterine contractions. There are however no studies of the effect of lactate on the myometrium. We have therefore investigated its effects and mechanism of action on myometrial strips from term pregnant rats. The effects on spontaneous and oxytocin-induced contractility in response to sodium lactate and other weak acids (1-20 mm) were investigated. In some experiments simultaneous force and intracellular Ca or pH (pHi ) were measured with Indo-1 or carboxy-Snarf respectively. Statistical differences were tested using non-parametric tests and significance taken as P<0.05. Lactate significantly decreased spontaneous contractility with an IC50 of 3.9 mm. Propionate, butyrate and pyruvate also reduced contractions with similar potency. The effects of lactate were reduced in the presence of oxytocin but remained significant. Lactate decreased pHi and nulling the fall of pHi abolished its effects. We also show that lactate inhibited Ca transients and these changes mirrored those produced on force. If Ca entry was enhanced by depolarization (high KCl) or applying the Ca channel agonist, Bayk4644, the effects of lactate were abolished. Together these data show that lactate in the physiological range potently decreases myometrial contractility, due to its inhibition of Ca transients, which can be attributed to the induced acidification. This study suggests accumulation of extracellular lactate will reduce myometrial contractions and could therefore contribute to labour dystocia. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
- [Show abstract] [Hide abstract] ABSTRACT: For successful birth, contractions need to become progressively stronger. The underlying mechanisms are unknown, however. We have found that a novel mechanism, hypoxia-induced force increase (HIFI), is switched on selectively, at term, and is essential to strengthening contractions. HIFI is initiated as contractions cyclically reduce blood flow and produce repeated hypoxic stresses, with associated metabolic and transcriptomic changes. The increases in contractility are a long-lasting, oxytocin-independent, intrinsic mechanism present only in the full-term pregnant uterus. HIFI is inhibited by adenosine receptor antagonism and blockade of cyclooxygenase-2 signaling, and partially reproduced by brief episodes of acidic (but not alkalotic) pH. HIFI explains how labor can progress despite paradoxical metabolic challenge, and provides a new mechanistic target for the 1 in 10 women suffering dysfunctional labor because of poor contractions.
- [Show abstract] [Hide abstract] ABSTRACT: Maternal obesity is associated with increased birthweight, and obesity and premature mortality in adult offspring. The mechanism by which maternal obesity leads to these outcomes is not well understood, but maternal hyperglycaemia and insulin resistance are both implicated. We aimed to establish whether the insulin sensitising drug metformin improves maternal and fetal outcomes in obese pregnant women without diabetes. We did this randomised, double-blind, placebo-controlled trial in antenatal clinics at 15 National Health Service hospitals in the UK. Pregnant women (aged ≥16 years) between 12 and 16 weeks' gestation who had a BMI of 30 kg/m(2) or more and normal glucose tolerance were randomly assigned (1:1), via a web-based computer-generated block randomisation procedure (block size of two to four), to receive oral metformin 500 mg (increasing to a maximum of 2500 mg) or matched placebo daily from between 12 and 16 weeks' gestation until delivery of the baby. Randomisation was stratified by study site and BMI band (30-39 vs ≥40 kg/m(2)). Participants, caregivers, and study personnel were masked to treatment assignment. The primary outcome was Z score corresponding to the gestational age, parity, and sex-standardised birthweight percentile of liveborn babies delivered at 24 weeks or more of gestation. We did analysis by modified intention to treat. This trial is registered, ISRCTN number 51279843. Between Feb 3, 2011, and Jan 16, 2014, inclusive, we randomly assigned 449 women to either placebo (n=223) or metformin (n=226), of whom 434 (97%) were included in the final modified intention-to-treat analysis. Mean birthweight at delivery was 3463 g (SD 660) in the placebo group and 3462 g (548) in the metformin group. The estimated effect size of metformin on the primary outcome was non-significant (adjusted mean difference -0·029, 95% CI -0·217 to 0·158; p=0·7597). The difference in the number of women reporting the combined adverse outcome of miscarriage, termination of pregnancy, stillbirth, or neonatal death in the metformin group (n=7) versus the placebo group (n=2) was not significant (odds ratio 3·60, 95% CI 0·74-17·50; p=0·11). Metformin has no significant effect on birthweight percentile in obese pregnant women. Further follow-up of babies born to mothers in the EMPOWaR study will identify longer-term outcomes of metformin in this population; in the meantime, metformin should not be used to improve pregnancy outcomes in obese women without diabetes. The Efficacy and Mechanism Evaluation (EME) Programme, a Medical Research Council and National Institute for Health Research partnership. Copyright © 2015 Chiswick et al. Open Access article distributed under the terms of CC BY. Published by Elsevier Ltd.. All rights reserved.
- [Show abstract] [Hide abstract] ABSTRACT: Obesity is a major health problem worldwide. The prevalence of obesity is increasing in both developed and developing countries. In the UK, for example, 60% of adults are overweight and 25% are obese. Obesity is associated with many pathological complications including respiratory, cardiovascular and endocrine, but it also affects fertility and is associated with many reproductive complications. This has led us and others to investigate links between women with high BMI, pregnancy outcome and uterine function. These studies in turn have led investigators to ask how obesity can have such an impact on reproduction and, as part of this, to consider the role of the adipokines released from adipose tissue. Our focus in this short review is on adipokines and myometrial activity, and for completeness we overview their effects on other smooth muscles. To date four adipokines (leptin, visfatin, apelin and ghrelin) have been investigated and all affect myometrial contractility, but some more potently than others. We consider the possible mechanisms involved in how adipokines may modify uterine contractility, and discuss the potential impact on labour and delivery. Copyright © 2015. Published by Elsevier Inc.
- [Show abstract] [Hide abstract] ABSTRACT: The purpose of this study was to investigate the effect of visfatin on in vitro myometrial contractility in human and rat, and compare it to leptin. Myometrial strips from term pregnant women having a caesarean section or rats were dissected, superfused with physiological saline and the effects of visfatin (500pM-25nM) or leptin (1nM-1μM), on spontaneous and oxytocin-induced contractions were studied. After establishment of regular contractions, tissues were incubated for control and test response at 37°C for 20min, and then contractility was assayed. In human and rat myometrium, visfatin had similar dose dependent effects on contractility. In the human myometrium, compared with that of controls (100%), 10nM produced a significant (paired t-test) decrease in the 20min integral of spontaneous (64±8%, n=13) and oxytocin-induced contractions (55±9%, n=5), mean±SEM. In rat tissue the decrease was also significant (spontaneous, 76±7%, n=7; oxytocin-induced 68±6%, n=3). Leptin at this concentration (10nM) had no effect in rat or human, and even at a higher concentration (1μM) produced only a small inhibitory effect (~80%) on contractions. These data are the first to show that visfatin inhibits myometrial contractility and does so more potently than leptin. Our data suggest that increased output of visfatin and leptin in obese pregnant women may impair uterine contractility resulting in an unplanned Caesarean delivery. Copyright © 2015 Elsevier Inc. All rights reserved.
Dataset: Reviewer comments
- [Show abstract] [Hide abstract] ABSTRACT: Introduction Increasing evidence suggests obesity has its origins prior to birth. There is clear correlation between maternal obesity, high birthweight and offspring risk of obesity in later life. It is also clear that women who are obese during pregnancy are at greater risk of adverse outcomes, including gestational diabetes and stillbirth. The mechanism(s) by which obesity causes these problems is unknown, although hyperglycaemia and insulin resistance are strongly implicated. We present a protocol for a study to test the hypothesis that metformin will improve insulin sensitivity in obese pregnant women, thereby reducing the incidence of high birthweight babies and other pregnancy complications. Methods and analysis The Efficacy of Metformin in Pregnant Obese Women, a Randomised controlled (EMPOWaR) trial is a double-masked randomised placebo-controlled trial to determine whether metformin given to obese (body mass index >30 kg/m2) pregnant women from 16 weeks’ gestation until delivery reduces the incidence of high birthweight babies. A secondary aim is to test the mechanism(s) of any effect. Obese women with a singleton pregnancy and normal glucose tolerance will be recruited prior to 16 weeks’ gestation and prescribed study medication, metformin or placebo, to be taken until delivery. Further study visits will occur at 28 and 36 weeks’ gestation for glucose tolerance testing and to record anthropometric measurements. Birth weight and other measurements will be recorded at time of delivery. Anthropometry of mother and baby will be performed at 3 months postdelivery. As of January 2014, 449 women had been randomised across the UK. Ethics and dissemination The study will be conducted in accordance with the principles of Good Clinical Practice. A favourable ethical opinion was obtained from Scotland A Research Ethics Committee, reference number 10/MRE00/12. Results will be disseminated at conferences and published in peer-reviewed journals. Trial registration number ISRCTN51279843.
- [Show abstract] [Hide abstract] ABSTRACT: Ginseng Java or Talinum paniculatum (Jacq.) Geartn has long been used in herbal recipes because of its various therapeutic properties. Ginseng Java is believed to be beneficial to the female reproductive system by inducing lactation and restoring uterine functions after the postpartum period. There are, however, no scientific data on verifying the effects on the uterus to support its therapeutic relevance. Therefore, the purpose of this study was to investigate the effects of Ginseng Java root extract and its possible mechanism(s) of action on uterine contractility. Female virgin rats were humanely killed by CO2 asphyxia and uteri removed. Isometric force was measured in strips of longitudinal myometrium. The effects of Ginseng Java root extract at its IC50 concentration (0.23 mg/mL) on spontaneous, oxytocin-induced (10 nmol/L), and depolarized (KCl 40 mmol/L) contraction were investigated. After establishing regular phasic contractions, the application of Java root extract significantly inhibited spontaneous uterine contractility (n = 5). The extract also significantly inhibited the contraction induced by high KCl solution (n = 5) and oxytocin (n = 5). The extract also inhibited oxytocin-induced contraction in the absence of external Ca entry (n = 7) and the tonic force induced by oxytocin in the presence of high KCl solution. Taken together, the data demonstrate a potent and consistent ability of extract from Ginseng Java root to reduce myometrial contractility. The tocolytic effects were demonstrated on both spontaneous and agonist-induced contractions. The fact that force was inhibited in depolarized conditions suggests that the possible mechanisms may be blockade of Ca influx via L-type Ca channels. The data in Ca-free solutions suggest that the extract also reduces IP3-induced Ca release from the internal store. These tocolytic effects do not support the use of ginseng to help with postpartum contractility, but instead suggest it may be helpful in reducing inappropriate uterine contractions, such as in threatened preterm delivery. © 2014 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.
- [Show abstract] [Hide abstract] ABSTRACT: In this review we give a state of the art account of uterine contractility, focussing on excitation-contraction (electro-mechanical) coupling (ECC). This will show how electrophysiological data and intracellular calcium measurements, can be related to more modern techniques such as confocal microscopy and molecular biology, to advance our understanding of mechanical output and its modulation in the smooth muscle of the uterus, the myometrium. This new knowledge and understanding, for example concerning the role of the sarcoplasmic reticulum (SR), or stretch activated K channels, when linked to biochemical and molecular pathways, provides a clearer and better informed basis for the development of new drugs and targets. These are urgently needed to combat dysfunctions in excitation contraction coupling that are clinically challenging, such as preterm labour, slow to progress labours and post-partum haemorrhage. It remains the case that scientific progress still needs to be made in areas such as pacemaking and understanding interactions between the uterine environment and ion channel activity.This article is protected by copyright. All rights reserved.
- [Show abstract] [Hide abstract] ABSTRACT: Apolipoprotein-E knockout (ApoE−/−) mice develop hypercholesterolemia and are a useful model of atherosclerosis. Hypercholesterolemia alters intracellular Ca2+ signalling in vascular endothelial cells but our understanding of these changes, especially in the early stages of the disease process, is limited. We therefore determined whether carbachol-mediated endothelial Ca2+ signals differ in plaque-prone aortic arch compared to plaque-resistant thoracic aorta, of wild-type and ApoE−/− mice, and how this is affected by age and the presence of hypercholesterolemia. The extent of plaque development was determined using en-face staining with Sudan IV. Tissues were obtained from wild-type and ApoE−/− mice at 10 weeks (pre-plaques) and 24 weeks (established plaques). We found that even before development of plaques, significantly increased Ca2+ responses were observed in arch endothelial cells. Even with aging and plaque formation, ApoE−/− thoracic responses were little changed, however a significantly enhanced Ca2+ response was observed in arch, both adjacent to and away from lesions. In wild-type mice of any age, 1–2% of cells had oscillatory Ca2+ responses. In young ApoE−/− and plaque-free regions of older ApoE−/−, this is unchanged. However a significant increase in oscillations (~13–15%) occurred in thoracic and arch cells adjacent to lesions in older mice. Our data suggest that Ca2+ signals in endothelial cells show specific changes both before and with plaque formation, that these changes are greatest in plaque-prone aortic arch cells, and that these changes will contribute to the reported deterioration of endothelium in atherosclerosis.
- [Show abstract] [Hide abstract] ABSTRACT: In the myometrium SR Ca(2+) depletion promotes an increase in force but unlike several other smooth muscles, there is no Ca(2+) sparks-STOCs coupling mechanism to explain this. Given the importance of the control of contractility for successful parturition, we have examined, in pregnant rat myometrium, the effects of SR Ca(2+)-ATPase (SERCA) inhibition on the temporal relationship between action potentials, Ca(2+) transients and force. Simultaneous recording of electrical activity, calcium and force showed that SERCA inhibition, by cyclopiazonic acid (CPA 20μM), caused time-dependent changes in excitability, most noticeably depolarization and elevations of baseline [Ca(2+)]i and force. At the onset of these changes there was a prolongation of the bursts of action potentials and a corresponding series of Ca(2+) spikes, which increased the amplitude and duration of contractions. As the rise of baseline Ca(2+) and depolarization continued a point was reached when electrical and Ca(2+) spikes and phasic contractions ceased, and a maintained, tonic force and Ca(2+) was produced. Lanthanum, a non-selective blocker of store-operated Ca(2+) entry, but not the L-type Ca(2+) channel blocker nifedipine (1-10μM), could abolish the maintained force and calcium. Application of the agonist, carbachol, produced similar effects to CPA, i.e. depolarization, elevation of force and calcium. A brief, high concentration of carbachol, to cause SR Ca(2+) depletion without eliciting receptor-operated channel opening, also produced these results. The data obtained suggest that in pregnant rats SR Ca(2+) release is coupled to marked Ca(2+) entry, via store operated Ca(2+) channels, leading to depolarization and enhanced electrical and mechanical activity.
Universidad de La LagunaSan Cristóbal de La Laguna, Canary Islands, Spain
The University of ManchesterManchester, England, United Kingdom