J R Challis

Samuel Lunenfeld Research Institute, Toronto, Ontario, Canada

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Publications (275)907.92 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Rates of preterm birth vary between different populations and ethnic groups. Epidemiologic studies have suggested that the incidence of preterm birth is also higher in pregnancies carrying a male fetus; the male:female difference is greater in earlier preterm pregnancy. Placental or chorion trophoblast cells from pregnancies with a male fetus produced more pro-inflammatory TNFα in response to LPS stimulation and less anti-inflammatory IL-10 and granulocyte colony stimulating factor (G-CSF) than cells from pregnancies with a female fetus, more prostaglandin synthase (PTGS-2) and less prostaglandin dehydrogenase (PGDH). These results suggest that in the presence of a male fetus the trophoblast has the potential to generate a more pro-inflammatory environment. Maturation of the fetal hypothalamic-pituitary-adrenal axis and expression of placental genes, particularly 11β hydroxysteroid dehydrogenase-2 are also expressed in a sex dependent manner, consistent with the sex-biasing influences on gene networks. Sex differences in these activities may affect clinical outcomes of pre- and post-dates pregnancies and fetal/newborn wellbeing. These factors need consideration in studies of placental function and in the development of personalized strategies for the diagnosis of preterm labor and postnatal health.
    Placenta 12/2012; · 3.12 Impact Factor
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    ABSTRACT: In human pregnancy, cortisol and PGs are involved in the onset of labor and play an important role in the mechanisms leading to parturition. Recent studies have shown that at term, cortisol increases PG synthesis and decreases PG metabolism in chorion trophoblast (CT) cells. In CT, 11 beta-hydroxysteroid oxidase type 1 (11 beta-HSD1) converts biologically inactive cortisone to cortisol to regulate cortisol availability. In the present study, we have investigated whether 11 beta-HSD1 activity could be influenced by PGs. We have shown that in CT, PGF2alpha rapidly increased 11 beta-HSD1 reductase activity in a dose-dependent manner via the PGF2alpha receptor, localized in the fetal membranes. PGF2alpha stimulated 11 beta-HSD1 activity through increased intracellular calcium mobilization, activation of PKC, and the phosphorylation of the 11 beta-HSD enzyme. We propose that within CT there is a novel feed forward loop by which PGF2alpha acts to promote cortisol production from cortisone through increases in 11beta-HSD1, and this in turn leads to further net PG output for the onset of labor and birth.
    Journal of Clinical Endocrinology &amp Metabolism 12/2001; 86(11):5585-92. · 6.43 Impact Factor
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    ABSTRACT: Our aim was to determine the postnatal effects of single and repeated glucocorticoid injections during late gestation. Repeated (104, 111, 118, 125 days) or single (104 days) injections of betamethasone or saline were given to the ewe or by ultrasound guided injection to the fetus (term 150 days). Lambs were born spontaneously and studied at 3 and 6 mo and 1 yr of age. Arterial pressure was measured at each age, and we performed intravenous glucose tolerance tests at 6 mo and 1 yr. Repeated maternal, but not single maternal or fetal, betamethasone injections prolonged gestation, reduced weight at birth and 3 mo, and was associated with low arterial pressure at 3 mo but not at 6 mo and 1 yr. Glucose metabolism was altered in all betamethasone treatment groups, regardless of the number or route of injections. Our data demonstrate that glucocorticoid-induced fetal growth restriction is associated with a transient reduction in postnatal arterial pressure, but glucocorticoid exposure with or without growth restriction alters glucose metabolism.
    AJP Regulatory Integrative and Comparative Physiology 10/2001; 281(3):R960-70. · 3.28 Impact Factor
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    M Fraser, G A Braems, J R Challis
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    ABSTRACT: Responsiveness of the fetal sheep adrenal gland to adrenocorticotrophin (ACTH) increases in late pregnancy, resulting in increased glucocorticoid production. Development of this responsiveness is an important determinant of fetal hypothalamic-pituitary-adrenal function and depends, in part, on the potential for ACTH binding to adrenal tissue. In the present study, we have examined the developmental pattern of ACTH receptor (ACTH-R) expression during the latter half of pregnancy and in neonatal and adult life. As hypoxaemia induces increases in cortisol and ACTH secretion, in addition to increasing fetal adrenal responsiveness, a further aim of this study was to investigate whether hypoxaemia was associated with altered expression of the ACTH-R gene. Whole adrenal glands were removed from fetal sheep, lambs and adult sheep at different stages of development for measurement of ACTH-R mRNA. Moderate hypoxaemia was induced for 48 h beginning on days 124-128, or on days 132-134 of gestation, by decreasing the maternal fractional inspired oxygen. ACTH-R mRNA was detected by northern blotting using a cDNA cloned in our laboratory and by in situ hybridisation. ACTH-R mRNA (3.6 kb major transcript) was detected in adrenal tissue at day 63 of gestation. Its relative abundance increased significantly (P<0.05) between days 126-128 and 140-141 of pregnancy, increased further with the onset of spontaneous labour, and remained increased in newborn lambs at 7 h-7 days after birth. ACTH-R mRNA levels then decreased in adrenal tissue from lambs and adult sheep (P<0.05). Hypoxaemia for 48 h significantly increased ACTH-R mRNA expression in adrenals of the older fetuses (days 134-136) compared with that in controls (P<0.05), but was without effect in younger fetuses. We conclude that levels of ACTH-R mRNA in the fetal adrenal gland increase as term approaches, coincident with the endogenous prepartum surge in plasma ACTH and cortisol. Sustained hypoxaemia resulted in an upregulation of mRNA encoding for ACTH-R, but only in older fetuses and in association with a sustained increase in plasma cortisol. These results are consistent with cortisol, ACTH, or both, contributing to increased fetal adrenal responsiveness, by increasing expression of fetal adrenal receptors for ACTH.
    Journal of Endocrinology 05/2001; 169(1):1-10. · 4.06 Impact Factor
  • A C Holloway, W L Whittle, J R Challis
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    ABSTRACT: We hypothesized that in the late-gestation sheep fetus there is an interaction between the prepartum rise in cortisol and the increase in placental estradiol production that allows expression of key components of the fetal hypothalamic-pituitary-adrenal (HPA) axis. Therefore, the goal of this study was to investigate the effects of cortisol on the fetal HPA axis in the presence and absence of increased placental estradiol production. We obtained fetal plasma samples and pituitary tissue from animals that had received an infusion of either cortisol, cortisol and 4-hydroxyandrostenedione (40HA, an aromatase inhibitor), saline, or saline + 40HA controls. Cortisol significantly decreased plasma adrenocorticotropic hormone concentrations, and in the presence of 40HA reduced pituitary proopiomelanocortin (POMC) mRNA levels in the pars distalis. There was no effect of any treatment on the expression of the key POMC processing enzymes, prohormone convertase-1 or -2 in the fetal pituitary. Conversely, levels of glucocorticoid receptor (GR) mRNA in the pituitary were increased with cortisol treatment in the absence of increased estradiol. We suggest that in the late-gestation sheep fetus, cortisol and estradiol have opposite effects on pituitary POMC and GR mRNA expression, and interact to regulate these key components of the fetal HPA axis.
    Endocrine 05/2001; 14(3):343-8. · 3.53 Impact Factor
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    ABSTRACT: Birth in many animal species and in humans is associated with activation of hypothalamic-pituitary-adrenal function in the fetus and the increased influence of glucocorticoids on trophoblast cells of the placenta and fetal membranes. We suggest that in ovine pregnancy glucocorticoids directly increase fetal placental prostaglandin production, and indirectly increase prostaglandin production by maternal uterine tissues through the stimulation of placental estradiol synthesis. The events of ovine parturition are compared with those of human parturition. In the latter, we suggest similar direct effects of glucocorticoids on prostaglandin synthesis and metabolism in fetal membranes and similar indirect effects mediated by glucocorticoid-stimulated increases in intrauterine corticotropin-releasing hormone expression.
    Biology of Reproduction 05/2001; 64(4):1019-32. · 4.03 Impact Factor
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    J R Challis
    Clinical and investigative medicine. Médecine clinique et experimentale 03/2001; 24(1):60-7. · 1.09 Impact Factor
  • F A Patel, J R Challis
    Frontiers of hormone research 02/2001; 27:31-56. · 1.24 Impact Factor
  • J R Challis, S K Smith
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    ABSTRACT: Increased uterine contractility at term and preterm results from activation and then stimulation of the myometrium. Activation can be provoked by mechanical stretch of the uterus and by an endocrine pathway resulting from increased activity of the fetal hypothalamic-pituitary-adrenal axis. Cortisol, derived from the fetal adrenal in cases of intrauterine compromise or from the maternal adrenal in response to stress, or generated locally from cortisone in choriodecidual trophoblasts, provides a crucial link to uterine stimulation. Cortisol contributes to the increased production of prostaglandins (PGs) by fetal membranes and the decidua through the upregulation of PG synthase and the downregulation of PG dehydrogenase enzymes. Cortisol also stimulates placental corticotropin-releasing hormone (CRH) output, although CRH may both relax and stimulate uterine activity depending on the distribution and affinity of its receptor subtypes. Other agents such as cytokines may intercede in this sequence to stimulate PGs and/or CRH, giving rise to a cascade phenomenon that results in preterm birth.
    Biology of the Neonate 02/2001; 79(3-4):163-7. · 1.90 Impact Factor
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    ABSTRACT: Term and preterm labor are associated with increased fetal hypothalamic-pituitary-adrenal (HPA) activation and synthesis of prostaglandins (PGs) generated through the increased expression of prostaglandin H synthase-II (PGHS-II) in the placenta. Inhibition of PGHS-II has been advocated as a means of producing uterine tocolysis, but the effects of such treatment on fetal endocrine functions have not been thoroughly examined. Because PGE(2) is known to activate the fetal HPA axis, we hypothesized that administration of meloxicam, a PGHS-II inhibitor, to sheep in induced labor would suppress fetal HPA function. Chronically catheterized pregnant ewes were treated with RU486, a progesterone receptor antagonist, to produce active labor, and then treated with either high-maintenance-dose meloxicam, graded-maintenance-dose meloxicam, or a saline infusion. Maternal uterine contraction frequency increased 24 h after the RU486 injection and the animals were in active labor by 48 +/- 4 h. RU486 injection led to increased concentrations of PGE(2), ACTH, and cortisol in the fetal circulation, and increased concentrations of 13,14 dihydro 15-ketoprostaglandin F(2 alpha) (PGFM) in the maternal circulation. Uterine activity was inhibited within 12 h of beginning meloxicam infusion at both infusion regimes. During meloxicam infusion there were significant decreases in fetal plasma PGE(2), ACTH, and cortisol concentrations, and PGFM concentrations in maternal plasma. In control animals, frequency of uterine contractions, maternal plasma PGFM, fetal plasma PGE(2), ACTH, and cortisol concentrations increased after RU486 administration, and continued to rise during saline infusion until delivery occurred. We conclude that RU486-provoked labor in sheep is associated with activation of fetal HPA function, and that this is attenuated during meloxicam treatment to a level considered compatible with pregnancy maintenance.
    Biology of Reproduction 01/2001; 63(6):1899-904. · 4.03 Impact Factor
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    ABSTRACT: Birth in most animal species is triggered by the fetus through activation of the fetal hypothalamic-pituitary-adrenal (HPA) axis. Preterm birth, may be associated with precocious activation of fetal HPA function, reflecting the fetal response to an adverse intrauterine environment. There is a progressive and concurrent increase of ACTH1-39 and cortisol (F) in the circulation of fetal sheep during the last 15-20 days of pregnancy (term, day 145-150) associated with increased expression of hypothalamic CRH pituitary POMC and adrenal ACTH receptor and steroidogenic enzymes, particularly P450 C17. Similar changes occur with fetal hypoxemia. Negative feedback is ameliorated by decreased pituitary and hypothalamic glucocorticoid receptor, increased CBG, and altered fetal pituitary 11B-hydroxysteroid dehydrogenase type 1. Repeated fetal hypoxemia, diminishes the fetal-pituitary ACTH response, but increases fetal adrenal responsiveness. Fetuses exposed to maternal glucocorticoid in late gestation are growth restricted with altered postnatal HPA responsiveness and glycemic responses that reproduce the insulin resistance of type 2 diabetes. We conclude that the level of fetal HPA activity is crucial not only for determining gestation length, but also predicts pathophysiologic adjustment in later life.
    Endocrine Research 12/2000; 26(4):489-504. · 1.03 Impact Factor
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    ABSTRACT: A current hypothesis of ovine parturition proposes that fetal adrenal cortisol induces placental E2 production, which, in turn, triggers intrauterine PG production. However, recent evidence suggests that cortisol may directly increase PG production in trophoblast-derived tissues. To separate cortisol-dependent and estrogen-dependent PG production in sheep intrauterine tissues, we infused singleton, chronically catheterized fetuses beginning on day 125 of gestation (term, 147-150 days) with 1) cortisol (1.35 mg/h; n = 5); 2) cortisol and 4-hydroxyandrostendione, a P450aromatase inhibitor (4-OHA: 1.44 mg/h; n = 5); 3) saline (n = 5); or 4) saline and 4-OHA (n = 5). Fetal and maternal arterial blood samples were collected at 12-h intervals starting 24 h before infusion and continuing during treatment for 80 h or until active labor. Uterine contractility was measured by electromyogram recording of myometrial activity. Plasma E2, progesterone (P4), PGE2, and 13,14-dihydro- 15-keto-PGF2alpha were quantified by RIA. PGHS-II messenger RNA (mRNA) and protein expression were determined by in situ hybridization and Western blot analysis, respectively. Data were analyzed by ANOVA (P < or = 0.05). Labor-type uterine contractions were present after 68 h of cortisol infusion and had increased significantly by 80 h. Labor-type uterine contractions were induced after 68 h of cortisol plus 4-OHA infusion, but the contraction frequency remained less than that in the cortisol-treated animals. Fetal cortisol infusion increased fetal and maternal plasma E2 concentrations and decreased the maternal plasma P4 concentration significantly; concurrent 4-OHA infusion attenuated the increase in fetal and maternal plasma E2, but not the decrease in maternal plasma P4. The fetal plasma PGE2 concentration increased after both cortisol and cortisol plus 4-OHA infusion. The maternal plasma 13,14-dihydro-15-keto-PGF2alpha concentration rose after fetal cortisol infusion, but not after cortisol plus 4-OHA infusion. Placental trophoblast PGHS-II mRNA and protein expression were increased significantly after both cortisol and cortisol plus 4-OHA infusion. Endometrial PGHS-II mRNA and protein expression increased after cortisol infusion, but not after cortisol plus 4-OHA infusion. Plasma steroid and PG concentrations, uterine activity pattern, and intrauterine PGHS-II expression were not altered in either control group. We conclude that these data suggest distinct pathways of intrauterine PG synthesis: a cortisol-dependent/E2-independent mechanism within trophoblast tissue leading to elevations in fetal plasma PGE2, and an E2-dependent mechanism within maternal endometrium that leads to increased maternal plasma PGF2alpha and appears necessary for uterine activity and parturition.
    Endocrinology 10/2000; 141(10):3783-91. · 4.72 Impact Factor
  • A C Holloway, S Gyomorey, J R Challis
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    ABSTRACT: We hypothesized that the concurrent prepartum rise in adrenocorticotropic hormone (ACTH) and cortisol in the plasma of fetal sheep might be attributable to altered expression of pituitary endoproteases, prohormone convertase (PC)-1, and PC-2, or to changes in pituitary expression of glucocorticoid receptor (GR) that would influence negative feedback potential. We obtained pituitary tissue from fetal sheep during late pregnancy (d 100-d 145, term) and at precise times during the process of labor and used in situ hybridization to localize and quantify mRNA levels. Proopiomelanocortin (POMC) mRNA was regionally distributed (pars intermedia > inferior pars distalis > superior pars distalis) and increased within the pars distalis during late pregnancy and with labor. At term, levels of PC-1 and PC-2 mRNA were higher in the pars intermedia than pars distalis; PC-1 but not PC-2 in the pars distalis increased with gestational age, although it did not change further at labor. GR mRNA levels in the pars distalis increased between d 135 and term, then decreased during labor. We suggest that the concomitant rise in plasma ACTH and cortisol of fetal sheep during late gestation may be attributable, in part, to increased expression of PC-1 leading to increased POMC processing. Furthermore, the negative feedback effects of cortisol on pituitary POMC synthesis and/or ACTH release during active parturition may be lessened by downregulation of anterior pituitary GR.
    Endocrine 09/2000; 13(1):17-23. · 3.53 Impact Factor
  • W L Whittle, W Gibb, J R Challis
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    ABSTRACT: The amnion, a single layer of epithelial cells (EC) overlying layers of mesenchymal cells (MC) has been identified as a source of intrauterine prostaglandins (PG). The objectives of the present study were: (1) to establish a technique for the isolation and culture of pure amnion EC and MC preparations, (2) to characterize the cellular expression of PGHS-II and PGHS activity within these separated amnion cells and (3) to characterize the pattern of glucocorticoid stimulation of these separated amnion cells. Term gestation human amnion was collected after elective caesarean section or vaginal delivery. A trypsin digestion was used to isolate EC and a mechanical digestion and collagenase dispersion was used to isolate MC. Following 48 or 96 h in culture, cells were incubated for 24 h in the presence or absence of 1 microm arachidonic acid and treated with cortisol (F: 10-1000 nm) or 1 microm dexamethasone (DEX). Cell types were identified by immunohistochemistry (IHC). Immunoreactive PGHS-II (ir-PGHS-II) and glucocorticoid receptor (ir-GR) were localized by IHC. PGHS activity was measured as PGE(2)output determined by radioimmunoassay. Mean PGE(2)production by MC at 72 h was 22-fold greater (P<0.05) and at 120 h was 32-fold greater (P<0.03) than PGE(2)output by EC. Administration of arachidonic acid stimulated a 5.0-fold increase in PGE(2)output (P<0.0002) by EC after 72 h and a 3.6-fold increase (P<0.05) after 120 h but did not alter MC PGE(2)output. Despite exogenous substrate, EC PGE(2)output remained significantly less than PGE(2)output by MC. There was no difference in PG production by EC and MC with the onset of labour. Ir-GR expression was found in both EC and MC. F and/or DEX with and without arachidonic acid (AA) stimulated PGE(2)output by EC. Only DEX and not F increased PGE(2)output by MC. These data suggest that relatively pure EC and MC preparations can be established from amnion. PG output and its regulation appears to differ within these two amnion cell types, dependent upon (1) substrate availability and (2) the regulation of PGHS activity.
    Placenta 06/2000; 21(4):394-401. · 3.12 Impact Factor
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    W Gibb, M Sun, S Gyomorey, S J Lye, J R Challis
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    ABSTRACT: Increased prostaglandin production by tissues in the sheep uterus and placenta are thought to be important for the onset of parturition. In the sheep placenta, this is most likely due to increased expression of prostaglandin synthase type-2 (PGHS-2) rather than prostaglandin synthase type-1 (PGHS-1). However, there is no information concerning expression of PGHS isoenzymes in maternal uterine tissues during pregnancy. Therefore, the purpose of the present study was to examine the expression of PGHS-1 and PGHS-2 in the sheep myometrium and endometrium during late gestation using in situ hybridization and immunohistochemistry. Using (35)S-labelled oligonucleotide probes, which give specific hybridization signals in other tissues, we localized PGHS-2 mRNA to endometrial epithelium, and apparently to other cells in both endometrium and myometrium. This artefactual signal was still present with 100-fold excess unlabelled oligonucleotide probe and with sense probes, but was resolved with the use of (33)P-oligonucleotides. Using (33)P-labelled oligonucleotide probes we could not detect either PGHS-1 or PGHS-2 mRNA in myometrium, and found expression only of PGHS-2 mRNA in endometrium. PGHS-2 mRNA localized to the endometrial epithelium and was undetectable in glandular epithelium. The level of PGHS-2 expression rose significantly between days 80 and 85 of pregnancy and term, and this corresponded to the appearance of immunoreactive PGHS-2 protein, measured by immunohistochemistry, in the endometrial epithelium. Therefore we conclude that (33)P-labelled probes are preferred for detection of mRNAs encoding PGHS-2 in ovine uterine tissues. Expression of PGHS-2 mRNA is greater than that of PGHS-1, increases during gestation, and predominates in the endometrial epithelium, consistent with the site of PGHS-2 protein localization.
    Journal of Endocrinology 05/2000; 165(1):51-8. · 4.06 Impact Factor
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    ABSTRACT: cDNAs for ovine surfactant-associated protein (SP) A, SP-B, and SP-C have been cloned and shown to possess strong similarity to cDNAs for surfactant apoproteins in other species. These reagents were employed to examine the effect of fetal hypoxia on the induction of surfactant apoprotein expression in the fetal lamb. Postnatal lung function is dependent on adequate growth and maturation during fetal development. Insulin-like growth factor (IGF) I and IGF-II, which are present in all fetal tissues studied, possess potent mitogenic and proliferative actions, and their effects can be modulated by IGF-specific binding proteins (IGFBPs). Hypoxia can lead to increases in circulating cortisol and catecholamines that can influence lung maturation. Therefore, the effects of mild hypoxia in chronically catheterized fetal lambs at gestational days 126-130 and 134-136 (term 145 days) on the expression of pulmonary surfactant apoproteins and IGFBPs were examined. Mild hypoxia for 48 h resulted in an increase in plasma cortisol that was more pronounced at later gestation, and in these animals, there was a twofold increase in SP-A mRNA. SP-B mRNA levels also increased twofold, but this was not significant. SP-C mRNA was not altered. No significant changes in apoprotein mRNA were observed with the younger fetuses. However, these younger animals selectively exhibited reduced IGFBP-5 mRNA levels. IGF-I mRNA was also reduced at 126-130 days, although this conclusion is tentative due to low abundance. IGF-II levels were not affected at either gestational age. We conclude that these data suggest that mild prolonged fetal hypoxia produces alterations that could affect fetal cellular differentiation early in gestation and can induce changes consistent with lung maturation closer to term.
    AJP Lung Cellular and Molecular Physiology 05/2000; 278(4):L754-64. · 3.52 Impact Factor
  • S Gyomorey, S J Lye, W Gibb, J R Challis
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    ABSTRACT: We examined whether spontaneous parturition in sheep was associated with tissue-specific changes in prostaglandin H(2) synthase-2 (PGHS-2) expression and/or with altered expression of myometrial EP and FP receptors. Placental and uterine tissues were collected from three groups of chronically catheterized sheep in relation to term spontaneous labor: late pregnancy, not in labor; early labor; and active labor. Expression of PGHS-2 mRNA and protein was determined by in situ hybridization, Western blotting, and immunohistochemistry. Semiquantitative reverse transcription-polymerase chain reaction was used to assess the presence of and changes in prostaglandin (PG) receptor subtypes. In placenta, PGHS-2 mRNA and protein localized to trophoblast uninucleate cells and tended to increase with early labor. PGHS-2 mRNA and protein localized to endometrial epithelium and to myometrium, where PGHS-2 protein levels rose in active labor tissues. Concentrations of PGE(2) in fetal plasma rose progressively with labor, whereas 13,14-dihydro-15-keto-PGF(2alpha) in maternal plasma increased significantly only in active labor. Messenger RNA encoding four EP receptor subtypes and FP receptor were present in myometrium, but levels did not change with labor. We suggest that spontaneous labor in sheep is associated with a progressive increase in PGHS-2 expression in a temporal and tissue-specific manner from trophoblast to maternal tissues, rather than alteration in PG receptor gene expression.
    Biology of Reproduction 04/2000; 62(3):797-805. · 4.03 Impact Factor
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    D M Sloboda, J P Newnham, J R Challis
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    ABSTRACT: Synthetic glucocorticoids have become an important clinical tool with which to advance fetal lung maturation in women at risk of early preterm birth, and this has succeeded in reducing neonatal mortality and morbidity from respiratory distress syndrome. Although previous studies have shown that glucocorticoids have deleterious consequences on fetal development, there is little information regarding the effects of clinically relevant repeated maternal doses of glucocorticoids on fetal growth and hypothalamic-pituitary-adrenal (HPA) function. We hypothesised that repeated prenatal exposure to increased concentrations of glucocorticoids would alter fetal growth and HPA axis development. Pregnant ewes were injected with betamethasone (0.5 mg/kg) or vehicle at 104, 111 and 118 days of gestation (term 150 days). Animals were sacrificed at 125 and 146 days of gestation, at which time fetal weights were recorded. Maternal and fetal blood samples were gathered and fetal tissue collected. Maternal oestradiol concentrations were significantly greater than those in controls at 125 days of gestation, but were not different at 146 days. Maternal plasma progesterone concentrations were similar between groups at both 125 and 146 days of gestation. Weight at birth was significantly reduced by 23% at 125 days and 19% at 146 days of gestation (P<0.05) after exposure to glucocorticoid. Cord plasma ACTH concentrations were not significantly different between groups at day 125, but were significantly increased in day 146 fetuses of ewes that had received betamethasone (P<0.05). Cord plasma cortisol concentrations followed the same trend, although differences were not statistically significant. Cord plasma corticosteroid binding capacity (CBC) was significantly increased at 125 days of gestation in fetuses of betamethasone-treated animals (P<0.05), but not at 146 days of gestation. To examine the mechanisms regulating the increase in cord plasma ACTH of 146-day fetuses, we used in situ hybridisation to determine the distribution and levels of mRNA encoding key pituitary and hypothalamic neuropeptides of the HPA axis. In pituitaries of 146-day fetuses, there were no significant differences in the regional pattern of distribution or amounts of pro-opiomelanocortin (POMC) mRNA between betamethasone-treated animals and controls, in either the pars intermedia or the inferior and superior regions of the pars distalis. Neither prohormone convertase (PC)-1 nor PC-2 mRNA levels in pituitaries of 146-day fetuses were significantly different between treatment groups. After maternal betamethasone, immunoreactive ACTH peptide content in the fetal pars distalis was not different but glucocorticoid receptor (GR) mRNA levels in the pars distalis were increased significantly (P<0.05). No significant difference in distribution pattern or concentrations of corticotrophin-releasing hormone (CRH) mRNA, GR mRNA, oxytocin mRNA and pre-proenkephalin mRNA were found in hypothalami from fetuses at 146 days of gestation after betamethasone treatment. We conclude that antenatal betamethasone given to pregnant sheep in a manner similar to that used in human obstetric practice results in reduced weight at birth at 125 and 146 days, and altered basal cord levels of plasma ACTH and corticosteroid binding capacity, but these changes are not reflective of changes in steady state concentrations of POMC and CRH mRNA in the fetal pituitary or hypothalamus.
    Journal of Endocrinology 04/2000; 165(1):79-91. · 4.06 Impact Factor
  • F Pomini, F A Patel, S Mancuso, J R Challis
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    ABSTRACT: The aim of this study was to investigate whether any changes occurred at term before and with labor in the 15-hydroxyprostaglandin dehydrogenase messenger ribonucleic acid level and in the 15-hydroxyprostaglandin dehydrogenase activity in cultured chorionic and villous trophoblast cells and in chorionic explants. Twelve placentas (labor group [vaginal delivery], n = 6; nonlabor group [elective cesarean delivery], n = 6) were collected. Chorionic trophoblast and villous trophoblast cells and chorionic disks were obtained, cultured, and incubated with 282-nmol/L prostaglandin F(2)(alpha). Medium was collected to measure the 13,14-dihydro-15-keto metabolite of prostaglandin F(2)(alpha), and the cells and disks were snap-frozen to quantify 15-hydroxyprostaglandin dehydrogenase messenger ribonucleic acid expression by Northern blot analysis. The formation of the 13,14-dihydro-15-keto metabolite of prostaglandin F(2)(alpha) was significantly lower in the labor group than in the nonlabor group for both sets of cultured cells and for chorionic explants. 15-Hydroxyprostaglandin dehydrogenase messenger ribonucleic acid expression was lower in the chorionic trophoblast cells and chorionic disks of the labor group than those of the nonlabor group. However, the 15-hydroxyprostaglandin dehydrogenase messenger ribonucleic acid level in the villous trophoblast cells did not differ between the labor and nonlabor groups. Prostaglandin metabolic activity in the chorion is reduced significantly at the time of labor.
    American Journal of Obstetrics and Gynecology 02/2000; 182(1 Pt 1):221-6. · 3.88 Impact Factor
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    ABSTRACT: Labour in the sheep is preceded by increased tissue and plasma prostaglandin (PG) concentrations, and PGs could potentially contribute to the regulation of P450(C17)in placental tissue. Therefore, we determined the cellular localization and temporal pattern of expression of P450(C17)and prostaglandin H synthase type 2 (PGHS-2), the primary PG synthetic enzyme, in intrauterine tissues from three groups of pregnant ewes at term; animals not in labour (NIL;n=5; 140-145 days of gestation), animals in early labour (EL;n=6; 143-149 days) and animals in active labour (L;n=6; 145-149 days). Allocation of animals into the three groups was based on continuous monitoring and assessment of myometrial contractile activity (EMG) and changes in the intrauterine pressure (IUP). Levels of mRNA encoding PGHS-2 and P450C17 were determined by in situ hybridization. Localization and levels of immunoreactive (ir-) P450(C17)and ir-PGHS-2 protein were determined by immunohistochemistry and Western blotting. PGHS-2 mRNA and ir-PGHS-2 were already elevated in placentomes of NIL animals and did not increase further with the progression of labour, whereas P450C17 mRNA increased progressively with labour, and ir-P450C17 rose significantly only in animals in active labour. The rise in P450C17 expression corresponded temporally to a progressive increase in maternal plasma concentration of oestradiol. We suggest that the temporal relationship and subsequent co-localization of PGHS-2 and P450(C17)proteins in the uninucleate trophoblast cells of the placentomes are consistent with the possibility that placental PGs could act to enhance placental output of oestrogen leading to labour and delivery.
    Placenta 01/2000; 21(5-6):478-86. · 3.12 Impact Factor

Publication Stats

4k Citations
907.92 Total Impact Points

Institutions

  • 1999–2012
    • Samuel Lunenfeld Research Institute
      Toronto, Ontario, Canada
  • 2001
    • University of Cambridge
      • Department of Obstetrics & Gynaecology
      Cambridge, ENG, United Kingdom
  • 1996–2001
    • University of Toronto
      • • Department of Physiology
      • • Faculty of Medicine
      Toronto, Ontario, Canada
  • 1996–2000
    • University of Ottawa
      • Department of Obstetrics and Gynecology
      Ottawa, Ontario, Canada
  • 1980–1999
    • The University of Western Ontario
      • Department of Obstetrics and Gynaecology
      London, Ontario, Canada
  • 1998
    • Sapienza University of Rome
      • Department of Gynecology-Obstetrics & Urology
      Roma, Latium, Italy
  • 1995–1998
    • Odense University Hospital
      Odense, South Denmark, Denmark
  • 1997
    • Leiden University Medical Centre
      Leyden, South Holland, Netherlands
  • 1988–1996
    • Lawson Health Research Institute
      London, Ontario, Canada
  • 1993
    • Lawson Health Research Institute
      Guilford, England, United Kingdom
  • 1992
    • MRC Mitochondrial Biology Unit
      Cambridge, England, United Kingdom
  • 1987
    • Saint Joseph Hospital
      Chicago, Illinois, United States
  • 1977
    • McGill University
      • Department of Obstetrics and Gynecology
      Montréal, Quebec, Canada
  • 1976–1977
    • University of Oxford
      • Nuffield Department of Obstetrics and Gynaecology
      Oxford, ENG, United Kingdom