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Biomedical subjects

M D Mitchell

Publications and source records attributed to M D Mitchell.

At least 19 recordsLinked to original sources
PubMed2005

Suppressors of cytokine signaling proteins in human preterm placental tissues.

Decreased suppressors of cytokine signaling (SOCS) activity in human gestational tissues may play a part in the onset/progression of term labor. Since SOCS proteins negatively regulate cytokine-mediated inflammatory processes, we hypothesized that SOCS proteins are elevated in gestational tissues from spontaneous preterm deliveries with intrauterine infection. SOCS1, -2 and -3 mRNAs and proteins were detectable by RT-PCR and immunoblotting respectively, in preterm amnion, choriodecidua and placenta, irrespective of infection status. Immunoperoxidase staining localized SOCS1, -2 and -3 to all cell types of the gestational membranes, with infiltrating leukocytes reacting strongly in infected tissues. In villous placenta, SOCS was immunolocalized to the syncytiotrophoblast with marked staining of round mesenchymal cells, possibly Hofbauer cells. Nuclear SOCS staining was seen in amnion, chorion and placental syncytiotrophoblasts. SOCS proteins were, in general, significantly more abundant in placenta compared with amnion or choriodecidua. Placental SOCS1 and interleukin-1beta concentrations were positively correlated (r(2)=0.47; P<0.05). However, no changes in SOCS levels in any tissues were observed with intrauterine infection. The relatively large amounts of SOCS proteins in the placenta may reflect a placenta-specific immunoprotective response to minimize the elaboration and effects of cytokines with potential to harm the placenta and fetus. Lack of labor-associated changes in SOCS levels suggests that the regulation of SOCS expression in preterm gestational tissues differs from those at term, perhaps reflecting roles in regulating placental somatotropic responses.

Amnion↗
PubMed2003

Epithelial cell-derived neutrophil-activating peptide-78 is present in fetal membranes and amniotic fluid at increased concentrations with intra-amniotic infection and preterm delivery.

Intra-amniotic secretion and abundance of epithelial cell-derived neutrophil-activating peptide (ENA)-78, a potent chemoattractant and activator of neutrophils, was studied in the context of term and preterm parturition. Staining of ENA-78 immunoperoxidase was localized predominantly to chorionic trophoblasts and amniotic epithelium in term and preterm gestational membranes, with weaker and less consistent staining in decidual cells. The abundance of ENA-78 in membrane tissue homogenates was significantly increased ( approximately 4-fold) with term labor in amnion (n = 15), and with preterm labor ( approximately 30-fold) in amnion and choriodecidua (n = 31). In amnion tissue homogenate extracts, ENA-78 levels were positively correlated with the degree of leukocyte infiltration (r2 = 0.481). In amniotic fluids, median ENA-78 levels from pregnancies with preterm labor without intra-amniotic infection were significantly lower (P < 0.01 by ANOVA) than those from pregnancies with preterm deliveries with infection; levels in samples derived from term pregnancies were similar before and after labor. Production of ENA-78 by amnion monolayers was stimulated in a concentration-dependent fashion by both interleukin-1beta and tumor necrosis factor alpha. Production of ENA-78 by choriodecidual explants was increased modestly after 2-4 h of exposure to lipopolysaccharide (5 microg/ml). An immunoreactive doublet ( approximately 8 kDa) was detected in choriodecidual explant-conditioned media by immunoblotting. We conclude that ENA-78, derived from the gestational membranes, is present in increased abundance in the amniotic cavity in response to intrauterine infection and, hence, may play a role in the mechanism of infection-driven preterm birth and rupture of membranes secondary to leukocyte recruitment and activation.

Amniotic Fluid↗
PubMed2003

Identification of the CB1 cannabinoid receptor and fatty acid amide hydrolase (FAAH) in the human placenta.

Synthetic cannabinoids, the psychoactive components of the Cannabis sativa (marijuana) plant and their endogenous counterparts, act through two G protein-coupled receptors, CB1 and CB2. The endocannabinoids are metabolized by fatty acid amide hydrolase (FAAH). Previous research has described the impact of cannabis consumption on pregnancy, potential roles of endocannabinoids and abnormalities of FAAH expression in recurrent miscarriage and pregnancy. However, the cellular localization of the CB1 cannabinoid receptor and FAAH in the human placenta has not been determined. We have examined CB1 receptor and FAAH expression in human term placenta by immunohistochemistry. CB1 receptor was found to be present in all layers of the membrane, with particularly strong expression in the amniotic epithelium and reticular cells and cells of the maternal decidua layer. Moderate expression was observed in the chorionic cytotrophoblasts. The expression of FAAH was highest in the amniotic epithelial cells, chorionic cytotrophoblast and maternal decidua layer. Our results suggest that the human placenta is a likely target for cannabinoid action and metabolism. This is consistent with a placental site of action of endocannabinoids and cannabis being responsible, at least in part, for the poor outcomes associated with cannabis consumption and pathology in the endocannabinoid system during pregnancy.

Adult↗
PubMed2003

Identification of the CB1 cannabinoid receptor and fatty acid amide hydrolase (FAAH) in the human placenta.

Synthetic cannabinoids, the psychoactive components of the Cannabis sativa (marijuana) and their endogenous counterparts, act through two G protein-coupled receptors, CB1 and CB2. The endocannabinoids are metabolized by fatty acid amide hydrolase (FAAH). Previous research has described the impact of cannabis consumption on pregnancy, potential roles of endocannabinoids and abnormalities of FAAH expression in recurrent miscarriage and pregnancy. However, the cellular localization of the CB1 cannabinoid receptor and FAAH in the human placenta has not been determined. We have examined CB1 receptor and FAAH expression in human term placenta by immunohistochemistry. CB1 receptor was found to be present in all layers of the membrane, with particularly strong expression in the amniotic epithelium and reticular cells and cells of the maternal decidua layer. Moderate expression was observed in the chorionic cytotrophoblasts. The expression of FAAH was the highest in amniotic epithelial cells, chorionic cytotrophoblast and maternal decidua layer. Our results suggest that the human placenta is a likely target for cannabinoid action and metabolism. This is consistent with a placental site of action of endocannabinoids and cannabis being responsible, at least in part, for the poor outcomes associated with cannabis consumption and pathology in the endocannabinoid system during pregnancy.

Adult↗
PubMed2003

Cytokines, prostaglandins and parturition--a review.

The elaboration of cytokines, chemokines and immunomodulatory proteins in the placenta and gestational membranes has been extensively investigated in the context of both normal and abnormal pregnancy and delivery. Patterns of expression of cytokines in the foetal membranes and decidua suggest that inflammatory activation occurs modestly with term labour, but much more robustly in preterm delivery, particularly in the presence of intrauterine infection. Enhanced chemokine expression, particularly evident in deliveries with an infected amniotic cavity, is presumably responsible for recruiting infiltrating leukocytes into the membranes thereby amplifying the inflammatory process and hastening membrane rupture and delivery. Anti-inflammatory cytokines suppress inflammatory reactions in the placenta, but under some circumstances may act in a pro-inflammatory fashion in the membranes. Intracellular signalling by cytokines is modulated by proteins such as SOCS (Silencer Of Cytokine Signalling)-1, -2 and -3. Changes in the abundance of these proteins occur with term labour, implicating them as modulators of cytokine actions around the time of parturition. Prostaglandins, released by the membranes in response to stretch and the actions of pro-inflammatory cytokines, act not only upon the myometrium and cervix, but may also exert paracrine/autocrine effects on cell viability and matrix protein integrity. The localization and regulation of prostanoid isomerases, responsible for converting PGH(2) (derived from prostaglandin H synthase-1 and -2) to bioactive prostanoids, are being studied in these tissues, particularly in the context of cytokine interactions. Although the gestational tissues are known to be sources of PGD(2), PGJ(2) and its derivatives, the regulation of production of these prostaglandins has yet to be studied in any detail and their actions, which may include apoptosis and suppression of inflammation, remain poorly defined. A more complete understanding of these aspects of cytokine-prostaglandin interactions in pregnancy and parturition will, no doubt, unfold as current studies come to fruition.

Chemokines↗
PubMed2003

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), TRAIL receptors, and the soluble receptor osteoprotegerin in human gestational membranes and amniotic fluid during pregnancy and labor at term and preterm.

We have studied TNF-related apoptosis-inducing ligand (TRAIL) and its membrane-bound (R1-R4) and soluble receptors [osteoprotegerin (OPG)] in gestational membranes to assess their significance in preterm parturition and premature rupture of membranes (PROM). TRAIL was detected by ELISA in extracts of term choriodecidual (but not amnion) tissues and explant-conditioned media. Concentrations of OPG (determined using ELISA) in gestational membranes were 20- to 50-fold greater than those of TRAIL. Median OPG concentrations in amniotic fluid (AF) at 15-17 wk gestation were similar to those at term before and during labor, whereas levels in pregnancies sampled preterm were significantly elevated. OPG levels in AF from women with preterm PROM were similar to those from women in preterm labor. In contrast, in pooled AF samples (n = 23-33), TRAIL concentrations at term with and without labor were elevated compared with samples from preterm deliveries. TRAIL-R3 and -R4 decoy receptors were detected in term amnion and choriodecidual extracts by immunoblotting and were localized by immunohistochemistry to amnion epithelial cells and chorionic trophoblasts. TRAIL (100 ng/ml) had little or no effect on amnion or choriodecidual cell viability or apoptosis, although these tissues responded to TNF-alpha with increased prostaglandin E(2) production. Our findings suggest that OPG is abundant in gestational membranes and, in concert with TRAIL decoy receptors, may protect resident cells of the fetal membranes against the proapoptotic effects of TRAIL and other related ligands during pregnancy.

Adult↗
PubMed2002

Hypoxia inhibits activin A production by term villous trophoblast in vitro.

Elevated activin A and inhibin A levels have been associated with pre-eclampsia, a pregnancy-related disorder associated with placental hypoxaemia. We investigated the effect of in vitro hypoxia on the production of inhibin A, activin A and its binding protein follistatin in term villous placental explants (n=4-7) and trophoblast monolayer cultures (n=4). Explants and trophoblasts were incubated for 24-72 h under either normoxic (21 per cent O(2)) or hypoxic (2 per cent O(2)) conditions. Production of activin A, inhibin A, and follistatin was determined by specific ELISA. After 48 h of hypoxia, villous explants exhibited a significant reduction in activin A production rates to 53.2 +/- 8.9 per cent (mean +/- SEM, P<0.05) of normoxic controls which was sustained after 72 h in culture (46.8 +/- 5.9 per cent), whereas production by trophoblast monolayers was not affected by hypoxia. Follistatin production was decreased to 53.7 +/- 9.2 per cent of control (P<0.05) after 48 h of hypoxia. Inhibin A production remained unaltered in both culture systems. Our data demonstrate for the first time that hypoxia lowers term placental activin A and follistatin production in vitro. These findings do not support the notion that elevated circulating activin A levels in pre-eclampsia originate from the placenta as a result of placental hypoxia. Other as yet unknown maternal/placental factors may contribute to elevated activin A production in women with severe pre-eclampsia.

Activins↗
PubMed2002

Cytokines of the placenta and extra-placental membranes: biosynthesis, secretion and roles in establishment of pregnancy in women.

Virtually all known cytokines have been demonstrated to be expressed in the placenta and associated fetal and maternal membranes during normal gestation. In addition to playing their traditional roles as modulators of immunological function, cytokines derived from the placenta and extraplacental membranes, together with other locally-derived growth factors, appear to be implicated in various aspects of implantation and placental development. Imbalances in the intrauterine cytokine milieu around the time of implantation and invasion may play a causative role in disorders associated with early pregnancy failure, and are also associated with the abnormal trophoblast development seen in gestational trophoblastic disease. Cytokines thus appear to be an important component of a paracrine/autocrine communication network operating within the feto-maternal interface to ensure the successful establishment of pregnancy.

Abortion, Habitual↗
PubMed2002

Cytokines of the placenta and extra-placental membranes: roles and regulation during human pregnancy and parturition.

Summary In an earlier, companion, review, we concluded that cytokines produced by the placenta and associated membranes are likely to be involved in control of the processes of implantation and placental development (Bowen et al., 2002). In this review, we discuss evidence that cytokines continue to be part of a paracrine/autocrine regulatory network in the placenta and membranes throughout the mid and late stages of gestation. Cytokines are involved in regulation of placental growth during these later stages of pregnancy and also function to protect the fetus from pathological organisms. The evidence, while not entirely consistent, suggests that production of certain cytokines within the extraplacental membranes is altered during normal term parturition, whereas in the villous placenta evidence of labour-associated changes is much more equivocal. Roles for cytokines have been postulated in many facets of parturition, including expulsion of the fetus by uterine contractions, membrane rupture, and dilation of the cervix. Imbalances and disruptions to the cytokine milieu have been implicated in a number of diseases of pregnancy involving abnormalities of both placental growth/establishment and initiation of parturition. Cytokine secretion induced by intrauterine infection is associated with increased occurrence or severity of some neonatal diseases. This wealth of data supports the view that cytokines are an integral part of a functional regulatory/communication network operating within the placental-maternal unit during normal gestation.

Bronchopulmonary Dysplasia↗
PubMed2002

Use of cDNA arrays to generate differential expression profiles for inflammatory genes in human gestational membranes delivered at term and preterm.

Inflammatory processes are implicated in preterm labour (PTL). To identify potential novel markers for PTL, we have used commercial cDNA arrays to generate profiles of differential expression of inflammation-associated genes in gestational membranes with term and PTL. RNA for cDNA probe synthesis was isolated from reflected human amnion and choriodecidua membranes delivered following Caesarean section at term before the onset of labour (TNL, n = 4), spontaneous labour at term (TSL, n = 4), and PTL with and without chorioamnionitis (PTL(+INF) and PTL(-INF) respectively, n = 4 each). Profiles were displayed relative to TNL and statistical comparisons of TSL versus TNL and PTL(+INF) versus PTL(-INF) were performed. Elevated expression of chemokines macrophage inflammatory protein 1beta(MIP-1beta) and pulmonary and activation-regulated chemokine (PARC) was observed in PTL(+INF) compared to PTL(-INF) amnion and choriodecidua respectively (P = 0.03). Likewise, the cytokines oncostatin-M and pre-B cell enhancing factor (PBEF) were more highly expressed in PTL(+INF) compared with PTL(-INF) and in TSL compared with TNL respectively (P = 0.03). Conversely, inhibin A, tissue inhibitors of matrix metalloproteinase (TIMP)-3 and TIMP-4 were all significantly elevated in PTL(-INF) compared with PTL(+INF) (P = 0.03). Furthermore, differential expression patterns of classes of genes, grouped according to function (e.g. chemokines), were noted. The cDNA array approach holds promise for identification of new candidate markers or combinations thereof for prediction or diagnosis of PTL, as well as for increasing our understanding of the particular aetiologies involved.

Cytokines↗
PubMed2001

Prevention of pneumonia in elderly stroke patients by systematic diagnosis and treatment of dysphagia: an evidence-based comprehensive analysis of the literature.

We conducted a systematic literature review and analysis of programs for evaluating swallowing in order to prevent aspiration pneumonia. This article derives from an evidence report on diagnosis and treatment of swallowing disorders (dysphagia) in acute-car stroke patients prepared by us as an Evidence-based Practice Center (EPC) under contract to the U.S. Agency for Healthcare Research and Quality (AHRQ). Available evidence on the diagnosis and treatment of dysphagia for preventing pneumonia is limited. We found reported pneumonia rates in one historical controlled study of a program using bedside exams (BSE) for acute stroke patients; one uncontrolled case series study of acute stroke patient-reporting of swallowing difficulty; one controlled case series study of videofluoroscopic study of swallowing (VFSS) for acute stroke patients; and one historical controlled study of fiberoptic endoscopic examination of swallowing (FEES) for patients referred for swallowing evaluation in rehabilitation centers. Comparing these results with historical controls indicates that implementation of dysphagia programs is accompanied by substantial reductions in pneumonia rates. While all these methods appeared effective, the small sizes of available studies did not allow determination of the relative efficacy of BSE, VFSS, or FEES.

Aged↗
PubMed2001

Is interleukin-3 important in antiphospholipid antibody-mediated pregnancy failure?

OBJECTIVE: To investigate the effect of interleukin-3 (IL-3) on trophoblast proliferation and expression of beta2-glycoprotein I. DESIGN: In vitro cell culture using primary trophoblasts and the cell lines Jeg-3, Jar, and BeWo. SETTING: Department of Obstetrics and Gynaecology, University of Auckland. PATIENT(S): Women with normal pregnancies. INTERVENTION(S): Increasing amounts of IL-3 were added to cultures of primary human trophoblasts, cell lines, or cells treated with a proliferation inhibiting antiphospholipid-like antibody. RNA was extracted from primary human trophoblasts or cell lines. MAIN OUTCOME MEASURE(S): We examined basal and IL-3-stimulated cellular proliferation by [3H] thymidine incorporation assay and secretion of beta2-glycoprotein I into culture medium by semiquantitative immunoblot analysis. Reverse transcriptase-polymerase chain reaction analysis was used to demonstrate the presence of IL-3 receptor transcripts. RESULT(S): The IL-3 treatment did not induce proliferation of highly purified primary trophoblast cultures or cell lines but did induce proliferation of contaminating CD45+ cells in trophoblast cultures. The IL-3 did not overcome the antiproliferative effect of an antiphospholipid-like monoclonal antibody on trophoblast. Secretion of beta2-glycoprotein I by trophoblast cultures was time dependent but unaltered by IL-3 treatment. CONCLUSION(S): Our results question the proposed importance of IL-3 in antiphospholipid antibody-mediated fetal death.

Abortion, Spontaneous↗
PubMed2001

Transcriptional regulation of prostaglandin-H-synthase-1 in the amnion-derived AV3 cell line.

Prostaglandin-H-synthase-1 (PGHS-1), while constitutively expressed in most tissues, increases in abundance in human gestational membranes at term. This suggests that PGHS-1 may be up-regulated in preparation for labor, and thus might be a key determinant in timing labor onset. We conducted transient transfection experiments in amnion-derived AV3 cells utilizing pPGHS1CAT to identify substances that might regulate PGHS-1 expression in amnion. Transforming growth factor-beta (1 ng/ml) and 15-deoxy-delta(12,14) prostaglandin J2 (1 microM) significantly (P < 0.05) (33% and 44% respectively) increased PGHS-1 promoter activity. The activity decreased significantly (P < 0.05) in response to interleukin-1 (IL-1)beta (1 ng/ml) (45%), tumor necrosis factor (TNF)-alpha (50 ng/ml) (34%), epidermal growth factor (10 ng/ml) (54%), phorbol myristate acetate (10 nM) (70%), IL-4 (10 ng/ml) (50%), IL-8 (100 ng/ml) (72%) and Activin A (25 ng/ml) (32%). Whether this degree of change in promoter activity leads to physiologically relevant alterations in the amounts of PGHS-1 present in cells remains to be determined.

Amnion↗
PubMed2001

Expression of prostaglandin H synthase-1 and -2 in murine intrauterine and gestational tissues from mid pregnancy until term.

These studies were undertaken to evaluate the changes in mRNA expression of prostaglandin H synthase (PGHS)-1 and -2 in murine gestational tissues during the latter half of pregnancy. Gestational tissues (decidual caps, membranes surrounding the fetus, and placentae), uterus, and cervix were collected from pregnant mice at days 12, 14, 16, 18, and 19 (am and pm) of gestation (n = 4), and total RNA was isolated and evaluated for PGHS-1 and PGHS-2 expression by northern blot analysis. Expression was normalized to GAPDH. There were no significant increases in PGHS-2 mRNA expression in any of the tissues studied through gestation. In contrast, expression of PGHS-1 mRNA increased significantly at term in the uterus and fetal membranes. In the placenta, mRNA for PGHS-1 was elevated at day 18 and remained elevated over the remainder of the study. These findings suggest that, in the mouse, increased production of PGs by uterine and intrauterine tissues during pregnancy is associated with up-regulation of PGHS-1 and not PGHS-2.

Animals↗
PubMed2001

Predicting preterm delivery: comparison of cervicovaginal interleukin (IL)-1beta, IL-6 and IL-8 with fetal fibronectin and cervical dilatation.

OBJECTIVE: To compare the cervicovaginal cytokines IL-1beta, IL-6 and IL-8 with fetal fibronectin (fFN) and cervical dilatation in the prediction of preterm delivery. STUDY DESIGN: Cervicovaginal cytokine concentration and fFN status were measured in 104 women with symptoms of preterm labour and intact membranes between 24(0) and 33(6) weeks and related to delivery within 2 and 7 days. RESULTS: A group of 18% had cervical dilatation > or = 1cm and 18% were positive for fFN. Preterm delivery within 2 and 7 days occurred in 5 and 12%, respectively. Only IL-6 demonstrated any ability to predict delivery within 2 and 7 days (area under the ROC curve = 0.63 and 0.75, respectively). Using 35pg/ml (75th centile) as a cut-off, IL-6 had a sensitivity and specificity of 60 and 77% for predicting delivery within 2 days, and 62 and 80% for predicting delivery within 7 days. This is similar to the performance of cervical dilatation or fFN status. CONCLUSIONS: Measurement of cervicovaginal cytokines has limited ability to predict imminent delivery apart from cervicovaginal IL-6 concentrations, which, in this population, is equivalent to that of fFN status and cervical dilatation > or = 1cm.

Adult↗
PubMed2001

Expression of interleukin-1beta mRNA in murine uterine and gestational tissues: relationship with gestational age.

PROBLEM: The pro-inflammatory cytokine interleukin (IL)-1beta has been shown to stimulate the production of prostaglandins (PG) in gestational tissues. Increased PG synthesis is considered a key step in the initiation of labor both at term and preterm. In this study. IL-1beta mRNA in the uterus and gestational tissues of mice during mid to late pregnancy was studied to characterize its tissue specific as well as gestational age expression. METHOD OF STUDY: Gestational tissues (placenta. decidual cap and fetal membranes). uterus, and cervix were collected from pregnant mice during gestation. Total RNA was isolated and probed for the expression of IL-1beta mRNA. RESULTS: There was a significantly increased expression of IL-1beta mRNA in the uterus on day 18 of pregnancy. In the decidual caps, there was increased expression of IL-1beta mRNA on day 14 of pregnancy and a decrease in expression with the onset of labor. In the fetal membranes and placenta, IL-1beta mRNA expression significantly increased on days 14 and 18 of pregnancy. respectively, and then remained elevated for the duration of pregnancy. In the cervix, there was a decrease in expression with labor onset. CONCLUSIONS: The increases in IL-1beta mRNA in the fetal membranes and placenta late in pregnancy are consistent with a localized, tissue specific inflammatory activation involved in the initiation of parturition.

Animals↗
PubMed2001

Hypoxia attenuates PGE(2)but increases prostacyclin and thromboxane production in human term villous trophoblast.

Prostanoids have been proposed to play a major role in the regulation of uteroplacental blood flow. We examined the effect of hypoxia on the production of prostaglandin E(2)(PGE(2)) thromboxane B(2)(TXB(2)), and prostacyclin (measured as 6-keto-PGF(1alpha)) by human term trophoblast cells and villous placental explants. Explants (n=8) and purified trophoblast cells (n=5) were incubated for 24-72 h under either normoxic (21 per cent O(2)) or hypoxic (2 per cent O(2)) conditions. In trophoblast monolayer cultures, hypoxia attentuated PGE(2)production rates to 52+/-9.4 per cent (mean+/-sem, P< 0.05) but recovered to control rates within 48 h. In villous explants, PGE(2)production was significantly decreased after 48 and 72 h of hypoxia versus the normoxic control, accompanied by increased production of 6-keto-PGF(1alpha)to 173.9+/-26.7 per cent after 48 h. TXB(2)production was increased to 172.3+/-25.9 per cent and 653.2+/-135.7 per cent (P< 0.05) control after 48 and 72 h of hypoxia, respectively. These results were confirmed in villous explants (n=3) cultured in the presence of exogenous 10 microm arachidonic acid. Hypoxia had no significant effect on TXB(2)and 6-keto-PGF(1alpha)in trophoblast cells. In summary, our findings suggest that hypoxia could be responsible for abnormal profiles of prostanoid production commonly observed in women with pre-eclampsia. These results indicate a putative link between hypoxia and compromised placental perfusion.

6-Ketoprostaglandin F1 alpha↗