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Biomedical subjects

P R Stone

Publications and source records attributed to P R Stone.

At least 19 recordsLinked to original sources
PubMed2006

Activated endothelial cells resist displacement by trophoblast in vitro.

BACKGROUND: Transformation of the spiral arteries by invading trophoblasts is an essential prerequisite to the development of a healthy fully grown fetus. Reduced transformation of the spiral arteries is a characteristic feature of pregnancies complicated by several diseases of pregnancy including preeclampsia. The aim of this study was to investigate further the hypothesis that spiral artery endothelial cells can contribute to the mechanism of shallow trophoblast invasion. METHOD: Fluorescently labeled Jar cells were added to monolayers of fluorescently-labeled endothelial cells that had been activated by treatment with TNFalpha, INF gamma or necrotic cell bodies. The ability of the Jars to displace endothelial cells from the monolayers was quantified by measuring the area of Jar cells "islands" formed in the endothelial cell monolayers by confocal microscopy and digital image. RESULTS: The area of Jar cell islands formed in monolayers of activated endothelial cells was significantly smaller that the area of islands formed in control resting/non-activated endothelial cell monolayers regardless of the activator. DISCUSSION: This work demonstrates that activated endothelial cells are more resistant to trophoblast displacement than resting endothelial cells and adds weight to the suggestion that endothelial cells could contribute to shallow invasion of the spiral arteries by trophoblasts in diseases such as preeclampsia.

Cell Line↗
PubMed2006

An in vitro model of human placental trophoblast deportation/shedding.

Deportation of trophoblast shed from the placenta into the maternal circulation was first described over 100 years ago. Despite this, little is known about the quantity or nature of the shed and deported trophoblasts. Neither do we have a clear understanding of the fate of deported trophoblasts nor do we have a clear understanding of their effects on the maternal physiology. This deficiency is largely due to the inaccessibility of deported trophoblasts in vivo. This study aimed to produce a model that would allow us to study deported trophoblasts. We devised a system for culturing placental explants of 12-week gestation in cell culture inserts with a stainless steel mesh bottom that allowed the ready harvesting of shed/deported trophoblasts. Immunohistochemical and morphologic investigations demonstrated that these in vitro shed/deported trophoblasts are similar to those found in vivo and that apoptotic, necrotic and viable trophoblasts were shed from the explants. Inhibiting caspases induced a change from predominantly apoptotic to predominantly necrotic trophoblast shedding. We have devised an in vitro model that allows the collection of shed/deported trophoblasts which will significantly enhance our ability to study these cells. Our preliminary investigations confirm that apoptosis plays an important role in trophoblast shedding/deportation.

Apoptosis↗
PubMed2006

The effects of apoptotic, deported human placental trophoblast on macrophages: possible consequences for pregnancy.

During pregnancy, trophoblasts are shed into maternal blood from the placenta as they die. Trophoblasts are fetal cells and are therefore immunologically foreign to the maternal immune system, but the effects of shed trophoblasts on the maternal immune system are poorly characterized. We have used an in vitro villous explant model to harvest shed trophoblasts. These shed trophoblasts consist of multinucleated syncytial knots as well as mononuclear cells, and approximately 90% are apoptotic as determined by immunostaining with antibodies recognizing activated caspase-3 and the M30 cytokeratin neoepitope. U937 cells phagocytosed the shed apoptotic trophoblasts and, subsequently, secretion of the anti-inflammatory cytokine IL-10 was increased. In contrast, secretion of the proinflammatory cytokine Il-1beta by U937 cells was decreased after phagocytosis of apoptotic trophoblasts and the changes in both IL-10 and IL-1beta secretion were blocked by co-incubation with the phagocytosis inhibitor cytochalasin B. Shed trophoblasts caused a significant increase also in expression of the, immunosuppressive, tryptophan-metabolizing enzyme indoleamine 2,3-dioxygenase. We speculate that the shedding of trophoblasts may not be simply a mechanism the fetus uses to dispose of aged trophoblasts but rather shed apoptotic trophoblasts may provide a chronic source of tolerizing paternally derived antigens to regulate maternal immune responses to the fetus.

Apoptosis↗
PubMed2006

The effects of oxygen concentration and gestational age on extravillous trophoblast outgrowth in a human first trimester villous explant model.

BACKGROUND: In the first trimester of human pregnancy, extravillous trophoblasts from placental villi invade the decidua temporarily occluding the spiral arteries, preventing maternal blood flow and creating a low-oxygen environment, which is believed to play an important role in the regulation of extravillous trophoblast outgrowth. This work aimed to quantify the effects of gestational age and oxygen concentration on extravillous trophoblast outgrowth. METHODS: A quantitative first trimester villous explant model was used to measure the frequency and area of extravillous trophoblast outgrowths from villi grown in 1.5 or 8% oxygen. RESULTS: The percentage of explants producing outgrowth declined independently of oxygen concentration as gestation increased from 8 to 12 weeks. Culture in 1.5% oxygen significantly reduced the frequency and area of outgrowths in comparison with 8% oxygen. HLA-G and alpha1 integrin were both expressed throughout outgrowths, with no difference in the expression between oxygen concentrations. Gestation influenced the response of explants to oxygen, with a significant differential response to oxygen concentration in placentae under 11 weeks of gestation, whereas in villi from placentae of 11 or 12 weeks, no differential response was observed. CONCLUSIONS: In the first trimester, oxygen and gestational age both regulate extravillous trophoblast outgrowth.

Abortion, Induced↗
PubMed2006

Comparison of the expression of human leukocyte antigen (HLA)-G and HLA-E in women with normal pregnancy and those with recurrent miscarriage.

Recurrent miscarriage affects 1% of all couples attempting pregnancy. Immunological factors are postulated to play a role in the aetiology of recurrent miscarriage because the fetus and placenta are immunologically different from the mother. In particular, altered expression of the, non-classical, class I histocompatibility leukocyte antigen (HLA) molecules has been postulated to play a role in the aetiology of recurrent miscarriage as the fetus and placenta are semi-allogenic to the mother. This study was conducted to examine whether altered expression of the non-classical class I HLA molecules, HLA-G and HLA-E, by cells at the maternofetal interface could play a role in the aetiology of recurrent miscarriage. First-trimester placental and decidual biopsies were obtained from 45 women with recurrent miscarriage and 17 gestation-matched normal controls. These biopsies were screened by immunohistochemistry for HLA-G and HLA-E and isotype-matched control antibodies. Staining was analysed by light microscopy and digital image analysis. In both recurrent miscarriage and normal pregnancy, HLA-G was localised to the extravillous trophoblast. There was no difference in the pattern of HLA-G expression between women with recurrent miscarriage and those with normal pregnancies. HLA-E was localised to the syncytiotrophoblast, villous mesenchymal cells, extravillous trophoblast and several decidual cell types, but staining for HLA-E appeared to be confined primarily to the cytoplasm. There was no difference in the pattern of HLA-E expression between women with recurrent miscarriage and those with normal pregnancies.

Abortion, Habitual↗
PubMed2005

Antiphospholipid antibodies in serum and follicular fluid--is there a correlation with IVF implantation failure?

BACKGROUND: Antiphospholipid antibodies (aPLs) are associated with infertility, but the mechanism underlying this statistical association is currently obscure. We aimed to investigate the finding that aPLs are concentrated in follicular fluid and to establish if this is associated with a poorer outcome from IVF. METHODS AND RESULTS: In 19.2% of 99 women undergoing IVF, at least one aPL was detected in their serum and/or follicular fluids, but the antibody levels in follicular fluid were not higher than in serum. Women with aPLs had a lower implantation rate (14%) than women without these antibodies (24.1%), but this difference was not significant (P=0.127). There was also a non-significant reduction in the live birth rate for women with aPLs. In a parallel investigation, 10 sheep immunized with beta2 glycoprotein I (beta2GPI) or irrelevant control antigens showed strong immune responses, but there were no significant differences between the levels of antibodies in the follicular fluid or serum from beta2GPI or control immunized sheep. CONCLUSION: aPLs do not appear to be selectively concentrated in follicular fluids and, when present, do not adversely affect the reproductive outcome of women undergoing IVF.

Adult↗
PubMed2005

The regulation of trophoblast differentiation by oxygen in the first trimester of pregnancy.

In the first trimester of human pregnancy villous cytotrophoblasts are able to differentiate to form either the overlying syncytiotrophoblast layer or, in anchoring villi, extravillous trophoblasts which grow out from the villi and invade into the maternal decidua, acting to both physically attach the placenta to the decidua, and modify the maternal spiral arteries to sustain pregnancy. During the first 10-12 weeks of gestation, extravillous trophoblast plugs block the spiral arteries and prevent maternal blood flow entering the intervillous space, thereby creating an environment of physiological hypoxia in which placental and fetal development occur. As extravillous trophoblasts migrate away from the villus they differentiate from a proliferative to an invasive phenotype. The hypoxic environment of the first trimester is believed to play an important role in the regulation of trophoblast differentiation. However, there is currently a large body of conflicting experimental evidence concerning this topic. This review examines the experimental evidence to date on the role of oxygen in trophoblast differentiation.

Apoptosis Regulatory Proteins↗
PubMed2004

Interaction of Jar choriocarcinoma cells with endothelial cell monolayers.

During human pregnancy the uterine spiral arteries are invaded by placental trophoblasts which replace the endothelial cells that line the non-pregnant spiral arteries and transform these vessels into large-bore conduits enabling adequate perfusion of the placenta with maternal blood. Failure of this process may predispose to preeclampsia and fetal growth restriction [Brosens I, Robertson WB, Dixon HG. The physiological response of the vessels of the placental bed to normal pregnancy. Journal of Pathology and Bacteriology 1967;93:569-79; Khong TY, De Wolf F, Robertson WB, Brosens I. Inadequate maternal vascular response to placentation in pregnancies complicated by pre-eclampsia and by small-for-gestational age infants. British Journal of Obstetrics and Gynaecology 1986;93:1049-59]. There is a paucity of data on the role of maternal endothelial cells in this process. In this study we investigated the cellular interactions between trophoblast-derived Jar cells and endothelial cells (HUVECs and HMEC-1). The effect of coculturing Jar cells with endothelial cell monolayers was determined by confocal microscopy, DNA fragmentation assay and flow cytometry. We demonstrated that Jar cells migrate into focal areas in endothelial cell monolayers, where they induce endothelial cell death and, then phagocytose the dead endothelial cells. Our results suggest that endothelial cells may not simply be passive targets for invading trophoblasts during the remodeling of the spiral arteries.

Adult↗
PubMed2004

Antiphospholipid antibodies bind to activated but not resting endothelial cells: is an independent triggering event required to induce antiphospholipid antibody-mediated disease?

INTRODUCTION: Antiphospholipid antibodies (aPL) cause thrombotic disease and recurrent pregnancy loss. Despite their name it is now clear that the antigen for most antiphospholipid antibodies is the phospholipid-binding protein beta(2) glycoprotein I (beta(2)GPI). However, beta(2) glycoprotein I is only antigenic for antiphospholipid antibodies when the protein is immobilised on a suitable surface such as phosphatidyl serine. It has been suggested that antiphospholipid antibodies bind to beta(2) glycoprotein I on the surface of resting endothelial cells and this in turn leads to endothelial activation and the initiation of thrombosis. However, as phosphatidyl serine is absent from resting endothelial cell membranes, we questioned this hypothesis. MATERIALS AND METHODS: The ability of human antiphospholipid antibody-containing sera and monoclonal antiphospholipid antibodies to interact with endothelial cells was examined using cell-based ELISAs employing human umbilical vein endothelial cells (HUVECs) as the antigen. The expression of adhesion molecules in response to treatment with antiphospholipid antibodies was also measured by a cell-based ELISA. Activation of NF kappa beta was examined using electrophoretic mobility shift assays (EMSAs). RESULTS: Neither monoclonal antiphospholipid antibodies nor human sera containing antiphospholipid antibodies bound to resting endothelial cells. In contrast, one monoclonal antiphospholipid antibody did bind to both activated and apoptotic endothelial cells. CONCLUSIONS: Antiphospholipid antibodies do not bind to resting endothelial cells nor do antiphospholipid antibodies activate resting endothelial cells. Rather, an independent triggering event is required to activate endothelial cells and subsequently some antiphospholipid antibodies may then bind to the activated endothelial cells and initiate a thrombogenic process.

Antibodies, Antiphospholipid↗
PubMed2002

Early-onset neonatal group B streptococcal infections in New Zealand 1998-1999.

OBJECTIVE: To determine in New Zealand infants the attack rates, risk factors, preventive policies, strain serotype and antibiotic susceptibilities of early-onset neonatal group B streptococcus (GBS) infection. METHOD: A 2-year prospective active surveillance study was conducted in New Zealand's 19 neonatal units. Cases had to present within 48 h of delivery, be unwell, possess abnormal haematological indices and have GBS isolated from sterile sites. RESULTS: Of the 112 402 infants born in New Zealand during 1998-1999, 56 had early-onset GBS infection, an attack rate of 0.5 per 1000 live births (95% confidence interval [CI] 0.38, 0.65). Seven had meningitis and there was one death (case fatality rate of 1.8%; upper 95% CI 9.5%). Univariate analysis identified young maternal age, parity, preterm labour, prolonged membrane rupture, maternal fever and assisted delivery as risk factors. Preventive policies for GBS were reported by 14 (74%) obstetric centres associated with neonatal units. Of the 56 cases, five (9%) were born to mothers receiving intrapartum antibiotics, 32 (57%) had mothers with risk factors but were not treated with antibiotics, and 19 (34%) were born to mothers without identifiable risk factors for GBS prevention. Serotypes Ia and III predominated, while two isolates were resistant to erythromycin and/or clindamycin. CONCLUSIONS: Rates of early-onset GBS infection are similar to other countries following the introduction of prevention policies. Further reductions are possible with full implementation of these guidelines. Meanwhile, emergence of antibiotic resistance complicates the management of women with penicillin allergy. Vaccine development therefore remains a priority.

Adult↗
PubMed2000

Severe oligohydramnios induced by cyclooxygenase-2 inhibitor nimesulide.

BACKGROUND: Cyclooxygenase-2 inhibitors might have fewer adverse fetal effects than conventional nonsteroidal anti-inflammatory drugs that inhibit both isoforms of the enzyme. Although cyclooxygenase-2 is expressed in fetal kidneys, there are no reports of adverse effects in human pregnancy. CASE: A 27-year-old woman, gravida 2, para 0, with a twin pregnancy at 24 weeks' gestation had placement of a cervical cerclage. Nimesulide was prescribed for postoperative preterm labor prophylaxis. Three weeks later, severe oligohydramnios was identified in both sacs, despite normal growth, renal anatomy, and umbilical artery and renal artery Doppler flow velocimetry. After stopping the drug, amniotic fluid volumes returned to normal over 2 weeks. There were no adverse neonatal renal effects. CONCLUSION: Selective cyclooxygenase-2 inhibition might cause severe oligohydramnios. If it is used, we advise close fetal surveillance.

Adult↗
PubMed1999

Acidic isoforms of chorionic gonadotrophin in European and Samoan women are associated with hyperemesis gravidarum and may be thyrotrophic.

OBJECTIVE: There is conflicting evidence concerning the role of human chorionic gonadotrophin (hCG) in the aetiology of hyperemesis gravidarum (HG); particular isoforms of hCG may be the critical factor. Ethnic differences in HG prevalence and putative thyrotrophic effects of hCG may also relate to differences in hCG isoform profiles. To address these issues we examined the relationship of hCG isoforms to HG and thyroid function tests in two groups of women from ethnic backgrounds with significantly different HG prevalence rates. PATIENTS AND DESIGN: We enrolled 10 European and 10 Samoan women with HG and an equally sized non-hyperemetic, gestational stage matched control group. MEASUREMENTS: We administered a questionnaire, generated serum hCG charge-isoform profiles by chromatofocusing and measured the serum concentrations of total hCG, oestradiol (E2), thyrotrophin (TSH) and free thyroxine (FT4). RESULTS: The mean serum total hCG levels were highest in the Samoan hyperemetics (176,268 IU/l), and overall higher in hyperemetics compared with controls (159,770 IU/l vs. 86,420 IU/l, P < 0.001). When compared with controls, hyperemetics displayed increased hCG concentrations in the more acidic half (pH < 4) of the chromatofocusing pH range (89,843 IU/l vs. 41,146 IU/l, P < 0.003). Serum E2 levels did not differ between the four groups, but correlated with the hCG concentration between pH 5.2 and 4.01. Mean serum TSH levels were significantly lower in hyperemetics than in controls (0.33 mIU/l vs. 1.19 mIU/l, P < 0.001) and correlated with the hCG concentration between pH 4.6 and 2.8, while serum FT4 correlated with the hCG concentration below pH 4.0. CONCLUSIONS: Acidic isoforms of hCG may play a role in the aetiology of HG and gestational thyrotoxicosis. Minor ethnic differences in hCG isoform profiles were observed, but the relationship of acidic hCG isoforms to HG and serum thyroid hormone levels was largely independent of the patients' ethnicity. The mechanisms by which acidic isoforms might provoke nausea remain uncertain, but do not seem to involve E2, while the longer half-life of acidic hCG isoforms may result in increased in vivo TSH receptor cross-talk with resultant thyrotrophic effects.

Adult↗
PubMed1998

Vaginal dinoprostone versus oral misoprostol for predilatation of the cervix in first trimester surgical abortion.

Prostaglandins are effective in predilatation of the cervix prior to first trimester surgical termination of pregnancy under local analgesia. Arandomized open comparative trial was devised to compare the effectiveness and acceptability of vaginal dinoprostone with oral misoprostol. Two groups were randomized to control for age, parity and ethnicity. The operation was easier and less painful in older, parous, and Polynesian women. Both methods were effective with respect to ease of dilatation. Both were acceptable and equal with respect to the level of pain experienced by the woman during the operation. Vaginal dinoprostone is more gradual in its action, but it is more expensive, has to be refrigerated and self-insertion may sometimes cause problems. Oral misoprostol is considerably cheaper and does not require refrigeration, but it was associated with more preoperative nausea, cramping and occasional heavy bleeding.

Abortifacient Agents, Nonsteroidal↗
PubMed1994

Use of Laplace transform analysis to describe the effect of placental embolisation on umbilical arterial Doppler waveforms in fetal sheep.

This is the first study to investigate changes in umbilical arterial Doppler shift waveforms caused by placental embolisation in fetal lambs described by a Laplace transform analysis method. The complete maximum velocity envelope of the waveform was quantified mathematically by the coefficients of the Laplace transform. The changes in the dominant coefficient were significantly correlated with changes in umbilico-placental vascular resistance. The Doppler shift waveforms reproduced those seen clinically in some growth-retarded pregnancies and were acquired in a clinically realistic manner. Increasing vascular resistance two fold in this experiment appeared to produce more consistent changes in the dominant coefficient of the Laplace transform than in the pulsatility index. Both analysis techniques correlated with umbilico-placental vascular resistance and these correlations were not significantly different from each other.

Animals↗
PubMed1992

Tissue heating effect of pulsed Doppler ultrasound in the live fetal lamb brain.

A series of experiments in fetal lambs investigated the heating effects of pulsed Doppler ultrasound on fetal brain tissue. In dead lamb brain, tissue heating was observed at the skull bone-to-brain interface. Minimal or no temperature rise was found in the live lamb, suggesting that the intact circulation conducts away any potential heating. The choice of animal model and the state of the circulation influence the results obtained. This will of course have implications for clinical practice.

Animals↗
PubMed1990

Fetal Doppler shift waveforms in intrauterine growth retardation: laplace transform analysis technique.

An approach to the analysis of fetal blood flow velocity/time waveforms is described using a Doppler shift flowmeter. The waveform shape is described in terms of its Laplace transform. Variations in the value of the dominant coefficient in the Laplace transform in the descending thoracic aorta appear to distinguish growth retarded from normally grown fetuses early in pregnancy. Growth retardation was defined by an index of size specifically aimed at detecting the disproportionately grown fetus. Simpler methods of waveform shape description fail to detect the growth retarded fetus early in the second trimester.

Aorta, Abdominal↗