Blood flow velocities and neonatal asphyxia.
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Apgar Score↗
Biomedical subjects
S J Elliott
Publications and source records attributed to S J Elliott.
Reductant substrate for glutathione peroxidase modulates oxidant inhibition of Ca2+ signaling in endothelial cells.
Oxidant stress mediated by tert-butyl hydroperoxide (t-BOOH) inhibits agonist-stimulated Ca2+ entry and internal store Ca2+ release in cultured endothelial cells. The role of intracellular glutathione in modulating the effects of oxidant stress on Ca2+ signaling was determined in cells preincubated with buthionine-[S,R]-sulfoximine (BSO), an inhibitor of gamma-glutamylcysteine synthetase, or 1-chloro-2,4-dinitrobenzene (CDNB), a cosubstrate for glutathione-S-transferase. BSO and CDNB decreased endothelial cell glutathione content by 85 and 97%, respectively (control glutathione, 21.5 +/- 2.3 nmol/mg protein). Each agent accelerated the time-dependent effects of t-BOOH on Ca2+ signaling in fura 2-loaded cells and potentiated the inhibition of bradykinin-stimulated 45Ca2+ efflux induced by t-BOOH. These results indicate that decreased availability of reduced glutathione, the primary cosubstrate for glutathione peroxidase, potentiates the effect of hydroperoxide oxidant stress on receptor-operated Ca2+ entry across the plasmalemma and Ca2+ release from internal stores. The present findings suggest that intracellular glutathione availability and/or glutathione redox cycle activity are critically important modulators of oxidant inhibition of Ca(2+)-dependent signal transduction.
Animals↗
The H2O2-generating enzyme, xanthine oxidase, decreases luminal Ca2+ content of the IP3-sensitive Ca2+ store in vascular endothelial cells.
OBJECTIVE: Xanthine oxidase inhibits agonist-stimulated Ca2+ signaling in calf pulmonary artery endothelial cells by an H2O2-dependent mechanism. We investigated the effect of xanthine oxidase on luminal Ca2+ content of the inositol-1,4,5-trisphosphate (IP3)-sensitive Ca2+ store. METHODS: Luminal Ca2+ content was estimated from the net release of Ca2+ activated by 2,5-di-t-butylhydroquinone (BHQ), an inhibitor of microsomal Ca2+ pumps. RESULTS: Initially, xanthine oxidase depleted the IP3-sensitive Ca2+ store of releasable Ca2+, but with more prolonged incubation, the enzyme also depleted non-IP3-sensitive stores. In addition, xanthine oxidase inhibited capacitative Ca2+ influx. Similar results were observed when thapsigargin was substituted for BHQ. CONCLUSIONS: Depletion of luminal Ca2+ content within the IP3-sensitive Ca2+ store contributes to xanthine oxidase inhibition of Ca2+ signaling in vascular endothelial cells.
Animals↗
Puncture wound infections.
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Anti-Bacterial Agents↗
Hydrogen peroxide activates agonist-sensitive Ca(2+)-flux pathways in canine venous endothelial cells.
The effect of the biological oxidant H2O2 on purinergic-receptor-stimulated Ca2+ signalling was determined in canine venous endothelial cells. H2O2 increased cytosolic free [Ca2+] ([Ca2+]i), the rate of rise of which was dose-dependently related to H2O2 concentration. The response of [Ca2+]i to H2O2 resulted in part from release of Ca2+ from internal stores. The H2O2-sensitive intracellular Ca2+ pool was characterized in cells suspended in Ca(2+)-free/EGTA buffer and stimulated in sequence with H2O2 and ionomycin or ATP. Under this condition, the rank order of apparent compartment size sensitive to each compound was ionomycin > H2O2 > ATP. Stimulation of cells with H2O2 eliminated any response of [Ca2+]i to subsequent addition of ATP. To test more directly whether H2O2 accesses the inositol trisphosphate-sensitive Ca2+ store, cells were pretreated with thapsigargin, a selective inhibitor of that store's Ca2+ pump. Release of Ca2+ from internal Ca2+ stores by H2O2 declined as the interval after thapsigargin addition increased, a finding that supports the contention that H2O2 accesses the inositol trisphosphate-sensitive Ca2+ store. H2O2-stimulated Ca2+ influx across the cell membrane was sensitive to Ni2+, La3+, and 1-(beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl)-1H-imidazole HCl (SKF-96365), a selective inhibitor of the agonist-stimulated Ca(2+)-influx pathway. Ca2+ entry triggered by H2O2 appears to occur via the agonist-sensitive Ca2+ influx pathway. Together, these results suggest that H2O2, which is normally secreted by activated neutrophils and monocytes, may act as an intercellular messenger and stimulate Ca2+ signalling in target endothelial cells.
Adenosine Triphosphate↗
Psychosocial effects of PCB contamination and remediation: the case of Smithville, Ontario.
A cross-sectional study design was used to investigate psychosocial effects in the population exposed to PCB contamination and remediation in Smithville, Ontario, Canada. Psychosocial effects were defined as the complex of distress, dysfunction and disability manifested in a wide range of psychological, social and behavioural outcomes as a consequence of actual or perceived contamination. This paper describes the results of logistic regression analyses conducted to investigate the determinants of psychosocial effects of exposure. The data come from an epidemiologic survey of a sample (N = 272) of Smithville households within 3 km of the site, and a sample from a matched comparison community (N = 263). Two types of outcome variables were used as indicators of psychosocial effects. Scores on the general measures of psychosocial health and well-being (the GHQ-20 and the somatic complaints checklist of the SCL-90) for the Smithville sample did not differ from those expected in a 'normal' population, nor did they differ from those in the comparison community. Scores on these outcomes were associated with plausibly linked independent variables, but were not associated with exposure to the PCB site. Results for site-specific outcome measures (concern and health concern) showed that moderate levels of concern reported by Smithville respondents were explained by concern about another local hazardous waste issue and could not be explained by PCB site exposure. We conclude from these results that local community context exerts an important influence on psychosocial effects of environmental contamination. Furthermore, the types of outcome measures employed and the timing of the research in the context of the site history were important factors in our ability to detect psychosocial effects of the PCB contamination and remediation in Smithville.
Adult↗
Xanthine oxidase inhibits transmembrane signal transduction in vascular endothelial cells.
The effect of xanthine oxidase (XO)-mediated oxidant stress on endothelial cell signal transduction was determined in bradykinin-stimulated cells loaded with the Ca+(+)-sensitive probe fura-2. Calf pulmonary artery endothelial cells were incubated with a reaction mixture containing XO (50 mU/ml) and its substrate, hypoxanthine (HX) (0.5 mM), for periods of 0.5 to 2.0 hr. HX/XO time dependently increased basal cytosolic free Ca++ ([Ca++]i) and decreased the response of [Ca++]i to bradykinin, so that incubation of cells with HX/XO for 1.5 hr or longer eliminated responsiveness to agonist. In presence of XO, HX dose dependently increased basal [Ca++]i (EC50 approximately 3 x 10(-5) M) and decreased the response of [Ca++]i to bradykinin. Sequential application of bradykinin and Ca++ to cells suspended in Ca+(+)-free/EGTA buffer was performed to characterize the effects of HX/XO on receptor-activated Ca++ entry and release of Ca++ from internal stores. HX/XO attenuated internal store Ca++ release and inhibited the bradykinin-stimulated Ca++ influx pathway in a time-dependent manner. When the HX dose was decreased by an order of magnitude, HX/XO selectively inhibited the agonist-stimulated influx pathway with little effect on internal store Ca++ release. Coincubation with superoxide dismutase tended to potentiate the effects of HX/XO, whereas catalase provided almost complete protection. Similar results to HX/XO-induced alterations in Ca++ signaling were observed when glucose-glucose oxidase (G/GO) was used as the oxidant-generating system. Inhibition of Ca++ signaling by HX/XO and G/GO occurred in the absence of decreased cell viability. Together, these results suggest that HX/XO-induced inhibition of signal transduction in endothelial cells is a function of H2O2-mediated oxidant stress and represents an early dysfunction in the process of oxidant injury.
Animals↗
Oxidant stress inhibits the store-dependent Ca(2+)-influx pathway of vascular endothelial cells.
Oxidant stress induced by t-butyl hydroperoxide (t-BuOOH) inhibits bradykinin-stimulated Ca2+ signalling in vascular endothelial cells. The effect of t-BuOOH on intracellular Ca2+ pools was determined by addition of Ca(2+)-releasing agents to fura-2-loaded cells suspended in Ca(2+)-free/EGTA buffer. In control cells, sequential additions of bradykinin and ionomycin produced similar increases in cytosolic free [Ca2+] ([Ca2+]i). By contrast, incubation with t-BuOOH progressively decreased the response of [Ca2+]i to bradykinin and increased that to ionomycin, suggesting that the total (ionomycin-releasable) Ca2+ pool remains replete during oxidant stress. The effect of t-BuOOH on the InsP3-sensitive Ca2+ pool was measured by the increase in [Ca2+]i or efflux of 45Ca2+ stimulated by 2,5-di-t-butylhydroquinone (BHQ). Incubation with t-BuOOH did not inhibit BHQ-stimulated increases in [Ca2+]i or 45Ca2+ efflux, suggesting that the InsP3-sensitive Ca2+ pool remains replete and releasable. Activity of the Ca(2+)-influx pathway stimulated by release of internal Ca2+ stores was determined via re-addition of Ca2+ to BHQ-stimulated cells suspended in Ca(2+)-free/EGTA buffer and via BHQ-stimulated 45Ca2+ uptake. Incubation of cells with t-BuOOH for 1 h significantly inhibited the influx pathway. At later time points, t-BuOOH increased basal [Ca2+]i and potentiated the response of [Ca2+]i to BHQ. Similar results were demonstrated with thapsigargin. Together, these findings suggest that (1) the inhibitory effect of t-BuOOH on bradykinin-stimulated release of Ca2+ from internal stores is not related to depletion of these stores, and (2) inhibition of the store-dependent Ca(2+)-influx pathway occurs by a direct effect of the influx pathway or by inhibition of the mechanism which links the internal Ca2+ store to plasmalemmal Ca2+ influx.
Animals↗
Modelling psychosocial effects of exposure to solid waste facilities.
A parallel case study design was used to investigate psychosocial effects in populations exposed to solid waste facilities. Psychosocial effects were defined as a complex of distress, dysfunction and disability, manifested in a range of psychological, social and behavioural outcomes, as a consequence of actual or perceived environmental contamination. This paper presents the results of logistic regression analyses designed to identify determinants of psychosocial effects of exposure. The data come from an epidemiologic survey of residents (N = 696) living within a prescribed radius from each of three solid waste facilities in southern Ontario. The analytical model has three main components: external variables (e.g. individual and exposure-related variables); mediating variables (e.g. social network membership and involvement, general health status measures); and outcome variables (e.g. concern, effects and actions). Results for a series of site specific analyses show that outcome measures can be successfully explained by a combination of external and mediating factors. In general, variables from each of the three main components enter the concern-related models while the action models are clearly dominated by social network variables. Analyses using data from all three sites indicate the explanatory power of site-related characteristics. However, given the number and diversity of variables in the models, there is no support for a simple cause and effect relationship. The implication is that strategies aimed to address and alleviate psychosocial effects need to be specific to the characteristics of the populations in particular settings.
Adaptation, Psychological↗
Diffuse and enteroaggregative patterns of adherence of enteric Escherichia coli isolated from aboriginal children from the Kimberley region of Western Australia.
Escherichia coli from 138 fecal samples from aboriginal children, in whom no other enteric pathogen was isolated (including enterovirulent E. coli), were examined for HEp-2 cell adhesion. Twenty-five (36.8%) of 68 children with diarrhea and 32 (45.7%) of 70 without diarrhea had diffusely adherent isolates, which were thus not associated with diarrhea (P > .25). However, after age stratification, children > or = 18 months showed a significant association of diffusely adherent E. coli with diarrhea (P < or = .05). Enteroaggregative E. coli were isolated from 12 children with diarrhea (17.6%) and 15 without diarrhea (21.4%); thus, there was no association with diarrhea (P > or = .5). Sixteen children with diarrhea (23.5%) and 6 without diarrhea (8.6%) carried isolates that caused detachment of the HEp-2 cell monolayer from the glass coverslip when examined in the adhesion assay and were significantly associated with diarrhea (P < or = .05). These isolates, termed cell-detaching E. coli, were different from all recognized classes of enterovirulent E. coli.
Age Factors↗
Oxidant stress responses in premature infants during exposure to hyperoxia.
To assess oxidant stress responses in newborn infants treated with elevated concentrations of oxygen, we measured plasma concentrations of glutathione (GSH) and glutathione disulfide (GSSG) in newborn infants ranging from 23 to 42 wk gestational age. All infants recruited into the study were mechanically ventilated and had catheters placed in their umbilical arteries as part of their normal clinical management. Blood samples were obtained on d 1, 3, and 5 and weekly thereafter or until the catheters were removed. We observed plasma concentrations of GSSG in these infants that were frequently an order of magnitude higher than the 0.1 to 0.3 microM we find in adults. Interestingly, plasma GSSG concentrations were inversely correlated to the inspired oxygen tensions. This effect appeared to arise from the patient selection criteria whereby, of the infants studied, those breathing the lowest partial pressures of oxygen were the smallest and gestationally youngest. A second observation was that plasma concentrations of GSH in the premature infants were substantially, indeed often dramatically, lower than we have observed in adult humans (6 to 10 microM). Finally, we found that in patients with both umbilical arterial and umbilical venous catheters arterial GSSG concentrations were consistently higher than venous concentrations; conversely, arterial GSH concentrations were lower than venous concentrations. The elevated GSSG concentrations we observed in these infants indicate marked oxidant stress responses in prematurely born infants, even in those infants exposed only to room air. The positive arteriovenous gradients of GSSG concentrations across the lungs of these infants suggest that at least some of the increased plasma GSSG originates in the lung.(ABSTRACT TRUNCATED AT 250 WORDS)
Biomarkers↗
Role of lipid peroxidation in tert-butylhydroperoxide-induced inhibition of endothelial cell calcium signaling.
The potential of lipid peroxidation in inhibition of Ca++ signaling by the membrane-permeant oxidant, tertiary butylhydroperoxide (tert-buOOH), was investigated in calf pulmonary vascular endothelial cells. The oxidant dose-dependently increased lipid peroxidation between concentrations of 10(-5) and 10(-3) M, with an ED50 of approximately 0.05 mM. In addition, the effect of tert-buOOH was time-dependent through the experimental period (3 h). Preincubation of cells with the 21-amino-steroid compound, 21-[4-(5,6-bis(diethylamino)-2-pyridinyl)-1-piperazinyl]-16 alpha-methyl-pregna-1,4,9(11)-triene-3,20-dione hydrochloride (U74500A), reduced tert-buOOH-induced lipid peroxidation to undetectable levels. The effect of U74500A was dose dependent with an IC50 of approximately 10(-6) M. Brief incubation of cells with the aminosteroid resulted in greater than 90% inhibition of lipid peroxidation during subsequent 2-h incubations with tert-buOOH and addition of U74500A during treatment of cells with tert-buOOH halted further lipid peroxidation. In contrast, the iron-containing moiety, hemin, potentiated the effect of tert-buOOH on lipid peroxidation. The ED50 of hemin was approximately 10(-6) M when cells were preincubated with this agent before treatment with tert-buOOH. The potentiating effect of hemin was time-dependent and reached a near maximum upon incubation of cells for 1 h before tert-buOOH. Preincubation of cells with U74500A before treatment with hemin and tert-buOOH decreased lipid peroxidation by 75%. Ca++ signaling was monitored in-cells loaded with the Ca(++)-sensitive fluorescent indicator, fura-2.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
The contribution of increased collagen synthesis to human glomerulosclerosis: a quantitative analysis of alpha 2IV collagen mRNA expression by competitive polymerase chain reaction.
We previously reported that one of the main components of the sclerotic material in human glomerular diseases was type IV collagen. In this study we examined the contribution of increased synthesis to this process at the gene expression level. Sufficient material has not been available to study type IV collagen synthesis by normal or sclerotic glomeruli in humans. We took advantage of the availability of nephrectomy specimens from patients with renal carcinoma, and of the observation that approximately 50% of these patients develop varying degrees of glomerulosclerosis. We microdissected glomeruli from 10 patients and analyzed them using in situ reverse transcription coupled with polymerase chain reaction (PCR) analyses (in situ RT-PCR). alpha 2IV collagen mRNA, after reverse transcription into cDNA, was detected in all patients and appeared to be increased in those with glomerulosclerosis (n = 5). A competitive PCR assay was developed to quantitate this change. There was an average 3.7-fold increase in glomerular type IV collagen cDNA in patients with significant sclerosis. This change was not due to an increased number of glomerular cells. Thus, glomerulosclerosis in humans is associated with an elevation of glomerular type IV collagen gene expression, suggesting that increased synthesis of type IV collagen may represent one component of this process.
Adult↗
Antismoking adverts and sports sponsorship.
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Advertising↗
Effect of oxidant stress on calcium signaling in vascular endothelial cells.
The endothelial cell is recognized as a critical modulator of blood vessel tone and reactivity. This regulatory function of endothelial cells occurs via synthesis and release of diffusible paracrine substances which induce contraction or relaxation of adjacent vascular smooth muscle. In response to stimulation by blood-borne agonists such as bradykinin or histamine, the endothelial cell utilizes cytosolic ionic Ca2+ as a trigger in the transduction of the stimulatory signal into a paracrine response. Considerable evidence has accumulated to indicate that various forms of biologically important oxidant stress alter vascular function in an endothelium-dependent manner. Further, oxidant stress is known to alter the mechanisms which govern Ca2+ homeostasis in the endothelial cell. Recently, we have described a model in which the oxidant tert-butylhydroperoxide is utilized to examine the effects of oxidant stress on Ca(2+)-dependent signal transduction in vascular endothelial cells. In this model, three temporal phases are evident and consist of (1) inhibition of the agonist-stimulated Ca2+ influx pathway, (2) inhibition of receptor-activated release of Ca2+ from internal stores and elevation of resting cytosolic free Ca2+ concentration, and (3) progressive increase in resting cytosolic Ca2+ concentration and loss of responsiveness to agonist stimulation. In this review, the mechanisms which characterize agonist-stimulated Ca2+ signaling in vascular endothelial cells, and the effects of oxidant stress on signal transduction will be described. The mechanisms potentially responsible for oxidant-induced inhibition of Ca2+ signaling will be considered.
Animals↗
Ca2+ signaling mechanisms of vascular endothelial cells and their role in oxidant-induced endothelial cell dysfunction.
Endothelial cell function may be compromised in disease states as a result of oxidative injury, which may arise from a variety of sources. Oxidant stress appears to influence vascular reactivity and permeability via alteration in the production, release, or effect of endothelium-derived paracrine substances. An early event associated with endothelial cell dysfunction involves alteration in transmembrane signaling mechanisms. In particular, substantial evidence suggests that oxidant stress alters Ca2+ homeostatic mechanisms of the endothelial cell. Because an increase in the free cytosolic Ca2+ concentration ([Ca2+]i) of the endothelial cell is important for release of paracrine factors responsible for regulation of vascular tone and reactivity, oxidant stress-induced changes in Ca2+ signaling could explain much of the observed pathophysiology associated with oxidative injury. Under normal conditions, agonists such as bradykinin and ATP cause a biphasic increase in [Ca2+]i of the endothelial cell; an initial transient component reflects release of Ca2+ from internal stores, whereas a more long-lasting elevation in [Ca2+]i reflects Ca2+ influx from the extracellular space. After incubation with tert-butyl hydroperoxide, a time-dependent inhibition of the agonist-stimulated changes in [Ca2+]i is observed. The underlying molecular mechanisms associated with normal Ca2+ signaling and how these may be altered in the endothelial cell by oxidative stress is the subject of this review.
Animals↗
Oxidant stress alters Na+ pump and Na(+)-K(+)-Cl- cotransporter activities in vascular endothelial cells.
We have previously shown that oxidant stress activates Ca(2+)-dependent K+ efflux in pulmonary vascular endothelial cells. The present study was performed to determine the effect of oxidant stress on Na+ and K+ homeostasis using the radiotracers, 22Na+ and 86Rb+. Cellular ion contents at equilibrium were determined after incubation of cells with tert-butyl hydroperoxide (t-BOOH; 0.4 mM) for various durations. Cell content of 86Rb+ was unchanged through incubation periods of 2 h but was significantly decreased at 3 h, whereas cell content of 22Na+ progressively increased with increasing incubation duration. The effect of t-BOOH on Na+ pump and Na(+)-K(+)-Cl- cotransporter activities was examined via measurement of 86Rb+ influx in the absence or presence of ouabain and bumetanide, respectively. Oxidant stress time dependently increased ouabain-sensitive 86Rb+ influx, with little alteration in specific ouabain binding. In contrast, bumetanide-sensitive 86Rb+ influx was decreased by incubation with the oxidant. These findings suggest that the oxidant-induced increase in cellular Na+ content is associated with increased plasmalemmal Na(+)-K(+)-adenosinetriphosphatase activity. Furthermore, inward ion movement via the bumetanide-sensitive pathway is decreased, suggesting that oxidant stress inhibits the Na(+)-K(+)-Cl- cotransporter.
Adenine↗
Neonatal extracorporeal membrane oxygenation: how not to assess novel technologies.
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Ethics, Medical↗