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Biomedical subjects

Y M O'Meara

Publications and source records attributed to Y M O'Meara.

15 recordsLinked to original sources
PubMed1999

Serum from hemodialysis patients inhibits basal and cytokine-stimulated tissue factor expression in vitro.

Hemorrhagic complications are common among hemodialysis (HD) patients. The mechanisms by which HD perturbs the coagulation cascade are still being defined. This study evaluated the influence of HD serum on cellular expression of tissue factor (TF), a procoagulant membrane-associated protein that is a pivotal regulator of blood coagulation. Serum was collected immediately before dialysis and 15, 30, and 180 min into HD using polysulfone membranes. Serum was then assessed for its ability to influence basal and cytokine-stimulated TF activity in human umbilical vein endothelial cells and ECV304 cells. Predialysis serum did not influence basal levels of TF activity. HD was associated with the appearance of a serum factor that suppressed basal TF activity (TF units/microg protein: predialysis serum 8.2 +/- 0.9; 180-min dialysis serum 4.9 +/- 0.6; P < 0.05) and TF activity induced by the cytokine tumor necrosis factor-alpha (TNFalpha) (TF units/microg protein: TNFalpha alone 15.9 +/- 0.7; TNFalpha + 180-min dialysis serum 5.9 +/- 0.9; P < 0.01). This response was not mimicked by heparin, suggesting production of an endogenous inhibitor of TF activity during HD. Dialysis was associated with a striking increase in circulating levels of tissue factor pathway inhibitor (TFPI), a physiologic inhibitor of the TF/VIIa complex. The lack of temporal correlation between TFPI levels and suppression of TF activity, however, suggested the presence of additional TFPI independent pathway(s) for modulation of TF activity. Dialysis-related suppression of TF expression may contribute to hemorrhagic complications in HD patients.

Adult↗
PubMed1997

Leukocytes, cell adhesion molecules and ischemic acute renal failure.

Ischemic acute renal failure (ARF) is a common clinical syndrome, associated with high morbidity and mortality, for which there is no specific therapy. Polymorphonuclear neutrophils (PMN) recruited during reperfusion have been implicated as mediators of renal parenchymal injury in ischemic ARF. Leukocyte adhesion molecules appear to facilitate PMN recruitment in this setting. Complementary studies using monoclonal antibodies, antisense oligonucleotides and gene "knock-out" indicate that blockade of CD11/CD18 integrins and intercellular adhesion molecule-1 (ICAM-1) attenuates ARF in some experimental models of renal ischemia. These exciting observations may herald the development of novel anti-adhesion strategies for use in human disease.

Acute Kidney Injury↗
PubMed1997

Treatment of hypertension in the elderly.

Hypertension is present in over 50% of elderly patients and constitutes a major risk factor for cardiovascular morbidity and mortality. This paper reviews the rationale for treating hypertension in the elderly, discusses the choice of antihypertensive therapy and optimal target blood pressure, and summarizes ongoing clinical trials. The major questions that remain to be answered are the optimal level of blood pressure reduction in the elderly and the long-term efficacy and safety of newer antihypertensive agents compared with diuretics and beta-blockers.

Aged↗
PubMed1997

Lipoxins, leukocyte recruitment and the resolution phase of acute glomerulonephritis.

The resolution phase of inflammation is being increasingly recognized as a dynamic multifaceted process whose components may be amenable to pharmacological manipulation for therapeutic gain. Here, we review evidence that the lipoxins (LX), a family of lipoxygenase-derived eicosanoids generated during cell-cell interactions within the vascular lumen, are potential endogenous inhibitors of polymorphonuclear neutrophil (PMN) recruitment during glomerular inflammation. LX are generated in nanogram quantities in kidneys of rats with Concanavalin A-ferritin (Con A-F) immune complex glomerulonephritis and of mice with acute nephrotoxic serum nephritis (NSN). PMN-platelet transcellular pathways appear to be the major route to LX formation in these settings, PMN donating the labile epoxide intermediate leukotriene A4 for conversion by platelet LX synthase to LXA4. Complementary approaches using monoclonal antibodies and gene knockout suggest that PMN-platelet adhesion through P-selectin promotes transcellular LXA4 biosynthesis in vitro and in vivo. In support of a modulatory role in PMN trafficking; LXA4 and LXB4, the LX generated in greatest quantities by mammalian cells, inhibit PMN chemotaxis, adhesion to endothelial cells, and migration across endothelium and epithelium induced leukotrienes and some other mediators in vitro. Exposure of PMN to LXA4 ex vivo attenuates their recruitment in Con A-F glomerulonephritis. Furthermore, PMN recruitment is exaggerated during NSN in P-selectin knockout mice, coincident with reduced efficiency of transcellular LXA4 generation and reduced renal LXA4 levels. Replenishment of platelet P-selectin by transfusion of null mice with wild-type platelets reverses this defect in LXA4 synthesis and approximates PMN infiltrates in null and wild-type animals. Against this background, LXA4 stable analogues have been designed that retain the biologic activity of native LXA4 in vitro and should be useful tools for probing the therapeutic potential of LXA4 in disease. In the presence of aspirin, endothelial cell cyclooxygenase II (COX-II) transforms arachidonic acid to 15R-hydroxyeicosatetraenoic acid which, in the context of PMN-endothelial cell interaction, is converted by PMN 5-lipoxygenase to 15-epi-LX. Intriguingly, these novel LX also attenuate PMN adhesion and transmigration in model in vitro systems. Together, these observations suggest that LX may not only play important regulatory roles in the "stop programs" of renal inflammation, but also contribute to the anti-inflammatory activity of aspirin and related inhibitors of COX-II.

Acute Disease↗
PubMed1995

Magnetic resonance angiography in the evaluation of living-related renal donors.

Live-donor kidney donation requires an accurate determination of renal arterial anatomy. Traditionally, conventional angiography has supplied this information. The present study was undertaken to determine the accuracy of magnetic resonance angiography (MRA) compared with conventional angiography (CA) in the evaluation of potential living renal donors. Fifteen potential living renal donors underwent both conventional angiography (midstream aortic injection) and three-dimensional phase contrast MRA. Two overlapping volumes of 64 slices (slice thickness 1.5 mm) were obtained in the axial plane to allow coverage from the celiac trunk to the aortic bifurcation. Conventional angiography demonstrated single renal arteries in 24 kidneys and multiple renal arteries in 6 kidneys. Magnetic resonance angiography demonstrated multiple renal arteries in 5 of the 6 kidneys. The sensitivity of MRA in determining kidneys with multiple renal arteries was 83% (5/6). One kidney with an accessory 2-mm polar artery was incorrectly identified as having a single renal artery by MRA. The overall accuracy of MRA in identifying the number of renal arteries was 97% (29/30). Fibromuscular dysplasia was demonstrated in 2 patients by CA, but was not visualized prospectively by MRA. Based on standard physician and hospital fees for each procedure, use of MRA alone would represent a cost savings of approximately $1900 over CA. Despite its minimally invasive and economic attractions, MRA does not achieve the level of accuracy required to replace CA in the evaluation of potential living kidney donors.

Female↗
PubMed1994

The nephritogenic immune response.

The past year has witnessed continued advances along several fronts in understanding the initiation and effects of a nephritogenic immune response. New information on the major histocompatibility complex in autoimmunity suggests that major histocompatibility complex class I and class II expression is important in the initiation of the immune response. The complex pathways involved in the regulation of leukocyte recruitment in inflammation continue to unravel and the role of cytokines in these processes is being defined. The ability of antibodies directed against leukocyte adhesion molecules to attenuate inflammation in experimental glomerulonephritis opens up the possibility of new therapeutic agents for human disease. The need to reexamine the role of complement as an effector in immune renal disease is suggested by evidence of intrinsic renal complement component production. Recent information on the pathogenesis of renal scarring in crescentic glomerulonephritis suggests the importance of leukocyte-endothelial cell interaction and of delayed-type hypersensitivity in this process. The ability of the growth factors transforming growth factor-beta and platelet-derived growth factor to induce glomerulosclerosis has been documented in an innovative study using selective renal gene transfer. Finally, the potential importance of apoptosis of inflammatory cells as a mechanism limiting injury is a new focus of attention.

Animals↗
PubMed1993

Expression of type I collagen mRNA in glomeruli of rats with passive Heymann nephritis.

In passive Heymann nephritis (PHN) glomeruli exhibit marked basement membrane expansion around subepithelial immune deposits but they fail to show any change in mRNA levels of type IV collagen, laminin or fibronectin by Northern and slot-blot analysis, or in the amount or distribution of type IV collagen or laminin by immunohistology for up to 12 weeks after disease onset. On the other hand, in situ hybridization (ISH) revealed the appearance of positive cells exhibiting mRNA for the alpha 1 chain of rat type I collagen two to three weeks after the onset of PHN in all glomeruli of all rats. Positive cells persisted for at least eight weeks. In many glomeruli, the location of the clusters of silver grains suggested that they were in visceral epithelial cells. In controls injected with normal sheep IgG, and in early PHN (< 11 days after sheep anti-Fx1A), glomeruli were negative but cells in the renal capsule and adventitia of vessels showed strong ISH and served as positive controls. RNAse pre-treatment and the "sense" probe gave appropriately negative results. RNA from PHN glomeruli contained an alpha 1 type I collagen transcript of the same size as that from rat fibroblasts. These results show that the evolution of glomerular basement membrane expansion in rat membranous nephropathy coincides with the induction of a matrix gene that is not normally expressed in glomerular cells. Further, they suggest that the intercalation of ectopically-expressed matrix molecules may contribute to the production of a disorganized basement membrane.

Animals↗
PubMed1993

Fish oil has protective and therapeutic effects on proteinuria in passive Heymann nephritis.

Passive Heymann nephritis (PHN) is a rat model of membranous nephropathy induced by injecting anti-Fx1A. The onset of proteinuria in PHN is caused by complement-mediated injury to glomerular epithelial cells (GEC) accompanied by enhanced glomerular eicosanoid production. In addition, sublethal injury by complement of rat GECs in culture leads to phospholipase activation, phospholipid hydrolysis and release of arachidonic acid and dienoic prostanoids. Based on these findings, we undertook to determine if substituting arachidonic acid (omega-6) in GEC membrane phospholipids with omega-3 fatty acids derived from fish oil would alter the development and course of proteinuria in PHN. We found that rats fed a diet containing 10% fish oil for four weeks prior to antibody injection developed 50 to 60% less proteinuria between two and six weeks after anti-Fx1A than rats fed an equivalent diet containing 10% safflower oil, and had substantial enrichment of glomerular phospholipids with omega-3 fatty acids and displacement of arachidonic acid. This outcome was associated with a 50% reduction in release of glomerular thromboxane B2 (stable metabolite of thromboxane A2) in the fish oil group. More importantly, when PHN rats with well established proteinuria while on regular chow were randomized to three dietary groups, those fed fish oil had a 25 to 50% decline in proteinuria as compared to those fed lard or safflower oil. This difference was evident within two weeks of randomization and persisted until the end of the study after eight weeks. In neither study could the differences in urine protein excretion be accounted for by protein or calorie deprivation, or by differences in blood pressure, renal function, immune response to sheep IgG, or glomerular deposition of IgG or complement. Thus, our results indicate that dietary fish oil has protective and therapeutic effects with regard to proteinuria in PHN. These benefits may relate to alterations in membrane phospholipid composition in favor of omega-3 fatty acids and release of less reactive trienoic eicosanoids.

Animals↗
PubMed1992

Management of glomerular diseases of primary and secondary origin.

Most recent information on the management of glomerular diseases is clustered in three areas. In nephrotic syndrome, interest has focused on the use of cyclosporine in steroid-resistant patients, treatment of progressive membranous nephropathy with alkylating agents, and symptomatic management of unresponsive cases with angiotensin-converting enzyme inhibitors. The most recent data on lupus nephritis establish the efficacy of intravenous cyclophosphamide in the long-term preservation of renal function and the lack of benefit of plasmapheresis in patients with severe disease. In rapidly progressive glomerulonephritis, the discovery of circulating antibodies to neutrophil cytoplasmic antigens has proved valuable in diagnosing certain forms of renal vasculitis. A rational approach to treating such patients is beginning to crystallize.

Adjuvants, Immunologic↗
PubMed1992

Production and polarized secretion of basement membrane components by glomerular epithelial cells.

To study the formation of basement membrane by glomerular epithelial cells (GECs), production and secretion of type IV collagen and laminin by rat GECs in culture were evaluated. GECs produced two chains of type IV collagen (180 and 170 kDa) in the ratio of approximately 2 to 1, when immunoprecipitated with antibody to type IV collagen of mouse Engelbreth-Holm-Swarm (EHS) sarcoma. GECs also produced proteins that were precipitated by antibody to EHS laminin, i.e., two bands each in the positions of the A and B chains of mouse laminin. On enzyme-linked immunosorbent assay (ELISA), type IV collagen and laminin were found mainly in the cell-associated fraction and in the subepithelial culture medium. Confluent GECs on membrane filters formed a tight barrier against the flux of macromolecules. Under these conditions, 80% of newly synthesized and secreted matrix proteins were detected in the basolateral medium. Moreover, treatment with ammonium chloride, which is known to affect polarized secretion, caused both type IV collagen and laminin to be secreted via the basolateral and apical surfaces in similar amounts. These results indicate that cultured GECs are polarized and that they produce and secrete basement membrane components via the basolateral side.

Animals↗
PubMed1992

Nephrotoxic antiserum identifies a beta 1-integrin on rat glomerular epithelial cells.

A postulated mechanism of immune glomerular injury is a direct interaction between antibody and glomerular epithelial cell (GEC) surface antigens. To explore this hypothesis, we examined the interaction of the noncomplement-fixing gamma 2-subclass of sheep anti-rat nephrotoxic serum (NTS), which causes immediate complement- and neutrophil-independent proteinuria in vivo, with rat GECs in culture. Reactivity of NTS with GEC surface antigens was determined by positive immunofluorescence of GEC plasma membranes and by the ability of NTS-coated tissue culture wells to provide an adhesive substrate for GECs. NTS immunoprecipitated two proteins (135 and 118 kDa) from surface-labeled GECs. Proteins of similar molecular mass were precipitated by a polyclonal rabbit antibody that identifies the beta 1-integrin chain of the mouse fibronectin receptor (anti-FnR). In addition, NTS identified similarly sized bands on Western blot analysis of cell membranes from isolated rat glomeruli. Similar reactivity was eluted from the glomeruli of proteinuric rats injected with NTS. NTS significantly inhibited GEC adhesion to laminin, types I and IV collagen, and fibronectin and prevented GEC spreading on types I and IV collagen. Anti-FnR similarly inhibited GEC adhesion. Cell viability was not affected. These results show that NTS recognizes a pair of GEC surface proteins that have the characteristics of an alpha- and beta 1-integrin and, at low concentrations, disrupt cell-matrix interactions.

Animals↗
PubMedDate not supplied

The Short Form 36 (SF-36) Health Survey: normative data for the Irish population.

BACKGROUND: Generic measures of quality of life have a wide application in health research. They measure disease impact by comparing scores in patient groups with a healthy population. They also facilitate comparative studies between different patient groups. The SF-36 Health Survey quantifies respondents' perceptions of their functioning in eight dimensions of daily life. AIM: The aim of this study was to set normative values for the SF-36 in the Irish population aged 18 years and over. METHOD: A random sample of 800 subjects was drawn from the electoral register using the RANSAM method of sampling. RESULTS: Two hundred and ninety five (37%) valid questionnaires were returned for analysis. The SF-36 was found to have acceptable internal consistency and validity. Normative values for the total population are presented, in addition to results for males and females across seven age groups. Ageing was associated with a decline in the physical dimensions of health. CONCLUSIONS: There was no evidence to suggest that there were significant differences in health status between males and females, or between this Irish sample and the published norms for the US population.

Adolescent↗
PubMedDate not supplied

Physical function, employment and quality of life in end-stage renal disease.

INTRODUCTION: The impact of end-stage renal disease (ESRD) on quality of life (QoL) can be measured in terms of physical, psychological and social consequences, including the ability to work. SUBJECTS AND METHODS: This multi-center, cross-sectional study explored relationships between QoL, employment status and physical function in ESRD patients aged 18-65 years, via a customised interviewer-administered questionnaire, which included the SF-36 health survey. The International Labour Office method was applied to describe employment rate. RESULTS: 144 patients (85 male, 49 female), comprising 49 haemodialysis (HD), 35 peritoneal dialysis (PD) and 60 renal transplant (TX) patients were studied. Mean age was 44 +/- 12 years. 32 were voluntarily not working, leaving 112 in the labour force. Of the latter, 49% were unemployed, in contrast with the concurrent national rate of 10%. QoL in the ESRD group was reduced in the SF-36 physical and social dimensions compared to population norms. Unemployed ESRD patients scored significantly lower than those employed in physical function, role physical, bodily pain, general health, vitality and role emotional scales. Logistic regression demonstrated that multiple comorbidities (p<0.005), a premorbid physical occupation (p<0.05) and poor physical function (p<0.05) predicted unemployment in ESRD independent of all other variables. Multiple regression showed that age (p<0.05), female sex (p<0.05) and a diagnosis of musculoskeletal disease (p<0.005) were independent predictors of poor physical function. CONCLUSIONS: These findings suggest that vocational rehabilitation of ESRD patients must consider physical function and occupational demands as well as co-morbidity and that musculoskeletal disease is key factor in impaired physical function.

Adolescent↗