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M J Lewis

Publications and source records attributed to M J Lewis.

At least 73 records · Page 4Linked to original sources
PubMed2000

Specific retrieval of the exocytic SNARE Snc1p from early yeast endosomes.

Many endocytosed proteins in yeast travel to the vacuole, but some are recycled to the plasma membrane. We have investigated the recycling of chimeras containing green fluorescent protein (GFP) and the exocytic SNARE Snc1p. GFP-Snc1p moves from the cell surface to internal structures when Golgi function or exocytosis is blocked, suggesting continuous recycling via the Golgi. Internalization is mediated by a conserved cytoplasmic signal, whereas diversion from the vacuolar pathway requires sequences within and adjacent to the transmembrane domain. Delivery from the Golgi to the surface is also influenced by the transmembrane domain, but the requirements are much less specific. Recycling requires the syntaxins Tlg1p and Tlg2p but not Pep12p or proteins such as Vps4p and Vps5p that have been implicated in late endosome-Golgi traffic. Subtle changes to the recycling signal cause GFP-Snc1p to accumulate preferentially in punctate internal structures, although it continues to recycle to the surface. The internal GFP-Snc1p colocalizes with Tlg1p, and immunofluorescence and immunoelectron microscopy reveal structures that contain Tlg1p, Tlg2p, and Kex2p but lack Pep12p and Sec7p. We propose that these represent early endosomes in which sorting of Snc1p and late Golgi proteins occurs, and that transport can occur directly from them to the Golgi apparatus.

Amino Acid Sequence↗
PubMed2000

Retrospective analysis of cisapride-induced QT changes in end-stage renal disease patients.

BACKGROUND: This study involves a retrospective in-patient chart review of end-stage renal disease (ESRD) patients receiving haemodialysis to observe if cisapride significantly increases heart rate (HR), QT, and corrected QT (QTc) intervals on 12-lead electrocardiograms (ECGs). METHODS: Medical records for 23 patients who were being treated with chronic maintenance haemodialysis and had >/=2 ECGs while on cisapride and >/=2 ECGs while off cisapride were obtained and reviewed. HR, QT, and QTc on all 12-lead ECGs, reason for admission, and past medical history were analysed. RESULTS: A total of 529 ECGs (279 on/250 off cisapride) for 23 patients were included. The results, as calculated by each patient's individual averages (n=23), on vs off cisapride respectively, were HR, 88+/-14 vs 84+/-17 beats/min (P:=0.18); QT, 373+/-39 vs 382+/-45 ms (P:=0.24); and QTc, 443+/-27 vs 441+/-21 ms (P:=0.39). No significant difference was found in the number of admissions per month while on or off cisapride. No patient had an average QTc on or off cisapride that was >500 ms. One patient died from ventricular arrhythmia 12 days after discontinuing cisapride. The patient's QTc was significantly longer on vs off cisapride (487 vs 462 ms, P:=0. 007); however, this patient had an extensive cardiac history and multiple syncopal episodes prior to the use of cisapride. CONCLUSIONS: This study found no significant overall difference in HR, QT, and QTc interval or admissions/month on vs off cisapride in ESRD patients receiving haemodialysis.

Arrhythmias, Cardiac↗
PubMed2000

Homocysteine-induced inhibition of endothelium-dependent relaxation in rabbit aorta: role for superoxide anions.

Hyperhomocysteinemia is associated with endothelial dysfunction, although its mechanism is unknown. Isometric tension recordings and lucigenin chemiluminescence were used to assess the effects of homocysteine exposure on endothelium-dependent and -independent relaxation in isolated rabbit aortic rings and superoxide anion (O(2)(-)) production by cultured porcine aortic endothelial cells, respectively. Homocysteine (0.1 to 10 mmol/L) produced a significant (P<0.001) concentration- and time-dependent inhibition of endothelium-dependent relaxation in response to both acetylcholine and the calcium ionophore A23187. Only the intracellular O(2)(-) scavenger 4,5-dihydroxy-1,3-benzene disulfonic acid (Tiron, 10 mmol/L) significantly (P<0.001) inhibited the effect of homocysteine on acetylcholine- and A23187-induced relaxation. Incubation of porcine aortic endothelial cells with homocysteine (0.03 to 1 mmol/L for up to 72 hours) caused a significant (P<0.001) time-dependent increase in the O(2)(-) released by these cells on the addition of Triton X-100 (1% [vol/vol]), with levels returning to values comparable to those of control cells at the 72-hour time point. These changes in O(2)(-) levels were associated with a time-dependent increase in endothelial cell superoxide dismutase activity, becoming significant (P<0.001) after 72 hours. Furthermore, the homocysteine-induced increase in endothelial cell O(2)(-) levels was completely inhibited (P<0.001) by the concomitant incubation with either Tiron (10 mmol/L), vitamin C (10 micromol/L), or vitamin E (10 micromol/L). These data suggest that the inhibitory effect of homocysteine on endothelium-dependent relaxation is due to an increase in the endothelial cell intracellular levels of O(2)(-) and provide a possible mechanism for the endothelial dysfunction associated with hyperhomocysteinemia.

Acridines↗
PubMed2000

Enhancing the financial performance of a health system laboratory network using an information system.

We describe the improvements created by successful implementation of a laboratory information system for a multi-institutional integrated delivery system, including an analysis of the financial results. Conditions at the outset of the project, methods of management and project design, selected aspects of services redesign and consolidation, integration of services among the sites and their effects on laboratory staff and productivity are illustrated. A method for and example of measuring the financial outcomes in the sense of quantifiable improvements in operating expenses and new revenue for a whole health system clinical laboratory computer system are discussed. In this health system, the measurable financial improvements facilitated by an information system were the ability to control operating expenses and to grow the hospital laboratory network through the development of an outreach program. With organizational commitment to process innovation and improvement, using team processes and customer-driven decision-making criteria, the financial performance of our consolidated laboratory network was enhanced substantially. A fully implemented laboratory information system is considered the major enabler of positive change when combined with a genuine commitment from all levels of staff and leadership. Over time, this system's financial return is several times that of the information system investment.

Clinical Laboratory Information Systems↗
PubMed2000

The effect of GH replacement therapy on endothelial function and oxidative stress in adult growth hormone deficiency.

OBJECTIVES: Controversy persists with regard to the atherogenic risk associated with adult growth hormone deficiency (GHD). Endothelial dysfunction and enhanced oxidative stress are early features of atherogenesis. Therefore, we have studied the effect of three months of low dose GH replacement therapy (0.03IU/kg/day) on these parameters in GHD adults. SUBJECTS AND METHODS: Eight hypopituitary GHD adults (4 male, 4 female), who were receiving conventional hormone replacement therapy, were studied before and after 3 months of GH replacement (0.03IU/kg/day). All observations obtained were compared with similar measurements made in 8 matched control subjects. All study subjects were non-smokers, normotensive and gave no personal or family history of premature vascular disease. Endothelial function was assessed using a specialised vessel wall tracking system to measure endothelium-dependent, flow-mediated, brachial artery dilatation (FMD). Measurements were repeated following glyceryl-trinitrate (GTN) (endothelium-independent dilatation). Oxidative stress was assessed by directly measuring lipid-derived free radicals in venous blood by electron paramagnetic resonance spectroscopy. Fasting lipids, insulin, plasma glucose and IGF-I were also measured at baseline and following GH replacement. RESULTS: FMD, expressed as a percentage change from resting base-line diameter, was significantly impaired in the pre-treatment GHD patients compared with controls (3.1+/-2.1% vs 6.1+/-0.9%, P<0. 001; means+/-s.d.) indicating endothelial dysfunction. Significant increase in FMD was noted following GH therapy (3.1+/-2.1% vs 6. 5+/-1.9%, P<0.001). Free radicals (arbitrary units) were elevated in the pre-treatment GHD patients compared with controls (0.36+/-0.09 vs 0.11+/-0.12, P<0.05) and fell significantly following GH therapy (0.23+/-0.03 vs 0.36+/-0.09, P<0.05), although they remained elevated compared with controls. Fasting insulin was significantly higher (25.9+/-18.8 vs 13.9+/-6.7mu/l, P<0.05) and IGF-I concentrations lower (10.8+/-4.7 vs 20.2+/-6.3nmol/l, P<0.05) in the pre-treatment GHD subjects. After treatment there were no changes in insulin concentration, although IGF-I levels were normalised (10. 8+/-2.3 vs 23.6+/-11.4nmol/l, P<0.05). CONCLUSIONS: Endothelial dysfunction and enhanced oxidative stress are features of adult GHD. This study suggests plausible mechanisms underlying any proatherogenic tendency in adult GHD and demonstrates improvement of these factors following GH replacement.

Adult↗
PubMed2000

Strategies to eradicate rubella in the English-speaking Caribbean.

OBJECTIVE: This report presents the strategies used to eradicate rubella in the Caribbean region and the challenges faced by that effort. METHODS: Using the surveillance system for measles cases that was instituted in all countries in the Caribbean Community (CARICOM), 12 countries confirmed cases of rubella between 1992 and 1996. Rubella infections occurred in epidemic proportions in 6 countries during that period. RESULTS: On the basis of the rubella prevalence data, rubella-congenital rubella syndrome (CRS) cost-benefit analysis, and cost-effectiveness of the mass campaign, the Council for Human and Social Development of CARICOM resolved, on April 21, 1998, that every effort would be made to eradicate rubella, as well as to prevent the occurrence of new cases of CRS by the end of 2000. Using the Pan American Health Organization's template for measles eradication, CARICOM proposed and implemented the main strategies for rubella and CRS eradication, and rubella mass campaigns were conducted in 18 countries. The target population, which included males and females (aged 20-40 years), was approximately 2.2 million. CONCLUSION: The major challenges for rubella eradication are attaining high vaccine coverage in the adult population and maintaining an effective surveillance system able to detect rubella activity.

Adolescent↗
PubMed2000

Production of C20 polyunsaturated fatty acids (PUFAs) by pathway engineering: identification of a PUFA elongase component from Caenorhabditis elegans.

Using a combination of database-mining and functional characterization, we have identified a component of the polyunsaturated fatty acid (PUFA) elongase. Co-expression of this elongating activity with fatty acid desaturases has allowed us to heterologously reconstitute the PUFA biosynthetic pathway. Both these enzymes (desaturases and elongase components) have undergone gene-duplication events which provide a paradigm for the diverged nature of PUFA biosynthetic activities.

Acetyltransferases↗
PubMed1999

High rate of human T lymphotropic virus type IIa infection in HIV type 1-infected intravenous drug abusers in Ireland.

Serological and molecular analyses of a cohort of HIV-1-infected intravenous drug abusers (IVDAs) (n = 103) in Dublin, Ireland have demonstrated that 15 of 103 (14.6%) were infected with HTLV-II, which is the highest infection rate yet recorded for any European country. Restriction fragment length polymorphism (RFLP) analysis of the env region of the provirus demonstrated that the infection involved only the HTLV-IIa subtype; the HTLV-IIb subtype was not detected. Phylogenetic analysis of the nucleotide sequences of the long terminal repeat (LTR) confirmed infection with the HTLV-IIa subtype, and demonstrated that the viruses clustered closely with HTLV-IIa isolates from North American IVDAs. Previous observations that IVDAs in southern Europe, specifically Spain and Italy, appear to be infected predominantly with the HTLV-IIb subtype, along with the present report and evidence that IVDAs in Sweden are infected with the HTLV-IIa subtype, suggest different origins of HTLV-II infection in Europe.

Adult↗
PubMed1999

Endothelial function in Marfan syndrome: selective impairment of flow-mediated vasodilation.

BACKGROUND: The cardiovascular complications of Marfan syndrome arise due to alterations in the structural and functional properties of fibrillin, a constituent of vascular connective tissues. Fibrillin-containing microfibrils are closely associated with arterial endothelial cells, indicating a possible functional role for fibrillin in the endothelium. Plasma concentrations of endothelial cell products are elevated in Marfan subjects, which indirectly indicates endothelial dysfunction. This study directly assessed flow- and agonist-mediated endothelium-dependent brachial artery reactivity in Marfan subjects. METHODS AND RESULTS: In 20 Marfan and 20 control subjects, brachial artery diameter, blood flow, and blood pressure were measured by ultrasonic wall tracking, Doppler ultrasound, and photoplethysmography, respectively. Measurements were taken during hand hyperemia (a stimulus for endothelium-derived nitric oxide [NO] release in the upstream brachial artery) and after sublingual administration of the endothelium-independent vasodilator nitroglycerin. In 9 Marfan and 6 control subjects, the above parameters were also assessed during intra-arterial infusions of acetylcholine and bradykinin (agonists that stimulate NO production) and NG-monomethyl-L-arginine (L-NMMA, an inhibitor of NO production). Flow-mediated responses differed markedly between Marfan and control subjects (-1.6+/-3.5% versus 6. 50+/-4.1%, respectively; P<0.0001), whereas nitroglycerin produced similar vasodilation (14.2+/-5.7% versus 15.2+/-7.8%; P=NS). Agonist-induced vasodilation to incremental intra-arterial infusions of acetylcholine and bradykinin were not significantly different between Marfan and control subjects, and intra-arterial L-NMMA produced similar reductions in brachial artery diameter in both groups. CONCLUSIONS: These data demonstrate impaired flow-mediated but preserved agonist-mediated endothelium-dependent vasodilation in Marfan subjects and suggest preservation of basal NO release. Selective loss of flow-mediated dilation suggests a role for fibrillin in endothelial cell mechanotransduction.

Acetylcholine↗
PubMed1999

Phenotypic changes in rat and guinea pig coronary microvascular endothelium after culture: loss of nitric oxide synthase activity.

OBJECTIVES: Coronary microvascular endothelial cells (CMVEs) can modulate the contractile performance of the adjacent myocardium by the release of agents such as nitric oxide (NO). Most previous studies using CMVEs have been done in situ, in the intact organ. We set out to study possible differences in NO synthase (NOS) regulation between freshly isolated and cultured rat and guinea pig CMVEs. METHODS: CMVEs were isolated from Wistar rats and Dunkin Hartley guinea pigs and then grown in culture for varying times. Fura-2 fluorescence was used to measure agonist-induced changes in CMVE intracellular calcium levels. Agonist-induced changes in CMVE cGMP levels were measured by commercial radioimmunoassay kit. Western blot analysis was used to measure endothelial, constitutive NOS (ecNOS) and soluble guanylate cyclase (sGC) protein levels. Reverse transcription, polymerase chain reactions and Southern blotting were used to measure ecNOS mRNA transcripts. RESULTS: In both fresh (1 h post-isolation) and cultured (14 days with one passage) CMVEs of the rat and guinea pig, bradykinin (BK) and the calcium ionophore A23187 (both 1 microM) elicited significant (P < 0.01) increases in the fura-2 340/380 fluorescence ratio. In cultured CMVEs, basal cGMP levels were unaffected by exposure to BK or A23187. Exposure to sodium nitroprusside (SNP) or atrial natriuretic peptide (ANP) (both 1 microM) induced significant (P < 0.01) increases in cGMP in guinea pig cells, whereas in rat cells only ANP produced a significant (P < 0.01) response. By contrast, freshly isolated CMVEs of both species had higher basal cGMP levels than cultured cells, and on exposure to BK and A23187, responded with significant (P < 0.01) increases in cGMP. Moreover, exposure of both fresh rat and guinea pig CMVEs to SNP or ANP also resulted in significant (P < 0.01) increases in cGMP. Western blot analysis demonstrated that ecNOS and sGC protein were lost from the rat CMVEs following culture. Furthermore, there was also a significant loss of ecNOS mRNA from the rat cells following culture. CONCLUSIONS: These data demonstrate that freshly isolated rat and guinea pig CMVEs possess ecNOS activity, and that this activity is downregulated following culture. At least for the rat, this effect would seem to lie at both the transcriptional and translational level. Furthermore, rat CMVEs have reduced activity of sGC following culture.

Analysis of Variance↗
PubMed1999

Sex difference in the relationship of calcium and magnesium excretion to glycaemic control in type 1 diabetes mellitus.

In order to assess the variability and possible causes of calcium and magnesium losses in diabetes mellitus, urinary calcium and magnesium excretion were monitored six monthly over a 3-year period in 108 stable, type 1 diabetic patients who were having assessment of their clinical status and glycaemic control over the same period. In the patients studied the ranges of excretion of both calcium and magnesium were considerably wider than our non-diabetic reference ranges but the within subject variation in excretion was high. However, using mean values obtained over the study period, a direct relationship was observed between the excretion of both calcium and magnesium and HbA1 in female patients (P < 0.01) but not in males who had similar HbA1 values. The urinary excretion of calcium and magnesium did not relate to any of the other clinical or biochemical indices measured, including body mass index, daily insulin dose, retinal status or albumin excretion. It is suggested that, in poorly controlled patients, females may have a greater risk than males of developing the complications associated with chronic calcium and magnesium loss.

Adult↗
PubMed1999

Reciprocal changes in endothelial and inducible nitric oxide synthase expression following carotid angioplasty in the pig.

OBJECTIVE: Nitric oxide produced by nitric oxide synthase appears to have an important role in the regulation of arterial tone, platelet adhesion and smooth muscle cell proliferation. Our aim was to investigate the effects of balloon angioplasty on expression of endothelial NO synthase (cNOS) and inducible NO/synthase (iNOS) in the pig carotid artery and to relate any changes in expression to the processes of reendothelialisation and vascular repair. METHODS: Pigs were sacrificed at various time points to follow NOS expression in the neointima, media and regenerated endothelium. Immunocytochemical staining was used to localize cNOS and iNOS expression in the vessel wall. Relative amounts of cNOS were measured using quantitative in vitro alitoradiography. cNOS mRNA and iNOS mRNA was quantified by competitive PCR based on the sequenced cDNA of porcine cNOS and iNOS. RESULTS: Uninjured carotid arteries exhibited dense uniform luminal endothelial staining for cNOS. Balloon angioplasty caused denudation of cNOS immunoreactive cells and a marked reduction of cNOS gene expression but a complete recovery was noted by day 35. In normal uninjured carotid arteries no evidence of iNOS immunoreactivity was demonstrable but 24 h after injury, marked homogeneous iNOS immunoreactivity was detected in medial vascular smooth muscle cells. By 5 days, staining was evident in cells within the forming neointimal layer with no evidence of iNOS immunoreactivity in the media. iNOS immunoreactivity persisted in cells at the luminal surface at 7 days and iNOS gene expression appeared to be sustained in some animals with ruptured internal elastic lamina at 21 days. CONCLUSION: Balloon injury is associated with de-endothelialisation and a marked reduction in cNOS gene expression and activity. iNOS is induced throughout the arterial media within VSMC soon after balloon injury and persists for up to 21 days. These observations imply an important regulatory role for locally generated NO in the pathophysiological response to balloon injury.

Amino Acid Sequence↗
PubMed1999

Contribution of the lactoperoxidase system to the keeping quality of pasteurized milk.

The lactoperoxidase system is a naturally occurring antimicrobial system found in milk, with lactoperoxidase, thiocyanate and hydrogen peroxide as its components. The keeping quality of milk pasteurized at 72 degrees C for 15 s was found to be better than that of milk heated at 80 degrees C for 15 s. This agrees with previous findings and is usually attributed to heat shocking of spores. However, complete deactivation of lactoperoxidase occurred at 80 degrees C-15 s, whereas at 72 degrees C-15 s residual lactoperoxidase activity was approximately 70%, which may provide an alternative explanation. Higher levels of hypothiocyanite (the major antimicrobial agent produced by the lactoperoxidase system) were also detected in milk processed at 72 than at 80 degrees C, which supports the theory that the lactoperoxidase system has a role in the keeping quality of pasteurized milk. Of all the methods evaluated, titratable acidity and alcohol stability gave the most consistent estimates of keeping quality, while dissolved oxygen was a good indication of the onset of spoilage. Lactoperoxidase activity decreased with temperature more rapidly between 70 and 80 degrees C than is usual for an enzyme over a 10 deg C range.

Animals↗
PubMed1999

Oral folate enhances endothelial function in hyperhomocysteinaemic subjects.

BACKGROUND: Elevated plasma homocysteine (Hcy) is a risk factor for vascular disease. A postulated mechanism is vascular endothelial damage by homocysteine. Hcy levels are inversely related to blood concentrations of folate and can be lowered by folate supplements. The effect of oral folic acid on endothelial function was investigated in healthy adults with mild hyperhomocysteinaemia. PATIENTS AND METHODS: Eighteen healthy subjects (Hcy > 13 micromol L-1 at entry), from a screening population of 890 volunteers, were entered into a randomised double-blind placebo-controlled crossover study of oral folic acid (5 mg daily for six weeks) with a six week interval between treatments. Flow-mediated (endothelium-dependent) and (endothelial-independent) glyceryl trinitrate (GTN)-mediated brachial artery dilatation were measured by high resolution wall tracking. RESULTS: Folate supplementation enhanced endothelium-dependent responses (+0.08 +/- 0.05 vs. +0.04 +/- 0.04 mm, P = 0.015) but endothelium-independent responses (GTN) were unchanged. Folate reduced Hcy (8.7 +/- 2.5 vs. 12.1 +/- 3.6 micromol L-1). CONCLUSION: High dose folic acid supplementation enhances endothelium-dependent vascular function and lowers plasma Hcy. This provides preliminary evidence that folate may have beneficial cardiovascular effects in adults with mild hyperhomocysteinaemia.

Administration, Oral↗