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Biomedical subjects

M J Dunn

Publications and source records attributed to M J Dunn.

At least 91 records · Page 5Linked to original sources
PubMed1996

Characterisation of proteins from two-dimensional electrophoresis gels by matrix-assisted laser desorption mass spectrometry and amino acid compositional analysis.

Amino acid compositional analysis and peptide mass fingerprinting by matrix assisted laser desorption mass spectrometry have been used to characterise proteins obtained from two-dimensional electrophoresis (2-DE) separations of human cardiac proteins. A group of twelve protein spots was selected for analysis. The identities of eight of the proteins had been determined by conventional protein characterisation methods, two were unknown proteins and two had putative identities from protein database spot comparison. Amino acid analysis and peptide mass fingerprinting gave corresponding identities for seven of the twelve proteins, which also agreed with our initial identifications. Three proteins which had been identified previously were not confirmed in this study and putative identities were obtained for the two unknown proteins. The advantages, problems and use of amino acid analysis and peptide mass fingerprinting for the analysis of proteins from 2-DE are discussed. The data highlight the need to use orthogonal techniques for the unequivocal identification of proteins from 2-DE gels.

Amino Acids↗
PubMed1996

Kinetics of induction and protective effect of heat-shock proteins after cardioplegic arrest.

BACKGROUND: Heat-shock proteins are known to enhance cardiac resistance to ischemia. METHODS: To evaluate the kinetics of heat-shock protein 70 in relation to its effect on postischemic recovery of cardiac mechanical (cardiac output) and endothelial function (as percentage increase of coronary flow in response to 5-hydroxytryptamine), isolated rat hearts were subjected to prolonged hypothermic cardioplegic arrest at different intervals ranging from 12 to 96 hours after heat stress (n = 6 in each interval). RESULTS: Immunoblotting showed the maximal level of heat-shock protein 70, 0.65 +/- 0.10 (arbitrary units +/- standard error of the mean), at 24 hours after heat shock and similar values at 26 and 30 hours (p = not significant). Postischemic recovery of cardiac output and endothelial function (percentage of preischemic value +/- standard error of the mean) observed at 24 hours was 74.0 +/- 2.4 and 58.3 +/- 7.2, respectively. Similar values were observed at 26 and 30 hours (p = not significant). CONCLUSIONS: In a protocol mimicking conditions for cardiac transplantation, postischemic recovery of cardiac output and endothelial function was improved when the interval between heat stress and ischemia ranged from 24 to 30 hours. This correlated with an apparently critical amount of heat-shock protein 70.

Animals↗
PubMed1996

Histological abnormalities of muscle from limb, thorax and diaphragm in chronic heart failure.

The aim of the study was to compare histological findings in limb and respiratory muscles from control subjects and patients with heart failure of two different aetiologies. Biopsies of the quadriceps femoris, strap, diaphragm and pectoralis major muscles were taken from each group. The control subjects all had normal left ventricular function, and comprised seven undergoing surgical ablation of electrical pathways and 10 undergoing coronary artery surgery. The heart failure group had severely impaired left ventricular function, and were undergoing cardiac transplantation in all except one case. Ten patients with idiopathic dilated cardiomyopathy and seven with heart failure of ischaemic origin were studied. Conventional histochemical techniques and specific anti-myosin immunofluorescent stains were used. There were no consistent differences in fibre type prevalence or diameter between the groups. There were no important histological abnormalities in the two control groups. There were minor/major changes in four of seven patients with ischaemic heart failure but no major abnormality, whilst in the dilated cardiomyopathy group there were five of 10 patients with minor/major changes and three of 10 with major abnormalities (P < 0.001 vs controls). A variety of changes were seen in both groups of heart failure subjects. These were more marked in the dilated cardiomyopathy than ischaemic group, and suggest the presence of fibre type regeneration and/or transformation. Amongst the findings were tubular aggregates, internalization of nuclei, bizzare staining of myosin and staining of neonatal myosin (seven of 14) and the presence of cores (five of 14). Such changes were more prominent in the diaphragm than in the other muscles. In conclusion, histological abnormalities are present in the limb and respiratory muscles from subjects with heart failure. The changes are most marked in subjects with idiopathic dilated cardiomyopathy, suggesting that there may be a generalized cardiac and skeletal myopathy in these subjects. The presence of histological abnormalities in the respiratory muscles may contribute to the pathogenesis of dyspnoea in heart failure.

Adolescent↗
PubMed1996

Differential long-term regulation of MEK and of p42 MAPK in rat glomerular mesangial cells.

Constitutive stimulation of the mitogen-activated protein kinase (MAPK) activator MAPK/ERK kinase (MEK) is sufficient to promote long-term events such as cell differentiation, proliferation, and transformation. To evaluate a possible mechanism for the chronic regulation of MEK and p42 MAPK, we studied the long-term effects of fetal bovine serum (FBS), the G protein-coupled receptor agonist endothelin-1 (ET-1), and the protein tyrosine kinase-coupled receptor agonist platelet-derived growth factor BB (PDGF BB) on MEK and p42 MAPK in glomerular mesangial cells (GMC). FBS, ET-1, and PDGF BB led to a time-dependent increase in MEK-1 mRNA and protein expression without altering p42 MAPK mRNA and protein levels. FBS also induced MEK-1 mRNA expression in diverse cell types, including NIH/3T3 fibroblasts, A7r5 vascular smooth muscle cells, and Chinese hamster ovary cells. In GMC, cycloheximide inhibited MEK-1 mRNA induction but stimulated p42 MAPK mRNA expression in the absence and presence of FBS, ET-1, or PDGF. The FBS-induced increase in MEK-1 mRNA was accompanied by a sustained enhancement of MEK activity, as assessed by the ability of immunoprecipitated p45 MEK to activate recombinant p42 MAPK and hence phosphorylate myelin basic protein, and p42 MAPK activity. We conclude that, in GMC, MEK-1 acts like a delayed-early gene and that it can be chronically induced at the mRNA and protein level.

Animals↗
PubMed1996

Roles of calcium and kinases in regulation of thrombin-stimulated preproendothelin-1 transcription.

The release of the vasoactive peptide endothelin-1 (ET-1) is Ca2+ dependent after thrombin stimulation; however, little is known about the pathways involved. We studied the importance of Ca(2+)-dependent signal transduction pathways on preproET-1 mRNA induction in human endothelial cells. Thrombin-mediated preproET-1 mRNA induction was inhibited after clamping of cytosolic free CA2+ concentration ([Ca2+]i) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid. Chelation of extracellular Ca2+ with ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid also had a significant inhibitory effect on the induction of preproET-1 mRNA. The Ca2+ ionophore A23187 induced constitutive as well as thrombin-stimulated preproET-1 mRNA expression. Mobilization of Ca2+ stores into the cytosol by inhibition of endoplasmic reticulum Ca(2+)-adenosinetriphosphatase with thapsigargin was effective also in inducing preproET-1 mRNA. Calmodulin antagonists W-7 and calmidazolium, as well as Ca2+/calmodulin-dependent kinase II inhibitor KN-62, significantly reduced thrombin-induced preproET-1 mRNA. Inhibition by cyclosporin A of the Ca(2+)-calmodulin-dependent phosphatase calcineurin potentiated constitutive preproET-1 mRNA. These data suggest that, in human endothelial cells, thrombin-mediated preproET-1 gene induction is regulated by a stimulatory Ca2+/calmodulin kinase II-dependent pathway.

Calcineurin↗
PubMed1996

Alcohol and the heart: biochemical alterations.

A considerable amount of attention has focused on the cardiovascular events associated with ethanol consumption. The available evidence suggests that moderate ethanol consumption is associated with reduced risk of coronary heart disease, i.e., vessel events. In contrast, this review is primarily concerned with ethanol and heart muscle damage. Clinical features of the consequences of prolonged and excessive ethanol consumption encompass defects in myocardial contractility and derangement of cellular architecture, including disarray of the contractile elements. Although the incidence of heart muscle abnormalities in alcohol misusers is generally higher than previously considered, the mechanisms are only just being elucidated. This process has been facilitated by laboratory based studies in which animals receive either a single dose of ethanol (acute studies) or a continuous supply of ethanol in their daily diets (chronic studies). Results from these models show that acute ethanol dosage causes a marked decrease in the synthesis of contractile proteins. This occurs in the absence of overt mitochondrial abnormalities: ATP concentrations are generally unaffected. Paradoxically, the synthesis of mitochondrial proteins is reduced. Use of metabolic inhibitors suggests that the deleterious effects of acetaldehyde contribute to these reductions in protein synthesis. In chronic studies, ethanol causes a reduction in the amount of contractile proteins, and two dimensional protein profiling implicates selective loss of individual myocardial proteins. The differential activities of lysosomal proteases may contribute to this patterned response. However, in chronic ethanol feeding, adaptive mechanisms also become important, as the synthesis of the myofibrillary proteins increases. Overall, the mechanisms inherent in these biochemical responses may contribute to the genesis of a distinct disease entity, alcoholic heart muscle disease.

Animals↗
PubMed1995

Ca2+ signalling in K562 human erythroleukaemia cells: effect of dimethyl sulphoxide and role of G-proteins in thrombin- and thromboxane A2-activated pathways.

The human leukaemic cell line K562 is a pluripotent stem cell with the potential to mature along a megakaryocytic or erythroid line. In these cells, thrombin and U46619 (9,11-dideoxy-9 alpha, 11 alpha-methanoepoxy prostaglandin F2 alpha), a thromboxane A2 analogue, increased intracellular Ca2+ in a rapid and concentration-dependent manner. The peak transient observed with both thrombin and U46619 was preserved upon stimulation in the absence of extracellular calcium and blunted with phorbol myristate acetate, suggestive of activation of phospholipase C. Short-term treatment with leupeptin abolished the calcium response to thrombin, but did not alter that to U46619. Both pertussis toxin (PT) and DMSO pretreatment inhibited thrombin- but not U46619-stimulated intracellular calcium elevation, indicating that these agonists signal through different G-proteins. Western blot analysis of crude membranes from K562 cells revealed the presence of G12 alpha and G13 alpha; the other known PT-substrates, Gi1 alpha and G0 alpha, were not detected. Consistent with this observation, ADP-ribosylation experiments revealed the presence of two PT substrates which co-migrated with human erythrocyte G12 alpha and G13 alpha. An antibody raised against Gq/11 alpha, a subfamily of G-protein alpha subunits unmodified by PT, specifically recognized 42 kDa protein(s) in K562 cells. PCR amplification of reverse-transcribed K562 RNA followed by DNA sequencing showed that these cells express messages for both Gq alpha and G11 alpha. Treatment of K562 cells with DMSO reduced the levels of thrombin receptor mRNA, without simultaneous changes in the expression of G12 alpha and G13 alpha. We have thus identified Ca(2+)-mobilizing agonists and related G-proteins in K562 cells, together with changes induced by DMSO in this signalling pathway.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1995

Sequence analysis of wheat grain allergens separated by two-dimensional electrophoresis with immobilized pH gradients.

Micropreparative two-dimensional (2-D) gel electrophoresis with immobilized pH gradients (4-8) in the first dimension (IPG-DALT) was optimized for the separation of salt-soluble wheat grain proteins, associated with bakers' asthma disease. The resolved polypeptides were electroblotted onto a polyvinylidene difluoride (PVDF) membrane and incubated with the pooled sera from four asthmatic bakers. Bound IgE was demonstrated by alkaline phosphatase conjugated anti-human IgE. Major IgE binding was detected in the 27 kDa, 37 kDa and, to a lesser extent, in the 14-18 kDa area of the 2-D immunoblots, respectively. Since the main purpose of our study was to determine the N-terminal amino acid sequences of the major wheat grain allergens, N-terminal sequencing was performed for six out of a total of eleven major allergens located in the 27 kDa area, for one out of two 37 kDa allergens, and for two out of four 14-18 kDa allergens. Our results revealed that two of the 27 kDa polypeptides are clearly related to several Acyl-CoA oxidase variants of barley and rice, whereas no significant homologies were found for the remaining four 27 kDa allergens analyzed. The N-terminus of the 37 kDa allergen appeared to be blocked so that no sequence information was obtained, while the two 14-18 kDa allergens analyzed were identified as members of the wheat alpha-amylase-inhibitor family.

Allergens↗
PubMed1995

Coelectrophoresis of cardiac tissue from human, dog, rat and mouse: towards the establishment of an integrated two-dimensional protein database.

We have investigated the feasibility of identifying homologous proteins in whole tissue protein extracts of dog, mouse and rat hearts by comparison with our human heart two-dimensional (2-D) database. Samples of ventricular myocardial tissue from each of these species were coelectrophoresed with a human tissue sample. Gels were silver stained and patterns were analysed using PDQUEST. The number of proteins comigrating with human proteins was 301, 201 and 356 for the dog, mouse and rat, respectively. In the dog pattern, 33 of these comigrating proteins were tentatively identified from the similarity between their migration properties and those of known human proteins. Twenty-nine such proteins were identified in the mouse pattern while 30 comigrating rat proteins were identified. While these tentative identifications require confirmation, we feel that this technique offers a useful shortcut in the characterisation of proteins present in similar tissue samples from different species and avoids the necessity for duplicating laborious procedures, such as protein microsequencing, otherwise used in the identification of these proteins in each species.

Animals↗
PubMed1995

Identification of myocardial proteins from two-dimensional gels by peptide mass fingerprinting.

Two-dimensional gels offer a powerful method for separating complex protein mixtures, but subsequent methods for analysing individual components, such as protein sequencing and Western immunoblotting, are laborious and slow. The identification of proteins can be accelerated by using a combination of protease digestion and matrix assisted laser desorption-mass spectrometry (MALDI-MS). The peptide mass spectrum of a protein represents a unique fingerprint determined by the amino acid sequence and the cleavage properties of the protease. Software has been developed so that peptide masses can be used to search a mass-based peptide database generated from established protein sequence databases. A list of the closest matching proteins is produced to allow identification of the sample. The strategy was applied to 52 protein spots from human myocardial tissue separated by two-dimensional electrophoresis (2-DE) gels and analysed blind. Conditions for optimal trypsin digestion of proteins electroblotted onto polyvinylidene difluoride (PVDF) membranes are described. Mass data were generated from both Coomassie Brilliant Blue and sulforhodamine B-stained proteins, though the former required destaining prior to digestion. Alkylation of cysteine and oxidation of methionine were significant modifications that influenced the successful identification of a protein spot. Examples are presented to illustrate the advantages and disadvantages of this approach.

Electrophoresis, Gel, Two-Dimensional↗
PubMed1995

The effects of angiotensin II receptor blockade with losartan on systemic blood pressure and renal and extrarenal prostaglandin synthesis in women with essential hypertension.

The major antihypertensive effect of losartan, a nonpeptide angiotensin II antagonist, is thought to be due to inhibition of the pressor effects of angiotensin II. It is possible, however, that losartan alters the synthesis of vasodilator or vasoconstrictor prostaglandins (PG), thus contributing to its antihypertensive effect. Sixteen postmenopausal women with essential hypertension, with a mean age of 59 years and diastolic blood pressures of 95 to 115 mm Hg, were enrolled in a 12-week, single-blind study to determine the effects of losartan on blood pressure, renal and extrarenal PG production, plasma renin activity (PRA), plasma aldosterone, and routine biochemical parameters. The subjects received placebo during weeks 1 to 4, 50 mg losartan daily during weeks 5 to 8, and placebo during weeks 9 to 12. During the 4-week treatment period, there were no significant, sustained changes in renal or extrarenal synthesis of PGE2, PGI2, or thromboxane A2. Losartan significantly reduced systolic blood pressure from 155 +/- 11 mm Hg (mean +/- SD) to 139 +/- 13 mm Hg (P = .001) and diastolic blood pressure from 100 +/- 2 mm Hg to 87 +/- 5 mm Hg (P < .001) despite the fact that the majority of patients had low PRA. Plasma aldosterone concentration decreased from 9.7 +/- 6.5 ng/dL to 5.1 +/- 3.9 ng/dL (P = .002) and serum uric acid declined from 4.6 +/- 0.8 mg/dL to 4.2 +/- 0.8 mg/dL (P = .018) after 4 weeks of treatment with losartan. We conclude that 1) losartan decreases blood pressure in women with essential hypertension and low plasma renin activity; 2) the antihypertensive effect is not associated with sustained changes in renal or extrarenal PG production; and 3) losartan reduces plasma aldosterone and serum uric acid concentrations in patients with essential hypertension.

Aged↗
PubMed1995

Pre-transplant anti-epithelial cell antibodies and graft failure after single lung transplantation.

Eighty-five patients undergoing single lung transplantation have been studied to determine the presence of anti-epithelial cell antibodies (AECA) prior to transplantation using the human lung carcinoma epithelial cell line A549 in a microcytotoxicity assay. In addition, 29 healthy volunteers were also assayed for the presence of AECA. Twenty-seven of the 85 recipients exhibited AECA prior to transplantation compared to none of the 29 control subjects (p = 0.0001). Actuarial graft survival at 1 year was 78% for the AECA negative group compared to 56% for AECA positive recipients (p = 0.01). No correlation was seen between the presence of AECA and graft rejection as determined by transbronchial biopsy. However, there was an association between AECA and post-transplant infection (p = NS) where 16 (64%) of the AECA positive recipients had postoperative infection episodes compared to 25 (47%) of the negative recipients. Sodium dodecylsulphate polyacrylamide gel electrophoresis and Western blotting was also performed for 68 of the recipients and antibody reactivity was detected in 22 patients compared to 26 patients exhibiting AECA detectable by microcytotoxicity. The presence of AECA demonstrable by Western blotting did not correlate with graft survival, rejection or infection. In conclusion, AECA detectable prior to single lung transplantation are associated with a decrease in graft survival and with postoperative infections.

Adult↗