bluuebunny/crossref_metadata_2025_split huggingface dataset:
Erythrocyte membrane thiol proteins associated with changes in the kinetics of Na/Li countertransport: a possible molecular explanation of changes in disease
Authors: Thomas  , Rutherford  , Vareesangthip  , Wilkinson  , West  
Published: March 2003

BackgroundAbnormal erythrocyte Na/Li countertransport is associated with diseases such as essential hypertension and diabetic renal disease. Although it seems unlikely that Na/Li countertransport contributes to any disease process, it may be abnormal because of a change in the cell membrane that is part of the disease process.MethodsWe have shown that Na/Li countertransport kinetics are modified by two types of thiol group. One of these, which we have called ‘type 1’, is rapidly alkylated by N‐ethylmaleimide to give a kinetic pattern similar to that in the above diseases.ResultsAt pH 6 and 2 °C, both N‐ethylmaleimide and iodoacetamide cause the Km of Na/Li countertransport to decrease to completion in 300 s, with 78% (SEM 6%) of the decrease occurring in 30 s. Using these reaction conditions, N‐ethylmaleimide reacted with a unique thiol group on a 33‐kD protein, blocking its subsequent reaction with biotin maleimide. This 33‐kD protein was present in rabbit erythrocytes, which have high levels of Na/Li countertransport, but absent from rat erythrocytes, which have no Na/Li countertransport. Iodoacetyl biotin labelled a 60‐kD protein that was specifically blocked by iodoacetamide.ConclusionWe suggest that these proteins are members of a cluster of membrane proteins that can modify Na/Li countertransport and may have a functional role in the disease processes.
Antioxidant defences are reduced during the oral glucose tolerance test in normal and non‐insulin‐dependent diabetic subjects
Authors: Ceriello  , Bortolotti  , Crescentini  , Motz  , Lizzio  , Russo  , Ézsol  , Tonutti  , Taboga  
Published: March 2003

BackgroundFree radical production has been reported to be increased in patients with diabetes mellitus, and it has been suggested that hyperglycaemia may directly contribute to the generation of oxidative stress. The aim of the present study was to evaluate the effects of an acute increase in glycaemia on plasma antioxidant defences.ResultsDuring the oral glucose tolerance test (OGTT), plasma concentration of protein‐bound sulphydryl (SH) groups, vitamin C, vitamin E and uric acid significantly decreased in normal as well as non‐insulin‐dependent diabetes mellitus (NIDDM) subjects. Total plasma radical‐trapping activity, which evaluates plasma antioxidant capacity due to known and unknown antioxidants present in the plasma as well as their mutual co‐operation, was also significantly reduced.ConclusionThis finding supports the hypothesis that hyperglycaemia may, even acutely, induce an oxidative stress.
Growth effects of α‐interferon but not of bombesin or angiotensin II are mediated by activation of STAT proteins
Authors: Pansky  , Hildebrand  , Heim  , Eberhard  , Kissel  , Beglinger  
Published: March 2003

BackgroundThe recently discovered Jak/STAT signal transduction pathway is associated with cytokine or growth factor receptors; whether members of the G protein‐coupled receptor superfamily also activate this pathway is not yet clear. As a first member, the angiotensin (AT)1A receptor has been demonstrated to phosphorylate Jak and STAT proteins. Bombesin, a neurotransmitter and growth factor in many cells and tissues, activates its G protein‐coupled receptor and in addition phosphorylates proteins that might be members of the Jak/STAT family. This study investigated whether bombesin‐ or angiotensin‐mediated growth effects are associated with STAT protein activation.MethodsFunctional receptors were characterized using ligand‐binding studies, second‐messenger activation and determination of ligand‐mediated growth effects. STAT protein activation was analysed by electrophoretic mobility shift assay (EMSA) using labelled DNA response elements recognizing all known STAT proteins.ResultsFunctional bombesin receptors mediating mitogenic effects were demonstrated on Swiss 3T3 fibroblasts, human melanoma cells (A375‐6) and primary human lung fibroblasts; however, bombesin‐related STAT protein activation was not observed by EMSA. Interferon‐α typically activated a STAT1‐STAT2‐p48 heterotrimer, as well as STAT1‐3 hetero‐ and homodimers in human melanoma cells and significantly inhibited growth of this cell line in vitro. Functional AT1A receptors on primary rat cardiac fibroblasts mediated angiotensin‐stimulated growth effects but, in contrast to recently published data, did not activate any known STAT protein.ConclusionInterferon α‐stimulated growth inhibition is mediated by activation of the Jak/STAT pathway, whereas bombesin or AT1A receptor‐mediated effects on cellular proliferation do not involve phosphorylation of STAT proteins.
Acute and chronic exposure of rat intestinal mucosa to dextran promotes SGLT1‐mediated glucose transport
Authors: Debnam  , Denholm  , Grimble  
Published: March 2003

BackgroundThe intestinal handling of dextran, an α‐1,6‐linked glucose polymer, is poor compared with starch, and some ingested dextran might therefore reach the lower small intestine. As luminal sugar up‐regulates SGLT1 (sodium‐dependent glucose transporter) locally, we report the effects of a dextran‐enriched diet on jejunal and ileal brush border membrane (BBM) glucose uptake.MethodsRats were maintained on a diet containing 65% maltodextrin or 32.5% maltodextrin + 32.5% dextran (10 kD or 40 kD) for 8–10 days, and the kinetics of phlorizin‐sensitive [3H]‐glucose uptake by purified BBM vesicles was determined.ResultsIngestion of 40‐kD but not 10‐kD dextran increased Vmax for jejunal and ileal glucose uptake (+64.3% and +61.8% respectively, both P < 0.02). The transport response to 40‐kD dextran was in keeping with lower levels of expired H2 at the end of the feeding period. High‐performance liquid chromatography (HPLC) analysis of luminal contents indicated extensive hydrolysis of ingested dextran. Finally, 3‐h jejunal exposure to 40‐kD dextran in vivo increased the Vmax for glucose uptake by jejunal BBM.ConclusionIt is likely that increased SGLT1‐mediated glucose uptake after short or longer term mucosal exposure to dextran results from luminal dextran per se or a hydrolysis product. The clinical implications of this up‐regulation are discussed.
Plasma acylation stimulating protein (ASP) as a predictor of impaired cellular biological response to ASP in patients with hyperapoB
Authors: Zhang  , Cianflone  , Genest  , Sniderman  
Published: March 2003

BackgroundThe objective of this study was to examine specific membrane binding of [125I]‐acylation stimulating protein (ASP) in cultured human skin fibroblasts obtained from normal subjects and patients with hyperapoB. ASP is a small basic protein isolated from human plasma that stimulates triglyceride synthesis (TGS) and glucose transport (GT) in human skin fibroblasts and adipocytes.DesignIn the present study, three groups were studied: normal (NASP‐NB) subjects, hyperapoB subjects with normal plasma ASP (NASP‐HB) and hyperapoB subjects with high plasma ASP (HASP‐HB).ResultsASP‐induced TGS in fibroblasts from HASP‐HB subjects was significantly less than in the two control groups with normal plasma ASP (NASP‐NB and NASP‐HB). Similarly, ASP stimulation of GT was less in HASP‐HB fibroblasts than in the NASP‐HB fibroblasts or the NASP‐NB subjects. Insulin‐induced TGS was similar in all three groups as was insulin‐stimulated GT. As well, protein kinase C‐mediated stimulation was equivalent among the three groups both for GT and for TGS. There was no significant difference in the binding affinity (Kd) of [125I]‐ASP to intact cells in any group. By contrast, binding of [125I]‐ASP revealed a significantly lower Bmax of the HASP‐HB cell lines than the NASP‐NB cells and the NASP‐HB cells.ConclusionA decrease in the ASP cell‐surface receptor concentration is responsible for decreased ASP stimulation of TGS, and GT and may contribute to the inefficient post‐prandial triglyceride (TG) clearance in HASP‐HB subjects.
Death risk factor analysis in primary hyperparathyroidism
Authors: Hedbäck  , Odén  
Published: March 2003

BackgroundPatients treated for primary hyperparathyroidism run an increased risk of death. The aim of this study was to analyse several factors that may influence their risk of death.MethodsGeneral, laboratory, physical and clinical variables, altogether 34 variables, were defined as possible risk factors for death and were studied in a patient series of 845 patients operated on during the period 1953–82. Mean follow‐up time was 10.5 years (SD 5.9); 253 patients were deceased at follow‐up. Cox's proportional hazard model was used.ResultsWe found seven variables with independent influence on the risk of death: age, sex, diabetes, cardiovascular disease, glomerular filtration rate, renal tubular concentration capacity and amount of diseased parathyroid tissue. The remaining 27 variables were separately tested, one at a time, using the same method and with the influence of age and sex eliminated. In this test situation, the year of surgery, peak serum calcium, serum creatinine level, body mass index, hypertension, psychiatric symptoms and a history of crisis were all significantly related to the risk of death. The analyses also gave information on the direction and magnitude of the effect of the variables on the risk of death.ConclusionPrimary hyperparathyroidism itself is a risk factor for death, but it was concluded that well‐preserved renal function at surgery seems to have a protective role. We also found that the greater the amount of diseased parathyroid tissue the lesser the renal function and, furthermore, that hyperparathyroidism of substantial degree or long duration may bring about renal impairment that is not necessarily disclosed by the creatinine value alone.
Neurone‐specific enolase and N‐acetyl‐aspartate as potential peripheral markers of ischaemic stroke
Authors: Stevens  , Jakobs  , De Jager  , Cunningham  , Korf  
Published: March 2003

BackgroundAfter stroke, brain‐specific proteins (including neurone‐specific enolase) leak into the blood. The question addressed in the present study was whether N‐acetyl‐aspartate (amino acid derivative localized in cerebral neurones) could also serve as a peripheral marker of ischaemic damage. N‐acetyl‐aspartate levels were determined in the blood of stroke patients and related to clinical outcome, volume of infarction and to serum neurone‐specific enolase.MethodsBlood samples from 19 patients (seven women, 12 men, mean age of 73 years, range 56–88 years) were collected during the first 4 days after stroke and analysed for neurone‐specific enolase (radioimmunoassay) and/or N‐acetyl‐aspartate (mass spectrometry). Clinical outcome was assessed using the Glasgow Outcome Score, and volume of infarction was calculated using computerized tomography (CT). Control values of N‐acetyl‐aspartate, determined in six female and nine male volunteers (mean age 47.4 years; range 28–73 years) were 0.26 ± 0.02 μmol L−1.ResultsThe increase in serum N‐acetyl‐aspartate was highly significant (P < 0.0001) within the first 24 h and at 72 h after stroke and correlated (P < 0.05) with volume of infarction only in patients with a bad prognosis (Glasgow Outcome Score < 5). Serum N‐acetyl‐aspartate at 24 h and neurone‐specific enolase at 72 h were negatively correlated, suggesting that more N‐acetyl‐aspartate reaches the blood when brain tissue is less irreversibly affected.ConclusionSerum N‐acetyl‐aspartate appears to be an early peripheral marker of ischaemically affected brain neurones, and the ratio of N‐acetyl‐aspartate to a protein marker, such as NSE, may serve as an index of irreversibility.
Characterization of antigens from the human exocrine pancreatic tissue (Pag) relevant as target antigens for autoantibodies in Crohn's disease
Authors: Fricke  , Birkhofer  , Folwaczny  , Meister  , Scriba  
Published: March 2003

BackgroundThe present study was performed to analyse the immunological properties of the autoantigens recognized by autoantibodies against exocrine pancreas (PAb), which have been described in Crohn's disease.MethodsAutoantibodies were detected by indirect immunofluorescence. Inhibition studies were performed by preincubating tissue sections with various glycoproteins and the different fractions obtained in fractioned salt precipitation of pancreas homogenate with ammonium sulphate. Immunoblotting of human pancreas homogenate was conducted using PAb‐positive sera.ResultsIn size exclusion chromatography, the molecular weight of the pancreas autoantigen (PAg) was determined as > 800 kD. In the fractionated salt precipitation, the autoantigen could be detected in fractions I (0–25% ammonium sulphate) and III (50–90% ammonium sulphate). In immunoblotting, a number of protein bands were observed (at 16, 18, 19, 24, 27, 29, 31 and 34 kD), and the binding pattern showed little variation between individual patients.ConclusionsThe protein that is recognized by PAb appears to be a large protein complex consisting of several subunits which exhibit reactivity to PAb.
Pulmonary surfactant protein A binds to Cryptococcus neoformans without promoting phagocytosis
Authors: Walenkamp  , Verheul  , Scharringa  , Hoepelman  
Published: March 2003

BackgroundEvidence is accumulating that the alveolar collectin surfactant protein A (SP‐A) plays an important role in the first line of defence against infiltrating pathogenic micro‐organisms and viruses. The ability of SP‐A to facilitate the binding and uptake of acapsular Cryptococcus neoformans by monocyte‐derived macrophages, human alveolar macrophages, monocytes and polymorphonuclear leucocytes was investigated.Materials and methodsBinding, competition and phagocytosis experiments were performed using a flow cytometry technique.ResultsSP‐A bound to both the acapsular and the encapsulated form of C. neoformans in a concentration‐dependent manner. SP‐A showed a threefold better binding to the acapsular yeast: this binding was partly calcium dependent and could be inhibited by mannose (ID50 = 3 mmol L−1) and glucose (ID50 = 2.1 mmol L−1) but not by galactose (ID50 = 391 mmol L−1). SP‐A did not function as an opsonin in phagocytosis of acapsular C. neoformans for any of the phagocytes studied.ConclusionOur results indicate that SP‐A binds in a concentration‐dependent manner to both encapsulated and acapsular C. neoformans. Despite SP‐A binding to the acapsular C. neoformans, phagocytosis by various phagocytes was not enhanced.
Lipid and lipoprotein analysis of cats with lipoprotein lipase deficiency
Authors: Ginzinger  , Clee  , Dallongeville  , Lewis  , Henderson  , Bauje  , Rogers  , Jensen  , Eckel  , Dyer  , Innis  , Jones  , Fruchart  , Hayden  
Published: March 2003

BackgroundWe have previously described a colony of domestic cats with a naturally occurring mutation in the lipoprotein lipase (LPL) gene. We have now further characterized cats homozygous for LPL deficiency (LPL −/−, homozygotes), and have contrasted these with heterozygotes (LPL +/−) and normal cats (LPL +/+).Materials and methodsDensity gradient ultracentrifugation with subsequent lipid analysis, agarose and polyacrylamide gel electrophoresis was used to examine detailed liproprotein differences between the genotypes. Oral fat loading studies and breast milk fatty acid analysis were also performed to further characterize the phenotypic expression of LPL deficiency in this model system.ResultsSeveral lipid abnormalities associated with homozygosity for LPL deficiency were evident. Triglyceride‐rich lipoprotein‐triglycerides (TRL‐TG) and cholesterol (TRL‐C) were higher (TRL‐TG 2.09 ± 1.14 vs. 0.15 ± 0.04 mmol L−1, P < 0.001; TRL‐C 0.42 ± 0.30 vs. 0.11 ± 0.16 mmol L−1, P < 0.05) in male −/− than in male +/+ cats, as was HDL‐cholesterol (HDL‐C, 1.75 ± 0.24 vs. 1.41 ± 0.14 mmol L−1, P < 0.05). LDL‐C levels were lower in homozygous cats than in control cats, similar to what is seen in human LPL deficiency. Oral fat loading studies revealed that homozygous cats have a marked reduced ability to clear plasma TGs in terms of peak time (7 h vs. 3 h), peak height (9.36 vs. 1.1 mmol L−1), area under the TG clearance curve (AUC, 280.3 vs. 2.2 h mmol L−1) and time to return to baseline. Fasting lipid and lipoprotein levels were not significantly different between heterozygous and normal cats. However, oral fat loading in heterozygotes revealed an intermediate phenotype (peak of 2.35 mmol L−1 at 5 h, AUC 13.1 h mmol L−1), highlighting the impaired TG clearance in these animals.ConclusionThus, LPL deficiency in the cat results in a lipid and lipoprotein phenotype that predominantly parallels human LPL deficiency, further validating the use of these animals in studies on the pathobiology of LPL.
Salt sensitivity correlates positively with insulin sensitivity in healthy volunteers
Authors: Ter Maaten  , Voordouw  , Bakker  , Donker  , Gans  
Published: March 2003

BackgroundThe aim of the study was to assess the relationship between insulin sensitivity and salt sensitivity in healthy subjects who display a wide range of insulin sensitivity. As a secondary objective, we assessed the relationship between salt sensitivity and the other characteristics of the insulin resistance syndrome.Study designForty‐seven normotensive volunteers (age 34 ± 15 years) with a normal glucose tolerance test were selected. We measured insulin sensitivity using the hyperinsulinaemic euglycaemic clamp (50 mU kg−1 h−1), blood pressure, waist‐to‐hip ratio, fasting insulin levels, serum lipids and uric acid levels. In a subset of 21, representing a wide range of insulin sensitivity, salt sensitivity was determined as the difference in mean arterial blood pressure (MAP) at the end of a high‐salt diet (10 g of NaCl per day for 1 week) vs. a low‐salt diet (2 g of NaCl per day for 1 week).ResultsInsulin sensitivity (M/I value, range 0.49–4.41 mg kg−1 min−1 per pmol L−1 × 100) was negatively correlated with MAP (r = –0.54, P < 0.001) and waist‐to‐hip ratio (r = − 0.59, P < 0.001) but positively correlated with salt sensitivity (r = 0.47, P = 0.03). Salt sensitivity also correlated with high‐density lipoprotein (HDL)‐cholesterol (r = 0.46, P = 0.038) but not with waist‐to‐hip ratio, fasting insulin levels, low‐density lipoprotein cholesterol, serum triglycerides or serum uric acid.ConclusionsIn healthy normotensive subjects who display a wide range of insulin sensitivity, as measured with the euglycaemic clamp technique, salt sensitivity correlates positively with insulin sensitivity and HDL‐cholesterol, but not with the other characteristics of the insulin resistance syndrome.
Nitric oxide diffusion across membrane lungs protects platelets during simulated extracorporeal circulation
Authors: Keh  , Gerlach  , Kürer  , Spielmann  , Kerner  , Busch  , Hansen  , Falke  , Gerlach  
Published: March 2003

BackgroundThe absence of a protective endothelial surface on membrane oxygenators during extracorporeal circulation (ECC) promotes platelet trapping and damage, leading to increased bleeding complications. We investigated the effects of transmembranous diffusion of gaseous nitric oxide (NO) on platelets during simulated ECC.Material and methodsTwo paired circuits were run in parallel with fresh, heparinized (1 U mL−1) blood from healthy human donors for 240 min. To one of the paired circuits, 20 ppm NO was added transmembranously.ResultsNO significantly attenuated platelet trapping and reduced intracircuit platelet activation evaluated by the release of β‐thromboglobulin, platelet factor 4 and soluble P‐selectin. Furthermore, NO significantly preserved platelet reactivity to stimulating agents (ADP and adrenaline), evaluated as the ability to expose P‐selectins and activate glycoprotein (GP)‐IIb‐IIIa. Nevertheless, circulating activated platelets expressing P‐selectin or activated GPIIb‐IIIa were not different and were not significantly increased. The mean fluorescence intensity of GPIb and GPIIb‐IIIa decreased in both circuits equally.ConclusionsTransmembranous diffusion of gaseous NO revealed protective effects on platelets by reducing thrombocytopenia/pathia and preserving platelet reactivity.
Perioperative catecholamine changes in cardiac risk patients
Authors: Sametz  , Metzler  , Gries  , Porta  , Sadjak  , Supanz  , Juan  
Published: March 2003

BackgroundIt has previously been found that in cardiac risk patients undergoing non‐cardiac surgery post‐operative cardiac complications are correlated with high post‐operative serum levels of troponin T (TNT) and troponin I (TNI). We investigated whether perioperative changes in the release of free (fCAs) and conjugated catecholamines (cCAs) correlate with the increased serum level of TN (TN↑).Materials and methodsPlasma levels of CAs were determined in 28 patients at risk for or with definite coronary artery disease. Blood sampling was performed in the morning on the day before surgery, on the day of surgery before induction of anaesthesia and until the fifth post‐operative day for measurement of CAs by high‐performance liquid chromatography.ResultsThe plasma concentrations of free and conjugated noradrenaline (fNA and cNA) as well as of free and conjugated adrenaline (fA and cA) were increased significantly in TN↑ patients post‐operatively. The plasma levels of free as well as of conjugated NA and A in TN↑ patients were significantly higher than in TN0 patients over the whole post‐operative period.ConclusionThis study demonstrates that increased post‐operative release of fNA and fA as well as of cNA and cA correlates with high post‐operative serum levels of troponins in cardiac risk patients undergoing non‐cardiac surgery.
Oral folate enhances endothelial function in hyperhomocysteinaemic subjects
Authors: Bellamy  , W. McDowell  , Ramsey  , Brownlee  , Newcombe  , Lewis  
Published: March 2003

BackgroundElevated 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 methodsEighteen healthy subjects (Hcy > 13μmol 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.ResultsFolate 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 μmol L−1).ConclusionHigh 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.