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  • 11
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 182-184 (Feb. 1995), p. 735-738 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 13
    ISSN: 1432-0428
    Keywords: Radioimmune assay ; enzyme linked immunosorbent assay ; insulin antibodies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Human sera were tested for insulin antibodies by fluid and solid phase assays. Radioimmune titres determined with 125-I Tyr A14 insulin were not correlated with those obtained using insulin coated microplates and enzyme linked immunodetection (n=60). Several reasons for this lack of correlation were found. Iodine substitution on the A14 residue of insulin may significantly alter the avidity of some insulin antibodies for their ligand; hence, disclosing a heretofore unsuspected pitfall for antibody determination by radio-immunoassay. Specificity for bovine insulin was easily demonstrable in fluid phase by comparing the binding of monoiodinated bovine, porcine and human insulin. By contrast, in solid phase assay, titres obtained with microplates coated with bovine or human insulin were almost equal, regardless of the serum specificity for bovine insulin. This lack of specificity of the solid phase assay is not due to denaturation or unavailability of the bovine specific epitope because: bovine specificity could be demonstrated by competitive assay, after preincubation of the serum with insulin of the different species; and, coating with crosslinked insulin dimers or oligomers instead of monomers did not unmask bovine specificity. It is concluded that radioimmune methods are best suited to study specificity but may be biased by the presence of the radioiodine label whereas solid phase assay detects low avidity antibodies with great efficiency but is less appropriate to study specificity.
    Type of Medium: Electronic Resource
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  • 14
    ISSN: 1432-0428
    Keywords: Standardization ; insulin-antibodies ; insulin-auto-antibodies ; radioimmunoassay ; enzyme linked immunosorbent assay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Nine selected sera were studied using radioim-munoassay and enzyme linked immunosorbent assay; eight contained insulin antibodies and were from Type 1 (insulin-dependent) diabetic patients, one of whom had antibody-mediated insulin resistance, and one contained insulin-auto-antibodies and was from an asymptomatic blood donor. Sera were assayed in serial dilution to assess their suitability for use as reference standards. Dilution curves were non-parallel in radioimmunoassay but were parallel in immunosorbent assay. In all sera, insulin antibodies were readily detected in both assays whereas the low avidity insulin autoantibodies were only detected by immunosorbent assay and not at all by radioimmunoassay, suggesting that the assays respond differently to antibodies of different avidity. Avidity was estimated in liquid phase from the dissociation rate of preformed complexes of antibody and 125-iodinated insulin. When high avidity antibodies are used as a reference in radioimmunoassay, lower avidity antibodies are underestimated and vice versa. In contrast, in immunosorbent assay, any serum could be used as a reference regardless of avidity; furthermore competition experiments comparing the highest avidity insulin antibodies, from the insulin-resistant patient, with the insulin autoantibodies from the asymptomatic blood donor yielded nearsuperimposable curves. We conclude that radioimmunoassay is selective for high avidity antibodies whereas enzyme linked immunosorbent assay is not; computer modelling of the two assays supports this conclusion. In practice immunosorbent assay can be standardized using a reference serum, whereas experimental findings and mathematical considerations preclude the use of a standard serum in radioimmunoassay.
    Type of Medium: Electronic Resource
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  • 15
    ISSN: 1432-0428
    Keywords: Proinsulin monoclonal antibodies ; affinity ; solid-liquid phase assay ; radiobinding assay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Hybridomas producing proinsulin antibodies were cloned by limiting dilution of cell cultures obtained by fusion of splenocytes of immunized mice with immortal myeloma cells. Some proinsulin monoclonal antibodies crossreacted with labelled insulin but none did with labelled C-peptide indicating that the involved epitopes were at one of the insulin/C-peptide junctions or included in the insulin moiety. Hybridoma supernatants were assayed for IgG concentration by a solid phase assay and for ligand binding by a radiobinding assay and an enzyme linked immunosorbent assay. The half-life of immune complexes formed with radioligand was measured and, as expected, correlated with affinity as measured by the method of Scatchard. Antibody titres determined by enzyme linked immunosorbent assay did not correlate to those measured by radiobinding assay. IgG concentration correlated to enzyme linked immunosorbent assay titres but not to radiobinding assay titres. Finally, a significant correlation was found between radiobinding assay titre and the product of enzyme linked immunosorbent assay titre by the period of immune complexes. It is concluded that, except for very low affinity antibodies, enzyme linked immunosorbent assay is a capacity assay whereas radiobinding assay is influenced by both antibody concentration and affinity. The former assay is thus best suited to detecting low affinity antibodies whereas the latter is more efficient in the presence of low levels of high affinity antibodies.
    Type of Medium: Electronic Resource
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  • 16
    ISSN: 1432-0428
    Keywords: Insulin autoantibodies ; IgG isotype ; light chain ; species specificity ; blood donors ; affinity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Serum samples of 2200 blood donors were screened for anti-insulin IgG by enzyme-linked immunosorbent assay. Specificity of detected antibodies was verified by competition with an excess of insulin and observation that saturated anti-insulin IgG were no longer measurable. The upper limit of measured signal in the population was defined as the mean plus three SD. In the direct assay, 32 sera were positive. Among these, 22 (1%) contained saturable insulin antibodies (true positive) and 10 were non-saturable and considered as non-insulin-specific. The positive blood donors were requested to answer a questionnaire and according to their answers, none had ever received insulin, was a first degree relative of a Type 1 (insulin-dependent) diabetic patient or had experienced a hypoglycaemic episode. None of the 22 true positive sera detected by enzyme-immunosorbent assay bound 125-I-insulin to any significant extent. The nine sera yielding the highest signal were further characterized with regard to heavy and light chains as well as species specificity of ligand. Anti-insulin IgG from healthy blood donors contained only one heavy (γ1 2/9; γ3 7/9) and one light (κ 8/9; λ 1/9) chain. Three sera were human insulin specific; two were non-species-specific; the other four bound insulin in the order human = porcine 〉 bovine. These results indicate that low affinity clonally restricted antibodies against insulin are present in unselected blood donors with a prevalence of 1%.
    Type of Medium: Electronic Resource
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  • 17
    ISSN: 1432-0428
    Keywords: Keywords Insulin resistance, Type II diabetes, tumour necrosis factor-α, promotor polymorphisms, first-degree relatives.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Aims/hypothesis. Tumour necrosis factor-α (TNF-α) is believed to influence skeletal muscle insulin resistance. Two G → A transitions in the promoter region of TNF- α at position –238 and –308 have been identified that could play a part in transcriptional regulation of the gene. Insulin resistance is an independent familial trait that predicts the development of Type II (non-insulin-dependent) diabetes mellitus. We investigated the influence on insulin sensitivity and insulin secretion of both polymorphisms in a cohort of young healthy relatives of patients with Type II diabetes.¶Methods. We examined 109 first-degree relatives of Caucasian patients with a history of Type II diabetes, who underwent extensive metabolical and anthropometrical phenotyping, and determined the TNF- α –238 and –308 G→ A promoter polymorphisms.¶Results. For the –238 polymorphism, 83 probands (76.1 %) were homozygous for the G-allele, 25 probands (22.9 %) were heterozygous and 1 proband (0.9 %) was homozygous for the A-allele. For the –308 polymorphism, 83 probands (76.1 %) were homozygous for the G-allele, 24 probands (22.0 %) were heterozygous and 2 probands (1.18 %) were homozygous for the A-allele. Probands with and without the polymorphism did not differ in insulin sensitivity (p = 0.78), insulin-concentrations and C-peptide concentrations in oral glucose tolerance tests (p 〉 0.05).¶Conclusions/interpretation. We could not detect an association between insulin sensitivity or insulin secretion and TNF- α promoter polymorphisms in our cohort. The polymorphisms occur at the same frequencies in probands with either low or high insulin sensitivity. [Diabetologia (2000) 43: 181–184]
    Type of Medium: Electronic Resource
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  • 18
    ISSN: 1432-0428
    Keywords: Keywords leptin ; leptin receptor ; insulin receptor ; phosphatidylinositol kinase ; janus kinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have recently shown that leptin mimicks insulin effects on glucose transport and glycogen synthesis through a phosphatidylinositol-3 (PI) kinase dependent pathway in C2C12 myotubes. The aim of the present study was to identify the signalling path from the leptin receptor to the PI-3 kinase. We stimulated C2C12 myotubes with insulin (100 nmol/l, 5 min) or leptin (0.62 nmol/l, 10 min) and determined PI-3 kinase activity in immunoprecipitates with specific non-crossreacting antibodies against insulin-receptor substrate (IRS 1/IRS 2) and against janus kinase (JAK 1 and JAK 2). While insulin-stimulated PI-3 kinase activity is detected in IRS-1 and IRS-2 immunoprecipitates, leptin-stimulated PI-3 kinase activity is found only in IRS-2 immunoprecipitates, suggesting that the leptin signal to PI-3 kinase occurs via IRS-2 and not IRS-1. Leptin-, but not insulin-stimulated PI-3 kinase activity is also detected in immunoprecipitates with antibodies against JAK-2, but not JAK-1. The data suggest that JAK-2 and IRS-2 couple the leptin signalling pathway to the insulin signalling chain. Since we have also detected leptin-stimulated tyrosine phosphorylation of JAK-2 and IRS-2 in C2C12 myotubes it can be assumed that leptin activates JAK-2 which induces tyrosine phosphorylation of IRS-2 leading to activation of PI-3 kinase. As we could not detect the long leptin receptor isoform in C2C12 myotubes we conclude that this signalling pathway is activated by a short leptin receptor isoform. [Diabetologia (1997) 40: 1358–1362]
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    Springer
    Diabetologia 36 (1993), S. 1113-1117 
    ISSN: 1432-0428
    Keywords: Diabetes mellitus ; uraemia ; haemodialysis ; cardiovascular death ; myocardial infarction ; hypertension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The objective of this study was to examine diabetic patients at the time of admission to maintenance haemodialysis and to follow them for 36 months in order to define predictors of cardiovascular and non-cardiovascular death. This prospective study comprised all consecutive diabetic patients admitted to 28 German dialysis centres between January 1985 and October 1987; 196 patients were examined, 67 Type 1 (insulin-dependent) diabetic (43 male, 24 female; median age 49 years, range 22–73) and 129 Type 2 (non-insulin-dependent) diabetic patients (54 male, 75 female; 64 years, range 37–82). Outcome measures were death, i.e. myocardial infarction, sudden death, cardiac death of other causes, stroke and noncardiovascular death. Actuarial survival 36 months after the beginning of dialysis was similar in Type 1 (40%) and Type 2 diabetic patients (43%) despite the age difference. Causes of death were myocardial infarction (18%), sudden death (18%), other cardiac causes (18%); stroke (6%); septicaemia (17%) mostly originating from diabetic foot problems; and interruption of therapy. Survival rates and the proportion dying from cardiac causes were similar in patients with diabetic nephropathy or with other primary chronic renal disease and coincidental diabetes. On dialysis, de novo amaurosis or de novo amputation was not observed in any patient. The strongest predictor of myocardial infarction or sudden death was serum lipids on admission. Duration of hypertension, blood pressure at the time of admission to dialysis, left ventricular hypertrophy or end-diastolic diameter by echocardiography, Sokolow index and average predialysis blood pressure, smoking, interdialytic weight gain and type of dialysis were not predictive of cardiovascular death or death by all causes. Patients with myocardial infarction were more frequently male (70% of myocardial infarction), tended to be younger, more frequently had a history of myocardial infarction (relative risk 3.0) and more frequently had angina pectoris, proliferative retinopathy (relative risk 2.8) or somatosensory polyneuropathy (relative risk 3.0). Patients dying from myocardial infarction or other cardiac causes had more frequent episodes of intradialytic hypotension and tended to be less frequently on beta blocker treatment. We conclude that cardiac death accounts for most fatalities of diabetic patients on dialysis. Some, but not all, classic risk factors are predictive of cardiac death.
    Type of Medium: Electronic Resource
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  • 20
    ISSN: 1432-0428
    Keywords: Keywords Insulin resistance ; Type II diabetes ; obesity ; peroxisome proliferator activated receptors ; Pro 12 Ala mutation.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Aims/hypothesis. Recently a mutation in the coding sequence of the adipocyte specific isoform peroxisome proliferator-activated receptor γ2 (PPARγ2) was described, leading to the substitution of Proline to Alanine at codon 12. Mutations in PPARγ2 could have a role in people who are at increased risk for the development of obesity and Type II (non-insulin-dependent) diabetes mellitus. Methods. Non-diabetic first-degree relatives (n = 108) of subjects with Type II diabetes were characterized by oral glucose tolerance tests and euglycaemic hyperinsulinaemic glucose clamp to determine insulin sensitivity. Results. We found 75 (69 %) probands without the PPARγ ProAla12 substitution, 28 heterozygotes (26 %) and 5 (4 %) homozygotes. When the whole group was analysed for an association between the mutation and insulin sensitivity, no statistical significance could be shown. Only in the group with severe obesity more than 30 kg/m2, an association (p = 0.016) of the polymorphism with an increase in insulin sensitivity was found. Conclusion/interpretation. These observations suggest that the mutation in the PPARγ2 molecule may have a role in subgroups prone to the development of obesity and Type II diabetes. [Diabetologia (1999) 42: 758–762]
    Type of Medium: Electronic Resource
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