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June 1, 2005
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Kinetic disturbances of lipoprotein metabolism are important to know for a better understanding of lipid diseases or effects of drugs. These kinetic aspects were previously studied with radioactive tracers. The ethical concerns related to these tracers can be now overcome at a reasonable cost with the new development of small bench top mass spectrometers and the increased production of stable isotope tracers. In this review, we will discuss some methodological aspects related to stable isotope tracers and the analysis of the data with non-compartmental or compartmental models.
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June 1, 2005
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Abnormalities of immune system compartments were determined in 12 patients with Huntington's disease (eight males, four females; age 42.4 ± 11.7 years) and 11 controls (7 males, 4 females; age 47.0 ± 12.0). All patients were free from infectious diseases. Serum concentrations of a panel of serum soluble markers of immune activation were investigated, namely neopterin, 55-kDa-type soluble tumor necrosis factor receptor (sTNF-R), interleukin-2-receptor (sIL-2R), kynurenine, tryptophan, immunoglobulins (Ig) A, M and G as well as routine laboratory tests. Compared to controls, we found significantly higher serum levels of IgA (p < 0.01), sTNF-R, sIL-2R, neopterin, and complement component C3 (all p < 0.05), and serum tryptophan was decreased (p < 0.001). Higher concentrations of circulating immune complexes, cardiolipin antibodies, IgM, neopterin and lower tryptophan were associated with loss of cognitive function as assessed by the minimental-test. Five patients died within 1 year after measurements were performed. In these patients IgM, circulating immune complexes and neopterin concentrations were higher compared to survivors and serum tryptophan was lower. The data indicate an activation of various immune system compartments in Huntington's disease and that systemic immunological alterations might be important in the course of the disease.
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June 1, 2005
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Group II phospholipase A 2 has been proposed to play an important role in the pathophysiology of inflammatory bowel diseases. This enzyme has also been linked to host defence mechanisms against bacteria. The current study aimed at measuring the mass concentrations of group II phospholipase A 2 in serum and colonic mucosa of patients with Crohn's disease of different severity and of appropriate control patients without any inflammatory disease. The activity of the disease was determined by clinical factors (the simple index score) and endoscopic and histological scoring. The mass concentration of group II phospholipase A 2 was measured by a time-resolved fluoroimmunoassay. The mass concentrations of group II phospholipase A 2 in serum and colonic mucosa were significantly higher both in patients with active and inactive Crohn's disease when compared with controls. There was statistically significant difference in the mass concentration of group II phospholipase A 2 in colonic mucosa but not in serum between inactive and active Crohn's disease. The current results indicate that the mass concentration of group II phospholipase A 2 is increased in serum and colonic mucosa of patients with Crohn's disease and that the latter is associated with the degree of the inflammatory activity in the intestinal wall. These results support the idea that group II phospholipase A 2 is involved in the local and generalised pathological processes of Crohn's disease.
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June 1, 2005
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The results of a simultaneous determination of the pH value in erythrocytes with the potentiometric measuring method and the 14 C-labelled 5,5-dimethyl-2,4-oxazolidinedione (DMO) method showed a mean method difference of 0.026 pH units. The cause of this discrepancy was assumed to be matrix-inherent liquid-junction potentials in the potentiometric measurement. Taking these into account in the calculation leads to consistent values for the methods investigated. The DMO method proved to be free of systematic errors. Another indication of this is that its mean ratio of extracellular to intracellular H + ion concentration (H e + /H i + ) substantially agreed with the distribution ratios of other freely diffusible ions and their pH dependence.
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June 1, 2005
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Erythropoietic protoporphyria (EPP) is an autosomal dominant inherited disorder with incomplete penetrance. It is caused by partial deficiency of ferrochelatase, the last enzyme in the heme biosynthetic pathway. Measurement of protoporphyrin concentrations in red cells and feces, although sufficient for diagnosis of symptomatic EPP patients, fails to detect asymptomatic gene carriers. We have developed a molecular diagnostic procedure for rapid and reliable screening of five known mutations in the ferrochelatase gene among Swiss EPP patients in a single denaturing gradient gel electrophoresis (DGGE) gel.
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June 1, 2005
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In this study the impact of vitamin C supplementation on oxidative damage as assessed by thiobarbituric acid reactive substances and markers of antioxidant status: namely Cu/Zn superoxide dismutase, glutathione peroxidase, glutathione reductase and glutathione were investigated in 24 hyperthyroid patients under propylthiouracil therapy (3×100 mg/day) for five days and in 15 healthy controls. Ascorbic acid (1000 mg/day) was given as a supplement for 1 month to both the patients and controls during the study period. Heparinised blood samples were taken at the beginning and the end of one month ascorbic acid supplementation. Comparison of the hyperthyroid patients with the controls revealed higher lipid peroxidation (p<0.001), higher Cu/Zn superoxide dismutase activity (p<0.001), higher glutathione level (p<0.001) and lower glutathione reductase activity (p<0.001). Vitamin C supplementation to hyperthyroid patients caused significant increases in glutathione concentration (p<0.001) and glutathione peroxidase activity (p<0.001), whereas there were significant decreases in glutathione reductase (p<0.001) and Cu/Zn superoxide dismutase activities (p<0.01). Thiobarbituric acid reactive substances and thiobarbituric acid reactive substances/glutathione ratio were significantly decreased (p<0.01). Vitamin C supplementation to euthyroid controls caused significant increases in glutathione concentration (p<0.001) and glutathione peroxidase and Cu/Zn superoxide dismutase activities (p<0.001), whereas there was a significant decrease in glutathione reductase (p<0.001). The thiobarbituric acid reactive substances/glutathione ratio was significantly decreased (p<0.05). Our findings reveal the potentiation of antioxidant status and a relief in oxidative stress in both propylthiouracil treated hyperthyroid patients and controls in response to vitamin C supplementation.
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June 1, 2005
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The effect of aminoguanidine (AG) on the malondialdehyde (MDA) concentration and activities of superoxide dismutase (SOD), catalase and glutathione peroxidase (GSH-Px) in erythrocytes of rats with streptozotocin-induced diabetes was studied. Induction of diabetes resulted in an increase of MDA concentration and decreases of SOD and catalase activities after 6 and 12 weeks. GSH-Px activity increased after 6 weeks and returned to control values after 12 weeks. AG administration did not affect body weight, blood glucose level and HbA 1c content in diabetic rats but led to a decrease of MDA concentration and SOD and catalase activities after 12 weeks of treatment, with no significant effect after 6 weeks. AG attenuated the GSH-Px increase after 6 weeks but augmented the activity of this enzyme after 12 weeks. These results confirm the presence of oxidative stress in streptozotocin-induced experimental diabetes and point to the beneficial antioxidant effect of AG.
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June 1, 2005
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The aim of this work was to check the suitability of control materials to normalize intermethod results for the measurement of free triiodothyronine in patient sera. In the main experiment, 108 patient sera and 11 commercially available control materials were assayed by a pair of methods. In a confirmatory experiment, two of the control materials and 142 patient sera were assayed with an alternative pair of methods. In the main experiment, the intermethod variability of 6/11 control materials differed significantly from that of patient sera (i. e. control materials were non-commutable). Recalculation of patient results using control materials as calibrators lowered the intermethod difference only if commutable materials were used. The confirmatory experiment demonstrated that the pattern of commutability changed if a different pair of methods was used. We conclude that in the case of free triiodothyronine the commutability of control materials should be tested if they are to be used to normalize patient results obtained by different methods.
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June 1, 2005
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We have evaluated the analytical performance of a predictive kinetic procedure for the enzymatic measurement of serum creatinine in comparison with equilibrium and kinetic fixed-time procedures. The procedure uses commercially available reagents and is based on calculating the total change in absorbance expected if the reaction were to proceed to equilibrium by fitting the initial part of the absorbance-time curve to a three-parameter function by non-linear regression. Total imprecision for different concentrations of creatinine ranges from 1.47 to 1.86% and is significantly better than that obtained for the fixed-time procedure. The results with the predictive procedure are less dependent on creatinine amidohydrolase activity in the reagent, pH of the reagent and temperature of analysis than are the results with the fixed-time procedure. All the procedures are interfered with by bilirubin and ascorbic acid to about the same extent. Recovery and linearity are quite acceptable, and the estimated accuracy is below 2.1%. However, in comparison with the equilibrium procedure, the predictive procedure tends to underestimate creatinine concentrations at values below 100 μmol/l, and the results obtained by the two procedures are not transferable. In conclusion, the predictive approach substantially improves the imprecision but not the specificity of the enzymatic assay of serum creatinine.
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June 1, 2005
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We present the results of a pre-evaluation of the thyroid function test free thyroxine, free triiodothyronine and third generation TSH using the Elecsys ® electrochemiluminescence immunoassay system. A collaborative field study between the development center of the manufacturer and a clinical chemistry laboratory addressed the reliability and comparability of the new Elecsys ® assays to established methods under clinical laboratory conditions using samples from routine in vitro thyroid testing. Preliminary (reference) formulations of the reagents and several electrochemiluminescent pilot models were used for assay measurements, either in the company's research center or in the clinical setting. The new thyroid assays were compared with the respective Enzymun-Test ® assays, performed on the ES 300 automated immunoassay analyzer. A WHO standard was used for standardization of TSH, whereas an equilibrium dialysis method was applied for free triiodothyronine. The free thyroxine assay was standardized against the Enzymun-Test ® free thyroxine assay, which had previously been calibrated against equilibrium dialysis. The aim of this field study was to support the optimization of the technology used for Elecsys ® in an early stage of development and thereby prepare the ground for the adaptation of the immunoassays to the final Elecsys ® 2010 random access analyzer. A subsequent multicenter evaluation demonstrated that the requirements of routine thyroid testing in terms of reliability were fulfilled by the system.
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June 1, 2005
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Serum levels of Interleukin-6 (IL-6), a proinflammatory cytokine, are increased in early stages of inflammatory diseases such as infection and sepsis. Assay systems which permit its measurement within a few hours and as a single measurement have not been reported so far. We therefore evaluated a now commercially available automated method for IL-6 measurement on the Cobas Core ® immunological analyzer (Roche Diagnostic Systems) which enables single IL-6 measurement within about 1 hour. The automated assay correlates well with an established, manual microtiter plate assay (Biosource GmbH) which uses the same antibodies and reagents (r=0.98). Accuracy of the automated method was established by adding known amounts of IL-6 international reference preparation. Recovery of the international standard was in the range of 92–104 %. The automated assay had a precision of singletons below 6% and was linear up to 2800 pg/ml. This automated assay provides a suitable, convenient and time saving method for measurement of IL-6 serum levels in the routine clinical laboratory.
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June 1, 2005
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Ninety eight urine samples were analysed with an immunoassay benzodiazepine kit. A total of 68 urine specimens that were presumptively positive for benzodiazepines were evaluated by the REMEDi HS urine benzodiazepine assay (BIO-RAD, Munich, Germany). Of this number, 53 (78 %) specimens were found by REMEDi to contain one or more benzodiazepines or their metabolites, and 15 (22 %) were found to be negative. From the discordant group of 15 samples, eight were found to be negative using conventional chromatographic procedures (HPLC or GC/MS), while seven contained one or more benzodiazepines or metabolites, each of which were below the individual cut-off level specified by the manufacturer. Additionally 30 urine specimens that were negative for benzodiazepines using immunoassay were also tested by REMEDi. Two samples were found to be positive. These results could not be confirmed by other chromatographic techniques. The REMEDi HS benzodiazepine assay can be a very useful complementary technique in the clinical/forensic toxicology laboratory, especially for the identification of the parent benzodiazepines administered. The assay provides a rapid result in emergency situations and is useful in confirmation of preliminary positive immunoassay results.
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June 1, 2005
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June 1, 2005
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July 27, 2005
