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Biomedical subjects

H Wieland

Publications and source records attributed to H Wieland.

At least 73 records · Page 4Linked to original sources
PubMed1998

Fluorometric determination of total retinyl esters in triglyceride-rich lipoproteins.

A time-consuming sample preparation and measuring procedure is required for the quantitation of retinyl palmitate by HPLC. We developed a fluorometric method for the determination of total retinyl esters in chylomicrons, chylomicron remnants, and VLDL. This method is precise, sensitive, rapid, simple, and particularly useful for large-scale studies of postprandial lipid metabolism. Because the turbidity of postprandial lipemic samples interferes with the fluorescence measurement, all samples were incubated for 10 min with a clearing buffer containing esterase and detergents. This buffer eliminates the turbidity and hydrolyzes all retinyl esters to retinol. The fluorescence signal (excitation wavelength, 330 nm; emission wavelength, 490 nm) was linear from 0.1 mg/L up to 4 mg/L retinyl palmitate, and the CVs were 3.6% within-run and 5.1% within-series. A first application studied postprandial lipoproteins, which were first separated by ultracentrifugation and then subjected to size exclusion chromatography. Fluorescence analysis revealed that the chylomicron density fraction contains large amounts of chylomicron remnants.

Buffers↗
PubMed1998

Hemoglobin Rambam (beta69[E13]Gly-->Asp), a pitfall in the assessment of diabetic control: characterization by electrospray mass spectrometry and HPLC.

Hemoglobin (Hb) Rambam, or beta69[E13]Gly-->Asp, has been identified in a German woman also suffering from non-insulin-dependent diabetes mellitus and chronic obstructive pulmonary disease. This is the first observation of this Hb variant in a German family thus far. The detailed evaluation of its structure using electrospray mass spectrometry revealed new minor glycohemoglobin components and showed that the attachment of glucose to the beta NH2 terminus occurred at an almost identical rate in both wild-type and mutant beta-chains. However, the introduction of a carboxyl group at beta69 seems to increase the glycation of epsilon-amino groups of lysine residues. The glycemic state in the propositus was well reflected by the total glycohemoglobin concentrations but not by the Hb A1c values, which did not reflect hemoglobin glycation in this patient. This case demonstrates that Hb A1c cannot be used reliably in the management of diabetic patients carrying Hb variants such as Hb Rambam. Functional studies of the whole blood of the heterozygous carrier demonstrated extremely low oxygen affinity, which may have been caused by increased 2,3-diphosphoglycerate related to chronic obstructive pulmonary disease and hyperthyroidism. None of the clinical symptoms could be directly associated to Hb Rambam.

Amino Acid Sequence↗
PubMed1997

The effect of simvastatin on progression of coronary artery disease. The Multicenter coronary Intervention Study (CIS).

BACKGROUND: In several angiographic trials, HMG-CoA reductase inhibitors have shown a beneficial effect on the progression of coronary artery disease. Using 20 mg simvastatin, day-1, a treatment period of up to 4 years was necessary to show a significant reduction in coronary artery disease progression. The question remains however whether higher dosages of simvastatin would be more advantageous in respect to the magnitude of the effect and the required time interval to demonstrate treatment efficacy. METHODS AND RESULTS: In the Coronary Intervention Study (CIS), a multicentre randomized double-blind placebo-controlled study, the effects of lipid-lowering therapy with simvastatin on progression of coronary artery disease in 254 men with documented coronary artery disease and hypercholesterolaemia were investigated. Following a period of lipid-lowering diet, treatment with 40 mg simvastatin or placebo was maintained for an average of 2.3 years. Two primary angiographic endpoints were chosen: the global change score (visual evaluation according to the method of Blankenhorn) and the per patient mean change of minimum lumen diameter (evaluated by the CAAS I system). The mean simvastatin dose was 34.5 mg day-1. In the placebo group, the serum lipids remained unchanged; in comparison to the placebo group the simvastatin group showed a 35% LDL-cholesterol decrease. Coronary angiography was repeated in 205 patients (81%) and 203 film pairs (80%,) were evaluable by quantitative coronary angiography. In the simvastatin and placebo groups, the mean global change scores were +0.20 and +0.58 respectively, demonstrating a significantly slower progression of coronary artery disease in the treatment group (P = 0.02). The change in minimum lumen diameter assessed by computer-assisted quantitative evaluation with the CAAS I system was -0.02 mm in the simvastatin group and -0.10 mm in the placebo group (P = 0.002). In the simvastatin group, there was a significant correlation between the LDL cholesterol levels achieved therapeutically and the per patient mean loss of minimum lumen diameter (r = 0.29; P = 0.003). During the study period, there was no significant difference in the incidence of serious cardiac events (15 of 129 patients in the simvastatin group and 19 of 125 patients in the placebo group, ns). CONCLUSION: Treatment with 40 mg simvastatin day-1 reduces serum cholesterol and slows the progression of coronary artery disease significantly within a short period of treatment time. In the treatment group, retardation of progression is inversely correlated to the LDL-cholesterol levels achieved.

Adult↗
PubMed1997

Induction of vascular endothelial growth factor by platelet-activating factor and platelet-derived growth factor is downregulated by corticosteroids.

Vascular endothelial growth factor (VEGF) is a potent peptide growth factor specific for vascular endothelial cells, which promotes neovascularization and increases vascular permeability in vivo. Enhanced microvascular permeability and edema are common characteristics of inflammatory and neoplastic disorders. Two proinflammatory mediators, platelet-activating factor (PAF) and platelet-derived growth factor (PDGF), are known to contribute to cellular damage and tissue remodeling in a number of lung diseases. To determine whether PAF or PDGF induce VEGF gene expression in primary cultures of human pulmonary fibroblasts and pulmonary vascular smooth-muscle cells (VSMCs), we performed Northern-blot analysis and enzyme-linked immunosorbent assays (EIA). PAF and all three isoforms of PDGF (PDGF-AA, -AB, and -BB) increased VEGF mRNA in a time- and dose-dependent manner. While PAF was shown to increase VEGF mRNA at picomolar concentrations, all PDGF isoforms were effective in inducing VEGF mRNA at nanomolar concentrations. The transcriptional activation was accompanied by increased levels of VEGF protein as determined by EIA in culture medium. These results indicate that VEGF gene expression in VSMCs and fibroblasts is mediated by PAF and/or PDGF isoforms. In a paracrine mode of action, secreted VEGF may then lead to altered endothelial cell functions and vascular hyperpermeability. In the presence of the corticosteroids cortisone, hydrocortisone, dexamethasone, or prednisolone at nanomolar concentrations, this stimulus-dependent transcription of VEGF was abolished. The inhibitory effect of corticosteroids on VEGF expression could explain the clinically well-known antiedematous potency of corticosteroids on a molecular level.

Adrenal Cortex Hormones↗
PubMed1997

Lifibrol: first member of a new class of lipid-lowering drugs?

Management of dyslipoproteinaemia is one of the key strategies in the prevention of cardiovascular disease. The major target of hypolipidaemic drugs is the reduction of low density lipoprotein (LDL) cholesterol. Lifibrol, a novel lipid-lowering agent, is highly potent in reducing total cholesterol, LDL cholesterol, and apolipoprotein B. Its efficacy in lowering serum triglycerides, lipoprotein(a) and fibrinogen implies additional benefit in the prophylaxis and treatment of coronary heart disease. Thus, lifibrol appears to be a multivalent anti-atherosclerotic agent. The hypolipidaemic properties of lifibrol have been examined in several clinical trials and in various animal models. The mode of action of lifibrol involves at least three mechanisms: lifibrol enhances LDL catabolism by sterol-independent stimulation of LDL receptor activity, reduces cholesterol absorption from the intestine, and slightly decreases hepatic cholesterol biosynthesis. Lifibrol's lipid-lowering profile and putative mode of action clearly distinguish it from other classes of hypolipidaemic drugs, such as HMG-CoA reductase inhibitors or fibric acid derivatives. Thus, lifibrol may represent a new class of agents affecting lipid metabolism.

Journal Article↗
PubMed1997

Comparability of a new turbidimetric digoxin test with other immunochemical tests and with HPLC--a multicenter evaluation.

A new turbidimetric inhibition immunoassay for digoxin (Tina-quant [a] Digoxin, Boehringer Mannheim) was evaluated in seven laboratories. It can be performed without sample pretreatment with ready-to-use reagents on nondedicated analyzers in combination with routine clinical chemistry. The studies revealed a good analytical performance: lower limit of detection 0.12 microg/L (3 SD from mean of blank); linearity up to 7.5 microg/L; median between-run CVs 8.1% (0.6 microg/L), 2.8% (1.5 microg/L), 1.9% (3 microg/L); mean analytical recovery in control sera 98-102%; slopes from 0.97 to 1.09 and intercepts from -0.28 to 0.10 microg/L in comparison with four immunoassays; and a high resistance to common interferents. The test was more resistant to digoxin-like immunoreactive factor (DLIF) interference than other methods, showing cross-reactivity only in some intensive care patient samples. Among 192 patients in whom DLIF is expected (e.g., pregnant women, patients with renal failure, newborns), 90% of results were < or =0.26 microg/L digoxin. Cortisol showed no cross-reactivity and digoxigenin had a low reactivity. An interlaboratory survey revealed a good comparability of the Tina-quant [a] test with the median of all methods (slope 0.99, intercept -0.06 microg/L). An HPLC method for digoxin based on isocratic separation of samples on an RP-18 column followed by detection by an immunoassay yielded a reasonable comparability with the immunochemical tests with noncritical samples. Divergent results of immunoassays caused by DLIFs or different cross-reactivities with digoxin metabolites or derivatives can be explained by the use of this HPLC method.

Anticoagulants↗
PubMed1997

Influence of an unaccustomed increase in training volume vs intensity on performance, hematological and blood-chemical parameters in distance runners.

The hypothesis was tested that high-volume endurance training can be monitored using hematological and blood-chemical parameters as markers of an early stage in the overtraining process. Eight experienced distance runners participated in a prospective, experimental, controlled study. The study consisted of an unaccustomed average 103% increase in training volume (ITV) within 4 weeks (average final volume: 174.6 km per week). A year later, 9 runners performed the additional 4-week control study that consisted of an unaccustomed average 152% increase in intensive training measures (ITI). Average total volume amounted to 61.7 km (week 1) and 84.7 km (week 4). Seven athletes participated in both studies. Simultaneously to performance diagnostics, a comprehensive pattern of hematological and blood-chemical parameters was determined. During ITV, submaximum running performance was improved after 2 weeks, stopped improving between week 3 and 4; maximum performance did not increase rather was decreased after week 4 compared to baseline as indication of an early stage in the overtraining process. During ITI, submaximum and maximum running performances increased continuously. In contrast to ITI, the following parameters decreased significantly during ITV: White blood cell count, serum iron, ferritin, VLDL-(very low density lipoproteins), LDL (low density lipoproteins)-cholesterol, albumin, resting and maximum free fatty acid, maximum lactate, resting, submaximum and maximum glucose, summed amino acid, resting, submaximum and maximum ammonia concentrations, whereas prothrombin time increased significantly. During high-volume endurance training a multifactorial and longitudinal approach considering either a performance incompetence and an individually different range of symptoms and alterations in hematological and blood-chemical parameters can help to recognize an early stage in the overtraining process.

Blood Chemical Analysis↗
PubMed1997

Multicenter evaluation of a homogeneous assay for HDL-cholesterol without sample pretreatment.

We evaluated a new homogeneous assay for the measurement of HDL-cholesterol (HDL-C) in six European laboratories. The assay includes two reagents and is applicable to most autoanalyzers, which allows full automation. The total CVs of the new method ranged between 1.3% and 6.7%. Thereby determined HDL-C values were in good agreement with those obtained by precipitation with phosphotungstic acid/MgCl2 or by a combination of ultracentrifugation and precipitation (0.956 < r < 0.994). The assay was linear up to at least 1500 mg/L HDL-C. Hemoglobin did not interfere, whereas icteric samples with bilirubin > 100 mg/L showed discrepancies between the homogeneous and the precipitation assay. Lipemia up to total triglyceride concentrations of 8000 mg/L did not interfere with the homogeneous HDL-C assay. The homogeneous HDL-C assay was easy to handle and produced similar results in all laboratories participating in this study. This method will significantly facilitate the screening of individuals at increased risk for cardiovascular disease.

Artifacts↗
PubMed1996

Heterogeneity of hemoglobin A1d: assessment and partial characterization of two new minor hemoglobins, A1d3a and A1d3b, increased in uremic and diabetic patients, respectively.

We have separated and quantified two new minor hemoglobins named HbA1d3a and HbA1d3b. The level of HbA1d3a was significantly higher in uremic than in non-uremic patients (3.00 +/- 0.50% vs. 1.28 +/- 0.26% of total hemoglobin). It correlated well with carbamylated hemoglobin (r = 0.80, n = 81, p < 0.002) and with plasma urea concentration (r = 0.78, n = 81, p < 0.002). These data and the electrospray ionization mass spectrometric analysis provide strong evidence that HbA1d3a is an alpha-chain modified by carbamylation. The HbA1d3b level an diabetic patients was found to be 1.6-fold that in non-diabetic subjects (3.00 +/- 0.49 vs. 1.90 +/- 0.33). This was attributed to HbA1d3 modified by glycation. Indeed HbA1d3b correlated significantly with HbA1c (r = 0.71, p < 0.002) and with serum glucose level (r = 0.62, p < 0.002). These two new minor hemoglobins may serve as complements for the objective assessment of averaged long-term uremia and glycemia in uremic and diabetic patients.

Chromatography, High Pressure Liquid↗
PubMed1996

Clearance of postprandial lipoproteins in normolipemics: role of the apolipoprotein E phenotype.

The hepatic clearance of triglyceride-rich lipoproteins is mediated via apolipoprotein (apo) E which occurs in three common isoforms, apoE2, apoE3 and apoE4. To study the importance of the apoE isoforms on the response curves of different triglyceride-rich lipoproteins and the effect of chylomicron remnants on the composition of HDL, 37 normolipemics were investigated after a standardized fatty meal (8 apoE2/E2, 8 apoE2/E3, 8 apoE3/E3, 7 apoE3/E4 and 6 apoE4/E4). These individuals were matched for age, body mass index, fasting triglycerides, HDL-cholesterol, and apoA-I. A delayed chylomicron remnant clearance was observed only in apoE2 homozygotes, and this delay was neither correlated with fasting lip ds nor with peak lipoprotein concentrations. In apoE2/E3 heterozygotes, in contrast, the defective isoform E2 appears to be compensated for by the normal apoE isoform E3. In non-apo-E2/E2 individuals, the chylomicron remnant response was highly correlated with the magnitude of chylomicron and VLDL responses, with fasting triglycerides, and with the triglycerides enrichment and cholesterol depletion of HDL. These correlations were not observed in apoE2/E2. From these results we conclude that the chylomicron remnant response curve is an indicator of the extent of postprandial lipemia in non-apoE2/E2 individuals only.

Adult↗
PubMed1996

VLDL and LDL metabolism in human and rat mesangial cells.

Human low-density lipoprotein (LDL) is taken up by rat mesangial cells in a receptor-dependent manner, although lipoprotein metabolism and lipoprotein receptors differ substantially between rodents and humans. We therefore compared binding and uptake kinetics as well as intracellular cholesterol metabolism of apoB- and apoB,E-containing lipoproteins in rat and human mesangial cells. Uptake of very-low-density lipoprotein (VLDL) and LDL in both human and rat mesangial cells occurred in a receptor-specific, concentration-dependent manner and the process was saturable. However, LDL uptake specificity, receptor affinity and maximal degradation capacity was remarkably lower in rat than in human mesangial cells. Exposure of cells to LDL suppressed intracellular sterol synthesis more effectively in the human than in the rat cell line (87 vs. 36%, respectively). Additionally, cholesteryl ester formation was enhanced 23-fold by LDL in human as compared to rat mesangial cells. In contrast, degradation capacities of VLDL were higher in rat and uptake specificity as well as receptor affinity were similar. Inhibition of intracellular cholesterol synthesis and oleate formation rate by VLDL occurred to a similar extent in both cell lines. The data demonstrate that mesangial cell uptake of apoB-containing lipoproteins depends on the species investigated, whereas apoE-rich lipoprotein particles are taken up independent of species. Therefore, human mesangial cells should be preferred over rat mesangial cells when investigating lipoprotein metabolism to elucidate the potential role of lipoproteins in mediating glomerular injury and progression of renal disease in man.

Acetates↗
PubMed1996

Homogeneous assay for direct determination of high-density lipoprotein cholesterol evaluated.

We evaluated a new homogeneous assay for quantifying high-density lipoprotein cholesterol (HDL-C). The assay included four reagents: polyethylene glycol for "wrapping" chylomicrons, very-low-density lipoproteins (VLDL), and low-density lipoproteins (LDL); antibodies specific for apolipoprotein (apo) B and apo C-III to produce aggregates of chylomicrons, VLDL, and LDL; enzymes for the enzymatic cholesterol determination of the noncomplexed lipoproteins with 4-aminoantipyrine as the color reagent; and guanidine salt to stop the enzymatic reaction and to solubilize the complexes of apo B-containing lipoproteins, which would otherwise interfere with the reading of absorbance. The total CVs of the new method ranged between 2.4% and 8.4%. The HDL-C values (y) were in good agreement with those by a comparison phosphotungstic acid/MgCl2 method (x): y= 0.987x + 17.2 mg/L (68th percentile of the residuals on the regression line= 21.49, r= 0.970). At triglyceride concentrations of 20 g/L (Intralipid) the homogeneous HDL-C concentrations increased by 2%. Hemoglobin markedly increased the results, whereas bilirubin reduced them. The homogeneous HDL-C assay was easy to handle and allows full automation. This test should considerably facilitate the screening of individuals at an increased risk of cardiovascular disease.

Apolipoprotein A-I↗
PubMed1996

Low-density lipoprotein susceptibility to in vitro oxidation in healthy smokers and nonsmokers.

We analyzed the susceptibility of low-density lipoproteins (LDL) to oxidation in 17 healthy smokers (43.3 +/- 16.8 pack-years) and 19 healthy nonsmokers, matched for age (smokers: 52 +/- 7 years; nonsmokers: 53 +/- 7 years), gender, and relative body mass. Cholesterol, triglycerides, LDL cholesterol, HDL cholesterol, and apolipoprotein (apo) B were not different between smokers and nonsmokers; apo A-I was slightly lower in smokers (one-tailed P = 0.066). To study whether LDL from smokers were prone to in vitro oxidation than LDL from nonsmokers, we measured the time kinetics of diene formation and the production of malondialdehyde during oxidation of LDL in vitro. In smokers and nonsmokers, respectively, the mean (+/-SD) lag times (tinh) of diene formation were 111 +/- 26 and 100 +/- 27 min, the peak rates of diene formation (Vmax) were 5.99 +/- 2.34 and 6.34 +/- 2.30 mmol x min-1 x g-1, and the amounts of dienes produced during the propagation phase (dmax) were 250 +/- 264 and 248 +/- 56 mmol x g-1. Neither the malondialdehyde content of LDL (measured as thiobarbituric acid-reactive substances) before oxidation nor the amount of malondialdehyde generated during oxidation (smokers: 57.0 +/- 14.2 micromol x g-1; nonsmokers: 63.2 +/- 15.2 micromol x g-1 indicated any statistically significant effect of smoking. When nonsmokers and smokers were considered together, the amount of malondialdehyde generated during oxidation correlated with age (nonparametric rs = 0.405), body mass index (r2 = 0.573), and concentrations of apo B (rs = 0.480), cholesterol (rs = 0.448), triglycerides (rs = 0.436), and LDL cholesterol (rs = 0.398). Our data show that smoking is not associated with increased oxidizability of LDL in healthy men and women at ages 42-63 years.

Adult↗
PubMed1996

Hair iron content: possible marker to complement monitoring therapy of iron deficiency in patients with chronic inflammatory bowel diseases?

Measurements of the concentration of iron in hair from 10 patients with chronic inflammatory bowel diseases and from 10 healthy controls showed that the iron concentrations were significantly (P < 0.05) lower in patients before iron intake than in controls. Three weeks after beginning iron treatment, the hair iron concentrations were found to be significantly correlated (r = 0.68; P < 0.05) to reticulocyte counts. Changes in the hair iron concentrations were accompanied by similar changes in the concentrations of the markers most commonly used to diagnose and monitor iron deficiency. The results suggest that quantification of hair iron may be useful to complement evaluations of the body iron status.

Biomarkers↗
PubMed1996

Apolipoprotein E5 (Glu212-->Lys): increased binding to cell surface proteoglycans but decreased uptake and lysosomal degradation in cultured fibroblasts.

A new apolipoprotein (apo) E variant, apoE5 (Glu212-->Lys) was identified in a Turkish family. The variant was due to a point mutation (CAG-->AAG) at the first nucleotide position of the codon encoding amino acid residue 212 of the mature apoE. The 23-year-old index patient was heterozygous for the mutation. Examination of the proband's kindred revealed six heterozygous and two homozygous mutation carriers. Compared to non-carriers, carriers of the mutation had slightly higher triglycerides (1.25 versus 1.11 g/l) and lower HDL cholesterol (0.36 versus 0.41 g/l). Very low density lipoproteins (VLDL) from an apoE5 (Glu212-->Lys) homozygote displayed enhanced binding (+17%, P < 0.05), but decreased uptake (-35%, P < 0.0001) and degradation (-51%, P < 0.0001) in cultured fibroblasts, compared to E3/3-VLDL. The region of the apoE molecule surrounding residue 212 contains a heparin binding domain. Consistently, the enhanced cell surface binding of E5/5-VLDL was observed in "wild-type" Chinese hamster ovary cells (+19%, P < 0.05), but not in proteoglycan-deficient cells. The binding of E5/5-VLDL to heparin was increased (+22%, P < 0.05). As the endocytosis of apoE-containing particles involves the transfer of proteoglycan-bound ligands to lipoprotein receptors, the stronger binding of apoE5 (Glu212-->Lys) to proteoglycans could reduce the rate at which the mutant is finally delivered to endocytotic pathways. These data may provide evidence for a functionally important heparin binding site around amino acid residue 212 of the apoE molecule in vivo.

Adolescent↗