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R Siekmeier

Publications and source records attributed to R Siekmeier.

At least 37 records · Page 2Linked to original sources
PubMed1995

Determination of triglycerides in lipoproteins separated by agarose gel electrophoresis.

We developed a simple method for the quantitation of triglycerides in electrophoretically separated lipoproteins by specific enzymatic staining. After electrophoresis, glycerol is liberated from triglycerides by the action of cholesterol esterase. Glycerol is oxidized by a sequence of enzymatic reactions. Due to the presence of triosephosphate isomerase and glyceraldehyde-3-phosphate dehydrogenase in the reaction mixture, two moles of the precipitating dye formazane are generated per mole glycerol. The relative amounts of alpha, pre-beta, and beta lipoproteins are determined by densitometric scanning at 570 nm. Absolute triglyceride concentrations of the respective lipoprotein fractions are calculated from total triglycerides. When tested with purified very low density lipoproteins, the electrophoresis assay was linear between 0.08 and 6.5 g/l pre-beta lipoprotein triglycerides. The intra-assay and inter-assay coefficients of variation were between 5.2% and 9.8%, and between 3.2% and 12.9%, respectively. Comparison of the electrophoresis method with a combined ultracentrifugation/precipitation method in 172 sera resulted in the following correlation coefficients: alpha lipoprotein versus high density lipoprotein triglycerides, r = 0.847; pre-beta lipoprotein versus very low density lipoprotein triglycerides, r = 0.989; beta lipoprotein versus low density lipoprotein triglycerides, r = 0.815. This method is easy to perform, and is a precise and accurate technique for the determination of lipoprotein triglycerides. It is the first reliable method that allows the direct quantification of LDL triglycerides without ultracentrifugation.

Analysis of Variance↗
PubMed1995

Pseudo-pseudohypertriglyceridemia: a case of increased free glycerol without evidence for glycerol kinase deficiency.

High concentrations of glycerol in plasma may result in overestimation of triglycerides in chemical and enzymatic assays. Known causes of increased glycerol concentrations in blood include glycerol-contaminated blood-collector tubes and pseudohypertriglyceridemia, a condition caused by genetic defects in the gene for glycerol kinase. We report a patient with sudden hearing loss who presented with an increased blood glycerol concentration after undergoing an oral glycerol test.

Adult↗
PubMed1995

[Differential diagnostic significance of complex values of gas exchange during submaximal physical effort in patients with emphysema and pulmonary fibrosis].

The aim of this study was to clarify a) whether the behaviour of functional dead space ratio (VD/VE), alveolo-arterial difference of oxygen tensions (AaDO2) and the venous admixture ratio (QVA/Qt) differed at rest and during submaximal exercise, between patients with pulmonary emphysema and interstitial pulmonary fibrosis as well as from the respective findings in healthy controls, and b) whether a differentiation between these two diseases could be achieved by investigations of complex pulmonary gas exchange. Eleven patients with pulmonary fibrosis (F), which had been diagnosed by pulmonary biopsies, 11 patients with pulmonary emphysema (E) and 11 healthy controls (C) were subjected to conventional pulmonary function tests (PFTs: spirometry, bodyplethysmography, DCO) immediately followed by examinations of pulmonary gas exchange conducted at rest and during an incremental submaximal cycle spiroergometry (ERGO). With normal PFTs for C, vital capacity was diminished in F and the 1" timed vital capacity (FEV1) as well as Tiffeneau's index were reduced in E, while air way resistance and functional residual capacity were augmented in the latter group. In all patients the CO-diffusing capacity was lower compared to C, however, without differences between F and E. In both E and F, the arterial O2 tension were lower at rest as well as during ERGO when compared to C, whereas VD/VE, QVA/Qt and AaDO2 as well as the specific ventilation for O2 were higher, respectively. Alveolar ventilation was similar in all groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Isolation of lipoprotein (a) using the regenerate of a dextran sulfate cellulose LDL apheresis system.

A simple method for the preparation of lipoprotein (a) is presented. The procedure uses the eluate of an LDL apheresis system operating on the basis of LDL adsorbing dextran sulfate cellulose. The eluate is concentrated by tangential flow membrane filtration and subjected to ultracentrifugation, first at a density of 1.125 kg/liter and then at 1.050 kg/liter. The crude lipoprotein (a)-containing fraction is chromatographed on agarose (Bio-Gel A-15m) to remove contaminating low-density and high-density lipoproteins. As demonstrated by immunoelectrophoresis with intermediate gel, the method provides lipoprotein (a) completely free of LDL. SDS-polyacrylamide gel electrophoresis showed that apolipoprotein E was associated with purified lipoprotein (a). On agarose gel electrophoresis and two-dimensional immunoelectrophoresis, lipoprotein (a) prepared by the proposed method cannot be distinguished from native lipoprotein (a). The major advantage of the procedure is that it allows the isolation of large amounts of lipoprotein (a) from a single donor.

Adsorption↗
PubMed1994

Elevated endothelin levels in patients with hyperlipoproteinemia.

We determined lipoproteins, apolipoproteins, and endothelin in 98 patients (58 female and 40 male, age 18-72 years) with hyperlipidemia (plasma cholesterol > 2.5 g/l and/or triglycerides > 2.0 g/l) and in 50 healthy subjects (20 female, 30 male, age 19-68 years). In patients with hyperlipidemia endothelin levels were elevated compared to healthy controls. Patients with plasma cholesterol above 2.5 g/l had higher endothelin and lipoprotein(a) concentrations than patients with plasma cholesterol levels less than 2.5 g/l. A positive correlation was found between the concentrations of endothelin and apolipoprotein B (r = 0.2137; P < 0.013). Smoking patients with lipoprotein (a) above 300 mg/l had higher endothelin levels than both nonsmoking patients with lipoprotein (a) above 300 mg/l and smokers with normal lipoprotein(a). In smokers endothelin correlated positively with Lp(a) (r = 0.709; P < 0.01). No correlation was found between endothelin and triglycerides nor between endothelin and age or sex. The results suggest that the vasoconstrictor endothelin contributes to the increased vasal tone in hyperlipidemia. Because endothelin also has mitogenic properties, it may play a relevant role in the development of premature atherosclerosis in patients with hyperlipidemia.

Adolescent↗
PubMed1994

Unspecific bronchial reactivity to carbachol in healthy subjects--effect of age and smoking habits.

Chronic inflammatory processes of the airways induced by long-time cigarette consumption are a crucial factor in the pathogenesis of chronic obstructive pulmonary disease. In contrast, the role of cigarette smoking in the pathogenesis of bronchial hyperreactivity (BHR) is still unclear. The aim of this study was to assess the effect of chronic cigarette consumption on pulmonary function tests and BHR in healthy subjects. 63 healthy smokers and 63 lifetime nonsmokers matched for sex, age, height and weight were evaluated. Pulmonary function was determined by body plethysmography and spirometry. Bronchial provocation was performed by inhalation of increasing doses of carbachol (up to 25 g/l) in isotonic NaCl solution. Pulmonary function tests were within normal limits in all subjects. Nevertheless, midexpiratory flow at 25% of forced vital capacity was significantly smaller, and functional residual capacity was significantly greater in middle-aged smokers (age: 40-60 years) compared to middle-aged nonsmokers (p < 0.05, both comparisons). In young smokers and nonsmokers (age: 20-30 years) pulmonary function tests were not different (p > 0.28, all comparisons). Importantly, the carbachol concentration that provoked a 50% rise in specific airway resistance (PD50sRaw) was similar in smokers and nonsmokers of both age groups (p > 0.05, both comparisons) and did not correlate with the age of the subjects (p > 0.2). No correlations between baseline values of pulmonary function tests and PD50sRaw were observed (p > 0.34, all comparisons). The observations confirm that the distribution profile of BHR is unimodal and apparently not affected by age and smoking habits.

Adult↗
PubMed1994

[Long-term effect of the beta 2-sympathomimetic formoterol in young smokers--study of duration and site of effect of bronchodilatation using conventional methods of lung function and monodispersed aerosols].

Formoterol is a novel selective beta 2-sympathomimetic inducing bronchodilatation after inhalation or oral application. Compared to other beta 2-sympathicomimetics the substance begins to act very rapidly even at a much lower dosage level, while it remains effective for at least 12 hours. In the present study the bronchodilatory effect of 24 micrograms MDI formoterol was investigated in 18 healthy smokers between 20 and 30 years of age means. Measurement was effected by means of conventional lung function diagnostics (body plethysmography, spirometry) and an biophysical aerosol measurement method for determining the effective airways dimensions (EAD). This method is based on the gravitational losses of a previously inspired monodisperse model aerosol during apnoea periods of different duration. It enables determination of the EAD as a function of the volumetric lung depth (VLT). A marked and universally measurable bronchodilatation is detectable directly after formoterol has been inhaled. The longterm action of formoterol was confirmed for more than 15 hours after application, using the conventional lung function test and the EAD method. Over and above this the EAD determination showed that the bronchodilatory effect was much more marked in the central airways than in the periphery of the lungs, thus confirming the effect generally described for beta 2-sympathomimetics as being mainly directed towards the central airways region.

Administration, Inhalation↗
PubMed1994

Effects of lovastatin (20-80 mg daily) on lipoprotein fractions in patients with severe primary hypercholesterolemia.

The effect of lovastatin on lipids, lipoproteins and apolipoproteins was studied in 10 patients with primary hypercholesterolemia. After four weeks diet/placebo alone, patients received diet plus lovastatin at daily doses of 20 mg (weeks 1-4), 40 mg (weeks 5-8) and 80 mg (weeks 9-12). Twelve weeks of treatment with lovastatin resulted in a lowering of total cholesterol and LDL-cholesterol by 34% and 41%, respectively. Triglycerides and VLDL-cholesterol decreased by 19% and by 42%, respectively. HDL-cholesterol and HDL2-cholesterol increased, whereas HDL3-cholesterol was not affected. IDL-cholesterol decreased by 50%, suggesting that the clearance of remnant lipoproteins was enhanced by lovastatin. In the VLDL and the IDL fraction, the triglyceride to cholesterol mass ratio increased significantly after twelve weeks of therapy. Lipoprotein(a) was not affected. Lovastatin was well tolerated and the data shows that lovastatin exerts favorable effects on plasma lipoprotein fractions. It may, therefore, prove a useful drug in the primary and secondary prevention of atherosclerotic vessel diseases.

Adult↗
PubMed1994

[The value of studies of pulmonary gas exchange during exercise for evaluation of reduced arterial oxygenation at rest in asymptomatic long-term smokers].

The aim of this study was to elucidate extent and nature of an impairment of gas exchange after long time cigarette-smoking. Pulmonary gas exchange at rest as well as during steady state exercise and conventional lung function tests (LFTs) were studied in 32 clinically healthy, asymptomatic severe cigarette-smokers (S; 48.1 +/- 15.7 pack-years) and 32 healthy lifetime nonsmokers (N) between 40 and 60 years of age, respectively, individually matched for age, body height, body weight and gender. Pulmonary function tests of all subjects were within the limits of normal values. Except for a slight reduction of MEF25 in S (p < 0.05) and a slight increase of FRC (p < 0.05), the groups did not differ with respect to LFTs. At rest, however, S had markedly lower values for PaO2, TLO2, DCO and KCO, and higher values for AaDO2 and QVA/Qt. Resting measurements for VD/VE and PaCO2 did not differ between N and S. During ergometry PaO2 and TLO2 increased respectively; AaDO2 and QVA/Qt fell concomitantly with VD/VE and PaCO2. On termination of exercise no significant difference between N and S for the above variables could be discerned any longer. Our findings confirm that even in clinically healthy asymptomatic cigarette-smokers a distinct impairment of gas exchange is present. Their improvement during physical exercise primarily indicates the presence of reversible ventilation-perfusion mismatching and excludes relevant morphologic changes in the lung in these cases.

Adult↗
PubMed1993

Heterogeneous lipoprotein (a) size isoforms differ by their interaction with the low density lipoprotein receptor and the low density lipoprotein receptor-related protein/alpha 2-macroglobulin receptor.

Lipoprotein (a) (Lp(a)) is a complex of low density lipoprotein (LDL) with apolipoprotein (apo) (a). To examine the size distribution of Lp(a), plasma was separated by fast flow gel filtration and Lp(a):B complexes were determined in the eluate by enzyme immunoassays, in which detection was performed with monoclonal antibodies specific for apoB. Lp(a):B particles displayed apparent molecular masses (M(r)) of 2 x 10(6) to at least 10 x 10(6). Lp(a) size isoforms differed by the expression of apoB epitopes and their interaction with cultured human skin fibroblasts. LDL was more effective in inhibiting binding, uptake, and degradation of low M(r) Lp(a) than of high M(r) Lp(a). In contrast, Glu-plasminogen, alpha 2-macroglobulin and tissue-type plasminogen activator were more effective in competing for the cellular degradation of high M(r) Lp(a) than of low M(r) Lp(a). Ligand blotting revealed that Lp(a) bound to the low density lipoprotein receptor, the low density lipoprotein receptor-related protein/alpha 2-macroglobulin receptor (LRP) and to two other endosomal membrane proteins. We propose that the LDL receptor preferentially internalizes low M(r) Lp(a), whereas LRP may have a role in the clearance of high M(r) Lp(a).

Cells, Cultured↗
PubMed1993

Determination of lipoprotein(a): enzyme immunoassay and immunoradiometric assay compared.

Lipoprotein(a) (Lp(a)) concentration in plasma is a strong independent risk factor for pre-mature atherosclerosis. Lp(a) closely resembles LDL. Its protein moiety contains apolipoprotein (apo) B-100 and apo(a). Two enzyme immunoassays (EIAs) for Lp(a) have been developed. In both, polyclonal antibodies for apo(a) are used as capturing antibodies. In the first, Lp(a) is detected with anti-apo(a) (apo(a)-EIA). In the second, detection is carried out with anti-apo B (Lp(a):B-EIA). Neither plasminogen nor LDL cross-reacted in the assays. Lp(a) was also measured using a commercial sandwich immunoradiometric assay (IRMA). This assay uses two monoclonal antibodies for apo(a). One of them, the solid phase antibody, cross-reacted with plasminogen. However, at physiological plasminogen concentrations there was no competition for solid phase binding sites. A quantity of plasma samples (201) were assayed for Lp(a) with the three methods. The best correlation was obtained between the IRMA and the Lp(a):B-EIA (r = 0.909). Correlations between the apo(a)-EIA and the IRMA or the Lp(a):B-EIA were 0.763 and 0.695, respectively. As compared to the EIAs, the IRMA overestimated Lp(a) by about 30%. It is concluded that both the Lp(a):B-EIA and the IRMA reflect the concentration of Lp(a) particles in plasma. In contrast, the apo(a)-EIA measures apo(a) antigen and may therefore be susceptible to the size polymorphism of apo(a).

Humans↗
PubMed1993

Effect on lipid metabolism of a biphasic desogestrel-containing oral contraceptive: divergent changes in apolipoprotein B and E and transitory decrease in Lp(a) levels.

The effect of a low dose biphasic oral contraceptive containing 40 micrograms ethinylestradiol + 25 micrograms desogestrel (7 tablets) and 30 micrograms ethinylestradiol + 125 micrograms desogestrel (15 tablets) on lipid metabolism was investigated in 19 women during 6 cycles of treatment and compared to the values of the pre- and post-treatment cycle. During treatment, all components of HDL increased reversibly by 10 to 30%. The levels of total cholesterol (CH), LDL-CH and IDL-CH rose only slightly, while those of total triglycerides (TG), VLDL-TG and LDL-TG rose continuously by more than 100% until the 6th cycle. At the same time, plasma levels of VLDL-CH increased by 60% and of apolipoprotein B by 20%. Contrary to this, apolipoprotein E decreased by 25% during treatment, and Lp(a) was transitorily reduced during the 3rd cycle. After termination of intake, total CH, LDL-CH, IDL-CH and apolipoprotein B remained elevated, while total TG, VLDL-TG, VLDL-CH and LDL-TG decreased significantly, but were still elevated during the post-treatment cycle. The levels of apolipoprotein E returned to pre-treatment values. The results indicate a marked preponderance of the effect of the estrogen component. The rise in TG and VLDL synthesis seems to be outweighed by an enhanced removal of apolipoprotein E-containing remnants which might offer protection from the development of atherosclerosis.

Adult↗
PubMed1993

Type III hyperlipoproteinemia acquired by liver transplantation.

A case of type III hyperlipoproteinemia (HLP) (dysbetalipoproteinemia) acquired by liver transplantation is reported. The 50-year-old female patient was referred to the Frankfurt University Hospital for orthotopic liver transplantation. She had suffered from ethylic liver cirrhosis. The donor liver showed discrete signs of steatosis. The postoperative course of the patient was satisfactory. Enzyme levels and blood coagulation tests returned to normal within thirty days. However, both cholesterol and triglycerides gradually increased from approximately 2.00 g/L to values ranging from 2.50 to 3.50 g/L within 200 days after transplantation. Cutaneous xanthomas did not develop. The patient's lipoprotein pattern met the criteria of type III HLP: the cholesterol to triglyceride ratio in very low-density lipoproteins (VLDL) was 0.64. Intermediate-density lipoprotein(IDL) cholesterol was 0.48 g/L. Lipoprotein electrophoresis showed a broad beta-band, and beta-migrating particles were present in VLDL. Immunoblotting of apolipoprotein (apo) E from the patient's plasma revealed an E2/2 phenotype. However, restriction isotyping of an in vitro amplified apoE gene fragment showed the genotype of the patient to be epsilon 3/epsilon 4. These data suggest that the development of type III HLP in this patient was due to a change in the apoE phenotype from E3/4 to E2/2 after liver transplantation.

Apolipoproteins E↗
PubMed1993

Apolipoprotein E to B ratio: a marker for type III hyperlipoproteinaemia.

Apolipoproteins B and E were determined in 40 patients with type III hyperlipoproteinaemia (familial dysbetalipoproteinaemia) and in 48 patients with other types of hyperlipoproteinaemia matched for cholesterol and triacylglycerols. In type III patients, apolipoprotein E was increased and apolipoprotein B was lower than in other types of hyperlipoproteinaemia. The apolipoprotein E to apolipoprotein B ratio almost completely discriminated between type III and other types of hyperlipoproteinaemia. Assuming a cut-off value of 0.09 for the apolipoprotein E to apolipoprotein B ratio, diagnostic sensitivity was 95% and specificity was 88%. It is concluded that the apolipoprotein E to apolipoprotein B ratio represents the first-line screening quantity of choice for the identification of patients with type III hyperlipoproteinaemia in the clinical laboratory.

Adult↗
PubMed1993

Determination of lipoprotein(a): evaluation of three methods.

Lipoprotein(a) (Lp(a)) is a strong independent risk factor for premature atherosclerosis. Structurally, Lp(a) closely resembles LDL. Its protein moiety contains apolipoprotein B-100 and apolipoprotein(a). We evaluated two commercial enzyme immunoassays (EIAs) and an immunoradiometric assay (IRMA) for Lp(a). The three assays differed in their design and they used different antibodies. In the immunoradiometric assay, two different monoclonal antibodies were used. In the first EIA, monoclonal anti-apolipoprotein(a) was bound to the solid phase and Lp(a) was detected with polyclonal anti-apolipoprotein B (Lp(a):B-EIA). In the second EIA, polyclonal anti-apolipoprotein(a) was used as capturing antibody and as detecting antibody (apo(a)-EIA). Ninety three plasma samples were assayed for Lp(a) with the three methods. The best correlation was obtained between the IRMA and the Lp(a):B-EIA (r = 0.971). Correlations between the apo(a)-EIA on the one hand and the IRMA or the Lp(a):B-EIA on the other hand were 0.889 and 0.836, respectively. The methods significantly differed in their calibration. This resulted in different mean Lp(a) concentrations. When tested against purified Lp(a), the apo(a)-EIA appeared accurately calibrated, whereas the IRMA and the Lp(a):B-EIA overestimated Lp(a) by approximately twofold. In the Lp(a):B-EIA, the detecting antibody is directed against apolipoprotein B. The Lp(a):B-EIA is, therefore, not affected by apolipoprotein(a) size polymorphism. This allows expression of the concentration of Lp(a):B complexes on a molar basis. In contrast, the polyclonal antibody-based apo(a)-EIA measures the concentration of apolipoprotein(a) antigen, and may, therefore, be susceptible to inter- and intra-individual polydispersity of apolipoprotein(a) and Lp(a) particles.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
PubMed1993

Fast lipoprotein chromatography: new method of analysis for plasma lipoproteins.

Fast lipoprotein chromatography (FLPC) is a novel method for quantifying lipoproteins. Plasma proteins are separated by fast-flow gel filtration. Lipoproteins are detected by post-column derivatization with an enzymatic cholesterol reagent. FLPC resolves very-low-, low-, and high-density lipoproteins (VLDL, LDL, and HDL, respectively) and completely separates apolipoprotein Al- and apolipoprotein B-containing lipoproteins. CVs for VLDL-cholesterol, LDL-cholesterol, and HDL-cholesterol are 5.8%, 2.0%, and 1.9%, respectively. We compared FLPC with a combined ultracentrifugation and precipitation method and obtained correlation of r = 0.979, 0.978, and 0.933 for VLDL-cholesterol, LDL-cholesterol, and HDL-cholesterol, respectively. Triglyceride concentrations up to 9.00 g/L did not interfere with the quantification of lipoproteins by FLPC. We conclude that FLPC is a precise and reliable method for the analysis of plasma lipoproteins that complements conventional techniques.

Apolipoprotein A-I↗
PubMed1992

[Cholesterol--a marker for multiple risk factors? A comparison between coronary disease and coronary health].

Comparison was made in a cross-sectional study between 658 patients in whom coronary arteriography had shown (n = 304) or excluded coronary artery disease (CHD) (n = 354) and a clinically healthy group as controls (n = 1658), to assess possible risk factors. Patients aged 31-40 years with CHD had the highest total cholesterol levels (286 +/- 43 mg/dl) and the highest number of risk factors (3.6 +/- 0.9) compared to patients without CHD of the same age (204 +/- 30 mg/dl; 2.0 +/- 0.5) and healthy controls (216 +/- 45 mg/dl; 1.7 +/- 0.5) (P less than 0.001). In older patients with CHD, total cholesterol levels were lower (age group 61-70 years: 231 +/- 49 mg/dl), reaching about the same level as that of patients without CHD (232 +/- 54 mg/dl) or healthy controls of the same age (228 +/- 55 mg/dl). Furthermore, it was demonstrated that increased total cholesterol concentration can indicate the presence of other risk factors. It would thus appear that the level of total cholesterol in patients with CHD is decisively influenced by age and the presence of other risk factors.

Adult↗