Biomedical subjects

R Siekmeier

Publications and source records attributed to R Siekmeier.

42 records · Page 3Linked to original sources

PubMed1991

[Comparison of the characteristics of methacholine and of propranolol in the assessment of aspecific hyperreactivity of the airways].

Quantitative bronchial challenge tests with methacholine and propranolol were performed in volunteers with bronchial asthma (n = 17) and in normal controls (n = 13), in order to test the earlier assumption that propranolol might be more useful to assess nonspecific bronchial responsiveness in bronchial asthma. The investigations were performed in random order, with a minimum interval of 24-hours. The aerosol was administered by a dosimeter (APS, Jaeger), using doubling concentrations, with a maximum of 25 mg/ml (2.5%), the lowest concentrations being 0.26 mg/ml (propranolol) and 0.03 mg/ml (methacholine), respectively. The provocation dose at a decrease in sGaw of 50% (PD50) was calculated from the dose-response curve. While methacholine induced an airways obstruction sufficient to calculate a PD50 in 29/30 subjects, propranolol was similarly effective in only 19/30 cases the rank correlation coefficient was 0.4368 (p less than 0.025). At a methacholine-PD50 greater than 0.2 mg(= concentration greater than 1 mg/ml) no propranolol-PD50 could be determined. In accordance with the literature, in the asthmatic subgroup the PD50sGaw [geometric means] were 25 (2.7-109.6) micrograms for methacholine, and 900 (75.9-3331) micrograms for propranolol, or 0.13 mumol and 3.46 mumol, respectively. The inhalation of propranolol in the highest possible concentration (limited solubility) induced airways obstruction only in subjects with asthmatic hyper-responsiveness. A similar distinction between asthmatic and normal subjects is possible by methacholine using a threshold concentration (in this study: cumulative PD50sGaw 0.2 mg or provocation concentration 1 mg/ml). Moreover, methacholine allows a determination of minor degrees of hyperresponsiveness, in mild airways obstruction or normal subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1990

[Fast lipoprotein chromatography: a new method for determining plasma lipoproteins].

Fast Lipoprotein Chromatography (FLPC) is a novel method for the quantitation of lipoprotein fractions. Plasma proteins are separated by fast flow gel filtration and lipoproteins are detected after post-column derivatization with an enzymatic cholesterol reagent. FLPC resolves VLDL, LDL, and HDL. Coefficients of variation for determinations of VLDL-, LDL-, and HDL-cholesterol are 5.8%, 2.0%, and 1.9%, respectively. Comparison of FLPC with a combined ultracentrifugation and precipitation method obtained correlation coefficients of 0.983, 0.973, and 0.941 for VLDL-C, LDL-C, and HDL-C, respectively.

Apolipoprotein A-I↗

PubMed1990

Insufficient accuracy and specificity of polyanion precipitation methods for quantifying low-density lipoproteins.

Recently, polyanion precipitation assays for low-density lipoprotein (LDL)-cholesterol have been found to underestimate their analyte in normolipidemic samples (Siekmeier et al., Clin Chim Acta 1988;177:221-30). Therefore, accuracy, specificity, and interference by nonesterified fatty acids have been studied for three precipitants (obtained by heparin, dextran sulfate, or polyvinyl sulfate precipitation). At normal concentrations of LDL, precipitation is incomplete, whereas it is nearly quantitative at high concentrations of LDL. The polyvinyl sulfate reagent markedly responds to variations in the amount of non-LDL protein present in the precipitation mixture. In the dextran sulfate and the polyvinyl sulfate method, but not in the heparin method, the percentages of LDL precipitated notably increase as the concentration of the polyanion compound is decreased. In either assay, very-low-density lipoproteins, but not high-density lipoproteins, are significantly coprecipitated (dextran sulfate 28%, polyvinyl sulfate and heparin 66%) in a concentration-independent fashion. Increased concentrations of nonesterified fatty acids markedly interfere with the dextran sulfate and polyvinyl sulfate assay, but do not much affect results with the heparin reagent.

Adult↗

PubMed1988

Precipitation of LDL with sulfated polyanions: three methods compared.

Three precipitation methods for the determination of low density lipoproteins have been evaluated. In n = 113 normolipidemic samples mean LDL-cholesterol levels have been 2.90 mmol/l, 2.77 mmol/l, 3.21 mmol/l after precipitation with heparin, dextran sulfate, and polyvinylsulfate, respectively. As compared to a combined ultracentrifugation and precipitation reference procedure (mean 3.22 mmol/l) two precipitation methods tend to underrate LDL-cholesterol. Elevated plasma triglycerides may interfere with the precipitation of LDL. The clinical relevance of the precipitation procedures has been studied by discriminant analysis in n = 28 consecutive patients admitted for coronary bypass operation and n = 28 controls. The data suggest that, statistically, the determination of LDL-cholesterol with either precipitation method only provides redundant information as in relation to the Friedewald approximation for LDL-cholesterol. Immunologically determined apolipoprotein B proved a better predictor for group separation than either precipitation method.

Adult↗

PubMedDate not supplied

Pulmonary deposition of monodisperse aerosols in patients with chronic obstructive pulmonary disease.

In order to improve patient convenience and drug availability for patients with alpha 1-protease inhibitor deficiency, the administration via the inhalation route has been considered. This study investigated if it is possible to obtain high values of peripheral aerosol deposition by using optimized and controlled inhalation conditions. Therefore, peripheral deposition was studied in 10 patients with alpha 1-protease inhibitor deficiency (phenotype PiZ) and moderate to severe chronic obstructive pulmonary disease by measuring the 24-hour Clearance of radiolabeled inert iron oxide particles with diameters of 2 microns, 3 microns, and 4 microns. Patients inhaled a large volume of aerosol (1000 to 2000 cm3), which was normalized to the individual lung function, with a flow rate of 200 cm3/S. Due to this breathing pattern, peripheral deposition was for all particle sizes above 50% of the inhaled aerosol. The highest peripheral deposition (68%) was found for 3-microns particles.

Administration, Inhalation↗

PubMedDate not supplied

Isolation of fungi, especially Exophiala dermatitidis, in patients suffering from cystic fibrosis. A prospective study.

BACKGROUND: Patients with cystic fibrosis (CF) are at an increased risk of pulmonary colonisation by opportunistic micro-organisms. Using specialised methods, the black yeast Exophiala dermatitidis could consistently be cultured from CF patients. Isolation rates from sputum samples ranged between 1.8 and 15.7%. Occasionally, infection could be recognised. OBJECTIVES: This study aimed at investigating the isolation rates of E. dermatitidis in samples taken from CF patients at the University of Bonn, Germany. METHODS: Altogether, 439 respiratory specimens taken from 81 CF patients were screened for the occurrence of E. dermatitidis over a period of 18 months. For the selective isolation of this fungus erythritol-chloramphenicol agar (ECA) produced in house was applied. RESULTS: The isolation rate of E. dermatitidis was 1.1% from all specimens, 1.6% from all sputum samples and 6.2% in all patients examined. CONCLUSIONS: Prior to the introduction of ECA, E. dermatitidis had never been isolated in our laboratory, either from CF, or from any other patient. During this study, E. dermatitidis was found to colonise the respiratory tract of some CF patients. The use of additional selective culture media is necessary for the recognition of uncommon fungi, e.g. E. dermatitidis, in CF patients.

Adolescent↗