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Biomedical subjects

D Seidel

Publications and source records attributed to D Seidel.

At least 37 records · Page 2Linked to original sources

[Hyperlipoproteinemia and LDL apheresis. Clinical experiences with the H.E.L.P. system].

No question, one of the leading causal factors for early atherosclerosis and coronary heart disease (CHD) is the abundance of LDL-cholesterol in the blood, exceeding limits of 100 mg/dl. Thus, recommendations for therapy focus on LDL-levels less than 100 mg/dl. With the introduction of the statins--a very potent family of lipid lowering agents--such target levels can be achieved in most of the patients, resulting in a drastic decrease of LDL, CHD incidences, as well as in a reduction of cardiac and total mortality. There is, however, a remaining small group of patients, who is more or less resistant to an adequate combination of dietary and drug therapy. For these patients, various techniques of apheresis are available for over 15 years. Some of them have been approved by the FDA in the US and comparable regulatory offices in Europe. The most extensive experimental and clinical experience was gathered with the H.E.L.P.-system of B. Braun Melsungen, which differs from other apheresis techniques by its efficiency to eliminate LDL, Lp(a), Fibrinogen and CRP simultaneously. The clinical results obtained up to day with the apheresis clearly demonstrate a significant reduction of risk factors and clinical events, as well as an excellent long-term tolerance.

Blood Component Removal↗

A simple turbidimetric assay designed for the routine screening as well as therapeutic monitoring of native LDL particles.

We describe the development and performance of a homogeneous assay for the direct turbidimetric determination of LDL particles in human serum. The assay is based upon the specific agglutination of LDL particles by the polyanion PAMPS. The co-agglutination of VLDL is avoided by the addition of a zwitterionic detergent. Yielding results within 10 min, the assay requires only a small sample volume taken directly from primary serum tubes, i.e., no pretreatment of the sample is necessary. It can be easily applied to routine clinical chemistry analyzers. The results are highly correlated with LDL cholesterol determinations by ultracentrifugation (r>0.95) and dextran sulfate precipitation (r>0.95), but an increased recovery of small, high density LDL particles is observed, which more adequately reflects the atherogenic risk of LDL. The assay provides excellent intra- and inter-assay CVs in the range of 0.6--1.6 and 1.7--2.4%, respectively, on Roche Diagnostics/Hitachi analyzers. The method is well suited to the high-throughput screening of LDL cholesterol levels.

Artifacts↗

The metabolism of lipoprotein(a) and other apolipoprotein B-containing lipoproteins: a kinetic study in humans.

Lipoprotein(a) is a risk factor for cardiovascular disease composed of an apolipoprotein B-containing lipoprotein to which a second protein, apolipoprotein(a), is attached. We investigated in seven subjects with Lp(a) levels of 39--85 mg/dl the metabolism of four apo B-containing lipoproteins (VLDL(1), VLDL(2), IDL and LDL) together with that of apo B and apo(a) isolated from Lp(a). Rates of secretion, catabolism and where appropriate, transfer were determined by intravenous administration of d(3)-leucine, mass spectrometry for measurements of leucine tracer/tracee ratios and kinetic data analysis using multicompartmental metabolic modeling. Apo B in Lp(a) was secreted at a rate of 0.28 (0.17--0.40) mg/kg per day. It was found to originate from two sources -- 53% (43--67) were derived from preformed lipoproteins, i.e. IDL and LDL, the remainder was accounted for by apo B, directly secreted by the liver. The fractional catabolic rates (FCRs) of apo B and of apo(a) prepared from Lp(a) were determined as 0.27 (0.16--0.38) and 0.24 (0.12--0.40) pools per day, respectively, which is less than half of the FCR observed for LDL. Our in vivo data from humans support the view that Lp(a) assembly is an extracellular process and that its two protein components, apo(a) and apo B, are cleared from the circulation at identical rates.

Adult↗

Consistent lowering of clotting factors for the treatment of acute cardiovascular syndromes and hypercoagulability: a different pathophysiological approach.

Hypercoagulability is a key contributor to acute cardiovascular syndromes and to various microcirculatory disorders. The use of heparin-mediated extracorporeal low-density lipoprotein/fibrinogen precipitation (HELP) apheresis makes a controlled, immediately effective reduction of clotting factors possible, and induces subsequent positive effects on plasma viscosity, erythrocyte aggregation, and microcirculation. Oxygen supply to an ischemic artery can thus be increased without hemodilution, qualifying the HELP system as a possible therapeutic tool in the treatment of acute cardiovascular syndromes and microcirculatory disorders.

Aged↗

Circulating nucleosomes in serum.

In the nucleus of eukaryotic cells, DNA is associated with several protein components and forms complexes known as nucleosomes. During cell death, particularly during apoptosis, endonucleases are activated that cleave the chromatin into multiple oligo- and mononucleosomes. Subsequently, these nucleosomes are packed into apoptotic bodies and are engulfed by macrophages or neighboring cells. In cases of high rates of cellular turnover and cell death, they also are released into the circulation and can be detected in serum or plasma. As enhanced cell death occurs under various pathologic conditions, elevated amounts of circulating nucleosomes are not specific for any benign or malignant disorder. However, the course of change in the nucleosomal levels in circulation of patients with malignant tumors during chemotherapy or radiotherapy is associated with the clinical outcome and can be useful for the therapeutic monitoring and the prediction of the therapeutic efficacy.

Antineoplastic Agents↗

Nucleosomes in serum as a marker for cell death.

The concentration of nucleosomes is elevated in blood of patients with diseases which are associated with enhanced cell death. In order to detect these circulating nucleosomes, we used the Cell Death Detection-ELISAplus (CDDE) from Roche Diagnostics (Mannheim, Germany) (details at http:\\biochem.roche.com). For its application in liquid materials we performed various modifications: we introduced a standard curve with nucleosome-rich material, which enabled direct quantification and improved comparability of the values within (CVintraassay:3.0-4.11%) and between several runs (CVinterassay:8.6-13.5%), and tested the analytical specificity of the ELISA. Because of the fast elimination of nucleosomes from circulation and their limited stability, we compared plasma and serum matrix and investigated in detail the pre-analytical handling of serum samples which can considerably influence the test results. Careless venipuncture producing hemolysis, delayed centrifugation and bacterial contamination of the blood samples led to false-positive results; delayed stabilization with EDTA and insufficient storage conditions resulted in false-negative values. At temperatures of -20 degrees C, serum samples which were treated with 10 mM EDTA were stable for at least 6 months. In order to avoid possible interfering factors, we recommend a schedule for the pre-analytical handling of the samples. As the first stage, the possible clinical application was investigated in the sera of 310 persons. Patients with solid tumors (n=220; mean=361 Arbitrary Units (AU)) had considerably higher values than healthy persons (n=50; mean=30 AU; p=0.0001) and patients with inflammatory diseases (n=40; mean= 296 AU; p=0.096). Within the group of patients with tumors, those in advanced stages (UICC 4) showed significantly higher values than those in early stages (UICC 1-3) (p=0.0004).

Anti-Bacterial Agents↗

Novel synthesis of hybrid calixphyrin macrocycles

The reaction of benzaldehyde with excess pyrrole at room temperature in the absence of solvent affords a mixture of meso-substituted polypyrranes species. After separation by column chromatography, these may be used to prepare a range of calix[4]phyrin macrocycles by condensation with acetone under conditions of acid catalysis.

Journal Article↗

Amplification of cyclin D1 gene in multiple myeloma: clinical and prognostic relevance.

Approximately 30% of myeloma patients express cyclin D1 RNA and protein. The low incidence of translocation t(11; 14) detected by conventional cytogenetics suggests that the up-regulation of cyclin D1 protein might result from other mechanisms as well as from gene amplification. Therefore, the frequency and the clinical and prognostic implications of cyclin D1 amplification were examined. We highly purified myeloma cells from bone marrow by magnetic cell sorting and analysed 50 myelomas by fluorescence in situ hybridization (FISH) using probes specific for cyclin D1 and 20 samples by immunoblotting to detect cyclin D1 expression. The amplification of cyclin D1 gene was found in 19 of 50 analysed patients and was associated with expression of cyclin D1 protein. The amplification correlated significantly with the bone marrow infiltration, plasma cell morphology and labelling index as well as serum beta2-microglobulin, C-reactive protein (CRP) and creatinine levels. In univariate analysis, the amplification of the cyclin D1 gene was a significantly unfavourable parameter with regard to overall survival (P = 0.0064) and progression-free survival (P = 0. 0005). In multivariate analysis, cyclin D1 amplification and serum beta2-microglobulin were independent and well-suited parameters for predicting survival. The detection of cyclin D1 amplification seems to be of promising prognostic value in multiple myeloma.

Adolescent↗

Compound heterozygosity for a Wolman mutation is frequent among patients with cholesteryl ester storage disease.

Cholesteryl ester storage disease and Wolman disease are rare autosomal recessive lipoprotein-processing disorders caused by mutations in the gene encoding human lysosomal acid lipase. Thus far we have elucidated the genetic defects in 15 unrelated CESD patients. Seven were homozygotes for the prevalent hLAL exon 8 splice junction mutation which results in incomplete exon skipping, while eight probands were compound heterozygotes for E8SJM and a rare mutation on the second chromosome. In this report, we describe the molecular basis of CESD in three compound heterozygous subjects of Czech and Irish origin. RFLP and DNA sequence analysis revealed that they were heteroallelic for the common G(934)-->A substitution in exon 8 of the hLAL gene and a mutation which, if inherited on both alleles, would be expected to result in complete loss of enzyme activity and to cause Wolman disease. In patients A. M. and J. J., two nucleotide deletions in exons 7 and 10 were detected, involving a T at position 722, 723, or 724 and a G in a stretch of five guanosines at positions 1064;-1068 of the hLAL cDNA. Both mutations result in premature termination of protein translation at residues 219 and 336, respectively, and in the production of truncated, inactive enzymes. Subject D. H., in contrast, is a compound heterozygote for the Arg(44)-->Stop mutation previously described in a French CESD proband. Combined with data in the literature, our results demonstrate that compound heterozygosity for a mutation causing Wolman disease is common among cholesteryl ester storage disease patients.

Base Sequence↗

Apolipoprotein B metabolism and the distribution of VLDL and LDL subfractions.

Apolipoprotein B (apoB) metabolism was investigated in 20 men with plasma triglyceride 0.66-2.40 mmol/l and plasma cholesterol 3.95-6. 95 mmol/l. Kinetics of VLDL(1) (S(f) 60-400), VLDL(2) (S(f) 20-60), IDL (S(f) 12-20), and LDL (S(f) 0;-12) apoB were analyzed using a trideuterated leucine tracer and a multicompartmental model which allowed input into each fraction. VLDL(1) apoB production varied widely (from 5.4 to 26.6 mg/kg/d) as did VLDL(2) apoB production (from 0.18 to 8.4 mg/kg/d) but the two were not correlated. IDL plus LDL apoB direct production accounted for up to half of total apoB production and was inversely related to plasma triglyceride (r = -0.54, P = 0.009). Percent of direct apoB production into the IDL/LDL density range (r = 0.50, P < 0.02) was positively related to the LDL apoB fractional catabolic rate (FCR). Plasma triglyceride in these subjects was determined principally by VLDL(1) and VLDL(2) apoB fractional transfer rates (FTR), i.e., lipolysis. IDL apoB concentration was regulated mainly by the IDL to LDL FTR (r = -0.71, P < 0.0001). LDL apoB concentration correlated with VLDL(2) apoB production (r = 0.48, P = 0.018) and the LDL FCR (r = -0.77, P < 0. 001) but not with VLDL(1), IDL, or LDL apoB production. Subjects with predominantly small, dense LDL (pattern B) had lower VLDL(1) and VLDL(2) apoB FTRs, higher VLDL(2) apoB production, and a lower LDL apoB FCR than those with large LDL (pattern A). Thus, the metabolic conditions that favored appearance of small, dense LDL were diminished lipolysis of VLDL, resulting in a raised plasma triglyceride above the putative threshold of 1.5 mmol/l, and a prolonged residence time for LDL. This latter condition presumably permitted sufficient time for the processes of lipid exchange and lipolysis to generate small LDL particles.

Adult↗

Heparin-mediated extracorporeal LDL/fibrinogen precipitation--H.E.L.P.--in coronary and cerebral ischemia.

Cerebral and myocardial infarctions share common aspects of pathobiochemistry. The central problem is the oxygen supply of the infarcted region. To maintain this supply, H.E.L.P.-apheresis (Heparin-mediated Extracorporeal LDL/Fibrinogen Precipitation) has already proven beneficial in the prevention and therapy of myocardial infarction. Since H.E.L.P.-apheresis can lower significantly plasma viscosity and erythrocyte aggregation without reducing the oxygen transport capacity, patients with cerebral infarction (stroke) may also benefit from our experiences in myocardial ischemia. The system is designed to remove selectively plasma fibrinogen, LDL-cholesterol and lipoprotein(a) from blood circulation, simultaneously. The removal of the plasma compounds is achieved by extracorporeal precipitation with heparin at low pH. Excess heparin is completely removed by an adsorber before the plasma is given back to the patient. H.E.L.P.-apheresis has proved to be safe in patients with coronary heart disease and allows a controlled reduction of thrombogenic plasma compounds. It is therefore hoped to be effective also in patients with acute ischemic stroke.

Blood Component Removal↗