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Biomedical subjects

D Seidel

Publications and source records attributed to D Seidel.

At least 217 records · Page 12Linked to original sources
PubMed1983

[Accuracy of HDL cholesterol measurements].

The widespread use of different methods for the determination of HDL-cholesterol (in Europe: sodium phosphotungstic acid/MgCl2) in connection with enzymatic procedures (in the USA: heparin/MnCl2 followed by the Liebermann-Burchard method) but common reference values makes it necessary to evaluate not only accuracy, specificity, and precision of the precipitation step but also of the subsequent cholesterol determination. A high ratio of serum vs. concentrated precipitation reagent (10:1 V/V) leads to the formation of variable amounts of delta-3.5-cholestadiene. This substance is not recognized by cholesterol oxidase but leads to an 1.6 times overestimation by the Liebermann-Burchard method. Therefore, errors in HDL-cholesterol determination should be considered and differences up to 30% may occur between HDL-cholesterol values determined by the different techniques (heparin/MnCl2 - Liebermann-Burchard and NaPW/MgCl2-CHOD-PAP).

Chemical Phenomena↗
PubMed1983

A simple specific method for precipitation of low density lipoproteins.

A simple method is described for precipitation of low density lipoproteins. The results correlate well with those from ultracentrifugation in combination with polyanion precipitation (135 +/- 35 vs 136 +/- 35, r = 0.984, n = 13) or quantitative lipoprotein electrophoresis (r = 0.9287, n = 6394). In addition to lipoprotein analysis, this method may be used for the extracorporeal elimination of plasma low density lipoproteins.

Adult↗
PubMed1983

[Candidate selected method for the enzymatic determination of total cholesterol in serum].

An enzymatic method is described for the determination of total cholesterol in serum using a single aqueous reagent which can easily be prepared from commercial substrates and enzymes. The determination is carried out manually, the resulting stable chromogen is measured at a wavelength of 500-550 nm. The cholesterol concentration may be calculated either using a primary cholesterol standard or a constant factor for a given wavelength. The reliability of the method is reported: Data for the imprecision are given on the basis of a survey in 3 laboratories, the accuracy is established by comparison with a definitive and a reference method. Analytical and biological interferances are briefly discussed and results with this enzymatic method are reported concerning the reference values for serum cholesterol.

Cholesterol↗
PubMed1982

[The influence of oral contraceptives on lipoprotein status (author's transl)].

Sera from 500 female blood donors, aged 18-40 years, were examined by quantitative lipoprotein electrophoresis. 218 women had been taking oral contraceptives for more than 3 months; the remaining 282 not on contraceptives acted as controls. The two groups were similar as to age distribution, weight and smoking habits. There were five sub-groups according to the composition of the contraceptives. It was found that all contraceptives had a favourable influence on the atherogenic beta-lipoprotein fraction. The pure progestogen preparations were less advantageous because they in particular reduced the concentration of potentially anti-atherogenic alpha-lipoproteins.

Adolescent↗
PubMed1982

[The significance of LP-X cholesterol in the differential diagnosis of cholestasis (author's transl)].

The aim of this study was to investigate whether quantification of Lipoprotein X (LP-X) through its cholesterol moiety is advantageous in the differential diagnosis of obstructive jaundice. In the case of mechanic cholestasis, LP-X cholesterol never exceeds 22% of the total serum cholesterol. Lipoprotein-X cholesterol exceeded 70 mg/dl in the plasma of 85% of all cases of acute hepatitis. The combination of lipoprotein with the activities of alkaline phosphatase and GPT allows the recognition of almost 80% of cases acute hepatitis and thereby excludes all other causes of obstructive jaundice. In addition, 84% of all patients investigated can be correctly classified using a combination of LP-X with classical parameters for cholestasis. The concentration of LP-X cholesterol alone apparently is as powerful as the usually used clinical chemical parameters. A combination of lipoprotein and the classical parameters allows a better differentiation of cholestatic liver disease with regard to the underlying cause as it is possible with each group of parameters alone.

Alanine Transaminase↗
PubMed1982

Apolipoprotein AIMarburg: studies on two kindreds with a mutant of human apolipoprotein AI.

Three probands heterozygous for a mutant of apolipoprotein AI (apo AIMarburg, Utermann et al. 1982a) were detected by screening of 2282 unrelated individuals resulting an a frequency estimate of about 1/750 in the German population. All three probands with apo AIMarburg had hypertriglyceridemia (triglyceride above 250 mg/dl) and subnormal HDL-cholesterol (below 30 mg/dl), but no other lipoprotein abnormalities. The kindreds of two probands with AIMarburg were studied. The family data are consistent with an autosomal codominant inheritance of the trait. A total of 16 heterozygous blood relatives with the mutant AIMarburg were detected in these kindreds. Analysis of the plasma lipid and lipoprotein levels in relation to the apo AI phenotype was complicated by the high prevalence of diabetes mellitus and thyroid disease in one kindred and of hyperlipidemia in both kindreds. No consistent relationship between plasma lipid and lipoprotein levels, and the mutant apo AI could be demonstrated. Instead the mutant apo AI and the dyslipoproteinemia seem to co-exist independently in these kindreds. Three sibs with the homozygous apo E-2/2 phenotype were detected in one kindred, and all three sibs had subnormal LDL-cholesterol and beta-VLDL, e.g., the lipoprotein abnormality characterizing primary dysbetalipoproteinemia. Genetic apo E phenotypes and the apo AI mutant segregated independently, indicating that the structural gene loci for apo E and apo AI are not closely linked.

Adult↗
PubMed1982

[Polyunsaturated (essential) fatty acids and their importance in pathogenesis, diagnosis and therapy of multiple sclerosis].

Various aspects concerning the pathogenetic involvement of poly-unsaturated (essential) fatty acids as biochemical co-factors in developing multiple sclerosis (MS) are reported in great detail. Our own studies have also confirmed that differences in the intake or utilization of essential fatty acids do not biochemically induce significant changes in myelin, serum or blood cells. This has long been suspected. The concept of nutritionally or metabolically induced generalized defects in all membranes, especially in the myelin sheath, as a predisposing factor to an increased susceptibility for the development of MS, provoked a gamut of pertinent studies frequently producing controversial results. Hence, these conceptions concerning the pathogenetic involvement of essential fatty acids in MS have been put to rest--even more so after the role of prostaglandins in immunoregulation had become more apparent whose biological precursors are essential fatty acids. Thus, the immunosuppressive effect of high dosage of essential fatty acids under experimental conditions could be explained, disclosing new assessments concerning therapy, new pathogenetic models and further biochemical research.

Blood Cells↗
PubMed1982

Determination of apolipoprotein B by kinetic (rate) nephelometry.

Determination of apoB by rate nephelometry is a simple, rapid and precise method, which is also suitable for a routine laboratory. It can be standardized with lipoprotein-B or LDL fractions, but only if these fractions are diluted with fresh whole serum. The standardization is also valid for VLDL if the samples are diluted with hydroxypolyethoxydodecane (trade name: Thesit) in a concentration of 0.33 g/liter. Using rate nephelometry, a strong correlation between the contents of cholesterol and apoB of VLDL as well as of LDL can be demonstrated. Similar high correlations are achieved if apoB is determined chemically in isolated lipoprotein fractions. The ratio of apoB to cholesterol is constant but not the same in both VLDL and LDL. There is also a strong correlation between the concentration of apoB in whole serum with the LDL cholesterol values in a normotriglyceridemic population. Therefore, the assay of apoB in whole serum by rate nephelometry is proposed as a screening method for dyslipoproteinemia (increased concentrations of atherogenic lipoproteins at normal or elevated levels of cholesterol in plasma).

Cholesterol↗
PubMed1982

Improved assessment of plasma lipoprotein patterns. IV. Simple preparation of a lyophilized control serum containing intact human plasma lipoproteins.

Addition of sucrose (413-825 mmol/L) to human serum allows plasma lipoproteins to be lyophilized without denaturation. A control serum so prepared is especially suited for use in monitoring determinations of apolipoproteins and quantitative lipoprotein electrophoresis. It is clear upon reconstitution; hence, the described procedure may also be useful for preparation of control sera for general clinical chemistry without de-lipoproteinization.

Blood Protein Electrophoresis↗
PubMed1982

Morphologic studies on adult neuronal-ceroid lipofuscinosis (NCL).

This report concerns morphologic findings in two middle-aged women, who died of sporadic adult neuronal ceroid-lipofuscinosis (NCL) and whose brains were studied histologically, by electron microscopy and by pigmentoarchitectonic techniques. In addition, the brain of a 35-year-old woman, who died of familial protracted juvenile NCL, was also investigated using pigmentoarchitectonic methods. Clinical, light and electron microscopic findings were compatible with the above-mentioned diagnosis. Pigmentoarchitectural analysis of homotypical isocortex in these three brains revealed (1) loss of pigment-laden stellate cells in layer II, (2) axonal enlargements of layer IIIab-pyramidal cells, and (3) considerable cell loss in layer Va. The changes were more pronounced in the brain affected by protracted juvenile NCL than in the two brains affected by adult NCL. The study emphasizes the value of the pigmentoarchitectonic technique, both in diagnostic neuropathology and in ascertaining patients afflicted with adult NCL. The ultrastructure of the lipopigments showed a motley spectrum of membrane formation such as curvilinear, fingerprint, or straight membranes and was less granular than regular senile lipofuscin.

Adult↗
PubMed1981

An optimized method for measuring lecithin : cholesterol acyltransferase activity, independent of the concentration and quality of the physiological substrate.

The aim of the study was to achieve the measurement of lecithin : cholesterol acyltransferase (EC 2.3.1.43) activity independent of and uninfluenced by equilibration of lipids between different lipoproteins, their molar ratios or by possible differences in their substrate quality. A mixture of sodium phosphotungstic acid/MgCl2 was added to serum samples to achieve total precipitation of all plasma lipoproteins. The filtrate containing the total plasma lecithin : cholesterol acyltransferase activity, apolipoprotein A-I and major plasma proteins was used for the assay. Liposomes comprised of phosphatidylcholine, cholesterol and dicetylphosphate served as substrate. The decrease in free cholesterol was determined enzymatically after incubation for 60 min at 37 degrees C. The assay followed zero-order kinetics and was linear for more than 60 min. The following Km values for various substrates were obtained: liposomes, 0.43 mM; HDL, 0.63 mM; LDL, 0.0; VLDL, 0.0; abnormal lipoprotein, found in cholestasis, (LP-X), 0.0. Comparison with generally used lecithin : cholesterol acyltransferase assay methods revealed similar activities for healthy controls, but in different forms of dyslipoproteinemia higher values were obtained with our method and, in special cases, the activity could be enhanced by addition of apolipoprotein A-I.

Cholestasis↗
PubMed1981

Determination of apolipoprotein A-I by kinetic nephelometry.

Apolipoprotein A-I concentration in human serum was determined by kinetic nephelometry. Under optimal reaction conditions and within the normal physiological range the relation between apolipoprotein A-I concentration and measured rate units it approximately linear. The detection limit of the assay lies at 2 micrograms/ml. The coefficient of variation within one series is 1.44%. The correlation coefficient with alpha-cholesterol, as determined by agarose electrophoresis followed by polyanion precipitation, is better than 0.94. Addition of detergent to serum dilutions increases the reaction rate, suggesting that delipidation changes the antigenic expression of apolipoprotein A-I. The magnitude of this change is constant in normal controls, but not in special pathological cases. The described technique can be recommended for routine use in clinical chemistry for measurement of apolipoprotein A-I.

Animals↗
PubMed1981

Late-onset metachromatic leukodystrophy: diagnostic problems elucidated by a case report.

A 20-year-old female had psychiatric symptoms of organic brain disease for five years but without clinical or neurophysiological signs of polyneuropathy. Late-onset metachromatic leukodystrophy was confirmed by finding severely reduced arylsulfatase A activity in her urine and leukocytes, marked excretion of sulfatides in the urine and the presence of lysosomal residual bodies in a sural nerve biopsy. This case report emphasizes the need to screen patients with early onset dementia of unknown origin or atypical hebephrenia, who are often confined to mental institutions early in the course of their disease.

Adult↗
PubMed1981

Effects of clofibric acid and bezafibrate administration on activities of alkaline phosphatase and other enzymes in livers of rats.

Administration of clofibric acid and bezafibrate to rats lowers plasma lipids, increases the liver weight, and causes a slight decrease in the activity of alkaline phosphatase in plasma. However, both these drugs increase the activity of alkaline phosphatase in liver over threefold. The activity of other enzymes did not change by the same magnitude. The increase in the alkaline phosphatase activity in liver tissue appears to be due to increase in the activity of this enzyme in parenchymal cells. Clofibric acid and bezafibrate increase the activity of bilirubin-glucuronyl transferase activity over twofold in liver microsomes. It is thus evident that both these drugs cause similar changes in various enzyme activities in liver even though bezafibrate has been reported to have a much shorter biologic halflife than clofibric acid.

Alkaline Phosphatase↗