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Biomedical subjects

E Koller

Publications and source records attributed to E Koller.

At least 73 records · Page 4Linked to original sources
PubMed1987

Autoxidation of human low density lipoprotein: loss of polyunsaturated fatty acids and vitamin E and generation of aldehydes.

The alteration of structural and biological properties of human plasma low density lipoprotein (LDL) exposed to oxidative conditions is in part ascribed to lipid peroxidation. The objective of this investigation was to measure quantitatively several parameters in oxidizing LDL indicative for lipid peroxidation. Exposure of freshly prepared EDTA-free LDL to an oxygen-saturated buffer led to a complete depletion of alpha- and gamma-tocopherol within 6 hr, thereafter lipid peroxidation commenced as indicated by the kinetics of the loss of linoleic (18:2) and arachidonic (20:4) acids, the formation of aldehydic lipid peroxidation products and fluorescent apoB. Within 24 hr of oxidation, on average 79 nmol of 18:2 (initial 345) and 12.8 nmol of 20.4 (initial 25.6) were oxidized per mg of LDL and the sample contained in total 7.1 nmol of aldehydes with the following molar distribution: 36.6% malonaldehyde, 25% hexanal, 8.9% propanal, 8.2% 4-hydroxynonenal, 7.6% butanal, 4.1% 2.4-heptadienal, 3.4% pentanal, 3.4% 4-hydroxyhexenal, and 2.5% 4-hydroxyoctenal. Malonaldehyde was predominantly (93%) in the aqueous phase, whereas the other aldehydes remained mostly (34-98%) within the LDL particle, where the total aldehyde concentration was in the range of 12 mM. Oxidized LDL exhibited a 1.6-fold enhanced electrophoretic mobility. Similarily, native LDL incubated for 5 hr with aldehydes showed increased electrophoretic mobility. At equal concentrations (5 mM) 4-hydroxynonenal was most effective, followed by 2,4-heptadienal, hexanal, and malonaldehyde. This study reports for the first time the rate and extent of the change of LDL constituents occurring during lipid peroxidation.

Aldehydes↗
PubMed1986

Possible involvement of the lipid-peroxidation product 4-hydroxynonenal in the formation of fluorescent chromolipids.

The effects of the lipid-peroxidation product 4-hydroxynonenal on the formation of fluorescent chromolipids from microsomes, mitochondria and phospholipids were studied. Incubation of freshly prepared rat liver microsomes or mitochondria with 4-hydroxynonenal results in a slow formation of a fluorophore with an excitation maximum at 360 nm and an emission maximum at 430 nm. The rate and extent of the development of the 430 nm fluorescence can be significantly enhanced by ADP-iron (Fe3+). With microsomes, yet not with mitochondria. NADPH has a catalytic effect similar to that of ADP-iron. Fluorescent chromolipids with maximum excitation and emission at 360/430 nm are also formed during the NADPH-linked ADP-iron-stimulated lipid peroxidation. Phosphatidylethanolamine and phosphatidylserine react with 4-hydroxynonenal revealing a fluorophore with the same spectral characteristics as that obtained in the microsomal and mitochondrial system. The findings suggest that the fluorescent chromolipids formed by lipid peroxidation are not derived from malonaldehyde, but are formed from 4-hydroxynonenal or similar reactive aldehydes via a NADPH and/or ADP-iron-catalysed reaction with phosphatidylethanolamine and phosphatidylserine contained in the membrane.

Adenosine Diphosphate↗
PubMed1986

Lipoprotein-binding proteins in the human platelet plasma membrane.

The binding of homologous plasma lipoproteins to specific receptor proteins in the plasma membrane of human blood platelets was studied by ligand blotting techniques. HDL3, HDL2 and LDL showed saturable binding to three bands of 156, 130 and 115 kDa, respectively. This binding was not markedly affected by the presence or absence of Ca2+ nor by covalent modification of lysine and arginine residues of the apoprotein moieties. However, it can be almost completely reversed by the addition of heparin or suramin.

Blood Platelets↗
PubMed1986

Investigation of human plasma low density lipoprotein by three-dimensional fluorescence spectroscopy.

Human plasma LDL exhibits a diffuse fluorescence (excitation 360 nm) in the 400-600 nm range. Application of three-dimensional fluorescence spectroscopy shows the presence of 7 fluorophores in the lipid and 6 fluorophores in the protein domain. The 430 nm fluorescence in freshly prepared LDL and its apo-B is most likely indicative for remnants of in vivo lipid peroxidation.

Apolipoproteins B↗
PubMed1984

Photometric and fluorometric continuous kinetic assay of acid phosphatases with new substrates possessing longwave absorption and emission maxima.

A direct and continuous kinetic method for the photometric and fluorometric determination of various acid phosphatases is described. It is based on new coumarin-derived phosphates, which after enzymatic hydrolysis undergo dissociation to form intensely colored and strongly fluorescent phenolate anions. The latter have absorption maxima ranging from 385 to 505 nm, and fluorescence maxima between 470 and 595 nm. The new substrates were compared with respect to their rate of enzymatic hydrolysis, optimum pH, and detection limits of acid phosphatase from potato and wheat germ. Detection limits of 0.001 unit/ml were found by photometry, and as low as 0.00006 unit/ml by fluorometry. The principal advantages of the new substrates over existing ones are longwave absorptions and emissions, large Stokes shifts, and the low pKa values of the corresponding phenols, thus allowing a direct and continuous assay of acid phosphatase even in weakly acidic solutions.

Acid Phosphatase↗
PubMed1984

Affinity chromatography of myo-inositol oxygenase from rat kidney by means of an insoluble D-galacto-hexodialdose derivative.

Following partial acid hydrolysis, Sepharose 6B-CL was treated with galactose oxidase, leading to an insoluble matrix containing 3-O-substituted D-galacto-hexodialdose. The latter substance strongly binds to myo-inositol oxygenase from rat kidneys, obviously because of its structural relationship to a reaction intermediate. Free apo-monomers, reconstituted iron(II)-containing monomers and fully active reassociated tetramers of the enzyme all interact with the affinity matrix, the degree of affinity increasing in this order. Thermodynamic analysis led to the conclusion that the ligand coordinates directly to the protein-bound iron ions, but this attachment is strengthened by interactions within and between the protein moiety of the oligomeric enzyme. These interactions seem to be essentially hydrophobic.

Animals↗
PubMed1983

Fluorimetric assay of hydrolases at longwave excitation and emission wavelengths with new substrates possessing unique water solubility.

A direct and continuous kinetic method for the fluorimetric assay of various hydrolases by using new, highly water-soluble substrates is described. The latter consist of esters of strongly fluorescent 1-hydroxypyren-3,6,8-trisulfonic acid trisodium salt with acetic, butyric, caprylic, and oleic acid. Km and vmax values are given for the hydrolytic activity of porcine liver carboxylic ester hydrolase, wheat germ lipase, candida cylindracea lipase, hog kidney acylase I, and bovine pancreas alpha-chymotrypsin, while others (acetylesterase, trypsin, and cholinesterase) were studied qualitatively. By proper choice of the substrate, a fair selectivity may be achieved. Detection limits as low as 1 microgram enzyme/ml are found in some cases. Advantages of these new substrates over existing ones are briefly discussed.

Animals↗
PubMed1982

Specific binding sites on human blood platelets for plasma lipoproteins.

Scatchard analysis of the binding of homologous plasma low density lipoproteins (LDL) to human blood platelets shows the existence of a uniform class of saturable specific binding sites. Platelets from healthy donors bound 1470 +/- 640 molecules of LDL per platelet, the constant of association Ka = (6.2 +/- 2.2) X 10-7 l x mol-1. Binding kinetics, temperature dependence, and experiments with formaldehyde-fixed platelets showed that internalization of LDL (at least the labelled apoprotein moiety) did not occur to any considerable degree under the experimental conditions employed. Both very low density lipoproteins (VLDL) and high density lipoproteins 3 (HDL3) markedly inhibited the binding of LDL. In contrast to LDL, HDL3 bound to 3200 +/- 410 binding sites per platelet with a Ka = (9 +/- 1.7) X 10(7) l x mol-1. Additionally, the results of inhibition experiments using both LDL and HDL3 in combination gave evidence, that the sites for HDL3 binding were not identical with those for LDL binding and each inhibited binding of the other noncompetitively with reduction of the binding affinity and the number of available binding sites. VLDL bound to the platelet plasma membrane in a nonspecific-nonsaturable way. Possible significances of the presence of specific LDL receptors on the platelet plasma membrane for recognized functions of these blood elements are discussed.

Binding, Competitive↗
PubMed1980

[Factor VIII preparations of varying purity-examination of physico-chemical parameters (author's transl)].

Commerical preparations of cryoprecipitates, factor VIII concentrates of intermediate purity, and factor VIII concentrates of high purity were studied for their factor VIII related clotting- and platelet-aggregating activities as well as their content of factor VIII antigen. The ratios of the values obtained of these three parameters were used to determine the extent of inactivation of the factor in the preparations. By means of two-dimensional immunelectrophoresis and gel chromatography on Sepharose 4B, the preparations were tested for the presence of atypical factor VIII molecules. Investigations were made to qualify and quantify some of the concomitant proteins in the factor VIII preparations.

Antigens↗
PubMed1979

The influence of thrombin on the platelet-aggregating activity of human factor VIII. A study with insolubilized thrombin.

A study was made of the influence of thrombin on the platelet-aggregating activity of human factor VIII with Ristocetin as cofactor. Purified factor VIII and different amounts of a thrombin-Sepharose 2B complex were mixed and incubated for various periods of time. The factor VIII-related platelet-aggregating activities of the filtrates of the incubation mixtures were determined in a test system using formalin-fixed platelets and Ristocetin as cofactor. The results so obtained indicate that thrombin inactivates the platelet-aggregating activity of factor VIII. The filtrates of the incubation mixtures were also tested by a two-stage test system for the clotting activities. Comparison of the influence of thrombin on the clotting- and the platelet-aggregating activities of factor VIII is presented and discussed.

Animals↗
PubMed1978

The influence of thrombin on the clotting activity of factor VIII. A study with insolubilized thrombin.

An investigation of the influence of thrombin on the clotting activity of factor VIII was made. Purified factor VIII and different amounts of thrombin complexed to Sepharose 4 B were mixed and incubated for various periods of time. The factor VIII activities of these incubation mixtures were determined by the one- and two-stage analytical procedures in the presence of the thrombin-sepharose and in its absence following the latter removal from the test sample by filtration. The results so obtained confirm the view that thrombin inactivates factor VIII. Evidences for a thrombin-induced potentiation of the factor VIII activity, seen only in the thrombin-sepharose containing test samples analyzed by the one-stage method, are here interpreted as thrombin-effects peculiar to this factor VIII test system and not as potentiation by thrombin of the factor itself.

Blood Coagulation↗
PubMed1977

[Lipoprotein analysis by means of the fluorescence probe 8-anilino-1-naphthalene sulphonic acid (author's transl)].

Single and mixed lipoprotein fractions were successfully analyzed by utilizing the fluorescent propertby of the applied reagent, 8-anilino-naphthalene sulphonic acid. The described method is especially useful for determination of lipoproteins present in high dilution, as found in chromatographic column effluents. The concentration dependence of the developed fluorescence was determined and this served as basis for quantitation. Furthermore, the measured activation spectra show two peaks for each lipoprotein class, the relative intesities being different for each class. The intensity quotient shows a tendency towards linear concentration dependence. Investigation of binary and ternary mixtures showed that the ratio of the two maximum intensities is additive, in contrast to the intensities themselves.

Humans↗
PubMed1977

[Separation and stability of australia antigen in human plasma fractions (author's transl)].

Commercially-produced human plasma protein fractions were investigated by a radio-immunological method for their content of Australia antigen (HBsAg). Albumin and gamma globulin solutions in which this antigen was present, were fractionated by isoelectric focussing and gel filtration on Sepharose 4 B. Characterization as to size and electrical charge of the HBsAs was carried out on these preparations. Inactivation studies were performed at different temperatures and concentrations to clarify the question of heat stability of HBsAg in plasma derivates. The importance of additional test methods is discussed.

Chromatography, Gel↗
PubMed1977

[Formation of sub-units of antihaemophilic globulin (factor VIII) by means of high centrifugal force (author's transl)].

The human coagulation factor VIII with a molecular weight greater than 1 X 10(6) Daltons forms active subunits under conditions of high centrifugal force, namely, 200.000 g at 20 degrees C for 32 minutes, as demonstrated by sedimentation analysis. This result was confirmed by Sepharose 4 B gel filtration analysis of the ultracentrifuged product, which revealed, in additon to mateial with a molecular weight of more than 1 X 10(6) Daltons, three F VIII-active fractions with smaller molecular weight values. These observations indicate that these sub-units so produced are not united in the starting matrial by covalent bonds.

Chemical Phenomena↗
PubMed1977

[Problems of aged people in rural regions of the Swiss Canton St. Gall (author's transl)].

Based on the structure of the mountain population, the living conditions of the aged (in rural communities 11-17% are older than 65) are shown. By public planning and cooperation of private organizations a material security of the aged has been strived after and mostly reached in the last 15 years--with the tendency to leave the aged in his own house or at least in the environment of his native village. Homes for the aged were built--if possible in every community--on the basis of 50 beds in a home for the aged and 35 beds in a nursing home for 10.000 inhabitants (83% in nursing homes an 17% in acute hospitals with geriatric departments). The individual help for the aged: activation by offering common institutions, ingenious activity, non-public advice offices, household help is deduced and the planning for the coming decade mentionned.

Aged↗