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J Arnhold

Publications and source records attributed to J Arnhold.

At least 73 records · Page 4Linked to original sources
PubMed1991

Partition of serum lipoproteins in a polyethylene glycol/dextran two-phase system.

Aqueous two-phase systems containing polyethylene glycol (PEG) and dextran as phase forming polymers were used for the partition of unmodified and hypochlorite modified lipoproteins. Low density lipoprotein (LDL) was separated from high density lipoprotein (HDL) by sequential ultracentrifugation from human plasma. In agreement with the higher electrophoretic mobility, high density lipoprotein shows a higher value of the partition coefficient in contrast to low density lipoprotein. An increase in the concentration of chloride ions reduces the enrichment of lipoprotein in the top phase and favours the accumulation of aggregated material at the interface. The partition coefficient strongly depends on the age of the lipoprotein sample. Differences in the value of the partition coefficient could be obtained for the lipoprotein fractions HDL-2 and HDL-3. Hypochlorite modified LDL shows higher values of the partition coefficient due to the higher negative charge of the modified lipoprotein particle.

Chemical Phenomena↗
PubMed1991

Modification of low density lipoproteins by sodium hypochlorite.

Human low density lipoproteins (LDL) were incubated with increasing amounts of sodium hypochlorite. A decrease of the number of free amino groups on the LDL surface starts only upon addition of 30-40 moles NaOCl per mole apoB, whereas all detectable SH groups are oxidized after addition of nearly 17-20 moles NaOCl. All hypochlorite-modified LDL samples have a higher electronegative surface charge compared with native LDL as revealed by agarose gel electrophoresis and partition of LDL in an aqueous polyethylene glycol/dextran two-phase system. The more NaOCl is used to alter LDL, the higher is the electrical surface charge. Changes in surface charge are found already at low NaOCl concentrations where no decrease of amino groups is detected. It is assumed that changes in surface charge are caused by the formation of monochloramines and especially at low degrees of modification by a further unknown contribution. An effect on the primary structure of apoB or peroxidation-like changes in NaOCl-altered LDL could not be found under our experimental conditions. The results are discussed with respect to such modifications under in vivo conditions by hypochlorous acid generated in stimulated phagocytosing cells.

Dextrans↗
PubMed1991

Aggregation of human plasma high density lipoproteins induced by poly(ethylene glycol).

The influence of different surface charge densities (induced by varying pH, addition of positively charged amphiphilic molecules and chemical modification) of high density lipoproteins (isolated by ultracentrifugation) on poly(ethylene glycol) induced aggregation was studied. The effects of different molecular masses of PEG, HDL concentration and the presence of other serum proteins on the PEG mediated aggregation were investigated. The PEG concentration necessary for HDL aggregation is inversely proportional to the used HDL concentration and its molecular weight, and is directly proportional to the presence of other proteins and the magnitude of the negative surface charge density of HDL. The results are in accordance with the predictions of the volume exclusion theory taking into account the influence of repulsive electrostatic forces on the interaction of HDL particles.

Chemical Precipitation↗
PubMed1990

On the action of hypochlorite on human serum albumin.

The luminol-enhanced chemiluminescence of zymosan-stimulated polymorphonuclear leukocytes is continuously diminished in the presence of increasing amounts of human serum albumin (from 1 to 30 mg/ml). HSA competes with luminol for hypochlorite as shown by adding sodium hypochlorite to luminol solutions containing HSA. Titration of HSA with NaOCl affects firstly the sulfhydryl and probably the thioether groups and then the amino groups. Coincubation of zymosan-stimulated polymorphonuclear leukocytes and HSA at a ratio corresponding to normal values of healthy men causes a continuous oxidation of sulphur containing functional groups in HSA.

Fluorescence↗
PubMed1989

Characterization of chemical modifications of surface properties of low density lipoproteins.

Low density lipoproteins (LDL) were modified by incubation with formaldehyde and malondialdehyde and by autoxidation. Different methods were developed to measure alterations of surface properties of LDL. A method based on fluorescamine fluorescence was used to measure changes of free amino groups. All modified LDL samples have a decreased number of amino groups. As shown by gel electrophoresis, the negative surface charge of LDL increases. Aggregation of LDL induced by poly(ethylene glycol) (PEG) is influenced by LDL modification. The PEG 6000 concentration necessary for LDL aggregation is shifted to higher values for modified LDL due to the increased negative surface charge. This result may be of interest for the application of PEG for selective separation of different classes of lipoproteins. The formation of aggregates of LDL induced by dextran sulphate is reduced due to the loss of positive charges of amino groups on the LDL surface.

Dextran Sulfate↗
PubMed1979

[The formation of lipofuscin (author's transl)].

The article deals with the present knowledge of the lipofuscin-formation. Lipofuscin is regarded as a lysosomal residue body and as a product of peroxidation and polymerisation of unsaturated fatty acids. Starting from this aspects conditions are derived, which favour the lipofuscin-formation. These factors are divided into three groups according to their effects.

Lipofuscin↗
PubMedDate not supplied

Modulation of luminol chemiluminescence of fMet-Leu-Phe-stimulated neutrophils by affecting dephosphorylation and the metabolism of phosphatidic acid.

This paper is addressed to study how PKC-mediated effects and phosphatidic acid interact together in activation of NADPH-oxidase in formyl-methionyl-leucyl-phenylalanine (fMet-Leu-Phe) stimulated neutrophils as detected by luminol chemiluminescence. The early luminescence response in fMet-Leu-Phe-stimulated cells (up to 5 min after stimulation) depends mainly on reactive oxygen species generated extracellularly, whereas all later events are caused by oxidation of luminol inside the cells. The two protein phosphatase inhibitors, okadaic acid and calyculin A, dramatically increased the late luminescence of cells. This enhancement was totally inhibited by the phospholipase D modulator butanol, while the protein kinase C (PKC) inhibitor bisindolylmaleimide I was insensitive. The early luminescence response of the cells was slightly inhibited by both protein phosphatase inhibitors and depended on protein kinase C as well as on phospholipase D activities. Propranolol, an inhibitor of phosphatidate phosphohydrolase, enhanced all parts of luminescence response of fMet-Leu-Phe-stimulated neutrophils at concentrations up to 2.5 x 10(-5) mol/L. While the late luminescence response of propranolol-treated cells was not inhibited by the PKC inhibitor bisindolylmaleimide I, the first response depended on protein kinase C. The inhibitor of diacylglycerol kinase R59949 enhanced the luminescence signal only during the first 4 min in fMet-Leu-Phe-stimulated cells. Only diacylglycerols derived from phospholipase C, such as 1-stearoyl-2-arachidonoyl-sn-glycerol, were able to initiate an oxidative burst in cells. Saturated diacylglycerols (e.g. 1,2-dipalmitoyl-sn-glycerol or 1,2-distearoyl-sn-glycerol) did not yield any luminol chemiluminescence, although they were incorporated into the plasma membrane, as evidenced by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Our results demonstrate that phosphatidic acid produced by phospholipase D is responsible for NADPH-oxidase activity in fMet-Leu-Phe-stimulated neutrophils over the entire measuring time, whereas PKC-mediated processes are only involved during the first 5 min.

Diglycerides↗
PubMedDate not supplied

Chemiluminescence intensities and spectra of luminol oxidation by sodium hypochlorite in the presence of hydrogen peroxide.

Hydrogen peroxide amplifies the chemiluminescence in the oxidation of luminol by sodium hypochlorite. A linear relationship between concentration of hydrogen peroxide and light intensity was found in the concentration range 5 x 10(-8)-7.5 x 10(-6) mol/l. At 7.5 x 10(-6) mol/l H2O2 the chemiluminescence is amplified 550-fold. The chemiluminescence spectra of these reactions have a wavelength maximum at 431 nm independent of the concentration of hydrogen peroxide. The results indicate that hydrogen peroxide is a necessary component in the chemiluminescent oxidation of the luminol by sodium hypochlorite.

Hydrogen Peroxide↗
PubMedDate not supplied

Mechanisms of inhibition of chemiluminescence in the oxidation of luminol by sodium hypochlorite.

Two different mechanisms of inhibition of chemiluminescence in the oxidation of luminol by sodium hypochlorite were found. Most substances investigated in these experiments acted by scavenging NaOCl. This mechanism was independent of the concentration of hydrogen peroxide and the incubation time between luminol and inhibitors. The most potent inhibitors were substances containing SH groups. Compounds with amino groups as a target for HOCl/OCl- to yield chloramines were much less effective inhibitors. Another mechanism of inhibition was found for catalase. It depended on the presence of hydrogen peroxide in the incubation medium and the incubation time between luminol and catalase. The enzyme inhibited the luminescence by removing H2O2 at molar concentrations much smaller than those found for all other inhibitors. Our results confirm the present models of the mechanism of generation of luminescence in luminal oxidation.

Kinetics↗
PubMedDate not supplied

Increased native chemiluminescence in granulocytes isolated from synovial fluid and peripheral blood of patients with rheumatoid arthritis.

Polymorphonuclear leukocytes (PMNs) isolated from peripheral blood and synovial fluid of patients with rheumatoid arthritis and from peripheral blood of volunteers were stimulated with 12-phorbol-13-myristate acetate (PMA). No significant differences in luminol-amplified chemiluminescence were found between different patients and control groups. However, two distinct patterns of native chemiluminescence were observed. Type I showed no, or only a small, increase in native chemiluminescence with integral counts over 30 min less than 3 x 10(5) cpm, and the majority of samples from volunteers were of this type. Type II was characterized by a burst of native chemiluminescence starting 8 to 15 min after cell stimulation. It was found in most PMN samples from patients with rheumatoid arthritis. Integral counts over 30 min were always higher than 10(6) cpm and as high as 10(8) cpm in some cases. A strong inhibition of the Type II native chemiluminescence was caused by desferal, catalase, thiourea, and glutathione. However, the luminol-amplified chemiluminescence remained unchanged or was only slightly decreased under the same experimental conditions. Sodium azide strongly inhibited both kinds of luminescence. Hydroxyl radicals, formed in a Fenton reaction, may be important intermediates in the Type II native chemiluminescence.

Arthritis, Rheumatoid↗
PubMedDate not supplied

Fast and sensitive chemiluminescence determination of H2O2 concentration in stimulated human neutrophils.

A fast and sensitive chemiluminescence assay for the determination of H2O2 in stimulated neutrophils without the use of enzymes was developed. The method is based on the oxidation of luminol by hypochlorous acid. The chemiluminescence of this reaction is highly dependent on the concentration of hydrogen peroxide. Changes in H2O2 concentration in PMA-stimulated neutrophils were followed by injection of NaOCI to cell suspension at different times after cell stimulation. The short integration time of 2 s permits calculation of actual concentrations of H2O2 without influence of H2O2 decomposition by cellular enzymes or newly produced H2O2 due to dismutation of superoxide anion radicals. Concentrations of H2O2 were diminished by catalase and enhanced by sodium azide owing to inhibition of cellular catalase and myeloperoxidase. Changes in H2O2 concentration upon stimulation could be observed at 3000 cells/mL.

Azides↗
PubMedDate not supplied

Action of hypochlorous acid on polymeric components of cartilage. Use of 13C NMR spectroscopy.

It is a well known fact that neutrophil-derived hypochlorous acid plays an important role in cartilage destruction during rheumatoid arthritis. It has been shown by 1H NMR spectroscopy in a previous paper (Schiller et al. (1994), Biol. Chem. Hoppe-Seyler 375, 167-172) that sodium hypochlorite affects primarily the N-acetyl side chains of polymeric carbohydrates of cartilage like chondroitinsulphate and hyaluronic acid. An instable intermediate, likely to be a chloramine, is involved in these processes. The present paper deals with the application of carbon NMR spectroscopy for the study of these degradation processes, because carbon NMR gives the opportunity to detect changes on the single sugar ring carbons. Although it was not possible to prove the involvement of an intermediate, because of its fast hydrolysis, we were able to show that the reaction between sodium hypochlorite and N-acetylglucosamine affects mainly the side chain, accompanied by the formation of acetate. The application of a large excess of sodium hypochlorite leads to a breakdown of the carbohydrate ring under the formation of formiate.

Acetylgalactosamine↗
PubMedDate not supplied

Reaction of hypochlorous acid with bovine nasal cartilage comparison to pig articular cartilage.

The action of sodium hypochlorite (NaOCl) on bovine nasal cartilage was studied by proton nuclear magnetic resonance (1H-NMR) spectroscopy in order to model degradation processes of cartilage caused by neutrophil-derived hypochlorous acid. Nasal cartilage was chosen as a mean of comparison because it differs from articular cartilage in its composition. It contains some more proteoglycans, i.e. polymeric carbohydrates and less collagen than articular cartilage. This is important for studying the influence of hypochlorous acid on cartilage components (collagen and polysaccharides). Cartilage samples were incubated at 37 degrees C with phosphate buffer in the presence or absence of NaOCl. Supernatants were collected and assayed by NMR-spectroscopy. In the presence of pure phosphate buffer, the supernatants of bovine nasal cartilage were less rich in low molecular mass metabolites (e.g. amino acids, lactate) than articular cartilage. However, intense signals for highly mobile N acetyl groups of cartilage polysaccharides were detectable in nasal cartilage. NaOCl caused an increase in signals for acetate and formiate. Signals for N-acetyl groups rose only during the first 25 minutes of incubation with NaOCl. Then, their concentration decreased markedly. These changes were related to an enhanced release of chondroitinsulfate from nasal cartilage.

Animals↗
PubMedDate not supplied

Nuclear magnetic resonance and mass spectrometric studies on the action of proteases on pig articular cartilage.

Rheumatic diseases are accompanied by a progradient diminution of the cartilage layer. Unfortunately, degradation mechanisms (role of different enzymes and reactive oxygen species) are not yet understood. Since nuclear magnetic resonance (NMR) spectroscopy was often used for the investigation of synovial fluids, the aim of the present work was to detect cartilage degradation products upon proteolytic digest of cartilage. Cartilage samples were incubated at 37 degrees C with phosphate buffer in the absence or presence of different proteases (collagenase, trypsin and papain). Supernatants were subsequently assayed towards their content of carbohydrate and protein degradation products by NMR (1H- and 13C-) and MALDI-TOF mass spectrometry. Intense resonances of relatively mobile N-acetyl side chains (ca. 2.01 ppm) of polysaccharides of cartilage were only detectable on digestion with papain. The appearance of these resonances indicates intense degradation of the core protein of proteoglycan aggregate of cartilage, whereby polysaccharides are released. Additionally, broad resonances at 0.85 ppm arising from collagen degradation products were observed upon the action of all applied proteases. However, glycine as a marker of exhaustive collagen degradation was only observed, if cartilage was digested by collagenase. Using more vigorous incubation conditions, additionally high-abundant amino acids of collagen (proline, hydroxyproline) could be detected in the 13C-NMR- and the MALDI spectra. The observed differences are correlated with the different selectivities of the applied enzymes. It is concluded that NMR allows the detection of characteristic protein and polysaccharide degradation products. The observed differences may be of some relevance for the diagnosis of rheumatic diseases.

Animals↗
PubMedDate not supplied

Pancreatic phospholipase A2--mediated enhancement of the respiratory burst response of human neutrophils.

The aim of this study was to investigate the effects of exogenously added pancreatic phospholipase A2 (pPLA2) on the production of reactive oxygen species by human polymorphonuclear leukocytes (PMNs). Pancreatic PLA2 was used because PMNs do not possess a receptor for that enzyme and, therefore, the receptor-mediated effects could be excluded. Respiratory burst activity of PMNs was monitored by luminol-amplified chemiluminescence and the lipid composition of neutrophils after treatment with pPLA2 was determined by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. Our results show that the products of the pPLA2 digestion of the PMN membrane--lysophospholipids and the corresponding free fatty acids--significantly enhanced the respiratory burst response of human neutrophils.

Humans↗
PubMedDate not supplied

[Interaction of tert-butyl hydroperoxide with hypochlorite induces peroxyl radicals. A chemiluminescence study].

The interaction of hypochlorite (HOCl/OCl-) with tert-butyl hydroperoxide ((CH3)3COOH) was investigated by chemiluminescence. It was shown that the addition of HOCl/OCl- to (CH3)3COOH induces a fast chemiluminescent flash. The intensity of this flash increases with the increase in both HOCl/OCl- and (CH3)3COOH concentration. The chemiluminescence is quenched in a concentration-dependent manner in the presence of free radical spin traps N-tert-butyl nitrone and alpha-(4-pyridyl-1-oxyl)-N-tert-butyl nitrone. This fact proves that free radicals take part in the interaction of HOCl/OCl- and (CH3)3COOH. Hypochlorite yielded a very similar chemiluminescence spectrum in its reaction with (CH3)3COOH as Ce4+. It differed considerably from the spectrum in the system H2O2 and HOCl/OCl-. It is well known that the interaction of Ce4+ and (CH3)3COOH produces peroxyl radicals. These results confirm the hyothesis that the interaction of HOCl/OCl- and (CH3)3COOH is mediated by peroxyl radicals. Thus, organic hydroperoxides always present in unsaturated lipids can induce lipid peroxidation processes in the reaction with HOCl/OCl-.

Electron Spin Resonance Spectroscopy↗