bluuebunny/crossref_metadata_2025_split huggingface dataset:
Whole plasma oxidation assay as a measure of lipoprotein oxidizability
Authors: Kontush Anatol , Spranger Torsten , Reich Axel , Djahansouzi Sirus , Karten Barbara , Braesen Jan Hinrich , Finckh Barbara , Kohlschütter Alfried , Beisiegel Ulrike 
Published: December 2008

AbstractLipoprotein oxidation induced in vitro in whole plasma is expected to be a more relevant model of the lipoprotein oxidation in the arterial wall than the in vitro oxidation of single isolated lipoproteins, e.g., low density lipoprotein (LDL). However, it is unclear, whether the oxidizability of whole plasma may serve as an adequate measure of the oxidizability of plasma lipoproteins. We measured the oxidizability of whole plasma diluted 150‐fold as an absorbance increase at 234 nm known to reflect the level of conjugated dienes in the samples. Plasma oxidation was induced by Cu(II), 2,2′‐azobis‐(2‐amidinopropane) hydrochloride (AAPH), lipoxygenase or myeloperoxidase+H2O2. Oxidizability of human plasma measured in the presence of Cu(II) was found to correlate with the oxidizability of LDL measured in the common Cu(II)‐based LDL oxidation assay. The plasma oxidizability also correlated positively with plasma oxidizable fatty acid and negatively with plasma antioxidant content. Supplementation of human plasma with different antioxidants (albumin, urate, ascorbate, bilirubin, α‐tocopherol and ubiquinol‐10) in vitro decreased its oxidizability. Supplementation of Watanabe heritable hyperlipidaemic rabbits with different antioxidants (vitamin E, ubiquinone‐10, probucol, carvedilol) in vivo lowered the oxidizability of rabbit plasma in comparison with rabbits fed standard diet. When plasma from hyperlipidaemic patients with or without coronary heart disease and from age‐matched healthy controls was studied, the plasma oxidizability was found to be highest in the patients with coronary heart disease and lowest in the controls. Taken together, these data indicate that the plasma oxidation assay (i) provides information similar to that obtained using the common LDL oxidation assay, (ii) upgrades the latter, taking into account the effect of hydrophilic antioxidants on lipoprotein oxidation and characterizing the oxidizability of all plasma lipoproteins, and (iii) offers important practical advantages, such as fast and simple sample processing, low amount of plasma required and avoidance of artefactual oxidation during lipoprotein isolation. We propose the measurement of plasma oxidizability at 234 nm as an adequate practical index of the oxidizability of plasma lipoproteins.
The role of oxidative stress in the long‐term glycation of LDL
Authors: Menzel E. J. , Sobal G. , Staudinger A. 
Published: December 2008

AbstractAdvanced glycation is a major pathway for the posttranslational modification of plasma and tissue proteins. The initiating reaction is the nonenzymatic addition of sugars such as glucose to the primary amino groups of proteins, i.e., mainly to lysine residues. These ‘early’ Schiff base and Amadori products then undergo a series of inter‐ and intramolecular rearrangements to produce the ‘late’ products termed advanced glycation end products (AGEs). Incubation of LDL with glucose or glucose‐6‐phosphate produces AGE moieties on both the lipid and apolipoprotein B components. In addition, we tried to generate AGE‐LDL by reaction with AGE‐peptides (<10 kD) obtained by enzymatic digestion of long‐term glycated fibronectin as a model for connective tissue AGE‐peptides. AGE‐formation can be assessed by monitoring of fluorescence (370/440 nm) which is easily differentiated from the much lower autofluorescence of oxidized low density lipoproteins (oxLDL). Alternatively, AGE formation was detected by an AGE‐specific ELISA using antibodies elicited in rabbits against bovine AGE‐RNAse. In the present study we investigated the influence of oxidative stress on the long‐term glycation of LDL and the modulation of LDL‐oxidation by AGE‐modification. We observed (a) that the rate of AGE formation is reduced by BHT/EDTA both on LDL and serum albumin (glycation vs.glycoxidation), (b) long‐term glycated LDL is more readily oxidized than unglycated LDL, (c) oxLDL is more prone to AGE‐modification, (d) AGE‐modification of LDL strongly alters its epitope spectrum and (e) that aminoguanidine at higher concentrations (1–10 mM) inhibits copper‐catalyzed LDL oxidation in the way of a classical antioxidant.
Interactions between macrophages and oxidized low density lipoprotein in the presence of type I collagen
Authors: Chen Qi , Wei Enhui , Chen Xiuying , Wang Nan , Jürgens Günther 
Published: December 2008

AbstractIn order to investigate the influence of collagen on the interactions between macrophages and oxidatively modified low density lipoprotein (ox‐LDL), type I collagen was isolated from rat tail tendon and prepared as a gel. The binding of 125I‐ox‐LDL, 125I‐malondialdehyde (MDA)‐LDL and 125I‐acetyl‐LDL to collagen was higher but the binding of 125I‐4‐hydroxynonenal (HNE)‐LDL was lower than that of native 125I‐LDL. When mouse peritoneal macrophages were cultivated on this collagen gel, most of the modified LDL was bound to the collagen gel rather than taken up by macrophages. The amount of modified 125I‐LDL degraded by the macrophages decreased in the presence of the collagen gel. In the absence of gel a similar degree of reduction in degradation of modified 125I‐LDL by macrophages was obtained when the cells were treated with cytochalasin D, an inhibitor of non‐specific phagocytosis. However, the treatment of the macrophages cultivated on the collagen gel with cytochalasin D did not influence the degradation of 125I‐ox‐LDL and 125I‐HNE‐LDL. These results suggest that the uptake of ox‐LDL by macrophages grown on collagen gels is primarily mediated via the scavenger receptors pathway, whereas in the absence of collagen also other mechanisms of uptake are operating.
Pathways for oxidation of low density lipoprotein by myeloperoxidase: tyrosyl radical, reactive aldehydes, hypochlorous acid and molecular chlorine
Authors: Heinecke Jay W. 
Published: December 2008

AbstractMany lines of evidence implicate oxidation of low density lipoprotein (LDL) in the pathogenesis of atherosclerosis, a chronic inflammatory disease. The physiologically relevant mechanisms have not been identified, but phagocytic white cells may play an important role because macrophage‐rich lesions characterize the disorder.Recent studies have shown that myeloperoxidase, a heme enzyme secreted only by phagocytes, is present in human atherosclerotic tissue. The enzyme is a potent catalyst of LDL oxidation in vitro, it co‐localizes with macrophages in lesions, and it generates products that are detectable in atherosclerotic plaque. These findings suggest that myeloperoxidase may promote LDL oxidation in the artery wall.This article reviews the enzyme's ability to generate a range of oxidants, including tyrosyl radical, reactive aldehydes, hypochlorous acid and molecular chlorine. These products have the potential to damage host molecules as well as microbes, suggesting a mechanism that may contribute to atherosclerotic vascular disease.
The mechanism of the hypochlorite‐induced lipid peroxidation
Authors: Panasenko Oleg M. 
Published: December 2008

AbstractThe article reviews data related to the role of exogenic hypochlorite (HOCl/OCl−) and hypochlorite produced by myeloperoxidase catalysis in initiation of lipid peroxidation (LPO) in phospholipid membranes and human blood lipoproteins (LP). It has been shown that HOCl/OCl− promotes free radical lipid oxidation in liposomes and LP that is followed by the formation of LPO products: hydroperoxides, conjugated dienes, TBARS, and fluorescent products. Water soluble reactive substances •O2−, H2O2, Fe2+) which can be present in the reaction mixture as a dopant are not the source of free radicals and do not participate in HOCl/OCl−‐induced LPO at the initiation step. The main reaction of HOCl/OCl− with unsaturated lipid is probably the generation of chlorohydrins. However, this reaction is not accompanied by generation of free radicals and LPO. HOCl/OCl− reacts efficiently with TBARS of aldehydic nature. It is likely that the reaction proceeds without the participation of free radicals. Among the compounds of a peroxide nature (hydro‐, dialkyl‐, diacyl‐, alkyl‐acyl‐peroxide groups and epoxides) only hydroperoxides react with HOCl/OCl−. This reaction is accompanied by the production of free radicals (but not singlet oxygen), probably alkoxyl radicals, which may play a role in the initiation of HOCl/OCl−‐induced LPO.
Farnesyl: proteintransferase inhibitors as agents to inhibit tumor growth
Authors: Omer Ch. A. , Anthony N. J. , Buser‐Doepner C. A. , Burkhardt A. L. , Desolms S. J. , Dinsmore Ch. J. , Gibbs J. B. , Hartman G. D. , Koblan K. S. , Lobell R. B. , Oliff A. , Williams T. M. , Kohl N. E. 
Published: December 2008

AbstractRas, a signal‐transducing protein involved in mediating growth factor‐stimulated proliferation, is mutationally activated in over 30% of human tumors. To be functional Ras must bind to the inner surface of the plasma membrane, with post‐translational lipid modifications being necessary for this localization. The essential, first modification of Ras is farnesylation catalyzed by the enzyme farnesyl: proteintransferase (FPTase). Inhibitors of FPTase (FTIs) are currently being tested to determine if they are capable of tumor growth inhibition. Here we describe our efforts, along with those of other groups, in testing the biological and biochemical effects of FTIs.
Molecular basis of α‐tocopherol control of smooth muscle cell proliferation
Authors: Azzi Angelo , Aratri Elisabetta , Boscoboinik Daniel , Clément Sophie , Özer Nesrin K. , Ricciarelli Roberta , Spycher Stefan 
Published: December 2008

AbstractRat and human vascular smooth muscle cell proliferation is specifically sensitive to α‐tocopherol, but not β‐tocopherol. The former, but not the latter, is capable of limiting proliferation and inhibiting protein kinase C activity in a dose‐dependent manner. The phenomenon occurs at concentrations in the range 10–50 μM. β‐tocopherol addition together with α‐tocopherol, prevents both cell growth and protein kinase C inhibition. α‐tocopherol increases de novo synthesis of protein kinase C molecules. The enzyme specific activity, however, is diminished, due to a decreased phosphorylation of protein kinase C, occurring in the presence of α‐tocopherol. Experiments with protein kinase C isoform‐specific inhibitors and precipitating antibodies show that the only isoform affected by α‐tocopherol is protein kinase C‐α. The effect of α‐tocopherol is prevented by okadaic acid indicating a phosphatase of the PP2A type as responsible for protein kinase C‐α dephosphorylation produced in the presence of α‐tocopherol. At a gene level α‐tocopherol but not β‐tocopherol induces a transient activation of α‐tropomyosin gene transcription and protein expression. It is proposed that, by inhibiting protein kinase C activity via an activation of a phosphatase PP2A, α‐tocopherol controls smooth muscle cell proliferation through changes in gene expression.
d‐α‐tocopherol treatment prevents glomerular dysfunctions in diabetic rats through inhibition of protein kinase C‐diacylglycerol pathway
Authors: Koya Daisuke , Haneda Masakazu , Kikkawa Ryuichi , King George L. 
Published: December 2008

AbstractSince diabetes now accounts for 35% of all new cases of end‐stage renal disease in the United States, it is really important to prevent the onset of diabetic nephropathy. Activation of protein kinase C (PKC) is implicated to be one of the causal factors in the development of renal dysfunctions in diabetes. In this study, we have demonstrated that total diacylglycerol (DAG) contents and PKC activity in glomeruli were significantly increased in diabetic rats as compared to control rats, but intraperitoneal injection of d‐α‐tocopherol prevented these biochemical abnormalities in parallel with normalization of glomerular dysfunction such as increased glomerular filtration rate (GFR) in diabetic rats. Albuminuria in diabetic rats was also significantly increased as compared to control rats, whereas d‐α‐tocopherol treatment again ameriolated increased albuminuria in parallel with the inhibition of glomerular PKC activation by diabetes. Moreover, we have observed that the activity of DAG kinase, which metabolizes DAG to phosphatidic acid and acts as an attenuator for the DAG‐PKC pathway, was enchanced by d‐α‐tocopherol treatment. These results suggest that the increase in the DAG‐PKC pathway might play an important role for the development of glomerular dysfunctions in diabetes and d‐α‐tocopherol treatment could be helpful in diabetic nephropathy.
Developmental changes in the expression of α‐tocopherol transfer protein during the neonatal period of rat
Authors: Tamai Hiroshi , Kim Han‐Suk , Arai Hiroyuki , Inoue Keizo , Mino Makoto 
Published: December 2008

AbstractIt is well known that the cellular concentration of α‐tocopherol (α‐toc) is about 10‐fold greater than that of γtocopherol (γtoc) despite the ingestion of a large amount of γtoc in the diet. Recently, this discrimination of tocopherol is considered to be attributed to α‐tocopherol transfer protein (α‐TTP) which binds to α‐toc in preference to the other forms of tocopherol in the liver. In the present study, developmental changes in expression of α‐TTP after birth were investigated using rats with respect to plasma changes of tocopherols. The expression of α‐TTP in the neonatal rat liver, which was very low immediately after birth, increased steadily during the two weeks of life before weanling and reached the adult level at four weeks. During the suckling period, the plasma ratio of α‐toc to γtoc linearly increased, because plasma α‐toc which was low immediately after birth, increased rapidly during the period, while γtoc remained unchanged. The increase in the ratio seemed to correlate with the developmental expression of α‐TTP in the liver during this period.
Plasma membrane receptor for beta‐lactoglobulin and retinol‐binding protein in murine hybridomas
Authors: Mansouri Abdelali , Guéant Jean‐Louis , Capiaumont Josette , Pelosi Paolo , Nabet Pierre , Haertlé Thomas 
Published: December 2008

AbstractThe aim of the present work was to study the binding of [125I]‐BLGA (β‐lactoglobulin variant A) to the plasma membrane fraction of hybrid cells. This binding increased as a function of time with on‐rate and off‐rate constant at 4.47 ± 0.18× 106 M−1 min−1 and 0.17 ± 0.07 min−1, respectively (n = 3). The saturation study showed a single binding site type corresponding to a Kd at 8.26 ± 2.98 nM and 14.02 ± 2.61× 1012 sites per mg of the plasma membrane protein (n = 3). Competitive of binding BLGA was observed with BLGA, complexed with retinol and also with RBP (retinol‐binding protein). Gel filtration of [125I]‐BLGA incubated with Triton X‐100 solubilized membrane showed the formation of a ligand‐receptor complex. Cross‐linking of the tracer to plasma membrane showed a complex with a Mr at 69 kDa, suggesting a receptor M_r of 51 kDa, as seen by autoradiography of SDS‐PAGE.
Search for novel redox groups in mitochondrial NADH:ubiquinone oxidoreductase (complex I) by diode array UV/VIS spectroscopy
Authors: Schulte Ulrich , Abelmann Anke , Amling Natascha , Brors Benedikt , Friedrich Thorsten , Kintscher Lars , Rasmussen Tim , Weiss Hanns 
Published: December 2008

AbstractThe proton‐translocating NADH:ubiquinone oxidoreductase of mitochondria (complex I) is a large L‐shaped multi‐subunit complex. The peripheral matrix arm contains one FMN and a number of iron‐sulfur (FeS) clusters and is involved in NADH oxidation and electron transfer to the membrane intrinsic arm. There, following a yet unknown mechanism, the redox‐driven proton translocation and the ubiquinone reduction take place. Redox groups that would be able to link electron transfer with proton translocation have not been found so far in the membrane arm. We searched for such groups in complex I isolated from Neurospora crassa. Under anaerobic conditions, the preparation was analyzed in different redox states by means of UV/VIS and EPR spectroscopy. Absorption bands in the UV/VIS redox difference spectra were found which cannot be attributed to the FMN or the EPR detectable FeS clusters. The existence of two novel groups is postulated and their possible locations in the electron pathway and their roles in proton translocation are discussed.
The molecular structure of mitochondrial contact sites. Their role in regulation of energy metabolism and permeability transition
Authors: Brdiczka Dieter , Beutner Gisela , Rück Alexander , Dolder Max , Wallimann Theo 
Published: December 2008

AbstractContact sites between the outer and peripheral inner membrane of mitochondria are involved in protein precursor uptake and energy transfer. Hexokinase and mitochondrial creatine kinase could be attributed by different techniques to the energy transfer contacts. Kinetic analyses suggested a functional interaction between the kinases, outer membrane pore protein, and inner membrane adenylate translocator (ANT). This suggestion was strongly supported by isolation of hexokinase and creatine kinase complexes that were constituted of kinase oligomers, porin and ANT. Phospholipid vesicles carrying reconstituted kinase—porin—ANT complexes enclosed internal ATP in contrast to vesicles containing free porin only. This indicated that unspecific transport through porin was regulated by its interaction with a specific antiporter, ANT. A direct interaction between porin and ANT in the hexokinase complex conferred the reconstituted system with permeability properties reminiscent of the mitochondrial permeability transition (PT) pore. In the creatine kinase complex this interaction between porin and ANT was replaced by contact of both with the kinase octamer. Thus PT‐pore‐like functions were not observed unless the creatine kinase octamer was dissociated, suggesting that the ANT was locked in the antiporter state by interaction with the octamer. Indeed, reconstituted pure ANT showed PT‐pore‐like properties concerning Ca2+ sensitivity. However, as cyclophilin was missing, sensitivity against cyclosporin was not observed.
New light on mitochondrial calcium
Authors: Pinton Paolo , Brini Marisa , Bastianutto Carlo , Tuft Richard A. , Pozzan Tullio , Rizzuto Rosario 
Published: December 2008

AbstractThe possibility of specifically addressing recombinant probes to mitochondria is a novel, powerful way to study these organelles within living cells. We first showed that the Ca2+‐sensitive photoprotein aequorin, modified by the addition of a mitochondrial targeting sequence, allows to monitor specifically the Ca2+concentration in the mitochondrial matrix ([Ca2+]m) of living cells. With this tool, we could show that, upon physiological stimulation, mitochondria undergo a major rise in [Ca2+]m, well in the range of the Ca2+sensitivity of the matrix dehydrogenases, in a wide variety of cell types, ranging from non excitable, e.g., HeLa and CHO, and excitable, e.g., cell lines to primary cultures of various embryological origin, such as myocytes and neurons. This phenomenon, while providing an obvious mechanism for tuning mitochondrial activity to cell needs, appeared at first in striking contrast with the low affinity of mitochondrial Ca2+uptake mechanisms. Based on indirect evidence, we proposed that the mitochondria might be close to the source of the Ca2+signal and thus exposed to microdomains of high [Ca2+], hence allowing the rapid accumulation of Ca2+into the organelle. In order to verify this intriguing possibility, we followed two approaches. In the first, we constructed a novel aequorin chimera, targeted to the mitochondrial intermembrane space (MIMS), i.e., the region sensed by the low‐affinity Ca2+uptake systems of the inner mitochondrial membrane. With this probe, we observed that, upon agonist stimulation, a portion of the MIMS is exposed to saturating Ca2+concentrations, thus confirming the occurrence of microdomains of high [Ca2+] next to mitochondria. In the second approach, we directly investigated the spatial relationship of the mitochondria and the ER, the source of agonist‐releasable Ca2+in non‐excitable cells. For this purpose, we constructed GFP‐based probes of organelle structure; namely, by targeting to these organelles GFP mutants with different spectral properties, we could label them simultaneously in living cells. By using an imaging system endowed with high speed and sensitivity, which allows to obtain high‐resolution 3D images, we could demonstrate that close contacts (<80 nm) occur in vivo between mitochondria and the ER.
Acquisition of selenium tolerance by a selenium non‐accumulating Astragalus species via selection
Authors: Wang Y. , Böck A. , Neuhierl B. 
Published: December 2008

AbstractSelection of cultured cells of the selenium sensitive and non‐accumulating Astragalus cicer for tolerance to stepwise increasing concentrations of selenite in the medium lead to a variant able to grow at 75 μM selenite. The Se‐tolerant culture synthesized a selenocysteine methyltransferase immunologically related but not identical to that of the accumulating A. bisulcatus species and produced Se‐methyl‐selenocysteine in vivo. Re‐cultivation in selenium‐free medium lead to breakdown of tolerance and the disappearance of the methyltransferase from cellular proteins. The results prove that the non‐accumulating species A. cicer has the cryptic capacity for synthesis of a selenocysteine methyltransferase and also demonstrate that synthesis of the organoselenium compounds in Se‐accumulating plants are contributing to selenium tolerance.
Characteristics of the production of active oxygen species from adherent and non‐adherent neutrophils
Authors: Yoshida N. , Yoshikawa T. , Nakagawa S. , Miyajima T. , Nakamura Y. , Naito Y. , Tanigawa T. , Kondo M. 
Published: December 2008

AbstractOur objective was to evaluate the characteristics of the production of AOS from the neutrophils that had adhered to the endothelial cells, fibronectin or polystyrene, using the method of electron paramagnetic resonance (EPR) spin trapping. Neutrophils and endothelial cells were isolated from human venous blood and umbilical veins, respectively. AOS production from neutrophils was not elicited only by adhesion. The stimulation of adherent neutrophils with phorbol myristate acetate (PMA) induced the production of AOS. The production of AOS from adherent neutrophils to endothelial cells, but not to fibronectin or polystyrene, decreased with the interval time between the adhesion and the stimulation by PMA. The amount of AOS produced by the neutrophils adherent to fibronectin or polystyrene was maintained for one hour after stimulation with PMA, whereas that by suspended neutrophils gradually decreased with the time after stimulation.Results indicate that adherent and non‐adherent neutrophils exhibit differing time course of AOS production.