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Chelator
Kinds of Chelator Selected AbstractsSpectral Properties of Pro-multimodal Imaging Agents Derived from a NIR Dye and a Metal ChelatorPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2005Zongren Zhang ABSTRACT Monomolecular multimodal imaging agents (MOMIAs) are able to provide complementary diagnostic information of a target diseased tissue. We developed a convenient solid-phase approach to construct two pro-MOMIAs (before incorporating radiometal) derived from 1,4,7,10-tetraazacy-clododecane-1,4,7,10-tetraacetic acid (DOTA) and cypate, a near-infrared (NIR) fluorescent dye analogous to indocyanine green (ICG). The possible interaction between d orbitals of transition metal DOTA complexes or free metals and the p orbitals of cypate chromophore could quench the fluorescence of pro-MOMIAs. However, we did not observe significant changes in the spectral properties of cypate upon conjugation with DOTA and subsequent chelation with metals. The fluorescence intensity of the chelated and nonmetal-chelated PRO-MOMIAs remained fairly the same in dilute 20% aqueous dimethylsulfoxide (DMSO) solution (1 × 10,6M). Significant reduction in the fluorescence intensity of pro-MOMIAs occurred in the presence of a large excess of metal ions (> 1 molar ratio for indium and 20-fold for a copper relative to pro-MOMIA). This study suggests the feasibility of using MOMIAs for combined optical and radioisotope imaging. [source] Imparting Multivalency to a Bifunctional Chelator: A Scaffold Design for Targeted PET Imaging Probes,ANGEWANDTE CHEMIE, Issue 40 2009Wei Liu Zwei sind besser als einer: Mehrbindige Gerüste für Imaging-Sonden für die zielgerichtete Positronenemissionstomographie enthalten Chelatliganden, die stabile, neutrale Komplexe mit Radiometallen bilden und funktionelle Gruppen zum Anbringen mehrerer Targeting-Moleküle tragen. Die Synthese eines zweibindigen Gerüsts und dessen Kupplung mit einem Targeting-Liganden ergab eine Sonde, mit deren Hilfe sich effizient Tumoren in vivo abbilden lassen (siehe Bild). [source] Efficient stabilization of bulk fish oil rich in long-chain polyunsaturated fatty acidsEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 4 2008Stephan Drusch Abstract The aim of the present study was to systematically investigate the possibilities of stabilizing a bulk oil rich in long-chain polyunsaturated fatty acids under ambient conditions. Combinations of different antioxidants (,-, ,- and/or ,-tocopherol, rosmarinic acid and rosemary extract rich in carnosic acid) as well as lecithin and citric acid were systematically investigated. Efficient stabilization was achieved by choosing a combination of tocopherols rich in ,- or ,-tocopherol and low in ,-tocopherol, by including tocopherol-sparing synergists like ascorbyl palmitate and carnosic acid from rosemary extract and metal-chelating agents. For carnosic acid, a concentration of 400,mg/kg oil provides sufficient protection; the concentration of the metal chelator should be adapted to the concentration of metal ions present in the oil. As an alternative ingredient with metal-chelating and tocopherol-sparing activity, lecithin may be included in the formulation, but its poor solubility in bulk oils limits its use. [source] Influence of calcium on the proteolytic degradation of the calmodulin-like skin protein (calmodulin-like protein 5) in psoriatic epidermisEXPERIMENTAL DERMATOLOGY, Issue 6 2006Bruno Méhul Abstract:, The calmodulin-like skin protein (CLSP) or so-called calmodulin-like protein 5, a recently discovered skin-specific calcium-binding protein, is closely related to keratinocyte differentiation. The 16-kDa protein is proteolytically degraded in the upper layers of the stratum corneum (SC) of healthy skin. With the use of specific new monoclonal antibodies to CLSP, we were able to demonstrate that the abnormal elevated levels of CLSP, characteristic of psoriatic epidermis, were probably not due to an overexpression of the protein, but most likely the result of its non-degradation. Further in vitro experiments using recombinant CLSP and in situ data clearly showed that calcium protected and chelator accelerated CLSP degradation. These data indicate that CLSP degradation in the SC of psoriatic skin might be hindered by the abnormally elevated calcium concentration. No degradation of CLSP in psoriatic epidermis keeping its ability to bind protein as transglutaminase 3 may have a physiological role in skin diseases such as psoriasis. [source] Stimulation of fibroblast proliferation by neokyotorphin requires Ca2+ influx and activation of PKA, CaMK II and MAPK/ERKFEBS JOURNAL, Issue 2 2007Olga V. Sazonova Neokyotorphin [TSKYR, hemoglobin ,-chain fragment (137,141)] has previously been shown to enhance fibroblast proliferation, its effect depending on cell density and serum level. Here we show the dependence of the effect of neokyotorphin on cell type and its correlation with the effect of protein kinase A (PKA) activator 8-Br-cAMP, but not the PKC activator 4,-phorbol 12-myristate, 13-acetate (PMA). In L929 fibroblasts, the proliferative effect of neokyotorphin was suppressed by the Ca2+L -type channel inhibitors verapamil or nifedipine, the intracellular Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane- N,N,N,,N, - tetraacetic acid acetoxymethyl ester, kinase inhibitors H-89 (PKA), KN-62 (Ca2+/calmodulin-dependent kinase II) and PD98059 (mitogen-activated protein kinase). The proliferative effect of 8-Br-cAMP was also suppressed by KN-62 and PD98059. PKC suppression (downregulation with PMA or inhibition with bisindolylmaleimide XI) did not affect neokyotorphin action. The results obtained point to a cAMP-like action for neokyotorphin. [source] Characterization of depolarization and repolarization phases of mitochondrial membrane potential fluctuations induced by tetramethylrhodamine methyl ester photoactivationFEBS JOURNAL, Issue 7 2005Angela M. Falchi Depolarization and repolarization phases (D and R phases, respectively) of mitochondrial potential fluctuations induced by photoactivation of the fluorescent probe tetramethylrhodamine methyl ester (TMRM) were analyzed separately and investigated using specific inhibitors and substrates. The frequency of R phases was significantly inhibited by oligomycin and aurovertin (mitochondrial ATP synthase inhibitors), rotenone (mitochondrial complex I inhibitor) and iodoacetic acid (inhibitor of the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase). Succinic acid (mitochondrial complex II substrate, given in the permeable form of dimethyl ester) abolished the rotenone-induced inhibition of R phases. Taken together, these findings indicate that the activity of both respiratory chain and ATP synthase were required for the recovery of the mitochondrial potential. The frequency of D phases prevailed over that of R phases in all experimental conditions, resulting in a progressive depolarization of mitochondria accompanied by NAD(P)H oxidation and Ca2+ influx. D phases were not blocked by cyclosporin A (inhibitor of the permeability transition pore) or o -phenyl-EGTA (a Ca2+ chelator), suggesting that the permeability transition pore was not involved in mitochondrial potential fluctuations. [source] Iron-mediated suppression of bloom-forming cyanobacteria by oxine in a eutrophic lakeFRESHWATER BIOLOGY, Issue 5 2010LEWIS A. MOLOT Summary 1. Published studies show that cyanobacteria have higher Fe requirements than eukaryotic algae. To test whether Fe availability can affect formation of a cyanobacterial bloom, a strong Fe chelator, oxine (8-hydroxyquinoline, C9H7NO), was added to enclosures in eutrophic Lake 227 in the Experimental Lakes Area (ELA) (northwestern Ontario). 2. Aphanizomenon schindlerii growth was suppressed, and growth of eukaryotic chlorophytes significantly promoted in enclosures to which oxine had been added. Significant eukaryotic growth did not occur in enclosures treated with ammonium, suggesting that N supplied by degradation of oxine was not responsible for eukaryotic success in the oxine enclosures. 3. In situ Fe2+ measurements were unreliable because of interference from high concentrations of dissolved organic compounds. However, oxine rapidly promoted oxidation of Fe2+ to Fe3+ in deionised water, suggesting that rapid removal of Fe2+ also occurred in the oxine-treated enclosures. 4. In batch cultures, 10 ,m Fe and 10 ,m oxine (a 1 : 1 ratio) completely inhibited the growth of the cyanobacteria Synechococcus sp. and Anabaena flos-aquae and the chlorophytes Pseudokirchneriella subcapitata and Scenedesmus quadricauda. Increasing Fe 10-fold to 100 ,m Fe completely and partially reversed oxine inhibition in the two chlorophytes but could not overcome inhibition of the cyanobacteria, indicating that inhibition was Fe-mediated at least in the eukaryotes. Since oxine binds Fe3+ in a 1 : 3 ratio (Fe : oxine), inhibition at a 1 : 1 ratio indicates that not all of the Fe is bound, and a mechanism involving Fe other than chelation was at least partly responsible for inhibition. 5. Collectively, the enclosure and laboratory results suggest that the outcome of competition between cyanobacteria and eukaryotic algae in the oxine-treated enclosures in Lake 227 was likely a result of decreased availability of Fe, especially Fe2+. 6. The results suggest that remediation methods that dramatically restrict the supply rate of Fe2+ could reduce the relative abundance of cyanobacteria in eutrophic systems. [source] Cellular iron status influences the functional relationship between microglia and oligodendrocytesGLIA, Issue 8 2006X. Zhang Abstract Previously, we have reported that there is a spatiotemporal relationship between iron accumulation in microglia and oligodendrocytes during normal development and in remyelination following injury. This in vivo observation has prompted us to develop a cell culture model to test the relationship between iron status of microglia and survival of oligodendrocytes. We found that conditioned media from iron-loaded microglia increases the survival of oligodendrocytes; but conditioned media from iron loaded activated microglia is toxic to oligodendrocytes. In the trophic condition, one of the proteins released by iron-loaded microglia is H-ferritin, and transfecting the microglia with siRNA for H-ferritin blocks the trophic response on oligodendrocytes. Lipopolysaccharide (LPS) activation decreases the amount of H-ferritin that is released from microglia and increases the release of the proinflammatory cytokines tumor necrosis factor-, and interleukin-1. LPS activation of iron-enriched microglia results in the activation of NF-kB and greater release of cytokines when compared with that of control microglia; whereas treating microglia with an iron chelator is associated with less NF-kB activation and less release of cytokines. These results indicate that microglia play an important role in iron homoeostasis and that their iron status can influence how microglia influence growth and survival of oligodendrocytes. The results further indicate that ferritin, released by microglia, is a significant source of iron for oligodendrocytes. © 2006 Wiley-Liss, Inc. [source] Chlorotoxin-sensitive Ca2+ -activated Cl, channel in type R2 reactive astrocytes from adult rat brainGLIA, Issue 4 2003Stanislava Dalton Abstract Astrocytes express four types of Cl, or anion channels, but Ca2+ -activated Cl, (ClCa) channels have not been described. We studied Cl, channels in a morphologically distinct subpopulation (, 5% of cells) of small (10,12 ,m, 11.8 ± 0.6 pF), phase-dark, GFAP-positive native reactive astrocytes (NRAs) freshly isolated from injured adult rat brains. Their resting potential, ,57.1 ± 4.0 mV, polarized to ,72.7 ± 4.5 mV with BAPTA-AM, an intracellular Ca2+ chelator, and depolarized to ,30.7 ± 6.1 mV with thapsigargin, which mobilizes Ca2+ from intracellular stores. With nystatin-perforated patch clamp, thapsigargin activated a current that reversed near the Cl, reversal potential, which was blocked by Cl, channel blockers, 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB) and Zn2+, by I, (10 mM), and by chlorotoxin (EC50 = 47 nM). With conventional whole-cell clamp, NPPB- and Zn2+ -sensitive currents became larger with increasing [Ca2+]i (10, 150, 300 nM). Single-channel recordings of inside-out patches confirmed Ca2+ sensitivity of the channel and showed open-state conductances of 40, 80, 130, and 180 pS, and outside-out patches confirmed sensitivity to chlorotoxin. In primary culture, small phase-dark NRAs developed into small GFAP-positive bipolar cells with chlorotoxin-sensitive ClCa channels. Imaging with biotinylated chlorotoxin confirmed the presence of label in GFAP-positive cells from regions of brain injury, but not from uninjured brain. Chlorotoxin-tagged cells isolated by flow cytometry and cultured up to two passages exhibit positive labeling for GFAP and vimentin, but not for prolyl 4-hydroxylase (fibroblast), A2B5 (O2A progenitor), or OX-42 (microglia). Expression of a novel chlorotoxin-sensitive ClCa channel in a morphologically distinct subpopulation of NRAs distinguishes these cells as a new subtype of reactive astrocyte. GLIA 42:325,339, 2003. © 2003 Wiley-Liss, Inc. [source] Cold-induced apoptosis of rat liver cells in University of Wisconsin solution: The central role of chelatable ironHEPATOLOGY, Issue 3 2002Uta Kerkweg Although University of Wisconsin (UW) solution aims at the prevention of cold-induced cell injury, it failed to protect against cold-induced apoptosis of hepatocytes and liver endothelial cells: when incubated in UW solution at 4°C for 24 hours and subsequently rewarmed at 37°C, 72% ± 8% of rat hepatocytes and 81% ± 5% of liver endothelial cells lost viability. In both cell types, the observed cell damage occurred under an apoptotic morphology; it appeared to be mediated by a rapid increase in the cellular chelatable iron pool by a factor ,2 (as determined in hepatocytes) and subsequent formation of reactive oxygen species (ROS). Consequently, this cell injury was decreased by iron chelators to 6 to 25% (hepatocytes) and 4% ± 2% (liver endothelial cells). Deferoxamine nearly completely inhibited the occurrence of apoptotic morphology in both cell types. In liver endothelial cells, cold-induced apoptosis occurring during rewarming after 24 hours of cold incubation in UW solution was far more pronounced than in cell culture medium (loss of viability: 81% ± 5% vs. 28% ± 13%), but viability could even be maintained for 2 weeks of cold incubation by use of deferoxamine. In conclusion, this pathological mechanism might be an explanation for the strong endothelial cell injury known to occur after cold preservation. With regard to the extent of this iron-mediated injury, addition of a suitable iron chelator to UW solution might markedly improve the outcome of liver preservation. [source] Critical Role of Reactive Oxygen Species and Mitochondrial Permeability Transition in Microcystin-Induced Rapid Apoptosis in Rat HepatocytesHEPATOLOGY, Issue 3 2000Wen-Xing Ding Microcystin-LR (M-LR) is a specific hepatotoxin. At present, the exact toxic mechanism of its action remains unclear though apoptosis is believed to be involved. This study was designed to investigate the role of reactive oxygen species (ROS) and mitochondrial permeability transition (MPT) in the M-LR,induced apoptotic process. Morphologic changes such as cell shrinkage, externalization of cell membrane phosphatidylserine, DNA fragmentation, and nuclear condensation suggest that M-LR causes rapid apoptosis in hepatocytes. Confocal microscopy revealed that M-LR exposure led to the onset of MPT and mitochondrial depolarization, evidenced by (1) redistribution of calcein fluorescence from cytosol to mitochondria, and (2) loss of mitochondrial tetramethyrhodamine methyl ester (TMRM) fluorescence; both occurred before apoptosis. Moreover, there was a significant and rapid increase of ROS level before the onset of MPT and loss of MMP, indicating a critical role of ROS in M-LR,induced apoptosis. Deferoxamine (DFO), an iron chelator, prevented the increase of ROS production, delayed the onset of MPT, and, subsequently, cell death. In addition, a specific MPT inhibitor, cyclosporin A (CsA), blocked the M-LR,induced ROS formation, onset of MPT, and mitochondrial depolarization as well as cell death. Thus, we conclude that the M-LR,induced ROS formation leads to the onset of MPT and apoptosis. [source] Anti-Fenton reaction activity of three taxa of water yam (Dioscorea alata L.)INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 9 2007Tsu-Shing Wang Summary In the present study, we compared the anti-Fenton reaction activity of three taxa of water yam (Dioscorea alata L.): DS2, TN2 and PSY [D. alata L. var. purpurea (Roxb.) M. Pouch]. Anti-Fenton reaction activity was evaluated by measuring the damage inflicted on calf thymus DNA by copper ions combined with hydrogen peroxide with the use of an ethidium bromide binding assay and agarose gel electrophoresis. We found that extracts of tuber pulp from all three taxa of yam had significant anti-Fenton reaction activity. The protection pattern of the three tuber pulp extracts was similar to that of EDTA, a typical divalent metal ion chelator, which displayed a significant protection lag-phase. With the use of thin-layer chromatography, we found that a common, major ansialdehyde-sulphuric acid stained spot (possibly a polysaccharide mucilage) with an Rf of 0.09 may be the most likely contributor to the anti-Fenton reaction activities of the yam tuber extracts investigated. The present study identifies the mechanism of the health benefit of the Dioscorea family. The copper-chelating and absorbing capability of yam tuber pulp extracts may be useful in functional screening. [source] Desorption of zinc by extracellularly produced metabolites of Trichoderma harzianum, Trichoderma reesei and Coriolus versicolorJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2007P. Adams Abstract Aims:, To determine the role of fungal metabolites in the desorption of metals. Methods and Results:, Desorption of Zn from charcoal by three different fungi was compared against metal desorption with reverse osmosis water, a 0·1% Tween 80 solution and a 0·1 mol l,1 CaCl2 solution. All three fungal filtrates desorbed three times more Zn than either 0·1% Tween 80 or 0·1 mol l,1 CaCl2. Metal chelator production in Trichoderma harzianum and Coriolus versicolor was constitutively expressed while chelator production in Trichoderma reesei was induced by Zn. The presence of Zn inhibited the production of metal chelators by C. versicolor. Only C. versicolor was found to produce oxalic acid (a strong metal chelator). All fungi caused a marked decrease in pH, although this was not enough to explain the increased desorption of the metals by the different fungal filtrates. Conclusions:, Metal chelation via organic acids and proteins are the main mechanisms by which the fungal filtrates increase zinc desorption. Significance and Impact of the Study:, The results of this study explain why plants inoculated with T. harzianum T22 take up more metal from soil, than noninoculated plants while metabolites produced by fungi could be used for metal leaching from contaminated soils. [source] Haematological, hepatic and renal alterations after repeated oral or intraperitoneal administration of monoisoamyl DMSA.JOURNAL OF APPLIED TOXICOLOGY, Issue 6 2002Abstract Monoisoamyl 2,3-dimercaptosuccinic acid (MiADMSA), a vicinal thiol chelator, is gaining recognition recently as a better chelator than meso 2,3-dimercaptosuccinic acid (DMSA) in decreasing heavy metal burden in tissues because of its lipophilic character. There is, however, little information available on the toxicological properties of this chelator after repeated administration in animals. In the present study, we investigated the dose-dependent effect of MiADMSA on various biochemical parameters suggestive of alterations in haem biosynthesis and hepatic, renal and brain oxidative stress after 21 days of repeated intraperitoneal (i.p.) or oral (p.o.) administration to rats. The concentration of essential metals in blood and soft tissues was determined along with histopathological observations of hepatic and renal tissues. The results suggest that MiADMSA administration had no effect on blood ,-aminolevulinic acid dehydratase activity. However, an increase in zinc protoporphyrin and a decrease in haemoglobin levels were noted in animals given MiADMSA i.p. A moderate increase in serum alkaline phosphatase suggested mild hepatotoxicity at the highest dose (100 mg kg,1, i.p.). This was confirmed by histopathological examinations, which identified basophilic stippling, granulation of the cytoplasm, haemorrhage and congestion. At the highest dose, levels of hepatic thiobarbituric acid reactive substance and oxidized glutathione were increased above those of control values. Levels of hepatic reduced glutathione were decreased. Taken together, these observations point to oxidative stress. In animals administered MiADMSA i.p. there was an increase in the brain malondialdehyde levels at the two higher doses (50 and 100 mg kg,1). Essential metal status revealed a significant effect of MiADMSA (p.o.) in increasing blood zinc while significantly decreasing the kidney zinc level. The most significant adverse effect of MiADMSA was on copper concentration, which showed significant depletion from almost all major organs. Magnesium levels in blood decreased but increased in liver of MiADMSA-administered rats. Histopathological observations of liver and kidneys suggest few moderate lesions. It can be concluded that repeated administration of MiADMSA is compromised with some mild toxic effect, particularly the loss of copper. The effects during oral administration are comparatively less pronounced than by the i.p. route. Copyright © 2002 John Wiley & Sons, Ltd. [source] Basic Fibroblast Growth Factor Stimulates Vascular Endothelial Growth Factor Release in Osteoblasts: Divergent Regulation by p42/p44 Mitogen-Activated Protein Kinase and p38 Mitogen-Activated Protein KinaseJOURNAL OF BONE AND MINERAL RESEARCH, Issue 12 2000Haruhiko Tokuda Abstract We previously showed that basic fibroblast growth factor (bFGF) activates p38 mitogen-activated protein (MAP) kinase via Ca2+ mobilization, resulting in interleukin-6 (IL-6) synthesis in osteoblast-like MC3T3-E1 cells. In the present study, we investigated the effect of bFGF on the release of vascular endothelial growth factor (VEGF) in these cells. bFGF stimulated VEGF release dose dependently in the range between 10 and 100 ng/ml. SB203580, an inhibitor of p38 MAP kinase, markedly enhanced the bFGF-induced VEGF release. bFGF induced the phosphorylation of both p42/p44 MAP kinase and p38 MAP kinase. PD98059, an inhibitor of upstream kinase of p42/p44 MAP kinase, reduced the VEGF release. SB203580 enhanced the phosphorylation of p42/p44 MAP kinase induced by bFGF. The enhancement by SB203580 of the bFGF-stimulated VEGF release was suppressed by PD98059. The depletion of extracellular Ca2+ by [ethylenebis-(oxyethylenenitrilo)]tetracetic acid (EGTA) or 1,2-bis-(O -aminophinoxy)-ethane- N,N,N,N -tetracetic acid tetracetoxymethyl ester (BAPTA/AM), a chelator of intracellular Ca2+, suppressed the bFGF-induced VEGF release. A23187, a Ca ionophore, or thapsigargin, known to induce Ca2+ release from intracellular Ca2+ store, stimulated the release of VEGF by itself. A23187 induced the phosphorylation of p42/p44 MAP kinase and p38 MAP kinase. PD98059 suppressed the VEGF release induced by A23187. SB203580 had little effect on either A23187-induced VEGF release or the phosphorylation of p42/p44 MAP kinase by A23187. These results strongly suggest that bFGF stimulates VEGF release through p42/p44 MAP kinase in osteoblasts and that the VEGF release is negatively regulated by bFGF-activated p38 MAP kinase. [source] Role of calcium and ROS in cell death induced by polyunsaturated fatty acids in murine thymocytesJOURNAL OF CELLULAR PHYSIOLOGY, Issue 3 2010Aparna Prasad We investigated the mechanisms whereby omega-3 and -6 polyunsaturated fatty acids (PUFAs) cause cell death of mouse thymocytes using flow cytometry, focusing on the respective roles of intracellular calcium concentration, [Ca2+]i and reactive oxygen species (ROS). We applied the C-22, 20, and 18 carbon omega-3 (DHA, EPA, ALA) and omega-6 (DTA, ARA, and LNA) fatty acids to isolated thymocytes and monitored cell death using the DNA-binding dye, propidium iodide. When applied at 20,µM concentration, omega-3 fatty acids killed thymocytes over a period of 1,h with a potency of DHA,>,EPA,>,ALA. The omega-6 PUFAs were more potent. The C18 omega-6 fatty acid, LNA, was the most potent, followed by DHA and ARA. Cell death was always accompanied by an increase in the levels of [Ca2+]i and ROS. Both increases were in proportion to the potency of the PUFAs in inducing cell death. Removing extracellular calcium did not prevent the elevation in [Ca2+]i nor cell death. However, the intracellular calcium chelator, BAPTA, almost totally reduced both the elevation in [Ca2+]i and cell death, while vitamin E reduced the elevation in ROS and cell death. BAPTA also prevented the elevation in ROS, but vitamin E did not prevent the elevation in [Ca2+]i. Thapsigargin, which depletes endoplasmic reticulum calcium, blocked the elevation in [Ca2+]i, but CCCP, a mitochondrial calcium uptake inhibitor, did not. These results suggest that the six PUFAs we studied kill thymocytes by causing release of calcium from endoplasmic reticulum, which causes release of ROS from mitochondria which leads to cell death. J. Cell. Physiol. 225: 829,836, 2010. © 2010 Wiley-Liss, Inc. [source] Integrating laccase,mediator treatment into an industrial-type sequence for totally chlorine-free bleaching of eucalypt kraft pulpJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2006David Ibarra Abstract Enzymatic delignification using the high-redox potential thermostable laccase from the fungus Pycnoporus cinnabarinus and a chemical mediator (1-hydroxybenzotriazole) was investigated to improve totally chlorine-free (TCF) bleaching of Eucalyptus globulus kraft pulps. Different points of incorporation of the enzyme treatment into an industrial-type bleaching sequence (consisting of double oxygen, chelation and peroxide stages) were investigated in pressurized laboratory reactors. The best final pulp properties were obtained using an OOLQPoP sequence, where a laccase,mediator stage (L) was incorporated between double oxygen and chelation. The worse results, when the enzymatic and chelation treatments were combined in a unique stage, seemed related to partial inhibition of laccase-mediator activity by the chelator. The new TCF sequence including the laccase stage permitted to improve eucalypt pulp delignification to values around kappa 5 (hexenuronic acid contribution over 50%) compared to kappa 7 using only TCF chemical reagents. In a similar way, the final brightness obtained, over 91% ISO, was 3,4 points higher than that obtained in the chemical sequences. Although technical and economic issues are to be solved, the results obtained show the feasibility of integrating a laccase,mediator treatment into a TCF sequence for bleaching eucalypt kraft pulp. Copyright © 2006 Society of Chemical Industry [source] LISTERIA MONOCYTOGENES AND ESCHERICHIA COLI O157:H7 INHIBITION IN VITRO BY LIPOSOME-ENCAPSULATED NISIN AND ETHYLENE DIAMINETETRAACETIC ACIDJOURNAL OF FOOD SAFETY, Issue 2 2008T. MATTHEW TAYLOR ABSTRACT Encapsulation technologies that effectively reduce antimicrobial interaction with food components or protect antimicrobial compounds from food processing measures have the potential to improve the microbiological safety of ready-to-eat foods. Recent application of liposomes for the preservation of cheese has spurred research into their utility in other food matrices. To ascertain the feasibility of encapsulated antimicrobial for the control of Listeria monocytogenes and Escherichia coli O157:H7 growth in a model system, nisin (5.0 and 10.0 µg/mL) and the chelator ethylene diaminetetraacetic acid were entrapped in phospholipid liposomes. While phosphatidylcholine (PC) liposomes did not produce significant inhibition of target pathogens, PC/phosphatidylglycerol 8/2 and 6/4 (mol%) produced significant inhibition of pathogens. Near-complete inhibition of E. coli O157:H7 with liposomal antimicrobials at concentrations below those reported necessary for unencapsulated antimicrobial and chelator suggests that liposomes may represent a powerful technology for the encapsulation of antimicrobials and the control of foodborne pathogens. PRACTICAL APPLICATIONS The activity of many antimicrobials is abolished in many food products for a variety of reasons. Interference and cross-reactions of the antimicrobial and various food constituents, such as protein and fat, are difficult to overcome and often require large amounts of antimicrobial in order to gain significant reductions in the pathogen load in a product. Loss of solubility of some antimicrobials based on pH or ionic strength will negatively affect the antimicrobial potential of a compound like nisin. Liposome encapsulation technologies, such as that reported here, may allow for the maintenance of antimicrobial activity by protecting the antimicrobial against cross-reactions with food components. Additionally, the liposome core represents a microenvironment which can be manipulated by the manufacturer in order to preserve optimal antimicrobial solubility and stability conditions until the time of release. [source] A pyrazolylamine-phosphonate monoester chelator for the fac -[M(CO)3]+ core (M = Re, 99mTc): synthesis, coordination properties and biological assessmentJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 13 2007Elisa Palma Abstract Aiming to develop new strategies for the labeling of hydroxyl-containing biomolecules with the organometallic core fac -[99mTc(CO)3]+, we have prepared a new model bifunctional chelator, L4 (ethyl hydrogen (2-{[2-(3,5-dimethyl-1H -pyrazol-1-yl)ethyl]amino}ethyl)phosphonate), combining a pyrazolyl-amine chelating group and a monophosphonate ethyl ester function (,P(O)OHOEt). The phosphonate group allows metal stabilization, and, simultaneously, can be considered as a potential attachment site for a biomolecule. Reaction of L4 with the precursor [99mTc(H2O)3(CO)3]+ gave the model radiocomplex [99mTc(CO)3(k3 -L4)] (6a). This radiocomplex was identified by comparing its chromatographic profile with that of the corresponding Re analog (6) under the same conditions, also prepared and fully characterized by the usual analytical techniques. Radiocomplex 6a is moderately lipophilic (log Po/w = 1.07), presenting high stability in vitro without any measurable decomposition or ligand exchange, even in the presence of strong competing chelators such as histidine and cysteine (37°C, 24 h). Biodistribution studies of the complex in CD-1 mice indicated a rapid blood clearance, and a rapid clearance from main organs, occurring primarily through the hepatobiliary pathway. Complex 6a presents also a high robustness in vivo, demonstrated by its resistance to metabolic degradation in blood, and intact excretion into the urine, after RP-HPLC analysis of blood and urine samples. Copyright © 2007 John Wiley & Sons, Ltd. [source] Synthesis and evaluation of a water-soluble polymer to reduce Ac-225 daughter migrationJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 2 2007Jonathan Fitzsimmons Abstract The actinium decay chain has been promoted as an in vivo alpha generator for therapy, but migration of daughters from the primary conjugate has lead to increased toxicity away from the target organ. To reduce daughter migration, polyethylenimine (PEI) was used with a primary chelator and secondary chelators. The primary chelator, DOTA, was used to coordinate 225Actinium and secondary chelators-acetate and DTPA, were added to the polymer for coordination of daughters formed by decay. The 225Actinium polymer derivatives containing secondary chelators were found to retain radioactive daughters better than the 225Actinium bond to the primary alone. The retention of 213Bismuth and 209Thallium had the following order from highest retained to lowest DOTA-PEI-DTPA,DOTA-PEI-CH2OO- > DOTA-PEI. The data suggests this polymer approach could be used to reduce daughter migration and has potential for development of actinium labeled radiopharmaceuticals. Copyright © 2007 John Wiley & Sons, Ltd. [source] Self-assembly and recrystallization of bacterial S-layer proteins at silicon supports imaged in real time by atomic force microscopyJOURNAL OF MICROSCOPY, Issue 3 2003E. S. Györvary Summary The self-assembly of bacterial surface-layer (S-layer) proteins (SbpA of Bacillus sphaericus CCM 2177) at silicon supports (hydrophobic, non-plasma-treated and hydrophilic, O2 plasma-treated silicon supports) was imaged in real time by atomic force microscopy (AFM). A closed mosaic layer consisting of small crystals (less than 200 nm in diameter) was formed at a hydrophobic silicon support, whereas a coherent crystalline lattice consisting of large domains (2,10 µm in size) was generated at O2 plasma-treated, hydrophilic silicon wafers. The structure of the formed layers was a monolayer (9 nm in height) at the hydrophobic silicon and a bilayer (15 nm in height) at the hydrophilic silicon. In situ AFM measurements confirmed the importance of ionic bonds in the formation of crystalline SbpA layers at silicon supports. Rupture of the protein subunits with a metal chelator from the crystalline lattice of SbpA was visualized in situ by AFM. The stability of solid-supported SbpA layers could be enhanced by cross-linking the S-layers with amino,amino or amino,carboxyl group directed cross-linkers. [source] Manganese chelation therapy extends survival in a mouse model of M1000 prion diseaseJOURNAL OF NEUROCHEMISTRY, Issue 2 2010Marcus W. Brazier J. Neurochem. (2010) 114, 440,451. Abstract Previous in vitro and in vivo investigations have suggested manganese (Mn2+) may play a role in pathogenesis through facilitating refolding of the normal cellular form of the prion protein into protease resistant, pathogenic isoforms (PrPSc), as well as the subsequent promotion of higher order aggregation of these abnormal conformers. To further explore the role of Mn2+ in pathogenesis, we undertook a number of studies, including an assessment of the disease modifying effects of chelation therapy in a well-characterized mouse model of prion disease. The di-sodium, calcium derivative of the chelator, cyclohexanediaminetetraacetic acid (Na2CaCDTA), was administered intraperitoneally to mice inoculated intra-cerebrally with either high or low-dose inocula, with treatment beginning early (shortly after inoculation) or late (at the usual mid-survival point of untreated mice). Analyses by inductively coupled plasma-mass spectrometry demonstrated brain Mn2+ levels were selectively reduced by up to 50% in treated mice compared with untreated controls, with copper, iron, zinc and cobalt levels unchanged. In mice administered high-dose inocula, none of the treatment groups displayed an increase in survival although western blot analyses of early intensively treated mice showed reduced brain PrPSc levels; mice infected using low-dose inocula however, showed a significant prolongation of survival (p = 0.002). Although our findings support a role for Mn2+ in prion disease, further studies are required to more precisely delineate the extent of pathogenic involvement. [source] Calcium in the mechanism of ammonia-induced astrocyte swellingJOURNAL OF NEUROCHEMISTRY, Issue 2009Arumugam R. Jayakumar Abstract Brain edema, due largely to astrocyte swelling, is an important clinical problem in patients with acute liver failure. While mechanisms underlying astrocyte swelling in this condition are not fully understood, ammonia and associated oxidative/nitrosative stress appear to be involved. Mechanisms responsible for the increase in reactive oxygen/nitrogen species (RONS) and their role in ammonia-induced astrocyte swelling, however, are poorly understood. Recent studies have demonstrated a transient increase in intracellular Ca2+ in cultured astrocytes exposed to ammonia. As Ca2+ is a known inducer of RONS, we investigated potential mechanisms by which Ca2+ may be responsible for the production of RONS and cell swelling in cultured astrocytes after treatment with ammonia. Exposure of cultured astrocytes to ammonia (5 mM) increased the formation of free radicals, including nitric oxide, and such increase was significantly diminished by treatment with the Ca2+ chelator 1,2-bis-(o -aminophenoxy)-ethane- N,N,- N,,N, -tetraacetic acid tetraacetoxy-methyl ester (BAPTA). We then examined the activity of Ca2+ -dependent enzymes that are known to generate RONS and found that ammonia significantly increased the activities of NADPH oxidase (NOX), constitutive nitric oxide synthase (cNOS), and phospholipase A2 (PLA2) and such increases in activity were significantly diminished by BAPTA. Pre-treatment of cultures with 7-nitroindazole, apocyanin, and quinacrine, respective inhibitors of cNOS, NOX, and PLA2, all significantly diminished RONS production. Additionally, treatment of cultures with BAPTA or with inhibitors of cNOS, NOX, and PLA2 reduced ammonia-induced astrocyte swelling. These studies suggest that the ammonia-induced rise in intracellular Ca2+ activates free radical producing enzymes that ultimately contribute to the mechanism of astrocyte swelling. [source] Glutamate receptors modulate sodium-dependent and calcium-independent vitamin C bidirectional transport in cultured avian retinal cellsJOURNAL OF NEUROCHEMISTRY, Issue 2 2009Camila Cabral Portugal Abstract Vitamin C is transported in the brain by sodium vitamin C co-transporter 2 (SVCT-2) for ascorbate and glucose transporters for dehydroascorbate. Here we have studied the expression of SVCT-2 and the uptake and release of [14C] ascorbate in chick retinal cells. SVCT-2 immunoreactivity was detected in rat and chick retina, specially in amacrine cells and in cells in the ganglion cell layer. Accordingly, SVCT-2 was expressed in cultured retinal neurons, but not in glial cells. [14C] ascorbate uptake was saturable and inhibited by sulfinpyrazone or sodium-free medium, but not by treatments that inhibit dehydroascorbate transport. Glutamate-stimulated vitamin C release was not inhibited by the glutamate transport inhibitor l -,-threo-benzylaspartate, indicating that vitamin C release was not mediated by glutamate uptake. Also, ascorbate had no effect on [3H] d -aspartate release, ruling out a glutamate/ascorbate exchange mechanism. 2-Carboxy-3-carboxymethyl-4-isopropenylpyrrolidine (Kainate) or NMDA stimulated the release, effects blocked by their respective antagonists 6,7-initroquinoxaline-2,3-dione (DNQX) or (5R,2S)-(1)-5-methyl-10,11-dihydro-5H -dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (MK-801). However, DNQX, but not MK-801 or 2-amino-5-phosphonopentanoic acid (APV), blocked the stimulation by glutamate. Interestingly, DNQX prevented the stimulation by NMDA, suggesting that the effect of NMDA was mediated by glutamate release and stimulation of non-NMDA receptors. The effect of glutamate was neither dependent on external calcium nor inhibited by 1,2-bis (2-aminophenoxy) ethane-N,,N,,N,,N,,-tetraacetic acid tetrakis (acetoxy-methyl ester) (BAPTA-AM), an internal calcium chelator, but was inhibited by sulfinpyrazone or by the absence of sodium. In conclusion, retinal cells take up and release vitamin C, probably through SVCT-2, and the release can be stimulated by NMDA or non-NMDA glutamate receptors. [source] Response of extracelluar zinc in the ventral hippocampus against novelty stressJOURNAL OF NEUROCHEMISTRY, Issue 2 2006Atsushi Takeda Abstract An extensive neuronal activity takes place in the hippocampus during exploratory behavior. However, the role of hippocampal zinc in exploratory behavior is poorly understood. To analyze the response of extracellular zinc in the hippocampus against novelty stress, rats were placed for 50 min in a novel environment once a day for 8 days. Extracellular glutamate in the hippocampus was increased during exploratory behavior on day 1, whereas extracellular zinc was decreased. The same phenomenon was observed during exploratory behavior on day 2 and extracellular zinc had returned to the basal level during exploratory behavior on day 8. To examine the significance of the decrease in extracellular zinc in exploratory activity, exploratory behavior was observed during perfusion with 1 mm CaEDTA, a membrane-impermeable zinc chelator. Locomotor activity in the novel environment was decreased by perfusion with CaEDTA. The decrease in extracellular zinc and the increase in extracellular glutamate in exploratory period were abolished by perfusion with CaEDTA. These results suggest that zinc uptake by hippocampal cells is linked to exploratory activity and is required for the activation of the glutamatergic neurotransmitter system. The zinc uptake may be involved in the response to painless psychological stress or in the cognitive processes. [source] A novel role of hippocalcin in bFGF-induced neurite outgrowth of H19-7 cellsJOURNAL OF NEUROSCIENCE RESEARCH, Issue 7 2008Doo-Yi Oh Abstract Hippocalcin is a Ca2+ -binding protein that is expressed mainly in pyramidal nerve cells of the hippocampus. However, its functions and mechanism in the brain remain unclear. To elucidate the role of hippocalcin, we used a conditionally immortalized hippocampal cell line (H19-7) and showed that bFGF treatment increased the expression of hippocalcin during bFGF-induced neurite outgrowth of H19-7 cells. Overexpression of hippocalcin dramatically elongated neurites and increased the expression of basic helix,loop,helix transcription factor, that is, NeuroD without bFGF stimulation. Treatment of the cells with hippocalcin siRNA completely blocked bFGF-induced neurite outgrowth and NeuroD expression. bFGF stimulation resulted in activation of phospholipase C,, (PLC-,) and an increased level of intracellular Ca2+. Hippocalcin expression by bFGF stimulation was fully blocked by both the PLC-, inhibitor U73122 and BAPTA-AM, a chelator of intracellular Ca2+, suggesting that hippocalcin expression by bFGF is dependent on PLC-, and Ca2+. Moreover, both U73122 and BAPTA-AM completely blocked bFGF-induced neurite outgrowth and NeuroD expression. Taken together, these results suggest for the first time that bFGF induces hippocalcin expression in H19-7 cells through PLC-, activation, which leads to neurite outgrowth. © 2008 Wiley-Liss, Inc. [source] Pituitary adenylate cyclase-activating polypeptide-induced differentiation of embryonic neural stem cells into astrocytes is mediated via the , isoform of protein kinase CJOURNAL OF NEUROSCIENCE RESEARCH, Issue 8 2006Jun Watanabe Abstract We have found previously that pituitary adenylate cyclase-activating polypeptide (PACAP) increases the number of astrocytes generated from cultured mouse neural stem cells (NSCs) via a mechanism that is independent of the cyclic AMP/protein kinase A pathway (Ohno et al., 2005). In the present study, the signaling pathway involved in the differentiation process was further investigated. PACAP-induced differentiation was inhibited by the phospholipase C inhibitor, U73122, the protein kinase C (PKC) inhibitor, chelerythrine, and the intracellular calcium chelator, BAPTA-AM, and was mimicked by phorbol 12-myristate 13-acetate (PMA), but not by 4,-PMA. These results suggest that the PACAP-generated signal was mediated via the PACAP receptor, PAC1 stimulated heterotrimeric G-protein, resulting in activation of phospholipase C, followed by calcium- and phospholipid-dependent protein kinase C (cPKC). To elucidate the involvement of the different isoforms of cPKC, their gene and protein expression were examined. Embryonic NSCs expressed , and ,II PKC, but lacked PKC,. When NSCs were exposed to 2 nM PACAP, protein expression levels of the ,II isoform transiently increased two-fold before differentiation, returning to basal levels by Day 4, whereas the level of PKC, increased linearly up to Day 6. Overexpression of PKC,II with adenovirus vector synergistically enhanced differentiation in the presence of 1 nM PACAP, whereas expression of the dominant-negative mutant of PKC,II proved inhibitory. These results indicate that the , isoform of PKC plays a crucial role in the PACAP-induced differentiation of mouse embryonic NSCs into astrocytes. © 2006 Wiley-Liss, Inc. [source] Areca nut extracts-activated secretion of leukotriene B4, and phosphorylation of p38 mitogen-activated protein kinase and elevated intracellular calcium concentrations in human polymorphonuclear leukocytesJOURNAL OF PERIODONTAL RESEARCH, Issue 5 2007S.-L. Hung Background and Objective:, Polymorphonuclear leukocytes are the major source of leukotriene B4, which is synthesized via the 5-lipoxygenase pathway. Activation of the 5-lipoxygenase pathway is regulated by intracellular calcium and the phosphorylation of p38 mitogen-activated protein kinase (MAPK). The impact of areca nut extracts on the biosynthesis of leukotriene B4 by human polymorphonuclear leukocytes was evaluated, and some of the possible mechanisms underlying the responses were examined. Material and Methods:, Polymorphonuclear leukocytes were treated with various concentrations of areca nut extracts. The concentrations of leukotriene B4 released into the supernatants were evaluated using enzyme immunoassay. The phosphorylation of p38 MAPK was monitored using immunoblotting, and the cytosolic calcium kinetics were assessed fluorometrically using Fura-2. Results:, Exposure of polymorphonuclear leukocytes to areca nut extracts led to a dose-dependent increase in the production of leukotriene B4, with levels peaking at 30 min and decreasing thereafter. Areca nut extracts enhanced the phosphorylation of p38 MAPK, an enzyme known to activate 5-lipoxygenase. Incubation with areca nut extracts also resulted in a rapid elevation of intracellular calcium concentrations in polymorphonuclear leukocytes. The induction of leukotriene B4 by areca nut extracts was suppressed with the p38 MAPK inhibitor, SB203580, or with the intracellular calcium chelator, BAPTA-AM. Conclusion:, The interaction of areca nut extracts with polymorphonuclear leukocytes activated the arachidonic acid metabolic cascade. Incubation of polymorphonuclear leukocytes with areca nut extracts resulted in the activation of intracellular events, such as phosphorylation of p38 MAPK and Ca2+ mobilization, involved in the release of pro-inflammatory lipid mediators. The results of this study emphasize the potential importance of polymorphonuclear leukocytes as a source of leukotriene B4, which may modulate the inflammatory response in areca chewers. [source] Design, synthesis and properties of novel iron(III)-specific fluorescent probesJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 4 2004Wei Luo ABSTRACT Bidentate chelators such as hydroxypyridinones and hydroxypyranones are highly iron selective. The synthesis of two novel fluorescent probes N -[2-(3-hydroxy-2-methyl-4-oxopyridin-1(4H)-yl)ethyl]-2-(7-methoxy-2-oxo-2H -chromen-4-yl)acetamide (CP600) and N -[(3-hydroxy-6-methyl-4-oxo-4H -pyran-2-yl)methyl]-2-(7-methoxy-2-oxo-2H -chromen-4-yl)acetamide (CP610) is reported. The method involves coupling the bidentate ligands, 3-hydroxypyridin-4-one and 3-hydroxypyran-4-one, with the well-characterised fluorescent probe methoxycoumarin. Fluorescence emission of both probes at 380 nm is readily quenched by Fe3+. The fluorescence was quenched to a greater extent by Fe3+ than by Mn2+, Co2+, Zn2+, Ca2+, Mg2+, Na+ and K+ and to approximately the same extent as Cu2+. Comparison of the fluorescence-quenching ability by a range of metal ions on CP600 and CP610 and the hexadentate chelator, calcein, under in-vitro conditions, demonstrated advantages of the two novel fluorescent probes with respect to both iron(III) sensitivity and selectivity. Chelation of iron(III) by CP600 and CP610 leads to the formation of a complex with a metal-to-ligand ratio of 1:3. Fluorescence is quenched on formation of such complexes. These probes possess a molecular weight less than 400 and thus they are predicted to permeate biological membranes by passive diffusion, and have potential for reporting intracellular organelle labile iron levels. [source] Chromatographic methods for the separation of biocompatible iron chelators from their synthetic precursors and iron chelatesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 17-18 2004Petra Kova, ķkovį Abstract Chromatographic methods have been developed for the separation of the three novel biocompatible iron chelators pyridoxal isonicotinoyl hydrazone (PIH), salicylaldehyde isonicotinoyl hydrazone (SIH), and pyridoxal 2-chlorobenzoyl hydrazone (o-108) from their synthetic precursors and iron chelates. The chromatographic analyses were achieved using analytical columns packed with 5 ,m Nucleosil 120-5 C18. For the evaluation of all chelators in the presence of the synthetic precursors, EDTA was added to the mobile phase at a concentration of 2 mM. The best separation of PIH and its synthetic precursors was achieved using a mixture of phosphate buffer (0.01 M NaH2PO4, 5 mM 1-heptanesulfonic acid sodium salt; pH 3.0) and methanol (55 : 45, v/v). For separation of SIH and its synthetic precursors, the mobile phase was composed of 0.01 M phosphate buffer (pH 6.0) and methanol (60 : 40, v/v). o-108 was analyzed employing a mixture of 0.01 M phosphate buffer (pH 7.0), methanol, and acetonitrile (60 : 20 : 20, v/v/v). These mobile phases were slightly modified to separate each chelator from its iron chelate. Furthermore, a RP-TLC method has also been developed for fast separation of all compounds. The chromatographic methods described herein could be applied in the evaluation of purity and stability of these drug candidates. [source] | |||||||||||||||||||||||||||||||