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Chromium
Kinds of Chromium Terms modified by Chromium Selected AbstractsCharacteristics of Voltammetric Determination and Speciation of Chromium , A ReviewELECTROANALYSIS, Issue 13 2009Andrzej Bobrowski Abstract This article reviews the voltammetric methods of chromium determination, including adsorptive and catalytic adsorptive stripping voltammetry at liquid mercury, metallic films, and modified carbon paste electrodes. The principle applications of the catalytic adsorptive stripping voltammetric method of chromium(VI) determination in the presence of DTPA and nitrate, most useful in the analysis of chromium traces and its speciation, is presented in detail. Special emphasis is put on the presentation and characterization of the voltammetric procedures which make it possible to conduction speciation studies of chromium(VI) in the presence of a great excess of chromium(III) and surfactants. This survey is based on 173 articles. [source] Catalytic Adsorptive Stripping Voltammetric Procedure for Determination of Total Chromium in Environmental MaterialsELECTROANALYSIS, Issue 12 2006gorzata Grabarczyk Abstract A sensitive catalytic adsorptive stripping voltammetric procedure for determination of traces of total chromium in environmental samples is reported. The method is based on the preconcentration of a Cr(III)H2DTPA complex by adsorption at the HMDE from an acetate buffer solution at the potential ,1.0,V vs. Ag/AgCl. Total chromium was determined as Cr(III) after reduction of Cr(VI) to Cr(III) by NaHSO3. In order to stabilize the signal of Cr(III) the measurements were performed at 5,°C. The calibration graph for chromium for an accumulation time of 60,s was linear in the range from 5×10,10 to 5×10,8,mol L,1. The relative standard deviation for a chromium concentration of 1×10,8,mol L,1 was 3.9% (n=5). The detection limit for accumulation time of 60,s was about 8×10,11,mol L,1. The validation of the procedure was performed by the analysis of the certified reference materials. [source] Trace Determination of Chromium by Square-Wave Adsorptive Stripping Voltammetry on Bismuth Film ElectrodesELECTROANALYSIS, Issue 21 2004Eleni Chatzitheodorou Abstract This works reports the use of adsorptive stripping voltammetry (AdSV) for the trace determination of chromium on a rotating-disk bismuth-film electrode (BFE). During the reductive accumulation step, all the chromium species in the sample were reduced to Cr(III) which was complexed with cupferron and the complex was accumulated by adsorption on the surface of a preplated BFE. The stripping step was carried out by using a square-wave (SW) potential-time voltammetric signal. Electrochemical cleaning of the bismuth film was employed, enabling the same bismuth film to be used for a series of measurements in the presence of dissolved oxygen. The experimental variables as well as potential interferences were investigated and the figures of merit of the method were established. Using the selected conditions, the 3, limit of detection for chromium was 100,ng L,1 (for 120,s of preconcentration) and the relative standard deviation was 3.6% at the 2,,g L,1 level (n=8). Finally, the method was applied to the determination of chromium in real samples with satisfactory results. [source] Study of the Complexation, Adsorption and Electrode Reaction Mechanisms of Chromium(VI) and (III) with DTPA Under Adsorptive Stripping Voltammetric ConditionsELECTROANALYSIS, Issue 19 2003Sylvia Sander Abstract The complexation of Cr(III) and Cr(VI) with diethylenetriaminepentaacetic acid (DTPA), the redox behavior of these complexes and their adsorption on the mercury electrode surface were investigated by a combination of electrochemical techniques and UV/vis spectroscopy. A homogenous two-step reaction was observed when mixing Cr(III), present as hexaquo complex, with DTPA. The first reaction product, the electroactive 1,:,1 complex, turns into an electroinactive form in the second step. The results indicate that the second reaction product is presumably a 1,:,2 Cr(III)/DTPA complex. The electroreduction of the DTPA-Cr(III) complex to Cr(II) was found to be diffusion rather than adsorption controlled. The Cr(III) ion, generated in-situ from Cr(VI) at the mercury electrode at about ,50,mV (vs. Ag|AgCl) (3,mol,L,1 KCl), was found to form instantly an electroactive and adsorbable complex with DTPA. By means of electrocapillary measurements its surface activity was shown to be 30 times higher than that of the complex built by homogenous reaction of DTPA with the hydrated Cr(III). Both components, DTPA and the in-situ built complex Cr(III) ion were found to adsorb on the mercury electrode. The effect of nitrate, used as catalytic oxidant in the voltammetric determination method, on the complexation reaction and on the adsorption processes was found to be negligible. The proposed complex structures and an overall reaction scheme are shown. [source] Speciation and Environmental Fate of Chromium in Rivers Contaminated with Tannery EffluentsENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 2 2007J. Dominik Abstract Redox and size speciation of chromium in rivers contaminated with tannery wastewater was carried out to provide insight into its transport and removal mechanisms. Total chromium was determined with Inductively Coupled Plasma-Mass Spectrometry and Cr,(VI) with Catalytic Adsorption Stripping Voltammetry. For the size speciation, particles were retained with a cartridge filter (cut-off 1.2,,m) and the total filterable fraction was further fractionated with Tangential Flow Filtration to determine the concentrations of chromium associated with the High Molecular Weight Colloidal (HMWC), Low Molecular Weight Colloidal (LMWC) and Truly Dissolved (TD) fractions. Two fluvial systems of similar sizes, but located in contrasting climatic zones, were selected for comparison: the Sebou-Fez system in Morocco and Dunajec River-Czorsztyn Reservoir system in Poland. Particulate Cr dominated in the Sebou-Fez system (about 90,%); while in the Dunajec-Czorsztyn system, it represented only 17,53,% of the total chromium in raw water. Still, the partition coefficients [Kd] were of the same magnitude. Chromium,(III) was the only form detected in Sebou-Fez, whereas in Dunajec-Czorsztyn Cr,(VI) was also present with its proportion increasing downstream from the input of tannery wastewater due to the preferential removal of Cr,(III). In the filtered water in Morocco a large fraction of Cr occurred in the HMWC fraction (50,70,%) at the two most contaminated sites, while the LMWC and TD forms prevailed at the non-contaminated sites in the Sebou River. At a very high concentration, in the water in the proximity of tanneries (well above the theoretical saturation level) Cr precipitated as polynuclear Cr-hydroxide. In Dunajec-Czorsztyn, the partition of Cr,(III) was approximately equal between the HMWC, LMWC and TD fractions, in contrast to Cr,(VI) which occurred almost exclusively in the TD fraction. In both systems, Cr,(III) was rapidly removed from the water to the sediments. The confluence of the Sebou with the Fez and the Czorsztyn reservoir trapped efficiently Cr,(III) preventing its spreading over long distances. Cr,(VI) showed conservative behavior and bypassed the Czorsztyn Reservoir. This study provides a first set of data on the partitioning of Cr,(III) and Cr,(VI) between the particulate, the colloidal and truly dissolved fractions in fluvial systems contaminated with tannery effluents. It also suggests that, in these systems, truly dissolved Cr,(III) can be adequately modeled from the total filterable concentrations. [source] Nickel potentiates the genotoxic effect of benzo[a]pyrene in Chinese hamster lung V79 cellsENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 3 2006Cheng Z. Deng Abstract The modulating effect of acute exposure to NiCl2 on the induction of chromosome aberrations by a model carcinogen, benzo[a]pyrene (B[a]P), was examined in Chinese hamster V79 lung cells. At concentrations up to 20 ,g/ml (84.2 ,M), NiCl2 did not significantly increase the frequency of chromosome aberrations in V79 cells when the cells were exposed concomitantly to 0.5 ,g/ml B[a]P. Addition of the S15 liver microsomal fraction together with the B[a]P did not alter the results. Addition of NiCl2 2 hr before treatment of cells with 0.5 ,g/ml B[a]P also did not result in a significant elevation of the frequency of chromosome aberrations, even at NiCl2 concentrations as high as 20 ,g/ml. Contrasting sharply with these findings, when V79 cells were treated with NiCl2 immediately after B[a]P exposure, a significant increase in the frequency of chromosome damage was observed at NiCl2 concentrations as low as 5 ,g/ml (21.1 ,M). NiCl2 -mediated enhancement of chromosome damage was also observed when V79 cells were exposed to the reactive B[a]P intermediate, benzo[a]pyrene,r,7,t,8-dihydrodiol- t,9,10-epoxide (BPDE). In the BPDE-treated cells, the level of NiCl2 -mediated enhancement was similar to that observed with the tumor promoter 12- o -tetradecanoylphorbol-13-acetate (TPA, 100 ng/ml). These results are consistent with the view that the effect of nickel (II) on B[a]P-induced genetic damage is dependent on the relative times of exposure to Ni2+ and B[a]P. NiCl2 did not enhance the frequency of chromosome aberrations induced by Chromium (VI), regardless of the order of addition of the chemicals to the V79 cells. These results suggest that nickel may act as a promoter of chemically-induced genetic damage through induction of error-prone repair. Environ. Mol. Mutagen., 2006. © 2005 Wiley-Liss, Inc. [source] Application of DNA diffusion assay in earthworm coelomocytesENVIRONMENTAL TOXICOLOGY, Issue 2 2008A. A. Apte Abstract We have applied the DNA diffusion assay proposed by Singh (2000) Exp Cell Res 256:328,337, for quantitative estimation of apoptosis in earthworm coelomocytes, exposed to Chromium (VI) and cypermethrin as model toxicants in vitro. The DNA diffusion assay was originally described for mammalian cells. H2O2, Sodium ascorbate, and hyperthermia were used as positive controls in present study. Apoptosis such as DNA diffusion occurred in dose-dependent manner for Chromium (VI) and cypermethrin at very low concentration (1, 3, and 10 ppm for Chromium (VI) and 4, 8, and 16 ppm for cypermethrin). Three distinct patterns (apoptosis like DNA diffusion, necrosis, and normal) were observed in exposed and nonexposed cells. Present study is probably the first report of application of the DNA diffusion technique in earthworm coelomocytes. Findings of this study indicate that this assay has potential for use in invertebrate cells to differentiate between apoptosis and necrosis. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008. [source] Phytotoxicity and phytoaccumulation of trivalent and hexavalent chromium in brake fernENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2005Yi Su Abstract A recently recognized hyperaccumulator plant, Chinese brake fern (Pteris vittata), has been found to extract very high concentration of arsenic from arsenic-contaminated soil. Chromium usually is a coexisting contaminant with arsenic in most contaminated soils. The potential application of ferns for phytoremediation of chromium(III)- and chromium(VI)-contaminated soils and their phytotoxicity to ferns has not been studied before. In this study, chromium distribution and phytotoxicity at the plant and cellular levels of brake ferns were studied using chemical analyses and scanning electron microscopy. The results show a higher phytotoxicity of Cr from Cr(VI)-contaminated soil to Chinese brake fern than from Cr(III)-contaminated soil. Phytotoxicity symptoms included significant decreases both in fresh biomass weight and relative water content (RWC), and also in leaf chlorosis during the late stage of growing. At higher concentrations (500 mg/kg Cr[VI] and 1,000 mg/kg Cr[III] addition), plants showed reduction in the number of palisade and spongy parenchyma cells in leaves. Compared with other plant species reported for phytoremediation of Cr(VI)-contaminated soil, brake fern took up and accumulated significant amounts of Cr (up to 1,145 mg/kg in shoots and 5,717 mg/kg in roots) and did not die immediately from phytotoxicity. Our study suggests that Chinese brake fern is a potential candidate for phytoremediation of Cr(VI)-contaminated soils, even though plants showed severe phytotoxic symptoms at higher soil Cr concentrations. [source] Predicting the toxicity of chromium in sedimentsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2004Walter J. Berry Abstract Chromium exists in sediments in two oxidation states: Cr(III), which is relatively insoluble and nontoxic, and Cr(VI), which is much more soluble and toxic. Chromium(VI) is thermodynamically unstable in anoxic sediments, and acid-volatile sulfide (AVS) is formed only in anoxic sediments; therefore sediments with measurable AVS concentrations should not contain toxic Cr(VI). If this hypothesis holds true, measuring AVS could form the basis for a theoretically based guideline for Cr in sediments. Ten-day water-only and spiked sediment toxicity tests with the amphipod Ampelisca abdita were performed with Cr(VI) and Cr(III), along with sediments collected from a site contaminated with high concentrations of Cr. In sediments where AVS exceeded analytical detection limits, Cr concentrations in interstitial water were very low (<100 ,g/L) and no significant toxicity to A. abdita was observed. In sediments in which AVS was not significantly greater than zero, Cr concentrations in interstitial waters increased significantly, with greater than 90% of the Cr present as Cr(VI), and mortality of A. abdita was elevated. These results demonstrate that measurements of AVS and interstitial water chromium can be useful in predicting the absence of acute effects from Cr contamination in sediments. [source] Sediment chemical contamination and toxicity associated with a coastal golf course complex,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2001Michael A. Lewis Abstract The increasing density of golf courses represents a potential source of sediment contamination to nearby coastal areas, the chemical and biological magnitude of which is almost unknown. The objective of this study was to determine the concentrations of contaminants and toxicities of sediments impacted by a coastal golf course complex. Sediment contaminant concentrations were determined at least twice during the two-year study period at 14 sampling stations. In addition, a combination of acute and chronic bioassays were conducted exposing four invertebrate test species to whole sediments and associated pore waters. Overall, the Florida, USA, golf course complex had a measurable impact on sediment chemical quality, particularly in near-field areas. Higher concentrations of several trace metals and organochlorine pesticides were detected in many golf course-associated sediments compared with reference areas; however, concentrations decreased seaward and only a few, primarily chlorinated pesticides, exceeded proposed sediment quality guidelines. Chromium, zinc, and mercury were detected more frequently than other trace metals. The DDT and associated metabolites, dieldrin and chlordane, were the more commonly detected organic contaminants. Acute toxicity was uncommon and occurred consistently for sediment collected from one coastal location. In contrast, chronic toxicity occurred at several study sites based on the response of Mysidopsis bahia. It was concluded that the impact of golf course runoff on sediment quality may be subtle and sensitive biological assessment methods, such as chronic toxicity tests, will be needed to detect adverse effects. [source] Synthesis, Structures, and Magnetic Properties of N -Trialkylsilyl-8-amidoquinoline Complexes of Chromium, Manganese, Iron, and Cobalt as well as of Wheel-Like Hexanuclear Iron(II) and Manganese(II) Bis(8-amidoquinoline)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2010Astrid Malassa Abstract The transamination of 8-(tert -butyldimethylsilylamino)quinoline with (thf)2Cr[N(SiMe3)2]2 yields monomeric bis[8-(tert -butyldimethylsilylamido)quinoline]chromium(II) (1). Similar reactions of M[N(SiMe3)2]2 (M = Mn, Fe, Co) with 8-(trialkylsilylamino)quinoline lead to the formation of monomeric bis[8-(trialkylsilylamido)quinoline]metal(II) [M = Mn, SiR3 = SiMe2tBu (2a), SiiPr3 (2b); M = Fe, SiR3 = SiMe2tBu (3a),SiiPr3 (3b); M = Co, SiR3 = SiMe2tBu (4a), SiiPr3 (4b)]. The transamination of 8-aminoquinoline with M[N(SiMe3)2]2 (M = Mn, Fe, Co) allows the isolation of the heteroleptic 1:1 and homoleptic 2:1 products. The 1:1 complexes bis[8-amidoquinoline metal(II)bis(trimethylsilyl)amide] [M = Mn (5), Fe (6), Co (7)] are dimeric with bridging 8-amidoquinoline moieties. The 2:1 complexes of Mn and Fe, bis(8-amidoquinoline)manganese(II) (8) and bis(8-amidoquinoline)iron(II) (9), form hexamers with wheel-like molecular structures consisting of metal-centered nitrogen octahedra interconnected by common N···N edges. The cobalt complex, bis(8-amidoquinoline)cobalt(II) (10), precipitates as a microcrystalline powder. Investigations of the magnetic properties by DFT corroborate the experimental data for the Mn derivative 8, where an antiferomagnetic coupling is observed. By contrast, calculations on the Fe6 -wheel 9 yield very close-lying ferromagnetically and antiferromagnetically coupled states. [source] Redox Modification of EMACs Through the Tuning of Ligands: Heptametal(II) Complexes of Pyrazine-Modulated Oligo-,-pyridylamido LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2009Rayyat Huseyn Ismayilov Abstract Using pyrazine-modulated oligo-,-pyridylamido ligands N2 -(pyrazin-2-yl)- N6 -[6-(pyrazin-2-ylamino)pyridin-2-yl]pyridine-2,6-diamine (H3pzpz) and N2 -(pyrazin-2-yl)- N6 -[6-(pyridin-2-ylamino)pyridin-2-yl]pyridine-2,6-diamine (H3tpz), linear heptametal(II) extended metal atom chains (EMACs) [M7(,7 -L)4X2] [L = pzpz3,, M = NiII, X = Cl, (1), NCS, (2); M = CrII, X = Cl, (3), NCS, (4); L = tpz3,, M = CrII, X = Cl, (5), NCS, (6)] were synthesized and structurally characterized. Electrochemical studies showed that heptanickel(II) complexes can undergo one reversible oxidation at +0.46 V for 1 and +0.52 V for 2. Chromium(II) species 3 exhibited two reversible, one-electron oxidation peaks at +0.61 and +0.88 V, and 5 exhibited three reversible, one-electron oxidation peaks at +0.40, +0.68 and +1.07 V. The redox peaks shifted positively when axial ligands changed from chloride to thiocyanate anions, at +0.67 and +0.92 V for 4 and +0.44, +0.73 and +1.11 V for 6. The introduction of electron-withdrawing pyrazine rings to the spacer ligand retarded oxidation of the heptametal EMACs and stabilized the complexes. In nickel(II) species 1 and 2, both terminal nickel atoms exist in spin state S = 1 whereas all the inner nickel atoms exist in spin state S = 0. Temperature-dependent magnetic research revealed an antiferromagnetic interaction between the two terminal atoms through a superexchange pathway along metal cores with a parameter of about,4 cm,1. Chromium(II) species 3,6 showed a localized structure consisting of three quadruple Cr,Cr bonds and a single terminal CrII atom. Magnetic study revealed a quintet ground state resulting from the isolated, high-spin CrII atom.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Effects of chromium on the immune systemFEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 1 2002Richa Shrivastava Abstract Chromium is a naturally occurring heavy metal found commonly in the environment in trivalent, Cr(III), and hexavalent, Cr(VI), forms. Cr(VI) compounds have been declared as a potent occupational carcinogen among workers in chrome plating, stainless steel, and pigment industries. The reduction of Cr(VI) to Cr(III) results in the formation of reactive intermediates that together with oxidative stress oxidative tissue damage and a cascade of cellular events including modulation of apoptosis regulatory gene p53, contribute to the cytotoxicity, genotoxicity and carcinogenicity of Cr(VI)-containing compounds. On the other hand, chromium is an essential nutrient required to promote the action of insulin in body tissues so that the body can use sugars, proteins and fats. Chromium is of significant importance in altering the immune response by immunostimulatory or immunosuppressive processes as shown by its effects on T and B lymphocytes, macrophages, cytokine production and the immune response that may induce hypersensitivity reactions. This review gives an overview of the effects of chromium on the immune system of the body. [source] Eolian Transport of Geogenic Hexavalent Chromium to Ground WaterGROUND WATER, Issue 1 2010Warren W. Wood A conceptual model of eolian transport is proposed to address the widely distributed, high concentrations of hexavalent chromium (Cr+6) observed in ground water in the Emirate of Abu Dhabi, United Arab Emirates. Concentrations (30 to more than 1000 ,g/L Cr+6) extend over thousands of square kilometers of ground water systems. It is hypothesized that the Cr is derived from weathering of chromium-rich pyroxenes and olivines present in ophiolite sequence of the adjacent Oman (Hajar) Mountains. Cr+3 in the minerals is oxidized to Cr+6 by reduction of manganese and is subsequently sorbed on iron and manganese oxide coatings of particles. When the surfaces of these particles are abraded in this arid environment, they release fine, micrometer-sized, coated particles that are easily transported over large distances by wind and subsequently deposited on the surface. During ground water recharge events, the readily soluble Cr+6 is mobilized by rain water and transported by advective flow into the underlying aquifer. Chromium analyses of ground water, rain, dust, and surface (soil) deposits are consistent with this model, as are electron probe analyses of clasts derived from the eroding Oman ophiolite sequence. Ground water recharge flux is proposed to exercise some control over Cr+6 concentration in the aquifer. [source] Micellar catalysis on the redox reaction of glycolic acid with chromium(VI)INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 6 2001Kabir-ud-Din Chromium(VI) oxidation of glycolic acid in the absence and presence of cetyltrimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPB) followed the same mechanism as shown by kinetic study. The reaction followed second-order kinetics, first-order in each reactant. The oxidation is strongly catalyzed by manganese(II) and cationic micelles of CTAB or CPB. The catalytic effect of micelles can be fitted to a model in which the reaction rate depends upon the concentration of both reactants in the micellar pseudophase. Some added inorganic salts (NaCl, NaBr, NaNO3, and Na2SO4) reduce the micellar catalysis by excluding glycolic acid from the reaction site. The reactivity of glycolic acid towards chromium(VI) has been discussed and also compared with those obtained previously for the reaction between chromium(VI) and the reductants oxalic and lactic acids. On the basis of the observed results, probable mechanisms have been proposed. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 377,386, 2001 [source] Metallurgical characterization, galvanic corrosion, and ionic release of orthodontic brackets coupled with Ni-Ti archwiresJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2007Myrsini S. Darabara Abstract In orthodontics, a combination of metallic alloys is placed into the oral cavity during medical treatment and thus the corrosion resistance and ionic release of these appliances is of vital importance. The aim of this study is to investigate the elemental composition, microstructure, hardness, corrosion properties, and ionic release of commercially available orthodontic brackets and Copper Ni-Ti archwires. Following the assessment of the elemental composition of the orthodontic wire (Copper Ni-TiÔ) and the six different brackets (Micro Loc, Equilibrium, OptiMESHXRT, Gemini, Orthos2, and Rematitan), cyclic polarization curves were obtained for each material to estimate the susceptibility of each alloy to pitting corrosion in 1M lactic acid. Galvanic corrosion between the orthodontic wire and each bracket took place in 1M lactic acid for 28 days at 37°C and then the ionic concentration of Nickel and Chromium was studied. The orthodontic wire is made up from a Ni-Ti alloy with copper additions, while the orthodontic brackets are manufactured by different stainless steel grades or titanium alloys. All tested wires and brackets with the exception of Gemini are not susceptible to pitting corrosion. In galvanic corrosion, following exposure for 28 days, the lowest potential difference (,250 mV) appears for the orthodontic wire Copper Ni-Ti and the bracket made up from pure titanium (Rematitan) or from the stainless steel AISI 316 grade (Micro Loc). Following completion of the galvanic corrosion experiments, measurable quantities of chromium and nickel ions were found in the residual lactic acid solution. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source] Chromium (VI) inhibits heme oxygenase-1 expression in vivo and in arsenic-exposed human airway epithelial cellsJOURNAL OF CELLULAR PHYSIOLOGY, Issue 1 2006Kimberley A. O'Hara Inhaled hexavalent chromium (Cr(VI)) promotes lung injury and pulmonary diseases through poorly defined mechanisms. One hypothesis for this lung pathogenesis is that Cr(VI) silences induction of cytoprotective genes, such as heme oxygenase-1 (HO-1), whose total lung mRNA levels were reduced 21 days after nasal instillation of potassium dichromate in C57BL/6 mice. To investigate the mechanisms for this inhibition, Cr(VI) effects on basal and arsenic (As(III))-induced HO-1 expression were examined in cultured human bronchial epithelial (BEAS-2B) cells. An effect of Cr(VI) on the low basal HO-1 mRNA and protein levels in BEAS-2B cells was not detectible. In contrast, Cr(VI) added to the cells before As(III), but not simultaneously with As(III), attenuated As(III)-induced HO-1 expression. Transient transfection with luciferase reporter gene constructs controlled by the full length ho-1 promoter or deletion mutants demonstrated that this inhibition occurred in the E1 enhancer region containing critical antioxidant response elements (ARE). Cr(VI) pretreatment inhibited As(III)-induced activity of a transiently expressed reporter construct regulated by three ARE tandem repeats. The mechanism for this Cr(VI)-attenuated transactivation appeared to be Cr(VI) reduction of the nuclear levels of the transcription factor Nrf2 and As(III)-stimulated Nrf2 transcriptional complex binding to the ARE cis element. Finally, exposing cells to Cr(VI) prior to co-exposure with As(III) synergized for apoptosis and loss of membrane integrity. These data suggest that Cr(VI) silences induction of ARE-driven genes required for protection from secondary insults. The data also have important implications for understanding the toxic mechanisms of low level, mixed metal exposures in the lung. J. Cell. Physiol. 209: 113,121, 2006. © 2006 Wiley-Liss, Inc. [source] Hypoxia-like effect of Cobalt Chromium alloy micro particles on fibroblasts in vitroJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 10 2010Bernadette K. Madathil Abstract Periprosthetic osteolysis leading to asceptic loosening remains the primary cause of failure of joint replacement. Although many inflammatory cell types have been implicated, the exact pathomechanisms of asceptic loosening have not been delineated. In the present study we have adopted a proteomic approach to elucidate the initial signals that are expressed to particulate material, using an in vitro cell culture system. Human lung fibroblasts MRC-5 were cultured with Cobalt Chromium (CoCr ASTM F-75, 1,7,µm) particles. Cells were harvested after 72,h incubation and total cellular proteins extracted for downstream analysis via 2D Gel Electrophoresis and tandem mass spectrometry using MALDI-TOF-TOF-MS. Thirteen protein spots showed greater than twofold increase, following 72,h incubation of fibroblast with CoCr particles. Four of these proteins were identified by tandem mass spectrometry. These were Annexin II, Pyruvate kinase, Triose phosphate isomerase, and N-myc downstream regulated gene 1 protein. Cobalt is a hypoxia mimicking agent and N-myc downstream regulated gene 1 protein, Triose phosphate isomerase, Pyruvate kinase, and Annexin II are important hypoxia regulated gene products that are found to be over expressed in cellular oxidative stress response. Our data indicates that exposure of fibroblast to CoCr alloy induces the transition of these cells into a hypoxia like state and oxidative stress even in normoxic culture conditions. The study reflects the possibility of the presence of a hypoxic environment in the periprosthetic tissue surrounding metallic implants. Published by Wiley Periodicals, Inc. J Orthop Res 28:1360,1367, 2010 [source] Pressureless Sintering and Properties of Titanium Diboride Ceramics Containing Chromium and IronJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2001Shin H. Kang The simultaneous addition of 0.5 wt% Cr and Fe was found to enhance the densification of TiB2. The densities of specimens that were sintered for 2 h at 1800° and 1900°C were 97.6% and 98.8% of the theoretical value, respectively. The mechanical properties of the specimen sintered at 1800°C, which had a strength of 506 MPa and a fracture toughness of 6.16 MPa·m1/2, were much better than those observed in the specimen sintered at 1900°C. [source] Serum Zinc, Chromium, and Iron Concentrations in Dogs with Lymphoma and OsteosarcomaJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 6 2001Kathy J. Kazmierski We compared serum concentrations of zinc, chromium, and iron in dogs with cancer to those of normal dogs. Dogs with lymphoma (n = 50) and osteosarcoma (n = 52) were evaluated. Dogs with lymphoma had significantly lower (P= .0028) mean serum zinc concentrations (mean ± SD; 1.0 ± 0.3 mg/L) when compared to normal dogs (1.2 ± 0.4 mg/L). Dogs with osteosarcoma also had lower mean serum zinc concentrations (1.1 ± 0.4 mg/L), but this difference was not significant (P= .075). Serum chromium concentrations were significantly lower in dogs with lymphoma (2.6 ± 2.6 ,g/L, P= .0007) and osteosarcoma (2.4 ± 3.1 ,g/L, P= .0001) compared to normal dogs (4.7 ± 2.8 ,g/L). Serum iron concentrations and total iron-binding capacity were significantly lower in dogs with lymphoma (110.8 ± 56.7 ,g/dL, P < .0001, and 236.6 ± 45.6 ,g/dL, P < .0001, respectively) and osteosarcoma (99.6 ± 49.3 ,g/dL, P < .0001, and 245.0 ± 43.8 ,g/dL, P= .0011, respectively) when compared to normal dogs (175.1 ± 56.7 ,g/dL and 277.1 ± 47.4 ,g/dL). Mean ferritin concentration was significantly higher in dogs with lymphoma (1291.7 ± 63.0 ,g/L) than in normal dogs (805.8 ± 291.1 ,g/L, P < .0001) and dogs with osteosarcoma (826.5 ± 309.2 ,g/L, P < .0001). Further investigation is needed to explore the clinical significance of these mineral abnormalities in dogs with cancer. [source] Chromium(VI) as a novel MRI contrast agent for cerebral white matter: Preliminary results in mouse brain in vivoMAGNETIC RESONANCE IN MEDICINE, Issue 1 2006Takashi Watanabe Abstract This work demonstrates that intraventricular microinjections of a low dose of potassium dichromate (0.4 ,L of 10 mM solution) yield a specific contrast enhancement of white matter (WM) tracts in T1 -weighted 3D MRI of mouse brain in vivo. Pronounced and persistent signal increases (40,100% at 24 hr after injection) were observed in the corpus callosum, anterior commissure, fornix, and stria medullaris, as well as in the mammillothalamic tract and fasciculus retroflexus. These results suggest that the extracellular diffusion of diamagnetic chromium(VI) (Cr(VI)) after injection is followed by a tissue-specific reduction to paramagnetic Cr(V) and (III), which relies predominantly on the oxidation of myelin lipids. Because Cr(VI)-induced contrast leads to only a mild unspecific enhancement (10,20%) of gray matter (GM) structures, such as the hippocampal formation, the method reveals novel information that differs from that obtainable using other paramagnetic ions, such as manganese. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc. [source] Increased metal allergy in patients with failed metal-on-metal hip arthroplasty and peri-implant T-lymphocytic inflammationALLERGY, Issue 8 2009P. Thomas Background:, In 16 patients with revised metal-on-metal arthroplasty and peri-implant lymphocytic inflammation, we verified the role of metal hypersensitivity by patch testing (PT) and lymphocyte transformation test (LTT). Methods:, In the 16 patients with lymphocyte dominated periprosthetic inflammation, allergy history was obtained by a questionnaire, specific serum IgE to aeroallergens was measured to assess atopy, PT to standard and metal series was performed and metal sensitivity was further assessed by LTT using blood mononuclear cells. Results:, Revision surgery was performed because of pain (8/16), osteolysis (4/16), dislocation (3/16) and loosening of the stem (1/16). Histological examination showed perivascular infiltrates of T lymphocytes, high endothelial venules, fibrin exudation and accumulation of macrophages with drop-like inclusions. Five patients had a history of cutaneous metal allergy and atopy was found in 25% of the patients. In 13/16 patients (81%), systemic metal sensitivity was found based on PT and/or LTT. Patch test reactions were seen in 11/16 patients (69%; partly multiple reactions/patient): 7/16 to Cobalt (Co), 7/16 to Chromium (Cr), 4/16 to Nickel (Ni), and one each to Molybdenum (Mo) and Manganese (Mn). Ten of 16 patients (62%) showed enhanced LTT reactivity to metals: 7/16 to Ni, 7/16 to Co, 5/16 to Cr, 5/16 to Mo and 4/16 to Mn. Conclusions:, The lymphocyte dominated peri-implant inflammation may well reflect an allergic hyper-reactivity in these patients, given the high rate of concomitantly found metal allergy. Despite the overall incidence of metal implant allergy being low, allergic reactions should be included as differential diagnosis in failed metal-on-metal arthroplasty. [source] PALS investigation of chromium effect in ferritic/martensitic steels implanted with heliumPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2009Stanislav Sojak Abstract Chromium is an element with significant effect on the elevated temperature corrosion resistance and the low radiation induced void swelling. There were several studies carried out with regard to effect of Cr on the defect creation and stability [1, 2], but this issue is not fully understood yet. This paper contributes to this research with the study of Fe-Cr binary alloys with different Cr content, implanted by helium by the use of cascade accelerator and investigated by conventional PALS set-up. Our measurements show that chromium plays a role in the formation of small vacancy clusters, affecting the size and distribution of these defects. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Chromium-based clinopyroxene-type germanates NaCrGe2O6 and LiCrGe2O6 at 298,KACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2008Günther J. Redhammer The structure analyses of sodium chromium digermanate, NaCrGe2O6, (I), and lithium chromium digermanate, LiCrGe2O6, (II), provide important structural information for the clinopyroxene family, and form part of our ongoing studies on the phase transitions and magnetic properties of clinopyroxenes. (I) shows C2/c symmetry at 298,K, contains one Na, one Cr (both site symmetry 2 on special position 4e), one Ge and three O-atom positions (on general positions 8f) and displays the well known clinopyroxene topology. The basic units of the structure of (I) are infinite zigzag chains of edge-sharing Cr3+O6 octahedra (M1 site), infinite chains of corner-sharing GeO4 tetrahedra, connected to the M1 chains by common corners, and Na sites occupying interstitial space. (II) was found to have P21/c symmetry at 298,K. The structure contains one Na, one Cr, two distinct Ge and six O-atom positions, all on general positions 4e. The general topology of the structure of (II) is similar to that of (I); however, the loss of the twofold symmetry makes it possible for two distinct tetrahedral chains, having different conformation states, to exist. While sodium is (6+2)-fold coordinated, lithium displays a pure sixfold coordination. Structural details are given and chemical comparison is made between silicate and germanate chromium-based clinopyroxenes. [source] Toxic Effects of Chromium(VI) on Anaerobic and Aerobic Growth of Shewanella oneidensis MR-1BIOTECHNOLOGY PROGRESS, Issue 1 2004Sridhar Viamajala Cr(VI) was added to early- and mid-log-phase Shewanella oneidensis ( S. oneidensis) MR-1 cultures to study the physiological state-dependent toxicity of Cr(VI). Cr(VI) reduction and culture growth were measured during and after Cr(VI) reduction. Inhibition of growth was observed when Cr(VI) was added to cultures of MR-1 growing aerobically or anaerobically with fumarate as the terminal electron acceptor. Under anaerobic conditions, there was immediate cessation of growth upon addition of Cr(VI) in early- and mid-log-phase cultures. However, once Cr(VI) was reduced below detection limits (0.002 mM), the cultures resumed growth with normal cell yield values observed. In contrast to anaerobic MR-1 cultures, addition of Cr(VI) to aerobically growing cultures resulted in a gradual decrease of the growth rate. In addition, under aerobic conditions, lower cell yields were also observed with Cr(VI)-treated cultures when compared to cultures that were not exposed to Cr(VI). Differences in response to Cr(VI) between aerobically and anaerobically growing cultures indicate that Cr(VI) toxicity in MR-1 is dependent on the physiological growth condition of the culture. Cr(VI) reduction has been previously studied in Shewanellaspp., and it has been proposed that Shewanella spp.may be used in Cr(VI) bioremediation systems. Studies of Shewanella spp. provide valuable information on the microbial physiology of dissimilatory metal reducing bacteria; however, our study indicates that S. oneidensis MR-1 is highly susceptible to growth inhibition by Cr(VI) toxicity, even at low concentrations [0.015 mM Cr(VI)]. [source] ChemInform Abstract: Oxo-Diels,Alder Reaction of Danishefsky,s Diene with Aldehydes, Catalyzed by Chiral Tridentate Chromium(III),Schiff Base Complexes.CHEMINFORM, Issue 42 2010Slawomir Miesowicz Abstract The reaction is highly effective in the presence of CSB. [source] Chiral Chromium(III) Porphyrins as Highly Enantioselective Catalysts for Hetero-Diels,Alder Reactions Between Aldehydes and Dienes.CHEMINFORM, Issue 23 2006Albrecht Berkessel Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Zeolite-Supported Chromium(VI) Oxide: A Mild, Efficient, and Inexpensive Reagent for Oxidative Deprotection of Trimethylsilyl Ethers under Microwave Irradiation.CHEMINFORM, Issue 52 2004Majid M. Heravi No abstract is available for this article. [source] Novel Chromium(VI) Catalyzed Oxidation of N-Alkylamides to Imides with Periodic Acid.CHEMINFORM, Issue 47 2004Liang Xu Abstract For Abstract see ChemInform Abstract in Full Text. [source] Preparation of ,-Ketophosphonates by Oxidation of ,-Hydroxyphosphonates with Chromium-Based Oxidants.CHEMINFORM, Issue 39 2004Habib Firouzabadi Abstract For Abstract see ChemInform Abstract in Full Text. [source] | |||||||||||||||||||||||||||||||||||||||||||