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PubMed1996

[Molecular effects of chromium compound activity].

Chromium(VI) compounds produce a variety of DNA damage such as DNA single strand breaks, alkali-labile sites and DNA-protein cross-links in vivo and in cultured cells. Chromium(III) compounds bound to isolated DNA and proteins. Cr(VI) readily entered cell through general anion channels. In contrast, Cr(III) did not readily cross cell membranes. Inside cells Cr(VI) is reduced through intermediates to Cr(III) by cellular reductants. Reactive intermediates formed during intracellular Cr(VI) reduction might be responsible for some chromate genotoxicity. Ascorbic acid decreases chromate induced alkali-labile sites and chromium inhibition of glutathione reductase, but it enhances DNA-protein cross-links and cytotoxicity caused by this metal.

Animals↗
PubMedDate not supplied

Determination of chromium in wine and other alcoholic beverages consumed in spain by electrothermal atomic absorption spectrometry.

A reliable and rapid method is described for the determination of chromium in alcoholic beverages by electrothermal atomic absorption spectrometry (ETAAS) after optimization of the temperature-time program for the graphite furnace. Chromium in wines was determined directly without sample pretreatment. Other samples were first mineralized with HNO3 and V2O5. The method was validated, and its analytical characteristics were checked. The detection limit was 1 pg (for a sample volume of 10 microL). Accuracy was 99.20 +/- 3.80% for wines and 98.90 +/- 2.00% for other beverages. Precision ranged from 3.50 to 4.50%. The proposed method was applied to 124 samples of alcoholic beverages frequently consumed in Spain. Mean values obtained (microgram/L) were 20.28 for wines, 8.75 for beer, 7.85 for cider, 14.60 for brandy, 7.50 for rum, 10.25 for whisky, 8.80 for gin, 9.25 for vodka, 24.45 for anisette, and 10.08 for liquors. The advantages of the proposed method (rapidity, sensitivity) and versatility) make it useful for routine analyses and for estimations of dietary intake of chromium.

Alcoholic Beverages↗
PubMed2002

Chromium-salen-mediated alkene epoxidation: a theoretical and experimental study indicates the importance of spin-surface crossing and the presence of a discrete intermediate.

The mechanism of alkene epoxidation by chromium(v) oxo salen complexes has been studied by DFT and experimental methods. The reaction is compared to the closely related Mn-catalyzed process in an attempt to understand the dramatic difference in selectivity between the two systems. Overall, the studies show that the reactions have many similarities, but also a few critical differences. In agreement with experiment, the chromium system requires a change from low- to high-spin in the catalytic cycle, whereas the manganese system can proceed either with spin inversion or entirely on the high-spin surface. The low-spin addition of metal oxo species to an alkene leads to an intermediate which forms epoxide either with a barrier on the low-spin surface or without a barrier after spin inversion. Supporting evidence for this intermediate was obtained by using vinylcyclopropane traps. The chromium(v) oxo complexes can adopt a stepped shape or form a more concave surface, analogous to previous results on manganese salen complexes.

Journal Article↗
PubMed2006

Exposure of pregnant mice to chromium picolinate results in skeletal defects in their offspring.

BACKGROUND: Chromium(III) picolinate, [Cr(pic)(3)], is a widely marketed dietary supplement. However, Cr(pic)(3) has been associated with oxidative damage to DNA in rats and mutations and DNA fragmentation in cell cultures. In isolated case reports, Cr(pic)(3) supplementation has been said to cause adverse effects, such as anemia, renal failure, liver dysfunction, and neuronal impairment. To date, no studies have been published regarding the safety of chromium picolinate supplementation to a developing fetus, although Cr(pic)(3) has been recommended for pregnant women who are diagnosed with gestational diabetes. METHODS: From gestation days (GD) 6-17, pregnant CD-1 mice were fed diets containing either 200 mg/kg Cr(pic)(3), 200 mg/kg CrCl(3), 174 mg/kg picolinic acid, or the diet only to determine if Cr(pic)(3), CrCl(3), or picolinic acid could cause developmental toxicity. Dams were sacrificed on GD 17, and their litters were examined for adverse effects. RESULTS: The incidence of bifurcated cervical arches was significantly increased in fetuses from the Cr(pic)(3) group as compared to the diet-only group. Fetuses in the picolinic acid-treated group had an incidence double that of the control group; however, this increase was not statistically significant. Fetuses in the CrCl(3) group did not differ from the controls in any variable examined. No maternal toxicity was observed in any of the treatment groups. CONCLUSIONS: High maternal oral exposures to chromium picolinate can cause morphological defects in developing offspring of mice.

Abnormalities, Drug-Induced↗
PubMed2000

Thermodynamics of Chromium(VI) Anionic Species Sorption onto Surfactant-Modified Montmorillonite Clay.

Batch sorption experiments performed on Cr(VI) species sorption showed a significantly enhanced removal of inorganic hexavalent chromium anionic species from aqueous solution by montmorillonite clays modified with quaternary amine, hexadecyltrimethylammonium (HDTMA) bromide. Unmodified clay had no affinity for chromium(VI) species. The sorption of Cr(VI) species has been carried out as a function of pH, contact time, adsorbate concentration (4.14x10(-5) to 8.62x10(-3) M), and temperature (5-45 degrees C). The surfactant-modified clay surface was stable when exposed to extremes in pH. The optimum pH for maximum sorption of Cr(VI) species was found to be at pH 1 and was constant between pH 2 and pH 6. The sorption data obtained was well described by DKR and Langmuir sorption isotherms. Sorption energy (E) for (i) surfactant sorption by montmorillonite clay and (ii) sorption of chromium(VI) species by surfactant modified clay have been computed from the DKR equation. Sorption energy evaluated for the sorption of both surfactant and Cr(VI) species showed that an ion-exchange mechanism was operative. The mechanism of retention appears to be replacement of counterion of the surfactant by Cr(VI) anionic species. Adsorbent capacity for the sorption of Cr(VI) species has been evaluated from the Langmuir sorption isotherm data. Thermodynamic parameters (Delta H degrees, Delta S degrees and Delta G degrees ) for surfactant sorption on montmorillonite clay and Cr(VI) sorption by modified clay have been evaluated. The specific rate constant for sorption of Cr(VI) species on modified montmorillonite was rapid during the first 10 min and equilibrium was found to be attained within 30 min. The sorption of Cr(VI) species onto modified montmorillonite clay followed first-order rate kinetics. Copyright 2000 Academic Press.

Journal Article↗
PubMed1994

Apoptosis is the mode of cell death caused by carcinogenic chromium.

The role of apoptosis in the mechanism of toxicity of hexavalent chromium, a human carcinogen, was investigated. Chinese hamster ovary (CHO) cells were treated with 150 or 300 microM sodium chromate for 2 hr, doses which decreased colony-forming efficiency to 53 and 5% of control, respectively. Cell growth was inhibited at least up to Day 8 after treatment. DNA synthesis was inhibited to 30 and 19% of control at 1 hr after treatment, and did not begin to recover until Day 4 after treatment. Protein synthesis was inhibited by 52 and 60% in 150 and 300 microM treated cells, respectively, 1 h after treatment, and recovered to 142 and 93%, respectively, at 24 hr. Incubation of cells with nontoxic doses of cycloheximide for 24 hr after treatment produced synergistic toxicity with chromate in colony-forming efficiency assays. Ion gradients persisted to Day 2 as revealed by exclusion of trypan blue dye in 97% of treated cells. Fluorescence microscopy of acridine orange-stained cells revealed morphological features of apoptosis including nuclear fragmentation in more than 90% of detached nonadherent cells and up to 22% of adherent cells by Day 2 after treatment. Untreated cells remained morphologically normal. Transmission electron microscopy of chromate treated cells showed characteristic features of apoptosis including chromatin margination and fragmentation, and cytoplasmic condensation with intact membrane and organelle structure. Internucleosomal DNA fragmentation (IDF) was delayed for at least 24 hr, whereafter it was detected in both adherent and nonadherent cells through Day 5 after treatment. These results indicate apoptosis as the mode of cell death caused by chromium and imply that apoptosis must be considered as a component of chromium-induced multistage carcinogenesis.

Animals↗
PubMed1995

Hexavalent-chromium reduction by a chromate-resistant Bacillus sp. strain.

Bacillus strain QC1-2, isolated from a chromium-polluted zone, was selected by its high ability to both tolerate and reduce hexavalent chromium [Cr(VI)] to less-toxic trivalent chromium [Cr(III)]. Cell suspensions of strain QC1-2 rapidly reduced Cr(VI), in both aerobic and anaerobic conditions, to Cr(III) which remained in the supernatant. Cr(VI) reduction was dependent on the addition of glucose but sulfate, an inhibitor of chromate transport, had no effect. Studies with permeabilized cells and cell extracts showed that the Cr(VI) reductase of strain QC1-2 is a soluble NADH-dependent enzyme.

Aerobiosis↗
PubMed1997

Protective effect of deferoxamine on chromium (VI)-induced DNA single-strand breaks, cytotoxicity, and lipid peroxidation in primary cultures of rat hepatocytes.

Incubation of primary cultures of rat hepatocytes with K2CR2O7 and deferoxamine (DFO), an iron chelator, resulted in a marked decrease in cellular levels of DNA single-strand breaks caused by K2Cr2O7. Cellular treatment with DFO also suppressed both dichromate-induced cytotoxicity--evaluated by the leakage of lactate dehydrogenase, and lipid peroxidation--as monitored by malondialdehyde formation. In addition, treatment with DFO attenuated the suppression of the levels of vitamin E and C as well as the inhibition of alkaline phosphatase and glutathione peroxidase activity attributed to K2Cr2O7. However, DFO had no influence on the cellular level of glutathione or the activity of glutathione reductase and superoxide dismutase suppressed by dichromate. Under the same experimental conditions, cellular uptake and distribution of chromium were not affected by DFO. These results indicate that DFO protects cells from chromium (VI)-induced DNA strand breaks, cytotoxicity, lipid peroxidation, vitamin E and C depression, and glutathione peroxidase inhibition The role of antioxidants in chromium (VI)-induced cytotoxicity, DNA breaks, and lipid peroxidation is discussed.

Alkaline Phosphatase↗
PubMed2005

Use of multivariate curve resolution for determination of chromium in tanning samples using sequential injection analysis.

We report a method for determining total chromium in tanning samples using sequential injection analysis (SIA) with a diode-array spectrophotometric detector. With a suitable analytical sequence CrO4(2-) is converted to Cr2O7(2-) inside the tubes of the SIA system, after total oxidation of chromium(III). A data matrix is obtained and analysed by several chemometric techniques based on multivariate analysis: principal components analysis, simple-to-use interactive self-modelling mixture analysis, and multivariate curve resolution-alternating least-squares. We studied several samples from different stages of a tanning process. Two of these samples were easily oxidized but the others needed more extreme conditions. The analytical sequence prepared, which was based on obtaining a pH gradient and used H2SO4 as reagent, is valid and independent of the level of oxidation needed for the sample. We established a calibration model and evaluated the figures of merit. In some samples we found interferents. With this method the amounts of chromium in each sample were quantified and the results were statistically similar to those obtained by use of the reference method, atomic absorption spectrometry.

Journal Article↗
PubMed2005

Determination of hexavalent chromium by using speciated isotope-dilution mass spectrometry after microwave speciated extraction of environmental and other solid materials.

Precise and accurate determination of hexavalent chromium in different types of solid environmental sample is regarded as a technical challenge with significant potential error if historically accepted methods are used. Microwave-assisted alkaline extraction (0.5 mol L(-1) NaOH + 0.28 mol L(-1) Na2CO3) followed by anion-exchange chromatographic separation and inductively coupled plasma mass spectrophotometric detection has been shown to provide accurate and precise results. To obtain a better understanding of potential species conversion during and/or after extraction steps, speciated isotope-dilution mass spectrometry (SIDMS) (EPA Method 6800) metrology has been successfully applied as a diagnostic tool with the modified accompanying extraction version of EPA Method 3060A. In our study, aggregate materials distributed over a large area of a major western US state were found to contain a high concentration of total chromium (195 +/- 13 to 709 +/- 19 microg g(-1)) and significant amounts of Cr6+ (141 +/- 6 to 341 +/- 29 microg g(-1)) which are at least three orders of magnitude higher than the US EPA threshold limit (0.5 microg g(-1)). Sediment samples from a major western US state, studied independently, were found to contain less (1.77 +/- 0.34 microg g(-1)) or no Cr6+ in the presence of significant total chromium.

Journal Article↗
PubMed2006

Qualitative and quantitative investigation of chromium-polluted soils by laser-induced breakdown spectroscopy combined with neural networks analysis.

Laser-induced breakdown spectroscopy (LIBS) has been applied to the analysis of three chromium-doped soils. Two chemometric techniques, principal components analysis (PCA) and neural networks analysis (NNA), were used to discriminate the soils on the basis of their LIBS spectra. An excellent rate of correct classification was achieved and a better ability of neural networks to cope with real-world, noisy spectra was demonstrated. Neural networks were then used for measuring chromium concentration in one of the soils. We performed a detailed optimization of the inputs of the network so as to improve its predictive performances and we studied the effect of the presence of matrix-specific information in the inputs examined. Finally the inputs of the network--the spectral intensities--were replaced by the line areas. This provided the best results with a prediction accuracy and precision of about 5% in the determination of chromium concentration and a significant reduction of the data, too.

Journal Article↗
PubMed2001

Spectrophotometric determination of chromium with diphenylcarbazide in the presence of vanadium, molybdenum, and iron after separation by solid-phase extraction.

A method has been developed for the determination of chromium in presence of V(V), Mo(VI), and Fe(III). The effects of interferences were evaluated by using the apparent content curves method, and their separation was performed by solid-phase extraction with an anionic exchanger. The sample-treatment conditions and the influence of the sample conductivity were studied. Tolerance limits were established, and the proposed procedure was used to determine chromium in certified samples and for speciation of chromium in waste water. Our results were always in agreement with the theoretical content.

Journal Article↗
PubMed1996

Comparison of chromium and nickel uptake of plants grown in different soils.

The chromium and nickel uptake of ryegrass has been examined in pot experiments in extremely different soils, poor sandy and fertile black chernozem. The effect of calcium carbonate doses and nitrogen supply on heavy metal uptake of the plant has been studied for chromium and nickel loadings (0-100 mg/kg Cr(3+) or Ni(2+)) applied as inorganic salts. The ability to uptake Cr(3+) and Ni(2+) differs significantly and is highly affected by the characteristics of soils, and depends on the metal investigated. The heavy metal uptake of the plant differs significantly in acid, colloid deficient sandy soils; while artificial chromium contamination did not modify the dry-matter production in the pots in either soil, a large quantity of nickel reduced the yields significantly. Nitrogen application did not change significantly the uptake of heavy metals. Lime application reduced the Ni(2+) uptake of plants considerably, especially in sandy soil. In case of a calcium carbonate addition the dry-matter production of the plant was not affected by nickel. In chernozem soil the effect of lime application - i.e., the reduction of nickel uptake - was of a lesser degree. The significantly lesser Cr(3+) uptake was further limited by a calcium carbonate application for both soils studied. A graphic presentation of these effects is given.

Journal Article↗
PubMed1996

Speciation of chromium by coupled column HPLC-ICP-MS - the effects of interfering ions.

ICP-MS is used as an element selective detector for chromium species in aquatic samples using a coupled columm system consisting of a cation guard column and an anion column. The effects of large concentrations of disturbing ions, like NO(3)(-), Cl(-), CO(3)(2-) and SO(4)(2-), are discussed and the comparison with the use of different chromium isotopes for data acquisition is given. Quite low concentrations such as 100 mg/l of CO(3)(2-), 10 mg/l Cl(-) and even 5 mg/l SO(4)(2-) can cause an overestimation of chromium if not properly resolved1995 / Accepted: 24 October 1995

Journal Article↗
PubMed2006

Occupational asthma due to chromium and nickel salts.

BACKGROUND: Exposure to chromium and nickel salts is a poorly characterized cause of occupational asthma. METHODS: We describe four patients with work-related asthma due to metallic salts. Skin-prick tests to potassium dichromate and nickel sulfate were performed. The patients underwent methacholine inhalation tests and specific inhalation challenges (SIC) with both chromium and nickel salts. RESULTS: Two patients showed positive skin-prick tests to potassium dichromate and nickel sulfate. All patients had bronchial hyperresponsiveness to methacholine, which increased 24 h after SIC with metallic salts. SIC with potassium dichromate elicited late asthmatic reactions (LAR) in two workers, one subject had an early asthmatic reaction (EAR), and another subject showed a dual asthmatic reaction (DAR). SIC with nickel sulfate induced a DAR in one subject and a late asthmatic reaction in another. CONCLUSIONS: Chromium and nickel salts can give rise to occupational asthma in exposed workers. The underlying mechanism may be IgE-mediated in some cases.

Adult↗
PubMedDate not supplied

Chromium(VI) and apparent phenotypic reversion in Salmonella TA100.

After treatment with potassium chromate at concentrations causing ultramicroscopic cellular lesions, a significant proportion (up to 75%) of TA100 colonies fail to replicate on fresh minimal plates containing biotin. This suggests that chromium(VI) may not always induce his- reversion to his+ in Salmonella TA100. The terms 'false' or phenotypic reversion have been used to distinguish such instances from 'true' or genotypic reversion, where progeny his+ cells readily grow on biotin replica plates. Results of the present study indicate that the majority of chromate-exposed colonies, initially scored as his-, are identifiable as his+ after 24 h culture on nutrient agar. Moreover, chromate exerts a cytostatic effect on TA100 since early colony development is suppressed at high chromate concentrations. A gradual chemical reduction of chromium(VI) ions by normal media compounds is probably responsible for the re-emergence of colony growth during prolonged incubation of test plates. Thus, temporary growth inhibition at high chromate concentration appears to be responsible for most of the non-replicating colonies detected in mutagenicity assays of chromium(VI).

Chromates↗
PubMed2006

Chromium picolinate improves insulin sensitivity in obese subjects with polycystic ovary syndrome.

Trivalent chromium (1000 microg), as chromium picolinate, given without change in diet or activity level, caused a 38% mean improvement in glucose disposal rate in five obese subjects with polycystic ovary syndrome who were tested with a euglycemic hyperinsulinemic clamp technique. This suggests that chromium picolinate, an over-the-counter dietary product, may be useful as an insulin sensitizer in the treatment of polycystic ovary syndrome.

Adult↗
PubMed2004

Removal of lead and chromium from wastewater using bagasse fly ash--a sugar industry waste.

An inexpensive and effective adsorbent was developed from bagasse fly ash, obtained from a sugar industry, for the dynamic uptake of lead and chromium. Lead and chromium are sorbed by the developed adsorbent up to 96-98%. The removal of these two metal ions up to 95-96% was achieved by column experiments at a flow rate of 0.5 mlmin(-1). The adsorption was found to be exothermic in nature. The adsorbent was successfully tried for the removal of lead and chromium from wastewater in our laboratory. The developed system for the removal of two ions is very useful, economic, rapid, and reproducible.

Journal Article↗