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At least 1,423 records · Page 79Linked to original sources
PubMed1987

Insulin-like activity of chromium-binding fractions from brewer's yeast.

51CrCl3 was added to the incubation medium of Saccharomyces cerevisiae for up to 48 hr. After repeated freezing and thawing, lysing in 9 M urea with 1% NP-40 detergent, and dialysis against water, the lower molecular weight (Mr less than 3500) dialysate was retained on a SE53 cationic exchange column, eluted with 0.25 M NH4OH and fractionated on a Bio-gel P-2 column. The insulin-like biological activity of the fractions was measured by the 14C-glucose oxidation in isolated rat adipocytes. The biological activity that was found in two of nine fractions did not correspond to their chromium content. Moreover, identical findings were obtained when chromium was added not to the live yeast but to the yeast extract, which showed that its binding was a chemical process not requiring cellular activity. No fraction demonstrated insulin-potentiating activity on rat adipocytes.

Adipose Tissue↗
PubMed1983

High sensitivity of Salmonella TA102 in detecting hexavalent chromium mutagenicity and its reversal by liver and lung preparations.

The recently developed strain TA102, particularly suited to the detection of oxidative mutagens (Levin et al., 1983), was the most sensitive out of 9 strains of S. typhimurium his- in revealing the mutagenicity of Cr(VI) compounds (sodium dichromate, calcium chromate and chromium trioxide). The rank of sensitivity was the following: TA102, TA100, TA97, TA92, TA1978, TA98, TA1538 and TA1537, TA1535 being the only insensitive strain. Cr(III) compounds (chromic acetate, chromic nitrate and chromic potassium sulfate) were totally inactive with all strains. The direct mutagenicity of Cr(VI) was markedly decreased, through NADPH-requiring mechanisms, by rat-liver S9 fractions and, to a lower extent, by human lung S12 fractions, which supports the hypothesis of a metabolically regulated threshold in chromium pulmonary carcinogenicity.

Animals↗
PubMed1985

Conditions that influence the genetic activity of potassium dichromate and chromium chloride in Saccharomyces cerevisiae.

Potassium dichromate and chromium chloride were analyzed for their ability to induce mitotic gene conversion and point reverse mutation in D7 diploid strain of S. cerevisiae. We used cells from the stationary phase of growth with and without metabolic activation (S9 hepatic fraction) and cells from the logarithmic phase, that contain a high level of cytochrome P-450 and have a greater permeability. In the present work we confirmed the genetic activity of K2Cr2O7 in cells from the stationary phase, with and without S9 fraction and in cells from the logarithmic growth phase. A slight increase in genetic activity was observed in experiments with CrCl3 using phosphate buffer, but no genetic effects were noted in Tris-HCl buffer. Our studies suggest that phosphate ion may be the carrier responsible of the entrance of trivalent chromium in the cells. The higher cellular permeability may account for the different results obtained with both compounds in cells from the stationary and logarithmic phases of growth.

Biotransformation↗
PubMed1993

Differential protection of chlorophyllin against clastogenic effects of chromium and chlordane in mouse bone marrow in vivo.

The anticlastogenic activity of sodium-copper-chlorophyllin was tested against two known clastogens, chromium(VI) oxide and the pesticide chlordane, both of which occur as environmental toxicants. The chemicals were administered to male Swiss albino mice by gavage and chromosomes were studied from bone marrow cells 24 h after the exposure, following colchicine-air drying-Giemsa preparation. The end-points screened were the frequencies of chromosomal aberrations and damaged cells. The clastogenic effects induced by chromium in aqueous solution (20 mg/kg body weight) were reduced to a significant level by chlorophyllin (1.5 mg/kg body weight), when administered both before and simultaneously with the toxicant. The effects of chlordane in olive oil (10 mg/kg body weight) were, however, not reduced by the administration of chlorophyllin (1.5 and 3 mg/kg body weight).

Analysis of Variance↗
PubMed2006

Corrosion by galvanic coupling between amalgam and different chromium-based alloys.

OBJECTIVES: In recent years there has been an increase in the use of dental casting alloys in prosthodontic treatment. Many patients have metals or alloys, as well as amalgam fillings, in their mouth, and will have them for many years. The aim of this study was to evaluate and compare, in vitro, the galvanic corrosion behavior of chromium-cobalt alloy (Remanium GM 380) and chromium-nickel alloy (Remanium CS) when bound together or coupled with silver-based amalgam (Amalcap plus). METHODS: An electrochemical characterization of the alloys was performed by potentiostatic and potentiodynamic methods, i.e. the open circuit potential (OCP), the corrosion potential (E(CORR)), corrosion current density (i(CORR)) and corrosion resistance (R(P)). The electromotive force (EMF) of the bimetallic cells was also tested. Electroanalytical techniques were used to estimate the release of any respective element from the dental alloys under study into the artificial saliva solution. RESULTS: It was found that a bimetallic cell consisting of Remanium CS and Remanium GM 380 alloys has a very low EMF (a few mV) and is not a potential source of galvanic currents in the oral cavity. However, galvanic cells prepared from Amalcap plus and Remanium CS or Remanium GM 380 showed a much greater EMF: 104 and 109mV, respectively. This clearly indicates that in these latter cases it is possible to expect some metal ions in the saliva solution as a result of the work of galvanic currents. It was found, by adsorptive stripping voltammetry analysis, that nickel or cobalt, depending on the alloy used, appeared in the saliva solution and increased in concentration over time. SIGNIFICANCE: The results indicate that the correct design and use of dental alloys are important when determining the appropriate treatment for a specific patient.

Chromium↗
PubMed2006

Application of the Rietveld method to assess chromium(VI) speciation in chromite ore processing residue.

The Rietveld method allows the quantification of crystalline phases and amorphous material identified by X-ray powder diffraction (XRPD) and other diffraction methods. The method assists in determining the speciation of contaminants in solid matrices both qualitatively and quantitatively in a statistically defensible approach, as it does not focus on a microscale. Rietveld was applied to chromite ore processing residue (COPR), a cementitious waste containing hexavalent chromium. Calcium aluminum chromium oxide hydrates (CACs) were the crystalline phases identified by XRPD that bind Cr(6+) in COPR according to their chemical formula. Rietveld quantification, combined with mass balances on Cr(6+), showed that CACs may bind Cr(6+) in variable percentages, ranging from 25% to 85%. Analysis of duplicate samples showed that material variability is the predominant factor of uncertainty in evaluating the role of CACs in Cr(6+) speciation, provided that a consistent quantification strategy is pursued. The choice of strategy was performed on the basis of the pertinent literature, preliminary analyses of the equipment and the software settings, and mass balances. The correlation between the average CAC-bound Cr(6+) concentration and the total Cr(6+) for five samples (R(2)=0.94), extracted from different zones and soil borings, suggests that CACs are a primary sink for Cr(6+) in COPR.

Aluminum Oxide↗
PubMed2006

Incision of trivalent chromium [Cr(III)]-induced DNA damage by Bacillus caldotenax UvrABC endonuclease.

Some hexavalent chromium [Cr(VI)]-containing compounds are lung carcinogens. Once within cells, Cr(VI) is reduced to trivalent chromium [Cr(III)] which displays an affinity for both DNA bases and the phosphate backbone. A diverse array of genetic lesions is produced by Cr including Cr-DNA monoadducts, DNA interstrand crosslinks (ICLs), DNA-Cr-protein crosslinks (DPCs), abasic sites, DNA strand breaks and oxidized bases. Despite the large amount of information available on the genotoxicity of Cr, little is known regarding the molecular mechanisms involved in the removal of these lesions from damaged DNA. Recent work indicates that nucleotide excision repair (NER) is involved in the processing of Cr-DNA adducts in human and rodent cells. In order to better understand this process at the molecular level and begin to identify the Cr-DNA adducts processed by NER, the incision of CrCl(3) [Cr(III)]-damaged plasmid DNA was studied using a thermal-resistant UvrABC NER endonuclease from Bacillus caldotenax (Bca). Treatment of plasmid DNA with Cr(III) (as CrCl(3)) increased DNA binding as a function of dose. For example, at a Cr(III) concentration of 1 microM we observed approximately 2 Cr(III)-DNA adducts per plasmid. At this same concentration of Cr(III) we found that approximately 17% of the plasmid DNA contained ICLs ( approximately 0.2 ICLs/plasmid). When plasmid DNA treated with Cr(III) (1 microM) was incubated with Bca UvrABC we observed approximately 0.8 incisions/plasmid. The formation of endonuclease IV-sensitive abasic lesions or Fpg-sensitive oxidized DNA bases was not detected suggesting that the incision of Cr(III)-damaged plasmid DNA by UvrABC was not related to the generation of oxidized DNA damage. Taken together, our data suggest that a sub-fraction of Cr(III)-DNA adducts is recognized and processed by the prokaryotic NER machinery and that ICLs are not necessarily the sole lesions generated by Cr(III) that are substrates for NER.

Bacillus↗
PubMed2005

Serum levels of cobalt and chromium in patients with Sikomet metal-metal total hip replacements.

Metal/metal total hip replacements (M/M THRs) made of CoCr-based alloys were reintroduced in hip arthroplasty in order to avoid the problem of polyethylene wear and consequently to diminish the wear debris-related osteolysis. Emerging concerns accompanying the reintroduction of M/M THRs are related to the possibility increase of Co and Cr serum levels and, therefore, a careful surveillance of M/M patients is recommended. In the present work three groups of patients with Sikomet SM21 low-carbon alloy were investigated: retrospective group, prospective group and revision group. The investigation of these different groups of patients provided data concerning the metal concentration as a function of time in situ, as well as time ex situ, i.e., following the removal of M/M bearing. A retrospective group of 25 patients sampled at average 60 +/- 20 months postoperatively showed a 3-fold increase in cobalt and a 4.4-fold increase in chromium compared with the control group. In the prospective group of seven patients both cobalt and chromium increase with time and at average 140 +/- 80 days achieved a significant increase compared with preoperative values. An important contribution of this study to the current knowledge on M/M bearings is achieved by the measurements in the revision group of 10 patients, where we observed a decline of serum Co and Cr levels following the removal of M/M articulation. While the link between the increase in metal serum levels and the presence of M/M THR is proved, the biological impact of these results remains to be elucidated.

Adult↗
PubMed1992

Defining conditions for the efficient in vitro cross-linking of proteins to DNA by chromium(III) compounds.

The formation of cross-links between bovine serum albumin and DNA in the presence of chromium(III) chloride was found to be highly pH dependent. In vitro, such lesions were only formed at acidic values of pH, but were not detected at neutral pH. Complexes of chromium(III) and GSH/GSSG similarly failed to induce DNA-protein cross-links at physiological values of pH. Our findings indicate that the cross-links generated in vitro at acidic pH may not be directly relevant to the observed formation of such lesions in cultured cells and that a physiologically relevant in vitro model for the efficient cross-linking of proteins to DNA has yet to be devised.

Bacteriophages↗
PubMed1982

Biliary excretion of chromium in the rat: a role of glutathione.

The relative amount of chromium excreted in rat bile after injection of Cr-III is much less than after injection of Cr-VI, about 0.1% and from 6-8% during 5 hours respectively, for corresponding dose levels. The liver to bile ratio was 50-100 for Cr-III injection, for Cr-VI the ratio was 2-3. With doses up to 18 mumol Cr/kg, only Cr-III was found in bile even after injection of Cr-VI. Glutathione depletion of the liver with cyclohexene oxide decreased chromium excretion in bile. Such treatment also decreased the reduction of Cr-VI to Cr-III in the liver cell as only Cr-VI was found in bile. A different distribution of Cr-III in the liver dependent on whether derived from Cr-VI or taken up by the liver as such must be assumed. Taking into account the usual low penetration of biological membranes by Cr-III, a possible active transport mechanism or a specific diffusable Cr-III compound must be postulated.

Animals↗
PubMed2004

Hydrocarbons in hydrothermal vent fluids: the role of chromium-bearing catalysts.

Fischer-Tropsch type (FTT) synthesis has long been proposed to account for the existence of hydrocarbons in hydrothermal fluids. We show that iron- and chromium-bearing minerals catalyze the abiotic formation of hydrocarbons. In addition to production of methane (CH4aq), we report abiotic generation of ethane (C2H6aq) and propane (C3H8aq) by mineral-catalyzed hydrothermal reactions at 390 degrees C and 400 bars. Results suggest that the chromium component in ultramafic rocks could be an important factor for FTT synthesis during water-rock interaction in mid-ocean ridge hydrothermal systems. This in turn could help to support microbial communities now recognized in the subsurface at deep-sea vents.

Archaea↗
PubMed1984

Induction of immunological tolerance by oral administration of nickel and chromium.

Oral administration of nickel-chromium to guinea pigs by way of a fixed occlusal splint, or the incorporation of metallic powder or salts into the pelleted food, did not induce hypersensitivity to these metals. In addition, a subsequent attempt to immunize the pre-treated guinea pigs failed in most animals, whereas non-pre-treated guinea pigs became clearly hypersensitive. These results show that oral administration of nickel and chromium induced a state of (partial) tolerance to both metals.

Administration, Oral↗
PubMed2003

Effects of neutral, cationic, and anionic chromium ascorbate complexes on isolated human mitochondrial and genomic DNA.

The relative activities of neutral, cationic, and anionic chromium ascorbate complexes toward isolated human mitochondrial and genomic DNA were investigated at physiologically relevant conditions by agarose gel electrophoresis. A direct relationship between the charge of the Cr(III) species and their DNA-damaging properties was found. The cationic species were found to be fully capable of DNA-cleavage, even in short incubation periods. Incubations were also performed in the presence of amino acids. No apparent effect was observed under the applied experimental conditions to facilitate or prevent damage through the ternary amino acid-Cr-DNA adduct formation or binary chromium-amino acid complex formation.

Amino Acids↗
PubMed1965

Percutaneous absorption of trivalent and hexavalent chromium. A comparative investigation in the guinea pig by means of 51Cr.

By means of an in vivo isotope technique, the so-called disappearance measurements, a comparison was made during a five-hour period between the percutaneous absorption in the guinea pig of a trivalent (chromic chloride) and a hexavalent (sodium chromate) chromium compound. Nine different concentrations of each substance were studied. We found that in the concentration interval 0.017-0.239 molar the relative absorption of the hexavalent compound was somewhat higher, but the differences were not statistically significant. On the other hand, in the higher concentrations (0.261-0.398 molar) more of the hexavalent compound was absorbed, and the differences were statistically significant. This difference in percutaneous absorption for various concentrations can perhaps account for the divergent results, in respect to the absorption of trivalent and hexavalent chromium compounds, which have recently been published.

Animals↗
PubMed1989

Ultrastructure of the predentinal-dentinal border zone of human teeth exposed to basic chromium (III) sulfate. A method for contrasting of collagen fibrils.

An electron microscopic investigation was undertaken to study a method for contrasting predentine collagen fibrils by their cross-striations after exposure of tissue to chromium solution for various periods. After 1 day of treatment, the cross-striations of collagen fibrils in predentine were clearly visible. The contrast of the cross-striations increased with longer periods of exposure to chromium. This method makes it possible to study the orientation of crystallites as well as collagen fibrils.

Adolescent↗
PubMed1988

[Methodology and evaluation of exposure to fumes formed during welding of chromium-nickel steel].

Using various methods for determination of welding fumes components and taking into account a simultaneous determination of soluble compounds of chromium III and IV, hygienic evaluation in two working places employing different systems of MMA/SS welding, TIG/SS welding and padding was carried out. As it is indicated by the results, proper hygienic evaluation of working conditions is possible owing to the measurements of individual exposure of workers in the breathing zone, allowing for determination of chromium manganese, nickel, and, while applying low-hydrogen electrodes, also fluorides, in every test.

Air Pollutants, Occupational↗
PubMed1986

Hypersensitivity to mercury, nickel and chromium in relation to dental materials.

Three metals which are used in dental materials are recognized as causing sensitization sufficiently frequently to consider whether problems might arise from their use in dentistry. These metals are, mercury, nickel and chromium. Nickel is by far the commonest sensitizer, 10 per cent of women are allergic to nickel; sensitization usually occurs through jewellery or fasteners on articles of clothing. Chromium (as chromate) is a much less common sensitizer for several reasons. Sensitization only occurs through hexavalent salts of chromate and the degree of exposure of humans to these salts is much less than to either nickel or mercury. The true incidence of mercury sensitization is difficult to ascertain because many of the materials which were used for patch testing previously and on which statistics were based, contained unnecessarily high concentrations of mercury, and the pattern of mercury allergy is changing because many substances which contain mercury and were used frequently are not now employed. Although metallic mercury can sensitize the evidence would suggest that if dental amalgams ever cause people to become allergic to mercury, it is an extremely rare occurrence. Problems with mercury-containing amalgams in those sensitized are also rare, only 28 cases have been recorded in the literature. Thus, it is likely that at the present time sensitization to mercury is uncommon and decreasing. There is even less evidence that nickel or chromate in dental materials actively sensitize and it is exceptionally rare to have problems with these metals in a prosthesis in someone who is already sensitized.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromium↗
PubMed1995

In vivo corrosion of cobalt-chromium and titanium wear particles.

Tissue reaction to wear particles from metal implants may play a major role in the aseptic loosening of implants. We used electron microprobe elemental analysis to determine the chemical composition of wear particles embedded in the soft tissues around hip and knee implants from 11 patients at revision surgery for aseptic loosening. The implants were made of cobalt-chromium-molybdenum alloy or titanium-aluminium-vanadium alloy. Histological examination showed a widespread giant-cell reaction to the particles. Elemental analysis showed that the chemical composition of the particles was different from that of the implanted alloys: cobalt and titanium were reduced, often down to zero, whereas chromium and aluminium persisted. Our findings indicate that corrosion is continually changing the shape, size and chemical composition of the implanted alloy. This may alter the biochemical environment of the tissue surrounding an implant to favour bone resorption.

Aluminum↗