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PubMed1999

ESR characterization and metallokinetic analysis of Cr(V) in the blood of rats given carcinogen chromate(VI) compounds.

It has been shown that bio-trace metal elements are related to many diseases and the aging process. For many years, carcinogen hexavalent chromium (VI) has been known to be toxic to animals, but its dynamic toxicological mechanism is not sufficiently elucidated. Bioinorganic chemistry in terms of metallokinetic analysis of beneficial or toxic metal ions and their complexes is an important investigation for understanding their biochemical and physiological roles. We have tried to examine the real-time behavior of paramagnetic metal ions and complexes in animals, in which electron spin resonance (ESR) was capable of measuring paramagnetic species in chemical and biological systems. On the basis of our previous results on stable nitroxide spin probes, we have developed the in vivo blood circulation monitoring-electron spin resonance (BCM-ESR) method to analyze time-dependent ESR signal changes due to paramagnetic metal ions and their complexes in real time. When K2Cr2O7 or Na2Cr2O7 in saline was intravenously administered to rats, two ESR signals due to pentavalent chromium(V) were detectable in the circulating blood of rats. Cr(V) detected in the blood was indicated to be in the CrO(O4) and CrO(S2O2) coordination modes after the study on model complexes. From the changes of ESR signal intensities due to Cr(V) in the blood, the metallokinetic parameters were obtained using the pharmacokinetic analysis and the curve-fitting methods. The obtained results are important for understanding carcinogen chromate in terms of the formation of Cr(V) in animals. In addition, we propose the BCM-ESR method, which is useful to analyze the disposition of paramagnetic metal species in the blood of living animals.

Animals↗
PubMed1986

Chromate, molybdate, tungstate and vanadate behave as substrates of yeast diadenosine 5',5'''-p1,p4-tetraphosphate alpha, beta-phosphorylase.

Diadenosine 5',5'''-p1,p4-tetraphosphate (Ap4A) alpha, beta-phosphorylase from yeast Saccharomyces cerevisiae catalyzes two reactions: Ap4A cleavage and nucleoside diphosphate--phosphate (NDP-Pi) exchange. In both reactions phosphate can be substituted by arsenate, chromate, molybdate, tungstate or vanadate. In the presence of each anion, nucleoside 5'-monophosphate (NMP) always accumulates as a product of the reaction. This indicates that an unstable NMP anion is formed as an intermediate.

Anions↗
PubMed2004

Reduction of aqueous chromate by Fe(II)/Fe(III) carbonate green rust: kinetic and mechanistic studies.

This work describes the heterogeneous reaction between FeII in carbonate green rust and aqueous chromate, in NaHCO3 solutions at 25 degrees C, and at pH values of 9.3-9.6. Evidence for reduction of CrVI to CrIII and concomitant solid-state oxidation of lattice FeII to FeIII was found from FeII titration and from structural analysis of the solids using FTIR, XRD, SEM, and XPS methods. Results indicate the formation of ferric oxyhydroxycarbonate and the concomitant precipitation of CrIII monolayers at the surface of the iron compound that induce passivation effects and progressive rate limitations. The number of CrIII monolayers formed at the completion of the reaction depends on [FeII]t=0, the molar concentration of FeII(solid) at t=0; on [n(o)]t=0, the molar concentration of reaction sites present at the surface of the solid phase at t=0; and on [CrVI]t=0, the molar concentration of CrVI at t=0. Kinetic data were modeled using a model based on the formation of successive CrIII monolayers, -(d[CrVI]/dt) = sigma(1)j k(i)[S] [CrVI]([n(i - 1)] - [n(i)]) with k(i)[S] (in s(-1) L mol(-1)), the rate coefficient of formation of CrIII monolayer i, and [n(i)] and [n(i - 1)], the molar concentration of CrIII precipitated in monolayer i and monolayer i - 1, respectively. Good matching curves were obtained with kinetic coefficients: k(1)[S] = 5-8 x 10(-4), k(2)[S] = 0.5-3 x 10(-5), and k(3)[S] about 1.7 x 10(-6) s(-1) m(-2) L. The CrVI removal efficiency progressively decreases along with the accumulation of CrIII monolayers at the surface of carbonate green rust particles. In the case of thick green rust particles resulting from the corrosion of iron in permeable reactive barriers, the quantity of FeII readily accessible for efficient CrVI removal should be rather low.

Carbonates↗
PubMed2006

Molecular and electronic structures of oxo-bis(benzene-1,2-dithiolato)chromate(V) monoanions. A combined experimental and density functional study.

Two oxo-bis(benzene-1,2-dithiolato)chromate(V) complexes, namely, [CrO(L(Bu))2]1- and [CrO(L(Me))2]1-, have been synthesized and studied by UV-vis, EPR, magnetic circular dichroism (MCD), and X-ray absorption spectroscopy and by X-ray crystallography; their electro- and magnetochemistries are reported. H2L(Bu) represents the pro-ligand 3,5-di-tert-butylbenzene-1,2-dithiol, and H2L(Me) is the corresponding 4-methyl-benzene-1,2-dithiol. A structural feature of interest for both the complexes is the folding of the dithiolate ligands about the S-S vector providing Cs symmetry to the complexes. Geometry optimizations using all-electron density functional theory with scalar relativistic corrections at the second-order Douglas-Kroll-Hess (DKH2) and zeroth-order regular approximation (ZORA) levels result in excellent agreement with the experimentally determined structures and electronic and S K-edge X-ray absorption spectra. From DFT calculations, the Cs instead of C2v symmetry for the complexes is attributed to the strong S(3p) --> Cr(3d(x2-y2)) pi-donation in Cs geometry providing additional stability to the complexes.

Anions↗
PubMedDate not supplied

Production of activated species of oxygen during the chromate(VI)-ascorbate reaction: implication in carcinogenesis.

The reaction of chromate and ascorbate in a 1:1 molar ratio at pH 7.4 and 37 degrees C produces a Cr(V) signal observable by EPR at g = 1.980. When this reaction is carried out in aerated media and in the presence of formate, carboxylate radicals (COO.-) can be trapped as DMPO-COO.- spin adducts (DMPO, 5,5-dimethyl-1-pyrroline N-oxide). The use of a known complexant of Cr(V), 2-ethyl-2-hydroxybutyric acid, produces a different Cr(V) signal at g = 1.978 and a decrease of the DMPO-COO.- signal. Hydroxyl radicals are not detected in the media. The oxidizing behavior is suggested to be produced by activation of molecular oxygen present in the reaction mixture.

Ascorbic Acid↗
PubMed1997

A follow-up study of progression from dysplasia to squamous cell carcinoma with immunohistochemical examination of p53 protein overexpression in the bronchi of ex-chromate workers.

Squamous cell carcinoma (SCC) of the bronchus is considered to develop from preneoplastic 'dysplasia', but reports of sequential observation of this dysplasia-carcinoma sequence in humans are very few. We followed four dysplastic lesions found in the bronchi of three ex-chromate workers by bronchoscopy and biopsy and found that all of them progressed to SCC. Of the four lesions, three were severe dysplasias at the first biopsy which progressed to SCCs in 7-13 months. The last one was a slight dysplasia at the first biopsy and showed progression of the atypia to carcinoma in 6 years and 10 months. An immunohistochemical analysis of the chronological change in p53 protein expression in these lesions and in normal ciliated epithelium taken from the surroundings was conducted in each case. Overexpression of p53 protein was observed in two of the severe dysplasias and the one slight dysplasia, as well as their eventual SCCs. However, no such change was apparent in one case of severe dysplasia or its eventual SCC. Normal epithelium was consistently negative. Our results provide direct proof of the dysplasia-carcinoma sequence and suggest that alteration in the expression of p53 protein might be an important early event which persists. Therefore, the immunohistochemical detection of p53 overexpression in biopsy specimens of bronchial epithelium might be useful for evaluation of preneoplastic lesions in high-risk group individuals and for early diagnosis of bronchial cancer.

Aged↗
PubMed2002

Reduction of chromate by fixed films of sulfate-reducing bacteria using hydrogen as an electron source.

The ability of sulfate-reducing bacteria (SRB) to reduce chromate, Cr(VI), was evaluated using fixed-film growth systems and H2 as the electron source. A main objective of the experiment was to distinguish between direct enzymatic reduction and indirect reduction by hydrogen sulfide, in order to subsequently verify and control the synergy of these two mechanisms. In batch experiments with the sulfate-reducing consortium CH10 selected from a mining site, 50 mg l(-1) Cr(VI) was reduced in 15 min in the presence of 500 mg l(-1) hydrogen sulfide compared to 16 mg l(-1) reduced in 1 h without hydrogen sulfide. Fixed films of a CH10 population and Desulfomicrobium norvegicum were fed-batch grown in a column bioreactor. After development of the biofilm, hydrogen sulfide was removed and the column was fed continuously with a 13-mg l(-1) Cr(VI) solution. Specific Cr(VI) reduction rates on pozzolana were close to 90 mg Cr(VI) h(-1) per gram of protein. Exposure to Cr(VI) had a negative effect on the subsequent ability of CH10 to reduce sulfate, but the inhibited bacteria remained viable.

Chromates↗
PubMedDate not supplied

Long-term study of the distribution of soluble chromate-51 in the rat after a single intratracheal administration.

Soluble chromate-51 (as sodium dichromate dihydrate) was applied intratracheally in rats, after which distribution of radioactivity was followed for 40 d by autoradiograph and gamma scintillation counting. Doses were 0.01 and 0.25 mg/kg in physiological saline solution. After administration of a 0.25-mg/kg dose, lung radioactivity declined rapidly for 2 to 3 d, at which time about a third of the total dose remained in the lung. The radioactivity in the lung was localized mainly intracellularly in the parenchyma. Microautoradiography indicated that the 51Cr was localized mostly in the type II alveolar cells. At the end of the experiment (40 d after administration), approximately 10% of the applied dose was found in the lung. The highest 51Cr quantities and concentrations were determined in the lung throughout. In the blood serum, the decline of radioactivity concentration was characterized by an apparent half-life of 3 to 4 d for the period from 2 to 15 d. The concentration time courses for the other tissues and organs indicated longer apparent half-lives, ranging from 14 to 50 d. Kidney, erythrocytes, and testis maintained their Cr levels for a period of 10 to 15 d, after which the decrease of concentration became evident. The results obtained at the lower dose level of 0.01 mg/kg were largely dose-proportional to those obtained at the higher dose level of 0.25 mg/kg.

Animals↗
PubMed1987

An ion chromatographic method for insoluble chromates in paint aerosol.

Potential exposure to Cr(VI) extends to over a million U.S. workers in the plating, paint, steel, tanning and chrome ore processing industries. Historically, Cr(VI) exposure has been monitored using a colorimetric method. This colorimetric method requires acidification of the sample for color development, a step that could cause reduction of Cr(VI) to Cr(III), thus underestimating the Cr(VI) content of the sample. A new method of analysis has been developed that uses ion chromatography (IC) for the measurement and which does not require acidification of the sample. In this method, the same extraction solution of hot 2% NaOH and 3% Na2CO3 as used in the earlier methods is used to dissolve both soluble and insoluble chromates (e.g., PbCrO4, ZnCrO4 and BaCrO4), but it can be carried through the method with only a dilution step before sample injection. Therefore, this method has the advantage of minimizing the potential for Cr(VI) loss by reduction. Another advantage is provided by the IC measurement step, which is not interfered with by colored samples that may affect the colorimetric method. The new method was tested with filter samples of paint aerosol containing PbCrO4 and ZnCrO4. Complete extraction of Cr(VI) from the filter samples was verified by comparison to an independent method in which the filter was completely ashed and analyzed by inductively coupled plasma-atomic emission spectroscopy method. Nothing in the paint samples interfered with the Cr(VI) measurement, nor did five common anions used in a separate test. The method had the sensitivity needed for monitoring at the ACGIH TLV of 0.05 mg Cr(VI)/m3.

Aerosols↗
PubMed2006

Lung cancer mortality in the German chromate industry, 1958 to 1998.

OBJECTIVES: We conducted a mortality study of two German chromate production facilities and evaluated possible dose-response relationships between hexavalent chromium exposure and lung cancer. METHODS: Mortality was followed-up through 1998 and limited to those employed since each plant converted to a no-lime production process. More than 12,000 urinalysis results of chromium levels were available, as was smoking information. RESULTS: All-cause mortality indicated a healthy worker effect (standardized mortality ratio [SMR] = 0.80, 95% confidence interval [CI] = 0.67-0.96); however, lung cancers appeared to be increased (SMR = 1.48, 95% CI = 0.93-2.25). No clear dose-response was found in stratified analyses by duration of employment and time since hire. On the basis of urinary chromium data, lung cancer risk was elevated only in the highest exposure group (SMR = 2.09, 95% CI = 1.08-3.65). CONCLUSIONS: These data suggest a possible threshold effect of occupational hexavalent chromium exposure on lung cancer.

Adult↗
PubMed1985

Chromate sensitivity in Singapore.

The incidence of chromate sensitivity in a South East Asian country was found to be 3.22%, the female:male ratio being 1:5, with the majority of the allergies being occupational in origin in men and unexplained in women. Cement was the most common cause among the occupational allergies. Housewives and office workers were the most common occupations in those with unexplained allergies.

Adult↗
PubMed1979

A postal survey of patients with nickel and chromate dermatitis.

A postal survey was made of 75 patients with nickel and chromate dermatitis who had been discharged from the clinic; 69% of patients replied to the questionnaire and in 81% of these the dermatitis was still active. In many patients (48%) this was causing significant disability long after initial presentation to the clinic (average of 56.5 months). All patients had patch tests performed and the relevance of this is discussed with reference to nickel dermatitis.

Allergens↗
PubMed1983

Elbow eruptions in nickel and chromate dermatitis.

In 7 patients with nickel or chromate allergy and dyshidrotic hand eczema, we observed symmetric hyperkeratotic lesions on the elbows which ran a similar course to the hand dermatitis. Histopathological examinations show findings suggestive of lichen simplex chronicus and subacute-chronic dermatitis, but exclude psoriasis. We conclude that these elbow lesions are a characteristic of systemic allergic contact dermatitis.

Adult↗
PubMed1985

Formulation of a barrier cream against chromate.

A topical cosmetic cream has been developed for use on patients occupationally sensitized to chromate. With the components of this preparation, an in vitro study was carried out, which demonstrated the efficiency of each component. An in vivo experiment on 25 volunteer patients proved a failure. The formula was modified to produce a new cream. The in vitro and in vivo experiences showed satisfactory results in 60 volunteer patients, 60% of whom benefitted from using it.

Administration, Topical↗
PubMed1980

Small animal inhalation chambers and the significance of dust ingestion from the contaminated coat when exposing rats to zinc chromate.

The relative significance of dust ingestion during and after short-term inhalation exposure to a zinc chromate aerosol has been studied. Two groups of rats were exposed in the same dust cloud, one in open wire cages and the other in fiber glass tubes. The chromium excretion during the following 2 1/2 days was 8.4 times higher in faeces and 5.5 times higher in urine in the animals exposed in cages, compared with those exposed in tubes.

Aerosols↗
PubMed1968

Identification of the toxic component of Brucella abortus endotoxin and its labeling with radioactive chromate.

The evidence obtained from immuno-gel diffusion, centrifugation, and toxicity studies employing the serum iron assay proved that most of the toxicity in an ether-water brucella endotoxin preparation lies in the slow-diffusing component identified as the biologically active endotoxin. Subsequent destruction of the slow-diffusing component by acid hydrolysis resulted in a corresponding loss of toxicity. Chromate-51 was found to attach almost entirely on the slow-diffusing biologically active component and, hence, is a valid label for endotoxin derived from smooth Brucella abortus by the ether-water method.

Animals↗
PubMed1969

Distribution of chromate-labeled Brucella abortus endoxin in tolerant mice.

Endotoxin tolerance as manifested by a lesser degree of hypoferremia was demonstrated in mice when both pretreatment (10 mug per injection) and challenge (100 mug) does of Brucella abortus endotoxin were administered intraperitoneally. Qualitative and quantitative studies on the distribution of chromate-labeled endotoxin in normal mice revealed that the endotoxin localized predominately in the liver and hypoferremia could be related to a high uptake of endotoxin by this organ. In tolerant mice, the labeled endotoxin was found mainly in the mesenteric lymph nodes (MLN) with smaller quantities in the blood, spleen, and liver. Experiments with splenectomized mice provided supporting evidence that the liver was the target organ of the hypoferremic response to endotoxin. High localization of endotoxin in the MLN with lower quantities in the blood, livers, and spleens of tolerant mice indicated that tolerance may be the result of a blockage by the MLN, preventing the endotoxin from reaching the liver. This inference was supported by the finding that hypoferremic tolerance did not occur when the hypoferremia-provoking dosage of endotoxin (100 mug) was given intravenously to mice pretreated intraperitoneally. There was less hypoferremia in normal mice injected with a mixture of antiserum and 100 mug of endotoxin than in mice given the same dosage of endotoxin in saline. Distribution studies on endotoxin treated with specific antiserum revealed that the endotoxin localized principally in the MLN, thus preventing most of the endotoxin from reaching the liver, the target organ of the hypoferremic response.

Animals↗
PubMed1981

Microcell-mediated cotransfer of genes specifying methotrexate resistance, emetine sensitivity, and chromate sensitivity with Chinese hamster chromosome 2.

Many selectable mutants of somatic Chinese hamster cells have been described, but very few of the mutations have been mapped to specific chromosomes. We have utilized the microcell-mediated gene transfer technique to establish the location of three selectable genetic markers on chromosome 2 of Chinese hamster. Microcells were prepared from the methotrexate-resistant MtxRIII line of Flintoff et al. (Somatic Cell Genet. 2:245-261, 1976) and fused to wild-type CHO cells, and microcell hybrids (transferants) were selected in medium containing methotrexate. All transferants were karyotyped and found to contain a marker chromosome from the donor MtxRIII line. This marker chromosome, called 2p-, consisted of a chromosome 2 with a reduced short arm resulting from a reciprocal translocation between 2p and 5q. In experiments utilizing emetine-resistant (Emtr) or chromate-resistant (Chrr) recipient cells it was found that the emt+ and chr+ wild-type genes were cotransferred with the 2p- chromosomes. Karyotype analysis of several transferants with rearranged or broken 2p- markers allowed regional localization of the emt and chr loci to the proximal third of the long arm and localization of the gene or genes conferring methotrexate resistance to the short arm. These results confirm our earlier assignment of the emt and chr loci to chromosome 2 in Chinese hamster.

Animals↗