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PubMed1978

Accommodation and chromatic aberration in young children.

Retinoscopy through colored filters (chromoretinoscopy) was used to determine the portion of the chromatic aberration interval in focus when young children (2 to 6 years of age) fixate at far and near. The results indicate that the children may be divided into three distinct groups. In the youngest group there is haphazard focusing within the chromatic aberration interval at far and near. The middle group shows selective focusing of the red end of the chromatic interval at both far and near. Children in the oldest group focus the red end when fixating at far and the green end when fixating at near, thereby sparing accommodation. These results suggest that the eye's use of the chromatic aberration interval to spare accommodation, as found in previous studies carried out on adults, is learned by about the fourth year of a child's life.

Accommodation, Ocular↗
PubMed1998

Residual processing of chromatic signals in the absence of a geniculostriate projection.

We have investigated the residual processing of chromatic signals in a subject with unilateral damage to the primary visual cortex using psychophysical, pupillometric and functional magnetic resonance imaging (fMRI) methods. Of particular interest was to establish the correlation between the subject's ability to make use of chromatic signals in the blind hemifield to discriminate between different coloured targets, the corresponding residual pupil colour responses and the level and location of cortical activation generated by the same stimuli as revealed by fMRI. The results obtained using the three different experimental approaches are consistent and suggest that retrograde degeneration of thalamic and retinal chromatic processing mechanisms caused by damage to the primary visual cortex in man does not abolish completely the ability to process chromatic signals particularly when large, long-wavelength stimuli are employed.

Color Perception↗
PubMed1987

Chromium content of organs of chromate workers with lung cancer.

The content of chromium was measured in organs of six chromate workers who had worked in a chromate chemical manufacturing plant, had been exposed to a considerable amount of chromium for over 10 years, and had died of lung cancer. The chromium in the lungs of workers averaged 51.5 micrograms/g (range 24.8-210 micrograms/g), while levels in the lungs of non-exposed controls were 0.07-1.01 micrograms/g. Organs other than the lungs of the workers also had more chromium than those of the controls. Moreover, it was apparent that the metal remained in the lungs long after exposure to chromate had ceased.

Adult↗
PubMed2003

Barium chromate is cytotoxic and genotoxic to human lung cells.

Hexavalent chromium (Cr(VI)) compounds are widely accepted as human lung carcinogens. However, there have been few investigations of the genotoxicity of Cr(VI) in human lung cells. Moreover, our knowledge of the effects of Cr(VI) in human lung cells is further limited because the available data generally focus on the effects of only lead chromate (PbCrO(4)) and sodium chromate (Na(2)CrO(4)). To fully understand these carcinogenic compounds, the genotoxic effects to its target cells need to be evaluated for additional Cr(VI) salts. Accordingly, we investigated the cytotoxicity and clastogenicity of barium chromate (BC) in a human lung cell culture model (WTHBF-6 cells). We found that BC induced concentration-dependent cytotoxicity in WTHBF-6 cells, with relative survival of 88%, 74%, 67%, 12%, 3%, and 0.1% after exposure to 0.01, 0.05, 0.1, 0.5, 1, and 5 microg/cm(2) BC, respectively. Similarly, the amount of chromosomal damage also increased with concentration after a 24-h exposure. Specifically, 0.01, 0.05, 0.1, and 0.5 microg/cm(2) BaCrO(4) damaged 5%, 9%, 22%, and 49% of metaphase cells, with the total damage reaching 5, 10, 28, and 65 aberrations per 100 metaphases, respectively. Concentrations of 1 and 5 microg/cm(2) BC induced a profound cell cycle delay, and no metaphases were observed. The spectrum of damage included chromatid and chromosome-type lesions consistent with mechanistic events associated with the activation of oncogenes and inactivation of tumor suppressor genes. Overall the data indicate that BC is cytotoxic and genotoxic to human lung cells.

Barium↗
PubMed1989

Lung cancer in chromate workers: high-risk group for multiple lung cancer.

We diagnosed eight (8.9%) lung cancer patients in 90 workers exposed to chromate compounds. The duration of exposure ranged from 8 to 31 years, with a mean value of 18 +/- 8 years. The histological classification was squamous-cell carcinoma in seven patients and adenocarcinoma in one patient. The site of origin of the primary tumors was located peripherally in two (25%) and centrally in six (75%). All but one of these patients underwent surgery. In three (37.5%) of these patients, lung cancer foci were detected during the postoperative follow-up by sputum cytology and bronchoscopy. Two of these three patients had multicentric cancer foci: double primary early squamous-cell carcinoma in one and early squamous-cell carcinoma + small-cell lung cancer in the other. In a high-risk group such as chromate workers, we should emphasize early detection of lung cancer by serial sputum cytology, chest x-rays, and bronchoscopy. Lung cancer patients with chromate exposure should be treated with due regard to the possibility of synchronous or metachronous cancer.

Adult↗
PubMed1983

Lung cancer mortality of workers employed in chromate pigment factories. A multicentric European epidemiological study.

This study was designed in an attempt to quantify the mortality from cancer and other diseases among workers of European factories producing chromate pigments. The prevailing mixed exposures to zinc as well as lead chromate pigment--although the latter was produced predominantly over the whole period of time made it impossible to distinguish those persons exposed to lead chromate pigment. This report deals with cancer of the respiratory tract and lung cancer in particular. The total workforce of each factory included in the study was followed up, more successfully when they were employed before 1960 than after that time owing to the rising number of foreign nationals. Observed deaths from five factories were compared with expected deaths calculated on the basis of mortality figures for the region in which a given factory was located. Further analysis concerned data of relevant cohorts, which comprised only persons observed for a minimum of 10 years (i.e., exposure beginning before 1965), certainty of complete records for the entire staff to assure a complete cohort instead of prevailing healthy survivors, and exclusion of all foreign nationals. As a result, the overall mortality did not deviate from the expected rates. Lung-cancer rates were always in excess of expected numbers, although only in one cohort to a statistically significant extent. The pattern of duration of exposure indicates that the lung-cancer risk does not show a clear dose-response effect with time of employment. Due to the mixed nature of exposure, conclusions must be limited with the effect that the results obtained are consistent with the hypothesis that working in a chrome-processing plant environment is associated with an increased incidence of lung cancer and with a higher probability of dying from lung cancer compared with the general population.

Adult↗
PubMed1989

A comparison of the effects of chromate, molybdate and cadmium oxide on respiration in the yeast Saccharomyces cerevisiae.

Growth of Saccharomyces cerevisiae on non-fermentable medium was more sensitive to inhibition by chromate than growth on fermentable medium. Chromate was selectively toxic against oxygen uptake in cells grown in non-fermentable medium and also induced petite mutations. CdO demonstrated similar but lesser effects on growth and respiration. However, molybdate had little toxicity to yeast non-fermentable growth and stimulated oxygen uptake in cells grown in fermentable and non-fermentable media. These results suggest that chromate, a carcinogen, may act more directly against the mitochondria of S. cerevisiae than related chemical species, CdO and molybdate.

Cadmium↗
PubMed2004

[Developments in chromate allergy in the German construction industry].

For decades potassium dichromate has been the most important allergen in the construction industry. In Scandinavian countries the prevalence of potassium dichromate sensitization declined following the introduction of low-chromate cement. In contrast, analysis of our register in Northern Bavaria and the data of workers compensation board show no significant decline in potassium dichromate sensitization in the German construction industry during the 1990s. In 1993, German legislation provided an Approved Code of Practice and the cement manufacturers committed themselves to reduce the level of water-soluble chromates to less than 2 ppm in bag cement. Since 2000 this agreement has also included ready-mixed concrete. It remains to be seen, if sensitization against potassium dichromate will decline in the upcoming years. Based on our data, it would be desirable if only low-chromate cement was used in the construction industry in Germany as in Scandinavia.

Adolescent↗
PubMed2005

Comparison of 16S rRNA and 16S rDNA T-RFLP approaches to study bacterial communities in soil microcosms treated with chromate as perturbing agent.

Transcripts of ribosomal RNA have been used for assessing the structure and dynamics of active bacterial populations; however, it remains unclear whether the information provided by community profiling derived from RNA is different from that derived from DNA, particularly when a selective pressure is applied on the bacterial community. In the present work, terminal-restriction fragment length polymorphism (T-RFLP) community profiles based on DNA and RNA extracted from soil microcosms treated with a toxic concentration of chromate were compared. Microcosms of a nonpolluted agricultural soil and of a heavy-metal-rich soil (serpentine) were treated with chromate and DNA and RNA were extracted. T-RFLP analysis was performed on amplified and retro-amplified 16SrRNA gene sequences, and band profiles obtained from samples of DNA and of RNA were compared. Some of the T-RFLP bands, identified as peculiar peaks in the profiles, were cloned and sequenced for taxonomic interpretation. Results indicated that: (1) community profiles derived from RNA and DNA were partly overlapping; (2) there was a strong correlation between the dynamics shown by RNA- and DNA-based T-RFLP profiles; (3) chromate addition exerted a clear effect on both agricultural and serpentine soil bacterial communities, either at the DNA and at the RNA level; however, the profiles derived from RNA showed sharper differences between treated and control samples than that of DNA-based profiles.

Agriculture↗
PubMed2006

Community structure and function in a H(2)-based membrane biofilm reactor capable of bioreduction of selenate and chromate.

Two different H(2)-based, denitrifying membrane-biofilm reactors (MBfRs) initially reduced Se(VI) or Cr(VI) stably to Se(0) or Cr(III). When the oxidized contaminants in the influent were switched, each new oxidized contaminant was reduced immediately, and its reduction soon was approximately the same or greater than it had been in its original MBfR. The precipitation of reduced selenium and chromium in the biofilm was verified by scanning electron microscopy and energy dispersive X-ray analysis. These results on selenate and chromate reduction are consistent with the interpretation that the H(2)-based biofilm community had a high level of functional diversity. The communities' structures were assessed by cloning analysis. Dechloromonas spp., a known perchlorate-reducing bacteria, dominated the clones from both reactors during selenate and chromate reductions, which suggests that it may have functional diversity capable of reducing selenate and chromate as secondary and dissimilatory acceptors.

Bacteria↗
PubMed1989

Comparison between the chromate inhibition test and a cytochemical method for the determination of glucose-6-phosphate dehydrogenase deficiency in erythrocytes.

The sensitivity and specificity of the chromate inhibition test for the determination of glucose-6-phosphate dehydrogenase (G6PD) deficiency in erythrocytes were compared with a cytochemical staining method. Fifty blood samples were used in a double blind study. The samples were selected from 600 blood samples on the basis of two biochemical criteria, viz. either G6PD activity less than 4.8 IU/g Hb as analysed spectrophotometrically and/or G6PD activity less than glutathione reductase (GSSG-R) activity. The cytochemical assay was taken as reference because it has been proved to be sensitive and specific for the detection of heterozygous and homo/hemizygous forms of deficiency. Cytochemically, one hemizygously deficient patient, 19 heterozygotes and 30 normals were detected. When applying the chromate inhibition test a somewhat different result was obtained with the same samples: one of the 30 normals was classified as heterozygously deficient (3% false positives) and 5 of the 19 heterozygously deficient patients were classified as normal (26% false negatives). It is concluded that the chromate inhibition test is a more sensitive biochemical test than the fluorescence spot test or spectrophotometric assays. However, it is less reliable than the cytochemical test for the detection of heterozygously G6PD deficient patients.

Chromates↗
PubMed1986

Effects of potassium chromate on atherosclerosis prevention and regression in rabbits.

The effect of intraperitoneal injections of potassium chromate on prevention and regression of atherosclerosis was observed in New Zealand White rabbits. In rabbits fed a 1% cholesterol diet for 90 days, potassium chromate injection was not associated with a significant difference in weight, serum cholesterol, total cholesterol content per 8.5 cm aorta, cholesterol content per gram of aorta or percent intima covered with plaque compared to controls. Similarly, significant differences were not seen in rabbits fed a 1% cholesterol diet for 90 days followed by 60 days of potassium chromate or distilled water injections and a standard diet. These results are in keeping with recent studies suggesting a more limited role for chromium in a variety of lipid-related disorders.

Animals↗
PubMed1990

The DNA cleavage induced by a chromium(V) complex and by chromate and glutathione is mediated by activated oxygen species.

The number of strand breaks induced by the combination of chromate and glutathione (GSH) in PM2 DNA was effectively reduced upon addition of the hydroxyl radical scavengers dimethyl sulphoxide (DMSO), formate and benzoate. Administration of catalase also led to a depression of DNA degradation whereas superoxide dismutase (SOD) had very little influence. Essentially the same results were obtained in experiments employing a chromium(V) complex Na4(GSH)4Cr.8H20, which is an intermediate chromium species isolated from the reduction of chromate by glutathione. DNA cleavage was dependent on the presence of iron (FeCl3). When compared with the number of breaks produced by FeCl3 and GSH alone, chromate stimulated the generation of single-strand breaks. These findings suggest that hydroxyl radicals are one ultimate DNA cleaving agent in both reactions. A reaction scheme for the production of hydroxyl radicals is proposed.

Catalase↗
PubMed1995

Unusual findings in a fatal case of poisoning with chromate compounds.

An interesting case of acute poisoning by chromate compounds is reported. A 51-year-old man committed suicide by ingesting a fatal dose of sodium chromate solution. He unexpectedly lost consciousness 6 h after the ingestion and died approximately 20.5 h later. An examination of the blood showed noticeable hepatic damage and thrombocytopenia. The postmortem examination revealed extensive bleeding in the alimentary tract and a severe hepatic lesion due to hepatocellular necrosis. However, the renal disorder was unusually light in the microscopic and clinical findings. Moreover, the renal lesion was observed mainly in the distal tubules instead of the proximal tubules which is more typical in cases of acute poisonings by diverse heavy metals including chromium. The patient's death was assumed to have been caused by circulatory collapse due to internal bleeding and the direct toxicity of chromate compounds with hepatic malfunction and possibly disseminated intravascular coagulation (DIC).

Chemical and Drug Induced Liver Injury↗
PubMed2006

Synthesis of a quaternary amine anion exchange resin and study [of] its adsorption behaviour for chromate oxyanions.

Glycidyl methacrylate/N,N'-methylene bis-acrylamide (GMA/MBA) was prepared and allowed to react with tetraethylenepentamine (TEP) to give glycidyl methacrylate amine resin (RPA) followed by treatment with glycidyl trimethylammonium chloride (GTA) to give glycidyl methacrylate resin bearing quaternary ammonium chloride moieties (RQA). Zeta potential measurements showed that RQA particles are positively charged over pH 2-10 indicating the strong basic nature of the quaternary amine sites. The effect of pH on the recovery of chromate by RPA and RQA was examined. The results indicated that RQA is an efficient sorbent for chromate from both acidic and basic media. The repeated use of RQA was tested through stripping the adsorbed chromate using a mixture of 0.05 NaOH and 2 M NaCl in the case of the uptake from acidic media and using 2 M NaCl solution in the case of alkaline solutions.

Adsorption↗
PubMed2004

Aerobic chromate reduction by chromium-resistant bacteria isolated from serpentine soil.

A group of 34 chromium-resistant bacteria were isolated from naturally occurring chromium percolated serpentine soil of Andaman (India). These isolates displayed different degrees of chromate reduction under aerobic conditions. One of the 34 isolates identified as Bacillus sphaericus was tolerant to 800 mgl(-1) Cr(VI) and reduced > 80% Cr(VI) during growth. In Vogel Bonner broth, B. sphaericus cells (10(10) cells ml(-1)) reduced 62% of 20mg l(-1) of Cr(VI) in 48h with concomitant discoloring of yellow medium to white one. Reduction of chromate was pronounced by the addition of glucose and yeast extract as electron donors. In the presence of 4.0 g l(-1) of glucose, 20mg l(-1) of Cr(VI) was reduced to 2.45mg l(-1) after 96h of incubation. Optimum pH and temperature for reduction were 6.0 and 25 degrees C, respectively. Increase in cell density and initial Cr(VI) concentration increased chromate reduction but was inhibited by metal ions like, Ni2+, Co2+, Cd2+ and Pb2+. Experiments with cell-free extracts indicated that the soluble fraction of the cell was responsible for aerobic reduction of Cr(VI) by this organism.

Aerobiosis↗
PubMed2005

Involvement of DNA helicases in chromate resistance by Pseudomonas aeruginosa PAO1.

Chromate-hypersensitive mutants of the Pseudomonas aeruginosa PAO1 strain were isolated using transposon insertion mutagenesis. Comparison of the nucleotide sequences of the regions interrupted within the PAO1 genome showed that mutant strains GGP-64 and AJ-22 were affected in open reading frames PA0967 and PA5345, which correspond to the ruvB and recG genes, respectively. These genes encode helicases RuvB and RecG involved in DNA replication, recombination and repair. The chromate resistance phenotype in mutants GGP-64 and AJ-22 was restored by cosmids bearing wild type ruvB or recG genes, respectively. Also, both mutant strains showed an increased susceptibility to the toxic oxyanions tellurite and selenite as well as to mitomycin C, but not to arsenite, paraquat and hydrogen peroxide. It was concluded that P. aeruginosa RuvB and RecG helicases are involved in repairing DNA damage caused by chromate or its derivatives.

Base Sequence↗
PubMed1988

On the mechanism of the chromate reduction by glutathione: ESR evidence for the glutathionyl radical and an isolable Cr(V) intermediate.

With a view of elucidating the role of glutathione (GSH) in the biochemical pathways of the chromate-exposure related carcinogenesis, we carried out electron spin resonance (ESR) spectroscopic investigations of the chromate-GSH redox reactions. The ESR measurements, employing spin-traps, provide evidence for the involvement of the glutathione (GS) radical, as well as an isolable Cr(V)-glutathione intermediate. These results indicate a new mechanism for the reduction of chromate by GSH in in vitro cellular environment and help understand the (unexpected) increase in Cr(VI)-induced DNA strand breaks at elevated GSH levels.

Chromates↗