Showing papers on "Chromium published in 1979"

Chromium deficiency during total parenteral nutrition.

Abstract: Chromium is required for maintenance of normal glucose tolerance. After complete bowel resection and five months of total parenteral nutrition, severe glucose intolerance, weight loss, and a metabolic encephalopathylike confusional state developed in a patient. Serum chromium levels were at the lowest normal level. Supplementation of 150 μg of chromium per day reversed the glucose intolerance, reduced insulin requirements, and resulted in weight gain and the disappearance of encephalopathy. The low levels of chromium and response to chromium supplementation suggest that chromium deficiency can arise in long-term total parenteral nutrition. ( JAMA 241:496-498, 1979)

Chromate metabolism in liver microsomes.

Abstract: The carcinogenicity and mutagenicity of various chromium compounds have been found to be markedly dependent on the oxidation state of the metal. The carcinogen chromate was reduced to chromium(III) by rat liver microsomes in vitro. Metabolism of chromate by microsomal enzymes occurred only in the presence of either NADPH or NADH as cofactor. The chromium(III) generated upon metabolism formed a complex with the NADP(+) cofactor. Significant binding of chromium to DNA occurred only when chromate was incubated in the presence of microsomes and NADPH. Specific inhibitors of the mixed function oxidase enzymes, 2'-AMP, metyrapone, and carbon monoxide, inhibited the rate of reduction of chromate by microsomes and NADPH. The possible relationship of metabolism of chromate and its interaction with nucleic acids to its carcinogenicity and mutagenicity is discussed.

Reduction of chromate in cement by iron sulfate.

Abstract: Cement dermatitis is connected with chromate sensitivity. It can therefore be expected that "elimination" of chromate in cement would decrease the number of cases of cement dermatitis. Iron sulfate added to cement reduces the chromate completely and the 3-valent chromium is precipitated. An amount of 0.35% (w/w) iron sulfate, FeSO4 . 7H2O, is enough to reduce 20 microgram Cr6+/g cement. There is no technical side effect to the concrete. The iron sulfate is preferably added to cement when there is an intimate contact with skin, e.g. at floor laying, repairs and hand-made casting.

The cytotoxic, mutagenic and clastogenic effects of chromium-containing compounds on mammalian cells in culture

Abstract: Examples of chromic and chromate salts have been examined for their effects on a cultured Chinese hamster cell line. The responses studied were cytotoxicity, mutagenesis and clastogenesis. Chromate (hexavalent chromium) salts of both high and medium water solubility were active in producing all three classes of response, whereas an insoluble chromate salt and a soluble chromic (trivalent chromium) salt were inactive. In addition to illustrating the value of using mammalian cells in culture for screening chemicals for biological activity, the results of this study reinforce current views regarding the genotoxic properties of chromates.

Single-phase ferritic solidification mode in austenitic-ferritic stainless steel welds

Abstract: The macro- and microstructures of about 50 different stainless welds of the AISI/AWS 300 series are analyzed. The results indicate that under conditions corresponding to a typical SMA welding, those and only those welds in which the ratio Creq/Nieq≳1.95, where Nieq and Creq are the nickel and chromium equivalents on the Schaeffler diagram, solidify as single-phase ferrite: Austenite subsequently forms from ferrite in the solid state by a Widmanstatten mechanism. The microstructure at room temperature (RT) is characterized by straight phase boundaries and a distinct orientation relationship between the austenite and ferrite. The compositional differences observed at RT are mainly a consequence of the solid state transformation, not of solidification.

Elastic moduli of paramagnetic chromium and Ti-V-Cr alloys

Abstract: The single-crystal elastic moduli of chromium have been measured ultrasonically to 5 kbar and from 80 to 700K. In the paramagnetic phase the shear moduli are found to be approximately linear functions of pressure and temperature for pressures and temperatures above the Neel transition line. At atmospheric pressure, the compressional modulus C11 increases with temperature above TN up to a maximum at about 475K, and then decreases and becomes a linear function of T above 550K.C11 is not a linear function P for temperatures up to 473K. The results for paramagnetic chromium are combined with previous results on Ti-V and V-Cr alloys to discuss the relationship of the elastic properties to the electronic bandstructure of these alloys.

The role of chromium accumulation in the relationship between airborne and urinary chromium in welders.

Abstract: Twenty-two welders working with high chromium alloyed electrodes have been examined. Biological monitoring of exposure was accompanied by measurement of the hydrosoluble fraction of chromium in the air. Several indices of early renal tubular damage were also determined. The close relationship between airborne and urinary chromium suggests that the urinary excretion of the metal at the end of exposure, and particularly its increase above baseline values, are reliable indicators of absorption rate. The measurement of the renal clearance of diffusible chromium—taken as an index of body burden-showed the influence of the lower exchange rate compartment on the relationship between environmental and urinary chromium. Although the degree of exposure was the same, the urinary excretion of chromium was higher in the workers with a greater chromium body burden. The evaluation of some early nephrotoxicity indicators yielded no dose-effect relationship, even if a more frequent pathological “response” was observed in the subjects with a higher degree of exposure to chromium.

Particle adhesion and removal in model systems. Part 2.—Monodispersed chromium hydroxide on steel

Abstract: The adhesion of uniform spherical colloidal particles of chromium hydroxide (modal diameter 0.28 µm) on stainless steel surface and their subsequent removal by rinse solutions of various pH and Ca(NO3)2 concentrations were studied using the packed column technique. The particles were deposited on steel at pH 5. The pH of the rinse solution had to be adjusted to ≈ 11 before appreciable particle desorption occurred, although the isoelectric point of the steel used was ≈ 5 and that of the chromium hydroxide particles was ≈ 8. Desorption increased at still higher pH, reached a maximum at pH ≈ 12, and then decreased again with increasing rinse solution pH. An addition of Ca(NO3)2 in concentration as low as 10–3 mol dm–3 completely inhibited the removal of chromium hydroxide from the steel surface at pH 11.7. The results obtained are analysed in terms of the existing theory of the electrical double layer and the diffusional escape of the particles across the interaction energy barrier. No chemical bonding between the particles and the substrate could be detected.

Chromium accumulation and distribution in crop plants

Abstract: Crop plants accumulated chromium from nutrient solutions labelled with either 51CrIII or 51CrVI and retained approximately 98 % of the elements in the roots. Of the 9 crop species examined, cauliflower plants accumulated the most chromium in both shoots and roots and mung bean seedlings the least. Species differences of approximately 10-fold in the tops and 5-fold in the roots were recorded. The roots of each species supplied with 51CrIII contained more chromium than those supplied with 51CrVI but the reverse was found in the shoots. There was a greater proportion of soluble chromium in plants supplied with 51CrVI than in those supplied with 51CrIII, the major soluble compound being tentatively identified as trioxalato-CrIII. Little chromium was associated with cell organdies or soluble proteins.

Redox reactions involving chromium, plutonium, and manganese in soils

Abstract: Plutonium speciation in soils is discussed. Chromium was selected as a model for studying soil Pu. Similarities between Cr and Pu are pointed out, and a hypotheses concerning Pu speciation in soils is presented. Findings from Cr oxidation studies that may be relevant to the problem of Pu oxidation in soils are discussed. (JGB)

Oxidation of high-chromium Ni-Cr alloys

Abstract: The oxidation of binary Ni-Cr alloys containing 44 and 50 wt. % Cr has been studied over a range of oxygen partial pressures at temperatures between 800 and 1100°C. The effects of cold work, surface preparation, and distribution of the Cr-rich second phase have been studied. The oxidation behavior is complex and cannot be described by a single model. The oxide grows by short-circuit diffusion as well as bulk transport through Cr 2 O 3 scales. The scale-growth mechanism includes extensive metal-oxide separation requiring Cr vapor transport to the scale, compressive stresses within the oxide which result in scale bulging and cracking, and the formation of a second oxide layer which results in voids being incorporated into the scale. Any factor which reduces the oxide grain size, such as cold work, finer distribution of the Cr-rich α phase or reduced oxygen pressure, results in an increased oxidation rate of binary alloys because of an increased number of grain-boundary short-circuit diffusion paths.