The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform
Masayasu Sugiyama - One of the best experts on this subject based on the ideXlab platform.
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Role of paramagnetic Chromium in Chromium(VI)-induced damage in cultured mammalian cells.
Environmental Health Perspectives, 1994Co-Authors: Masayasu SugiyamaAbstract:Chromium(VI) compounds are known to be potent toxic and carcinogenic agents. Because Chromium(VI) is easily taken up by cells and is subsequently reduced to Chromium(III), the formation of paramagnetic Chromium such as Chromium(V) and Chromium(III) is believed to play a role in the adverse biological effects of Chromium(VI) compounds. The present report, uses electron spin resonance (ESR) spectroscopy; the importance of the role of paramagnetic Chromium in Chromium(VI)-induced damage in intact cultured cells is discussed, based upon our studies with antioxidants including vitamin E (alpha-tocopherol), B2 (riboflavin), C (ascorbic acid), and so on. These studies appear to confirm the participation of paramagnetic Cr such as Chromium(V) and Chromium(III) in Chromium(VI)-induced cellular damage.
John B. Vincent - One of the best experts on this subject based on the ideXlab platform.
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Chromium.
Advances in nutrition (Bethesda Md.), 2018Co-Authors: John B. Vincent, Henry C LukaskiAbstract:Two oxidation states of Chromium are considered to be biologically and environmentally relevant based on their stability in the presence of water and oxygen. Compounds containing Chromium(6 + ) are mutagenic and carcinogenic when inhaled and potentially when ingested orally in large quantity as well. Chromium as the trivalent will be the focus of this work as it was proposed to be an essential element for mammals ∼60 y ago; however, in the last 2 decades its status has been questioned. Chromium has been postulated to be involved in regulating carbohydrate and lipid (and potentially also protein) metabolism by enhancing insulin's efficacy (1). However, in 2014, the European Food Safety Authority found no convincing evidence that Chromium is an essential element (2). Dietary Chromium apparently is absorbed via passive diffusion and the extent of absorption is low (∼1%). Chromium is maintained in the bloodstream bound to the protein transferrin. It is generally believed to be delivered to tissues by transferrin via endocytosis (1). No unambiguous animal model of Chromium deficiency has been established (2). One limitation in characterizing Chromium deficiency in humans is the lack of an accepted biomarker of Chromium nutritional status. Attempts to identify a glucose tolerance factor have not provided a chemically defined functional compound that conforms with the proposed physiologic role of Chromium as a facilitator of insulin action in vivo.
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Mass Spectrometric and Spectroscopic Studies of the Nutritional Supplement Chromium(III) Nicotinate
Biological Trace Element Research, 2009Co-Authors: Nicholas R. Rhodes, Tatyana A. Konovalova, Qiaoli Liang, Carolyn J. Cassady, John B. VincentAbstract:Despite Chromium nicotinate’s popular use as a Chromium nutritional supplement, the structure and composition of Chromium nicotinate have only been poorly described. As solid Chromium nicotinate is intractable, being insoluble or unstable in common solvents, studies on the solid have been limited, and studies of the solution from which the “compound” precipitates have additionally provided little additional data. The results of mass spectrometric and spectroscopic investigations designed to further elucidate the structure and composition of Chromium nicotinate are described. The results demonstrated that the three common methods for producing “Chromium nicotinate” all yield different compounds, all of which are polymers of Cr(III), oxygen-bound nicotinate, hydroxide, and water. Implications for interpreting results of nutritional studies of “Chromium nicotinate” are discussed.
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The bioinorganic chemistry of Chromium(III)
Polyhedron, 2001Co-Authors: John B. VincentAbstract:Abstract The biochemistry of Chromium(III) has been a poorly understood field of endeavor. Despite four decades of investigation, only recently has a somewhat clear picture of the role of Cr been refined. Chromium(III) is required for proper carbohydrate and lipid metabolism in mammals, although Chromium deficiency is difficult to achieve. Conditions that increase circulating glucose and insulin concentrations increase urinary Chromium output. Chromium is excreted after an insulin challenge in the form of the oligopeptide chromodulin. Chromodulin may be the key to understanding the role of Chromium at a molecular level as the molecule has been found to bind to activated insulin receptor, stimulating its kinase activity. An examination of the history of studies of Chromium picolinate and glucose tolerance factor illustrates the difficulties and problems associated with biochemical studies dealing with Chromium(III).
Stanley A. Brown - One of the best experts on this subject based on the ideXlab platform.
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Release of hexavalent Chromium from corrosion of stainless steel and cobalt-Chromium alloys.
Journal of biomedical materials research, 1995Co-Authors: Katharine Merritt, Stanley A. BrownAbstract:Experiments were undertaken to determine whether hexavalent Chromium was released during corrosion of orthopedic implants. Uptake of Chromium (Cr) by cells and separation using amberlite resin were the methods used to determine that hexavalent Cr was present. We used salts of Chromium as trivalent Chromium (chromic chloride) and hexavalent Chromium (potassium dichromate) to verify that the amberlite separation technique separates hexavalent Cr into the upper phase and trivalent Cr into the lower phase. The use of the salts also verified that only the hexavalent Cr became red blood cell-associated and that most of this was intracellular rather than membrane bound. The use of the amberlite separation technique demonstrated that the hexavalent Cr in the red blood cells was rapidly reduced to trivalent Cr. Cellular uptake of Chromium was documented in red blood cells following corrosion of stainless-steel and cobalt-Chromium implants in vivo, in the red blood cells of patients undergoing total joint revisions, and in fibroblasts subjected to products of fretting corrosion of stainless-steel and cobalt-Chromium implants. Thus, corrosion of implants can lead to the release of the biologically active hexavalent Chromium into the body. This Chromium is rapidly reduced to trivalent Chromium in cells.
Joan F Brennecke - One of the best experts on this subject based on the ideXlab platform.
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hard Chromium composite electroplating on high strength stainless steel from a cr iii ionic liquid solution
Electrochemistry Communications, 2019Co-Authors: Hadi Khani, Joan F BrenneckeAbstract:Abstract A composite Chromium coating has been potentiostatically electroplated on high-strength stainless steel substrates from a trivalent Chromium bath. The electrolyte solvent consists of 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]) to which water, hexadecyltrimethylammonium bromide (CTAB), poly(diallyldimethylammonium chloride) (PDDA), and Al2O3 particles (≈3–4 μm) were added to improve the ion transport properties, the wettability at the electrolyte–substrate interface, the metallic Chromium content, and the microhardness of the coating, respectively. The X-ray photoelectron spectrum of the coating reveals 85% metallic Chromium and 15% Chromium oxides and Chromium hydroxide. Characterization of the coating shows the existence of Chromium carbide-type bonds, resulting from the incorporation of carbon atoms into the Chromium crystal lattice, leading to a high degree of amorphization of the coating. Optimization of electroplating conditions yielded a uniform Chromium composite coating with a Vicker's microhardness of 860 (±10) HV and a thickness of 42 μm (±4), which is comparable to a Chromium coating obtained from conventional chromic acid baths.
Katharine Merritt - One of the best experts on this subject based on the ideXlab platform.
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Release of hexavalent Chromium from corrosion of stainless steel and cobalt-Chromium alloys.
Journal of biomedical materials research, 1995Co-Authors: Katharine Merritt, Stanley A. BrownAbstract:Experiments were undertaken to determine whether hexavalent Chromium was released during corrosion of orthopedic implants. Uptake of Chromium (Cr) by cells and separation using amberlite resin were the methods used to determine that hexavalent Cr was present. We used salts of Chromium as trivalent Chromium (chromic chloride) and hexavalent Chromium (potassium dichromate) to verify that the amberlite separation technique separates hexavalent Cr into the upper phase and trivalent Cr into the lower phase. The use of the salts also verified that only the hexavalent Cr became red blood cell-associated and that most of this was intracellular rather than membrane bound. The use of the amberlite separation technique demonstrated that the hexavalent Cr in the red blood cells was rapidly reduced to trivalent Cr. Cellular uptake of Chromium was documented in red blood cells following corrosion of stainless-steel and cobalt-Chromium implants in vivo, in the red blood cells of patients undergoing total joint revisions, and in fibroblasts subjected to products of fretting corrosion of stainless-steel and cobalt-Chromium implants. Thus, corrosion of implants can lead to the release of the biologically active hexavalent Chromium into the body. This Chromium is rapidly reduced to trivalent Chromium in cells.
