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...The reduced form of GSH donates an electron to reactive oxygen species in order to stabilise them, and then the now reactive GSH readily combines with another GSH molecule to form glutathione disulphide (GSSG) in the presence of enzyme glutathione peroxidase. In lead induced oxidative stress GSSG concentrations are higher than GSH. (Flora, Gupta and Tiwari, 2012) Lead inactivates the glutathione by binding to the sulfhydryl group on glutathione reductase, acting as a toxic ligand to block the binding site for GSSG and inhibits reduction back to GSH causing the reactive oxygen species to be in excess (Kathuria and Rowden, 2016; Zitka et al.,...
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...from the toxic effects of Pb exposure, that may further, increase the predisposition of membranes by altering their integrity. As well as directly inducing the (11) production of ROS, a molecule can be indirectly induced with oxidative stress by degradation of the cell wall to the attack of ROS. The foremost constituents of biological membranes are lipids and proteins. The antioxidant defences of the body target the generated ROS to limit oxidative stress. The most vital antioxidant in cells is glutathione (GSH). It is a tripeptide with sulfhydryl groups that occur in millimolar concentrations in tissue. It is an essential antioxidant for reducing free radicals. Glutathione exists in both the reduced state as (GSH) and oxidized state as (GSSG). The reduced state of GSH donates its reducing equivalents (H+ & e–) from its thiol group in the cysteine residues to the ROS giving stability. (8) The drawback in the usefulness of (8) antioxidants is their meagre bioavailability due to low solubility and rapid clearance rates. The attack of any ROS species with sufficient reactivity to release an H+ from the methylene groups of fatty acids. The incidence of multiple double bonds in the fatty acid weakens the (10) carbon-hydrogen (CH) adjacent to the double bond and therefore makes H+ removal easier. So, fatty acids with up to two double bonds are less prone to oxidative attack than those with 3 or more double bonds. An investigation of the harmful impact of Pb (11) by measuring the effects...
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...The Classifier’s Handbook TS-107 August 1991 THE CLASSIFIER'S HANDBOOK Table of Contents (Also See The Introduction to the Position Classification Standards.) PREFACE ..................................................................................................................................................... 3 CHAPTER 1, POSITION CLASSIFICATION STANDARDS........................................................................ 4 DEVELOPMENT OF STANDARDS ......................................................................................................... 5 FORMAT OF STANDARDS ..................................................................................................................... 5 CHAPTER 2, THE FACTOR EVALUATION SYSTEM ................................................................................ 7 THE STRUCTURE OF FES...................................................................................................................... 7 FES FACTORS......................................................................................................................................... 7 EVALUATING A POSITION USING FES ................................................................................................ 9 FES EVALUATION STATEMENT.......................................................................................................... 13 FACTOR LEVEL RELATIONSHIPS ............................................................................
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...REGULATION OF PHYSIOLOGICAL SYSTEMS BY NUTRIENTS Free Radicals, Antioxidants, and Nutrition Yun-Zhong Fang, Sheng Yang, and Guoyao Wu, PhD From the Department of Biochemistry and Molecular Biology, Beijing Institute of Radiation Medicine, Beijing, China; the Division of Animal Nutrition, Department of Animal Science, China Agricultural University, Beijing, China; and the Department of Animal Science and Faculty of Nutrition, Texas A&M University, College Station, Texas, USA Radiation hazards in outer space present an enormous challenge for the biological safety of astronauts. A deleterious effect of radiation is the production of reactive oxygen species, which result in damage to biomolecules (e.g., lipid, protein, amino acids, and DNA). Understanding free radical biology is necessary for designing an optimal nutritional countermeasure against space radiation–induced cytotoxicity. Free radicals (e.g., superoxide, nitric oxide, and hydroxyl radicals) and other reactive species (e.g., hydrogen peroxide, peroxynitrite, and hypochlorous acid) are produced in the body, primarily as a result of aerobic metabolism. Antioxidants (e.g., glutathione, arginine, citrulline, taurine, creatine, selenium, zinc, vitamin E, vitamin C, vitamin A, and tea polyphenols) and antioxidant enzymes (e.g., superoxide dismutase, catalase, glutathione reductase, and glutathione peroxidases) exert synergistic actions in scavenging free radicals. There has been growing evidence over the past three decades...
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