Oxidative stress metals

The rigidity of the y axis prevents the development of spherical surfaces for all but very small displacements. Morton suggests that the limit is reached when the displacement is equal to the metal thickness. This condition was satisfied in the high-temperature studies of Appleby and Tylecote and spherical doming of the disc specimen occurred. When the oxide is not very thin compared with the metal both the moduli for oxide and metal must be considered. Stringer" , in his excellent review of stress generation and relief in oxide layers, quotes a corrected formula, originally due to Brenner and Senderoff ... 

Okada et al. examined the effects of TBT on cellular content of glutathione (GSH) in rat thymocites using a flow cytometer and 5-chloromethylfluorescein diacetate, a fluorescent probe for monitoring the change in the cellular content of GSH. TBT at nanomolar concentrations reduced the cellular content of GSH. There is an important implication on the TBT-induced depletion of cellular GSH since GSH has an important role in protecting the cells against oxidative stress and chemical and metal intoxications. TBT-induced decrease in cellular content of GSH in thymocytes may increase the vulnerability of the immune system. ° ... 

Variation of the content of impurities in the different CNT preparations [21] offers additional challenges in the accurate and consistent assessment of CNT toxicity. As-produced CNTs generally contain high amounts of catalytic metal particles, such as iron and nickel, used as precursors in their synthesis. The cytotoxicity of high concentrations of these metals is well known [35, 36], mainly due to oxidative stress and induction of inflammatory processes generated by catalytic reactions at the metal particle surface [37]. Another very important contaminant is amorphous carbon, which exhibits comparable biological effects to carbon black or relevant ambient air particles. 

Iron chelators can also be used to selectively bind iron in areas where oxidative stress is observed, thereby preventing the iron from taking part in Fenton reactions without interfering with normal iron homeostasis. Charkoudian et al. have developed boronic acid and boronic ester masked prochelators, which do not bind metals unless exposed to hydrogen peroxide (237,238). The binding of these chelators to iron(III) prevents redox cycling. Similar studies of these systems have been performed by a separate group (239,240). 

A battery of different biochemical quantitative assays was applied to many different tissues and species. DNA damage and lipid peroxidation assays measure the direct impact of genotoxics and oxidant pollutants [16,17] whereas alteration of GSH levels in liver is a marker for oxidative stress [18]. Mercury and other heavy metals are known to induce metallothionein levels in different tissues although this effect is variable in different species and organs [19-22]. 

Redox reactions involving nitric oxide have important implications beyond their fundamental chemistry as demonstrated by the controversy in the biomedical literature regarding conditions under which generation of NO leads to the amelioration or the exacerbation of oxidative stress in mammalian systems (95). Oxidative stress is defined as a disturbance in the balance between production of reactive oxygen species (pro-oxidants) and antioxidant defenses (96). Reactive oxygen species include free radicals and peroxides as well as other reactants such as oxidative enzymes with metal ion sites in high oxidation states. The... 

REDOX METAL IONS, OXIDATIVE STRESS AND NEURODEGENERATIVE DISEASES... 

There is considerable evidence that defective homeostasis of redox-active metals, i.e. iron and copper, together with oxidative stress, contributes to the neuropathology of AD. The characteristic histology of AD is the deposition of both Ap, as neurotic plaques (Figure 18.12a), and of the protein tau, as neurofibrillary tangles NFT (Figure 18.12b), predominantly in the cerebral cortex and hippocampus. 

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