Calcium superoxide

Superoxides are used in breathing appHcations requiring no auxHiary source of oxygen. Sodium superoxide is ca 10 times as expensive as potassium superoxide because high temperature, high pressure autoclaves are required for its production. Use of calcium superoxide is experimental. Potassium superoxide is the most commonly used superoxide oxygen generator. 

Calcium superoxide [12133-35-6] strontium superoxide [12169-21 -0] Sr(02)2 and barium superoxide [55837-89-3] Ba(02)2, have all been... 

CALCIUM SULFOCYANATE see CAY250 CALCIUM SUPEROXIDE see CAV500 CALCIUM THIOCYANATE see CAY250 CALCIUM TRISODIUM CHEL 330 see CAY500... 

CAS 1305-79-9 EINECS/ELINCS 215-139-4 UN 1457 (DOT) INS930 Synonyms Calcium dioxide Calcium superoxide... 

Calcium sulfocyanate. See Calcium thiocyanate Calcium sulfonate. See Calcium sulfate Calcium superoxide. See Calcium peroxide Calcium tartarate (INCI). See Calcium tartrate Calcium tartrate... 

Of the binary peroxides made from hydrogen peroxide, calcium peroxide is the most important. World production is about 2000 t/yr, which is dominated by the dough-conditioning market in the United States. The markets for the other binary peroxides, such as those of zinc, magnesium, and strontium, total only a few hundred metric tons. Sodium peroxide and potassium superoxide are made from the alkaU metals and thek total markets are in the hundreds of tons. 

Kanerud, L., Hafttrom, 1. and Ringertz, B. (1990). Effect of sulphasalazine and sulphapyridine on neutrophil superoxide production role of cytosolic free calcium. Ann. Rheum. Dis. 49, 296-300. 

Impact sensitivities of mixtures of red phosphorus with various oxidants were determined in a direct drop-ball method, which indicated higher sensitivities than those determined with an indirect striker mechanism. Mixtures with silver chlorate were most sensitive, those with bromates, chlorates and chlorites were extremely sensitive, and mixtures with sodium peroxide and potassium superoxide were more sensitive than those with barium, calcium, magnesium, strontium or zinc peroxides. Mixtures with perchlorates or iodates had sensitivities comparable to those of unmixed explosives, such as lead azide, 3,5-dinitrobenzenediazonium-2-oxide etc. 

Because NO synthases belong to the same superfamily of enzymes as cytochrome P-450, they are able to produce not only nitric oxide (although it is undoubtedly their main function) but also other free radicals, first of all, superoxide. In 1992, Pou et al. [148] showed that brain nitric oxide synthase (NOS I) produced superoxide identified as a DMPO—OOH adduct in a calcium- or calmodulin-dependent manner. This finding was confirmed in numerous studies for all three isoforms of NO synthase. Although the structures of all the three NO oxidase... 

It has been shown that the activity of NO synthases is regulated by cofactors calcium binding protein calmodulin and tetrahydrobiopterin (H4B). Abu-Soud et al. [149] have studied the effect of H4B on the activity of neuronal nNOS I, using the isolated heme-containing oxygenase domain nNOSoxy. It was found that nNOSoxy rapidly formed an oxygenated complex in the reaction with dioxygen, which dissociated to produce superoxide (Reaction (6)) ... 

The functions of mtNOS in mitochondria have been studied (see Chapter 23). Ghafourifar et al. [177] found that the calcium-induced stimulation of mtNOS caused the release of cytochrome c from mitochondria and induced apoptosis. On the other hand, the same group of authors [178] showed that the production of NO by mtNOS and superoxide in mitochondria resulted in the formation of peroxynitrite and stimulated calcium release, indicating the existence of a feedback loop which prevents calcium overload in mitochondria. 

Calcium oxalate monohydrate responsible for the formation of most kidney stones significantly increased mitochondrial superoxide production in renal epithelial cells [42], Recombinant human interleukin IL-(3 induced oxygen radical generation in alveolar epithelial cells, which was suppressed by mitochondrial inhibitors 4 -hydroxy-3 -methoxyacetophe-none and diphenylene iodonium [43]. Espositio et al. [44] found that mitochondrial oxygen radical formation depended on the expression of adenine nucleotide translocator Anti. Correspondingly, mitochondria from skeletal muscle, heart, and brain from the Antl-deficient mice sharply increased the production of hydrogen peroxide. 

Similar to dihydropyridine calcium blockers, many 0-adrenoreceptor antagonists exhibit antioxidant activity. Mak and Weglinski [290] showed that the pretreatment of canine myocytic sarcolemmal membranes with 0-adrenoreceptor antagonists (propranolol, pindolol, metoprolol, atenolol, or sotalol) (Figure 29.15) inhibited superoxide-induced sarcolemmal... 

NO may react with superoxide to yield the highly reactive peroxynitrite, ONOO-. Superoxide may also be converted into H202 and the reactive hydroxyl radical, OH. In this way excessive activation of glutamate receptors leads to oxidative damage. The calcium influx has a major effect on mitochondria and causes them to depolarize and swell. This leads to a pore being formed in the outer mitochondrial membrane, which allows the escape of cytochrome c and procaspases from the mitochondria into the cytosol. Cytochrome c activates the caspase cascade, which leads to apoptotic cell death (Ch. 35). 

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