Rainer Fried

Effects of superoxide radicals on transport (Na + K) adenosine triphosphatase and protection by superoxide dismutase.

Membrane (Na+K)ATPase isolated from rat brain was preincubated in a medium in which superoxide radicals were generated enzymatically. Exposure to superoxide radicals caused an irreversible inactivation, which could be prevented by further addition of superoxide dismutase. (Na+K)ATPase was also protected by addition of allopurinol, a xanthine oxidase inhibitor, during preincubation. The K-activated nitrophenylphosphatase associated with (Na+K)ATPase was also found to be inactivated by preincubation with superoxide radicals, which could be prevented by superoxide dismutase.

Xanthine Oxidase (Xanthine Dehydrogenase)

Publisher Summary This chapter focuses on xanthine oxidase (XOD), which is a metal-flavoprotein containing FAD, molybdenum and iron in the ratio of 2:2:8. It oxidizes aldehydes to the corresponding acids and other substances, including pterins, purines, and certain drugs such as allopurinol and 6-mercaptopurine. It is assumed that it takes part in alcohol metabolism; it plays a role in the incorporation of iron in ferritin. High concentrations of enzyme have been found in the intestinal mucosa; this enzyme contains copper instead of molybdenum. Xanthine oxidase has been studied as a model for mitochondrial electron transport and the enzyme has been the subject of many reviews. Xanthine oxidase has a substrate optimum between 0.1 and 0.2 mM xanthine or hypoxanthine. Human blood or serum contains no xanthine oxidase activity. Mazur and Sackler report a range of 5.49–1.92 units of xanthine oxidase in samples obtained from normal human livers, while very low values or no activity was found in livers of cirrhotic patients and in cases of hemochromatosis.

Regional distribution of superoxide dismutase in rat brain during postnatal development

Superoxide dismutase in nervous system protects readily oxidizable compounds such as catecholamines against toxic effects of oxygen. We investigated superoxide dismutase activity during development in 5 brain regions selected for a wide range of catecholamine concentration and turnover: cerebellum, neocortex, striatum, hypothalamus and medulla-pons. The cytosolic and the particulate enzyme were measured from birth to 6 months of age. In cerebellum the cytosolic enzyme shows considerable activity on the first postnatal days; the particulate enzyme is less active, both reach a maximum at 3 months. In cortex and striatum both activities were low during the postnatal days and reach a plateau at 3 months. In hypothalamus both activities are higher during the postnatal days and reach a maximum at 3 months. In medulla-pons the values are 2 times higher than in all other regions; the cytosolic enzyme reaches a maximum at 2 months whereas the particulate enzyme reaches a plateau at 3 months. Thus our results show an increase of superoxide dismutase activity during development in all brain regions; the highest activities were found in regions with high catecholamine content.

Colorimetric determination of xanthine dehydrogenase by tetrazolium reduction

Abstract 1. (1) Xanthine dehydrogenase can be determined colorimetrically or spectrophotometrically by means of reduction of Nitro-BT tetrazolium salt as electron acceptor. The method is about eight times more sensitive than the usual photometric assay. 2. (2) The reaction rate is enhanced by the addition of gelatin, phenazine methosulfate, and EDTA. 3. (3) The method can be readily adapted to the colorimetric assay of xanthine or hypoxanthine.

Familial Factors in Bladder Carcinoma

Surprisingly, little is known about host factors in cases of bladder carcinoma. We investigated 2 families prone to transitional cell carcinoma of the bladder. A high degree of pathology verification of cancer of all anatomic sites and a meticulous recording of genealogy, associated diseases and environmental exposures, when known, have allowed a more cogent appraisal of cancer etiology. It is reasonable to assume that members of the subject families may be more susceptible to variable carcinogenic exposures, a concept that is in accord with a genetic-environmental interaction hypothesis for cancer etiology. In addition to increased surveillance of high risk patients for earlier detection of bladder cancer, cancer control measures also should take into consideration preventive programs directed toward the avoidance of known carcinogenic exposures, such as cigarette smoking in high risk relatives of cancer-affected probands. We propose that the etiology of familial bladder cancer may be complex, involving possible other associated malignant neoplasms and/or certain non-neoplastic disorders, in addition to specific carcinogenic exposures. There is a serious need for the detailed reporting of families prone to bladder cancer wherein all of these potentially important associated factors are considered, so that a fuller appraisal of etiology might be achieved.

Superoxide dismutase and life span ofDrosophila melanogaster

Comparison of superoxide dismutase activity in homogenates of wild and vestigial strains ofD. melanogaster revealed a lower enzyme activity in the short-living vestigial strain.

Inhibition of oxidizing enzymes by metronidazole

Eine unerwartete Möglichkeit, wie Metronidazol zu einer nur scheinbaren Hemmung der Alkoholdehydrogenase führen könnte, wird aufgedeckt.

Is superoxide dismutase a physiological radioprotector

Prolonged treatment with relatively low doses of ionizing radiation did not induce synthesis of superoxide dismutase, either inDrosophila melanogaster or in mice liver.

Superoxide dismutase activity in nerve cell culture.

Superoxide dismutase (EC 1.15.1.1) activity was assayed in preparations obtained from several clonal lines of nerve cell culture, by enzymatic and nonenzymatic assays. The enzyme was found in dialyzed homogenates of washed cells and in partially purified fractions. The enzyme was also found in cells which had been grown in media containing 5-bromodeoxyuridine, where cell differentiation was observed.

Enzymatic oxidation of diethyldithiocarbamate by xanthine oxidase and its colorimetric assay.

Diethyldithiocarbamate is oxidized in vitro by purified cream xanthine oxidase in the presence of nitro blue tetrazolium and phenazine methosulfate. Disulfiram is formed during the enzymatic or nonenzymatic oxidation. When diethyldithiocarbamate is mixed nonenzymatically with nitro blue tetrazolium, the dye is rapidly reduced, but only in the presence of certain organic solvents. This reaction can be used as a convenient colorimetric assay for diethyldithiocarbamate, which gives a stable color over a wide concentration range.