Protective Role Of Antioxidants Research Articles

An evaluation of vitamin E status in premature infants

Prematurely born, low birth weight infants are abnormal by their very existence ex utero. Thus, the well-documented finding in such infants of low plasma vitamin E concentrations when compared to the adult poses philosophical and pragmatic difficulties as to whether or not a true deficiency state exists: do these low levels represent age-adjusted reference values or do they in fact represent a deficiency state, warranting treatment? We examined multiple measures of vitamin E status in 62 prematurely born, low birth weight infants in order to address this issue. Mathematical and statistical modeling of these measures during the first 21 days of life lead us to conclude that the ex utero antioxidant protective role of vitamin E is best achieved at plasma concentrations of tocopherol very close to those observed in the adult; specifically, when total tocopherol is >0.64 mg/dl and a-tocopherol is >0.50 mg/dl. Thus, at birth, a true deficiency in vitamin E exists for most preterm, low birth weight infants and early treatment is warranted.

Ageing of Neurospora crassa. II. Organic hydroperoxide toxicity and the protective role of antioxidant and the antioxygenic enzymes

Cumene hydroperoxide and tert.-butyl hydroperoxide at sublethal concentrations initially prevent growth of mycelia of wild-type Neurospora crassa, but after a time the cells grow at a subnormal steady-state rate. The antioxidant nordihydroguaiaretic acid protects unadapted cells from hydroperoxide inhibition, leading to a decrease in the time before growth begins, an increase in steady-state growth rate and an increase in biomass production. The results of growth transfer experiments and enzyme measurements indicated that the acquired resistance to the hydroperoxides is physiological and most likely involves the induction of the synthesis of the antioxygenic enzymes superoxide dismutase, glutathione peroxidase and glutathione reductase. Nordihydroguaiaretic acid normalizes the levels of activities of glutathione peroxidase and glutathione reductase during culture with hydroperoxide. Molecular-induced homolysis of the hydroperoxides, a process that is induced by unsaturated fatty acids of membrane lipids, leads to lipid autoxidation in a chain reaction which produces lipid hydroperoxides, which in turn decomposes to form more free radicals. Nordihydroguaiaretic acid, a well-known free radical scavenger, probably serves to minimize hydroperoxide decomposition, lipid autoxidation and molecular damage from free radicals, whereas the coupled enzyme system glutathione peroxidase and glutathione reductase minimizes these processes by decomposing the hydroperoxides to harmless alcohols. We suggest that either free radicals derived from these processes or some consequent non-radical products may serve as the inducers of this enzyme system, rather than the hydroperoxide substrates.