Katherine Terell., Popsáno podle obálky, Pod názvem: Center for Economic Research and Graduate Education. Faculty of Social Sciences. Charles University, and Obsahuje bibliografii
Oxidative stress plays an important role in the pathogenesis of numerous chronic age-related free radical-induced diseases. Improved antioxidant status minimizes oxidative damage to DNA, proteins, lipids and other biomolecules. Diet-derived antioxidants such as vitamin C, vitamin E, carotenoids and related plant pigments are important in antioxidative defense and maintaining health. The results of long-term epidemiological and clinical studies suggest that protective vitamin C plasma concentration for minimum risk of free radical disease is higher than 50 μmol/l. Products of oxidative damage to DNA (DNA strand breaks with oxidized purines and pyrimidines), proteins (carbonyls) and lipids (conjugated dienes of fatty acids, malondialdehyde) were estimated in a group of apparently healthy adult non-smoking population in dependence on different vitamin C plasma concentrations. Under conditions of protective plasma vitamin C concentrations (>50 μmol/l) significantly lower values of DNA, protein and lipid oxidative damage were found in comparison with the vitamin C-deficient group (<50 μmol/l). The inhibitory effect of higher fruit and vegetable consumption (leading to higher vitamin C intake and higher vitamin C plasma concentrations) on oxidation of DNA, proteins and lipids is also expressed by an inverse significant correlation between plasma vitamin C and products of oxidative damage. The results suggest an important role of higher and frequent consumption of protective food (fruit, vegetables, vegetable oils, nuts, seeds and cereal grains) in prevention of free radical disease.
In the present article we provide an example of two closed non-$\sigma $-lower porous sets $A, B \subseteq \mathbb R $ such that the product $A\times B$ is lower porous. On the other hand, we prove the following: Let $X$ and $Y$ be topologically complete metric spaces, let $A\subseteq X$ be a non-$\sigma $-lower porous Suslin set and let $B\subseteq Y$ be a non-$\sigma $-porous Suslin set. Then the product $A\times B$ is non-$\sigma $-lower porous. We also provide a brief summary of some basic properties of lower porosity, including a simple characterization of Suslin non-$\sigma $-lower porous sets in topologically complete metric spaces.
Tissue hypoxia is less effective in increasing erythropoietin plasma levels in animals with post-transfusion polycythaemia. Since more red blood cells are decomposed under this condition, the effects of exogenous haemin and of lysed or heat-damaged red blood cells on activation of the erythropoietin gene have been studied in mice rendered hypoxic. Total RNA was extracted from the kidney and the liver and subjected to northern blot analysis with a probe containing part of the murine erythropoietin gene. Blood plasma was collected and erythropoietin levels were determined by radioimmunoassay. Erythropoietin gene activation was suppressed by haemin and increased red blood cell haemolysis. Tin (Sn) protoporphyrin, a haeme analogue which cannot bind oxygen, did not share the effect of haemin. On the other hand, when injected with haemin, Sn-protoporphyrin potentiated the suppressive effect of haemin, probably through inhibition of haemin catabolism. We conclude that the intracellular haeme concentration inhibits the kidney oxygen sensor and that this inhibition, mediated by products red blood cell degradation, is a physiological safeguard mechanism against excessive polycythaemia and its deleterious effects upon blood circulation.