are the Lebesgue functions and Lebesgue constants of the interpolation, respectively . We now prove this statement in full detail . The detailed proof turned out to be quite complicated and several unsuspected difficulties had to be overcome . In the same paper P. Erdős also stated, that there is a pointgroup {x kn } so that for every continuous f (x) (-1 x:1) L,,(f, x,) -f (xo) holds for at le...

The local positivity of solutions to logarithmically singular diffusion equations is investigated in some space-time domain E×(0, T ]. It is shown that if at some time level to ∈ (0, T ] and some point xo ∈ E the solution u(·, to) is not identically zero in a neighborhood of xo, in a measure-theoretical sense, then it is strictly positive in a neighborhood of (xo, to). The precise form of this ...

BACKGROUND/AIM A number of in vitro and in vivo studies have investigated the potential preventive activity of grape extracts against different diseases, and have mostly focused on their antioxidant properties. The present study examined the effects of 21 extracts from stem, skin and berry from Greek grape varieties on the activity of enzymes involved in regulation of oxidative stress, namely x...

We examined the effects of superoxide anion (O) generated by xanthine plus xanthine oxidase (X/XO) on the intracellular Ca(2+) concentration ([Ca(2+)](i)) and muscle contractility in cultured bovine aortic smooth muscle cells (BASMC). Cells were grown on collagen-coated dish for the measurement of [Ca(2+)](i). Pretreatment with X/XO inhibited ATP-induced Ca(2+) transient and Ca(2+) release-acti...

The iron chelator deferoxamine has been reported to inhibit both xanthine oxidase (XO) and xanthine dehydrogenase activity, but the relationship of this effect to the availability of iron in the cellular and tissue environment remains unexplored. XO and total xanthine oxidoreductase activity in cultured V79 cells was increased with exposure to ferric ammonium sulfate and inhibited by deferoxami...

Hypertension may alter kidney functions negatively. Purine metabolism may be affected from constricted blood vessels and increased cardiac output, because of hypertension. Nitric oxide synthase (NOS) inhibition by N sup omega Nitro-LArginine Methyl Ester (L-NAME) produces hypertension in rats. The aim of this study was to investigate adenosine deaminase (AD) and xanthine oxidase (XO) activities...

Exercise-induced proteinuria is a common consequence of physical activity and is caused predominantly by alterations in renal hemodynamics. Although it has been shown that exercise-induced oxidative stress can also contribute to the occurrence of postexercise proteinuria, the sources of reactive oxygen species that promote it are unknown. We investigated the enzymes nicotinamide adenine dinucle...

Recent evidence suggests that reactive oxygen species (ROS), including superoxide, are not only neurotoxic but function as small messenger molecules in normal neuronal processes such as synaptic plasticity. Consistent with this idea, we show that brief incubation of hippocampal slices with the superoxide-generating system xanthine/xanthine oxidase (X/XO) produces a long-lasting potentiation of ...

During chemical hypoxia induced by cobalt chloride (CoCl2), hypoxia-inducible factor 1A (HIF1-A) mediates the induction of a variety of genes including erythropoietin and vascular endothelial growth factor. We used glioma cells with oxidative phosphorylation–dependent (D54-MG) and glycolytic-dependent (U251-MG) phenotypes to monitor HIF1-A regulation in association with redox responsiveness to ...

A (bounded) manifold of circular type is a complex manifold M of dimension n admitting a (bounded) exhaustive real function u, defined on M minus a point xo, so that: a) it is a smooth solution on M \{xo} to the MongeAmpère equation (ddcu)n = 0; b) xo is a singular point for u of logarithmic type and eu extends smoothly on the blow up of M at xo; c) ddc(eu) > 0 at any point of M \ {xo}. This cl...