Topic
Xanthine
About: Xanthine is a research topic. Over the lifetime, 4046 publications have been published within this topic receiving 129820 citations. The topic is also known as: Xanthine.
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TL;DR: Large rises in hypoxanthine and to a lesser extent xanthine occur for about 24 h after hypoxia and high concentrations were associated with later evidence of brain damage or subsequent death, and changes in CSF could be independent of those in plasma.
Abstract: CSF obtained for clinical purposes from newborn, children and adults has been analysed by high pressure liquid chromatography for hypoxanthine, xanthine, inosine, uridine and urate. Large rises in hypoxanthine and to a lesser extent xanthine occur for about 24 h after hypoxia. High concentrations were associated with later evidence of brain damage or subsequent death. Changes in CSF could be independent of those in plasma. Small or negligible rises were associated with localised and generalised infections including bacterial meningitis, fits, or both. Marked and rapid rises were found after death. These estimations may "predict" the extent of brain damage or brain death.
93 citations
TL;DR: The results indicate that chronic caffeine affects functions of adenosine and cholinergic receptors related to regulation of locomotor exploratory activity.
Abstract: Chronic ingestion of caffeine by mice caused a marked reduction in locomotor exploratory activity. At least 4 days of withdrawal were required to restore activity to normal levels. Stimulatory effects of injected caffeine were lower in chronically treated mice and the biphasic dose-response (stimulatory followed by depressant) curve for injected caffeine was left shifted. Seven days of withdrawal were required before the dose-response curve to caffeine was identical to that of control mice. The depressant effects of a potent xanthine phosphodiesterase inhibitor, 1,3-dipropyl-7-methylxanthine, were blunted in caffeine-treated mice. The depressant effects of A1- and A2-selective adenosine analogs were enhanced after chronic caffeine. There was little or no effect of chronic caffeine on the stimulatory effects of dopaminergic agents (amphetamine, caffeine), while both depressant and stimulatory effects of cholinergic agents (nicotine, oxotremorine, scopolamine) were reduced. The results indicate that chronic caffeine affects functions of adenosine and cholinergic receptors related to regulation of locomotor exploratory activity.
93 citations
TL;DR: The results suggest that an early cellular response to oxidative stress is the activation of K+ channels, suggesting that the induction of currents regulates biochemical changes in response to stress.
Abstract: Active oxygen species are generated during pathophysiologic conditions such as inflammation and ionizing radiation exposure. We tested the hypothesis that an early cellular event in response to these species involves regulation of ion channels. We exposed cells to gamma-irradiation or treated them with hydrogen peroxide, xanthine/xanthine oxidase, or [3H]thymidine and then monitored channel activity by the technique of whole-cell voltage clamping. Recordings showed that both normal and tumor cells exhibit an increase in K+ currents after treatment with radiation, H2O2, and xanthine/xanthine oxidase but not with high specific activity [3H]thymidine, suggesting that the signal for K+ channel activation originates at the cell membrane. A single noncytotoxic dose of 10 cGy induced measurable levels of K+ currents, suggesting that the induction of currents regulates biochemical changes in response to stress. To test whether channel activity is sensitive to active oxygen species, we pretreated cells with N-acetyl-L-cysteine (NAC) to increase cellular pools of free radical scavengers before radiation. In NAC-pretreated cells, K+ channel activation by gamma-irradiation was abolished. It has previously been shown that protein kinase C (PKC) is activated by ionizing radiation and can regulate K+ channels in some cells. However, the effect of radiation on induction of K+ channel activity was independent of PKC, since cells chronically exposed to phorbol esters still produced K+ currents after radiation. These results suggest that an early cellular response to oxidative stress is the activation of K+ channels.
93 citations
TL;DR: The results suggest that marked changes in myofibrillar ATPase activities by different species of oxygen free radicals may be mediated by the oxidation of SH groups.
92 citations
TL;DR: In this article, a poly l -methionine modified GC electrode was fabricated by electrochemical polymerization of the l-methionsine on a glassy carbon electrode, which exhibited excellent electrocatalytic activity toward the oxidation of uric acid, xanthine and hypoxanthine.
Abstract: A poly l -methionine modified GC electrode was fabricated by electrochemical polymerization of the l -methionine on a glassy carbon electrode. The electrochemical behaviors of uric acid, xanthine and hypoxanthine at the modified electrode were studied by cyclic voltammetry and differential pulse voltammetry. The results showed that this modified electrode exhibited excellent electrocatalytic activity toward the oxidation of the uric acid, xanthine and hypoxanthine. Also, electrode was used for simultaneous determination of uric acid, xanthine and hypoxanthine. This modified electrode possesses high sensitivity, and the detection limits as values 0.007, 0.004 and 0.008 μM for uric acid, xanthine and hypoxanthine, respectively. Finally, the poly l -methionine modified electrode was successfully employed to detect uric acid, xanthine and hypoxanthine in the serum samples with good selectivity and high sensitivity.
92 citations