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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

By using the spin-trapping technique and electron spin resonance spectroscopy (ESR), we detected directly oxygen-derived free radicals in the brain exposed to ischemia and reperfusion. Forebrain ischemia was produced in the rat by bilateral occlusion of the common carotid arteries combined with hemorrhagic hypotension. The whole cerebral cortex was homogenized in the presence of the spin trap agent, N-tert-butyl-alpha-phenylnitrone, followed by a Folch extract. Spin-adducts were detected using ESR. As the index of tissue injury, the lipid peroxidation was estimated from both the amount of thiobarbituric acid reactive substance and the formation of conjugated diene. After 10 or 20 min of ischemia, reperfusion induced a burst of spin adduct formation which peaked at 5 min reperfusion time. The peak value increased with the ischemia time. The degree of lipid peroxidation, which was measured after 20 min of reperfusion, also increased with the ischemia time. When the oligomeric derivative was administered (9 mg . kg-1, i.p.) 30 min before ischemic insult, both spin adduct formation and lipid peroxidation were reduced. The results support the current view that free radicals produced upon reperfusion may be the direct cause of the subsequent lipid peroxidation.
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PMID:[ESR study of free radical formation during ischemia-reperfusion injury in the rat brain and the protective effect of a new antioxidant]. 131 80

The extraction of reliable and useful relaxation time data for tissue characterization by NMR requires strict protocols, optimized for each type of biological tissue, which include parameters like storage duration and temperature as well as measurement parameters. Spin-lattice relaxation times in liver tissue vary not only with NMR frequency but also with their "time-after-excision characteristics," while spin-spin relaxation times are almost independent of most parameters which influence T1 at 20 MHz in normal liver tissue (e.g., species, sex, circadian rythm, starvation). T2, however, being more sensitive to water content and pH changes, is well suited for detecting nonspecific tissue alterations (e.g., due to ischemia, chemical toxins). Following the suggestions outlined herein, investigation of at least 120 min of time-after-excision (storage) effects allows the significant distinguishing of various physiological differences in normal liver tissue as well as improvement of early detection of liver pathologies.
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PMID:Liver tissue characterization by in vitro NMR: tissue handling and biological variation. 156 62

Forebrain ischemia was produced in the rat by bilateral occlusion of the common carotid arteries combined with hemorrhagic hypotension (30 mmHg). The whole cerebral cortex was homogenized in the presence of the spin trap agent N-tert-butyl-alpha-phenyl-nitrone, followed by a Folch extract. Spin-adducts were detected using electron spin resonance spectroscopy. The lipid peroxidation was estimated from both the amount of thiobarbituric acid reactive substance and the formation of conjugated diene. After 10 or 20 min of ischemia, reperfusion was initiated which induced an abrupt burst of free radical formation. The formation peaked at 5 min, and the peak value increased with the ischemia time. The degree of lipid peroxidation, which was measured after 20 min of reperfusion, also increased with the ischemia time. The results suggest that the lipid peroxidation may be the direct consequence of the action of free radicals formed during ischemia and reperfusion periods.
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PMID:Relationship between free radical production and lipid peroxidation during ischemia-reperfusion injury in the rat brain. 165 86

A new oligomeric derivative was synthesized from prostaglandin B2 and ascorbic acid, and its effect on rat brain ischemia-reperfusion injury was studied. Brain ischemia was produced in the rat by the combination of bilateral common carotid artery occlusion and hemorrhagic hypotension (30 mmHg, 20 min). The cerebral cortex was homogenized in the presence of the spin trap agent, N-tert-butyl-alpha-phenyl-nitrone (PBN). Spin-adducts were detected using an electron spin resonance spectrometer (EPR). Lipid peroxidation was estimated from the amounts of both thiobarbituric acid reactive substances (TBAR) and conjugated diene. In control experiments, reperfusion induced a burst of free radical formation which peaked at 5 min reperfusion time (238 +/- 41%). Lipid peroxidation increased significantly after 20 min of reperfusion (TBAR, 161 +/- 50%; conjugated diene, 160 +/- 29%). When the oligomeric derivative was administered (9 mg/kg i.p. 30 min before ischemic insult), it significantly reduced both spin adduct formation (103 +/- 13%) and lipid peroxidation (TBAR, 109 +/- 14%; conjugated diene, 97 +/- 33%).
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PMID:Protective effect of a new anti-oxidant on the rat brain exposed to ischemia-reperfusion injury: inhibition of free radical formation and lipid peroxidation. 166 37

The effects of cerebral ischemia in rat brain were monitored as a function of time using proton MR imaging. Spin-spin relaxation time (T2), proton density, and magnetization transfer contrast (MTC) were measured by MR imaging at various time intervals during a 1-week period following the induction of ischemic damage. Ischemic injury was characterized by a maximization of both T2 value and MTC appearance at 24 hr postischemic injury. These changes were accompanied by a gradual increase in MR observable water density over the first few days of ischemia. A reduction in the magnetization exchange rate between "free" and "bound" water protons as measured by MTC imaging is at least partially responsible for the elevation in T2 values observed during ischemia, and may accompany breakdown of cellular structure.
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PMID:Investigation of cerebral ischemia using magnetization transfer contrast (MTC) MR imaging. 176 13

A new approach for in vivo spin trapping and quantitation of oxygen-derived free radicals has been developed using a continuous flow high speed ESR detection system. Spin adducts of OH. were detected as 1:1:1:1:1:1 sextets (aN=15.2 G, aH=16.8 G, g=2.0055) in the isolated rat heart when perfused with 3,3,5,5-tetramethyl-1-pyrroline-1-oxide (40 mM) during a 10-min control pretreatment (14 ml/min) followed by 50 min of low-flow ischemia (1 ml/min), 30 min of global ischemia and subsequent reperfusion at 14 ml/min. The ESR signals appeared within 15-20 min of low-flow ischemia and grew moderately during the remaining 30 min at a rate of 2-6 nmoles of spin adduct released per minute. Post-ischemic reperfusion was characterized by a burst of spin adduct formation at 30 s-1 min, corresponding to 51.8 nmoles of spin adduct released between 30 s and 1 min.
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PMID:Use of 3,3,5,5-tetramethyl-1-pyrroline-1-oxide spin trap for the continuous flow ESR monitoring of hydroxyl radical generation in the ischemic and reperfused myocardium. 255 23

The spin trapping agent 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) was used to investigate oxy-radical production in post-ischemic rat hearts previously exposed to 20, 30, or 40 minutes of global ischemia. A hydroxyl spin adduct (DMPO-OH) was identified in coronary effluent during the initial seconds of reperfusion by Electron Spin Resonance (ESR) Spectroscopy. The intensity of the ESR signal in post-ischemic effluent increased as ischemic duration was prolonged; however, regardless of the duration of ischemia, maximal spin adduct detection occurred 3 minutes after initiation of reperfusion. Superoxide dismutase inhibited the formation of DMPO-OH, suggesting that superoxide anion was initially generated and is the principle source for the production on the hydroxyl adduct. Our investigations indicate that superoxide anion is produced during the early moments of reperfusion and that its production in the post-ischemic heart is related to the severity of ischemia.
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PMID:Spin-trapping evidence that graded myocardial ischemia alters post-ischemic superoxide production. 282 47

Oxygen free radical injury has been postulated to occur during myocardial ischemia. We have used Electron Spin Resonance and Spin Trapping techniques to directly demonstrate the production of carbon-centered (R.) and oxygen-centered lipid radical (RO.) in ischemic canine heart. In addition, venous effluent from the ischemic region showed that conjugated dienes (lipid peroxidation products) increased with ischemic duration. Our results suggest that the formation of the oxygen-centered and carbon-centered lipid radical species during ischemia are a consequence of oxy-radical peroxidation of myocardial membrane lipids.
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PMID:Spin trapping of oxygen and carbon-centered free radicals in ischemic canine myocardium. 282 5

Spin trapping technique has been applied to the detection of free radicals generated in NADPH stimulated lipid peroxidation process in ischemic brain homogenate. Using male Wistar rats, complete cerebral ischemia for 30 min, 60 min or 120 min was produced by decapitation followed by preservation of the heads at 37 degrees C. Global cerebral ischemia of 30 min or 60 min duration was induced by occlusions of three vessels (bilateral common carotid and basilar artery) in the ventilated rats. In some animals, bilateral carotid occlusions were released for 30 min following 30 min of ischemia to study postischemic event. Two reaction mixtures containing of brain homogenate, NADPH, Fe-EDTA and spin trapping reagent, phenyl-t-buthylnitrone (PBN), were prepared from each brain sample--one to be incubated in air and the other to be incubated in nitrogen gas. After the incubation for 20 min at 37 degrees C, free radical adducts of PBN were measured by electron spin resonance (ESR). In preliminary experiments, no ESR signals were obtained from the reaction mixtures without the addition of NADPH and Fe-EDTA. And the dependence of ESR signal intensity upon the NADPH concentration was observed. The six-line signals (triplet of doublets), which hyperfine splitting constants were AN = 16.2-16.5 G and A beta H = 3.6-3.8 G, were obtained from both ischemic models. These signals were dependent upon the presence of oxygen in the reaction systems, as evidenced by the fact that the signal intensity obtained from aerobic incubation was consistently stronger than that obtained from anaerobic incubation in each brain sample.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Detection of free radicals generated in NADPH-dependent lipid peroxidation in ischemic brain homogenates--use of the spin trapping technic]. 300 94

The purpose of developing the experimental model described in this study was to verify the hypothesis that free radicals are formed during ischemia-reperfusion of skeletal muscle. Spin trapping technique, along with electron spin resonance spectroscopy (ESR), directly indicates the presence of reactive radicals, which are widely considered to be important in tissue injury. The experimental model was a rat pedicled rectus femoris muscle flap. The femoral artery and vein were cannulated to inject the "spin trap" and collect the effluent flow. The spin trap agent was phenyl-t-butyl nitrone (PBN) and Hank's balanced salt solution. Three injections and collections were made: a) before ischemia; b) after ischemia of 15, 30, 60, 120, and 180 minutes, but before blood flow had been restored; and c) after blood flow had been restored. No ESR signal was detected either before the ischemic period or after only 15 minutes of ischemia. PBN radical adducts were detected after 30, 60, 120, and 180 minutes of ischemia. A similar signal was detected when PBN was injected during reperfusion 10 minutes after the ischemic periods. The study demonstrated the presence of free radicals in an in vivo intact skeletal muscle ischemia-reperfusion model.
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PMID:Microsurgical model of ischemia reperfusion in rat muscle: evidence of free radical formation by spin trapping. 784 96


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