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

Numerous studies have indirectly suggested that oxygen-derived free radicals play an important pathogenetic role in the prolonged depression of contractile function observed in myocardium reperfused after reversible ischemia (myocardial "stunning"). In order to provide direct evidence for the oxy-radical hypothesis of stunning, we administered the spin trap, alpha-phenyl N-tert-butyl nitrone (PBN), to open-chest dogs undergoing a 15-min coronary artery occlusion followed by reperfusion. Plasma of local coronary venous blood was analyzed by electron paramagnetic resonance (EPR) spectroscopy. EPR signals characteristic of radical adducts of PBN appeared during ischemia and increased dramatically in the first few minutes after reperfusion. After this initial burst, the production of adducts abated but did not cease, persisting up to 3 h after reflow. The production of PBN adducts after reperfusion was inversely related to collateral flow during ischemia. PBN itself enhanced recovery of contractile function, indicating that the radicals trapped may play a pathogenetic role in myocardial stunning. Superoxide dismutase plus catalase attenuated PBN adduct production and, at the same time, improved recovery of contractile function. Antioxidant therapy given 1 min before reperfusion suppressed PBN adduct production and improved contractile recovery; however, the same therapy given 1 min after reperfusion did not suppress early radical production and did not attenuate contractile dysfunction. After i.v. administration, the elimination half-life of PBN was estimated to be approximately 4-5 h. The results demonstrate that 1) free radicals are produced in the stunned myocardium in intact animals; 2) inhibition of free radical production results in improved contractile recovery; and 3) the free radicals important in causing dysfunction are produced in the first few minutes of reperfusion. Taken together, these studies provide cogent evidence supporting the oxy-radical hypothesis of stunning in open-chest dogs. It is now critical to determine whether these results can be reproduced in conscious animal preparations.
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PMID:Use of spin traps in intact animals undergoing myocardial ischemia/reperfusion: a new approach to assessing the role of oxygen radicals in myocardial "stunning". 216 54

Myeloperoxidase (MPO) is an enzyme found in granulocytes of neutrophils, but not in mammalian tissues. Previous studies have directly correlated MPO activity with neutrophil accumulation in tissues. This study presents a method for determining MPO activity in liver. Neutrophil accumulation in rat liver was provoked by creating partial ischemia followed by reperfusion. Liver homogenates prepared by a standard procedure showed no MPO activity. The homogenate was applied to Sephadex G100 and DEAE Sepharose CL6B columns which separated MPO activity from inhibitory activity. The inhibitor was identified as catalase based upon its elution from the columns and removal with 3-amino- 1,2,4-triazole (AT), a catalase inhibitor. Based upon these findings, it was determined that full MPO activity can be assayed in unfractionated liver homogenates by first inactivating catalase with AT.
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PMID:The determination of myeloperoxidase activity in liver. 217 63

Efforts to reduce reperfusion injury have focused on exogenous therapies; however, endogenous attenuation of reperfusion injury can be induced by a single sublethal dose of endotoxin (ETX) prior to ischemia. The purposes of this study were to investigate (i) the early neutrophil-endothelial (PMN-EC) adherence, (ii) the associated myocardial oxidant stress, (iii) the relationship of oxidant stress to antioxidant enzyme activity, and (iv) the correlation of increased antioxidant enzyme activity to myocardial recovery following ischemia/reperfusion (I-R) injury at 36 hr. Rats were administered a sublethal dose (2% of LD50) of endotoxin (500 micrograms/kg, ip, Salmonella typhimurium). At 6 hr, myocardial neutrophil accumulation (histology), hydrogen peroxide (H2O2) levels, and myocardial tissue glutathione (glutathione and oxidized glutathione) levels were determined. At 24 hr myocardial tissue glutathione levels and catalase (CAT) activity were assayed. At 36 hr, myocardial tissue superoxide dismutase, glutathione peroxidase, glutathione reductase, catalase, and glucose-6-phosphate dehydrogenase (G-6-PD) were assayed. At 36 hr, hearts were subjected to a standard (20 min, global, 37 degrees C) ischemic insult followed by reperfusion. At 40 min of reperfusion, ventricular function was assessed (ventricular balloon; ventricular developed pressure +dP/dt, and -dP/dt).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Induction of endogenous tissue antioxidant enzyme activity attenuates myocardial reperfusion injury. 219 33

Free radicals have recently been implicated in a number of biochemical and chemical reactions in the body. Lipid peroxidation induced by free radical reaction is believed to be one of the major causes of cell damage and injuries in cell membranes. In recent years, reports have appeared citing the contribution of free radicals and active oxygen species in the etiology of various digestive diseases. For example, gastric mucosal injuries and the increases in thiobarbituric acid-reactive substances in the gastric mucosa induced by ischemia or ischemia/reperfusion were significantly inhibited by treatment with superoxide dismutase and catalase. It has been suggested that superoxide radical or hydroxyl radical may be the major oxygen radicals contributing to ischemia or ischemia/reperfusion injury in the stomach, small intestine, and liver. There reactive species can attack and damage important biological molecules. Within cellular membranes, hydroxyl radical can initiate a free radical chain reaction known as lipid peroxidation, in which polyunsaturated fatty acids are broken down into water soluble products and toxic lipid peroxides are produced with the consequent destruction of membrane integrity. The major source of active oxygen species produced after ischemia or ischemia/reperfusion seems to be the enzymatic xanthine oxidase and activated polymorphonuclear leukocytes (PMN). In the large intestine which has little activity in xanthine oxidase, PMNs are a more important source of active oxygen species and play a role in the pathogenesis of the inflammatory bowel diseases. The above information suggests that oxygen-derived free radicals are involved in the fundamental mechanism of tissue injury in various disorders of the digestive system.
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PMID:[Free radicals in digestive diseases]. 220 Sep 14

The role of oxygen-derived free radicals and lipid peroxidation in the pathogenesis of acute gastric mucosal erosion was investigated in rat models produced by burn shock stress, by treatment with regional hyperthermia, platelet activating factor, and compound 48/80, and by ischemia-reperfusion. In all experimental models, the increase in the gastric erosions and in TBA reactants in the gastric mucosa were significantly inhibited by the treatment with superoxide dismutase (SOD) and/or catalase. Pretreatment with allopurinol, a competitive inhibitor of xanthine oxidase, prevented considerably the gastric injury (a) induced by burn shock, (b) produced by treatment with compound 48/80, and (c) caused by ischemia-reperfusion. By the treatment with anti-rat neutrophil antibody, the gastric mucosal injuries induced by regional hyperthermia, platelet activating factor, and compound 48/80 were significantly inhibited; however, burn shock and ischemia-reperfusion injuries were not inhibited. These results suggest that oxygen-free radical and lipid peroxidation contribute to the formation of gastric mucosal lesions, and that the sources of oxygen radicals seem to be different among these experimental models.
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PMID:Role of oxygen-derived free radicals in the pathogenesis of gastric mucosal lesions in rats. 221 51

Intestinal ischemia, however, caused, is still a serious and growing clinical problem with an unacceptable mortality rate of over 60%. This high mortality rate is mainly due to the fact that the patients are not admitted to the hospital or not treated early enough. Even if the patients are operated on within 24 h, their mortality rate is still over 50%, and those surviving the initial treatment suffer from postischemic complications. These damages have been accounted until now to tissue ischemia. It has been proven experimentally that also reperfusion or revascularization after time-limited ischemia add to the tissue damages observed, due to the formation of O2-radicals. Thereby the prerequisites for the production of these radicals (the conversion of xanthine dehydrogenase to xanthine oxidase and the increase of hypoxanthine concentrations in the tissue and plasma) are generated during tissue ischemia. These radicals damage directly or initiate several vicious circles leading to mucosal lesions, impaired intestinal function and an enhanced absorption of bacteria and endotoxin. Various substances (SOD, catalase, DMSO, allopurinol, deferoxamine etc.) detoxify oxygen radicals or inhibit the pathomechanisms leading to the enhanced radical generation. Hopefully, the combination of early revascularization with these already available scavengers will improve the high mortality and morbidity of patients suffering from intestinal ischemia.
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PMID:Oxygen radicals in intestinal ischemia and reperfusion. 222 27

Epilepsy complicates severe head trauma. Development of persistent seizures appears to correlate with the extent of trauma. Although early reports suggested that prophylactic administration of antiepileptic drugs would prevent epileptogenesis, controlled studies have failed to corroborate this assumption. Head trauma initiates a sequence of responses that includes altered blood flow and vasoregulation, disruption of the blood-brain barrier, increases in intracranial pressure, focal or diffuse ischemia, hemorrhage, inflammation, necrosis, and disruption of fiber tracts. The presence of an intracranial hematoma has a robust association with the development of post-traumatic epilepsy. Extravasation of blood is followed by hemolysis and deposition of heme-containing compounds into the neuropil, initiating a sequence of univalent redox reactions and generating various free radical species, including superoxides, hydroxyl radicals, peroxides, and perferryl ions. Free radicals initiate peroxidation reactions by hydrogen abstraction from methylene groups adjacent to double bonds of fatty acids and lipids within cellular membranes. Intrinsic enzymatic mechanisms for control of free radical reactions include activation of catalase, peroxidase, and superoxide dismutase. Steroids, proteins, and tocopherol also terminate peroxidative reactions. Tocopherol and selenium are effective in preventing tissue injury initiated by ferrous chloride and heme compounds. Treatment strategies for prevention or prophylaxis of post-traumatic epilepsy must await absolute knowledge of mechanisms. Antioxidants and chelators may be useful, given the speculation that peroxidative reactions may be an important component of brain injury responses. However, potential treatment strategies involving gamma-aminobutyric acid (GABA) agonists, NMDA receptor antagonists, and barbiturates need further scientific assessment.
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PMID:Post-traumatic epilepsy: cellular mechanisms and implications for treatment. 222 73

We show that the production of Luminol reactive oxygen radicals in the perfused rat heart under ischemia and reperfusion can be monitored continuously by measuring the chemiluminescence of Luminol-perfused hearts. Luminol did not affect the monitored physiological parameters of the hearts. Chemiluminescence increased during ischemia and reperfusion. Superoxide dismutase treatment of the heart before ischemia, but not catalase, abolished these increases.
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PMID:Luminol enhanced chemiluminescence of the perfused rat heart during ischemia and reperfusion. 222 23

We have previously demonstrated that induction of the heat-shock response in rats results in improved recovery of isolated Langendorff-perfused rat hearts subjected to low-flow ischemia followed by reperfusion (Currie et al., 1988). The mechanisms underlying this protective effect of heat-shock are uncertain although the protection was associated with enhanced content of the antioxidant enzyme catalase but not superoxide dismutase or glutathione peroxidase (Currie et al., 1988). Various investigators have suggested the importance of improved energy metabolism in determining recovery following ischemia (Pasque and Wechsler, 1984; Haas et al., 1984; Devous and Lewandowski, 1987). We therefore examined, using a working rat heart model subjected to 10 or 15 min zero flow ischemia whether changes in energy metabolites could account for the protective effect of the heat-shock response. Hearts perfused 24 h after induction of heat-shock failed to demonstrate significant improvement of recovery following 10 min ischemia, however recovery was significantly enhanced in hearts reperfused after 15 min ischemia. Ischemia produced a depression in both ATP and creatine phosphate (CP) content whereas a moderate elevation in ADP and AMP and a marked increase in tissue lactate were evident. These changes were unaffected by prior heat-shock treatment. For both durations of ischemia tissue metabolites were determined during early (5 min) and late (30 min) reperfusion. Although partial recovery in high energy phosphates and a return of ADP, AMP and lactate to near-normal levels were evident, no differences in energy products were observed between hearts from normal or heat-shocked animals, in spite of significantly enhanced recovery.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Improved post-ischemic ventricular recovery in the absence of changes in energy metabolism in working rat hearts following heat-shock. 223 33

The present study was performed to clarify whether the combination of superoxide dismutase (SOD) and catalase (CAT) can reduce Ca2+ overload and improve recovery of function and metabolites during reperfusion in isolated globally ischemic rat hearts. In non-treated hearts, left ventricular developed pressure (LVDP) recovered to only 30% of the preischemic value with elevation of left ventricular end-diastolic pressure (LVEDP) after 30 min of reperfusion following 30 min of global zero-flow ischemia. ATP and CP fell by 40% and 60%, respectively with 13 fold increase in Ca2+ uptake. A combined administration of SOD and CAT at low concentrations improved recovery of function (LVDP to 60%), reduced Ca2+ uptake (10 fold) without any improvement in high energy phosphates. However a combination of SOD and CAT at higher concentrations did not improve, or even deteriorate functional and metabolic recovery with increased Ca2+ overload (12 to 14 fold). These results indicated that the extracellular free radical scavengers, SOD and CAT, had a biphasic effect on reperfusion injury and could be partially beneficial at low concentrations.
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PMID:[Biphasic effects of a combined administration of SOD and CAT on Ca overload and recovery of function and metabolites]. 223 62


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