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

Anesthesized male rabbits having a resting mean arterial pressure of 81 +/- 4 mm Hg and superior mesenteric artery blood flow of 91 +/- 7 mL min-1 were subjected to 60 min of splanchnic ischemia followed by 60 min of reperfusion. Upon reperfusion, mean arterial pressure fell. Splanchnic blood flow also decreased but not in parallel with blood pressure; consequently, vascular resistance was increased over the reperfusion period. This increase in splanchnic vascular resistance was not affected by intravenous t-PA (0.5 mg kg-1 + 5 mg kg-1 hr-1) for 30 min prior to and throughout the reperfusion period or by intravenous L-NAME (1 mg kg-1 x 2). However, intravenous infusions of TGF-beta (18 or 54 micrograms kg-1) at the time of reperfusion dose dependently attenuated the increases in vascular resistance (p < 0.05). This effect of TGF-beta was enhanced by coadministration of t-PA and inhibited by the coadministration of L-NAME. We propose that the effects of TGF-beta are ultimately mediated via nitric oxide release, and conclude that this may be useful therapy for the prevention of reperfusion-associated injury following surgery or as an adjunct to thrombolytic therapy.
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PMID:Transforming growth factor-beta 1 inhibits postischemic increases in splanchnic vascular resistance. 130 30

The potential role of nitric oxide (NO) and its reaction product with superoxide, peroxynitrite, was investigated in a model of hepatic ischemia-reperfusion injury in male Fischer rats in vivo. Pretreatment with the NO synthase inhibitor nitro-L-arginine (10 mg/kg) did neither affect the post-ischemic oxidant stress and liver injury during the initial reperfusion phase nor the subsequent infiltration of neutrophils into the liver and the later, neutrophil-induced injury phase. Furthermore, no evidence was found for a postischemic increase of the urinary excretion of nitrite, a stable oxidation metabolite of NO. In contrast, the administration of Salmonella enteritidis endotoxin (1 mg/kg) induced a significant diuresis in Fischer rats and an 800-fold enhancement of the urinary nitrite excretion. Nitro-L-arginine pretreatment inhibited the endotoxin-induced nitrite formation by 97%. Hepatic cGMP levels, as index of NO formation in the liver, were only increased significantly after endotoxin administration but not after ischemia and reperfusion. Our results provide no evidence for any enhanced generation of NO or peroxynitrite either systemically or locally during reperfusion and therefore it is unlikely that any of these metabolites are involved in the oxidant stress and liver injury during reperfusion after hepatic ischemia.
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PMID:Role of nitric oxide in the oxidant stress during ischemia/reperfusion injury of the liver. 137 73

Radicals are species containing one or more unpaired electrons, such as nitric oxide (NO.). The oxygen radical superoxide (O2.-) and the nonradical hydrogen peroxide (H2O2) are produced during normal metabolism and perform several useful functions. Excessive production of O2.- and H2O2 can result in tissue damage, which often involves generation of highly reactive hydroxyl radical (.OH) and other oxidants in the presence of "catalytic" iron or copper ions. An important form of antioxidant defense is the storage and transport of iron and copper ions in forms that will not catalyze formation of reactive radicals. Tissue injury, e.g., by ischemia or trauma, can cause increased metal ion availability and accelerate free radical reactions. This may be especially important in the brain because areas of this organ are rich in iron and CSF cannot bind released iron ions. Oxidative stress on nervous tissue can produce damage by several interacting mechanisms, including increases in intracellular free Ca2+ and, possibly, release of excitatory amino acids. Recent suggestions that free radical reactions are involved in the neurotoxicity of aluminum and in damage to the substantia nigra in patients with Parkinson's disease are reviewed. Finally, the nature of antioxidants is discussed, it being suggested that antioxidant enzymes and chelators of transition metal ions may be more generally useful protective agents than chain-breaking antioxidants. Careful precautions must be used in the design of antioxidants for therapeutic use.
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PMID:Reactive oxygen species and the central nervous system. 140 8

Peroxynitrite (ONOO-), the reaction product of superoxide (O2-) and nitric oxide (NO), may be a major cytotoxic agent produced during inflammation, sepsis, and ischemia/reperfusion. Bovine Cu,Zn superoxide dismutase reacted with peroxynitrite to form a stable yellow protein-bound adduct identified as nitrotyrosine. The uv-visible spectrum of the peroxynitrite-modified superoxide dismutase was highly pH dependent, exhibiting a peak at 438 nm at alkaline pH that shifts to 356 nm at acidic pH. An equivalent uv-visible spectrum was obtained by Cu,Zn superoxide dismutase treated with tetranitromethane. The Raman spectrum of authentic nitrotyrosine was contained in the spectrum of peroxynitrite-modified Cu,Zn superoxide dismutase. The reaction was specific for peroxynitrite because no significant amounts of nitrotyrosine were formed with nitric oxide (NO), nitrogen dioxide (NO2), nitrite (NO2-), or nitrate (NO3-). Removal of the copper from the Cu,Zn superoxide dismutase prevented formation of nitrotyrosine by peroxynitrite. The mechanism appears to involve peroxynitrite initially reacting with the active site copper to form an intermediate with the reactivity of nitronium ion (NO2+), which then nitrates tyrosine on a second molecule of superoxide dismutase. In the absence of exogenous phenolics, the rate of nitration of tyrosine followed second-order kinetics with respect to Cu,Zn superoxide dismutase concentration, proceeding at a rate of 1.0 +/- 0.1 M-1.s-1. Peroxynitrite-mediated nitration of tyrosine was also observed with the Mn and Fe superoxide dismutases as well as other copper-containing proteins.
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PMID:Peroxynitrite-mediated tyrosine nitration catalyzed by superoxide dismutase. 141 74

Neural injury due to ischemia and related insults is thought to involve the action of excitatory amino acids at N-methyl-D-aspartate receptors, which results in the influx of extracellular Ca2+ and the generation of nitric oxide. Because ethanol inhibits physiologic responses to excitatory amino acids, we examined its effect on toxicity induced by N-methyl-D-aspartate and by the nitric oxide donor sodium nitroprusside in neuron-enriched cultures prepared from rat cerebral cortex. Both N-methyl-D-aspartate and sodium nitroprusside were cytotoxic, as measured by the release of lactate dehydrogenase and by microfluorescent determination of cell viability. Ethanol (3-1,000 mM) protected cultures from N-methyl-D-aspartate but not sodium nitroprusside toxicity, and the ability of a series of n-alkanols to reproduce the effect of ethanol was related to carbon-chain length. Neuroprotection by ethanol was accompanied by a decrease in the N-methyl-D-aspartate-evoked elevation of free intracellular Ca2+ and did not appear to involve gamma-aminobutyric acid- or cyclic GMP-mediated mechanisms. These findings suggest that ethanol inhibits excitotoxicity at an early step in the N-methyl-D-aspartate signaling pathway, probably by reducing Ca2+ influx, and not by interfering with the action of nitric oxide.
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PMID:Ethanol and excitotoxicity in cultured cortical neurons: differential sensitivity of N-methyl-D-aspartate and sodium nitroprusside toxicity. 143

Nitric oxide (NO) and prostacyclin (PGI2) were determined in effluents of Langendorff-perfused rabbit hearts subjected to 2 h of global low-flow ischemia and subsequent reperfusion. PGI2 release [6-oxo-prostaglandin (PG) F1 alpha] was significantly enhanced during early reperfusion and remained elevated. NO formation was reduced during ischemia but did increase substantially during reperfusion. Indomethacin (3 microM) significantly suppressed ischemia-related 6-oxo-PGF1 alpha and NO release. This was accompanied by severely diminished myocardial recovery. NG-nitro-L-arginine (L-NNA) (100 microM) suppressed NO generation without major effects on 6-oxo-PGF1 alpha generation and cardiac dysfunction but with a remarkable increase in coronary perfusion pressure. These effects of L-NNA were antagonized by L-arginine, whereas the effects of indomethacin were not. There was a substantial loss of creatine kinase specific activity from reperfused ischemic hearts, which was further aggravated by indomethacin but not by L-NNA. These data demonstrate a cardioprotective and endothelium-protective role of PGI2 in myocardial ischemia, which also involves preservation of NO generation. Endogenous NO appears to be important for local regulation of coronary flow.
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PMID:Prostacyclin rather than endogenous nitric oxide is a tissue protective factor in myocardial ischemia. 144 94

The effect of the nitric oxide (NO) synthesis inhibitor Ng-nitro-L-arginine methylester (L-NAME) on ischaemic brain damage was determined in a rat model of focal cerebral ischaemia. Ischaemia was induced by permanent occlusion of the left middle cerebral artery (MCA) and infarction assessed 4 h post-occlusion by quantitative histopathology. L-NAME (30 mg/kg s.c.), administered 30 min pre- and 30 min post-MCA occlusion, did not significantly alter the volume of ischaemic damage in the cerebral hemisphere, neocortex or caudate nucleus compared with saline controls. This result provides no support for the view that NO generation is a key component in the post-ischaemic cascade leading to acute neuronal death.
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PMID:Inhibition of nitric oxide synthesis does not reduce infarct volume in a rat model of focal cerebral ischaemia. 145 9

Bradykinin perfusion (BK 1 x 10(-12) to 1 x 10(-8) mol/l) of isolated working rat hearts with postischemic reperfusion arrhythmias induced a reduction of the incidence as well as duration of ventricular fibrillation, improvement of cardiodynamics via increased left ventricular pressure, contractility, and coronary flow without changes in heart rate. These beneficial effects were accompanied by reduced activities of the cytosolic enzymes lactate dehydrogenase and creatine kinase as well as lactate output. In the myocardial tissue lactate content was reduced and the energy rich phosphates increased compared to saline perfused control hearts. Glycogen stores were also preserved. These beneficial effects of BK were concentration-dependently abolished by perfusion of the B2 kinin receptor antagonist HOE 140 and the nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine (L-NNA). These results suggest that improved cardiac function during and after myocardial ischemia as well as increased energy rich phophates and glycogen stores are mediated by BK and the subsequent release of NO, shifting myocardial metabolism during ischemia and reperfusion to the glucose pathway which leads to changes indicative for cardioprotection.
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PMID:Bradykinin-mediated metabolic effects in isolated perfused rat hearts. 146 41

Experiments were performed with Mongolian gerbils to study the effect of the specific nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine (L-NNA) on ischemic brain damage induced by 5 min bilateral carotid occlusion. A single i.p. injection of L-NNA did not result in any neuronal loss in the central nervous system. In animals undergoing ischemia, a selective destruction of hippocampal CA1 cells was observed whereas pretreatment with 50 mg/kg L-NNA 4 h before administration of ischemia produced significantly more extensive cell damage in the hippocampus and other brain regions. These findings demonstrate that in this model inhibition of nitric oxide generation augments ischemia-induced neuronal cell injury in the brain.
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PMID:NG-nitro-L-arginine enhances neuronal death following transient forebrain ischemia in gerbils. 149 79

Acetylcholine (ACh) and nitroglycerin (NTG) were used as probes to study endothelium-dependent and endothelium-independent vascular relaxation in isolated perfused transverse paraumbilical human skin flaps. It was observed that ACh (10(-6) M) significantly (p < 0.05) decreased the vascular resistance and increased dermal capillary perfusion (assessed by surface fluorometry) in norepinephrine (NE, 10(-6) M) preconstricted skin flaps, despite the presence of a cyclooxygenase inhibitor (indomethacin, 3 x 10(-5) M) and a beta-adrenergic receptor antagonist (propranolol, 10(-6) M). The ability of ACh to induce vascular relaxation in NE-preconstricted skin flaps was lost after damaging the vascular endothelial lining with saponin perfusion (100 mg.L-1, 5 min). In contrast, NTG (10(-6) M) induced vascular relaxation to a similar extent before and after saponin treatment. In a separate study, ACh was seen to induce vascular relaxation in a concentration-dependent manner in skin flaps preconstricted with NE (10(-6) M). This vascular relaxation effect of ACh over the dose range of 10(-9)-10(-5) M was significantly (p < 0.01) inhibited in the presence of N omega-nitro-L-arginine (10(-5) M), a nitric oxide (NO) synthesis inhibitor. These observations were taken to indicate the presence of endothelium-dependent and endothelium-independent vascular relaxation in human skin flaps and that the ACh-induced endothelium-dependent relaxation is probably mediated by NO. The importance of impairment of endothelium-dependent relaxation in the pathogenesis of skin flap ischemia, and the potential use of topical nitrovasodilators or NO donors for prevention and (or) treatment of skin flap ischemia were also discussed.
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PMID:Evidence for endothelium-dependent and endothelium-independent vasodilation in human skin flaps. 149 89


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