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Query: UMLS:C0917798 (cerebral ischemia)
 17,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

After the middle cerebral artery of rats was occluded, changes in the content of 14 free amino acids and the activity of antioxidant enzymes in the ischemic striatum were assessed with respect to the duration of ischemia. Glu and Asp levels were significantly reduced by 60 min of ischemia, GABA was increased by 30 and 60 min and Ala was increased by 5, 15, and 30 min. During ischemia, the levels of striatal Gln, Asn, Ser, Tau, Gly and Pro were found to be normal. In comparison with the sham-operated rats, the changes in the content of Thr, His, Arg and Tyr were inconclusive, since the effect of operative stress could not be ruled out on such occasion. Concomitantly, the Zn-Cu superoxide dismutase and glutathione peroxidase activity were significantly reduced by 30 min of ischemia. It revealed that the reduced capacity to scavenge the oxygen free radicals occurred during the early stage of cerebral ischemia. The above changes of Glu, Gln, GABA and Pro level might be considered as the final outcome of the decrease of glutamate synthesis, the acceleration of its conversion to GABA, and the extracellular leakage of glutamate. According to our data, the oxygen free radicals might be involved in the evolution of primary neuronal damage at the ischemic striatum.
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PMID:[Mechanism of neuronal damage caused by cerebral ischemia]. 133 25

To investigate the role of glutamate release in cerebral ischemia, the amounts of amino acids (glutamate, taurine, alanine, glycine and glutamine) released in the hippocampal CA1 region of stroke-prone SHR (SHRSP), stroke-resistant SHR (SHRSR) and normotensive rats (WKY) were determined during and after cerebral ischemia by the microdialysis method under halothane anesthesia. Cerebral ischemia was produced by the occlusion of both common carotid arteries for 20 min. The basal amino acids release did not differ among the three strains of rats, but ischemic glutamate and taurine releases were more marked in SHRSP than in other strains. These results suggest that the massive glutamate release during cerebral ischemia of SHRSP might be related with severe neuronal cell injury.
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PMID:Changes in extracellular concentration of amino acids in the hippocampus during cerebral ischemia in stroke-prone SHR, stroke-resistant SHR and normotensive rats. 162 92

It is well established that excitatory amino acid neurotransmitters are extensively liberated during ischemia and that they have neurotoxic properties contributing to neuronal injury. To study changes in the liberation of excitatory and other amino acids during cerebral ischemia, we measured their extracellular concentrations and related them to blood flow levels and electrophysiologic activity (electrocorticogram and auditory evoked potentials) before and for up to 2 hours after multiple cerebral vessel occlusion in 14 anesthetized cats. Blood flow levels between 0 and 43 ml/100 g/min were reached. Concentrations of the excitatory amino acid neurotransmitters increased most (aspartate 10-fold, glutamate 30-fold, and gamma-aminobutyric acid 300-fold compared with control values) below a blood flow threshold of 20 ml/100 g/min. The total power of the electrocorticogram and the amplitude of the auditory evoked potentials were affected below the same blood flow threshold. In contrast, concentrations of the nontransmitter amino acids taurine, alanine, asparagine, serine, and glutamine increased 1.5-5-fold as blood flow decreased, while concentrations of the essential amino acids phenylalanine, valine, leucine, and isoleucine did not change during cerebral ischemia. The great increases in concentrations of the excitatory amino acid neurotransmitters below a blood flow threshold close to that for functional disturbance is in accordance with the role of these amino acids in ischemic cell damage. Their release at blood flow levels compatible with cell survival and the increase in their concentrations with severity and duration of cerebral ischemia imply that excitotoxic antagonists may have potential as therapeutic agents.
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PMID:Differences in ischemia-induced accumulation of amino acids in the cat cortex. 197 18

The aim of this study was to measure changes in the extracellular fluid (ECF) concentration of lactate, pyruvate, purines, amino acids, dopamine, and dopamine metabolites in the striatum of rats subjected to focal cerebral ischemia, using intracerebral microdialysis as the sampling technique. Microdialysis probes were inserted into the lateral part of the caudate-putamen bilaterally 2 h before the experiment. Ischemia was induced by permanent middle cerebral artery occlusion (MCAO) on the left side. Microdialysis samples were analyzed by high performance liquid chromatography. Following MCAO, the concentration of lactate, adenosine, inosine, and hypoxanthine rose markedly in the ECF on the occluded side, while there was no significant change in pyruvate. These changes were accompanied by dramatically elevated levels of aspartate, glutamate, taurine, gamma-aminobutyric acid, and dopamine. There was also a marked increase in alanine/tyrosine, while minor or no changes occurred with other amino acids. Concomitantly, the ECF level of the dopamine metabolites 3,4-dihydroxyphenylacetate and homovanillic acid decreased. There was no significant increase in any of the metabolites measured on the right, nonoccluded side. In relation to the concept of excitotoxicity in brain ischemia, it is concluded that during the acute stage of focal cerebral ischemia, the ECF is flooded with both potentially harmful (e.g., aspartate, glutamate, and DA) and protective (e.g., taurine, GABA, and adenosine) agents. The relative importance of these events for the development of cell death in the ischemic penumbra needs to be elucidated. In addition, lactate, inosine, and hypoxanthine, measured in the ECF by intracerebral microdialysis, may prove to have diagnostic and/or prognostic value in neurometabolic monitoring of the ischemic brain.
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PMID:Dynamics of extracellular metabolites in the striatum after middle cerebral artery occlusion in the rat monitored by intracerebral microdialysis. 277 32

Changes in cerebral free amino acids, catecholamines and uric acid levels were explored for up to 7 days after cerebral ischemia in the rat. Fifty male Sprague-Dawley rats were subjected to occlusion of the middle cerebral artery on the olfactory tract, under halothane anesthesia. The animals were decapitated at 2, 4, 6, 12, 24 hours and 2, 3, 5, 7 days after the surgery, respectively. The brains were rapidly removed. The cerebral hemispheres were divided into right and left halves, and homogenized in sulfosalicylic acid solution. Free amino acids were analyzed by colormetric method. Cathecholamines and uric acid were analyzed by high-performance liquid chromatography. Each parameters were measured both on the ischemic and contralateral hemispheres. The time course of changes in each parameters were observed by means of the ratio, which is the value of ischemic side divided by that of contralateral side. Free amino acids Dicarboxylic group; Decreases in glutamate and increases in glutamine suggest one aspect of detoxication of ammonia within the ischemia tissue. Monocarboxylic group; GABA, glycine, alanine were increased in early ischemic state, and gradually lowered to the normal values. These suggest the impairment of tricarboxylic acid (TCA) cycle in the ischemic tissues, since these amino acids are closely related to TCA cycle. Essential amino acids, except for tryptophan, were increased until the end of study. These increases suggest the utilization of essential amino acids for protein synthesis might be disturbed in the ischemic tissues. Catecholamines and precursors; Norepinephrine and dopamine were lowered gradually. On the other hand, phenylalanine and tyrosine were increased during ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Biochemical studies of the cerebral ischemia in the rat--changes in cerebral free amino acids, catecholamines and uric acid]. 370 75

Dichloroacetate (DCA) is known to prevent the phosphorylation of the pyruvate dehydrogenase complex (PDHC) by blocking the action of PDH kinase. This action allows the active PDHC to exert its effect on the metabolism of glucose, lactate and alanine to acetyl CoA. DCA has been shown to reduce serum lactate levels in humans and animals in such conditions as diabetes, phenformin-induced hepatic failure, exercise, and endotoxin-induced shock. Lactic acidosis in the brain has often been postulated as a cause of neuronal damage following ischemia and hypoxia. Therefore, we examined the effect of intravenously administered DCA (100 mg/kg) in rats that were rendered hyperglycemic by intravenous glucose (2 g/kg), and then made to undergo 15 minutes of incomplete cerebral ischemia by bilateral carotid ligation and systemic hypotension (mean arterial pressure of 50 mm Hg). DCA significantly reduced serum lactate levels pre-ischemia, but had no effect on serum lactate levels after ischemia induction. Brain levels of lactate, ATP and PCr after 15 minutes of incomplete ischemia were unaffected by DCA. We conclude that in this in-vivo model the control of PDHC activity in the brain may be different than that in the periphery, and that DCA was not effective in reducing brain tissue lactate levels.
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PMID:The effect of dichloroacetate on brain lactate levels following incomplete ischemia in the hyperglycemic rat. 371 55

The crystalloid solutions used to prime cardiopulmonary bypass pumps frequently contain metabolically active substrates. However, there is a lack of controlled studies to investigate the metabolic response to cardiac operations using different pump primes. We have carried out a prospective, randomized study of 24 patients divided into four groups, each group receiving a different crystalloid prime. The primes contained glucose, lactate, glucose and lactate, or neither glucose nor lactate. Using identical anesthetic, surgical, and perfusion techniques, we estimated the metabolic response to cardiac operation in all patients by frequent blood sampling for measurement of hormone (insulin, glucagon, cortisol, and growth hormone) and metabolite concentrations (glucose, lactate, pyruvate, glycerol, alanine, and 3-hydroxybutyrate) from the day before operation to the seventh postoperative day. The results demonstrated that, after 4 hours postoperatively, the endocrine and metabolic response to cardiac operation was unaffected by the nature of the priming fluid. However, major endocrine and metabolic changes occurred before that time, which were related directly to the glucose and lactate contents of the prime. Very high concentrations of both glucose and lactate were observed at the end of bypass if they were induced in the prime. Given the known dangers of hyperglycemia in cerebral ischemia and the potential gluconeogenic effects of infused lactate, we suggest that glucose-free and lactate-free primes be employed in the extracorporeal circuit.
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PMID:The effects of four different crystalloid bypass pump-priming fluids upon the metabolic response to cardiac operation. 389 72

Brain ischemia was induced for 10 or 30 min by clamping the common carotid arteries in rabbits whose vertebral arteries had previously been electrocauterized. EEG and tissue content of high energy phosphates were used to verify the ischemic state and to evaluate the degree of postischemic recovery. Extracellular levels and total contents of amino acids were followed in the hippocampus during ischemia and 4 h of recirculation. At the end of a 30-min ischemic period, GABA had increased 250 times, glutamate 160 times, and aspartate and taurine 30 times in the extracellular phase. The levels returned to normal within 30 min of reflow. A delayed increase of extracellular phosphoethanolamine and ethanolamine peaked after 1-2 h of reflow. Ten minutes of ischemia elicited considerably smaller but similar effects. With respect to total amino acids in the hippocampus, glutamate and aspartate decreased to 30-50% of control while GABA appeared unaffected after 4 h of reflow. Alanine, valine, phenylalanine, leucine, and isoleucine increased severalfold. The importance of toxic extracellular levels of excitatory amino acids, as well as of high extracellular levels of inhibitory amino acids, are considered in relation to the pathophysiology of neuronal cell loss during cerebral ischemia.
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PMID:Ischemia-induced shift of inhibitory and excitatory amino acids from intra- to extracellular compartments. 403 Sep 18

Rats were implanted with 0.3-mm-diameter dialysis tubing through the hippocampus and subsequently perfused with Ringer's solution at a flow rate of 2 microliter/min. Samples of the perfusate representing the extracellular fluid were collected over 5-min periods and subsequently analyzed for contents of the amino acids glutamate, aspartate, glutamine, taurine, alanine, and serine. Samples were collected before, during, and after a 10-min period of transient complete cerebral ischemia. The extracellular contents of glutamate and aspartate were increased, respectively, eight- and threefold during the ischemic period; the taurine concentration also was increased 2.6-fold. During the same period the extracellular content of glutamine was significantly decreased (to 68% of the control value), whereas the concentrations of alanine and serine did not change significantly during the ischemic period. The concentrations of gamma-aminobutyric acid (GABA) were too low to be measured reliably. It is suggested that the large increase in the content of extracellular glutamate and aspartate in the hippocampus induced by the ischemia may be one of the causal factors in the damage to certain neurons observed after ischemia.
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PMID:Elevation of the extracellular concentrations of glutamate and aspartate in rat hippocampus during transient cerebral ischemia monitored by intracerebral microdialysis. 614 59

The effects of acetyl-L-carnitine (ALCAR) treatment on brain energy state recovery and lactic acid levels following 20 min ischemia and 2, 24 and 48 h reperfusion were investigated by 31P and 1H-NMR spectroscopy. Transient forebrain ischemia was induced by four-vessel occlusion method in fed 6-month-old Fischer rats. ALCAR or saline was administered by intraperitoneal route immediately after 20 min ischemia and again at 1, 4, 24 and 30 h during reperfusion. Twenty-min severe forebrain ischemia was associated with a marked decrease in phosphocreatine (PCr) and ATP levels and a corresponding increase in lactic acid, inorganic phosphate (Pi), AMP, creatine, glycerol 3-phosphate and alanine levels. Following reperfusion, a general tendency to restore pre-ischemic metabolite levels was observed. However, after 2 h reperfusion in saline-treated rats, lactic acid and Pi levels remained significantly higher, while ATP levels were still significantly lower than in non-ischemic controls. On the contrary, in ALCAR-treated animals a complete recovery of all metabolites including Pi and ATP was observed, while PCr levels were even more elevated compared with those in saline-treated rats. Furthermore lactic acid content was significantly lower than that in both saline-treated and non-ischemic control rats. It is concluded that a potential therapeutic role may be claimed for ALCAR in the treatment of cerebral ischemia through mechanisms that include faster recovery and improvement of brain energy production as well as a decreased lactic acid content during early post-ischemic reperfusion.
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PMID:Effect of acetyl-L-carnitine on recovery of brain phosphorus metabolites and lactic acid level during reperfusion after cerebral ischemia in the rat--study by 13P- and 1H-NMR spectroscopy. 803 36


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