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

Transient focal ischemia was produced in rat brain using simultaneous, reversible occlusion of the middle cerebral artery (MCA) and both carotid arteries. NADH tissue fluorescence and regional levels of ATP and lactate were measured after occlusion for 1 or 2.5 h and after reperfusion for 1 or 24 h following a 2.5-h insult. Occlusion for 1 or 2.5 h caused a marked but microheterogenous increase in NADH fluorescence, which was restricted to the MCA territory of the ipsilateral cortex. In this ischemic core, tissue levels of ATP were nearly depleted, while lactate accumulated to 10-13 mmol/kg. Metabolic alterations were less pronounced in regions adjacent to the ischemic core; however, one border region experienced a progressive increase in lactate between 1 and 2.5 h. NADH fluorescence and metabolite levels were not significantly altered in subcortical structures. In animals reperfused after a 2.5-h insult, NADH fluorescence diminished in the ischemic core to abnormally low levels, ATP was restored only to 37-50% of control, and lactate remained elevated. By 24 h, histologic infarction was evident in the regions with metabolic impairment. These results indicate that focal depletion of energy metabolites for 2.5 h caused irreversible impairment of energy metabolism and focal infarction even though lactate accumulation was moderate.
J Cereb Blood Flow Metab 1991 May
PMID:NADH fluorescence and regional energy metabolites during focal ischemia and reperfusion of rat brain. 201 54

Animal studies have shown cerebral lactate uptake under conditions of anoxia and ischemia. Cerebral lactate uptake in humans during cardiopulmonary resuscitation (CPR) has not been previously reported in the literature. Forty-five patients receiving CPR underwent simultaneous sampling through jugular venous bulb, right atrial, and central aortic catheterization. The mean net cerebral lactate uptake (central aortic minus jugular venous bulb) was 0.76 +/- 1.86 and 0.80 +/- 2.03 mM on initial measurement and 10 min later, respectively. Both measurements were statistically significant (p = 0.01) compared to normal controls who have net cerebral output of lactate of -0.18 +/- 0.1 mM. Seventy-one percent of all patients had a cerebral uptake on initial sampling and this gradient persisted upon sampling 10 min later in 68% of the remaining 40 patients who did not have a return of spontaneous circulation. Among multiple variables measured, patients who exhibited a cerebral lactate uptake were 13.2 years younger (p = 0.004), received an additional 7.6 min of CPR (p = 0.05), and had a mean arterial lactate concentration of 4.8 mM higher (p = 0.005) than the nonuptake group. The pathophysiologic explanation of cerebral lactate uptake during CPR is multifactorial and includes utilization and/or diffusion.
J Cereb Blood Flow Metab 1991 May
PMID:Cerebral lactate uptake during cardiopulmonary resuscitation in humans. 201 56

Substantial evidence exists that reactive oxygen species participate in the pathogenesis of brain damage following both sustained and transient cerebral ischemia, adversely affecting the vascular endothelium and contributing to the formation of edema. One likely triggering event for free radical damage is delocalization of protein-bound iron. The binding capacity for some iron-binding proteins is highly pH sensitive and, consequently, the release of iron is enhanced by acidosis. In this study, we explored whether enhanced acidosis during ischemia triggers the production of reactive oxygen species. To that end, enhanced acidosis was produced by inducing ischemia in hyperglycemic rats, with normoglycemic ones serving as controls. Production of H2O2, estimated from the decrease in catalase activity after 3-amino-1,2,4-triazole (AT) administration, was measured in the cerebral cortex, caudoputamen, hippocampus, and substantia nigra (SN) after 15 min of ischemia followed by 5, 15, and 45 min of recovery, respectively (in substantia nigra after 45 min of recovery only). Free iron in cerebrospinal fluid (CSF) was measured after ischemia and 45 min of recovery. Levels of total glutathione (GSH + GSSH) in cortex and hippocampus, and levels of alpha-tocopherol in cortex, were also measured after 15 min of ischemia followed by 5, 15, and 45 min of recovery. The results confirm previous findings that brief ischemia in normoglycemic animals does not measurably increase H2O2 production in AT-injected animals. Ischemia under hyperglycemic conditions likewise failed to induce increased H2O2 production. No difference in free iron in CSF was observed between animals subjected to ischemia under hyper- and normoglycemic conditions. The moderate decrease in total glutathione or alpha-tocopherol levels did not differ between normo- and hyperglycemic animals in any brain region or at any recovery time. Thus, the results failed to give positive evidence for free radical damage following brief periods of ischemia complicated by excessive acidosis. However, it is possible that free radical production is localized to a small subcellular compartment within the tissue, thereby escaping detection. Also, the results do not exclude the possibility that free radicals are pathogenetically important after ischemia of longer duration.
J Cereb Blood Flow Metab 1991 Jul
PMID:Acidosis-induced ischemic brain damage: are free radicals involved? 205 Jul 47

Following complete global cerebral ischemia and reperfusion, a brief period of reactive hyperemia is followed by a prolonged period of low flow commonly referred to as the delayed postischemic hypoperfusion state. It is generally assumed that this low-flow state may be injurious because of inadequate substrate delivery, thus implying that flow is no longer coupled to metabolic needs. This relationship of CBF to CMRO2 was examined in six anesthetized dogs that were subjected to 12 min of complete ischemia induced either by CSF compression or aortic occlusion. Following reperfusion and onset of the low-flow state, which stabilized at 45 min postischemia, control normothermic (37 degrees C) measurements of CBF and CMRO2 were determined. Thereafter, femoral arterial blood was circulated through a heat exchanger (42.5 degrees C), and brain temperature was increased to 40 degrees C and measurements were repeated. The brain was then cooled back to 37 degrees C for a final set of normothermic measurements. Thereafter, brain biopsies were taken to determine the energy state of the brain. CMRO2 changed approximately 6%/degrees C. CBF paralleled the change in CMRO2. Accordingly, the ratio of CBF to CMRO2 remained constant throughout at a value of 8 to 9, demonstrating maintained coupling. The brain energy state was normal at the end of the study. The authors conclude that postischemic CBF is modulated by the brain's metabolic needs.
J Cereb Blood Flow Metab 1991 Jul
PMID:Postischemic canine cerebral blood flow is coupled to cerebral metabolic rate. 205 Jul 48

Transient global and transient focal ischemia induced the 72 kDa heat shock protein (hsp72) in neurons in cortex, striatum, and other regions known to be injured during transient ischemia. A novel finding was the induction of hsp72 in islands (cylinders in three dimensions) of cells composed of astrocytes around the perimeter and neurons in the interior. Since histology showed pale staining in these regions, it is proposed that these islands represent areas of focal infarction in the distribution of small cortical and lenticulostriate arteries. Although the factors responsible for hsp72 induction during ischemia and infarction are unknown, these results suggest differences in mechanisms of hsp72 induction in astrocytes compared to neurons.
J Cereb Blood Flow Metab 1991 Jul
PMID:Heat shock protein hsp72 induction in cortical and striatal astrocytes and neurons following infarction. 205 Jul 50

Following transient ischemia of the brain, the coupling between somatosensory activation and the hemodynamic-metabolic response is abolished for a certain period despite the partial recovery of somatosensory evoked responses. To determine whether this disturbance is due to alterations of the stimulus-induced neuronal excitation or to a breakdown of the coupling mechanisms, cortical spreading depression was used as a metabolic stimulus in rats before and after ischemia. Adult rats were subjected to 30 min of global forebrain ischemia and 3-6 h of recirculation. EEG, cortical direct current (DC) potential, and laser-Doppler flow were continuously recorded. Local CBF (LCBF), local CMRglc (LCMRglc), regional tissue contents of ATP, glucose, and lactate, and regional pH were determined by quantitative autoradiography, substrate-induced bioluminescence, and fluorometry. Amplitude and frequency of the DC shifts did not differ between groups. In control animals, spreading depression induced a 77% rise in cortical glucose consumption, a 66% rise in lactate content, and a drop in tissue pH of 0.3 unit. ATP and glucose contents were not depleted. During the passage of DC shifts, transient increases (less than 2 min) in laser-Doppler flow were observed, followed by a post-spreading depression hypoperfusion. A comparable although less expressed pattern of hemodynamic and metabolic changes was observed in the postischemic rats. Although baseline LCMRglc was depressed after ischemia, it was activated 47% during spreading depression. Lactate increased by 26%, pH decreased by 0.3 unit, and ATP and glucose remained unchanged. The extent of the transient increase in laser-Doppler flow did not differ from that of the control group, and a post-spreading depression hypoperfusion was also found.(ABSTRACT TRUNCATED AT 250 WORDS)
J Cereb Blood Flow Metab 1990 Jul
PMID:Metabolic and hemodynamic activation of postischemic rat brain by cortical spreading depression. 211 36

The cerebral protective actions of a new thyrotropin releasing hormone (TRH) analogue, YM-14673, [Na-[[(S)-4-oxo-2-azetidinyl-carbonyl]-L-histidyl-L-prolinamide] dihydrate), were compared with those of CDP-choline (cerebral metabolic enhancer) and naloxone in rats rats subjected to unilateral carotid artery ligation and anoxic exposure (Levine rats). Drugs were administered intraperitoneally or orally 20, 80, and 140 min after anoxia. YM-14673 (0.03 to 1 mg/kg i.p. and 0.3 to 10 mg/kg p.o.) decreased the incidence of neurological deficits, such as hemiplegia and convulsion followed by coma and death, for 48 h after ischemia and anoxia. Both the increase in the brain water content and the degeneration of neurons in the cerebral cortex and thalamus were prevented by YM-14673 at a dose of 0.1 mg/kg (i.p.). CDP-choline (400 mg/kg i.p.), which is currently used in the therapy of cerebral vascular diseases, and naloxone (3 mg/kg i.p.) also decreased the incidence of the neurological deficits. These results suggest that YM-14673 protects Levine rats against neurological deficits, presumably by attenuating the development of brain edema and preventing neuronal damage. This compound may be useful in the therapeutic treatment of cerebral vascular diseases.
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PMID:Pharmacological actions of a new TRH analogue, YM-14673, in rats subjected to cerebral ischemia and anoxia. 211 71

The dose-dependent effects of MK-801, a glutamate receptor antagonist, on changes in CBF, CBF-PaCO2 responsiveness (133Xe clearance), EEG, and blood-brain barrier (methylene blue) were examined after a 15-min period of reversible complete global ischemia induced in halothane-anesthetized cats by occlusion of the vertebral and carotid arteries. Pretreatment with doses of MK-801 of greater than or equal to 0.5 mg/kg had no effect on resting CBF measures and produced a dose-dependent slowing of the dominant EEG frequency. In animals receiving this agent, there was an almost immediate return of baseline EEG patterns upon reinstitution of flow, no hypoperfusion after 2 h of reflow, preservation of CBF and CBF-PaCO2 responsiveness, and maintenance of blood-brain barrier integrity. In contrast, parallel control animals and animals treated with MK-801 at a dose of 0.1 mg/kg exhibited poor recovery based on the above parameters. MK-801 also diminished in a dose-dependent manner the CSF levels of 6-keto-prostaglandin (PG) F1 alpha (stable metabolite of PGI2) and thromboxane (Tx) B2 (stable metabolite of TxA2), which were otherwise elevated in vehicle-treated animals 2 h after reflow. Of particular interest, the CSF TxB2/6-keto-PGF1 alpha ratio in vehicle-treated animals was near 2. In animals pretreated with MK-801, at doses of greater than or equal to 0.5 mg/kg, this ratio was nearly 1. These observations are consistent with a possible triggering role of glutamate release in initiating at least part of the acute sequelae of ischemia. Such release in an electrically silent cell would increase Ca2+ influx and activate free fatty acid metabolism, leading to probable changes in vascular function and changes in blood-brain barrier permeability.
J Cereb Blood Flow Metab 1990 Jan
PMID:Systematic studies on the effects of the NMDA receptor antagonist MK-801 on cerebral blood flow and responsivity, EEG, and blood-brain barrier following complete reversible cerebral ischemia. 215 92

We have administered antagonists acting competitively or noncompetitively at the N-methyl-D-aspartate receptor after a short period of incomplete ischaemia and evaluated selective neuronal loss in the CA1 region of the rat hippocampus. The competitive antagonists D-(-)-2-amino-7-phosphonoheptanoate (2APH); 100 or 330 mg/kg; 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonate (CPP); 3.3 or 10 mg/kg; and CGS 19755 (cis-4-phosphonomethyl-2-piperidine carboxylate) 3.3 or 10 mg/kg; and the noncompetitive antagonists MK801 [+)5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate), 0.3, 1, or 3 mg/kg, and dextrorphan, 2, 6, 18, or 54 mg/kg, were administered intraperitoneally 15 min and 5 h after a 10-min incomplete ischaemia period; additionally MK801 (1 or 3 mg/kg) and CGS 19755 (10 or 30 mg/kg) were administered 5 and 10 h postischaemia. Seven days after ischaemia, the brains were fixed by perfusion. CA1 pyramidal cell counts were performed on Nissl-stained sections using an ocular grid piece. Ventilated (no ischaemia) control animals had a mean of 406 +/- 13 CA1 neurones/3 grid lengths. Ischaemia reduced this mean to 157 +/- 23. A significant protective effect against this cell loss was seen after two injections (at 15 min and 5 h postischaemia) of 2APH, CPP (10 mg/kg), CGS 19755 (10 mg/kg), MK801 (1 mg/kg), and dextrophan (54 mg/kg). Delayed injection (5 and 10 h postischaemia) of CGS 19755 (10 and 30 mg/kg) and MK801 (1 and 3 mg/kg) did not provide any protection against pyramidal cell loss.
J Cereb Blood Flow Metab 1990 May
PMID:Protection by NMDA antagonists against selective cell loss following transient ischaemia. 215 99

We investigated the long-term (up to 1 week) relationships between the duration of cerebral ischemia and postischemic energy metabolic profile, pH, and tissue edema in the rat. Ten rats each were subjected to 8 or 12 min of forebrain ischemia induced by bicarotid occlusion concurrent with systemic hypotension, and the results were compared with those of 10 sham-operated rat controls. In vivo 31P nuclear magnetic resonance spectroscopy was performed prior to ischemia and at intervals up to 168 h after ischemia. Cerebral edema (measured by specific gravity) was assessed prior to ischemia and at 24, 72, and 168 h after ischemia. The data revealed significant differences in the brain tissue pH profile over time between the ischemic groups (p less than 0.03). The 12-min ischemic animals exhibited brain tissue alkalosis (pH = 7.27 +/- 0.12) at 24 h compared with both sham (pH = 7.09 +/- 0.08) at 24 h and preischemic (pH = 7.06 +/- 0.04) pH values. The pH remained alkalotic (pH = 7.23 +/- 0.15) through the 48-h time period. In contrast, in the 8-min group, the onset of alkalosis was delayed until 48 h after ischemia (pH = 7.24 +/- 0.15), and pH remained alkalotic for only 24 h. No difference in high-energy phosphate metabolism was detected between groups. A different time dependence of tissue pH and specific gravity changes after 12 min of ischemia was detected. The present study suggests that the duration of an ischemic event marks the time of onset of brain tissue alkalosis and its duration and that cerebral edema alone cannot explain the pH changes.
J Cereb Blood Flow Metab 1990 Nov
PMID:Time course of postischemic intracellular alkalosis reflects the duration of ischemia. 221 79


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