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

Local cerebral ischemia was produced in rats by internal carotid artery injection of 35 mu carbon microspheres, and brain norepinephrine (NE), dopamine, and cyclic adenosine 3, 5-monophosphate (cAMP) were measured in embolized and intact hemispheres at intervals up to four hours. Sham-operated animals were controls. There was an instantaneous increase of cAMP. Norepinephrine was reduced within two minutes after embolization and remained low for four hours. Dopamine increased by five minutes after embolization and returned to normal after four hours. Results were qualitatively similar, but less, in the nonembolized hemisphere. Accumulation of cAMP is thought to be due to a direct effect of ischemic hypoxia and may be the initiating factor in increased glycolysis that occurs in ischemia. Decrease in NE may be secondary to its generalized release from presynaptic terminals throughout the brain and could be a factor in cortical vasocontriction that follows embolization. Dopamine changes are a reflection of alterations in energy metabolism.
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PMID:Catecholamines in experimental brain ischemia. 23 32

As soon as there is evidence of left ventricular dysfunction, even before clinical signs of chronic cardiac failure (CCF) have developed, intrinsic and extrinsic compensatory mechanisms are brought into play by the body. The majority of these mechanisms are under the influence of neurohumoral systems. When neurohormonal responses persist, as in CCF, they take on a beneficial nature since they participate in adaptation of the cardiovascular system as a whole, but they are also harmful since they worsen the working conditions of the myocardium by their cardiac and peripheral effects. Hyperactivity of the noradrenergic sympathetic nervous system is seen in CCF with levels 2 to 3 times higher as compared with subjects with normal left ventricular function. The circadian rhythm of catecholamines is modified. The increase in circulatory catecholamines is all the greater when cardiac failure is advanced. This release of noradrenaline (NA) is under the control of arterial baroreceptors which normally send to the central nervous system inhibitory inflow from the sympathetic nervous system. Inhibitory tone is released in case of a fall in blood pressure. Noradrenaline acts on beta-predominant myocardial receptors (inotropic and tachycardic) and alpha-predominant vascular receptors, resulting in arteriolar vasoconstriction. There is rapid onset of down regulation of myocardial beta-receptors. This fall essentially concerns beta 1, but beta 2 also, since they may be affected according to the etiology of CCF (ischemia). The Renin Angiotensin System (RAS) is also activated by the fall in systemic blood pressure. This consists of a cascade of reactions leading to the synthesis of angiotensin II responsible for powerful vasoconstriction of all arterial areas, including the coronary vessels.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Metabolic changes in cardiac failure]. 130 Sep 20

Phospholipase A2 (PLA2) activity results in the formation of lysophospholipids and free fatty acids which may contribute to ischemic myocardial dysfunction. We evaluated the cardioprotective activity of two putative PLA2 inhibitors, quinacrine and 7,7-dimethyleicosadienoic acid (DEDA), in isolated globally ischemic rat hearts. Pretreatment with 1, 5 and 50 microM quinacrine before ischemia did not alter coronary flow but did cause significant cardiodepression. Twenty five minutes of global ischemia and 30 min of reperfusion caused severe myocardial dysfunction and lactate dehydrogenase release. Quinacrine significantly improved reperfusion contractile function and reduced lactate dehydrogenase release, indicative of cardioprotection. In contrast, 30 to 100 microM DEDA produced neither preischemic cardiodepression nor cardioprotective activity. PLA2 inhibition was inferred from measurements of the prostacyclin metabolite, 6-keto-prostaglandin F1 alpha in the coronary effluent and myocardial palmitoyl-lysophosphatidylcholine. Quinacrine and DEDA reduced both 6-keto-prostaglandin F1 alpha and palmitoyl-lysophosphatidylcholine by similar degrees. These results suggest that the cardioprotective activity of quinacrine is independent of PLA2 inhibition. A possible role of calcium inhibition was investigated in rat aortic smooth muscle strips. Norepinephrine-, KCl- and BAY K8644-induced contractions were antagonized in the presence of 5 and 50 microM quinacrine, but were unaffected by 30 to 60 microM DEDA. The ability of quinacrine to inhibit calcium was investigated further in cardiac ventricular myocytes. Measurement of mean whole cell calcium currents showed that quinacrine (5 microM) could inhibit this current up to 70%. Thus, these results suggest that quinacrine-induced cardioprotection may not be due to PLA2 inhibition, but may be related to calcium entry blocking activity.
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PMID:Effect of the phospholipase A2 inhibitors quinacrine and 7,7-dimethyleicosadienoic acid in isolated globally ischemic rat hearts. 138 29

Local anesthetic agents in high concentrations may cause local irritation by ischemia especially after the use of adrenaline whereas felypressin has no tissue-irritating properties. Adrenaline but not felypressin increases the intravenous systemic toxicity. Noradrenaline has to be avoided as a vasoconstrictor. An aspiration test before injection will decrease the risk of inadvertent intravenous injection.
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PMID:[Can choice of medications and adjuvants reduce risks of local anesthetic complications?]. 187 40

The effects of the calcium antagonists verapamil, gallopamil, nifedipine, felodipine and diltiazem on noradrenaline release during ischemia were studied in isolated perfused rat hearts. Endogenous levels of noradrenaline and its intraneuronal metabolite dihydroxyphenylethyleneglycol (DOPEG) were determined by high pressure liquid chromatography. Global isothermic ischemia of 20 min caused a release of endogenous noradrenaline amounting to 180 +/- 15 pmol/g. The calcium antagonists tested significantly suppressed ischemia-induced noradrenaline release (IC50 in mumols/l: verapamil 1, gallopamil 0.3, nifedipine 1, felodipine 3). Noradrenaline release during ischemia and the inhibitory effect of the calcium antagonists, were independent of extracellular calcium, indicating a nonexocytotic release mechanism. Interaction of the calcium antagonists with the major components of nonexocytotic release, intraneuronal storage and carrier-mediated transport, was tested in normoxic rat hearts. Vesicular storage was not stabilized by the calcium antagonists. In fact, verapamil, gallopamil, diltiazem and felodipine disturbed storage function, as indicated by an increased DOPEG release. Direct interaction with the noradrenaline carrier (uptake1) was demonstrated for verapamil, gallopamil, and diltiazem in a model of 3H-noradrenaline uptake. In conclusion, the calcium antagonists investigated inhibit noradrenaline release in ischemia by a mechanism which is different from blockade of neuronal calcium influx, and is rather due to an interaction with carrier-mediated transport of noradrenaline across the plasma membrane.
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PMID:Calcium antagonists and cardiac noradrenaline release in ischemia. 188 Aug 12

In this study, 16 patients matched with 16 controls were hypnotized prior to angioplasty. The hypnotized patients had a 25% increase in the time the cardiologist was able to keep the balloon inflated compared to the controls. Of the hypnotized patients, 13% required additional narcotic pain medication during the procedure as compared to 44% for the controls. Although we found no differences in rhythm, ischemia, blood pressure, or pulse between the two groups, the results of arterial catecholamine levels drawn at the start and at the end of the procedure were unexpected and seemed paradoxical. Norepinephrine levels were significantly higher in the hypnotized group (432 pg/ml, SE 51) than in the control group (281 pg/ml, SE 23) at the start of the procedure and fell more during the procedure than in control patients. Because catecholamines reportedly act as a barometer of neuroanxiety, further studies defining their role are needed.
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PMID:Use of hypnosis before and during angioplasty. 195 Nov 41

The changes in acetylcholine (ACh), monoamine and monoamine metabolite levels following cerebral ischemia in Mongolian gerbils were examined. In addition, the effects of Sho-saiko-to-go-keishi-ka-shakuyaku-to (TJ-960), which is a spray-dried mixture of 9 herbal drugs, on these changes were also examined. The dramatic decrement of ACh levels in ischemic gerbils was significantly inhibited by p.o. administration of TJ-960 at a daily dose of 3.5 g/kg or 700 mg/kg for one month. Norepinephrine (NE) was also reduced in all ischemic brain regions, and TJ-960 also recovered the level of NE. In ischemic gerbil brains, the dopamine (DA) levels decreased and its metabolites increased in the striatum, but DA and its metabolites in the thalamus + midbrain region increased. The serotonin (5HT) level was reduced in the cerebral cortex and hippocampus. TJ-960 inhibited these monoaminergic changes in ischemic gerbils. This suggests that TJ-960 may provide anti-ischemic action and beneficial effects on various symptoms induced by ischemia.
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PMID:The effects of sho-saiko-to-go-keishi-ka-shakuyaku-to (TJ-960) on ischemia-induced changes of brain acetylcholine and monoamine levels in gerbils. 237 Sep 41

The effects of a stable prostacyclin mimetic, iloprost (30 nmol/l), and of indomethacin (3 mumol/l) on ischemia-plus-reperfusion-induced changes in myocardial hemodynamics and sympathetic nerve function were examined in Langendorff-perfused rabbit heart isolated except for the postganglionic sympathetic cardiac nerves. Noradrenaline overflow was measured during an initial 1-min period of nerve stimulation (S1), compared with an identical stimulation (S2) made after 2 h of low-flow ischemia followed by a 30-min reperfusion period. Myocardial catecholamine content of left ventricular tissue was also measured. Pretreatment with iloprost, indomethacin, or vehicle began 10 min before ischemia. Global ischemia plus reperfusion reduced myocardial catecholamine content by 19% (vehicle), and the reduction was greater in indomethacin-pretreated hearts (37%, p less than 0.05), whereas iloprost increased tissue noradrenaline 18% above vehicle control (p less than 0.05). Initially, nerve stimulation-induced noradrenaline overflow ranged from 213 to 247 pmoles, and was significantly reduced after ischemia and reperfusion, the difference (S1-S2) being 198 pmoles (vehicle) and 117 pmoles (indomethacin), but only 44 pmoles after iloprost pretreatment (all groups p less than 0.01). In addition, iloprost improved the recovery of active systolic pressure development, coronary perfusion and left ventricular compliance on reperfusion, whereas a tendency toward further deterioration was observed in indomethacin-pretreated hearts. The results suggest that iloprost may protect both myocardial muscle and nerve cells from ischemia-plus-reperfusion injury. Preservation of myocardial catecholamine levels and sympathetic nerve responsiveness may contribute to improved recovery of reperfused ischemic myocardium.
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PMID:Prostaglandins and myocardial noradrenaline overflow after sympathetic nerve stimulation during ischemia and reperfusion. 241 Jul 36

Recently, this laboratory has demonstrated an enhanced susceptibility toward the development of ischemia-related lethal ventricular arrhythmias in the presence of therapeutic serum concentrations of digoxin in conscious dogs after myocardial infarction. The present study was performed to assess the effect of the interruption of cardiac sympathetic influences, via subacute left stellate ganglionectomy (LSGX), on digitalis-mediated ischemic ventricular arrhythmias. Commencing 4-5 days after anterior myocardial infarction, 11 dogs with LSGX and 14 sham controls were administered digoxin (0.0125 mg/kg/day i.v.) for 5-7 consecutive days. At baseline testing, programmed ventricular stimulation failed to initiate ventricular tachycardia in any postinfarction dog entered into this evaluation. After treatment, 11/11 digoxin + LSGX (1.33 +/- 0.10 ng/ml serum digoxin) and 14/14 digoxin-treated sham (1.23 +/- 0.14 ng/ml serum digoxin) dogs remained nonresponsive to programmed stimulation testing. The incidence of arrhythmic mortality in response to subsequent ischemia at a site remote from the infarcted anterior region was greater in the digoxin-treated sham group (1.22 +/- 0.21 ng/ml serum digoxin) than in the digoxin + LSGX group (1.33 +/- 0.10 ng/ml serum digoxin); mortality was 6/10 (60%) digoxin sham vs. 1/10 (10%) digoxin + LSGX, p less than 0.005. The underlying anterior myocardial infarct sizes (% of left ventricle: 6.8 +/- 2.3 vs. 6.6 +/- 1.1) did not differ between the digoxin sham and digoxin + LSGX groups. However, the digoxin sham controls developed larger posterolateral myocardial infarctions than did the digoxin + LSGX animals (% of left ventricle: 27.4 +/- 3.0 vs. 16.7 +/- 2.7, p less than 0.05). Norepinephrine concentrations in posterolateral through posteroseptal ventricular sections were not altered by LSGX in a separate group of digoxin-treated postinfarct dogs. The results suggest that left stellate ganglionectomy may reduce the incidence of digitalis-mediated malignant ventricular arrhythmias during ischemia, possibly due to a reduction in the severity of ischemic injury.
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PMID:Antiarrhythmic actions of left stellectomy in digitalis-mediated malignant ventricular arrhythmias in the postinfarcted canine heart. 245 51

The aim of this study was to examine the electrophysiological effects of isoprenaline, phenylephrine, and noradrenaline on sheep Purkinje fibers in vitro, superfused either with a normal or with a modified physiological salt solution (PSS) designed to mimic some of the conditions occurring during mild myocardial ischemia (hyperkalemia, hypoxia, and acidosis). Intracellular microelectrode recording techniques were used to record resting and action potentials. Noradrenaline (10(-7) to 10(-5) M) and phenylephrine (10(-7) to 10(-5) M) prolonged the action potential of normal fibers in a concentration-dependent manner, the effect of phenylephrine being greater than that of noradrenaline. The only effect of isoprenaline (10(-7) to 10(-5) M) was a slight hyperpolarization. The modified PSS caused marked reductions in resting membrane potential, upstroke, and duration of the action potential. On these depressed fibers isoprenaline, noradrenaline, and phenylephrine all prolonged the action potential, and in the case of noradrenaline the duration of the abbreviated action potential was restored beyond control. This effect of noradrenaline and isoprenaline was more marked under ischemic than normal conditions, whereas the opposite was true of phenylephrine. In the presence of effective alpha- or beta-adrenoceptor blockade, the noradrenaline-induced prolongation of the "ischemia"-abbreviated action potential was attenuated. In some of the preparations exposed to simulated ischemia, noradrenaline caused inexcitability. In conclusion, isoprenaline, phenylephrine, and noradrenaline exhibited different electrophysiological effects on mildly "ischemic" sheep Purkinje fibers compared to their effects on normal fibers.
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PMID:Cardiac electrophysiological effects of isoprenaline, phenylephrine, and noradrenaline on normal and mildly "ischaemic" sheep Purkinje fibers. 246 60


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