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

Myoglobin is the oxygen-binding protein characteristic of skeletal and cardiac muscle. With muscle disease or dysfunction, myoglobin may enter the circulation, and after renal clearance, it may also appear in the urine. Therefore, the presence of myoglobinemia and myoglobinuria may serve as indicators of the presence and severity of muscle disease. With newly developed methods of detection, myoglobinemia and myoglobinuria are now recognized as complications of trauma, ischemia, surgery, states of exertion and stress, metabolic abnormalities, inherited enzyme disorders, toxin and drug actions, and inflammatory states. Infarction of the heart muscle also can be detected by myoglobin assay. Persistent myoglobinuric states may be complicated by renal failure and electrolyte imbalance. The diagnosis of myoglobinemia and myoglobinuria can be now confirmed with the use of immunoassay techniques. Although not yet widely available, they offer the possibility of the specificity and sensitivity needed for clinical use.
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PMID:Myoglobin: methods and diagnostic uses. 40 72

Anoxic perfusion prior to sustained ischemia (anoxic preperfusion), reportedly improves postischemic functional recovery of the heart, but its mechanism has not been well understood. The present study aimed to characterize the cardioprotective effects of anoxic preperfusion and its relationship to extracellular Ca++ levels. Following 10 min of aerobic perfusion, isolated rat hearts were assigned to a 10 min aerobic perfusion or to a 10 min anoxic perfusion. The hearts were then subjected to 30 min of global ischemia and 30 min of aerobic reperfusion. When the perfusate-free Ca++ concentration was 2.0 mM, postischemic recovery of left ventricular developed pressure was significantly improved by anoxic preperfusion (91.9 +/- 2.9% of baseline value vs. 50.5 +/- 12.9% after 30 min reperfusion in the controls). However, the improvement of postischemic ventricular function by anoxic preperfusion was abolished when perfusate Ca++ was reduced to 1.0 mM and the contractile function was rather suppressed during early reperfusion by anoxic preperfusion when the Ca++ level was 0.7 mM (87.5 +/- 11.8% vs. 115.6 +/- 13.9% after 10 min of reperfusion). On the other hand, lactate accumulation during the global ischemia was significantly less in anoxic preperfused hearts compared with untreated hearts both when perfusate Ca++ was 0.7 mM (61.3 +/- 5.1 vs. 85.9 +/- 6.8 mumol/g dry) and when it was 2.0 mM (43.8 +/- 2.0 vs. 140.3 +/- 14.1 mumol/g dry). The amount of myoglobin released after global ischemia was not different between untreated and anoxic preperfused hearts regardless of the perfusate Ca++ level. The results suggest that anoxic preperfusion does not reduce ischemic myocardial necrosis, but it attenuates myocardial stunning. That effect of anoxic preperfusion on the stunning is dependent on the extracellular Ca++ level and is not totally explained by suppression of ischemia-induced lactate accumulation.
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PMID:Effect of anoxic preperfusion on ischemic myocardial injury in isolated rat hearts. 128 98

The stability properties of the iron(II)-dioxygen bond in myoglobin and hemoglobin are of particular importance, because both proteins are oxidized easily to the ferric met-form, which cannot be oxygenated and is therefore physiologically inactive. In this paper, we have formulated all the possible pathways leading to the oxidation of myoglobin to metmyoglobin with each required rate constant in 0.1 M buffer (pH 7.0) at 25 degrees C, and have set up six rate equations for the elementary processes going on in a simultaneous way. By using the Runge-Kutta method to solve these differential equations, the concentration progress curves were then displayed for all the reactive species involved. In this complex reaction, the primary event was the autoxidation of MbO2 to metMb with generation of the superoxide anion, this anion being converted immediately and almost completely into H2O2 by the spontaneous dismutation. Under air-saturated conditions (PO2 = 150 Torr), the H2O2 produced was decomposed mostly by the metMb resulting from the autoxidation of MbO2. At lower pressures of O2, however, H2O2 can act as the most potent oxidant of the deoxyMb, which increases with decreasing O2 pressures, so that there appeared a well defined maximum rate in the formation of metMb at approximately 5 Torr of oxygen. Such examinations with the aid of a computer provide us, for the first time, with a full picture of the oxidation reaction of myoglobin as a function of oxygen pressures. These results also seem to be of primary importance from a point of view of clinical biochemistry of the oxygen supply, as well as of pathophysiology of ischemia, in red muscles such as cardiac and skeletal muscle tissues.
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PMID:Hydrogen peroxide plays a key role in the oxidation reaction of myoglobin by molecular oxygen. A computer simulation. 142 Aug 96

Several studies indicate the presence of hydroxyl radical (OH.) as well as its involvement in the myocardial reperfusion injury. A transition metal-like iron is necessary for the conversion of superoxide anion (O2-) to a highly reactive and cytotoxic hydroxyl radical (OH.). In the present study, we have examined the generation of OH. and free iron in reperfused hearts following either normothermic (37 degrees C) or hypothermic ischemia (5 degrees C). Employing the Langendorff technique, isolated rat hearts were subjected to global ischemia for 30 min at 37 degrees C or 5 degrees C and were then reperfused for 15 min at 37 degrees C. The results of the study suggest that both the OH. generation in myocardium and free iron release into perfusate were significantly lower in hearts made ischemic at 5 degrees C as compared to 37 degrees C. Release of myoglobin and lactic acid dehydrogenase into perfusate also followed a similar pattern. Furthermore, in in vitro studies, chemically generated O2- at 5 degrees C caused a significantly lower rate of oxidation of oxymyoglobin as well as generation of OH. and free iron as compared to 37 degrees C. These results suggest that (1) reperfusion of hypothermic ischemic heart is associated with a reduction in the generation of OH. and cellular damage compared to that of normothermic ischemic heart, and (2) myoglobin, an intracellular protein, is a source of free iron and plays a role in the reperfusion injury mediated by free radicals.
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PMID:Reduced free radical generation during reperfusion of hypothermically arrested hearts. 158 48

The paper discusses if it is advisable to use kallikrein-kinin system inhibitors earlier. A total of 122 patients with acute ischemia and infarction of the myocardium were studied. Contrykal and heparin infused in the prehospital period, followed by hospital treatment are optimal to prevent vascular wall lesions, maximally retain retrograde blood flow, and substantially reduce the size of myocardial infarction. Therapy with protease inhibitors proved to be most beneficial within the first 2 hours of the disease, as evidenced by a profound improvement in the clinical course of myocardial infarction, a decrease in ECG and precordial mapping signs of ischemia, a positive change in myoglobin and MB creatine phosphokinase levels, and a significant reduction in the rehabilitative period.
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PMID:[Rationale for using kinin system inhibitors in patients with acute ischemia and infarction of the myocardium during the prehospital phase]. 171 6

There have been recent reports of rhabdomyolysis associated with cocaine abuse. The pathologic findings from these cases have not been described. Pathologic abnormalities in two fatalities with cocaine-associated rhabdomyolysis, including one with hyperpyrexia, acute renal failure, and disseminated intravascular coagulation, are discussed in detail. Skeletal muscle in both cases showed necrosis without evidence of vasculitis, polarizable foreign crystals, or other specific lesions. The individual with renal failure showed acute tubular necrosis with granular myoglobin casts in tubules. The mechanism of cocaine-associated rhabdomyolysis is unclear, but potentially includes ischemia due to vasoconstriction, direct toxicity, hyperpyrexia, and increased muscle activity from agitation or seizure. Adulterants may also play a role. In unexplained cases of rhabdomyolysis, toxicologic evidence of cocaine should be sought. In those cases of rhabdomyolysis associated with acute renal failure, the presence of cocaine in blood may be prolonged because of impaired renal clearance.
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PMID:Rhabdomyolysis associated with cocaine abuse. 174 98

It is generally thought that the oxidative modification of hemoproteins leads to their inactivation. In the current study, however, a transiently activated form of myoglobin was shown to be formed when the prosthetic heme group became covalently bound to the polypeptide during the reaction of myoglobin with low levels of HOOH. In the presence of an enzymatic metmyoglobin reducing system containing diaphorase and methylene blue with excess NADH, this HOOH-altered myoglobin catalyzed NADH oxidation and oxygen consumption; the overall stoichiometry indicated a two-electron reduction of oxygen to HOOH. This reaction was not catalyzed by iron released from heme, as desferrioxamine had no effect on the activity. Stoichiometric amounts of HOOH were sufficient to produce the activated oxidase state of myoglobin, whereas larger amounts of HOOH lead to heme destruction, iron release, and inactivation of the oxidase activity. The alteration of myoglobin to an enzyme that can form toxic oxygen metabolites may have pathological importance, especially in myocardial injury caused by ischemia and reperfusion, where myoglobin is present in large amounts and HOOH is formed. Furthermore, the oxidase form may be involved in the mechanism of destruction of the heme seen with oxidative treatment of myoglobin.
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PMID:Oxidative modification by low levels of HOOH can transform myoglobin to an oxidase. 187 Nov 23

The relationship between myocardial cell contracture and injury during total metabolic inhibition (amylobarbital and iodoacetic acid) and ischemia was examined, using 5-50 mM butanedione monoxime (BDM) as an inhibitor of contracture. BDM had no apparent effect on control myocytes during 180 min incubations, but inhibited contracture following anoxia or ischemia in a dose-dependent fashion, as directly quantitated by length/width ratios. Cellular ATP levels decreased at a similar rate in the absence or presence of BDM, following metabolic inhibition. BDM-mediated inhibition of contracture was associated with accelerated cell injury, as defined by: the uptake of an extracellular marker (trypan blue) by the cardiomyocytes, by direct analysis of myoglobin released into the supernatant and by ultrastructural demonstration of defects in sarcolemmal membrane integrity. Calcium was not required for BDM's enhancement of injury, in that cells incubated in calcium free-EGTA buffer showed a similar BDM-mediated acceleration of injury. In the presence or absence of calcium, enhancement of injury was more marked in cells osmotically stressed with a brief incubation in hypotonic buffer, than in cells resuspended in isotonic media. It is concluded that BDM enhances development of osmotic fragility of inhibited or ischemic cardiomyocytes and that contracture is not a necessary contributing factor to myocardial cell death.
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PMID:Effects of 2,3-butanedione monoxime (BDM) on contracture and injury of isolated rat myocytes following metabolic inhibition and ischemia. 194 93

To assess the effects of fasting on recovery of function and exogenous glucose metabolism after 15 minutes of total ischemia, we perfused isolated working rat hearts from fed and fasted animals. Hearts were perfused in a recirculating system with bicarbonate buffer containing glucose (10 mM). Mechanical performance, release of marker proteins for ischemic membrane damage (lactate dehydrogenase, myoglobin, citrate synthase), and the concentrations of lactate and glucose in the perfusion medium were measured serially. Tissue metabolites were also measured. Fasting raised the myocardial glycogen content by 25%. Cardiac performance of perfused hearts from fed and fasted animals was the same during the preischemic and the post-ischemic period. The time of return of function to preischemic values was significantly less in hearts from fasted rats (2.3 versus 7.8 minutes, p less than 0.025). The release of cytosolic and mitochondrial marker proteins was significantly lower in hearts from fasted rats than in hearts from fed rats. Glucose metabolic rates during control and reperfusion were unchanged for hearts from fasted rats, but decreased for hearts from fed rats during reperfusion. The adenine nucleotide content at the end of ischemia was higher in hearts from fasted animals than in hearts from fed animals. We conclude that increasing glycogen levels prior to ischemia improves recovery of function, lessens membrane damage, and prevents loss of adenine nucleotides.
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PMID:Fasting in vivo delays myocardial cell damage after brief periods of ischemia in the isolated working rat heart. 200 7

Postoperative changes in serum myoglobin levels have been studied in 47 patients undergoing open heart surgery. The patients were retrospectively divided into two groups according to the time to peak myoglobin level during reperfusion. In 38 patients, myoglobin levels increased rapidly to a peak within 3 hours after reperfusion, after which it was cleared from the blood (group 1). Contrarily, a rise in myoglobin levels was persistent for 24 hours and its time to peak was greater than 3 hours after reperfusion in nine patients (group 2). There were no differences in preoperative and early reperfusion (within 1 hour of reperfusion) values of myoglobin between the two groups. At 3, 6, and 12 hours of reperfusion, myoglobin levels were significantly greater in group 2: 448 +/- 196 vs 1,149 +/- 900 ng/ml, 359 +/- 172 vs 2,653 +/- 3,179 ng/ml, 184 +/- 95 vs 1,896 +/- 1,387 ng/ml, respectively, p less than 0.0001 in each. The maximum activities of both myoglobin and CK-MB were significantly higher in group 2 (myoglobin-max: 771 +/- 257 vs 3,221 +/- 3,024 ng/ml, p less than 0.0001; CK-MBmax: 107 +/- 60 vs 227 +/- 219 IU/L, p less than 0.005). Five of nine patients in group 2 required post-operative assistance with intra-aortic balloon pumping (p less than 0.0005 compared with one of 38 in group 1) and perioperative myocardial infarction developed in three patients (33.3 percent) in this group (p less than 0.005 compared with 0 percent in group 1). Thus, patients with a delayed peak of serum myoglobin level exhibited detrimental cardiac failure postoperatively. These findings suggest that myocardial injury accelerated by reperfusion following ischemia might progress in these patients.
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PMID:Delayed time to peak serum myoglobin level as an indicator of cardiac dysfunction following open heart surgery. 203 22


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