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

After establishing a model of ischemia, perfusion in the ischemic area was considerably disturbed. Examination by means of 133xenon-clearance after intramyocardiac injection showed strongly delayed flowing-off compared with controls. Counterpulsation accelerates the flowing-off (perfusion). Untreated control animals reveal after inducing the model ischemia a crucial decrease of ATP concentration and an excessive increase of lactate concentration in the ischemic area. Counterpulsation may inhibit further decrease of ATP in the ischemic area.
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PMID:[Assisted circulation. The effect of cardio-synchronous peripheral arterio-arterial counterpulsation on perfusion and metabolism in the area of acute transmural myocardial ischemia]. 105 76

A new experimental model for the study of two important aspects of ischemia, namely, oxygen and substrate deprivation, is proposed: the intact, beating fetal mouse heart in organ culture. This model offers long-term stability, ease and reproducibility of preparation, and the ability to manipulate experimental conditions. Hearts deprived of oxygen and glucose ceased beating immediately. After 3-4 hr of deprivation, biochemical and ultrastructural changes consistent with ischemic injury were evident. These include depletion of ATP and glycogen levels, loss of cytoplasmic enzymes, and extensive swelling and disruption of mitochondrial structure. Glucose and insulin partially protected against ATP depletion. Upon resupply of oxygen and glucose , beating resumed immediately, ATP levels rapidly increased to control levels and, consistent with this, mitochondrial structure returned toward normal. During the recovery phase autophagic vacuoles containing damaged mitochondria and myofibrils were seen, indicating that repair mechanisms were activated. Consistent with this, the proportion of lysosomal enzymes that were present in the nonsedimentable fraction of the tissue homogenate increased. We conclude that the cultured fetal mouse heart is a model useful for studying myocardial responses to anoxia and/or substrate deprivation and for assessing interventions designed to limit damage or to stimulate repair after ischemic injury.
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PMID:Fetal mouse hearts: a model for studying ischemia. 105 96

The tolerance of ischemia in normal and less perfused myocard during an ischemic and cardioplegic heart standstill was investigated. A decrease of ATP and ADP and an increase of the lactate, pyruvate and AMP was established during an ischemia of 20 minutes. The less perfused hearts gave considerably worse results regarding the energy transformation than normal hearts. In less perfused hearts the energy reserve of myocardial metabolism showed a considerably better behaviour during a cardioplegic heart standstill of 45 minutes than an ischemic one of 20 minutes. During the recuperation period this trend was emphasised.
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PMID:[The effect of ischemic and cardioplegic heart standstill on the myocard metabolism in normal and less perfused heart (author's transl)]. 108 Jun 11

An in situ working swine heart preparation is described in which total coronary perfusion was controlled. At normal rates of coronary flow, oxygen, glucose, and fatty acid utilization were stable for at least a 60-min perfusion period. With a 50% reduction in coronary flow, oxygen and glucose consumption were reduced during 30 min of perfusion and fatty acid extraction was lower at the end of 30 min. Glycogen utilization was increased, but tissue levels of creatine phosphate, ATP, and lactate were similar to those in hearts receiving normal flow. With a 60% reduction in coronary flow, uptake of oxygen, glucose, and fatty acids were further decreased. Tissue levels of high-energy phosphates and glycogen were decreased and ADP, AMP, and lactate increased. Mechanical performance progressively deteriorated in these hearts, and ventricular fibrillation developed after about 20 min (19.8 plus or minus 3.0 min). The data indicate that this preparation is suitable for the study of myocardial metabolism during mild and severe ischemia and may be useful for the evaluation of pharmacological interventions designed for the treatment of myocardial ischemia.
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PMID:Metabolic responses to varying restrictions of coronary blood flow in swine. 111 86

The extent of cellular metabolic deterioration and its reversibility was studied on human skeletal muscle needle biopsies during operations in bloodless field. The tissue levels of high energy phosphates and glycolytic metabolites were analyzed after various times of tourniquet ischemia and compared to contralateral control extremity levels. In the ischemic extremity the phosphocreatine (CrP) levels decreased by 40% within 30-60 min and after 60-90 min a 60% reduction was found. No significant ATP changes occurred. Lactate levels increased by 225% after 30-60 min and by 300% after 60-90 min. The glucose and G-6-P levels increased slightly and indicated glycogenolysis. The rate of the metabolic changes decreased with ischemia time. In the control leg no significant metabolic changes could be seen. After the release of the tourniquet there was a rapid restoration of the phosphagen content and clearance of lactate in the ischemic leg. Near control levels of these substances were seen already after 5 min. The present results show that clinical tourniquet ischemia of up to 90 min duration produces less pronounced metabolic alterations than those seen in working muscle.
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PMID:Human skeletal muscle energy metabolism during and after complete tourniquet ischemia. 114 14

Adult rhesus monkeys were subjected to complete cerebral ischemia for one hour and subsequent recirculation for up to 24 h. Animals with signs of functional recovery (e.g. spontaneous EEG activity) exhibited a partial replenishment of cellular energy sources (ATP, phosphocreatine) and a progressive normalization of cerebral lactate levels. Glucose and pyruvate concentrations showed a transient increase over control values during the early stages of postischemic recirculation. Monkeys without functional recovery lacked a significant resynthesis of energy-rich compounds; adenine nucleotides continued to decrease and lactate concentrations were higher than in animals subjected to ischemia without recirculation. Cerebral polysome profiles remained unaltered during the ischemic period but in all animals a marked disaggregation of polyribosomes with a concomitant increase in ribosomal subunits occurred after the onset of recirculation. In monkeys with indications of functional recovery these changes were reversible but a normal polysome profile was only observed after 24 h of recirculation. The results obtained indicate a postischemic depression of protein synthesis due to an inhibition of peptide chain initiation. After recirculation of the brain for 3-6 h there was evidence for an induction of enzymes involved in polyamine synthesis (ornithine decarboxylase and S-adenosylmethionine decarboxylase). No changes in the activity of these enzymes were observed at the end of the ischemic period, indicating that during complete cerebral ischemia not only the synthesis but also the catabolism of proteins is inhibited.
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PMID:Resuscitation of the monkey brain after one hour complete ischemia. III. Indications of metabolic recovery. 115 69

The capacity for recovery of the normothermic left ventricular myocardium from a regional complete ischemia (RCI) was investigated using changes in the myocardial metabolic status (ATP, ADP, AMP, creatine phosphate (CrP), free creatine, glycogen, glucose, lactate) and alterations of the morphology as parameters. In dogs, an area of the anterior wall of the left ventricular myocardium was temporarily deprived completely of its blood supply by 5--7 overlapping ligatures extending into the heart cavity. The metabolites of the adenylic acid-CrP system returned to normal tissue levels after 30 and 60 min of RCI within 14 and 35 days of recovery, respectively; restoration averaged 82% after 100 min, 74% after 140 min, and 38% after 180 min of RCI after 5 weeks of recovery. At the same time glycogen amounted to 163% after 100 min, 114% min, and 65% after 180 min of RCI. The biochemical data correlated well with the structural changes in the affected myocardium, especially with the amount of de- and regenerating heart muscle cells. These obviously were functionally defect and were not comparable with normal structured and functioning heart muscle cells.
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PMID:Metabolic and structural recovery of left ventricular canine myocardium from regional complete ischemia. 115 19

The cortical evoked potential of the two cerebral hemispheres of the cat is taken as the parameter of brain function; its course is studied during strangulation which determines its disappearance, and especially during strangulation release (recovery phase). Under these experimental conditions, the injection of 9% NaCl solution in each carotid does not modify the symmetry of recovery in the two cerebral hemispheres. The unilateral injection of increasing doses of 1,6-dimethyl-8beta-(5-bromonicotinoyl-oxymethyl)-10alpha-methoxyergoline tartrate (nicergoline) (20 to 400 mug) produces more rapid recovery on the treated side. This is also the case for the unilateral injection of 40 mg of sodium malonate. Observation of this effect in the hypoventilated, hypercapnic animal, with an already dilated cerebral network suggests that the mechanism of the protection afforded is not due to vasodilatation of the cerebral network produced by either of the two products. The effect of nicergoline disappears when a previous i.v. injection of sodium malonate has inhibited anoxic depolarization of the cellular membrane and inhibited the fall in cerebral ATP caused by ischemia. It would thus appear that the anti-ischemic properties of nicergoline, acting at the level of the central nervous system, are due to an effect on the cellular membrane or to an inhibiting effect on the metabolism of the brain cell. Supplementary experiments, involving the use of more specific pharmacological reagents should allow its action to be localized at the level of the membrane and/or of cellular metabolism.
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PMID:Study of the protection on afforded by nicergoline against the effects of cerebral ischemia in the cat. 117 43

The metabolic states of various tissues of newborn rabbits were studied before and after periods of ischemia of 5-40 min. The contents of substances of the energy distributing adenylic acid-creatine phosphate system as well as glycogen, glucose and lactate were determined and the results are discussed in comparison with the well-known values from ischemic tissues of adult rabbits. The preservation of high energy phosphates as well as the rate of glycolytic energy production during the course of ischemia was quite identical in the myocardium of newborns and adults in contrast to the different ability of newborn and adult rabbits to maintain circulation in anaerobic conditions. In the central nervous system the ATP contents decreased to very low levels within a few minutes in both groups although the glycolytic energy production was rather different. But the larger amounts of adenine nucleotides present in the newborns at any time of ischemia indicate a better chance of postischemic recovery. In the livers and the kidneys of the newborns higher rates of glycolytic energy production led to better preservation of the energy-rich substances while in skeletal muscle and the lung only slight differences occurred between newborns and adults.
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PMID:Metabolic patterns in several tissues of newborn rabbits during ischemia. 118 44

In 17 patients who underwent openheart surgery with cardiopulmonary bypass using heparinized fresh blood for priming the heart-lung machine the following investigations were done: Blood samples taken at different periods of surgery were assayed for total calcium (Catot), ionized calcium (Ca++), magnesium (Mg), hemoglobin, total pasma proteins, and the acid-base-status. Considering the different kinds of cardiopulmonary bypass the patients were divided into three groups: In the first group the results ofsurgical procedure with and without hemodilution perfusion were compared. During hemodilution perfusion Catot decreased markedly whereas Ca++ remained nearly constant. In the second group the influence of different calcium concentrations of the prime solution on Catot and Ca was tested. A low calcium content of 2.8 mEq/1 lowered Catot and Ca++ to subnormal levels. In the third group results of Mg-induced cardioplegia were compared with findings during surgical procedure with anoxic cardiac arrest. A remarkable increase of magnesium at the perfusion onset could be observed. Magnesium remained within the upper level of normal range until surgery end and decreased to normal values in the postoperative stage. Since energy requirements of the arrested heart and thus the velocity of ATP-breakdown during ischemia are closely related to the Ca++ concentration of the extracellular space low plasma calcium levels are considered to be advantageous during cardiopulmonary bypass. Only at the end of partial bypass before the heart fully takes over circulating work a sufficient calcium substitution is recommended.
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PMID:Divalent ions and myocardial function during cardiopulmonary by-pass (CPB). Changes of total calcium, ionized calcium, and magnesium in plasma. 119 32


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