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Biomedical subjects

D A Mickle

Publications and source records attributed to D A Mickle.

At least 91 records · Page 5Linked to original sources
PubMed1990

Subcellular distribution of peroxidized lipids in myocardial reperfusion injury.

Previous studies in our laboratory have demonstrated the peroxidation of myocardial phospholipid in a canine model of reversible global normothermic ischemia and reperfusion while on cardiopulmonary bypass. The present study examines the distribution of phospholipid peroxidation products in three major cellular organelle fractions of myocardium prepared by established centrifugal fractionation procedures (sarcolemma, sarcoplasmic reticulum, and mitochondria). These organelles were isolated from control (nonischemic) and ischemic-reperfused myocardium harvested during early reperfusion (5 min), when previous studies indicated maximal peroxidative injury in whole myocardial biopsies. Utilizing a more rapid analytic procedure for measuring phospholipid containing the conjugated diene chromophore in the polyunsaturated fatty acyl substituents, we were able to establish the fidelity of this procedure by comparing the results obtained with it to the previous more laborious analytic procedure (involving phospholipid hydrolysis with phospholipase A2 and subsequent derivatization for high-pressure liquid chromatography followed by gas chromatographic-mass spectrometric analysis). Analysis of phospholipid extracts from organelle fractions for evidence of peroxidative conjugated diene formation revealed that sarcolemmal membranes had the highest content of oxidized phospholipid containing the conjugated diene chromophore (mean 2.2 +/- 1.2 nmol phospholipid-conjugated diene/mumol phospholipid phosphorus, P less than 0.02 compared with control). Both sarcoplasmic reticulum and mitochondrial membranes were also peroxidized but to a much smaller extent (mean 0.4 +/- 0.2 and 0.3 +/- 0.25 nmol phospholipid conjugated diene/mumol phospholipid phosphorus).

Animals↗
PubMed1990

Right ventricular function and metabolism.

Right ventricular protection may be limited with current methods of cardioplegic delivery. Sensitive measurements of right and left ventricular function and metabolism were made in 30 patients undergoing elective coronary artery bypass surgery with cold cardioplegic arrest. Myocardial adenine nucleotide concentrations decreased with cardioplegia and reperfusion in both the right and left ventricles despite adequate levels of precursors, suggesting perioperative mitochondrial dysfunction. Postoperatively, right and left ventricular pressures were measured with micromanometer catheters and volumes were measured by nuclear ventriculography. Right and left ventricular systolic elastance was calculated by the isochronic method and by the end-systolic method. Both methods provided sensitive indexes of end-systolic elastance. This study demonstrated that right ventricular function and metabolism can be evaluated by methods analogous to methods used in the left ventricle. These results suggest that right ventricular functional and metabolic recovery are delayed despite apparently adequate myocardial protection. Sensitive measurements may permit improved assessment of alternative methods of right ventricular protection.

Adenine Nucleotides↗
PubMed1990

Calcium paradox in an in vivo model of multidose cardioplegia and moderate hypothermia. Prevention with diltiazem or trace calcium levels.

The production and prevention of calcium paradox injury in myocardium was studied in a canine model of cardiopulmonary bypass with multidose, moderately hypothermic, crystalloid cardioplegic solution. During 4 1/2 hours of global ischemia, three groups of six dogs each received one of three histidine-buffered cardioplegic solutions (500 ml initially and 250 ml every 30 minutes) at 27 degrees C. Group 1 cardioplegic solution was calcium free, group 2 solution contained a trace amount of calcium chloride (70 mumols /L), and group 3 cardioplegic solution was calcium free but contained diltiazem (150 micrograms/kg body weight). Left ventricular function measured as percent control of developed pressure revealed significantly greater (p less than 0.05) recovery in groups 2 and 3. Triphenyltetrazolium chloride staining showed 35% +/- 9% (mean +/- standard error) of heart mass necrosis in group 1 versus 0% and 0.5% +/- 0.4% in groups 2 and 3, respectively (p less than 0.001). Electron microscopy revealed ultrastructural changes characteristic of calcium paradox injury in group 1 myocardium. Calcium paradox injury was produced in an in vivo model of global myocardial ischemia and multidose cardioplegia despite moderate hypothermia and non-coronary collateral flow. The addition of either trace levels of calcium or diltiazem to the cardioplegic solution was effective in preventing this injury.

Animals↗
PubMed1989

The quantitation of human ventricular myosin light chain 1 in serum after myocardial necrosis and infarction.

To determine the clinical utility of human ventricular myosin light chain 1 (HVLC1) in the diagnosis of myocardial necrosis, we established a radioimmunoassay for serum HVLC1 using polyclonal antibodies raised against the purified human protein. HVLC1 levels were measured in sera from 110 control patients and 38 patients immediately after cardiovascular surgery and in serial specimens from 10 patients with uncomplicated myocardial infarctions. The HVLC1 assay was found to be equal in sensitivity for the first 48 hours to the CK-MB for myocardial necrosis after cardiovascular surgery and for myocardial infarction. In virtually all myocardial infarct patients, HVLC1 levels in sera rose within hours of the onset of chest pain. From thereon, two sub-trends were discerned. For many, the HVLC1 levels remain elevated for 9-12 days beyond. In some, the HVLC1 levels returned to normal levels 1-2 days after the initial rise, but became elevated again for the next 5-9 days. In either instance, the diagnosis of myocardial infarction was permitted as late as 10-12 days after the onset of chest pain which is in stark contrast to all conventionally used biochemical markers.

Antibodies↗
PubMed1989

Myocardial salvage with trolox and ascorbic acid for an acute evolving infarction.

Both Trolox (a water-soluble analogue of alpha-tocopherol) and ascorbic acid were more effective than superoxide dismutase or catalase in protecting myocyte cell cultures from free radical attack (induced by hypoxanthine and xanthine oxidase). In a canine model of two hours of left anterior descending coronary artery occlusion followed by four hours of reperfusion, Trolox and ascorbic acid reduced the area of infarction within the area at risk. The Trolox group received 500 mL of deoxygenated saline solution containing 2.0 g of Trolox, 3.0 g of ascorbic acid, and 18 mg of EDTA (ethylenediaminetetraacetic acid) infused into the ascending aorta 30 seconds before and four minutes after reperfusion. Saline controls received 500 mL of deoxygenated saline solution containing 18 mg of EDTA. The angioplasty group had unmodified reperfusion by simple release of the occlusion. The area at risk and the area infarcted were estimated with Evans blue and triphenyl tetrazolium hydrochloride stains, respectively. The ratio of the area infarcted to the area at risk was significantly lower with Trolox (angioplasty, 30.4% +/- 5.1%; saline, 20.8% +/- 2.9%; and Trolox, 8.7% +/- 4.0%; p less than 0.01). In summary, the antioxidants Trolox and ascorbic acid effectively reduced myocardial necrosis after ischemia.

Animals↗
PubMed1989

Effect of oxygen tension on the anti-oxidant enzyme activities of tetralogy of Fallot ventricular myocytes.

Since the chronically cyanotic tetralogy of Fallot (TOF) myocardium is more sensitive to reperfusion injury after cardiac surgery than the adult myocardium, we decided to study the regulation of myocardial superoxide dismutase (SOD), catalase and glutathione peroxidase by oxygen tension. TOF myocytes were cultured at a Po2 of 150 mmHg for 30 days to establish the culture. The cells were then cultured at Po2 of 150 and 40 mmHg and the myocyte antioxidant enzymes measured at days 3, 7, 14 and 21. On day 21 the myocytes cultured at Po2 of 40 mmHg were then cultured at 150 mmHg and SOD and catalase activities measured on days 28 and 35. Although there were no differences in the rates of incorporation of 35S-methionine into the myocytes at either Po2 on these days, the myocytes scavenger enzyme levels were significantly higher by day 14 when cultured at a Po2 of 150 mmHg than at a Po2 of 40 mmHg. With the increase in oxygen tension from 40 to 150 mmHg, SOD and catalase activities increased significantly by day 35. The myocytes cultured at Po2 40 mmHg were more sensitive by day 7 to an hypoxanthine-xanthine oxidase generated free radical injury than the Po2 150 mmHg cultured cells. The regulation of these enzyme activities by oxygen tension and the increased sensitivity to free radical injury of the myocytes cultured at an oxygen tension of 40 mmHg provide putative evidence that the chronically cyanotic myocardium may be less well protected than the normally perfused myocardium against oxygen-mediated free radical injury and be at higher risk for cardiovascular surgery.

Catalase↗
PubMed1989

Maturational difference in functional/metabolic sequelae of free radical formation on reperfusion.

To detect maturational differences with ischemia/reperfusion injury on cardiac metabolism and function, isolated nonworking rabbit hearts were subjected to 30 min of 37 degrees C ischemic arrest and reperfusion. Pre- and postischemic high energy phosphate contents (ATP, ADP, AMP), conjugated diene (products of free radical mediated lipid peroxidation) production, and peak isovolumic developed pressure (PDP) were measured in newborn (3-5 days, n = 8), 2- to 3-week-old (n = 8), and adult (2-4 months, n = 8) rabbits. ATP content decreased significantly during ischemia in all three age groups but recovered significantly toward preischemic levels in the newborn and 2-week-old groups but not in adult animals. AMP was much better preserved in the two younger groups with significantly higher levels at end-ischemia. Conjugated dienes were present in newborn and adult heart in small amounts at preischemia and rose slightly by end-ischemia. Newborn hearts accumulated large amounts of dienes by 10 min of reperfusion, which were significantly greater than those adult hearts. PDP returned to 85 and 91% of control in newborn and 2-week-old hearts, respectively, and to only 66% of control in adult hearts (P less than 0.05). These data suggest that the postischemic immature heart recovers energy stores and ventricular function faster than the adult heart which can be attributed to preservation of the total adenine nucleotide pool during ischemia. This improved recovery occurs despite a greater amount of free radical-mediated lipid peroxidation with reperfusion in newborn hearts.

Adenine Nucleotides↗
PubMed1989

Asanguineous reperfusion in a canine model of cardiopulmonary bypass and controlled postischemic work.

This study was designed to test the hypothesis that asanguineous reperfusion with a standard crystalloid cardioplegic solution results in improved myocardial salvage after a period of global ischemia. Four groups of 6 dogs each were placed on cardiopulmonary bypass. Control group A (work only) performed two hours of controlled work by contracting against a saline-filled left intraventricular balloon. Control group B (ischemia only) underwent 45 minutes of global normothermic ischemia before simple blood reperfusion while supported on bypass. Groups C and D were subjected to ischemia and reperfusion as in group B, followed by controlled work stress as in group A. Group D, however, received 500 mL of St. Thomas' Hospital solution immediately before blood reperfusion. Morphological analysis showed no significant injury in groups A and B, whereas group C had 11.4% +/- 2.4% necrosis of heart mass versus 2.5% +/- 1.1% in group D (p less than 0.001). Biochemical data from left ventricular biopsies showed no significant differences between groups B, C, and D. Functional analyses showed deterioration of diastolic compliance in group C (p less than 0.05), although a significant difference in systolic functional indexes could not be detected. Myocardial protection and salvage was improved by initial reperfusion with an asanguineous cardioplegic solution versus reperfusion with blood alone.

Animals↗
PubMed1989

Delayed myocardial metabolic recovery after blood cardioplegia.

Previous studies have demonstrated that both myocardial metabolism and ventricular function were depressed after blood cardioplegic arrest for elective coronary artery bypass grafting. To evaluate the etiology of this metabolic defect, we measured the levels of adenine nucleotides and their precursors in 29 patients undergoing elective coronary revascularization. Myocardial biopsy specimens were obtained at 37 degrees C before cardioplegic arrest, immediately after 74 +/- 4 minutes of cardioplegic arrest, and after 30 minutes of reperfusion. Biopsy specimens were analyzed for levels of adenine nucleotides and their precursors by high-performance liquid chromatography. Adenosine triphosphate concentrations decreased with cardioplegic arrest and with reperfusion. Adenosine monophosphate concentrations increased after cardioplegic arrest and remained nearly twice the initial values after reperfusion. The ratio of adenosine monophosphate to adenosine triphosphate doubled after reperfusion, suggesting defective conversion of adenosine monophosphate to adenosine triphosphate. Levels of adenine nucleotide degradation products (adenosine, inosine, and hypoxanthine) increased after cardioplegia and decreased with reperfusion, suggesting a washout of soluble precursors. This study suggests that improvements in myocardial protection should attempt to stimulate mitochondrial energy production and preserve adenine nucleotide precursors.

Adenosine Diphosphate↗
PubMed1989

Myocardial free-radical injury after cardioplegia.

Although cold blood cardioplegia provides excellent myocardial protection for elective coronary bypass surgery, myocardial metabolic recovery is delayed postoperatively, perhaps because of free-radical injury during reperfusion. To assess free-radical reperfusion injury, we measured the products of lipid peroxidation and the cardiac concentrations of alpha tocopherol in 10 patients undergoing elective surgical revascularization. Arterial and coronary sinus blood measurements revealed a delayed recovery of myocardial oxygen consumption and lactate utilization and the myocardial release of conjugated dienes (chemical signatures of free-radical injury) at 3 and 60 minutes after reperfusion. In addition, myocardial concentrations of alpha tocopherol decreased after reperfusion, suggesting consumption of the major membrane antioxidant. These results support the hypothesis that oxygen-derived free radicals contribute to myocardial injury after cardioplegic arrest and that antioxidant therapy should improve myocardial protection.

Free Radicals↗
PubMed1988

Effects of anesthetic induction on myocardial function and metabolism: a comparison of fentanyl, sufentanil and alfentanil.

Anaesthetic induction may induce myocardial ischaemia. A prospective randomized trial was instituted to compare the effect on ventricular function and myocardial metabolism of induction with fentanyl (FEN) or its analogues sufentanil (SUF) or alfentanil (ALF) in 96 patients undergoing elective coronary artery bypass grafting (CABG). Haemodynamic, metabolic (coronary sinus oxygen and lactate extraction) and gated ventriculographic measurements were made awake pre-induction (PRE), after induction (IND) and after intubation (INT). Induction was performed with FEN 75 micrograms.kg-1, SUF 15 micrograms.kg-1 or ALF 125 micrograms.kg-1 and metocurine. Fentanyl induction was associated with the greatest stability of mean arterial pressure (MAP), cardiac performance, and systolic function without associated myocardial lactate production. SUF produced the greatest depression of systolic function (p less than 0.05) but without haemodynamic instability or myocardial lactate production in all but one patient. Induction with ALF produced the greatest reduction in MAP (p less than 0.05) associated with the greatest decrease in diastolic compliance (p less than 0.05) and 50 per cent incidence of myocardial lactate production (p less than 0.05) with no significant change in coronary blood flow or myocardial oxygen consumption.

Alfentanil↗
PubMed1988

Decreased postoperative myocardial fatty acid oxidation.

Myocardial substrate preferences following cardioplegic arrest for coronary bypass surgery have not been established. Fatty acids are believed to be the major fuel source for aerobic metabolism. Following cardioplegic arrest arterial fatty acid levels are elevated and myocardial fatty acid accumulation without oxidation may contribute to reperfusion injury. Perioperative fatty acid metabolism was evaluated in 18 patients undergoing elective coronary bypass surgery who were randomized to receive either blood (n = 11) or crystalloid (n = 7) cardioplegia. Palmitate labeled with 14carbon was infused perioperatively and arterial and coronary sinus blood samples were obtained to calculate myocardial fatty acid extraction and oxidation before and after cardioplegic arrest. Lactate and glycerol were released from the heart during both blood and crystalloid cardioplegia, suggesting ischemic glycolysis and lipolysis. Myocardial oxygen consumption was depressed and the myocardial consumptions of lactate, glucose, and fatty acids were minimal during the first 60 min after aortic clamp removal in both groups despite high arterial concentrations. Fatty acid oxidation was minimal after blood cardioplegia and was not found after crystalloid cardioplegia. Fatty acids were extracted by the heart, but were not aerobically metabolized following cardioplegic arrest. Myocardial fatty acid accumulation without oxidation may have been deleterious. The inability of the heart to oxidize exogenous fatty acids may reflect altered myocardial exogenous substrate preferences during reperfusion following coronary bypass surgery.

Cardioplegic Solutions↗
PubMed1988

Measurement of hydroxy-conjugated dienes after ischemia-reperfusion in canine skeletal muscle.

Recent studies have suggested that oxygen-derived free radicals are involved in the reperfusion injury of ischemic skeletal muscle. Although postischemic necrosis and increased vascular permeability have been attenuated with the addition of free radical scavengers, no unequivocal chemical evidence for free radical injury in skeletal muscle is available. The purpose of this study was to identify products of free radical-mediated membrane injury by isolation of lipid oxidation products (hydroxy-conjugated dienes) from postischemic skeletal muscle. The bilateral canine gracilis muscle model was used, and in each pair one muscle was exposed to 3 and the other to 5 h of normothermic ischemia. Muscle biopsies were taken before and at end ischemia, as well as during the first 3 h of reperfusion. Phospholipids were extracted from the muscle biopsies and the fatty acids hydrolyzed from the 2 position. After methylation, the oxidized fatty acid esters were separated by high-performance liquid chromatography. Hydroxy diene peaks absorbing at 235 nm were collected and subjected to gas chromatography-mass spectrometry (GC-MS) for positive structural identification. No significant increase in the level of conjugated dienes occurred during ischemia. Significant increases, however, were detected during the period of reperfusion, although the time when peak levels were achieved varied between animals. The cumulative sum of dienes produced during reperfusion in both 3- and 5-h muscles was significantly increased over pre- and end-ischemic values. The hydroxy-conjugated diene isomers of 18:2 and 20:4 were positively identified in reperfusion biopsies by GC-MS. These studies provide chemical evidence of free radical-mediated lipid oxidation during reperfusion of ischemic skeletal muscle.

Animals↗
PubMed1988

Inadequate myocardial protection with cold cardioplegic arrest during repair of tetralogy of Fallot.

Postoperative low cardiac output is the most common cause of death in patients undergoing elective repair of tetralogy of Fallot. The incidence is much higher than in elective adult bypass operations for coronary artery disease. To explain this difference, we investigated 16 children having elective repair of tetralogy (mean age 6.3 years). Myocardial biopsy specimens obtained during bypass before arrest, at the end of cold arrest by blood cardioplegia, and after 30 minutes of reperfusion were studied for adenosine triphosphate and lactate levels. Myocardium was submitted for microscopic study shortly after the onset of ischemia. The operation was successful in reducing right ventricular-pulmonary artery gradients from 82 +/- 28 to 9 +/- 1 mm Hg, yet seven patients required significant inotropic support (dopamine, greater than 5 micrograms/kg/min) for more than 24 hours and 12 patients needed prolonged use of digoxin and diuretics for right ventricular failure. Tissue levels of adenosine triphosphate and lactate in the tetralogy groups were compared with those in 20 adults with coronary artery disease having similar myocardial protection techniques. Adenosine triphosphate levels in the tetralogy group decreased during cross-clamping (41 +/- 8 minutes) from 24 +/- 3 to 16 +/- 2 mmol/kg dry weight (mean +/- 1 standard error), with a marked further drop after reperfusion to 9 +/- 2 mmol/kg (p less than 0.01). Adenosine triphosphate levels in the group with coronary disease also decreased from 20 +/- 1 to 16 +/- 1 mmol/kg after a longer cross-clamp time (70 +/- 17 minutes) but remained at 15 +/- 2 mmol/kg after reperfusion. Tissue lactate levels in the tetralogy group rose markedly during ischemia and remained elevated after reperfusion. In contrast, lactate levels in the group with coronary disease rose moderately during ischemia and returned to normal early on reperfusion. Microscopic study revealed focal myocyte necrosis in tetralogy of Fallot. Our findings, which demonstrate inadequate myocardial protection of patients with tetralogy during repair, with depression of adenosine triphosphate and increased lactate during ischemia and reperfusion, suggest a defect in oxidative metabolism. The drop in adenosine triphosphate after reperfusion in the patients with tetralogy implicates reperfusion injury as a mechanism of myocardial damage.

Adenosine Triphosphate↗
PubMed1988

Right and left ventricular metabolites.

Current methods of cardioplegic delivery may delay the recovery of right ventricular metabolism and function. To evaluate right and left ventricular metabolism, we performed biopsies in 37 patients undergoing elective coronary bypass operation with aortic root blood cardioplegia. Right ventricular temperatures were warmer than left ventricular temperatures during cardioplegic arrest (right ventricle: 16.8 degrees +/- 3.8 degrees C, left ventricle: 14.3 degrees +/- 3.7 degrees C, p = 0.02). Adenosine triphosphate concentrations were lower in the right ventricle than in the left ventricle before cardioplegic arrest (right ventricle: 13.8 +/- 7.8 mmol/kg, left ventricle: 21.5 +/- 8.7 mmol/kg, p = 0.02). After reperfusion, right ventricular adenosine triphosphate concentrations fell to low levels (10 +/- 6 mmol/kg). Postoperative left and right ventricular high energy phosphate concentrations (the sum of adenosine triphosphate and creatine phosphate levels) correlated inversely with myocardial temperatures during cardioplegia (r = -0.29, p = 0.048). Aortic root cardioplegia did not cool the right ventricle as well as it did the left ventricle. The lower preoperative high energy phosphate concentrations may have increased the susceptibility of the right ventricle to ischemic injury. Alternative methods of myocardial preservation may improve right ventricular cooling and protection.

Adenosine Triphosphate↗
PubMed1988

Improving myocardial metabolic and functional recovery after cardioplegic arrest.

The myocardial oxidation of fatty acids and glucose, the predominant substrates for aerobic metabolism, is impaired after cardioplegic arrest for coronary revascularization. Because lactate can be readily metabolized to pyruvate, it may be the preferred substrate for aerobic metabolism after cardioplegic arrest when arterial concentrations are elevated. Nineteen patients undergoing elective coronary revascularization with blood cardioplegia were randomized to receive LOW (nine patients, no exogenous lactate) or HIGH (10 patients, a perioperative infusion of Ringer's lactate) arterial lactate concentrations. Coronary sinus catheterization and lactate labeled with carbon 14 permitted calculation of myocardial oxygen consumption and lactate oxidation which were significantly increased during reperfusion in the group with HIGH arterial lactate concentrations. Atrial pacing at 110 beats/min on cardiopulmonary bypass resulted in myocardial lactate production (suggesting ischemic anaerobic metabolism) in the LOW lactate group, but atrial pacing increased lactate consumption and oxidation in the HIGH lactate group (suggesting increased aerobic metabolism). Systolic function (the relation between end-systolic pressure and volume) as assessed by nuclear ventriculography 3 hours postoperatively was significantly better (p less than 0.05 by analysis of covariance) in the HIGH lactate group. Postoperative myocardial creatine kinase release was significantly lower in the HIGH lactate group, which suggested less perioperative ischemic injury. Lactate was the preferred substrate for myocardial oxidative metabolism after cardioplegic arrest, and the higher arterial lactate concentrations improved myocardial metabolic and functional recovery and reduced perioperative ischemic injury.

Cardiac Pacing, Artificial↗