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Biomedical subjects

J Barwinsky

Publications and source records attributed to J Barwinsky.

18 recordsLinked to original sources
PubMed1993

Characteristics and mechanisms of tachyphylaxis of cardiac contractile response to insulin.

Although insulin is known to cause internalization of its own receptors, the physiological significance of this phenomenon is not clear. In the isolated rat heart we observed that the positive inotropic effect of 25 munits/ml insulin was completely abolished if the heart was preperfused with insulin for 10 min. This tachyphylactic response to insulin began to appear 3-4 min after starting preperfusion with insulin and was partially reversible after 30 min of washing. Preperfusion with insulin did not affect the action of vanadate, which has insulin-like effect on glucose transport, or the actions of the other positive inotropic agents, isoproterenol and ouabain. The presence of propranolol in the perfusion medium, unlike atenolol, phenoxybenzamine, guanethidine, verapamil or quinidine, modified the inotropic as well as tachyphylactic responses to insulin. The positive inotropic and tachyphylactic responses to insulin were not altered in hearts from reserpine-treated animals. Perfusion of heart with glucose-free solution abolished the tachyphylaxis due to insulin. Likewise, no tachyphylactic response to insulin was evident when iodoacetate, but not sodium fluoride, was added in medium containing glucose. These results suggest that ATP formed during glycolysis may play an important role in insulin-induced tachyphylaxis with respect to cardiac contractile activity.

Adenosine Triphosphate↗
PubMed1991

Experimental congestive heart failure due to myocardial infarction: sarcolemmal receptors and cation transporters.

Rats, subsequent to loss of a large amount of left ventricular free wall due to surgically-induced myocardial infarction, form a good model of congestive heart failure. Since depressed cardiac pump function is the hallmark of heart failure, it is suspected that decreased influx of Ca2+ into the cardiac cell is responsible for depressed contractile function. Because Ca2+ movements in the sarcolemmal membrane are known to involve Ca(2+)-channels, Na(+)-Ca2+ exchange, Ca(2+)-pump, Na(+)-K+ ATPase, beta-adrenoceptors and alpha-adrenoceptors directly or indirectly, the status of these mechanisms was examined by employing rats at different degrees of congestive heart failure. The left coronary artery was ligated and hearts were examined 4, 8, and 16 weeks later; sham-operated animals served as controls. The number of Ca2+ channels in the myocardium was depressed in moderate and severe stages of heart failure. Furthermore, depressions in sarcolemmal Na(+)-Ca2+ exchange activity and beta-adrenoceptor number were associated with the development of early stages of heart failure, whereas sarcolemmal Na(+)-K+ ATPase activity was decreased and the number of alpha-adrenoceptors was increased at moderate and severe stages. The Ca(2+)-pump activities were not altered in failing hearts. Thus it appears that changes in Na(+)-Ca2+ exchange as well as beta-adrenoceptors and Ca2+ channels may contribute towards decreasing Ca2+ influx at early and moderate stages of congestive heart failure, respectively. On the other hand, changes in alpha-adrenoceptors and Na(+)-K+ ATPase may act as compensatory mechanisms for maintaining Ca2+ influx at moderate and late stages of congestive heart failure.

Animals↗
PubMed1989

Repair of a false aneurysm of the aortic arch.

A 66-year-old man having previously undergone repair of aneurysms of the ascending, transverse and infrarenal aorta, presented with a large false aneurysm of the aortic arch. Successful repair of the aneurysm was achieved under a state of profound hypothermia and circulatory arrest. The patient remains well and free from aortic aneurysmal disease two years after surgery.

Aged↗
PubMed1988

Bjork-Shiley cardiac valves long term results: Winnipeg experience.

Between April 1970 and December 1984, 1183 Bjork-Shiley cardiac valve prostheses were implanted in 915 patients (470 males, 445 females). Four types of valves were used; Delrin disc prostheses in 75 patients, pyrolytic carbon spherical disc valves in 645 patients, the 60 degrees convexo-concave disc model in 197 patients and the 70 degrees model in seven patients. Isolated mitral valve replacement was performed in 278 patients, isolated aortic valve replacement in 363 and double valve replacement in 153. Concomitant surgery was performed in 121 patients, including a modified Bentall procedure in 15. Perioperative mortality was 6.4% (nine patients undergoing isolated aortic valve replacement; 16 in mitral valve group, 18 with double valve replacement and 16 undergoing concomitant surgery). The cumulative follow-up was 4592 patient-years, to a maximum of 15 years. There were 130 late deaths, 60% due to cardiac events. Actuarial survival for the mitral valve group was as follows: four of six patients with Delrin disc valves were alive at 13.4 years; in the pyrolytic group, survival was 82% at 10 years; in the 60 degrees convexo-concave group survival was 87.5% at seven years. In the aortic valve replacement group, 83% of patients with pyrolytic valves were alive at 10 years and 85.7% of the 60 degree convexo-concave group were alive at seven years. For patients undergoing double valve replacement, 72% were still alive after seven years. Thromboembolic events averaged 1.4 per 100 patient-years. There were seven complete valve thromboses in the mitral position requiring reoperation; six of these patients were long term survivors.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

Risks and benefits of open-heart surgery in patients 70 years of age and older.

From January 1978 to December 1982, 165 consecutive patients aged 70 to 81 years underwent various open-heart surgical procedures at the St. Boniface General Hospital in Winnipeg. Preoperatively, most of the patients were in functional class III or IV (New York Heart Association classification). Overall operative mortality for the series was 10.9%. Isolated coronary artery bypass surgery, performed in 71 patients, had an operative mortality of 2.8%. Results were also good in isolated single and double valve replacement in 58 patients (operative mortality 8.6%); there were no deaths in a group of 27 patients who underwent isolated aortic valve replacement. Thirty-six patients with various combined, extensive procedures had the poorest result (operative mortality 30.5%). More than 90% of surviving patients were in functional class I or II postoperatively. The complication rate, although high, was acceptable. Immediate and long-term clinical improvement in the majority of patients justifies a surgical approach except in patients who require combined, extensive procedures.

Aged↗
PubMed1978

Unusual vascular complications of dissecting thoracic aortic aneurysms.

Nondissecting, chronic, thoracic aortic aneurysms (TAA) may be associated with such vascular complications as aorto-cardiac, aorto-superior vena caval (SVC) and aorto-pulmonary arterial (PA) fistual formation, and/or SVC or PA compression. Dissecting TAA have been associated with these lesions far less often. This report summarizes the occurence and outcome of the following complications of dissecting TTA: (1) SVC obstruction; (2) aorto-right and -left atrial, aorta-right ventricular and aorto-PA fistula formation; (3) compression of the PA and (4) hematoma of the interatrial septum. Two patients are described with aortic dessection complicated by: (1) SVC obstruction and aorto-left atrial fistula; and (2) aorto-PA fistula. These complications are rarer with aortic dissection, because of the acute, catastrophic nature of this lesion. When dissection is chronic, however, arteriovenous fistulae are often well tolerated, and urgent surgical intervention seems to be unnecessary.

Aged↗
PubMed1978

Arterio-venous difference in lactate levels in myocardial ischemia and reperfusion.

The effects of 30-, 60-, and 90-min occlusion of the left anterior descending coronary artery and 60-min reperfusion were studied on the left ventricular dP/dt, myocardial ultrastructure, and tissue as well as blood lactate levels in dogs. The dP/dt was depressed by the occlusion, and reperfusion instituted after 30 min resulted in full recovery whereas that after 90 min had an adverse effect. Varying degrees of ultrastructural damage were noted after 60 and 90 min of occlusion and this was further exaggerated by reperfusion. Coronary occlusion markedly increased lactate content of ischemic myocardium, and the same returned to normal upon reperfusion. Myocardial ischemia for 30 or 60 min did not affect net arterial lactate extraction by the heart, but ischemia for 90 min reversed net lactate extraction to net lactate production by the heart. Reperfusion after 30 min of occlusion significantly increased lactate extraction, but reperfusion after 60 and 90 min of ischemia significantly decreased net lactate extraction and increased net production, respectively. The results indicate that estimation of net lactate exchange across the heart can be of value in assessing the viability of myocardium following coronary bypass surgery.

Animals↗
PubMed1975

Alterations in energy metabolism and ultrastructure upon reperfusion of the ischemic myocardium after coronary occlusion.

The effects on myocardial function, metabolism and ultrastructure of 60 minutes of reperfusion, instituted after 30, 60 and 90 minutes of occlusion of the left anterior descending coronary artery, were studied in 48 dogs. Twelve sham-operated dogs served as controls. Coronary occlusion for 60 or 90 minutes caused significant depression in the first derivative of left ventricular pressure (dP/dt) (P less than 0.05) that could not be reversed by reperfusion. Upon reperfusion, creatine phosphate stores in myocardium made ischemic for 30 and 60 minutes, but not for 90 minutes, returned toward control levels, but stores of adenosine triphosphate (ATP) and total nucleotides and the ATP/adenosine diphosphate ratio of myocardium subjected to 60 and 90 minutes of ischemia were further decreased. After 60 and 90 minutes of ischemia, swelling of the sarcoplasmic reticulum and mitochondrial damage (swelling, decreased matrix density and partial loss of cristae) were seen. Myofibrils were relaxed in all these groups. Reperfusion produced gross contraction of myofibrils and aggravated these changes in mitochondria and sarcoplasmic reticulum. In the hearts subjected to 90 minutes of ischemia these changes were gross. The levels of creatine phosphokinase, glutamic oxaloacetic transaminase and lactic dehydrogenase in the coronary sinus blood increased dramatically (P less than 0.05) upon reperfusion after 60 or 90 minutes of occlusion, indicating severe impairment of cell membranes. This secondary rise in serum enzyme activity during reperfusion should be taken into consideration when estimating the size of a myocardial infarct from enzyme changes alone. It appears that 60 and 90 minutes of ischemia cause severe myocardial damage that is not reversed by reperfusion maintained for 1 hour although longer periods of reperfusion may be beneficial.

Animals↗
PubMed1975

Role of mitochondrial calcium transport in failing heart.

Mitochondrial calcium uptake, but not binding, like microsomal calcium uptake in failing human hearts, was less than the control values for dog, rabbit, and hamster hearts. Decrease in mitochondrial calcium binding and uptake was observed in genetically myopathic hamsters (BIO 14.6) at early, moderate, and late stages of congestive heart failure. Inhibitors of mitochondrial calcium transport, Dicumarol, dinitrophenol, and sodium azide, were found to produce a rapid fall in contractility of the isolated rat heart. Inability of rat hearts to generate contractile force on perfusion with Na+- or K+-free medium was associated with an increase in mitochondrial calcium uptake. A dramatic increase in mitochondrial calcium uptake was observed on perfusing rat hearts with control medium after CA++-free medium. No change in mitochondrial calcium uptake was noted in acute ischemic dog myocardium or hypoxic rat heart in which contractile force was severely depressed. Both mitochondrial calcium transport and contractility were decreased on perfusing rat hearts with substrate-free medium; however, the change in calcium uptake was secondary to the fall in contractile force. Decrease in pH, ATP:ADP ratio, ATP6AMP ratio, and K+:Na+ ratio were found to reduce the dog heart mitochondrial calcium uptake. It is likely that various factors such as pH, ATP:ADP ration, ATP:AMP ratio, and K+ :Na+ ration, in addition to damage in mitochondrial structure, play an important role in inhibiting mitochondrial calcium transport in failing hearts. The results also suggest that alterations in mitochondrial calcium transport are dependent upon the degree and type of heart failure.

Adenine Nucleotides↗
PubMed1972

Ventricular septal defects due to penetrating injuries of the heart.

Four patients with traumatic ventricular septal defect following stab wound underwent successful open heart repair. All were symptomatic in spite of minimal hemodynamic disturbances. An additional lesion in the form of a fistulous tract between the aorta and the right atrium occurred in one case.

Adolescent↗
PubMedDate not supplied

Cardiac valve replacement: Canadian review 1978-86.

The total number of cardiac patients requiring valve surgery in Canada has remained relatively constant over the years 1978-86, at about 2900 cases per year. However, the type of valve used has changed with most centres now using bioprosthetic valves as compared to mechanical valves which were popular until 1978. Unfortunately, there is a lack of uniform follow-up data on cardiac valve replacement patients and a countrywide registry is needed in order to monitor morbidity, mortality and long term results.

Aortic Valve↗