Left-ventricular heart muscle and pectoralis major muscle of the rat were studied to determine the intracellular localization of lactic dehydrogenase (LDH) isoenzymes . Fixation of tissue for 2 hr in 2 % buffered formaldehyde provided the best preservation of the ultrastructure and enzyme activity . Total LDH activity was found diffusely in the ground substance of the sarcoplasm and in the mitochondria of the heart muscle . In skeletal muscle a strong reaction was noted in the sarcoplasmic reticulum, and moderate activity was seen in the ground substance of the sarcoplasm and in the mitochondria . Differentiation of the isoenzymes of LDH was accomplished by addition of 4 M urea or application of heat . Hearttype isoenzymes were mainly localized in the mitochondria and sarcoplasm, whereas muscletype isoenzymes were localized mainly in the sarcoplasmic reticulum of the skeletal muscle . It is speculated that the sarcoplasmic reticulum of the skeletal muscle is the site of anaerobic glycolysis and that the sarcoplasm and mitochondria are involved primarily in aerobic metabolism of pyruvate .

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This study describes six generations of a family with autosomal dominant cardiac conduction system and myocardial disease with recognizable clinical stages. A 20 year follow-up of nine family members, a medical questionnaire of 196, electrocardiographic screening of 91, noninvasive testing of 20, and catheterization with endomyocardial biopsy of six are the basis of this report. The clinical stages are as follows: Stage I occurs in the second and third decades of life and is characterized by an absence of symptoms, normal heart size, sinus bradycardia, and premature atrial contractions. Stage II is marked by first-degree atrioventricular block in the third and fourth decades. Stage III occurs in the fourth and fifth decades and is accompanied by chest pain, fatigue, lightheadedness, and advanced atrioventricular block followed by the development of atrial fibrillation or flutter. Stage IV, in the fifth and sixth decades of life, is characterized by congestive heart failure and recurrent ventricular arrhythmias. Light microscopy of right ventricular endomyocardial biopsy specimens from patients in stage II revealed very mild fibrosis; electron microscopy of the specimens demonstrated mild dilatation of tubules, mitochondrial swelling, and minimal myofibrillar loss. Biopsy specimens from patients with stage III disease were similar to those from patients with stage IL disease except for an increase of myofibrillar loss. The stage IV specimens had diffuse fibrosis and more severe tubular dilatation, mitochondrial cristolysis, and myofibrillar loss. At autopsy in the proband, the atrial changes were more severe than the ventricular and were especially marked in the sinoatrial and atrial myocardium. Early recognition of the disease and use of pacemakers and antiarrhythmic agents have proved beneficial for affected family members. Thorough family studies of patients with conduction system disease and/or dilated cardiomyopathy are necessary to better understand the hereditary basis and natural course of this category of disease.Circulation 74, No. 1, [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] 1986

A B ST R A CT Employing an isolated perfused rat heart preparation, we investigated the contriblution of anaerobic metabolic energy to the lerformance, recoverability, and ultrastructure of the heart perfused at 320C in 5% albumin in Krebs-Ringer Bicarbonate solution. During exposure to anoxia for 30 min, inclusion in the perfusate of the anaerobic substrate, glucose, resulted in marked improvement in electrical and mechanical performance of the heart and in enhanced recovery during the subsequent period of reoxygeiiation. Lactate production was fivefold greater in the glucose-supported anoxic heart than in the anoxic heart without glucose. Electron microscope sections of the hearts exposed to anoxia in the absence of glucose anaerobically derived metabolic energy to the electrical and mechanical performance of the heart, to functional recoverability after exposure to anoxia, or to the prevention of intracellular structural alterations accompanying anoxic exposure.Induction of myocardial hypoxia by simple cessation of coronary perfusion, in vivo or in vitro, does not permit a steady supply of anaerobic substrate to the myocardium. Furthermore, the effects of accumulated end products of anaerobic metabolism are not controlled under these circumstances. Studies with perfused myocardial strips, which avoid these difficulties, do not yield information on spontaneous electrical activity or on electromechanical integration of cardiac function. With these considerations in mind the present studies on the effects of anoxia on the isolated perfused rat heart were initiated. This preparation permits study of electrical and mechanical performance of the isolated heart during relatively prolonged experiments and instantaneous addition or deletion of anaerobic substrate while perfusion is maintained at a constant rate. The studies were designed to determine the degree to which the presence of the anaerobic substrate, glucose, affects the performance, recoverability, and ultrastructure of the perfused anoxic heart. METHODSThe hearts used in these studies were removed from male albino (Wistar) rats, weighing from 180 to 235 g. The rats were fed ad lib. with standard Purina laboratory chow until they were sacrificed. The animals were decapitated, the chest opened within 30 sec with a subxiphoid incision, and the heart flooded immediately with ice-cold Ringer's solution. This maneuver produced rapidThe Journal of Clinical Investigation Volume 47 1968 403 cessation of the heart beat, after which the heart was dissected from the mediastinum with an attached aortic stump 5 mm long. The heart was then mounted on the perfusion cannula which consisted of a No. 17 TW needle with a rounded and smoothed end and notched 3 mm above the tip. The tip of the cannula was placed in the aortic root which was attached firmly via a silk 3-0 ligature applied to the notch in the cannula. The time from extirpation of the heart to in vitro perfusion was 3-5 min.The perfusion system, as illustrated in Fig. 1, was recirculating in type and consisted o...

SUMMARY We studied the morphologic and histologic characteristics of redundant prolapsing ("myxomatous") mitral valves from 12 symptomatic patients with severe mitral regurgitation who required mitral valve replacement and compared our findings with those in 13 control valves.The mean surface area of the "myxomatous" mitral valves (MMVs)