The myocardial sleeves of the pulmonary veins: potential implications for atrial fibrillation

Atrial fibrillation (AF) is the most common abnormal heart rhythm and contributes to cardiac morbidity and mortality. Electrophysiological studies with pacing have shown that AF is initiated by ectopic beats localized in the pulmonary vein (PV) walls. The aim of this work was to look for some anatomical or histological particularities to explain these ectopic beats. Ten autopsied hearts were examined (6 males, 4 females). The myocardium was studied from the left atrium to the PV. Histological sections were made from 39 PVs. Myocardial cells were localized to PV between 9 and 38 mm from the PV-atrial junction. The sleeve was composed of circularly and longitudinally oriented bundles of cardiomyocytes. The peripheral end of the myocardial sleeve was irregular. The longest myocardial sleeves were found in the superior veins and were longitudinally oriented. At the PV-atrial junction, the circular bundles were not often circumferential. PV myocardial architecture confirmed the possibility of initiating AF. This fact is important for therapeutic radiofrequency ablation and explains why PV disconnection is essential.     

Confocal microscopy of Tomes’ granular layer in dog premolar teeth

Tomes’ granular layer is the hypomineralized area of radicular dentin, but knowledge concerning it is limited. The present study was designed to investigate the structural characteristics of Tomes’ granular layer in the dog’s teeth by confocal microscopy. Permanent premolars of four beagles, two at 7 months and the other two at 14 months of age, were used for observation. During premolar root formation, the 7-month-old dogs were injected with calcien and alizarin red S for vital staining of dentin, and ground sections of the teeth were prepared. Both ground and decalcified-paraffin sections were made from the teeth of the 14-month-old dogs and stained with basic fuchsin or with hematoxylin and eosin. All sections were examined by fluorescence and confocal microscopy. In the ground sections, granules of Tomes’ layer and dentinal tubules were stained with basic fuchsin and with calcein. The granules of Tomes’ layer stained with calcein were seen only near the labeling lines by calcein. The granules of Tomes’ layer appeared as bright spots in cross sections, and as lines in longitudinal sections. When the sections were cut tangentially through the surface of dentin, the granules of Tomes’ layer showed a reticular structure. Most of the dentinal tubules were seen to pass between the granules and terminated in the dentin-cementum junction. Looped tubules were not found in this area. In the paraffin sections stained with hematoxylin and eosin, extracellular matrix of dentin showed fluorescence of various intensities and dentinal tubules appeared dark. At the surface of the radicular dentin, the granules of Tomes’ layer appeared as fluorescent fibers running parallel to the surface of dentin in the longitudinal sections. The fibers appeared as bright spots in the cross sections and as a mesh in the tangential sections. In the periodontal ligament, collagen fibers showed intense fluorescence, whereas most cells were negative. From these results we conclude that Tomes’ granular layer of dog’s teeth may be the collagen fiber bundles that remained uncalcified or hypocalcified within the radicular dentin.     

The local expression of adult chicken heart myosins during development

Summary Immunofluorescence studies were performed on serial sections of three days embryonic chicken hearts using antibodies specific for adult atrial and ventricular myosin heavy chains respectively.The anti-ventricular myosin serum reacted with the entire myocardium showing a decreasing intensity going from the truncus arteriosus to the atrial part; however, the antiatrial myosin serum reacted weakly with the myocardium of the atrial part.Two other interesting observations were made, i) the anti-atrial myosin serum reacted with non-myocardial cells the cardiac jelly, ii) both antisera reacted with a thin myocardial layer, extending from the ventral wall of the atrial part via the medio-dorsal wall of the atrio-ventricular canal to the dorsal wall of the ventricular part     

Confocal microscopy of Tomes' granular layer in dog premolar teeth

Tomes’ granular layer is the hypomineralized area of radicular dentin, but knowledge concerning it is limited. The present study was designed to investigate the structural characteristics of Tomes’ granular layer in the dog’s teeth by confocal microscopy. Permanent premolars of four beagles, two at 7 months and the other two at 14 months of age, were used for observation. During premolar root formation, the 7-month-old dogs were injected with calcien and alizarin red S for vital staining of dentin, and ground sections of the teeth were prepared. Both ground and decalcified-paraffin sections were made from the teeth of the 14-month-old dogs and stained with basic fuchsin or with hematoxylin and eosin. All sections were examined by fluorescence and confocal microscopy. In the ground sections, granules of Tomes’ layer and dentinal tubules were stained with basic fuchsin and with calcein. The granules of Tomes’ layer stained with calcein were seen only near the labeling lines by calcein. The granules of Tomes’ layer appeared as bright spots in cross sections, and as lines in longitudinal sections. When the sections were cut tangentially through the surface of dentin, the granules of Tomes’ layer showed a reticular structure. Most of the dentinal tubules were seen to pass between the granules and terminated in the dentin-cementum junction. Looped tubules were not found in this area. In the paraffin sections stained with hematoxylin and eosin, extracellular matrix of dentin showed fluorescence of various intensities and dentinal tubules appeared dark. At the surface of the radicular dentin, the granules of Tomes’ layer appeared as fluorescent fibers running parallel to the surface of dentin in the longitudinal sections. The fibers appeared as bright spots in the cross sections and as a mesh in the tangential sections. In the periodontal ligament, collagen fibers showed intense fluorescence, whereas most cells were negative. From these results we conclude that Tomes’ granular layer of dog’s teeth may be the collagen fiber bundles that remained uncalcified or hypocalcified within the radicular dentin. Accepted: 17 July 1999     

Diagnostic value of morphometry in feline hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common form of feline heart disease. To date, reliable morphometric reference data for anatomical or histological changes are unavailable. The aim of this study was to identify diagnostically relevant morphometric criteria that clearly distinguish feline HCM from normal hearts. Hearts from 15 cats with HCM had increased weights (g per distance between the first and eighth vertebral bodies) when compared with hearts from 15 matched control cats. Several anatomically defined and digitally scanned areas of standardized cross sections were significantly increased in HCM when compared with controls, including the area across the entire heart half-way between the coronary sulcus and apex, the right and left ventricular walls and the ventricular septum. Differences were similar when the papillary muscles were included in the measurements of the right and left ventricular walls and the ventricular septum. Histological morphometric analyses failed to identify any significant differences, including the diameter and cross-sectional area of cardiomyocytes and the length, width or areas of cross-sectioned nuclei. In addition, morphometric analyses failed to identify any differences in the amount of cardiomyocyte fibre branching or myocardial fibrosis. Thus, only the relative weight and macroscopical analyses proved useful in distinguishing feline hearts with HCM from normal hearts. The results do not uphold the hypothesis that increased cardiomyocyte diameter is a principal change in feline HCM.     

Three-dimensional architecture of the left ventricular myocardium

Concepts for ventricular function tend to assume that the majority of the myocardial cells are aligned with their long axes parallel to the epicardial ventricular surface. We aimed to validate the existence of aggregates of myocardial cells orientated with their long axis intruding obliquely between the ventricular epicardial and endocardial surfaces and to quantitate their amount and angulation. To compensate for the changing angle of the long axis of the myocytes relative to the equatorial plane of the ventricles with varying depths within the ventricular walls, the so-called helical angle, we used pairs of cylindrical knives of different diameters to punch semicircular slices from the left ventricular wall of pigs, the slices extending from the epicardium to the endocardium. The slices were pinned flat, fixed in formaldehyde, embedded in paraffin, sectioned, stained with azan or hematoxilin and eosin, and analyzed by a new semiautomatic procedure. We made use of new techniques in informatics to determine the number and angulation of the aggregates of myocardial cells cut in their long axis. The alignment of the myocytes cut longitudinally varied markedly between the epicardium and the endocardium. Populations of myocytes, arranged in strands, diverge by varying angles from the epicardial surface. When paired knives of decreasing diameter were used to cut the slices, the inclination of the diagonal created by the arrays increases, while the lengths of the array of cells cut axially decreases. The visualization of the size, shape, and alignment of the myocytic arrays at any side of the ventricular wall is determined by the radius of the knives used, the range of helical angles subtended by the alignment of the myocytes throughout the thickness of the wall, and their angulation relative to the epicardial surface. Far from the majority of the ventricular myocytes being aligned at angles more or less tangential to the epicardial lining, we found that three-fifths of the myocardial cells had their long axes diverging at angles between 7.5 and 37.5 degrees from an alignment parallel to the epicardium. This arrangement, with the individual myocytes supported by connective tissue, might control the cyclic rearrangement of the myocardial fibers. This could serve as an important control of both ventricular mural thickening and intracavitary shape.     

Altered distribution of desmin filaments in hypertrophic cardiomyopathy: an immunohistochemical study.

Hypertrophic cardiomyopathy (HCM) is characterized by myofiber hypertrophy and disarray. Intermediate filaments play an important role in maintaining of normal cell shape. Desmin filaments have been detected in adult cardiomyocytes, and vimentin and keratin filaments in cardiomyocytes during embryonic development. The pattern of arrangement of intermediate filaments in HCM has not been reported. We examined the distribution of intermediate filaments in formalin-fixed tissue sections of the disarrayed myofibers from 10 hearts with HCM using an immunohistochemical technique and antibodies to desmin, vimentin, and high and low molecular weight keratins. The controls consisted of subaortic tissue from surgically explanted hearts of patients with ischemic heart disease. In the ischemic hearts, desmin was detected in the Z bands and intercalated disks. In all HCM cases, three patterns of staining for desmin were noted: (a) individual myocytes showing a parallel arrangement along Z bands; (b) focal myofibers with decreased or complete loss of labeling of Z bands; and (c) individual myocytes with intense granular cytoplasmic staining especially in disarrayed myofibers. No staining for vimentin or keratins was noted in the cardiomyocytes from either the HCM or ischemic cases. The altered arrangement of desmin filaments in the disarrayed cardiac muscle fibers may play a role in the altered contractility that occurs in patients with HCM.     

Histochemical studies on the conduction system of diabetic rat hearts

We studied the metabolism of the conduction system and the working myocardium in diabetic rat hearts by enzyme histochemistry. The experiment was performed three weeks following the administration of streptozotocin (65 mg/kg) to male Wistar rats. The hearts were quickly excised and tissue was frozen immediately by immersion in isopentane at -30 degrees C and cut into 16 microns thick sections in a cryostat. The PAS positive reaction was increased in the conduction system compared to the working myocardium in control rats. In diabetic rat hearts, these reactions in the working myocardium and the conduction system were strongly increased compared to control hearts. Several enzyme activities, such as phosphofructokinase, pyruvate dehydrogenase, glucose-6-phosphate dehydrogenase, Na-K ATPase, were reduced in both the working myocardium and conduction system of diabetic rat hearts. These results suggest that the changes in metabolic condition also exist in the conduction system of the diabetic rat hearts as well as the working myocardium.     

Postnatal persistence of spongy myocardium with embryonic blood supply.

Focal presence of the embryonic pattern of myoarchitecture and of a lacunary blood supply was found in the left ventricular wall of five infant hearts. Four of these hearts showed various malformations; one was a case of cardiac fibroma. The persisting intertrabecular spaces and sinusoids communicated with the ventricular lumen; there appeared to be some communication with the coronary branches. The intertrabecular spaces of the spongy myocardium were lined with a continuous layer of endothelial cells, thus resembling the microscopical appearance of myocardium of adult cold-blooded vertebrates rather than the embryonic phase of myocardial development of warm-blooded animals.     

Developmental patterning of the myocardium

The heart in higher vertebrates develops from a simple tube into a complex organ with four chambers specialized for efficient pumping at pressure. During this period, there is a concomitant change in the level of myocardial organization. One important event is the emergence of trabeculations in the luminal layers of the ventricles, a feature which enables the myocardium to increase its mass in the absence of any discrete coronary circulation. In subsequent development, this trabecular layer becomes solidified in its deeper part, thus increasing the compact component of the ventricular myocardium. The remaining layer adjacent to the ventricular lumen retains its trabeculations, with patterns which are both ventricle- and species-specific. During ontogenesis, the compact layer is initially only a few cells thick, but gradually develops a multilayered spiral architecture. A similar process can be charted in the atrial myocardium, where the luminal trabeculations become the pectinate muscles. Their extent then provides the best guide for distinguishing intrinsically the morphologically right from the left atrium. We review the variations of these processes during the development of the human heart and hearts from commonly used laboratory species (chick, mouse, and rat). Comparison with hearts from lower vertebrates is also provided. Despite some variations, such as the final pattern of papillary or pectinate muscles, the hearts observe the same biomechanical rules, and thus share many common points. The functional importance of myocardial organization is demonstrated by lethality of mouse mutants with perturbed myocardial architecture. We conclude that experimental studies uncovering the rules of myocardial assembly are relevant for the full understanding of development of the human heart.     

A pattern formed by preferential orientation of tangential fibres in layer I of the rabbit's cerebral cortex

1. The tangential organization of layer I has been studied in frozen sections impregnated according to a modified Liesegang method and in Bodian impregnated paraffin sections cut tangentially to the dorsal surface of the rabbit's cerebral cortex. 2. It is shown that sublamina tangentialis of layer I contains a system of parallel nerve fibres forming a distinct pattern in the tangential plane. 3. This pattern has been reconstructed for a large region of the dorsal surface of the cerebral cortex including the striate areas as well as the peristriate, parietal and precentral agranular regions and parts of the retrosplenial area. 4. In most parts of the region investigated, the tangential fibres of layer I are oriented in an antero-medial to postero-lateral direction, forming an angle of about 50 degrees with the sagittal plane. 5. Deviations from this pattern are found in the furrows formed by the lateral sulcus and the frontal impression and also in the caudal part of the retrosplenial area. In these regions, which are characterized by comparatively steep changes of the cortical relief, the fibres course in a more sagittal direction.     

Chronic hemodynamic unloading regulates the morphologic development of newborn mouse hearts transplanted into the ear of isogeneic adult mice.

The morphologic development of newborn mouse hearts transplanted into the pinna of the ears of isogeneic adult mice was assessed in comparison to in situ ventricular myocardium of recipients. The grafted hearts became vascularized from the auricular artery at the base of the ear, and although these preparations appeared not to be intrinsically innervated, most of them showed grossly visible pulsatile activity. Since they were not subjected to hemodynamic load due to working against a pressure gradient, this technique provided an interesting experimental model for studies on the growth of chronically unloaded tissue. The ultrastructure of the myocardium from neonatal mouse hearts, which were fixed immediately after dissection, revealed no differences in comparison to previously published observations. By 2 months, there was virtually no change in the myocardial cell size as compared with newborn mouse cardiac tissue. The heterotopic hearts showed a mature ultrastructural appearance, with parallel bands of myofibrils alternating with rows of mitochondria and differentiated intercalated discs comparable to in situ myocardium. The interstitial space was widened due to fibrous tissue, with activated fibroblasts and a few mononuclear cells. In contrast, by 6 months after transplantation, the heterotopic myocardium showed a dispersion of the measured cell diameter of myocytes, with atrophy of a certain population of cells and hypertrophy in others; nevertheless, the mean cell diameter was similar to that observed in 2-month grafts. The myocytes showed significant dissociation from each other in fibrous tissue and a cellular infiltrate composed predominantly of mononuclear cells, and greater variability of the parallel arrangement of cells. They often contained myofibrils coursing in different directions rather than in parallel. Normal-sized or predominantly atrophic degenerated myocytes, characterized by a wide variety of ultrastructural alterations, were present. By 12 months after transplantation, the myocytes of heterotopic hearts were smaller in size in comparison to those after 2 or 6 months. The graft cells were separated from each other by fibrous tissue and mononuclear cells and were not aligned in parallel within the tissue; often, they appeared to have lost their connections with adjacent cells. The myofibrils within cells were strikingly disorganized, coursing in different directions. Severely degenerated myocytes were commonly seen. These results, without precluding the possible role of neural and hormonal stimuli, clearly indicate that hemodynamic work load regulates the developmental growth of newborn mouse heart transplanted into the pinna of the ear of isogeneic adult recipient mice. In other words, the mass of cardiac tissue would be adjusted to meet the prevailing hemodynamic demands.(ABSTRACT TRUNCATED AT 400 WORDS)     

Immunohistochemical characterization of lymphocytes in uninflamed ventricular myocardium. Implications for myocarditis

Evaluation of endomyocardial biopsy specimens for lymphocytic myocarditis requires accurate identification of lymphocytes, a task at times difficult considering that other myocardial interstitial cells mimic lymphocyte morphology. To wit, the number of mononuclear cells present in normal (uninflamed) myocardium has remained in doubt. We studied the myocardium from hearts that were obtained at autopsy and transvenous endomyocardial biopsy specimens with monoclonal antibodies and immunohistochemical stains to determine the normal numbers and distribution of lymphocytes in uninflamed hearts. In the ventricular myocardium of hearts obtained at autopsy, total immunohistochemically marked lymphocytes averaged 3.6/sq mm, with most being T-cell marker-positive. The ratio of T-helper to T-suppressor-cytotoxic (OKT-4:OKT-8) cells was 1.44. The number of myocardial lymphocytes demonstrated by immunohistochemical staining correlated well with, but was consistently less than, the number obtained by quantitative light microscopic studies on unmarked samples. Thus, the immunohistochemical technique allows for objective enumeration of cells and provides avenues for quantitation of lymphocyte subpopulations in inflamed hearts.     

MYOCARDIAL FIBER DISARRAY IN THE NORMAL AND HYPERTENSIVE HEARTS

Hypertrophic cardiomyopathy is histologically characterized by marked hypertrophy and myocardial fiber disarray in the septal region. This finding has been considered important as a diagnostic indicator. In the present study, we examined 127 hearts, especially the interventricular septa, from newborns, children, adults and hypertensives. A local myocardial fiber disarray was detected in all cases at the anterior and the posterior areas of the septum where the left and the right ventricular myocardia meet. The extent varied from case to case. In adults, local disarray was also found in other regions, usually in the left ventricle-facing longitudinal to the middle layers of the septum. The left ventricle-facing longitudinal myocardium of the septum in hypertensives showed a hypertrophy change in the sites near the middle layer. The myocardium in this portion was further stratified into several sublayers in some cases. When compared with the findings of hypertrophic cardiomyopathy, septal myocardium of hypertensives still retained a certain degree of regularity in fiber arrangement. Biopsy might be of great value for diagnosing hypertrophic cardiomyopathy, although differentiation from secondary hypertrophic changes due to hypertension or cor pulmonale may be difficult in some cases.     

Intramural Purkinje Cell Network of Sheep Ventricles as the Terminal Pathway of Conduction System

To identify the anatomical basis for cardiac electrical signal conduction, particularly seeking the intramural terminals of conduction pathway within the ventricles, sheep hearts were examined compared with human hearts utilizing the characteristic morphology of Purkinje cells as a histological marker. In 15 sheep and five human autopsies of noncardiac death, prevalence of Purkinje or Purkinje‐type cells were histologically examined in the atrioventricular node, its distal conduction pathway, the interventricular septum, and the right‐ and left‐ventricular free walls. Myocardial tissue cleavages were examined in the transmural sections (along cardiac base‐to‐apex axis) obtained from the septum and ventricular free walls. Serial histological sections through virtually the entirety of the septum in selected sheep were used as the basis of a three‐dimensional reconstruction of the conduction pathway, particularly of the intramural Purkinje cell network. Purkinje cells were found within the mural myocardium of sheep ventricles whereas no intramural Purkinje‐type cell was detected within the human ventricles. In the sheep septum, every intramural Purkinje cell composed a three‐dimensional network throughout the mural myocardium, which proximally connected to the subendocardial extension of the bundle branches and distally formed an occasional junction with ordinary working myocytes. The Purkinje‐cell network may participate in the ventricular excitation as the terminal conduction pathway. Individual connections among the Purkinje cells contain the links of through‐wall orientation which would benefit the signal conduction crossing the architectural barriers by cleavages in sheep hearts. The myocardial architectural changes found in diseased hearts could disrupt the network links including those with transmural orientation. Anat Rec, 2009. © 2008 Wiley‐Liss, Inc.     

Quantitative changes in mast cell populations after left ventricular assist device implantation

Mast cells have been implicated as important in tissue remodeling and fibrosis. We investigated the effect of mechanical ventricular unloading upon myocardial fibrosis and cardiac mast cell density in patients undergoing left ventricular assist device (LVAD) implantation. Paired myocardial tissue samples were obtained from 30 patients with end-stage cardiomyopathy at the time of LVAD implantation and at the time of removal and were compared with samples taken from donor hearts. Tissue sections were stained and quantitated for mast cells and myocardial fibrosis. Mast cell density (tryptase positive cells) in cardiomyopathy was higher than that in donor hearts (33.5 +/- 3.6 SEM cells/10 fields vs.15.2 +/- 2.0 SEM cells/10 fields respectively, p = 0.04) and was lower than LVAD supported hearts (33.5 +/- 3.6 SEM cells/10 fields vs. 49.8 +/- 5.7 SEM cells/10 fields respectively, p = 0.01). Mast cells are primarily localized in areas of increased interstitial fibrosis adjacent to myocardial cells and not vessels. There was statistically significant correlation between mast cells and interstitial collagen (p = 0.03) in patients before LVAD implantation that did not persist after mechanical support (p = 0.18). These results suggest that mechanical support with left ventricular assist devices induces an increase in mast cell number in the myocardium and an associated decrease in myocardial fibrosis. We believe these data demonstrate a dual role for cardiac mast cells in the increase in fibrosis in heart failure and the decrease after LVAD and its associated cardiac improvement.     

Does the progression of myocardial fibrosis lead to atrial fibrillation in patients with hypertrophic cardiomyopathy?

The majority of left ventricular (LV) inflow volumes in hypertrophic cardiomyopathy (HCM) depend on atrial contraction because of impaired LV relaxation. If HCM is complicated by atrial fibrillation (AF), heart failure can develop because of the loss of atrial contraction. The purpose of this study was to determine the relationship between the development of AF and myocardial fibrosis or intramyocardial small artery (IMSA) stenosis in autopsied hearts with HCM. Studies were performed in five HCM hearts with AF (AF group) and five HCM hearts without AF (non-AF group). LV specimens were divided into the inner (IT), middle (MT), and outer (OT) thirds. We selected at random 120 fields and 20 IMSAs from each layer and assessed them quantitatively using an image analyzer. We determined the extent of fibrosis (%F) and the degree of stenosis of each IMSA (%L). The %F in the AF group was greater than in the non-AF group (P<.01). In the AF group, the %F of the IT was greater than in the MT and the OT (P<.01). In the non-AF group, the %F of the IT was greater than in the MT (P<.05), and the %F of the MT was greater than in the OT (P<.01). The %L was similar in the AF and non-AF groups. In both groups, the %L of the IT was lower than in the MT (P<.01), which was lower than that of the OT (P<.05). LV fibrosis is more severe in patients with HCM and AF than in those without AF. Therefore, myocardial fibrosis might impair LV relaxation, resulting in hemodynamic intolerance to AF.     

Atriopeptin distribution in the developing rat heart

Summary The embryonic distribution of atriopeptin (atrial natriuretic factor) in the Sprague-Dawley rat heart was mapped by immunoperoxidase staining of embryonic and neonatal hearts using rabbit antiserum to atriopeptigen purified from adult rat atrium. During the period of cardiac septation (days 14 and 16), immune serum reacted strongly with myocardial cytoplasmic granules in two sites: the inner cell layer along the cephalic curvature of the atria and the trabeculae of the incompletely divided ventricles. The youngest hearts studied (gestational day 11) displayed only nonspecific diffuse peroxidase reactivity within blood cells, indistinguishable from control sections incubated with normal rabbit serum. One week following birth, intense antiatriopeptin reactivity was widely distributed through both atria. In addition, immunoreactive cytoplasmic granules were found at several sites in the ventricular myocardium. Along the fiber tracts of the concentric layers of the ventricahar walls and interventricular septum, scattered granular foci were seen between nuclei of contiguous elongated myocytes. Positive staining was also seen within the papillary muscles and trabeculae carnae, regions shown by Alcian blue/periodic acid-Schiff base staining of sister sections to be relatively rich in glycogen. These patterns of antibody reactivity suggest the coupling of early atriopeptin secretory activity with developing cardiac function.     

Myocardial lesions in the offspring of female rats fed a copper deficient diet

Cardiac disease occurred in the offspring of dams fed a copper deficient diet from weaning. The usual age incidence at death for animals succumbing with heart failure was 5 to 7 weeks; the age of rapid growth when copper deficient offspring were slightly anemic. At necropsy the hearts were enlarged and usually pale. The most common histopathologic change was diffuse fatty change in the myocardium with small to large areas of necrosis in the ventricular and atrial musculature. Aneurysm of the apex developed in some severely involved hearts. Hemopericardium and hemothorax also occurred but specific rupture sites were not found. Myocardial cell hypertrophy with large vesicular nuclei was the only histopathologic change observed in some grossly enlarged hearts. Histochemical studies of the heart from copper deficient offspring demonstrated reductions in myocardial cytochrome oxidase activity especially in the myocardial sections from hearts with gross and histopathologic change. The activities of other mitochondrial oxidative enzymes, including NAD diaphorase, succinic, malic and glutamic dehydrogenase and glycolytic enzyme, lactic dehydrogenase, were increased. The myocardium from young control rats had little or no activity when stained for monoamine oxidase, however, the qualitative activity for this enzyme was consistently increased in the hearts from copper deficient offspring. Copper deficient offspring supplemented with copper had improved growth rate and there was evidence for return of myocardial enzyme activities to control levels.     

Histological assessment of apoptotic cell death in cardiomyopathies

Apoptosis in the myocardium is complex and often difficult to recognise. Myocyte apoptosis is scattered across the myocardial wall and is restricted to individual cells. In the present study, we describe the amount of apoptosis in 50 endomyocardial biopsies taken from 50 patients with dilated cardiomyopathy, in 14 hearts with hypertrophic cardiomyopathy and in five hearts with arrhythmogenic dysplasia of the right ventricle. As a control group, 15 endomyocardial biopsies from 15 transplanted hearts (of live patients) were used. Apoptosis was immunohistochemically determined in paraffin sections with the TUNEL method. In each specimen the TUNEL index was calculated as the percentage of TUNEL-positive nuclei among a total number of 200 counted nuclei. Cellular morphology was assessed in conjunction with TUNEL staining. The mean percentage of TUNEL-positive myocardial cells varied from 4% for dilated cardiomyopathy to 17.5% for arrhythmogenic right ventricle dysplasia and 18.5% for hypertrophic cardiomyopathy, whereas no signs of apoptotic myocardial cell death were found in normal subjects. The numbers of apoptotic cells in dilated cardiomyopathy specimens were significantly lower by comparison with both those of hypertrophic cardiomyopathy and those of arrhythmogenic right ventricular dysplasia specimens. It is evident that apoptosis constitutes a major biological phenomenon in the development of at least some heart diseases, but its role in their pathophysiology has yet to be delineated.