Ultrastructure of the ventricular myocardium of the bat Eidolon helvum

Ultrastructural studies, including a preliminary morphometric analysis, of the right ventricular myocardium in the West African bat Eidolon helvum show that the myocytes contain a wider T-tubule system and a higher proportion of mitochondria and lipid droplets than in typical terrestrial mammals such as the rat; these features in the bat are even mor pronounced than in hibernating species such as the golden hamster. In addition to having coupling arrangements with T-tubules and surface sarcolemma, cisterns of junctional sarcoplasmic reticulum are closely apposed to mitochondria and lipid droplets.     

Ultrastructure, peroxisomes and lipid peroxidation in reperfused myocardium

Reperfusion injury was studied in dog myocardium using a transmission electron microscope and 3,3'-diaminobenzidine (DAB) to locate areas of peroxidatic activity. Dark electron dense DAB reaction product was observed in peroxisomes and damaged mitochondria. These results suggest attack by reactive oxygen species on mitochondrial membranes, which might result in the formation of lipid peroxides and prostaglandin-like compounds. It is suggested that the release of lipid peroxide or prostaglandins from the injured cells may contribute to reactive hyperaemia, ventricular fibrillation and angina.     

Ultrastructure of the epimyocardium and myocardium in early embryos of white rats

The atrial walls in 10-13-day-old white rat embryos have been studied electron microscopically. The epimyocardium consists of 1-2 rows of cells and has an epitheliomorphic structure. At first the basal membrane is formed on the endocardial surface of cardiomyocytes; intercellular contacts in the lateral parts of the cells possess endo-epicardial polarity. The epicardial layer is formed on the 11th day of the prenatal development, the basal membrane begins to form at the same time on the epicardial surface of cardiomyocytes. Dynamics of differentiation of some cardiomyocytic organelles in cardiomyocytes is described.     

Ultrastructure of the chronically vagotomised atrial myocardium in the monkey (Macaca fascicularis)

The ultrastructure of the atrial myocardium in the monkey (Macaca fascicularis) was studied after bilateral cervical vagotomy and survival times of 100, 175 and 367 days. Changes were observed in the nucleus and the cytoplasm of the myocyte. Sequestered within the nuclei of the affected myocytes were cytoplasmic organelles and inclusions. In the late stages, there was a tendency towards condensation and margination of the heterochromatin. Changes in the cytoplasm included increased glycogen, mitochondrial degeneration and myofibrillar disorganisation and degeneration. There was increased collagen and mononuclear cell infiltration in the extracellular space in the later stages. This study has shown that the long term structural integrity of the atrial myocyte depends on an intact vagal innervation. The survival of the monkey after chronic bilateral vagotomy suggests that this nonhuman primate is a suitable model for functional studies of the parasympathetically denervated heart.     

Morpho-biochemical study of catecholamine metabolism in the myocardium of dogs with fibrillation and autolysis]

The balance of catecholamines (CA) and their metabolites in the canine heart during myocardial fibrillation and 1, 2, 3, 4, 5, 6 hours after death was studied. The fibrillation was caused by low myocardial electrostimulation. The comparative neuro-morphometric analysis of the CA-containing structures in 1 and 5 min of the fibrillation and the determination of the norepinephrine, its precursors and metabolites by HPLC-ED method was done. There was an increase of the myocardial norepinephrine (20%), 3-4-dihydroxyphenylethyleneglycol (25%) and decrease of the dopamine (50%) contents without any qualitative changes of CA metabolism. Autolysis leads to the successive decrease of the norepinephrine and dopamine contents without any qualitative changes of the CA metabolism too. These data suggest that autopsies could be used for the determination of the myocardial CA content and the qualitative characteristics of the CA metabolism before death in those who died suddenly.     

Electrically induced automaticity in ventricular myocardium

Pacemaker-like activity can be induced in ventricular myocardial fibers by small depolarizing currents. Diastolic depolarization occurs at physiologic temperatures and pH and is partially membrane potential dependent. It is slowed by inhibitors of Na and Ca currents and can be abolished by a combination of both types of inhibitors. Such automaticity is a potential source of arrhytmias which might be resistant to conventional antiarrhythmic drugs.     

Ultrastructure of the vocal muscle and its morphological differences from the myocardium]

A comparative ultrastructural investigation of the M. vocalis in mammals has been carried out. Morphological differences between the vocal muscle and cardiac tissue are reported; a distinct classification of the M. vocalis according to a typisation of skeletal muscle fibers is presented. In all species investigated (man, dog, cat, guinea-pig and rat) the general ultrastructure of the sarcomeres as well as their mitochondrial content and the innervation pattern allow to classify the M. vocalis as to belong to the "fast twitch (white) skeletal muscle fibers. A single innervation was found with large motor endplates containing numerous synaptic infoldings. Structural specializations known to be characteristic for cardiac tissue, e.g. intercalated discs, T-tubules at the level of the Z-band and nuclei in a midst postion of the muscle cell could not be observed. The m. vocalis, therefore, cannot be considered to have histologically any relationship with cardiac tissue. The vocal muscle is described as a special type of skeletal muscle very similar to the extraocular muscles. The electron microscopic findings are discussed with respect to current theories of phonation. The myoleastic theory of phonation can be favoured according to our ultrastructural results.     

Ultrastructure of cementum formation on partially formed teeth in dogs

Cementum crystals and matrix vesicles on the root surface of partially formed teeth in dogs were examined with a transmission electron microscope. Fine filamentous crystals were observed in the cementum calcifying fronts. The running pattern was mainly parallel to the root surface in the apical region and perpendicular to the root surface in lateral and coronal regions. Matrix vesicles were observed at the apical half of the periodontium, but not observed at the coronal region. These findings suggest that the parallel-arranged cementum would become the light-microscopic lamellar type and the perpendicular one the light-microscopic dense-line structure when fully developed. Moreover, cementum formation occurs due to two kinds of mechanisms: participation of matrix vesicles and secondary calcification (= additional cementogenesis).     

Biochemical and morphofunctional changes in the myocardium of dogs with occlusion of the terminal portion of the aorta

The occlusion of the terminal aortic region was experimentally induced in 48 dogs. It has been shown that myocardial lesions localized predominantly in the papillary muscles and subendocardially appear already 3 hours after the occlusion. The number of the affected cardiomyocytes increases and their size enlarges. The duration of ischemia directly correlates with metabolic disturbances: changes in the function of adenylate cyclase system, ion imbalance, damages in the energy metabolism. Metabolic and morphologic changes are accompanied by disturbances in the cardiac function manifested in the decrease of myocardial contractility.     

Ultrastructural alterations of the myocardium induced by doxorubicin

Morphologic changes in Doxorubicin (DXR)-induced cardiomyopathy are characterized by marked dilatation of the sarcoplasmic reticulum (SR). DXR was administered to New Zealand White rabbits for 5 or 8 weeks and the three-dimensional structure of the sarcotubular system in cardiac muscle cells from each rabbit was examined under a field-emission type scanning electron microscope (SEM) after removal of cytoplasmic matrices by the osmium-DMSO-osmium procedure. Five weeks after the initial injection of DXR, partial dilatation of the SR and damaged mitochondria with lysis of cristae were observed three-dimensionally. After 8 weeks, the three-dimensional structure of the SR showed extensive spherical ballooning which could be seen clearly in bold relief. Thus, we could directly visualize structural alterations of the sarcotubular system in DXR-induced cardiomyopathy using the SEM.     

Superoxide radical formation in diverse organs of rats with experimentally induced obstructive jaundice

Oxidative stress seems to be a cardinal feature of cholestasis, implicated in the pathophysiology of organ injury not only in the liver, but also in several extrahepatic tissues. The present study was designed to assess directly oxidative stress in vital organs of experimentally jaundiced rats by measuring the key oxidative stress marker superoxide radical (O2(*-)). Twelve male Wistar rats underwent laparotomy and were divided into two groups - group I (n = 6) sham operated, and group II (n = 6) bile-duct ligated. Ten days later, the O2(*-) formation rate was quantified in liver, intestine, kidney and heart of all animals. These measurements were done by application of a new ultrasensitive fluorescent assay for the in vivo quantification of O2(*-), which is based on the 1:1 molar stoichiometric reaction of O2(*-) with dihydroethidine (DHE, an O2(*-) trap) that results in the formation of the specific product 2-OH-ethidium. 2-OH-Ethidium was measured by fluorescence in rats' organs and its formation rate was converted to O2(*-) production rate. As compared to sham-operated rats, in jaundiced rats there was a significant increase of O2(*-) in the intestine (136%, P < 0.01), liver (104%, P < 0.01), and kidney (95%, P < 0.01), whereas there was no significant difference in heart O2(*-) levels. Superoxide radical may play an important role in the pathophysiology of cholestatic liver injury, intestinal barrier failure and renal failure, associated with postoperative morbidity and mortality in obstructive jaundice. On the contrary, O2(*-) and oxidative stress are possibly not implicated in the pathophysiology of hepatic cardiomyopathy.