Mitochondrial ultrastructure was studied in endomyocardial biopsies of patients with different forms of cardiomyopathy and arrhythmias so as in animal models of alcoholic and adriamycin cardiomyopathies. Alterations in ultrastracture of mitochondria, their arrangment and quantity per cell were obtained. Both mitochondria accumulation near the nucleus and migration into the nucleus were found in patients and in experiments. Authors propose that mitochondria are the central echelon in pathology development and progress.
A combined morphophysiologic study of the rat heart sinus node pacemaker cells showed this conductive formation to comprise true and latent pacemakers. The latent pacemaker cell population is heterogeneous in terms of electric activity as well as morphology. The electrophysiologic and morphologic characteristics of latent pacemaker cells undergo a smooth change from centre to periphery of the sinus node. No criteria could be identified for accurate correlation of morphologic and electrophysiologic characteristics of sinus node pacemaker cells, not even by intracellular labelling of cardiomyocytes that belonged to definite electric activity types. The differences between these cells are assumed to be largely related to specific membrane structures, such as ion channels and receptors.
The authors studied the action of the physiological concentrations of catecholamines on the major parameters of the action potentials of the true pacemakers, using a graphic analysis of their electric activity at the intracellular microelectrode lead. Desympathization was carried out with the help of daily intraperitoneal injections of guanethidine solution for six weeks. Noradrenaline and dopamine have a similar effect on the electrogenesis of the pacemakers by decreasing a relative threshold of auto-stimulation and decreasing the steepness of the potential growth in phase 4 on the curve of the action potential. Pharmacological desympathization leads to the development of hyper-reactivity of the true pacemakers to noradrenaline and dopamine and triggers off changes in the regulation of the electric activity of these cells by catecholamines.
Ultrastructure of the cells generating the action potential, specific for the pacemaker of the sinuous-auricular node has been studied. The cells are labelled with lanthanum chloride by means of the registrating microelectrode. Two types of pacemakers are revealed. The cells of one type contain specific auricular granules, while those of the other type do not contain them. The pacemaker-cells of the sinuous-auricular node have some peculiarities in the structure of the contractile apparatus, mitochondria, Golgi complex, intercellular contacts owing to which their morphological identification is possible.