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Quantitative neurohistochemical study of adrenergic elements of the myocardium and the adrenal medulla in victims of sudden death revealed an unequal and focal depletion of catecholamines attributable to prior pathologic processes in the myocardium. The greatest changes in cardiac innervation were found in cases of acute myocardial infarction and alcoholic cardiomyopathy, and the adrenergic plexuses were better preserved in cases of coronary heart disease without focal myocardial changes. Ultrastructural study of cardiac innervation in patients who died suddenly showed more pronounced changes in the nerve plexuses of the sinus node than in the perinodal nerves of the working myocardium. The changes in coronary artery innervation were usually related to the severity of stenosis due to fibrous plaque; desympathization of the vessels and the adjoining myocardial zone was also found in cases with 50% or greater occlusion of the lumen. The bulk of chromaffinocytes were depleted and weakly luminescent in the adrenal glands of patients with acute myocardial infarction who died suddenly. In contrast, chromaffinocytes with moderate and bright luminescence were prevalent in cases of sudden death with scarring from previous myocardial infarction and with alcoholic cardiomyopathy. Ultrastructural and histochemical examinations demonstrated that changes in the neurons of sympathetic ganglia increased with more severe atherosclerotic lesions of the aorta and with greater changes in the vessels supplying the ganglia. In experiments on rabbits and dogs, both coronary artery ligation and electrostimulation produced cardiac fibrillation followed by a local increase in luminescence intensity of the myocardial nerve plexuses when their density remained high. Chemoreceptors located along the coronary vessels and pulmonary artery in dogs included small cells with bright fluorescence and adrenergic nerve fibers.

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The majority of the ganglia of the vegetative nervous system are derivatives of the neural crest (NC) (ganglionic layer), a temporary formation consisting of cells which have migrated from the dorsal divisions of the closing neural tube [i, 7, 15, 17]. In addition to the neural ganglia, the melanocytes, the connective tissue formations of the heart, and several tissues of the head [13,15], are also classed as derivatives of the NC.The properties of the NC of the truncal division have been studied in greatest detail [15,16,24,26,34,35]; cells migrate from this division along the ventromedial (mainly cells of neuronal determination) and the dorsolateral (the future melanocytes) pathways by means of homo-and heterotransplantation.It has been proven that the direction of migration and the subsequent differentiation of cells into sensory (spinal ganglia) and cholinor adrenergic motor neurons are determined primarily by local factors of the microenvironment, and are not strictly programmed genetically.A large number of investigations have been devoted to the mechanisms of the emergence of cells from the neural tube and to the subsequent goal-directedness of their migration to the sites of definitive location [2,4,21,25]. Fundamental significance has in the process been ascribed to the extracellular matrix which is rich in glycosaminoglycans, collagens, and fibronectin [6,14,29].The preponderant portion of the investigations into the NC, including the electron microscopic investigations, has been carried out on chick embryos. Ruthenium red has only been used in several studies, and only for the study of the extracellular matrix [ii, 23].The purpose of the present study is the investigation of the ultrastructure of the NC cells of the truncal division up to the point of their exit from the neuroepithelial layer and in the process of migration.Material and Methods. The study was carried out on nine daylold white rat embryos. The first day after mating was considered the zero day of the pregnancy. After extraction from the cavity of the uterus, the embryos were fixed whole by submersion in 3% glutaraldehyde in a 0.i M cacodylate buffer (pH 7.3). Prefixation, dehydration, and embedding in Eponaraldite were carried out by the traditional methods. In order to identify the components of the extracellular matrix, and to analyze the glycocalyx of the NC cells, the embryos were fixed with ruthenium red [19]. Before the preparation of the ultrathin sections, semithin sections were made up which were stained with toluidine blue for orientation. The ultrathin sections were obtained on an Ultracut Om-U3 ultramicrotone, were contrasted with uranyl acetate and lead citrate, and were examined in an EMV-100B electron microscope.Investigation Results and Discussion. The neural tube in the nine-day-old white rat embryos is found in the stage of formation, the closing neural groove is located in the caudal portion of the truncal division; the neural tube is already closed more cranially, and the ectoderm is separated from it by a space (Fig...