Specific features of the morphology of the spinal nodes of homeothermal vertebrate animals in the comparative and anatomical series

Abstract

Scientific studies that reflect the evolutionary morphology of the nervous system, namely the spinal nodes of homoeothermic vertebrates, allow us to identify specific patterns, trends, and criteria that relate to the structural organization of the organ at the population and cellular levels of their organization. The evolutionary direction of research into the macro- and microstructure of spinal cord nodes provides an opportunity to investigate the patterns of formation of optimal relationships of their structural components: nerve and glial cells, capillaries concerning the level of development of the organism, and their motor activity. The article contains the results of the morphometric characteristics of the spinal nodes of warm-blooded vertebrates in a comparative aspect: class Aves – Birds (Gallus gallus, forma domestica L., 1758 – domestic chicken); class Mammalia – Mammals (Oryctolagus cuniculus L., 1758 – European krill, Canis lupus familiaris L., 1758 – domestic dog, Sus scrofa, forma domestica L., 1758 – domestic pig, Bos taurus taurus L., 1758 – domestic bull). When performing this work, complex research methods were used: anatomical, neurohistological, morphometric, and statistical. The morphological study of the structural components of the organs of the nervous system was studied on histological sections by the method of light microscopy following the requirements of the international principles of the “European Convention for the Protection of Vertebrate Animals Used in Experiments and for Other Scientific Purposes” (Strasbourg, 1986), a decision of the First National Congress on Bioethics (Kyiv, 2001), Law of Ukraine No. 692 “On the Protection of Animals from Cruel Treatment” (3447-IV) dated February 21, 2006. For histological examination, the newly selected material was immediately fixed in a 10% aqueous neutral formalin solution, with a fixation period of 30 days, followed by step-by-step embedding in paraffin. Using a sled microtome, histological sections with a thickness of 6–10 μm were obtained. The general histological structure and microstructural changes in histological preparations were studied under a light microscope MC (Micros Austria) at magnifications from 70 to 600 times. Photomicrographs of histological preparations were carried out using a CAM V200 video camera mounted in a Micros MC microscope. The work aims to conduct a complex morpho-functional study of spinal nodes in a comparative anatomical series of representatives of higher vertebrates. It was investigated that in phylogenesis, a particular structural and morphofunctional rearrangement of the central and peripheral nervous system organs, namely the spinal nodes, takes place. They differ in shape and size. It was established that the neurocytic organization of the spinal cord nodes of all species of animals studied is characterized by the presence of large, medium, and small nerve cells. Adaptation to various living conditions of animals was formed based on morphometric indicators (the volume of neurocytes and their nuclei), their morphological structures, the density of nerve cells per 0.1 mm2, the number of glial cells per 0.1 mm2, an indicator of nuclear-cytoplasmic ratio, degree of polymorphism chromatophilia. Nissl staining of histopreparations of spinal nodes of homoothermic animals showed that the neuroplasm of nerve cells contains well-defined depths of basophilic substance, compared with lower animals, as evidence of a higher degree of development in nerve cells of the protein-synthesizing apparatus. According to the method of impregnation of spinal cord nodes with silver nitrate in all studied animals, a different intensity of coloring of nerve cells is revealed: dark, light-dark, light, which is related to the peculiarities of species and age neuromorphology, the morphofunctional state of the nervous system and the type of higher nervous activity. The obtained morpho-functional features of the organs of the nervous system are essential not only for evolutionary and comparative morphology but also for developing issues of physiology, pathology, and treatment of peripheral nervous system diseases.