The scientific article presents the results of investigating the spinal cord`s morphology of a domestic bull (Bos Taurus). Data on the histo- and cytostructure of the spinal cord are given according to the results of histological, neurohistological, and morphometric studies. For their implementation, the selected material (spinal cord n = 8) was subjected to fixation in 10–12 % neutral formalin solution, followed by pouring into paraffin. Histological sections were made from paraffin blocks on a sliding microtome MS-2 with a thickness of not more than ten μm. Staining of sections with hematoxylin and eosin, according to Van Gieson's methods, as well as neuro-histological methods of impregnation of nerve tissue with silver nitrate according to the Bilshovskym-Gross method, was used for the morphometric studies, investigating the morphology of the cell, conducting and obtaining the review histological preparations. The histostructure of the spinal cord, the localization of neurons in the gray matter, and morphometric studies of structural elements were examined on histological specimens by light microscopy. The entire experimental part of the research was conducted following the requirements of the international principles of the "European Convention for the Protection of Vertebrate Animals for Experimental and Other Scientific Purposes" (Strasbourg, 1986). The spinal cord, medulla spinalis, an organ of the central nervous system of vertebrates, is located in the spinal canal. The spinal cord is protected externally by soft, arachnoid, and hard meninges. The space between the membranes and the spinal canal is filled with cerebrospinal fluid. It is well known that groups of multipolar nerve cells with the same functional value form the nuclei of the gray matter of the spinal cord. According to the results of our histological studies, a pronounced differentiation of nerve cells, which have different shapes and sizes. Among them are large, medium, and small nerve cells. The shape of nerve cells is different, which, in turn, depends on their location in certain areas of the gray matter of the spinal cord and the size of the cell. In general, there are multifaceted, stellate, spindle-shaped, elongated, rounded, and oval neurons. Small nerve cells have an oval or round, less often – irregularly rounded shape, medium – round, oval, spindle-shaped. Large nerve cells are dominated by a multifaceted shape with distinct processes. The nuclei of large nerve cells, in most cases, have a rounded shape, less often – oval, mostly in the center of the cells, seldom – eccentrically. According to the results of morphological studies, it is noted that the neurons of the gray matter of the spinal cord have different shapes and sizes. Consequently, in the gray matter, small cells are the highest quantity (47.91 ± 0.32 %) of the total number of nerve cells. The second place is occupied by average neurons (33.70 ± 0.46 %). The large cells are detected in the smallest amount (18.37 ± 0.50 %).

From among a great number of digestive system diseases in domestic animals there is pancreatitis which is caused by an early zymogenesis in the acinar cells. The problem of studying the structural organization of a pancreata in sick cats is topical because of a progressive spreading of pancreatitis in domestic animals. Thus, the purpose of the research was to study out the morphological changes of cats pancreata under acute pancreatitis. Working with vertebrate animals we were guided by “European Convention for the Protection of Vertebtate Animals used for Experimental and other Scientific Purposes” (Strasbourg, 1986). The results of the histological examination of cats pancreata under acute pancreatitis show some pathological changes both in endocrine and exocrine pancreas. Such changes were manifested in necrosis of exocrine pancreatitis as well as in spreading and swelling of acinar space, that testified to the infancy of an inflammatory process. Some dystrophic changes, followed by karyolysis, were found in the focus of tissue nicrosis. Pancreatocyte cytoplasm was cloudy, its basal and apical zones were obscure, clearly defined interstitial tissue swelling was found between the particles and unequal swelling was found inside the particles. Intercellular space was exaggerated. Morphometrically in a group of sick animals was detected an increase in specific weihgt of stromal component (р<0,05),which equalled 22,44±0,24 %, in a control group it equalled 17,78±0,15 %. Some hemorrhage and distrophicvally changed hormone- active cells as well as nonregular distribution of cells were detected under a histological examination of Langerhans islets. In most islets the cells had swelled vacuolar cytoplasm. While analyzing the morphometric indices it was stated that the cats exocrine pancreas under acute pancreatitis was 1.12 as large and occupied 48258,05±135,07 mkm2, (97,88±0,05 %). The cats endocrine pancreas under this pathology occupied 6858,85±315,05 mkm2, (2,12±0,05 %). In cats of a control group this index equalled 6784,71±285,04 mkm2 (1,95±0,06 %). The diameter of sick cats acinus as well as of Langerhans islets equalled respectively 31,85±0,05 and 71,81±2,45 mkm, which reliably (р<0,001) was 1.13 and 1.15 as large. In clinically healhty cats these indices are 28,12±0,11; 70,20±2,48 mkm.

The study aimed to establish the parameters of chronic toxicity of the newly developed drug based on phosphodiesterase-3 inhibitor and ethylmethylhydroxypyridine succinate in experiments on laboratory animals. The analysis was performed on white sexually mature young male Wistar rats weighing 170–185 g. Four groups of white rats were formed. The first experimental group was administered Bendamine based on a phosphodiesterase-3 inhibitor and ethylmethylhydroxypyridine succinate at a therapeutic dose. Rats of the second experimental group were injected with the experimental drug in a 5-fold dose. Rats of the third experimental group were administered the drug in a 10-fold dose. The fourth group served as control. The study of chronic toxicity of Bendamine in white rats indicates that long-term 30-day administration in therapeutic doses or 5-fold dose does not cause clinical signs of poisoning, as evidenced by the physiological limits of fluctuations in the studied morphological and biochemical parameters of blood rats. Prolonged administration of Bendamine to rats in a 10-fold dose is accompanied by a slight suppression of the body's physiological state, as indicated by a decrease in total erythrocytes and hemoglobin by 10.1 % against an increase in white blood cells by 59.8% (P < 0.001). In addition, there was a decrease in the functional state of the liver, as evidenced by a probable reduction in total protein by 8.0% and urea – by 13.5 %, as well as an increase in ALT, AST, and alkaline phosphatase by 31.6 %, 7.4 %, and 53.9% respectively. Probable changes in the coefficients of liver and spleen mass have been established. When administered intramuscularly to rats with the drug Bendamine for 30 days, the macroscopic and microscopic structure of the studied internal organs is preserved in all groups of animals. The second experimental group revealed reversible moderate histostructural changes in the liver and kidneys. In rats treated with ten times the therapeutic dose of the drug, histologically found hemodynamic disorders and alterations in dystrophic nature, mainly of protein origin, with focal localization in the parenchyma of the liver, kidneys, and myocardium, which in most cases are reversible and result from the compensatory response. Macroorganism on the introduction of a high dose of the study drug.

In the article, following the results of complex methods (anatomic, histologic, organometric, histometric and statistical) researches are shown the features of morphological structure and morphometric parameters of the lungs of mature rabbits. It was found out, that macro- and microscopic architecture of rabbit lungs has similar histoarchitectonics, inherent in other species of farm animals of the class "mammals" and the characteristic features of morphological structures. Lungs in clinically healthy rabbits structurally reflect the shape of thoracic cavity and gradually expand ventrally. Subsequent to the results of performed organometry, the absolute lung mass of mature rabbits is 18,05±1,32 g, relative 0,624±0,013 %. The Right and left rabbit lungs are surrounded by pleural sacs (right and left): in rabbits pleural spaces of the right and left lungs are not connected. According to morphological and organometric investigations the rabbit lungs are relating to VIII type – the reduction of the superior lobe of left lung is observed, consequently right lung is more developed than left ( the length of right lung is 6,40±0,45 mm, the width – 3,54±0,30 mm, the thickness – 3,28±0,30 mm; the length of left lung is 6,84±0,40 mm; 4,18±0,30 mm and 1,52±0,30 mm relatively) and the coefficient of lung asymmetry (right to left) according to their absolute mass is 1.16. Although, rabbit lungs have dilatated base and superior. Right lung divides into four lobes – cranial (the superior), cardio, diaphragmatic and ancilla, left one divides into three lobes – the reduced superior, cardio and diaphragmatic. Histoarchitecture of lungs is formed by lobes of the lungs, that are separated by connective tissue, which contains blood and lymphatic vessels. Lung parenchyma is created by airways and respiratory divisions that blood vessels accompany to. Respiratory lung parenchyma is formed by respiratory bronchioles, alveolar ducts and alveolar saccules, in which walls the alveolus are located and shape the alveolar tree. According to the analysis of histometry results, respiratory (breathing) lobe of lungs of experimental rabbits is 52,3± 0,62 %, connective tissue base – 69,6±1,27 %, and the average volume of alveolus (small, middle and big) is equal to 42,3±4,35 thousand mkm3.

Acute pancreatitis is a common non-communicable pathology in dogs, the untimely diagnosis and treatment of which is lethal (27-58% of cases). One of the most common medical tests for acute pancreatitis is to determine the concentration of triglycerides and other fractions of blood lipids. The purpose of the study was to investigate changes in lipid fractions and other biochemical parameters in dogs with acute pancreatitis. For the experiment, two groups of dogs of 10 individuals each were formed. The control group included healthy animals, the experimental group – dogs with acute pancreatitis. It was found that in dogs with acute pancreatitis, the concentration of triglycerides increased by 67% compared with healthy individuals. Cholesterol and phospholipid concentrations also increased by 23 and 9%, respectively. Inflammatory processes in the pancreas led to the development of cytolytic processes in its acini, as well as hepatocytes of the liver, as indicated by increased activity of indicator enzymes ALT, AST, LF and bilirubin. In addition, in sick dogs, the protein-synthesising function of the liver was impaired: a reduced proportion of albumin was registered against the background of increased total serum protein. Acute pancreatitis leads to a decrease in insulin synthesis, which is manifested by hyperglycaemia – in sick dogs, glucose levels are probably twice as high as in healthy animals. In pancreatitis, the violation of digestion and absorption of nutrients caused by intensive use of high-energy compounds (in particular, creatine phosphate) and an increase in creatinine (3.8 times). At the same time, the catabolism of proteins increased and the products of their intermediate and final metabolism – ammonia and urea – accumulated (by 60 and 57%, respectively), which is a sign of reduced filtration capacity of the kidneys. In addition, in acute pancreatitis within the physiological norm, the concentration of calcium decreased, and inorganic phosphorus – increased