The aim of the study was to analyze the distribution of vimentin and alpha-smooth muscle actin (α-SMA) in the liver at various stages of regeneration after chemically induced fibrosis. Material and methods. Four experimental groups of animals were formed, consisting of white male rats representing different stages of liver recovery (no recovery, 4, 8, and 12 weeks of recovery) after chemically induced liver fibrosis, and a control group of intact animals, with 8 animals in each group. The dynamics of the distribution of intermediate filaments of mesenchymal cells were analyzed on preparations stained by immunohistochemical method using antibodies to vimentin and α-SMA. Results. After chemically induced liver fibrosis, a significant increase in the specific area of vimentin and α-SMA was observed, suggesting an important role of mesenchymal cells in the remodeling of the liver parenchyma. At the 4th week, the increased number of vimentin- and α-SMA-positive cells persisted, with these cells localized along fibrous septa and around blood vessels. At this stage, regenerative rosette-like structures consisting of vimentin- and α-SMA-positive mesenchymal cells surrounded by young regenerating hepatocytes were formed. By the 8th–12th weeks of regeneration, a decrease in the specific area of these markers was noted; however, vimentin- and α-SMA-positive cells were still present near portal triads and blood vessels, indicating ongoing regeneration processes. Conclusion. Vimentin and α-SMA play a key role in the formation of the fibrous matrix and the activation of perisinusoidal cells and myofibroblasts. The observed correlation between changes in vimentin and α-SMA indicates their coordinated involvement in the processes of fibrosis and regeneration.

Currently, worldwide research is being conducted on the development of new drugs for viscosupplementation therapy. However, there are a very few studies dedicated to the spatial distribution of proteoglycans in articular cartilage after the use of these drugs. Pulmonary surfactant proteins, which have lubricative functions similar to those of articular cartilage proteoglycans, are possible promising substances for viscosupplementation therapy. The aim of this study is to investigate the effect of a mixture of allogenic surfactant proteins (MASP) on the spatial distribution of proteoglycans and the expression of IL-1 in articular cartilage after their intra-articular injection. Morphological and immunohistochemical studies were conducted using antibodies to aggrecan and lubricin to assess the spatial distribution of proteoglycans, and antibodies to IL-1 were used to identify potential pro-inflammatory processes. Three weeks after intra-articular injection of MASP, the thickness of the articular cartilage and the relief of the joint surface did not change compared to intact rats. However, a decrease in the number of immunopositive chondrocytes to aggrecan in the intermediate zone of the articular cartilage and an increase in IL-1 were observed after MASP injection. The obtained data during the study can be used for further research on MASP in the conditions of experimental osteoarthritis.

In recent years, there has been increasing understanding that the molecular mechanisms of liver morphogenesis are also involved in the mechanisms of regeneration and pathogenesis of some organ diseases. Epithelial-mesenchymal and mesenichymal-epithelial transitions play a significant role in embryogenesis, morphogenesis and regeneration. The aim of the study was to characterize the localization and ratio of epithelial and mesenchymal cells in the liver tissue during embryonic and postnatal development of rat liver as a possible criterion for mesenchymal-epithelial transition. We have analyzed immunohistochemically the production and distribution of vimen-tin (mesenchymal marker) and cytokeratin 18 (epithelial marker) in the liver tissue of rats from day 1 0 of embryonic development to adults. The relative area of hybrid cells has determined by double immunofluorescence followed by morphometry. The study showed that as the liver develops, the content of the epithelial marker (cy-tokeratin 18) increases, while the production of the mesenchymal marker (vimentin) decreases, with the exception of the period from 1 to 17 days after birth, when the amount of vimentin increases. In addition, hybrid cells were found in the liver of embryos on days 10 and 17 of gestation, which synthesized both intermediate microfilaments - vimentin and cytokeratin 1 8. Thus, based on the ratio of vimentin and cytokeratin 18 in the process of embryonic and postnatal liver morphogenesis and the presence of hybrid cells allow make an assumption about the origin of a part of hepatocytes by mesenchymal-epithelial transition.

Epithelial-mesenchymal (EMT) and mesenchymal-epithelial (MEP) transitions play a significant role in the processes of embryogenesis, organogenesis and cell differentiation. The epithelial-mesenchymal transition also promotes the regeneration of damaged tissues, but in the case of its aberrant activation, it can initiate and aggravate the course of pathological processes such as fibrosis, metastasis, and carcinogenesis. In this review, we described the history of the study of these processes in the context of embryonic development, and also discussed the problems of terminology and different views on the concept of the determinism of the pathway of mature cells.

The article presents a literary review of domestic and foreign studies that reflect the possibility of using the biological model of Danio rerio (Zebrafish) in preclinical research. Data on the use of the toxicology Biomodel, determination of toxic and teratogenic effects of embryogenic substances, including certain medications, are presented. The use of zebrafish in modeling depression and stress, hypo- and hyperthyroidism, diabetes mellitus and in reproductive technologies is described. The proven effectiveness of the use of Danio rerio in preclinical studies and in modeling a number of human diseases is noted. The data of proteomic studies of the protein composition of cells are summarized zebrafish with the ability to determine the toxic effect at the molecular level.

The article provides an analysis of risk factors, pathogenesis and its molecular features, morphology and clinical picture of Merkel cell carcinoma (MCC) - a rare aggressive neuroendocrine tumor (NET) of the skin with a high frequency of recurrence and local metastasis. Modern methods of diagnosis and treatment, including surgical treatment. Clinical cases of CM are given.

The analysis of the structure of mortality from the toxic effect of phenobarbital in the city of Volgograd for the period 2014-2018 was carried out. It was revealed that the mortality rate as a result of taking phenobarbital for the indicated period more than doubled, especially among the working age population (35-50 years). When comparing this indicator with a similar one for the period 1994-1998 an increase in the number of lethal poisoning with phenobarbital by 26 % was noted. It was found that taking phenobarbital is often combined with other toxic substances (ethyl alcohol - in 36 % of cases, opiates and opioids - in 11 %, benzodiazepines - in 7 %, antidepressants and neuroleptics - in 6 %, etc.) In most cases, with phenobarbital poisoning, the presence of pathological signs of secondary cardiomyopathy, chronic ischemic heart disease, ventricular fibrillation, acute alveolar emphysema, edema of the substance and membranes of the brain, toxic encephalopathy, necronephrosis was revealed. The results obtained can be considered as additional data when conducting forensic medical diagnostics of acute phenobarbital poisoning and will be useful already at the stage of studying the primary documentation, as well as during the forensic medical examination of the corpse.

The aim is to evaluate the effectiveness of Stillavit in the treatment of dry eye syndrome (DES) and its effect on the density of conjunctival goblet cells and the functional parameters of tear production. Methods. There were analyzed treatment results of 18 patients (36 eyes) with DES at the age of 48 to 80 years (average 60.6 ± 1.3 years) including 17 women and 1 male before and after 1 and 3 months after Stillavit prescription. In all patients in addition to a standard ophthalmological examination the results of Schirmer I, Norn, as well as the LIPCOF test were evaluated and the density of conjunctival goblet cells was examined. Results. After 1 and 3 months there was a significant improvement in the results of the Norn test: from 5.17 ± 0.22 seconds to 7.18 ± 0.17 seconds which indicated an increase in the stability of the tear film. After 3 months there was a significant increase in the density of conjunctival goblet cells, improvement in the Schirmer sample: from 9.26 ± 0.89 to 11.7 ± 0.6 mm (t = 2.28, p < 0.05) and LIPCOF test (t = 2.18, p < 0.05) which indicated an increase in tear production and a significant decrease in the inflammatory process and edema of the conjunctiva. Conclusion. Treatment of DES with the use of Stillavit leads after 3 months to a significant increase in the density of conjunctival goblet cells, increases tear production and stability of the tear film.

The retinas of white male laboratory rats of two age groups (12 and 24 months; 10 animals in each group) subjected to chronic combined stress were studied. Animals were subjected to stress by simultaneous exposure to pulsatile light, loud noise, shaking, and movement restriction for 30 min/day for seven days. Controls consisted of retinas from intact rats of the same age (n = 20). Enucleated eyes from stressed and control animals were processed by standard histological methods; sections were stained by the Nissl method and with hematoxylin and eosin. Retinas from stressed animals of both age groups were characterized by decreases in the numbers of cells and deranged ordering of cell layers, most marked in the photoreceptor neuron and ganglion cell layers. Morphometric analysis demonstrated decreases in layer thicknesses and the numerical densities of cells in the retinas of stressed animals, both young (12 months) and old (24 months), as compared with control animals.

НАСЫЩЕНИЕ РОГОВИЦЫ РИБОФЛАВИНOM ПРИ ПРОВЕДЕНИИ КРОССЛИНКИНГА РОГОВИЧНОГО КОЛЛАГЕНАВ. П

The article describes the use of sodium azide at various concentrations for preservation and fixation of biological specimens. At a concentration of 0.5% the parathyroid glands retain their consistency shape, color and texture for two years.

A study of morphological and functional changes in neurons and glial cells of the cerebral cortex of white rats at the stages of aging and stress-induced neurodegeneration under experiment was investigated. It was found that the age-related neurodegenerative changes in somatosensory cortex neurons of white rats at the age of 30 months are characterized with pronounced signs of proteoinopathy and developing of apoptosis, which is enhanced by exposure to stress factors in clear violation of protein metabolism in the form of accumulation of intra- and extracellular amyloid.

We investigated the process of spontaneous liver regeneration after chemically induced experimental fibrosis. The obtained data about activity of some liver metalloproteinases, shown important role of each metalloproteinases at different stages of liver recovery.

A combination of primary hyperparathyroidism and acute pancreatitis is a rare pathology. Ectopic mediastinal parathyroid adenomas cause primary hyperparathyroidism in 5-10 % cases. The removal of adenoma cures the disease. A 71-old woman with acute pancreatitis and hypercalcemia was consulted. In the course of investigation the computer tomography revealed an ectopic mediastinal parathyroid adenoma. The tumor was removed via collar incision on the neck. Later, the calcium level and parathyroid hormone indicators became normal. Acute pancreatitis in combination with increased level of calcium in blood may indicate the presence of primary hyperparathyroidism. Precise preoperative diagnostics of the location of an adenoma using computer tomography of the neck can make surgical treatment successful.

The article provides information about the topography and morphology of the parathyroid gland depending on sex, age and ethno-territorial somatotypological features. Establishing of relations between shapes, sizes with topography and morphological parameters of parathyroid gland allow to predict the location of the parathyroid gland before operation, and therefore to optimize the performance of operations on the thyroid and parathyroid glands.

Morphological changes of white rats cerebral cortex neurons under stress-induced experimental neurodegeneration with amyloidogenesis. It is revealed that neurodegenerative disorders of somatosensory cortex neurons occurs with apoptosis of neurons and with violation of protein metabolism in the form of intraand the extracellular amyloid accumulation.