The aim of the study was to investigate morphological changes in neurons, glia and synaptic terminals in cytoarchitectonic fields CA1 and CA3 of the hippocampus in white rats after severe traumatic brain injury (STBI).

   Material and methods. This experimental study involved outbred adult white Wistar rats. STBI (main group, n = 30) was simulated under anesthesia (Zoletil-100) on the tailor-made device. Intact animals (n = 6) were used as controls. Morphological assessment of the hippocampal nervous tissue (in fields CA1 and CA3) was carried out using light microscopy (staining with hematoxylin and eosin, thionin according to Nissl), immunohistochemical reactions for synaptophysin (p38), Caspase 3, GFAP, and morphometric investigation techniques (ImageJ 1.53 program) in animals of the control group and in experimental animals in 1, 3, 7, 14, 30 days after STBI. Statistically hypotheses were tested using nonparametric tests (Kolmogorov–Smirnov, Kruskal–Wallis, Mann–Whitney, Wilcoxon, Spearman tests) in the Statistica program. 10.0.

   Results. In a day after STBI, there were noted degeneratively altered dark neurons, shadow cells, small foci of neuron prolapse, pronounced manifestations of edema-swelling in the perikarya and neuropil. Coagulative-ischemic mechanisms of neuronal death prevailed, structural and immunohistochemical signs of apoptosis activation (Caspase 3 in the perikarya) were detected in sporadic cells of the field CA1. In the late period of the study (in 30 days), hydropic changes, chromatolysis with cytoplasmic clearing, hyperchromia without and with homogenization of neuronal structures persisted. An increased neuroglial index was distinctive. Statistically significant differences in the main morphometric parameters were revealed between segments and terms. The total number density of neurons decreased by 43.8 % in CA1 and in CA3 by 22.0 % in 30 days after injury; a significant (20–40 %) deficit of neuropil synapse terminals remained. Thus, the compensatory-restorative reorganization of the hippocampal neuronal networks occurred combined with its structural and functional insufficiency. Probably, Caspase 3 was crucial in implementing neuroplasticity.

   Conclusion. Post-STBI diffuse-focal pathomorphological changes were revealed in CA1 and CA3 cells of the hippocampus. An increased relative content of glial cells indicated the realization of sanogenesis of the nervous tissue. Reorganization of interneuronal connections occurred during 30 days of observation, caspases might be participants of this process.

   The effect of altered gravity on the digestive system is one of the challenging issues in space biology and medicine. The study of the effect of weightlessness on the mast cell (MC) functioning in the gastrointestinal organs is determined by their multifunctionality and participation in the developing adaptive and pathological processes.

   The aim of the study was to investigate the morphofunctional state of MCs in the stomach membranes of Wistar rats during 14 days of ground-based simulated weightlessness conditions and in a 3-day recovery period.

   Material and methods. The experiment involved 3 groups of Wistar rats: control, experimental – exposed to antiorthostatic suspension – and a 3-day-recovery group, 7 animals each, respectively. Identification of MCs was carried out using May-Grunwald staining with additional staining with Giemsa solution and immunohistochemical tryptase detection. The results obtained were statistically processed with SPSS 13 using parametric and non-parametric criteria.

   Results. A significantly increased number of metachromatic MC population was found only in the mucosa in animals of the antiorthostatic suspension and 3-day-recovery groups compared to the vivarium control. There was a sharp decrease in degranulating forms of MCs in the submucosal
coat in animals of the 3-day-recovery group compared to the control. A significantly increased number of degranulating forms of MCs was revealed in the muscle membrane in animals of the antiorthostatic suspension group. Immunohistochemical staining of MCs with antibodies to tryptase, in contrast to staining for metachromasia, allowed identifying a significant representation of tryptase-positive cells in the gastric mucosa in animals of the 3-day-recovery group.

   Conclusion. The results obtained support gravisensitivity of certain structural components of the stomach, and also evidence MC and their secretome participation in the developing adaptive responses to the effects of altered gravity both at the cellular and tissue levels.

   Due to the prevalence of thyroid diseases among women, there is a need for a detailed study of the morphometric parameters of this endocrine organ in diverse age groups.

   The aim of the study was to investigate the linear sizes and the thyroid gland shapes using sectional method and intravital sonography in women of mature age residing in St. Petersburg.

   Material and methods. The ultrasound diagnostics was used to examine thyroid glands in 117 women of mature age. The exclusion criteria were neck surgery, thyroid nodules and endocrine system diseases. All women were divided into age groups according to the scheme of age periodization of human ontogenesis adopted in 1965. There were 42 thyroid glands obtained from the women died at the mature age, whose fatal outcome was not associated with the pathology of the endocrine system or the thyroid gland; they were allocated into a separate group.

   Results. Significant differences were registered in the thickness of the left lobe of the thyroid gland in women of the first and second adulthood periods; there was also detected a significant predominance of the size and volume of the right lobe over the left one. Cluster analysis, relying on the thickness of the isthmus of the thyroid gland and the symmetry of its lobes, allows differentiating three shapes of the thyroid gland: “butterfly-shaped”, semilunar and indefinite.

   Conclusion. The asymmetry of the thyroid lobes is a typical feature of this organ of the endocrine system at the studied age periods in mature women. When determining the shape of the thyroid gland, dissecting and morphometry are more informative options than ultrasound examination. To compare the findings on the shape of the thyroid gland obtained by various researchers, it is necessary to standardize the technique and apply a unified classification of the thyroid gland shapes.

   Exhausting physical activity leads to sarcomere overstrain, destruction of the cell membrane, hydrolysis of structural proteins, thus, resulting in irreversible damage to muscle fibers. Allogeneic biomaterial (AB) is applied to regenerate various tissues and organs.

   The aim of the study was to identify morphofunctional features of the skeletal muscle tissue after physical exertion and under AB application.

   Material and methods. This experimental study involved male Wistar rats. Anaerobic physical exertion was simulated using the Porsolt test with a load equal 10 % of the body weight for 30 days. After training, animals of the main group (n = 10) were injected AB suspension: 4 ml of a 0.2 % solution into the muscles of the fore and hind limbs totally. Animals of the control group (n = 10) received physiological saline into similar zones. Tolerant load was investigated in 5 and 21 days after injection. Then the animals were withdrawn from the experiment, and muscles of the hind limbs were studied histologically, the total number, the average cross-sectional area of muscle fibers, and the number of necrotic fibers were measured.

   Results. In 5 and 21 days animals from the control group manifested dystrophic changes in muscle fibers: type III, IV contractures, microcirculation disorders, mosaic necrosis of muscle fibers, inflammatory cell infiltration, and a decreased tolerant load. In 21 days fibrosis was detected. The AB introduction provided rhabdomyogenesis as soon as in 5 days. Inflammatory cell infiltration decreased, the polygonality of muscle fiber profiles was restored, and edematous phenomena were leveled. There was hyperplasia of muscle fibers, a decreased number of necrotic muscle fibers, inhibited fibrosis, and an increased tolerant load. AB further biodegraded.

   Conclusion. AB contributed to the reduced manifestations of dystrophic changes in muscle fibers, strengthened actoprotective mechanism, and restored physical activity in the early stages.

   Benign breast papilloma is considered a lesion with uncertain malignant potential and, in most cases, it is recommended to be removed. The molecular pathology of ductal hyperplasia of the epithelium in fibroadenomatosis is under intensive study, but at the moment there is no strong enough evidence of diagnostically significant causes of its occurrence.

   The aim of the study was to determine the presence of E6 and L1 proteins of the human papillomavirus (HPV) in biopsy specimens of breast tissue in fibroadenomatosis.

   Material and methods. Viral proteins were detected using an immunohistochemical method with primary polyclonal antibodies to the E6 protein of HPV types 16 and 18 and capsid protein L1 of HPV types 1, 6, 11, 16, 18, and 31.

   Results. In biopsy specimens with fibroadenomatosis of the mammary gland, ductal hyperplasia without atypical proliferation of luminal epithelial cells (NOS 65 %) was most often detected, while atypical ductal hyperplasia (ADH) was detected in 35 %. Viral proteins E6 and L1 were found in more than 90 % of biopsies, with no significant difference between the synthesis of these proteins depending on the type of epithelial proliferation. There was a moderate correlation between the level of intensity of the capsid protein L1 and proliferation marker Ki-67 syntheses in biopsies with atypical epithelial proliferation. The simultaneous presence of the viral proteins E6, L1 synthesis and the index of Ki-67 cell proliferation in breast tissues with fibroadenomatosis increased under transition of epitheliocytes from typical proliferation to atypical ductal hyperplasia.

   Conclusion. As demonstrated, there is a correlation between the presence of HPV types 16/18 and atypical changes in the epithelium in breast fibroadenomatosis. The analysed intensity of the E6, L1 and Ki-67 protein syntheses and their simultaneous expression in tissues in benign tumors allows evaluating the risk of epithelial cell malignancy.

   The study of morphometric parameters of the thoracic diaphragm in diverse body constructions is of applied relevance in thoracic and abdominal surgery.

   The aim of the study was to investigate regional morphometric parameters of the thoracic diaphragm in diverse body constructions.

   Material and methods. The study involved 40 specially embalmed corpses (with preserved tissue elasticity), aged 35-75 when dying. To assess the morphometric parameters of the diaphragm, there was tailor-made an organocomplex represented by the abdominal cavity covered by an intact diaphragm. Longitudinal, transverse dimensions, the area of the diaphragm and its parts were investigated.

   Results. The analysed morphometric features allowed specifying that in extreme body constructions, there were considerable statistically significant differences in the morphometric parameters of the diaphragm and its parts. It was established that the largest area of the diaphragm, central tendon, costal part and its pericardial surface were observed in people with a brachymorphic body construction; the highest statistical significance was observed between extreme body constructions. The ratio of the tendon part to the total area was also the largest in the brachymorphic form, and the smallest in the dolichomorphic form. There were specific morphometric parameters typical of all types of body constructions: the ratio of the muscular and tendon parts of the diaphragm, the depth of the pleural sinuses, and the areas of the weak points of the diaphragm. The largest linear dimensions of all parts of the diaphragm were recorded in individuals with a brachymorphic body construction. On the contrary, people with dolichomorphic body type had the lowest values. However, the diaphragm domes were the highest in individuals with a dolichomorphic form, and the shortest in those with a brachymorphic form.

   Conclusion. The study of the morphometric parameters of the thoracic diaphragm allowed recording the major linear dimensions and areas of definite parts specific for all body constructions. The results obtained can be introduced into clinical practice to plan surgical interventions on the upper floor of the peritoneal cavity, including diaphragmatic peritonectomy.

   According to the latest data, up to 80 % of people in the world are carriers of Demodex mites. Light microscopy is used to detect mites during standardized superficial skin biopsy, skin scraping, etc. The study of histological preparations of the skin affected by Demodex helps analyse morphological changes in the skin structures, specify the structure and localization of insect units.

   The aim of the study was to analyse the morphofunctional changes in human skin affected by Demodex mites.

   Material and methods. The authors studied material from 16 male volunteers aged 26–74 years. All participants had signs of dermatitis. Pathological changes in the skin areas affected by Demodex mites and in the normal skin were analysed and compared. The study participants were punch-biopsied and then the preparations were stained with hematoxylin and eosin according to the standard technique. Skin layers were morphometrically detected, the coefficient of sclerosis of the sebaceous glands, the degree of destructive changes in the collagen fibers of the dermis and presence of leukocyte infiltration were also determined.

   Results. The histological picture of the skin affected by Demodex mites demonstrated hypertrophy and destruction of the epidermis layers. The presence of “capsules” with Demodex mites and their metabolic products was manifested as hyperplasia of the epithelium and sebaceous glands. The inflammatory process caused by Demodex mites led to the formation of inflammatory mononuclear infiltration and disruption of the structure of collagen fibers, changes in the lumen of the capillaries, partial loosening of their basement membrane. In the sebaceous glands, processes of sclerosis, shape changes, hypertrophy of the walls, atrophy of sebocytes and disruption of the basement membrane were registered.

   Conclusion. Demodex mites have a pronounced effect on the morphological structure of the histo-hematic barrier of the skin. This is manifested in the impaired integrity of its basement membranes, and in the pathology of the microcirculatory blood vessels. Histological preparations revealed multiple leukocyte infiltrates and thinned collagen fibers of the dermis at the sites of Demodex mites localisation.

   The aim of the study was to reveal associations between the number of functioning microvessels and formation of adrenergic control (nerve endings containing catecholamine) of the dental pulp in children and adolescents of Udmurtia during the period of permanent teeth eruption.

   Material and methods. The study included neurovascular bundle of the pulp of teeth extracted for medical reasons at the age of 5 to 14 years. At the light-optical level, the number of functioning capillaries was counted; an electron microscopic technique was used to qualitative assess the microvascular bed. Identification of catecholamines and counting the number of adrenergic nerve endings were performed histochemically using glyoxylic acid.

   Results. The process of permanent teeth eruption is accompanied by an intensively increased number of functioning capillaries and an increased density of adrenergic nerve endings. The number of functioning microvessels increases significantly (by 3.36 times) during childhood (from 5 to 9 years); the number of capillaries stabilizes in adolescence. The increased number of nerve endings by the end of the childhood period (9 years) is 45.2 ± 12.4 % compared with the age of 5 years. Notably, adrenergic nerve endings modify qualitatively: a pronounced variety of mediatorcontaining forms is replaced by their isomorphic phenotype. With age, predominant distribution of nerve endings along the vessels of the microvasculature tends to increase.

   Conclusion. Active formation of the microvascular bed during the eruption of permanent teeth is accompanied by an age-dependent increase in the density of localization and qualitative restructuring of adrenergic nerve endings, which provides full catecholaminergic control from the sympathetic nervous system.

   This paper presents a literature review evaluating virtopsy options, its development over time and the scope of application nowadays. To analyze the literature sources, we searched for the keyword “virtopsy” in Scopus, Web of Science, Medline, PubMed, and RSCI databases for the period 2006–2022, the results included 199 sources. Of these, 73 publications including original and review papers were selected for review. It is known that diagnosis verification and therapy correction are largely possible only thanks to the work of pathologists. The coincidence of the post-mortem diagnosis with the lifetime diagnosis opens up the possibility to optimize the course of therapy in similar cases. The literature analysis allows us to conclude that the level of imaging accuracy and frequency of successful interpretations of post-mortem radiological examinations have increased significantly, the fact being associated both with an improved quality of X-ray optical and scanning equipment, and formation of a relatively extensive database containing previously obtained findings. Thus, virtopsy is currently a powerful auxiliary tool applicable in post-mortem diagnosis. The combined use of classical autopsy and virtopsy can increase the accuracy of diagnosis, which, together with digital data processing and storage tools, will bring the work of specialists to a new level of interdisciplinary interaction.

   The paper discusses diverse aspects of the concept of epithelial-mesenchymal transition and compares the basics of this concept with the classical concepts of tissue biology. The idea of the epithelial-mesenchymal transition was first suggested by Elizabeth Hay (1927–2007) in 1968 based on the analysis of tridermogenesis in the development and growth of the avian embryo. In the late 80^s – early 90^s of the twentieth century, the concept of epithelial–mesenchymal transition won supporters-pathomorphologists in our country who applied the concept to explain mechanisms of multiple pathological processes. The controversial issue arises: to which extent the concept of epithelial-mesenchymal transition is validated. It should be noted that a number of its basic principles are open to question. Thus, it is hardly correct to consider the cells of the ectoderma as epithelial cells, since they do not express immunohistochemical markers of epithelial tissue cells. That is, cells with a true epithelial phenotype are not yet represented at this stage of embryogenesis. It should also be taken into account that all evidence for the epithelial-mesenchymal transition is based on indirect immunocytochemical findings (decreased expression of epithelial markers, increased expression of markers of mesenchymal tissue genesis). Moreover, saying about the “epithelial-mesenchymal transition” specialists mean cell populations and not specific cells, which is hardly the same. All the above allows arguing the existence of the epithelial-mesenchymal transition; this issue needs additional research and more fact-based support.

   Since the beginning of the COVID-19 pandemic, there have been a number of studies related to the impact of SARS-CoV-2 on the course of pregnancy and fetus condition. As observed, the placentas of women who have had a new coronavirus infection often contain more villous agglutination and subchorionic thrombi than placentas in SARS-CoV-2-negative women. To date, several isolated publications have reported clinical cases of fetal death in mothers infected with coronavirus infection. The authors have made an assumption on the association of adverse outcomes with placental lesions.

   The aim of the study was to analyse a clinical case of a moderate-course new coronavirus infection in a pregnant woman at a long gestation period who underwent an antenatal fetal death, and evaluate the features of placental histopathology and their impact on adverse gestational outcomes.

   Material and methods. The authors have analysed Russian and international research publications from various sources, including eLIBRARY.RU, CyberLeninka, PubMed databases etc. and, considering the data obtained, investigated a clinical case of intrauterine fetal death in a pregnant woman infected with SARS-CoV-2. The placenta was studied in accordance with the clinical recommendations of the Russian Society of Pathologists "Rules for placental pathological and anatomical examination" and the international classification of placental lesions (Amsterdam, 2015).

   Results. The results obtained support the association between acute diseases of the upper respiratory tract and developing severe hemodynamic disorders in the "mother-placenta-fetus" system in pregnant women infected with SARS-CoV-2. Systemic inflammation associated with new coronavirus infection appears to be one of the mechanisms for developing placental disorders.

   Developmental anomalies of the aortic arch and its large vessels can be accompanied not only by hemodynamic disorders, but also affect the functions of internal organs. This report analyzes the case of an autopsy finding of the right aberrant subclavian artery in an 80-year-old patient, which was clinically manifested by the development of dysphagia and cachexia. An autopsy revealed the absence of the brachiocephalic trunk, which normally originates from the arch of the authors, as well as an abnormal origin of the right subclavian artery from the posterior surface of the aortic arch, 1,1 cm to the left and distal to the orifice of the left subclavian artery. The proximal segment of the abnormal vessel, up to 1,0 cm in diameter, was located between the spinal column and the esophagus, leading to its compression.