[Specific features of the pathology of the respiratory system in SARS-CoV-2 (Coronaviridae: Coronavirinae: Betacoronavirus: Sarbecovirus) infected Syrian hamsters (Mesocricetus auratus)].

INTRODUCTION: Verification of histological changes in respiratory system using Syrian (golden) hamsters (Mesocricetus auratus) as experimental model is an important task for preclinical studies of drugs intended for prevention and treatment of the novel coronavirus infection COVID-19.The aim of this work was to study pathological changes of pulmonary tissue in SARS-CoV-2 (Coronaviridae: Coronavirinae: Betacoronavirus; Sarbecovirus) experimental infection in Syrian hamsters. MATERIAL AND METHODS: Male Syrian hamsters weighting 80-100 g were infected by intranasal administration of culture SARS-CoV-2 at dose 4 × 104 TCID50/ml (TCID is tissue culture infectious dose). Animals were euthanatized on 3, 7 and 14 days after infection, with gravimetric registration. The viral load in lungs was measured using the polymerase chain reaction (PCR). Right lung and trachea tissues were stained with hematoxylin-eosin and according to Mallory. RESULTS AND DISCUSSION: The highest viral replicative activity in lungs was determined 3 days after the infection. After 7 days, on a background of the decrease of the viral load in lungs, a pathologically significant increase of the organ's gravimetric parameters was observed. Within 3 to 14 days post-infection, the lung histologic pattern had been showing the development of inflammation with a succession of infiltrative-proliferative, edematousmacrophagal and fibroblastic changes. It was found that initial changes in respiratory epithelium can proceed without paranecrotic interstitial inflammation, while in the formation of multiple lung parenchyma lesions, damage to the epithelium of bronchioles and acinar ducts can be secondary. The appearance of epithelioid large-cell metaplastic epithelium, forming pseudoacinar structures, was noted as a pathomorphological feature specific to SARS-CoV-2 infection in Syrian hamsters. CONCLUSION: As a result of the study, the specific features of the pathology of the respiratory system in SARSCoV-2 infected Syrian hamsters were described. These findings are of practical importance as reference data that can be used for preclinical studies to assess the effectiveness of vaccines and potential drugs.

Mechanisms of Pulmonary Toxicity of Perfluoro-n-Alkane Pyrolysis Products with Consideration of the Structural Features of the Blood-Air Barriers.

Perfluoroisobutylene a is pulmonotoxic chemical generated during pyrolysis of perfluoro-nalkanes (polytetrafluoroethylene). The mechanisms of acute pulmonary toxicity induced by perfluoroisobutylene have not been studied yet. The analysis of tissues of brown frogs showed that the products of polytetrafluoroethylene pyrolysis induce typical inflammatory response in the lungs (fluid accumulation, erythrocyte stasis, desquamation of the epithelium, and capillary plethora in lung septa) and oropharyngeal cavity (degeneration of ciliated epithelium, hyperemia of underlying vessels with plasmatic imbibition of the connective tissue, and margination of segmented leukocytes and monocytes). The absence of surfactant is a specific feature of the blood-air barrier of the oropharyngeal cavity in frogs compared to the lungs. It can be hypothesized that toxic effects of perfluoroisobutylene are determined by its influence on epithelial (pneumocytes and cells of nonkeratinized stratified ciliated epithelium) and endothelial cells. Even though the effects of the agent on surfactant cannot be excluded, they do not determine the probability of development of inflammatory response.

A model of cerebral circulation disorders created by staged ligation of the common carotid arteries.

A model of brain ischemia induced by staged ligation of the left and right common carotid arteries has been developed in experiments on rats. The use to this model led to reduction of animal mortality. On days 2-5 after the second ligature, the animals lost weight, the level of their CNS vulnerability increased, the volume of perceived information reduced, adaptation to environmental conditions and reproduction of conditioned reflexes were disordered. Focal and diffuse destructive changes in the nerve and glia cells were found in the cerebral cortex, hippocampus, and thalamic nuclei. The severity of disorders in the blood supply to the brain depended on the interval between ligation of the carotid arteries. This recommends this model for evaluation of the efficiency of drugs of various pharmacological groups.

[Ultrastructural organization of the gastric ganglion in the crayfish]. / Ul'trastrukturnaia organizatsiia zheludochnogo gangliia rechnogo raka.

Anatomy of the gastric ganglion in the stomatogastric region of the vegetative nerve system has been studied in Astacus astacus at light optic and ultrastructural levels. Topography, neuroglial and interneuronal relationships of its elements have been described. Various types of synapses of the ganglionic neuropil have been described. The role of the ganglionic structural elements in receiving and treating sensory information and in regulation of gastric movements is discussed.