Vol 143, No 4 (2023)

The tendon sheaths (peritenones) of the paravertebral tendons of the tails of Wistar rats were studied using scanning electron microscopy. A phenomenological classification of the osteoid structures of the peritenons is given, with the identification of their persistent and permanent varieties. Sesamoid islets, needle-like and lamellar growths, rudiments of osteons are classified as persistent. Persistent osteoid structures are well prepared for transformations aimed at strengthening the intracellular matrix under mechanical stress. Permanent osteoid structures are microgranules and faceted deposits of calcium phosphates involved in structural and mechanical processes, hetero- and homogeneous nucleation. Hyaluronate loosens the matrix of sesamoid islets, which increases the mobility of sesamoid globules and creates the prerequisites for their directed migration to areas of increased mechanical stress and foci of possible mineralization of extracellular substance, including fibrillar collagen. Hyaluronate sticks together granules and deposits of structured calcium phosphates. contribute to their growth and fixation in areas of increased risk of mechanical stress. This is a fundamentally important adaptive mechanism for strengthening the tendon tissue, acting in advance.

The review highlights the mechanism of development of hypercoagulation and thrombosis in severe forms of COVID-19. The introduction of the SARS-CoV-2 virus into the host organism is carried out by the interaction of the spike protein S with the angiotensin-converting enzyme ACE-2, which is located in type 2 alveocytes, vascular endothelium, kidneys, liver and other organs. In the event of a serious condition in patients with COVID-19, both nonspecific and adaptive immunity are activated. Stimulation of the complement system with the appearance of C3a, C3b, C5a fragments and the membrane attack complex (MAC) creates conditions for the development of hypercoagulability. The involvement of the renin-angiotensin-aldosterone system in this process and the appearance of angiotensin 2 (Ang-2) further increase the intensity of hypercoagulability. When the SARS-CoV-2 virus enters cells, the protective reaction of the adaptive immune system can turn into a pathological one (a cytokine storm develops), characterized by a high level of pro-inflammatory cytokines IL-1α, IL-6, Il-8, TNF-α, IL-17, etc.) and chemokines (CCL-2, CCL-11, etc.), which ultimately leads to the development of thromboangiopathy or otherwise immunothrombosis in seriously ill patients with COVID-19. Patients with more severe lesions may develop a condition similar to DIC. At the same time, patients with COVID-19 have mild thrombocytopenia, elevated levels of fibrinogen, D-dimer, fibrinogen degradation products (FDP), which indicates intense thrombus formation, as well as short PT and APTT, due to a largely increased level of FVIII. In COVID-19, along with the classical one, an alternative pathway (bypassing thrombin) of regulation of the hemostasis system and thrombus formation appears, mainly associated with the influence of the spike protein S (PS, PROS1) of the SARS-CoV-2 virus and papain-like protease (PROS1). Protein S directly affects the conversion of fibrinogen to fibrin, as well as the activation of individual plasma coagulation factors. The alternative pathway of blood coagulation is also due to the activation of the complement system via the lectin pathway with the inclusion of metalloproteinases MASP-1, 2 and 3. In addition, the S protein activates tPA, which may be accompanied by hyperfibrinolysis. In seriously ill patients with COVID-19, platelets play an important role in the occurrence of thromboembolic complications. During the release reaction, platelets are released from the cytoplasm into the blood α and dense granules containing inflammatory cytokines and chemokines, which enhances the cytokine storm and, consequently, thrombus formation. By acting on the spike protein S, platelets enhance an alternative way of regulating the hemostasis system and thrombus formation.

Most of the heat that is released in the vertebrate body is produced in the muscles during contractive (during movement or trembling) and non-contractive (without muscle activity) thermogenesis. Contractive thermogenesis is characteristic for all vertebrates, but it is not able to constantly maintain a high body temperature in animals. The main idea discussed in this article, and based on a large number of publications in recent years: the main biochemical base of warm-bloodedness in vertebrates is part of the cycle of contraction–relaxation of striated skeletal muscles, in which the act of muscle contraction somehow falls out, and the energy that should have been used for it is dissipated in the form of heat. This non-contractive thermogenesis, which is able to support the regional and general endothermy in vertebrates, can be considered the real biochemical basis of warm-bloodedness. Thus, the presence of skeletal muscles in all vertebrates and the common biochemical foundations of the contraction–relaxation cycle represent a single preadaptive property of the manifestation of non-contractive thermogenesis in all vertebrates, starting with fish, which is the basis for the evolution of warm-bloodedness. Therefore, it is understandable and unsurprising modern data that the first terrestrial vertebrates were most likely animals with high levels of both metabolism and body temperature.

The study of soil microbial biomass and enzymatic activity of natural and anthropogenically transformed ecosystems was carried out. The catenas of virgin luvisols and chernozems of the Belogorye Natural Reserve and the catenas of arable soils were studied under similar geomorphological and lithological conditions. The activities of enzymes involved in the cycles of carbon (β-glucosidase and xylosidase), nitrogen (chitinase), and phosphorus (acid and alkaline phosphatase) was studied. It has been established that a decrease in soil microbial biomass as a result of ploughing is not accompanied by an equivalent decrease in the enzymatic activity of the soil. Differences in the enzymatic activity of different soils types were revealed, which indicates differences in the structure of the microbial community and the type of phytocenoses. Patterns of changes in the enzymatic activity of soils in watershed areas, in the transit and accumulative parts of catenas have been established. The values of specific enzymes activities (enzymatic activities per unit of microbial biomass) were calculated. The obtained patterns of changes in the specific enzymatic activity of arable soils indicate that, despite the loss of organic matter and a decrease in microbial biomass as a result of plowing, the physiological efficiency of the microbial community of agrochernozem is higher than in virgin soil. High specific enzymatic activity in arable soils is associated with higher rate of enzyme production by soil microorganisms due to land use changes.