One of the problems which ectothermic animals have to face during the fall of the ambient temperature is the negative change in parameters of the cardiac electrical activity leading to the decrease in the cardiac output. This is crucially important for those ectotherms which remain highly active during the cold season. The present review discusses the known physiological mechanisms which allow the ectothermic vertebrates, primarily various fish species, to reduce at least partially the cold-induced changes of cardiac electrical activity and to maintain the functional capacity of the heart at sufficient level for the active life during the winter. These mechanisms include the increase of density and/or changes in steady-state activation and inactivation parameters of ionic currents in cardiac myocytes. The acute temperature-dependent changes in ionic currents and electrical activity are also discussed, including the temperature effects on the excitability of cardiac myocytes.

One of the factors contributing to the development of colorectal cancer is inflammation. Chronic ulcerative colitis may be the cause of the Colitis-Associated Colorectal cancer (CAC) development in 1.6–3.7% of cases. The main regulator of the cellular response to inflammation is the NF-κB protein, which induces the expression and synthesis of the transcription factor HIF-1α (Hypoxia-Inducible Factor 1α) due to the presence of a binding site in the corresponding gene. Oxidative stress that occurs during the inflammatory process often leads to mutations in cells. The DNA of rapidly proliferating colonic epithelial cells becomes a target for reactive oxygen species, eventually leading to tumor initiation and progression. The rate of CAC development depends largely on the initial hypoxia resistance of organisms. Susceptible to hypoxia animals have faster rates of CAC initiation and progression compared to tolerant, which is characterized by a higher frequency of adenocarcinoma development, high expression levels of Hif3a, Vegf, Tnfa, Il10, Tgfb, Cmet, Egf, Egfr, Bax, Muc1 and Cldn7 genes in tumors, pronounced changes in hematological parameters and imbalance of lymphocyte subpopulations in tumors, mesenteric lymph nodes and blood. Understanding the interrelation mechanisms of hypoxia resistance, HIF activity, peculiarities of the chronic inflammatory and tumor processes course is necessary for the development of new approaches to personalized therapy of diseases accompanied by oxygen deficiency.

The study was aimed at determining tissue antioxidant levels in juvenile and adult the northern birch mouse (Sicista betulina Pallas, 1779) at the northern periphery of its range (Republic of Karelia). Our results are indicating a mixed pattern of age-related changes in the antioxidant defense system: aging was accompanied by a decrease the catalase activity in the kidneys as well as an increase in heart catalase activity and kidney, cardiac and skeletal muscle superoxide dismutase activity. The levels of low-molecular antioxidants – reduced glutathione (GSH) (kidneys and heart) and α-tocopherol (heart and skeletal muscle) were lower in the of the northern birch mouse young compared to adult animals, which is probably associated not only with the active growth and high mobility of the juvenile mouse during the dispersal period, but also with the stress of physiological systems due to living in the Northern conditions and preparing for hibernation. Higher levels of GSH and α-tocopherol were found in the hearts of adult northern birch mouse compared to other small mammal species of the order Rodentia living in the Republic of Karelia, which indicates the important role of low-molecular weight antioxidants in protecting tissues against oxidative injury in this species.

Signal cascade NO → soluble guanylate cyclase (sGC) → сyclic guanosine monophosphate (cGMP) → protein kinase G (PKG) plays a significant role in vascular dilation. Its disorders can cause the development of cerebrovascular diseases. The key unit in the NO → PKG signaling system is cGMP. Intracellular cGMP levels are largely regulated by cGMP-hydrolyzing phosphodiesterase (PDE) enzymes that break down cGMP. Aging is accompanied by a decrease in NO synthesis and cGMP levels and an increase in PDE activity. Under these conditions, it is possible to increase the contribution of compensatory mechanisms of activation of individual sections of the NO → PKG signaling pathway, in particular with the participation of intermediaries that change the cGMP level. Hydrogen sulfide (H₂S) is currently considered as one of the activators of the NO → PKG pathway, which can increase cGMP levels in cells by inhibiting PDE or its direct interaction with cGMP to form biologically active compounds that are less susceptible to enzymatic break down. H₂S-mediated cGMP activation has been shown in cardiomyocytes and smooth muscle cells of mesenteric and aortic vessels, but this mechanism has not been studied in cerebral vessels. The aim of the work was to study the contribution of H₂S to the regulation of cGMP-induced vasodilation of cerebral vessels and changes in this mechanism of regulation of vasoactive reactions during aging. In Sprague-Dawley 4 (young) and 18-month-old (aging) rats, a comparative study of the pial arteries dilatation to the effect of the penetrating into cells analog cGMP – 8-Br-cGMP was performed using intravital microphotography, and an assessment of the effect of exogenous (donor – NaHS) and endogenous H₂S on the cGMP-induced vasodilation. Propargylglycine was used as a blocker of endogenous H₂S. It was shown that in 4-month-old rats, the H₂S-mediated regulation of cGMP-induced dilation of the pial arteries was expressed only at the level of large arteries with a diameter of more than 40 microns. Aging leads to an increased contribution of endogenous H₂S to cGMP-induced dilation of the pial arteries of all calibers and an increased sensitivity of cGMP-mediated reactions of small pial arteries to exogenous H₂S.

Viroporins are small membrane proteins of enveloped viruses. They play an important role both in the life cycle of the virus and in the development of disease pathogenesis. In this regard, inhibition of viroporins is considered a promising strategy in the treatment of many diseases caused by enveloped viruses, such as coronavirus, herpes virus, human immunodeficiency virus, Ebola virus and many others. An important step in the search for highly effective inhibitors of such channels is the study of the interaction of potential antiviral drugs with the amino acid residues of the viroporin channel. In turn, methylene blue is a well-known effective antiviral agent and is widely used in medical practice. In this work, we carried out molecular dynamic calculations of the interaction of methylene blue with the viroporin channel of the SARS-CoV-2 coronavirus using the umbrella sampling method. Analysis of the contacts formed between the methylene blue molecule and the amino acid residues of viroporin showed that the key role in binding is played by non-covalent stacking interactions between the system of aromatic rings of methylene blue and the phenylalanine residues located in the center of the viroporin channel. The results obtained bring us closer to understanding the mechanisms of the antiviral action of methylene blue. Conducting such computational experiments seems to be an effective approach in the search for viroporin inhibitors.

Molecular oxygen is an important factor in plant life. Its deficiency leads to hypoxia, which can occur with excessive moisture of the underground parts of plants. In response to hypoxia, many plants form lysigenous aerenchyma, which performs the functions of oxygen supply. The mechanisms of aerenchyma formation are not entirely clear. Our work describes the anatomical, morphological, physiological and biochemical changes in roots of barley (Hordeum vulgare L.) during the formation of aerenchyma under hypoxia in hydroponic conditions. Oxygen deficiency inhibited root growth and reduced the intensity of respiration rate in them, but did not affect the development of the aboveground organs. Under hypoxic conditions aerenchyma in roots was formed on the 8th day, which was associated with the 2.6-fold increase in the amount of H₂O₂ compared to the control. The low activity of antioxidant enzymes led to the high H₂O₂ level. By the 28^th day under hypoxic conditions, the activity of benzidine, guaiacol and ascorbate peroxidases increased, which led to a decrease in the H₂O₂ concentration. We suppose, that the increase of H₂O₂ concentration in roots triggered the formation of aerenchyma at the early stages of their growth (day 8). Later, antioxidant enzymes utilized reactive oxygen species, ensuring the survival of the roots under hypoxic conditions.

Rice plays a huge role in the nutrition of the world population In Russia, as in Europe and America, rice is mainly sown by direct seeding, while in Asian countries, seedling technology is used. Direct seeding is followed by flooding of the field, which can lead to a low percentage of seedlings and death of young plants. On the other hand, flooding of rice fields helps in the fight against weeds and rodents. Despite the fact that rice is a hydrophyte plant, water can lead to hypoxia or even anoxia, contributing to the suppression of young shoots. In general, most rice varieties at the early stages of development under water stress have low survival, so it is necessary to screen 8 genotypes and select breeding material capable of withstanding stressful conditions. One of the factors of tolerance to water stress conditions is the germination energy AG (anaerobic germination), which is a complex trait controlled by several genes mapped on different chromosomes. Foreign scientists have identified varieties with the AG germination energy genes (Khao Hlan On, Mazhan Red and others). In our country, there are currently few varieties with genes for resistance to anaerobic conditions. Currently, a small number of local varieties and populations have been studied for tolerance to anaerobic conditions using QTL, so it is necessary to expand the study of a large number of samples to select resistant genotypes. Therefore, the purpose of the study was to screen dihaploid androgenic rice plants for the presence of AG1, AG2 germination energy genes and to select promising genotypes of particular interest for breeding work. The source material was 25 regenerated plants obtained by in vitro anther culture from four hybrids whose parental lines were donors of germination energy (Khao Hlan On), resistance to deep-water flooding (Inbara-3, IR-64) and Russian varieties (Contact, Magnat, Novator). Molecular genetic analysis was performed using molecular markers AG1 (qAG–9–2) and AG2 (qAG–7–1). In total, the AG1 gene was identified in 17 rice lines, the AG2 gene in 11 lines, and both genes in 9 rice lines (4641/1, 4641/2, 4641/3, 4641/4, 4641/6, 4641/8, 4641/9, 4641/10, 5010/4). Laboratory experiment on dihaploid lines resistance to anaerobic stress revealed samples with high germination energy. Promising dihaploid androgenic rice plants were selected as source material for breeding.

The activity of ecto-ATPase and the size characteristics of erythrocytes in two species of cartilaginous and ten species of bony fishes, as well as the heat-production activity of the erythrocyte suspension in Scorpaena porcus and Raja clavata were studied. It was shown that the activity of ecto-ATPase of red blood cells (RBC) between cartilaginous fishes differs by 1.5 times and is 3.1 nmol Fn/min/μl RBC in Raja clavata, and 2.1 nmol Fn/min/μl RBC in Dasyatis pastinaca. Erythrocytes of teleost fish are characterized by a more significant variability of ecto-ATPase activity, which differed between its extreme values by more than 60 times (in Scorpaena porcus it was 6.4 nmol Fn/min/μl RBC, in Spicara flexuosa and some other species – 0.1 nmol Fn/min/μl RBC). When comparing the size characteristics of erythrocytes and the values of ecto-ATPase activity, a direct relationship was shown between these indicators. A study of heat production in suspensions of thresher and scorpionfish erythrocytes showed that adding ATP to a suspension of isolated cells (1 mg/ml) significantly increased the temperature in the experimental cell. The erythrocytes of the thresher and scorpionfish demonstrated different heat generation dynamics. Thus, ΔT generated by stingray erythrocytes was almost two times lower than in scorpionfish erythrocytes. The total duration of the heat generation process to the maximum ΔT in the thresher erythrocyte suspension was almost four times shorter than in the thresher. However, the process of temperature reduction in the thresher erythrocyte suspension occurred more than two times slower than in the thresher. The results obtained showed that ecto-ATPases of fish erythrocytes apparently function as a source of local heat generation on the erythrocyte surface and, thus, can be deeply integrated into the functioning of the cell membrane and the entire blood flow as a whole.