Volume 59, Nº 4 (2023)

The paper considers the structure of intermuscular synergetic interaction that ensures the athlete’s body stopping on the trampoline after a jump. We compared the spatio-temporal characteristics of muscle synergies extracted from the skeletal muscles electroactivity amplitude and frequency of biopotentials data. The objective of the study was to find out whether the extracted kinematic modules represent the central mechanisms for the movement structure controlling as well as to determine the variables which should be stabilized by muscle synergies activity. The extraction of synergies was carried out using the matrix factorization method. It has been established that trampoline jump stopping can be performed using common patterns of muscle synergies spatio-temporal activation. The synergistic effects obtained using different approaches of instrumental assessment of skeletal muscle electroactivity probably reflect different control mechanisms implemented at different levels of the central nervous system. Muscle synergies are aimed at the stabilizing of the certain anthropometric points movement, as well as body segments, combined into kinematic modules. The structure of the kinematic modules themselves indicates the effective organization of intermuscular interaction, indirectly reflecting the central control mechanisms of complex multi-joint movement.

The state of hibernation is characterized by increased resistance to the effects of prolonged deep hypothermia, hypoxia, lack of food and water. At the same time, the restructuring of the adaptive mechanisms of animals at low temperatures, even for a short time, causes significant changes in metabolism, reflected in the pattern of amino acids. The change in the metabolism of free myocardial amino acids during hibernation has not yet been studied by anyone, but the idea of it is necessary to understand the mechanisms of the hibernation state, which is relevant for clinical medicine. In this regard, the task of this work was to study the changes in the composition of free amino acids of the myocardium of the ground squirrel U. undulatus at different stages of hibernation. A negative interdependence of glutamic acid and alanine pools at different stages of torpor was revealed. The decrease in the level of glutamic acid compared to the summer control (5.08 ± 0.44 μmolе/g wet weight) began in the first, December bout, continued with prolonged torpor (up to 1.57 ± 0.14 μmolе/g) and was accompanied by a corresponding increase in the alanine pool. During the winter awakening, the glutamic acid pool rose above the summer level; The pool of alanine fell below the summer level, but their total level did not change. The pools of aspartic acid and glycine decreased in parallel with the decrease in pools of glutamate and aspartate, but during the winter awakening, glycine was not even detected. Taking into account the participation of glutamic acid and aspartate in the anaplerotic reactions of the Krebs cycle and the reciprocal relationship of glutamic acid and alanine, it is concluded that the change in the content of these metabolites at different stages of bouts is associated with a gradual transition of aerobic glycolysis (Krebs cycle and oxidative phosphorylation) to anaerobic, and during euthermia, on the contrary, with a return to aerobic.

Dysfunction of the brain serotonergic system is thought to play a leading role in the pathogenesis of chronic abdominal pain and comorbid somatic hyperalgesia, which disturb a significant proportion of patients with digestive tract diseases, even in remission. However, the specific changes in the serotonergic structures nociceptive properties that can be initiated by organic pathology and persist after its resolution remain unclear. The aim of our neurophysiological study on anesthetized rats – healthy and recovered from colitis – was to identify the alterations in the raphe magnus (RMg) and dorsal raphe (DR) nuclei neuronal responses to visceral (colorectal distension) and somatic (squeezing of the tail) noxious stimulations that persist after resolution of intestinal inflammation. It has been shown that both nuclei contain different groups of nociceptive neurons: 1) responding with activation only to colorectal distension (visceral); 2) excited only by tail squeezing (somatic); 3) reacting with excitation to the both irritations (general); 4) responding with discharge inhibition to any of the stimulations (inhibited). Compared with healthy animals, in RMg of colitis-exposed rats the number of the inhibited cells was increased and the total proportion of excited nociceptive neurons was reduced. Distension of the inflammation-undergone intestine caused enhanced RMg neuronal inhibition, whereas squeezing of the pathology-unaffected tail led to increased excitation of the RMg selective somatic and general nociceptive cells. In turn, in the DR of postcolitis rats the inhibited neuron proportion was reduced, while the increased population of excited neurons included fewer visceral and more somatic selective cells. This was accompanied by an increase in the selective reactions of the latter to somatic pain stimuli and by an increase in non-selective DR neuron excitation by visceral and somatic pain signals. The identified neuronal alterations can contribute to the postcolitis impairment of the studied raphe nuclei functions in the endogenous control of visceral and somatic pain sensitivity.

One of the most vulnerable brain structures to hypoxia is the hippocampus. Maintenance of the neurogenic niche cell pool in the subgranular zone of the hippocampus (SGZ) is provided by adaptive mechanisms. Among them are changes in the functional activity of mitochondrial respiratory chain complexes and the reaction of astroglia, which provides metabolic support for neurons. In order to study the dynamics of adaptive changes in neurons and glia in the dentate gyrus of the hippocampus under hypoxic conditions on a model of intermitten hypobaric hypoxia (5000 m, equivalent to 10.5% O₂), with a single (60 min) and multiple (8 and 20 episodes) exposure in low-resistant rats, immunomorphological methods revealed the features of localization and content in the neurons of complex IV mitochondrial respiratory chain (MTCO1), astrocyte marker proteins glutamine synthetase (GS) and GFAP, and doublecortin (DCX) in immature neurons. With a single hypoxia, the content of MTCO1 in neurons significantly increased, and after eight exposures, the amount of glutamine synthetase (GS) in astrocytes of the dentate gyrus of the hippocampus increased. Changes in the content of GS were most pronounced in the processes of astrocytes, which indicates a redistribution of GS. The number of DCX+ neurons in the SGZ significantly decreased after 20 episodes of hypoxia. At the same time, DCX+ cells of glial morphology were found in the polymorphic layer, and staining for GFAP showed an increase in the number of astrocytes. This may be due to a shift in the direction of cell differentiation in the neurogenic niche. Thus, in hypoxia, at the initial stage, a functional restructuring of the respiratory chain of neurons of the granular layer occurs. Subsequently, it is noted by the activation of astrocytes that modulate glutamate metabolism. The presence of a relationship between the dynamics of adaptive reactions of energy exchange in neurons and glia and changes in neurogenesis during 20 episodes of hypoxia suggests that during long-term hypoxia, the differentiation of neural precursors of SGZ in the direction of astroglia occurs, however, this issue requires further study in order to more accurately determine the nature of DCX+ cells.