Effects Of Weightlessness Research Articles

Weightlessness damaged the ultrastructure of knee cartilage and quadriceps muscle, aggravated the degeneration of cartilage.

Long-term exposure to weightlessness can result in bone and muscle degradation, significantly impacting musculoskeletal function. Recent studies have also indicated damage to articular cartilage due to weightlessness. This study aims to observe the effects of simulated weightlessness on the cartilage microstructure of the quadriceps muscle and the muscular knee joint in rats. A total of 30 rats were used in this study, of which 20 rats were subjected to simulated weightlessness by tail suspension, which may be suitable for clinical long-term bedridden patients. At 14 and 28 days, the microscopic morphology of knee cartilage and quadriceps femoris muscle was observed by transmission electron microscopy, and the collagen and water content of cartilage was evaluated by magnetic resonance imaging. The mitochondrial activity of knee muscle and the levels of inflammatory factors in synovial fluid were detected by enzyme-linked immunosorbent assay (ELISA). Biomechanical and histological evaluation of cartilage was performed. On day 14, T2 mapping revealed no significant loading effect. However, transmission electron microscopy revealed altered mitochondrial inner membrane structure in cartilage, with vacuolization, disrupted endoplasmic reticulum, alongside mitochondrial ultrastructural damage in muscle. ELISA results showed that a large number of mitochondria in muscle were inactivated, and the levels of inflammatory factors in synovial fluid were increased. The staining results showed slight fracture of the cartilage surface and the type II collagen-positive cells were reduced. Nanoindentation showed that the cartilage microsurface was uneven, and the elastic modulus and hardness were decreased. On day 28, T2 mapping analysis indicated increased cartilage T2 values. Transmission electron microscopy showed alterations in the structure of the mitochondrial inner membrane in cartilage, severe vacuolization, disrupted endoplasmic reticulum, and substantial mitochondrial damage in muscle tissue. Muscle mitochondrial activity was markedly decreased, inflammatory factors levels were elevated, and the cartilage surface exhibited severe damage. The type II collagen positive cells were further reduced, the micro-surface of cartilage was uneven, and the elastic modulus and hardness were significantly decreased. The weightless environment resulted in the damage of endoplasmic reticulum and mitochondria of cartilage, mitochondrial damage of quadriceps muscle, inactivation of muscle mitochondria (P=0.01), increased intra-articular inflammation (P=0.01), decreased elastic modulus and hardness (P=0.03), and damaged cartilage surface, which aggravated cartilage degeneration.

Numerical analysis of blood flow in the abdominal aorta under simulated weightlessness and earth conditions

Blood flow through the abdominal aorta and iliac arteries is a crucial area of research in hemodynamics and cardiovascular diseases. To get in to the problem, this study presents detailed analyses of blood flow through the abdominal aorta, together with left and right iliac arteries, under Earth gravity and weightless conditions, both at the rest stage, and during physical activity. The analysis were conducted using ANSYS Fluent software. The results indicate, that there is significantly less variation in blood flow velocity under weightless conditions, compared to measurement taken under Earth Gravity conditions. Study presents, that the maximum and minimum blood flow velocities decrease and increase, respectively, under weightless conditions. Our model for the left iliac artery revealed higher blood flow velocities during the peak of the systolic phase (systole) and lower velocities during the early diastolic phase (diastole). Furthermore, we analyzed the shear stress of the vessel wall and the mean shear stress over time. Additionally, the distribution of oscillatory shear rate, commonly used in hemodynamic analyses, was examined to assess the effects of blood flow on the blood vessels. Countermeasures to mitigate the negative effects of weightlessness on astronauts health are discussed, including exercises performed on the equipment aboard the space station. These exercises aim to maintain optimal blood flow, prevent the formation of atherosclerotic plaques, and reduce the risk of cardiovascular complications.

Influence of 21-day antiortostatic hypokinesia on the functional state of the musculoskeletal system of human

The influence of antiorthostatic hypokinesia with an inclination angle relative to the horizon of -6 degrees for 21 days was used as a ground model of the physiological effects of weightlessness. 10 practically healthy male volunteers (30.7 ± 5.4 years, 78.0 ± 8.5 kg, 179.7 ± 5.3 cm) took part in the experimental study, who successfully passed the medical expert commission of the SSC RF-IMBP RAS, familiarized with the study program and signed a voluntary informed consent to participate in the study. The state of the musculoskeletal system was assessed according to the results of speed-strength testing on an isokinetic dynamometer before hypokinesia and on the 3rd day after its completion. Staying in conditions of 21-day anti-orthostatic hypokinesia with a body inclination angle of –6° relative to the horizon, as a model of the physiological effects of weightlessness, leads to changes in the functional state of the musculoskeletal lower limbs which manifests itself during speed-strength testing after hypokinesia by a decrease in maximum voluntary force (MPF) of the knee joint extensor muscles from 9 to 15% compared with the base level. The decrease in MPF did not depend on a change in the force gradient, which reflects the ability to exert greater force in the shortest possible time. This indicated that the decrease in the MPF level after hypokinesia was mainly due to a change in the activity of slow motor units. At the same time, we assume that exposure to hypokinesia did not cause a significant change in the activity of fast motor units. This is confirmed by the results of the analysis of the electromyographic activity of the extensor muscles of the knee joint during testing on an isokinetic dynamometer. Also, after hypokinesia, the possibility of using muscle potential significantly decreased - the physiological cost of work increased with a decrease in strength indicators.

Amorphous calcium carbonate enhances osteogenic differentiation and myotube formation of human bone marrow derived mesenchymal stem cells and primary skeletal muscle cells under microgravity conditions

Astronauts are exposed to severely stressful physiological conditions due to microgravity and increased space radiation. Space environment affects every organ and cell in the body and the significant adverse effects of long-term weightlessness include muscle atrophy and deterioration of the skeleton (spaceflight osteopenia). Amorphous Calcium Carbonate (ACC) emerges as a promising candidate for prevention of these effects, owing to its unique physicochemical properties and its potential to address the intricately linked nature of bone-muscle crosstalk. Reported here are two studies carried out on the International Space Station (ISS). The first, performed in 2018 as a part of the Ramon-Spacelab project, was a preliminary experiment, in which stromal murine cells were differentiated into osteoblasts when ACC was added to the culture medium. A parallel experiment was done on Earth as a control. The second study was part of Axiom-1‘s Rakia project mission launched to the ISS on 2022 utilizing organ-on-a-chip methodology with a specially designed autonomous module. In this experiment, human bone-marrow derived mesenchymal stem cells (hBM-MSCs) and human primary muscle cells were cultured in the presence or absence of ACC, in duplicates. The results showed that ACC enhanced differentiation of human primary skeletal muscle cells into myotubes. Similarly, hBM-MSCs were differentiated significantly better into osteocytes in the presence of ACC leading to increased calcium deposits. The results, combined with previous data, support the use of ACC as an advantageous supplement for preventing muscle and bone deterioration in outer space conditions, facilitating extended extraterrestrial voyages and colonization.

Project activities in extreme and space environments

Project activity in extreme and space conditions has its own specifics and requires a special approach. Extreme and space environments are conditions that differ from normal conditions on Earth. Space environments are even more extreme, people encounter them during flights into space, on space stations and ships. Project activity in such conditions has its own characteristics and requires special knowledge and skills. For example, when designing space stations, it is necessary to take into account the effects of radiation, weightlessness and other factors. In addition to factors that are associated with physical danger to humans, it is important not to lose sight of psychological factors and features of the functioning of “space ecosystems”. Project activities in extreme and space conditions require careful preparation and planning, as well as taking into account all possible risks and problems.

Changes in the pattern of sleep disturbances in healthy subjects under 21-day antiorthostatic hypokinesia

Background. Antiorthostatic hypokinesia (ANOH) reproduces some of the effects of weightlessness on the human body and is used to study adaptation to space flight conditions. It is known that ANOH affects nighttime sleep, but there is no information in the literature on the sequence of occurrence of sleep disorders in ANOH.The aim of the research was to study the dynamics of subjective changes in assessing sleep quality under conditions of antiorthostatic hypokinesia.Materials and methods. Six healthy male volunteers (age from 26 to 34 years) participated in the experiment with 21-day ANOH. They were on a medical bed with a body inclination angle relative to the horizon of –6° for 21 days. To assess sleep quality, a structured questionnaire was used that assessed sleep duration, rate of falling asleep, night awakenings, the presence of daytime sleepiness, and daytime falling asleep.Results. Based on the assessment of the dynamics of the sleep efficiency index (SEI), three stages of adaptation were identified. At the stage of acute adaptation (the first 3 days), there is a decrease in SEI from 96.4 to 91.3 (p < 0.01), a statistically significant prolongation of falling asleep from 17.6 to 33.6 minutes (p < 0.01), an increase duration of night awakenings up to 17.4 minutes, increase in daytime sleepiness by 11 %. In the next 3 days (the “recovery” stage), there is a statistically significant increase in SEI compared to the 1st stage to 94.7 (p < 0.01), but it remains statistically significantly lower than the background values (p < 0.004). The number of complaints about daytime sleepiness increases (up to 42 %), evening bedtime shifts later by 26 minutes. At the 3rd stage (the remaining nights) there is a relative stabilization of the sleep-wake cycle.Conclusion. Under conditions of 21-day ANOH, a gradual change in the pattern of sleep disturbances occurs. The most negative changes in terms of subjective assessment were noted in the first three days. Then there is an improvement in falling asleep, a decrease in night awakenings, combined with an increase in daytime sleepiness and the formation of a schedule with a later bedtime.

Effects of weightlessness on the cardiovascular system: a systematic review and meta-analysis.

Background: The microgravity environment has a direct impact on the cardiovascular system due to the fluid shift and weightlessness that results in cardiac dysfunction, vascular remodeling, and altered Cardiovascular autonomic modulation (CAM), deconditioning and poor performance on space activities, ultimately endangering the health of astronauts. Objective: This study aimed to identify the acute and chronic effects of microgravity and Earth analogues on cardiovascular anatomy and function and CAM. Methods: CINAHL, Cochrane Library, Scopus, Science Direct, PubMed, and Web of Science databases were searched. Outcomes were grouped into cardiovascular anatomic, functional, and autonomic alterations, and vascular remodeling. Studies were categorized as Spaceflight (SF), Chronic Simulation (CS), or Acute Simulation (AS) based on the weightlessness conditions. Meta-analysis was performed for the most frequent outcomes. Weightlessness and control groups were compared. Results: 62 articles were included with a total of 963 participants involved. The meta-analysis showed that heart rate increased in SF [Mean difference (MD) = 3.44; p = 0.01] and in CS (MD = 4.98; p < 0.0001), whereas cardiac output and stroke volume decreased in CS (MD = -0.49; p = 0.03; and MD = -12.95; p < 0.0001, respectively), and systolic arterial pressure decreased in AS (MD = -5.20; p = 0.03). According to the qualitative synthesis, jugular vein cross-sectional area (CSA) and volume were greater in all conditions, and SF had increased carotid artery CSA. Heart rate variability and baroreflex sensitivity, in general, decreased in SF and CS, whereas both increased in AS. Conclusion: This review indicates that weightlessness impairs the health of astronauts during and after spaceflight, similarly to the effects of aging and immobility, potentially increasing the risk of cardiovascular diseases. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/, identifier CRD42020215515.

Assessment of the effect of 21-day head-down bed rest on the cardiovascular system by blood protein composition.

Head-down bed rest (HDBR) is one of the models of the physiological effects of weightlessness used, among other things, to assess the effect of hypokinesia on the physiological systems of the human body and, first of all, on the cardiovascular system. The aim of the work was to study the effect of 21 days of HDBR factors on the cardiovascular system based on blood proteomic profile data. It was revealed that HDBR conditions led to an increase in the levels of proteins of the complement and the coagulation cascade systems, platelet degranulation, fibrinolysis, acute phase proteins, post-translational modification of proteins, retinol-binding protein 4 (RBP4), apolipoprotein B, which are associated with cardiovascular diseases, and other proteins that affect the functions of endothelial cells. Blood levels of proteins involved in cytoskeletal remodelling, oxygen transport, heme catabolism, etc. have been shown to decrease during HDBR.

LLLT accelerates experimental wound healing under microgravity conditions via PI3K/AKT-CCR2 signal axis.

The risk of skin injuries in space is increasing with longer space missions and a growing astronaut population. This highlights the importance of understanding the adverse effects of weightlessness on wound healing. The objective of this research was to examine the therapeutic potential of Low-Level Light Therapy (LLLT) on skin healing processes under simulated microgravity (SMG) conditions and uncover the underlying molecular mechanisms, thus providing innovative solutions and a sound theoretical basis for space skin injuries. Hindlimb unloading (HU) mice models were used to simulate weightlessness conditions, with or without a complete management of LLLT for 14 days. A systematic testing consisting of HE, Masson and immunohistochemical staining was performed against the standardized mouse tissue specimens. In vitro assessment of cellular biological functions under SMG conditions was carried out in the rotation system of culture (RSOC) using HaCaT and NIH3T3 cell-lines. Under SMG conditions, LLLT significantly reduced skin wound area in HU mice, especially on Days 10 (p < 0.001), accompanied by increased collagen deposition and elevated levels of Ki67 and CD31. Moreover, LLLT showed impressive anti-inflammatory effects represented by the reduced in pro-inflammatory markers including LY6G, F4/80 and CD86, as well as the decreased levels of IL-1β, IL-6 and TNF-α. Conversely, an elevation in the anti-inflammatory marker CD206 was observed. By employing bioinformatics technology, we further found the PI3K/AKT signaling was prominent in the KEGG pathway analysis and CCR2 acted as a hub gene in the interaction network. Therefore, we demonstrated that LLLT could enhance the phosphorylation of PI3K/AKT and reduce CCR2 expression under SMG conditions, while CCR2 knockdown promoted the phosphorylation of PI3K/AKT, suggesting an important role of CCR2/PI3K/AKT signal axis in LLLT-accelerated wound healing under SMG conditions. LLLT induced activation of the PI3K/AKT signaling pathway through suppression of CCR2 expression, which significantly enhanced skin wound healing under SMG conditions.s.

Influence of Factors of 21-Day Head-Down Bed Rest on the Level of Myocardial Extensibility Biomarker ST2 in the Blood

Head-down bed rest (HDBR) is one of the best known models of the effects of weightlessness. The responses of the cardiovascular system to thoracocranial blood redistribution continue to be studied in relation to changes in the volumes of the heart chambers and the structure of the heart muscle. The assessment of myocardial stretch, individual response of the heart muscle to HDBR and stratification of the risk of developing heart failure according to the dynamics of a cardiomarker, independent of the influence of such factors as gender, age, body weight, glomerular filtration rate, anemia and hypovolemia, is relevant. The aim of the work was to investigate the influence of factors of 21-day HDBR on the level of the ST2 myocardial stretch biomarker. The effect of 21-day HDBR on the level of ST2 cardiomyocyte stretch marker was studied for the first time. The level of ST2 significantly decreased by the end of HDBR. The data obtained are of practical importance in relation to the problems of medical selection of cosmonauts and test volunteers. Background levels, variability of indicators during HDBR and the recovery period indicate the absence of risks for the development of heart failure and cardiofibrosis in this sample of subjects in this study.

Роль быстрого бега в предотвращении негативных влияний пребывания человека в невесомости

The prospects of deep space exploration necessitate modification of the principles and methods underlying the system designed to prevent negative impact of weightlessness on the human body. This work aimed to determine how fast running, as part of locomotor training during a space flight (SF), helps maintain physical ability of a person. The study involved 10 cosmonauts; their physical performance was assessed at all stages of the SF with the help of the Individual Strategies Test (IST). The parameters registered when the participants were doing the IST included heart rate (HR), gas exchange, capillary blood lactate concentration. The cosmonauts were divided into two groups based on the differences in the mean distance covered while fast running on a treadmill (single session). Group A (n = 4) run 949 m/day on average, group B (n = 6) — 2669 m/day. After SF, HR in group A increased at speeds from 5 to 8 km/h (p &lt; 0.05), pulmonary ventilation indicators grew at speeds from 8 to 15 km/h (p &lt; 0.05), and the capillary blood lactate concentration measured during the post-test recovery period increased by 37% (p = 0.03). Moreover, after SF, the pulse sum recorded under load and during recovery was 14% (p = 0.02) and 15% (p = 0.03) in group A, respectively, while in group B we registered no differences. Thus, our hypothesis that fast running triggers sensory reactions simulatingEarth conditions for the body, which consequently activates physiological mechanisms counteracting the negative effects of weightlessness, has been confirmed in a space experiment.

Human gut microbiome and metabolite dynamics under simulated microgravity

ABSTRACT The Artificial Gravity Bed Rest – European Space Agency (AGBRESA) study was the first joint bed rest study by ESA, DLR, and NASA that examined the effect of simulated weightlessness on the human body and assessed the potential benefits of artificial gravity as a countermeasure in an analog of long-duration spaceflight. In this study, we investigated the impact of simulated microgravity on the gut microbiome of 12 participants during a 60-day head-down tilt bed rest at the :envihab facilities. Over 60 days of simulated microgravity resulted in a mild change in the gut microbiome, with distinct microbial patterns and pathway expression in the feces of the countermeasure group compared to the microgravity simulation-only group. Additionally, we found that the countermeasure protocols selectively increased the abundance of beneficial short-chain fatty acids in the gut, such as acetate, butyrate, and propionate. Some physiological signatures also included the modulation of taxa reported to be either beneficial or opportunistic, indicating a mild adaptation in the microbiome network balance. Our results suggest that monitoring the gut microbial catalog along with pathway clustering and metabolite profiling is an informative synergistic strategy to determine health disturbances and the outcome of countermeasure protocols for future space missions.

Space-Flight- and Microgravity-Dependent Alteration of Mast Cell Population and Protease Expression in Digestive Organs of Mongolian Gerbils.

Mast cell (MC)-specific proteases are of particular interest for space biology and medicine due to their biological activity in regulating targets of a specific tissue microenvironment. MC tryptase and chymase obtain the ability to remodel connective tissue through direct and indirect mechanisms. Yet, MC-specific protease expression under space flight conditions has not been adequately investigated. Using immunohistochemical stainings, we analyzed in this study the protease profile of the jejunal, gastric, and hepatic MC populations in three groups of Mongolian gerbils-vivarium control, synchronous experiment, and 12-day orbital flight on the Foton-M3 spacecraft-and in two groups-vivarium control and anti-orthostatic suspension-included in the experiment simulating effects of weightlessness in the ground-based conditions. After a space flight, there was a decreased number of MCs in the studied organs combined with an increased proportion of chymase-positive MCs and MCs with a simultaneous content of tryptase and chymase; the secretion of specific proteases into the extracellular matrix increased. These changes in the expression of proteases were observed both in the mucosal and connective tissue MC subpopulations of the stomach and jejunum. Notably, the relative content of tryptase-positive MCs in the studied organs of the digestive system decreased. Space flight conditions simulated in the synchronous experiment caused no similar significant changes in the protease profile of MC populations. The space flight conditions resulted in an increased chymase expression combined with a decreased total number of protease-positive MCs, apparently due to participating in the processes of extracellular matrix remodeling and regulating the state of the cardiovascular system.

Loss and recovery of myocardial mitochondria in mice under different tail suspension time: Apoptosis and mitochondrial fission, fusion and autophagy.

Long-term weightlessness in animals can cause changes in myocardial structure and function, in which mitochondria play an important role. Here, a tail suspension (TS) Kunming mouse (Mus musculus) model was used to simulate the effects of weightlessness on the heart. We investigated the effects of 2 and 4weeks of TS (TS2 and TS4) on myocardial mitochondrial ultrastructure and oxidative respiratory function and on the molecular mechanisms of apoptosis and mitochondrial fission, autophagy and fusion-related signalling. Our study revealed significant changes in the ultrastructural features of cardiomyocytes in response to TS. The results showed: (1) mitochondrial swelling and disruption of cristae in TS2, but mitochondrial recovery and denser cristae in TS4; (2) an increase in the total number of mitochondria and number of sub-mitochondria in TS4; (3) no significant changes in the nuclear ultrastructure or DNA fragmentation among the two TS groups and the control group; (4) an increase in the bax/bcl-2 protein levels in the two TS groups, indicating increased activation of the bax-mediated apoptosis pathway; (5) no change in the phosphorylation ratio of dynamin-related protein 1 in the two TS groups; (6) an increase in the protein levels of optic atrophy 1 and mitofusin 2 in the two TS groups; and (7) in comparison to the TS2 group, an increase in the phosphorylation ratio of parkin and the ratio of LC3II to LC3I in TS4, suggesting an increase in autophagy. Taken together, these findings suggest that mitochondrial autophagy and fusion levels increased after 4weeks of TS, leading to a restoration of the bax-mediated myocardial apoptosis pathway observed after 2weeks of TS. NEW FINDINGS: What is the central question of this study? What are the effects of 2 and 4weeks of tail suspension on myocardial mitochondrial ultrastructure and oxidative respiratory function and on the molecular mechanisms of apoptosis and mitochondrial fission, autophagy and fusion-related signalling? What is the main finding and its importance? Increased mitochondrial autophagy and fusion levels after 4weeks of tail suspension help to reshape the morphology and increase the number of myocardial mitochondria.

Under pressure—the influence of hypergravity on electrocortical activity and neurocognitive performance

The effects of hypergravity and the associated increased pressure on the human body have not yet been studied in detail, but are of great importance for the safety of astronauts on space missions and could have a long-term impact on rehabilitation strategies for neurological patients. Considering the plans of international space agencies with the exploration of Mars and Moon, it is important to explore the effects of both extremes, weightlessness and hypergravity. During parabolic flights, a flight manoeuvre that artificially creates weightlessness and hypergravity, electrocortical activity as well as behavioural parameters (error rate and reaction time) and neuronal parameters (event-related potentials P300 and N200) were examined with an electroencephalogram. Thirteen participants solved a neurocognitive task (mental arithmetic task as a primary task and oddball paradigm as a secondary task) within normal as well as hypergravity condition in fifteen consecutive parabolas for 22 s each. No changes between the different gravity levels could be observed for the behavioural parameters and cortical current density. A significantly lower P300 amplitude was observed in 1 G, triggered by the primary task and the target sound of the oddball paradigm. The N200, provoked by the sounds of the oddball paradigm, revealed a higher amplitude in 1.8 G. A model established by Kohn et al. (2018) describing changes in neural communication with decreasing gravity can be used here as an explanatory approach. The fluid shift increases the intracranial pressure, decreases membrane viscosity and influences the open state probability of ion channels. This leads to an increase in the resting membrane potential, and the threshold for triggering an action potential can be reached more easily. The question now arises whether the observed changes are linear or whether they depend on a specific threshold.

Inertial mass in the balance body of &lt;i&gt;Pomacea Diffusa&lt;/i&gt;. Experiment on the biosatellite “Bion-11”

The inertial mass in the balance organ-statocyst of Pomacea diffusa was studied from the moment of hatching from eggs until the end of the life cycle, as well as the effects of weightlessness on the inertial mass during a 14-day orbital flight on the biosatellite “Bion-11”. As the snails grew older, the diameter of the statocyst increased from 150 μm to 650 μm, and the inertial mass contained in it increased from 11–13 statoconia to 700 statoconia. The internal structure of the statoconia had a layered structure with a nucleus in its central region. The main mineral element that gives statoconia heaviness is calcium carbonate, presented in the form of aragonite crystals. A 14-day exposure in weightlessness led to noticeable changes in the morphometric pattern of the inertial mass in the statocyst of flight snails in comparison with the control snails of synchronous tracking. In most of the statoconia, the form factor, length, and width indicators increased, which could indicate the stimulating effect of weightlessness on the inertial mass in the balance organ of Pomacea diffusa.

The Remodeling of Dermal Collagen Fibrous Structures in Mice under Zero Gravity: The Role of Mast Cells.

Mechanisms of adaptive rearrangements of the fibrous extracellular matrix of connective tissues under microgravity practically remain unexplored, despite the most essential functions of the stroma existing to ensure the physiological activity of internal organs. Here we analyzed the biomaterial (the skin dermis) of C57BL/6J mice from the Rodent Research-4 experiment after a long stay in space flight. The biomaterial was fixed onboard the International Space Station. It was found that weightlessness resulted in a relative increase in type III collagen-rich fibers compared to other fibrous collagens in the skin. The number of mast cells in the skin did not change, but their secretory activity increased. At the same time, co-localization of mast cells with fibroblasts, as well as impregnated fibers, was reduced. Potential molecular-cellular causes of changes in the activity of fibrillogenesis under zero-gravity conditions and the slowdown of the polymerization of tropocollagen molecules into supramolecular fibrous structures, as well as a relative decrease in the number of fibrous structures with a predominant content of type-I collagen, are discussed. The data obtained evidence of the different sensitivity levels of the fibrous and cellular components of a specific tissue microenvironment of the skin to zero-gravity conditions. The obtained data should be taken into account in the systematic planning of long-term space missions in order to improve the prevention of undesirable effects of weightlessness.

ANTIGRAVIDADE SIMULADA LEVOU À TRANSFORMAÇÃO DO METABOLISMO DE GLICOLIPÍDIOS NO FÍGADO DE CAMUNDONGOS

ABSTRACT Objectives: The effects of weightlessness on the liver were studied using a tail suspension (TS) male mouse model. Methods: The effects of 0-, 2- and 4-week TS (CON, TS2 and TS4 groups) on glycogen and lipid content, as well as on the molecular processes of the synthesis and degradation pathways, were examined. Results: (1) The number of glycogenosomes under ultrastructure and the glycogen content were considerably larger in the TS4 group than in the other two groups. (2) In the TS4 group, glycogen synthase activity remained constant while glycogen phosphorylase activity dropped, indicating that glycogen breakdown was reduced. (3) The livers of the TS2 group had the highest lipid and triglyceride content, indicating lipid buildup in the liver at this time. (4) In the TS2 group, the activities of the fatty acid synthesis-related factors acetyl-CoA carboxylase and fatty acid synthase increased, while hepatic lipase decreased, indicating that lipid synthesis increased, while decomposition decreased. (5) In the TS2 group, the protein expression of glucose transporters 1 and 2 increased. Conclusions: From TS2 weeks to TS4 weeks, the main energy consumption mode in the livers of mice transitioned from glucose metabolism to lipid metabolism as glucose use decreased. Level of evidence II; Comparative prospective study.

КОНТРАСТНАЯ ЧУВСТВИТЕЛЬНОСТЬ И МИКРОДВИЖЕНИЯ ГЛАЗ КАК МАРКЕРЫ АДАПТАЦИИ И РЕАДАПТАЦИИ В МОДЕЛЬНОМ ЭКСПЕРИМЕНТЕ ПО ИЗУЧЕНИЮ ВЛИЯНИЯ ИЗМЕНЕНИЙ ГРАВИТАЦИИ

Visual perception plays a crucial role in providing the brain with the information it needs to make decisions, build a picture of the world, and adapt to changing environmental conditions. Under conditions of "dry" immersion, which simulates the effects of weightlessness on the human body, contrast sensitivity and tremor eye movements were studied under changing environmental conditions. The study involved 10 volunteers (mean age 30.8±4.6 years). The contrast sensitivity of the visual system was recorded using the method of visocontrastometry. We presented the Gabor elements with a spatial frequency: 0.4; 0.8; 1.0; 3.0; 6.0 and 10.0 cycle/deg. The parameters of eye micromovements, i.e., the amplitude and frequency of eye tremor oscillations, were recorded using an optical system providing high-frequency video recording. The measurements were carried out the day before immersion in the immersion bath, on days 1, 3, 5, and 7 of “dry” immersion, as well as the next day after its completion. A change in contrast sensitivity in the range of low and high spatial frequencies, as well as in the amplitude of eye micromovements, was established. The data obtained today are a new step in the search for methods for an objective assessment of the functional state under changing environmental conditions.

Assessing the effects of artificial gravity in an analog of long-duration spaceflight: The protocol and implementation of the AGBRESA bed rest study.

A comprehensive strategy is required to mitigate risks to astronauts’ health, well-being, and performance. This strategy includes developing countermeasures to prevent or reduce adverse responses to the stressors astronauts encounter during spaceflight, such as weightlessness. Because artificial gravity (AG) by centrifugation simultaneously affects all physiological systems, AG could mitigate the effects of weightlessness in multiple systems. In 2019, NASA and the German Aerospace Center conducted a 60-days Artificial Gravity Bed Rest Study with the European Space Agency (AGBRESA). The objectives of this study were to 1) determine if 30 min of AG daily is protective during head down bed rest, and 2) compare the protective effects of a single daily bout (30 min) of AG versus multiple daily bouts (6 × 5 min) of AG (1 Gz at the center of mass) on physiological functions that are affected by weightlessness and by head-down tilt bed rest. The AGBRESA study involved a comprehensive suite of standard and innovative technologies to characterize changes in a broad spectrum of physiological systems. The current article is intended to provide a detailed overview of the methods used during AGBRESA.