Long-term dry immersion: review and prospects

Dry immersion, which is a ground-based model of prolonged conditions of microgravity, is widely used in Russia but is less well known elsewhere. Dry immersion involves immersing the subject in thermoneutral water covered with an elastic waterproof fabric. As a result, the immersed subject, who is freely suspended in the water mass, remains dry. For a relatively short duration, the model can faithfully reproduce most physiological effects of actual microgravity, including centralization of body fluids, support unloading, and hypokinesia. Unlike bed rest, dry immersion provides a unique opportunity to study the physiological effects of the lack of a supporting structure for the body (a phenomenon we call \u27supportlessness\u27). In this review, we attempt to provide a detailed description of dry immersion. The main sections of the paper discuss the changes induced by long-term dry immersion in the neuromuscular and sensorimotor systems, fluid-electrolyte regulation, the cardiovascular system, metabolism, blood and immunity, respiration, and thermoregulation. The long-term effects of dry immersion are compared with those of bed rest and actual space flight. The actual and potential uses of dry immersion are discussed in the context of fundamental studies and applications for medical support during space flight and terrestrial health care

Skin vascular resistance in the standing position increases significantly after 7 days of dry immersion

Actual and simulated microgravity induces hypovolemia and cardiovascular deconditioning, associated with vascular dysfunction. We hypothesized that vasoconstriction of skin microcirculatory bed should be altered following 7 days of simulated microgravity in order to maintain cardiovascular homeostasis during active standing. Eight healthy men were studied before and after 7 days of simulated microgravity modeled by dry immersion (DI). Changes of plasma volume and orthostatic tolerance were evaluated. Calf skin blood flow (laser-Doppler flowmetry), ECG and blood pressure signal during a 10-min stand test were recorded, and skin vascular resistance, central hemodynamics, baroreflex sensitivity and heart rate variability were estimated. After DI we observed increased calf skin vascular resistance in the standing position (12.0 +/- 1.0 AU-after- vs. 6.8 +/- 1.4 AU-before), while supine it was unchanged. Cardiovascular deconditioning was confirmed by greater tachycardia on standing and by hypovolemia (-16 +/- 3% at day 7 of DI). Total peripheral resistance and indices of cardiovascular autonomic control were not modified. In conclusion, unchanged autonomic control and total peripheral resistance suggest that increased skin vasoconstriction to standing involves rather local mechanisms-as venoarteriolar reflex-and might compensate insufficient vasoconstriction of other vascular beds

Постоянные белки мочи здорового человека в эксперименте с 520-суточной изоляцией

Purpose of the study was to track permanent proteins of urine proteome in the 520-day isolation experiment at the IBMP Ground-Based Test Facility with controlled environmental parameters. Object of the investigation was urine sampled from 6 normal male subjects at the age of 25 to 37 years. Second morning aliquots were gathered during baseline data collection, on days 50, 93, 124, 153, 180, 251, 274, 303, 330, 371, 400 and 427 of isolation, and in 7 days after its completion. Samples were subject to chromatography-mass spectrometry; results were analyzed with the help of bioinformatics resources. The following 7 permanent proteins were observed in urine over the entire length of the investigation: epidermal growth factor, polymer immunoglobulin receptor, plasma serine protease inhibitor, protein AMBP, keratin, type II cytoskeletal 1, collagen alpha-1 (vi) chain, serum albumin

Dynamics of Body Composition Indices and Biochemical Parameters in Participants of Countermeasure-Free 21-Day “Dry” Immersion

Abstract: Time-dependent changes in body composition and the levels of hormones involved in regulating energy metabolism and eating behavior were studied in ten healthy volunteers who were exposed to dry immersion (DI) for 21 days without the use of countermeasures to prevent the negative effects of the experimental conditions. Bioimpedance analysis (BIA) was used to assess the body composition in the test subjects. The proportion of lean mass decreased, while the fat component increased in the subjects under the influence of factors of 21-day DI. Cluster analysis isolated two equal homogeneous groups of subjects with a reduced group variability of the parameters of body composition and systemic regulation of energy metabolism. A significant decrease (p < 0.05) in relative skeletal muscle mass (SMM%) was observed after 21-day DI in the group with a higher relative body fat mass (FM), a lower relative fat-free mass (FFM), and a higher basal metabolic rate. SMM was stable, while SMM% increased (p < 0.05) after 21-day DI in the group with a lower relative FM, a higher FFM, and a lower basal metabolic rate. A significant increase in blood insulin was observed during DI in this group. Leptin and triglyceride concentrations differed between the groups in different periods of the experiment. © 2021, Pleiades Publishing, Inc

Changes in the Profile of Urine Proteins Associated with the Cardiovascular System in a Group of Healthy Young Men in Response to a Locomotor Test with a Stepwise Increasing Load

Abstract: The prospects of interplanetary missions make it relevant to develop standard tests to find criteria for the correction of preventive measures in a long space flight in order to ensure a peak in physical performance by the time the interplanetary activity is completed. Currently, tests are being developed to assess physical performance. One of them can be the currently developed locomotor test with a stepwise increasing load in the active mode of movement of the treadmill. It is of interest to assess the effect of this load on changes in the profile of proteins associated with the cardiovascular system from the standpoint of the possibility of using them as markers of its response to physical activity. In article analyzes the results of an experimental study of the proteome of human urine after a dosed step-increasing load and discusses the possible role of the identified proteins that can be attributed to the functioning of the cardiovascular system. The study involved practically healthy volunteers aged 18.6 ± 0.7 years, weighing 75.7 ± 8 kg (n = 12). The urine proteome was evaluated by chromatography-mass spectrometry and analyzed by bioinformatics methods. For the first time, data on the proteomic response to a locomotor test with a stepwise increasing load in the active mode of web movement in a group homogeneous in autonomic status are presented. As a result of the analysis, 429 proteins were identified, 69 of which significantly changed. Based on bioinformatics analysis, processes related to the work of the heart, vascular tone, and vascular permeability were identified. Ten proteins are described that are associated with the processes of the quick response of the cardiovascular system to dosed physical activity. The obtained results will help in choosing standard criteria for assessing the physiological cost of physical activity. © 2021, Pleiades Publishing, Inc