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Navasiolava N.M.,French Institute of Health and Medical Research | Navasiolava N.M.,Institute of Physiology of Minsk | Navasiolava N.M.,CaDyWEC International Laboratory | Navasiolava N.M.,Russian Academy of Sciences | And 7 more authors.
European Journal of Applied Physiology | Year: 2011

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 'supportlessness'). 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. © Springer-Verlag 2010.

Navasiolava N.M.,French Institute of Health and Medical Research | Navasiolava N.M.,Russian Academy of Sciences | Navasiolava N.M.,CaDyWEC International Laboratory | Pajot A.,University of Angers | And 11 more authors.
European Journal of Applied Physiology | Year: 2011

Immersion is a useful tool for studying fluid-volume homeostasis. Natriuretic peptides play a vital role in renal, humoral, and cardiovascular regulation under changing environmental conditions. We hypothesized that dry immersion would rapidly induce a new steady state for water and sodium metabolism, and that serum NT-proBNP levels, a proxy measure for brain natriuretic peptide (BNP), would decrease during long-term dry immersion and increase during recovery. Eight healthy young men were studied before, during, and after 7 days of dry immersion. Body weight, water balance, and plasma volume changes were evaluated. Plasma and serum samples were analyzed for active renin, NT-proBNP, aldosterone, electrolytes, osmolality, total protein, and creatinine. Urine samples were analyzed to determine levels of electrolytes, osmolality, creatinine, and free cortisol. A stand test was performed before and after dry immersion to evaluate cardiovascular deconditioning. Long-term dry immersion induced acute changes in water and sodium homeostasis on day 1, followed by a new steady state. Plasma volume decreased significantly during dry immersion. The serum levels of NT-proBNP increased significantly in recovery (10 ± 3 ng/L before dry immersion vs. 26 ± 5 ng/L on the fourth recovery day). Heart rate in the standing position was significantly greater after immersion. Results suggest that chronic dry immersion rapidly induced a new level of water-electrolyte homeostasis. The increase in NT-proBNP levels during the recovery period may be related to greater cardiac work and might reflect the degree of cardiovascular deconditioning. © Springer-Verlag 2011.

Navasiolava N.M.,French National Center for Scientific Research | Navasiolava N.M.,Institute of Physiology of Minsk | Navasiolava N.M.,CaDyWEC International Laboratory | Navasiolava N.M.,Institute of Biomedical Problems | And 13 more authors.
American Journal of Physiology - Heart and Circulatory Physiology | Year: 2010

A sedentary lifestyle has adverse effects on the cardiovascular system, including impaired endothelial functions. Subjecting healthy men to 7 days of dry immersion (DI) presented a unique opportunity to analyze the specific effects of enhanced inactivity on the endothelium. We investigated endothelial properties before, during, and after 7 days of DI involving eight subjects. Microcirculatory functions were assessed with laser Doppler in the skin of the calf. We studied basal blood flow and endothelium-dependent and -independent vasodilation. We also measured plasma levels of microparticles, a sign of cellular dysfunction, and soluble endothelial factors, reflecting the endothelial state. Basal flow and endothelium-dependent vasodilation were reduced by DI (22 ± 4 vs. 15 ± 2 arbitrary units and 29 ± 6% vs. 12 ± 6%, respectively, P < 0.05), and this was accompanied by an increase in circulating endothelial microparticles (EMPs), which was significant on day 3 (42 ± 8 vs. 65 ± 10 EMPs/μl, P < 0.05), whereas microparticles from other cell origins remained unchanged. Plasma soluble VEGF decreased significantly during DI, whereas VEGF receptor 1 and soluble CD62E were unchanged, indicating that the increase in EMPs was associated with a change in antiapoptotic tone rather than endothelial activation. Our study showed that extreme physical inactivity in humans induced by 7 days of DI causes microvascular impairment with a disturbance of endothelial functions, associated with a selective increase in EMPs. Microcirculatory endothelial dysfunction might contribute to cardiovascular deconditioning as well as to hypodynamia-associated pathologies. In conclusion, the endothelium should be the focus of special care in situations of acute limitation of physical activity. Copyright © 2010 the American Physiological Society.

Pastushkova L.K.,Russian Academy of Sciences | Pakharukova N.A.,Russian Academy of Sciences | Novoselova N.M.,University of Angers | Novoselova N.M.,CaDyWEC International Laboratory | And 5 more authors.
Human Physiology | Year: 2015

Changes in the proteome of urine and blood serum obtained from 14 healthy humans (aged 21–29 years), medically approved for the experiment with dry immersion, have been studied. Urine and serum samples were fractionated and concentrated using MB–WCX and MB–HIC magnetic particles, respectively. Direct mass spectrometry profiling by MSLDI–TOF was carried out using a ClinProt robotic device (Bruker Daltonics). As a result, on average, 143 proteins peaks in urine samples have been identified. The most plastic fraction of the urine proteome has been identified by a high variation coefficient (double of technical variation) in 23.7% of protein peaks. In blood serum, 175 peaks per sample have been identified, on average. Comparison of immersion mass spectra of the blood proteome and baseline revealed significant differences. It is concluded that the identified increase in peak areas for several protein fragments, including fragments of the C3 and C4 serum complement components and high-molecular-weight kinogen and fibrinogen, can be ascribed to human body adaptation to the experimental conditions. © 2015, Pleiades Publishing, Inc.

Larina I.M.,Russian Academy of Sciences | Baevsky R.M.,Russian Academy of Sciences | Pastushkova L.K.,Russian Academy of Sciences | Navasiolava N.M.,CaDyWEC International Laboratory | And 5 more authors.
Human Physiology | Year: 2011

The results of an experiment with a seven-day dry immersion are presented. Eight healthy men were examined before, during, and after the exposure. It was shown that the primary response involved hemodynamic and water-electrolyte changes. The mechanisms of cardiovascular adaptation to the immersion conditions were revealed. In particular, some electrophysiological shifts in the propagation of myocardial excitation were found, leading to an increase in the variance of natural small oscillations of the electric potential of the heart. The revealed significant reduction of the functional reserves of the cardiovascular regulatory mechanisms during adaptation to dry immersion is of great practical importance. The results suggest that the water-electrolyte balance shifts induced by dry immersion are the basis and the first phase of further changes in the autonomic regulation and functional state of the myocardium. © 2011 Pleiades Publishing, Ltd.

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