Microgravity or simulated microgravity induces acute and chronic cardiovascular responses, whose mechanism is pivotal for understanding of physiological adaptation and pathophysiological consequences. We investigated hemodynamic responses of conscious Wistar rats to 45º head-down tilt (HDT) for 7 days. Arterial blood pressure (BP) was recorded by telemetry. Heart rate (HR), spectral properties and the spontaneous baroreflex sensitivity (sBRS) were calculated. Head-up tilt (HUT) was applied for 2 h before and after HDT to assess the degree of any possible cardiovascular deconditio ning. Horizontal control BP and HR were 112.5±2.8 mmHg and 344.7±10 bpm, respectively. HDT elicited an elevation in BP and HR by 8.3 % and 8.8 %, respectively, in less than 1 h. These elevations in BP and HR were maintained for 2 and 3 days, respectively, and then normalized. Heart rate variability was unchanged, while sBRS was permanently reduced from the beginning of HDT (1.01±0.08 vs. 0.74±0.05 ms/mmHg). HUT tests before and after HDT resulted in BP elevations (6.9 vs. 11.6 %) and sBRS reduction (0.44 vs. 0.37 ms/mmHg), respectively. The pressor response during the post-HDT HUT test was accompanied by tachycardia (13.7 %). In conclusion, chronic HDT does not lead to symptoms of cardiovascular deconditioning. However the depressed sBRS and tachycardic response seen during the post-HDT HUT test may indicate disturbances in cardiovascular control., G. Raffai ... [et al.]., and Obsahuje seznam literatury
Tomato seeds exposed to space conditions for nearly six years on board the Long Duration Exposure Facility (LDEF) satellite were subsequently germinated and the resultant seedlings grown on earth under controlled conditions for analysis. Photosynthesis, biomass, and water relations were compared between mature plants grown from earth-based control seeds and space-exposed seeds under both well-watered and drought-stressed conditions. No consistent significant differences in photosynthesis and water relations were observed in the two sets of plants at any level of drought stress. Fruit production, however, though limited and variable, was significantly greater in plants grown from space-exposed seeds than in plants grown from earth-based seeds. Overall, exposure of seeds to space had only minor effects on the physiology and growth of plants grown from such seed. and M. S. Marmor, C. E. Martin.
Numerous countermeasures have been proposed to minimize microgravity-induced physical deconditioning, but their benefits are limited. The present study aimed to investigate whether personalized aerobic exercise based on artificial gravity (AG) mitigates multisystem physical deconditioning. Fourteen men were assigned to the control group (n=6) and the countermeasure group (CM, n=8). Subjects in the CM group were exposed to AG (2 Gz at foot level) for 30 min twice daily, during which time cycling exercise of 80-95 % anaerobic threshold (AT) intensity was undertaken. Orthostatic tolerance (OT), exercise tests, and blood assays were determined before and after 4 days head-down bed rest (HDBR). Cardiac systolic function was measured every day. After HDBR, OT decreased to 50.9 % and 77.5 % of pre-HDBR values in control and CM groups, respectively. Exercise endurance, maximal oxygen consumption, and AT decreased to 96.5 %, 91.5 % and 91.8 % of pre-HDBR values, respectively, in the control group. Nevertheless, there were slight changes in the CM group. HDBR increased heart rate, sympathetic activity, and the pre-ejection period, but decreased plasma volume, parasympathetic activity and left-ventricular ejection time in the control group, whereas these effects were eliminated in the CM group. Aldosterone had no change in the control group but increased significantly in the CM group. Our study shows that 80-95 % AT aerobic exercise based on 2 Gz of AG preserves OT and exercise endurance, and affects body fluid regulation during short-term HDBR. The underlying mechanisms might involve maintained cardiac systolic function, preserved plasma volume, and improved sympathetic responses to orthostatic stress., X.-T. Li, C.-B. Yang, Y.-S. Zhu, J. Sun, F. Shi, Y.-C. Wang, Y. Gao, J.-D. Zhao, X.-Q. Sun., and Obsahuje bibliografii
Článek se zabývá hlavními fyzikálními a fyziologickými determinantami výkonnosti člověka v kosmu a zároveň poukazuje na doposud méně reflektované psychické souvislosti pobytu jedince v tomto extrémním prostředí. Největší pozornost věnuje problematice mikrogravitace, radiace a cirkadiánních rytmů s důrazem na adaptační změny nejen ve fyziologických a psychofyziologických, ale především v psychických procesech. Zaobírá se otázkou pozměněné kvality zpracovávaných informací v prostředí mikrogravitace, a izolace od běžných podnětů a ukazatelů a navozuje otázku dostupnosti a adekvátnosti signálů nejenom pro kognitivní, ale i afektivní a konativní procesy. Autorka soudí, že vedle fyziologické a psychofyziologické adaptace na kosmické prostředí nutně dochází i k adaptaci psychické, respektive k adaptaci psychických procesů. Stať dospívá k závěru, že k plnějšímu pochopení adaptace kognitivních, afektivních a konativních procesů je potřeba především hloubkových kvalitativních šetření průběhu psychické adaptace jedinců pobývajících v kosmu., This paper deals with the main physical and physiological determinants of human performance during a spaceflight and also addresses so far insufficiently discussed psychological context of being in this extreme environment. The greatest attention is paid to the issue of microgravity, radiation and circadian rhythms, with emphasis on the adaptive changes in physiological and psycho-physiological processes. The study explores the issue of data acquisition and the quality of information processing under the condition of isolation and confinement from natural stimuli and indicators. In this way, the paper further deals with the signals available to crew members about the changes in their cognitive, affective and motivational processes. The paper claims that besides the physiological and psycho-physiological adaptation to the space environment, psychological adaptation necessarily goes on at the same time It is concluded that the in-depth qualitative investigation of the psychological adaptation could provide a more complete understanding of the accommodation of cognitive, affective and motivational processes during spaceflights., Iva Poláčková Šolcová., and Obsahuje seznam literatury