Advances in space biology and medicine最新文献

The aim of this study was to find the mechanisms leading to the weight changes that have frequently been observed during isolation and in spaceflight. Isolation studies with small groups impose limitations on the measurements that can be performed to simple, noninvasive methods. In this study the simple parameters of body weight and body composition, along with sodium and potassium excretion, were determined in three males and one female subject before, during and after 60 days of isolation. Our assumption was that application of these simple methods might provide valuable information, when measurements are done on a daily basis and when the pre- and post-isolation periods are taken into account. Three subjects gained weight before isolation, while one lost weight. All four subjects gradually lost weight during isolation, 1-4% of their weight on the first day of isolation. During the first post-isolation week weight remained stable. During isolation one subject lost body fat, whereas another lost body water and lean body mass, but gained body fat. The urinary electrolyte excretion pattern reflected the changes in body composition: sodium loss coincided with a decrease of total body water, and potassium loss with a decrease of lean body mass. The Bioelectrical Impedance Analysis method, used in defining changes in body composition, provided data in good agreement with those obtained with the double-labeled water method. The results reported here are in agreement with observations reported by other investigators with respect to the body weight changes and the body composition. However, it is still not understood why some subjects lose fat and others gain fat under identical conditions. Psychological factors may be involved in these individual differences. Two further points have become clear from these studies: (1) the pre- and post-isolation periods should be taken into account, (2) urinary electrolyte excretion must be seen in the context of changes in body composition, not only in the context of kidney function.

The present study describes the effects of a 60-day isolation period on the salivary levels of cortisol and secretory IgA. The study took place in the context of the EXEMSI project in which four volunteers were isolated in a space station-like chamber in the DLR Institute of Aerospace Medicine in order to examine the effects of long term isolation. Inspection of the individual immunoglobulin A secretion rates revealed different patterns of cyclic variation with respect to the weekday-weekend schedule, and different time lags for the adaptation leading to a plateau for this parameter. The salivary cortisol levels showed a circadian rhythm with high concentrations in the early morning (7:30 am) and lower concentrations in the late evening (11:00 pm). Moreover, in all subjects marked increases of salivary cortisol were observed in a 12- to 14-day cycle. In two subjects the marked morning-evening differences were only visible at the weekends. The salivary cortisol and immunoglobulin A levels were determined twice weekly before and after completion of a complex decision-making test. The results reveal a changed responsiveness in all subjects at different times.

A crew of four (three males and one male) were isolated for 60 days in hyperbaric chambers at DLR, Cologne, Germany. The aim of the study was to investigate how group functioning, relations with ground control, and interaction between crew members would change during isolation. A broad array of methods was used, including analysis of communication, peer ratings, questionnaires, and a post-isolation interview. The main findings are: 1. Group functioning declined at three times, immediately before and after the start of isolation, and in weeks 2 and 5; 2. Conflicts were often focused on project management. 3. Crew members showed a marked tendency to deny team conflicts, making them vulnerable to "group think;" 4. Towards the end of isolation, social factors were given more importance than task-related factors; 5. Lasting antagonism between two of the male crew members were noted, which made one of them withdraw from interaction, while the other one--the most dominant crew member--developed an alliance with the Commander. Several findings in this study are consistent with our earlier results from the ISEMSI study. The existence of several interpersonal issues has been identified, which are also likely to occur during actual space missions. Many of the interpersonal problems could probably be prevented or reduced through behavioral and sensitivity training, composition of crews according to compatibility, and monitoring of group functioning during the flight. We suggest that future simulation studies should be directed towards gaining practical experience in how to influence interpersonal relations in a desirable way. The joint training of ground crew and chamber crew created good co-operation between the two crews, but the adjustment to management requires more experience and new training procedures. The lack of formalized rules caused serious frustrations and negative feelings in both crews towards project management. Data from management and principal investigators were not available, but we suggest that such information should be collected in future simulation studies.

ESA has been studying a small-scale bioregenerative system to support long-term biological experiments on-board spacecraft with oxygen, water, and food. Core component of this system is a special photo-bioreactor in which a maltose-producing strain of the green alga Chlorella is cultivated. In initial experiments this bioreactor has been tested, and the physiology of Chlorella has been studied. The optimal conditions for CO2 to O2 conversion and maltose production have been determined, and the possibility of controlling the culture so as to match the needs of the consumer has been established. A microgravity-compatible photo-bioreactor, and a maltose separator have been developed and are functioning on the ground according to the design specifications. Tests in weightlessness will have to be performed in the future. The components are to be integrated to a complete bioregenerative life support system, which will then be subjected to extensive testing. The EXEMSI project afforded an opportunity to study the mutual influence of a Chlorella culture and real biological oxygen consumers, the four crew members in the laboratory module of the isolation facility. Chlorella 241.80 was batch cultured in an airlift bioreactor by the crew for 25 days with air aspirated from the module. The crew members determined pH and cell density in samples withdrawn from the culture. Microscopic observations showed no evidence of contamination of the culture by other organisms. Growth rates were smaller than those observed in laboratory conditions. This is attributed to the relatively low average CO2 concentration in the module atmosphere: 0.1% against 0.5% in the air supply during the laboratory experiments. The data show no evidence of trace contaminant accumulation in the Chlorella culture. The results are encouraging and suggest the value of further simulated operational testing of the system.

Extended spaceflights seem to be similar to lengthy sport trials, in which top athletes are stressed by confinement and are still asked to maintain a high level of performance, staving off fatigue and performance decrements. The athletes use coping strategies and recovery techniques in order to compensate for unexpected workoverload during sustained operation. Astronauts probably experience similar conditions, and they may use similar coping strategies and recovery techniques. Since sustained and continuous operation preferably affects the mental capabilities required for complex tasks, particular attention should be paid to decrements of mental and psychological performance and to techniques that could be used specifically for the recovery of a satisfactory level of performance.