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PubMed1996

Body weight and body composition during sixty days of isolation.

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.

Adult↗
PubMed1996

Neuroendocrine system and immune responses after confinement.

A confinement experiment in a normobaric diving chamber was undertaken to obtain more understanding of the effects of confinement and isolation on human psychology and physiology. Pre- and post-confinement blood samples were obtained from four test subjects and five control subjects for the analysis of plasma proteins, hormone levels and immune responses. The absence of significant changes in the immune responses correlates with the absence of major changes in neurohormones and other hormones such as cortisol, prolactin, growth hormone, insulin-like growth factor 1, triiodothyronin, thyrotrophin and 1,25-dihydroxyvitamin D. It is increasingly recognized that the immune system is not an independent physiological system, but a system that interacts multidirectionally with other organs and body functions. It seems that the conditions of this confinement experiment were not stressful from a psychological point of view. The presence of a female crew member had probably a positive effect on group behavior of the test subjects. In conclusion, the data suggest that confinement for 60 days in a small habitat without particularly stressful situations has no significant impact on a variety of neuroimmunological parameters.

Adult↗
PubMed1996

Local immunocompetence and salivary cortisol in confinement.

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.

Adult↗
PubMed1996

Cardiovascular and respiratory responses during a complex decision-making task under prolonged isolation.

Self-administered psychophysiological assessment during a mission is not only feasible, but yields reliable data that can be related to mission demands in a meaningful way. The unique methodology that has been employed during the EXEMSI campaign, may be of great promise for the development of techniques that provide daily monitoring of physiological cost of mission demands. This approach can thus be used for obtaining a better understanding of problems that can arise with regard to the functioning of individual crew members. The response profiles of the individual crew members showed remarkable quantitative and qualitative differences during isolation. Due to the limitations of this study, these differences could by no means all be explained in terms of mission demands, operator workload or other relevant parameters. However, the findings do seem to permit some tentative conclusions. In subjects B and D the cardiovascular response profiles suggested that cumulative stress effects emerged, in particular during the second part of the mission. It is important to note that both subjects carried specific responsibilities for the success of the mission, and that there was evidence for a conflict between them. Concerning the question which physiological measures are most appropriate for in-mission psychophysiological assessment, these results can appear to imply that cardiovascular measures yield more valid information about the effects of mission demands that respiratory measures. However, it should be noted that important aspects of respiratory activity, namely, respiratory volume measures and ventilation, could not be reliably determined in this study. Therefore, definitive conclusions concerning the choice of measures wait until the validity of the measures has been more extensively evaluated. Although the methodology that was developed for this study appears to be promising, it is obvious that its value can only be properly assessed when the physiological findings are correlated with behavioral, performance and subjective data. An extensive analysis of the covariation of the daily variations in physiological response, performance measures, and subjective assessments of workload and mood, is currently in progress in collaboration with Hockey and Sauer. Finally, if the usefulness and validity of this type of in-mission self-administered psychophysiological assessment are confirmed in ongoing and future studies (e.g., the 1994 HUBES mission), protocols will have to be worked out for practical implementation during actual spaceflights. In this regard, it has been advocated that psychophysiological monitoring techniques should include feedback and support policies, make crew members aware of potential risks for breakdown, and enable them to take appropriate measures when necessary. Initially, this can perhaps best be realized by procedures which include a data-link between the spacecraft and ground mission control. On the basis of ground-based analysis and evaluation of the data, psychologists at mission control may decide to provide information to the crew concerning potential individual or intragroup overload or stress problems, and to implement specific supportive measures. The effectiveness of the supportive activities should be closely monitored by mission control. Future work should also be aimed at developing expert-systems, which will enable the crew to maintain an appropriate degree of inflight biobehavioral self-regulation by providing a range of support techniques, like biofeedback, coping techniques against individual and group stressors, work/rest and sleep/wake schedules, and emergency procedures.

Adult↗
PubMed1996

Performance and brain electrical activity during prolonged confinement.

A subset of the AGARD-STRES battery including memory search, unstable tracking, and a combination of both tasks (dual-task), was applied repeatedly to the four chamber crew members before, during, and after the 60-day isolation period of EXEMSI. Five ground control group members served as a control group. A subjective state questionnaire was also included. The results were subjected to a quantitative single-subject analysis. Electroencephalograms (EEG) were recorded to permit correlation of changes in task performance with changes in the physiological state. Evaluation of the EEG focused on spectral parameters of spontaneous EEG waves. No physiological data were collected from the control group. Significant decrements in tracking ability were observed in the chamber crew. The time course of these effects followed a triphasic pattern with initial deterioration, intermediate recovery to pre-isolation baseline scores after the first half of the isolation period, and a second deterioration towards the end. None of the control group subjects displayed such an effect. Memory search (speed and accuracy) was only occasionally impaired during isolation, but the control group displayed a similar pattern of changes. It is suggested that a state of decreased alertness causes tracking deterioration, which leads to a reduced efficiency of sustained cue utilization. The assumption of low alertness was further substantiated by higher fatigue ratings by the chamber crew compared to those of the control group. Analysis of the continuous EEG recordings revealed that only two subjects produced reliable alpha wave activity (8-12 Hz) over Pz and, to a much smaller extent, Fz-theta wave activity (5-7 Hz) during task performance. In both subjects Pz-alpha power decreased consistently under task conditions involving single-task and dual-task tracking. Fz-theta activity was increased more by single-task and dual-task memory search than by single-task tracking. The alpha attenuation appears to be associated with an increasing demand on perceptual cue utilization required by the tracking performance. In one subject marked attenuation of alpha power occurred during the first half of the confinement period, where he also scored the highest fatigue ratings. A striking increase in fronto-central theta activity was observed in the same subject after six weeks of isolation. The change was associated with an efficient rather than a degraded task performance, and a high rating of the item "concentrated" and a low rating of the item "fatigued." This finding supports the hypothesis that the activation state associated with increased fronto-central theta activity accompanies efficient performance of demanding mental tasks. The usefulness of standardized laboratory tasks as monitoring instruments is demonstrated by the direct comparability with results of studies obtained from other relevant research applications using the same tasks. The feasibility of a self-administered integrated psychophysiological assessment of the individual state was illustrated by the nearly complete collection of data. The large number of individual data collected over the entire period permitted application of quantitative single-subject analysis, allowing reliable determination of changes in the individual state in the course of time. It thus appears that this assessment technique can be adapted for in-flight monitoring of astronauts during prolonged spaceflights. Parallel EEG recording can provide relevant supplementary information for diagnosing the individual activation state associated with task performance. The existence of large individual differences in the generation of task-sensitive EEG rhythms forms an important issue for further studies.

Adult↗
PubMed1996

Attention and mental performance in confinement: evidence from cognitive psychophysiology.

In summary, the results provide several lines of evidence for the assumption that confinement and isolation for a period of 60 days attenuate attentional capacity differentially during auditory classification: the extraction of information from low probability events, but not from high probability events, is decreased by attentional limitations. With the advent of automatic control systems there is an increasing number of operations which require the monitoring of information sources for low probability critical stimuli for extended periods of time. Given the functional similarities of the task employed in this study and the monitoring tasks in practical settings, the results of this study should be considered as a human factor concern for control operations taking place under conditions of confinement and isolation.

Adult↗
PubMed1996

Group dynamics and crew interaction during isolation.

The Homeostat test system was used to determine the interaction effectiveness of the chamber crew during isolation. The group had a complex and unique structure, reflected in the fact that all four subjects expressed considerable leadership activity. The course of the Homeostat task solution parameters testifies to the formation of an intergroup communicative net, which was not completed. This phenomenon was accompanied by emotional tension in the group. The individual contributions to the interaction were investigated. The crew represents a small group with a complex communicative structure. This was due to the presence of above normal leadership activity in all four crew members. The complex course of the leadership activity parameter and the presence of elements of group management allow us to label the crew as a complementary group, which is capable of coping with a wide range of tasks in problem situations. At the same time, the complex group structure caused a certain level of emotional tension in the group. This tension was drained to the outside world by conflicts with the project management. Subjects B and H played a positive role in the reduction of intergroup tension.

Astronauts↗
PubMed1997

Changes in the immune system during and after spaceflight.

The results of immunological analyses before, during and after spaceflight, have established the fact that spaceflight can result in a blunting of the immune mechanisms of human crew members and animal test species. There is some evidence that the immune function changes in short-term flights resemble those occurring after acute stress, while the changes during long-term flights resemble those caused by chronic stress. In addition, this blunting of the immune function occurs concomitant with a relative increase in potentially infectious microorganisms in the space cabin environment. This combination of events results in an increased probability of inflight infectious events. The realization of this probability has been shown to be partially negated by the judicious use of a preflight health stabilization program and other operational countermeasures. The continuation of these countermeasures, as well as microbial and immunological monitoring, are recommended for continued spaceflight safety.

Acute Disease↗
PubMed1997

Frog experiment onboard space station Mir.

Japanese tree frogs (Hyla japonica) showed unique postures and behavior during an 8-day flight to the Russian space station Mir. When floating in the air, the animals arched their back and extended their four limbs. This posture resembles that observed during jumping or parachuting of the animals on the ground. Frog sitting on a surface bent their neck backward sharply, did not fold their hind limbs completely, and pressed their abdomen against the substrate. They walked backwards in this posture. The typical posture resembles that adopted during the emetic behavior process on the ground, although the posture in space lasts much longer. The possible mechanism of induction of this unique posture in orbit is discussed. Frogs in this posture might be in an emetic state, possibly due to motion sickness. Response behavior to some stimuli was observed in orbit. Body color change in response to the background color appeared to be delayed or slowed down. Response behavior to other stimuli showed little change as long as the animal maintained contact with a substrate. Once it left the surface, the floating frog could not control its movements so as to provide coordinated motility for locomotion and orientation. Adaptation to microgravity was observed in the landing behavior after jumping. Readaptation of the frogs to the Earth environment took place within a few hours after return. Postflight histological and biochemical analysis of organs and tissues showed some changes after the 8-day spaceflight. Weakening and density loss in vertebrae was noted. The beta-adrenoreceptor activity of the gastrocnemius was natriuretic decreased. Skin collagen and liver protein synthesis were lowered. The distribution of the atrial factor-like peptides in the brain was changed.

Adaptation, Physiological↗
PubMed2001

CYP2C19 genotype related effect of omeprazole on intragastric pH and antimicrobial stability.

PURPOSE: A combination of proton pump inhibitors and antimicrobials has been applied as an anti-Helicobacter pylori (H. pylori) therapy. Omeprazole, one of the proton pump inhibitors, is metabolized by CYP2C19. which exhibits genetic polymorphism. It was reported previously that the overall anti-H. pylori efficacy can be related to the CYP2C19 genotype. The main aim of the present study was to obtain a rational explanation for the relationship between the overall anti-H. pylori efficacy and the CYP2C19 genotype. METHODS: Six healthy volunteers were classified as extensive metabolizers and poor metabolizers, according to their CYP2C19 genotypes. Plasma concentrations and intragastric pH were monitored prior to and until 24 h after the administration of 20 mg omeprazole. The stability of amoxicillin, clarithromycin, and metronidazole was examined using buffer solutions with monitored intragastric pH, and their remaining percentage in the intragastric space was simulated. RESULTS: The poor metabolizers, classified by the CYP2C19 genotypes, showed the higher effectiveness in anti-H. pylori therapy, via the higher plasma concentration of omeprazole and the higher intragastric pH, and possibly the higher stability of antimicrobials in the higher intragastric pH. CONCLUSIONS: CYP2C19 genotyping is a very useful method to determine the effective and safe dosage regimen including the selection of the dual and triple therapy in anti-H. pylori therapy.

Amoxicillin↗
PubMed2005

Your highness: vertical positions as perceptual symbols of power.

Metaphorically, power equals up. Drawing on embodied theories of cognition, the author argues that thinking about power involves mental simulation of space and can be interfered with by perception of vertical differences. Study 1 assessed image schemas for power and found a shared vertical difference metaphor. Studies 2, 3, and 4 showed that the judgment of a group's power is influenced by the group's vertical position in space and motor responses implying vertical movement. Study 5 ruled out that the influence of vertical position on power judgments is driven by valence differences. Study 6 showed that vertical position also influences the power judgment result itself. The evidence suggests that the concept of power is partly represented in perceptual form as vertical difference.

Adult↗
PubMed2006

The size of the sync basin.

We suggest a new line of research that we hope will appeal to the nonlinear dynamics community, especially the readers of this Focus Issue. Consider a network of identical oscillators. Suppose the synchronous state is locally stable but not globally stable; it competes with other attractors for the available phase space. How likely is the system to synchronize, starting from a random initial condition? And how does the probability of synchronization depend on the way the network is connected? On the one hand, such questions are inherently difficult because they require calculation of a global geometric quantity, the size of the "sync basin" (or, more formally, the measure of the basin of attraction for the synchronous state). On the other hand, these questions are wide open, important in many real-world settings, and approachable by numerical experiments on various combinations of dynamical systems and network topologies. To give a case study in this direction, we report results on the sync basin for a ring of n >> 1 identical phase oscillators with sinusoidal coupling. Each oscillator interacts equally with its k nearest neighbors on either side. For k/n greater than a critical value (approximately 0.34, obtained analytically), we show that the sync basin is the whole phase space, except for a set of measure zero. As k/n passes below this critical value, coexisting attractors are born in a well-defined sequence. These take the form of uniformly twisted waves, each characterized by an integer winding number q, the number of complete phase twists in one circuit around the ring. The maximum stable twist is proportional to n/k; the constant of proportionality is also obtained analytically. For large values of n/k, corresponding to large rings or short-range coupling, many different twisted states compete for their share of phase space. Our simulations reveal that their basin sizes obey a tantalizingly simple statistical law: the probability that the final state has q twists follows a Gaussian distribution with respect to q. Furthermore, as n/k increases, the standard deviation of this distribution grows linearly with square root of n/k. We have been unable to explain either of these last two results by anything beyond a hand-waving argument.

Journal Article↗
PubMed2002

Neurovestibular modulation of circadian and homeostatic regulation: vestibulohypothalamic connection?

Chronic exposure to increased force environments (+G) has pronounced effects on the circadian and homeostatic regulation of body temperature (T(b)), ambulatory activity (Act), heart rate, feeding, and adiposity. By using the Brn 3.1 knockout mouse, which lacks vestibular hair cells, we recently described a major role of the vestibular system in mediating some of these adaptive responses. The present study used the C57BL6JEi-het mouse strain (het), which lacks macular otoconia, to elucidate the contribution of specific vestibular receptors. In this study, eight het and eight WT mice were exposed to 2G for 8 weeks by means of chronic centrifugation. In addition, eight het and eight WT mice were maintained as 1G controls in similar conditions. Upon 2G exposure, the WT exhibited a decrease in T(b) and an attenuated T(b) circadian rhythm. Act means and rhythms also were attenuated. Body mass and food intake were significantly lower than the 1G controls. After 8 weeks, percent body fat was significantly lower in the WT mice (P < 0.0001). In contrast, the het mice did not exhibit a decrease in mean T(b) and only a slight decrease in T(b) circadian amplitude. het Act levels were attenuated similarly to the WT mice. Body mass and food intake were only slightly attenuated in the het mice, and percent body fat, after 8 weeks, was not different in the 2G het group. These results link the vestibular macular receptors with specific alterations in homeostatic and circadian regulation.

Acceleration↗
PubMed2003

Work design and analysis for space-based manufacturing: a case analysis of initial design issues.

The purpose of the present research was to investigate the nature of potential manufacturing tasks humans may execute in a space environment. The success of space-based manufacturing (SBM) is suggested to be a precursor to permanent human presence in space. A working hypothesis for this study was that human work in the SBM environment would be substantially different from terrestrial manufacturing work. To investigate this hypothesis, a case analysis approach was developed that employed a function allocation and task analysis of a representative SBM process: the production of tailored industrial crystals. This research approach was chosen as the current state of engineering design for SBM is in the conceptual and early flow sheeting phases of a system life cycle. Results of the task analysis and function allocation process suggest response to corrective maintenance functions and to abnormal system conditions should be allocated to humans as opposed to automation. These results are discussed in relation to human factors engineering challenges associated with long-duration human presence in an SBM environment.

Crystallization↗
PubMed1999

Manned missions to Mars and chromosome damage.

PURPOSE: To estimate the frequencies of dicentric chromosomes in peripheral lymphocytes of astronauts on missions to Mars. MATERIALS AND METHODS: Calculations of expected frequencies of dicentrics are based on dose estimations and lymphocyte biology. RESULTS: Frequencies of dicentrics are predicted to be 10-40 times higher than the background level. CONCLUSIONS: Stressing the importance of careful mission planning and optimized shielding of transfer vehicle to Mars.

Astronauts↗
PubMed1993

Extreme environments and exobiology.

Ecological research on extreme environments can be applied to exobiological problems such as the question of life on Mars. If life forms (fossil or extant) are found on Mars, their study will help to solve fundamental questions about the nature of life on Earth. Extreme environments that are beyond the range of adaptability of their inhabitants are defined as "absolute extreme". Such environments can serve as terrestrial models for the last stages of life in the history of Mars, when the surface cooled down and atmosphere and water disappeared. The cryptoendolithic microbial community in porous rocks of the Ross Desert in Antarctica and the microbial mats at the bottom of frozen Antarctic lakes are such examples. The microbial communities of Siberian permafrost show that, in frozen but stable communities, long-term survival is possible. In the context of terraforming Mars, selected microorganisms isolated from absolute extreme environments are considered for use in creation of a biological carbon cycle.

Antarctic Regions↗