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At least 433 records · Page 24Linked to original sources
PubMed2000

Rhesus leg muscle EMG activity during a foot pedal pressing task on Bion 11.

Rhesus monkeys (Macaca mulatta) were trained to perform a foot lever pressing task for a food reward. EMG activity was recorded from selected lower limb muscles of 2 animals before, during, and after a 14-day spaceflight and from 3 animals during a ground-based simulation of the flight. Integrated EMG activity was calculated for each muscle during the 20-min test. Comparisons were made between data recorded before any experimental manipulations and during flight or flight simulation. Spaceflight reduced soleus (Sol) activity to 25% of preflight levels, whereas it was reduced to 50% of control in the flight simulation. During flight, medial gastrocnemius (MG) activity was reduced to 25% of preflight activity, whereas the simulation group showed normal activity levels throughout all tests. The change in MG activity was apparent in the first inflight recording, suggesting that some effect of microgravity on MG activity was immediate.

Adaptation, Physiological↗
PubMed1998

Animats: computer-simulated animals in behavioral research.

The term animat refers to a class of simulated animals. This article is intended as a nontechnical introduction to animat research. Animats can be robots interacting with the real world or computer simulations. In this article, the use of computer-generated animats is emphasized. The scientific use of animats has been pioneered by artificial intelligence and artificial life researchers. Behavior-based artificial intelligence uses animats capable of autonomous and adaptive activity as conceptual tools in the design of usefully intelligent systems. Artificial life proponents view some human artifacts, including informational structures that show adaptive behavior and self-replication, as animats may do, as analogous to biological organisms. Animat simulations may be used for rapid and inexpensive evaluation of new livestock environments or management techniques. The animat approach is a powerful heuristic for understanding the mechanisms that underlie behavior. The simple rules and capabilities of animat models generate emergent and sometimes unpredictable behavior. Adaptive variability in animat behavior may be exploited using artificial neural networks. These have computational properties similar to natural neurons and are capable of learning. Artificial neural networks can control behavior at all levels of an animat's functional organization. Improving the performance of animats often requires genetic programming. Genetic algorithms are computer programs that are capable of self-replication, simulating biological reproduction. Animats may thus evolve over generations. Selective forces may be provided by a human overseer or be part of the simulated environment. Animat techniques allow researchers to culture behavior outside the organism that usually produces it. This approach could contribute new insights in theoretical ethology on questions including the origins of social behavior and cooperation, adaptation, and the emergent nature of complex behavior. Animat studies applied to domestic animals have been few so far, and have involved simulations of space use by swine. I suggest other applications, including modeling animal movement during human handling and the effects of environmental enrichment on the satisfaction of behavioral needs. Appropriate use of animat models in a research program could result in savings of time and numbers of animals required. This approach may therefore come to be viewed as both ethically and economically advantageous.

Animal Welfare↗
PubMed2006

Survival and germinability of Bacillus subtilis spores exposed to simulated Mars solar radiation: implications for life detection and planetary protection.

Bacterial spores have been considered as microbial life that could survive interplanetary transport by natural impact processes or human spaceflight activity. Deposition of terrestrial microbes or their biosignature molecules onto the surface of Mars could negatively impact life detection experiments and planetary protection measures. Simulated Mars solar radiation, particularly the ultraviolet component, has been shown to reduce spore viability, but its effect on spore germination and resulting production of biosignature molecules has not been explored. We examined the survival and germinability of Bacillus subtilis spores exposed to simulated martian conditions that include solar radiation. Spores of B. subtilis that contain luciferase resulting from expression of an sspB-luxAB gene fusion were deposited on aluminum coupons to simulate deposition on spacecraft surfaces and exposed to simulated Mars atmosphere and solar radiation. The equivalent of 42 min of simulated Mars solar radiation exposure reduced spore viability by nearly 3 logs, while germination-induced bioluminescence, a measure of germination metabolism, was reduced by less than 1 log. The data indicate that spores can retain the potential to initiate germination-associated metabolic processes and produce biological signature molecules after being rendered nonviable by exposure to Mars solar radiation.

Aluminum↗
PubMed2000

Team play with a powerful and independent agent: a full-mission simulation study.

One major problem with pilot-automation interaction on modern flight decks is a lack of mode awareness; that is, a lack of knowledge and understanding of the current and future status and behavior of the automation. A lack of mode awareness is not simply a pilot problem; rather, it is a symptom of a coordination breakdown between humans and machines. Recent changes in automation design can therefore be expected to have an impact on the nature of problems related to mode awareness. To examine how new automation properties might affect pilot-automation coordination, we performed a full-mission simulation study on one of the most advanced automated aircraft, the Airbus A-320. The results of this work indicate that mode errors and "automation surprises" still occur on these advanced aircraft. However, there appear to be more opportunities for delayed or missing interventions with undesirable system activities, possibly because of higher system autonomy and coupling.

Adult↗
PubMedDate not supplied

Bubble detector characterization for space radiation.

In light of the importance of the neutron contribution to the dose equivalent received by space workers in the near-Earth radiation environment, there is an increasing need for a personal dosimeter that is passive in nature and able to respond to this neutron field in real time. Recent Canadian technology has led to the development of a bubble detector, which is sensitive to neutrons, but insensitive to low linear energy transfer (LET) radiation. By changing the composition of the bubble detector fluid (or "superheat"), the detectors can be fabricated to respond to different types of radiation. This paper describes a preliminary ground-based research effort to better characterize the bubble detectors of different compositions at various charged-particle accelerator facilities, which are capable of simulating the space radiation field.

Calibration↗
PubMed1998

[Fatty acid composition of the lipids in human blood plasma and erythrocyte membranes during simulation of extravehicular activities of cosmonauts].

Dynamics of the lipoacidic content of total plasma lipids and erythtocyte membranes was studied in 32 experiments with ten apparently healthy male subjects aged 27 to 41 years who were exposed to repeated decompression from the normal ground down to 40-35 kPa. For two hours of exposure to lowered pressure the subjects were breathing pure oxygen in mask and performing incremental physical work mimicking loading of the upper extremities of cosmonauts doing extravehicular activities (EVA) at the energy cost of 3 kcal/min. Decompression sessions were repeated with intervals from 3 to 5 days. In seven experiments, the subjects developed symptoms of the decompression sickness (DCS). Penetration of gas bubbles (GB) into the pulmonary artery was registered in 27 cases (84.4%). In 24 cases maximal intensity of the US signals from GB reached 3 to 4 Spencer's points. No changes in the lipidoacidic content of blood plasma or erythrocyte membranes were determined following the first exposure to decompression. BY the onset of repeated decompression, total number of lipids in erythrocyte membranes decreased from 54.6 to 40.4 mg% in the group of subjects who had not displayed DCS symptoms (n = 5) and from 51.2 to 35.2 mg% (p < 0.05) in the group of subjects with DCS symptoms (n = 5). In the subjects with DCS, polyunsaturated linoleic acid (18:2) tended to decrease against the upward trend of saturated fatty acids (16:0, 18:0). In these subjects, arachidonic acid in erythrocyte membranes (20:4) decreased following each decompression exposure and significantly increased (p < 0.05) in-between. In both groups, blood plasma showed slight fluctuations in the lipoacidic contents. These data suggest that exposure to the variety of the EVA-simulating factors may entail quite distinct but reversible modifications in the lipid metabolism in blood and the structural/functional state of erythrocyte membranes. The most marked alterations were observed in the subjects with the DCS symptoms during high intensity of US signals from GB in the venous blood flow.

Adult↗
PubMed1997

Evidence for increased beta-adrenoreceptor responsiveness induced by 14 days of simulated microgravity in humans.

We studied hemodynamic responses to alpha- and beta-receptor agonists in eight healthy men before and after 14 days of 6 degrees head-down tilt (HDT) to test the hypothesis that increased adrenoreceptor responsiveness is induced by prolonged exposure to simulated microgravity. Steady-state infusions of isoproterenol (Iso) at rates of 0.005, 0.01, and 0.02 microgram.kg-1.min-1 were used to assess beta 1- and beta 2-adrenoreceptor responsiveness. Infusions of phenylephrine (PE) at rates of 0.25, 0.50, and 1.00 microgram.kg-1.min-1 were used to assess responsiveness of alpha 1-vascular adrenoreceptors. Slopes calculated from linear regressions between Iso and PE doses and changes in beat-to-beat heart rate, blood pressure, and leg vascular resistance (occlusion plethysmography) for each subject were used as an index of alpha- and beta-adrenoreceptor responsiveness. HDT increased the slopes of heart rate (1,056 +/- 107 to 1,553 +/- 83 beats micrograms-1.kg-1.min-1; P = 0.014) and vasodilation (-469 +/- 111 to -1,446 +/- 309 peripheral resistance units.microgram-1.kg-1.min-1; P = 0.0224) to Iso infusion. There was no alteration in blood pressure or vascular resistance responses to PE infusion after HDT. Our results provide evidence that simulated microgravity causes selective increases in beta 1- and beta 2-adrenoreceptor responsiveness without affecting alpha 1-vascular adrenoreceptor responses.

Adult↗
PubMed1995

Animal research in microgravity and flight environment: lessons from the past for the future.

The use of animals, and more particularly the use of non-human primates, takes on importance when studying the physiological responses involved in the adaptation to changes in gravitational loading. The "Rhesus project", now canceled, was a joint program between CNES and NASA designed to carry out simultaneous experiments of various physiological disciplines using the Rhesus monkey as a human surrogate. The choice of this species was supported by several strong arguments such as the possibility of studying several physiological systems without over-instrumenting, as well as the morphological and phylogenetical closeness with man. Within this framework, building the inflight animal facilities necessary to achieve the ambitious scientific program that was established, required state of art design and technology. Spacelab flight simulations were conducted with the goal both to obtain baseline data and to evaluate the impact of the cabin environment on the circadian timekeeping system which is involved in the regulation of almost all physiological functions and behavior. Even if this project would never fly, the results from these experiments have been a source of thoughts and lessons for the future animal research in microgravity.

Animals↗
PubMed1997

Evolution of sleep and wakefulness organization in Macaca mulatta during Spacelab flight simulation.

NASA and CNES agencies planned to perform neurophysiological studies aboard Spacelab using rhesus monkeys as human models. The present study was conducted to assess the influence of restraint and confinement conditions on the circadian sleep-wake rhythm before an actual flight. Three experimental 18-day flight simulations were performed on 6 adult Macaca mulatta, chair-restrained in a high-fidelity mock-up of the Spacelab compartment. Wakefulness, non-REM sleep and REM-sleep were determined by analysis of animal behavior from video recordings. As the experiment progressed significant changes were observed, characterized by a progressive increase of non-REM sleep of around one hour, mainly during the light period (7 am - 11 pm) at the expense of wakefulness. Duration and number of sleepiness episodes and phases of inactivity increased. A clear, new, pattern of sleep-wake cycles occurred, mainly in the last 3 days with a sharp rise in total non-REM sleep. The observed disturbances were determined to be a consequence of the confinement, the limited space and the reduced motor activity as well as of restraint. The evolution of sleep-wake cycles in 3 stages reflected the fact that the organism appeared to have adapted to the new situation. These results suggest that future studies of monkeys during orbital flight should take into account the effects of external factors such as the conditions of confinement and of restraint as well as the effects of microgravity.

Adaptation, Physiological↗
PubMed2001

Carbon and silicate grains in the laboratory as analogues of cosmic dust.

Carbon and silicate grains are the two main components of cosmic dust. There is increasing spectroscopic evidence that their composition varies according to the cosmic environment and the experienced processing. Irradiation from ultraviolet photons and cosmic rays, as well as chemical interactions with the interstellar gas play a crucial role for grain transformation. The study of 'laboratory analogues' represents a powerful tool to better understand the nature and evolution of cosmic materials. In particular, simulations of grain processing are fundamental to outline an evolutionary pathway for interstellar particles. In the present work, we discuss the ultraviolet and infrared spectral changes induced by thermal annealing, ultraviolet irradiation, ion irradiation and hydrogen atom bombardment in carbon and silicate analogue materials. The laboratory results give the opportunity to shed light on the long-standing problems of the attribution of ultraviolet and infrared interstellar spectral features.

Astronomical Phenomena↗
PubMed2003

Development and research program for a soil-based bioregenerative agriculture system to feed a four person crew at a Mars base.

For humans to survive during long-term missions on the Martian surface, bioregenerative life support systems including food production will decrease requirements for launch of Earth supplies, and increase mission safety. It is proposed that the development of "modular biospheres"--closed system units that can be air-locked together and which contain soil-based bioregenerative agriculture, horticulture, with a wetland wastewater treatment system is an approach for Mars habitation scenarios. Based on previous work done in long-term life support at Biosphere 2 and other closed ecological systems, this consortium proposes a research and development program called Mars On Earth(TM) which will simulate a life support system designed for a four person crew. The structure will consist of 6 x 110 square meter modular agricultural units designed to produce a nutritionally adequate diet for 4 people, recycling all air, water and waste, while utilizing a soil created by the organic enrichment and modification of Mars simulant soils. Further research needs are discussed, such as determining optimal light levels for growth of the necessary range of crops, energy trade-offs for agriculture (e.g. light intensity vs. required area), capabilities of Martian soils and their need for enrichment and elimination of oxides, strategies for use of human waste products, and maintaining atmospheric balance between people, plants and soils.

Air Conditioning↗
PubMed1997

On the Way to New Horizons: Telemedicine in Oncology.

Breathtaking insights into carcinogenesis and tumor biology have been gained mainly by recent technical advances in molecular-biological and genetic techniques. Thus, dimensions of earlier diagnosis and the development of new concepts in therapy arise, which were previously unavailable. There is no doubt that through these techniques the future role and tasks of surgical oncology will change. New indications will result, for example, in the context of prophylactic therapy of hereditary malignant disease or the removal of tissue predisposed to tumors. However, modes of therapy orientated toward molecular biology will still be dependent on specialist surgical interventions in the future. Examples are such innovative concepts of therapy as transport of a therapeutic device to or into tumor cells (e.g., gene gun), or even simply obtaining the necessary tumor tissue for therapy (vaccination with transfected autologous tumor cells). Therefore, the future of surgical oncology will be influenced quantitatively as well as conceptually by new qualitative requirements. Improving precision of the surgical intervention will have to go hand-in-hand with a further reduction in surgical trauma. The consistent use of laser, video, computer and communication technology can be seen as an important predeterminant here for optimizing diagnostic and therapeutic procedures. If correctly guided, the professional experience of the individual surgeon and his personal efficiency can also be positively influenced by the swift conversion of society to multimedia and information technology. Major advances in interdisciplinary communication, as one important factor in the choice and the course of suitable complex therapies in oncology, will have to target and help to overcome former weak spots. Communication in and outside one department or hospital, as well as external communication between different medical disciplines and specialists, is being developed further and increasingly refined. The possibilities of modern technology in addition to verbal exchange include visual and interactive "tele"-communication. This renders a new option to the physician, as without direct patient contact he is able to observe, counsel and actively interact - the latter even more so in the future. In oncology the increase of knowledge thus far has gone hand-in-hand with further specialization. This explains the difficulties one encounters in the correct evaluation of relevant data of one specific patient. Telemedicine will help to focus on the advantages of specialist knowledge by rendering access to all available data. These possibilities should furthermore be accessible during a consultation, an examination or in the course of a surgical intervention. Real-time modalities are referred to as telepresence and exceed by far a mere electronic version of the patient's medical folder. Especially in oncology, interdisciplinary collaboration is immensely important for successful therapy. Preoperative diagnostic data are still to be evaluated according to the intraoperative findings. At this decisive moment, it is necessary to involve specialists of other oncological disciplines. Real-time communication devices have to be present in order to transfer image data and clinical observations and ensure the best possible transmission quality to resident and geographically distant experts. With further technological perfection and widespread availability of interactive consultation, other applications include the "second opinion" in the daily routine. Another fascinating option in oncology is offered by visual computer simulation in virtual reality (VR). Medical data are visualized according to the human perception by the means of scenic simulation. From that point of view, VR technologies represent a practicable user interface between computer technology and the individual human being. Through VR, three-dimensional worlds containing virtual objects, which consist of computer-generated data, are created, which the user may explore and liberally interact with. The perfect simulation of realistic settings offers a method of training that may be extended to the field of oncology, as it has been known for a comparatively long period of time from flight simulators in space and air technology. In contrast, medical training is currently achieved mainly by "training-on-the-job." There is well-proven and widely acknowledged certainty of the tremendous influence that the number of surgical interventions-in other words, the training skills of the surgeon-has on the success of a diagnostic or therapeutic intervention. Previously, the subjective experience of the physician acquired from earlier cases determined his efficiency to a large extent. It was, in addition, influenced essentially by perception, "performance on the day" and personal attitude. The goal must be to strengthen the objective criteria as the basis for consistent decision-making processes and clear instructions for therapy. Strict quality management as practiced in air technology has clearly led to a reduction in accidents, and, accordingly, a similar effect is imaginable in oncology with continuous training using VR simulators, leading to improved therapeutic outcome. Other possibilities for use are principally implied and similarly useful for medical school and postgraduate training. The idea of computer-guided medical procedures or medical robots is therefore no longer a mere utopia. Telepresence, telerobotic and VR techniques should, in principle, effectively support the physician in diagnostic processes and therapy. The responsibility for coordination and sensible use of new technological developments will still remain with the physician, such as improving and simplifying medical procedures. Technology should be used according to the situation, not to adapt the patient to a technocratic environment, but to emphasize human treatment of the individual patient. From the opinion of the telephone being a futile technical invention to the other extreme of computed technology as a substitute for the physician (Dr. Cyber), the future role of telemedical techniques and their potential for medical advantage or support, especially in the field of oncology, should be critically viewed and evaluated.

Journal Article↗
PubMed1971

Survival of bacterial spores under some simulated lunar surface conditions.

Spores of Bacillus subtilis were exposed to simulated lunar environmental factors, in order to estimate the chance of living matter to survive on the moon. Vacuum, radiation and extreme temperature were selected and their individual and combined influence was tested. High vacuum up to 2 x 10(-7) torr and ultra-high vacuum up to 5 x 10(-9) torr, ultraviolet rays (254 nm) and a temperature of 80 degrees C were used. The results were compared with those of experiments on vegetative cells.

Bacillus subtilis↗
PubMed2006

Effect of estradiol and dihydrotestosterone on hypergravity-induced MAPK signaling and occludin expression in human umbilical vein endothelial cells.

Female astronauts have been reported to have a higher incidence of post-flight orthostatic intolerance (POI) compared with that of their male counterparts. POI may result from increased permeability of the endothelial cell (EC) layer in the vasculature. The goal of this study has been to determine whether estradiol (E(2)) and dihydrotesterone (DHT) alter human umbilical vein ECs (HUVECs) responses to short term (10 min) hypergravity (1-3 g) mimicking the g force experienced by astronauts during liftoff. E(2) and DHT rapidly (within 5 min) activated MAPK (mitogen-activated protein kinase) in HUVEC at 1 g in a receptor-dependent manner. Liftoff inhibited MAPK phosphorylation, and rapid E(2) and DHT activation of MAPK was blocked. Liftoff simulation or brief (5-90 min) treatment with E(2) or DHT at 1 g had no effect on the expression of the EC tight-junction protein occludin. However, 24-h pre-treatment of HUVECs with E(2) and DHT prior to liftoff simulation significantly increased occludin expression, and hypergravity exposure did not alter this increase. These data provide evidence for a possible protective effect of E(2) and DHT on EC function as indicated by increased occludin; this may help maintain the integrity of EC tight junction and could thus retard or reduce the incidence of POI.

Base Sequence↗
PubMed1997

Establishment of a three-dimensional human prostate organoid coculture under microgravity-simulated conditions: evaluation of androgen-induced growth and PSA expression.

A novel in vitro human prostate cancer model was established by using a coculture technique in which isolated human prostate fibroblasts were observed to grow as a mixed culture with isolated human prostate cancer cells (LNCaP) on microcarrier beads under microgravity-simulated conditions. This model appears to be promising and deserves further exploration because: (a) cocultured human prostate fibroblasts and cancer epithelial cells appear to undergo patterns of histogenesis similar to those observed in human prostate tumors and (b) unlike the conventional cell culture on plastic dishes, cocultured human prostate fibroblasts and LNCaP cells in microgravity-simulated conditions responded to the inductive signals of growth and differentiation from dihydrotestosterone in a manner similar to that observed in the in vivo condition. These results offer an opportunity to examine molecular mechanisms of cellular signaling in response to androgen stimulation during normal and aberrant human prostate development. The microgravity-simulated three-dimensional prostate epithelial cell culture with prostate fibroblasts can be further explored as an ideal in vitro model for the study of normal and neoplastic prostate development. This model could also be adopted as a drug screening program for the discovery of novel therapeutic agents in the treatment of human prostate cancer and benign hyperplastic growth.

Bioreactors↗
PubMedDate not supplied

[Development of a basic ration out of commercial foods for nutrition in ground-based simulation experiments].

Food rations composed of canned products were given the physiological and hygienic evaluation in the context of their fitness for human volunteers in experiments with head-down bedrest in isolation and confinement. As a result, the food rations were proven to contain the desired quantities of nutrients. Evaluation of food fitness for human subjects was made based on the data of clinical-physiological and biochemical investigations. The rations met the energy and anabolic metabolism demands of human subjects during extreme chamber experiments and were favorable to maintaining good level of vital processes.

Commerce↗
PubMed2006

S.A.M., the Italian Martian simulation chamber.

The Martian Environment Simulator (SAM "Simulatore di Ambiente Marziano") is a interdisciplinary project of Astrobiology done at University of Padua. The research is aimed to the study of the survival of the microorganisms exposed to the "extreme" planetary environment. The facility has been designed in order to simulate Mars' environmental conditions in terms of atmospheric pressure, temperature cycles and UV radiation dose. The bacterial cells, contained into dedicated capsules, will be exposed to thermal cycles simulating diurnal and seasonal Martian cycles. The metabolism of the different biological samples will be analysed at different phases of the experiment, to study their survival and eventual activity of protein synthesis (mortality, mutations and capability of DNA repairing). We describe the experimental facility and provide the perspectives of the biological experiments we will perform in order to provide hints on the possibility of life on Mars either autochthonous or imported from Earth.

Bacteria↗
PubMed2002

Physiological ecology of Mesozoic polar forests in a high CO2 environment.

Fossils show that coniferous forests extended into polar regions during the Mesozoic, a time when models and independent paleo-CO2 indicators suggest that the atmospheric CO2 concentration was at least double that of the present day. Consequently, such polar forests would have experienced high CO2 interacting with an extreme variation in light. Here we describe an experiment investigating this plant-environment interaction for extant tree species that were important components of polar forests, and give results from the first year of treatment. Specifically, we tested the hypotheses that growth in elevated CO2 (1) stimulates photosynthesis; (2) reduces photoinhibition during the polar summer; and (3) reduces respiration of above- and below-ground plant organs. Our results indicate that CO2 fertilization generally does not affect photosynthesis under continuous daylight characteristic of the polar summer but does increase it when the period of illumination is shorter. Growth in elevated CO2 did not alter the potential for photoinhibition. CO2 enrichment significantly reduced leaf and root respiration rates by 50 and 25 %, respectively, in a range of evergreen taxa. Incorporating these observed CO2 effects into numerical simulations using a process-based model of coniferous forest growth indicates that a high paleo-CO2 concentration would have increased the productivity of Cretaceous conifer forests in northern Alaska. This results from decreased respiratory costs that more than compensate for the absence of high CO2-high temperature interactions during the polar summer. The longer-term effects of CO2 enrichment on seasonal changes in the above- and below-ground carbon balance of trees are discussed.

Atmosphere↗