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PubMed1994

Autogenic-feedback training: a potential treatment for orthostatic intolerance in aerospace crews.

Postflight orthostatic intolerance has been identified as a serious biomedical problem associated with long-duration exposure to microgravity in space. High priority has been given to the development of countermeasures for this disorder that are both effective and practical. A considerable body of clinical research has demonstrated that people can be taught to increase their own blood pressure voluntarily, and that this is an effective treatment for chronic orthostatic intolerance in paralyzed patients. The current pilot study was designed to examine the feasibility of adding training in control of blood pressure to an existing preflight training program designed to facilitate astronaut adaptation to microgravity. Using an operant conditioning procedure, autogenic-feedback training (AFT), three men and two women participated in four to nine training (15-30-minute) sessions. At the end of training, the average increase in systolic and diastolic pressure, as well as mean arterial pressures, that the subjects made ranged between 20 and 50 mm Hg under both supine and 45 degrees head-up tilt conditions. These findings indicate that AFT may be a useful alternative treatment or supplement to existing approaches for preventing postflight orthostatic intolerance. Furthermore, the use of operant conditioning methods for training cardiovascular responses may contribute to the general understanding of the mechanisms of orthostatic intolerance.

Adult↗

PubMed1994

Changes in hypothalamic [correction of hypothalmic] staining for c-Fos following 2G exposure in rats.

The static gravitational field of the earth has been an important selective pressure that has shaped the evolution of biological organisms. This is illustrated by the evolution of tetrapods from a water environment where gravitational force was partially negated to a terrestrial environment where gravity is of greater consequence. Terrestrial invasion resulted in a series of new structural, physiological, and behavioral features. Therefore, it is not surprising that alterations in the gravitational field can cause widespread effects in many physiological systems and behaviors. Our previous studies have demonstrated that both exposure to hyperdynamic fields and the microgravity condition of space flight have significant effects on body temperature, heartrate, activity, feeding, drinking, and circadian rhythms. However, it has not been determined whether these physiological adaptations are associated with changes in neural activity within the hypothalamic nuclei that regulate these functions. This study examined the changes in body temperature, activity, body weight and food and water intake in rats caused by exposure to a hyperdynamic field. In addition, the immediate early gene activation marker, c-Fos, was used to examine potential protein synthesis changes in the hypothalamic nuclei that regulate these functions.

Animals↗

PubMed1995

Neuromuscular adaptations during 30 days of cast-immobilization and head-down bedrest.

Prolonged skeletal muscle disuse, during space flights and on Earth, produces distinct adaptive changes in the neuromuscular system of human subjects. There is a significant decline in muscle mass and strength, exercise capacity, fatigue resistance, integrated EMG (IEMG) output and time-dependent alterations in the behavior of Hoffman (H) and deep tendon reflexes. The objective of this study was to examine the changes in excitability of segmental motoneuronal network and its influence upon gastrocnemius-soleus (G-S) function in healthy male and female subjects, who underwent either 6 degrees head-down bedrest (HDB) or unilateral cast-immobilization (CIM) for a period of 30 days.

Adult↗

PubMed1993

Changes in the dark focus of accommodation associated with simulator sickness.

The relationship between the dark focus of accommodation and simulator sickness, a form of motion sickness, was examined in three experiments. In Experiment 1, dark focus was measured in 18 college students in a laboratory setting before and after they viewed a projected motion scene depicting low altitude helicopter flight. In Experiments 2 and 3, dark focus was measured in pilots (N = 16 and 23, respectively) before and after they "flew" in moving-base helicopter flight simulators with optical infinity CRT visual systems. The results showed that individuals who experienced simulator sickness had either an inward (myopic) change in dark focus (Experiments 1 and 3) or attenuated outward shifts in dark focus (Experiment 2) relative to participants who did not get sick. These results are consonant with the hypothesis that parasympathetic activity, which may be associated with simulator sickness, should result in changes in dark focus that are in a myopic direction. Night vision goggles, virtual environments, extended periods in microgravity, and heads-up displays all produce related visual symptomatology. Changes in dark focus may occur in these conditions, as well, and should be measured.

Accommodation, Ocular↗

PubMedDate not supplied

New frontiers in design synthesis.

The Intelligent Synthesis Environment (ISE), which is one of the major strategic technologies under development at NASA centers and the University of Virginia, is described. One of the major objectives of ISE is to significantly enhance the rapid creation of innovative affordable products and missions. ISE uses a synergistic combination of leading-edge technologies, including high performance computing, high capacity communications and networking, human-centered computing, knowledge-based engineering, computational intelligence, virtual product development, and product information management. The environment will link scientists, design teams, manufacturers, suppliers, and consultants who participate in the mission synthesis as well as in the creation and operation of the aerospace system. It will radically advance the process by which complex science missions are synthesized, and high-tech engineering Systems are designed, manufactured and operated. The five major components critical to ISE are human-centered computing, infrastructure for distributed collaboration, rapid synthesis and simulation tools, life cycle integration and validation, and cultural change in both the engineering and science creative process. The five components and their subelements are described. Related U.S. government programs are outlined and the future impact of ISE on engineering research and education is discussed.

Astronauts↗

PubMed2000

Microgravity as a novel environmental signal affecting Salmonella enterica serovar Typhimurium virulence.

The effects of spaceflight on the infectious disease process have only been studied at the level of the host immune response and indicate a blunting of the immune mechanism in humans and animals. Accordingly, it is necessary to assess potential changes in microbial virulence associated with spaceflight which may impact the probability of in-flight infectious disease. In this study, we investigated the effect of altered gravitational vectors on Salmonella virulence in mice. Salmonella enterica serovar Typhimurium grown under modeled microgravity (MMG) were more virulent and were recovered in higher numbers from the murine spleen and liver following oral infection compared to organisms grown under normal gravity. Furthermore, MMG-grown salmonellae were more resistant to acid stress and macrophage killing and exhibited significant differences in protein synthesis than did normal-gravity-grown cells. Our results indicate that the environment created by simulated microgravity represents a novel environmental regulatory factor of Salmonella virulence.

Acids↗

PubMedDate not supplied

Quantitative electrocardiography during extended space flight.

To assess the effects of prolonged space flight on the electrophysiological properties of the heart, vectorcardiograms (VCG) were obtained on the Skylab crews at regular intervals during flight and the pre- and postflight periods. The VCG signals were telemetered from Skylab and analyzed by digital computer. Conventional 12-lead electrocardiograms were derived from the VCG signals by a lead transformation program. Standardized exercise loads were incorporated into the experiment protocol to increase the sensitivity of the VCG for effects of deconditioning and to detect susceptibility for arrhythmias. In Skylab II, 24 preflight, 21 inflight, and 19 postflight experiments were analyzed. Statistically significant inflight changes observed in two or more crew members included: decreased resting heart rate, increased QRS duration, anterior shift QRS vector, increased QRS vector magnitude, anterior shift T vector, and increased T vector magnitude. One astronaut had occasional premature ventricular contractions (PVC) during the pre- and postflight phases. He had a single episode of multiple PVC's during heavy-load exercise testing in flight. A second astronaut had no arrhythmia during pre- or inflight testing. On postflight day 21 he had multiple PVC's and salvos of ectopic ventricular beats. He has had no recurrence of the arrhythmia. With the exception of the cardiac arrhythmias, no deleterious electrophysiological changes were observed during Skylab II.

Arrhythmias, Cardiac↗

PubMed2007

Technical developments at the NASA Space Radiation Laboratory.

The NASA Space Radiation Laboratory (NSRL) located at Brookhaven National Laboratory (BNL) is a center for space radiation research in both the life and physical sciences. BNL is a multidisciplinary research facility operated for the Office of Science of the US Department of Energy (DOE). The BNL scientific research portfolio supports a large and diverse science and technology program including research in nuclear and high-energy physics, material science, chemistry, biology, medial science, and nuclear safeguards and security. NSRL, in operation since July 2003, is an accelerator-based facility which provides particle beams for radiobiology and physics studies (Lowenstein in Phys Med 17(supplement 1):26-29 2001). The program focus is to measure the risks and to ameliorate the effects of radiation encountered in space, both in low earth orbit and extended missions beyond the earth. The particle beams are produced by the Booster synchrotron, an accelerator that makes up part of the injector sequence of the DOE nuclear physics program's Relativistic Heavy Ion Collider. Ion species from protons to gold are presently available, at energies ranging from <100 to >1,000 MeV/n. The NSRL facility has recently brought into operation the ability to rapidly switch species and beam energy to supply a varied spectrum onto a given specimen. A summary of past operation performance, plans for future operations and recent and planned hardware upgrades will be described.

Biophysics↗

PubMed2002

How do we get from cell and animal data to risks for humans from space radiations?

After four decades of human exploration in space, many scientists consider the medical consequences from radiation exposures to be the major biological risk associated with long-term missions. This conclusion is based upon results from a research program that has evolved over the past thirty years. Despite the diversity in both opinions and approaches that necessarily arise in research endeavors such as this, a commonality has emerged from our community. We need epidemiological data for humans, animal data in areas where no human data exist, and data on mechanisms to get from animal to humans. We need a programmatic infrastructure that addresses specific goals as well as basic research. These concepts might be deemed overly simplistic and even tautologous were it not for the fact that they are frequently underutilized and even ignored. This article examines the goals, premises, and infrastructures proposed by expert panels and agencies to address radiation risks in space. It is proposed that the required level of effort and the resources available demand a unified, focused international effort that is, at the same time, subjected to rigorous peer review if it is to be successful. There is a plan; let us implement it.

Animals↗

PubMed2002

Rate controlling steps in fatty acid oxidation by unloaded rodent soleus muscle.

In response to decreased usage skeletal muscle undergoes an adaptive reductive remodeling due to the decrease in tension on the weight bearing components of the musculo-skeletal system. Accompanying a shift in fiber type is an increased reliance of carbohydrate metabolism and decreased reliance on fat for energy. These responses have been found with both space flight and ground based models of disuse atrophy including the chronically adapted rodent hind limb suspended (HLS) rat (1, 4-7, 10, 11). In addition, after space flight, the ability of soleus muscle homogenates to oxidize palmitate is decreased. We have previously shown that expression of the mRNA of enzymes involved in beta-oxidation is reduced in the soleus muscle of HLS rats. At the same time mRNA expression of enzymes involved in glycolysis was increased. This study extends these observations to address the question of whether the decrease in beta-oxidation is caused by a reduction in the capacity of the pathway to oxidize fat or the regulation is effected before fatty acids enter the mitochondria, i.e. the reduced capacity of the fatty acid oxidation pathway is because less fat is available for oxidation. The two key steps involved in fatty acid uptake into the cells are lipoprotein lipase and the transport of the free fatty acids produced by lipoprotein lipase into the cell via the carnitine acyltransferase system.

NASA Discipline Regulatory Physiology↗

PubMed2003

Electronic nose for space program applications.

The ability to monitor air contaminants in the shuttle and the International Space Station is important to ensure the health and safety of astronauts, and equipment integrity. Three specific space applications have been identified that would benefit from a chemical monitor: (a) organic contaminants in space cabin air; (b) hypergolic propellant contaminants in the shuttle airlock; (c) pre-combustion signature vapors from electrical fires. NASA at Kennedy Space Center (KSC) is assessing several commercial and developing electronic noses (E-noses) for these applications. A short series of tests identified those E-noses that exhibited sufficient sensitivity to the vapors of interest. Only two E-noses exhibited sufficient sensitivity for hypergolic fuels at the required levels, while several commercial E-noses showed sufficient sensitivity of common organic vapors. These E-noses were subjected to further tests to assess their ability to identify vapors. Development and testing of E-nose models using vendor supplied software packages correctly identified vapors with an accuracy of 70-90%. In-house software improvements increased the identification rates between 90 and 100%. Further software enhancements are under development. Details on the experimental setup, test protocols, and results on E-nose performance are presented in this paper along with special emphasis on specific software enhancements.

Air Pollutants↗

PubMed1987

The Diogene 4 pi detector at Saturne.

Diogene, an electronic 4 pi detector, has been built and installed at the Saturne synchrotron in Saclay. The forward angular range (0 degree-6 degrees) is covered by 48 time-of-flight scintillator telescopes that provide charge identification. The trajectories of fragments emitted at larger angles are recorded in a cylindrical 0.4-m3 Pictorial Drift Chamber (PDC) surrounding the target. The PDC is inside a 1-T magnetic field; the axis of the PDC cylinder and the magnetic field are parallel to the beam. Good identification has been obtained for both positive and negative pi mesons and for hydrogen and helium isotopes. Multiplicities in relativistic nucleus-nucleus reactions up to 40 have been detected, limited mainly by the present electronics.

Elementary Particles↗

PubMed2000

Thyroid function changes related to use of iodinated water in the U.S. Space Program.

BACKGROUND: The National Aeronautics and Space Administration (NASA) has used iodination as a method of microbial disinfection of potable water systems in U.S. spacecraft and long-duration habitability modules. A review of thyroid function tests of NASA astronauts who had consumed iodinated water during spaceflight was conducted. METHODS: Thyroid function tests of all past and present astronauts were reviewed. Medical records of astronauts with a diagnosis of thyroid disease were reviewed. Iodine consumption by space crews from water and food was determined. Serum thyroid-stimulating hormone (TSH) and urinary iodine excretion from space crews were measured following modification of the Space Shuttle potable water system to remove most of the iodine. RESULTS: Mean TSH significantly increased in 134 astronauts who had consumed iodinated water during spaceflight. Serum TSH, and urine iodine levels of Space Shuttle crewmembers who flew following modification of the potable water supply system to remove iodine did not show a statistically significant change. There was no evidence supporting association between clinical thyroid disease and the number of spaceflights, amount of iodine consumed, or duration of iodine exposure. CONCLUSIONS: It is suggested that pharmacological doses of iodine consumed by astronauts transiently decrease thyroid function, as reflected by elevated serum TSH values. Although adverse effects of excess iodine consumption in susceptible individuals are well documented, exposure to high doses of iodine during spaceflight did not result in a statistically significant increase in long-term thyroid disease in the astronaut population.

Astronauts↗

PubMed1989

LET spectra of cosmic-ray nuclei for near earth orbits.

Measurements of cosmic-ray LET spectra were part of the radiobiological space research programs during the Spacelab 1 (SL-1) and the D1 missions. We analyzed CR-39 plastic nuclear track detectors of the Advanced Biostack experiment of SL-1 and of the Dosimetric Mapping and Carausius morosus experiments in the BIORACK on D1. The particle tracks in the CR-39 were detected and measured by an automatic scanning and measuring system. An in-flight calibration was derived from track measurements of minimum ionizing oxygen and iron nuclei and of stopping nuclei as a function of the residual range. LET spectra measured at different locations in the space shuttle are presented and discussed for both missions. A model describing the effects of the geomagnetic field of the earth on charged cosmic-ray particles and the shielding by matter is used to calculate LET spectra for the two missions and for typical space station orbits at low inclinations. A comparison of measured LET spectra and LET spectra calculated for different flight parameters shows that besides geomagnetic shielding the shielding by matter is most important in comparison to solar modulation and to variation of particle flux with flight altitude. Model calculations must be improved and must consider more detailed sectored shielding by matter and the influence of trapped radiation. The last item is of importance in the case of low-inclination orbits.

Cosmic Radiation↗

PubMed1998

Sweet potato in a vegetarian menu plan for NASA's Advanced Life Support Program.

Sweet potato has been selected as one of the crops for NASA's Advanced Life Support Program. Sweet potato primarily provides carbohydrate--an important energy source, beta-carotene, and ascorbic acid to a space diet. This study focuses on menus incorporating two sets of sweet potato recipes developed at Tuskegee University. One set includes recipes for 10 vegetarian products containing fom 6% to 20% sweet potato on a dry weight basis (pancakes, waffles, tortillas, bread, pie, pound cake, pasta, vegetable patties, doughnuts, and pretzels) that have been formulated, subjected to sensory evaluation, and determined to be acceptable. These recipes and the other set of recipes, not tested organoleptically, were substituted in a 10-day vegetarian menu plan developed by the American Institute of Biological Sciences (AIBS) Kennedy Space Center Biomass Processing Technical Panel. At least one recipe containing sweet potato was included in each meal. An analysis of the nutritional quality of this menu compared to the original AIBS menu found improved beta-carotene content (p<0.05). All other nutrients, except vitamin B6, and calories were equal and in some instances greater than those listed for NASA's Controlled Ecological Life Support Systems RDA. These results suggest that sweet potato products can be used successfully in menus developed for space with the added benefit of increased nutrient value and dietary variety.

Diet, Vegetarian↗

PubMed1999

Memory processes and motor control in extreme environments.

Cognitive-performance and motor-performance activities in multi-task, high-workload environments were assessed during astronaut performance in space flight and in isolation. Data was collected in microgravity on the International Micro-gravity Laboratory (IML) space shuttle mission (STS-42), and the Canadian Astronaut Program Space Unit Life Simulation (CAPSULS) mission offered an ideal opportunity to collect data for individuals in extreme isolation to complement the space flight data using similar hardware, software, and experimental protocols. The mental workload and performance experiment (MWPE) was performed during the IML-1 space flight mission, and the memory processes and motor control (MEMO) experiment was performed during the CAPSULS isolation mission. In both experiments, short-term exhaustive memory and fine motor control associated with human-computer interaction was studied. Memory processes were assessed using a Sternberg-like exhaustive memory search containing 1, 2, 4, or 7 letters. Fine motor control was assessed using velocity-controlled (joystick) and position-controlled (trackball) computer input devices to acquire targets as displayed on a computer screen. Subjects repeated the tasks under two conditions that tested perceptual motor adaptation strategies: 1) During adaptation to the microgravity environment; and 2) While wearing left-right reversing prism goggles during the CAPSULS mission. Both conditions significantly degraded motor performance but not cognitive performance. The data collected during both the MEMO experiment and the MWPE experiments enhance the knowledge base of human interface technology for human performance in extreme environments.

Adaptation, Psychological↗

PubMed1995

Predicting human heat strain and performance with application to space operations.

This Institute has developed a USARIEM Heat Strain Prediction Model for predicting physiological responses and soldier performance in the heat, which has been programmed for use by hand-held calculators and personal computers, and incorporated into the development of a heat strain decision aid. This model is demonstrated to predict accurately (generally within +/- 1 SD/SEM) rectal temperature (Tre) responses for soldiers wearing various military clothing ensembles during U.S. or non-U.S. military scenarios in the heat at home or abroad. The value of this model is shown presently for three NASA scenarios involving the Launch and Entry Suit (LES). The LES (ventilated or unventilated) is modeled during pre-launch/launch, re-entry/landing, and emergency egress after re-entry/landing scenarios, predominately to evaluate heat acclimation and hydration state effects. During the pre-launch/launch scenario, predicted final Tre closely agrees with observed values suggesting minimal heat strain (Tre approximately 38.0 degrees C). In contrast, dehydrated (3%) unacclimated individuals show moderate levels of heat strain (Tre approximately 38.5 degrees C) for this same scenario. During the re-entry/landing and emergency egress scenarios, dehydrated unacclimated individuals are predicted to exhibit excessive heat strain (Tre > 39.0 degrees C). Thermal tolerance time is predicted to be only 6 min during emergency egress if individuals are dehydrated and unacclimated to heat while wearing the LES. If heat transfer values for space operations clothing are known, NASA can use this prediction model to help avoid undue heat strain involving astronauts for most scenarios during spaceflight.

Acclimatization↗

PubMed2002

Nutrition and renal stone disease in space.

There is a growing body of evidence from the National Aeronautics and Space Administration and the Russian space program showing that humans exposed to the microgravity environment of space have a greater risk for developing renal stones. Increased bone resorption and the attendant hypercalciuria and hyperphosphaturia contribute significantly to raising the urinary state of saturation with respect to the calcium salts, namely calcium oxalate and calcium phosphate. In addition, other environmental and dietary factors may adversely affect urine composition and increase stone formation risk during space flight. For example, reductions in urinary volume, pH, and citrate contribute to raising stone formation risk. In addition to raising the risk for calcium stone formation, this metabolic profile is conducive to the formation of uric acid stones. Although observations to date have suggested that there may actually be a reduced food intake during the early phase of flight, crew members on longer-duration flights may increase food intake and be at increased risk for stone formation. Taken together, these findings support the use of nutritional recommendations for crew members that would serve to reduce the stone-forming propensity of the urinary environment. Pharmacologic intervention should be directed at raising urinary volumes, diminishing bone losses, and preventing reductions in urinary pH and citrate. Success in reducing the risk for stone formation in astronauts would also be of potential major benefit to the estimated 20 million Americans with nephrolithiasis.

Aerospace Medicine↗