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NASA NTRS2002

From Milk to Bones, Moving Calcium Through the Body: Calcium Kinetics During Space Flight

Did you know that when astronauts are in space, their height increases about two inches? This happens because the weightlessness of space allows the spine, usually compressed in Earth's gravity, to expand. While this change is relatively harmless, other more serious things can happen with extended stays in weightlessness, notably bone loss. From previous experiments, scientists have observed that astronauts lose bone mass at a rate of about one percent per month during flight. Scientists know that bone is a dynamic tissue - continually being made and repaired by specialized bone cells throughout life. Certain cells produce new bone, while other cells are responsible for removing and replacing old bone. Research on the mechanisms of bone metabolism and the effects of space flight on its formation and repair are part of the exciting studies that will be performed during STS-107. Calcium plays a central role because 1) it gives strength and structure to bone and 2) all types of cells require it to function normally. Ninety-nine percent of calcium in the body is stored in the skeleton. However, calcium may be released, or resorbed, from bone to provide for other tissues when you are not eating. To better understand how and why weightlessness induces bone loss, astronauts will participate in a study of calcium kinetics - that is, the movement of calcium through the body, including absorption from food, and its role in the formation and breakdown of bone.

Scott Smith↗
NASA NTRS2000

Effects of orbital spaceflight on human osteoblastic cell physiology and gene expression

During long-term spaceflight, astronauts lose bone, in part due to a reduction in bone formation. It is not clear, however, whether the force imparted by gravity has direct effects on bone cells. To examine the response of bone forming cells to weightlessness, human fetal osteoblastic (hFOB) cells were cultured during the 17 day STS-80 space shuttle mission. Fractions of conditioned media were collected during flight and shortly after landing for analyses of glucose utilization and accumulation of type I collagen and prostaglandin E(2) (PGE(2)). Total cellular RNA was isolated from flight and ground control cultures after landing. Measurement of glucose levels in conditioned media indicated that glucose utilization occurred at a similar rate in flight and ground control cultures. Furthermore, the levels of type I collagen and PGE(2) accumulation in the flight and control conditioned media were indistinguishable. The steady-state levels of osteonectin, alkaline phosphatase, and osteocalcin messenger RNA (mRNA) were not significantly changed following spaceflight. Gene-specific reductions in mRNA levels for cytokines and skeletal growth factors were detected in the flight cultures using RNase protection assays. Steady-state mRNA levels for interleukin (IL)-1alpha and IL-6 were decreased 8 h following the flight and returned to control levels at 24 h postflight. Also, transforming growth factor (TGF)-beta(2) and TGF-beta(1) message levels were modestly reduced at 8 h and 24 h postflight, although the change was not statistically significant at 8 h. These data suggest that spaceflight did not significantly affect hFOB cell proliferation, expression of type I collagen, or PGE(2) production, further suggesting that the removal of osteoblastic cells from the context of the bone tissue results in a reduced ability to respond to weightlessness. However, spaceflight followed by return to earth significantly impacted the expression of cytokines and skeletal growth factors, which have been implicated as mediators of the bone remodeling cycle. It is not yet clear whether these latter changes were due to weightlessness or to the transient increase in loading resulting from reentry.

Non-NASA Center↗
NASA NTRS2004

The Art of Space Flight Exercise Hardware: Design and Implementation

The design of space flight exercise hardware depends on experience with crew health maintenance in a microgravity environment, history in development of flight-quality exercise hardware, and a foundation for certifying proper project management and design methodology. Developed over the past 40 years, the expertise in designing exercise countermeasures hardware at the Johnson Space Center stems from these three aspects of design. The medical community has steadily pursued an understanding of physiological changes in humans in a weightless environment and methods of counteracting negative effects on the cardiovascular and musculoskeletal system. The effects of weightlessness extend to the pulmonary and neurovestibular system as well with conditions ranging from motion sickness to loss of bone density. Results have shown losses in water weight and muscle mass in antigravity muscle groups. With the support of university-based research groups and partner space agencies, NASA has identified exercise to be the primary countermeasure for long-duration space flight. The history of exercise hardware began during the Apollo Era and leads directly to the present hardware on the International Space Station. Under the classifications of aerobic and resistive exercise, there is a clear line of development from the early devices to the countermeasures hardware used today. In support of all engineering projects, the engineering directorate has created a structured framework for project management. Engineers have identified standards and "best practices" to promote efficient and elegant design of space exercise hardware. The quality of space exercise hardware depends on how well hardware requirements are justified by exercise performance guidelines and crew health indicators. When considering the microgravity environment of the device, designers must consider performance of hardware separately from the combined human-in-hardware system. Astronauts are the caretakers of the hardware while it is deployed and conduct all sanitization, calibration, and maintenance for the devices. Thus, hardware designs must account for these issues with a goal of minimizing crew time on orbit required to complete these tasks. In the future, humans will venture to Mars and exercise countermeasures will play a critical role in allowing us to continue in our spirit of exploration. NASA will benefit from further experimentation on Earth, through the International Space Station, and with advanced biomechanical models to quantify how each device counteracts specific symptoms of weightlessness. With the continued support of international space agencies and the academic research community, we will usher the next frontier in human space exploration.

Beyene, Nahom M.↗
NASA NTRS2005

Journal of Gravitational Physiology, Volume 12, Number 1

The following topics were covered: System Specificity in Responsiveness to Intermittent -Gx Gravitation during Simulated Microgravity in Rats; A Brief Overview of Animal Hypergravity Studies; Neurovestibular Adaptation to Short Radius Centrifugation; Effect of Artificial Gravity with Exercise Load by Using Short-Arm Centrifuge with Bicycle Ergometer as a Countermeasure Against Disused Osteoporosis; Perception of Body Vertical in Microgravity during Parabolic Flight; Virtual Environment a Behavioral and Countermeasure Tool for Assisted Gesture in Weightlessness: Experiments during Parabolic Flight; Artificial Gravity: Physiological Perspectives for Long-Term Space Exploration; Comparison of the Effects of DL-threo-Beta-Benzyloxyaspartate on the Glutamate Release from Synaptosomes before and after Exposure of Rats to Artificial Gravity; Do Perception and Postrotatory Vestibulo-Ocular Reflex Share the Same Gravity Reference?; Vestibular Adaptation to Changing Gravity Levels and the Orientation of Listing's Plane; Compound Mechanism Hypothesis on +Gz - Induced Brain Injury and Dysfunction of Learning and Memory; Environmental Challenge Impairs Prefrontal Brain Functions; Effect of 6-Days of Support Withdrawal on Characteristics of Balance Function; Hypergravity-Induced Changes of Neuronal Activities in CA1 Region of Rat Hippocampus; Audiological Findings in Antiorthostatic Position Modelling Microgravitation; Investigating Human Cognitive Performance during Spaceflight; The Relevance of the Minimization of Torque Exchange with the Environment in Weightlessness is Confirmed by Asimulation Study; Characteristics of the Eyes Pursuit Function during Readaptation to Terrestrial Gravity after Prolonged Flights Aboard the International Space Station; Comparison of Cognitive Performance Tests for Promethazine Pharmacodynamics in Human Subjects; Structural Reappraisal of Dendritic Tree of Cerebellar Purkinje Cell for Novel Functional Modeling of Elementary Sensorimotor Adaptive Processes; Orpheus 0 G or Ear in Microgravity to Establish Symptoms Concomittant of Inner and Middle Ear and Osteoporosis in Microgravity; Understanding Visual Perception in the Perspective of Gravity; Cortical Regions Associated with Orthostatic Stress in Conscious Humans; Restoration of Central Blood Volume: Application of a Simple Concept and Simple Device to Counteract Cardiovascular Instability in Syncope and Hemorrhage; WISE-2005: Integrative Cardiovascular Responses with LBNP during 60-Day Bed Rest in Women; Intracranial Pressure Increases during Weightlessness. A Parabolic Flights Study; Lower Limb & Portal Veins Echography for Predicting Risk of Thrombosis during a 90-D Bed Rest; Calf Tissue Liquid Stowage and Muscular and Deep Vein Distension in Orthostatic Tests after a 90-Day Head Down Bed Rest; Morphology of Brain Vessels in the Tail Suspended Rats Exposed to Intermittent 2 G; Alterations in Vasoreactivity of Femoral Artery Induced by Hindlimb Unweighting are Related to the Changes of Contractile Protein in Rats; and Respiratory Sinus Arrhythmia: A Marker of Decreased Parasympathetic Modulation after Short Duration.

Fuller, Charles A.↗
NASA NTRS2005

Neurovestibular and Sensorimotor Studies in Space and Earth Benefits

This review summarizes what has been learned from studies of human neurovestibular system in weightless conditions, including balance and locomotion, gaze control, vestibular-autonomic function and spatial orientation, and gives some examples of the potential Earth benefits of this research. Results show that when astronauts and cosmonauts return from space flight, both the peripheral and central neural processes are physiologically and functionally altered. There are clear distinctions between the virtually immediate adaptive compensations to weightlessness and those that require longer periods of time to adapt. However, little is known to date about the adaptation of sensory-motor functions to long-duration space missions in weightlessness and to the transitions between various reduced gravitational levels, such as on the Moon and Mars. Results from neurovestibular research in space have substantially enhanced our understanding of the mechanisms and characteristics of postural, gaze, and spatial orientation deficits, analogous to clinical cases of labyrinthine-defective function. Also, space neurosciences research has participated in the development and application of significant new technologies, such as video recording and processing of three-dimensional eye movements and posture, hardware for the unencumbered measurement of head and body movement, and procedures for investigating otolith function on Earth. In particular, devices such as centrifugation or off-vertical axis rotation could enhance clinical neurological testing because it provides linear acceleration which specifically stimulates the otolith organs in a frequency range close to natural head and body movement.

Clement, Gilles↗
NASA NTRS2012

International Space Station as Analog of Interplanetary Transit Vehicle For Biomedical Research

Astronaut missions lasting up to six months aboard the International Space Station (ISS) have much in common with interplanetary flights, especially the outbound, Earth-to-Mars transit portion of a Mars mission. Utilization of ISS and other appropriate platforms to prepare for crewed expeditions to planetary destinations including Mars has been the work of NASA's Human Research Program (HRP) since 2005. HRP is charged specifically to understand and reduced the risks to astronaut health and performance in space exploration missions: everything HRP does and has done is directly related to that responsibility. Two major categories of human research have capitalized on ISS capabilities. The first category centers on the biomedical aspects of long-duration exposure to spaceflight factors, including prolonged weightlessness, radiation exposure, isolation and confinement, and actual risk to life and limb. These studies contribute to astronaut safety, health and efficiency on any long-duration missions, whether in low Earth orbit (LEO) or beyond. Qualitatively, weightlessness is weightlessness, whether in LEO or en route to Mars. The HRP sponsors investigations into losses in muscle and bone integrity, cardiovascular function, sensory-motor capability, immune capacity and psychosocial health, and development and demonstration of appropriate treatments and preventative measures. The second category includes studies that are focused on planetary expeditions beyond LEO. For these, ISS offers a high fidelity analog to investigate the combined effects of spaceflight factors (described above) plus the isolation and autonomy associated with simulated increasing distance from Earth. Investigations address crew cohesion, performance and workload, and mission control performance. The behavioral health and performance and space human factors aspects of planetary missions dominate this category. Work has already begun on a new investigation in this category which will examine the effects of a simulated lag in communications (mimicking that expected in transit to Mars) on astronaut performance aboard ISS. Extension of the current ISS increment duration from six months to nine or even twelve months would provide opportunities for expanded research relevant to long duration missions, albeit at the cost of fewer astronauts as subjects for those investigations. Given the possible limited access to ISS after 2020, if ISS is intended to facilitate future exploration missions, then the in-flight human investigations should focus on those that clearly enable future exploration missions.

Charles, John B.↗
NASA NTRS2016

Bringing Gravity to Space

This panel will present NASA's plans for ongoing and future research to define the requirements for Artificial Gravity (AG) as a countermeasure against the negative health effects of long-duration weightlessness. AG could mitigate the gravity-sensitive effects of spaceflight across a host of physiological systems. Bringing gravity to space could mitigate the sensorimotor and neuro-vestibular disturbances induced by G-transitions upon reaching a planetary body, and the cardiovascular deconditioning and musculoskeletal weakness induced by weightlessness. Of particular interest for AG during deep-space missions is mitigation of the Visual Impairment Intracranial Pressure (VIIP) syndrome that the majority of astronauts exhibit in space to varying degrees, and which presumably is associated with weightlessness-induced fluid shift from lower to upper body segments. AG could be very effective for reversing the fluid shift and thus help prevent VIIP. The first presentation by Dr. Charles will summarize some of the ground-based and (very little) space-based research that has been conducted on AG by the various space programs. Dr. Paloski will address the use of AG during deep-space exploration-class missions and describe the different AG scenarios such as intra-vehicular, part-of-vehicle, or whole-vehicle centrifugations. Dr. Clement will discuss currently planned NASA research as well as how to coordinate future activities among NASA's international partners. Dr. Barr will describe some possible future plans for using space- and ground-based partial-G analogs to define the relationship between physiological responses and G levels between 0 and 1. Finally, Dr. Stenger will summarize how the human cardiovascular system could benefit from intermittent short-radius centrifugations during long-duration missions.

Norsk, P.↗
NASA NTRS2016

Compiling a Comprehensive EVA Training Dataset for NASA Astronauts

Training for a spacewalk or extravehicular activity (EVA) is considered a hazardous duty for NASA astronauts. This places astronauts at risk for decompression sickness as well as various musculoskeletal disorders from working in the spacesuit. As a result, the operational and research communities over the years have requested access to EVA training data to supplement their studies. The purpose of this paper is to document the comprehensive EVA training data set that was compiled from multiple sources by the Lifetime Surveillance of Astronaut Health (LSAH) epidemiologists to investigate musculoskeletal injuries. The EVA training dataset does not contain any medical data, rather it only documents when EVA training was performed, by whom and other details about the session. The first activities practicing EVA maneuvers in water were performed at the Neutral Buoyancy Simulator (NBS) at the Marshall Spaceflight Center in Huntsville, Alabama. This facility opened in 1967 and was used for EVA training until the early Space Shuttle program days. Although several photographs show astronauts performing EVA training in the NBS, records detailing who performed the training and the frequency of training are unavailable. Paper training records were stored within the NBS after it was designated as a National Historic Landmark in 1985 and closed in 1997, but significant resources would be needed to identify and secure these records, and at this time LSAH has not pursued acquisition of these early training records. Training in the NBS decreased when the Johnson Space Center in Houston, Texas, opened the Weightless Environment Training Facility (WETF) in 1980. Early training records from the WETF consist of 11 hand-written dive logbooks compiled by individual workers that were digitized at the request of LSAH. The WETF was integral in the training for Space Shuttle EVAs until its closure in 1998. The Neutral Buoyancy Laboratory (NBL) at the Sonny Carter Training Facility near JSC opened in March 1997 and is the current site for US EVA training. Other space agencies also have used water to simulate weightlessness and train for EVAs. Russia has a training facility similar to the NBL named the Hydro Lab. The Hydro Lab began operations at the Gagarin Cosmonaut Training Center (GCTC) in 1980 and has been used extensively to the present. Although a majority of training in the Hydro Lab uses the Russian Orlan suit, a small number of sessions have been conducted using a NASA suit. The Japanese Weightlessness Environment Test System (WETS) went into service at the Tsukuba Space Center in 1997 but was closed in 2011 due to extensive earthquake damage. Several sessions were performed using a NASA suit, but these sessions were short and considered "development" runs. LSAH has assembled records from the WETF, NBL and Hydro Lab. Recording of the EVA training data has changed considerably from 1967 to present. The goal of early record keeping was to track use of hardware components, and the person involved was treated as a suited operator, not as a focus of interest. Records from the past two decades are fairly precise with the person, date, suit type and size noted. On occasion the length of the session was listed, but this data is not included on all records. Records were merged from data sources and extensive cleaning of the records was required since the multiple sources frequently overlapped and duplicated records. To date the LSAH EVA training dataset includes over 12,500 EVA training sessions performed by NASA astronauts since 1981. The following variables are included for most records: Name, Sex, Event date, Event name, HUT type, HUT size, Facility, and Estimated run time. For a smaller subset of records, the following variables are available: Actual run time, Time inverted, and the suit components Waist bearing type, Shoulder harness, Shoulder pads, and Teflon inserts. The LSAH dataset is currently the most complete resource for data regarding EVA training sessions performed by NASA astronauts. However, it is not 100 percent complete since the WETS (Japan) and NBS (Marshall) training facility data were not included. This dataset has been compiled by LSAH to study the relationship of EVA training to musculoskeletal injuries but has many other non-medical applications. This dataset can be provided to other groups in order to respond to program and research questions with appropriate board approvals.

Laughlin, M. S.↗
NASA NTRS2016

Regulation of Bone Formation During Disuse by miRNA

Astronauts lose bone structure during long-duration spaceflight. These changes are due, in part, to insufficient bone formation by the osteoblast cells. Little is known about the role that small (approximately 22 nucleotide), non-coding micro-RNAs (miRNAs) play in the osteoblast response to microgravity. We hypothesize that osteoblast-lineage cells alter their miRNA status during microgravity exposure, contributing to impaired bone formation during weightlessness. To simulate weightlessness, female mice (C57BL/6, Charles River, 10 weeks of age, n = 6) were hindlimb unloaded for 12 days. Age-matched and normally ambulating mice served as controls (n=6). To assess the expression of miRNAs in skeletal tissue, the right and left tibia of the mice were collected ex vivo and cleaned of soft-tissue and marrow. Total RNA was collected from tibial bone and relative abundance was measured for miRNAs of interest using quantitative real time PCR array looking at 372 unique and well-characterized mature miRNAs using the delta-delta Ct method. Transcripts of interest were normalized to an average of 6 reference RNAs. Preliminary results show that hindlimb unloading decreased the expression of 14 miRNAs to less than 1.4-2.9X control levels and increased the expression of 5 miRNAs relative to the control mice greater than 1-2-1.5X (p less than 0.05, respectively). Using the miRSystem we assessed overlapping target genes predicted to be regulated by multiple members of the 19 differentially expressed miRNAs as well as in silico predicted targets of our individual miRNAs. Our miRSystem results indicated that a number of our differentially expressed miRNAs were regulators of genes related to the Wnt-Beta Catenin pathway-a known regulator of bone health-and, interestingly, the estrogen-mediated cell-cycle regulation pathway, which may indicate that simulated weightlessness induced systemic hormonal changes that contributed to bone loss. We plan to follow up these findings by measuring gene expression of miRNA-regulated genes within these two pathways with the aim of furthering our understanding of the function of miRNAs in the skeletal response to spaceflight.

bone↗
NASA NTRS2016

Acute Effects of Simulated Space Radiation and Micro-Gravity on Cancellous Bone Loss in Mice Tibiae

Space radiation and micro-gravity are the two major obstacles impeding human exploration of Mars and beyond. Long-duration space flights expose astronauts to high doses of high linear energy transfer (LET) radiation as well as prolonged periods of skeletal disuse due to weightlessness. One important consequence of both radiation exposure and micro-gravity is acute bone loss. However, biological responses to different radiation types and combined radiation and micro-gravity environments remain unknown. Thus, the purpose of this study is to compare the acute effects of different radiation species and simulated weightlessness on bone degeneration for the purpose of developing accurate risk assessments of prolonged space flight. Mouse models were used to simulate space flight-relevant doses of different radiation types as well as weightlessness via hind-limb unloading. Three groups of mice (n 9) were irradiated with 1 Gy (Gray) H+, 1 Gy 56Fe, and 1 Gy combined H+ and 56Fe (dual ion) respectively and compared to sham irradiated (n 9) and 2 Gy 56Fe irradiated positive controls (n 6). Two groups of mice (n 9) were hind-limb unloaded for three days and then either sham irradiated or dual ion irradiated respectively, followed by subsequent hind-limb unloading for 11 days. Cancellous tissue from tibiae metaphyses were harvested 11 days post-irradiation for ex vivo micro-computed tomography analysis. Microarchitecture parameters including bone volume to total volume ratio (BVTV), trabecular thickness (Tb.Th), trabecular number (Tb.N), trabecular spacing (Tb.S), and connectivity density (Conn.D) will be quantified using a novel automated segmentation procedure developed in our lab. The anticipated results will be instrumental in developing counter-measures against micro-gravity and radiation-induced bone loss. Moreover, possible synergistic effects may provide insight into underlying mechanisms mediating biological response.

Micro-Gravity↗
NASA NTRS2021

Customized Science Carrier Modules and Accessories Developed for Microgravity Simulation Devices

Because the access to the true weightless environment of the ISS and other Low Earth Orbit (LEO) vehicles is limited and cost prohibitive, the need for ground-based microgravity simulation analogs to bridge the gravity continuum gap between 1g gravity and costly space flight studies with true weightlessness was realized. As such, the Microgravity Simulation Support Facility (MSSF) was established at NASA John F. Kennedy Space Center (KSC) to fulfill the need of the scientific community. Our facility provides the US science community with a focal point in the field of gravitational research by granting access to an array of two-dimensional(2D) and three-dimensional (3D)clinostats, and Random Positioning Machine (RPM) platforms developed by teams throughout the world. The availability of these capabilities will allow further understanding the role of altered gravity vectors from “functional weightlessness”, partial gravity conditions (1 x 10-3to 0.9g, and Moon and Mars ‘g vectors), to hypergravity (up to3g) on biological processes. We have designed and 3D printed a variety of specialized attachments(and associated “static control” hardware)to allow researchers to mount their samples onto these microgravity simulation devices to meet their unique science requirements. A summary of each attachment module will be presented below. Note: All software or code information should be requested to the author Ye Zhang, Kennedy Space Center ye.zhang-1@nasa.gov

Ye Zhang↗
NASA NTRS2002

Percutaneous aspiration of fluid for management of peritonitis in space

BACKGROUND: As a medical emergency that can affect even well-screened, healthy individuals, peritonitis developing during a long-duration space exploration mission may dictate deviation from traditional clinical practice due to the absence of otherwise indicated surgical capabilities. Medical management can treat many intra-abdominal processes, but treatment failures are inevitable. In these circumstances, percutaneous aspiration under sonographic guidance could provide a "rescue" strategy. Hypothesis: Sonographically guided percutaneous aspiration of intra-peritoneal fluid can be performed in microgravity. METHODS: Investigations were conducted in the microgravity environment of NASA's KC-135 research aircraft (0 G). The subjects were anesthetized female Yorkshire pigs weighing 50 kg. The procedures were rehearsed in a terrestrial animal lab (1 G). Colored saline (500 mL) was introduced through an intra-peritoneal catheter during flight. A high-definition ultrasound system (HDI-5000, ATL, Bothell, WA) was used to guide a 16-gauge needle into the peritoneal cavity to aspirate fluid. RESULTS: Intra-peritoneal fluid collections were easily identified, distinct from surrounding viscera, and on occasion became more obvious during weightless conditions. Subjectively, with adequate restraint of the subject and operators, the procedure was no more demanding than during the 1-G rehearsals. CONCLUSIONS: Sonographically guided percutaneous aspiration of intra-peritoneal fluid collections is feasible in weightlessness. Treatment of intra-abdominal inflammatory conditions in spaceflight might rely on pharmacological options, backed by sonographically guided percutaneous aspiration for the "rescue" of treatment failures. While this risk mitigation strategy cannot guarantee success, it may be the most practical option given severe resource limitations.

Non-NASA Center↗
NASA NTRS1990

Circumnutations of sunflower hypocotyls in satellite orbit

The principal objective of the research reported here was to determine whether a plant's periodic growth oscillations, called circumnutations, would persist in the absence of a significant gravitational or inertial force. The definitive experiment was made possible by access to the condition of protracted near weightlessness in an earth satellite. The experiment, performed during the first flight of Spacelab on the National Aeronautics and Space Administration shuttle, Columbia, in November and December, 1983, tested a biophysical model, proposed in 1967, that might account for circumnutation as a gravity-dependent growth response. However, circumnutations were observed in microgravity. They continued for many hours without stimulation by a significant g-force. Therefore, neither a gravitational nor an inertial g-force was an absolute requirement for initiation [correction of initation] or continuation of circumnutation. On average, circumnutation was significantly more vigorous in satellite orbit than on earth-based clinostats. Therefore, at least for sunflower (Helianthus annuus L.) circumnutation, clinostatting is not the functional equivalent of weightlessness.

NASA Discipline Plant Biology↗
NASA NTRS2002

Effects of space flight, clinorotation, and centrifugation on the substrate utilization efficiency of E. coli

Cultures of Escherichia coli grown in space reached a 25% higher average final cell population than those in comparably matched ground controls (p<0.05). However, both groups consumed the same quantity of glucose, which suggests that space flight not only stimulated bacterial growth as has been previously reported, but also resulted in a 25% more efficient utilization of the available nutrients. Supporting experiments performed in "simulated weightlessness" under clinorotation produced similar trends of increased growth and efficiency, but to a lesser extent in absolute values. These experiments resulted in increases of 12% and 9% in average final cell population (p<0.05), while the efficiency of substrate utilization improved by 6% and 9% relative to static controls (p=0.12 and p<0.05, respectively). In contrast, hypergravity, produced by centrifugation, predictably resulted in the opposite effect--a decrease of 33% to 40% in final cell numbers with corresponding 29% to 40% lower net growth efficiencies (p<0.01). Collectively, these findings support the hypothesis that the increased bacterial growth observed in weightlessness is a result of reduced extracellular mass transport that occurs in the absence of sedimentation and buoyancy-driven convection, which consequently also improves substrate utilization efficiency in suspended cultures.

manned↗
NASA NTRS2005

Jumping in simulated and true microgravity: response to maximal efforts with three landing types

BACKGROUND: Exercise is a promising countermeasure to the physiological deconditioning experienced in microgravity, but has not proven effective in eliminating the ongoing loss of bone mineral, most likely due to the lack of high-impact forces and loading rates during in-flight activity. We wanted to determine lower-extremity response to high-impact jumping exercises in true and simulated microgravity and establish if 1-G force magnitudes can be achieved in a weightless environment. METHODS: Jumping experiments were performed in a ground-based zero-gravity simulator (ZGS) in 1 G, and during parabolic flight with a gravity-replacement system. There were 12 subjects who participated in the study, with 4 subjects common to both conditions. Force, loading rates, jump height, and kinematics were analyzed during jumps with three distinct landings: two-footed toe-heel, one-footed toe-heel, and flat-footed. Gravity replacement loads of 45%, 60%, 75%, and 100% bodyweight were used in the ZGS; because of time constraints, these loads were limited to 60% and 75% bodyweight in parabolic flight. RESULTS: Average peak ground-reaction forces during landing ranged between 1902+/-607 and 2631+/-663 N in the ZGS and between 1683+/-807 and 2683+/-1174 N in the KC-135. No significant differences were found between the simulated and true microgravity conditions, but neither condition achieved the magnitudes found in 1 G. CONCLUSION: Data support the hypothesis that jumping exercises can impart high-impact forces during weightlessness and that the custom-designed ZGS will replicate what is experienced in true microgravity.

short duration↗
NASA NTRS1963

Biomedical and Human Factors Requirements for a Manned Earth-Orbiting Station

The study reported here has presented a measurement data pool for the determination of biomedical and behavioral effects of long-term exposure to weightlessness. This includes measures, techniques, equipment, and requirements in terms of weight, power, volume, time, crew activities, subsystem interfaces and experimental programs and designs, and confidence ratings for their effectiveness for determining weightlessness effects.

MANNED ORBITAL SPACE STATION /MOSS/↗
NASA NTRS1995

Gravitropic responses of the Avena coleoptile in space and on clinostats. I. Gravitropic response thresholds

We conducted a series of gravitropic experiments on Avena coleoptiles in the weightlessness environment of Spacelab. The purpose was to test the threshold stimulus, reciprocity rule and autotropic reactions to a range of g-force stimulations of different intensities and durations The tests avoided the potentially complicating effects of earth's gravity and the interference from clinostat ambiguities. Using slow-speed centrifuges, coleoptiles received transversal accelerations in the hypogravity range between 0.l and 1.0 g over periods that ranged from 2 to 130 min. All responses that occurred in weightlessness were compared to clinostat experiments on earth using the same apparatus. Characteristic gravitropistic response patterns of Atuena were not substantially different from those observed in ground-based experiments. Gravitropic presentation times were extrapolated. The threshold at 1.0 g was less than 1 min (shortest stimulation time 2 min), in agreement with values obtained on the ground. The least stimulus tested, 0.1 g for 130 min, produced a significant response. Therefore the absolute threshold for a gravitropic response is less than 0.1 g.

Flight Experiment↗
NASA NTRS1986

Understanding metabolic alterations in space flight using quantitative models: fluid and energy balance

This report summarizes many of the results obtained during the Skylab program, on metabolic changes during weightlessness. The examination of the data was conducted following an integrated multi-disciplinary and multi-experimental approach. Emphasis is given on several major aspects of metabolic adaptation to space flight: fluid-electrolyte regulation, mechanisms of hormone disturbances, energy balance and etiology of weight loss. The aim is to obtain a composite picture of the fluid, electrolyte and energy response to weightlessness.

Non-NASA Center↗