Ocular rigidity and choroidal thickness changes in response to microgravity: A case study

Purpose

To evaluate ocular rigidity and choroidal thickness changes in response to microgravity and the Valsalva maneuver in a private astronaut.

Methods

Ophthalmological examination and Optical Coherence Tomography were performed before, during, and after space flight. Choroidal thickness was measured at all time points at rest and during the Valsalva maneuver. Ocular rigidity was obtained before and after flight using a non-invasive method enhanced with deep learning-based choroid segmentation.

Results

Ocular rigidity decreased after space flight compared to baseline. There was an increase in average choroidal thickness during the Valsalva maneuver compared to the resting condition before, during, and after space flight, and such increase was greater when the Valsalva maneuver was performed during space flight.

Conclusions and importance

The data indicates biomechanical changes to ocular tissues because of space flight and greater choroidal thickness increase. The findings could lead to a better understanding of space flight-associated neuro-ocular syndrome and may have repercussions for short duration missions in a nascent industry.

Migration of surface-associated microbial communities in spaceflight habitats

Astronauts are spending longer periods locked up in ships or stations for scientific and exploration spatial missions. The International Space Station (ISS) has been inhabited continuously for more than 20 years and the duration of space stays by crews could lengthen with the objectives of human presence on the moon and Mars. If the environment of these space habitats is designed for the comfort of astronauts, it is also conducive to other forms of life such as embarked microorganisms. The latter, most often associated with surfaces in the form of biofilm, have been implicated in significant degradation of the functionality of pieces of equipment in space habitats. The most recent research suggests that microgravity could increase the persistence, resistance and virulence of pathogenic microorganisms detected in these communities, endangering the health of astronauts and potentially jeopardizing long-duration manned missions. In this review, we describe the mechanisms and dynamics of installation and propagation of these microbial communities associated with surfaces (spatial migration), as well as long-term processes of adaptation and evolution in these extreme environments (phenotypic and genetic migration), with special reference to human health. We also discuss the means of control envisaged to allow a lasting cohabitation between these vibrant microscopic passengers and the astronauts.

Cholesterol: An Important Determinant of Muscle Atrophy in Astronauts

Since cholesterol is not routinely measured in astronauts before and after their return from space, there is no data on the role of blood cholesterol level in muscle atrophy and microgravity. Since the first moon landing, aerospace medicine became outdated and has not pushed boundaries like its rocket engineering counterpart. Since the 2019 astronaut twin study, there has yet to be another scientific breakthrough for aerospace medicine. Microgravity-induced muscle atrophy is the most known consequence of spaceflight. Yet, so far, there is no therapeutic solution to prevent it or any real efforts in understanding it on a cellular or molecular level. The most obvious reason to this unprecedented level of research is due to the small cohort of astronauts. With the establishment of private space industries and exponential recruitment of astronauts, there is more reason to push forward spaceflight-related health guidelines and ensure the safety of the brave humans who risk their lives for the progression of mankind. Spaceflight is considered the most challenging job and the failure to prevent injury or harm should be considered reckless negligence by the institutions that actively prevented sophistication of aerospace medicine. In this critical review, role of cholesterol is analyzed across the NASA-established parameters of microgravity-induced muscle atrophy with a focus on potential therapeutic targets for research.

Carcinogenesis induced by space radiation: A systematic review

The carcinogenic risk from space radiation has always been a health risk issue of great concern during space exploration. In recent years, a large number of cellular and animal experiments have demonstrated that space radiation, composed of high-energy protons and heavy ions, has shown obvious carcinogenicity. However, different from radiation on Earth, space radiation has the characteristics of high energy and low dose rate. It is rich in high-atom-number and high-energy particles and, as it is combined with other space environmental factors such as microgravity and a weak magnetic field, the study of its carcinogenic effects and mechanisms of action is difficult, which leads to great uncertainty in its carcinogenic risk assessment. Here, we review the latest progress in understanding the effects and mechanisms of action related to cell transformation and carcinogenesis induced by space radiation in recent years and summarize the prediction models of cancer risk caused by space radiation and the methods to reduce the uncertainty of prediction to provide reference for the research and risk assessment of space radiation.

Cardiovascular autonomic nervous system responses and orthostatic intolerance in astronauts and their relevance in daily medicine

Background

The harsh environmental conditions during space travel, particularly weightlessness, impose a major burden on the human body including the cardiovascular system. Given its importance in adjusting the cardiovascular system to environmental challenges, the autonomic nervous system has been in the focus of scientists and clinicians involved in human space flight. This review provides an overview on human autonomic research under real and simulated space conditions with a focus on orthostatic intolerance.

Methods

The authors conducted a targeted literature search using Pubmed.

Results

Overall, 120 articles were identified and included in the review.

Conclusions

Postflight orthostatic intolerance is commonly observed in astronauts and could pose major risks when landing on another celestial body. The phenomenon likely results from changes in volume status and adaptation of the autonomic nervous system to weightlessness. Over the years, various non-pharmacological and pharmacological countermeasures have been investigated. In addition to enabling safe human space flight, this research may have implications for patients with disorders affecting cardiovascular autonomic control on Earth.

Effect of space flight on the behavior of human retinal pigment epithelial ARPE-19 cells and evaluation of coenzyme Q10 treatment

Astronauts on board the International Space Station (ISS) are exposed to the damaging effects of microgravity and cosmic radiation. One of the most critical and sensitive districts of an organism is the eye, particularly the retina, and > 50% of astronauts develop a complex of alterations designated as spaceflight-associated neuro-ocular syndrome. However, the pathogenesis of this condition is not clearly understood. In the current study, we aimed to explore the cellular and molecular effects induced in the human retinal pigment ARPE-19 cell line by their transfer to and 3-day stay on board the ISS in the context of an experiment funded by the Agenzia Spaziale Italiana. Treatment of cells on board the ISS with the well-known bioenergetic, antioxidant, and antiapoptotic coenzyme Q10 was also evaluated. In the ground control experiment, the cells were exposed to the same conditions as on the ISS, with the exception of microgravity and radiation. The transfer of ARPE-19 retinal cells to the ISS and their living on board for 3 days did not affect cell viability or apoptosis but induced cytoskeleton remodeling consisting of vimentin redistribution from the cellular boundaries to the perinuclear area, underlining the collapse of the network of intermediate vimentin filaments under unloading conditions. The morphological changes endured by ARPE-19 cells grown on board the ISS were associated with changes in the transcriptomic profile related to the cellular response to the space environment and were consistent with cell dysfunction adaptations. In addition, the results obtained from ARPE-19 cells treated with coenzyme Q10 indicated its potential to increase cell resistance to damage.

A bespoke health risk assessment methodology for the radiation protection of astronauts

An alternative approach that is particularly suitable for the radiation health risk assessment (HRA) of astronauts is presented. The quantity, Radiation Attributed Decrease of Survival (RADS), representing the cumulative decrease in the unknown survival curve at a certain attained age, due to the radiation exposure at an earlier age, forms the basis for this alternative approach. Results are provided for all solid cancer plus leukemia incidence RADS from estimated doses from theoretical radiation exposures accumulated during long-term missions to the Moon or Mars. For example, it is shown that a 1000-day Mars exploration mission with a hypothetical mission effective dose of 1.07 Sv at typical astronaut ages around 40 years old, will result in the probability of surviving free of all types of solid cancer and leukemia until retirement age (65 years) being reduced by 4.2% (95% CI 3.2; 5.3) for males and 5.8% (95% CI 4.8; 7.0) for females. RADS dose-responses are given, for the outcomes for incidence of all solid cancer, leukemia, lung and female breast cancer. Results showing how RADS varies with age at exposure, attained age and other factors are also presented. The advantages of this alternative approach, over currently applied methodologies for the long-term radiation protection of astronauts after mission exposures, are presented with example calculations applicable to European astronaut occupational HRA. Some tentative suggestions for new types of occupational risk limits for space missions are given while acknowledging that the setting of astronaut radiation-related risk limits will ultimately be decided by the Space Agencies. Suggestions are provided for further work which builds on and extends this new HRA approach, e.g., by eventually including non-cancer effects and detailed space dosimetry.

Cancer incidence risks above and below 1 Gy for radiation protection in space

The risk assessment quantities called lifetime attributable risk (LAR) and risk of exposure-induced cancer (REIC) are used to calculate the cumulative cancer incidence risks for astronauts, attributable to radiation exposure accumulated during long term lunar and Mars missions. These risk quantities are based on the most recently published epidemiological data on the Life Span Study (LSS) of Japanese A-bomb survivors, who were exposed to γ-rays and neutrons. In order to analyze the impact of a different neutron RBE on the risk quantities, a model for the neutron relative biological effectiveness (RBE) relative to gammas in the LSS is developed based on an older dataset with less follow-up time. Since both risk quantities are based on uncertain quantities, such as survival curves, and REIC includes deterministic radiation induced non-cancer mortality risks, modelled with data based on the general population, the risks for astronauts may not be optimally estimated. The suitability of these risk assessment measures for the use of cancer risk calculation for astronauts is discussed. The work presented here shows that the use of a higher neutron RBE than the value of 10, traditionally used in the LSS risk models, can reduce the risks up to almost 50%. Additionally, including an excess absolute risk (EAR) baseline scaling also increases the risks by between 0.4% and 8.1% for the space missions considered in this study. Using just an EAR model instead of an equally weighted EAR and excess relative risk (ERR) model can decrease the cumulative risks for the considered missions by between 0.4% and 4.1% if no EAR baseline scaling is applied. If EAR baseline scaling is included, the calculated risks with the EAR- and the mixed model, as well as the risks calculated with just the ERR model are almost identical and only small differences in the uncertainties are visible.

Population analysis of space travelers

Although many space missions have been completed in the last 60 years, space exploration is still technologically and medically challenging. While large-scale medical studies are impossible in space travelers, meta-analysis allows combining data from small crews that participated in space missions over several decades. Our primary objective was to examine space-travelers' sociodemographic characteristics and spaceflight activities, and their changes with time from the first spaceflight. Our secondary objective was to evaluate the publication practices to assess data availability for health-related meta-analytic studies. Based on state-funded space agencies used as primary sources, and third-party websites used as secondary sources, 565 humans (501 males/64 females) have currently completed spaceflight. The average age of space-travelers increased from 34±4 in the 1960s to 45±4 in the 2010s. While the duration of space missions has increased consistently, the number of missions per year varied in correlation with technological events. Using papers identified in the systematic review of bone health in astronauts, we examined the changes in reporting practices with time. The reported sample size varied from 1 to 58 people, in total providing data for 148 individuals. Data confidentiality significantly improved with time; however, the corresponding decrease in the availability of individual parameters did not allow stratification even by age, sex, and mission duration. Thus, space travelers represent a diverse population suitable for comparative studies, however, it is important to develop reporting practices that ensure consistent, transparent, and ethical presentation of outcomes to support meta-analyses that are critical for understanding the scope of spaceflight-induced health issues.

Changes in human skeletal muscle architecture and function induced by extended spaceflight

The aim of this study was to quantitatively describe the relationships between joint angles and muscle architecture (lengths (L_f) and angles (Θ_f) of fascicles) of human triceps surae [medial (MG) and lateral (LG) gastrocnemius and soleus (SOL) muscles] invivo for three men-cosmonaut after long-duration spaceflight. Sagittal sonographs of MG, LG, SOL were taken at ankle was positioned at 15° (dorsiflexion), 0° (neutral position), +15°, and +30° (plantarflexion), with the knee at 90° at rest and after a long-duration spaceflight. At each position, longitudinal ultrasonic images of the MG and LG and SOL were obtained while the cosmonauts was relaxed from which fascicle lengths and angles with respect to the aponeuroses were determined. After space flight plantarflexor force declined significantly (26%; p < 0.001). The internal architecture of the GM, and LG, and SOL muscle was significantly altered. In the passive condition, L_f changed from 45, 53, and 39 mm (knee, 0°, ankle, -15°) to 26, 33, and 28 mm (knee, 90° ankle, 30°) for MG, LG, and SOL, respectively. Different lengths and angles of fascicles, and their changes by contraction, might be related to differences in force-producing capabilities of the muscles and elastic characteristics of tendons and aponeuroses. The three heads of the triceps surae muscle substantially differ in architecture, which probably reflects their functional roles. Differences in fiber length and pennation angle that were observed among the muscles and could be associated with differences in force production and in elastic properties of musculo-tendinous complex and aponeuroses.

Effects of chronic exposure to a mixed field of neutrons and photons on behavioral and cognitive performance in mice

To simulate the space radiation environment astronauts are exposed to, most studies involve acute exposures but during a space mission there will be chronic (long-lasting) exposures. To address this knowledge gap, a neutron irradiator using a ²⁵²Cf (²⁵²Californium) source was used to generate a mixed field of neutrons and photons to simulate chronic, low dose rate exposures to high LET radiation. In the present study, we assessed the effects chronic neutron exposure starting at 60 days of age on behavioral and cognitive performance of BALB/c female and C3H male mice at 600 and 700 days of age as part of an opportunistic study that took advantage of the availability of neutron and sham-irradiated mice from a radiation carcinogenesis experiment. There were profound dose- and time point-dependent effects of chronic neutron exposure. At the 600-day time point, irradiated BALB/c female mice showed improved nest building at all three doses. At the 700-day, but not 600-day, time point slightly but significantly increased body weights were seen in C3H male mice exposed to 0.118 Gy. At the 600-day time point BALB/c female mice irradiated with 0.2 Gy did, like sham-irradiated, not show preferential exploration of the novel object that was seen in mice irradiated with 0.118 or 0.4 Gy. In C3H male mice exposed to 0.4 Gy and at the 600-day time point, increased measures of anxiety were observed on days 1 and 2 in the open field. Thus, different outcome measures show distinct dose-response relationships, with some anticipated to worsen performance during space missions, like increased measures of anxiety, while other anticipated to enhance performance, such as increased nest building and object recognition.

Dataset for dose and time-dependent transcriptional response to ionizing radiation exposure

Exposure to ionizing radiation associated with highly energetic and charged heavy particles is an inherent risk astronauts face in long duration space missions. We have previously considered the transcriptional effects that three levels of radiation (0.3 Gy, 1.5 Gy, and 3.0 Gy) have at an immediate time point (1 hr) post-exposure [1]. Our analysis of these results suggest effects on transcript levels that could be modulated at lower radiation doses [2]. In addition, a time dependent effect is likely to be present. Therefore, in order to develop a lab-on-a-chip approach for detection of radiation exposure in terms of both radiation level and time since exposure, we developed a time- and dose-course study to determine appropriate sensitive and specific transcript biomarkers that are detectable in blood samples. The data described herein was developed from a study measuring exposure to 0.15 Gy, 0.30 Gy, and 1.5 Gy of radiation at 1 hr, 2 hr, and 6 hr post-exposure using Affymetrix® GeneChip® PrimeView™ microarrays. This report includes raw gene expression data files from the resulting microarray experiments representing typical radiation exposure levels an astronaut may experience as part of a long duration space mission. The data described here is available in NCBI's Gene Expression Omnibus (GEO), accession GSE63952.

Replacement of daily load attenuates but does not prevent changes to the musculoskeletal system during bed rest

The dose-response effects of exercise in reduced gravity on musculoskeletal health have not been well documented. It is not known whether or not individualized exercise prescriptions can be effective in preventing the substantial loss in bone mineral density and muscle function that have been observed in space flight and in bed rest. In this study, typical daily loads to the lower extremities were quantified in free-living subjects who were then randomly assigned to control or exercise groups. Subjects were confined to 6-degree head-down bed rest for 84 days. The exercise group performed individually prescribed 1 g loaded locomotor exercise to replace their free-living daily load. Eleven subjects (5 exercise, 6 control) completed the protocol. Volumetric bone mineral density results from quantitative computed tomography demonstrated that control subjects lost significant amounts of bone in the intertrochanteric and total hip regions (p < 0.0125), whereas the exercise group showed no significant change from baseline in any region (p > 0.0125). Pre-and post-bed rest muscle volumes were calculated from analysis of magnetic resonance imaging data. The exercise group retained a larger percentage of their total quadriceps and gastrocnemius muscle volume (− 7.2% ± 5.9, − 13.8% ± 6.1, respectively) than their control counterparts (− 23.3% ± 5.9, − 33.0 ± 8.2, respectively; p < 0.01). Both groups significantly lost strength in several measured activities (p < 0.05). The declines in peak torque during repeated exertions of knee flexion and knee extension were significantly less in the exercise group than in the control group (p < 0.05) but work done was not significantly different between groups (p > 0.05). The decline in VO_2max was 17% ± 18 in exercising subjects (p < 0.05) and 31% ± 13 in control subjects (p = 0.003; difference between groups was not significant p = 0.26). Changes in blood and urine measures showed trends but no significant differences between groups (p > 0.05). In summary, the decline in a number of important measures of musculoskeletal and cardiovascular health was attenuated but not eliminated by a subject-specific program of locomotor exercise designed to replace daily load accumulated during free living. We conclude that single daily bouts of exposure to locomotor exercise can play a role in a countermeasures program during bed rest, and perhaps space flight, but are not sufficient in their own right to ensure musculoskeletal or cardiovascular health.

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Daily loads were quantified in subjects who were then randomly assigned to control or exercise groups.

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Eleven subjects (5 exercise, 6 control) completed the protocol of 84-days head-down bedrest.

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In 2 hip regions, bone loss was significant in controls but not in exercising subjects.

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The exercise group retained a larger percentage ofquadriceps and gastrocnemius muscle volumes and VO_2max than controls.

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1x day locomotor exercise attenuates changes but does not maintain musculoskeletal or cardiovascular health during bedrest.

Temporal dynamics of the gut microbiota in people sharing a confined environment, a 520-day ground-based space simulation, MARS500

BACKGROUND

The intestinal microbial communities and their temporal dynamics are gaining increasing interest due to the significant implications for human health. Recent studies have shown the dynamic behavior of the gut microbiota in free-living, healthy persons. To date, it is not known whether these dynamics are applicable during prolonged life sharing in a confined and controlled environment.

RESULTS

The MARS500 project, the longest ground-based space simulation ever, provided us with a unique opportunity to trace the crew microbiota over 520 days of isolated confinement, such as that faced by astronauts in real long-term interplanetary space flights, and after returning to regular life, for a total of 2 years. According to our data, even under the strictly controlled conditions of an enclosed environment, the human gut microbiota is inherently dynamic, capable of shifting between different steady states, typically with rearrangements of autochthonous members. Notwithstanding a strong individuality in the overall gut microbiota trajectory, some key microbial components showed conserved temporal dynamics, with potential implications for the maintenance of a health-promoting, mutualistic microbiota configuration.

CONCLUSIONS

Sharing life in a confined habitat does not affect the resilience of the individual gut microbial ecosystem, even in the long term. However, the temporal dynamics of certain microbiota components should be monitored when programming future mission simulations and real space flights, to prevent breakdowns in the metabolic and immunological homeostasis of the crewmembers.

Hypergravity hinders axonal development of motor neurons in Caenorhabditis elegans

As space flight becomes more accessible in the future, humans will be exposed to gravity conditions other than our 1G environment on Earth. Our bodies and physiology, however, are adapted for life at 1G gravity. Altering gravity can have profound effects on the body, particularly the development of muscles, but the reasons and biology behind gravity’s effect are not fully known. We asked whether increasing gravity had effects on the development of motor neurons that innervate and control muscle, a relatively unexplored area of gravity biology. Using the nematode model organism Caenorhabditis elegans, we examined changes in response to hypergravity in the development of the 19 GABAergic DD/VD motor neurons that innervate body muscle. We found that a high gravity force above 10G significantly increases the number of animals with defects in the development of axonal projections from the DD/VD neurons. We showed that a critical period of hypergravity exposure during the embryonic/early larval stage was sufficient to induce defects. While characterizing the nature of the axonal defects, we found that in normal 1G gravity conditions, DD/VD axonal defects occasionally occurred, with the majority of defects occurring on the dorsal side of the animal and in the mid-body region, and a significantly higher rate of error in the 13 VD axons than the 6 DD axons. Hypergravity exposure increased the rate of DD/VD axonal defects, but did not change the distribution or the characteristics of the defects. Our study demonstrates that altering gravity can impact motor neuron development.

Exercise in space: the European Space Agency approach to in-flight exercise countermeasures for long-duration missions on ISS

Background

To counteract microgravity (µG)-induced adaptation, European Space Agency (ESA) astronauts on long-duration missions (LDMs) to the International Space Station (ISS) perform a daily physical exercise countermeasure program. Since the first ESA crewmember completed an LDM in 2006, the ESA countermeasure program has strived to provide efficient protection against decreases in body mass, muscle strength, bone mass, and aerobic capacity within the operational constraints of the ISS environment and the changing availability of on-board exercise devices. The purpose of this paper is to provide a description of ESA’s individualised approach to in-flight exercise countermeasures and an up-to-date picture of how exercise is used to counteract physiological changes resulting from µG-induced adaptation. Changes in the absolute workload for resistive exercise, treadmill running and cycle ergometry throughout ESA’s eight LDMs are also presented, and aspects of pre-flight physical preparation and post-flight reconditioning outlined.

Results

With the introduction of the advanced resistive exercise device (ARED) in 2009, the relative contribution of resistance exercise to total in-flight exercise increased (33–46 %), whilst treadmill running (42–33 %) and cycle ergometry (26–20 %) decreased. All eight ESA crewmembers increased their in-flight absolute workload during their LDMs for resistance exercise and treadmill running (running speed and vertical loading through the harness), while cycle ergometer workload was unchanged across missions.

Conclusion

Increased or unchanged absolute exercise workloads in-flight would appear contradictory to typical post-flight reductions in muscle mass and strength, and cardiovascular capacity following LDMs. However, increased absolute in-flight workloads are not directly linked to changes in exercise capacity as they likely also reflect the planned, conservative loading early in the mission to allow adaption to µG exercise, including personal comfort issues with novel exercise hardware (e.g. the treadmill harness). Inconsistency in hardware and individualised support concepts across time limit the comparability of results from different crewmembers, and questions regarding the difference between cycling and running in µG versus identical exercise here on Earth, and other factors that might influence in-flight exercise performance, still require further investigation.

Incorporation of omics analyses into artificial gravity research for space exploration countermeasure development

The next major steps in human spaceflight include flyby, orbital, and landing missions to the Moon, Mars, and near earth asteroids. The first crewed deep space mission is expected to launch in 2022, which affords less than 7 years to address the complex question of whether and how to apply artificial gravity to counter the effects of prolonged weightlessness. Various phenotypic changes are demonstrated during artificial gravity experiments. However, the molecular dynamics (genotype and molecular phenotypes) that underlie these morphological, physiological, and behavioral phenotypes are far more complex than previously understood. Thus, targeted molecular assessment of subjects under various G conditions can be expected to miss important patterns of molecular variance that inform the more general phenotypes typically being measured. Use of omics methods can help detect changes across broad molecular networks, as various G-loading paradigms are applied. This will be useful in detecting off-target, or unanticipated effects of the different gravity paradigms applied to humans or animals. Insights gained from these approaches may eventually be used to inform countermeasure development or refine the deployment of existing countermeasures. This convergence of the omics and artificial gravity research communities may be critical if we are to develop the proper artificial gravity solutions under the severely compressed timelines currently established. Thus, the omics community may offer a unique ability to accelerate discovery, provide new insights, and benefit deep space missions in ways that have not been previously considered.

Acclimation during space flight: effects on human emotion

Recently, studies on the extent to which spaceflight affects the psychology of individuals has received attention. In order to reveal the mental challenges that humans face in space, we need practical viewpoints to integrate the psychological effects, behavior, performance and the environment itself for space exploration. The present review discusses the individual variables related to space psychology and manned spaceflight, in addition to their growing trends. These items include patterns of emotional changes in extreme environments and the approaches to evaluating emotions. Moreover, the review concludes with suggested future research on emotion during spaceflight and its analogs. These data and information are needed to plan for the exploration of the Moon and Mars, along with contributions to the construction of the international space station (ISS) and astronaut training.

V̇O2 and HR kinetics before and after International Space Station missions

PURPOSE

Heart rate (HR), pulmonary and muscle oxygen uptake ([Formula: see text]O2pulm, [Formula: see text]O2musc) kinetics after changes of work rate (WR) indicate regulatory characteristics related to aerobic metabolism. We analysed whether the kinetics of HR, [Formula: see text]O2pulm and [Formula: see text]O2musc are slowed after missions to the International Space Station (ISS). The changes of the kinetics were correlated with [Formula: see text]O2peak data.

METHODS

10 astronauts [4 females, 6 males, age: 48.0 ± 3.8 years, height: 176 ± 7 cm, mass: 74.5 ± 15.9 kg (mean ± SD)] performed an incremental test to determine [Formula: see text]O2peak (before missions on L-110 days, after return on R+1/+10/+36 days), and a cardio-respiratory kinetics test (CRKT) with randomized 30-80 W WR changes to determine HR, [Formula: see text]O2pulm and [Formula: see text]O2musc kinetics by time-series analysis (L-236/-73, R+6/+21). Kinetics were summarized by maximum and related lag of cross-correlation function (CCFmax, CCFlag) of WR with the analysed parameter.

RESULTS

Statistically, significant changes were also found for CCFmax([Formula: see text]O2musc) between L-236 and R+6 (P = 0.010), L-236 and R+21 (P = 0.030), L-72 and R+6 (P = 0.043). Between pre-to-post mission change in [Formula: see text]O2peak and CCFmax(HR), a correlation was shown (r SP = 0.67, P = 0.017).

CONCLUSION

The [Formula: see text]O2musc kinetics changes indicate aerobic detraining effects which are present up to 21 days following space flight. The correlations between changes in [Formula: see text]O2peak and HR kinetics illustrate the key role of cardiovascular regulation in [Formula: see text]O2peak. The addition of CRKT to ISS flight is recommended to obtain information regarding the potential muscular and cardiovascular deconditioning. This allows a reduction in the frequency of higher intensity testing during flight.

Microgravity-driven remodeling of the proteome reveals insights into molecular mechanisms and signal networks involved in response to the space flight environment

Space is a hostile environment characterized by high vacuum, extreme temperatures, meteoroids, space debris, ionospheric plasma, microgravity and space radiation, which all represent risks for human health. A deep understanding of the biological consequences of exposure to the space environment is required to design efficient countermeasures to minimize their negative impact on human health. Recently, proteomic approaches have received a significant amount of attention in the effort to further study microgravity-induced physiological changes. In this review, we summarize the current knowledge about the effects of microgravity on microorganisms (in particular Cupriavidus metallidurans CH34, Bacillus cereus and Rhodospirillum rubrum S1H), plants (whole plants, organs, and cell cultures), mammalian cells (endothelial cells, bone cells, chondrocytes, muscle cells, thyroid cancer cells, immune system cells) and animals (invertebrates, vertebrates and mammals). Herein, we describe their proteome's response to microgravity, focusing on proteomic discoveries and their future potential applications in space research.

BIOLOGICAL SIGNIFICANCE

Space experiments and operational flight experience have identified detrimental effects on human health and performance because of exposure to weightlessness, even when currently available countermeasures are implemented. Many experimental tools and methods have been developed to study microgravity induced physiological changes. Recently, genomic and proteomic approaches have received a significant amount of attention. This review summarizes the recent research studies of the proteome response to microgravity inmicroorganisms, plants, mammalians cells and animals. Current proteomic tools allow large-scale, high-throughput analyses for the detection, identification, and functional investigation of all proteomes. Understanding gene and/or protein expression is the key to unlocking the mechanisms behind microgravity-induced problems and to finding effective countermeasures to spaceflight-induced alterations but also for the study of diseases on earth. Future perspectives are also highlighted.

Pancreas of C57 black mice after long-term space flight (Bion-M1 Space Mission)

In this study, we analysed the pancreases of C57BL/6N mice in order to estimate the effects of long-term space flights. Mice were flown aboard the Bion-M1 biosatellite, or remained on ground in the control experiment that replicated environmental and housing conditions in the spacecraft. Vivarium control group was used to account for housing effects. Each of the groups included mice designated for recovery studies. Mice pancreases were dissected for histological and immunohistochemical examinations. Using a morphometry and statistical analysis, a strong correlation between the mean islet size and the mean body weight was revealed in all groups. Therefore, we propose that hypokinesia and an increase in nutrition play an important role in alterations of the endocrine pancreas, both in space flight and terrestrial conditions.

Electromyographic evaluation of countermeasures during the terrestrial simulation of interplanetary spaceflight in Mars500 project

The efficiency of six countermeasures (CM) for muscle atrophy was compared over 520 days of confinement during the terrestrial simulation of round space flight to Mars using surface electromyography (sEMG). Three of CM were cyclic exercises (a motor-driven and leg-driven treadmill, cycle ergometer), resistive exercises (the multifunctional dynamometer for space-MDS, and expanders), and vibration platform. Each of CM was applied for each crew member (n=6) once over the experiment, for 70 days in a row, in prescribed order. sEMG was collected during the "force step test" in which the subject voluntarily produced pressure by lower limb, with minimal force increment. The mean frequency (MNF) and average amplitude of sEMG were analyzed. The MNF of sEMG decreased from 104.3±4.2 to 95.3±2.9Hz (P<0.05) in the soleus muscle after 70 days of exercising on the leg-driven treadmill and after 35 days-on vibration platform. It can be caused by earlier (10-250ms) recruitment of the soleus in respect with the medial gastronemius on the leg-driven treadmill, while on the motor-driven treadmill synergists activated synchronously. In other lower leg muscles, MNF decreased from 180 to 200 to 165-180Hz after 70 days of resistive exercises on the MDS device. CM caused no effect on sEMG amplitude. In conclusion, (1) the leg-driven treadmill, the MDS and vibration platform significantly depressed MNF of sEMG of lower extremity muscles; (2) the leg-driven treadmill and vibration platform specifically affected the soleus muscle. Therefore, these CM can be recommended for a more extensive use on ISS board.

Reliability of a new test battery for fitness assessment of the European Astronaut corps

BACKGROUND

To optimise health for space missions, European astronauts follow specific conditioning programs before, during and after their flights. To evaluate the effectiveness of these programs, the European Space Agency conducts an Astronaut Fitness Assessment (AFA), but the test-retest reliability of elements within it remains unexamined. The reliability study described here presents a scientific basis for implementing the AFA, but also highlights challenges faced by operational teams supporting humans in such unique environments, especially with respect to health and fitness monitoring of crew members travelling not only into space, but also across the world. The AFA tests assessed parameters known to be affected by prolonged exposure to microgravity: aerobic capacity (VO2max), muscular strength (one repetition max, 1 RM) and power (vertical jumps), core stability, flexibility and balance. Intraclass correlation coefficients (ICC3.1), standard error of measurement and coefficient of variation were used to assess relative and absolute test-retest reliability.

RESULTS

Squat and bench 1 RM (ICC3.1 = 0.94-0.99), hip flexion (ICC3.1 = 0.99) and left and right handgrip strength (ICC3.1 = 0.95 and 0.97), showed the highest test-retest reliability, followed by VO2max (ICC3.1 = 0.91), core strength (ICC3.1 = 0.78-0.89), hip extension (ICC3.1 = 0.63), the countermeasure (ICC3.1 = 0.76) and squat (ICC3.1 = 0.63) jumps, and single right- and left-leg jump height (ICC3.1 = 0.51 and 0.14). For balance, relative reliability ranged from ICC3.1 = 0.78 for path length (two legs, head tilted back, eyes open) to ICC3.1 = 0.04 for average rotation velocity (one leg, eyes closed).

CONCLUSIONS

In a small sample (n = 8) of young, healthy individuals, the AFA battery of tests demonstrated acceptable test-retest reliability for most parameters except some balance and single-leg jump tasks. These findings suggest that, for the application with astronauts, most AFA tests appear appropriate to be maintained in the test battery, but that some elements may be unreliable, and require either modification (duration, selection of task) or removal (single-leg jump, balance test on sphere) from the battery. The test battery is mobile and universally applicable for occupational and general fitness assessment by its comprehensive composition of tests covering many systems involved in whole body movement.

Selective weighting of cutaneous receptor feedback and associated balance impairments following short duration space flight

The present study investigated the perception of low frequency (3 Hz) vibration on the foot sole and its relationship to standing balance following short duration space flight in nine astronauts. Both 3 Hz vibration perception threshold (VPT) and standing balance measures increased on landing day compared to pre-flight. Contrary to our hypothesis, a positive linear relationship between these measures was not observed; however astronauts with the most sensitive skin (lowest 3 Hz VPT) were found to have the largest sway on landing day. While the change in foot sole sensitivity does not appear to directly relate to standing balance control, an exploratory strategy may be employed by astronauts whose threshold to pressure information is lower. Understanding sensory adaptations and balance control has implications to improve balance control strategies following space flight and in sensory impaired populations on earth.

Comparison of space flight and heavy ion radiation induced genomic/epigenomic mutations in rice (Oryza sativa)

Rice seeds, after space flight and low dose heavy ion radiation treatment were cultured on ground. Leaves of the mature plants were obtained for examination of genomic/epigenomic mutations by using amplified fragment length polymorphism (AFLP) and methylation sensitive amplification polymorphism (MSAP) method, respectively. The mutation sites were identified by fragment recovery and sequencing. The heritability of the mutations was detected in the next generation. Results showed that both space flight and low dose heavy ion radiation can induce significant alterations on rice genome and epigenome (P<0.05). For both genetic and epigenetic assays, while there was no significant difference in mutation rates and their ability to be inherited to the next generation, the site of mutations differed between the space flight and radiation treated groups. More than 50% of the mutation sites were shared by two radiation treated groups, radiated with different LET value and dose, while only about 20% of the mutation sites were shared by space flight group and radiation treated group. Moreover, in space flight group, we found that DNA methylation changes were more prone to occur on CNG sequence than CG sequence. Sequencing results proved that both space flight and heavy ion radiation induced mutations were widely spread on rice genome including coding region and repeated region. Our study described and compared the characters of space flight and low dose heavy ion radiation induced genomic/epigenomic mutations. Our data revealed the mechanisms of application of space environment for mutagenesis and crop breeding. Furthermore, this work implicated that the nature of mutations induced under space flight conditions may involve factors beyond ion radiation.

Personalized medicine in human space flight: using Omics based analyses to develop individualized countermeasures that enhance astronaut safety and performance

Space flight is one of the most extreme conditions encountered by humans. Advances in Omics methodologies (genomics, transcriptomics, proteomics, and metabolomics) have revealed that unique differences exist between individuals. These differences can be amplified in extreme conditions, such as space flight. A better understanding of individual differences may allow us to develop personalized countermeasure packages that optimize the safety and performance of each astronaut. In this review, we explore the role of "Omics" in advancing our ability to: (1) more thoroughly describe the biological response of humans in space; (2) describe molecular attributes of individual astronauts that alter the risk profile prior to entering the space environment; (3) deploy Omics techniques in the development of personalized countermeasures; and (4) develop a comprehensive Omics-based assessment and countermeasure platform that will guide human space flight in the future. In this review, we advance the concept of personalized medicine in human space flight, with the goal of enhancing astronaut safety and performance. Because the field is vast, we explore selected examples where biochemical individuality might significantly impact countermeasure development. These include gene and small molecule variants associated with: (1) metabolism of therapeutic drugs used in space; (2) one carbon metabolism and DNA stability; (3) iron metabolism, oxidative stress and damage, and DNA stability; and (4) essential input (Mg and Zn) effects on DNA repair. From these examples, we advance the case that widespread Omics profiling should serve as the foundation for aerospace medicine and research, explore methodological considerations to advance the field, and suggest why personalized medicine may become the standard of care for humans in space.

Effects of Space Flight on the Chemical Constituents and Anti-Inflammatory Activity of Licorice (Glycyrrhiza uralensis Fisch)

Licorice, the oldest Chinese traditional medicine, is widely used in the treatment of human diseases. Due to the deficiency of wild resource, selecting and breeding becomes a key issue to expanding the supply of licorice. Spaceflight technology will become a new method for medicinal plants. The aim of this study was to investigate the effect of spaceflight on the components and anti-inflammatory activity in licorice. After flowing on a recoverable satellite for 18 days, licorice seeds were germinated and grown to maturity and the parallel ground-based seeds were also planted under the same conditions. The main components in licorice root were analyzed through HPLC. The contents of two components in spaceflight groups were higher than that of the ground control ones. Three acute inflammatory models including xylene-induced auricular edema, carrageenan-induced paw edema and acetic acid-induced vascular permeability were utilized to compare the anti-inflammatory activity of licorice pre and post spaceflight. The licorice extract showed the significant anti-inflammation activity. After the spaceflight, the pharmacological activity of licorice got higher than that of the ground control one. All of the models gained the tendency that the spaceflight group of species Hangjinqi had the strongest activity than other groups. The research provided the scientific data for a new breeding of medicinal plant through the spaceflight and indicated that the technology of space flight may be a new effective method for the breeding and cultivation of licorice.