Muscle synergies of multidirectional postural control in astronauts on Earth after a long-term stay in space.

Movements of the human biological system have adapted to the physical environment under the 1-g gravitational force on Earth. However, the effects of microgravity in space on the underlying functional neuromuscular control behaviors remain poorly understood. Here, we aimed to elucidate the effects of prolonged exposure to a microgravity environment on the functional coordination of multiple muscle activities. The activities of 16 lower limb muscles of 5 astronauts who stayed in space for at least 3 mo were recorded while they maintained multidirectional postural control during bipedal standing. The coordinated activation patterns of groups of muscles, i.e., muscle synergies, were estimated from the muscle activation datasets using a factorization algorithm. The experiments were repeated a total of five times for each astronaut, once before and four times after spaceflight. The compositions of muscle synergies were altered, with a constant number of synergies, after long-term exposure to microgravity, and the extent of the changes was correlated with the increased velocity of postural sway. Furthermore, the muscle synergies extracted 3 mo after the return were similar in their activation profile but not in their muscle composition compared with those extracted in the preflight condition. These results suggest that the modularity in the neuromuscular system became reorganized to adapt to the microgravity environment and then possibly reoptimized to the new sensorimotor environment after the astronauts were reexposed to a gravitational force. It is expected that muscle synergies can be used as physiological markers of the status of astronauts with gravity-dependent change.NEW & NOTEWORTHY The human neuromuscular system has adapted to the gravitational environment on Earth. Here, we demonstrated that prolonged exposure to a microgravity environment in space changes the functional coordination of multiple muscle activities regarding multidirectional standing postural control. Furthermore, the amount of change led to a greater regulatory balancing activity needed for postural control immediately after returning to Earth and differences in muscular coordination before space flight and 3 mo after the return to Earth.

Long-duration spaceflight alters estimated intracranial pressure and cerebral blood velocity.

KEY POINTS: During long-duration spaceflights, some astronauts develop structural ocular changes including optic disc oedema that resemble signs of intracranial hypertension. In the present study, intracranial pressure was estimated non-invasively (nICP) using a model-based analysis of cerebral blood velocity and arterial blood pressure waveforms in 11 astronauts before and after long-duration spaceflights. Our results show that group-averaged estimates of nICP decreased significantly in nine astronauts without optic disc oedema, suggesting that the cephalad fluid shift during long-duration spaceflight rarely increased postflight intracranial pressure. The results of the two astronauts with optic disc oedema suggest that both increases and decreases in nICP are observed post-flight in astronauts with ocular alterations, arguing against a primary causal relationship between elevated ICP and spaceflight associated optical changes. Cerebral blood velocity increased independently of nICP and spaceflight-associated ocular alterations. This increase may be caused by the reduced haemoglobin concentration after long-duration spaceflight. ABSTRACT: Persistently elevated intracranial pressure (ICP) above upright values is a suspected cause of optic disc oedema in astronauts. However, no systematic studies have evaluated changes in ICP from preflight. Therefore, ICP was estimated non-invasively before and after spaceflight to test whether ICP would increase after long-duration spaceflight. Cerebral blood velocity in the middle cerebral artery (MCAv) was obtained by transcranial Doppler sonography and arterial pressure in the radial artery was obtained by tonometry, in the supine and sitting positions before and after 4-12 months of spaceflight in 11 astronauts (10 males and 1 female, 46 ± 7 years old at launch). Non-invasive ICP (nICP) was computed using a validated model-based estimation method. Mean MCAv increased significantly after spaceflight (ANOVA, P = 0.007). Haemoglobin decreased significantly after spaceflight (14.6 ± 0.8 to 13.3 ± 0.7 g/dL, P < 0.001). A repeated measures correlation analysis indicated a negative correlation between haemoglobin and mean MCAv (r = -0.589, regression coefficient = -4.68). The nICP did not change significantly after spaceflight in the 11 astronauts. However, nICP decreased significantly by 15% in nine astronauts without optic disc oedema (P < 0.005). Only one astronaut increased nICP to relatively high levels after spaceflight. Contrary to our hypothesis, nICP did not increase after long-duration spaceflight in the vast majority (>90%) of astronauts, suggesting that the cephalad fluid shift during spaceflight does not systematically or consistently elevate postflight ICP in astronauts. Independently of nICP and ocular alterations, the present results of mean MCAv suggest that long-duration spaceflight may increase cerebral blood flow, possibly due to reduced haemoglobin concentration.

The skin mycobiome of an astronaut during a 1-year stay on the International Space Station.

Analysis of the skin mycobiome of an astronaut during a 1-year stay on the International Space Station (ISS) revealed an increased relative abundance of Malassezia restricta and level of Malassezia colonization, and the presence of Cyberlindnera jadinii and Candida boidinii, uncommon skin mycobiome taxa. Similar observations were made in astronauts during a 6-month stay on the ISS (Med Mycol. 2016; 54: 232-239). Future plans for extended space travel should consider the effect of high levels of Malassezia colonization over long periods on astronauts' skin, and the abnormal proliferation of uncommon microorganisms that may occur in closed environments such as the ISS.

Identification of fungi isolated from astronaut nasal and pharyngeal smears and saliva.

As part of a series of studies regarding the microbiota in manned space environments, we isolated the fungal strains from nasal and pharyngeal smears and saliva of 21 astronauts preflight, in-flight, and postflight. On the ground, 120 strains from 43 genera of environmental fungi were isolated from the astronauts. The dominant fungal genera were Cladosporium, Penicillium, and Aspergillus. Only 18 strains from four genera were isolated from the astronauts inside the International Space Station. These fungi are currently thought to be harmless, but regular screening and cleaning are necessary to prevent fungus-related health disorders.

Comprehensive analysis of the skin fungal microbiota of astronauts during a half-year stay at the International Space Station.

The International Space Station (ISS) is a huge manned construct located approximately 400 km above the earth and is inhabited by astronauts performing space experiments. Because the station is within a closed microgravity environment, the astronauts are subject to consistent stress. This study analyzed the temporal changes in the skin fungal microbiota of 10 astronauts using pyrosequencing and quantitative PCR assay before, during, and after their stay in the ISS. Lipophilic skin fungi, Malassezia predominated most samples regardless of the collection period, body site (cheek or chest), or subject. During their stay in the ISS, the level of Malassezia colonization changed by 7.6- ± 7.5-fold (mean ± standard deviation) and 9.5- ± 24.2-fold in cheek and chest samples, respectively. At the species level, M. restricta, M. globosa, and M. sympodialis were more abundant. In the chest samples, the ratio of M. restricta to all Malassezia species increased, whereas it did not change considerably in cheek samples. Fungal diversity was reduced, and the ratio of Malassezia to all fungal colonization increased during the astronauts' stay at the ISS. The ascomycetous yeast Cyberlindnera jadinii was detected in abundance in the in-flight sample of 5 of the 10 astronauts. The microorganism may have incidentally adhered to the skin during the preflight period and persisted on the skin thereafter. This observation suggests the ability of a specific or uncommon microorganism to proliferate in a closed environment. Our study is the first to reveal temporal changes in the skin fungal microbiota of ISS astronauts. These findings will provide information useful for maintaining the health of astronauts staying in the space environment for long periods and for preventing infection due to the human skin microbiota.

Temporal changes in the skin Malassezia microbiota of members of the Japanese Antarctic Research Expedition (JARE): A case study in Antarctica as a pseudo-space environment.

The International Space Station (ISS) is located approximately 400 km above the Earth. Astronauts staying at the ISS are under microgravity and are thus unable to bathe or shower; instead, they wash their bodies using wet tissues. For astronauts, skin hygiene management is important to maintain the quality of life during long-term stays on the ISS. In Antarctica, members of a Japanese geological investigation team negotiate their way over land using snowmobiles. During their 3-month stay, they are subject to a "pseudo-space" environment similar to that experienced by ISS astronauts, including the inability to bathe or shower. In this study, temporal changes in the colonization levels of skin lipophilic fungi, Malassezia were investigated in 16 team members. Compared to the levels before their trip to Antarctica, the fold changes in Malassezia colonization levels during the researchers' stay in Antarctica were in the range of 3.0 ± 1.9 to 5.3 ± 7.5 in cheek samples, 8.9 ± 10.6 to 22.2 ± 40.0 in anterior chest samples, 6.2 ± 5.4 to 16.9 ± 25.5 in behind-the-ear samples, and 1.7 ± 0.9 to 17.4 ± 33.4 in sole-of-the-foot samples. On the scalp, the level of Malassezia colonization increased dramatically, by 96.7 ± 113.8 to 916.9 ± 1251.5 fold. During their stay in Antarctica, the team members experienced itchy scalps and produced a large number of scales. The relative proportions of Malassezia globosa and M. restricta shifted to seborrheic dermatitis/dandruff types. These results provide useful information for the development of skin hygiene management plans for astronauts staying at the ISS.

MnSOD downregulation induced by extremely low 0.1 mGy single and fractionated X-rays and microgravity treatment in human neuroblastoma cell line, NB-1.

A human neuroblastoma cell line, NB-1, was treated with 24 h of microgravity simulation by clinostat, or irradiated with extremely small X-ray doses of 0.1 or 1.0 mGy using single and 10 times fractionation regimes with 1 and 2 h time-intervals. A quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) examination was performed for apoptosis related factors (BAX, CYTC, APAF1, VDAC1-3, CASP3, CASP8, CASP9 P53, AIF, ANT1 and 2, BCL2, MnSOD, autophagy related BECN and necrosis related CYP-40. The qRT-PCR results revealed that microgravity did not result in significant changes except for a upregulation of proapoptotic VDAC2, and downregulations of proapoptotic CASP9 and antiapoptotic MnSOD. After 0.1 mGy fractionation irradiation, there was increased expression of proapoptotic APAF1 and downregulation of proapoptotic CYTC, VDAC2, VDAC3, CASP8, AIF, ANT1, and ANT2, as well as an increase in expression of antiapoptotic BCL2. There was also a decrease in MnSOD expression with 0.1 mGy fractionation irradiation. These results suggest that microgravity and low-dose radiation may decrease apoptosis but may potentially increase oxidative stress.

Low-volume, high-intensity, aerobic interval exercise for sedentary adults: VO2max, cardiac mass, and heart rate recovery.

PURPOSE: The aim of this study was to compare the effects of low-volume, high-intensity aerobic interval training (HAIT) on maximal oxygen consumption (VO2max), left ventricular (LV) mass, and heart rate recovery (HRR) with high-volume, moderate-intensity continuous aerobic training (CAT) in sedentary adults. METHODS: Twenty-four healthy but sedentary male adults (aged 29.2 ± 7.2 years) participated in an 8-week, 3-day a week, supervised exercise intervention. They were randomly assigned to either HAIT (18 min, 180 kcal per exercise session) or CAT (45 min, 360 kcal). VO2max, LV mass (3T-MRI), and HRR at 1 min (HRR-1) and 2 min (HRR-2) after maximal exercise were measured pre- and post-intervention. RESULTS: Changes in VO2max during the 8-week intervention were significant (P < 0.01) in both groups (HAIT, 8.7 ± 3.2 ml kg(-1) min(-1), 22.4 ± 8.9%; CAT, 5.5 ± 2.8 ml kg(-1) min(-1), 14.7 ± 9.5%), while the VO2max improvement in HAIT was greater (P = 0.02) than in CAT. LV mass in HAIT increased (5.1 ± 8.4 g, 5.7 ± 9.1%, P = 0.05), but not in CAT (0.9 ± 7.8 g, 1.1 ± 8.4%, P = 0.71). While changes in HRR-1 were not significant in either group, change in HRR-2 for HAIT (9.5 ± 6.4 bpm, 19.0 ± 16.0%, P < 0.01) was greater (P = 0.03) than for CAT (1.6 ± 10.9 bpm, 3.9 ± 16.2%, P = 0.42). CONCLUSIONS: This study suggests that HAIT has potential as a time-efficient training mode to improve cardiorespiratory capacity and autonomic nervous system function in sedentary adults.

Methods for assessing change in brain plasticity at night and psychological resilience during daytime between repeated long-duration space missions.

This study was designed to examine the feasibility of analyzing heart rate variability (HRV) data from repeat-flier astronauts at matching days on two separate missions to assess any effect of repeated missions on brain plasticity and psychological resilience, as conjectured by Demertzi. As an example, on the second mission of a healthy astronaut studied about 20 days after launch, sleep duration lengthened, sleep quality improved, and spectral power (ms2) co-varying with activity of the salience network (SN) increased at night. HF-component (0.15-0.50 Hz) increased by 61.55%, and HF-band (0.30-0.40 Hz) by 92.60%. Spectral power of HRV indices during daytime, which correlate negatively with psychological resilience, decreased, HF-component by 22.18% and HF-band by 37.26%. LF-component and LF-band, reflecting activity of the default mode network, did not change significantly. During the second mission, 24-h acrophases of HRV endpoints did not change but the 12-h acrophase of TF-HRV did (P < 0.0001), perhaps consolidating the circadian system to help adapt to space by taking advantage of brain plasticity at night and psychological resilience during daytime. While this N-of-1 study prevents drawing definitive conclusions, the methodology used herein to monitor markers of brain plasticity could pave the way for further studies that could add to the present results.

An exercise protocol designed to control energy expenditure for long-term space missions.

INTRODUCTION: Astronauts experience weight loss during spaceflight. Future space missions require a more efficient exercise program not only to maintain work efficiency, but also to control increased energy expenditure (EE). When discussing issues concerning EE incurred through exercise, excess post-exercise energy expenditure (EPEE) must also be considered. The aim of this study was to compare the total EE, including EPEE, induced by two types of interval cycling protocols with the total EE of a traditional, continuous cycling protocol. METHODS: There were 10 healthy men, ages 20 to 31 yr, who completed 3 exercise sessions: sprint interval training (SIT) consisting of 7 sets of 30-s cycling at 120% VO2max with a 15-s rest between each bout; high-intensity interval aerobic training (HIAT) consisting of 3 sets of 3-min cycling at 80-90% VO2max with a 2-min active rest at 50% VO2max; and continuous aerobic training (CAT) consisting of 40 min of cycling at 60-65% VO2max. During each session, resting metabolic rate, exercise EE, and a 180-min post-exercise EE were measured. RESULTS: The EPEEs during the SIT, HIAT, and CAT averaged 32 +/- 19, 21 +/- 16, and 13 +/- 13 kcal, and the total EE for an entire exercise/ rest session averaged 109 +/- 20, 182 +/- 17, and 363 +/- 45 kcal, respectively. While the EPEE after the CAT was significantly less than after the SIT, the total EE with the CAT was the greatest of the three. DISCUSSION: The SIT and HIAT would be potential protocols to control energy expenditure for long space missions.

[Space flight/bedrest immobilization and bone. In-flight exercise device to support a health of astronauts].

Despite the fact that astronauts living in the International Space Station (ISS) conduct daily two-hour intensive exercise programs to maintain their health, many health problems persist. These problems which include adverse effects of microgravity to bone, muscle and stamina, have not completely been countered. For example, bone mass reduction (about 1.6%/month at the neck of femur) , muscle atrophy (about 0.8%/day at the calf) , and exercise capacity reduction (about 10-20% decrease in the maximum oxygen uptake) have been reported. Interdisciplinary research approaches, such as various exercise countermeasures, a nutrition treatment, and medicine (bone absorption inhibitor) are employed in order to lower an astronaut's health risk and to promote productivity of work in space. This paper introduces the exercise equipment currently used in the ISS.

Unconscious mind activates central cardiovascular network and promotes adaptation to microgravity possibly anti-aging during 1-year-long spaceflight.

The intrinsic cardiovascular regulatory system (ß, 0.00013-0.02 Hz) did not adapt to microgravity after a 6-month spaceflight. The infraslow oscillation (ISO, 0.01-0.10 Hz) coordinating brain dynamics via thalamic astrocytes plays a key role in the adaptation to novel environments. We investigate the adaptive process of a healthy astronaut during a 12-month-long spaceflight by analyzing heart rate variability (HRV) in the LF (0.01-0.05 Hz) and MF1 (0.05-0.10 Hz) bands for two consecutive days on four occasions: before launch, at 1-month (ISS01) and 11-month (ISS02) in space, and after return to Earth. Alteration of ß during ISS01 improved during ISS02 (P = 0.0167). During ISS01, LF and MF1 bands, reflecting default mode network (DMN) activity, started to increase at night (by 43.1% and 32.0%, respectively), when suprachiasmatic astrocytes are most active, followed by a 25.9% increase in MF1-band throughout the entire day during ISS02, larger at night (47.4%) than during daytime. Magnetic declination correlated positively with ß during ISS01 (r = 0.6706, P < 0.0001) and ISS02 (r = 0.3958, P = 0.0095). Magnetic fluctuations may affect suprachiasmatic astrocytes, and the DMN involving ISOs and thalamic astrocytes may then be activated, first at night, then during the entire day, a mechanism that could perhaps promote an anti-aging effect noted in other investigations.

Acquirement of the autonomic nervous system modulation evaluated by heart rate variability in medaka (Oryzias latipes).

Small teleosts have recently been established as models of human diseases. However, measuring heart rate by electrocardiography is highly invasive for small fish and not widely used. The physiological nature and function of vertebrate autonomic nervous system (ANS) modulation of the heart has traditionally been investigated in larvae, transparent but with an immature ANS, or in anesthetized adults, whose ANS activity may possibly be disturbed under anesthesia. Here, we defined the frequency characteristics of heart rate variability (HRV) modulated by the ANS from observations of heart movement in high-speed movie images and changes in ANS regulation under environmental stimulation in unanesthetized adult medaka (Oryzias latipes). The HRV was significantly reduced by atropine (1 mM) in the 0.25-0.65 Hz and by propranolol (100 µM) at 0.65-1.25 Hz range, suggesting that HRV in adult medaka is modulated by both the parasympathetic and sympathetic nervous systems within these frequency ranges. Such modulations of HRV by the ANS in adult medaka were remarkably suppressed under anesthesia and continuous exposure to light suppressed HRV only in the 0.25-0.65 Hz range, indicating parasympathetic withdrawal. Furthermore, pre-hatching embryos did not show HRV and the power of HRV developed as fish grew. These results strongly suggest that ANS modulation of the heart in adult medaka is frequency-dependent phenomenon, and that the impact of long-term environmental stimuli on ANS activities, in addition to development of ANS activities, can be precisely evaluated in medaka using the presented method.

[Approach to elucidating the influences and factors affecting circulation system in humans in space environment].

Many physiological changes associated with spaceflight, including decreases in orthostatic tolerance, exercise capacity, and blood volume have been reported. Orthostatic intolerance is a problem affecting many astronauts immediately postspaceflight. In particular, the relationship between orthostatic intolerance and cerebral autoregulation has been the focus of study in our research group. Although impairment of cerebral autoregulation was speculated to be one of the factors resulting in reduced post flight orthostatic tolerance, a 2-wk spaceflight study revealed that human cerebral autoregulation is preserved or even improved during and immediately after spaceflight in nonsymptomatic astronauts. To investigate the influences of the different kinds of reduction in central blood volume, we performed two ground-based studies. It is suggested that the mild intravascular dehydration partly explains the improved dynamic cerebral autoregulation observed during and immediately after a short-term spaceflight. Moreover, we also studied the relationship between orthostatic intolerance and cerebral autoregulation under hyperthermic conditions, because hyperthermia leads to orthostatic intolerance. Furthermore, we planned to conduct a study at the International Space Station (ISS) and ground-based studies to elucidate the influences and factors affecting the circulation system in humans in a space environment.

Astronauts well-being and possibly anti-aging improved during long-duration spaceflight.

This study assesses how circadian rhythms of heart rate (HR), HR variability (HRV) and activity change during long-term missions in space and how they relate to sleep quality. Ambulatory 48-h ECG and 96-h actigraphy were performed four times on ten healthy astronauts (44.7 ± 6.9 years; 9 men): 120.4 ± 43.7 days (Before) launch; 21.1 ± 2.5 days (ISS01) and 143.0 ± 27.1 days (ISS02) after launch; and 86.6 ± 40.6 days (After) return to Earth. Sleep quality was determined by sleep-related changes in activity, RR-intervals, HRV HF- and VLF-components and LF-band. The circadian amplitude of HR (HR-A) was larger in space (ISS01: 12.54, P = 0.0099; ISS02: 12.77, P = 0.0364) than on Earth (Before: 10.90; After: 10.55 bpm). Sleep duration in space (ISS01/ISS02) increased in 3 (Group A, from 370.7 to 388.0/413.0 min) and decreased in 7 (Group B, from 454.0 to 408.9/381.6 min) astronauts. Sleep quality improved in Group B from 7.07 to 8.36 (ISS01) and 9.36 (ISS02, P = 0.0001). Sleep-related parasympathetic activity increased from 55.2% to 74.8% (pNN50, P = 0.0010) (ISS02). HR-A correlated with the 24-h (r = 0.8110, P = 0.0044), 12-h (r = 0.6963, P = 0.0253), and 48-h (r = 0.6921, P = 0.0266) amplitudes of the magnetic declination index. These findings suggest associations of mission duration with increased well-being and anti-aging benefitting from magnetic fluctuations.

[Effect of lunar dust on humans: -lunar dust: regolith-].

We reviewed the effect of lunar dust (regolith) on humans by the combination of the hazard/exposure of regolith and microgravity of the moon. With regard to the physicochemical properties of lunar dust, the hazard-related factors are its components, fibrous materials and nanoparticles. Animal exposure studies have been performed using a simulant of lunar dust, and it was speculated that the harmful effects of the simulant lies between those of crystalline silica and titanium dioxide. Fibrous materials may not have a low solubility judging from their components. The nanoparticles in lunar dust may have harmful potentials from the view of the components. As for exposure to regolith, there is a possibility that particles larger than ones in earth (1 gravity) are respirable. In microgravity, 1) the deposition of particles of less than 1 µm in diameter in the human lung did not decrease, 2) the functions of macrophages including phagocytosis were suppressed, 3) pulmonary inflammation was changed. These data on hazard/exposure and microgravity suggest that fine and ultrafine particles in regolith may have potential hazards and risks for humans.

Effects of Low-Intensity Cycle Training with Restricted Leg Blood Flow on Thigh Muscle Volume and VO2MAX in Young Men.

Concurrent improvements in aerobic capacity and muscle hypertrophy in response to a single mode of training have not been reported. We examined the effects of low-intensity cycle exercise training with and without blood flow restriction (BFR) on muscle size and maximum oxygen uptake (VO2max). A group of 19 young men (mean age ± SD: 23.0 ± 1.7 years) were allocated randomly into either a BFR-training group (n=9, BFR-training) or a non-BFR control training group (n=10, CON-training), both of which trained 3 days/wk for 8 wk. Training intensity and duration were 40% of VO2max and 15 min for the BFR-training group and 40% of VO2max and 45 min for the CON-training group. MRI-measured thigh and quadriceps muscle cross-sectional area and muscle volume increased by 3.4-5.1% (P < 0.01) and isometric knee extension strength tended to increase by 7.7% (p < 0.10) in the BFR-training group. There was no change in muscle size (~0.6%) and strength (~1.4%) in the CON-training group. Significant improvements in VO2max (6.4%) and exercise time until exhaustion (15.4%) were observed in the BFR-training group (p < 0.05) but not in the CON-training group (-0.1 and 3. 9%, respectively). The results suggest that low-intensity, short-duration cycling exercise combined with BFR improves both muscle hypertrophy and aerobic capacity concurrently in young men. Key pointsConcurrent improvements in aerobic capacity and muscle hypertrophy in response to a single mode of training have not been reported.In the present study, low-intensity (40% of VO2max) cycle training with BFR can elicit concurrent improvement in muscle hypertrophy and aerobic capacity.

Author Correction: Changes in mitochondrial homeostasis and redox status in astronauts following long stays in space.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Anti-aging effects of long-term space missions, estimated by heart rate variability.

Reports that aging slows down in space prompted this investigation of anti-aging effects in humans by analyzing astronauts' heart rate variability (HRV). Ambulatory 48-hour electrocardiograms from 7 astronauts (42.1 ± 6.8 years; 6 men) 20.6 ± 2.7 days (ISS01) and 138.6 ± 21.8 days (ISS02) after launch were divided into 24-hour spans of relative lower or higher magnetic disturbance, based on geomagnetic measures in Tromso, Norway. Magnetic disturbances were significantly higher on disturbed than on quiet days (ISS01: 72.01 ± 33.82 versus 33.96 ± 17.90 nT, P = 0.0307; ISS02: 71.06 ± 51.52 versus 32.53 ± 27.27 nT, P = 0.0308). SDNNIDX was increased on disturbed days (by 5.5% during ISS01, P = 0.0110), as were other HRV indices during ISS02 (SDANN, 12.5%, P = 0.0243; Triangular Index, 8.4%, P = 0.0469; and TF-component, 17.2%, P = 0.0054), suggesting the action of an anti-aging or longevity effect. The effect on TF was stronger during light (12:00-17:00) than during darkness (0:00-05:00) (P = 0.0268). The brain default mode network (DMN) was activated, gauged by increases in the LF-band (9.7%, P = 0.0730) and MF1-band (9.9%, P = 0.0281). Magnetic changes in the magnetosphere can affect and enhance HRV indices in space, involving an anti-aging or longevity effect, probably in association with the brain DMN, in a light-dependent manner and/or with help from the circadian clock.

Dietary intervention of mice using an improved Multiple Artificial-gravity Research System (MARS) under artificial 1 g.

Japan Aerospace Exploration Agency (JAXA) has developed mouse habitat cage units equipped with an artificial gravity-producing centrifuge, called the Multiple Artificial-gravity Research System (MARS), that enables single housing of a mouse under artificial gravity (AG) in orbit. This is a report on a hardware evaluation. The MARS underwent improvement in water leakage under microgravity (MG), and was used in the second JAXA mouse mission to evaluate the effect of AG and diet on mouse biological system simultaneously. Twelve mice were divided into four groups of three, with each group fed a diet either with or without fructo-oligosaccharide and housed singly either at 1 g AG or MG for 30 days on the International Space Station, then safely returned to the Earth. Body weight tended to increase in AG mice and decrease in MG mice after spaceflight, but these differences were not significant. This indicates that the improved MARS may be useful in evaluating AG and dietary intervention for space flown mice.