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Microgravity has been shown to lead to both muscle atrophy and impaired muscle regeneration. The purpose was to study the efficacy of microgravity to model impaired muscle regeneration in an engineered muscle platform and then to demonstrate the feasibility of performing drug screening in this model. Engineered human muscle was launched to the International Space Station National Laboratory, where the effect of microgravity exposure for 7 days was examined by transcriptomics and proteomics approaches. Gene set enrichment analysis of engineered muscle cultured in microgravity, compared to normal gravity conditions, highlighted a metabolic shift toward lipid and fatty acid metabolism, along with increased apoptotic gene expression. The addition of pro-regenerative drugs, insulin-like growth factor-1 (IGF-1) and a 15-hydroxyprostaglandin dehydrogenase inhibitor (15-PGDH-i), partially inhibited the effects of microgravity. In summary, microgravity mimics aspects of impaired myogenesis, and the addition of these drugs could partially inhibit the effects induced by microgravity.

Microgravity exposure induces a cephalad fluid shift and an overall reduction in physical activity levels which can lead to cardiovascular deconditioning in the absence of countermeasures. Future spaceflight missions will expose crew to extended periods of microgravity among other stressors, the effects of which on cardiovascular health are not fully known. In this study, we determined cardiac responses to extended microgravity exposure using the rat hindlimb unloading (HU) model. We hypothesized that exposure to prolonged simulated microgravity and subsequent recovery would lead to increased oxidative damage and altered expression of genes involved in the oxidative response. To test this hypothesis, we examined hearts of male (three and nine months of age) and female (3 months of age) Long-Evans rats that underwent HU for various durations up to 90 days and reambulated up to 90 days post-HU. Results indicate sex-dependent changes in oxidative damage marker 8-hydroxydeoxyguanosine (8-OHdG) and antioxidant gene expression in left ventricular tissue. Three-month-old females displayed elevated 8-OHdG levels after 14 days of HU while age-matched males did not. In nine-month-old males, there were no differences in 8-OHdG levels between HU and normally loaded control males at any of the timepoints tested following HU. RNAseq analysis of left ventricular tissue from nine-month-old males after 14 days of HU revealed upregulation of pathways involved in pro-inflammatory signaling, immune cell activation and differential expression of genes associated with cardiovascular disease progression. Taken together, these findings provide a rationale for targeting antioxidant and immune pathways and that sex differences should be taken into account in the development of countermeasures to maintain cardiovascular health in space.

Cardiovascular deconditioning in microgravity presents a significant challenge for astronauts on extended space missions. As astronauts contend with microgravity complexities, such as altered fluid distribution, reduced cardiac output, and vascular adaptations, understanding the multifaceted influence of ANP becomes vital for developing precise interventions. The findings are from various research approaches, including human analog studies, murine models, aquatic models, and primate studies. Human analog studies, utilizing methods like bedrest head-down techniques, lower body positive pressure, and parabolic flights, offer valuable insights into potential countermeasures by simulating microgravity conditions. Further, the studies involving aquatic models and primates contribute additional layers of complexity, enriching our understanding of cardiovascular changes in biological systems more analogous to humans. Ground studies, integrating lower body positive pressure and Gz centrifugation, establish controlled environments to simulate gravity-like conditions, refining potential countermeasures. Space flight simulations subject individuals to varying gravitational forces, replicating real-world space mission conditions. Current countermeasures, including fluid intake protocols, negative pressure breathing maneuvers, and innovative technologies like the Countermeasure Evaluation and Validation System (CEVIS), are reviewed as cutting-edge approaches to address cardiovascular deconditioning. The forward-looking perspective envisions the future of cardiovascular deconditioning research, emphasizing the development of personalized interventions tailored to individual responses, advanced exercise protocols, and the exploration of novel technologies such as artificial gravity generators. • Cardiovascular deconditioning is a key challenge for astronauts in microgravity for the deeper space mission. • Research involves animal models, and microgravity simulation techniques for the astronaut's health and well-being. • Current countermeasures involve fluid intake, and gravity suits, supporting the overall mission success in microgravity. • Future research on personalized interventions and artificial gravity solutions that will safeguard cardiovascular health. [ABSTRACT FROM AUTHOR]

With crewed deep space exploration on the horizon, preparation for potential astronaut health crises in space missions has become vital. Administration of anaesthesia and analgesia presents many challenges owing to constraints specific to space (physiologic and ergonomic challenges associated with microgravity) and nonspecific factors (isolation and lack of supplies). Regional anaesthesia can be the safest option; however, we hypothesised that the ergonomics of microgravity would compromise ease and accuracy of nerve blocks. We evaluated the feasibility of regional anaesthesia in a simulated microgravity environment (free-floating underwater conditions) using a meat (bovine muscle) model. Forty meat models were randomised for injection under simulated microgravity or normal gravity conditions. Success rates were determined by blinded assessors after injection. Parameters assessed included time to block, ease of image acquisition, and ease of needle placement. The median time to block in normal gravity was 27 (interquartile range 21–69) s vs 35 (interquartile range 22–48) s in simulated microgravity (P =0.751). Ease of image acquisition was similar in both conditions, as was ease of needle placement. There was no significant difference in the rate of accidental intraneural injections (5% vs 5%), with block success rates comparable in both scenarios (80% normal gravity vs 85% microgravity, P >0.999). Regional anaesthesia appears feasible for experts in simulated microgravity despite the ergonomic challenges. Although our model has limitations and might not fully capture the complexities of actual space conditions, it provides a foundation for future research into anaesthesia and analgesia during deep space missions. [ABSTRACT FROM AUTHOR]

The exploration of microgravity has garnered substantial scholarly attention due to its potential to offer unique insights into the behavior of biological systems. This study presents a preliminary investigation into the effects of simulated microgravity on esophageal cancer cells, examining various aspects such as morphology, growth behavior, adhesion, inhibition rate, and DNA damage. To achieve this, a novel microgravity simulator named "Gravity Challenge" was utilized for its effectiveness in minimizing external influences that could compromise microgravity conditions. The international cell line SK-GT-4 was utilized as the focal point of this investigation. Results revealed noticeable alterations in the growth behavior of cancer cells following exposure to simulated microgravity for 24 h, characterized by a loss of adhesion properties compared to control cells. Concurrently, cell viability exhibited a decline, as evidenced by cytotoxicity testing. Furthermore, the comet assay test demonstrated that cells subjected to microgravity simulation experienced a higher incidence of DNA damage compared to their control counterparts. In conclusion, this comprehensive examination of the impact of simulated microgravity on esophageal cancer cells extends beyond morphological changes, delving into genetic implications through observed DNA damage. The diminished vitality of cells under microgravity conditions underscores the multifaceted effects on cellular behavior in response to environmental variations. These findings represent a significant step towards understanding the dynamics of cancer cells, laying the groundwork for future research aimed at identifying potential therapeutic strategies for this disease. [ABSTRACT FROM AUTHOR]

According to the existing scenarios of interplanetary missions, the Moon is considered as an intermediate base on the way to deep space. In order to prepare for landing and work on the Moon, it is important to study the applicability of countermeasures in such missions. The paper presents the results of a pilot study performed during a short-term spaceflight (12 days). A new experience of using countermeasure impacts of lower body negative pressure (LBNP) at the early stages of adaptation to microgravity conditions has been gained. To assess the effectiveness of LBNP and changes in human physical performance after the spaceflight, we conducted tests on a treadmill, a bicycle ergometer, and testing with model tasks of on-planetary activity "express test". Regulatory mechanisms of the cardiovascular system proved to be quite effective when creating decompression up to -20 mm Hg, which is less than in preparation for returning to Earth. In the treadmill test, a lower speed was achieved after the spaceflight than before (13 km/h and 15 km/h, respectively) and cardiovascular system response to the change in load was slower. At the same time changes in such physiological parameters as oxygen consumption, respiratory rate and pulmonary ventilation were minimal. In the bicycle ergometer test, peak heart rate values were higher after the spaceflight than before, the physiological value of the standard exercise increased. «Express test» showed the positive dynamics from the first day to the third after returning to Earth: the performance of a dual task, the task of controlling the movement of the non-leading hand, and getting up from the supine position improved. Thus, assessment of the state of gravity-dependent physiological systems after short-term flight indicates the decrease of functional reserves of the organism and the necessity to develop appropriate countermeasures. The study was one of the first steps in the development of new medical control operations at the stage of paradigm shift from orbital flights to deep space exploration. [ABSTRACT FROM AUTHOR]

This work summarizes the first results from a cloud seeding in microgravity experiment built by the Saudi Space Agency (SSA) and conducted on the International Space Station (ISS). The microgravity conditions provided in the ISS enable examining the interaction between the seeding agent, silver iodide, and the water droplets. Silver iodide particles dynamics of radius of 0.6, 0.3, 0.2, and 0.1 μm are examined in the ground and at the ISS at room temperature and atmospheric pressure in four 5cm3 chambers. Meanwhile, computer simulations are employed to examine the dynamics of seeding agent falling under the effect of gravity. It is found that microgravity conditions along with reducing seeding particles’ size enhance the interaction between seeding particles and the water droplets by increasing the period at which particles staying in the air before dropping down to the floor of the experiment. Humidity level in the experiment is observed to decrease onboard of the ISS because of the interaction between seeding agent and the water droplets. [ABSTRACT FROM AUTHOR]

In the present study, opposed flow flame spread over several fuel configurations of thin cellulosic fuels are investigated experimentally in normal gravity and microgravity environments. The fuel is configured in different shapes, namely, planar, hollow cylindrical (circular duct), C channel, and L channel, with the help of specifically designed fuel sample holders. The flame spread phenomena are examined for each configuration in both normal gravity and microgravity environments under ambient conditions of 21% oxygen and 1 atm. pressure. The microgravity experiments are conducted using a 2.5 s drop tower facility. The flame spread rates are measured at various opposed flow speeds. The effective flow speed accounts for the induced reference buoyant flow speed and externally imposed flow. The flame spread rates for each configuration are plotted against the effective flow speed ranging from 10 cm/s to 40 cm/s. While there is a nonmonotonic increasing-decreasing flame spread rate trend with respect to the effective opposed flow speed for all configurations, the flame spread rate can vary significantly with changes in the configuration. The C-channel configuration shows the highest flame spread rate compared with the other configurations of the same scale and identical experimental conditions. The effect of fuel size on the flame spread rate is also investigated for the duct configuration. The flame spread rate is noted to increase with the increase in fuel diameter. [ABSTRACT FROM AUTHOR]

Two-stage autoignition of n-dodecane droplets with varying ambient oxygen concentrations in oxygen-nitrogen mixtures are investigated experimentally under microgravity conditions using high-speed shadowgraphy. The ambient pressure and temperature are held constant at 3 atm and 650 K, respectively, while the droplet initial diameter is fixed approximately at 1.2 mm. During the two-stage autoignition process, first a cool-flame front forms in the leaner regions farther away from the evaporating droplet, and it then propagates toward the fuel-rich region closer to the droplet surface, eventually encompassing the droplet. A hot-flame kernel is then initiated in the wake of the cool flame and very quickly expands, establishing a classical diffusion flame around the droplet. The first and second ignition delay times are measured from shadowgraphic images captured at 3000 frames per second. The first induction time is found to be insensitive to the ambient oxygen concentration, while the second induction time varies approximately as the negative 2 power of the oxygen mole fraction. [ABSTRACT FROM AUTHOR]

This paper investigates the effects of hemispherical mounds on filmwise condensation heat transfer in micro-channels. Also investigated were the impacts that spatial orientation of the three-sided condensation surface (i.e., gravitational effects) on steam condensation, where the cooled surfaces were either the lower surface (i.e., gravity pulls liquid towards the condensing surfaces) or upper surface (i.e., gravity pulls liquid away from the condensing surfaces). Two test coupons were used with 1.9-mm hydraulic diameters and either a plain copper surface or a copper surface modified with 2-mm diameter hemispherical mounds. Heat transfer coefficients, film visualization, and pressure drop measurements were recorded for both coupons in both orientations at mass fluxes of 50 kg/m2s and 125 kg/m2s. For all test conditions, the mounds were found to increase condensation heat transfer coefficients by at minimum 13% and at maximum 79%. When the test section was inverted (i.e., condensing surface on the top of flowing steam), minimal differences were found in mound performance, while the plain coupon reduces heat transfer coefficients by as much as 14%. Flow visualization suggests that the mounds enhanced heat transfer due to the disruption of the film as well as by reducing the thermal resistance of the film. Pressure drops followed parabolic behavior with quality, being higher in the mound coupon than the plain coupon. No significant pressure drop differences in the inverted orientation were observed. [ABSTRACT FROM AUTHOR]

Long-duration spaceflight creates a variety of stresses due to the unique environment, which can lead to compromised functioning of the skeletal and immune systems. However, the mechanisms by which organisms respond to this stress remain unclear. The present study aimed to investigate the impact of three different gravitational loadings (microgravity, 1/6 g [lunar gravity], and 1 g) on the behavior, bone, thymus, and spleen of mice housed for 25–35 days in the International Space Station. The bone density reduction under microgravity was mostly recovered by 1 g but only partially recovered by 1/6 g. Both 1 g and 1/6 g suppressed microgravity-induced changes in some osteoblast and osteoclast marker gene expression. Thymus atrophy induced by microgravity was half recovered by both 1 g and 1/6 g, but gene expression changes were not fully recovered by 1/6 g. While no histological changes were observed due to low gravity, alterations in gene expression were noted in the spleen. We found that in bone and thymus, lunar gravity reduced microgravity-induced histological alterations and partially reversed gene expression changes. This study highlighted organ-specific variations in responsiveness to gravity, serving as an animal test for establishing a molecular-level gravity threshold for maintaining a healthy state during future spaceflight. [ABSTRACT FROM AUTHOR]

The control of plant diseases represents a significant challenge in agriculture, particularly with the current emphasis on reducing pesticide use, necessitating alternative approaches. Among them, resistant plant breeding programs offer a promising alternative. Considering the stressful conditions in space, space conditions emerge as an innovative method for advancing crop improvement. This study explored the unique potential of the International Space Station (ISS) environment to induce beneficial modifications in grapevine, resulting in plants with reduced susceptibility to diseases. Canes of two Vitis vinifera L. cultivars, Cabernet Sauvignon (CS) and Merlot (Me), have undergone a 10-month space journey on-board the ISS, while others stayed on Earth (Ground Control, GC). We conducted a 2-year analysis of the response to downy mildew (Plasmopara viticola) of plants developed from ISS and GC canes, called Mother plants. The disease development of progenies produced from Merlot Mother plants was also evaluated. A higher proportion of individuals with low-susceptibility was noted in the ISS Mother group compared to the controls for both cultivars. This trend was also observed for the Merlot progenies. Finally, 11% of Merlot individuals (Mother and progenies, and for the 2 years of study) were distributed in the low susceptibility class. This study suggests that grapevine canes exposure to ISS conditions resulted in an enhanced percentage of plants showing reduction of susceptibility to downy mildew. [ABSTRACT FROM AUTHOR]

Space travel, particularly long-duration missions, poses unique physiological challenges due to microgravity, radiation exposure, confinement, and isolation. This systematic review aims to synthesize the current understanding of the physiological changes that occur in astronauts during space travel. Using the PRISMA methodology, a total of 50 studies were included, focusing on cardiovascular deconditioning, musculoskeletal degradation, neurocognitive impairments, immune system dysregulation, and sensory changes. Cardiovascular effects include fluid redistribution, reduced plasma volume, and orthostatic intolerance. Musculoskeletal degradation manifests as bone density loss and muscle atrophy, primarily in weight-bearing muscles and bones. Neurocognitive impairments, including decreased executive function, are often accompanied by psychological challenges such as mood changes and sleep disturbances. Immune dysregulation, characterized by altered cytokine profiles and reduced immune response, increases the risk of infection. Sensory changes, including altered proprioception and spatial disorientation, affect astronauts' ability to perform tasks effectively in space. Various countermeasures such as exercise protocols, nutritional supplementation, and pharmacological interventions have been explored, but gaps remain in fully mitigating these physiological challenges, particularly in the context of deep-space missions to Mars. This review highlights the need for further research to develop comprehensive strategies for long-term astronaut health maintenance. [ABSTRACT FROM AUTHOR]

Simple Summary: In the past few years, scientists have been studying the effects of microgravity on the human body during long-term space missions. They have found that being in space for a prolonged time can lead to muscle and bone complications, cardiovascular changes, and even a weaker immune system. One potential way to help the body cope with these changes involves heat-shock proteins. These proteins seem to help protect the body during stressful conditions, like those found in space. Studies have shown that HSPs are more active when cells are exposed to conditions similar to microgravity, and could, thus, be used to study stress reactions in space. In the future, researchers might be able to develop drugs or other techniques to change how these proteins work, helping astronauts stay healthier during long space missions. In recent years, the increasing number of long-duration space missions has prompted the scientific community to undertake a more comprehensive examination of the impact of microgravity on the human body during spaceflight. This review aims to assess the current knowledge regarding the consequences of exposure to an extreme environment, like microgravity, on the human body, focusing on the role of heat-shock proteins (HSPs). Previous studies have demonstrated that long-term exposure to microgravity during spaceflight can cause various changes in the human body, such as muscle atrophy, changes in muscle fiber composition, cardiovascular function, bone density, and even immune system functions. It has been postulated that heat-shock proteins (HSPs) may play a role in mitigating the harmful effects of microgravity-induced stress. According to past studies, heat-shock proteins (HSPs) are upregulated under simulated microgravity conditions. This upregulation assists in the maintenance of the proper folding and function of other proteins during stressful conditions, thereby safeguarding the physiological systems of organisms from the detrimental effects of microgravity. HSPs could also be used as biomarkers to assess the level of cellular stress in tissues and cells exposed to microgravity. Therefore, modulation of HSPs by drugs and genetic or environmental techniques could prove to be a potential therapeutic strategy to reduce the negative physiological consequences of long-duration spaceflight in astronauts. [ABSTRACT FROM AUTHOR]

Space flight modulates the functions of the cardiovascular system. The exposure to space conditions can alter the cerebral blood flow, as well as the venous return. Anemia, cardiac output changes, and increased activity of the sympathetic nervous system can also be seen. Understanding cardiac changes prepares astronauts for both better in-flight adaptations and long-term protection against cardiovascular diseases. The heart could undergo radio-degenerative effects when exposed to space radiation, increasing the risk of cardiovascular diseases in the long run. A high frequency of arrhythmias, such as ventricular/atrial premature complexes, have been reported during the Gemini and Apollo missions. Additionally, microgravity can lead to progressive degeneration of the myocytes and muscle atrophy with altered gene expression and calcium handling, along with impaired contractility. This review summarizes the potential cardiovascular effects of spaceflight and prevention measures. [ABSTRACT FROM AUTHOR]

Exposure to the spaceflight environment causes adaptations in most human physiological systems, many of which are thought to affect women differently from men. Since only 11.5% of astronauts worldwide have been female, these issues are largely understudied. The physiological nuances affecting the female body in the spaceflight environment remain inadequately defined since the last thorough published review on the subject. A PubMed literature search yielded over 2200 publications. Using NASA's 2014 review series ‘The effects of sex and gender on adaptation to space’ as a benchmark, we identified substantive advancements and persistent knowledge gaps in need of further study from the nearly 600 related articles that have been published since the initial review. This review highlights the most critical issues to mitigate medical risk and promote the success of missions to the Moon and Mars. Salient sex‐linked differences observed terrestrially should be studied during upcoming missions, including increased levels of inflammatory markers, coagulation factors and leptin levels following sleep deprivation; correlation between body mass and the severity of spaceflight‐associated neuro‐ocular syndrome; increased incidence of orthostatic intolerance; increased severity of muscle atrophy and bone loss; differences in the incidence of urinary tract infections; and susceptibility to specific cancers after exposure to ionizing radiation. To optimize health and well‐being among all astronauts, it is imperative to prioritize research that considers the physiological nuances of the female body. A more robust understanding of female physiology in the spaceflight environment will support crew readiness for Artemis missions and beyond. [ABSTRACT FROM AUTHOR]

Different gravity fields have important effects on the structural morphology of bone. The fluid flow caused by loadings in the bone lacunar-canalicular system (LCS), converts mechanical signals into biological signals and regulates bone reconstruction by affecting effector cells, which ensures the efficient transport of signaling molecules, nutrients, and waste products. In this study, the fluid flow and mass transfer effects of bone lacunar-canalicular system at multi-scale were firstly investigated, and a three-dimensional axisymmetric fluid-solid coupled finite element model of the LCS within three continuous osteocytes was established. The changes in fluid pressure field, flow velocity field, and fluid shear force variation on the surface of osteocytes within the LCS were studied comparatively under different gravitational fields (0 G, 1 G, 5 G), frequencies (1 Hz, 1.5 Hz, 2 Hz) and forms of cyclic compressive loading. The results showed that different frequencies represented different exercise intensities, suggesting that high-intensity exercise may accelerate the fluid flow rate within the LCS and enhance osteocytes activity. Hypergravity enhanced the transport of solute molecules, nutrients, and signaling molecules within the LCS. Conversely, the mass transfer in the LCS may be inhibited under microgravity, which may cause bone loss and eventually lead to the onset of osteoporosis. This investigation provides theoretical guidance for rehabilitative training against osteoporosis. [ABSTRACT FROM AUTHOR]

Safe operation of orbital platforms relies heavily on stability of fluid flows in microgravity. The inherent instability of two-phase flows under microgravity conditions could be a threat to fluid transporting equipment operation in Space thus altering Space flight safety conditions. The paper considers a multiphase flow in a Hele-Shaw cell. A dimensionless criterion characterizing the flow in such cells is described. If one changes the parameters of the experiment in such a way that the dimensionless criterion retains its value, then one can observe similar processes in microgravity and in terrestrial gravity. The paper describes the results of experiments on the flow in a Hele-Shaw cell in microgravity during parabolic flights, as well as laboratory experiments in normal gravity. It is shown that the generally accepted mathematical model used to model flows in the Hele-Shaw cell is not suitable for describing multiphase flows. A modified semi-empirical mathematical model is proposed, which gives a satisfactory coincidence of the experimental data with the analytical solution. Non-linear analysis of three fluids displacing each other is performed demonstrating the growth of viscous fingers on both interfaces and their interactions. • Safe operation of orbital platforms relies heavily on stability of fluid flows in microgravity. • The Hele-Shaw cell can be used to simulate microgravity flows in an Earth laboratory. • The existing theory does not correspond to the experimental data. • A new modified mathematical model with a correction factor is proposed. • The results of numerical simulation of the flow in the Hele-Shaw cell are presented. [ABSTRACT FROM AUTHOR]

A simple method of demonstrating apparent weightlessness in free fall is described. The Apollo 15 hammer and feather drop experiment can be recreated in the classroom using a book to shield the feather from air resistance. Plastic toys and a feather thrown together in a plastic bottle can be used to recreate an apparent weightless environment close to the surface of the Earth. Since the bottle follows a parabolic trajectory, the objects within also follow a parabolic path and are seen to float as if in a space ship in orbit around the Earth. This demonstration is useful for demonstrating to students that apparent weightlessness is not confined to outer space. The use of toy fish in the experiments makes a connection with the neutral buoyancy training of astronauts. The experiments also exemplify Newton's second law that force is mass times acceleration. [ABSTRACT FROM AUTHOR]

Vitamin E (Vit E) deficiency studies underline the relevance of this vitamin in skeletal muscle (SkM) homeostasis. The knowledge of the effectors and modulators of Vit E action in SkM cells is limited, especially in aging and chronic diseases characterized by a decline in musculoskeletal health. Vit E comprises eight fat-soluble compounds grouped into tocopherols and tocotrienols, which share the basic chemical structure but show different biological properties and potentials to prevent diseases. Vit E has antioxidant and non-antioxidant activities and both favorable and adverse effects depending on the specific conditions and tissues. In this review, we focus on the actual knowledge of Vit E forms in SkM functions and new potential signaling effectors (i.e., bioactive sphingolipids and myokines). The possible advantages of Vit E supplementation in counteracting SkM dysfunctions in sarcopenia and under microgravity will also be discussed. [ABSTRACT FROM AUTHOR]

The space environment is incredibly hostile, and humans are vulnerable in such conditions. Astronauts encounter various stress factors during a space journey, including radiation, microgravity, forceful acceleration during launch, altered magnetic fields, and confinement. These stressors significantly impact the human body homeostasis, leading to physio-pathological adaptations, loss of bone density, muscle atrophy, cardiovascular deconditioning, alterations in liver function, vestibular adaptations, and immune system dysregulation. These alterations can potentially influence drug pharmacokinetics and pharmacodynamics, affecting the efficacy and safety of medications administered to astronauts. Due to the limited number of studies on pharmaceuticals conducted in microgravity conditions, it's challenging to assess the effectiveness and stability of these medications during spaceflight. The objective of the present work is to compare the state-of-the-art knowledge on PK/PD changes and factors likely to affect them during spaceflight, with the subjective perception of the problem by a collection of separate interviews conducted with seven experts in the field. The interviewees were chosen as "experts," i.e., representatives in a specific discipline, who possess knowledge and experience in space pharmacology, physiology, or biology. Thus, our panel included astronauts, space surgeons, and scientists aiming to bridge the lack of experimental data in the literature. Each interview explores assorted aspects of space physiology and pharmacology, including drug use and storage onboard the ISS; notable consideration has arisen regarding the current research gaps and future space expeditions. All the interviews were held remotely using online conferencing software. None of the interviewees could provide a comprehensive overview regarding potential changes in drugs PK/PD in microgravity conditions. Further, any medication brought on board (whether as part of an astronaut's medical kit or stored in the ISS pharmacy) is destroyed, thereby suppressing the possibility of analyzing any degradation products resulting from long-term exposure to microgravity and radiation. According to these results, the use of drugs without understanding how they are genuinely absorbed, distributed, metabolized, and excreted in microgravity conditions is concerning, posing risks for drug effectiveness. Conducting genotyping and phenotyping on astronauts would be beneficial for developing personalized pharmacological countermeasures for each astronaut and anticipating expected drug metabolism changes during space missions. [ABSTRACT FROM AUTHOR]

Numerical simulations are used to study effects of ozone (O3) and thermal enhancement on autoignition and subsequent burning characteristics of isolated n-heptane droplets in microgravity conditions. Particular focus is given to effects of O3 on low temperature combustion, or cool flames. Levels of ambient O3 mole fraction and ambient temperature are varied from 0 to 0.03 and 400 K to 750 K, respectively. A comparison between two low temperature chemistry enhancement strategies – O3 addition and temperature increase – are investigated on an equivalent energy addition basis to evaluate relative effects on combustion characteristics. Results of this study are analyzed using physical and mixture fraction approaches because of unique insights offered by these frameworks. Ignition and ensuing flame propagation are investigated via a most reactive mixture analysis, evaluated using homogeneous reactor simulations of mixture compositions and temperatures surrounding the droplet. Lastly, a Damköhler number analysis is performed to explore oscillatory ignition dynamics. [ABSTRACT FROM AUTHOR]

Long-duration spaceflight is associated with pathophysiological changes in the intracranial compartment hypothetically linked to microgravity-induced headward fluid shift. This study aimed to determine whether daily artificial gravity (AG) sessions can mitigate these effects, supporting its application as a countermeasure to spaceflight. Twenty-four healthy adult volunteers (16 men) were exposed to 60 days of 6° head-down tilt bed rest (HDTBR) as a ground-based analog of chronic headward fluid shift. Subjects were divided equally into three groups: no AG (control), daily 30-min intermittent AG (iAG), and daily 30-min continuous (cAG). Internal carotid artery (ICA) stroke volume (ICASV), ICA resistive index (ICARI), ICA flow rate (ICAFR), aqueductal cerebral spinal fluid flow velocity (CSFV), and intracranial volumetrics were quantified at 3 T. MRI was performed at baseline, 14 and 52 days into HDTBR, and 3 days after HDTBR (recovery). A mixed model approach was used with intervention and time as the fixed effect factors and the subject as the random effect factor. Compared with baseline, HDTBR was characterized by expansion of lateral ventricular, white matter, gray matter, and brain + total intracranial cerebral spinal fluid volumes, increased CSFv, decreased ICASV, and decreased ICAFR by 52 days into HBTBR (All Ps < 0.05). ICARI was only increased 14 days into HDTBR (P < 0.05). Neither iAG nor cAG significantly affected measurements compared with HDTBR alone, indicating that 30 min of daily exposure was insufficient to mitigate the intracranial effects of headward fluid shift. Greater AG session exposure time, gravitational force, or both are suggested for future countermeasure research. NEW & NOTEWORTHY: Brief exposure to continuous or intermittent artificial gravity via short-arm centrifugation was insufficient in mitigating the intracranial pathophysiological effects of the headward fluid shift simulated during head-down tilt bed rest (HDTBR). Our results suggest that greater centrifugation session duration, gravitational force, or both may be required to prevent the development of spaceflight-associated neuro-ocular syndrome and should be considered in future ground-based countermeasure studies. [ABSTRACT FROM AUTHOR]

Gut serves as the largest interface between humans and the environment, playing a crucial role in nutrient absorption and protection against harmful substances. The intestinal barrier acts as the initial defense mechanism against non-specific infections, with its integrity directly impacting the homeostasis and health of the human body. The primary factor attributed to the impairment of the intestinal barrier in previous studies has always centered on the gastrointestinal tract itself. In recent years, the concept of the “gut-organ” axis has gained significant popularity, revealing a profound interconnection between the gut and other organs. It speculates that disruption of these axes plays a crucial role in the pathogenesis and progression of intestinal barrier damage. The evaluation of intestinal barrier function and detection of enterogenic endotoxins can serve as “detecting agents” for identifying early functional alterations in the heart, kidney, and liver, thereby facilitating timely intervention in the disorders. Simultaneously, consolidating intestinal barrier integrity may also present a potential therapeutic approach to attenuate damage in other organs. Studies have demonstrated that diverse signaling pathways and their corresponding key molecules are extensively involved in the pathophysiological regulation of the intestinal barrier. Aberrant activation of these signaling pathways and dysregulated expression of key molecules play a pivotal role in the process of intestinal barrier impairment. Microgravity, being the predominant characteristic of space, can potentially exert a significant influence on diverse intestinal barriers. We will discuss the interaction between the “gut-organ” axes and intestinal barrier damage, further elucidate the signaling pathways underlying intestinal barrier damage, and summarize alterations in various components of the intestinal barrier under microgravity. This review aims to offer a novel perspective for comprehending the etiology and molecular mechanisms of intestinal barrier injury as well as the prevention and management of intestinal barrier injury under microgravity environment. [ABSTRACT FROM AUTHOR]

• Infiltration rates under low gravities were agreed with 1G based predictions. • The air entrapped little in fine porous media may have prevented the infiltration rate reduction. • The infiltration theory is applicable to fine uniform porous media under low gravities. The applicability of the theory of water infiltration in porous media under low gravities is controversial. We evaluated the hypothesis that infiltration under low gravities can be simulated from horizontal infiltration experiments under 1G. Parabolic flights provided low gravity conditions, assuming in the space station (µG), on the moon (0.19 G), and Mars (0.38 G). We measured infiltration rates in uniform particle-size porous media. No significant differences existed between infiltration rates under low gravities and ground-based predictions, i.e. the 1G condition. The air was entrapped little in this study, which may have prevented the infiltration rate reduction reported in previous studies. We concluded that the current infiltration theory adequately simulated water infiltration in fine uniform porous media under low gravity conditions. [ABSTRACT FROM AUTHOR]

As interest in deep space travel grows exponentially, understanding human adaptation in becoming an interplanetary species is crucial. This includes the prospect of reproduction. This review summarizes recent updates and innovations in assisted reproductive technologies (ART) on Earth, while also discussing current challenges and areas for improvement in adapting ART studies to the space environment. We discuss the critical components of ART - gamete handling and preparation, fertilization, embryo culture, and cryopreservation - from the daily practice perspective of clinical embryologists and reproductive endocrinologists and lay out the complicated path ahead. In vitro embryo development in low Earth orbit and beyond remains questionable due to synergetic effects of microgravity and radiation-induced damage observed in simulated and actual in-space mammalian studies. Cryopreservation and long-term storage of frozen samples face substantial obstacles - temperature limitations, lack of trained personnel, and absence of adapted cosmic engineering options. We touch on recent innovations, which may offer potential solutions, such as microfluidic devices and automated systems. Lastly, we stress the necessity for intensive studies and the importance of an interdisciplinary approach to address numerous practical challenges in advancing reproductive medicine in space, with possible implications for both space exploration and terrestrial fertility treatments. [ABSTRACT FROM AUTHOR]

The surface‐wrinkled shrinkage structure of spheres is very common and also quite intriguing to explore and reveal the analogous droplet solidification kinetics in the space environment. Here, a liquid‐to‐solid phase transition experiment of floating refractory alloy droplets is designed to study the surface wrinkled shrinkage structures aboard China Space Station with a 10−5 gravity level. The experimental Ti‐Ni‐V alloy droplets undergo an extremely high overheating temperature beyond 1800 K and then achieve a supercooling of 307 K, displaying a strong thermodynamic metastability. The spherical surface deformation structures of this alloy under microgravity coupled with extreme metastable solidification are explored. Moreover, through the active control of metastable rapid solidification, a surface monophasic structure and a B2 structure capable of stress‐induced martensitic transformation are facilitated by wrinkled shrinkage dynamics under microgravity. Their findings shed further light on the surface deformation structures during the microgravity solidification process. [ABSTRACT FROM AUTHOR]

Rare earth elements (REEs) are indispensable in modern industry and technology, driving an urgent demand for innovative, eco-friendly recovery technologies. As space exploration advances, the impact of microgravity on microorganisms has become a focal point, yet the effects on microbial growth and REEss recovery remain uncharted. This study investigates the biosorption of REEs by Burkholderia cepacia (B. cepacia) and Aspergillus niger (A. niger) from a mixed solution containing La, Ce, Pr, Nd, Sm, Er, and Y under varying initial concentrations, pH levels, and microgravity conditions. We observed that the medium's pH rose with B. cepacia and fell with A. niger when cultured in normal gravity conditions, suggesting distinct metabolic responses. Notably, microgravity significantly altered microbial morphology and metabolite profiles, significantly enhancing REEs recovery efficiency. Specifically, the recovery of B. cepacia of Ce and Pr peaked at 100%, and A. niger achieved full recovery of all tested REEs at pH 1.5 (suboptimal growth conditions). This study pioneers the application of biosorption for the recovery of REEs in microgravity conditions, presenting a promising strategy for future resource exploitation by space biomining. [ABSTRACT FROM AUTHOR]

With current plans for manned missions to Mars and beyond, the need to better understand, prevent, and counteract the harmful effects of long-duration spaceflight on the body is becoming increasingly important. In this study, an automated heart-on-a-chip platform was flown to the International Space Station on a 1-mo mission during which contractile cardiac function was monitored in real-time. Upon return to Earth, engineered human heart tissues (EHTs) were further analyzed with ultrastructural imaging and RNA sequencing to investigate the impact of prolonged microgravity on cardiomyocyte function and health. Spaceflight EHTs exhibited significantly reduced twitch forces, increased incidences of arrhythmias, and increased signs of sarcomere disruption and mitochondrial damage. Transcriptomic analyses showed an up-regulation of genes and pathways associated with metabolic disorders, heart failure, oxidative stress, and inflammation, while genes related to contractility and calcium signaling showed significant down-regulation. Finally, in silico modeling revealed a potential link between oxidative stress and mitochondrial dysfunction that corresponded with RNA sequencing results. This represents an in vitro model to faithfully reproduce the adverse effects of spaceflight on three-dimensional (3D)-engineered heart tissue. [ABSTRACT FROM AUTHOR]

Little is known about the effects of low gravity on human gametes. The aim of this study was to analyze if fresh human sperm samples after fast gravity load changes suffered any detrimental effect in comparison to the splits maintained in Earth's gravity. Fifteen fresh samples from normozoospermic donors were analyzed. Statistically significant differences in vitality (69.7 ± 9.9 % vs 72.4 ± 9.7 %, [95 % CI: 0.002,0.07]); motile sperm concentration (23.7 ± 15.3 M/ml vs 31.5 ± 25.1 M/ml, [95 % CI: 1.03,14.65]); grade "a" sperm concentration (8.7 ± 6.5 M/ml vs 11.7 ± 9.9 M/ml, [95 % CI: 0.71,5.28]); percentage of progressive motility sperm (30 ± 12.9 % vs 36 ± 14.3 %, [95 % CI: 0.10,0.37]) and curvilinear velocity VCL: 45.7 ± 12.8 μm/s vs 47.7 ± 13.3 μm/s, [95 % CI: 0.79,3.22]) were observed. No statistical differences were observed in other sperm kinematic parameters, morphology, DNA fragmentation, apoptosis, and oxidative stress. In conclusion, even though it did not result in a total loss, heavy gravity load changes including microgravity causes a significant decrease in sperm vitality and motility suggesting that negative consequences would be even higher if the exposure were longer. The results obtained indicate that further research is really needed before Assisted Reproduction will be considered for the future human reproduction outside the Earth. • Motility and Vitality of human sperm are significantly decreased after parabolic flight including short periods of microgravity. • Curvilinear Velocity of human male gametes was particularly decreased. • No changes were found in other sperm kinematic parameters, morphology, DNA fragmentation, apoptosis and oxidative stress. • Results were found after short exposure; suggesting more negative consequences regarding human fertility in a longer time exposure. • More studies needed before Assisted Reproduction Techniques can be considered for the likelihood of Human Reproduction in Space. [ABSTRACT FROM AUTHOR]

In this study, we analyzed the transcriptome sequences of Kupffer cells exposed to simulated microgravity for 3 d and conducted biological experiments to determine how microgravity initiates apoptosis in Kupffer cells. Rotary cell culture system was used to construct a simulated microgravity model. GO and KEGG analyses were conducted using the DAVID database. GSEA was performed using the R language. The STRING database was used to conduct PPI analysis. qPCR was used to measure the IL1B, TNFA, CASP3 , CASP9, and BCL2L11 mRNA expressions. Western Blotting was performed to detect the level of proteins CASP3 and CASP 9. Flow cytometry was used to detect apoptosis and mitochondrial membrane cells. Transmission electron microscopy was used to detect changes in the ultrastructure of Kupffer cells. Transcriptome Sequencing indicated that simulated microgravity affected apoptosis and the inflammatory state of Kupffer cells. Simulated microgravity improved the CASP3 , CASP9, and BCL2L11 expressions in Kupffer cells. Annexin-V/ PI and JC-1 assays showed that simulated microgravity promoted apoptosis in Kupffer cells. Simulated microgravity causes M1 polarization in Kupffer cells. Our study found that simulated microgravity facilitated the apoptosis of Kupffer cells through the mitochondrial pathway and activated Kupffer cells into M1 polarization, which can secrete TNFA to promote apoptosis. [ABSTRACT FROM AUTHOR]

The heat transfer analysis and time dependent magneto hydrodynamics boundary layer flow of three dimensional viscous incompressible Newtonian fluid in rotating frame across the extending surface subject to microgravity g ∗ (t) (= g o [ 1 + ϵ cos (π ω t) ] k) is investigated. The gravity modulation and gradient of fluid temperature typically generate buoyant convective flows in case of various situation, most likely in environment of low gravity or microgravity, the systems can operate under purely diffusive conditions in this environment since buoyancy-driven fluid flows and sedimentations are significantly diminished. Recent years have seen a growing interest of researchers in mixed convection that is regulated by microgravity environment due to highly extensive modern technological applications. The innovative aspect of the current study is the consideration of the impacts of gravity jitters (g-jitter) in rotating Newtonian fluid. The leading governing equations of elaborated fluid flow problem transformed into form of non dimensional coupled non-linear PDEs (partial differential equations) by the help of appropriate similarity functions. For seek of numerical solution, a very powerful technique, finite element method is used via MATLAB. The flexibility, robustness, and exactness of this technique make it a strong tool for solving fluid flow problems. The magnitude of average Nusselt number exhibits 16% & 17% decline against 46.31% increment in Coriolis and magnetic forces. Rising the amplitude of modulation results in proportional rise and decline in skin friction and heat transfer. By increasing strength of rotating parameter, magnetic parameter and frequency modulation parameter, the velocity profile declined while, temperature field has opposite trend against these parameters. The comparison of current results with existing results is given and found a very good agreement between them. [ABSTRACT FROM AUTHOR]

The article analyzes how long-duration space missions’ effect on the heart rate variability parameters and invariable blood proteins. The results are discussed taking into correlation between them. Seven Russian cosmonauts took part in the research during their missions to the International Space Station. Samples of dry blood drops were collected as part of the space experiment ''OMICs-DBS'', electrocardiogram samples were collected as part of the space experiment "Cardiovector". We have established a linear relationship between the concentrations of the following proteins: complement C1q subcomponent subunit A (encoded by the C1QA gene), complement C1r subcomponent (encoded by the C1R gene), fibrinogen gamma chain (encoded by the FGG gene),galectin-3 (encoded by the LGALS3 gene), interstitial collagenase or matrix metalloproteinase-1 (encoded by the MMP-1 gene), pigment epithelium-derived factor (encoded by the PEDF gene) and frequency-domain heart rate variability (HRV) parameters at some stages of space flight. Three proteins were associated with of total power parameters, and either positively correlated with the low-frequency (LF) domain as in the case of the C1QA (complement C1q subcomponent subunit A) or negatively - LGALS3, MMP-1 (galectin-3, matrix metalloproteinase-1) correlated with the high-frequency domain (HF). One of the proteins, the PEDF (pigment epithelium-derived factor), positively correlated with the HF, which correspondingly reflected the effect of vagal modulation on the SA node. The Complement C1r subcomponent had positive correlations with both HF and LF. The FGG (fibrinogen gamma chain) was negatively correlated with both individual components of the frequency-domain (HF, ms2 and LF ms2) also its total power. We assume that such statistical relationships reflect the tension of regulatory mechanisms, which is consistent with classical studies of autonomic regulation in space flight. [ABSTRACT FROM AUTHOR]

This paper investigates the instability of FC-72 vapor–liquid interface in a rectangular channel under different gravity conditions employing short-term microgravity experimental systems designed based on the drop tower platform. Visual observations and numerical simulations were conducted to monitor the behavior of vapor–liquid interface. The study reveals significant fluctuations, with liquid climbing along both sides of the channel after drop cabin releases. Higher initial liquid levels result in increased maximum liquid phase heights and decreased minimum values, with noticeable fluctuations. In microgravity, the maximum height gradually rises with significant fluctuations, while minimum height remains relatively stable. Increasing contact angle leads to reduced variation in maximum and minimum heights, with a distinctive upward slope of vapor–liquid interface observed at a 90° contact angle. The temporal evolution of vapor–liquid interface observed in simulations closely aligns with experimental findings. This study highlights the importance of considering various factors in designing experiments involving fluid systems with low surface tension, particularly in aerospace applications, and calls for further research to develop more sophisticated models and techniques for understanding and controlling vapor–liquid interface instability. [ABSTRACT FROM AUTHOR]

An integration of both passive and active techniques to enhance the heat exchange has emerged as a promising research area over the past few decades. Our present investigation focuses on the heat exchange due to thermal convection in a square cavity driven by a channel, utilizing ternary hybrid nanofluid. The governing equations were derived from the averaged formulations describing thermal vibrational convection, illustrated using the vorticity of the mean velocity and stream functions relevant to both the mean and fluctuating flows. The influence of vibration on the system is quantified using a dimensionless vibration factor, denoted as Gershuni number (Gs), which is proportional to the ratio of the mean vibrational buoyancy force to the product of momentum and thermal diffusivities. All computations were conducted with fixed values of the Prandtl number (Pr = 6.1) and Reynolds number (Re = 100). The influence of physical parameters, including the Grashof number ( 10 3 ≤ G r ≤ 10 6 ), Gershuni number ( 10 3 ≤ G s ≤ 10 6 ), and volume fraction of nanomaterials ( 0 % ≤ Φ ≤ 4 % ), particularly under two scenarios: microgravity ( G r = 0 ) and terrestrial conditions, on the streamlines for both the mean and fluctuating flows, isotherms, and mean Nusselt number are discussed graphically. Numerical results indicate that an increase of Grashof number boosts heat exchange by 250% under buoyancy effects. Elevating nanomaterial volume fractions enhances thermal conductivity, increasing heat exchange by 30%. However, heightened thermal vibration reduces heat exchange. [ABSTRACT FROM AUTHOR]

The velocity profiles and volumetric concentrations were measured using a laser doppler anemometer for a vertically ascending two-phase liquid–liquid droplet flow in a cylindrical tube, where the density difference between the phases is relatively small. This regime simulates the flow of a two-phase gas–liquid mixture in microgravity. The small phase slip velocity was experimentally measured. New methods have been developed for using a laser doppler anemometer to measure the velocity and volumetric concentration of phases in a dispersed two-phase flow. [ABSTRACT FROM AUTHOR]

Active exploration of cosmic area makes it relevant not only to understand physiological changes in microgravity conditions, but also to decipher the mechanisms of their development at the cellular level. The development of gravitational biology and cell physiology can help to understand the processes occurring at the organismal level when the gravitational factor changes, as well as the mechanisms of mechanosensitivity. The purpose of this review is to systematize knowledge about the most significant studies in vitro described changes in cultured mammalian embryonic stem cells (ESCs) both under real microgravity conditions and when simulating its effects on Earth. Analysis of the literature data revealed that spaceflight did not reduce the pluripotency of cells, but produced changes in their transcriptome. Mesodermal differentiation of ESCs occurred normally, but the early development of the cardiovascular system under simulated and real microgravity conditions was slowed down. Real microgravity promoted an increase in cardiomyocyte contractions in embryoid bodies and suppressed the expression of genes responsible for pluripotency, which can lead to disturbances in further development in the later stages of embryogenesis. [ABSTRACT FROM AUTHOR]

Spaceflight-induced brain changes have been commonly reported in astronauts. The role of microgravity in the alteration of the brain structure, microstructure, and function can be tested with magnetic resonance imaging (MRI) techniques. Here, we aim to provide a comprehensive overview of Spaceflight studies exploring the potential role of brain alterations identified by MRI in astronauts. We conducted a search on PubMed, Web of Science, and Scopus to find neuroimaging correlates of spaceflight experience using MRI. A total of 20 studies (structural MRI n = 8, diffusion-based MRI n = 2, functional MRI n = 1, structural MRI and diffusion-weighted MRI n = 6, structural MRI and functional MRI n = 3) met our inclusion criteria. Overall, the studies showed that regardless of the MRI techniques, mission duration significantly impacts the human brain, prompting the inclusion of various brain regions as features in the analyses. After spaceflight, notable alterations were also observed in the superior occipital gyrus and the precentral gyrus which show alterations in connectivity and activation during spaceflight. The results provided highlight the alterations in brain structure after spaceflight, the unique patterns of brain remodeling, the challenges in drawing unified conclusions, and the impact of microgravity on intracranial cerebrospinal fluid volume. [ABSTRACT FROM AUTHOR]

Abstract Background Astronauts in Earth's orbit experience microgravity, resulting in a decline of skeletal muscle mass and function. On Earth, models simulating microgravity have shown that the extent of the loss in muscle force is greater than the loss in muscle mass. The reasons behind this disproportionate loss of muscle force are still poorly understood. In the present study, we hypothesize that alongside the loss in skeletal muscle mass, modifications in the expression profile of genes encoding critical determinants of resting membrane potential, excitation‐contraction coupling and Ca2+ handling contribute to the decline in skeletal muscle force. Methods Healthy male volunteers (n = 18) participated in a 5‐day dry immersion (DI) study, an Earth‐based model of simulated microgravity. Muscle force measurement and MRI analysis of the cross‐sectional area of thigh muscles were performed before and after DI. Biopsies of the vastus lateralis skeletal muscle performed before and after DI were used for the determination Ca2+ properties of isolated muscle fibres, molecular and biochemical analyses. Results The extent of the decline in force, measured as maximal voluntary contraction of knee extensors (−11.1%, P

Guillermo Ceniza-Bordallo,1,&ast; Eric Zimmermann,2,&ast; Marie Vigouroux,2 Kacper Niburski,3 Maryse Fortin,4 Jean Ouellet,5– 7 Juan Pablo Cata,8,9 Pablo M Ingelmo2,7,10,11 1Department of Radiology, Rehabilitation and Physiotherapy, Faculty of Nursing, Physiotherapy, and Podiatry, University Complutense of Madrid, Madrid, Spain; 2Edwards Family Interdisciplinary Center for Complex Pain, Montreal Children’s Hospital, Montreal, QC, Canada; 3Department of Anesthesia, University of British Columbia, Vancouver, BC, Canada; 4Department of Health, Kinesiology & Applied Physiology, Concordia University, Montreal, QC, Canada; 5Department of Paediatric Surgery & Surgery, McGill University Health Centre, Montreal, QC, Canada; 6Department of Scoliosis & Spine Surgery, Shriner’s Hospital for Children, Montreal, QC, Canada; 7Alan Edwards Centre for Research on Pain, McGill University, Montreal, QC, Canada; 8Department of Anesthesia and Perioperative Medicine, the University of Texas – MD Anderson Cancer Center, Houston, TX, USA; 9Anesthesiology and Surgical Oncology Research Group, Houston, TX, USA; 10Department of Anesthesia. McGill University, Montreal, Canada; 11Research Institute, McGill University Health Center, Montreal, Canada&ast;These authors contributed equally to this workCorrespondence: Guillermo Ceniza-Bordallo, Email gceniza@ucm.esAbstract: Space flights can produce physiological changes in the spine, leading to the development of acute and chronic pain in passengers. However, there is a lack of comprehensive literature exploring physiological spine changes and acute and chronic pain in space passengers (astronauts and animals). The first aim of this study was to identify the physiological changes experienced by passengers (humans and animals) after space flight. The second aim was to identify the incidence of low back pain during and after space flight. This systematic review was conducted following PRISMA guidelines and was pre-registered in PROSPERO (ID 451144). We included Randomized Controlled Trials or longitudinal studies in humans and animals, and the variables must be assessed either in-flight or post-flight. We conducted a literature search in major databases combining the keywords: Pain; Space; Low Back Pain; Astronauts; Spine Changes; Microgravity; Physiological Changes; Humans; Animals. Risk of bias and quality of studies were analyzed, and the level of evidence was assessed using the GRADE system. After duplicates were removed, 115 abstracts were screened by two reviewers, and finally, 11 articles were included in this review. The evidence indicates that astronauts experience muscle atrophy in the lumbar multifidus with a moderate to large effect, especially in the L4-L5 and L5-S1 segments. Space flights also decrease the range of motion with a moderate effect, along with disc herniations and disc dehydration. 77% of astronauts experience pain during spaceflight, and 47% develop acute pain after spaceflight. Chronic pain was reported by 33% of the astronauts. After space flights, astronauts suffer from lumbar muscle atrophy, reduced range of motion, disc herniations, and disc dehydration, with a high incidence of both acute and chronic pain.Plain Language Summary: Space travel affects the spine and can cause both immediate and long-term pain. Our study aimed to understand what changes happen in the spine during and after space travel and how often these changes lead to low back pain.Why was the study done?We wanted to investigate the specific spinal changes and the frequency of low back pain in both astronauts and animals exposed to space travel. This is important because understanding these effects can help improve health interventions for space travelers.What did the researchers do?We reviewed studies that examined spine changes and pain in humans and animals during and after space flights. We used a systematic approach to find relevant research, following strict guidelines and assessing the quality of each study.What did the researchers find?Astronauts often experience muscle loss in the lower back, particularly in the lumbar spine.Space travel reduces the spine’s range of motion.There is a significant occurrence of disc herniations and disc dehydration.77% of astronauts report pain during space flights.47% experience acute pain after returning to Earth.33% suffer from chronic pain post-mission.What do these results mean?Our findings show that space travel can lead to serious spinal issues and a high risk of pain. These results highlight the need for better health strategies to protect astronauts during and after their missions. Understanding these effects is crucial for developing effective interventions and ensuring the well-being of space travelers.Keywords: chronic low back pain, space flight, physiological changes, microgravity

Abstract Long-duration spaceflight creates a variety of stresses due to the unique environment, which can lead to compromised functioning of the skeletal and immune systems. However, the mechanisms by which organisms respond to this stress remain unclear. The present study aimed to investigate the impact of three different gravitational loadings (microgravity, 1/6 g [lunar gravity], and 1 g) on the behavior, bone, thymus, and spleen of mice housed for 25–35 days in the International Space Station. The bone density reduction under microgravity was mostly recovered by 1 g but only partially recovered by 1/6 g. Both 1 g and 1/6 g suppressed microgravity-induced changes in some osteoblast and osteoclast marker gene expression. Thymus atrophy induced by microgravity was half recovered by both 1 g and 1/6 g, but gene expression changes were not fully recovered by 1/6 g. While no histological changes were observed due to low gravity, alterations in gene expression were noted in the spleen. We found that in bone and thymus, lunar gravity reduced microgravity-induced histological alterations and partially reversed gene expression changes. This study highlighted organ-specific variations in responsiveness to gravity, serving as an animal test for establishing a molecular-level gravity threshold for maintaining a healthy state during future spaceflight.

Abstract Variable viscosity, activation energy and microgravity effects on Darcy nanofluid for the thermal performance improvement in thermal energy storage systems through stretching flat plate solar collector is the focus of this research. Thermal energy storage (TES) can be improved though solar collectors, phase change materials and photovoltaic cells using nanofluid in the base liquid. To increase the reaction rate in nanoparticles, the activation energy and solar radiations are used for the efficiency of TES. The viscosity of nanofluid improves the heat and mass transmission. Due to solar radiations, nanofluid plays prominent role in TES applications such as heat exchangers, electronic cooling devices and solar power generation through solar plate collector. Solar energy based mathematical model is developed to execute the frequency of oscillating heat transfer in TES numerically. Primitive and Stokes coefficients are used for feasible programming. Finite difference analysis is performed to display oscillatory thermal energy using Gaussian-elimination matrix scheme. Steady velocity, surface temperature and concentrations are plotted and utilized in oscillatory formula to perform oscillatory skin friction, oscillatory heat transfer and oscillatory mass transfer along π⁄4 angle. Fluid velocity enhances but temperature and concentration variation decreases as viscosity decreases. High amplitude in velocity, temperature and concentration is sketched as activation energy and microgravity increases. Steady heat and mass transmission enhances as thermophoretic and Brownian motion enhances. Amplitude and frequency of oscillations in heat transport, skin friction and mass transport enhances as Prandtl and Schmidt component enhances. In validation of results, the 0.00064% percentage error for heat transport and 0.00102% percentage error for mass transmission are deduced.

The heat transfer analysis and time dependent magneto hydrodynamics boundary layer flow of three dimensional viscous incompressible Newtonian fluid in rotating frame across the extending surface subject to microgravity g∗(t)(=go[1+ϵcos(πωt)]k) is investigated. The gravity modulation and gradient of fluid temperature typically generate buoyant convective flows in case of various situation, most likely in environment of low gravity or microgravity, the systems can operate under purely diffusive conditions in this environment since buoyancy-driven fluid flows and sedimentations are significantly diminished. Recent years have seen a growing interest of researchers in mixed convection that is regulated by microgravity environment due to highly extensive modern technological applications. The innovative aspect of the current study is the consideration of the impacts of gravity jitters (g-jitter) in rotating Newtonian fluid. The leading governing equations of elaborated fluid flow problem transformed into form of non dimensional coupled non-linear PDEs (partial differential equations) by the help of appropriate similarity functions. For seek of numerical solution, a very powerful technique, finite element method is used via MATLAB. The flexibility, robustness, and exactness of this technique make it a strong tool for solving fluid flow problems. The magnitude of average Nusselt number exhibits 16% & 17% decline against 46.31% increment in Coriolis and magnetic forces. Rising the amplitude of modulation results in proportional rise and decline in skin friction and heat transfer. By increasing strength of rotating parameter, magnetic parameter and frequency modulation parameter, the velocity profile declined while, temperature field has opposite trend against these parameters. The comparison of current results with existing results is given and found a very good agreement between them.

BACKGROUND: In long-distance spaceflight, the challenges of communication delays and the impracticality of rapid evacuation necessitate the management of medical emergencies by onboard physicians. Consequently, these physicians must be proficient in tools, such as ultrasound, which has proven itself a strong diagnostic imaging tool in space. Yet, there remains a notable gap in the discourse surrounding its efficacy in handling acute medical scenarios. This scoping review aims to present an updated analysis of the evidence supporting the role of ultrasound in diagnosing acute conditions within microgravity environments. METHODS: A systematic search was executed across three bibliographic databases: PubMed, EMBASE (Embase.com), and the Web of Science Core Collection. We considered articles published up to February 25, 2023, that highlighted the application of ultrasound in diagnosing acute medical conditions in either microgravity or microgravity-simulated settings. Exclusions were made for review papers, abstracts, and in-vitro studies. RESULTS: After removing duplicates, and filtering papers by pre-determined criteria, a total of 15 articles were identified that discuss the potential use of ultrasound in managing acute medical conditions in space. The publication date of these studies ranged from 1999 to 2020. A relatively similar proportion of these studies were conducted either on the International Space Station or in parabolic flight, with one performed in supine positioning to simulate weightlessness. The included studies discuss acute pathologies, such as abdominal emergencies, decompression sickness, deep venous thrombosis, acute lung pathologies, sinusitis, musculoskeletal trauma, genitourinary emergencies, and ocular emergencies. CONCLUSIONS: While ultrasound has shown promise in addressing various acute conditions, significant knowledge gaps remain, especially in gastrointestinal, cardiac, vascular, and reproductive emergencies. As we venture further into space, expanding our medical expertise becomes vital to ensure astronaut safety and mission success.

Objective: To assess the impact of microgravity exposure on ocular rigidity (OR), intraocular pressure (IOP), and ocular pulse amplitude (OPA) following long-term space missions. OR was evaluated using optical coherence tomography (OCT) and deep learning-based choroid segmentation. IOP and OPA were measured with the PASCAL Dynamic Contour Tonometer (DCT). Results: The study included 26 eyes from 13 crew members who spent 157 to 186 days on the International Space Station. Post-mission results showed a 25% decrease in OPA (p < 0.005), an 11% decrease in IOP from 16.0 mmHg to 14.2 mmHg (p = 0.04), and a 33% reduction in OR (p = 0.04). No significant differences were observed between novice and experienced astronauts. Conclusions: These findings reveal previously unknown effects of microgravity on the eye's mechanical properties, contributing to a deeper understanding of Spaceflight-Associated Neuro-ocular Syndrome (SANS). Long-term space missions significantly alter ocular biomechanics and have the potential to become biomarkers of disease progression.

Outer space is an austere environment filled with unique and potentially dangerous stressors that can impact the physiologic function of astronauts during and after their stay above the atmosphere. Within 24 h of flight, astronauts may experience nausea and malaise, coined space motion sickness, due to vestibular and ocular sensory mismatch and changes in cranial and other fluid pressures. Although temporary, long-lasting conditions also arise. Spaceflight Associated Neuro-Ocular Syndrome is associated optic disc edema, globe flattening, and hyperopic refractive error shifts, and may lead to permanent structural changes. In addition, astronauts during space flight can lose up to 30 % of their muscle mass and 8–12 % of bone density. Some of these changes require months of rehabilitation and adaptation to make a full recovery. Radiation and secondary cellular alterations can lead to carcinogenesis, microbiome shifts, and immunological dysfunction. To combat these changes, NASA has continually researched ways to improve the spaceflight experience. New spin off technology from NASA to address these astronaut health concerns often find their way into the terrestrial consumer and healthcare markets. This paper aims to identify NASA associated breakthroughs in medical innovation including cutting-edge technology created for laser tracking of ballistic missiles, durable polymers for high-speed air travel, refractive eye surgery, and cardiac resynchronization devices. • Comprehensive query of medical innovations from NASA's Spinoff program since 1976. • Summary of physiologic adaptations due to vestibular, gravity, and radiation changes. • Similarities with space associated technology and medical derivatives. • Industry defining innovations within medical domains including, but not limited to, ophthalmology, cardiology, and oncology. • Evidence behind the benefit of space research within the terrestrial environment. [ABSTRACT FROM AUTHOR]

[Display omitted] In order to understand the basic mechanisms affecting emulsion stability, the intrinsic dynamics of the drop population must be investigated. We hypothesize that transient ballistic motion can serve as a marker of interactions between drops. In 1G conditions, buoyancy-induced drop motion obscures these interactions. The microgravity condition onboard the International Space Station enable this investigation. We performed Diffusing Wave Spectroscopy (DWS) experiments in the ESA Soft Matter Dynamics (SMD) facility. We used Monte Carlo simulations of photon trajectory to support data analysis. The analysis framework was validated by ground-based characterizations of the initial drop size distribution (DSD) and the properties of the oil/water interface in the presence of surfactant. We characterized the drop size distribution and found to be bi-disperse. Drop dynamics shows transient ballistic features at early times, reaching a stationary regime of primarily diffusion-dominated motion. This suggests different ageing mechanisms: immediately after emulsification, the main mechanism is coalescence or aggregation between small drops. However at later times, ageing proceeds via coalescence or aggregation of small with large drops in some emulsions. Our results elucidate new processes relevant to emulsion stability with potential impact on industrial processes on Earth, as well as enabling technologies for space exploration. [ABSTRACT FROM AUTHOR]

Abstract The advancement in extraterrestrial exploration has highlighted the crucial need for studying how the human cardiovascular system adapts to space conditions. Human development occurs under the influence of gravity, shielded from space radiation by Earth’s magnetic field, and within an environment characterized by 24-hour day-night cycles resulting from Earth’s rotation, thus deviating from these conditions necessitates adaptive responses for survival. With upcoming manned lunar and Martian missions approaching rapidly, it is essential to understand the impact of various stressors induced by outer-space environments on cardiovascular health. This comprehensive review integrates insights from both actual space missions and simulated experiments on Earth, to analyze how microgravity, space radiation, and disrupted circadian affect cardiovascular well-being. Prolonged exposure to microgravity induces myocardial atrophy and endothelial dysfunction, which may be exacerbated by space radiation. Mitochondrial dysfunction and oxidative stress emerge as key underlying mechanisms along with disturbances in ion channel perturbations, cytoskeletal damage, and myofibril changes. Disruptions in circadian rhythms caused by factors such as microgravity, light exposure, and irregular work schedules, could further exacerbate cardiovascular issues. However, current research tends to predominantly focus on disruptions in the core clock gene, overlooking the multifactorial nature of circadian rhythm disturbances in space. Future space missions should prioritize targeted prevention strategies and early detection methods for identifying cardiovascular risks, to preserve astronaut health and ensure mission success.

This study examines the effects of microgravity and space radiation on astronauts’ muscle and bone health during space missions. Microgravity leads to muscle atrophy and alterations in muscle tissue composition, whereas space radiation impacts bone cells by increasing osteoclast activity and decreasing osteoblast activity. The findings underscore the critical need for preventive measures, postmission rehabilitation, and the use of specialized equipment and technology—such as microgravity-adapted treadmills and nutritional supplements—to sustain astronaut health. This study lays the groundwork for developing effective protection and intervention strategies for long-duration space exploration, highlighting the necessity of a thorough understanding of how the space environment affects the human body to ensure optimal health and performance in space.

Abstract The gut microbiota and its secreted metabolites play a significant role in cardiovascular and musculoskeletal health and diseases. The dysregulation of the intestinal microbiota poses a significant threat to cardiovascular and skeletal muscle well-being. Nonetheless, the precise molecular mechanisms underlying these changes remain unclear. Furthermore, microgravity presents several challenges to cardiovascular and musculoskeletal health compromising muscle strength, endothelial dysfunction, and metabolic changes. The purpose of this review is to critically examine the role of gut microbiota metabolites on cardiovascular and skeletal muscle functions and dysfunctions. It also explores the molecular mechanisms that drive microgravity-induced deconditioning in both cardiovascular and skeletal muscle. Key findings in this review highlight that several alterations in gut microbiota and secreted metabolites in microgravity mirror characteristics seen in cardiovascular and skeletal muscle diseases. Those alterations include increased levels of Firmicutes/Bacteroidetes (F/B) ratio, elevated lipopolysaccharide levels (LPS), increased in para-cresol (p-cresol) and secondary metabolites, along with reduction in bile acids and Akkermansia muciniphila bacteria. Highlighting the potential, modulating gut microbiota in microgravity conditions could play a significant role in mitigating cardiovascular and skeletal muscle diseases not only during space flight but also in prolonged bed rest scenarios here on Earth.