A magnetically enabled simulation of microgravity represses the auxin response during early seed germination on a microfluidic platform

For plants on Earth, the phytohormone auxin is essential for gravitropism-regulated seedling establishment and plant growth. However, little is known about auxin responses under microgravity conditions due to the lack of a tool that can provide an alteration of gravity. In this paper, a microfluidic negative magnetophoretic platform is developed to levitate Arabidopsis seeds in an equilibrium plane where the applied magnetic force compensates for gravitational acceleration. With the benefit of the microfluidic platform to simulate a microgravity environment on-chip, it is found that the auxin response is significantly repressed in levitated seeds. Simulated microgravity statistically interrupts auxin responses in embryos, even after chemical-mediated auxin alterations, illustrating that auxin is a critical factor that mediates the plant response to gravity alteration. Furthermore, pretreatment with an auxin transportation inhibitor (N-1-naphthylphthalamic acid) enables a decrease in the auxin response, which is no longer affected by simulated microgravity, demonstrating that polar auxin transportation plays a vital role in gravity-regulated auxin responses. The presented microfluidic platform provides simulated microgravity conditions in an easy-to-implement manner, helping to study and elucidate how plants correspond to diverse gravity conditions; in the future, this may be developed into a versatile tool for biological study on a variety of samples.

Sensitivity of Visual System in 5-Day “Dry” Immersion With High-Frequency Electromyostimulation

The aim of this work was to study the sensitivity of the visual system in 5-day “dry” immersion with a course of high-frequency electromyostimulation (HFEMS) and without it. “Dry” immersion (DI) is one of the most effective models of microgravity. DI reproduces three basic effects of weightlessness: physical inactivity, support withdrawal and elimination of the vertical vascular gradient. The “dry” immersion included in the use of special waterproof and highly elastic fabric on of immersion in a liquid similar in density to the tissues of the human body. The sensitivity of the visual system was assessed by measuring contrast sensitivity and magnitude of the Müller-Lyer illusion. The visual contrast sensitivity was measured in the spatial frequency range from 0.4 to 10.0 cycles/degree. The strength of visual illusion was assessed by means of motor response using “tracking.” Measurements were carried out before the start of immersion, on the 1st, 3rd, 5th days of DI, and after its completion. Under conditions of “dry” immersion without HFEMS, upon the transition from gravity to microgravity conditions (BG and DI1) we observed significant differences in contrast sensitivity in the low spatial frequency range, whereas in the experiment with HFEMS—in the medium spatial frequency range. In the experiment without HFEMS, the Müller-Lyer illusion in microgravity conditions was absent, while in the experiment using HFEMS it was significantly above zero at all stages. Thus, we obtained only limited evidence in favor of the hypothesis of a possible compensating effect of HFEMS on changes in visual sensitivity upon the transition from gravity to microgravity conditions and vice versa. The study is a pilot and requires further research on the effect of HFEMS on visual sensitivity.

Cancer Studies under Space Conditions: Finding Answers Abroad

In this review article, we discuss the current state of knowledge in cancer research under real and simulated microgravity conditions and point out further research directions in this field. Outer space is an extremely hostile environment for human life, with radiation, microgravity, and vacuum posing significant hazards. Although the risk for cancer in astronauts is not clear, microgravity plays a thought-provoking role in the carcinogenesis of normal and cancer cells, causing such effects as multicellular spheroid formation, cytoskeleton rearrangement, alteration of gene expression and protein synthesis, and apoptosis. Furthermore, deleterious effects of radiation on cells seem to be accentuated under microgravity. Ground-based facilities have been used to study microgravity effects in addition to laborious experiments during parabolic flights or on space stations. Some potential ‘gravisensors’ have already been detected, and further identification of these mechanisms of mechanosensitivity could open up ways for therapeutic influence on cancer growth and apoptosis. These novel findings may help to find new effective cancer treatments and to provide health protection for humans on future long-term spaceflights and exploration of outer space.

Morphofunctional Changes in Peripheral Immune Organs in Space Flight and Weightlessness Modeling

Currently, there are many studies devoted to the problems of immunity in space flights. It has been proven that both short-term and long-term stay in space significantly reduces the immune function of the body. There are cases of the development of infectious diseases in astronauts during the flight, there is evidence of an increase in the activity of viruses and microorganisms that can affect the health of crew members. In the light of the upcoming expedition to Mars, it is especially important to study exactly what changes in the immune system can be triggered by prolonged stay in zero gravity and other factors of space flight and what preventive measures can help preserve the health of astronauts both during the flight itself and after its completion. The state of the immune system in space has been studied at various levels, from molecular to organ. There was a change in the morphological parameters of the immune system organs, violations of the ratio of their morpho-functional zones, and cellular composition. Various disorders in signaling pathways of differentiation, activation and death of immune system cells are shown. One of the most studied topics is the decrease in the activity of T-lymphocytes recorded by many researchers, however, even in this matter, the mechanisms of the violations occurring and their connection with the conditions of space flight have not been fully clarified. The relevance of methods for modeling microgravity conditions, such as various types of hanging, rotation on a clinostat, and immobilization is due both to their greater availability for research compared to space flights, and the importance of studying the role of various factors associated with flight in changes occurring in the human and animal bodies. This article presents an overview of publications devoted to a wide range of issues related to the state of the immune system in space flights and ground simulation conditions and attempts to combine the results of various levels of research – molecular, cellular and morphological.

Effects of Simulated Microgravity and Hypergravity Conditions on Arm Movements in Normogravity

The human sensorimotor control has evolved in the Earth’s environment where all movement is influenced by the gravitational force. Changes in this environmental force can severely impact the performance of arm movements which can be detrimental in completing certain tasks such as piloting or controlling complex vehicles. For this reason, subjects that are required to perform such tasks undergo extensive training procedures in order to minimize the chances of failure. We investigated whether local gravity simulation of altered gravitational conditions on the arm would lead to changes in kinematic parameters comparable to the full-body experience of microgravity and hypergravity onboard a parabolic flight. To see if this would be a feasible approach for on-ground training of arm reaching movements in altered gravity conditions we developed a robotic device that was able to apply forces at the wrist in order to simulate micro- or hypergravity conditions for the arm while subjects performed pointing movements on a touch screen. We analyzed and compared the results of several kinematic parameters along with muscle activity using this system with data of the same subjects being fully exposed to microgravity and hypergravity conditions on a parabolic flight. Both in our simulation and in-flight, we observed a significant increase in movement durations in microgravity conditions and increased velocities in hypergravity for upward movements. Additionally, we noted a reduced accuracy of pointing both in-flight and in our simulation. These promising results suggest, that locally simulated altered gravity can elicit similar changes in some movement characteristics for arm reaching movements. This could potentially be exploited as a means of developing devices such as exoskeletons to aid in training individuals prior to undertaking tasks in changed gravitational conditions.

Dynamics of bubble growth during boiling at microgravity

The purpose of this investigation is to study the mechanisms of boiling heat transfer in microgravity conditions. The RUBI (Reference mUltiscale Boiling Investigation) is an experiment where the basic phenomena of boiling heat transfer processes on a heated surface are investigated on the ISS (International Space Station). The special focus is paid to the coupling of macroscopic bubble dynamics from nucleation, growth and detachment combined with the microscopic phenomena in the thin films and micro layers on the heater, underneath the boiling bubbles. The image treatment program has been developed in order to extract the bubble volume as well as the contact angle from the experimental images. The first data of the bubble growth dynamics have been obtained and analysed.

Stick-slip Dynamics in Penetration Experiments on Simulated Regolith

The surfaces of many planetary bodies, including asteroids and small moons, are covered with dust to pebble-sized regolith held weakly to the surface by gravity and contact forces. Understanding the reaction of regolith to an external perturbation will allow for instruments, including sensors and anchoring mechanisms for use on such surfaces, to implement optimized design principles. We analyze the behavior of a flexible probe inserted into loose regolith simulant as a function of probe speed and ambient gravitational acceleration to explore the relevant dynamics. The EMPANADA experiment (Ejecta-Minimizing Protocols for Applications Needing Anchoring or Digging on Asteroids) flew on several parabolic flights. It employs a classic granular physics technique, photoelasticity, to quantify the dynamics of a flexible probe during its insertion into a system of bi-disperse, centimeter-sized model grains. We identify the force chain structure throughout the system during probe insertion at a variety of speeds and for four different levels of gravity: terrestrial, Martian, lunar, and microgravity. We identify discrete, stick-slip failure events that increase in frequency as a function of the gravitational acceleration. In microgravity environments, stick-slip behaviors are negligible, and we find that faster probe insertion can suppress stick-slip behaviors where they are present. We conclude that the mechanical response of regolith on rubble-pile asteroids is likely quite distinct from that found on larger planetary objects, and scaling terrestrial experiments to microgravity conditions may not capture the full physical dynamics.

Direct foam writing in microgravity

Herein we report 2D printing in microgravity of aqueous-based foams containing metal oxide nanoparticles. Such hierarchical foams have potential space applications, for example for in situ habitat repair work, or for UV shielding. Foam line patterns of a TiO2-containing foam have been printed onto glass substrates via Direct Foam Writing (DFW) under microgravity conditions through a parabolic aircraft flight. Initial characterization of the foam properties (printed foam line width, bubble size, etc.) are presented. It has been found that gravity plays a significant role in the process of direct foam writing. The foam spread less over the substrate when deposited in microgravity as compared to Earth gravity. This had a direct impact on the cross-sectional area and surface roughness of the printed lines. Additionally, the contact angle of deionized water on a film exposed to microgravity was higher than that of a film not exposed to microgravity, due to the increased surface roughness of films exposed to microgravity.

Potential of Acidithiobacillus ferrooxidans to Grow on and Bioleach Metals from Mars and Lunar Regolith Simulants under Simulated Microgravity Conditions

The biomining microbes which extract metals from ores that have been applied in mining processes worldwide hold potential for harnessing space resources. Their cell growth and ability to extract metals from extraterrestrial minerals under microgravity environments, however, remains largely unknown. The present study used the model biomining bacterium Acidithiobacillus ferrooxidans to extract metals from lunar and Martian regolith simulants cultivated in a rotating clinostat with matched controls grown under the influence of terrestrial gravity. Analyses included assessments of final cell count, size, morphology, and soluble metal concentrations. Under Earth gravity, with the addition of Fe3+ and H2/CO2, A. ferrooxidans grew in the presence of regolith simulants to a final cell density comparable to controls without regoliths. The simulated microgravity appeared to enable cells to grow to a higher cell density in the presence of lunar regolith simulants. Clinostat cultures of A. ferrooxidans solubilised higher amounts of Si, Mn and Mg from lunar and Martian regolith simulants than abiotic controls. Electron microscopy observations revealed that microgravity stimulated the biosynthesis of intracellular nanoparticles (most likely magnetite) in anaerobically grown A. ferrooxidans cells. These results suggested that A. ferrooxidans has the potential for metal bioleaching and the production of useful nanoparticles in space.