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Parabolic flight and ISS

How Does Weightlessness Affect Nerve Cells?

| Author / Editor: Florian Kohn and Claudia Koch* / Marc Platthaus

Fig. 1: Claudia Koch and Florian Kohn in the parabolic plane.
Fig. 1: Claudia Koch and Florian Kohn in the parabolic plane. (Source: Universität Hohenheim)

Research under modified gravity conditions requires the researchers and engineers to change their thinking. When there is suddenly no longer top nor bottom, this is not only exciting for the researcher — also particular demands in the analytical technique are made.

Life on earth developed under relatively constant gravity (9.81 m/s2or 1 g) and adjusted superbly to these conditions during evolution. For example, plants recognize where the top and bottom are, and we humans can orientate superbly (mostly) in the three-dimensional space thanks to our sense of equilibrium. However, what happened when gravity conditions changes? Since human has decided to explore the universe, scientists are occupied with this issue. In astronauts, who returned from the space missions, the most diverse health problems are established. This leads to a reduction of muscle and bone mass, impairment of the cardiovascular system, deterioration of visual capacity and activation of dormant viruses, which affect the immune system.

What these reactions trigger in the body is a subject of current research of different researcher groups throughout the world.

Nerve cells in focus

In Hohenheim, attention focuses on the nerve cells, in particular the cell line SH-SY5Y. It is known of the nervous system that under weighlessness, it leads to a decelerated stimulus conduction. To express it otherwise, the reaction capacity is reduced. Why is that? To address this question, understanding of the molecular mechanisms in a cell is important: The obvious probability of ionic channels in the cell membrane decreases, which leads to a milder excitability of the cell, however, decreases the conduction speed. This knowledge was obtained in experiments in the parabolic plane.

During these experiments, it is possible for researchers to implement their own projects in the plane, per mission on three to four campaign days and for 31 parabols per day. The converted Airbus A 310 offers sufficient space for around 44 scientists. After starting, this can return within the shortest period to their experimental structures, prepare the experiments and they check them during the hyper- and hypo-g phases.

During the parabolic flight, everybody on board experiences first 25 seconds of hypergravity, namely 1.8 g, followed by a phase of 0 g (22 sec) and a renewed 25-second phase with 1.8 g. The advantage of the parabolic flight campaigns are obvious– almost like in the separate laboratory, scientists can monitor, control and — if necessary — modify their experiments. However, the weightlessness period is only short and it must be precisely considered and weighed what is learned in 22 seconds.

Microscope for space

In the parabolic plane, two different approaches are currently performed by scientists from the University of Hohenheim. On the one hand, the characteristics of the cytoskeleton, that is the inner structure of the cell, is observed. On the other hand, different properties of the cell membrane are looked after.

To study the cytoskeleton, a special confocal laser-scanning fluorescence microscope was developed for biological and biomedical space applications in cooperation with DLR and Airbus Defence & Space and tested for the first time in 2014 in the parabolic flight. This system, called FLUMIAS (Fluorescence-Microscopic Analysis Systems for Space Application), allows for the first time to take into consideration the changes of the live cells in real time as highly dissolved, the structures of interest of which were marked first for the researcher by means of a fluorescence dye. The central component of Flumias is a spinning disc, which enables to provide the parallel scan of several thousand observation points. The system offers a good axial (∆z ~ 1.5 µm) and lateral (∆x,∆y ~ 0.4 µm) resolution, low photobleaching compared with a point scanner, and a rapid picture analysis in combination with a modern sCMOS camera. The potential wavelengths at the moment are 405/488/561/642 nm. Flumias allows visibility of temporal experiments and 3D-microscopic analyses of rapid cellular and intracellular processes, such as ionic flow, movement of the organelles and dynamics of the cytoskeleton as well as protein relocalisation. After the first parabolic flight, the system of 2015 was employed in a so-called Sounding Rocket, which offers — in different to the parabolic flight — about six minutes of weighlessness. The planning for use operates on the ISS is ongoing.

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