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Gravitational Biology

The evolution of life on Earth occurred under the persistent influence of gravity. As gravity is constant with respect to its direction and magnitude, the vectorial information of gravitational acceleration is a most reliable reference point for orientation. Sensors for the gravity stimulus, specialized organelles for gravity sensing and mechanisms for active responses have been found in unicellular organisms as well as in multicellular animal and plant systems. Recent studies support the hypothesis that gravity is perceived either by intracellular receptors (statocyst-like organelles), heavy cell organelles (such as nucleus) and/or by sensing the cell mass by means of ion channels located in the cell membrane. Consequently the question arises about a general gravisensitivity of cells including mammalian cells.

Though severe effects of microgravity on cells (e.g. lymphocytes) have been stated, the development of complex organisms occurs more or less undisturbed under this condition. However, a systematic approach and multi-generation experiments with animals and plants in microgravity are necessary as they are the key players in life support systems which are necessary for long-term manned space missions.

In addition to rather exclusive experiments under real microgravity conditions, different ground-based methods have been developed to achieve either the status of simulated microgravity (this term has been adopted by international convention) or hypergravity (artificial gravity) conditions.

The DLR Institute of Aerospace Medicine has a long-term experience in developing and using space simulation facilities: so-called clinostats enable the rotation of a sample perpendicular to the gravitational field assuming that a continuously reoriented biological system does not perceive the gravitational stimulus. The results of some experiments also performed in real microgravity conditions support this hypothesis.

Various clinostat devices have been constructed enabling a broad variety of experimental performances (e.g. microscopic observation of the sample during rotation in a clinostat).

Combination with our irradiation facilities (see section Radiation Biology) enables the investigation of the combined effect of functional weightlessness and radiation. Correspondingly, different centrifuge devices – such as centrifuge microscope (NIZEMI = Niedergeschwindigkeits-Zentrifugenmikroskop) - complete our experimental scenario.

Furthermore, the Institute of Aerospace Medicine is the facility responsible centre for Biolab, a laboratory facility on the ISS. Biolab provides the possibility to investigate various cell types and small biological systems (plants and animals) under microgravity conditions.