Dieter Seibt

Comparative studies on gravisensitive protists on ground (2D and 3D clinostats) and in microgravity

In order to prepare and support space experiments, 2D and 3D clinostats are widely applied to study the influence of simulated weightlessness on biological systems. In order to evaluate the results a comparison between the data obtained in simulation experiments and in real microgravity is necessary. We are currently analyzing the gravity-dependent behavior of the protists Paramecium biaurelia (ciliate) and Euglena gracilis (photosynthetic flagellate) on these different experimental platforms. So far, first results are presented concerning the behaviour of Euglena on a 2D fast rotating clinostat and a 3D clinostat as well as under real microgravity conditions (TEXUS sounding rocket flight), of Paramecium on a 2D clinostat and in microgravity. Our data show similar results during 2D and 3D clinorotation compared to real microgravity with respect to loss of orientation (gravitaxis) of Paramecium and Euglena and a decrease of linearity of the cell tracks of Euglena. However, the increase of the mean swimming velocities, especially during 3D clinorotation (Euglena) and 2D clinorotation of Paramecium might indicate a persisting mechanostimulation of the cells. Further studies including long-term 2D and 3D clinostat exposition will enable us to demonstrate the qualification of the applied simulation methods.

Fertilization of Sea Urchin Eggs and Sperm Motility Are Negatively Impacted under Low Hypergravitational Forces Significant to Space Flight

Abstract Sperm and other flagellates swim faster in microgravity (μG) than in 1 G, raising the question of whether fertilization is altered under conditions of space travel. Such alterations have implications for reproduction of plant and animal food and for long-term space habitation by man. We previously demonstrated that μG accelerates protein phosphorylation during initiation of sperm motility but delays the sperm response to the egg chemotactic factor, speract. Thus sperm are sensitive to changes in gravitational force. New experiments using the NiZeMi centrifugal microscope examined whether low hypergravity (hyperG) causes effects opposite to μG on sperm motility, signal transduction, and fertilization. Sperm % motility and straight-line velocity were significantly inhibited by as little as 1.3 G. The phosphorylation states of FP130, an axonemal phosphoprotein, and FP160, a cAMP-dependent salt-extractable flagellar protein, both coupled to motility activation, showed a more rapid decline in hyperG. Most critically, hyperG caused a ∼50% reduction in both the rate of sperm-egg binding and fertilization. The similar extent of inhibition of both fertilization parameters in hyperG suggests that the primary effect is on sperm rather than eggs. These results not only support our earlier μG data demonstrating that sperm are sensitive to small changes in gravitational forces but more importantly now show that this sensitivity affects the ability of sperm to fertilize eggs. Thus, more detailed studies on the impact of space flight on development should include studies of sperm function and fertilization.

BIOLAB on the International Space Station (ISS): Facility and Experiments

The BIOLAB is a multi-user facility of the European Space Agency ESA, accommodated in the European COLUMBUS Module of the International Space Station. The BIOLAB flight facility enables biological and biomedical experiments investigating the effects of weightlessness and/or space radiation on microorganisms, cell cultures of various origins, lower organisms and small plants and animals. The proposals for Life Sciences experiments are selected by an ESA peer group. The BIOLAB facility consists of an automated left part and a right part which is manually operated by the astronauts on orbit. The biological and biomedical samples are accommodated in experiment-specific containers, dedicated to each individual experiment. Sample preparation can be performed in the Bioglovebox, storage of biosamples in a cooler/freezer. On-orbit analyses can be performed by means of a microscope. The incubator as the heart piece of BIOLAB includes a life support system and two rotor platforms. Furthermore the video camera system mounted on the rotor platforms enables a regular control of the biosamples via telescience from/to ground. The BIOLAB facility is controlled and monitored by the Microgravity User Support Center (MUSC) as Facility Responsible Center (FRC) at DLR, Cologne, Germany, on behalf of the European Space Agency. MUSC is interfacing with the astronauts on orbit and the partners of the ISS ground segment, space hardware developers and the COLUMBUS Control Center. Main MUSC tasks for BIOLAB are increment preparation, experiment optimization and flight qualification, on-orbit operations via telescience, as well as post-increment evaluation. BIOLAB ground models - complemented by hyper-g and µg simulation devices - are available for experiments. DLR MUSC is supported by the specific expertise of BIOTESC (Lucerne, Switzerland). This review encompasses a description of the BIOLAB facility and exemplarily some experiments hitherto flown.