Life science experiments during the German-Russian MIR '97 mission.

Manned spaceflight has been an important element of the German space program over the last decades. This is demonstrated by the nationally managed space missions Spacelab D-l (1985), D-2 (1993), and MIR '92 as well as by the participation in the 1st Spacelab mission FSLP (1983), the NASA missions IML-1 (1992) and IML-2 (1994), as well as in the ESA missions EUROMIR '94 and '95. On February 12th, this year, the German cosmonaut Reinhold Ewald was launched together with his Russian colleagues Wasilij Zibliew and Alexander Lasudkin onboard of a Soyuz spacecraft for another stay of a German cosmonaut onboard of the Russian Space Station MIR. This mission--the so-called German/Russian MIR '97--was, of course, another cornerstone with regard to the cooperation between Russian and German space organizations. The cooperation in the area of manned missions began 1978 with the flight of the German cosmonaut Sigmund Jahn onboard of Salyut 6, at that time a cooperation between the Soviet Union and the German Democratic Republic in the frame of the Interkosmos Program. In March 1992, it was followed by the flight of Klaus Dietrich Flade with his stay onboard of MIR. After two further successful ESA missions, EUROMIR '94 and '95 with the two German cosmonauts Ulf Merbold and Thomas Reiter and with a marked contribution of German scientists, the decision was taken to perform another German/Russian MIR mission, the so-called MIR '97. In Germany, MIR'97 was managed and performed in a joint effort between several partners. DARA, the German Space Agency, was responsible for the overall program and project management, while DLR, the German Aerospace Research Establishment, was responsible for the cosmonaut training, for medical operations, for the mission control at GSOC in Oberpfaffenhofen as well as for user support.

DARA vestibular equipment onboard MIR.

In space, the weightless environment provides a different stimulus to the otolith organs of the vestibular system, and the resulting signals no longer correspond with the visual and other sensory signals sent to the brain. This signal conflict causes disorientation. To study this and also to understand the vestibular adaptation to weightlessness, DARA has developed scientific equipment for vestibular and visuo-oculomotoric investigations. Especially, two video-oculography systems (monocular--VOG--and binocular--BIVOG, respectively) as well as stimuli such as an optokinetic stimulation device have successfully been employed onboard MIR in the frame of national and European missions since 1992. The monocular VOG was used by Klaus Flade during the MIR '92 mission, by Victor Polyakov during his record 15 months stay onboard MIR in 1993/94 as well as by Ulf Merbold during EUROMIR '94. The binocular version was used by Thomas Reiter and Sergej Avdeyev during the 6 months EUROMIR '95 mission. PIs of the various experiments include H. Scherer and A. Clarke (FU Berlin), M. Dieterichs and S. Krafczyk (LMU Munchen) from Germany as well as C.H. Markham and S.G. Diamond from the United States. Video-Oculography (VOG) is a technique for examining the function of the human balance system located in the inner ear (vestibular system) and the visio-oculomotor interactions of the vestibular organ. The human eye movements are measured, recorded and evaluated by state-of-the-art video techniques. The method was first conceived and designed at the Vestibular Research Laboratory of the ENT Clinic in Steglitz, FU Berlin (A. Clarke, H. Scherer). Kayser-Threde developed, manufactured and tested the facilities for space application under contract to DARA. Evaluation software was first provided by the ENT Clinic, Berlin, later by our subcontractor Sensomotoric Instruments (SMI), Teltow. Optokinetic hardware to support visuo-oculomotoric investigations, has been shipped to MIR for EUROMIR '95 and has successfully been used in conjunction with VOG by ESA astronaut Thomas Reiter. Most recently, BIVOG aboard MIR will be reused in the frame of German/Russian joint experiment sessions employing two Russian cosmonauts from August 1997 to January 1998.

Dynamics of the cytoskeleton in Amoeba proteus. I. Redistribution of microinjected fluorescein-labeled actin during locomotion, immobilization and phagocytosis.

Fluorescein-labeled muscle actin was microinjected into Amoeba proteus and followed during intracellular redistribution by means of the image-intensification technique. The fully polymerization-competent protein becomes part of the endogenous actomyosin system undergoing dynamic changes over time periods of several hours. Single-frame analysis of long-term sequences enabled the direct demonstration of both the contractile activities and morphological transformations of microfilaments in normally locomoting, immobilized and phagocytozing specimens. In normally locomoting cells the filament layer undergoes continuous changes in spatial distribution depending on the actual pattern of cytoplasmic streaming and cell shape. The highest degree of differentiation is always maintained in the intermediate region between the front and the uroid, thus indicating this segment of the cortex to be the most important site in generating motive force for pseudopodium formation and ameboid movement. In immobilized cells contracted by the application of ruthenium red or relaxed by different anesthetics, the filament layer forms a continuous thick sheath beneath the cell surface or becomes completely disintegrated. In phagocytozing cells the local polymerization of actin at the tip of pseudopodia forming the food-cup and around the nascent phagosome points to a significant participation of the actomyosin system in the process of capturing and constricting prey organisms. Although our results provide clear evidence for the overall importance of motive force generation according to the hydraulic pressure theory, some motile phenomena exist in Amoeba proteus that cannot exclusively be explained by this mechanism.

Spatial organization and fine structure of the cortical filament layer in normal locomoting Amoeba proteus.

The fine structural organization of a cortical filament layer in normal locomoting Amoeba proteus was demonstrated using improved fixation and embedding techniques. Best results were obtained after application of PIPES-buffered glutaraldehyde in connection with substances known to prevent the depolymerization of F-actin, followed by careful dehydration and freeze-substitution. The filament layer is continuous along the entire surface; it exhibits a varying thickness depending on the cell polarity, measuring several nm in advancing regions and 0.5-1 micron in retracting ones. Two different types of filaments are responsible for the construction of the layer: randomly distributed thin (actin) filaments forming an unordered meshwork beneath the plasma membrane, and thick (myosin) filaments mostly restricted to the uroid region in close association with F-actin. The cortical filament layer generates the motive force for amoeboid movement by contraction at posterior cell regions and induces a pressure flow that continues between the uroid with a high hydrostatic pressure and advancing pseudopodia with low one. The local destabilization of the cell surface as a precondition for the formation of pseudopodia is enabled by the detachment of the cortical filament layer from the plasma membrane. This results in morphological changes by the active separation of peripheral hyaloplasmic and central granuloplasmic regions.

Studies on microplasmodia of Physarum polycephalum. I. Classification and locomotion behavior.

Depending on the conditions of the axenic shuttle culture, microplasmodia of the acellular slime mold Physarum polycephalum can be subdivided into three classes regarding fine structural organization and protoplasmic streaming activity: (1) spherical and rod-shaped types, (b) ameboid types, and (c) symmetrical types. In ameboid microplasmodia, the motive force for the irregular protoplasmic streaming activity is generated by alternative contraction and relaxation of a membrane-associated layer, morphologically consisting exclusively of thin filaments (probably actin). The protoplasm flows along a hydraulic pressure gradient produced by the filament layer within limited regions of the cell periphery. In dumbbell-shaped microplasmodia the motive force for the regular protoplasmic shuttle streaming between the two spherical heads is generated both by volume changes of the peripheral cell region (caused by the contractile activity of the membrane-associated filament layer), and by volume changes of the internal cell membrane invagination system (caused by fibrils attached to the basal region of the invaginations). The development from the unordered protoplasmic streaming pattern and less complicated fine structural organization in ameboid microplasmodia to the highly organized protoplasmic shuttle streaming and the more complicated morphology in dumbbell-shaped microplasmodia can be explained by intermediate stages. Whereas the motive force for the transport of smaller amounts of protoplasm can be generated by the exclusive action of a cortical filament layer, the existence of a filament cortex, the display of cytoplasmic fibrils, and the development of plasma membrane invaginations appear to be a necessary precondition for the transport of large amounts of protoplasm.

[The nitrogen retention of early weaned lambs]. / Untersuchungen zum Stickstoffansatz frühabgesetzter Lämmer.

At 30-to-60-day-old lambs reared without mothers 23 different feed mixtures were tested in N-balance experiments. The following results were achieved: The concentration of digestible crude protein and energy as well as the relation between them (PEQ) have no significant influence on the lambs' nitrogen retention. The energy intake and the intake of digestible crude protein have an intensive, significant influence on nitrogen retention. Rising energy and N-intake within the limits on which the investigation is based increased nitrogen retention. Of the protein feedstuffs tested, a 6 ... 7% higher nitrogen retention was realised from soybean oil meal as the sole source of proteins with 35% retained nitrogen related to the nitrogen intake in comparison to the combinations soybean oil meal/dried skim milk resp. fish meal. Increasing dried yeast portions (greater than 5%--20%) in the feed mixture diminished nitrogen retention. On the basis of the existing results the following recommendations for the use of the tested protein feedstuffs in rearing feed for lambs can be formulated: Soybean oil meal can be used as the sole source of protein in rearing lambs. The use of up to 5% dried yeast in the rearing feed as protein source and for vitaminisation is possible; 20% however diminish nitrogen retention. Because of the positive effect on feed intake it appears suitable to use fishmeal in the rearing feed for lambs.

[The ultrastructure of the terminal segments of the human lacrimal gland (author's transl)]. / Die Ultrastruktur von Drüsenendstücken der menschlichen Tränendrüse.

Eleven human lacrimal glands of patients between the age of 13 months and 42 years were examined. The following results were obtained: 1. The human lacrimal gland shows a tubuloacinous structure. 2. The cells of the gland epithelium are high cylindrical to conical. The height of the cells depends on the functional state. 3. The secretory epithelium shows different cell types: Most cells have pale cytoplasm and different coloured prosecretory granules. Also there are cells with pale cytoplasm and few prosecretory granules, and cells with dark cytoplasm and many osmiophile prosecretory granules and finally a few cells with dark cytoplasm and very few prosecretory granules. 4. The different cell types represent most likely different stages of the cycle of secretion within the lacrimal gland. 5. The myopithelial cells show a dependence of the functional state of the gland epithelium.

[Light and electron microscopic studies of the lacrimal gland of the monkey (Macaca mulatta)]. / Licht- und elektronenmikroskopische Untersuchungen an der Tränendrüse des Affen (Macaca mulatta).

The following results were obtained by light and electron microscopical investigations of the lacrimal gland of the rhesus monkey (Macaca mulatta): 1. The lacrimal gland of the monkey is a tubulo-acinous gland having intra and extra lobar excretory ducts. Intercalated and striated ducts are lacking. 2. The secretory epithelium consists of two cell types: a) cells which have a light cytoplasm and dark secretory granules, b) cells with a dark cytoplasm and granules of different electron density. 3. The difference in the types of cells observed and in the appearance of secretory granules reflect classes due to a secretory cycle. 4. Both cell types have a parenchymal innervation, the cells with dark cytoplasm being only scarcely innervated. 5. The parenchymal innervation is cholinerg. 6. The epithelium of the intra and inter lobular excretory ducts shows secretory activity. It is surrounded by myoepithelial cells and receives a parenchymal cholinerg innervation.