The most relevant data obtained from the experiments are summarised in Table 1.2. The findings demonstrate the usefulness of sounding rockets in biological basic research as well as in biotechnology. Important stimulation of the metabolism of mesophyll protoplasts indicates that cells not specialised in sensing gravity (as the statocytes are) also experience gravitational effects. Studies of the statoliths' function show that their interaction with the cytoskeleton plays an important role in the transduction of the gravitropic signal. Flagellated cells change their swimming behaviour and motion velocity seconds after µg onset. This is true for organisms as different as algae, protozoa and spermatozoa. Lack of extrusion of trichocysts in Paramecium at µg indicates that the cells undergo only limited mechanical stress. Egg fertilisation occurs normally in µg. Experiments with lymphocytes contributed to clarifying the surprising loss of mitogenic stimulation at 0 g. While cell movements, interactions and binding of the mitogen concanavalin A to the cell membrane occur normally in µg, important rearrangements of cytoskeletal structures are observed.
Sounding rockets are also suitable for studying the expression of early genes during the signal transduction chain. The discovery of the reduced expression of c-fos and c-jun in epidermoid cells exposed to growth factor contributes to understanding the mechanisms of gravity effects at the level of single cells and opens the way to molecular biological investigations in sounding rockets. Technological studies on the electrofusion and the electrophoretic separation of cells showed the potential advantages of such bioprocesses in µg. Plant and mammalian cells showed a significant increase of yields of hybrids, while the separation of mixtures of erythrocytes from different species was better than at 1 g.
Table 1.2. Overview of the findings of life sciences experiments on sounding
rockets 1985-1994
Organism Major findings (number of experiments) Authors
Heteromyeloma cells, human lymphocytes, Significant enhancement of electrofusion efficacy and U. Zimmermann, R. Schnettler, G. Klock,
different strains of yeast cells yields of hybrid cells(9) B. Herrmann & P. Gessner
Mixtures of red blood cells from different Sharperi separationvbyyfree-flow1electrophoresis of U. Zimmermann, R Schnettler, G. Klock,
species cells in microgravity than at 1 g (3) B. Herrmann, P. Gessner & K. Hannig
Protoplasts of the tobacco plant Significant increase of homo/heterospecific fusion R. Hampp & E. Hoffmann
(Nicotina tabacum) products by electrofusion of vacuolated and evacuolated
mixtures (2). Metabolism: fluctuation of ATP/ADP ratios
and increase of the pool size of fructose, 2,6-biphosphate
on exposure to 0 g. Conclusion: decreased rates of
gluconeogenesis (2)
Frog eggs and sperm (Xenopus laevis) The first successful monospermic fertilisation and histological G. A. Ubbels, J. Narraway, R. de Groot,
fixation of amphibian eggs in µg, aldo showing that cell S. Kerkvliet, M. Reijnen,
biological experiments are feasible on sounding rockets, in R. A. De Maziere & J. Gonzalez-Jurado
µg the gametes fuse and sperm penetrates with similar
rates as 1 g. Unifixed fertilised eggs survive reentry alive
but, when grown on Earth, the 0 g form an abnormal blastocoel
and those from the 1 g centrifuge a normal blastocoel.
The ultimate development is normal in both cases, which
also holds after fertilisation and development in a clinostat (3)
Seedlings of cress plants During 6 min of µg there is a significant displacement D. Volkmann & M. Tewinkel
(Lepidium sativum) of 3 µm of statoliths in the opposite direction to the
originally acting gravity vector. It is concluded that the
stotaliths' position depend on the gravitational field and
intracellular forces exerted by cytoskeleton elements (3)
Bull sperm Significant increase of motility. The alterations are observed U. Engelmann, F. Krassnigg & W.-B. Schill
in the straight and curvilinear velocity as well as in linearity
values (2)
Gametes of unicellular algae Diminished sexual activation of the gametes in the flight H. van den Ende, R. Demets, A. M. Tomson, M. L. van den Briel,
(Chlamydomonas eugametos) samples compared to the 1 g ground activation of the gametes A.J.A. Nederbragt & J. de Wit
in the flight samples compared to the 1 g ground coltrols.
The changes are attributed to the launch environment rather
than to 0 g (1)
A431 human epidermoid cells Depression of the expression of c-fos and c-jun genes induced J. Boonstra, P. J. Rijken, A. J. Verkleij, P.
by epidermal growth factor (EGF). The decrease is caused by the T. van der Saag, A. F. L. van Puijenbroek & S. W. de Laat
EGF receptor and protein kinase C-mediated signal transduction
pathway, but not by the calcium or protein kinase A pathways.
binding of EGF to the receptor clustering are not changed at 0 g.
Increase of the filamentous actin content and alteration of the
actin filament organisation. No alteration of microtubule and
keratination (5)
Human leukocytes Normal attachment of concanavalin A to the cell membrane, M. Cogoli-Greuter, P. Pippia, L. Sciola & A. Cogoli
retarded patching and capping, cells show autonomous movements and
interactions at 0 g (3)
Jurkat cells Rearrangement of intermediate filaments (vimentin) and tubulin M. Cogoli-Greuter, P. Pippia,
immediately after exposure to 0 g (1) L. Sciola & A. Cogoli
Rhizoids of algae (Chara) Statoliths move towards the base of the cell, i.e. in the opposite B. Buchen, M. Braun & A. Sievers
direction to the originally acting gravity vector; the movement
does not occur when the actin filaments are destroyed; the data
prove that, at 1 g, statoliths exert tensional forces on the
cytoskeleton and that their correct positioning is controlled by a
balance of gravity and a counteracting
force mediated by actin filaments (5)
Flagellate algae (Euglena gracilis) Loss of gravitaxis, increase in swimming velocity, improvement D.-P. Hader
in phototaxis (4)
Sea urchin eggs and sperm (Paracentrotus Normal fertilisation; scanning and transmission electron H.-J. Marthy
lividus) microscopy do not show apparent changes; normal
development on ground of eggs fertilised in flight (2)
Fertilised sea urchin eggs (Sphaerechinus Normal development continued in cleaving eggs after H.-J. Marthy
granularis) exposure to 0 g (1)
Protozoa (Paramecium biaurelia) Loss of gravitaxis (random but straight cell tracks R. Hemmersbach
indicate no depolarisation of the cell membrane to the
degree of an action potential, transient increase in velocity);
attached trichocysts indicate no increased stress (2)
Mesophyll of plant protoplasts Massive stimulation of ubiquitin-dependent metabolic H. Schnabl, C. Hunte, M. Schulz, D. Wolf, C. Ghiena-Rahlenbeck,
(Vicia Faba) activities; drastic loss of actin isoforms (2)H. Schnabl, M. Bramer, M. Graab, M. Jan en & H. Kalweit
Human fibroblasts Changes in the cytoskeleton due to launch rather than to J. F. Jongkind, P.
µg effects. The electrofusion yield of confluent Visser & A. Verkerk
monolayers of primary skin fibroplasts was not affected
after 6 min of µg compared to the 1 g ground controls
and to the launch control after 0 min of µg (1)
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