Cell Growth in Microgravity
317
of cell function, while in others there is
an encouragement of three-dimensional
cell aggregate formation and secretion
of bioactive products. Cellular mechan-
otransduction properties change, as does
transmembrane signaling. These changes
are more often than not selective. Across
phyla from plant cells where subcellular
responses, cell division, and growth and
development are altered to bacterial vir-
ulence, which is enhanced in the case
of
Salmonella typhimurium
, microgravity
has multiple effects. In mammalian cells,
cytoskeletal distortion is probably one of
the major methods by which a cell ini-
tiates response to microgravity. In plant
cells and in microbes with cell walls, the
mechanism may be substantially differ-
ent. The whole organism, cell or tissue
could possibly act as a gravity sensor as
opposed to having individual gravity sens-
ing subcellular organelles. The concept of
tensegrity
offers a focus on mechanical en-
ergy at speciFc points and allows testing
of hypotheses of how changes in gravity
translate into a cellular response. Gene
expression changes are also profound in-
dicating the magnitude of gravity in the
adaptational responses in cells in space.
Genomic and proteomic analysis of differ-
ent cells on the ISS will greatly enhance the
existing knowledge. Utilization of simple,
deFned, and well-studied model systems
such as
Escherichia coli
,
Caenorhabditis el-
egans
,
Drosophila melanogaster
,p
i
s
c
e
an
s
,
and amphibians will also provide insight
into microgravity effects on many funda-
mental processes as they transcend the cell
to tissues, organs, systems, and organisms.
Microgravity as an experimental tool has
gained impetus, and with the establish-
ment of the ISS and reliable ground-based
analogs, microgravity will provide new in-
roads into cell biology.
Acknowledgments
The authors thank Ms. Mildred D. Young
for
her
invaluable
help
in
the
preparation
of
this
manuscript.
We
also
thank
Dr. Steven
R. Gonda
and
Mr. Charles M. Lundquist for reviewing
the manuscript.
See
also
Bacterial
Growth
and
Division; Cellular Interactions.
Bibliography
Books and Reviews
Darwin, C. (1859)
On the Origin of Species by
Means of Natural Selection
,
John
Murray,
London.
Einstein, A. (1961)
Relativity: The Special and the
General Theory
, (Lawson, R.W. trans), Three
Rivers Press, New York.
Montgomery, P.O., Cook, J.E., Reynolds, R.C.,
Paul, J.S., Hayflick, L., Stock, D., Schulz,
W.W., Kimzey, S., Thirolf, R.G., Rogers, T.,
Campbell, D., Murrell, J. (1977) The Response
of Single Human Cells to Zero Gravity, in:
Johnson, R.S., Dietlein, L. (Eds.)
Biomedical
Results of Skylab
, NASA SP 377.
Nicogossian, A.E.,
Pool, S.L.,
Uri, J.J.
(1993)
Historical Perspectives, in: Nicogossian, A.E.,
Huntoon, C.L.,
Pool, S.L.
(Eds.)
Space
Physiology
and
Medicine
,
Lea
&
±ebiger,
Philadelphia, pp. 3–49.
Pollard, E.C.
(1971)
Physical
Determinants
of
Receptor
Mechanisms,
in:
Gordon, A.,
Cohen, M. (Eds.)
Gravity and the Organism
,
University
of
Chicago
Press,
Chicago,
pp. 25–34.
Primary Literature
Armstrong, J.W., Nelson, K.A., Simske, S.J.,
Luttgers, M.W., Iandolo, J.J., Chapes, S.K.
(1993)
Skeletal
unloading
causes
organ-
speciFc changes in immune cell responses,
J. Appl. Physiol.
75
, 2734–2739.
Backup, P.,
Westerlind, K.,
Harris, S.,
Spels-
berg, T., Kline, B., Turner, R. (1994) Space
previous page 991 Encyclopedia of Molecular Cell Biology and Molecular Medicine read online next page 993 Encyclopedia of Molecular Cell Biology and Molecular Medicine read online Home Toggle text on/off