The purpose of this project was to test the hypothesis that the generalized,
whole- body decrease in synthetic activity due to microgravity conditions encountered
during space flight would be demonstrable in cells and tissue characterized
by a rapid rate of turnover. Jejunal mucosal cells were chosen as a model since
these cells are among the most proliferative in the body.
Sections 1 µm thick were cut from each of the five sample segments from
each of the three jejunal regions per animal and stained with toluidine blue.
To accu- rately determine the mitotic index for each respective region, at least
2,000 cells per region per animal were examined. To determine villus length
and crypt depth, at least twenty villi and crypts were measured per region per
animal using a computerized image analysis system coupled to a bright field
microscope equipped with a 4x objective and video camera. All data were statistically
analyzed by analysis of variance and differences between means were detected.
The percentage of mitotic cells present on the crypts of Lieberkuhn in the proxi-
mal, middle, and distal regions of flight rats did not differ significantly
from con- trols. Although the ability of jejunal cells to divide by mitosis
was not impaired in the flight group, there was, however, a reduction in the
length of villi and depth of crypts. Since villi in flight rats were lined by
normal mucosal cells, the con- comitant reduction in villi height and crypt
depth probably reflects changes (e.g. shrinkage) in the connective tissue core
of villi and is not due to an impairment in the migration of newly proliferated
cells needed to replace those desquamated.
Phillips, R.W. et al.: Effects of Spaceflight on the Proliferation of Jejunal
Mucosal Cells. Final Reports of the U.S. Experiments Flown on the Soviet Biosatellite
Cosmos 2044. Vol. 2. J.P. Connolly, R.E. Grindeland, and R.W. Ballard, eds.,
NASA TM-108802, 1994, pp. 25-32.
Sawyer, H.R. et al.: Proliferation of Jejunal Mucosal Cells in Rats Flown in
Space. Journal of Applied Physiology, supl., vol. 73, no. 2, 1992, pp. S148-S150.
¥ = publication of related ground-based study