5 Basal, 5 Vivarium, 5 Synchronous,5 Tail-Suspended

Cosmos 2044 Russian Hardware Suite

Experiments flown on Cosmos 1887 were complicated by unexpected postflight processing delays. To differentiate between flight response with minimal recov- ery time and flight response with extended recovery superimposed, this experi- ment was repeated with the addition of a tail-suspended model as a control group. Data from this study are difficult to compare with that from Cosmos 1887 due to a 25-day age difference; the larger bones of these animals agree with the older age of the rats.

Bone area and perimeter were measured at the tibiofibular junction of space-flown and ground control rats. Bone vascularity and bone cells within the tibial diaphy- sis, and collagen fibrils in the tendons of the foot were studied at the light and electron microscope level. The portion of the tibial shaft immediately proximal to the tibiofibular junction was sawed into 50 µm cross-sections, mounted on slides, and exposed to incident and polarized light.

Visual observations of tibial cross-sections under brightfield or polarized light did not show any obvious differences. Likewise, area and periosteal perimeter meas- urements showed no significant differences. The lack of any increase in bone mass during the flight period indicates that animals were adults; thus bone mass was not accumulating rapidly during the flight period. Larger, adult rats may require a longer flight period to demonstrate bone changes, particularly in cortical bone since the skeleton is turning over more slowly.

Morey-Holton, E.R.: Gravity and Skeletal Growth: I. Gravity and Skeletal Growth. Final Reports of the U.S. Experiments Flown on the Soviet Biosatellite Cosmos 2044. Vol. 1. J.P. Connolly, R.E. Grindeland, and R.W. Ballard, eds., NASA TM-108802, 1994, pp. 189-192.

¥ = publication of related ground-based study