6 Simulated Flight Control

Research Animal Holding Facility (RAHF); RAHF Rodent Cage Modules

Ultrastructural studies of epiphyseal plates from young rats flown aboard Cosmos 1129 showed that production and mineralization of matrix vesicles were delayed in flight rats. Also, the matrix of metaphyseal trabeculae contained fewer collagen fibers than did the matrix of ground controls, and the collagen was less mature as shown by smaller fiber size and lack of banding. A comprehensive analysis of plate and zone height was not carried out but no apparent difference was seen in height of zones or numbers of cells per zone. This study was to determine if differences in bone matrix formation could be observed after seven days in microgravity.

Proximal tibial epiphyseal plates were dissected from right tibias of six flight and six control rats and prepared for microprobe analysis using a freeze substitution method. Measurements of matrix composition were made in longitudinal septi of each of the four zones: resting, proliferative, hypertrophic, and calcifying. Na, Mg, P, Ca, and K distributions were among the parameters measured. Portions of these plates were also analyzed extensively by light and electron microscopy to detect differences in height and cell number per plate and zone, as well as ultra- structure of collagens, proteoglycan granule size and number per area, and matrix vesicle distribution.

In control plates, all zones had high levels of Na, and in unmineralized regions, low levels of Mg, P, and Ca. K and S levels were high and increased from the proliferative to the calcifying zones. The level of P rose in the mineralized regions of the matrix and Ca/P ratios ranged from 1.2-1.4. In contrast, flight animals had very low Na and K values; Mg levels were unaffected. S levels were less than half of control values, and Ca values were less in both unmineralized and mineralized regions, although the Ca/P ratio was similar to that of controls. These data indicate that even a short space flight can alter bone mineralization, and that the primary defect is at the level of initial matrix production. Data is consistent with other flight studies, and in contrast to the increased matrix for- mation seen in studies of embryonic limbs centrifuged in vitro. Less matrix formation is also consistent with analyses of growth plate height and the hypo- thesis that decreased gravity causes decreased differentiation.

Duke, P.J. and D. Montufar-Solis: Proteogrlycan Granules in Growth Plates of Spacelab-3 Rats. Chemistry and Biology of Mineralized Tissues, Proceedings of the Third International Conference on the Chemistry and Biology of Mineralized Tissues, Chatham, Mass., October 16-21, 1988, M.J. Glimcher and J.B. Lian, eds. Gordon and Breach, 1989, p. 836.

Duke, P.J. and D. Montufar-Solis: Spaceflight Induced Changes in Rat Growth Plates. Bone and Mineral Research, vol. 4, no. 1, 1989, p. S410.

Duke, P.J. et al.: Growth and Differentiation of Mammalian Embryonic Tissue Exposed to Hypergravity In Vivo and In Vitro. Physiologist, supl., vol. 28, no. 6, 1985, pp. S77-S78.¥

Duke, P.J. et al.: Microprobe Analysis of Epiphyseal Plates from Spacelab 3 Rats. Physiologist, supl., vol. 28, no. 6, 1985, pp. S217-S218.

Duke, P.J. et al.: Microprobe Analysis of Epiphyseal Plates from Spacelab 3 Rats. Abstract S-217. Proceedings of the Seventh Annual Meeting on the IUPS Commission on Gravitational Physiology, Niagara Falls, N.Y., October 13-18, 1985.

Duke, P.J. et al.: Microprobe Analysis of Epiphyseal Plates from Spacelab 3 Rats. Abstract 83.19. 36th Annual Fall Meeting of the American Physiological Society, Buffalo, N.Y., October 13-18, 1985, Physiologist, vol. 28, no. 4, 1985, p. 378

Montufar-Solis, D. and P.J. Duke: Altered Distribution of Matrix Vesicles Sizes in Spacelab-3 Rats. American Society for Gravitational and Space Biology (ASGSB) Bulletin, vol. 3, no. 1, 1989, p. 113.

Montufar-Solis, D. and P.J. Duke: Changes in Rat Growth Plates Due to Strain, Diet and Housing. American Society for Gravitational and Space Biology (ASGSB) Bulletin, vol. 3, no. 1, 1989, p. 114.¥

Montufar-Solis, D. and P.J. Duke: Effect of Simulated Spaceflight on Tibial and Epiphyseal Plates. American Society for Gravitational and Space Biology (ASGSB) Bulletin, vol. 1, 1988, p. 34.¥

Montufar-Solis, D. and P.J. Duke: Effect of Strain, Diet and Housing on Rat Growth Plates: a Cosmos '87-Spacelab-3 Comparison. Physiologist, supl., vol. 34, no. 1, 1991, pp. S183-S184.

¥ = publication of related ground-based study