CELL-TYPES AND EVIDENCES FOR TRAUMATIC CELL-DEATH IN A PRESSURE-BEARING TENDON OF RANA-CATESBEIANA

Tendon fibrocartilages appear in areas subjected to compressive forces . The bullfrog plantaris longus tendon was shown to be subjected to co mpression and to develop a modified region which differs from fibrocar tilage in many respects. Ultrastructural analyses of the compression r egion of the bullfrog tendon demonstrated the existence of typical fib roblasts in the fibrous areas and large cells with abundant cytoplasm filled with intermediate type filaments. This large cell type has orga nelles restricted to a small perinuclear area or dispersed in the netw ork of intermediate type filaments. Other cells were also found and ex hibited less abundant deposition of intermediate filaments, showing an organization intermediate between Fibroblasts and typical cells from the compression region. These intermediate type cells are closely asso ciated with collagen bundles while the large cells seemed to have no c onnection with the fibrous components, but are immersed in a glycosami noglycan-rich extracellular matrix. Aspects of cell death in associati on with extracellular matrix disruption were observed in some instance s and it is likely that these are associated with traumatic stimulatio n of the tendon, especially when it is submitted to the sudden and str ong mechanical loading expected to occur during jumping. Since the dam age occurred mainly in cells of the intermediate type, it is assumed t hat accumulating intermediate type filaments is a protective mechanism against compressive forces to which this tendon is subjected.