ISOLATION OF INTACT COLLAGEN FIBRILS FROM HEALING LIGAMENT

The inability to isolate intact collagen fibrils has limited the study of their growth and structure. Although intact fibrils have been isol ated from echinoderms and from embryonic chick tissues, no method has previously succeeded in isolating intact collagen fibrils from a postf oetal vertebrate tissue. Having previously observed that gentamicin we akens rat tail tendon, we hypothesized that gentamicin may weaken inte rfibrillar bonds and that intact collagen fibrils might be isolated fr om tissue treated with gentamicin. In this study medial collateral kne e ligaments of Sprague Dawley rats were transected and then harvested 24, 48 or 96 h postoperatively. These specimens were placed in gentami cin or phosphate-buffered saline for 72 h, vortexed for 1 h, incubated in gentamicin for an additional 24 h, and vortexed again for 1 h. Neg atively stained specimens were examined with a transmission electron m icroscope. The phosphate-buffered saline specimens yielded only broken fibrils. The,gentamicin specimens yielded both broken and intact fibr ils. The latter had tapering ends and consisted of molecules orientate d such that their amino termini pointed toward the tip and their carbo xy termini pointed toward a short central region where the molecular p olarity reversed.