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.