Collagen fibrils from various rapidly frozen mammalian tissues were examined by the technique of straightforward freeze-fracture, freeze-fracture followed by sublimation and surface sublimation technique. Fixed and non-fixed specimens cryoprotected either with glycerol or dimethylsulphoxide (DMSO), as well as non-cryoprotected ones, were examined. Fibrils were observed either with a banded pattern or as helically twisted strands, and in some cases as a combination of both arrangements. Minimally processed fibrils presented a clearcut banded appearance, while the helical pattern seemed to be associated with the presence of the cryoprotectant, glycerol and DMSO. It is concluded that the banded appearance is in all probability a normal feature of the collagen fibrils in vivo, and that the helical pattern is an abnormal feature resulting from various pretreatments of tissue.

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