eonardi L

Collagen fibril arrangement and size distribution in monkey oral mucosa

Collagen fibre organisation and fibril size were studied in the buccal gingival and hard palate mucosa of Macacus rhesus monkey. Light and electron microscopy analysis showed connective papillae exhibiting a similar inner structure in the different areas examined, but varying in distribution, shape and size. Moving from the deep to surface layers of the buccal gingival mucosa (free and attached portions), large collagen fibril bundles became smaller and progressively more wavy with decreasing collagen fibril diameter. This gradual diameter decrease did not occur in the hard palate mucosa (free portion, rugae and interrugal regions) where the fibril diameter remained constant. A link between collagen fibril diameter and mechanical function is discussed.

Light microscopy, electron microscopy, and X-ray diffraction analysis of glycerinated collagen fibers.

Light microscopy, transmission electron microscopy (freeze-fracture replicas and thin sections), and X-ray diffraction techniques were used to investigate the structure of rat tail tendon collagen fibers subjected to one of the following treatments: water, phosphate buffer, glutaraldehyde, glutaraldehyde followed by glycerol, glycerol, and glycerol followed by phosphate buffer. As seen by light microscopy, only treatment with glycerol induces a remarkable swelling of the native (untreated) collagen specimens. Replicas and thin sections show that this swelling is due to an expansion of the interfibrillar space, and to a dissociation of the collagen fibrils into microfibrils. X-Ray diffraction analysis reveals great disorder in the glycerol-swollen collagen fibers. However, this does not appreciably involve the microfibrillar and molecular structure. Light and electron microscopy as well as X-ray diffraction techniques show that the collagen fiber swelling induced by glycerol is an almost completely reversible process.

THE BANDING PATTERN OF RAT TAIL TENDON FREEZE-ETCHED COLLAGEN FIBRILS?

Banding patterns of freeze-etched and replicated rat tail tendon collagen fibrils were studied. Better banding definition was obtained by freezing the samples without using a cryoprotectant and by prolonging etching. Under these conditions, the banding pattern was characterized by a sequence of elevated and depressed segments with a D-period of 65 nm, by two ridges at the margins of the elevations and by a third ridge at an intermediate point in the depressions. A comparison between replicas and isolated negatively stained collagen fibril micrographs as well as densitometric determinations have allowed interpretation of the elevations and depressions as overlap and gap zones and of the three ridges as the main bands with higher molecular density. Estimates, carried out on densitometric diagrams obtained from replicas, gave values which may represent a new parameter in the study of collagen banding and led to the calculation of a 0.55 D long gap zone and of a 0.45 D long overlap zone.