No abstract

The results presented in this paper show that collagen fibers can be clearly distinguished from reticular fibers using the picrosirius-polarization method. A morphologic and morphometric study of these two types of fibers with electron microscopy shows that reticular fibers are characterized by the smaller diameter of their fibrillar components and the higher content of interfibrillar material, resulting in a loose arrangement of the fibrils. The evidences presented suggest that the amorphous matrix in which fibrils are embedded is responsible for the silver impregnation of reticular fibers. Our results show that the matrix of reticular fibers is characteristically rich in heparitin sulfate, and that the glycosaminoglycans present show a high interaction with the fibrillar component of these fibers.

The collagen arrangement of different cartilages of several mammals was studied by the Picrosirius-polarization method applied to tissue sections whose proteoglycans had been previously removed by enzymatic digestion. This procedure not only increases collagen birefringency but it also enhances the optical resolution, permitting an accurate observation of the collagen disposition in this tissue. Our observations led to the conclusion that in the material studied at least five general patterns of collagen arrangement occur. When studied with the aid of electron microscopy, different cartilages showed variable values in their collagen fibril diameter. The results obtained suggest a greater variability in the collagen fibril diameters of those cartilages submitted to strong pressures.

Arteries of representative species from the main vertebrate classes were studied by a method that quantitates collagen-proteoglycans interaction, by the histochemical Picro-sirius polarization method and by electron microscopy. The collagen of the adventitia presents features which are characteristic of collagen type I. The collagen in the tunica media revealed histochemical and ultrastructural aspects which are typical of collagen type III. As these results were consistently observed in all species studied, they suggest the presence of a general structural pattern of collagen distribution in vertebrate arteries.