Atherosclerotic alterations in human carotid observed by scanning electron microscopy.

Atherosclerosis involves all the layers of the artery wall, but the events involving the intimal portion are fundamental to understand the evolution and gravity of lesions. This study shows that scanning microscopy is instrumental for better understanding the physiopathology of this disease

COLLAGEN FIBRIL ULTRASTRUCTURE ALTERS AFTER GLYCANOLYTIC DIGESTION

Fixed fragments of bovine nasal septum cartilage were digested for six hours either with testicular hyaluronidase or streptomyces hyaluronidase or flavobacter chondroitinase ABC, and observed with a transmission electron microscope. Collagen fibril diameters (D) were measured to evaluate the effect of enzymatic digestion on the fibril size. This resulted in an increased frequency (17 % to 47 %) of "thin" fibrils (80 to 32 nm), followed by a decrease (65 % to 31 %) of the frequency of "mid" fibrils (32 to 64 nm). The frequency of "thick" fibrils (over 64 nm) showed a moderate increase (18 % to 22 %). Considering the relationship between fibril diameter, fibril volume and collagen content, the apparently relevant increase in number of the "thin" fibrils corresponds to an alteration of only 4 % of the total collagen. On the other hand the increase of the "thick" fibrils implies a conspicuous alteration of 20 % of the total collagen. The observed fibril rearrangement after digestion may be explained in terms of the wrap of matrix proteoglycans around each fibril. The enzymatic removal of the proteoglycans could make "mid" collagen fibrils free to regress into "thin" as well as to merge together into "thick" fibrils

Morphological aspects of rat metaphyseal cartilage pericellular matrix.

In order to verify whether it is possible to observe morphological evidence of a Ca-P amorphous phase (the first step of Ca-P crystalline deposition), the pericellular area of metaphyseal cartilage was investigated. In the pericellular zone of proliferative, maturation, hypertrophic, degeneration and calcification cartilage, many electron-opaque granules, having a very regular diameter of about 12 nm, disposed in closely-packed chains (chain granules) and increasing in number from the proliferation to the calcification zone, are evident. These chain granules, which are closely connected with proteoglycans, disappear after decalcification and are spatially related to ALPase and ATPase activities. They may be the morphological reflection of the Ca-P amorphous phase