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Types I and III collagen were identified in four segments of human aorta using pepsin and cyanogen bromide digestion followed by sodium dodecyl sulphate polyacrylamide gel electrophoresis. Collagen is not uniformly distributed in the different segments of the arterial wall. Collagen type I is always the major collagen present. With ageing collagen type III decrease in quantity from the heart to the distal portion of the aorta. Histologically the elastic tissue is more altered in the lower abdominal section of aorta than in the arch. This study allowed a correlation between morphological observations and biochemical changes.

Elastin was prepared from calf ligamentum nuchae with several methods using the following solvents for the extraction of extraneous (non-elastin) proteins : 0.1 N NaOH a t 100 "C, 88 formic acid a t 45 "C, 7001, trichloracetic acid at + 4 "C, 5 M guanidine HCl with a thiol reagent and autoclaving in water. All elastin samples contained small amounts of carbohydrate. Electron microscopy showed the presence in all samples of electron-translucent lamellae and osmiophilic uranyl-lead stainable "microfibrillar" eIements.The osmiophilic "microfibrils" decreased strongly in the elastin preparations after extractionThese solvents extracted a significant proportion of the hexose content of the elastin samples with only 6--7O/, o f their protein content. Similar results were obtained with chymotrypsin digestion although this enzyme acts less selectively than the above mentioned solvents and degrades elastin also.When 1Z5I-labelled elastin was used for extraction with 8 M urea-0.1 M mercaptoethanol the extracted glycopeptides had a significantly higher specific activity than the residual elastin. These results suggest that the microfibrillar elements are derived from or are identical with the structural glycoproteins which were extracted from elastin-rich tissues by identical proceduresThe presence of glycoprotein in varying proportions in purified elastin preparations can explain the variation of its amino acid content (ratio of polar to non-polar amino acids) with age or in certain pathological conditions (atheromatosis, emphysema) and some of its immsnochemical properties (cross reactions with structural glycoproteins). r121.Electron microscopic stiidies performed by several investigators on elastic fibers showed the presence of essentially two distinct types of structural elements : a homogenous, electron-transparent material, and a "microfibrillar" component, stainable with uranyl acetate and lead [I-51. Our recent studies indicated a chemical and immunological heterogeneity of purified elastin preparations [ 17,181 ; the structural glycoprotein fractions of aorta gave cross reactions with kappaelastin prepared from purified aorta elastin [18]. These results suggested the presence of common antigenic determinants in structural glycoprotein and elastin preparations. Therefore it appeared essential to

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With ageing there are progressive modifications in the connective tissue of the dermis. In ten young subjects the collagenous bundles are thick and the fibroblasts are active cells in close contact with collagen fascicles. In ten elderly subjects collagen fibres are fragmented and the fibroblasts are quiescent, without any contact with collagen. In ageing the most important lesion is the destruction of the relationship between fibroblasts and interstitial matrix. A role for fibronectin in this adhesion is suggested: in old subjects the papillary network of fibronectin is poorly developed. Furthermore, in the fibroblast we can see architectural changes in the cytoskeleton; this modification breaks up the cytoskeleton - plasma membrane - fibronectin unit and explains the secretory and metabolic changes observed in ageing, the dysfunction of the cell-interstitial matrix unit, and also the structural changes.