Elastic fibres ageing

Aortic samples, free of atherosclerotic lesions, were obtained from haemodialysis patients with end-stage renal disease and from age-matched controls.437 The media, but not the intima, proved positive immunohistochemically for pentosidine, which was observed along and between elastic fibres. In both groups, pentosidine-linked fluorescence was higher in elastin than in collagen, and the HPLC level of pentosidine was higher in the elastin from patients than in that from the controls. 

Elastin shows a distinct increase with age (Blu-MENTHAL et al. 1964). Amino acid composition of elastins isolated from human pidmonary connective tissue by alkahne digestion demonstrated an increase in glutamic and aspartic acids (Fitzpatrick and Hospelhorn 1962). Within skin elastic fibres, starting of the fourth decade of hfe, electron dense materials accumidate in an age-dependent manner (Pasquali-Ronchetti and Baccarani-CoNTRi 1997). In very old subjects, these materials seem to have disappeared, leaving behind holes, which give to the fibre a cribriform appearance. 

In view of the presence of the special ITZ microstructure several models were developed, assuming a three phase material bulk, ITZ and fibre. In these models specific characteristics (i.e. modulus of elasticity) were assigned to the ITZ. Li et a/ [75] calculated a parameter related to the stiffness of the ITZ to resolve its value for different systems. Mobasher and Li [76] extended a fracture mechanics model to describe the pull-out curves in terms of adhesional and frictional bond, stiffness of the interface and interface toughness. They demonstrated that all of these parameters influence the pull-out behaviour, and their change with age could account for the variation in the pull-out behaviour, as discussed further in Chapter 5. 

Petrification of the fibre apparently increased its strength and rigidity, and led to the increase in strength and modulus of elasticity shown in Table 11.9, for natural ageing and accelerated ageing in CO2. The effect of increased rigidity, combined... 

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