90 Albert I. Lansing 



when these two lesions co-exist the accumulation of choles- 

 terol in the intima occurs after the elastic tissue of the 

 underlying media has broken down. 



Whether or not this formal hypothesis is sound is not too 

 important. The cardinal point is that in human arterio- 

 sclerosis there is an almost invariable association of medial 

 elastic tissue degeneration with the conspicuous atheromata. 

 The questions are: what relation is there between cholesterol 

 accumulation in the intima and elastic tissue breakdown in 

 the media; and, is there a common factor responsible for the 

 production of both of these lesions? 



It would be excessively repetitious to present once again 

 all of the histological and analytical data which have contri- 

 buted to the development of the point of view of my labora- 

 tory. For the purposes of this discussion it might be more 

 appropriate to make a few points on the chemistry of elastic 

 tissue in relation to age and arteriosclerosis and to attempt 

 to evaluate factors that condition elastic tissue in these two 

 states. Since all of our data depend upon the method of 

 preparation of elastin this procedure will be described before 

 making three points; first, that although elasticity of arteries 

 decreases with age, there is no apparent loss of elastin; 

 second, that elastin extractable from old human aortas has 

 an amino acid composition distinct from that of young elastic 

 tissue; and third, that elastic tissue degeneration as measured 

 by calcification thereof occurs as a function of age. 



Preparation of elastic tissue 



Elastin may be prepared in a reproducible form and with 

 several objective measures of purity. A slight modification 

 of the method of Lowry, Gilligan and Katersky (1941) was 

 applied to the tunica media of fresh aortas. The tissue was 

 refluxed in methanol or ethanol for one hour and in acetone 

 for a second hour. This defatted material was then digested 

 at 98° C in • 1 N NaOH and small samples taken off at five 

 minute time intervals for chromatographic, histological, and 

 chemical analyses. 



