General Discussion 107 



Tunbridge: I tiike you up on two points there. Collagen aeted on 

 chemically or enzymatically, for example with pepsin, will then take up 

 stains which are said to be characteristic for elastin, so I think that 

 classifying tissue as elastin on staining data alone is a generalization we 

 should use with care. Then there is the question of enzyme digestion. 

 The elastase which you mentioned, which Balo and Banga first isolated, 

 definitely seems to have a dual function, at least one component appear- 

 ing to be more in the nature of a mucase than anything else. The point 

 about pH I want to raise particularly. Owing to the retention of 

 sulphated polysaccharide in our elastin preparations and its subsequent 

 release after elastase action there is a marked lowering in pH, the opti- 

 mum effect being at two pH values, namely 8-7 and 7-8. The aorta 

 acts very differently from ligamentum nuchae, which as you are aware 

 has a much simpler form of elastic tissue, a smaller percentage of 

 collagen interwoven with the elastic fibres, and what is more important 

 a lower polysaccharide content. Therefore in the absence of adequate 

 buffering you get far more acid liberated when you act on aortic media 

 than you have from ligamentum nuchae, this may carry the pH from the 

 optimum of one enzyme component (8 • 7) to that of the other (7-8) with 

 a consequent alteration in the nature of the liberated products. In 

 adequately buffered systems you find your elastase first liberates poly- 

 saccharide and acid in a combination which is very closely allied to that 

 of chondroitin sulphuric acid. You then get an action which is proteo- 

 lytic in nature, and so far no elastase has been purified to such a degree 

 as to be without this; its first action therefore is on the carbohydrate and 

 secondly there is a delayed action on the protein itself. 



Lansing: You mean in England it hasn't been purified; it has in the 

 States. 



Tunbridge: Well, we have been very careful, and Banga agrees with us 

 on this entirely, that once you get rid of the polysaccharide, trypsin then 

 has a most dramatic action. 



Lansing: I would like to reaffirm that this is material which morpho- 

 logically looks like elastic tissue, tinctorially shows all the reactions of 

 elastic tissue, and is entirely dissolved by elastase. These are the chief 

 criteria we have for defining elastic tissue. It appears that there is 

 presumptive evidence that this is elastic tissue. 



Comfort: I wonder if I might ask the combatants whether this material 

 in the skin possesses structure under the electron microscope? 



Lansing: One slide I showed [not published] was of a section serially 

 adjacent to a somewhat thicker specimen which was viewed in the phase 

 contrast microscope to make sure we were dealing with the right area 

 of senile elastosis. 



Comfort: And that is the material which you describe as elastin and 

 Prof. Tunbridge as modified collagen? 



Lansing: Yes. 



Tunbridge: I think under the electron microscope this so-called 

 elastin-like substance has a high percentage of broken fibres, an enormous 

 amoimt of debris and amorphous material, and only when you have 

 cleared it by enzymatic action with trypsin do you find a few normal 



