THE MAST-CELL GRANULE 



plastids (Gicklhorn, 1932) is outstanding. There is now abundant evidence 

 (cf. Frey Wyssling, 1948) that such structures are composed mainly of bimolecular 

 leaflets of phospholipid, often cross-linked by divalent calcium ions, and that 

 mild saponification by alkali is sufficient to admit water between the leaflets 

 and so produce visible swelling and the emergence of strange, worm-like tubes 

 as the process of hydration travels through the system. Nils Berg (1951) using 

 benzpyrene-cafTein as a 'stain' followed by examination of the preparation in 

 ultra-violet light for the detection of fluorescent lipoids has shown that both 

 nerve sheaths and mast-cell granules 'stain' positively for phospholipids which, 

 in the natural state of the tissues are either so finely dispersed or so tightly 

 bound to protein that they fail to stain with conventional methods. Hedbom 

 and Snellman (1955) isolated the mast granules from the cells in ox liver capsule 

 and subjected them to various analytical procedures. They state that the lipid 

 fraction comprised no less than 23 -9 per cent of the total dry weight and that 

 (p. 154) 'the main part of the lipid fraction was not soluble in acetone, which 

 indicated a high percentage of lecithin'. It is, of course, the lecithin which is 

 believed to provide the physical basis for the hydration of the myelin in nerve 

 sheaths and plant cells. On the other hand, as we have observed earlier in 

 a study of the effects of compound 48 80 on the rat, the nerve sheaths appear to 

 be among the tissues in the skin which are not affected by compound 48/80: even 

 the mast cells within the nerve sheaths remain intact. A more subtle mechanism 

 is required to explain how histamine-release is 'triggered' in the mast cell. 



Seeking another component of the mast granule which might respond 

 either to the effects of a histamine-liberator, or even to the released histamine 

 itself, my attention was caught by a report of some physico-chemical experi- 

 ments on artificial surface films, carried out by Dr. R. Hirt in Bern. Briefly, 

 Hirt and his colleagues (1952) were able to show by a tensiometric technique, 



O 



II 

 ii 



that a primary (but not a secondary), phosphatide of the type R/ — O — P — OH 



I 

 OH 



reacts specifically with histamine, as is shown by a sudden and decisive drop 

 in the surface tension of the film at a liquid-liquid interface when histamine 

 is applied. Further, the film can be protected by pre-treatment with an 

 antihistamine drug. It will be recalled that I found that the injection of 

 mepyramine into a rat shielded its mast cells against the disruptive action of 

 stilbamidine, despite the fact that the diamidine still reached the cells, as 

 shown by their vivid fluorescence in ultra-violet light. 



A preliminary investigation has therefore been started in co-operation with 

 Dr. R. M. C. Dawson of Cambridge who has made a detailed study of the 



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