STAINING, PRACTICAL AND THEORETICAL 



6. Immerse in cedarwood oil for clearing, for five minutes. 



7. Mount in D.P.X. or other synthetic neutral mountant. 



Results: 



Chromatin: clear green. Nucleoli: bright red. RNA of cyto- 

 plasm: red. Eosinophil granules and osteoid: red. 



Notes: 



[a) The quality of the pyronin Y, as the author demonstrates 

 in his paper, is a very important factor in the success of this 

 method. Only two brands of the dye were found satisfactory, 

 and these were from British sources. 



{b) It is also stated in the original paper that pyronin Y of 

 American and of British manufacture appears to be different dyes. 

 Differences were noted not only in the staining characteristics, 

 such as slightly greater staining of protein by the American dye, 

 complete elimination of the British but not the American by water, 

 differentiation of the British but not the American by normal 

 butyl alcohol, but also solubility in chloroform. 



(c) Staining with pyronins alone indicated that the British 

 samples of pyronin Y produced less staining of structures known 

 to be devoid of nucleic acid than did any of the other pyronins 

 studied. There appeared to be no staining of protein. Osteoid 

 and eosinophil granules were the only nucleic acid-free structures 

 observed by Kurnick to stain in mammalian tissues. Both 

 polymerized and depolymerized DNA were stained when pyronin 

 was used alone. However, in the methyl green-pyronin mixture 

 (solution C, above), the methyl green competed successfully for 

 the polymerized DNA. 



{d) Kurnick shows that it is possible, in the animal tissues 

 stained with the mixture (solution C, above), to interpret green 

 staining as being due to polymerized DNA (except cartilage 

 matrix); and red staining due to RNA (except partially de- 

 polymerized DNA, osteoid, and eosinophilic granules). 



{e) As previously reported by the author (Kurnick, 1952), 

 tertiary butyl alcohol is not satisfactory for differentiation. 



(/) For more detailed information and colour plates, readers 

 should consult the original paper. 



Reference: Kurnick, N. B. (1955). 



298 



