SECTION IX. MICROSCOPIE ELECTRONIQUE 



THE USE OF THE ELECTRON MICROSCOPE 



AS A TOOL FOR THE INVESTIGATIONS 



OF PROBLEMS IN CYTOCHEMISTRY* 



R. J. BARRNETT and L. W. TIGE** 



From the Department of Anatomy 

 Yale University School of Medicine 

 New Haven 11, Connecticut, U.S. A. 



Although each of the fields of histochemistry, cytochemistry and électron 

 microscopy hâve their individual requirements, compromises can be made 

 so that thèse fields may be combined and information obtained relating 

 fine structure with biochemical function. 



When cytochemistry is combined with électron microscopy, it.requires 

 either the isolation and purification of an enzyme or enzyme system or 

 the isolation by centrifugation of a morphologically homogenous popula- 

 tion of a distinguishable particle that contain an enzyme system to be 

 investigated. However, in each of thèse cases the isolated material 

 must be identified with électron microscopy and related to similar struc- 

 tures occurring in the intact cells from which the isolated material was 

 obtained. In addition, the pellets obtained by homogenization and centrifu- 

 gation may be treated as tissues and stained with histochemical techni- 

 ques and further prepared and examined with électron microscopy. Thèse 

 results may be compared with those of biochemical analysis of the enzyme 

 content of the pellets obtained, and with électron microscopy of histo- 

 chemically treated intact blocks of the same tissue. 



When enzyme histochemistry is combined with électron microscopy, 

 a variety of methodological approaches may be utilized in which the 

 reaction produces either metallic or non-metallic final products.A variety 

 of preparative procédures may be used successfully prior to the histo- 

 chemical tests, the simplest of which utilizes fresh tissue for in vivo 

 or in vitro experiments. The histochemical incubations must be carried 

 out in a manner to assure cytological localization of the final product 

 and therefore may be classified as cytochemical. This can be largely 

 accomplished by protection of tissue fine structure from damage and by 

 assuring that the rate of production of the products of enzymatic activity 

 from the substrate does not exceed the local concentration of the reagent 

 at the enzymatic site. 



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