50 STUDIES ON ALKALINE PHOSPHATASE 



is quite possible, for example, that the detailed distribution of 

 phosphatase on the chromosomes is not an accurate representa- 

 tion of the enzyme distribution in vivo. With the techniques 

 involving azo dyes, less accuracy is possible. It is quite pos- 

 sible to say whether the nucleus of a mammalian somatic cell 

 has phosphatase or not. But it is not possible with the azo-dye 

 techniques to determine the details of the distribution of phos- 

 phatase within a given nucleus of this size. Neumann, and 

 Martin and Jacoby, have expressed considerable pessimism 

 about some of these techniques. This pessimism, however, is 

 based partly upon results obtained with techniques which to me 

 appear to be defective in certain essentials, and particularly 

 upon failure to use adequate methods of studying diffusion 

 artefacts, so as to make a quantitative estimate of the extent 

 of diffusion. 



Alkaline Phosphatases of Cell Nuclei 



Studies have been made by many investigators on mass prep- 

 arations of cell nuclei prepared by various methods. However, 

 as was pointed out in the first chapter of this book, there are 

 two major difficulties which make it impossible at the present 

 time to evaluate studies on mass preparations of cell compo- 

 nents prepared by maceration techniques. These difficulties are 

 that substances diffuse in and out of nuclei fairly readily when 

 nuclei are suspended in aqueous solutions, and that in addition 

 to this the nuclei prepared from most organs cannot consist com- 

 pletely of nuclei from one cell type only. In view of these 

 difficulties, the only method which at present can provide reli- 

 able information as to whether there is alkaline phosphatase 

 in cell nuclei is the cytochemical method. A typical result is 

 that obtained with rat kidney, shown in Plate IV, Fig. A. 

 There is a certain amount of phosphatase in the nuclei of the 

 kidney tubule cells, particularly in the nuclei of the cells of the 

 proximal tubules. There is a very much greater amount of 

 phosphatase present in the brush border of the proximal tubule 

 cells. It is clearly quite possible that the phosphatase in the 

 nuclei may not be intrinsic phosphatase of the nuclei, but may 

 have reached the nuclei by diffusion from the brush-border 

 regions. It is, therefore, necessary to examine this material by 



