CHAPTER 3 



TISSUE PREPARATIONS AND GENERAL 

 METABOLISM 



The chapters of the preceding section have summarized data 

 relating to the composition of the brain with respect to phosphates 

 and have illustrated ways in which their quantities and metabolism 

 are affected m vivo under a variety of conditions. Such information 

 has provided the basis for regarding the metabolism of the phos- 

 phates to be intimately linked with the functioning of the brain. 

 The chapters of the present section are concerned with data 

 relating to the changes occurring in vivo but obtained from a more 

 detailed study of brain metabolism in tissue slices, homogenates 

 and particulate preparations. In such preparations the metabolic 

 potential of cerebral tissues can be displayed and detailed examina- 

 tion can be made of the response to different conditions. A 

 detailed discussion of the merits, demerits and experimental 

 arrangements with such preparations is not given here since 

 adequate accounts have already been provided (Elliot, 1955; 

 Mcllwain, 1959). 



Tissue Slices 



Cerebral tissues can be sliced by hand using either a guide 

 (Umbreit et al., 1949) or a recessed plate and a strip of razor blade 

 moistened with an appropriate saline (Mcllwain, 1951), to yield 

 slices approximately 0-35 mm thick. Slices or small sections of 

 tissue may also be chopped into fragments either with scissors or 

 with a mechanical chopper. Mechanically chopped tissue still 

 retains the metabolic characteristics of the intact slice and can be 

 pipetted as a suspension. This technique is particularly useful in 

 dealing with small quantities of tissue excized from different areas 

 of the brain. Although cutting a tissue must damage cellular 

 elements and sever many processes, the actual extent of such 

 damage appears to be remarkably small. Mcllwain (1959) estimates 

 it at not more than 0-2% of the total surface. The slice technique 



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