VIL DEDUCTIVE METHODS 



In certain instances deductive methods can be applied to obtain 

 histochemical data from macrochemical analyses, i.e., if the total 

 amount of a constituent in a tissue and the amount in the entire 

 extracellular portion is known, one can calculate the amount in the 

 intracellular fraction. This method has been exploited by Lowry 

 (1943) and the principle may be illustrated by one of his examples: 



"As a first approximation, a tissue such as skeletal muscle may be considered 

 to be composed of 5 separate fractions, blood, fat, collagen plus elastin, extra- 

 cellular fluid, and cells. If the amount of the first 4 fractions can be determined, 

 the amount of the remaining intracellular fraction can be calculated. Further- 

 more, if one knows the composition of the blood and extracellular fluid, it be- 

 comes possible to calculate the concentration of a particular substance. A, in 

 the cells by simply (1) measuring the total amount of A, (2) calculating the 

 amount of A in the several extracellular fractions, (3) subtracting the extra- 

 cellular A from the whole, and finally, (4) dividing the net intracellular A by 

 the calculated amount of intracellular fraction. This is similar to the calcula- 

 tion of the concentration of chloride in red cells when the hematocrit and the 

 concentration of chloride in whole blood and serum are known." 



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