Discussion on Animal Tissue Respiration 



C. A. ELVEHJEM, University of Wisconsin, Chairman 



FACTORS AFFECTING THE PREPARATION OF TISSUE FOR 

 METABOLIC STUDIES 



EPHRAIM SHORR 

 Cornell Medical College, New York 



My comments will be restricted to certain difficulties encountered 

 in the preparation of tissue for in vitro studies of metabolism. They 

 touch on the various methods of preparing tissue, such as the slice 

 and mince method and on the influence of certain chemical changes 

 that are inevitable during the handling of the tissue prior to the 

 experimental run. 



The Slice Method— Most workers use the limiting formula of War- 

 burg without testing the permissible thickness of the specific tissue 

 with which they are working. The general tendency is to get a slice 

 as thin as possible. Histological studies, as well as comparative 

 studies of the rate of respiration, show that this is not altogether wise. 

 The superficial layers can be shown to undergo degeneration to 

 variable depth. The thinner the slice the larger is the proportion of 

 damaged tissue. This is particularly important for tissues such as 

 cardiac muscle, where a whole large cell unit at the surface must 

 inevitably undergo degeneration. Thicker slices can be shown to 

 have a higher rate of respiration than very thin ones. The maximum 

 thickness which is permissible is therefore better. Not infrequently 

 thicknesses which exceed the formula behave very well. This points 

 to the possibility that there may be mechanisms for maintaining 

 oxygen pressure other than the gradient set up by the tension in the 

 solution— perhaps the iron-carrying compounds of the tissue, which 

 serve as a storehouse. The slice method is of course best adapted to 

 parenchymatous organs, least well to muscle. Unfortunately cardiac 

 muscle does not lend itself to dissection as does skeletal. However, 

 the individual muscle cells are much shorter than skeletal muscle 

 cells, hence the degeneration occurring at the surface is not extensive 

 enough to do much harm. As regards the brain, there seems to be 

 little evidence that the more convenient method of chopping the 

 tissue with a razor is less good than slicing. 



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