CHANGES WITH AGE IN DIFFUSION 



COEFFICIENTS OF SOLUTES FOR HUMAN TISSUE 



MEMBRANES 



J. E. Kirk, m.d., f.a.c.p., and T. J. S. Laursen, m.d., 



Division of Gerontology, Washington University, St. Louis, Mo. 



The determination of diffusion coefficients of solutes for 

 preparations of tissue membranes constitutes a valuable 

 method of measuring the permeability of the tissue. In the 

 field of gerontolgy this technique may be applied to the 

 investigation of the effect of age on the permeability. In the 

 present communication the results of diffusion coefficient 

 measurements on samples of the human aorta and human 

 tentorium cerebelli are reported. 



Experimental 



Samples of the thoracic aorta and tentorium cerebelli were 

 obtained at the St. Louis City Morgue. Sterile instruments 

 were employed for the removal of the tissues. The adven- 

 titia was stripped off the aorta, after which the intima (with 

 attached subintimal tissue) was separated from the media. 

 A preparation of each layer was then inserted in a sterile 

 diffusion apparatus. The tentorium cerebelli was employed 

 directly for diffusion studies. 



The diffusion coefficient measurements were carried out 

 under sterile conditions by the procedure of Kirk and Johnsen 

 (1951). This method permits determination of diffusion 

 coefficients of both gaseous and non-gaseous solutes under a 

 constant total pressure. 



The details of the assembled diffusion apparatus are shown 

 in Fig. 1. The apparatus consists of two 50 ml. glass syringes; 

 the bottoms of the barrels have been removed and the barrel 



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