alterations of hydrogen ion ( h+ ) concentration in the myocardium of 60 cats were determined before release of coronary ligation of 30 , 45 , 60 , 90 or 180 minutes ' duration , or 5 , 30 and 90 minutes after release of the occlusion , by pressing ph indicator paper on unfixed frozen heart sections .
C0027061
myocardium
C0018787
heart