in seven arbitrarily selected groups of 3- , 5- , 9- , 11- , 15- , and 21-week and one-year-old spontaneously hypertensive rats ( shr ) ( f25-26 ) , qualitative as well as quantitative light and electron microscope studies were conducted on the myocardium in the left ventricular papillary muscle and lateral wall .
C0027061
myocardium
C0030352
papillary muscle