1970 Volume 7 Issue 6 Pages 351-364
Comparative micromeasuring studies have been made on the senile changes of various kinds of muscle tissues.
Albino rats of the Wistar and Donryu strains of 3, 6, 12 and 24 months of age were used in this experiment, and M. tibialis anterior and M. psoas major were used as skeletal muscle and the muscle layer of the aorta as smooth muscle. Differentiation between white and red muscle fibers of the skeletal muscle was made with Sudan black B staining.
In rats of 24 months of age, the skeletal muscles were decreased in weight, and the weight loss of the skeletal muscle was far more marked than that of the body weight of the animals.
The decrease in weight of the skeletal muscle in the aged rats was observed to be due to decrease in number and in volume of the muscle fibers; in case of the white fibers, the senile decrease was due mainly to a decrease in volume and not to decrease in number, on the contrary, in case of the senile change of the red fibers, there was noticed a marked decrease in number of the fiber without decrease in volume.
These differences in the decrease in number and volume of the two kinds of muscle fibers were statistically significant.
In the muscle layer of the aorta of aged rats, the muscle cells were not atrophic but rather hypertrophic and showed no decrease in number of the cells.
Some discussions have been made on the difference in the process of senile changes of various kinds of muscle cells, with special references to their morphology and function.