Effects of viral and mycoplasma infections on ultrastructure and enzyme activities in human skeletal muscle.

The effect on skeletal muscle of acute viral and mycoplasma infections in thirteen men of ages ranging between 20-42 years has been studied. Comparisons are made with eight healthy men in the age group 22-29 years who were confined to bed for periods of time of lengths similar to the confinement to bed of the patients. Muscle samples were taken from the thigh. Glyceraldehyde-3-phosphate (triosephosphate) dehydrogenase (TPD), lactate dehydrogenase (LDH), citrate synthetase (CS) and cytochrome oxidase (cytox) activities were measured and the ultrastructure of the muscle specimens was studied by electron microscopy. Immobilization of the healthy persons induced decreased activities of CS, but those of TPD, LDH and cytox remained unaffected. Return to normal life restored the CS activity. The activities of the four enzymes were lower in the patients than in the healthy subjects after immobilization. During normal life, the activities slowly rose to levels as those seen in the healthy subjects. In connection with the acute disease, focal ultrastructural changes within the muscle were found. The changes were similar to those reported to occur in other, more specific muscle diseases.