Muscle involvement during postnatal protein calorie malnutrition and recovery in rhesus monkeys

The effect of protein calorie malnutrition (PCM) and, thereafter, nutritional rehabilitation on neuromuscular dysfunction was evaluated electromyographically, histopathologically and biochemically in 24 young, growing, healthy rhesus monkeys. There were 2 control and 2 PCM groups with 6 animals in each group. Animals of one control and one PCM group were killed at 10-12 weeks and those of the second PCM group were rehabilitated and killed together with the second control group at 20-22 weeks. The animals with PCM demonstrated irritability, muscular wasting, weight loss and reduced physical activity. The electromyographic findings showed a myopathic pattern revealed by significant reduction in motor unit potential duration and amplitude, and amplitude of interference pattern at maximum effort. The histopathological abnormalities were non-specific and consisted of rare obliterations of cross striations and streaming fibrillar appearance, mild increase in epimysial and perimysial tissue and 29-34% reduction in fibre size. A statistically significant reduction in motor nerve conduction velocity of median, ulnar, common peroneal and tibial nerves was found. The muscle Na and K were evaluated in all groups of animals. Muscle K content was reduced and Na concentration was augmented following PCM. The change in concentration of electrolytes within the fibres and reduction in the diameter of muscle fibres could be related to the observed functional alterations. These changes returned to normal in rehabilitated group.