The effect of undernutrition in the early postnatal period on skeletal muscle tissue

Guinea-pigs were undernourished from birth by first, cross-fostering in groups of six (in pairs for control animals) and then by feeding a diet of 60% of ad lib. intake from 2 to 6 weeks. The changing characteristics of muscle fibre types in the biceps brachii and soleus muscles were monitored by histochemistry. Undernutrition appeared to delay maturation of muscle fibres. Fibre cross-sectioned area was reduced in all fibres of the 60% of ad lib. intake group. Fibres of the biceps brachii were more affected than those of the soleus. Fibre area vulnerability was partly associated with a high relative growth rate in biceps brachii at this time. Total protein content in the semitendinosus muscle was depressed in the undernourished group compared with the control group. DNA concentrations were initially higher in the control group but decreased in both groups to similar levels by 6 weeks. RNA concentration increased up to 5 weeks in the control group and then decreased, but decreased after 2 weeks in the undernourished group.