The effect of early postnatal protein malnutrition on the development of soleus muscle was investigated in 26 mice (13 males, 13 females). The control group received a balanced diet containing 18% lactalbumin while the protein-malnourished group received protein deficient diet containing 0.5% lactalbumin. The body weight was determined both at 3 weeks (weaning age) and 12 weeks of age. The soleus muscle weight, total number and sizes of muscle fibres were also determined at 12 weeks of age for each mouse. There was considerable retardation of body weight and soleus muscle weight. The smaller soleus muscle mass of protein-malnourished mice resulted from loss of muscle fibres and hypotrophy of the remaining fibres. Permanent retardation of body weight after recovery from early postnatal protein malnutrition may be as a result of loss of muscle fibres during that period.

The effect of oestrogen on muscle development was determined in 8 muscles (biceps brachii, triceps brachii, common digital extensor, soleus, superficial digital flexor, cranial tibialis, gastrocnemius and long digital extensor muscles of sexually immature male and female mice. Each mouse was killed at a mature age of 16 weeks. The muscle development as determined by increase in muscle weight was significantly smaller in muscles of oestrogen-treated male and oestrogen-treated female mice as compared to the muscles of normal male and normal female mice. The muscles of normal male mice were very significantly larger than those of normal female mice. There was, on the other hand, no significant difference between the muscle mass of oestrogen-treated male and oestrogen-treated female mice. This indicated that the smaller muscle mass of normal female mice when compared to normal male mice was connected with inhibitory effect of oestrogen on the muscle development of female mice.

The effect of prenatal exposure to phenobarbital on muscle development was determined in 4 muscles (biceps brachii, triceps brachii, soleus and cranial tibial) of 34 mice (16 males, 18 females) at 12 weeks of age. The control group received unadulterated food ad libitum throughout the period of study. The phenobarbital-exposed group received 3 g of phenobarbital per kilogram of food from gestation day 7 to 18 as the only source of food. Outside this period they received unadulterated food and water ad libitum. Each mouse was killed at 12 weeks of age. The muscle mass of control mice was significantly larger than that of the phenobarbital-exposed group in both sexes. The smaller muscle mass of the phenobarbital-exposed group as observed from the analysis of the soleus muscle was due to a smaller number of muscle fibres being present than in the control group, since the muscle fibre sizes were similar in both groups. This indicated that prenatal administration of phenobarbital inhibits normal hyperplasia of muscle fibres.

The effect of maternal alcohol consumption during pregnancy as well as the neonatal period on allometric growth of skeletal muscles of fore and himdlimbs was studied in 252 rats (126 males and 126 females). At the inception of the study the dams of alcohol-exposed groups received 10% ethanol (v/v) in water for 2 weeks and 20% ethanol (v/v) for another 3 weeks. They were then bred overnight by introducing 1 male per 4 females into the cage. Following diagnosis of pregnancy, the two alcohol-exposed groups received 30% ethanol (v/v) till delivery. Neonatally the pre- and postnatal alcohol-exposed group continued to receive alcohol till weaning at 21 days of age. The offspring randomly selected (7 males and 7 females) from each group were killed at 3, 5, 7, 9, 11 and 14 weeks of age. The body weights, muscle weights and percentage of body weights contributed by each muscle were significantly smaller in the offspring of the alcohol-exposed groups as compared to the controls. These parameters were significantly higher in the group exposed to alcohol only prenatally as compared to those exposed both pre- and postnatally up to the 7th week of age, and thereafter were similar in the subsequent weeks. Although the alcohol-exposed groups grew faster than the controls from 9 to 14 weeks of age, they were, however, not able to catch up. This demonstrated that allometric growth of muscles of fetal and neonatal rats was adversely affected by maternal consumption of alcohol during pregnancy and neonatally.

Effects of cassava (Munihot escuknta Crantz)-borne organic cyanide and inorganic cyanide in the form of sodium cyanide on bone and muscle development were investigated in eighteen dogs of Nigerian breed. After 16 weeks of stabilization in the laboratory from the time of purchase when the dogs were fed on the same diet, they were randomly assigned to three experimental groups of six dogs each. The control group was fed on rice while the other two groups were fed on either cassava (gari) or rice plus cyanide. The three diets were made isoenergetic and isonitrogenous by varying the quantity of meat incorporated into them. The results obtained after 14 weeks of feeding the respective diets indicated that there was retardation of muscle development in the gari-fed dogs. This may have resulted from gluconeogenesis from muscle protein associated with suppression of production of insulin by the pancreas in this group. The results indicated also that the effects of inorganic dietary cyanides on muscle development were different. Both forms of dietary cyanides, however, had no adverse effect on bone development.