STAGES OF DEVELOPMENT OF HUMAN FOETAL MUSCLES WITH REFERENCE TO SOME MUSCULAR DISEASES

Oxidative enzyme activity in the centre of the muscle fibres was observed in muscle from human foetus aged from 6 to 14 weeks of embryonal life. The activity was uniform in all muscle fibres independent of their size. ATPase activity was localised in the circumference of the muscle fibre and increased with the age of the foetus. Phosphorylase activity first appeared in foetal muscles at about the 11th week of embryonal life. Areas of ACHE activity were observed at the beginning of the 9th week of embryonal life. From the 10th week of embryonal life, areas of ACHE activity could be observed in the region of the musculo-tendinous junctions. Muscle spindles could be observed from the 10th week of embryonal life. In the period between the 6th and 14th week of intrauterine life, differentiation into metabolic fibre types, as typically seen in mature muscle, had not yet developed. The development of distinctive metabolic types of muscle fibre appears to run parallel with the development of the innervation of the muscle fibres. In the quadriceps femoris muscles of the foetus aged 24 weeks isolated single fibres of one histochemical type, much larger than the others were seen and corresponded to Wohlfart B fibres. There are several similarities between the histochemical pattern of foetal muscle and that seen in diseased muscle in some cases of muscle disease but these similarities should be interpreted with caution. © 1968.