Abstract
Development of extraocular muscles was studied in externally normal human embryos (Carnegie stages 13 to 21), using three antibodies as molecular markers of muscle differentiation: brain type (CK-B) and muscle type (CK-M) creatine kinase isoenzymes, and muscle type enolase isoenzyme (β-enolase). The innervation of extraocular muscles was also studied immunohistochemically, using antibody against neuron specific enolase (NSE). Periodic acid-Schiff (PAS) and modified PAS stainings were used to demonstrate glycogen. During stages 13-17, neither immunoreactivity to CK-B, CK-M, β-enolase and NSE nor glycogen could be detected around the optic vesicle. At stage 18, myogenic cells around the optic vesicle became immunoreactive to CK-B, CK-M, and β-enolase antibodies, and the nerve fibers in each extraocular muscle were immunoreactive to NSE antibody; however, glycogen was still undetectable. Glycogen began to appear at stage 19 in the clusters of the myogenic cells. These findings suggest that some of the muscle-type isoenzymes for glycolytic pathway and ATP production appear synchronously in human extraocular muscles, and they are in close association with the storage of glycogen and innervation of extraocular muscles.
