Effect of hemolymph and nervous-tissue components on the in vitro development of flight-muscle myoblasts of Manduca sexta

Abstract. Flight-muscle myoblasts from pupae of Manduca sexta were grown in the presence of either hemolymph or nerve extract. The cells exhibited distinctly different growth patterns: the addition of hemolymph yielded a branched network consisting of short, thin myofibers, while the addition of nerve extract resulted in parallel, extended fiber arrays. Spontaneous contractions were frequently observed. Other medium supplements (muscle extract, mouse-liver extract, β-ecdysone) had no detectable effect on myoblast development. Electron micrographs of explants grown in hemolymph revealed the presence of only a few myofibrils with a parallel filament arrangement but without cross striation, whereas explants grown with nerve extract exhibited cross striation within the voluminous filament arrays.