Skeletal muscle consists of a wide variety of physiologically and biochemically distinct phenotypes.
Many of the molecular bases of differences among muscle protein isoforms are known but the underlying regulatory programs that direct differentiation to these particular end-points in particular muscles is largely unknown. Mammalian skeletal muscle fiber type is determined by various inputs acting at different times during myogenesis and fiber differentiation. Neural, endocrine, and muscle contractile activity inputs have all been implicated in fiber type specification. We have developed an in vitro system that combines some of the reliability and stability of explant culture with the flexibility of monolayer, dissociated cell systems. Axon growth and branching during development and regeneration Many kinds of neurons grow and differentiate well in tissue culture, elaborating axons and dendrites and forming synapses on target cells.