Fig. 3. (A) An activated satellite cell on a muscle fibre 10 min following injury (arrow). (Original micrograph taken at x350; H&E staining.) (B) Schematic depicting the relative location of NOS-1-derived nitric oxide release from a muscle fibre and diffusing through satellite cell toward the interstitial space (after Anderson, 2000). (C) Micrograph of NOS-1 expression in an activated satellite cell in skeletal muscle. (Original micrograph x350; in situ hybridization) (after Anderson and Vargas, 2003). (D) A schematic describing potential communication and feedback signaling among various compartments, cells and tissues in skeletal muscle, suggesting that satellite cells are active as filters for signaling during structural and functional plasticity.