The fine structure of differentiating muscle in the salamander tail.

摘要: Thin methacrylate sections of developing tails Amblystoma opacum larvae were examined in the electron microscope and a series stages differentiation myotome musculature was reconstructed from micrographs earlier light microscopic studies living muscle. The earliest muscle cell precursor that can be clearly identified is round or oval with abundant cytoplasm containing scattered myofilaments free ribonucleoprotein granules, but little endoplasmic reticulum. These cells sometimes form syncytium they may also fused adjacent formed fibers by lateral processes. Nuclei are large nucleoli prominent. This cell, called “myoblast” here, distinctly different its appearance mesenchymal which have granular both thick thin varieties distributed disorganized fashion cytoplasm. filaments similar to actin myosin described Huxley present at an stage than heretofore suspected microscopy studies. first myofibrils heterogeneous combination dense Z bands not homogeneous as so many microscopists contended. As development progresses, cross striations become more orderly definitive sarcomeres formed. Thereafter, new seem added surfaces distal ends existing myofibrils.