Muscle satellite cells in urodele amphibians: Facilitated identification of satellite cells using ruthenium red staining

The ruthenium red (RR) stained forelimb musculature of three species of urodeles Triturus (Notophthalmus) viridescens, Amblystoma maculatum, Amblystoma opacum in various stages of growth were examined with the electron microscope for the presence of satellite cells. It was found that RR staining facilitated greatly the identification of satellite cells. In young larvae of all three species satellite cells were detected with a frequency of 29% to 48% per total number of nuclei. In adult Triturus and Amblystoma maculatum satellite cells were no longer detected; instead "pericytes" as described by Hay ('74) were seen with a frequency of 12% and 3% respectively. During metamorphosis of Triturus satellite cells, with part of their myofiber-satellite cell intercellular space filled with basement membrane material, occurred at a peak frequency. The cells presumably are intermediate in the formation of "pericytes." At ten days after metamorphosis satellite cells and intermediate cells were no longer detected and the limb musculature contained only "pericytes" similar to the ones observed in adult newts. The significance of the presence of satellite cells in relation to limb regeneration and muscle regeneration is discussed.