Fig. 5

Evidence of downregulation of muscle-specific markers following treatment with newt extract. C2C12 myotubes were microinjected with a GFP tracer and subsequently treated with newt extract for 4 days in growth medium. They were then fixed and stained for myosin heavy chain (MHC). a The arrow identifies GFP-labeled cells that were not positive for MHC, suggesting that they had downregulated the MHC marker. Not all myotubes responded to the extract, as can be seen by GFP-labeled cells that were also positive for MHC. b Cell counts of multinucleated myotubes (left panel) and mononucleated myocytes (within the same cultures) showed that only extract-treated cultures had GFP-positive cells that were negative for MHC. This experiment was performed in triplicate, and multiple wells were counted for each replicate