Tail regeneration after spinal cord labelling or grafting. (A) Electroporation of GFP plasmid into the spinal cord lumen labels some spinal cord cells. (B) GFP+ cells were observed only within the regenerating spinal cord. (C) Enlarged view of the section in (B), showing neurons with GFP+ve axons. (D-F) Spinal cord grafting in stage 48 tadpole (D) and its regeneration (E, F). GFP was only observed in spinal cord of the regenerate (F). White arrowheads indicate amputation level. Scale bars: 500 μm. (G, H) GFP expression in the regenerating tail from spinal cord-grafted tadpoles. GFP is green and nuclei are stained with DAPI (blue). In this case a single cell with GFP expression is found outside of the regenerating spinal cord (red arrow in H). Scale bars: 20 μm.