Fig. 6. Early stages of graft cell migration: double-labelled donor grafted into unlabelled host, GFP/nLacZ to 0/0, two different experiments (A-D and E,F), both 52 days p.o. The same region of the host (h)/graft(g) border is shown in the adjacent cross (A-D) and longitudinal (E,F) sections. (A,C,E) Fluorescence to show donor GFP; (B,D,F) Xgal plus eosin, to show donor-labelled nuclei. (A-D) Arrows indicate GFP/nLacZ-positive donor cells `on their way' into host muscle; arrow heads indicate a cell in which no blue nucleus was seen. (E,F) GFP-positive fibres in the host muscle with no nLacZ-positive nucleus visible. In the graft, low GFP level and strong ß-galactosidase activity indicate myotubes and immature muscle fibres. Bars, 100 µm.