Fig. 3. Expression of PCNA in 10 day neural crest cultures. (A,C,E) Fluorescent images showing PCNA staining. (B,D,F) Corresponding phase contrast micrographs (n=4 of each treatment type). (A,B) Most cells in untreated cultures are negative for PCNA with very few cells staining positively (arrow). (C,D) A large proportion of cells in 1 ng/ml FGF2 express PCNA. (E,F) Very few cells within a differentiated nodule in 10 ng/ml FGF2 express PCNA (arrow), while the proliferative non-differentiated cells at the edge of the nodule are intensely immunoreactive (arrowheads). Scale bars: 100 µm.