Figure 2

Stages of axon regeneration. Images are montages of single confocal planes (except where indicated) of longitudinal thick sections. Rostral is to the left. Descending (A, C, E, G, I, K) or ascending (B, D, F, H, J, L) axons were labeled with the axon tracer (magenta), and nuclei are shown in green. Time after injury is indicated in the upper right corner of each panel. (A, B) Retraction and (C, D) growth initiation stages. Arrowheads, end of cord; asterisk, injury site; dotted line, unlabeled cord opposite the injury site. (B) is a z-projection of four planes to highlight growth cones. (B^', B^", D^', D^") Enlargements of dotted boxes in (B) and (D) showing that growth cones (primed boxes) and dystrophic axons (double primed boxes) are present at both stages. (E, F) Wrapping stage. (G, H) Wisping stage. (I, J) Spiking stage. (H) and (I) are z-projections of two confocal planes to show wrapping axons with wisping (H) or spiking (I) axons. (K, L) Contact and growth beyond the injury site stage. The animal in (K) had recovered swimming function, while the one in (L) had not. Open arrowheads, residual wrapping axons; arrows, meninges. TV, terminal vesicle; R, rostral; C, caudal. Scale bars: 200 μm (A-L); 50 μm (B', B", D', D").