TUNEL labeling in retinas after mechanical lesions.

<p>Transverse sections of lesioned chick retinas were submitted to terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL, green) to characterize the apoptosis spatial pattern, and counterstained with propidium iodide (PI, red). A–C, after 6 h of the mechanical trauma, we could observe TUNEL-positive nuclei in the focus of the lesion (arrows). D–F, in 24 h-lesioned retinas, we observed a peak in the number of the TUNEL-positive cells, mainly located in the focus of the lesion. These cells were mainly distributed in the inner nuclear layer (INL), but also in the outer nuclear layer (ONL). Notice that some cells located in the lower part of the image were actually from the INL and displaced by the mechanical trauma. G–I, after 3 days, we observed a decrease in the number of TUNEL-positive cells. Moreover, these cells were located away from the focus, in the penumbra area (arrowheads), evidencing the secondary cell death. In 7-day lesioned retinas, we typically observed very few or no TUNEL-positive cells in retinal transverse sections. Scale bar: 60 µm.