Fig. 4.

Apoptosis induced in the flight muscle by hyperoxia. (A) Flight muscle from a control fly, maintained under normoxia for 4 days, exhibits no TUNEL-positive nuclei, whereas flies exposed to hyperoxia for 4 days (B), and assayed by TUNEL staining 2 days later, have many apoptotic nuclei (green). (Scale bars indicate 100 μm.)