Fig. 1. Induction of apoptosis by heat shock and X-rays. (A-C) A set of wing, haltere and leg discs fixed 24 hours after heat shock and doubly stained with TUNEL and Caspase 3. Note that the two stainings are co-extensive. (D-G) X-rayed wing discs fixed different times after irradiation and stained for caspase 3. High apoptotic levels can be observed until 48 hours after the irradiation. After 72 hours (G), the apoptotic levels have dropped to normal.