FIG. 7.

Heat-induced changes in the PER and TIM biochemical cycles similar to those observed at T21.5 also occur at other times in the late night. During the last dark period of LD, two groups of wild-type CS flies were exposed to a 30-min 37°C heat pulse beginning at either T20.5 or T23; another group served as controls. Total protein extracts were prepared from isolated heads and analyzed by immunoblotting in the presence of antibodies to either PER (A) or TIM (B). The positions of PER and TIM are indicated at the left; the time of fly collection (in hours since the last dark-light transition at ZT0) is shown at the top. Each experiment was done at least two independent times (data not shown), and representative examples are shown.