The analysis of the phase response to temperature cycles.

<p><b>A</b>: Wistar rat (blue) and SHR (green) fibroblasts were subjected to four-day temperature cycles (see Fig. 2C for details). The phase shift after the entrainment shows a strong correlation with the variable endogenous period of the free-running circadian oscillations of the individual samples. <b>B</b>: Wistar rat (blue) and SHR (green) fibroblasts were divided into two groups, which were synchronized by medium exchange at two time points separated by 11.5 h. After three days of recording, both groups were subjected to temperature cycles (2×12 h at 38.5°C/12 h at 36°C) just before their rhythm reached a peak or trough, respectively. The magnitude of the resulting phase shift depends on the oscillation phase at the beginning of the temperature cycle. <b>C</b>: The PRC of Wistar rat (blue) and SHR (green) fibroblasts of the two-day temperature cycles (12 h at 38.5°C/12 h at 36°C) constructed from 4 independent experiments. For clarity, the data were separated according to the breakpoint between the phase delays/advances, and the linear portions of the curves were fitted with regression lines.