Twenty‐Four Hour Rhythms in Cardiovascular Physiology

Figures

• 

  FIGURE 1. Parameters obtained from a four‐parameter fit to experimental data with a 24 h diurnal rhythm. The mesor is the mean value of the parameter; the amplitude is the maximum deviation from the mesor. Thus, the distance from peak to trough is two times the amplitude. The period is the time duration of one full oscillation and is 24 h here. The phase is the time point of the maximal amplitude, which can be in hours or in a fraction of 2π, which is the full period.

• 

  FIGURE 2. RR and QT intervals from 8 wild‐type mice. Light is the only external time cue, or ‘zeitgeber’, and is turned on at 6 AM, which then becomes ‘zeitgeber time’ 0:00. At 6 PM, zeitgeber time 12:00, the light is turned off. In all panels, the 1 h mean is illustrated by the data point; the upper and lower range of the 95% confidence intervals are given by the dotted lines. A cosinor fit is made and the amplitude (A) is given in each panel. Panel A shows the hourly mean of all RR intervals throughout the 24 h recording. Panel B shows the corresponding QT intervals to the beats analyzed in panel A. In panels C and D, only ECG complexes with an RR interval between 114.5 and 115.5 ms are selected for analysis. Due to this selection, the confidence intervals of the RR intervals are below 0.2 ms and the amplitude of the fit is 0. In panel D, QT intervals from the selected complexes are shown alongside two representative ECG traces from ZT4 (above) and ZT16 (below). The amplitude of the 24 h rhythm is smaller when RR intervals are constant; however, there is still a significant amplitude. Thus, this data suggests that there is a 24 h rhythm in repolarization that is independent of the heart…

• 

  FIGURE 3. Systolic and diastolic blood pressure from 15 wild‐type mice. In both panels, the 1 h mean is illustrated by the data point; the upper and lower range of the 95% confidence intervals are given by the dotted lines. A cosinor fit is made, and the amplitude (A) is given in each panel.