Figure 3.

Central and peripheral clock markers relative to sleep/wake schedules. Individual data for melatonin (A), cortisol (B), HPER1 (C), HPER2 (D), HBMAL1 (E) sampled during 24-hr blood sampling sessions performed before and during the maintenance of a night shift work schedule. Group mean phase ±SEM is shown for each marker as an inverted triangle. Sleep/darkness periods are shown as hatched rectangles. For illustrative purposes, bedtimes for nighttime and daytime sleep episodes were assigned relative clock times of 00:00 and 10:00, respectively. The expression of markers of the endogenous circadian pacemaker and of clock genes in PBMCs were measured from 24-hr blood sampling sessions performed at baseline before the start of simulated night shifts (experimental day 2), after three days on the shifted schedule (shift 1; experimental days 5-6), and at the end of the shifted schedule (shift 2; experimental days 11-12).