Quantitative RTPCR analysis of circadian clock gene expression in the spleen. Plotted dark circles represent the mean ± SEM in each experimental group. The dashed line represents the fitted plot of cosinor analysis utilizing linear harmonic regression. Values are represented as the number of transcript copies/1000 Gapdh transcripts. Abscissa labels indicate ZT time values every 3 hrs under DD conditions; crosshatched indicates darkness. Clock genes display robust 24 hr oscillations with maximal amplitudes occurring in the late subjective night and early day for cry1 (pANOVA < .001; pcosinor = .001), cry2 (pANOVA = .006; pcosinor = .005), per2 (pANOVA < .001; pcosinor < .003), and per3 (pANOVA = .03; pcosinor = .006), bmal1 (pANOVA < .001; pcosinor = .003), bmal2 (pANOVA < .001; pcosinor = .003), and clock (pANOVA < .001; pcosinor = .002).