Circadian time

Melatonin advances the circadian timing of EEG sleep and directly facilitates sleep without altering its duration in extended sleep opportunities in humans. J. Physiol 561, 339-51. 

FIG. 1. Firing-rate patterns in SCN slices from wild-type mice kept in constant darkness (DD) or in 12 h light-12 h dark (LD) cycles. The running wheel activity patterns of the mice over the last 7 days prior to slice preparation is indicated above the records. (A) Circadian rhythm in multiunit activity (MUA) in the SCN of a wild-type mouse, previously kept under DD conditions and isolated at CT2 (B) Circadian rhythm in MUA activity in the SCN of a wild-type mouse, previously kept under LD conditions, and isolated at CT2. Black/ grey and black/white bars above each plot indicate the subjective night/day and night/day respectively. CT, circadian time. (Reprinted from Albus et al 2002, with permission from Elsevier Science.)... 

Albus H, Bonnefont X, Chaves I et al 2002 Cryptochrome-deficient mice lack circadian electrical activity in the suprachiasmatic nuclei. Curr Biol 12 1130—1133 Balsalobre A, Brown SA, Marcacci L et al 2000 Resetting of circadian time in peripheral tissues by glucocorticoid signaling. Science 289 2344—2347 Berson DM, Dunn FA, Takao M 2002 Phototransduction by retinal ganghon cells that set the circadian clock. Science 295 1070—1073... 

Reppert SM, Weaver DR 2002 Coordination of circadian timing in mammals. Nature 418 935-941... 

Balsalobre A, Brown SA, Marcacci L et al 2000 Resetting of circadian time in peripheral tissues by glucocorticoid signaling. Science 289 2344—2347... 

Hastings We have been involved in some work with Andrew Louden in the (au mutant hamster. Looking at the peripheral gene expression in those mutant hamsters, surprisingly Perl and DBF take up phases which you wouldn t predict simply on the basis of the period shortening in the mutant. Looking at the phase in circadian time we should correct for that difference in period, but the gene expression cycles remain inappropriately phased in the mutant. They are internally desynchronized. 

VIVID (VVD), a novel member of the PAS protein superfamily, identifies an autoregulatory negative feedback loop that closes outside of the core oscillator but which impacts all aspects of circadian timing (Heintzen et al 2001). Expression of... 

If the model for the oscillator is correct. Per and Cry expression will define solar/ circadian time, driving the activity—rest cycle rather than just being a passive reflection of the activity cycle. Therefore, their expression patterns should exhibit the same phase in the SCN of nocturnal and diurnal species. This is confirmed by examination of Per expression in the SCN of the diurnally active ground squirrel, Spermophilus (Mrosovsky et al 2001). The rhythm of Per1 and Per2 expression in... 

Further studies have implicated a second feedback loop in circadian timing. Like per and tim, Clk and cry RNAs also oscillate with respect to time of day (Bae et al... 

Rivard GE, Infante-Rivard C, Dresse MF et al. Circadian time-dependent response of childhood lymphoblastic leukemia to chemotherapy a long-term follow-up study of survival. Chronobiol Int 1993 10 201-204. 

Czeisler CA, Khalsa SBS. The human circadian timing system and sleep-wake regulation. In Kryger MH, Roth T, Dement WC, eds. Principles and Practice of Sleep Medicine. Philadelphia WB Saunders, 2000 353-376. 

VI. Experimental Studies of Sleep Restriction/Disruption and Circadian Timing... 

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