Circadian Rhythm and Sleep Disruption: Causes, Metabolic Consequences, and Countermeasures.

Circadian (∼24-hour) timing systems pervade all kingdoms of life and temporally optimize behavior and physiology in humans. Relatively recent changes to our environments, such as the introduction of artificial lighting, can disorganize the circadian system, from the level of the molecular clocks that regulate the timing of cellular activities to the level of synchronization between our daily cycles of behavior and the solar day. Sleep/wake cycles are intertwined with the circadian system, and global trends indicate that these, too, are increasingly subject to disruption.

Nutrition and the circadian system.

The human circadian system anticipates and adapts to daily environmental changes to optimise behaviour according to time of day and temporally partitions incompatible physiological processes. At the helm of this system is a master clock in the suprachiasmatic nuclei (SCN) of the anterior hypothalamus. The SCN are primarily synchronised to the 24-h day by the light/dark cycle; however, feeding/fasting cycles are the primary time cues for clocks in peripheral tissues.

1,1-Bis[4-(trifluoro-meth-yl)phen-yl]germetane.

The inter-nal C-Ge-C bond angle in the germacyclo-butane ring of the title compound, C(17)H(14)F(6)Ge or [Ge(C(3)H(6))(C(7)H(4)F(3))(2)], is 77.8 (3)°. The -CF(3) groups display rotational disorder [occupancies 0.