Biological Clock! Separate Day and Night

Circadian clock-mediated control of stem cell division and differentiation: beyond night and day.

A biological 'circadian' clock conveys diurnal regulation upon nearly all aspects of behavior and physiology to optimize them within the framework of the solar day. From digestion to cardiac function and sleep, both cellular and systemic processes show circadian variations that coincide with diurnal need. However, recent research has shown that this same timekeeping mechanism might have been co...

Differential contribution of Ca2+ sources to day and night BK current activation in the circadian clock

Large conductance K+ (BK) channels are expressed widely in neurons, where their activation is regulated by membrane depolarization and intracellular Ca2+ (Ca2+i). To enable this regulation, BK channels functionally couple to both voltage-gated Ca2+ channels (VGCCs) and channels mediating Ca2+ release from intracellular stores. However, the relationship between BK channels and their specific Ca2...

Flies by Night Effects of Changing Day Length on Drosophila's Circadian Clock

In Drosophila, two intersecting molecular loops constitute an autoregulatory mechanism that oscillates with a period close to 24 hr. These loops touch when proteins from one loop, PERIOD (PER) and TIMELESS (TIM), repress the transcription of their parent genes, period (per) and timeless (tim), by blocking positive transcription factors from the other loop. The arrival of PER and TIM into the nu...

The difference between night and day.

Day and Night: Circadian Rhythms in Worms

Most organisms seem to show ‘‘circadian rhythms’’—cycles of behaviour or gene expression that repeat roughly every 24 hours. Such cycles represent an internal circadian clock that can be ‘‘entrained,’’ or synchronized, to a regular light/dark or temperature cycle, and will then continue to cycle in the absence of the light or temperature stimulus. In the nematode worm Caenorhabditis elegans, ho...