Circadian rhythms work cycle

Our laboratory started to work on circadian rhythms by serendipity, while studying the liver-specific transcription of the serum albumin gene. We isolated a cDN A copy for a transcription factor that we dubbed DBP (for albumin promoter D-element Binding Protein). DBP, a basic leucine zipper (bZip) transcription factor, is the founding member of the PAR (proline-acidic amino acid rich)-domain bZip transcription factors, a small subfamily of bZip proteins consisting of DBP, TEF and HLF. It turned out that DBP protein and mRNA accumulation undergo circadian cycles with amplitudes in excess of one hundred-fold (Wuarin Schibler 1990). 

The sleep-wake cycle is under the circadian control of oscillators and can be disrupted by misalignment between an individual s biological clock and external demands on the sleep cycle. Circadian rhythm sleep disorders usually present with either insomnia or hypersomnia, depending on the individual s performance requirements. Two commonly occurring circadian rhythm sleep disorders are jet lag and shift work sleep problems. 

In humans, circadian rhythms governed by the SCN affect a large number of physiological functions, including the sleep-wake cycle and nutrition (Moore-Ede et al, 1982 Touitou Haus, 1992). Moreover, a variety of hormone levels (Van Cauter Aschoff, 1989) or enzyme activities display circadian patterns. Circadian rhythms, accordingly, play important roles in both health and disease (Moore-Ede, Czeisler Richardson, 1983). Clinical applications of circadian rhythm research include the use of light to treat maladaptation to night work (Czeisler et al, 1990), jet lag, or seasonal affective disorder (Lewy et al, 1987). 

We should identify or classify classes of network structures that, from their structures alone, it is possible to tell whether they have the capacity to exhibit certain behavior. Given a biochemical reaction network, we can ask the following question Under which circumstances would this network exhibit phenomena like periodic oscillations and/or bistability For example, we would want to know the answer to this question when modeling the cell division cycle and circadian rhythm where periodic oscillations are required. For mass-action kinetics models, an extensive theoretical work already exists that answers this type of question for large classes of reaction networks. One such set of results is the deficiency theory.The deficiency 8 of a reaction... 

The most important characteristic of the human circadian system for the shiftworker is that much of it is resistant to abrupt changes in schedule. This means that the circadian rhythm will continue to cycle in a way that is not adapted to current working patterns for some time, possibly weeks or even months. Note that circadian rhythms never fully adapt, even in cases where the operator is working on a permanent night shift The practical effect of this is that the operator s circadian rhythm can be caUing for sleep when... 

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