scholarly journals Coupling protocol of interlocked feedback oscillators in circadian clocks

2020 ◽  
Vol 17 (167) ◽  
pp. 20200287
Author(s):  
Md. Mamunur Rashid ◽  
Hiroyuki Kurata
Keyword(s):  
Coupled Oscillators ◽  
Random Parameter ◽  
Feedback Loops ◽  
Circadian Clocks ◽  
Negative Feedback Loops ◽  
Phase Cycle ◽  
Parameter Perturbations ◽  
Coupling Parameters ◽  
Coupling Time ◽  
Master Clock

Circadian rhythms (approx. 24 h) show the robustness of key oscillatory features such as phase, period and amplitude against external and internal variations. The robustness of Drosophila circadian clocks can be generated by interlocked transcriptional–translational feedback loops, where two negative feedback loops are coupled through mutual activations. The mechanisms by which such coupling protocols have survived out of many possible protocols remain to be revealed. To address this question, we investigated two distinct coupling protocols: activator-coupled oscillators (ACO) and repressor-coupled oscillators (RCO). We focused on the two coupling parameters: coupling dissociation constant and coupling time-delay. Interestingly, the ACO was able to produce anti-phase or morning–evening cycles, whereas the RCO produced in-phase ones. Deterministic and stochastic analyses demonstrated that the anti-phase ACO provided greater fluctuations in amplitude not only with respect to changes in coupling parameters but also to random parameter perturbations than the in-phase RCO. Moreover, the ACO deteriorated the entrainability to the day–night master clock, whereas the RCO produced high entrainability. Considering that the real, interlocked feedback loops have evolved as the ACO, instead of the RCO, we first proposed a hypothesis that the morning–evening or anti-phase cycle is more essential for Drosophila than achieving robustness and entrainability.

scholarly journals Post-translational Modifications are Required for Circadian Clock Regulation in Vertebrates

2019 ◽  
Vol 20 (5) ◽  
pp. 332-339 ◽  
Author(s):  
Yoshimi Okamoto-Uchida ◽  
Junko Izawa ◽  
Akari Nishimura ◽  
Atsuhiko Hattori ◽  
Nobuo Suzuki ◽  
...  
Keyword(s):  
Transcriptional Activity ◽  
Molecular Mechanisms ◽  
Feedback Loops ◽  
Circadian Clocks ◽  
Post Translational Modification ◽  
Post Translational Modifications ◽  
Negative Feedback Loops ◽  
Genetic Techniques ◽  
External Signals ◽  
Exact Timing

Circadian clocks are intrinsic, time-tracking systems that bestow upon organisms a survival advantage. Under natural conditions, organisms are trained to follow a 24-h cycle under environmental time cues such as light to maximize their physiological efficiency. The exact timing of this rhythm is established via cell-autonomous oscillators called cellular clocks, which are controlled by transcription/ translation-based negative feedback loops. Studies using cell-based systems and genetic techniques have identified the molecular mechanisms that establish and maintain cellular clocks. One such mechanism, known as post-translational modification, regulates several aspects of these cellular clock components, including their stability, subcellular localization, transcriptional activity, and interaction with other proteins and signaling pathways. In addition, these mechanisms contribute to the integration of external signals into the cellular clock machinery. Here, we describe the post-translational modifications of cellular clock regulators that regulate circadian clocks in vertebrates.

scholarly journals Stability and Hopf Bifurcation Analysis of Coupled Optoelectronic Feedback Loops

2013 ◽  
Vol 2013 ◽  
pp. 1-11
Author(s):  
Gang Zhu ◽  
Junjie Wei
Keyword(s):  
Hopf Bifurcation ◽  
Normal Form ◽  
Center Manifold ◽  
Stable Equilibrium ◽  
Feedback Loops ◽  
Asymptotically Stable ◽  
Center Manifold Theorem ◽  
Feedback Strength ◽  
Coupling Parameters ◽  
Normal Form Method

The dynamics of a coupled optoelectronic feedback loops are investigated. Depending on the coupling parameters and the feedback strength, the system exhibits synchronized asymptotically stable equilibrium and Hopf bifurcation. Employing the center manifold theorem and normal form method introduced by Hassard et al. (1981), we give an algorithm for determining the Hopf bifurcation properties.

scholarly journals Genetic interactions between clock mutations in Neurospora crassa : can they help us to understand complexity?

2001 ◽  
Vol 356 (1415) ◽  
pp. 1717-1724 ◽  
Author(s):  
Louis W. Morgan ◽  
Jerry F. Feldman ◽  
Deborah Bell-Pedersen
Keyword(s):  
Coupled Oscillators ◽  
Temperature Compensation ◽  
White Collar ◽  
Circadian System ◽  
Genetic Interactions ◽  
Circadian Clocks ◽  
Metabolic Effects ◽  
Clock Model ◽  
Number Of Genes ◽  
Single Oscillator

Recent work on circadian clocks in Neurospora has primarily focused on the frequency ( frq ) and white–collar ( wc ) loci. However, a number of other genes are known that affect either the period or temperature compensation of the rhythm. These include the period (no relationship to the period gene of Drosophila ) genes and a number of genes that affect cellular metabolism. How these other loci fit into the circadian system is not known, and metabolic effects on the clock are typically not considered in single–oscillator models. Recent evidence has pointed to multiple oscillators in Neurospora , at least one of which is predicted to incorporate metabolic processes. Here, the Neurospora clock–affecting mutations will be reviewed and their genetic interactions discussed in the context of a more complex clock model involving two coupled oscillators: a FRQ/WC–based oscillator and a ‘ frq –less’ oscillator that may involve metabolic components.

Delay model of circadian gene expression with two negative feedback loops

2006 ◽  
Vol 37 (5) ◽  
pp. 405-417
Author(s):  
Andreas Bohn ◽  
José R. Lopes ◽  
Luís A. Diambra ◽  
Luiz S. Menna-Barreto
Keyword(s):  
Gene Expression ◽  
Negative Feedback ◽  
Feedback Loops ◽  
Delay Model ◽  
Circadian Gene ◽  
Negative Feedback Loops

Delay stabilization of periodic orbits in coupled oscillator systems

2010 ◽  
Vol 368 (1911) ◽  
pp. 319-341 ◽  
Author(s):  
B. Fiedler ◽  
V. Flunkert ◽  
P. Hövel ◽  
E. Schöll
Keyword(s):  
Normal Form ◽  
Numerical Simulations ◽  
Periodic Orbits ◽  
Coupled Oscillators ◽  
Coupled Oscillator ◽  
Non Invasive ◽  
Coupling Parameters ◽  
Necessary And Sufficient ◽  
Time Delayed Feedback ◽  
Coupled Oscillator Systems

We study diffusively coupled oscillators in Hopf normal form. By introducing a non-invasive delay coupling, we are able to stabilize the inherently unstable anti-phase orbits. For the super- and subcritical cases, we state a condition on the oscillator’s nonlinearity that is necessary and sufficient to find coupling parameters for successful stabilization. We prove these conditions and review previous results on the stabilization of odd-number orbits by time-delayed feedback. Finally, we illustrate the results with numerical simulations.

scholarly journals An ultradian feeding schedule in rats affects metabolic gene expression in liver, brown adipose tissue and skeletal muscle with only mild effects on circadian clocks

2018 ◽  
Author(s):  
Paul de Goede ◽  
Satish Sen ◽  
Yan Su ◽  
Ewout Foppen ◽  
Vincet-Joseph Poirel ◽  
...  
Keyword(s):  
Gene Expression ◽  
Skeletal Muscle ◽  
Feeding Behavior ◽  
Circadian Clocks ◽  
Daily Rhythm ◽  
Feeding Schedule ◽  
Metabolic Gene Expression ◽  
Brown Adipose ◽  
Peripheral Clocks ◽  
Master Clock

Restricted feeding is well known to affect expression profiles of both clock and metabolic genes. However, it is unknown whether these changes in metabolic gene expression result from changes in the molecular clock or in feeding behavior. Here we eliminated the daily rhythm in feeding behavior by providing 6-meals evenly distributed over the light/dark-cycle. Animals on this 6-meals-a-day feeding schedule retained the normal day/night difference in physiological parameters including body temperature and locomotor activity. The daily rhythm in respiratory exchange ratio (RER), however, was significantly phase-shifted through increased utilization of carbohydrates during the light phase and increased lipid oxidation during the dark phase. This 6-meals-a-day feeding schedule did not have a major impact on the clock gene expression rhythms in the master clock but did have mild effects on peripheral clocks. By contrast, genes involved in glucose and lipid metabolism showed differential expression. Concluding, eliminating the daily rhythm in feeding behavior in rats does not affect the master clock and only mildly affects peripheral clocks, but disturbs metabolic rhythms in liver, skeletal muscle and brown adipose tissue in a tissue-dependent manner. Thereby a clear daily rhythm in feeding behavior strongly regulates timing of peripheral metabolism, separately from circadian clocks.

How the Group Affects the Mind: A Cognitive Model of Idea Generation in Groups

2006 ◽  
Vol 10 (3) ◽  
pp. 186-213 ◽  
Author(s):  
Bernard A. Nijstad ◽  
Wolfgang Stroebe
Keyword(s):  
Associative Memory ◽  
Group Decision ◽  
Cognitive Model ◽  
Idea Generation ◽  
Feedback Loops ◽  
Negative Feedback Loops ◽  
Cognitive Failures ◽  
Research Findings ◽  
Knowledge Activation ◽  
The Mind

A model called search for ideas in associative memory (SIAM) is proposed to account for various research findings in the area of group idea generation. The model assumes that idea generation is a repeated search for ideas in associative memory, which proceeds in 2 stages (knowledge activation and idea production), and is controlled through negative feedback loops and cognitive failures (trials in which no idea is generated). We show that (a) turn taking (production blocking) interferes with both stages of the process; (b) ideas suggested by others aid the activation of problem-relevant knowledge; and (c) cognitive failures are important determinants of brainstorming persistence, satisfaction, and enjoyment. Implications for group decision making and group recall are discussed.

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