scholarly journals Multi-Modal Regulation of Circadian Physiology by Interactive Features of Biological Clocks

Biology ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 21
Author(s):  
Yool Lee ◽  
Jonathan P. Wisor
Keyword(s):  
Circadian Clock ◽  
Neurological Diseases ◽  
Night Shift ◽  
Hormone Secretion ◽  
Local Environment ◽  
Biological Clocks ◽  
Tightly Coupled ◽  
Peripheral Clocks ◽  
Living Organisms ◽  
Circadian Physiology

The circadian clock is a fundamental biological timing mechanism that generates nearly 24 h rhythms of physiology and behaviors, including sleep/wake cycles, hormone secretion, and metabolism. Evolutionarily, the endogenous clock is thought to confer living organisms, including humans, with survival benefits by adapting internal rhythms to the day and night cycles of the local environment. Mirroring the evolutionary fitness bestowed by the circadian clock, daily mismatches between the internal body clock and environmental cycles, such as irregular work (e.g., night shift work) and life schedules (e.g., jet lag, mistimed eating), have been recognized to increase the risk of cardiac, metabolic, and neurological diseases. Moreover, increasing numbers of studies with cellular and animal models have detected the presence of functional circadian oscillators at multiple levels, ranging from individual neurons and fibroblasts to brain and peripheral organs. These oscillators are tightly coupled to timely modulate cellular and bodily responses to physiological and metabolic cues. In this review, we will discuss the roles of central and peripheral clocks in physiology and diseases, highlighting the dynamic regulatory interactions between circadian timing systems and multiple metabolic factors.

scholarly journals Integration of mammalian circadian clock signals: from molecule to behavior

2003 ◽  
Vol 177 (1) ◽  
pp. 3-6 ◽  
Author(s):  
H Okamura
Keyword(s):  
Gene Transcription ◽  
Clock Gene ◽  
Hormone Secretion ◽  
Living Organism ◽  
Biological Clocks ◽  
Nucleus Neuron ◽  
The Core ◽  
Behavioral Rhythm ◽  
Oscillatory Mechanism ◽  
Peripheral Clocks

The core oscillatory mechanism consisting of gene transcription and translation is a unique feature and the astonishing discovery in circadian biology is that the rhythm of gene transcription reflects the behavioral rhythm almost perfectly. This means that the clock gene oscillation generated by the core loop in each suprachiasmatic nucleus neuron is coupled and amplified, and harmonized strongly so that oscillating activities are spread into the whole brain and to all those peripheral organs which contain peripheral clocks. Additionally, circadian changes are induced in behavior and hormone secretion. Investigations of biological clocks open the fascinating perspective to analyze the integrational mechanism of 'time', providing a bridge between single genes and the living organism as a whole.

Modulation of Gonadotrophin-Releasing Hormone Secretion by an Endogenous Circadian Clock

2009 ◽  
Vol 21 (4) ◽  
pp. 339-345 ◽  
Author(s):  
P. E. Chappell ◽  
C. P. Goodall ◽  
K. J. Tonsfeldt ◽  
R. S. White ◽  
E. Bredeweg ◽  
...  
Keyword(s):  
Circadian Clock ◽  
Hormone Secretion ◽  
Releasing Hormone ◽  
Gonadotrophin Releasing Hormone

scholarly journals Circadian Deregulation as Possible New Player in Pollution-Induced Tissue Damage

Atmosphere ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 116
Author(s):  
Mascia Benedusi ◽  
Elena Frigato ◽  
Cristiano Bertolucci ◽  
Giuseppe Valacchi
Keyword(s):  
Cardiovascular Diseases ◽  
Air Pollutants ◽  
Environmental Stressors ◽  
Common Mechanism ◽  
Particulate Matters ◽  
Circadian Misalignment ◽  
Pathological Conditions ◽  
Peripheral Clocks ◽  
Living Organisms ◽  
Almost All

Circadian rhythms are 24-h oscillations driven by a hypothalamic master oscillator that entrains peripheral clocks in almost all cells, tissues and organs. Circadian misalignment, triggered by industrialization and modern lifestyles, has been linked to several pathological conditions, with possible impairment of the quality or even the very existence of life. Living organisms are continuously exposed to air pollutants, and among them, ozone or particulate matters (PMs) are considered to be among the most toxic to human health. In particular, exposure to environmental stressors may result not only in pulmonary and cardiovascular diseases, but, as it has been demonstrated in the last two decades, the skin can also be affected by pollution. In this context, we hypothesize that chronodistruption can exacerbate cell vulnerability to exogenous damaging agents, and we suggest a possible common mechanism of action in deregulation of the homeostasis of the pulmonary, cardiovascular and cutaneous tissues and in its involvement in the development of pathological conditions.

scholarly journals Survival is reduced when endogenous period deviates from 24 h in a non-human primate, supporting the circadian resonance theory

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Clara Hozer ◽  
Martine Perret ◽  
Samuel Pavard ◽  
Fabien Pifferi
Keyword(s):  
Circadian Rhythms ◽  
Circadian Clock ◽  
Microcebus Murinus ◽  
Circadian Period ◽  
Biological Functions ◽  
Resonance Theory ◽  
Aging Research ◽  
Mouse Lemurs ◽  
Living Organisms ◽  
Human Primate

Abstract Circadian rhythms are ubiquitous attributes across living organisms and allow the coordination of internal biological functions with optimal phases of the environment, suggesting a significant adaptive advantage. The endogenous period called tau lies close to 24 h and is thought to be implicated in individuals’ fitness: according to the circadian resonance theory, fitness is reduced when tau gets far from 24 h. In this study, we measured the endogenous period of 142 mouse lemurs (Microcebus murinus), and analyzed how it is related to their survival. We found different effects according to sex and season. No impact of tau on mortality was found in females. However, in males, the deviation of tau from 24 h substantially correlates with an increase in mortality, particularly during the inactive season (winter). These results, comparable to other observations in mice or drosophila, show that captive gray mouse lemurs enjoy better fitness when their circadian period closely matches the environmental periodicity. In addition to their deep implications in health and aging research, these results raise further ecological and evolutionary issues regarding the relationships between fitness and circadian clock.

scholarly journals Attenuated SIRT1 Activity Leads to PER2 Cytoplasmic Localization and Dampens the Amplitude of Bmal1 Promoter-Driven Circadian Oscillation

2021 ◽  
Vol 15 ◽  
Author(s):  
Atsushige Ashimori ◽  
Yasukazu Nakahata ◽  
Toshiya Sato ◽  
Yuichiro Fukamizu ◽  
Takaaki Matsui ◽  
...  
Keyword(s):  
Subcellular Localization ◽  
Circadian Clock ◽  
Posttranslational Modifications ◽  
Cultured Cells ◽  
Circadian Oscillation ◽  
Clock Proteins ◽  
Circadian Clock Proteins ◽  
Circadian Physiology ◽  
And Behavior ◽  
Robust Systems

The circadian clock possesses robust systems to maintain the rhythm approximately 24 h, from cellular to organismal levels, whereas aging is known to be one of the risk factors linked to the alternation of circadian physiology and behavior. The amount of many metabolites in the cells/body is altered with the aging process, and the most prominent metabolite among them is the oxidized form of nicotinamide adenine dinucleotide (NAD+), which is associated with posttranslational modifications of acetylation and poly-ADP-ribosylation status of circadian clock proteins and decreases with aging. However, how low NAD+ condition in cells, which mimics aged or pathophysiological conditions, affects the circadian clock is largely unknown. Here, we show that low NAD+ in cultured cells promotes PER2 to be retained in the cytoplasm through the NAD+/SIRT1 axis, which leads to the attenuated amplitude of Bmal1 promoter-driven luciferase oscillation. We found that, among the core clock proteins, PER2 is mainly affected in its subcellular localization by NAD+ amount, and a higher cytoplasmic PER2 localization was observed under low NAD+ condition. We further found that NAD+-dependent deacetylase SIRT1 is the regulator of PER2 subcellular localization. Thus, we anticipate that the altered PER2 subcellular localization by low NAD+ is one of the complex changes that occurs in the aged circadian clock.

PREMONition: An algorithm for predicting the circadian clock-regulated molecular network

2018 ◽  
Author(s):  
Jasper Bosman ◽  
Zheng Eelderink-Chen ◽  
Emma Laing ◽  
Martha Merrow
Keyword(s):  
Circadian Clock ◽  
Clock Gene ◽  
Clock Genes ◽  
Circadian Clocks ◽  
Model Systems ◽  
Functional Relationships ◽  
Growth Assay ◽  
Living Organisms ◽  
Clock Mechanism ◽  
Transcriptional Feedback

AbstractA transcriptional feedback loop is central to clock function in animals, plants and fungi. The clock genes involved in its regulation are specific to - and highly conserved within - the kingdoms of life. However, other shared clock mechanisms, such as phosphorylation, are mediated by proteins found broadly among living organisms, performing functions in many cellular sub-systems. Use of homology to directly infer involvement/association with the clock mechanism in new, developing model systems, is therefore of limited use. Here we describe the approach PREMONition,PREdictingMolecularNetworks, that uses functional relationships to predict molecular circadian clock associations. PREMONition is based on the incorporation of proteins encoded by known clock genes (when available), rhythmically expressed clock-controlled genes and non-rhythmically expressed but interacting genes into a cohesive network. After tuning PREMONition on the networks derived for human, fly and fungal circadian clocks, we deployed the approach to predict a molecular clock network forSaccharomyces cerevisiae, for which there are no readily-identifiable clock gene homologs. The predicted network was validated using gene expression data and a growth assay for sensitivity to light, a zeitgeber of circadian clocks of most organisms. PREMONition may be used to identify candidate clock-regulated processes and thus candidate clock genes in other organisms.

Sanemori's Revenge: Insects, Eco-System Accidents, and Policy Decisions in Japan's Environmental History

2007 ◽  
Vol 19 (1) ◽  
pp. 113-144
Author(s):  
Brett L. Walker
Keyword(s):  
Environmental History ◽  
Policy Decisions ◽  
Technological Systems ◽  
Advanced Technologies ◽  
Technological Artifacts ◽  
Production And Consumption ◽  
Tightly Coupled ◽  
Living Organisms

Normally we do not think of living organisms as machines or as relays in complex, tightly coupled technological systems. Nonetheless, in recent years this is precisely the manner in which many environmental historians have come to approach the study of certain organisms and their natural or anthropogenic environments. Over the millennia and across the globe, humans have so manipulated certain organisms that they have come to exist solely as parts of technological systems or industrialized chains of production and consumption. Technological artifacts are, of course, only nature refashioned: nonetheless, modern industrialized societies tend to view themselves as gradually distancing themselves from, replacing, or, in some instances, even killing nature with their advanced technologies and gadgetries, when actually they are only refashioning their inseparable relationship to it.

scholarly journals Species-Habitat Associations: Spatial data, predictive models, and ecological insights

2020 ◽  
Author(s):  
Jason Matthiopoulos ◽  
John Fieberg ◽  
Geert Aarts
Keyword(s):  
Spatial Data ◽  
State Of The Art ◽  
Anthropogenic Impacts ◽  
Local Environment ◽  
Statistical Technique ◽  
Habitat Associations ◽  
New Methods ◽  
Spatiotemporal Scales ◽  
Ecological Mechanisms ◽  
Living Organisms

Ecologists develop species-habitat association (SHA) models to understand where species occur, why they are there and where else they might be. This knowledge can be used to designate protected areas, estimate anthropogenic impacts on living organisms and assess risks from invasive species or disease spill-over from wildlife to humans. Here, we describe the state of the art in SHA models, looking beyond the apparent correlations between the positions of organisms and their local environment. We highlight the importance of ecological mechanisms, synthesize diverse modelling frameworks and motivate the development of new analytical methods. Above all, we aim to be synthetic, bringing together several of the apparently disconnected pieces of ecological theory, taxonomy, spatiotemporal scales, and mathematical and statistical technique in our field. The first edition of this ebook reviews the ecology of species-habitat associations, the mechanistic interpretation of existing empirical models and their shared statistical foundations that can help us draw scientific insights from field data. It will be of interest to graduate students and professionals looking for an introduction to the ecological and statistical literature of SHAs, practitioners seeking to analyse their data on animal movements or species distributions and quantitative ecologists looking to contribute new methods addressing the limitations of the current incarnations of SHA models.

scholarly journals Telling the Seasons Underground: The Circadian Clock and Ambient Temperature Shape Light Exposure and Photoperiodism in a Subterranean Rodent

2021 ◽  
Vol 12 ◽  
Author(s):  
Danilo E. F. L. Flôres ◽  
Milene G. Jannetti ◽  
Giovane C. Improta ◽  
Patricia Tachinardi ◽  
Veronica S. Valentinuzzi ◽  
...  
Keyword(s):  
Circadian Clock ◽  
Laboratory Experiments ◽  
Light Exposure ◽  
Seasonal Patterns ◽  
Subterranean Rodents ◽  
Subterranean Rodent ◽  
Lighting Conditions ◽  
Oscillatory Structure ◽  
Exposure Patterns ◽  
Living Organisms

Living organisms anticipate the seasons by tracking the proportion of light and darkness hours within a day—photoperiod. The limits of photoperiod measurement can be investigated in the subterranean rodents tuco-tucos (Ctenomys aff. knighti), which inhabit dark underground tunnels. Their exposure to light is sporadic and, remarkably, results from their own behavior of surface emergence. Thus, we investigated the endogenous and exogenous regulation of this behavior and its consequences to photoperiod measurement. In the field, animals carrying biologgers displayed seasonal patterns of daily surface emergence, exogenously modulated by temperature. In the laboratory, experiments with constant lighting conditions revealed the endogenous regulation of seasonal activity by the circadian clock, which has a multi-oscillatory structure. Finally, mathematical modeling corroborated that tuco-tuco’s light exposure across the seasons is sufficient for photoperiod encoding. Together, our results elucidate the interrelationship between the circadian clock and temperature in shaping seasonal light exposure patterns that convey photoperiod information in an extreme photic environment.

scholarly journals The Circadian Clock Is Sustained in the Thyroid Gland of VIP Receptor 2 Deficient Mice

2021 ◽  
Vol 12 ◽  
Author(s):  
Birgitte Georg ◽  
Jan Fahrenkrug ◽  
Henrik L. Jørgensen ◽  
Jens Hannibal
Keyword(s):  
Circadian Clock ◽  
Clock Genes ◽  
Hormone Secretion ◽  
Heart Rhythm ◽  
Thyroid Stimulating Hormone ◽  
Constant Darkness ◽  
Receptor Signaling ◽  
Knockout Animals ◽  
The Impact ◽  
Deficient Mice

VIP/VPAC2-receptor signaling is crucial for functioning of the circadian clock in the suprachiasmatic nucleus (SCN) since the lack results in disrupted synchrony between SCN cells and altered locomotor activity, body temperature, hormone secretion and heart rhythm. Endocrine glands, including the thyroid, show daily oscillations in clock gene expression and hormone secretion, and SCN projections target neurosecretory hypothalamic thyroid-stimulating hormone (TSH)-releasing hormone cells. The aim of the study was to gain knowledge of mechanisms important for regulation of the thyroid clock by evaluating the impact of VIP/VPAC2-receptor signaling. Quantifications of mRNAs of three clock genes (Per1, Per2 and Bmal1) in thyroids of wild type (WT) and VPAC2-receptor deficient mice were done by qPCR. Tissues were taken every 4th h during 24-h 12:12 light-dark (LD) and constant darkness (DD) periods, both genders were used. PER1 immunoreactivity was visualized on sections of both WT and VPAC2 lacking mice during a LD cycle. Finally, TSH and the thyroid hormone T4 levels were measured in the sera by commercial ELISAs. During LD, rhythmic expression of all three mRNA was found in both the WT and knockout animals. In VPAC2-receptor knockout animals, the amplitudes were approximately halved compared to the ones in the WT mice. In the WT, Per1 mRNA peaked around “sunset”, Per2 mRNA followed with approximately 2 h, while Bmal1 mRNA was in antiphase with Per1. In the VPAC2 knockout mice, the phases of the mRNAs were advanced approximately 5 h compared to the WT. During DD, the phases of all the mRNAs were identical to the ones found during LD in both groups of mice. PER1 immunoreactivity was delayed compared to its mRNA and peaked during the night in follicular cells of both the thyroid and parathyroid glands in the WT animals. In WT animals, TSH was high around the transition to darkness compared to light-on, while T4 did not change during the 24 h cycle. In conclusion, sustained and identical rhythms (phases and amplitudes) of three clock genes were found in VPAC2 deficient mice during LD and DD suggesting high degree of independence of the thyroid clock from the master SCN clock.

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