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1
Rea, Mark S., Mariana G. Figueiro, Andrew Bierman, and John D. Bullough. "Circadian light." Journal of Circadian Rhythms 8 (February 13, 2010): 2. http://dx.doi.org/10.1186/1740-3391-8-2.
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Walker, William H., Jacob R. Bumgarner, James C. Walton, Jennifer A. Liu, O. Hecmarie Meléndez-Fernández, Randy J. Nelson, and A. Courtney DeVries. "Light Pollution and Cancer." International Journal of Molecular Sciences 21, no. 24 (December 8, 2020): 9360. http://dx.doi.org/10.3390/ijms21249360.
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For many individuals in industrialized nations, the widespread adoption of electric lighting has dramatically affected the circadian organization of physiology and behavior. Although initially assumed to be innocuous, exposure to artificial light at night (ALAN) is associated with several disorders, including increased incidence of cancer, metabolic disorders, and mood disorders. Within this review, we present a brief overview of the molecular circadian clock system and the importance of maintaining fidelity to bright days and dark nights. We describe the interrelation between core clock genes and the cell cycle, as well as the contribution of clock genes to oncogenesis. Next, we review the clinical implications of disrupted circadian rhythms on cancer, followed by a section on the foundational science literature on the effects of light at night and cancer. Finally, we provide some strategies for mitigation of disrupted circadian rhythms to improve health.
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Zhao, Kankan, Bin Ma, Yan Xu, Erinne Stirling, and Jianming Xu. "Light exposure mediates circadian rhythms of rhizosphere microbial communities." ISME Journal 15, no. 9 (March 21, 2021): 2655–64. http://dx.doi.org/10.1038/s41396-021-00957-3.
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AbstractMicrobial community circadian rhythms have a broad influence on host health and even though light-induced environmental fluctuations could regulate microbial communities, the contribution of light to the circadian rhythms of rhizosphere microbial communities has received little attention. To address this gap, we monitored diel changes in the microbial communities in rice (Oryza sativa L.) rhizosphere soil under light–dark and constant dark regimes, identifying microbes with circadian rhythms caused by light exposure and microbial circadian clocks, respectively. While rhizosphere microbial communities displayed circadian rhythms under light–dark and constant dark regimes, taxa possessing circadian rhythms under the two conditions were dissimilar. Light exposure concealed microbial circadian clocks as a regulatory driver, leading to fewer ecological niches in light versus dark communities. These findings disentangle regulation mechanisms for circadian rhythms in the rice rhizosphere microbial communities and highlight the role of light-induced regulation of rhizosphere microbial communities.
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Depres-Brummer, P., F. Levi, G. Metzger, and Y. Touitou. "Light-induced suppression of the rat circadian system." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 268, no. 5 (May 1, 1995): R1111—R1116. http://dx.doi.org/10.1152/ajpregu.1995.268.5.r1111.
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In a constant environment, circadian rhythms persist with slightly altered period lengths. Results of studies with continuous light exposure are less clear, because of short exposure durations and single-variable monitoring. This study sought to characterize properties of the oscillator(s) controlling the rat's circadian system by monitoring both body temperature and locomotor activity. We observed that prolonged exposure of male Sprague-Dawley rats to continuous light (LL) systematically induced complete suppression of body temperature and locomotor activity circadian rhythms and their replacement by ultradian rhythms. This was preceded by a transient loss of coupling between both functions. Continuous darkness (DD) restored circadian synchronization of temperature and activity circadian rhythms within 1 wk. The absence of circadian rhythms in LL coincided with a mean sixfold decrease in plasma melatonin and a marked dampening but no abolition of its circadian rhythmicity. Restoration of temperature and activity circadian rhythms in DD was associated with normalization of melatonin rhythm. These results demonstrated a transient internal desynchronization of two simultaneously monitored functions in the rat and suggested the existence of two or more circadian oscillators. Such a hypothesis was further strengthened by the observation of a circadian rhythm in melatonin, despite complete suppression of body temperature and locomotor activity rhythms. This rat model should be useful for investigating the physiology of the circadian timing system as well as to identify agents and schedules having specific pharmacological actions on this system.
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Metz, Henry S. "Light and the circadian clock." Journal of American Association for Pediatric Ophthalmology and Strabismus 7, no. 4 (August 2003): 229–30. http://dx.doi.org/10.1016/s1091-8531(03)00119-8.
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Yoshii, Taishi, Christiane Hermann-Luibl, and Charlotte Helfrich-Förster. "Circadian light-input pathways inDrosophila." Communicative & Integrative Biology 9, no. 1 (December 4, 2015): e1102805. http://dx.doi.org/10.1080/19420889.2015.1102805.
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Pyatin, V., N. Romanchuk, P. Romanchuk, and A. Volobuev. "Brain, Eyes, Light: Biological Electrical Magnetism of Light and Neurorehabilitation of Cognitive Impairment." Bulletin of Science and Practice 5, no. 12 (December 15, 2019): 129–55. http://dx.doi.org/10.33619/2414-2948/49/14.
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Biological electrical magnetism of light and neural networks of the brain is the adaptation and optimization of external and internal lighting conditions (type, nature, duration) to improve the cognitive brain. Homo sapiens brain operates in a 24-hour biological electrical magnetic environment. Light is the strongest synchronizing signal for the circadian system, and therefore keeps most biological and psychological rhythms internally synchronized, which is important for the optimal functioning of H. sapiens brain. Circadian Sleep–Wake disorders and chronic circadian misalignment, often seen in psychiatric and neurodegenerative diseases, may be effective in neurorehabilitation of cognitive impairment. Beneficial effects on circadian synchronization, sleep quality, mood and cognitive performance-depend on the time, intensity and spectral composition of light exposure. Multidisciplinary and multimodal interaction in the triad “brain–eyes–vessels” allows to identify early biomarkers of both General accelerated and pathological aging, and timely diagnose neurodegeneration, and conduct effective neurorehabilitation of cognitive disorders. Control and treatment of vascular risk factors and endocrine disorders can reduce the prevalence of long-term disability among the elderly population. Combined and hybrid methods of neuroimaging in conjunction with artificial intelligence technologies, allow to understand and diagnose neurological disorders and find new methods of neurorehabilitation and medical and social support that will lead to improved mental health. To restore circadian neuroplasticity of the brain, a multimodal scheme is proposed: circadian glasses, functional nutrition and physical activity. A combined and hybrid cluster in the diagnosis, treatment, prevention and rehabilitation of cognitive disorders and cognitive disorders has been developed and implemented.
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Stupfel, M., V. Gourlet, A. Perramon, P. Merat, G. Putet, and L. Court. "Comparison of ultradian and circadian oscillations of carbon dioxide production by various endotherms." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 268, no. 1 (January 1, 1995): R253—R265. http://dx.doi.org/10.1152/ajpregu.1995.268.1.r253.
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Carbon dioxide emission (VCO2) was computed every 20 min from continuous CO2 concentration recordings taken during 3-30 consecutive days, in strictly controlled environmental conditions, in 54 OF1 mice, 99 Japanese quail, 66 Sprague-Dawley rats, 50 Hartley guinea pigs, 7 chicks, for 7-15 days on 2 Cynomolgus monkeys, and for 24 h on 7 premature infants. This VCO2 shows circadian and ultradian oscillations that were analyzed for frequencies and amplitudes in light-dark 12-h alternation (LD 12:12), continuous light (LL), and continuous dark (DD). Circadians were not always identified or were often masked in LL or DD (mostly in guinea pigs, quail, and rats), while ultradians (tau > or = 40 min) were found in all species, at every time, and in all light regimens. Analysis of variance and chi 2 show significant (P < 0.001) interspecies differences for ultradian (1.07 < tau < 1.40 h) intervals and for circadian and ultradian VCO2 amplitudes. Relationships between ultradian and circadian VCO2 oscillations differ according to the species, ultradians appearing as an entity characteristic for each endotherm species.
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Moore-Ede, Martin, Anneke Heitmann, and Rainer Guttkuhn. "Circadian Potency Spectrum with Extended Exposure to Polychromatic White LED Light under Workplace Conditions." Journal of Biological Rhythms 35, no. 4 (June 16, 2020): 405–15. http://dx.doi.org/10.1177/0748730420923164.
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Electric light has enabled humans to conquer the night, but light exposure at night can disrupt the circadian timing system and is associated with a diverse range of health disorders. To provide adequate lighting for visual tasks without disrupting the human circadian timing system, a precise definition of circadian spectral sensitivity is required. Prior attempts to define the circadian spectral sensitivity curve have used short (≤90-min) monochromatic light exposures in dark-adapted human subjects or in vitro dark-adapted isolated retina or melanopsin. Several lines of evidence suggest that these dark-adapted circadian spectral sensitivity curves, in addition to 430- to 499-nm (blue) wavelength sensitivity, may include transient 400- to 429-nm (violet) and 500- to 560-nm (green) components mediated by cone- and rod-originated extrinsic inputs to intrinsically photosensitive retinal ganglion cells (ipRGCs), which decay over the first 2 h of extended light exposure. To test the hypothesis that the human circadian spectral sensitivity in light-adapted conditions may have a narrower, predominantly blue, sensitivity, we used 12-h continuous exposures of light-adapted healthy human subjects to 6 polychromatic white light-emitting diode (LED) light sources with diverse spectral power distributions at recommended workplace levels of illumination (540 lux) to determine their effect on the area under curve of the overnight (2000–0800 h) salivary melatonin. We derived a narrow steady-state human Circadian Potency spectral sensitivity curve with a peak at 477 nm and a full-width half-maximum of 438 to 493 nm. This light-adapted Circadian Potency spectral sensitivity permits the development of spectrally engineered LED light sources to minimize circadian disruption and address the health risks of light exposure at night in our 24/7 society, by alternating between daytime circadian stimulatory white light spectra and nocturnal circadian protective white light spectra.
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Klerman, E. B., D. J. Dijk, R. E. Kronauer, and C. A. Czeisler. "Simulations of light effects on the human circadian pacemaker: implications for assessment of intrinsic period." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 270, no. 1 (January 1, 1996): R271—R282. http://dx.doi.org/10.1152/ajpregu.1996.270.1.r271.
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The sensitivity of the human circadian system to light has been the subject of considerable debate. Using computer simulations of a recent quantitative model for the effects of light on the human circadian system, we investigated these effects of light during different experimental protocols. The results of the simulations indicate that the nonuniform distribution over the circadian cycle of exposure to ordinary room light seen in classical free-run studies, in which subjects select their exposure to light and darkness, can result in an observed period of approximately 25 h, even when the intrinsic period of the subject's endogenous circadian pacemaker is much closer to 24 h. Other simulation results suggest that accurate assessment of the true intrinsic period of the human circadian pacemaker requires low ambient light intensities (approximately 10-15 lx) during scheduled wake episodes, desynchrony of the imposed light-dark cycle from the endogenous circadian oscillator, and a study length of at least 20 days. Although these simulations await further experimental substantiation, they highlight the sensitivity to light of the human circadian system and the potential confounding influence of light on the assessment of the intrinsic period of the circadian pacemaker.
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REA, MARK S., and MARIANA G. FIGUEIRO. "WHAT IS "HEALTHY LIGHTING?"." International Journal of High Speed Electronics and Systems 20, no. 02 (June 2011): 321–42. http://dx.doi.org/10.1142/s0129156411006623.
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It is well-known that the light/dark cycle incident on the retina regulates the timing of the human circadian system. Disruption of a regular, 24-hour pattern of light and dark can significantly affect our health and well-being. A wide range of modern maladies, from sleep disorders to cancer, have been linked to light-induced circadian disruption. Light has been defined, however, only in terms of the human visual system, not the circadian system. Thus, the study of light-induced circadian disruption is in need of a new definition of light (and dark). Here we contrast light as a stimulus for the human visual system with that for the human circadian system to elucidate the significance of developing a new definition of circadian light as it might ultimately be used to improve health and well-being.
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Kjaer, Katrine Heinsvig, and Carl-Otto Ottosen. "Growth of Chrysanthemum in Response to Supplemental Light Provided by Irregular Light Breaks during the Night." Journal of the American Society for Horticultural Science 136, no. 1 (January 2011): 3–9. http://dx.doi.org/10.21273/jashs.136.1.3.
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Circadian rhythms are believed to be of great importance to plant growth and performance under fluctuating climate conditions. However, it is unclear how plants with a functioning circadian clock will respond to irregular light environments that disturb circadian-regulated parameters related to growth. Chrysanthemum (Chrysanthemum morifolium ‘Coral Charm’) was exposed to supplemental light provided as irregular light breaks during the night, achieved by controlling the light based on forecasted solar irradiance and electricity prices. Growth, in terms of carbon gain, was linearly correlated to both daylength and daily light integral. This response was observed irrespective of the irregularity of the light breaks and despite circadian-regulated processes of carbohydrate metabolism, chlorophyll fluorescence, and leaf chlorophyll content being affected. Leaf expansion and stem elongation occurred at a faster rate in plants grown in short days with irregular light breaks during the night period compared with plants grown in a climate with a consecutive long light period, showing that low average light intensity promoted expansion of the photosynthetic area of the plants. These results are important to gain an understanding of the relationship between circadian-regulated processes and plant growth. These results will also contribute to increased energy savings in the use of supplemental light in greenhouse production.
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Meiliana, Anna, Nurrani Mustika Dewi, and Andi Wijaya. "Chronodisruption and Obesity." Indonesian Biomedical Journal 7, no. 3 (December 1, 2015): 117. http://dx.doi.org/10.18585/inabj.v7i3.184.
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BACKGROUND: Attempts to understand the causes of obesity and develop new therapeutic strategies have mostly focused on caloric intake and energy expenditure. Recent studies have shown that the circadian clock controls energy homeostasis by regulating circadian expression and/or activity of enzymes, hormones, and transport systems involved in metabolism. Moreover, disruption of circadian rhythms leads to obesity and metabolic disorders.CONTENT:Regularly alternating periods of light and darkness, such as normally occur with the rising and the setting of the sun, are essential for the maintenance of undisturbed circadian rhythms in all organisms including humans. The light-dark environment, as detected by specialized photoreceptors in the retinas, impacts the endogenous circadian clock in the anterior hypothalamus, the suprachiasmatic nuclei. These nuclei, via both neural and humoral signals, communicate with cells throughout the organism to establish regular circadian rhythms. The introduction of artificial sources of light roughly 150 years ago has significantly undermined the naturally occurring light-dark environment and, likewise, has disturbed circadian rhythms since light is now available at unusual times, i.e., at night. Light at night is known to cause circadian disruption and melatonin suppression. Many potentially pathophysiological consequences of these artificial light-mediated changes, include cancer, cardiovascular diseases, insomnia, metabolic syndrome, diabetes, and cognitive disorders may be aggravated by the increased exposure to light at night, which is inevitable in well-developed societies that have undergone extensive electrification.SUMMARY: Therefore, it is plausible that resetting of the circadian clock can be used as a new approach to attenuate obesity. Feeding regimens, such as restricted feeding, calorie restriction and intermittent fasting, provide a time cue and reset the circadian clock and lead to better health. In contrast, high-fat diet leads to disrupted circadian expression of metabolic factors and obesity.KEYWORDS: obesity, circadian clock, metabolism, chronodisruption
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Lemmer, Björn, Thomas Brühl, Klaus Witte, Burkhard Pflug, Wilfried Köhler, and Yvan Touitou. "Effects of bright light on circadian patterns of cyclic adenosine monophosphate, melatonin and cortisol in healthy subjects." European Journal of Endocrinology 130, no. 5 (May 1994): 472–77. http://dx.doi.org/10.1530/eje.0.1300472.
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Lemmer B, Brühl T, Witte K, Pflug B, Köhler W, Touitou Y. Effects of bright light on circadian patterns of cyclic adenosine monophosphate, melatonin and cortisol in healthy subjects. Eur J Endocrinol 1994; 130:472–7. ISSN 0804–4643 Bright light is known as a strong zeitgeber on human circadian rhythms and influences several endocrine and neuroendocrine functions. In the present study we examined the influence of a 3-h bright light stimulus, given at different times during the day (morning or evening), on circadian patterns of cyclic adenosine monophosphate (cAMP), melatonin and cortisol. Two groups of synchronized healthy volunteers (lights on: 05.00–23.00 h) were exposed to bright light (2500 lux) for 3 h over 6 days either in the morning (05.00–08.00 h) or in the evening (18.00–21.00 h). The results showed a significant phase advance in the circadian rhythms of melatonin and cortisol when bright light was given in the morning but not when given in the evening. Rhythm in plasma cAMP basically was not affected by either light treatment. Björn Lemmer, Zentrum der Pharmakologie, JW Goethe Universität, Theodor-Stern-Kai 7, D-60590 Frankfurt/M, Germany
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Li, Min, Peiyu Wu, Jianhua Ding, Qi Yao, and Jiaqi Ju. "The Circadian Effect Versus Mesopic Vision Effect in Road Lighting Applications." Applied Sciences 10, no. 19 (October 6, 2020): 6975. http://dx.doi.org/10.3390/app10196975.
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Several models on the circadian effect have been applied to indoor circadian lighting design, but applications in road lighting have not yet been clarified. Based on existing models and circadian research, we examined equivalent melanopic lux (EML), circadian light (CLA), and circadian stimulus (CS) representing the circadian effect and the S/P ratio representing the mesopic vision effect, among a dataset of light sources at photopic adaptation illuminance values of 1, 3, 10, 30, and 100 lx. The results show that the S/P ratio correlates with EML and CS (or CLA) much stronger than it correlates with color temperature. The EMLs of light sources are below 50 EML in mesopic vision, and the CSs of most light sources are below or around the threshold value of 0.05. We conclude that the circadian effect is not a significant issue in mesopic vision under most conditions and that optimization for mesopic efficiency is still a good strategy. There are quite a few light sources that may achieve both ideal mesopic efficiency and low CS. This work clarifies the circadian effect and mesopic vision effect performance of light sources in mesopic vision and will help guide choosing suitable light sources and optimization strategies for road lighting.
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Stone, Julia E., Elise M. McGlashan, Nina Quin, Kayan Skinner, Jessica J. Stephenson, Sean W. Cain, and Andrew J. K. Phillips. "The Role of Light Sensitivity and Intrinsic Circadian Period in Predicting Individual Circadian Timing." Journal of Biological Rhythms 35, no. 6 (October 16, 2020): 628–40. http://dx.doi.org/10.1177/0748730420962598.
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There is large interindividual variability in circadian timing, which is underestimated by mathematical models of the circadian clock. Interindividual differences in timing have traditionally been modeled by changing the intrinsic circadian period, but recent findings reveal an additional potential source of variability: large interindividual differences in light sensitivity. Using an established model of the human circadian clock with real-world light recordings, we investigated whether changes in light sensitivity parameters or intrinsic circadian period could capture variability in circadian timing between and within individuals. Healthy participants ( n = 12, aged 18-26 years) underwent continuous light monitoring for 3 weeks (Actiwatch Spectrum). Salivary dim-light melatonin onset (DLMO) was measured each week. Using the recorded light patterns, a sensitivity analysis for predicted DLMO times was performed, varying 3 model parameters within physiological ranges: (1) a parameter determining the steepness of the dose-response curve to light ( p), (2) a parameter determining the shape of the phase-response curve to light ( K), and (3) the intrinsic circadian period ( tau). These parameters were then fitted to obtain optimal predictions of the three DLMO times for each individual. The sensitivity analysis showed that the range of variation in the average predicted DLMO times across participants was 0.65 h for p, 4.28 h for K, and 3.26 h for tau. The default model predicted the DLMO times with a mean absolute error of 1.02 h, whereas fitting all 3 parameters reduced the mean absolute error to 0.28 h. Fitting the parameters independently, we found mean absolute errors of 0.83 h for p, 0.53 h for K, and 0.42 h for tau. Fitting p and K together reduced the mean absolute error to 0.44 h. Light sensitivity parameters captured similar variability in phase compared with intrinsic circadian period, indicating they are viable targets for individualizing circadian phase predictions. Future prospective work is needed that uses measures of light sensitivity to validate this approach.
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Arble, Deanna M., Jenna Holland, Nickki Ottaway, Joyce Sorrell, Joshua W. Pressler, Rachel Morano, Stephen C. Woods, et al. "The Melanocortin-4 Receptor Integrates Circadian Light Cues and Metabolism." Endocrinology 156, no. 5 (March 2, 2015): 1685–91. http://dx.doi.org/10.1210/en.2014-1937.
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The melanocortin system directs diverse physiological functions from coat color to body weight homoeostasis. A commonality among melanocortin-mediated processes is that many animals modulate similar processes on a circannual basis in response to longer, summer days, suggesting an underlying link between circadian biology and the melanocortin system. Despite key neuroanatomical substrates shared by both circadian and melanocortin-signaling pathways, little is known about the relationship between the two. Here we identify a link between circadian disruption and the control of glucose homeostasis mediated through the melanocortin-4 receptor (Mc4r). Mc4r-deficient mice exhibit exaggerated circadian fluctuations in baseline blood glucose and glucose tolerance. Interestingly, exposure to lighting conditions that disrupt circadian rhythms improve their glucose tolerance. This improvement occurs through an increase in glucose clearance by skeletal muscle and is food intake and body weight independent. Restoring Mc4r expression to the paraventricular nucleus prevents the improvement in glucose tolerance, supporting a role for the paraventricular nucleus in the integration of circadian light cues and metabolism. Altogether these data suggest that Mc4r signaling plays a protective role in minimizing glucose fluctuations due to circadian rhythms and environmental light cues and demonstrate a previously undiscovered connection between circadian biology and glucose metabolism mediated through the melanocortin system.
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Rumanova, Valentina S., Monika Okuliarova, and Michal Zeman. "Differential Effects of Constant Light and Dim Light at Night on the Circadian Control of Metabolism and Behavior." International Journal of Molecular Sciences 21, no. 15 (July 31, 2020): 5478. http://dx.doi.org/10.3390/ijms21155478.
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The disruption of circadian rhythms by environmental conditions can induce alterations in body homeostasis, from behavior to metabolism. The light:dark cycle is the most reliable environmental agent, which entrains circadian rhythms, although its credibility has decreased because of the extensive use of artificial light at night. Light pollution can compromise performance and health, but underlying mechanisms are not fully understood. The present review assesses the consequences induced by constant light (LL) in comparison with dim light at night (dLAN) on the circadian control of metabolism and behavior in rodents, since such an approach can identify the key mechanisms of chronodisruption. Data suggest that the effects of LL are more pronounced compared to dLAN and are directly related to the light level and duration of exposure. Dim LAN reduces nocturnal melatonin levels, similarly to LL, but the consequences on the rhythms of corticosterone and behavioral traits are not uniform and an improved quantification of the disrupted rhythms is needed. Metabolism is under strong circadian control and its disruption can lead to various pathologies. Moreover, metabolism is not only an output, but some metabolites and peripheral signal molecules can feedback on the circadian clockwork and either stabilize or amplify its desynchronization.
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Swaminathan, Krithika, Elizabeth B. Klerman, and Andrew J. K. Phillips. "Are Individual Differences in Sleep and Circadian Timing Amplified by Use of Artificial Light Sources?" Journal of Biological Rhythms 32, no. 2 (April 2017): 165–76. http://dx.doi.org/10.1177/0748730417699310.
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Within the human population, there is large interindividual variability in the timing of sleep and circadian rhythms. This variability has been attributed to individual differences in sleep physiology, circadian physiology, and/or light exposure. Recent experimental evidence suggests that the latter is necessary to evoke large interindividual differences in sleep and circadian timing. We used a validated model of human sleep and circadian physiology to test the hypothesis that intrinsic differences in sleep and circadian timing are amplified by self-selected use of artificial light sources. We tested the model under 2 conditions motivated by an experimental study (Wright et al., 2013): (1) a “natural” light cycle, and (2) a “realistic” light cycle that included attenuation of light due to living indoors when natural light levels are high and use of electric light when natural light levels are low. Within these conditions, we determined the relationship between intrinsic circadian period (within the range of 23.7-24.6 h) and timing of sleep onset, sleep offset, and circadian rhythms. In addition, we simulated a work week, with fixed wake time for 5 days and free sleep times on weekends. Under both conditions, a longer intrinsic period resulted in later sleep and circadian timing. Compared to the natural condition, the realistic condition evoked more than double the variation in sleep timing across the physiological range of intrinsic circadian periods. Model predictions closely matched data from the experimental study. We found that if the intrinsic circadian period was long (>24.2 h) under the realistic condition, there was significant mismatch in sleep timing between weekdays and weekends, which is known as social jetlag. These findings indicate that individual tendencies to have very delayed schedules can be greatly amplified by self-selected modifications to the natural light/dark cycle. This has important implications for therapeutic treatment of advanced or delayed sleep phase disorders.
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Beaulé, Christian, and Hai-Ying M. Cheng. "The Acetyltransferase CLOCK Is Dispensable for Circadian Aftereffects in Mice." Journal of Biological Rhythms 26, no. 6 (November 30, 2011): 561–64. http://dx.doi.org/10.1177/0748730411416329.
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Recent demonstration of the histone acetyltransferase activity of the Clock gene greatly expanded the regulatory role of circadian clocks in gene transcription. Clock and its partner Bmal1 are responsible for the generation of circadian oscillations that are synchronized (entrained) to the external light cycle. Entraining light often produces long-lasting changes in the endogenous period called aftereffects. Aftereffects are light-dependent alterations in the speed of free-running rhythms that persist for several weeks upon termination of light exposure. How light causes such long-lasting changes is unknown. However, the persistent nature of circadian aftereffects in conjunction with the long-term effects of epigenetic modifications on development and various aspects of brain physiology prompted us to hypothesize that the histone acetyltransferase CLOCK was required for circadian aftereffects. The authors exposed Clock knockout mice to 25-hour light cycles and report that these mice retain the ability to display circadian aftereffects, indicating that Clock is dispensable for this form of circadian plasticity.
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Curtis, Annie. "Sussing out sensitivity to light: How evening light impacts individuals’ circadian systems." Science Translational Medicine 11, no. 498 (June 26, 2019): eaax9568. http://dx.doi.org/10.1126/scitranslmed.aax9568.
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WILKINSON, SOPHIE. "Shedding light on the circadian clock." Chemical & Engineering News 77, no. 30 (July 26, 1999): 9–10. http://dx.doi.org/10.1021/cen-v077n030.p009a.
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Van Gelder, R. N. "Blue light and the circadian clock." British Journal of Ophthalmology 88, no. 10 (October 1, 2004): 1353. http://dx.doi.org/10.1136/bjo.2004.042861/045120.
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REA, Mark S. "Toward a Definition of Circadian Light." Journal of Light & Visual Environment 35, no. 3 (2011): 250–54. http://dx.doi.org/10.2150/jlve.35.250.
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Basu, Priyoneel, Naomi Ie, Adrienne L. Wensel, Joelle D. Baskerville, Victoria M. Smith, and Michael C. Antle. "Triptans attenuate circadian responses to light." European Journal of Neuroscience 42, no. 7 (August 25, 2015): 2489–95. http://dx.doi.org/10.1111/ejn.13032.
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Harrington, Monica. "Shedding light on circadian clock control." Lab Animal 44, no. 7 (June 19, 2015): 247. http://dx.doi.org/10.1038/laban.808.
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Persson, P. B., and A. Bondke Persson. "Light and darkness in circadian rhythms." Acta Physiologica 222, no. 3 (February 2, 2018): e13036. http://dx.doi.org/10.1111/apha.13036.
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Foster, RG. "Fundamentals of circadian entrainment by light." Lighting Research & Technology 53, no. 5 (July 20, 2021): 377–93. http://dx.doi.org/10.1177/14771535211014792.
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Light at dawn and dusk is the key signal for the entrainment of the circadian clock. Light at dusk delays the clock. Light at dawn advances the clock. The threshold for human entrainment requires relatively bright light for a long duration, but the precise irradiance/duration relationships for photoentrainment have yet to be fully defined. Photoentrainment is achieved by a network of photosensitive retinal ganglion cells (pRGCs) which utilise the short-wavelength light-sensitive photopigment, melanopsin. Although rods and cones are not required, they do play a role in photoentrainment, by projecting to and modulating the endogenous photosensitivity of the pRGCs, but in a manner that remains poorly understood. It is also important to emphasise that the age and prior light exposure of an individual will modify the efficacy of entrainment stimuli. Because of the complexity of photoreceptor interactions, attempts to develop evidence-based human centric lighting are not straightforward. We need to study how humans respond to dynamic light exposure in the ‘real world’ where light intensity, duration, spectral quality and the time of exposure vary greatly. Defining these parameters will allow the development of electric lighting systems that will enhance human circadian entrainment.
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Rea, MS, and MG Figueiro. "Light as a circadian stimulus for architectural lighting." Lighting Research & Technology 50, no. 4 (December 6, 2016): 497–510. http://dx.doi.org/10.1177/1477153516682368.
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Consideration is being given to the adoption of a new metric characterizing light as it affects the human circadian system. Much has been learned over the past couple of decades about light as a stimulus for circadian system regulation, so it is appropriate that these discussions take place. The present paper develops an argument for adopting circadian stimulus as a metric for quantifying light in architectural spaces. The circadian stimulus metric (a) was developed from several lines of biophysical research, including those from basic retinal neurophysiology; (b) has been validated in several controlled experiments; and (c) has been used successfully in a number of real-world applications. Any discussions of new metrics should take each of these foundational points into consideration.
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Eo, Yun Jae, Seohyeon Kim, Keyong Nam Lee, Dae Hwan Kim, Changwook Kim, Seung Min Lee, and Young Rag Do. "Fabrication of Circadian Light Meter with Non-Periodic Optical Filters to Evaluate the Non-Visual Effects of Light on Humans." Applied Sciences 11, no. 18 (September 7, 2021): 8283. http://dx.doi.org/10.3390/app11188283.
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Given that light is known to function as a zeitgeber, having the greatest influence on the human circadian rhythm, it is necessary to assess the effects of light on humans with the goal of maintaining the circadian rhythm. Herein, we fabricated a simple circadian light meter that directly measures the non-visual effects of light using optical filters that mimic the non-visual action spectrum. The fabricated light meter was calibrated and verified through the values obtained from a conventional illuminance spectrophotometer. Furthermore, during 24 h of everyday life, 11 participants wore hats equipped with the developed light meter so that we could investigate the effects of the light environment to which they were exposed to, both indoors and outdoors. For comparison, natural outdoor illumination was also measured with the same light meter. Based on the considerable difference between the light exposure levels during the daytime and nighttime, it is possible that the participant’s melatonin levels would be impacted by the light exposure measured by the light meter. Consequently, based on the light exposure measurements made in this study, the proposed circadian light meter would be a valuable tool for real world circadian lighting studies that require actual light dose to the eyes of the test subjects.
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Heussen, Raphaela, and David Whitmore. "The Importance of Stochastic Effects for Explaining Entrainment in the Zebrafish Circadian Clock." Computational and Mathematical Methods in Medicine 2015 (2015): 1–9. http://dx.doi.org/10.1155/2015/254979.
Full textAbstract:
The circadian clock plays a pivotal role in modulating physiological processes and has been implicated, either directly or indirectly, in a range of pathological states including cancer. Here we investigate how the circadian clock is entrained by external cues such as light. Working with zebrafish cell lines and combining light pulse experiments with simulation efforts focused on the role of synchronization effects, we find that even very modest doses of light exposure are sufficient to trigger some entrainment, whereby a higher light intensity or duration correlates with strength of the circadian signal. Moreover, we observe in the simulations that stochastic effects may be considered an essential feature of the circadian clock in order to explain the circadian signal decay in prolonged darkness, as well as light initiated resynchronization as a strong component of entrainment.
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Alzate-Correa, Diego, Sydney Aten, Moray J. Campbell, Kari R. Hoyt, and Karl Obrietan. "Light-induced changes in the suprachiasmatic nucleus transcriptome regulated by the ERK/MAPK pathway." PLOS ONE 16, no. 6 (June 30, 2021): e0249430. http://dx.doi.org/10.1371/journal.pone.0249430.
Full textAbstract:
The mammalian master circadian pacemaker within the suprachiasmatic nucleus (SCN) maintains tight entrainment to the 24 hr light/dark cycle via a sophisticated clock-gated rhythm in the responsiveness of the oscillator to light. A central event in this light entrainment process appears to be the rapid induction of gene expression via the ERK/MAPK pathway. Here, we used RNA array-based profiling in combination with pharmacological disruption methods to examine the contribution of ERK/MAPK signaling to light-evoked gene expression. Transient photic stimulation during the circadian night, but not during the circadian day, triggered marked changes in gene expression, with early-night light predominately leading to increased gene expression and late-night light predominately leading to gene downregulation. Functional analysis revealed that light-regulated genes are involved in a diversity of physiological processes, including DNA transcription, RNA translation, mRNA processing, synaptic plasticity and circadian timing. The disruption of MAPK signaling led to a marked reduction in light-evoked gene regulation during the early night (32/52 genes) and late night (190/191 genes); further, MAPK signaling was found to gate gene expression across the circadian cycle. Together, these experiments reveal potentially important insights into the transcriptional-based mechanisms by which the ERK/MAPK pathway regulates circadian clock timing and light-evoked clock entrainment.
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Lowden, A., and G. Kecklund. "Considerations on how to light the night-shift." Lighting Research & Technology 53, no. 5 (July 20, 2021): 437–52. http://dx.doi.org/10.1177/14771535211012251.
Full textAbstract:
Electric lighting has decreased dependence on natural light to illuminate the workplace. Humans are genetically predisposed to be day-oriented (diurnal) and depend on daylight to regulate circadian rhythms. Shift work will force workers to sleep and work at non-biological times, inducing circadian disruption with implications for workers’ safety and health. The scientific literature may be used in practice in shift work settings to improve safety, performance and health in the workplace by reducing circadian misalignment. Alertness profiles at work and degree of melatonin suppression may indicate degree of circadian disruption among workers. However, when considering lighting solutions at night, there are several factors that need consideration. Light measures based on biological effectiveness should be used rather than room illuminance giving better predictions of performance and long-term health among workers. Also, large individual differences in light sensitivity and preferences suggest not only to rely on common lighting alone but also to implement complementary individual lighting solutions at work. Lighting advice should consider shift scheduling characteristics such as speed of turnover and shift timing to guide decisions of preferred circadian phase influence. Lighting should also include the flexibility to be fit for morning, afternoon and evening work.
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Stack, Nora, David Barker, Mary Carskadon, and Cecilia Diniz Behn. "A Model-Based Approach to Optimizing Ultradian Forced Desynchrony Protocols for Human Circadian Research." Journal of Biological Rhythms 32, no. 5 (September 27, 2017): 485–98. http://dx.doi.org/10.1177/0748730417730488.
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The human circadian system regulates internal 24-h rhythmicity and plays an important role in many aspects of human health and behavior. To investigate properties of the human circadian pacemaker such as intrinsic period and light sensitivity, experimental researchers have developed forced desynchrony (FD) protocols in which manipulations of the light-dark (LD) cycle are used to desynchronize the intrinsic circadian rhythm from the rest-activity cycle. FD protocols have typically been based on exposure to long LD cycles, but recently, ultradian FD protocols with short LD cycles have been proposed as a new methodology for assessing intrinsic circadian period. However, the effects of ultradian FD protocol design, including light intensity or study duration, on estimates of intrinsic circadian period have not, to our knowledge, been systematically studied. To address this gap, we applied a light-sensitive, dynamic mathematical model of the human circadian pacemaker to simulate ultradian FD protocols and analyze the effects of protocol design on estimates of intrinsic circadian period. We found that optimal estimates were obtained using protocols with low light intensities, at least 10 d of exposure to ultradian cycling, and a 7-h LD cycle duration that facilitated uniform light exposure across all circadian phases. Our results establish a theoretical framework for ultradian FD protocols that can be used to provide insights into data obtained under existing protocols and to optimize protocols for future experiments.
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Jakubowski, Piotr. "Artificial light sources as light pollutant of humans melatonin suppression." Photonics Letters of Poland 11, no. 3 (September 30, 2019): 78. http://dx.doi.org/10.4302/plp.v11i3.925.
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Blue light emitted by LEDs might influence on natural biological rhythm of human being, what can be considered as environment pollution. In this paper the effect of the latest commercially available LEDs on melatonin suppression index (MSI) was analyzed. Research was done based on spectral power distribution of given LED (SPD) and melatonin suppression function in reference to melatonin suppression under daylight (illuminant D65). Results of calculations shows strong correlation between CCT and MSI, however MSI factor might vary for different LEDs with same CCT. Full Text: PDF ReferencesC. C. Sun, et al., Packaging efficiency in phosphor-converted white LEDs and its impact to the limit of luminous efficacy, Journal of Solid State Lighting, 1:19, (2014). CrossRef M. S. Rea, M. G. Figueiro, J. D. Bullough, "Circadian photobiology: An emerging framework for lighting practice and research", Light Research Technology Vol. 34(3), (2002). CrossRef I. Fryc, P. Jakubowski, K. Kołacz, Analysis of optical radiation parameters of compact discharge HID lamps and LED COB modules used for illuminating shop windows, Przeglad Elektrotechniczny, R. 93, No. 11, (2017). CrossRef G. C. Brainard, J. P. Hanifin, J.M. Greeson, B. Byrne, E. Gerner, D. D. Rollang, "Action spectrum for melatonin regulation in humans: evidence for a novel circadian photoreceptor", Journal of Neuroscience vol. 21, (2001). CrossRef K. Thapan, J. Arendt, D. J. Skene, "An action spectrum for melatonin supression: evidence for a novel non-rod, non-cone photoreceptor system in humans," Journal of Physiology vol. 535, (2001). CrossRef I. Fryc, J. Fryc, P. Jakubowski, K. A. Wąsowski, Technical, medical and legal aspects of domestic light sources photobiological safety, Przeglad Elektrotechniczny, R. 93, No. 3, (2017). CrossRef J. Enzi et. al, A "Melanopic" Spectral Efficiency Function Predicts the Sensitivity of Melanopsin Photoreceptors to Polychromatic Lights Journal of biological rhytms, Vol. 26 No. 4, (2011). CrossRef M. Aube, J. Roby J, M. Kocifaj, Evaluating Potential Spectral Impacts of Various Artificial Lights on Melatonin Suppression, Photosynthesis, and Star Visibility. PLOS ONE, Vol. 8, (2013). CrossRef P. Jakubowski, I. Fryc, Metrological requirements for measurements of circadian radiation, Optica Applicata, Vol. 48 Issue 4, (2018). CrossRef P. Jakubowski, I. Fryc, Measurement methods of optical radiation in circadian active range, Zeszyty Naukowe Wydziału Elektrotechniki i Automatyki Politechniki Gdańskiej, nr 54 (2017). DirectLink P. Jakubowski, Comparative analysis of light parameters of LEDs and OLEDs in context of blue light emission, Polish Journal for Sustainable Development 21 (2), (2017). CrossRef CIE TN003:2015, "Report on the First International Workshop on Circadian and neurophysiological Photometry", (2015). DirectLink
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Bano-Otalora, Beatriz, Franck Martial, Court Harding, David A. Bechtold, Annette E. Allen, Timothy M. Brown, Mino D. C. Belle, and Robert J. Lucas. "Bright daytime light enhances circadian amplitude in a diurnal mammal." Proceedings of the National Academy of Sciences 118, no. 22 (May 24, 2021): e2100094118. http://dx.doi.org/10.1073/pnas.2100094118.
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Mammalian circadian rhythms are orchestrated by a master pacemaker in the hypothalamic suprachiasmatic nuclei (SCN), which receives information about the 24 h light–dark cycle from the retina. The accepted function of this light signal is to reset circadian phase in order to ensure appropriate synchronization with the celestial day. Here, we ask whether light also impacts another key property of the circadian oscillation, its amplitude. To this end, we measured circadian rhythms in behavioral activity, body temperature, and SCN electrophysiological activity in the diurnal murid rodent Rhabdomys pumilio following stable entrainment to 12:12 light–dark cycles at four different daytime intensities (ranging from 18 to 1,900 lx melanopic equivalent daylight illuminance). R. pumilio showed strongly diurnal activity and body temperature rhythms in all conditions, but measures of rhythm robustness were positively correlated with daytime irradiance under both entrainment and subsequent free run. Whole-cell and extracellular recordings of electrophysiological activity in ex vivo SCN revealed substantial differences in electrophysiological activity between dim and bright light conditions. At lower daytime irradiance, daytime peaks in SCN spontaneous firing rate and membrane depolarization were substantially depressed, leading to an overall marked reduction in the amplitude of circadian rhythms in spontaneous activity. Our data reveal a previously unappreciated impact of daytime light intensity on SCN physiology and the amplitude of circadian rhythms and highlight the potential importance of daytime light exposure for circadian health.
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Binkley, S., and K. Mosher. "Photoperiod modifies circadian resetting responses in sparrows." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 251, no. 6 (December 1, 1986): R1156—R1162. http://dx.doi.org/10.1152/ajpregu.1986.251.6.r1156.
Full textAbstract:
Circadian responses to photoperiod were studied in house sparrows (Passer domesticus) by subjecting them to 4-h light pulses and measuring the subsequent phases of their circadian rhythms. The direction and magnitude of phase shifts in response to 4-h light pulses following pretreatment with light-dark cycles (LD) 16:8 or LD 8:16 varied with time of day; advances (3.4 h) occurred when pulses were imposed in the late subjective night on both groups of birds; delays (-2.1 h) occurred when the pulses were imposed in the early subjective night on the LD 8:16 birds. The time profiles for responses to light pulses that scanned 24 h (phase-response curves) were modified by long and short photoperiod. Short photoperiod 1) increased amplitude (1.7 h), 2) increased time from the prior lights-out to the peak of advances (6 h), and 3) decreased the mean phase shift (0.9 h).
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Roccaro, Ilaria, and Daniela Smirni. "Fiat Lux: The Light Became Therapy. An Overview on the Bright Light Therapy in Alzheimer’s Disease Sleep Disorders." Journal of Alzheimer's Disease 77, no. 1 (September 1, 2020): 113–25. http://dx.doi.org/10.3233/jad-200478.
Full textAbstract:
Background: A system of photosensitive retinal ganglion cells provides ‘non-visual’ information on the circadian sequences of light to the suprachiasmatic nucleus (SCN), which, as the ‘master clock’, synchronizes the chronobiological mechanisms of all the biological clocks. Damage to SCN structure alters circadian behavioral and hormonal rhythms and interferes with a regular sleep-wake pattern. Several studies have shown that, in aging and in Alzheimer’s disease (AD), circadian rhythms change their synchronization with the environment and behavior loses sync with light. Objective: The current overview aims to examine research studies showing the effect of bright light therapy (BLT) on sleep disorders and sleep-wake patterns in AD. Methods: A literature search was conducted, taking into consideration the relevant studies over the last 20 years. Fifteen studies have been thorough: seven followed an environmental-architectural approach and eight followed a treatment devices approach. Results: Studies agree in considering BLT as a promising non-pharmacological intervention to compensate for circadian rhythm alterations and they support the need for standardized protocols that allow a comparison between multicenter studies. Conclusion: Interestingly, in an attempt to contain the spread of the COVID-19 pandemic, health authorities have forced the population to stay home. Therefore, AD people are not currently able to enjoy exposure to sunlight. It is predictable that they may experience an exacerbation of circadian disturbances and that the BLT can be an effective response to prevent such exacerbation.
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Hannay, Kevin M., Victoria Booth, and Daniel B. Forger. "Macroscopic Models for Human Circadian Rhythms." Journal of Biological Rhythms 34, no. 6 (October 16, 2019): 658–71. http://dx.doi.org/10.1177/0748730419878298.
Full textAbstract:
Mathematical models have a long and influential history in the study of human circadian rhythms. Accurate predictive models for the human circadian light response have been used to study the impact of a host of light exposures on the circadian system. However, generally, these models do not account for the physiological basis of these rhythms. We illustrate a new paradigm for deriving models of the human circadian light response. Beginning from a high-dimensional model of the circadian neural network, we systematically derive low-dimensional models using an approach motivated by experimental measurements of circadian neurons. This systematic reduction allows for the variables and parameters of the derived model to be interpreted in a physiological context. We fit and validate the resulting models to a library of experimental measurements. Finally, we compare model predictions for experimental measurements of light levels and discuss the differences between our model’s predictions and previous models. Our modeling paradigm allows for the integration of experimental measurements across the single-cell, tissue, and behavioral scales, thereby enabling the development of accurate low-dimensional models for human circadian rhythms.
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Nagare, Rohan, May Woo, Piers MacNaughton, Barbara Plitnick, Brandon Tinianov, and Mariana Figueiro. "Access to Daylight at Home Improves Circadian Alignment, Sleep, and Mental Health in Healthy Adults: A Crossover Study." International Journal of Environmental Research and Public Health 18, no. 19 (September 23, 2021): 9980. http://dx.doi.org/10.3390/ijerph18199980.
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As the primary environmental cue for the body’s master biological clock, light–dark patterns are key for circadian alignment and are ultimately fundamental to multiple dimensions of health including sleep and mental health. Although daylight provides the proper qualities of light for promoting circadian alignment, our modern indoor lifestyles offer fewer opportunities for adequate daylight exposure. This field study explores how increasing circadian-effective light in residences affects circadian phase, sleep, vitality, and mental health. In this crossover study, 20 residents spent one week in their apartments with electrochromic glass windows and another week with functionally standard windows with blinds. Calibrated light sensors revealed higher daytime circadian-effective light levels with the electrochromic glass windows, and participants exhibited consistent melatonin onset, a 22-min earlier sleep onset, and higher sleep regularity. In the blinds condition, participants exhibited a 15-min delay in dim light melatonin onset, a delay in subjective vitality throughout the day, and an overall lower positive affect. This study demonstrates the impact of daytime lighting on the physiological, behavioral, and subjective measures of circadian health in a real-world environment and stresses the importance of designing buildings that optimize daylight for human health and wellbeing.
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Smith, Kristina M., Gencer Sancar, Rigzin Dekhang, Christopher M. Sullivan, Shaojie Li, Andrew G. Tag, Cigdem Sancar, et al. "Transcription Factors in Light and Circadian Clock Signaling Networks Revealed by Genomewide Mapping of Direct Targets for Neurospora White Collar Complex." Eukaryotic Cell 9, no. 10 (July 30, 2010): 1549–56. http://dx.doi.org/10.1128/ec.00154-10.
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ABSTRACT Light signaling pathways and circadian clocks are inextricably linked and have profound effects on behavior in most organisms. Here, we used chromatin immunoprecipitation (ChIP) sequencing to uncover direct targets of the Neurospora crassa circadian regulator White Collar Complex (WCC). The WCC is a blue-light receptor and the key transcription factor of the circadian oscillator. It controls a transcriptional network that regulates ∼20% of all genes, generating daily rhythms and responses to light. We found that in response to light, WCC binds to hundreds of genomic regions, including the promoters of previously identified clock- and light-regulated genes. We show that WCC directly controls the expression of 24 transcription factor genes, including the clock-controlled adv-1 gene, which controls a circadian output pathway required for daily rhythms in development. Our findings provide links between the key circadian activator and effectors in downstream regulatory pathways.
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Van Den Pol, Anthony N., Vinh Cao, and H. Craig Heller. "Circadian system of mice integrates brief light stimuli." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 275, no. 2 (August 1, 1998): R654—R657. http://dx.doi.org/10.1152/ajpregu.1998.275.2.r654.
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Light is the primary sensory stimulus that synchronizes or entrains the internal circadian rhythms of animals to the solar day. In mammals photic entrainment of the circadian pacemaker residing in the suprachiasmatic nuclei is due to the fact that light at certain times of day can phase shift the pacemaker. In this study we show that the circadian system of mice can integrate extremely brief, repeated photic stimuli to produce large phase shifts. A train of 2-ms light pulses delivered as one pulse every 5 or 60 s, with a total light duration of 120 ms, can cause phase shifts of several hours that endure for weeks. Single 2-ms pulses of light were ineffective. Thus these data reveal a property of the mammalian circadian clock: it can integrate and store latent sensory information in such a way that a series of extremely brief photic stimuli, each too small to cause a phase shift individually, together can cause a large and long-lasting change in behavior.
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Lockley, Steven W., George C. Brainard, and Charles A. Czeisler. "High Sensitivity of the Human Circadian Melatonin Rhythm to Resetting by Short Wavelength Light." Journal of Clinical Endocrinology & Metabolism 88, no. 9 (September 1, 2003): 4502–5. http://dx.doi.org/10.1210/jc.2003-030570.
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The endogenous circadian oscillator in mammals, situated in the suprachiasmatic nuclei, receives environmental photic input from specialized subsets of photoreceptive retinal ganglion cells. The human circadian pacemaker is exquisitely sensitive to ocular light exposure, even in some people who are otherwise totally blind. The magnitude of the resetting response to white light depends on the timing, intensity, duration, number and pattern of exposures. We report here that the circadian resetting response in humans, as measured by the pineal melatonin rhythm, is also wavelength dependent. Exposure to 6.5 h of monochromatic light at 460 nm induces a two-fold greater circadian phase delay than 6.5 h of 555 nm monochromatic light of equal photon density. Similarly, 460 nm monochromatic light causes twice the amount of melatonin suppression compared to 555 nm monochromatic light, and is dependent on the duration of exposure in addition to wavelength. These studies demonstrate that the peak of sensitivity of the human circadian pacemaker to light is blue-shifted relative to the three-cone visual photopic system, the sensitivity of which peaks at ∼555 nm. Thus photopic lux, the standard unit of illuminance, is inappropriate when quantifying the photic drive required to reset the human circadian pacemaker.
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Lusczek, Elizabeth R., and Melissa P. Knauert. "Light Levels in ICU Patient Rooms: Dimming of Daytime Light in Occupied Rooms." Journal of Patient Experience 8 (January 1, 2021): 237437352110331. http://dx.doi.org/10.1177/23743735211033104.
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One-third of patients report disruption of sleep by overnight light. Importantly, light causes both immediate sleep disturbance and influences circadian function, a fundamental process underpinning high-quality sleep. Short bursts of light at night and/or lack of bright daytime light disrupt circadian alignment, leading to sleep deficiency. To improve understanding of 24-hour light patterns, we conducted a longitudinal study of light levels in intensive care unit (ICU) rooms. Over 450 room-days, we observed high variability, dim daytime light, and active dimming of natural sunlight in occupied rooms. Such noncircadian light patterns have multifactorial influences on sleep and are a key target for sleep improvement in the ICU.
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Kalustova, D., V. Kornaga, A. Rybalochka, and S. Valyukh. "Space of visual and circadian parameters of RGBW lighting systems." Lighting engineering and power engineering 1, no. 57 (April 6, 2020): 16–21. http://dx.doi.org/10.33042/2079-424x-2020-1-57-16-21.
Full textAbstract:
Due to the proven effect of light on human circadian rhythms, nowadays researchers and developers of lighting systems (LS) concentrate on the non-visual parameters of light and methods of ensuring a safe comfortable light environment. This requires optimisation of spectral power distribution (SPD). In this view the most promising and functional are RGBW systems due to their ability to change dynamically SPD and, hence, light parameters. In this work we explore two RGBW (red-greenblue-white) systems with different white LEDs (warm white and neutral white) and the space of visual and non-visual parameters that they can ensure. Visual parameters are studied in terms of colour rendering index, colour fidelity index and visual corneal illuminance while non-visual parameters are studied in terms of circadian light, circadian stimulus and circadian action factor. These parameters are calculated for different contribution of the components in a correlated colour temperature (CCT) range of 2500 – 7000K. In addition, acceptable criterion of the colour fidelity index above 85 is used. It is shown that under this condition the circadian action factor in the range of 0.33-0.98 can be obtained by changing the CCT and (or) colour fidelity index. Also an achievable area of the circadian stimulus versus corneal illuminance space for RGBW systems is found. It enables to choose optimal combination of CCT, circadian stimulus and corneal illuminance to provide the desired level of circadian effect with sufficient visual comfort depending on the daytime and field of system's implementation. This data is useful for LS manufacturers and lighting designers to create a comfortable lighting environment. Keywords - RGBW colour mixing, tunable white light, circadian effect, colour rendering, colour fidelity index.
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Kujur, Pratibha. "Locomotor activity rhythm of catfish Heteropneustes fossilis are prominently regulated by light-dark cues." South Asian Journal of Experimental Biology 11, no. 2 (April 15, 2021): 128–35. http://dx.doi.org/10.38150/sajeb.11(2).p128-135.
Full textAbstract:
It is interesting to explore, the circadian locomotor activity rhythm of dark adapted fishes. Therefore, it is aimed to investigate the circadian locomotor activity rhythm of catfish, Heteropneustes fossilis under different light regi-mens- light-dark condition LD 12:12, constant dark condition DD, constant light LL and dark-light condition DL 12:12 in both male and female. The study was conducted sequentially under LD 12: 12 (LON 0500 and LOFF 1700) and thereafter under the DD, LL and DL each for at least 10-12 consecutive days. The locomotor activity was monitored using Stanford Chronobiology Kit at a fixed period of 24 h. The three rhythm parameters obtained were Mesor (M, rhythm-adjusted 24-h average), amplitude (A) and acrophase (peak, Ø). All fish exhibited a statistically significant (p<0.001) circadian rhythm in locomo-tor activity under all light regimens LD, DD, LL and DL. The circadian ampli-tude was significantly declined under constant DD and LL. A significant shift was displayed in the circadian acrophase in all fish under each photic re-gimes LD, DD, LL and DL. The effect of light condition on M, A and Ø was sig-nificant, while gender imposed no effect. Chi-square periodogram revealed τ > 24 h in locomotor activity of most of the replicates under DD and LL. The respective study suggests that the endogenous circadian clocks in catfish H.fossilis are weakly expressed under constant conditions and requires light-dark LD or dark- light DL cues to generate/express the circadian rhythm in locomotor activity.
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Ngarambe, Jack, Inhan Kim, and Geun Young Yun. "Influences of Spectral Power Distribution on Circadian Energy, Visual Comfort and Work Performance." Sustainability 13, no. 9 (April 26, 2021): 4852. http://dx.doi.org/10.3390/su13094852.
Full textAbstract:
Spectral power distribution (SPD) is an essential element that has considerable implications on circadian energy and the perception of lit environments. The present study assessed the potential influences of SPD on energy consumption (i.e., considering circadian energy), visual comfort, work performance and mood. Two lighting conditions based on light-emitting diode (LED) and organic light-emitting diode (OLED) were used as proxies for SPDs of different spectral content: dominant peak wavelength of 455 nm (LED) and 618 nm (OLED). Using measured photometric values, the circadian light (CL), melatonin suppression (MS), and circadian efficacy (CE) of the two lighting sources were estimated via a circadian-phototransduction model and compared. Additionally, twenty-six participants were asked to evaluate the said lit environments subjectively in terms of visual comfort and self-reported work performance. Regarding circadian lighting and the associated energy implications, the LED light source induced higher biological actions with relatively less energy than the OLED light source. For visual comfort, OLED lighting-based conditions were preferred to LED lighting-based conditions, while the opposite was true when considering work performance and mood. The current study adds to the on-going debate regarding human-centric lighting, particularly considering the role of SPD in energy-efficient and circadian lighting practices.
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Challet, Etienne, Olivier van Reeth, and Fred W. Turek. "Altered circadian responses to light in streptozotocin-induced diabetic mice." American Journal of Physiology-Endocrinology and Metabolism 277, no. 2 (August 1, 1999): E232—E237. http://dx.doi.org/10.1152/ajpendo.1999.277.2.e232.
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Diabetes mellitus affects the daily expression of many behavioral and metabolic processes. Recent studies indicate that changes in brain glucose metabolism alter the entraining effects of light of the circadian pacemaker. To test whether diabetes-associated diurnal changes are related to alterations in the responses of the circadian pacemaker to light, photic phase resetting of the circadian rhythm of locomotor activity was analyzed in diabetic mice housed in constant darkness. Multiple low doses of streptozotocin, which damages pancreatic β-insulin-producing cells, were used to render C57BL/6J mice mildly diabetic. In those mice treated with streptozotocin, serum glucose was increased by 25% and circadian responses to light either were increased by 40% for phase delays or were close to those observed in control animals for phase advances. Furthermore, insulin-induced hypoglycemia normalized light-induced phase delays in diabetic animals, without altering those in nondiabetic mice. These results show that abnormalities of daily temporal organization associated with diabetes can result from altered circadian responses to the daily variation in ambient light. Such alterations could be normalized with appropriate insulin therapy.
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Salazar-Juárez, Alberto, Carolina Escobar, and Raúl Aguilar-Roblero. "Anterior paraventricular thalamus modulates light-induced phase shifts in circadian rhythmicity in rats." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 283, no. 4 (October 1, 2002): R897—R904. http://dx.doi.org/10.1152/ajpregu.00259.2002.
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The reciprocal connections between the paraventricular thalamic nucleus (PVT) and the suprachiasmatic nuclei suggest that PVT may participate in the regulation of circadian rhythms. We studied in rats the effect of lesions of the anterior and midposterior regions of the PVT on phase shifts of drinking circadian rhythm induced by light pulses at circadian times 6, 12, and 23, as well as the phase shifts produced by electrical or glutamatergic stimulation of the anterior PVT at the same circadian times. Lesion of the anterior PVT abolishes the advances induced by light during late subjective night, whereas midposterior PVT lesions did not affect the phase shifts. Electrical stimulation or glutamate injections in the anterior PVT mimic the phase-shifting effects of light pulses. These results indicate the participation of the anterior PVT as a modulator of entrainment of circadian rhythms to light.
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Kronauer, Richard E., Melissa A. St. Hilaire, Shadab A. Rahman, Charles A. Czeisler, and Elizabeth B. Klerman. "An Exploration of the Temporal Dynamics of Circadian Resetting Responses to Short- and Long-Duration Light Exposures: Cross-Species Consistencies and Differences." Journal of Biological Rhythms 34, no. 5 (August 2019): 497–514. http://dx.doi.org/10.1177/0748730419862702.
Full textAbstract:
Light is the most effective environmental stimulus for shifting the mammalian circadian pacemaker. Numerous studies have been conducted across multiple species to delineate wavelength, intensity, duration, and timing contributions to the response of the circadian pacemaker to light. Recent studies have revealed a surprising sensitivity of the human circadian pacemaker to short pulses of light. Such responses have challenged photon counting–based theories of the temporal dynamics of the mammalian circadian system to both short- and long-duration light stimuli. Here, we collate published light exposure data from multiple species, including gerbil, hamster, mouse, and human, to investigate these temporal dynamics and explore how the circadian system integrates light information at both short- and long-duration time scales to produce phase shifts. Based on our investigation of these data sets, we propose 3 new interpretations: (1) intensity and duration are independent factors of total phase shift magnitude, (2) the possibility of a linear/log temporal function of light duration that is universal for all intensities for durations less than approximately 12 min, and (3) a potential universal minimum light duration of ~0.7 sec that describes a “dead zone” of light stimulus. We show that these properties appear to be consistent across mammalian species. These interpretations, if confirmed by further experiments, have important practical implications in terms of understanding the underlying physiology and for the design of lighting regimens to reset the mammalian circadian pacemaker.