scholarly journals Circadian phase, circadian period and chronotype are reproducible over months

2017 ◽  
Vol 35 (2) ◽  
pp. 280-288 ◽  
Author(s):  
Thomas Kantermann ◽  
Charmane I Eastman
Keyword(s):  
Circadian Period ◽  
Circadian Phase

scholarly journals 0433 Targeting Light Sensitivity Parameters to Optimize Circadian Phase Predictions

SLEEP ◽  
2020 ◽  
Vol 43 (Supplement_1) ◽  
pp. A166-A166
Author(s):  
J E Stone ◽  
E M McGlashan ◽  
S W Cain ◽  
A J Phillips
Keyword(s):  
Sensitivity Analysis ◽  
Circadian Clock ◽  
Mean Absolute Error ◽  
Light Response ◽  
Absolute Error ◽  
Light Sensitivity ◽  
Model Parameters ◽  
Circadian Period ◽  
Individual Level ◽  
Circadian Phase

Abstract Introduction Existing models of the human circadian clock accurately predict phase at group-level but not at individual-level. Interindividual variability in light sensitivity is not currently accounted for in these models and may be a practical approach to improving individual-level predictions. Using the gold-standard predictive model, we (i) identified whether varying light sensitivity parameters produces meaningful changes in predicted phase in field conditions; and (ii) tested whether optimizing parameters can significantly improve accuracy of circadian phase prediction. Methods Healthy participants (n=12, 7 women, aged 18-26) underwent continuous light and activity monitoring for 3 weeks (Actiwatch Spectrum). Salivary dim light melatonin onset (DLMO) was measured each week. A model of the human circadian clock and its response to light was used to predict the three weekly DLMO times using the individual’s light data. A sensitivity analysis was performed varying three model parameters within physiological ranges: (i) amplitude of the light response [p]; (ii) advance vs. delay bias of the light response [K]; and (iii) intrinsic circadian period [tau]. These parameters were then fitted using least squares estimation to obtain optimal predictions of DLMO for each individual. Accuracy was compared between optimized parameters and default parameters. Results The default model predicted DLMO with mean absolute error of 1.02h. Sensitivity analysis showed the average range of variation in predicted DLMOs across participants was 0.65h for p, 4.28h for K and 3.26h for tau. Fitting parameters independently, we found mean absolute error of 0.85h for p, 0.71h for K and 0.75h for tau. Fitting p and K together reduced mean absolute error to 0.57h. Conclusion Light sensitivity parameters capture similar or greater variability in phase as intrinsic circadian period, indicating they are a viable option for individualising circadian phase predictions. Future prospective work is needed using measures of light sensitivity to validate this approach. Support N/A

scholarly journals Mutations in EID1 and LNK2 caused light-conditional clock deceleration during tomato domestication

2018 ◽  
Vol 115 (27) ◽  
pp. 7135-7140 ◽  
Author(s):  
Niels A. Müller ◽  
Lei Zhang ◽  
Maarten Koornneef ◽  
José M. Jiménez-Gómez
Keyword(s):  
Clock Gene ◽  
Genetic Basis ◽  
Allelic Variation ◽  
Genomic Region ◽  
Circadian Period ◽  
Circadian Phase ◽  
Signatures Of Selection ◽  
Period Lengthening ◽  
Phytochrome B1 ◽  
Light Input

Circadian period and phase of cultivated tomato (Solanum lycopersicum) were changed during domestication, likely adapting the species to its new agricultural environments. Whereas the delayed circadian phase is mainly caused by allelic variation of EID1, the genetic basis of the long circadian period has remained elusive. Here we show that a partial deletion of the clock gene LNK2 is responsible for the period lengthening in cultivated tomatoes. We use resequencing data to phylogenetically classify hundreds of tomato accessions and investigate the evolution of the eid1 and lnk2 mutations along successive domestication steps. We reveal signatures of selection across the genomic region of LNK2 and different patterns of fixation of the mutant alleles. Strikingly, LNK2 and EID1 are both involved in light input to the circadian clock, indicating that domestication specifically targeted this input pathway. In line with this, we show that the clock deceleration in the cultivated tomato is light-dependent and requires the phytochrome B1 photoreceptor. Such conditional variation in circadian rhythms may be key for latitudinal adaptation in a variety of species, including crop plants and livestock.

Circadian sleep-wake cycle organization in squirrel monkeys

1985 ◽  
Vol 248 (3) ◽  
pp. R353-R362 ◽  
Author(s):  
D. B. Wexler ◽  
M. C. Moore-Ede
Keyword(s):  
Sleep Onset ◽  
Nrem Sleep ◽  
Squirrel Monkeys ◽  
Circadian Cycle ◽  
Circadian Period ◽  
Constant Illumination ◽  
Circadian Phase ◽  
Internal Phase ◽  
The Difference ◽  
The Relationship

To investigate the relationship between circadian rhythms of body temperature and sleep-wake stages, four squirrel monkeys were prepared for unrestrained monitoring of temperature, locomotor activity, electroencephalogram, electroculogram, and electromyogram. Continuous records for each animal were made for several 12-h light-dark (LD) cycles and then after a few days in constant illumination (LL). All animals maintained consolidated sleep-wake cycles and had a longer circadian period (mean 24.7 h) in LL than in LD (mean 24.1 h). The increased period reflected greater time per circadian cycle spent awake in LL (mean 14.0 h) than in LD (mean 12.8 h). Total night NREM sleep was less in LL (mean 6.5 h) than in LD (mean 8.2 h). Sleep onset occurred at later phases in LL (187 +/- 6 degrees) than in LD (170 +/- 2 degrees). Because the circadian phase measure of NREM sleep was unchanged between LD and LL conditions, the difference in sleep onsets reflected balanced changes in NREM circadian waveforms. Wake-up phases were the same in both conditions (mean 342 degrees). In summary, during free run squirrel monkeys maintain a stable consolidated circadian sleep-wake cycle with a period greater than 24 h, but they exhibit only minimal internal phase restructuring.

scholarly journals A functional context for heterogeneity of the circadian clock in cells

PLoS Biology ◽  
2020 ◽  
Vol 18 (10) ◽  
pp. e3000927
Author(s):  
Martha Merrow ◽  
Mary Harrington
Keyword(s):  
Circadian Clock ◽  
Building Blocks ◽  
Circadian Period ◽  
Top Down ◽  
Bottom Up ◽  
Stochastic Generation ◽  
Circadian Phase ◽  
Functional Context ◽  
Definition Of

Characterization of circadian systems at the organism level—a top-down approach—has led to definition of unifying properties, a hallmark of the science of chronobiology. The next challenge is to use a bottom-up approach to show how the molecular workings of the cellular circadian clock work as building blocks of those properties. We review new studies, including a recently published PLOS Biology paper by Nikhil and colleagues, that show how programmed but also stochastic generation of variation in cellular circadian period explain important adaptive features of entrained circadian phase.

Association of intrinsic circadian period with morningness–eveningness, usual wake time, and circadian phase.

2001 ◽  
Vol 115 (4) ◽  
pp. 895-899 ◽  
Author(s):  
Jeanne F. Duffy ◽  
David W. Rimmer ◽  
Charles A. Czeisler
Keyword(s):  
Circadian Period ◽  
Wake Time ◽  
Circadian Phase

scholarly journals Separate and interacting effects of the endogenous circadian system and behaviors on plasma aldosterone in humans

2019 ◽  
Vol 316 (2) ◽  
pp. R157-R164 ◽  
Author(s):  
Saurabh S. Thosar ◽  
Jose F. Rueda ◽  
Alec M. Berman ◽  
Michael R. Lasarev ◽  
Maya X. Herzig ◽  
...  
Keyword(s):  
Circadian System ◽  
Plasma Aldosterone ◽  
Jet Lag ◽  
Circadian Cycle ◽  
Circadian Period ◽  
Nocturnal Sleep ◽  
Circadian Phase ◽  
Dim Light ◽  
And Behaviors ◽  
Healthy Participants

Measurements of aldosterone for diagnosis of primary aldosteronism are usually made from blood sampled in the morning when aldosterone typically peaks. We tested the relative contributions and interacting influences of the circadian system, ongoing behaviors, and prior sleep to this morning peak in aldosterone. To determine circadian rhythmicity and separate effects of behaviors on aldosterone, 16 healthy participants completed a 5-day protocol in dim light while all behaviors ranging from sleep to exercise were standardized and scheduled evenly across the 24-h circadian period. In another experiment, to test the separate effects of prior nocturnal sleep or the inactivity that accompanies sleep on aldosterone, 10 healthy participants were studied across 2 nights: 1 with sleep and 1 with maintained wakefulness (randomized order). Plasma aldosterone was measured repeatedly in each experiment. Aldosterone had a significant endogenous rhythm ( P < 0.001), rising across the circadian night and peaking in the morning (~8 AM). Activity, including exercise, increased aldosterone, and different behaviors modulated aldosterone differently across the circadian cycle (circadian phase × behavior interaction; P < 0.001). In the second experiment, prior nocturnal sleep and prior rested wakefulness both increased plasma aldosterone ( P < 0.001) in the morning, to the same extent as the change in circadian phases between evening and morning. The morning increase in aldosterone is due to effects of the circadian system plus increased morning activities and not prior sleep or the inactivity accompanying sleep. These findings have implications for the time of and behaviors preceding measurement of aldosterone, especially under conditions of shift work and jet lag.

scholarly journals Green notes: The rhythms of cyanobacteria exoelectrogenesis as de-composed by the Hilbert-Huang transform

2021 ◽  
Author(s):  
Tonny Ipael Okedi ◽  
Kamran Yunus ◽  
Adrian Fisher
Keyword(s):  
Photosystem Ii ◽  
Current Density ◽  
Applied Research ◽  
State Of The Art ◽  
Circadian Period ◽  
Density Profiles ◽  
Glycogen Accumulation ◽  
Hilbert Huang Transform ◽  
Circadian Phase ◽  
Instantaneous Frequencies

Electrons from cyanobacteria photosynthetic and respiratory systems are implicated in current generated in biophotovoltaic (BPV) devices. However, the pathway that electrons follow to electrodes remains largely unknown, limiting progress of applied research. Here we use Hilbert-Huang transforms to decompose Synechococcus elongatus sp. PCC7942 BPV current density profiles into physically meaningful oscillatory components, and compute their instantaneous frequencies. We develop hypotheses for the genesis of the oscillations via repeat experiments with iron-depleted and 20% CO2 enriched biofilms. The oscillations exhibit rhythms that are consistent with the state of the art cyanobacteria circadian model, and putative exoelectrogenic pathways. In particular, we observe oscillations consistent with: rhythmic D1:1 (photosystem II core) expression; circadian-controlled glycogen accumulation; circadian phase shifts under modified intracellular %ATP; and circadian period shortening in the absence of the iron-sulphur protein LdpA. We suggest that the extracted oscillations may be used to reverse-identify proteins and/or metabolites responsible for cyanobacteria exoelectrogenesis.

Morning bright light therapy: a helpful tool for reducing comorbid symptoms of affective and behavioral dysregulation in juvenile depressed inpatients? A pilot trial

2017 ◽  
Vol 45 (1) ◽  
pp. 34-41 ◽  
Author(s):  
Sarah Bogen ◽  
Tanja Legenbauer ◽  
Stephanie Gest ◽  
Martin Holtmann
Keyword(s):  
Pilot Trial ◽  
Secondary Analysis ◽  
Bright Light ◽  
Light Therapy ◽  
Bright Light Therapy ◽  
Circadian Phase ◽  
Behavioral Dysregulation ◽  
Sleep Parameters ◽  
Circadian Effect ◽  
Dysregulation Profile

Abstract. Objective: In recent years, bright light therapy (BLT) has been used to treat depression and to stabilize circadian rhythms. In this study we evaluated whether it is also helpful for comorbid symptoms of affective and behavioral dysregulation in depressive inpatients. Method: This article reports a secondary analysis comparing two subgroups of depressive participants with comorbid affective and behavioral dysregulation, captured with the dysregulation-profile of the Strengths and Difficulties Questionnaire (SDQ-DP; n = 16 vs. n = 11). Participants were randomly allocated to active BLT (10,000 lux) or control BLT (approx. 100 lux), and received 45 minutes of BLT for 2 weeks. SDQ-DP scores, sleep parameters, and circadian preference were assessed at baseline, after the intervention, and 3 weeks later. Results: No direct effects on SDQ-DP scores were observed. Sleep improved in both conditions. Only in the active BLT condition was a circadian phase advance found. Correlation and regression analyses indicated an indirect, circadian effect for improved SDQ-DP scores. Conclusions: The data of this pilot trial should be considered preliminary and merely descriptive. Further research is warranted.


Sign in / Sign up

Export Citation Format

Share Document