Tau Response Curves Can Explain Entrainment of Rat Circadian Rhythm to Saw-Tooth Light Intensity Cycles

1997 ◽  
Vol 28 (sup1) ◽  
pp. 25-38 ◽  
Author(s):  
S Usui ◽  
Y Takahashi ◽  
T Okazaki
Keyword(s):  
Circadian Rhythm ◽  
Light Intensity ◽  
Response Curves

scholarly journals Comment Concerning the Effects of Light Intensity on Melatonin Suppression in the Review “Light Modulation of Human Clocks, Wake, and Sleep” by A. Prayag et al.

2021 ◽  
Vol 3 (1) ◽  
pp. 181-188
Author(s):  
Peter Bracke ◽  
Eowyn Van de Putte ◽  
Wouter R. Ryckaert
Keyword(s):  
Phase Shift ◽  
Light Intensity ◽  
Dose Response ◽  
Light Modulation ◽  
Response Curves ◽  
Practical Applications ◽  
Circadian Phase ◽  
Melatonin Suppression ◽  
Dose Response Curves ◽  
Circadian Phase Shift

Dose-response curves for circadian phase shift and melatonin suppression in relation to white or monochromatic nighttime illumination can be scaled to melanopic weighed illumination for normally constricted pupils, which makes them easier to interpret and compare. This is helpful for a practical applications.

Are membrane properties essential for the circadian rhythm of Gonyaulax?

1984 ◽  
Vol 247 (2) ◽  
pp. R250-R256
Author(s):  
H. G. Scholubbers ◽  
W. Taylor ◽  
L. Rensing
Keyword(s):  
Circadian Rhythm ◽  
Phase Shift ◽  
Fluorescence Polarization ◽  
The Other ◽  
Membrane Properties ◽  
Response Curves ◽  
Whole Cells ◽  
Different Temperatures ◽  
Free Running ◽  
Free Running Period

Membrane properties of whole cells of Gonyaulax polyedra were measured by fluorescence polarization. Circadian changes of fluorescence polarization exist in exponentially growing cultures. They show an amplitude larger than that of stationary cultures, indicating that a part of the change is due to or amplified by an ongoing cell cycle. Measurements of parameters of the circadian glow rhythm were analyzed for possible correlation with the membrane data. Considerable differences (Q10 = 2.5-3.0) in fluorescence polarization were found in cultures kept at different temperatures ranging from 15 to 27.5 degrees C. The free-running period length at different temperatures, on the other hand, differed only slightly (Q10 = 0.9-1.1). Stationary cultures showed higher fluorescence polarization compared with growing cultures, whereas the free-running period lengths did not differ in cultures of various densities and growth rates. Temperature steps of different sign changed the fluorescence polarization slightly in different directions. The phase shift of 4-h pulses (-5, -9, +7 degrees C) resulted in maximal phase advances of 4, 6, and 2 h, respectively. The phasing of the phase-response curves was identical in all these experiments, a finding not to be expected if the pulses act via the measured membrane properties. Pulses of drugs that change the fluorescence polarization (e.g., chlorpromazine and lidocaine) did not or only slightly phase-shift the circadian rhythm.

scholarly journals Photochemical Acclimation of Three Contrasting Species to Different Light Levels: Implications for Optimizing Supplemental Lighting

2017 ◽  
Vol 142 (5) ◽  
pp. 346-354 ◽  
Author(s):  
Shuyang Zhen ◽  
Marc W. van Iersel
Keyword(s):  
Electron Transport ◽  
Light Intensity ◽  
Photochemical Efficiency ◽  
Light Response ◽  
High Light ◽  
Photon Flux ◽  
Ambient Light ◽  
Response Curves ◽  
Low Light ◽  
Supplemental Lighting

Photosynthetic responses to light are dependent on light intensity, vary among species, and can be affected by acclimation to different light environments (e.g., light intensity, spectrum, and photoperiod). Understanding how these factors affect photochemistry is important for improving supplemental lighting efficiency in controlled-environment agriculture. We used chlorophyll fluorescence to determine photochemical light response curves of three horticultural crops with contrasting light requirements [sweetpotato (Ipomea batatas), lettuce (Lactuca sativa), and pothos (Epipremnum aureum)]. We also quantified how these responses were affected by acclimation to three shading treatments-full sun, 44% shade, and 75% shade. The quantum yield of photosystem II (ΦPSII), a measure of photochemical efficiency, decreased exponentially with increasing photosynthetic photon flux (PPF) in all three species. By contrast, linear electron transport rate (ETR) increased asymptotically with increasing PPF. Within each shading level, the high-light-adapted species sweetpotato used high light more efficiently for electron transport than light-intermediate lettuce and shade-tolerant pothos. Within a species, plants acclimated to high light (full sun) tended to have higher ΦPSII and ETR than those acclimated to low light (44% or 75% shade). Nonphotochemical quenching (NPQ) (an indicator of the amount of absorbed light energy that is dissipated as heat) was upregulated with increasing PPF; faster upregulation was observed in pothos as well as in plants grown under 75% shade. Our results have implications for supplemental lighting: supplemental light is used more efficiently and results in a greater increase in ETR when provided at low ambient PPF. In addition, high-light-adapted crops and crops grown under relatively high ambient light can use supplemental light more efficiently than low-light-adapted crops or those grown under low ambient light.

Circadian rhythm of cortisol confounds cortisol responses to exercise: implications for future research

1995 ◽  
Vol 78 (5) ◽  
pp. 1657-1664 ◽  
Author(s):  
J. R. Thuma ◽  
R. Gilders ◽  
M. Verdun ◽  
A. B. Loucks
Keyword(s):  
Circadian Rhythm ◽  
Oxygen Consumption ◽  
Salivary Cortisol ◽  
Treadmill Exercise ◽  
Maximal Oxygen Consumption ◽  
Future Research ◽  
Response Curves ◽  
Baseline Method ◽  
Cortisol Responses

To investigate whether measurements of cortisol responses to exercise are confounded by neglect of the hormone's circadian rhythm, we measured the serum and salivary cortisol responses of eight women to 40 min of 70% maximal oxygen consumption treadmill exercise beginning at 0800 and 2000. Responses were calculated relative to the usually employed preexercise concentrations and also to concentrations at the same times of another day while subjects were at rest. Compared with areas under response curves (AUCs) calculated relative to their circadian baselines, AUCs for serum and salivary cortisol calculated by reference to preexercise concentrations were underestimated (serum, P < 0.001; salivary, P < 0.01) by 93 and 84% in the morning and by 37 and 35% in the evening, respectively. Calculated by the usual preexercise baseline method, rises in serum and salivary cortisol were similarly underestimated. More accurately calculated relative to their circadian baselines, serum and salivary cortisol AUCs were similar (P = 0.63 and P = 0.37, respectively) in the morning and evening, as were their rises (P = 0.23 and P = 0.70, respectively). In future investigations of the existence and magnitude of cortisol responses, those responses must be calculated relative to the hormone's circadian baseline.

scholarly journals A Review of Silent Substitution Devices for Melanopsin Stimulation in Humans

Photonics ◽  
2020 ◽  
Vol 7 (4) ◽  
pp. 121
Author(s):  
Vincent Conus ◽  
Martial Geiser
Keyword(s):  
Circadian Rhythm ◽  
Light Intensity ◽  
Cognitive Functions ◽  
Specific Response ◽  
Light Stimulation ◽  
Sleep Regulation ◽  
Human Relationships ◽  
Silent Substitution ◽  
Optical Setup ◽  
Year 2000

One way to study the specific response of the non-visual melanopsin photoreceptors of the human eye is to silence the response of cones and rods. Melanopsin photoreceptors (ipRGC), highlighted in the early 2000s, are intimately linked to the circadian rhythm and therefore to our sleep and wakefulness. Rest and sleep regulation, health and cognitive functions are all linked to ipRGC and play an important role in work and human relationships. Thus, we believe that the study of ipRGC responses is important.We searched and reviewed scientific articles describing instrumentation dedicated to these studies. PubMed lists more than 90,000 articles created since the year 2000 that contain the word circadian but only 252 with silent substitution. In relation to melanopsin, we found 39 relevant articles from which only 11 give a device description for humans, which is incomplete in most cases. We did not find any consensus for light intensity description, melanopsin contrast, sequences of melanopsin light stimulation and optical setup to expose the retina to the light.

Improved Concept for Nipiin and PIIIN Color Sensitive Two-Terminal Devices with High Linearity

1997 ◽  
Vol 467 ◽  
Author(s):  
D. Knipp ◽  
H. Stiebig ◽  
J. Fölsch ◽  
R. Carius ◽  
H. Wagner
Keyword(s):  
Light Intensity ◽  
Dynamic Range ◽  
Layer Structure ◽  
Spectral Response ◽  
Incident Light ◽  
High Dynamic Range ◽  
Optical Signal ◽  
Optimized Design ◽  
Defect States ◽  
Response Curves

ABSTRACTThe detection of the fundamental components of the visible light (blue, green, red) is achieved with two terminal photo diodes based on amorphous silicon. By changing the bias voltage the preferential carrier collection region is shifted which leads to a color sensitivity. In order to obtain a high dynamic range, independent voltage controlled spectral response curves as well as a linear response of the photocurrent on the incident light intensity the μτ-product and the bandgap in the device have to be specially designed to deconvolute the optical signal and generate an RGB-signal. Since the light intensity can strongly influence the spectral sensitivity by recharging of defect states, an optimized design of the multi-layer structure is necessary. Therefore, an improved concept for the design of nipiin- and piiin-detectors is presented which results in a good suppression of these non-linearities. Our concept is based on a decreasing bandgap profile from the front to the back contact and an increasing μτ-product of the individual i-layers in direction of the p-layer.

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