Circadian rhythms of finches under steadily changing light intensity: Are self-sustaining circadian rhythms self-excitatory?

1980 ◽  
Vol 140 (2) ◽  
pp. 113-119 ◽  
Author(s):  
R�tger A. Wever
Keyword(s):  
Circadian Rhythms ◽  
Light Intensity ◽  
Changing Light

scholarly journals PHOTOKINESIS AND TONIC EFFECT OF LIGHT IN UNIONICOLA

1932 ◽  
Vol 16 (2) ◽  
pp. 349-355 ◽  
Author(s):  
John H. Welsh
Keyword(s):  
Light Intensity ◽  
Simple Relation ◽  
Combined Effect ◽  
Direct Proportion ◽  
Water Mite ◽  
Locomotor Muscles ◽  
Leg Movement ◽  
Changing Light ◽  
Effect Of Light

1. The speed of progression of Unionicola, a water mite, is influenced by light; and over a certain range increases as a function of the light intensity. 2. The relation between speed and light intensity is not a simple one, as the speed of progression is due to the combined effect of amplitude of steps and frequency of leg movement. 3. The amplitude of stride increases in direct proportion to the logarithm of the light intensity, while the frequency of stepping has no such simple relation to intensity. 4. The change in length of stride with changing light intensity indicates a tonic effect of light on the locomotor muscles. Such an effect has been observed previously in studies of orientation, due to unequal illumination, which produces changes in posture.

scholarly journals PSB27: A thylakoid protein enabling Arabidopsis to adapt to changing light intensity

2015 ◽  
Vol 112 (5) ◽  
pp. 1613-1618 ◽  
Author(s):  
Xin Hou ◽  
Aigen Fu ◽  
Veder J. Garcia ◽  
Bob B. Buchanan ◽  
Sheng Luan
Keyword(s):  
Photosystem Ii ◽  
Light Intensity ◽  
Light Adaptation ◽  
Light Exposure ◽  
Starch Accumulation ◽  
State Transitions ◽  
Potential Candidate ◽  
Subsequent Work ◽  
Variable Intensity ◽  
Changing Light

In earlier studies we have identified FKBP20-2 and CYP38 as soluble proteins of the chloroplast thylakoid lumen that are required for the formation of photosystem II supercomplexes (PSII SCs). Subsequent work has identified another potential candidate functional in SC formation (PSB27). We have followed up on this possibility and isolated mutants defective in the PSB27 gene. In addition to lack of PSII SCs, mutant plants were severely stunted when cultivated with light of variable intensity. The stunted growth was associated with lower PSII efficiency and defective starch accumulation. In response to high light exposure, the mutant plants also displayed enhanced ROS production, leading to decreased biosynthesis of anthocyanin. Unexpectedly, we detected a second defect in the mutant, namely in CP26, an antenna protein known to be required for the formation of PSII SCs that has been linked to state transitions. Lack of PSII SCs was found to be independent of PSB27, but was due to a mutation in the previously described cp26 gene that we found had no effect on light adaptation. The present results suggest that PSII SCs, despite being required for state transitions, are not associated with acclimation to changing light intensity. Our results are consistent with the conclusion that PSB27 plays an essential role in enabling plants to adapt to fluctuating light intensity through a mechanism distinct from photosystem II supercomplexes and state transitions.

scholarly journals Elaborate pupils in skates may help camouflage the eye

2018 ◽  
Author(s):  
Sean Youn ◽  
Corey Okinaka ◽  
Lydia M Mäthger
Keyword(s):  
Light Intensity ◽  
Spatial Frequency ◽  
Experimental Evidence ◽  
Pupillary Response ◽  
Pupil Dilation ◽  
Primary Factor ◽  
Natural Substrate ◽  
Spatial Frequencies ◽  
Pupillary Responses ◽  
Changing Light

AbstractThe little skate Leucoraja erinacea has elaborately shaped pupils, whose characteristics and functions have not been studied extensively. It has been suggested that such pupil shapes may camouflage the eye; yet, no experimental evidence has been presented to support this claim. Skates are bottom-dwellers that often bury into the substrate with their eyes protruding. If these pupils serve any camouflage function, we expect there to be a pupillary response related to the spatial frequency (“graininess”) of the background against which the eye is viewed. Here, we tested whether skate pupils dilate or constrict in response to background spatial frequency. We placed skates on background substrates with different spatial frequencies and recorded pupillary responses at three light intensities. In experiment 1, the skates’ pupillary response to three artificial checkerboards of different spatial frequencies was recorded. Skates responded to changing light intensity with pupil dilation/constriction; yet, their pupils did not change in response to spatial frequency. In experiment 2, in which skates could bury into three natural substrates with different spatial frequencies, such that their eyes protruded above the substrate, the pupils showed a subtle but statistically significant response to changes in substrate spatial frequency. Given the same light intensity, the smaller the spatial frequency of the natural substrate, the more constricted the pupil. While light intensity is the primary factor determining pupil dilation, these experiments are the first to show that pupils also change in response to background spatial frequency, which suggests that the pupil may aid in camouflaging the eye.

Eutrophication and algal blooms in channel type reservoirs: A novel enclosure experiment by changing light intensity

2011 ◽  
Vol 23 (10) ◽  
pp. 1660-1670 ◽  
Author(s):  
Chengjin Cao ◽  
Binghui Zheng ◽  
Zhenlou Chen ◽  
Minsheng Huang ◽  
Jialei Zhang
Keyword(s):  
Light Intensity ◽  
Algal Blooms ◽  
Enclosure Experiment ◽  
Changing Light ◽  
Channel Type

Range of entrainment of rat circadian rhythms to sinusoidal light-intensity cycles

2000 ◽  
Vol 278 (5) ◽  
pp. R1148-R1156 ◽  
Author(s):  
Setsuo Usui ◽  
Yasuro Takahashi ◽  
Terue Okazaki
Keyword(s):  
Circadian Rhythms ◽  
Light Intensity ◽  
Lower Limit ◽  
Phase Angle ◽  
Light Exposure ◽  
Sprague Dawley ◽  
Lighting Conditions ◽  
Behavioral Rhythm ◽  
Sprague Dawley Rats ◽  
Daily Cycles

The range of entrainment of the circadian behavioral rhythm was compared between two groups of Sprague-Dawley rats (each n = 10) exposed to daily cycles of rectangular light-dark alternation (LD) and sinusoidal fluctuations of light intensity (SINE), respectively. The maximum illuminance (20 lx), the minimum illuminance (0.01 lx), and the total amount of light exposure per cycle were the same under the two lighting conditions. The periods (Ts) of both lighting cycles were lengthened stepwise from 24 through 25, 26, 26.5, 27, 27.5, and 28 h to 28.5 h in experiment 1 and were shortened stepwise from 24 through 23.5, 23, and 22.5 h to 22 h in experiment 2. Each T cycle lasted for 30 cycles. In experiment 1, 60% of rats under the LD condition entrained up to T = 28.5 h, whereas 50% of rats under the SINE condition entrained up to T = 28.5 h. In experiment 2, no animal under the LD condition entrained to T < 23.5 h, whereas 40% of rats under the SINE condition entrained down to T = 23 h and 20% of rats remained to entrain down to T = 22 h cycles. The phase angle of entrainment was systematically changed, depending on T under both conditions. These results suggest that the lower limit of entrainment is expanded under the SINE condition compared with the LD condition.

scholarly journals Rhythmicity of the intestinal microbiota is regulated by gender and the host circadian clock

2015 ◽  
Vol 112 (33) ◽  
pp. 10479-10484 ◽  
Author(s):  
Xue Liang ◽  
Frederic D. Bushman ◽  
Garret A. FitzGerald
Keyword(s):  
Circadian Rhythms ◽  
Circadian Clock ◽  
Fecal Microbiota ◽  
Circadian Rhythmicity ◽  
Absolute Amount ◽  
Gene Encoding ◽  
Host Behavior ◽  
Clock Component ◽  
Time Of Feeding ◽  
Changing Light

In mammals, multiple physiological, metabolic, and behavioral processes are subject to circadian rhythms, adapting to changing light in the environment. Here we analyzed circadian rhythms in the fecal microbiota of mice using deep sequencing, and found that the absolute amount of fecal bacteria and the abundance of Bacteroidetes exhibited circadian rhythmicity, which was more pronounced in female mice. Disruption of the host circadian clock by deletion of Bmal1, a gene encoding a core molecular clock component, abolished rhythmicity in the fecal microbiota composition in both genders. Bmal1 deletion also induced alterations in bacterial abundances in feces, with differential effects based on sex. Thus, although host behavior, such as time of feeding, is of recognized importance, here we show that sex interacts with the host circadian clock, and they collectively shape the circadian rhythmicity and composition of the fecal microbiota in mice.

Photic responses of geniculo-hypothalamic tract neurons in the Syrian hamster

1989 ◽  
Vol 2 (4) ◽  
pp. 367-375 ◽  
Author(s):  
Mary E. Harrington ◽  
Benjamin Rusak
Keyword(s):  
Circadian Rhythms ◽  
Light Intensity ◽  
Syrian Hamster ◽  
Great Majority ◽  
Ambient Light ◽  
Suprachiasmatic Nuclei ◽  
Discharge Rates ◽  
Electrophysiological Recordings ◽  
Diffuse Illumination ◽  
Intensity Changes

AbstractThe putative neural pacemaker controlling circadian rhythms in mammals is contained in the suprachiasmatic nuclei of the hypothalamus. These nuclei receive a projection, the geniculo-hypothalamic tract (GHT), from neurons in the intergeniculate leaflet (IGL) and portions of the ventral lateral geniculate nucleus (vLGN) of the thalamus. We examined the responses of putative GHT neurons to diffuse illumination using extracellular electrophysiological recordings. The great majority of IGL neurons showed sustained ON responses to diffuse retinal illumination; vLGN neurons showed more variation in their responses. Discharge rates of sustained ON neurons increased monotonically as light intensity was increased and saturated over 2–3 log units of intensity changes. Many IGL neurons had binocular input, and input from the ipsilateral eye was often inhibitory. These results indicate that GHT neurons may provide information about ambient light intensity to the suprachiasmatic nuclei.

A Controller for a Light Source

1957 ◽  
Vol 48 (3) ◽  
pp. 463-465
Author(s):  
S. W. Bailey ◽  
J. B. McCabe
Keyword(s):  
Light Intensity ◽  
Light Source ◽  
And Control ◽  
Changing Light

An instrument is described that will brighten and dim a light source and control its “on” and “off” timing.The periods of brightening and dimming and the period of full illumination are both adjustable.The instrument is being used successfully for studying the effects of changing light intensity and photoperiod on the activity and development of insects.

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