Comparison of cortisol and rectal temperature circadian rhythms in horses: the role of light/dark cycle and constant darkness

2012 ◽  
Vol 43 (6) ◽  
pp. 681-687 ◽  
Author(s):  
Claudia Giannetto ◽  
Francesco Fazio ◽  
Irene Vazzana ◽  
Michele Panzera ◽  
Giuseppe Piccione
Keyword(s):  
Circadian Rhythms ◽  
Rectal Temperature ◽  
Constant Darkness ◽  
Dark Cycle ◽  
Role Of Light

Circadian rhythms of dopamine in mouse retina: The role of melatonin

2002 ◽  
Vol 19 (5) ◽  
pp. 593-601 ◽  
Author(s):  
SUSAN E. DOYLE ◽  
MICHAEL S. GRACE ◽  
WILSON McIVOR ◽  
MICHAEL MENAKER
Keyword(s):  
Circadian Rhythm ◽  
Circadian Rhythms ◽  
High Performance ◽  
Mouse Retina ◽  
Constant Darkness ◽  
Dark Cycle ◽  
Melatonin Synthesis ◽  
Dopamine Content ◽  
C3h Mice

Both dopamine and melatonin are important for the regulation of retinal rhythmicity, and substantial evidence suggests that these two substances are mutually inhibitory factors that act as chemical analogs of day and night. A circadian oscillator in the mammalian retina regulates melatonin synthesis. Here we show a circadian rhythm of retinal dopamine content in the mouse retina, and examine the role of melatonin in its control. Using high-performance liquid chromatography (HPLC), we measured levels of dopamine and its two major metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), in retinas of C3H+/+ mice (which make melatonin) and C57BL/6J mice that are genetically incapable of melatonin synthesis. In a light/dark cycle both strains of mice exhibited daily rhythms of retinal dopamine, DOPAC, and HVA content. However, after 10 days in constant darkness (DD), a circadian rhythm in dopamine levels was present in C3H, but not in C57 mice. C57 mice given ten daily injections of melatonin in DD exhibited a robust circadian rhythm of retinal dopamine content whereas no such rhythm was present in saline-injected controls. Our results demonstrate that (1) a circadian clock generates rhythms of dopamine content in the C3H mouse retina, (2) mice lacking melatonin also lack circadian rhythms of dopamine content, and (3) dopamine rhythms can be generated in these mice by cyclic administration of exogenous melatonin. Our results also indicate that circadian rhythms of retinal dopamine depend upon the rhythmic presence of melatonin, but that cyclic light can drive dopamine rhythms in the absence of melatonin.

scholarly journals Bright light during lactation alters the functioning of the circadian system of adult rats

2000 ◽  
Vol 278 (1) ◽  
pp. R201-R208 ◽  
Author(s):  
M. M. Canal-Corretger ◽  
T. Cambras ◽  
J. Vilaplana ◽  
A. Díez-Noguera
Keyword(s):  
Motor Activity ◽  
Activity Rhythm ◽  
Bright Light ◽  
Circadian System ◽  
Constant Darkness ◽  
Adult Rats ◽  
Light Pulses ◽  
Circadian Time ◽  
Role Of Light

To examine the role of light in the maturation of the circadian pacemaker, twelve groups of rats were raised in different conditions of exposure to constant bright light (LL) during lactation: both duration and timing of LL were varied. We studied the motor activity rhythm of the rats after weaning, first under LL and then under constant darkness (DD). In DD, two light pulses [at circadian time 15 (CT15) and CT22] were applied to test the response of the pacemaker. Greater exposure to LL days during lactation increased the number of rhythmic animals and the amplitude of their motor activity rhythm in the LL stage and decreased the phase delay due to the light pulse at CT15. The timing of LL during lactation affected these variables too. Because the response of the adult to light depended on both the number and timing of LL days during lactation, the exposure to light at early stages may influence the development of the circadian system by modifying it structurally or functionally.

Role of suprachiasmatic nuclei in circadian and light-entrained behavioral rhythms of lizards

2000 ◽  
Vol 279 (6) ◽  
pp. R2121-R2131 ◽  
Author(s):  
Cristiano Bertolucci ◽  
Valeria Anna Sovrano ◽  
Maria Chiara Magnone ◽  
Augusto Foà
Keyword(s):  
Circadian Rhythms ◽  
Constant Temperature ◽  
Locomotor Behavior ◽  
Functional Similarity ◽  
Daily Rhythm ◽  
Constant Darkness ◽  
Suprachiasmatic Nuclei ◽  
Podarcis Sicula ◽  
Behavioral Rhythms

To establish whether the suprachiasmatic nuclei (SCN) of the Ruin lizard ( Podarcis sicula) play a role in entrainment of circadian rhythms to light, we examined the effects of exposure to 24-h light-dark (LD) cycles on the locomotor behavior of lizards with SCN lesions. Lizards became arrhythmic in response to complete SCN lesion under constant temperature and constant darkness (DD), and they remained arrhythmic after exposure to LD cycles. Remnants of SCN tissue in other lesioned lizards were sufficient to warrant entrainment to LD cycles. Hence, the SCN of Ruin lizards are essential both to maintain locomotor rhythmicity and to mediate entrainment of these rhythms to light. We also asked whether light causes expression of Fos-like immunoreactivity (Fos-LI) in the SCN. Under LD cycles, the SCN express a daily rhythm in Fos-LI. Because Fos-LI is undetectable in DD, the rhythm seen in LD cycles is caused by light. We further showed that unilateral SCN lesions in DD induce dramatic period changes. Altogether, the present data support the existence of a strong functional similarity between the SCN of lizards and the SCN of mammals.

scholarly journals Locomotor activity in the Namaqua rock mouse (Micaelamys namaquensis): entrainment by light manipulations

2014 ◽  
Vol 92 (12) ◽  
pp. 1083-1091 ◽  
Author(s):  
I. van der Merwe ◽  
N.C. Bennett ◽  
A. Haim ◽  
M.K. Oosthuizen
Keyword(s):  
Locomotor Activity ◽  
Activity Rhythm ◽  
Light Cycle ◽  
Nocturnal Activity ◽  
Dark Cycle ◽  
Subjective Night ◽  
Activity Onset ◽  
Role Of Light ◽  
Constant Dark

The locomotor activity rhythms of wild-caught Namaqua rock mice (Micaelamys namaquensis (A. Smith, 1834)) were examined under four light-cycle regimes to quantitatively describe the daily expression of locomotor activity and to study the innate relationship between activity and the light–dark cycle. Activity was always significantly higher at night than during the day; we note four trends. (1) The LD1 light cycle (12 h light : 12 h dark) established a distinct light-entrained and strongly nocturnal activity rhythm (99.11% nocturnal activity). The activity onset was prompt (zeitgeber time (ZT) 12.2 ± 0.04) and activity continued without any prominent peaks or extended times of rest until the offset of activity at ZT 23.73 ± 0.08. (2) Evidence for the internal maintenance of locomotor activity was obtained from the constant dark cycle (DD) in which locomotor activity free ran (mean τ = 23.89 h) and 77.58% of the activity was expressed during the subjective night. (3) During re-entrainment (LD2; 12 h light : 12 h dark), a nocturnal activity rhythm was re-established (98.65% nocturnal activity). (4) The inversion of the light cycle (DL; 12 h dark : 12 h light) evoked a shift in activity that again revealed dark-induced locomotor activity (95.69% nocturnal activity). Females were consistently more active than males in all of the light cycles, but only under the DD and LD2 cycles were females significantly more active than males. Although this species is considered nocturnal from field observations, information regarding its daily expression of activity and the role of light in its entrainment is lacking. To the best of our knowledge, this study is the first to report quantitatively on the species’ daily rhythm of activity and to investigate its relationship to the light–dark cycle.

scholarly journals Light exposure mediates circadian rhythms of rhizosphere microbial communities

2021 ◽  
Author(s):  
Kankan Zhao ◽  
Bin Ma ◽  
Yan Xu ◽  
Erinne Stirling ◽  
Jianming Xu
Keyword(s):  
Circadian Rhythms ◽  
Microbial Communities ◽  
Light Exposure ◽  
Circadian Clocks ◽  
Ecological Niches ◽  
Host Health ◽  
Regulation Mechanisms ◽  
Role Of Light ◽  
Constant Dark

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.

scholarly journals Differential impacts of the head onPlatynereis dumeriliiperipheral circadian rhythms

2019 ◽  
Author(s):  
Enrique Arboleda ◽  
Martin Zurl ◽  
Kristin Tessmar-Raible
Keyword(s):  
Circadian Rhythms ◽  
Circadian Clock ◽  
Clock Genes ◽  
Functional Model ◽  
Circadian Clocks ◽  
Constant Darkness ◽  
Dark Cycle ◽  
Peripheral Tissues ◽  
Platynereis Dumerilii ◽  
Strong Control

AbstractBackgroundThe marine bristle wormPlatynereis dumeriliiis a useful functional model system for the study of the circadian clock and its interplay with others, e.g. circalunar clocks. The focus has so far been on the worm’s head. However, behavioral and physiological cycles in other animals typically arise from the coordination of circadian clocks located in the brain and in peripheral tissues. Here we focus on peripheral circadian rhythms and clocks, revisit and expand classical circadian work on the worm’s chromatophores, investigate locomotion as read-out and include molecular analyses.ResultsWe establish that different pieces of the trunk exhibit synchronized, robust oscillations of core circadian clock genes. These circadian core clock transcripts are under strong control of the light-dark cycle, quickly losing synchronized oscillation under constant darkness, irrespective of the absence or presence of heads. Different wavelengths are differently effective in controlling the peripheral molecular synchronization. We have previously shown that locomotor activity is under circadian clock control. Here we show that upon decapitation it still follows the light-dark cycle, but does not free-run under constant darkness. We also observe the rhythmicity of pigments in the worm’s individual chromatophores, confirming that chromatophore size changes follow a circadian pattern. These size changes continue under constant darkness, but cannot be re-entrained by light upon decapitation.ConclusionsHere we provide the first basic characterization of the peripheral circadian clock ofPlatynereis dumerilii. In the absence of the head, light is essential as a major synchronization cue for peripheral molecular and locomotor circadian rhythms. Circadian changes in chromatophore size can however continue for several days in the absence of light/dark changes and the head. Thus, the dependence on the head depends on the type of peripheral rhythm studied. These data show that peripheral circadian rhythms and clocks should be considered when investigating the interactions of clocks with different period lengths, a notion likely also true for other organisms with circadian and non-circadian clocks.

Twilight and day length affects the seasonality of entrainment and endogenous circadian rhythms in a fish, Couesius plumbeus

1981 ◽  
Vol 59 (7) ◽  
pp. 1326-1334 ◽  
Author(s):  
Martin Kavaliers ◽  
Donald M. Ross
Keyword(s):  
Circadian Rhythms ◽  
Seasonal Changes ◽  
Phase Relationship ◽  
Day Length ◽  
Constant Darkness ◽  
Diurnal Activity ◽  
Circadian Period ◽  
Dark Cycle ◽  
Environmental Light ◽  
Couesius Plumbeus

Twilight and day-length portions of the light-dark cycle determine the seasonal course of (i) the phase relationship (ψ) between activity and the daily environmental light–dark cycle, (ii) the duration of activity (α), and (iii) the circadian period (τ) under constant darkness of the lake chub (Couesius plumbeus). With fish held under seasonally appropriate light–dark cycles with twilight (LD + t), the onset of diurnal activity occurred during dawn and its timing (ψonset) followed a bimodal annual pattern that was correlated with seasonal changes in the duration and physical characteristics of twilight. The end of activity occurred during dusk (ψoffset) and followed a unimodal annual pattern that was determined by day length. α followed a sigmoidal annual pattern under LD + t. The circadian period underwent significant seasonal changes with maximum and minimum τ values occurring during summer and winter, respectively. Fish that were entrained to rectangular light–dark cycles that excluded twilights (LD) failed to show any seasonal changes in ψ and τ and the sigmoidal relation between α and day length was absent.

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