scholarly journals Melatonin rhythm and other outputs of the master circadian clock in the desert goat ( Capra hircus ) are entrained by daily cycles of ambient temperature

2020 ◽  
Vol 68 (3) ◽  
Author(s):  
Hicham Farsi ◽  
Driss Harti ◽  
Mohamed R. Achaâban ◽  
Mohammed Piro ◽  
Véronique Raverot ◽  
...  
Keyword(s):  
Ambient Temperature ◽  
Circadian Clock ◽  
Capra Hircus ◽  
Melatonin Rhythm ◽  
Daily Cycles

Entrainment of the circadian clock by daily ambient temperature cycles in the camel (Camelus dromedarius)

2013 ◽  
Vol 304 (11) ◽  
pp. R1044-R1052 ◽  
Author(s):  
Khalid El Allali ◽  
Mohamed R. Achaâban ◽  
Béatrice Bothorel ◽  
Mohamed Piro ◽  
Hanan Bouâouda ◽  
...  
Keyword(s):  
Phase Shift ◽  
Ambient Temperature ◽  
Circadian Clock ◽  
Camelus Dromedarius ◽  
Systematic Effect ◽  
Continuous Darkness ◽  
Experimental Conditions ◽  
Daily Cycles ◽  
Desert Areas ◽  
The Mean

In mammals the light-dark (LD) cycle is known to be the major cue to synchronize the circadian clock. In arid and desert areas, the camel ( Camelus dromedarius) is exposed to extreme environmental conditions. Since wide oscillations of ambient temperature (Ta) are a major factor in this environment, we wondered whether cyclic Ta fluctuations might contribute to synchronization of circadian rhythms. The rhythm of body temperature (Tb) was selected as output of the circadian clock. After having verified that Tb is synchronized by the LD and free runs in continuous darkness (DD), we submitted the animals to daily cycles of Ta in LL and in DD. In both cases, the Tb rhythm was entrained to the cycle of Ta. On a 12-h phase shift of the Ta cycle, the mean phase shift of the Tb cycle ranged from a few hours in LD (1 h by cosinor, 4 h from curve peaks) to 7–8 h in LL and 12 h in DD. These results may reflect either true synchronization of the central clock by Ta daily cycles or possibly a passive effect of Ta on Tb. To resolve the ambiguity, melatonin rhythmicity was used as another output of the clock. In DD melatonin rhythms were also entrained by the Ta cycle, proving that the daily Ta cycle is able to entrain the circadian clock of the camel similar to photoperiod. By contrast, in the presence of a LD cycle the rhythm of melatonin was modified by the Ta cycle in only 2 (or 3) of 7 camels: in these specific conditions a systematic effect of Ta on the clock could not be evidenced. In conclusion, depending on the experimental conditions (DD vs. LD), the daily Ta cycle can either act as a zeitgeber or not.

scholarly journals Temperature-modulated Alternative Splicing and Promoter Use in the Circadian Clock Gene frequency

2005 ◽  
Vol 16 (12) ◽  
pp. 5563-5571 ◽  
Author(s):  
Hildur V. Colot ◽  
Jennifer J. Loros ◽  
Jay C. Dunlap
Keyword(s):  
Alternative Splicing ◽  
Circadian Clock ◽  
Clock Gene ◽  
Transcription Unit ◽  
Central Component ◽  
Temperature Sensitive ◽  
Circadian Clock Gene ◽  
Mrna Species ◽  
Daily Cycles ◽  
Evolutionary Comparisons

The expression of FREQUENCY, a central component of the circadian clock in Neurospora crassa, shows daily cycles that are exquisitely sensitive to the environment. Two forms of FRQ that differ in length by 99 amino acids, LFRQ and SFRQ, are synthesized from alternative initiation codons and the change in their ratio as a function of temperature contributes to robust rhythmicity across a range of temperatures. We have found frq expression to be surprisingly complex, despite our earlier prediction of a simple transcription unit based on limited cDNA sequencing. Two distinct environmentally regulated major promoters drive primary transcripts whose environmentally influenced alternative splicing gives rise to six different major mRNA species as well as minor forms. Temperature-sensitive alternative splicing determines AUG choice and, as a consequence, the ratio of LFRQ to SFRQ. Four of the six upstream ORFs are spliced out of the vast majority of frq mRNA species. Alternative splice site choice in the 5′ UTR and relative use of two major promoters are also influenced by temperature, and the two promoters are differentially regulated by light. Evolutionary comparisons with the Sordariaceae reveal conservation of 5′ UTR sequences, as well as significant conservation of the alternative splicing events, supporting their relevance to proper regulation of clock function.

scholarly journals The Circadian Clock Modulates Global Daily Cycles of mRNA Ribosome Loading

2015 ◽  
Vol 27 (9) ◽  
pp. 2582-2599 ◽  
Author(s):  
Anamika Missra ◽  
Ben Ernest ◽  
Tim Lohoff ◽  
Qidong Jia ◽  
James Satterlee ◽  
...  
Keyword(s):  
Circadian Clock ◽  
Daily Cycles

scholarly journals Biochemical Evidence for a Timing Mechanism in Prochlorococcus

2009 ◽  
Vol 191 (17) ◽  
pp. 5342-5347 ◽  
Author(s):  
Ilka M. Axmann ◽  
Ulf Dühring ◽  
Luiza Seeliger ◽  
Anne Arnold ◽  
Jens T. Vanselow ◽  
...  
Keyword(s):  
Gene Expression ◽  
Circadian Clock ◽  
Biological Activities ◽  
Circadian Oscillator ◽  
Biochemical Evidence ◽  
Timing Mechanism ◽  
The Third ◽  
Stable Environment ◽  
Daily Cycles

ABSTRACT Organisms coordinate biological activities into daily cycles using an internal circadian clock. The circadian oscillator proteins KaiA, KaiB, and KaiC are widely believed to underlie 24-h oscillations of gene expression in cyanobacteria. However, a group of very abundant cyanobacteria, namely, marine Prochlorococcus species, lost the third oscillator component, KaiA, during evolution. We demonstrate here that the remaining Kai proteins fulfill their known biochemical functions, although KaiC is hyperphosphorylated by default in this system. These data provide biochemical support for the observed evolutionary reduction of the clock locus in Prochlorococcus and are consistent with a model in which a mechanism that is less robust than the well-characterized KaiABC protein clock of Synechococcus is sufficient for biological timing in the very stable environment that Prochlorococcus inhabits.

scholarly journals Behaviour, temperature and terrain slope impact estimates of energy expenditure using oxygen and dynamic body acceleration

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Eleanor R. Dickinson ◽  
Philip A. Stephens ◽  
Nikki J. Marks ◽  
Rory P. Wilson ◽  
David M. Scantlebury
Keyword(s):  
Energy Expenditure ◽  
Ambient Temperature ◽  
Capra Hircus ◽  
Energetic Costs ◽  
Extrinsic Factors ◽  
Rest Energy ◽  
Body Acceleration ◽  
Energy Expenditures ◽  
Terrain Slope ◽  
Free Ranging

AbstractThe energy used by animals is influenced by intrinsic (e.g. physiological) and extrinsic (e.g. environmental) factors. Accelerometers within biologging devices have proven useful for assessing energy expenditures and their behavioural context in free-ranging animals. However, certain assumptions are frequently made when acceleration is used as a proxy for energy expenditure, with factors, such as environmental variation (e.g. ambient temperature or slope of terrain), seldom accounted for. To determine the possible interactions between behaviour, energy expenditure and the environment (ambient temperature and terrain slope), the rate of oxygen consumption ($${\dot{\text{V}}\text{O}}_{2}$$ V ˙ O 2 ) was measured in pygmy goats (Capra hircus aegarus) using open-flow indirect calorimetry. The effect of temperature (9.7–31.5 °C) on resting energy expenditure was measured. The relationship between $${\dot{\text{V}}\text{O}}_{2}$$ V ˙ O 2 and dynamic body acceleration (DBA) was measured at different walking speeds (0.8–3.0 km h−1) and on different inclines (0, + 15°, − 15°). The daily behaviour of individuals was measured in two enclosures: enclosure A (level terrain during summer) and enclosure B (sloped terrain during winter) and per diem energy expenditures of behaviours estimated using behaviour, DBA, temperature, terrain slope and $${\dot{\text{V}}\text{O}}_{2}$$ V ˙ O 2 . During rest, energy expenditure increased below 22 °C and above 30.5 °C. $${\dot{\text{V}}\text{O}}_{2}$$ V ˙ O 2 (ml min−1) increased with DBA when walking on the level. Walking uphill (+ 15°) increased energetic costs three-fold, whereas walking downhill (− 15°) increased energetic costs by one third. Based on these results, although activity levels were higher in animals in enclosure A during summer, energy expenditure was found to be significantly higher in the sloped enclosure B in winter (means of enclosures A and B: 485.3 ± 103.6 kJ day−1 and 744.5 ± 132.4 kJ day−1). We show that it is essential to account for extrinsic factors when calculating animal energy budgets. Our estimates of the impacts of extrinsic factors should be applicable to other free ranging ungulates.

scholarly journals Why Lungs Keep Time: Circadian Rhythms and Lung Immunity

2020 ◽  
Vol 82 (1) ◽  
pp. 391-412 ◽  
Author(s):  
Charles Nosal ◽  
Anna Ehlers ◽  
Jeffrey A. Haspel
Keyword(s):  
Circadian Rhythms ◽  
Circadian Clock ◽  
Respiratory System ◽  
Lung Diseases ◽  
Environmental Changes ◽  
Biological Processes ◽  
General Introduction ◽  
Daily Cycles ◽  
Ancient Times ◽  
Lung Immunity

Circadian rhythms are daily cycles in biological function that are ubiquitous in nature. Understood as a means for organisms to anticipate daily environmental changes, circadian rhythms are also important for orchestrating complex biological processes such as immunity. Nowhere is this more evident than in the respiratory system, where circadian rhythms in inflammatory lung disease have been appreciated since ancient times. In this focused review we examine how emerging research on circadian rhythms is being applied to the study of fundamental lung biology and respiratory disease. We begin with a general introduction to circadian rhythms and the molecular circadian clock that underpins them. We then focus on emerging data tying circadian clock function to immunologic activities within the respiratory system. We conclude by considering outstanding questions about biological timing in the lung and how a better command of chronobiology could inform our understanding of complex lung diseases.

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