Ambient temperature cycles entrain the free-running circadian rhythms of the stripe-faced dunnart, Sminthopsis macroura

1990 ◽  
Vol 167 (3) ◽  
Author(s):  
AndrewJ.P. Francis ◽  
GrahameJ. Coleman
Keyword(s):  
Circadian Rhythms ◽  
Ambient Temperature ◽  
Temperature Cycles ◽  
Free Running ◽  
Sminthopsis Macroura

scholarly journals Entrainment of circadian rhythms of locomotor activity by ambient temperature cycles in the dromedary camel

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Hicham Farsi ◽  
Mohamed R. Achaâban ◽  
Mohammed Piro ◽  
Béatrice Bothorel ◽  
Mohammed Ouassat ◽  
...  
Keyword(s):  
Locomotor Activity ◽  
Body Temperature ◽  
Circadian Rhythms ◽  
Ambient Temperature ◽  
Cycle Phase ◽  
Dromedary Camel ◽  
Dark Cycle ◽  
Free Running ◽  
Activity Onset ◽  
Master Clock

Abstract In the dromedary camel, a well-adapted desert mammal, daily ambient temperature (Ta)-cycles have been shown to synchronize the central circadian clock. Such entrainment has been demonstrated by examining two circadian outputs, body temperature and melatonin rhythms. Locomotor activity (LA), another circadian output not yet investigated in the camel, may provide further information on such specific entrainment. To verify if daily LA is an endogenous rhythm and whether the desert Ta-cycle can entrain it, six dromedaries were first kept under total darkness and constant-Ta. Results showed that the LA rhythm free runs with a period of 24.8–24.9 h. After having verified that the light–dark cycle synchronizes LA, camels were subjected to a Ta-cycle with warmer temperatures during subjective days and cooler temperatures during subjective nights. Results showed that the free-running LA rhythm was entrained by the Ta-cycle with a period of exactly 24.0 h, while a 12 h Ta-cycle phase advance induced an inversion of the LA rhythm and advanced the acrophase by 9 h. Similarly, activity onset and offset were significantly advanced. All together, these results demonstrate that the Ta-cycle is a strong zeitgeber, able to entrain the camel LA rhythm, hence corroborating previous results concerning the Ta non-photic synchronization of the circadian master clock.

scholarly journals Shared Components of the FRQ-Less Oscillator and TOR Pathway Maintain Rhythmicity in Neurospora

2021 ◽  
pp. 074873042199994
Author(s):  
Rosa Eskandari ◽  
Lalanthi Ratnayake ◽  
Patricia L. Lakin-Thomas
Keyword(s):  
Circadian Rhythms ◽  
Clock Genes ◽  
Nutrient Sensing ◽  
Mass Spectrometry Analysis ◽  
Growth Responses ◽  
Tor Pathway ◽  
Spectrometry Analysis ◽  
Binding Partner ◽  
Binding Partners ◽  
Free Running

Molecular models for the endogenous oscillators that drive circadian rhythms in eukaryotes center on rhythmic transcription/translation of a small number of “clock genes.” Although substantial evidence supports the concept that negative and positive transcription/translation feedback loops (TTFLs) are responsible for regulating the expression of these clock genes, certain rhythms in the filamentous fungus Neurospora crassa continue even when clock genes ( frq, wc-1, and wc-2) are not rhythmically expressed. Identification of the rhythmic processes operating outside of the TTFL has been a major unresolved area in circadian biology. Our lab previously identified a mutation ( vta) that abolishes FRQ-less rhythmicity of the conidiation rhythm and also affects rhythmicity when FRQ is functional. Further studies identified the vta gene product as a component of the TOR (Target of Rapamycin) nutrient-sensing pathway that is conserved in eukaryotes. We now report the discovery of TOR pathway components including GTR2 (homologous to the yeast protein Gtr2, and RAG C/D in mammals) as binding partners of VTA through co-immunoprecipitation (IP) and mass spectrometry analysis using a VTA-FLAG strain. Reciprocal IP with GTR2-FLAG found VTA as a binding partner. A Δ gtr2 strain was deficient in growth responses to amino acids. Free-running conidiation rhythms in a FRQ-less strain were abolished in Δ gtr2. Entrainment of a FRQ-less strain to cycles of heat pulses demonstrated that Δ gtr2 is defective in entrainment. In all of these assays, Δ gtr2 is similar to Δ vta. In addition, expression of GTR2 protein was found to be rhythmic across two circadian cycles, and functional VTA was required for GTR2 rhythmicity. FRQ protein exhibited the expected rhythm in the presence of GTR2 but the rhythmic level of FRQ dampened in the absence of GTR2. These results establish association of VTA with GTR2, and their role in maintaining functional circadian rhythms through the TOR pathway.

A temperature-compensated model for circadian rhythms that can be entrained by temperature cycles

2007 ◽  
Vol 246 (1) ◽  
pp. 195-204 ◽  
Author(s):  
Tsutomu Takeuchi ◽  
Takamichi Hinohara ◽  
Gen Kurosawa ◽  
Kenko Uchida
Keyword(s):  
Circadian Rhythms ◽  
Temperature Cycles

Restricted food access and light-dark: impact of conflicting zeitgebers on circadian rhythms of the rabbit

1993 ◽  
Vol 264 (4) ◽  
pp. R708-R715 ◽  
Author(s):  
B. Jilge ◽  
H. Stahle
Keyword(s):  
Circadian Rhythms ◽  
Phase Difference ◽  
Food Access ◽  
Activity Rhythm ◽  
Light Period ◽  
The Other ◽  
Behavioral Rhythms ◽  
Activity Component ◽  
Common Control ◽  
Free Running

Free-running circadian rhythms of rabbits were exposed to a 11:55-11:55-h light-dark (LD) schedule. After complete entrainment (63 +/- 22 days), the predominantly nocturnally active rabbits were exposed to an additional zeitgeber, restricted food access (RF), which was imposed during the light period. In five animals RF had the same period (T) as the LD cycle (23:50 h), and in five other animals TRF was 24:10 h. At a period of 23:50 h for both zeitgebers, the rhythms of four animals were stably entrained to RF, while in one animal a component of the rhythm broke away from RF and entrained to the LD zeitgeber. In animals exposed to zeitgebers of different periods most of the activity rhythm also entrained to RF, but 20 +/- 7% of the activity entrained to the LD zeitgeber. The light-entrained activity component merged with the RF component when the zeitgebers crossed, and decomposition occurred when the phase difference exceeded 4-6 h. The results indicate that two circadian oscillator systems exist in the rabbit, one entrained by light-dark cycles and the other by feeding-fasting cycles. Both exert common control over a number of overt behavioral rhythms.

scholarly journals The Cell Division Cycle of Euglena gracilis Indicates That the Level of Circadian Plasticity to the External Light Regime Changes in Prolonged-Stationary Cultures

Plants ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1475
Author(s):  
Shota Kato ◽  
Hong Gil Nam
Keyword(s):  
Cell Division ◽  
Circadian Rhythms ◽  
Euglena Gracilis ◽  
Cell Cycle Progression ◽  
Light Signal ◽  
Cell Division Cycle ◽  
Regime Changes ◽  
Fitness Advantage ◽  
Subjective Night ◽  
Free Running

In unicellular photosynthetic organisms, circadian rhythm is tightly linked to gating of cell cycle progression, and is entrained by light signal. As several organisms obtain a fitness advantage when the external light/dark cycle matches their endogenous period, and aging alters circadian rhythms, senescence phenotypes of the microalga Euglena gracilis of different culture ages were characterized with respect to the cell division cycle. We report here the effects of prolonged-stationary-phase conditions on the cell division cycles of E. gracilis under non-24-h light/dark cycles (T-cycles). Under T-cycles, cells established from 1-month-old and 2-month-old cultures produced lower cell concentrations after cultivation in the fresh medium than cells from 1-week-old culture. This decrease was not due to higher concentrations of dead cells in the populations, suggesting that cells of different culture ages differ in their capacity for cell division. Cells from 1-week-old cultures had a shorter circadian period of their cell division cycle under shortened T-cycles than aged cells. When algae were transferred to free-running conditions after entrainment to shortened T-cycles, the young cells showed the peak growth rate at a time corresponding to the first subjective night, but the aged cells did not. This suggests that circadian rhythms are more plastic in younger E. gracilis cells.

Ambient Temperature as a Strong Zeitgeber of Circadian Rhythms in Response to Temperature Sensitivity and Poor Heat Dissipation Abilities in Subterranean African Mole-Rats

2021 ◽  
pp. 074873042110342
Author(s):  
Daniel W. Hart ◽  
Barry van Jaarsveld ◽  
Kiara G. Lasch ◽  
Kerryn L. Grenfell ◽  
Maria K. Oosthuizen ◽  
...  
Keyword(s):  
Circadian Rhythms ◽  
Ambient Temperature ◽  
Heat Dissipation ◽  
Direct Consequence ◽  
Ecological Constraints ◽  
Photic Entrainment ◽  
Mole Rat ◽  
Intimate Link ◽  
Response To Temperature ◽  
First Time

Mammals have evolved circadian rhythms in internal biological processes and behaviors, such as locomotor activity (LA), to synchronize to the environmental conditions they experience. Photic entrainment of LA has been well established; however, non-photic entrainment, such as ambient temperature ( Ta), has received much less attention. To address this dearth of knowledge, we exposed two subterranean endothermic-homeothermic African mole-rat species, the solitary Cape mole-rat ( Georychus capensis [GC]) and social Mahali mole-rat ( Cryptomys hottentotus mahali [CHM]), to varying Ta cycles in the absence of light. We showed that the LA rhythms of these two species entrain to Ta cycles and that the majority of LA occurred during the coolest 12-h period. LA confined to the coolest Ta periods may be the direct consequence of the poor heat dissipation abilities of African mole-rats brought about by physiological and ecological constraints. Recently, it has been hypothesized that Ta is only a strong zeitgeber for circadian rhythms in species whose thermoregulatory abilities are sensitive to changes in Ta (i.e., heterotherms and ectotherms), which previously has excluded endothermic-homeothermic mammals. However, this study demonstrates that Ta is a strong zeitgeber or entrainer for circadian rhythms of LA in subterranean endothermic-homeothermic mammals as a consequence of their sensitivity to changes in Ta brought about by their poor heat dissipation abilities. This study reinforces the intimate link between circadian rhythms and thermoregulation and conclusively, for the first time, provides evidence that Ta is a strong zeitgeber for endothermic-homeothermic mammals.

Organization of rat circadian rhythms during daily infusion of melatonin or S20098, a melatonin agonist

1999 ◽  
Vol 277 (3) ◽  
pp. R812-R828 ◽  
Author(s):  
B. Pitrosky ◽  
R. Kirsch ◽  
A. Malan ◽  
E. Mocaer ◽  
P. Pevet
Keyword(s):  
Body Temperature ◽  
Circadian Rhythms ◽  
Phase Response Curve ◽  
Constant Darkness ◽  
Time Interval ◽  
General Activity ◽  
Activity Peak ◽  
Free Running ◽  
Wheel Activity ◽  
Free Running Period

Daily administration of melatonin or S20098, a melatonin agonist, is known to entrain the free-running circadian rhythms of rats. The effects of the duration of administration on entrainment were studied. The animals demonstrated free-running circadian rhythms (running-wheel activity, body temperature, general activity) in constant darkness. Daily infusions of melatonin or S20098 for 1, 8, or 16 h entrained the circadian rhythms to 24 h. Two daily infusions of 1 h (separated by 8 h) entrained the activity peak within the shorter time interval. The entraining properties of melatonin and S20098 were similar and were affected neither by pinealectomy nor by infusion of 1- or 8-h duration. However, with 16-h infusion, less than half of the animals became entrained. Once entrained, the phase angle between the onset of infusion and the rhythms (onset of activity or acrophase of body temperature) increased with the duration of infusion. Before entrainment, the free-running period increased with the duration of infusion, an effect that was not predictable from the phase response curve.

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