A circadian rhythm of behavioural thermoregulation in a freshwater gastropod, Helisoma trivolis

1980 ◽  
Vol 58 (11) ◽  
pp. 2152-2155 ◽  
Author(s):  
Martin Kavaliers
Keyword(s):  
Circadian Rhythm ◽  
Constant Darkness ◽  
Dark Phase ◽  
Behavioural Thermoregulation ◽  
Dark Cycle ◽  
Preferred Temperature ◽  
Temperature Selection ◽  
Freshwater Gastropod ◽  
Free Running ◽  
Maximum Temperatures

The behaviour of the aquatic gastropod Helisoma trivolis was examined in a thermal gradient. Under a 12 h light: 12 h dark cycle gastropods displayed a diel rhythm of preferred temperature selection. Maximum temperatures (21–22 °C) were selected during the dark phase and minimum temperatures (17–18 °C) were selected during the light phase of the light–dark cycle. Under constant darkness temperature selection continued as an endogenous free-running circadian rhythm of behavioural thermoregulation.

Rhythmic thermoregulation in larval cranefly (Diptera: Tipulidae)

1981 ◽  
Vol 59 (3) ◽  
pp. 555-558 ◽  
Author(s):  
Martin Kavaliers
Keyword(s):  
Circadian Rhythm ◽  
Thermal Gradient ◽  
Fourth Instar ◽  
Behavioural Thermoregulation ◽  
Dark Cycle ◽  
Constant Illumination ◽  
Temperature Selection ◽  
Preferred Temperatures ◽  
Free Running ◽  
Maximum Temperatures

The behaviour of fourth-instar larvae of a cranefly Tipula plutonis was examined in a horizontal thermal gradient. Under a 12 h light: 12 h dark cycle, larvae displayed a diel rhythm of preferred temperatures. Maximum temperatures (16–18 °C) were selected during the scotophase and minimum temperatures (12–14 °C) were selected during the photophase of the light–dark cycle. Under constant illumination, temperature selection continued as an endogenous free-running circadian rhythm of behavioural thermoregulation.

Circadian and estrous cycle-dependent variations in blood pressure and heart rate in female rats

1994 ◽  
Vol 267 (5) ◽  
pp. R1250-R1256 ◽  
Author(s):  
H. Takezawa ◽  
H. Hayashi ◽  
H. Sano ◽  
H. Saito ◽  
S. Ebihara
Keyword(s):  
Heart Rate ◽  
Estrous Cycle ◽  
Female Rats ◽  
Constant Darkness ◽  
Dark Phase ◽  
Daily Rhythms ◽  
Abrupt Decrease ◽  
Internal Phase ◽  
Free Running ◽  
Cycle Dependent

To determine whether cardiovascular functions are controlled by the endogenous circadian system and whether they change with the estrous cycle in female rats, we measured mean arterial pressure (MAP), heart rate (HR), and spontaneous activity (ACT) of female rats using an implantable radiotelemetry device and a computerized data-collecting system. Under a 12:12-h light-dark (LD) cycle, these parameters exhibited daily rhythms that were entrained to the photic cycle. The patterns of the daily rhythms varied with estrous cycles, and variations were particularly marked in the proestrous stage. During the dark period of this stage, ACT levels were significantly higher, but HR was significantly lower than in other stages. Although the peak MAP occurred within 2 h after the onset of the dark phase in three of the estrous stages, it occurred around midnight in the proestrous stage. Such estrous cycle-dependent variations were eliminated by ovariectomy. The implantation of 17 beta-estradiol produced a gradual increase in MAP and an abrupt decrease in HR. During constant darkness, all three parameters were free running, maintaining the same internal phase relationships with each other as during LD cycles. These results indicate that daily variations in these parameters were controlled by the endogenous circadian oscillating system, that they vary with the estrous cycle in female rats, and that estrogen may be responsible for these estrous cycle-dependent variations.

Circadian rhythm and response to light of extracellular glutamate and aspartate in rat suprachiasmatic nucleus

1996 ◽  
Vol 271 (3) ◽  
pp. R579-R585 ◽  
Author(s):  
S. Honma ◽  
Y. Katsuno ◽  
K. Shinohara ◽  
H. Abe ◽  
K. Honma
Keyword(s):  
Circadian Rhythm ◽  
Suprachiasmatic Nucleus ◽  
Light Pulse ◽  
Continuous Light ◽  
In Vivo Microdialysis ◽  
Dark Phase ◽  
Dark Cycle ◽  
Complete Darkness ◽  
Endogenous Circadian Rhythm

Extracellular concentrations of glutamate and aspartate were measured in the vicinity of rat suprachiasmatic nucleus (SCN) by means of in vivo microdialysis. The concentrations of both excitatory amino acids (EAAs) were higher during the dark phase than during the light under the light-dark cycle, showing pulsatile fluctuations throughout the day. When rats were released into the complete darkness, the 24-h pattern in the aspartate continued for at least one cycle, whereas that in the glutamate disappeared. The nocturnal increases in the EAA levels were not due to the increase of locomotor activity during the nighttime, because the 24-h rhythms were also detected in animals under urethan anesthesia. The patterns of extracellular EAA levels were changed when rats were released into the continuous light. Circadian rhythm was not detected in the glutamate, whereas the 24-h pattern was maintained in the aspartate with the levels increased to various extents. A 30-min light pulse given either at zeitgber time (ZT) 1 or ZT 13 elevated the EAA levels during the latter half of the light pulse, except glutamate by a pulse at ZT 1. The extracellular EAA levels in the vicinity of the rat SCN showed the circadian rhythm with a nocturnal peak and increased in response to the continuous light and a brief light pulse. The aspartate level is considered to be regulated by the endogenous circadian rhythm, but the glutamate levels seems to be modified by the light-dark cycle.

Cortisol-mediated synchrinization of circadian rhythm in urinary potassium excretion

1977 ◽  
Vol 233 (5) ◽  
pp. R230-R238 ◽  
Author(s):  
M. C. Moore-ede ◽  
W. S. Schmelzer ◽  
D. A. Kass ◽  
J. A. Herd
Keyword(s):  
Circadian Rhythm ◽  
Saimiri Sciureus ◽  
Potassium Excretion ◽  
Dark Cycle ◽  
Urinary Potassium ◽  
Timing System ◽  
Daily Dose ◽  
Circadian Timing System ◽  
Free Running ◽  
Renal Potassium Excretion

Conscious chair-acclimatized squirrel monkeys (Saimiri sciureus) studied with lights on (600 lx) from 0800 to 2000 h daily (LD 12:12) display a prominent circadian rhythm in renal potassium excretion. The characteristics of this rhythm were reproduced in adrenalectomized monkeys by infusing 5 mg cortisol and 0.001 mg aldosterone, or 5 mg cortisol alone, between 0800 and 0900 h daily. When the timing of cortisol adminisration (with or without aldosterone) was phase-delayed by 8 h, the urinary potassium rhythm resynchronized by 80% of the cortisol phase shift, but only after a transient response lasting 3–4 days. With the same daily dose of adrenal steroids given as a continuous infusion throughout each 24 h, urinary potassium excretion showed free-running oscillations no longer synchronized to the light-dark cycle. These results indicate that the cirdacian rhythm of plasma cortisol concentration acts as an internal mediator in the circadian timing system, synchronizing a potentially autonomous oscillation in renal potassium excretion to environmental time cues and to other circadian rhythms within the animal.

Visual receptor cycle in normal and period mutant Drosophila: Microspectrophotometry, electrophysiology, and ultrastructural morphometry

1992 ◽  
Vol 9 (2) ◽  
pp. 125-135 ◽  
Author(s):  
De-Mao Chen ◽  
J. Scott Christianson ◽  
Randall J. Sapp ◽  
William S. Stark
Keyword(s):  
Circadian Rhythm ◽  
Visual Pigment ◽  
Constant Darkness ◽  
Wild Type ◽  
Dark Cycle ◽  
Light Onset ◽  
Cross Sectional ◽  
Ultrastructural Morphometry ◽  
Em Morphometry ◽  
Visual Receptor

AbstractVisual pigment, sensitivity, and rhabdomere size were measured throughout a 12-h light/12-h dark cycle in Drosophila. Visual pigment and sensitivity were measured during subsequent constant darkness [dark/dark (D/D)]. MSP (microspectrophotometry) and the ERG (electroretinogram) revealed a cycling of visual pigment and sensitivity, respectively. A visual pigment decrease of 40% was noted at 4 h after light onset that recovered 2–4 h later in white-eyed (otherwise wild-type, w per+) flies. The ERG sensitivity [in w per+ flies in light/dark (L/D)] decreased by 75% at 4 h after light onset, more than expected if mediated by visual pigment (MSP) changes alone. ERG sensitivity begins decreasing 8 h before light onset while decreases in visual pigment begin 2 h after light onset. These cycles continue in constant darkness (D/D), suggesting a circadian rhythm. White-eyed period (per) mutants show similar cycles of visual pigment level and sensitivity in L/D; per's alterations, if any on the D/D cycles were subtle. The cross-sectional areas of rhabdomeres in w per+ were measured using electron micrographic (EM) morphometry. Area changed little through the L/D cycle.

The chronobiology of the brushtail possum, Trichosurus vulpecula (Marsupialia:Phalangeridae): tests of internal and external control of timing

1999 ◽  
Vol 47 (6) ◽  
pp. 579 ◽  
Author(s):  
P. A. Herbert ◽  
R. D. Lewis
Keyword(s):  
Internal Control ◽  
Internal Clock ◽  
External Control ◽  
Constant Darkness ◽  
Brushtail Possum ◽  
Dark Phase ◽  
Trichosurus Vulpecula ◽  
Direct Response ◽  
Natural Behaviour ◽  
Free Running

The chronobiology of the brushtail possum (Trichosurus vulpecula) was investigated in a vivarium and in light-controlled cabinets to determine what controls the timing of natural patterns of activity and rest. It is proposed that the timing of natural behaviour of the possum is not regulated entirely by direct response to environmental factors, but that it may have an element of internal control. Unless perturbed by wind and/or rain, the onset of activity is precisely timed each day, beginning as light intensity declines following sunset. In tests of an internal clock hypothesis, possums in constant darkness exhibited free-running circadian rhythms of activity with periods initially slightly shorter than 24 h, spontaneously reducing to c.22 h 40 min after c. 40 days. The internal rhythm of the possum could be entrained by 24-h light/dark cycles with activity initiated at the onset of the dark phase. We propose that the timing of the onset of natural behaviour of the possum is controlled through the output of a circadian clock that may be modulated by direct responses to wind and rain.

CIRCADIAN RHYTHM OF PLASMA CORTICOSTEROID IN ADULT FEMALE RATS: CHRONOLOGICAL SHIFTS IN ABNORMAL LIGHTING REGIMENS AND CONNECTION WITH OESTROUS CYCLE

1975 ◽  
Vol 80 (3) ◽  
pp. 527-541 ◽  
Author(s):  
Yasuhiko Morimoto ◽  
Tatsuo Oishi ◽  
Kazutaka Arisue ◽  
Zensuke Ogawa ◽  
Fumiko Tanaka ◽  
...  
Keyword(s):  
Circadian Rhythm ◽  
Adult Female ◽  
Female Rats ◽  
Constant Light ◽  
Constant Darkness ◽  
Vaginal Smear ◽  
Free Running ◽  
Normal Light ◽  
Lighting Regimen ◽  
Day By Day

ABSTRACT The circadian rhythm of plasma corticosteroid (CS) levels in adult female rats was studied chronologically under the following conditions: normal light-dark (LD), inverted light-dark (DL), constant dark (DD) and constant light (LL). Animals were accustomed to LD condition for 7 days before exposure to each abnormal lighting regimen. Normal circadian rhythm established under LD condition was clearly inverted on the third day of DL regimen, and the inverted rhythm persisted thereafter under DL condition. The circadian CS rhythm persisted essentially unchanged throughout DD condition, but lost its regular periodicity showing "free running" and changed day by day under LL condition. The average CS levels over a 24 h period were higher under LL than under DD condition. Plasma CS levels in each lighting regimen exhibited diurnal variations regardless of the vaginal smear patterns of autopsied animals. Exposure of rats to LL for 21 days made the circadian CS rhythm flat, but induced persistent oestrus in only a few animals. The data suggest that (1) an unexpectedly rapid inversion of the circadian CS rhythm occurs if animals are exposed to inverted light-dark environment; (2) constant darkness seems to be a near-natural environment for rats, and changes little of the pre-established circadian CS rhythm; (3) constant light, on the contrary, is assumed to be a stress for rats, and disrupts the circadian CS rhythm and elevates CS levels; (4) the change in circadian CS rhythm in adult female rats is not mediated by a change in gonadal function and the two conditions may not be connected directly with each other.

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.

Hypoxic depression of circadian rhythms in adult rats

2000 ◽  
Vol 88 (2) ◽  
pp. 365-368 ◽  
Author(s):  
Jacopo P. Mortola ◽  
Erin L. Seifert
Keyword(s):  
Oxygen Consumption ◽  
Circadian Rhythms ◽  
Sleep Disturbances ◽  
Circadian Oscillation ◽  
Dark Phase ◽  
Dark Cycle ◽  
Adult Rats ◽  
Normal Cycle ◽  
Open Flow ◽  
Free Running

Because the circadian rhythms of oxygen consumption (V˙o 2) and body temperature (Tb) could be contributed to by differences in thermogenesis and because hypoxia depresses thermogenesis in its various forms, we tested the hypothesis that hypoxia blunts the normal daily oscillations in V˙o 2and Tb. Adult rats were instrumented for measurements of Tb and activity by telemetry;V˙o 2 was measured by an open-flow method. Animals were exposed to normoxia (21% O2), hypoxia (10.5% O2), and normoxia again, each 1 wk in duration, in either a 12:12-h light-dark cycle (“synchronized”) or constant light (“free running”). In this latter case, the period of the cycle was ∼25 h. In synchronized conditions, hypoxia almost eliminated the Tb circadian oscillation, because of the blunting of the Tb rise during the dark phase. On return to normoxia, Tb rapidly increased toward the maximum normoxic values, and the normal cycle was then reestablished. In hypoxia, the amplitude of the activity andV˙o 2 oscillations averaged, respectively, 37 and 56% of normoxia. In free-running conditions, on return to normoxia the rhythm was reestablished at the expected phase of the cycle. Hence, the action of hypoxia was not on the clock itself but probably at the hypothalamic centers of thermoregulation. Hyperoxia (40% O2) or hypercapnia (3% CO2) had no significant effects on circadian oscillations, indicating that the effects of hypoxia did not reflect an undifferentiated response to changes in environmental gases. Modifications of the metabolism and Tb rhythms during hypoxia could be at the origin of sleep disturbances in cardiorespiratory patients and at high altitude.

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