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Daniel Janik, Justin Frey
Most work looking at nonphotic effects on circadian rhythms is conducted when animals are held under freerunning conditions, usually constant darkness. However, for nonphotic effects to be functionally significant, they should be demonstrable under conditions in which most animals live, i.e., a 24-hr light-dark cycle (LD). Syrian hamsters held in LD 6:18 were administered nonphotic stimulation in the form of a 3-hr confinement to a novel wheel starting about 6 hr before the start of their normal nightly activity bout...
May 29, 2018: Chronobiology International
Nima Derakhshan, Tony Machejefski
No abstract text is available yet for this article.
2015: Chinese Journal of Traumatology, Zhonghua Chuang Shang za Zhi
Clément Vinauger, Claudio R Lazzari
Despite the drastic consequences it may have on the transmission of parasites, the ability of disease vectors to learn and retain information has just begun to be characterised. The kissing bug Rhodnius prolixus, a vector of Chagas disease, is an excellent model, particularly because conditioning the proboscis extension response (PER) constitutes a valuable paradigm to study their cognitive abilities under carefully controlled conditions. Another characteristic of these bugs is the temporal organisation of their different activities in a bimodal endogenous daily rhythm...
October 2015: Journal of Experimental Biology
Fred C Davis, Michael Menaker
The freerunning period (τ) of the circadian pacemaker underlying the wheel-running activity rhythm of Mus musculus was found to be unaffected by the periods of environmental cycles (maternal and light/dark) under which the mice are raised. Mice born to mothers entrained to periods (T) of 28 or 20 h (ratio of light to dark of 14/10) and maintained on those cycle until beyond puberty showed only a temporary difference in freerunning period when placed into constant darkness. Such temporary 'after-effects ' of entrainment were shown, as had been previously, to occur in animals exposed to non-24-h cycles as adults only...
December 1, 1981: Journal of Comparative Physiology
S J Britz, W E Hungerford, D R Lee
Photosynthesis and photosynthate partitioning in leaves of Sorghum bicolor (L.) Moench exhibited a cyclic dependence on the duration (10-62 h) of dark periods inserted prior to bright light test periods (550 μmol·s(-1)·m(-2), photosynthetic photon flux). Maximum rates of net photosynthesis and of accumulation of starch and soluble sugars were, in the order given, two-, three- and fourfold greater than minimum values. Between 14 and 53% of photosynthate was retained in leaves depending on the length of the dark period...
July 1987: Planta
S M Hsiao, A H Meier
Gulf killifish, Fundulus grandis, exhibit rhythmic reproductive activities that are synchronized with semilunar tidal fluctuations in their Gulf coast habitat. These cyclic activities, monitored through daily egg collections, persist in the laboratory for as long as four months with periods near the tidal period of 13.7 days. In nature, a specific semilunar spawning phase is maintained with respect to tidal cycles. However, in the laboratory, the phase may gradually advance or delay. These phase changes occur as a result of small differences between the periods of the spawning cycle and concurrent tidal cycle...
October 1992: Fish Physiology and Biochemistry
T L Hennessey, A L Freeden, C B Field
Persistent circadian rhythms in photosynthesis and stomatal opening occurred in bean (Phaseolus vulgaris L.) plants transferred from a natural photoperiod to a variety of constant conditions. Photosynthesis, measured as carbon assimilation, and stomatal opening, as conductance to water vapor, oscillated with a freerunning period close to 24 h under constant moderate light, as well as under light-limiting and CO2-limiting conditions. The rhythms damped under constant conditions conducive to high photosynthetic rates, as did rates of carbon assimilation and stomatal conductance, and this damping correlated with the accumulation of carbohydrate...
March 1993: Planta
Keith M Studholme, Heinrich S Gompf, Lawrence P Morin
Light exerts a variety of effects on mammals. Unexpectedly, one of these effects is the cessation of nocturnal locomotion and the induction of behavioral sleep (photosomnolence). Here, we extend the initial observations in several ways, including the fundamental demonstration that core body temperature (T(c)) drops substantially (about 1.5°C) in response to the light stimulation at CT15 or CT18 in a manner suggesting that the change is a direct response to light rather than simply a result of the locomotor suppression...
March 15, 2013: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
Barbara M Tomotani, Danilo E F L Flores, Patrícia Tachinardi, José D Paliza, Gisele A Oda, Verônica S Valentinuzzi
South American subterranean rodents (Ctenomys aff. knighti), commonly known as tuco-tucos, display nocturnal, wheel-running behavior under light-dark (LD) conditions, and free-running periods >24 h in constant darkness (DD). However, several reports in the field suggested that a substantial amount of activity occurs during daylight hours, leading us to question whether circadian entrainment in the laboratory accurately reflects behavior in natural conditions. We compared circadian patterns of locomotor activity in DD of animals previously entrained to full laboratory LD cycles (LD12:12) with those of animals that were trapped directly from the field...
2012: PloS One
Jyoti Singh, Sangeeta Rani, Vinod Kumar
The present study investigated whether the circadian oscillators controlling rhythms in activity behavior and melatonin secretion shared similar functional relationship with the external environment. We simultaneously measured the effects of varying illuminations on rhythms of movement and melatonin levels in Indian weaver birds under synchronized (experiment 1) and freerunning (experiment 2) light conditions. In experiment 1, weaverbirds were exposed to 12h light: 12h darkness (12L:12D; L = 20 lx, D = 0.1 lx) for 2...
April 2012: Hormones and Behavior
Roxanne Sterniczuk, Richard H Dyck, Frank M Laferla, Michael C Antle
Circadian disturbances, including a fragmented sleep-wake pattern and sundowning, are commonly reported early in the progression of Alzheimer's disease (AD). These changes are distinctly different from those observed in non-pathological aging. Transgenic models of AD are a promising tool in understanding the underlying mechanisms and cause of disease. A novel triple-transgenic model of AD, 3xTg-AD, is the only model to exhibit both Abeta and tau pathology, and mimic human AD. The present study characterized changes pertaining to circadian rhythmicity that occur prior to and post-AD pathology...
August 12, 2010: Brain Research
M Germ, K Tomioka
The effect of direct 5,7-dihydroxytryptamine (5,7-DHT) injection into the medulla region of the optic lobe on the locomotor activity was investigated in the adult male cricket, Gryllus bimaculatus. After a 6 hr phase advance of a light-dark cycle, the 5,7-DHT injected animals needed significantly longer time for resynchronization to the new cycle (6.55 +/- 0.62 days) than the control, Ringer's solution injected animals (3.17 +/- 0.15 days; P < 0.001, t-test). Light induced a bout of activity (i.e., masking effect) when light-dark cycle was phase advanced by 6 hr and the duration of the masking effect was significantly longer in 5,7-DHT injected animals...
June 1, 1998: Zoological Science
M Germ, K Tomioka
Effects of 15 min light pulses given at various intervals (every 1, 2, 4, 6, 8 and 12 hr) under constant darkness on the locomotor rhythm were investigated in the adult male cricket, Gryllus bimaculatus. A single pulse per 24 hr induced period modulation in a circadian phase dependent manner, yielding a period modulation curve (PMC): the 15 min light pulse lengthened the period in the early subjective night (CT11-16) and shortened it during the late subjective night to the early subjective day (CT20-5). Frequent light pulses modulated the freerunning period of the rhythm dependent on the interval of the pulses: when compared with the freerunning period in DD (23...
June 1, 1998: Zoological Science
L N Edmunds, D E Tay, D L Laval-Martin
The cell division rhythm in Euglena gracilis Klebs (Z strain) freeruns with a circadian period (30.2 +/- 1.8 hours for 156 monitored oscillations) in aerated, magnetically stirred, 8-liter, axenic batch cultures grown photoautotrophically at 25 degrees C in LD: 3,3, (7,500 lux, cool-white fluorescent) 6-hour light cycles from the moment of inoculation. Cell number was measured at 2-hour intervals with an automatic fraction collector and Coulter Electronic Particle Counter. At different circadian times throughout the 30-hour division cycle, 3-hour light perturbations were imposed on free-running cell populations by giving light during one of the intervals when dark would have fallen in the LD: 3,3 regimen...
July 1982: Plant Physiology
Helge A Slotten, Sturla Krekling, Paul Pévet
The main purpose of the study was to compare behavioural properties of entrainment to photic (30 min; 200lx) and nonphotic (melatonin: 1 h; 100 microg) stimuli in the diurnal rodent Arvicanthis ansorgei. Male animals (n=38) were used, and running wheel activity was recorded. Following entrainment to 12:12 h LD the animals were transferred to DD (dim red light) to freerun before treatment started. A phase response curve (PRC) to light was determined showing a phase delay region in the early subjective night (CT 8-16) and a phase advance region in the late subjective night (CT 18-4)...
November 30, 2005: Behavioural Brain Research
Florian Geier, Sabine Becker-Weimann, Achim Kramer, Hanspeter Herzel
To adapt the timing of processes regulated by the circadian clock to seasonally varying photoperiods, the phase relation between the circadian clock and dusk or dawn ("phase of entrainment") must be tightly adjusted. The authors use a mathematical model of the molecular mammalian circadian oscillator to investigate the influence of the free-running period (tau) and the shape of the PRC on the phase of entrainment. They find that a phase-dependent sensitivity ("gating") of light-induced period gene transcription enables a constant phase relation to dusk or dawn under different photoperiods...
February 2005: Journal of Biological Rhythms
Shizufumi Ebihara, Satoru Miyazaki, Hirotake Sakamaki, Takashi Yoshimura
In mice, genetic differences between inbred strains have been shown for several parameters of sleep and circadian activity rhythms. Our previous studies have demonstrated that CS mice have three remarkable characteristics in the circadian rhythm of locomotor activity: (1) high activity both during the day and night, (2) unstable freerunning period and (3) spontaneous rhythm splitting. In order to characterize sleep properties of CS mice, we compared circadian sleep patterns of CS with those of C57BL/6J and C3H/He mice which have normal circadian activity rhythms...
August 1, 2003: Brain Research
We reared wild type (Canton-S) and period mutant flies, i.e., per(S) and per(L), of Drosophila melanogaster in constant darkness, constant light or 24h light dark cycles with various light to dark ratios throughout the development from embryo to early adult. The locomotor activity rhythms of newly eclosed individuals were subsequently monitored in the lighting conditions, in which they had been reared, for several days and then in constant darkness. Circadian rhythms were clearly exhibited in constant darkness even in flies reared in constant light and constant darkness as well as flies reared in light-dark cycles, but the freerunning period differed among groups...
March 1997: Journal of Insect Physiology
Christopher T Steele, Bora D Zivkovic, Thomas Siopes, Herbert Underwood
Our previous studies showed that the eyes of Japanese quail contain a biological clock that drives a daily rhythm of melatonin synthesis. Furthermore, we hypothesized that these ocular clocks are pacemakers because eye removal abolishes freerunning rhythms in constant darkness (DD). If the eyes are indeed acting as pacemakers, we predicted that the two ocular pacemakers in an individual bird must remain in phase in DD and, furthermore, the two ocular pacemakers would rapidly regain coupling after being forced out of phase...
January 2003: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
T L. Page, C Mans, G Griffeth
The freerunning period of circadian clocks in constant environmental conditions can be history-dependent, and one effect of entrainment of circadian clocks by light cycles is to cause long-lasting changes in the freerunning period that are termed after-effects. We have studied after-effects of entrainment to 22-h (LD 8:14) and 26-h (LD 8:18) light cycles in the cockroach Leucophaea maderae. We find that in cockroaches, the freerunning period of the locomotor activity rhythm, measured in constant darkness (DD), is 0...
September 2001: Journal of Insect Physiology
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