Measured circadian rhythms consist of endogenous (clock-driven) and exogenous (lifestyle-driven) components. The exogenous components cause difficulties of interpretation of phase and amplitude information. Such effects can be removed by "constant routines", but these protocols are restricted to the laboratory. By contrast, the process of "purification" of circadian rhythms uses the ...

Telemetered body temperature (BT), heart rate (HR), and activity (AC) data were collected in vasopressin-containing Long-Evans (LE) and vasopressin-deficient Brattleboro (DI) rats. The rats were exposed to a 12/12 h light/dark cycle under three conditions: 1) ad lib feeding throughout the 24-h cycle, 2) two scheduled-feeding periods during the diurnal ...

Rhythmicity is part of our life. All living organisms exhibit in some way or another a form of rhythmicity. Some of these rhythms have a geophysical counterpart in the environment. These are the so-called biological rhythms. This paper gives an introduction to the circadian rhythms, i.e., those rhythms with a ...

Field work in chronobiology usually is based on observations which differ from those in laboratory studies which are experimental. Non-invasive protocols are recommended in the field in order not to introduce additional variables. We propose an alternative strategy here. The effect of environmental cycles on biological rhythms can be estimated ...

This survey summarizes the findings concerning endogenous oscillations of three unicellular organisms: the dinophyte Gonyaulax polyedra, the ciliate Tetrahymena thermophila and the euglenophyte Euglena gracilis. All of them behave rhythmically and show the common features of zeitgeber action, differential sensitivity and temperature compensation; however, they exhibit some species-specific peculiarities that ...

The purpose of this work was to investigate whether the ultradian rhythms that are present prior the electroretinogram (ERG) amplitude circadian rhythm, and are superimposed upon it, during the different stages of development of the crayfish Procambarus clarkii are temperature sensitive, as well as the circadian rhythm. Temperature sensitivity was ...

Virtually all organisms have developed an internal timing system capable of reacting to and anticipating environmental stimuli with a program of appropriately timed metabolic, physiologic, and behavioral events. The predominant biological rhythms coincide with the geophysical cycle of day and night-the circadian rhythms. The suprachiasmatic nuclei comprise the primary pace-maker ...

Axon calibre in monopolar cells L1 and L2 of the fly's lamina can change dynamically. Swelling by day, L2 exhibits a daily rhythm of changing size apparently mediated by wide-field LBO5HT and PDH cells. L1/L2 axon profiles were measured planimetrically in the housefly, Musca domestica, from 1 microns cross sections. ...

Circadian rhythms of urinary excretion of corticosterone and catecholamines were examined in the rat before and after phase reversal of a 12-hour light and 12-hour dark cycle. After the reversal, the acrophase of rhythm was delayed and became constant again on the 6th day for corticosterone and on the 7th ...

Two experiments are described in which the effects of acoustic parameters, and changes in those acoustic parameters, on the salience of 42 pre-selected adjectives are explored. In experiment 1 four sets of seven stimuli each varying only along one of the four acoustic parameters pitch, speed, inharmonicity and rhythm were ...

Dynamic functional coupling between contralateral sensorimotor and supplementary motor areas during unilateral finger movements is studied using event-related coherence analysis. It is demonstrated in 3 subjects that the intrinsic rhythm of the sensorimotor area (mu rhythm) is phase coupled to intrinsic rhythmic activity of the supplementary motor area during rest. ...

Circadian activity patterns were measured in the solitary, subterranean Cape molerat, Georychus capensis, under fixed 12:12 LD, constant dark DD, and constant light LL photoperiods for 250 consecutive days using passive infra-red activity sensors. The molerats displayed significant nocturnal activity rhythms under 12:12 LD and free-running rhythms (23.5 h < ...

Most biochemical, physiological, and behavioral processes in vertebrates show significant daily rhythms. Under constant conditions, these rhythms exhibit an endogenous periodicity around 24 h showing that they are driven by an internal circadian clock. In Japanese quail, the circadian clock driving activity and body temperature rhythms is functionally organized as ...

Mastication is a typical rhythmical behavior in mammals. Like respiration, it is now generally accepted that the motor command for the basic pattern of rhythmical oral-facial movements is generated by a neuronal population in the brainstem (central pattern generator, CPG). The central pattern generation of rhythmical masticatory movements can be ...

Mapping of organized rhythms like sinus rhythm uses activation times from individual electrograms, and often assumes that the map for a single activation is similar to maps for subsequent activations. However, during fibrillation, activation times and electrograms are not easy to define, and maps change from activation to activation. Volume ...

By recording the locomotor activity rhythm of hagfish, Eptatretus burgeri, in which surgical lesions of the pretectal areas were made, we searched for the route of light information from the eyes to the circadian pacemaker, which is considered to be located in the preoptic nucleus. The entrainment of circadian activity ...

Examination of the influence of the light-dark cycle on circadian rhythmicity has been a fundamental aspect of chronobiology since its inception as a scientific discipline. Beginning with Bünning's hypothetical phase response curve in 1936, the impact of timed light exposure on circadian rhythms of literally hundreds of species has been ...

In a constant environment, circadian rhythms persist with slightly altered period lengths. Results of studies with continuous light exposure are less clear, because of short exposure durations and single-variable monitoring. This study sought to characterize properties of the oscillator(s) controlling the rat's circadian system by monitoring both body temperature and ...

To investigate the development of Arg-vasopressin (AVP) content and its diurnal rhythm in the suprachiasmatic nucleus (SCN), AVP was measured by enzyme immunoassay in the rat pup SCN punched out from tissue slices obtained at postnatal day (PD) 1, 5, 10, 12 and 20 from animals maintained under a light-dark ...

Breathing is regulated by a central neural oscillator that produces rhythmic output to the respiratory muscles. Pathological disturbances in rhythm (dysrhythmias) are observed in the breathing pattern of children and adults with neurological and cardiopulmonary diseases. The mechanisms responsible for genesis of respiratory dysrhythmias are poorly understood. The present studies ...

Rearing Drosophila melanogaster in constant darkness (DD) for multiple generations disrupts the circadian activity rhythm of adults. In order to determine under what conditions normal rhythms can be initiated, DD-reared Drosophila (either the wild type or the periodshort [pers] mutant) were exposed to light either as embryos, third-instar larvae, or ...

Upon exposure to sustained and synchronized diurnal activity, most human variables exhibit rhythms with a 24 h period. The best-fitting cosine curve to the data with a selected period (24 h) may yield parameters like acrophase (estimated peak time), amplitude, and mesor (rhythm adjusted mean). The sequential array of the ...

The circadian timing system (CTS) provides internal and external temporal coordination of an animal's physiology and behavior. In mammals, the generation and coordination of these circadian rhythms is controlled by a neural pacemaker, the suprachiasmatic nucleus (SCN), located within the hypothalamus. The pacemaker is synchronized to the 24 hour day ...

1. Sympathetic discharges from multifibre nerve recordings vary in their frequency of occurrence which displays both slow and fast rhythms and in their amplitude which reflects the number of activated fibres. It has been shown that the frequency of occurrence of these rhythms varies according to baroreceptor activity (via blood ...

The basic electrical rhythm (BER) of the small intestine in rat proves its physiological usefulness in generating the basic mechanical rhythm (BMR) as a specific form of muscular tonus in the interdigestive (respite) phases BMR is susceptible to amplitude modifications under the influence of factors that are intrinsic or extrinsic ...

To clarify the time course of circadian rhythm adaptation to a phase shift of the light-dark (LD) cycle, urinary excretion of catecholamines was measured in rats before and after a 12-hour or 6-hour phase delay of a 12-hour light and 12-hour dark schedule. In rats under a basal condition, distinct ...

Two types of monopolar cell interneurons, each with a single representative in every unit cartridge of the first optic neuropil, or lamina, of the housefly's optic lobe, have axons that undergo cyclical changes in diameter. The axons are largest during the beginning of day in a normal LD light cycle ...

Circadian rhythms in aqueous protein concentration (APC) and intraocular pressure (IOP) were examined in Dutch rabbits using the laser flare-cell meter and a pneumatonometer. The reproducibility and seasonal changes in circadian rhythm were also investigated. Rabbits were trained to a lighting cycle of 12-hour light and 12-hour darkness. The mean ...

Carbon dioxide emission (VCO2) was computed every 20 min from continuous CO2 concentration recordings taken during 3-30 consecutive days, in strictly controlled environmental conditions, in 54 OF1 mice, 99 Japanese quail, 66 Sprague-Dawley rats, 50 Hartley guinea pigs, 7 chicks, for 7-15 days on 2 Cynomolgus monkeys, and for 24 ...

The availability of sufficient zeitgebers is essential for entrainment of circadian rhythms. Bright light is an important human zeitgeber. However, social cues acting through the sleep-wake cycle may also be important in the entrainment of human rhythms. Current research suggests that humans receive inadequate and sporadic exposure to bright light. ...

The influence of environmental stimuli on a daily rhythm of immune activity during scale allograft rejection was investigated in gulf killifish, Fundulus grandis. Although melanophore destruction in the grafts is largely restricted to the scotophases in killifish held on 12 h daily photoperiods (LD 12:12), timed daily netting (tank-transfer "stress"), ...

The intergeniculate leaflet (IGL) receives retinal input and sends afferents to the hypothalamic suprachiasmatic nucleus (SCN), a circadian oscillator. The effect of IGL ablation on the circadian rhythm of wheel-running activity was examined in mice maintained in constant dark (DD) and in two intensities of constant light (LL). IGL-lesioned animals ...

In a network of excitatory and inhibitory neurons, hyperpolarization-activated inward currents can help to produce population rhythms in which individual cells participate sparsely and randomly. A shift in the activation curve of such a current changes the fraction of the cells participating in any given cycle of the population rhythm, ...

Most of the extensive literature concerning the resynchronization of circadian rhythms after a Zeitgeber shift is devoted to the dependence of resynchronization on the mode of the shift and the strength of the Zeitgeber, as well as on the circadian function investigated. Ontogenetic influences have rarely been investigated. Therefore, we ...

The effects of two different light regimens and the frequency of blood sampling on the diurnal plasma corticosterone concentrations in racing pigeons (Columba livia domestica) were investigated. The daily light regimens tested were a period of light during the day (DL; lights on 0515-2215) and shifting of the light period ...

To assess the spatial extent and temporal behavior of rolandic rhythms we recorded neuromagnetic signals from four healthy subjects with a 24-channel magnetometer. The subjects performed self-paced thumb movements or the motions were triggered by electrical stimulation of the median nerve at the wrist. The main frequency components of the ...

Field observations and laboratory experiments were performed to analyze the burrow plugging behavior of U. uruguayensis and to analyze its relation to two environmental cycles: light-dark cycle and tides. Field observations showed that burrow plugging is a rhythmic behavior synchronized with both environmental cycles such that burrows are open during ...

The sensitivity of terminal 5-HT1B autoreceptors in the cerebral cortex and hippocampus to both agonist and antagonist was determined at four different time points in the light:dark cycle of the rat to evaluate whether changes in their responsiveness underlie the circadian rhythm in 5-hydroxytryptamine (5-HT) release. No significant circadian differences ...

Chronotypic effects of rubidium (Rb) were examined in hamsters whose circadian activity rhythms had split into two components while they were housed in bright constant light. Seven of 12 hamsters receiving RbCl in drinking water for 10 weeks showed fusing of the components into an intact rhythm compared with none ...

Free-running circadian rhythms of locomotor activity of Tenebrionid beetles Trigonoscelis gigas Reitt., taken from the Turkmenian sand desert, were monitored in DD. The effects of microgravity --11 days in space flight aboard the Russian BION-10 "COSMOS" satellite, and of 2G hypergravity--seven days on a centrifuge, were determined. Two kinds of ...

The body temperatures (Tb) of golden-mantled ground squirrels maintained under constant dim light (< 20 1x red light) at an ambient temperature of 10 degrees C were monitored via telemetry throughout the hibernation season. During euthermia, when Tb ranged from 34 to 39 degrees C, these animals exhibited robust circadian ...

Non-linear interactions between low-frequency rhythms (0.1 Hz) of beat-to-beat variability series of sympathetic discharge and respiratory rhythm (0.3 Hz) are observed in decerebrate artificially ventilated cats. Simple graphical tools as Poincaré and recurrence maps are used to detect, in a qualitative way, phase-locking phenomena. Non-parametric bispectral analysis is also carried ...

Results from experiments on two strains of domestic rabbit show that despite their hopping gait, circadian locomotor rhythms can be successfully measured using running wheels specially designed for large laboratory mammals. Three female rabbits of an English outbred strain were monitored in a 13:11 light:dark (LD) cycle and in constant ...

Well-expressed endogenous circadian rhythms in Acetabularia acetabulum were spectrally analyzed and recorded in time-period distributions. The stability of the circadian periods under constant conditions and their changes could be monitored continually in step sizes close to the circadian period length. The resolution of period estimates of the circadian component was ...

Electrolytic lesions to 85-95% of both optic nerves at the level of the optic chiasm (OC-X) induce a significant shortening of the free-running period (tau) of locomotor rhythms in Podarcis sicula held in constant temperature (29 degrees C) and constant darkness. Together with previous data in P. sicula, showing that ...

The circadian timing system (CTS) is responsible for daily temporal coordination of physiological and behavioral functions both internally and with the external environment. Experiments in altered gravitational environments have revealed changes in circadian rhythms of species ranging from fungi to primates. The altered gravitational environments examined included both the microgravity ...

In a recent review of cellular mechanisms of entrainment, an ocular circadian rhythm of Bulla was reported (1). The isolated retina of this marine mollusk is described to contain a circadian oscillator. A glance at the spontaneous impulse frequency from eyes recorded in darkness at 15 degrees C suggests lower-frequency ...

The present results demonstrate that 5-7 days on a reversed light-dark cycle (12:12 h) is sufficient for the synchronization of spontaneous locomotor activity with the new circadian rhythm in rats. Once established, the circadian rhythm is stable for at least 3 days under constant illumination conditions. Reversal of the light-dark ...

Chronobiology--derived from chronos (time), bios (life), and logos (study of)--is the objective description of biological time structures and plays an important role in medicine. Circadian rhythms regulate the behaviour, physiology and function of living organisms at many biochemical levels. The influence of the rhythmic manifestation of life may be shown ...

The phosphorylation potentials of two proteins (M(r) 81 kDa and 63 kDa) in extracts of murine erythroleukemic (MEL) cells both vary in an oscillatory manner, sometimes changing by as much as 100-fold in 10 min. Direct analysis of the temporal changes indicates the existence of periodic modulation of the frequencies, ...