Vital signs and several constituents of the serum and urine show a circadian rhythm. Such a rhythm is also seen in the onset of various diseases. Time dependent changes in the blood volume, functions of liver and kidney etc. have implications for drug availability and circadian changes should be taken in account in pharmacokinetic studies. These changes are the subject of chronopharmacokinetics.

In ten healthy, nonsmoking, non-atopic, young volunteers, specific airway conductance and bronchial response to aerosolized histamine were measured plethysmographically at intervals of 4.8 h during two periods of 24 h, i.e. one day without, the other with, a parasympatholytic aerosol (0.20-0.24 mg ipratropium bromide) inhaled 1 h before each measurement, in order to determine the role of the pa...

Circadian oscillators are known to regulate the timing of cell division in many organisms. In the case of Chlamydomonas reinhardtii, however, this conclusion has been challenged by several investigators. We have reexamined this issue and find that the division behavior of Chlamydomonas meets all the criteria for circadian rhythmicity: persistence of a cell division rhythm (a) with a period of a...

Circadian systems include slave oscillators and central pacemakers, and the cores of eukaryotic circadian clocks described to date are composed of transcription and translation feedback loops (TTFLs). In the model system Neurospora, normal circadian rhythmicity requires a TTFL in which a White Collar complex (WCC) activates expression of the frequency (frq) gene, and the FRQ protein feeds back ...

BACKGROUND Circadian rhythm sleep disorder-advanced sleep-phase type is a relatively uncommon disorder, mostly seen among the elderly population. Impaired circadian rhythms have been reported in neurodegenerative conditions; however, there are no reports of any circadian rhythm sleep disorder among patients with Parkinsonian syndromes. We report two patients who presented with this circadian rh...

Although the prevailing paradigm has held that the polar night is a period of biological quiescence, recent studies have detected noticeable activity levels in marine organisms. In this study, we investigated the circadian rhythm of the scallop Chlamys islandica by continuously recording the animal's behaviour over 3 years in the Arctic (Svalbard). Our results showed that a circadian rhythm per...

The olfactory response in antennae of the cockroach, Leucophaea maderae, was investigated by measuring electroantennograms (EAGs) in restrained animals. The amplitude of the EAG response to pulses of ethyl acetate, octanol, or fenchone, exhibited a robust, light entrained, circadian rhythm that persisted at least 14 days in constant darkness. Dilution-response curves measured at the peak and tr...

Dijk, Derk-Jan, and Steven W. Lockley. Invited Review: Integration of human sleep-wake regulation and circadian rhythmicity. J Appl Physiol 92: 852–862, 2002; 10.1152/japplphysiol.00924.2001.—The human sleep-wake cycle is generated by a circadian process, originating from the suprachiasmatic nuclei, in interaction with a separate oscillatory process: the sleep homeostat. The sleep-wake cycle is...

Plant circadian systems are composed of a large number of self-sustained cellular circadian oscillators. Although the light-dark signal in the natural environment is known to be the most powerful Zeitgeber for the entrainment of cellular oscillators, its effect is too strong to control the plant rhythm into various forms of synchrony. Here, we show that the application of pulse perturbations, i...

BACKGROUND Animals, including humans, exhibit a variety of biological rhythms. This article describes a method for the detection and simultaneous comparison of multiple nycthemeral rhythms. METHODS A statistical method for detecting periodic patterns in time-related data via harmonic regression is described. The method is particularly capable of detecting nycthemeral rhythms in medical data. ...