A genetic approach was used to investigate whether the emergence of circadian rhythms in murine pups is dependent on a functional maternal clock. Arrhythmic females bearing either the mPer1Brdm1/Per2Brdm1 or mPer2Brdm1/Cry1-/- double-mutant genotype were crossed with wild-type males under constant darkness. The heterozygous offspring have the genetic constitution for a functional circadian cloc...

1. In order to discriminate between homeostatic and circadian control of energy expenditure, this paper considers whether a shorter circadian cycle will produce a proportional reduction in energy expenditure (so that expenditure per unit time is conserved) or alternatively whether energy expenditure will be compressed into the shorter cycle (so that energy expenditure per cycle is conserved). T...

PURPOSE To test whether Müller glia of the mammalian retina have circadian rhythms. METHODS We used Müller glia cultures isolated from mouse lines or from humans and bioluminescent reporters of circadian clock genes to monitor molecular circadian rhythms. The clock gene dependence of the Müller cell rhythms was tested using clock gene knockout mouse lines or with siRNA for specific clock gene...

The master clock driving mammalian circadian rhythms is located in the suprachiasmatic nuclei (SCN) of the hypothalamus and entrained by daily light/dark cycles. SCN lesions abolish circadian rhythms of behavior and result in a loss of synchronized circadian rhythms of clock gene expression in peripheral organs (e.g., the liver) and of hormone secretion (e.g., corticosterone). We examined rhyth...

We previously reported emergence and disappearance of circadian molecular oscillations during differentiation of mouse embryonic stem (ES) cells and reprogramming of differentiated cells, respectively. Here we present a robust and stringent in vitro circadian clock formation assay that recapitulates in vivo circadian phenotypes. This assay system first confirmed that a mutant ES cell line lacki...

Circadian clocks are believed to confer an advantage to plants, but the nature of that advantage has been unknown. We show that a substantial photosynthetic advantage is conferred by correct matching of the circadian clock period with that of the external light-dark cycle. In wild type and in long- and short-circadian period mutants of Arabidopsis thaliana, plants with a clock period matched to...

PURPOSE The purpose of this study was to investigate sleep habits, sleep disturbance, and circadian types, and to identify factors influencing sleep disturbance in nursing students. METHODS Participants were 140 senior nursing students. The data were collected from May 19 to 27, 2008 using self-report questionnaires. RESULTS 1) Evening type delayed sleep-wake schedules were more frequent th...

background variations in diurnal preferences for activity and sleep are classified as morning and evening chronotypes. morning and evening-type individuals differ regarding a number of psychological and biological variables such as sleep. objectives the current study aimed to investigate the relationship between chronotypes and sleep quality. patients and methods in this descriptive, correlatio...