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Journal of Biological Rhythms

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https://www.readbyqxmd.com/read/28480817/plasticity-in-the-period-of-the-circadian-pacemaker-induced-by-phase-dispersion-of-its-constituent-cellular-clocks
#1
Domien G M Beersma, Kim A Gargar, Serge Daan
The mammalian circadian pacemaker is commonly thought to be a rigid oscillator that generates output under a variety of circumstances that differ only in phase, period, and/or amplitude. Yet the pacemaker is composed of many cells that each can respond to varying circumstances in different ways. Computer simulations demonstrate that networks of such pacemaker cells behave differently under a light-dark cycle compared with constant darkness. The differences demonstrate that the circadian pacemaker is plastic: The pacemaker shapes its properties in response to the circumstances...
May 1, 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28466676/daily-rhythm-in-plasma-n-acetyltryptamine
#2
Peter S Backlund, Henryk F Urbanski, Mark A Doll, David W Hein, Marjan Bozinoski, Christopher E Mason, Steven L Coon, David C Klein
Normal physiology undergoes 24-h changes in function that include daily rhythms in circulating hormones, most notably melatonin and cortical steroids. This study focused on N-acetyltryptamine, a little-studied melatonin receptor mixed agonist-antagonist and the likely evolutionary precursor of melatonin. The central issue addressed was whether N-acetyltryptamine is physiologically present in the circulation. N-acetyltryptamine was detected by LC-MS/MS in daytime plasma of 3 different mammals in subnanomolar levels (mean ± SEM: rat, 0...
May 1, 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28452287/akt1-controls-the-timing-and-amplitude-of-vascular-circadian-gene-expression
#3
Amelia K Luciano, Jeans M Santana, Heino Velazquez, William C Sessa
The AKT signaling pathway is important for circadian rhythms in mammals and flies ( Drosophila). However, AKT signaling in mammals is more complicated since there are 3 isoforms of AKT, each performing slightly different functions. Here we study the most ubiquitous AKT isoform, Akt1, and its role at the organismal level in the central and vascular peripheral clocks. Akt1(-/-) mice exhibit relatively normal behavioral rhythms with only minor differences in circadian gene expression in the liver and heart. However, circadian gene expression in the Akt1(-/-) aorta, compared with control aorta, follows a distinct pattern...
April 1, 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28452286/clock-gene-expression-in-the-suprachiasmatic-nucleus-of-hibernating-arctic-ground-squirrels
#4
Tomoko Ikeno, Cory T Williams, C Loren Buck, Brian M Barnes, Lily Yan
Most organisms have a circadian system, entrained to daily light-dark cycles, that regulates 24-h rhythms of physiology and behavior. It is unclear, however, how circadian systems function in animals that exhibit seasonal metabolic suppression, particularly when this coincides with the long-term absence of a day-night cycle. The arctic ground squirrel, Urocytellus parryii, is a medium-sized, semi-fossorial rodent that appears above-ground daily during its short active season in spring and summer before re-entering a constantly dark burrow for 6 to 9 months of hibernation...
April 1, 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28452285/daily-light-exposure-patterns-reveal-phase-and-period-of-the-human-circadian-clock
#5
Tom Woelders, Domien G M Beersma, Marijke C M Gordijn, Roelof A Hut, Emma J Wams
Light is the most potent time cue that synchronizes (entrains) the circadian pacemaker to the 24-h solar cycle. This entrainment process is an interplay between an individual's daily light perception and intrinsic pacemaker period under free-running conditions. Establishing individual estimates of circadian phase and period can be time-consuming. We show that circadian phase can be accurately predicted (SD = 1.1 h for dim light melatonin onset, DLMO) using 9 days of ambulatory light and activity data as an input to Kronauer's limit-cycle model for the human circadian system...
April 1, 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28470124/andreas-oksche
#6
Horst-Werner Korf, David C Klein, Josephine Arendt, Paul Pévet
No abstract text is available yet for this article.
April 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28470123/carbachol-induces-phase-dependent-phase-shifts-of-per1-transcription-rhythms-in-cultured-suprachiasmatic-nucleus-slices
#7
Kumiko Dojo, Yoshiaki Yamaguchi, Jean-Michel Fustin, Masao Doi, Masaki Kobayashi, Hitoshi Okamura
Among nonphotic stimulants, a classic cholinergic agonist, carbachol, is known to have a strong and unique phase-resetting effect on the circadian clock: Intracerebroventricular carbachol treatment causes phase delays during the subjective early night and phase advances in the subjective late night, but the effects of this drug on the suprachiasmatic nucleus (SCN) in vivo and in vitro are still controversial. In the present study, we succeeded in reproducing the biphasic phase-shifting effect of carbachol on clock gene expression in organotypic SCN slices prepared from mice carrying a Per1-promoter fused luciferase gene ( Per1-luc)...
April 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28470122/daily-cycles-in-body-temperature-in-a-songbird-change-with-photoperiod-and-are-weakly-circadian
#8
Alistair Dawson
Although it is well known that body temperature (Tb) is higher during the day in diurnal birds than at night, no data are available regarding exactly how Tb varies during a 24-h period, how this differs under different photoperiods, and how it responds to a change in photoperiod. This study used implanted temperature loggers in starlings ( Sturnus vulgaris) to address these questions. The duration of elevated Tb was directly related to photoperiod, but the amplitude of the daily cycle was significantly greater under shorter photoperiods...
April 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28470121/shift-work-and-cognitive-flexibility-decomposing-task-performance
#9
Philip Cheng, Gabriel Tallent, Thomas John Bender, Kieulinh Michelle Tran, Christopher L Drake
Deficits in cognitive functioning associated with shift work are particularly relevant to occupational performance; however, few studies have examined how cognitive functioning is associated with specific components of shift work. This observational study examined how circadian phase, nocturnal sleepiness, and daytime insomnia in a sample of shift workers ( N = 30) were associated with cognitive flexibility during the night shift. Cognitive flexibility was measured using a computerized task-switching paradigm, which produces 2 indexes of flexibility: switch cost and set inhibition...
April 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28470120/cell-intrinsic-bmal1-dependent-circadian-regulation-of-temozolomide-sensitivity-in-glioblastoma
#10
Emily A Slat, Jasmin Sponagel, Luciano Marpegan, Tatiana Simon, Najla Kfoury, Albert Kim, Andrea Binz, Erik D Herzog, Joshua B Rubin
The safety and efficacy of chemotherapeutics can vary as a function of the time of their delivery during the day. This study aimed to improve the treatment of glioblastoma (GBM), the most common brain cancer, by testing whether the efficacy of the DNA alkylator temozolomide (TMZ) varies with the time of its administration. We found cell-intrinsic, daily rhythms in both human and mouse GBM cells. Circadian time of treatment affected TMZ sensitivity of murine GBM tumor cells in vitro. The maximum TMZ-induced DNA damage response, activation of apoptosis, and growth inhibition occurred near the daily peak in expression of the core clock gene Bmal1...
April 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28470119/acute-effects-of-morning-light-on-plasma-glucose-and-triglycerides-in-healthy-men-and-men-with-type-2-diabetes
#11
Ruth I Versteeg, Dirk J Stenvers, Dana Visintainer, Andre Linnenbank, Michael W Tanck, Gooitzen Zwanenburg, Age K Smilde, Eric Fliers, Andries Kalsbeek, Mireille J Serlie, Susanne E la Fleur, Peter H Bisschop
Ambient light intensity is signaled directly to hypothalamic areas that regulate energy metabolism. Observational studies have shown associations between ambient light intensity and plasma glucose and lipid levels, but human data on the acute metabolic effects of light are scarce. Since light is the main signal indicating the onset of the diurnal phase of physical activity and food intake in humans, we hypothesized that bright light would affect glucose and lipid metabolism. Therefore, we determined the acute effects of bright light on plasma glucose and lipid concentrations in 2 randomized crossover trials: (1) in 8 healthy lean men and (2) in 8 obese men with type 2 diabetes...
April 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28367676/are-individual-differences-in-sleep-and-circadian-timing-amplified-by-use-of-artificial-light-sources
#12
Krithika Swaminathan, Elizabeth B Klerman, Andrew J K Phillips
Within the human population, there is large interindividual variability in the timing of sleep and circadian rhythms. This variability has been attributed to individual differences in sleep physiology, circadian physiology, and/or light exposure. Recent experimental evidence suggests that the latter is necessary to evoke large interindividual differences in sleep and circadian timing. We used a validated model of human sleep and circadian physiology to test the hypothesis that intrinsic differences in sleep and circadian timing are amplified by self-selected use of artificial light sources...
April 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28347188/circadian-misalignment-increases-c-reactive-protein-and-blood-pressure-in-chronic-shift-workers
#13
Christopher J Morris, Taylor E Purvis, Joseph Mistretta, Kun Hu, Frank A J L Scheer
Shift work is a risk factor for inflammation, hypertension, and cardiovascular disease. This increased risk cannot be fully explained by classical risk factors. Shift workers' behavioral and environmental cycles are typically misaligned relative to their endogenous circadian system. However, there is little information on the impact of acute circadian misalignment on cardiovascular disease risk in shift workers, independent of differences in work stress, food quality, and other factors that are likely to differ between night and day shifts...
April 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28347186/aryl-hydrocarbon-receptor-deficiency-alters-circadian-and-metabolic-rhythmicity
#14
Cassie Jaeger, Ali Q Khazaal, Canxin Xu, Mingwei Sun, Stacey L Krager, Shelley A Tischkau
PAS domain-containing proteins can act as environmental sensors that capture external stimuli to allow coordination of organismal physiology with the outside world. These proteins permit diverse ligand binding and heterodimeric partnership, allowing for varied combinations of PAS-dependent protein-protein interactions and promoting crosstalk among signaling pathways. Previous studies report crosstalk between circadian clock proteins and the aryl hydrocarbon receptor (AhR). Activated AhR forms a heterodimer with the circadian clock protein Bmal1 and thereby functionally inhibits CLOCK/Bmal1 activity...
April 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28326911/vijay-kumar-sharma
#15
Vinod Kumar, Nishikant Subhedar
No abstract text is available yet for this article.
February 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28326910/circadian-rhythms-in-plasma-brain-derived-neurotrophic-factor-differ-in-men-and-women
#16
Sean W Cain, Anne-Marie Chang, Irma Vlasac, Archana Tare, Clare Anderson, Charles A Czeisler, Richa Saxena
The measurement of circulating levels of brain-derived neurotrophic factor (BDNF) has been proposed to be a marker of disease and an indicator of recovery. Thus, knowing the temporal pattern and influence of potential circadian rhythms is important. Although several studies have measured BDNF at different times of day, no studies have done so while controlling for potential masking influences such as sleep and activity. Further, no previous study has examined circadian rhythms within individuals. We examined circadian rhythms in plasma BDNF while minimizing masking from behavioral and environmental factors using a 30-h constant routine (CR) protocol...
February 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28326909/resynchronization-dynamics-reveal-that-the-ventral-entrains-the-dorsal-suprachiasmatic-nucleus
#17
Stephanie R Taylor, Thomas J Wang, Daniel Granados-Fuentes, Erik D Herzog
Although the suprachiasmatic nucleus (SCN) has long been considered the master circadian clock in mammals, the topology of the connections that synchronize daily rhythms among SCN cells is not well understood. We combined experimental and computational methods to infer the directed interactions that mediate circadian synchrony between regions of the SCN. We analyzed PERIOD2 (PER2) expression from SCN slices during and after treatment with tetrodotoxin, allowing us to map connections as cells resynchronized their daily cycling following blockade and restoration of cell-cell communication...
February 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/27836939/statistics-for-sleep-and-biological-rhythms-research
#18
Elizabeth B Klerman, Wei Wang, Andrew J K Phillips, Matt T Bianchi
This article is part of a Journal of Biological Rhythms series exploring analysis and statistical topics relevant to researchers in biological rhythms and sleep research. The goal is to provide an overview of the most common issues that arise in the analysis and interpretation of data in these fields. In this article, we address issues related to the collection of multiple data points from the same organism or system at different times, since such longitudinal data collection is fundamental to the assessment of biological rhythms...
February 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/27836938/statistics-for-sleep-and-biological-rhythms-research
#19
Matt T Bianchi, Andrew J K Phillips, Wei Wang, Elizabeth B Klerman
The Journal of Biological Rhythms will be publishing articles exploring analysis and statistical topics relevant to researchers in biological rhythms and sleep research. The goal is to provide an overview of the most common issues that arise in the analysis and interpretation of data in these fields. By using case examples and highlighting the pearls and pitfalls of statistical inference, the authors will identify and explain ways in which experimental scientists can avoid common analytical and statistical mistakes and use appropriate analytical and statistical methods in their research...
February 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28088873/developmental-changes-in-ultradian-sleep-cycles-across-early-childhood
#20
Sean Lopp, William Navidi, Peter Achermann, Monique LeBourgeois, Cecilia Diniz Behn
Nocturnal human sleep is composed of cycles between rapid eye movement (REM) sleep and non-REM (NREM) sleep. In adults, the structure of ultradian cycles between NREM and REM sleep is well characterized; however, less is known about the developmental trajectories of ultradian sleep cycles across early childhood. Cross-sectional studies indicate that the rapid ultradian cycling of active-quiet sleep in infancy shifts to a more adult-like pattern of NREM-REM sleep cycling by the school-age years, yet longitudinal studies elucidating the details of this transition are scarce...
January 1, 2017: Journal of Biological Rhythms
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