Journal of Circadian Rhythms

Circadian Biology intersects with diverse scientific domains, intricately woven into the fabric of organismal physiology and behavior. The rhythmic orchestration of life by the circadian clock serves as a focal point for researchers across disciplines. This retrospective examination delves into several of the scientific milestones that have fundamentally shaped our contemporary understanding of circadian rhythms. From deciphering the complexities of clock genes at a cellular level to exploring the nuances of coupled oscillators in whole organism responses to stimuli...

Chronobiology investigations have revealed much about cellular and physiological clockworks but we are far from having a complete mechanistic understanding of the physiological and ecological implications. Here we present some unresolved questions in circadian biology research as posed by the editorial staff and guest contributors to the Journal of Circadian Rhythms. This collection of ideas is not meant to be comprehensive but does reveal the breadth of our observations on emerging trends in chronobiology and circadian biology...

We aimed to examine the difference in rest-activity rhythm (RAR) and light exposure rhythm (LER) between patients with mild cognitive impairment (MCI) and normal controls (NC), and to verify their relationships with cognitive functions. The neuropsychological battery was administered to participants above 50 years old. The MCI diagnosis was made according to Petersen's criteria. Ten patients with MCI (77.90 ± 6.95 years) and eight NC (74.75 ± 5.06 years) were studied. Actigraphy (Actiwatch 2; Philips Respironics) was recorded at home for 5 days...

The human circadian timing system depends on the light/dark cycle as its main cue to synchronize with the environment, and thus with solar time . However, human activities depend also on social time , i.e. the set of time conventions and restrictions dictated by society, including Daylight Saving Time (DST), which adds an hour to any degree of desynchrony between social and solar time . Here, we used Google Trends as a data source to analyze diurnal variation, if any, and the daily peak in the relative search volume of 26 Google search queries in relation to the transitions to/from DST in Italy from 2015 to 2020...

The circadian clock is adjusted by light inputs via the retinohypothalamic tract. Because environmental light is controllable for modern humans at the individual's preference although under social schedules, individual differences in time-related psychology and behavior may be associated with morningness-eveningness preference (M-E preference). To examine this hypothesis, we used the Time Management Scale and Time Anxiety Scale to quantify time-related psychology and behavior. These scales aim to evaluate "awareness of effective time management and utilization" and "anxiety about uncontrollable time schedule and unexpected time-related outcome", respectively...

The circadian clock regulates the "push-pull" of the molecular signaling mechanisms that arrange the rhythmic organization of the physiology to maintain cellular homeostasis. In mammals, molecular clock genes tightly arrange cellular rhythmicity. It has been shown that this circadian clock optimizes various biological processes, including the cell cycle and autophagy. Hence, we explored the dynamic crosstalks between the circadian rhythm and endoplasmic reticulum (ER)-quality control (ERQC) mechanisms. ER-associated degradation (ERAD) is one of the most important parts of the ERQC system and is an elaborate surveillance system that eliminates misfolded proteins...

Many critical life processes are regulated by input from 24-hour external light/dark cycles, such as metabolism, cellular homeostasis, and detoxification. The circadian clock, which helps coordinate the response to these diurnal light/dark cycles, remains rhythmic across lifespan; however, rhythmic transcript expression is altered during normal aging. To better understand how aging impacts diurnal expression, we present an improved Fourier-based method for detecting and visualizing rhythmicity that is based on the relative power of the 24-hour period compared to other periods (RP24)...

Background: To address a critical gap for application of cancer chronotherapy of when would be the best time(s) for treating an individual cancer patient, we conducted a pilot study to characterize diurnal variations of gene expression in oral mucosal tissue, which is vulnerable to damage from cancer therapies. Methods: We conducted RNA-seq assay on individual oral mucosal samples collected from 11 healthy volunteers every 4 hours (6 time points). Using a cosine-based method, we estimated the individual and average values of peak-time and amplitude for each gene...

The progression of amyloid plaques and neurofibrillary tangles in different brain areas is associated with the effects of Alzheimer's disease (AD). In addition to cognitive impairment, circadian alterations in locomotor activity have also been detected, but they have not been characterized in a jet lag protocol. Therefore, the present study aimed to compare 3xTg-AD and non-transgenic mice in changes of 24 h cycles of spontaneous locomotor activity in a jet lag protocol, in an environment without a running wheel, at 3 different states of neuronal damage: early, intermediate and advanced (3, 8 and 13 months, respectively)...

The circadian timing system (CTS) is a complex set of cyclic cellular mechanisms which serve to synchronize discrete cell groups across multiple organ systems to adapt the bodys physiology to a (roughly) 24-hour clock. Many genes and hormones have been shown to be strongly associated with the CTS, some of which include the genes Bmal1, Period1, Period2, Cryptochrome1 , and Cryptochrome2 , and the hormone melatonin. Previous data suggest that microtubule dynamics play an important role in melatonin function as it relates to the CTS in vitro, though this relationship has never been explored in vivo...

Increased adenosine levels throughout the day promote sleepiness. A single nucleotide polymorphism (SNP) in the adenosine deaminase ADA gene (rs73598374) has been shown to affect sleep regulation. The extent to which lower ADA enzymatic activity is associated with the homeostatic sleep factor, melatonin, is uncertain. To test this possibility, we assessed the relationship between the ADA polymorphism and evening melatonin levels, as well as self-reported sleep behavior. Given the close relationship between mood and sleep behavior, we further tested the impact of ADA genotype on self-reported mood...

Female reproductive success relies on proper integration of circadian- and ovarian- signals to the hypothalamic-pituitary-gonadal axis in order to synchronize the preovulatory LH surge at the end of the ovarian follicular stage with the onset of the main active period. In this study, we used a combination of neuroanatomical and electrophysiological approaches to assess whether the hypothalamic neurons expressing Arg-Phe amide-related peptide (RFRP-3), a gonadotropin inhibitory peptide, exhibit daily and estrous stage dependent variations in female mice...

This ecological study examined whether geographical differences in the physique of Japanese children and adolescents can be explained from the perspective of photoperiodicity induced by effective day length (light duration exceeding a certain threshold of illuminance) using prefecture-level anatomical data and Mesh Climatic Data. Multiple regression analysis for height prediction demonstrated that when controlled by weight, effective day lengths of the longest and shortest months were inversely correlated with height distribution...

Epidemiological studies have indicated that a disturbed circadian rhythm resulting from night-shift work is a potential risk factor for breast cancer. However, the mechanism of increased risk of breast cancer by night-shift work remains unclear, and there have been few in vivo studies conducted to definitively associate the two factors. In this study, BJMC3879Luc2 mouse breast cancer cells were transplanted into BALB/c mice. Mice were maintained under lighting conditions that modeled the two-shift system and were investigated for the effect of light/dark cycle disruption on tumor growth and lymph node metastasis...

Chronobiology is not routinely taught to biology or medical students in most European countries. Here we present the results of the chronobiology practicals of a group of students of the University of Padova, with a view to highlight some interesting features of this group, and to share a potentially interesting cross-faculty teaching experience. Thirty-eight students (17 males; 22.9 ± 1.6 yrs) completed a set of self-administered electronic sleep quality [Pittsburgh Sleep Quality Index (PSQI)], chronotype and sleepiness [Epworth Sleepiness Scale (ESS)] questionnaires...

The purpose of this study was to analyze the light-dark variations in the concentrations of several neurotransmitters in the lumbar spinal cord of rats. Six groups of male Wistar rats were exposed to a 12 h light-12 h dark cycle for 70 days. At different time points of the experimental day (8, 12, 16, 20, 24 and 4 h), one of the groups of rats was randomly selected to be sacrificed, and the spinal cords were removed. The gamma-aminobutyric acid (GABA), glutamate (GLU), dopamine, serotonin, epinephrine (E), and norepinephrine (NE) levels in each extracted spinal cord were measured with high-pressure liquid chromatography (HPLC)-EQ and HPLC-fluorescence systems...

Critical biological processes are under control of the circadian clock. Disruption of this clock, e.g. during aging, results in increased risk for development of chronic disease. Exercise is a protective intervention that elicits changes in both age and circadian pathologies, yet its role in regulating circadian gene expression in peripheral tissues is unknown. We hypothesized that voluntary wheel running would restore disrupted circadian rhythm in aged mice. We analyzed wheel running patterns and expression of circadian regulators in male and female C57Bl/6J mice in adult (~4 months) and old (~18 months) ages...

Background: Circadian misalignment can impair healthcare shift workers' physical and mental health, resulting in sleep deprivation, obesity, and chronic disease. This multidisciplinary research team assessed eating patterns and sleep/physical activity of healthcare workers on three different shifts (day, night, and rotating-shift). To date, no study of real-world shift workers' daily eating and sleep has utilized a largely-objective measurement. Method: During this fourteen-day observational study, participants wore two devices (Actiwatch and Bite Technologies counter) to measure physical activity, sleep, light exposure, and eating time...

Objective: Review relationships among circadian clocks, core body temperature (CBT), and fertility in women. Methods: Scoping literature review. Results: Circadian clocks are a ubiquitous adaptation to the most predictable environmental events - the daily cycles of light and dark. Core body temperature (CBT) also follows a circadian rhythm. Additionally, CBT is tightly controlled by a combination of neuronal circuits that begin in the hypothalamus and involve many other portions of the brain as well as a wide range of peripheral mechanisms...

Shift work is an inconsistent and atypical work schedule. This study aimed to investigate the influence of shift work on the Quality of Sleep (QOS) and Executive Functions (EF). Thirty shift workers and thirty day workers first completed a demographic questionnaire. They then were tested using the Pittsburgh Sleep Quality Index (PSQI) and EF tests, including the Corsi Block-Tapping Task (CBTT), Berg's Card Sorting Task (BCST), and the Continuous Performance Task (CPT). Results were subjected to non-parametric Chi-Square Tests, the Mann-Whitney U Test, and Independent T-Tests...