Harmonization of three different accelerometers to classify the 24 h activity cycle

Increasing interest in measuring key components of the 24 h activity cycle (24-HAC) [sleep, sedentary behavior (SED), light physical activity (LPA), and moderate to vigorous physical activity (MVPA)] has led to a need for better methods. Single wrist-worn accelerometers and different self-report instruments can assess the 24-HAC but may not accurately classify time spent in the different components or be subject to recall errors.Objective. To overcome these limitations, the current study harmonized output from multiple complimentary research grade accelerometers and assessed the feasibility and logistical challenges of this approach.Approach. Participants (n= 108) wore an: (a) ActiGraph GT9X on the wrist, (b) activPAL3 on the thigh, and (c) ActiGraph GT3X+ on the hip for 7-10 d to capture the 24-HAC. Participant compliance with the measurement protocol was compared across devices and an algorithm was developed to harmonize data from the accelerometers. The resulting 24-HAC estimates were described within and across days.Main results. Usable data for each device was obtained from 94.3% to 96.7% of participants and 89.4% provided usable data from all three devices. Compliance with wear instructions ranged from 70.7% of days for the GT3X+ to 93.2% of days for the activPAL3. Harmonized estimates indicated that, on average, university students spent 34% of the 24 h day sleeping, 41% sedentary, 21% in LPA, and 4% in MVPA. These behaviors varied substantially by time of day and day of the week.Significance. It is feasible to use three accelerometers in combination to derive a harmonized estimate the 24-HAC. The use of multiple accelerometers can minimize gaps in 24-HAC data however, factors such as additional research costs, and higher participant and investigator burden, should also be considered.

Restless nights when sick: ectoparasite infections alter rest-activity cycles of diurnal fish hosts

Circadian rhythms are timekeeping mechanisms responsible for an array of biological processes. Disruption of such cycles can detrimentally affect animal health. Circadian rhythms are critical in the co-evolution of host–parasite systems, as synchronization of parasite rhythms to the host can influence infection dynamics and transmission potential. This study examines the circadian rhythms in behaviour and activity of a model fish species (Poecilia reticulata) in isolation and in shoals, both when uninfected and infected with an ectoparasite (Gyrodactylus turnbulli). Additionally, the rhythmical variance of parasite activity under different light conditions as well as rhythmical variance in parasite transmissibility was explored. Overall, infection alters the circadian rhythm of fish, causing nocturnal restlessness. Increased activity of gyrodactylids on the host's skin at night could potentially contribute to this elevated host activity. Whilst migration of gyrodactylids across the host's skin may have caused irritation to the host resulting in nocturnal restlessness, the disruption in guppy activity rhythm caused by the expression of host innate immunity cannot be excluded. We discuss the wider repercussions such behavioural responses to infection have for host health, the implications for animal behaviour studies of diurnal species as well as the application of chronotherapeutic approaches to aquaculture.

The 24-h activity cycle and cardiovascular outcomes: establishing biological plausibility using arterial stiffness as an intermediate outcome

This review proposes a biologically plausible working model for the relationship between the 24-h activity cycle (24-HAC) and cardiovascular disease. The 24-HAC encompasses moderate-to-vigorous physical activity (MVPA), light physical activity, sedentary behavior (SB), and sleep. MVPA confers the greatest relative cardioprotective effect, when considering MVPA represents just 2% of the day if physical activity guidelines (30 min/day) are met. While we have well-established guidelines for MVPA, those for the remaining activity behaviors are vague. The vague guidelines are attributable to our limited mechanistic understanding of the independent and additive effects of these behaviors on the cardiovascular system. Our proposed biological model places arterial stiffness, a measure of vascular aging, as the key intermediate outcome. Starting with prolonged exposure to SB or static standing, we propose that the reported transient increases in arterial stiffness are driven by a cascade of negative hemodynamic effects following venous pooling. The subsequent autonomic, metabolic, and hormonal changes further impair vascular function. Vascular dysfunction can be offset by using mechanistic-informed interruption strategies and by engaging in protective behaviors throughout the day. Physical activity, especially MVPA, can confer protection by chronically improving endothelial function and associated protective mechanisms. Conversely, poor sleep, especially in duration and quality, negatively affects hormonal, metabolic, autonomic, and hemodynamic variables that can confound the physiological responses to next-day activity behaviors. Our hope is that the proposed biologically plausible working model will assist in furthering our understanding of the effects of these complex, interrelated activity behaviors on the cardiovascular system.

The behavior of Broad-tailed hummingbirds is altered by cycles of human activity in a forested area converted into agricultural land

Background

By changing the circumstances in which animals make their behavioral decisions, weekly cycles of human activity might cause changes in wildlife behavior. For example, when there is more human activity in a location, animals may become more vigilant, which can decrease the time they spend foraging, or roam farther from home, leading to increased home range size. Overall, there has been little exploration of how animal species living in locations that have undergone land use change are affected by the temporal dynamics of human activity levels. In this study, we aimed to analyze the effect of the weekend on agricultural activities and hummingbird territorial activity. We examined differences between weekdays and weekends in factors previously shown to follow weekly cyclical patterns, such as pedestrian presence, traffic, and the presence of domestic animals. We hypothesized that territorial hummingbirds would respond to these weekly cycles of human activity by altering their behavior.

Methods

We studied Broad-tailed hummingbird territories in forested areas that had been transformed to agriculture lands in central Mexico. We evaluated whether territorial individuals changed their behaviors (i.e., chases of intruders, foraging within their territory, number of intruders allowed to forage in the territory) in response to variation between weekdays and weekends in the number of pedestrians, cyclists, dogs, farm animals and vehicles.

Results

We found that the level of agriculture-related human activities showed a weekly cycle at our study site. On weekdays there was higher traffic of pedestrians, cyclists, dogs, farm animals and vehicles, compared to the weekends. Hummingbirds responded to these weekday-weekends differences by changing their territorial behavior. Compared to weekends, on weekdays hummingbirds showed a decrease in defense (number of chases) as well as the use of their territory (number of flowers visited), which allowed increased access to intruders (number of visited flowers by intruders).

Conclusions

Our findings suggest that variation in agriculture-related human activities between weekdays and weekends can alter the territorial behavior of hummingbirds. Behavioral shifts seem to be related to these human activity cycles, leading hummingbirds to reduce chases and feeding during weekdays when human activity is highest, but increasing both behaviors during times of minimal disturbance.

Modified Wavelet Analyses Permit Quantification of Dynamic Interactions Between Ultradian and Circadian Rhythms

Circadian rhythms provide daily temporal structure to cellular and organismal biological processes, ranging from gene expression to cognition. Higher-frequency (intradaily) ultradian rhythms are similarly ubiquitous but have garnered far less empirical study, in part because of the properties that define them-multimodal periods, non-stationarity, circadian harmonics, and diurnal modulation-pose challenges to their accurate and precise quantification. Wavelet analyses are ideally suited to address these challenges, but wavelet-based measurement of ultradian rhythms has remained largely idiographic. Here, we describe novel analytical approaches, based on discrete and continuous wavelet transforms, which permit quantification of rhythmic power distribution across a broad ultradian spectrum, as well as precise identification of period within empirically determined ultradian bands. Moreover, the aggregation of normalized wavelet matrices allows group-level analyses of experimental treatments, thereby circumventing limitations of idiographic approaches. The accuracy and precision of these wavelet analyses were validated using in silico and in vivo models with known ultradian features. Experiments in male and female mice yielded robust and repeatable measures of ultradian period and power in home cage locomotor activity, confirming and extending reports of ultradian rhythm modulation by sex, gonadal hormones, and circadian entrainment. Seasonal changes in day length modulated ultradian period and power, and exerted opposite effects in the light and dark phases of the 24 h day, underscoring the importance of evaluating ultradian rhythms with attention to circadian phase. Sex differences in ultradian rhythms were more prominent at night and depended on gonadal hormones in male mice. Thus, relatively straightforward modifications to the wavelet procedure allowed quantification of ultradian rhythms with appropriate time-frequency resolution, generating accurate, and repeatable measures of period and power which are suitable for group-level analyses. These analytical tools may afford deeper understanding of how ultradian rhythms are generated and respond to interoceptive and exteroceptive cues.

Daytime rest: Association with 24-h rest-activity cycles, circadian timing and cognition in older adults

Growing epidemiological evidence points toward an association between fragmented 24-h rest-activity cycles and cognition in the aged. Alterations in the circadian timing system might at least partially account for these observations. Here, we tested whether daytime rest (DTR) is associated with changes in concomitant 24-h rest probability profiles, circadian timing and neurobehavioural outcomes in healthy older adults. Sixty-three individuals (59-82 years) underwent field actigraphy monitoring, in-lab dim light melatonin onset assessment and an extensive cognitive test battery. Actimetry recordings were used to measure DTR frequency, duration and timing and to extract 24-h rest probability profiles. As expected, increasing DTR frequency was associated not only with higher rest probabilities during the day, but also with lower rest probabilities during the night, suggesting more fragmented night-time rest. Higher DTR frequency was also associated with lower episodic memory performance. Moreover, later DTR timing went along with an advanced circadian phase as well as with an altered phase angle of entrainment between the rest-activity cycle and circadian phase. Our results suggest that different DTR characteristics, as reflective indices of wake fragmentation, are not only underlined by functional consequences on cognition, but also by circadian alteration in the aged.

Night shift schedule causes circadian dysregulation of DNA repair genes and elevated DNA damage in humans

Circadian disruption has been identified as a risk factor for health disorders such as obesity, cardiovascular disease, and cancer. Although epidemiological studies suggest an increased risk of various cancers associated with circadian misalignment due to night shift work, the underlying mechanisms have yet to be elucidated. We sought to investigate the potential mechanistic role that circadian disruption of cancer hallmark pathway genes may play in the increased cancer risk in shift workers. In a controlled laboratory study, we investigated the circadian transcriptome of cancer hallmark pathway genes and associated biological pathways in circulating leukocytes obtained from healthy young adults during a 24-hour constant routine protocol following 3 days of simulated day shift or night shift. The simulated night shift schedule significantly altered the normal circadian rhythmicity of genes involved in cancer hallmark pathways. A DNA repair pathway showed significant enrichment of rhythmic genes following the simulated day shift schedule, but not following the simulated night shift schedule. In functional assessments, we demonstrated that there was an increased sensitivity to both endogenous and exogenous sources of DNA damage after exposure to simulated night shift. Our results suggest that circadian dysregulation of DNA repair may increase DNA damage and potentiate elevated cancer risk in night shift workers.

Relationship between locomotor activity rhythm and corticosterone levels during HCC development, progression, and treatment in a mouse model

Cancer-related fatigue (CRF) and stress are common symptoms in cancer patients and represent early side effects of cancer treatment which affect the life quality of the patients. CRF may partly depend on disruption of the circadian rhythm. Locomotor activity and corticosterone rhythms are two important circadian outputs which can be used to analyze possible effects on the circadian function during cancer development and treatment. The present study analyzes the relationship between locomotor activity rhythm, corticosterone levels, hepatocellular carcinoma (HCC) development, and radiotherapy treatment in a mouse model. HCC was induced in mice by single injection of diethylnitrosamine (DEN) and chronic treatment of phenobarbital in drinking water. Another group received chronic phenobarbital treatment only. Tumor bearing animals were divided randomly into four groups irradiated at four different Zeitgeber time points. Spontaneous locomotor activity was recorded continuously; serum corticosterone levels and p-ERK immunoreaction in the suprachiasmatic nucleus (SCN) were investigated. Phenobarbital treated mice showed damped corticosterone levels and a less stable 24 hours activity rhythm as well as an increase in activity during the light phase, reminiscent of sleep disruption. The tumor mice showed an increase in corticosterone level during the inactive phase and decreased activity during the dark phase, reminiscent of CRF. After irradiation, corticosterone levels were further increased and locomotor activity rhythms were disrupted. Lowest corticosterone levels were observed after irradiation during the early light phase; thus, this time might be the best to apply radiotherapy in order to minimize side effects.

Robust stability of melatonin circadian phase, sleep metrics, and chronotype across months in young adults living in real-world settings

Appropriate synchronization of the timing of behaviors with the circadian clock and adequate sleep are both important for almost every physiological process. The timing of the circadian clock relative to social (ie, local) clock time and the timing of sleep can vary greatly among individuals. Whether the timing of these processes is stable within an individual is not well-understood. We examined the stability of circadian-controlled melatonin timing, sleep timing, and their interaction across ~ 100 days in 15 students at a single university. At three time points ~ 35-days apart, circadian timing was determined from the dim-light melatonin onset (DLMO). Sleep behaviors (timing and duration) and chronotype (ie, mid-sleep time on free days corrected for sleep loss on school/work days) were determined via actigraphy and analyzed in ~ 1-month bins. Melatonin timing was stable, with an almost perfect relationship strength as determined via intraclass correlation coefficients ([ICC]=0.85); average DLMO timing across all participants only changed from the first month by 21 minutes in month 2 and 5 minutes in month 3. Sleep behaviors also demonstrated high stability, with ICC relationship strengths ranging from substantial to almost perfect (ICCs = 0.65-0.85). Average DLMO was significantly associated with average chronotype (r²  = 0.53, P <.01), with chronotype displaying substantial stability across months (ICC = 0.61). These findings of a robust stability in melatonin timing and sleep behaviors in young adults living in real-world settings holds promise for a better understanding of the reliability of previous cross-sectional reports and for the future individualized strategies to combat circadian-associated disease and impaired safety (ie, "chronomedicine").

Quantitative investigation reveals distinct phases in Drosophila sleep

The fruit fly, Drosophila melanogaster, has been used as a model organism for the molecular and genetic dissection of sleeping behaviors. However, most previous studies were based on qualitative or semi-quantitative characterizations. Here we quantified sleep in flies. We set up an assay to continuously track the activity of flies using infrared camera, which monitored the movement of tens of flies simultaneously with high spatial and temporal resolution. We obtained accurate statistics regarding the rest and sleep patterns of single flies. Analysis of our data has revealed a general pattern of rest and sleep: the rest statistics obeyed a power law distribution and the sleep statistics obeyed an exponential distribution. Thus, a resting fly would start to move again with a probability that decreased with the time it has rested, whereas a sleeping fly would wake up with a probability independent of how long it had slept. Resting transits to sleeping at time scales of minutes. Our method allows quantitative investigations of resting and sleeping behaviors and our results provide insights for mechanisms of falling into and waking up from sleep.

Microglial ablation in rats disrupts the circadian system

Microglia, the key neuroimmune cells of the central nervous system, are best known for their function in defending an individual from pathogens and injury. Recent findings, including our own, suggest microglia also have several immune-independent roles, including in regulating satiety, promoting memory, and modifying pain responses. Many of these microglia-associated functions are affected by circadian rhythmicity, thus, varying substantially depending upon the time of day. To gain further insight into this link, we used a Cx3cr1-Dtr transgenic Wistar rat model to acutely deplete microglia and examined if this could lead to a disruption in diurnal temperature, metabolism, and activity measures. We also examined if differences in the physiological rhythms corresponded with changes in the expression of key circadian rhythm-regulating genes and proteins. Our data show that in the absence of microglia there is a pronounced disruption of diurnal rhythms in several domains consistent with a shift toward the inactive phase, in conjunction with changes in circadian rhythm-regulating genes and proteins. These data suggest microglia are involved in the regulation of circadian rhythms and indicate an exciting potential to manipulate these cells to improve disrupted circadian rhythms such as with shift-work or jet-lag.

Exercise training elicits superior metabolic effects when performed in the afternoon compared to morning in metabolically compromised humans

The circadian clock and metabolism are tightly intertwined. Hence, the specific timing of interventions that target metabolic changes may affect their efficacy. Here we retrospectively compared the metabolic health effects of morning versus afternoon exercise training in metabolically compromised subjects enrolled in a 12-week exercise training program. Thirty-two adult males (58 ± 7 yrs) at risk for or diagnosed with type 2 diabetes performed 12 weeks of supervised exercise training either in the morning (8.00-10.00 a.m., N = 12) or in the afternoon (3.00-6.00 p.m., N = 20). Compared to participants who trained in the morning, participants who trained in the afternoon experienced superior beneficial effects of exercise training on peripheral insulin sensitivity (+5.2 ± 6.4 vs. -0.5 ± 5.4 μmol/min/kgFFM, p = .03), insulin-mediated suppression of adipose tissue lipolysis (-4.5 ± 13.7% vs. +5.9 ± 11%, p = .04), fasting plasma glucose levels (-0.3 ± 1.0 vs. +0.5 ± 0.8 mmol/l, p = .02), exercise performance (+0.40 ± 0.2 vs. +0.2 ± 0.1 W/kg, p = .05) and fat mass (-1.2 ± 1.3 vs. -0.2 ± 1.0 kg, p = .03). In addition, exercise training in the afternoon also tended to elicit superior effects on basal hepatic glucose output (p = .057). Our findings suggest that metabolically compromised subjects may reap more pronounced metabolic benefits from exercise training when this training is performed in the afternoon versus morning. CLINICALTRIALS.GOV ID: NCT01317576.

Assemblage variation of mosquitoes (Diptera: Culicidae) in different land use and activity periods within a lowland tropical forest matrix in Campeche, Mexico

Most mosquito species are active during a certain part of the day, but climatic factors such as light intensity and relative humidity play an important role in the control of their activity. We selected three types of land use that were sampled in state of Campeche in 2018 (low semi-evergreen forest, secondary low semi-evergreen forest, and mango plantation), using ten CDC light traps baited with CO₂ , that were active during nine hours of three activity periods (dawn, noon, and nightfall). A GLM was used to investigate changes in the assembly of mosquitoes between different types of land use and temporal variations. Rank abundance curves were used to detect changes in the spatial and activity period of the mosquitoes and we then calculated the Exponential Shannon Index. A total of 6,110 mosquitoes belonging to 23 species were captured. The greatest richness and abundance were found in the secondary low semi-evergreen forest, with greater richness and lower abundance than the mango plantation which showed more abundance. Of the activity periods, dusk had the greatest abundance and richness followed by dawn and finally noon.

Twenty-Four Hour Activity and Sleep Profiles for Adults Living with Arthritis: Habits Matter

OBJECTIVE

To identify 24-hour activity-sleep profiles in adults with arthritis and explore factors associated with profile membership.

METHODS

Our study comprised a cross-sectional cohort and used baseline data from 2 randomized trials studying activity counseling for people with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), or knee osteoarthritis (OA). Participants wore activity monitors for 1 week and completed surveys for demographic information, mood (Patient Health Questionnaire 9), and sitting and walking habits (Self-Reported Habit Index). A total of 1,440 minutes/day were stratified into minutes off body (activity unknown), sleeping, resting, nonambulatory, and intermittent or purposeful ambulation. Latent class analysis determined cluster numbers; baseline-category multinomial logit regression identified factors associated with cluster membership.

RESULTS

Our cohort included 172 individuals, including 51% with RA, 30% with OA, and 19% with SLE. We identified 4 activity-sleep profiles (clusters) that were characterized primarily by differences in time in nonambulatory activity: high sitters (6.9 hours sleep, 1.6 hours rest, 13.2 hours nonambulatory activity, and 1.6 hours intermittent and 0.3 hours purposeful walking), low sleepers (6.5 hours sleep, 1.2 hours rest, 12.2 hours nonambulatory activity, and 3.3 hours intermittent and 0.6 hours purposeful walking), high sleepers (8.4 hours sleep, 1.9 hours rest, 10.4 hours nonambulatory activity, and 2.5 hours intermittent and 0.3 hours purposeful walking), and balanced activity (7.4 hours sleep, 1.5 hours sleep, 9.4 hours nonambulatory activity, and 4.4 hours intermittent and 0.8 hours purposeful walking). Younger age (odds ratio [OR] 0.95 [95% confidence interval (95% CI) 0.91-0.99]), weaker occupational sitting habit (OR 0.55 [95% CI 0.41-0.76]), and stronger walking outside habit (OR 1.43 [95% CI 1.06-1.91]) were each associated with balanced activity relative to high sitters.

CONCLUSION

Meaningful subgroups were identified based on 24-hour activity-sleep patterns. Tailoring interventions based on 24-hour activity-sleep profiles may be indicated, particularly in adults with stronger habitual sitting or weaker walking behaviors.

Impact of noise exposure on the circadian clock in the auditory system

Circadian rhythms control the timing of all bodily functions, and misalignment in the rhythms can cause various diseases. Moreover, circadian rhythms are highly conserved and are regulated by a transcriptional-translational feedback loop of circadian genes that has a periodicity of approximately 24 h. The cochlea and the inferior colliculus (IC) have been shown to possess an autonomous and self-sustained circadian system as demonstrated by recording, in real time, the bioluminescence from PERIOD2::LUCIFERASE (PER2::LUC) mice. The cochlea and IC both express the core clock genes, Per1, Per2, Bmal1, and Rev-Erbα, where RNA abundance is rhythmically distributed with a 24 h cycle. Noise exposure alters clock gene expression in the cochlea and the IC after noise stimulation, although in different ways. These findings highlight the importance of circadian responses in the cochlea and the IC and emphasize the importance of circadian mechanisms for understanding the differences in central and peripheral auditory function and the subsequent molecular changes that occur after daytime (inactive phase) or nighttime (active phase) noise trauma.

Delayed feedback embedded in perception-action coordination cycles results in anticipation behavior during synchronized rhythmic action: A dynamical systems approach

Dancing and playing music require people to coordinate actions with auditory rhythms. In laboratory perception-action coordination tasks, people are asked to synchronize taps with a metronome. When synchronizing with a metronome, people tend to anticipate stimulus onsets, tapping slightly before the stimulus. The anticipation tendency increases with longer stimulus periods of up to 3500ms, but is less pronounced in trained individuals like musicians compared to non-musicians. Furthermore, external factors influence the timing of tapping. These factors include the presence of auditory feedback from one’s own taps, the presence of a partner performing coordinated joint tapping, and transmission latencies (TLs) between coordinating partners. Phenomena like the anticipation tendency can be explained by delay-coupled systems, which may be inherent to the sensorimotor system during perception-action coordination. Here we tested whether a dynamical systems model based on this hypothesis reproduces observed patterns of human synchronization. We simulated behavior with a model consisting of an oscillator receiving its own delayed activity as input. Three simulation experiments were conducted using previously-published behavioral data from 1) simple tapping, 2) two-person alternating beat-tapping, and 3) two-person alternating rhythm-clapping in the presence of a range of constant auditory TLs. In Experiment 1, our model replicated the larger anticipation observed for longer stimulus intervals and adjusting the amplitude of the delayed feedback reproduced the difference between musicians and non-musicians. In Experiment 2, by connecting two models we replicated the smaller anticipation observed in human joint tapping with bi-directional auditory feedback compared to joint tapping without feedback. In Experiment 3, we varied TLs between two models alternately receiving signals from one another. Results showed reciprocal lags at points of alternation, consistent with behavioral patterns. Overall, our model explains various anticipatory behaviors, and has potential to inform theories of adaptive human synchronization.

When navigating a busy sidewalk, people coordinate their behavior in an orderly manner. Other activities require people to carefully synchronize periodic actions, as in a group rowing or marching. When individuals tap in synchrony with a metronome, their taps tend to anticipate the metronome. Experiments have revealed that factors like musical expertise, the presence of a synchronizing partner, auditory feedback, and the sound travel time, all systematically affect the tendency to anticipate. While researchers have hypothesized a number of potential mechanisms for such anticipatory behavior, none have successfully accounted for all of the effects. Previous research on coupled physical systems has shown that when one system receives input from a second system, plus its own delayed signal as input, this causes system 1 to anticipate system 2. We hypothesize that the tendency to anticipate is the result of delayed communication between neurons. Our work demonstrates the ability of delay-coupled physical systems to capture human anticipation and the effect of external factors in the anticipation tendency. Our model supports the theory that delayed communication within the nervous system is crucial to understanding anticipatory coordinative behavior.

Associations between chronotype, morbidity and mortality in the UK Biobank cohort

Later chronotype (i.e. evening preference) and later timing of sleep have been associated with greater morbidity, including higher rates of metabolic dysfunction and cardiovascular disease (CVD). However, no one has examined whether chronotype is associated with mortality risk to date. Our objective was to test the hypothesis that being an evening type is associated with increased mortality in a large cohort study, the UK Biobank. Our analysis included 433 268 adults aged 38-73 at the time of enrolment and an average 6.5-year follow-up. The primary exposure was chronotype, as assessed through a single self-reported question-defining participants as definite morning types, moderate morning types, moderate evening types or definite evening types. The primary outcomes were all-cause mortality and mortality due to CVD. Prevalent disease was also compared among the chronotype groups. Analyses were adjusted for age, sex, ethnicity, smoking, body mass index, sleep duration, socioeconomic status and comorbidities. Greater eveningness, particularly being a definite evening type, was significantly associated with a higher prevalence of all comorbidities. Comparing definite evening type to definite morning type, the associations were strongest for psychological disorders (OR 1.94, 95% CI 1.86-2.02, p = < 0.001), followed by diabetes (OR 1.30, 95% CI 1.24-1.36, p = < 0.001), neurological disorders (OR 1.25, 95% CI 1.20-1.30, p = < 0.001), gastrointestinal/abdominal disorders (OR 1.23, 95% CI 1.19-1.27, p = < 0.001) and respiratory disorders (OR 1.22, 95% CI 1.18-1.26, p = < 0.001). The total number of deaths was 10 534, out of which 2127 were due to CVD. Greater eveningness, based on chronotype as an ordinal variable, was associated with a small increased risk of all-cause mortality (HR 1.02, 95% CI 1.004-1.05, p = 0.017) and CVD mortality (HR 1.04, 95% CI 1.00-1.09, p = 0.06). Compared to definite morning types, definite evening types had significantly increased risk of all-cause mortality (HR 1.10, 95% CI 1.02-1.18, p = 0.012). This first report of increased mortality in evening types is consistent with previous reports of increased levels of cardiometabolic risk factors in this group. Mortality risk in evening types may be due to behavioural, psychological and physiological risk factors, many of which may be attributable to chronic misalignment between internal physiological timing and externally imposed timing of work and social activities. These findings suggest the need for researching possible interventions aimed at either modifying circadian rhythms in individuals or at allowing evening types greater working hour flexibility.

Characterization and comparison of activity profiles exhibited by the cave and surface morphotypes of the blind Mexican tetra, Astyanax mexicanus

Departure from normal circadian rhythmicity and exposure to atypical lighting cues has been shown to adversely affect human health and wellness in a variety of ways. In contrast, adaptation to extreme environments has led many species to alter or even entirely abandon their reliance upon cyclic environmental inputs, principally daily cycles of light and darkness. The extreme darkness, stability and isolation of cave ecosystems has made cave-adapted species particularly attractive systems in which to study the consequences of life without light and the strategies that allow species to survive and even thrive in such environments. In order to further explore these questions, we have assessed the rhythmicity of locomotion in the blind Mexican tetra, Astyanax mexicanus, under controlled laboratory conditions. Using high-resolution video tracking assays, we characterized patterns in locomotor activity and spatial tank usage for members of the surface and Pachón cave populations. Here we demonstrate that cavefish have a higher overall level of activity and use the space within the trial tank differently than surface fish. Further, Pachón cavefish show circadian rhythmicity in both activity and spatial tank usage under a 12:12 light/dark cycle. We provide further evidence that these cavefish retain a weakly light-entrainable, endogenous circadian oscillator with limited capability to sustain rhythms in activity, but not spatial tank usage, in the absence of photic cues. Finally, we demonstrate a putative behavioral "masking effect" contributing to behavioral rhythms and provide evidence that exposure to constant darkness during development may alter behavioral patterns later in life.

Physical Activity and Sedentary Patterns among Metabolically Healthy Individuals Living with Obesity

BACKGROUND

Some individuals living with obesity are free from typical cardiometabolic risk factors and are termed metabolically healthy obese (MHO). The patterns of physical activity and sedentary behaviors among MHO are currently unknown.

METHODS

This study includes 414 youth (12-18 years old), 802 adults (19-44 years old), and 1230 older adults (45-85 years old) living with obesity from the 2003-2004 or 2005-2006 NHANES cycles. Time spent in bouts of 1, 5, 10, 30, and 60 minutes for moderate-to-vigorous physical activity (MVPA) and sedentary time was measured objectively using accelerometers. Participants were categorized as MHO if they had no cardiometabolic risk factors above the identified thresholds (triglycerides, high-density lipoprotein cholesterol, systolic blood pressure, diastolic blood pressure, and glucose).

RESULTS

The proportion of MHO was 19%, 14%, and 12% in youth, adults, and older adults, respectively. MHO adults displayed a higher 1-minute bout of MVPA per day compared to non-MHO (p = 0.02), but no difference was observed for MVPA and sedentary behavior patterns for youth and older adults. When adjusted for confounders, all bouts of sedentary behavior patterns in youth were significantly associated with being classified as MHO.

CONCLUSION

This study suggests that greater sedentary time is associated with cardiometabolic risk factors in youth even if they are physically active.

Exploration of Circadian Rhythms in Patients with Bilateral Vestibular Loss

BACKGROUND

New insights have expanded the influence of the vestibular system to the regulation of circadian rhythmicity. Indeed, hypergravity or bilateral vestibular loss (BVL) in rodents causes a disruption in their daily rhythmicity for several days. The vestibular system thus influences hypothalamic regulation of circadian rhythms on Earth, which raises the question of whether daily rhythms might be altered due to vestibular pathology in humans. The aim of this study was to evaluate human circadian rhythmicity in people presenting a total bilateral vestibular loss (BVL) in comparison with control participants.

METHODOLOGY AND PRINCIPAL FINDINGS

Nine patients presenting a total idiopathic BVL and 8 healthy participants were compared. Their rest-activity cycle was recorded by actigraphy at home over 2 weeks. The daily rhythm of temperature was continuously recorded using a telemetric device and salivary cortisol was recorded every 3 hours from 6:00AM to 9:00PM over 24 hours. BVL patients displayed a similar rest activity cycle during the day to control participants but had higher nocturnal actigraphy, mainly during weekdays. Sleep efficiency was reduced in patients compared to control participants. Patients had a marked temperature rhythm but with a significant phase advance (73 min) and a higher variability of the acrophase (from 2:24 PM to 9:25 PM) with no correlation to rest-activity cycle, contrary to healthy participants. Salivary cortisol levels were higher in patients compared to healthy people at any time of day.

CONCLUSION

We observed a marked circadian rhythmicity of temperature in patients with BVL, probably due to the influence of the light dark cycle. However, the lack of synchronization between the temperature and rest-activity cycle supports the hypothesis that the vestibular inputs are salient input to the circadian clock that enhance the stabilization and precision of both external and internal entrainment.

Sympathetic Hyperactivity, Sleep Fragmentation, and Wake-Related Blood Pressure Surge During Late-Light Sleep in Spontaneously Hypertensive Rats

BACKGROUND

Many cardiovascular disease events occur before morning awaking and are more severe in hypertensive patients. Sleep-related cardiovascular regulation has been suggested to play an important role in the pathogenesis. In this study, we explored whether such impairments are exaggerated during late sleep (before the active phase) in spontaneously hypertensive rats (SHRs).

METHODS

Polysomnographic recording was performed through wireless transmission in freely moving SHRs and Wistar-Kyoto rats (WKYs) over 24 hours. The SHRs were injected with saline and an α1-adrenergic antagonist (prazosin: 5 mg/kg) on 2 separate days. Cardiovascular and autonomic functions were assessed by cardiovascular variability and spontaneous baroreflex analysis.

RESULTS

Compared with the early-light period (Zeitgeber time (ZT) 0-6 hours), both the WKYs and SHRs during the late-light period (ZT 6-12 hours) showed sleep fragmentation, sympathovagal imbalance, and baroreflex impairment, which were exaggerated and more advanced in the SHRs. Like the morning blood pressure (BP) surge in humans, we found that there was a wake-related blood pressure surge (WBPS) during the late-light period in both groups of rats. The WBPS was also greater and occurred earlier in the SHRs, and was accompanied by a surge in vascular sympathetic index. Under α1-adrenergic antagonism, the late-light period-related sleep fragmentation and BP surge in the SHRs were partially reversed.

CONCLUSIONS

Our results reveal that sleep-related sympathetic overactivity, baroreflex sensitivity impairment, WBPS, and sleep fragmentation in SHRs deteriorates during the late-light period can be partially alleviated by treatment with an α1-adrenoceptor antagonist.

Ambulatory Aortic Stiffness Is Associated With Narrow Retinal Arteriolar Caliber in Hypertensives: The SAFAR Study

BACKGROUND

Arterial stiffness measured under static conditions reclassifies significantly cardiovascular (CV) risk and associates with narrower retinal arterioles. However, arterial stiffness exhibits circadian variation, thus single static stiffness recordings do not correspond to the "usual" 24 hr, awake, and asleep average arterial stiffness. We aimed to test the hypothesis that ambulatory 24 hr, awake, and asleep aortic (a) pulse wave velocity (PWV) associate with retinal vessel calibers, independently of confounders and of static arterial stiffness, in hypertensive individuals free from diabetes and CV disease.

METHODS

Digital retinal images were obtained (181 individuals, age: 53.9±10.7 years, 55.2% men) and retinal vessel calibers were measured with validated software to determine central retinal arteriolar and venular equivalents (CRAE and CRVE, respectively); ambulatory (24 hr, awake, asleep) and static office aPWV were estimated by Mobil-O-Graph; and static office carotid to femoral (cf) PWV by SphygmoCor.

RESULTS

Regression analysis performed in 320 gradable retinal images showed that, after adjustment for confounders: (i) ambulatory aPWV was significantly associated with narrower retinal arterioles but not with venules; (ii) asleep aPWV had stronger associations with CRAE than awake aPWV; (iii) both ambulatory aPWV and cfPWV were associated mutually independently with narrower retinal arterioles; aPWV introduction in the model of cfPWV, improved model's R2 (P = 0.012). Similar discriminatory ability of 24 hr aPWV and of cfPWV to detect the presence of retinal arteriolar narrowing was found.

CONCLUSION

Ambulatory aPWV, estimated by an operator-independent method, provides additional information to cfPWV regarding the associations of arterial stiffness with the retinal vessel calibers.

Circadian variation of scalp EEG: a novel measure based on wavelet packet transform and differential entropy

We propose a novel entropy-based measure to quantify the circadian variations of scalp electroencephalogram (EEG) by analyzing waking epochs of nap opportunities under an ultradian sleep-wake cycle (USW) protocol. To compute this circadian measure for a nap opportunity, each waking epoch (~1 sec) is decomposed using wavelet packet transform and the relative energy for the desired frequency band (here, 10-12 Hz) is calculated. Then, in a bootstrapping procedure, a shape statistic (skewness or kurtosis) of the relative energy distribution, after each resampling, is computed. Finally, the probability density function of this statistic is estimated, and the corresponding differential entropy is considered as the circadian measure. This measure was evaluated using EEG recordings from 4 healthy subjects during a 72-h USW procedure. According to the results, the proposed measure showed a significant circadian variation both for individual and group data, with peak values occurring near the core body temperature minimum. The performance of the entropy-based measure was also compared with that of two other measures, namely mean energy logarithm and mean energy ratio, revealing the superiority of this measure.

Daily and annual cycles in thermoregulatory behaviour and cardio-respiratory physiology of black and white tegu lizards

This study was designed to determine the manner in which metabolism is suppressed during dormancy in black and white tegu lizards (Tupinambis merianae). To this end, heart rate (fH), respiration rate (fR), and deep body temperature (Tb) were continuously monitored in outdoor enclosures by radio-telemetry for nine months. There was a continuous decline in nighttime breathing and heart rate, at constant Tb, throughout the late summer and fall suggestive of an active metabolic suppression that developed progressively at night preceding the entrance into dormancy. During the day, however, the tegus still emerged to bask. In May, when the tegus made a behavioural commitment to dormancy, Tb (day and night) fell to match burrow temperature, accompanied by a further reduction in fH and fR. Tegus, under the conditions of this study, did arouse periodically during dormancy. There was a complex interplay between changes in fH and Tb associated with the direct effects of temperature and the indirect effects of thermoregulation, activity, and changes in metabolism. This interplay gave rise to a daily hysteresis in the fH/Tb relationship reflective of the physiological changes associated with warming and cooling as preferred Tb alternated between daytime and nighttime levels. The shape of the hysteresis curve varied with season along with changes in metabolic state and daytime and nighttime body temperature preferences.

Effectiveness of internet-supported cognitive behavioral and chronobiological interventions and effect moderation by insomnia subtype: study protocol of a randomized controlled trial

BACKGROUND

DSM-V criteria for insomnia disorder are met by 6 to 10% of the adult population. Insomnia has severe consequences for health and society. One of the most common treatments provided by primary caregivers is pharmacological treatment, which is far from optimal and has not been recommended since a 2005 consensus report of the National Institutes of Health. The recommended treatment is Cognitive Behavioral Therapy for Insomnia. Effectiveness, however, is still limited. Only a few studies have evaluated the effectiveness of chronobiological treatments, including the timed application of bright light, physical activity and body warming. Another opportunity for optimization of treatment is based on the idea that the people suffering from insomnia most likely represent a heterogeneous mix of subtypes, with different underlying causes and expected treatment responses. The present study aims to evaluate the possibility for optimizing insomnia treatment along the principles of personalized and stratified medicine. It evaluates the following: 1. The relative effectiveness of internet-supported cognitive behavioral therapy, bright light, physical activity and body warming; 2. Whether the effectiveness of internet-supported cognitive behavioral therapy for insomnia can be augmented by simultaneous or prior application of bright light, physical activity and body warming; and 3. Whether the effectiveness of the interventions and their combination are moderated by the insomnia subtype.

METHODS/DESIGN

In a repeated measures, placebo-controlled, randomized clinical trial that included 160 people diagnosed with insomnia disorder, we are evaluating the relative effectiveness of 4 intervention weeks. Primary outcome is subjective sleep efficiency, quantified using a sleep diary. Secondary outcomes include other complaints of sleep and daytime functioning, health-related cost estimates and actigraphic objective sleep estimates. Compliance will be monitored both subjectively and objectively using activity, light and temperature sensors. Insomnia subtypes will be assessed using questionnaires. Mixed effect models will be used to evaluate intervention effects and moderation by insomnia subtype ratings.

DISCUSSION

The current study addresses multiple opportunities to optimize and personalize treatment of insomnia disorder.

TRIAL REGISTRATION

Netherlands National Trial Register NTR4010, 4 June 2013.

[EFFECTS OF ELECTRICAL STIMULATION OF NUCLEUS RETICULARIS PONTIS ORALIS ON THE SLEEP-WAKING STATES IN KRUSHINSKII-MOLODKINA STRAIN RATS]

The effects of electrical stimulation of nucleus reticularis pontis oralis on the behavior and brain electrical activity during all phases of the sleep-waking cycle was studied in Krushinskii-Molodkina strain rats, which have an inherited predisposition to audiogenic seizures. Electrical stimulation with 7 Hz frequency in the deep stage of slow-wave sleep cause appearance the fast-wave sleep. Similar stimulation during fast-wave sleep periods did not effects on the electrographic patterns and EEG spectral characteristics of hippocampus, visual, auditory and somatocnen nrnrenc nf the cnrtey ThPe sfimul1stinns did nnt break a fast-wave sleenhut increased almost twice due the duration of these sleep episodes. After electrical stimulation by same frequency during the wakeftlness and superficial slow-wave sleep states, the patterns and spectral characteristics of brain electrical activity in rats showed no significant changes as compared with controls. The results of this study indicate that the state of the animals sleep-waking cycle at the time of stimulation is a critical variable that influences the responses which are induced by electrical stimulation of the nucleus reticularis pontis oralis.

Circadian rhythm genes CLOCK and PER3 polymorphisms and morning gastric motility in humans

Background

Clock genes regulate circadian rhythm and are involved in various physiological processes, including digestion. We therefore investigated the association between the CLOCK 3111T/C single nucleotide polymorphism and the Period3 (PER3) variable-number tandem-repeat polymorphism (either 4 or 5 repeats 54 nt in length) with morning gastric motility.

Methods

Lifestyle questionnaires and anthropometric measurements were performed with 173 female volunteers (mean age, 19.4 years). Gastric motility, evaluated by electrogastrography (EGG), blood pressure, and heart rate levels were measured at 8:30 a.m. after an overnight fast. For gastric motility, the spectral powers (% normal power) and dominant frequency (DF, peak of the power spectrum) of the EGG were evaluated. The CLOCK and PER3 polymorphisms were determined by polymerase chain reaction (PCR) restriction fragment length polymorphism analysis.

Results

Subjects with the CLOCK C allele (T/C or C/C genotypes: n = 59) showed a significantly lower DF (mean, 2.56 cpm) than those with the T/T genotype (n = 114, 2.81 cpm, P < 0.05). Subjects with the longer PER3 allele (PER3^4/5 or PER3^5/5 genotypes: n = 65) also showed a significantly lower DF (2.55 cpm) than those with the shorter PER3^4/4 genotype (n = 108, 2.83 cpm, P < 0.05). Furthermore, subjects with both the T/C or C/C and PER3^4/5 or PER3^5/5 genotypes showed a significantly lower DF (2.43 cpm, P < 0.05) than subjects with other combinations of the alleles (T/T and PER3^4/4 genotype, T/C or C/C and PER3^4/4 genotypes, and T/T and PER3^4/5 or PER3^5/5 genotypes).

Conclusions

These results suggest that minor polymorphisms of the circadian rhythm genes CLOCK and PER3 may be associated with poor morning gastric motility, and may have a combinatorial effect. The present findings may offer a new viewpoint on the role of circadian rhythm genes on the peripheral circadian systems, including the time-keeping function of the gut.

[The psychometric properties of the Hungarian version of the Morningness-Eveningness Questionnaire (MEQ-H): the separate factors of Morning Freshness and Circadian Rhythmicity]

INTRODUCTION

A large body of research has been accumulated concerning the relationship between circadian preferences (chronotype) and certain personality traits and psychopathological symptoms. Given that chronotype is related to clinically relevant personality traits, risk factors as well as diurnal variations in behavioural performance, the reliable measurement of circadian preferences might become an important step in daily psychiatric practice. In the present study, we examined the psychometric properties of the Hungarian adaptation of the Morningness- Eveningness Questionnaire (MEQ-H).

METHODS

Based on the (online) questionnaire data of 840 healthy individuals, we examined the factor structure and the internal reliability of the questionnaire. The validity was assessed by different scales (sensory seeking, depressive symptoms and sleep complaints) that were previously shown to be associated with chronotype. Test-retest reliability was calculated from the data of 55 participants who completed the questionnaire twice (eight months apart).

RESULTS

We identified two strongly correlated but separate factors, that we called Morning freshness and Circadian rhythm. According to our results, the questionnaire is a reliable instrument in order to measure individual differences in these factors, however, to increase the reliability of the scale as well as in light of practical considerations, the use of a shortened 13-itemed version might be reasonable. The two factors of the MEQ-H showed the expected associations with the examined constructs, however, the independent predictors of Morning freshness were age, gender, depressive symptoms and sleep complaints (insomniac symptoms and morning misalignment), while the independent predictors of Circadian rhythm were age, gender, depressive symptoms, circadian misalignment and sensory seeking.

CONCLUSION

The MEQ-H fulfils the methodological requirements of reliability and validity testing, and proved to be an adequate instrument in order to measure circadian preferences: an important factor that could be included in experimental or clinical investigations.

Associations between longer habitual day napping and non-alcoholic fatty liver disease in an elderly Chinese population

Context

Both longer habitual day napping and Non-Alcoholic Fatty Liver Disease (NAFLD) are associated with diabetes and inflammation, but the association between day napping and NAFLD remains unexplored.

Objective

To investigate the association between the duration of habitual day napping and NAFLD in an elderly Chinese population and to gain insight into the role of inflammatory cytokines in this association.

Design and Setting

We conducted a series of cross-sectional studies of the community population in Chongqing, China, from 2011 to 2012.

Participants

Among 6998 participants aged 40 to 75 years, 6438 eligible participants were included in the first study and analyzed to observe the association between day napping duration and NAFLD. In a separate study, 80 non-nappers and 90 nappers were selected to identify the role of inflammatory cytokines in this association. Logistic regression models were used to examine the odds ratios (ORs) of day nap duration with NAFLD.

Results

Day nappers had a significantly higher prevalence of NAFLD (P<0.001). Longer day napping duration was associated in a dose-dependent manner with NAFLD (P trend <0.001). After adjustment for potential confounders, the ORs were 1.67 (95% CI 1.13–2.46) for those reporting 0.5–1 h and 1.49 (95% CI 1.01–2.19) for those reporting >1 h of day napping compared with individuals who did not take day naps (all P<0.05). Longer-duration day nappers had higher levels of IL-6 and progranulin (PGRN) but lower levels of Secreted frizzled-related protein-5 (SFRP5, all P trend <0.001). After adjusting for IL-6, PGRN, and SFRP5, the association between day napping duration and NAFLD disappeared (all P>0.05).

Conclusion

Longer day napping duration is associated with a higher prevalence of NAFLD, and inflammatory cytokines may be an essential link between day napping and NAFLD.

Morning surge of ventricular arrhythmias in a new arrhythmogenic canine model of chronic heart failure is associated with attenuation of time-of-day dependence of heart rate and autonomic adaptation, and reduced cardiac chaos

Patients with chronic heart failure (CHF) exhibit a morning surge in ventricular arrhythmias, but the underlying cause remains unknown. The aim of this study was to determine if heart rate dynamics, autonomic input (assessed by heart rate variability (HRV)) and nonlinear dynamics as well as their abnormal time-of-day-dependent oscillations in a newly developed arrhythmogenic canine heart failure model are associated with a morning surge in ventricular arrhythmias. CHF was induced in dogs by aortic insufficiency & aortic constriction, and assessed by echocardiography. Holter monitoring was performed to study time-of-day-dependent variation in ventricular arrhythmias (PVCs, VT), traditional HRV measures, and nonlinear dynamics (including detrended fluctuations analysis α1 and α2 (DFAα1 & DFAα2), correlation dimension (CD), and Shannon entropy (SE)) at baseline, as well as 240 days (240 d) and 720 days (720 d) following CHF induction. LV fractional shortening was decreased at both 240 d and 720 d. Both PVCs and VT increased with CHF duration and showed a morning rise (2.5-fold & 1.8-fold increase at 6 AM-noon vs midnight-6 AM) during CHF. The morning rise in HR at baseline was significantly attenuated by 52% with development of CHF (at both 240 d & 720 d). Morning rise in the ratio of low frequency to high frequency (LF/HF) HRV at baseline was markedly attenuated with CHF. DFAα1, DFAα2, CD and SE all decreased with CHF by 31, 17, 34 and 7%, respectively. Time-of-day-dependent variations in LF/HF, CD, DFA α1 and SE, observed at baseline, were lost during CHF. Thus in this new arrhythmogenic canine CHF model, attenuated morning HR rise, blunted autonomic oscillation, decreased cardiac chaos and complexity of heart rate, as well as aberrant time-of-day-dependent variations in many of these parameters were associated with a morning surge of ventricular arrhythmias.

Blood pressure circadian pattern and physical exercise assessment by accelerometer and 7-day physical activity recall scale

BACKGROUND

The relationship between regular physical activity, measured objectively and by self-report, and the circadian pattern of 24-hour ambulatory arterial blood pressure (BP) has not been clarified.

METHODS

We performed a cross-sectional study in a cohort of healthy patients. We included 1,345 patients from the EVIDENT study (mean age 55 ± 14 years; 59.3% women). Physical activity was assessed using the 7-day physical activity recall (PAR) questionnaire (metabolic equivalents (MET)/hour/week) and the Actigraph GT3X accelerometer (counts/minute) for 7 days; ambulatory arterial BP was measured with a radial tonometer (B-pro device).

RESULTS

The dipper-pattern patients showed a higher level of activity than nondipper patients, as assessed by accelerometer and 7-day PAR. Physical activity measures correlated positively with the percent drop in systolic BP (SBP; ρ = 0.19 to 0.11; P < 0.01) and negatively with the systolic and diastolic sleep to wake ratios (ρ = -0.10 to -0.18; P < 0.01) and heart rate (ρ = -0.13; P < 0.01). In logistic regression, considering the circadian pattern (1, dipper; 0, nondipper) as the dependent variable, the odds ratio of the third tertile of counts/minute was 1.79 (95% confidence interval [CI], 1.35-2.38; P < 0.01) and of MET/hour/week was 1.33 (95% CI, 1.01-1.75; P = 0.04) after adjustment for confounding variables.

CONCLUSIONS

Physical activity, as evaluated by both the accelerometer and the 7-day PAR, was associated with a more marked nocturnal BP dip and, accordingly, a lower SBP and diastolic BP sleep to wake ratio.

CLINICAL TRIAL REGISTRATION

Clinical Trials.gov Identifier: NCT01083082.

Interpreting frequency responses to dose-conserved pulsatile input signals in simple cell signaling motifs

Many hormones are released in pulsatile patterns. This pattern can be modified, for instance by changing pulse frequency, to encode relevant physiological information. Often other properties of the pulse pattern will also change with frequency. How do signaling pathways of cells targeted by these hormones respond to different input patterns? In this study, we examine how a given dose of hormone can induce different outputs from the target system, depending on how this dose is distributed in time. We use simple mathematical models of feedforward signaling motifs to understand how the properties of the target system give rise to preferences in input pulse pattern. We frame these problems in terms of frequency responses to pulsatile inputs, where the amplitude or duration of the pulses is varied along with frequency to conserve input dose. We find that the form of the nonlinearity in the steady state input-output function of the system predicts the optimal input pattern. It does so by selecting an optimal input signal amplitude. Our results predict the behavior of common signaling motifs such as receptor binding with dimerization, and protein phosphorylation. The findings have implications for experiments aimed at studying the frequency response to pulsatile inputs, as well as for understanding how pulsatile patterns drive biological responses via feedforward signaling pathways.

Ambient intelligence might support increased longevity

Several technologies entered our homes to change our lives. First electricity brought light and comfort, now communication technologies are transforming our living place into a connected place allowing new services to be invented, comfort, security, wellness and health services. The ICTs in homes can now help prolonge our longevity.

Transitions in the heartbeat pattern during pupal diapause and adult development in the flesh fly, Sarcophaga crassipalpis

The heartbeat of diapausing pupae of the flesh fly Sarcophaga crassipalpis was investigated using electrocardiographic methods including gravimetry, thermography, and optocardiography. During deep diapause, characterized by minimum metabolic activity, the heart exhibited discontinuous bouts of exclusively unidirectional, anterograde pulsations (40-60 contractions/min) that lasted only a few seconds. These bouts of cardiac pulsations were separated by periods of rest lasting 5-30 min. During infradian peaks of metabolic activity (4-day cycles) that occur throughout diapause, periods of rest were shortened and frequency of the anterograde heartbeat increased more than two-fold. Throughout diapause, the heart consistently exhibited a simple, bi-phasic pattern of pulsations generated by bouts of anterograde heartbeats interspersed with periods of cardiac rest. When the fly broke diapause and initiated pharate adult development, a new tri-phasic pattern was observed: the new pattern incorporated heartbeat reversal, as noted by the appearance of retrograde pulsations that directed hemolymph in a posterior direction. These retrograde heartbeats occurred exclusively in the abdominal portion of the dorsal vessel and were not observed in the head or thorax. The transition to pharate adult development was also accompanied by the appearance of extremely strong extracardiac pulsations that served a respiratory function. Although these pulsations made it more challenging to record heartbeat patterns in pharate adults, we observed progressive shortening of the resting periods and a continual increase in the rate of both anterograde and retrograde pulsations, a trend that was further magnified in the adult fly (anterograde contractions up to 300/min and retrograde contractions approximately 125/min). These results imply that the circulatory function of the heart is homeostatically regulated and is responsive to developmental changes and the diverse metabolic rate demands of larvae, diapausing pupae, pharate adults and adult flies.

Diel activity patterns of male Aedes albopictus in the laboratory

This study was conducted to investigate the flight and dispersal behavior of male Aedes albopictus under laboratory conditions. Two different methods, the Observer and Ethovision software devices, were used to determine the total duration, the mean and maximum flight speed, and the distance covered by these mosquitoes. During 24 h, mosquitoes were more active from 0800 to 1200 h and from 1700 to 2100 h than during the rest of the day. Male Ae. albopictus displayed different activities at different times. The flight activity was 47 min and 57 sec over 24 h. During this period, sugar-fed males flew an average distance of 236.20 m at an average speed of 8.5 cm/sec. The unfed males flew significantly faster than recently fed males, with maximum flight speeds of 44.9 cm/sec and 33.6 cm/sec, respectively. The time used for resting (22 h 2 min +/- 13 min) was significantly higher (P < 0.0001) than walking and flying times (68 min +/- 10 sec and 49 min +/- 5 min, respectively). Overall, both methods allowed observations on flight activity, and the camera recordings allowed these activities to be quantified.

Influence of environmental factors on activity patterns of Incisitermes minor (Isoptera: Kalotermitidae) in naturally infested logs

Acoustic emission (AE) activity patterns were measured from seven loquat [Eriobotrya japonica (Thunb.) Lindl.] logs, five containing live western drywood termite [Incisitermes minor (Hagen)] infestations, and two without an active drywood termite infestation. AE activity, as well as temperature, were monitored every 3 min under unrestricted ambient conditions in a small wooden building, under unrestricted ambient conditions but in constant darkness, or in a temperature-controlled cabined under constant darkness. Logs with active drywood termite infestations displayed similar diurnal cycles of AE activity that closely followed temperature with a peak of AE activity late in the afternoon (1700-1800 hours). When light was excluded from the building, a circadian pattern continued and apparently was driven by temperature. When the seven logs were kept at a relatively constant temperature (approximately 23 +/- 0.9 degrees C) and constant darkness, the pattern of activity was closely correlated with temperature, even with minimal changes in temperature. Temperature is the primary driver of activity of these drywood termites, but the effects are different when temperature is increasing or decreasing. At constant temperature, AE activity was highly correlated with the number of termites in the logs. The possible implications of these findings on our understanding of drywood termite biology and how this information may affect inspections and posttreatment evaluations are discussed.

Circadian Eating and Sleeping Patterns in the Night Eating Syndrome

OBJECTIVE

To compare the eating and sleep-wake patterns of persons with the night eating syndrome (NES) with those of matched control subjects.

RESEARCH METHODS AND PROCEDURES

Forty-six overweight/obese NES subjects (mean age 43.3 +/- 9.8 years; 32 women) and 43 similar controls (mean age 39.0 +/- 11.0 years; 28 women) wore wrist actigraphs for 7 days and completed sleep and food diaries at home.

RESULTS

There was no difference between the total energy intake of the NES and the control subjects, but the pattern of energy intake differed greatly. Relative to control subjects, the temporal pattern of food intake of night eaters was delayed. Food intake after the evening meal, as a proportion of the 24-hour intake, was more than 3-fold greater in NES subjects than in controls (34.6 +/- 10.1% vs. 10.0 +/- 6.9%, p = 0.001). NES subjects had sleep onset, offset, and total sleep duration times comparable with those of controls. NES subjects reported more nocturnal awakenings than did controls (1.5 +/- 1.0 per night vs. 0.5 +/- 0.5; p < 0.001), and their actigraphically monitored arousals occurred earlier during sleep (at 128 minutes after sleep onset vs. 193 minutes, p = 0.01). NES subjects consumed food on 74% of the awakenings vs. 0% for the controls.

DISCUSSION

The pattern of cumulative energy intake of the night eaters suggests a phase delay in energy consumption relative to sleep-wake times. NES may involve a dissociation of the circadian control of eating relative to sleep.

Questing behavior of Dermacentor reticulatus adults (Acari: Amblyommidae) during diurnal activity periods in eastern Poland

Studies on diurnal activity and factors affecting the questing behavior in Dermacentor reticulatus (F.) adults were conducted in an open-type habitat in eastern Poland (51 degrees 15' N, 22 degrees 36' E). Observations, for 25 min each, were made at 2-h intervals between 1000 and 1800 hours, during the autumn (from late September to mid-October 2000) and spring (from late April to mid-May 2001) activity peaks. The questing behavior of adult D. reticulatus ticks depended on the time of the day and season. The autumn activity was higher than that in spring, yet both these periods were characterized by a rising trend from the morning to early afternoon with a peak at approximately 1400 hours (on average 40 and 30 specimens per one collection, respectively). In spring, the high activity (on average 31.8 specimens/ collection) persisted until late afternoon (1800 hours), while in the autumn period it declined before nightfall (on average 21.4 specimens/collection at 1800 hours). Females predominated over males in both seasonal periods of activity and greater differences in the sex ratio were recorded in the spring. We found a negative correlation between the diurnal activity of the adult ticks and temperature and between the number of active ticks and the length of day both in the autumn and spring. However, no statistically significant correlation was demonstrated between the diurnal activity of adult ticks and humidity. The investigations show that, in addition to environmental factors, tick host-seeking behavior is dependent on the activity of their hosts and biological traits of this species.

Molecular dynamics of ultradian glucocorticoid receptor action

In recent years it has become evident that glucocorticoid receptor (GR) action in the nucleus is highly dynamic, characterized by a rapid exchange at the chromatin template. This stochastic mode of GR action couples perfectly with a deterministic pulsatile availability of endogenous ligand in vivo. The endogenous glucocorticoid hormone (cortisol in man and corticosterone in rodent) is secreted from the adrenal gland with an ultradian rhythm made up of pulses at approximately hourly intervals. These two components - the rapidly fluctuating ligand and the rapidly exchanging receptor - appear to have evolved to establish and maintain a system that is exquisitely responsive to the physiological demands of the organism. In this review, we discuss recent and innovative work that questions the idea of steady state, static hormone receptor responses, and replaces them with new concepts of stochastic mechanisms and oscillatory activity essential for optimal function in molecular and cellular systems.

Ultradian rhythms during day and night in normal and COPD subjects

The analysis of heart rate variability (HRV) is a powerful tool in the study of the autonomic control of the heart. While circadian HRV rhythms have widely been characterized by traditional spectral measures, ultradian oscillations are not commonly investigated. In this study the identification of HRV ultradian rhythms is assigned to a quantitative measure characterizing the fractal-like behavior of the time series: the fractal dimension (FD). In order to assess ultradian regulation in Chronic Obstructive Pulmonary Disease (COPD) 24-h Holter ECG recordings of 52 COPD and 10 normal (healthy) subjects were analyzed. The FD was calculated by Higuchi's algorithm both during daytime and nighttime to highlight possible wake-sleep states differences. All subjects showed a similar common rhythm (0.06mHz) that persists with generally higher amplitude during night-time. A further rhythm becomes predominant in normal subjects in the day-to-night transition (0.15mHz), probably under the influence of the REM/non-REM ultradian sleep cycle. A very large difference between night and day amplitudes of this rhythm and of the next one (at about 0.22mHz) characterize the HRV fractal dimension of the Normal in respect of COPD. In conclusion, the FD could be used as a marker of ultradian cardiac autonomic regulation providing new insights into autonomic physiology of normal and COPD patients.

Assessing the effects of cognitive experiments on the welfare of captive chimpanzees (Pan troglodytes) by direct comparison of activity budget between wild and captive chimpanzees

We investigated the effects of cognitive experiments by direct comparison of activity budgets between wild and captive chimpanzees. One goal of captive management is to ensure that the activity budgets of captive animals are as similar as possible to those of their wild counterparts. However, such similarity has rarely been achieved. We compared the activity budget among three groups of chimpanzees: wild chimpanzees in Bossou (Guinea, n = 10), and captive chimpanzees who participated in cognitive experiments (experimental chimpanzees, n = 6) or did not participate in the experiments (nonexperimental chimpanzees, n = 6) at the Primate Research Institute (Japan). The experimental chimpanzees voluntarily participated in computer-controlled cognitive tasks and small pieces of fruits were provided as rewards. The data from captivity were obtained on the experimental days (weekdays) and nonexperimental days (weekends). In both study sites, we followed each chimpanzee from about 7 a.m. until the time when chimpanzees started to rest in the evening. The behaviors were recorded every 1 min. The results showed that on weekdays, feeding time and resting time of the experimental chimpanzees were almost the same as those of wild chimpanzees. However, for the nonexperimental chimpanzees, feeding time was significantly shorter and resting time was longer than those of the wild chimpanzees. In contrast, no difference was found in feeding time or resting time of the two groups of captive chimpanzees on weekends. The results suggested that the cognitive experiments worked as an efficient method for food-based enrichment.

Early presymptomatic and long-term changes of rest activity cycles and cognitive behavior in a MPTP-monkey model of Parkinson's disease

Background

It is increasingly recognized that non-motor symptoms are a prominent feature of Parkinson's disease and in the case of cognitive deficits can precede onset of the characteristic motor symptoms. Here, we examine in 4 monkeys chronically treated with low doses of the neurotoxin MPTP the early and long-term alterations of rest-activity rhythms in relationship to the appearance of motor and cognitive symptoms.

Methodology/Principal Findings

Behavioral activity recordings as well as motor and cognitive assessments were carried out continuously and in parallel before, during and for several months following MPTP-treatment (12–56 weeks). Cognitive abilities were assessed using a task that is dependent on the functional integrity of the fronto-striatal axis. Rest-activity cycles were monitored continuously using infrared movement detectors of locomotor activity. Motor impairment was evaluated using standardized scales for primates. Results show that MPTP treatment led to an immediate alteration (within one week) of rest-activity cycles and cognitive deficits. Parkinsonian motor deficits only became apparent 3 to 5 weeks after initiating chronic MPTP administration. In three of the four animals studied, clinical scores returned to control levels 5–7 weeks following cessation of MPTP treatment. In contrast, both cognitive deficits and chronobiological alterations persisted for many months. Levodopa treatment led to an improvement of cognitive performance but did not affect rest-activity rhythms in the two cases tested.

Conclusions/Significance

Present results show that i) changes in the rest activity cycles constituted early detectable consequences of MPTP treatment and, along with cognitive alterations, characterize the presymptomatic stage; ii) following motor recovery there is a long-term persistence of non-motor symptoms that could reflect differential underlying compensatory mechanisms in these domains; iii) the progressive MPTP-monkey model of presymptomatic ongoing parkinsonism offers possibilities for in-depth studies of early non-motor symptoms including sleep alterations and cognitive deficits.

[Thermophysiology of the paradoxical sleep]

Data on interactions between the paradoxical sleep (PS) and thermoregulation under thermo-comfortable and extreme conditions (in high and low temperatures, forced and spontaneous fasting, acclimation to cold and acclimation to natural winter conditions) are reviewed. The hypothesis of the PS role in synchronising and endogenous "kindling" of the visceral function ultradian rhythms is substantiated. Some new data are presented on entering torpor as a phenomenon of the "dramatic" neuronal plasticity.

Reply to Lawler: feeding competition, cooperation, and the causes of primate sociality

This is a reply to Richard Lawler's commentary on our previous work [Lawler, 2011; this issue] in which he develops a set of operational models to test socioecological theories of the evolutionary importance of feeding competition. We strongly agree that we need to critically re-evaluate the basic assumptions of all models of primate sociality, and to verify the explanatory power of alternative models. We also feel Lawler's commentary provides an important opportunity to broaden the debate concerning the fundamental roles of cooperation, competition, and aggression in understanding primate social systems. Lawler provides a number of suggestions as to how models developed in primate socioecology might be tested. We agree with these suggestions, make further suggestions, and call for specific operational definitions so that researchers might begin to develop and test various methodologies. However, we also call for testing alternative theories. Current socioecological theory is based on the assumption that competition and positive selection is always in operation and has driven the evolution of living organisms. We believe that this "explanation of choice" often is treated as an assumed truth to which data are forced to fit, rather than being seen as a theory to be tested. Furthermore, we agree with Weiss and Buchanan [2009. The Mermaid's Tale: Four Billion Years of Cooperation in the Making of Living Things] that on ecological and developmental scales, where organisms actually live out their lives, cooperation may play a more fundamental role than competition.

Predictive modeling of the hypothalamic-pituitary-adrenal (HPA) axis response to acute and chronic stress

Detailed dynamics of the hypothalamic-pituitary-adrenal (HPA) axis is complex, depending on the individual metabolic load of an organism, its current status (healthy/ill, circadian phase (day/night), ultradian phase) and environmental impact. Therefore, it is difficult to compare the HPA axis activity between different individuals or draw unequivocal conclusions about the overall status of the HPA axis in an individual using single time-point measurements of cortisol levels. The aim of this study is to identify parameters that enable us to compare different dynamic states of the HPA axis and use them to investigate self-regulation mechanisms in the HPA axis under acute and chronic stress. In this regard, a four-dimensional stoichiometric model of the HPA axis was used. Acute stress was modeled by inducing an abrupt change in cortisol level during the course of numerical integration, whereas chronic stress was modeled by changing the mean stationary state concentrations of CRH. Effects of acute stress intensity, duration and time of onset with respect to the ultradian amplitude, ultradian phase and the circadian phase of the perturbed oscillation were studied in detail. Bifurcation analysis was used to predict the response of the HPA axis to chronic stress. Model predictions were compared with experimental findings reported in the literature and relevance for pharmacotherapy with glucocorticoids was discussed.

Disrupted corticosterone pulsatile patterns attenuate responsiveness to glucocorticoid signaling in rat brain

Chronically elevated circulating glucocorticoid levels are although to enhance vulnerability to psychopathology. Here we hypothesized that such sustained glucocorticoid levels, disturbing corticosterone pulsatility, attenuate glucocorticoid receptor signaling and target gene responsiveness to an acute challenge in the rat brain. Rats were implanted with vehicle or 40 or 100% corticosterone pellets known to flatten ultradian and circadian rhythmicity while maintaining daily average levels or mimic pathological conditions. Additionally, recovery from constant exposure was studied in groups that had the pellet removed 24 h prior to the challenge. Molecular markers for receptor responsiveness (receptor levels, nuclear translocation, promoter occupancy, and target gene expression) to an acute challenge mimicking the stress response (3 mg/kg ip) were studied in the hippocampal area. Implantation of 40 and 100% corticosterone pellets dose-dependently down-regulated glucocorticoid receptor and attenuated mineralocorticoid receptor and glucocorticoid receptor translocation to the acute challenge. Interestingly, whereas target gene Gilz expression to the challenge was already attenuated by tonic daily average levels (40%), Sgk-1 was affected only after constant high corticosterone exposure (100%), indicating altered receptor responsiveness due to treatment. Washout of 100% corticosterone recovered all molecular markers (partial), whereas removal of the 40% corticosterone pellet still attenuated responsiveness to the challenge. We propose that corticosteroid pulsatility is crucial in maintaining normal responsiveness to glucocorticoids. Whereas the results with 100% corticosterone are likely attributed to receptor saturation, subtle changes in the pattern of exposure (40%) induces changes at least as severe for glucocorticoid signaling as overt hypercorticism, suggesting an underlying mechanism sensitive to the pattern of hormone exposure.