A cycle of Zap70 kinase activation and release from the TCR amplifies and disperses antigenic stimuli.

Cell-surface-receptor pathways amplify weak, rare and local stimuli to induce cellular responses. This task is accomplished despite signaling components that segregate into nanometer-scale membrane domains. Here we describe a 'catch-and-release' mechanism that amplified and dispersed stimuli by releasing activated kinases from receptors lacking intrinsic catalytic activity. Specifically, we discovered a cycle of recruitment, activation and release for Zap70 kinases at phosphorylated T cell antigen receptors (TCRs). This turned the TCR into a 'catalytic unit' that amplified antigenic stimuli. Zap70 released from the TCR remained at the membrane, translocated, and phosphorylated spatially distinct substrates. The mechanisms described here are based on widely used protein domains and post-translational modifications; therefore, many membrane-associated pathways might employ similar mechanisms for signal amplification and dispersion.

Beyond circadian rhythms: emerging roles of ultradian rhythms in control of liver functions.

The mammalian liver must cope with various metabolic and physiological changes that normally recur every day and primarily stem from daily cycles of rest-activity and fasting-feeding. Although a large body of evidence supports the reciprocal regulation of circadian rhythms and liver function, the research on the hepatic ultradian rhythms have largely been lagging behind. However, with the advent of more cost-effective high-throughput omics technologies, high-resolution time-lapse imaging, and more robust and powerful mathematical tools, several recent studies have shed new light on the presence and functions of hepatic ultradian rhythms. In this review, we will first very briefly discuss the basic principles of circadian rhythms, and then cover in greater details the recent literature related to ultradian rhythms. Specifically, we will highlight the prevalence and mechanisms of hepatic 12-h rhythms, and 8-h rhythms, which cycle at the second and third harmonics of circadian frequency. Finally, we also refer to ultradian rhythms with other frequencies and examine the limitations of the current approaches as well as the challenges related to identifying ultradian rhythm and addressing their molecular underpinnings.

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 host­parasite 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.

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.

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.

Association of physical activity intensity and bout length with mortality: An observational study of 79,503 UK Biobank participants.

BACKGROUND: Spending more time active (and less sedentary) is associated with health benefits such as improved cardiovascular health and lower risk of all-cause mortality. It is unclear whether these associations differ depending on whether time spent sedentary or in moderate-vigorous physical activity (MVPA) is accumulated in long or short bouts. In this study, we used a novel method that accounts for substitution (i.e., more time in MVPA means less time sleeping, in light activity or sedentary) to examine whether length of sedentary and MVPA bouts associates with all-cause mortality. METHODS AND FINDINGS: We used data on 79,503 adult participants from the population-based UK Biobank cohort, which recruited participants between 2006 and 2010 (mean age at accelerometer wear 62.1 years [SD = 7.9], 54.5% women; mean length of follow-up 5.1 years [SD = 0.73]). We derived (1) the total time participants spent in activity categories-sleep, sedentary, light activity, and MVPA-on average per day; (2) time spent in sedentary bouts of short (1 to 15 minutes), medium (16 to 40 minutes), and long (41+ minutes) duration; and (3) MVPA bouts of very short (1 to 9 minutes), short (10 to 15 minutes), medium (16 to 40 minutes), and long (41+ minutes) duration. We used Cox proportion hazards regression to estimate the association of spending 10 minutes more average daily time in one activity or bout length category, coupled with 10 minutes less time in another, with all-cause mortality. Those spending more time in MVPA had lower mortality risk, irrespective of whether this replaced time spent sleeping, sedentary, or in light activity, and these associations were of similar magnitude (e.g., hazard ratio [HR] 0.96 [95% CI: 0.94, 0.97; P < 0.001] per 10 minutes more MVPA, coupled with 10 minutes less light activity per day). Those spending more time sedentary had higher mortality risk if this replaced light activity (HR 1.02 [95% CI: 1.01, 1.02; P < 0.001] per 10 minutes more sedentary time, with 10 minutes less light activity per day) and an even higher risk if this replaced MVPA (HR 1.06 [95% CI: 1.05, 1.08; P < 0.001] per 10 minutes more sedentary time, with 10 minutes less MVPA per day). We found little evidence that mortality risk differed depending on the length of sedentary or MVPA bouts. Key limitations of our study are potential residual confounding, the limited length of follow-up, and use of a select sample of the United Kingdom population. CONCLUSIONS: We have shown that time spent in MVPA was associated with lower mortality, irrespective of whether it replaced time spent sleeping, sedentary, or in light activity. Time spent sedentary was associated with higher mortality risk, particularly if it replaced MVPA. This emphasises the specific importance of MVPA. Our findings suggest that the impact of MVPA does not differ depending on whether it is obtained from several short bouts or fewer longer bouts, supporting the recent removal of the requirement that MVPA should be accumulated in bouts of 10 minutes or more from the UK and the United States policy. Further studies are needed to investigate causality and explore health outcomes beyond mortality.

The impact of the 24-h movement spectrum on vascular remodeling in older men and women: a review.

Aging is associated with increased risk of cardiovascular and cerebrovascular events, which are preceded by early, negative remodeling of the vasculature. Low physical activity is a well-established risk factor associated with the incidence and development of disease. However, recent physical activity literature indicates the importance of considering the 24-h movement spectrum. Therefore, the purpose of this review was to examine the impact of the 24-h movement spectrum, specifically physical activity (aerobic and resistance training), sedentary behavior, and sleep, on cardiovascular and cerebrovascular outcomes in older adults, with a focus on recent evidence (<10 yr) and sex-based considerations. The review identifies that both aerobic training and being physically active (compared with sedentary) are associated with improvements in endothelial function, arterial stiffness, and cerebrovascular function. Additionally, there is evidence of sex-based differences in endothelial function: a blunted improvement in aerobic training in postmenopausal women compared with men. While minimal research has been conducted in older adults, resistance training does not appear to influence arterial stiffness. Poor sleep quantity or quality are associated with both impaired endothelial function and increased arterial stiffness. Finally, the review highlights mechanistic pathways involved in the regulation of vascular and cerebrovascular function, specifically the balance between pro- and antiatherogenic factors, which mediate the relationship between the 24-h movement spectrum and vascular outcomes. Finally, this review proposes future research directions: examining the role of duration and intensity of training, combining aerobic and resistance training, and exploration of sex-based differences in cardiovascular and cerebrovascular outcomes.

An anti-narcolepsy drug reveals behavioral and fitness costs of extreme activity cycles in arctic-breeding songbirds.

Sleep loss impairs cognitive function, immunological responses and general well-being in humans. However, sleep requirements in mammals and birds vary dramatically. In circumpolar regions with continuous summer light, daily sleep duration is reduced, particularly in breeding birds. The effect of an anti-narcolepsy drug (modafinil) to putatively extend wakefulness was examined in two species of closely related arctic-breeding passerine birds: Lapland longspurs (Calcarius lapponicus) and snow buntings (Plectrophenax nivalis). Free-living adult males were implanted during the nestling phase on day 4 (D4; 4 days post-hatching) with osmotic pumps containing either vehicle or modafinil to extend the active period for 72 h. Nestlings were weighed on D2 and D7 to measure growth rates. Additionally, focal observations were conducted on D6. Male longspurs receiving modafinil made fewer feeding visits and spent less time at the nest but tended to spend more time near the nest than controls. We observed no change in longspur nestling growth rates, but fledging occurred significantly later when males received modafinil, suggesting a fitness cost. In contrast, modafinil had no measurable impact on male or female snow bunting behavior, nestling growth rates or time to fledging. We suggest male longspurs compromise and maintain vigilance at their nests in lieu of sleeping because of the increased predation risk that is characteristic of their tundra nesting habitat. Snow buntings are cavity nesters, and their nests do not require the same vigilance, allowing males to presumably rest following provisioning. These life-history differences between species highlight the role of predation risk in mediating behavioral modifications to prolonged wakefulness in arctic-breeding songbirds.

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").

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.

Evaluation of rest-activity cycles in patients with severe acquired brain injury: an observational study.

BACKGROUND: There is little knowledge about rest-activity cycles (RAC) in patients with severe-acquired brain injury (sABI) during early in-hospital rehabilitation. This study aimed to investigate if patients with sABI displayed unconsolidated RACs at the beginning of in-hospital rehabilitation, and how these changed over time. METHODS: This study was a prospective observational study. All patients consecutively admitted to one ward were screened for eligibility. We recorded accelerometric activity for 20 days. The Daytime Activity Ratio (DAR) of activity between daytime (7-22) and the total activity during the entire day was calculated and used to estimate consolidation. RESULTS: Fifty-five patients were screened and 20 patients were included. Complete day 1 & 2 data was obtained on 18 patients. Fifty-six percentage of these had a consolidated RAC at the beginning of rehabilitation. On day 19 & 20, complete data could be obtained from 15 patients, 80% of these had consolidation of RAC. When comparing these a significant mean increase of 5.8% 95%CI(0.52; 11.01) in DAR was found p < .05, and the model of all data also showed a significant increase in median DAR over time p < .01. CONCLUSION: RAC consolidation improves over time in patients admitted for in-hospital early neurorehabilitation.

Are southern African solitary mole-rats homeothermic or heterothermic under natural field conditions?

Abandoning of a stable body temperature (Tb), a phenomenon known as heterothermy, is an adaptation to cope mainly with a lack of food and water, especially in species inhabiting daily or seasonally variable environments. There is increasing evidence that African mammals avoid adverse conditions by heterothermy and eventually by entering torpor. Members of subterranean rodent family, the African mole-rats (Bathyergidae), are suitable candidates to study both phenomena, because of the diversity of their strategies in respect of maintaining stable Tb ranging from homeothermic species to a mammal with the most labile Tb, the naked mole-rat. Currently, there are field data on daily and seasonal Tb in one social species only and such information are lacking for any solitary mole-rat. In our study, we recorded yearly Tb in two solitary bathyergids, the Cape mole-rat Georychus capensis and the Cape dune mole-rat Bathyergus suillus from South Africa using intraperitoneally implanted dataloggers. Since this region is characterised by changing ecological characteristics, we expected either decreases of Tb within 24 h indicating daily torpor and/or longer-term decreases of Tb, which would indicate multiday torpor. Although we found seasonally phase shifted low amplitude daily Tb cycles, we did not find any remarkable and regular daily and/or seasonal Tb deviations, likely showing an absence of torpor in both species. Due to absence of this energy saving mechanism, we may speculate that both species could be vulnerable to ongoing global climatic change.

Greater natriuretic response to ENaC inhibition in male versus female Sprague-Dawley rats.

Genes for the epithelial sodium channel (ENaC) subunits are expressed in a circadian manner, but whether this results in time-of-day differences in activity is not known. Recent data show that protein expression of ENaC subunits is higher in kidneys from female rats, yet females are more efficient in excreting an acute salt load. Thus, our in vivo study determined whether there is a time-of-day difference as well as a sex difference in the response to ENaC inhibition by benzamil. Our results showed that the natriuretic and diuretic responses to a single dose of benzamil were significantly greater in male compared with female rats whether given at the beginning of the inactive period [Zeitgeber time 0 (ZT0), 7 AM] or active period (ZT12, 7 PM). However, the response to benzamil was not significantly different between ZT0 and ZT12 dosing in either male or female rats. There was no difference in renal cortical α-ENaC protein abundance between ZT0 and ZT12 or males and females. Given previous reports of flow-induced stimulation of endothelin-1 (ET-1) production and sex differences in the renal endothelin system, we measured urinary ET-1 excretion to assess the effects of increased urine flow on intrarenal ET-1. ET-1 excretion was significantly increased following benzamil administration in both sexes, but this increase was significantly greater in females. These results support the hypothesis that ENaC activity is less prominent in maintaining Na+ balance in females independent of renal ET-1. Because ENaC subunit genes and protein expression vary by time of day and are greater in female rat kidneys, this suggests a clear disconnect between ENaC expression and channel activity.

Does 24-h Activity Cycle Influence Plasma PCSK9 Concentration? A Systematic Review and Meta-Analysis.

PURPOSE OF REVIEW: Higher plasma proprotein convertase subtilisin/kexin type 9 (PCSK9) concentration has been associated with a higher risk of atherosclerotic cardiovascular disease (ASCVD). Animal and human studies have examined the relationship between 24-h activity cycles (24-HAC) and PCSK9, but conflicting results exist. Therefore, this review aimed to examine the relationship between 24-HAC and plasma PCSK9 concentration in animals and humans.Three databases (PubMed, CINAHL, and Web of Science) were searched for eligible articles. Descriptive data were summarized using network meta-analysis. The effect size was estimated using pairwise meta-analysis. RECENT FINDINGS: The interventions designed to increase moderate to vigorous physical activities (MVPA) did not significantly change plasma PCSK9 concentration (Hedges' g = 0.137; p = 0.337). However, the effect was influenced by statin therapy and intervention delivery mode. Specifically, physical activity interventions in conjunction with statin therapy significantly increased plasma PCSK9 concentration (Hedges' g = 0.275; p = 0.007). Supervised exercise training significantly increased plasma PCSK9 concentration (Hedges' g = 0.630; p = 0.001), but physical activity counseling did not (p = 0.845). The effects of MVPA on plasma PCSK9 may be moderated by statin therapy, intervention delivery mode, or other potential unknown mechanistic factors. Thus, caution should be taken when using plasma PCSK9 as an outcome indicator for physical activity interventions aimed at decreasing the risk of ASCVD. Graphical abstract.

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.

Objective rest-activity cycle analysis by actigraphy identifies isolated rapid eye movement sleep behavior disorder.

BACKGROUND AND PURPOSE: Isolated rapid eye movement (REM) sleep behavior disorder (iRBD) is characterized by abnormal behaviours during REM sleep. Several studies showed that iRBD is a prodromal stage of synucleinopathies. Therefore, identifying iRBD in the general population is of utmost importance. In this study, we explore whether the assessment of rest-activity rhythm features can distinguish patients with iRBD from patients with disorders characterized by other pathological motor activity during sleep and healthy controls. METHODS: Nineteen patients with video-polysomnographic diagnosis of iRBD, 39 patients with other disorders with motor activity during sleep [19 with restless leg syndrome (RLS) and 20 with untreated sleep apnea syndrome (SAS)] and 16 healthy controls underwent 2-week actigraphy and video-polysomnography, and completed REM sleep behavior disorder screening questionnaires. Non-parametric analyses were applied to assess the rest-activity rhythm features. RESULTS: Patients with iRBD showed lower sleep efficiency, increased estimated wake after sleep onset and increased frequency of prolonged activity bouts compared to those with RLS and controls, while no difference emerged compared with SAS patients. Moreover, patients with iRBD presented increased occurrence of estimated nap in comparison to those with RLS, those with SAS and controls. The I < O, a 24-h measure that expresses the relationship between nocturnal and diurnal motor activity intensity, distinguished patients with iRBD from those with RLS, those with SAS and controls, with an area under the curve greater than that of REM sleep behavior disorder screening questionnaires. An I < O of 98.32 shows the best balance between sensitivity (63.2%) and specificity (89.1%). DISCUSSION: The I < O index distinguished iRBD patients from those with other pathological motor activity during sleep and controls, confirming its use as an objective measure suitable to screen large at-risk populations.

Twenty four-hour activity cycle in older adults using wrist-worn accelerometers: The seniors-ENRICA-2 study.

OBJECTIVES: This study aimed: (a) to provide a detailed description of sleep, sedentary behavior (SED), light physical activity (LPA), and moderate-to-vigorous physical activity (MVPA) over the complete 24-hours period using raw acceleration data in older adults; and (b) to examine the differences in the 24-hours activity cycle by sex, age, education, and body mass index (BMI). METHODS: Population-based cohort comprising 3273 community-dwelling individuals (1739 women), aged 71.8 ± 4.5 years, participating in the Seniors-ENRICA-2 study. Participants wore a wrist-worn ActiGraph GT9X accelerometer for 7 consecutive days, and the raw signal was processed using the R-package GGIR. RESULTS: Participants reached 21.5 mg as mean acceleration over the whole day; 32.3% (7.7 h/d) of time was classified as sleep, 53.2% (12.7 h/d) as SED, 10.4% (148.6 min/d) as LPA, and 4.1% (59.0 min/d) as MVPA. No marked differences were found in sleep-related variables between socio-demographic and BMI groups. However, women showed higher LPA but lower SED and MVPA than men. Moreover, SED increased whereas LPA and MVPA decreased with age. Participants with obesity (BMI ≥ 30 kg/m2 ) accumulated more SED and less LPA and MVPA than those without obesity. As expected, adherence to physical activity recommendations varied widely (9.2%-76.6%) depending on the criterion of MVPA accumulation. CONCLUSION: Objective assessment of the 24-hour activity cycle provides extensive characterization of daily activities distribution in older adults and may inform health-promotion interventions in this population. Women, the oldest old, and those with obesity offer relevant targets of strategies to improve lifestyle patterns.

Body temperature and time of day both affect nocturnal lizard performance: An experimental investigation.

The locomotor performance of reptiles is profoundly influenced by temperature, but little is known about how the time of day when the animal is usually active may influence performance. Time of day may be particularly relevant for studies on nocturnal reptiles that thermoregulate by day, but are active at night when ambient temperatures are cooler. If selection favours individuals that match their performance to activity times, then nocturnal species should perform better during the night, when they are normally active, than during the day. To test this hypothesis, we investigated how the time of day and body temperature affected the locomotor performance of adult females of the velvet gecko (Amalosia lesueurii). We measured the sprint speeds, running speeds and number of stops of 43 adult females at four different body temperatures (20, 25, 30 and 35 °C) during the day and at night. At night, sprint speeds were higher at 20 and 35 °C but sprint speeds were similar at 25 and 30 °C. By day, sprint speed increased with body temperature, peaking at 30 °C, before declining at 35 °C. However, gecko speeds over 1 m was higher at night at all four test temperatures than by day. Number of stops showed broadly similar patterns and females stopped almost twice as often on the racetrack during the day than they did at night. Furthermore, the thermal breadth of performance differed depending on when geckos were tested. Our results demonstrate that both body temperature and the time of day affects the behaviour and locomotor performance of female velvet geckos, with geckos running faster at night, the time of day when they are usually active. This study adds to evidence that both body temperature and the time of day are crucial for estimating the performance of ectotherms and evaluations and predictions of their vulnerability to climate warming should consider the context of laboratory experimental design.