Endogenous Rhythm Research Articles

Diversity in rest-activity patterns among Lake Malawi cichlid fishes suggests a novel axis of habitat partitioning.

ABSTRACTAnimals display remarkable diversity in rest and activity patterns that are regulated by endogenous foraging strategies, social behaviors and predator avoidance. Alteration in the circadian timing of activity or the duration of rest–wake cycles provide a central mechanism for animals to exploit novel niches. The diversity of the >3000 cichlid species throughout the world provides a unique opportunity to examine variation in locomotor activity and rest. Lake Malawi alone is home to over 500 species of cichlids that display divergent behaviors and inhabit well-defined niches throughout the lake. These species are presumed to be diurnal, though this has never been tested systematically. Here, we measured locomotor activity across the circadian cycle in 11 Lake Malawi cichlid species. We documented surprising variability in the circadian time of locomotor activity and the duration of rest. In particular, we identified a single species, Tropheops sp. ‘red cheek’, that is nocturnal. Nocturnal behavior was maintained when fish were provided shelter, but not under constant darkness, suggesting that it results from acute response to light rather than an endogenous circadian rhythm. Finally, we showed that nocturnality is associated with increased eye size after correcting for evolutionary history, suggesting a link between visual processing and nighttime activity. Together, these findings identify diversity of locomotor behavior in Lake Malawi cichlids and provide a system for investigating the molecular and neural basis underlying variation in nocturnal activity.

Сезонная динамика длины междоузлий Salix triandra L. (Salicaceae) на фоне кратковременной атмосферной засухи

Almond willow (Salix triandra L.) is a valuable basket species that is used to create plantings for various purposes. He occupies a special place in the system of the genus Salix. He can be used as a model object to identify patterns of morphogenesis of shoots. Object of research: model inbred population of almond willow in culture. Subject of research: seasonal dynamics of internode length on annual shoots of three-year-old seedlings willow of almond willow. The purpose of the research: to identify the seasonal dynamics of the length of internodes on annual shoots of almond willow against the background of a sharp change in early summer drought by cold rainy weather. Empirical methods for obtaining initial data: comparative-morphological. The obtained data were processed using the methods of analysis of dynamics series. It is found that seasonal trends in the dynamics of internode length are described by second-order regression equations with varying reliability. The configuration and topology of nonlinear seasonal trends are determined by individual differences between seedlings. The dynamics of deviations of internode length from seasonal trends correlates with the dynamics of hydrothermic conditions. Deviations in the length of internodes from seasonal trends are cyclical. The empirical series of deviations of the internode length from seasonal trends with high reliability are approximated by the sums of harmonic oscillations. The maximum contribution to the cyclical deviations of the internode length from seasonal trends is made by the rhythm with a period of fluctuations of 54 days. On most shoots, the influence of rhythms with a period of fluctuations of 36 and 27 days can be traced. Short-period rhythms detected on different shoots are irregular. In most observations, the specific rhythms of seasonal dynamics of internode length are determined by differences between shoots. The identified rhythms do not depend on hydrothermic conditions, on the length of shoots, on the length of internodes, or on seasonal trends in the dynamics of internode length. The hypothesis that the relationship between the dynamics of deviations in the length of internodes from seasonal trends and the dynamics of hydrothermic conditions is random is substantiated. Cyclicity deviations of internode length from seasonal trends are determined by endogenous rhythms of development.

External induction and stabilization of brain oscillations in the human

BackgroundNeural oscillations in the cerebral cortex are associated with a range of cognitive processes and neuropsychiatric disorders. However, non-invasively modulating oscillatory activity remains technically challenging, due to limited strength, duration, or non-synchronization of stimulation waveforms with endogenous rhythms. ObjectiveWe hypothesized that applying controllable phase-synchronized repetitive transcranial magnetic stimulation pulses (rTMS) with alternating currents (tACS) may induce and stabilize neuro-oscillatory resting-state activity at targeted frequencies. MethodsUsing a novel circuit to precisely synchronize rTMS pulses with phase of tACS, we empirically tested whether combined, 10-Hz prefrontal bilateral stimulation could induce and stabilize 10-Hz oscillations in the bilateral prefrontal cortex (PFC). 25 healthy participants took part in a repeated-measures design. Whole-brain resting-state EEG in eyes-open (EO) and eyes-closed (EC) was recorded before (baseline), immediately (1-min), and 15- and 30-min after stimulation. Bilateral, phase-synchronized rTMS aligned to the positive tACS peak was compared with rTMS at tACS trough, with bilateral tACS or rTMS on its own, and to sham. Results10-Hz resting-state PFC power increased significantly with peak-synchronized rTMS + tACS (EO: 44.64%, EC: 46.30%, p < 0.05) compared to each stimulation protocol on its own, and sham, with effects spanning between prefrontal and parietal regions and sustaining throughout 30-min. No effects were observed with the sham protocol. Moreover, rTMS timed to the negative tACS trough did not induce local or global changes in oscillations. ConclusionPhase-synchronizing rTMS with tACS may be a viable approach for inducing and stabilizing neuro-oscillatory activity, particularly in scenarios where endogenous oscillatory tone is attenuated, such as disorders of consciousness or major depression.

Spatial Organization and Coordination of the Plant Circadian System.

The plant circadian clock has a pervasive influence on many aspects of plant biology and is proposed to function as a developmental manager. To do so, the circadian oscillator needs to be able to integrate a multiplicity of environmental signals and coordinate an extensive and diverse repertoire of endogenous rhythms accordingly. Recent studies on tissue-specific characteristics and spatial structure of the plant circadian clock suggest that such plasticity may be achieved through the function of distinct oscillators, which sense the environment locally and are then coordinated across the plant through both intercellular coupling and long-distance communication. This review summarizes the current knowledge on tissue-specific features of the clock in plants and their spatial organization and synchronization at the organismal level.

Circadian Rhythm Disturbance in Agitation of Alzheimer's Disease

<h3>Introduction</h3> Neuropsychiatric symptoms (NPS) affect nearly all individuals with AD. Agitation in AD (Agit-AD) is one of the most common NPS, with an estimated prevalence over 40%. Agit-AD is a major cause of distress and burden for AD caregivers and may be driven by disrupted circadian rhythms and sleep. In healthy individuals, the circadian clock that generates these rhythms regulates patterns in mood, wakefulness, and other physiologic processes, such as body temperature and hormone levels. Individuals with Agit-AD may experience disturbance in their circadian rhythms such that aggressive and disruptive behavior is increased. This project aims to examine if agitated AD subjects (AgitAD+) express delayed circadian phases and reduced rhythm strength as compared to non-agitated AD subjects (AgitAD-) and healthy controls. Additionally, we seek to 1) evaluate if circadian phase and rhythm strength vary between subtypes of Agit-AD (affective dysregulation vs. executive dysfunction); and to 2) compare sleep amount, sleep quality, and degree of sleep disordered breathing among AgitAD+ subjects vs. AgitAD- subjects and healthy controls. <h3>Methods</h3> We studied 25 subjects (Table 1): 15 AgitAD+ subjects, 8 AgitAD- subjects, and 2 age-matched healthy controls (HC). Participants completed wrist actigraphy for one week to quantify rest/activity rhythms and sleep; consumed an ingestible, disposable temperature sensor for 1-2 days to quantify core body temperature, a marker of the endogenous circadian rhythm; and completed a single night of home sleep testing (HST; Table 2). Inclusion criteria were diagnosis of AD and age 55-90 years, and exclusion criteria include seizures, significant tremors, delirium, using CPAP for sleep apnea, restless legs syndrome, and circadian rhythm disorders. NPS were measured with the Neuropsychiatric Inventory-Clinician Version (NPI-C), the Cohen Mansfield Agitation Inventory (CMAI), the Neurobehavioral Rating Scale (NBRS), and the Cornell Scale for Depression in Dementia (CSDD). Agit-AD was defined using criteria from the International Psychogeriatric Association. AgitAD+ subjects had clinically significant agitation, defined as NPI-C Agitation or Aggression subtotals ≥ 4. Disease progression was measured using the Clinical Dementia Rating Scale (CDR), and subjects underwent a physical and neurological exam. Cognition was assessed using the Montreal Cognitive Assessment (MOCA), the Hopkins Verbal Learning Test (HVLT), the Controlled Oral Word Association Test (COWAT), Animal Naming (AN), and the Trail-Making Test (parts A & B). Sleep questionnaires included the Pittsburgh Sleep Quality Index (PSQI), the Epworth Sleepiness Scale (ESS), and the Morningness-Eveningness Questionnaire (MEQ). Caregivers were asked to complete a sleep diary for subjects and an agitation log over the week they completed actigraphy. Due to the COVID-19 pandemic, we implemented hybrid visits with telemedicine to limit in-person interactions. <h3>Results</h3> 25 subjects have completed the study to date. There were no statistically significant differences observed in actigraphy-derived sleep parameters between agitated and non-agitated AD subjects (2-group t-test); see Table 1). However, significant differences between the groups have been observed in the rest/activity rhythms: compared to subjects without agitation (AgitAD-), AgitAD+ subjects had lower levels of activity in the morning and greater activity in the afternoon and evening (Figure 1). We also have performed function-on-scalar regression (FOSR) (Goldsmith et al., 2015<i>,</i> Biometrics 71:344-353) using subject-specific activity profiles as outcomes and age and agitation/control status as predictors. Figure 2 shows functional effects of age on rest/activity rhythm (left panel) and the functional effect of agitation status (right panel); the red background shows times of day during which there were statistically significant differences, using the pointwise method of analysis (p<0.05). After adjustment for age, agitation was associated with lower activity in the morning period and a trend towards greater activity in the afternoon and evening period (not statistically significant). This preliminary finding may suggest that AgitAD+ subjects express lower and delayed activity rhythms. Additionally, the HST results show a trend toward less REM sleep and longer initial REM latency in the AgitAD+ group (Table 2). Updated results will be presented at AAGP (estimated 6-10 additional subjects). <h3>Conclusions</h3> The collection of multimodal noninvasive data on sleep, activity, and core body temperature is feasible in agitated AD outpatients. This study could provide evidence for CRD/sleep disturbance as a driver of Agit-AD and could identify Agit-AD subtypes who are most likely to benefit from chronobiotic or sleep interventions for Agit-AD. Furthermore, this study could provide evidence for the use of actigraphy as a surrogate biomarker in proof-of-concept intervention studies targeting Agit-AD. <h3>Funding</h3> National Institute on Aging, R01AG054771

Unacylated ghrelin, leptin, and appetite display diurnal rhythmicity in lean adults.

Constant routine and forced desynchrony protocols typically remove the effects of behavioral/environmental cues to examine endogenous circadian rhythms, yet this may not reflect rhythms of appetite regulation in the real world. It is therefore important to understand these rhythms within the same subjects under controlled diurnal conditions of light, sleep, and feeding. Ten healthy adults (9 M/1 F, means ±SD: age, 30 ± 10 yr; body mass index, 24.1 ± 2.7 kg·m-2) rested supine in the laboratory for 37 h. All data were collected during the final 24 h of this period (i.e., 0800-0800 h). Participants were fed hourly isocaloric liquid meal replacements alongside appetite assessments during waking before a sleep opportunity from 2200 to 0700 h. Hourly blood samples were collected throughout the 24-h period. Dim light melatonin onset occurred at 2318 ± 46 min. A diurnal rhythm in mean plasma unacylated ghrelin concentration was identified (P = 0.04), with the acrophase occurring shortly after waking (0819), falling to a nadir in the evening with a relative amplitude of 9%. Plasma leptin concentration also exhibited a diurnal rhythm (P < 0.01), with the acrophase occurring shortly after lights-out (0032 h) and the lowest concentrations at midday. The amplitude for this rhythm was 25%. Diurnal rhythms were established in all dimensions of appetite except for sweet preference (P = 0.29), with both hunger (2103 h) and prospective food consumption (1955 h) reaching their peak in the evening before falling to their nadir shortly after waking. Under controlled diurnal conditions, simultaneous measurement of leptin, unacylated ghrelin, and subjective appetite over a 24-h period revealed rhythmicity in appetite regulation in lean, healthy humans.NEW & NOTEWORTHY Simultaneous assessment of subjective appetite, unacylated ghrelin, and leptin was carried out over a continuous 37-h protocol for the first time under conditions of controlled light, sleep, and feeding in healthy, lean adults. Rhythms were observed in unacylated ghrelin, leptin, and components of subjective appetite, such as hunger, prospective consumption, and fullness. Concurrent measurement of rhythms in these variables is important to fully understand the temporal relationships between components of appetite as well as the influence of diurnal factors such as sleep, light, and feeding.

Testing Jump-Diffusion in Epileptic Brain Dynamics: Impact of Daily Rhythms.

Stochastic approaches to complex dynamical systems have recently provided broader insights into spatial-temporal aspects of epileptic brain dynamics. Stochastic qualifiers based on higher-order Kramers-Moyal coefficients derived directly from time series data indicate improved differentiability between physiological and pathophysiological brain dynamics. It remains unclear, however, to what extent stochastic qualifiers of brain dynamics are affected by other endogenous and/or exogenous influencing factors. Addressing this issue, we investigate multi-day, multi-channel electroencephalographic recordings from a subject with epilepsy. We apply a recently proposed criterion to differentiate between Langevin-type and jump-diffusion processes and observe the type of process most qualified to describe brain dynamics to change with time. Stochastic qualifiers of brain dynamics are strongly affected by endogenous and exogenous rhythms acting on various time scales—ranging from hours to days. Such influences would need to be taken into account when constructing evolution equations for the epileptic brain or other complex dynamical systems subject to external forcings.

The Principle of a Closed Feedback Loop of Human Endogenous Rhythms in Modern Neurofeedback and Adaptive Neurostimulation Technologies

The Principle of a Closed Feedback Loop of Human Endogenous Rhythms in Modern Neurofeedback and Adaptive Neurostimulation Technologies

Transgenic rats expressing dominant negative BMAL1 showed circadian clock amplitude reduction and rapid recovery from jet lag.

The circadian rhythms are endogenous rhythms of about 24h, and are driven by the circadian clock. The clock centre locates in the suprachiasmatic nucleus. Light signals from the retina shift the circadian rhythm in the suprachiasmatic nucleus, but there is a robust part of the suprachiasmatic nucleus that causes jet lag after an abrupt shift of the environmental lighting condition. To examine the effect of attenuated circadian rhythm on the duration of jet lag, we established a transgenic rat expressing BMAL1 dominant negative form under control by mouse Prnp-based transcriptional regulation cassette [BMAL1 DN (+)]. The transgenic rats became active earlier than controls, just after light offset. Compared to control rats, BMAL1 DN (+) rats showed smaller circadian rhythm amplitudes in both behavioural and Per2 promoter driven luciferase activity rhythms. A light pulse during the night resulted in a larger phase shift of behavioural rhythm. Furthermore, at an abrupt shift of the light-dark cycle, BMAL1 DN (+) rat showed faster entrainment to the new light-dark cycle compared to controls. The circadian rhythm has been regarded as a limit cycle phenomenon, and our results support the hypothesis that modification of the amplitude of the circadian limit cycle leads to alteration in the length of the phase shift.

Online and offline effects of transcranial alternating current stimulation of the primary motor cortex

Transcranial alternating current stimulation (tACS) is a non-invasive brain stimulation technique that allows interaction with endogenous cortical oscillatory rhythms by means of external sinusoidal potentials. The physiological mechanisms underlying tACS effects are still under debate. Whereas online (e.g., ongoing) tACS over the motor cortex induces robust state-, phase- and frequency-dependent effects on cortical excitability, the offline effects (i.e. after-effects) of tACS are less clear. Here, we explored online and offline effects of tACS in two single-blind, sham-controlled experiments. In both experiments we used neuronavigated transcranial magnetic stimulation (TMS) of the primary motor cortex (M1) as a probe to index changes of cortical excitability and delivered M1 tACS at 10 Hz (alpha), 20 Hz (beta) and sham (30 s of low-frequency transcranial random noise stimulation; tRNS). Corticospinal excitability was measured by single pulse TMS-induced motor evoked potentials (MEPs). tACS was delivered online in Experiment 1 and offline in Experiment 2. In Experiment 1, the increase of MEPs size was maximal with the 20 Hz stimulation, however in Experiment 2 neither the 10 Hz nor the 20 Hz stimulation induced tACS offline effects. These findings support the idea that tACS affects cortical excitability only during online application, at least when delivered on the scalp overlying M1, thereby contributing to the development of effective protocols that can be applied to clinical populations.

Workshop report. Circadian rhythm sleep-wake disorders: gaps and opportunities.

This White Paper presents the results from a workshop cosponsored by the Sleep Research Society (SRS) and the Society for Research on Biological Rhythms (SRBR) whose goals were to bring together sleep clinicians and sleep and circadian rhythm researchers to identify existing gaps in diagnosis and treatment and areas of high-priority research in circadian rhythm sleep–wake disorders (CRSWD). CRSWD are a distinct class of sleep disorders caused by alterations of the circadian time-keeping system, its entrainment mechanisms, or a misalignment of the endogenous circadian rhythm and the external environment. In these disorders, the timing of the primary sleep episode is either earlier or later than desired, irregular from day-to-day, and/or sleep occurs at the wrong circadian time. While there are incomplete and insufficient prevalence data, CRSWD likely affect at least 800,000 and perhaps as many as 3 million individuals in the United States, and if Shift Work Disorder and Jet Lag are included, then many millions more are impacted. The SRS Advocacy Taskforce has identified CRSWD as a class of sleep disorders for which additional high-quality research could have a significant impact to improve patient care. Participants were selected for their expertise and were assigned to one of three working groups: Phase Disorders, Entrainment Disorders, and Other. Each working group presented a summary of the current state of the science for their specific CRSWD area, followed by discussion from all participants. The outcome of those presentations and discussions are presented here.

Examining motor evoked potential amplitude and short-interval intracortical inhibition on the up-going and down-going phases of a transcranial alternating current stimulation (tacs) imposed alpha oscillation.

Many brain regions exhibit rhythmical activity thought to reflect the summed behaviour of large populations of neurons. The endogenous alpha rhythm has been associated with phase-dependent modulation of corticospinal excitability. However, whether exogenous alpha rhythm, induced using transcranial alternating current stimulation (tACS) also has a phase-dependent effect on corticospinal excitability remains unknown. Here, we triggered transcranial magnetic stimuli (TMS) on the up- or down-going phase of a tACS-imposed alpha oscillation and measured motor evoked potential (MEP) amplitude and short-interval intracortical inhibition (SICI). There was no significant difference in MEP amplitude or SICI when TMS was triggered on the up- or down-going phase of the tACS-imposed alpha oscillation. The current study provides no evidence of differences in corticospinal excitability or GABAergic inhibition when targeting the up-going (peak) and down-going (trough) phase of the tACS-imposed oscillation.

Cortisol circadian rhythm and jet-lag syndrome: evaluation of salivary cortisol rhythm in a group of eastward travelers

PurposeThe activity of the hypothalamus–pituitary–adrenal axis plays a crucial role as an endogenous stress-reactive system. Lifestyle and work often interfere with the endogenous circadian rhythms and can modify the physiological patterns of stress-hormones secretion, including cortisol. We evaluated the cortisol circadian rhythm in the “jet-lag syndrome” that is the most known condition associated with the desynchronization of the circadian rhythm.MethodsTo assess the modifications of cortisol secretion after a long-haul flight, we compared baseline and post-travel salivary cortisol rhythm in a group of 28 healthy eastward travelers (from the U.S.A. or Canada to Italy). The salivary samples were collected about 1 week before the departure at 11 p.m. on day 0 and at 8 a.m., 12 a.m. (midday) and 11 p.m. on day 1 (R0). The same samples were obtained after the landing, the day they flew back home (R1).ResultsStatistical analysis showed a significant difference between R0 and R1 for each sample considered (p < 0.005). In particular, the post-travel salivary cortisol levels detected at 11 p.m. both on day 0 and on day 1, were significantly higher than at baseline. Post-travel morning salivary cortisol levels were lower compared with basal rhythm and increased during the morning, reaching the acrophase at 12 a.m.ConclusionsIn eastward travelers, crossing more than five time zones, the cortisol circadian rhythm after the return to the East “remained behind,” being synchronized with the West time. This impaired cortisol secretion can contribute to the pathogenesis of the jet-lag syndrome.

Seasonal changes in adenosine kinase in tanycytes of the Arctic ground squirrel (Urocitellus parryii)

Hibernation is a seasonal strategy to conserve energy, characterized by modified thermoregulation, an increase in sleep pressure and drastic metabolic changes. Glial cells such as astrocytes and tanycytes are the brain metabolic sensors, but it remains unknown whether they contribute to seasonal expression of hibernation. The onset of hibernation is controlled by an undefined endogenous circannual rhythm in which adenosine plays a role through the activation of the A1 adenosine receptor (A1AR). Seasonal changes in brain levels of adenosine may contribute to an increase in A1AR sensitivity leading to the onset of hibernation. The primary regulator of extracellular adenosine concentration is adenosine kinase, which is located in astrocytes. Using immunohistochemistry to localize and quantify adenosine kinase in Arctic ground squirrels’ brain collected during different seasons, we report lower expression of adenosine kinase in the third ventricle tanycytes in winter compared to summer; a similar change was not seen in astrocytes. Moreover, for the first time, we describe adenosine kinase expression in tanycyte cell bodies in the hypothalamus and in the area postrema, both brain regions involved in energy homeostasis. Next we describe seasonal changes in tanycyte morphology in the hypothalamus. Although still speculative, our findings contribute to a model whereby adenosine kinase in tanycytes regulates seasonal changes in extracellular concentration of adenosine underling the seasonal expression of hibernation.

Mice held at an environmental photic cycle oscillating at their tau-like period length do not show the high-fat diet-induced obesity that develops under the 24-hour photic cycle

ABSTRACT Circadian disruptions precede high-fat diet (HFD)-induced obesity (DIO). Deviation of the endogenous circadian rhythm period length (tau) from 24 hours correlates with mice inter-strain DIO under the 24-hour light-dark cycle (T-cycle). Additionally, entrainment to a tau-resembling T-cycle attenuates DIO, to some extent, in muted mice. These phenomena suggest that entrainment to a 24-hour T-cycle promotes DIO beyond that expected from the HFD-induced metabolic disruptions. However, the hypothesis that entrainment to a tau-resembling T-cycle attenuates DIO has not been tested in wild-type mice. Therefore, we examined, in newborn female FVB/N mice, whether DIO found under their ‘regular’ 24-hour T-cycle is attenuated under a T-cycle oscillating at their tau-resembling period of 23.7 h, which is diverted from 24 hours by only 0.3 h. Compared to mice fed a low-fat diet, those fed an HFD under the 24-hour T-cycle showed a disrupted pattern of circadian locomotor activity prior to DIO onset. Both these phenomena were absent under the tau-like T-cycle. DIO developed under the 24-hour T-cycle despite similar caloric intake, and was associated with the lower locomotor activity of HFD-fed mice compared to the other mouse groups. These results demonstrated that DIO is secondary to HFD-induced circadian disruptions that are not harmonized by the strongest Zeitgeber (light-dark cycle) when oscillating at a period that diverts by as little as ca. 0.3-h from tau. More importantly, imposing a light-dark cycle oscillating at a tau-like period length, which enhances entrainment and presumably reinforces endogenous circadian rhythms, prevented HFD-induced circadian disruptions and enabled tighter control of energy homeostasis, as manifested by the absence of DIO, even under ad-lib HFD feeding. These results support the identification of tau-related biomarkers, which may be considered as risk-factors for DIO. Moreover, these findings may promote the development of clock-related pharmaceutical interventions that will reduce the gap between tau and 24 hours, and increase the robustness of the endogenous and entrained circadian rhythms. This will enable reducing DIO, even without caloric restriction or time-restricted feeding.

Effects of prolonged night-time light exposure and traffic noise on the behavior and body temperature rhythmicity of the wild desert rodent, Gerbillus tarabuli

ABSTRACT The aim of this study was to demonstrate for the first time in Tarabul’s gerbils (Gerbillus tarabuli), the effects of simultaneous exposure to two major environmental stressors – light and noise pollutions – on the body temperature rhythm and anxious behavior. Seven groups, each consisting of 6 adult male gerbils, were subjected to a standard LD cycle (12 L:12D) with lights on at 08:00 h and off at 20:00 h, constant conditions (total darkness, DD), prolonged nighttime exposure to light (PEL: 18 L:6D) with lights on at 08:00 h and off at 02:00 h, mimicking prolonged exposure to light pollution in peri-urban areas, exposure to auditory stress (TNS) of 80 dB, and conditions combining PEL&TNS. The body temperature circadian rhythm was recorded, and behavioral tests were performed at the end of experimental phases. The results revealed the existence, for the first time in Gerbilus tarabuli, of an endogenous circadian rhythm of body temperature with a period of 23.8 ± 0.04 h. Prolonged exposure to light at night (PEL) induced a significant phase delay (02 h 09 min ± 0.16 h) of the rhythm, with an acrophase (peak time) occurring at 04:42 ± 0.13 h instead of 02:33 ± 0.21 h. Exposure to TNS for 4 hours per night induced a significant increase of the amplitude of the rhythm and a decrease of the rhythm regularity (robustness of 73.26% in TNS vs. 82.32 in control condition). While combining TNS and PEL significantly delayed the phase of the Tb rhythm by 3 h 10 min (acrophase at 06:39 ± 0.37 h instead of 02:33 ± 0.21 h), increased the amplitude, and significantly reduced the stability of the rhythm (robustness of 67.25% in PEL&TNS vs. 82.32 in control condition). PEL&TNS and TNS environments induce an important stress in gerbils highlighted by a significant decrease of the number of line crossings and time spent in the center area of the open field test. Furthermore, elevated plus maze test revealed gerbils of the PEL&TNS and TNS conditions significantly visited the lowest number of open arms and spent a shorter amount of time in it. In addition, these conditions were responsible for less activity (total number of entries in arms) than in the control and PEL conditions. These results indicate clearly that in the desert area, peri-urban light and noise pollutions disturb the circadian rhythm components and alter the behavior of Tarabul’s gerbils inducing an anxious state.

How to cope in heterogeneous coastal environments: Spatio-temporally endogenous circadian rhythm of valve gaping by mussels

Transitional coastal zones are subject to high degrees of temporal fluctuation in environmental conditions, with these patterns varying in space. Gaining an in depth understanding of how sessile organisms cope with and respond to such environmental changes at multiple scales is needed to i) advance fundamental knowledge, ii) predict how organisms may react to stressors and iii) support the management of halieutic resources in transitional coastal areas. We addressed this question using mussels (Mytilus galloprovincialis) as model system. Valve-gaping sensor were deployed at multiple sites within the southern Venice Lagoon over a period of 6 months, to investigate the existence of periodicity in valve-gaping and its relationship with environmental variables, such as temperature and chlorophyll-a.Gaping behaviour was found to have periodic rhythms, of ~12 h and ~ 24 h, which were most pronounced in the inner part of lagoon part and were strongest during summer months. In autumn, the dual periodicity became weaker and mostly the 12 h remained. Gaping was closely linked with tide, but the relationship in terms of phasing varied upon location. Surprisingly, no clear direct relationships were found with chlorophyll-a, but food delivery may be mediated by tide itself. The results highlight the heterogeneity of behaviour and the endogenic nature of circadian rhythms in space and time. These findings have important implications for management of transitional areas where tidal alteration may have impacts on key behaviours, and emphasize the importance of characterizing their rhythms before using these as stress indicator. Moreover, the described tidal relationships should be included in growth models of bivalves in these systems.

Elevated ambient temperature accelerates aspects of torpor phenology in an obligate hibernator.

The thirteen-lined ground squirrel (Ictidomys tridecemlineatus) is assumed to be an obligate hibernator - commencing and terminating hibernation on a circannual rhythm, regardless of environmental conditions - but, until now, this assumption had never been fully tested. We housed three groups of captive-born ground squirrels from Aug. 2017 to Aug. 2018 under constant photoperiod (12hL:12h D) at 5, 16 or 25°C, and monitored hibernation using body temperature loggers. At 5 and 16°C all animals hibernated from autumn to spring with no differences in date of first/last torpor or duration of interbout euthermic periods (IBE), but torpor bout duration was 25% shorter at 16°C. One of 4 animals housed at 25°C did not hibernate. For the other three 25°C animals, the first torpor date did not differ from the other groups, but the last torpor bout (5 Feb.) occurred almost 8 weeks earlier. These animals aroused from torpor more frequently and IBE lasted significantly longer, so the total time spent torpid was less than 50% of the other groups. Unlike the 5 or 16°C animals, 25°C animals re-entered torpor in late spring 2018. Taken together these data suggest that this species is an obligate hibernator, but that high ambient temperatures can accelerate the endogenous circannual hibernation rhythm.

Recognition of CCA1 alternative protein isoforms during temperature acclimation.

CCA1α and CCA1β protein variants respond to environmental light and temperature cues, and higher temperature promotes CCA1β protein production and causes its retention detectable in the cytoplasm. CIRCADIAN CLOCK ASSOCIATED1 (CCA1), as the core transcription factor of circadian clock, is involved in the regulation of endogenous circadian rhythm in Arabidopsis. Previous studies have shown that CCA1 consists of two abundant splice variants, fully spliced CCA1α and intron-retaining CCA1β. CCA1β is believed to form a nonfunctional heterodimer with CCA1α and its closed-related homolog LHY. Many studies have established that CCA1β is a transcription product, while how CCA1β protein is produced and how two CCA1 isoforms respond to environmental cues have not been elucidated. In this study, we identified CCA1α and CCA1β protein variants under different photoperiods with warm or cold temperature cycles, respectively. Our results showed that CCA1 protein production is regulated by prolonged light exposure and warm temperature. The protein levels of CCA1α and CCA1β peak in the morning, but the detection of CCA1β is dependent on immunoprecipitation enrichment at 22°C. Higher temperature of 37°C promotes CCA1β protein production and causes its retention to be detectable in the cytoplasm. Overall, our results indicate that two splice variants of the CCA1 protein respond to environmental light and temperature signals and may, therefore, maintain the circadian rhythms and give individuals the ability to adapt to environment.

Downregulation of Arntl mRNA Expression in Women with Hypertension: A Case-Control Study

Background: Previous studies have reported that disturbance of endogenous circadian rhythms enhances the chance of hypertension and suggested that circadian clock genes could have a crucial function in the onset of the disease. This case-control study was aimed to investigate the association of the mRNA expression of aryl hydrocarbon receptor nuclear translocator like (Arntl), clock circadian regulator (Clock), and period circadian regulators 1 and 2 (Per1 and Per2) with hypertension and blood pressure levels. Methods: A total of 172 subjects were recruited in this study, including 86 hypertension and 86 nonhypertension controls. The mRNA expression levels in peripheral blood mononuclear cells were determined by real-time quantitative polymerase chain reaction. The differences in Arntl, Clock, Per1, and Per2 mRNA expression were compared between the 2 groups, and the relationship between mRNA expression and cardiometabolic risk profiles was also assessed. Results: We found that the mRNA expression of Arntl was downregulated in the hypertension cases compared with controls in women (1.10 [0.66, 1.71] vs. 1.30 [0.99, 2.06], p = 0.031). There was a significant negative correlation between the Arntl mRNA expression and SBP (r = −0.301, p = 0.004) and DBP (r = −0.222, p = 0.034) in women. In men, a negative correlation between the Per1 mRNA expression and SBP (r = −0.247, p = 0.026) was found. Conclusions: The Arntl mRNA expression may play an important role in progression of hypertension in women.