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The study is aimed at assessing individual and age-related features of the functional state of various parts of the brain and the patterns of their ontogenetic changes based on the structural analysis of resting-state electroencephalogram (EEG) patterns in 5–7-years-old children. The study involved 266 children, who were divided into different age groups: Group 1—5-years-old (mean age 4.98 ± 0.33), Group 2—6-years-old (mean age 6.03 ± 0.35), and Group 3—7-years-old (mean age 6.85 ± 0.22). Alpha-rhythm parameters recorded mainly in the occipital areas may serve as an indicator for the functional maturation of the brain. Significant age-related changes in the alpha-rhythm parameters have been revealed. The presence of a regular alpha-rhythm with a frequency of 8–10 Hz increases from 5 to 7 years of age. The occurrence of the alpha-rhythm of low frequency significantly decreases by the age of 7 years, and the occurrence of the polyrhythmic alpha-rhythm—by the age of 6 years. These changes are caused both by complications of the structural and functional organization of the cerebral cortex at the cellular level, which occur throughout the studied age period, and the improvement of its relationships with subcortical structures. A decrease in the occurrence of high-amplitude alpha-band electrical activity (EA) with signs of hypersynchrony in the caudal regions may indicate the maturation of the system of nonspecific activation of the brainstem reticular formation from 5 to 7 years of age. Age dynamics is also manifested in a significant decrease in the EEG occurrence of theta-band EA, and in its zonal distribution in 5–7-years-old children aged. Such changes specify the process of progressive formation of functional connections between individual areas of the cortex, as well as the cortex and subcortical structures, in particular thalamo-cortical ones. The occurrence of alpha-band EA (less than 5.0%) and beta-band EA (about 13.0%) arranged topographically in the anterior cortex did not differ significantly with age. However, generalized EEG activity in the form of different frequency band waves, which characterizes the functional state of predominantly hypothalamic structures, occurs reliably more often in 7-years-old children rather than in 5-year-old children. Such dynamics is presumably associated with an increased reactivity of the hypothalamic-pituitary system in response to adaptive stresses caused by the transition to systematic learning and can be considered as a distinctive feature of this age period. Due to great restructuring of the brain functioning, all its structures become especially sensitive to high intellectual and emotional stress, which is characteristic of preschool children nowadays. The novelty of this study is highlighted by the identification of patterns, structure and nature of EA changes in 5- to 7-year-old normotypical children's brain to assess the functional state of the cortex and regulatory brain systems. The research results based on a large sample of children, growing up in modern social and cultural conditions, would provide guidance for the formation of age standards. [ABSTRACT FROM AUTHOR]

Square-wave bursting is an activity pattern common to a variety of neuronal and endocrine cell models that has been linked to central pattern generation for respiration and other physiological functions. Many of the reduced mathematical models that exhibit square-wave bursting yield transitions to an alternative pseudo-plateau bursting pattern with small parameter changes. This susceptibility to activity change could represent a problematic feature in settings where the release events triggered by spike production are necessary for function. In this work, we analyze how model bursting and other activity patterns vary with changes in a timescale associated with the conductance of a fast inward current. Specifically, using numerical simulations and dynamical systems methods, such as fast-slow decomposition and bifurcation and phase-plane analysis, we demonstrate and explain how the presence of a slow negative feedback associated with a gradual reduction of a fast inward current in these models helps to maintain the presence of spikes within the active phases of bursts. Therefore, although such a negative feedback is not necessary for burst production, we find that its presence generates a robustness that may be important for function. [ABSTRACT FROM AUTHOR]

The mammalian brain has an endogenous central circadian clock that regulates central and peripheral cellular activities. At the molecular level, this day-night cycle induces the expression of upstream and downstream transcription factors that influence the immune system and the severity of viral infections over time. In addition, there are also circadian effects on host tolerance pathways. This stimulates adaptation to normal changes in environmental conditions and requirements (including light and food). These rhythms influence the pharmacokinetics and efficacy of therapeutic drugs and vaccines. The importance of circadian systems in regulating viral infections and the host response to viruses is currently of great importance for clinical management. With the knowledge gained from the COVID-19 pandemic, it is important to address any outbreak of viral infection that could become endemic and to quickly focus research on any knowledge gaps. For example, responses to booster vaccination COVID-19 may have different time-dependent patterns during circadian cycles. There may be a link between reactivation of latently infected viruses and regulation of circadian rhythms. In addition, mammals may show different seasonal antiviral responses in winter and summer. This article discusses the importance of the host circadian clock during monkeypox infection and immune system interactions. [ABSTRACT FROM AUTHOR]

Neuronal systems are subject to rapid fluctuations both intrinsically and externally. These fluctuations can be disruptive or constructive. We investigate the dynamic mechanisms underlying the interactions between rapidly fluctuating signals and the intrinsic properties of the target cells to produce variable and/or coherent responses. We use linearized and non-linear conductance-based models and piecewise constant (PWC) inputs with short duration pieces. The amplitude distributions of the constant pieces consist of arbitrary permutations of a baseline PWC function. In each trial within a given protocol we use one of these permutations and each protocol consists of a subset of all possible permutations, which is the only source of uncertainty in the protocol. We show that sustained oscillatory behavior can be generated in response to various forms of PWC inputs independently of whether the stable equilibria of the corresponding unperturbed systems are foci or nodes. The oscillatory voltage responses are amplified by the model nonlinearities and attenuated for conductance-based PWC inputs as compared to current-based PWC inputs, consistent with previous theoretical and experimental work. In addition, the voltage responses to PWC inputs exhibited variability across trials, which is reminiscent of the variability generated by stochastic noise (e.g., Gaussian white noise). Our analysis demonstrates that both oscillations and variability are the result of the interaction between the PWC input and the target cell's autonomous transient dynamics with little to no contribution from the dynamics in vicinities of the steady-state, and do not require input stochasticity. [ABSTRACT FROM AUTHOR]

We systematically investigate the response of neurons to oscillatory currents and synaptic-like inputs and we extend our investigation to non-structured synaptic-like spiking inputs with more realistic distributions of presynaptic spike times. We use two types of chirp-like inputs consisting of (i) a sequence of cycles with discretely increasing frequencies over time, and (ii) a sequence having the same cycles arranged in an arbitrary order. We develop and use a number of frequency-dependent voltage response metrics to capture the different aspects of the voltage response, including the standard impedance (Z) and the peak-to-trough amplitude envelope ( V ENV ) profiles. We show that Z-resonant cells (cells that exhibit subthreshold resonance in response to sinusoidal inputs) also show V ENV -resonance in response to sinusoidal inputs, but generally do not (or do it very mildly) in response to square-wave and synaptic-like inputs. In the latter cases the resonant response using Z is not predictive of the preferred frequencies at which the neurons spike when the input amplitude is increased above subthreshold levels. We also show that responses to conductance-based synaptic-like inputs are attenuated as compared to the response to current-based synaptic-like inputs, thus providing an explanation to previous experimental results. These response patterns were strongly dependent on the intrinsic properties of the participating neurons, in particular whether the unperturbed Z-resonant cells had a stable node or a focus. In addition, we show that variability emerges in response to chirp-like inputs with arbitrarily ordered patterns where all signals (trials) in a given protocol have the same frequency content and the only source of uncertainty is the subset of all possible permutations of cycles chosen for a given protocol. This variability is the result of the multiple different ways in which the autonomous transient dynamics is activated across cycles in each signal (different cycle orderings) and across trials. We extend our results to include high-rate Poisson distributed current- and conductance-based synaptic inputs and compare them with similar results using additive Gaussian white noise. We show that the responses to both Poisson-distributed synaptic inputs are attenuated with respect to the responses to Gaussian white noise. For cells that exhibit oscillatory responses to Gaussian white noise (band-pass filters), the response to conductance-based synaptic inputs are low-pass filters, while the response to current-based synaptic inputs may remain band-pass filters, consistent with experimental findings. Our results shed light on the mechanisms of communication of oscillatory activity among neurons in a network via subthreshold oscillations and resonance and the generation of network resonance. [ABSTRACT FROM AUTHOR]

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Technologies for the analysis of time series with gaps are considered. Some algorithms of signal extraction (purification) and evaluation of its characteristics, such as rhythmic components, are discussed for series with gaps. Examples are given for the analysis of data obtained during long-term observations at the Garm geophysical test site and in other regions. The technical solutions used in the WinABD software are considered to most efficiently arrange the operation of relevant algorithms in the presence of observational defects. [ABSTRACT FROM AUTHOR]

The results of monitoring radon emanations in the territory of Gorno-Altaisk due to seismic activity and their influence on human health are considered. It is shown that the level of activity of subsoil radon in the vicinity of the fault zone in the territory of Gorno-Altaisk exceeds such a level recorded in Moscow by 3-4 times. There is ambiguity in the behavior of radon as a precursor of a seismic event. Some radon anomalies are synchronous with moments of earthquakes and others correspond to quiet periods. The radon activity is more closely associated with the earthquakes localized in the aftershock zone of the Chuya earthquake. This is assumed to be caused by the network of fluid-conducting channels within the active fault between this region and the observation station. [ABSTRACT FROM AUTHOR]

The circadian timing system controls about 40 % of the transcriptome and is important in the regulation of a wide variety of biological processes including metabolic and proliferative functions. Disruption of the circadian clock could have significant effect on human health and has an important role in the development of cancer. Here, we compared the expression levels of core clock genes in primary colorectal cancer (CRC), colorectal liver metastases (CRLM), and liver tissue within the same patient. Surgical specimens of 15 untreated patients with primary CRC and metachronous CRLM were studied. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to measure the expression of 10 clock genes: CLOCK, BMAL1, PER1, PER2, PER3, CRY1, CRY2, CSNK1E, TIM, TIPIN, and 2 clock-controlled genes: Cyclin-D1, and WEE1. Expression levels of 7 core clock genes were downregulated in CRLM: CLOCK ( p = 0.006), BMAL1 ( p = 0.003), PER1 ( p = 0.003), PER2 ( p = 0.002), PER3 ( p < 0.001), CRY1 ( p = 0.002), and CRY2 ( p < 0.001). In CRC, 5 genes were downregulated: BMAL1 ( p = 0.02), PER1 ( p = 0.004), PER2 ( p = 0.008), PER3 ( p < 0.001), and CRY2 ( p < 0.001). CSNK1E was upregulated in CRC ( p = 0.02). Cyclin-D1 and WEE1 were both downregulated in CRLM and CRC. Related to clinicopathological factors, a significant correlation was found between low expression of CRY1 and female gender, and low PER3 expression and the number of CRLM. Our data demonstrate that the core clock is disrupted in CRLM and CRC tissue from the same patient. This disruption may be linked to altered cell-cycle dynamics and carcinogenesis. [ABSTRACT FROM AUTHOR]

We consider the dynamics of some meteorological parameters in Gorny Altai from 2000 to 2011. We analyzed the variations in the meteorological parameters related to the strong Chuya earthquake (September 27, 2003). A number of anomalies were revealed in the time series. Before this strong earthquake, the winter temperatures at the nearest meteorological station to the earthquake source increased by 8-10°C (by 2009 they returned to the mean values), while the air humidity in winter decreased. In the winter of 2002, we observed a long negative anomaly in the time series of the atmospheric pressure. At the same time, the decrease in the released seismic energy was replaced by the tendency to its increase. Using wavelet analysis we revealed the synchronism in the dynamics of the atmospheric parameters, variations in the solar and geomagnetic activities, and geodynamic processes. We also discuss the relationship of the atmospheric and geodynamic processes and the comfort conditions of the population in the climate analyzed here. [ABSTRACT FROM AUTHOR]

Structural features of rhythmically zoned florencite and xenotime crystals from quartz veins of the Au-REE occurrences of the Near-Polar Urals are considered. The crystals were studied in the growth zones 0.01-0.15 mm wide. Rhythms consist of small structural elements: oriented intergrowths of several mineral species, layered-block distribution of Sr and Ca, syntaxic intergrowths of minerals of the same structural type, cocrystallization caverns, and late dissolution cavities with inclusions of argentite and pitchblende. The growth zones of crystals show successive change in lanthanides: from light to heavy REEs in florencite, and, vice versa, in xenotime, which is explained by the Ce and Y activity. The mechanism of element fractionation in the crystals is of dual nature. The rare-earth intergrowths contain four lanthanide groups: (La-Ce-Pr), (Nd-Sm-Eu-Gd), (Gd-Tb-Dy), (Ho-Er-Tm-Yb-Lu). This is caused by complexing ability of the elements, which is expressed in the tetrad effect of REE fractionation. Crystals, in turn, separate isomorphic complexes according to the properties of its facets and concentrations of elements in solutions. The structures of crystals and their growth elements are considered from the crystallochemical viewpoint. [ABSTRACT FROM AUTHOR]

Acute experiments on 22 anesthetized and immobilized cats were performed to produce dynamic time-slices maps of 83 on and/or off receptive fields of 47 visual cortex field 17 neurons using classical and combined mapping. These experiments showed that the areas and weightings of neuron fields during response generation using classical mapping changed in a wavelike manner. Mathematical processing of these data showed that the dynamics of receptive field characteristics consisted of the sum of a slow aperiodic and a rapid periodic component. The slow aperiodic component showed biphasic receptive field dynamics. The oscillation frequency of the periodic component in most cases was distributed into the alpha and, more rarely, beta EEG ranges. Additional activation of the discharge center of the receptive field of the neuron in combined mapping had no effect on the frequency of periodic oscillations but elicited significant reductions in the duration and amplitude of the aperiodic component. The mechanisms underlying the dynamics of neuron receptive fields in the primary visual cortex are discussed, as is the functional significance of these dynamics. [ABSTRACT FROM AUTHOR]

We performed a correlation and spectral analysis of time series of data on epizootics, epidemics, and famine in Siberia and Mongolia. We have found that periods T of approximately 100 years prevail in their structures, which are also typical for time series of solar activity. [ABSTRACT FROM AUTHOR]

The diurnal and seasonal regulation of the complex burrowing behavior of Nephrops norvegicus complicates population assessment for this species. Population assessment is traditionally carried out by Virtual Population Analysis (Length Cohort Analysis; LCA) and swept area density estimations from catch data. However, burrow counting from visual surveys has also acquired increasing importance in recent years as an alternative and apparently efficient method. All these approaches produced non-equivalent assessment results in the literature, and therefore, a comparison and critical discussion of these methods is warranted. In this review, we pursued this goal by using already published and unpublished fishery data for a commercially exploited western Mediterranean shelf (60-100 m) population as an example. The cross-assessment was carried out by LCA, the swept area method and burrow counting in different seasons (spring-summer and autumn-winter) to highlight biases in abundance estimations in relation to Nephrops behavior. We also used novel trawl density data for other fish and decapod species in the area because the burrowing behavior of these species may deeply bias Nephrops abundance in visual surveys. LCA provided intermediate assessment values when compared to the swept area and photographic estimates, which over- and underestimated the abundance, respectively. We reviewed the problems related to the peculiar burrowing behavior of the species that generate assessment estimations of such different magnitude. [ABSTRACT FROM AUTHOR]

Previous functional imaging studies have pointed to the compensatory recruitment of cortical circuits in old age in order to counterbalance the loss of neural efficiency and preserve cognitive performance. Recent electroencephalographic (EEG) analyses reported age-related deficits in the amplitude of an early positive-negative working memory (PN) component as well as changes in working memory (WM)-load related brain oscillations during the successful performance of the n-back task. To explore the age-related differences of EEG activation in the face of increasing WM demands, we assessed the PN component area, parietal alpha event-related synchronization (ERS) as well as frontal theta ERS in 32 young and 32 elderly healthy individuals who successfully performed a highly WM demanding 3-back task. PN area increased with higher memory loads (3- and 2-back > 0-back tasks) in younger subjects. Older subjects reached the maximal values for this EEG parameter during the less WM demanding 0-back task. They showed a rapid development of an alpha ERS that reached its maximal amplitude at around 800 ms after stimulus onset. In younger subjects, the late alpha ERS occurred between 1,200 and 2,000 ms and its amplitude was significantly higher compared with elders. Frontal theta ERS culmination peak decreased in a task-independent manner in older compared with younger cases. Only in younger individuals, there was a significant decrease in the phasic frontal theta ERS amplitude in the 2- and 3-back tasks compared with the detection and 0-back tasks. These observations suggest that older adults display a rapid mobilization of their neural generators within the parietal cortex to manage very low demanding WM tasks. Moreover, they are less able to activate frontal theta generators during attentional tasks compared with younger persons. [ABSTRACT FROM AUTHOR]

The dynamics of first-aid calls in Gorno-Altaisk from 2002 to 2003 and its changes in relation to the Chuisk severe earthquake (September 27, 2003) are analyzed. The correlation of the number of diseases with variations in solar and geomagnetic activities, effective temperature, and atmospheric pressure are considered. [ABSTRACT FROM AUTHOR]

The relatively complete late Danian-initial Lutetian succession of biotic events, which are suitable to serve as biostratigraphic reference levels for interregional correlations are defined in the section of the Novouzensk reference borehole based on dinocyst and nannoplankton assemblages. The analysis of palynological and nannofossil assemblages allows dynamics of basin development and sea-level fluctuations to be traced. Three major stages reflecting different sedimentation regimes are established in the borehole section: (1) Danian with terrigenous-carbonate sedimentation regime corresponding to the Algai and Tsyganovka formations; (2) Selandian-Thanetian (initial Eocene included) characterized largely by siliceous-terrigenous sediments of the Syzran, Novouzensk, and, partly, Bostandyk formations; (3) Ypresian-Lutetian with the carbonate-terrigenous sedimentation regime corresponding to the upper part of the Ypresian Bostandyk and Lutetian Kopterek formations. The composition of dinoflagellate and nannoplankton assemblages characterizes the North Caspian basin as an internal largely shallow sea with a changeable temperature regime. The paleoecological analysis of phytocoenoses made it possible to define basin fluctuations comparable with third-order rhythms. Four Danian rhythms definable in the Algai and Tsyganovka formations indicate conditions of an open warm-water basin. Dynamics of the step-wise shoaling of the basin was characteristic of the Selandian-early Thanetian ages with subsequent restoration of the marine regime in the late Thanetian. The Syzran Formation corresponds to two Selandian rhythms, which were formed in shallower settings of the restricted sea basin. Four Thanetian rhythms are established in the Novouzensk Formation. The early Thanetian basin was characterized by the shallowest disturbed marine conditions, which were followed by the restored normal marine regime in the late Thanetian. Six Ypresian rhythms correspond to the Bostandyk Formation (Yp-0, Yp-1, Yp-5-Yp-8) reflecting transition from initial Ypresian coastal (Yp-0, Yp-1) to normal marine conditions during the Yp-5 rhythm. The early (Yp-2-Yp-4) and late (Yp-9-Yp-10) Ypresian corresponded to the sedimentation break. Most abundant and diverse microbiotic assemblages characteristic of the Yp-7 rhythm are correlative with the EECO event. The marly Kopterek Formation corresponding to the early Lutetian rhythm (Lu-1) is characterized by diverse thermophilic biota. [ABSTRACT FROM AUTHOR]

Caring for the elderly is becoming a key challenge for society, given the shortage of trained personnel and the increased age of the population. Innovative approaches are needed to help the elderly remain at home longer and more safely, that is, to age in place. One popular strategy is to monitor the activity of the elderly: this focuses on obtaining information for caregivers rather than supporting the elderly directly. We propose an alternative, i.e. to enhance their inter-personal communication. We report the results of a user study with 14 independent elderly women and discuss the existing role that communication plays in maintaining their independence and well-being. We highlight the importance of peer support relationships, which we call PeerCare, and how awareness of each other’s rhythms and routines helps them to stay in touch. We then describe the deployment of a technology probe, called markerClock, which a pair of elderly friends used to improve their awareness of each other’s rhythms and routines. We conclude with a discussion of how such communication appliances enhance the awareness of rhythms and routines among elderly peers and can improve their quality of life and provide safer and more satisfying aging in place. [ABSTRACT FROM AUTHOR]

What differentiates the living from the nonliving? What is life? These are perennial questions that have occupied minds since the beginning of cultures. The search for a clear demarcation between animate and inanimate is a reflection of the human tendency to create borders, not only physical but also conceptual. It is obvious that what we call a living creature, either bacteria or organism, has distinct properties from those of the normally called nonliving. However, searching beyond dichotomies and from a global, more abstract, perspective on natural laws, a clear partition of matter into animate and inanimate becomes fuzzy. Based on concepts from a variety of fields of research, the emerging notion is that common principles of biological and nonbiological organization indicate that natural phenomena arise and evolve from a central theme captured by the process of information exchange. Thus, a relatively simple universal logic that rules the evolution of natural phenomena can be unveiled from the apparent complexity of the natural world. [ABSTRACT FROM AUTHOR]

Most plants are constructed from repeating modular units such as phytomers, merophytes, and cell packets. Even an organism as simple as the filamentous cyanobacterium Anabaena shows recurrent patterns of differentiated cellular structures, notably with respect to its heterocysts. These examples reflect the inherent rhythms established within developmental processes of living organisms. In the present article, attention is paid to repetitious production of idioblasts—isolated cells, or clusters of cells, with an identity different to that of neighbouring cells from which they are derived. In higher plant root tissues, idioblasts are contained within cell packets that grow up from mother cells during the course of a number of cycles of cell production. The heterocysts of Anabaena are also discussed; they, too, are a type of idioblast. The idioblasts of root tissues originate as small cells which result from unequal cell divisions. Such divisions are usually the final ones within a cell packet which has already undergone a number of division cycles and are characteristically located at one or both ends of a packet. The packet end walls are suggested to have a role in regulating division asymmetry. Idioblastic systems discussed are root cortical trichosclereids and diaphragm cells; in their earliest stage, the cells from which lateral root primordia arise are also considered as clusters of idioblasts because they, too, are the products of asymmetric divisions of pericyclic mother cells. The division patterns of all these idioblastic systems were modelled in a consistent way using L-systems, with the assumption that the age of a cell-packet end wall plays a special role in cell determination. [ABSTRACT FROM AUTHOR]

The article relates the author's experiences as a researcher. His first research effort concerned bioenergetics. He claims that his research career was influenced by several inspirational scientists, including Cledwyn Kiff and Frederick Weaver. While at Cardiff University, he became interested in continuous culture and oscillatory dynamics.

Sleep is a neurochemical process involving sleep promoting and arousal centers in the brain. Sleep performs an essential restorative function and facilitates memory consolidation in humans. The remarkably standardized bouts of consolidated sleep at night and daytime wakefulness reflect an interaction between the homeostatic sleep need that is manifested by increase in sleep propensity after sleep deprivation and decrease during sleep and the circadian pacemaker. Melatonin, the hormone produced nocturnally by the pineal gland, serves as a time cue and sleep-anticipating signal. A close interaction exists between the sleep-wake, melatonin, core temperature, blood pressure, immune and hormonal rhythms leading to optimization of the internal temporal order. With age the robustness of the circadian system decreases and the prevalence of sleep disorders, particularly insomnia, increases. Deviant sleep patterns are associated with increased risks of morbidity, poor quality of life and mortality. Current sleep pharmacotherapies treat insufficient sleep quantity, but fail to improve daytime functioning. New treatment modalities for sleep disorders that will also improve daytime functioning remain a scientific and medical challenge. [ABSTRACT FROM AUTHOR]

Examples are presented of nocturnal animals becoming diurnal or vice versa as a result of mutations, genetic manipulations, or brain lesions. Understanding these cases could give insight into mechanisms employed when switches of temporal niche occur as part of the life cycle, or in response to circumstances such as availability of food. A two-process account of niche switching is advocated, involving both a change in clock-controlled outputs and a change in the direct response to light (i.e. masking). An emerging theme from this review is the suggestion that retinal inputs have a greater role in switching than suspected previously. [ABSTRACT FROM AUTHOR]

Abstract: Natural hybridisation in plants is one of the most striking modes of evolution, when looking at the effects reticulation may have on patterns and processes of the evolutionary history of the affected system. Among other functional constraints, symmetry is regarded as a major factor of or for evolution. A loss of symmetry, that means origin of asymmetrical phenomena can in some cases be linked to environmental or genetic stresses, such as hybridisation. It has been shown that the discussion on reticulation and symmetrical evolution is strongly influenced by a zoocentric evolutionary view, but more focus is needed on the differences between the organisms subject to the study. Plant hybridogenic evolution with the subsequent possibility of polyploidisation and the consequent reduced homology is a completely different phenomenon compared to animal evolution. This article examines the role of symmetry for plant evolution by concentration on two topics: (a) spatial asymmetry on multiple levels caused by hybridisation, and (b) temporal asymmetry (changes of rhythms inherent to specific systems) as an effect of reticulation. [Copyright &y& Elsevier]

Synchronization of an internal clock (entrainment) and a direct response to light (masking) are complementary ways of restricting activity of an animal to day or night. The protein CLOCK has an important role in the oscillatory mechanism of mammalian pacemakers. Our data show that it is also involved in masking responses. Mice with theClock/Clockmutation reduced their wheel running less than wildtypes when given 1-h light pulses of light (2-1,600 lx) in the night. With dimmer lights (<2 lx), there were no significant differences between mutant and wildtype mice. Impaired masking responses to light inClock/Clockmice were confirmed in tests with ultradian light-dark cycles (3.5:3.5 h and 1:1 h). Tests with pulses of light longer than 1 h revealed that, although the mutants responded more slowly to light, they sustained the suppression of activity over the course of the 3-h tests better than wildtypes. [ABSTRACT FROM AUTHOR]

We caught smolts of Arctic charr, Salvelinus alpinus (L.), Atlantic salmon, Salmo salar L., and brown trout, Salmo trutta L., in a trap situated at the mouth of the river Halselva (70° N 23° E), northern Norway during a 5-year period. Salmon and charr were the first to leave freshwater at the end of May, while most trout left freshwater about 14 days later. Whereas the midnight sun shines continuously during the downstream migration period, the light intensity has a diel intensity pattern. The majority of the descending migrants were recorded during the night. The number of descending fish was relatively low at water temperatures below 3°C. The increase in water level was largely caused by snowmelt and thus correlated with lower water temperatures. The number of migrants of all three species increased with increasing water level and decreased with increasing water temperature, with the exception of trout, which increased with water temperature. Notably, the increase in number of migrants was also correlated with the increase in water level the following day, indicating that fish movements represent an early response to a later spate. There was no significant relationship between the number of migrants and the daily change in water level or temperature. The three species were highly synchronised in their daily number of migrants. The strongest synchronisation was found between Arctic charr and Atlantic salmon, followed by Arctic charr and brown trout. [ABSTRACT FROM AUTHOR]

Many shallow-water organisms are subjected to regular, frequent and considerable changes in their environment imposed by the tides. Such changes range from complex alterations in local conditions, as in the intertidal zone, to simpler variations in current speed and direction offshore. To take advantage of the opportunities these changes provide, many animals undertake regular vertical and/or horizontal migratory movements in synchrony with the tidal cycle. Others use tidal currents selectively for transport to new habitats. Such movements vary in extent from a few mm to several km and may be modulated by the diel cycle of light intensity. This paper reviews the existence of tidal migration in marine animals from various taxa and habitats. Crustacean and fish examples illustrate the various functions of tidal migration, including transport, feeding, predator avoidance and reproduction. These functions are not necessarily mutually exclusive and may change throughout ontogeny. The mechanisms involved in migration are discussed in terms of direct reactions to environmental stimuli and the interaction of these responses with endogenous rhythms of activity and responsiveness. [ABSTRACT FROM AUTHOR]

In many fish species, some individuals arediurnal while others are nocturnal. Sometimes,the same individual can be diurnal at first andthen switch to nocturnalism, or vice-versa.This review examines the factors that areassociated with such plasticity. It covers thebreakdown of activity rhythms during migration,spawning, and the parental phase; reversals ofactivity patterns during ontogeny or from oneseason to the next; effects of light intensity,temperature, predation risk, shoal size, foodavailability, and intraspecific competition.Case studies featuring goldfish ( Carassiusauratus), golden shiner ( Notemigonuscrysoleucas), lake chub ( Couesiusplumbeus), salmonids, sea bass ( Dicentrarchus labrax), and parentalsticklebacks and cichlids illustrate some ofthese influences. It is argued that mostspecies have a circadian system but that havingsuch a system does not necessarily imply strictdiurnalism or nocturnalism. Rigidity ofactivity phase seems more common in species,mostly marine, that display behavioral sleep,and for these animals the circadian clock canhelp maintain the integrity of the sleepperiod and ensure that its occurrence takes place atthat time of day to which the animal's sensoryequipment is not as well adapted. However, inother fishes, mostly from freshwater habitats,the circadian clock seems to be used mainly foranticipation of daily events such as thearrival of day, night, or food, and possiblyfor other abilities such as time-place learningand sun compass orientation, rather than forstrict control of activity phase. In thesespecies, various considerations relating toforaging success and predation risk maydetermine whether the animal is diurnal ornocturnal at any particular time and place. [ABSTRACT FROM AUTHOR]

Population heterogeneity in cespitose, fibrous-rooted, brevirhizomatous, stoloniferous, and tap-rooted herbaceous and woody plants is described. This heterogeneity is caused by the multivariant character of plant ontogeny (i.e., its dimensional, morphological, rhythmological, and temporal multiversality), which is regarded as the main adaptation mechanism operating in plant populations because it provides for the diversity of ontogenetic pathways under different ecological conditions. [ABSTRACT FROM AUTHOR]

Neocortical networks of excitatory and inhibitory neurons can display alpha(α)-frequency rhythms when an animal is in a resting or unfocused state. Unlike some γ- and β-frequency rhythms, experimental observations in cats have shown that these α-frequency rhythms need not synchronize over long cortical distances. Here, we develop a network model of synaptically coupled excitatory and inhibitory cells to study this asynchrony. The cells of the local circuit are modeled on the neurons found in layer V of the neocortex where α-frequency rhythms are thought to originate. Cortical distance is represented by a pair of local circuits coupled with a delay in synaptic propagation. Mathematical analysis of this model reveals that the h and T currents present in layer V pyramidal (excitatory) cells not only produce and regulate the α-frequency rhythm but also lead to the occurrence of spatial asynchrony. In particular, these inward currents cause excitation and inhibition to have nonintuitive effects in the network, with excitation delaying and inhibition advancing the firing time of cells; these reversed effects create the asynchrony. Moreover, increased excitatory to excitatory connections can lead to further desynchronization. However, the local rhythms have the property that, in the absence of excitatory to excitatory connections, if the participating cells are brought close to synchrony (for example, by common input), they will remain close to synchrony for a substantial time. [ABSTRACT FROM AUTHOR]

Running wheels are widely used in studies on biological rhythms. In mice wheel diameters have ranged from 11 cm to 23 cm. We provided mice with running wheels of two different sizes: 15 cm diameter and 11 cm diameter. The amount of running in the 12-h light:12-h dark condition and the endogenous period of wheel running in constant darkness was determined over 40 days. On the 1st day in constant darkness all animals were exposed to a 15-min light pulse at circadian time 13. The animals in the small wheel ran significantly less both in 12 h light:12 h dark and constant darkness, and showed a longer endogenous period in constant darkness compared to animals in the large wheel. Moreover, after the light pulse at circadian time 13, mice in the small wheel showed a significantly smaller phase delay in running wheel activity than mice in the larger wheels. The data suggest that the magnitude of a photic phase shift depends on the amount and timing of activity the animals display in relation to this stimulus. It can be concluded that technical features of the running wheel can influence the circadian period of wheel running. [ABSTRACT FROM AUTHOR]

Dynamic systems theory offers conceptual andmathematical tools for describing the performance ofneural systems at very different levels oforganization. Three aspects of the dynamic paradigmare discussed, namely neural rhythms, neural andmental development, and macroscopic brain theories andmodels. [ABSTRACT FROM AUTHOR]

The importance of circadian timing was evaluated for 18 months from late-April 1997 through October 1998 in a high-density population of free-living eastern chipmunks, Tamias striatus, at a 4-ha forest site in the Allegheny Mountains. Included in the radio-collared field group were 30 chipmunks with supra-chiasmatic nucleus-targeted lesions, 24 surgical controls, and 20 intact controls. An additional 17 chipmunks were used in a laboratory study as lesion-calibration controls to correlate degree of circadian arrhythmicity with extent of supra-chiasmatic nucleus deletion. Survival was documented in the field by daily radio tracking and by regular trapping censuses except during winter hibernation. A significantly higher proportion of supra-chiasmatic nucleus-lesioned than surgical control chipmunks or intact controls were killed by weasel predation during the first 80 days after repatriation. A 28-h continuous census found no surface activity of any chipmunks during hours of darkness. However, episodes of nocturnal movement were detected within the permanent dens by radio telemetric data logging, especially in supra-chiasmatic nucleus-lesioned animals. Excavation and mapping of six chipmunk burrow systems aided in the interpretation of the telemetric activity data. Nighttime restlessness of supra-chiasmatic nucleus-lesioned animals may have acted as a clue to the predator for locating its prey. [ABSTRACT FROM AUTHOR]

Mutant mice with retinal degeneration ( rd/rd) were given 1-h pulses of light of varying brightness at times of the night when they would normally be active. The mutant mice showed a significantly greater inhibition of locomotor activity to light (negative masking) than wildtype controls. Lack of impairment, or even enhancement of negative masking suggests that this response may depend on sparing in retinally degenerate mice of the same receptor type that mediates clock resetting, because synchronization of the circadian system is known to be unimpaired in these mutants. With very dim light pulses, mutants did not change their activity, but wildtypes actually became more active (positive masking). Positive and negative masking appear to depend on different sensory and central processes. [ABSTRACT FROM AUTHOR]

A simple raster-scan display, using a small interactive microcomputer with graphics capability, is described and gives visual indication of various entrainment-type phenomena. In particular, almostentrainment and transient behaviour are easily detectable. The display is illustrated using entrainment conditions in heart-rate variability data and blood-flow measurements. [ABSTRACT FROM AUTHOR]

Non-aggressive social behaviour rhythms of Bandicota bengalensis were studied in the laboratory. The species exhibited 95% rhythmicity for social behaviour but the rhythms were uni- or bimodal and were influenced by the number and sex of interacting conspecifics. Peaks occurred at 0900 and 1800 hr. Males were more socially active than females. [ABSTRACT FROM AUTHOR]

Cyanothece sp. strain ATCC 51142 is an aerobic, unicellular, diazotrophic cyanobacterium that temporally separates O2-sensitive N2 fixation from oxygenic photosynthesis. The energy and reducing power needed for N2 fixation appears to be generated by an active respiratory apparatus that utilizes the contents of large interthylakoidal carbohydrate granules. We report here on the carbohydrate and protein composition of the granules of Cyanothece sp. strain ATCC 51142. The carbohydrate component is a glucose homopolymer with branches every nine residues and is chemically identical to glycogen. Granule-associated protein fractions showed temporal changes in the number of proteins and their abundance during the metabolic oscillations observed under diazotrophic conditions. There also were temporal changes in the protein pattern of the granule-depleted supernatant fractions from diazotrophic cultures. None of the granule-associated proteins crossreacted with antisera directed against several glycogen-metabolizing enzymes or nitrogenase, although these proteins were tentatively identified in supernatant fractions. It is suggested that the granule-associated proteins are structural proteins required to maintain a complex granule architecture. [ABSTRACT FROM AUTHOR]

The effects of photoperiod and melatonin treatment on reproductive and immune function were assessed in two subspecies of Peromyscus maniculatus from different latitudes of origin. In experiment 1, P. m. bairidii (latitude = 42°51′ N) and P. m. luteus (latitude = 30°37′ N) were housed in either long (LD 16∶8) or short days (LD 8∶16) for 8 weeks. Short-day P. m. bairdii displayed reproductive regression and elevated splenocyte proliferation in response to the T-cell mitogen concanavalin A, as compared to long-day mice. In contrast, P. m. luteus did not undergo reproductive regression or exhibit any increase in lymphocyte proliferation in short days. In experiment 2, individuals of both P. m. bairdii and P. m. luteus were implanted with empty capsules or capsules that contained melatonin. Individual P. m. bairdii implanted with melatonin underwent reproductive regression. Individuals of this subspecies also displayed elevated lymphocyte proliferation compared to control mice. Conversely, P. m. luteus implanted with melatonin did not undergo reproductive regression and displayed no significant changes in lymphocyte proliferation. These results suggest that reproductive responsiveness to melatonin mediates short-day enhancement of immune function in deer mice. These data also imply that melatonin may not possess universal immunoenhancing properties. Rather, the effectiveness of melatonin to influence immune responses may be constrained by reproductive responsiveness to this indole-amine. [ABSTRACT FROM AUTHOR]

Recordings made from decerebrated, paralyzed eels ( Anguilla anguilla) producing rhythmical spinal motoneuronal activity showed that around 65% of identified reticulospinal units, belonging to the inferior reticular division, discharged rhythmically. The reticulospinal bursts, lasting from 300 up to 3000 ms, were in time with spinal motoneuronal bursting activity. In different fish the modal cycle period varied between 2 to 4 s and burst duration and firing frequency of each neuron showed large changes from cycle to cycle. Burst responses similar in form to those occurring spontaneously were evoked from reticular neurons when the ophthalmic nerve was stimulated regularly (intervals of 1 to 10 s) but the cycle period, firing frequency and burst duration were now more predictable. For stimulation intervals between 2 and 5 s, each ophthalmic nerve stimulus was normally followed by a burst from the reticulospinal neuron. The cycle period of the reticular rhythm then became equal to the interstimulus interval and the reticulospinal unit was entrained by the stimulus. Beyond this range of interstimulus intervals, complete entrainment was lost. We suggest that regular sensory input provides a powerful stabilising influence to rhythmically active motor systems in the brainstem and spinal cord. [ABSTRACT FROM AUTHOR]

Twenty-two years of monthly values of birth data for the USA, 1967 through 1988, were analyzed by visual inspection. The data were transformed to remove the influence of length of month and of linear trend, and the values were lagged 9 months to approximate the time of conception. Then, 11-year monthly averages were obtained and plotted as standard scores. Thus two 11-year sets of data were independently analyzed, providing the opportunity of replication. Four distinct temporal patterns were found, differing in month of occurrence of the initial trough and peak and the relative sizes of the two troughs; these characteristics of the temporal pattern change systematically with latitude in the eastern and midwestern states. Data from two other continents, the United Kingdom and Australia, also were analyzed using the same method and found to exhibit a temporal pattern during the year similar to the northern states of the USA. Two biologically relevant variables, temperature and photoperiod, were considered as possible controllers and regulators of the annual rhythmicity. Comparisons of the trends in conceptions with these environmental variables, and inspections of the temperatures and photoperiods at which peaks and troughs in conceptions were found, indicated that these environmental variables could not account for the annual rhythmicity in conceptions. [ABSTRACT FROM AUTHOR]

The various effects that temperature can exert on biological periodicities are reviewed. Particular consideration is given to the remarkable capability of many rhythms either to respond in a temperature dependent manner, especially in nonsteady-state conditions, or to behave almost independently of temperature ('temperature compensated') in the steady state. Therefore, organisms are able both to use temperature changes as synchronization cues and to measure time at different temperatures. Moreover, changes of temperature can induce transients, after-effects, and eventually alterations in the phase response behaviour, sometimes even the rhythmicity itself. Treatment with low temperatures can, at least in some cases, hold the circadian clock, and considerably reduce the sensitivity of rhythms towards certain drugs. [ABSTRACT FROM AUTHOR]

In correspondence to the geophysical cycle of the solar day, the majority of eucaryotic organisms exhibit the phenomenon of circadian periodicity. This type of biological rhythm is reviewed, mainly as cytological aspects, with regard to the temporal organization of the eucaryote, the question of endogeneity, the occurrence in cells of multicellular organisms, and attempts to explain the molecular mechanism of the basic oscillator. [ABSTRACT FROM AUTHOR]

The chick pineal gland exhibits circadian rhythms in melatonin synthesis under in vivo and in vitro conditions. A daily rhythm of melatonin production was first detectable in pineal glands isolated from chick embryos at embryonic day 16 and incubated under a LD cycle. All pineal glands isolated from 17-day-old and older embryos were rhythmic while no gland isolated at embryonic day 14 and 15 exhibited a daily rhythm in melatonin synthesis. Melatonin production in static cultures of embryonic pineal cells was rhythmic over 48 h if the cells were kept under a LD cycle. When embryonic pineal cells were incubated in constant darkness the rhythm in melatonin production was damped within 48 h. These results suggest that chick pineal cells from embryonic day 16 onwards are photosensitive but that the endogenous component of the melatonin rhythm is not completely developed at that age. A soluble analogue of cAMP stimulated and norepinephrine inhibited melatonin synthesis in cultured embryonic pineal cells. These findings indicate that the stimulatory and inhibitory pathways controlling melatonin synthesis in the mature pineal gland are effective in pineal cells isolated from chick embryos at least 2 days before hatching. [ABSTRACT FROM AUTHOR]

Extracellular single-unit recordings were made during day- and night-time in the pineal gland of urethane-anesthetized adult male Sprague-Dawley rats. All cells exhibiting spontaneous electrical activity had firing frequencies from less than 1 Hz to about 100 Hz, and their discharge patterns were characterized as regular, irregular or bursting. While most of the spontaneously active cells (n=63) showed a uniform activity level throughout the recording period (30-120 min), a group of 9 cells exhibited oscillatory rhythms with periods of 4-8 min. In addition, long-term recordings across day- and night-time from five cells revealed increasing activity during night-time in three cells, while the remaining two units showed constant activity throughout the recording time (8-20 h). Comparison of day- and night-data in general indicated an overall higher level of activity at night. [ABSTRACT FROM AUTHOR]

The heptadecapeptide ACTH 1-17 is the analogue of corticotropin with β-alanine in position 1, lysine instead of 17-arginine and a basic amide instead of 18 arginine-amide. These modifications give enhanced biological activity and longer duration of the action. Several researchers investigated the acute effect of the analogue after administration at different time points along the 24 h cycle, and discovered that glucocorticoid and mineralocorticoid responses are dissociated in terms of doses and timing. Cortisol and urinary 17 OH-CS rise more after morning injections whereas for aldosterone the maximum effect was noted at 14. The most interesting finding that concerns ACTH 1-17 is the chronizing effect. ACTH 1-17 can be a chronizer because its administration resets, for instance, the toleration to antimitotic drugs, to a more convenient time. At clinical level, a group of researchers studied, in some case correctly from a chronobiological point of view, the effect of the ACTH 1-17 on patients and on healthy subjects. It is useful to remember the concept of hierarchies of rhythms: each different periodic function is regulated or, better, intermodulated by a network of other periodic variables of the same organ or of other organs and systems. So the necessity of large samplings to evidentiate periodic phenomena, and the utility of investigating pertiment marker rhythms significantly correlated with those to be studied are evident. Autorhythmometry and automatic monitoring can help very much on this purpose. [ABSTRACT FROM AUTHOR]

The paper explores the linkage between ecological and social systems of the Gurung people in the Nhāson Valley of Nepal, accounting for the interconnectedness of social life and seasons. The main themes of the paper are the local people's understanding and experience of seasons, and the ways in which their social life moves according to those seasons. The paper is based on 9 months of ethnographic fieldwork undertaken from 2012 to 2018 in Nhāson, a small mountain valley located in the central Himalayan region of Nepal. Informal interaction and conversation with the local people were the key sources of understanding the seasonality and sociality. The findings reveal that a single cultural group has multiple frameworks for marking and counting the year which are contextual and culturally specific. Likewise, seasons and social life in the mountain region are closely interlinked to each other. Local people see that the transformation of seasons from one to the next is related to socio-cultural changes that reflect the rhythm of life. The social and ecological systems in this Himalayan region of Nepal are gradually being affected by climate change. [ABSTRACT FROM AUTHOR]

The effect of rhythmic stimulation of subthalamic nucleus on grooming movements and their rhythmicity was studied on mature rats and on 13- and 14-day rat pups. Unilateral monopolar stimulation of subthalamic nucleus was performed on unrestrained animals via implanted electrodes. This stimulation activated virtually all grooming movements (scratching, hair-plucking, licking, and body-shaking); the effect was most pronounced in pups. Acceleration of the rhythm of grooming movements was observed only in rat pups for hair-plucking and scratching on the contralateral side relatively to the stimulated nucleus. In mature rats stimulation of the subthalamic nucleus prolonged grooming movements in most cases, but did not increase their number and rhythm. [ABSTRACT FROM AUTHOR]

This is meant to alert people to potentially major effects of construction projects on research results. Because we study the effects of stress on regulation of ACTH and corticosterone secretion and of serotonin receptors and stress on energy balance, we serve as an early warning system when things go awry. Most of our experiments include taking daily, or twice daily, measurements of rat or mouse weights and food intake as well as stress hormone levels. We are highly sensitized to environmental disruption and we've shown previously the effects of construction on stress hormones (1). However, we did not anticipate the change and disruption in energy balance that may occur in response to environmental perturbation. We provide two examples of these, below. [ABSTRACT FROM AUTHOR]

Blood loss-induced ischemia reduced intestinal electrical spike activity and delayed or blocked the migrating myoelectric complex. A single session of mesodiencephalic modulation significantly intensified electrical discharges, stimulated contractions of the small intestine, and restored normal cycles of the migrating myoelectric complex. [ABSTRACT FROM AUTHOR]