Quantitative analysis of regulatory flexibility under changing environmental conditions

The circadian clock controls 24-h rhythms in many biological processes, allowing appropriate timing of biological rhythms relative to dawn and dusk. Known clock circuits include multiple, interlocked feedback loops. Theory suggested that multiple loops contribute the flexibility for molecular rhythms to track multiple phases of the external cycle. Clear dawn- and dusk-tracking rhythms illustrate the flexibility of timing in Ipomoea nil. Molecular clock components in Arabidopsis thaliana showed complex, photoperiod-dependent regulation, which was analysed by comparison with three contrasting models. A simple, quantitative measure, Dusk Sensitivity, was introduced to compare the behaviour of clock models with varying loop complexity. Evening-expressed clock genes showed photoperiod-dependent dusk sensitivity, as predicted by the three-loop model, whereas the one- and two-loop models tracked dawn and dusk, respectively. Output genes for starch degradation achieved dusk-tracking expression through light regulation, rather than a dusk-tracking rhythm. Model analysis predicted which biochemical processes could be manipulated to extend dusk tracking. Our results reveal how an operating principle of biological regulators applies specifically to the plant circadian clock

Sleep, Health, and Aging

As people grow older, getting a good night's sleep remains essential to maintaining good health. Insomnia is a common complaint in older adults, and although occasional sleep complaints may not be associated with age, chronic sleep difficulties are experienced more often by older adults than by younger adults

First light for avian embryos: eggshell thickness and pigmentation mediate variation in development and UV exposure in wild bird eggs

Article first published online: 29 JUL 20141. The avian embryo's development is influenced by both the amount and the wavelength of the light that passes through the eggshell. Commercial poultry breeders use light of specific wavelengths to accelerate embryonic growth, yet the effects of the variably patterned eggshells of wild bird species on light transmission and embryonic development remain largely unexplored. 2. Here, we provide the first comparative phylogenetic analysis of light transmission, through a diverse range of bird eggshells (74 British breeding species), in relation to the eggshell's thickness, permeability, pigment concentration and surface reflectance spectrum (colour). 3. The percentage of light transmitted through the eggshell was measured in the spectral range 250–700 nm. Our quantitative analyses confirm anecdotal reports that eggshells filter the light of the externally coloured shell. Specifically, we detected a positive relationship between surface eggshell reflectance (‘brightness’) and the percentage of light transmitted through the eggshell, and this relationship was strongest at wavelengths in the human-visible blue-green region of the spectra (c. 435 nm). 4. We show that less light passes through thicker eggshells with greater total pigment concentrations. By contrast, permeability (measured as water vapour conductance) did not covary significantly with light transmission. Eggs of closed-nesting species let more light pass through, compared with open nesters. 5. We postulate that greater light transmission is required to assist embryonic development under low light exposure. Importantly, this result provides an ecological explanation for the repeated evolution of immaculate, white- or pale-coloured eggshells in species nesting in enclosed spaces. 6. Finally, we detected correlative support for the solar radiation hypothesis, in that eggshells of bird species with a longer incubation period let significantly less of the potentially harmful, ultraviolet (UV) light pass through the eggshell. In summary, we demonstrate suites of avian eggshell properties, including eggshell structure and pigmentation, which are consistent with an evolutionary pressure to both enhance and protect embryonic development.Golo Maurer, Steven J. Portugal, Mark E. Hauber, Ivan Mikšík, Douglas G. D. Russell and Phillip Casse

Unexpected diversity in socially synchronized rhythms of shorebirds

The behavioural rhythms of organisms are thought to be under strong selection, influenced by the rhythmicity of the environment. Such behavioural rhythms are well studied in isolated individuals under laboratory conditions, but free-living individuals have to temporally synchronize their activities with those of others, including potential mates, competitors, prey and predators. Individuals can temporally segregate their daily activities (for example, prey avoiding predators, subordinates avoiding dominants) or synchronize their activities (for example, group foraging, communal defence, pairs reproducing or caring for offspring). The behavioural rhythms that emerge from such social synchronization and the underlying evolutionary and ecological drivers that shape them remain poorly understood. Here we investigate these rhythms in the context of biparental care, a particularly sensitive phase of social synchronization where pair members potentially compromise their individual rhythms. Using data from 729 nests of 91 populations of 32 biparentally incubating shorebird species, where parents synchronize to achieve continuous coverage of developing eggs, we report remarkable within-and between-species diversity in incubation rhythms. Between species, the median length of one parent's incubation bout varied from 1-19 h, whereas period length-the time in which a parent's probability to incubate cycles once between its highest and lowest value-varied from 6-43 h. The length of incubation bouts was unrelated to variables reflecting energetic demands, but species relying on crypsis (the ability to avoid detection by other animals) had longer incubation bouts than those that are readily visible or who actively protect their nest against predators. Rhythms entrainable to the 24-h light-dark cycle were less prevalent at high latitudes and absent in 18 species. Our results indicate that even under similar environmental conditions and despite 24-h environmental cues, social synchronization can generate far more diverse behavioural rhythms than expected from studies of individuals in captivity. The risk of predation, not the risk of starvation, may be a key factor underlying the diversity in these rhythms.</p

The Double-edged Sword: A Mixed Methods Study of the Interplay between Bipolar Disorder and Technology Use

Human behavior is increasingly reflected or acted out through technology. This is of particular salience when it comes to changes in behavior associated with serious mental illnesses including schizophrenia and bipolar disorder. Early detection is crucial for these conditions but presently very challenging to achieve. Potentially, characteristics of these conditions\u27 traits and symptoms, at both idiosyncratic and collective levels, may be detectable through technology use patterns. In bipolar disorder specifically, initial evidence associates changes in mood with changes in technology-mediated communication patterns. However much less is known about how people with bipolar disorder use technology more generally in their lives, how they view their technology use in relation to their illness, and, perhaps most crucially, the causal relationship (if any exists) between their technology use and their disease. To address these uncertainties, we conducted a survey of people with bipolar disorder (N = 84). Our results indicate that technology use varies markedly with changes in mood and that technology use broadly may have potential as an early warning signal of mood episodes. We also find that technology for many of these participants is a double-edged sword: acting as both a culprit that can trigger or exacerbate symptoms as well as a support mechanism for recovery. These findings have implications for the design of both early warning systems and technology-mediated interventions

Morning-evening type and burnout level as factors influencing sleep quality of shift nurses: a questionnaire study

Aim To assess the relationship between sleep quality and demographic variables, morning-evening type, and burnout in nurses who work shifts. Methods We carried out a cross-sectional self-administered study with forced choice and open-ended structured questionnaires – Pittsburg Sleep Quality Index, Morningness- eveningness Questionnaire, and Maslach Burnout Inventory. The study was carried out at Gazi University Medicine Faculty Hospital of Ankara on 524 invited nurses from July to September 2008, with a response rate of 89.94% (n = 483). Descriptive and inferential statistics were applied to determine the risk factors of poor sleep quality. Results Most socio-demographic variables did not affect sleep quality. Participants with poor sleep quality had quite high burnout levels. Most nurses who belonged to a type that is neither morning nor evening had poor sleep quality. Nurses who experienced an incident worsening their sleep patterns (P < 0.001) and needlestick or sharp object injuries (P = 0.010) in the last month had poor sleep quality. The subjective sleep quality and sleep latency points of evening types within created models for the effect of burnout dimensions were high. Conclusions Nurses working consistently either in the morning or at night had better sleep quality than those working rotating shifts. Further studies are still needed to develop interventions that improve sleep quality and decrease burnout in nurses working shifts

Origins:A brief account of the ancestry of circadian biology

Who were the investigators and what was the path that enabled the launch of modern mechanistic research on circadian biology in the 1970s? Here we trace the origins of ideas from antiquity to the experimental study of the daily movements of leaves; on to the twentieth-century realization that circadian rhythms are widespread, endogenous, and innate; and finally to the appreciation that such rhythms could be utilized by organisms for the measurement of time. The conceptualization of the internal "clock" metaphor was key to the wave of mathematical, neurobiological, and molecular genetic advances that has transformed the field over the last 50 years.</p

Diel Periodicity in Activity and Location in the Web of the Common House Spider (Achaearanea tepidariorum).

Circadian rhythm is a type of endogenous clock that controls daily behavioral patterns in most organisms. Spiders have been shown to exhibit both circadian and non-circadian rhythms in their behaviors. This rhythmicity may allow spiders to cope with diel changes in environmental conditions. Both diurnal and nocturnal behavior have different sets of costs and benefits to a species’ survival. Achaearanea tepidariorum is one species in which potential circadian rhythmicity has never been studied. Due to its foraging behavior, it was predicted that its daily activity would be arrhythmic. We recorded the positions within the web of forty individuals throughout the day, and then observed their daily activity via use of an actogram apparatus. Analysis of the resulting actograms and web position data revealed a significant nocturnal periodicity in the spiders’ activity, as well as possible anticipation of the daily cycle. This nocturnal periodicity, coupled with specific web-building behavior, may be the result of this species balancing the costs and benefits of predation and foraging. More studies are needed to provide more information about the circadian behavioral patterns of A. tepidariorum

The circadian night depression of photosynthesis analyzed in a herb, Pulmonaria vallarsae. Day/night quantitative relationships

Although many photosynthesis related processes are known to be controlled by the circadian system, consequent changes in photosynthetic activities are poorly understood. Photosynthesis was investigated during the daily cycle by chlorophyll fluorescence using a PAM fluorometer in Pulmonaria vallarsae subsp. apennina, an understory herb. A standard test consists of a light induction pretreatment followed by light response curve (LRC). Comparison of the major diagnostic parameters collected during day and night showed a nocturnal drop of photosynthetic responses, more evident in water-limited plants and consisting of: (i) strong reduction of flash-induced fluorescence peaks (FIP), maximum linear electron transport rate (Jmax, ETREM) and effective PSII quantum yield (phi(PSII)); (ii) strong enhancement of nonphotochemical quenching (NPQ) and (iii) little or no change in photochemical quenching qP, maximum quantum yield of linear electron transport (phi), and shape of LRC (theta). A remarkable feature of day/night LRCs at moderate to high irradiance was their linear-parallel course in double-reciprocal plots. Photosynthesis was also monitored in plants subjected to 2-3 days of continuous darkness ("long night"). In such conditions, plants exhibited high but declining peaks of photosynthetic activity during subjective days and a low, constant value with elevated NPQ during subjective night tests. The photosynthetic parameters recorded in subjective days in artificial darkness resembled those under natural day conditions. On the basis of the evidence, we suggest a circadian component and a biochemical feedback inhibition to explain the night depression of photosynthesis in P. vallarsae

Clock gene oscillation in the copepod Calanus finmarchicus in the Arctic: the effect of latitude and season

Life evolved under the permanent influence of environmental cycles, the most prominent being the daily light/dark cycle, caused by the earth’s rotation about its axis. As a consequence almost all organisms have developed biological clocks that allow them to anticipate cyclic changes in the environment and thus to adjust their behavior and physiology accordingly. A biological clock has also been identified in the copepod Calanus finmarchicus, where it is thought to underpin diel and seasonal rhythms in behavior and physiology. C. finmarchicus plays a central role in sustaining the food webs of the North Atlantic and Subarctic regions, however, climate change induced latitudinal range shifts have introduced C. finmarchicus into the Arctic region, where it experiences extreme light conditions, with almost constant light throughout the Summer months and constant darkness in Winter. Therefore, this thesis centers on the question whether the C. finmarchichus clock stays functional throughout the High Arctic Summer, when diel fluctuations in light reach a minimum. Net based 24 h samplings have been conducted at two stations along a latitudinal gradient from the southern Barents Sea (74.5 °N, 30 °E) to the Nansen Basin (82.56 °N, 30.85 °E) north of Svalbard, within 9 days of the Summer Solstice 2018. Further, temporal expression patterns of clock genes have been analyzed and the behavioral activity of individual C. finmarchicus has been assessed in onboard laboratory experiments. Results from gene expression analysis show significant rhythmic oscillations in a number of core clock genes in wild caught C. finmarchicus, suggesting a functional and synchronized endogenous clock during periods of minimal fluctuations in light intensity. Further, a period shortening could be observed in several clock genes at the northern station associated with lower diel oscillations in light properties. Results from behavioral experiments indicate overall low rhythmic behavioral activity during Summer in the High Arctic. The findings from this study are further discussed in the context of seasonal timing, concluding that the circadian clock likely stays functional throughout the whole active phase at high latitudes, including periods of Midnight Sun. This may further point out the importance of the circadian clock as a tool to track the progression of the season and help to time seasonal events, which is of fundamental importance for C. finmarchicus to survive in the extreme conditions of the Arctic