Night Cycle Research Articles

The effect of voluntary exercise on light cycle stress-induced metabolic resistance.

Disruption of circadian genes affects metabolic homeostasis. Regular exercise programs prevent metabolic dysfunction and alter circadian gene expression In this study, we investigated whether exercise affects light stress-induced circadian rhythm derangement and metabolic resistance. A circadian rhythm derangement mouse model was designed by extending the light exposure by two hours (14 L/10 D) for three weeks. Nine-weekold male mice were single-caged and divided into four groups: sedentary groups with or without light stress, and voluntary wheel-trained groups with or without light stress. In addition, differentiated myotubes were cultured in the presence of dexamethasone with or without 5-aminoimidazole-4-carboxamide-1-beta-4-ribofuranoside (AICAR). The comprehensive laboratory animal monitoring system was used to analyze the metabolic changes in mice. Moreover, reverse transcription-polymerase chain reaction (RT-PCR) was used to quantify the mRNA expression levels of circadian genes in animal and cell culture models. Three weeks of light stress reduced the running distance and increased the weight of mice. In addition, VO2 consumption and heat production were increased during the night cycle under non-stress conditions but not under stress conditions. PCR analysis revealed that exercise and stress altered the expression levels of circadian genes in the hypothalamus and quadriceps muscles. mRNA expression levels of period circadian regulator 1 were downregulated in the quadriceps muscles of the stressed sedentary group compared to that in muscles of the non-stressed sedentary group. Furthermore, differentiated myotube cells cultured in the presence of dexamethasone, with or without AICAR, showed distinct oscillation patterns at various time points. Our study demonstrates that exercise partially prevents metabolic disruption by regulating the circadian gene expression in skeletal muscles.

Thermal and electrical conductive 2D CuO evaporator for all-day steam generation

Solar energy-driven water evaporation is an effective way to obtain clean water through seawater desalination. Due to the day and night cycle, all-day steam generation is an urgent project. Here, 2D evaporators with effective heat management were designed and constructed by facile folding, in which superhydrophilic CuO coatings with honeycomb-like pores were in situ deposited on brass plates via electroplating and heat oxidation. In the daytime, the 2D evaporator has excellent photothermal performance due to the appropriate pore structure, light absorption, and water supply. The evaporation rate reaches 1.4 kg m−2 h−1, and the energy conversion efficiency of 93.5% under 1 sun in 3.5% artificial seawater for ten cycles. Except forsolar-driven water evaporation, some heat converts into electricity due to the temperature difference between the two surfaces of the high thermal conductive 2D evaporator. At night, steam is generated through the flexible photoelectric transition. The evaporation rate is 5.8 kg m−2 h−1 at an input voltage of 6 V. The stable evaporation performance of this evaporation system and the advantages of all-day steam generation show considerable prospects. It may be widely used in pure water production in the future.

Influence of night-time light pollution on the photosynthesis and physiological characteristics of the urban plants Euonymus japonicus and Rosa hybrida

BackgroundNight-time light pollution (NLP), which breaks the natural cycle of day and night, has become a new threat to urban ecosystems. Plants are the main component of urban ecosystems and play an irreplaceable role in maintaining urban ecological balance. The effects of NLP with various radiation sources, including green, white, blue and red light provided by light-emitting diodes, on urban plants, Euonymus japonicus and Rosa hybrida, were examined in a block field experiment.ResultsNLP caused photoinhibition and oxidative stress in plants, and the extent of the deleterious effects varied with the spectral distribution of artificial light sources and species. Both E. japonicus and R. hybrida were more sensitive to blue and red light, which reduced the pigment concentration, net photosynthetic rate, stomatal limit value, effective quantum yield, apparent electron transfer rate and photochemical quenching coefficient, and markedly increased the malondialdehyde content and total antioxidant capacity. However, those negative effects under white light were only present in E. japonicus and not in R. hybrida. Furthermore, blue and red light significantly decreased the stomatal conductance of E. japonicus. In contrast, green light had no significant effect on the above indices for both species. All spectra did not significantly change the sugars and starch contents for either species.ConclusionsConsidering that the spectral distribution of artificial light at night in cities has great heterogeneity and that its effect varies with plant species, it is important to arrange tree species with NLP tolerance and install appropriate light sources in urban areas based on the corresponding physiological responses and adaptation of urban trees.

Consequences and management of sleep-wake rhythm disorders resulting from social jetlag and nightshifts

Our day to night cycle is ruled by a social, biological and sun clock. The social clock being a local time is aligned with others’ lives. The biological clock (circadian time) that controls our physiology and the sun clock that defines natural light and darkness. Social jetlag refers to the misalignment between local and circadian time. This term is usually used in reference to travels to places in different time zones. Nevertheless, it is worth noticing that “jetlag” also applies to people working in a medical industry such as doctors, nurses, paramedics, and others involved in an on-call work. Thus, I would like to look closer to the physiology of social jetlag and to analyze its implications.

Artificial Light at Night (ALAN) causes size-dependent effects on intertidal fish decision-making

Artificial Light at Night (ALAN) alters cycles of day and night, potentially modifying species' behavior. We assessed whether exposure to ALAN influences decision-making (directional swimming) in an intertidal rockfish (Girella laevisifrons) from the Southeastern Pacific. Using a Y-maze, we examined if exposure to ALAN or natural day/night conditions for one week affected the number of visits and time spent in three Y-maze compartments: dark and lit arms (“safe” and “risky” conditions, respectively) and a neutral “non-decision” area. The results showed that fish maintained in natural day/night conditions visited and spent more time in the dark arm, regardless of size. Instead, fish exposed to ALAN visited and spent more time in the non-decision area and their response was size-dependent. Hence, prior ALAN exposure seemed to disorient or reduce the ability of rock fish to choose dark conditions, deemed the safest for small fish facing predators or other potential threats.

Sleep, oscillations, and epilepsy.

Sleep and wake are defined through physiological and behavioral criteria and can be typically separated into non-rapid eye movement (NREM) sleep stages N1, N2, and N3, rapid eye movement (REM) sleep, and wake. Sleep and wake states are not homogenous in time. Their properties vary during the night and day cycle. Given that brain activity changes as a function of NREM, REM, and wake during the night and day cycle, are seizures more likely to occur during NREM, REM, or wake at a specific time? More generally, what is the relationship between sleep-wake cycles and epilepsy? We will review specific examples from clinical data and results from experimental models, focusing on the diversity and heterogeneity of these relationships. We will use a top-down approach, starting with the general architecture of sleep, followed by oscillatory activities, and ending with ionic correlates selected for illustrative purposes, with respect to seizures and interictal spikes. The picture that emerges is that of complexity; sleep disruption and pathological epileptic activities emerge from reorganized circuits. That different circuit alterations can occur across patients and models may explain why sleep alterations and the timing of seizures during the sleep-wake cycle are patient-specific.

Altered transposable elements expression and gene networks remodeling precede disruptions in sleep/wake cycles in a tauopathy mouse model of AD

AbstractBackgroundAlzheimer’s Disease (AD) is an widespread neurodegenerative disorder, common in elder and Veterans communities, culminating in dementia with non‐cognitive behavioral and metabolic symptoms, such as hyperactivity and altered sleep/wake patterns. In demented patients, sleep/wake cycle disruptions facilitate weight loss, which is associated with adverse outcomes like accelerated AD progression and higher institutionalization. Tg4510 mice, which express a P301L mutant variant of human tau, develop both cognitive and non‐cognitive symptoms. Several mouse models of tau deposition, including Tg4510 mice, also have negative energy balance. To identify early factors affecting AD, we measured locomotor, sleep/wake patterns in vivo, and analyzed RNA‐seq data from Tg4510 mice to identify gene and transposable elements (TE) expression changes involved in behavioral derangements in AD.MethodLocomotor activity, sleep and wake intervals and patterns were measured using in vivo metabolic cages for two weeks over 24 hr and day and night cycles from Tg4510 mice (n = 5‐7) vs. controls (n = 7‐10) before and after the onset of tauopathy (at 2 and 7 months of age respectively). In additional experiments, we analyzed RNA‐seq from hippocampi of Tg4510 mice (n = 5) vs. controls (n = 6). Using our established TTESA bioinformatics pipeline, reads were aligned to reference genome and expression of genes or TEs was measured with featureCounts. Pathway enrichment analysis using Visual Annotation Display was used to discover common functional and disease pathways using Gene Ontology, Protein Ontology, and Mammalian Phenotype Ontology.ResultWe observed altered locomotor and sleep patterns during the night phase starting in young Tg4510 vs. controls. TTESA results detected the majority of significantly differentially expressed TEs were retrotransposons (70%), which consisted mainly of long terminal repeats (LTRs; 70%) and some LINE retroelements (30%) and SINEs (<8%) in transgenic mice. VLaD pathway analysis revealed several biological processes upregulated in transgenic mice, including non‐cognitive behavioral pathways were downregulated, such as the regulation of circadian sleep/wake cycle with changes in the expression levels of Per2, Per3 (p<0.0001).ConclusionEarly dysregulation of TEs may be involved in rewiring gene expression networks underlying behavioral changes in wake and sleep cycles and other circadian patterns of behavior in this humanized mouse model of AD.

First report of a Panax notoginseng leaf disease caused by Alternaria alternata in China.

Panax notoginseng (Burk.) F. H. Chen is a perennial plant species in the family Araliaceae, and its roots and rhizome are precious materials for the production of traditional Chinese medicine. From April to June, 2018, new disease symptoms were detected on the mature leaves of 2- and 3-year-old Panax notoginseng (P. notoginseng) in Wenshan Autonomous Prefecture, Yunnan Province, China, and the disease incidence was about 10%-15% among the analyzed fields (3.6 ha, 23°49'46.99″ N, 104°06'12.99″ E, 1,631 m elevation). The diseased leaves had dark brown necrotic lesions (0.9-2.5 × 1.0-3.5 cm) and curled downward. As the disease progressed, the necrosis gradually spread along the vein to other leaf parts, eventually covering the whole leaf. In the late disease stage, the whole leaf was decayed and yellowed. For pathogen isolation, infected leaves (n=20) were surface sterilized in 1% sodium hypochlorite and washed with sterilized distilled water for 3 mins before being cut into smaller pieces (~1cm2), then placed onto potato dextrose agar (PDA) medium and incubated at 28°C under aseptic conditions for 3 days. The hypha around leaf discs were transferred onto the new PDA. A total of 20 colonies (SQ1~20) were obtained and purified by single spore culture for morphological characterization and molecular biological identification. The colonies of all isolates were nearly round, grayish white at the initial stage, and then turned to grayish brown. In addition, microscopic examination (100× magnification) of 20 isolates revealed dark, septate, and sparsely branched conidiophores as well as dark brown conidia with short conical beaks at their tip. Additionally, conidia (solitary or in short chains) were typically oval or club-shaped and had 0-2 longitudinal septa and 2-4 transverse septa (20-35 × 8-12 μm) (n = 50). Moreover, the conidia had a smooth or verrucose surface. Their morphological characteristics were similar to those descriptions given for members of section Alternaria by Lawrence et al. (2016). In order to further identify pathogenic species, genomic DNA was extracted from the colonies (SQ1~20) using a modified cetyltrimethylammonium bromide (CTAB) method (Loganathan et al. 2014). The sequences of internal transcribed spacer regions of ribosomal DNA (rDNA ITS) and partial RNA polymerase II second subunit gene (RPB2) were amplified by PCR using fungal universal primers ITS1/ITS4 (White et al. 1990) and fRPB2-5F/fRPB2-7cR (Liu et al. 1999), respectively. The DNA sequencing shows that ITS sequences from 20 isolates were totally same, and so did the RPB2 sequences (supplementary material). BLASTN analysis of NCBI database indicated that the RPB2 and ITS sequences have the highest nucleotide homology to A. Alternata ITS (MW008974) and RPB2 (LC132700), respectively. These two gene sequences were submitted to GenBank [Accession numbers ON075466 (ITS) and OP572232 (RPB2)]. Phylogenetic trees based on the combined ITS and RPB2 sequences were constructed by maximum parsimony method. The referenced ITS and RPB2 sequences of Alternaria were from three published articles (Rama et al. 2020; Sun et al. 2021; Wee et al. 2006). Phylogenetic analysis revealed that this isolate was clustered with A. alternata. Therefore, the morphology-based preliminary identification was verified by the phylogenetic analysis, and the isolate from diseased P. notoginseng leaves was A. alternata. To confirm its pathogenicity, the fungal isolate was assessed with 40 1-year-old healthy P. notoginseng plants in a greenhouse. Among them, the leaves of 20 of P. notoginseng plants were wounded using a sterile needle (seven or eight wounds per leaf) and then inoculated with 1mL conidial suspension (1 × 106 conidia/mL) prepared from 7-day-old fungal cultures grown on PDA medium. The inoculated plants were covered with plastic bags at 25°C for 24 h to maintain humidity, and then transferred to the greenhouse maintained at 28°C with a 16-h day/8-h night cycle and continuous misting. The other 20 control plants were only wounded and sprayed with sterile water. Typical necrotic lesions were detected on all of the inoculated P. notoginseng leaves cultivated in the greenhouse for 1 week post-inoculation. As the disease continued to develop, the necrotic lesions enlarged, and the infected leaves turned yellow and withered. These symptoms were similar to those observed on the naturally infected P. notoginseng. In contrast, the mock-inoculated control plants remained healthy. Furthermore, the fungus re-isolated from the infected P. notoginseng leaves in the pot experiment had similar morphological characteristics as the original strain. In addition, its genomic DNA was extracted for PCR analysis of ITS and RPB2 sequences, and the following DNA sequencing shows that the two DNA sequences were same as those of isolates SQ1~20, which confirmed that the re-isolated fungus was A. alternata. To the best of our knowledge, this is the first report of A. alternata causing a P. notoginseng leaf disease in China.

Sandman Send Me a Dream: Case of Non-24-Hour Sleep-Wake Disorder in a Sighted Pediatric Patient (P11-9.005)

<h3>Objective:</h3> Non-24-hour sleep-wake disorder (N24SWD) is a circadian rhythm disorder that leads to the inability to consistently sync the sleep wake (SW) pattern to the 24 hour day night cycle. Patients with N24SWD have progressively delayed SW patterns that occur in a cyclic fashion leading to significant interruptions to daily life. N24SWD is most commonly observed in non-sighted individuals impacting an estimated 50% of that population. It is exceedingly rare in patients with sight, with the first published case in 1971. Furthermore, this is even rarer, if ever, previously described in the pediatric population. <h3>Background:</h3> A 12-year-old male was referred for excessive daytime sleepiness and abnormal sleeping patterns. His bedtime is progressively more delayed each day. During periods of unrestricted sleep, sleep onset delays 2–3 hours each night, with a sleep latency of about 30 minutes and 8–10 hours of sleep duration. Return to a normal bedtime of 9:00pm occurs every 7–10 days. There was no other significant sleep history. He denies sleep paralysis, hypnogogic and hypnopompic hallucinations, and snoring. Melatonin had inconsistent success and adverse effects. The patient’s neurological examination was unremarkable. <h3>Design/Methods:</h3> NA <h3>Results:</h3> Actigraphy confirmed the diagnosis of N24SWD demonstrating cycling of SW when allowed a free sleep schedule. Brain MRI without contrast was unremarkable. The patient was initiated on tasimelteon which led to significant improvements in his ability to maintain a consistent bedtime. <h3>Conclusions:</h3> This case demonstrates that not only can N24SWD occur in sighted individuals, but it can certainly be present in the sighted pediatric population. If not identified, it can lead to long term effects on a child’s life, affecting their development and education. This case also demonstrated the benefits of selective melatonin agonists in the treatment of this condition. <b>Disclosure:</b> Dr. Hart has nothing to disclose. Dr. Smith has nothing to disclose. Dr. Morse has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for Jazz Pharmaceuticals. Dr. Morse has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for Avadel. Dr. Morse has received personal compensation in the range of $10,000-$49,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Jazz Pharmaceuticals. Dr. Morse has received personal compensation in the range of $10,000-$49,999 for serving on a Speakers Bureau for Jazz Pharmaceuticals. Dr. Morse has received personal compensation in the range of $50,000-$99,999 for serving as an Expert Witness for Hayes solicitors. The institution of Dr. Morse has received research support from NIH.

Modeling the Circadian Control of the Cell Cycle and Its Consequences for Cancer Chronotherapy.

The mammalian cell cycle is governed by a network of cyclin/Cdk complexes which signal the progression into the successive phases of the cell division cycle. Once coupled to the circadian clock, this network produces oscillations with a 24 h period such that the progression into each phase of the cell cycle is synchronized to the day-night cycle. Here, we use a computational model for the circadian clock control of the cell cycle to investigate the entrainment in a population of cells characterized by some variability in the kinetic parameters. Our numerical simulations showed that successful entrainment and synchronization are only possible with a sufficient circadian amplitude and an autonomous period close to 24 h. Cellular heterogeneity, however, introduces some variability in the entrainment phase of the cells. Many cancer cells have a disrupted clock or compromised clock control. In these conditions, the cell cycle runs independently of the circadian clock, leading to a lack of synchronization of cancer cells. When the coupling is weak, entrainment is largely impacted, but cells maintain a tendency to divide at specific times of day. These differential entrainment features between healthy and cancer cells can be exploited to optimize the timing of anti-cancer drug administration in order to minimize their toxicity and to maximize their efficacy. We then used our model to simulate such chronotherapeutic treatments and to predict the optimal timing for anti-cancer drugs targeting specific phases of the cell cycle. Although qualitative, the model highlights the need to better characterize cellular heterogeneity and synchronization in cell populations as well as their consequences for circadian entrainment in order to design successful chronopharmacological protocols.

The Complex Effects of Light on Metabolism in Humans.

Light is an essential part of many life forms. The natural light-dark cycle has been the dominant stimulus for circadian rhythms throughout human evolution. Artificial light has restructured human activity and provided opportunities to extend the day without reliance on natural day-night cycles. The increase in light exposure at unwanted times or a reduced dynamic range of light between the daytime and nighttime has introduced negative consequences for human health. Light exposure is closely linked to sleep-wake regulation, activity and eating patterns, body temperature, and energy metabolism. Disruptions to these areas due to light are linked to metabolic abnormalities such as an increased risk of obesity and diabetes. Research has revealed that various properties of light influence metabolism. This review will highlight the complex role of light in human physiology, with a specific emphasis on metabolic regulation from the perspective of four main properties of light (intensity, duration, timing of exposure, and wavelength). We also discuss the potential influence of the key circadian hormone melatonin on sleep and metabolic physiology. We explore the relationship between light and metabolism through circadian physiology in various populations to understand the optimal use of light to mitigate short and long-term health consequences.

Light, rather than circadian rhythm, regulates gas exchange in ferns and lycophytes.

Circadian regulation plays a vital role in optimizing plant responses to the environment. However, while circadian regulation has been extensively studied in angiosperms, very little is known for lycophytes and ferns, leaving a gap in our understanding of the evolution of circadian rhythms across the plant kingdom. Here, we investigated circadian regulation in gas exchange through stomatal conductance and photosynthetic efficiency in a phylogenetically broad panel of 21 species of lycophytes and ferns over a 46 h period under constant light and a selected few under more natural conditions with day-night cycles. No rhythm was detected under constant light for either lycophytes or ferns, except for two semi-aquatic species of the family Marsileaceae (Marsilea azorica and Regnellidium diphyllum), which showed rhythms in stomatal conductance. Furthermore, these results indicated the presence of a light-driven stomatal control for ferns and lycophytes, with a possible passive fine-tuning through leaf water status adjustments. These findings support previous evidence for the fundamentally different regulation of gas exchange in lycophytes and ferns compared to angiosperms, and they suggest the presence of alternative stomatal regulations in Marsileaceae, an aquatic family already well known for numerous other distinctive physiological traits. Overall, our study provides evidence for heterogeneous circadian regulation across plant lineages, highlighting the importance of broad taxonomic scope in comparative plant physiology studies.

Root exudation of carbon and nitrogen compounds varies over the day-night cycle in pea: The role of diurnal changes in internal pools.

Rhizodeposition is the export of organic compounds from plant roots to the soil. Carbon allocation towards rhizodeposition has to be balanced with allocation for other physiological functions, which depend on both newly assimilated and stored nonstructural carbohydrate (NSC). To test whether the exudation of primary metabolites scales with plant NSC status, we studied diurnal dynamics of NSC and amino acid (AA) pools and fluxes within the plant and the rhizosphere. These diurnal dynamics were measured in the field and under hydroponic-controlled conditions. Further, C-limiting treatments offered further insight into the regulation of rhizodeposition. The exudation of primary metabolites fluctuated diurnally. The diurnal dynamics of soluble sugars (SS) and AA concentrations in tissues coincided with exudate pool fluctuations in the rhizosphere. SS and AA pools in the rhizosphere increased with NSC and AA pools in the roots. C starvation treatments offset the balance of exudates: AA exudate content in the rhizosphere significantly decreased while SS exudate content remained stable. Our results suggest that rhizodeposition is to some extent controlled by plant C:N status. We propose that SS exudation is less controlled than AA exudation because N assimilation depends on controlled C supply while SS exudation relies to a greater extent on passive diffusion mechanisms.

Limits of entrainment of circadian neuronal networks.

Circadian rhythmicity lies at the center of various important physiological and behavioral processes in mammals, such as sleep, metabolism, homeostasis, mood changes, and more. Misalignment of intrinsic neuronal oscillations with the external day-night cycle can disrupt such processes and lead to numerous disorders. In this work, we computationally determine the limits of circadian synchronization to external light signals of different frequency, duty cycle, and simulated amplitude. Instead of modeling circadian dynamics with generic oscillator models (e.g., Kuramoto-type), we use a detailed computational neuroscience model, which integrates biomolecular dynamics, neuronal electrophysiology, and network effects. This allows us to investigate the effect of small drug molecules, such as Longdaysin, and connect our results with experimental findings. To combat the high dimensionality of such a detailed model, we employ a matrix-free approach, while our entire algorithmic pipeline enables numerical continuation and construction of bifurcation diagrams using only direct simulation. We, thus, computationally explore the effect of heterogeneity in the circadian neuronal network, as well as the effect of the corrective therapeutic intervention of Longdaysin. Last, we employ unsupervised learning to construct a data-driven embedding space for representing neuronal heterogeneity.

Optimizing solar energy utilization and energy efficiency through thermal energy storage with phase change materials in a solar water heating system

Solar energy (SE) is non-polluting and sustainable. However, the strength of the sun’s rays shifts as the seasons change, the weather shifts, and the day and night cycles. It is possible to store energy as heat, which can then be used for a variety of applications in the future. The primary objective of this research was to extend the time that high water temperature (HWT) was maintained by using phase change materials (PCM) to reduce energy consumption. To test the efficacy of an FPSWHS using 18 % (63 kg) of PCM condensed paraffin wax of type RT42, an experimental rig was constructed. To further expand PCM surface area and speed up charging and discharging, 18 aluminium cylinders were employed. Given the varying weather patterns in the India, this research was also useful in settling on a suitable PCM for SWHS. At 60°C input temperature of water (Tin) and 0.11 kg.s-1 flow rate of mass in water (mw), including RT42 into a water-PCM storage tank reduced power consumption by as much as 5.75 kWh, for a total system energy consumption of 31.4 kWh. The results showed a 27 % drop in daily average carbon footprint and a 27 % increase in overall system efficiency.

The Cycle of Night and Day In The Ball and the Cross by G. K. Chesterton

Part of Chesterton’s imagery that he often employs in his writing is the motif of light and darkness, which in The Ball and the Cross takes the form of the cycle of night and day. This cycle dictates a specific rhythm, which rules over both the ongoing duel and other events. Thus, the evening and night time is rather reserved for considerable and profound insights, found in, for instance, the opening and closing scenes and in all the events that reflect or decide about the characters’ spiritual growth. The day time seems to contribute more to the development of the protagonists’ relationship with each other and the world around.

Perceiving "Complex Autonomous Systems" in Symmetry Dynamics: Elementary Coordination Embedding in Circadian Cycles.

This study explored the biological autonomy and control of function in circumstances that assessed the presumed relationship of an organism with an environmental cycle. An understanding of this behavior appeals to the organism-environment system rather than just the organism. Therefore, we sought to uncover the laws underlying end-directed capabilities by measuring biological characteristics (motor synchrony) in an environmental cycle (circadian temperature). We found that the typical elementary coordination (bimanual) stability measure varied significantly as a function of the day-night temperature cycle. While circadian effects under artificially manipulated temperatures were not straightforward during the day-night temperature cycle, the circadian effect divided by the ordinary circadian rhythm remained constant during the day-night cycle. Our observation of this direct, robust relationship between the biological characteristics (body temperature and motor synchrony) and environmental processes (circadian temperature cycle) could mirror the adaptation of our biological system to the environment.

Simultaneous photoautotrophic production of DHA and EPA by Tisochrysis lutea and Microchloropsis salina in co-culture

Marine microalgae have received much attention as a sustainable source of the two health beneficial omega-3-fatty acids docosahexaenoic acid (DHA, C22:6) and eicosapentaenoic acid (EPA, C20:5). However, photoautotrophic monocultures of microalgae can only produce either DHA or EPA enriched biomass. An alternative may be the photoautotrophic co-cultivation of Tisochrysis lutea as DHA-producer with Microchloropsis salina for simultaneous EPA production to obtain EPA- and DHA-rich microalgae biomass in a nutritionally balanced ratio. Photoautotrophic co-cultivation processes of T. lutea and M. salina were studied, applying scalable and fully controlled lab-scale gas-lift flat-plate photobioreactors with LED illumination for dynamic climate simulation of a repeated sunny summer day in Australia [day–night cycles of incident light (PAR) and temperature]. Monocultures of both marine microalgae were used as reference batch processes. Differences in the autofluorescence of both microalgae enabled the individual measurement, of cell distributions in co-culture, by flow cytometry. The co-cultivation of T. lutea and M. salina in artificial sea water with an inoculation ratio of 1:3 resulted in a balanced biomass production of both microalgae simultaneously with a DHA:EPA ratio of almost 1:1 (26 mgDHA gCDW−1, and 23 mgEPA gCDW−1, respectively) at harvest after depletion of the initially added fertilizer. Surprisingly, more microalgae biomass was produced within 8 days in co-cultivation with an increase in the cell dry weight (CDW) concentration by 31%, compared to the monocultures with the same amount of light and fertilizer. What is more, DHA-content of the microalgae biomass was enhanced by 33% in the co-culture, whereas EPA-content remained unchanged compared to the monocultures.Graphical

The two-process model for sleep–wake regulation: A nonsmooth dynamics perspective

Since its inception four decades ago the two-process model introduced by Borbély has provided the conceptual framework to explain sleep–wake regulation across many species, including humans. At its core, high level notions of circadian and homeostatic processes are modelled with a low dimensional description in the form of a one dimensional nonautonomous and nonsmooth flow, with the rate of change of homeostatic sleep pressure switching at specific times. These events in time can be described by an implicit map from one switching time to another and have given rise to an elegant mathematical description of periodic orbits and their instabilities using the theory of iterated maps. In this paper we show that an equivalent description can be obtained from a direct analysis of the underlying nonsmooth flow. We further show how to construct the Lyapunov exponent of the nonsmooth flow and use this to uncover a more detailed picture of the Arnol’d tongue structure of the model.Given the growing interest in studying networks of sleepers, where interactions may occur continuously throughout the day–night cycle and not just at event times, we advocate for the future use of techniques from nonsmooth dynamical systems in studying networks of the two-process model.

Phytochromes and Their Role in Diurnal Variations of ROS Metabolism and Plant Proteome.

Plants are sessile organisms forced to adapt to environmental variations recurring in a day-night cycle. Extensive research has uncovered the transcriptional control of plants' inner clock and has revealed at least some part of the intricate and elaborate regulatory mechanisms that govern plant diel responses and provide adaptation to the ever-changing environment. Here, we analyzed the proteome of the Arabidopsis thaliana mutant genotypes collected in the middle of the day and the middle of the night, including four mutants in the phytochrome (phyA, phyB, phyC, and phyD) and the circadian clock protein LHY. Our approach provided a novel insight into the diel regulations, identifying 640 significant changes in the night-day protein abundance. The comparison with previous studies confirmed that a large portion of identified proteins was a known target of diurnal regulation. However, more than 300 were novel oscillations hidden under standard growth chamber conditions or not manifested in the wild type. Our results indicated a prominent role for ROS metabolism and phytohormone cytokinin in the observed regulations, and the consecutive analyses confirmed that. The cytokinin signaling significantly increased at night, and in the mutants, the hydrogen peroxide content was lower, and the night-day variation seemed to be lost in the phyD genotype. Furthermore, regulations in the lhy and phyB mutants were partially similar to those found in the catalase mutant cat2, indicating shared ROS-mediated signaling pathways. Our data also shed light on the role of the relatively poorly characterized Phytochrome D, pointing to its connection to glutathione metabolism and the regulation of glutathione S-transferases.