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Improving the synchronization between the pattern of milk synthesis and nutrient availability throughout the day could enhance production efficiency. In this study, we evaluated the effects of changing feed delivery time on milk production, feeding behavior, and the daily rhythms of blood biomarkers. Eight multiparous Holstein cows housed in a tie-stall barn with controlled environmental conditions were enrolled in a crossover experimental design with three periods of 14 days and three treatments each. Cows were milked twice daily (0530 and 1730 h) and were individually fed with two equal meals of forage and eight equal meals of concentrate during the day. Forage meals were provided at 12-hour intervals either: (i) 5 h before each milking (0030 and 1230 h; BM), (ii) at the end of each milking (0530 and 1730 h; ME), (iii) or 2 h after (0730 and 1930 h; AM). Feed intake and feeding behavior were monitored, and milk production and composition were measured. Blood samples were collected every 4 days at 0700 h and, during the last day of each period, 15 times daily to determine metabolic profiles, hormones, and their daily rhythmicity by the cosinor analysis. Changing forage delivery time did not affect milk yield and dry matter intake. No difference was observed in feeding behavior when expressed relative to the first meal. There were no significant differences in milk component contents and yields. In samples collected at 0700 h, ME had reduced plasma calcium (Ca), magnesium (Mg), and potassium (K) and increased sodium (Na). AM had increased inflammation, as suggested by the greater blood globulin and ceruloplasmin. The patterns of metabolic biomarkers had limited variations when expressed relative to the first forage meal. Nevertheless, the daily rhythms of these biomarkers were remarkably different. Under our conditions, feeding forage meals to cows at different times of the day did not influence productive performance but highlighted the importance of considering the sampling time when interpreting metabolic profiles. [ABSTRACT FROM AUTHOR]

Ageing is an inherent and intricate biological process that takes place in living organisms as time progresses. It involves the decline of multiple physiological functions, leading to body structure and overall performance modifications. The ageing process differs among individuals and is influenced by various factors, including lifestyle, environment and genetic makeup. Metabolic changes and reduced locomotor activity are common hallmarks of ageing. Our study focuses on exploring these phenomena in prematurely ageing PolgA(D257A/D257A) mice (also known as PolgA) aged 41–42 weeks, as they closely mimic human ageing. We assess parameters such as oxygen consumption (VO2), carbon dioxide production (VCO2), respiratory exchange ratio (RER) and locomotor activity using a metabolic cage for 4 days and comparing them with age‐matched wild‐type littermates (WT). Our findings revealed that VO2, VCO2, RER, locomotor activities, water intake and feeding behaviour show a daily rhythm, aligning with roughly a 24‐h cycle. We observed that the RER was significantly increased in PolgA mice compared to WT mice during the night‐time of the light–dark cycle, suggesting a shift towards a higher reliance on carbohydrate metabolism due to more food intake during the active phase. Additionally, female PolgA mice displayed a distinct phenotype with reduced walking speed, walking distance, body weight and grip strength in comparison to male PolgA and WT mice, indicating an early sign of ageing. Taken together, our research highlights the impact of sex‐specific patterns on ageing traits in PolgA mice aged 41–42 weeks, which may be attributable to human ageing phenotypes. The unique genetic composition and accelerated ageing characteristics of PolgA mice make them invaluable in ageing studies, facilitating the investigation of underlying biological mechanisms and the identification of potential therapeutic targets for age‐related diseases. [ABSTRACT FROM AUTHOR]

Feeding habits of salmon are examined on the data from “Trophology” and “Zooplankton” databases for 1988–2023, taking into account calendar dates and spatial localiza tion of the salmon size classes. The dominant zooplankton species and groups in salmon food are defined and their availability in terms of time and depth of habitat is determined. Daily rhythm of salmon feeding is found uniform for all size groups. The areas and time (months) of maximum concentrations of salmon are determined, by size groups, and those ones are considered as the areas and periods of their most active consumption. A trophological calendar is constructed to show where, when, and what type of food is consumed by certain species and size group of salmon. Daily food rations are calculated for all salmon species and size groups. The rations are similar with those in the Bering Sea, with small differences possibly caused by different structure of the plankton communities. The application tables are compiled for operational calculations of total food consumption by size groups of salmon species with a predominant zooplankton prey (pink, chum and sockeye). According to the forecast published at VNIRO website vniro.ru, the salmon catch in the Far Eastern basin will decrease by more than 2 times in 2024, primarily due to pink salmon. In this case, significant reduction in salmon pressure on plankton community can be expected.

Ageing is an inherent and intricate biological process that takes place in living organisms as time progresses. It involves the decline of multiple physiological functions, leading to body structure and overall performance modifications. The ageing process differs among individuals and is influenced by various factors, including lifestyle, environment and genetic makeup. Metabolic changes and reduced locomotor activity are common hallmarks of ageing. Our study focuses on exploring these phenomena in prematurely ageing PolgA(D257A/D257A) mice (also known as PolgA) aged 41–42 weeks, as they closely mimic human ageing. We assess parameters such as oxygen consumption (VO2), carbon dioxide production (VCO2), respiratory exchange ratio (RER) and locomotor activity using a metabolic cage for 4 days and comparing them with age‐matched wild‐type littermates (WT). Our findings revealed that VO2, VCO2, RER, locomotor activities, water intake and feeding behaviour show a daily rhythm, aligning with roughly a 24‐h cycle. We observed that the RER was significantly increased in PolgA mice compared to WT mice during the night‐time of the light–dark cycle, suggesting a shift towards a higher reliance on carbohydrate metabolism due to more food intake during the active phase. Additionally, female PolgA mice displayed a distinct phenotype with reduced walking speed, walking distance, body weight and grip strength in comparison to male PolgA and WT mice, indicating an early sign of ageing. Taken together, our research highlights the impact of sex‐specific patterns on ageing traits in PolgA mice aged 41–42 weeks, which may be attributable to human ageing phenotypes. The unique genetic composition and accelerated ageing characteristics of PolgA mice make them invaluable in ageing studies, facilitating the investigation of underlying biological mechanisms and the identification of potential therapeutic targets for age‐related diseases.

The daily rhythm is a critical regulatory factor in fish growth and development, governing internal functions and organismal responses to environmental cues. This rhythm influences not only metabolism but also water quality parameters in recirculating aquaculture systems (RAS). However, research on the daily rhythm of hybrid groupers in RAS remains limited. Consequently, this study is aimed at investigating the metabolic daily rhythm of hybrid groupers in RAS and its impact on water quality. Feeding time was designated as the starting point for this investigation. Initially, we measured the levels of dissolved oxygen (DO), total ammonia nitrogen (TAN), and nitrite nitrogen (Nitrite-N) in the RAS. Subsequently, we assessed oxygen consumption rates (OCR), digestive enzyme activities, and the expression levels of metabolism-related genes in the pearl gentian grouper (Epinephelus lanceolatus♂ × Epinephelus fuscoguttatus♀). Finally, we conducted a comprehensive analysis of these factors. The results indicated that DO was negatively correlated with OCR, pepsin and lipase activities, and GK gene expression. TAN exhibited a positive correlation with OCR and the expression levels of the target of rapamycin (TOR) gene. Similarly, Nitrite-N showed a positive correlation with OCR and TOR gene expression levels. We also speculated on the internal relationship between fish daily rhythms and water quality parameters, noting a certain degree of synchronicity. These findings can minimize stress on fish, and it can contribute to optimizing RAS performance through management adjustments. [ABSTRACT FROM AUTHOR]

Introduction: Animal welfare in aquaculture is becoming increasingly important, and detailed knowledge of the species concerned is essential for further optimization on farms. Every organism is controlled by an internal clock, the circadian rhythm, which is crucial for metabolic processes and is partially influenced by abiotic factors, making it important for aquaculture practices. Objective: In order to determine the circadian rhythm of adult turbot (Scophthalmus maximus), blood samples were collected over a 24-h period and plasma metabolite profiles were analyzed by 1H-NMR spectroscopy. Methods: The fish were habituated to feeding times at 9 am and 3 pm and with the NMR spectroscopy 46 metabolites could be identified, eight of which appeared to shift throughout the day. Results: We noted exceptionally high values around 3 pm for the amino acids isoleucine, leucine, valine, phenylalanine, lysine, and the stress indicator lactate. These metabolic peaks were interpreted as either habituation to the usual feeding time or as natural peak levels in turbot in a 24-h circle because other indicators for stress (glucose, cortisol and lysozymes) showed a stable baseline, indicating that the animals had no or very little stress during the experimental period. Conclusion: This study provides initial insights into the diurnal variation of metabolites in adult turbot; however, further studies are needed to confirm present findings of possible fluctuations in amino acids and sugars. Implementing optimized feeding times (with high levels of sugars and low levels of stress metabolites) could lead to less stress, fewer disease outbreaks and overall improved fish welfare in aquaculture facilities. [ABSTRACT FROM AUTHOR]

Improving the synchronization between the pattern of milk synthesis and nutrient availability throughout the day could enhance production efficiency. In this study, we evaluated the effects of changing feed delivery time on milk production, feeding behavior, and the daily rhythms of blood biomarkers. Eight multiparous Holstein cows housed in a tie-stall barn with controlled environmental conditions were enrolled in a crossover experimental design with three periods of 14 days and three treatments each. Cows were milked twice daily (0530 and 1730 h) and were individually fed with two equal meals of forage and eight equal meals of concentrate during the day. Forage meals were provided at 12-hour intervals either: (i) 5 h before each milking (0030 and 1230 h; BM), (ii) at the end of each milking (0530 and 1730 h; ME), (iii) or 2 h after (0730 and 1930 h; AM). Feed intake and feeding behavior were monitored, and milk production and composition were measured. Blood samples were collected every 4 days at 0700 h and, during the last day of each period, 15 times daily to determine metabolic profiles, hormones, and their daily rhythmicity by the cosinor analysis. Changing forage delivery time did not affect milk yield and dry matter intake. No difference was observed in feeding behavior when expressed relative to the first meal. There were no significant differences in milk component contents and yields. In samples collected at 0700 h, ME had reduced plasma calcium (Ca), magnesium (Mg), and potassium (K) and increased sodium (Na). AM had increased inflammation, as suggested by the greater blood globulin and ceruloplasmin. The patterns of metabolic biomarkers had limited variations when expressed relative to the first forage meal. Nevertheless, the daily rhythms of these biomarkers were remarkably different. Under our conditions, feeding forage meals to cows at different times of the day did not influence productive performance but highlighted the importance of considering the sampling time when interpreting metabolic profiles.

Dogs are the common pets adopted by humans, and their circadian behavior and physiology are influenced by human habits. In many families, there is a change of lifestyle with respect to the natural daylight (NDL) cycle. Exposure to constant light disrupts some central and peripheral circadian rhythms. The aim of the present study was to improve the knowledge about the circadian changes of clock components in the peripheral blood in dogs housed under NDL and constant light (LL) conditions. Blood samples were collected on five female Beagle dogs (2 years old, 14 ± 0.5 kg) every 4 hours for a 24-hour period during an NDL (Sunrise 05:05 h – Sunset 20:55 h) and 24-hour period of constant light (LL). Blood samples were stored in a PAX gene Blood RNA Tube, real-time RT-quantitative polymerase chain reaction was performed to determine Clock, Per1–3, and Cry1–2 gene expression. During the NDL, all genes investigated showed robust diurnal daily rhythmicity. During the constant light, only Clock maintained its daily rhythmicity. Clock acrophase was observed close to sunrise (ZT 0) and was statistically different from the other clock genes except for Per3. Per3 daily oscillations were not statistically significant. No differences were observed among the clock genes tested in the amplitude and robustness values. Our results can be considered preliminary data to provide new insights into the adaptation mechanism of the canine peripheral circadian clock. The persistence of Clock gene expression during the LL indicated the presence of an endogenously generated signal in blood. Because peripheral blood is an easily accessible sample in dogs, the analysis of clock gene expression in this tissue could be useful to investigate the adaptive capacity of this species housed in different environmental conditions linked to the owner's lifestyle. [ABSTRACT FROM AUTHOR]

The circadian clock regulates the behavior, physiology, and metabolism of mammals, and these characteristics, such as sleep-wake cycles, exercise capacity, and hormone levels, exhibit circadian rhythms. Light signaling is the main stimulator of the mammalian circadian system. The photoperiod regulates the reproductive cycle of seasonal breeding animals, and the circadian clock plays a pivotal role in this process. However, the role of the clock in coordinating animal behavior and physiology in response to photoperiodic changes needs further investigation. The present study investigated the changes and correlation of behavioral activities, physiological indicators, and gene expression in female striped hamsters (Cricetulus barabensis) within 24 h under a 12L:12D photoperiod. We found that the daily rhythms of sleep-wake and open field were significant in hamsters. The expression of clock genes, melatonin receptor genes, and genes involved in general metabolism oscillated significantly in central and peripheral tissues (brain, hypothalamus, liver, ovary, and thymus) and was significantly associated with behavior and physiology. Our results revealed that the neuroendocrine system regulated the rhythmicity of behavior and physiology, and central and peripheral clock genes (Bmal1, Clock, Per1, Per2, Cry1, and Cry2), melatonin receptor genes (MT1, MT2, and GPR50), and metabolizing genes (SIRT1, FGF21, and PPARa) played important roles. Our results suggest that central and peripheral circadian clocks, melatonin receptors, and genes involved in general metabolism may play key roles in maintaining circadian behavior and metabolic homeostasis in striped hamsters. Our results may have important implication for rodent pest control. [ABSTRACT FROM AUTHOR]

BACKGROUND: Vibrational signal plays a crucial role in courtship communication in many insects. However, it remains unclear whether insect vibrational signals exhibit daily rhythmicity in response to changes in environmental cues. RESULTS: In this study, we observed daily rhythms of both female vibrational signals (FVS) and male vibrational signals (MVS) in the brown planthopper (BPH), Nilaparvata lugens (Stål), one of the most notorious rice pests across Asia. Notably, oscillations of FVS and MVS in paired BPHs were synchronized as part of male–female duetting interactions, displaying significant day‐night rhythmicity. Furthermore, we observed light dependency of FVS emissions under different photoperiodic regimes (18 L:6 D and 6 L:18 D) and illumination intensity levels (>300 lx, 50 lx, and 25 lx). Subsequently, the potential role of circadian clock genes cryptochromes (Nlcry1 and Nlcry2) in regulating FVS daily oscillations was examined using gene knockdown via RNA interference. We observed sharp declines and disrupted rhythms in FVS frequencies when either of the Nlcrys was downregulated, with Nlcry2 knockdown showing a more prominent effect. Moreover, we recorded a novel FVS variant (with a dominant frequency of 361.76 ± 4.31 Hz) emitted by dsNlcry1‐treated BPH females, which significantly diminished the impact of courtship stimuli on receptive males. CONCLUSION: We observed light‐dependent daily rhythms of substrate‐borne vibrational signals (SBVS) in BPH and demonstrated essential yet distinct roles of the two Nlcrys. These findings enhanced our understanding of insect SBVS and illustrated the potential of novel precision physical control strategies for disrupting mating behaviors in this rice pest. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

ABSTRACT: Milk synthesis exhibits a daily rhythm that is modified by the timing of feed intake. However, it is unknown how specific nutrients entrain this daily rhythm. Amino acids have an important role in milk synthesis, and may have a role in entrainment of mammary circadian rhythms. The objective of this study was to determine the effects of intestinally absorbed protein on daily rhythms of milk and milk component synthesis and key plasma hormones and metabolites. Nine lactating Holstein cows were assigned to 1 of 3 treatment sequences in a 3 × 3 Latin square. Treatments included abomasal infusions of 500 g/d of sodium caseinate either continuously throughout the day (CON), for 8 h/d from 0900 to 1700 h (DAY), or for 8 h/d from 2100 to 0500 h (NGT). Cows were milked every 6 h during the final 8 d of each period. A 24-h rhythm was fit to data using cosine analysis and the amplitude and acrophase were determined. Night infusion of protein decreased the daily milk yield and milk protein yield by 8.2% and 9.2%, respectively. Milk fat yield was increased 5.5% by DAY and milk fat concentration was increased 8.8% by NGT. Milk yield exhibited a daily rhythm in all treatments, with NGT increasing the amplitude of the daily rhythm 33% compared with CON. Milk fat concentration fit a daily rhythm in CON and NGT, but not DAY, whereas milk protein concentration fit a daily rhythm in CON and DAY, but not NGT. Moreover, DAY abolished the daily rhythm of plasma glucose concentration, but induced rhythms of plasma insulin and nonesterified fatty acid concentrations. Results suggest that feeding increased protein levels during the early part of the day may increase milk fat yield and modify energy metabolism through increased daily variation in insulin-stimulated lipid release, but additional research focused on feeding multiple diets across the day is required.

Artificial light at night (ALAN) constitutes a growing threat to coastal ecosystems by altering natural light cycles, which could impair organisms' biological rhythms, with resulting physiological and ecological consequences. Coastal ecosystems are strongly exposed to ALAN, but its effects on coastal organisms are poorly studied. Besides ALAN's intensity, ALAN's quality exposure may change the impacts on organisms. This study aims to characterize the effects of different ALAN's spectral compositions (monochromatic wavelength lights in red (peak at 626 nm), green (peak at 515 nm), blue (peak at 467 nm), and white (410–680 nm) light) at low and realistic intensity (1 lx) on the oyster Crassostrea gigas daily rhythm. Results reveal that all ALAN's treatments affect the oysters' daily valve activity rhythm in different manners and the overall expression of the 13 studied genes. Eight of these genes are involved in the oyster's circadian clock, 2 are clock-associated genes, and 3 are light perception genes. The blue light has the most important effects on oysters' valve behavior and clock and clock-associated gene expression. Interestingly, red and green lights also show significant impacts on the daily rhythm, while the lowest impacts are shown with the green light. Finally, ALAN white light shows the same impact as the blue one in terms of loss of rhythmic oysters' percentage, but the chronobiological parameters of the remaining rhythmic oysters are less disrupted than when exposed to each of the monochromatic light's treatments alone. We conclude that ALAN's spectral composition does influence its effect on oysters' daily rhythm, which could give clues to limit physiological and ecological impacts on coastal environments. [ABSTRACT FROM AUTHOR]

The cricket Velarifictorus aspersus (Walker) (Orthoptera: Gryllidae) exhibits a wing dimorphism mediating two distinct life‐history strategies during early adulthood; long‐winged (LW) females mainly invest resources in flight, whereas short‐winged (SW) females invest more heavily in reproduction than LW females. To understand the relationships among juvenile hormone (JH), flight capacity, and energy accumulation, the daily rhythm of JH titer and flight activity, the concentrations of flight energy substances, and the influence of exogenous JH on flight activity and flight energy substances were investigated in V. aspersus. The results showed that the hemolymph JH titer exhibited a high‐amplitude daily rhythm in 5‐day‐old LW V. aspersus females, and the JH titer rose about 10× at 18:00 hours (6 h before lights off) and dropped to baseline levels after lights off. The females flew inactively (i.e., they floated in the air) from 14:00 to 19:00 hours during the light period, whereas they had a stronger flight capacity in the initial photophase and before lights out. The flight ability of LW females with 20 μg μL−1 JH treatments was significantly improved during periods of flight inactivity. After the peak JH titer, the concentrations of glycogen and trehalose in the flight muscles increased significantly. The LW females treated with JH during the inactive flight period had a significant increase in glycogen after 1 h and trehalose after 3 h. These results suggested that the high‐amplitude daily rhythm of the JH titer was correlated with accumulation of flight energy substance and flight capacity; that is, an elevated JH titer promoted the biosynthesis of flight energy substances, resulting in improvement of flight capacity. [ABSTRACT FROM AUTHOR]

Marine species exhibit a multitude of biological rhythms, in accordance with their complex ecosystem governed by sun, earth and moon trajectories. Because of the inclination of the earth's axis, the high Arctic ecosystem is characterized by several months of permanent illumination during the polar day. The persistence of biological rhythms in this photic context remains unclear. Yet, this information is crucial for the understanding of polar ecosystems functioning, as well as to predict the impact of future climate changes. Particularly, the impact of extreme photoperiods on recent invasive species remains largely unknown. Here, we investigate how environmental cycles shape the behavior of a re-emerging polar resident, the mussel Mytilus sp. during polar day (17 April to 26 August 2020; Svalbard, Ny-Ålesund, 78°56ʹ N, 11°56ʹ E). Our results show that in the high Arctic polar day, mussels' behavior is shaped by both the photoperiod and the diel sun trajectories above the horizon. In addition, mussels also exhibit tidal, semi-lunar, and lunar rhythms of valve opening amplitude. We argue that these rhythms may have ecosystems functioning implications, and that the mussels' ability to deal with drastic light regimes may explain their northward expansion and new resettlement in high Arctic. [ABSTRACT FROM AUTHOR]

Milk synthesis exhibits a daily rhythm that is modified by the timing of feed intake. However, it is unknown how specific nutrients entrain this daily rhythm. Amino acids have an important role in milk synthesis, and may have a role in entrainment of mammary circadian rhythms. The objective of this study was to determine the effects of intestinally absorbed protein on daily rhythms of milk and milk component synthesis and key plasma hormones and metabolites. Nine lactating Holstein cows were assigned to 1 of 3 treatment sequences in a 3 × 3 Latin square. Treatments included abomasal infusions of 500 g/d of sodium caseinate either continuously throughout the day (CON), for 8 h/d from 0900 to 1700 h (DAY), or for 8 h/d from 2100 to 0500 h (NGT). Cows were milked every 6 h during the final 8 d of each period. A 24-h rhythm was fit to data using cosine analysis and the amplitude and acrophase were determined. Night infusion of protein decreased the daily milk yield and milk protein yield by 8.2% and 9.2%, respectively. Milk fat yield was increased 5.5% by DAY and milk fat concentration was increased 8.8% by NGT. Milk yield exhibited a daily rhythm in all treatments, with NGT increasing the amplitude of the daily rhythm 33% compared with CON. Milk fat concentration fit a daily rhythm in CON and NGT, but not DAY, whereas milk protein concentration fit a daily rhythm in CON and DAY, but not NGT. Moreover, DAY abolished the daily rhythm of plasma glucose concentration, but induced rhythms of plasma insulin and nonesterified fatty acid concentrations. Results suggest that feeding increased protein levels during the early part of the day may increase milk fat yield and modify energy metabolism through increased daily variation in insulin-stimulated lipid release, but additional research focused on feeding multiple diets across the day is required. [ABSTRACT FROM AUTHOR]

Dynamic cerebral autoregulation (dCA) in healthy young adults displays a daily variation. Whether the rhythm exists in patients with stroke is unknown. We studied 28 stroke patients (age: 26–83 years, 7 females) within 48 hours after thrombolysis. dCA was assessed 54 times in these patients during supine rest (twice in 26 and once in 2 patients): 9 assessments between 0–9AM, 12 between 9AM–2PM, 20 between 2–7PM, and 13 between 7PM–12AM. To estimate dCA, phase shifts between spontaneous oscillations of cerebral blood flow velocity (CBFV) in the middle cerebral artery and arterial blood pressure (BP) were obtained in four frequency bands: <0.05 Hz, 0.05–0.1 Hz, 0.1–0.2 Hz, and >0.2 Hz. CBFV-BP phase shifts at <0.05 Hz were significantly larger between 2–7PM, suggesting better dCA, than those at other times (p < 0.0001), and the daily rhythm was consistent for stroke and non-stroke sides. No significant rhythms were observed at higher frequencies (all p > 0.2). All results were independent of age, sex, stroke type and severity, and other cardiovascular conditions. dCA after stroke showed a daily rhythm, leading to a better regulation of CBFV at <0.05 Hz during the afternoon. The finding may have implications for daily activity management of stroke patients. [ABSTRACT FROM AUTHOR]

Excessive Internet use is a health concern among higher education students leading to reduced academic performance and problems in everyday life. This study aimed to explore the relationship between health and problems of studying and daily rhythm caused by time spent online among students (n=3,050). A cross-sectional survey was carried out. The data were analyzed using descriptive and chi-square tests and logistic regression analyses. Findings indicated that one fifth of students reported having problems of studying and daily rhythm caused by time spent online. Psychological health symptoms such as anxiety (p<0.001) and physical health symptoms including lower back problems (p<0.001) were associated with these problems. According to the logistic regression analyses, problems of studying and daily rhythm caused by time spent online and higher amount of Internet use by time were associated with psychological and physical health symptoms. The findings suggest that problems of studying and daily rhythm and spending more time online are related to health symptoms among the students. The study's findings can be used from a prevention standpoint for early identification and further to identify the need for seeking professional treatment. [ABSTRACT FROM AUTHOR]

Adaptation of reproductive activity to environmental changes is essential for breeding success and offspring survival. In mammals, the reproductive system displays regular cycles of activation and inactivation which are synchronized with seasonal and/or daily rhythms in environmental factors, notably light intensity and duration. Thus, most species adapt their breeding activity along the year to ensure that birth and weaning of the offspring occur at a time when resources are optimal. Additionally, female reproductive activity is highest at the beginning of the active phase during the period of full oocyte maturation, in order to improve breeding success. In reproductive physiology, it is therefore fundamental to delineate how geophysical signals are integrated in the hypothalamo-pituitary-gonadal axis, notably by the neurons expressing gonadotropin releasing hormone (GnRH). Several neurochemicals have been reported to regulate GnRH neuronal activity, but recently two hypothalamic neuropeptides belonging to the superfamily of (Arg)(Phe)-amide peptides, RFRP-3 and kisspeptin, have emerged as critical for the integration of environmental cues within the reproductive axis. The goal of this review is to survey the current understanding of the role played by RFRP-3 in the temporal regulation of reproduction, and consider how its effect might combine with that of kisspeptin to improve the synchronization of reproduction to environmental challenges.

Parvalbumin‐positive neurons (PVs) are the main class of inhibitory neurons in the mammalian central nervous system. By examining diurnal changes in synaptic and neuronal activity of PVs in the supragranular layer of the mouse primary visual cortex (V1), we found that both PV input and output are modulated in a time‐ and sleep‐dependent manner throughout the 24‐h day. We first show that PV‐evoked inhibition is stronger by the end of the light cycle (ZT12) relative to the end of the dark cycle (ZT0), which is in line with the lower inhibitory input of PV neurons at ZT12 than at ZT0. Interestingly, PV inhibitory and excitatory synaptic transmission slowly oscillate in opposite directions during the light/dark cycle. Although excitatory synapses are predominantly regulated by experience, inhibitory synapses are regulated by sleep, via acetylcholine activating M1 receptors. Consistent with synaptic regulation of PVs, we further show in vivo that spontaneous PV activity displays daily rhythm mainly determined by visual experience, which negatively correlates with the activity cycle of surrounding pyramidal neurons and the dorsal lateral geniculate nucleus‐evoked responses in V1. These findings underscore the physiological significance of PV's daily modulation. Synopsis: Unveiling the modulatory mechanism of cortical parvalbumin‐positive neurons (PVs) in the mature mammalian brain is critical for understanding how cognitive function is regulated in normal and diseased brains. Here the behavior of PVs in area V1 of the mouse visual cortex is investigated ex vivo and in vivo and a circadian output is identified. The excitatory and inhibitory synaptic transmissions of PV neurons bidirectionally oscillate in opposite directions during the 24‐h day.Experience and sleep dominate the daily regulation of the excitatory and inhibitory synapses onto PV neurons, respectively.ACh mediates the daily regulation of PV inhibitory synaptic transmission via targeting the presynaptic M1Rs.In line with synaptic modulation of PVs, evoked PV output ex vivo and spontaneous PV activity in vivo are both altered at different times of the day.Functional oscillation of PVs negatively correlates with the spontaneous activity of surrounding pyramidal neurons and dorsal lateral geniculate nucleus‐evoked responses in area V1 of the mouse visual cortex. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the influence of different reproductive stages and livestock management conditions on the pattern of the daily rhythm of total locomotor activity in Pampinta dairy ewes. We recorded 24 hour(h)/day of total locomotor activity in 10 Pampinta dairy ewes during 2 different stages of 60 days each: in stage 1, the animals were pregnant and not lactating, and were subjected to a natural 10/14 light/dark (L/D) cycle with an ambient temperature of 17°C and relative humidity of 70%; in stage 2, the animals were lactating. During stage 2, the animals were divided into 2 equal groups, one group was milked 1 time a day with an automatic machine, and the animals of the other group only suckled the lamb. During this stage, all animals were subjected to a natural 13/11 L/D photoperiod with an ambient temperature of 25°C and relative humidity of 73%. A trigonometric statistical model was used to describe the main rhythmic parameters: mesor, amplitude, acrophase, and robustness of rhythm. Our results showed a daily rhythm of total locomotor activity in all periods considered. Two-way for repeated measure analysis of variance (ANOVA) was applied to study the effect of time (days of monitoring) and the experimental conditions on the studied parameters. The onset and offset times were defined as the time points at which the threshold amount of activity was reached at the rising and declining limbs of the daily pattern. The daily rhythm of total locomotor activity was different in the 2 stages considered and between the 2 groups during stage 2. The highest daily amount of activity per 24 hours was observed in the nursing ewes followed by the ewes milked by an automatic machine and pregnant ewes. Robustness of rhythm was highest in nursing ewes followed by the pregnant ewes and the ewes milked by an automatic machine. Only the acrophase was similar in the 2 stages and between the 2 groups of lactating ewes. In conclusion, the daily rhythm of total locomotor activity in Pampinta dairy ewes showed a low robustness value and was influenced by the different management conditions. The lamb's presence, and the consequent maternal care, strengthen the robustness of rhythm. Considering the total locomotor activity as an index of wellness in livestock, further studies are necessary to establish the characteristics of the daily rhythm of total locomotor activity in Pampita dairy ewes for the improvement of the wellness of this species widely used in Argentina. [ABSTRACT FROM AUTHOR]

Glucocorticoids mediate physiological processes to obtain energy, presenting daily variation in basal levels that may be related to behavioural activity pattern. Identification of plasticity in the secretion of these hormones is essential to understand their effects on physiology and behaviour of wild birds and, therefore, their success in their natural or artificial environment. Serial endocrine evaluations are facilitated by implementing non-invasive methodologies that minimize possible effects of manipulation on the animal's physiological variables. However, non-invasive endocrine-behavioural studies in nocturnal birds, such as owls, are immature. The present work aimed to validate an enzyme immunoassay (EIA) to quantify glucocorticoid metabolites (MGC) in Megascops choliba as well as to evaluate differences in their production at the individual, sexual or daily level. We recorded the behaviour of nine owls during three continuous days to establish activity budget under captive conditions and aiming to correlate with daily MGC variation. The EIA proved to be effective in analytical assays and in pharmacological testing with synthetic ACTH, validating this immunoassay for the species. Additionally, individual differences in MGC production were confirmed in relation to the time of day, especially at 1700 and 2100, but not in relation to sex. During night hours, the owls showed greater behavioural activity, positively related to MGC values. Higher MGC concentrations were significantly related to greater expressions of active behaviours, such as maintenance, while lower MGC concentrations were recorded during moments of higher alertness and resting. The results presented show daily MGC variation to be inversed in this nocturnal species. Our findings can aid future theoretical studies of daily rhythm and evaluations of challenging and/or disturbing situations that result in changes in behaviour or hormonal cascades of these changes in ex situ populations of owls. [ABSTRACT FROM AUTHOR]

Simple Summary: Intensive farm conditions have an impact on welfare and can reduce the locomotor behavior of calves. The Actiwatch-Mini® (Cambridge Neurotechnology Ltd., Cambridg, UK), an actigraphy-based data logger was used to record the total locomotor behavior of 30-day-old calves, which showed diurnal daily rhythmicity. An individual daily rhythm of total locomotor behavior has also been found and varied in the same subject from day to day, and from subject to subject, and these variabilities need to be taken into account during the farm monitoring. Housing confinement, adaptation to different light/dark conditions, and social deprivation could modify the amount of total locomotor behavior of calves recommended for their psychophysical health. Total locomotor behavior was recorded by means of an activity data logger every 5 min for 6 consecutive days. To do that eight clinically healthy 30-day-old Holstein calves living in calf boxes under natural photoperiod and environmental conditions were enrolled. ANOVA (analysis of variance) showed a statistical effect of the day of monitoring and animal. In the temporal distribution of the resting–activity frequency, it was observed that the calves presented periods of total locomotor behavior with the existence of two peaks, one between 06:00–07:00 and another between 17:00–18:00, which corresponds to time of food intake. In all animals, a diurnal daily rhythm of total locomotor behavior was observed during time of monitoring. Intrasubject and intersubject variabilities were statistically different in mesor, amplitude, and robustness of rhythm. In conclusion, the total locomotor behavior showed a diurnal daily rhythmicity in 30-day-old calves. The characteristics of rhythm were different from individual to individual and from day to day. The recorded intersubject variability must be taken in consideration during the monitoring of farm animals and justifies the application of the device to each animal, as precision livestock farming suggests. [ABSTRACT FROM AUTHOR]

In the wild, most animals experience daily fluctuations in threats and resources that are synchronised with environmental time cues such as the light-dark cycle. Consequently, animals have evolved daily behavioural patterns (i.e., diurnal or nocturnal) that enhance their fitness by, for example, reducing the temporal overlapping with predators. In fish, previous studies revealed stronger physiological stress responses during the resting period of the species. However, little is known about the circadian modulation of stress indicators and how they are influenced by daily behavioural patterns. In this research, we investigated the behavioural stress responses of two farmed fish species with different activity patterns: the diurnal Nile tilapia (Oreochromis niloticus) and the nocturnal tench (Tinca tinca). To this end, we examined the behavioural response of individuals exposed to the diving test every 4 h over a 24 h cycle (n = 12 fish/species/time point). Results indicated that most behavioural indicators varied according to the time of day, aligning with the daily rhythmic pattern of the two species. Tilapia exhibited stronger stress responses to novelty during the dark phase, while tench displayed higher stress during the light phase. This was supported by stress-related behaviours such as freezing and erratic movements (in both tilapia and tench) and bottom-dwelling (in tench only). These results indicated that stress responses peaked during the resting phase of each species, although behavioural indicators exhibiting this daily variation did not completely coincide between the studied species. Overall, these findings suggest interspecific differences in the daily modulation of behavioural stress indicators in farmed fish, an effect with potential relevance for welfare. Understanding the activity rhythmic patterns, resting periods, and associated daily variation in stress for each fish species of interest can precisely help tailor farming procedures to minimise suffering. • Behavioural stress indicators varied according to the time of day in both diurnal and nocturnal species. • Behavioural stress response was stronger during the resting phase of each species. • Behavioural stress indicators did not completely overlap between species. • Biological rhythms should be considered to improve fish welfare in captivity. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate some physiological parameters as total locomotor activity and subcutaneous temperature in two different bovine breeds under tropical environment. In this study, total locomotor activity and subcutaneous temperature were evaluated in 18 clinically healthy female cows. All cows were divided into 3 groups: group A1 was constituted by 6 Holstein Bos taurus, group A2 was constituted by 6 female Herford Bos taurus cows, and group B was constituted by 6 female Bradford Bos indicus cows. Data recording of total locomotor activity (TLA) and subcutaneous temperature (ST) was performed by means of a subcutaneous thermometer (Thermocron) and an actimeter ACTIWATCH® (Cambridge Neurotechnology Ltd.) based on accelerometer technologies equipped on all subjects to record TLA. At the same time, thermal and hygrometric recording were carried out, considering the subtropical climate of Santa Fe. The application of GLM for statistical analysis showed a significant effect (P < 0.05) on statistical model and time of the day on TLA and ST for all groups; no significative effects on animal parameters were found for ST and TLA except for group B. Circadian parameters have been evaluated according to the single cosinor procedure of ST that showed a diurnal daily rhythmicity for all investigated groups and TLA which is focused almost during the photophase for groups A1 and A2 and during scotophase for group B. Considering different species and breeds, and different environmental conditions, this study suggested that some subjects may be much more able to adapt themselves to environmental stress than others. During their evolution from Bos taurus, zebu cattle (Bos indicus) have acquired genes that confer thermotolerance. Subjects from Bos indicus breeds are better able to regulate body temperature in response to heat stress than Bos taurus subjects. [ABSTRACT FROM AUTHOR]

We investigated prey-search activity of a predatory ladybird, Cheilomenes propinqua Mulsant (Coleoptera: Coccinellidae), evaluated as the mean walking speed of males and females in relation to temperature (20, 25, and 30 °C), photoperiod (L:D 12:12 and 24:0), and degree of starvation. On average, the walking speed increased with temperature; it was greater in light than in dark conditions; starved adults moved faster than fed ones and (other conditions being the same) males moved faster than females. The observed daily rhythm of C. propinqua walking activity is mostly exogenous: under constant light it disappeared after the first cycle. An increase in walking speed was recorded during the first day of starvation and persisted almost until the death of females. These results are important for the potential use of C. propinqua for biological pest control in greenhouses. [ABSTRACT FROM AUTHOR]

The circadian clock of vertebrates regulates many biological processes, including the immune system. This paper investigated whether responsiveness to poly (I:C), a synthetic analog of double-stranded RNA used as an immunostimulant, exhibits day/night differences in zebrafish. Fish were intraperitoneally (IP) injected with either phosphate-buffered saline (PBS) or poly (I:C) at two different time points: "Zeitgeber Time" (ZT) 4 (day) and ZT16 (night). Then, 6 h later, fish were euthanized, and tissue samples (skin, liver and kidney) were collected. A control group (intact fish) was also sampled at the same time points. The effect of poly (I:C) on the expression of antioxidant and immune genes was time-of-day-dependent, and the response was stronger following poly (I:C) administration in the day than at night. Time-dependent differences were observed for some genes in the PBS and control groups. However, these differences were tissue-specific. In liver, almost all the genes were affected by time of day. In kidney, poly (I:C) affected the expression of all the gene markers regardless of administration time. These findings highlight the importance of considering the time to administer poly (I:C) when evaluating the fish immune response. [ABSTRACT FROM AUTHOR]

Turtles as many other reptiles are capable of orientating their bodies toward the sun. This conduct requires the presence of an internal biological chronometer in the organism that regulates this behavior. Thus, a description of the internal clock in these reptiles is of interest. The assessment of locomotor activity can be considered a reliable indicator of biological clock function. This study aimed to investigate the effect of different artificial photoperiod and ambient temperature schedules on total locomotor activity of female Chelonoidis chilensis and its rhythmicity. Six C. chilensis specimens were exposed to different artificial photoperiods and temperature regimes each fixed for seven days. It was observed that the activity period during the different experimental schedules was close to the 24 hours indicating a daily rhythmicity. Moreover, all tortoises showed a similar total locomotor activity pattern displaying the most of motion during light phase. Under the condition of constant light tortoises exhibited a self-sustaining rhythm not entrained to light and temperature zeitgebers, thus, suggesting its possible endogenous periodicity. Though this study deepens the knowledge on the rhythmic system of C. chilensis , further investigations are needed to achieve a more detailed understanding of tortoise biological clock. [ABSTRACT FROM AUTHOR]

The daily rhythm affects a series of physiological functions in crustaceans. To study its effect on the physiological function in Eriocheir sinensis, a crustacean species of high economic value, we analyzed the hemolymph transcriptome during the daily rhythm by high-throughput sequencing. We sampled the hemolymph from crabs at four time points in a single day (06:00, 12:00, 18:00, and 24:00 h) and identified 3,01,661 and 1,03,998 transcripts and unigenes, respectively; some of the unigenes were annotated as core clock genes. Moreover, 15,564 differentially expressed genes (DEGs) were divided into nine different clusters. Functional enrichment analysis of DEGs indicated that the molting, metabolism, and immunity processes in E. sinensis were impacted by its daily rhythm. In addition, we mapped the DEGs involved in the daily entrainment pathway. To the best of our knowledge, this is the first comparative transcriptome analysis of crustacean hemolymph during the day–night cycle, and provides multi-level information for unraveling the finer regulatory effects of the daily cycle in crustaceans. [ABSTRACT FROM AUTHOR]

This study aimed to verify the daily variation in the chromatic visual sensitivity of healthy subjects. The study included 35 male adults, aged between 20 and 40 years old (M = 24.97; SD = 4.9). The evaluation of color perception was made through the Cambridge Colour Test, using the Trivector and Ellipse tests. The Pittsburgh Sleep Quality Index, the Sleep Diary, and the Karolinska Sleepiness Scale were used to assess possible influences of circadian rhythmicity. Significant differences were found for the protan confusion axes at 8 am (Z = 2.9; p = 0.012) and at 8 pm (Z = 2.8; p = 0.01), and deutan at 8 am (Z = 2.6; p = 0.028) and at 8 pm (Z = 3.5; p = 0.001), and for the A1 ellipses areas at 8 am (Z = 2.5; p = 0.037) and at 8 pm (Z = 2.4; p = 0.018), and A3 at 8 am (Z = 2.1; p = 0.039) and at 8 pm (Z = 3.6; p = 0.001). Thus, chromatic sensitivity can be characterized by an inverted U-shaped curve, with peak sensitivity in the morning and evening, and attenuation in the afternoon. [ABSTRACT FROM AUTHOR]

Emotional stability is of great importance for undergraduates and has significant predictive power for mental health. Emotions are associated with individuals' daily lives and routines. Undergraduates commonly post their opinions and feelings on social networks, providing a huge amount of data for studying their emotional states and rhythms. Based on the construction of the emotion dictionary of undergraduates' Tencent tweets (TTs)—a social network for users to share their life situations and express emotions and feelings to friends—we used big data text analysis technology to analyze the emotion words in 45,996 Tencent tweets published by 894 undergraduates. Then, we used hierarchical linear modeling to further analyze the daily rhythms of undergraduate students' emotions and how demographic variables are associated with the daily rhythmic changes. The results were as follows: (1) Undergraduates tweeted about more positive emotions than negative emotions (love was most common and fear was the least common); (2) The emotions in undergraduates' tweets changed considerably from 1 a.m. to 6 a.m., but were fairly stable during the day; (3) There was a rising trend in the frequency of using emotion words in Tencent tweets during the day as each hour progressed, and there was a higher increase in positive emotion than negative emotion; and (4) The word frequencies and daily rhythms of emotions varied depending on demographic variables. Gender was correlated with the frequencies of gratitude and the daily rhythms of anger. As the grade increased, the frequency of emotion words in most subcategories in TTs decreased and the fluctuation in daily rhythms became smaller. There was no significant difference in the frequency and daily rhythm of emotion words used in TTs based on having had a left-behind experience. The results of the present study provided emotion expression in social networks in Chinese collectivist culture. This study added new evidence to support the notion that positive and negative emotions are independent dimensions. [ABSTRACT FROM AUTHOR]

Abstract Genetic diversity within a population, such as polymorphisms and personality, is considered to improve population performance because such intraspecific variations have the potential to alleviate the competition for a limited resource or the risk of predation and sexual harassment at a population level. Variation in the level and rhythm of daily activity in a population could also affect population performance by directly altering ecological, social, and sexual interactions among individuals. However, it remains to be elucidated whether such intra‐population variation in the level and rhythms of daily activity exists in a natural population. Here, we investigated the genetic variation in daily activity within a single natural population of Drosophila immigrans. We established 21 isofemale lines from a single natural population and measured larval activity level and the level and daily pattern of adult activity over a 24 hr period. Larval activity level significantly varied among isofemale lines. Likewise, the activity level in the adult stage significantly varied among lines. The significant variation was also found in the daily pattern of adult activity; some lines showed greater activity level in the daytime, and others showed greater activity level in the night. Our results consistently suggest that there is a genetic variation in behavioral activity in a natural population, probably contributing to shaping the population performance.

Food consumption during the rest phase promotes circadian desynchrony, which is corrected with harmful physiological and mental disorders. Previously, we found that circadian desynchrony was involved in isoflurane-induced cognitive impairment. Here, we scheduled food access to modulate daily rhythm to examine its impact on isoflurane-induced cognitive impairments. Mice were randomly transferred to restricted feeding (RF) time groups: Control group (Zeitgeber time (ZT) 0–ZT24, ad libitum feeding), Day-Feeding group (ZT0–ZT12, misaligned feeding), and Night-Feeding group (ZT12–ZT24, aligned feeding). Then, some of them were subjected to 5 h of 1.3% isoflurane anaesthesia from ZT14 to ZT19 and were divided into the Control + Anes group, the Day-Feeding + Anes group, and the Night-Feeding + Anes group. Mini-Mitter was used to monitor the daily rhythm. Fear conditioning system was conducted to assess cognition of mice. We observed that the Night-Feeding group adapted to RF gradually, whereas the Day-Feeding group exhibited a disturbed daily rhythm. The Night-Feeding + Anes group exhibited a partially enhanced daily rhythm, whereas the Day-Feeding + Anes group exhibited sustained phase advances and diurnality score increase 7 days after isoflurane anaesthesia. Notably, in tests of hippocampus-dependent contextual memory, the Night-Feeding + Anes group demonstrated decreased deficits; the Day-Feeding + Anes group showed prolonged post-anaesthetic deficits 14 days after isoflurane anaesthesia. However, amygdala-dependent cued-fear conditioning post-anaesthesia was not altered by the RF schedule. In conclusion, we demonstrated that misaligned feeding disturbed the daily rhythm and led to persistent post-anaesthetic cognitive dysfunction. Aligned feeding enhanced the daily rhythm partially and improved post-anaesthetic cognitive dysfunction.

Abstract Background Many animals in coral reefs exhibit lunar cycles in their reproduction, showing synchronous gametogenesis and spawning at a particular moon phase. How these lunar reproductive cycles are endogenously regulated remains unknown, although changes in moonlight between the new moon and full moon are likely involved in this rhythmic event. Results This study evaluated the possible role of cryptochrome (cry1, cry2, cry3) in phase shifting and setting in the honeycomb grouper Epinephelus merra, which is a typical lunar spawner with full moon preference. qPCR analysis revealed that when fish were reared under alternating light-dark conditions, the transcript levels of cry1 and cry2, but not of cry3, in the diencephalon and pituitary gland showed daily variations. Weekly collection at midnight showed increases in the transcript levels of cry1 and cry2 in the diencephalon, but not the pituitary gland, from the first quarter moon through the last quarter moon. In comparison to the new moon, these transcript levels were significantly lower at all other sampling times. The artificial full moon conditions for 1 month resulted in increased cry transcript levels in both tissues at 2 (cry1) or 2 and 4 (cry2) weeks after the initiation of full moon conditions. Conclusions These results indicate the importance of transient changes in “brightness at night” in the response to moonlight for the phase shift and of “darkness at night” during the new moon for the phase set to the determined moon phase. We concluded that the moon phase-dependent oscillation of clock genes plays a role in lunar cycle-dependent behaviors in fish.

Emotional stability is of great importance for undergraduates and has significant predictive power for mental health. Emotions are associated with individuals’ daily lives and routines. Undergraduates commonly post their opinions and feelings on social networks, providing a huge amount of data for studying their emotional states and rhythms. Based on the construction of the emotion dictionary of undergraduates’ Tencent tweets (TTs)—a social network for users to share their life situations and express emotions and feelings to friends—we used big data text analysis technology to analyze the emotion words in 45,996 Tencent tweets published by 894 undergraduates. Then, we used hierarchical linear modeling to further analyze the daily rhythms of undergraduate students’ emotions and how demographic variables are associated with the daily rhythmic changes. The results were as follows: (1) Undergraduates tweeted about more positive emotions than negative emotions (love was most common and fear was the least common); (2) The emotions in undergraduates’ tweets changed considerably from 1 a.m. to 6 a.m., but were fairly stable during the day; (3) There was a rising trend in the frequency of using emotion words in Tencent tweets during the day as each hour progressed, and there was a higher increase in positive emotion than negative emotion; and (4) The word frequencies and daily rhythms of emotions varied depending on demographic variables. Gender was correlated with the frequencies of gratitude and the daily rhythms of anger. As the grade increased, the frequency of emotion words in most subcategories in TTs decreased and the fluctuation in daily rhythms became smaller. There was no significant difference in the frequency and daily rhythm of emotion words used in TTs based on having had a left-behind experience. The results of the present study provided emotion expression in social networks in Chinese collectivist culture. This study added new evidence to support the notion that positive and negative emotions are independent dimensions.

Housing confinement, adaptation to different light/dark conditions, and social deprivation could modify the amount of total locomotor behavior of calves recommended for their psychophysical health. Total locomotor behavior was recorded by means of an activity data logger every 5 min for 6 consecutive days. To do that eight clinically healthy 30-day-old Holstein calves living in calf boxes under natural photoperiod and environmental conditions were enrolled. ANOVA (analysis of variance) showed a statistical effect of the day of monitoring and animal. In the temporal distribution of the resting–activity frequency, it was observed that the calves presented periods of total locomotor behavior with the existence of two peaks, one between 06:00–07:00 and another between 17:00–18:00, which corresponds to time of food intake. In all animals, a diurnal daily rhythm of total locomotor behavior was observed during time of monitoring. Intrasubject and intersubject variabilities were statistically different in mesor, amplitude, and robustness of rhythm. In conclusion, the total locomotor behavior showed a diurnal daily rhythmicity in 30-day-old calves. The characteristics of rhythm were different from individual to individual and from day to day. The recorded intersubject variability must be taken in consideration during the monitoring of farm animals and justifies the application of the device to each animal, as precision livestock farming suggests.

An innate 24 h circadian clock drives various behavioral processes via expression of clock genes that regulate circadian rhythmicity and temporal signals. Elucidating the gene expression in goats may contribute to improving the knowledge of the regulation of circadian rhythms in this species. Five nonpregnant and nonlactating Maltese goats with no evidence of disease were kept in an indoor pen under the natural long photoperiod (05:05–20:56 h) and natural environmental temperature (23°C and 60% RH). They were fed an Alfalfa hay and concentrate mixture provided twice a day; water was available ad libitum. Blood samples were collected every 4 h over a 48 h period into PAX gene Blood RNA Tubes and stored at −80°C until processing. Clock genes (Clock; Cry1; Cry2; Per2; Per3) were determined using real-time quantitative polymerase chain reaction. During the experimental period, locomotor activity was monitored by an actigraphy-based data logger that records a digitally integrated measure of motor activity as a means to assess indices of discomfort during study and stability of the circadian rhythm. All of the tested genes showed daily rhythmicity in their expression in whole blood. Differences in their circadian parameters were observed. Mesor and amplitude were statistically different among the tested gene (Mesor: F(4.30) = 205.30; p <.0001; amplitude: F(4.30) = 104.80; p <.0001), with each gene showing its acrophase at a different time of day (F(4.30) = 81.17; p <.0001), and differences were observed between the two days of monitoring (F(1.30) = 10.25; p =.003). The application of two-way analysis of variance (ANOVA) on robustness of rhythm values did not show statistical differences among the tested genes (F(4.30) = 1.83; p =.14) and between the two days of monitoring (F(1.30) = 1.16; p =.28). Locomotor activity data recording were in accordance with the data reported in literature, indicating the absence of discomfort or alteration of circadian rhythms during the experimental period. Our results support the presence of a cyclic transcription of clock genes in whole blood of healthy goats housed under a long light natural photoperiod and natural environmental conditions. [ABSTRACT FROM AUTHOR]

Elucidation of the molecular mechanisms by which plants sense and respond to environmental stimuli that influence their growth and yield is a prerequisite for understanding the adaptation of plants to climate change. Plants are sessile organisms and one important factor for their successful acclimation is the temporal coordination of the 24 h daily cycles and the stress response. The crosstalk between second messengers, such as Ca2+, reactive oxygen species (ROS), and hormones is a fundamental aspect in plant adaptation and survival under environmental stresses. In this sense, the circadian clock, in conjunction with Ca2+- and hormone-signalling pathways, appears to act as an important mechanism controlling plant adaptation to stress. The relationship between the circadian clock and ROS-generating and ROS-scavenging mechanisms is still not fully understood, especially at the post-transcriptional level and in stress situations in which ROS levels increase and changes in cell redox state occur. In this review, we summarize the information regarding the relationship between the circadian clock and the ROS homeostasis network. We pay special attention not only to the transcriptional regulation of ROS-generating and ROS-scavenging enzymes, but also to the few studies that have been performed at the biochemical level and those conducted under stress conditions. [ABSTRACT FROM AUTHOR]

Man is not as consistently predictable in performance as are other things we might choose to observe. This is unfortunate but obvious. We can borrow information from the related areas to apply it to sport, as another alternative. Whatever method is used, the so-called truths are at best loosely structured. We must then try to logically deduce the facts from empirical as it pertains to sports. Variation in the daily rhythm of the functional capacity of different systems which are synchronized to a 24-hour day, observe two peculiar aspects. One of them is the time dependent alternation in the levels of physiological process, expressed as circadian range or circadian amplitude. Athletic performances that occur several hours before or after the circadian peak "window" will be potentially subjected to less-than-optimal performance. This Paper tries to find out the effects of Circadian rhythm in different seasons. [ABSTRACT FROM AUTHOR]

The neuropeptide orexin/hypocretin is implicated in sleep and arousal, energy expenditure, reward, affective state and cognition. Our previous work using diurnal Nile grass rats (Arvicanthis niloticus) found that orexin mediates the effects of environmental light, particularly daytime light intensity, on affective and cognitive behaviours. The present study further investigated how daytime light intensity affects the central orexin system in male and female grass rats. Subjects were housed for 4 weeks in 12:12 hr dim light:dark (50 lux, dimLD) or in 12:12 hr bright light:dark cycle (1000 lux, brightLD). Day/night fluctuations in some orexin measures were also assessed. Despite similar hypothalamic prepro‐orexin mRNA expression across all conditions, there were significantly more orexin‐immunoreactive neurons, larger somata, greater optical density or higher orexin A content at night (ZT14) than during the day (ZT2), and/or in animals housed in brightLD compared to dimLD. Grass rats in brightLD also had higher cisternal CSF levels of orexin A. Furthermore, orexin receptor OX1R and OX2R proteins in the medial prefrontal cortex were higher in brightLD than dimLD males, but lower in brightLD than dimLD females. In the CA1 and dorsal raphe nucleus, females had higher OX1R than males without any significant effects of light condition, and OX2R levels were unaffected by sex or light. These results reveal that daytime light intensity alters the central orexin system of both male and female diurnal grass rats, sometimes sex‐specifically, and provides insight into the mechanisms underlying how daytime light intensity impacts orexin‐regulated functions. [ABSTRACT FROM AUTHOR]

Purpose of the study is to study the effect of the drug AQUAVIT-D3 on the state of peripheral red blood cells and the circadian rhythm and blood pressure variability in patients with chronic heart failure with vitamin D deficiency. Object and methods of the research. Surveyed 100 patients (mean age 59.5 ± 5.5 years) with chronic heart failure Class II A with vitamin D deficiency. 75 people constituted the main group who, in combination with basic therapy, used the drug AQUAVIT-D3 (at a dose of 12.5 mg/day for 1 month). According to the level of vitamin D deficiency, patients of the main group were divided into three subgroups: the first subgroup with a level of up to 10.9 ng/ml, the second subgroup with a level of 10.9-23.7 ng/ml and the third subgroup with a level of 23.7 ng/ml and niche. 25 patients were in the control group who used only basic therapy. In all patients, the daily rhythm and blood pressure variability were assessed using daily monitoring of this indicator. Erythrocyte preparations were prepared according to the standard technique and studied in a JEOL scanning microscope (Japan) with a parallel determination of the trace element composition in the X-REDA prefix. Results and discussion. Complex therapy with the preparation AQUAVIT-D3 promotes improvement of daily rhythm and reduction of the variability of blood pressure in patients with chronic heart failure complicated by vitamin D deficiency. Such vitamin therapy is safe, well tolerated, has no side effects and can be recommended for the correction of daily rhythm and blood pressure variability in patients with chronic heart failure with vitamin D deficiency. Complex therapy with the preparation AQUAVIT-D3 has led to a significant decrease in the values of «pressure loading» values: the time index of mean and diastolic blood pressure, the index of the median and diastolic blood pressure (mean, day, night) of patients in all three clinical subgroups. Dynamics of adaptive transformations of peripheral blood red blood cells can serve as a criterion for assessing the level of functional state of the organism as a whole and the direction of the adaptation process, taking into account the chronological features of the development of chronic heart failure with vitamin D deficiency and the complex treatment of AQUAVIT-D3. Improvement of the basic hemodynamic parameters in patients with chronic heart failure with vitamin D deficiency after complex treatment is accompanied by structural rearrangement of peripheral blood red blood cells, which in themselves are nonspecific, but their combination and chronological sequence are specific features in restoring the functional state of the cardiovascular system in such patients.

Female reproductive success relies on proper integration of circadian- and ovarian- signals to the hypothalamic-pituitary-gonadal axis in order to synchronize the preovulatory LH surge at the end of the ovarian follicular stage with the onset of the main active period. In this study, we used a combination of neuroanatomical and electrophysiological approaches to assess whether the hypothalamic neurons expressing Arg-Phe amiderelated peptide (RFRP-3), a gonadotropin inhibitory peptide, exhibit daily and estrous stage dependent variations in female mice. Furthermore, we investigated whether arginine vasopressin (AVP), a circadian peptide produced by the suprachiamatic nucleus regulates RFRP-3 neurons. The number of c-Fos–positive RFRP-3 immunoreactive neurons is significantly reduced at the day-to-night transition with no difference between diestrus and proestrus. Contrastingly, RFRP neuron firing rate is higher in proestrus as compared to diestrus, independently of the time of the day. AVP immunoreactive fibers contact RFRP neurons with the highest density observed during the late afternoon of diestrus and proestrus. Application of AVP increases RFRP neurons firing in the afternoon (ZT6-10) of diestrus, but not at the same time point of proestrus, indicating that AVP signaling on RFRP neurons may depend on circulating ovarian steroids. Together, these studies show that RFRP neurons integrate both daily and estrogenic signals, which downstream may help to properly time the preovulatory LH surge.

• Bdnf and Trkb expression display a daily variation. • Daily rhythms of Apo E protein are observed in the rat temporal cortex. • BMAL1 and RORα levels vary rhythmically in this brain area. • An i.c.v injection of aggregated Aβ (1-42) modifies those temporal patterns. Alzheimer's disease (AD) is a devastating disease characterized by loss of synapses and neurons in the elderly. Accumulation of the β-amyloid peptide (Aβ) in the brain is thought to be central to the pathogenesis of AD. ApoE plays a key role in normal and physiological clearance of Aß, since it facilitates the peptide intra- and extracellular proteolytic degradation. Besides the cognitive deficit, AD patients also show alterations in their circadian rhythms. The objective of this study was to investigate the effects of an i.c.v. injection of Aβ (1-42) peptide on the 24 h rhythms of Apo E, BMAL1, RORα, Bdnf and trkB mRNA and Aβ levels in the rat temporal cortex. We found that an i.c.v. injection of Aβ aggregates phase shifts daily Bdnf expression as well as Apo E, BMAL1, RORα, Aβ and decreased the mesor of TrkB rhythms. Thus, elevated Aβ peptide levels might modify the temporal patterns of cognition-related factors, probably; by affecting the clock factors rhythms as well as in the 24 h rhythms of Apo E. [ABSTRACT FROM AUTHOR]

The aim of the study was to extend the knowledge about to the total locomotor activity behavior in maned wolves (Chrysocyon brachyurus) through the comparison with domestic dogs (Canis familiaris). Five maned wolves housed individually in 4 m2 dens with nest boxes and runs allowing them to move in outdoors area of 250 m2 with natural vegetation; and five Beagles dogs living individually in a 12 m2 box with an outside area of 50 m2 were subjected to natural light-dark (L/D) cycle (maned wolves: 15 L/9D; dogs 14 L/10D) and environmental conditions (maned wolves: 22-26°C, 64Rh%; dogs 17-23°C, 65Rh%). In each animal, the monitoring of locomotor activity was performed for 2 days by means of an activity data logger (Actiwatch Cambridge Neurotechnology, Cambridge, UK), applied on a neck collar. Data were analyzed by the single Cosinor method. At the obtained rhythmic parameters, two-way analysis of variance was applied to verify differences due to day of monitoring and species. Maned wolves showed a nocturnal daily rhythm of locomotor activity. Dogs showed a diurnal daily rhythm of locomotor activity. The diurnality index was 0.29 and 0.93, respectively, for maned wolves and dogs. The two studied species showed statistically difference in mesor and amplitude of rhythm, higher in maned wolves (mesor: 3256.64 ± 364.87 arbitrary unit; amplitude: 3726.32 ± 327.50 arbitrary unit) than dogs (mesor: 414.06 ± 9.68 arbitrary unit; amplitude: 502.35 ± 18.78 arbitrary unit). We can claim that maned wolves, housed in captivity are more active than dogs and showed an opposed daily rhythm of locomotor activity. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the daily total locomotor activity in captive Chrysocyon brachyurus. Three maned wolves were housed individually under natural light–dark cycle and environmental conditions. In each animal, locomotor activity was monitoored for 30 days by means of an activity data logger (Actiwatch Cambridge©Neurotechnology, Cambridge, UK), applied on a neck collar. Locomotor activity was evaluated by visual inspection of actograms. The average amount of activity during light and dark phases and Cosine 20 Peak were calculated using Actiwatc Activity Analysis 5.06. Subject A was more active during the light phase, and subjects B and C were more active during the dark phase. The single cosinor method applied on the amount of activity recorded every hour showed a daily rhythm of locomotor activity only in subject B (2 years old). Acrophase was observed between 03:20 and 07:30, and robustness had a value between 37.00% and 63.40%. Only one subject due to their early withdrawal from its natural habitat, developed a manifest anthropic dependence, with a marked adaptation to the habitat of captivity presenting an anthropophilic behavior. This study would help to define more appropriate management and conservation strategies for this emblematic mammal of South America. [ABSTRACT FROM AUTHOR]

Ecophysiological studies have highlighted the relevance of the avian immune system in individual fitness prospects in the wild. However, studies on the ontogeny of avian immunity are scarce. We analyse age-related changes in the cellular constitutive immunity throughout nestling development, as well as its relationship with sex and brood size. We found that cellular constitutive immunity could be affected by age, sex, brood size, or daily rhythm. Early-stage nestlings relied more on cells of the innate immunity rather than on cells linked to the adaptive immune system. Cellular immunity may not be fully mature in fledglings, as reflected by differences in phagocytic cell counts with regard to adults. Beyond the age-dependent effects, agranulocyte cell counts were affected by sibling competition while granulocyte cell counts showed a daily rhythm. We also show that the heterophil to lymphocyte ratio was negatively related to body weight when nestlings become more independent. Our study contributes knowledge to the fields of developmental immunology and ecological immunology based on essential components of the cellular immune system. [ABSTRACT FROM AUTHOR]

Female reproductive success relies on proper integration of circadian- and ovarian- signals to the hypothalamic-pituitary-gonadal axis in order to synchronize the preovulatory LH surge at the end of the ovarian follicular stage with the onset of the main active period. In this study, we used a combination of neuroanatomical and electrophysiological approaches to assess whether the hypothalamic neurons expressing Arg-Phe amide- related peptide (RFRP-3), a gonadotropin inhibitory peptide, exhibit daily and estrous stage dependent variations in female mice. Furthermore, we investigated whether arginine vasopressin (AVP), a circadian peptide produced by the suprachiamatic nucleus regulates RFRP-3 neurons. The number of c-Fos-positive RFRP-3 immunoreactive neurons is significantly reduced at the day-to-night transition with no difference between diestrus and proestrus. Contrastingly, RFRP neuron firing rate is higher in proestrus as compared to diestrus, independently of the time of the day. AVP immunoreactive fibers contact RFRP neurons with the highest density observed during the late afternoon of diestrus and proestrus. Application of AVP increases RFRP neurons firing in the afternoon (ZT6-10) of diestrus, but not at the same time point of proestrus, indicating that AVP signaling on RFRP neurons may depend on circulating ovarian steroids. Together, these studies show that RFRP neurons integrate both daily and estrogenic signals, which downstream may help to properly time the preovulatory LH surge. [ABSTRACT FROM AUTHOR]

This article reviews evidence for maternal-fetal communication about the time of day. We explore the hypothesis that key maternal hormones synchronize daily rhythms in the fetus to regulate gestation duration. These findings may help to predict and prevent preterm birth.

Genetic diversity within a population, such as polymorphisms and personality, is considered to improve population performance because such intraspecific variations have the potential to alleviate the competition for a limited resource or the risk of predation and sexual harassment at a population level. Variation in the level and rhythm of daily activity in a population could also affect population performance by directly altering ecological, social, and sexual interactions among individuals. However, it remains to be elucidated whether such intra‐population variation in the level and rhythms of daily activity exists in a natural population. Here, we investigated the genetic variation in daily activity within a single natural population of Drosophila immigrans. We established 21 isofemale lines from a single natural population and measured larval activity level and the level and daily pattern of adult activity over a 24 hr period. Larval activity level significantly varied among isofemale lines. Likewise, the activity level in the adult stage significantly varied among lines. The significant variation was also found in the daily pattern of adult activity; some lines showed greater activity level in the daytime, and others showed greater activity level in the night. Our results consistently suggest that there is a genetic variation in behavioral activity in a natural population, probably contributing to shaping the population performance. [ABSTRACT FROM AUTHOR]