Dark Period Research Articles

Effects of light regimes on circadian gene co‐expression networks in Arabidopsis thaliana

AbstractLight/dark (LD) cycles are responsible for oscillations in gene expression, which modulate several aspects of plant physiology. Those oscillations can persist under constant conditions due to regulation by the circadian oscillator. The response of the transcriptome to light regimes is dynamic and allows plants to adapt rapidly to changing environmental conditions. We compared the transcriptome of Arabidopsis under LD and constant light (LL) for 3 days and identified different gene co‐expression networks in the two light regimes. Our studies yielded unforeseen insights into circadian regulation. Intuitively, we anticipated that gene clusters regulated by the circadian oscillator would display oscillations under LD cycles. However, we found transcripts encoding components of the flavonoid metabolism pathway that were rhythmic in LL but not in LD. We also discovered that the expressions of many stress‐related genes were significantly increased during the dark period in LD relative to the subjective night in LL, whereas the expression of these genes in the light period was similar. The nocturnal pattern of these stress‐related gene expressions suggested a form of “skotoprotection.” The transcriptomics data were made available in a web application named Cyclath, which we believe will be a useful tool to contribute to a better understanding of the impact of light regimes on plants.

Violet Light Effects on the Circadian Rest-Activity Rhythm and the Visual System.

Rooms illuminated by "black light" (<400 nm wavelength) has become popular, but there is not enough scientific evidence to support its implementation. This study aims to assess the effects of violet light (392 nm) on the circadian rest-activity rhythm and the visual system through animal experimentation. Five groups of four mice were exposed to different white light, violet light, and dark periods, and their circadian rhythm was analyzed by measuring the circadian period using rest-activity cycles. Electroretinographic recordings and structural analysis of the retina were also performed on experimental animals. Our study demonstrates that mice present normal circadian activity during exposure to violet light, taking rest not only under white light but under violet lighting periods. However, mice suffered a decrease in electrical retinal response after exposure to violet light as measured by electroretinography. Nevertheless, no structural changes were observed in the retinas of the animals under different lighting conditions. Violet light elicits circadian rest-activity rhythm in mice but alters their visual function, although no structural changes are observed after short periods of violet light exposure.

Role of the Controlled Periodic Illumination (CPI) for Enhancing the Photonic Efficiency of a Photocatalytic System

AbstractPhotonic efficiency measurements of the photoeffects at semiconductor surfaces for pollutant abatement and value‐added product generation (e. g. H2 in the hydrogen evolution reaction, HER) are usually carried out under continuous irradiation of the catalyst. In the last decades, Controlled Periodic Illumination (CPI) was proposed as a way to increase the photonic efficiency of irradiated semiconductor systems. CPI consists in the modulation of the incident radiant power, alternating light and dark periods with given duty cycle (γ), intensity (I) and frequency (f). The rationale underlying the use of CPI to enhance photonic efficiency is the exploitation of dark periods to allow slow reactions proceed, to induce new reactions or to free up space on the surface of the catalyst. In this short review, we will highlight the strengths and weaknesses of some of the works published so far on the abatement of pollutants and the production of hydrogen using CPI.

Investigating the Effects of Dark Period Light Exposure on Sex Expression In Female Cannabis sativa

Hermaphroditism in female plants is a common problem in the cannabis industry. Cannabis sativa florogenesis is dependent on photoperiod, and industry experts suspect disruptions to the photoperiod contribute to hermaphroditism. The goals of this report are to (i) determine the relationship between hermaphroditism and dark period light exposure in C. sativa, (ii) identify a causal mechanism that could explain female hermaphroditism, and (iii) recommend a course of action for indoor cultivators. A literature search suggested that hermaphroditism in C. sativacould be the result of a very low fluence response. To test this idea, 403 plants grown indoors were inspected for male flowers. The distance of each plant from the nearest grow room door—the proposed source of dark period light—was used to calculate relative dark period light intensity values for each plant. Linear regression analysis was used to assess the relationship between relative light intensity and males per plant. The average males per plant was 0.136, compared with an intercept coefficient of 0.125 (p=0.00197, R2=0.0162). Based on these results, proximity to a door does not affect hermaphroditism. Because the actual light intensities during dark periods in this study were likely too low to cause very low fluence responses, this study cannot confidently evaluate the relationship between dark period light exposure and hermaphroditism in C. sativa. Management at the study site would be advised not to spend resources addressing grow room door light leaks.

The effect of light availability and light wavelength on growth, 2-MIB biosynthesis, and 2-MIB-related gene expression in Pseudanabaena foetida var. intermedia.

2-methylisoborneol (2-MIB) is an odiferous metabolite mainly produced by cyanobacteria, contributing to taste and odor problems in drinking water. The mechanisms involved in 2-MIB biosynthesis in cyanobacteria are not yet completely understood. This study investigated the effect of light availability and wavelength on growth, 2-MIB synthesis, and related gene expression in Pseudanabaena foetida var. intermedia. A significantly lower 2-MIB production was observed in P. foetida var. intermedia during the dark period of a 12-h photoperiod. Exposure to green light resulted in a significant decrease in 2-MIB production compared to white light and red light. The relative expression levels of 2-MIB-related genes in P. foetida var. intermedia were significantly lower during the dark period of a 12-h photoperiod and when cultured under green light. The expression of 2-MIB-related genes in cyanobacteria appears to be light-dependent. This study suggests that the demand for photopigment synthesis under unfavorable light conditions affects the 2-MIB synthesis in cyanobacteria.

Far-Right Orientalism and the Uyghurs: Revisiting Gunnar Jarring

No scholar has had a greater impact on the study of Xinjiang and the Uyghurs than the Swedish Orientalist and diplomat Gunnar Jarring (1907–2002). This is thanks, above all, to the remarkable archive of manuscripts from the region that he collected and curated. Known as the Jarring Collection, it may be the largest assemblage of manuscripts by Xinjiang Muslims held anywhere in the world outside China. How was this collection created, and what biases may have informed its development? By exploring the context in which the core of the Jarring Collection was developed, this article reveals unsettling allegations about Jarring’s activities during a shadowy, little-known period in his life — a dark period in Sweden’s history, during which academic and political elites were in thrall to a far-right zeitgeist that dovetailed with Germany’s Nazi movement. The article concludes by considering some implications of the Jarring Collection's biases for the study of Xinjiang and the Uyghurs.

The novel estuarine bioremediation target Gracilaria transtasmanica has high tolerance to light limitation, air-exposure and a broad range of salinities

AbstractIn-situ macroalgal bioremediation could help prevent and reduce estuarine eutrophication. However, estuaries are dynamic ecosystems characterized by fluctuating abiotic conditions. Therefore, target macroalgal species for in-situ estuarine bioremediation must be able to maintain productivity under a range of challenging abiotic conditions. The aim of this study was to assess the tolerance of the novel bioremediation target Gracilaria transtasmanica to ambient and extreme levels of salinity, air-exposure, and light limitation that occur in estuarine environments. Three separate experiments were conducted to assess tolerance to each factor and photosynthetic functioning and growth were used to quantify the tolerance range of G. transtasmanica in each experiment. Specific Growth Rate (SGR) was significantly affected by salinity, air-exposure, and light limitation. Gracilaria transtasmanica was able to grow in salinities of 5 to 35 ppt, but growth rates decreased with decreasing salinity. Air-exposure periods of up to 9 h were tolerated, but growth rates decreased as air-exposure period increased. Gracilaria transtasmanica was able to maintain growth with a loss of up to 75% of ambient light and was also able to tolerate short periods (48 h) of continuous darkness. Photosynthetic function was unaffected by salinity, air-exposure, or light limitation. These results demonstrate the high tolerance of G. transtasmanica to light limitation, air-exposure and a broad range of salinities. Consequently, this species could be cultivated in a range of habitat types within estuaries. However, the optimal habitats for cultivation will be submerged subtidal channels and lower intertidal mudflats where the impacts of freshwater inflows and air-exposure are reduced.

1500-Year Sedimentary Records of the East Asian Summer Monsoon and Yellow Sea Warm Current from the Muddy Area of the North Yellow Sea, China

Advances in reconstructing the East Asian monsoon have provided important insights into the natural climate variability in Asia during the pre-instrumental period. However, there are still unresolved paleoclimate issues that necessitate the use of geological proxy data to further our understanding of past climate changes. This study focused on core B13, located in the muddy area of the North Yellow Sea (NYS), to investigate the evolutionary history over the past 1500 years and reconstruct the records of the East Asian summer monsoon (EASM) and Yellow Sea warm current (YSWC). The mean grain size of sediment ranged from 4.2 Φ to 5.6 Φ, with the sorting coefficient ranging from 1.9 to 2.2, indicating poor sorting. The C–M pattern showed a limited range of values, with the M values being between 33 and 83 μm and the C values being between 165 and 287 μm, suggesting uniform-suspension transport. The L* index ranged from 40.41 to 44.12, while the a* and b* indexes ranged from 0.55 to 1.78 and 2.86 to 5.94, respectively. A stable and relatively strong sedimentary environment is indicated through a comprehensive analysis of the C–M plot, triangular plot, the relationship between the mean grain size and sorting, and the changes in grain-size and color parameters. The sedimentary evolution in the muddy area of the NYS over the past 1500 years can be categorized into three distinct stages. In this study, proxies for the EASM and YSWC were extracted using the VPCA method from the sediment grain size and diffuse spectral reflectance (DSR) data, respectively. The reliability of these proxies has been confirmed through comparison with other validated proxies. The results indicated that the strength of the EASM and YSWC also exhibited three stages, corresponding to the Dark Ages Cold Period (DACP), Medieval Warm Period (MWP), and Little Ice Age (LIA), respectively. On a centennial scale, the correlation between the EASM and YSWC was predominantly negative. This research validates the reliability of the VPCA method for paleoclimate reconstruction, contributes important climate records in a special muddy area, and provides a new perspective on how to eliminate temporal errors in verifying the correlation between the two climate systems.

Sleep-wake behavior and responses to sleep deprivation and immune challenge of protein kinase RNA-activated knockout mice

Protein Kinase RNA-activated (PKR) is an enzyme that plays a role in many systemic processes, including modulation of inflammation, and is implicated in neurodegenerative diseases, such as Alzheimer’s disease (AD). PKR phosphorylation results in the production of several cytokines involved in the regulation / modulation of sleep, including interleukin-1β, tumor necrosis factor-α and interferon-γ. We hypothesized targeting PKR would alter spontaneous sleep of mice, attenuate responses to sleep deprivation, and inhibit responses to immune challenge. To test these hypotheses, we determined the sleep-wake phenotype of mice lacking PKR (knockout; PKR-/-) during undisturbed baseline conditions; in responses to six hours of sleep deprivation; and after immune challenge with lipopolysaccharide (LPS). Adult male mice (C57BL/6J, n = 7; PKR-/-, n = 7) were surgically instrumented with EEG recording electrodes and an intraperitoneal microchip to record core body temperature. During undisturbed baseline conditions, PKR -/- mice spent more time in non-rapid eye movement sleep (NREMS) and rapid-eye movement sleep (REMS), and less time awake at the beginning of the dark period of the light:dark cycle. Delta power during NREMS, a measure of sleep depth, was less in PKR-/- mice during the dark period, and core body temperatures were lower during the light period. Both mouse strains responded to sleep deprivation with increased NREMS and REMS, although these changes did not differ substantively between strains. The initial increase in delta power during NREMS after sleep deprivation was greater in PKR-/- mice, suggesting a faster buildup of sleep pressure with prolonged waking. Immune challenge with LPS increased NREMS and inhibited REMS to the same extent in both mouse strains, whereas the initial LPS-induced suppression of delta power during NREMS was greater in PKR-/- mice. Because sleep regulatory and immune responsive systems in brain are redundant and overlapping, other mediators and signaling pathways in addition to PKR are involved in the responses to acute sleep deprivation and LPS immune challenge.

UVC (254 nm) and Far UVC (222 nm) Irradiation Affects In Vitro Growth of Colletotrichum sp. Isolates and Their Infection of Detached Strawberry Leaves

Conventional ultraviolet C at 254 nm (UVC) and Far UVC at 222 nm (Far UVC) were evaluated as alternatives to fungicides for disease control. Conidia of 13 isolates of strawberry anthracnose pathogens (five Colletotrichum species in two complexes: C. acutatum and C. gloeosporioides) were uniformly dispersed onto agar and irradiated with UVC and Far UVC doses ranging from 52 to 1,248 J·m−2. After 48 h of incubation, a UVC dose of 1,248 J·m−2 and Far UVC doses from 234 to 935 J·m−2 reduced Colletotrichum colony counts to &lt;10 colonies/Petri dish. Cultures exposed to UVC light followed by 4 h of darkness had lower colony counts than cultures incubated under continuous light. This dark incubation period was not required for Far UVC to obtain optimal lethality, indicating Far UVC irradiation can be applied during the day or night and achieve similar fungal lethality. Inoculation of detached leaves of three anthracnose-susceptible strawberry cultivars with conidial suspensions of Colletotrichum spp. revealed that UV irradiation can affect development of anthracnose symptoms. Leaves receiving UVC doses of 312 and 624 J·m−2 or a Far UVC dose of 467 J·m−2 reduced anthracnose infection with little or no plant injury. A UVC dose of 1,248 J·m−2 and Far UVC doses ≥ 467 J·m−2 inflicted varying degrees of plant injury. Disease control intended to reduce the number of fungicidal applications could be developed with moderate doses of UVC and Far UVC irradiation while slowing the evolution of pesticide-resistant strains. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2024.

Deciphering the dual role of persistent luminescence materials: Toxicity and photoreception effects on rice development

Studies on the toxicity of micro- and nanomaterials in plants have primarily focused on their intrinsic effects. However, there is often oversight when considering the potential perceptual responses that plants may exhibit in response to these materials. In this investigation, we assessed the impact of three commercially available persistent luminescence materials (PLMs) that emit red, green, or blue light under various environmental conditions. We subjected rice (Oryza sativa L.), a short-day plant, to nine distinct treatments, including exposure to particles in isolation, their nocturnal afterglow, or a combination of both. We thoroughly examined rice seedling morphology, photosynthesis patterns, metabolite dynamics, and flowering gene expression to determine the biological responses of plants to these particles. These findings demonstrated that PLMs stably interact with rice, and their emitted afterglow precisely matches the perceptual bandwidth of rice photoreceptors. Notably, the nocturnal afterglow from the red and blue PLMs enhanced the vegetative growth of rice seedlings while inhibiting their reproductive development. The blue PLMs exhibited the most pronounced positive effects, while the red PLMs exhibited inhibitory effects. When exposed to a combination of red and blue PLMs, rice displays enhanced growth and development. The observed alterations in the expression patterns of genes responsible for flowering supported these effects. We concluded that PLMs influence rice growth and development due to their inherent properties and intermittent illumination during dark periods. Both factors collectively shape rice growth and development.

Disruption of the peripheral biological clock may play a role in sleep deprivation-induced dysregulation of lipid metabolism in both the daytime and nighttime phases

Study objectivesThis study aimed to examine the effect of sleep deprivation (SD) on lipid metabolism or lipid metabolism regulation in the liver and white adipose tissue (WAT) during the light and dark phases and explored the possible mechanisms underlying the diurnal effect of SD on lipid metabolism associated with clock genes. MethodsMale C57BL/6J mice aged 2 months were deprived of sleep daily for 20 h for ten consecutive days with weakly forced locomotion. The body weights and food consumption levels of the SD and control mice were recorded, and the mice were then sacrificed at ZT (zeitgeber time) 2 and ZT 14. The peripheral clock genes, enzymes involved in fat synthesis and catabolism in the WAT, and melatonin signalling pathway-mediated lipid metabolism in the liver were assessed. Untargeted metabolomics and tandem mass tag (TMT) proteomics were used to identify differential lipid metabolism pathways in the liver. ResultsBodyweight gain and daily food consumption were dramatically elevated after SD. Profound disruptions in the diurnal regulation of the hepatic peripheral clock and enzymes involved in fat synthesis and catabolism in the WAT were observed, with a strong emphasis on hepatic lipid metabolic pathways, while melatonin signalling pathway-mediated lipid metabolism exhibited moderate changes. ConclusionsIn mice, ten consecutive days of SD increased body weight gain and daily food consumption. In addition, SD profoundly disrupted lipid metabolism in the WAT and liver during the light and dark periods. These diurnal changes may be related to disorders of the peripheral biological clock.

Intervening dark periods negatively affect the photosynthetic performance of Chlamydomonas reinhardtii during growth under fluctuating high light.

The acclimation of the green algae Chlamydomoas reinhardtii to high light (HL) has been studied predominantly under continuous illumination of the cells. Here, we investigated the impact of fluctuating HL in alternation with either low light (LL) or darkness on photosynthetic performance and on photoprotective responses. Compared to intervening LL phases, dark phases led to (1) more pronounced reduction of the photosystem II quantum efficiency, (2) reduced degradation of the PsbS protein, (3) lower energy dissipation capacity and (4) an increased pool size of the xanthophyll cycle pigments. These characteristics indicate increased photo-oxidative stress when HL periods are interrupted by dark phases instead of LL phases. This overall trend was similar when comparing long (8 h) and short (30 min) HL phases being interrupted by long (16 h) and short (60 min) phases of dark or low light, respectively. Only the degradation of PsbS was clearly more efficient during long (16 h) LL phases when compared to short (60 min) LL phases.

Anya’s Posttraumatic Growth Over Her Loss Trauma as Reflected in Natassa’s Critical Eleven

It has been commonly assumed that trauma only lead to a negative impact on its survivors. However, on another hand, trauma can bring positive changes. This situation is commonly said as post-traumatic growth (PTG). The PTG process takes a quite long time and each survivor has different capabilities and processes to achieve it. Anya, the main character in the novel of Critical Eleven, experiences the trauma of loss after her first baby dies. Since her baby left, Anya has been in a dark period. This research aims to determine the type of loss trauma experienced by Anya. As a trauma survivor, Anya's post-traumatic growth was also explained in this research. Two theories were utilized in this research. Freud's theory of mourning and melancholia was used to analyze the type of loss trauma that Anya experienced. Meanwhile, the post-traumatic growth theory (PTG) proposed by Tedeschi and Calhoun was used to determine Anya's post-traumatic growth domain. The primary data for this research were taken from the novel of Critical Eleven written by Ika Natassa. In addition, research related to traumatic loss and post-traumatic growth was used as supporting data. The research results show that the trauma of loss experienced by Anya is grief or mourning. Furthermore, the PTG domains found in Anya's personality reflected personal strength, inter-personal relationships, and spiritual change. In addition, this research also found that not all trauma survivors can achieve the five domains of post-traumatic growth due to the respective capabilities and life processes of each survivor.

Climate variability in northern Africa during the late Holocene: A multiproxy perspective from El-Beida Lake (Wadi El-Natrun, Egypt)

North Africa is a key region hosting ca. 230 million people that are dependent on climate to maintain their subsistence through agriculture. Because of the current global changes, understanding the mechanisms behind the climate variations that occurred in this region is extremely important. To contribute to a more accurate modelling projection, we reconstructed the paleoclimatic and paleoenvironmental variations from the Meghalayan (∼1,500 ka) to recent using palynological and geochemical data from a sediment core from El-Beida Lake (Wadi El-Natrun area, north Western Desert of Egypt). North Africa underwent significant shifts in climatic conditions forced by different drivers since the Roman Warm Period (RWP) until recent. Our sediment core record indicates that this region experienced a persistent dry and warm climate during the RWP until the first half of the Medieval Climate Anomaly (MCA). The positive North Atlantic Oscillation was the main driver for controlling the precipitation pattern and pushing the precipitation towards central and north Europe and favoring the dry climate in North Africa during the RWP. The dry and slightly cold conditions in the study area during the Dark Age Cold Period (DACP) can be ascribed to the coupling between the more southward position of the Azores Front and the weak Atlantic Meridional Overturning Circulation. Northern Africa showed variable climatic conditions during the Medieval Climate Anomaly (MCA) due to the complicated thermohaline circulation of the Mediterranean Sea. During this time, the Eastern Mediterranean experienced a cold or partially cold MCA that may be extended to the present study area. An abrupt change to humid and cold climatic conditions occurred in northern Africa during the Little Ice Age (LIA) due to large-scale processes like the ENSO and NAO. The SST warming of the North Tropical Atlantic (NTA), significantly influenced by ENSO, causes the position of the Atlantic ITCZ to be shifted northward affecting precipitation in Africa.

Brexpiprazole: A new option in treating agitation in Alzheimer's dementia-Insights from transgenic mouse models.

Brexpiprazole is the first FDA-approved treatment for agitation associated with dementia due to Alzheimer's disease. Agitation in Alzheimer's dementia (AAD) occurs in high prevalence and is a great burden for patients and caregivers. Efficacy, safety, and tolerability of brexpiprazole were demonstrated in the AAD clinical trials. To demonstrate the agitation-ameliorating effect of brexpiprazole in animals, we evaluated brexpiprazole in two AAD mouse models. The resident-intruder test was conducted in 5- to 6-month-old Tg2576 mice, given vehicle or brexpiprazole (0.01 or 0.03 mg/kg) orally 1 h before the test. Locomotor activity was measured in 6-month-old APPSL-Tg mice given vehicle or brexpiprazole (0.01 or 0.03 mg/kg) orally the evening before the start of locomotor measurement for 3 days. In the resident-intruder test, Tg2576 mice showed significantly higher attack number and shorter latency to first attack compared to non-Tg mice. In the Tg mice, brexpiprazole treatment (0.03 mg/kg) significantly delayed the latency to first attack and showed a trend toward a decrease in attack number. APPSL-Tg mice (≧6 months old) showed significantly higher locomotion during dark period Phase II (Zeitgeber time [ZT] 16-20) and Phase III (ZT20-24) compared to non-Tg mice, correlating with the clinical observations of late afternoon agitation in Alzheimer's disease. Brexpiprazole treatment (0.01 and 0.03 mg/kg) significantly decreased hyperlocomotion during the Phase III in APPSL-Tg mice. The suppression of attack behavior and the reduction of nocturnal hyperlocomotion in these Tg mice may be indicative of the therapeutic effect of brexpiprazole on AAD, as demonstrated in the clinical trials.

Utilizing excitation-emission matrix fluorescence spectroscopy and convolutional neural networks for dark tea brand and aging period identification

This study utilized excitation-emission matrix (EEM) fluorescence spectroscopy in conjunction with convolutional neural networks (CNNs) to identify the dark tea brands and their aging periods, which were both key factors of market value. The adaptation of EEM data to the CNN model was examined, encompassing the configuration of the data structure and the implementation of data augmentation. Three typical CNN models including AlexNet, GoogLeNet, and ResNet were evaluated. ResNet was selected because it demonstrated the highest classification accuracy on the test set and superior clustering performance in the t-SNE visualization of extracted features. Analysis of feature contribution suggested that the CNN model exhibited enhanced sensitivity towards the boundaries of the fluorescence region. Furthermore, transfer learning was proved to be effective in facilitating adaptation of dark tea recognition models to databases with different sample sizes, which was meaningful for the application of this method in dark tea market supervision. Finally, the multi-task model was developed and achieved a 96.9 % accuracy in brand identification and 87.5 % in aging period determination, suggesting the advantages of multi-task learning in enhancing model generalization and training efficiency.

Isoflurane anesthesia and sleep deprivation trigger delayed and selective sleep alterations

Isoflurane anesthesia (IA) partially compensates NREM sleep (NREMS) and not REM sleep (REMS) requirement, eliciting post-anesthetic REMS rebound. Sleep deprivation triggers compensatory NREMS rebounds and REMS rebounds during recovery sleep as a result of the body’s homeostatic mechanisms. A combination of sleep deprivation and isoflurane anesthesia is common in clinical settings, especially prior to surgeries. This study investigates the effects of pre-anesthetic sleep deprivation on post-anesthetic sleep–wake architecture. The effects of isoflurane exposure (90 min) alone were compared with the effects of isoflurane exposure preceded by experimental sleep deprivation (6 h, gentle handling) on recovery sleep in adult mice by studying the architecture of post-anesthetic sleep for 3 consecutive post-anesthetic days. Effects of isoflurane anesthesia on recovery sleep developed only during the first dark period after anesthesia, the active phase in mice. During this time, mice irrespective of preceding sleep pressure, showed NREMS and REMS rebound and decreased wakefulness during recovery sleep. Additionally, sleep deprivation prior to isoflurane treatment caused a persistent reduction of theta power during post-anesthetic REMS at least for 3 post-anesthetic days. We showed that isoflurane causes NREMS rebound during recovery sleep which suggests that isoflurane may not fully compensate for natural NREMS. The study also reveals that isoflurane exposure preceded by sleep deprivation caused a persistent disruption of REMS quality. We suggest that preoperative sleep deprivation may impair postoperative recovery through lasting disruption in sleep quality.

The 4.2 ka event: A review of palaeoclimate literature and directions for future research

In recent years, much evidence has been presented on the 4.2 ka event. A review of 317 palaeoclimate papers shows that dry conditions were common during the event, especially from Eastern Mediterranean to India. The 4.2 ka event was not, however, a global drought event. Wet conditions were reported especially for central/northern Europe and sub-Saharan Africa. The 4.2 ka event is typically characterized either as short (4.2–4.0 ka) or long (4.4–3.8 ka) episode, possibly developing over an extended interval of time, in keeping with the North Atlantic forcing and correlating with the Bond 3 event of ice-rafted debris. This forcing is understood to drive a southward migration of the Inter-Tropical Convergence Zone (ITCZ), resulting in decreased rainfall over most of the Asian monsoon region, with possibility that an interplay of El Niño–Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO) has modulated the global circulation. Cold conditions were also reported but less frequently, in comparison to other Bond events such as the 8.2 ka event, Dark Ages Cold Period and Little Ice Age. Some high-resolution records show a double peak structure of which two anomalies are tree-ring dated to 4.14–4.05 ka and 3.97 ka. Accurately and precisely dated high-resolution records indicative of various climatic variables, especially outside of the traditional study region (Mediterranean–Middle East–India–China), including reconstructions of the ENSO and NAO histories and ITCZ migrations, are crucially needed for rigorous examination of the global scale characteristics of the 4.2 ka event and its forcings. Such research seems to be just beginning.

Altered Metabolism during the Dark Period in Drosophila Short Sleep Mutants.

Sleep is regulated via circadian mechanisms, but effects of sleep disruption on physiological rhythms, in particular metabolic cycling, remain unclear. To examine this question, we probed diurnal metabolic alterations of two Drosophila short sleep mutants, fumin and sleepless. Samples were collected with high temporal sampling (every 2 h) over 24 h under a 12:12 light:dark cycle, and profiling was done using an ion-switching LCMS/MS method. Fewer metabolites with 24 h oscillations were noted with short sleep (50 and 46 in fumin and sleepless, BH. Q < 0.2 by RAIN analysis) compared to a wild-type control (iso31, 63 with BH. Q < 0.2), and peak phases of the sleep mutants were consolidated into two major phase peaks at mid-day and middle of night. Overall, altered nicotinate/nicotinamide, alanine/aspartate/glutamate, acetylcholine, glyoxylate/dicarboxylate, and TCA cycle metabolism were observed in the short sleep mutants, indicative of increased energetic demand and oxidative stress compared to wild type. Both changes in cycling and discriminant models suggest unique alterations in the dark period indicative of constrained metabolic networks. Thus, we conclude that sleep loss alters metabolic function uniquely throughout the day, and further examination of specific mechanisms is warranted.