Cortical diurnal rhythms remain intact with microglial depletion

Microglia are subject to change in tandem with the endogenously generated biological oscillations known as our circadian rhythm. Studies have shown microglia harbor an intrinsic molecular clock which regulates diurnal changes in morphology and influences inflammatory responses. In the adult brain, microglia play an important role in the regulation of condensed extracellular matrix structures called perineuronal nets (PNNs), and it has been suggested that PNNs are also regulated in a circadian and diurnal manner. We sought to determine whether microglia mediate the diurnal regulation of PNNs via CSF1R inhibitor dependent microglial depletion in C57BL/6J mice, and how the absence of microglia might affect cortical diurnal gene expression rhythms. While we observe diurnal differences in microglial morphology, where microglia are most ramified at the onset of the dark phase, we do not find diurnal differences in PNN intensity. However, PNN intensity increases across many brain regions in the absence of microglia, supporting a role for microglia in the regulation of PNNs. Here, we also show that cortical diurnal gene expression rhythms are intact, with no cycling gene changes without microglia. These findings demonstrate a role for microglia in the maintenance of PNNs, but not in the maintenance of diurnal rhythms.

Dynamic changes in gas solubility of xylem sap reiterate the enigma of plant water transport under negative pressure

Despite a long research history, we do not fully understand why plants are able to transport xylem sap under negative pressure without constant failure. Microbubble formation via direct gas entry is assumed to cause hydraulic failure, while the concentration of gas dissolved in xylem sap is traditionally supposed to be constant, following Henry's law. Here, the concentration of soluble gas in xylem sap was estimated in vivo using well-watered Citrus plants under varying levels of air temperature and photoperiodic exposure, and compared to modelled data. The gas concentration in xylem sap showed non-equilibrium curves, with a minimum over-or undersaturation of 5% compared to gas solubility based on Henry's law. A similar diurnal pattern was obtained from the gas concentration in the cut-open conduits and discharge tube, and oversolubility was strongly associated with decreasing xylem water potentials during transpiration. Although our model did not explain the daily changes in gas solubility for an anisobaric situation, oversolubility characterises nanoconfined liquids, such as sap inside cell walls. Thus, plants are able to transport sap under negative pressure with relatively high amounts of dissolved gas, providing them with a buffering capacity to prevent hydraulic failure, despite diurnal changes in pressure and temperature.

Effect of diurnal changes on the auditory working memory in individuals with normal hearing

The human circadian rhythmicity is an internal biological clock mechanism that enables them to effectively perform tasks during a particular time of the day, due to which they exhibit diurnal effects. The morningness-eveningness questionnaire classifies individuals as definitely morning, moderately morning, intermediate, moderately evening, and definitely evening type individuals based on their active performance during different times of the day. Literature show variations in visual, memory, audition, and other cognitive tasks throughout the day in every individual. The current study aimed to document the diurnal effects on auditory working memory, a phenomenon crucial for learning and academic outcomes and holds its role in various clinical and research fields. Thirty-two participants were enrolled (21 females and 11 males) and were classified based on the morningness-eveningness questionnaire. The Auditory Working Memory tests were carried out during the morning and evening for all the participants. Based on a parametric paired t-test, results reveal no significant differences between morning time and evening time across moderately morning, intermediate, and moderately evening groups implying that working memory is a higher-order function that shows no or negligible diurnal effects, unlike other lower-order functions like temporal processing of auditory signals.

Adaptation of Temperate Seagrass to Arctic Light Relies on Seasonal Acclimatization of Carbon Capture and Metabolism

Due to rising global surface temperatures, Arctic habitats are becoming thermally suitable for temperate species. Whether a temperate species can immigrate into an ice-free Arctic depends on its ability to tolerate extreme seasonal fluctuations in daylength. Thus, understanding adaptations to polar light conditions can improve the realism of models predicting poleward range expansions in response to climate change. Plant adaptations to polar light have rarely been studied and remain unknown in seagrasses. If these ecosystem engineers can migrate polewards, seagrasses will enrich biodiversity, and carbon capture potential in shallow coastal regions of the Arctic. Eelgrass (Zostera marina) is the most widely distributed seagrass in the northern hemisphere. As the only seagrass species growing as far north as 70°N, it is the most likely candidate to first immigrate into an ice-free Arctic. Here, we describe seasonal (and diurnal) changes in photosynthetic characteristics, and in genome-wide gene expression patterns under strong annual fluctuations of daylength. We compared PAM measurements and RNA-seq data between two populations at the longest and shortest day of the year: (1) a Mediterranean population exposed to moderate annual fluctuations of 10–14 h daylength and (2) an Arctic population exposed to high annual fluctuations of 0–24 h daylength. Most of the gene expression specificities of the Arctic population were found in functions of the organelles (chloroplast and mitochondrion). In winter, Arctic eelgrass conserves energy by repressing respiration and reducing photosynthetic energy fluxes. Although light-reactions, and genes involved in carbon capture and carbon storage were upregulated in summer, enzymes involved in CO2 fixation and chlorophyll-synthesis were upregulated in winter, suggesting that winter metabolism relies not only on stored energy resources but also on active use of dim light conditions. Eelgrass is unable to use excessive amounts of light during summer and demonstrates a significant reduction in photosynthetic performance under long daylengths, possibly to prevent photoinhibition constrains. Our study identified key mechanisms that allow eelgrass to survive under Arctic light conditions and paves the way for experimental research to predict whether and up to which latitude eelgrass can potentially migrate polewards in response to climate change.

Diurnal Variations in Physiological Characteristics, Photoassimilates, and Total Ascorbate in Early and Late Sown Indian Wheat Cultivars under Exposure to Elevated Ozone

Rising tropospheric ozone (O3) in the atmosphere is detrimental to crop’s productivity and is one of the reasons for a warmer climate. The present study describes diurnal changes in gaseous exchange, chlorophyll fluorescence, ascorbic acid, and photoassimilate parameters in flag leaves of four Indian wheat (Triticum aestivum L.) cultivars (two early sown and two late sown cultivars) under ambient and elevated O3 treatments, using the open-top chambers (OTCs). Results showed that the diurnal pattern of photosynthetic rate (Ps), sucrose, and ascorbic acid content varied according to changes in photosynthetically active radiation (PAR) and O3 concentrations during the daytime and were maximum between 10:00 to 12:00. The present study suggested that elevated O3 caused more negative effects on photosystem II in early sown compared to late sown cultivars. The greater loss of photosynthesis led to lower production of photoassimilates in early sown cultivars, which utilized more assimilates in ascorbic acid formation for detoxification of ROS formed due to elevated O3. This work will also help to identify the robustness of physiological machinery in different wheat cultivars under elevated levels of O3, and may be used for selection of suitable cultivars during future breeding programs.

A Synthetic Chrono Genetic Therapy Gene for Consecutive Drug Delivery

Chronotherapy, the delivery of therapeutic interventions personalized to patient's circadian rhythms, has shown enhanced therapeutic efficacy and reduced side effects. Patients exhibit diurnal changes in cytokines in rheumatoid arthritis that lead to inflammatory flares and enhanced disease severity in the early morning. There has been important work showing the administration of anti-inflammatory treatments in the early morning, immediately before the inflammatory flare, in reducing symptoms of RA. Using synthetic biology, we developed chronotherapy-based gene chromogenic therapies that produce our prescribed transgene downstream of the core circadian clock component, Per2. We transduced these lentiviral chromogenic therapies into murine-induced pluripotent stem cells and developed tissue-engineered cartilage as our model system for timed drug delivery. Our anti-inflammatory chromogenic could produce interleukin-1 receptor antagonist (IL-1Ra) in an oscillatory manner tracking with circadian rhythms in vitro. Additionally, the tissue-engineered pellets could entrain host circadian rhythms when implanted into mice and produce different levels of IL-1Ra in the serum at other times of the day. The chromogenic synthetic gene provides a novel cell therapy driving by the circadian clock for controlled biologic delivery at prescribed times of the day.

Diurnal Response of Photosystem I to Fluctuating Light Is Affected by Stomatal Conductance

Upon a sudden transition from low to high light, electrons transported from photosystem II (PSII) to PSI should be rapidly consumed by downstream sinks to avoid the over-reduction of PSI. However, the over-reduction of PSI under fluctuating light might be accelerated if primary metabolism is restricted by low stomatal conductance. To test this hypothesis, we measured the effect of diurnal changes in stomatal conductance on photosynthetic regulation under fluctuating light in tomato (Solanum lycopersicum) and common mulberry (Morus alba). Under conditions of high stomatal conductance, we observed PSI over-reduction within the first 10 s after transition from low to high light. Lower stomatal conductance limited the activity of the Calvin–Benson–Bassham cycle and aggravated PSI over-reduction within 10 s after the light transition. We also observed PSI over-reduction after transition from low to high light for 30 s at the low stomatal conductance typical of the late afternoon, indicating that low stomatal conductance extends the period of PSI over-reduction under fluctuating light. Therefore, diurnal changes in stomatal conductance significantly affect the PSI redox state under fluctuating light. Moreover, our analysis revealed an unexpected inhibition of cyclic electron flow by the severe over-reduction of PSI seen at low stomatal conductance. In conclusion, stomatal conductance can have a large effect on thylakoid reactions under fluctuating light.

Eye temperature, an indicator for stress levels in young buffalo bulls – A case study of micro-environment modification

The present study was undertaken with an objective to determine diurnal changes of the eye temperature of buffalo young bulls under different shelter management to determine the effect of heat stress. Twenty four buffalo bulls were randomly divided into two groups, each group comprising of 12 animals based on age (16–18 months) and body weight (Control = 301 ± 8.24 kg and Treatment = 311.45 ± 6.24 kg). The control group was housed under normal management practices followed, and the height of the shed was 10 ft. and width was 12 ft. with concrete floor. Whereas, the treatment group was housed in shed having 15 ft. height and 25 ft. width along with rubber mat as flooring and the total area provided for each animal in both the groups was 45.96 sq. feet. They were also provided with dairy fans and mist cooling in day time to ameliorate the heat stress. The thermal humidity index (THI), floor and roof temperature variation of the shed was recorded. The eye temperature of bulls was measured to evaluate the effect of different housing on the animals’ thermal status under hot dry summer conditions.Results revealed that the THI of treatment shed was significantly (P< 0.01) lower than the control at different times. The floor and roof surface temperature of the treatment shed was significantly (P<0.05) lower than the control shed. Diurnal patterns of eye temperature measured in both the groups showed increased eye temperature in control group bulls compared to treatment group. The eye temperature at 7.00 hrs was similar in both groups, whereas it was highly significant (P<0.01) at 13.00 and 19.00 hrs. The heat stress in the buffalo bulls was exhibited by increased eye temperature. Thus, the variation in the eye temperature can be effectively used as an indicator of heat stress and the dairy fans and mist cooling along with rubber mat flooring can be utilized to ameliorate the heat stress in the buffalo bulls.

Detection of Possible Short-Term Ionospheric Precursors of Strong Earthquakes Based on Changes in Diurnal Es Characteristics

The changes in two characteristics of the sporadic Е layer are studied for a pair of stations: the probability of the occurrence PEs and the limiting frequency of the ordinary wave of the sporadic E layer of the ionosphere foEs during a 10-day period of the preparation of 19 crustal earthquakes in the Pacific region with М = 6.5–7.4. The stations are located hundreds of kilometers from each other, but they fall within the zone of the preparation of a particular earthquake (the sizes of the earthquake preparation zone are estimated with formulas known in the scientific literature that relate the size of the radius of the earthquake preparation zone and the earthquake magnitude). The measurement data obtained at the ground stations of ionospheric vertical sounding are analyzed. The deviations of diurnal values of PEs (δPEs) from the median over the studied time interval and the integral diurnal values of the total irregular fluctuations in foEs (ΔfEsΣ) are used to identify possible ionospheric earthquake precursors. The coincidence of the time of appearance of the deviation maxima for both parameters before the earthquakes at each of the stations on the same day (from 1 to 4 days before the earthquake day) is recorded in the diurnal changes in the indicated values during the preparation periods of all of the considered earthquakes. The criteria for the identification of a short-term ionospheric earthquake precursor is discussed. Comparison of the analysis results for manual and automatic ionogram processing showed the prospects for the use the proposed parameters obtained according to the data of the distant ionosondes to identify the short-term ionospheric precursors of an earthquake with М = 6.5–7.0.