Early Dark Research Articles

Brain somatostatin receptor 2 mediates the dipsogenic effect of central somatostatin and cortistatin in rats: role in drinking behavior.

Intracerebroventricular injection of stable somatostatin (SST) agonists stimulates food and water intake in rats. We investigated the receptor subtype(s) involved in the dipsogenic effect of intracerebroventricular injection of SST agonists, mechanisms of action, and role. In nonfasted and non-water-deprived male rats with chronic intracerebroventricular cannula, intake of water without food or food without water was monitored separately to avoid any interactions compared with intracerebroventricular vehicle. SST-14 and cortistatin (CST-14) (1 μg/rat icv) increased water intake by 3.1- and 2.7-fold, respectively, while both peptides did not alter food intake at 1 h postinjection in the light phase. By contrast, the stable pan-somatostatin agonist ODT8-SST (1 μg/rat icv) increased both water and food intake by 4.9- and 3.7-fold, respectively. S-346-011, a selective receptor 2 (sst2) agonist (1 μg/rat icv) induced water ingestion, while sst1 or sst4 agonist, injected under the same conditions, did not. The sst2 antagonist S-406-028 (1 μg/rat icv) prevented the 1-h water intake induced by intracerebroventricular ODT8-SST and CST-14. Losartan (100 μg/rat icv), an angiotensin receptor 1 (AT1) antagonist, completely blocked the water consumption induced by intracerebroventricular ODT8-SST, whereas intracerebroventricular injection of S-406-028 did not modify the intracerebroventricular ANG II-induced dipsogenic response. The sst2 antagonist reduced by 40% the increase of the 3-h water intake in the early dark phase. These data indicate that SST-14 and CST-14 interact with sst2 to exert a potent dipsogenic effect, which is mediated downstream by angiotensin-AT1 signaling. These data also indicate that sst2 activation by brain SST-14 and/or CST-14 may play an important role in the regulation of drinking behavior.

Full investigation on the dynamics of power-law kinetic quintessence

We give a full investigation on the dynamics of power-law kinetic quintessence $L(X,\ensuremath{\phi})=V(\ensuremath{\phi})(\ensuremath{-}X+{X}^{2})$ by considering the potential related parameter $\mathrm{\ensuremath{\Gamma}}(=\frac{V{V}^{\ensuremath{'}\ensuremath{'}}}{{{V}^{\ensuremath{'}}}^{2}})$ as a function of another potential parameter $\ensuremath{\lambda}(=\frac{{V}^{\ensuremath{'}}}{\ensuremath{\kappa}{V}^{3/2}})$, which correspondingly extends the analysis of the dynamical system of our Universe from two dimensional to three dimensional. In addition to the critical points found in previous papers, we find a new de Sitter-- like dominant attractor ($cp6$) and give its stable condition using the center manifold theorem. For the dark energy dominant solution ($cp6$ and $cp7$), it could be distinguished from canonical quintessence and tachyon models since the sound speed ${c}_{s}^{2}=0$ or ${c}_{s}^{2}\ensuremath{\ll}1$. For the scaling solution ($cp8$), it is very interesting that the sound speed ${c}_{s}^{2}=1/5$, while it behaves as ordinary matter. We therefore point out that the power-law kinetic quintessence should have different signatures on the cold dark matter power spectrum and the cosmic microwave background both at early time, when this scalar field is an early dark energy with ${\mathrm{\ensuremath{\Omega}}}_{\ensuremath{\phi}}$ being non-negligible at high redshift, and at late time, when it drives the accelerating expansion. We still do not know whether there are any degeneracies of the impacts between these two epoches. They are expected to be investigated in future.

Daily behavioral activities of bullfrog Lithobates catesbeianus (Shaw 1802)

Studies on the daily behavioral activities of bullfrogs in laboratories may indicate avenues for appropriate technical management for this specie culture. Twenty-four post-metamorphic phase Lithobates catesbeianus (Shaw 1802) bullfrogs had their daily activities described. The animals were housed in six experimental stalls and feed was offered once a day at random times over 10 days of filming. Behavioral activity in each stall was recorded for the first 15 minutes of every hour in a 24-hour period. As results, we observed that ingestion and movement on dry ground were more common at dawn and rare in dark; inactivity on dry ground occurred more in the late night and at dawn. Consequently, there was preference for sheltering less at dawn and in the end of dark phases. The inactivity behavior in the water was more frequent during the early dark phase, showing an inverse relationship with respect to preferred times for feed ingestion. As a result of observed behaviors, we recommended that feed offerings for bullfrogs in captivity are during the light phase of day and that it is available until the following morning.

Dark energy coupling with electromagnetism as seen from future low-medium redshift probes

Beyond the standard cosmological model the late-time accelerated expansion of the universe can be reproduced by the introduction of an additional dynamical scalar field. In this case, the field is expected to be naturally coupled to the rest of the theory's fields, unless a (still unknown) symmetry suppresses this coupling. Therefore, this would possibly lead to some observational consequences, such as space-time variations of nature's fundamental constants. In this paper we investigate the coupling between a dynamical Dark Energy model and the electromagnetic field, and the corresponding evolution of the fine structure constant ($\alpha$) with respect to the standard local value $\alpha_0$. In particular, we derive joint constraints on two dynamical Dark Energy model parametrizations (the Chevallier-Polarski-Linder and Early Dark Energy model) and on the coupling with electromagnetism $\zeta$, forecasting future low-medium redshift observations. We combine supernovae and weak lensing measurements from the Euclid experiment with high-resolution spectroscopy measurements of fundamental couplings and the redshift drift from the European Extremely Large Telescope, highlighting the contribution of each probe. Moreover, we also consider the case where the field driving the $\alpha$ evolution is not the one responsible for cosmic acceleration and investigate how future observations can constrain this scenario.

Snake bite poisoning: A neglected life-threatening occupational hazard

Snake bite poisoning: A neglected life-threatening occupational hazard

Late Barremian–early Aptian dark facies of the Subbetic (Betic Cordillera, southern Spain): Calcareous nannofossil quantitative analyses, chemostratigraphy and palaeoceanographic reconstructions

In order to determine the driving mechanism behind the deposition of the Aptian dark facies in the pelagic Subbetic Basin (southern Spain), two latest Barremian–early Aptian complementary sections embracing the Oceanic Anoxic Event 1a, were selected for a multidisciplinary study. Quantitative and statistical analyses of calcareous nannofossil assemblages are complemented with planktonic foraminifera, radiolaria, and geochemical data (C and O isotopes and biomarkers). The results indicate that most of the latest Barremian was characterized by oligotrophic conditions with a low nutricline and neritic influence, which were interrupted by short-lived episodes of mesotrophic surface waters. In contrast, broadly meso-eutrophic surface waters with a high nutricline and a probable development of water stratification are inferred for most of the early Aptian. It is suggested that an increased runoff, as a consequence of a more humid climate in the adjacent continental area, caused this fertilization. Neritic dwellers, such as nannoconids and pentaliths, experienced a drastic decrease in abundance as the result of the combined effects of a biocalcification crisis (‘nannoconid crisis’) and the deepening of the basin. High productivity and enhanced surface-water stratification favoured low oxygen content in the bottom waters, increasing organic matter preservation. A reduction in surface water fertility and a shift towards generally cooler conditions occurred during the late early Aptian. It is postulated that a cooler and drier climate leads to a reduction in runoff and decreased nutrient flux into the basin. The obtained results suggest that the formation of the Aptian dark facies was mainly controlled by enhanced production of organic matter in the upper water column and not enhanced preservation.

Freezing out early dark energy

A phenomenological model of dark energy that tracks the baryonic and cold dark matter at early times but resembles a cosmological constant at late times is explored. In the transition between these two regimes, the dark energy density drops rapidly as if it were a relic species that freezes out, during which time the equation of state peaks at +1. Such an adjustment in the dark energy density, as it shifts from scaling to potential-domination, could be the signature of a trigger mechanism that helps explain the late-time cosmic acceleration. We show that the non-negligible dark energy density at early times, and the subsequent peak in the equation of state at the transition, leave an imprint on the cosmic microwave background anisotropy pattern and the rate of growth of large scale structure. The model introduces two new parameters, consisting of the present-day equation of state and the redshift of the freeze-out transition. A Monte Carlo Markov Chain analysis of a ten-dimensional parameter space is performed to compare the model with pre-Planck cosmic microwave background, large scale structure and supernova data and measurements of the Hubble constant. We find that the transition described by this model could have taken place as late as a redshift z~400. We explore the capability of future cosmic microwave background and weak lensing experiments to put tighter constraints on this model. The viability of this model may suggest new directions in dark-energy model building that address the coincidence problem.

Geology, isotopes and geochronology of the Caijiaping Pb–Zn deposit in the North Wuyi area, South China: Implications for petrogenesis and metallogenesis

The Caijiaping Pb–Zn deposit is a recently discovered subvolcanic hydrothermal deposit in the North Wuyi area. Its mineralization is generally distributed at the contact of rhyolite porphyry and sandstone, and in the interlayer crushed zone of Early Jurassic sandstone. Sulfide minerals in this deposit mainly consist of abundant sphalerite, galena, pyrite and chalcopyrite. Silicification, chloritization and sericitization are widely developed and closely related to the Pb–Zn mineralization. The δ34S values of early dark brown sphalerite (marmatite), main-stage sphalerite and galena (−1.1–2.5‰, average 0.83‰) suggest that the sulfur was mainly sourced from a magmatic system. Lead isotope ratios in the sulfide minerals, rhyolite porphyry and sandstone are relatively homogeneous (206Pb/204Pb=17.786–18.612, 207Pb/204Pb=15.504–15.635, 208Pb/204Pb=38.115–38.798), and are compatible with metamorphic rocks of Mesoproterozoic Zhoutan Group (Wuyi metamorphosed basement). Early Jurassic sandstone, deposited in an active continental margin or continental arc setting, exhibits low textural maturity and displays geochemical similarities to the Zhoutan Group. The rhyolite porphyry, with features of volcanic arc granite, also shows an affinity with the Zhoutan Group. SIMS zircon U–Pb dating shows that the rhyolite porphyry was emplaced at 156.0±1.2Ma, indicating that Caijiaping mineralization formed later than 156Ma. Hf isotope compositions of the rhyolite porphyry [εHf(t)=−14.3 to −8.5, average −10.6] imply that it was mainly derived from reworking of ancient crust. Potassium feldspar selected from felsic veins within the ore-cutting F4 fault yields a 40Ar/39Ar age of 120.0±4.0Ma, indicating that the Pb–Zn mineralization formed before 120Ma. Therefore, the age of mineralization is bracketed between 156 and 120Ma. Combined with regional geological information, we propose that the Caijiaping mineralization mainly formed from magmatic hydrothermal processes in a regionally extensional setting, and the Wuyi metamorphosed basement significantly contributed to diagenetic and metallogenic processes in this deposit.

Drugs that prevent mouse sleep also block light-induced locomotor suppression, circadian rhythm phase shifts and the drop in core temperature

Exposure of mice to a brief light stimulus during their nocturnal active phase induces several simultaneous behavioral or physiological responses, including circadian rhythm phase shifts, a drop in core body temperature (Tc), suppression of locomotor activity and sleep. Each response is triggered by light, endures for a relatively fixed interval and does not require additional light for expression. The present studies address the ability of the psychostimulant drugs, methamphetamine (MA), modafinil (MOD) or caffeine (CAF), to modify the light-induced responses. Drug or vehicle (VEH) was injected at CT11 into constant dark-housed mice then exposed to 5-min 100μW/cm2 light or no light at CT13. Controls (VEH/Light) showed approximately 60-min phase delays. In contrast, response was substantially attenuated by each drug (only 12–15min delays). Under a 12-h light:12-h dark (LD12:12) photoperiod, VEH/light-treated mice experienced a Tc drop of about 1.3°C coincident with locomotor suppression and both effects were abolished by drug pre-treatment. Each drug elevated activity during the post-injection interval, but there was also evidence for CAF-induced hypoactivity in the dark prior to the photic test stimulus. CAF acutely elevated Tc; MA acutely lowered it, but both drugs reduced Tc during the early dark (ZT12.5–ZT13). The ability of the psychostimulant drugs to block the several effects of light exposure is not the result of drug-induced hyperactivity. The results raise questions concerning the manner in which drugs, activity, sleep and Tc influence behavioral and physiological responses to light.

An epidemiological study of the risk of cycling in the dark: The role of visual perception, conspicuity and alcohol use

To curtail the rising numbers of cyclists seriously injured in road crashes, more insights are needed into the factors that contribute to these crashes. For instance, darkness is known to be associated with higher injury rates, but little is known about the relative influence of factors such as poor conspicuity, impaired perception and alcohol use among cyclists. To examine these factors, the present study analyzed the epidemiological crash data for three meteorological light conditions: daylight, late evening darkness and early morning darkness; for two crash types: crashes with (M-crashes) and without motorized traffic (NM-crashes); and for different age groups. The relative injury rates (injury risk per distance travelled in darkness corrected for daylight injury risks for each age group) confirmed findings from earlier studies that cycling in late evening darkness is associated with higher injury rates than cycling in daylight conditions. This is the case for both crash types with only small differences between the age groups suggesting that poor conspicuity (M-crashes) and impaired perception (NM-crashes) may play a role. In comparison to late evening darkness, relative injury rates in early morning darkness are much higher. This is the case for both crash types with large differences among the age groups, suggesting that in addition to the absence of daylight also age related risk factors are at play. Support for this hypothesis was found from the analyses of hospital records, showing that the proportion of seriously injured cyclists who have been drinking is highest in early morning darkness and has strongly increased over the last decades. These insights provide input for the selection of countermeasures such as improved lighting (both street and bicycle lights) and interventions targeting alcohol use among cyclists.

Cluster probes of dark energy clustering

Cluster abundances are oddly insensitive to canonical early dark energy. Early dark energy with sound speed equal to the speed of light cannot be distinguished from a quintessence model with the equivalent expansion history for $z<2$ but negligible early dark energy density, despite the different early growth rate. However, cold early dark energy, with a sound speed much smaller than the speed of light, can give a detectable signature. Combining cluster abundances with cosmic microwave background (CMB) power spectra can determine the early dark energy fraction to 0.3% and distinguish a true sound speed of 0.1 from 1 at 99% confidence. We project constraints on early dark energy from the Euclid cluster survey, as well as the Dark Energy Survey, using both current and projected Planck CMB data, and assess the impact of cluster mass systematics. We also quantify the importance of dark energy perturbations, and the role of sound speed during a crossing of $w=\ensuremath{-}1$.

New Constraints on the Early Expansion History of the Universe

Cosmic microwave background measurements have pushed to higher resolution, lower noise, and more sky coverage. These data enable a unique test of the early Universe's expansion rate and constituents such as effective number of relativistic degrees of freedom and dark energy. Using the most recent data from Planck and WMAP9, we constrain the expansion history in a model-independent manner from today back to redshift z=10(5). The Hubble parameter is mapped to a few percent precision, limiting early dark energy and extra relativistic degrees of freedom within a model-independent approach to 2%-16% and 0.71 equivalent neutrino species, respectively (95% C.L.). Within dark radiation, barotropic ether, and Doran-Robbers models, the early dark energy constraints are 3.3%, 1.9%, and 1.2%, respectively.

Generalized holographic dark energy model in the Hubble length

We generalize the holographic dark energy model described in Hubble length IR cutoff by assuming a slowly time varying function for holographic parameter $c^2$. We calculate the evolution of EoS parameter and the deceleration parameter as well as the evolution of dark energy density in this generalized model. We show that the phantom line is crossed from quintessence regime to phantom regime which is in agreement with observation. The evolution of deceleration parameter indicates the transition from decelerated to accelerated expansion. Eventually, we show that the GHDE with HIR cutoff can interpret the pressureless dark matter era at the early time and dark energy dominated phase later.

Constraints on neutrino mass and light degrees of freedom in extended cosmological parameter spaces

From a combination of probes including the cosmic microwave background (WMAP7+SPT), Hubble constant (HST), baryon acoustic oscillations (SDSS+2dFGRS), and supernova distances (Union2), we have explored the extent to which the constraints on the effective number of neutrinos and sum of neutrino masses are affected by our ignorance of other cosmological parameters, including the curvature of the universe, running of the spectral index, primordial helium abundance, evolving late-time dark energy, and early dark energy. In a combined analysis of the effective number of neutrinos and sum of neutrino masses, we find mild (2.2 sigma) preference for additional light degrees of freedom. However, the effective number of neutrinos is consistent with the canonical expectation of 3 massive neutrinos and no extra relativistic species to within 1 sigma when allowing for evolving dark energy and relaxing the strong inflation prior on the curvature and running. The agreement improves with the possibility of an early dark energy component, itself constrained to be less than 5% of the critical density (95% CL) in our expanded parameter space. In extensions of the standard cosmological model, the derived amplitude of linear matter fluctuations sigma_8 is found to closely agree with low-redshift cluster abundance measurements. The sum of neutrino masses is robust to assumptions of the effective number of neutrinos, late-time dark energy, curvature, and running at the level of 1.2 eV (95% CL). The upper bound degrades to 2.0 eV (95% CL) when further including the early dark energy density and primordial helium abundance as additional free parameters. Even in extended cosmological parameter spaces, Planck alone could determine the possible existence of extra relativistic species at 4 sigma confidence and constrain the sum of neutrino masses to 0.2 eV (68% CL).

How early is early dark energy?

We investigate constraints on early dark energy (EDE) from the Cosmic Microwave Background (CMB) anisotropy, taking into account data from WMAP9 combined with latest small scale measurements from the South Pole Telescope (SPT). For a constant EDE fraction we propose a new parametrization with one less parameter but still enough to provide similar results to the ones previously studied in literature. The main emphasis of our analysis, however, compares a new set of different EDE parametrizations that reveal how CMB constraints depend on the redshift epoch at which Dark Energy was non negligible. We find that bounds on EDE get substantially weaker if dark energy starts to be non-negligible later, with early dark energy fraction Omega_e free to go up to about 5% at 2 sigma if the onset of EDE happens at z < 100. Tight bounds around 1-2% are obtained whenever dark energy is present at last scattering, even if its effects switch off afterwards. We show that the CMB mainly constrains the presence of Dark Energy at the time of its emission, while EDE-modifications of the subsequent growth of structure are less important.

Low home cage social behaviors in BTBR T+tf/J mice during juvenile development

BTBR T+tf/J (BTBR) is a genetically homogenous inbred strain of mice that displays abnormal social behaviors, deficits in vocalizations, and high levels of repetitive behaviors, relevant to the three diagnostic symptoms of autism spectrum disorder, leading to the use of this strain as a mouse model of autism. Comprehensive observations of BTBR social behaviors within the home cage during early stages of development have not been conducted. Here we evaluate the home cage behaviors of BTBR in two laboratory environments (NIMH, Bethesda, Maryland vs. UC Davis, Davis, California), starting from the day of weaning and continuing into adulthood. Extensive ethogram parameters were scored for BTBR in home cages that contained four BTBR conspecifics, versus home cages that contained four C57BL/6J (B6) conspecifics. BTBR were considerably less interactive than B6 in the home cage at both sites, as measured during the early dark stage of their circadian cycle. A novel home cage behavioral measure, frequency of long interactions, was found to be more frequent and of longer duration in B6 versus BTBR home cages across experimental sites. Significant strain differences in the occurrence of investigative and affiliative behaviors were also seen, however these findings were not fully consistent across the two testing sites. At the end of the 30-day home cage observation period, each seven-week old subject mouse was tested in the three-chambered social approach task. BTBR displayed lack of sociability and B6 displayed significant sociability, consistent with previous reports. Our findings reveal that BTBR engaged in lower levels of some components of spontaneous conspecific social interactions in the home cage environment throughout juvenile development, consistent with their deficits in juvenile and adult sociability as measured in specialized social tasks.

Impaired leukocyte trafficking and skin inflammatory responses in hamsters lacking a functional circadian system

The immune system is under strong circadian control, and circadian desynchrony is a risk factor for metabolic disorders, inflammatory responses and cancer. Signaling pathways that maintain circadian rhythms (CRs) in immune function in vivo, and the mechanisms by which circadian desynchrony impairs immune function, remain to be fully identified. These experiments tested the hypothesis that the hypothalamic circadian pacemaker in the suprachiasmatic nucleus (SCN) drives CRs in the immune system, using a non-invasive model of SCN circadian arrhythmia. Robust CRs in blood leukocyte trafficking, with a peak during the early light phase (ZT4) and nadir in the early dark phase (ZT18), were absent in arrhythmic hamsters, as were CRs in spleen clock gene (per1, bmal1) expression, indicating that a functional pacemaker in the SCN is required for the generation of CRs in leukocyte trafficking and for driving peripheral clocks in secondary lymphoid organs. Pinealectomy was without effect on CRs in leukocyte trafficking, but abolished CRs in spleen clock gene expression, indicating that nocturnal melatonin secretion is necessary for communicating circadian time information to the spleen. CRs in trafficking of antigen presenting cells (CD11c(+) dendritic cells) in the skin were abolished, and antigen-specific delayed-type hypersensitivity skin inflammatory responses were markedly impaired in arrhythmic hamsters. The SCN drives robust CRs in leukocyte trafficking and lymphoid clock gene expression; the latter of which is not expressed in the absence of melatonin. Robust entrainment of the circadian pacemaker provides a signal critical to diurnal rhythms in immunosurveilliance and optimal memory T-cell dependent immune responses.

Molecular Mechanism Regulating 24-Hour Rhythm of Dopamine D3 Receptor Expression in Mouse Ventral Striatum

The dopamine D3 receptor (DRD3) in the ventral striatum is thought to influence motivation and motor functions. Although the expression of DRD3 in the ventral striatum has been shown to exhibit 24-hour variations, the mechanisms underlying the variation remain obscure. Here, we demonstrated that molecular components of the circadian clock act as regulators that control the 24-hour variation in the expression of DRD3. The transcription of DRD3 was enhanced by the retinoic acid-related orphan receptor α (RORα), and its activation was inhibited by the orphan receptor REV-ERBα, an endogenous antagonist of RORα. The serum or dexamethasone-induced oscillation in the expression of DRD3 in cells was abrogated by the downregulation or overexpression of REV-ERBα, suggesting that REV-ERBα functions as a regulator of DRD3 oscillations in the cellular autonomous clock. Chromatin immunoprecipitation assays of the DRD3 promoter indicated that the binding of the REV-ERBα protein to the DRD3 promoter increased in the early dark phase. DRD3 protein expression varied with higher levels during the dark phase. Moreover, the effects of the DRD3 agonist 7-hydroxy-N,N-dipropyl-2-aminotetralin (7-OH-DPAT)-induced locomotor hypoactivity were significantly increased when DRD3 proteins were abundant. These results suggest that RORα and REV-ERBα consist of a reciprocating mechanism wherein RORα upregulates the expression of DRD3, whereas REV-ERBα periodically suppresses the expression at the time of day when REV-ERBα is abundant. Our present findings revealed that a molecular link between the circadian clock and the function of DRD3 in the ventral striatum acts as a modulator of the pharmacological actions of DRD3 agonists/antagonists.

NEW LIMITS ON THE FUNDAMENTAL CONSTANTS FROM THE CMB DATA

The Cosmic Microwave Background anisotropies provide a unique opportunity to constrain simultaneous variations of the fine-structure constant α and Newton's gravitational constant G. Those correlated variations are possible in a wide class of theoretical models. In this brief paper we show that the current data, assuming that particle masses are constant, gives no clear indication for such variations, but already prefers that any relative variations in α should be of the same sign of those of G for variations of ≈ 1%. We also show that a cosmic complementarity is present with Big Bang Nucleosynthesis, and that a combination of current CMB and BBN data strongly constraints simultaneous variations in α and G. We finally discuss the future bounds achievable by the Planck satellite mission. We discuss present and future cosmological constraints on variations of the fine structure constant α induced by an early dark energy component having the simplest allowed (linear) coupling to electromagnetism. We find that current cosmological data show no variation of the fine structure constant at recombination respect to the present-day value, with α/α0 = 0.975 ± 0.020 at 95% c.l., constraining the energy density in early dark energy to Ωe &lt; 0.060 at 95% c.l.

Model independent early expansion history and dark energy

We examine model independent constraints on the high redshift and prerecombination expansion history from upcoming cosmic microwave background observations, using a combination of principal component analysis and other techniques. This can be translated to model independent limits on early dark energy and the number of relativistic species ${N}_{\mathrm{eff}}$. Models such as scaling (Doran-Robbers), dark radiation ($\ensuremath{\Delta}{N}_{\mathrm{eff}}$), and barotropic aether fall into distinct regions of eigenspace and can be easily distinguished from each other. Incoming CMB data will map the expansion history from $z=0--{10}^{5}$, achieving subpercent precision around recombination, and enable determination of the amount of early dark energy and valuable guidance to its nature.