Although sleep appears to be broadly conserved in animals, the physiological functions of sleep remain unclear. In this study, we sought to identify a physiological defect common to a diverse group ...of short-sleeping Drosophila mutants, which might provide insight into the function and regulation of sleep. We found that these short-sleeping mutants share a common phenotype of sensitivity to acute oxidative stress, exhibiting shorter survival times than controls. We further showed that increasing sleep in wild-type flies using genetic or pharmacological approaches increases survival after oxidative challenge. Moreover, reducing oxidative stress in the neurons of wild-type flies by overexpression of antioxidant genes reduces the amount of sleep. Together, these results support the hypothesis that a key function of sleep is to defend against oxidative stress and also point to a reciprocal role for reactive oxygen species (ROS) in neurons in the regulation of sleep.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Within the Local Universe galaxies can be studied in great detail star by star, and here we review the results of quantitative studies in nearby dwarf galaxies. The color-magnitude diagram synthesis ...method is well established as the most accurate way to determine star-formation histories of galaxies back to the earliest times. This approach received a large boost from the exceptional data sets that wide-field CCD imagers on the ground and the Hubble Space Telescope could provide. Spectroscopic studies using large ground-based telescopes such as VLT, Magellan, Keck, and HET have allowed the determination of abundances and kinematics for significant samples of stars in nearby dwarf galaxies. These studies have shown how the properties of stellar populations can vary spatially and temporally. This leads to important constraints to theories of galaxy formation and evolution. The combination of spectroscopy and imaging and what they have taught us about dwarf galaxy formation and evolution is the aim of this review.
Objective To determine whether the use of hypotonic vs isotonic maintenance fluids confers an increased risk of hyponatremia in hospitalized children. Study design A search of MEDLINE (1946 to ...January 2013), the Cochrane Central Registry (1991 to December 2012), Cumulative Index for Nursing and Allied Health Literature (1990 to December 2012), and Pediatric Academic Societies (2000-2012) abstracts was conducted using the terms “hypotonic fluids/saline/solutions” and “isotonic fluids/saline/solutions,” and citations were reviewed using a predefined protocol. Data on the primary and secondary outcomes were extracted from original articles by 2 authors independently. Meta-analyses of the primary and secondary outcomes were performed when possible. Results A total of 1634 citations were screened. Ten studies (n = 893) identified as independent randomized controlled trials were included. Five studies examined subjects in the intensive care unit setting, including 4 on regular wards and 1 in a mixed setting. In hospitalized children receiving maintenance intravenous fluids, hyponatremia was seen more often in those receiving hypotonic fluids than in those receiving isotonic fluids, with an overall relative risk of 2.37 (95% CI, 1.72-3.26). Receipt of hypotonic fluids was associated with a relative risk of moderate hyponatremia (<130 mmol/L) of 6.1 (95% CI, 2.2-17.3). A subgroup analysis of hypotonic fluids with half-normal saline found a relative risk of hyponatremia of 2.42 (95% CI, 1.32-4.45). Conclusion In hospitalized children in intensive care and postoperative settings, the administration of hypotonic maintenance fluids increases the risk of hyponatremia when compared with administration of isotonic fluids. For patients on general wards, insufficient data are available based on the reviewed studies, and individual risk factors must be assessed.
Tired and stressed: Examining the need for sleep Hill, Vanessa M.; O'Connor, Reed M.; Shirasu-Hiza, Mimi
European journal of neuroscience/EJN. European journal of neuroscience,
January 2020, Letnik:
51, Številka:
1
Journal Article
Recenzirano
Odprti dostop
A key feature of circadian rhythms is the sleep/wake cycle. Sleep causes reduced responsiveness to the environment, which puts animals in a particularly vulnerable state; yet sleep has been conserved ...throughout evolution, indicating that it fulfils a vital purpose. A core function of sleep across species has not been identified, but substantial advances in sleep research have been made in recent years using the genetically tractable model organism, Drosophila melanogaster. This review describes the universality of sleep, the regulation of sleep, and current theories on the function of sleep, highlighting a historical and often overlooked theory called the Free Radical Flux Theory of Sleep. Additionally, we summarize our recent work with short‐sleeping Drosophila mutants and other genetic and pharmacological tools for manipulating sleep which supports an antioxidant theory of sleep and demonstrates a bi‐directional relationship between sleep and oxidative stress.
Abstract
Although true metal-free “Population III” stars have so far escaped discovery, their nature, and that of their supernovae, is revealed in the chemical products left behind in the next ...generations of stars. Here we report the detection of an ultra-metal-poor star in the Sculptor dwarf spheroidal galaxy AS0039. With Fe/H
LTE
= −4.11, it is the most metal-poor star discovered in any external galaxy thus far. Contrary to the majority of Milky Way stars at this metallicity, AS0039 is clearly not enhanced in carbon, with C/Fe
LTE
= −0.75, and
A
(C) = +3.60, making it the lowest detected carbon abundance in any star to date. Furthermore, it lacks
α
-element uniformity, having extremely low Mg/Ca
NLTE
= −0.60 and Mg/Ti
NLTE
= −0.86, in stark contrast with the near solar ratios observed in C-normal stars within the Milky Way halo. The unique abundance pattern indicates that AS0039 formed out of material that was predominantly enriched by a ∼20
M
⊙
progenitor star with an unusually high explosion energy
E
= 10 × 10
51
erg. Therefore, star AS0039 represents some of the first observational evidence for zero-metallicity hypernovae and provides a unique opportunity to investigate the diverse nature of Population III stars.
Bedtime procrastination is defined as the volitional delay of going to bed, without any external circumstances causing the delay, and is associated with inadequate sleep. Alleviating bedtime ...procrastination is an important target for interventions promoting adequate sleep, yet the correlates of bedtime procrastination are poorly understood. This study examined (1) correlates of bedtime procrastination, and (2) strength and direction of the association between bedtime procrastination and sleep outcomes. Six databases (CINAHL, EMBASE, PsychINFO, PubMed, Scopus, Web of Science) were searched from inception to September 2021 against pre-determined eligibility criteria. Forty-three studies were included (GRADE = low). Meta-analysis revealed that bedtime procrastination had a moderate negative association with self-control (z = −0.39; CI: −0.45, −0.29) and a moderate positive association with evening chronotype (z = 0.43; CI: 0.32, 0.48). Furthermore, bedtime procrastination was moderately negatively associated with sleep duration (z = −0.31; CI: −0.37, −0.24), sleep quality (z = −0.35; CI: −0.42, −0.27) and moderately positively associated with daytime fatigue (z = 0.32; CI: 0.25, 0.38). Further high-quality studies are needed to identify causal relationships between bedtime procrastination and correlates, as well as bedtime procrastination and sleep. Future work will guide the development of interventions targeting bedtime procrastination for improved sleep outcomes.
PROSPERO registration number CRD42021248891.
We present a detailed study of the faint Milky Way satellite Draco II (Dra II) from deep CFHT/MegaCam broad-band g and i photometry and narrow-band metallicity-sensitive CaHK observations, along with ...follow-up Keck II/DEIMOS multi-object spectroscopy. Forward modelling of the deep photometry allows us to refine the structural and photometric properties of Dra II: the distribution of stars in colour-magnitude space implies Dra II is old (13.5 ± 0.5 Gyr), very metal-poor, very faint (L_V = 180 ^{+124}_{-72} { L_⊙}), and at a distance d = 21.5 ± 0.4 { kpc}. The narrow-band, metallicity-sensitive CaHK Pristine photometry confirms this very low metallicity (Fe/H = -2.7 ± 0.1 dex). Even though our study benefits from a doubling of the spectroscopic sample size compared to previous investigations, the velocity dispersion of the system is still only marginally resolved (σ _{vr}< 5.9 { km s^{-1}} at the 95 per cent confidence level) and confirms that Dra II is a dynamically cold stellar system with a large recessional velocity (< vr> = -342.5^{+1.1}_{-1.2}{ km s^{-1}}). We further show that the spectroscopically confirmed members of Dra II have a mean proper motion of (μ _α ^*,μ _δ)=(1.26 ± 0.27,0.94 ± 0.28) { mas/yr} in the Gaia DR2 data, which translates to an orbit with a pericentre and an apocentre of 21.3 ^{+0.7}_{-1.0} and 153.8 ^{+56.7}_{-34.7} { kpc}, respectively. Taken altogether, these properties favour the scenario of Dra II being a potentially disrupting dwarf galaxy. The low-significance extra-tidal features we map around the satellite tentatively support this scenario.
ABSTRACT
A chemo-dynamical analysis of 115 metal-poor candidate stars selected from the narrow-band Pristine photometric survey is presented based on CFHT high-resolution ESPaDOnS spectroscopy. We ...have discovered 28 new bright (V < 15) stars with Fe/H < −2.5 and 5 with Fe/H < −3.0 for success rates of 40 (28/70) and 19 per cent (5/27), respectively. A detailed model atmosphere analysis is carried out for the 28 new metal-poor stars. Stellar parameters were determined from SDSS photometric colours, Gaia DR2 parallaxes, MESA/MIST stellar isochrones, and the initial Pristine survey metallicities, following a Bayesian inference method. Chemical abundances are determined for 10 elements (Na, Mg, Ca, Sc, Ti, Cr, Fe, Ni, Y, and Ba). Most stars show chemical abundance patterns that are similar to the normal metal-poor stars in the Galactic halo; however, we also report the discoveries of a new r-process-rich star, a new CEMP-s candidate with Y/Ba > 0, and a metal-poor star with very low Mg/Fe. The kinematics and orbits for all of the highly probable metal-poor candidates are determined by combining our precision radial velocities with Gaia DR2 proper motions. Some stars show unusual kinematics for their chemistries, including planar orbits, unbound orbits, and highly elliptical orbits that plunge deeply into the Galactic bulge (Rperi < 0.5 kpc); also, eight stars have orbital energies and actions consistent with the Gaia-Enceladus accretion event. This paper contributes to our understanding of the complex chemo-dynamics of the metal-poor Galaxy, and increases the number of known bright metal-poor stars available for detailed nucleosynthetic studies.
Background
Bedtime procrastination, the volitional delay of going to bed without any external circumstances causing the delay, is linked to multiple indicators of inadequate sleep. Intervening to ...reduce bedtime procrastination may be an important avenue to improve sleep outcomes, yet the phenomenon remains poorly understood in populations at risk for bedtime procrastination. New career starters, those who have graduated from tertiary education and started a new full‐time job within the past 12 months, may be susceptible to problematic bedtime procrastination and are at an opportune time for a ‘fresh start’ to change behaviour.
Aims
The objectives of this study were to understand how bedtime procrastination is experienced and perceived by new career starters, to identify the enablers and barriers to behaviour change in new career starters and to explore themes for future interventions.
Materials & Methods:
Data were collected through in‐depth semi‐structured interviews with 28 participants.
Results
Inductive thematic analysis was used to find seven themes: (1) negative feelings before and during bedtime procrastination; (2) wanting to versus knowing I shouldn't; (3) difficulty falling asleep; (4) influence of automatic processes; (5) consequences of bedtime procrastination; (6) lack of self‐control and (7) technology captures late‐night attention. Participants emphasised the need for me‐time, self‐negotiation to continue procrastinating and knowledge of the value of sleep.
Discussion & Conclusion
Findings suggest that bedtime procrastination involves both reflective and automatic cognitive processes. Future interventions would benefit from a dual‐process approach, using cognitive and behavioural techniques to reduce bedtime procrastination.
Objective To determine the incidence of apnea in infants hospitalized with respiratory syncytial virus (RSV) bronchiolitis and identify relevant risk factors from the available literature. Study ...design A systematic search of available databases for studies reporting the rate of apnea in a consecutive cohort of infants hospitalized with RSV infection was performed. The overall incidence of apnea was extracted and analyzed in relation to preterm birth, age, and potentially confounding illnesses. Results The incidence of apnea in the study population of 5575 hospitalized patients with RSV ranged from a high of 23.8% to a low of 1.2%. Comparison of the cohort by term and preterm birth revealed an expected excess in apnea incidence in preterms, even in the absence of information about chronologic age. Many studies appeared to be confounded by the inclusion of impaired infants with neuromuscular disorders. Conclusions Based on the available data, precisely quantifying the risk of apnea attributable to RSV infection is not possible. Factors intrinsic to the individual infants may account for a significant percentage of the apnea attributed to RSV. Recent studies have found a < 1% incidence of apnea with RSV in previously healthy term infants.