27 research outputs found
Mangafodipir Protects against Hepatic Ischemia-Reperfusion Injury in Mice
Mangafodipir is a contrast agent used in magnetic resonance imaging that concentrates in the liver and displays pleiotropic antioxidant properties. Since reactive oxygen species are involved in ischemia-reperfusion damages, we hypothesized that the use of mangafodipir could prevent liver lesions in a mouse model of hepatic ischemia reperfusion injury. Mangafodipir (MnDPDP) was compared to ischemic preconditioning and intermittent inflow occlusion for the prevention of hepatic ischemia-reperfusion injury in the mouse.Mice were subjected to 70% hepatic ischemia (continuous ischemia) for 90 min. Thirty minutes before the ischemic period, either mangafodipir (10 mg/kg) or saline was injected intraperitoneally. Those experimental groups were compared with one group of mice preconditioned by 10 minutes' ischemia followed by 15 minutes' reperfusion, and one group with intermittent inflow occlusion. Hepatic ischemia-reperfusion injury was evaluated by measurement of serum levels of aspartate aminotransferase (ASAT) activity, histologic analysis of the livers, and determination of hepatocyte apoptosis (cytochrome c release, caspase 3 activity). The effect of mangafodipir on the survival rate of mice was studied in a model of total hepatic ischemia.<0.01), and by higher rates of survival in treated than in untreated animals (P<0.001). The level of protection by mangafodipir was similar to that observed following intermittent inflow occlusion and higher than after ischemic preconditioning.Mangafodipir is a potential new preventive treatment for hepatic ischemia-reperfusion injury
A broadband thermal emission spectrum of the ultra-hot Jupiter WASP-18b
Close-in giant exoplanets with temperatures greater than 2,000 K (''ultra-hot
Jupiters'') have been the subject of extensive efforts to determine their
atmospheric properties using thermal emission measurements from the Hubble and
Spitzer Space Telescopes. However, previous studies have yielded inconsistent
results because the small sizes of the spectral features and the limited
information content of the data resulted in high sensitivity to the varying
assumptions made in the treatment of instrument systematics and the atmospheric
retrieval analysis. Here we present a dayside thermal emission spectrum of the
ultra-hot Jupiter WASP-18b obtained with the NIRISS instrument on JWST. The
data span 0.85 to 2.85 m in wavelength at an average resolving power of
400 and exhibit minimal systematics. The spectrum shows three water emission
features (at 6 confidence) and evidence for optical opacity,
possibly due to H, TiO, and VO (combined significance of 3.8).
Models that fit the data require a thermal inversion, molecular dissociation as
predicted by chemical equilibrium, a solar heavy element abundance
(''metallicity'', M/H = 1.03 solar), and a
carbon-to-oxygen (C/O) ratio less than unity. The data also yield a dayside
brightness temperature map, which shows a peak in temperature near the
sub-stellar point that decreases steeply and symmetrically with longitude
toward the terminators.Comment: JWST ERS bright star observations. Uploaded to inform JWST Cycle 2
proposals. Manuscript under review. 50 pages, 14 figures, 2 table
Early Release Science of the Exoplanet WASP-39b with JWST NIRSpec G395H
Measuring the abundances of carbon and oxygen in exoplanet atmospheres is
considered a crucial avenue for unlocking the formation and evolution of
exoplanetary systems. Access to an exoplanet's chemical inventory requires
high-precision observations, often inferred from individual molecular
detections with low-resolution space-based and high-resolution ground-based
facilities. Here we report the medium-resolution (R600) transmission
spectrum of an exoplanet atmosphere between 3-5 m covering multiple
absorption features for the Saturn-mass exoplanet WASP-39b, obtained with JWST
NIRSpec G395H. Our observations achieve 1.46x photon precision, providing an
average transit depth uncertainty of 221 ppm per spectroscopic bin, and present
minimal impacts from systematic effects. We detect significant absorption from
CO (28.5) and HO (21.5), and identify SO as the
source of absorption at 4.1 m (4.8). Best-fit atmospheric models
range between 3 and 10x solar metallicity, with sub-solar to solar C/O ratios.
These results, including the detection of SO, underscore the importance of
characterising the chemistry in exoplanet atmospheres, and showcase NIRSpec
G395H as an excellent mode for time series observations over this critical
wavelength range.Comment: 44 pages, 11 figures, 3 tables. Resubmitted after revision to Natur
Early Release Science of the exoplanet WASP-39b with JWST NIRCam
Measuring the metallicity and carbon-to-oxygen (C/O) ratio in exoplanet
atmospheres is a fundamental step towards constraining the dominant chemical
processes at work and, if in equilibrium, revealing planet formation histories.
Transmission spectroscopy provides the necessary means by constraining the
abundances of oxygen- and carbon-bearing species; however, this requires broad
wavelength coverage, moderate spectral resolution, and high precision that,
together, are not achievable with previous observatories. Now that JWST has
commenced science operations, we are able to observe exoplanets at previously
uncharted wavelengths and spectral resolutions. Here we report time-series
observations of the transiting exoplanet WASP-39b using JWST's Near InfraRed
Camera (NIRCam). The long-wavelength spectroscopic and short-wavelength
photometric light curves span 2.0 - 4.0 m, exhibit minimal systematics,
and reveal well-defined molecular absorption features in the planet's spectrum.
Specifically, we detect gaseous HO in the atmosphere and place an upper
limit on the abundance of CH. The otherwise prominent CO feature at 2.8
m is largely masked by HO. The best-fit chemical equilibrium models
favour an atmospheric metallicity of 1-100 solar (i.e., an enrichment
of elements heavier than helium relative to the Sun) and a sub-stellar
carbon-to-oxygen (C/O) ratio. The inferred high metallicity and low C/O ratio
may indicate significant accretion of solid materials during planet formation
or disequilibrium processes in the upper atmosphere.Comment: 35 pages, 13 figures, 3 tables, Nature, accepte
Identification of carbon dioxide in an exoplanet atmosphere
Carbon dioxide (CO2) is a key chemical species that is found in a wide range of planetary atmospheres. In the context of exoplanets, CO2 is an indicator of the metal enrichment (that is, elements heavier than helium, also called ‘metallicity’), and thus the formation processes of the primary atmospheres of hot gas giants. It is also one of the most promising species to detect in the secondary atmospheres of terrestrial exoplanets. Previous photometric measurements of transiting planets with the Spitzer Space Telescope have given hints of the presence of CO2, but have not yielded definitive detections owing to the lack of unambiguous spectroscopic identification. Here we present the detection of CO2 in the atmosphere of the gas giant exoplanet WASP-39b from transmission spectroscopy observations obtained with JWST as part of the Early Release Science programme. The data used in this study span 3.0–5.5 micrometres in wavelength and show a prominent CO2 absorption feature at 4.3 micrometres (26-sigma significance). The overall spectrum is well matched by one-dimensional, ten-times solar metallicity models that assume radiative–convective–thermochemical equilibrium and have moderate cloud opacity. These models predict that the atmosphere should have water, carbon monoxide and hydrogen sulfide in addition to CO2, but little methane. Furthermore, we also tentatively detect a small absorption feature near 4.0 micrometres that is not reproduced by these models
Cycle more with virtual reality: a proof of concept study in an institutionalised able-bodied geriatric population
International audienceBackground/Objectives: Physical activity (PA) has significant benefits for older adults. However, the recommended PA is rarely achieved in nursing homes. In this proof of concept study, we assessed whether virtual reality (VR) could help to increase spontaneous PA during a stationary cycling session. Design: Prospective crossover proof of concept study. Setting: Nursing home. Participants: Twelve participants (10 men) aged 63-88, able-bodied but with moderate cognitive impairment. Intervention: TWO stationary cycling sessions with and without VR. Measurements: Cycling distance, pedalling duration, average speed, mean pedalling cadence and the modified Borg rating of perceived exertion scale. Results: Cycling distance and duration were significantly higher in the VR condition. Most participants would rather repeat cycling sessions with VR than without. Conclusion: The use of VR seems feasible to help achieve PA recommendations for able-bodied people living in nursing homes, even with moderate cognitive impairments
Prevention of lipid peroxidation following ischemia-reperfusion of the liver using on mangafodipir and intermittent clamping.
<p>The concentrations of 4-hydroxyalkenals (4-HNE) and malondialdehyde (MDA) were measured spectrophotometrically in whole liver homogenates. The level of lipid peroxidation was expressed as the amounts of 4-HNE + MDA per mg of proteins. Bars represent means ± SEM; nine mice in each group.</p
Mangafodipir and intermittent clamping prevent the increase in transaminase activities following reperfusion injury.
<p>Serum levels of aspartate amino-transferase activities (ASAT) served as markers of hepatocyte injury. ASAT levels were measured after 24 hours of reperfusion. Bars represent means ± SEM, nine mice in each group.</p