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Gene expression differs in susceptible and resistant amphibians exposed to Batrachochytrium dendrobatidis.
Chytridiomycosis, the disease caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), has devastated global amphibian biodiversity. Nevertheless, some hosts avoid disease after Bd exposure even as others experience near-complete extirpation. It remains unclear whether the amphibian adaptive immune system plays a role in Bd defence. Here, we describe gene expression in two host species-one susceptible to chytridiomycosis and one resistant-following exposure to two Bd isolates that differ in virulence. Susceptible wood frogs (Rana sylvatica) had high infection loads and mortality when exposed to the more virulent Bd isolate but lower infection loads and no fatal disease when exposed to the less virulent isolate. Resistant American bullfrogs (R. catesbeiana) had high survival across treatments and rapidly cleared Bd infection or avoided infection entirely. We found widespread upregulation of adaptive immune genes and downregulation of important metabolic and cellular maintenance components in wood frogs after Bd exposure, whereas American bullfrogs showed little gene expression change and no evidence of an adaptive immune response. Wood frog responses suggest that adaptive immune defences may be ineffective against virulent Bd isolates that can cause rapid physiological dysfunction. By contrast, American bullfrogs exhibited robust resistance to Bd that is likely attributable, at least in part, to their continued upkeep of metabolic and skin integrity pathways as well as greater antimicrobial peptide expression compared to wood frogs, regardless of exposure. Greater understanding of these defences will ultimately help conservationists manage chytridiomycosis
Single-kernel ionomic profiles are highly heritable indicators of genetic and environmental influences on elemental accumulation in maize grain (Zea mays)
Peer reviewedPublisher PD
A Deep Search for Prompt Radio Emission from Thermonuclear Supernovae with the Very Large Array
Searches for circumstellar material around Type Ia supernovae (SNe Ia) are
one of the most powerful tests of the nature of SN Ia progenitors, and radio
observations provide a particularly sensitive probe of this material. Here we
report radio observations for SNe Ia and their lower-luminosity thermonuclear
cousins. We present the largest, most sensitive, and spectroscopically diverse
study of prompt (delta t <~ 1 yr) radio observations of 85 thermonuclear SNe,
including 25 obtained by our team with the unprecedented depth of the Karl G.
Jansky Very Large Array. With these observations, SN 2012cg joins SN 2011fe and
SN 2014J as a SN Ia with remarkably deep radio limits and excellent temporal
coverage (six epochs, spanning 5--216 days after explosion, yielding Mdot/v_w
<~ 5 x 10^-9 M_sun/yr / (100 km/s), assuming epsilon_B = 0.1 and epsilon_e =
0.1).
All observations yield non-detections, placing strong constraints on the
presence of circumstellar material. We present analytical models for the
temporal and spectral evolution of prompt radio emission from thermonuclear SNe
as expected from interaction with either wind-stratified or uniform density
media. These models allow us to constrain the progenitor mass loss rates, with
limits ranging from Mdot <~ 10^-9--10^-4 M_sun/yr, assuming a wind velocity
v_w=100 km/s. We compare our radio constraints with measurements of Galactic
symbiotic binaries to conclude that <~10% of thermonuclear SNe have red giant
companions.Comment: Submitted to Ap
Radial dyssynchrony assessed by cardiovascular magnetic resonance in relation to left ventricular function, myocardial scarring and QRS duration in patients with heart failure
Radial dyssynchrony is almost universal in patients with heart failure. This vies against the notion that a lack of response to CRT is related to a lack of dyssynchrony
A High-Resolution Spectroscopic Search for the Remaining Donor for Tycho's Supernova
In this paper, we report on our analysis using Hubble Space Telescope
astrometry and Keck-I HIRES spectroscopy of the central six stars of Tycho's
supernova remnant (SN 1572). With these data, we measured the proper motions,
radial velocities, rotational velocities, and chemical abundances of these
objects. Regarding the chemical abundances, we do not confirm the unusu- ally
high [Ni/Fe] ratio previously reported for Tycho-G. Rather, we find that for
all metrics in all stars, none exhibit the characteristics expected from
traditional SN Ia single-degenerate-scenario calculations. The only possible
exception is Tycho-B, a rare, metal-poor A-type star; however, we are unable to
find a suitable scenario for it. Thus, we suggest that SN 1572 cannot be
explained by the standard single-degenerate model.Comment: 34 pages, 11 Figures, revised and resubmitted to Ap
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