87 research outputs found
Early Observations and Analysis of the Type Ia SN 2014J in M82
We present optical and near infrared (NIR) observations of the nearby Type Ia
SN 2014J. Seventeen optical and twenty-three NIR spectra were obtained from 10
days before (10d) to 10 days after (+10d) the time of maximum -band
brightness. The relative strengths of absorption features and their patterns of
development can be compared at one day intervals throughout most of this
period. Carbon is not detected in the optical spectra, but we identify CI
1.0693 in the NIR spectra. We find that MgII lines with high
oscillator strengths have higher initial velocities than other MgII lines. We
show that the velocity differences can be explained by differences in optical
depths due to oscillator strengths. The spectra of SN 2014J show it is a normal
SN Ia, but many parameters are near the boundaries between normal and
high-velocity subclasses. The velocities for OI, MgII, SiII, SII, CaII and FeII
suggest that SN 2014J has a layered structure with little or no mixing. That
result is consistent with the delayed detonation explosion models. We also
report photometric observations, obtained from 10d to +29d, in the
and bands. SN 2014J is about 3 magnitudes fainter than a normal SN Ia at
the distance of M82, which we attribute to extinction in the host. The template
fitting package SNooPy is used to interpret the light curves and to derive
photometric parameters. Using = 1.46, which is consistent with previous
studies, SNooPy finds that for mag.
The maximum -band brightness of mag was reached on
February 1.74 UT days and the supernova had a decline parameter of
mag.Comment: 6 figures, 6 tables, submitted to the Ap
Hydrogen absorption in epitaxial W/Nb(001) and polycrystalline Fe/Nb(110) multilayers studied in situ by X-ray/neutron scattering techniques and X-ray absorption spectroscopy
Excitatory effect of ATP on rat area postrema neurons
ATP-induced inward currents and increases in the cytosolic Ca2+ concentration ([Ca]in) were investigated in neurons acutely dissociated from rat area postrema using whole-cell patch-clamp recordings and fura-2 microfluorometry, respectively. The ATP-induced current (IATP) and [Ca]in increases were mimicked by 2-methylthio-ATP and ATP-γS, and were inhibited by P2X receptor (P2XR) antagonists. The current–voltage relationship of the IATP exhibited a strong inward rectification, and the amplitude of the IATP was concentration-dependent. The IATP was markedly reduced in the absence of external Na+, and the addition of Ca2+ to Na+-free saline increased the IATP. ATP did not increase [Ca]in in the absence of external Ca2+, and Ca2+ channel antagonists partially inhibited the ATP-induced [Ca]in increase, indicating that ATP increases [Ca]in by Ca2+ influx through both P2XR channels and voltage-dependent Ca2+ channels. There was a negative interaction between P2XR- and nicotinic ACh receptor (nAChR)-channels, which depended on the amplitude and direction of current flow through either channel. Current occlusion was observed at Vhs between −70 and −10 mV when the IATP and ACh-induced current (IACh) were inward, but no occlusion was observed when these currents were outward at a Vh of +40 mV. The IATP was not inhibited by co-application of ACh when the IACh was markedly decreased either by removal of permeant cations, by setting Vh close to the equilibrium potential of IACh, or by the addition of d-tubocurarine or serotonin. These results suggest that the inhibitory interaction is attributable to inward current flow of cations through the activated P2XR- and nAChR-channels
In Vitro and In Vivo Antagonism of a G Protein-Coupled Receptor (S1P3) with a Novel Blocking Monoclonal Antibody
Background: S1P 3 is a lipid-activated G protein-couple receptor (GPCR) that has been implicated in the pathological processes of a number of diseases, including sepsis and cancer. Currently, there are no available high-affinity, subtypeselective drug compounds that can block activation of S1P3. We have developed a monoclonal antibody (7H9) that specifically recognizes S1P3 and acts as a functional antagonist. Methodology/Principal Findings: Specific binding of 7H9 was demonstrated by immunocytochemistry using cells that over-express individual members of the S1P receptor family. We show, in vitro, that 7H9 can inhibit the activation of S1P3mediated cellular processes, including arrestin translocation, receptor internalization, adenylate cyclase inhibiton, and calcium mobilization. We also demonstrate that 7H9 blocks activation of S1P3 in vivo, 1) by preventing lethality due to systemic inflammation, and 2) by altering the progression of breast tumor xenografts. Conclusions/Significance: We have developed the first-reported monoclonal antibody that selectively recognizes a lipidactivated GPCR and blocks functional activity. In addition to serving as a lead drug compound for the treatment of sepsi
A large topographic feature on the surface of the trans-Neptunian object (307261) 2002 MS measured from stellar occultations
This work aims at constraining the size, shape, and geometric albedo of the
dwarf planet candidate 2002 MS4 through the analysis of nine stellar
occultation events. Using multichord detection, we also studied the object's
topography by analyzing the obtained limb and the residuals between observed
chords and the best-fitted ellipse. We predicted and organized the
observational campaigns of nine stellar occultations by 2002 MS4 between 2019
and 2022, resulting in two single-chord events, four double-chord detections,
and three events with three to up to sixty-one positive chords. Using 13
selected chords from the 8 August 2020 event, we determined the global
elliptical limb of 2002 MS4. The best-fitted ellipse, combined with the
object's rotational information from the literature, constrains the object's
size, shape, and albedo. Additionally, we developed a new method to
characterize topography features on the object's limb. The global limb has a
semi-major axis of 412 10 km, a semi-minor axis of 385 17 km, and
the position angle of the minor axis is 121 16. From
this instantaneous limb, we obtained 2002 MS4's geometric albedo and the
projected area-equivalent diameter. Significant deviations from the fitted
ellipse in the northernmost limb are detected from multiple sites highlighting
three distinct topographic features: one 11 km depth depression followed by a
25 km height elevation next to a crater-like depression with an
extension of 322 39 km and 45.1 1.5 km deep. Our results present an
object that is 138 km smaller in diameter than derived from thermal
data, possibly indicating the presence of a so-far unknown satellite. However,
within the error bars, the geometric albedo in the V-band agrees with the
results published in the literature, even with the radiometric-derived albedo
Variation in chromosome numbers and the sex determination system in the Gerromorpha with special reference to the family Gerridae (Hemiptera)
L-type calcium channels in type I cells of the rat carotid body
1. Whole-cell and cell-attached patch-clamp recordings were made from enzymatically isolated type I cells from the carotid body of adult rats. Voltage-dependent K+ and Ca2+ channels were observed, but there was no detectable Na+ current. In this respect, rat carotid body cells are unlike those from rabbit, which have Na+ currents and Na(+)-dependent action potentials. 2. The observed Ca2+ channels had the following properties: 1) activation requires voltage steps above -20 mV; 2) little inactivation occurred with holding voltages below -40 mV; 3) one single-channel conductance of 21 pS was found with 90 or 110 mM Ba2+ in the cell-attached pipette and this was the only conductance observed; 4) open probability was increased by the dihydropyridine Ca2+ channel agonist Bay K 8644 and was decreased by the antagonist nifedipine; and 5) omega-conotoxin had little or no effect on the channels. These are properties expected of L-type Ca2+ channels. 3. To investigate whether these voltage-dependent channels would be available for opening on membrane depolarization, we measured the type I cell resting membrane potential noninvasively using unitary openings of the L-type Ca2+ channel with Bay K 8644 in the cell-attached pipette. Resting potentials ranged from -62 to -13 mV, with a mean of -32 mV in 12 cells. 4. Judging from single-channel conductance and pharmacology, the Ca2+ current is mostly, if not solely, carried by L channels. Thus it should be possible to use modulators of L channel activity to determine the role of Ca2+ channels in stimulus-secretion coupling in the rat carotid body
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Structural properties of voltage-dependent calcium channels
Following purification using Ca2+ channel drugs as ligands, the skeletal muscle Ca2+ channel was shown to be a five-subunit structure containing one large (175 kDa) protein that is the pore and four auxiliary subunits. Each subunit has been cloned and expression studies are proceeding rapidly. Particular success has been made in structure-function studies of excitation-contraction coupling using a Ca2+ channel-free mutant muscle. The work confirmed the suggestion made from physiological studies that muscle Ca2+ channels serve dual roles: passing Ca2+ and triggering Ca2+ release from an intracellular organelle. A variety of other predictions about the structure of Ca2+ channels have been reviewed here and these may soon be possible to test. Such concrete predictions along with analogies to studies on other voltage-dependent ion channels should speed progress in structure-function studies of Ca2+ channels
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Aquatic animal models of human disease: Selected papers from the 5th Conference
Hydrogen absorption in epitaxial W/Nb(001) and polycrystalline Fe/Nb(110) multilayers studied in situ by X-ray/neutron scattering techniques and X-ray absorption spectroscopy
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