2,175 research outputs found
Roles for transforming growth factor-alpha in gastric physiology and pathophysiology.
Transforming growth factor alpha (TGF alpha) is a 5.6 kd single-chain polypeptide that acts through binding to the epidermal growth factor receptor (EGFR). TGF alpha is produced in a wide range of normal as well as embryonic and neoplastic cells and tissues. TGF alpha and EGFR, but not EGF, are expressed in normal gastric mucosa. We have identified the following biological roles for TGF alpha in the stomach, using a variety of primate and rodent models: inhibition of acid secretion; stimulation of mucous cell growth; protection against ethanol- and aspirin-induced injury. This last effect is associated with a time- and dose-dependent increase in levels of insoluble gastric mucin. Based on these known biological actions of TGF alpha, we have examined TGF alpha production in Ménétrier's disease, a disorder characterized by foveolar hyperplasia, hypochlorhydria, and increased gastric mucin content. In four patients with Ménétrier's disease, there was enhanced TGF alpha immunostaining throughout the gastric mucosa. Furthermore, metallothionein (MT)-TGF alpha transgenic mice which overproduce TGF alpha in the stomach exhibit histopathological and biochemical features characteristic of and consistent with the diagnosis of Ménétrier's disease. Thus locally produced TGF alpha may mediate a number of biological processes in the stomach, and its altered production may participate in the pathogenesis of selected pathological states
Sharp and Smooth Boundaries of Quantum Hall Liquids
We study the transition between sharp and smooth density distributions at the
edges of Quantum Hall Liquids in the presence of interactions. We find that,
for strong confining potentials, the edge of a liquid is described by
the Fermi Liquid theory, even in the presence of interactions, a
consequence of the chiral nature of the system. When the edge confining
potential is decreased beyond a point, the edge undergoes a reconstruction and
electrons start to deposit a distance magnetic lengths away from the
initial QH Liquid. Within the Hartree-Fock approximation, a new pair of
branches of gapless edge excitations is generated after the transition. We show
that the transition is controlled by the balance between a long-ranged
repulsive Hartree term and a short-ranged attractive exchange term. Such
transition also occurs for Quantum Dots in the Quantum Hall Regime, and should
be observable in resonant tunneling experiments. Electron tunneling into the
reconstructed edge is also discussed.Comment: 28 pages, REVTeX 3.0, 18 figures available upon request,
cond-mat/yymmnn
Acute Ethanol Administration Rapidly Increases Phosphorylation of Conventional Protein Kinase C in Specific Mammalian Brain Regions in Vivo
Background
Protein kinase C (PKC) is a family of isoenzymes that regulate a variety of functions in the central nervous system including neurotransmitter release, ion channel activity, and cell differentiation. Growing evidence suggests that specific isoforms of PKC influence a variety of behavioral, biochemical, and physiological effects of ethanol in mammals. The purpose of this study was to determine whether acute ethanol exposure alters phosphorylation of conventional PKC isoforms at a threonine 674 (p-cPKC) site in the hydrophobic domain of the kinase, which is required for its catalytic activity.
Methods
Male rats were administered a dose range of ethanol (0, 0.5, 1, or 2 g/kg, intragastric) and brain tissue was removed 10 minutes later for evaluation of changes in p-cPKC expression using immunohistochemistry and Western blot methods.
Results
Immunohistochemical data show that the highest dose of ethanol (2 g/kg) rapidly increases p-cPKC immunoreactivity specifically in the nucleus accumbens (core and shell), lateral septum, and hippocampus (CA3 and dentate gyrus). Western blot analysis further showed that ethanol (2 g/kg) increased p-cPKC expression in the P2 membrane fraction of tissue from the nucleus accumbens and hippocampus. Although p-cPKC was expressed in numerous other brain regions, including the caudate nucleus, amygdala, and cortex, no changes were observed in response to acute ethanol. Total PKC? immunoreactivity was surveyed throughout the brain and showed no change following acute ethanol injection
Quantitative magneto-optical investigation of superconductor/ferromagnet hybrid structures
We present a detailed quantitative magneto-optical imaging study of several
superconductor/ferromagnet hybrid structures, including Nb deposited on top of
thermomagnetically patterned NdFeB, and permalloy/niobium with erasable and
tailored magnetic landscapes imprinted in the permalloy layer. The
magneto-optical imaging data is complemented with and compared to scanning Hall
probe microscopy measurements. Comprehensive protocols have been developed for
calibrating, testing, and converting Faraday rotation data to magnetic field
maps. Applied to the acquired data, they reveal the comparatively weaker
magnetic response of the superconductor from the background of larger fields
and field gradients generated by the magnetic layer.Comment: 21 pages, including 2 pages of supplementary materia
Magnetoplasmon excitations in arrays of circular and noncircular quantum dots
We have investigated the magnetoplasmon excitations in arrays of circular and
noncircular quantum dots within the Thomas-Fermi-Dirac-von Weizs\"acker
approximation. Deviations from the ideal collective excitations of isolated
parabolically confined electrons arise from local perturbations of the
confining potential as well as interdot Coulomb interactions. The latter are
unimportant unless the interdot separations are of the order of the size of the
dots. Local perturbations such as radial anharmonicity and noncircular symmetry
lead to clear signatures of the violation of the generalized Kohn theorem. In
particular, the reduction of the local symmetry from SO(2) to results in
a resonant coupling of different modes and an observable anticrossing behaviour
in the power absorption spectrum. Our results are in good agreement with recent
far-infrared (FIR) transmission experiments.Comment: 25 pages, 6 figures, typeset in RevTe
A New Class of Resonances at the Edge of the Two Dimensional Electron Gas
We measure the frequency dependent capacitance of a gate covering the edge
and part of a two-dimensional electron gas in the quantum Hall regime. In
applying a positive gate bias, we create a metallic puddle under the gate
surrounded by an insulating region. Charging of the puddle occurs via electron
tunneling from a metallic edge channel. Analysis of the data allows direct
extraction of this tunneling conductance. Novel conductance resonances appear
as a function of gate bias. Samples with gates ranging from 1-170~m along
the edge display strikingly similar resonance spectra. The data suggest the
existence of unexpected structure, homogeneous over long length scales, at the
sample edge.Comment: 13 pages (revtex) including 4 figure
Unravelling the nature of HD 81032 - a new RS CVn Binary
BVR photometric and quasi-simultaneous optical spectroscopic observations of
the star HD 81032 have been carried out during the years 2000 - 2004. A
photometric period of d has been detected for this star. A
large group of spots with a migration period of years is
inferred from the first three years of the data. H and Ca II H and K
emissions from the star indicate high chromospheric activity. The available
photometry in the BVRIJHK bands is consistent with spectral type of K0 IV
previously found for this star. We have also examined the spectral energy
distribution of HD 81032 for the presence of an infrared colour excess using
the 2MASS JHK and IRAS photometry, but found no significant excess in any band
abovethe normal values expected for a star with this spectral type. We have
also analyzed the X-ray emission properties of this star using data obtained by
the ROSAT X-ray observatory during its All-Sky Survey phase. An X-ray flare of
about 12 hours duration was detected during the two days of X-ray coverage
obtained for this star. Its X-ray spectrum, while only containing 345 counts,
is inconsistent with a single-temperature component solar-abundance coronal
plasma model, but implies either the presence of two or more plasma components,
non-solar abundances, or a combination of both of these properties. All of the
above properties of HD 81032 suggest that it is a newly identified, evolved RS
CVn binary.Comment: 18 pages, 10 figures, 3 tables, Accepted for the publication in JAp
Correlations in Nuclear Arrhenius-Type Plots
Arrhenius-type plots for multifragmentation process, defined as the
transverse energy dependence of the single-fragment emission-probability,
-ln(p_{b}) vs 1/sqrt(E_{t}), have been studied by examining the relationship of
the parameters p_{b} and E_{t} to the intermediate-mass fragment multiplicity
. The linearity of these plots reflects the correlation of the fragment
multiplicity with the transverse energy. These plots may not provide thermal
scaling information about fragment production as previously suggested.Comment: 12 pages, Latex, 3 Postscript figures include
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