591 research outputs found
Caveolin-1 protects B6129 mice against Helicobacter pylori gastritis.
Caveolin-1 (Cav1) is a scaffold protein and pathogen receptor in the mucosa of the gastrointestinal tract. Chronic infection of gastric epithelial cells by Helicobacter pylori (H. pylori) is a major risk factor for human gastric cancer (GC) where Cav1 is frequently down-regulated. However, the function of Cav1 in H. pylori infection and pathogenesis of GC remained unknown. We show here that Cav1-deficient mice, infected for 11 months with the CagA-delivery deficient H. pylori strain SS1, developed more severe gastritis and tissue damage, including loss of parietal cells and foveolar hyperplasia, and displayed lower colonisation of the gastric mucosa than wild-type B6129 littermates. Cav1-null mice showed enhanced infiltration of macrophages and B-cells and secretion of chemokines (RANTES) but had reduced levels of CD25+ regulatory T-cells. Cav1-deficient human GC cells (AGS), infected with the CagA-delivery proficient H. pylori strain G27, were more sensitive to CagA-related cytoskeletal stress morphologies ("humming bird") compared to AGS cells stably transfected with Cav1 (AGS/Cav1). Infection of AGS/Cav1 cells triggered the recruitment of p120 RhoGTPase-activating protein/deleted in liver cancer-1 (p120RhoGAP/DLC1) to Cav1 and counteracted CagA-induced cytoskeletal rearrangements. In human GC cell lines (MKN45, N87) and mouse stomach tissue, H. pylori down-regulated endogenous expression of Cav1 independently of CagA. Mechanistically, H. pylori activated sterol-responsive element-binding protein-1 (SREBP1) to repress transcription of the human Cav1 gene from sterol-responsive elements (SREs) in the proximal Cav1 promoter. These data suggested a protective role of Cav1 against H. pylori-induced inflammation and tissue damage. We propose that H. pylori exploits down-regulation of Cav1 to subvert the host's immune response and to promote signalling of its virulence factors in host cells
Explicit BCJ Numerators from Pure Spinors
We derive local kinematic numerators for gauge theory tree amplitudes which
manifestly satisfy Jacobi identities analogous to color factors. They naturally
emerge from the low energy limit of superstring amplitudes computed with the
pure spinor formalism. The manifestation of the color--kinematics duality is a
consequence of the superstring computation involving no more than (n-2)!
kinematic factors for the full color dressed n-point amplitude. The bosonic
part of these results describe gluon scattering independent on the number of
supersymmetries and captures any N^kMHV helicity configuration after
dimensional reduction to D=4 dimensions.Comment: 32 pages, harvma
Memory consolidation in the cerebellar cortex
Several forms of learning, including classical conditioning of the eyeblink, depend upon the cerebellum. In examining mechanisms of eyeblink conditioning in rabbits, reversible inactivations of the control circuitry have begun to dissociate aspects of cerebellar cortical and nuclear function in memory consolidation. It was previously shown that post-training cerebellar cortical, but not nuclear, inactivations with the GABA(A) agonist muscimol prevented consolidation but these findings left open the question as to how final memory storage was partitioned across cortical and nuclear levels. Memory consolidation might be essentially cortical and directly disturbed by actions of the muscimol, or it might be nuclear, and sensitive to the raised excitability of the nuclear neurons following the loss of cortical inhibition. To resolve this question, we simultaneously inactivated cerebellar cortical lobule HVI and the anterior interpositus nucleus of rabbits during the post-training period, so protecting the nuclei from disinhibitory effects of cortical inactivation. Consolidation was impaired by these simultaneous inactivations. Because direct application of muscimol to the nuclei alone has no impact upon consolidation, we can conclude that post-training, consolidation processes and memory storage for eyeblink conditioning have critical cerebellar cortical components. The findings are consistent with a recent model that suggests the distribution of learning-related plasticity across cortical and nuclear levels is task-dependent. There can be transfer to nuclear or brainstem levels for control of high-frequency responses but learning with lower frequency response components, such as in eyeblink conditioning, remains mainly dependent upon cortical memory storage
On-shell Recursion in String Theory
We prove that all open string theory disc amplitudes in a flat background
obey Britto-Cachazo-Feng-Witten (BCFW) on-shell recursion relations, up to a
possible reality condition on a kinematic invariant. Arguments that the same
holds for tree level closed string amplitudes are given as well. Non-adjacent
BCFW-shifts are related to adjacent shifts through monodromy relations for
which we provide a novel CFT based derivation. All possible recursion relations
are related by old-fashioned string duality. The field theory limit of the
analysis for amplitudes involving gluons is explicitly shown to be smooth for
both the bosonic string as well as the superstring. In addition to a proof a
less rigorous but more powerful argument based on the underlying CFT is
presented which suggests that the technique may extend to a much more general
setting in string theory. This is illustrated by a discussion of the open
string in a constant B-field background and the closed string on the level of
the sphere.Comment: 36 + 9 pages text, one figure, v3: added discussion on relation to
old-fashioned factorization, typos corrected, published versio
Molecular, morphological and acoustic identification of Eumops maurus and Eumops hansae (Chiroptera: Molossidae) with new reports from Central Amazonia
Eumops maurus and Eumops hansae are rarely captured Neotropical molossid bats for
which information on taxonomy, natural history, and spatial distribution are scarce.
This translates into a poor understanding of their ecology and limits the delimitation
of useful characters for their identification. Here, we describe records of these two
molossids from the Central Brazilian Amazon, providing data on their external and
craniodental morphology, DNA barcode (COI) sequences complemented by acoustic
data for the species. Morphological characters, DNA sequence data and phylogenetic
relationships within the genus Eumops were consistent with those previously described
for both species. Echolocation call characteristics did not differ significantly so as to be
useful for separating E. maurus and E. hansae from other congeners. Our records are,
respectively the first and the second for Central Amazonia as one individual previously
attributed to Eumops amazonicus from Manaus may be considered a junior synonym
for E. hansae. These new records increase the extent of the species’ known ranges,
partially filling in previous existing gaps in their distribution in central South America.
Our data further suggest that these molossid bats forage in a wider range of habitats
than previously thought
Fuzzy Scalar Field Theory as Matrix Quantum Mechanics
We study the phase diagram of scalar field theory on a three dimensional
Euclidean spacetime whose spatial component is a fuzzy sphere. The
corresponding model is an ordinary one-dimensional matrix model deformed by
terms involving fixed external matrices. These terms can be approximated by
multitrace expressions using a group theoretical method developed recently. The
resulting matrix model is accessible to the standard techniques of matrix
quantum mechanics.Comment: 1+17 pages, 4 figures, minor improvements, version published in JHE
Anomalous diffusion for a correlated process with long jumps
We discuss diffusion properties of a dynamical system, which is characterised
by long-tail distributions and finite correlations. The particle velocity has
the stable L\'evy distribution; it is assumed as a jumping process (the
kangaroo process) with a variable jumping rate. Both the exponential and the
algebraic form of the covariance -- defined for the truncated distribution --
are considered. It is demonstrated by numerical calculations that the
stationary solution of the master equation for the case of power-law
correlations decays with time, but a simple modification of the process makes
the tails stable. The main result of the paper is a finding that -- in contrast
to the velocity fluctuations -- the position variance may be finite. It rises
with time faster than linearly: the diffusion is anomalously enhanced. On the
other hand, a process which follows from a superposition of the
Ornstein-Uhlenbeck-L\'evy processes always leads to position distributions with
a divergent variance which means accelerated diffusion.Comment: 10 pages, 6 figure
Identification and Gene Expression Analysis of a Taxonomically Restricted Cysteine-Rich Protein Family in Reef-Building Corals
The amount of genomic sequence information continues to grow at an exponential rate, while the identification and characterization of genes without known homologs remains a major challenge. For non-model organisms with limited resources for manipulative studies, high-throughput transcriptomic data combined with bioinformatics methods provide a powerful approach to obtain initial insights into the function of unknown genes. In this study, we report the identification and characterization of a novel family of putatively secreted, small, cysteine-rich proteins herein named Small Cysteine-Rich Proteins (SCRiPs). Their discovery in expressed sequence tag (EST) libraries from the coral Montastraea faveolata required the performance of an iterative search strategy based on BLAST and Hidden-Markov-Model algorithms. While a discernible homolog could neither be identified in the genome of the sea anemone Nematostella vectensis, nor in a large EST dataset from the symbiotic sea anemone Aiptasia pallida, we identified SCRiP sequences in multiple scleractinian coral species. Therefore, we postulate that this gene family is an example of lineage-specific gene expansion in reef-building corals. Previously published gene expression microarray data suggest that a sub-group of SCRiPs is highly responsive to thermal stress. Furthermore, data from microarray experiments investigating developmental gene expression in the coral Acropora millepora suggest that different SCRiPs may play distinct roles in the development of corals. The function of these proteins remains to be elucidated, but our results from in silico, transcriptomic, and phylogenetic analyses provide initial insights into the evolution of SCRiPs, a novel, taxonomically restricted gene family that may be responsible for a lineage-specific trait in scleractinian corals
Cardiac Complications in Patients with Community-Acquired Pneumonia: A Systematic Review and Meta-Analysis of Observational Studies
Vicente Corrales-Medina and colleagues report estimates of the risk of cardiac complications among patients with community-acquired pneumonia from a systematic review and meta-analysis
Interventional radiology at the meetings of the German Radiological Society from 1998 to 2008: evaluation of structural changes and radiation issues
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