1,139 research outputs found
The prognostic effect of PTEN expression status in colorectal cancer development and evaluation of factors affecting it: MiR-21 and promoter methylation
Background: PTEN is a tumor suppressor gene which is involved in cellular proliferation, differentiation, and apoptosis. Loss or down-regulation of PTEN plays an important role in human cancers development. In this study, we investigated the effect of miR-21 and promoter methylation on the PTEN expression status in CRC tissues and analyzed association of the PTEN expression status with clinicopathological features in patients with CRC. Results: The PTEN expression was positively detected in 67.2 CRC tissues and all adjacent non-cancerous samples. PTEN mRNA level was negatively correlated with miR-21 level (r = -0.595, P < 0.001). PTEN expression was also correlated directly with the PTEN mRNA level (r = 0.583, P < 0.001) and conversely with miR-21 level (r = -0.632, P < 0.001). PTEN Promoter methylation was significantly associated with PTEN expression status (p = 0.013). PTEN expression was negatively associated with tumor size (p = 0.007) and advanced tumor stage (P = 0.011). Multivariate analysis indicated that tumor stage, tumor differentiation and PTEN expression status were independent prognostic factors for overall carcinoma in CRC patients (P < 0.05). The Kaplan-Meier curve indicated a negative correlation between PTEN expression levels and survival of CRC patients (P = 0.013). Conclusions: This study suggests a high frequency of miR-21 overexpression and aberrant promoter methylation in down-regulation of PTEN expression in colorectal carcinoma. Loss of PTEN may be a prognostic factor for patients with CRC. © 2016 Yazdani et al
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Bearing damage characteristics of fibre-reinforced countersunk composite bolted joints subjected to quasi-static shear loading
This paper studies the progression of damage in carbon fibre-reinforced polymer (CFRP) countersunk composite bolted joints (CBJs) with neat-fit clearance, subjected to quasi-static loading. Damage mechanisms, comprising of fibre buckling and breakage, matrix damage, shear damage and inter-laminar delamination within the CFRP composite parts of the joints have been studied. Load-displacement curves, X-ray and optical microscopic images in single- and three-bolt CBJs were used to investigate damage and deformation characteristics. The observations were then employed to further investigate the type of failure and the extent of damage. The evolution of damage within the composite parts was correlated to the failure characteristics of the joints: It was found that the type and extension of damage is strongly correlated with the ultimate failure load point of the joint in single-bolt CBJs. A combined inter/intra-laminar damage consisting of fibre cluster breakage, extensive fibre buckling, debonding and delamination was observed at the ultimate failure load. This study was then extended to three-bolt CBJ where damage surrounding each bolt and its corresponding failure load was strongly correlated: The final study showed that the ultimate failure point in single-bolt CBJ and the first-bolt-failure point in three-bolt CBJ correspond to the composite plies undergoing intra-laminar damage with the size reaching to the edge of the countersunk head. This damage developed extensively through the thickness of the composite parts underneath the countersink, and in the direction opposite to the loading direction. Outside the countersunk head, debonding and delamination were found to be the dominant damage driving mechanisms. Finally, a new design rule has been proposed to predict the response of multi-bolt joints (damage area and failure load) by using the response in single-bolt CBJ as an initial baseline
Promoter methylation analysis of WNT/β-catenin pathway regulators and its association with expression of DNMT1 enzyme in colorectal cancer
Background: Aberrant DNA methylation as the most important reason making epigenetic silencing of genes is a main mechanism of gene inactivation in patients with colorectal cancer. In this study, we decided to identify promoter methylation status of ten genes encoding WNT negative regulators, and measure the expression of DNMT1 enzyme in colorectal cancer samples. Results: Aberrant methylation of APC gene was statistically significant associated with age over 50 (p = 0.017), DDK3 with male (p < 0.0001), SFRP4, WIF1, and WNT5a with increasing tumor stage (p = 0.004, p = 0.029, and p = 0.004), SFRP4 and WIF1 with tumor differentiation (p = 0.009 and p = 0.031) and SFRP2 and SFRP5 with histological type (p = 0.001 and p = 0.025). The increasing number of methylated genes correlated with the expression levels of the DNMT1 mRNA. Conclusions: The rate of gene promoter methylation of WNT pathway regulators is high in colorectal cancer cells. Hyper-methylation is associated with increased expression of the DNMT1 enzyme. © 2014 Mansour Samaei et al.; licensee BioMed Central
Mapping the wavefunction of transition metal acceptor states in the GaAs surface
We utilize a single atom substitution technique with spectroscopic imaging in
a scanning tunneling microscope (STM) to visualize the anisotropic spatial
structure of magnetic and non-magnetic transition metal acceptor states in the
GaAs (110) surface. The character of the defect states play a critical role in
the properties of the semiconductor, the localization of the states influencing
such things as the onset of the metal-insulator transition, and in dilute
magnetic semiconductors the mechanism and strength of magnetic interactions
that lead to the emergence of ferromagnetism. We study these states in the GaAs
surface finding remarkable similarities between the shape of the acceptor state
wavefunction for Mn, Fe, Co and Zn dopants, which is determined by the GaAs
host and is generally reproduced by tight binding calculations of Mn in bulk
GaAs [Tang, J.M. & Flatte, M.E., Phys. Rev. Lett. 92, 047201 (2004)]. The
similarities originate from the antibonding nature of the acceptor states that
arise from the hybridization of the impurity d-levels with the host. A second
deeper in-gap state is also observed for Fe and Co that can be explained by the
symmetry breaking of the surface.Comment: 19 pages, 6 figure
Topology- and symmetry-protected domain wall conduction in quantum Hall nematics
We consider domain walls in nematic quantum Hall ferromagnets predicted to
form in multivalley semiconductors, recently probed by scanning tunnelling
microscopy experiments on Bi(111) surfaces. We show that the domain wall
properties depend sensitively on the filling factor of the underlying
(integer) quantum Hall states. For and in the absence of impurity
scattering we argue that the wall hosts a single-channel Luttinger liquid whose
gaplessness is a consequence of valley and charge conservation. For , it
supports a two-channel Luttinger liquid, which for sufficiently strong
interactions enters a symmetry-preserving thermal metal phase with a charge gap
coexisting with gapless neutral intervalley modes. The domain wall physics in
this state is identical to that of a bosonic topological insulator protected by
symmetry, and we provide a formal mapping between these
problems. We discuss other unusual properties and experimental signatures of
these `anomalous' one-dimensional systems.Comment: 11 pages, 3 figures, published versio
Molecular cloning and expression of novel fibroblast growth factor-2 conjugated with immunodominant domains of pseudomonas exotoxin
Angiogenesis is very important in cancer growth and metastasis. Basic fibroblast growth factor (bFGF) as one of the most important angiogenesis factors is an attractive target for cancer vaccine. Due to low immunogenicity, it cannot stimulate an effective immune response. Theoretically, pseudomonas exotoxin (PE) as a potent immunogenic carrier protein when fused to low immunogenic antigens such as bFGF significantly increased immunogenicity of it. In this study, we tried to molecular cloning and expression of bFGF conjugated with immunodominant domains of pseudomonas exotoxin. The coding sequence of fusion protein composed of bFGF linked to PE domains 1b and 2 using EAAAK poly linker. The KDEL sequence was also used in C-terminal coding sequence. It was synthesized and expressed using recombinant DNA technology in the bacterial expression system. Expression of recombinant protein verified using SDS-PAGE and western blot analyses. Finally, it purified using Ni-affinity chromatography. The band close to 37 kDa in SDS-PAGE and western blot analyses was aligned completely to designed sequence. Purified recombinant protein also showed as a clear single band near to 37 kDa
M-atom conductance oscillations of a metallic quantum wire
The electron transport through a monoatomic metallic wire connected to leads
is investigated using the tight-binding Hamiltonian and Green's function
technique. Analytical formulas for the transmittance are derived and M-atom
oscillations of the conductance versus the length of the wire are found. Maxima
of the transmittance function versus the energy, for the wire consisted of N
atoms, determine the (N+1) period of the conductance. The periods of
conductance oscillations are discussed and the local and average quantum wire
charges are presented. The average charge of the wire is linked with the period
of the conductance oscillations and it tends to the constant value as the
length of the wire increases. For M-atom periodicity there are possible (M-1)
average occupations of the wire states.Comment: 8 pages, 5 figures. J.Phys.: Condens. matter (2005) accepte
Transport Properties of Carbon Nanotube C Peapods
We measure the conductance of carbon nanotube peapods from room temperature
down to 250mK. Our devices show both metallic and semiconducting behavior at
room temperature. At the lowest temperatures, we observe single electron
effects. Our results suggest that the encapsulated C molecules do not
introduce substantial backscattering for electrons near the Fermi level. This
is remarkable given that previous tunneling spectroscopy measurements show that
encapsulated C strongly modifies the electronic structure of a nanotube
away from the Fermi level.Comment: 9 pages, 4 figures. This is one of two manuscripts replacing the one
orginally submitted as arXiv:cond-mat/0606258. The other one is
arXiv:0704.3641 [cond-mat
Impact of hepcidin antimicrobial peptide on iron overload in tuberculosis patients
Background: Iron acquisition is essential for the growth of Mycobacterium tuberculosis. Hepcidin is known as an antimicrobial peptide and a component of the innate immune response. Hepcidin inhibits M. tuberculosis growth in vitro. In this study, we decided to identify-582A> G variants of the HAMP promoter in patients with tuberculosis (TB) and investigate its effect on serum iron, ferritin, and hepcidin levels. Methods: The sample population consisted of 105 patients with TB and 104 healthy individuals. The-582A> G polymorphism was genotyped using a tetra-primers PCR set. Serum levels of hepcidin were determined using an ELISA kit. Statistical analysis was performed using SPSS software. Results: The G allele is meaningfully associated with TB disease (95% confidence interval = 2-4.8, p G polymorphism genotypes. There was significant reverse correlation between hepcidin and iron (r =-0.849, p = 0.006). Conclusion: A high association was found between serum hepcidin levels and the HAMP-582A> G variants in patients with TB. These observations indicate a hypothetical role of this polymorphism in iron metabolism. Hepcidin could perhaps be an option for the treatment of TB. © 2014 Informa Healthcare
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