2,495 research outputs found
Cells assemble invadopodia-like structures and invade into matrigel in a matrix metalloprotease dependent manner in the circular invasion assay
The ability of tumor cells to invade is one of the hallmarks of the metastatic phenotype. To elucidate the mechanisms by which tumor cells acquire an invasive phenotype, in vitro assays have been developed that mimic the process of cancer cell invasion through basement membrane or in the stroma. We have extended the characterization of the circular invasion assay and found that it provides a simple and amenable system to study cell invasion in matrix in an environment that closely mimics 3D invasion. Furthermore, it allows detailed microscopic analysis of both live and fixed cells during the invasion process. We find that cells invade in a protease dependent manner in this assay and that they assemble focal adhesions and invadopodia that resemble structures visualized in 3D embedded cells. We propose that this is a useful assay for routine and medium throughput analysis of invasion of cancer cells in vitro and the study of cells migrating in a 3D environment
Differential expression of PKD1 and PKD2 in gastric cancer and analysis of PKD1 and PKD2 function in the model system
Aim: To study the differential expression of PKD1 and PKD2 in primary gastric cancer samples and to examine the role of PKD1 and PKD2 protein kinases in regulation of gastric tumor cell biology in the model system. Methods: Tumor samples of different histological variants of primary gastric cancer were analyzed. PKD1 and PKD2 expression levels in tumor samples were accessed by Western blot analysis and quantitative polymerase chain reaction (Q-PCR). As a model system we have used gastric adenocarcinoma сell line AGS sublines constitutively transfected by pcDNA3.1 coding PKD1 or PKD2, or empty pcDNA3.1 vector. These cell lines were analyzed by Western blot, Q-PCR, MTT and proliferation assays, in vitro scratch and Transwell assays, clonogenic assay. Results: It was found that primary gastric tumors possess different levels of PKD1 and PKD2 expression on mRNA and protein levels. Low level of PKD1 expression on protein and mRNA level was detected in low differentiated adenocarcinoma and ring cell gastric cancer — disorders with poor clinical prognosis. The high level of PKD2 expression was also found in gastric tumors with poor prognosis: low differentiated adenocarcinoma and adenogen cancer. To find out whether differential expression of PKD1 and PKD2 could affect biology of gastric tumor cells in vitro, we used a model system based on AGS cell line that constitutively expressed PKD1 or overexpressed PKD2. PKD1 transfection led to the inhibition of cell proliferation, migration and colony formation, in the meanwhile, the PKD2 overexpression enhanced proliferation, migration and colony formation capacities of AGS cells. Conclusions: Our data suggest that both downregulation of PKD1 or upregulation of PKD2 expression may determine the behavior of gastric tumor cells, which promotes invasive phenotype and could result in general poor prognosis
Social and cultural origins of motivations to volunteer a comparison of university students in six countries
Although participation in volunteering and motivations to volunteer (MTV) have received substantial attention on the national level, particularly in the US, few studies have compared and explained these issues across cultural and political contexts. This study compares how two theoretical perspectives, social origins theory and signalling theory, explain variations in MTV across different countries. The study analyses responses from a sample of 5794 students from six countries representing distinct institutional contexts. The findings provide strong support for signalling theory but less so for social origins theory. The article concludes that volunteering is a personal decision and thus is influenced more at the individual level but is also impacted to some degree by macro-level societal forces
D-optimal designs via a cocktail algorithm
A fast new algorithm is proposed for numerical computation of (approximate)
D-optimal designs. This "cocktail algorithm" extends the well-known vertex
direction method (VDM; Fedorov 1972) and the multiplicative algorithm (Silvey,
Titterington and Torsney, 1978), and shares their simplicity and monotonic
convergence properties. Numerical examples show that the cocktail algorithm can
lead to dramatically improved speed, sometimes by orders of magnitude, relative
to either the multiplicative algorithm or the vertex exchange method (a variant
of VDM). Key to the improved speed is a new nearest neighbor exchange strategy,
which acts locally and complements the global effect of the multiplicative
algorithm. Possible extensions to related problems such as nonparametric
maximum likelihood estimation are mentioned.Comment: A number of changes after accounting for the referees' comments
including new examples in Section 4 and more detailed explanations throughou
Catalytic imaging-guided cancer therapy using non-coordinated and coordinated nanozymes
Nanozymes with and without coordinated structures, in addition to performing enzyme-mimic activities through converting O2[rad]– to H2O2 or H2O2 into O2 and [rad]OH, are of interest in the development of diagnostic imaging and image-guided therapy platforms. Controlled catalytic activity, high selectivity/sensitivity, low cost, easy generation, stability and biodegradability, and combination therapy, make the use of nanozymes promising for imaging-guided cancer therapy. Therefore, in this review, we attempt to describe the improved imaging resolution relied on the catalytic activity of nanozymes in the TME mediated by the accumulation of contrast agents (such as metal ions, contrast agents, and organic compounds) or molecules that provide the high-resolution imaging of tumor cells. The following section delves into important approaches, including tumor inhibition, nanocarrier clearance, biocompatibility, as well as the efficacy of nanozymes with and without coordinated structures in catalytic cancer therapy. Finally, with an overview of the challenges, we highlighted the main obstacles in the development of nanoscale catalysts in the advancement of multimodal imaging for improved diagnosis and cancer therapy. We hope that this review may clarify the important aspects regarding the utilization of nanozymes, both with and without coordinated structures in multi-modal imaging and image-guided cancer therapy.</p
Perturbative Formulation and Non-adiabatic Corrections in Adiabatic Quantum Computing Schemes
Adiabatic limit is the presumption of the adiabatic geometric quantum
computation and of the adiabatic quantum algorithm. But in reality, the
variation speed of the Hamiltonian is finite. Here we develop a general
formulation of adiabatic quantum computing, which accurately describes the
evolution of the quantum state in a perturbative way, in which the adiabatic
limit is the zeroth-order approximation. As an application of this formulation,
non-adiabatic correction or error is estimated for several physical
implementations of the adiabatic geometric gates. A quantum computing process
consisting of many adiabatic gate operations is considered, for which the total
non-adiabatic error is found to be about the sum of those of all the gates.
This is a useful constraint on the computational power. The formalism is also
briefly applied to the adiabatic quantum algorithm.Comment: 5 pages, revtex. some references adde
Synchronization of fractional order chaotic systems
The chaotic dynamics of fractional order systems begin to attract much
attentions in recent years. In this brief report, we study the master-slave
synchronization of fractional order chaotic systems. It is shown that
fractional order chaotic systems can also be synchronized.Comment: 3 pages, 5 figure
History-dependent relaxation and the energy scale of correlation in the Electron-Glass
We present an experimental study of the energy-relaxation in
Anderson-insulating indium-oxide films excited far from equilibrium. In
particular, we focus on the effects of history on the relaxation of the excess
conductance dG. The natural relaxation law of dG is logarithmic, namely
dG=-log(t). This may be observed over more than five decades following, for
example, cool-quenching the sample from high temperatures. On the other hand,
when the system is excited from a state S_{o} in which it has not fully reached
equilibrium to a state S_{n}, the ensuing relaxation law is logarithmic only
over time t shorter than the time t_{w} it spent in S_{o}. For times t>t_{w}
dG(t) show systematic deviation from the logarithmic dependence. It was
previously shown that when the energy imparted to the system in the excitation
process is small, this leads to dG=P(t/t_{w}) (simple-aging). Here we test the
conjecture that `simple-aging' is related to a symmetry in the relaxation
dynamics in S_{o} and S_{n}. This is done by using a new experimental procedure
that is more sensitive to deviations in the relaxation dynamics. It is shown
that simple-aging may still be obeyed (albeit with a modified P(t/t_{w})) even
when the symmetry of relaxation in S_{o} and S_{n} is perturbed by a certain
degree. The implications of these findings to the question of aging, and the
energy scale associated with correlations are discussed
Communicating Josephson Qubits
We propose a scheme to implement a quantum information transfer protocol with
a superconducting circuit and Josephson charge qubits. The information exchange
is mediated by an L-C resonator used as a data bus. The main decoherence
sources are analyzed in detail.Comment: 4 pages, 2 figure
- …