4,540 research outputs found
Not only P-glycoprotein: amplification of the ABCB1-containing chromosome region 7q21 confers multidrug resistance upon cancer cells by coordinated overexpression of an assortment of resistance-related proteins
The development of drug resistance continues to be a dominant hindrance toward curative cancer treatment.
Overexpression of a wide-spectrum of ATP-dependent efflux pumps, and in particular of ABCB1 (P-glycoprotein
or MDR1) is a well-known resistance mechanism for a plethora of cancer chemotherapeutics including for example
taxenes, anthracyclines, Vinca alkaloids, and epipodopyllotoxins, demonstrated by a large array of published
papers, both in tumor cell lines and in a variety of tumors, including various solid tumors and hematological
malignancies. Upon repeated or even single dose treatment of cultured tumor cells or tumors in vivo with
anti-tumor agents such as paclitaxel and doxorubicin, increased ABCB1 copy number has been demonstrated,
resulting from chromosomal amplification events at 7q11.2-21 locus, leading to marked P-glycoprotein overexpression,
and multidrug resistance (MDR). Clearly however, additional mechanisms such as single nucleotide
polymorphisms (SNPs) and epigenetic modifications have shown a role in the overexpression of ABCB1 and of
other MDR efflux pumps. However, notwithstanding the design of 4 generations of ABCB1 inhibitors and the
wealth of information on the biochemistry and substrate specificity of ABC transporters, translation of this vast
knowledge from the bench to the bedside has proven to be unexpectedly difficult.
Many studies show that upon repeated treatment schedules of cell cultures or tumors with taxenes and anthracyclines
as well as other chemotherapeutic drugs, amplification, and/or overexpression of a series of genes
genomically surrounding the ABCB1 locus, is observed. Consequently, altered levels of other proteins may
contribute to the establishment of the MDR phenotype, and lead to poor clinical outcome. Thus, the genes
contained in this ABCB1 amplicon including ABCB4, SRI, DBF4, TMEM243, and RUNDC3B are overexpressed in
many cancers, and especially in MDR tumors, while TP53TG1 and DMTF1 are bona fide tumor suppressors. This
review describes the role of these genes in cancer and especially in the acquisition of MDR, elucidates possible
connections in transcriptional regulation (co-amplification/repression) of genes belonging to the same ABCB1
amplicon region, and delineates their novel emerging contributions to tumor biology and possible strategies to
overcome cancer MDR
Monitoring dispersive samples with single photons: the role of frequency correlations
The physics that governs quantum monitoring may involve other degrees of
freedom than the ones initialised and controlled for probing. In this context
we address the simultaneous estimation of phase and dephasing characterizing a
dispersive medium, and we explore the role of frequency correlations within a
photon pair generated via parametric down-conversion, when used as a probe for
the medium. We derive the ultimate quantum limits on the estimation of the two
parameters, by calculating the corresponding quantum Cram\'er-Rao bound; we
then consider a feasible estimation scheme, based on the measurement of Stokes
operators, and address its absolute performances in terms of the correlation
parameters, and, more fundamentally, of the role played by correlations in the
simultaneous achievability of the quantum Cram\'er-Rao bounds for each of the
two parameters.Comment: to appear in Quantum Measurements and Quantum Metrolog
Confronto di solutori FEM e solutori BEM per lo sloshing in contenitori
Ė stato studiato il fenomeno di sloshing attraverso due diversi algoritmi numerici: il primo consiste in una discretizzazione con elementi finiti dell’equazione di Navier Stokes in formulazione Arbitrary Lagrangian Eulerian, è indicato nel seguito come FEM ed è descritto in [3]; il secondo è basato sulla discretizzazione delle equazioni agli integrali di contorno e delle equazioni di evoluzione della superficie libera ed è indicato come BEM e descritto in [2]. Per verificare la validità dei due codici sono stati confrontati i loro risultati con quelli presenti in letteratura, sia derivanti da altri codici numerici, sia ottenuti come risultati sperimentali. Il confronto è stato effettuato per un’ampia gamma di situazioni, in modo da studiare il comportamento dei due codici al variare delle caratteristiche della sollecitazione e delle dimensioni del dominio
Noisy quantum walks of two indistinguishable interacting particles
We investigate the dynamics of continuous-time two-particle quantum walks on
a one-dimensional noisy lattice. Depending on the initial condition, we show
how the interplay between particle indistinguishability and interaction
determines distinct propagation regimes. A realistic model for the environment
is considered by introducing non-Gaussian noise as time-dependent fluctuations
of the tunneling amplitudes between adjacent sites. We observe that the
combined effect of particle interaction and fast noise (weak coupling with the
environment) provides a faster propagation compared to the noiseless case. This
effect can be understood in terms of the band structure of the Hubbard model,
and a detailed analysis as a function of both noise and system parameters is
presented.Comment: 9 pages, 8 figure
Multiparameter quantum estimation of noisy phase shifts
Phase estimation is the most investigated protocol in quantum metrology, but
its performance is affected by the presence of noise, also in the form of
imperfect state preparation. Here we discuss how to address this scenario by
using a multiparameter approach, in which noise is associated to a parameter to
be measured at the same time as the phase. We present an experiment using
two-photon states, and apply our setup to investigating optical activity of
fructose solutions. Finally, we illustrate the scaling laws of the attainable
precisions with the number of photons in the probe state
Neuropragmatics: Extralinguistic communication after closed head injury
This work is concerned with the decay of communicative abilities after head trauma. A protocol composed of 16 videotaped scenes was devised in order to investigate the comprehension of several types of communicative actions realized with extralinguistic means, like pointing or clapping. The protocol was administered to 30 closed head injured individuals. The results showed a decreasing performance from simple standard acts, to complex standard acts, deceits, and ironies. The subjects' performance was worse with the scenes reproducing failing, rather than successful, communicative actions. The results are compared with those we previously obtained with a linguistic protocol. A theory of the cognitive processes underlying intentional communication is outlined and used to explain the results
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