12,648 research outputs found
Point: From animal models to prevention of colon cancer. Systematic review of chemoprevention in min mice and choice of the model system.
The Apc(Min/+) mouse model and the azoxymethane (AOM) rat model are the main animal models used to study the effect of dietary agents on colorectal cancer. We reviewed recently the potency of chemopreventive agents in the AOM rat model (D. E. Corpet and S. Tache, Nutr. Cancer, 43: 1-21, 2002). Here we add the results of a systematic review of the effect of dietary and chemopreventive agents on the tumor yield in Min mice. The review is based on the results of 179 studies from 71 articles and is displayed also on the internet http://corpet.net/min.(2) We compared the efficacy of agents in the Min mouse model and the AOM rat model, and found that they were correlated (r = 0.66; P < 0.001), although some agents that afford strong protection in the AOM rat and the Min mouse small bowel increase the tumor yield in the large bowel of mutant mice. The agents included piroxicam, sulindac, celecoxib, difluoromethylornithine, and polyethylene glycol. The reason for this discrepancy is not known. We also compare the results of rodent studies with those of clinical intervention studies of polyp recurrence. We found that the effect of most of the agents tested was consistent across the animal and clinical models. Our point is thus: rodent models can provide guidance in the selection of prevention approaches to human colon cancer, in particular they suggest that polyethylene glycol, hesperidin, protease inhibitor, sphingomyelin, physical exercise, epidermal growth factor receptor kinase inhibitor, (+)-catechin, resveratrol, fish oil, curcumin, caffeate, and thiosulfonate are likely important preventive agents
How shall we use the proteomics toolbox for biomarker discovery?
Biomarker discovery for clinical purposes is one of the major areas in which
proteomics is used. However, despite considerable effort, the successes have
been relatively scarce. In this perspective paper, we try to highlight and
analyze the main causes for this limited success, and to suggest alternate
strategies, which will avoid them, without eluding the foreseeable weak points
of these strategies. Two major strategies are analyzed, namely, the switch from
body fluids to cell and tissues for the initial biomarker discovery step or, if
body fluids must be analyzed, the implementation of highly selective protein
selection strategies
Semiclassical magnetotransport in graphene n-p junctions
We provide a semiclassical description of the electronic transport through
graphene n-p junctions in the quantum Hall regime. This framework is known to
experimentally exhibit conductance plateaus whose origin is still not fully
understood. In the magnetic regime (E < vF B), we show the conductance of
excited states is essentially zero, while that of the ground state depends on
the boundary conditions considered at the edge of the sample. In the electric
regime (E > vF B), for a step-like electrostatic potential (abrupt on the scale
of the magnetic length), we derive a semiclassical approximation for the
conductance in terms of the various snake-like trajectories at the interface of
the junction. For a symmetric configuration, the general result can be
recovered using a simple scattering approach, providing a transparent analysis
of the problem under study. We thoroughly discuss the semiclassical predicted
behavior for the conductance and conclude that any approach using fully
phase-coherent electrons will hardly account for the experimentally observed
plateaus.Comment: 22 pages, 19 figure
Fingerprints of Majorana fermions in current-correlations measurements from a superconducting tunnel microscope
We compute various current correlation functions of electrons flowing from a
topological nanowire to the tip of a superconducting scanning tunnel microscope
and identify fingerprints of a Majorana bound state. In particular, the spin
resolved cross-correlations are shown to display a clear distinction between
the presence of a such an exotic state (negative correlations) and an Andreev
bound state (positive correlations). Similarity and differences with
measurements with a normal tunnel microscope are also discussed, like the
robustness to finite temperature for instance.Comment: 7 pages, 2 figure
Graphene n-p junction in a strong magnetic field: a semiclassical study
We provide a semiclassical description of the electronic transport through
graphene n-p junctions in the quantum Hall regime. A semiclassical
approximation for the conductance is derived in terms of the various snake-like
trajectories at the interface of the junction. For a symmetric (ambipolar)
configuration, the general result can be recovered by means of a simple
scattering approach, providing a very transparent qualitative description of
the problem under study. Consequences of our findings for the understanding of
recent experiments are discussed.Comment: 10 pages, 2 figure
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