96 research outputs found
Acetate-induced apoptosis in colorectal carcinoma cells involves lysosomal membrane permeabilization and cathepsin D release
Colorectal carcinoma (CRC) is one of the most common causes of cancer-related mortality. Short-chain fatty acids secreted by
dietary propionibacteria from the intestine, such as acetate, induce apoptosis in CRC cells and may therefore be relevant in CRC
prevention and therapy. We previously reported that acetic acid-induced apoptosis in Saccharomyces cerevisiae cells involves
partial vacuole permeabilization and release of Pep4p, the yeast cathepsin D (CatD), which has a protective role in this process.
In cancer cells, lysosomes have emerged as key players in apoptosis through selective lysosomal membrane permeabilization
(LMP) and release of cathepsins. However, the role of CatD in CRC survival is controversial and has not been assessed in
response to acetate. We aimed to ascertain whether LMP and CatD are involved in acetate-induced apoptosis in CRC cells. We
showed that acetate per se inhibits proliferation and induces apoptosis. More importantly, we uncovered that acetate triggers
LMP and CatD release to the cytosol. Pepstatin A (a CatD inhibitor) but not E64d (a cathepsin B and L inhibitor) increased acetateinduced
apoptosis of CRC cells, suggesting that CatD has a protective role in this process. Our data indicate that acetate induces
LMP and subsequent release of CatD in CRC cells undergoing apoptosis, and suggest exploiting novel strategies using acetate
as a prevention/therapeutic agent in CRC, through simultaneous treatment with CatD inhibitors.This work was supported by the Fundação para a
Ciência e Tecnologia (FCT) research project PTDC/BIA-BCM/69448/2006 and FCT
PhD grants for SA (SFRH/BD/64695/2009) and CO (SFRH/BD/77449/2011). This
work was also supported by FEDER through POFC—COMPETE, and by national
funds from FCT through the project PEst-C/BIA/UI4050/2011
Novel water-soluble cyclodextrin–calix[4]arene host molecules with strongly enhanced binding properties
Nef Alleles from All Major HIV-1 Clades Activate Src-Family Kinases and Enhance HIV-1 Replication in an Inhibitor-Sensitive Manner
The HIV-1 accessory factor Nef is essential for high-titer viral replication and AIDS progression. Nef function requires interaction with many host cell proteins, including specific members of the Src kinase family. Here we explored whether Src-family kinase activation is a conserved property of Nef alleles from a wide range of primary HIV-1 isolates and their sensitivity to selective pharmacological inhibitors. Representative Nef proteins from the major HIV-1 subtypes A1, A2, B, C, F1, F2, G, H, J and K strongly activated Hck and Lyn as well as c-Src to a lesser extent, demonstrating for the first time that Src-family kinase activation is a highly conserved property of primary M-group HIV-1 Nef isolates. Recently, we identified 4-amino substituted diphenylfuropyrimidines (DFPs) that selectively inhibit Nef-dependent activation of Src-family kinases as well as HIV replication. To determine whether DFP compounds exhibit broad-spectrum Nef-dependent antiretroviral activity against HIV-1, we first constructed chimeric forms of the HIV-1 strain NL4-3 expressing each of the primary Nef alleles. The infectivity and replication of these Nef chimeras was indistinguishable from that of wild-type virus in two distinct cell lines (U87MG astroglial cells and CEM-T4 lymphoblasts). Importantly, the 4-aminopropanol and 4-aminobutanol derivatives of DFP potently inhibited the replication of all chimeric forms of HIV-1 in both U87MG and CEM-T4 cells in a Nef-dependent manner. The antiretroviral effects of these compounds correlated with inhibition of Nef-dependent activation of endogenous Src-family kinases in the HIV-infected cells. Our results demonstrate that the activation of Hck, Lyn and c-Src by Nef is highly conserved among all major clades of HIV-1 and that selective targeting of this pathway uniformly inhibits HIV-1 replication
Molecular Design, Functional Characterization and Structural Basis of a Protein Inhibitor Against the HIV-1 Pathogenicity Factor Nef
Increased spread of HIV-1 and rapid emergence of drug resistance warrants development of novel antiviral strategies. Nef, a critical viral pathogenicity factor that interacts with host cell factors but lacks enzymatic activity, is not targeted by current antiviral measures. Here we inhibit Nef function by simultaneously blocking several highly conserved protein interaction surfaces. This strategy, referred to as “wrapping Nef”, is based on structure-function analyses that led to the identification of four target sites: (i) SH3 domain interaction, (ii) interference with protein transport processes, (iii) CD4 binding and (iv) targeting to lipid membranes. Screening combinations of Nef-interacting domains, we developed a series of small Nef interacting proteins (NIs) composed of an SH3 domain optimized for binding to Nef, fused to a sequence motif of the CD4 cytoplasmic tail and combined with a prenylation signal for membrane association. NIs bind to Nef in the low nM affinity range, associate with Nef in human cells and specifically interfere with key biological activities of Nef. Structure determination of the Nef-inhibitor complex reveals the molecular basis for binding specificity. These results establish Nef-NI interfaces as promising leads for the development of potent Nef inhibitors
Functional response and life history parameters of Apanteles taragamae, a larval parasitoid of Maruca vitrata
Automatic lung segmentation of magnetic resonance images: A new approach applied to healthy volunteers undergoing enhanced Deep-Inspiration-Breath-Hold for motion-mitigated 4D proton therapy of lung tumors.
BACKGROUND AND PURPOSE
Respiratory suppression techniques represent an effective motion mitigation strategy for 4D-irradiation of lung tumors with protons. A magnetic resonance imaging (MRI)-based study applied and analyzed methods for this purpose, including enhanced Deep-Inspiration-Breath-Hold (eDIBH). Twenty-one healthy volunteers (41-58 years) underwent thoracic MR scans in four imaging sessions containing two eDIBH-guided MRIs per session to simulate motion-dependent irradiation conditions. The automated MRI segmentation algorithm presented here was critical in determining the lung volumes (LVs) achieved during eDIBH.
MATERIALS AND METHODS
The study included 168 MRIs acquired under eDIBH conditions. The lung segmentation algorithm consisted of four analysis steps: (i) image preprocessing, (ii) MRI histogram analysis with thresholding, (iii) automatic segmentation, (iv) 3D-clustering. To validate the algorithm, 46 eDIBH-MRIs were manually contoured. Sørensen-Dice similarity coefficients (DSCs) and relative deviations of LVs were determined as similarity measures. Assessment of intrasessional and intersessional LV variations and their differences provided estimates of statistical and systematic errors.
RESULTS
Lung segmentation time for 100 2D-MRI planes was ∼ 10 s. Compared to manual lung contouring, the median DSC was 0.94 with a lower 95 % confidence level (CL) of 0.92. The relative volume deviations yielded a median value of 0.059 and 95 % CLs of -0.013 and 0.13. Artifact-based volume errors, mainly of the trachea, were estimated. Estimated statistical and systematic errors ranged between 6 and 8 %.
CONCLUSIONS
The presented analytical algorithm is fast, precise, and readily available. The results are comparable to time-consuming, manual segmentations and other automatic segmentation approaches. Post-processing to remove image artifacts is under development
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LWBR Development Program
An experiment has been performed to determine the effect of motion of a thermal shield on the neutron signal expected from ex-core detectors. Using a mockup of the LWBR reactor vessel, thermal shield, and core barrel in conjunction with a /sup 252/Cf neutron source, the change in detector signal with displacement of the various components was investigated. It was found that moving the thermal shield would produce a significant change in detector signal, although the effect was smaller than would be produced by moving the source and core barrel together. The results were substantiated by two-dimensional discrete-ordinate calculations
On the Size of Minimal Visibility Graphs
The main goal of a recent article [3] by X. Shen and H. Edelsbruner is to establish a lower bound on the number of edges in the visibility graph of a finite set of line segments. As was pointed out by Campbell and Higins in [2], Shen and Edelsbruner’s proof of this lower bound is flawed. However, the alternate proof supplied by Campbell and Higgins is also incorrect
Polymerization of Isobutylene by GaCl<sub>3</sub> or FeCl<sub>3</sub>/Ether Complexes in Nonpolar Solvents
The carbocationic polymerization of isobutylene (IB),
co-initiated
by GaCl<sub>3</sub> or FeCl<sub>3</sub>·dialkyl ether 1:1 complexes
has been investigated in hexanes in the −20 to 10 °C temperature
range. In contrast to AlCl<sub>3</sub>·diisopropyl ether (AlCl<sub>3</sub>·<i>i</i>-Pr<sub>2</sub>O) complexes, GaCl<sub>3</sub>·<i>i</i>-Pr<sub>2</sub>O and FeCl<sub>3</sub>·<i>i</i>-Pr<sub>2</sub>O readily co-initiate polymerization with 2-chloro-2,4,4-trimethylpentane
(TMPCl) or <i>tert</i>-butyl chloride (<i>t</i>-BuCl) in the presence or absence of proton trap. In the absence
of proton trap, chain transfer to monomer readily proceeded, resulting
in close to complete monomer conversion and up to 85% exo-olefinic
end group content. Diisopropyl ether complexes gave the highest polymerization
rates, while nonbranched alkyl ether complexes were completely inactive.
A polymerization mechanism is proposed to involve ether-assisted proton
elimination to yield PIB exo-olefin, and the abstracted proton can
subsequently start a new polymer chain by protonation of IB. Alternatively
PIB<sup>+</sup> may be deactivated by ion collapse to yield PIBCl,
which can be reactivated by the Lewis acid. The reasons for the difference
in behavior between the Ga and Fe catalysts and the Al-based catalysts
are described
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