169,750 research outputs found
Elucidation of a molecular mechanism controlling inflammation during bacterial infection
No full textRecently we described a mechanism of gap junction-mediated communication between infected and uninfected epithelial cells that potentiates innate immunity during infection by the enteroinvasive bacterium Shigella flexneri. We showed that although S. flexneri secretes multiple effector proteins that downregulate inflammation in infected epithelial cells, NF-κB and the MAP kinases p38, JNK and ERK are activated in uninfected cells surrounding the sites of infection. The propagation of these proinflammatory signals leads to massive secretion of proinflammatory cytokines such as interleukin-8 (IL-8) by uninfected bystander cells. A genome wide RNAi-screen on Shigella-induced bystander activation confirmed the roles of the proteins TAK1 and NF-κB. Besides this, new candidates for bystander activation were found, including Na+/K+-ATPase (ATP1A1), the TRAF-interacting protein with a FHA domain (TIFA) and the TNF receptor-associated factor 6 (TRAF6). These proteins together with NOD1 and RIPK2, members of the NOD1 signaling pathway, which is induced by invasive Shigella, were studied in more detail. To our surprise we found that signals underlying cell-cell communication are produced independently of the receptor NOD1 and the downstream signaling proteins RIPK2, TAK1 and NF-κB as well as independent of TIFA and TRAF6. Unexpectedly, in bystander cells NOD1 and RIPK2 contribute to the proinflammatory response, whereas TAK1, NF-κB, TIFA and TRAF6 are indispensable for the production of cytokines. Furthermore, TIFA and TRAF6 are upstream of TAK1 and are required for TAK1 activation. In addition, selective stimulation of TIFA or TRAF6 depleted cells with the NOD1 ligand iE-DAP unraveled that TIFA and TRAF6 contribute to NOD1 signaling in bystander cells of S. flexneri infection. And finally, we propose a link between intercellular calcium signaling triggered by invasive S. flexneri and bystander IL-8 expression, since inhibition of calcium signals via a calcium chelator or inhibition of the IP3-receptor or phospholipase C (PLC) lead to a decreased bystander IL-8 response
Host protein phosphorylation during "Shigella flexneri" infection : a phosphoproteomic based systems biology approach
No full textThe enteroinvasive bacterium Shigella flexneri triggers its uptake into epithelial cells by injecting several effector proteins via its type three secretion system (TTSS) and interferes with various host cell processes at later stages of infection. In this study, we systematically addressed the impact of S. flexneri infection on the host signaling network by quantitative phosphoproteomics. We were able to identify several hundreds of proteins undergoing a change in their phosphorylation state during the first two hours of infection. Using bioinformatic tools, we could demonstrate that many phosphoproteins are related to the
cytoskeleton, signal transduction, cell cycle, and transcription regulation. The temporal phosphorylation patterns were addressed by fuzzy c-means clustering, revealing six temporally distinct phosphorylation profiles as well as kinases potentially responsible for these phosphorylations. In particular, we found a cluster of ataxia telangiectasia mutated (ATM) substrates, related to genotoxic stress, that became phosphorylated at a late
stage of infection. We identified mTOR as the most overrepresented signaling pathway and could demonstrate that both, mTORC1 and mTORC2, become activated during S. flexneri infection. To identify phosphoproteins commonly regulated during bacterial infection, we compared our dataset to a published phosphoproteome of cells infected with Salmonella typhimurium. This analysis revealed a large subset of co-regulated phosphoproteins, indicating that both pathogens interfere with similar cellular signaling cascades. Furthermore, we addressed the impact of the S. flexneri effector protein OspF on the host phosphorylation network. OspF is known to inactivate the MAPKs p38 and ERK. The phosphorylation of several hundred proteins was affected in an OspF-dependent manner, demonstrating the massive impact a single bacterial effector can have on the host signaling network.
In a second project we addressed the activation mechanism of AKT and mTOR during S. flexneri infection by studying the effector IpgD. IpgD is a phosphoinositide 4-phosphatase
generating PI5P from PI(4,5)P2 leading to activation of AKT. We could demonstrate that the effector protein IpgD is sufficient to induce mTOR activation by the use of a protein
delivery tool based on the TTSS of Yersinia enterocolitica. Interestingly, AKT activation was independent of canonical PI3K activity shortly after IpgD translocation, whereas at
later timepoints AKT activation was PI3K-dependent. These data suggest two distinct IpgD-dependent AKT activation mechanisms. Finally, we could show that the Inositol polyphosphate multikinase IPMK contributes to AKT phosphorylation during infection
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Mitomycin C in highly myopic eyes - Author reply
No full textOphthalmology. 2005 Feb;112(2):208-18; discussion 219.
Mitomycin C modulation of corneal wound healing after photorefractive keratectomy in highly myopic eyes.
Gambato C, Ghirlando A, Moretto E, Busato F, Midena E.
SourceRefractive Surgery Service and Antimetabolite Therapy Research Unit, Department of Ophthalmology, University of Padova, Padova, Italy.
Abstract
PURPOSE: To evaluate the role of topical mitomycin C in corneal wound healing (CWH) after photorefractive keratectomy (PRK) in highly myopic eyes.
DESIGN: Prospective, double-masked, randomized clinical trial.
PARTICIPANTS: Seventy-two eyes of 36 patients affected by high (>7 diopters) myopia.
METHODS: In each patient, one eye was randomly assigned to PRK with intraoperative topical 0.02% mitomycin C application, and the fellow eye was treated with a placebo. Postoperatively, mitomycin C-treated eyes received artificial tears (3 times daily, tapered in 3 months), whereas the fellow eye was treated with fluorometholone sodium 2% and artificial tears (3 times daily, tapered in 3 months).
MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity, manifest refraction, and biomicroscopy. Contrast sensitivity was determined using the Pelli-Robson chart. Corneal confocal microscopy documented CWH.
RESULTS: Mean follow-up was 18 months (range, 12-36). No side effects or toxic effects were documented. At 12-month follow-up examination, UCVAs (logarithm of the minimum angle of resolution) were 0.4+/-0.48 and 0.5+/-0.53 (P = .03) in mitomycin C-treated eyes and corticosteroid-treated eyes, respectively. At 1 year, corneal haze developed in 20% of corticosteroid-treated eyes, versus 0% of mitomycin C-treated eyes. At 12, 24, and 36 months, corneal confocal microscopy showed activated keratocytes and extracellular matrix significantly more evident in untreated eyes (Ps = 0.004, 0.024, and 0.046, respectively).
CONCLUSION: Topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK.
Comment in
Ophthalmology. 2006 Feb;113(2):357; author reply 357-8
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Amplifying the innate immune response : cell-cell propagation of proinflammatory signals during bacterial infection
No full textThe enteroinvasive bacterium Shigella flexneri uses multiple secreted effector proteins to downregulate interleukin-8 (IL-8) expression in infected epithelial cells. Nevertheless, massive IL-8 secretion is observed in shigellosis. In this thesis, a novel host mechanism of cell-cell communication that circumvents the effectors and strongly amplifies IL-8 expression during bacterial infection is reported. By monitoring proinflammatory signals at the single-cell level during Shigella infection, we found that activation of the transcription factor NF-kappaB and the MAP kinases JNK, ERK and p38 rapidly propagates from infected to uninfected adjacent cells leading to massive IL-8 production by uninfected bystander cells. Bystander IL-8 production was also observed during Listeria monocytogenes and Salmonella typhimurium infection. It was reproduced by microinjection of the Nod1 ligand L-Ala-D-gamma-Glu-meso-diaminopimelic acid and blocked by gap junction inhibitors. Thus, a novel gap junction-mediated mechanism of cell-cell communication was identified that broadly amplifies innate immunity against bacterial infection by rapidly spreading proinflammatory signals to yet uninfected cells
Studies on the role of Coronin 1 and the actin cytoskeleton in T cell signaling and survival
No full textCalcium ions (Ca2+) function as universal second messengers in most if not all eukaryotic cells, including the cells of the immunesystem. Ca2+ signals are required for the proper activation of lymphocytes, such as T-lymphocytes, their proliferation, differentiation and effector functions. In lymphocytes store-operated calcium entry (SOCE) through calcium release activated calcium (CRAC) channels in the plasma membrane is the major mechanism to increase cytosolic Ca2+ concentrations and is essential for the activation of T and B cells as well as induction of their cytokine gene production. How exactly store operated calcium entry operates in T cells has remained unclear. While one model, based on results obtained using a variety of F-actin-modulating drugs, involves the cortical actin cytoskeleton, the function of F-actin in SOCE has remained controversial during the last decade, since independent studies have found no effects of the same drugs on SOCE in other model systems such as the rat basophile leukemia (RBL) cell line. The first part of this thesis aims at defining the role of the actin cytoskeleton during SOCE in human T cells.
The data presented in this thesis clearly demonstrate that the F-actin cytoskeleton in human T cells has no role in SOCE. These results therefore contribute to our understanding of calcium signaling in cells of the immunesystem.
The second part of this thesis focuses on coronin 1, a member of the conserved WD repeat containing protein family which is encoded in mice (and human) by the gene coro1a. Coronin 1, which is specifically expressed in leukocytes, was originally identified as a protein that is maintained around phagosomes containing live mycobacteria, thereby preventing the fusion of the mycobacterial phagosome with lysosomes and mycobacterial destruction.
The aim of this part of the thesis was to define the function of coronin 1 in immune cells by characterizing coronin 1 deficient mice with a special focus on T cell development, T cell receptor signaling, migration and survival as well as the proposed regulatory role of coronin 1 in F-actin dependent processes. We found, in contrast to the long held dogma of coronin 1 being a major regulator of the F-actin cytoskeleton, that coronin 1 regulates cellular signaling rather that F-actin modulation.
Coronin 1 was shown to interact with phospholipase C γ1 (PLC γ1) thereby being an important regulator of inositol-1,4,5-trisphosphate (IP3) generation from phosphatidylinositol-4,5-bisphosphate (PIP2). The absence of coronin 1, although not affecting T cell development, resulted in a profound defect in Ca2+ mobilization, interleukin-2 (IL-2) production, T cell proliferation and T cell survival in naïve T-cells.
Finally in the last part of this thesis we provide data showing that coronin 1 maintains the balance between survival and apoptosis in naive T cells independent of F-Actin via a calcium/calcineurin dependent pathway.
The data presented in part two and three of this thesis establish the leukocyte specific protein coronin 1 as an essential regulator of T cell receptor signaling as well as naïve T cell homeostasis and survival. This work refutes the proposed role of coronin 1 in the regulation of the F-actin cytoskeleton, instead providing evidence for coronin 1 being a central regulator of Ca2+-dependent signaling in T cells. The work described here further offers new possibilities for the development of compounds for the treatment of T cell mediated disorders of the immunesystem
A Multi-Language Comparison of Influences on Author Verification using Character N-Grams
No full textWe create a new multi-language corpus for author verification based on Wikipedia talkpages, and evaluate the influence that differences in topic and time have on character n-gram author profiles. Topic alignment between two texts is found to increase author verification precision, and an authors writing style is found to change over time, but not more significantly after 3 years than after 1 year.Information ArchitectureWISElectrical Engineering, Mathematics and Computer Scienc
A 0.12mm<sup>2</sup> Wien-Bridge Temperature Sensor with 0.1°C (3σ) Inaccuracy from -40°C to 180°C
No full text Resistor-based temperature sensors can achieve much higher resolution and energy efficiency than conventional BJT-based sensors [1], but they typically occupy more area (> 0.25 mm 2 ) and have lower operating temperatures (le 125 {circ} {C}) [2]-[4]. This work describes a 0.12mm 2 resistor-based sensor that uses a Wien-bridge (WB) filter to achieve 0.1 {circ} {C} (3 sigma) inaccuracy from - 40 {circ} {C} to 180 {circ} {C}. Compared to a state-of-the-art WB sensor [4], it occupies 6 × less area and achieves comparable relative accuracy over a 76% wider operating range. Session 10.3 Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic InstrumentationMicroelectronic
A ±25A Versatile Shunt-Based Current Sensor with 10kHz Bandwidth and ±0.25% Gain Error from -40°C to 85°C Using 2-Current Calibration
No full textAccurate current sensing is critical in many industrial applications, such as battery management and motor control. Precise shunt-based current sensors have been reported with gain errors of less than 1% over the industrial temperature range (-40°C to 85°C) [1]–[4]. However, since they are intended for coulomb counting, their bandwidth is limited to a few tens of Hz, making them unsuitable for battery impedance or motor-current sensing. This paper presents a current sensor with a wide (10kHz) bandwidth and a tunable temperature compensation scheme (TCS), which allows it to be flexibly used with different types of shunts while maintaining high accuracy. A low-cost room-temperature calibration scheme is proposed to optimize gain flatness over temperature by exploiting the shunt's self-heating at large currents. Over the industrial temperature range and a ±25A current range, it achieves state-of-the-art gain error (±0.25%) with both low-cost PCB and stable metal-alloy shunts.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic InstrumentationMicroelectronic
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