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Search Results: 1 - 10 of 29209 matches for " Robert CS Chua "
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In vitro inhibition of human influenza A virus replication by chloroquine
Eng Ooi, Janet Chew, Jin Loh, Robert CS Chua
Virology Journal , 2006, DOI: 10.1186/1743-422x-3-39
Abstract: Antiviral drugs against influenza virus play an important role in the treatment and prevention of human influenza infection. The adamantanes have been used for decades and resistance to this class of drugs has become prevalent in some parts of the world [1]. The neuraminidase inhibitor, oseltamivir, is currently regarded as the first line of defence against a pandemic until a suitable vaccine can be produced in sufficient quantities. Emergence of resistance to this drug in human influenza A viruses [2], as well as the H5N1 subtype in Vietnam [3] is thus a cause for concern. Resistance has not been reported for zanamivir, another neuraminidase inhibitor [4]. Expanding the range of antiviral drugs that effectively inhibit influenza A virus replication is thus a matter of urgency.A recent review has suggested that the anti-malarial drug, chloroquine, may have antiviral activity [5]. As a lysosomotropic weak base, it impairs replication of some viruses through reducing the efficiency of endosome-mediated virus entry or through inhibiting the low-pH dependent proteases in trans-Golgi vesicles [5]. Its antiviral activities against the human immunodeficiency virus (HIV) [6] and the SARS coronavirus have been demonstrated [7,8]. Previously, chloroquine had been used to study influenza virus replication in vitro [9]. However, the 0.1 mM concentration used was too high to indicate its therapeutic usefulness [9]. We thus carried out an in vitro antiviral assay to determine the 50% and 90% inhibitory concentration (IC50 and IC90, respectively) of chloroquine against influenza A virus subtypes H1N1 and H3N2.The in vitro antiviral screening assay was modified from a previously described method [10] and carried out in triplicates. Influenza A viruses H1N1 (ATCC: VR1520) and H3N2 (ATCC: VR544) were used in this study. Briefly, 50 μl of serial 2-fold dilutions of the chloroquine were incubated overnight with 100 μl of MDCK cells giving a final cell count of 30,000 cells per well in
The Role of Parts-of-Speech in Feature Selection
Stephanie Chua
Lecture Notes in Engineering and Computer Science , 2008,
Placing Music Video: A new audiovisual modality
Collin Chua
Transforming Cultures , 2009,
Abstract: Music, as Jacques Attali emphasises, “is a way of perceiving the world” (1985:4). Sarah Cohen also suggests that: “Individuals can use music as a cultural ‘map of meaning’, drawing upon it to locate themselves in different imaginary geographies… and to articulate both individual and collective identities” (1998: 286-287). Tia DeNora extends on this, pointing out that: “Music can be used as a device for the reflexive process of remembering/constructing who one is, a technology for spinning the apparently continuous tale of who one is” (DeNora 2000: 63). Music has served various integral social and cultural functions in human societies throughout history. It seems clear that as music has changed shape and form through the advent of various reproduction technologies, the ways in which we consume as well as produce music, and the shape and form of music-as-cultural map and music as way of perceiving the world, have also changed over time. In his book The Sight of Sound, Richard Leppert points out: “Precisely because musical sound is abstract, intangible, and ethereal – lost as soon as it is gained – the visual experience of its production is crucial… for locating and communicating the place of music and musical sound within society and culture” (1993: xx-xxi). This paper will focus on what Michel Chion describes as “a very influential new audiovisual form, the music video, which has opened the doors to infinite possibilities in representing relations between a voice and its source” (1999: 172). The paper argues that the contemporary articulation of music and images, built on “infinite possibilities in representing relations between a voice and its source”, has come to shape a persuasive new audiovisual modality for “locating and communicating the place of music and musical sound within society and culture”. In order to examine this new audiovisual modality, I will move away from a conventional approach based upon looking at music video in terms of its non-narrative structure, and instead propose a conceptual approach based on looking at music video in terms of its production of space. This line of discussion will be navigated not by providing close textual readings of various music videos, but rather by examining and theorising the music video as cultural/media form.
Bombarded by soundful images: An audiovisual account of 9/11
Colin Chua
PRism Online PR Journal , 2006,
Abstract: Images have become an important aspect of, and shaping force on, society. However, the evolving articulation taking place between images and sounds tends to be undertheorised. This article argues that, as images have become more ‘soundful’, that is, as images have become naturalised as a ‘source’ of sounds, and as sounds are increasingly seen to emanate directly from images, mediated sounds have come to reinforce images in hegemonic fashion. In this essay, a discussion of 9/11 as a televisual event will be used as a starting point to investigate implications of the interactions between images and sounds in increasingly audiovisual cultures.
A Large Sample of Photometric Rotation Periods for FGK Pleiades Stars
Joel D. Hartman,Gáspár á Bakos,Géza Kovács,Robert W. Noyes
Physics , 2010,
Abstract: Using data from the HATNet survey for transiting exoplanets we measure photometric rotation periods for 368 Pleiades stars with 0.4 Msun < M < 1.3 Msun. We detect periodic variability for 74% of the cluster members in this mass range that are within our field-of-view, and 93% of the members with 0.7 Msun < M < 1.0 Msun. This increases, by a factor of five, the number of Pleiades members with measured periods. Included in our sample are 14 newly identified probable cluster members which have proper motions, photometry, and rotation periods consistent with membership. We compare this data to the rich sample of spectroscopically determined projected equatorial rotation velocities (vsini) available in the literature for this cluster. For stars with M > 0.85 Msun the rotation periods, vsini and radius estimates are consistent with the stars having an isotropic distribution of rotation axes, if a moderate differential rotation law is assumed. For stars with M < 0.85 Msun the inferred sini values are systematically larger than 1.0. These observations imply that the combination of measured parameters P(vsini)/R is too large by \sim 24% for low-mass stars in this cluster. By comparing our new mass-period relation for the Pleiades to the slightly older cluster M35, we confirm previous indications that the spin-down stalls at \sim 100 Myr for the slowest rotating stars with 0.7 Msun < M < 1.1 Msun a fact which may indicate that the internal transport of angular momentum is inefficient in slowly rotating solar mass stars.
Improved Recovery of Erythropoietin and Darbepoetin from Equine Plasma by the Application of a Wheat Germ Agglutinin Mediated Pre-Extraction Prior to Immunoaffinity Chromatography  [PDF]
Shawn M. R. Stanley, Danny Chua
Advances in Bioscience and Biotechnology (ABB) , 2014, DOI: 10.4236/abb.2014.57077

We describe a two-step method that uses wheat germ agglutinin immobilized on Sepharose gel followed by immunoaffinity chromatography (IAC) to extract recombinant human erythropoietin and Darbepoetin from equine plasma. Lectin affinity chromatography was shown to be an effective approach for isolating these epoetins from plasma and in combination with IAC; this method gave superior recovery when compared to the use of the latter technique alone. Moreover, due to the ease with which it can be scaled up, it is particularly well suited for pre-concentrating larger volumes of samples prior to IAC and this provides a facile way of improving the overall sensitivity with which these foreign proteins can be detected in equine plasma.

International Journal of Bioinformatics Research , 2011,
Abstract: One of the major tasks carried by biologist today is to understand the nature of proteins. How this largeprotein molecule folds themselves into some form and carryout the prescribed biochemical reactions.Hydrophobic interaction is the dominant force towards this task. To understand this interaction, a simple statisticalanalysis on the contribution of hydrophobic residues was carried out. Large Hydrophobic Residues (LHR) such asPhenylalanine (F), Isoleucine (I), Leucine (L), Methionine (M) and Valine (V) – (FILMV) as well as smallhydrophobic residues (SHR) Glycine (G), Alanine (A), Proline (P), Cysteine (C) and Tryptophan (W) - (GAPCW)were studied in all proteins of given organisms. The organisms include Homo sapiens, Macaca Mullatta, Pantroglodytes, Canis familiaris, Gallus gallus, Mus musculus, Rattus norvegicus, Bos taurus, Drosophilamelonogaster, Monodelphis domestica, Danio rerio, Stronglycentrolus purpuratus, Anopheles gambiae, Apismellifera, Arabidopsis thaliana, Tribolium castaneum, Saccharomyces cerevisae, Schizosaccharomyces pombeand Caenorhabditis elegans. It is observed that the protein prefers to have 27% large hydrophobic residues tomaintain the required hydrophobicity. In animal, particularly in human, it is observed less. It is interesting to notethat small hydrophobic residues balance this lack in number by a factor of 1:3. So is the reason why the length ofthe animal proteins increases. This new finding on the contribution of hydrophobic residues in protein stability willbe discussed in detail
Morphogenesis and Cell Fate Determination within the Adaxial Cell Equivalence Group of the Zebrafish Myotome
Mai E. Nguyen-Chi,Robert Bryson-Richardson,Carmen Sonntag,Thomas E. Hall,Abigail Gibson,Tamar Sztal,Wendy Chua,Thomas F. Schilling,Peter D. Currie
PLOS Genetics , 2012, DOI: 10.1371/journal.pgen.1003014
Abstract: One of the central questions of developmental biology is how cells of equivalent potential—an equivalence group—come to adopt specific cellular fates. In this study we have used a combination of live imaging, single cell lineage analyses, and perturbation of specific signaling pathways to dissect the specification of the adaxial cells of the zebrafish embryo. We show that the adaxial cells are myogenic precursors that form a cell fate equivalence group of approximately 20 cells that consequently give rise to two distinct sub-types of muscle fibers: the superficial slow muscle fibers (SSFs) and muscle pioneer cells (MPs), distinguished by specific gene expression and cell behaviors. Using a combination of live imaging, retrospective and indicative fate mapping, and genetic studies, we show that MP and SSF precursors segregate at the beginning of segmentation and that they arise from distinct regions along the anterior-posterior (AP) and dorsal-ventral (DV) axes of the adaxial cell compartment. FGF signaling restricts MP cell fate in the anterior-most adaxial cells in each somite, while BMP signaling restricts this fate to the middle of the DV axis. Thus our results reveal that the synergistic actions of HH, FGF, and BMP signaling independently create a three-dimensional (3D) signaling milieu that coordinates cell fate within the adaxial cell equivalence group.
Contribution of Herpesvirus Specific CD8 T Cells to Anti-Viral T Cell Response in Humans
Elena Sandalova,Diletta Laccabue,Carolina Boni,Anthony T. Tan,Katja Fink,Eng Eong Ooi,Robert Chua,Bahar Shafaeddin Schreve,Carlo Ferrari,Antonio Bertoletti
PLOS Pathogens , 2010, DOI: 10.1371/journal.ppat.1001051
Abstract: Herpesviruses infect most humans. Their infections can be associated with pathological conditions and significant changes in T cell repertoire but evidences of symbiotic effects of herpesvirus latency have never been demonstrated. We tested the hypothesis that HCMV and EBV-specific CD8 T cells contribute to the heterologous anti-viral immune response. Volume of activated/proliferating virus-specific and total CD8 T cells was evaluated in 50 patients with acute viral infections: 20 with HBV, 12 with Dengue, 12 with Influenza, 3 with Adenovirus infection and 3 with fevers of unknown etiology. Virus-specific (EBV, HCMV, Influenza) pentamer+ and total CD8 T cells were analyzed for activation (CD38/HLA-DR), proliferation (Ki-67/Bcl-2low) and cytokine production. We observed that all acute viral infections trigger an expansion of activated/proliferating CD8 T cells, which differs in size depending on the infection but is invariably inflated by CD8 T cells specific for persistent herpesviruses (HCMV/EBV). CD8 T cells specific for other non-related non persistent viral infection (i.e. Influenza) were not activated. IL-15, which is produced during acute viral infections, is the likely contributing mechanism driving the selective activation of herpesvirus specific CD8 T cells. In addition we were able to show that herpesvirus specific CD8 T cells displayed an increased ability to produce the anti-viral cytokine interferon-γ during the acute phase of heterologous viral infection. Taken together, these data demonstrated that activated herpesvirus specific CD8 T cells inflate the activated/proliferating CD8 T cells population present during acute viral infections in human and can contribute to the heterologous anti-viral T cell response.
Focal Bronchiectasis Causing Abnormal Pulmonary Radioiodine Uptake in a Patient with Well-Differentiated Papillary Thyroid Carcinoma
Ash Gargya,Elizabeth Chua
Case Reports in Endocrinology , 2012, DOI: 10.1155/2012/452758
Abstract: Background. False-positive pulmonary radioactive iodine uptake in the followup of differentiated thyroid carcinoma has been reported in patients with certain respiratory conditions. Patient Findings. We describe a case of well-differentiated papillary thyroid carcinoma treated by total thyroidectomy and radioiodine ablation therapy. Postablation radioiodine whole body scan and subsequent diagnostic radioiodine whole body scans have shown persistent uptake in the left hemithorax despite an undetectable stimulated serum thyroglobulin in the absence of interfering thyroglobulin antibodies. Contrast-enhanced chest computed tomography has confirmed that the abnormal pulmonary radioiodine uptake correlates with focal bronchiectasis. Summary. Bronchiectasis can cause abnormal chest radioactive iodine uptake in the followup of differentiated thyroid carcinoma. Conclusions. Recognition of potential false-positive chest radioactive iodine uptake, simulating pulmonary metastases, is needed to avoid unnecessary exposure to further radiation from repeated therapeutic doses of radioactive iodine.
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