Academic literature on the topic 'Interaction Env/CD4'
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Journal articles on the topic "Interaction Env/CD4"
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Douagi, Iyadh, Mattias N. E. Forsell, Christopher Sundling, Sijy O'Dell, Yu Feng, Pia Dosenovic, Yuxing Li, et al. "Influence of Novel CD4 Binding-Defective HIV-1 Envelope Glycoprotein Immunogens on Neutralizing Antibody and T-Cell Responses in Nonhuman Primates." Journal of Virology 84, no. 4 (December 2, 2009): 1683–95. http://dx.doi.org/10.1128/jvi.01896-09.
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ABSTRACT The high-affinity in vivo interaction between soluble HIV-1 envelope glycoprotein (Env) immunogens and primate CD4 results in conformational changes that alter the immunogenicity of the gp120 subunit. Because the conserved binding site on gp120 that directly interacts with CD4 is a major vaccine target, we sought to better understand the impact of in vivo Env-CD4 interactions during vaccination. Rhesus macaques were immunized with soluble wild-type (WT) Env trimers, and two trimer immunogens rendered CD4 binding defective through distinct mechanisms. In one variant, we introduced a mutation that directly disrupts CD4 binding (368D/R). In the second variant, we introduced three mutations (423I/M, 425N/K, and 431G/E) that disrupt CD4 binding indirectly by altering a gp120 subdomain known as the bridging sheet, which is required for locking Env into a stable interaction with CD4. Following immunization, Env-specific binding antibody titers and frequencies of Env-specific memory B cells were comparable between the groups. However, the quality of neutralizing antibody responses induced by the variants was distinctly different. Antibodies against the coreceptor binding site were elicited by WT trimers but not the CD4 binding-defective trimers, while antibodies against the CD4 binding site were elicited by the WT and the 423I/M, 425N/K, and 431G/E trimers but not the 368D/R trimers. Furthermore, the CD4 binding-defective trimer variants stimulated less potent neutralizing antibody activity against neutralization-sensitive viruses than WT trimers. Overall, our studies do not reveal any potential negative effects imparted by the in vivo interaction between WT Env and primate CD4 on the generation of functional T cells and antibodies in response to soluble Env vaccination.
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Liu, Qingbo, Peng Zhang, and Paolo Lusso. "Quaternary Interaction of the HIV-1 Envelope Trimer with CD4 and Neutralizing Antibodies." Viruses 13, no. 7 (July 20, 2021): 1405. http://dx.doi.org/10.3390/v13071405.
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The entry of HIV-1 into host cells is initiated by the interaction of the viral envelope (Env) spike with the CD4 receptor. During this process, the spike undergoes a series of conformational changes that eventually lead to the exposure of the fusion peptide located at the N-terminus of the transmembrane glycoprotein, gp41. Recent structural and functional studies have provided important insights into the interaction of Env with CD4 at various stages. However, a fine elucidation of the earliest events of CD4 contact and its immediate effect on the Env conformation remains a challenge for investigation. Here, we summarize the discovery of the quaternary nature of the CD4-binding site in the HIV-1 Env and the role of quaternary contact in the functional interaction with the CD4 receptor. We propose two models for this initial contact based on the current knowledge and discuss how a better understanding of the quaternary interaction may lead to improved immunogens and antibodies targeting the CD4-binding site.
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Salzwedel, Karl, Erica D. Smith, Barna Dey, and Edward A. Berger. "Sequential CD4-Coreceptor Interactions in Human Immunodeficiency Virus Type 1 Env Function: Soluble CD4 Activates Env for Coreceptor-Dependent Fusion and Reveals Blocking Activities of Antibodies against Cryptic Conserved Epitopes on gp120." Journal of Virology 74, no. 1 (January 1, 2000): 326–33. http://dx.doi.org/10.1128/jvi.74.1.326-333.2000.
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ABSTRACT We devised an experimental system to examine sequential events by which the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (Env) interacts with CD4 and coreceptor to induce membrane fusion. Recombinant soluble CD4 (sCD4) activated fusion between effector cells expressing Env and target cells expressing coreceptor (CCR5 or CXCR4) but lacking CD4. sCD4-activated fusion was dose dependent, occurred comparably with two- and four-domain proteins, and demonstrated Env-coreceptor specificities parallel to those reported in conventional fusion and infectivity systems. Fusion activation occurred upon sCD4 preincubation and washing of the Env-expressing effector cells but not the coreceptor-bearing target cells, thereby demonstrating that sCD4 exerts its effects by acting on Env. These findings provide direct functional evidence for a sequential two-step model of Env-receptor interactions, whereby gp120 binds first to CD4 and becomes activated for subsequent functional interaction with coreceptor, leading to membrane fusion. We used the sCD4-activated system to explore neutralization by the anti-gp120 human monoclonal antibodies 17b and 48d. These antibodies reportedly bind conserved CD4-induced epitopes involved in coreceptor interactions but neutralize HIV-1 infection only weakly. We found that 17b and 48d had minimal effects in the standard cell fusion system using target cells expressing both CD4 and coreceptor but potently blocked sCD4-activated fusion with target cells expressing coreceptor alone. Both antibodies strongly inhibited sCD4-activated fusion by Envs from genetically diverse HIV-1 isolates. Thus, the sCD4-activated system reveals conserved Env-blocking epitopes that are masked in native Env and hence not readily detected by conventional systems.
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Sundling, Christopher, Sijy O'Dell, Iyadh Douagi, Mattias N. Forsell, Andreas Mörner, Karin Loré, John R. Mascola, Richard T. Wyatt, and Gunilla B. Karlsson Hedestam. "Immunization with Wild-Type or CD4-Binding-Defective HIV-1 Env Trimers Reduces Viremia Equivalently following Heterologous Challenge with Simian-Human Immunodeficiency Virus." Journal of Virology 84, no. 18 (July 7, 2010): 9086–95. http://dx.doi.org/10.1128/jvi.01015-10.
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ABSTRACT We recently reported that rhesus macaques inoculated with CD4-binding-competent and CD4-binding-defective soluble YU2-derived HIV-1 envelope glycoprotein (Env) trimers in adjuvant generate comparable levels of Env-specific binding antibodies (Abs) and T cell responses. We also showed that Abs directed against the Env coreceptor binding site (CoRbs) were elicited only in animals immunized with CD4-binding-competent trimers and not in animals immunized with CD4-binding-defective trimers, indicating that a direct interaction between Env and CD4 occurs in vivo. To investigate both the overall consequences of in vivo Env-CD4 interactions and the elicitation of CoRbs-directed Abs for protection against heterologous simian-human immunodeficiency virus (SHIV) challenge, we exposed rhesus macaques immunized with CD4-binding-competent and CD4-binding-defective trimers to the CCR5-tropic SHIV-SF162P4 challenge virus. Compared to unvaccinated controls, all vaccinated animals displayed improved control of plasma viremia, independent of the presence or absence of CoRbs-directed Abs prior to challenge. Immunization resulted in plasma responses that neutralized the heterologous SHIV challenge stock in vitro, with similar neutralizing Ab titers elicited by the CD4-binding-competent and CD4-binding-defective trimers. The neutralizing responses against both the SHIV-SF162P4 stock and a recombinant virus pseudotyped with a cloned SHIV-SF162P4-derived Env were significantly boosted by the SHIV challenge. Collectively, these results suggest that the capacity of soluble Env trimers to interact with primate CD4 in vivo and to stimulate the production of moderate titers of CoRbs-directed Abs did not influence the magnitude of the neutralizing Ab recall response after viral challenge or the subsequent control of viremia in this heterologous SHIV challenge model.
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CIMINALE, VINCENZO, BARBARA K. FELBER, MEL CAMPBELL, and GEORGE N. PAVLAKIS. "A Bioassay for HIV-1 Based on Env-CD4 Interaction." AIDS Research and Human Retroviruses 6, no. 11 (November 1990): 1281–87. http://dx.doi.org/10.1089/aid.1990.6.1281.
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LaBranche, Celia C., Trevor L. Hoffman, Josephine Romano, Beth S. Haggarty, Terri G. Edwards, Thomas J. Matthews, Robert W. Doms, and James A. Hoxie. "Determinants of CD4 Independence for a Human Immunodeficiency Virus Type 1 Variant Map outside Regions Required for Coreceptor Specificity." Journal of Virology 73, no. 12 (December 1, 1999): 10310–19. http://dx.doi.org/10.1128/jvi.73.12.10310-10319.1999.
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ABSTRACT Although infection by human immunodeficiency virus (HIV) typically requires an interaction between the viral envelope glycoprotein (Env), CD4, and a chemokine receptor, CD4-independent isolates of HIV and simian immunodeficiency virus have been described. The structural basis and underlying mechanisms for this phenotype are unknown. We have derived a variant of HIV-1/IIIB, termed IIIBx, that acquired the ability to utilize CXCR4 without CD4. This virus infected CD4-negative T and B cells and fused with murine 3T3 cells that expressed human CXCR4 alone. A functional IIIBx env clone exhibited several mutations compared to the CD4-dependent HXBc2 env, including the striking loss of five glycosylation sites. By constructing env chimeras with HXBc2, the determinants for CD4 independence were shown to map outside the V1/V2 and V3 hypervariable loops, which determine chemokine receptor specificity, and at least partly within an area on the gp120 core that has been implicated in forming a conserved chemokine receptor binding site. We also identified a point mutation in the C4 domain that could render the IIIBx env clone completely CD4 dependent. Mutations in the transmembrane protein (TM) were also required for CD4 independence. Remarkably, when the V3 loop of a CCR5-tropic Env was substituted for the IIIBx Env, the resulting chimera was found to utilize CCR5 but remained CD4 independent. These findings show that Env determinants for chemokine receptor specificity are distinct from those that mediate CD4-independent use of that receptor for cell fusion and provide functional evidence for multiple steps in the interaction of Env with chemokine receptors. Combined with our observation that the conserved chemokine receptor binding site on gp120 is more exposed on the IIIBx gp120 (T. L. Hoffman, C. C. LaBranche, W. Zhang, G. Canziani, J. Robinson, I. Chaiken, J. A. Hoxie, and R. W. Doms, Proc. Natl. Acad. Sci. USA 96:6359–6364, 1999), the findings from this study suggest novel approaches to derive and design Envs with exposed chemokine receptor binding sites for vaccine purposes.
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Fernando, Kathy, Haitao Hu, Houping Ni, James A. Hoxie, and Drew Weissman. "Vaccine-delivered HIV envelope inhibits CD4+ T-cell activation, a mechanism for poor HIV vaccine responses." Blood 109, no. 6 (December 7, 2006): 2538–44. http://dx.doi.org/10.1182/blood-2006-08-038661.
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AbstractThe human immunodeficiency virus (HIV) causes impairment of the immune system in part by targeting CD4+ T cells for infection and dysfunction. HIV envelope (Env) present on free virions and infected cells causes dysfunction of uninfected bystander CD4+ T cells via interaction with both CD4 and coreceptors. Env is commonly used as part of a cocktail of HIV antigens in current vaccines. In DNA and viral vector vaccine approaches, antigen-presenting cells (APCs) and non-APCs in the vicinity of the vaccine delivery site and draining lymph node express vaccine-derived antigens. The studies here demonstrate that cell-surface expression of Env on APCs and non-APCs as part of the vaccine action causes an inhibition of antigen-induced CD4+ T-cell activation and proliferation mediated by CD4 binding and suggests a potential mechanism for reduced activity of Env-containing HIV vaccines. Similar studies using a functional Env lacking CD4 binding circumvented suppression, suggesting an alternative and potentially superior approach to HIV vaccine design.
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Prévost, Jérémie, Jonathan Richard, Halima Medjahed, Audrey Alexander, Jennifer Jones, John C. Kappes, Christina Ochsenbauer, and Andrés Finzi. "Incomplete Downregulation of CD4 Expression Affects HIV-1 Env Conformation and Antibody-Dependent Cellular Cytotoxicity Responses." Journal of Virology 92, no. 13 (April 18, 2018): e00484-18. http://dx.doi.org/10.1128/jvi.00484-18.
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ABSTRACTHIV-1-infected cells expressing envelope glycoproteins (Env) in the CD4-bound conformation on their surfaces are targeted by antibody-dependent cellular cytotoxicity (ADCC) mediated by CD4-induced (CD4i) antibodies and sera from HIV-1-infected individuals (HIV+sera). By downregulating the surface expression of CD4, Nef prevents Env-CD4 interaction, thus protecting HIV-1-infected cells from ADCC. HIV-1 infectious molecular clones (IMCs) are widely used to measure ADCC. In order to facilitate the identification of infected cells and high-throughput ADCC analysis, reporter genes (e.g., theRenillaluciferase [LucR] gene) are often introduced into IMC constructs. We evaluated the susceptibility of HIV-1-infected CD4+T lymphocytes to ADCC using a panel of parental IMCs and derivatives that expressed the LucR reporter gene, utilizing different molecular strategies, including one specifically designed to retain Nef expression. We found that in some of these constructs, Nef expression in CD4+T cells was suboptimal, and consequently, CD4 downregulation was incomplete. CD4 molecules remaining on the cell surface resulted in the exposure of ADCC-mediating CD4i epitopes on Env and a dramatic increase in the susceptibility of the infected cells to ADCC. Strikingly, protection from ADCC was observed when cells were infected with the parental IMC, which exhibited strong CD4 downregulation. This discrepancy between the parental and Nef-impaired viruses was independent of the strains of Env expressed, but rather, it was correlated with the levels of CD4 surface expression. Overall, our results indicate that caution should be taken when selecting IMCs for ADCC measurements and that CD4 downregulation needs to be carefully monitored when drawing conclusions about the nature and magnitude of ADCC.IMPORTANCEIn-depth understanding of the susceptibility of HIV-1-infected cells to ADCC might help establish correlates of vaccine protection and guide the development of HIV-1 vaccine strategies. Different ADCC assays have been developed, including those using infectious molecular clones (IMCs) carrying a LucR reporter gene that greatly facilitates large-scale quantitative analysis. We previously reported different molecular strategies for introducing LucR while maintaining Nef expression and function and, consequently, CD4 surface downregulation. Here, we demonstrate that utilizing IMCs that exhibit impaired Nef expression can have undesirable consequences due to incomplete CD4 downregulation. CD4 molecules remaining on the cell surface resulted in the exposure of ADCC-mediating CD4i epitopes on Env and a dramatic increase in the susceptibility of the infected cells to ADCC. Overall, our results indicate that CD4 downregulation needs to be carefully monitored when drawing conclusions about the nature and magnitude of ADCC.
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Finnegan, Catherine M., Werner Berg, George K. Lewis, and Anthony L. DeVico. "Antigenic Properties of the Human Immunodeficiency Virus Envelope during Cell-Cell Fusion." Journal of Virology 75, no. 22 (November 15, 2001): 11096–105. http://dx.doi.org/10.1128/jvi.75.22.11096-11105.2001.
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ABSTRACT Human immunodeficiency virus (HIV) fusion and entry involves sequential interactions between the viral envelope protein, gp120, cell surface CD4, and a G-protein-coupled coreceptor. Each interaction creates an intermediate gp120 structure predicted to display distinct antigenic features, including key functional domains for viral entry. In this study, we examined the disposition of these features during the fusion of HeLa cells expressing either HIVHXB2 envelope (Env cells) or CXCR4 and CD4 (target cells). Cell-cell fusion, indicated by cytoplasmic dye transfer, was allowed to progress for various times and then arrested. The cells were then examined for reactivity with antibodies directed against receptor-induced epitopes on gp120. Analyses of cells arrested by cooling to 4°C revealed that antibodies against the CD4-induced coreceptor-binding domain, i.e., 17b, 48d, and CG10, faintly react with Env cells even in the absence of target cell or soluble CD4 (sCD4) interactions. Such reactivity increased after exposure to sCD4 but remained unchanged during fusion with target cells and was not intensified at the Env-target cell interface. Notably, the antibodies did not react with Env cells when treated with a covalent cross-linker either alone or during fusion with target cells. Immunoreactivity could not be promoted or otherwise altered on either temperature arrested or cross-linked cells by preventing coreceptor interactions or by using a 17b Fab. In comparison, two other gp120-CD4 complex-dependent antibodies against epitopes outside the coreceptor domain, 8F101 and A32, exhibited a different pattern of reactivity. These antibodies reacted with the Env-target cell interface only after 30 min of cocultivation, concurrent with the first visible transfer of cytoplasmic dye from Env to target cells. At later times, the staining surrounded entire syncytia. Such binding was entirely dependent on the formation of gp120-CD4-CXCR4 tricomplexes since staining was absent with SDF-treated or coreceptor-negative target cells. Overall, these studies show that access to the CD4-induced coreceptor-binding domain on gp120 is largely blocked at the fusing cell interface and is unlikely to represent a target for neutralizing antibodies. However, new epitopes are presented on intermediate gp120 structures formed as a result of coreceptor interactions. Such findings have important implications for HIV vaccine approaches based on conformational alterations in envelope structures.
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Swanstrom, Adrienne E., Gregory Q. Del Prete, Claire Deleage, Samra E. Elser, Andrew A. Lackner, and James A. Hoxie. "The SIV Envelope Glycoprotein, Viral Tropism, and Pathogenesis: Novel Insights from Nonhuman Primate Models of AIDS." Current HIV Research 16, no. 1 (April 19, 2018): 29–40. http://dx.doi.org/10.2174/1570162x15666171124123116.
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Background: Cellular tropism of human immunodeficiency virus (HIV-1) is closely linked to interactions between the viral envelope glycoprotein (Env) with CD4 and chemokine receptor family members, CCR5 and CXCR4. This interaction plays a key role in determining anatomic sites that are infected in vivo and the cascade of early and late events that result in chronic immune activation, immunosuppression and ultimately, AIDS. CD4+ T cells are critical to adaptive immune responses, and their early and rapid infection in gut lamina propria and secondary lymphoid tissues in susceptible hosts likely contributes to viral persistence and progression to disease. CD4+ macrophages are also infected, although their role in HIV-1 pathogenesis is more controversial.Methods: Pathogenic infection by simian immunodeficiency viruses (SIV) in Asian macaques as models of HIV-1 infection has enabled the impact of cellular tropism on pathogenesis to be directly probed. This review will highlight examples in which experimental interventions during SIV infection or the introduction of viral mutations have altered cellular tropism and, subsequently, pathogenesis.Results: Alterations to the interaction of Env and its cellular receptors has been shown to result in changes to CD4 dependence, coreceptor specificity, and viral tropism for gut CD4+ T cells and macrophages.Conclusion: Collectively, these findings have yielded novel insights into the critical role of the viral Env and tropism as a driver of pathogenesis and host control and have helped to identify new areas for targeted interventions in therapy and prevention of HIV-1 infection.
Dissertations / Theses on the topic "Interaction Env/CD4"
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Li, Helen Hai Yan. "An exploration of relationship development and management in international business schools : MBA Students' perspectives." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/an-exploration-of-relationship-development-and-management-in-international-business-schools-mba-students-perspectives(5f0237e8-cd42-421a-8d65-06787380a410).html.
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Given the increasing importance of international higher education (HE) markets from a business perspective (Chadee and Naidoo, 2009; Anonymous, 2011a, 2012a), this research responds to the review of Hemsley-Brown and Oplatka (2006) that highlighted a lack of holistic approaches and theoretical models to address the nature of the HE service; and built on scholarly work (Mazzarol and Hosie, 1996; Mazzarol, 1998; Naude and Ivy, 1999; Ivy and Naude, 2004; Ivy, 2008) relating to HE marketing strategies. The research moves from the traditional marketing approach adopted predominantly in the existing literature of HE marketing (i.e. Mazzarol et al., 2003; Hemsley-Brown and Oplatka, 2006) and instead adopts a relational approach. This offers an alternative way of investigating the HE service, and contributes towards a broader theoretical perspective on HE strategy and a deeper understanding of the complex nature of the HE service. The theoretical background of this research was based on both the Interaction Approach (Håkansson ed., 1982) and the Relationship Life-Cycle Model (Ford, 1980; Wilkinson and Young, 1994). In response to limited existing research on the students’ perspective in HE (Trowler, 2010), this study provides a means of exploring HE marketing from the perspective of a markets-as-networks tradition (Håkansson and Snehota, 1995; Ford et al., 2002). Due to the adoption of a social constructivist epistemological stance (Gergen, 1985; Tashakkori and Teddlie, 1998), a case studies research approach (Yin, 2003, 2011) and semi-structured interviews (Denzin and Lincoln, 1994; Miles and Huberman, 1994) were utilised. Template analysis was chosen for data examination and interpretation (King, 1998, 2004), from a longitudinal contextual time-space of prospective students, current students and future alumni viewpoints (Halinen and Törnroos, 2005). The research findings suggest that the HE service is interactive and relational by nature, comprising six key relationships that are fundamentally important from the perspective of students being the focal-actor. These include relationships with alumni, other students, academic staff, administrative staff, multi-national companies (MNCs), and overseas exchange partner higher education institutions (HEIs). Despite the multiple roles of students, as clients (Mills et al., 1983; Hill, 1995), producers (Armstrong, 1995), products (Emery, et al., 2001; Modell, 2005) and customers (Kotler and Fox, 1985; Conway et al., 1994) of the HEIs, students are the users of these networks. They are also the beneficiaries of these key relationships, as they perceive and seek the added-value of the HE service, such as knowledge enrichment and employability enhancement. The synergy of these relationships and networks collectively contribute to the added-value of the HE service, enhance students’ overall positive experience and satisfaction with their institutions, and also have the potential to significantly impact on the HEIs’ competencies and business strategies. Practically, managing and influencing these relationships provide an opportunity for HE managers in resource allocation, strategic planning and policy-making, and the quality of service provision at the operational level.
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Lévesque, Karine. "Rôle de la protéine virale Vpu dans le cycle de multiplication du virus de l'immunodéficience humaine de type 1 (VIH-1)." Thèse, 2003. http://hdl.handle.net/1866/15051.
Full textBook chapters on the topic "Interaction Env/CD4"
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Vladislavov Ostoich, Peter, Michaela Beltcheva, and Roumiana Metcheva. "Nefarious, but in a Different Way: Comparing the Ecotoxicity, Gene Toxicity and Mutagenicity of Lead (Pb) and Cadmium (Cd) in the Context of Small Mammal Ecotoxicology." In Genotoxicity and Mutagenicity - Mechanisms and Test Methods [Working Title]. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.89850.
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Lead and cadmium are long established toxic and carcinogenic metals. Still, the mechanisms of their interaction with eukaryotic DNA are not unequivocally understood. New data provide evidence on the influence of both metals on DNA repair, particularly non-homologous end joining (NHEJ) and mismatch repair (MMR). This may help explain the weak direct mutagenicity of both Pb2+ and Cd2+ ions in the Ames test, as opposed to the proven carcinogenicity of both metals; it has long been proposed that lead and cadmium may induce an imbalance in mammalian systems of DNA damage repair and promote genomic instability. While new evidence for mechanistic interactions of metals with DNA repair emerges, some of the old questions involving dose distribution, pathways of exposure and bioaccumulation/detoxification kinetics still remain valid. To help place the current state of the art in the genetic toxicology of lead and cadmium within the context of ecotoxicology, the current authors propose an integrative approach and offer a review of other authors’ work as well as some of their own data on systemic and organ-specific toxicities in laboratory mice. The current chapter is a comparative analysis of the state of the art in the specific toxicity and genotoxicity of Pb and Cd, presenting some new and little-known information.
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Dulac, Jean-Claude. "4. An Intelligent Front End for Interactive Seismic Processing." In Expert Systems in Exploration, 85–112. Society of Exploration Geophysicists, 1991. http://dx.doi.org/10.1190/1.9781560802532.ch4.
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Rahman, Hakikur. "Interactive Multimedia Technologies for Distance Education Systems." In Encyclopedia of Multimedia Technology and Networking, Second Edition, 742–48. IGI Global, 2009. http://dx.doi.org/10.4018/978-1-60566-014-1.ch100.
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Information is typically stored, manipulated, delivered, and retrieved using a plethora of existing and emerging technologies. Businesses and organizations must adopt these emerging technologies to remain competitive. However, the evolution and progress of the technology (object orientation, high-speed networking, Internet, and so on) has been so rapid, that organizations are constantly facing new challenges in end-user training programs. These new technologies are impacting the whole organization, creating a paradigm shift which, in turn, enables them to do business in ways never possible before (Chatterjee & Jin, 1997). Information systems based on hypertext can be extended to include a wide range of data types, resulting in hypermedia, providing a new approach to information access with data storage devices, such as magnetic media, video disk, and compact disk. Along with alphanumeric data, today’s computer systems can handle text, graphics, and images, thus bringing audio and video into everyday use. DETF Report (2000) refers that technology can be classified into noninteractive and time-delayed interactive systems, and interactive distance learning systems. Noninteractive and time-delayed interactive systems include printed materials, correspondence, one-way radio, and television broadcasting. Interactive distance learning systems can be termed as “live interactive” or “stored interactive,” and range from satellite and compressed videoconferencing, to standalone computer-assisted instruction with two or more participants linked together, but situated in locations that are separated by time and/or place. Different types of telecommunications technology are available for the delivery of educational programs to single and multiple sites throughout disunited areas and locations. Diaz (1999) indicated that there are numerous multimedia technologies that can facilitate self-directed, practice-centered learning and meet the challenges of educational delivery to the adult learner. Though, delivering content via the WWW has been tormented by unreliability and inconsistency of information transfer, resulting in unacceptable delays and the inability to effectively deliver complex multimedia elements, including audio, video, and graphics. A CD/Web hybrid, a Web site on a compact disc (CD), combining the strengths of the CD-ROM and the WWW, can facilitate the delivery of multimedia elements by preserving connectivity, even at constricted bandwidth. Compressing a Web site onto a CD-ROM can reduce the amount of time that students spend interacting with a given technology, and can increase the amount of time they spend learning. University teaching and learning experiences are being replicated independently of time and place via appropriate technology-mediated learning processes, like the Internet, the Web, CD-ROM, and so on. However, it is possible to increase the educational gains possible by using the Internet while continuing to optimize the integration of other learning media and resources through interactive multimedia communications. Among other conventional interactive teaching methods, Interactive Multimedia Methods (IMMs) seems to be adopted as another mainstream in the path of distance learning system.
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DOUMENG, Marie, Karl DELBÉ, Florentin BERTHET, Olivier MARSAN, Jean DENAPE, and France CHABERT. "Effets de taille et de nature des charges sur les propriétés thermiques et mécaniques des composites à matrice PEEK." In Nanocomposites, 97–146. ISTE Group, 2021. http://dx.doi.org/10.51926/iste.9031.ch4.
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Les rôles de la taille et de la nature des charges dans les composites sont mis en évidence en comparant quatre types de charges : carbure de silicium, alumine, nitrure de bore et graphite. Leur nature chimique semble être prépondérante sur la taille car elle gouverne les interactions interfaciales charge/matrice qui se traduisent par de meilleures propriétés mécaniques.
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Painter, Kirstin, and Maria Scannapieco. "Treatment for Conduct Disorder and Oppositional Defiant Disorder." In Understanding the Mental Health Problems of Children and Adolescents, 180–90. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780190927844.003.0012.
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This chapter focuses on evidence-based and promising treatments and interventions for conduct disorder (CD) and oppositional defiant disorders (ODD). Unlike some mental health problems, psychosocial and behavioral interventions are the first line of treatment for CD and ODD. Psychotropic medication is not a first-line treatment for either disorder; however, they are sometime prescribed to manage distressing symptoms or to treat co-occurring disorders. Chapter 12 presents evidence-based and promising practices aimed at the youth only, the caregiver only, or a combination. Multisystemic therapy, multidimensional treatment foster care, functional family therapy, and parent–child interaction therapy are all evidence-based treatments described. The end of the chapter returns to the case studies presented in Chapter 11 and describes the real-life outcomes followed by questions for class discussion.
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Gammack, John, and Christopher Hodkinson. "Virtual Reality, Involvement and the Consumer Interface." In Advances in End User Computing, 161–82. IGI Global, 2004. http://dx.doi.org/10.4018/978-1-59140-257-2.ch009.
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Consumer purchasing online is considered, with interactivity highlighted as a critical end-user issue. Levels of user interactivity up to and including virtual reality environments are now realistic in e-tailing. Conceptualizing interactivity to recognize the relevance of perceptions to consumer engagement motivates a focus on the user interface. Aspects relating to trust, usability and involvement are identified, and examined in a series of linked studies focusing on hedonic and high-involvement products, particularly surfboards. Preliminary studies across a range of businesses and products indicated consumer willingness to purchase hedonic products online, but many businesses imposed a high workload on online purchasers. Despite successful web marketing of hedonic products such as CDs, we found that no contemporary providers of customized surfboards offered finished product e-tailing, nor used virtual reality technology to demonstrate performance. A real case study of online swimwear purchase demonstrated an improved purchase process. “Beachtown”, a virtual reality e-tailing environment related to a coastal tourism economy allowed further examination of apparel, surfboard and holiday purchase. Results indicate that an enhanced interactive virtual environment increases end user involvement and willingness to purchase.
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Stone, Robert W., and John W. Henry. "Roles of Computer Self-Efficacy and Outcome Expectancy in Influencing the Computer End-User's Organizational Commitment." In Advances in End User Computing, 183–201. IGI Global, 2004. http://dx.doi.org/10.4018/978-1-59140-257-2.ch010.
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Consumer purchasing online is considered, with interactivity highlighted as a critical end-user issue. Levels of user interactivity up to and including virtual reality environments are now realistic in e-tailing. Conceptualizing interactivity to recognize the relevance of perceptions to consumer engagement motivates a focus on the user interface. Aspects relating to trust, usability and involvement are identified, and examined in a series of linked studies focusing on hedonic and high-involvement products, particularly surfboards. Preliminary studies across a range of businesses and products indicated consumer willingness to purchase hedonic products online, but many businesses imposed a high workload on online purchasers. Despite successful web marketing of hedonic products such as CDs, we found that no contemporary providers of customized surfboards offered finished product e-tailing, nor used virtual reality technology to demonstrate performance. A real case study of online swimwear purchase demonstrated an improved purchase process. “Beachtown”, a virtual reality e-tailing environment related to a coastal tourism economy allowed further examination of apparel, surfboard and holiday purchase. Results indicate that an enhanced interactive virtual environment increases end user involvement and willingness to purchase.
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Dostert, G., V. Jouan-Hureaux, H. Louis, and É. Velot. "Umbilical Mesenchymal Stem Cell-Derived Extracellular Vesicle Conditioning Has an Immunosuppressive Effect on NK Cells." In Stem Cells and Regenerative Medicine. IOS Press, 2021. http://dx.doi.org/10.3233/bhr210028.
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Background: In peripheral blood, human natural killer (NK) cells are immunological cells that nearly don’t express the ectonucleotidase CD73 on their plasma membrane. When exposed to mesenchymal stem cells (MSCs), NK cells are able to acquire CD73. MSCs are known to be CD73-positive (CD73+) and also to modulate the immune system, e.g. through adenosynergic pathway by ectonucleosidases, such as CD73. Extracellular vesicles (EVs) are involved in cell-to-cell communication. Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) have emerged as paracrine mediators that are part of MSC immunomodulatory effects including immunosuppressive properties and immune privilege. Objective: The aim of our work was to study if CD73 could be acquired by NK cells through cell-to-cell communication with MSC-EVs as cell culture additives. We also hypothesised that MSC-EVs would act as tolerance inducers to attenuate NK cell cytotoxicity. Methods: Cell isolation was made from human umbilical cords for MSCs and from human peripheral blood for NK cells. MSC-EVs were isolated by ultracentrifugation and filtration, then characterized by nanoparticle tracking assay and flow cytometry (CD9, 63, 81 and 73). MSC-EV interaction with NK cells was monitored by PKH67 staining. NK cell activation was followed by measuring the expression of CD73 and NK-activating receptor natural-killer group 2, member D (NKG2D) by flow cytometry. The cytotoxicity of NK cells or EV-conditioned NK cells was evaluated after co-culture with K562 cells. Results: We showed that MSC-EVs are nanoparticles able to express CD73 and interact with NK cells. MSC-EV conditioned NK cells seem to increase CD73 and decrease NKG2D through an EV-mediated mechanism. MSC-EVs have an immunosuppressive effect on NK cells by preventing NK cell activation and NK cell cytotoxicity towards K562 cells. Conclusions: Our results demonstrate that MSC-EVs could influence NK cell behaviour and act as immunosuppressant cell-based products.
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Scott, Andrew C. "Prometheus." In Burning Planet. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198734840.003.0010.
Full textAbstract:
It is sometimes said that humans were born of fire. While a wide range of animal species interact with fire, we appear to be the only species to have learned to tame it, and more importantly to make it. There is evidence that early humans were aware of fire and may have exploited naturally occurring fire, but only later did they control and manage it. Human interaction with fire must have proceeded through various levels, the first of which can be described as the opportunistic phase. In this phase, natural fire may have been exploited to help in hunting, for example. When, how, and why did this happen? It is widely agreed that our story begins in Africa. It is here that we see the evolution of hominins, a group of related genera that include the Australopithecines and later the genus Homo. How common would fire have been in the environments in which they lived? We already know from the study of fossil plants, as well as isotope data, that there were important changes in both the vegetation and climate over the past 10 million years. It is also during this time interval that hominins emerged from apes. Through the Oligocene and Miocene (30–8 million years ago), Africa was largely covered by tropical rainforest, where fire was present but infrequent, started both by lightning strikes and volcanic activity. As the climate began to dry and C4 grasses spread at the end of the Miocene Epoch, around 8 million years ago, habitats became more open. Fire became more frequent, and from an animal perspective would have become more visible, not just from flames but also smoke. Frequent fire in the landscape would have had many consequences for the early hominins, not just because game was more easily killed, but burned animals (naturally cooked meat) would have made a useful addition to the diet, and the new flush of growth following fire would also have attracted large herds of herbivores. Fire may have been conserved through adding fuel, including dung, which is slow burning.
Conference papers on the topic "Interaction Env/CD4"
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Mao, Jianfeng, Weizhe Wang, Yingzheng Liu, and Junhui Zhang. "Multiaxial Creep-Fatigue Life Prediction on the Rotor of a 1000MW Supercritical Steam Turbine." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-69135.
Full textAbstract:
Damage of a high temperature rotor subjected to the creep-fatigue interaction was numerically investigated. Toward that end, a high temperature rotor of a 1000MW supercritical steam turbine was chosen for the study. A continuum damage mechanics model (CDM), which depicts the fatigue-creep interaction, was developed in the present paper. During the practical startup and shutdown processes, the influence of the multiaxial creep-fatigue interaction on strength of the rotor was analyzed in terms of stress, strain and damage. Comparison of the results from linear damage accumulation model (LDA) and CDM demonstrated that CDM was more reasonable to predict the lifetime of the rotor due to the multiaxial creep-fatigue interaction.