1,971 research outputs found
Slc11a1 limits intracellular growth of Salmonella enterica sv. Typhimurium by promoting macrophage immune effector functions and impairing bacterial iron acquisition
No full textThe natural resistance-associated macrophage protein 1, Slc11a1, is a phagolysosomal transporter for protons and divalent ions including iron that confers host protection against diverse intracellular pathogens including Salmonella. We investigated and compared the regulation of iron homeostasis and immune function in RAW264.7 murine phagocytes stably transfected with non-functional Slc11a1 and functional Slc11a1 controls in response to an infection with Salmonella enterica serovar Typhimurium. We report that macrophages lacking functional Slc11a1 displayed an increased expression of transferrin receptor 1, resulting in enhanced acquisition of transferrin-bound iron. In contrast, cellular iron release mediated via ferroportin 1 was significantly lower in Salmonella-infected Slc11a1-negative macrophages in comparison with phagocytes bearing Slc11a1. Lack of Slc11a1 led to intracellular persistence of S.?enterica serovar Typhimurium within macrophages, which was paralleled by a reduced formation of nitric oxide, tumour necrosis factor-alpha and interleukin-6 in Slc11a1-negative macrophages following Salmonella infection, whereas interleukin-10 production was increased. Moreover, Slc11a1-negative phagocytes exhibited higher cellular iron content, resulting in increased iron acquisition by intracellular Salmonella. Our observations indicate a bifunctional role for Slc11a1 within phagocytes. Slc11a restricts iron availability, which first augments pro-inflammatory macrophage effector functions and second concomitantly limits microbial iron access. <br/
Catalytic and non-catalytic functions of human IIA phospholipase A2
No full textGroup IIA phospholipase A2 (PLA2) is a low-molecular-mass secreted PLA2 enzyme that has been identified as an acute phase protein with a role in the inflammatory response to infection and trauma. The protein is possibly unique in being highly cationic and having a global distribution of surface arginine and lysine residues. This structure supports two functions of the protein. (1) An anti-bacterial role where the enzyme is targeted to the anionic cell membrane of Gram-positive bacteria and phospholipid hydrolysis assists in bacterial killing. (2) A proposed non-catalytic role in which the protein forms supramolecular aggregates with anionic phospholipid vesicles or debris. These aggregates are then internalized via interactions with cell surface heparin sulphate proteoglycans and macropinocytosis for disposal by macrophages
Immunolocalisation of the D-melanogaster Nramp homologue Malvolio to gut and Malpighian tubules provides evidence that Malvolio and Nramp2 are orthologous
No full textNramp (Slc11a1) genes in mammals are associated with the transport of iron and other divalent cations; Nramp1 in macrophages involved in the innate immune response against intracellular pathogens, and Nramp2 with duodenal iron uptake and the transferrin–transferrin-receptor pathway of iron assimilation. The Drosophila melanogaster Nramp-related gene is known as Malvolio. The localisation of Malvolio protein was inferred from the enhancer trap line initially used to isolate Malvolio in a screen for mutants with defects in taste perception. Here we describe the generation of a Malvolio-reactive polyclonal antibody and apply it to evaluate Malvolio localisation during stages of D. melanogaster development, and compare the results with the localisation of the enhancer trap line identified with beta-galactosidase. All immunolocalisation studies have been confirmed to be specific with Malvolio-blocking peptides. Our results demonstrated expression within Malpighian tubules, testis, brain, the amnioserosa of embryos, the larval and adult alimentary canal. Expression within the gut was of significant interest, as mammalian Nramp2 in the gut plays a primary role in the acquisition of dietary iron. We confirm expression within the central nervous system and in cells of the haematopoietic system. By immunohistochemistry we showed that expression within cells was either punctuate, diffuse cytoplasmic or plasma membrane associated, or both. The staining within the gut indicates a degree of conservation of components for iron acquisition between flies and mammals, suggesting that a comparable mechanism has been retained during evolution
A catalytically independent physiological function for human acute phase protein group IIA phospholipase A2: cellular uptake facilitates cell debris removal
No full textHuman group IIA phospholipase A2 (IIA PLA2) is an acute phase protein first identified at high concentrations in synovial fluid from patients with rheumatoid arthritis. Its physiological role has since been debated; the enzyme has a very high affinity for anionic phospholipid interfaces but expresses almost zero activity with zwitterionic phospholipid substrates, because of a lack of interfacial binding. We have prepared the cysteine-containing mutant (S74C) to allow the covalent attachment of fluorescent reporter groups. We show that fluorescently labeled IIA was taken up by phorbol 12-myristate 13-acetate-activated THP-1 cells in an energy-dependent process involving cell surface heparan sulfate proteoglycans. Uptake concurrently involved significant cell swelling, characteristic of macropinocytosis and the fluorescent enzyme localized to the nucleus. The endocytic process did not necessitate enzyme catalysis, ruling out membrane phospholipid hydrolysis as an essential requirement. The enzyme produced supramolecular aggregates with anionic phospholipid vesicles as a result of bridging between particles, a property that is unique to this globally cationic IIA PLA2. Uptake of such aggregates labeled with fluorescent anionic phospholipid was dramatically enhanced by the IIA protein, and uptake involved binding to heparan sulfate proteoglycans on activated THP-1 cells. A physiological role for this protein is proposed that involves the removal of anionic extracellular cell debris, including anionic microparticles generated as a result of trauma, infection, and the inflammatory response, and under such conditions serum levels of IIA PLA2 can increase approximately 1000-fold. A similar pathway may be significant in the uptake into cells of anionic vector DNA involving cationic lipid transfection protocols.<br/
Nramp1-functionality increases iNOS expression via repression of IL-10 formation
No full textIn mice, resistance to certain intracellular microbes depends on the expression of a late phagosomal protein termed natural-resistance associated macrophage protein 1 (Nramp1, Slc11a1). Nramp1-functionality is associated with alterations of cellular iron homeostasis and a sustained pro-inflammatory immune response, including the formation of the antimicrobial effector molecule NO. To investigate the underlying mechanism we used RAW-264.7 murine macrophage cells stably transfected with a functional Nramp1 allele (RAW-37) or Nramp1 non-functional controls (RAW-21). We found that the production of and signalling by the anti-inflammatory cytokine IL-10 was significantly enhanced in macrophages lacking functional Nramp1. Upon infection of macrophages with Salmonella typhimurium pathogen survival was significantly better in RAW-21 than in RAW-37, which inversely correlated to NO and TNF- formation. Addition of a neutralising anti-IL-10 antibody to RAW-21 cells led to a significantly reduced survival of S. typhimurium within these cells and enhanced formation of NO and TNF- reaching levels comparable to that observed in cells bearing functional Nramp1. Oppositely, supplementation of iron to RAW-21 cells further increased IL-10 formation. Thus, Nramp1 mediates effective host defence in part via suppression of excessive IL-10 production which may relate to Nramp1-mediated reduction of cellular iron pools, thus strengthening antimicrobial effector mechanisms. <br/
The potential of two electrostatic powders as the basis for an autodissemination control method of Plodia interpunctella (Hu¨bner)
No full textA comparison of the retention, horizontal transmission and effect on mating of two electrostatic powders (Entomag™ and Entostat™) was made to evaluate their potential as a component of an autodissemination method for the control of Plodia interpunctella. Both powders were shown to have some effects on mating behaviour and the ability of treated males to locate a pheromone source when applied in high doses. However, no effects were observed at rates consistent with the amount of powder that was actually taken up when the moths visited a prototype autodissemination device. Male and females lost 69.9% and 64.3% by weight, respectively, of Entomag by 48 h after exposure but lost more Entostat, 89.8% and 75.9%, over the same period. Critical to the efficacy of autodissemination is the transfer of powder from males to females and on average a 49% greater weight of Entostat was transferred than Entomag. Due to the different densities of the powders, it was calculated that a 49% increase in transfer of powder equated to over three times more Entostat than Entomag particles being passed from male to female. It was concluded that Entostat would appear to be the carrier of choice for a prototype P. interpunctella autodissemination system
Elements of botany, or Outlines of the natural history of vegetables ([Reprod.]) / by Benjamin Smith Barton,... ; a new ed. rev. and condensed with an account of the life and writing of the author, by William P. C. Barton,...
No full textEl futuro de la educación cívica. Entrevista con Keith C. Barton
No full textIn this interview with researcher Keith Barton, a critical reflection is offered on the teaching of social studies and civic education in recent decades. Barton, author of Teaching History for the Common Good and Curriculum for Justice and Harmony, among other influential books, advocates for an education centered on action, justice, and hope, defending a model that prepares students to transform the world.En esta entrevista al investigador estadounidense Keith Barton se ofrece una reflexión crítica sobre la enseñanza de las ciencias sociales y la educación cívica en las últimas décadas. Barton, autor de Teaching History for the Common Good y Curriculum for Justice and Harmony, entre otros libros de gran calado, aboga por una educación centrada en la acción, la justicia y la esperanza, defendiendo un modelo que prepare a los estudiantes para transformar el mundo
Bootstrapping a culture of sharing to facilitate open educational resources
No full textIt seems self evident that life for teachers would be simplified if there existed a large corpus of relevant resources that was available for them to re-use, and for inquisitive students to download. The learning object community has worked for the past decade and more to provide the necessary infrastructure, standards and specifications to facilitate such beneficial activity, but the take-up has been disappointingly small, particularly in University and Higher Education, which is the subject of this research. The problem has been that practitioners have not deposited their teaching resources, or have not made them openly available, in the quantity that would achieve critical mass for uptake. EdShare and the Language Box are two initiatives that have concentrated on the issue of facilitating and improving the practice of sharing, the former in an institutional setting and the latter in a subject community of practice. This paper describes and analyses the motivations for these projects, the design decisions they took in implementing their repositories, the approaches they took to change agency and practice within their communities, and the changes in practice that have so far been observed. The contribution of this paper is an improved understanding of how to encourage educational communities to share
Cane Ridge in Context: Perspectives on Barton W. Stone and the Revival
No full textThe year 1991 was the 200th anniversary year of the construction of the Cane Ridge Meetinghouse by a Presbyterian congregation in frontier Kentucky. To celebrate this event, the Disciples of Christ Historical Society hosted a number of special events, including lectures and addresses on the legacy of Barton W. Stone as well as on the background and meaning of the revival. This volume brings together several of these addresses and the chapters are arranged to proceed from reflections upon the various ways Barton W. Stone has been remembered in the Stone-Campbell traditions. Contributors include Anthony L. Dunnavant, Richard L. Harrison Jr, Paul Blowers, C. Leonard Allen, D. Newell Williams, Ronald P. Byars, Newton B. Fowler, Samuel S. Hill, and Howard E. Short.https://digitalcommons.acu.edu/acu_library_books/1012/thumbnail.jp
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