693 research outputs found

    Measurements of Total Hemispherical Emissivity of Several Stably Oxidized Nickel-Titanium Carbide Cemented Hard Metals from 600 F to 1,600 F

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    The total hemispherical emissivity of several nickel-titanium carbide cemented hard metals have been measured over a temperature range from 600 F to l,600 F. A variety of cemented hard metals were obtained from the Kennametal Corporation. A brief discussion of the apparatus employed and the procedures used for this investigation is included. The results of the tests of specimens in the as-received and polished states indicate a nearly constant emissivity for each material tested over the temperature range considered and only slight differences in emissivity values for the different materials. Values obtained on the stably oxidized specimens range from 0.90 to 0.94 at 6000 F and o.88 to 0.92 at 1,600 F for the as-received specimens and from 0.82 to 0.89 at 600 F and 0.85 to 0.87 at 1,600 F for the polished specimens. The surface analysis of the oxidized materials as obtained by X-ray diffraction methods and metallographic techniques are presented as an aid to reproducing the surface on which these measurements were made

    A Vibrio cholerae Classical TcpA Amino Acid Sequence Induces Protective Antibody That Binds an Area Hypothesized To Be Important for Toxin-Coregulated Pilus Structure

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    Vibrio cholerae is a gram-negative bacterium that has been associated with cholera pandemics since the early 1800s. Whole-cell, killed, and live-attenuated oral cholera vaccines are in use. We and others have focused on the development of a subunit cholera vaccine that features standardized epitopes from various V. cholerae macromolecules that are known to induce protective antibody responses. TcpA protein is assembled into toxin-coregulated pilus (TCP), a type IVb pilus required for V. cholerae colonization, and thus is a strong candidate for a cholera subunit vaccine. Polypeptides (24 to 26 amino acids) in TcpA that can induce protective antibody responses have been reported, but further characterization of their amino acid targets relative to tertiary or quaternary TCP structures has not been done. We report a refinement of the TcpA sequences that can induce protective antibody. One sequence, TcpA 15 (residues 170 to 183), induces antibodies that bind linear TcpA in a Western blot as well as weakly bind soluble TcpA in solution. These antibodies bind assembled pili at high density and provide 80 to 100% protection in the infant mouse protection assay. This is in sharp contrast to other anti-TcpA peptide sera (TcpA 11, TcpA 13, and TcpA 17) that bind very strongly in Western blot and solution assays yet do not provide protection or effectively bind TCP, as evidenced by immunoelectron microscopy. The sequences of TcpA 15 that induce protective antibody were localized on a model of assembled TCP. These sequences are centered on a site that is predicted to be important for TCP structure

    Neuromyelitis optica pathogenesis and aquaporin 4

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    Neuromyelitis optica (NMO) is a severe, debilitating human disease that predominantly features immunopathology in the optic nerves and the spinal cord. An IgG1 autoantibody (NMO-IgG) that binds aquaporin 4 (AQP4) has been identified in the sera of a significant number of NMO patients, as well as in patients with two related neurologic conditions, bilateral optic neuritis (ON), and longitudinal extensive transverse myelitis (LETM), that are generally considered to lie within the NMO spectrum of diseases. NMO-IgG is not the only autoantibody found in NMO patient sera, but the correlation of pathology in central nervous system (CNS) with tissues that normally express high levels of AQP4 suggests NMO-IgG might be pathogenic. If this is the case, it is important to identify and understand the mechanism(s) whereby an immune response is induced against AQP4. This review focuses on open questions about the "events" that need to be understood to determine if AQP4 and NMO-IgG are involved in the pathogenesis of NMO. These questions include: 1) How might AQP4-specific T and B cells be primed by either CNS AQP4 or peripheral pools of AQP4? 2) Do the different AQP4-expressing tissues and perhaps the membrane structural organization of AQP4 influence NMO-IgG binding efficacy and thus pathogenesis? 3) Does prior infection, genetic predisposition, or underlying immune dysregulation contribute to a confluence of events which lead to NMO in select individuals? A small animal model of NMO is essential to demonstrate whether AQP4 is indeed the incipient autoantigen capable of inducing NMO-IgG formation and NMO. If the NMO model is consistent with the human disease, it can be used to examine how changes in AQP4 expression and blood-brain barrier (BBB) integrity, both of which can be regulated by CNS inflammation, contribute to inductive events for anti-AQP4-specific immune response. In this review, we identify reagents and experimental questions that need to be developed and addressed to enhance our understanding of the pathogenesis of NMO. Finally, dysregulation of tolerance associated with autoimmune disease appears to have a role in NMO. Animal models would allow manipulation of hormone levels, B cell growth factors, and other elements known to increase the penetrance of autoimmune disease. Thus an AQP4 animal model would provide a means to manipulate events which are now associated with NMO and thus demonstrate what set of events or multiplicity of events can push the anti-AQP4 response to be pathogenic

    Neuromyelitis Optica Pathogenesis and Aquaporin 4

    Get PDF
    Neuromyelitis optica (NMO) is a severe, debilitating human disease that predominantly features immunopathology in the optic nerves and the spinal cord. An IgG1 autoantibody (NMO-IgG) that binds aquaporin 4 (AQP4) has been identified in the sera of a significant number of NMO patients, as well as in patients with two related neurologic conditions, bilateral optic neuritis (ON), and longitudinal extensive transverse myelitis (LETM), that are generally considered to lie within the NMO spectrum of diseases. NMO-IgG is not the only autoantibody found in NMO patient sera, but the correlation of pathology in central nervous system (CNS) with tissues that normally express high levels of AQP4 suggests NMO-IgG might be pathogenic. If this is the case, it is important to identify and understand the mechanism(s) whereby an immune response is induced against AQP4. This review focuses on open questions about the events that need to be understood to determine if AQP4 and NMO-IgG are involved in the pathogenesis of NMO. These questions include: 1) How might AQP4-specific T and B cells be primed by either CNS AQP4 or peripheral pools of AQP4? 2) Do the different AQP4-expressing tissues and perhaps the membrane structural organization of AQP4 influence NMO-IgG binding efficacy and thus pathogenesis? 3) Does prior infection, genetic predisposition, or underlying immune dysregulation contribute to a confluence of events which lead to NMO in select individuals? A small animal model of NMO is essential to demonstrate whether AQP4 is indeed the incipient autoantigen capable of inducing NMO-IgG formation and NMO. If the NMO model is consistent with the human disease, it can be used to examine how changes in AQP4 expression and blood-brain barrier (BBB) integrity, both of which can be regulated by CNS inflammation, contribute to inductive events for anti-AQP4-specific immune response. In this review, we identify reagents and experimental questions that need to be developed and addressed to enhance our understanding of the pathogenesis of NMO. Finally, dysregulation of tolerance associated with autoimmune disease appears to have a role in NMO. Animal models would allow manipulation of hormone levels, B cell growth factors, and other elements known to increase the penetrance of autoimmune disease. Thus an AQP4 animal model would provide a means to manipulate events which are now associated with NMO and thus demonstrate what set of events or multiplicity of events can push the anti-AQP4 response to be pathogenic

    Interacting Factors Driving a Major Loss of Large Trees with Cavities in a Forest Ecosystem

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    Large trees with cavities provide critical ecological functions in forests worldwide, including vital nesting and denning resources for many species. However, many ecosystems are experiencing increasingly rapid loss of large trees or a failure to recruit new large trees or both. We quantify this problem in a globally iconic ecosystem in southeastern Australia--forests dominated by the world's tallest angiosperms, Mountain Ash (Eucalyptus regnans). Tree, stand and landscape-level factors influencing the death and collapse of large living cavity trees and the decay and collapse of dead trees with cavities are documented using a suite of long-term datasets gathered between 1983 and 2011. The historical rate of tree mortality on unburned sites between 1997 and 2011 was >14% with a mortality spike in the driest period (2006-2009). Following a major wildfire in 2009, 79% of large living trees with cavities died and 57-100% of large dead trees were destroyed on burned sites. Repeated measurements between 1997 and 2011 revealed no recruitment of any new large trees with cavities on any of our unburned or burned sites. Transition probability matrices of large trees with cavities through increasingly decayed condition states projects a severe shortage of large trees with cavities by 2039 that will continue until at least 2067. This large cavity tree crisis in Mountain Ash forests is a product of: (1) the prolonged time required (>120 years) for initiation of cavities; and (2) repeated past wildfires and widespread logging operations. These latter factors have resulted in all landscapes being dominated by stands ≤72 years and just 1.16% of forest being unburned and unlogged. We discuss how the features that make Mountain Ash forests vulnerable to a decline in large tree abundance are shared with many forest types worldwide.This work was supported by Australian Research Council DP1097170; Parks Victoria; and Victorian Department of Sustainability and Environment. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

    Role of 4-1BB Ligand in Costimulation of T Lymphocyte Growth and its Upregulation on M12 B Lymphomas by cAMP

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    K46J B lymphomas express a T cell costimulatory activity that is not inhibited by CTLA-4Ig, anti-B7-1, anti-B7-2, anti-intercellular adhesion molecule 1 or antibodies to heat stable antigen. In this paper we report that this costimulatory activity is mediated at least in part by 4-1BB ligand, a member of the tumor necrosis factor (TNF) gene family that binds to 4-1BB, a T cell activation antigen with homology to the TNF/nerve growth factor receptor family. A fusion protein between 4-1BB and alkaline phosphatase (4-1BB-AP) blocks T cell activation by K46J lymphomas in both an antigen-specific system and with polyclonally (anti-CD3) activated T cells. 4-1BB-AP also blocks antigen presentation by normal spleen cells. When the antigen-presenting cells express B7 molecules as well as 4-1BB ligand, we find that B7 molecules and 4-1BB-AP both contribute to T cell activation. These data suggest that 4-1BB ligand plays an important role in costimulation of IL-2 production and proliferation by T cells. The B lymphoma M12 expresses low levels of 4-1BB-L but can be induced to express higher levels by treatment of the B ceils with cAMP, which also induces B7-1 and B7-2 in these cells. Thus cAMP appears to coordinately induce several costimulatory molecules on B cells

    Interacting factors driving a major loss of large trees with cavities in a forest ecosystem

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    Large trees with cavities provide critical ecological functions in forests worldwide, including vital nesting and denning resources for many species. However, many ecosystems are experiencing increasingly rapid loss of large trees or a failure to recruit new large trees or both. We quantify this problem in a globally iconic ecosystem in southeastern Australia - forests dominated by the world's tallest angiosperms, Mountain Ash (Eucalyptus regnans). Tree, stand and landscape-level factors influencing the death and collapse of large living cavity trees and the decay and collapse of dead trees with cavities are documented using a suite of long-term datasets gathered between 1983 and 2011. The historical rate of tree mortality on unburned sites between 1997 and 2011 was >14% with a mortality spike in the driest period (2006-2009). Following a major wildfire in 2009, 79% of large living trees with cavities died and 57-100% of large dead trees were destroyed on burned sites. Repeated measurements between 1997 and 2011 revealed no recruitment of any new large trees with cavities on any of our unburned or burned sites. Transition probability matrices of large trees with cavities through increasingly decayed condition states projects a severe shortage of large trees with cavities by 2039 that will continue until at least 2067. This large cavity tree crisis in Mountain Ash forests is a product of: (1) the prolonged time required (>120 years) for initiation of cavities; and (2) repeated past wildfires and widespread logging operations. These latter factors have resulted in all landscapes being dominated by stands <= 72 years and just 1.16% of forest being unburned and unlogged. We discuss how the features that make Mountain Ash forests vulnerable to a decline in large tree abundance are shared with many forest types worldwide
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