bluuebunny/crossref_metadata_2025 huggingface dataset:
Microstructure and Mechanical Properties of Plasma Arc Welding Joint for Laser Melting-Deposited AerMet100 Ultrahigh-Strength Steel
Authors: Ran X.Z. , Cheng H. , Liu D. , Zhang S.Q. , Tang H.B. , Wang H.M.
Published: April 2014

The repair of laser melting-deposited AerMet100 ultrahigh strength steel (UHSS) heat-treated samples with groove machined was conducted by low-cost plasma arc welding (PAW). And the microstructure and mechanical properties of welding joint were examined by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), micro-hardness test and the tensile mechanical test. The experimental results indicated that the welding zone with low hardness values mainly consisted of columnar grains with about 200μm width which epitaxial growth from substrate grains, and in which the cellular morphology character appearing at the bottom in comparison with dendrite with lateral branching appearing at the top. Three zones, i.e., sufficient quenched zone, insufficient quenched zone and high-temperature tempered zone, were divided by heating affected temperature and microstructure characteristic in heat affected zone (HAZ), and there was a lowest hardness value region distributed in high-temperature tempered zone. Compared to that of undamaged heat treated forged one, the tensile mechanical property of the repaired laser melting deposited sample got a few decrease but was still well, in which the tensile strength σb, yield strength σs, elongation δ5 and reduction of area Ψ was 1627Mpa, 1285Mpa, 10.5% and 45% respectively. In addition, the isothermal thermal simulation test surveyed that the tensile fracture position locating in high-temperature tempered zone with the lowest hardness value could ascribe to the growth of alloy carbide and increase of reverted austenite in over-aged temperature.
Fabrication of Cu Heat Sink on Silicon Substrate Using Direct Laser Sintering
Authors: He Chong Wen , Zhu Hai Hong , Hu Pan Pan
Published: April 2014

Silicon is applied widely because of its good electrical properties, thermal conductivity and optical processing. It is necessary to fabricate a heat sink on silicon substrate to improve the heat dissipation ability for modern industrial application. There are many traditional methods of processing heat sink on silicon substrate. However, it is hardly to meet the requirements of today’s technology for the disadvantages such as residual stress exist, processing shape limited and inefficiency. The investigation on fabricating heat sink silicon substrate by direct later sintering was conducted in this study. By sintering a transition layer, coppery heat sink with channel width of several hundred micrometers and circinate shape has been fabricated by direct laser sintering. Furthermore, the bonding mechanism and the influence of the powder components on the interface morphology and structure have been investigated.
Assessment of Mobilities of the B2 Phase in the Nickel-Chromium-Aluminum System
Authors: Zhang Hong Yu , Tian Jin Sen , Liang Li Hong , Wei Hua , Zheng Qi , Jin Tao , Sun Xiao Feng
Published: April 2014

A model for diffusion is applied to the nickel-chromium-aluminum (Ni-Cr-Al) system to optimize the mobility parameters for the B2 phase by fitting the experimentally obtained inter-diffusivities. In the model, the activation energy for diffusion is expressed as a function of the degree of ordering which is evaluated from thermodynamic data. These data are used to evaluate the thermodynamic factors of the B2 phase in the Ni-Cr-Al ternary system. The interdiffusivities from the model are used to simulate diffusion experiments. The results are generally agreed with the experimental data.
Diffusion Behavior of Interface between 6061 Aluminum Substrate and Ni–5wt.%Al Coating
Authors: Feng Ri Bao , Qiao Ning Ning , Gong Shao Jia
Published: April 2014

In this article, the diffusion behavior between 6061 aluminum alloy substrate and Ni–5wt.%Al coating was studied by changing the heat treatment temperature and processing time. The experiment results of EDS and XRD showed that a diffusion zone generated between coating and substrate even if there was no change in phase compositions of the coating. The thickness of diffusion zone increased with the process temperature accompanied with the scale-up of Al concentration. In the decrease direction of aluminum concentration, the results of computation indicated that the phase composition transformed into NiAl3, Ni2Al3 and Ni solid solution in the diffusion zone. It was concluded that microstructure and phase composition in diffusion zone between 6061 aluminum substrate and Ni–5wt.%Al coating was mainly controlled by aluminum diffusion during different heating conditions.
Research and Application Status of Atmospheric Plasma Spray Torch in Internal Feedstock Mode
Authors: Qiao Xin Yi , Wang Rui Jun
Published: April 2014

In comparison with typical external feedstock mode, powders internal injecting method can effectively enhance plasma sprayed ceramic coatings performance and improve powder deposition efficiency. In this feedstock mode, spray powders were injected into the hotter regions of a plasma jet, which had enough heat capacity to melt most of the particles instantly. Currently, several plasma spray guns in internal feedstock mode, such as Axial III and SG100, have been developed and commercialized. In this paper, characteristics of plasma spray guns in internal and external feedstock methods were summarized. And the research status of the plasma spray torch in internal feedstock mode was particularly presented. Finally, the development trend of different feedstock modes adopted by plasma spray gun was discussed.
Microstructure and Properties of Zirconia Co-Doped with Yttria and Cenosphere Coating Prepared by Air Plasma Spraying
Authors: Shao Hui Liang , Qi Xin Ying , Song Jing Jing
Published: April 2014

Conventional yttria partially stabilized zirconia (YSZ) coating and zirconia co-doped with yttria and cenosphere (ZCYC) coating have been deposited by air plasma spraying (APS). Scanning electron microscope, energy spectrum analysis equipment were used to characterize the microstructure of the coatings. Pore structures made by cenosphere were found inside the ZCYC. It is noticed that adding 20% volume fraction of cenosphere in the YSZ poweders can reduce the density of the coating by 13.2%, compared with the conventional coating. The co-doping with yttria and cenophere improves the the corrosion resistance of the coating. The coating has good shock thermal and abrasion resistances with cenosphere.
Molecular Dynamics Simulation of Porous Layer-Induced Stress in α-Iron Single Crystal and Twin Crystal
Authors: Li D. , Meng Fan Yan , Ma X.Q. , Qiao Lie Jie , Chu W.Y.
Published: April 2014

Molecular dynamics (MD) simulation was carried out to investigate the stress distribution and the macro tensile stress for the α-iron single crystal and twin crystal. The results show that there was a maximum tensile stress located at the matrix near the interface between the porous layer and the matrix for the two crystals. It has been found that a steep drop of stress generated at the twin boundary of the twin crystal. The deflection and the macro tensile stress of the single crystal and the twin crystal increased with an increase of the relative depth of the porous layer. The value of the deflection and the macro tensile stress of the single crystal were larger than that for the twin crystal, because there is a steep drop of stress generated at the twin boundary due to the effect of twin interface.
Microstructure and Properties of Ni70.2Si29.8 Eutectic Alloy Produced by Directional Solidification
Authors: Meng Qing Hui , Lu Yi Ping , Dong Yong , Li Ting Ju
Published: April 2014

The directional solidification of Ni70.2Si29.8 eutectic alloy was carried out, and the solidification microstructure and compression properties of Ni2Si – Ni31Si12 eutectic composite were systematically studied. Directional solidification samples were obtained by induction heating and down – draw process. During directional solidification, well-aligned lamellar structure with a micron scale was obtained in directional solidified Ni70.2Si29.8 eutectic alloy. Despite it is a kind of faceted – faceted eutectic alloys, highly regular and homogeneous structure was obtained through directional solidification. Compared with other methods, the compress test results showed that fracture strength of Ni70.2Si29.8 eutectic alloy obtained through directional solidification was improved obviously, reaching 2100 MPa.
Helium Diffusion in Tungsten Studied by Molecular Dynamics Method
Authors: Shu Xiao Lin , Tao Peng
Published: April 2014

The interstitial helium (He) atom diffusion in tungsten (W) was studied by the Molecular Dynamics Simulation with the drag method, the Nudged Elastic Band method (NEB) and the mean square displacement (MSD) method. The diffusion barriers and the possible microscopic diffusion path were calculated by the drag method. It has the characteristics of simple, intuitive, and occupies less computer resources, but can't get the diffusion equation. The NEB method is more reasonable than the drag method to calculate the diffusion barriers, and determine the diffusion path which, but the former spends more computer resources than the latter, and it also can't get the diffusion equation. The diffusion equation is obtained by MSD method, including the diffusion per-factor and diffusion barriers. It is suggested that the mechanism of He diffusion changes with difference temperature, which spends the most computer resources among the three methods.
Modeling of Flow Fields of Different Delivery Chamfers in Spray Forming Process
Authors: Liu Yang , Li Zhou , Zhang Guo Qing , Xu Wen Yong
Published: April 2014

The computational fluid dynamic (CFD) software was used to calculate the velocity field in atomization chamber of spray forming equipment. The relationship between melt flow rates, gas aspiration of the atomizer and operating pressure are complex, and the above mentioned parameters are closely related to the atomization process. The influences of different delivery chamfers on gas flow field, which is determined by atomizer structure, were analyzed. Using K-epsilon model with a symmetrical domain, the gas dynamic of different delivery chamfer conditions were investigated. The results indicate that the sharp point of delivery tube causes detachment of flow field, and 56°, 45° and 34° chamfer conditions have same diffusion angle. Gas was aspirated from delivery tube when chamfer was 0°, which is beneficial to liquid metal flow in atomization process.
Prediction Model for Adhesive Thickness-Dependence of Bonding Structures for Aeronautic Lightweight Alloy
Authors: Xu Wei , Yu Hui Chen , Tao Chun Hu
Published: April 2014

In the present research, the influence of the adhesive thickness on the cohesive properties and the overall strength of metallic adhesive bonding structures were investigated with the cohesive zone model to equivalently simulate the adhesive layers with various thicknesses. A theoretical approach was developed to determine the cohesive parameters for the present model when the adhesive thickness varied. And then some numerical examples were given to explore the adhesive thickness-dependence overall strength of the adhesive joints, followed by the comparison with the existing experimental results. Furthermore, the variations of both the cohesive parameters and the overall strength with the various thicknesses were influenced by the ductility of adhesives, which were investigated finally. The results showed that both the cohesive parameters and overall strength of metallic adhesive bonding structures were dependent on the adhesive thickness. Moreover, the variation of overall strength corresponding to brittle adhesive was more remarkable compared to that of ductile adhesive, especially in the comparatively small thickness range.
Fe-Based Bulk Metallic Glass with Good Soft Magnetic Properties
Authors: Xu Min , Wang Qun Jiao
Published: April 2014

Bulk Fe73Nb3Al2Ge2P9C6B4Si1 metallic glass with the diameter of 2 mm was prepared by copper mold casting. The Fe-based metallic glass exhibits good magnetic properties with high saturation magnetization and low saturated magnetostriction. The saturation magnetization and coercive force remains almost unchanged with annealing temperature below the crystallization temperature. The crystallization leads to the decrease in the softness of magnetic properties. The Fe-based glass exhibits a good correspondence between large glass-forming ability and good soft magnetic properties.
A Calculation Model of Carbon Diffusion Coefficient in the Austenite for Spheroidal Graphite Cast Iron
Authors: Zheng Hong Liang , Li Lin , Yuan Xin Xin , Tian Xue Lei
Published: April 2014

This paper presents the relationship between the carbon atom diffusion coefficient in the austenite and the temperature during the nodular cast iron solidification under different cooling rates or with different carbon contents. Pouring the wedge-shaped casting explores the influence of cooling rate on the diffusion coefficient. The other part explores the change of the diffusion coefficient with different carbon contents by water quenching to save the organization in the solidification. Results show that both the cooling rate and the carbon content can affect the diffusion coefficient, and it decreases as the cooling rate increases. More attempts were also done to correlate the diffusion coefficient with the temperature in different carbon content. It has been found that the diffusion coefficient decreases as the temperature increase.
Design and Realization of the Process Tracking System for Plate Plant
Authors: Liu Yu Jia , Hou Shuai , Li Jia Dong , Wang Zhao Dong , Wang Guo Dong , Wang Huai Jiu , Li Chang
Published: April 2014

The purpose of this paper is to improve the process tracking system, in order to meet the factory MES system requirements. Through the research process control systems and single process control system used in iron and steel enterprises in home and abroad, the integrated process control system, tracking control system and data acquisition system were established, and applied to the heat treatment lines of JISCO. In this system, the store procedure was used to complete the transaction processing in the database for improve the flexibility of the system. Practical applications validate the security and stability of performance system.
Hardness Regulation of Fe-Based Amorphous Composite Coatings by Laser Remelting
Authors: Wang Yong Tian , Yuan Ming Ming , Duan Jing Kang , Jiang Run Sen , Hu Lin , Xue Zhi Yong , Xu Gang
Published: April 2014

A Fe-based amorphous composite coating was deposited on a carbon steel substrate by arc spraying, and remelted with different laser energies by the Nd: YAG laser cladding system, in order to improve the mechanical properties of the coatings. The microstructure and microhardness of the composite coatings were investigated. The variation of harndness was measured as a function of the modified layer depth, which indicates that the laser remelting improves the bonding strength and hardness. Increasing the laser power, the quality of coating gets better, but the amorphous volume fraction decreases. It is obtained that the optimal laser electric current for the coating of 280 μm thickness is about 300 A, in which the remelted coating with medium energy densities has the highest average Vickers hardness of 741. Through the volume fraction change of the nanocrytals, the hardness of the composite coating is regulated by the laser power input, which amplified the application fields of the amorphous coatings.
Synthesis and Characterization of Monodisperse and Micro-Structured Polyaniline by Soap-Free Emulsion Polymerization
Authors: Wang Yan Min , Li Hui Min , Li Ting Xi , Gu Yi Jie
Published: April 2014

In this paper, polyaniline was successfully synthesized by soap-free emulsion polymerization with glycolic acid ethoxylate lauryl ether as dopant and characterized by particle size and distribution measurement, electron microprobe, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The particle size and distribution measurement indicated that the doped polyaniline is monodisperse and micro-structured. Electron microprobe results showed that its morphology is square slice with different square area and almost the same thickness of about 0.5μm. XRD result illustrated that the polymer possess high crystallinity of 31.43%. FT-IR spectrum revealed the chemical structure of the polyaniline doped with glycolic acid ethoxylate lauryl ether. TGA result showed its good thermal stability and purity.
Influence of Laser Remelting on the Corrosion Resistance of Fe-Based Amorphous Composite Coatings
Authors: Liu Chao , Wang Yong Tian , Hu Lin , Jiang Run Sen , Duan Jing Kang , Xue Zi Gong , Xu Gang
Published: April 2014

The microstructure and corrosion resistance of Fe-based amorphous coatings prepared by laser remelting after arc spraying were studied. The laser remelting process was carried out under different energy inputs, and the processing parameters varied with the different currents, pulse widths and scanning speeds. The corrosion behavior of the coatings in 1 mol/L NaCl solution was studied through potentiodynamic and potentiostatic polarization test. The morphology and microstructure of the coatings were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical analyzer. A Vickers hardness tester was also used to measure the microhardness of the coatings. The analysis of the microstructure shows that the amorphous coatings are composed of amorphous matrix and nanocrystalline phases. The diffusion of elements indicates a metallurgical bonding between the coating and substrate. The electrochemical corrosion results obtained from the Tafel polarization curves verify that the amorphous composite coatings prepared by different methods show no significant differences in their corrosion resistance, while the microhardness of laser remelting coatings increase obviously with the increase of laser currents. The corrosion resistance of laser remelting coatings is improved extensively due to the amorphous matrix and embedded nanocrystals, which popularizes the applications of amorphous coatings to a large extent.
Microstructural Evolution and Hardness of CoxCrCuFeNi High-Entropy Alloys
Authors: Gao Xing Yan , Liu Ning , Jin Yun Xue , Zhu Zhi Xuan
Published: April 2014

The effects of Co contents on the microstructure characteristic and phase structure of CoxCrCuFeNi high-entropy alloys were investigated by SEM, EDS and XRD. The microstructures consisted of dendrites and many nanoprecipitations in the interdendritic. Increase Co contents,the size of nanoprecipitated phase in the interdendritic firstly increased and then decreased slightly. According to XRD analysis, two simple FCC phases, dendrite phase and Cu-rich interdendritic phase were found. As a result of slow diffusion, supersaturated solid solution was formed during solidification and then nanophase was precipitated during the following cooling process. The results of EDS revealed that Fe、Co and Cr were rich in dendrites, while Cu was rich at the interdendritic. For element Ni, which was rich in dendrites when x≤1.0, but was almost the normal value in dendrites for x>1.0. The reason for segregation was related to the positive mixing enthalpy between elements. The contents of Co had little impact on the hardness of CoxCrCuFeNi high-entropy alloys according to micro-hardness testing.
TEMPO-Mediated Oxidation of Bacterial Cellulose in Buffer Solution
Authors: Lu Chuan , Chen Shi Yan , Zheng Yi , Zheng Wei Li , Xiang Cao , Wang Hua Ping
Published: April 2014

Oxidized bacterial cellulose (BC) was prepared in Na2CO3-NaHCO3buffer solution using NaClO as a primary oxidant with catalytic amounts of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) and NaBr at pH 10.5. Ethylenediamine was used as activators to pretreat BC in order to increase the accessibility of primary hydroxyl groups. The structures and properties of oxidized BC were characterized by attenuated total reflection infrared spectroscopy (ATR-IR), elemental analysis (EA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicate that the reformative oxidation successfully introduces carboxyl groups into BC, and the carboxyl content was found to be 1.34mmol per gram cellulose, higher than that of BC without pretreatment (0.81 mmol/g carboxyl introduced) under the same condition. In addition, the oxidized BC maintained the original structure which could expand the application of BC.
Facile Preparation of Gradient Structure Bacterial Cellulose Using Potato Starch
Authors: Yang Jing Xuan , Chen Shi Yan , Wang Hua Ping
Published: April 2014

Membranes of bacterial cellulose (BC) produced by Gluconacetobacter xylinus combines well-known cellulose properties with the outstanding features of nanoscale materials. As a remarkable benefit of BC, the property-controlling fiber network and pore system formed by self-assembly of the cellulose molecules can be modified in situ using additives during biosynthesis. The addition of potato starch (PS) caused the double-stage morphology of the BC/PS pellicles with an opaque dense upper part and a transparent porous lower part. Moreover, as the starch content went up, the double-stage morphology of BC/PS pellicle could be easily controlled. A gradient cross-section structure could be observed through the scanning electron microscopy (SEM) as potato starch addition level increased. The BC/PS nanocomposite structure was studied using X-ray diffraction and ATR-FTIR spectroscopy, and with the introduction of gelatinized starch, the crystallinity index (CrI) of BC/PS nanocomposite reduced from 82.40 % to 72.15 %. Meanwhile, tensile strength of the freeze-dried sample reached maximum as starch content was 0.5 wt%.
Leukocyte HMGB1 Is Required for Vessel Remodeling in Regenerating Muscles
Authors: Campana Lara , Santarella Francesco , Esposito Antonio , Maugeri Norma , Rigamonti Elena , Monno Antonella , Canu Tamara , Del Maschio Alessandro , Bianchi Marco E. , Manfredi Angelo A. , Rovere-Querini Patrizia
Published: April 2014

Signals of tissue necrosis, damage-associated molecular patterns (DAMPs), cause inflammation. Leukocytes migrating into injured tissues tonically release DAMPs, including the high mobility group box 1 protein (HMGB1). In the absence of suitable models, the relative role of DAMPs released because of necrosis or leukocyte activation has not, so far, been dissected. We have generated a mouse model lacking Hmgb1 in the hematopoietic system and studied the response to acute sterile injury of the skeletal muscle. Regenerating fibers are significantly less numerous at earlier time points and smaller at the end of the process. Leukocyte Hmgb1 licenses the skeletal muscle to react to hypoxia, to express angiopoietin-2, and to initiate angiogenesis in response to injury. Vascularization of the regenerating tissue is selectively jeopardized in the absence of leukocyte Hmgb1, revealing that it controls the nutrient and oxygen supply to the regenerating tissue. Altogether, our results reveal a novel nonredundant role for leukocyte Hmgb1 in the repair of injured skeletal muscle.
Inhibition of Functional T Cell Priming and Contact Hypersensitivity Responses by Treatment with Anti-Secondary Lymphoid Chemokine Antibody During Hapten Sensitization
Authors: Engeman Tara M. , Gorbachev Anton V. , Gladue Ronald P. , Heeger Peter S. , Fairchild Robert L.
Published: April 2014

Recent studies have suggested a pivotal role for secondary lymphoid chemokine (SLC) in directing dendritic cell trafficking from peripheral to lymphoid tissues. As an extension of these studies, we examined the consequences of anti-SLC Ab treatment during Ag priming on T cell function in an inflammatory response. We used a model of T cell-mediated inflammation, contact hypersensitivity (CHS), where priming of the effector T cells is dependent upon epidermal dendritic cell, Langerhans cells, and migration from the hapten sensitization site in the skin to draining lymph nodes. A single injection of anti-SLC Ab given at the time of sensitization with FITC inhibited Langerhans cell migration into draining lymph nodes for at least 3 days. The CHS response to hapten challenge was inhibited by anti-SLC Ab treatment in a dose-dependent manner. Despite the inhibition of CHS, T cells producing IFN-γ following in vitro stimulation with anti-CD3 mAb or with hapten-labeled cells were present in the skin-draining lymph nodes of mice treated with anti-SLC Ab during hapten sensitization. These T cells were unable, however, to passively transfer CHS to naive recipients. Animals treated with anti-SLC Ab during hapten sensitization were not tolerant to subsequent sensitization and challenge with the hapten. In addition, anti-SLC Ab did not inhibit CHS responses when given at the time of hapten challenge. These results indicate an important role for SLC during sensitization for CHS and suggest a strategy to circumvent functional T cell priming for inflammatory responses through administration of an Ab inhibiting dendritic cell trafficking.
Bcl-2 Expression in Synovial Fibroblasts Is Essential for Maintaining Mitochondrial Homeostasis and Cell Viability
Authors: Perlman Harris , Georganas Constantinos , Pagliari Lisa J. , Koch Alisa E. , Haines Kenneth , Pope Richard M.
Published: April 2014

The regulation of proliferation and cell death is vital for homeostasis, but the mechanism that coordinately balances these events in rheumatoid arthritis (RA) remains largely unknown. In RA, the synovial lining thickens in part through increased proliferation and/or decreased synovial fibroblast cell death. Here we demonstrate that the anti-apoptotic protein, Bcl-2, is highly expressed in RA compared with osteoarthritis synovial tissues, particularly in the CD68-negative, fibroblast-like synoviocyte population. To determine the importance of endogenous Bcl-2, an adenoviral vector expressing a hammerhead ribozyme to Bcl-2 (Ad-Rbz-Bcl-2) mRNA was employed. Ad-Rbz-Bcl-2 infection resulted in reduced Bcl-2 expression and cell viability in synovial fibroblasts isolated from RA and osteoarthritis synovial tissues. In addition, Ad-Rbz-Bcl-2-induced mitochondrial permeability transition, cytochrome c release, activation of caspases 9 and 3, and DNA fragmentation. The general caspase inhibitor zVAD.fmk blocked caspase activation, poly(ADP-ribose) polymerase cleavage, and DNA fragmentation, but not loss of transmembrane potential or viability, indicating that cell death was independent of caspase activation. Ectopically expressed Bcl-xL inhibited Ad-Rbz-Bcl-2-induced mitochondrial permeability transition and apoptosis in Ad-Rbz-Bcl-2-transduced cells. Thus, forced down-regulation of Bcl-2 does not induce a compensatory mechanism to prevent loss of mitochondrial integrity and cell death in human fibroblasts.
Na+-Dependent High-Affinity Glutamate Transport in Macrophages
Authors: Rimaniol Anne-Cécile , Haïk Stéphane , Martin Marc , Le Grand Roger , Boussin François Dominique , Dereuddre-Bosquet Nathalie , Gras Gabriel , Dormont Dominique
Published: April 2014

Excessive accumulation of glutamate in the CNS leads to excitotoxic neuronal damage. However, glutamate clearance is essentially mediated by astrocytes through Na+-dependent high-affinity glutamate transporters (excitatory amino acid transporters (EAATs)). Nevertheless, EAAT function was recently shown to be developmentally restricted in astrocytes and undetectable in mature astrocytes. This suggests a need for other cell types for clearing glutamate in the brain. As blood monocytes infiltrate the CNS in traumatic or inflammatory conditions, we addressed the question of whether macrophages expressed EAATs and were involved in glutamate clearance. We found that macrophages derived from human blood monocytes express both the cystine/glutamate antiporter and EAATs. Kinetic parameters were similar to those determined for neonatal astrocytes and embryonic neurons. Freshly sorted tissue macrophages did not possess EAATs, whereas cultured human spleen macrophages and cultured neonatal murine microglia did. Moreover, blood monocytes did not transport glutamate, but their stimulation with TNF-α led to functional transport. This suggests that the acquisition of these transporters by macrophages could be under the control of inflammatory molecules. Also, monocyte-derived macrophages overcame glutamate toxicity in neuron cultures by clearing this molecule. This suggests that brain-infiltrated macrophages and resident microglia may acquire EAATs and, along with astrocytes, regulate extracellular glutamate concentration. Moreover, we showed that EAATs are involved in the regulation of glutathione synthesis by providing intracellular glutamate. These observations thus offer new insight into the role of macrophages in excitotoxicity and in their response to oxidative stress.
ChlamydiapneumoniaeInhibits Apoptosis in Human Peripheral Blood Mononuclear Cells Through Induction of IL-10
Authors: Geng Yuemei , Shane Ryan B. , Berencsi Klara , Gonczol Eva , Zaki Mohamed H. , Margolis David J. , Trinchieri Giorgio , Rook Alain H.
Published: April 2014

Chlamydia pneumoniae is a common cause of pulmonary infection, with serum positivity in at least 50% of the general population. In this study, we report that human PBMCs exposed to C. pneumoniae are resistant to apoptosis induced by the potent photoactivated chemotherapeutic agents 8-methoxypsoralen and hypericin. In contrast, PBMCs treated with a heat-inactivated inoculum exhibit normal susceptibility to apoptosis. We also observed that human PBMCs are responsive to C. pneumoniae infection by secretion of key immune regulatory cytokines, including IL-12 and IL-10. While IL-12 may play an important role in limiting C. pneumoniae proliferation within cells, IL-10 serves an anti-inflammatory function by down-regulating proinflammatory cytokines such as IL-12 and TNF-α. Depletion of endogenous IL-10, but not of IL-12, abolished the apoptosis resistance of C. pneumoniae-infected PBMCs. Furthermore, addition of exogenous IL-10, but not IL-12, significantly increased the resistance of control inoculum-treated PBMCs to photoactivated 8-methoxypsoralen- and hypericin-induced apoptosis. Therefore, we conclude that C. pneumoniae possesses an antiapoptotic mechanism. The resistance to apoptosis observed in PBMCs exposed to C. pneumoniae is due, at least partially, to the IL-10 induced during C. pneumoniae infection.
Cutting Edge: IL-15 Costimulates the Generalized Shwartzman Reaction and Innate Immune IFN-γ Production In Vivo
Authors: Fehniger Todd A. , Yu Haixin , Cooper Megan A. , Suzuki Kazuhiro , Shah Manisha H. , Caligiuri Michael A.
Published: April 2014

Sequential administration of LPS to SCID mice results in the generalized Shwartzman reaction, manifesting as rapid mortality via cytokine-induced shock. Here we demonstrate that in vivo neutralization of IL-15 before LPS priming significantly reduced lethality in this reaction (p = 0.0172). We hypothesize that LPS priming induces IL-12 and IL-15 that costimulate NK cell-derived IFN-γ. Such IFN-γ may then in turn sensitize macrophages to elicit the Shwartzman reaction following a subsequent LPS challenge. Supporting this, IL-12 and IL-15 synergized to induce murine NK cell IFN-γ production in vitro. LPS stimulation of SCID mouse splenocytes resulted in measurable IFN-γ production, which was reduced when IL-15 was neutralized or IL-2/15Rβ was blocked. Pretreatment with either anti-IL-2/15Rβ or anti-IL-15 Abs reduced serum IFN-γ protein following LPS administration to SCID mice. Collectively, these data provide the first in vivo evidence that IL-15 participates in LPS-induced innate immune IFN-γ production and significantly contributes to the lethal Shwartzman reaction.
MHC Polymorphism Can Enrich the T Cell Repertoire of the Species by Shifts in Intrathymic Selection
Authors: Dyall Ruben , Messaoudi Ilhem , Janetzki Sylvia , Nikolić-Z̆ugić Janko
Published: April 2014

The murine class I molecule H-2Kb and its natural gene conversion variant, H-2Kbm8, which differs from H-2Kb solely at 4 aa at the bottom of the peptide-binding B pocket, are expressed in coisogenic mouse strains C57BL/6 (B6) and B6.C-H-2bm8 (bm8). These two strains provide an excellent opportunity to study the effects of Mhc class I polymorphism on the T cell repertoire. We recently discovered a gain in the antiviral CTL repertoire in bm8 mice as a consequence of the emergence of the Mhc class I allele H-2Kbm8. In this report we sought to determine the mechanism behind the generation of this increased CTL diversity. Our results demonstrate that repertoire diversification occurred by a gain in intrathymic positive selection. As previously shown, the emergence of the same Mhc allele also caused a loss in positive selection of T cell repertoire specific for another Ag, OVA-8. This indicates that a reciprocal loss-and-gain pattern of intrathymic selection exists between H-2Kb and H-2Kbm8. Therefore, in the thymus of an individual, a new Mhc allele can select new T cell specificities, while abandoning some T cell specificities selected by the wild-type allele. A byproduct of this repertoire shift is a net gain of T cell repertoire of the species, which is likely to improve its survival fitness.
Transcription Factor PU.1 Is Necessary for Development of Thymic and Myeloid Progenitor-Derived Dendritic Cells
Authors: Anderson Karen L. , Perkin Hugh , Surh Charles D. , Venturini Sara , Maki Richard A. , Torbett Bruce E.
Published: April 2014

Dendritic cells (DCs) are a heterogeneous population of cells that are specialized for Ag processing and presentation. These cells are believed to derive from both myeloid- and lymphoid-committed precursors. Normal human PBMC-derived, human CD14+ cell (monocyte)-derived, and mouse hematopoietic progenitor-derived DCs were shown to express the hematopoietic cell-restricted, ets family transcription factor PU.1. These populations represent myeloid progenitor-derived DCs. Hematopoietic progenitor cells from PU.1 gene-disrupted (null) mice were unable to generate MHC class IIhigh, CD11c+ myeloid-derived DCs in vitro. Mouse thymic DCs are proposed to be derived from a committed lymphoid progenitor cell that can give rise to T cells as well as DCs. Previously, we showed that CD4 and CD8 T cells developed in PU.1 null mice in a delayed manner and in reduced number. We examined the thymus of 10- to 12-day-old PU.1 null mice and found no evidence of DEC-205+, MIDC-8+ DCs in this tissue. Our findings indicate that PU.1 regulates the development of both thymic and myeloid progenitor-derived populations of DCs, and expand its known role in hematopoietic development.
Cloning and Characterization of the Bovine MHC Class I-Like Fc Receptor
Authors: Kacskovics Imre , Wu Zhen , Simister Neil E. , Frenyó László V. , Hammarström Lennart
Published: April 2014

In the cow, maternal immunity is exclusively mediated by colostral Igs, but the receptor responsible for the IgG transport has not yet been identified. The role of an IgG-Fc receptor (FcRn) that resembles a class I MHC Ag in transporting IgGs through epithelial cells was recently shown in selected species. We now report the cloning and characterization of the bovine FcRn (bFcRn). The cDNA and deduced amino acid sequences show high similarity to the FcRn in other species, and it consists of three extracellular domains, a hydrophobic transmembrane region, and a cytoplasmic tail. Despite the high similarity of the extracellular domains with other species, the bovine cytoplasmic tail is the shortest thus far analyzed. Aligning the known FcRn sequences, we noted that the bovine protein shows a 3-aa deletion compared to the rat and mouse sequences in the α1 loop. Furthermore, we found a shorter transcript of the bFcRn reflecting an exon 6-deleted mRNA, which results from an inadequate splice acceptor site in intron 5 and produces a transmembrane-deficient molecule, as was previously demonstrated in the related MHC class I gene family in mouse and humans. The presence of bFcRn transcripts in multiple tissues, including the mammary gland, suggests their involvement both in IgG catabolism and transcytosis.
Virulent Mycobacterium tuberculosis Strains Evade Apoptosis of Infected Alveolar Macrophages
Authors: Keane Joseph , Remold Heinz G. , Kornfeld Hardy
Published: April 2014

Human alveolar macrophages (AMφ) undergo apoptosis following infection with Mycobacterium tuberculosis in vitro. Apoptosis of cells infected with intracellular pathogens may benefit the host by eliminating a supportive environment for bacterial growth. The present study compared AMφ apoptosis following infection by M. tuberculosis complex strains of differing virulence and by Mycobacterium kansasii. Avirulent or attenuated bacilli (M. tuberculosis H37Ra, Mycobacterium bovis bacillus Calmette-Guérin, and M. kansasii) induced significantly more AMφ apoptosis than virulent strains (M. tuberculosis H37Rv, Erdman, M. tuberculosis clinical isolate BMC 96.1, and M. bovis wild type). Increased apoptosis was not due to greater intracellular bacterial replication because virulent strains grew more rapidly in AMφ than attenuated strains despite causing less apoptosis. These findings suggest the existence of mycobacterial virulence determinants that modulate the apoptotic response of AMφ to intracellular infection and support the hypothesis that macrophage apoptosis contributes to innate host defense in tuberculosis.
Viral IL-10 Gene Transfer Decreases Inflammation and Cell Adhesion Molecule Expression in a Rat Model of Venous Thrombosis
Authors: Henke Peter K. , DeBrunye Lisa A. , Strieter Robert M. , Bromberg Jonathan S. , Prince Martin , Kadell Amy M. , Sarkar Minakshi , Londy Frank , Wakefield Thomas W.
Published: April 2014

Post-thrombotic inflammation probably contributes to chronic venous insufficiency, and little effective treatment exists. IL-10 is an anti-inflammatory cytokine that previously has been shown to decrease perithrombotic inflammation and thrombosis. We investigated in a rat model whether local expression of viral IL-10 (vIL-10) in a segment of vein that undergoes thrombosis would confer an anti-inflammatory effect and how this effect might be mediated. Rats underwent inferior vena cava isolation, cannulation, and instillation of saline or adenovirus encoding either β-galactosidase or vIL-10. Two days after transfection, thrombosis was induced, 2 days after this the rats underwent gadolinium (Gd)-enhanced magnetic resonance venography exam, and the vein segments were harvested. Tissue transfection was confirmed by either RT-PCR of vIL-10 or positive 5-bromo-4-chloro-3-indolyl β-d-galactopyranoside (X-Gal) staining. vIL-10 significantly decreased both leukocyte vein wall extravasation and area of Gd enhancement compared with those in controls, suggesting decreased inflammation. Immunohistochemistry demonstrated decreased endothelial border staining of P- and E-selectin, while ELISA of vein tissue homogenates revealed significantly decreased P- and E-selectin and ICAM-1 levels in the vIL-10 group compared with those in controls. Importantly, native cellular IL-10 was not significantly different between the groups. However, neither clot weight nor coagulation indexes, including tissue factor activity, tissue factor Ag, or von Willebrand factor levels, were significantly affected by local vIL-10 expression. These data suggest that local transfection of vIL-10 decreases venous thrombosis-associated inflammation and cell adhesion molecule expression, but does not directly affect local procoagulant activity.
Clonotype Analysis of Human Alloreactive T Cells: A Novel Approach to Studying Peripheral Tolerance in a Transplant Recipient
Authors: Kusaka Satoshi , Grailer Alan P. , Fechner John H. , Jankowska-Gan Ewa , Oberley Terry , Sollinger Hans W. , Burlingham William J.
Published: April 2014

The recognition of allo-MHC and associated peptides on the surface of graft-derived APC by host T cells (direct pathway allorecognition) plays an important role in acute rejection after organ transplantation. However, the status of the direct pathway T cells in stable long term transplants remains unclear. To detect alloreactive T cell clones in PBL and the allograft during the transplant tolerance, we utilized RT-PCR instead of functional assays, which tend to underestimate their in vivo frequencies. We established alloreactive CD4+ and CD8+ T cell clones from peripheral blood sampled during the stable tolerance phase of a patient whose graft maintained good function for 9 years, 7 without immunosuppression. We analyzed the sequence of TCR Vβ and Vα genes and made clonotype-specific probes that allowed us to detect each clone in peripheral blood or biopsy specimens obtained during a 1-year period before and after the rapid onset of chronic rejection. We found an unexpectedly high level of donor HLA-specific T cell clonotype mRNA in peripheral blood during the late tolerance phase. Strong signals for two CD4+ clonotypes were detected in association with focal T cell infiltrates in the biopsy. Chronic rejection was associated with a reduction in direct pathway T cell clonotype mRNA in peripheral blood and the graft. Our data are inconsistent with the hypothesis that direct pathway T cells are involved only in early acute rejection events and suggest the possibility that some such T cells may contribute to the maintenance of peripheral tolerance to an allograft.
Cutting Edge: The Ets1 Transcription Factor Is Required for the Development of NK T Cells in Mice
Authors: Walunas Theresa L. , Wang Bin , Wang Chyung-Ru , Leiden Jeffrey M.
Published: April 2014

Ets1-deficient mice develop B and T cells but display a severe defect in the development of the NK cell lineage. In this report, we demonstrate that Ets1 is also required for the development of NK1.1+ T (NK T) cells. We observed significantly decreased numbers of NK T cells in the thymus, spleen, and liver of Ets1-deficient mice. These organs also contained markedly decreased levels of the canonical Vα14-Jα281 TCRα transcript seen in NK T cells. Unlike wild-type NK T cells, Ets1-deficient thymocytes failed to produce detectable levels of IL-4 following anti-CD3 stimulation. The absence of NK T cells in the Ets1-deficient mice was not associated with defective expression of CD1, an MHC class I molecule required for NK T cell development. We conclude that Ets1 defines a novel transcriptional regulatory pathway that is required for the development of both the NK and NK T cell lineages.
A Population of In Vivo Anergized T Cells with a Lower Activation Threshold for the Induction of CD25 Exhibit Differential Requirements in Mobilization of Intracellular Calcium and Mitogen-Activated Protein Kinase Activation
Authors: Utting Oliver , Teh Soo-Jeet , Teh Hung-Sia
Published: April 2014

Chronic exposure of mature T cells with specificity for self-Ags can lead to the induction of a nonfunctional state which is referred to as T cell anergy. It is unclear whether anergic T cells are destined for cell death and thereby harmless or whether they can contribute to the induction of autoimmunity and/or regulation of anti-self reactivity. We have begun to address this issue. In a recent study, we showed that a population of mature CD4−CD8− T cells that express a transgenic TCR specific for the Ld MHC class I molecule are rendered anergic in Ld-expressing mice. In this study, we show that this population of anergic T cells possess a lower activation threshold for the induction of CD25 and CD69 in response to stimulation by antigenic ligands. Furthermore, these anergic T cells undergo extensive proliferation when stimulated with a low-affinity ligand in the presence of an exogenous source of IL-2. Biochemical analysis of the early intracellular signaling events of these in vivo anergized T cells showed that they have a signaling defect at the level of ZAP-70 and linker for the activation of T cell (LAT) phosphorylation. They also exhibit a defect in mobilization of intracellular calcium in response to TCR signaling. However, these anergic T cells demonstrate no defect in SLP-76 phosphorylation and extracellular signal-regulated kinase 1/2 activation. These biochemical characteristics of the anergic T cells were associated with an elevated level of Fyn, but not Lck expression. The potential contributions of these anergic T cells in the induction and/or regulation of autoimmune responses are discussed.
CD28, Ox-40, LFA-1, and CD4 Modulation of Th1/Th2 Differentiation Is Directly Dependent on the Dose of Antigen
Authors: Rogers Paul R. , Croft Michael
Published: April 2014

The involvement of specific accessory/costimulatory molecules in differentiation to Th1 and Th2 phenotypes is controversial. Reports suggest that molecules such as CD4, CD28, and Ox-40 support Th2 differentiation and suppress Th1 differentiation, whereas others such as LFA-1 support Th1 responses and suppress Th2 responses. We have previously defined an in vitro model of differentiation that is absolutely dependent on the initial dose and affinity of peptide presented to a naive CD4 cell. The dose and affinity of Ag regulate autocrine production of IL-2, IL-4, and IFN-γ, which in turn govern differentiation to Th1 and Th2 phenotypes. We have used this system to confirm that CD4, CD28, and Ox-40 interactions can promote, and LFA-1 interactions can suppress, differentiation of cells secreting the Th2 cytokines IL-5 and IL-13. However, for CD4 and LFA-1, this is only seen over a certain range of peptide doses. In addition, CD28 and Ox-40 interactions also promote Th1 differentiation. In general, agonist Abs to accessory molecules shifted the response curves for IFN-γ, IL-5, and IL-13 to lower doses, whereas antagonist reagents resulted in similar curves shifted toward the higher doses. We conclude that ligation of cell surface accessory receptors enables low doses of Ag to promote responses normally induced only by higher doses. Individual receptors do not intrinsically regulate one cytokine phenotype or another, suggesting that differentiation is controlled by the level of expression of multiple accessory molecule pairs integrated with the number and affinity of peptide/MHC complexes.
CD4 and CD8 Expression by Dendritic Cell Subtypes in Mouse Thymus and Spleen
Authors: Vremec David , Pooley Joanne , Hochrein Hubertus , Wu Li , Shortman Ken
Published: April 2014

The dendritic cells (DC) of mouse spleen and thymus were examined for expression of CD4 and CD8. Provided care was taken to avoid selective extraction or selective depletion of DC subpopulations, three main types of DC were detected in mouse spleen: a major new population of CD4+8− DEC-205low CD11bhigh DC, together with the previously described CD4−8− DEC-205low CD11bhigh DC and CD4−8αα+ DEC-205high CD11blow DC. The CD4 on the surface of the CD4+ splenic DC subpopulation was produced by the DC themselves, and CD4 RNA transcripts were present. Likewise, the CD8α on the surface of the splenic CD8+ DC was shown to be a product of the DC themselves, in agreement with earlier evidence. All three spleen DC types would be considered as mature, based on expression of CD80, CD86, and CD40 as well as on T cell stimulating function. Mouse thymuses appeared to contain two DC types; both were DEC-205highCD11blow, but they differed in the level of CD8αα expression. However, as well as this authenticated marker expression, immunofluorescent staining was also found to reflect a series of artifacts, due to the autofluorescence of contaminating cells and due to pickup of CD4 and CD8αβ. By constructing mice chimeric for the hemopoietic lineages using mixtures of wild-type bone marrow with CD4null or CD8αnull bone marrow, a marked pickup by thymic DC of Ags derived from thymocytes was demonstrated.