bluuebunny/crossref_metadata_2025 huggingface dataset:
Injection level lifetime spectroscopy of impurities in semiconductors
Authors: Ahrenkiel R.K. , Keyes B.M. , Johnston S.
Published: June 2004

The identification of semiconductor defects is a major task in photovoltaic and most solid state electronic technologies. A variety of techniques are used in materials analysis and many have been extensively described in the literature. Especially desirable are non-contact techniques that are sensitive to impurities in metals. Photoluminescence spectroscopy comes close to meeting this need, however it usually requires cryogenic cooling of the test specimen. The present authors have found that techniques based on measurement of recombination lifetime over a wide range of injection levels can be powerful and sensitive for materials characterisation. Not only is recombination lifetime sensitive to chemical and structural defects, but when a single defect dominates the recombination process that defect can be identified by observing the details of excess carrier decay over several orders of magnitude. This method of defect characterisation and identification will be the focus of this paper.
Density of states from transient photoconductivity in polycrystalline CdSe films
Authors: Grabtchak S. , Cocivera M.
Published: June 2004

To interpret power law decays observed for excess electrons and trapped electrons in CdSe thin films, two approaches have been compared: first, a method based on the Orenstein and Kastner model for exponential distribution of localised states, and second, an approach based on numerical solution of multiple trapping rate equations. It is shown that the second approach removes some inconsistencies inherent in the Orenstein and Kastner model. To provide a complete quantitative characterisation of the CdSe sample, saturation-bimolecular recombination effects must be included in the multiple trapping model.
Preparation of platinum and palladium films by MOCVD and their electrochemical properties
Authors: Montes de Oca J.A. , Godinez J.
Published: June 2004

Platinum and palladium films with various compositions and structures were prepared by metal organic chemical vapour deposition (MOCVD) by controlling the deposition conditions. The films were deposited as electrodes on zirconia solid electrolyte and their electrochemical properties were examined by impedance spectroscopy. Carbon containing (Pt-C and Pd-C) films consisted of agglomerated fine particles (2–5 nm in diameter) and exhibited higher electrode conductivities than conventional Pt paste electrodes at temperatures below 873 K. However, sintering of the fine particles and/or oxidation of impurity carbon or Pd spoil the electrochemical performance. On the other hand, two phase Pt–ZrO2 films show promise as electrode materials for zirconia electrolyte at low temperatures because of their higher conductivity than Pt paste electrodes (below 973 K) and their thermal stability.
Virtual substrate model for in situ thin film thickness determination
Authors: Navarro M. , Fandiño J.
Published: June 2004

A computational system has been developed for in situ monitoring of the optical properties of transparent thin films, grown by the spray pyrolysis technique on specular semi-infinite substrates, using the virtual substrate model for normal incidence reflectance. The system consists of a PC, a custom made data acquisition board, and software capable of in situ thickness monitoring and post-deposition analysis of optical parameters using the R = R(t) curve. The Levenberg– Marquardt numerical procedure was used in order to fit theoretical and experimental values of the normal incidence reflectance data with a small percentage error.
Deposition of NiOx thin films by sol–gel technique
Authors: Jiménez-González A.E. , Cambray J.G.
Published: June 2004

High quality NiOx thin films have been prepared by the sol–gel technique following alternative routes to the classic metal alkoxide route. Using nickel (II) diacetate as precursor reagent, a nickel complex was deposited on glass substrates. The nickel complex transforms to NiOx after a heat treatment in air above 250°C. X-ray diffraction analysis confirmed the crystalline → amorphous phase transition during annealing of the films. The NiOx thin films prepared in this way are very homogeneous and mostly amorphous. Compared with intrinsic single crystals, they have relatively high electrical conductivity and low optical transmittance in the visible and infrared regions. An optical band gap narrowing from 3·90 to 3·80 eV with increasing film thickness was measured in the films. Sol–gel prepared NiOx thin films are well suited for use as electrochromic films.
Surface Conditioning of Nickel–titanium Alloy Stents for Improving Biocompatibility
Authors: Zhao H. , van Humbeeck J. , de Scheerder I.
Published: June 2004

It has been shown that the surface quality of cardiovascular stents has a significant influence on the biocompatibility. In particular, a smooth surface is required. The major objective of the present study is to explore the optimal methods for polishing NiTi stents. Electrochemical polishing was mainly explored, in which several parameters were investigated including applied voltage, polishing time, as well as acid pickling prior to polishing. As a comparison, chemical polishing was also conducted. Both mechanical and electrochemical polishing of NiTi sheet material were employed in order to study the influence of electrochemical polishing on the surface composition of the NiTi stent. Pickling was necessary prior to electrochemical polishing for removing the oxide films covering the stent surface. An optimal condition for polishing was found and could provide a significant improvement of the surface quality of the NiTi stents.
A New Tool for Evaluation of Intrinsic Mechanical Properties of Multilayered Coatings
Authors: Nordin M. , Jacobson S.
Published: June 2004

A new tool is proposed for characterising intrinsic mechanical properties and wear mechanisms of multilayered coatings. In the present work multilayered coatings have been investigated with respect to their tendency to interlamella spalling in abrasion, i.e. the tendency for spalling within the coating at the lamella interfaces. This tendency is proposed to be caused by an excessive difference in the residual stress between the lamella materials and is triggered by the additional stresses imposed by abrasive diamond grits. Thick lamellae will have a stronger tendency for spalling than will thinner layers, as a result of a higher shear force in the lamella interfaces. The method is evaluated on a set of five multilayered PVD coatings, including both metallic/ceramic (Cr/CrN and Ti/TiB2) and ceramic/ceramic systems (TiN/CrN, TiN/NbN, and TiN/TaN). Each coating is represented by a number of different lamella thicknesses, ranging from approximately 50 to 900 nm.
Quantification of Plasma Sprayed Coating Adhesion Using Pulsed Laser Induced Decohesion Technique
Authors: Rosa G. , Oltra R. , Coddet C. , Costil S. ,   Nadal M.-H.
Published: June 2004

The aim of the present study is to compare a laser ultrasonic technique with a conventional indentation test for the determination of intrinsic properties and the adhesion of alumina coatings, of different thicknesses (30–350 µm), deposited on stainless steel substrates by atmospheric plasma spraying (APS). For this purpose, a pulsed Nd:YAG laser is used to irradiate the coated specimens, and the ultrasonic waves generated by the laser are recorded at the epicenter using a laser interferometer. In the thermoelastic regime, the good agreement between the experiment and computation allows determination of the longitudinal wave velocity as well as the Young's modulus of the oxide coatings versus the porosity. For a critical value of the laser energy, breakdown at the coating/substrate interface occurs. An analytical model connected the acoustic waveforms with the length of the interfacial cracks and the time delay of the debonding. The critical tensile stress at the interface is calculated using a numerical model, and the practical adhesion defined by the laser technique was compared with indentation test results.
Influence of Laser Surface Preparation on Adhesion of Thermally Sprayed Coatings
Authors: Folio F. , Michler J. , Barbezat G.
Published: June 2004

Laser treatment was used to prepare substrate surfaces for thermal spray deposition. The interaction between aluminium and titanium alloys and short Nd: YAG laser pulses was investigated. In particular, the topography of laser treated surfaces has been observed and analysed using scanning electron microscopy, atomic force microscopy, and laser profilometry. The coating/substrate adhesion was quantified for various surface preparation parameters by means of tensile tests and Rockwell indentations for Al2O3–13 wt-%TiO2 coatings. The influences of the laser energy density and the time interval between the laser treatment and the plasma spraying were studied. Compared with conventional degreasing and grit blasting, laser treatment produces better adhesion. The mechanisms of adhesion after laser treatment were investigated by transmission electron microscopy and electron energy loss spectrometry for a pure copper coating on a pure aluminium substrate. It appears that the adhesion is owing to metallurgical bonding.
Elastic Modulus of Pulse Electrode Surface Deposited Composite Boride Coating Using Nanoindentation
Authors: Agarwal A. , Dahotre N.B. , Riester L. , Sudarshan T.S.
Published: June 2004

A composite titanium diboride coating has been deposited on AISI 1010 steel using a pulse electrode surfacing (PES) technique. Such a boride coating processed by the PES process is ultrafine grained, hard, tough, and free from cracks. An attempt has been made to evaluate the elastic modulus of the composite boride coating using the nanoindentation technique. The experimental elastic modulus of the coating was found to be 347 GPa. The computed elastic modulus value (318·4 GPa) is lower than the experimental elastic modulus (347 GPa) as the latter includes the effect of metastable phase formation such as FexBy and TiaBb in minor amounts.
Thermal Fatigue Characteristics of Pta Hardfaced Steels
Authors: Kang S.H. , Shinoda T. , Kato Y. , Jeong H.S.
Published: June 2004

Many types of hard material are coated on the surface to improve their wear resistance. Addition of vanadium carbide to Co based alloys (stellite no. 21) as a hard material powder is one of the ways to improve the wear resistance characteristics of the surface layer. The plasma transfer arc (PTA) welding process was introduced as a coating technology for elevated temperature surface modification. This process has recently generated interest in the surface modification field owing to its operability, low initial cost of equipment, high deposition rate, and small dilution rate. Coated layers produced by PTA considerably improve the hardness and wear resistance of surface layers for elevated temperature applications. Vanadium carbide (VC) addition into stellite powder showed a significant improvement in wear resistance. However, alloys containing VC showed pronounced sensitivity to hot cracking under repeated heating and cooling environments. This study clarifies the cause of thermal fatigue cracking in Co based alloy deposits with VC powder additions. Cracks result from the difference in thermal expansion coefficient between the matrix and the carbides. Cracks initiate in the central part of the surface region and grow in a perpendicular direction towards the surface. The tendency for thermal fatigue crack initiation seems to increase with increasing carbide volume fraction and decrease as the volume fraction of the dendritic region decreases.
Experimental study. Effects of Thermal Spray Procedure and Thermal Fatigue on Microstructure and Properties of NiCrAlMoFe Coating
Authors: Higuera Hidalgo V. , Belzunce Varela J. , Carriles Menéndez A. , Poveda Martínez S.
Published: June 2004

This study deals with the behaviour of a nickel based alloy, NiCrMoAlFe, which was thermally sprayed, using flame, plasma, high velocity oxyfuel (HVOF), and high frequency pulse detonation (HFPD) methods, onto a stainless steel substrate. This alloy is used as a coating for heat transfer and structural elements in high temperature regions of boilers, such as superheater and reheater tubes. The microstructure, porosity, oxide content, and microhardness of the various coatings were determined. Thermal fatigue tests, under an atmosphere similar to that of power plant service conditions, were conducted in an experimental combustion chamber and, finally, the adhesion between the substrate and the coating layer was evaluated by means of tensile tests. The results obtained are discussed, with special attention being paid to the specific characteristics of the various spraying procedures.
Technical note. Effects of Laser Hardening on Fretting Wear Behaviour of Ti Alloy
Authors: Zhang H. , Dai Z.D. , Shi Y. , Xu C.Y.
Published: June 2004

Fretting wear is a serious problem with titanium alloys. Surface treatments may be good methods for improving the fretting wear resistance of titanium alloys. This paper investigates the effects of the slip amplitudes and normal loads on the fretting wear of titanium alloys before and after laser surface hardening. The results of the fretting wear experiments show that laser hardening can increase the fretting wear resistance of titanium alloys significantly. This improvement is a result of the reduction in grain size induced by laser hardening.
Evolution of interface in pulsed electrode deposited titanium diboride on copper and steel
Authors: Agarwal A. , Dahotre N.B. , Sudarshan T.S.
Published: June 2004

Pulsed electrode surfacing (PES) is a microwelding surfacing process for the successful deposition of ultrahard wear and erosion resistant ceramic coatings on metals. The present study investigates titanium diboride deposition on oxygen free high conductivity Cu. A thin and irregular coating with cracks was obtained on the Cu substrate, with the ceramic/metal interface distinct in TiB2 deposited on Cu leading to decohesion at the interface. The present work has been compared with an earlier study on TiB2 coatings deposited on 1018 steel using the PES technique. The difference in nature of the interfaces has been related to wettability, and the role of copper and iron as binders for TiB2 ceramics has been addressed. Iron acts as an excellent binder for TiB2, providing a crack free coating and a strong interface, whereas Cu is a poor binder, leading to a weak ceramic/metal interface.
Study of tin films by filtered cathodic vacuum arc techniques
Authors: Tay B.K. , Shi X. , Yang H.S. , E.J.  , Cheah L.K. , Tan H.S.
Published: June 2004

Thin TiN was grown on Si wafers (100) using a filtered cathodic vacuum arc technique. The films were characterised by their structural and mechanical behaviour. It was found that the properties of the deposited films are strongly dependent on the bias applied to the substrate. An increasing negative substrate bias results in a decrease in film compressive stress from 7·5 to 3·5 GPa and in hardness from 27·5 to 18·5 GPa. X-ray diffraction shows a preferred alignment from the (200) to the (111) direction with increasing negative sub strate bias. Atomic force microscopy results also show increasing surface roughness and grain size.
Design and performance analysis of TiCN coated cemented carbide milling cutters
Authors: Su Y.L. , Yao S.H. , Wei C.S. , Kao W.H. , Wu C.T.
Published: June 2004

The Taguchi method was employed to analyse and optimise the use of TiCN films on cemented carbide (WC–6Co–10TiC–8TaC) indexable milling cutters with respect to machining conditions. Six variables, i.e. film construction, cutting speed, feedrate, depth of cut, workpiece hardness, and milling type, were considered. The results showed that the film construction was the most dominant variable, with a percentage contribution as high as 46·10% to the overall performance of the milling system. Through statistical calculation an optimal variable combination was obtained, and the optimal film construction was found to be 3 μm TiN + 2 μm TiCN (from the substrate to the surface) rather than 5 μm TiCN alone. The resultant flank wear showed 380 and 280% improvement over the uncoated and 5 μm TiN coated cutters respectively.
In situ X-ray stress analysis at high temperatures in CVD steel–substrate compounds
Authors: Tomala V. , Hirsch T. , Mayr P.
Published: June 2004

Thin hard coatings deposited by chemical vapour deposition (CVD) techniques on to various substrate materials lead to considerable improvement in the tribological and corrosion behaviour of coated components, provided that suitable residual stresses are present. The distinction between deposition induced intrinsic and thermally induced residual stresses in coated parts is well accepted. Thermal stresses were introduced into the coating–substrate compound upon cooling to room temperature from the high temperatures applied in CVD processes. The resulting residual stress states, which affect the mechanical and tribological behaviour of the coatings, are attributed to the different thermal expansion coefficients of substrate materials and hard coatings. The calculation of residual stresses in CVD hard coatings often differs from the experimentally examined stresses measured by X-ray diffraction. The development of residual stresses in steel substrates coated with CVD TiCN was studied in situ while heating specimens from 21 up to 800°C, with subsequent cooling to room temperature. The measurements clearly show non-linear behaviour in the development of residual stresses in the substrate resulting from plastic deformation.
Control of defects during laser surface alloying
Authors: Goswami G.L. , Kumar D. , Grover A.K. , Pappachan A.L. , Totlani M.K.
Published: June 2004

Laser surface alloying is a new and promising technique for generating surface alloys having a wide range of favourable properties. The process involves altering the surfaces of inexpensive substrates by adding small quantities of alloying elements to a pool of molten metal produced by local melting using the intense heat of a laser. Certain defects such as cracks, porosity, surface roughness, compositional inhomogeneity, and excessive dilution have been observed during laser alloying (pulsed Nd : YAG laser) with chromium on mild steel, and with molybdenum and Ni–Mo on stain less steel. Specific deterioration in surface properties has been observed and discussed and the techniques utilised to control such defects have been outlined.
Role of protein kinase Cζ in thrombin-induced endothelial permeability changes: inhibition by angiopoietin-1
Authors: Li Xiaochun , Hahn Christopher N. , Parsons Michelle , Drew Jenny , Vadas Mathew A. , Gamble Jennifer R.
Published: June 2004

Endothelial cell leakiness is regulated by mediators such as thrombin, which promotes endothelial permeability, and anti-inflammatory agents, such as angiopoietin-1. Here we define a new pathway involved in thrombin-induced permeability that involves the atypical protein kinase C isoform, PKCζ. Chemical inhibitor studies implicated the involvement of an atypical PKC isoform in thrombin-induced permeability changes in human umbilical vein endothelial cells. Thrombin stimulation resulted in PKCζ, but not the other atypical PKC isoform, PKCλ, translocating to the membrane, an event known to be critical to enzyme activation. The involvement of PKCζ was confirmed by overexpression of constitutively active PKCζ, resulting in enhanced basal permeability. Dominant-negative PKCζ prevented the thrombin-mediated effects on endothelial cell permeability and inhibited thrombin-induced activation of PKCζ. Rho activation does not appear to play a role, either upstream or downstream of PKCζ, as C3 transferase does not block thrombin-induced PKCζ activation and dominant-negative PKCζ does not block thrombin-induced Rho activation. Finally, we show that angiopoietin-1 inhibits thrombin-induced PKCζ activation, Rho activation, and Ca++ flux, thus demonstrating that the powerful antipermeability action of angiopoietin-1 is mediated by its action on a number of signaling pathways induced by thrombin and implicated in permeability changes. (Blood. 2004; 104:1716-1724)
Pathobiology of hemophilic synovitis I: overexpression of mdm2 oncogene
Authors: Hakobyan Narine , Kazarian Tamara , Jabbar Adnan A. , Jabbar Kausar J. , Valentino Leonard A.
Published: June 2004

Hemophilia is a genetic disease caused by a deficiency of blood coagulation factor VIII or IX. Bleeding into joints is the most frequent manifestation of hemophilia. Hemarthrosis results in an inflammatory and proliferative disorder termed hemophilic synovitis (HS). In time, a debilitating, crippling arthritis, hemophilic arthropathy, develops. Although the clinical sequence of events from joint bleeding to synovitis to arthropathy is well documented, the component or components in blood and the molecular changes responsible for hemophilic synovitis are not known. Iron has long been suspected to be the culprit but direct evidence has been lacking. Previously, we showed that iron increased human synovial cell proliferation and induced c-myc expression. Here we show that bleeding into a joint in vivo and iron in vitro result in increased expression of the p53-binding protein, mdm2. Iron induced the expression of mdm2 by normal human synovial cells approximately 8-fold. In a murine model of human hemophilia A, hemarthrosis resulted in pathologic changes observed in human hemophilic synovitis and a marked increase in synovial cell proliferation. Iron, in vitro, induced the expression of mdm2. The molecular changes induced by iron in the blood may be the basis of the increase in cell proliferation and the development of hemophilic synovitis. (Blood. 2004;104:2060-2064)
Multiple myeloma cells catalyze hepatocyte growth factor (HGF) activation by secreting the serine protease HGF-activator
Authors: Tjin Esther P.M. , Derksen Patrick W.B. , Kataoka Hiroaki , Spaargaren Marcel , Pals Steven T.
Published: June 2004

Multiple myeloma (MM) is a common hematologic neoplasm consisting of malignant plasma cells, which expand in the bone marrow. A potential key signal in the evolution of MM is hepatocyte growth factor (HGF), which acts as a potent paracrine and/or autocrine growth factor and survival factor for MM cells. Proteolytic conversion of HGF into its active form is a critical limiting step in HGF/MET signaling. Here, we show that malignant MM plasma cells convert HGF into its active form and secrete HGF-activator (HGFA), a serine protease specific for HGF activation. By using serine protease inhibitors and neutralizing antibodies, we demonstrate that HGFA produced by the MM cells is responsible for their ability to catalyze HGF activation. We, therefore, suggest that autocatalyzation of HGF conversion by MM cells is an important step in HGF/MET-induced myeloma growth and survival, which may have implications for the management of this incurable form of cancer. (Blood. 2004;104:2172-2175)
Activated protein C variants with normal cytoprotective but reduced anticoagulant activity
Authors: Mosnier Laurent O. , Gale Andrew J. , Yegneswaran Subramanian , Griffin John H.
Published: June 2004

Recombinant activated protein C (APC), a well-defined anticoagulant enzyme, reduced mortality in severe sepsis patients in a phase 3 trial. However, 2 potent anticoagulants, antithrombin III and recombinant tissue factor pathway inhibitor, failed to do so, implying the physiologic relevance of APC's less well-defined anti-inflammatory and antiapoptotic activities. Recombinant APC therapy conveys an increased risk of serious bleeding complications due to APC anticoagulant activity. To generate recombinant APC variants with reduced risk of bleeding due to reduced anticoagulant activity, we dissected APC's anticoagulant activity from its cytoprotective activity by site-directed mutagenesis. Using staurosporine-induced endothelial cell apoptosis assays, we show here that Ala mutations (RR229/230AA and KKK191_ 193AAA) in 2 APC surface loops that severely reduce anticoagulant activity result in 2 APC variants that retain normal antiapoptotic activity that requires protease activated receptor-1 and endothelial cell protein C receptor. Thus, it is possible to reduce anticoagulant activity while preserving antiapoptotic activity of recombinant APC variants. We suggest that therapeutic use of such APC variants may reduce serious bleeding risks while providing the beneficial effects of APC acting directly on cells. (Blood. 2004;104: 1740-1744)
Creation of a mouse expressing defective human factor IX
Authors: Jin Da-Yun , Zhang Tai-Ping , Gui Tong , Stafford Darrel W. , Monahan Paul E.
Published: June 2004

The majority of cases of human hemophilia B are the result of missense mutations in the coagulation factor IX gene and defective circulating factor IX is detectable in most patients. The available mouse factor IX knockout models of hemophilia B (FIXKO mouse) reproduce the bleeding phenotype of human hemophilia B, but because the models produce no factor IX they fail to reproduce the dominant human phenotype. We have created a human factor IX mouse model of hemophilia B (R333Q-hFIX mouse) by homologous recombination in embryonic stem cells. The mouse expresses no mouse factor IX, but instead expresses a missense mutant human factor IX from the mouse FIX promoter. Mutant human factor IX mRNA transcript and circulating human factor IX are detectable throughout development, but factor IX activity is less than 1% and the mouse exhibits the hemophilic phenotype. When R333Q-hFIX mice were challenged by intramuscular injection of adeno-associated virus expressing human factor IX, factor IX expression without the development of antibodies was observed. In contrast, given the same treatment, FIXKO mice consistently develop antibodies. Our R333Q-hFIX mice strain will complement the FIXKO mice for studying factor IX circulating kinetics and gene therapy. (Blood. 2004;104:1733-1739)
Self-reactive memory-phenotype CD8 T cells exhibit both MHC-restricted and non-MHC-restricted cytotoxicity: a role for the T-cell receptor and natural killer cell receptors
Authors: Dhanji Salim , Teh Soo-Jeet , Oble Darryl , Priatel John J. , Teh Hung-Sia
Published: June 2004

We have recently shown that interleukin-2 (IL-2)-activated CD8+CD44hi cells from normal mice express both adaptive and innate immune system receptors and specifically kill syngeneic tumor cells, particularly those that express NKG2D ligands. Here we show that CD8+ T cells from antigen-expressing H-Y T-cell receptor (TCR) transgenic mice also exhibit characteristics of both T cells and natural killer (NK) cells. Interaction with cognate self-antigen was required for the optimal expansion of these cells in peripheral lymphoid tissues. Although these cells possess a higher activation threshold relative to naive T cells, they can be activated by cytokine alone in vitro. They also undergo bystander proliferation in response to a bacterial infection in vivo. Interestingly, upon activation, the cells express the NKG2D receptor as well as the DNAX activation protein 12 (DAP12) adaptor protein. We provide evidence that NKG2D can act additively with the TCR in the killing of target cells, and it can also function as a directly activating receptor in non-major histocompatibility complex (MHC)-restricted killing of target cells. These properties of CD8+ T cells from H-Y TCR transgenic mice are remarkably similar to CD8+CD44hi cells that are found in normal mice. The H-Y TCR transgenic mice provide a well-defined system for characterizing the developmental biology and function of these cells. (Blood. 2004;104:2116-2123)
Roles of MITF for development of mast cells in mice: effects on both precursors and tissue environments
Authors: Morii Eiichi , Oboki Keisuke , Ishihara Katsuhiko , Jippo Tomoko , Hirano Toshio , Kitamura Yukihiko
Published: June 2004

The mutant tg/tg mice, which do not express mi transcription factor (MITF), lack mast cells in most tissues. Since MITF is expressed in both mast cells and tissues where mast cells develop, there is a possibility that the tg/tg mice may show abnormalities in both mast cell precursors and tissue environments. We examined this possibility by bone marrow and skin transplantation. When bone marrow cells of tg/tg mice were transplanted to W/Wv mice that possess normal tissue environment, mast cells did not develop in all tissues examined. The number of developing mast cells in the skin of W/Wv mice was much lower when grafted to tg/tg recipients than when grafted to normal (+/+) recipients. These results indicated that mast cell precursors of tg/tg mice were defective. When bone marrow cells of +/+ mice were transplanted, the number of developing mast cells was significantly lower in examined tissues of tg/tg recipients than in those of W/Wv recipients, suggesting that the tissue environment for mast cell development was defective in tg/tg mice. MITF appeared essential for the function of both mast cell precursors and tissue environments for their development. (Blood. 2004;104:1656-1661)
FcγRIII discriminates between 2 subsets of Vγ9Vδ2 effector cells with different responses and activation pathways
Authors: Angelini Daniela F. , Borsellino Giovanna , Poupot Mary , Diamantini Adamo , Poupot Rémy , Bernardi Giorgio , Poccia Fabrizio , Fournié Jean-Jacques , Battistini Luca
Published: June 2004

Upon recognition of nonpeptidic phosphoantigens, human Vδ2 T lymphocytes enter a lineage differentiation pattern that determines the generation of memory cells with a range of effector functions. Here, we show that within the effector memory Vδ2 population, 2 distinct and complementary subsets with regard to phenotype, mode of activation, and type of responses can be identified: Vδ2 TEMh cells, which express high levels of chemokine receptors, but low levels of perforin and of natural killer receptors (NKRs) and which produce large amounts of interferon γ (IFN-γ) and tumor necrosis factor α (TNF-α) in response to T-cell receptor (TCR)–specific stimulation by phosphoantigens; and Vδ2TEMRA cells, which constitutively express several NKRs, high amounts of perforin, but low levels of chemokine receptors and of IFN-γ. These NK-like cells are refractory to phosphoantigen but respond to activation via FcγRIII (CD16) and are highly active against tumoral target cells. Thus, circulating Vδ2T lymphocytes comprise 2 functionally diverse subsets of effector memory cells that may be discriminated on the basis of CD16 expression.
Functional characterization of highly purified human hematopoietic repopulating cells isolated according to aldehyde dehydrogenase activity
Authors: Hess David A. , Meyerrose Todd E. , Wirthlin Louisa , Craft Timothy P. , Herrbrich Phillip E. , Creer Michael H. , Nolta Jan A.
Published: June 2004

Human hematopoietic stem cells (HSCs) are commonly purified by the expression of cell surface markers such as CD34. Because cell phenotype can be altered by cell cycle progression or ex vivo culture, purification on the basis of conserved stem cell function may represent a more reliable way to isolate various stem cell populations. We have purified primitive HSCs from human umbilical cord blood (UCB) by lineage depletion (Lin-) followed by selection of cells with high aldehyde dehydrogenase (ALDH) activity. ALDHhiLin- cells contained 22.6% ± 3.0% of the Lin- population and highly coexpressed primitive HSC phenotypes (CD34+ CD38- and CD34+CD133+). In vitro hematopoietic progenitor function was enriched in the ALDHhiLin- population, compared with ALDHloLin- cells. Multilineage human hematopoietic repopulation was observed exclusively after transplantation of ALDHhiLin- cells. Direct comparison of repopulation with use of the nonobese diabetic/severe combined immunodeficient (NOD/SCID) and NOD/SCID β2 microglobulin (β2M) null models demonstrated that 10-fold greater numbers of ALDHhi-Lin- cells were needed to engraft the NOD/SCID mouse as compared with the more permissive NOD/SCID β2M null mouse, suggesting that the ALDHhiLin- population contained committed progenitors as well as primitive repopulating cells. Cell fractionation according to lineage depletion and ALDH activity provides a viable and prospective purification of HSCs on the basis of cell function rather than cell surface phenotype. (Blood. 2004;104:1648-1655)
Late effects in survivors of chronic myeloid leukemia treated with hematopoietic cell transplantation: results from the Bone Marrow Transplant Survivor Study
Authors: Baker K. Scott , Gurney James G. , Ness Kirsten K. , Bhatia Ravi , Forman Stephen J. , Francisco Liton , McGlave Philip B. , Robison Leslie L. , Snyder David S. , Weisdorf Daniel J. , Bhatia Smita
Published: June 2004

The purpose of this study was to analyze medical late effects among patients with chronic myeloid leukemia (CML) treated with hematopoietic cell transplantation (HCT). Subjects included 248 CML survivors who received an HC transplant (related donors [RDs], n = 150; unrelated donors [URDs], n = 70; or autologous, n = 28) and had survived at least 2 years, and a comparison group of 317 siblings. Subjects completed a 238-item survey on medical late effects. Compared with siblings, survivors were at a higher risk of developing ocular, oral health, endocrine, gastrointestinal, musculoskeletal, neurosensory, and neuromotor impairments. Multivariate analysis limited to RD and URD recipients found that chronic graft-versus-host disease (cGVHD) was associated with a higher risk of hypothyroidism, osteoporosis, cardiopulmonary, neurosensory, and neuromotor impairments. Overall health was reported as excellent, very good, or good in 78% of subjects, although those with cGVHD were more likely to report poor overall health. URD survivors were more likely to report a need for assistance with routine activities and that their current health prevented work or school attendance. This study demonstrates that HCT survivors, regardless of donor type, have a high prevalence of long-term health-related complications. However, adverse medical late effects with significant morbidity were uncommon. Chronic GVHD is the most important predictor of adverse medical late effects and poor overall health.
Association of Foxp3 regulatory gene expression with graft-versus-host disease
Authors: Miura Yuji , Thoburn Christopher J. , Bright Emilie C. , Phelps Michele L. , Shin Tahiro , Matsui Elizabeth C. , Matsui William H. , Arai Sally , Fuchs Ephraim J. , Vogelsang Georgia B. , Jones Richard J. , Hess Allan D.
Published: June 2004

Graft-versus-host disease (GVHD) is characterized by an impairment of mechanisms that underlie the development of immunologic tolerance. Although the cytokine storm associated with GVHD leads to expression of cell surface markers on both effector and regulatory T cells, regulatory CD4+ T cells that play an instrumental role in the maintenance of tolerance appear to uniquely express the Foxp3 transcriptional repressor. Foxp3 mRNA expression was significantly decreased in peripheral blood mononuclear cells from patients with either allogeneic GVHD or autologous GVHD compared with patients without GVHD. Expression of Foxp3 negatively correlated with the severity of GVHD but positively correlated with recent thymic emigrants. The results suggest that defective thymic function contributes to the impaired reconstitution of immune regulatory mechanisms following transplantation. The decrease in regulatory mechanisms after transplantation appears to provide an environment permissive to the development of GVHD. (Blood. 2004;104:2187-2193)
Heparin-activated antithrombin interacts with the autolysis loop of target coagulation proteases
Authors: Yang Likui , Manithody Chandrashekhara , Rezaie Alireza R.
Published: June 2004

A unique pentasaccharide fragment of heparin can enhance the reactivity of antithrombin with coagulation proteases factors IXa and Xa by 300- to 600-fold through a conformational activation of the serpin, without having a significant effect on the reactivity of antithrombin with thrombin. In this study, it was hypothesized that differences in the structure of the autolysis loop of coagulation proteases (residues 143-154 in chymotrypsin numbering) may be responsible for their differential reactivity with the native and heparin-activated antithrombin. To test this hypothesis, the autolysis loops of both thrombin and the anticoagulant serine protease-activated protein C were replaced with the corresponding loop of factor Xa. Inhibition studies revealed that in contrast to the approximately 1.5-fold difference in the reactivity of thrombin with antithrombin in the absence and presence of pentasaccharide, the difference in reactivity was increased to approximately 37-fold for the mutant thrombin. In the case of the activated protein C mutant, similar to factor Xa, pentasaccharide accelerated the reaction 375-fold. These results suggest that structural differences in the autolysis loop of coagulation proteases play a key role in their differential reactivity with the native and heparin-activated conformations of antithrombin. (Blood. 2004;104:1753-1759)
Immobilization of rolling NK cells on platelet-borne P-selectin under flow by proinflammatory stimuli, interleukin-12, and leukotriene B4
Authors: Sheikh S , Parhar R S , Bakheet R , Saleh S , Collison K , Al-Mohanna F
Published: June 2004

Recruitment of leukocytes from bloodstream to extrahematic sites is tightly regulated by a variety of adhesion molecules that are expressed on the leukocytes and the vessel walls. In this manuscript, wedescribe the interactions between natural killer (NK) cells and activated, autologous platelets under physiologic flow. We found that surface-adherent human platelets are capable of recruiting human NK cells from flow and that this recruitment is characterized by an initial tethering followed by a rolling phase. Both phases were dependent on the adhesion molecule P-selectin and its counter-ligand on the NK cells (P-selectin glycoprotein ligand 1). Activation of rolling NK cells with inflammatory mediators commonly found in atherosclerotic plaques (interleukin-12 and leukotriene B4) causes immediate cessation of the rolling process and conversion to stationary adhesion. Blocking antibodies to the adhesion molecules membrane-activated complex-1 and leukocyte function antigen-1 inhibited this conversion. Our data suggest that platelets deposited at sites of vascular injury may provide an alternative substrate to endothelial cells for initial recruitment of NK cells to the vessel wall. This may result in extravasation of the NK cells if the appropriate chemotactic signal is applied. These data implicate the P-selectin and integrin family of adhesion molecules in the recruitment of NK cells to atherosclerotic sites.
Endogenous ligands of Toll-like receptors
Authors: Tsan Min-Fu , Gao Baochong
Published: June 2004

Extensive work has suggested that a number of endogenous molecules such as heat shock proteins (hsp) may be potent activators of the innate immune system capable of inducing proinflammatory cytokine production by the monocyte-macrophage system and the activation and maturation of dendritic cells. The cytokine-like effects of these endogenous molecules are mediated via the Toll-like receptor (TLR) signal-transduction pathways in a manner similar to lipopolysaccharide (LPS; via TLR4) and bacterial lipoproteins (via TLR2). However, recent evidence suggests that the reported cytokine effects of hsp may be a result of the contaminating LPS and LPS-associated molecules. The reasons for previous failure to recognize the contaminant(s) being responsible for the putative TLR ligands of hsp include failure to use highly purified hsp free o LPS contamination; failure to recognize the heat sensitivity of LPS; and failure to consider contaminant(s) other than LPS. Whether other reported putative endogenous ligands of TLR2 and TLR4 are a result of contamination of pathogen-associated molecular patterns is not clear. It is essential that efforts should be directed to conclusively determine whether the reported putative endogenous ligands of TLRs are a result of the endogenous molecules or of contaminant(s), before exploring further the implication and therapeutic potential of these putative TLR ligands.
Human epidermal Langerhans cells differ from monocyte-derived Langerhans cells in CD80 expression and in secretion of IL-12 after CD40 cross-linking
Authors: Peiser Matthias , Wanner Reinhard , Kolde Gerhard
Published: June 2004

Langerhans cells (LCs) represent an immature population of myeloid dendritic cells (DCs). As a result of their unique Birbeck granules (BGs), langerin expression, and heterogeneous maturation process, they differ from other immature DCs. Monocyte-derived LCs (MoLCs) mimic epidermal LCs. MoLCs with characteristic BGs are generated by culturing blood-derived monocytes with granulocyte macrophage-colony stimulating factor, interleukin (IL)-4, and transforming growth factor-β1. Here, we compare maturation-induced antigen expression and cytokine release of LCs with MoLCs. To achieve comparable cell populations, LCs and MoLCs were isolated by CD1c cell sorting, resulting in high purity. In unstimulated cells, CD40 was expressed at equal levels. After stimulation with CD40 ligand (CD40L), LCs and MoLCs acquired CD83 and increased CD86. High CD80 expression was exclusively detected in CD1c-sorted MoLCs. Human leukocyte antigen-DR and CD54 expression was found in all cell populations, however, at different intensities. CD40 triggering increased the potency of LCs and MoLCs to stimulate CD4+ T cell proliferation. Activated MoLCs released IL-12p70 and simultaneously, anti-inflammatory IL-10. The application of the Toll-like receptor ligands peptidoglycan, flagellin, and in particular, lipoplysaccharide (LPS) increased the corelease of these cytokines. LCs secreted IL-10 at a comparable level with MoLCs but failed to produce high amounts of IL-12p70 after application of danger signals. These data indicate that MoLCs as well as LCs display no maturation arrest concerning CD83 and CD86 expression. In difference to MoLCs, LCs resisted activation by CD40L and LPS in terms of IL-12 production. This shows that natural and generated LCs share similar features but differ in relevant functions.
Human neutrophils synthesize IL-8 in an IgE-mediated activation
Authors: Monteseirín Javier , Chacón Pedro , Vega Antonio , El Bekay Rajaa , Alvarez Moisés , Alba Gonzalo , Conde Manuel , Jiménez Juan , Asturias Juan A , Martínez Alberto , Conde José , Pintado Elizabeth , Bedoya Francisco J , Sobrino Francisco
Published: June 2004

It has been demonstrated that neutrophils are responsible for the release of large amounts of the inflammatory chemokine interleukin-8 (IL-8), associated with inflammation. To further define the mechanisms implicated, we have analyzed the response of human neutrophils from allergic patients to specific antigens or challenge with anti-immunoglobulin (Ig)E antibodies. Neutrophils showed a dose- and time-dependent production of IL-8. The release of the cytokine was parallel to expression of IL-8 mRNA analyzed by the polymerase chain reaction. This expression was transient—it occurred after 3 h of anti-IgE treatment and was maintained for 18 h. Trifluoperazine, EGTA, reduced nicotinamide adenine dinucleotide phosphate-oxidase inhibitors, and reactive oxygen species (ROS) scavengers inhibited IL-8 production, indicating a critical dependence of calcium and oxidative stress. Moreover, an inhibitory effect of cyclosporin A, an immunosuppressor that inhibits calcineurin activity, on IL-8 release and IL-8 mRNA expression was observed. This is the first evidence of the involvement of ROS and calcium/calcineurin in IgE-dependent IL-8 production. These findings open new perspectives into the functional role of neutrophils in IgE-associated diseases.
IFN-α regulates IL-21 and IL-21R expression in human NK and T cells
Authors: Strengell Mari , Julkunen Ilkka , Matikainen Sampsa
Published: June 2004

Interleukin (IL)-21 is a T cell-derived cytokine that regulates innate and adaptive immune responses. IL-21 receptor (IL-21R), which is expressed in natural killer (NK) and T cells, is structurally homologous to IL-2Rβ and IL-15Rα. These receptors also share a common cytokine receptor γ-chain with IL-4, IL-7, and IL-9. Macrophage- or dendritic cell-derived interferon (IFN)-α/β is a key cytokine in regulation of NK and T cell functions. We demonstrate here that in addition to activating IFN-γ gene expression, IFN-α/β and IL-12 enhance the mRNA expression of IL-21 in activated human T cells. In addition, IFN-α/β enhanced T cell receptor stimulation-induced IL-21 and IFN-γ gene expression in resting T cells. The promoter analysis of IL-21 gene revealed a putative IFN-γ activation site element, which was found to bind signal transducer and activator of transcription 1 (STAT1), STAT2, STAT3, and STAT4 proteins in IFN-α/β-stimulated NK or T cell extracts. In contrast to IL-21 expression, IFN-α/β down-regulated IL-21R mRNA expression in NK and T cells. IFN-α/β-induced down-regulation of IL-21R expression resulted in reduced STAT3 phosphorylation and DNA binding after IL-21 stimulation. In conclusion, our results suggest a novel role for IFN-α/β in the regulation of IL-21 response.
Lysophosphatidylcholine up-regulates CXCR4 chemokine receptor expression in human CD4 T cells
Authors: Han Ki Hoon , Hong Kyung Hee , Ko Jesang , Rhee Kyong Suk , Hong Myeong Ki , Kim Jae Joong , Kim You Ho , Park Seung Jung
Published: June 2004

Oxidized low-density lipoprotein (OxLDL) is an inflammatory modulator in the atherosclerotic plaque. We examined the effect of lysophosphatidylcholine (lysoPC), a main phospholipid component of OxLDL, on inflammatory responses in human CD4 T cells. We found that lysoPC dose- and time-dependently increased expression of CXCR4, the chemokine receptor on CD4 T cells. This increase was inhibited by caffeic acid phenethyl ester or SN50, nuclear factor-κB inhibitors, and also by suppression of G2A expression, the specific receptor for lysoPC, using antisense oligonucleotide. lysoPC enhanced CD4 T cell chemotaxis in response to stromal cell-derived factor-1 (SDF-1), the exclusive ligand for CXCR4. lysoPC also enhanced SDF-1-stimulated production of inflammatory cytokines interleukin-2 and interferon-γ by CD4 T cells activated by anti-CD3 immunoglobulin G. In conclusion, this study demonstrates that lysoPC directly modulates inflammatory responses in human CD4 T cells. The data suggest that the presence of lysoPC and SDF-1 in atherosclerotic lesions may trigger inflammatory responses mediated by CD4 T cells, which may play an important role in progression of atherosclerosis.
Insulin cell mass is altered inCsf1op/Csf1opmacrophage-deficient mice
Authors: Banaei-Bouchareb Linda , Gouon-Evans Valerie , Samara-Boustani Dinane , Castellotti Marie Claire , Czernichow Paul , Pollard Jeffrey W , Polak Michel
Published: June 2004

Macrophages play an important role in organ development, tissue homeostasis, and remodeling. Thus, we monitored the presence of F4/80-positive macrophages in the pancreas of wild-type mice, and some developmental features of this complex tissue were compared throughout life in wild-type and macrophage-deficient Csf1op/Csf1op (op/op) mice. The combined use of immunohistochemistry, morphometry, and cell quantification allows us to evaluate insulin and glucagon cell mass, total and insulin cell proliferation, and apoptosis in fetuses (E18.5), weanings (postnatal day 21), nonpregnant adults, and adults in late pregnancy (18.5 days). F4/80-positive macrophages were found in pancreases recovered from Csf1op/Csf1+ (op/+) mice but were extremely scarce or absent in pancreas recovered from op/op ones at all studied time-points. The macrophage-deficient op/op phenotype was clearly associated with a major insulin mass deficit in fetuses and adults, abnormal postnatal islet morphogenesis, and impaired pancreatic cell proliferation at weaning and late pregnancy. We also obtained indirect evidence of increased neogenesis in this model at time-points when pancreatic remodeling does occur. The demonstration of the colony-stimulating factor 1-dependent macrophage involvement in life-time pancreas development/remodeling allows us to pinpoint the tissue-modeling and remodeling functions of this leukocyte lineage.