bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pertussis toxin can replace T cell receptor signals that induce positive selection of CD8 T cells
Authors: Takahama Yousuke , Tokoro Yayoi , Sugawara Takehiko , Negishi Izumi , Nakauchi Hiromitsu 
Published: March 2007

AbstractCD4+ helper T lymphocytes and CD8+ killer T lymphocytes are both generated in the thymus from common precursor cells expressing CD4 and CD8. The development of immature CD4+ CD8+ thymocytes into mature ‘single‐positive’ T cells requires T cell antigen‐receptor (TCR)‐mediated positive selection signals. Although it is known that the recognition specificity of TCR expressed by CD4+ CD8+ thymocytes determines their fate to become either CD4+ or CD8+ T cells, the molecular signals that direct precursor thymocytes to become CD4+ and CD8+ T cells are unclear. By using ZAP‐70− mutant thymus organ cultures in which T cell development is arrested at the CD4+ CD8+ thymocyte stage, the present study shows that distinct biochemical treatments can selectively restore the generation of mature CD4+ and CD8+ T cells, bypassing TCR‐induced positive selection signals. The combination of phorbol ester and ionomycin selectively restores the generation of CD4+CD8− TCRhigh cells consistent with previous results. On the other hand, we find that the generation of CD4− CD8+ TCRhigh cells is selectively induced by pertussis toxin. Interestingly, the signals generated by pertussis toxin, which increase Notch expression, can dominate the signals by phorbol ester and ionomycin, steering thymocyte development to CD8 lineage. These results indicate that distinct biochemical signals replace TCR signals that selectively induce positive selection of CD4+ and CD8+ T cells, and that biochemical treatment can manipulate the development and choice of CD4+ and CD8+ T cells.
Control of B cell lymphoma recognition via natural killer inhibitory receptors implies a role for human Vγ9/Vδ2 T cells in tumor immunity
Authors: Fisch Paul , Meuer Eva , Pende Daniela , Rothenfußer Simon , Viale Oriane , Kock Sylvia , Ferrone Soldano , Fradelizi Didier , Klein George , Moretta Lorenzo , Rammensee Hans‐Georg , Boon Thierry , Coulie Pierre , van der Bruggen Pierre 
Published: March 2007

AbstractThe Vγ9/Vδ2 T cell receptor (TCR) is expressed by most human γδ T cells. We show here that cytotoxic T lymphocytes of the Vγ9/Vδ2 subset, but not of the Vδ1 subset of human γδ T cells, express natural killer inhibitory receptors (KIR) with specificity for different HLA class I alleles that down‐regulate TCR‐mediated signaling in response to HLA class I‐expressing B cell lymphomas. Vγ9/Vδ2 T cell clones with a T helper cell phenotype lack KIR and produce lymphokines in response to most human B cell lymphomas, just as they do upon recognition of the HLA class l‐deficient human Burkitt's lymphoma Daudi. Thus, human Vγ9/Vδ2 T cells have an innate specificity for nonpolymorphic cell surface structures expressed by many lymphoma cells and their cytotoxic activity is controlled by KIR. These results imply a general role of human Vγ9/Vδ2 T cells in the defense against hematopoietic tumors that is distinct from NK cells.
A functional and kinetic comparison of antiviral effector and memory cytotoxic T lymphocyte populations in vivo and in vitro
Authors: Ehl Stephan , Klenerman Paul , Aichele Peter , Hengartner Hans , Zinkernagel Rolf M. 
Published: March 2007

AbstractTo analyze the critical parameters for effective antiviral cytotoxic T lymphocyte (CTL) activity in vivo, control of lymphocytic choriomeningitis virus (LCMV) infection in the spleen was studied after adoptive transfer of different spleen cell populations into preinfected recipients. The quantitative, qualitative and kinetic requirements for virus control were defined and related to in vitro assays to compare the antiviral protective function of CTL from naive, acutely infected and memory mice. Treatment of mice with an established but limited LCMV infection by adoptive transfer of spleen cells from acutely LCMV‐infected mice led to complete virus elimination mainly mediated by donor‐derived CD8+ T cell‐mediated, perforin‐dependent cytotoxicity. Since virus is continuously spreading and the number of infected target cells rapidly increases, the time until target cell lysis is achieved was critical: if release of viral progeny was not prevented early, additional time to perform effector function did not improve overall virus control. When the function of various cell populations was compared in this model, we found that CTL from naive and memory mice perform considerably less well than CTL from acutely infected mice. In vitro studies indicated that this is probably due to the fact that they can not fulfill the limiting time requirements for immediate antiviral protection: while CTL from acutely infected mice can perform lytic effector function immediately, memory CTL require a considerable reactivation time before they can lyse infected target cells. This reactivation does not necessarily involve cell division. These findings illustrate how critical time limitations are for CTL to mediate early control of a dynamic virus infection in vivo.
Functional characterization of receptor‐type protein tyrosine phosphatase CD148 (HPTPη/DEP‐1) in Fcγ receptor IIa signal transduction of human neutrophils
Authors: Hundt Matthias , Schmidt Reinhold E. 
Published: March 2007

AbstractActivation of the 40‐kDa low‐affinity receptor for IgG (FcγRIIa, CD32) leads to tyrosine phosphorylation, increase of cytosolic free calcium concentration ([Ca2+]i), and production of superoxide anions (O2−) in neutrophils (PMN). It has been established that protein tyrosine kinases (PTK) and phosphatases (PTP) are essential for the regulation of intracellular signaling. CD45 is a type I receptor‐type protein tyrosine phosphatase (RPTP) with two PTP domains. Recently it has been demonstrated that co‐cross‐linking of CD45 modulates the signal transduction pathway of FcγRIIa in PMN. In contrast, the functional characteristics of CD148 (HPTPη/DEP‐1), a new RPTP with only one PTP domain, is unknown. CD148 is expressed on PMN in slightly lower density than CD45, and in higher density than on lymphocytes. [Ca2+]i measured with fluo‐3‐loaded PMN by flow cytometry and O2− production determined by lucigenin‐dependent chemiluminescence were inhibited by co‐cross‐linking of CD45 with FcγRIIa in comparison to isotype control monoclonal antibody (mAb). In contrast, preincubation with CD148 mAb 143‐41 abolished O2− generation, but did not inhibit [Ca2+]i rise. In summary, both clustered human RPTP, CD45 and CD148, inhibit FcγRIIa‐induced O2− production in PMN, but they differ in regulation of [Ca2+]i. Therefore, it is suggested that co‐cross‐linking of FcγRII with CD45 and CD148 leads to dephosphorylation of different substrates. These distinct functional capacities may be important for differential regulation of FcγR signaling by currently unknown ligands.
Photochemical Generation of Cyclophanes from 1,3,5‐Trisubstituted Benzenes with Chalcone Chromophores
Authors: Karpuk Elena , Schollmeyer Dieter , Meier Herbert 
Published: March 2007

Abstract(E,E,E)‐1,3,5‐Tricinnamoylbenzene (7a) photodimerizes in solution to the [4.4.4](1,3,5)cyclophane 8a. The process consists of three consecutive steps in which cisoid enone conformations of 7a react in regio‐ and stereoselective anti‐head‐to‐head cycloadditions. (E,E,E)‐1,3,5‐Tris(3‐oxo‐3‐phenylpropenyl)benzene (13a), an isomer of 7 with reversed enone units, shows a single [2π+2π] cycloaddition of the same type. Due to steric reasons, it is afterwards not capable of intramolecular processes and oligomerizes by intermolecular photocycloadditions. Photolyses in the crystalline state yield dimers by topochemically controlled syn‐head‐to‐tail processes (7a → 10a, 13a → 15a). An efficient dimerization of 13a takes place, although the distance between the olefin centers exceeds with 5.07 Å by far the limit postulated in Schmidt's rule.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Olefin Metathesis: A Reversible Stimulus for a Conformational Switch
Authors: Garcia M.‐Elisa Juarez , Fröhlich Ute , Koert Ulrich 
Published: March 2007

AbstractA ring‐closing olefin metathesis (RCM) to an eight‐membered ring is suitable to induce a conformational switch of a 2,3,6,7‐tetrasubstituted cis‐decalin. The double‐ring flip of the decalin scaffold can be reversed by a ring‐opening metathesis. The corresponding RCM to a 14‐membered ring does not force the double ring flip to occur. A ring‐size competition experiment resulted in the exclusive formation of an eight‐membered ring. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Myelin transcription factor 1 (Myt1) expression in demyelinated lesions of rodent and human CNS
Authors: Vana Adam C. , Lucchinetti Claudia F. , Le Tuan Q. , Armstrong Regina C. 
Published: March 2007

AbstractMyelin transcription factor 1 (Myt1) is a zinc‐finger DNA binding protein that influences developing oligodendrocyte progenitor (OP) cell proliferation, differentiation, and myelin gene transcription in vitro. The potential of Myt1 to play a role in OP responses leading to remyelination was examined using murine hepatitis virus strain A59 (MHV) to induce spinal cord demyelination and potential relevance to human pathology was evaluated in multiple sclerosis (MS) lesions. In MHV‐infected mice, the density of Myt1 expressing cells markedly increased in lesioned areas of spinal cord white matter. Myt1 expressing cells proliferated most extensively during active demyelination and subsequently accumulated to maximal levels during early remyelination. Cells with nuclear Myt1 immunoreactivity were mainly OP cells, identified by co‐localization with platelet‐derived growth factor alpha receptor, with additional phenotypes being either oligodendrocytes or neural stem cells, identified by CC1 antigen and Musashi1, respectively. The density of OP cells expressing Myt1 was significantly increased in white matter of MHV‐infected mice during demyelination and early remyelination then as remyelination advanced the values returned to levels comparable to PBS‐injected control mice. In MHV lesions, Myt1 was not expressed in astrocytes, lymphocytes, or macrophage/microglial cells. MS lesions demonstrated increased Myt1 expression in both the periplaque white matter adjacent to lesions and within early remyelinating lesions. These results suggesta potential role for Myt1 in the regeneration of oligodendrocyte lineage cells in response to demyelination. © 2007 Wiley‐Liss, Inc.
Anionic ring‐opening polymerization of small phosphorus heterocycles and their borane adducts: An ab initio investigation
Authors: Coote Michelle L. , Hodgson Jennifer L. , Krenske Elizabeth H. , Wild S. Bruce 
Published: March 2007

AbstractThe kinetics and thermodynamics of anionic ring‐opening reactions of phosphiranes, phosphetanes, and phospholanes and their borane adducts have been studied by high‐level ab initio procedures. For the free heterocycles, model propagation reactions involving nucleophilic attack by Me2P− at the ring α‐carbon were found to be feasible for the three‐ and four‐membered rings, but not for the five‐membered ring. For the borane adducts, nucleophilic attack by Me2(BH3)P− was only facile for the three‐membered ring, despite an increased thermodynamic tendency toward ring opening for the borane adducts of both the three‐ and four‐membered rings. The formation constants of the borane adducts of methylphosphirane and methylphosphetane were K = 2.6 × 1013 L mol−1 and K = 1.2 × 1020 L mol−1, respectively. A Marcus analysis of the ring‐opening reactions of methylphosphirane, methylphosphetane, and their borane adducts showed that the release of ring strain and an “additional factor'' contribute to rate enhancement compared with their strain‐free analogues. The additional factor was larger for the three‐membered rings than for the four‐membered rings and was larger in the free heterocycles than in their borane adducts. The additional factor is complex in origin and appears to reflect an increase in the separation between the bonding and antibonding orbitals of the breaking bond on going from the three‐membered rings to the four‐membered rings, and on going from the free heterocycles to the borane adducts. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:118–128, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20323
Dynamic aspects of hypervalent compounds effected by the formation of three center‐four electron bond in heteroatoms
Authors: Akiba Kin‐ya , Yamamoto Yohsuke 
Published: March 2007

AbstractHypervalent bond (three center‐four electron bond: 3c‐4e) is the central feature of the structure and reactivity of hypervalent compounds. The SSS bond of thiathiophthene, the so‐called no‐bond resonance compound, is realized as one of the examples of 3c‐4e bond centered at the sulfur atom (10‐S‐3). A variety of reactions such as cycloaddition‐elimination, bond‐switching rearrangement, and bond‐switching equilibration of sulfur‐containing heterocycles are exemplified to proceed through the presence of hypervalent 10‐S‐3 species. In the transition state of edge inversion, it is predicted that a vacant p‐type orbital is perpendicular to the square planar species. Antimony(III) and bismuth(III) compounds bearing a bidentate Martin ligand and a phenyl, or 2‐dimethylaminomethylphenyl, or 2,6‐bis(dimethylaminomethyl)phenyl group were prepared. The rates of inversion of these compounds at the central atom of Sb or Bi were accelerated significantly by the coordination of the dimethylamino group and also of pyridine from the solvent, where 3c‐4e bond is formed by the coordination to stabilize the transition state. Finally, the presence of rapid bond‐switching equilibration between NB···N bond of 1,8‐bis(dimethylamino)‐9‐(substituted)borylanthracenes was shown to proceed through 10‐B‐5 species at the transition state. It is concluded that the bond‐switching equilibration takes place as a piston rod in the range of 1.32 Å. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:161–175, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20326
Halogen bonding and isostructurality in 2,4,6‐tris(2‐halophenoxy)‐1,3,5‐triazines
Authors: Saha Binoy K. , Nangia Ashwini 
Published: March 2007

AbstractCrystal structures of 2,4,6‐tris(2‐halophenoxy)‐1,3,5‐triazines (halo = fluoro, chloro, bromo, iodo; 2‐XPOT) are discussed in the background of 3‐halophenoxy (3‐XPOT) and 4‐halophenoxy (4‐XPOT) structures. Among inter‐halogen interactions, the electrostatic L‐shaped type II interactions are generally shorter than the inversion‐related type I geometry in 2‐halo compounds. π‐Stacking of triazine rings at van der Waals separation (∼3.5 Å) makes the well‐known Piedfort Unit assembly and the halogen atoms form a trimer motif. 2‐FPOT and 2‐ClPOT are 2D isostructural but there are differences in the complete 3D molecular packing. 2‐BrPOT and 2‐IPOT are a 3D isostructural pair and their isomorphous unit cells have a similarity index of 0.008. The position of the halogen atom causes structural differences in 2‐, 3‐, and 4‐XPOT compounds, with the para‐series showing guest inclusion and the ortho‐ and meta‐compounds having single‐component close‐packed structures. The Cambridge Structural Database is analyzed for structural mimicry upon halogen GRoup eXchange (GRX). Chloro‐, bromo‐, and iodo‐substituted compounds of the same molecule (56 clusters) are isostructural in 30% cases, Cl/Br are identical in 66% pairs, and Br/I in 50% examples of the subdatabase. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:185–194, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20328
Treatment of contaminated bone defects with clindamycin‐reconstituted bone xenograft‐composites
Authors: Bi Long , Hu Yunyu , Fan Hongbin , Meng Guolin , Liu Jian , Li Dan , Lv Rong 
Published: March 2007

AbstractContaminated or infected bone defects and osteomyelitis after trauma are frequently encountered in clinical practice. It is difficult to make a successful bone graft and control infection at the same time. To find a better method to resolve this dilemma, we prepared a novel clindamycin‐reconstituted bone xenograft‐composite (C‐RBX‐C) that comprised of crude bBMP (bovine bone morphogenetic protein), clindamycin, and cancellous bone scaffold, and investigated the morphology, biocompatibility, antibiotic release profile and osteoinductive potential of this composite. The ultrastructure of C‐RBX‐C was evaluated by scanning electron microscopy; the biocompatibility and osteoinductive potential were assessed by testing ectopic implants. The antibiotic release profile was evaluated using a disc‐diffusion assay. Finally, this composite was used to repair a Staphylococcus aureus contaminated bone defect in a rabbit model. 16 weeks after the implantation of C‐RBX‐C, the radial defect had been completely recuperated, with significantly better formation of lamellar bone and recanalization of the marrow cavity, than in the controls (scaffolds without clindamycin or bBMP). These results demonstrate that our novel composite, with its concomitant osteoinductive and antibiotic properties, has significant potential for the treatment of contaminated or infected bone defects and osteomyelitis. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007
Linear regression model of DNA sequences and its application
Authors: Dai Qi , Liu Xiao‐Qing , Wang Tian‐Ming , Vukicevic Damir 
Published: March 2007

AbstractWe constructed six new models to analyze the DNA sequences. First, we regarded a DNA primary sequence as a random process in t and gave three ways to define nucleotides' random distribution functions. We extracted some parameters from the linear model and analyzed the changes of the nucleotides' distributions. In order to facilitate the comparison of DNA sequences, we proposed two ways to measure their similarities. Finally, we compared the six models by analyzing the similarities of the DNA primary sequences presented in Table 1 and selected the optimal one. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
A DFT study on the dimerization of C62, H2C62, and F2C62
Authors: Qiang Hou Jin , Seok Kang Hong 
Published: March 2007

AbstractOn the basis of calculations using the density functional theory, we show that C62, a recently synthesized nonclassical fullerene, will presumably undergo dimerization with various isomers at elevated temperatures. This is shown by calculating the dimerization energy and the activation barrier of the dimerization. Eight possible isomers of the dimer were identified, all of which are more stable than the two isolated monomers. The relative stability of various isomers depends upon the kind of CC bonds within the four‐membered carbon ring involved in the dimerization. In addition, similar calculations were performed for the monomers and dimers of H2C62 and F2C62. Six isomers were identified for each of the dimers. Although less pronounced than the case of the C62 dimer, all isomers of the H2C62 dimer are appreciably more stable than the individual monomers. Although a large steric repulsion due to F atoms significantly reduces the stability of F2C62 dimer, its two isomers are still more stable than separate monomers. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
A dynamic lattice searching method with constructed core for optimization of large lennard‐jones clusters
Authors: Yang Xiaoli , Cai Wensheng , Shao Xueguang 
Published: March 2007

AbstractA variation of the previous dynamic lattice searching (DLS) method, named as DLS with constructed core (DLSc), was proposed for structural optimization of Lennard‐Jones (LJ) clusters. In the new method, the starting random structure is generated with an icosahedron or a decahedron as a core. For a cluster with n shells, the atoms in the inner n − 2 shells are set as a fixed core, and the remaining atoms in the outer 2 shells are optimized by DLS. With applications of DLSc to optimization of LJ100–200 and LJ660–670, it was found that all the putative global minima can be obtained by using the DLSc method, and the method was proved to be high efficient compared with the previous DLS, because the searching space is reduced by the use of the fixed core. However, although DLSc is still an unbiased approach for smaller LJ clusters, it turned out to be biased for large ones. Further works are still needed to make it to be a more general method for cluster optimization problem. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Correlations between anti‐albumin antibodies and HBsAG in hepatic patients
Authors: Lenkei R. , Babes V. T. , Dan M. E. , Mustea A. , Dobre I. 
Published: March 2007

AbstractA new category of autoantibodies ‐ antipolymerized albumin antibodies (AAA) ‐ was discovered in 1974. Studies performed from 1974 to 1976 showed their diagnosis and prognostic values in hepatic diseases; the AAA tests [immunodiffusion (ID) and hemagglutination (HS)] made possible a good estimation of the total liver cell function. Without being specific for a viral hepatitis B infection, highly significant linear correlations were found for AAA precipitin and agglutinin positivities with presence of HBsAg. High titre of AAA agglutinins unaccompanied by a positive ID test, characterise the “healthy carrier” of the HBsAg, while the isolated AAA positivity in ID is met in more severe, long‐standing hepatic diseases.
A persistent infection of baby hamster kidney‐21 cells with mumps virus and the role of temperature‐sensitive variants
Authors: Truant Allan L. , Hallum Jules V. 
Published: March 2007

AbstractA persistent infection of baby hamster kidney‐21 (BHK‐21) cells with mumps virus (BHKpi) was maintained for over 60 cell passages in the absence of antiserum. Viral persistence was demonstrated in the cultures by hemadsorption, immunofluorescence, multinucleate syncytia, and released mumps virus at the level of 102–103 fluorescent focus‐forming units/ml. No detectable levels of interferon were found in cultures persistently infected with mumps virus. Approximately 85–95% of the cells contained viral antigens. Nuclear fluorescence was observed in the persistently infected cells. Mumps virus from persistently infected cultures (MuVpi) was more heat‐labile than wild‐type mumps (MuVo) when subjected to 40°C. BHKpi cells had a more rapid doubling time and a higher cloning efficiency in soft agar in comparison to BHK‐21 cells. MuVpi was also found to be temperature‐sensitive. The temperature‐sensitivity of MuVpi was determined by the efficiency of plating at 33° and 39°C. MuVpi readily established a persistent infection in BHK‐21 cells with less cytopathology than MuVo, and released temperature‐sensitive virus.
Rotavirus infections in adults in association with acute gastroenteritis
Authors: von Bonsdorff C.‐H. , Hovi T. , Mäkelä P. , Mörttinen A. 
Published: March 2007

AbstractDuring an epidemic of acute gastroenteritis in Helsinki, in March – May 1976, 18 out of 40 adult patients showed electron microscopic and/or serologic evidence for rotavirus infection. Rotavirus was most frequently seen in the fecal suspensions from 2 to 6 days after the onset of the symptoms but persisted in one patient for as long as 10 days. An increase in the complement‐fixing (CF) serum antibody titers against the related Nebraska calf diarrhea virus (NCDV), or an initially high titer and subsequent significant decrease, was seen in all but one patient with rotavirus‐positive feces, and in 6 additional patients. This suggests that using electron microscopy as the only diagnostic procedure a considerable number of rotavirus infections in adults remain undectected.Immune response against autologous or homologous rotavirus was also documented by immunoelectron microscopy. Complement‐fixing antibody titers against NCDV decreased significantly from the convalescence values over a half‐year observation period, but still remained clearly above the titers of a gastroenteritis‐negative control population.