bluuebunny/crossref_metadata_2025_split huggingface dataset:
Induction of Primary Virus-Cross-Reactive Human Immunodeficiency Virus Type 1-Neutralizing Antibodies in Small Animals by Using an Alphavirus-Derived In Vivo Expression System
Authors: Dong Ming , Zhang Peng Fei , Grieder Franziska , Lee James , Krishnamurthy Govindaraj , VanCott Thomas , Broder Christopher , Polonis Victoria R. , Yu Xiao-Fang , Shao Yiming , Faix Dennis , Valente Patricia , Quinnan, Gerald V. 
Published: February 2003

ABSTRACT
We have studied the induction of neutralizing antibodies by in vivo expression of the human immunodeficiency virus type 1 (HIV-1) envelope by using a Venezuelan equine encephalitis virus (VEE) replicon system with mice and rabbits. The HIV-1 envelope, clone R2, has broad sensitivity to cross-reactive neutralization and was obtained from a donor with broadly cross-reactive, primary virus-neutralizing antibodies (donor of reference serum, HIV-1-neutralizing serum 2 [HNS2]). It was expressed as gp160, as secreted gp140, and as gp160ΔCT with the cytoplasmic tail deleted. gp140 was expressed in vitro at a high level and was predominantly uncleaved oligomer. gp160ΔCT was released by cells in the form of membrane-bound vesicles. gp160ΔCT induced stronger neutralizing responses than the other forms. Use of a helper plasmid for replicon particle packaging, in which the VEE envelope gene comprised a wild-type rather than a host range-adapted sequence, also enhanced immunogenicity. Neutralizing activity fractionated with immunoglobulin G. This activity was cross-reactive among a panel of five nonhomologous primary clade B strains and a Chinese clade C strain and minimally reactive against a Chinese clade E (circulating recombinant form 1) strain. The comparative neutralization of these strains by immune mouse sera was similar to the relative neutralizing effects of HNS2, and responses induced in rabbits were similar to those induced in mice. Together, these results demonstrate that neutralizing antibody responses can be induced in mice within 2 to 3 months that are similar in potency and cross-reactivity to those found in the chronically infected, long-term nonprogressive donor of HNS2. These findings support the expectation that induction of highly cross-reactive HIV-1 primary virus-neutralizing activity by vaccination may be realized.
Human Herpesvirus 8 Envelope Glycoprotein B Mediates Cell Adhesion via Its RGD Sequence
Authors: Wang Fu-Zhang , Akula Shaw M. , Sharma-Walia Neelam , Zeng Ling , Chandran Bala 
Published: February 2003

ABSTRACT
Human herpesvirus 8 (HHV-8) or Kaposi's sarcoma-associated herpesvirus, implicated in the pathogenesis of Kaposi's sarcoma, utilizes heparan sulfate-like molecules to bind the target cells via its envelope-associated glycoproteins gB and gpK8.1A. HHV-8-gB possesses the Arg-Gly-Asp (RGD) motif, the minimal peptide region of many proteins known to interact with subsets of host cell surface integrins. HHV-8 utilizes α3β1 integrin as one of the receptors for its entry into the target cells via its gB interaction and induces the activation of focal adhesion kinase (FAK) (S. M. Akula, N. P. Pramod, F.-Z. Wang, and B. Chandran, Cell 108:407-419, 2002). Since FAK activation is the first step in the outside-in signaling necessary for integrin-mediated cytoskeletal rearrangements, cell adhesions, motility, and proliferation, the ability of HHV-8-gB to mediate the target cell adhesion was examined. A truncated form of gB without the transmembrane and carboxyl domains (gBΔTM) and a gBΔTM mutant (gBΔTM-RGA) with a single amino acid mutation (RGD to RGA) were expressed in a baculovirus system and purified. Radiolabeled HHV-8-gBΔTM, gBΔTM-RGA, and ΔTMgpK8.1A proteins bound to the human foreskin fibroblasts (HFFs), human dermal microvascular endothelial (HMVEC-d) cells, human B (BJAB) cells, and Chinese hamster ovary (CHO-K1) cells with equal efficiency, which was blocked by preincubation of proteins with soluble heparin. Maxisorp plate-bound gBΔTM protein induced the adhesion of HFFs and HMVEC-d and monkey kidney epithelial (CV-1) cells in a dose-dependent manner. In contrast, the gBΔTM-RGA and ΔTMgpK8.1A proteins did not mediate adhesion. Adhesion mediated by gBΔTM was blocked by the preincubation of target cells with RGD-containing peptides or by the preincubation of plate-bound gBΔTM protein with rabbit antibodies against gB peptide containing the RGD sequence. In contrast, adhesion was not blocked by the preincubation of plate-bound gBΔTM protein with heparin, suggesting that the adhesion is mediated by the RGD amino acids of gB, which is independent of the heparin-binding domain of gB. Integrin-ligand interaction is dependent on divalent cations. Adhesion induced by the gBΔTM was blocked by EDTA, thus suggesting the role of integrins in the observed adhesions. Focal adhesion components such as FAK and paxillin were activated by the binding of gBΔTM protein to the target cells but not by gBΔTM-RGA protein binding. Inhibition of FAK phosphorylation by genistein blocked gBΔTM-induced FAK activation and cell adhesion. These findings suggest that HHV-8-gB could mediate cell adhesion via its RGD motif interaction with the cell surface integrin molecules and indicate the induction of cellular signaling pathways, which may play roles in the infection of target cells and in Kaposi's sarcoma pathogenesis.
As
2
O
3
Enhances Retroviral Reverse Transcription and Counteracts Ref1 Antiviral Activity
Authors: Berthoux Lionel , Towers Greg J. , Gurer Cagan , Salomoni Paolo , Pandolfi Pier Paolo , Luban Jeremy 
Published: February 2003

ABSTRACT

Potent drugs such as cyclosporine have provided effective probes of signal transduction pathways and, as well, of human immunodeficiency virus type 1 (HIV-1) replication mechanisms. Recently, it was reported that As
2
O
3
, a drug used to treat acute promyelocytic leukemia (PML), stimulates HIV-1 replication. We found that As
2
O
3
accelerates the kinetics of a spreading HIV-1 infection in human T cells and increases the number of cells bearing HIV-1 provirus after a single round of infection. The stimulatory effect occurred after membrane fusion and resulted in increased steady-state levels of newly synthesized viral cDNA. Stimulation was independent of HIV-1
env
and most viral accessory genes, and As
2
O
3
had no detectable effects on viral expression postintegration or virion assembly. Murine leukemia virus (MLV) transduction was enhanced by As
2
O
3
to the same extent as HIV-1 transduction, but As
2
O
3
had no additional effect on
Fv1
restriction. In contrast, As
2
O
3
largely overcame the specific block to N-tropic MLV reverse transcription posed by human Ref1. As
2
O
3
disrupts PML bodies, nuclear structures named for a major component, the PML protein. We observed no changes in PML bodies in response to HIV-1 infection. Experiments with PML-null target cells indicated that PML has no effect on HIV-1 infectivity and is dispensable for the stimulatory effect of As
2
O
3
. As
2
O
3
caused cell death in uninfected cells at the same concentrations which stimulate HIV-1 replication. Among four additional apoptosis-inducing agents, a boost in HIV-1 infectivity was observed only with carbonyl cyanide
m
-chlorophenylhydrazone, a compound which, like As
2
O
3
, disrupts the mitochondrial transmembrane potential. In summary, As
2
O
3
stimulates retroviral reverse transcription, perhaps via effects on mitochondria, and provides a useful tool for characterizing Ref1.
Inhibition of Gammaherpesvirus Replication by RNA Interference
Authors: Jia Qingmei , Sun Ren 
Published: February 2003

ABSTRACT
RNA interference (RNAi) is a conserved mechanism in which double-stranded, small interfering RNAs (siRNAs) trigger a sequence-specific gene-silencing process. Here we describe the inhibition of murine herpesvirus 68 replication by siRNAs targeted to sequences encoding Rta, an immediate-early protein known as an initiator of the lytic viral gene expression program, and open reading frame 45 (ORF 45), a conserved viral protein. Our results suggest that RNAi can block gammaherpesvirus replication and ORF 45 is required for efficient viral production.
Replacement of Murine Leukemia Virus Readthrough Mechanism by Human Immunodeficiency Virus Frameshift Allows Synthesis of Viral Proteins and Virus Replication
Authors: Brunelle Marie-Noëlle , Brakier-Gingras Léa , Lemay Guy 
Published: February 2003

ABSTRACT
Retroviruses use unusual recoding strategies to synthesize the Gag-Pol polyprotein precursor of viral enzymes. In human immunodeficiency virus, ribosomes translating full-length viral RNA can shift back by 1 nucleotide at a specific site defined by the presence of both a slippery sequence and a downstream stimulatory element made of an extensive secondary structure. This so-called frameshift mechanism could become a target for the development of novel antiviral strategies. A different recoding strategy is used by other retroviruses, such as murine leukemia viruses, to synthesize the Gag-Pol precursor; in this case, a stop codon is suppressed in a readthrough process, again due to the presence of a specific structure adopted by the mRNA. Development of antiframeshift agents will greatly benefit from the availability of a simple animal and virus model. For this purpose, the murine leukemia virus readthrough region was rendered inactive by mutagenesis and the frameshift region of human immunodeficiency virus was inserted to generate a chimeric provirus. This substitution of readthrough by frameshift allows the synthesis of viral proteins, and the chimeric provirus sequence was found to generate infectious viruses. This system could be a most interesting alternative to study ribosomal frameshift in the context of a virus amenable to the use of a simple animal model.
Growth form of TiO2
Authors: Nicolov M. F. , Woensdregt C. F. 
Published: February 2003

AbstractComputation of attachment energies, which are considered to be directly related to the growth rates of the corresponding F faces of the TiO2 crystal structure, have been calculated in an electrostatic point charge model. Corrections using van der Waals attractions and Born repulsions were used in normal calculations and then in calculations of attachment energies, crystal energies and surface energies using Buckingam potentials potentials and short range potentials according to Post. With this were constructed growth and equilibrium form of TiO2 crystals.
Atomic force microscopy studies on surface morphologies of CdHg(SCN)4 crystals grown in solutions containing excessive amount of Cd(II) cations
Authors: Jiang X. N. , Xu D. , Sun D. L. , Yuan D. R. , Zhang Q. Y. 
Published: February 2003

AbstractSurface morphologies of CdHg(SCN)4 (CMTC) crystals grown from solutions with excessive amount of Cd(II) cations (5%, 20% and 50% in molar ratio) have been investigated by atomic force microscopy (AFM). [Cd(SCN)n]2‐n (n ≤ 4) complex anions formed by addition of excessive Cd(II) cations in the solutions have been found to act either as growth units or impurities during CMTC crystal growth. On the prismatic faces, incorporation of [Cd(SCN)n]2‐n (n ≤ 4) complex anions as growth units leads to the formation of well‐oriented protuberance trains at the step fronts, named as “locally anisotropic crystal growth”. These protuberances become fewer, less distinct and nearly disappeared with the increase of excessive Cd(II) cations in the solutions. The pyramidal face, however, varies from regular 2D nucleation growth at a low concentration of Cd(II) to much rougher growth surfaces at high concentrations, exhibiting typical surface morphologies where crystal growth is completely inhibited by impurities. Observations in this experiment provide a new picture of crystal growth.
Fatty acid composition of wild and cultivated gilthead seabream (Sparus aurata) and sea bass (Dicentrarchus labrax)
Authors: Sağglık Serap , Alpaslan Mustafa , Gezgin Tuncay , Çetintürkc Kartal , Tekinay Adem , Güven Kasım Cemal 
Published: February 2003

AbstractTotal lipid content and fatty acid composition were determined for wild and cultivated gilthead seabream and sea bass. Fatty acid analyses were carried out by gas chromatography‐ mass spectrometry. Respective total lipid content of flesh in cultivated gilthead seabream and sea bass were 1.7‐5.0‐times those of wild samples. Palmitic acid (C16:0) and oleic acid (C18:1n‐9) were the major fatty acids respectively among the saturated fatty acids and monounsaturated fatty acids of each fish species. It is noteworthy that both linoleic acid (C18:2n‐6) and arachidonic acid (C20:4n‐6) were predominant in total n‐6 polyunsaturated fatty acids in the respective cultivated and wild types. Eicosapentaenoic acid (C20:5n‐3) and docosahexaenoic acid (C22:6n‐3) amounts were significantly higher in flesh of cultivated fish than in wild fish.
Side‐Chain‐Functionalized Dipeptides Derived from 6,5‐Fused Bicyclic Thiazolidinlactams
Authors: Tremmel Peter , Brand Jörg , Knapp Volker , Geyer Armin 
Published: February 2003

AbstractCondensation of D‐arabinuronolactone (2) with L‐cysteine methyl ester yields the bicyclic thiazolidinlactam 3 as a single diastereoisomer with the new bridgehead stereocenter in the (S) configuration. Regioselective activation of the α‐hydroxy group leads to the triflate 4 without requiring protecting groups on the residual hydroxy groups. Subsequent azide exchange, reduction, and Boc protection, yields the epimeric dipeptide mimetics 6 and 7. Compound 3 forms the single acetonide 9, which permits the regioselective alkylation of the γ‐hydroxy group of the bicyclic framework. Subsequent deprotection and exchange of the α‐hydroxy functionality against a Boc‐protected amino group (13) demonstrates the regioselective side‐chain modification of bicyclic dipeptides. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
High Pressure‐Promoted [2+2] Cycloaddition Reactions of 4‐Methylphenyl 1,2‐Propadienyl Sulfone with Enol Ethers
Authors: Aben René W. M. , Braverman Samuel , Scheeren Hans W. 
Published: February 2003

AbstractUnder high pressure conditions, 4‐methylphenyl 1,2‐propadienyl sulfone (1) and enol ethers (6) undergo regioselective [2+2] cycloaddition reactions to give (3‐alkoxycyclobutylidene)methyl 4‐methylphenyl sulfones (7). The cycloaddition reaction has a broad scope with respect to the substituents allowed at the enol ether. The synthetic potential of the obtained cycloadducts is illustrated by a stereoselective addition of dimethylamine to the double bond of 7a and 7b to yield 11a and 11b and by a tertiary amine‐induced double bond isomerisation of 7a and 7b, followed by ring‐opening of the cyclobutene intermediate to yield 1‐alkoxybuta‐1,3‐dienes 12a and 12b. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
A New, Rapid, General Procedure for the Synthesis of Organic Molecules Supported on Methoxy‐Polyethylene Glycol (MeOPEG) under Microwave Irradiation Conditions
Authors: Porcheddu Andrea , Ruda Gian Filippo , Sega Alessandro , Taddei Maurizio 
Published: February 2003

AbstractThe procedure for the precipitation of molecules supported on MeOPEG (molecular mass 5000) and their purification by fractional crystallization has been made easier by use of microwave irradiation. A correct choice of the solvent employed for reaction or purification (DME, THF, 1,2‐dichlorobenzene, iPrOH, ethylene glycol) allows working with 10 g of MeOPEG‐OH, dissolved in 100 mL of solvent, under microwave irradiation conditions and for crystallization to be induced just by removal of the reaction flask from the microwave oven. No additional precipitation solvents are needed, thus reducing the reaction times and the potential hazards of working with large amounts of flammable solvents. The syntheses of several peptides and of a tetrasubstituted pyridine are reported. Large amounts of MeOPEG‐OH may be used in this procedure, and so polyethylene glycol assisted organic synthesis can be regarded as a valid preparative technique. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Operator–valued Fourier multiplier theorems on Besov spaces
Authors: Girardi Maria , Weis Lutz 
Published: February 2003

AbstractPresented is a general Fourier multiplier theorem for operator–valued multiplier functions on vector–valued Besov spaces where the required smoothness of the multiplier functions depends on the geometry of the underlying Banach space (specifically, its Fourier type). The main result covers many classical multiplier conditions, such as Mihlin and Hörmander conditions.
Explaining the growth of international R&D alliances in China
Authors: Li Jiatao , Zhong Jing 
Published: February 2003

AbstractThis paper explores two key research questions: (1) what are the growth trends of international research and development (R&D) collaborations in China; and (2) what factors determine the choice of international R&D alliance objectives in terms of a research or development orientation? It examines the rapid growth of international R&D alliances in China over the 1995–2000 period and explains multinational firms' motivations for undertaking R&D investments there. Based on the 276 international R&D alliances established in China over the study period, the paper examines the effects of some key alliance factors such as location, nationality and nature of partners, experience of partners, and alliance structure on the choice of international R&D alliance objectives in China. The findings suggest that location, number of partner, nature of local partner, and national origin of foreign partner are significantly related to the formation of research‐oriented alliances. Copyright © 2003 John Wiley & Sons, Ltd.
Human Parvovirus B19 Nonstructural Protein (NS1) Induces Cell Cycle Arrest at G
1
Phase
Authors: Morita Eiji , Nakashima Akitoshi , Asao Hironobu , Sato Hiroyuki , Sugamura Kazuo 
Published: February 2003

ABSTRACT

Human parvovirus B19 infects predominantly erythroid precursor cells, leading to inhibition of erythropoiesis. This erythroid cell damage is mediated by the viral nonstructural protein 1 (NS1) through an apoptotic mechanism. We previously demonstrated that B19 virus infection induces G
2
arrest in erythroid UT7/Epo-S1 cells; however, the role of NS1 in regulating cell cycle arrest is unknown. In this report, by using paclitaxel, a mitotic inhibitor, we show that B19 virus infection induces not only G
2
arrest but also G
1
arrest. Interestingly, UV-irradiated B19 virus, which has inactivated the expression of NS1, still harbors the ability to induce G
2
arrest but not G
1
arrest. Furthermore, treatment with caffeine, a G
2
checkpoint inhibitor, abrogated the B19 virus-induced G
2
arrest despite expression of NS1. These results suggest that the B19 virus-induced G
2
arrest is not mediated by NS1 expression. We also found that NS1-transfected UT7/Epo-S1 and 293T cells induced cell cycle arrest at the G
1
phase. These results indicate that NS1 expression plays a critical role in G
1
arrest induced by B19 virus. Furthermore, NS1 expression significantly increased p21/WAF1 expression, a cyclin-dependent kinase inhibitor that induces G
1
arrest. Thus, G
1
arrest mediated by NS1 may be a prerequisite for the apoptotic damage of erythroid progenitor cells upon B19 virus infection.
Persistent Replication of Hepatitis C Virus Replicons Expressing the β-Lactamase Reporter in Subpopulations of Highly Permissive Huh7 Cells
Authors: Murray Edward M. , Grobler Jay A. , Markel Eric J. , Pagnoni Marco F. , Paonessa Giacomo , Simon Adam J. , Flores Osvaldo A. 
Published: February 2003

ABSTRACT

Progress toward development of better therapies for the treatment of hepatitis C virus (HCV) infection has been hampered by poor understanding of HCV biology and the lack of biological assays suitable for drug screening. Here we describe a powerful HCV replication system that employs HCV replicons expressing the β-lactamase reporter (
bla
replicons) and subpopulations of Huh7 cells that are more permissive (or “enhanced”) to HCV replication than naïve Huh7 cells. Enhanced cells represent a small fraction of permissive cells present among naïve Huh7 cells that is enriched during selection with replicons expressing the neomycin phosphotransferase gene (
neo
replicons). The level of permissiveness of cell lines harboring
neo
replicons can vary greatly, and the enhanced phenotype is usually revealed upon removal of the
neo
replicon with inhibitors of HCV replication. Replicon removal is responsible for increased permissiveness, since this effect could be reproduced either with alpha interferon or with an HCV NS5B inhibitor. Moreover, adaptive mutations present in the replicon genome used during selection do not influence the permissiveness of the resulting enhanced-cell population, suggesting that the mechanisms governing the permissiveness of enhanced cells are independent from viral adaptation. Because the β-lactamase reporter allows simultaneous quantitation of replicon-harboring cells and reporter activity, it was possible to investigate the relationship between genome replication activity and the frequency with which transfected genomes can establish persistent replication. Our study demonstrates that differences in the replication potential of the viral genome are manifested primarily in the frequency with which persistent replication is established but modestly affect the number of replicons observed per replicon-harboring cell. Replicon copy number was found to vary over a narrow range that may be defined by a minimal number required for persistent maintenance and a maximum that is limited by the availability of essential host factors.
Role of the 5′-Proximal Stem-Loop Structure of the 5′ Untranslated Region in Replication and Translation of Hepatitis C Virus RNA
Authors: Luo Guangxiang , Xin Shaojie , Cai Zhaohui 
Published: February 2003

ABSTRACT

Sequences of the untranslated regions at the 5′ and 3′ ends (5′UTR and 3′UTR) of the hepatitis C virus (HCV) RNA genome are highly conserved and contain
cis
-acting RNA elements for HCV RNA replication. The HCV 5′UTR consists of two distinct RNA elements, a short 5′-proximal stem-loop RNA element (nucleotides 1 to 43) and a longer element of internal ribosome entry site. To determine the sequence and structural requirements of the 5′-proximal stem-loop RNA element in HCV RNA replication and translation, a mutagenesis analysis was preformed by nucleotide deletions and substitutions. Effects of mutations in the 5′-proximal stem-loop RNA element on HCV RNA replication were determined by using a cell-based HCV replicon replication system. Deletion of the first 20 nucleotides from the 5′ end resulted in elimination of cell colony formation. Likewise, disruption of the 5′-proximal stem-loop by nucleotide substitutions abolished the ability of HCV RNA to induce cell colony formation. However, restoration of the 5′-proximal stem-loop by compensatory mutations with different nucleotides rescued the ability of the subgenomic HCV RNA to replicate in Huh7 cells. In addition, deletion and nucleotide substitutions of the 5′-proximal stem-loop structure, including the restored stem-loop by compensatory mutations, all resulted in reduction of translation by two- to fivefold, suggesting that the 5′-proximal stem-loop RNA element also modulates HCV RNA translation. These findings demonstrate that the 5′-proximal stem-loop of the HCV RNA is a
cis
-acting RNA element that regulates HCV RNA replication and translation.