bluuebunny/crossref_metadata_2025 huggingface dataset:
The Human Herpesvirus 8 Homolog of Epstein-Barr Virus SM Protein (KS-SM) Is a Posttranscriptional Activator of Gene Expression
Authors: Gupta Ashish K. , Ruvolo Vivian , Patterson Cam , Swaminathan Sankar
Published: July 2002

Homologs of the Epstein-Barr virus (EBV) SM protein exist in several human and nonhuman herpesviruses. Structure and function differ significantly among these proteins. We have cloned and characterized the human herpesvirus 8 (HHV8) gene, KS-SM, which is homologous to the EBV SM and herpes simplex virus ICP27 genes, from an HHV8-infected primary effusion lymphoma. KS-SM is shown to be a posttranscriptional activator of gene expression in cotransfection studies. KS-SM activated gene expression in a gene-specific, promoter-independent manner. In particular, KS-SM enhanced the expression of KDR/flk-1, a receptor for vascular endothelial growth factor (VEGF), in cotransfection studies. Since expression of KDR/flk-1 is increased in Kaposi's sarcoma and HHV8-infected cell cultures and VEGF enhances the proliferation of HHV8-infected cells, KS-SM may play a pathogenic role in Kaposi's sarcoma.
Prevention of Adult T-Cell Leukemia-Like Lymphoproliferative Disease in Rats by Adoptively Transferred T Cells from a Donor Immunized with Human T-Cell Leukemia Virus Type 1 Tax-Coding DNA Vaccine
Authors: Ohashi Takashi , Hanabuchi Shino , Kato Hirotomo , Tateno Hiromi , Takemura Fumiyo , Tsukahara Tomonori , Koya Yoshihiro , Hasegawa Atsuhiko , Masuda Takao , Kannagi Mari
Published: July 2002

Human T-cell leukemia virus type 1 (HTLV-1) causes adult T-cell leukemia (ATL) in infected individuals after a long incubation period. To dissect the mechanisms of the development of the disease, we have previously established a rat model of ATL-like disease which allows examination of the growth and spread of HTLV-1 infected tumor cells, as well assessment of the effects of immune T cells on the development of the disease. In the present study, we induced HTLV-1 Tax-specific cytotoxic T lymphocyte (CTL) immunity by vaccination with Tax-coding DNA and examined the effects of the DNA vaccine in our rat ATL-like disease model. Our results demonstrated that DNA vaccine with Tax effectively induced Tax-specific CTL activity in F344/N Jcl-rnu/+ (nu/+) rats and that these CTLs were able to lyse HTLV-1 infected syngeneic T cells in vitro. Adoptive transfer of these immune T cells effectively inhibited the in vivo growth of HTLV-1-transformed tumor in F344/N Jcl-rnu/rnu (nu/nu) rats inoculated with a rat HTLV-1 infected T cell line. Vaccination with mutant Tax DNA lacking transforming ability also induced efficient anti-tumor immunity in this model. Our results indicated a promising effect for DNA vaccine with HTLV-1 Tax against HTLV-1 tumor development in vivo.
Comparison of Second-Strand Transfer Requirements and RNase H Cleavages Catalyzed by Human Immunodeficiency Virus Type 1 Reverse Transcriptase (RT) and E478Q RT
Authors: Snyder Christine Smith , Roth Monica J.
Published: July 2002

Truncated tRNA-DNA mimics were examined in an in vitro assay for second-strand transfer during human immunodeficiency virus type 1 (HIV-1) reverse transcription. Strand transfer in this system requires the progressive degradation of the RNA within the 18-mer tRNA-DNA (plus-strand strong stop DNA) intermediate to products approximately 8 nucleotides in length. The ability of the truncated substrates to substitute for directional processing by RNase H or reverse transcriptase (RT) was examined. Using wild-type HIV-1 RT, substrates which truncated the 5′ end of the tRNA primer by 6, 9, and 12 nucleotides (Δ6, Δ9, and Δ12, respectively) were recognized by RNase H and resulted in strand transfer. An overlap of 5 nucleotides between the acceptor and newly synthesized DNA template was sufficient for strand transfer. The mutant RT, E478Q correctly catalyzed the initial cleavage of the 18-mer tRNA-DNA mimic in the presence of Mn
2+
; however, no directional processing was observed. In contrast, no RNase H activity was observed with the Δ6, Δ9, and Δ12 substrates with E478Q RT in this strand transfer assay. However, when complemented with
Escherichia coli
RNase H, E478Q RT supported strand transfer with the truncated substrates. E478Q RT did cleave the truncated forms of the substrates, Δ6, Δ9, and Δ12, in a polymerase-independent assay. The size requirements of the substrates which were cleaved by the polymerase-independent RNase H activity of E478Q RT are defined.
Core Protein-Coding Sequence, but Not Core Protein, Modulates the Efficiency of Cap-Independent Translation Directed by the Internal Ribosome Entry Site of Hepatitis C Virus
Authors: Wang Ting-Hsien , Rijnbrand René C. A. , Lemon Stanley M.
Published: July 2002

Among a myriad of putative functions assigned to the hepatitis C virus (HCV) core protein, several studies suggest that it may modulate internal ribosome entry site (IRES)-mediated initiation of translation. We compared the translational activity of dicistronic reporter transcripts containing the HCV IRES within the intercistronic space fused to downstream sequence encoding either 22 amino acids (aa) or 173 aa of the core protein. The inclusion of the nearly full-length core protein-coding sequence significantly suppressed translation in vitro and in transfected HepG2 cells. However, this suppression was not eliminated by frameshift mutations introduced into the core sequence, suggesting that it occurred at the RNA level and not as a result of core protein expression incis. Similarly, the expression of core protein (aa 1 to 191) intransfrom a recombinant baculovirus did not suppress IRES-directed translation from any of these transcripts in transfected Huh-7 cells. While core protein expression did decrease IRES activity in HepG2 cells (up to 79% suppression), the expression of β-galactosidase from a control baculovirus also suppressed IRES activity (up to 56%), strongly suggesting that this suppression was nonspecific. Finally, the addition of purified recombinant core protein (aa 1 to 179) to in vitro translation reactions at concentrations up to a 10-fold molar excess over the RNA transcripts resulted in no significant reduction in IRES activity. Consistent with these results, a gel retention assay indicated no difference in the affinities of the recombinant HCV core protein and a recombinant Venezuelan equine encephalitis virus capsid protein for HCV IRES-containing RNA transcripts. We conclude that while the inclusion of core protein-coding sequence downstream of the IRES may reduce the efficiency of cap-independent translation on HCV RNA, the core protein itself has no biologically relevant activity in modulating HCV IRES activity.
Sint1
, a Common Integration Site in SL3-3-Induced T-Cell Lymphomas, Harbors a Putative Proto-Oncogene with Homology to the Septin Gene Family
Authors: Sørensen Annette Balle , Lund Anders H. , Ethelberg Steen , Copeland Neal G. , Jenkins Nancy A. , Pedersen Finn Skou
Published: July 2002

The murine retrovirus SL3-3 is a potent inducer of T-cell lymphomas when inoculated into susceptible newborn mice. Previously, DNAs from twenty SL3-3-induced tumors were screened by PCR for provirus integration sites. Two out of 20 tumors demonstrated clonal provirus insertion into a common region. This region has now been isolated and characterized. The region, named SL3-3 integration site 1 (
Sint1
), maps to the distal end of mouse chromosome 11, corresponding to human chromosome 17q25, and may be identical to a mouse mammary tumor virus integration site in a T-cell lymphoma,
Pad3
. Two overlapping genomic λ clones spanning about 35 kb were isolated and used as a starting point for a search for genes in the neighborhood of the virus integration sites. A genomic fragment was used as a hybridization probe to isolate a 3-kb cDNA clone, the expression of which was upregulated in one of two tumors harboring a provirus in
Sint1
. The cDNA clone is predicted to encode a protein which shows 97.0% identity to a human septin-like protein encoded by a gene which has been found as a fusion partner gene of MLL in an acute myeloid leukemia with a t(11;17)(q23;q25). Together these findings raise the possibility that a proto-oncogene belonging to the septin family, and located about 15 kb upstream of the provirus integration sites, is involved in murine leukemia virus-induced T-cell lymphomagenesis.
Downregulation of p56lckTyrosine Kinase Activity in T Cells of Squirrel Monkeys (Saimiri sciureus) Correlates with the Nontransforming and Apathogenic Properties of Herpesvirus Saimiri in Its Natural Host
Authors: Greve Timm , Tamgüney Gültekin , Fleischer Bernhard , Fickenscher Helmut , Bröker Barbara M.
Published: July 2002

Herpesvirus saimiri is capable of transforming T lymphocytes of various primate species to stable growth in culture. The interaction of the T-cellular tyrosine kinase p56lckwith the transformation-associated viral protein Tip has been shown before to activate the kinase and provides one model for the T-cell-specific transformation by herpesvirus saimiri subgroup C strains. In contrast to other primate species, squirrel monkeys (Saimiri sciureus) are naturally infected with the virus without signs of lymphoma or other disease. Although the endogenous virus was regularly recovered from peripheral blood cells from squirrel monkeys, we observed that the T cells lost the virus genomes in culture. Superinfection with virus strain C488 did not induce growth transformation, in contrast to parallel experiments with T cells of other primate species. Surprisingly, p56lckwas enzymatically inactive in primary T-cell lines derived from different squirrel monkeys, although the T cells reacted appropriately to stimulatory signals. The cDNA sequence revealed minor point mutations only, and transfections in COS-7 cells demonstrated that theS. sciureus lckgene codes for a functional enzyme. InS. sciureus, the tyrosine kinase p56lckwas not activated after T-cell stimulation and enzymatic activity could not be induced by Tip of herpesvirus saimiri C488. However, the suppression of p56lckwas partially released after administration of the phosphatase inhibitor pervanadate. This argues for unique species-specific conditions in T cells ofS. sciureuswhich may interfere with the transforming activity and pathogenicity of herpesvirus saimiri subgroup C strains in their natural host.
Protective Mechanisms Induced by a Japanese Encephalitis Virus DNA Vaccine: Requirement for Antibody but Not CD8+Cytotoxic T-Cell Responses
Authors: Pan Chien-Hsiung , Chen Hsin-Wei , Huang Hui-Wen , Tao Mi-Hua
Published: July 2002

We have previously shown that a plasmid (pE) encoding the Japanese encephalitis virus (JEV) envelope (E) protein conferred a high level of protection against a lethal viral challenge. In the present study, we used adoptive transfer experiments and gene knockout mice to demonstrate that the DNA-induced E-specific antibody alone can confer protection in the absence of cytotoxic T-lymphocyte (CTL) functions. Plasmid pE administered by either intramuscular or gene gun injection produced significant E-specific antibodies, helper T (Th)-cell proliferative responses, and CTL activities. Animals receiving suboptimal DNA vaccination produced low titers of anti-E antibodies and were only partially or not protected from viral challenge, indicating a strong correlation between anti-E antibodies and the protective capacity. This observation was confirmed by adoptive transfer experiments. Intravenous transfer of E-specific antisera but not crude or T-cell-enriched immune splenocytes to sublethally irradiated hosts conferred protection against a lethal JEV challenge. Furthermore, experiments with gene knockout mice showed that DNA vaccination did not induce anti-E titers and protective immunity in Igμ−/−and I-Aβ−/−mice, whereas in CD8α−/−mice the pE-induced antibody titers and protective rate were comparable to those produced in the wild-type mice. Taken together, these results demonstrate that the anti-E antibody is the most critical protective component in this JEV challenge model and that production of anti-E antibody by pE DNA vaccine is dependent on the presence of CD4+T cells but independent of CD8+T cells.
Granulocyte-Macrophage Colony-Stimulating Factor Expressed by Recombinant Respiratory Syncytial Virus Attenuates Viral Replication and Increases the Level of Pulmonary Antigen-Presenting Cells
Authors: Bukreyev Alexander , Belyakov Igor M. , Berzofsky Jay A. , Murphy Brian R. , Collins Peter L.
Published: July 2002

An obstacle to developing a vaccine against human respiratory syncytial virus (RSV) is that natural infection typically does not confer solid immunity to reinfection. To investigate methods to augment the immune response, recombinant RSV (rRSV) was constructed that expresses murine granulocyte-macrophage colony-stimulating factor (mGM-CSF) from a transcription cassette inserted into the G-F intergenic region. Replication of rRSV/mGM-CSF in the upper and lower respiratory tracts of BALB/c mice was reduced 23- to 74- and 5- to 588-fold, respectively, compared to that of the parental rRSV. Despite this strong attenuation of replication, the level of RSV-specific serum antibodies induced by rRSV/mGM-CSF was comparable to, or marginally higher than, that of the parental rRSV. The induction of RSV-specific CD8+cytotoxic T cells was moderately reduced during the initial infection, which might be a consequence of reduced antigen expression. Mice infected with rRSV/mGM-CSF had elevated levels of pulmonary mRNA for gamma interferon (IFN-γ) and interleukin 12 (IL-12) p40 compared to animals infected by wild-type rRSV. Elevated synthesis of IFN-γ could account for the restriction of RSV replication, as was observed previously with an IFN-γ-expressing rRSV. The accumulation of total pulmonary mononuclear cells and total CD4+T lymphocytes was accelerated in animals infected with rRSV/mGM-CSF compared to that in animals infected with the control virus, and the level of IFN-γ-positive or IL-4-positive pulmonary CD4+cells was elevated approximately twofold. The number of pulmonary lymphoid and myeloid dendritic cells and macrophages was increased up to fourfold in mice infected with rRSV/mGM-CSF compared to those infected with the parental rRSV, and the mean expression of major histocompatibility complex class II molecules, a marker of activation, was significantly increased in the two subsets of dendritic cells. Enhanced antigen presentation likely accounts for the maintenance of a strong antibody response despite reduced viral replication and would be a desirable property for a live attenuated rRSV vaccine.
Mad-1 Is the Exclusive JC Virus Strain Present in the Human Colon, and Its Transcriptional Control Region Has a Deleted 98-Base-Pair Sequence in Colon Cancer Tissues
Authors: Ricciardiello Luigi , Chang Dong K. , Laghi Luigi , Goel Ajay , Chang Christina L. , Boland C. Richard
Published: July 2002

JC virus (JCV), along with other members of the polyomavirus family, encodes a class of highly conserved proteins, T antigens, that are capable of inducing aneuploidy in cultured cells. We have previously isolated T-antigen DNA variants of JCV from both colon cancer tissues and the corresponding nonneoplastic gastrointestinal tissues, raising new questions about the role of JCV in the development of chromosomal instability of the colon. Based on the sequence of the transcriptional control region (TCR), JCV can be classified as archetype or tandem repeat variants. Among the latter, Mad-1, the prototype virus first isolated from a patient with progressive multifocal leukoencephalopathy, is characterized by lacking the 23- and 66-bp sequences that are present in the archetype and by duplication of a 98-bp sequence. In this study, we evaluated differences in the TCR of JCV isolated from colon cancer tissues and nonneoplastic epithelium. To characterize JCV variants, we first treated eight pairs of DNA samples from colon cancers and noncancerous tissue with topoisomerase I and then amplified and cloned the JCV TCR. We obtained 285 recombinant clones from the JCV TCR, 157 from nonneoplastic samples, and 128 from colon cancer tissues. Of these clones, 262 spanned the length of the JCV Mad-1 TCR: 99.3% from nonneoplastic samples and 82.8% from colon cancer tissues. In sequencing 54 clones in both directions, we did not find archetype JCV either in the nonneoplastic tissue or in the cancer samples. From all colon cancer tissues, 18 clones had a deletion of one 98-bp tandem repeat. This deleted strain was not detected in any of the nonneoplastic tissues (14 versus 0% [χ
2
= 23.6;
P
< 0.001]). Our study demonstrates that the only JCV strain present in the human colon is Mad-1, and the variant with a single 98-bp sequence is found exclusively in the cancer tissues. This strain may be involved in the development of chromosomal instability.
Analysis of Protein Expression from within the Region Encoding the 2.0-Kilobase Latency-Associated Transcript of Herpes Simplex Virus Type 1
Authors: Lock Martin , Miller Cathie , Fraser Nigel W.
Published: July 2002

During latent infections of sensory neurons, herpes simplex virus type 1 gene expression is restricted to the latency-associated transcripts (LATs). The association of the stable 2.0-kb LAT intron with polysomes has suggested that it might represent a novel mRNA. In this work, we investigated expression of 2.0-kb LAT open reading frames (ORFs) by inserting the gene for green fluorescent protein (GFP) within the 2.0-kb LAT sequence, both within a LAT expression plasmid and in the context of the virus. Upon transient transfection of cells of both neuronal and nonneuronal origin with LAT-GFP expression vectors, low-level GFP fluorescence was distributed over the cell cytoplasm and likely resulted from infrequent initiation at a GFP AUG codon, on either unspliced or alternately spliced LAT RNAs. A second nucleolar GFP expression pattern which resulted from fusion of GFP to a conserved ORF in exon 1 of the LAT gene was also observed. However, the abundant expression of this fusion protein was dependent upon an artificially added translation initiation codon. Expression was much reduced and restricted to a small subset of transfected cells when this initator codon was removed. Neither the 2.0-kb LAT-GFP intron itself nor transcripts originating from the latency-associated promoter 2 (LAP2) were responsible for GFP expression. Abundant alternate splicing involving the 1.5-kb LAT splice acceptor and including splicing between the 1.5-kb LAT splice donor and acceptor, was observed in the nonneuronal Cos-1 cell line. Contrary to the results of our transfection studies, GFP expression could not be detected from a LAT-GFP virus at any stage of the infection cycle. Our results suggest that the inhibition of LAT ORF expression during viral infection occurred primarily at the level of translation.
Human B Cells Immortalized with Epstein-Barr Virus Upregulate CCR6 and CCR10 and Downregulate CXCR4 and CXCR5
Authors: Nakayama Takashi , Fujisawa Ryuichi , Izawa Dai , Hieshima Kunio , Takada Kenzo , Yoshie Osamu
Published: July 2002

Compared to peripheral blood resting B cells, Epstein-Barr virus (EBV)-immortalized B cells consistently express CCR6 and CCR10 at high levels and CXCR4 and CXCR5 at low levels. Accordingly, these cells vigorously responded to the ligands of CCR6 and CCR10 but not to those of CXCR4 and CXCR5. In a human EBV-negative B-cell line, BJAB, stable expression of EBNA2 upregulated CCR6, while stable expression of EBNA2 as well as LMP1 downregulated CXCR4. On the other hand, upregulation of CCR10 or downregulation of CXCR5 was not induced in BJAB by stable expression of EBNA2 or LMP1. Thus, these changes may be due to a plasmablast-like stage of B-cell differentiation fixed by EBV immortalization. EBV-infected B cells in infectious mononucleosis are known to avoid germinal centers and accumulate under the mucosal surfaces. EBV-associated opportunistic lymphomas also tend to occur in extranodal sites. These preferred sites of in vivo localization are consistent with the unique profile of chemokine receptor expression exhibited by EBV-immortalized B cells.
The Crystal and Molecular Structure of a Zinc(II) Complex with a New Non-Symmetrical Tetradentate Schiff Base, [Zn(C15H18N3O)Br]
Authors: Ondráček Jan , Kratochvíl Bohumil , Haber Václav
Published: July 2002

The structure of (1-(2-(2-aminoethylamino)ethylimino)methyl-2-napththolato-O,N,N',N")bromozinc(II), [Zn(naden)Br], containing a new Schiff base ligand, naden, was solved by Patterson and Fourier techniques and refined anisotropically to R = 0.047 for 1 426 unique observed reflections. The complex crystallizes in the space group Pbca with lattice parameters a = 14.024(1), b = 10.699(1), c = 21.635(2) Å, Z = 8. The structure of [Zn(C15H18N3O)Br] complex molecule consists of two six-membered aromatic rings and one six-membered and two five-membered chelate rings. The distorted coordinate polyhedron around Zn atom is formed by N1, N2, N3 and O atoms of the naden ligand and Br anion. Unusually short C-C bond in five-membered rings as well as small N-C-C-N torsion angles and somewhat large C4-C3-N2 and N2-C2-C1 angles are probably connected with intense thermal vibrations of C2 and C3 atoms. The structure is hold together by weak hydrogen bonds.
Spectrophotometric Determination of Dimethyl Disulfide in Air Pollutants from the Rubber Industry
Authors: Turek Anna , Skrzydlinska Monika , Ptaszynski Bogdan
Published: July 2002

A spectrophotometric method was developed for the determination of dimethyl disulfide (DMDS) in complex gas mixtures emitted by the rubber industry. The method allows organic disulfides to be quantitated in amounts exceeding 1.5 mg/m3 gas (expressed as DMDS) and can be applied to the determination of disulfides in air at workplace as well as in gaseous products of thermal and biological decomposition of solid substances. The method enables disulfides and mercaptans to be determined simultaneously.
Is a Gas-Phase Cannizzaro-Type Reaction Perspective?
Authors: Šroubková Libuše , Horák Václav , Zahradník Rudolf
Published: July 2002

Quantum chemical calculations for model processes CH2=O + CH2=O-• ⇌ CH3O- + CH=O• and C6H5CH=O + C6H5CH=O-• ⇌ C6H5CH2O- + C6H5C=O• indicate convincingly their endoergicity. Therefore, spontaneous gas-phase Cannizzaro-type reaction between formaldehyde and benzaldehyde and their radical anions is unlikely to occur. This suggests a significant difference between the gas phase reaction under investigation and the classical Cannizzaro reaction.
Inhibition of Plasma Cholinesterase by O-Alkylfluorophosphonates
Authors: Cabal Jiří , Kassa Jiří , Patočka Jiří
Published: July 2002

Inhibition of plasma cholinesterase by three methylfluorophosphonates (MFF), sarin, soman and cyclosin, and by the products of their hydrolysis and alcoholysis was examined. Inhibition by phosphonic acids and by methyl esters derived from MFF was purely competitive while that by MFF was irreversible. The rate of phosphorylation of cholinesterase by MFF differs, depending on the structure of the alkoxy group in the MFF and decreases in the sequence soman-sarin-cyclosin. The affinity values of MFF, phosphonic acids and methyl esters of phosphonic acid for cholinesterase are comparable. The in vitro kinetic parameters suggest that plasma cholinesterase might act as a natural detoxicating agent in cases of poisoning with the above inhibitors of acetylcholinesterase.
Metallaborane Reaction Chemistry. Part 3. Reaction of Carbon Monoxide with [6-H-6-(PPh3)-6P,5C-μ-(2-Ph2PC6H4)-nido-6-IrB9H12] and the Isolation and Characterisation of Two arachno-6-Monoiridadecaboranes [6-(CO)-6-H-6,9-(PPh3)2-6P,5C-μ-(2-Ph2PC6H4)-arachno-6-IrB9H11] and sym-[6-(CO)-6-H-6,6-(PMe2Ph)2-9-(PPh3)-arachno-6-IrB9H11]
Authors: Bould Jonathan , Brint Paul , Kennedy John D. , Thornton-Pett Mark , Barton Lawrence , Rath Nigam P.
Published: July 2002

[6-(CO)-6-H-6,9-(PPh3)2-6P,5C-μ-(2-Ph2PC6H4)-arachno-6-IrB9H11] (1) results from the reaction of [6-H-6-(PPh3)-6P,5C-μ-(2-Ph2PC6H4)-nido-6-IrB9H12] (2) with carbon monoxide in refluxing benzene. It is characterised by NMR spectroscopy and by single-crystal X-ray diffraction analysis. Crystals were triclinic, space group P1, with a = 10.688(2), b = 13.114(3), c = 22.356(5) Å, α = 78.33(2), β = 89.482(10), γ = 70.884(12)°, and Z = 2. The compound is of the little-examined arachno ten-vertex metallaborane structural type. A second compound of this type, [6-(CO)-6-H-6,6-(PMe2Ph)2-9-(PPh3)-arachno-6-IrB9H11] (3), isolated from a reaction system involving [Ir(CO)Cl(PPh3)2], PMe2Ph and the [nido-B9H12]- anion, has also been characterised crystallographically. Crystals were triclinic, space group P1, with a = 10.389(1), b = 10.511(1), c = 19.699(3) Å, α = 75.03(1), β = 85.53(1), γ = 74.88(1)°, and Z = 2.
Opening of Closed Azadecaboranes RNB9H9 by Amines
Authors: Roth Martin , Meyer Franc , Paetzold Peter
Published: July 2002

The aza-closo-decaborane RNB9H9 (4a; R = 4-ClC6H4) is opened to give the nido-cluster RNB9H9(tmeda) (7a) by the addition of Me2N(CH2)2NMe2 (tmeda). The cluster 7a contains the same type of asymmetric hydrogen bridge as is present in the isoelectronic nido-anion [RNB9H10]- (10b, 10c; R = Ph, PhCH2), obtained by the action of KBHEt3 on the corresponding arachno-cluster RNB9H11(NH2t-Bu) (9b, 9c). Secondary amines HNR1R2 yield the azaboranes RNB9H10(NR1R2) (11a-11c; R1/R2 = H/t-Bu, Et/Et, i-Pr/i-Pr). From 2D-1H/11B NMR correlations, concerning the two non-terminal H atoms, and from the 11B NMR shifts, a nido/arachno hybrid structure is deduced for 11a-11c, governed by the contribution of pi-bonding between the lone pair of the amino group and the neighbouring B atom. Amines, like nucleophiles generally, attack the closo-boranes RNB9H9 at one of the B atoms adjacent to the N atom, as expected.
Cyclopropanation of Phenyl Styryl Sulfones with Phenacylsulfonium Ylides Under Phase-Transfer Catalysis
Authors: Padmaja Adivireddi , Reddy Kalluru Ramachandra , Padmavathi Venkatapuram , Bhaskar Reddy Dandu
Published: July 2002

Cyclopropanation of substituted phenyl styryl sulfones 1 with dimethylsulfonium phenacylides was carried out by two different methods (under PTC catalysis with in situ generation of the ylides and by direct addition of ylides) to obtain a series of substituted 1-benzenesulfonyl-2-benzoyl-3-phenylcyclopropanes 2. The PTC method was found to be more facile and efficient. The spectral data of cyclopropanes 2 are discussed.
Pd-Cu Supported on Anionic Polymers - Promising Catalysts for Removal of Nitrates from Drinking Water
Authors: Gašparovičová Dana , Králik Milan , Hronec Milan
Published: July 2002

Removal of nitrates from drinking water by catalytic hydrogenation over polymer supported Pd-Cu catalysts was studied. Precursors of the catalysts were prepared by ion exchange using microporous polymer cation-exchange resin Dowex 50 W X 4 in acid form and acetone-water solution of Pd and Cu acetates. The metals (approximately 2 and 0.5 wt.% of Pd and Cu, respectively) were reduced with NaBH4 in ethanol at room temperature or with H2 in MeOH at 50 °C and 1 MPa. Catalysts made it possible to reduce nitrate content in water from 100 mg/l to less than 50 mg/l after 4 h of batch treatment with hydrogen-nitrogen mixture (43 vol.% H2) at ambient temperature and atmospheric pressure under vigorous stirring of the reaction mixture. The importance of acid sites of the catalyst for the selective hydrogenation of nitrates to nitrogen was demonstrated by a higher overall selectivity (about 60 mole %) obtained on catalysts containing acid sites than on catalysts without acid sites (about 20 mole %). Catalysts bearing acid sites are promising candidates for removal of nitrates, formed ammonia, as well as other cations because of parallel acting as catalysts and cation exchangers. The used catalysts were regenerated with a low concentrated mineral acid.
The Influence of pH on the Structure of Templated Mesoporous Silicas Prepared from Sodium Metasilicate
Authors: Kooyman Patricia J. , Slabová Markéta , Bosáček Vladimír , Čejka Jiří , Rathouský Jiří , Zukal Arnošt
Published: July 2002

A recently developed homogeneous precipitation method was used for the investigation of the influence of pH on the structure of mesoporous silicas prepared from sodium metasilicate in the presence of a quaternary alkyl ammonium surfactant as a structure directing agent. The rate of pH decrease affects the assembly of mesoscopically ordered composites and, consequently, the porous structure of mesoporous silicas prepared from them by calcination. Pure MCM-41 molecular sieve was prepared by controlling the pH decrease of the reaction mixture so as to achieve the final pH 7.8. The as-made material prepared at higher pH (final value 10.1) is characterized by a lower degree of silica polycondensation. Due to the shrinkage of this material during calcination, a less well-ordered silica with extraordinary large surface area was prepared. A large decrease in pH (final value 5.2) led to non-organized polycondensation of silica species besides the organized assembly of the ordered material, which resulted in the formation of silica with a bimodal mesoporous structure.
Traumatic duodenal rupture in a soccer player: Figure 1
Authors: Houshian Shirzad
Published: July 2002

Traumatic duodenal rupture resulting from blunt trauma during soccer is an extremely rare occurrence. A case report of this unusual condition is presented together with a review of the literature.
Perception of changes in wall tension of the proximal stomach in humans
Authors: Piessevaux H , Tack J , Wilmer A , Coulie B , Geubel A , Janssens J
Published: July 2002

BACKGROUND

Hypersensitivity to distension of the stomach is a frequent finding in functional dyspepsia. During gastric distension studies both wall tension and elongation are increased.

AIM

We wished to distinguish changes in wall tension from changes in elongation in the genesis of perception of mechanical stimuli originating from the proximal stomach in healthy subjects.

SUBJECTS AND METHODS

Twenty six volunteers were studied using gastric barostat and antroduodenal manometry. In 14 subjects, stepwise isobaric and isovolumetric distensions were performed before and during erythromycin infusion. In all volunteers, on a separate occasion, phasic contractions of the proximal stomach were detected as intraballoon pressure increases during fixed volume inflation. These contractions were matched with perception changes during two 10 minute periods, before and during administration of erythromycin.

RESULTS

Erythromycin significantly lowered the perception and discomfort thresholds during stepwise gastric distension. During fixed volume inflation, erythromycin increased the number and amplitude of fundic contractions and enhanced their perception from 51.1 (7.4)% to 64.0 (4.7)%. The proportion of perception score increases coinciding with fundic contractions increased from 47.3 (0.7)% to 81.5 (0.5)%. The amplitude of correctly identified isolated fundic pressure waves was higher compared with non-identified waves.

CONCLUSIONS

These results support the hypothesis that changes in gastric wall tension may be involved in the genesis of symptoms originating from the stomach.
Seasonal weight limits on prairie region highways: opportunities for rationalization and harmonization
Authors: Montufar Jeannette , Clayton Alan
Published: July 2002

There are a myriad of laws, regulations, and policies governing the operating weights and dimensions of trucks. In Canada and many northern states, these regulations form a continuum of basic limits, seasonal variations, and overweight/overdimension limits that are legally permitted. This paper deals with the seasonal aspects of weight limits (winter weight premiums and spring weight restrictions) governing trucking within and to and from the prairie region. This region encompasses Manitoba, Saskatchewan, and Alberta, and the northern tier states of Minnesota, North Dakota, and Montana. The paper presents results of research conducted for the transportation departments of the three prairie provinces and Public Works and Government Services Canada. It discusses existing winter weight premium and spring weight restriction regulations, as well as basic weight regulations in the region, and their technical rationale. It examines possibilities for using advanced technologies to help harmonize and rationalize seasonal truck size and weight regulations and enforcement practices, and identifies immediate opportunities for rationalization and harmonization of spring weight restrictions and winter weight premiums.Key words: trucking, weight regulations, spring restrictions, winter premiums, prairie region, harmonization, rationalization.
Minimal promoter for the NAD+-specific glutamate dehydrogenase gene ofNeurospora crassa
Authors: Kapoor M , Curle C A , Kalia S , Achari Y
Published: July 2002

The expression of the NAD+-specific glutamate dehydrogenase (NAD-GDH) gene of Neurospora crassa is subject to catabolite repression. To identify the minimal sequence necessary for promoter function, the 5'-flanking region of the NAD-GDH gene was screened for potential protein-binding sites. Fragments of DNA, containing sequences upstream from the ATG initiation codon, were employed as probes of Southwestern blots of total cellular protein from cells grown in media promoting repression and induction of NAD-GDH. Two polypeptides interacted differentially with a promoter probe; one was present in greater abundance in repressed cells and a higher relative level of the second was witnessed in induced cells. Electrophoretic mobility shift assays with labeled promoter fragments exhibited preferential interaction with proteins in the induced cultures. The upstream sequence containing the putative protein-binding sites was fused with the coding sequence of the green fluorescent protein (GFP). The resulting plasmid was introduced into the microconidia of an albino mutant of N. crassa by electroporation. Stable integration of the plasmid and expression of GFP in the hyphae and conidia of the transformants were demonstrated by Southern and Western blot analysis and fluorescence microscopy.Key words: Neurospora crassa, repression, induction, GFP fusion, electroporation, microconidia.
High-level heterologous expression and secretion inStreptomyces lividansof two major antigenic proteins fromMycobacterium tuberculosis
Authors: Tremblay Donald , Lemay Johanne , Gilbert Michel , Chapdelaine Yvan , Dupont Claude , Morosoli Rolf
Published: July 2002

Two major antigens from Mycobacterium tuberculosis were produced by Streptomyces lividans as secreted extracellular proteins. An expression-secretion vector had been constructed that contained the promoter of xylanase A and the signal sequence of cellulase A. The latter contained two initiation codons preceded by a Shine-Dalgarno sequence plus eight nucleotides complementary to the 16S rRNA. The genes encoding the 38-kDa (Rv0934) and 19-kDa (Rv3763) proteins, respectively, were amplified by polymerase chain reaction and cloned into that vector. The recombinant proteins were then purified from the culture supernatants of the clones. The yields after purification were 80 mg/L for the 38-kDa protein and 200 mg/L for the 19-kDa protein. Sequence analysis of the N-terminal sequences showed a deletion of seven or eight amino acids for the 38-kDa protein, while in the 19-kDa protein 22 or 23 amino acids were lost, as compared with the respective wild-type proteins. However, the 19 kDa recombinant protein had the same N-terminal sequence as the one recovered from the M. tuberculosis culture supernatant. The high yields obtained for these two proteins demonstrated the potential of S. lividans as an alternative host for the production of recombinant proteins from M. tuberculosis. The culture conditions have yet to be worked out to minimize proteolytic degradation and to recover intact products.Key words: streptomycetes, downstream box, signal peptide, protein secretion, Mycobacterium tuberculosis.
The role of hepatocyte growth factor (scatter factor) in epithelialmesenchymal transition and breast cancer
Authors: Elliott Bruce E , Hung Wesley L , Boag Alexander H , Tuck Alan B
Published: July 2002

North American women have a one in eight lifetime risk of developing breast cancer, and approximately one in three women with breast cancer will die of metastases. We, and others, have recently shown that high levels of expression of hepatocyte growth factor (HGF) and its receptor Met are associated with invasive human breast cancer and may be causally linked to metastasis. This high level of HGF and Met expression has been considered as a possible indicator of earlier recurrence and shortened survival in breast cancer patients. In contrast, HGF expression (but not Met) is strongly suppressed in normal breast epithelial cells. HGF and Met are therefore candidate targets for therapeutic intervention in the treatment of breast cancer. We have recently demonstrated that sustained activation or hyper-activation of c-Src and Stat3, which occurs in invasive breast cancer, can stimulate strong expression of HGF in carcinoma cells. In contrast, transient induction of Stat3 occurs in normal epithelium and promotes mammary tubulogenesis. We hypo thesize that increased autocrine HGFMet signaling is a critical downstream function of c-SrcStat3 activation in mammary tumorigenesis. Future studies will identify novel Stat3 consensus sites that regulate HGF promoter activity and HGF expression preferentially in carcinoma cells and could lead to novel therapeutic drugs that specifically block HGF expression in mammary carcinoma cells, and which could be used in combined treatments to abrogate metastasis.Key words: HGF, SrcStat3 signaling, epithelialmesenchymal transition, breast cancer.
THE PRIME GEODESIC THEOREM AND QUANTUM MECHANICS ON FINITE VOLUME GRAPHS: A REVIEW
Authors: HURT NORMAN E.
Published: July 2002

The prime geodesic theorem is reviewed for compact and finite volume Riemann surfaces and for finite and finite volume graphs. The methodology of how these results follow from the theory of the Selberg zeta function and the Selberg trace formula is outlined. Relationships to work on quantum graphs are surveyed. Extensions to compact Riemannian manifolds, in particular to three-dimensional hyperbolic spaces, are noted. Interconnections to the Selberg eigenvalue conjecture, the Ramanujan conjecture and Ramanujan graphs are developed.
GEOMETRY OF UNIVERSAL GRASSMANN MANIFOLD FROM ALGEBRAIC POINT OF VIEW
Authors: TAKASAKI KANEHISA
Published: July 2002

An algebraic formulation of the geometry of the universal Grassmann manifold is presented along the line sketched by Sato and Sato [32]. General issues underlying the notion of infinite-dimensional manifolds are also discussed. A particular choice of affine coordinates on Grassmann manifolds, for both the finite- and infinite-dimensional case, turns out to be very useful for the understanding of geometric structures therein. The so-called “Kac-Peterson cocycle”, which is physically a kind of “commutator anomaly”, then arises as a cocycle of a Lie algebra of infinitesimal transformations on the universal Grassmann manifold. The action of group elements for that Lie algebra is also discussed. These ideas are extended to a multi-component theory. A simple application to a non-linear realization of current and Virasoro algebras is presented for illustration.
SEMI-CLASSICAL INELASTIC S-MATRIX FOR ONE-DIMENSIONAL N-STATES SYSTEMS
Authors: MARTIN PH.A. , NENCIU G.
Published: July 2002

A mathematically fully controlled study of the semi-classical S-matrix associated with one-dimensional N-states systems is presented for energies above the barriers. The transmission coefficients are described by an “effective evolution” model which at high energies approaches the usual “common trajectory” model. In the two-states case a refined Landau-Zener formula describing the cross-over regime between avoided and real crossings is obtained.
A RIGOROUS CONSTRUCTION OF ABELIAN CHERN-SIMONS PATH INTEGRALS USING WHITE NOISE ANALYSIS
Authors: LEUKERT PETER , SCHÄFER JÖRG
Published: July 2002

Using recent results in white noise analysis we rigorously construct Feynman path integrals for abelian Chern-Simons theory. We define Wilson loop variables and show that their expectation is a topological invariant, namely computable in terms of pairwise linking numbers as conjectured by E. Witten.
DIRECT EXPLANATIONS FOR THE DEVELOPMENT AND USE OF A MULTI-LAYER PERCEPTRON NETWORK THAT CLASSIFIES LOW-BACK-PAIN PATIENTS
Authors: VAUGHN M. L. , CAVILL S. J. , TAYLOR S. J. , FOY M. A. , FOGG A. J. B.
Published: July 2002

Using a new method published by the first author, this article shows how direct explanations can be provided to interpret the classification of any input case by a standard multilayer perceptron (MLP) network. The method is demonstrated for a real-world MLP that classifies low-back-pain patients into three diagnostic classes. The application of the method leads to the discovery of a number of mis-diagnosed training and test cases and to the development of a more optimal low-back-pain MLP network.
NEURAL NETWORK BASED AUTOMATIC DIAGNOSIS OF CHILDREN WITH BRAIN DYSFUNCTION
Authors: CHO SUNGZOON , SHIN MIN SUP
Published: July 2002

This paper proposes the use of multilayer perceptron for brain dysfunction diagnosis. The performance of MLP was better than that of Discriminant Analysis and Decision Tree classifiers, with an 85% accuracy rate in an experimental test involving 332 subjects. In addition, the neural network employing Bayesian learning was able to identify the most important input variable. These two results demonstrate that the neural network can be effectively used in the diagnosis of children with brain dysfunction.
SELF-DUAL POINCARÉ GAUGE THEORY OF GRAVITATION
Authors: ZET G. , MANTA V.
Published: July 2002

A model of Poincaré gauge self-dual theory over the Minkowski space–time, endowed with spherical symmetry, is considered. The self-duality (S-D) conditions are imposed and two sets of the self-duality equations for the gauge fields are obtained: one for the torsion tensor and another for the curvature tensor. An analytical solution of the gauge field equations is also obtained. The Yang–Mills (Y–M) equations of the gauge fields are also derived. It is shown that these Y–M equations can be obtained from the S-D equations, a result which is generally true for any S-D gauge theory. Most of all calculations are performed using the GRTensorII package, running on the MapleV platform.
SOME MARKET EFFECTS OF E-COMMERCE
Authors: FREEBAIRN JOHN
Published: July 2002

An important characteristic of E-commerce is that it is a form of technological change. The effects of E-commerce induced reductions in business production costs and on seller to buyer transaction costs are assessed. Comparative static models for different market structures are used to assess the effects of E-commerce on prices, quantities, aggregate efficiency gains, and the distribution of benefits and costs. Ultimately consumers are the principal beneficiaries via lower prices. Competitive forces and profit incentives induce firms to adopt cost reducing E-commerce technology.
A GENERAL RELATIVISTIC MODEL FOR SAX J1808.4-3658
Authors: SHARMA R. , MUKHERJEE S. , DEY MIRA , DEY JISHNU
Published: July 2002

We discuss the physical applicability of a model for a class of compact stars, employing Vaidya–Tikekar12 geometry of space–time. It is shown that the model can generate an equation of state (EOS) very similar to the one obtained by earlier workers for SAX J1808.4-3658 (SAX in short), assumed to be a strange star. The stellar configuration, as described by the model, is shown to be stable under radial perturbations. This may explain why the star SAX is known to be very stable compared to other low mass binary X-ray emitters.
THEORY OF ELECTROWEAK INTERACTIONS WITHOUT SPONTANEOUS SYMMETRY BREAKING
Authors: LI BING AN
Published: July 2002

An electroweak theory without spontaneous symmetry breaking is studied in this paper. A new symmetry breaking of SU (2)L × U (1), axial-vector symmetry breaking, caused by the combination of the axial-vector component of the intermediate boson and the fermion mass is found in electroweak theory. The mass of the W boson is resulted in the combination of the axial-vector symmetry breaking and the explicit symmetry breaking by the fermion masses. The Z boson gains mass from the axial-vector symmetry breaking only. [Formula: see text], [Formula: see text], and [Formula: see text] are obtained. They are in excellent agreement with data. The SU (2)L × U (1) invariant generating functional of the Green functions is constructed and the theory is proved to be renormalizable.
DEPENDENCE OF EXCITON FORMATION ON ITS CENTER-OF-MASS MOMENTUM IN QUANTUM WELLS
Authors: OH I.-K. , SINGH JAI
Published: July 2002

We present a comprehensive study of the process of exciton formation due to exciton-phonon interaction. Using the exciton-phonon interaction arising from deformation potential, piezoelectric, and polar couplings, we have calculated the rate of formation of an exciton as a function of carrier densitiies, temperatures, and center-of-mass momentum ( K ‖) in quantum wells. Our results show that excitons are dominantly formed at non-zero K ‖, which agrees very well with experiments. The formation of an exciton due to emission of longitudinal optical phonon is found to be more efficient at relatively small values of K ‖, and that due to acoustic phonon emission is more efficient at relatively large K ‖ values for carrier temperature Te-h≲50 K.
SCALING APPROACH TO THE ANISOTROPIC NONLOCAL KARDAR–PARISI–ZHANG EQUATION WITH SPATIALLY CORRELATED NOISE
Authors: TANG GANG , MA BENKUN
Published: July 2002

The scaling approach proposed by Hentschel and Family [Phys. Rev. Lett.66, 1982 (1991)] is generalized to the studies of the scaling of the anisotropic nonlocal Kardar–Parisi–Zhang equation with spatially correlated noise. The scaling exponents in both the weak- and strong-coupling regions are obtained, respectively. The scaling exponents obtained in the weak-coupling region can well match the results of the dynamic renormalization-group analysis.
QUANTUM PROTECTORATE AND MICROSCOPIC MODELS OF MAGNETISM
Authors: KUZEMSKY A. L.
Published: July 2002

Some physical implications involved in a new concept, termed the "quantum protectorate" (QP), are developed and discussed. This is done by considering the idea of quantum protectorate in the context of quantum theory of magnetism. It is suggested that the difficulties in the formulation of quantum theory of magnetism at the microscopic level, that are related to the choice of relevant models, can be understood better in the light of the QP concept. We argue that the difficulties in the formulation of adequate microscopic models of electron and magnetic properties of materials are intimately related to dual, itinerant and localized behaviour of electrons. We formulate a criterion of what basic picture describes best this dual behaviour. The main suggestion is that quasi-particle excitation spectra might provide distinctive signatures and good criteria for the appropriate choice of the relevant model.
NANOCRYSTALLINE DIAMOND THIN FILMS AS INFRARED OPTICAL PROTECTIVE COATINGS
Authors: LI JINGQI , HE DEYAN , GUO WANTU , ZHANG JIHUA , SUN YINING , LEI QINGSONG , GAO XIN
Published: July 2002

Nanocrystalline diamond thin films have been grown on both sides of Si wafer by microwave plasma-enhanced chemical vapor deposition using a mixture of CH4 and H2 as source gas. It was shown that infrared transmission of Si has been greatly enhanced and the maximum transmittance reaches 85%. By optimizing the film thickness, we can obtain the maximum increment in the desired infrared wavelength range. Sand spraying test showed that, while the bare Si substrate exhibited obvious surface damage, no damage could be observed on the diamond surface after the sand spraying. The results confirm that the nanocrystalline diamond films coated on Si can not only increase the infrared transmission but also act as a protective coating.