bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of Gamma Interferon in Chemokine Expression in the Ileum of Mice and in a Murine Intestinal Epithelial Cell Line afterCryptosporidium parvumInfection
Authors: Lacroix-Lamandé Sonia , Mancassola Roselyne , Naciri Muriel , Laurent Fabrice
Published: July 2002

Cryptosporidium parvumis a protozoan parasite that infects intestinal epithelial cells and induces inflammation of the intestine. To better understand the inflammatory process occurring during cryptosporidiosis, we investigated in this study the kinetics of chemokine expression in the mucosa of mice by quantitative reverse transcription-PCR. Our results demonstrate that among the chemokine mRNAs studied, gamma interferon (IFN-γ)-inducible protein 10 (IP-10), monokine induced by IFN-γ (MIG), i-TAC, lymphotactin, macrophage inflammatory protein 1β (MIP-1β), and RANTES mRNAs were strongly up-regulated in infected neonate mice, which correlated with the immunofluorescence staining results showing T-cell and macrophage infiltration in the mucosa. Our in vitro data showed that intestinal epithelial cells infected byC. parvumor stimulated by the proinflammatory cytokines (IFN-γ, interleukin-1β, and tumor necrosis factor alpha) produce a pattern of chemokine secretion similar to that observed in vivo, suggesting that these cells may take part in the initial production of chemokines. In order to identify the chemokines responsible for the recruitment of the inflammatory cells leading to a protective immune response, we compared the patterns of chemokine expression in a healing neonate mouse model and a nonhealing IFN-γ knockout (GKO) mouse model of cryptosporidiosis. In the absence of IFN-γ, the chemokine response was altered for IP-10, MIG, i-TAC, RANTES, and MIP-1β mRNAs, while the three ELR C-X-C chemokine mRNAs studied (lipopolysaccharide-induced C-X-C chemokine, MIP-2α, and KC mRNAs) were strongly overexpressed. These results are consistent with the neutrophil recruitment observed in the lamina propria of GKO mice at day 9 postinfection but are not consistent with the hypothesis that these cells play an important role in the resolution of the infection. On the contrary, the altered response of chemokines responsible for the recruitment of macrophages and T cells in GKO mice suggests that these two populations may be critical in the development of a protective immune response.
The Promoter of the Yeast
INO4
Regulatory Gene: a Model of the Simplest Yeast Promoter
Authors: Robinson Kelly A. , Lopes John M.
Published: July 2002

In
Saccharomyces cerevisiae
, the phospholipid biosynthetic genes are transcriptionally regulated in response to inositol and choline. This regulation requires the transcriptional activator proteins Ino4p and Ino2p, which form a heterodimer that binds to the UAS

INO

element. We have previously shown that the promoters of the
INO4
and
INO2
genes are among the weakest promoters characterized in yeast. Because little is known about the promoters of weakly expressed yeast genes, we report here the analysis of the constitutive
INO4
promoter. Promoter deletion constructs scanning 1,000 bp upstream of the
INO4
gene identified a small region (−58 to −46) that is absolutely required for expression. S1 nuclease mapping shows that this region contains the transcription start sites for the
INO4
gene. An additional element (−114 to −86) modestly enhances
INO4
promoter activity (fivefold). Thus, the region required for
INO4
transcription is limited to 68 bp. These studies also found that
INO4
gene expression is not autoregulated by Ino2p and Ino4p, despite the presence of a putative UAS

INO

element in the
INO4
promoter. We further report that the
INO4
steady-state transcript levels and Ino4p levels are regulated twofold in response to inositol and choline, suggesting a posttranscriptional mechanism of regulation.
Cholate Resistance in
Lactococcus lactis
Is Mediated by an ATP-Dependent Multispecific Organic Anion Transporter
Authors: Yokota Atsushi , Veenstra Marloes , Kurdi Peter , van Veen Hendrik W. , Konings Wil N.
Published: July 2002

The cholate-resistant
Lactococcus lactis
strain C41-2, derived from wild-type
L. lactis
MG1363 through selection for growth on cholate-containing medium, displayed a reduced accumulation of cholate due to an enhanced active efflux. However,
L. lactis
C41-2 was not cross resistant to deoxycholate or cationic drugs, such as ethidium and rhodamine 6G, which are typical substrates of the multidrug transporters LmrP and LmrA in
L. lactis
MG1363. The cholate efflux activity in
L. lactis
C41-2 was not affected by the presence of valinomycin plus nigericin, which dissipated the proton motive force. In contrast, cholate efflux in
L. lactis
C41-2 was inhibited by
ortho
-vanadate, an inhibitor of P-type ATPases and ATP-binding cassette transporters. Besides ATP-dependent drug extrusion by LmrA, two other ATP-dependent efflux activities have previously been detected in
L. lactis
, one for the artificial pH probe 2′,7′-bis-(2-carboxyethyl)-5(and 6)-carboxyfluorescein (BCECF) and the other for the artificial pH probe
N
-(fluorescein thio-ureanyl)-glutamate (FTUG). Surprisingly, the efflux rate of BCECF, but not that of FTUG, was significantly enhanced in
L. lactis
C41-2. Further experiments with
L. lactis
C41-2 cells and inside out membrane vesicles revealed that cholate and BCECF inhibit the transport of each other. These data demonstrate the role of an ATP-dependent multispecific organic anion transporter in cholate resistance in
L. lactis.
Effects of Nonpolar Mutations in Each of the SevenBacillus subtilis mrpGenes Suggest Complex Interactions among the Gene Products in Support of Na+and Alkali but Not Cholate Resistance
Authors: Ito Masahiro , Guffanti Arthur A. , Wang Wei , Krulwich Terry A.
Published: July 2002

TheBacillus subtilis mrp(multiple resistance and pH) operon supports Na+and alkali resistance via an Na+/H+antiport, as well as cholate efflux and resistance. Among the individual mutants with nonpolar mutations in each of the sevenmrpgenes, only themrpFmutant exhibited cholate sensitivity and a cholate efflux defect that were complemented by expression of the deleted genein trans. Expression ofmrpFin themrpnull (VKN1) strain also restored cholate transport and increased Na+efflux, indicating that MrpF does not require even low levels of othermrpgene expression for its own function. In contrast to MrpF, MrpA function had earlier seemed to depend upon at least modest expression of othermrpgenes, i.e.,mrpArestored Na+resistance and efflux to strain VK6 (a polarmrpAmutant which expresses low levels ofmrpBto -G) but not to the null strain VKN1. In a wild-type background, each nonpolar mutation in individualmrpgenes caused profound Na+sensitivity at both pH 7.0 and 8.3. ThemrpAandmrpDmutants were particularly sensitive to alkaline pH even without added Na+. While transport assays in membrane vesicles from selected strains indicated that MrpA-dependent antiport can occur by a secondary, proton motive force-dependent mechanism, the requirement for multiplemrpgene products suggests that there are features of energization, function, or stabilization that differ from typical secondary membrane transporters. Northern analyses indicated regulatory relationships amongmrpgenes as well. All themrpmutants, especially themrpA,-B,-D,-E, and-Gmutants, had elevated levels ofmrpRNA relative to the wild type. Expression of an upstream gene,maeN, that encodes an Na+/malate symporter, was coordinately regulated withmrp, although it is not part of the operon.
The N-Terminal Region of the
Oenococcus oeni
Bacteriophage fOg44 Lysin Behaves as a Bona Fide Signal Peptide in
Escherichia coli
and as a
cis
-Inhibitory Element, Preventing Lytic Activity on Oenococcal Cells
Authors: São-José Carlos , Parreira Ricardo , Vieira Graça , Santos Mário A.
Published: July 2002

The function of the N-terminal region of the
Oenococcus oeni
phage fOg44 lysin (Lys44) as an export signal was investigated. We observed that when induced in
Escherichia coli
, Lys44 was cleaved between residues 27 and 28 in a SecA-dependent manner. Lys44 processing could be blocked by a specific signal peptidase inhibitor and was severely reduced by modification of the cleavage site. The lethal effect of Lys44 expression observed in
E. coli
was ascribed to the presence of its N-terminal 27-residue sequence, as its deletion resulted in the production of a nontoxic, albeit active, product. We have further established that lytic activity in oenococcal cells was dependent on Lys44 processing. An active protein with the molecular mass expected for the cleaved enzyme was detected in extracts from
O. oeni
-infected cells. The temporal pattern of its appearance suggests that synthesis and export of Lys44 in the infected host progress along with phage maturation. Overall, these results provide, for the first time, experimental evidence for the presence of a signal peptide in a bacteriophage lysin. Database searches and alignment of protein sequences support the prediction that other known
O. oeni
and
Lactococcus lactis
phages also encode secretory lysins. The evolutionary significance of a putative phage lysis mechanism relying on secretory lytic enzymes is tentatively discussed, on the basis of host cell wall structure and autolytic capacity.
Regulation of the
glv
Operon in
Bacillus subtilis
: YfiA (GlvR) Is a Positive Regulator of the Operon That Is Repressed through CcpA and
cre
Authors: Yamamoto Hiroki , Serizawa Masakuni , Thompson John , Sekiguchi Junichi
Published: July 2002

Maltose metabolism and the regulation of the
glv
operon of
Bacillus subtilis
, comprising three genes,
glvA
(6-phospho-α-glucosidase),
yfiA
(now designated
glvR
), and
glvC
(EIICB transport protein), were investigated. Maltose dissimilation was dependent primarily upon the
glv
operon, and insertional inactivation of either
glvA, glvR
, or
glvC
markedly inhibited growth on the disaccharide. A second system (MalL) contributed to a minor extent to maltose metabolism. Northern blotting revealed two transcripts corresponding to a monocistronic mRNA of
glvA
and a polycistronic mRNA of
glvA-glvR-glvC
. Primer extension analysis showed that both transcripts started at the same base (G) located 26 bp upstream of the 5′ end of
glvA
. When
glvR
was placed under control of the
spac
promoter, expression of the
glv
operon was dependent upon the presence of isopropyl-β-
d
-thiogalactopyranoside (IPTG). In regulatory studies, the promoter sequence of the
glv
operon was fused to
lacZ
and inserted into the
amyE
locus, and the resultant strain (AMGLV) was then transformed with a citrate-controlled
glvR
plasmid, pHYCM2VR. When cultured in Difco sporulation medium containing citrate, this transformant [AMGLV(pHYCM2VR)] expressed LacZ activity, but synthesis of LacZ was repressed by glucose. In an isogenic strain, [AMGLVCR(pHYCM2VR)], except for a mutation in the sequence of a catabolite-responsive element (
cre
), LacZ activity was expressed in the presence of citrate and glucose. Insertion of a citrate-controlled
glvR
plasmid at the
amyE
locus of
ccpA
+
and
ccpA
mutant organisms yielded strains AMCMVR and AMCMVRCC, respectively. In the presence of both glucose and citrate, AMCMVR failed to express the
glv
operon, whereas under the same conditions high-level expression of both mRNA transcripts was found in strain AMCMVRCC. Collectively, our findings suggest that GlvR (the product of the
glvR
gene) is a positive regulator of the
glv
operon and that glucose exerts its effect via catabolite repression requiring both CcpA and
cre
.
Involvement of a Cytochrome P450 Monooxygenase in Thaxtomin A Biosynthesis by
Streptomyces acidiscabies
Authors: Healy F. G. , Krasnoff S. B. , Wach M. , Gibson D. M. , Loria R.
Published: July 2002

The biosynthesis of the thaxtomin cyclic dipeptide phytotoxins proceeds nonribosomally via the thiotemplate mechanism. Acyladenylation, thioesterification,
N
-methylation, and cyclization of two amino acid substrates are catalyzed by the
txtAB
-encoded thaxtomin synthetase. Nucleotide sequence analysis of the region 3′ of
txtAB
in
Streptomyces acidiscabies
84.104 identified an open reading frame (ORF) encoding a homolog of the P450 monooxygenase gene family. It was proposed that thaxtomin A phenylalanyl hydroxylation was catalyzed by the monooxygenase homolog. The ORF was mutated in
S. acidiscabies
84.104 by using an integrative gene disruption construct, and culture filtrate extracts of the mutant were assayed for the presence of dehydroxy derivatives of thaxtomin A. Reversed-phase high-performance liquid chromatography (HPLC) and HPLC-mass spectrometry indicated that the major component in culture filtrate extracts of the mutant was less polar and smaller than thaxtomin A. Comparisons of electrospray mass spectra as well as
1
H- and
13
C-nuclear magnetic resonance spectra of the purified compound with those previously reported for thaxtomins confirmed the structure of the compound as 12,15-
N
-dimethylcyclo-(
l
-4-nitrotryptophyl-
l
-phenylalanyl), the didehydroxy analog of thaxtomin A. The ORF, designated
txtC
, was cloned and the recombinant six-His-tagged fusion protein produced in
Escherichia coli
and purified from cell extracts. TxtC produced in
E. coli
exhibited spectral properties similar to those of cytochrome P450-type hemoproteins that have undergone conversion to the catalytically inactive P420 form. Based on these properties and the high similarity of TxtC to other well-characterized P450 enzymes, we conclude that
txtC
encodes a cytochrome P450-type monooxygenase required for postcyclization hydroxylation of the cyclic dipeptide.
Use of an Enzyme Immunoassay Does Not Eliminate the Need To Analyze Multiple Stool Specimens for Sensitive Detection of
Giardia lamblia
Authors: Hanson Kevan L. , Cartwright Charles P.
Published: July 2002

The relative sensitivities of a commercially available enzyme immunoassay (EIA) (ProSpecT
Giardia
; Alexon-Trend Inc., Ramsey, Minn.) and conventional ovum-and-parasite (O&P) examination for the detection of
Giardia lamblia
in preserved stool specimens were determined. Paired stool samples collected independently within a 7-day period from 103 patients were analyzed by both methods. A total of 54 specimens from 30 patients (18 asymptomatically infected with
G. lamblia
and 12 with symptoms consistent with intestinal giardiasis) were determined to be positive for
G. lamblia
, of which 48 (88.9%) were positive by microscopy and 52 (96.3%) were positive by EIA. Both specimens submitted were positive for
G. lamblia
by O&P examination for 66.7% (20 of 30) of the positive patients; for 26.7% (8 of 30) a single specimen was positive by O&P examination, and for 6.7% (2 of 30) of those determined to be infected with
G. lamblia
, both samples were negative by microscopy. The sensitivity of conventional O&P examination was somewhat higher in symptomatically infected individuals, with 75% (9 of 12) of patients in this category having
G. lamblia
detected in both samples, compared with 61% (11 of 18) of asymptomatic patients. A total of 24 positive patients (80%) had
G. lamblia
antigen detected by EIA in both submitted samples, 4 positive patients (13.3%) had one specimen positive by EIA, and the EIA was negative in both specimens from 2 infected individuals (6.5%), the sensitivity of EIA was substantially equivalent in asymptomatic and symptomatic individuals (77 versus 83% of patients with positive results on both specimens). Although the sensitivity of EIA for the detection of
G. lamblia
on a single stool specimen was somewhat higher than that of conventional O&P examination in symptomatic patients (83 versus 75%), in asymptomatic patients (77 versus 61%), and overall (80 versus 67%), examination of two specimens by either EIA or microscopy was necessary to achieve a diagnostic sensitivity of greater than 90%.
Rapid and Sensitive Oligonucleotide Ligation Assay for Detection of Mutations in Human Immunodeficiency Virus Type 1 Associated with High-Level Resistance to Protease Inhibitors
Authors: Beck Ingrid A. , Mahalanabis Madhumita , Pepper Gregory , Wright Amy , Hamilton Shannon , Langston Erika , Frenkel Lisa M.
Published: July 2002

A sensitive, specific, and high-throughput oligonucleotide ligation assay (OLA) for the detection of genotypic human immunodeficiency virus type 1 (HIV-1) resistance to Food and Drug Administration-approved protease inhibitors was developed and evaluated. This ligation-based assay uses differentially modified oligonucleotides specific for wild-type or mutant sequences, allowing sensitive and simple detection of both genotypes in a single well of a microtiter plate. Oligonucleotides were designed to detect primary mutations associated with high-level resistance to amprenavir, nelfinavir, indinavir, ritonavir, saquinavir, and lopinavir, including amino acid substitutions D30N, I50V, V82A/S/T, I84V, N88D, and L90M. Plasma HIV-1 RNA from 54 infected patients was amplified by reverse transcription-PCR and sequenced by using dideoxynucleotide chain terminators for evaluation of mutations associated with drug resistance. These same amplicons were genotyped by the OLA at positions 30, 50, 82, 88, 84, and 90 for a total of 312 codons. The sensitivity of detection of drug-resistant genotypes was 96.7% (87 of 90 mutant codons) in the OLA compared to 92.2% (83 of 90) in consensus sequencing, presumably due to the increased sensitivity of the OLA. The OLA detected genetic subpopulations more often than sequencing, detecting 30 mixtures of mutant and wild-type sequences and two mixtures of drug-resistant sequences compared to 15 detected by DNA sequencing. Reproducible and semiquantitative detection of the mutant and the wild-type genomes by the OLA was observed by analysis of wild-type and mutant plasmid mixtures containing as little as 5% of either genotype in a background of the opposite genome. This rapid, simple, economical, and highly sensitive assay provides a practical alternative to dideoxy sequencing for genotypic evaluation of HIV-1 resistance to antiretrovirals.
Interaction of Epstein-Barr Virus Nuclear Antigen Leader Protein (EBNA-LP) with HS1-Associated Protein X-1: Implication of Cytoplasmic Function of EBNA-LP
Authors: Kawaguchi Yasushi , Nakajima Kaori , Igarashi Mie , Morita Tomoko , Tanaka Michiko , Suzuki Mikiko , Yokoyama Akihiko , Matsuda Go , Kato Kentaro , Kanamori Mikiko , Hirai Kanji
Published: July 2002

Epstein-Barr virus (EBV) nuclear antigen leader protein (EBNA-LP) consists of W1W2 repeats and a unique C-terminal Y1Y2 domain and has been suggested to play an important role in EBV-induced transformation. To identify the cellular factors interacting with EBNA-LP, we performed a yeast two-hybrid screen, using EBNA-LP cDNA containing four W1W2 repeats as bait and an EBV-transformed human peripheral blood lymphocyte cDNA library as the source of cellular genes. Our results were as follows. (i) All three cDNAs in positive yeast colonies were found to encode the same cellular protein, HS1-associated protein X-1 (HAX-1), which is localized mainly in the cytoplasm and has been suggested to be involved in the regulation of B-cell signal transduction and apoptosis. (ii) Mutational analysis of EBNA-LP revealed that the association with HAX-1 is mediated by the W1W2 repeat domain. (iii) A purified chimeric protein consisting of glutathioneS-transferase fused to EBNA-LP specifically formed complexes with HAX-1 transiently expressed in COS-7 cells. (iv) When EBNA-LP and HAX-1 were coexpressed in COS-7 cells, EBNA-LP was specifically coimmunoprecipitated with HAX-1. (v) Careful cell fractionation experiments of an EBV-infected lymphoblastoid cell line revealed that EBNA-LP is localized in the cytoplasm as well as in the nucleus. (vi) When EBNA-LP containing four W1W2 repeats was expressed in COS-7 cells, EBNA-LP was detected mainly in the nucleus by immunofluorescence assay. Interestingly, when EBNA-LP containing a single W1W2 repeat was expressed in COS-7 cells, EBNA-LP was localized predominantly in the cytoplasm and was colocalized with HAX-1. These results indicate that EBNA-LP is in fact present and may have a significant function in the cytoplasm, possibly by interacting with and affecting the function of HAX-1.
Recessive Resistance in
Pisum sativum
and Potyvirus Pathotype Resolved in a Gene-for-Cistron Correspondence between Host and Virus
Authors: Johansen I. Elisabeth , Lund Ole Søgaard , Hjulsager Charlotte K. , Laursen Jesper
Published: July 2002

Pea seed-borne mosaic potyvirus (PSbMV) isolates are divided into pathotypes P-1, P-2, and P-4 according to their infection profile on a panel of
Pisum sativum
lines.
P. sativum
PI 269818 is resistant to P-1 and P-2 isolates and is susceptible to P-4 isolates. Resistance to P-1 is inherited as a single recessive gene, denoted
sbm-1,
and the pathogenicity determinant has previously been mapped to the virus-coded protein VPg. In the cultivar Bonneville, a second recessive gene,
sbm-2,
confers specific resistance to P-2. By exchanging cistrons between a P-2 and a P-4 isolate, the P3-6k1 cistron was identified as the PSbMV host-specific pathogenicity determinant on Bonneville. Exchange of P3-6k1 did not affect infection on PI 269818, and infection of Bonneville was not altered by substitution of the VPg cistron, indicating that P3-6k1 and VPg are independent determinants of pathotype-specific infectivity. On PI 269818 the pathogenicity determinant of both P-1 and P-2 mapped to the N terminus of VPg. This suggests that VPg from the P-1 and P-2 isolates are functionally similar on this host and that resistance to P-1 and P-2 in PI 269818 may operate by the same mechanism. Identification of VPg–
sbm-1
and P3-6k1–
sbm-2
as independent pairs of genetic interactors between PSbMV and
P. sativum
provides a simple explanation of the three known pathotypes of PSbMV. Furthermore, analysis of β-glucuronidase-tagged P-2 virus indicated that
sbm-2
resistance affected an early step in infection, implying that the P3-6k1 region plays a critical role in potyvirus replication or cell-to-cell movement.
Reovirus ςNS Protein Is Required for Nucleation of Viral Assembly Complexes and Formation of Viral Inclusions
Authors: Becker Michelle M. , Goral Mehmet I. , Hazelton Paul R. , Baer Geoffrey S. , Rodgers Steven E. , Brown Earl G. , Coombs Kevin M. , Dermody Terence S.
Published: July 2002

Progeny virions of mammalian reoviruses are assembled in the cytoplasm of infected cells at discrete sites termed viral inclusions. Studies of temperature-sensitive (
ts
) mutant viruses indicate that nonstructural protein ςNS and core protein μ2 are required for synthesis of double-stranded (ds) RNA, a process that occurs at sites of viral assembly. We used confocal immunofluorescence microscopy and
ts
mutant reoviruses to define the roles of ςNS and μ2 in viral inclusion formation. In cells infected with wild-type (wt) reovirus, ςNS and μ2 colocalize to large, perinuclear structures that correspond to viral inclusions. In cells infected at a nonpermissive temperature with ςNS-mutant virus
tsE320
, ςNS is distributed diffusely in the cytoplasm and μ2 is contained in small, punctate foci that do not resemble viral inclusions. In cells infected at a nonpermissive temperature with μ2-mutant virus
tsH11.2
, μ2 is distributed diffusely in the cytoplasm and the nucleus. However, ςNS localizes to discrete structures in the cytoplasm that contain other viral proteins and are morphologically indistinguishable from viral inclusions seen in cells infected with wt reovirus. Examination of cells infected with wt reovirus over a time course demonstrates that ςNS precedes μ2 in localization to viral inclusions. These findings suggest that viral RNA-protein complexes containing ςNS nucleate sites of viral replication to which other viral proteins, including μ2, are recruited to commence dsRNA synthesis.
Efficient Activation of Viral Genomes by Levels of Herpes Simplex Virus ICP0 Insufficient To Affect Cellular Gene Expression or Cell Survival
Authors: Hobbs William E. , Brough Douglas E. , Kovesdi Imre , DeLuca Neal A.
Published: July 2002

Herpes simplex virus (HSV) ICP0 can effectively activate gene expression from otherwise silent promoters contained on persisting viral genomes. However, the expression of high levels of ICP0, as from ICP4
−
HSV type 1 (HSV-1) vectors, results in marked toxicity. We have analyzed the results of ICP0 expressed from an E1
−
E4
−
adenovirus vector (AdS.11E4ICP0) in which ICP0 expression is controlled from the endogenous adenoviral E4 promoter. In this system, the expression level of ICP0 was reduced more than 1,000-fold relative to the level of expression from HSV-1 vectors. This low level of ICP0 did not affect cellular division or greatly perturb cellular metabolism as assessed by gene expression array analysis comparing the effects of HSV and adenovirus vector strains. However, this amount of ICP0 was sufficient to quantitatively destroy ND10 structures as measured by promyelocytic leukemia immunofluorescence. The levels of adenovirus-expressed ICP0 were sufficient to activate quiescent viral genomes in
trans
and promote persistent transgene expression in
cis
. Moreover, infection of complementing cells with AdS.11E4ICP0 promoted viral growth and resulted in a 20-fold increase in the plaquing efficiency of
d
109, a virus defective for all five immediate-early genes. Thus, the low level expression of ICP0 from the E1
−
E4
−
adenovirus vector may increase the utility of adenovirus vectors and also provides a means to efficiently quantify and possibly propagate HSV vectors defective in ICP0. Importantly, the results demonstrate that the activation function of ICP0 may not result from changes in cellular gene expression, but possibly as a direct consequence of an enzymatic function inherent to the protein that may involve its action at ND10 resulting in the preferential activation of viral genomes.
Palindromic Sequence Plays a Critical Role in Human Foamy Virus Dimerization
Authors: Cain Dionne , Erlwein Otto , Grigg Andrew , Russell Rebecca A. , McClure Myra O.
Published: July 2002

The retroviral RNA genome is dimeric, consisting of two identical strands of RNA linked near their 5′ ends by a dimer linkage structure. Previously it was shown that human foamy virus (HFV) RNA transcribed in vitro contained three sites, designated SI, SII, and SIII, which contributed to the dimerization process (O. Erlwein, D. Cain, N. Fischer, A. Rethwilm, and M. O. McClure, Virology 229:251–258, 1997). To characterize these sites further, a series of mutants were designed and tested for their ability to dimerize in vitro. The primer binding site and a G tetrad in SI were dispensable for dimerization. However, a mutant that changed the 3′ end of SI migrated slower on nondenaturing gels than wild-type RNA dimers. The sequence composition of the SII palindrome, consisting of 10 nucleotides, proved to be critical for in vitro dimerization, since mutations within this sequence or replacement of the sequence with a different palindrome of equal length impaired in vitro dimerization. The length of the palindrome also seems to play an important role. A moderate extension to 12 nucleotides was tolerated, whereas an extension to 16 nucleotides or more impaired dimerization. When nucleotides flanking the palindrome were mutated in a random fashion, dimerization was unaffected. Changing the SIII sequence also led to decreased dimer formation, confirming its contribution to the dimerization process. Interesting mutants were cloned into the infectious molecular clone of HFV, HSRV-2, and were transfected into BHK-21 cells. Mutations in SII that reduced dimerization in vitro also abolished virus replication. In contrast, constructs containing mutations in SI and SIII replicated to some extent in cell culture after an initial drop in viral replication. Analysis of the SIM1 mutant revealed reversion to the wild type but with the insertion of an additional two nucleotides. Analysis of cell-free virions demonstrated that both replication-competent and replication-defective mutants packaged nucleic acid. Thus, efficient dimerization is a critical step for HFV to generate infectious virus, but HFV RNA dimerization is not a prerequisite for packaging.
Some Observations on Effect of Fluorescent Substances on Lucigenin Chemiluminescent Reaction
Authors: Tomová Viera , Magdolen Peter
Published: July 2002

The effect of several substances (e.g. fluorescein, eosin B, pyronin G, coumarin, glucose etc.) on the chemiluminescent reaction of lucigenin was examined. The best enhancer of the initial light intensity is eosin B (2.3 times). Fluorescein and pyronin G enhance the intensity of chemiluminescent reaction in time (t1/2 = 8.6 versus t1/2 = 7.49 min and t1/2 = 12.6 versus t1/2 = 7.09 min, respectively).
Synthesis of Some New 8-Quinolinyloxy-5-sulfonamide Derivatives
Authors: Abdel Hafez Ali A. , Geies Ahmed A. , Hozien Zeinab A. , Khalil Zarif H.
Published: July 2002

5-Sulfonyl-8-quinolinol was used for the synthesis of various derivatives. This attempt was directed by knowledge that 8-quinolinol was utilized in the synthesis of biologically active heterocycles as bactericides, fungicides and bioregulators. The biological and pesticidal activity of 1,3,4-oxadiazoles, as well as the pharmacological interest of the quinoline moiety, are well known, too.
Salt Separation by Charged Membranes
Authors: Schauer Jan , Kobayashi Takaomi
Published: July 2002

Two negatively charged membranes made from poly(acrylonitrile-co-sodium styrenesulfonate) having ion exchange capacity of 0.058 and 0.15 meq/g dry matter were tested in ultrafiltration of aqueous solutions of dextrans and low-molecular-weight electrolytes. The former membrane, though permeable to bulky dextrans (molecular weight cut-off approximately 500 000), fairly retained small electrolytes. The latter, extremely hydrophilic membrane showed little resistance to the feed solution and no retention of solutes was observed. The influence of the feed concentration, electrolyte type, and operating pressure on the solute retention was determined.
On Flow Dynamics in a Jet-Loop Reactor
Authors: Kmiec Andrzej , Szczepaniak Lilla , Abdul-Latif Sahar S. H.
Published: July 2002

Results of experimental investigation of liquid flow velocity distribution, gas hold-up, and backmixing in the liquid phase in a jet-loop reactor with chambers of square cross-section are presented. Liquid velocity profiles in the draft tubes have been described applying the boundary layer theory. Aeration rates have been found to be comparable to those reported earlier for the reactor with chambers of circular shape as well as those obtained for reactors with other types of injectors. The axial dispersion coefficients in liquid phase have been found to depend very strongly on the air velocity in the draft tubes.
Conformational Structure of N-Methyl-8-octanelactam and Poly(N-methyl-8-octanelactam) as Studied by NMR, Infrared and Raman Spectroscopy and by Theoretical Calculations
Authors: Dybal Jiří , Doskočilová Danica , Schneider Bohdan , Puffr Rudolf
Published: July 2002

It was proved by 1H and 13C NMR spectra that in N-methyl-8-octanelactam in CDCl3 solution, the amide bond assumes only the cis form. Mirror inversion about the plane of the amide bond occurs with an activation enthalpy ∆H# = 44.7 kJ/mol. Molecular mechanics and quantum mechanical calculations yielded four favoured conformational structures for the isolated molecule. By vibrational spectra, one of two distinguishable structures strongly predominates. From 1H NMR spectra, this predominant conformation was identified with one of the calculated stable forms. By 13C NMR evidence, poly(N-methyl-8-octanelactam) in tetrachloroethane solution contains equal populations of the cis and trans amide forms; the structure of this polymer in the rubbery solid state seems to be similar to its structure in solution.
Effect of Structural Variability of the Ceramide Part on the Saccharide-Ceramide Linkage in Model Glycolipids Studied by Molecular Mechanics and Molecular Dynamics Methods
Authors: Gálová Zuzana , Kožár Tibor
Published: July 2002

Conformational analysis was performed for model glycosphingolipid molecules with a view to studying the effect of structural variability of the lipidic part and its flexibility on the saccharide-ceramide linkage. In addition to systematic and random molecular mechanics sampling techniques (the RAMM program), molecular dynamics simulations (Biosym DISCOVER program) were carried out to analyze the conformational energy surface of the model glycolipid molecules. The influence of the structural variability and flexibility of the lipidic part is demonstrated by prediction of the stability of different conformations around the carbohydrate-ceramide linkage. The α2, α1 and Θ1 torsional angles are the most important structural parameters with respect to the carbohydrate-ceramide connection. Two dominant conformations for the saccharide-ceramide linkage were observed, with the α2/α1/Θ1 dihedral angles in the -sc/+ac/ap and -sc/ap/-sc regions. While each of the calculation methods predicts similar flexibility in the α2/α1 space, the flexibility around the Θ1 angle differs considerably, reflecting the parametrization and set-up of the modelling protocol.
Polymerization of Nitrophenyl and 3-Diethylaminophenyl Prop-2-yn-1-yl Ethers with PdCl2. Polymers and Copolymers Characterization
Authors: Balcar Hynek , Holler Petr , Sedláček Jan , Blechta Vratislav
Published: July 2002

2-, 3- and 4-Nitrophenyl prop-2-yn-1-yl ethers were polymerized with PdCl2 in N,N-dimethylformamide (DMF) giving brown polymers soluble in DMF, dimethyl sulfoxide and N-methylpyrrolidone. Broad (mostly bimodal) molecular weight distributions were observed by size-exclusion chromatography (SEC) with maxima at molecular weight of about 4 . 103 and 1 . 105. With the same catalyst, 3-diethylaminophenyl prop-2-yn-1-yl ether gave predominantly low molecular weight homopolymer (Mn = 4 200) soluble in DMF, N-methylpyrrolidone, CHCl3 and tetrahydrofuran-soluble copolymers with 4-nitrophenyl prop-2-yn-1-yl ether (Mn about 3 000). IR, NMR and UV-VIS spectra of prepared polymers and copolymers proved the structure to consist of the polyene-type main chain with phenoxymethyl pendant groups bearing nitro or diethylamino substituents.
Sorption and Sorption Kinetics of Ethylbenzene in MFI-Type Zeolites Studied by a Barometric Technique
Authors: Schumacher Richard , Karge Hellmut G.
Published: July 2002

The sorption and sorption kinetics of ethylbenzene in H-ZSM-5 zeolites was studied varying the experimental conditions over a broad range of temperature and concentration. Isotherms and heats of adsorption as well as intracrystalline diffusivities have been determined. The isosteric heat of adsorption decreases with increasing sorbate loading due to repulsive sorbate-sorbate interaction. The diffusivity remains independent of sorbate concentration at loadings lower than a critical value of about four molecules per unit cell, while a sharp decrease is observed at higher loadings. The critical concentration slightly depends on the temperature. The relationship between diffusivity, concentration and temperature can be tentatively interpreted in terms of a complex sorbate-sorbent interaction.
Analysis of the Electrode Kinetics of Ni(II) Reduction in Thiocyanate Media on the Dropping Mercury Electrode
Authors: Crespo-Pinilla María S. , Mata-Pérez Fernando , Villamañán Rosa M.
Published: July 2002

A study of two prewaves of the Ni(II)-SCN- system was carried out under the experimental conditions when the influence of electroreduction of SCN- is negligible. Kinetics of Ni(II) reduction in thiocyanate media on the dropping mercury electrode was studied by DC Tast Polarography (DCTP) via determination of Koutecký's parameter χ; the influence of different variables was analyzed. The study of prewaves was performed using various polarographic techniques. Values of χ depend on the SCN- concentration, pH, ionic strength (Ψ-effect) and on the nature of the supporting electrolyte. The number of electrons n, the transfer coefficient α, the stoichiometric number ν, ∆H≠, and ∆S≠ were determined (compensation effect). The first prewave has character of a reaction in the solution, the second prewave is a surface process. Main features of both mechanisms are common: catalytic nature, one-electron step discharge and the rate-determining process between species of opposite charges.
Miscibility and Crosslinking of Polybutadiene-Based Polyurethanes
Authors: Pekař Miloslav , Kopecký Pavel
Published: July 2002

Rheokinetics of polybutadiene-based polyurethanes was studied. Sixteen mixtures differing in the miscibility of reactive components and hard segments contents were prepared. Regardless of the miscibility of the components, the rheokinetics behaviour is qualitatively very similar. The viscous response part is formed and finished much earlier than the elastic part. The quantitative dissimilarities, caused by cooperative effect of miscibility and differences in reactivity, are described. Using a well miscible initial mixture need not give the best results as a reactive crosslinker can easily react with isocyanate and separate from the rest of the reaction mixture thus impairing the final phase structure.
Is transcutaneous electrical nerve stimulation an effective analgesia during colonoscopy?
Authors: Robinson R , Darlow S , Wright S J , Watters C , Carr I , Gadsby G , Mayberry J
Published: July 2002

OBJECTIVES

To evaluate the efficacy of transcutaneous electrical nerve stimulation (TENS) as analgesia during colonoscopy.

DESIGN

In a randomised controlled trial, patients undergoing diagnostic colonoscopy were assigned to one of three groups: standard medication only (midazolam); active TENS plus standard medication; or non-functioning TENS and standard medication. Efficacy of TENS was determined using numerical rating scores for pain and the post-procedural evaluation questionnaire.

SETTING

Patients undergoing diagnostic colonoscopy in a teaching hospital.

MAIN OUTCOME

There was no statistically significant differences between the three groups. However in the active TENS group there was a greater variation in “physical discomfort” and “psychological distress”, suggesting TENS may be effective in subgroup of patients.
Channel head dynamics: capelin (Mallotus villosus) aggregation in the tidally driven upwelling system of the Saguenay - St. Lawrence Marine Park's whale feeding ground
Authors: Simard Yvan , Lavoie Diane , Saucier François J
Published: July 2002

Capelin (Mallotus villosus) tridimensional distribution at the head of the Laurentian Channel in the St. Lawrence estuary was investigated using 38- and 120-kHz acoustic surveys in the summers of 1994, 1995, 1997, and 1998. The results are interpreted with the help of a high-resolution tridimensional tidal circulation model. Total biomasses were small (934583 t) and showed rapid fluctuations, whereas mesoscale distribution was more constant. Capelin tended to occupy the very end of the channel head, especially the slopes and shallows surrounding the basins. This pattern did not coincide with the krill distribution, but the two total biomass series were significantly correlated. Capelin tidal dynamics is characterized by herding of capelin against the channel head slopes by the starting flooding currents, followed by an upwelling over the sills and shallows during maximum flood currents, and a return to the channel by the surface outflow during ebb. Each side of the channel head has a distinct capelin retention tidal cycle involving passive advection, swimming, and the two-layer estuarine circulation. This capelin distribution and tidal dynamics closely match the local fin whale (Balaenoptera physalus) and minke whale (Balaenoptera acutorostrata) distributions observed from the whale-watching fleet and typical tidal feeding strategies at the channel head.
A REMARK ON SMOOTHING OUT HIGHER CODIMENSION BRANES
Authors: CORRADINI OLINDO , IGLESIAS ALBERTO , KAKUSHADZE ZURAB , LANGFELDER PETER
Published: July 2002

We discuss some issues arising in studying (linearized) gravity on non-BPS higher co-dimension branes in an infinite-volume bulk. In particular, such backgrounds are badly singular for codimension-3 and higher δ-function-like branes with nonzero tension. As we discuss in this note, nontrivial issues arise in smoothing out such singularities. Thus, adding higher curvature terms might be necessary in this context.
POLCHINSKI ERG EQUATION IN O(N) SCALAR FIELD THEORY
Authors: KUBYSHIN YURI , NEVES RUI , POTTING ROBERTUS
Published: July 2002

We investigate the Polchinski ERG equation for d-dimensional O(N) scalar field theory. In the context of the non-pertubative derivative expansion we find families of regular solutions and establish their relation with the physical fixed points of the theory. Special emphasis is given to the limit N=∞ for which many properties can be studied analytically.
DUALITY AND THE EQUIVALENCE PRINCIPLE OF QUANTUM MECHANICS
Authors: ISIDRO JOSÉ M.
Published: July 2002

Following a suggestion by Vafa, we present a quantum-mechanical model for S duality symmetries observed in the quantum theories of fields, strings and branes. Our formalism may be understood as the topological limit of Berezin's metric quantization of the upper half-plane H, in that the metric dependence of Berezin's method has been removed. Being metric-free, our prescription makes no use of global quantum numbers. Quantum numbers arise only locally, after the choice of a local vacuum to expand around. Our approach may be regarded as a manifestly nonperturbative formulation of quantum mechanics, in that we take no classical phase space and no Poisson brackets as a starting point. Position and momentum operators satisfying the Heisenberg algebra are defined and their spectra are analysed. We provide an explicit construction of the Hilbert space of states. The latter carries no representation of SL (2,R), due to the lifting of the metric dependence. Instead, the reparametrization invariance of H under SL (2,R) induces a natural SL (2,R) action on the quantum-mechanical operators that implements S duality. We also link our approach with the equivalence principle of quantum mechanics recently formulated by Faraggi–Matone.
MARGINAL DEFORMATIONS OF N=4 SYM AND NON-COMMUTATIVE MODULI SPACES OF VACUA
Authors: LEIGH ROBERT G.
Published: July 2002

We review recent work on the application of the non-commutative geometric framework to an interpretation of the moduli space of vacua of marginal deformations of N = 4 super Yang-Mills theories. At rational values of couplings, different regions of moduli space may be associated with D5-branes of various topologies, and orbifold dual descriptions exist which may be accessed by T-duality. Singularities in the moduli space are associated with topology change.
BEC IN NONEXTENSIVE STATISTICAL MECHANICS: SOME ADDITIONAL RESULTS
Authors: SALASNICH LUCA
Published: July 2002

In a recent paper1 we discussed the Bose–Einstein condensation (BEC) in the framework of Tsallis's nonextensive statistical mechanics. In particular, we studied an ideal gas of bosons in a confining harmonic potential. In this memoir we generalize our previous analysis by investigating an ideal Bose gas in a generic power-law external potential. We derive analytical formulas for the energy of the system, the BEC transition temperature and the condensed fraction.
TWO-LOOP RENORMALIZATION OF THE QUASIPARTICLE WEIGHT IN TWO-DIMENSIONAL ELECTRON SYSTEMS
Authors: KISHINE JUN-ICHIRO , FURUKAWA NOBUO , YONEMITSU KENJI
Published: July 2002

We apply the renormalization-group (RG) approach to two model systems where the two-dimensional Fermi surface has portions which give rise to the logarithmically singular two-loop self-energy process.
X-RAY PHOTO-EMISSION SPECTROSCOPIC STUDY ON Sm0.85Nd0.15Se
Authors: ARIPONNAMMAL S. , JAYAVEL R. , NATARAJAN S.
Published: July 2002

The X-ray photo-emission spectroscopy (XPS) measurements have been performed on Sm0.85Nd0.15Se . The results have shown that the Sm ion in the compound is existing in divalent state and there is no inter configuration mixing (ICF). Theoretically calculated valence also supports the conclusion drawn from XPS studies.
RELAXATION OF EXCITONS IN IONIC HALIDES: MOLECULAR DYNAMICS STUDY
Authors: Song K. S. , Fu Chun-Rong
Published: July 2002

We report here the preliminary results of molecular dynamics simulation of exciton and hole relaxation in KBr and NaBr. The previously used semi-classical program has been modified to implement the solutions of Newton's equations with a time step of 0.50 femtosecond. Hole self-trapping process is studied at 80K. In both materials, there is a rapid bond-length oscillation. The oscillation, however, is damped faster is NaBr than in KBr. The relaxation of a Frenkel-type exciton (localized on a single site) is studied at 10 and 30K. It is found that the localization of the excited electron at an anion site drives the relaxation process, resulting in the formation of H and F centers simultaneously. There is a conspicuous absence of molecular bond oscillation which was observed in the Vk -center relaxation. In KBr, the FH-pair created is about 10 A apart (third neighbor). In NaBr, the separation is about 3A. The maximum relaxation is achieved in about 1-2 picosecond, depending on the temperature. These results are discussed in comparison with recent experimental works.
ENERGY RELAXATION AND TRANSFER IN TRIMER
Authors: HEŠMAN PAVEL , BARVÍK IVAN
Published: July 2002

We consider the relaxation and transfer in a symmetric trimer coupled to a phonon bath. The energy transfer within the trimer occurs via resonance interactions and coupling between the trimer and the bath occurs via modulation of the monomer energies by phonons. We compare the model introduced by Čápek with the Redfield model used commonly with secular approximation. We discuss two initial conditions: a) The highest eigenstate of the trimer is initially excited, and b) the initial excitation is local. We find that the occupation probabilities in the representation of eigenstates are the same in both models. But it is not so for off-diagonal density matrix elements. Only if the off-diagonal elements vanish initially (initial conidtion a), they vanish at arbitrary time in both models. If the initial excitation is local, off-diagonal elements differ essentially even in the long time limit.
q-SYMMETRIES IN DNLS-AL CHAINS AND EXACT SOLUTIONS OF QUANTUM DIMERS
Authors: ELLINAS DEMOSTHENES , MANIADIS PANAGIOTIS
Published: July 2002

Dynamical symmetries of Hamiltonians quantized models of discrete nonlinear Schrödinger chain (DNLS) and of Ablowitz–Ladik chain (AL) are studied. It is shown that for n-sites the dynamical algebra of DNLS Hamilton operator is given by the su(n) algebra, while the respective symmetry for the AL case is the quantum algebra suq(n). The q-deformation of the dynamical symmetry in the AL model is due to the non-canonical oscillator-like structure of the raising and lowering operators at each site.

Invariants of motions are found in terms of Casimir central elements of su(n) and suq(n) algebra generators, for the DNLS and QAL cases respectively. Utilizing the representation theory of the symmetry algebras we specialize to the n=2 quantum dimer case and formulate the eigenvalue problem of each dimer as a nonlinear (q)-spin model. Analytic investigations of the ensuing three-term nonlinear recurrence relations are carried out and the respective orthonormal and complete eigenvector bases are determined.

The quantum manifestation of the classical self-trapping in the QDNLS-dimer and its absence in the QAL-dimer, is analysed by studying the asymptotic attraction and repulsion respectively, of the energy levels versus the strength of nonlinearity. Our treatment predicts for the QDNLS-dimer, a phase-transition like behaviour in the rate of change of the logarithm of eigenenergy differences, for values of the nonlinearity parameter near the classical bifurcation point.