bluuebunny/crossref_metadata_2025 huggingface dataset:
The PmlI-PmlR Quorum-Sensing System in
Burkholderia pseudomallei
Plays a Key Role in Virulence and Modulates Production of the MprA Protease
Authors: Valade E. , Thibault F. M. , Gauthier Y. P. , Palencia M. , Popoff M. Y. , Vidal D. R.
Published: April 2004

Burkholderia pseudomallei
is the causative agent of melioidosis, an often fatal infection of humans and animals. The virulence of this pathogen is thought to depend on a number of secreted proteins, including the MprA metalloprotease. We observed that MprA is produced upon entry into the stationary phase, when the cell density is high, and this prompted us to study cell density-dependent regulation in
B. pseudomallei
. A search of the
B. pseudomallei
genome led to identification of a quorum-sensing system involving the LuxI-LuxR homologs PmlI-PmlR. PmlI directed the synthesis of an
N
-acylhomoserine lactone identified as
N
-decanoylhomoserine lactone. A
B. pseudomallei pmlI
mutant was significantly less virulent than the parental strain in a murine model of infection by the intraperitoneal, subcutaneous, and intranasal routes. Inactivation of
pmlI
resulted in overproduction of MprA at the onset of the stationary phase. A wild-type phenotype was restored following complementation with
pmlI
or addition of cell-free culture supernatant. In contrast, there was no significant difference between the virulence of a
B. pseudomallei mprA
mutant and the virulence of the wild-type strain. These results suggest that the PmlI-PmlR quorum-sensing system of
B. pseudomallei
is essential for full virulence in a mouse model and downregulates the production of MprA at a high cell density.
Characterization of the
cis
-Acting Regulatory Element Controlling HrpB-Mediated Activation of the Type III Secretion System and Effector Genes in
Ralstonia solanacearum
Authors: Cunnac Sébastien , Boucher Christian , Genin Stéphane
Published: April 2004

The ability of
Ralstonia solanacearum
to cause disease on plants depends on its type III secretion system (TTSS) encoded by
hrp
genes. The expression of
hrp
genes and known TTSS substrates is coordinately regulated by HrpB, a member of the AraC family of transcriptional regulators. Two HrpB-regulated promoters (
hrpY
and
popABC
) were characterized by deletion analysis, and the HrpB-dependent activation of these promoters was found to be conferred by a 25-nucleotide DNA element, the
hrp
II
box (TTCGn16TTCG), which is present in other
hrp
promoters. The
hrp
II
box element is an imperfect plant inducible promoter box, an element which was originally found in
hrp
promoters of
Xanthomonas campestris
(S. Fenselau and U. Bonas, Mol. Plant-Microbe Interact. 8:845-854, 1995) but which was not characterized at the molecular level. Site-directed mutagenesis showed that the
hrp
II
box is essential for
hrpY
promoter activation in vivo. Functional analysis of the
hrp
II
box element identified critical parameters that are required for HrpB-dependent activity. Further mapping analyses of several other
hrpB
-dependent promoters also indicated that the position of the
hrp
II
box is conserved, at −70 to −47 bp from the transcriptional start. As a first step toward identifying novel TTSS effectors, we used the
hrp
II
box consensus sequence to search for potential HrpB-regulated promoters in the complete genome sequence of
R. solanacearum
strain GMI1000. Among the 114 genes identified, a subset of promoters was found to have a structural relationship with
hrp
promoters, thus providing a pool of candidate genes encoding TTSS effectors.
Conserved Target for Group II Intron Insertion in Relaxase Genes of Conjugative Elements of Gram-Positive Bacteria
Authors: Staddon Jack H. , Bryan Edward M. , Manias Dawn A. , Dunny Gary M.
Published: April 2004

The lactococcal group II intron Ll.ltrB interrupts theltrBrelaxase gene within a region that encodes a conserved functional domain. Nucleotides essential for the homing of Ll.ltrB into an intronless version ofltrBare found exclusively at positions required to encode amino acids broadly conserved in a family of relaxase proteins of gram-positive bacteria. Two of these relaxase genes,pcfGfrom the enterococcal plasmid pCF10 and the ORF4 gene in the streptococcal conjugative transposon Tn5252, were shown to support Ll.ltrB insertion into the conserved motif at precisely the site predicted by sequence homology withltrB. Insertion occurred through a mechanism indistinguishable from retrohoming. Splicing and retention of conjugative function was demonstrated for pCF10 derivatives containing intron insertions. Ll.ltrB targeting of a conserved motif of a conjugative element suggests a mechanism for group II intron dispersal among bacteria. Additional support for this mechanism comes from sequence analysis of the insertion sites of the E.c.I4 family of bacterial group II introns.
Protein-Protein Interactions of Proteins from the ESAT-6 Family ofMycobacterium tuberculosis
Authors: Okkels Limei Meng , Andersen Peter
Published: April 2004

In the present study, we demonstrate that, in analogy with the genes encoding ESAT-6 and CFP-10, the genesrv0287andrv0288from the ESAT-6 gene family are cotranscribed. Using Western-Western blotting and protein-print overlay methodologies, we demonstrate that ESAT-6 and CFP-10, as well as the protein pair Rv0288/Rv0287, interact pairwise in a highly specific way. Most notably, the ESAT-6 proteins interact directly with Rv3873, a possible cell envelope component of the ESAT-6 secretion pathway.
Characterization of Cfa1, a Monofunctional Acyl Carrier Protein Involved in the Biosynthesis of the Phytotoxin Coronatine
Authors: Seidle Heather , Rangaswamy Vidhya , Couch Robin , Bender Carol L. , Parry Ronald J.
Published: April 2004

Cfa1 was overproduced in
Escherichia coli
and
Pseudomonas syringae
, and the degree of 4′-phosphopantetheinylation was determined. The malonyl-coenzyme A:acyl carrier protein transacylase (FabD) of
P. syringae
was overproduced and shown to catalyze malonylation of Cfa1, suggesting that FabD plays a role in coronatine biosynthesis. Highly purified Cfa1 did not exhibit self-malonylation activity.
Molecular cytogenetic characterization of an alloplasmic durum wheat line with a portion of chromosome 1D ofTriticum aestivumcarrying thescsaegene
Authors: Hossain Khwaja G , Riera-Lizarazu Oscar , Kalavacharla Venugopal , Vales M Isabel , Rust Jamie L , Maan Schivcharan S , Kianian Shahryar F
Published: April 2004

Triticum aestivum (2n = 6x = 42, AABBDD) with Triticum longissimum (2n = 2x = 14; S1S1) cytoplasm ((lo) cytoplasm) has normal fertility and plant vigor. However, the nucleus of durum wheat (Triticum turgidum (2n = 4x = 28, AABB)) is incompatible with the T. longissimum cytoplasm, producing non-viable progeny. This incompatibility is alleviated by scsae, a species cytoplasm-specific (scs) gene, on the long arm of chromosome 1D (1DL) of common wheat. The hemizygous (lo) durum scsaeline is male sterile and is maintained by crossing to normal durum wheat. After pollination, the seeds produced are either plump and viable (with scsae) or shriveled and inviable (without scsae). Thus, the chromosome with scsaeis inherited as a whole without recombination. The objectives of this study were to characterize the chromosome carrying scsaeand to determine the process through which this gene was introgressed into the (lo) durum background. Molecular marker analysis with 27 probes and primers mapped to homoeologous group 1 and genomic in situ hybridization using differentially labeled total genomic DNA of durum wheat and Aegilops tauschii suggest the presence of a 1AL segment in place of the distal region of 1DL. Owing to the absence of any detectable duplications or deletions, homoeologous recombination is the most likely mechanism by which this introgression occurred.Key words: homoeologous recombination, in situ hybridization, nuclear-cytoplasmic interaction, species cytoplasm specific gene
A molecular linkage map of olive (Olea europaeaL.) based on RAPD, microsatellite, and SCAR markers
Authors: Wu Shu-Biao , Collins Graham , Sedgley Margaret
Published: April 2004

An integrated molecular linkage map of olive (Olea europaea L.) was constructed based on randomly amplified polymorphic DNA (RAPD), sequence characterized amplified region (SCAR), and microsatellite markers using the pseudo-testcross strategy. A mapping population of 104 individuals was generated from an F1full-sib family of a cross between 'Frantoio' and 'Kalamata'. The hybridity of the mapping population was confirmed by genetic similarity and nonmetric multidimensional scaling. Twenty-three linkage groups were mapped for 'Kalamata', covering 759 cM of the genome with 89 loci and an average distance between loci of 11.5 cM. Twenty-seven linkage groups were mapped for 'Frantoio', covering 798 cM of the genome with 92 loci and an average distance between loci of 12.3 cM. For the integrated map, 15 linkage groups covered 879 cM of the genome with 101 loci and an average distance between loci of 10.2 cM. The size of the genomic DNA was estimated to be around 3000 cM. A sequence characterized amplified region marker linked to olive peacock disease resistance was mapped to linkage group 2 of the integrated map. These maps will be the starting point for studies on the structure, evolution, and function of the olive genome. When the mapping progeny pass through their juvenile phase and assume their adult characters, mapping morphological markers and identification of quantitative trait loci for adaptive traits will be the primary targets.Key words: genome mapping, RAPD, SSR, SCAR, Olea europea, peacock disease resistance.
Duplicate chlorophyll-deficient loci in soybean
Authors: Kato K K , Palmer R G
Published: April 2004

Three lethal-yellow mutants have been identified in soybean (Glycine max (L.) Merr.), and assigned genetic type collection numbers T218H, T225H, and T362H. Previous genetic evaluation of T362H indicated allelism with T218H and T225H and duplicate-factor inheritance. Our objectives were to confirm the inheritance and allelism of T218H and T225H and to molecularly map the locus and (or) loci conditioning the lethal-yellow phenotype. The inheritance of T218H and T225H was 3 green : 1 lethal yellow in their original parental source germplasm of Glycine max 'Illini' and Glycine max 'Lincoln', respectively. In crosses to unrelated germplasm, a 15 green : 1 lethal yellow was observed. Allelism tests indicated that T218H and T225H were allelic. The molecular mapping population was Glycine max 'Minsoy' × T225H and simple sequence repeat (SSR) markers were used. The first locus, designated y18_1, was located on soybean molecular linkage group B2, between SSR markers Satt474 and Satt534, and linked to each by 4.4 and 13.4 cM, respectively. The second locus, designated y18_2, was located on soybean molecular linkage group D2, between SSR markers Satt543 and Sat_001, and linked to each by 2.2 and 4.4 cM, respectively.Key words: duplicate gene, Glycine max, homoeologous genomic segment, genome evolution, lethal-yellow mutant.
Resistance genes for rye stem rust (SrR) and barley powdery mildew (Mla) are located in syntenic regions on short arm of chromosome
Authors: Mago R , Spielmeyer W , Lawrence G J , Ellis J G , Pryor A J
Published: April 2004

Genetic stocks were developed for the localization and eventual cloning of the stem rust resistance gene SrR that occurs in wheat lines carrying the 1RS translocation from Secale cereale 'Imperial' rye. We have used a mutation-based approach for molecular analysis of the SrR region in rye. Forty-one independent mutants resulting in loss of SrR resistance were isolated: many of these were deletions of various sizes that were used to locate SrR with respect to chromosome group 1S markers. The analysis of the mutants showed that markers about 1 Mb apart flanking the barley Mla locus also flank SrR. Additionally, three of the approximately 20 closely related sequences of Mla in rye are deleted in each of six interstitial deletion mutants of SrR. The results indicate that the SrR region in rye is syntenic to the Mla region in barley or that SrR is possibly orthologous to the Mla locus.Key words: DRA-1, Gabo 1BL.1RS, imperial rye, interstitial deletion, resistance gene analog (RGA).
Heterochromatin and rDNA sites distribution in the holocentric chromosomes of Cuscuta approximata Bab. (Convolvulaceae)
Authors: Guerra Marcelo , García Miguel A
Published: April 2004

Cuscuta is a widely distributed genus of holoparasitic plants. Holocentric chromosomes have been reported only in species of one of its subgenera (Cuscuta subg. Cuscuta). In this work, a representative of this subgenus, Cuscuta approximata, was investigated looking for its mitotic and meiotic chromosome behaviour and the heterochromatin distribution. The mitotic chromosomes showed neither primary constriction nor Rabl orientation whereas the meiotic ones exhibited the typical quadripartite structure characteristic of holocentrics, supporting the assumption of holocentric chromosomes as a synapomorphy of Cuscuta subg. Cuscuta. Chromosomes and interphase nuclei displayed many heterochromatic blocks that stained deeply with hematoxylin, 4',6-diamidino-2-phenylindole (DAPI), or after C banding. The banded karyotype showed terminal or subterminal bands in all chromosomes and central bands in some of them. The single pair of 45S rDNA sites was observed at the end of the largest chromosome pair, close to a DAPI band and a 5S rDNA site. Two other 5S rDNA site pairs were found, both closely associated with DAPI bands. The noteworthy giant nuclei of glandular cells of petals and ovary wall exhibited large chromocentres typical of polytenic nuclei. The chromosomal location of heterochromatin and rDNA sites and the structure of the endoreplicated nuclei of C. approximata seemed to be similar to those known in monocentric nuclei, suggesting that centromeric organization has little or no effect on chromatin organization.Key words: Cuscuta, holocentric chromosomes, heterochromatin.
Phylogenetic distribution of TTAGG telomeric repeats in insects
Authors: Frydrychová Radmila , Grossmann Petr , Trubac Pavel , Vítková Magda , Marec Frantiek
Published: April 2004

We examined the presence of TTAGG telomeric repeats in 22 species from 20 insect orders with no or inconclusive information on the telomere composition by single-primer polymerase chain reaction with (TTAGG)6 primers, Southern hybridization of genomic DNAs, and fluorescence in situ hybridization of chromosomes with (TTAGG)n probes. The (TTAGG)n sequence was present in 15 species and absent in 7 species. In a compilation of new and published data, we combined the distribution of (TTAGG)n telomere motif with the insect phylogenetic tree. The pattern of phylogenetic distribution of the TTAGG repeats clearly supported a hypothesis that the sequence was an ancestral motif of insect telomeres but was lost repeatedly during insect evolution. The motif was conserved in the "primitive" apterous insect orders, the Archaeognatha and Zygentoma, in the "lower" Neoptera (Plecoptera, Phasmida, Orthoptera, Blattaria, Mantodea, and Isoptera) with the exception of Dermaptera, and in Paraneoptera (Psocoptera, Thysanoptera, Auchenorrhyncha, and Sternorrhyncha) with the exception of Heteroptera. Surprisingly, the (TTAGG)n motif was not found in the "primitive" pterygotes, the Palaeoptera (Ephemeroptera and Odonata). The Endopterygota were heterogeneous for the occurrence of TTAGG repeats. The motif was conserved in Hymenoptera, Lepidoptera, and Trichoptera but was lost in one clade formed by Diptera, Siphonaptera, and Mecoptera. It was also lost in Raphidioptera, whereas it was present in Megaloptera. In contrast with previous authors, we did not find the motif in Neuroptera. Finally, both TTAGG-positive and TTAGG-negative species were reported in Coleoptera. The repeated losses of TTAGG in different branches of the insect phylogenetic tree and, in particular, in the most successful lineage of insect evolution, the Endopterygota, suggest a backup mechanism in the genome of insects that enabled them frequent evolutionary changes in telomere composition.Key words: chromosomes, fluorescence in situ hybridization, FISH, insects, phylogeny, single primer PCR, Southern hybridization, telomere, telomeric repeats.
Isolation and characterization of RNase LTR sequences of Ty1-copiaretrotransposons in common bean (Phaseolus vulgarisL.)
Authors: Galindo Leonardo Miguel , Gaitán-Solís Eliana , Baccam Prasith , Tohme Joe
Published: April 2004

Retroelements have proved useful for molecular marker studies and play an important role in genome evolution. Ty1-copia retrotransposons are ubiquitous and heterogeneous in plant genomes, and although many elements have been isolated and characterized, almost no information about them is available in the literature for Phaseolus vulgaris L. We report here the isolation and characterization of new RNase long terminal repeat (LTR) sections of the Ty1-copia group for this crop plant. RNAse sections showed conserved amino acids with the downstream sections corresponding to the polypurine-tract and 5' sections of 3' LTRs. The RNase sections were aligned using ClustalX to find potential relationships between sequences. A comparison with this analysis was made using the partition analysis of quasispecies package (PAQ), which is specific for quasispecies-like populations. The analysis revealed eight distinct groups. To uncover LTR variability and potential conserved promoter motifs, we also designed new primers from the presumed polypurine-tract regions. A similarity search found short stretches similar to upstream and downstream regions of some genes. Conserved motifs, corresponding to transcription factor binding sites, were discovered through MatInspector software and two sequences characterized. From a putative LTR fragment, we then designed a new primer, which, through sequence-specific amplification polymorphism (SSAP), showed numerous polymorphic bands between two distinct P. vulgaris accessions.Key words: Phaseolus vulgaris, quasispecies, retrotransposon, RNase-LTR, transcription factor binding site.
Interspecific androgenetic restoration of rosy barb using cadaveric sperm
Authors: Kirankumar S , Pandian T J
Published: April 2004

Interspecific androgenetic rosy barb (Puntius conchonius) was generated using its cadaveric (-20 °C) or fresh sperm to activate nuclear genome inactivated oocytes of gray tiger barb (Puntius tetrazona). UV irradiation was used to inactivate nuclear genome of tiger barb oocytes. Thermal shock restored diploidy of rosy barb in the oocytes of tiger barb. Survival of androgenotes was 14% or 7% when fresh or cadaveric sperm was used. The diploid or haploid nuclear genome of rosy barb, individually or jointly with that of tiger barb, regulated the time sequence of embryonic development in an alien cytoplasm of tiger barb oocytes. Androgenetic males (Y2Y2) attained sexual maturity earlier and had significantly higher gonadosomatic index and sperm concentration, albeit suffering a slight decrease in fertilizing ability. Conversely, androgenetic females (X2X2) suffered extended interspawning period, reduced fecundity, and poor hatchability of their progenies. These results are discussed with respect to their significance for conservation biology.Key words: nuclear genome inactivation, tiger barb, cadaveric sperm, rosy barb, interspecific androgenotes, Tc1 transposon.
Phospholipid synthesis in yeast: regulation by phosphorylation
Authors: Carman George M , Kersting Michael C
Published: April 2004

The yeast Saccharomyces cerevisiae is a model eukaryotic organism for the study of the regulation of phospholipid synthesis. The major phospholipids (phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, and phosphatidylserine) are synthesized by complementary (CDPdiacylglycerol and Kennedy) pathways. The regulation of these pathways is complex and is controlled by genetic and biochemical mechanisms. Inositol plays a major role in the regulation of phospholipid synthesis. Inositol-mediated regulation involves the expression of genes and the modulation of enzyme activities. Phosphorylation is a major mechanism by which enzymes and transcription factors are regulated, and indeed, key phospholipid biosynthetic enzymes have been identified as targets of phosphorylation. Protein kinase A phosphorylates CTP synthetase, choline kinase, Mg2+-dependent phosphatidate phosphatase, phosphatidylserine synthase, and the transcription factor Opi1p. CTP synthetase and Opi1p are also phosphorylated by protein kinase C. The phosphorylation of these proteins plays a role in regulating their activities and (or) function in phospholipid synthesis.Key words: phospholipids, yeast, phospholipid synthesis, phosphorylation, protein kinase A, protein kinase C.
Cell biology of cardiac mitochondrial phospholipids
Authors: Hatch Grant M
Published: April 2004

Phospholipids are important structural and functional components of all biological membranes and define the compartmentation of organelles. Mitochondrial phospholipids comprise a significant proportion of the entire phospholipid content of most eukaroytic cells. In the heart, a tissue rich in mitochondria, the mitochondrial phospholipids provide for diverse roles in the regulation of various mitochondrial processes including apoptosis, electron transport, and mitochondrial lipid and protein import. It is well documented that alteration in the content and fatty acid composition of phospholipids within the heart is linked to alterations in myocardial electrical activity. In addition, reduction in the specific mitochondrial phospholipid cardiolipin is an underlying biochemical cause of Barth Syndrome, a rare and often fatal X-linked genetic disease that is associated with cardiomyopathy. Thus, maintenance of both the content and molecular composition of phospholipids synthesized within the mitochondria is essential for normal cardiac function. This review will focus on the function and regulation of the biosynthesis and resynthesis of mitochondrial phospholipids in the mammalian heart.Key words: phospholipid, metabolism, heart, cardiolipin, mitochondria.
SRCgene expression in human cancer: the role of transcriptional activation
Authors: Dehm Scott M , Bonham Keith
Published: April 2004

Human pp60c-Src(or c-Src) is a 60 kDa nonreceptor tyrosine kinase encoded by the SRC gene and is the cellular homologue to the potent transforming v-Src viral oncogene. c-Src functions at the hub of a vast array of signal transduction cascades that influence cellular proliferation, differentiation, motility, and survival. c-Src activation has been documented in upwards of 50% of tumors derived from the colon, liver, lung, breast, and pancreas. Therefore, a major focus has been to understand the mechanisms of c-Src activation in human cancer. Early studies concentrated on post-translational mechanisms that lead to increased c-Src kinase activity, which often correlated with overexpression of c-Src protein. More recently, the discovery of an activating SRC mutation in a small subset of advanced colon tumors has been reported. In addition, elevated SRC transcription has been identified as yet another mechanism contributing significantly to c-Src activation in a subset of human colon cancer cell lines. Interestingly, histone deacetylase (HDAC) inhibitors, agents with well-documented anti-cancer activity, repress SRC transcription in a wide variety of human cancer cell lines. Analysis of the mechanisms behind HDAC inhibitor mediated repression could be utilized in the future to specifically inhibit SRC gene expression in human cancer.Key words: c-Src, tyrosine kinase, gene expression, transcription, colon cancer.
Re-expression of estrogen receptor α using a tetracycline-regulated gene expression system induced estrogen-mediated growth inhibition of the MDA-MB-231 breast cancer cell line
Authors: Barrón-González Arturo , Romero Ivone Castro
Published: April 2004

Estrogen receptor (ER)-negative breast carcinomas are often difficult to treat with antiestrogens. This work was performed to determine if the re-expression of the human ERα could restore the hormone response of these cells. We have transfected the human wild-type ERα to an ER-negative breast cancer cell line (MDA-MB-231) using a tetracycline-regulated gene expression system. We obtained a new cell line, MDA-A4-5/2. Cell count and flow cytometry "S" phase cell fraction showed that 17-β-estradiol induced an inhibition on the proliferation of these cells; on the contrary, the antiestrogens ICI 182 780, and tamoxifen blocked this effect. Finally, we demonstrated an induction of the endogenous progesterone receptor gene when ERα was present. These results suggest that the re-expression of ERα in ER-negative breast cancer cells recreate, at least partially, a hormone-responsive phenotype and may be useful as a therapeutic approach to control this pathology.Key words: human breast carcinoma, MDA-MB-231 cells, estrogen receptor α, tetracycline-regulated gene expression system, cell proliferation.
Lipids and atherosclerosis
Authors: Choy Patrick C , Siow Yaw L , Mymin David , O Karmin
Published: April 2004

Atherosclerosis is the leading cause of death in North America and within the next two decades will be the leading cause worldwide. Atherosclerosis is characterized by vascular obstruction from the deposits of plaque, resulting in reduced blood flow. Plaque rupture and the consequent thrombosis may lead to sudden blockage of the arteries and cause heart attack. High serum lipid levels, especially the elevated level of low-density lipoprotein (LDL), have been shown to be strongly related to the development of atherosclerosis. It is generally accepted that atherosclerotic lesions are initiated via an enhancement of LDL uptake by monocytes and macrophages. In the liver, uptake of plasma LDL is mediated via specific LDL receptors, but a scavenger receptor system is employed by macrophages. Plasma LDL must be modified prior to uptake by macrophages. Analysis of the lipid content in the oxidatively modified LDL from hyper lipidemic patients revealed that the level of lysophosphatidylcholine was greatly elevated, and the high level of the lysolipid was shown to impair the endothelium-dependent relaxation of the blood vessels. In a separate study, we showed that a high level of homocysteine caused the increase in cholesterol production and apolipoprotein B-100 secretion in hepatic cells. Statins have been used effectively to control the production of cholesterol in the liver, and recently, ezetimibe has been shown to supplement the efficacy of statins by inhibiting cholesterol absorption. The factor of elevated levels of triglyceride-rich lipoproteins in association with depressed high-density lipoproteins, usually in the context of insulin resistance, is an important contributor to atherosclerosis and can be effectively treated with fibric acid derivatives. In hyperhomocysteinemia, folic acid supplements may have a role in the control of cholesterol by reducing the plasma homocysteine level.Key words: atherosclerosis, low density lipoprotein (LDL), homocysteine, statin, folate.
Lime softening clarifier modeling with artificial neural networks
Authors: Shariff Riyaz , Cudrak Audrey , Stanley Stephen J
Published: April 2004

This paper examines the application of the artificial neural network (ANN) modeling technique to model a lime softening process at a full-scale drinking water treatment facility. The modeling was done for the Rossdale Water Treatment Plant (WTP) operated by EPCOR Water Services Inc. in Edmonton, Alberta. It was determined that ANN can model a lime clarifier accurately and with superior performance to other modeling methods. During the development stage, a prediction of alum clarifier pH also becomes necessary, and a very accurate inferential (virtual) sensor for pH was developed using ANN. The ANN models were also integrated with the Supervisory Control and Data Acquisition (SCADA) system of the plant so that real-time predictions of lime doses and effluent total hardness could be monitored. It was shown that the performance of the ANN models that were developed using average daily values for the parameters also work well when they are executed in real time.Key words: artificial neural networks, water softening, hardness, virtual analyzer, forward and inverse models.
Application of artificial neural networks in wastewater treatment
Authors: El-Din Ahmed Gamal , Smith Daniel W , El-Din Mohamed Gamal
Published: April 2004

In the past few years, artificial neural networks (ANNs) have been used in describing and modelling wastewater treatment processes. Artificial neural network models can be identified without a detailed knowledge of the kinetics of the system to be modelled. Also, ANN models can potentially contain a great deal of information about the system itself, including the same type of information contained in conventional deterministic models. The fact that these models can be continuously updated with minimal resource requirements makes them very attractive for application in a real-time control scenario. In the current paper, applications of ANNs in the field of wastewater treatment performance prediction are reviewed. In addition, this paper presents a case study that reports some comprehensive modelling work to develop nonlinear neural network prediction models for the Gold Bar Wastewater Treatment Plant (GBWWTP), the largest sewage treatment facility in Edmonton, Alberta. Key words: wastewater treatment, artificial neural networks, flow prediction, primary sedimentation, activated sludge.
An exploration of artificial neural network rainfall-runoff forecasting combined with wavelet decomposition
Authors: Anctil François , Tape Doha Guy
Published: April 2004

This study compares the one-day-ahead stream flow forecasting performance of multiple-layer artificial neurons and a neuro-wavelet hybrid system at two sites. Morlet power spectra are used to identify the period-scale structure of the available rainfall and runoff time series. The time series are wavelet decomposed into three sub-series depicting the rainfall-runoff processes: short, intermediate, and long wavelet periods. Then, multiple-layer artificial neurons are trained for each wavelet sub-series. Results show that the short wavelet periods are responsible for most of the final neuro-wavelet hybrid forecasting error. Short period fluctuations are thus the key to any further improvements in artificial neural network (ANN) rainfall-runoff forecasting models. The final performance of the neuro-wavelet hybrid forecasting system and of the classic forecasting multiple-layer artificial neuron system is very similar. The slight advantage in performance of the neuro-wavelet system may be attributed to a better usage of the evapotranspiration time series. Key words: surface-water hydrology, rainfall-runoff, artificial neural networks, wavelet decomposition.
A comparison of artificial neural networks and multiple regression methods for the analysis of pilot-scale data
Authors: Baxter C W , Smith Daniel W , Stanley S J
Published: April 2004

Pilot-scale testing is widely used in the drinking water supply industry to test treatment theories, develop new processes, and enhance process operations. The data sets derived from pilot testing are usually small owing to financial and time considerations. The analysis of such data is extremely complex, since treatment processes are highly complex and nonlinear. Multiple regression analysis is widely considered to be the best available technology for analysing data collected from pilot-scale experiments in the drinking water supply industry. Unfortunately, this technique is limited in its ability to handle the combinations of fixed and random variables that are characteristic of water treatment processes. This paper demonstrates the applicability and advantages of artificial network modelling for pilot-scale data analysis. Data collected at two separate pilot-scale facilities are analysed using the artificial neural network (ANN) technique and multiple regression methods, and performance assessments of the two are made. Key words: artificial neural networks, pilot plant, data analysis.
Ionic liquids derived from trialkylsulfonium bromides: Physicochemical properties and potential applications
Authors: Xiao Li , Johnson Keith E
Published: April 2004

Several new ionic liquids were prepared from trialkylsulfonium bromides and AlCl3 or HCl. They include both Lewis basic and acidic combinations of Et3SBr with AlCl3, which are liquid at ambient temperatures. Density, molarity, conductivity, NMR, infrared, and electrochemical data are presented. The sulfonium cations are not hydrogen bonding, are unattacked by hydride, provide NMR windows in the aromatic regions, and offer different solubility prospects from ionic liquids derived from aromatic cations.Key words: ionic liquids, triethylsulfonium, haloaluminates, halohydrogenates, molarities, NMR, voltammetry, hydride.
Biosensors for the detection of bacteria
Authors: Deisingh Anil K , Thompson Michael
Published: April 2004

This review will consider the role of biosensors towards the detection of infectious bacteria, although non-infectious ones will be considered where necessary. Recently, there has been a heightened interest in developing rapid and reliable methods of detection. This is especially true for detection of organisms involved in bioterrorism, food poisoning, and clinical problems such as antibiotic resistance. Biosensors can assist in achieving these goals, and sensors using several of the different types of transduction modes are discussed: electrochemical, high frequency (surface acoustic wave), and optical. The paper concludes with a discussion of three areas that may make a great impact in the next few years: integrated (lab-on-a-chip) systems, molecular beacons, and aptamers.Key words: biosensor, acoustic wave, electronic nose, bacterial detection, molecular beacon.
Real-time PCR analysis of carbon catabolite repression of cellobiose dehydrogenase gene transcription inTrametes versicolor
Authors: Stapleton P C , O'Mahony J , Dobson A D.W
Published: April 2004

Cellobiose dehydrogenase production in Trametes versicolor is repressed when additional carbon sources, such as glucose, maltose, galactose, arabinose, and xylose, are added to the fungal cultures growing on cellulose. Real-time quantitative reverse transcription – polymerase chain reaction has been used to demonstrate that the addition of galactose, arabinose, and xylose results in 19-, 92-, and 114-fold reductions, respectively, in cdh transcript levels 96 h post-addition. Glucose exhibits the greatest repressive effect, resulting in a 3400-fold decrease in cdh transcript levels.Key words: cellobiose dehydrogenase, carbon repression, real-time PCR.
Role of cyanobacteria in the persistence of Vibrio cholerae O139 in saline microcosms
Authors: Islam M S , Mahmuda S , Morshed M G , Bakht H B.M , Khan M N.H , Sack R B , Sack D A
Published: April 2004

Recently, a new strain of cholera, Vibrio cholerae O139, has emerged as an epidemic strain, but there is little information about its environmental reservoir. The present investigation was aimed to determine the role of cyanobacteria in the persistence of V. cholerae O139 in microcosms. An environmental isolate of V. cholerae O139 and three cyanobacteria (Anabaena sp., Nostoc sp., and Hapalosiphon sp.) were used in this study. Survival of culturable V. cholerae O139 in microcosms was monitored using taurocholate-tellurite gelatin agar medium. Viable but nonculturable V. cholerae O139 were detected using a fluorescent antibody technique. Vibrio cholerae O139 could be isolated for up to 12 days in a culturable form in association with cyanobacteria but could not be isolated in the culturable form after 2 days from control water without cyanobacteria. The viable but nonculturable V. cholerae O139 could be detected in association with cyanobacteria for up to 15 months. These results, therefore, suggest that cyanobacteria can act as a long-term reservoir of V. cholerae O139 in an aquatic environment.Key words: cyanobacteria, persistence, Vibrio cholerae, microcosm, reservoir.
Wind tunnel measurements of crown streamlining and drag relationships for three conifer species
Authors: Rudnicki Mark , Mitchell Stephen J , Novak Michael D
Published: April 2004

Estimating the wind force or drag acting on tree crowns is central to understanding both the chronic effects of wind and the calculation of critical wind speed in windthrow prediction models. The classical drag equation is problematic for porous, flexible tree crowns whose frontal area declines as wind speeds increase and branches streamline. Juvenile crowns of three morphologically different conifers, western redcedar (Thuja plicata Donn ex D. Don), western hemlock (Tsuga heterophylla (Raf.) Sarg.), and lodgepole pine (Pinus contorta Dougl. ex Loud.), were exposed to wind speeds from 4 to 20 m/s in a wind tunnel. At 20 m/s, streamlining reduced the frontal area by 54% for redcedar, 39% for hemlock, and 36% for lodgepole pine. Crown drag coefficients calculated using frontal area in still air varied with wind speed. At 20 m/s, they were 0.22, 0.47, and 0.47 for these species, respectively. Drag was proportional to the product of mass and wind speed and also to the product of wind speed squared and wind speed specific frontal area. Lodgepole pine and redcedar had lower drag per unit of branch mass than did hemlock. Removing branches by pruning had little effect on drag per unit branch mass.
Spectroscopic study of fast-neutron-irradiated chromatin
Authors: Radu Liliana , Gazdaru Doina , Constantinescu B
Published: April 2004

The effects produced by fast neutrons (0-100 Gy) on chromatin structure were analyzed by (i) [1H]-NMR spectroscopy, (ii) time resolved spectroscopy, and (iii) fluorescence resonance energy transfer (FRET). Two types of chromatin were tested: (i) a chromatin from a normal tissue (liver of Wistar rats) and (ii) a chromatin from a tumoral tissue (Guerin limphotrope epithelioma, a rat solid tumor). The fast-neutron action on chromatin determines greater values of the [1H]-NMR transverse relaxation time, indicating a more injured structure. Time-resolved fluorescence measurements show that the relative contribution of the excited state lifetime of bound ethidium bromide to chromatin DNA diminishes with increasing irradiation doses. This reflects the damage that occurs in DNA structure: production of single- and double-strand breaks due to sugar and base modifications. By the FRET method, the distance between dansyl chloride and acridine orange coupled at chromatin was determined. This distance increases upon fast-neutron action. The radiosensitivity of the tumor tissue chromatin seems higher than that of the normal tissue chromatin, probably because of its higher (loose) euchromatin/(compact) heterochromatin ratio. As the values of the physical parameters analyzed are specific for a determined dose, the establishment of these parameters may constitute a criterion for the microdosimetry of chromatin radiolesions produced by fast neutrons.Key words: chromatin, spectroscopic study, radiolesions, fast neutrons, microdosimetry.
Functional and structural alterations of epithelial barrier properties of rat ileum following X-irradiation
Authors: Dublineau I , Lebrun F , Grison S , Griffiths N M
Published: April 2004

Irradiation of the digestive system leads to alterations of the small intestine. We have characterized the disruption of the barrier integrity in rat ileum from 1 to 14 days following irradiation ranging from 6 to 12 Gy. The intestinal permeability to14C-mannitol and3H-dextran 70 000 was measured in vitro in Ussing chambers. In parallel to these functional studies, immunohistochemical analyses of junctional proteins (ZO-1 and β-catenin) of ileal epithelium were performed by confocal microscopy. Irradiation with 10 Gy induced a marked decrease in epithelial tissue resistance at three days and a fivefold increase in mannitol permeability, without modifications of dextran permeability. A disorganization of the localization for ZO-1 and β-catenin was also observed. At 7 days after irradiation, we observed a recovery of the organization of junctional proteins in parallel to a return of intestinal permeability to control value. In addition to these time-dependent effects, a gradual effect on epithelial integrity of the radiation doses was observed 3 days after irradiation. This study shows a disruption of the integrity of the intestinal barrier in rat ileum following abdominal X-irradiation, depending on the time postirradiation and on the delivered dose. The loss of barrier integrity was characterized by a disorganization of proteins of tight and adherent junctions, leading to increased intestinal permeability to mannitol.Key words: intestinal permeability, ZO-1, β-catenin, tight and adherent junctions.
Chronic β-adrenoreceptor stimulation in vivo decreased Bcl-2 and increased Bax expression but did not activate apoptotic pathways in mouse heart
Authors: Dostanic Stevan , Servant Nicolas , Wang Chunlei , Chalifour Lorraine E
Published: April 2004

Prolonged activation of the sympathetic nervous system is deleterious to heart function. In vitro β1-adrenergic activation promotes apoptosis, whereas β2-adrenergic activation reduces apoptosis in cultured adult cardiomyocytes. To determine the effect of chronic catecholamine infusion in vivo, we measured apoptosis marker expression in C57Bl/6 and catecholamine-sensitive Egr-1 deficient mice after treatment with the nonspecific β-adrenergic agonist, isoproterenol, the β1-specific agonist, dobutamine, or the β2-specific agonist, metaproterenol. Antiapoptotic and proapoptotic protein expression, cytochrome c release and caspases 3, 9, and 12 activation products were measured on immunoblots. Catecholamine-treated mice had decreased Bcl-2 and increased Bax and BNIP1 expression, suggesting mitochondria-dependent apoptosis pathway activation. However, cytosolic cytochrome c or caspase 3 or 9 activation products were not detected. In mice, increased molecular chaperone expression and caspase 12 activation characterize endoplasmic-reticulum-driven apoptosis. Clusterin expression was increased in catecholamine-treated mice, but GRP78 expression was not increased, and caspase 12 activation products were not detected. Thus, neither the mitochondrial nor the endoplasmic apoptotic pathway was fully activated. Further, Egr-1 deficiency did not increase cardiac apoptosis. We conclude that although chronic in vivo infusion of β1- or β2-adrenergic receptor agonists partially activates the apoptosis program, full activation of the caspase cascade requires more, or other, cardiac insults.Key words: apoptosis, catecholamine infusion, mice, Egr-1.
Angiotensin-converting enzyme inhibitor captopril prevents volume overload cardiomyopathy in experimental chronic aortic valve regurgitation
Authors: Plante Eric , Gaudreau Martin , Lachance Dominic , Drolet Marie-Claude , Roussel Élise , Gauthier Cindy , Lapointe Evelyne , Arsenault Marie , Couet Jacques
Published: April 2004

The efficacy of angiotensin-converting enzyme inhibitors (ACEIs) in the treatment of chronic aortic regurgitation (AR) is not well established and remains controversial. The mechanisms by which ACEIs may protect against left-ventricular (LV) volume overload are not well understood, and clinical trials performed until now have yielded conflicting results. This study was therefore performed to assess the effectiveness of two different doses of the ACEI captopril in a rat model of chronic AR. We compared the effects of a 6-month low-dose (LD) (25 mg/kg) or higher dose (HD) (75 mg/kg) treatment with captopril on LV function and hypertrophy in Wistar rats with severe AR. Untreated animals developed LV eccentric hypertrophy and systolic dysfunction. LD treatment did not prevent hypertrophy and provided modest protection against systolic dysfunction. HD treatment preserved LV systolic function and dimensions and tended to slow hypertrophy. The cardiac index remained high and similar among all AR groups, treated or not. Tissue renin–angiotensin system (RAS) analysis revealed that ACE activity was increased in the LVs of AR animals and that only HD treatment significantly decreased angiotensin II receptor mRNA levels. Fibronectin expression was increased in the LV or AR animals, but HD treatment almost completely reversed this increase. The ACE inhibitor captopril was effective at high doses in this model of severe AR. These effects might be related to the modulation of tissue RAS and the control of fibrosis.Key words: aortic valve, insufficiency, rat, echocardiography, volume overload, ACE inhibitors.
Cisplatin enhances the cytotoxicity of fast neutrons in a murine lymphoma cell line
Authors: Fischer B , Benzina S , Ganansia-Leymarie V , Denis J M , Bergerat J P , Dufour P , Gueulette J , Bischoff P
Published: April 2004

The utilization of high linear energy transfer (LET) radiations, such as fast neutrons or carbon ions (hadrontherapy), offers promising perspectives in radiotherapy. While it is well known that by combining radiotherapy and chemotherapy, important therapeutic advantages can be obtained to cure cancer, there have been, so far, very few investigations on the effects of treatments combining an irradiation with high-LET particles and cancer drugs. The present study was therefore undertaken to examine the effects of exposure to 65 MeV fast neutrons combined with cisplatin in a murine T cell lymphoma (RDM4) in vitro. The cells were irradiated at doses ranging from 2 to 8 Gy without or with addition of cisplatin shortly before the irradiation, at concentrations between 0.3 and 12.5 µM. These treatments were applied concomitantly. Proliferation and apoptosis were assessed at different time intervals thereafter. The combination of irradiation with cisplatin was found to be more cytotoxic than either treatment alone. Furthermore, the cytotoxicity induced by this cotreatment resulted not only from apoptosis but also from other forms of cell death.Key words: apoptosis, cancer cells, fast neutrons, cisplatin.
Food habits of European badgers (Meles meles) along an altitudinal gradient of Mediterranean environments: a field test of the earthworm specialization hypothesis
Authors: Virgós Emilio , Mangas Julián G , Blanco-Aguiar José Antonio , Garrote Germán , Almagro Nuria , Viso Raquel P
Published: April 2004

Food specialization by European badgers (Meles meles) is a largely debated controversy. Data from Mediterranean areas indicate small importance of earthworms (Lumbricus spp.) in badger diet and support the idea that badgers are generalist predators. Nevertheless, only dry areas have been sampled so far. We studied badger diet in six areas along an elevation gradient with different rainfall and habitat conditions, which influenced earthworm availability. We evaluated the influence of earthworm availability on badger diet along this environmental gradient. Badgers used a wide range of prey items in the different habitats and seasons sampled. In contrast with other Mediterranean studies, earthworms made an important contribution to badger diet (27% of estimated volume). Earthworm occurrence in the diet was high in elevated and wet habitats and in spring and autumn–winter. Earthworm consumption was nonlinearly related to availability, indicating high intake compared with availability in wet areas. Moreover, in summer, availability was virtually zero in all habitats, whereas consumption averaged 15% volume of the diet. We tentatively suggest that badgers compensate for variations in earthworm availability by changing their foraging tactics. This suggests that badgers could be viewed as specialist foragers for earthworms in some Mediterranean environments.