bluuebunny/crossref_metadata_2025 huggingface dataset:
A Novel Class of Developmentally Regulated Noncoding RNAs in
Leishmania
Authors: Dumas Carole , Chow Conan , Müller Michaela , Papadopoulou Barbara
Published: December 2006

Leishmania
is a protozoan parasite that causes serious morbidity and mortality in humans worldwide. The ability of these parasites to survive within the phagolysosomes of mammalian macrophages is dependent on the developmental regulation of a variety of genes. Identifying genomic sequences that are preferentially expressed during the parasite's intracellular growth would provide new insights about the mechanisms controlling stage-specific gene regulation for intracellular development of the parasite. Using a genomic library that differentially hybridized to probes made from total RNA from
Leishmania infantum
amastigote or promastigote life cycle stages, we identified a new class of noncoding RNAs (ncRNAs) ranging from ∼300 to 600 nucleotides in size that are expressed specifically in the intracellular amastigote stage. These ncRNAs are transcribed by RNA polymerase II from genomic clusters of tandem head-to-tail repeats, which are mainly located within subtelomeric regions. Remarkably, both the sense and antisense orientations of these ncRNAs are transcribed and are processed by
trans
splicing and polyadenylation. The levels of antisense transcripts are at least 10-fold lower than those of the sense transcripts and are tightly regulated. The sense and antisense ncRNAs are cytosolic as shown by fluorescence in situ hybridization studies and cosediment with a small ribonucleoprotein complex. Amastigote-specific regulation of these ncRNAs possibly occurs at the level of RNA stability. Interestingly, overexpression of these ncRNAs in promastigotes, as part of an episomal expression vector, failed to produce any transcript, which further highlights the instability of these RNAs in the promastigote stage. This is the first report describing developmentally regulated ncRNAs in protozoan parasites.
Targeted Deletion of
MIC5
Enhances Trimming Proteolysis of
Toxoplasma
Invasion Proteins
Authors: Brydges Susannah D. , Zhou Xing Wang , Huynh My-Hang , Harper Jill M. , Mital Jeffrey , Adjogble Koku D. Z. , Däubener Walter , Ward Gary E. , Carruthers Vern B.
Published: December 2006

Limited proteolysis of proteins transiently expressed on the surface of the opportunistic pathogen
Toxoplasma gondii
accompanies cell invasion and facilitates parasite migration across cell barriers during infection. However, little is known about what factors influence this specialized proteolysis or how these proteolytic events are regulated. Here we show that genetic ablation of the micronemal protein MIC5 enhances the normal proteolytic processing of several micronemal proteins secreted by
Toxoplasma
tachyzoites. Restoring MIC5 expression by genetic complementation reversed this phenotype, as did treatment with the protease inhibitor ALLN, which was previously shown to block the activity of a hypothetical parasite surface protease called MPP2. We show that, despite its lack of obvious membrane association signals, MIC5 occupies the parasite surface during invasion in the vicinity of the proteins affected by enhanced processing. Proteolysis of other secretory proteins, including GRA1, was also enhanced in MIC5 knockout parasites, indicating that the phenotype is not strictly limited to proteins derived from micronemes. Together, our findings suggest that MIC5 either directly regulates MPP2 activity or it influences MPP2's ability to access substrate cleavage sites on the parasite surface.
Xyr1 (Xylanase Regulator 1) Regulates both the Hydrolytic Enzyme System and
d
-Xylose Metabolism in
Hypocrea jecorina
Authors: Stricker Astrid R. , Grosstessner-Hain Karin , Würleitner Elisabeth , Mach Robert L.
Published: December 2006

Xyr1 (xylanase regulator 1) of the ascomycete
Hypocrea jecorina
(anamorph
Trichoderma reesei
) was recently demonstrated to play an essential role in the transcriptional regulation of the
xyn1
(xylanase 1-encoding) gene expression. Consequently, this study reports on the deletion of the
xyr1
gene from the
H. jecorina
genome. Comparative studies of the growth behavior of the different mutant strains (deleted and retransformed
xyr1
) grown on various carbon sources pointed to the strongly reduced ability of the
xyr1
deletion strain to utilize
d
-xylose and xylan. Transcriptional analysis of the
xyl1
(
d
-xylose reductase 1-encoding) gene as well as measurements of corresponding enzymatic activities gave evidence that Xyr1 takes part in the control of the fungal
d
-xylose pathway, in particular in the regulation of
d
-xylose reductase. It could be demonstrated that the uptake of
d
-xylose into the fungal cell is uninfluenced in the Δ
xyr1
strain. Furthermore, transcriptional regulation of the major hydrolytic enzyme-encoding genes
xyn1
and
xyn2
(xylanases 1 and 2),
cbh1
and
cbh2
(cellobiohydrolases 1 and 2), and
egl1
(endoglucanase 1) is strictly dependent on Xyr1. Regulation of the respective genes via Xyr1 is not affected by the substances mediating induction (xylose, xylobiose, and sophorose) and is indispensable for all modes of gene expression (basal, derepressed, and induced). Moreover, Xyr1, it was revealed, activated transcriptional regulation of inducer-providing enzymes such as β-xylosidase BXLI and β-glucosidase BGLI but was not shown to be involved in the regulation of BGLII.
Transcriptional Regulation of
MDR1
, Encoding a Drug Efflux Determinant, in Fluconazole-Resistant
Candida albicans
Strains through an Mcm1p Binding Site
Authors: Riggle Perry J. , Kumamoto Carol A.
Published: December 2006

Constitutive, high-level transcription of the gene encoding the drug efflux facilitator Mdr1p is commonly observed in laboratory and clinical strains of
Candida albicans
that are resistant to the antifungal drug fluconazole (FLC). In five independently isolated FLC
R
laboratory strains, introduction of a wild-type
MDR1
promoter fragment fused to the yeast enhanced green fluorescent protein (
yEGFP
) reporter gene resulted in high-level expression of GFP, demonstrating that overexpression of
MDR1
is dependent on a
trans-
acting factor. This study identified a 35-bp
MDR1
promoter element, termed the MDRE, that mediates high-level
MDR1
transcription. When inserted into a heterologous promoter, the MDRE was sufficient to mediate high-level expression of the
yEGFP
reporter gene specifically in
MDR1 trans
-activation strains. The MDRE promoted transcription in an orientation-independent and dosage-dependent manner. Deletion of the MDRE in the full-length promoter did not abolish
MDR1 trans-
activation, indicating that elements upstream of the MDRE also contribute to transcription of
MDR1
in these overexpression strains. Analysis of the MDRE sequence indicated that it contains an Mcm1p binding site very similar in organization to the site seen upstream of the
Saccharomyces cerevisiae MFA1
and
STE2
genes. Electrophoretic mobility shift analysis demonstrated that both wild-type, FLC-sensitive and
MDR1 trans
-activated, FLC-resistant strains contain a factor that binds the MDRE. Depletion of Mcm1p, by use of a strain in which
MCM1
expression is under the control of a regulated promoter (44), resulted in a loss of MDRE binding activity. Thus, the general transcription factor Mcm1p participates in the regulation of
MDR1
expression.
Identification and Biochemical Characterization of Serine Hydroxymethyl Transferase in the Hydrogenosome of
Trichomonas vaginalis
Authors: Mukherjee Mandira , Sievers Stuart A. , Brown Mark T. , Johnson Patricia J.
Published: December 2006

Serine hydroxymethyl transferase (SHMT) is a pyridoxal phosphate (PLP)-dependent enzyme that catalyzes the reversible conversion of serine and tetrahydrofolate to glycine and methylenetetrahydrofolate. We have identified a single gene encoding SHMT in the genome of
Trichomonas vaginalis
, an amitochondriate, deep-branching unicellular protist. The protein possesses a putative N-terminal hydrogenosomal presequence and was shown to localize to hydrogensomes by immunofluorescence analysis, providing evidence of amino acid metabolism in this unusual organelle. In contrast to the tetrameric SHMT that exists in the mammalian host, we found that the
T. vaginalis
SHMT is a homodimer, as found in prokaryotes. All examined SHMT contain an 8-amino-acid conserved sequence, VTTTTHKT, containing the active-site lysyl residue (Lys 251 in TvSHMT) that forms an internal aldimine with PLP. We mutated this Lys residue to Arg and Gln and examined structural and catalytic properties of the wild-type and mutant enzymes in comparison to that reported for the mammalian protein. The oligomeric structure of the mutant K251R and K251Q TvSHMT was not affected, in contrast to that observed for comparable mutations in the mammalian enzyme. Likewise, contrary to that observed for mammalian SHMT, the catalytic activity of K251R TvSHMT was unaffected in the presence of PLP. The K251Q TvSHMT, however, was found to be inactive. These studies indicate that the active site of the parasite enzyme is distinct from its prokaryotic and eukaryotic counterparts and identify TvSHMT as a potential drug target.
Regulation of the Nucleocytoplasmic Distribution of Snf1-Gal83 Protein Kinase
Authors: Hedbacker Kristina , Carlson Marian
Published: December 2006

Snf1 protein kinase containing the β subunit Gal83 is localized in the cytoplasm during growth of
Saccharomyces cerevisiae
cells in abundant glucose and accumulates in the nucleus in response to glucose limitation. Nuclear localization of Snf1-Gal83 requires activation of the Snf1 catalytic subunit and depends on Gal83, but in the
snf1Δ
mutant, Gal83 exhibits glucose-regulated nuclear accumulation. We show here that the N terminus of Gal83, which is divergent from those of the other β subunits, is necessary and sufficient for Snf1-independent, glucose-regulated localization. We identify a leucine-rich nuclear export signal in the N terminus and show that export depends on the Crm1 export receptor. We present evidence that catalytically inactive Snf1 promotes the cytoplasmic retention of Gal83 in glucose-grown cells through its interaction with the C terminus of Gal83; cytoplasmic localization of inactive Snf1-Gal83 maintains accessibility to the Snf1-activating kinases. Finally, we characterize the effects of glucose phosphorylation on localization. These studies define roles for Snf1 and Gal83 in determining the nucleocytoplasmic distribution of Snf1-Gal83 protein kinase.
Genetic Architecture of Hsp90-Dependent Drug Resistance
Authors: Cowen Leah E. , Carpenter Anne E. , Matangkasombut Oranart , Fink Gerald R. , Lindquist Susan
Published: December 2006

Hsp90 potentiates the evolution of azole resistance in the model yeast
Saccharomyces cerevisiae
and the opportunistic pathogen
Candida albicans
via calcineurin. Here, we explored effectors downstream of calcineurin regulating this Hsp90-dependent trait. Using
S. cerevisiae erg3
mutants as a model, we determined that both Crz1 and Hph1 modulate azole resistance.
Nucleocytoplasmic Shuttling of the Rpb4p and Rpb7p Subunits ofSaccharomyces cerevisiaeRNA Polymerase II by Two Pathways
Authors: Selitrennik Michael , Duek Lea , Lotan Rona , Choder Mordechai
Published: December 2006

Rpb4p and Rpb7p are subunits of the RNA polymerase II ofSaccharomyces cerevisiaethat form a dissociable heterodimeric complex. Whereas the only reported function of Rpb7p is related to transcription, Rpb4p has been found to also act in mRNA export and in the major mRNA decay pathway that operates in the cytoplasm, thus raising the possibility that Rpb4p links between the nuclear and cytoplasmic processes. Here we show that both Rpb4p and Rpb7p shuttle between the nucleus and the cytoplasm. Shuttling kinetics of the two proteins are similar as long as their interaction is possible, suggesting that they shuttle as a heterodimer. Under normal conditions, shuttling of Rpb4p and Rpb7p depends on ongoing transcription. However, during severe stresses of heat shock, ethanol, and starvation, the two proteins shuttle via a transcription-independent pathway. Thus, Rpb4p and Rpb7p shuttle via two pathways, depending on environmental conditions.
Skp1p Regulates Soi3p/Rav1p Association with Endosomal Membranes but Is Not Required for Vacuolar ATPase Assembly
Authors: Brace E. J. , Parkinson Leah P. , Fuller Robert S.
Published: December 2006

Skp1p is an essential component of SCF-type E3 ubiquitin ligase complexes and associates with these through binding to F-box proteins. Skp1p also binds F-box proteins in a number of non-SCF complexes. The Skp1p-associated yeast protein Soi3p/Rav1p (hereafter referred to as Rav1p) is a component of the RAVE complex required for regulated assembly of vacuolar ATPase (V-ATPase). Rav1p is also involved in transport of TGN proteins and endocytic cargo between early and late endosomes. To evaluate the role of Skp1p in the RAVE complex, we made use of the fact that overexpression of Rav1p is toxic because it sequesters Skp1p from essential interactions. We isolated a separation of function allele of
SKP1
,
skp1
(
Asn108Tyr
), that completely abrogated the Rav1p interaction but allowed Skp1p to perform other essential cellular functions. Cells containing the
skp1
(
Asn108Tyr
) allele as the sole source of Skp1p exhibited normal V-ATPase assembly and activity. However, in the
skp1
(
Asn108Tyr
) mutant strain, the membrane-associated pool of Rav1-green fluorescent protein was increased, suggesting that Skp1p is important for the release of Rav1p from endosomal membranes where it functions in V-ATPase assembly. Thus, although part of the RAVE complex, Skp1p does not appear to be involved in V-ATPase assembly but instead in the cycling of the complex off membranes. This work also provides a generalizable approach to defining the roles of interactions of Skp1p with individual F-box proteins through the isolation of special alleles of
SKP1
.
Messing with Bacterial Quorum Sensing
Authors: González Juan E. , Keshavan Neela D.
Published: December 2006

Quorum sensing is widely recognized as an efficient mechanism to regulate expression of specific genes responsible for communal behavior in bacteria. Several bacterial phenotypes essential for the successful establishment of symbiotic, pathogenic, or commensal relationships with eukaryotic hosts, including motility, exopolysaccharide production, biofilm formation, and toxin production, are often regulated by quorum sensing. Interestingly, eukaryotes produce quorum-sensing-interfering (QSI) compounds that have a positive or negative influence on the bacterial signaling network. This eukaryotic interference could result in further fine-tuning of bacterial quorum sensing. Furthermore, recent work involving the synthesis of structural homologs to the various quorum-sensing signal molecules has resulted in the development of additional QSI compounds that could be used to control pathogenic bacteria. The creation of transgenic plants that express bacterial quorum-sensing genes is yet another strategy to interfere with bacterial behavior. Further investigation on the manipulation of quorum-sensing systems could provide us with powerful tools against harmful bacteria.
The Bacterial Actin-Like Cytoskeleton
Authors: Carballido-López Rut
Published: December 2006

Recent advances have shown conclusively that bacterial cells possess distant but true homologues of actin (MreB, ParM, and the recently uncovered MamK protein). Despite weak amino acid sequence similarity, MreB and ParM exhibit high structural homology to actin. Just like F-actin in eukaryotes, MreB and ParM assemble into highly dynamic filamentous structures in vivo and in vitro. MreB-like proteins are essential for cell viability and have been implicated in major cellular processes, including cell morphogenesis, chromosome segregation, and cell polarity. ParM (a plasmid-encoded actin homologue) is responsible for driving plasmid-DNA partitioning. The dynamic prokaryotic actin-like cytoskeleton is thought to serve as a central organizer for the targeting and accurate positioning of proteins and nucleoprotein complexes, thereby (and by analogy to the eukaryotic cytoskeleton) spatially and temporally controlling macromolecular trafficking in bacterial cells. In this paper, the general properties and known functions of the actin orthologues in bacteria are reviewed.
Impact of Protein Kinase PKR in Cell Biology: from Antiviral to Antiproliferative Action
Authors: García M. A. , Gil J. , Ventoso I. , Guerra S. , Domingo E. , Rivas C. , Esteban M.
Published: December 2006

The double-stranded RNA-dependent protein kinase PKR is a critical mediator of the antiproliferative and antiviral effects exerted by interferons. Not only is PKR an effector molecule on the cellular response to double-stranded RNA, but it also integrates signals in response to Toll-like receptor activation, growth factors, and diverse cellular stresses. In this review, we provide a detailed picture on how signaling downstream of PKR unfolds and what are the ultimate consequences for the cell fate. PKR activation affects both transcription and translation. PKR phosphorylation of the alpha subunit of eukaryotic initiation factor 2 results in a blockade on translation initiation. However, PKR cannot avoid the translation of some cellular and viral mRNAs bearing special features in their 5′ untranslated regions. In addition, PKR affects diverse transcriptional factors such as interferon regulatory factor 1, STATs, p53, activating transcription factor 3, and NF-κB. In particular, how PKR triggers a cascade of events involving IKK phosphorylation of IκB and NF-κB nuclear translocation has been intensively studied. At the cellular and organism levels PKR exerts antiproliferative effects, and it is a key antiviral agent. A point of convergence in both effects is that PKR activation results in apoptosis induction. The extent and strength of the antiviral action of PKR are clearly understood by the findings that unrelated viral proteins of animal viruses have evolved to inhibit PKR action by using diverse strategies. The case for the pathological consequences of the antiproliferative action of PKR is less understood, but therapeutic strategies aimed at targeting PKR are beginning to offer promising results.
DNA Replication in the Archaea
Authors: Barry Elizabeth R. , Bell Stephen D.
Published: December 2006

The archaeal DNA replication machinery bears striking similarity to that of eukaryotes and is clearly distinct from the bacterial apparatus. In recent years, considerable advances have been made in understanding the biochemistry of the archaeal replication proteins. Furthermore, a number of structures have now been obtained for individual components and higher-order assemblies of archaeal replication factors, yielding important insights into the mechanisms of DNA replication in both archaea and eukaryotes.
An optimization model for workgroup-based repetitive scheduling
Authors: Huang Rong-yau , Sun Kuo-Shun
Published: December 2006

Most construction repetitive scheduling methods developed so far have been based on the premise that a repetitive project is comprised of many identical production units. Recently, Huang and Sun (2005) developed a workgroup-based repetitive scheduling method that takes the view that a repetitive construction project consists of repetitive activities of workgroups. Instead of repetitive production units, workgroups with repetitive or similar activities in a repetitive project are identified and employed in the planning and scheduling. The workgroup-based approach adds more flexibility to the planning and scheduling of repetitive construction projects and enhances the effectiveness of repetitive scheduling. This work builds on previous research and develops an optimization model for workgroup-based repetitive scheduling. A genetic algorithm (GA) is employed in model formation for finding the optimal or near-optimal solution. A chromosome representation, as well as specification of other parameters for GA analysis, is described in the paper. Two sample case studies, one simple and one sewer system project, are used for model validation and demonstration. Results and findings are reported.Key words: construction scheduling, repetitive project, workgroup, optimization, genetic algorithm.
Seismic hazard analysis: a comparative study
Authors: Hong H P , Goda K , Davenport A G
Published: December 2006

The quantitative seismic hazard maps for the 1970s National Building Code of Canada were evaluated using the Davenport–Milne method. The Cornell–McGuire method is employed to develop recent seismic hazard maps of Canada. These methods incorporate the information on seismicity, magnitude-recurrence relations, and ground motion (or response) attenuation relations. The former preserves and depends completely on details of the historical seismicity; the latter smoothes the irregular spatial occurrence pattern of the historical seismicity into seismic source zones. Further, the Epicentral Cell method, which attempts to incorporate the preserving and smoothing aspect of these methods, has been developed. However, the impact of the adopted assumptions on the estimated quantitative seismic hazard has not been investigated. This study provides a comparative seismic hazard assessment using the above-mentioned methods and simulation-based algorithms. The analysis results show that overall the Davenport–Milne method gives quasi-circular seismic hazard contours near significant historical events, and the Cornell–McGuire method smoothes the transition of contours. The Epicentral Cell method provides estimates approximately within the former and the latter. Key words: epicentral cell method, probability, seismic hazard, Thiessen polygon, Voronoi, uniform hazard spectra.
Fatigue behaviour of concrete beams post-tensioned with unbonded carbon fibre reinforced polymer tendons
Authors: Braimah Abass , Green Mark F , Campbell T Ivan
Published: December 2006

Much research has been conducted in the past decade to evaluate the suitability of fibre reinforced polymer (FRP) reinforcement in concrete structures. Most of the research has concentrated on the short-term performance of FRP prestressed and reinforced concrete beams. Only a limited amount of research has considered the fatigue behaviour of FRP prestressed beams. This paper presents an experimental research program designed to examine the fatigue behaviour of unbonded carbon fibre reinforced polymer (CFRP) post-tensioned concrete beams. The fatigue test program consisted of five large-scale (4.0 m span) concrete T-beams. Three of the beams were post-tensioned with CFRP tendons, and the remaining two beams were post-tensioned with steel prestressing strands. The fatigue load limits were chosen to produce an additional stress range of about 100 MPa in the lower prestressing reinforcement. During fatigue testing, some of the prestressing strands fractured at the anchor location. In the steel post-tensioned beams, fracture of wires in the seven-wire prestressing strands did not result in total failure of the steel post-tensioned beams, as the unbroken wires continued to carry prestress force. In the CFRP post-tensioned beams, however, fracture led to splintering of the tendon between the anchors and total loss of prestress force. In general, the CFRP post-tensioned beams performed satisfactorily in fatigue, in comparison with the steel post-tensioned beams, as long as premature failure of the tendons near the anchor location was prevented.Key words: fibre reinforced polymer (FRP), anchorage, tendon, fatigue, post-tension, concrete, beam, dynamic, testing.
Flexural strength of cold-formed steel joists with reinforced web openings
Authors: Sivakumaran K S , Ng Ming Yin , Fox Steven R
Published: December 2006

The floor joists of cold-formed steel (CFS) structures often require large web openings. Reinforcement of such openings may mitigate the detrimental effects of such web openings. This paper is based on an experimental investigation that considered 203 mm deep (base thickness 1.89 mm) galvanized, lipped channel sections with circular, square, and rectangular openings and two associated reinforcement schemes (screw fastening of 31.8 mm × 1.1 mm thick bridging channel). Since the focus of this investigation was on the flexural strength of such joists, the test specimens were simply supported and were subjected to two equal point loads at equal distance from the supports. Two lipped channel sections were set face-to-face to form the test specimen assembly. Based on 11 sets of three identical flexural tests, it was determined that (i) the tension zones of the web with a large opening need not be reinforced, (ii) closely spaced screw fastening of reinforcements (bridging channel) is essential, and (iii) the reinforcements need to be fastened as close as possible to the compression edges of the opening to minimize local buckling of these edges. This paper demonstrates that it is possible to establish cost-effective reinforcement schemes for CFS sections with large web openings.Key words: cold-formed steel, joists, flexural strength, web openings, reinforcements, experimental.
Adaptive gradual plastic hinge model for nonlinear analysis of steel frameworks
Authors: Gong Yanglin
Published: December 2006

This paper presents a new refined plastic hinge method for nonlinear analysis of steel frameworks. The unique feature of the method is a newly developed adaptive plastic hinge model that is capable of modeling the degradation of stiffness of a steel frame member due to the spread of plasticity both through the section depth and along the member length. Subsequently, it has been identified that there are two key parameters in the modeling. The first involves mimicking the spread of plasticity through a section depth, while the second incorporates the spread of plasticity along a member length. Procedures to determine the key parameters are then developed using moment–curvature–thrust relationship for beam-columns. The proposed analysis method is perceived to be especially advantageous when the spread of plasticity along a member length is modeled using various discretization schemes. Two numerical examples are performed to demonstrate the accuracy and simplicity of the method. Key words: steel frames, plasticity, second-order analysis, plastic hinge, beam-columns.
Erosional properties of the sediments in the Petitcodiac River estuary at Moncton, New Brunswick
Authors: Haralampides Katy , Rodriguez Andres
Published: December 2006

The Petitcodiac River estuary was modified after the construction of a causeway in 1968 at Moncton, New Brunswick. To address some of the sediment-related issues associated with recent proposed changes to the causeway, it is essential to characterize the sediment properties. Several samples were obtained in 2003 and 2004 at eight sites from the upper 5 km of the existing estuary to determine sediment properties including particle size, bulk density, in situ water content, and organic content. These properties were determined from cores extracted from the field and reconstituted cores prepared in the laboratory. Facilities to evaluate the erosion rates of relatively undisturbed sediment cores from the field were constructed; four box cores were tested in a 10 m flume to determine erosion rates with depth. In most cases, erosion rates increased with an increase in the applied boundary shear stress and were strongly dependent on sediment properties and the depositional history of the bed.Key words: cohesive sediments, sediment transport, local boundary shear stress, erosion rates.
Remediation of white phosphorus contamination in an Alaskan wetland
Authors: Walsh Michael R , Zufelt Jon E , Collins Charles M
Published: December 2006

Eagle River Flats, an estuarine salt marsh located on Fort Richardson near Anchorage, Alaska, has been utilized as a military impact area for almost 60 years and is contaminated with white phosphorus, a highly toxic element used as an obscurant. When munitions containing white phosphorus were fired into the cool, wet glacial sediments of the Flats, particles of the disbursed chemical became extinguished. Dabbling ducks and swans sieve these seed-size particles from the bottoms of ponds throughout the range. The persistence of the particles in the saturated sediments has resulted in thousands of waterfowl deaths that continue 15 years after the cessation of the munition's use. A remediation method was devised to attenuate the contaminant that will be effective in the short, cool summer season while minimally impacting the environment. Although the cold climate limits the efficiency of the remediation, we were also able to use it to our advantage. Key words: white phosphorus, remediation, dabbling ducks, cold, ice, glacial silt, contamination, impact range, pumping, unexploded ordnance.
Ozone treatment for the degradation of resin and unsaturated fatty acids at low temperatures
Authors: El-Din Mohamed Gamal , Smith Daniel W , Momani Fares Al , Ikehata Keisuke
Published: December 2006

Ozonation of abietic and linoleic acids (resin and fatty acids; RFAs) was investigated at various pHs and low temperatures (0 to 10 °C) using a rapid-scan stopped-flow spectrophotometer. Degradation of abietic and linoleic acids could be enhanced by manipulating reaction conditions, including ozone dose, temperature, and pH. Improved degradation of RFAs at higher pHs suggests hydroxyl radical reaction is playing an important role during the ozonation. The apparent overall second order rate constants were determined based on the pseudo-first order rate constants for acids and for ozone. At pH 11 and 10 °C, they were calculated as 6.6 x 103 M–1· s–1 and 1.0 x 104 M–1· s–1 for abietic and linoleic acids, respectively. The acute toxicity assessed by Microtox® bioassay increased after ozonation by 140% in the case of abietic acid, whereas it reduced to half in the case of linoleic acid. Key words: ozone, oxidation kinetics, resin acids, fatty acids, toxicity, rapid-scan stopped-flow spectrophotometry, pulp mill effluent.
Pyrolysis-GC/MS analysis of leachates for differentiating the parent matter of DOM
Authors: Seelen Sarah , White Daniel , Yoshikawa Kenji , Autier Vincent
Published: December 2006

The purpose of this study was to better understand the link between dissolved organic matter (DOM) in soil leachates and the different vegetation cover types in a boreal forest. Soil cores were collected from the Caribou Poker Creeks Research Watershed (CPCRW) and subjected to a laboratory leaching procedure. The leachates were subjected to a number of analytical tests, including pyrolysis-gas chromotagraphy/mass spectrometry (py-GC/MS). Py-GC/MS is a molecular fingerprinting technique that proved capable of characterizing the DOM obtained from the various soil leachates. The molecular fingerprint and vegetation types were compared with Student's t test and principal component analysis. Results from these tests support a conclusion that the characteristics of cover vegetation can be detected in leachates. Coniferous and deciduous trees could be statistically differentiated based on their molecular fingerprints with statistical significance (p < 0.005). By using, the combination of py-GC/MS and rigorous multivariate statistical analysis one can better understand the source of DOM based on characteristics it retains. Key words: py-GC/MS, DOM, molecular fingerprint, leachate.
Residence time distribution analysis of an intermittently operating truck fill facility to determine effective contact time
Authors: Svrcek Clark , Guest Rodney K , Smith Daniel W
Published: December 2006

Two tracer studies were performed on a First Nations water treatment plant (WTP) reservoir in order to determine the reactor mixing pattern as well as the effective contact time, or t10, value. A unique characteristic of the reservoir in question was that the major outlet from the tank was a truck fill station that operated intermittently throughout the day as water haul trucks filled up for delivery. Almost three times the flowrate was removed as was added, and coupled with the undersized reservoir resulted in major short-circuiting in the unbaffled contact chamber. The reservoir showed an almost ideal completely mixed flow regime, and the lowest t10 value determined from 2 days of testing was 14 min, much lower than what was required for chlorine Ct compliance. The residence time distribution curves also showed a unique step shape that resulted from the intermittent operation of the truck fill. With the introduction of a lagged time factor a generalized approach for analysis of existing truck fills and the design of new facilities was developed using easily quantifiable variables. An alternative approach for the design of new truck fill facilities was also provided and is somewhat more conservative than the lagged time factor method but allows for a more flexible water delivery schedule. Given the prevalence of truck fill stations in northern communities and the upcoming need for infrastructure upgrades to comply with new standards and guidelines this approach will help ensure the continued protection of public health through the potable water system. Key words: truck fill, residence time distribution, Ct concept, tracer study, water treatment facility design, public health.
Indoor and outdoor SO2 in a community near oil sand extraction and production facilities in northern Alberta
Authors: Kindzierski W B , Ranganathan H. K.S.
Published: December 2006

A baseline study measuring indoor and outdoor sulfur dioxide (SO2) levels was undertaken in a small native community (Fort McKay) in northern Alberta. The objective was to assess whether proximity of numerous oil sand operations affected air quality in the community. A passive sampling device was deployed for 96 h durations at 30 randomly selected homes over a 6 week period such that 75% of homes were sampled during weekdays and 25% during weekends. The common living area of each home (kitchen or family room) was sampled indoors. Outdoor passive samplers were attached to a sampling stand under a shelter in the yard. Indoor SO2 levels were all less than a method detection limit of 1.3 µg/m3 (n = 30). The median outdoor level was 1.7 µg/m3 (n = 28, range 1.3 to 3.7 µg/m3, 70% > method detection level). Results of testing to determine accuracy and precision of the monitors showed both measures to be within 35% based on a 96 h average measurement. Overall, these levels are considered very low and consistent with levels observed elsewhere in Alberta. Key words: sulfur dioxide, passive sampling, indoor and outdoor air.
Public health evaluation of drinking water systems for First Nations reserves in Alberta, Canada
Authors: Smith D W , Guest R K , Svrcek C P , Farahbakhsh K
Published: December 2006

Fifty-six drinking water systems on First Nations reserves in Alberta, Canada were evaluated for their ability to protect public health. A detailed survey form was used during each site visit to collect information necessary for the public health evaluation of the water supply system from source water to the end consumer, based on a variety of potential risk factors. For the 56 water systems evaluated, 50 of the water supply systems were ranked as high risk, 5 were ranked as medium risk, and there was 1 low risk site. The numerical scores ranged from a low of 7.5 to a high of 92.5 out of 100.0, with a higher score representing a water system better equipped to supply water meeting the Guidelines for Canadian Drinking Water Quality. In addition to the unique cultural, political, social, and economic environment on First Nations reserves a major factor that made it difficult to comprehensively assess the level of potential risk at these sites was the lack of source water characterization for pathogens (especially protozoan parasites). A major challenge in these small communities was providing meaningful training to First Nations public works personnel in the context of their cultural beliefs so that they develop a feeling of responsibility and ownership in helping protect their community's health. Additionally, there were prevalent inadequacies in the bacteriological monitoring and testing programs on the reserves. Addressing these issues would allow for a better assessment of potential health risks on First Nation reserves in Alberta and allow these communities to better manage the risks to their drinking water systems on a continual basis. Key words: risk evaluation, drinking water treatment and distribution, small systems, First Nations.
Membrane filtration for cold regions – impact of cold water on membrane integrity monitoring tests
Authors: Farahbakhsh Khosrow , Smith Daniel W
Published: December 2006

Low-pressure water treatment membranes, microfiltration (MF) and ultrafiltration (UF) have enjoyed unprecedented growth during the past decade. These systems are particularly suited for cold region communities because of their operational simplicity, small footprint, and consistent performance despite the fluctuations in raw water characteristics. Effective operation of MF and UF membrane systems in cold regions, however, must account for the impact of low water temperatures on membrane operation. Of particular interest is the impact of cold water on direct membrane integrity monitoring tests. Most regulatory bodies require that regular integrity monitoring tests be performed for low-pressure membranes to ensure the integrity of the membrane systems. Currently, the most widely-used integrity monitoring test is the pressure decay test. Our studies, however, indicated that the pressure-based direct integrity monitoring tests are affected by variations in water temperature, especially in the range of 0 to 5 °C. The considerable drop in diffusive air flow rates and consequent decrease in pressure decay rate for an intact membrane as water temperatures approach 0 may mask the impact of a defect and should be accounted for. It is suggested that the criteria for membrane integrity tests in cold regions shift downward to account for the effect of temperature. This paper presents the results obtained from studies on the effect of water temperature on the pressure-based direct integrity monitoring tests. Key words: membrane integrity monitoring, pressure decay test, diffusive air flow test, low-pressure membranes, microfiltration, ultrafiltration, water treatment, pathogen removal.
Induction of apoptosis in K562 cells by jolkinolide B
Authors: Luo Huiying , Wang Aiqin
Published: December 2006

Jolkinolide B, a bioactive diterpene isolated from the roots of Euphorbia fischeriana Steud, has various biological and pharmacological properties. In this study, the cytotoxicity of highly purified jolkinolide B was tested in human chronic myeloid leukemia (K562) and 2 other cell lines (human esophageal carcinoma Eca-109 and human hepatoma HepG2). The results indicate a significant decrease in the proliferation of all the 3 cell lines when treated with jolkinolide B for 24 h; the IC50 value of cytotoxicity was 12.1 μg/mL (for K562 cells), >50.0 μg/mL (for HepG2 cells), and 23.7 μg/mL (for Eca-109 cells). Further study of K562 cells involving fluorescence and transmission electron microscopy revealed characteristic apoptotic features, such as cell shrinkage, membrane blebbing, loss of microvilli, and nuclear condensation. Agarose electrophoresis of genomic DNA showed a typical fragmentation pattern for apoptotic cells. A kinetic cell-cycle analysis demonstrated that the cell cycle was arrested in the G1 phase. All these results suggest that the anti-proliferation effect of jolkinolide B on K562 cells is achieved by arresting the cell cycle in the G1 phase and subsequently inducing apoptosis.
Effect of stress on hepatic 11β-hydroxysteroid dehydrogenase activity and its influence on carbohydrate metabolism
Authors: Altuna María Eugenia , Lelli Sandra Marcela , Martín de Viale Leonor C. San , Damasco María Cristina
Published: December 2006

Stress activates the synthesis and secretion of catecholamines and adrenal glucocorticoids, increasing their circulating levels. In vivo, hepatic 11β-hydroxysteroid dehydrogenase 1 (HSD1) stimulates the shift of 11-dehydrocorticosterone to corticosterone, enhancing active glucocorticoids at tissue level. We studied the effect of 3 types of stress, 1 induced by bucogastric overload with 200 mmol/L HCl causing metabolic acidosis (HCl), the second induced by bucogastric overload with 0.45% NaCl (NaCl), and the third induced by simulated overload (cannula), on the kinetics of hepatic HSD1 of rats and their influence on the activity of the gluconeogenic enzyme phosphoenolpyruvate carboxykinase, glycemia, and glycogen deposition. Compared with unstressed controls, all types of stress significantly increased HSD1 activity (146% cannula, 130% NaCl, and 253% HCl), phosphoenolpyruvate carboxykinase activity (51% cannula, 48% NaCl, and 86% HCl), and glycemia (29% cannula, 30% NaCl, and 41% HCl), but decreased hepatic glycogen (68% cannula, 68% NaCl, and 78% HCl). Owing to these results, we suggest the following events occur when stress is induced: an increase in hepatic HSD1 activity, augmented active glucocorticoid levels, increased gluconeogenesis, and glycemia. Also involved are the multiple events indirectly related to glucocorticoids, which lead to the depletion of hepatic glycogen deposits, thereby contributing to increased glycemia. This new approach shows that stress increments the activity of hepatic HSD1 and suggests that this enzyme could be involved in the development of the Metabolic Syndrome.
Effects of sympathetic stimulation during cooling on hypothermic as well as posthypothermic hemodynamic function
Authors: Kondratiev T.V. , Tveita T.
Published: December 2006

This experimental study was performed to explore hemodynamic effects of a moderate dose epinephrine (Epi) during hypothermia and to test the hypothesis whether sympathetic stimulation during cooling affects myocardial function following rewarming. Two groups of male Wistar rats (each, n = 7) were cooled to 15 °C, maintained at this temperature for 1 h, and then rewarmed. Group 1 received 1 μg/min Epi, i.v., for 1 h during cooling to 28 °C, a dose known to elevate cardiac output (CO) by approximately 25% at 37 °C. Group 2 served a saline solution control. At 37 °C, Epi infusion elevated CO, left ventricular systolic pressure, maximum rate of left ventricle pressure rise, and mean arterial pressure. During cooling to 28 °C, these variables, with the exception of mean arterial pressure, decreased in parallel to those in the saline solution group. In contrast, in the Epi group, mean arterial pressure remained increased and total peripheral resistance was significantly elevated at 28 °C. Compared with corresponding prehypothermic values, most hemodynamic variables were lowered after 1 h at 15 °C in both groups (except for stroke volume). After rewarming, alterations in hemodynamic variables in the Epi-treated group were more prominent than in saline solution controls. Thus, before cooling, continuous Epi infusion predominantly stimulates myocardial mechanical function, materialized as elevation of CO, left ventricular systolic pressure, and maximum rate of left ventricle pressure rise. Cooling, on the other hand, apparently eradicates central hemodynamic effects of Epi and during stable hypothermia, elevation of peripheral vascular vasopressor effects seem to take over. In contrast to temperature-matched, non-Epi stimulated control rats, a significant depression of myocardial mechanical function occurs during rewarming following a moderate sympathetic stimulus during initial cooling.
Protective effects of polysaccharide from Euphorbia kansui (Euphorbiaceae) on the swimming exercise-induced oxidative stress in mice
Authors: Yu Farong , Lu Shunqing , Yu Fahong , Feng Shutao , McGuire Peter M. , Li Rende , Wang Rui
Published: December 2006

The present study examined the effects of derivatives of galactosides and glucosides in a polysaccharide extract from Euphorbia kansui (Euphorbiaceae) on exercise-induced oxidative stress in mice. Exhaustive swimming exercise significantly increases the degree of lipid peroxidation in terms of malondialdehyde content and reduces the antioxidant activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx). Our findings revealed that chronic oral treatment with the extract elevates enzymatic activities of SOD and GPx accompanied by a corresponding decrease in malondialdehyde. The antioxidative activities of these compounds against exercise-induced oxidative stress are correlated with various activities such as reducing the production of superoxide and hydroxyl radicals, inhibiting lipid peroxidation, enhancing antioxidative defenses, and increasing the production of SOD and GPx activity and expression in different tissues. These compounds may be involved in glycogen metabolism to meet the requirement of working skeletal muscles and act as antioxidants by terminating the chain reaction of lipid peroxidation to maintain the morphological stability of mitochondria in spinal motor neurons. These observations suggest that E. kansui has antioxidative and antifatigue properties and can be given as prophylactic and (or) therapeutic supplements for increasing antioxidant enzyme activities and preventing lipid peroxidation during strenuous exercise.
The role of caspase-3 in lipopolysaccharide-mediated disruption of intestinal epithelial tight junctions
Authors: Chin Alex C. , Flynn Andrew N. , Fedwick Jason P. , Buret Andre G.
Published: December 2006

The mechanisms responsible for microbially induced epithelial apoptosis and increased intestinal permeability remain unclear. This study assessed whether purified bacterial lipopolysaccharide (LPS) increases epithelial apoptosis and permeability and whether these changes are dependent on caspase-3 activation. In nontumorigenic epithelial monolayers, Escherichia coli O26:B6 LPS increased apoptosis, as shown by nuclear breakdown, caspase-3 activation, and PARP cleavage, and induced disruption of tight junctional ZO-1. Apical, but not basolateral, exposure to LPS increased epithelial permeability. Addition of a caspase-3 inhibitor abolished the effects of LPS. The findings describe a novel mechanism whereby apical LPS may disrupt epithelial tight junctional ZO-1 and barrier function in a caspase-3-dependent fashion.
Parasites of spottail shiners (Notropis hudsonius) in the St. Lawrence River: effects of municipal effluents and habitat
Authors: Marcogliese David J , Gendron Andrée D , Plante Céline , Fournier Michel , Cyr Daniel
Published: December 2006

Parasite communities were examined from spottail shiners (Notropis hudsonius (Clinton, 1824)) collected from nine localities in the St. Lawrence River around the Island of Montréal and downstream from its municipal effluents in June and September 1998–2000. A total of 30 taxa were found, the most common being Diplostomum spp. Parasite communities were dominated by digeneans, most of which were larval stages that infect birds as definitive hosts. Mean abundance of the most common parasites varied among localities and years. Component community and mean infracommunity species richness fluctuated within and among years at the various localities. Similarity analyses demonstrated that parasite component communities from the different localities could be partitioned according to season, year, and water mass. Canonical correspondence analysis demonstrated that the parasite component communities from the different localities could be distinguished clearly, indicating that the fish in the different localities compose separate populations or stocks. Year, season, and water mass correlated most strongly among the species–environment relationships. The abundance and distribution of parasite species appeared to be subtly influenced by environmental contaminants and urban effluents, leading to slight reductions in parasite diversity. However, the parasite species composition at the various localities more clearly reflected the local food-web structure and biodiversity in terms of the distributions of various invertebrate groups, piscivorous fish, and waterfowl along the St. Lawrence River.