bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification and Characterization of a Novel Uropathogenic
Escherichia coli
-Associated Fimbrial Gene Cluster
Authors: Buckles Eric L. , Bahrani-Mougeot Farah K. , Molina Anita , Lockatell C. Virgina , Johnson David E. , Drachenberg Cinthia B. , Burland Valerie , Blattner Fred R. , Donnenberg Michael S.
Published: June 2004

Recently, we identified a fimbrial usher gene in uropathogenic
Escherichia coli
strain CFT073 that is absent from an
E. coli
laboratory strain. Analysis of the CFT073 genome indicates that this fimbrial usher gene is part of a novel fimbrial gene cluster,
aufABCDEFG
. Analysis of a collection of pathogenic and commensal strains of
E. coli
and related species revealed that the
auf
gene cluster was significantly associated with uropathogenic
E. coli
isolates. For in vitro expression analysis of the
auf
gene cluster, RNA was isolated from CFT073 bacteria grown to the exponential or stationary phase in Luria-Bertani broth and reverse transcriptase PCR (RT-PCR) with oligonucleotide primers specific to the major subunit,
aufA
, was performed. We found that
aufA
is expressed in CFT073 only during the exponential growth phase; however, no expression of AufA protein was observed by Western blotting, indicating that under these conditions, the expression of the
auf
gene cluster is low. To determine if the
auf
gene cluster is expressed in vivo, RT-PCR was performed on bacteria from urine samples of mice infected with CFT073. Out of three independent experiments, we were able to detect expression of
aufA
at least once at 4, 24, and 48 h of infection, indicating that the
auf
gene cluster is expressed in the murine urinary tract. Furthermore, antisera from mice infected with CFT073 reacted with recombinant AufA in an enzyme-linked immunosorbent assay. To identify the structure encoded by the
auf
gene cluster, a recombinant plasmid containing the
auf
gene cluster under the T7 promoter was introduced into the
E. coli
BL-21 (AI) strain. Immunogold labeling using AufA antiserum revealed the presence of amorphous material extending from the surface of BL-21 cells. No hemagglutination or cellular adherence properties were detected in association with expression of AufA. Deletion of the entire
auf
gene cluster had no effect on the ability of CFT073 to colonize the kidney, bladder, or urine of mice. In addition, no significant histological differences between the parent and
aufC
mutant strain were observed. Therefore, Auf is a uropathogenic
E. coli-
associated structure that plays an uncertain role in the pathogenesis of urinary tract infections.
Relative Importance of Heat-Labile Enterotoxin in the Causation of Severe Diarrheal Disease in the Gnotobiotic Piglet Model by a Strain of Enterotoxigenic
Escherichia coli
That Produces Multiple Enterotoxins
Authors: Berberov Emil M. , Zhou You , Francis David H. , Scott Michael A. , Kachman Stephen D. , Moxley Rodney A.
Published: June 2004

Enterotoxigenic
Escherichia coli
(ETEC) strains that produce multiple enterotoxins are important causes of severe dehydrating diarrhea in human beings and animals, but the relative importance of these enterotoxins in the pathogenesis is poorly understood. Gnotobiotic piglets were used to study the importance of heat-labile enterotoxin (LT) in infection with an ETEC strain that produces multiple enterotoxins. LT
−
(Δ
eltAB
) and complemented mutants of an F4
+
LT
+
STb
+
EAST1
+
ETEC strain were constructed, and the virulence of these strains was compared in gnotobiotic piglets expressing receptors for F4
+
fimbria. Sixty percent of the piglets inoculated with the LT
−
mutant developed severe dehydrating diarrhea and septicemia compared to 100% of those inoculated with the nalidixic acid-resistant (Nal
r
) parent and 100% of those inoculated with the complemented mutant strain. Compared to piglets inoculated with the Nal
r
parent, the mean rate of weight loss (percent per hour) of those inoculated with the LT
−
mutant was 67% lower (
P
< 0.05) and that of those inoculated with the complemented strain was 36% higher (
P
< 0.001). Similarly, piglets inoculated with the LT
−
mutant had significant reductions in the mean bacterial colony count (CFU per gram) in the ileum; bacterial colonization scores (square millimeters) in the jejunum and ileum; and clinical pathology parameters of dehydration, electrolyte imbalance, and metabolic acidosis (
P
< 0.05). These results indicate the significance of LT to the development of severe dehydrating diarrhea and postdiarrheal septicemia in ETEC infections of swine and demonstrate that EAST1, LT, and STb may be concurrently expressed by porcine ETEC strains.
Effect of Anaerobiosis on Expression of Virulence Factors inVibrio cholerae
Authors: Krishnan H. H. , Ghosh Amalendu , Paul Kalidas , Chowdhury Rukhsana
Published: June 2004

InVibrio cholerae, the transmembrane DNA binding proteins, ToxR and TcpP, activate expression of the regulatory genetoxTin response to specific environmental signals. The resulting enhanced level of ToxT leads to a coordinated increase in the production of a subset of virulence factors, including cholera toxin (CT) and toxin-coregulated pilus (TCP). The effect of anaerobiosis on expression of theV. choleraevirulence regulatory cascade was examined. The expression of the major regulatory genes,tcpP,toxR, andtoxT, in anaerobically grownV. choleraewas comparable to that in cells grown under aerobic conditions, and no significant difference in the ToxT-dependent expression oftcpAwas detected when aerobic and anaerobic cultures were compared. However, in spite of the presence of functional ToxT,ctxABexpression was drastically reduced, and practically no CT was detected in cells grown under anaerobic conditions. In aV. cholerae hnsmutant, however, high levels ofctxABexpression occurred even under anaerobic conditions. Also, deletion of the H-NS binding site from thectxABpromoter eliminated anaerobic repression ofctxABexpression. These results suggest that H-NS directly repressesctxABexpression under anaerobic growth conditions. It has been reported that in the first stage of infection of infant miceby V. cholerae,tcpAis expressed butctxABexpression is shut off (S. H. Lee, D. L. Hava, M. K. Waldor, and A. Camilli, Cell99:625-634, 1999). This pattern is similar to the pattern in anaerobic cultures ofV. cholerae. Under all other in vitro conditions,ctxABandtcpAare known to be coordinately expressed.
Identification of theEntamoeba histolyticaGalactose-Inhibitable Lectin Epitopes Recognized by Human Immunoglobulin A Antibodies following Cure of Amebic Liver Abscess
Authors: Abd-Alla Mohamed D. , Jackson Terry F. G. H. , Soong Ginny C. , Mazanec Mary , Ravdin Jonathan I.
Published: June 2004

Immunity toEntamoebaspecies intestinal infection is associated with the presence of intestinal IgA antibodies against the parasite's galactose-inhibitable adherence lectin. We determined the epitope specificity of serum and intestinal antilectin IgA antibodies by enzyme-linked immunosorbent assay using overlapping fragments of a recombinant portion of the lectin heavy subunit, designated LC3. These findings were correlated with the effects of epitope-specific murine antilectin immunoglobulin A (IgA) monoclonal antibodies (MAbs) on amebic in vitro galactose-specific adherence. LC3 is a highly antigenic and immunogenic cysteine-rich protein (amino acids [aa] 758 to 1150) that includes the lectin's carbohydrate binding domain. The study subjects, from Durban, South Africa, were recently cured of amebic liver abscess (ALA) with or without concurrentEntamoeba histolyticaintestinal infection or were infection free 1 year after cure. We also studied seropositive subjects that were infected withE. histolytica, disease free, and asymptomatic. Serum anti-LC3 IgA antibodies from all study groups exclusively recognized the third (aa 868 to 944) and the seventh (aa 1114 to 1134) LC3 epitopes regardless of clinical status; epitope 6 (aa 1070 to 1114) was also recognized by serum anti-LC3 IgG antibodies. However, IgG antibody recognition of epitope 6 but not 3 or 7 was lost 1 year following cure of ALA. We produced 14 murine anti-LC3 IgA MAbs which collectively recognized five of the seven LC3 epitopes. The majority of the murine MAbs recognized the first epitope (aa 758 to 826), which was not recognized by human IgA antibodies. Interestingly, adherence ofE. histolyticatrophozoites to CHO cells was inhibited by MAbs against epitopes 1, 3, 4 (aa 944 to 987), and 6 (P< 0.01). The LC3 epitopes recognized by human IgA antibodies (3 and 7) were further characterized by use of overlapping synthetic peptides. We identified four peptides (aa 891 to 903, 918 to 936, 1114 to 1134, and 1128 to 1150) that in linear or cyclized form were recognized by pooled intestinal IgA antibodies and serum IgG antibodies from subjects with ALA and asymptomatic, seropositive infected subjects. This study identifies the lectin epitopes to be studied in an amebiasis subunit vaccine designed to elicit mucosal immunity mimicking that of humans cured of ALA.
Characterization of a Complement-Binding Protein, DRS, from Strains of
Streptococcus pyogenes
Containing the
emm12
and
emm55
Genes
Authors: Binks Michael , Sriprakash K. S.
Published: June 2004

An extracellular protein of
Streptococcus pyogenes
, streptococcal inhibitor of complement (SIC), and its variant, called DRS (distantly related to SIC), are expressed by some
S. pyogenes
strains. SIC from type 1 (M1) isolates of
S. pyogenes
interferes with complement-mediated cell lysis, reportedly via its interaction with complement proteins. In this study we demonstrate that
S. pyogenes
strains carrying
emm12
and
emm55
(the genes for the M12 and M55 proteins, respectively) express and secrete DRS. This protein, like SIC, binds to the C6 and C7 complement proteins, and competition enzyme-linked immunosorbent assay experiments demonstrate that DRS competes with SIC for C6 and C7 binding. Similarly, SIC competes with DRS for binding to the complement proteins. Despite this, the recombinant DRS preparation showed no significant effect on complement function, as determined by lysis of sensitized sheep erythrocytes. Furthermore, the presence of DRS is not inhibitory to SIC activity.
Yersinia enterocolitica
Type III Secretion Depends on the Proton Motive Force but Not on the Flagellar Motor Components MotA and MotB
Authors: Wilharm Gottfried , Lehmann Verena , Krauss Kristina , Lehnert Beatrix , Richter Susanna , Ruckdeschel Klaus , Heesemann Jürgen , Trülzsch Konrad
Published: June 2004

The flagellum is believed to be the common ancestor of all type III secretion systems (TTSSs). In
Yersinia enterocolitica
, expression of the flagellar TTSS and the Ysc (Yop secretion) TTSS are inversely regulated. We therefore hypothesized that the Ysc TTSS may adopt flagellar motor components in order to use the pathogenicity-related translocon in a drill-like manner. As a prerequisite for this hypothesis, we first tested a requirement for the proton motive force by both systems using the protonophore carbonyl cyanide
m
-chlorophenylhydrazone (CCCP). Motility as well as type III-dependent secretion of Yop proteins was inhibited by CCCP. We deleted
motAB
, which resulted in an immotile phenotype. This mutant, however, secreted amounts of Yops to the supernatant comparable to those of the wild type. Translocation of Yops into host cells was also not affected by the
motAB
deletion. Virulence of the mutant was comparable to that of the wild type in the mouse oral infection model. Thus, the hypothesis that the Ysc TTSS might adopt flagellar motor components was not confirmed. The finding that, in addition to consumption of ATP, Ysc TTSS requires the proton motive force is discussed.
Disruption of the Phagosomal Membrane and Egress ofLegionella pneumophilainto the Cytoplasm during the Last Stages of Intracellular Infection of Macrophages andAcanthamoeba polyphaga
Authors: Molmeret Maëlle , Bitar Dina M. , Han Lihui , Kwaik Yousef Abu
Published: June 2004

Although the early stages of intracellular infection byLegionella pneumophilaare well established at the ultrastructural level, a detailed ultrastructural analysis of late stages of intracellular replication has never been done. Here we show that the membrane of theL. pneumophila-containing phagosome (LCP) is intact for up to 8 h postinfection of macrophages andAcanthamoeba polyphaga. At 12 h, 71 and 74% of the LCPs are disrupted within macrophages andA. polyphaga, respectively, while the plasma membrane remains intact. At 18 and 24 h postinfection, cytoplasmic elements such as mitochondria, lysosomes, vesicles, and amorphous material are dispersed among the bacteria and these bacteria are considered cytoplasmic. At 18 h, 77% of infected macrophages and 32% of infectedA. polyphagaamoebae harbor cytoplasmic bacteria. At 24 h, 99 and 78% of infected macrophages and amoebae, respectively, contain cytoplasmic bacteria. On the basis of lysosomal acid phosphatase staining of infected macrophages andA. polyphaga, the lysosomal enzyme is present among the bacteria when host vesicles are dispersed among bacteria. Our data indicate that bacterial replication proceeds despite physical disruption of the phagosomal membrane. We also show that anlspGmutant that is defective in the type II secretion system and therefore does not secrete the hydrolytic enzymes metalloprotease,p-nitrophenol phosphorylcholine hydrolase, lipase, phospholipase A, and lysophospholipase A is as efficient as the wild-type strain in disruption of the LCP. Therefore,L. pneumophiladisrupts the phagosomal membrane and becomes cytoplasmic at the last stages of infection in both macrophages andA. polyphaga. Lysosomal elements, mitochondria, cytoplasmic vesicles, and amorphous material are all dispersed among the bacteria, after phagosomal disruption, within both human macrophages andA. polyphaga. The disruption of the LCP is independent of the hydrolytic enzymes exported by the type II secretion system.
Protection Afforded by Heat Shock Protein 60 fromFrancisella tularensisIs Due to Copurified Lipopolysaccharide
Authors: Hartley M. G. , Green M. , Choules G. , Rogers D. , Rees D. G. C. , Newstead S. , Sjostedt A. , Titball R. W.
Published: June 2004

Heat shock proteins (Hsps) have attracted significant attention as protective antigens against a range of diseases caused by bacterial pathogens. However, more recently there have been suggestions that the protective response is due to the presence of peptide components other than Hsps. We have shown that mice that had been immunized with purified heat shock protein 60 (Hsp60) isolated fromFrancisella tularensiswere protected against a subsequent challenge with some strains of the bacterium. However, this protection appeared to be due to trace amounts of lipopolysaccharide, which were too low to be detected by using theLimulusamoebocyte lysate assay. This finding raises the possibility that the protection afforded by other bacterial Hsp60 proteins may be due to trace quantities of polysaccharide antigens carried by and acting in conjunction with the Hsps.
Toxoplasma gondiiAntigen-Pulsed-Dendritic Cell-Derived Exosomes Induce a Protective Immune Response againstT. gondiiInfection
Authors: Aline Fleur , Bout Daniel , Amigorena Sébastian , Roingeard Philippe , Dimier-Poisson Isabelle
Published: June 2004

It was previously demonstrated that immunizing mice with spleen dendritic cells (DCs) that had been pulsed ex vivo withToxoplasma gondiiantigens triggers a systemic Th1-biased specific immune response and induces protection against infection.T. gondiican cause severe sequelae in the fetuses of mothers who acquire the infection during pregnancy, as well as life-threatening neuropathy in immunocompromised patients, in particular those with AIDS. Here, we investigate the efficacy of a novel cell-free vaccine composed of DC exosomes, which are secreted antigen-presenting vesicles that express functional major histocompatibility complex class I and II and T-cell-costimulatory molecules. They have already been shown to induce potent antitumor immune responses. We investigated the potential of DC2.4 cell line-derived exosomes to induce protective immunity against toxoplasmosis. Our data show that most adoptively transferredT. gondii-pulsed DC-derived exosomes were transferred to the spleen, elicited a strong systemic Th1-modulatedToxoplasma-specific immune response in vivo, and conferred good protection against infection. These findings support the possibility that DC-derived exosomes can be used forT. gondiiimmunoprophylaxis and for immunoprophylaxis against many other pathogens.
Mycobacterium bovisBCG Urease Attenuates Major Histocompatibility Complex Class II Trafficking to the Macrophage Cell Surface
Authors: Sendide Khalid , Deghmane Ala-Eddine , Reyrat Jean-Marc , Talal Amina , Hmama Zakaria
Published: June 2004

We have previously shown thatMycobacterium tuberculosisattenuates cell surface expression of major histocompatibility complex class II molecules in response to gamma interferon (IFN-γ) by a mechanism dependent on intracellular sequestration of α,β dimers. In this study we examined whether intracellular alkalinization due to mycobacterial urease could account for the defect in intracellular trafficking of class II molecules. Phagocytosis of wild-typeMycobacterium bovisBCG was associated with secretion of ammonia intracellularly, which increased substantially upon addition of exogenous urea to the culture medium. Increased intracellular ammonia, due to urea degradation by the bacterium, correlated with inhibition of class II surface expression. Conversely, no ammonia was detected in cells infected with a urease-negative mutant strain ofM. bovisBCG, which also displayed a reduced effect on surface expression of class II molecules. A direct cause-effect relationship between urease and class II molecule trafficking was established with experiments where cells ingesting beads coated with purified urease showed an increased ammonia level and decreased surface expression of class II in response to IFN-γ. In contrast to BCG, infection of macrophages withMycobacterium smegmatis, which expresses relatively greater urease activity in cell-free culture, had a marginal effect on both the intracellular level of ammonia and class II expression. The limited effect ofM. smegmatiswas consistent with a failure to resist intracellular killing, suggesting that urease alone is not sufficient to resist macrophage microbicidal mechanisms and that this is required for a more distal effect on cell regulation. Our results demonstrate that alkalinization of critical intracellular organelles by pathogenic mycobacteria expressing urease contributes significantly to the intracellular retention of class II dimers.
NadA Diversity and Carriage in
Neisseria meningitidis
Authors: Comanducci Maurizio , Bambini Stefania , Caugant Dominique A. , Mora Marirosa , Brunelli Brunella , Capecchi Barbara , Ciucchi Laura , Rappuoli Rino , Pizza Mariagrazia
Published: June 2004

NadA is a novel vaccine candidate recently identified in
Neisseria meningitidis
and involved in adhesion to host tissues. The
nadA
gene has been found in approximately 50% of the strains isolated from patients and in three of the four hypervirulent lineages of non-serogroup A strains. Here we investigated the presence of the
nadA
gene in 154 meningococcal strains isolated from healthy people (carrier strains). Only 25 (16.2%) of the 154 carrier isolates harbored the
nadA
gene. The commensal species
Neisseria lactamica
was also found not to have the
nadA
gene. Eighteen of the carrier strains belonged to the ET-5 and ET-37 hypervirulent clusters, indicating that only the 5.1% of the genuine carrier population actually harbored
nadA
(7 of 136 strains). Five of the seven strains harbored a novel allele of the
nadA
gene that was designated
nadA4
. The NadA4 protein was present on the bacterial surface as heat-stable high-molecular-weight oligomers. Antibodies against the recombinant NadA4 protein were bactericidal against homologous strains, whereas the activity against other NadA alleles was weak. In conclusion, the
nadA
gene segregates differently in the population of strains isolated from healthy individuals and in the population of strains isolated from patients. The presence of NadA can therefore be used as a tool to study the dynamics of meningococcal infections and understand why this bacterium, which is mostly a commensal, can become a severe pathogen.
Structural Relationships and Cellular Tropism of Staphylococcal Superantigen-Like Proteins
Authors: Al-Shangiti Ali M. , Naylor Claire E. , Nair Sean P. , Briggs David C. , Henderson Brian , Chain Benjamin M.
Published: June 2004

The staphylococcal superantigen-like proteins (SSLs) are a family of polymorphic paralogs encoded in the Staphylococcus aureusgenome whose function is unknown. The crystal structure of SSL7 was determined and compared to that of SSL5 and that of a classical superantigen, streptococcal pyrogenic exotoxin. Although the overall architecture of the superantigen family is retained in both SSL7 and SSL5, there are significant differences in the structures which suggest that the characteristic major histocompatibility complex binding site of superantigens has been lost. To complement these data, the abilities of SSL7 and a closely related paralog, SSL9, to interact with cells of the immune system were investigated. In populations of human white blood cells, both SSLs interacted selectively with monocytes via specific saturable but separate binding sites, which led to rapid uptake of the SSLs. In addition, SSLs were rapidly taken up by dendritic cells, but not by macrophages, into the same endosomal compartment as dextran. The ability of these secreted proteins to target antigen-presenting cells may enhance a misplaced antibody response against the proteins, which may facilitate bacterial colonization rather than contribute to host protection. Like classical superantigens, therefore, SSLs may distract the host's immune system, but they may do so via entirely different molecular mechanisms.
Immunization with Native or Recombinant
Streptococcus pneumoniae
Neuraminidase Affords Protection in the Chinchilla Otitis Media Model
Authors: Long J. P. , Tong H. H. , DeMaria T. F.
Published: June 2004

Streptococcus pneumoniae
neuraminidase has been implicated as a virulence factor in the pathogenesis of pneumococcal otitis media. In this study, native neuraminidase was partially purified from cultures of
S. pneumoniae
by serial chromatography with DEAE-Sepharose and Sephacryl S-200. Recombinant neuraminidase, a 3,038-bp fragment of the neuraminidase A (
nanA
) gene, was cloned into the pET-28b vector and then expressed at high levels in
Escherichia coli
. Chinchillas were immunized subcutaneously with either the gel-purified native or recombinant neuraminidase, and all responded with elevated titers of antineuraminidase antibody in serum. Immunization with neuraminidase resulted in a significant reduction in nasopharyngeal colonization as well as in the incidence of otitis media with effusion. These data demonstrate for the first time that neuraminidase affords protection against
S. pneumoniae
nasopharyngeal colonization and experimental otitis media.
Identification of a Point Mutation Resulting in Loss of Cell Wall Anchoring Activity of SrtA of
Streptococcus mutans
NG5
Authors: Lee Song F. , McGavin Mary K. H.
Published: June 2004

Streptococcus mutans
NG5 failed to anchor antigen P1 to the cell surface, and such a failure could be attributed to a defective SrtA, which was made defective by a point mutation within the
srtA
gene. Without a functional SrtA,
S. mutans
NG5 was not able to perform a number of cell surface-related activities, including saliva-mediated adherence and aggregation.
Oral Inoculation of A/J Mice for Detection of Invasiveness Differences betweenListeria monocytogenesEpidemic and Environmental Strains
Authors: Kim So Hyun , Bakko Marlene K. , Knowles Don , Borucki Monica K.
Published: June 2004

Four-week-old Harlan A/J mice were orally infected with six epidemic and six environmental strains ofListeria monocytogenes. Epidemic strains were significantly more invasive as a group than were environmental strains (P< 0.05), and the intestines of some mice infected with epidemic strains had extensive hemorrhage. Mice inoculated with epidemic strains were significantly more likely to become systemically infected than mice inoculated with environmental strains (P< 0.01).
Highly Purified Lipoteichoic Acid fromStaphylococcus aureusInduces Procoagulant Activity and Tissue Factor Expression in Human Monocytes but Is a Weak Inducer in Whole Blood: Comparison with Peptidoglycan
Authors: Mattsson Eva , Hartung Thomas , Morath Siegfried , Egesten Arne
Published: June 2004

Lipoteichoic acid fromStaphylococcus aureuswas a potent inducer of procoagulant activity in isolated mononuclear cells but not in whole blood. In contrast, staphylococcal peptidoglycan showed equal levels of potency in isolated mononuclear cells and whole blood, suggesting that peptidoglycan is an important inducer of procoagulant activity in severe sepsis involving gram-positive bacteria.
Docosahexaenoic Acid and Eicosapentaenoic Acid Antagonize the Proinflammatory Interactions of Pneumolysin with Human Neutrophils
Authors: Cockeran Riana , Theron Annette J. , Feldman Charles , Mitchell Timothy J. , Anderson Ronald
Published: June 2004

Pneumolysin (4.18 ng/ml)-mediated influx of Ca
2+
and augmentation of the chemoattractant-activated generation of reactive oxidants was antagonized by pretreatment of human neutrophils with the omega-3 polyunsaturated fatty acids docosahexaenoic acid and eicosapentaenoic acid (1.25 to 5 μg/ml). These agents may have potential in attenuating the proinflammatory properties of this pneumococcal toxin.
A bimodal model for the high values of a river flow
Authors: Lefebvre Mario
Published: June 2004

In previous work, it was found that the best short-term forecasts of the flow of the Mistassibi River, in the province of Quebec (Canada), were obtained by making use of linear regression. Here, a theoretical justification for this fact is provided by showing that an excellent fit to the data is obtained with a certain bimodal distribution. This distribution is used for values of the river flow greater than or equal to 500 m3/s. For values between 500 and 1000 m3/s, a truncated exponential distribution is proposed, while for flow values greater than 1000 m3/s, a Gaussian distribution is appropriate. In the latter two cases, if we consider two-dimensional versions of the distributions, we find that the conditional expectation of the future flow value, given the current value x, is an affine function of x, thus justifying the use of linear regression to predict future flow values.Key words: stochastic modeling, hydrological forecasting, linear regression, goodness of fit, bivariate exponential.
Stream-barb installations for narrow channel bends — a laboratory study
Authors: Matsuura Troy , Townsend Ronald
Published: June 2004

Phase 1 of an ongoing laboratory study of a novel form of stream-bank protection structure is described. "Barbs" are dike-like stone structures designed to protect the (usually unstable) outside-bank regions of channel bends. These low-profile structures point upstream into the flow and typically extend to about 1/4-way across the channel. By disrupting near-bank velocity gradients they promote sediment deposition along the eroding outside-bank region. Their presence also modifies the "helicoidal"-type flow pattern of the bend such that secondary currents, which would otherwise attack the outside-bank, are redirected towards the center of the channel. This novel form of bank protection structure is currently undergoing field tests on selected bends on a number of shallow "wide" streams in Illinois, USA. While initial results are encouraging, additional studies are necessary to develop design criteria for their wider application. In phase 1 of this study, the effectiveness of different arrangements of barb groups, in both 90° and 135° moveable-bed bend sections of a hydraulically "narrow" rectangular channel, are investigated. For each hydraulic condition considered, the channel-bed scour profiles generated by the different barb groups are compared to corresponding "reference" profiles generated in the absence of barbs. Judging the effectiveness of the different barb groups in promoting long-term stability of the outside-bank region is based on two criteria: (i) percent reduction achieved in scouring in the vicinity of the outside-bank and (ii) degree to which the channel thalweg (deepest portion) is moved from the outside-bank region towards the center of the channel.Key words: barb, channel bends, local scouring, bank erosion, bank protection, secondary currents.
Sequence analysis of bacterial redox enzyme maturation proteins (REMPs)
Authors: Turner Raymond J , Papish Andriyka L , Sargent Frank
Published: June 2004

The twin-arginine protein transport (Tat) system is a remarkable molecular machine dedicated to the translocation of fully folded proteins across energy-transducing membranes. Complex cofactor-containing Tat substrates acquire their cofactors prior to export, and substrate proteins actually require to be folded before transport can proceed. Thus, it is very likely that mechanisms exist to prevent wasteful export of immature Tat substrates or to curb competition between immature and mature substrates for the transporter. Here we assess the primary sequence relationships between the accessory proteins implicated in this process during assembly of key respiratory enzymes in the model prokaryote Escherichia coli. For each respiratory enzyme studied, a redox enzyme maturation protein (REMP) was assigned. The main finding from this review was the hitherto unexpected link between the Tat-linked REMP DmsD and the nitrate reductase biosynthetic protein NarJ. The evolutionary link between Tat transport and cofactor insertion processes is discussed.Key words: Tat translocase, twin-arginine leader, hydrogenase, nitrate reductase, TMAO reductase, DMSO reductase, formate dehydrogenase, Tor, Dms, Hya, Hyb, Fdh, Nap.
Molecular and physiological comparison ofAzospirillumspp. isolated fromRhizoctonia solanimycelia, wheat rhizosphere, and human skin wounds
Authors: Cohen Michael F , Han Xiang Y , Mazzola Mark
Published: June 2004

Four phenotypically similar bacterial strains isolated from fungal, plant, and human sources were identified as Azospirillum species. Strains RC1 and LOD4 were isolated from the mycelium of the apple root pathogen Rhizoctonia solani AG 5 and from the rhizosphere of wheat grown in apple orchard soil, respectively. Strains C610 and F4626 isolated from human wounds were previously misclassified as Roseomonas genomospecies 3 and 6. All four strains demonstrated close similarities in 16S rRNA gene sequences, having [Formula: see text]97% identity to Azospirillum brasilense type strain ATCC 29145 and <90% identity to Roseomonas gilardii, the Roseomonas type strain. Extensive phenotypic similarities among the four strains included the ability of free-living cells to fix N2. Cells of strains RC1, LOD4, and C610 but not of strain F4626 could be induced to flocculate by incubation with 10 mmol·L–1glycerol or fructose in medium containing 0.5 mmol·L–1NO3–. Our results indicate a wide range of potential sources for Azospirillum spp. with the isolation of Azospirillum spp. from human wounds warranting further investigation.Key words: Azospirillum brasilense, Roseomonas fauriae, flocculation, Rhizoctonia solani.
Bacterial formyl peptides affect the innate cellular antimicrobial responses of larvalGalleria mellonella(Insecta: Lepidoptera)
Authors: Alavo Thiery B.C , Dunphy Gary B
Published: June 2004

The non-self cellular (hemocytic) responses of Galleria mellonella larvae, including the attachment to slides and the removal of the bacteria Xenorhabdus nematophila and Bacillus subtilis from the hemolymph, were affected by N-formyl peptides. Both N-formyl methionyl-leucyl-phenylalanine (fMLF) and the ester derivative decreased hemocyte adhesion in vitro, and both elevated hemocyte counts and suppressed the removal of both X. nematophila and B. subtilis from the hemolymph in vivo. The amide derivative and the antagonist tertiary-butoxy-carbonyl-methionyl-leucyl-phenylalanine (tBOC) increased hemocyte attachment to glass. The fMLF suppressed protein discharge from monolayers of granular cells with and without bacterial stimulation, while tBOC stimulated protein discharge. The peptide tBOC offset the effects of fMLF in vitro and in vivo. This is the first report implying the existence of formyl peptide receptors on insect hemocytes in which the compounds fMLF and tBOC inhibited and activated hemocyte activity, respectively.Key words: formyl peptides, hemocytes, Xenorhabdus, Bacillus.
Flagellar motors of marine bacteriaHalomonasare driven by both protons and sodium ions
Authors: Kita-Tsukamoto K , Wada M , Yao K , Nishino T , Kogure K
Published: June 2004

Bacterial cells in aquatic environments are able to reach or stay near nutrient patches by using motility. Motility is usually attained by rotating flagellar motors that are energized by electrochemical potential of H+or Na+. In this paper, the ion specificity for flagellar rotation of two marine isolates Halomonas spp. strains US172 and US201 was investigated. Both isolates require sodium for growth and possess a respiratory-driven primary sodium pump. They are motile because of lateral flagella regardless of the presence of sodium ions. Their swimming speed under various concentrations of sodium ions with and without carbonylcyanide m-chlorophenylhydrazone, a proton conductor, and with and without phenamil, a specific inhibitor for the sodium-driven flagellar motors, was examined. The effect of carbonylcyanide m-chlorophenylhydrazone on the transmembrane proton gradient was also determined. Our results showed that the flagellar motors of the Halomonas strains were energized by both H+and Na+in one cell. The bimodal nature of Halomonas spp. motility with respect to the driving energy source may reflect ecophysiological versatility to adapt to a wide range of salt conditions of the marine environment.Key words: marine bacteria, Halomonas, flagellar motor, sodium, proton.
A glycerol-inducible thermostable lipase fromBacillussp.: medium optimization by a Plackett–Burman design and by response surface methodology
Authors: Gupta Namita , Mehra Gauri , Gupta Rani
Published: June 2004

The production of a neutral lipase from a Bacillus sp. was improved tremendously (193-fold) following media optimization involving both the "one-at-a-time" and the statistical designing approaches. The present lipase was poorly induced by oils, instead its production was induced in the presence of sugars and sugar alcohols, mainly galactose, lactose, glycerol, and mannitol. A high inoculum density of 15% v/v (A550= 0.8) led to maximum lipase production. Interestingly, the enzyme induction was growth independent, a property very different from most of the lipases investigated to date. The optimal composition of the growth medium to achieve maximum lipase production was determined to be as follows: NH4Cl, 35 g·L–1; glycerol, 10 mL·L–1; K2HPO4, 3 g·L–1; KH2PO4, 1 g·L–1; MgSO4·7H2O, 0.1 g·L–1; glucose, 2 g·L–1; MgCl2, 0.6 mmol·L–1, with 15% inoculum density and an incubation period of 24 h. About 62 U·mL–1of enzyme production was achieved in the optimized medium.Key words: lipase, glycerol inducible, statistical designing.
Effects of double-stranded RNA inMetarhizium anisopliaevar.acridumandPaecilomyces fumosoroseuson protease activities, conidia production, and virulence
Authors: Tiago Patricia Vieira , Fungaro Maria Helena Pelegrinelli , Rodrigues de Faria Marcos , Furlaneto Marcia Cristina
Published: June 2004

Isogenic strains (with and without dsRNA) of the entomogenous fungi Metarhizium anisopliae var. acridum and Paecilomyces fumosoroseus were investigated for correlation between the presence of dsRNA and the production of cuticle-degrading proteases that play an important role in host parasitism, total secreted protein, and conidia production. Similar levels of cuticle-degrading subtilisin-like (Pr1) protease were observed for isogenic strains of M. anisopliae var. acridum after growth in medium supplemented with the cuticle of the grasshopper Rhammatocerus schistocercoides. Similarly, no statistical differences were observed for protease production, detected using the chromogenic substrate azocasein. For P. fumosoroseus isogenic strains, no significant differences in protease activity were observed after growth in the presence of either Euschistus heros or Nezara viridula (Hemiptera: Pentatomidae) cuticle. Similarly, no statistical differences were observed in virulence against E. heros. A comparison of mean conidia production showed a significantly higher production in the dsRNA-free isogenic strains of M. anisopliae var. acridum. Although, for most of the fungal phenotypes analysed, no overt effects were associated with the presence of these dsRNA infections, the reduction in conidia production by the isogenic strains of M. anisopliae var. acridum with dsRNA suggested that it may not be entirely accurate to describe these infections as latent.Key words: Metarhizium anisopliae var. acridum, Paecilomyces fumosoroseus, double-stranded RNA (dsRNA), proteases, conidia production, virulence.
Genotoxicity of cis-Pt(II) complex of 3-aminoflavone in comparison with cis-DDP in A549 cells evaluated by comet assay
Authors: Kosmider Beata , Zyner Elzbieta , Osiecka Regina , Ochocki Justyn
Published: June 2004

Cis-diamminedichloroplatinum(II) (cis-DDP) is one of the most successful antineoplastic drugs. However, besides effectiveness it gives many side effects. Therefore, current studies are concentrated on searching for new analogs equally effective in chemotherapy but less toxic. Comparison of genotoxic properties of cis-Pt(II) complex of 3-aminoflavone and cis-DDP in a comet assay with and without H2O2 application was performed in A549 cell line. The higher tail moment values were noticed for the former compound contrary to the latter one in both variants. It suggests mainly DNA breaks (besides cross-links) appearance after cis-Pt(II) complex of 3-aminoflavone application and might indicate DNA degradation in comparison with cis-DDP.Key words: cis-Pt(II) complex of 3-aminoflavone, cis-DDP, comet assay, A549 cells.
Effect of estrogen replacement treatment on ischemic preconditioning in isolated rat hearts
Authors: Peng Wei-Jie , Yu Jing , Deng Sheng , Jiang Jun-Ling , Deng Han-Wu , Li Yuan-Jian
Published: June 2004

In the present study, we tested the effects of long-term estrogen replacement treatment on myocardial ischemia-reperfusion injury and on the cardioprotection of ischemic preconditioning in isolated hearts from ovariectomized rats. Ovariectomized rats were treated with 17β-estradiol (30 µg/kg/d, s.c.) for 12 weeks. Isolated rat hearts were perfused in the Langendorff mode. Heart rate, coronary flow, left ventricular pressure and its first derivative (±LVdp/dtmax) were recorded. Fifteen-min global ischemia and 30-min reperfusion caused a significant decrease of cardiac mechanical function, which were not affected by ovariectomy or estrogen replacement treatment. The isolated hearts in all groups could be preconditioned, and the cardioprotection afforded by preconditioning in the sham-operated rats was greater compared with ovariectomized rats with or without estrogen treatment. These results suggest that long-term estrogen replacement treatment exerts no effect on the inhibition of mechanical function after ischemia-reperfusion, and this study also suggests that estrogen does not affect ischemic preconditioning in isolated hearts of ovariectomized rats.Key words: ERT (estrogen replacement treatment), ischemia-reperfusion, ischemic preconditioning, heart, rat.
Synergy between the antinociceptive effects of morphine and NSAIDs
Authors: Miranda H F , Silva E , Pinardi G
Published: June 2004

The intraperitoneal administration of morphine, diclofenac, ketoprofen, meloxicam, metamizol, paracetamol and piroxicam induced dose-dependent antinociception in mice tested with the acetic acid writhing test. The isobolographic analysis of the simultaneous intraperitoneal administration of fractions of the ED50's of morphine with each nonsteroidal anti-inflammatory drug (NSAID) demonstrated the existence of a supra-additive interaction (synergy). The selective antagonist of µ-opioid receptors naltrexone partially reversed the supra-additive interactions to additive interactions; however, the combinations of morphine/metamizol and morphine/paracetamol were completely antagonized, resulting in subadditive interactions. The selective antagonist of δ-opioid receptors naltrindole failed to significantly attenuate the combinations of morphine with ketoprofen, meloxicam and piroxicam, but decreased the activity of the combinations of morphine with diclofenac, metamizol and paracetamol, transforming the interactions from supra-additive to additive. Nor-binaltorphimine was used to evaluate the involvement of κ-opioid receptors. Nor-binaltor phimine did not modify the supra-additive interaction of morphine and NSAIDs and the additive interaction of the co-administration of morphine and metamizol. The synergy between morphine and NSAIDs could be related to different pathways of pain transmission, probably related to the different intracellular signal transduction mechanisms of action of opioid and non-opioid agents.Key words: writhing test, NSAIDs, morphine, antinociception, isobolographic analysis, synergy.
Caveolae-associated signalling in smooth muscle
Authors: Bergdahl Andreas , Swärd Karl
Published: June 2004

Caveolae are flask-shaped invaginations in the membrane that depend on the contents of cholesterol and on the structural protein caveolin. The organisation of caveolae in parallel strands between dense bands in smooth muscle is arguably unique. It is increasingly recognised, bolstered in large part by recent studies in caveolae deficient animals, that caveolae sequester and regulate a variety of signalling intermediaries. The role of caveolae in smooth muscle signal transduction, as inferred from studies on transgenic animals and in vitro approaches, is the topic of the current review. Both G-protein coupled receptors and tyrosine kinase receptors are believed to cluster in caveolae, and the exciting possibility that caveolae provide a platform for interactions between the sarcoplasmic reticulum and plasmalemmal ion channels is emerging. Moreover, messengers involved in Ca2+sensitization of myosin phosphorylation and contraction may depend on caveolae or caveolin. Caveolae thus appear to constitute an important signalling domain that plays a role not only in regulation of smooth muscle tone, but also in proliferation, such as seen in neointima formation and atherosclerosis.Key words: caveolin, RhoA, transient receptor potential channel, endothelin, spontaneous transient outward currents.
The impact of long-term continuous risk of predation on two species of gerbils
Authors: Abramsky Zvika , Rosenzweig Michael L , Belmaker Jonathan , Bar Avihad
Published: June 2004

Individuals of Gerbillus allenbyi Thomas, 1918 were subjected to artificial illumination in large field enclosures (2-ha sandy-substrate plots in the Negev Desert, Israel). The illumination was similar to that provided by a full moon and was used to mimic the elevated risk of avian predation that accompanies a full moon. We artificially illuminated the enclosures during all hours of darkness for 3 consecutive months. In some cases, we also added individuals of Gerbillus pyramidum Geoffroy, 1825 to provide a competitive challenge for the G. allenbyi. In the presence of the light source, individuals of G. allenbyi shifted their foraging activity to favor experimental areas of darkness. They also foraged less in the open and more beneath bushes. In the absence of the light source, G. allenbyi shifted its activity from the subplot with G. pyramidum to the subplot without the competitor. However, the competitive effect of the G. pyramidum disappeared in plots that were artificially illuminated. These results closely resemble those of earlier experiments during which we increased the apparent risk of predation in brief pulses lasting only 2 h/night.
Stress protein expression is related to tail loss in two species of iguanid lizards
Authors: Merino S , Blázquez M C , Martínez J , Rodríguez-Estrella R
Published: June 2004

During the spring of 1999, two species of iguanid lizards were captured in southern Baja California peninsula, Mexico. Blood was obtained from the tail to check for the presence of blood parasites in smears and stress proteins in cells. Levels of HSP70- and HSP60-like proteins from Sceloporus licki Van Denburgh, 1895 and Petrosaurus thalassinus (Cope, 1863) were analyzed with Western blot using antisera to human HSP60 and bovine HSP70. The potential effects of sex, tail regeneration, and haemoparasites on the expression of these proteins were also investigated. Both species differ significantly in stress protein levels and infection by haemoparasites. Petrosaurus thalassinus show the lower stress protein levels and the higher proportion of infection. Although blood parasites apparently affect the condition of P. thalassinus, stress protein levels are not significantly related with haemoparasites or condition. However, S. licki lizards showing tail regeneration have lower levels of HSP60-like protein. A negative relationship exists between the length of the regenerated part of the tail and the level of HSP60-like protein for S. licki. Based on what is known of the function of HSP60, down-regulation of the protein in blood cells may be linked to reallocation of energies to other tissues more active metabolically.
Variability in broods of the seastar Leptasterias aequalis
Authors: Bingham Brian L , Giles Kehaulani , Jaeckle William B
Published: June 2004

Enormous variation exists in the reproductive output of marine invertebrates (e.g., in the numbers of embryos produced, the volumes of embryos, and the energy that they contain). It is not clear why there is such great variability or what the population-level consequences are. We sampled a population of the brooding seastar Leptasterias aequalis (Stimpson, 1862) to collect basic information on brood sizes, embryo volume, and embryo energy content with a goal to better understand the reproductive ecology of this species. We collected brooding females in February and again in April. We measured the size of their broods and sampled the broods to estimate volume and energy content of the embryos. There was great variability in the volume and energy content of embryos produced by individual females and among the embryos in a single female's brood. Larger adults produced larger embryos, which generally had greater energy content and may be of a higher quality. The average energy content of embryos appeared to increase during the brooding period. Larger females produced larger broods but lost a greater proportion of the embryos. The net result is that larger individuals may not produce any more juveniles than smaller individuals, but those that they do produce may be of a higher quality.