bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of
ENA1
as a Virulence Gene of the Human Pathogenic Fungus
Cryptococcus neoformans
through Signature-Tagged Insertional Mutagenesis
Authors: Idnurm Alexander , Walton Felicia J. , Floyd Anna , Reedy Jennifer L. , Heitman Joseph
Published: January 2009

A library of more than 4,500 signature-tagged insertion mutants of the human pathogenic fungus
Cryptococcus neoformans
was generated, and a subset was screened in a murine inhalation model to identify genes required for virulence. New genes that regulate aspects of
C. neoformans
virulence were also identified by screening the entire library for in vitro phenotypes related to the ability to cause disease, including melanin production, growth at high temperature, and growth under conditions of nutrient limitation. A screen of 10% of the strain collection in mice identified an avirulent mutant strain with an insertion in the
ENA1
gene, which is predicted to encode a fungus-specific sodium or potassium P-type ATPase. The results of the deletion of the gene and complementation experiments confirmed its key role in mammalian virulence.
ena1
mutant strains exhibited no change in sensitivity to high salt concentrations but were sensitive to alkaline pH conditions, providing evidence that the fungus may have to survive at elevated pH during infection of the mammalian host. The mutation of the well-characterized virulence factor calcineurin (
CNA1
) also rendered
C. neoformans
strains sensitive to elevated pH.
ENA1
transcripts in wild-type and
cna1
mutant strains were upregulated in response to high pH, and
cna1 ena1
double mutant strains exhibited increased sensitivity to elevated pH, indicating that at least two pathways in the fungus mediate survival under alkaline conditions. Signature-tagged mutagenesis is an effective strategy for the discovery of new virulence genes in fungal pathogens of animals.
Property Differences among the Four Major
Candida albicans
Strain Clades
Authors: MacCallum Donna M. , Castillo Luis , Nather Kerstin , Munro Carol A. , Brown Alistair J. P. , Gow Neil A. R. , Odds Frank C.
Published: January 2009

A selection of 43
Candida albicans
isolates, chosen to represent the four major strain clades of the species and also intraclade diversity, was screened for their virulence in the murine intravenous challenge model of
C. albicans
infection, for a range of properties measurable in vitro that might relate to virulence, and for the numbers of midrepeat sequences in genes of the
ALS
and
HYR
families. Heterozygosity at the mating type locus and low whole-cell acid phosphatase activity and growth rate at 40°C were found to be significantly positively associated with the most virulent isolates. Acid phosphatase activity and growth in 2 M NaCl were statistically significant variables between clades by univariate analysis. Isolates in different clades also differed significantly in midrepeat sequence alleles of
ALS2
,
ALS4
,
ALS6
,
ALS7
,
ALS9
,
HYR1
, and
HYR2
. There was no association between the midrepeat alleles of any
ALS
or
HYR
gene and the virulence of isolates to mice. Genome-wide transcript profiles of 20 isolates (5 per clade) grown under two conditions showed considerable variation between individual isolates, but only a small number of genes showed statistically significant differential gene expression between clades. Analysis of the expression profiles by overall strain virulence revealed 18 open reading frames differing significantly between isolates of high, intermediate, and low virulence. Four of these genes encoded functions related to phosphate uptake and metabolism. This finding and the significant association between whole-cell acid phosphatase activity and virulence led us to disrupt
PHO100
, which encodes a predicted periplasmic acid phosphatase. The
pho100
Δ mutant was mildly but significantly attenuated in terms of survival curves in the mouse model. The study has extended the range of properties known to differ between
C. albicans
clades and suggests a possible but minor role of phosphate metabolism in the virulence of the species.
Population Variability of the FimH Type 1 Fimbrial Adhesin in
Klebsiella pneumoniae
Authors: Stahlhut Steen G. , Chattopadhyay Sujay , Struve Carsten , Weissman Scott J. , Aprikian Pavel , Libby Stephen J. , Fang Ferric C. , Krogfelt Karen Angeliki , Sokurenko Evgeni V.
Published: January 2009

FimH is an adhesive subunit of type 1 fimbriae expressed by different enterobacterial species. The enteric bacterium
Klebsiella pneumoniae
is an environmental organism that is also a frequent cause of sepsis, urinary tract infection (UTI), and liver abscess. Type 1 fimbriae have been shown to be critical for the ability of
K. pneumoniae
to cause UTI in a murine model. We show here that the
K. pneumoniae fimH
gene is found in 90% of strains from various environmental and clinical sources. The
fimH
alleles exhibit relatively low nucleotide and structural diversity but are prone to frequent horizontal-transfer events between different bacterial clones. Addition of the
fimH
locus to multiple-locus sequence typing significantly improved the resolution of the clonal structure of pathogenic strains, including the K1 encapsulated liver isolates. In addition, the
K. pneumoniae
FimH protein is targeted by adaptive point mutations, though not to the same extent as FimH from uropathogenic
Escherichia coli
or TonB from the same
K. pneumoniae
strains. Such adaptive mutations include a single amino acid deletion from the signal peptide that might affect the length of the fimbrial rod by affecting FimH translocation into the periplasm. Another FimH mutation (S62A) occurred in the course of endemic circulation of a nosocomial uropathogenic clone of
K. pneumoniae.
This mutation is identical to one found in a highly virulent uropathogenic strain of
E. coli
, suggesting that the FimH mutations are pathoadaptive in nature. Considering the abundance of type 1 fimbriae in
Enterobacteriaceae
, our present finding that
fimH
genes are subject to adaptive microevolution substantiates the importance of type 1 fimbria-mediated adhesion in
K. pneumoniae
.
Differential Interactions between Tat-Specific Redox Enzyme Peptides and Their Chaperones
Authors: Chan Catherine S. , Chang Limei , Rommens Kenton L. , Turner Raymond J.
Published: January 2009

The twin-arginine translocase (Tat) system is used by many bacteria to move proteins across the cytoplasmic membrane. Tat substrates are prefolded and contain a conserved SRRxFLK twin-arginine (RR) motif at their N termini. Many Tat substrates in
Escherichia coli
are cofactor-containing redox enzymes that have specific chaperones called redox enzyme maturation proteins (REMPs). Here we characterized the interactions between 10 REMPs and 15 RR peptides of known and predicted Tat-specific redox enzyme subunits. A combination of in vitro and in vivo experiments demonstrated that some REMPs were specific to a redox enzyme(s) of similar function, whereas others were less specific and bound peptides of unrelated enzymes. Results from Biacore surface plasmon resonance (SPR) and bacterial two-hybrid experiments identified interactions in addition to those found in far-Western experiments, suggesting that conformational freedom and/or other cellular factors may be required. Furthermore, we show that the interaction of the two prevents both from being proteolytically degraded in vivo, and kinetic data from SPR show up to 10-fold-tighter binding to the expected RR substrate when multiple binding partners existed. Investigations using full-length sequences of the RR proteins showed that the mature portion for some redox enzyme subunits is required for detection of the interactions. Sequence alignments among the REMPs and RR peptides indicated that homology between the REMPs and the hydrophobic regions following the RR motifs in the peptides correlates to cross-recognition.
Organization and PprB-Dependent Control of the
Pseudomonas aeruginosa tad
Locus, Involved in Flp Pilus Biology
Authors: Bernard Christophe S. , Bordi Christophe , Termine Elise , Filloux Alain , de Bentzmann Sophie
Published: January 2009

Bacterial attachment to the substratum involves several cell surface organelles, including various types of pili. The
Pseudomonas aeruginosa
Tad machine assembles type IVb pili, which are required for adhesion to abiotic surfaces and to eukaryotic cells. Type IVb pili consist of a major subunit, the Flp pilin, processed by the FppA prepilin peptidase. In this study, we investigated the regulatory mechanism of the
tad
locus. We showed that the
flp
gene is expressed late in the stationary growth phase in aerobic conditions. We also showed that the
tad
locus was composed of five independent transcriptional units. We used transcriptional fusions to show that
tad
gene expression was positively controlled by the PprB response regulator. We subsequently showed that PprB bound to the promoter regions, directly controlling the expression of these genes. We then evaluated the contribution of two genes,
tadF
and
rcpC
, to type IVb pilus assembly. The deletion of these two genes had no effect on Flp production, pilus assembly, or Flp-mediated adhesion to abiotic surfaces in our conditions. However, our results suggest that the putative RcpC protein modifies the Flp pilin, thereby promoting Flp-dependent adhesion to eukaryotic cells.
Genetics and Proteomics of
Aeromonas salmonicida
Lipopolysaccharide Core Biosynthesis
Authors: Jimenez Natalia , Lacasta Anna , Vilches Silvia , Reyes Mercé , Vazquez Judit , Aquillini Eleonora , Merino Susana , Regué Miguel , Tomás Juan M.
Published: January 2009

Comparison between the lipopolysaccharide (LPS) core structures of
Aeromonas salmonicida
subsp.
salmonicida
A450 and
Aeromonas hydrophila
AH-3 shows great similarity in the inner LPS core and part of the outer LPS core but some differences in the distal part of the outer LPS core (residues
ld
-Hep,
d
-Gal, and
d
-GalNAc). The three genomic regions encoding LPS core biosynthetic genes in
A. salmonicida
A450, of which regions 2 and 3 have genes identical to those of
A. hydrophila
AH-3, were fully sequenced.
A. salmonicida
A450 region 1 showed seven genes: three identical to those of
A. hydrophila
AH-3, three similar but not identical to those of
A. hydrophila
AH-3, and one without any homology to any well-characterized gene.
A. salmonicida
A450 mutants with alterations in the genes that were not identical to those of
A. hydrophila
AH-3 were constructed, and their LPS core structures were fully elucidated. At the same time, all the
A. salmonicida
A450 genes identical to those of
A. hydrophila
AH-3 were used to complement the previously obtained
A. hydrophila
AH-3 mutants for each of these genes. Combining the gene sequence and complementation test data with the structural data and phenotypic characterization of the mutant LPSs enabled a presumptive assignment of all LPS core biosynthesis gene functions in
A. salmonicida
A450. Furthermore, hybridization studies with internal probes for the
A. salmonicida
-specific genes using different
A
.
salmonicida
strains (strains of different subspecies or atypical strains) showed a unique or prevalent LPS core type, which is the one fully characterized for
A. salmonicida
A450.
A DNase Encoded by Integrated Element CJIE1 Inhibits Natural Transformation of
Campylobacter jejuni
Authors: Gaasbeek Esther J. , Wagenaar Jaap A. , Guilhabert Magalie R. , Wösten Marc M. S. M. , van Putten Jos P. M. , van der Graaf-van Bloois Linda , Parker Craig T. , van der Wal Fimme J.
Published: January 2009

The species
Campylobacter jejuni
is considered naturally competent for DNA uptake and displays strong genetic diversity. Nevertheless, nonnaturally transformable strains and several relatively stable clonal lineages exist. In the present study, the molecular mechanism responsible for the nonnatural transformability of a subset of
C. jejuni
strains was investigated. Comparative genome hybridization indicated that
C. jejuni
Mu-like prophage integrated element 1 (CJIE1) was more abundant in nonnaturally transformable
C. jejuni
strains than in naturally transformable strains. Analysis of CJIE1 indicated the presence of
dns
(CJE0256), which is annotated as a gene encoding an extracellular DNase. DNase assays using a defined
dns
mutant and a
dns
-negative strain expressing Dns from a plasmid indicated that Dns is an endogenous DNase. The DNA-hydrolyzing activity directly correlated with the natural transformability of the knockout mutant and the
dns
-negative strain expressing Dns from a plasmid. Analysis of a broader set of strains indicated that the majority of nonnaturally transformable strains expressed DNase activity, while all naturally competent strains lacked this activity. The inhibition of natural transformation in
C. jejuni
via endogenous DNase activity may contribute to the formation of stable lineages in the
C. jejuni
population.
Comparative Structural and Molecular Characterization of Ribitol-5-Phosphate-Containing
Streptococcus oralis
Coaggregation Receptor Polysaccharides
Authors: Yang Jinghua , Ritchey Mary , Yoshida Yasuo , Bush C. Allen , Cisar John O.
Published: January 2009

The antigenically related coaggregation receptor polysaccharides (RPS) of
Streptococcus oralis
strains C104 and SK144 mediate recognition of these bacteria by other members of the dental plaque biofilm community. In the present study, the structure of strain SK144 RPS was established by high resolution NMR spectroscopy as [6Gal
f
β1-6GalNAcβ1-3Galα1-2ribitol-5-PO
4
−
-6Gal
f
β1-3Galβ1]
n
, thereby indicating that this polysaccharide and the previously characterized RPS of strain C104 are identical, except for the linkage between Gal and ribitol-5-phosphate, which is α1-2 in strain SK144 versus α1-1 in strain C104. Studies to define the molecular basis of RPS structure revealed comparable genes for six putative transferases and a polymerase in the
rps
loci of these streptococci. Cell surface RPS production was abolished by disrupting the gene for the first transferase of strain C104 with a nonpolar
erm
cassette. It was restored in the resulting mutant by plasmid-based expression of either
wcjG
, the corresponding gene of
S. pneumoniae
for serotype 10A capsular polysaccharide (CPS) biosynthesis or
wbaP
for the transferase of
Salmonella enterica
that initiates O-polysaccharide biosynthesis. Thus, WcjG, like WbaP, appears to initiate polysaccharide biosynthesis by transferring galactose-1-phosphate to a lipid carrier. In further studies, the structure of strain C104 RPS was converted to that of strain SK144 by replacing the gene (
wefM
) for the fourth transferase in the
rps
locus of strain C104 with the corresponding gene (
wcrC
) of strain SK144 or
Streptococcus pneumoniae
serotype 10A. These findings identify genetic markers for the different ribitol-5-phosphate-containing types of RPS present in
S. oralis
and establish a close relationship between these polysaccharides and serogroup 10 CPSs of
S. pneumoniae
.
Seawater-Regulated Genes for Two-Component Systems and Outer Membrane Proteins in
Myxococcus
Authors: Pan Hong-wei , Liu Hong , Liu Ting , Li Cheng-yun , Li Zhi-feng , Cai Ke , Zhang Cui-ying , Zhang Yong , Hu Wei , Wu Zhi-hong , Li Yue-zhong
Published: January 2009

When salt-tolerant
Myxococcus
cells are moved to a seawater environment, they change their growth, morphology, and developmental behavior. Outer membrane proteins and signal transduction pathways may play important roles in this shift. Chip hybridization targeting the genes predicted to encode 226 two-component signal transduction pathways and 74 outer membrane proteins of
M. xanthus
DK1622 revealed that the expression of 55 corresponding genes in the salt-tolerant strain
M. fulvus
HW-1 was significantly modified (most were downregulated) by the presence of seawater. Sequencing revealed that these seawater-regulated genes are highly homologous in both strains, suggesting that they have similar roles in the lifestyle of
Myxococcus
. Seven of the genes that had been reported in
M. xanthus
DK1622 are involved in different cellular processes, such as fruiting body development, sporulation, or motility. The outer membrane (Om) gene Om031 had the most significant change in expression (downregulated) in response to seawater, while the two-component system (Tc) gene Tc105 had the greatest increase in expression. Their homologues MXAN3106 and MXAN4042 were knocked out in DK1622 to analyze their functions in response to changes in salinity. In addition to having increased salt tolerance, sporulation of the MXAN3106 mutant was enhanced compared to that of DK1622, whereas mutating gene MXAN4042 produced contrary results. The results indicated that the genes that are involved in the cellular processes that are significantly changed in response to salinity may also be involved the salt tolerance of
Myxococcus
cells. Regulating the expression levels of these multifunctional genes may allow cells to quickly and efficiently respond to changing conditions in coastal environments.
Differential Binding Profiles of StpA in Wild-Type and
hns
Mutant Cells: a Comparative Analysis of Cooperative Partners by Chromatin Immunoprecipitation-Microarray Analysis
Authors: Uyar Ebru , Kurokawa Ken , Yoshimura Mika , Ishikawa Shu , Ogasawara Naotake , Oshima Taku
Published: January 2009

We performed chromatin immunoprecipitation-microarray analysis to investigate differences in function between StpA and H-NS in
Escherichia coli
cells. StpA binding regions essentially overlap those of H-NS in wild-type cells, while they are reduced to one-third in the
hns
mutant. The H-NS binding profile was unaffected by
stpA
inactivation.
The NS4A Protein of Hepatitis C Virus Promotes RNA-Coupled ATP Hydrolysis by the NS3 Helicase
Authors: Beran Rudolf K. F. , Lindenbach Brett D. , Pyle Anna Marie
Published: January 2009

Nonstructural protein 3 (NS3) is an essential replicative component of the hepatitis C virus (HCV) and a member of the DExH/D-box family of proteins. The C-terminal region of NS3 (NS3hel) exhibits RNA-stimulated NTPase and helicase activity, while the N-terminal serine protease domain of NS3 enhances RNA binding and unwinding by NS3hel. The nonstructural protein 4A (NS4A) binds to the NS3 protease domain and serves as an obligate cofactor for NS3 serine protease activity. Given its role in stimulating protease activity, we sought to determine whether NS4A also influences the activity of NS3hel. Here we show that NS4A enhances the ability of NS3hel to bind RNA in the presence of ATP, thereby acting as a cofactor for helicase activity. This effect is mediated by amino acids in the C-terminal acidic domain of NS4A. When these residues are mutated, one observes drastic reductions in ATP-coupled RNA binding and duplex unwinding by NS3. These same mutations are lethal in HCV replicons, thereby establishing in vitro and in vivo that NS4A plays an important role in the helicase mechanism of NS3 and its function in replication.
Distribution, host preference, and impact of parasitic mistletoes (Loranthaceae) in young eucalypt plantations in New South Wales, AustraliaThis article is one of a collection of papers based on a presentation from the Stem and Shoot Fungal Pathogens and Parasitic Plants: the Values of Biological Diversity session of the XXII International Union of Forestry Research Organization World Congress meeting held in Brisbane, Queensland, Australia, in 2005.
Authors: Carnegie Angus J. , Bi Huiquan , Arnold Scott , Li Yun , Binns Doug
Published: January 2009

Mistletoe is a common sight in mature eucalypt trees in Australia, especially in remnant stands in agricultural and pastoral areas, where they have been associated with debility and death. We surveyed over 450 eucalypt plantations in New South Wales, Australia, for mistletoe, and report for the first time that mistletoe infestation is becoming a problem in young eucalypt plantations. Forty-three plantations were infected, but only 9 of these had levels of mistletoe of 20% or more trees infected; 4 had levels of 38%, 40%, 65%, and 68%. Mistletoe was observed in plantations ranging in age from 3–10 years old. Species of Corymbia ( Corymbia maculata  (Hook.) K.D. Hill & L.A.S. Johnson and Corymbia citriodora subsp. variegata (F. Muell.) K.D. Hill & L.A.S. Johnson) were the most susceptible to mistletoe. The mistletoe species Dendrophthoe vitellina (F. Muell.) Tiegh. was commonly observed in plantations in both lower and upper northeast New South Wales, while Amyema bifurcata (Benth.) Tiegh. was only observed in the upper northeast. We observed a significant impact on growth of mistletoe, affecting tree growth as young as four years old. Simulated analysis indicated that mistletoe infection can reduce stand basal area by 10% and stand volume by 13%. However, the impact of mistletoe on tree growth was variable across space and time.
Paleozoic plutonism in southeastern British Columbia
Authors: Okulitch Andrew V.
Published: January 2009

U–Pb dates from zircons indicate that plutonic events occurred during the Paleozoic in the Omineca Crystalline Belt in southeastern British Columbia. In the Kootenay Arc, granitoid cobbles in conglomerate of the Carboniferous Milford Group were derived from quartz monzonite and diorite plutons of probable Ordovician age. Near Little Shuswap Lake, gneissic granitoid units have yielded Cambro-Ordovician ages. At least one episode of deformation affected country rocks of unknown age before intrusion. In the Monashee Complex south of Thor–Odin Nappe in South Fosthall Creek, lineated quartz monzonite is of probable Ordovician age. Comparison of fabrics suggests that at least one episode of metamorphism and deformation occurred prior to intrusion. No clear relationship between the cobbles and these plutons can be demonstrated because major faults lie between them, but substantial revision to accepted models of Paleozoic paleogeography of this region will have to be made. In the Clachnaeudainn tectonic slice east of the Monashee Complex, granitic gneiss is of Paleozoic, possibly Siluro-Devonian, age. This pluton appears to be involved in all phases of deformation that affected its country rocks. Near Quesnel Lake, parts of a composite gneissic granitoid pluton appear to be of Devonian or earliest Carboniferous age.
Early diagenesis of copper and molybdenum in mine tailings and natural sediments in Rupert and Holberg inlets, British Columbia
Authors: Pedersen Thomas F.
Published: January 2009

The distribution and behaviour of Cu and Mo in interstitial waters collected from Cu- and Mo-rich mine tailings and natural sediments in Rupert and Holberg inlets (Vancouver Island, British Columbia) are discussed. Dissolved Fe, Mn, [Formula: see text], and Σ H2S distributions and solid-phase Cu, Mo, Mn, and organic carbon data are used to constrain the interpretation of Cu and Mo diagenesis in both tailings and natural sediment facies. Cu is released to solution at or near the sediment–water interface in both facies either by decomposing labile organic material or as a probable result of oxidation of sulphide minerals within the tailings. Mo is significantly enriched (up to 0.6 μmol L−1) in tailings pore water, probably as a result of dissolution of soluble Mo oxides produced initially by oxidation of MoS2 during milling of the ore.In natural sediments, both Cu and Mo are removed from solution at depth, probably by precipitation as their sulphides or in solid solution with an iron sulphide phase. Similar reactions appear to be occurring at depth in the tailings. The benthic flux of copper from the tailings into overlying seawater is similar in magnitude to that observed in natural sediments; there is no indication from the present data that remobilization of copper from the tailings is perturbing the pre-mine Cu distribution in Rupert Inlet. Unlike that of Cu, the benthic flux of Mo is unique to the tailings but is insufficient to produce a measureable anomaly in inlet waters because of the short water residence time and the relatively high Mo concentration characteristic of seawater.
Southeastward ice flow in central Quebec and its paleogeographic significance
Authors: Bouchard Michel A. , Martineau Ghismond
Published: January 2009

Directional glacial erosional marks located systematically on the southwest side of rock outcrops in the Chibougamau and Lac Mistassini areas in west-central Quebec indicate unequivocally a sustained regional event of southeast ice flow prior to the last or regional southwest flow from New Quebec. Striations from the former ice flow are consistently oriented at around 120° azimuth and are observed, albeit at scattered occurrences, within an area covering thousands of square kilometres. Although the age of the southeast ice flow event cannot be determined, it is considered more likely to be of Wisconsinan age on the basis of the well preserved state of its features and the lack of deep weathering on surfaces where these are observed. It is suggested that the early ice flow event might have been fed by a local outflow centre on the east side of James Bay, perhaps extending as a ridge east of Hudson Bay.
Diving behaviour of male and female western grebes
Authors: Forbes L. Scott , Sealy Spencer G.
Published: January 2009

We studied diving in western grebes (Aechmophorus occidentalis), which are sexually dimorphic, at Duck and Kootenay lakes in southeastern British Columbia to determine if differences in sex, and hence body size, resulted in differences in behaviour. Springing dives were used more frequently in deeper water and when wave action was higher, but there were no clear differences between males and females. As well, the dive–pause regressions for males and females did not differ. We conclude that differences in body size are not important determinants of diving behaviour in western grebes, but that habitat conditions (e.g., water depth, wave action) are.
Branchial mechanisms of ion and acid–base regulation in the freshwater rainbow trout, Salmo gairdneri
Authors: McDonald D. G. , Prior E. T.
Published: January 2009

Blood acid–base balance and branchial fluxes of Na+, Cl−, and acidic equivalents were examined in rainbow trout (Salmo gairdneri) in response to variations in external [NaCl] and following experimental acid or base loads (intravascular infusion of ammonium sulphate, lactic acid, or sodium bicarbonate). NaCl influx, NaCl efflux, and ammonia excretion covaried with external [NaCl]. Large fluxes of acidic equivalents across the gills were produced by infusion of both ammonium sulphate and sodium bicarbonate, but both treatments had little effect upon Na+ and Cl− uptake. We interpret this result as indicating that apical [Formula: see text] and [Formula: see text] exchange played little role in the branchial clearance of acidic equivalents. Instead, the results are consistent with the notion that acidic equivalents were excreted via diffusion through paracellular channels. A model is presented which suggests that the paracellular channels are the normal route for ionic efflux across the gills and that excretion of acidic equivalents results from modulation of the permselectivity of this pathway.
Temperature-dependent energy partitioning in the benthic copepods Acanthocyclops viridis and Macrocyclops albidus
Authors: Laybourn-Parry Johanna , Abdullahi B. A. , Tinson S. V.
Published: January 2009

Energy acquisition and partitioning by the benthic copepods Acanthocyclops viridis (Jurine) and Macrocyclops albidus (Jurine) from Esthwaite Water in the English Lake District were investigated at a range of temperatures within the normal environmental range (5–20 °C), in animals fed an excess of the ciliated protozoan Paramecium caudatum. Feeding rate increased with elevated temperature, while longevity, development time, adult size, clutch size, and interclutch period decreased. Temperature had a marked effect on the pattern of energy partitioning into reproduction: increasing temperature moved the balance towards reproduction. The ecological implications of temperature-induced changes on the energetics of these copepods is discussed.
Chromosomal variation and differentiation among insular populations of Peromyscus from the Pacific Northwest
Authors: Gunn Scott J.
Published: January 2009

Karyotypic data from 561 deer mice (Peromyscus spp.) from populations on islands off British Columbia and Washington indicate the presence of two distinct karyotypic groups, a low fundamental number (FN) group (FN = 74–78) and a high FN group (FN = 85–92). The absence of karyotypic intermediates at nine localities of sympatry is interpreted as demonstrating that the two FN groups represent distinct species. Based on data from comparable mainland forms, the low FN form is considered to represent Peromyscus maniculatus and the high FN form is suggested to be conspecific with Peromyscus areas. Chromosomal banding data indicate extensive chromosomal variation within each of these species and provide discrete karyotypic characters unique to each species. The inclusion of the high FN insular forms with P. oreas does not affect the chromosomally determined cladistic placement of P. oreas as a laxon derived from P. maniculatus.
Retinal structure relative to feeding in the rock bass (Ambloplites rupestris) and bluegill (Lepomis macrochirus)
Authors: Williamson Mark , Keast Allen
Published: January 2009

The morphology and organization of the retina of rock bass (Ambloplites rupestris) and bluegill (Lepomis macrochirus) were investigated relative to their feeding habits. Rock bass are primarily crepuscular benthic feeders (taking Anisoptera nymphs and crayfish), and bluegill are diurnal generalized predators of chironomid larvae, Cladocera, and Trichoptera. In individuals of equivalent body size, the rock bass was found to have a high-density area of double cone concentration (up to 18 000 cones/mm2) in the temporodorsal region of the retina. This indicates that the main visual direction for prey detection is below the horizontal plane. In the bluegill the distribution of photoreceptors is more even and the average value over much of the retina is 6000–7000/mm2, with accordingly greater intercone spacing. This is probably appropriate for a fish feeding throughout the water column under good light conditions. The eye of the rock bass is 20% greater in rostrocaudal diameter than that of bluegill of equivalent size, implying greater light-gathering capacity. Moreover, individual cones in the rock bass are larger in surface area. These features, and a greater degree of neural summation (with resultant high visual sensitivity), have been regarded as adaptations for feeding under dim light. Differences in diet and feeding behavior in these two species thus have a morphological basis.
Changes in the site specificity of Gyrodactylus turnbulli Harris, 1986 (Monogenea) during infections of individual guppies (Poecilia reticulata Peters, 1859)
Authors: Harris P. D.
Published: January 2009

Gyrodactylus turnbulli Harris, 1986 infected the caudal peduncle (42% of all flukes) and caudal fin (40%), of guppies (Poecilia reticulata Peters, 1859), occurring less frequently on the pectoral (8%), dorsal (5%), pelvic (2%), and anal (1%) fins. This distribution of parasites on the fish and their crowding varied with infection age. On newly infected guppies, G. turnbulli occurred less frequently on the peduncle, and mean nearest-neighbour distance was not correlated with population size. Over the first 4 days of the infection the proportion of parasites on the peduncle increased to 60%, and mean nearest-neighbour distance became correlated with population size. In declining infections (day 6 onwards) the proportion on the peduncle declined, and mean nearest-neighbour distance increased independent of population size. This pattern suggests random colonization of the fins followed by migration to the peduncle, from which dispersal occurred during the declining phase of the infection.
ISLES OF EDEN AND THE ZUK THEOREM IN ℝd
Authors: GARAY BARNABAS M. , CHUA LEON O.
Published: January 2009

The concept of isles of Eden when generalized from finite cellular automata to classical dynamical systems on ℝdcalls the attention to the ZUK Theorem — Z for [Zubov, 1957], U and K for [Ura & Kimura, 1960] — a fifty years old and almost forgotten result in topological dynamics, a classification theorem for compact isolated invariant sets. We provide a simple proof and discuss various consequences including a new result on pointwise Liapunov functions.
GLOBAL DYNAMIC PROPERTIES OF A SYNCHRONOUS MACHINE MODEL
Authors: LU PINGLI , YANG YING , HUANG LIN
Published: January 2009

In this paper, rich global dynamical properties are considered for a fundamental synchronous machine model: from global asymptotic stability of trivial equilibrium to chaotic oscillations. Based on Kalman–Yakubovich–Popov (KYP) lemma, static feedback controller is designed such that the synchronous machine model is global asymptotic stable which guarantees that the existence of limit cycles or chaotic oscillations is impossible.
LIMITING JULIA SETS FOR SINGULARLY PERTURBED RATIONAL MAPS
Authors: MORABITO MARK , DEVANEY ROBERT L.
Published: January 2009

In this paper, we consider the family of rational maps given by [Formula: see text] where n ≥ 2, and λ is a complex parameter. When λ = 0 the Julia set is the unit circle, as is well known. But as soon as λ is nonzero, the Julia set explodes. We show that, as λ tends to the origin along n - 1 special rays in the parameter plane, the Julia set of Fλ converges to the closed unit disk. This is somewhat unexpected, since it is also known that, if a Julia set contains an open set, it must be the entire Riemann sphere.
EFFECTS OF EXCESSIVE REACTANTS ON THE PROPERTIES OF CADMIUM SULFIDE THIN FILMS PREPARED BY CHEMICAL BATH DEPOSITION
Authors: LORYUENYONG VORRADA , RUANKUL NOPPANUT , SUPSO NATTAPON , CHUNPADUNGSUK PONGSATORN
Published: January 2009

Cadmium sulfide nanoparticles were synthesized and grown on glass substrates by chemical bath deposition. The method involves the preparation of aqueous solutions containing cadmium chloride ( CdCl 2) and thiourea [ CS ( NH 2)2] as source materials for cadmium and sulfur components, respectively. Ammonium hydroxide ( NH 4 OH )–ammonium chloride ( NH 4 Cl ) solution was used as a complexing agent in this study. The hexagonal and cubic crystal structure of as-deposited CdS films, determined by X-ray diffraction (XRD), is shown. The effects of Cd : S ratio variation on the surface morphology and optical properties of CdS films are also reported. The UV-vis transmission spectrum and SEM micrographs indicated that the Cd : S ratio in the aqueous solution had an impact on the band gap as well as the crystallite size and packing density of the CdS particles due to the quantum confinement effect.
A HYBRID DIFFERENCE SCHEME FOR SINGULARLY PERTURBED SECOND ORDER ORDINARY DIFFERENTIAL EQUATIONS WITH DISCONTINUOUS CONVECTION COEFFICIENT AND MIXED TYPE BOUNDARY CONDITIONS
Authors: MYTHILI PRIYADHARSHINI R. , RAMANUJAM N.
Published: January 2009

This paper presents, a hybrid difference scheme for singularly perturbed second order ordinary differential equations with a small parameter multiplying the highest derivative with a discontinuous convection coefficient subject to mixed type boundary conditions. Error bounds for the numerical solution and numerical derivative are established. Numerical results are provided to illustrate the theoretical results.
Photography's bright future
Authors: Kroeker Kirk L.
Published: January 2009

Researchers working in computational photography are using computer vision, computer graphics, and applied optics to bring a vast array of new capabilities to digital cameras.
Eliciting properties of probability distributions
Authors: Lambert Nicolas , Pennock David M. , Shoham Yoav
Published: January 2009

We investigate the problem of incentivizing an expert to truthfully reveal probabilistic information about a random event. Probabilistic information consists of one or more properties, which are any real-valued functions of the distribution, such as the mean and variance. Not all properties can be elicited truthfully. We provide a simple characterization of elicitable properties, and describe the general form of the associated payment functions that induce truthful revelation. We then consider sets of properties, and observe that all properties can be inferred from sets of elicitable properties. This suggests the concept of elicitation complexity for a property, the size of the smallest set implying the property.
Buffer sizing results for RCP congestion control under connection arrivals and departures
Authors: Lakshmikantha Ashvin , Srikant R. , Dukkipati Nandita , McKeown Nick , Beck Carolyn
Published: January 2009

Buffer sizing has received a lot of attention recently since it is becoming increasingly difficult to use large buffers in highspeed routers. Much of the prior work has concentrated on analyzing the amount of buffering required in core routers assuming that TCP carries all the data traffic. In this paper, we evaluate the amount of buffering required for RCP on a single congested link, while explicitly modeling flow arrivals and departures. Our theoretical analysis and simulations indicate that buffer sizes of about 10% of the bandwidth-delay product are sufficient for RCP to deliver good performance to end-users.
Firefox (In) security update dynamics exposed
Authors: Frei Stefan , Duebendorfer Thomas , Plattner Bernhard
Published: January 2009

Although there is an increasing trend for attacks against popular Web browsers, only little is known about the actual patch level of daily used Web browsers on a global scale. We conjecture that users in large part do not actually patch their Web browsers based on recommendations, perceived threats, or any security warnings. Based on HTTP useragent header information stored in anonymized logs from Google's web servers, we measured the patch dynamics of about 75% of the world's Internet users for over a year. Our focus was on the Web browsers Firefox and Opera. We found that the patch level achieved is mainly determined by the ergonomics and default settings of built-in auto-update mechanisms. Firefox' auto-update is very effective: most users installed a new version within three days. However, the maximum share of the latest, most secure version never exceeded 80% for Firefox users and 46% for Opera users at any day in 2007. This makes about 50 million Firefox users with outdated browsers an easy target for attacks. Our study is the result of the first global scale measurement of the patch dynamics of a popular browser.
Endothelin downregulates SERCA2 gene and protein expression in adult rat ventricular myocytes: regulation by pertussis toxin-sensitive Giprotein and cAMP
Authors: Hilal-Dandan Randa , He Huaping , Martin Jody L. , Brunton Laurence L. , Dillmann Wolfgang H.
Published: January 2009

Downregulation of the sarcoplasmic reticulum calcium ATPase (SERCA2) is associated with diastolic dysfunction in the failing heart. Elevated plasma endothelin-1 (ET) levels are correlated with congestive heart failure suggesting that ET may play a pathophysiological role. We have investigated the ability of ET to regulate SERCA2 gene expression in isolated adult rat ventricular myocytes. We find that ET enhances net protein synthesis by ∼40% but significantly downregulates SERCA2 mRNA expression, time dependently, by ∼30–50%, and the expression of SERCA2 protein by ∼ 50%. In myoyctes, ET binds to ETAreceptor that couples to Gqand Giproteins. Inhibition of Gq-PLC-induced phosphoinositide (PI) hydrolysis with U73122 (1 μM) or inhibition of Giprotein with pertussis toxin (PTX) abolishes the ability of ET to downregulate SERCA2 mRNA gene expression. Further investigation suggests that ET coupling to PTX-sensitive Giwith consequent lowering of cAMP is required for downregulation of SERCA2 mRNA levels. Increasing intracellular cAMP quantity using cAMP-specific PDE inhibitor Ro20-1724 or cAMP analog dibutyryl-cAMP reverses ET-induced downregulation of SERCA2 mRNA levels. The data indicate that, in adult myocytes, ET downregulates SERCA2 mRNA and protein levels, and the effect requires cross-talk between Gqand PTX-sensitive Gipathways.
Increased vascular angiotensin type 2 receptor expression and NOS-mediated mechanisms of vascular relaxation in pregnant rats
Authors: Stennett Amanda K. , Qiao Xiaoying , Falone Anthony E. , Koledova Vera V. , Khalil Raouf A.
Published: January 2009

Normal pregnancy is associated with reduced blood pressure (BP) and decreased pressor response to vasoconstrictors, even though the renin-angiotensin system is upregulated. Angiotensin II (ANG II) activates both angiotensin type 1 receptors (AT1Rs) and angiotensin type 2 receptors (AT2Rs). Although the role of the AT1R in vascular contraction is well documented, the role of the AT2R in vascular relaxation, particularly during pregnancy, is less clear. It was hypothesized that the decreased BP and vasoconstriction during pregnancy was, at least in part, due to changes in AT2R amount, distribution, and/or postreceptor mechanisms of vascular relaxation. To test this hypothesis, systolic BP was measured in virgin and pregnant ( day 19) Sprague-Dawley rats. Isometric contraction/relaxation was measured in isolated aortic rings, and nitric oxide (NO) production was measured using 4-amino-5-methylamino-2′,7′-difluorescein fluorescence. AT1R and AT2R mRNA expression and protein amount were measured in tissue homogenates using real-time RT-PCR and Western blots, and their local distribution was visualized in cryosections using immunohistochemistry and immunofluorescence. BP was lower in pregnant than virgin rats. Phenylephrine (Phe) caused concentration-dependent contraction that was reduced in the aorta of pregnant compared with virgin rats. Treatment with the AT2R antagonist PD-123319 caused greater enhancement of Phe contraction, and the AT2R agonist CGP-42112A caused greater relaxation of Phe contraction in the aorta of pregnant than virgin rats. ANG II plus the AT1R blocker losartan induced greater NO production in the aorta of pregnant than virgin rats. RT-PCR revealed increased mRNA expression of vascular endothelial NO synthase (eNOS), little change in AT1Rs, and increased AT2Rs in pregnant compared with virgin rats. Western blots revealed an increased protein amount of activated phospho-eNOS, little change in AT1Rs, and increased AT2Rs in pregnant compared with virgin rats. Immunohistochemistry and immunofluorescence analysis in aortic sections of virgin rats revealed abundant AT1R staining in tunica media that largely colocalized with actin in vascular smooth muscle and less AT2Rs mainly in the tunica intima and endothelium. In pregnant rats, AT1R staining in the smooth muscle layer and adventitia was reduced, and endothelial AT2R staining was enhanced. These data suggest an enhanced AT2R-mediated vascular relaxation pathway involving increased expression/activity of endothelial AT2Rs and increased postreceptor activated phospho-eNOS, which may contribute to the decreased BP during pregnancy.
Elevated cyclic stretch alters matrix remodeling in aortic valve cusps: implications for degenerative aortic valve disease
Authors: Balachandran Kartik , Sucosky Philippe , Jo Hanjoong , Yoganathan Ajit P.
Published: January 2009

Matrix metalloproteinases (MMPs) and cathepsins are proteolytic enzymes that are upregulated in diseased aortic valve cusps. The objective of this study was to investigate whether elevated cyclic stretch causes an increased expression and activity of these proteolytic enzymes in the valve cusp. Circumferentially oriented fresh porcine aortic valve cusp sections were stretched to 10% (physiological), 15% (pathological), and 20% (hyperpathological) in a tensile stretch bioreactor for 24 and 48 h. The expression and activity of MMP-1, MMP-2, MMP-9, tissue inhibitor of MMP-1, and cathepsin L, S, and K were quantified and compared with fresh controls. Cell proliferation and apoptosis were also analyzed. As a result, at 10% physiological stretch, the expression and activity of remodeling enzymes were comparable with fresh controls. At 15% stretch, the expression of MMP-1, -2, -9 and cathepsin S and K were upregulated, whereas the expression of cathepsin L was downregulated compared with controls. A similar trend was observed at 20% stretch, but the magnitudes of upregulation and downregulation of the expression were less than those observed at 15%. In addition, there were significantly higher cell proliferation and apoptosis at 20% stretch compared with those of other treatment groups. In conclusion, elevated mechanical stretch on aortic valve cusps may detrimentally alter the proteolytic enzyme expression and activity in valve cells. This may trigger a cascade of events leading to an accelerated valve degeneration and disease progression.
Combined therapy with cardioprotective cytokine administration and antiapoptotic gene transfer in postinfarction heart failure
Authors: Okada Hideshi , Takemura Genzou , Kosai Ken-ichiro , Tsujimoto Akiko , Esaki Masayasu , Takahashi Tomoyuki , Nagano Satoshi , Kanamori Hiromitsu , Miyata Shusaku , Li Yiwen , Ohno Takamasa , Maruyama Rumi , Ogino Atsushi , Li Longhu , Nakagawa Munehiro , Nagashima Kenshi , Fujiwara Takako , Fujiwara Hisayoshi , Minatoguchi Shinya
Published: January 2009

We hypothesized that therapy, composed of antiapoptotic soluble Fas (sFas) gene transfer, combined with administration of the cardioprotective cytokine granulocyte colony-stimulating factor (G-CSF), would markedly mitigate cardiac remodeling and dysfunction following myocardial infarction (MI). On the 3rd day after MI induced by ligating the left coronary artery in mice, four different treatments were initiated: saline injection (Group C, n = 26); G-CSF administration (Group G, n = 27); adenoviral transfer of sFas gene (Group F, n = 26); and the latter two together (Group G+F, n = 26). Four weeks post-MI, Group G+F showed better survival than Group C (96 vs. 65%, P < 0.05) and the best cardiac function among the four groups. In Group G, the infarct scar was smaller and less fibrotic, whereas in Group F the scar was thicker, without a reduction in area, and contained abundant myofibroblasts and vascular cells; Group G+F showed both phenotypes. G-CSF exerted a beneficial effect on infarct tissue dynamics through antifibrotic and proliferative effects on granulation tissue; however, it also exerts an adverse proapoptotic effect that leads to thinning of the infarct scar. sFas appeared to offset the latter drawback. In vitro study using cultured myofibroblasts derived from the infarct tissue revealed that G-CSF increased proliferating activity of those cells accompanying activation of Akt and signal transducer and activator of transcription 3, while accelerating Fas-mediated apoptosis with increasing Bax-to-Bcl-2 ratio. The results suggest that combined use of G-CSF administration and sFas gene therapy is a potentially powerful tool against post-MI heart failure.