bluuebunny/crossref_metadata_2025 huggingface dataset:
Malaria Chemoprophylaxis: Strategies for Risk Groups
Authors: Schlagenhauf Patricia , Petersen Eskild
Published: July 2008

The risk of malaria for travelers varies from region to region and depends on the intensity of transmission, the duration of the stay in the area of endemicity, the style of travel, and the efficacy of preventive measures. The decision to recommend chemoprophylaxis to travelers to areas with a low risk of malarial infection is especially difficult because the risk of infection must be balanced with the risk of experiencing side effects. If the risk of side effects by far exceeds the risk of infection, the traveler needs information on measures against mosquito bites and advice on prompt diagnosis and self-treatment. The risk is difficult to quantify, and the absolute risk for travelers to most areas is not known, especially because the populations at risk are unknown. We propose here that the best approximation of the risk to the traveler to a specific area is to use the risk to the indigenous population as a guideline for the risk to the traveler, and we provide examples on how risk in the indigenous population can be used for the estimation of risk of malarial infection for travelers. Special groups are long-term visitors and residents, who often perceive risk differently, cease using chemoprophylaxis, and rely on self-diagnosis and treatment. For long-term visitors, the problem of fake drugs needs to be discussed. Strategies for chemoprophylaxis and self-treatment of pregnant women and small children are discussed. So far, malaria prophylaxis is recommended to prevent
Plasmodium falciparum
infections, and primaquine prophylaxis against persistent
Plasmodium vivax
and
Plasmodium ovale
infections in travelers is not recommended.
Rho5p Is Involved in Mediating the Osmotic Stress Response in
Saccharomyces cerevisiae
, and Its Activity Is Regulated via Msi1p and Npr1p by Phosphorylation and Ubiquitination
Authors: Annan Robert B. , Wu Cunle , Waller Daniel D. , Whiteway Malcolm , Thomas David Y.
Published: July 2008

Small GTPases of the Rho family act as molecular switches, and modulation of the GTP-bound state of Rho proteins is a well-characterized means of regulating their signaling activity in vivo. In contrast, the regulation of Rho-type GTPases by posttranslational modifications is poorly understood. Here, we present evidence of the control of the
Saccharomyces cerevisiae
Rho-type GTPase Rho5p by phosphorylation and ubiquitination. Rho5p binds to Ste50p, and the expression of the activated
RHO5
(
Q91H
) allele in an Δ
ste50
strain is lethal under conditions of osmotic stress. An overexpression screen identified
RGD2
and
MSI1
as being high-copy suppressors of the osmotic sensitivity of this lethality. Rgd2p had been identified as being a possible Rho5p GTPase-activating protein based on an in vitro assay; this result supports its function as a regulator of Rho5p activity in vivo.
MSI1
was previously identified as being a suppressor of hyperactive Ras/cyclic AMP signaling, where it antagonizes Npr1p kinase activity and promotes ubiquitination. Here, we show that Msi1p also acts via Npr1p to suppress activated Rho5p signaling. Rho5p is ubiquitinated, and its expression is lethal in a strain that is compromised for proteasome activity. These data identify Rho5p as being a target of Msi1p/Npr1p regulation and describe a regulatory circuit involving phosphorylation and ubiquitination.
Polo-Like Kinase Is Expressed in S/G
2
/M Phase and Associated with the Flagellum Attachment Zone in both Procyclic and Bloodstream Forms of
Trypanosoma brucei
Authors: Umeyama Takashi , Wang Ching C.
Published: July 2008

Trypanosoma brucei
, the etiologic agent of African sleeping sickness, divides into insect (procyclic) and bloodstream forms. These two forms are subject to distinct cell cycle regulations, with cytokinesis controlled primarily by basal body/kinetoplast segregation in the procyclic form but by mitosis in the bloodstream form. Polo-like kinases (PLKs), known to play essential roles in regulating both mitosis and cytokinesis among eukaryotes, have a homologue in
T
.
brucei
, TbPLK, which regulates only cytokinesis. In our previous study, overexpressed triply hemagglutinin-tagged TbPLK (TbPLK-3HA) in the procyclic form localized to a mid-dorsal point and the anterior tip of the cell along the flagellum attachment zone (FAZ). In our current study, TbPLK-3HA expressed at the endogenous level was identified at the same dorsal location of both procyclic and bloodstream forms, albeit it was no longer detectable at the anterior tip of the cell. Endogenously expressed TbPLK fused with an enhanced yellow fluorescent protein (EYFP) localized to the same dorsal location along the FAZs in living procyclic and bloodstream cells. Fluorescence-activated cell sorter analysis of hydroxyurea-synchronized procyclic cells revealed that TbPLK-EYFP emerges during S phase, persists through G
2
/M phase, and vanishes in G
1
phase. An indicated TbPLK-EYFP association with the FAZs of G
2
/M cells may thus represent a timely localization to a potential initiation site of cytokinesis, which agrees with the recognized role of TbPLK in cytokinetic initiation.
Molecular Phylogenetic Analysis of a Geographically and Temporally Matched Set ofCandida albicansIsolates from Humans and Nonmigratory Wildlife in Central Illinois
Authors: Wrobel Lauren , Whittington Julia K. , Pujol Claude , Oh Soon-Hwan , Ruiz Marilyn O. , Pfaller Michael A. , Diekema Daniel J. , Soll David R. , Hoyer Lois L.
Published: July 2008

This study explored whether wildlife species serve as the reservoir for humanCandida albicansstrains in a given geographic area.C.albicansisolates were collected from nonmigratory wildlife admitted to the University of Illinois Wildlife Medical Clinic. A geographically and temporally matched set ofC.albicansoral isolates was collected from healthy human volunteers. Multilocus sequence typing was used to assign strains to genetic clades. Clade 1 isolates, particularly diploid sequence type 69 (DST 69), were most common in humans. Clade 1 strains were less frequently recovered from wildlife, while clade 8 strains, particularly DST 90, were overrepresented in the wildlife collection. All instances where a wildlife and human isolate shared the same DST occurred within clade 1. Clade distributions between human and wildlife isolates were significantly different, demonstrating population isolation between the groups. These differences may indicate limited strain transfer between groups or differential selection ofC.albicansisolates in humans and wildlife. Wildlife strains had an amphotericin B MIC significantly lower than that of human isolates; strains with increased susceptibility were from several clades.C.albicansisolates were collected from domestic animals to provide comparisons with human and wildlife data sets.C.albicansisolation from canine and feline oral and anal swabs was infrequent; companion animal isolates were closely related to clade 1 human isolates. Collectively, the data suggest a greater likelihood ofC.albicanstransfer from humans to animals than from animals to humans. The nontransient human population may maintain the connection between geography and theC.albicansgenetic groups recovered from humans.
Regulation of the Subcellular Localization of Cyclic AMP-Dependent Protein Kinase in Response to Physiological Stresses and Sexual Differentiation in the Fission Yeast
Schizosaccharomyces pombe
Authors: Matsuo Yasuhiro , McInnis Brittney , Marcus Stevan
Published: July 2008

We describe regulation of the subcellular localization of cyclic AMP (cAMP)-dependent protein kinase (PKA) regulatory (Cgs1p) and catalytic (Pka1p) subunits in the fission yeast
Schizosaccharomyces pombe
in response to physiological stresses and during sexual differentiation as determined by fluorescence microscopy of the Cgs1-green fluorescent protein (GFP) and Pka1-GFP fusion proteins, respectively. In wild-type
S. pombe
cells cultured to log phase under normal growth conditions, Cgs1p and Pka1p are concentrated in the nucleus and more diffusely present in the cytoplasm. Nuclear localization of both proteins is dependent on cAMP, since in cells lacking adenylate cyclase they are detectable only in the cytoplasm. In cells lacking Cgs1p or both Cgs1p and adenylate cyclase, Pka1p is concentrated in the nucleus, demonstrating a role for Cgs1p in the nuclear exclusion of Pka1p. Nuclear-cytoplasmic redistribution of Cgs1p and Pka1p is triggered by growth in glucose-limited or hyperosmotic media and in response to stationary-phase growth. In addition, both proteins are excluded from the nucleus in mating cells undergoing karyogamy and subsequently concentrated in postmeiotic spores. Cgs1p is required for subcellular redistribution of Pka1p induced by growth in glucose-limited and hyperosmotic media and during karyogamy but is not required for Pka1p redistribution triggered by stationary-phase growth or for the enrichment of Pka1p in spores. Our results demonstrate that PKA localization is regulated by cAMP and regulatory subunit-dependent and -independent mechanisms in
S. pombe
.
Analysis of a Growth-Phase-Regulated Two-Component Regulatory System in the Periodontal Pathogen
Treponema denticola
Authors: Frederick Jesse R. , Rogers Elizabeth A. , Marconi Richard T.
Published: July 2008

Nothing is currently known regarding the global regulatory networks of
Treponema denticola
and other oral spirochetes. In this report, we assess the properties and potential phosphotransfer capability of a putative two-component regulatory system (TCS) of
T. denticola
that is formed by the products of open reading frames tde0032 (a sensor kinase) and tde0033 (a response regulator), henceforth designated AtcS and AtcR, respectively. Using PCR and DNA sequence analyses,
atcS
and
atcR
were demonstrated to be widely distributed and conserved among
T. denticola
isolates. Reverse transcription-PCR (RT-PCR) analyses revealed that these genes are cotranscribed and may also be expressed as part of a larger operon that includes several flanking genes. Analyses using 5′ rapid amplification of cDNA ends identified the transcriptional start sites for these operons and provided evidence that some of these genes may be independently transcribed from internal promoters. Real-time RT-PCR and Western blot analysis revealed significant upregulation of
atcRS
during late-stage growth, indicating growth-phase-dependent expression. Lastly, the phosphorelay capability of the AtcRS system was assessed and demonstrated using recombinant proteins. AtcS was found to undergo autophosphorylation and to transfer phosphate to AtcR. These analyses represent the first description of a functional TCS in an oral spirochetes and provide insight into the transcriptional regulatory mechanisms of these important bacteria.
Characterization of the Accessory Sec System of
Staphylococcus aureus
Authors: Siboo Ian R. , Chaffin Donald O. , Rubens Craig E. , Sullam Paul M.
Published: July 2008

The SraP adhesin of
Staphylococcus aureus
is a member of a highly conserved family of serine-rich surface glycoproteins of gram-positive bacteria. For streptococci, export of the SraP homologs requires a specialized transport pathway (the accessory Sec system). Compared to streptococci, however, SraP is predicted to differ in its signal peptide and glycosylation, which may affect its dependence on a specialized system for transport. In addition, two genes (
asp4
and
asp5
) essential for export in
Streptococcus gordonii
are missing in
S. aureus
. Thus, the selectivity of the accessory Sec system in
S. aureus
may also differ compared to streptococci. To address these issues, the five genes encoding the putative accessory Sec system (
secY2
,
secA2
, and
asp1-3
) were disrupted individually in
S. aureus
ISP479C, and the resultant mutants were examined for SraP export. Disruption of
secA2
resulted in the near complete loss of SraP surface expression. Similar results were seen with disruption of
secY2
and
asp1
,
asp2
, or
asp3
. To assess whether the accessory Sec system transported other substrates, we compared secreted proteomes of ISP479C and a
secA2
isogenic mutant, by two-dimensional fluorescence difference gel electrophoresis. Although two consistent differences in proteome content were noted between the strains, neither protein appeared to be a likely substrate for accessory Sec export. Thus, the accessory Sec system of
S. aureus
is required for the export of SraP, and it appears to be dedicated to the transport of this substrate exclusively.
Salmonella enterica
Serovar Gallinarum Requires ppGpp for Internalization and Survival in Animal Cells
Authors: Jeong Jae-Ho , Song Miryoung , Park Sang-Ik , Cho Kyoung-Oh , Rhee Joon Haeng , Choy Hyon E.
Published: July 2008

To elucidate the pathogenic mechanism of
Salmonella enterica
serovar Gallinarum, we examined the expression of the genes encoded primarily in
Salmonella
pathogenicity island 1 (SPI-1) and SPI-2. These genes were found to be induced as cultures entered stationary phase under high- and low-oxygen growth conditions, as also observed for
Salmonella
serovar Typhimurium. In contrast,
Salmonella
serovar Gallinarum in the exponential growth phase most efficiently internalized cultured animal cells. Analysis of mutants defective in SPI-1 genes, SPI-2 genes, and others implicated in early stages of infection revealed that SPI-1 genes were not involved in the internalization of animal cells by
Salmonella
serovar Gallinarum. Following entry, however,
Salmonella
serovar Gallinarum was found to reside in LAMP1-positive vacuoles in both phagocytic and nonphagocytic cells, although internalization was independent of SPI-1. A mutation that conferred defects in ppGpp synthesis was the only one found to affect animal cell internalization by
Salmonella
serovar Gallinarum. It was concluded that
Salmonella
serovar Gallinarum internalizes animal cells by a mechanism independent of SPI-1 genes but dependent on ppGpp. Intracellular growth also required ppGpp for the transcription of genes encoded in SPI-2.
Artificial Septal Targeting ofBacillus subtilisCell Division Proteins inEscherichia coli: an Interspecies Approach to the Study of Protein-Protein Interactions in Multiprotein Complexes
Authors: Robichon Carine , King Glenn F. , Goehring Nathan W. , Beckwith Jon
Published: July 2008

Bacterial cell division is mediated by a set of proteins that assemble to form a large multiprotein complex called the divisome. Recent studies inBacillus subtilisandEscherichia coliindicate that cell division proteins are involved in multiple cooperative binding interactions, thus presenting a technical challenge to the analysis of these interactions. We report here the use of anE. coliartificial septal targeting system for examining the interactions between theB. subtiliscell division proteins DivIB, FtsL, DivIC, and PBP 2B. This technique involves the fusion of one of the proteins (the “bait”) to ZapA, anE. coliprotein targeted to mid-cell, and the fusion of a second potentially interacting partner (the “prey”) to green fluorescent protein (GFP). A positive interaction between two test proteins inE. colileads to septal localization of the GFP fusion construct, which can be detected by fluorescence microscopy. Using this system, we present evidence for two sets of strong protein-protein interactions betweenB. subtilisdivisomal proteins inE. coli, namely, DivIC with FtsL and DivIB with PBP 2B, that are independent of otherB. subtiliscell division proteins and that do not disturb the cytokinesis process in the host cell. Our studies based on the coexpression of three or four of theseB. subtiliscell division proteins suggest that interactions among these four proteins are not strong enough to allow the formation of a stable four-protein complex inE. coliin contrast to previous suggestions. Finally, our results demonstrate thatE. coliartificial septal targeting is an efficient and alternative approach for detecting and characterizing stable protein-protein interactions within multiprotein complexes from other microorganisms. A salient feature of our approach is that it probably only detects the strongest interactions, thus giving an indication of whether some interactions suggested by other techniques may either be considerably weaker or due to false positives.
Excess SeqA Leads to Replication Arrest and a Cell Division Defect inVibrio cholerae
Authors: Saint-Dic Djenann , Kehrl Jason , Frushour Brian , Kahng Lyn Sue
Published: July 2008

Although most bacteria contain a single circular chromosome, some have complex genomes, and allVibriospecies studied so far contain both a large and a small chromosome. In recent years, the divided genome ofVibrio choleraehas proven to be an interesting model system with both parallels to and novel features compared with the genome ofEscherichia coli. While factors influencing the replication and segregation of both chromosomes have begun to be elucidated, much remains to be learned about the maintenance of this genome and of complex bacterial genomes generally. An important aspect of replicating any genome is the correct timing of initiation, without which organisms risk aneuploidy. During DNA replication inE. coli, newly replicated origins cannot immediately reinitiate because they undergo sequestration by the SeqA protein, which binds hemimethylated origin DNA. This DNA is already methylated by Dam on the template strand and later becomes fully methylated; aberrant amounts of Dam or the deletion ofseqAleads to asynchronous replication. In our study, hemimethylated DNA was detected at both origins ofV. cholerae, suggesting that these origins are also subject to sequestration. The overproduction of SeqA led to a loss of viability, the condensation of DNA, and a filamentous morphology. Cells with abnormal DNA content arose in the population, and replication was inhibited as determined by a reduced ratio of origin to terminus DNA in SeqA-overexpressing cells. Thus, excessive SeqA negatively affects replication inV. choleraeand prevents correct progression to downstream cell cycle events such as segregation and cell division.
Membrane Morphology and Leukotoxin Secretion Are Associated with a Novel Membrane Protein ofAggregatibacter actinomycetemcomitans
Authors: Gallant Claude V. , Sedic Maja , Chicoine Erin A. , Ruiz Teresa , Mintz Keith P.
Published: July 2008

Gram-negative bacteria display either a flat or an irregular outer membrane. The periodontal pathogenAggregatibacter(Actinobacillus)actinomycetemcomitanshas an irregular outer membrane. We have identified a gene that is associated with the biogenesis of this morphology. The gene is part of a three-gene operon and codes for a 141-kDa protein designated morphogenesis protein C (MorC), which is conserved in several gram-negative bacteria includingHaemophilus influenzaeandPasteurella multocida. Insertional inactivation of this gene resulted in the conversion of an irregularly shaped membrane to a flat membrane. Associated with this morphological change were the autoaggregation of the bacteria during planktonic growth and a concomitant increase in the surface hydrophobicity of the bacterium. The absence of MorC also resulted in the loss of the secretion of leukotoxin but not theltxAtranscription. Our findings suggest that MorC is critical for membrane morphology and leukotoxin secretion inA. actinomycetemcomitans.
Biosynthesis of a Rare Di-N-Acetylated Sugar in the Lipopolysaccharides of both
Pseudomonas aeruginosa
and
Bordetella pertussis
Occurs via an Identical Scheme despite Different Gene Clusters
Authors: Westman Erin L. , Preston Andrew , Field Robert A. , Lam Joseph S.
Published: July 2008

Pseudomonas aeruginosa
and
Bordetella pertussis
produce lipopolysaccharide (LPS) that contains 2,3-diacetamido-2,3-dideoxy-
d
-mannuronic acid (
d
-ManNAc3NAcA). A five-enzyme biosynthetic pathway that requires WbpA, WbpB, WbpE, WbpD, and WbpI has been proposed for the production of this sugar in
P. aeruginosa
, based on analysis of genes present in the B-band LPS biosynthesis cluster. In the analogous
B. pertussis
cluster, homologs of
wbpB
to
wbpI
were present, but a putative dehydrogenase gene was missing; therefore, the biosynthetic mechanism for UDP-
d
-ManNAc3NAcA was unclear. Nonpolar knockout mutants of each
P. aeruginosa
gene were constructed. Complementation analysis of the mutants demonstrated that B-band LPS production was restored to
P. aeruginosa
knockout mutants when the relevant
B. pertussis
genes were supplied in
trans
. Thus, the genes that encode the putative oxidase, transaminase,
N
-acetyltransferase, and epimerase enzymes in
B. pertussis
are functional homologs of those in
P. aeruginosa
. Two candidate dehydrogenase genes were located by searching the
B. pertussis
genome; these have 80% identity to
P. aeruginosa wbpO
(serotype O6) and 32% identity to
wbpA
(serotype O5). These genes,
wbpO
1629
and
wbpO
3150
, were shown to complement a
wbpA
knockout of
P. aeruginosa
. Capillary electrophoresis was used to characterize the enzymatic activities of purified WbpO
1629
and WbpO
3150
, and mass spectrometry analysis confirmed that the two enzymes are dehydrogenases capable of converting UDP-
d
-GlcNAc, UDP-
d
-GalNAc, to a lesser extent, and UDP-
d
-Glc, to a much lesser extent. Together, these results suggest that
B. pertussis
produces UDP-
d
-ManNAc3NAcA through the same pathway proposed for
P. aeruginosa
, despite differences in the genomic context of the genes involved.
Different Pathways of Choline Metabolism in Two Choline-Independent Strains ofStreptococcus pneumoniaeand Their Impact on Virulence
Authors: Kharat Arun S. , Denapaite Dalia , Gehre Florian , Brückner Reinhold , Vollmer Waldemar , Hakenbeck Regine , Tomasz Alexander
Published: July 2008

The two recently characterizedStreptococcus pneumoniaestrains—R6Chi and R6Cho−—that have lost the unique auxotrophic requirement of this bacterial species for choline differ in their mechanisms of choline independence. In strain R6Chi the mechanism is caused by a point mutation intacF, a gene that is part of the pneumococcallic2operon, which is essential for growth and survival of the bacteria. Cultures oflic2mutants of the encapsulated strain D39Chi growing in choline-containing medium formed long chains, did not autolyze, had no choline in their cell wall, and were completely avirulent in the mouse intraperitoneal model. In contrast, while the Cho−strain carried a complete pneumococcallic2operon and had no mutations in thetacFgene, deletion of the entirelic2operon had no effect on the growth or phenotype of strain Cho−. These observations suggest that the biochemical functions normally dependent on determinants of the pneumococcallic2operon may also be carried out in strain Cho−by a second set of genetic elements imported fromStreptococcus oralis, the choline-independent streptococcal strain that served as the DNA donor in the heterologous transformation event that produced strain R6Cho−. The identification in R6Cho−of a large (20-kb)S. oralisDNA insert carrying bothtacFandlicDgenes confirms this prediction and suggests that these heterologous elements may represent a “backup” system capable of catalyzing P-choline incorporation and export of teichoic acid chains under conditions in which the nativelic2operon is not functional.
Protein Aggregates: an Aging Factor Involved in Cell Death
Authors: Maisonneuve Etienne , Ezraty Benjamin , Dukan Sam
Published: July 2008

In a previous study, we demonstrated the presence of protein aggregates in an exponentially grown
Escherichia coli
culture. In light of these observations, protein aggregates could be considered damage to cells that is able to pass from one generation to the next. Based on the assumption that the amount of aggregate protein could represent an aging factor, we monitored this amount in a bacterial culture during senescence. In doing so, we observed (i) a significant increase in the amount of aggregate protein over time, (ii) a proportional relationship between the amount of aggregate protein and the level of dead cells, (iii) a larger amount in dead cells than in culturable cells, (iv) a heterogeneous distribution of different amounts within a homogenous population of culturable cells entering stasis, and (v) that the initial amount of aggregate protein within a culturable population conditioned the death rate of the culture. Together, the results presented in this study suggest that protein aggregates indeed represent one aging factor leading to bacterial cell death.
Characterization of an Inducible, Antibiotic-Resistant Aminoacyl-tRNA Synthetase Gene in
Streptomyces coelicolor
Authors: Vecchione James J. , Sello Jason K.
Published: July 2008

Streptomyces coelicolor
has two genes encoding tryptophanyl-tRNA synthetases, one of which (
trpRS1
) is resistant to and transcriptionally activated by indolmycin. We found that this gene also confers resistance to chuangxinmycin (another antibiotic that inhibits bacterial tryptophanyl-tRNA synthetases) and that its transcription is not absolutely dependent on either antibiotic.
Identification of a σ
B
-Dependent Small Noncoding RNA in
Listeria monocytogenes
Authors: Nielsen Jesper Sejrup , Olsen Anders Steno , Bonde Mette , Valentin-Hansen Poul , Kallipolitis Birgitte H.
Published: July 2008

In
Listeria monocytogenes
, the alternative sigma factor σ
B
plays important roles in stress tolerance and virulence. Here, we present the identification of SbrA, a novel small noncoding RNA that is produced in a σ
B
-dependent manner. This finding adds the σ
B
regulon to the growing list of stress-induced regulatory circuits that include small noncoding RNAs.
Mutational Analysis of the Connector Segment in the HAMP Domain of Tsr, theEscherichia coliSerine Chemoreceptor
Authors: Ames Peter , Zhou Qin , Parkinson John S.
Published: July 2008

HAMP domains are ∼50-residue motifs, found in many bacterial signaling proteins, that consist of two amphiphilic helices joined by a nonhelical connector segment. The HAMP domain of Tsr, the serine chemoreceptor ofEscherichia coli, receives transmembrane input signals from the periplasmic serine binding domain and in turn modulates output signals from the Tsr kinase control domain to elicit chemotactic responses. We created random amino acid replacements at each of the 14 connector residues of Tsr-HAMP to identify those that are critical for Tsr function. In all, we surveyed 179 connector missense mutants and identified three critical residues (G235, L237, and I241) at which most replacements destroyed Tsr function and another important residue (G245) at which most replacements impaired Tsr function. The region surrounding G245 tolerated 1-residue deletions and insertions of up to 10 glycines, suggesting a role as a relatively nonspecific, flexible linker. The critical connector residues are consistent with a structural model of the Tsr-HAMP domain based on the solution structure of an isolated thermophile HAMP domain (M. Hulko, F. Berndt, M. Gruber, J. U. Linder, V. Truffault, A. Schultz, J. Martin, J. E. Schultz, A. N. Lupas, and M. Coles, Cell 126:929-940, 2006) in which G235 defines a critical turn at the C terminus of the first helix and L237 and I241 pack against the helices, perhaps to stabilize alternative HAMP signaling conformations. Most I241 lesions locked Tsr signal output in the kinase-on mode, implying that this residue is responsible mainly for stabilizing the kinase-off signaling state. In contrast, lesions at L237 resulted in a variety of aberrant output patterns, suggesting a role in toggling output between signaling states.
Salmonella entericaSerovar Typhimurium BipA Exhibits Two Distinct Ribosome Binding Modes
Authors: deLivron Megan A. , Robinson Victoria L.
Published: July 2008

BipA is a highly conserved prokaryotic GTPase that functions to influence numerous cellular processes in bacteria. InEscherichia coliandSalmonella entericaserovar Typhimurium, BipA has been implicated in controlling bacterial motility, modulating attachment and effacement processes, and upregulating the expression of virulence genes and is also responsible for avoidance of host defense mechanisms. In addition, BipA is thought to be involved in bacterial stress responses, such as those associated with virulence, temperature, and symbiosis. Thus, BipA is necessary for securing bacterial survival and successful invasion of the host. Steady-state kinetic analysis and pelleting assays were used to assess the GTPase and ribosome-binding properties ofS. entericaBipA. Under normal bacterial growth, BipA associates with the ribosome in the GTP-bound state. However, using sucrose density gradients, we demonstrate that the association of BipA and the ribosome is altered under stress conditions in bacteria similar to those experienced during virulence. The data show that this differential binding is brought about by the presence of ppGpp, an alarmone that signals the onset of stress-related events in bacteria.
Determination of Antibiotic Hypersensitivity among 4,000 Single-Gene-Knockout Mutants of
Escherichia coli
Authors: Tamae Cindy , Liu Anne , Kim Katherine , Sitz Daniel , Hong Jeeyoon , Becket Elinne , Bui Ann , Solaimani Parrisa , Tran Katherine P. , Yang Hanjing , Miller Jeffrey H.
Published: July 2008

We have tested the entire Keio collection of close to 4,000 single-gene knockouts in
Escherichia coli
for increased susceptibility to one of seven different antibiotics (ciprofloxacin, rifampin, vancomycin, ampicillin, sulfamethoxazole, gentamicin, or metronidazole). We used high-throughput screening of several subinhibitory concentrations of each antibiotic and reduced more than 65,000 data points to a set of 140 strains that display significantly increased sensitivities to at least one of the antibiotics, determining the MIC in each case. These data provide targets for the design of “codrugs” that can potentiate existing antibiotics. We have made a number of double mutants with greatly increased sensitivity to ciprofloxacin, and these overcome the resistance generated by certain
gyrA
mutations. Many of the gene knockouts in
E. coli
are hypersensitive to more than one antibiotic. Together, all of these data allow us to outline the cell's “intrinsic resistome,” which provides innate resistance to antibiotics.
ANALYTIC STUDY ON SPECIFIC HEAT OF ICOSAHEDRAL Al-Mn-Pd QUASICRYSTALS
Authors: WANG JIAN , FAN TIANYOU
Published: July 2008

A simple and explicit formula for specific heat of icoschedral Al-Mn-Pd quasicrystals is obtained, theoretical predictions of which are in good agreement with that given by experiment.
A NUMERICAL STUDY OF CAPSIZING: COMPARING CONTROL SET ANALYSIS AND MELNIKOV'S METHOD
Authors: COLONIUS FRITZ , MARQUARDT ALBERT , KREUZER EDWIN , SICHERMANN WOLFGANG
Published: July 2008

Two models for ship roll motion and capsizing under stochastic excitation are analyzed using Melnikov's method and control set analysis. The predictions given by these two methods are compared.
A USER INTERFACE DESIGN FOR ACQUIRING STATISTICS FROM VIDEO
Authors: LEUNG MAN-KANG , FU CHI-WING
Published: July 2008

This paper introduces a graphical user interface approach to facilitate an efficient and timely generation of statistic data from input videos. By means of a carefully-designed graphical user interface, users can interactively add in various kinds of markers, known as the statistic inducers, on the screen of an input video to specify the areas of interest corresponding to the locations of relevant events. These inducers are in the form of two-dimensional points, lines, polygons, and grids, and can be put on the video screen with great ease. Using these inducers, we not only can efficiently customize the system for a given statistic generation task; in addition, we can also precisely constrain the time-consuming space-time video analysis process (as well as any additional analysis process like optical flow computation or object recognition) on the user-specified areas. To demonstrate the efficacy of the proposed approach, we developed a prototypic system and experimented it in two different statistic generation cases: dormitory light switching and road traffic. In both cases, we just need a few minutes of UI customization time to set up the inducers; once this is done, timely statistics can be automatically generated subsequently.
VISUAL TRACKING WITH AUTOMATIC CONFIDENT REGION EXTRACTION
Authors: YANG TAO , LI JING , PAN QUAN , CHENG YONG-MEI
Published: July 2008

In this work, a novel efficient algorithm for visual object tracking in complex conditions is proposed. The main component of this work includes two parts: Bayesian decision based confident region extraction, and mean shift iteration based tracking. A unique characteristic of the proposed algorithm is that instead of tracking the entire object, the method automatically extracts the confident region of the object through fusing multiple cues in the Bayesian framework. Those cues contain object's color feature, motion character, and dynamic surrounding color information. We tested the performance of the algorithm with video sequences under difficult conditions (complex and dynamic background, fast camera motion, object maneuvering, rotations and partial occlusion) and achieved satisfied results.
VIDEO-BASED GAIT ANALYSIS BY SILHOUETTE CHAMFER DISTANCE AND KALMAN FILTER
Authors: CHAN K. L.
Published: July 2008

A markerless human gait analysis system using uncalibrated monocular video is developed. The background model is trained for extracting the subject silhouette, whether in static scene or dynamic scene, in each video frame. Generic 3D human model is manually fit to the subject silhouette in the first video frame. We propose the silhouette chamfer, which contains the chamfer distance of silhouette and region information, as one matching feature. This, combined dynamically with the model gradient, is used to search for the best fit between subject silhouette and 3D model. Finally, we use the discrete Kalman filter to predict and correct the pose of the walking subject in each video frame. We propose a quantitative measure that can be used to identify tracking faults automatically. Errors in the joint angle trajectories can then be corrected and the walking cycle is interpreted. Experiments have been carried out on video captured in static indoor as well as outdoor scenes.
BLIND WATERMARKING OF NON-UNIFORM B-SPLINE SURFACES
Authors: SUN SHUSEN , PAN ZHIGENG , KIM TAE-WAN
Published: July 2008

In this paper, we propose a watermarking scheme for non-uniform B-spline (NUBS) surface. Firstly, we first do sampling on a NUBS surface and get the sample points, then the watermark is embedded into the DCT coefficients of the sample points and the watermarked sample points are transformed back, finally the watermarked surface is reconstructed from watermarked sample points using global interpolation. A sign correlation detector is used to test for the presence of the watermark, and the original surface is not required at this stage. Experimental results show that our algorithm can preserve the shape of the original surface within a specified error, and that it is robust against attacks including knot insertion, order elevation, addition of white noise, rotation, scaling, translation and further watermarking.
TRACKING HUMAN MOTION FROM MONOCULAR SEQUENCES
Authors: SNIDARO LAURO , FORESTI GIAN LUCA , CHITTARO LUCA
Published: July 2008

In recent years, analysis of human motion has become an increasingly relevant research topic with applications as diverse as animation, virtual reality, security, and advanced human-machine interfaces. In particular, motion capture systems are well known nowadays since they are used in the movie industry. These systems require expensive multi-camera setups or markers to be worn by the user. This paper describes an attempt to provide a markerless low cost and real-time solution for home users. We propose a novel approach for robust detection and tracking of the user's body joints that exploits different algorithms as different sources of information and fuses their estimates with particle filters. This system may be employed for real-time animation of VRML or X3D avatars using an off-the-shelf digital camera and a standard PC.
Effect of heavy exercise on spectral baroreflex sensitivity, heart rate, and blood pressure variability in well-trained humans
Authors: Cottin François , Médigue Claire , Papelier Yves
Published: July 2008

The aim of the study was to assess the instantaneous spectral components of heart rate variability (HRV) and systolic blood pressure variability (SBPV) and determine the low-frequency (LF) and high-frequency baroreflex sensitivity (HF-BRS) during a graded maximal exercise test. The first hypothesis was that the hyperpnea elicited by heavy exercise could entail a significant increase in HF-SBPV by mechanical effect once the first and second ventilatory thresholds (VTs) were exceeded. It was secondly hypothesized that vagal tone progressively withdrawing with increasing load, HF-BRS could decrease during the exercise test. Fifteen well-trained subjects participated in this study. Electrocardiogram (ECG), blood pressure, and gas exchanges were recorded during a cycloergometer test. Ventilatory equivalents were computed from gas exchange parameters to assess VTs. Spectral analysis was applied on cardiovascular series to compute RR and systolic blood pressure power spectral densities, cross-spectral coherence, gain, and α index of BRS. Three exercise intensity stages were compared: below (A1), between (A2), and above (A3) VTs. From A1 to A3, both HF-SBPV (A1: 45 ± 6, A2: 65 ± 10, and A3: 120 ± 23 mm2Hg, P < 0.001) and HF-HRV increased (A1: 20 ± 5, A2: 23 ± 8, and A3:40 ± 11 ms2, P < 0.02), maintaining HF-BRS (gain, A1: 0.68 ± 0.12, A2: 0.63 ± 0.08, and A3: 0.57 ± 0.09; α index, A1: 0.58 ± 0.08, A2: 0.48 ± 0.06, and A3: 0.50 ± 0.09 ms/mmHg, not significant). However, LF-BRS decreased (gain, A1: 0.39 ± 0.06, A2: 0.17 ± 0.02, and A3: 0.11 ± 0.01, P < 0.001; α index, A1: 0.46 ± 0.07, A2: 0.20 ± 0.02, and A3: 0.14 ± 0.01 ms/mmHg, P < 0.001). As expected, once VTs were exceeded, hyperpnea induced a marked increase in both HF-HRV and HF-SBPV. However, this concomitant increase allowed the maintenance of HF-BRS, presumably by a mechanoelectric feedback mechanism.
C-reactive protein and vein graft disease: evidence for a direct effect on smooth muscle cell phenotype via modulation of PDGF receptor-β
Authors: Ho Karen J. , Owens Christopher D. , Longo Thomas , Sui Xin X. , Ifantides Cristos , Conte Michael S.
Published: July 2008

Plasma C-reactive protein (CRP) concentration is a biomarker of systemic atherosclerosis and may also be associated with vein graft disease. It remains unclear whether CRP is also an important modulator of biological events in the vessel wall. We hypothesized that CRP influences vein graft healing by stimulating smooth muscle cells (SMCs) to undergo a phenotypic switch. Distribution of CRP was examined by immunohistochemistry in prebypass human saphenous veins (HSVs, n = 21) and failing vein grafts ( n = 18, 25–4,400 days postoperatively). Quiescent HSV SMCs were stimulated with human CRP (5–50 μg/ml). SMC migration was assessed in modified Boyden chambers with platelet-derived growth factor (PDGF)-BB (5–10 ng/ml) as the chemoattractant. SMC viability and proliferation were assessed by trypan blue exclusion and reduction of Alamar Blue substrate, respectively. Expression of PDGF ligand and receptor (PDGFR) genes was examined at RNA and protein levels after 24–72 h of CRP exposure. CRP staining was present in 13 of 18 diseased vein grafts, where it localized to the deep media and adventitia, but it was minimally detectable in most prebypass veins. SMCs pretreated with CRP demonstrated a dose-dependent increase in migration to PDGF-BB ( P = 0.02), which was inhibited by a PDGF-neutralizing antibody. SMCs treated with CRP showed a dose-dependent increase in PDGFRβ expression and phosphorylation after 24–48 h. Exogenous CRP had no effect on SMC viability or proliferation. These data suggest that CRP is detectable within the wall of most diseased vein grafts, where it may exert local effects. Clinically relevant levels of CRP can stimulate SMC migration by a mechanism that may involve upregulation and activation of PDGFRβ.
Characterization of blood borne microparticles as markers of premature coronary calcification in newly menopausal women
Authors: Jayachandran Muthuvel , Litwiller Robert D. , Owen Whyte G. , Heit John A. , Behrenbeck Thomas , Mulvagh Sharon L. , Araoz Philip A. , Budoff Matthew J. , Harman S. Mitchell , Miller Virginia M.
Published: July 2008

While the risk for symptomatic atherosclerotic disease increases after menopause, currently recognized risk factors do not identify ongoing disease processes in low-risk women. This study tested the hypothesis that circulating cell-derived microparticles may reflect disease processes in women defined as low risk by the Framingham risk score. The concentration and phenotype of circulating microparticles were evaluated in a cross-sectional study of apparently healthy menopausal women, screened for enrollment into the Kronos Early Estrogen Prevention Study. Microparticles were evaluated by flow cytometry, and coronary artery calcification (CAC) was scored using 64-slice computed tomography scanners. The procoagulant activity of isolated microparticles was determined with a sensitive fluorescent thrombin generation assay. Chronological age, body mass index, serum lipids, systolic blood pressure (Framingham risk score < 10%, range 1–3%), and high-sensitivity C-reactive protein did not differ significantly among women with low (0 < 35; range, 0.3–32 Agatston units) or high (>50; range, 93–315 Agatston units) CAC compared with women without calcification. The total concentration and percentage of microparticles derived from platelets and endothelial cells were greatest in women with high CAC scores. The thrombin-generating capacity of the isolated microparticles correlated with phosphatidylserine expression, which also was greatest in women with high CAC scores. The percentages of microparticles expressing granulocyte and monocyte markers were not significantly different among groups. Therefore, the characterization of platelet and endothelial microparticles may identify early menopausal women with premature CAC who would not otherwise be identified by the usual risk factor analysis.
Material properties of the ovine mitral valve anterior leaflet in vivo from inverse finite element analysis
Authors: Krishnamurthy Gaurav , Ennis Daniel B. , Itoh Akinobu , Bothe Wolfgang , Swanson Julia C. , Karlsson Matts , Kuhl Ellen , Miller D. Craig , Ingels Neil B.
Published: July 2008

We measured leaflet displacements and used inverse finite-element analysis to define, for the first time, the material properties of mitral valve (MV) leaflets in vivo. Sixteen miniature radiopaque markers were sewn to the MV annulus, 16 to the anterior MV leaflet, and 1 on each papillary muscle tip in 17 sheep. Four-dimensional coordinates were obtained from biplane videofluoroscopic marker images (60 frames/s) during three complete cardiac cycles. A finite-element model of the anterior MV leaflet was developed using marker coordinates at the end of isovolumic relaxation (IVR; when the pressure difference across the valve is ∼0), as the minimum stress reference state. Leaflet displacements were simulated during IVR using measured left ventricular and atrial pressures. The leaflet shear modulus ( Gcirc-rad) and elastic moduli in both the commisure-commisure ( Ecirc) and radial ( Erad) directions were obtained using the method of feasible directions to minimize the difference between simulated and measured displacements. Group mean (±SD) values (17 animals, 3 heartbeats each, i.e., 51 cardiac cycles) were as follows: Gcirc-rad= 121 ± 22 N/mm2, Ecirc= 43 ± 18 N/mm2, and Erad= 11 ± 3 N/mm2( Ecirc> Erad, P < 0.01). These values, much greater than those previously reported from in vitro studies, may result from activated neurally controlled contractile tissue within the leaflet that is inactive in excised tissues. This could have important implications, not only to our understanding of mitral valve physiology in the beating heart but for providing additional information to aid the development of more durable tissue-engineered bioprosthetic valves.
Sex and limb-specific ischemic reperfusion and vascular reactivity
Authors: Nishiyama Steven K. , Wray D. Walter , Richardson Russell S.
Published: July 2008

With little known regarding sex and limb heterogeneity, we investigated vascular reactivity and ischemic reperfusion (IR) in the upper and lower extremities of 15 healthy men (26 ± 2 yr) and women (23 ± 1 yr). Doppler ultrasound was used to evaluate IR and flow-mediated dilation (FMD) after suprasystolic cuff occlusion in both the arm [brachial artery (BA)] and the leg [popliteal artery (PA)]. Cumulative IR [area under the curve (AUC)], normalized for muscle mass, revealed no sex-related differences in either limb (forearm: men 38 ± 3 and women 44 ± 4 ml/100 g; lower leg: men 12 ± 2 and women 14 ± 2 ml/100 g), while both groups revealed a greater IR per unit of arm muscle mass (AUC) compared with the lower leg ( P < 0.05). The BA and PA were smaller in women (BA 0.31 ± 0.1, PA 0.47 ± 0.1 cm) than in men (BA 0.41 ± 0.1, PA 0.6 ± 0.2 cm). Absolute FMD/shear rate revealed attenuated vascular function in the PA of the women [women 3.3 ± 0.6, men 5.0 ± 0.8 (all ×10−6) cm/s−1·s] and no sex difference in the BA [women 1.2 ± 0.2, men 1.6 ± 0.1 (all ×10−6) cm/s−1·s]. In both sexes the PA demonstrated greater vascular reactivity than the BA. Thus vascular reactivity in healthy young people is greater in the legs, regardless of sex, and women have vascular function similar to men in the upper extremities but appear to have poorer vascular function normalized for shear rate in the lower extremities.
iNOS in cardiac myocytes plays a critical role in death in a murine model of hypertrophy induced by calcineurin
Authors: Somers Julie R. , Beck Paul L. , Lees-Miller James P. , Roach Daniel , Li Yan , Guo J. , Loken Steven , Zhan Shan , Semeniuk Lisa , Duff Henry J.
Published: July 2008

Transgenic overexpression of calcineurin (CN/Tg) in mouse cardiac myocytes results in hypertrophy followed by dilation, dysfunction, and sudden death. Nitric oxide (NO) produced via inducible NO synthase (iNOS) has been implicated in cardiac injury. Since calcineurin regulates iNOS expression, and since phenotypes of mice overexpressing iNOS are similar to CN/Tg, we hypothesized that iNOS is pathogenically involved in cardiac phenotypes of CN/Tg mice. CN/Tg mice had increased serum and cardiac iNOS levels. When CN/Tg-iNOS−/−and CN/Tg mice were compared, some phenotypes were similar: extent of hypertrophy and fibrosis. However, CN/Tg-iNOS−/−mice had improved systolic performance ( P < 0.001) and less heart block ( P < 0.0001); larger sodium current density and lower serum TNF-α levels ( P < 0.03); and less apoptosis ( P < 0.01) resulting in improved survival ( P < 0.0003). To define tissue origins of iNOS production, chimeric lines were generated. Bone marrow (BM) from wild-type or iNOS−/−mice was transplanted into CN/Tg mice. iNOS deficiency restricted to BM-derived cells was not protective. Calcineurin activates the local production of NO by iNOS in cardiac myocytes, which significantly contributes to sudden death, heart block, left ventricular dilation, and impaired systolic performance in this murine model of cardiac hypertrophy induced by the overexpression of calcineurin.