bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cell-Cycle-Regulated Expression and Subcellular Localization of theCaulobacter crescentusSMC Chromosome Structural Protein
Authors: Jensen Rasmus B. , Shapiro Lucy 
Published: May 2003

ABSTRACTStructural maintenance of chromosomes proteins (SMCs) bind to DNA and function to ensure proper chromosome organization in both eukaryotes and bacteria.Caulobacter crescentuspossesses a single SMC homolog that plays a role in organizing and segregating daughter chromosomes. Approximately 1,500 to 2,000 SMC molecules are present per cell during active growth, corresponding to one SMC complex per 6,000 to 8,000 bp of chromosomal DNA. Although transcription from thesmcpromoter is induced during early S phase, a cell cycle transcription pattern previously observed with multiple DNA replication and repair genes, the SMC protein is present throughout the entire cell cycle. Examination of the intracellular location of SMC showed that in swarmer cells, which do not replicate DNA, the protein forms two or three foci. Stalked cells, which are actively engaged in DNA replication, have three or four SMC foci per cell. The SMC foci appear randomly distributed in the cell. Many predivisional cells have bright polar SMC foci, which are lost upon cell division. Thus, chromosome compaction likely involves dynamic aggregates of SMC bound to DNA. The aggregation pattern changes as a function of the cell cycle both during and upon completion of chromosome replication.
The
Escherichia coli
Fis Protein Stimulates Bacteriophage λ Integrative Recombination In Vitro
Authors: Esposito Dominic , Gerard Gary F. 
Published: May 2003

ABSTRACT

The
Escherichia coli
nucleoid-associated protein Fis was previously shown to be involved in bacteriophage lambda site-specific recombination in vivo, enhancing the levels of both integrative recombination and excisive recombination. While purified Fis protein was shown to stimulate in vitro excision, Fis appeared to have no effect on in vitro integration reactions even though a 15-fold drop in lysogenization frequency had previously been observed in
fis
mutants. We demonstrate here that
E. coli
Fis protein does stimulate integrative lambda recombination in vitro but only under specific conditions which likely mimic natural in vivo recombination more closely than the standard conditions used in vitro. In the presence of suboptimal concentrations of Int protein, Fis stimulates the rate of integrative recombination significantly. In addition, Fis enhances the recombination of substrates with nonstandard topologies which may be more relevant to the process of in vivo phage lambda recombination. These data support the hypothesis that Fis may play an essential role in lambda recombination in the host cell.
Identification ofrocA, a Positive Regulator ofcovRExpression in the Group A Streptococcus
Authors: Biswas Indranil , Scott June R. 
Published: May 2003

ABSTRACTIn the group A streptococcus (GAS;Streptococcuspyogenes), a two-component system known as CovRS (or CsrRS) regulates about 15% of the genes, including several important virulence factors like the hyaluronic acid capsule. Most of these genes, includingcovRitself, are negatively regulated by CovR. We have isolated two independent ISS1insertions in an open reading frame (ORF) that increases CovR expression as measured by a Pcov-gusAreporter fusion in single copy in the GAS chromosome. This ORF, namedrocAfor “regulator of Cov,” activatescovRtranscription about threefold. As expected, arocAmutant is mucoid and produces more transcript from thehaspromoter since this promoter is repressed by CovR. This effect is dependent on the presence of a wild-typecovRgene. In contrast to its activation of Pcov, RocA negatively regulates its own expression. This autoregulation is not dependent on the presence of thecovRgene. All the phenotypes of therocAmutant were complemented by the presence of therocAgene on a plasmid. TherocAgene is present in strains of all nine M serotypes of GAS tested and is absent from strains representing 11 other groups of streptococci and related bacteria, including strains of the closely related group C and G streptococci. It seems likely thatrocAplays an important role in the pathogenesis of GAS since it affects expression of the global regulator CovR.
PaeX, a Second Pectin Acetylesterase ofErwinia chrysanthemi3937
Authors: Shevchik Vladimir E. , Hugouvieux-Cotte-Pattat Nicole 
Published: May 2003

ABSTRACTErwinia chrysanthemicauses soft-rot diseases of various plants by enzymatic degradation of the pectin in plant cell walls. Pectin is a complex polysaccharide. The main chain is constituted of galacturonate residues, and some of them are modified by methyl and/or acetyl esterification. Esterases are necessary to remove these modifications and, thus, to facilitate the further degradation of the polysaccharidic chain. In addition to PaeY, the first pectin acetylesterase identified in theE.chrysanthemistrain 3937, we showed that this bacterium produces a second pectin acetylesterase encoded by the genepaeX. ThepaeXopen reading frame encodes a 322-residue precursor protein of 34,940 Da, including a 21-amino-acid signal peptide. Analysis ofpaeXtranscription, by using gene fusions, revealed that it is induced by pectic catabolic products and affected by catabolite repression. The expression ofpaeXis regulated by the repressor KdgR, which controls all the steps of pectin catabolism; by the repressor PecS, which controls most of the pectinase genes; and by catabolite regulatory protein, the global activator of sugar catabolism. ThepaeXgene is situated in a cluster of genes involved in the catabolism and transport of pectic oligomers. In induced conditions, the two contiguous geneskdgM, encoding an oligogalacturonate-specific porin, andpaeXare both transcribed as an operon from a promoter proximal tokdgM, but transcription ofpaeXcan also be uncoupled from that ofkdgMin noninduced conditions. PaeX is homologous to the C-terminal domain of theButyrivibrio fibriosolvensxylanase XynB and to a few bacterial esterases. PaeX contains the typical box (GxSxG) corresponding to the active site of the large family of serine hydrolases. Purified PaeX releases acetate from various synthetic substrates and from sugar beet pectin. The PaeX activity increased after previous depolymerization and demethylation of pectin, indicating that its preferred substrates are nonmethylated oligogalacturonides. PaeX is mostly found in the periplasmic space ofE.chrysanthemi. These data suggest that PaeX is mainly involved in the deacetylation of esterified oligogalacturonides that enter the periplasm by the KdgM porin.
Swarm-Cell Differentiation in
Salmonella
enterica
Serovar Typhimurium Results in Elevated Resistance to Multiple Antibiotics
Authors: Kim Wook , Killam Teresa , Sood Vandana , Surette Michael G. 
Published: May 2003

ABSTRACT

Although a wealth of knowledge exists about the molecular and biochemical mechanisms governing the swimming motility of
Salmonella
enterica
serovar Typhimurium, its surface swarming behavior has not been extensively characterized. When inoculated onto a semisolid agar medium supplemented with appropriate nutrients, serovar Typhimurium undergoes a morphological differentiation whereby single cells hyperflagellate and elongate into nonseptate, multinucleate swarm cells. Swarm migration is a collective behavior of groups of cells. We have isolated a
Mu
dJ insertion mutant of serovar Typhimurium 14028 that failed to swarm under any conditions. The site of the
Mu
dJ insertion was determined to be in the
pmrK
locus within the
pmrHFIJKLM
operon, which was previously demonstrated to confer resistance to cationic antimicrobial peptides. β-Galactosidase assays, using the
pmrK
::
lacZ
transcriptional fusion, showed increased expression of the
pmr
operon in swarm cells compared to that in vegetative cells. In concurrence with the expression data, swarm cells exhibited greater tolerance to polymyxin. To compare the profiles of vegetative and swarm-cell resistance to other antibiotics, E-test strips representing a wide range of antibiotic classes were used. Swarm cells exhibited elevated resistance to a variety of antibiotics, including those that target the cell envelope, protein translation, DNA replication, and transcription. These observations, in addition to the dramatic morphological changes associated with the swarming phenotype, provide an intriguing model for examining global differences between the physiological states of vegetative and swarm cells of serovar Typhimurium.
Global Stage-Specific Gene Regulation during the Developmental Cycle of
Chlamydia trachomatis
Authors: Nicholson Tracy L. , Olinger Lynn , Chong Kimberley , Schoolnik Gary , Stephens Richard S. 
Published: May 2003

ABSTRACT

Distinct morphological changes associated with the complex development cycle of the obligate intracellular bacterial pathogen
Chlamydia trachomatis
have been historically well characterized by microscopy. A number of temporally regulated genes have been characterized previously, suggesting that the chlamydial developmental cycle is regulated at the transcriptional level. This hypothesis was tested by microarray analysis in which the entire
C. trachomatis
genome was analyzed, providing a comprehensive assessment of global gene regulation throughout the chlamydial developmental cycle. Seven temporally cohesive gene clusters were identified, with 22% (189 genes) of the genome differentially expressed during the developmental cycle. The correlation of these gene clusters with hallmark morphological events of the chlamydial developmental cycle suggests three global stage-specific networks of gene regulation.
Identification of the
l
-Aspartate Transporter in
Bacillus subtilis
Authors: Lorca Graciela , Winnen Brit , Saier Milton H. 
Published: May 2003

ABSTRACT

YveA of
Bacillus subtilis
, a putative transporter of the amino acid/polyamine/organocation (APC) superfamily, is shown to mediate uptake of both
l
-aspartate and
l
-glutamate as well as having sensitivity to
l
-aspartate hydroxamate. This 14 TMS protein is the primary aspartate uptake system in
B. subtilis
and serves as the prototype for a new family within the APC superfamily.
Differential Expression of the Components of the Two Alkane Hydroxylases from
Pseudomonas aeruginosa
Authors: Marín Mercedes M. , Yuste Luis , Rojo Fernando 
Published: May 2003

ABSTRACT

Oxidation of
n
-alkanes in bacteria is normally initiated by an enzyme system formed by a membrane-bound alkane hydroxylase and two soluble proteins, rubredoxin and rubredoxin reductase.
Pseudomonas aeruginosa
strains PAO1 and RR1 contain genes encoding two alkane hydroxylases (
alkB1
and
alkB2
), two rubredoxins (
alkG1
and
alkG2
), and a rubredoxin reductase (
alkT
). We have localized the promoters for these genes and analyzed their expression under different conditions. The
alkB1
and
alkB2
genes were preferentially expressed at different moments of the growth phase; expression of
alkB2
was highest during the early exponential phase, while
alkB1
was induced at the late exponential phase, when the growth rate decreased. Both genes were induced by C
10
to C
22
/C
24
alkanes but not by their oxidation derivatives. However, the
alkG1
,
alkG2
, and
alkT
genes were expressed at constant levels in both the absence and presence of alkanes.
The
yggH
Gene of
Escherichia coli
Encodes a tRNA (m
7
G46) Methyltransferase
Authors: De Bie Lara G. S. , Roovers Martine , Oudjama Yamina , Wattiez Ruddy , Tricot Catherine , Stalon Victor , Droogmans Louis , Bujnicki Janusz M. 
Published: May 2003

ABSTRACT

We cloned, expressed, and purified the
Escherichia coli
YggH protein and show that it catalyzes the
S
-adenosyl-
l
-methionine-dependent formation of
N
7
-methylguanosine at position 46 (m
7
G46) in tRNA. Additionally, we generated an
E. coli
strain with a disrupted
yggH
gene and show that the mutant strain lacks tRNA (m
7
G46) methyltransferase activity.
Controlled Initiation of Chromosomal Replication inEscherichia coliRequires Functional Hda Protein
Authors: Camara Johanna Eltz , Skarstad Kirsten , Crooke Elliott 
Published: May 2003

ABSTRACTRegulatory inactivation of DnaA helps ensure that theEscherichia colichromosome is replicated only once per cell cycle, through accelerated hydrolysis of active replication initiator ATP-DnaA to inactive ADP-DnaA. Analysis ofΔhdastrains revealed that the regulatory inactivation of DnaA component Hda is necessary for maintaining controlled initiation but not for cell growth or viability.
Si AND SiGe BIPOLAR ICs FOR 10 TO 40 Gb/s OPTICAL-FIBER TDM LINKS
Authors: REIN H.-M. 
Published: May 2003

This paper gives an overview on very-high-speed ICs for optical-fiber systems with restriction to Si-based technologies. As a main aim, the circuit and system designer shall get an impression what operating speeds have already been achieved and, moreover, get a feeling for potential limitations. It is shown that all ICs in 10 Gb/s TDM systems can be fabricated in Si-bipolar production technologies, while for the speed-critical ICs in 20 Gb/s systems, present SiGe laboratory technologies are required if the circuit specifications, apart from the data rate, must remain unchanged. With uncritical circuits like time-division multiplexer (MUX) and demultiplexer (DEMUX), record data rates of 60 Gb/s systems were achieved with a SiGe laboratory technology, using an adequate mounting and measuring technique. Recent measuring results even showed that all ICs in a 40 Gb/s TDM system (i.e., also the speed-critical ones) can be realized in advanced SiGe technologies. However, compared to ICs in 10 and 20 Gb/s systems, some circuit specifications must be relaxed. This is possible by the use of optical amplifiers and improved opto-electronic components as well as by system modifications, which further make possible the elimination of some of the speed-critical circuits. It should be noted that all the experimental results presented are measured on mounted chips, using conventional wire bonding, and that most of the circuits have been used in experimental TDM links.
20–40 Gbit/s GaAs-HEMT CHIP SET FOR OPTICAL DATA RECEIVER
Authors: LAO Z. , LANG M. , HURM V. , WANG Z. , THIEDE A. , SCHLECHTWEG M. , BRONNER W. , KAUFEL G. , KÖHLER K. , HÜLSMANN A. , RAYNOR B. , JAKOBUS T. 
Published: May 2003

Using our 0.2 and 0.3 μm AlGaAs/GaAs/AlGaAs quantum well HEMT technology, we have developed a chip set for 20–40 Gbit/s fiber-optical digital transmission systems. In this paper we describe nine analog and digital receiver ICs: a 22 GHz high-gain transimpedance amplifier, a 20 Gbit/s OEIC front-end optical receiver, a 25 Gbit/s automatic-gain-control amplifier, a limiting amplifier with a differential gain of 26 dB and a bandwidth of 27.7 GHz, a 20–40 Gbit/s clock recovery, a 20 Gbit/s low-power Master-Slave-D-Flipflop with 24 mW power dissipation, a parallel data decision and a 1:4 demultiplexer, both for bit rates of 40 Gbit/s, and a 30 GHz static frequency divider, respectively. All chips were characterized on wafers with 50 Ω coplanar test probes.
InP-HBT ICs FOR 40 Gb/s OPTICAL LINKS
Authors: MOKHTARI MEHRAN , WESTERGREN URBAN , WILLÉN BO , SWAHN THOMAS , WALDEN ROBERT 
Published: May 2003

InP-based HBT technology has proven to be a strong candidate for ultra high speed electronic as well as optoelectronic integrated circuits. The cut-offs frequencies of the available devices exceed 100 GHz. To challenge the technology, a variety of circuits, suitable for a demonstrator for the 40 Gb/s fiber optical transmission system have been designed, fabricated, and tested. All the circuits show potential for 40 Gb/s applications. The electrical parts have been implemented in MSI/LSI AlInAs/InGaAs-HBT technology, while the monolithic optoelectronic receivers were realized in SSI- InP/InGaAs HBT technology. The verification of performance of the circuits have been mainly limited by available measurement equipment. All the electronic parts were operational with 3 volt supply voltage. All the circuits were fully functional after the first processing round. No redesign was necessary.
Protection against methacholine-induced bronchospasm: salbutamol pMDIversusClickhaler® DPI
Authors: Newhouse M.T. , Patel P. , Parry-Billings M. 
Published: May 2003

Passive dry-powder inhalers (DPIs) have been developed as an alternative to pressurised metered-dose inhalers (pMDIs) to improve aerosol delivery on inhalation and eliminate the need for propellants. However, new DPI formulations of generic drugs must be rigorously compared with conventional pMDI therapy.This randomised, double-blind, double-dummy, placebo-controlled, seven-way crossover study evaluated bronchoprotection from methacholine challenge in order to compare a novel salbutamol DPI (Clickhaler®) with a reference salbutamol pMDI (Ventolin®). Adult asthma patients with airway hyperresponsiveness to methacholine (provocative concentration of methacholine causing a 20% fall in the forced expiratory volume in one second (PC20) <4 mg·mL−1) were treated on separate days with 0, 100, 200 or 400 µg of salbutamolviathe DPI or pMDI. Methacholine challenge was performed before and after salbutamol treatment and the PC20ratios analysed by Finney's bioassay to test for therapeutic equivalence of the inhalers.Eighteen patients completed the study and showed significant dose-related responses to salbutamol. The relative potency of DPI:pMDI was 1.29 (90% confidence interval 1.04–1.63). There were no treatment differences in safety (cardiac frequency, blood pressure, adverse events).Methacholine-challenge methodology provides a sensitive bioassay and has demonstrated therapeutic equivalence of the salbutamol Clickhaler® dry-powder inhaler with the conventional salbutamol pressurised metered-dose inhaler.
Social position and mortality from respiratory diseases in males and females
Authors: Prescott E. , Godtfredsen N. , Vestbo J. , Osler M. 
Published: May 2003

Although social differences in respiratory diseases are considerable, few studies have focused on this disease entity using mortality as an outcome. Does mortality from respiratory disease, including chronic obstructive pulmonary disease (COPD) differ with social position measured by education, income, housing and employment grade?The study population consisted of 26,392 males and females from pooling of two population studies in the Copenhagen area. Data was linked with information from social registers in Statistics Denmark. The relationship between socioeconomic factors and risk of death from respiratory disease and COPD was assessed with an average duration of follow-up of 12 yrs.Education was strongly associated with respiratory mortality in both sexes. The association was stronger in later birth cohorts comparing the highest level of education (>11 yrs) with the lowest (<8 yrs). Although smoking rates were inversely associated with the level of education, the social gradient was not affected by adjustment for smoking. In males, but not in females, there was an additional effect of other indicators of social position,i.e.employment grade (white collarversusblue collar), household income, housing conditions (less than one person per roomversusmore), and cohabitation (cohabitingversusliving alone). Similar results were found for mortality from COPD.The results confirm the existence of a strong social gradient in respiratory mortality and chronic obstructive pulmonary disease, which is independent of smoking and is stronger in males. Social disadvantage is a potentially avoidable cause of death from respiratory disease and further research is needed to explain the excess risk in the socioeconomically disadvantaged.
Pulmonary perfusion quantified by electron-beam computed tomography: effects of hypoxia and inhaled NO
Authors: Jones A.T. , Hansell D.M. , Evans T.W. 
Published: May 2003

Patients with acute lung injury may benefit from the manipulation of pulmonary blood flow using inhaled nitric oxide (iNO) to optimise ventilation/perfusion matching. Current techniques for studying changes in regional pulmonary perfusion are difficult to apply clinically. This study therefore investigated the potential of electron-beam computed tomography (EBCT) to quantify the effects of hypoxia and iNO on regional pulmonary perfusion in five healthy subjects.Contrast-enhanced sections were obtained sequentially under conditions of normoxia, hypoxia (fractional concentration of oxygen in inspired gas (FI,O2) 0.12) and hypoxia, with iNO (14.8 parts per million (ppm)) administered during inspiration in the supine position. Regions of interest were placed along the nondependent to dependent axis and values for relative perfusion derived.Under normoxic conditions a vertical gradient of perfusion existed, which became less apparent due to increased perfusion in nondependent regions after the induction of hypoxia (FI,O20.12). The addition of iNO (FI,O20.12 and NO 14.8 ppm) increased perfusion in all regions of the lung section, suggesting redistribution of pulmonary perfusion from other regions of the lung. Absolute values of perfusion were comparable to those documented with existing techniques.The use of a high spatial-resolution technique confirmed the presence of marked perfusion heterogeneity between anatomically close regions of lung.
Triacylglycerol and phospholipid fatty acids of the silverleaf whitefly: Composition and biosynthesis
Authors: Buckner James S. , Hagen Marcia M. 
Published: May 2003

AbstractThe identification and composition of the fatty acids of the major lipid classes (triacylglycerols and phospholipids) within Bemisia argentifolii Bellows and Perring (Homoptera: Aleyrodidae) nymphs were determined. Comparisons were made to fatty acids from the internal lipids of B. argentifolii adults. The fatty acids, as ester derivatives, were analyzed by capillary gas chromatography (CGC) and CGC‐mass spectrometry (MS). All lipid classes contained variable distributions of eight fatty acids: the saturated fatty acids, myristic acid (14:0), palmitic acid (16:0), stearic acid (18:0), arachidic acid (20:0); the monounsaturated fatty acids, palmitoleic acid (16:1), oleic acid (18:1); the polyunsaturated fatty acids, linoleic acid (18:2), linolenic acid (18:3). Fourth instar nymphs had 5–10 times the quantities of fatty acids as compared to third instar nymphs and 1–3 times the quantities from adults. The fatty acid quantity differences between fourth and third instar nymphs were related to their size and weight differences. The percentage compositions for fatty acids from each lipid class were the same for the pooled groups of third and fourth instar nymphs. For nymphs and adults, triacylglycerols were the major source of fatty acids, with 18:1 and 16:0 acids as major components and the majority of the polyunsaturated fatty acids, 18:2 and 18:3 were present in the two phospholipid fractions, phosphatidylethanolamine and phosphatidylcholine. Evidence was obtained that whiteflies indeed synthesize linoleic acid and linolenic acid de novo: radiolabel from [2‐14C] acetate was incorporated into 18:2 and 18:3 fatty acids of B. argentifolii adults and CGC‐MS of pyrrolidide derivatives established double bonds in the Δ9,12 and Δ9,12,15 positions, respectively. Arch. Insect Biochem. Physiol. 53:66–79, 2003. Published 2003 Wiley‐Liss, Inc.