bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of violent video game habits on adolescent hostility, aggressive behaviors, and school performance
Authors: Gentile Douglas A , Lynch Paul J , Linder Jennifer Ruh , Walsh David A 
Published: January 2004

ABSTRACTVideo games have become one of the favorite activities of American children. A growing body of research is linking violent video game play to aggressive cognitions, attitudes, and behaviors. The first goal of this study was to document the video games habits of adolescents and the level of parental monitoring of adolescent video game use. The second goal was to examine associations among violent video game exposure, hostility, arguments with teachers, school grades, and physical fights. In addition, path analyses were conducted to test mediational pathways from video game habits to outcomes. Six hundred and seven 8th‐ and 9th‐grade students from four schools participated. Adolescents who expose themselves to greater amounts of video game violence were more hostile, reported getting into arguments with teachers more frequently, were more likely to be involved in physical fights, and performed more poorly in school. Mediational pathways were found such that hostility mediated the relationship between violent video game exposure and outcomes. Results are interpreted within and support the framework of the General Aggression Model.
Is graded exercise better than cognitive behaviour therapy for fatigue? A UK randomized trial in primary care
Authors: RIDSDALE L. , DARBISHIRE L. , SEED P. T. 
Published: January 2004

Background. Patients frequently present with unexplained fatigue in primary care, but there have been few treatment trials in this context. We aimed to test cognitive behaviour therapy (CBT) and graded exercise therapy (GET) for patients presenting to their family doctor with fatigue. Secondly, we described the outcome for a cohort of patients who presented to the same doctors with fatigue, who received standard care, plus a booklet.Method. This was a randomized trial, followed by a prospective cohort study. Twenty-two practices in SE England referred 144 patients aged 16 to 75 years with over 3 months of unexplained fatigue. Self-rated fatigue score, the hospital anxiety and depression rating scale, functional impairment, physical step-test performance and causal attributions were measured. In the trial six sessions of CBT or GET were randomly allocated.Results. In the therapy groups the mean fatigue score decreased by 10 points (95% confidence interval (CI)=−25 to −15), with no significant difference between groups (mean difference=−1·3; CI=−3·9 to 1·3). Fewer patients attended for GET. At outcome one-half of patients had clinically important fatigue in both randomized groups, but patients in the group offered CBT were less anxious. Twenty-seven per cent of the patients met criteria for CFS at baseline. Only 25% of this subgroup recovered, compared to 60% of the subgroup that did not meet criteria for CFS.Conclusions. Short courses of GET were not superior to CBT for patients consulting with fatigue of over 3 months in primary care. CBT was easier ‘to sell’. Low recovery in the CFS subgroup suggests that brief treatment is too short.
Redundancy in the function of mitochondrial phosphate transport in Saccharomyces cerevisiae and Arabidopsis thaliana
Authors: Hamel Patrice , Saint‐Georges Yann , De Pinto Brigida , Lachacinski Nicole , Altamura Nicola , Dujardin Geneviève 
Published: January 2004

SummaryMost cellular ATP is produced within the mitochondria from ADP and Pi which are delivered across the inner‐membrane by specific nuclearly encoded polytopic carriers. In Saccharomyces cerevisiae, some of these carriers and in particular the ADP/ATP carrier, are represented by several related isoforms that are distinct in their pattern of expression. Until now, only one mitochondrial Pi carrier (mPic) form, encoded by the MIR1 gene in S. cerevisiae, has been described. Here we show that the gene product encoded by the YER053C ORF also participates in the delivery of phosphate to the mitochondria. We have called this gene PIC2 for Pi carrier isoform 2. Overexpression of PIC2 compensates for the mitochondrial defect of the double mutant Δmir1 Δpic2 and restores phosphate transport activity in mitochondria swelling experiments. The existence of two isoforms of mPic does not seem to be restricted to S. cerevisiae as two Arabidopsis thaliana cDNAs encoding two different mPic‐like proteins are also able to complement the double mutant Δmir1 Δpic2. Finally, we demonstrate that Pic2p is a mitochondrial protein and that its steady state level increases at high temperature. We propose that Pic2p is a minor form of mPic which plays a role under specific stress conditions.
Thermoregulation of the Escherichia coli O157:H7 pO157 ecf operon and lipid A myristoyl transferase activity involves intrinsically curved DNA
Authors: Yoon Jang W. , Minnich Scott A. , Ahn Jong S. , Park Yong H. , Paszczynski Andrzej , Hovde Carolyn J. 
Published: January 2004

Summary Escherichia coli O157:H7 survives in diverse environments from the ruminant gastrointestinal tract to cool nutrient‐dilute water. We hypothesized that the gene regulation required for this flexibility includes intrinsically curved DNA that responds to environmental changes. Three intrinsically curved DNAs were cloned from the E. coli O157:H7 virulence plasmid (pO157), sequenced and designated Bent 1 through Bent 3 (BNT1, BNT2 and BNT3). Compared to BNT1 and BNT3, BNT2 had characteristics typical of intrinsically curved DNA including electrophoretic gel retardation at 4°C, six partially phased adenine:thymine tracts and transcriptional activation. BNT2::lacZ operon fusions showed that BNT2 activated transcription at 24°C compared to 37°C and was partially repressed by a bacterial nucleoid‐associated protein H‐NS. BNT2 regulated the E. coli attaching and effacing gene‐positive conserved fragments 1–4 (ecf1–4) that are conserved in Shiga toxin‐producing E. coli associated with human disease. Experimental analyses showed that ecf1–4 formed an operon. ecf1, 2 and 3 encoded putative proteins associated with bacterial surface polysaccharide biosynthesis and invasion and ecf4 complemented a chromosomal deletion of lpxM encoding lipid A myristoyl transferase. Mass spectrometric analysis of lipid A from ecf and lpxM single and double mutants showed that myristoylation was altered at lower temperature.
Evidence that putrescine acts as an extracellular signal required for swarming in Proteus mirabilis
Authors: Sturgill Gwen , Rather Philip N. 
Published: January 2004

SummaryIn a search for Proteus mirabilis genes that were regulated by cell‐to‐cell signalling, a lacZ fusion (cmr437::mini‐Tn5lacZ) was identified that was repressed 10‐fold by a self‐produced extracellular signal from wild‐type cells. However, the cmr437::mini‐Tn5lacZ insertion itself led to a marked reduction in this extracellular repressing signal. The cmr437::mini‐Tn5lacZ insertion was mapped to a speA homologue in P. mirabilis. Sequence analysis indicated that a speB homologue was encoded downstream of speA. Products of the SpeA and SpeB enzymes (agmatine and putrescine) were tested for repression of cmr437::lacZ. Agmatine did not have repressing activity. However, putrescine was an effective repressing molecule at concentrations down to 30 µM. A second prominent phenotype of the cmr437 (speA)::mini‐Tn5lacZ insertion was a severe defect in swarming motility. This swarming defect was also observed in a strain containing a disruption of the downstream speB gene. Differentiation of the speB mutant to swarmer cells was delayed by two hours relative to wild‐type cells. Furthermore, the speB mutant was unable to migrate effectively across agar surfaces and formed very closely spaced swarming rings. Exogenous putrescine restored both the normal timing of swarmer cell differentiation and the ability to migrate to speB mutants.
Mutations of the CK2 phosphorylation site of Sic1 affect cell size and S‐Cdk kinase activity in Saccharomyces cerevisiae
Authors: Coccetti Paola , Rossi Riccardo L. , Sternieri Flora , Porro Danilo , Russo Gian Luigi , Di Fonzo Andrea , Magni Fulvio , Vanoni Marco , Alberghina Lilia 
Published: January 2004

SummaryBy sequence analysis we found an amino acid stretch centred on Serine201 matching a stringent CK2 consensus site within the C‐terminal, inhibitory domain of Sic1. Here we show by direct mass spectrometry analysis that Sic1, but not a mutant protein whose CK2 phospho‐acceptor site has been mutated to alanine, Sic1S201A, is actually phosphorylated in vitro by CK2 on Serine 201. Mutation of Serine 201 alters the coordination between growth and cell cycle progression. A significant increase of average protein content and of the average protein content at the onset of DNA synthesis is observed for exponentially growing cells harbouring the Sic1S201A protein. A strong reduction of the same parameters is observed in cells harbouring Sic1S201E. The deregulated coordination between cell size and cell cycle is also apparent at the level of S‐Cdk activity.
Kinetics of plasmid segregation in Escherichia coli
Authors: Gordon Scott , Rech Jerôme , Lane David , Wright Andrew 
Published: January 2004

SummaryLow copy‐number bacterial replicons occupy specific locations in their host cells. Production of a GFP‐Lac repressor hybrid protein in cells carrying F or P1 plasmids tagged with a lac operator array reveals that in smaller (younger) cells these plasmids are seen mainly as a single fluorescent focus at mid‐cell, whereas larger cells tend to have two foci, one at each quarter‐cell position. Duplication of the central focus is presumed to represent active partition of plasmid copies. We report here our investigation by time‐lapse microscopy of the subsequent movement of these copies to the quarter positions. Following duplication of the central focus, the new foci migrated rapidly and directly to their quarter‐cell destinations, where they remained until the next cell cycle. The speed of movement was about five times faster than poleward migration of oriC and 50 times faster than cell elongation. Aberrant positioning of mini‐F lacking its sopC centromere demonstrated the requirement for the partition system in this localization process. From the measured number of F plasmid copies per cell it appears that each migrating focus contains two or more plasmid molecules. The molecular basis of this clustering, and evidence for phasing of the partition event in the cell cycle, are discussed.
From the inside out – processing of the Chlamydial autotransporter PmpD and its role in bacterial adhesion and activation of human host cells
Authors: Wehrl Wolfgang , Brinkmann Volker , Jungblut Peter R. , Meyer Thomas F. , Szczepek Agnes J. 
Published: January 2004

SummaryPolymorphic membrane protein (Pmp)21 otherwise known as PmpD is the longest of 21 Pmps expressed by Chlamydophila pneumoniae. Recent bioinformatical analyses annotated PmpD as belonging to a family of exported Gram‐negative bacterial proteins designated autotransporters. This prediction, however, was never experimentally supported, nor was the function of PmpD known. Here, using 1D and 2D PAGE we demonstrate that PmpD is processed into two parts, N‐terminal (N‐pmpD), middle (M‐pmpD) and presumably third, C‐terminal part (C‐pmpD). Based on localization  of  the  external  part  on  the  outer  membrane as shown by immunofluorescence, immuno‐electron microscopy and immunoblotting combined with trypsinization, we demonstrate that N‐pmpD translocates to the surface of bacteria where it non‐covalently binds other components of the outer membrane. We propose that N‐pmpD functions as an adhesin, as antibodies raised against N‐pmpD blocked  chlamydial  infectivity  in  the  epithelial  cells. In addition, recombinant N‐pmpD activated human monocytes in vitro by upregulating their metabolic activity and by stimulating IL‐8 release in a dose‐dependent manner. These results demonstrate that N‐PmpD is an autotransporter component of chlamydial outer membrane, important for bacterial invasion and host inflammation.
A CDP‐choline pathway for phosphatidylcholine biosynthesis in Treponema denticola
Authors: Kent Claudia , Gee Patricia , Lee Si Young , Bian Xuelin , Fenno J. Christopher 
Published: January 2004

SummaryThe genomes of Treponema denticola and Treponema pallidum contain a gene, licCA, which is predicted to encode a fusion protein containing choline kinase and CTP:phosphocholine cytidylyltransferase activities. Because both organisms have been reported to contain phosphatidylcholine, this raises the possibility that they use a CDP‐choline pathway for the biosynthesis of phosphatidylcholine. This report shows that phosphatidylcholine is a major phospholipid in T. denticola, accounting for 35–40% of total phospholipid. This organism readily incorporated [14C]choline into phosphatidylcholine, indicating the presence of a choline‐dependent biosynthetic pathway. The licCA gene was cloned, and recombinant LicCA had choline kinase and CTP:phosphocholine cytidylyltransferase activity. The licCA gene was disrupted in T. denticola by erythromycin cassette mutagenesis, resulting in a viable mutant. This disruption completely blocked incorporation of either [14C]choline or 32Pi into phosphatidylcholine. The rate of production of another phospholipid in T. denticola, phosphatidylethanolamine, was elevated considerably in the licCA mutant, suggesting that the elevated level of this lipid compensated for the loss of phosphatidylcholine in the membranes. Thus it appears that T. denticola does contain a licCA‐dependent CDP‐choline pathway for phosphatidylcholine biosynthesis.
Salmonella type III secretion‐associated chaperones confer secretion‐pathway specificity
Authors: Lee Sang Ho , Galán Jorge E. 
Published: January 2004

SummaryType III protein secretion systems (TTSSs) are ancestrally related to the flagellar export system and are essential for the virulence of many bacteria pathogenic for humans, animals and plants. Most proteins destined to travel the TTSS pathway possess at least two domains that specifically target them to the secretion apparatus. One of the domains is located within the amino terminal first ∼20 amino acids and the second domain, located within the first ∼140 amino acids, serves as a binding site for specific chaperones. It has been previously proposed that these two secretion signals are capable of operating independently of one another to facilitate secretion into the extracellular environment. We have found that in the absence of their chaperone‐binding domains, the Salmonella typhimurium TTSS‐secreted proteins SptP and SopE are no longer targeted for secretion through their cognate TTSS and, instead, are secreted through the flagellar export pathway. These results indicate the existence of an ‘ancestral’ flagellar secretion signal within TTSS‐exported proteins that is revealed in the absence of the chaperone‐binding domain. Furthermore, we found that secretion into culture supernatants as well as translocation into host cells by the cognate TTSS require both, the amino terminal and chaperone‐binding domains. We conclude from these studies that a critical function for the TTSS‐associated chaperones is to confer secretion‐pathway specificity to their cognate secreted proteins.
Flavonoids induce temporal shifts in gene‐expression of nod‐box controlled loci in Rhizobium sp. NGR234
Authors: Kobayashi Hajime , Graven Yamama Naciri , Broughton William J. , Perret Xavier 
Published: January 2004

SummaryRhizobia, soil bacteria of the Rhizobiales, enter the roots of homologous legumes, where they induce the formation of nitrogen‐fixing nodules. Signals emanating from both symbiotic partners control nodule development. Efficient nodulation requires precise, temporal regulation of symbiotic genes. Roots continuously release flavonoids that interact with transcriptional activators of the LysR family. NodD proteins, which are members of this family, act both as sensors of the environment and modulate the expression of genes preceded by conserved promoter sequences called nod‐boxes. The symbiotic plasmid of the broad host‐range Rhizobium sp. NGR234 caries 19 nod‐boxes (NB1 to NB19), all of which were cloned upstream of a lacZ‐reporter gene. A flavonoid, daidzein was able to induce 18 of the 19 nod‐boxes in a NodD1‐dependent manner. Interestingly, induction of four nod‐boxes (NB6, NB15, NB16 and NB17) is highly dependent on NodD2 and was delayed  in  comparison  with  the  others.  In  turn, NodD2 is involved in the repression of the NB8 nodABCIJnolOnoeI operon. Activation of transcription of nodD2 is also dependent on flavonoids despite  the  absence  of  a  nod‐box  like  sequence  in the upstream promoter region. Mutational analysis showed that syrM 2 (another member of the LysR family), which is controlled by NB19, is also necessary for expression of nodD 2. Thus, NodD1, NodD2 and SyrM2 co‐modulate a flavonoid‐inducible regulatory cascade that coordinates the expression of symbiotic genes with nodule development.
Hyperinitiation of DNA replication in Escherichia coli leads to replication fork collapse and inviability
Authors: Simmons Lyle A. , Breier Adam M. , Cozzarelli Nicholas R. , Kaguni Jon M. 
Published: January 2004

SummaryElevated dnaA expression from a multicopy plasmid induces more frequent initiation from the Escherichia coli replication origin, oriC, but viability is maintained. In comparison, chromosomally encoded dnaAcos also stimulates initiation, but this is lethal. By quantitative methods, we show that the level of initiation induced by elevated dnaA expression leads to collapsed replication forks that are mostly within 10 map units of oriC. Because forks collapse randomly, nucleoprotein complexes at specific sites such as datA are not the cause. When replication restart is blocked by a mutation in recB or priA, the increased initiations via elevated dnaA expression causes inviability. The amount of collapsed forks is substantially higher under elevated expression of dnaAcos compared to that of dnaA. We propose that the lethal phenotype of chromosomally encoded dnaAcos is a result of hyperinitiation that overwhelms the repair capacity of the cell.
Staphylococcus aureus multiresistance plasmid pSK41: analysis of the replication region, initiator protein binding and antisense RNA regulation
Authors: Kwong Stephen M. , Skurray Ronald A. , Firth Neville 
Published: January 2004

SummaryThe vast majority of large staphylococcal plasmids characterized to date appear to possess an evolutionarily common replication system, which has clearly had a major impact on the evolution of antimicrobial resistant staphylococci worldwide. Related systems have also been found in plasmids from other Gram‐positive genera, including enterococci, streptococci and bacilli. The 46.4 kb plasmid pSK41 is the prototype of a family of conjugative staphylococcal multiresistance plasmids. The replication region of pSK41 encodes a protein product, Rep, which was shown to be essential for replication; mutations that truncated Rep could be complemented in trans. Rep was found to bind in vitro to four tandem repeat sequences located centrally within the rep coding region. An A + T‐rich inverted repeat sequence upstream of rep was required for efficient replication, whereas no sequences downstream of rep were necessary. An antisense countertranscript, RNAI, encoded upstream of rep was identified and transcriptional start points for both RNAI and the rep‐mRNA were defined.
Individual RD1‐region genes are required for export of ESAT‐6/CFP‐10 and for virulence of Mycobacterium tuberculosis
Authors: Guinn Kristi M. , Hickey Mark J. , Mathur Sanjeev K. , Zakel Kelly L. , Grotzke Jeff E. , Lewinsohn David M. , Smith Sherilyn , Sherman David R. 
Published: January 2004

SummaryThe RD1 genomic region is present in virulent strains of Mycobacterium tuberculosis (MTB), missing from the vaccine strain M. bovis BCG, and its importance to virulence has been established experimentally. Based on in silico analysis, it has been suggested that RD1 may encode a novel secretion system, but the mechanism by which this region affects virulence is unknown. Here we examined mutants disrupted in five individual RD1 genes. Both in vitro and in vivo, each mutant displayed an attenuated phenotype very similar to a mutant missing the entire RD1 region. Genetic complementation of individual genes restored virulence. Attenuated mutants could multiply within THP‐1 cells, but they were unable to spread to uninfected macrophages. We also examined export of two immunodominant RD1 proteins, CFP‐10 and ESAT‐6. Export of these proteins was greatly reduced or abolished in each attenuated mutant. Again, genetic complementation restored a wild‐type phenotype. Our results indicate that RD1 genes work together to form a single virulence determinant, and argue that RD1 encodes a novel specialized secretion system that is required for pathogenesis of MTB.
An ER packaging chaperone determines the amino acid uptake capacity and virulence of Candida albicans
Authors: Martínez Paula , Ljungdahl Per O. 
Published: January 2004

SummaryThe Candida albicans CSH3 gene encodes a functional and structural homologue of Shr3p, a yeast protein that is specifically required for proper uptake and sensing of extracellular amino acids in Saccharomyces cerevisiae. A Candida csh3Δ/csh3Δ null mutant has a reduced capacity to take up amino acids, and is unable to switch morphologies on solid and in liquid media in response to inducing amino acids. CSH3/csh3Δ heterozygous strains display normal amino acid induced morphological switching. However, although heterozygous cells apparently sense and properly react to amino acid induced signals they cannot take up amino acids at wild‐type rates. Strikingly, both CSH3/csh3Δ heterozygous and csh3Δ/csh3Δ homozygous strains are unable to efficiently mount virulent infections in a mouse model. The haploinsufficiency phenotypes indicate that both CSH3 alleles contribute to maintain high‐capacity amino acid uptake in wild‐type strains. These results strongly suggest that C. albicans cells use amino acids, presumably as nitrogen sources, during growth in mammalian hosts.
Chromosomal constraints in Gram‐positive bacteria revealed by artificial inversions
Authors: Campo N. , Dias M. J. , Daveran‐Mingot M. ‐L. , Ritzenthaler P. , Le Bourgeois P. 
Published: January 2004

SummaryWe used artificial chromosome inversions to investigate the chromosomal constraints that preserve genome organization in the Gram‐positive bacterium Lactococcus lactis. Large inversions, 80–1260 kb in length, disturbing the symmetry of the origin and terminus of the replication axis to various extents, were constructed using the site‐specific Cre‐loxP recombination system. These inversions were all mechanistically feasible and fell into various classes according to stability and effect on cell fitness. The L. lactis chromosome supports only to some extent unbalance in length of its replication arms. The location of detrimental inversions allowed identification of two constrained chromosomal regions: a large domain covering one fifth of the genome that encompasses the origin of replication (Ori domain), and a smaller domain located at the opposite of the chromosome (Ter domain).