bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulatory network of acid resistance genes in Escherichia coli
Authors: Masuda Nobuhisa , Church George M. 
Published: December 2004

SummaryOverexpression of the response regulator EvgA confers an acid‐resistant phenotype to exponentially growing Escherichia coli. This acid resistance is partially abolished by deletion of ydeP, yhiE or ydeO, genes induced by EvgA overexpression. Microarray analysis identified two classes of operons (genes). The first class contains seven operons induced by EvgA overexpression in the absence of ydeO, an AraC/XylS regulator gene. The second class contains 12 operons induced by YdeO overexpression. Operons in the second class were induced by EvgA overexpression only in the presence of ydeO. EvgA is likely to directly upregulate operons in the first class, and indirectly upregulate operons in the second class via YdeO. Analysis using the motif‐finding program alignace identified an 18 bp inverted repeat motif in six upstream regions of all seven operons directly regulated by EvgA. Gel mobility shift assays showed the specific binding of EvgA to the six sequences. Introduction of mutations into the inverted repeats upstream of ydeP and b1500‐ydeO resulted in reduction in EvgA‐induced ydeP and ydeO expression and acid resistance. These results suggest that EvgA binds to the inverted repeats and upregulates the downstream genes. Overexpression of YdeP, YdeO and YhiE conferred acid resistance to exponentially growing cells, whereas GadX overexpression did not. Microarray analysis also identified several GadX‐activated genes. Several genes induced by overexpression of YdeO and GadX overlapped; however, yhiE was induced only by YdeO. The acid resistance induced by YdeO overexpression was abolished by deletion of yhiE, gadC, slp‐yhiF, hdeA or hdeD, genes induced by YdeO overexpression, suggesting that several genes orchestrate YdeO‐induced acid resistance. We propose a model of the regulatory network of the acid resistance genes.
The avilamycin resistance determinants AviRa and AviRb methylate 23S rRNA at the guanosine 2535 base and the uridine 2479 ribose
Authors: Treede Irina , Jakobsen Lene , Kirpekar Finn , Vester Birte , Weitnauer Gabriele , Bechthold Andreas , Douthwaite Stephen 
Published: December 2004

SummaryAvilamycin is an orthosomycin antibiotic that has shown considerable potential for clinical use, although it is presently used as a growth promoter in animal feed. Avilamycin inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit. The ribosomes of the producer strain, Streptomyces viridochromogenes Tü57, are protected from the drug by the action of three resistance factors located in the avilamycin biosynthetic gene cluster. Two of the resistance factors, aviRa and aviRb, encode rRNA methyltransferases that specifically target 23S rRNA. Recombinant AviRa and AviRb proteins retain their activity after purification, and both specifically methylate in vitro transcripts of 23S rRNA domain V. Reverse transcriptase primer extension indicated that AviRa is an N‐methyltransferase that targets G2535 within helix 91 of the rRNA, whereas AviRb modified the 2′‐O‐ribose position of nucleotide U2479 within helix 89. MALDI mass spectrometry confirmed the exact positions of each of these modifications, and additionally established that a single methyl group is added at each nucleotide. Neither of these two nucleotides have previously been described as a target for enzymatic methylation. Molecular models of the 50S subunit crystal structure show that the N−1 of the G2535 base and the 2′‐hydroxyl of U2479 are separated by approximately 10 Å, a distance that can be spanned by avilamycin. In addition to defining new resistance mechanisms, these data refine our understanding of the probable ribosome contacts made by orthosomycins and of how these antibiotics inhibit protein synthesis.
Architecture of the ParF•ParG protein complex involved in prokaryotic DNA segregation
Authors: Barillà Daniela , Hayes Finbarr 
Published: December 2004

SummaryThe mechanism by which low copy number plasmids are segregated at cell division involves the concerted action of two plasmid‐encoded proteins that assemble on a centromere‐like site. This study explores the topology of the DNA segregation machinery specified by the parFG locus of TP228, a partition system which is phylogenetically distinct from more well‐characterized archetypes. A variety of genetic, biochemical and biophysical strategies revealed that the ParG protein is dimeric. ParF, which is more closely related to the cell division regulator MinD than to the prototypical ParA partition protein of plasmid P1, is instead multimeric and its polymeric state appears to be modulated by ATP which correlates with the proposed ATP‐binding activity of ParF. ParG interacts in a sequence‐specific manner with the DNA region upstream of the parFG locus and this binding is modulated by ParF. Intriguingly, the ParF and ParG proteins form at least two types of discrete complex in the absence of this region suggesting that the assembly dynamics of these proteins onto DNA is intricate.
The Erwinia chrysanthemi phoP‐phoQ operon plays an important role in growth at low pH, virulence and bacterial survival in plant tissue
Authors: Llama‐Palacios Arancha , López‐Solanilla Emilia , Poza‐Carrión César , García‐Olmedo Francisco , Rodríguez‐Palenzuela Pablo 
Published: December 2004

SummaryWe have studied the role of acidic pH as a barrier for the colonization of the plant apoplast by Erwinia chrysanthemi. A minitransposon containing a promoterless reporter gene, gus, was used for random mutagenesis of the bacterial genome. An acid‐sensitive mutant, named BT119, was isolated and had the following differential features with respect to the wild‐type strain: (i) inability to grow at pH ≤ 5.5; (ii) decreased survival at acid pH and in plant tissues; (iii) increased susceptibility to antimicrobial peptides; (iv) decreased virulence in chicory leaves and pear fruits; (v) reduced polygalacturonase production; and (vi) reduced ability to alkalinize chicory tissues after infection. The sequence of the interrupted gene was highly similar to the phoQ gene, which is involved in environmental sensing in several bacteria, such as Yersinia pseudotuberculosis, Erwinia carotovora, Salmonella typhimurium and Escherichia coli and thus, this designation was used for the E. chrysanthemi system. This gene was induced at low Mg2+ concentrations and in planta. These results suggest that E. chrysanthemi PhoP‐PhoQ system plays an important role in bacterial survival in plant tissues during the initial infection stages.
Self‐association of EPEC intimin mediated by the β‐barrel‐containing anchor domain: a role in clustering of the Tir receptor
Authors: Touzé Thierry , Hayward Richard D. , Eswaran Jeyanthy , Leong John M. , Koronakis Vassilis 
Published: December 2004

SummaryOuter membrane intimin directs attachment of enteropathogenic Escherichia coli (EPEC) via its Tir receptor in mammalian target cell membranes. Phosphorylation of Tir triggers local actin polymerization and the formation of ‘pedestal‐like’ pseudopods. We demonstrate that the intimin protein contains three domains, a flexible N‐terminus (residues 40–188), a central membrane‐integrated β‐barrel (189–549), and a tightly folded Tir‐binding domain (550–939). Intimin was shown by electron microscopy to form ring‐like structures with a ∼7 nm external diameter and an electron dense core, and to form channels of 50picoSiemens conductance in planar lipid bilayers. Gel filtration, multiangle light scattering and cross‐linking showed that this central β‐barrel membrane‐anchoring domain directs intimin dimerization. Isothermal titration calorimetry revealed a high affinity, single‐binding site interaction of 2 : 1 stoichiometry between dimeric intimin and Tir, and modelling suggests that this interaction determines a reticular array‐like superstructure underlying receptor clustering. In support of this model, actin rearrangement induced in Tir‐primed cultured cells by intimin‐containing proteoliposomes was dependent on the concentration of both intimin and Tir, and co‐localized with clustered phosphorylated Tir.
Tomographic reconstruction of treponemal cytoplasmic filaments reveals novel bridging and anchoring components
Authors: Izard Jacques , McEwen Bruce F. , Barnard Rita M. , Portuese Thomas , Samsonoff William A. , Limberger Ronald J. 
Published: December 2004

SummaryAn understanding of the involvement of bacterial cytoplasmic filaments in cell division requires the elucidation of the structural organization of those filamentous structures. Treponemal cytoplasmic filaments are composed of one protein, CfpA, and have been demonstrated to be involved in cell division. In this study, we used electron tomography to show that the filaments are part of a complex with a novel molecular organization that includes at least two distinct features decorating the filaments. One set of components appears to anchor the filaments to the cytoplasmic membrane. The other set of components appears to bridge the cytoplasmic filaments on the cytoplasmic side, and to be involved in the interfilament spacing within the cell. The filaments occupy between 3 and 18% of the inner surface of the cytoplasmic membrane. These results reveal a novel filamentous molecular organization of independent filaments linked by bridges and continuously anchored to the membrane.
The function of RNase G in Escherichia coli is constrained by its amino and carboxyl termini
Authors: Deana Atilio , Belasco Joel G. 
Published: December 2004

SummaryRNase G is a homologue of the essential Escherichia coli ribonuclease RNase E. Whereas RNase E plays a key role in the degradation of mRNA and the processing of tRNA and rRNA in E. coli, the biological functions of RNase G appear more limited. We report here that this difference in function is not merely a consequence of the significantly lower cellular concentration of RNase G, but also reflects differences in the intrinsic properties of these ribonucleases, as overproducing wild‐type RNase G at a level up to 20 times the usual cellular concentration of RNase E cannot normally compensate for the absence of RNase E in E. coli. Instead, RNase G can sustain significant growth of RNase E‐deficient E. coli cells only when it bears an unnatural extension at its amino terminus (e.g. MRKGINM) or carboxyl terminus (e.g. GHHHHHH). These extensions presumably enable RNase G to cleave critically important cellular RNAs whose efficient processing or degradation ordinarily requires RNase E. That extending the amino terminus of RNase G restores growth to E. coli cells lacking RNase E without detectably improving tRNA processing suggests that RNase E is not essential for tRNA production and is required for cell growth because it plays an indispensable role in the maturation or decay of essential E. coli RNAs other than tRNA.
Effects of four generations of density-dependent selection on life history traits and their plasticity in a clonally propagated plant
Authors: Van Kleunen M. , Fischer M. 
Published: December 2004

Abstract
Life history evolution of many clonal plants takes place with long periods of exclusively clonal reproduction and under largely varying ramet densities resulting from clonal reproduction. We asked whether life history traits of the clonal herb Ranunculus reptans respond to density-dependent selection, and whether plasticity in these traits is adaptive. After four generations of exclusively clonal propagation of 16 low and 16 high ramet-density lines, we studied life history traits and their plasticities at two test ramet-densities. Plastic responses to higher test-density consisted of a shift from sexual to vegetative reproduction, and reduced flower production, plant size, branching frequency, and lengths of leaves and internodes. Plants of high-density lines tended to have longer leaves, and under high test-density branched less frequently than those of low-density lines. Directions of these selection responses indicate that the observed plastic branching response is adaptive, whereas the plastic leaf length response is not. The reverse branching frequency pattern at low test-density, where plants of high-density lines branched more frequently than those of low-density lines, indicates evolution of plasticity in branching. Moreover, when grown under less stressful low test-density, plants of high-density lines tended to grow larger than the ones of low-density lines. We conclude that ramet density affects clonal life-history evolution and that under exclusively clonal propagation clonal life-history traits and their plasticities evolve differently at different ramet densities.
Fitness-associated recombination on rugged adaptive landscapes
Authors: Hadany L. , Beker T. 
Published: December 2004

Abstract
A negative correlation between fitness and recombination rates seems to exist in various organisms. In this article we suggest that a correlation of that kind may play an important role in the evolution of complex traits. We study the effects of such fitness-associated recombination (FAR) in a simple two-locus deterministic model, as well as in a multi-loci NK rugged adaptive landscape. In both models studied, FAR results in faster adaptation and higher average population fitness, compared with uniform-rate recombination.
Morphological and microsatellite differentiation in Melospiza melodia (Aves) at a microgeographic scale
Authors: Chan Y. , Arcese P. 
Published: December 2004

Abstract
Geographical variation in microsatellite allele frequencies and morphology were compared for five subspecies of Melospiza melodia (song sparrow; M. m. samuelis, M. m. maxillaris, M. m. pusillula, M. m. gouldii, and M. m. heermanni) in 14 populations in the San Francisco Bay region to (a) assess divergence based on these estimates and (b) test the hypothesis that drift is responsible for morphological and genetic divergence. Morphological differentiation between subspecies was high despite low differentiation at microsatellite loci, indicating high gene flow and large effective population sizes. Low concordance of morphological and genetic estimates of divergence suggests that selection or phenotypic plasticity in morphology has caused morphological differentiation among the subspecies.
Characteristics of Lactoferrin Receptor in Bovine Intestine: Higher Binding Activity to the Epithelium Overlying Peyer's Patches
Authors: Talukder M. J. R. , Takeuchi T. , Harada E. 
Published: December 2004

SummarySeveral lines of evidence have recently demonstrated the occurrence of specific lactoferrin (Lf) receptors in different cells. We report here, for the first time, the characteristics of binding, and distribution of Lf receptors in the bovine intestinal tract with special emphasis on the epithelium overlying Peyer's patches (EOPP). Brush‐border membrane vesicles (BBMV) were prepared from the mucosa of duodenum, jejunum, ileum, colon, EOPP in jejunum and EOPP in ileum. Receptor binding assays were carried out using 125I‐labelled bovine Lf. Specific and saturable Lf receptors were found in BBMV of all the intestinal segments examined. Non‐linear regression and Scatchard plot analyses clearly revealed that EOPP had the highest binding maximal (Bmax), and lowest in colon. The maximum dissociation constant (Kd) 3.74 μm was in the ileum. We found that bovine transferrin competed with Lf for the same binding site of receptors. In contrast, no binding of bovine serum albumin occurred. It was concluded that Lf receptors in the mucosal lining are attributable to mediate multifunctional activities of Lf in the gut, especially in the EOPP.
Long‐term Follow‐up of Manipulative Treatment in a Horse with Back Problems
Authors: Faber M. J. , Van Weeren P. R. , Schepers M. , Barneveld A. 
Published: December 2004

SummaryIn order to objectively quantify the effect of manipulation on back‐related locomotion anomalies in the horse, a recently developed kinematic measuring technique for the objective quantification of thoracolumbar motion in the horse was applied in a dressage horse that was suffering from a back problem. In this horse, clinically, a right‐convex bending (scoliosis) from the 10th thoracic vertebra to the second lumbar vertebra was diagnosed. As a result, there was a marked asymmetric movement of the thoracolumbar spine. Functionally, there was severe loss of performance. Thoracolumbar motion was measured in terms of ventrodorsal flexion, lateral flexion, and axial rotation using an automated gait analysis system. Measurements were repeated before and 2 days after treatment, before the second treatment 3 weeks later, and at 4 weeks and 8 months after the second treatment to assess long‐term effect. At the same time, performance of the horse was assessed subjectively by the trainer as well. Symmetry of movement improved dramatically after the first treatment. After this, there was a slight decrease in symmetry, but 8 months after the last treatment the symmetry indexes for the various joints were still considerably better than during the first (pre‐treatment) measuring session. Subjectively, the trainer did not notice improvement until after measurement session 4. Between sessions 4 and 5 (at 4 weeks and 8 months after the second treatment) there was a change of trainer. The new trainer did not report any back problem, and succeeded in bringing the horse back to its former level in competition. It is concluded that manipulation had a measurable influence on the kinematics of the thoracolumbar spine. However, it is recognized that an improvement in symmetry of motion is not equivalent to clinical improvement and that other measures, such as changes in management, may be more decisive.
The Effect of Orally Administered Marbofloxacin on the Pharmacokinetics of Theophylline
Authors: Hirt R. A. , Teinfalt M. , Dederichs D. , Van Den Hoven R. 
Published: December 2004

SummaryAs certain quinolones can interfere with the metabolism of theophylline by competitive inhibition of the hepatic microsomal cytochrome P450 system, concomitant use of these drugs with theophylline could result in theophylline toxicity. This study investigated the effect of orally administered marbofloxacin (2 and 5 mg/kg each once daily) on steady‐state plasma pharmacokinetics of theophylline after concomitant oral administration of a sustained release theophylline preparation in dogs. Marbofloxacin caused some alteration in theophylline metabolism. A 2 mg/kg dose of marbofloxacin did not clearly result in an increased area under the concentration – time curve (AUC) or decreased clearance of theophylline, but at a dose of 5 mg/kg, a statistically significant increase in AUC and a decrease in the total clearance of theophylline was found. The 26% reduction in theophylline clearance is probably not clinically significant in healthy dogs, but for dogs with renal impairment, there might be a chance of theophylline accumulation when dosed concomitantly with marbofloxacin.
The Variations of White Blood Cell Count in Lipizzan Horses
Authors: Čebulj‐Kadunc N. , Kosec M. , Cestnik V. 
Published: December 2004

SummaryTotal and differential leucocyte counts (lymphocytes, neutrophils, monocytes, eosinophils and basophils) were measured in 140 stallions, 101 mares and 25 foals of Lipizzan breed. The values fell in the normal ranges for warm‐blooded horses. Differences between mares and stallions were not significant with the exception of foals, having higher white blood cell, neutrophil, lymphocyte, monocyte and basophil values in females than in males. Foals exhibited an age‐related increase of total leucocyte count during the first 4 months of life, accompanied by a decrease in neutrophil and increase in lymphocyte and eosinophil counts. In mares and stallions, the total number of leucocytes, lymphocytes, monocytes and basophils significantly decreased but the number of neutrophils and eosinophils remained almost unchanged with age gain.
In vitro antimicrobial activity of olive leaves. Antimikrobielle Wirksamkeit von Olivenblättern in vitro
Authors: Markin D. , Duek L. , Berdicevsky I. 
Published: December 2004

SummaryWe investigated the antimicrobial effect of olive leaves against bacteria and fungi. The microorganisms tested were inoculated in various concentrations of olive leaf water extract. Olive leaf 0.6% (w/v) water extract killed almost all bacteria tested, within 3 h. Dermatophytes were inhibited by 1.25% (w/v) plant extract following a 3‐day exposure whereas Candida albicans was killed following a 24 h incubation in the presence of 15% (w/v) plant extract. Olive leaf extract fractions, obtained by dialysis, that showed antimicrobial activity consisted of particles smaller than 1000 molecular rate cutoffs. Scanning electron microscopic observations of C. albicans, exposed to 40% (w/v) olive leaf extract, showed invaginated and amorphous cells. Escherichia coli cells, subjected to a similar treatment but exposed to only 0.6% (w/v) olive leaf extract showed complete destruction. These findings suggest an antimicrobial potential for olive leaves.
Pharmacokinetic investigation of oral itraconazole in stratum corneum level of tinea pedis
Authors: Morimoto K , Tanuma H , Kikuchi I , Kusunoki T , Kawana S 
Published: December 2004

SummaryIn the present study, the authors administered 100 mg itraconazole (ITCZ) twice daily for a period of 1 week to six patients with hyperkeratotic type tinea pedis, and examined its efficacy, safety profile, and usefulness. ITCZ concentration in stratum corneum was also measured to examine the mobility of the drug into the affected site of planta pedis. ITCZ concentration in the stratum corneum of the affected part was first detected at 1 week after the completion of administration, gradually increased over time, and peaked at 3 weeks, with the sum of ITCZ and hydroxyitraconazole (OH‐ITCZ) amounting to 163.7 ng g−1 on a average. It then gradually decreased to a total sum of 10.3 ng g−1 on average at 8 weeks following the completion of administration. When compared with the geometric mean minimum inhibitory concentration (MIC) of ITCZ against fresh clinical isolates of dermatophytes (Trichophyton rubrum) (0.06 μg ml−1), the stratum corneum ITCZ concentration in this study was 2.1‐fold of the geometric mean MIC at 2 weeks following the completion of administration, and 2.4‐fold at 4 weeks. Although ITCZ does not produce therapeutic effectiveness (fungistasis) during the period of administration, it starts appearing at 2 weeks after the completion of administration, and after it peaks out at 3–4 weeks, clinical symptoms started improving. These results suggest that satisfying effects can be achieved in a short‐term oral ITCZ at a dose of 100 mg twice daily for a period of 1 week in cases of hyperkeratotic type tinea pedis.
Diarrhea associated with lansoprazole
Authors: MUKHERJEE SANDEEP 
Published: December 2004

Abstract  Lansoprazole is a proton pump inhibitor widely prescribed for gastroesophageal reflux and benign peptic ulcer disease. According to the manufacturer's package insert (TAP Pharmaceuticals, Lake Forest, IL, USA), the most common side‐effects are diarrhea, headache and abdominal pain, which occur in approximately 3% of patients and are reversible with drug discontinuation. An unusual case of microscopic colitis is reported in a previously asymptomatic patient who developed new‐onset diarrhea after initiation of lansoprazole. The case is reviewed and possible mechanisms of diarrhea secondary to proton pump inhibitors are discussed.© 2003 Blackwell Publishing Asia Pty Ltd