bluuebunny/crossref_metadata_2025 huggingface dataset:
Horizontal Transfer of the High-Pathogenicity Island ofYersinia pseudotuberculosis
Authors: Lesic Biliana , Carniel Elisabeth
Published: May 2005

The horizontal transfer of genetic elements plays a major role in bacterial evolution. The high-pathogenicity island (HPI), which codes for an iron uptake system, is present and highly conserved in variousEnterobacteriaceae, suggesting its recent acquisition by lateral gene transfer. The aim of this work was to determine whether the HPI has kept its ability to be transmitted horizontally. We demonstrate here that the HPI is indeed transferable from a donor to a recipientYersinia pseudotuberculosisstrain. This transfer was observable only when the donor and recipient bacteria were cocultured at low temperatures in a liquid medium. When optimized conditions were used (bacteria actively growing in an iron-deprived medium at 4°C), the frequency of HPI transfer reached ∼10−8. The island was transferable to various serotype I strains ofY. pseudotuberculosisand toYersinia pestis, but not toY. pseudotuberculosisstrains of serotypes II and IV or toYersinia enterocolitica. Upon transfer, the HPI was inserted almost systematically into theasn3tRNA locus. Acquisition of the HPI resulted in the loss of the resident island, suggesting an incompatibility between two copies of the HPI within the same strain. Transfer of the island did not require a functional HPI-borne insertion-excision machinery and was RecA dependent in the recipient but not the donor strain, suggesting that integration of the island into the recipient chromosome occurs via a mechanism of homologous recombination. This lateral transfer also involved the HPI-adjacent sequences, leading to the mobilization of a chromosomal region at least 46 kb in size.
Defective O-Antigen Polymerization intolAandpalMutants ofEscherichia coliin Response to Extracytoplasmic Stress
Authors: Vinés Enrique D. , Marolda Cristina L. , Balachandran Aran , Valvano Miguel A.
Published: May 2005

We have previously shown that the TolA protein is required for the correct surface expression of theEscherichia coliO7 antigen lipopolysaccharide (LPS). In this work, ΔtolAand Δpalmutants ofE. coliK-12 W3110 were transformed with pMF19 (encoding a rhamnosyltransferase that reconstitutes the expression of O16-specific LPS), pWQ5 (encoding theKlebsiella pneumoniaeO1 LPS gene cluster), or pWQ802 (encoding the genes necessary for the synthesis ofSalmonella entericaO:54). Both ΔtolAand Δpalmutants exhibited reduced surface expression of O16 LPS as compared to parental W3110, but no significant differences were observed in the expression ofK. pneumoniaeO1 LPS andS. entericaO:54 LPS. Therefore, TolA and Pal are required for the correct surface expression of O antigens that are assembled in awzy(polymerase)-dependent manner (like those ofE. coliO7 and O16) but not for O antigens assembled bywzy-independent pathways (likeK. pneumoniaeO1 andS. entericaO:54). Furthermore, we show that the reduced surface expression of O16 LPS in ΔtolAand Δpalmutants was associated with a partial defect in O-antigen polymerization and it was corrected by complementation with intacttolAandpalgenes, respectively. Using derivatives of W3110ΔtolAand W3110ΔpalcontaininglacZreporter fusions tofkpAanddegP, we also demonstrate that the RpoE-mediated extracytoplasmic stress response is upregulated in these mutants. Moreover, an altered O16 polymerization was also detected under conditions that stimulate RpoE-mediated extracytoplasmic stress responses intol+andpal+genetic backgrounds. A Wzy derivative with an epitope tag at the C-terminal end of the protein was stable in all the mutants, ruling out stress-mediated proteolysis of Wzy. We conclude that the absence of TolA and Pal elicits a sustained extracytoplasmic stress response that in turn reduces O-antigen polymerization but does not affect the stability of the Wzy O-antigen polymerase.
In Vitro Characterization of theBacillus subtilisProtein Tyrosine Phosphatase YwqE
Authors: Mijakovic Ivan , Musumeci Lucia , Tautz Lutz , Petranovic Dina , Edwards Robert A. , Jensen Peter Ruhdal , Mustelin Tomas , Deutscher Josef , Bottini Nunzio
Published: May 2005

Both gram-negative and gram-positive bacteria possess protein tyrosine phosphatases (PTPs) with a catalytic Cys residue. In addition, many gram-positive bacteria have acquired a new family of PTPs, whose first characterized member was CpsB fromStreptococcus pneumoniae. Bacillus subtiliscontains one such CpsB-like PTP, YwqE, in addition to two class II Cys-based PTPs, YwlE and YfkJ. The substrates for both YwlE and YfkJ are presently unknown, while YwqE was shown to dephosphorylate two phosphotyrosine-containing proteins implicated in UDP-glucuronate biosynthesis, YwqD and YwqF. In this study, we characterize YwqE, compare the activities of the threeB. subtilisPTPs (YwqE, YwlE, and YfkJ), and demonstrate that the twoB. subtilisclass II PTPs do not dephosphorylate the physiological substrates of YwqE.
Identification of
cptA
, a PmrA-Regulated Locus Required for Phosphoethanolamine Modification of the
Salmonella enterica
Serovar Typhimurium Lipopolysaccharide Core
Authors: Tamayo R. , Choudhury B. , Septer A. , Merighi M. , Carlson R. , Gunn J. S.
Published: May 2005

In response to the in vivo environment, the
Salmonella enterica
serovar Typhimurium lipopolysaccharide (LPS) is modified. These modifications are controlled in part by the two-component regulatory system PmrA-PmrB, with the addition of 4-aminoarabinose (Ara4N) to the lipid A and phosphoethanolamine (pEtN) to the lipid A and core. Here we demonstrate that the PmrA-regulated STM4118 (
cptA
) gene is necessary for the addition of pEtN to the LPS core.
pmrC
, a PmrA-regulated gene necessary for the addition of pEtN to lipid A, did not affect core pEtN addition. Although imparting a similar surface charge modification as Ara4N, which greatly affects polymyxin B resistance and murine virulence, neither
pmrC
nor
cptA
plays a dramatic role in antimicrobial peptide resistance in vitro or virulence in the mouse model. Therefore, factors other than surface charge/electrostatic interaction contribute to resistance to antimicrobial peptides such as polymyxin B.
Mechanisms of Strand Replacement Synthesis for Plasmid DNA Transferred by Conjugation
Authors: Parker Christopher , Meyer Richard
Published: May 2005

A single strand of plasmid DNA is transferred during conjugation. We examined the mechanism of complementary strand synthesis in recipient cells following conjugative mobilization of derivatives of the IncQ plasmid R1162. A system for electroporation of donor cells, followed by immediate mating, was used to eliminate plasmid-specific replicative functions. Under these conditions,
Escherichia coli
recipients provided a robust mechanism for initiation of complementary strand synthesis on transferred DNA. In contrast, plasmid functions were important for efficient strand replacement in recipient cells of
Salmonella enterica
serovar Typhimurium. The mobilizing vector for R1162 transfer, the IncP1 plasmid R751, encodes a DNA primase with low specificity for initiation. This protein increased the frequency of transfer of R751 into
Salmonella
, but despite its low specificity, it was inactive on the R1162 derivatives. The R751 primase was slightly inhibitory for the transfer of both R751 and R1162 into
E. coli
. The results show that there is a chromosomally encoded mechanism for complementary strand synthesis of incoming transferred DNA in
E. coli
, while plasmid-specific mechanisms for this synthesis are important in
Salmonella
.
Role ofMycobacterium tuberculosisSer/Thr Kinase PknF: Implications in Glucose Transport and Cell Division
Authors: Deol Parampal , Vohra Reena , Saini Adesh Kumar , Singh Amit , Chandra Harish , Chopra Puneet , Das Taposh K. , Tyagi Anil K. , Singh Yogendra
Published: May 2005

Protein kinases have a diverse array of functions in bacterial physiology, with a distinct role in the regulation of development, stress responses, and pathogenicity.pknF, one of the 11 kinases ofMycobacterium tuberculosis, encodes an autophosphorylating, transmembrane serine/threonine protein kinase, which is absent in the fast-growing, nonpathogenicMycobacterium smegmatis. Herein, we investigate the physiological role of PknF using an antisense strategy withM. tuberculosisand expressing PknF and its kinase mutant (K41M) inM. smegmatis. Expression of PknF inM. smegmatisled to reduction in the growth rate and shortening and swelling of cells with constrictions. Interestingly, an antisense strain ofM. tuberculosisexpressing a low level of PknF displayed fast growth and a deformed cell morphology compared to the wild-type strain. Electron microscopy showed that most of the cells of the antisense strain were of a smaller size with an aberrant septum. Furthermore, nutrient transport analysis of these strains was conducted using3H-labeled and14C-labeled substrates. A significant increase in the uptake ofd-glucose but not of glycerol, leucine, or oleic acid was observed in the antisense strain compared to the wild-type strain. The results suggest that PknF plays a direct/indirect role in the regulation of glucose transport, cell growth, and septum formation inM. tuberculosis.
Piv Site-Specific Invertase Requires a DEDD Motif Analogous to the Catalytic Center of the RuvC Holliday Junction Resolvases
Authors: Buchner John M. , Robertson Anne E. , Poynter David J. , Denniston Shelby S. , Karls Anna C.
Published: May 2005

Piv, a unique prokaryotic site-specific DNA invertase, is related to transposases of the insertion elements from the IS
110
/IS
492
family and shows no similarity to the site-specific recombinases of the tyrosine- or serine-recombinase families. Piv tertiary structure is predicted to include the RNase H-like fold that typically encompasses the catalytic site of the recombinases or nucleases of the retroviral integrase superfamily, including transposases and RuvC-like Holliday junction resolvases. Analogous to the DDE and DEDD catalytic motifs of transposases and RuvC, respectively, four Piv acidic residues D9, E59, D101, and D104 appear to be positioned appropriately within the RNase H fold to coordinate two divalent metal cations. This suggests mechanistic similarity between site-specific inversion mediated by Piv and transposition or endonucleolytic reactions catalyzed by enzymes of the retroviral integrase superfamily. The role of the DEDD motif in Piv catalytic activity was addressed using Piv variants that are substituted individually or multiply at these acidic residues and assaying for in vivo inversion, intermolecular recombination, and DNA binding activities. The results indicate that all four residues of the DEDD motif are required for Piv catalytic activity. The DEDD residues are not essential for
inv
recombination site recognition and binding, but this acidic tetrad does appear to contribute to the stability of Piv-
inv
interactions. On the basis of these results, a working model for Piv-mediated inversion that includes resolution of a Holliday junction is presented.
The Iron-Regulated
iupABC
Operon Is Required for Saprophytic Growth of the Intracellular Pathogen
Rhodococcus equi
at Low Iron Concentrations
Authors: Miranda-CasoLuengo Raúl , Duffy Pamela S. , O'Connell Enda P. , Graham Brian J. , Mangan Michael W. , Prescott John F. , Meijer Wim G.
Published: May 2005

Rhodococcus equi
is a facultative intracellular pathogen which proliferates rapidly in both manure-enriched soil and alveolar macrophages. Although both environments are characterized by extremely low concentrations of free iron, very little is known regarding the strategies employed by
R. equi
to thrive under these conditions. This paper reports the characterization of an
R. equi
transposome mutant that fails to grow at low iron concentrations. The transposome was shown to be inserted into
iupA
, the first gene of the
iupABC
operon encoding an ABC transport system highly similar to siderophore uptake systems. Disruption of the
iupA
gene also resulted in a failure of
R. equi
to utilize heme and hemoglobin as a source of iron. Introduction of the
iupABC
operon in
trans
restored the wild-type phenotype of the mutant strain.
iupABC
transcripts were 180-fold more abundant in
R. equi
grown in iron-depleted medium than in organisms grown in iron-replete medium. Proliferation of the
iupABC
mutant strain in macrophages was comparable to that of the wild-type strain. Furthermore, the
iupABC
mutant was not attenuated in mice, showing that the
iupABC
operon is not required for virulence.
The
repA
Gene of the Linear
Yersinia enterocolitica
Prophage PY54 Functions as a Circular Minimal Replicon in
Escherichia coli
Authors: Ziegelin Günter , Tegtmeyer Nicole , Lurz Rudi , Hertwig Stefan , Hammerl Jens , Appel Bernd , Lanka Erich
Published: May 2005

The
Yersinia enterocolitica
prophage PY54 replicates as a linear DNA molecule with covalently closed ends. For replication of a circular PY54 minimal replicon that has been derived from a linear minireplicon, two phage-encoded loci are essential in
Escherichia coli
: (i) the reading frame of the replication initiation gene
repA
and (ii) its 212-bp origin located within the 3′ portion of
repA
. The RepA protein acts in
trans
on the origin since we have physically separated the PY54 origin and
repA
onto a two-plasmid origin test system. For this
trans
action, the
repA
3′ end carrying the origin is dispensable. Mutagenesis by alanine scan demonstrated that the motifs for primase and for nucleotide binding present in the protein are essential for RepA activity. The replication initiation functions of RepA are replicon specific. The replication initiation proteins DnaA, DnaG, and DnaB of the host are unable to promote origin replication in the presence of mutant RepA proteins that carry single residue exchanges in these motifs. The proposed origins of the known related hairpin prophages PY54, N15, and PKO2 are all located toward the 3′ end of the corresponding
repA
genes, where several structure elements are conserved. Origin function depends on the integrity of these elements.
Operation of the CO Dehydrogenase/Acetyl Coenzyme A Pathway in both Acetate Oxidation and Acetate Formation by the Syntrophically Acetate-Oxidizing Bacterium
Thermacetogenium phaeum
Authors: Hattori Satoshi , Galushko Alexander S. , Kamagata Yoichi , Schink Bernhard
Published: May 2005

Thermacetogenium phaeum
is a homoacetogenic bacterium that can grow on various substrates, such as pyruvate, methanol, or H
2
/CO
2
. It can also grow on acetate if cocultured with the hydrogen-consuming methanogenic partner
Methanothermobacter thermautotrophicus
. Enzyme activities of the CO dehydrogenase/acetyl coenzyme A (CoA) pathway (CO dehydrogenase, formate dehydrogenase, formyl tetrahydrofolate synthase, methylene tetrahydrofolate dehydrogenase) were detected in cell extracts of pure cultures and of syntrophic cocultures. Mixed cell suspensions of
T. phaeum
and
M. thermautotrophicus
oxidized acetate rapidly and produced acetate after addition of H
2
/CO
2
after a short time lag. CO dehydrogenase activity staining after native polyacrylamide gel electrophoresis exhibited three oxygen-labile bands which were identical in pure culture and coculture. Protein profiles of
T. phaeum
cells after sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that the strain exhibited basically the same protein patterns in both pure and syntrophic culture. These results indicate that
T. phaeum
operates the CO dehydrogenase/acetyl-CoA pathway reversibly both in acetate oxidation and in reductive acetogenesis by using the same biochemical apparatus, although it has to couple this pathway to ATP synthesis in different ways.
Biofilm Formation and Sloughing inSerratia marcescensAre Controlled by Quorum Sensing and Nutrient Cues
Authors: Rice S. A. , Koh K. S. , Queck S. Y. , Labbate M. , Lam K. W. , Kjelleberg S.
Published: May 2005

We describe here a role for quorum sensing in the detachment, or sloughing, ofSerratia marcescensfilamentous biofilms, and we show that nutrient conditions affect the biofilm morphotype. Under reduced carbon or nitrogen conditions,S. marcescensformed a classical biofilm consisting of microcolonies. The filamentous biofilm could be converted to a microcolony-type biofilm by switching the medium after establishment of the biofilm. Similarly, when initially grown as a microcolony biofilm,S. marcescenscould be converted back to a filamentous biofilm by increasing the nutrient composition. Under high-nutrient conditions, anN-acyl homoserine lactone quorum-sensing mutant formed biofilms that were indistinguishable from the wild-type biofilms. Similarly, other quorum-sensing-dependent behaviors, such as swarming motility, could be rendered quorum sensing independent by manipulating the growth medium. Quorum sensing was also found to be involved in the sloughing of the filamentous biofilm. The biofilm formed by the bacterium consistently sloughed from the substratum after approximately 75 to 80 h of development. The quorum-sensing mutant, when supplemented with exogenous signal, formed a wild-type filamentous biofilm and sloughed at the same time as the wild type, and this was independent of surfactant production. When we removed the signal from the quorum-sensing mutant prior to the time of sloughing, the biofilm did not undergo significant detachment. Together, the data suggest that biofilm formation byS. marcescensis a dynamic process that is controlled by both nutrient cues and the quorum-sensing system.
Solution Structure of the Carbon Storage Regulator Protein CsrA from
Escherichia coli
Authors: Gutiérrez Pablo , Li Yan , Osborne Michael J. , Pomerantseva Ekaterina , Liu Qian , Gehring Kalle
Published: May 2005

The carbon storage regulator A (CsrA) is a protein responsible for the repression of a variety of stationary-phase genes in bacteria. In this work, we describe the nuclear magnetic resonance (NMR)-based structure of the CsrA dimer and its RNA-binding properties. CsrA is a dimer of two identical subunits, each composed of five strands, a small α-helix and a flexible C terminus. NMR titration experiments suggest that the β1-β2 and β3-β4 loops and the C-terminal helix are important elements in RNA binding. Even though the β3-β4 loop contains a highly conserved RNA-binding motif, GxxG, typical of KH domains, our structure excludes CsrA from being a member of this protein family, as previously suggested. A mechanism for the recognition of mRNAs downregulated by CsrA is proposed.
Genetic Dissection of the Sporulation Protein SpoIIE and Its Role in Asymmetric Division inBacillus subtilis
Authors: Carniol Karen , Ben-Yehuda Sigal , King Nicole , Losick Richard
Published: May 2005

SpoIIE is a dual-function protein inBacillus subtilisthat contributes to the switch from medial to polar cell division during sporulation and is responsible for activating the cell-specific transcription factor σF. SpoIIE consists of an N-terminal domain with 10 membrane-spanning segments (region I), a C-terminal phosphatase domain (region III), and a central domain (region II) of uncertain function. To investigate the role of SpoIIE in polar division, we took advantage of a system for efficiently producing polar septa during growth in a SpoIIE-dependent manner using cells engineered to produce the sporulation protein in response to an inducer. The results show that regions II and III play a critical role in polar septum formation and that specific amino acid substitutions in those regions affect the abilities of SpoIIE both to promote polar division and to localize to the division machinery. Additionally, we show that neither the phosphatase function of SpoIIE nor the N-terminal, membrane-spanning region is needed for the switch to asymmetric division.
The Linear Double-Stranded DNA of Phage Bam35 Enters Lysogenic Host Cells, but the Late Phage Functions Are Suppressed
Authors: Gaidelytė Aušra , Jaatinen Silja T. , Daugelavičius Rimantas , Bamford Jaana K. H. , Bamford Dennis H.
Published: May 2005

Bam35, a temperate double-stranded DNA bacteriophage with a 15-kb linear genome, infects gram-positive
Bacillus thuringiensis
cells. Bam35 morphology and genome organization resemble those of PRD1, a lytic phage infecting gram-negative bacteria. Bam35 and PRD1 have an outer protein coat surrounding a membrane that encloses the viral DNA. We used electrochemical methods to investigate physiological changes of the lysogenic and nonlysogenic hosts during Bam35 DNA entry and host cell lysis. During viral DNA entry, there was an early temporal decrease of membrane voltage associated with K
+
efflux that took place when either lysogenic or nonlysogenic hosts were infected. Approximately 40 min postinfection, a second strong K
+
efflux was registered that was proposed to be associated with the insertion of holin molecules into the plasma membrane. This phenomenon occurred only when nonlysogenic cells were infected. Lysogenic hosts rarely were observed entering the lytic cycle as demonstrated by thin-section electron microscopy.
Gyrase Inhibitors and Thymine Starvation Disrupt the Normal Pattern of Plasmid RK2 Localization in
Escherichia coli
Authors: Johnson Erik P. , Yao Shiyin , Helinski Donald R.
Published: May 2005

Multicopy plasmids in
Escherichia coli
are not randomly distributed throughout the cell but exist as defined clusters that are localized at the mid-cell, or at the 1/4 and 3/4 cell length positions. To explore the factors that contribute to plasmid clustering and localization,
E. coli
cells carrying a plasmid RK2 derivative that can be tagged with a green fluorescent protein-LacI fusion protein were subjected to various conditions that interfere with plasmid superhelicity and/or DNA replication. The various treatments included thymine starvation and the addition of the gyrase inhibitors nalidixic acid and novobiocin. In each case, localization of plasmid clusters at the preferred positions was disrupted but the plasmids remained in clusters, suggesting that normal plasmid superhelicity and DNA synthesis in elongating cells are not required for the clustering of individual plasmid molecules. It was also observed that the inhibition of DNA replication by these treatments produced filaments in which the plasmid clusters were confined to one or two nucleoid bodies, which were located near the midline of the filament and were not evenly spaced throughout the filament, as is found in cells treated with cephalexin. Finally, the enhanced yellow fluorescent protein-RarA fusion protein was used to localize the replication complex in individual
E. coli
cells. Novobiocin and nalidixic acid treatment both resulted in rapid loss of RarA foci. Under these conditions the RK2 plasmid clusters were not disassembled, suggesting that a completely intact replication complex is not required for plasmid clustering.
Severity of the Streptomycin Resistance and Streptomycin Dependence Phenotypes of Ribosomal Protein S12 of
Thermus thermophilus
Depends on the Identity of Highly Conserved Amino Acid Residues
Authors: Carr Jennifer F. , Gregory Steven T. , Dahlberg Albert E.
Published: May 2005

The structural basis for the streptomycin dependence phenotype of ribosomal protein S12 mutants is poorly understood. Here we describe the application of site-directed mutagenesis and gene replacement of
Thermus thermophilus rpsL
to assess the importance of side chain identity and tertiary interactions as phenotypic determinants of drug-dependent mutants.
Virulence and the Environment: a Novel Role for
Vibrio cholerae
Toxin-Coregulated Pili in Biofilm Formation on Chitin
Authors: Reguera Gemma , Kolter Roberto
Published: May 2005

The toxin-coregulated pilus (TCP) of
Vibrio cholerae
is required for intestinal colonization and cholera toxin acquisition. Here we report that TCP mediates bacterial interactions required for biofilm differentiation on chitinaceous surfaces. We also show that undifferentiated TCP
−
biofilms have reduced ecological fitness and, thus, that chitin colonization may represent an ecological setting outside the host in which selection for a host colonization factor may take place.
TheSalmonellaTranslocated Effector SopA Is Targeted to the Mitochondria of Infected Cells
Authors: Layton Abigail N. , Brown Philip J. , Galyov Edouard E.
Published: May 2005

This study investigates theSalmonellaeffector protein SopA. We show that inSalmonella entericaserovar Dublin-infected cells, SopA1-347fused to two carboxy-terminal hemagglutinin tags partially colocalized with mitochondria. Transfection of eukaryotic cells with a panel of constructs encoding truncated versions of SopA identified that amino acids 100 to 347 were sufficient to target SopA to the mitochondria.
Purification and Properties of the
Klebsiella aerogenes
UreE Metal-Binding Domain, a Functional Metallochaperone of Urease
Authors: Mulrooney Scott B. , Ward Sarah K. , Hausinger Robert P.
Published: May 2005

Klebsiella aerogenes
UreE, a metallochaperone that delivers nickel ions during urease activation, consists of distinct “peptide-binding” and “metal-binding” domains and a His-rich C terminus. Deletion analyses revealed that the metal-binding domain alone is sufficient to facilitate urease activation. This domain was purified and shown to exhibit metal-binding properties similar to those of UreE lacking only the His-rich tail.
An Adenylyl Cyclase, CyaB, Acts as an Osmosensor in
Myxococcus xanthus
Authors: Kimura Yoshio , Ohtani Mika , Takegawa Kaoru
Published: May 2005

We have previously reported that a receptor-type adenylyl cyclase (CyaA) of
Myxococcus xanthus
undergoes an osmosensor mainly during spore germination (Y. Kimura et al., J. Bacteriol. 184:3578-3585, 2002). In the present study, we cloned another receptor-type adenylyl cyclase gene (
cyaB
) and characterized the function of the
cyaB
-encoded protein. Disruption of
cyaB
generates a mutant that showed growth retardation at high ionic (NaCl) or high nonionic (sucrose) osmolarity. When vegetative cells were stimulated with 0.15 M NaCl, the increases in intracellular cyclic AMP levels of
cyaB
mutant cells were lower than those of wild-type cells. Under nonionic osmostress, the
cyaB
mutant exhibited reduced spore germination; however, the germination rate of the
cyaB
mutant was significantly higher than that of the
cyaA
mutant.
Localization of Chaperones DnaK and GroEL in Bacterial Inclusion Bodies
Authors: Carrió M. Mar , Villaverde Antonio
Published: May 2005

By immunostaining and transmission electron microscopy, chaperones DnaK and GroEL have been identified at the solvent-exposed surface of bacterial inclusion bodies and entrapped within these aggregates, respectively. Functional implications of this distinct localization are discussed in the context of
Escherichia coli
protein quality control.
Expression of granulocyte colony stimulating factor receptor in human colorectal cancer
Authors: Yang X , Liu F , Xu Z , Chen C , Wu X , Li G , Li J
Published: May 2005

Aims

To discover if human colorectal cancer expresses granulocyte colony stimulating factor receptor (G-CSFR) and if granulocyte colony stimulating factor (G-CSF) plays an important part in the development and progression of human colorectal cancer.

Methods

Forty two specimens of colorectal cancer and normal colorectal mucosa were investigated, taken from the colon or rectum in group of colorectal cancer patients. Immunohistochemistry and reverse transcription polymerase chain reaction (RT-PCR) technique were used to show G-CSFR expression. The relation between expression of G-CSFR and clinical or pathological factors was analysed.

Results

Immucohistochemical analyses showed that G-CSFR was expressed in the human colorectal cancer (25 of 42, 59.52%) and seemed to be up-regulated compared with the normal mucosa (14 of 42, 33.33%, p<0.001). In pronounced contrast with mostly strongly positive tumours, corresponding normal colorectal mucosa was negative or weakly positive. A significant correlation was found between G-CSFR expression and tumour stage (p = 0.001), tumour differentiation (p<0.001), but there was no significant relation between the expression of G-CSFR and the age, sex, and tumour size (p = 0.346, p = 0.686, p = 0.459). In RT-PCR, 21 of all 42 tumours had G-CSFR mRNA expression, while only 11 of 42 normal colorectal mucosa had such expression.

Conclusions

These data show that G-CSFR is commonly expressed in human colorectal cancers, thus supporting a possible role for G-CSF in colorectal cancer physiology.
Epistaxis: an update on current management
Authors: Pope L E R , Hobbs C G L
Published: May 2005

Epistaxis is one of the commonest ENT emergencies. Although most patients can be treated within an accident and emergency setting, some are complex and may require specialist intervention. There are multiple risk factors for the development of epistaxis and it can affect any age group, but it is the elderly population with their associated morbidity who often require more intensive treatment and subsequent admission. Treatment strategies have been broadly similar for decades. However, with the evolution of endoscopic technology, new ways of actively managing epistaxis are now available. Recent evidence suggests that this, combined with the use of stepwise management plans, should limit patient complications and the need for admission. This review discusses the various treatment options and integrates the traditional methods with modern techniques.
Do consultants differ? Inferences drawn from hospital in-patient enquiry (HIPE) discharge coding at an Irish teaching hospital
Authors: Moloney E D , Smith D , Bennett K , O’Riordan D , Silke B
Published: May 2005

Objective

To find out if there was a difference between hospital consultants, all trained in acute general medicine, in length of stay (LOS), re-admission rates, resource utilisation, and diagnostic coding, among patients admitted as emergencies to St James’ Hospital (SJH) Dublin.

Methods

A retrospective analysis was performed of data on discharges from hospital, recorded in the hospital in-patient enquiry (HIPE) system, relating to 9204 episodes among 6968 emergency medical patients admitted to SJH between 1 January 2002 and 31 October 2003. For comparative analysis, four physician groups were defined consisting of gastroenterology (GI, n = 4), respiratory (n = 3), general internal medicine (GIM, n = 2), or specialty (n = 5).

Results

GIM consultants had the shortest LOS (median 5 days); GIM and respiratory consultants were less likely to have long stay patients (> 30 days, p<0.0001). Patients re-admitted under the same consultant had a longer LOS than those re-admitted under a different consultant (p<0.0001). Endoscopy and GI radiology investigations were used most by GI consultants, computed tomography of the thorax by respiratory, ECHO by respiratory and specialty, and computed tomography of brain by GIM and specialty consultants. GI diagnostic codings were more frequent with GI consultants (p<0.0001), respiratory diagnoses and malignancy with respiratory (p<0.0001 for both), diabetes and hypertension with specialty (p = 0.0017), and heart failure more with GIM consultants (p = 0.001).

Conclusions

This study found that the HIPE database was very powerful in predicting differences between hospital consultants in LOS, re-admission rates, resource utilisation, and disease coding. It would be of interest to examine the extent to which protocols and guidelines could reduce such variations.
Device based treatment of heart failure
Authors: Patwala A Y , Wright D J
Published: May 2005

As the population ages and survival from ischaemic heart disease improves, the incidence and prevalence of congestive cardiac failure has increased dramatically. Medical treatments including ACE inhibitors, β blockers, and aldosterone antagonists have improved the outlook for most patients. However, despite optimal medical treatment there is a significant group of patients who continue to suffer poor morbidity and mortality. Device based treatment consisting of implantable cardioverter defibrillators (ICD) and cardiac resynchronisation therapy (CRT) devices offer new modes of treatment to patients with symptomatic heart failure despite optimal medical therapy. ICDs have been shown to reduce mortality in patients with severe heart failure while CRT leads to an improvement in functional class, quality of life scores, physiological measures such as peak vo  2, and reduce hospitalisations. Combination devices, which provide both ICD and CRT functions, have now been seen to provide synergistic benefits in selected patients.
Multiple sclerosis: diagnosis and the management of acute relapses
Authors: Leary S M , Porter B , Thompson A J
Published: May 2005

Multiple sclerosis is an inflammatory demyelinating disease of the central nervous system that may result in a wide range of neurological symptoms and accumulating disability. Its course is unpredictable resulting in a changing pattern of clinical need. Diagnostic criteria for multiple sclerosis require objective evidence for dissemination in space and time. The diagnostic and management process should follow good practice guidelines with the person at the centre of the process. Appropriate support and information should be available from the time of diagnosis. Continuing education is key in enabling the person to actively participate in their management. In the event of an acute relapse the person should have direct access to the most appropriate local service. Provided medical causes have been excluded, corticosteroid treatment to hasten the recovery from the relapse should be considered. Management of an acute relapse should be comprehensive addressing any medical, functional, or psychosocial sequelae.
Host plant genetics affect hidden ecological players: links amongPopulus, condensed tannins, and fungal endophyte infection
Authors: Bailey Joseph K , Deckert Ron , Schweitzer Jennifer A , Rehill Brian J , Lindroth Richard L , Gehring Catherine , Whitham Thomas G
Published: May 2005

Recent studies have shown effects of host plant genetics on community and ecosystem processes, which makes understanding the impacts of genetically based traits on hidden or non-apparent organisms more important. Here we examined links among genetic variation in hybrid cottonwoods, plant phytochemistry, and twig fungal endophytes (i.e., a common hidden organism). We found three major patterns: (1) twig fungal endophyte infection was positively related to the introgression of Fremont cottonwood (Populus fremontii S. Wats.) RFLP genetic markers, (2) condensed tannin concentration in twig bark tissue was negatively correlated to the introgression of Fremont genetic markers, and (3) fungal endophyte infection was negatively related to condensed tannin concentration in twig bark. These data demonstrate that plant genotype can impact hidden ecological players (i.e., fungal endophytes) resulting in community and ecosystem consequences.Key words: ecological genetics, fungal endophytes, hidden players, hybridization, Populus, tannins.
Observations on new and rare species of freshwater diatoms from Cape Cod, Massachusetts, USA
Authors: Siver Peter A , Hamilton Paul B
Published: May 2005

The freshwater diatom flora of Cape Cod, Massachusetts, USA, was recently described using surface sediments from 56 largely glacial kettle lakes scattered over the narrow peninsula. During our examination we had the opportunity to study seven rare and interesting taxa with light (LM) and scanning electron microscopy (SEM). Two of these organisms, Neidium statuarium Hamilton & Siver sp.nov. and Stenopterobia pseudodelicatissima Siver & Hamilton sp.nov., are described as new species. Two new combinations, along with emended descriptions based on SEM, are provided for Nupela vitiosa (Schimanski) Siver & Hamilton comb.nov. and Tryblionella scalaris (Ehrenberg) Siver & Hamilton comb.nov. Morphological details of three additional and rare species, Neidium fasiatum Østrup, Neidium sp., and Tryblionella plana var. fennica (Hustedt) Simola are also provided. The relationships of each taxon to other similar species are discussed.Key words: Cape Cod, Neidium, new species, Nupela, Stenopterobia, Tryblionella.
Resource availability at the rosette stage and apical dominance in the strictly biennialErysimum strictum(Brassicaceae)
Authors: Piippo Sari , Huhta Ari-Pekka , Rautio Pasi , Tuomi Juha
Published: May 2005

In biennial plants, the age of flowering is constrained, but size at flowering is highly variable. This suggests that performance at the flowering stage depends largely on growth conditions at the rosette stage. We examined this possibility using Erysimum strictum P. Gaertn., B. Mey., and Scherb. (Brassicaceae), a strictly biennial herb, the reproductive output of which increases with increasing plant height and branch number. In a common garden experiment, we defoliated (50% of leaves removed twice) and fertilized (three times) individual plants at the rosette stage and studied their performance at the flowering stage in the following year. Rosette defoliation adversely affected all performance measures except seed number per fruit and seed weight. Fertilization did not alleviate these effects. Defoliation reduced seed set by 48% in fertilized plants and 29% in unfertilized plants. Fertilization stimulated branch production from the rosette base but did not significantly affect plant height. These observations suggest that, in the case of basally unbranched plants, apical dominance by the leading stalk suppresses the axillary meristems at the rosette base. Fertilization at the rosette stage can break this suppression. The induction for breakage presumably occurs before bolting since, in our earlier experiments, neither fertilization nor apical damage at the flowering stage stimulated branching from the base. Erysimum strictum is likely to be selected for fast vertical growth at the start of bolting, and hence plant height is a less plastic trait with respect to resource availability than branch number. Regression analysis suggested that, in response to rosette fertilization, small plants invest in height growth instead of branching, whereas large plants to a greater extent invest their supplemental resources in vigorous branching. Consequently, resource availability at the rosette stage influences apical dominance at the flowering stage. Unexpectedly, however, improved resource availability did not alleviate the cost of simulated rosette-stage herbivory.Key words: apical dominance, biennial, fitness, herbivory, resource availability, rosette stage.
Comparative analysis of axillary and floral meristem development
Authors: Grbić Vojislava
Published: May 2005

Axillary and floral meristems are shoot meristems that initiate postembryonically. In Arabidopsis, axillary meristems give rise to branches during vegetative development while floral meristems give rise to flowers during reproductive development. This review compares the development of these meristems from their initiation at the shoot apical meristem up to the establishment of their specific developmental fates. Axillary and floral meristems originate from lateral primordia that form at flanks of the shoot apical meristem. Initial development of vegetative and reproductive primordia are similar, resulting in the formation of a morphologically defined primordium partitioned into adaxial and abaxial domains. The adaxial primordial domain is competent to form a meristem, while the abaxial domain correlates with the formation of a leaf. This review proposes that all primordia partition into domains competent to form the meristem and the leaf. According to this model, a vegetative primordium develops as leaf-bias while a reproductive primordium develops as meristem-bias.Key words: SHOOTMERISTEMLESS, LATERAL SUPPRESSOR, AINTEGUMENTA, adaxial primordial domain, abaxial primordial domain, shoot morphogenesis.
Douglasdeweya: A new genus, with a new species and a new combination (Triticeae: Poaceae)
Authors: Yen C , Yang J L , Baum B R
Published: May 2005

The new genus Douglasdeweya C. Yen, J.L. Yang & B.R. Baum is based on results from cytogenetical and morphological findings  PPStSt genome  and is segregated from the genus Pseudoroegneria  StSt and StStStSt genome. Several characters, such as the erect spike with very finely spinulose pubescence along the two main angles of the rachis, and glumes and lemmas with a very strong midrib forming a keel-like structure distinguish Douglasdeweya from Pseudoroegneria, which has a rather lax spike, a rachis that is glabrous along the two main angles, and glumes and lemmas without a keel-like structure. The genus is named in memory of Dr. Douglas R. Dewey, an outstanding scientist who worked on the biosystematics of the perennial Triticeae. Two species are described, one of which is new, Douglasdeweya wangyii C. Yen, J.L. Yang & B. R. Baum and the other a new combination Douglasdeweya deweyi (K.B. Jensen, S.L. Hatch, & J.K. Wipff) C. Yen, J.L. Yang, & B.R. Baum. A key to the two species is provided, together with details on their taxonomy, nomenclature, distribution, and cytology.Key words: PPStSt genome, narrow endemic.
Effects of sodium fluoride on the mechanical activity in mouse gastric preparations
Authors: Amira Smain , Mulè Flavia
Published: May 2005

The aim of the present study was to investigate the responses induced by sodium fluoride (NaF) on gastric mechanical activity, using mouse whole-stomach preparations. The mechanical activity was recorded in vitro as changes of intraluminal pressure. In most of the preparations, NaF induced a tetrodotoxin-insensitive biphasic effect characterized by early relaxation followed by slowly developing contractile response. The contraction was dependent on the concentration of NaF, whereas the relaxation was observed at only 10–30 mmol/L NaF. The contractile effect was significantly reduced by nifedipine (an L-type Ca2+channel blocker), ryanodine or ruthenium red (inhibitors of Ca2+release from sarcoplasmic reticulum), and GF109203X (a protein kinase C inhibitor). Moreover, it was abolished by neomycin (an inhibitor of phospholipase C) and potentiated by SQ22536 (an inhibitor of adenylyl cyclase). All the drugs significantly increased the relaxation, except SQ22536, which abolished it. The present results suggest that NaF causes a complex mechanical response in the whole-stomach, which might explain gastric discomfort after fluoride ingestion. The relaxation appears owing to production of cAMP, while the contractile effects imply activation of phospholipase C, protein kinase C, influx of Ca2+, and release of Ca2+from ryanodine-sensitive intracellular store.Key words: gastric mechanical activity, mouse stomach, smooth muscle, sodium fluoride.
Increased incidence of hepatic insulin-sensitizing substance (HISS)-dependent insulin resistance in female rats prenatally exposed to ethanol
Authors: Sadri Parissa , Legare Dallas J , Takayama Shinichiro , Lautt W Wayne
Published: May 2005

Insulin causes the release of the hepatic insulin-sensitizing substance (HISS) from the liver. Hepatic parasympathetic nerves play a permissive role in the release of HISS. HISS-dependent insulin resistance (HDIR) occurs in the absence of HISS. Fetal ethanol exposure has been shown to cause dose-dependent HDIR in adult male rat offspring. Since female offspring are more severely affected by in utero ethanol toxicity, we hypothesized that fetal alcohol exposure causes higher incidence and more severe HDIR in adult female offspring. Adult female rat offspring prenatally exposed to different concentrations of ethanol (0%, 15%, and 20%) were tested for insulin sensitivity using the rapid insulin sensitivity test (RIST). The RIST index was significantly reduced in the 15% (134.1 ± 16.1 mg/kg) and the 20% (98.7 ± 9.7 mg/kg) group compared with the 0% (220.9 ± 27.6 mg/kg) group. Administration of atropine produced significant additional HDIR in the 15% group (82.9 ± 14.5 mg/kg) but not the 20% group (83.8 ± 20.5 mg/kg) indicating complete HDIR had been produced in this group, contrary to the adult male offspring in a previous study. The results are consistent with the hypothesis that adult-female offspring are more severely affected by in utero ethanol exposure compared with adult-male offspring.Key words: fetal, alcohol, insulin resistance, gender, HISS, teratology, diabetes.
Emerging issues in traditional Chinese medicine
Authors: Siow Yaw L , Gong Yuewen , Au-Yeung Kathy K.W , Woo Connie W.H , Choy Patrick C , O Karmin
Published: May 2005

Traditional Chinese medicine (TCM) has many beneficial effects and has been practiced for several thousand years. It is known to treat the cause of a disease rather than to alleviate its symptoms. Based on a belief that TCM is natural, safe, and of lower cost, consumers worldwide are spending more out-of-pocket money on this form of therapy. This increased spending, and reports of adverse reactions, has drawn the attention of many regulatory agencies. Scientists have called for more evidence-based and scientific research on the risks and benefits of TCM. In Canada, the Natural Health Product Regulations came into effect January 2004. TCM herbal product manufacturers will need to provide products of reputable quality to the market. Many will apply modern technology and good science to support their products. The issues facing producers, scientists, and consumers alike are quality control and assessment, standardization of bioactive components, mechanisms of actions, and integration of the evolved modern Chinese medicine into the healthcare system. Solid science, better regulation of the final product, and better education of consumers are necessary to extract the best of TCM to complement existing conventional medicine to deliver the best healthcare.Key words: bioactive components, chromatographic fingerprinting, integration, mechanisms, Natural Health Product (NHP) Regulations, standardization, traditional Chinese medicine.
DEFORMED DIMENSIONAL REGULARIZATION FOR ODD (AND EVEN) DIMENSIONAL THEORIES
Authors: ANSELMI DAMIANO
Published: May 2005

A deformation of the dimensional-regularization technique that is useful for theories where the common dimensional regularization does not apply is formulated. The Dirac algebra is not dimensionally continued, to avoid inconsistencies with the trace of an odd product of gamma matrices in odd dimensions. The regularization is completed with an evanescent higher-derivative deformation, which proves to be efficient in practical computations. This technique is particularly convenient in three dimensions for Chern–Simons gauge fields, two-component fermions and four-fermion models in the large N limit, eventually coupled with quantum gravity. Differently from even dimensions, in odd dimensions it is not always possible to have propagators with fully Lorentz invariant denominators. The main features of the deformed technique are illustrated in a set of sample calculations. The regularization is universal, local, manifestly gauge-invariant and Lorentz invariant in the physical sector of space–time. In flat space power-like divergences are set to zero by default. Infinitely many evanescent operators are automatically dropped.
TWO COUPLED HARMONIC OSCILLATORS ON NONCOMMUTATIVE PLANE
Authors: JELLAL AHMED , SCHREIBER MICHAEL , EL KINANI EL HASSAN
Published: May 2005

We investigate a system of two coupled harmonic oscillators on the noncommutative plane [Formula: see text] by requiring that the spatial coordinates do not commute. We show that the system can be diagonalized by a suitable transformation, i.e. a rotation with a mixing angle α. The obtained eigenstates as well as the eigenvalues depend on the noncommutativity parameter θ. Focusing on the ground state wave function before the transformation, we calculate the density matrix ρ0(θ) and find that its traces Tr (ρ0(θ)) and [Formula: see text] are not affected by the noncommutativity. Evaluating the Wigner function on [Formula: see text] confirms this. The uncertainty relation is explicitly determined and found to depend on θ. For small values of θ, the relation is shifted by a θ2 term, which can be interpreted as a noncommutativity correction. The calculated entropy does not change with respect to the normal case. We consider the limits α = 0 and α = π/2. In the first case, by identifying θ to the squared magnetic length, one can recover basic features of the Hall system.