bluuebunny/crossref_metadata_2025 huggingface dataset:
The mesolimbic dopaminergic response to novel palatable food consumption increases dopamine‐D1 receptor‐mediated signalling with complex modifications of the DARPP‐32 phosphorylation pattern
Authors: Rauggi Riccardo , Scheggi Simona , Cassanelli Anna , De Montis Maria Graziella , Tagliamonte Alessandro , Gambarana Carla
Published: February 2005

Acute cocaine administration increases extraneuronal dopamine and Thr34 phosphorylation of dopamine‐ and cAMP‐regulated phosphoprotein (Mr 32 kDa; DARPP‐32) in striatal and cortical areas. Novel palatable food consumption increases extraneuronal dopamine in the same areas. We examined the DARPP‐32 phosphorylation pattern in food non‐deprived rats at different times after vanilla sugar consumption. The phosphorylation state of DARPP‐32 and two cAMP‐dependent protein kinase (PKA) substrates, GluR1 and NR1, were detected by immunoblotting. Thirty to 45 min after vanilla sugar consumption, phospho‐Thr34 DARPP‐32, GluR1 and NR1 levels increased in the nucleus accumbens, and phospho‐Thr75 DARPP‐32 levels decreased. At 60 min, all parameters returned to baseline values. However, 2 and 3 h after vanilla sugar consumption, phospho‐Thr34 DARPP‐32 levels decreased, while phospho‐Thr75 DARPP‐32 levels increased. In contrast to the pattern observed in the NAcS, no delayed changes in DARPP‐32 phosphorylation were observed in the mPFC. Both early and delayed DARPP‐32, GluR1 and NR1 phosphorylation changes were prevented by a dopamine D1 receptor antagonist administration. The delayed modifications in nucleus accumbens DARPP‐32 phosphorylation were prevented by an mGluR5 antagonist administration. The mesolimbic dopaminergic response to an unfamiliar taste is correlated to a gustatory memory trace development, and the observed changes in DARPP‐32 phosphorylation may be part of this process.
Tech: a RhoA GEF selectively expressed in hippocampal and cortical neurons
Authors: Marx Ruth , Henderson Jennifer , Wang James , Baraban Jay M.
Published: February 2005

Recent studies implicating the Rho family of small G proteins in the regulation of neuronal morphology have focused attention on identifying key components of Rho signaling pathways in neurons. To this end, we have conducted studies aimed at defining the localization and function of Tech, a Rho guanine nucleotide exchange factor (GEF) family member that is highly enriched in brain. We have found that Tech is selectively expressed in cortical and hippocampal neurons with prominent Tech immunostaining apparent in the cell bodies and dendrites of these cells. In vitro studies with prototypical members of the major Rho subfamilies, RhoA, Rac1 and Cdc42, indicate that Tech binds selectively to and activates RhoA. To assess whether Tech may be involved in the regulation of neuronal morphology, we examined the effects of Tech constructs on the morphology of cortical neurons grown in primary culture. We found that a constitutively active Tech construct, Tech 245ΔC, decreases the number of dendritic processes present on these neurons. This reduction appears to be mediated by activation of RhoA as it is blocked by insertion of a point mutation into the DH domain of Tech which blocks its ability to activate RhoA or coexpression of a dominant negative RhoA construct. As Tech protein levels increase during post‐natal development and remain at peak levels into adulthood, these results indicate that Tech regulates RhoA signaling pathways in developing and mature forebrain neurons.
Neurofilament‐light increases the cell surface expression of the N‐methyl‐d‐aspartate receptor and prevents its ubiquitination
Authors: Ratnam Joseline , Teichberg Vivian I.
Published: February 2005

NMDA (N‐methyl‐d‐aspartate) subtype of glutamate receptors are core components of dendritic spine postsynaptic densities (PSDs), in which they are anchored via their carboxy‐terminal tails to cytoskeletal proteins. In this study, we examined the role of the neuronal intermediate filament protein, neurofilament‐light (NF‐L), also a component of the PSD, in the regulation of NMDA receptor (NMDAR) expression and function in a heterologous system. Coexpression of NF‐L with NR1 or NR2B subunits of the NMDAR in HEK293 (human embryonic kidney 293) cells did not result in surface expression as measured by surface biotinylation and cell ELISAs, whereas the combined expression of the three elements resulted in a 20% increase in the surface abundance of NR1, along with a concomitant increase in NMDAR‐mediated cytotoxicity. Investigating the origin of this increase, we found that the NR1 subunits are ubiquitinated in HEK293 cells, and that the coexpression of NF‐L antagonizes this process. These results suggest a possible means of stabilization of NR1 via its association with NF‐L.
Enhancement of glutamate uptake mediates the neuroprotection exerted by activating group II or III metabotropic glutamate receptors on astrocytes
Authors: Yao Hong‐Hong , Ding Jian‐Hua , Zhou Fang , Wang Fang , Hu Li‐Fang , Sun Tao , Hu Gang
Published: February 2005

We investigated whether the activation of astroglial group II and III metabotropic glutamate receptors (mGluRs) could exert neuroprotective effects and whether the neuroprotection was related to glutamate uptake. Our results showed that the activation of astroglial group II or III mGluRs exerted neuroprotection against 1‐methyl‐4‐phenylpyridinium (MPP+) astroglial conditioned medium‐induced neurotoxicity in midbrain neuron cultures. Furthermore, MPP+ decreased glutamate uptake of primary astrocytes and C6 glioma cells, which was recovered by activating group II or III mGluRs. Specific group II or III mGluRs antagonists completely abolished the neuroprotective effects and the enhancement of glutamate uptake of their respective agonists. Our results showed that the primary cultured rat astrocytes and C6 glioma cells expressed receptor proteins for group II mGluR2/3, group III mGluR4, mGluR6 and mGluR7. C6 glioma cells expressed mRNA for group II mGluR3, group III mGluR4, mGluR6, mGluR7 and mGluR8. In conclusion, we confirmed that the activation of astroglial mGluRs exerted neuroprotection, and demonstrated that the mechanism underlying this protective role was at least partially related to the enhancement of glutamate uptake.
Activation of c‐fos by lipopolysaccharide in glial cells via p38 mitogen‐activated protein kinase‐dependent activation of serum or cyclic AMP/calcium response element
Authors: Simi Anastasia , Edling Ylva , Ingelman‐Sundberg Magnus , Tindberg Niclas
Published: February 2005

Pathological conditions such as ischaemic stroke and inflammatory disorders cause c‐fos activation in the brain. This activation contributes to the initiation of the brain's inflammatory response, orchestrated by activated glial cells. The inflammatory signalling cascades leading to c‐fos activation in glial cells are not well characterized. Thus, we have attempted a detailed analysis of the cis‐acting elements, transcription factors and upstream kinase pathways involved in the activation of c‐fos by lipopolysaccharide (LPS) in primary rat cortical glial cells. We found that (1) LPS‐induced c‐fos mRNA levels were sensitive to p38 mitogen‐activated protein kinase (MAPK) inhibitors but not to mitogen‐activated/extracellular signal‐regulated kinase (ERK) or calcium–calmodulin‐dependent kinase inhibitors, (2) LPS activated both serum response element (SRE) and cyclic AMP/calcium response element (CRE)‐driven luciferase reporters in transient transfection assays, (3) LPS induced the phosphorylation of Elk1 CRE‐binding protein (CREB)/activated transcription factor‐1 (ATF‐1) and the activation of GAL4‐Elk1 and GAL4‐CREB chimeric proteins, and (4) mutation of both SRE and CRE elements was necessary and sufficient to completely abolish LPS induction of a rat c‐fos proximal promoter‐luciferase reporter. Thus, c‐fos activation by LPS in glial cells occurs via the SRE or CRE in an independent manner, and involves the Elk1 or CREB/ATF‐1 transcription factors. Elk1‐mediated transactivation was dependent on p38 MAPK, suggesting a crucial role of these factors in mediating inflammatory responses in the CNS.
Dolichol is the major lipid component of human substantia nigra neuromelanin
Authors: Fedorow Heidi , Pickford Russell , Hook James M. , Double Kay L. , Halliday Glenda M. , Gerlach Manfred , Riederer Peter , Garner Brett
Published: February 2005

Neuromelanin is a dark brown pigment present at high concentrations in dopaminergic neurones of the human substantia nigra (SN). Early electron microscopic examinations of neuromelanin fine structure revealed a significant neutral lipid component; however, the identity of this lipid has remained unknown. Here we show that the lipid component of neuromelanin pigment derived from human SN is the polyisoprenoid dolichol. Established methods were used to isolate the pigment from the SN of 32 brains and the lipid fraction was recovered in high purity and yield. Using reversed‐phase HPLC, atmospheric pressure chemical ionization mass spectrometry, and 1H‐ and 13C‐NMR techniques, we showed that the neuromelanin dolichol contained 17–23 isoprenoid units. Dolichol accounted for 14% of the mass of neuromelanin pigment; low levels of other hydrophobic compounds were detected (e.g. ubiquinone‐10, α‐tocopherol and cholesterol together accounted for < 0.5% of the neuromelanin lipid mass). This is the first time that dolichol has been identified in such a physiological setting and significantly advances our understanding of neuromelanin pigment structure and biosynthetic pathways. Furthermore, these studies identify a potential novel role for the isoprenoid pathway in the regulation of neuromelanin function and neurodegeneration within the SN.
Increased leaf reflectance in tropical trees under elevated CO2
Authors: Thomas Sean C.
Published: February 2005

Globally increasing atmospheric CO2 concentrations are known to affect many aspects of plant physiology and development; however, little attention has been given to leaf and canopy optical properties. Three tropical trees in the Leguminosae, an important canopy tree family in many tropical forests, responded similarly to an experimental doubling of CO2 partial pressure with a 9–23% increase in spectral leaf reflectance to light in the visible (400–700 nm) waveband. Decreased leaf chlorophyll content under elevated CO2 may explain part of the observed increase in reflectance. However, analyses that statistically corrected for chlorophyll content effects on reflectance still indicated a significant CO2 effect. This results, in conjunction with the spectral pattern of the response, suggests that the primary mechanism is increased optical masking of chlorophyll under elevated CO2. The magnitude of the increase in leaf reflectance is sufficient to suggest that increased canopy reflectance of tropical forests (and possibly other terrestrial ecosystems) may be an important negative feedback in the response of global net radiative climate forcing to increasing atmospheric CO2.
Knee surgery costs in football, floor ball, European team handball and ice hockey
Authors: Forssblad Magnus , Weidenhielm Lars , Werner Suzanne
Published: January 2005

The purpose of this study was first, to identify the health costs of knee surgery related to different sports (football, floor ball, European team handball and ice hockey) among players at competitive level in Stockholm 1997. Information was retrieved from three different databases, one containing information on all players in different sports, another one containing information on all surgery performed at S:t Görans Hospital, Stockholm, and a third one containing information on all surgery performed in Stockholm. The National Registration Number (NRN) was used to identify the patients. The NRN is a unique personal identifier assigned to all Swedish residents, which allows linkage between different registers and databases. In Stockholm in 1997, 6781 surgical procedures related to the knee were performed at a cost of SEK (Swedish Crowns) 39 026 657. On players in all studied sports, 762 knee surgical procedures were performed on 657 patients in Stockholm at a cost of SEK 4 884 076. At S:t Görans Hospital, 319 knee surgical procedures were performed on 288 patients, and 293 (92%) of these were directly related to sport participation. It was also found that only 74% of anterior cruciate ligament injuries that resulted in a surgical intervention were reported to the insurance company. Conclusion: The average cost for knee surgery in the studied sports was low. Knee surgery costs for European team handball players were the highest compared with other sports studied.
Hamstring injury occurrence in elite soccer players after preseason strength training with eccentric overload
Authors: Askling C. , Karlsson J. , Thorstensson A.
Published: January 2005

The primary purpose of this study was to evaluate whether a preseason strength‐training programme for the hamstring muscle group – emphasizing eccentric overloading – could affect the occurrence and severity of hamstring injuries during the subsequent competition season in elite male soccer players. Thirty players from two of the best premier‐league division teams in Sweden were divided into two groups; one group received additional specific hamstring training, whereas the other did not. The extra training was performed 1–2 times a week for 10 weeks by using a special device aiming at specific eccentric overloading of the hamstrings. Isokinetic hamstring strength and maximal running speed were measured in both groups before and after the training period and all hamstring injuries were registered during the total observational period of 10 months. The results showed that the occurrence of hamstring strain injuries was clearly lower in the training group (3/15) than in the control group (10/15). In addition, there were significant increases in strength and speed in the training group. However, there were no obvious coupling between performance parameters and injury occurrence. These results indicate that addition of specific preseason strength training for the hamstrings – including eccentric overloading – would be beneficial for elite soccer players, both from an injury prevention and from performance enhancement point of view.
Coupled Plastic Wave Propagation and Column Buckling
Authors: Vaughn Denzil G. , Canning James M. , Hutchinson John W.
Published: February 2005

The plastic buckling of columns is explored in a regime where plastic wave propagation and lateral buckling are nonlinearly coupled. Underlying the work is the motivation to understand and quantify the dynamic crushing resistance of truss cores of all-metal sandwich plates where each truss member is a clamped column. Members are typically fairly stocky such that they buckle plastically and their load carrying capacity decreases gradually as they buckle, even at slow loading rates. In the range of elevated loading rates of interest here, the columns are significantly stabilized by lateral inertia, resisting lateral motion and delaying buckling and loss of load carrying capacity to relatively large overall plastic strains. The time scale associated with dynamic axial behavior, wherein deformation spreads along the column as a plastic wave, is comparable to the time scale associated with lateral buckling such that the two phenomena are coupled. Several relevant problems are analyzed using a combination of analytical and numerical procedures. Material strain-rate dependence is also taken into account. Detailed finite element analyses are performed for axially loaded columns with initial imperfections, as well as for inclined columns in a truss core of a sandwich plate, with the aim of determining the resistance of the column to deformation as dependent on the loading rate and the relevant material and geometric parameters. In the range of loading rates of interest, dynamic effects result in substantial increases in the reaction forces exerted by core members on the faces of the sandwich plate with significant elevation in energy absorption.
Rayleigh Waves Generated by a Thermal Source: A Three-Dimensional Transient Thermoelasticity Solution
Authors: Georgiadis H. G. , Lykotrafitis G.
Published: February 2005

A three-dimensional transient thermoelastic solution is obtained for Rayleigh-type disturbances propagating on the surface of a half-space. These surface waves are generated by either a buried or surface thermal source, which has the form of a concentrated heat flux applied impulsively. In an effort to model this problem as realistically as possible, the half-space material is taken to respond according to Biot’s fully coupled thermoelasticity. The problem has relevance to situations involving heat generation due to: (i) laser action (impulsive electromagnetic radiation) on a surface target, (ii) underground nuclear activity, and (iii) friction developed during underground fault motions related to seismic activity. The problem was attacked with unilateral and double bilateral Laplace transforms, which suppress, respectively, the time variable and two of the space variables. The Rayleigh wave contribution is obtained as a closed-form expression by utilizing asymptotics, complex-variable theory and certain results for Bessel functions. The dependence of the normal displacement associated with the Rayleigh wave upon the distance from the source epicenter and the distance from the wavefront is also determined.
Experiment and Analysis on the Free Dynamics of a Shallow Arch After an Impact Load at the End
Authors: Chen Jen-San , Liao Chun-Yi
Published: February 2005

In this paper we consider a sinusoidal arch with one end pinned in space while the other end attached to a mass and supported by a spring. The supporting wall of the spring is moved a distance quasi-statically to initiate preload in the arch and the spring. The assembly is then set in motion by an impact at the attached mass. The condition under which the arch may snap to the other side dynamically depends on the initial speed of the attached mass due to impact. Sufficient condition on the initial speed against dynamic snap-through is formulated based on the concept of minimum energy barrier. The effects of damping on the transient response of the assembly are also discussed. An experimental setup is designed to measure the transient response of the arch following the impact and the critical initial speed of the attached mass. The experimental results are in good agreement with theoretical predictions.
Thermoelastic Fields in Boundary Layers of Isotropic Laminates
Authors: Mittelstedt Christian , Becker Wilfried
Published: February 2005

An approximate approach to the calculation of displacements, strains, and stresses near edges and corners in symmetric rectangular layered plates of dissimilar isotropic materials under thermal load is presented. In the thickness direction the plate is discretized into an arbitrary number of sublayers/mathematical layers. A layerwise linear displacement field is formulated such that the terms according to classical laminate plate theory are upgraded with unknown in-plane functions and a linear interpolation scheme through the layer thickness in order to describe edge and corner perturbations. By virtue of the principle of minimum potential energy the governing coupled Euler–Lagrange differential equations are derived, which in the case of free-edge effects allow a closed-form solution for the unknown inplane functions. Free-corner effects are investigated by combining the displacement formulations of the two interacting free-edge effects. Hence, all state variables in the plate are obtained in a closed-form manner. Boundary conditions of traction free plate edges are satisfied in an integral sense. The present methodology is easily applied and requires only reasonable computational expenses.
Mutations in PA2491 (
mexS
) Promote MexT-Dependent
mexEF-oprN
Expression and Multidrug Resistance in a Clinical Strain of
Pseudomonas aeruginosa
Authors: Sobel Mara L. , Neshat Shadi , Poole Keith
Published: February 2005

Disruption of the PA2491 gene in a mini-Tn
5
-
tet
insertion mutant of a clinical isolate of
Pseudomonas aeruginosa
increased expression of the
mexEF-oprN
multidrug efflux genes and decreased production of outer membrane protein OprD, concomitant with enhanced resistance to chloramphenicol, quinolones, and imipenem, which was reminiscent of previously described
nfxC
mutants. PA2491 encodes a probable oxidoreductase previously shown to be positively regulated by the MexT positive regulator of
mexEF-oprN
expression (T. Köhler, S. F. Epp, L. K. Curty, and J. C. Pechére, J. Bacteriol.
181:
6300-6305, 1999). Spontaneous multidrug-resistant mutants of the
P. aeruginosa
clinical isolate hyperexpressing
mexEF-oprN
and showing reduced production of OprD were readily selected in vitro, and all of them were shown to carry mutations in PA2491, highlighting the probable significance of such mutations as determinants of MexEF-OprN-mediated multidrug resistance in vivo.
Ectoine-Induced Proteins in
Sinorhizobium meliloti
Include an Ectoine ABC-Type Transporter Involved in Osmoprotection and Ectoine Catabolism
Authors: Jebbar Mohamed , Sohn-Bösser Linda , Bremer Erhard , Bernard Théophile , Blanco Carlos
Published: February 2005

To understand the mechanisms of ectoine-induced osmoprotection in
Sinorhizobium meliloti
, a proteomic examination of
S. meliloti
cells grown in minimal medium supplemented with ectoine was undertaken. This revealed the induction of 10 proteins. The protein products of eight genes were identified by using matrix-assisted laser desorption ionization-time-of-flight mass spectrometry. Five of these genes, with four other genes whose products were not detected on two-dimensional gels, belong to the same gene cluster, which is localized on the pSymB megaplasmid. Four of the nine genes encode the characteristic components of an ATP-binding cassette transporter that was named
ehu
, for ectoine/hydroxyectoine uptake. This transporter was encoded by four genes (
ehuA
,
ehuB
,
ehuC
, and
ehuD
) that formed an operon with another gene cluster that contains five genes, named
eutABCDE
for ectoine utilization. On the basis of sequence homologies,
eutABCDE
encode enzymes with putative and hypothetical functions in ectoine catabolism. Analysis of the properties of
ehuA
and
eutA
mutants suggests that
S. meliloti
possesses at least one additional ectoine catabolic pathway as well as a lower-affinity transport system for ectoine and hydroxyectoine. The expression of
ehuB
, as determined by measurements of UidA activity, was shown to be induced by ectoine and hydroxyectoine but not by glycine betaine or by high osmolality.
Putative Coiled-Coil Structural Elements of the BBA68 Protein of Lyme Disease Spirochetes Are Required for Formation of Its Factor H Binding Site
Authors: McDowell John V. , Harlin Matthew E. , Rogers Elizabeth A. , Marconi Richard T.
Published: February 2005

Factor H and factor H like-protein 1 (FHL-1) are complement regulatory proteins that serve as cofactors for the factor I-mediated cleavage of C3b. Some Lyme disease and relapsing fever spirochete species bind factor H to their surface to facilitate immune evasion. The Lyme disease spirochetes produce several factor H binding proteins (FHBPs) that form two distinct classes. Class I FHBPs (OspE orthologs and paralogs) bind only factor H, while class II FHBPs (BBA68) bind both factor H and FHL-1. BBA68 belongs to a large paralogous protein family, and of these paralogs, BBA69 is the member most closely related to BBA68. To determine if BBA69 can also bind factor H, recombinant protein was generated and tested for factor H binding. BBA69 did not exhibit factor H binding ability, suggesting that among family 54 paralogs, factor H binding is unique to BBA68. To identify the determinants of BBA68 that are involved in factor H binding, truncation and site-directed mutational analyses were performed. These analyses revealed that the factor H binding site is discontinuous and provide strong evidence that coiled-coil structural elements are involved in the formation of the binding site.
Overexpression of the Multidrug Efflux Pumps MexCD-OprJ and MexEF-OprN Is Associated with a Reduction of Type III Secretion in
Pseudomonas aeruginosa
Authors: Linares Juan F. , López Juan A. , Camafeita Emilio , Albar Juan P. , Rojo Fernando , Martínez Jose L.
Published: February 2005

The
Pseudomonas aeruginosa
genome contains several different multidrug resistance (MDR) efflux pumps. Overproduction of these pumps reduces susceptibility to a variety of antibiotics. Some recently published works have analyzed the effect of the overproduction of MDR efflux pumps on bacterial virulence. Here we have studied the effect of overproduction of the efflux pumps MexAB-OprM, MexCD-OprJ, MexEF-OprN, and MexXY on type III secretion (T3S) in
P. aeruginosa
. The type III secretion system (T3SS) is used by
P. aeruginosa
to deliver toxins directly into the cytoplasm of the host cell. Our data indicate that overexpression of either MexCD-OprJ or MexEF-OprN is associated with the impairment of T3S in
P. aeruginosa
. No effect on overexpression of either MexAB-OprM or MexXY was detected. The observed defect in T3S was due to a lack of expression of genes belonging to the T3SS regulon. Transcription of this regulon is activated by ExsA in response to environmental signals. Overexpression of this transcriptional regulator complemented the defect in T3S observed in the MexCD-OprJ- and MexEF-OprN-overproducing strains. Taken together, these results suggest that overproduction of either MexCD-OprJ or MexEF-OprN is associated with a reduction in the transcription of the T3SS regulon due to the lack of expression of the
exsA
gene, encoding the master regulator of the system. The relevance of potential metabolic and quorum-sensing imbalances due to overexpression of MDR pumps associated with this phenotype is also discussed.
Nonessential Genes of Phage φYeO3-12 Include Genes Involved in Adaptation to Growth onYersinia enterocoliticaSerotype O:3
Authors: Kiljunen Saija , Vilen Heikki , Pajunen Maria , Savilahti Harri , Skurnik Mikael
Published: February 2005

Bacteriophage φYeO3-12 is a T7/T3-related lytic phage that naturally infectsYersinia enterocoliticaserotype O:3 strains by using the lipopolysaccharide O polysaccharide (O antigen) as its receptor. The phage genome is a 39,600-bp-long linear, double-stranded DNA molecule that contains 58 genes. The roles of many of the genes are currently unknown. To identify nonessential genes, the isolated phage DNA was subjected to MuA transposase-catalyzed in vitro transposon insertion mutagenesis with alacZ′ gene-containing reporter transposon. Following electroporation intoEscherichia coliDH10B and subsequent infection ofE. coliJM109/pAY100, a strain that expresses theY. enterocoliticaO:3 O antigen on its surface, mutant phage clones were identified by their β-galactosidase activity, manifested as a blue color on indicator plates. Transposon insertions were mapped in a total of 11 genes located in the early and middle regions of the phage genome. All of the mutants had efficiencies of plating (EOPs) and fitnesses identical to those of the wild-type phage when grown onE. coliJM109/pAY100. However, certain mutants exhibited altered phenotypes when grown onY. enterocoliticaO:3. Transposon insertions in genes0.3to0.7decreased the EOP onY. enterocoliticaO:3, while the corresponding deletions did not, suggesting that the low EOP was not caused by inactivation of the genes per se. Instead, it was shown that in these mutants the low EOP was due to the delayed expression of gene1, coding for RNA polymerase. On the other hand, inactivation of gene1.3or3.5by either transposon insertion or deletion decreased phage fitness when grown onY. enterocolitica. These results indicate that φYeO3-12 has adapted to utilizeY. enterocoliticaas its host and that these adaptations include the products of genes1.3and3.5, DNA ligase and lysozyme, respectively.
New Pathway for Long-Chain
n
-Alkane Synthesis via 1-Alcohol in
Vibrio furnissii
M1
Authors: Park Myong-Ok
Published: February 2005

Alkane biosynthesis in the bacterium
Vibrio furnissii
M1 involves the synthesis of long-chain alkanes via 1-alcohol. Evidence for this novel pathway are the following. (i) Both even- and odd-carbon-number
n
-alkanes were produced from glucose, while only even-carbon-number fatty acids were produced in
V. furnissii
M1. This result cannot be explained by the decarbonylation pathway. (ii) Pentadecane and hexadecane were produced from 1-hexadecanoic acid by membrane fractions of
V. furnissii
M1, and radioisotope precursor-tracer experiments, in which 1-[1-
14
C]hexadecanoic acid was fed, identified the corresponding alcohol, aldehyde, and alkane derivatives. Since all metabolites maintained the radioisotope label at 1-C, they were produced by a pathway in which the carbon structure was retained, i.e., a reduction pathway. (iii)
n
-Hexadecane was produced when 1-hexadecanol was fed to membrane preparations.
Role of the
Escherichia coli glgX
Gene in Glycogen Metabolism
Authors: Dauvillée David , Kinderf Isabelle S. , Li Zhongyi , Kosar-Hashemi Behjat , Samuel Michael S. , Rampling Lynette , Ball Steven , Morell Matthew K.
Published: February 2005

A role for the
Escherichia coli glgX
gene in bacterial glycogen synthesis and/or degradation has been inferred from the sequence homology between the
glgX
gene and the genes encoding isoamylase-type debranching enzymes; however, experimental evidence or definition of the role of the gene has been lacking. Construction of
E. coli
strains with defined deletions in the
glgX
gene is reported here. The results show that the GlgX gene encodes an isoamylase-type debranching enzyme with high specificity for hydrolysis of chains consisting of three or four glucose residues. This specificity ensures that GlgX does not generate an extensive futile cycle during glycogen synthesis in which chains with more than four glucose residues are transferred by the branching enzyme. Disruption of
glgX
leads to overproduction of glycogen containing short external chains. These results suggest that the GlgX protein is predominantly involved in glycogen catabolism by selectively debranching the polysaccharide outer chains that were previously recessed by glycogen phosphorylase.
The BvgAS Signal Transduction System Regulates Biofilm Development inBordetella
Authors: Mishra Meenu , Parise Gina , Jackson Kara D. , Wozniak Daniel J. , Deora Rajendar
Published: February 2005

The majority ofBordetellasp. virulence determinants are regulated by the BvgAS signal transduction system. BvgAS mediates the control of multiple phenotypic phases and a spectrum of gene expression profiles specific to each phase in response to incremental changes in the concentrations of environmental signals. Studies highlighting the critical role of this signaling circuitry in theBordetellainfectious cycle have focused on planktonically growing bacterial cells. It is becoming increasingly clear that the major mode of bacterial existence in the environment and within the body is a surface-attached state known as a biofilm. Biofilms are defined as consortia of sessile microorganisms that are embedded in a matrix. During routine growth ofBordetellaunder agitating conditions, we noticed the formation of a bacterial ring at the air-liquid interface of the culture tubes. We show here that this surface adherence property reflects the ability of these organisms to form biofilms. Our data demonstrate that the BvgAS locus regulates biofilm development inBordetella. The results reported in this study suggest that the Bvg-mediated control in biofilm development is exerted at later time points after the initial attachment of bacteria to the different surfaces. Additionally, we show that these biofilms are highly tolerant of a number of antimicrobials, including the ones that are currently recommended for treatment of veterinary and human infections caused byBordetellaspp. Finally, we discuss the significance of the biofilm lifestyle mode as a potential contributor to persistent infections.
Host Gene Expression Changes and DNA Amplification during Temperate Phage Induction
Authors: Frye Jonathan G. , Porwollik Steffen , Blackmer Felisa , Cheng Pui , McClelland Michael
Published: February 2005

Salmonella enterica
serovar Typhimurium LT2 harbors four temperate prophages. The lytic cycle of these phages was induced with hydrogen peroxide or mitomycin C. Microarray analysis was used to monitor the increase in phage genome copy number and the changes in RNA expression. Phage gene transcription was classified temporally, and host genes that responded to hydrogen peroxide, mitomycin C, or phage induction were also identified. A region of the serovar Typhimurium LT2 host genome encompassing hundreds of genes, flanking the Fels-1 lambdoid prophage, was amplified manyfold during lytic induction, presumably due to Fels-1 runoff replication prior to excision, a phenomenon termed escape replication. An excisionase (
xis
) mutant of Fels-1 also induced escape replication but did not get packaged. Gifsy-1, a lambdoid prophage that does not normally produce escape replication, did so after deletion of either its integrase or excisionase genes. Escape replication is probably widespread; large regions of host genome amplification were also observed after phage induction in serovar Typhimurium strains SL1344 and 14028s at the suspected integration site of prophage genomes.
Potent Anti-R5 Human Immunodeficiency Virus Type 1 Effects of a CCR5 Antagonist, AK602/ONO4128/GW873140, in a Novel Human Peripheral Blood Mononuclear Cell Nonobese Diabetic-SCID, Interleukin-2 Receptor γ-Chain-Knocked-Out AIDS Mouse Model
Authors: Nakata Hirotomo , Maeda Kenji , Miyakawa Toshikazu , Shibayama Shiro , Matsuo Masayoshi , Takaoka Yoshikazu , Ito Mamoru , Koyanagi Yoshio , Mitsuya Hiroaki
Published: January 2005

We established human peripheral blood mononuclear cell (PBMC)-transplanted R5 human immunodeficiency virus type 1 isolate JR-FL (HIV-1
JR-FL
)-infected, nonobese diabetic-SCID, interleukin 2 receptor γ-chain-knocked-out (NOG) mice, in which massive and systemic HIV-1 infection occurred. The susceptibility of the implanted PBMC to the infectivity and cytopathic effect of R5 HIV-1 appeared to stem from hyperactivation of the PBMC, which rapidly proliferated and expressed high levels of CCR5. When a novel spirodiketopiperazine-containing CCR5 inhibitor, AK602/ONO4128/GW873140 (molecular weight, 614), was administered to the NOG mice 1 day after R5 HIV-1 inoculation, the replication and cytopathic effects of R5 HIV-1 were significantly suppressed. In saline-treated mice (
n
= 7), the mean human CD4
+
/CD8
+
cell ratio was 0.1 on day 16 after inoculation, while levels in mice (
n
= 8) administered AK602 had a mean value of 0.92, comparable to levels in uninfected mice (
n
= 7). The mean number of HIV-RNA copies in plasma in saline-treated mice were ∼10
6
/ml on day 16, while levels in AK602-treated mice were 1.27 × 10
3
/ml (
P
= 0.001). AK602 also significantly suppressed the number of proviral DNA copies and serum p24 levels (
P
= 0.001). These data suggest that the present NOG mouse system should serve as a small-animal AIDS model and warrant that AK602 be further developed as a potential therapeutic for HIV-1 infection.
Wiskott-Aldrich Syndrome Protein Is Needed for Vaccinia Virus Pathogenesis
Authors: Guerra Susana , Aracil Miguel , Conde Raquel , Bernad Antonio , Esteban Mariano
Published: January 2005

Smallpox, caused by variola virus, was a devastating disease in humans, but how the virus evolved a strategy to spread to tissue remains unknown. Through the use of microarrays, we identified the gene encoding the Wiskott-Aldrich syndrome protein (WASP), one of the five known WASP family members, which has been induced in the course of infection of human cells with different strains of vaccinia virus (VV) (S. Guerra, L. A. López-Fernández, A. Pascual-Montano, M. Muñoz, K. Harshman, and M. Esteban, J. Virol. 77:6493-6506, 2003; S. Guerra, L. A. López-Fernández, R. Conde, A. Pascual-Montano, K. Harshman, and M. Esteban, J. Virol. 78:5820-5834, 2004). In a mouse model, we evaluated the role of WASP in infection with VV, a close relative of variola virus. WASP−/−(KO) mice infected intranasally and intraperitoneally with VV showed reduced weight loss and mortality compared to wild-type (WT) mice. WASP expression correlated with VV replication in the ovaries but not in the liver or spleen. WT mouse macrophages express WASP but not N-WASP; after VV infection, WASP levels increase threefold. KO macrophages lack N-WASP expression and, when VV infected, are incapable of inducing actin tails and producing extracellular virus. These functions were rescued in KO macrophages after ectopic WASP expression. Overall, our findings demonstrate that WASP has a role in orthopoxvirus infections. Use of WASP proteins for virus spread via the actin tail provides a selective advantage for VV, and probably variola virus, dissemination to distant tissues.
Human Cytomegalovirus Infection of Endothelial Cells Triggers Platelet Adhesion and Aggregation
Authors: Rahbar Afsar , Söderberg-Nauclér Cecilia
Published: January 2005

Human cytomegalovirus (HCMV) is an opportunistic pathogen that has been implicated in the pathogenesis of vascular diseases. HCMV infection of endothelial cells may lead to vascular damage in vitro, and acute-phase HCMV infection has been associated with thrombosis. We hypothesized that viral infection of endothelial cells activates coagulation cascades and contributes to thrombus formation and acute vascular catastrophes in patients with atherosclerotic disease. To assess the effects of HCMV on thrombogenesis, we examined the adhesion and aggregation of blood platelets to uninfected and HCMV-infected endothelial cells. At 7 days after infection, platelet adherence and aggregation were greater in infected than in uninfected cultures (2,000 platelets/100 cells and 225 ± 15 [mean ± standard error of the mean] aggregates/five microscopic fields versus 100 platelets/100 cells and no aggregates). von Willebrand factor (vWF), ICAM-1, and VCAM-1 but not collagen IV, E-selectin, P-selectin, CD13, and CD31 were expressed at higher levels on infected cells than on uninfected cells. Platelet aggregation was inhibited by blocking of platelet GPIb (with blocking antibodies) or GPIIb/IIIa (with ReoPro) or by blocking of vWF (with polyclonal antibodies to vWF). Furthermore, blocking of vWF, platelet GPIb, and ICAM-1 but not of the endothelial cell marker CD13, α
5
β
3
-integrin, or HCMV glycoprotein B reduced platelet adherence to infected cells by 75% ± 5%, 74% ± 5%, or 18% ± 5%, respectively. The increased thrombogenicity was dependent on active virus replication and could be inhibited by foscarnet and ganciclovir; these results suggest that a late viral gene may be mediating this phenomenon, which may contribute to vascular catastrophes in patients with atherosclerotic disease.
The Murine Gammaherpesvirus 68 M2 Gene Is Required for Efficient Reactivation from Latently Infected B Cells
Authors: Herskowitz Jeremy , Jacoby Meagan A. , Speck Samuel H.
Published: January 2005

Murine gammaherpesvirus 68 (γHV68) infection of mice provides a tractable small-animal model system for assessing the requirements for the establishment and maintenance of gammaherpesvirus latency within the lymphoid compartment. The M2 gene product of γHV68 is a latency-associated antigen with no discernible homology to any known proteins. Here we focus on the requirement for the M2 gene in splenic B-cell latency. Our analyses showed the following. (i) Low-dose (100 PFU) inoculation administered via the intranasal route resulted in a failure to establish splenic B-cell latency at day 16 postinfection. (ii) Increasing the inoculation dose to 4 × 10
5
PFU administered via the intranasal route partially restored the establishment of B-cell latency at day 16, but no virus reactivation was detected upon explant into tissue cultures. (iii) Although previous data failed to detect a phenotype of the M2 mutant upon high-dose intraperitoneal inoculation, decreasing the inoculation dose to 100 PFU administered intraperitoneally revealed a splenic B-cell latency phenotype at day 16 that was very similar to the phenotype observed upon high-dose intranasal inoculation. (iv) After low-dose intraperitoneal inoculation, fractionated B-cell populations showed that the M2 mutant virus was able to establish latency in surface immunoglobulin D-negative (sIgD
−
) B cells; by 6 months postinfection, equivalent frequencies of M2 mutant and marker rescue viral genome-positive sIgD
−
B cells were detected. (v) Like the marker rescue virus, the M2 mutant virus also established latency in splenic naive B cells upon low-dose intraperitoneal inoculation, but there was a significant lag in the decay of this latently infected reservoir compared to that seen with the marker rescue virus. (vi) After low-dose intranasal inoculation, by day 42 postinfection, latency was observed in the spleen, although at a frequency significantly lower than that in the marker rescue virus-infected mice; by 3 months postinfection, nearly equivalent levels of viral genome-positive cells were observed in the spleens of marker rescue virus- and M2 mutant virus-infected mice, and these cells were exclusively sIgD
−
B cells. Taken together, these data convincingly demonstrate a role for the M2 gene product in reactivation from splenic B cells and also suggest that disruption of the M2 gene leads to dose- and route-specific defects in the efficient establishment of splenic B-cell latency.
The Proline-Rich Homeodomain (PRH/HEX) Protein Is Down-Regulated in Liver during Infection with Lymphocytic Choriomeningitis Virus
Authors: Djavani Mahmoud , Topisirovic Ivan , Zapata Juan Carlos , Sadowska Mariola , Yang Yida , Rodas Juan , Lukashevich Igor S. , Bogue Clifford W. , Pauza C. David , Borden Katherine L. B. , Salvato Maria S.
Published: January 2005

The proline-rich homeodomain protein, PRH/HEX, participates in the early development of the brain, thyroid, and liver and in the later regenerative processes of damaged liver, vascular endothelial, and hematopoietic cells. A virulent strain of lymphocytic choriomeningitis virus (LCMV-WE) that destroys hematopoietic, vascular, and liver functions also alters the transcription and subcellular localization of PRH. A related virus (LCMV-ARM) that does not cause disease in primates can infect cells without affecting PRH. Biochemical experiments demonstrated the occurrence of binding between the viral RING protein (Z) and PRH, and genetic experiments mapped the PRH-suppressing phenotype to the large (L) segment of the viral genome, which encodes the Z and polymerase genes. The Z protein is clearly involved with PRH, but other viral determinants are needed to relocate PRH and to promote disease. By down-regulating PRH, the arenavirus is able to eliminate the antiproliferative effects of PRH and to promote liver cell division. The interaction of an arenavirus with a homeodomain protein suggests a mechanism for viral teratogenic effects and for the tissue-specific manifestations of arenavirus disease.
CRITICAL CURRENT DENSITIES IN Bi1.7Pb0.3-xGdxSr2Ca3Cu4O12+y (x=0.01, 0.1) SUPERCONDUCTORS PREPARED BY MELT-QUENCHING METHOD AND ANNEALED IN DIFFERENT TIME INTERVALS
Authors: EKİCİBİL AHMET , COŞKUN ATILLA , ÖZÇELİK BEKIR , KIYMAÇ KERIM
Published: February 2005

We report critical current density (Jc) behaviors of the Bi 1.7 Pb 0.3-x Gd x Sr 2 Ca 3 Cu 4 O 12+y (x=0.01, 0.1) superconductors prepared by melt-quenching method and annealed in different time intervals at 840°C. The effects of annealing times are found to be very important. For example, for the sample B2, the highest value of Jc is 3.7×104 A / cm 2 at 9 K. This value is almost 1.5 and 2 times greater than that of the samples B3 and B1, respectively. With increasing annealing time, the 2223 phase increases, thus resulting in a decrease in the insulating phase. For lower annealing times, there are a large number of insulating phases. On the whole, our results indicate that there is an optimum annealing time t to form the 2223 phase, in a time interval of 120<t<192 h . It is clearly seen that Jc decreases smoothly with increasing temperature for all the samples studied. At lower temperatures, especially below 30 K, an extremely rapid decrease of Jc with increasing temperature has been observed. The experimental values also show that between the temperature interval from 9–45 K, Jc decreases by one order of magnitude. We have also observed that when the Gd – Pb substitution increases, the effective defect density increases, leading to small critical current densities.
MODELING, ANALYSIS AND DESIGN OF A THYRISTOR-BASED BI-DIRECTIONAL ac–dc CONVERTER
Authors: YIP S. C. , CHUNG HENRY S. H. , HUI S. Y. R. , CHIU Y. C.
Published: February 2005

This paper presents the modeling, analysis, and design of a thyristor-based ac–dc converter, featuring bi-directional power flow and unity power factor at the ac side in both powering and regenerating modes. By applying the y-parameter modeling technique and eliminating the effects of the high-frequency poles and zeros, small-signal models of the converter in both modes and a unified controller have been developed. The controller regulates the voltage at the dc side and operates as a feedback controller in the powering mode and a feedforward controller in the regenerating mode. Systematic procedures for determining the circuit component values of the power conversion stage and the controller are presented. The operation is illustrated with the design of a 500-W, 100-V (ac)/200-V (dc) prototype, supplying to a motor-generator set. Experimental results showing operation in the powering mode, regenerating mode, and during mode changeover are included. Circuit operations during the transient of the changeover operation are clearly identified.
SWITCHING MATRIX APPROACH BASED MODULATION FOR AC TO DC CONVERTER
Authors: MILANOVIC MIRO , PROSEN RUDI , MARTINEZ-SALAMERO LUIS
Published: February 2005

Modulation strategy for a matrix structured ac to dc converter is developed. This modulation strategy enables the input displacement factor correction without current sensing. Mathematical proof that ac to dc converter can operate with unity input displacement factor is provided by analysis based on the switching matrix approach. Theoretical analysis demonstrates the algorithm requirements. Computer simulation and experimental results supporting this ability are reported.
Poly(ADP-ribose) polymerase inhibitor PJ-34 reduces mesenteric vascular injury induced by experimental cardiopulmonary bypass with cardiac arrest
Authors: Andrási Terézia B. , Blázovics Anna , Szabó Gábor , Vahl Christian F. , Hagl Siegfried
Published: January 2005

The aim of this study was to investigate effects of poly(ADP-ribose) polymerase (PARP) inhibition on mesenteric vascular function and metabolism in an experimental model of cardiopulmonary bypass (CPB) with cardiac arrest. Twelve anesthetized dogs underwent 90-min hypothermic CPB. After 60 min of cardiac arrest, reperfusion was started for 40 min following application of either saline vehicle (control, n = 6) or a potent PARP inhibitor, PJ-34 (10 mg/kg iv bolus and 0.5 mg·kg−1·min−1 infusion for 20 min, n = 6). PJ-34 led to better recovery of cardiac output (2.2 ± 0.1 vs. 1.8 ± 0.2 l/min in control) and mesenteric blood flow (175 ± 38 vs. 83 ± 4 ml/min, P < 0.05 vs. control) after reperfusion. The impaired vasodilator response of the superior mesenteric artery to acetylcholine, assessed in the control group after CPB (−32.8 ± 3.3 vs. −57.6 ± 6.6% at baseline, P < 0.05), was improved by PJ-34 (−50.3 ± 3.6 vs. −54.3 ± 4.1% at baseline, P < 0.05 vs. control). Although plasma nitrate/nitrite concentrations were not significantly different between groups, mesenteric nitric oxide synthase activity was increased in the PJ-34 group ( P < 0.05). Moreover, the treated group showed a marked attenuation of mesenteric venous plasma myeloperoxidase levels after CPB compared with the control group (75 ± 1 vs. 135 ± 9 ng/ml, P < 0.05). Pharmacological PARP inhibition protects against development of post-CPB mesenteric vascular dysfunction by improving hemodynamics, restoring nitric oxide production, and reducing neutrophil adhesion.