bluuebunny/crossref_metadata_2025 huggingface dataset:
Newly born cells in the ageing dentate gyrus display normal migration, survival and neuronal fate choice but endure retarded early maturation
Authors: Rao Muddanna S. , Hattiangady Bharathi , Abdel‐Rahman Ali , Stanley Dirk P. , Shetty Ashok K.
Published: January 2005

Addition of new granule cells to the dentate gyrus (DG) from stem or progenitor cells declines considerably during ageing. However, potential age‐related alterations in migration, enduring survival and neuronal fate choice of newly born cells, and rate of maturation and dendritic growth of newly differentiated neurons are mostly unknown. We addressed these issues by analysing cells that are positive for 5′‐bromodeoxyuridine (BrdU), doublecortin (DCX), BrdU and DCX, and BrdU and neuron‐specific nuclear antigen (NeuN) in the DG of young adult, middle‐aged and aged F344 rats treated with daily injections of BrdU for 12 consecutive days. Analyses performed at 24 h, 10 days and 5 months after BrdU injections reveal that the extent of new cell production decreases dramatically by middle age but exhibits no change thereafter. Interestingly, fractions of newly formed cells that exhibit appropriate migration and prolonged survival, and fractions of newly born cells that differentiate into neurons, remain stable during ageing. However, in newly formed neurons of the middle‐aged and aged DG, the expression of mature neuronal marker NeuN is delayed and early dendritic growth is retarded. Thus, the presence of far fewer new granule cells in the aged DG is not due to alterations in the long term survival and phenotypic differentiation of newly generated cells but solely owing to diminished production of new cells. The results also underscore that the capability of the DG milieu to support neuronal fate choice, migration and enduring survival of newly born cells remains stable even during senescence but its ability to promote rapid neuronal maturation and dendritic growth is diminished as early as middle age.
A novel scaffold protein, TANC, possibly a rat homolog of Drosophila rolling pebbles (rols), forms a multiprotein complex with various postsynaptic density proteins
Authors: Suzuki Tatsuo , Li Weidong , Zhang Jing‐Ping , Tian Qing‐Bao , Sakagami Hiroyuki , Usada Nobuteru , Kondo Hisatake , Fujii Toshihiro , Endo Shogo
Published: January 2005

We cloned from the rat brain a novel gene, tanc (GenBankTM Accession No. AB098072), which encoded a protein containing three tetratricopeptide repeats (TPRs), ten ankyrin repeats and a coiled‐coil region, and is possibly a rat homolog of Drosophila rolling pebbles (rols). The tanc gene was expressed widely in the adult rat brain. Subcellular distribution, immunohistochemical study of the brain and immunocytochemical studies of cultured neuronal cells indicated the postsynaptic localization of TANC protein of 200 kDa. Pull‐down experiments showed that TANC protein bound PSD‐95, SAP97, and Homer via its C‐terminal PDZ‐binding motif, ‐ESNV, and fodrin via both its ankyrin repeats and the TPRs together with the coiled‐coil domain. TANC also bound the α subunit of Ca2+/calmodulin‐dependent protein kinase II. An immunoprecipitation study showed TANC association with various postsynaptic proteins, including guanylate kinase‐associated protein (GKAP), α‐internexin, and N‐methyl‐d‐aspartate (NMDA)‐type glutamate receptor 2B and AMPA‐type glutamate receptor (GluR1) subunits. These results suggest that TANC protein may work as a postsynaptic scaffold component by forming a multiprotein complex with various postsynaptic density proteins.
Centre‐surround interactions in response to natural scene stimulation in the primary visual cortex
Authors: Guo Kun , Robertson Robert G. , Mahmoodi Sasan , Young Malcolm P.
Published: January 2005

Centre–surround interaction in the primary visual cortex (area V1) has been studied extensively using artificial, abstract stimulus patterns, such as bars, gratings and simple texture patterns. In this experiment, we extend the study of centre–surround interaction by using natural scene images. We systematically varied the contrast of natural image surrounds presented outside the classical receptive field (CRF), and recorded neuronal response to a natural image patch presented within the CRF in area V1 of awake, fixating macaques. For the majority of neurons (67 out of 111), the natural image surrounds profoundly modulated, mainly by suppressing, neuronal responses to CRF images. These modulatory effects started at the earliest stage of neuronal responses, and often depended on the contrast and higher‐order structures of the surrounds. For 47 out of 67 neurons, randomising the phases of the Fourier spectrum of the natural image surround diminished the centre–surround interaction. Our results suggest that the centre–surround interaction in area V1 can be extended to natural vision, and is sensitive to the higher‐order structures of natural scene images, such as image contours.
Differential expression of two NMDA receptor interacting proteins, PSD‐95 and SynGAP during mouse development
Authors: Porter Karen , Komiyama Noboru H. , Vitalis Tania , Kind Peter C. , Grant Seth G. N.
Published: January 2005

Patterns of neural activity mediated by N‐methyl‐d‐aspartate (NMDA) receptors are known to play important roles in development of the central nervous system. However, the signalling pathways downstream from NMDA receptors that are critical for normal neuronal development are not yet clearly understood. NMDA receptors interact with various signalling proteins via scaffolding proteins, which are important in adult neuronal and behavioural plasticity. For example, the NR2B subunits of the NMDA receptor interact with postsynaptic density 95 (PSD‐95), which in turn binds to synaptic ras GTPase‐activating protein (SynGAP). Interestingly, the developmental phenotype of mice carrying null mutations in these genes differ. NR2B and SynGAP homozygote mice die within the first week of birth whereas PSD‐95 homozygote mice survive to adulthood. We therefore examined the expression patterns of PSD‐95 and SynGAP genes from embryonic stages to adult using lacZ (β‐galactosidase) marker gene knock‐in mice. Dramatic changes of expression were observed throughout development in brain and other tissues. Although SynGAP binds PSD‐95, both genes had distinct, as well as overlapping expression. SynGAP expression peaked at times of synaptogenesis and developmental plasticity in contrast to PSD‐95, which was expressed throughout the brain from early embryonic stages. Furthermore, SynGAP showed a more spatially restricted pattern as illustrated by its restriction to forebrain in contrast to PSD‐95, which was also found in mid‐ and hindbrain. These data support the model that synaptic signalling complexes are heterogeneous and individual components show temporal and spatial specificity during development.
The Effect of Development Impact Fees on Land Values*
Authors: EVANS‐COWLEY JENNIFER S. , FORGEY FRED A. , RUTHERFORD RONALD C.
Published: February 2005

ABSTRACT  This paper presents an empirical analysis of the effect of impact fees on the value of land used in residential development. A random effects model is estimated to examine the relationship between impact fees and land values using forty‐three Texas cities that impose impact fees. Prior research suggests that higher impact fees result in higher lot values, and the results of this research support this suggestion. Results indicate that for each $1,000 increase in impact fees, lot values increase by 1.3 percent. Additionally, these results suggest that developers are able to pass a small amount of the impact fee to the owners of developable land. However, for undeveloped land the results are mixed. For each $1,000 in assessed impact fees, undeveloped land values decrease by 0.042 percent. These results support prior evidence that suggests home buyers may ultimately bear the majority of the cost of impact fees.
Duration of α1‐antichymotrypsin gene activation by interleukin‐1 is determined by efficiency of inhibitor of nuclear factor κBα resynthesis in primary human astrocytes
Authors: Kiss Daniel L. , Xu Weili , Gopalan Sunita , Buzanowska Katarzyna , Wilczynska Katarzyna M. , Rydel Russell E. , Kordula Tomasz
Published: February 2005

Expression of α1antichymotrypsin (ACT) is significantly activated by interleukin‐1 (IL‐1) in human astrocytes; however, it is barely affected by IL‐1 in hepatocytes. This tissue‐specific regulation depends upon an enhancer that contains both nuclear factor κB (NF‐κB) and activating protein 1 (AP‐1) elements, and is also observed for an NF‐κB reporter but not for an AP‐1 reporter. We found efficient activation of NF‐κB binding in both cell types; however, this binding was persistent in glial cells and only transient in hepatocytes. IL‐1‐activated NF‐κB complexes consisted of p65 and p50, with p65 transiently phosphorylated on serine 536 in glial cells whereas more persistently in hepatic cells. Overexpression of p65 or constitutively active IKKβ (inhibitor of NF‐κB kinase β) resulted in an efficient activation of the ACT reporter in hepatic cells, indicating that a specific mechanism exists in these cells terminating IL‐1 signaling. IL‐1 effectively induced the degradation of inhibitor of NF‐κBα (IkBα) and IkBε in both cell types but IkBβ was not affected. However, IkBα was resynthesized much more rapidly in hepatic cells in comparison to glial cells. In addition, the initial levels of IkBα were much lower in glial cells. We propose that the tissue‐specific regulation of the ACT gene expression by IL‐1 is determined by different efficiencies of IkBα resynthesis in glial and hepatic cells.
Alteration of cytosolic free calcium homeostasis by SIN‐1: high sensitivity of L‐type Ca2+ channels to extracellular oxidative/nitrosative stress in cerebellar granule cells
Authors: Gutiérrez‐Martín Yolanda , Martín‐Romero Francisco Javier , Henao Fernando , Gutiérrez‐Merino Carlos
Published: February 2005

Exposure of cerebellar granule neurones in 25 mm KCl HEPES‐containing Locke's buffer (pH 7.4) to 50–100 µm SIN‐1 during 2 h decreased the steady‐state free cytosolic Ca2+ concentration ([Ca2+]i) from 168 ± 33 nm to 60 ± 10 nm, whereas exposure to ≥ 0.3 mm SIN‐1 produced biphasic kinetics: (i) decrease of [Ca2+]i during the first 30 min, reaching a limiting value of 75 ± 10 nm (due to inactivation of L‐type Ca2+ channels) and (ii) a delayed increase of [Ca2+]i at longer exposures, which correlated with SIN‐1‐induced necrotic cell death. Both effects of SIN‐1 on [Ca2+]i are blocked by superoxide dismutase plus catalase and by Mn(III)tetrakis(4‐benzoic acid)porphyrin chloride. Supplementation of Locke's buffer with catalase before addition of 0.5–1 mm SIN‐1 had no effect on the decrease of [Ca2+]i but further delayed and attenuated the increase of [Ca2+]i observed after 60–120 min exposure to SIN‐1 and also protected against SIN‐1‐induced necrotic cell death. α‐Tocopherol, the potent NMDA receptor antagonist (+)‐MK‐801 and the N‐ and P‐type Ca2+ channels blocker ω‐conotoxin MVIIC had no effect on the alterations of [Ca2+]i upon exposure to SIN‐1. However, inhibition of the plasma membrane Ca2+ ATPase can account for the increase of [Ca2+]i observed after 60–120 min exposure to 0.5–1 mm SIN‐1. It is concluded that L‐type Ca2+ channels are a primary target of SIN‐1‐induced extracellular nitrosative/oxidative stress, being inactivated by chronic exposure to fluxes of peroxynitrite of 0.5–1 μm/min, while higher concentrations of peroxynitrite and hydrogen peroxide are required for the inhibition of the plasma membrane Ca2+ ATPase and induction of necrotic cell death, respectively.
Solutions for the Inclined Borehole in a Porothermoelastic Transversely Isotropic Medium
Authors: Abousleiman Younane , Ekbote Shailesh
Published: February 2005

A porothermoelastic solution of the general problem of the inclined borehole in a transversely isotropic porous material is presented herein and compared with the isotropic porothermoelastic solution. The governing equations are outlined for the case of general anisotropy and specialized for a transversely isotropic poroelastic material under nonhydrostatic and nonisothermal in situ conditions. A superposition scheme is employed to obtain the analytical solutions within the isotropic and transversely isotropic poromechanics theory. The borehole generator is assumed to coincide with the material axis of symmetry, in the case of transverse isotropy, yet subjected to a three-dimensional state of stress. A systematic analysis has been carried out to evaluate the effect of the anisotropy of the poromechanical material parameters as well as the thermal material properties on stress and pore pressure distributions and the potential impact on the overall stability of deep wellbore drilling.
Axisymmetric Plane Stress States of an Annulus Subject to Displacive Shear Transformation
Authors: Chi Yuwei , Pence Thomas J. , Tsai Hungyu
Published: February 2005

We study the equilibrium stress field in an annulus composed of a material that admits stress-induced displacive phase transformation that preserves volume. A standard example is the austenite to martensite transformation in shape memory alloys. Attention is restricted to isothermal and axisymmetric load increase. The constitutive model follows a standard J2 formulation appropriate for small strains and incorporates a single internal variable (the martensite phase fraction). A plane-stress boundary value problem is analyzed so as to determine the partitioning of the annulus into regions of (pure) austenite, (pure) martensite, and austenite/martensite mixture. Structure maps are presented, giving concise descriptions of the phase partitioning as the loads increase.
GlnD Is Essential for NifA Activation, NtrB/NtrC-Regulated Gene Expression, and Posttranslational Regulation of Nitrogenase Activity in the Photosynthetic, Nitrogen-Fixing Bacterium
Rhodospirillum rubrum
Authors: Zhang Yaoping , Pohlmann Edward L. , Roberts Gary P.
Published: February 2005

GlnD is a bifunctional uridylyltransferase/uridylyl-removing enzyme and is thought to be the primary sensor of nitrogen status in the cell. It plays an important role in nitrogen assimilation and metabolism by reversibly regulating the modification of P
II
proteins, which in turn regulate a variety of other proteins. We report here the characterization of
glnD
mutants from the photosynthetic, nitrogen-fixing bacterium
Rhodospirillum rubrum
and the analysis of the roles of GlnD in the regulation of nitrogen fixation. Unlike
glnD
mutations in
Azotobacter vinelandii
and some other bacteria,
glnD
deletion mutations are not lethal in
R. rubrum
. Such mutants grew well in minimal medium with glutamate as the sole nitrogen source, although they grew slowly with ammonium as the sole nitrogen source (MN medium) and were unable to fix N
2
. The slow growth in MN medium is apparently due to low glutamine synthetase activity, because a Δ
glnD
strain with an altered glutamine synthetase that cannot be adenylylated can grow well in MN medium. Various mutation and complementation studies were used to show that the critical uridylyltransferase activity of GlnD is localized to the N-terminal region. Mutants with intermediate levels of uridylyltransferase activity are differentially defective in
nif
gene expression, the posttranslational regulation of nitrogenase, and NtrB/NtrC function, indicating the complexity of the physiological role of GlnD. These results have implications for the interpretation of results obtained with GlnD in many other organisms.
A Defect in the Acetyl Coenzyme A↔Acetate Pathway Poisons Recombinational Repair-Deficient Mutants ofEscherichia coli
Authors: Shi Idina Y. , Stansbury John , Kuzminov Andrei
Published: February 2005

Recombinational repair-dependent mutants identify ways to avoid chromosomal lesions. Starting with arecBC(Ts) strain ofEscherichia coli, we looked for mutants unable to grow at 42°C in conditions that inactivate the RecBCD(Ts) enzyme. We isolated insertions inackAandpta, which comprise a two-gene operon responsible for the acetate↔acetyl coenzyme A interconversion. Using precise deletions of eitherackAorpta, we showed that either mutation makesE. colicells dependent on RecA or RecBCD enzymes at high temperature, suggesting dependence on recombinational repair rather than on the RecBCD-catalyzed linear DNA degradation. Complete inhibition of growth ofpta/ackA recmutants was observed only in the presence of nearby growing cells, indicating cross-inhibition.pta recmutants were sensitive to products of the mixed-acid fermentation of pyruvate, yet none of these substances inhibited growth of the double mutants in low-millimolar concentrations.pta, but notackA, mutants also depend on late recombinational repair functions RuvABC or RecG.pta/ackA recFmutants are viable, suggesting, together with the inviability ofpta/ackA recBCmutants, that chromosomal lesions due to thepta/ackAdefect are of the double-strand-break type. We have isolated three insertional suppressors that allow slow growth ofpta recBC(Ts) cells under nonpermissive conditions; all three are in or near genes with unknown functions. Although they do not form colonies,ackA recandpta recmutants are not killed under the nonpermissive conditions, exemplifying a case of synthetic inhibition rather than synthetic lethality.
Analysis of the Piv Recombinase-Related Gene Family of
Neisseria gonorrhoeae
Authors: Skaar Eric P. , LeCuyer Brian , Lenich Anne G. , Lazio Matthew P. , Perkins-Balding Donna , Seifert H. Steven , Karls Anna C.
Published: February 2005

Neisseria gonorrhoeae
(the gonococcus) is an obligate human pathogen and the causative agent of the disease gonorrhea. The gonococcal pilus undergoes antigenic variation through high-frequency recombination events between unexpressed
pilS
silent copies and the pilin expression locus
pilE
. The machinery involved in pilin antigenic variation identified to date is composed primarily of genes involved in homologous recombination. However, a number of characteristics of antigenic variation suggest that one or more recombinases, in addition to the homologous recombination machinery, may be involved in mediating sequence changes at
pilE
. Previous work has identified several genes in the gonococcus with significant identity to the pilin inversion gene (
piv
) from
Moraxella
species and transposases of the IS
110
family of insertion elements. These genes were candidates for a recombinase system involved in pilin antigenic variation. We have named these genes
irg
for invertase-related gene family. In this work, we characterize these genes and demonstrate that the
irg
genes do not complement for
Moraxella lacunata
Piv invertase or IS
492
MooV transposase activities. Moreover, by inactivation of all eight gene copies and overexpression of one gene copy, we conclusively show that these recombinases are not involved in gonococcal pilin variation, DNA transformation, or DNA repair. We propose that the
irg
genes encode transposases for two different IS
110
-related elements given the names IS
Ngo2
and IS
Ngo3
. IS
Ngo2
is located at multiple loci on the chromosome of
N. gonorrhoeae
, and IS
Ngo3
is found in single and duplicate copies in the
N. gonorrhoeae
and
Neisseria meningitidis
genomes, respectively.
A Polysaccharide Deacetylase Homologue, PdaA, inBacillus subtilisActs as anN-Acetylmuramic Acid Deacetylase In Vitro
Authors: Fukushima Tatsuya , Kitajima Toshihiko , Sekiguchi Junichi
Published: February 2005

A polysaccharide deacetylase homologue, PdaA, was determined to act as anN-acetylmuramic acid deacetylase in vitro. Histidine-tagged truncated PdaA (with the putative signal sequence removed) was overexpressed inEscherichia colicells and purified. Measurement of deacetylase activity showed that PdaA could deacetylate peptidoglycan treated withN-acetylmuramoyl-l-alanine amidase CwlH but could not deacetylate peptidoglycan treated with or withoutdl-endopeptidase LytF (CwlE). Reverse-phase high-performance liquid chromatography and mass spectrometry (MS) and MS-MS analyses indicated that PdaA could deacetylate theN-acetylmuramic acid residues of purified glycan strands derived fromBacillus subtilispeptidoglycan.
Effects ofrecJ,recQ, andrecFORMutations on Recombination in Nuclease-DeficientrecB recDDouble Mutants ofEscherichia coli
Authors: Ivančić-Baće Ivana , Salaj-Šmic Erika , Brčić-Kostić Krunoslav
Published: February 2005

The two main recombination pathways inEscherichia coli(RecBCD and RecF) have different recombination machineries that act independently in the initiation of recombination. Three essential enzymatic activities are required for early recombinational processing of double-stranded DNA ends and breaks: a helicase, a 5′→3′ exonuclease, and loading of RecA protein onto single-stranded DNA tails. The RecBCD enzyme performs all of these activities, whereas the recombination machinery of the RecF pathway consists of RecQ (helicase), RecJ (5′→3′ exonuclease), and RecFOR (RecA-single-stranded DNA filament formation). The recombination pathway operating inrecB(nuclease-deficient) mutants is a hybrid because it includes elements of both the RecBCD and RecF recombination machineries. In this study, genetic analysis of recombination in arecB(nuclease-deficient)recDdouble mutant was performed. We show that conjugational recombination and DNA repair after UV and gamma irradiation in this mutant are highly dependent onrecJ, partially dependent onrecFOR, and independent ofrecQ. These results suggest that the recombination pathway operating in a nuclease-deficientrecB recDdouble mutant is also a hybrid. We propose that the helicase and RecA loading activities belong to the RecBCD recombination machinery, while the RecJ-mediated 5′→3′ exonuclease is an element of the RecF recombination machinery.
l
-Malyl-Coenzyme A/β-Methylmalyl-Coenzyme A Lyase Is Involved in Acetate Assimilation of the Isocitrate Lyase-Negative Bacterium
Rhodobacter capsulatus
Authors: Meister Michael , Saum Stephan , Alber Birgit E. , Fuchs Georg
Published: February 2005

Cell extracts of
Rhodobacter capsulatus
grown on acetate contained an apparent malate synthase activity but lacked isocitrate lyase activity. Therefore,
R. capsulatus
cannot use the glyoxylate cycle for acetate assimilation, and a different pathway must exist. It is shown that the apparent malate synthase activity is due to the combination of a malyl-coenzyme A (CoA) lyase and a malyl-CoA-hydrolyzing enzyme. Malyl-CoA lyase activity was 20-fold up-regulated in acetate-grown cells versus glucose-grown cells. Malyl-CoA lyase was purified 250-fold with a recovery of 6%. The enzyme catalyzed not only the reversible condensation of glyoxylate and acetyl-CoA to
l
-malyl-CoA but also the reversible condensation of glyoxylate and propionyl-CoA to β-methylmalyl-CoA. Enzyme activity was stimulated by divalent ions with preference for Mn
2+
and was inhibited by EDTA. The N-terminal amino acid sequence was determined, and a corresponding gene coding for a 34.2-kDa protein was identified and designated
mcl1
. The native molecular mass of the purified protein was 195 ± 20 kDa, indicating a homohexameric composition. A homologous
mcl1
gene was found in the genomes of the isocitrate lyase-negative bacteria
Rhodobacter sphaeroides
and
Rhodospirillum rubrum
in similar genomic environments. For
Streptomyces coelicolor
and
Methylobacterium extorquens
,
mcl1
homologs are located within gene clusters implicated in acetate metabolism. We therefore propose that
l
-malyl-CoA/β-methylmalyl-CoA lyase encoded by
mcl1
is involved in acetate assimilation by
R. capsulatus
and possibly other glyoxylate cycle-negative bacteria.
Substrate-Dependent Regulation of Anaerobic Degradation Pathways for Toluene and Ethylbenzene in a Denitrifying Bacterium, Strain EbN1
Authors: Kühner Simon , Wöhlbrand Lars , Fritz Ingo , Wruck Wasco , Hultschig Claus , Hufnagel Peter , Kube Michael , Reinhardt Richard , Rabus Ralf
Published: February 2005

Anaerobic biodegradation of toluene and ethylbenzene is of environmental concern and biochemical interest due to toxicity and novel reactions, respectively. The denitrifying strain EbN1 is unique in anaerobically degrading both alkylbenzenes via different pathways which converge at benzoyl coenzyme A. The organization of genes involved in both pathways was only recently determined for strain EbN1. In the present study, global expression analysis (DNA microarray and proteomics) indicated involvement of several thus-far-unknown proteins in the degradation of both alkylbenzenes. For example,
orf68
and
orf57
, framing the
ebd
operon, are implicated in ethylbenzene degradation, and the ebA1932 and ebA1936 genes, located 7.2 kb upstream of the
bbs
operon, are implicated in toluene degradation. In addition, expression studies were now possible on the level of the complete pathways. Growth experiments demonstrated that degradative capacities for toluene and ethylbenzene could be simultaneously induced, regardless of the substrate used for adaptation. Regulation was studied at the RNA (real-time reverse transcription-PCR and DNA microarray) and protein (two-dimensional-difference gel electrophoresis) level by using cells adapted to anaerobic growth with benzoate, toluene, ethylbenzene, or a mixture of toluene and ethylbenzene. Expression of the two toluene-related operons (
bss
and
bbs
) was specifically induced in toluene-adapted cells. In contrast, genes involved in anaerobic ethylbenzene degradation were induced in ethylbenzene- and toluene-adapted cells, suggesting that toluene may act as a gratuitous inducer. In agreement with the predicted sequential regulation of the ethylbenzene pathway, Ebd proteins (encoding subunits of ethylbenzene dehydrogenase) were formed in ethylbenzene- but not in acetophenone-adapted cells, while Apc proteins (subunits of predicted acetophenone carboxylase) were formed under both conditions.
Mutational Analysis of the Disulfide Catalysts DsbA and DsbB
Authors: Tan Jacqueline , Lu Ying , Bardwell James C. A.
Published: February 2005

In prokaryotes, disulfides are generated by the DsbA-DsbB system. DsbB functions to generate disulfides by quinone reduction. These disulfides are passed to the DsbA protein and then to folding proteins. To investigate the DsbA-DsbB catalytic system, we performed an in vivo selection for chromosomal
dsbA
and
dsbB
mutants. We rediscovered many residues previously shown to be important for the activity of these proteins. In addition, we obtained one novel DsbA mutant (M153R) and four novel DsbB mutants (L43P, H91Y, R133C, and L146R). We also mutated residues that are highly conserved within the DsbB family in an effort to identify residues important for DsbB function. We found classes of mutants that specifically affect the apparent

K
m

of DsbB for either DsbA or quinones, suggesting that quinone and DsbA may interact with different regions of the DsbB protein. Our results are consistent with the interpretation that the residues Q33 and Y46 of DsbB interact with DsbA, Q95 and R48 interact with quinones, and that residue M153 of DsbA interacts with DsbB. All of these interactions could be due to direct amino acid interactions or could be indirect through, for instance, their effect on protein structure. In addition, we find that the DsbB H91Y mutant severely affects the
k
cat
of the reaction between DsbA and DsbB and that the DsbB L43P mutant is inactive, suggesting that both L43 and H91 are important for the activity of DsbB. These experiments help to better define the residues important for the function of these two protein-folding catalysts.
Expression of
Pseudomonas aeruginosa aer
-
2
, One of Two Aerotaxis Transducer Genes, Is Controlled by RpoS
Authors: Hong Chang Soo , Kuroda Akio , Takiguchi Noboru , Ohtake Hisao , Kato Junichi
Published: February 2005

Pseudomonas aeruginosa
possesses two aerotaxis transducers, Aer and Aer-2. A deletion-insertion mutation of alternative sigma factor RpoS eliminated Aer-2-mediated aerotaxis but not Aer-mediated aerotaxis. Transcriptional analysis revealed that
cheY2
,
cheA2
,
cheW2
, and
aer
-
2
were expressed in an RpoS-dependent manner as a single transcript.
CAUSAL PERTURBATION THEORY IN TERMS OF RETARDED PRODUCTS, AND A PROOF OF THE ACTION WARD IDENTITY
Authors: DÜTSCH MICHAEL , FREDENHAGEN KLAUS
Published: January 2005

In the framework of perturbative algebraic quantum field theory a local construction of interacting fields in terms of retarded products is performed, based on earlier work of Steinmann [42]. In our formalism the entries of the retarded products are local functionals of the off-shell classical fields, and we prove that the interacting fields depend only on the action and not on terms in the Lagrangian which are total derivatives, thus providing a proof of Stora's "Action Ward Identity" [45]. The theory depends on free parameters which flow under the renormalization group. This flow can be derived in our local framework independently of the infrared behavior, as was first established by Hollands and Wald [32]. We explicitly compute non-trivial examples for the renormalization of the interaction and the field.
A MODEL FOR QUANTUM SYSTEMS OF TWO-BAND EIGENVALUE SPECTRUM
Authors: GRADO-CAFFARO M. A. , GRADO-CAFFARO M.
Published: February 2005

A matrix model to describe quantitatively certain physical properties of quantum systems of two-band eigenvalue spectrum is proposed. This formulation is a generalization of Wannier-type representations and is applicable to various situations where physical properties are defined in tensor form.
GEOMETRIC PHASE OF DICKE STATE OF EXCITONS IN N COUPLED QUANTUM DOTS
Authors: TONG D. M. , KWEK L. C. , COUTEAU CHRISTOPHE , OH C. H.
Published: February 2005

We investigate the nature of geometric phases generated by the evolution of the superposition of Dicke states of excitons in N coupled quantum dots. Based on a sequence of laser pulses, arbitrary superposition of the Dicke states of excitons can be generated. By properly choosing the superposition and using the controllable laser pulses, geometric phase with any expected value can be realized. The main advantage of using coupled quantum dots is that one uses a collective behavior, rather than addressing individually qubits, for instance, like with trapped ions configuration, which require a heavy setup in order to perform a gate.
SENSITIVITY ANALYSIS OF AN LCL-FILTER-BASED THREE-PHASE ACTIVE RECTIFIER VIA A "VIRTUAL CIRCUIT" APPROACH
Authors: BLAABJERG FREDE , CHIARANTONI ERNESTO , DELL'AQUILA ANTONIO , LISERRE MARCO , VERGURA SILVANO
Published: February 2005

Three-phase active rectifiers based on the voltage source converter topology can successfully replace traditional thyristor-based rectifiers or diode bridge plus chopper in interfacing dc-systems to the grid. However, if the application in which they are employed has a high safety issue or if there are other loads connected to the same Point of Common Coupling (PCC), and sensitive to the harmonics produced by the switching of the converter, an LCL-filter has to be used. This kind of solution has been studied in theory but its sensitivity to the value of the LCL-filter passive elements employed, to the grid side stiffness and to the parameters of the controller has never been considered in detail. In this paper the experimental results of an LCL-filter-based three-phase active rectifier are analyzed with the circuit theory approach. A "virtual circuit" is synthesized in role of the digital controller and of the feedback filters to have an homogenous model that allows a sensitivity analysis which is rigorous and straightforward for the industry.
EXPERIMENTAL VERIFICATION OF ACTIVE POWER CALCULATION IN NONSINUSOIDAL SINGLE PHASE CIRCUITS
Authors: MITEVA N. , SLONIM M. , BRAUNSTEIN A.
Published: February 2005

The active power in nonlinear single-phase circuit is measured by a new specially-developed experimental model. The experiments are carried out for sinusoidal and nonsinusoidal voltage and current waveforms. The results of the experiments show that the total active power is a sum of the active powers produced by the voltage and current harmonics with the same serial number.
SYNERGETIC CONTROL FOR POWER ELECTRONICS APPLICATIONS: A COMPARISON WITH THE SLIDING MODE APPROACH
Authors: SANTI E. , MONTI A. , LI D. , PRODDUTUR K. , DOUGAL R. A.
Published: February 2005

The theory of synergetic control was introduced in a power electronics context in a previous paper. In this paper we review the theory, then we focus on a comparison with the sliding mode approach. Common elements and main differences are underlined and illustrated through a comparative simulation example. The main advantages of synergetic control are that it is well-suited for digital implementation, it gives constant switching frequency operation, and it gives better control of the off-manifold dynamics. Finally, simulation and experimental results under transient conditions are compared. Advanced control laws with adaptation are presented and discussed to show how to better exploit the features of the synergetic control. The example used throughout the paper is the control of a boost converter operating in continuous conduction mode.
THE UNIFIED MODEL FOR CURRENT-MODE CONTROL: AN ALTERNATIVE DERIVATION
Authors: HONG SUNG-SOO , CHOI BYUNGCHO , AHN HYUN-SIK
Published: February 2005

The two prevalent s-domain models for current-mode control, the continuous-time model and the unified model, exhibit noticeable differences in their small-signal predictions and therefore have become the subject of comparisons and clarifications. The current letter presents an alternative way of deriving the unified model, thereby providing an additional guide for assessing the validity of the unified model. This letter also presents experimental data that support the accuracy of the unified model.
NEW TOPOLOGY FOR SOFT STARTING AND SPEED REGULATION OF WOUND ROTOR ASYNCHRONOUS MACHINE CONTROLLED BY MICROPROCESSOR
Authors: SHOIHET ARTHUR , SLONIM MICHAEL A.
Published: February 2005

A new topology for soft starting and speed regulation of wound rotor asynchronous machines is proposed. The feedback regulation is controlled by a microprocessor. A description of the microprocessor and its operation is presented. A theoretical analysis of the topology operation is carried out and verified by PSpice simulations. Experiments with 1.5 kW asynchronous machine are executed. Results of theoretical calculations, PSpice simulations and experiments are in good matching. The experimental investigations show that the proposed algorithm of soft starting is effective.
A NOVEL SPACE-VECTOR ALGORITHM FOR MULTILEVEL CONVERTERS BASED ON GEOMETRICAL CONSIDERATIONS USING A NEW SEQUENCE CONTROL TECHNIQUE
Authors: PRATS M. ÁNGELES MARTÍN , GALVÁN JOSE IGNACIO LEÓN , GUISADO RAMÓN PORTILLO , SOLÍS JUAN MANUEL CARRASCO , FRANQUELO LEOPOLDO GARCÍA
Published: February 2005

This paper presents a fast and simple space vector modulation algorithm for voltage source multilevel converters for calculating the switching times and the space vectors using simple geometrical considerations. This method provides the nearest switching vectors sequence to the reference vector and calculates the on-state durations of the respective switching state vectors without involving trigonometric functions, look-up tables or coordinate system transformations which increase the computational load corresponding to the modulation of a multilevel converter. The low computational cost of the proposed method is always the same and it is independent of the number of levels of the converter. In addition, a new switching sequence control technique is presented for reducing the ripple of the DC-link voltage approximately in 66%.
INVESTIGATION INTO AN ARTIFICIAL NEURAL NETWORK BASED FAULT IDENTIFICATION OF HVDC CONVERTER
Authors: BAWANE NARENDRA , KOTHARI A. G.
Published: February 2005

This paper explores the possibility of using neural network to identify faults that may occur in a HVDC converter system. Based on the ability of these networks to distinguish reliably between different types of faults, the feature can be suitably integrated with ANN based controller to improve the dynamic response of AC–DC power system. In this paper, different neural network architectures to distinguish different faults in HVDC converter are proposed, and comparison between them is made under different system perturbations and faults. The method is independent of the operating mode of the converter.
ANALYSIS AND DESIGN OF A QUASI-RESONANT FAST ON-LOAD TAP CHANGING REGULATOR
Authors: ECHAVARRÍA R. , SÁNCHEZ V. , PONCE M. , COTOROGEA M. , CLAUDIO A.
Published: February 2005

The main function of the on-load tap changing (OLTC) regulators consists of maintaining a constant voltage in order to feed critical loads despite the load changes or voltage changes in the ac mains. The traditional regulators are still used nowadays, but they present several disadvantages, like a slow response, which reaches from 100 ms to several seconds. These drawbacks can be overcome if the OLTC regulators would have shorter response time, commuting several times every cycle of the mains. There are two basic topologies for fast OLTC regulators. The first one consists of several taps and uses hard switching. The second one consists of two main switches commuting at high frequency, using soft-switching in order to reduce the power losses. The present topology is of the second type. This paper presents a mathematical model of the power stage of the proposed regulator. The model includes the parasitic resistances and the leakage inductances in order to obtain a better comprehension of the regulator operation. A parametric analysis has been done in order to observe the influence of the parasitic elements in the performance of the main parameters of the topology. The model is verified by experimental results obtained using a 500-W prototype.
SEQUENTIAL SUPPLY FOR ELECTRICAL TRANSPORTATION VEHICLES: PROPERTIES OF THE FAST ENERGY TRANSFER BETWEEN SUPERCAPACITIVE TANKS
Authors: RUFER ALFRED , BARRADE PHILIPPE , HOTELLIER DAVID , HAUSER SYLVAIN
Published: February 2005

A new feeding concept for electrical transportation systems is presented, based on supercapacitive energy storage. Supercapacitors are new and powerful components for energy storage. Compared with batteries, the amount of energy supercapacitors can store is low and does not allow large vehicle autonomy. Because supercapacitors have the property to be re-loadable in a few seconds, a sequential supply system has been developed, considering repetitive feeding at the stops. To solve the problem of the high power amount needed to reach short refill times, a solution is proposed, which consists of using an intermediary supercapacitive tank placed at fixed stations, which is refilled between the bus arrivals with a much lower power. In addition to the description of the needed power electronic converters, theoretical and experimental results are presented, defining the controlled profile of the instantaneous power level, in order to achieve a fast energy transfer between two supercapacitive tanks.
THE Hf-W ISOTOPIC SYSTEM AND THE ORIGIN OF THE EARTH AND MOON
Authors: Jacobsen Stein B.
Published: February 2005

▪ Abstract  The Earth has a radiogenic W-isotopic composition compared to chondrites, demonstrating that it formed while 182Hf (half-life 9 Myr) was extant in Earth and decaying to 182W. This implies that Earth underwent early and rapid accretion and core formation, with most of the accumulation occurring in ∼10 Myr, and concluding approximately 30 Myr after the origin of the Solar System. The Hf-W data for lunar samples can be reconciled with a major Moon-forming impact that terminated the terrestrial accretion process ∼30 Myr after the origin of the Solar System. The suggestion that the proto-Earth to impactor mass ratio was 7:3 and occurred during accretion is inconsistent with the W isotope data. The W isotope data is satisfactorily modeled with a Mars-sized impactor on proto-Earth (proto-Earth to impactor ratio of 9:1) to form the Moon at ∼30 Myr.
MOLECULAR PATHOPHYSIOLOGY OF PARKINSON'S DISEASE
Authors: Moore Darren J. , West Andrew B. , Dawson Valina L. , Dawson Ted M.
Published: January 2005

Parkinson's disease (PD) is a progressive neurodegenerative movement disorder that results primarily from the death of dopaminergic neurons in the substantia nigra. Although the etiology of PD is incompletely understood, the recent discovery of genes associated with rare monogenic forms of the disease, together with earlier studies and new experimental animal models, has provided important and novel insight into the molecular pathways involved in disease pathogenesis. Increasing evidence indicates that deficits in mitochondrial function, oxidative and nitrosative stress, the accumulation of aberrant or misfolded proteins, and ubiquitin-proteasome system dysfunction may represent the principal molecular pathways or events that commonly underlie the pathogenesis of sporadic and familial forms of PD .
PHYSIOLOGICAL FUNCTIONS OF CLC Cl−CHANNELS GLEANED FROM HUMAN GENETIC DISEASE AND MOUSE MODELS
Authors: Jentsch Thomas J. , Poët Mallorie , Fuhrmann Jens C. , Zdebik Anselm A.
Published: February 2005

▪ Abstract  The CLC gene family encodes nine different Cl− channels in mammals. These channels perform their functions in the plasma membrane or in intracellular organelles such as vesicles of the endosomal/lysosomal pathway or in synaptic vesicles. The elucidation of their cellular roles and their importance for the organism were greatly facilitated by mouse models and by human diseases caused by mutations in their respective genes. Human mutations in CLC channels are known to cause diseases as diverse as myotonia (muscle stiffness), Bartter syndrome (renal salt loss) with or without deafness, Dent's disease (proteinuria and kidney stones), osteopetrosis and neurodegeneration, and possibly epilepsy. Mouse models revealed blindness and infertility as further consequences of CLC gene disruptions. These phenotypes firmly established the roles CLC channels play in stabilizing the plasma membrane voltage in muscle and possibly in neurons, in the transport of salt and fluid across epithelia, in the acidification of endosomes and synaptic vesicles, and in the degradation of bone by osteoclasts.
Inclusion of low amounts of fructose with an intraportal glucose load increases net hepatic glucose uptake in the presence of relative insulin deficiency in dog
Authors: Shiota Masakazu , Galassetti Pietro , Igawa Kayano , Neal Doss W. , Cherrington Alan D.
Published: January 2005

The effect of small amounts of fructose on net hepatic glucose uptake (NHGU) during hyperglycemia was examined in the presence of insulinopenia in conscious 42-h fasted dogs. During the study, somatostatin (0.8 μg·kg−1·min−1) was given along with basal insulin (1.8 pmol·kg−1·min−1) and glucagon (0.5 ng·kg−1·min−1). After a control period, glucose (36.1 μmol·kg−1·min−1) was continuously given intraportally for 4 h with (2.2 μmol·kg−1·min−1) or without fructose. In the fructose group, the sinusoidal blood fructose level (nmol/ml) rose from <16 to 176 ± 11. The infusion of glucose alone (the control group) elevated arterial blood glucose (μmol/ml) from 4.3 ± 0.3 to 11.2 ± 0.6 during the first 2 h after which it remained at 11.6 ± 0.8. In the presence of fructose, glucose infusion elevated arterial blood glucose (μmol/ml) from 4.3 ± 0.2 to 7.4 ± 0.6 during the first 1 h after which it decreased to 6.1 ± 0.4 by 180 min. With glucose infusion, net hepatic glucose balance (μmol·kg−1·min−1) switched from output (8.9 ± 1.7 and 13.3 ± 2.8) to uptake (12.2 ± 4.4 and 29.4 ± 6.7) in the control and fructose groups, respectively. Average NHGU (μmol·kg−1·min−1) and fractional glucose extraction (%) during last 3 h of the test period were higher in the fructose group (30.6 ± 3.3 and 14.5 ± 1.4) than in the control group (15.0 ± 4.4 and 5.9 ± 1.8). Glucose 6-phosphate and glycogen content (μmol glucose/g) in the liver and glucose incorporation into hepatic glycogen (μmol glucose/g) were higher in the fructose (218 ± 2, 283 ± 25, and 109 ± 26, respectively) than in the control group (80 ± 8, 220 ± 31, and 41 ± 5, respectively). In conclusion, small amounts of fructose can markedly reduce hyperglycemia during intraportal glucose infusion by increasing NHGU even when insulin secretion is compromised.
Use of phospho-specific antibodies to determine the phosphorylation of endogenous Na+/H+ exchanger NHE3 at PKA consensus sites
Authors: Kocinsky Hetal S. , Girardi Adriana C. C. , Biemesderfer Daniel , Nguyen Thao , Mentone SueAnn , Orlowski John , Aronson Peter S.
Published: February 2005

Transfection studies using mutant constructs have implicated one or both protein kinase A (PKA) consensus phosphorylation sites [serines 552 and 605 in rat Na+/H+ exchanger type 3 (NHE3)] as critical for mediating inhibition of NHE3 in response to several stimuli including dopamine. However, whether one or both of these sites is actually phosphorylated in endogenous NHE3 in proximal tubule cells is unknown. The purpose of this study was to generate phosphospecific antibodies so that the state of phosphorylation of these serine residues in endogenous NHE3 could be assessed in vitro and in vivo. To this end, polyclonal and monoclonal phosphospecific peptide antibodies were generated against each PKA consensus site. Phosphospecificity was established by ELISA and Western blot assays. We then used these antibodies in vitro to evaluate the effect of dopamine on phosphorylation of the corresponding PKA sites (serines 560 and 613) in NHE3 endogenously expressed in opossum kidney cells. Baseline phosphorylation of both sites was detected that was significantly increased by dopamine. Next, we determined the baseline phosphorylation state of each serine in rat kidney NHE3 in vivo. We found that serine 552 of NHE3 is phosphorylated to a much greater extent than serine 605 at baseline in vivo. Moreover, we detected a distinct subcellular localization for NHE3 phosphorylated at serine 552 compared with total NHE3. Specifically, NHE3 phosphorylated at serine 552 localized to the coated pit region of the brush-border membrane, where NHE3 is inactive, while total NHE3 was found throughout the brush-border membrane. These findings strongly suggest that phosphorylation of NHE3 plays a role in its subcellular trafficking in vivo. In conclusion, we successfully generated phosphospecific antibodies that should be useful to assess the phosphorylation of endogenous NHE3 at its two PKA consensus sites under a variety of physiological conditions in vitro and in vivo.