bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation and resolution of ankylosis under application of recombinant human bone morphogenetic protein‐2 (rhBMP‐2) to class III furcation defects in cats
Authors: Takahashi D. , Odajima T. , Morita M. , Kawanami M. , Kato H.
Published: June 2005

Objectives:  Periodontal regeneration under application of bone morphogenetic protein (BMP) is compromised by ankylosis. Ankylosis disappearance following application of BMP has been observed in the case of a small defect, which might be beneficial change for periodontal regeneration. However, the histological observation of ankylosis disappearance has not been demonstrated in a large defect. The purpose of this present study was to confirm resolution of ankylosis during periodontal regeneration by recombinant human BMP‐2 (rhBMP‐2) applied to class III furcation defects.

Material and methods:  Class III furcation defects were created in the premolars of six adult cats. The rhBMP‐2 material, prepared by applying rhBMP‐2 to a combination of polylactic acid–polygricolic copolymer and gelatin sponge (PGS; 0.33 µg rhBMP‐2/mm3 PGS) or control material containing only PGS, was implanted into each defect. The cats were killed at 3, 6 or 12 weeks after surgery and serial sections were prepared for histological and histometrical observation.

Results:  Ankylosis was observed in some of the rhBMP‐2/PGS group at 3 and 6 weeks, but not at 12 weeks. At 6 weeks, osteoclast‐like cells were visible in the rhBMP‐2/PGS group with ankylosis. Residual PGS was evident between the bone and root surface in the rhBMP‐2/PGS group without ankylosis at 3 weeks.

Conclusions:  Resolution of ankylosis by osteoclast‐like cells possibly occurred under application of rhBMP‐2. Residual PGS might play an important role in preventing ankylosis formation.
Distinctive localization and function for lumican, fibromodulin and decorin to regulate collagen fibril organization in periodontal tissues
Authors: Matheson S. , Larjava H. , Häkkinen L.
Published: June 2005

Background:  Small leucine‐rich proteoglycans (SLRPs) decorin, biglycan, fibromodulin and lumican are secreted extracellular matrix molecules that associate with fibrillar collagens and regulate collagen fibrillogenesis. Collagens are the major extracellular matrix components of periodontal connective tissues where they provide mechanical attachment of the tooth to the bone and gingiva and mediate signals that regulate cell functions, including remodeling of the periodontal ligament and bone. Structural organization of collagen may also be important for the defense against periodontal disease, because in certain conditions abnormal collagen fibrils associate with increased susceptibility to periodontal disease.

Objectives:  The purpose of this study was to find out the role of SLRPs to regulate collagen fibril and fibril bundle formation in periodontal tissues.

Methods:  The localization of SLRPs in human and mouse periodontal tissues was studied using immunohistochemical methods. To assess the function of SLRPs we studied periodontal tissues of mice harboring targeted deletions of decorin, fibromodulin or lumican genes and lumican and fibromodulin double knockout mice using histological and electronmicroscopical methods.

Results:  The SLRPs were coexpressed in human and mouse gingival and periodontal ligament connective tissues where they colocalized with collagen fibril bundles. Teeth in the knockout animals were fully erupted and showed normal gross morphology. Targeted deletion of decorin, fibromodulin, lumican or both lumican and fibromodulin resulted in abnormal collagen fibril and fibril bundle morphology that was most evident in the periodontal ligament. Each of the gene deletions resulted in a unique fibril and fibril bundle phenotype.

Conclusions:  These findings indicate that decorin, fibromodulin and lumican coordinately regulate the fibrillar and suprafibrillar organization of collagen in the periodontal ligament.
Parenting Skills Training: An Effective Intervention for Internalizing Symptoms in Younger Children?
Authors: Cartwright‐Hatton Sam , McNally Deborah , White Caroline , Verduyn Chrissie
Published: June 2005

PROBLEM:  A number of interventions are effective in treating older children with internalizing symptoms. However, little is known about the efficacy of psychological interventions in treating younger children. This study examined the impact on internalizing symptoms of a parenting skills training program.

METHODS:  Forty‐three parents took part in a parenting skills training program. Externalizing and internalizing behaviors were measured before and after treatment and after a 6‐month period.

FINDINGS:  Externalizing symptoms fell after treatment. Interestingly, internalizing scores fell to an approximately equivalent degree.

CONCLUSIONS:  An intervention targeted towards parenting may be efficacious in the treatment of children's internalizing symptoms.
The Use of Selective Serotonin Reuptake Inhibitors in Children and Adolescents with Major Depression
Authors: Scahill Lawrence , Hamrin Vanya , Pachler Mary Ellen
Published: June 2005

TOPIC:  Recent warnings about suicidal thoughts and self‐injurious behavior in youth treated with selective serotonin reuptake inhibitors raise fundamental questions about the risk–benefit ratio of this class of medications.

METHODS:  Data from placebo‐controlled trials are used to elucidate the potential risks and benefits of the selective serotonin reuptake inhibitors (SSRIs) in children and adolescent with major depression. This analysis forms the basis of clinical recommendations.

SOURCES:  The review includes the six large‐scale, placebo‐controlled trials that have been published over the past decade. These data were augmented by information from regulatory hearings in 2003–2004 and selected open‐label reports.

CONCLUSIONS:  Emerging data from several clinical trials show that the SSRIs have modest effects on childhood depression. In addition, SSRI treatment may be associated with behavioral activation, self‐harm, and suicidal ideation. Appropriate use of SSRIs in children and adolescents requires careful diagnostic assessment, evaluation of co‐occurring conditions, and diligent monitoring, especially within the first weeks of treatment.
Homocysteine Toxicity inEscherichia coliIs Caused by a Perturbation of Branched-Chain Amino Acid Biosynthesis
Authors: Tuite Nina L. , Fraser Katy R. , O'Byrne Conor P.
Published: June 2005

InEscherichia colithe sulfur-containing amino acid homocysteine (Hcy) is the last intermediate on the methionine biosynthetic pathway. Supplementation of a glucose-based minimal medium with Hcy at concentrations greater than 0.2 mM causes the growth ofE. coliFrag1 to be inhibited. Supplementation of Hcy-treated cultures with combinations of branched-chain amino acids containing isoleucine or with isoleucine alone reversed the inhibitory effects of Hcy on growth. The last intermediate of the isoleucine biosynthetic pathway, α-keto-β-methylvalerate, could also alleviate the growth inhibition caused by Hcy. Analysis of amino acid pools in Hcy-treated cells revealed that alanine, valine, and glutamate levels are depleted. Isoleucine could reverse the effects of Hcy on the cytoplasmic pools of valine and alanine. Supplementation of the culture medium with alanine gave partial relief from the inhibitory effects of Hcy. Enzyme assays revealed that the first step of the isoleucine biosynthetic pathway, catalyzed by threonine deaminase, was sensitive to inhibition by Hcy. The gene encoding threonine deaminase,ilvA, was found to be transcribed at higher levels in the presence of Hcy. Overexpression of theilvAgene from a plasmid could overcome Hcy-mediated growth inhibition. Together, these data indicate that inE. coliHcy toxicity is caused by a perturbation of branched-chain amino acid biosynthesis that is caused, at least in part, by the inhibition of threonine deaminase.
DNA Binding-Uptake System: a Link between Cell-to-Cell Communication and Biofilm Formation
Authors: Petersen Fernanda C. , Tao Lin , Scheie Anne A.
Published: June 2005

DNA has recently been described as a major structural component of the extracellular matrix in biofilms. In streptococci, the competence-stimulating peptide (CSP) cell-to-cell signal is involved in competence for genetic transformation, biofilm formation, and autolysis. Among the genes regulated in response to the CSP are those involved in binding and uptake of extracellular DNA. We show in this study that a functional DNA binding-uptake system is involved in biofilm formation. AcomGBmutant ofStreptococcus mutansdeficient in DNA binding and uptake, but unaffected in signaling, showed reduced biofilm formation. During growth in the presence of DNase I, biofilm was reduced in the wild type to levels similar to those found with thecomGBmutant, suggesting that DNA plays an important role in the wild-type biofilm formation. We also showed that growth in the presence of synthetic CSP promoted significant release of DNA, with similar levels in the wild type and in thecomGBmutant. The importance of the DNA binding-uptake system in biofilm formation points to possible novel targets to fight infections.
Coupling of NAD+Biosynthesis and Nicotinamide Ribosyl Transport: Characterization of NadR Ribonucleotide Kinase Mutants ofHaemophilus influenzae
Authors: Merdanovic Melisa , Sauer Elizabeta , Reidl Joachim
Published: June 2005

Previously, we characterized a pathway necessary for the processing of NAD+and for uptake of nicotinamide riboside (NR) inHaemophilus influenzae. Here we report on the role of NadR, which is essential for NAD+utilization in this organism. Different NadR variants with a deleted ribonucleotide kinase domain or with a single amino acid change were characterized in vitro and in vivo with respect to cell viability, ribonucleotide kinase activity, and NR transport. The ribonucleotide kinase mutants were viable only in anadV+(nicotinamide phosphoribosyltransferase) background, indicating that the ribonucleotide kinase domain is essential for cell viability inH. influenzae. Mutations located in the Walker A and B motifs and the LID region resulted in deficiencies in both NR phosphorylation and NR uptake. The ribonucleotide kinase function of NadR was found to be feedback controlled by NAD+under in vitro conditions and by NAD+utilization in vivo. Taken together, our data demonstrate that the NR phosphorylation step is essential for both NR uptake across the inner membrane and NAD+synthesis and is also involved in controlling the NAD+biosynthesis rate.
Initiation and Synthesis of the
Streptococcus pneumoniae
Type 3 Capsule on a Phosphatidylglycerol Membrane Anchor
Authors: Cartee Robert T. , Forsee W. Thomas , Yother Janet
Published: June 2005

The type 3 synthase from
Streptococcus pneumoniae
is a processive β-glycosyltransferase that assembles the type 3 polysaccharide [3)-β-
d
-GlcUA-(1→4)-β-
d
-Glc-(1→] by a multicatalytic process. Polymer synthesis occurs via alternate additions of Glc and GlcUA onto the nonreducing end of the growing polysaccharide chain. In the presence of a single nucleotide sugar substrate, the type 3 synthase ejects its nascent polymer and also adds a single sugar onto a lipid acceptor. Following single sugar incorporation from either UDP-[
14
C]Glc or UDP-[
14
C]GlcUA, we found that phospholipase D digestion of the Glc-labeled lipid yielded a product larger than a monosaccharide, while digestion of the GlcUA-labeled lipid resulted in a product larger than a disaccharide. These data indicated that the lipid acceptor contained a headgroup and that the order of addition to the lipid acceptor was Glc followed by GlcUA. Higher-molecular-weight product synthesized in vitro was also sensitive to phospholipase D digestion, suggesting that the same lipid acceptor was being used for single sugar additions and for polymer formation. Mass spectral analysis of the anionic lipids of a type 3
S. pneumoniae
strain demonstrated the presence of glycosylated phosphatidylglycerol. This lipid was also observed in
Escherichia coli
strains expressing the recombinant type 3 synthase. The presence of the lipid primer in
S. pneumoniae
membranes explained both the ability of the synthase to reinitiate polysaccharide synthesis following ejection of its nascent chain and the association of newly synthesized polymer with the membrane. Unlike most
S. pneumoniae
capsular polysaccharides, the type 3 capsule is not covalently linked to the cell wall. The present data indicate that phosphatidylglycerol may anchor the type 3 polysaccharide to the cell membrane.
Phenylacetate Catabolism in
Rhodococcus
sp. Strain RHA1: a Central Pathway for Degradation of Aromatic Compounds
Authors: Navarro-Llorens Juana María , Patrauchan Marianna A. , Stewart Gordon R. , Davies Julian E. , Eltis Lindsay D. , Mohn William W.
Published: June 2005

In gram-negative bacteria, a pathway for aerobic degradation of phenylacetic acid (PAA) that proceeds via phenylacetyl-coenzyme A (CoA) and hydrolytic ring fission plays a central role in the degradation of a range of aromatic compounds. In contrast, the PAA pathway and its role are not well characterized in gram-positive bacteria. A cluster including 13
paa
genes encoding enzymes orthologous to those of gram-negative bacteria was identified on the chromosome of
Rhodococcus
sp. strain RHA1. These genes were transcribed during growth on PAA, with 11 of the genes apparently in an operon yielding a single transcript. Quantitative proteomic analyses revealed that at least 146 proteins were more than twice as abundant in PAA-grown cells of RHA1 than in pyruvate-grown cells. Of these proteins, 29 were identified, including 8 encoded by the
paa
genes. Knockout mutagenesis indicated that
paaN
, encoding a putative ring-opening enzyme, was essential for growth on PAA. However,
paaF
, encoding phenylacetyl-CoA ligase, and
paaR
, encoding a putative regulator, were not essential.
paaN
was also essential for growth of RHA1 on phenylacetaldehyde, phenylpyruvate, 4-phenylbutyrate, 2-phenylethanol, 2-phenylethylamine, and
l
-phenylalanine. In contrast, growth on 3-hydroxyphenylacetate, ethylbenzene, and styrene was unaffected. These results suggest that the range of substrates degraded via the PAA pathway in RHA1 is somewhat limited relative to the range in previously characterized gram-negative bacteria.
Characterization of Six Lipoproteins in the σERegulon
Authors: Onufryk Christina , Crouch Marie-Laure , Fang Ferric C. , Gross Carol A.
Published: June 2005

InEscherichia coli, σEregulon functions are required for envelope homeostasis during stress and are essential for viability under all growth conditions. TheE. coligenome encodes approximately 100 lipoproteins, and 6 of these are regulated by σE. Phenotypes associated with deletion of each of these lipoproteins are the subject of this report. One lipoprotein, YfiO, is essential for cellular viability. However, overexpression of this protein is not sufficient to alleviate the requirement of σEfor viability, suggesting that the σEregulon provides more than one essential function. The remaining five lipoproteins in the σEregulon are nonessential; cells are viable even when all five are removed simultaneously. Deletion of three nonessential lipoprotein genes (nlpB,yraP,ygfL) results in the exhibition of phenotypes that suggest they are important for maintenance of the integrity of the cell envelope. ΔnlpBcells are selectively sensitive to rifampin; ΔyraPcells are selectively sensitive to sodium dodecyl sulfate. Such selective sensitivity has not been previously reported. Both ΔyraPand ΔnlpBare synthetically lethal withsurA::Cm, which encodes a periplasmic chaperone and PPIase, suggesting that NlpB and YraP play roles in a periplasmic folding pathway that functions in parallel with that of SurA. Finally, the ΔyfgLmutant exhibits a broad range of envelope defects, including sensitivity to several membrane-impermeable agents, an altered outer membrane protein profile, synthetic lethality with bothsurA::Cmand ΔfkpA::Cmstrains, and sensitivity to a bactericidal permeability-increasing peptide. We suggest that this lipoprotein performs a very important but as-yet-unknown function in maintaining the integrity of the cell envelope.
Two NewSinorhizobium melilotiLysR-Type Transcriptional Regulators Required for Nodulation
Authors: Luo Li , Yao Shi-Yi , Becker Anke , Rüberg Silvia , Yu Guan-Qiao , Zhu Jia-Bi , Cheng Hai-Ping
Published: June 2005

The establishment of an effective nitrogen-fixing symbiosis betweenSinorhizobium melilotiand its legume host alfalfa (Medicago sativa) depends on the timely expression of nodulation genes that are controlled by LysR-type regulators. Ninety putative genes coding for LysR-type transcriptional regulators were identified in the recently sequencedS. melilotigenome. All 90 putativelysRgenes were mutagenized using plasmid insertions as a first step toward determining their roles in symbiosis. Two new LysR-type symbiosis regulator genes,lsrAandlsrB, were identified in the screening. Both thelsrAandlsrBgenes are expressed in free-livingS. meliloticells, but they are not required for cell growth. AnlsrA1mutant was defective in symbiosis and elicited only white nodules that exhibited no nitrogenase activity. Cells of thelsrA1mutant were recovered from the white nodules, suggesting that thelsrA1mutant was blocked early in nodulation. AnlsrB1mutant was deficient in symbiosis and elicited a mixture of pink and white nodules on alfalfa plants. These plants exhibited lower overall nitrogenase activity than plants inoculated with the wild-type strain, which is consistent with the fact that most of the alfalfa plants inoculated with thelsrB1mutant were short and yellow. Cells of thelsrB1mutant were recovered from both pink and white nodules, suggesting thatlsrB1mutants could be blocked at multiple points during nodulation. The identification of two new LysR-type symbiosis transcriptional regulators provides two new avenues for understanding the complexS. meliloti-alfalfa interactions which occur during symbiosis.
Analysis of Gene Islands Involved in Methanopterin-Linked C
1
Transfer Reactions Reveals New Functions and Provides Evolutionary Insights
Authors: Kalyuzhnaya Marina G. , Korotkova Natalia , Crowther Gregory , Marx Christopher J. , Lidstrom Mary E. , Chistoserdova Ludmila
Published: June 2005

In this study, the occurrence and chromosomal clustering of genes encoding C
1
transfer reactions linked to tetrahydromethanopterin (H
4
MPT) were analyzed in a variety of proteobacteria and in representatives of the
Planctomycetes
via genomic analysis or via partial sequencing by cosmid walking. Although a tendency for clustering was found common for the genes of interest, significant variations in gene order and the degree of clustering were uncovered both between and within different groups of
Proteobacteria
and between
Proteobacteria
and
Planctomycetes
. Phylogenetic analyses suggested that the evolution of genes encoding H
4
MPT-linked reactions in
Proteobacteria
involved lateral transfers within
Proteobacteria
and possibly between
Proteobacteria
and other phyla. Gene cluster comparisons revealed a number of novel genes potentially involved in the C
1
transfer reactions, and these were analyzed by mutation and expression analyses. Four genes, a homolog of
pabB
, and three genes conserved between methanogenic
Archaea
and
Bacteria
possessing H
4
MPT-linked functions,
orfY
,
orf1
, and
afpA
were shown to be involved in formaldehyde oxidation/detoxification, as judged by specific mutant phenotypes. In particular,
pabB
contributes to the biosynthesis of
para
-aminobenzoic acid, a precursor of both tetrahydrofolate and H
4
MPT, and
afpA
apparently encodes a novel dihydromethanopterin reductase, based on mutant complementation experiments.
Complete Genome Sequence and Analysis of the Multiresistant Nosocomial PathogenCorynebacterium jeikeiumK411, a Lipid-Requiring Bacterium of the Human Skin Flora
Authors: Tauch Andreas , Kaiser Olaf , Hain Torsten , Goesmann Alexander , Weisshaar Bernd , Albersmeier Andreas , Bekel Thomas , Bischoff Nicole , Brune Iris , Chakraborty Trinad , Kalinowski Jörn , Meyer Folker , Rupp Oliver , Schneiker Susanne , Viehoever Prisca , Pühler Alfred
Published: June 2005

Corynebacterium jeikeiumis a “lipophilic” and multidrug-resistant bacterial species of the human skin flora that has been recognized with increasing frequency as a serious nosocomial pathogen. Here we report the genome sequence of the clinical isolateC. jeikeiumK411, which was initially recovered from the axilla of a bone marrow transplant patient. The genome ofC. jeikeiumK411 consists of a circular chromosome of 2,462,499 bp and the 14,323-bp bacteriocin-producing plasmid pKW4. The chromosome ofC. jeikeiumK411 contains 2,104 predicted coding sequences, 52% of which were considered to be orthologous with genes in theCorynebacterium glutamicum,Corynebacterium efficiens, andCorynebacterium diphtheriaegenomes. These genes apparently represent the chromosomal backbone that is conserved between the four corynebacteria. Among the genes that lack an ortholog in the known corynebacterial genomes, many are located close to transposable elements or revealed an atypical G+C content, indicating that horizontal gene transfer played an important role in the acquisition of genes involved in iron and manganese homeostasis, in multidrug resistance, in bacterium-host interaction, and in virulence. Metabolic analyses of the genome sequence indicated that the “lipophilic” phenotype ofC. jeikeiummost likely originates from the absence of fatty acid synthase and thus represents a fatty acid auxotrophy. Accordingly, both the complete gene repertoire and the deduced lifestyle ofC. jeikeiumK411 largely reflect the strict dependence of growth on the presence of exogenous fatty acids. The predicted virulence factors ofC. jeikeiumK411 are apparently involved in ensuring the availability of exogenous fatty acids by damaging the host tissue.
The
Helicobacter pylori
CrdRS Two-Component Regulation System (HP1364/HP1365) Is Required for Copper-Mediated Induction of the Copper Resistance Determinant CrdA
Authors: Waidner Barbara , Melchers Klaus , Stähler Frank Nils , Kist Manfred , Bereswill Stefan
Published: June 2005

Here we describe that the
Helicobacter pylori
sensor kinase produced by HP1364 and the response regulator produced by HP1365 and designated CrdS and CrdR, respectively, are both required for transcriptional induction of the
H. pylori
copper resistance determinant CrdA by copper ions. CrdRS-deficient mutants lacked copper induction of
crdA
expression and were copper sensitive. A direct role of CrdR in transcriptional regulation of
crdA
was confirmed by in vitro binding of CrdR to the
crdA
upstream region. A 21-nucleotide sequence located near the
crdA
promoter was shown to be required for CrdR binding.
A study of the dielectric properties of PZT and PT ceramics depending on the lattice distortion
Authors: Zhang Duan -Ming , Han Xiang -Yun , Li Zhi -Hua , Zhong Zhi -Cheng , Yan Wen -Sheng , Sun Hong -Zhang , Yang Feng -Xia , Zheng Ke -Yu , Wei Nian
Published: June 2005

Depending on the lattice distortion, the dielectric properties of PZT and PT ceramics are studied from a structural phase transition point of view. The study involves a more profound physical process than the study of the relation between the dielectric properties and composition x. Two equations connecting the dielectric properties and the lattice distortions are established in the tetragonal and rhombohedral phase regions. In particular, the relation between the dielectric properties and the lattice distortion is investigated in the phase coexistence region of PZT ceramics using a phase statistical distribution model, and we determine the fitting value of the volume fraction of the tetragonal phase VT to composition x in the equation. All the fitting results indicate that our results are very consistent with the related experimental data for PZT and PT ceramics.PACS Nos.: 64.70.p, 77.22.d, 77.84.s
Principal-value integrals  Revisited
Authors: Cohen Scott M , Davies K TR , Davies R W , Lee M Howard
Published: June 2005

The principal-value (PV) integral has proved a useful tool in many fields of physics. The PV is a specific method for obtaining a finite result for an improper integral. When the integration passes through a simple pole, one speaks of a "first-order" PV. In this paper, we examine first-order PV integrals and analyze several of their important properties. First, we discuss how the PV agrees with one's naïve expectation about these integrals. Next, we show that the basic definition of the first-order PV gives a generalized formula for the complex-variable PV expression. Finally, we show the correspondence between the finite-limit PV integral of x1 along the real axis and the path integral of z1 (where z = x + iy) in the complex plane.PACS Nos.: 02.90.+p, 05.90.+m
The dynamics of brane-world cosmological models
Authors: Coley A A
Published: June 2005

Brane-world cosmology is motivated by recent developments in string/M-theory and offers a new perspective on the hierarchy problem. In the brane-world scenario, our Universe is a four-dimensional subspace or brane embedded in a higher-dimensional bulk spacetime. Ordinary matter fields are confined to the brane while the gravitational field can also propagate in the bulk, and it is not necessary for the extra dimensions to be small, or even compact, leading to modifications of Einstein's theory of general relativity at high energies. In particular, the RandallSundrum-type models are relatively simple phenomenological models that capture some of the essential features of the dimensional reduction of eleven-dimensional supergravity introduced by Hořava and Witten. These curved (or warped) models are self-consistent and simple and allow for an investigation of the essential nonlinear gravitational dynamics. The governing field equations induced on the brane differ from the general relativistic equations in that there are nonlocal effects from the free gravitational field in the bulk, transmitted via the projection of the bulk Weyl tensor, and the local quadratic energy-momentum corrections, which are significant in the high-energy regime close to the initial singularity. In this review, we investigate the dynamics of the five-dimensional warped RandallSundrum brane worlds and their generalizations, with particular emphasis on whether the currently observed high degree of homogeneity and isotropy can be explained. In particular, we discuss the asymptotic dynamical evolution of spatially homogeneous brane-world cosmological models containing both a perfect fluid and a scalar field close to the initial singularity. Using dynamical systems techniques, it is found that, for models with a physically relevant equation of state, an isotropic singularity is a past-attractor in all orthogonal spatially homogeneous models (including Bianchi type IX models). In addition, we describe the dynamics in a class of inhomogeneous brane-world models, and show that these models also have an isotropic initial singularity. These results provide support for the conjecture that typically the initial cosmological singularity is isotropic in brane-world cosmology. Consequently, we argue that, unlike the situation in general relativity, brane-world cosmological models may offer a plausible solution to the initial conditions problem in cosmology. PACS Nos.: 98.89.Cq/Jk, 04.20q
Short-term effects of fire and forest thinning on truffle abundance and consumption byNeotamias speciosusin the Sierra Nevada of California
Authors: Meyer Marc D , North Malcolm P , Kelt Douglas A
Published: June 2005

In many western North American forests, prescribed burning and mechanical thinning are widely used to reduce fuels and restore stand conditions after a century of fire suppression. Few studies have followed the relative impacts of these treatments on the production and consumption of truffles in forest ecosystems, particularly in the Sierra Nevada of California. Using a full-factorial completely randomized design, we examined the short-term impacts of prescribed burning (no burn and burn), mechanical thinning (no thin, light thin, and heavy thin), and combinations of these treatments on the production of truffles and their consumption by lodgepole chipmunks (Neotamias speciosus Merriam) in a mixed-conifer forest of the southern Sierra Nevada of California. Truffle frequency, biomass, and species richness were lower in thinned or burned plots than controls, as was the frequency and generic richness of truffles in the diet of N. speciosus. Truffle frequency, biomass, and species richness, and truffle consumption by N. speciosus were lower in heavily thinned and thinned and burned plots than in those exclusively burned. These results suggest that either thinning or burning can reduce short-term truffle production and consumption, and potentially the dispersal of ectomycorrhizal spores by small mammals. Moreover, truffles decreased with treatment intensity, suggesting heavy thinning and higher burn intensity, particularly when applied together, can significantly affect short-term truffle abundance and small mammal consumption.
Somatic embryogenesis for plant production of Abies lasiocarpa
Authors: Kvaalen Harald , Daehlen Ola Gram , Rognstad Anne Tove , Grønstad Borgny , Egertsdotter Ulrika
Published: June 2005

Seeds of Abies lasiocarpa (Hook.) Nutt. (subalpine fir) were dissected, and the different parts were analyzed for elemental composition. The data were used to design a novel growth medium for initiation of somatic embryogenesis. Embryogenic cultures were initiated from immature zygotic embryos from six open-pollinated families of A. lasiocarpa on three different media. The frequency of initiation was the highest in early to mid-July when the zygotic embryo explants were ca. 0.8 mm long. Thereafter the response declined rapidly. The culture media did not significantly affect the initiation frequencies, but the subsequent growth and culture survival was dependent on the culture medium. On the Schenk Hildebrandt medium, many cultures ceased to grow and died. Several of the decaying cultures were rescued after transfer to one of the new media. Proliferating cultures could be stimulated to produce mature embryos. Of 2510 mature somatic embryos, 212 (8.4%) converted to plants, and 35 plants have grown over two periods.
Sapwood area  leaf area relationships for coast redwood
Authors: Stancioiu Petru Tudor , O'Hara Kevin L
Published: June 2005

Coast redwood (Sequoia sempervirens (D. Don) Endl.) trees in different canopy strata and crown positions were sampled to develop relationships between sapwood cross-sectional area and projected leaf area. Sampling occurred during the summers of 2000 and 2001 and covered tree heights ranging from 7.7 to 45.2 m and diameters at breast height ranging from 9.4 to 92.7 cm. Foliage morphology varied greatly and was stratified into five types based on needle type (sun or shade) and twig color. A strong linear relationship existed between projected leaf area and sapwood area at breast height or sapwood at the base of the live crown despite the variability in foliage morphology. Ratios of leaf area to sapwood were 0.40 m2/cm2 at breast height and 0.57 m2/cm2 at crown base. Measurements of sapwood at the base of the live crown improved leaf area predictions because of sapwood taper below the crown base. A sapwood taper model was also developed.
Radial growth impact of pine false webworm defoliation on eastern white pine
Authors: Mayfield III Albert E , Allen Douglas C , Briggs Russell D
Published: June 2005

The impact of pine false webworm (Acantholyda erythrocephala (L.), Hymenoptera: Pamphiliidae) defoliation on the radial growth of mature eastern white pine (Pinus strobus L.) during an outbreak was assessed using a stem analysis comparison of two stands (defoliated vs. control) and increment cores collected from 21 defoliated stands and 5 control stands in northern New York State. Stem analysis revealed that whole-stem standardized annual volume increment (AVI) in a defoliated 67-year-old white pine stand (n = 10 sample trees) was reduced significantly below the AVI in the nondefoliated control stand (n = 8 sample trees) by the second year of moderate to heavy defoliation, and AVI was reduced by 97% by the fifth year of defoliation. No time lag between upper-bole and lower-bole impact was observed, and annual growth rings were more frequently missing or discontinuous at lower stem heights. The standardized latewood tracheid index was not reduced significantly below control stand levels until the third year of defoliation. Increment-core analysis revealed growth losses that corresponded with reported periods of defoliation in nearly all stands; sustained suppressions (516 continuous years) below a growth index of 0.5 occurred in over half of all defoliated stands. These results are discussed in relation to pine false webworm biology, comparisons with other conifer defoliators, environmental factors, and methods employed.
Provisional breeding zone determination modeled as a maximal covering location problem
Authors: Crowe Kevin A , Parker William H
Published: June 2005

This study was a first attempt to model the problem of delineating breeding zones as a maximal covering location problem. The method involves two steps. First, a comprehensive set of candidate breeding zones is generated for a region using the focal point seed zone method. This method allows for control over the adaptive difference of genetic material within each zone. A grid of points is used to create the set of candidate breeding zones: one zone per point. Next, candidate zones are entered into a maximal covering location model formulated to suit this problem. The objective of this model is to select a subset of candidate zones that maximally covers the area of the region, given a limit on the number of zones to be selected and on the adaptive dissimilarity allowed within zones. Through use of this method, decision-makers can gain insight into how many breeding zones are needed to cover the region. Using different inputs from the focal point seed zone method, it is also possible to explore the trade-offs between the quantity and the quality of breeding zones. The method was tested on data from a series of jack pine (Pinus banksiana Lamb.) common garden trials of 102 seed sources from northwestern Ontario.
In situ molecular detection of some white-rot and brown-rot basidiomycetes infecting temperate and tropical woods
Authors: Zaremski Alba , Ducousso Marc , Domergue Odile , Fardoux Joel , Rangin Cécile , Fouquet Daniel , Joly Hélène , Sales Christian , Dreyfus Bernard , Prin Yves
Published: June 2005

Wood-decay white-rot and brown-rot fungi have a major economic impact on commercial and manufactured tropical and temperate woods. The aim of this study was to design a molecular method, coupled with polymerase chain reaction (PCR) and DNA sequencing, to enable early identification of various forms of fungal decay in various types of wood. The resulting tool could be used to certify the healthiness of commercial woods and also to make more efficient use of chemicals and thus reduce their negative environmental impact. Sapwood plates of Distemonanthus benthamianus,Fagus sylvatica, Lophira alata, Pinus sylvestris, and Pycnanthus angolensis were incubated in vitro in the presence of Fibroporia vaillantii, Coniophora puteana, Gloeophyllum trabeum, Pycnoporus sanguineus, and Trametes versicolor according to the EN 113 standard method. Average mass losses ranging from 2.6% to 25.0% indicated that all wood samples had been actually infected and enabled us to test the reliability of our method. PCR products were obtained in 24 of 25 combinations, and DNA sequences were obtained in 21 of the 24 fungal PCR products. DNA sequences obtained from infected wood were compared with sequences from pure strains, thus confirming the identity of the infecting strains with 100% similarity for an average of 412 bp.
POTTS-LIKE MODEL FOR GHETTO FORMATION IN MULTI-CULTURAL SOCIETIES
Authors: SCHULZE CHRISTIAN
Published: June 2005

In a Potts-like model of Q ethnic groups, we follow Schelling1 and Meyer-Ortmanns2 and simulate the formation of ethnic ghettos as well as their prevention by an increasing social temperature.
DISCRETE SCALE INVARIANCE IN THE CASCADE HEART RATE VARIABILITY OF HEALTHY HUMANS
Authors: LIN D. C.
Published: June 2005

Evidence of discrete scale invariance (DSI) in daytime healthy heart rate variability (HRV) is presented based on the log-periodic power law scaling of the heart beat interval increment. Our analysis suggests multiple DSI groups and a dynamic cascading process. A cascade model is presented to simulate such a property.
AN EFFICIENT IMPLICIT MESH-FREE METHOD TO SOLVE TWO-DIMENSIONAL COMPRESSIBLE EULER EQUATIONS
Authors: CHEN H. Q. , SHU C.
Published: June 2005

Local radial basis function-based differential quadrature (RBF-DQ) method is a natural mesh-free approach, in which any derivative of a function at a point is approximated by a weighted linear sum of functional values at its surrounding scattered points. In this paper, the weighting coefficients in the spatial derivative approximation of the Euler equation are determined by using a weighted least-square procedure in the frame of RBFs, which enhances the flexibility of distributing points in the computational domain. An upwind method is further introduced to cope with discontinuities by using Roe's approximate Riemann solver for estimation of the inviscid flux on the virtual mid-point between the reference knot and its surrounding knot. The lower–upper symmetric Gauss–Seidel (LU-SGS) algorithm, which is implemented in a matrix-free form like the one used in the finite-volume method, is introduced in the work to speed up the convergence. The proposed approach is validated by its application to simulate transonic flows over a NACA 0012 airfoil. It was found that the present mesh-free results agree very well with available data in the literature, and the implicit LU-SGS algorithm can greatly save the computational time as compared with explicit time marching methods.
The Adequacy of Stellar Evolution Models for the Interpretation of the Color-Magnitude Diagrams of Resolved Stellar Populations
Authors: Gallart C. , Zoccali M. , Aparicio A.
Published: June 2005

▪ Abstract  Most of what we know about the stellar population of nearby, resolved galaxies comes from the interpretation of their color-magnitude diagrams, by comparison with stellar evolutionary models. We review how well current stellar evolution models reproduce the properties of simple stellar populations. Emphasis is given to the regions of the color-magnitude diagram which are most useful for deriving age, metallicity, or distance of a population. Extensive comparison is made between the predictions of the most-used stellar evolution libraries, in order to estimate how model dependent the results are. The present review, written from a user perspective, aims at emphasizing the strengths and weaknesses of the models, and is intended both for observers and theoreticians. We hope to encourage observers to provide stronger observational constraints where they are needed, and to stimulate theoreticians to isolate the input physics responsible for the different behavior between models and the reasons for the discrepancies with data.
THE GENETICS OF THE PERSISTENT INFECTION AND DEMYELINATING DISEASE CAUSED BY THEILER'S VIRUS
Authors: Brahic Michel , Bureau Jean-François , Michiels Thomas
Published: June 2005

Theiler's virus causes a persistent and demyelinating infection of the central nervous system of the mouse, which is one of the best animal models to study multiple sclerosis. This review focuses on the mechanism of persistence. The virus infects neurons for a few weeks and then shifts to white matter, where it persists in glial cells and macrophages. Oligodendrocytes are crucial host cells, as shown by the resistance to persistent infection of mice bearing myelin mutations. Two viral proteins, L and L*, contribute to persistence by interfering with host defenses. L, a small zinc-finger protein, restricts the production of interferon. L*, a unique example of a picornaviral protein translated from an overlapping open reading frame, facilitates the infection of macrophages. Susceptibility to persistent infection, which varies among inbred mouse strains, is multigenic. H2 class I genes have a major effect on susceptibility. Among several non-H2 susceptibility loci, Tmevp3 appears to regulate the expression of important cytokines.
Tetrahydrobiopterin correctsEscherichia coliendotoxin-induced endothelial dysfunction
Authors: Mittermayer Friedrich , Pleiner Johannes , Schaller Georg , Zorn Stefan , Namiranian Khodadad , Kapiotis Stylianos , Bartel Gregor , Wolfrum Mathias , Brügel Mathias , Thiery Joachim , MacAllister Raymond J. , Wolzt Michael
Published: June 2005

Acute inflammation causes endothelial dysfunction, which is partly mediated by oxidant stress and inactivation of nitric oxide. The contribution of depletion of tetrahydrobiopterin (BH4), the cofactor required for nitric oxide generation, is unclear. In this randomized, double-blind, three-way crossover study, forearm blood flow (FBF) responses to ACh and glyceryltrinitrate (GTN) were measured before and 3.5 h after infusion of Escherichia coli endotoxin (LPS, 20 IU/kg iv) in eight healthy men. The effect of intra-arterial BH4(500 μg/min), placebo, or vitamin C (24 mg/min) was studied on separate days 3.5 h after LPS infusion. In addition, human umbilical vein endothelial cells were incubated for 24 h with vitamin C and LPS. ACh and GTN caused dose-dependent forearm vasodilation. The FBF response to ACh, which was decreased by 23 ± 17% ( P < 0.05) by LPS infusion, was restored to baseline reactivity by BH4and vitamin C. FBF responses to GTN were not affected by BH4or vitamin C. LPS increased leukocyte count, high-sensitivity C-reactive protein, IL-6, IL-1β, IFN-γ, monocyte chemoattractant protein-1, pulse rate, and body temperature and decreased platelet count and vitamin C concentration. Vitamin C increased forearm plasma concentration of BH4by 32% ( P < 0.02). Incubation with LPS and vitamin C, but not LPS alone, increased intracellular BH4concentration in human umbilical vein endothelial cells. Impaired endothelial function during acute inflammation can be restored by BH4or vitamin C. Vitamin C may exert some of its salutary effects by increasing BH4concentration.
Atrial natriuretic peptide induces shedding of endothelial glycocalyx in coronary vascular bed of guinea pig hearts
Authors: Bruegger Dirk , Jacob Matthias , Rehm Markus , Loetsch Michael , Welsch Ulrich , Conzen Peter , Becker Bernhard Friedrich
Published: June 2005

Atrial natriuretic peptide (ANP) is reported to enhance vascular permeability in vivo. Our aim was to evaluate the impact of ANP on coronary extravasation of fluids and macromolecules and on the integrity of the endothelial glycocalyx. Isolated guinea pig hearts ( n = 6/group) were perfused with Krebs-Henseleit buffer in a Langendorff mode. A 6% hydroxyethyl starch (HES) solution was infused into the coronary system for 20 min without (Control group) and simultaneously with (ANP group) ANP at 10−9 M. In two further series, the glycocalyx was enzymatically degraded by means of heparinase (Hep) application (10 IU over 15 min), followed again by the infusion of HES in the absence (Hep group) and presence (ANP+Hep group) of ANP. Net fluid filtration, extravasation of HES, electron microscopic visualization of the glycocalyx, and quantification of shedding of syndecan-1, a component of the glycocalyx, were determined. An increase in fluid leak was observed in ANP, ANP+Hep, and Hep hearts [+29%, +31%, +14%, respectively; a decrease was observed in Control hearts (−13%)]. Similarly, an accelerated extravasation of colloid was observed in these three groups. Coronary release of syndecan-1 increased 9- to 18-fold during infusion of ANP. Electron microscopy revealed a dramatic degradation of the glycocalyx after ANP. These results indicate that the endothelial glycocalyx serves as a barrier to transmural exchange of fluid and colloid in the coronary vascular system. ANP causes rapid shedding of individual components of the glycocalyx and histologically detectable degradation. Thus the permeability-increasing effect of ANP may be at least partially related to changes in the integrity of the endothelial glycocalyx.
Three-dimensional systolic kinematics of the right ventricle
Authors: Haber Idith , Metaxas Dimitris N. , Geva Tal , Axel Leon
Published: June 2005

The right ventricle (RV) of the heart is responsible for pumping blood to the lungs. Its kinematics are not as well understood as that of the left ventricle (LV) due to its thin wall and asymmetric geometry. In this study, the combination of tagged MRI and three-dimensional (3-D) image-processing techniques was used to reconstruct 3-D RV-LV motion and deformation. The reconstructed models were used to quantify the 3-D global and local deformation of the ventricles in a set of normal subjects. When compared with the LV, the RV exhibited a similar twisting pattern, a more longitudinal strain pattern, and a greater amount of displacement.
Nitric oxide increases carbon monoxide production by piglet cerebral microvessels
Authors: Leffler Charles W. , Balabanova Liliya , Fedinec Alexander L. , Parfenova Helena
Published: June 2005

Carbon monoxide (CO) and nitric oxide (NO) can be involved in the regulation of cerebral circulation. Inhibition of production of either one of these gaseous intercellular messengers inhibits newborn pig cerebral arteriolar dilation to the excitatory amino acid glutamate. Glutamate can increase NO production. Therefore, the present study tests the hypothesis that NO, which is increased by glutamate, stimulates the production of CO by cerebral microvessels. Experiments used freshly isolated cerebral microvessels from piglets that express only heme oxygenase-2 (HO-2). CO production was measured by gas chromatography-mass spectrometry. Although inhibition of nitric oxide synthase (NOS) with Nω-nitro-l-arginine (l-NNA) did not alter basal HO-2 catalytic activity or CO production, l-NNA blocked glutamate stimulation of HO-2 activity and CO production. Furthermore, the NO donor sodium nitroprusside mimicked the actions of glutamate on HO-2 and CO production. The action of NO appears to be via cGMP because 8-bromo-cGMP mimics and 1 H-[1,2,4]oxadiazole-[4,3- a]quinoxalin-1-one (ODQ) blocks glutamate stimulation of CO production and HO-2 catalytic activity. Inhibitors of neither casein kinase nor phosphotidylinositol 3-kinase altered HO-2 catalytic activity. Conversely, inhibition of calmodulin with calmidazolium chloride blocked glutamate stimulation of CO production and reduced HO-2 catalytic activity. These data suggest that glutamate may activate NOS producing NO that leads to CO synthesis via a cGMP-dependent elevation of HO-2 catalytic activity. These results are consistent with the findings in vivo that either HO or NOS inhibition blocks cerebrovascular dilation to glutamate in piglets.