bluuebunny/crossref_metadata_2025 huggingface dataset:
Complete Genome Sequence of the Oral Pathogenic Bacterium
Porphyromonas gingivalis
Strain W83
Authors: Nelson Karen E. , Fleischmann Robert D. , DeBoy Robert T. , Paulsen Ian T. , Fouts Derrick E. , Eisen Jonathan A. , Daugherty Sean C. , Dodson Robert J. , Durkin A. Scott , Gwinn Michelle , Haft Daniel H. , Kolonay James F. , Nelson William C. , Mason Tanya , Tallon Luke , Gray Jessica , Granger David , Tettelin Hervé , Dong Hong , Galvin Jamie L. , Duncan Margaret J. , Dewhirst Floyd E. , Fraser Claire M.
Published: August 2003

The complete 2,343,479-bp genome sequence of the gram-negative, pathogenic oral bacterium
Porphyromonas gingivalis
strain W83, a major contributor to periodontal disease, was determined. Whole-genome comparative analysis with other available complete genome sequences confirms the close relationship between the
Cytophaga-Flavobacteria-Bacteroides
(CFB) phylum and the green-sulfur bacteria. Within the CFB phyla, the genomes most similar to that of
P. gingivalis
are those of
Bacteroides thetaiotaomicron
and
B. fragilis
. Outside of the CFB phyla the most similar genome to
P. gingivalis
is that of
Chlorobium tepidum
, supporting the previous phylogenetic studies that indicated that the
Chlorobia
and CFB phyla are related, albeit distantly. Genome analysis of strain W83 reveals a range of pathways and virulence determinants that relate to the novel biology of this oral pathogen. Among these determinants are at least six putative hemagglutinin-like genes and 36 previously unidentified peptidases. Genome analysis also reveals that
P. gingivalis
can metabolize a range of amino acids and generate a number of metabolic end products that are toxic to the human host or human gingival tissue and contribute to the development of periodontal disease.
Disparate Oxygen Responsiveness of Two Regulatory Cascades That Control Expression of Symbiotic Genes in
Bradyrhizobium japonicum
Authors: Sciotti Michel-Angelo , Chanfon Astrid , Hennecke Hauke , Fischer Hans-Martin
Published: August 2003

Two oxygen-responsive regulatory systems controlling numerous symbiotic genes in
Bradyrhizobium japonicum
were assayed in free-living cultures for their capacity to activate target genes under different oxygen conditions. NifA- and FixLJ-controlled target genes showed disparate relative expression patterns. Induction of NifA-dependent genes was observed only at oxygen concentrations below 2% in the gas phase, whereas that of FixLJ-controlled targets progressively increased when the oxygen concentration was lowered from 21 to 5, 2, or 0.5%. We propose that this reflects a response to a gradient of increasing oxygen deprivation as bacteria invade their host during root nodule development.
The Vpu Protein of Human Immunodeficiency Virus Type 1 Plays a Protective Role against Virus-Induced Apoptosis in Primary CD4+T Lymphocytes
Authors: Komoto Satoshi , Tsuji Shoutaro , Ibrahim Madiha S. , Li Yong-Gang , Warachit Jiranan , Taniguchi Koki , Ikuta Kazuyoshi
Published: September 2003

Previous data revealed that primary cultures of peripheral blood mononuclear cells (PBMCs) were killed by apoptosis at higher rates after infection with two CRF01_AE primary isolates of human immunodeficiency virus type 1 (HIV-1) than after infection with five other CRF01_AE primary isolates, five subtype B primary isolates, and two subtype B laboratory strains. Here, we show evidence that mutations at thevpugene which were exclusively identified only in the two CRF01_AE isolates mentioned above are involved in their abilities to induce massive apoptosis in primary CD4+T lymphocytes. The rates of virus production by these two isolates in the culture media of infected PBMCs were lower (the same as those of the other CRF01_AE isolates) than those of the subtype B isolates. To confirm the correlation between the higher apoptosis-inducing abilities and the mutations at thevpugene, infectious molecular clone pNL4-3-basedvpumutants were constructed and examined for their apoptosis induction levels. The apoptosis induction levels after introduction of thevpumutations were greatly increased in primary CD4+T lymphocytes. In contrast, the apoptosis induction abilities of thesevpumutants were lower in human T-cell line MT-4. Thus, the Vpu protein of HIV-1 could play a protective role against virus-induced apoptosis in primary CD4+T lymphocytes.
Determination of the Multimerization State of the Hepatitis Delta Virus Antigens In Vivo
Authors: Cornillez-Ty Cromwell T. , Lazinski David W.
Published: September 2003

Hepatitis delta virus expresses two essential proteins, the small and large delta antigens, and both are required for viral propagation. Proper function of each protein depends on the presence of a common amino-terminal multimerization domain. A crystal structure, solved using a peptide fragment that contained residues 12 to 60, depicts the formation of an octameric ring composed of antiparallel coiled-coil dimers. Because this crystal structure was solved for only a fragment of the delta antigens, it is unknown whether octamers actually form in vivo at physiological protein concentrations and in the context of either intact delta antigen. To test the relevance of the octameric structure, we developed a new method to probe coiled-coil structures in vivo. We generated a panel of mutants containing cysteine substitutions at strategic locations within the predicted monomer-monomer interface and the dimer-dimer interface. Since the small delta antigen contains no cysteine residues, treatment of cell extracts with a mild oxidizing reagent was expected to induce disulfide bond formation only when the appropriate pairs of cysteine substitution mutants were coexpressed. We indeed found that, in vivo, both the small and large delta antigens assembled as antiparallel coiled-coil dimers. Likewise, we found that both proteins could assume an octameric quaternary structure in vivo. Finally, during the course of these experiments, we found that unprenylated large delta antigen molecules could be disulfide cross-linked via the sole cysteine residue located within the carboxy terminus. Therefore, in vivo, the C terminus likely provides an additional site of protein-protein interaction for the large delta antigen.
Organization and Expression Strategy of the Ambisense Genome of Densonucleosis Virus of
Galleria mellonella
Authors: Tijssen P. , Li Y. , El-Far M. , Szelei J. , Letarte M. , Zádori Z.
Published: September 2003

The expression strategy of parvoviruses of the
Densovirus
genus has as yet not been reported. Clones were obtained from the densonucleosis virus of
Galleria mellonella
(
Gm
DNV) that yielded infectious virus upon transfection into LD652 cells. Its genome was found to be the longest (6,039 nucleotides [nt]), with the largest inverted terminal repeats (ITRs) (550 nt) among all parvoviruses. The distal 136 nt could be folded into hairpins with flop or flip sequence orientations. In contrast to vertebrate parvoviruses, the gene cassettes for the nonstructural (NS) and structural (VP) proteins were found on the 5′ halves of the opposite strands. The transcripts for both cassettes started 23 nt downstream of the ITRs. The TATA boxes, as well as all upstream promoter elements, were localized in the ITRs and, therefore, identical for the NS and VP transcripts. These transcripts overlapped for 60 nt at the 3′ ends (antisense RNAs) at 50 m.u. The NS cassette consisted of three genes of which NS2 was contained completely within NS1 but from a different reading frame. Most of the NS transcripts were spliced to remove the upstream NS3, allowing leaky scanning translation of NS1 and NS2, similar to the genes of RNA-6 of influenza B virus. NS3 could be translated from the unspliced transcript. The VP transcript was not spliced and generated four VPs by a leaky scanning mechanism. The 5′-untranslated region of the VP transcript was only 5 nt long. Despite the transcription and translation strategies being radically different from those of vertebrate parvoviruses, the capsid was found to have phospholipase A
2
activity, a feature thus far unique for parvoviruses.
Recombination in Circulating Enteroviruses
Authors: Lukashev Alexander N. , Lashkevich Vasilii A. , Ivanova Olga E. , Koroleva Galina A. , Hinkkanen Ari E. , Ilonen Jorma
Published: September 2003

Recombination is a well-known phenomenon for enteroviruses. However, the actual extent of recombination in circulating nonpoliovirus enteroviruses is not known. We have analyzed the phylogenetic relationships in four genome regions, VP1, 2A, 3D, and the 5′ nontranslated region (NTR), of 40 enterovirus B strains (coxsackie B viruses and echoviruses) representing 11 serotypes and isolated in 1981 to 2002 in the former Soviet Union states. In the VP1 region, strains of the same serotype expectedly grouped with their prototype strain. However, as early as the 2A region, phylogenetic grouping differed significantly from that in the VP1 region and indicated recombination within the 2A region. Moreover, in the 5′ NTR and 3D region, only 1 strain of 40 grouped with its prototype strain. Instead, we observed a major group in both the 5′ NTR and the 3D region that united most (in the 5′ NTR) or all (in the 3D region) of the strains studied, regardless of the serotype. Subdivision within that major group in the 3D region correlated with the time of virus isolation but not with the serotype. Therefore, we conclude that a majority, if not all, circulating enterovirus B strains are recombinants relative to the prototype strains, isolated mostly in the 1950s. Moreover, the ubiquitous recombination has allowed different regions of the enterovirus genome to evolve independently. Thus, a novel model of enterovirus genetics is proposed: the enterovirus genome is a stable symbiosis of genes, and enterovirus species consist of a finite set of capsid genes responsible for different serotypes and a continuum of nonstructural protein genes that seem to evolve in a relatively independent manner.
Epstein-Barr Virus Nuclear Protein EBNA3A Is Critical for Maintaining Lymphoblastoid Cell Line Growth
Authors: Maruo Seiji , Johannsen Eric , Illanes Diego , Cooper Andrew , Kieff Elliott
Published: September 2003

To evaluate the role of Epstein-Barr Virus (EBV) nuclear antigen 3A (EBNA3A) in the continuous proliferation of EBV-infected primary B lymphocytes as lymphoblastoid cell lines (LCLs), we derived LCLs that are infected with a recombinant EBV genome that expresses EBNA3A fused to a 4-hydroxy-tamoxifen (4HT)-dependent mutant estrogen receptor hormone binding domain (EBNA3AHT). The LCLs grew similarly to wild-type LCLs in medium with 4HT despite a reduced level of EBNA3AHT fusion protein expression. In the absence of 4HT, EBNA3AHT moved from the nucleus to the cytoplasm and was degraded. EBNA3AHT-infected LCLs were unable to grow in medium without 4HT. The precise time to growth arrest varied inversely with cell density. Continued maintenance in medium without 4HT resulted in cell death, whereas readdition of 4HT restored cell growth. Expression of other EBNAs and LMP1, of CD23, and of c-
myc
was unaffected by EBNA3A inactivation. Wild-type EBNA3A expression from an oriP plasmid transfected into the LCLs protected the EBNA3AHT-infected LCLs from growth arrest and death in medium without 4HT, whereas EBNA3B or EBNA3C expression was unable to protect the LCLs from growth arrest and death. These experiments indicate that EBNA3A has a unique and critical role for the maintenance of LCL growth and ultimately survival. The EBNA3AHT-infected LCLs are also useful for genetic and biochemical analyses of the role of EBNA3A domains in LCL growth.
Purification, Identification, and Biochemical Characterization of a Host-Encoded Cysteine Protease That Cleaves a
Leishmaniavirus
Gag-Pol Polyprotein
Authors: Carrion Ricardo , Ro Young-Tae , Patterson Jean L.
Published: September 2003

Leishmania RNA virus (LRV) is a double-stranded RNA virus that infects some strains of the protozoan parasite
Leishmania
. As with other totiviruses, LRV presumably expresses its polymerase by a ribosomal frameshift, resulting in a capsid-polymerase fusion protein. We have demonstrated previously that an LRV capsid-polymerase polyprotein is specifically cleaved by a
Leishmania
-encoded cysteine protease. This study reports the purification of this protease through a strategy involving anion-exchange chromatography and affinity chromatography. By using a Sepharose-immobilized lectin, concanavalin A, we isolated a fraction enriched with LRV polyprotein-specific protease activity. Analysis of the active fraction by sodium dodecyl sulfate-polyacrylamide gel electrophoreses and silver staining revealed a 50-kDa protein that, upon characterization by high-pressure liquid chromatography electrospray tandem mass spectrometry (electrospray ionization/MS/MS), was identified as a cysteine protease of trypanosomes. A partial amino acid sequence derived from the MS/MS data was compared with a protein database using BLAST software, revealing homology with several cysteine proteases of
Leishmania
and other trypanosomes. The protease exhibited remarkable temperature stability, while inhibitor studies characterized the protease as a trypsin-like cysteine protease—a novel finding for
Leishmania
. To elucidate substrate preferences, a panel of deletion mutations and single-amino-acid mutations were engineered into a Gag-Pol fusion construct that was subsequently transcribed and translated in vitro and then used in cleavage assays. The data suggest that there are a number of cleavage sites located within a 153-amino-acid region spanning both the carboxy-terminal capsid region and the amino-terminal polymerase domain, with LRV capsid exhibiting the greatest susceptibility to proteolysis.
Characterization of the Expression, Intracellular Localization, and Replication Complex Association of the Putative Mouse Hepatitis Virus RNA-Dependent RNA Polymerase
Authors: Brockway Sarah M. , Clay Corrie T. , Lu Xiao Tao , Denison Mark R.
Published: September 2003

Mouse hepatitis virus (MHV) RNA synthesis is mediated by a viral RNA-dependent RNA polymerase (RdRp) on membrane-bound replication complexes in the host cell cytoplasm. However, it is not known how the putative MHV RdRp (Pol) is targeted to and retained on cellular membranes. In this report, we show that a 100-kDa protein was stably detected by an anti-Pol antiserum as a mature product throughout the virus life cycle. Gradient fractionation and biochemical extraction experiments demonstrated that Pol was not an integral membrane protein but was tightly associated with membranes and coimmunoprecipitated with the replicase proteins 3CLpro, p22, and p12. By immunofluorescence confocal microscopy, Pol colocalized with viral proteins at replication complexes, distinct from sites of virion assembly, over the entire course of infection. To determine if Pol associated with cellular membranes in the absence of other viral factors, the
pol
domain of gene 1 was cloned and expressed in cells as a fusion with green fluorescent protein, termed Gpol. In Gpol-expressing cells that were infected with MHV, but not in mock-infected cells, Gpol relocalized from a diffuse distribution in the cytoplasm to punctate foci that colocalized with markers for replication complexes. Expression of Gpol deletion mutants established that the conserved enzymatic domains of Pol were dispensable for replication complex association, but a 38-amino-acid domain in the RdRp unique region of Pol was required. This study demonstrates that viral or virus-induced factors are necessary for Pol to associate with membranes of replication complexes, and it identifies a defined region of Pol that may mediate its interactions with those factors.
Human Cytomegalovirus UL99-Encoded pp28 Is Required for the Cytoplasmic Envelopment of Tegument-Associated Capsids
Authors: Silva Maria C. , Yu Qian-Chun , Enquist Lynn , Shenk Thomas
Published: September 2003

The human cytomegalovirus UL99-encoded pp28 is a myristylated phosphoprotein that is a constituent of the virion. The pp28 protein is positioned within the tegument of the virus particle, a protein structure that resides between the capsid and envelope. In the infected cell, pp28 is found in a cytoplasmic compartment derived from the Golgi apparatus, where the virus buds into vesicles to acquire its final membrane. We have constructed two mutants of human cytomegalovirus that fail to produce the pp28 protein, a substitution mutant (BAD
sub
UL99) and a point mutant (BAD
pm
UL99), and we have propagated them by complementation in pp28-expressing fibroblasts. Both mutant viruses are profoundly defective for growth in normal fibroblasts; no infectious virus could be detected after infection. Whereas normal levels of viral DNA and late proteins were observed in mutant virus-infected cells, large numbers of tegument-associated capsids accumulated in the cytoplasm that failed to acquire an envelope. We conclude that pp28 is required for the final envelopment of the human cytomegalovirus virion in the cytoplasm.
Nef Does Not Affect the Efficiency of Human Immunodeficiency Virus Type 1 Fusion with Target Cells
Authors: Tobiume Minoru , Lineberger Janet E. , Lundquist Christopher A. , Miller Michael D. , Aiken Christopher
Published: September 2003

The human immunodeficiency virus type 1 (HIV-1) accessory protein Nef stimulates viral infectivity by an unknown mechanism. Recent studies have suggested that Nef may act by regulating the efficiency of virus entry into cells. Here we provide evidence to the contrary. Using a quantitative assay of HIV-1 virus-cell fusion, we observed equivalent rates and extents of fusion of wild-type and Nef-defective HIV-1 particles with MT-4 cells and CD4-expressing HeLa cells. In studies using soluble CD4 (sCD4) to inhibit infection, wild-type and Nef-defective HIV-1 escaped the sCD4 block with similar kinetics. We conclude that Nef acts at a postentry step in infection, probably by facilitating intracellular transport of the HIV-1 ribonucleoprotein complex.
The power of experiments for estimating relative reproductive success of hatchery-born spawners
Authors: Hinrichsen Richard A
Published: September 2003

An a priori power analysis was conducted to aid the design of experiments aimed at estimating the reproductive success of hatchery-born spawners relative to wild-born spawners using parentage assignment. Power was defined as the probability of rejecting the null hypothesis of equal reproductive contributions of hatchery- and wild-born spawners. A maximum likelihood estimator of relative reproductive success and its variance were derived. The estimator allowed multiple brood years of data, which was an extension of current approaches. Power increased with stock productivity, initial spawner abundance, fraction of recruits and spawners sampled, and the number of brood years examined. Power decreased with error variance used in the production function. Assuming a fixed total number of spawners, power was a concave-down function of the fraction of hatchery-born spawners. Using nominal values of productivity, error variance, and fraction of hatchery-born spawners, an experiment could achieve 0.8 power if it was run for at least 5 years or if it was applied to a stock with high initial female spawners (>200) and run for at least 2 years.
Load factor calibration for the proposed 2005 edition of the National Building Code of Canada: Companion-action load combinations
Authors: Bartlett F M , Hong H P , Zhou W
Published: September 2003

The 2005 edition of the National Building Code of Canada (NBCC) will adopt a companion-action format for load combinations and specify wind and snow loads based on their 50 year return period values. This paper presents the calibration of these factors, based on statistics for dead load, live load due to use and occupancy, snow load, and wind load, which are summarized in a companion paper. A target reliability index of approximately 3 for a design life of 50 years was adopted for consistency with the 1995 NBCC. The load combinations and load factors for strength and stability checks recommended for the 2005 NBCC were based on preliminary values from reliability analysis that were subsequently revised slightly to address major inconsistencies with past practice. The recommended load combinations and factors generally give factored load effects similar to those in the 1995 NBCC, but are up to 10% more severe for the combination of dead load plus snow load and are generally less severe for the combination of dead load, snow load, and live load due to use and occupancy. Load factors less than one are recommended for checking serviceability limit states involving specified snow and wind loads. Importance factors for various classifications of structure are also presented. Revisions to the commentaries of the NBCC are recommended that will provide guidance on dead load allowances for architectural and mechanical superimposed dead loads and cast-in-place cover slabs and toppings.Key words: buildings, code calibration, companion action, dead loads, live loads, load combinations, load factors, reliability, safety, snow loads, wind loads.
Characteristics of ice in the St. Lawrence River
Authors: Morse Brian , Hessami Masoud , Bourel Céline
Published: September 2003

The main objective of this paper is to describe the characteristics of brash ice in the St. Lawrence River downstream of Montréal over a period of three winters. We used two instruments deployed in the St. Lawrence River navigation channel through Lake St. Pierre to measure ice parameters: an acoustic Doppler current profiler (ADCP) and an ice-profiling sonar (IPS). This paper discusses the capacities of these instruments to quantify ice characteristics and to predict the risk of ice congestion. It was found that wind velocity and air temperature play major roles in the variation in ice parameters and, consequently, in the occurrence of ice congestion in the navigation channel through Lake St. Pierre. Comparison of the IPS and ADCP data showed good agreement and demonstrated that these two instruments can be very effective for certain ice applications.Key words: ice characteristics, ice congestion, ADCP, IPS, fuzzy logic.
Microbially-mediated fugitive gas production from oil sands tailings and increased tailings densification rates
Authors: Fedorak P M , Coy D L , Dudas M J , Simpson M J , Renneberg A J , MacKinnon M D
Published: September 2003

Oil sands in northeastern Alberta, Canada, are strip mined and bitumen is separated from sand and clay by an alkaline hot water extraction process leaving millions of cubic metres of tailings for disposal. These include mature fine tailings (MFT) collected in settling ponds and consolidated or composite tailings (CT) that are produced by the addition of sand and gypsum to hasten dewatering and densification. This laboratory investigation monitored the potential for fugitive gas production in 0.9-m high columns that contained MFT or CT samples from three oil sands companies. Methane was found in columns that contained aged MFT, but not in those that contained fresh MFT. Dissolved or entrapped methane was found in columns containing each of the MFT samples and two of the CT samples. Ethylene was detected in columns containing MFT or CT. This may affect future plans to re-vegetate disturbed areas of the oil sands operations because ethylene strongly influences many phases of plant development. The densification rate of a methanogenic MFT was faster than that of a nonmethanogenic MFT that was placed in a similar column 6 years prior to the start of this investigation, suggesting that methane formation may increase the rate of densification. Key words: consolidated tailings, composite tailings, densification, ethylene, methane, methanogens, oil sands, sulfate-reducing bacteria.
Quantification of a single population in a mixed microbial community using a laser integrated microarray scanner
Authors: Callister Stephen J , Ayala-del-Rio Hector L , Hashsham Syed A
Published: September 2003

A laser integrated microarray scanner was used to quantify and compare the biomass of Burkholderia cepacia G4 alone, mixed with Afipia sp., and mixed with a trichloroethylene and phenol degrading community. Samples containing B. cepacia G4 were placed in 3-mm diameter wells on gelatin coated glass slides then fixed and immunofluorescently labeled using an IgG conjugate with an attached AlexaTM 546 fluorophore. Linearity and sensitivity of the scanner for biomass quantification were established, and a lower detection limit of 25 mg L1 (103104 cells mL1) was calculated. Growth of B. cepacia G4 alone and in the presence of the TCE degrading community was measured using the scanner. Results suggest that the microarray scanner can be used to quantify the biomass of a single population in a dense mixed microbial community. Key words: biomass, Burkholderia cepacia G4, fluorescent antibody, microarray scanner, mixed community.
Magnetic bead hybridization to detect enterotoxigenicEscherichia colistrains associated with cattle in environmental water sources
Authors: Tsai Yu-Li , Le Joanne Y , Olson Betty H
Published: September 2003

A magnetic capture hybridization  polymerase chain reaction (MCHPCR) method was used to increase the detection sensitivity of the enterotoxin gene LTIIa, used as a biomarker for waste in environmental samples. The samples were collected from cow lagoons of different farms and from environmental waters. Total DNA was extracted from colonies grown on mTEC medium or directly from environmental samples. The cow-specific Escherichia coli LTIIa gene was used as a DNA marker. A LTIIa-specific oligonucleotide probe was designed to capture the LTIIa marker during the MCH, followed by PCR. Varying levels of humic acid were added to the DNA extracts to evaluate the sensitivity and effectiveness of MCHPCR. The minimal detection limit of MCHPCR for the LTIIa gene was 2.5 ag/μL DNA. In the presence of humic acid, MCHPCR was able to increase the detection sensitivity 10 000-fold over that of conventional PCR. The MCHPCR could also detect one cell with the LTIIa DNA marker in a 1-L seeded environmental water sample. Results in this study indicate that MCHPCR is more sensitive than nested PCR in testing environmental samples.Key words: magnetic bead hybrid, LTIIa toxin gene, water-quality monitoring.
Effects of gypsophila saponins on bacterial growth kinetics and on selection of subterranean clover rhizosphere bacteria
Authors: Fons F , Amellal N , Leyval C , Saint-Martin N , Henry M
Published: September 2003

Plant secondary metabolites, such as saponins, have a considerable impact in agriculture because of their allelopathic effects. They also affect the growth of soil microorganisms, especially fungi. We investigated the influence of saponins on rhizosphere bacteria in vitro and in soil conditions. The effects of gypsophila saponins on the growth kinetics of rhizosphere bacteria were studied by monitoring the absorbance of the cultures in microtiter plates. Gypsophila saponins (1%) increased the lag phase of bacterial growth. The impact of gypsophila saponins on subterranean clover rhizosphere was also investigated in a pot experiment. The addition of gypsophila saponins did not modify clover biomass but significantly increased (twofold with 1% saponins) the weight of adhering soil. The number of culturable heterotrophic bacteria of the clover rhizosphere was not affected by the addition of gypsophila saponins. Nevertheless, the phenotypical characterization of the dominant Gram-negative strains of the clover rhizosphere, using the Biolog©system, showed qualitative and quantitative differences induced by 1% saponins. With the addition of saponins, the populations of Chryseomonas spp. and Acinetobacter spp., the two dominant culturable genera of control clover, were no longer detectable or were significantly decreased, while that of Aquaspirillum dispar increased and Aquaspirillum spp. became the major genus. Aquaspirillum dispar and Aquaspirillum spp. were also the dominant rhizosphere bacteria of Gypsophila paniculata, which greatly accumulates these saponins in its roots. These results suggest that saponins may control rhizosphere bacteria in soil through rhizodeposition mechanisms.Key words: bacteria, Gypsophila paniculata, rhizosphere, saponins, Trifolium subterraneum.
Inhibitors of nitric oxide synthesis block cold-induced thermogenesis in rats
Authors: Kamerman Peter R , Laburn Helen P , Mitchell Duncan
Published: September 2003

N-nitro-L-arginine methyl ester (L-NAME), an unspecific nitric oxide synthase inhibitor, was administered to individually caged SpragueDawley rats exposed to cold (18°C) and thermoneutral (30°C) environmental temperatures during the active phase of the animals' circadian cycle. Unrestrained rats were administered intraperitoneal injections of 100 mg·kg1 L-NAME or 1 mL·kg1 saline. Telemetry was used to measure abdominal temperature. On a separate occasion, metabolic rate and evaporative water loss were measured using indirect calorimetery, before and after the injection of 100 mg·kg1 L-NAME, in rats exposed to the two environments. Injection of L-NAME had no significant effect on body temperature, metabolic rate, or evaporative water loss in rats exposed to the 30°C environment. In the 18°C environment, L-NAME injection caused a prolonged fall in body temperature (F(1,12) = 17.43, P = 0.001) and a significant decrease in metabolic rate (Student's t test, P = 0.001) and evaporative water loss (one-sample t test, P = 0.04). Therefore, the effects that systemic injection of L-NAME has on body temperature are dependent on environmental temperature, with nitric oxide synthase inhibition seemingly preventing the metabolic component of cold defence.Key words: N-nitro-L-arginine methyl ester, thermoregulation, telemetry, oxygen consumption.
A comparison of adductor pollicis fatigue in older men and women
Authors: Cheng Arthur , Ditor David S , Hicks Audrey L
Published: September 2003

Sex differences in fatigue resistance of the adductor pollicis (AP) muscle were studied in 24 older adults who were divided into three groups: 12 older men (69.8 ± 4.60 years), 6 older women not on hormone replacement therapy (HRT) (70.2 ± 4.02 years), and 6 older women on HRT (68.7 ± 6.47 years). Fatigue in the AP muscle was induced using an intermittent (5 s contraction, 5 s rest) submaximal voluntary contraction (50% of maximal voluntary contraction (MVC)) protocol, which was continued until exhaustion (i.e., when subjects could either no longer maintain a 5-s contraction at 50% MVC or when the MVC was deemed to be lower than the target force). There was no effect of HRT on MVC or time to fatigue (TTF); therefore, the older women were pooled as one subject group. At baseline, men were stronger than women for MVC (75.9 ± 18.8 N in men vs. 56.8 ± 10.0 N in women; P < 0.05) and evoked twitch force (7.3 ± 1.7 N in men vs. 5.2 ± 0.8 N in women; P < 0.05). There was no difference in TTF between men and women (14.77 ± 7.06 min in men vs. 11.53 ± 4.91 min in women; P > 0.20), nor was there a significant relationship between baseline muscle force and TTF (r = 0.14). There was also no difference in the pattern of fatigue and recovery between the men and women. These results suggest that there is no difference in endurance or fatigue characteristics of the AP muscle in men and women over the age of 65 years, and that baseline muscle force does not predict fatigue resistance in this muscle.Key words: muscle fatigue, aging, gender differences.
Steady-state maternal and fetal plasma concentrations of glyceryl trinitrate (GTN) in the preterm sheep
Authors: Bustard Mark A , Farley Anne E , Bennett Brian M , Smith Graeme N
Published: September 2003

The administration of glyceryl trinitrate (GTN; nitroglycerin) is increasing during preterm pregnancies, yet its disposition and, importantly, the extent of fetal exposure remain to be elucidated. When used as a tocolytic (pharmacological agent that stops uterine contractions), it is administered transdermally (2448 h). Here, we quantified the maternal and fetal steady-state plasma concentrations of maternal intravenous GTN in preterm sheep and continuously monitored maternal and fetal vascular parameters to observe possible dose-dependant vascular effects. Preterm (120 days gestation) pregnant sheep (n = 6) were instrumented with maternal femoral arterial (MA) and venous (MV) and fetal femoral arterial (FA) and umbilical venous (UV) polyethylene blood-sampling catheters. During maternal GTN infusion (3.0 µg·kg1·min1, 60-min duration) the steady-state GTN concentrations ([GTN]) were as follows: MA, 98.6 ± 9.0 nM; UV, 17.4 ± 7.6 nM; and FA, <5 nM. There were no changes in maternal and fetal mean arterial pressure and heart rate or in uterine activity. Overall, the steady-state [GTN] was established by 5 min, and the UV/MA ratio of [GTN] was 0.18. The FA [GTN] (<5 nM) indicates that the fetus cleared essentially all GTN in the UV, and the maternal and fetal heart rate and mean arterial pressure appear to be independent of maternal GTN infusion.Key words: nitroglycerin, pharmacokinetics, maternal-fetal exchange, pregnancy, cardiovascular.
Population dynamics of hispid cotton rats (Sigmodon hispidus) across a nitrogen-amended landscape
Authors: Clark Jay E , Hellgren Eric C , Jorgensen Eric E , Tunnell Susan J , Engle David M , Leslie Jr. David M
Published: September 2003

We conducted a markrecapture experiment to examine the population dynamics of hispid cotton rats (Sigmodon hispidus) in response to low-level nitrogen amendments (16.4 kg nitrogen/ha per year) and exclosure fencing in an old-field grassland. The experimental design consisted of sixteen 0.16-ha plots with 4 replicates of each treatment combination. We predicted that densities, reproductive success, movement probabilities, and survival rates of cotton rats would be greater on nitrogen-amended plots because of greater aboveground biomass and canopy cover. Population densities of cotton rats tended to be highest on fenced nitrogen plots, but densities on unfenced nitrogen plots were similar to those on control and fenced plots. We observed no distinct patterns in survival rates, reproductive success, or movement probabilities with regard to nitrogen treatments. However, survival rates and reproductive success tended to be higher for cotton rats on fenced plots than for those on unfenced plots and this was likely attributable to decreased predation on fenced plots. As low-level nitrogen amendments continue to be applied, we predict that survival, reproduction, and population-growth rates of cotton rats on control plots, especially fenced plots with no nitrogen amendment, will eventually exceed those on nitrogen-amended plots as a result of higher plant-species diversity, greater food availability, and better quality cover.
Diving behaviour during the breeding season in the terrestrially breeding male grey seal: implications for alternative mating tactics
Authors: Lidgard Damian C , Boness Daryl J , Bowen W Don , McMillan Jim I
Published: September 2003

We examined the diving behaviour of breeding male grey seals (Halichoerus grypus) at Sable Island, Nova Scotia, from 1997 to 2001. The proportion of time spent at sea varied between 0 and 78% (N = 30). Males engaged in deep (43.4 ± 3.3 m (mean ± SE), N = 27) diving, and these dives were clustered into bouts, which mostly occurred during long trips (62.2 ± 14.7 h). We suggest that males spent time foraging during deep dives. Shallow diving (5.9 ± 0.1 m, N = 27) accounted for 40.8% of dives, which were also clustered into bouts that mostly occurred during short trips (2.1 ± 0.37 h). We suggest that shallow diving comprised a suite of behaviours, but included little foraging behaviour. Phenotypic traits had little influence on diving behaviour. Further work is required to understand the extent to which foraging behaviour enhances reproductive success, and whether shallow diving is a component of the mating tactics of male grey seals at Sable Island.
Sexual difference in habitat use of Texas map turtles (Emydidae: Graptemys versa) and its relationship to size dimorphism and diet
Authors: Lindeman Peter V
Published: September 2003

Sexual differences in habitat use of map turtles (Graptemys spp.) have been attributed to differences in swimming ability as influenced by body size, because females are much larger than males, or to sexual differences in diet. Captures of young female Graptemys versa, which had body sizes similar to those of adult males but diet and trophic morphology more similar to those of larger females, allowed testing of these alternative hypotheses. A variety of single habitat variables measured at the sites of capture performed poorly in separating the three groups of turtles, but multivariate analysis and variables relating to position within the stream produced greater separation, indicating that complex combinations of factors probably influence habitat use. Young females were more similar in their habitat use to large females than to males, and their diet was also more similar to that of larger females, due primarily to the quantities of mollusks consumed. The data supported the hypothesis that habitat separation was the result of dietary rather than body size differences. While dietary differences are probably facilitated by sexual size dimorphism, they may not be the ultimate selective force that produced the size dimorphism.
Dominance hierarchies and status recognition in the crayfishProcambarus acutus acutus
Authors: Gherardi Francesca , Daniels William H
Published: September 2003

In the eastern white river crayfish, Procambarus acutus acutus, the processes that act during hierarchy formation were explored by analyzing the behavior of 23 symmetric pairs of form I males. The experimental design comprised three subsequent phases: isolation, familiarization, and experimental phases. In the latter, pairs were formed of (i) unfamiliar opponents having different status, (ii, iii) unfamiliar opponents having the same status, either two alphas or two betas, and (iv) familiar opponents. The first result was that P. a. acutus is capable of establishing stable dominance hierarchies. Secondly, behavioral differences between the winners and the losers, a fast assessment of status, and self-reinforcing effects of recent experience were demonstrated. Thirdly, P. a. acutus was found to recognize the status of its rival but not its individual identity. In fact, even if paired with unfamiliar opponents, previous winners and losers behaved as in the preceding days. Conversely, both frequency and intensity of fighting increased when individuals of the same rank were opposed. These phenomena might be a consequence of "winning and losing effects". However, the increased readiness of former betas to attack contradicts the loser effect and validates the hypothesis of status recognition.
Effects of body size on male mating tactics and paternity in black bears,Ursus americanus
Authors: Kovach Adrienne I , Powell Roger A
Published: September 2003

The reproductive behaviour of large, solitary mammals is difficult to study. Owing to their secretive nature and wide-ranging habits, aspects of male mating behaviour are poorly documented in solitary than in social species. We used radiotelemetry and microsatellite DNA analysis to investigate the influence of body size on male mating tactics and short-term reproductive success in the black bear, Ursus americanus, a solitary carnivore. We investigated male ranging behaviour and documented male encounters with breeding females to determine whether males employed conditional mating tactics according to their body sizes. We found that male home-range sizes were not positively associated with body size, but encounter rates with breeding females were. Although all males searched widely for females, mating access appeared to be largely determined by fighting ability. Large males encountered more breeding females and had more frequent encounters during the females' estimated receptive periods than did small- and medium-sized males. Paternity was highly skewed toward the three dominant males who fathered 91% of the cubs sampled during the 3-year study. Paternity was correlated with the frequency of male encounters during female receptive periods. Male encounters, however, overestimated the success of medium-sized males and underestimated the overall variance in male reproductive success. Multiple paternity occurred in two of seven litters, indicating that sperm competition is important in black bear mating behaviour. Implications for male lifetime reproductive success are discussed.
Secure Error-Free Steganography for JPEG Images
Authors: Lee Yeuan-Kuen , Chen Ling-Hwei
Published: August 2003

The typical model of steganography has led the prisoners' problem, in which two persons attempt to communicate covertly without alerting the warden, that is, only the receiver knows the existence of the message sent by the sender. One available way to achieve this task is to embed the message in an innocuous-looking medium. In this paper, we propose a variation of the Quantization Index Modulation (QIM) for solving the prisoners' problem. We also propose a theorem to show that the error of mean intensity value of an image block caused by JPEG compression is bounded. The proposed method embeds the messages to be conveyed by modifying the mean intensity value, and the resulting stego-image can be stored in the JPEG format with a low quality setting. Besides, a specific pattern caused by using the QIM embedding method is also identified, and this pattern will be removed using the proposed embedding method. Experimental results and the proposed theorem show that the hidden message is error-free against the JPEG distortion under the quality setting as low as 25. Furthermore, the existence of the hidden message is not only visually imperceptible but also statistically undetectable.
Edge Detection Using Block Truncation Coding
Authors: Hu Yu-Chen , Chang Chin-Chen
Published: August 2003

In this paper, a new edge detection scheme based on block truncation coding (BTC) is proposed. As we know, the BTC is a simple and fast scheme for digital image compression. To detect an edge boundary using the BTC scheme, the bit plane information of each BTC-compressed block is exploited, and a simple block type classifier is introduced.

The experimental results show that the proposed scheme clearly detects the edge boundaries of digital images while requiring very little computational complexity. Meanwhile, the edge detection process can be incorporated into all BTC variant schemes. In other words, the newly proposed scheme provides a good approach for the detection of edge boundaries using block truncation coding.
Multiple People Tracking Based on Temporal Color Feature
Authors: Kang Seonghoon , Hwang Bon-Woo , Lee Seong-Whan
Published: August 2003

We present a method for detecting and tracking multiple people totally occluded or out of sight in a scene for some period of time in image sequences. Our approach is to use time weighted color information (i.e. the temporal color) for robust medium-term people tracking. The temporal color is the set of pairs of a color value and its associated weights. The weight is related to the size, duration and frequency of appearance of the color region, as well as the number of people adjacent to the target person. It assures our system to continuously track people moving in a group with occlusion. Most systems have built an appearance model for each person to solve occlusion problems. The appearance model contains certain information on the target person — color, shape, texture, position, velocity and face pattern. We use temporal color in the appearance model for the identification of the people occluded or out of sight in the scene upon their reappearance. Experimental results show that the temporal color is more stable than shape or intensity in various cases.
Detecting Eyelash and Reflection for Accurate Iris Segmentation
Authors: Kong Wai-Kin , Zhang David
Published: August 2003

Accurate iris segmentation is presented in this paper, which is composed of two parts, reflection detection and eyelash detection. Eyelashes are classified into two categories, separable and multiple. An edge detector is applied to detect separable eyelashes, and intensity variances are used to recognize multiple eyelashes. Reflection is also divided into two types, strong and weak. A threshold and statistical model is proposed to recognize the strong and weak reflection, respectively. We have developed an iris recognition approach for testing the effectiveness of the proposed segmentation method. The results show that the proposed method can reduce recognition error for the iris recognition approach.
Improvement and Invariance Analysis of Orthogonal Fourier–Mellin Moments
Authors: Ye Bin , Peng Jia-Xiong , Ren Qiu-Shi , Li Wan-Rong
Published: August 2003

Orthogonal Fourier–Mellin (OFM) moments have better feature representation capabilities, and are more robust to image noise than the conventional Zernike moments and pseudo-Zernike moments. However, OFM moments have not been extensively used as feature descriptors since they do not possess scale invariance. This paper discusses the drawbacks of the existing methods of extracting OFM moments, and proposes an improved OFM moments. A part of the theory, which proves the improved OFM moments possesses invariance of rotation and scale, is given. The performance of the improved OFM moments is experimentally examined using trademark images, and the invariance of the improved OFM moments is shown to have been greatly improved over the current methods.
An Efficient Algorithm for Fast Computation of Pseudo-Zernike Moments
Authors: Chong Chee-Way , Raveendran P. , Mukundan R.
Published: August 2003

Pseudo-Zernike moments have better feature representation capability, and are more robust to image noise than those of the conventional Zernike moments. However, due to the computation complexity of pseudo-Zernike polynomials, pseudo-Zernike moments are yet to be extensively used as feature descriptors as compared to Zernike moments. In this paper, we propose two new algorithms, namely coefficient method and p-recursive method, to accelerate the computation of pseudo-Zernike moments. Coefficient method calculates polynomial coefficients recursively. It eliminates the need of using factorial functions. Individual order or index of pseudo-Zernike moments can be derived independently, which is useful if selected orders or indices of moments are needed as pattern features. p-recursive method uses a combination of lower order polynomials to derive higher order polynomials with the same index q. Fast computation is achieved because it eliminates the requirements of calculating polynomial coefficients, Bpqk, and power of radius, rk, in each polynomial. The performance of the proposed algorithms on moment computation and image reconstruction, as compared to those of the present methods, are experimentally verified using a set of binary and grayscale images.
The Clamped Plate with Elastic Unilateral Obstacles: A Finite Element Approach
Authors: Tosone C. , Maceri A.
Published: August 2003

We consider the problem of a clamped elastic thin plate unilaterally constrained by an elastic obstacle. A discrete, finite element approach to solve this nonlinear problem is given here and its convergence properties are discussed.