bluuebunny/crossref_metadata_2025 huggingface dataset:
Waveguide invariant minimum variance scatterer depth classification for active sonar.
Authors: Goldhahn Ryan , Hickman Granger , Krolik Jeffrey
Published: March 2010

Active sonar systems are plagued by false alarms due to confusion between returns from water-column targets and backscatter from the bottom. Both feature-based and physics-based classifiers are notoriously susceptible to mismatch of the environment used for training and/or modeling active sonar returns. In this paper, in order to achieve more robust classification, uniformly sub-sampled DFT-coefficients from a single snapshot of the wideband active sonar return are used to define a waveguide-invariant spectral density matrix (WI-SDM). The WI-SDM facilitates adaptive matched-filtering based approaches for target depth estimation, where the waveguide invariant property is exploited to obtain uncorrelated snapshots without inflating covariance matrix rank. Depth classification is then performed by designing a waveguide-invariant minimum variance filter (WI-MVF) with adaptive weights which minimize ambiguous depth sidelobes. Simulation and real data results in a shallow-water Mediterranean environment are presented to illustrate the approach. [Work sponsored by ONR.]
Testing the temporal robustness of an automatic aural classifier.
Authors: Murphy Stefan , Hines Paul C.
Published: March 2010

Military sonar systems must detect and classify submarine threats at ranges safely outside their circle of attack. However, in littoral environments, echoes from geological features (clutter) are frequently mistaken for targets of interest, resulting in degraded performance. Perceptual signal features similar to those employed in the human auditory system can be used to automatically discriminate between target and clutter echoes, thereby improving sonar performance. [J. Acoust. Soc. Am. 122, 1502–1517 (2007)] The present work examines the temporal robustness of the aural classifier using data from two field trials: the first in 2007 and the second in 2009. The experiments were conducted on the Malta Plateau using a cardioid towed-array receiver, and a broadband source transmitting linear FM sweeps from 600–3500 Hz. The data set consists of hundreds of pulse-compressed echoes from several surrogate targets and geological clutter objects. The echoes are examined using an automatic classifier that processes each echo to extract perceptual features. Each echo is classified as target or clutter based on the position vector formed by these features. The classifier establishes a boundary between clutter and target echoes in the feature space using the 2007 experiment. Temporal robustness is investigated by testing the classifier on echoes from the 2009 experiment. In this work, the experiments are reviewed and initial results are presented.
Source depth classification of passive sonar signals using amplitude statistics.
Authors: Culver R. Lee , Jemmott Colin W. , Bissinger Brett E. , Bose N. K.
Published: March 2010

A number of at-sea measurements have shown that fluctuations in the amplitude of passive sonar signals are affected by source depth, range, and the propagation path from the source to the receiver. However, to date, received signal statistics have not been incorporated into passive sonar classification algorithms because the field results have not been accompanied by development of a statistics-based classifier architecture whose performance can be assessed using accepted signal processing metrics, e.g., a receiver operating characteristic curve. The performance of a statistics-based classifier depends critically upon statistical knowledge of the received signal, which in turn depends upon statistical knowledge of relevant environment parameters (sound speed in the water column and sediment, for example). Thus the classifier architecture must make use of the environmental information which in reality is only approximately known and must be described in statistical terms. Given a statistical description of the environment, an ocean acoustic propagation model and Monte Carlo simulation can be used to predict received signal statistics. Once received signal statistics are available for the different classes, a classifier can be designed. Here we examine a likelihood ratio binary source depth classifier for passive sonar. [Work sponsored by ONR Undersea Signal Processing.]
Minimum Hellinger distance classification for passive sonar in the presence of noise.
Authors: Bissinger Brett E. , Culver R. Lee , Bose N. K.
Published: March 2010

Passive source classification in the underwater environment is a challenging problem in part because propagation through the space- and time-varying media introduces variability and uncertainty in the signal. Acoustic propagation models can predict received fields accurately, but they are sensitive to input environmental parameters which cannot be known exactly. This uncertainty in environmental knowledge used in signal predictions results in imperfect statistical class models. Classifiers that rely on simulations of the environment must therefore be robust to these imperfections. The minimum Hellinger distance classifier (MHDC) has been shown to be robust to such mismatches in situations with no noise. Low-noise situations allow demonstration of the properties of the classifier; however, real passive sonar tends to have significant noise levels. Therefore the MHDC’s performance is examined and compared to that of a log-likelihood ratio classifier when applied to narrowband passive underwater acoustic signals in the presence of noise. Both classifiers are applied to synthetic Gaussian data, synthetic acoustic data, and actual acoustic data, all with noise. Classifiers are evaluated using receiver operating characteristic curves, a traditional performance metric in signal processing. [Work supported by ONR Undersea Signal Processing.]
Helmholtz-Rayleigh Interdisciplinary Silver Medal in Biomedical Ultrasound/Bioresponse to Vibration and Physical Acoustics
Authors: Roy Ronald A.
Published: March 2010

The Silver Medal is presented to individuals, without age limitation, for contributions to the advancement of science, engineering, or human welfare through the application of acoustic principles, or through research accomplishment in acoustics.
Gold Medal of the Acoustical Society of America
Authors: Tichy Jiri
Published: March 2010

The Gold Medal is presented in the spring to a member of the Society, without age limitation, for contributions to acoustics. The first Gold Medal was presented in 1954 on the occasion of the Society's Twenty-Fifth Anniversary Celebration and biennially until 1981. It is now an annual award.
Lymph Vessel Sites Defined by Monocytes
Authors: Gough Nancy R.
Published: March 2010

Monocytes release growth factors that regulate development of the lymphatic system.
Vitamin Stimulant
Authors: Foley John F.
Published: March 2010

Vitamin D receptor signaling enhances responsiveness to T cell receptor stimulation by increasing the abundance of PLC-γ1.
ER Calcium and Alzheimer’s Disease: In a State of Flux
Authors: Mattson Mark P.
Published: March 2010

Mutations in presenilin 1 may exaggerate Ca
2+
signaling in neurons, increasing their vulnerability.
Two Receptors, Two Kinases, and T Cell Lineage Determination
Authors: Alarcón Balbino , van Santen Hisse M.
Published: March 2010

Specification of T cell lineage in the thymus is controlled by the timing and strength of signaling of the tyrosine kinase Zap70.
Homozygous Triplicate Mutations in Three 16S rRNA Genes Responsible for High-Level Aminoglycoside Resistance inNocardia farcinicaClinical Isolates from a Canada-Wide Bovine Mastitis Epizootic
Authors: Kogure Takahisa , Shimada Reona , Ishikawa Jun , Yazawa Katsukiyo , Brown June M. , Mikami Yuzuru , Gonoi Tohru
Published: March 2010

Nocardia farcinicastrains showing high-level resistance to amikacin were isolated from clinical cases in a Canada-wide bovine mastitis epizootic. Shotgun cloning of the resistance genes in the amikacin-resistant mastitis isolateN. farcinicaIFM 10580 (W6220 [Centers for Disease Control and Prevention]) using a multicopy vector system revealed that the 16S rRNA gene with an A-to-G single-point mutation at position 1408 (inEscherichia colinumbering) conferred “moderate” cross-resistance to amikacin and other aminoglycosides to an originally susceptibleN. farcinicastrain IFM 10152. Subsequent DNA sequence analyses revealed that, in contrast to the susceptible strain, all three chromosomal 16S rRNA genes of IFM 10580, the epizootic clinical strain, contained the same A1408G point mutations. Mutant colonies showing high-level aminoglycoside resistance were obtained when the susceptible strainN. farcinicaIFM 10152 was transformed with a multicopy plasmid carrying the A1408G mutant 16S rRNA gene and was cultured in the presence of aminoglycosides for 3 to 5 days. Of these transformants, at least two of the three chromosomal 16S rRNA genes contained A1408G mutations. A triple mutant was easily obtained from a strain carrying the two chromosomal A1408G mutant genes and one wild-type gene, even in the absence of the plasmid. The triple mutant showed the highest level of resistance to aminoglycosides, even in the absence of the plasmid carrying the mutant 16S rRNA gene. These results suggest that the homozygous mutations in the three 16S rRNA genes are responsible for the high-level aminoglycoside resistance found inN. farcinicaisolates of the bovine mastitis epizootic.
Novel Mechanism of Glycopeptide Resistance in the A40926 Producer
Nonomuraea
sp. ATCC 39727
Authors: Marcone Giorgia Letizia , Beltrametti Fabrizio , Binda Elisa , Carrano Lucia , Foulston Lucy , Hesketh Andrew , Bibb Mervyn , Marinelli Flavia
Published: March 2010

In glycopeptide-resistant enterococci and staphylococci, high-level resistance is achieved by replacing the C-terminal
d
-alanyl-
d
-alanine of lipid II with
d
-alanyl-
d
-lactate, thus reducing glycopeptide affinity for cell wall targets. Reorganization of the cell wall in these organisms is directed by the
vanHAX
gene cluster. Similar self-resistance mechanisms have been reported for glycopeptide-producing actinomycetes. We investigated glycopeptide resistance in
Nonomuraea
sp. ATCC 39727, the producer of the glycopeptide A40926, which is the precursor of the semisynthetic antibiotic dalbavancin, which is currently in phase III clinical trials. The MIC of
Nonomuraea
sp. ATCC 39727 toward A40926 during vegetative growth was 4 μg/ml, but this increased to ca. 20 μg/ml during A40926 production.
vanHAX
gene clusters were not detected in
Nonomuraea
sp. ATCC 39727 by Southern hybridization or by PCR with degenerate primers. However, the
dbv
gene cluster for A40926 production contains a gene,
vanY
(ORF7), potentially encoding an enzyme capable of removing the terminal
d
-Ala residue of pentapeptide peptidoglycan precursors. Analysis of UDP-linked peptidoglycan precursors in
Nonomuraea
sp. ATCC 39727 revealed the predominant presence of the tetrapeptide UDP-MurNAc-
l
-Ala-
d
-Glu-
meso
-Dap-
d
-Ala and only traces of the pentapeptide UDP-MurNAc-
l
-Ala-
d
-Glu-
meso
-Dap-
d
-Ala-
d
-Ala. This suggested a novel mechanism of glycopeptide resistance in
Nonomuraea
sp. ATCC 39727 that was based on the
d
,
d
-carboxypeptidase activity of
vanY
. Consistent with this, a
vanY
-null mutant of
Nonomuraea
sp. ATCC 39727 demonstrated a reduced level of glycopeptide resistance, without affecting A40926 productivity. Heterologous expression of
vanY
in a sensitive
Streptomyces
species,
Streptomyces venezuelae
, resulted in higher levels of glycopeptide resistance.
PreclinicalIn VitroandIn VivoCharacterization of the Fully Human Monoclonal IgM Antibody KBPA101 Specific forPseudomonas aeruginosaSerotype IATS-O11
Authors: Horn Michael P. , Zuercher Adrian W. , Imboden Martin A. , Rudolf Michael P. , Lazar Hedvika , Wu Hong , Hoiby Niels , Fas Stefanie C. , Lang Alois B.
Published: March 2010

Pseudomonas aeruginosainfection in ventilator-associated pneumonia is a serious and often life-threatening complication in intensive care unit patients, and new treatment options are needed. We used B-cell-enriched peripheral blood lymphocytes from a volunteer immunized with aP. aeruginosaO-polysaccharide-toxin A conjugate vaccine to generate human hybridoma cell lines producing monoclonal antibodies specific for individualP. aeruginosalipopolysaccharide serotypes. The fully human monoclonal antibody secreted by one of these lines, KBPA101, is an IgM/κ antibody that bindsP. aeruginosaof International Antigenic Typing System (IATS) serotype O11 with high avidity (5.81 × 107M−1± 2.8 × 107M−1) without cross-reacting with other serotypes. KBPA101 specifically opsonized theP. aeruginosaof IATS O11 serotype and mediated complement-dependent phagocytosisin vitroby the human monocyte-like cell line HL-60 at a very low concentration (half-maximal phagocytosis at 0.16 ng/ml).In vivoevaluation of KBPA101 demonstrated a dose-response relationship for protection against systemic infections in a murine burn wound sepsis model, where 70 to 100% of animals were protected against lethal challenges withP. aeruginosaat doses as low as 5 μg/animal. Furthermore, a high efficacy of KBPA101 in protection from local respiratory infections in an acute lung infection model in mice was demonstrated. Preclinical toxicology evaluation on human tissue, in rabbits, and in mice did not indicate any toxicity of KBPA101. Based on these preclinical findings, the first human clinical trials have been initiated.
Characterization of DIM-1, an Integron-Encoded Metallo-β-Lactamase from a
Pseudomonas stutzeri
Clinical Isolate in the Netherlands
Authors: Poirel Laurent , Rodríguez-Martínez Jose-Manuel , Al Naiemi Nashwan , Debets-Ossenkopp Yvette J. , Nordmann Patrice
Published: March 2010

A carbapenem-resistant
Pseudomonas stutzeri
strain isolated from a Dutch patient was analyzed in detail. This isolate produced a metallo-β-lactamase (MBL) whose gene, with 43.5% GC content, was cloned and expressed in
Escherichia coli.
β-Lactamase DIM-1 (for
D
utch
im
ipenemase) was weakly related to other Ambler class B β-lactamases, sharing <52% amino acid identity with the most closely related MBL, GIM-1, and 45% identity with IMP-type MBLs. The β-Lactamase DIM-1 significantly hydrolyzed broad-spectrum cephalosporins and carbapenems and spared aztreonam. This MBL gene was embedded in a class 1 integron containing two other gene cassettes, encoding resistance to aminoglycosides and disinfectants, that was located on a 70-kb plasmid.
In Vitro
Properties of BAL30072, a Novel Siderophore Sulfactam with Activity against Multiresistant Gram-Negative Bacilli
Authors: Page Malcolm G. P. , Dantier Clothilde , Desarbre Eric
Published: March 2010

BAL30072 is a new monocyclic β-lactam antibiotic belonging to the sulfactams. Its spectrum of activity against significant Gram-negative pathogens with β-lactam-resistant phenotypes was evaluated and was compared with the activities of reference drugs, including aztreonam, ceftazidime, cefepime, meropenem, imipenem, and piperacillin-tazobactam. BAL30072 showed potent activity against multidrug-resistant (MDR)
Pseudomonas aeruginosa
and
Acinetobacter
sp. isolates, including many carbapenem-resistant strains. The MIC
90
s were 4 μg/ml for MDR
Acinetobacter
spp. and 8 μg/ml for MDR
P. aeruginosa
, whereas the MIC
90
of meropenem for the same sets of isolates was >32 μg/ml. BAL30072 was bactericidal against both
Acinetobacter
spp. and
P. aeruginosa
, even against strains that produced metallo-β-lactamases that conferred resistance to all other β-lactams tested, including aztreonam. It was also active against many species of MDR isolates of the
Enterobacteriaceae
family, including isolates that had a class A carbapenemase or a metallo-β-lactamase. Unlike other monocyclic β-lactams, BAL30072 was found to trigger the spheroplasting and lysis of
Escherichia
coli
rather than the formation of extensive filaments. The basis for this unusual property is its inhibition of the bifunctional penicillin-binding proteins PBP 1a and PBP 1b, in addition to its high affinity for PBP 3, which is the target of monobactams, such as aztreonam.
Population Pharmacokinetics of Micafungin in Neonates and Young Infants
Authors: Hope William W. , Smith P. Brian , Arrieta Antonio , Buell Donald N. , Roy Michael , Kaibara Atsunori , Walsh Thomas J. , Cohen-Wolkowiez Michael , Benjamin Daniel K.
Published: March 2010

Micafungin is an echinocandin with potent activity against
Candida
spp. Hematogenous
Candida
meningoencephalitis (HCME) is a frequent complication of disseminated
Candida
infection in premature infants. A preclinical model of HCME suggests that micafungin may be an effective agent for this syndrome, but relatively high weight-based dosages are required. This prompted the further study of the safety and pharmacokinetics (PK) of micafungin in infants. Here, we describe the population pharmacokinetics of micafungin in 47 infants with a proven or presumptive diagnosis of disseminated candidiasis, who received 0.75, 1.5, 3, 7, 10, and 15 mg/kg of micafungin. The drug was infused daily, and samples were taken in the first dosing interval and at steady state. Serum concentrations were measured using high-performance liquid chromatography (HPLC). Data were modeled using an allometric pharmacokinetic model using a three-fourths scaling exponent for clearance and parameters normalized to a 70-kg adult. Drug exposures were estimated using Monte Carlo simulation. Optimal sampling times were determined using D-optimal design theory. The fit of the allometric model to the data was highly acceptable. The pharmacokinetics of micafungin were linear. The weight-normalized estimates of clearance and volume of distribution approximated those previously described for adults. The original population parameter values could be recapitulated in the Monte Carlo simulations. A dosage of 10 mg/kg/day resulted in 82.6% of patients with areas under the concentration-time curve (AUCs) that are associated with near-maximal decline in fungal burden within the central nervous system (CNS).
Impact of Different Carbapenems and Regimens of Administration on Resistance Emergence for Three Isogenic
Pseudomonas aeruginosa
Strains with Differing Mechanisms of Resistance
Authors: Louie Arnold , Bied Adam , Fregeau Christine , Van Scoy Brian , Brown David , Liu Weiguo , Bush Karen , Queenan Anne-Marie , Morrow Brian , Khashab Mohammed , Kahn James B. , Nicholson Susan , Kulawy Robert , Drusano G. L.
Published: March 2010

We compared drugs (imipenem and doripenem), doses (500 mg and 1 g), and infusion times (0.5 and 1.0 [imipenem], 1.0 and 4.0 h [doripenem]) in our hollow-fiber model, examining cell kill and resistance suppression for three isogenic strains of
Pseudomonas aeruginosa
PAO1. The experiments ran for 10 days. Serial samples were taken for total organism and resistant subpopulation counts. Drug concentrations were determined by high-pressure liquid chromatography-tandem mass spectrometry (LC/MS/MS). Free time above the MIC (time > MIC) was calculated using ADAPT II. Time to resistance emergence was examined with Cox modeling. Cell kill and resistance emergence differences were explained, in the main, by differences in potency (MIC) between doripenem and imipenem. Prolonged infusion increased free drug time > MIC and improved cell kill. For resistance suppression, the 1-g, 4-h infusion was able to completely suppress resistance for the full period of observation for the wild-type isolate. For the mutants, control was ultimately lost, but in all cases, this was the best regimen. Doripenem gave longer free time > MIC than imipenem and, therefore, better cell kill and resistance suppression. For the wild-type organism, the 1-g, 4-h infusion regimen is preferred. For organisms with resistance mutations, larger doses or addition of a second drug should be studied.
Phenotypic Susceptibility to Bevirimat in Isolates from HIV-1-Infected Patients without Prior Exposure to Bevirimat
Authors: Margot Nicolas A. , Gibbs Craig S. , Miller Michael D.
Published: March 2010

Bevirimat (BVM) is the first of a new class of anti-HIV drugs with a novel mode of action known as maturation inhibitors. BVM inhibits the last cleavage of the Gag polyprotein by HIV-1 protease, leading to the accumulation of the p25 capsid-small peptide 1 (SP1) intermediate and resulting in noninfectious HIV-1 virions. Early clinical studies of BVM showed that over 50% of the patients treated with BVM did not respond to treatment. We investigated the impact of prior antiretroviral (ARV) treatment and/or natural genetic diversity on BVM susceptibility by conductingin vitrophenotypic analyses of viruses made from patient samples. We generated 31 recombinant viruses containing the entiregagand protease genes from 31 plasma samples from HIV-1-infected patients with (n= 21) or without (n= 10) prior ARV experience. We found that 58% of the patient isolates tested had a >10-fold reduced susceptibility to BVM, regardless of the patient's ARV experience or the level of isolate resistance to protease inhibitors. Analysis of mutants with site-directed mutations confirmed the role of the V370A SP1 polymorphism (SP1-V7A) in resistance to BVM. Furthermore, we demonstrated for the first time that a capsid polymorphism, V362I (CA protein-V230I), is also a major mutation conferring resistance to BVM. In contrast, none of the previously defined resistance-conferring mutations in Gag selectedin vitro(H358Y, L363M, L363F, A364V, A366V, or A366T) were found to occur among the viruses that we analyzed. Our results should be helpful in the design of diagnostics for prediction of the potential benefit of BVM treatment in HIV-1-infected patients.
Activity of Ceftaroline against Recent Emerging Serotypes of
Streptococcus pneumoniae
in the United States
Authors: Jacobs Michael R. , Good Caryn E. , Windau Anne R. , Bajaksouzian Saralee , Biek Donald , Critchley Ian A. , Sader Helio S. , Jones Ronald N.
Published: March 2010

The
in vitro
activity of ceftaroline against 891 pneumococci collected in 2008 from 22 centers in the United States was investigated. Ceftaroline was the most potent agent tested, with the MICs being <0.008 to 0.5 μg/ml and the MIC
90
s being <0.008 to 0.25 μg/ml against 11 prevailing serotypes. The overall rates of susceptibility were as follows: penicillin G, 86.2%; ceftriaxone, 90.7%; cefuroxime, 70.1%; erythromycin, 61.6%; clindamycin, 79.2%; levofloxacin, 99.4%; and vancomycin, 100%. Serotype 19A isolates were the least susceptible. These results support the use of ceftaroline for the treatment of pneumococcal infections, including those caused by pneumococci resistant to other agents.
Interactions ofEncephalitozoon cuniculiPolar Tube Proteins
Authors: Bouzahzah Boumediene , Nagajyothi Fnu , Ghosh Kaya , Takvorian Peter M. , Cali Ann , Tanowitz Herbert B. , Weiss Louis M.
Published: March 2010

Microsporidia are eukaryotic, obligate intracellular organisms defined by small spores that contain a single invasion organelle, the polar tube, which coils around the interior of the spore. When these parasites infect host cells, the polar tube is discharged from the anterior pole of the spore, pierces the cell, and transfers sporoplasm into the cytoplasm of the host. Three polar tube proteins (PTP1, PTP2, and PTP3) have been identified in this structure. The interactions of these proteins in the assembly and function of the polar tube are not known. This study was undertaken to examine the protein interactions of theEncephalitozoon cuniculipolar tube proteins (EcPTPs). Immunofluorescence and immunoelectron microscopy confirmed the colocalization of EcPTP1, EcPTP2, and EcPTP3 to the polar tube. Experiments using cross-linkers indicated that EcPTP1, EcPTP2, and EcPTP3 form a complex in the polar tube, which was confirmed by immunoprecipitation using EcPTP1 antiserum. Yeast two-hybrid analysis revealed that full-length EcPTP1, EcPTP2, and EcPTP3 interact with each otherin vivo. Both the N and C termini of EcPTP1 were involved in these interactions, but the central region of this protein, which contains a repetitive motif, was not. Further studies of polar tube proteins and their structural interactions may help elucidate the formation of the polar tube during the invasion process.
Probiotic Colonization of the Adherent Mucus Layer of HT29MTXE12 Cells Attenuates
Campylobacter jejuni
Virulence Properties
Authors: Alemka Abofu , Clyne Marguerite , Shanahan Fergus , Tompkins Thomas , Corcionivoschi Nicolae , Bourke Billy
Published: March 2010

The HT29MTXE12 (E12) cell line harbors an adherent mucus layer, providing a novel technique to model mucosal infection
in vitro
. In this study, we have characterized the interaction of
Campylobacter jejuni
with the E12 cell line and exploited its unique mucus layer to examine the potential efficacy of probiotic treatment to attenuate
C. jejuni
virulence properties.
C. jejuni
81-176 colonized and reproduced in E12 mucus. Adhesion to and internalization of
C. jejuni
were enhanced in E12 cells harboring mucus compared to parental cells without mucus. Translocation of
C. jejuni
occurred at early time points following infection.
C. jejuni
aligned with tight junctions and colocalized with the tight junction protein occludin, suggesting a paracellular route of translocation. Probiotic strains
Lactobacillus rhamnosus
R0011,
Lactobacillus helveticus
R0052,
Lactobacillus salivarius
AH102,
Bifidobacterium longum
AH1205, a commercial combination of
L. rhamnosus
R0011 and
L. helveticus
R0052 (Lacidofil), and a cocktail consisting of
L. rhamnosus
,
L. helveticus
, and
L. salivarius
(RhHeSa) colonized E12 mucus and bound to underlying cells. Probiotics attenuated
C. jejuni
association with and internalization into E12 cells and translocation to the basolateral medium of transwells. Live bacteria and prolonged precolonization of E12 cells with probiotics were necessary for probiotic action. These results demonstrate the potential for E12 cells as a model of mucosal pathogenesis and provide a rationale for the further investigation of probiotics as prophylaxis against human campylobacteriosis.
Modulation of Allergic Airway Inflammation by the Oral Pathogen
Porphyromonas gingivalis
Authors: Card Jeffrey W. , Carey Michelle A. , Voltz James W. , Bradbury J. Alyce , Ferguson Catherine D. , Cohen Eric A. , Schwartz Samuel , Flake Gordon P. , Morgan Daniel L. , Arbes Samuel J. , Barrow David A. , Barros Silvana P. , Offenbacher Steven , Zeldin Darryl C.
Published: March 2010

Accumulating evidence suggests that bacteria associated with periodontal disease may exert systemic immunomodulatory effects. Although the improvement in oral hygiene practices in recent decades correlates with the increased incidence of asthma in developed nations, it is not known whether diseases of the respiratory system might be influenced by the presence of oral pathogens. The present study sought to determine whether subcutaneous infection with the anaerobic oral pathogen
Porphyromonas gingivalis
exerts a regulatory effect on allergic airway inflammation. BALB/c mice sensitized and subsequently challenged with ovalbumin exhibited airway hyperresponsiveness to methacholine aerosol and increased airway inflammatory cell influx and Th2 cytokine (interleukin-4 [IL-4], IL-5, and IL-13) content relative to those in nonallergic controls. Airway inflammatory cell and cytokine contents were significantly reduced by establishment of a subcutaneous infection with
P. gingivalis
prior to allergen sensitization, whereas serum levels of ovalbumin-specific IgE and airway responsiveness were not altered. Conversely, subcutaneous infection initiated after allergen sensitization did not alter inflammatory end points but did reduce airway responsiveness in spite of increased serum IgE levels. These data provide the first direct evidence of a regulatory effect of an oral pathogen on allergic airway inflammation and responsiveness. Furthermore, a temporal importance of the establishment of infection relative to allergen sensitization is demonstrated for allergic outcomes.
Zebrafish as a Model Host for
Candida albicans
Infection
Authors: Chao Chun-Cheih , Hsu Po-Chen , Jen Chung-Feng , Chen I-Hui , Wang Chieh-Huei , Chan Hau-Chien , Tsai Pei-Wen , Tung Kai-Che , Wang Chian-Huei , Lan Chung-Yu , Chuang Yung-Jen
Published: March 2010

In this work, the zebrafish model organism was developed to obtain a minivertebrate host system for a
Candida albicans
infection study. We demonstrated that
C. albicans
can colonize and invade zebrafish at multiple anatomical sites and kill the fish in a dose-dependent manner. Inside zebrafish, we monitored the progression of the
C. albicans
yeast-to-hypha transition by tracking morphogenesis, and we monitored the corresponding gene expression of the pathogen and the early host immune response. We performed a zebrafish survival assay with different
C. albicans
strains (SC5314, ATCC 10231, an
hgc1
mutant, and a
cph1
/
efg1
double mutant) to determine each strain's virulence, and the results were similar to findings reported in previous mouse model studies. Finally, using zebrafish embryos, we monitored
C. albicans
infection and visualized the interaction between pathogen and host myelomonocytic cells
in vivo
. Taken together, the results of this work demonstrate that zebrafish can be a useful host model to study
C. albicans
pathogenesis, and they highlight the advantages of using the zebrafish model in future invasive fungal research.
Role of Excessive Inflammatory Response to
Stenotrophomonas maltophilia
Lung Infection in DBA/2 Mice and Implications for Cystic Fibrosis
Authors: Di Bonaventura Giovanni , Pompilio Arianna , Zappacosta Roberta , Petrucci Francesca , Fiscarelli Ersilia , Rossi Cosmo , Piccolomini Raffaele
Published: March 2010

Stenotrophomonas maltophilia
is a pathogen that causes infections mainly in immunocompromised patients. Despite increased
S. maltophilia
isolation from respiratory specimens of patients with cystic fibrosis (CF), the real contribution of the microorganism to CF pathogenesis still needs to be clarified. The aim of the present study was to evaluate the pathogenic role of
S. maltophilia
in CF patients by using a model of acute respiratory infection in DBA/2 mice following a single exposure to aerosolized bacteria. The pulmonary bacterial load was stable until day 3 and then decreased significantly from day 3 through day 14, when the bacterial load became undetectable in all infected mice. Infection disseminated in most mice, although at a very low level. Severe effects (swollen lungs, large atelectasis, pleural adhesion, and hemorrhages) of lung pathology were observed on days 3, 7, and 14. The clearance of
S. maltophilia
observed in DBA/2 mouse lungs was clearly associated with an early and intense bronchial and alveolar inflammatory response, which is mediated primarily by neutrophils. Significantly higher levels of interleukin-1β (IL-1β), IL-6, IL-12, gamma interferon (IFN-γ), tumor necrosis factor alpha (TNF-α), GROα/KC, MCP-1/JE, MCP-5, macrophage inflammatory protein 1α (MIP-1α), MIP-2, and TARC were observed in infected mice on day 1 with respect to controls. Excessive pulmonary infection and inflammation caused systemic effects, manifested by weight loss, and finally caused a high mortality rate. Taken together, our results show that
S. maltophilia
is not just a bystander in CF patients but has the potential to contribute to the inflammatory process that compromises respiratory function.
Depolymerization of microtubule arrays in root tip cells by oryzalin and their recovery with modified nucleation patterns
Authors: Cleary A. L. , Hardham A. R.
Published: March 2010

Immunofluorescence microscopy with anti-tubulin has been used to study the effects of the dinitroaniline herbicide, oryzalin, on microtubule arrays in root tip cells of a number of species of plants. All species of grasses that were examined showed rapid microtubule depolymerization, as did the nongrass Potamogeton. All other nongrass monocotyledons and dicotyledons tested required much longer treatment times to achieve microtubule depolymerization in the majority of root tip cells. Correlated immunofluorescence and electron microscopy have been used to obtain details of depolymerization and repolymerization of microtubules during treatment and recovery in a resistant plant, Zinnia elegans, and in a sensitive plant, Lolium rigidum. Although rates of disruption differ, both plants displayed similar patterns of microtubule depolymerization and repolymerization. The microtubules that comprise the different categories of array in the root tip cells were differentially sensitive to oryzalin. In order of increasing stability they were as follows: polar microtubules in mitotic cells < interphase arrays < preprophase bands ≤ phragmoplasts [Formula: see text] kinetochore microtubules. During recovery, microtubules are nucleated in the cell cortex in interphase and at the kinetochores during mitosis. The cells are able to reinstate cortical interphase arrays, preprophase bands, and phragmoplasts of apparently normal organization, but not normal, functional spindles. Our results provide basic information on the use of oryzalin in studying the organization and dynamics of microtubule arrays in higher plant cells.
Nonsummer stomatal conductance for the invasive vines kudzu and Japanese honeysuckle
Authors: Carter Gregory A. , Teramura Alan H.
Published: March 2010

A field study was conducted in Maryland to estimate nonsummer stomatal conductances on clear days for two invasive woody vine species common to the southeastern United States. Before the first frost in late October, stomatal conductances were similar for kudzu (Pueraria lobata) and Japanese honeysuckle (Lonicera japonica). When minimum predawn air temperature fell to −0.6 °C, kudzu leaves were irreversibly damaged, whereas maximum daily conductance in honeysuckle was unaffected. Maximum conductances in honeysuckle increased to 14 mm s−1 in late November and mid-December, similar to late-spring and summer values. When minimum air temperatures decreased to −2.8 °C in January, conductance still remained above 5 mm s−1. Maximum daily conductance was lowest in early March, corresponding with low leaf temperatures. By mid-April, maximum conductance increased to 10 mm s−1. Conductances suggested that rates of leaf gas exchange in honeysuckle during fall, winter, and spring were relatively high. Carbon gain during this period might thus contribute substantially to the invasive growth characteristic of the species.
The influence of elevated carbon dioxide concentrations on the partitioning of carbon in source leaves of Phaseolus vulgaris
Authors: Hoddinott John , Jolliffe Peter
Published: March 2010

Plants may alter their growth pattern in response to being grown in elevated CO2 concentrations. The nature of the change in carbon partitioning underlying those alterations was investigated in Phaseolus vulgaris cv. Gold Crop grown to the third trifoliate leaf stage in CO2 concentrations of 380, 800, and 1400 ppm. There was no effect of the CO2 concentration on plant height, leaf area, or dry weight, but the specific leaf weight increased significantly with the CO2, concentration, indicating a denser leaf structure. The starch content of the leaves also increased significantly as the CO2 level increased. A primary leaf was pulse labelled with 14CO2 and the depletion of label from that source leaf was monitored with a GM tube. The depletion of the count rate with time was described by a nonlinear curve fitting procedure that allowed the derivation of rate constants to describe the partitioning of carbon in a two-compartment model. Rates of carbon storage decreased in the light with increasing CO2 concentrations with no effect on the rates of export or remobilization. Both export and storage were reduced in the dark at all CO2 levels, with an increase in the residence time of carbon in the export pool. Reducing the CO2 concentration around the source leaf just after labelling did not change carbon partitioning compared to controls. Increasing the CO2 concentration around the source leaf just after labelling increased all carbon flux rates and reduced the residence times in the leaf pools.
The structure of the rhizosphere of maize seedling roots, a cryogenic scanning electron microscopy study
Authors: Fyson A. , Kerr P. , Lott J. N. A. , Oaks A.
Published: March 2010

The surface of primary roots of maize (Zea mays cv. W64A × 182E) seedlings grown in a field soil was examined after cryogenic preparation of samples for scanning electron microscopy. The very short preparation time of this method and the absence of fixation and drying procedures give excellent preservation of the spatial organization of the rhizosphere. As root hairs develop, they carry soil clear of the epidermal surface to form a distinct soil sheath layer. Root hairs remain turgid along the entire length of the primary root of the seedlings studied and are often distorted as a result of their growth around obstructing soil aggregates. The epidermal surface remains remarkably clean along the entire length of the root. Fractures of frozen roots reveal that the epidermis is covered by a thin layer that may be mucilage. Very few microorganisms are observed on the epidermal surface.
Genetic and environmental contributions to multivariate morphological pattern in Puccinellia (Poaceae)
Authors: Davis Jerrold I.
Published: March 2010

The contributions of genetic and environmental variation to multivariate patterns in morphology were investigated in a comparative analysis of two samples of plants representing the Puccinellia nuttalliana complex (Poaceae). The first sample is a series of individuals (genotypes) collected live, vegetatively divided, and grown under controlled environmental conditions. Phenotypic variation in this sample, in individual characters and in multivariate factors, can be apportioned between genetic (among genotype) and environmental (among treatment) causes. The second sample consists of field-collected individuals from throughout the North American range of the complex. Variation in this sample, as in most field-collected samples, cannot be assigned directly to its underlying causes. Multivariate patterns in the two samples were analyzed by identical principal-components analyses of 48 morphological characters. The strongest factor identified by the greenhouse principal-components analysis correlates with the strongest of the field principal-components analysis; they are similar in character makeup, both reflecting spikelet size and plant scabrousness. These factors have a genetic component and no environmental component and appear to differentiate Puccinellia distans from the rest of the complex. The second strongest factor of the greenhouse principal-components analysis correlates with the second of the field principal-components analysis. These axes reflect general vegetative stature; they have genetic and plastic components. The overall analysis indicates that multivariate patterns in phenotype can reflect both genetic and environmental effects, in varying proportions; patterns of genetic affinity therefore may be difficult to dissociate from those reflecting plasticity.
Ovule development in Brassica campestris: a light microscope study
Authors: Sumner M. J. , Caeseele L. Van
Published: March 2010

A light microscope study was made of ovule development in Brassica catnpestris L. cv. Candle (canola, rapeseed), from the initiation of the ovule to the mature megagametophyte. The ovule is bitegmic and campylotropous and exhibits the Polygonum-type of megagametophyte development. The inner integument is dermal in origin from a series of wedge-shaped initials. The outer integument is derived from both dermal and subdermal initials that originate proximal to the inner integument. The megasporocyte arises from an archesporial or primary sporogenous cell. The products of meiosis are a triad or tetrad of megaspores. Expansion of the megagametophyte is micropylar and coincides with the formation of a large central vacuole. The mature binucleate central cell is devoid of the large central vacuole characteristic of the coenocytic and early cellular stages of megagametophyte development. The cell walls of the mature egg apparatus and antipodals are periodic acid – Schiff positive. The antipodals, unlike the cells of the egg apparatus, do not increase in size following their formation.
Intracellular localization and morphology of rhabdovirus-like particles in dodder (Cuscuta sp.)
Authors: Roos Urs-Peter , Aldrich Henry C.
Published: March 2010

Rhabdovirus-like particles were discovered in a piece of vine with haustoria of the flowering parasitic plant dodder (Cuscuta sp.). The particles occurred in the perinuclear space or distensions of it and were often arranged in paracrystalline arrays. Most longitudinally sectioned particles were rod shaped and had a round tip, a planar base, and very frequently also a membranous basal bulb. The mean length from the base to the apex was 212.1 nm (SD 13.5 nm, n = 29). The mean outer diameter in cross sections was 63.4 nm (SD 3.7 nm, n = 50). Cross-section profiles comprised an outer coat, with the dimensions of a cellular membrane, and a core of mean diameter 24.9 nm (SD 2.4 nm, n = 20), which appeared as an electron-opaque annulus or stellate ring with an electron-lucent center. Bacilliform particles of approximately double length, with two rounded ends, some of which appeared as two rod-shaped ones joined base to base by a common coat, were observed infrequently. In their morphology, their dimensions, and their intracellular localization these particles resembled rhabdoviruses of unknown origin or significance. Intranuclear rodlets associated with heterochromatin may represent a stage in the assembly of the rhabdovirus-like particles, or a second type of virus-like particles. This is the first report that a species of Cuscuta can be a carrier of what most likely is a rhabdovirus of as yet unknown taxonomic affinities.
Microcolonies of bacteria as a nutrient source for lignicolous and other fungi
Authors: Barron G. L.
Published: March 2010

Under low nutrient conditions hyphae of certain fungi are strongly attracted to microcolonies of bacteria belonging to the genera Pseudomonas and Agrobacterium. Hyphae of the fungi penetrate the microcolonies and proliferate to produce coral-loid, haustorial-like masses of absorptive hyphae. The bacteria in the colonies are lysed and the contents apparently absorbed as a nutrient source by the fungi. The four fungi that demonstrated this capability were Agaricus brunnescens (= A. bisporus), Coprinus quadrifidus, Lepista nuda, and Pleurotus ostreatus. Approximately 100 additional species belonging to the Basidiomycota, Oomycota, Zygomycota, Deuteromycota, or Ascomycota were also tested, but none were found capable of attacking and digesting bacterial colonies in this way.
Citrus pollen tube development in cross-compatible gynoecia, self-incompatible gynoecia, and in vitro
Authors: Kahn Tracy L. , DeMason Darleen A.
Published: March 2010

The route of 'Orlando' tangelo (Citrus paradisi Macf. × C. reticulata Blanco) pollen tubes was traced and compared in self-incompatible pollinations and cross-compatible pollinations with 'Dancy' tangerine (C. reticulata Blanco). In both crosses, 'Orlando' pollen germinated in the stigmatic exudate and grew between the papillae on the stigma surface and inter-cellularly between the parenchymatous cells until reaching a stylar canal by 3 days. However, in the incompatible pollination, irregular deposition of callose occurred in the pollen tube walls as early as 1 day after pollination. By day 6, pollen tubes were in the upper portion of the ovary in the compatible pollination, whereas most pollen tubes from the incompatible pollination were still in the upper style. 'Orlando' pollen tube growth rate decreased substantially by day 3 in both the self-incompatible pollination and in vitro but increased rapidly after day 3 in the compatible combination. The generative cell divided between 1 and 3 days after pollination in the compatible cross. Generative cell division was observed by day 3 in only a few pollen tubes in the incompatible cross and in cultured tubes. Compatible pollen tubes grew slowly for the first 3 days after pollination, during which time generative cells divided and then grew rapidly until fertilization. In contrast, incompatible pollen tubes showed morphological features indicative of an incompatibility reaction by 1 day after pollination and grew slowly for a period of 6 days, and then ceased growth.
Improvements in the growth and yield of olive trees by transformation with the Ri plasmid of Agrobacterium rhizogenes
Authors: Strobel Gary A. , Nachmias Avi , Hess Wilford M.
Published: March 2010

Results of experiments to determine the beneficial effects of Agrobacterium rhizogenes inoculation on olive seedlings are reported herein. Young, bare root stock, olive trees treated with Agrobacterium rhizogenes 232 possessed a larger ratio of new root to older root mass, a larger total root mass, and a greater total top dry weight after 60 days than those treated with autoclaved A. rhizogenes 232 or a strain of the bacterium lacking the Ri plasmid. Over a course of 3 years, transformed trees grew more quickly and produced significantly more flowers, fruits, and oil than control trees, in the field. New secondary roots initiated by A. rhizogenes were well integrated into the existing vascular system of the older roots. The treatment of olive seedlings with A. rhizogenes should be seriously considered as an agronomic practice deserving further testing.
Measuring the contact angle of water droplets on foliar surfaces
Authors: Boyce Richard L. , Berlyn Graeme P.
Published: March 2010

We describe a novel technique for measuring static contact angles on foliar surfaces that uses a micromanipulator and a 35-mm camera equipped with a microlens, autobellows, focusing rail, and tripod. After placing droplets on foliage, the contact angle is photographed. Negatives are mounted as slides, and the contact angle is measured from the projected image. We suggest that this method has a number of advantages over those previously used.
Community organization and ecosystem theory
Authors: Mueller-Dombois Dieter
Published: March 2010

The community hypotheses of earlier European and North American vegetation ecologists stimulated much thought-provoking research on the nature of plant community organization. These research efforts can now be seen as providing an improved understanding of species patterning in broader ecosystem units, such as those defined by Krajina's biogeoclimatic zones. Built on this tradition, the author's research concept is outlined, which generally begins with the documentation of species distribution patterns, leading to autoecological studies of key species and then to a synthesis of species functions at the ecosystem level. This approach resulted in an ecosystem theory that explains periodic stand-level dieback in the Hawaiian rain forest as primarily a demographic phenomenon of the leading canopy species, Metrosideros polymorpha. The theory may have application to similar forests that are made up of mosaics of cohort stands. The theory also adds to a better understanding of the ecological concepts of climax and succession and provides for an important plant ecological criterion in the design of natural areas for ecosystem conservation.
Niche theory and community organization
Authors: Shugart H. H. , Bonan G. B. , Rastetter E. B.
Published: March 2010

The ecological niche concept was developed by animal ecologists, and the concept has only recently been applied to plant population studies to any great degree. Many different aspects of the niche concept have been explored to determine the manner in which plant communities are organized. In one approach, interest in understanding the response of plant populations to fine-scale heterogeneity has given plant ecologists an organism-oriented view of the plant community. One advantage of the concepts that are presently being developed in plant ecological studies is that individual-plant models can be used to scale the understanding of microscale plant phenomena to larger spatial scales. In this paper, we present two examples that show how these niche concepts can be incorporated into dynamic models that can be used to generate landscape-scale patterns.