bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Vivo
Emergence of Tigecycline Resistance in Multidrug-Resistant Klebsiella pneumoniae and Escherichia coli
Authors: Spanu Teresa , De Angelis Giulia , Cipriani Michela , Pedruzzi Barbara , D'Inzeo Tiziana , Cataldo Maria Adriana , Sganga Gabriele , Tacconelli Evelina 
Published: May 2012

ABSTRACT

Although resistance to tigecycline has been reported in surveillance studies, very few reports have described the emergence of resistance
in vivo
. We report two cases of patients with infections due to SHV-12-producing
Klebsiella pneumoniae
and
K. pneumoniae
carbapenemase-3 (KPC-3)-producing
Escherichia coli
, which developed tigecycline resistance
in vivo
after treatment. The reported limited experience underlines the risk of occurrence of a tigecycline MIC increase under treatment pressure.
Identification of Disubstituted Sulfonamide Compounds as Specific Inhibitors of Hepatitis B Virus Covalently Closed Circular DNA Formation
Authors: Cai Dawei , Mills Courtney , Yu Wenquan , Yan Ran , Aldrich Carol E. , Saputelli Jeffry R. , Mason William S. , Xu Xiaodong , Guo Ju-Tao , Block Timothy M. , Cuconati Andrea , Guo Haitao 
Published: May 2012

ABSTRACT

Hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) plays a central role in viral infection and persistence and is the basis for viral rebound after the cessation of therapy, as well as the elusiveness of a cure even after extended treatment. Therefore, there is an urgent need for the development of novel therapeutic agents that directly target cccDNA formation and maintenance. By employing an innovative cell-based cccDNA assay in which secreted HBV e antigen is a cccDNA-dependent surrogate, we screened an in-house small-molecule library consisting of 85,000 drug-like compounds. Two structurally related disubstituted sulfonamides (DSS), termed CCC-0975 and CCC-0346, emerged and were confirmed as inhibitors of cccDNA production, with low micromolar 50% effective concentrations (EC
50
s) in cell culture. Further mechanistic studies demonstrated that DSS compound treatment neither directly inhibited HBV DNA replication in cell culture nor reduced viral polymerase activity in the
in vitro
endogenous polymerase assay but synchronously reduced the levels of HBV cccDNA and its putative precursor, deproteinized relaxed circular DNA (DP-rcDNA). However, DSS compounds did not promote the intracellular decay of HBV DP-rcDNA and cccDNA, suggesting that the compounds interfere primarily with rcDNA conversion into cccDNA. In addition, we demonstrated that CCC-0975 was able to reduce cccDNA biosynthesis in duck HBV-infected primary duck hepatocytes. This is the first attempt, to our knowledge, to identify small molecules that target cccDNA formation, and DSS compounds thus potentially serve as proof-of-concept drug candidates for development into therapeutics to eliminate cccDNA from chronic HBV infection.
Tigecycline Resistance Can Occur Independently of the
ramA
Gene in Klebsiella pneumoniae
Authors: Veleba Mark , Schneiders Thamarai 
Published: May 2012

ABSTRACT

Tigecycline resistance in
Klebsiella pneumoniae
results from
ramA
upregulation that causes the overexpression of the efflux pump, AcrAB-TolC. Tigecycline mutants, derived from Ecl8Δ
ramA
, can exhibit a multidrug resistance phenotype due to increased transcription of the
marA
,
rarA
,
acrAB
, and
oqxAB
genes. These findings support the idea that tigecycline or multidrug resistance in
K. pneumoniae
, first, is not solely dependent on the
ramA
gene, and second, can arise via alternative regulatory pathways in
K. pneumoniae
.
Mechanism of Action of and Mechanism of Reduced Susceptibility to the Novel Anti-Clostridium difficile Compound LFF571
Authors: Leeds J. A. , Sachdeva M. , Mullin S. , Dzink-Fox J. , LaMarche M. J. 
Published: May 2012

ABSTRACT

LFF571 is a novel semisynthetic thiopeptide and potent inhibitor of Gram-positive bacteria. We report that the antibacterial activity of LFF571 against
Clostridium difficile
is due to inhibition of translation. Single-step mutants of
C. difficile
with reduced susceptibility to LFF571 were selected at frequencies of <4.5 × 10
−11
to 1.2 × 10
−9
. Sequencing revealed a G260E substitution in the thiopeptide-binding pocket of elongation factor Tu. Importantly, this mutation did not confer cross-resistance to clinically used antimicrobials. These results support the development of LFF571 as a treatment for
C. difficile
infection.
Identification of Coli Surface Antigen 23, a Novel Adhesin of Enterotoxigenic Escherichia coli
Authors: Del Canto Felipe , Botkin Douglas J. , Valenzuela Patricio , Popov Vsevolod , Ruiz-Perez Fernando , Nataro James P. , Levine Myron M. , Stine O. Colin , Pop Mihai , Torres Alfredo G. , Vidal Roberto 
Published: May 2012

ABSTRACT

Enterotoxigenic
Escherichia coli
(ETEC) is an important cause of diarrhea, mainly in developing countries. Although there are 25 different ETEC adhesins described in strains affecting humans, between 15% and 50% of the clinical isolates from different geographical regions are negative for these adhesins, suggesting that additional unidentified adhesion determinants might be present. Here, we report the discovery of Coli Surface Antigen 23 (CS23), a novel adhesin expressed by an ETEC serogroup O4 strain (ETEC 1766a), which was negative for the previously known ETEC adhesins, albeit it has the ability to adhere to Caco-2 cells. CS23 is encoded by an 8.8-kb locus which contains 9 open reading frames (ORFs), 7 of them sharing significant identity with genes required for assembly of K88-related fimbriae. This gene locus, named
aal
(
a
dhesion-
a
ssociated
l
ocus), is required for the adhesion ability of ETEC 1766a and was able to confer this adhesive phenotype to a nonadherent
E. coli
HB101 strain. The CS23 major structural subunit, AalE, shares limited identity with known pilin proteins, and it is more closely related to the CS13 pilin protein CshE, carried by human ETEC strains. Our data indicate that CS23 is a new member of the diverse adhesin repertoire used by ETEC strains.
Urease Activity Represents an Alternative Pathway for Mycobacterium tuberculosis Nitrogen Metabolism
Authors: Lin Wenwei , Mathys Vanessa , Ang Emily Lei Yin , Koh Vanessa Hui Qi , Martínez Gómez Julia María , Ang Michelle Lay Teng , Zainul Rahim Siti Zarina , Tan Mai Ping , Pethe Kevin , Alonso Sylvie 
Published: May 2012

ABSTRACTUrease represents a critical virulence factor for some bacterial species through its alkalizing effect, which helps neutralize the acidic microenvironment of the pathogen. In addition, urease serves as a nitrogen source provider for bacterial growth. Pathogenic mycobacteria express a functional urease, but its role during infection has yet to be characterized. In this study, we constructed a urease-deficientMycobacterium tuberculosisstrain and confirmed the alkalizing effect of the urease activity within the mycobacterium-containing vacuole in resting macrophages but not in the more acidic phagolysosomal compartment of activated macrophages. However, the urease-mediated alkalizing effect did not confer any growth advantage onM. tuberculosisin macrophages, as evidenced by comparable growth profiles for the mutant, wild-type (WT), and complemented strains. In contrast, the urease-deficient mutant exhibited impairedin vitrogrowth compared to the WT and complemented strains when urea was the sole source of nitrogen. Substantial amounts of ammonia were produced by the WT and complemented strains, but not with the urease-deficient mutant, which represents the actual nitrogen source for mycobacterial growth. However, the urease-deficient mutant displayed parental colonization profiles in the lungs, spleen, and liver in mice. Together, our data demonstrate a role for the urease activity inM. tuberculosisnitrogen metabolism that could be crucial for the pathogen's survival in nutrient-limited microenvironments where urea is the sole nitrogen source. Our work supports the notion thatM. tuberculosisvirulence correlates with its unique metabolic versatility and ability to utilize virtually any carbon and nitrogen sources available in its environment.
Selective Purification of Recombinant Neuroactive Peptides Using the Flagellar Type III Secretion System
Authors: Singer Hanna M. , Erhardt Marc , Steiner Andrew M. , Zhang Min-Min , Yoshikami Doju , Bulaj Grzegorz , Olivera Baldomero M. , Hughes Kelly T. 
Published: May 2012

ABSTRACT

The structure, assembly, and function of the bacterial flagellum involves about 60 different proteins, many of which are selectively secreted via a specific type III secretion system (T3SS) (J. Frye et al., J. Bacteriol. 188:2233–2243, 2006). The T3SS is reported to secrete proteins at rates of up to 10,000 amino acid residues per second. In this work, we showed that the flagellar T3SS of
Salmonella enterica
serovar Typhimurium could be manipulated to export recombinant nonflagellar proteins through the flagellum and into the surrounding medium. We translationally fused various neuroactive peptides and proteins from snails, spiders, snakes, sea anemone, and bacteria to the flagellar secretion substrate FlgM. We found that all tested peptides of various sizes were secreted via the bacterial flagellar T3SS. We subsequently purified the recombinant μ-conotoxin SIIIA (rSIIIA) from
Conus striatus
by affinity chromatography and confirmed that T3SS-derived rSIIIA inhibited mammalian voltage-gated sodium channel Na
V
1.2 comparably to chemically synthesized SIIIA.

IMPORTANCE
Manipulation of the flagellar secretion system bypasses the problems of inclusion body formation and cellular degradation that occur during conventional recombinant protein expression. This work serves as a proof of principle for the use of engineered bacterial cells for rapid purification of recombinant neuroactive peptides and proteins by exploiting secretion via the well-characterized flagellator type III secretion system.
Contribution of a Single Host Genetic Locus to Mouse Adenovirus Type 1 Infection and Encephalitis
Authors: Hsu Tien-Huei , Althaus Irene W. , Foreman Oded , Spindler Katherine R. 
Published: May 2012

ABSTRACTSusceptibility to mouse adenovirus type 1 (MAV-1) is mouse strain dependent; susceptible mice die from hemorrhagic encephalomyelitis. The MAV-1 susceptibility quantitative trait locusMsq1accounts for ~40% of the phenotypic (brain viral load) variance that occurs between resistant BALB/c and susceptible SJL mice after MAV-1 infection. Using an interval-specific congenic mouse strain (C.SJL-Msq1SJL), in which the SJL-derived alleleMsq1SJLis present in a BALB/c background, we demonstrate thatMsq1SJLcontrols the development of high brain viral titers in response to MAV-1 infection, yet does not account for the total extent of brain pathology or mortality in SJL mice. C.SJL-Msq1SJLmice had disruption of the blood-brain barrier and increased brain water content after MAV-1 infection, but these effects occurred later and were not as severe, respectively, as those noted in infected SJL mice. As expected, BALB/c mice showed minimal pathology in these assays. Infection of SJL- and C.SJL-Msq1SJL-derived primary mouse brain endothelial cells resulted in loss of barrier properties, whereas BALB/c-derived cells retained their barrier properties despite being equally capable of supporting MAV-1 infection. Finally, we provide evidence that organ pathology and inflammatory cell recruitment to the brain following MAV-1 infection were both influenced byMsq1. These results validateMsq1as an important host factor in MAV-1 infection and refine the major role of the locus in development of MAV-1 encephalitis. They further suggest that additional host factors or gene interactions are involved in the mechanism of pathogenesis in MAV-1-infected SJL mice.IMPORTANCEA successful viral infection requires both host and viral factors; identification of host components involved in viral replication and pathogenesis is important for development of therapeutic interventions. A genetic locus (Msq1) controlling mouse adenovirus type 1 (MAV-1) brain infection was previously identified. Genes inMsq1belong to the same family of genes associated with susceptibility to other encephalitic viruses, HIV-1 and West Nile virus. We constructed an interval-specific congenic mouse strain to examine the contribution ofMsq1to MAV-1 susceptibility and brain morbidity. We compared infected resistant, susceptible, and congenic mice regarding known MAV-1 disease manifestations in the brain (survival, viral loads, blood-brain barrier disruption, edema, mouse brain endothelial cell barrier properties, pathology, and inflammatory cell recruitment) to determine the extent to whichMsq1influences MAV-1 infection outcome. Our results showed thatMsq1is a critical host genetic factor that controls many aspects of MAV-1 infection.
Effects of different doses of medetomidine and tiletamine–zolazepam on the duration of induction and immobilization in free-ranging yearling brown bears (Ursus arctos)
Authors: Painer Johanna , Zedrosser Andreas , Arnemo Jon M. , Fahlman Åsa , Brunberg Sven , Segerström Peter , Swenson Jon E. 
Published: May 2012

We compared anesthetic protocols with different doses of tiletamine–zolazepam (TZ) combined with medetomidine (M) for 288 yearling brown bear ( Ursus arctos L., 1758) immobilizations with the objective of finding a combination of doses that would provide fast induction with a duration of anesthesia long enough to minimize the need for administering additional drug. The duration of induction time and immobilization was dose-dependent. Increasing the M dose resulted in significantly shorter induction times and a lower probability of giving supplemental drugs. Increasing the TZ dose prolonged duration of anesthesia. For yearling brown bears in Scandinavia, captured shortly after den emergence in April and May, we recommend total dart doses of 1.0–1.66 mg M/dart, plus 62.5–125 mg TZ/dart, depending on the individual requirements for the length and depth of anaesthesia.
ENTROPY AND HAUSDORFF DIMENSION IN RANDOM GROWING TREES
Authors: RUDAS ANNA , TÓTH IMRE PÉTER 
Published: May 2012

We investigate the limiting behavior of random tree growth in preferential attachment models. The tree stems from a root, and we add vertices to the system one-by-one at random, according to a rule which depends on the degree distribution of the already existing tree. The so-called weight function, in terms of which the rule of attachment is formulated, is such that each vertex in the tree can have at most K children. We define the concept of a certain random measure μ on the leaves of the limiting tree, which captures a global property of the tree growth in a natural way. We prove that the Hausdorff and the packing dimension of this limiting measure is equal and constant with probability one. Moreover, the local dimension of μ equals the Hausdorff dimension at μ-almost every point. We give an explicit formula for the dimension, given the rule of attachment.
Continental break-up mechanism; lessons from intermediate- and fast-extension settings
Authors: Nemčok M. , Stuart C. , Rosendahl B. R. , Welker C. , Smith S. , Sheya C. , Sinha S. T. , Choudhuri M. , Allen R. , Reeves C. , Sharma S. P. , Venkatraman S. , Sinha N. 
Published: May 2012

Abstract
Continental break-up mechanisms vary systematically between slow- and fast-extension systems. Slow-extension break-up has been established from studies of the Central Atlantic, European and Adria margins. This study focuses on the intermediate and fast cases from Gabon and East India, and draws from the interpretation of reflection seismic, gravimetric and magnetic data.
Interpretation indicates continental break-up via continental mantle unroofing in all systems, with modifications produced by magmatism in faster-extension systems. Break-up of the intermediate-extension Gabon system involves partial upper continental crustal decoupling from continental mantle; whereas, in the fast East Coast India system, decoupled and lower-crustal regimes underwent upwarping in ‘soggy’ zones in the footwalls of major normal faults. Usually, upper-crustal break-up is affected by pre-existing anisotropies, which form systems of constraining ‘rails’ for extending continental crust. This modifies the local stress regimes. They regain a regional character as the function of constraining rails vanishes during progressive unroofing of the upper mantle. Different regions attain different amounts of upper-crustal stretching prior to the break-up. The break-up location is then controlled by the upper-crustal energy balance principle of ‘wound linkage’, by which the minimum physical work is performed for linking upper-crustal ‘wounds’, leading to successful upper-crustal break-up.

Supplementary material:

Supplementary information and figures on the modelling of the mechanisms and architecture is available at
http://www.geolsoc.org.uk/SUP18525
.
Pyrophosphorolysis-Activated Polymerization Detects Circulating Tumor DNA in Metastatic Uveal Melanoma
Authors: Madic Jordan , Piperno-Neumann Sophie , Servois Vincent , Rampanou Aurore , Milder Maud , Trouiller Bénédicte , Gentien David , Saada Stéphanie , Assayag Franck , Thuleau Aurélie , Nemati Fariba , Decaudin Didier , Bidard François-Clément , Desjardins Laurence , Mariani Pascale , Lantz Olivier , Stern Marc-Henri 
Published: May 2012

Abstract
Purpose: To develop a molecular tool to detect circulating tumor–derived DNA (ctDNA) in the plasma from patients with uveal melanoma as a marker of tumor burden and monitor treatment efficacy.
Experimental Design: A real-time PCR was developed on the basis of bidirectional pyrophosphorolysis-activated polymerization (bi-PAP) for the quantification of ctDNA using 3′blocked primer pairs specific for the 3 recurrent mutually exclusive mutations of Gα subunits GNAQ and GNA11.
Results: Sensitivity and specificity of bi-PAP were assessed on serial dilutions of tumor DNA in normal DNA for the 3 recurrent mutations. Each assay could detect a single mutated molecule per reaction, whereas 104 copies of normal DNA were not detected. The ctDNA was readily detected in plasma of mice bearing uveal melanoma xenografts in amounts proportional to circulating human DNA. Finally, plasma was almost always found positive (20 of 21 tested patients) in a prospective analysis of patients with metastatic uveal melanoma.
Conclusions: Bi-PAP assays detect and quantify ctDNA in patients with metastatic uveal melanoma. A prospective study is ongoing to assess the clinical usefulness of ctDNA level in uveal melanoma. Clin Cancer Res; 18(14); 3934–41. ©2012 AACR.
Influence of Smoking on the Pharmacokinetics and Toxicity Profiles of Taxane Therapy
Authors: de Graan Anne-Joy M. , Loos Walter J. , Friberg Lena E. , Baker Sharyn D. , van der Bol Jessica M. , van Doorn Leni , Wiemer Erik A.C. , van der Holt Bronno , Verweij Jaap , Mathijssen Ron H.J. 
Published: May 2012

Abstract
Purpose: Cigarette smoke is known to interact with the metabolism of several anticancer drugs. It may also affect the incidence and severity of adverse events and efficacy of chemotherapy. The main objective of this study was to examine the effects of smoking on the pharmacokinetics and toxicities of patients treated with docetaxel or paclitaxel.
Experimental Design: Smoking status, toxicity profiles, and pharmacokinetic parameters (calculated by nonlinear mixed-effect modeling population analysis) were determined in 566 patients (429 nonsmokers and 137 smokers) treated with docetaxel or paclitaxel.
Results: Smokers treated with docetaxel showed less grade IV neutropenia (35% vs. 52%; P = 0.01) than nonsmokers. Smokers treated with paclitaxel had less grade III–IV leukopenia than nonsmokers (12% vs. 25%; P = 0.03), and the white blood cell (WBC) nadir was lower in nonsmokers (median, 2.7 × 109/L; range, 0.05 × 109 to 11.6 × 109/L) than in smokers (median, 3.3 × 109/L; range 0.8 × 109 to 10.2 × 109/L; P = 0.02). Of interest, significantly lower WBC counts and absolute neutrophil counts at baseline were seen in nonsmoking patients treated with paclitaxel (P = 0.0001). Pharmacokinetic parameters were similar in smokers and nonsmokers for both taxanes.
Conclusion: Cigarette smoking does not alter the pharmacokinetic determinants of docetaxel and paclitaxel. Smokers treated with docetaxel and paclitaxel have less neutropenia and leukopenia, but further research is warranted to elucidate this potential protective effect. Clin Cancer Res; 18(16); 4425–32. ©2012 AACR.
Trajectory of Functional Decline Before and After Ischemic Stroke
Authors: Dhamoon Mandip S. , Moon Yeseon P. , Paik Myunghee C. , Sacco Ralph L. , Elkind Mitchell S.V. 
Published: May 2012

Background and Purpose—
Previous research in our cohort showed a delayed decline in functional status after first ischemic stroke. We compared the long-term trajectory of functional status before and after ischemic stroke.

Methods—
The Northern Manhattan Study contains a prospective, population-based study of stroke-free individuals age ≥40 years, followed for a median of 11 years. The Barthel index (BI), a commonly used measure of activities of daily living, was assessed annually. Generalized estimating equations were used to assess functional decline over time before stroke and beginning 6 months after stroke. Follow-up was censored at the time of recurrent stroke.

Results—

Among 3298 participants, 210 participants had an ischemic stroke during follow-up and had poststroke BI assessed. Mean age (±SD) was 77±9 years, 38% were men, 52% were Hispanic, 37% had diabetes, and 31% had coronary artery disease. There was no difference in rate of functional decline over time before and after stroke (
P
=0.51), with a decline of 0.96 BI points per year before stroke (
P
<0.0001) and 1.24 BI points after stroke (
P
=0.001). However, when stratified by insurance status, among those with Medicaid or no insurance, in a fully adjusted model, there was a difference in slope before and after stroke (
P
=0.04), with a decline of 0.58 BI points per year before stroke (
P
=0.02) and 1.94 BI points after stroke (
P
=0.001).

Conclusions—
In this large, prospective, population-based study with long-term follow-up, there was a significantly steeper decline in functional status after ischemic stroke compared with before stroke among those with Medicaid or no insurance, after adjusting for confounders.