bluuebunny/crossref_metadata_2025_split huggingface dataset:
Induced Resistance to Methionyl-tRNA Synthetase Inhibitors in Trypanosoma brucei Is Due to Overexpression of the Target
Authors: Ranade Ranae M. , Gillespie J. Robert , Shibata Sayaka , Verlinde Christophe L. M. J. , Fan Erkang , Hol Wim G. J. , Buckner Frederick S. 
Published: April 2013

ABSTRACT

New classes of antiparasitic drugs active against
Trypanosoma brucei
are needed to combat human African trypanosomiasis. Inhibitors of methionyl-tRNA synthetase (MetRS) have excellent potential to be developed for this purpose (S. Shibata, J. R. Gillespie, A. M. Kelley, A. J. Napuli, Z. Zhang, K. V. Kovzun, R. M. Pefley, J. Lam, F. H. Zucker, W. C. Van Voorhis, E. A. Merritt, W. G. Hol, C. L. Verlinde, E. Fan, and F. S. Buckner, Antimicrob. Agents Chemother.
55
:1982–1989, 2011). In order to assess the potential for resistance to develop against this new class of inhibitors,
T. brucei
cultures were grown in the presence of MetRS inhibitors or comparison drugs. Resistance up to ∼50 times the baseline 50% inhibitory concentration (IC
50
) was induced against a MetRS inhibitor after ∼120 days. A similar level of resistance to the clinical drug eflornithine was induced after ∼50 days and for pentamidine after ∼80 days. Thus, resistance was induced more slowly against MetRS inhibitors than against clinically used drugs. The parasites resistant to the MetRS inhibitor were shown to overexpress MetRS mRNA by a factor of 35 over the parental strain. Southern analysis indicated that the MetRS gene was amplified in the genome by nearly 8-fold. When injected into mice, the MetRS inhibitor-resistant parasites caused a reduced level of infection, indicating that the changes associated with resistance attenuated their virulence. This finding and the fact that resistance to MetRS inhibitors developed relatively slowly are encouraging for further development of this class of compounds. Published studies on other antitrypanosomal drugs have primarily shown that alterations in membrane transporters were the mechanisms responsible for resistance. This is the first published report of induced drug resistance in the African trypanosome due to overexpression of the target enzyme.
Redefining the Role of the β-Lactamase Locus in Methicillin-Resistant Staphylococcus aureus: β-Lactamase Regulators Disrupt the MecI-Mediated Strong Repression on
mecA
and Optimize the Phenotypic Expression of Resistance in Strains with Constitutive
mecA
Expression
Authors: Arêde Pedro , Ministro Joana , Oliveira Duarte C. 
Published: April 2013

ABSTRACT

In response to β-lactam chemotherapy,
Staphylococcus aureus
has acquired two resistance determinants:
blaZ
, coding for β-lactamase, which confers resistance to penicillins only, and
mecA
, coding for an extra cell wall cross-linking enzyme with reduced affinity for virtually all other β-lactams. The transcriptional control of both resistance determinants is regulated by homologous repressors (BlaI and MecI, respectively) and sensor inducers (BlaR1 and MecR1, respectively). There is a cross-talk between the two regulatory systems, and it has been demonstrated that
bla
regulators stabilize the
mecA
acquisition. In a recent study, we have unexpectedly observed that in most MRSA strains, there was no significant change in the resistance phenotype upon the overexpression in
trans
of a MecI repressor, whereas in those few strains negative for the
bla
locus, there was a massive decrease of resistance (D. C. Oliveira and H. de Lencastre, PLoS One 6:e23287, 2011). Here, we demonstrate that, contrary to what is currently accepted, the
bla
regulatory system efficiently disrupts the strong MecI-mediated repression on
mecA
, enabling the optimal expression of resistance. This effect appears to be due to the formation of MecI::BlaI heterodimers that might bind less efficiently to the
mecA
promoter and become nonfunctional due to the proteolytic inactivation of the BlaI monomer. In addition, we have also observed that the presence of
bla
regulators may enhance dramatically the expression of β-lactam resistance in MRSA strains with constitutive
mecA
expression, compensating for the fitness cost imposed by the large β-lactamase plasmid. These observations point to important unrecognized roles of the
bla
locus for the expression of the methicillin-resistant
S. aureus
(MRSA) phenotype.
Roseomonas Spinal Epidural Abscess Complicating Instrumented Posterior Lumbar Interbody Fusion
Authors: Maraki Sofia , Bantouna Vasiliki , Lianoudakis Efstratios , Stavrakakis Ioannis , Scoulica Efstathia 
Published: April 2013

ABSTRACT

The first case of a spinal epidural abscess caused by
Roseomonas mucosa
following instrumented posterior lumbar fusion is presented. Although rare, because of its highly resistant profile,
Roseomonas
species should be included in the differential diagnosis of epidural abscesses in both immunocompromised and immunocompetent hosts.
Identical Miniature Inverted Repeat Transposable Elements Flank Class 1 Integrons in Clinical Isolates of Acinetobacter spp
Authors: Domingues Sara , Toleman Mark A. , Nielsen Kaare M. , da Silva Gabriela J. 
Published: April 2013

ABSTRACT

Miniature inverted repeat transposable elements (MITEs) have been identified flanking class 1 integrons. We have identified and characterized a 439-bp MITE-like structure in seven
Acinetobacter
species isolates from Portugal and Brazil. The complete sequence similarity of the elements and flanking regions suggests that MITEs may act as mobilizable vectors for the dissemination of integrons.
Direct Comparison of Xpert MTB/RIF Assay with Liquid and Solid Mycobacterial Culture for Quantification of Early Bactericidal Activity
Authors: Kayigire Xavier A. , Friedrich Sven O. , Venter Amour , Dawson Rodney , Gillespie Stephen H. , Boeree Martin J. , Heinrich Norbert , Hoelscher Michael , Diacon Andreas H. 
Published: April 2013

ABSTRACT

The early bactericidal activity of antituberculosis agents is usually determined by measuring the reduction of the sputum mycobacterial load over time on solid agar medium or in liquid culture. This study investigated the value of a quantitative PCR assay for early bactericidal activity determination. Groups of 15 patients were treated with 6 different antituberculosis agents or regimens. Patients collected sputum for 16 h overnight at baseline and at days 7 and 14 after treatment initiation. We determined the sputum bacterial load by CFU counting (log CFU/ml sputum, reported as mean ± standard deviation [SD]), time to culture positivity (TTP, in hours [mean ± SD]) in liquid culture, and Xpert MTB/RIF cycle thresholds (

C
T

,
n
[mean ± SD]). The ability to discriminate treatment effects between groups was analyzed with one-way analysis of variance (ANOVA). All measurements showed a decrease in bacterial load from mean baseline (log CFU, 5.72 ± 1.00; TTP, 116.0 ± 47.6;

C
T

, 19.3 ± 3.88) to day 7 (log CFU, −0.26 ± 1.23,
P
= 0.2112; TTP, 35.5 ± 59.3,
P
= 0.0002;

C
T

, 0.55 ± 3.07,
P
= 0.6030) and day 14 (log CFU, −0.55 ± 1.24,
P
= 0.0006; TTP, 54.8 ± 86.8,
P
< 0.0001;

C
T

, 2.06 ± 4.37,
P
= 0.0020). The best discrimination between group effects was found with TTP at day 7 and day 14 (
F
= 9.012,
P
< 0.0001, and
F
= 11.580,
P
< 0.0001), followed by log CFU (
F
= 4.135,
P
= 0.0024, and
F
= 7.277,
P
< 0.0001).

C
T

was not significantly discriminative (
F
= 1.995,
P
= 0.091, and
F
= 1.203,
P
= 0.316, respectively). Culture-based methods are superior to PCR for the quantification of early antituberculosis treatment effects in sputum.
Development and Evaluation of an Affordable Real-Time Qualitative Assay for Determining HIV-1 Virological Failure in Plasma and Dried Blood Spots
Authors: Aitken Susan C. , Kliphuis Aletta , Bronze Michelle , Wallis Carole L. , Kityo Cissy , Balinda Sheila , Stevens Wendy , Spieker Nicole , de Oliveira Tulio , Rinke de Wit Tobias F. , Schuurman Rob 
Published: April 2013

ABSTRACT

Virological failure (VF) has been identified as the earliest, most predictive determinant of HIV-1 antiretroviral treatment (ART) failure. Due to the high cost and complexity of virological monitoring, VF assays are rarely performed in resource-limited settings (RLS). Rather, ART failure is determined by clinical monitoring and to a large extent immunological monitoring. This paper describes the development and evaluation of a low-cost, dried blood spot (DBS)-compatible qualitative assay to determine VF, in accordance with current WHO guideline recommendations for therapy switching in RLS. The assay described here is an internally controlled qualitative real-time PCR targeting the conserved long terminal repeat domain of HIV-1. This assay was applied to HIV-1 subtypes A to H and further evaluated on HIV-1 clinical plasma samples from South Africa (
n
= 191) and Tanzania (
n
= 42). Field evaluation was performed in Uganda using local clinical plasma samples (
n
= 176). Furthermore, assay performance was evaluated for DBS. This assay is able to identify VF for all major HIV-1 group M subtypes with equal specificity and has a lower detection limit of 1.00E+03 copies/ml for plasma samples and 5.00E+03 copies/ml for DBS. Comparative testing yielded accurate VF determination for therapy switching in 89% to 96% of samples compared to gold standards. The assay is robust and flexible, allowing for “open platform” applications and producing results comparable to those of commercial assays. Assay design enables application in laboratories that can accommodate real-time PCR equipment, allowing decentralization of testing to some extent. Compatibility with DBS extends access of sampling and thus access to this test to remote settings.
Spectrum of Bacterial Colonization Associated with Urothelial Cells from Patients with Chronic Lower Urinary Tract Symptoms
Authors: Khasriya Rajvinder , Sathiananthamoorthy Sanchutha , Ismail Salim , Kelsey Michael , Wilson Mike , Rohn Jennifer L. , Malone-Lee James 
Published: April 2013

ABSTRACT

Chronic lower urinary tract symptoms (LUTS), such as urgency and incontinence, are common, especially among the elderly, but their etiology is often obscure. Recent studies of acute urinary tract infections implicated invasion by
Escherichia coli
into the cytoplasm of urothelial cells, with persistence of long-term bacterial reservoirs, but the role of infection in chronic LUTS is unknown. We conducted a large prospective study with eligible patients with LUTS and controls over a 3-year period, comparing routine urine cultures of planktonic bacteria with cultures of shed urothelial cells concentrated in centrifuged urinary sediments. This comparison revealed large numbers of bacteria undetected by routine cultures. Next, we typed the bacterial species cultured from patient and control sediments under both aerobic and anaerobic conditions, and we found that the two groups had complex but significantly distinct profiles of bacteria associated with their shed bladder epithelial cells. Strikingly,
E. coli
, the organism most responsible for acute urinary tract infections, was not the only or even the main offending pathogen in this more-chronic condition. Antibiotic protection assays with shed patient cells and
in vitro
infection studies using patient-derived strains in cell culture suggested that LUTS-associated bacteria are within or extremely closely associated with shed epithelial cells, which explains how routine cultures might fail to detect them. These data have strong implications for the need to rethink our common diagnoses and treatments of chronic urinary tract symptoms.
Both TRIF and IPS-1 Adaptor Proteins Contribute to the Cerebral Innate Immune Response against Herpes Simplex Virus 1 Infection
Authors: Menasria Rafik , Boivin Nicolas , Lebel Manon , Piret Jocelyne , Gosselin Jean , Boivin Guy 
Published: April 2013

ABSTRACT

Toll-like receptors (TLRs) and RNA helicases (RLHs) are important cell sensors involved in the immunological control of viral infections through production of type I interferon (IFN). The impact of a deficiency in the TRIF and IPS-1 adaptor proteins, respectively, implicated in TLR3 and RLH signaling pathways, was investigated during herpes simplex virus 1 (HSV-1) encephalitis. TRIF
−/−
, IPS-1
−/−
, and C57BL/6 wild-type (WT) mice were infected intranasally with 7.5 × 10
5
PFU of HSV-1. Mice were monitored for neurological signs and survival over 20 days. Groups of mice were sacrificed on days 3, 5, 7, 9, and 11 postinfection for determination of brain viral replication by quantitative PCR (qPCR), plaque assay, and immunohistochemistry and for alpha/beta interferon (IFN-α/β) levels and phosphorylation of interferon regulatory factors 3 and 7 (IRF-3 and -7) in brain homogenates by enzyme-linked immunosorbent assay (ELISA) and Western blotting, respectively. TRIF
−/−
and IPS-1
−/−
mice had higher mortality rates than WT mice (
P
= 0.02 and
P
= 0.09, respectively). Viral antigens were more disseminated throughout the brain, correlating with a significant increase in brain viral load for TRIF
−/−
(days 5 to 9) and IPS-1
−/−
(days 7 and 9) mice compared to results for the WT. IFN-β production was reduced in brain homogenates of TRIF
−/−
and IPS-1
−/−
mice on day 5 compared to results for the WT, whereas IFN-α levels were increased on day 7 in TRIF
−/−
mice. Phosphorylation levels of IRF-3 and IRF-7 were decreased in TRIF
−/−
and IPS-1
−/−
mice, respectively. These data suggest that both the TRIF and IPS-1 signaling pathways are important for the control of HSV replication in the brain and survival through IFN-β production.
Identification of the Human Herpesvirus 6A gQ1 Domain Essential for Its Functional Conformation
Authors: Maeki Takahiro , Hayashi Mayuko , Kawabata Akiko , Tang Huamin , Yamanishi Koichi , Mori Yasuko 
Published: April 2013

ABSTRACT
Human herpesvirus 6 is a T lymphotropic herpesvirus, long classified into variants A and B (HHV-6A and HHV-6B) based on differences in sequence and pathogenicity. Recently, however, HHV-6A and HHV-6B were reclassified as different species. Here, we isolated a neutralizing monoclonal antibody (Mab) named AgQ 1-1 that was specific for HHV-6A glycoprotein Q1 (AgQ1), and we showed that amino acid residues 494 to 497 of AgQ1 were critical for its recognition by this Mab. This region was also essential for AgQ1's complex formation with gH, gL, and gQ2, which might be important for viral binding to the cellular receptor, CD46. In addition, amino acid residues 494 to 497 are essential for viral replication. Interestingly, this sequence corresponds to the domain on HHV-6B gQ1 that is critical for recognition by an HHV-6B-specific neutralizing Mab. Within this domain, only Q at position 496 of HHV-6A is distinct from the HHV-6B sequence; however, the mutant AgQ1(Q496E) was still clearly recognized by the Mab AgQ 1-1. Surprisingly, replacement of the adjacent amino acid, in mutant AgQ1(C495A), resulted in poor recognition by Mab AgQ 1-1, and AgQ1(C495A) could not form the gH/gL/gQ1/gQ2 complex. Furthermore, the binding ability of mutant AgQ1(L494A) with CD46 decreased, although it could form the gH/gL/gQ1/gQ2 complex and it showed clear reactivity to Mab AgQ 1-1. These data indicated that amino acid residues 494 to 497 of AgQ1 were critical for the recognition by Mab AgQ 1-1 and essential for AgQ1's functional conformation.
Persistent Enteric Murine Norovirus Infection Is Associated with Functionally Suboptimal Virus-Specific CD8 T Cell Responses
Authors: Tomov Vesselin T. , Osborne Lisa C. , Dolfi Douglas V. , Sonnenberg Gregory F. , Monticelli Laurel A. , Mansfield Kathleen , Virgin Herbert W. , Artis David , Wherry E. John 
Published: April 2013

ABSTRACTNorovirus (NV) gastroenteritis is a major contributor to global morbidity and mortality, yet little is known about immune mechanisms leading to NV control. Previous studies using the murine norovirus (MNV) model have established a key role for T cells in MNV clearance. Despite these advances, important questions remain regarding the magnitude, location, and dynamics of the MNV-specific T cell response. To address these questions, we identified MNV-specific major histocompatibility complex (MHC) class I immunodominant epitopes using an overlapping peptide screen. One of these epitopes (amino acids 519 to 527 of open reading frame 2 [ORF2519-527]) was highly conserved among all NV genogroups. Using MHC class I peptide tetramers, we tracked MNV-specific CD8 T cells in lymphoid and mucosal sites during infection with two MNV strains with distinct biological behaviors, the acutely cleared strain CW3 and the persistent strain CR6. Here, we show that enteric MNV infection elicited robust T cell responses primarily in the intestinal mucosa and that MNV-specific CD8 T cells dynamically regulated the expression of surface molecules associated with activation, differentiation, and homing. Furthermore, compared to MNV-CW3 infection, chronic infection with MNV-CR6 resulted in fewer and less-functional CD8 T cells, and this difference was evident as early as day 8 postinfection. Finally, MNV-specific CD8 T cells were capable of reducing the viral load in persistently infectedRag1−/−mice, suggesting that these cells are a crucial component of NV immunity. Collectively, these data provide fundamental new insights into the adaptive immune response to two closely related NV strains with distinct biological behaviors and bring us closer to understanding the correlates of protective antiviral immunity in the intestine.
Characterising the progress in HIV/AIDS research in the Middle East and North Africa
Authors: Saba Hanan F , Kouyoumjian Silva P , Mumtaz Ghina R , Abu-Raddad Laith J 
Published: April 2013

ObjectivesThe Middle East and North Africa (MENA) region is perceived to have limited HIV data. The objective of this study was to quantitatively characterise the progress in HIV research in this region since the discovery of the epidemic.MethodsFour indices were defined and implemented to measure the progress of HIV research using the PubMed, Embase, MENA HIV/AIDS Epidemiology Synthesis Project and US Census Bureau HIV/AIDS Surveillance databases. The four indices provide complementary measures to characterise different aspects of the progress of HIV research.ResultsA total of 2118, 2352, 683 and 4889 records were identified through the PubMed, the Embase, the Synthesis Project and the HIV Prevalence indices, respectively. The proportion of the total global HIV records that relate to MENA is 1.2%. Overall, the indices show steady progress in the number of new records every year, with an accelerated pace in the last few years. The rate of progress in MENA was also higher than the rate of progress in HIV records globally. There is no evidence so far of stabilisation or a peak in the number of new records year by year. About half of the records were produced after the year 2005. The number of records shows large heterogeneity across countries.ConclusionsMENA has witnessed a rapid growth in HIV research over the last decade. However, there are still large gaps in HIV scientific evidence in the region, and the progress is far from being uniform across countries. Ongoing and future research needs to be geared towards academic standard and production of scientific publications.
MEMRISTOR MODELS IN A CHAOTIC NEURAL CIRCUIT
Authors: ASCOLI ALON , CORINTO FERNANDO 
Published: April 2013

The peculiar features of the memristor, a fundamental passive two-terminal element characterized by a nonlinear relationship between charge and flux, promise to revolutionize integrated circuit design in the next few decades. Besides its most popular potential application, ultra-dense nonvolatile memories, much research has been lately devoted to their use in chaotic neural networks for the emulation of brain activity. In the studies on neuromorphic circuits, it is common to characterize each memristor with a theoretical model based upon a single-valued odd-symmetric charge-flux nonlinearity. Memristive nano-films exhibit different dynamics depending on the way they behave at boundaries. We recently developed a mathematical model, applicable to memristive nano-structures of various nature, offering the opportunity to tune the boundary conditions so as to capture a wide gamut of distinct nonlinear behaviors. However, in general the proposed model exhibits a multivalued charge-flux nonlinearity dependent on input and initial state condition. In this paper, we first derive the necessary and sufficient set of boundary conditions under which single-valuedness is observed in this nonlinearity for any input/state initial condition combination. Then, after proving that, under such boundary conditions, the asymmetrical nonlinearities of memristors with opposite orientation are the odd-symmetric function of the other, we devise a pair of suitable memristor arrangements with odd-symmetric charge-flux characteristics. This analysis is confirmed by showing how a chaotic neural circuit employing one of such arrangements behaves similarly to its counterpart with the theoretically-modeled memristor.
Synthesis, Characterization, and Thermal Decomposition of Pure and Dysprosium Doped Yttrium Phosphate System
Authors: Bamzai K. K. , Kachroo Nidhi , Singh Vishal , Verma Seema 
Published: April 2013

Yttrium phosphate and dysprosium doped yttrium phosphate were synthesized from aqueous solutions using rare earth chloride, phosphoric acid, and traces of ammonium hydroxide. The synthesized material was then characterized for their structural investigations using powder X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) supplemented with energy dispersive X-ray analysis (EDAX). The spectroscopic investigations were carried out using Fourier transform infrared (FTIR) spectroscopy. The thermal stability was studied using differential thermogravimetric analysis (DTA), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) techniques. X-ray diffraction analysis reveals that both yttrium phosphate and dysprosium doped yttrium phosphate belong to tetragonal system with lattice parameter
Å,  Å and  Å,
Å, respectively. The stoichiometry of the grown composition was established by energy dispersive X-ray analysis. The EDAX analysis suggests the presence of water molecules. The presence of water molecules along with orthophosphate group and metallic ion group was confirmed by FTIR analysis. Thermogravimetric analysis suggests that decomposition in case of yttrium phosphate takes place in three different stages and the final product stabilizes after 706°C, whereas in case of dysprosium doped yttrium phosphate the decomposition occurs in two different stages, and the final product stabilizes after 519°C.