bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exploring the Inhibition of CTX-M-9 by β-Lactamase Inhibitors and Carbapenems
Authors: Bethel Christopher R. , Taracila Magdalena , Shyr Teresa , Thomson Jodi M. , Distler Anne M. , Hujer Kristine M. , Hujer Andrea M. , Endimiani Andrea , Papp-Wallace Krisztina , Bonnet Richard , Bonomo Robert A. 
Published: May 2011

ABSTRACT

Currently, CTX-M β-lactamases are among the most prevalent and most heterogeneous extended-spectrum β-lactamases (ESBLs). In general, CTX-M enzymes are susceptible to inhibition by β-lactamase inhibitors. However, it is unknown if the pathway to inhibition by β-lactamase inhibitors for CTX-M ESBLs is similar to TEM and SHV β-lactamases and why bacteria possessing only CTX-M ESBLs are so susceptible to carbapenems. Here, we have performed a kinetic analysis and timed electrospray ionization mass spectrometry (ESI-MS) studies to reveal the intermediates of inhibition of CTX-M-9, an ESBL representative of this family of enzymes. CTX-M-9 β-lactamase was inactivated by sulbactam, tazobactam, clavulanate, meropenem, doripenem, ertapenem, and a 6-methylidene penem, penem 1.

K
i

values ranged from 1.6 ± 0.3 μM (mean ± standard error) for tazobactam to 0.02 ± 0.01 μM for penem 1. Before and after tryptic digestion of the CTX-M-9 β-lactamase apo-enzyme and CTX-M-9 inactivation by inhibitors (meropenem, clavulanate, sulbactam, tazobactam, and penem 1), ESI-MS and matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) identified different adducts attached to the peptide containing the active site Ser70 (+52, 70, 88, and 156 ± 3 atomic mass units). This study shows that a multistep inhibition pathway results from modification or fragmentation with clavulanate, sulbactam, and tazobactam, while a single acyl enzyme intermediate is detected when meropenem and penem 1 inactivate CTX-M-9 β-lactamase. More generally, we propose that Arg276 in CTX-M-9 plays an essential role in the recognition of the C
3
carboxylate of inhibitors and that the localization of this positive charge to a “region of the active site” rather than a specific residue represents an important evolutionary strategy used by β-lactamases.
Establishment of a Novel Model of Onychomycosis in Rabbits for Evaluation of Antifungal Agents
Authors: Shimamura Tsuyoshi , Kubota Nobuo , Nagasaka Saori , Suzuki Taku , Mukai Hideki , Shibuya Kazutoshi 
Published: May 2011

ABSTRACT

We developed a novel model of onychomycosis in which we observed fungi in the deep layer of the nail, and we used the model to evaluate the efficacy of two topical antifungal drugs. To establish an experimental,
in vivo
model of onychomycosis, we applied
Trichophyton mentagrophytes
TIMM2789 to the nails of the hind limbs of rabbits that underwent steroid treatment. The nails were taken from the rabbits' feet at 0, 2, and 6 weeks after a 2-week infection. The localization of the fungi was evaluated histopathologically. Some fungi were seen to penetrate to the nail bed, and the infection rate in the sample at 0, 2, and 6 weeks after infection was 57, 87, and 93%, respectively. In addition, fungi proliferated and moved proximally into the nail plate in a manner that depended on the duration of infection. Second, using this model we evaluated antifungal efficacy both by the culture recovery method and histopathological examination. Two topical antifungal drugs, 8% ciclopirox nail lacquer and 5% amorolfine nail lacquer, were applied to the nail for 4 weeks in each group. On histopathological examination, two antifungal treatment groups showed no significant difference against the nontreated control group. However, there were a significantly low fungus-positive rate and intensity of the recovery of fungi on culture between antifungal treatment and nontreated control groups. We therefore suggest that we have established an
in vivo
model of onychomycosis that is useful for the evaluation of the efficacy of antifungal agents.
Population Pharmacokinetics of Colistin Methanesulfonate and Formed Colistin in Critically Ill Patients from a Multicenter Study Provide Dosing Suggestions for Various Categories of Patients
Authors: Garonzik S. M. , Li J. , Thamlikitkul V. , Paterson D. L. , Shoham S. , Jacob J. , Silveira F. P. , Forrest A. , Nation R. L. 
Published: May 2011

ABSTRACT

With increasing clinical emergence of multidrug-resistant Gram-negative pathogens and the paucity of new agents to combat these infections, colistin (administered as its inactive prodrug colistin methanesulfonate [CMS]) has reemerged as a treatment option, especially for critically ill patients. There has been a dearth of pharmacokinetic (PK) data available to guide dosing in critically ill patients, including those on renal replacement therapy. In an ongoing study to develop a population PK model for CMS and colistin, 105 patients have been studied to date; these included 12 patients on hemodialysis and 4 on continuous renal replacement therapy. For patients not on renal replacement, there was a wide variance in creatinine clearance, ranging from 3 to 169 ml/min/1.73 m
2
. Each patient was treated with a physician-selected CMS dosage regimen, and 8 blood samples for PK analysis were collected across a dosage interval on day 3 or 4 of therapy. A linear PK model with two compartments for CMS and one compartment for formed colistin best described the data. Covariates included creatinine clearance on the total clearance of CMS and colistin, as well as body weight on the central volume of CMS. Model-fitted parameter estimates were used to derive suggested loading and maintenance dosing regimens for various categories of patients, including those on hemodialysis and continuous renal replacement. Based on our current understanding of colistin PK and pharmacodynamic relationships, colistin may best be used as part of a highly active combination, especially for patients with moderate to good renal function and/or for organisms with MICs of ≥1.0 mg/liter.
Symmetry Requirements for Effective Blocking of Pore-Forming Toxins: Comparative Study with α-, β-, and γ-Cyclodextrin Derivatives
Authors: Yannakopoulou Konstantina , Jicsinszky Laszlo , Aggelidou Crysie , Mourtzis Nikolaos , Robinson Tanisha M. , Yohannes Adiamseged , Nestorovich Ekaterina M. , Bezrukov Sergey M. , Karginov Vladimir A. 
Published: May 2011

ABSTRACT

We compared the abilities of structurally related cationic cyclodextrins to inhibit
Bacillus anthracis
lethal toxin and
Staphylococcus aureus
α-hemolysin. We found that both β- and γ-cyclodextrin derivatives effectively inhibited anthrax toxin action by blocking the transmembrane oligomeric pores formed by the protective antigen (PA) subunit of the toxin, whereas α-cyclodextrins were ineffective. In contrast, α-hemolysin was selectively blocked only by β-cyclodextrin derivatives, demonstrating that both symmetry and size of the inhibitor and the pore are important.
Vibrio cholerae Requires the Type VI Secretion System Virulence Factor VasX To Kill Dictyostelium discoideum
Authors: Miyata Sarah T. , Kitaoka Maya , Brooks Teresa M. , McAuley Steven B. , Pukatzki Stefan 
Published: May 2011

ABSTRACT

The type VI secretion system (T6SS) is recognized as an important virulence mechanism in several Gram-negative pathogens. In
Vibrio cholerae
, the causative agent of the diarrheal disease cholera, a minimum of three gene clusters—one main cluster and two auxiliary clusters—are required to form a functional T6SS apparatus capable of conferring virulence toward eukaryotic and prokaryotic hosts. Despite an increasing understanding of the components that make up the T6SS apparatus, little is known about the regulation of these genes and the gene products delivered by this nanomachine. VasH is an important regulator of the
V. cholerae
T6SS. Here, we present evidence that VasH regulates the production of a newly identified protein, VasX, which in turn requires a functional T6SS for secretion. Deletion of
vasX
does not affect export or enzymatic function of the structural T6SS proteins Hcp and VgrG-1, suggesting that VasX is dispensable for the assembly of the physical translocon complex. VasX localizes to the bacterial membrane and interacts with membrane lipids. We present VasX as a novel virulence factor of the T6SS, as a
V. cholerae
mutant lacking
vasX
exhibits a phenotype of attenuated virulence toward
Dictyostelium discoideum.
Anaerobiosis-Induced Loss of Cytotoxicity Is Due to Inactivation of Quorum Sensing in Pseudomonas aeruginosa
Authors: Lee Kang-Mu , Yoon Mi Young , Park Yongjin , Lee Joon-Hee , Yoon Sang Sun 
Published: May 2011

ABSTRACT

Pseudomonas aeruginosa
, an opportunistic pathogen of clinical importance, causes chronic airway infections in patients with cystic fibrosis (CF). Current literature suggests that pockets with reduced oxygen tension exist in the CF airway mucus. However, virulence features of this opportunistic pathogen under such conditions are largely unknown. Cell-free supernatant of the standard laboratory
P. aeruginosa
strain PAO1 obtained from anaerobic culture, but not aerobic culture, failed to kill A549 human airway epithelial cells. Further investigation revealed that this reduced cytotoxicity upon anaerobiosis was due to the suppressed secretion of elastase, a virulence factor controlled by
P. aeruginosa
quorum sensing (QS). Both a
lacZ
-reporter fusion assay and quantitative real-time PCR (RT-PCR) analysis demonstrated that transcription of the elastase-encoding
lasB
gene was substantially decreased during anaerobic growth compared with aerobic growth. Moreover, transcription of other genes controlled by the LasI/R QS system, such as
rhlR
,
vqsR
,
mvfR
, and
rsaL
, was also repressed under the same anaerobic growth conditions. Importantly, synthesis of 3-oxo-C
12
-HSL (PAI-1), an autoinducer molecule that mediates induction of the LasI/R QS system, was >22-fold decreased during anaerobic growth while C
4
-HSL (PAI-2), which mediates RhlI/R QS, was nondetectable under the same growth conditions. Transcription of the
lasB
gene was restored by exogenous supplementation with autoinducers, with PAI-2 more effective than PAI-1 or
Pseudomonas
quinolone signal (PQS) at restoring transcription of the
lasB
gene. Together, these results suggest that anaerobiosis deprives
P. aeruginosa
of the ability to regulate its virulence via QS and this misregulation attenuates the pathogenic potential of this important pathogen.
Construction and characterization of Lactobacillus pentosus expressing the D antigenic site of the spike protein of Transmissible gastroenteritis virus
Authors: Di-qiu Liu , Xin-yuan Qiao , Jun-wei Ge , Li-jie Tang , Yan-ping Jiang , Yi-jing Li 
Published: May 2011

This study explored the feasibility of Lactobacillus pentosus as a live vehicle to deliver and express antigen. First of all, L. pentosus transformed by electroporation with the plasmids pg611-6D (anchored) and pg612-6D (secretory) based on the xylose operon generated the recombinant strains rLppg611-6D and rLppg612-6D, respectively, expressing the D antigenic site of the spike (S) protein of Transmissible gastroenteritis virus (TGEV), for intragastric administration in mice. Secondly, we collected serum, fecal, nasal, ophthalmic, and vaginal samples from pre-immune mice and after the first immunization (on days 7, 14, 21, 28, 35, and 42) that were used to analyze the levels of immunoglobulins G and A against TGEV by using ELISA. In addition, a plaque reduction assay was performed using sera from groups pg611, pg612-6D, pg11-6D, and phosphate-buffered saline (blank control) to analyze TGEV-neutralizing antibody activity in vitro. A statistically significant difference in serum tests between groups demonstrated that rLppg612-6D induced better immunogenicity than rLppg611-6D, making rLppg612-6D the better candidate for oral vaccine. Taken together, L. pentosus possessed the potential to become a novel vector for mucosal vaccine in the future.
FISH WARS WITH MANY PLAYERS
Authors: MAZALOV VLADIMIR V. , RETTIEVA ANNA N. 
Published: May 2011

Discrete-time game-theoretic models related to a bioresource management problem (fish catching) are investigated. There are some players (countries or fishing firms) which harvest the fish stock. Power population's growth function and logarithmic players' profits are considered. We derive the Nash and cooperative equilibria. We construct the characteristic function for cooperative game in two unusual forms and determine the Shapley value and time-consistent imputation distribution procedure [Petrosjan (1977)]. We propose the condition which gives an incentive for the players to keep cooperation at each stage and compare it with the "irrational-behavior-profness" condition [Yeung (2006)]. We propose the linear programming method to find the time-consistent "rational" solution in C-core. The numerical modelling and the results' comparison were carried out.
Nuclear ErbB2 Enhances Translation and Cell Growth by Activating Transcription of Ribosomal RNA Genes
Authors: Li Long-Yuan , Chen Hsiuyi , Hsieh Yi-Hsien , Wang Ying-Nai , Chu Hsiao-Ju , Chen Ya-Huey , Chen Hui-Yu , Chien Peng-Ju , Ma Haou-Tzong , Tsai Ho-Cheng , Lai Chien-Chen , Sher Yuh-Pyng , Lien Huang-Chun , Tsai Chang-Hai , Hung Mien-Chie 
Published: May 2011

Abstract
Aberrant regulation of rRNA synthesis and translation control can facilitate tumorigenesis. The ErbB2 growth factor receptor is overexpressed in many human tumors and has been detected in the nucleus, but the role of nuclear ErbB2 is obscure. In this study, we defined a novel function of nuclear ErbB2 in enhancing rRNA gene transcription by RNA polymerase-I (RNA Pol I). Nuclear ErbB2 physically associates with β-actin and RNA Pol I, coinciding with active RNA Pol I transcription sites in nucleoli. RNA interference–mediated knockdown of ErbB2 reduced pre-rRNA and protein synthesis. In contrast, wild-type ErbB2 augmented pre-rRNA level, protein production, and cell size/cell growth, but not by an ErbB2 mutant that is defective in nuclear translocation. Chromatin immunoprecipitation assays revealed that ErbB2 enhances binding of RNA Pol I to rDNA. In addition, ErbB2 associated with rDNA, RNA Pol I, and β-actin, suggesting how it could stimulate rRNA production, protein synthesis, and increased cell size and cell growth. Finally, ErbB2-potentiated RNA Pol I transcription could be stimulated by ligand and was not substantially repressed by inhibition of PI3-K and MEK/ERK (extracellular signal regulated kinase), the main ErbB2 effector signaling pathways. Together, our findings indicate that nuclear ErbB2 functions as a regulator of rRNA synthesis and cellular translation, which may contribute to tumor development and progression. Cancer Res; 71(12); 4269–79. ©2011 AACR.
Blocking EphB1 Receptor Forward Signaling in Spinal Cord Relieves Bone Cancer Pain and Rescues Analgesic Effect of Morphine Treatment in Rodents
Authors: Liu Su , Liu Wen-Tao , Liu Yue-Peng , Dong Hai-Long , Henkemeyer Mark , Xiong Li-Ze , Song Xue-Jun 
Published: May 2011

Abstract
Treating bone cancer pain continues to be a clinical challenge and underlying mechanisms of bone cancer pain remain elusive. Here, we report that EphB1 receptor forward signaling in the spinal cord is critical to the development of bone cancer pain and morphine tolerance in treating bone cancer pain. Tibia bone cavity tumor cell implantation (TCI) produces bone cancer–related thermal hyperalgesia, mechanical allodynia, spontaneous and movement-evoked pain behaviors, and bone destruction. Production and persistence of these pain behaviors are well correlated with TCI-induced upregulation of EphB1 receptor and its ligand ephrinB2 in the dorsal horn and primary sensory neurons. Spinal administration of an EphB1 receptor blocking reagent EphB2-Fc prevents and reverses bone cancer pain behaviors and the associated induction of c-Fos and activation of astrocytes and microglial cells, NR1 and NR2B receptors, Src within the N-methyl-D-aspartate receptor complex, and the subsequent Ca2+-dependent signals. The exogenous ligand ephrinB2-Fc upregulates level of phosphorylation of NR1 and NR2B receptors depending on the activation of EphB1 receptor. Spinal administration of EphB2-Fc and ephrinB2-Fc induces downregulation of EphB1 and ephrinB2, respectively, accompanied with increased activity of matrix metalloproteinase (MMP)-2/9. Blocking MMP-2 or MMP-9 reverses EphB1-Fc treatment–induced downregulation of EphB1 receptor. In addition, spinal blocking or targeted mutation of EphB1 receptor reverses morphine tolerance in treating bone cancer pain in rats and defensive pain in mice. These findings show a critical mechanism underlying the pathogenesis of bone cancer pain and suggest a potential target for treating bone cancer pain and improving analgesic effect of morphine clinically. Cancer Res; 71(13); 4392–402. ©2011 AACR.
TGFβ/TNFα-Mediated Epithelial–Mesenchymal Transition Generates Breast Cancer Stem Cells with a Claudin-Low Phenotype
Authors: Asiedu Michael K. , Ingle James N. , Behrens Marshall D. , Radisky Derek C. , Knutson Keith L. 
Published: May 2011

AbstractBreast cancer recurrence is believed to be caused by a subpopulation of cancer cells that possess the stem cell attribute of treatment resistance. Recently, we and others have reported the generation of breast cancer stem cells (BCSC) by epithelial–mesenchymal transition (EMT), although the physiologic process by which these cells may arise in vivo remains unclear. We show here that exposure of tumor cells to TGFβ and TNFα induces EMT and, more importantly, generates cells with a stable BCSC phenotype which is shown by increased self-renewing capacity, greatly increased tumorigenicity, and increased resistance to oxaliplatin, etoposide, and paclitaxel. Furthermore, gene expression analyses found that the TGFβ/TNFα-derived BCSCs showed downregulated expression of genes encoding claudin 3, 4, and 7 and the luminal marker, cytokeratin 18. These changes indicate a shift to the claudin-low molecular subtype, a recently identified breast cancer subtype characterized by the expression of mesenchymal and stem cell-associated markers and correlated with a poor prognosis. Taken together, the data show that cytokine exposure can be used to generate stable BCSCs ex vivo, and suggest that these cells may provide a valuable tool in the identification of stem cell-directed biomarkers and therapies in breast cancer. Cancer Res; 71(13); 4707–19. ©2011 AACR.
Targeting Hyaluronidase for Cancer Therapy: Antitumor Activity of Sulfated Hyaluronic Acid in Prostate Cancer Cells
Authors: Benitez Anaid , Yates Travis J. , Lopez Luis E. , Cerwinka Wolfgang H. , Bakkar Ashraf , Lokeshwar Vinata B. 
Published: May 2011

Abstract
The tumor cell–derived hyaluronidase (HAase) HYAL-1 degrades hyaluronic acid (HA) into proangiogenic fragments that support tumor progression. Although HYAL-1 is a critical determinant of tumor progression and a marker for cancer diagnosis and metastasis prediction, it has not been evaluated as a target for cancer therapy. Similarly, sulfated hyaluronic acid (sHA) has not been evaluated for biological activity, although it is an HAase inhibitor. In this study, we show that sHA is a potent inhibitor of prostate cancer. sHA blocked the proliferation, motility, and invasion of LNCaP, LNCaP-AI, DU145, and LAPC-4 prostate cancer cells, and induced caspase-8–dependent apoptosis associated with downregulation of Bcl-2 and phospho-Bad. sHA inhibited Akt signaling including androgen receptor (AR) phosphorylation, AR activity, nuclear factor κB (NFκB) activation, and VEGF expression. These effects were traced to a blockade in complex formation between phosphoinositide 3-kinase (PI3K) and HA receptors and to a transcriptional downregulation of HA receptors, CD44, and RHAMM, along with PI3K inhibition. Angiogenic HA fragments or overexpression of myristoylated Akt or HA receptors blunted these effects of sHA, implicating a feedback loop between HA receptors and PI3K/Akt signaling in the mechanism of action. In an animal model, sHA strongly inhibited LNCaP-AI prostate tumor growth without causing weight loss or apparent serum-organ toxicity. Inhibition of tumor growth was accompanied by a significant decrease in tumor angiogenesis and an increase in apoptosis index. Taken together, our findings offer mechanistic insights into the tumor-associated HA–HAase system and a preclinical proof-of-concept of the safety and efficacy of sHA to control prostate cancer growth and progression. Cancer Res; 71(12); 4085–95. ©2011 AACR.
Akt2 Regulates All Akt Isoforms and Promotes Resistance to Hypoxia through Induction of miR-21 upon Oxygen Deprivation
Authors: Polytarchou Christos , Iliopoulos Dimitrios , Hatziapostolou Maria , Kottakis Filippos , Maroulakou Ioanna , Struhl Kevin , Tsichlis Philip N. 
Published: May 2011

Abstract
The growth and survival of tumor cells in an unfavorable hypoxic environment depend upon their adaptability. Here, we show that both normal and tumor cells expressing the protein kinase Akt2 are more resistant to hypoxia than cells expressing Akt1 or Akt3. This is due to the differential regulation of microRNA (miR) 21, which is upregulated by hypoxia only in Akt2-expressing cells. By upregulating miR-21 upon oxygen deprivation, Akt2 downregulates PTEN and activates all three Akt isoforms. miR-21 also targets PDCD4 and Sprouty 1 (Spry1), and the combined downregulation of these proteins with PTEN is sufficient to confer resistance to hypoxia. Furthermore, the miR-21 induction by Akt2 during hypoxia depends upon the binding of NF-κB, cAMP responsive element–binding protein (CREB), and CBP/p300 to the miR-21 promoter, in addition to the regional acetylation of histone H3K9, all of which are under the control of Akt2. Analysis of the Akt2/miR-21 pathway in hypoxic MMTV-PyMT–induced mouse mammary adenocarcinomas and human ovarian carcinomas confirmed the activity of the pathway in vivo. Taken together, this study identifies a novel Akt2-dependent pathway that is activated by hypoxia and promotes tumor resistance via induction of miR-21. Cancer Res; 71(13); 4720–31. ©2011 AACR.
Sensitivity of the Aortic Dissection Detection Risk Score, a Novel Guideline-Based Tool for Identification of Acute Aortic Dissection at Initial Presentation
Authors: Rogers Adam M. , Hermann Luke K. , Booher Anna M. , Nienaber Christoph A. , Williams David M. , Kazerooni Ella A. , Froehlich James B. , O'Gara Patrick T. , Montgomery Daniel G. , Cooper Jeanna V. , Harris Kevin M. , Hutchison Stuart , Evangelista Arturo , Isselbacher Eric M. , Eagle Kim A. 
Published: May 2011

Background—
In 2010, the American Heart Association and American College of Cardiology released guidelines for the diagnosis and management of patients with thoracic aortic disease, which identified high-risk clinical features to assist in the early detection of acute aortic dissection. The sensitivity of these risk markers has not been validated.

Methods and Results—
We examined patients enrolled in the International Registry of Acute Aortic Dissection from 1996 to 2009. The number of patients with confirmed acute aortic dissection who presented with 1 or more of 12 proposed clinical risk markers was determined. An aortic dissection detection (ADD) risk score of 0 to 3 was calculated on the basis of the number of risk categories (high-risk predisposing conditions, high-risk pain features, high-risk examination features) in which patients met criteria. The ADD risk score was tested for sensitivity. Of 2538 patients with acute aortic dissection, 2430 (95.7%) were identified by 1 or more of 12 proposed clinical risk markers. With the use of the ADD risk score, 108 patients (4.3%) were identified as low risk (ADD score 0), 927 patients (36.5%) were intermediate risk (ADD score 1), and 1503 patients (59.2%) were high risk (ADD score 2 or 3). Among 108 patients with no clinical risk markers present (ADD score 0), 72 had chest x-rays recorded, of which 35 (48.6%) demonstrated a widened mediastinum.

Conclusions—
The clinical risk markers proposed in the 2010 thoracic aortic disease guidelines and their application as part of the ADD risk score comprise a highly sensitive clinical tool for the detection of acute aortic dissection.