bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular basis of activation of the arachidonate‐regulated Ca2+ (ARC) channel, a store‐independent Orai channel, by plasma membrane STIM1
Authors: Thompson Jill L. , Shuttleworth Trevor J. 
Published: May 2013

Key points
The two known endogenous Orai channels, the calcium store‐dependent CRAC channel and the store‐independent ARC channel, are both regulated by the protein STIM1.
However, whilst CRAC channel activation is regulated by STIM1 in the endoplasmic reticulum, it is the pool of STIM1 constitutively residing in the plasma membrane that regulates the ARC channels.
Here we show that, although the specific regions of STIM1 critical for the regulation of these channels are largely the same, the actual mechanism of activation is markedly different.
Specifically, STIM1 in the plasma membrane exists in a constitutive association with the ARC channel, only requiring arachidonic acid to induce opening of the channel.
As these channels are known to play critical roles in the generation and modulation of key intracellular calcium signals, such distinct modes of activation are likely to have important implications for the generation and modulation of such signals in diverse cell types.
Abstract  Currently, Orai proteins are known to encode two distinct agonist‐activated, highly calcium‐selective channels: the store‐operated Ca2+ release‐activated Ca2+ (CRAC) channels, and the store‐independent, arachidonic acid‐activated ARC channels. Surprisingly, whilst the trigger for activation of these channels is entirely different, both depend on stromal interacting molecule 1 (STIM1). However, whilst STIM1 in the endoplasmic reticulum membrane is the critical sensor for the depletion of this calcium store that triggers CRAC channel activation, it is the pool of STIM1 constitutively resident in the plasma membrane that is essential for activation of the ARC channels. Here, using a variety of approaches, we show that the key domains within the cytosolic part of STIM1 identified as critical for the activation of CRAC channels are also key for activation of the ARC channels. However, examination of the actual steps involved in such activation reveal marked differences between these two Orai channel types. Specifically, loss of calcium from the EF‐hand of STIM1 that forms the key initiation point for activation of the CRAC channels has no effect on ARC channel activity. Secondly, in marked contrast to the dynamic and labile nature of interactions between STIM1 and the CRAC channels, STIM1 in the plasma membrane appears to be constitutively associated with the ARC channels. Finally, specific mutations in STIM1 that induce an extended, constitutively active, conformation for the CRAC channels actually prevent activation of the ARC channels by arachidonic acid. Based on these findings, we propose that the likely role of arachidonic acid lies in inducing the actual gating of the channel.
HIV-1 Resistance Mechanism to an Electrostatically Constrained Peptide Fusion Inhibitor That Is Active against T-20-Resistant Strains
Authors: Shimane Kazuki , Kawaji Kumi , Miyamoto Fusako , Oishi Shinya , Watanabe Kentaro , Sakagami Yasuko , Fujii Nobutaka , Shimura Kazuya , Matsuoka Masao , Kaku Mitsuo , Sarafianos Stefan G. , Kodama Eiichi N. 
Published: May 2013

ABSTRACT
T-20EK is a novel fusion inhibitor designed to have enhanced α-helicity over T-20 (enfuvirtide) through engineered electrostatic interactions between glutamic acid (E) and lysine (K) substitutions. T-20EK efficiently suppresses wild-type and T-20-resistant variants. Here, we selected T-20EK-resistant variants. A combination of L33S and N43K substitutions in gp41 were required for high resistance to T-20EK. While these substitutions also caused resistance to T-20, they did not cause cross-resistance to other known fusion inhibitors.
Discovery of Antivirulence Agents against Methicillin-Resistant Staphylococcus aureus
Authors: Khodaverdian Varandt , Pesho Michelle , Truitt Barbara , Bollinger Lucy , Patel Parita , Nithianantham Stanley , Yu Guanping , Delaney Elizabeth , Jankowsky Eckhard , Shoham Menachem 
Published: May 2013

ABSTRACT

Antivirulence agents inhibit the production of disease-causing virulence factors but are neither bacteriostatic nor bactericidal. Antivirulence agents against methicillin-resistant
Staphylococcus aureus
(MRSA) strain USA300, the most widespread community-associated MRSA strain in the United States, were discovered by virtual screening against the response regulator AgrA, which acts as a transcription factor for the expression of several of the most prominent
S. aureus
toxins and virulence factors involved in pathogenesis. Virtual screening was followed by similarity searches in the databases of commercial vendors. The small-molecule compounds discovered inhibit the production of the toxins alpha-hemolysin and phenol-soluble modulin α in a dose-dependent manner without inhibiting bacterial growth. These antivirulence agents are small-molecule biaryl compounds in which the aromatic rings either are fused or are separated by a short linker. One of these compounds is the FDA-approved nonsteroidal anti-inflammatory drug diflunisal. This represents a new use for an old drug. Antivirulence agents might be useful in prophylaxis and as adjuvants in antibiotic therapy for MRSA infections.
Evaluation of Antimicrobial Susceptibility of Enterobacteriaceae Causing Urinary Tract Infections in Africa
Authors: Tansarli Giannoula S. , Athanasiou Stavros , Falagas Matthew E. 
Published: May 2013

ABSTRACT

Our objective was to evaluate the antimicrobial susceptibility of
Enterobacteriaceae
causing urinary tract infections (UTIs) in adults in Africa. The PubMed database was systematically searched to identify relevant studies published after 2000. Google, World Health Organization, and African Field Epidemiology networks were also searched. Twenty-eight studies, accounting for 381,899 urine isolates from 14 African countries, met the inclusion criteria.
Escherichia coli
,
Klebsiella
spp., and
Proteus
spp. were the most commonly encountered uropathogens. Cefotaxime, imipenem, fosfomycin, and ciprofloxacin were the antibiotics with the highest activity against
E. coli
isolates from outpatients, with susceptibility being 92 to 99, 100, 100, and 68 to 91%, respectively. The susceptibility among
Klebsiella
spp. isolates from outpatients varied from 80 to 100% for amikacin and from 53 to 100% for ciprofloxacin, while susceptibility was 74 to 78, 97, and 77% for ciprofloxacin, amikacin, and fosfomycin, respectively, among
Klebsiella
species isolates from inpatients or patients with hospital-acquired UTIs. With regard to
Proteus
spp., the highest activity was observed among fluoroquinolones; 71 to 100% of the
P. mirabilis
isolates were susceptible to ciprofloxacin in four studies, and 74 to 100% of the
P. vulgaris
isolates were susceptible to ofloxacin in two studies. The currently available evidence suggests that the antimicrobial susceptibility patterns of
Enterobacteriaceae
uropathogens in African countries were similar to those in countries of southeast Europe. Further original studies are warranted from African countries for which there is limited published data.
Clinical Validation of the Analysis of Linezolid and Clarithromycin in Oral Fluid of Patients with Multidrug-Resistant Tuberculosis
Authors: Bolhuis M. S. , van Altena R. , van Hateren K. , de Lange W. C. M. , Greijdanus B. , Uges D. R. A. , Kosterink J. G. W. , van der Werf T. S. , Alffenaar J. W. C. 
Published: May 2013

ABSTRACT
Linezolid plays an increasingly important role in the treatment of multidrug-resistant tuberculosis (MDR-TB). However, patients should be carefully monitored due to time- and dose-dependent toxicity. Clarithromycin plays a more modest role. Therapeutic drug monitoring may contribute to assessment of treatment regimens, helping to reduce toxicity while maintaining adequate drug exposure. Oral fluid sampling could provide a welcome alternative in cases where conventional plasma sampling is not possible or desirable. The aim of this study was to clinically validate the analysis of linezolid and clarithromycin and its metabolite hydroxyclarithromycin in oral fluid of patients with multidrug-resistant tuberculosis. Serum and oral fluid samples were simultaneously obtained and analyzed by using validated methods, after extensive cross-validation between the two matrices. Passing-Bablok regressions and Bland-Altman analysis showed that oral fluid analysis of linezolid and clarithromycin appeared to be suitable for therapeutic drug monitoring in MDR-TB patients. No correction factor is needed for the interpretation of linezolid oral fluid concentrations with a ratio of the linezolid concentration in serum to that in oral fluid of 0.97 (95% confidence interval [CI], 0.92 to 1.02). However, the clarithromycin concentration serum/clarithromycin concentration in oral fluid ratio is 3.07 (95% CI, 2.45 to 3.69). Analysis of hydroxyclarithromycin in oral fluid was not possible in this study due to a nonlinear relationship between the concentration in serum and that in oral fluid. In conclusion, the analysis of linezolid (no correction factor) and clarithromycin (correction factor of 3) in oral fluid is applicable for therapeutic drug monitoring in cases of multidrug-resistant tuberculosis as an alternative to conventional serum sampling. Easy sampling using a noninvasive technique may facilitate therapeutic drug monitoring for specific patient categories.
Identification of Cell-Penetrating Peptides That Are Bactericidal to Neisseria meningitidis and Prevent Inflammatory Responses upon Infection
Authors: Eriksson Olaspers Sara , Geörg Miriam , Sjölinder Hong , Sillard Rannar , Lindberg Staffan , Langel Ülo , Jonsson Ann-Beth 
Published: May 2013

ABSTRACT

Meningococcal disease is characterized by a fast progression and a high mortality rate. Cell-penetrating peptides (CPPs), developed as vectors for cargo delivery into eukaryotic cells, share structural features with antimicrobial peptides. A screen identified two CPPs, transportan-10 (TP10) and model amphipathic peptide (MAP), with bactericidal action against
Neisseria meningitidis
. Both peptides were active in human whole blood at micromolar concentrations, while hemolysis remained negligible. Additionally, TP10 exhibited significant antibacterial activity
in vivo
. Uptake of SYTOX green into live meningococci was observed within minutes after TP10 treatment, suggesting that TP10 may act by membrane permeabilization. Apart from its bactericidal activity, TP10 suppressed inflammatory cytokine release from macrophages infected with
N. meningitidis
as well as from macrophages stimulated with enterobacterial and meningococcal lipopolysaccharide (LPS). Finally, incubation with TP10 reduced the binding of LPS to macrophages. This novel endotoxin-inhibiting property of TP10, together with its antimicrobial activity
in vivo
, indicates the possibility to design peptide-based therapies for infectious diseases.
A Mouse Model of Acinetobacter baumannii-Associated Pneumonia Using a Clinically Isolated Hypervirulent Strain
Authors: Harris Greg , Kuo Lee Rhonda , Lam Christopher K. , Kanzaki Gregory , Patel Girishchandra B. , Xu H. Howard , Chen Wangxue 
Published: May 2013

ABSTRACT

Acinetobacter baumannii
is an important emerging pathogen in health care-acquired infections and is responsible for severe nosocomial and community-acquired pneumonia. Currently available mouse models of
A. baumannii
pneumonia show poor colonization with little to no extrapulmonary dissemination. Here, we describe a mouse model of
A. baumannii
pneumonia using a clinical isolate (LAC-4 strain) that reliably reproduces the most relevant features of human pulmonary
A. baumannii
infection and pathology. Using this model, we have shown that LAC-4 infection induced rapid bacterial replication in the lungs, significant extrapulmonary dissemination, and severe bacteremia by 24 h postintranasal inoculation. Infected mice showed severe bronchopneumonia and dilatation and inflammatory cell infiltration in the perivascular space. More significantly, 100% of C57BL/6 and BALB/c mice succumbed to 10
8
CFU of LAC-4 inoculation within 48 h. When this model was used to assess the efficacy of antimicrobials, all mice treated with imipenem and tigecycline survived a lethal intranasal challenge, with minimal clinical signs and body weight loss. Moreover, intranasal immunization of mice with formalin-fixed LAC-4 protected 40% of mice from a lethal (100× 100% lethal dose) intraperitoneal challenge. Thus, this model offers a reproducible acute course of
A. baumannii
pneumonia without requiring additional manipulation of host immune status, which will facilitate the development of therapeutic agents and vaccines against
A. baumannii
pneumonia in humans.
Intraocular Penetration of Intravenous Micafungin in Inflamed Human Eyes
Authors: Mochizuki Kiyofumi , Sawada Akira , Suemori Shinsuke , Kawakami Hideaki , Niwa Yoshiaki , Kondo Yuji , Ohkusu Kiyofumi , Yamada Noriaki , Ogura Shinji , Yaguchi Takashi , Nishimura Kazuko , Kishino Satoshi 
Published: May 2013

ABSTRACT
Eight eyes of 7 patients with fungal disease received intravenous injections of 150 to 300 mg micafungin, and samples of blood, cornea, retina-choroid, aqueous humor, and vitreous humor were collected. The micafungin levels in all collected samples exceeded the MICs; however, the levels in the vitreous and aqueous humors were lower. Our findings suggest that intravenous micafungin should be given in combination with intravitreal antifungal agents after vitrectomy in severe cases of intraocular fungal diseases.
Isoniazid, Rifampin, and Pyrazinamide Plasma Concentrations in Relation to Treatment Response in Indonesian Pulmonary Tuberculosis Patients
Authors: Burhan Erlina , Ruesen Carolien , Ruslami Rovina , Ginanjar Arum , Mangunnegoro Hadiarto , Ascobat Purwantyastuti , Donders Rogier , van Crevel Reinout , Aarnoutse Rob 
Published: May 2013

ABSTRACT

Numerous studies have reported low concentrations of antituberculosis drugs in tuberculosis (TB) patients, but few studies have examined whether low drug concentrations affect TB treatment response. We examined steady-state plasma concentrations of isoniazid, rifampin, and pyrazinamide at 2 h after the administration of drugs (
C
2 h
) among 181 patients with pulmonary tuberculosis in Indonesia and related these to bacteriological response during treatment.
C
2 h
values below reference values for either isoniazid, rifampin, or pyrazinamide were found in 91% of patients; 60% had at least two low
C
2 h
concentrations. The isoniazid
C
2 h
was noticeably lower in fast versus slow acetylators (0.9 mg/liter versus 2.2 mg/liter,
P
< 0.001). At the end of treatment, 82% of the patients were cured, whereas 30 patients (17%) had dropped out during the study, and 2 patients (1%) failed treatment. No association was found between
C
2 h
concentrations and sputum culture results at 8 weeks of treatment.
Post hoc
analysis showed that patients with low pyrazinamide
C
2 h
(
P
= 0.01) and patients with large extensive lung lesions (
P
= 0.01) were at risk of at least one positive culture at week 4, 8, or 24/32. Antituberculosis drug concentrations were often low, but treatment response was nevertheless good. No association was found between drug concentrations and 8 weeks culture conversion, but low pyrazinamide drug concentrations may be associated with a less favorable bacteriological response. The use of higher doses of pyrazinamide may warrant further investigation.
Treatment of High-Level Gentamicin-Resistant Enterococcus faecalis Endocarditis with Daptomycin plus Ceftaroline
Authors: Sakoulas George , Nonejuie Poochit , Nizet Victor , Pogliano Joseph , Crum-Cianflone Nancy , Haddad Fadi 
Published: May 2013

ABSTRACT

A recurrent case of left-sided endocarditis caused by high-level aminoglycoside-resistant
Enterococcus faecalis
was successfully treated with ceftaroline and daptomycin. This combination demonstrated excellent synergy
in vitro
. Mechanistically, ceftaroline enhanced binding of daptomycin to the cell membrane and sensitized
E. faecalis
to killing by human cathelicidin LL-37, a cationic innate host defense peptide. Daptomycin plus ceftaroline may be considered in salvage therapy in
E. faecalis
endovascular infections and requires further study.
Evaluation of Pharmacokinetic Interaction between PA-824 and Midazolam in Healthy Adult Subjects
Authors: Winter Helen , Egizi Erica , Erondu Ngozi , Ginsberg Ann , Rouse Doris J. , Severynse-Stevens Diana , Pauli Elliott , Everitt Daniel 
Published: May 2013

ABSTRACT

This study assessed the safety, tolerability, and pharmacokinetic interaction between PA-824, a novel antitubercular nitroimidazo-oxazine, and midazolam, a CYP3A4 substrate, in 14 healthy adult male and female subjects. The study followed up on observations
in vitro
that PA-824 caused weak and time-dependent inhibition of CYP3A4. Subjects received a single oral dose of midazolam (2 mg), followed by a 2-day washout. After the washout, all subjects received PA-824 (400 mg) once daily for 14 consecutive days. On day 14, all subjects received the final PA-824 dose coadministered with a 2-mg oral dose of midazolam. The pharmacokinetic endpoints AUC

0–
t

, AUC
0–∞
, and
C
max
for midazolam and 1-hydroxy midazolam were compared between midazolam administered alone versus midazolam coadministered with PA-824. Statistical analysis demonstrated that the mean midazolam values of
C
max
, AUC

0–
t

, and AUC
0–∞
parameters were reduced by ca. 16, 15, and 15%, respectively, when PA-824 was coadministered with midazolam. The total exposure (AUC) of 1-hydroxy midazolam was 13 to 14% greater when coadministered with PA-824 compared to midazolam administered alone. The
C
max
of 1-hydroxy midazolam was similar between treatments. Based on these results, PA-824 does not inhibit or induce CYP3A4 to a clinically meaningful extent and is not likely to markedly affect the pharmacokinetics of CYP3A4 metabolized drugs.
Malaria Modifies Neonatal and Early-Life Toll-Like Receptor Cytokine Responses
Authors: Gbédandé Komi , Varani Stefania , Ibitokou Samad , Houngbegnon Parfait , Borgella Sophie , Nouatin Odilon , Ezinmegnon Sem , Adeothy Adicatou-laï , Cottrell Gilles , Massougbodji Achille , Moutairou Kabirou , Troye-Blomberg Marita , Deloron Philippe , Fievet Nadine , Luty Adrian J. F. 
Published: May 2013

ABSTRACT

Protection from infections in early life relies extensively on innate immunity, but it is unknown whether and how maternal infections modulate infants' innate immune responses, thereby altering susceptibility to infections.
Plasmodium falciparum
causes pregnancy-associated malaria (PAM), and epidemiological studies have shown that PAM enhances infants' susceptibility to infection with
P. falciparum
. We investigated how PAM-mediated exposures
in utero
affect innate immune responses and their relationship with infection in infancy. In a prospective study of mothers and their babies in Benin, we investigated changes in Toll-like receptor (TLR)-mediated cytokine responses related to
P. falciparum
infections. Whole-blood samples from 134 infants at birth and at 3, 6, and 12 months of age were stimulated with agonists specific for TLR3, TLR4, TLR7/8, and TLR9. TLR-mediated interleukin 6 (IL-6) and IL-10 production was robust at birth and then stabilized, whereas tumor necrosis factor alpha (TNF-α) and gamma interferon (IFN-γ) responses were weak at birth and then increased. In multivariate analyses, maternal
P. falciparum
infections at delivery were associated with significantly higher TLR3-mediated IL-6 and IL-10 responses in the first 3 months of life (
P
< 0.05) and with significantly higher TLR3-, TLR7/8-, and TLR9-mediated TNF-α responses between 6 and 12 months of age (
P
< 0.05). Prospective analyses showed that higher TLR3- and TLR7/8-mediated IL-10 responses at birth were associated with a significantly higher risk of
P. falciparum
infection in infancy (
P
< 0.05). Neonatal and infant intracellular TLR-mediated cytokine responses are conditioned by
in utero
exposure through PAM late in pregnancy. Enhanced TLR-mediated IL-10 responses at birth are associated with an increased risk of
P. falciparum
infection, suggesting a compromised ability to combat infection in early life.
Binding of Pk-Trisaccharide Analogs of Globotriaosylceramide to Shiga Toxin Variants
Authors: Yosief Hailemichael O. , Iyer Suri S. , Weiss Alison A. 
Published: May 2013

ABSTRACT
The two major forms of Shiga toxin, Stx1 and Stx2, use the glycolipid globotriaosylceramide (Gb3) as their cellular receptor. Stx1 primarily recognizes the Pk-trisaccharide portion and has three Pk binding sites per B monomer. The Stx2a subtype requires glycolipid residues in addition to Pk. We synthesized analogs of Pk to examine the binding preferences of Stx1 and Stx2 subtypes a to d. Furthermore, to determine how many binding sites must be engaged, the Pk analogues were conjugated to biotinylated mono- and biantennary platforms, allowing for the display of two to four Pk analogues per streptavidin molecule. Stx binding to Pk analogues immobilized on streptavidin-coated plates was assessed by enzyme-linked immunosorbent assay (ELISA). Stx1, but not the Stx2 subtypes, bound to native Pk. Stx2a and Stx2c bound to the Pk analog with a terminal GalNAc (NAc-Pk), while Stx1, Stx2b, and Stx2d did not bind to this analog. Interestingly, the purified Stx2d B subunit bound to NAc-Pk, suggesting that the A subunit of Stx2d interferes with binding. Disaccharide analogs (Galα1-4Gal, GalNAcα1-4Gal, and Galα1-4GalNAc) did not support the binding of any of the Stx forms, indicating that the trisaccharide is necessary for binding. Studies with monoantennary and biantennary analogs and mixtures suggest that Stx1, Stx2a, and Stx2c need to engage at least three Pk analogues for effective binding. To our knowledge, this is the first study examining the minimum number of Pk analogs required for effective binding and the first report documenting the role of the A subunit in influencing Stx2 binding.
Clearance of Pseudomonas aeruginosa Foreign-Body Biofilm Infections through Reduction of the Cyclic Di-GMP Level in the Bacteria
Authors: Christensen Louise D. , van Gennip Maria , Rybtke Morten T. , Wu Hong , Chiang Wen-Chi , Alhede Morten , Høiby Niels , Nielsen Thomas E. , Givskov Michael , Tolker-Nielsen Tim 
Published: May 2013

ABSTRACT

Opportunistic pathogenic bacteria can engage in biofilm-based infections that evade immune responses and develop into chronic conditions. Because conventional antimicrobials cannot efficiently eradicate biofilms, there is an urgent need to develop alternative measures to combat biofilm infections. It has recently been established that the secondary messenger cyclic diguanosine monophosphate (c-di-GMP) functions as a positive regulator of biofilm formation in several different bacteria. In the present study we investigated whether manipulation of the c-di-GMP level in bacteria potentially can be used for biofilm control
in vivo
. We constructed a
Pseudomonas aeruginosa
strain in which a reduction in the c-di-GMP level can be achieved via induction of the
Escherichia coli
YhjH c-di-GMP phosphodiesterase. Initial experiments showed that induction of
yhjH
expression led to dispersal of the majority of the bacteria in
in vitro
-grown
P. aeruginosa
biofilms. Subsequently, we demonstrated that
P. aeruginosa
biofilms growing on silicone implants, located in the peritoneal cavity of mice, dispersed after induction of the YhjH protein. Bacteria accumulated temporarily in the spleen after induction of biofilm dispersal, but the mice tolerated the dispersed bacteria well. The present work provides proof of the concept that modulation of the c-di-GMP level in bacteria is a viable strategy for biofilm control.