bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Population Pharmacokinetic Modeling Approach Shows that Serum Penicillin G Concentrations Are Below Inhibitory Concentrations by Two Weeks after Benzathine Penicillin G Injection in the Majority of Young Adults
Authors: Neely Michael , Kaplan Edward L. , Blumer Jeffrey L. , Faix Dennis J. , Broderick Michael P. 
Published: September 2014

ABSTRACT

Serum penicillin G falls to low levels 2 weeks after injection as benzathine penicillin G (BPG) in young adults. Using Pmetrics and previously reported penicillin G pharmacokinetic data after 1.2 million units were given as BPG to 329 male military recruits, here we develop the first reported population pharmacokinetic model of penicillin G after BPG injection. We simulated time-concentration profiles over a broad range of pediatric and adult weights after alternative doses and dose frequencies to predict the probability of maintaining serum penicillin G concentrations of >0.02 mg/liter, a proposed protective threshold against group A
Streptococcus pyogenes
(GAS). The final population model included linear absorption into a central compartment, distribution to and from a peripheral compartment, and linear elimination from the central compartment, with allometrically scaled volumes and rate constants. With 1.2 million units of BPG given intramuscularly every 4 weeks in four total doses, only 23.2% of 5,000 simulated patients maintained serum penicillin G trough concentrations of >0.02 mg/liter 4 weeks after the last dose. When the doses were 1.8 million units and 2.4 million units, the percentages were 30.2% and 40.7%, respectively. With repeated dosing of 1.2 million units every 3 weeks and every 2 weeks for 4 doses, the percentages of simulated patients with a penicillin G trough concentration of >0.02 mg/liter were 37.8% and 65.2%, respectively. Our simulations support recommendations for more frequent rather than higher BPG doses to prevent recurrent rheumatic heart disease in areas of high GAS prevalence or during outbreaks.
Mutations in the
embC-embA
Intergenic Region Contribute to Mycobacterium tuberculosis Resistance to Ethambutol
Authors: Cui Zhenling , Li Yuanyuan , Cheng Song , Yang Hua , Lu Junmei , Hu Zhongyi , Ge Baoxue 
Published: September 2014

ABSTRACT

The rapid increase in
Mycobacterium tuberculosis
resistance to ethambutol (EMB) threatens the diagnosis and treatment of tuberculosis (TB). We investigated the role of mutations in the
embC-embA
intergenic region (IGR) in EMB-resistant clinical strains from east China. A total of 767
M. tuberculosis
clinical strains were collected and analyzed for their drug susceptibility to EMB using the MGIT 960 system and MIC assay, and the
embC-embA
IGRs of these strains were sequenced. The transcriptional activity of the
embC-embA
IGR mutations was examined by reporter gene assays in recombinant
Mycobacterium smegmatis
strains, and the effect of IGR mutations on its binding to EmbR, a transcription regulator of
embAB
, was analyzed by gel mobility shift assays. Correlation coefficient analysis showed that the
embC-embA
IGR mutation is associated with EMB resistance. The clinical strains carrying IGR mutations had a much higher level of
embA
and
embB
mRNA as well as higher MICs to EMB. IGR mutations had higher transcriptional activity when transformed into
M. smegmatis
strains. Mutated IGRs bound to EmbR with much higher affinity than wild-type fragments. The sensitivity of molecular drug susceptibility testing (DST) with IGR mutations as an additional marker increased from 65.5% to 73.5%. Mutations of the
embC-embA
IGR enhance the binding of EmbR to the promoter region of
embAB
and increase the expression of
embAB
, thus contributing to EMB resistance. Therefore, identification of IGR mutations as markers of EMB resistance could increase the sensitivity of molecular DST.
Comparative Pharmacodynamics of Posaconazole in Neutropenic Murine Models of Invasive Pulmonary Aspergillosis and Mucormycosis
Authors: Lewis Russell E. , Albert Nathaniel D. , Kontoyiannis Dimitrios P. 
Published: September 2014

ABSTRACT

We used two established neutropenic murine models of pulmonary aspergillosis and mucormycosis to explore the association between the posaconazole area under the concentration-time curve (AUC)-to-MIC ratio (AUC/MIC) and treatment outcome. Posaconazole serum pharmacokinetics were verified in infected mice to ensure that the studied doses reflected human exposures with the oral suspension, delayed-release tablet, and intravenous formulations of posaconazole. Sinopulmonary infections were then induced in groups of neutropenic mice with
Aspergillus fumigatus
strain 293 (posaconazole MIC, 0.5 mg/liter) or
Rhizopus oryzae
strain 969 (posaconazole MIC, 2 mg/liter) and treated with escalating daily dosages of oral posaconazole, which was designed to achieve AUCs ranging from 1.10 to 392 mg · h/liter. After 5 days of treatment, lung fungal burden was analyzed by quantitative real-time PCR. The relationships of the total drug AUC/MIC and the treatment response were similar in both models, with 90% effective concentrations (EC
90
s) corresponding to an AUC/MIC threshold of 76 (95% confidence interval [CI], 46 to 102) for strain 293 versus 87 (95% CI, 66 to 101) for strain 969. Using a provisional AUC/MIC target of >100, these exposures correlated with minimum serum posaconazole concentrations (
C
min
s) of 1.25 mg/liter for strain 293 and 4.0 mg/liter for strain 969. The addition of deferasirox, but not liposomal amphotericin or caspofungin, improved the activity of a suboptimal posaconazole regimen (AUC/MIC, 33) in animals with pulmonary mucormycosis. However, no combination was as effective as the high-dose posaconazole monotherapy regimen (AUC/MIC, 184). Our analysis suggests that posaconazole pharmacodynamics are similar for
A. fumigatus
and
R. oryzae
when indexed to pathogen MICs.
Quantification of Rifapentine, a Potent Antituberculosis Drug, from Dried Blood Spot Samples Using Liquid Chromatographic-Tandem Mass Spectrometric Analysis
Authors: Parsons Teresa L. , Marzinke Mark A. , Hoang Thuy , Bliven-Sizemore Erin , Weiner Marc , Mac Kenzie William R. , Dorman Susan E. , Dooley Kelly E. 
Published: September 2014

ABSTRACT

The quantification of antituberculosis drug concentrations in multinational trials currently requires the collection of modest blood volumes, centrifugation, aliquoting of plasma, freezing, and keeping samples frozen during shipping. We prospectively enrolled healthy individuals into the Tuberculosis Trials Consortium Study 29B, a phase I dose escalation study of rifapentine, a rifamycin under evaluation in tuberculosis treatment trials. We developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for quantifying rifapentine in whole blood on dried blood spots (DBS) to facilitate pharmacokinetic/pharmacodynamic analyses in clinical trials. Paired plasma and whole-blood samples were collected by venipuncture, and whole blood was spotted on Whatman protein saver 903 cards. The methods were optimized for plasma and then validated for DBS. The analytical measuring range for quantification of rifapentine and its metabolite was 50 to 80,000 ng/ml in whole-blood DBS. The analyte was stable on the cards for 11 weeks with a desiccant at room temperature and protected from light. The method concordance for paired plasma and whole-blood DBS samples was determined after correcting for participant hematocrit or population-based estimates of bias from Bland-Altman plots. The application of either correction factor resulted in acceptable correlation between plasma and whole-blood DBS (Passing-Bablok regression corrected for hematocrit;
y
= 0.98
x
+ 356). Concentrations of rifapentine may be determined from whole-blood DBS collected via venipuncture after normalization in order to account for the dilutional effects of red blood cells. Additional studies are focused on the application of this methodology to capillary blood collected by finger stick. The simplicity of processing, storage, shipping, and low blood volume makes whole-blood DBS attractive for rifapentine pharmacokinetic evaluations, especially in international and pediatric trials.
Zidovudine Induces Downregulation of Mitochondrial Deoxynucleoside Kinases: Implications for Mitochondrial Toxicity of Antiviral Nucleoside Analogs
Authors: Sun Ren , Eriksson Staffan , Wang Liya 
Published: September 2014

ABSTRACTMitochondrial thymidine kinase 2 (TK2) and deoxyguanosine kinase (dGK) catalyze the initial phosphorylation of deoxynucleosides in the synthesis of the DNA precursors required for mitochondrial DNA (mtDNA) replication and are essential for mitochondrial function. Antiviral nucleosides are known to cause toxic mitochondrial side effects. Here, we examined the effects of 3′-azido-2′,3′-dideoxythymidine (AZT) (zidovudine) on mitochondrial TK2 and dGK levels and found that AZT treatment led to downregulation of mitochondrial TK2 and dGK in U2OS cells, whereas cytosolic deoxycytidine kinase (dCK) and thymidine kinase 1 (TK1) levels were not affected. The AZT effects on mitochondrial TK2 and dGK were similar to those of oxidants (e.g., hydrogen peroxide); therefore, we examined the oxidative effects of AZT. We found a modest increase in cellular reactive oxygen species (ROS) levels in the AZT-treated cells. The addition of uridine to AZT-treated cells reduced ROS levels and protein oxidation and prevented the degradation of mitochondrial TK2 and dGK.In organellostudies indicated that the degradation of mitochondrial TK2 and dGK is a mitochondrial event. These results suggest that downregulation of mitochondrial TK2 and dGK may lead to decreased mitochondrial DNA precursor pools and eventually mtDNA depletion, which has significant implications for the regulation of mitochondrial nucleotide biosynthesis and for antiviral therapy using nucleoside analogs.
Nitrotriazole- and Imidazole-Based Amides and Sulfonamides as Antitubercular Agents
Authors: Papadopoulou Maria V. , Bloomer William D. , Rosenzweig Howard S. , Arena Alexander , Arrieta Francisco , Rebolledo Joseph C. J. , Smith Diane K. 
Published: September 2014

ABSTRACT

Twenty-three 3-nitrotriazole-based and 2-nitroimidazole-based amides and sulfonamides were screened for antitubercular (anti-TB) activity in aerobic
Mycobacterium tuberculosis
H37Rv by using the BacTiter-Glo (BTG) microbial cell viability assay. In general, 3-nitrotriazole-based sulfonamides demonstrated anti-TB activity, whereas 3-nitrotriazole-based amides and 2-nitroimidazole-based amides and sulfonamides were inactive. Three 3-nitrotriazole-based sulfonamides (compounds 4, 2, and 7) demonstrated 50% inhibitory concentration (IC
50
), IC
90
, and MIC values of 0.38, 0.43, and 1.56 μM (compound 4), 0.57, 0.98, and 3.13 μM (compound 2), and 0.79, 0.87, and 3.13 μM (compound 7), respectively. For 3-nitrotriazole-based sulfonamides, anti-TB activity increased with lipophilicity, whereas the one-electron reduction potential (E
1/2
) did not play a role. 2-Nitroimidazole-based analogs, which were inactive in the BTG assay, were significantly more active in the low-oxygen assay and more active than the 3-nitrotriazoles. All active nitrotriazoles in the BTG assay were similarly active or more potent (lower MIC values) against resistant strains, with the exception of compounds 2, 3, 4, and 8, which demonstrated greater MIC values against isoniazid-resistant strains. Five 3-nitrotriazole-based sulfonamides demonstrated activity in infected murine J774 macrophages, causing log reductions similar to those seen with rifampin. However, some compounds caused toxicity in uninfected macrophages. In conclusion, the classes of 3-nitrotriazole-based amides and sulfonamides merit further investigation as potential antitubercular agents.
Bacterial Lysis Liberates the Neutrophil Migration Suppressor YbcL from the Periplasm of Uropathogenic Escherichia coli
Authors: Lau Megan E. , Danka Elizabeth S. , Tiemann Kristin M. , Hunstad David A. 
Published: September 2014

ABSTRACT

Uropathogenic
Escherichia coli
(UPEC) modulates aspects of the innate immune response during urinary tract infection to facilitate bacterial invasion of the bladder epithelium, a requirement for the propagation of infection. For example, UPEC-encoded YbcL suppresses the traversal of bladder epithelia by neutrophils in both an
in vitro
model and an
in vivo
murine cystitis model. The suppressive activity of YbcL requires liberation from the bacterial periplasm, though the mechanism of release is undefined. Here we present findings on the site of action of YbcL and demonstrate a novel mode of secretion for a UPEC exoprotein. Suppression of neutrophil migration by purified YbcL
UTI
, encoded by cystitis isolate UTI89, required the presence of a uroepithelial layer; YbcL
UTI
did not inhibit neutrophil chemotaxis directly. YbcL
UTI
was released to a greater extent during UPEC infection of uroepithelial cells than during that of neutrophils. Release of YbcL
UTI
was maximal when UPEC and bladder epithelial cells were in close proximity. Established modes of secretion, including outer membrane vesicles, the type II secretion system, and the type IV pilus, were dispensable for YbcL
UTI
release from UPEC. Instead, YbcL
UTI
was liberated during bacterial death, which was augmented upon exposure to bladder epithelial cells, as confirmed by detection of bacterial cytoplasmic proteins and DNA in the supernatant and enumeration of bacteria with compromised membranes. As YbcL
UTI
acts on the uroepithelium to attenuate neutrophil migration, this mode of release may represent a type of altruistic cooperation within a UPEC population during colonization of the urinary tract.
Functional Characterization of Anopheles Matrix Metalloprotease 1 Reveals Its Agonistic Role during Sporogonic Development of Malaria Parasites
Authors: Goulielmaki Evi , Sidén-Kiamos I. , Loukeris Thanasis G. 
Published: September 2014

ABSTRACT

The ability to invade tissues is a unique characteristic of the malaria stages that develop/differentiate within the mosquitoes (ookinetes and sporozoites). On the other hand, tissue invasion by many pathogens has often been associated with increased matrix metalloprotease (MMP) activity in the invaded tissues. By employing cell biology and reverse genetics, we studied the expression and explored putative functions of one of the three MMPs encoded in the genome of the malaria vector
Anopheles gambiae
, namely, the
Anopheles gambiae
MMP1
(
AgMMP1
) gene, during the processes of blood digestion, midgut epithelium invasion by
Plasmodium
ookinetes, and oocyst development. We show that AgMMP1 exists in two alternative isoforms resulting from alternative splicing; one secreted (S-MMP1) and associated with hemocytes, and one membrane type (MT-MMP1) enriched in the cell attachment sites of the midgut epithelium. MT-MMP1 showed a remarkable response to ookinete midgut invasion manifested by increased expression, enhanced zymogen maturation, and subcellular redistribution, all indicative of an implication in the midgut epithelial healing that accompanies ookinete invasion. Importantly, RNA interference (RNAi)-mediated silencing of the
AgMMP1
gene revealed a postinvasion protective function of AgMMP1 during oocyst development. The combined results link for the first time an MMP with vector competence and mosquito-
Plasmodium
interactions.
Recognition of Streptococcus pneumoniae and Muramyl Dipeptide by NOD2 Results in Potent Induction of MMP-9, Which Can Be Controlled by Lipopolysaccharide Stimulation
Authors: Vissers Marloes , Hartman Yvonne , Groh Laszlo , de Jong Dirk J. , de Jonge Marien I. , Ferwerda Gerben 
Published: September 2014

ABSTRACTMatrix metallopeptidase 9 (MMP-9) is a protease involved in the degradation of extracellular matrix collagen. Evidence suggests that MMP-9 is involved in pathogenesis duringStreptococcus pneumoniaeinfection. However, not much is known about the induction of MMP-9 and the regulatory processes involved. We show here that the Gram-positive bacteria used in this study induced large amounts of MMP-9, in contrast to the Gram-negative bacteria that were used. An important pathogen-associated molecular pattern (PAMP) for Gram-positive bacteria is muramyl dipeptide (MDP). MDP is a very potent inducer of MMP-9 and showed a dose-dependent MMP-9 induction. Experiments using peripheral blood mononuclear cells (PBMCs) from Crohn's disease patients with nonfunctional NOD2 showed that MMP-9 induction byStreptococcus pneumoniaeand MDP is NOD2 dependent. Increasing amounts of lipopolysaccharide (LPS), an important PAMP for Gram-negative bacteria, resulted in decreasing amounts of MMP-9. Moreover, the induction of MMP-9 by MDP could be counteracted by simultaneously adding LPS. The inhibition of MMP-9 expression by LPS was found to be regulated posttranscriptionally, independently of tissue inhibitor of metalloproteinase 1 (TIMP-1), an endogenous inhibitor of MMP-9. Collectively, these data show thatStreptococcus pneumoniaeis able to induce large amounts of MMP-9. These high MMP-9 levels are potentially involved inStreptococcus pneumoniaepathogenesis.
DAP1, a Negative Regulator of Autophagy, Controls SubAB-Mediated Apoptosis and Autophagy
Authors: Yahiro Kinnosuke , Tsutsuki Hiroyasu , Ogura Kohei , Nagasawa Sayaka , Moss Joel , Noda Masatoshi 
Published: September 2014

ABSTRACT

Autophagy and apoptosis play critical roles in cellular homeostasis and survival. Subtilase cytotoxin (SubAB), produced by non-O157 type Shiga-toxigenic
Escherichia coli
(STEC), is an important virulence factor in disease. SubAB, a protease, cleaves a specific site on the endoplasmic reticulum (ER) chaperone protein BiP/GRP78, leading to ER stress, and induces apoptosis. Here we report that in HeLa cells, activation of a PERK (RNA-dependent protein kinase [PKR]-like ER kinase)-eIF2α (α subunit of eukaryotic initiation factor 2)-dependent pathway by SubAB-mediated BiP cleavage negatively regulates autophagy and induces apoptosis through death-associated protein 1 (DAP1). We found that SubAB treatment decreased the amounts of autophagy markers LC3-II and p62 as well as those of mTOR (mammalian target of rapamycin) signaling proteins ULK1 and S6K. These proteins showed increased expression levels in PERK knockdown or DAP1 knockdown cells. In addition, depletion of DAP1 in HeLa cells dramatically inhibited the SubAB-stimulated apoptotic pathway: SubAB-induced Bax/Bak conformational changes, Bax/Bak oligomerization, cytochrome
c
release, activation of caspases, and poly(ADP-ribose) polymerase (PARP) cleavage. These results show that DAP1 is a key regulator, through PERK-eIF2α-dependent pathways, of the induction of apoptosis and reduction of autophagy by SubAB.
cbb
3
-Type Cytochrome
c
Oxidases, Aerobic Respiratory Enzymes, Impact the Anaerobic Life of Pseudomonas aeruginosa PAO1
Authors: Hamada Masakaze , Toyofuku Masanori , Miyano Tomoki , Nomura Nobuhiko 
Published: September 2014

ABSTRACT

For bacteria, many studies have focused on the role of respiratory enzymes in energy conservation; however, their effect on cell behavior is poorly understood.
Pseudomonas aeruginosa
can perform both aerobic respiration and denitrification. Previous studies demonstrated that
cbb
3
-type cytochrome
c
oxidases that support aerobic respiration are more highly expressed in
P. aeruginosa
under anoxic conditions than are other aerobic respiratory enzymes. However, little is known about their role under such conditions. In this study, it was shown that
cbb
3
oxidases of
P. aeruginosa
PAO1 alter anaerobic growth, the denitrification process, and cell morphology under anoxic conditions. Furthermore, biofilm formation was promoted by the
cbb
3
oxidases under anoxic conditions.
cbb
3
oxidases led to the accumulation of nitric oxide (NO), which is produced during denitrification. Cell elongation induced by NO accumulation was reported to be required for robust biofilm formation of
P. aeruginosa
PAO1 under anoxic conditions. Our data show that
cbb
3
oxidases promote cell elongation by inducing NO accumulation during the denitrification process, which further leads to robust biofilms. Our findings show that
cbb
3
oxidases, which have been well studied as aerobic respiratory enzymes, are also involved in denitrification and influence the lifestyle of
P. aeruginosa
PAO1 under anoxic conditions.
Structural and Functional Characterization of Pseudomonas aeruginosa Global Regulator AmpR
Authors: Caille Olivier , Zincke Diansy , Merighi Massimo , Balasubramanian Deepak , Kumari Hansi , Kong Kok-Fai , Silva-Herzog Eugenia , Narasimhan Giri , Schneper Lisa , Lory Stephen , Mathee Kalai 
Published: September 2014

ABSTRACTPseudomonas aeruginosais a dreaded pathogen in many clinical settings. Its inherent and acquired antibiotic resistance thwarts therapy. In particular, derepression of the AmpC β-lactamase is a common mechanism of β-lactam resistance among clinical isolates. The inducible expression ofampCis controlled by the global LysR-type transcriptional regulator (LTTR) AmpR. In the present study, we investigated the genetic and structural elements that are important forampCinduction. Specifically, theampC(PampC) andampR(PampR) promoters and the AmpR protein were characterized. The transcription start sites (TSSs) of the divergent transcripts were mapped using 5′ rapid amplification of cDNA ends-PCR (RACE-PCR), and strong σ54and σ70consensus sequences were identified at PampRand PampC, respectively. Sigma factor RpoN was found to negatively regulateampRexpression, possibly through promoter blocking. Deletion mapping revealed that the minimal PampCextends 98 bp upstream of the TSS. Gel shifts using membrane fractions showed that AmpR binds to PampCin vitrowhereasin vivobinding was demonstrated using chromatin immunoprecipitation-quantitative PCR (ChIP-qPCR). Additionally, site-directed mutagenesis of the AmpR helix-turn-helix (HTH) motif identified residues critical for binding and function (Ser38 and Lys42) and critical for function but not binding (His39). Amino acids Gly102 and Asp135, previously implicated in the repression state of AmpR in the enterobacteria, were also shown to play a structural role inP. aeruginosaAmpR. Alkaline phosphatase fusion and shaving experiments suggest that AmpR is likely to be membrane associated. Lastly, anin vivocross-linking study shows that AmpR dimerizes. In conclusion, a potential membrane-associated AmpR dimer regulatesampCexpression by direct binding.
Redox-Responsive Repressor Rex Modulates Alcohol Production and Oxidative Stress Tolerance in Clostridium acetobutylicum
Authors: Zhang Lei , Nie Xiaoqun , Ravcheev Dmitry A. , Rodionov Dmitry A. , Sheng Jia , Gu Yang , Yang Sheng , Jiang Weihong , Yang Chen 
Published: September 2014

ABSTRACT

Rex, a transcriptional repressor that modulates its DNA-binding activity in response to NADH/NAD
+
ratio, has recently been found to play a role in the solventogenic shift of
Clostridium acetobutylicum
. Here, we combined a comparative genomic reconstruction of Rex regulons in 11 diverse clostridial species with detailed experimental characterization of Rex-mediated regulation in
C. acetobutylicum
. The reconstructed Rex regulons in clostridia included the genes involved in fermentation, hydrogen production, the tricarboxylic acid cycle, NAD biosynthesis, nitrate and sulfite reduction, and CO
2
/CO fixation. The predicted Rex-binding sites in the genomes of
Clostridium
spp. were verified by
in vitro
binding assays with purified Rex protein. Novel members of the
C. acetobutylicum
Rex regulon were identified and experimentally validated by comparing the transcript levels between the wild-type and
rex
-inactivated mutant strains. Furthermore, the effects of exposure to methyl viologen or H
2
O
2
on intracellular NADH and NAD
+
concentrations, expression of Rex regulon genes, and physiology of the wild type and
rex
-inactivated mutant were comparatively analyzed. Our results indicate that Rex responds to NADH/NAD
+
ratio
in vivo
to regulate gene expression and modulates fermentation product formation and oxidative stress tolerance in
C. acetobutylicum
. It is suggested that Rex plays an important role in maintaining NADH/NAD
+
homeostasis in clostridia.