bluuebunny/crossref_metadata_2025 huggingface dataset:
Replicon Typing of Plasmids Carrying CTX-M or CMY β-Lactamases Circulating among
Salmonella
and
Escherichia coli
Isolates
Authors: Hopkins Katie L. , Liebana Ernesto , Villa Laura , Batchelor Miranda , Threlfall E. John , Carattoli Alessandra
Published: August 2006

Replicon typing of plasmids carrying
bla
CTX-M
or
bla
CMY
β-lactamase genes indicates a predominance of I1 and A/C replicons among
bla
CMY
-carrying plasmids and five different plasmid scaffolds associated with the different types of
bla
CTX-M
genes (I1, FII, HI2, K, and N). These results demonstrate the association of certain β-lactamase genes with specific plasmid backbones.
Prior Antibacterial Peptide-Mediated Inhibition of Protein Folding in Bacteria Mutes Resistance Enzymes
Authors: Otvos Laszlo , de Olivier Inacio Vanessa , Wade John D. , Cudic Predrag
Published: August 2006

The antimicrobial activity of amoxicillin against TEM-1-expressing strains could be fully recovered when bacteria were preincubated with sublethal doses of an antibacterial peptide derivative. Assays with the simultaneous administration of antibiotics or synergy assays with kanamycin or ciprofloxacin, where resistance development does not involve properly folded proteins, failed to yield similar results.
Successful Therapy of Experimental Endocarditis Caused by Vancomycin-Resistant
Staphylococcus aureus
with a Combination of Vancomycin and β-Lactam Antibiotics
Authors: Fox Paige M. , Lampen Russell J. , Stumpf Katrina S. , Archer Gordon L. , Climo Michael W.
Published: August 2006

VRS1 is the first isolated strain of vancomycin-resistant
Staphylococcus aureus
(VRSA) found to carry the
vanA
gene complex previously described in
Enterococcus
. Under vancomycin pressure, VRS1 makes aberrant cell walls consisting of stem tetrapeptide and depsipeptide that lack the terminal
d
-Ala-
d
-Ala residues targeted by vancomycin. Previous data have suggested that this aberrant cell wall is not cross-linked by PBP2a, the enzyme responsible for cell wall transpeptidation in the presence of β-lactam antibiotics. We examined the efficacy of treating VRS1 with a combination of vancomycin and β-lactam antibiotics in vitro and in vivo. We found that the MIC of oxacillin for VRS1 decreased from >256 μg/ml to <1 μg/ml in the presence of vancomycin. Using the rabbit model of endocarditis, we treated VRS1-infected rabbits with nafcillin alone, vancomycin alone, or a combination of nafcillin and vancomycin. Treatment with nafcillin in combination with vancomycin cleared bloodstream infections within 24 h and sterilized 12/13 spleens (92%), as well as 8/13 kidneys (62%), following 3 days of treatment. Mean aortic valve vegetation counts were reduced 3.48 log
10
CFU/g with the combination therapy (compared to untreated controls) and were significantly lower than with either vancomycin or nafcillin given alone. VRS1 was extremely virulent in this model, as no untreated rabbits survived the 3-day trial. Treatment of clinical infections due to VRSA with the combination of vancomycin and β-lactams may be an option, based on these results.
Identification of RNase 8 as a Novel Human Antimicrobial Protein
Authors: Rudolph Bente , Podschun Rainer , Sahly Hany , Schubert Sabine , Schröder Jens M. , Harder Jürgen
Published: August 2006

The antimicrobial activity of the human RNase A superfamily member RNase 8 was evaluated. Recombinant RNase 8 exhibited broad-spectrum microbicidal activity against potential pathogenic microorganisms (including multidrug-resistant strains) at micro- to nanomolar concentrations. Thus, RNase 8 was identified as a novel antimicrobial protein and may contribute to host defense.
Molecular Characterization of Resistance to Macrolides in
Bartonella henselae
Authors: Biswas Silpak , Raoult Didier , Rolain Jean-Marc
Published: August 2006

We selected in vitro erythromycin-resistant strains of
Bartonella henselae
. The mutants obtained had point mutations in domain V of 23S rRNA and/or in ribosomal protein L4. One lymph node of a patient with cat-scratch disease had such a mutation in 23S rRNA, suggesting that natural resistant strains may infect humans.
Genetic Environment of Quinolone Resistance Gene
qnrB2
in a Complex
sul1
-Type Integron in the Newly Described
Salmonella enterica
Serovar Keurmassar
Authors: Garnier Fabien , Raked Nabil , Gassama Amy , Denis François , Ploy Marie-Cécile
Published: August 2006

A
qnrB2
determinant was described for a new complex
sul1
-type integron from
Salmonella enterica
serovar Keurmassar. The genetic structure contained two class 1 integrons surrounding two common regions (CRs) separated by a partial 3′ conserved segment. The
qnrB2
gene is adjacent to the first CR.
NIM811, a Cyclophilin Inhibitor, Exhibits Potent In Vitro Activity against Hepatitis C Virus Alone or in Combination with Alpha Interferon
Authors: Ma Sue , Boerner Joanna E. , TiongYip ChoiLai , Weidmann Beat , Ryder Neil S. , Cooreman Michael P. , Lin Kai
Published: August 2006

Host factors involved in viral replication are potentially attractive antiviral targets that are complementary to specific inhibitors of viral enzymes, since resistant mutations against the latter are likely to emerge during long-term treatment. It has been reported recently that cyclosporine, which binds to a family of cellular proteins, cyclophilins, inhibits hepatitis C virus (HCV) replication in vitro. Here, the activities of various cyclosporine derivatives were evaluated in the HCV replicon system. There was a strong correlation between the anti-HCV activity and cyclophilin-binding affinity of these compounds. Of these, NIM811 has been selected as a therapeutic candidate for HCV infection, since it binds to cyclophilins with higher affinity than cyclosporine but is devoid of the significant immunosuppressive activity associated with cyclosporine. NIM811 induced a concentration-dependent reduction of HCV RNA in the replicon cells with a 50% inhibitory concentration of 0.66 μM at 48 h. Furthermore, a greater than three-log
10
viral RNA reduction was achieved after treating the cells with as little as 1 μM of NIM811 for 9 days. In addition, the combination of NIM811 with alpha interferon significantly enhanced anti-HCV activities without causing any increase of cytotoxicity. Taken together, these promising in vitro data warrant clinical investigation of NIM811, an inhibitor of novel mechanism, for the treatment of hepatitis C.
In Vitro Activity of Tigecycline against Multiple-Drug-Resistant, Including Pan-Resistant, Gram-Negative and Gram-Positive Clinical Isolates from Greek Hospitals
Authors: Souli Maria , Kontopidou Flora V. , Koratzanis Evangelos , Antoniadou Anastasia , Giannitsioti Efthimia , Evangelopoulou Pinelopi , Kannavaki Sofia , Giamarellou Helen
Published: August 2006

The in vitro activities of tigecycline and selected antimicrobials were evaluated against a variety of multiple-drug-resistant clinical isolates, including extended-spectrum β-lactamase- and/or metallo-β-lactamase-producing gram-negative strains, colistin-resistant strains, vancomycin- and/or linezolid-resistant enterococci, and methicillin-resistant
Staphylococcus aureus
(MRSA). Tigecycline showed excellent activity against a collection of difficult-to-treat pathogens currently encountered in the hospital setting.
Evolution and Global Dissemination of Macrolide-Resistant Group A Streptococci
Authors: Robinson D. Ashley , Sutcliffe Joyce A. , Tewodros Wezenet , Manoharan Anand , Bessen Debra E.
Published: August 2006

Macrolide-resistant group A streptococci (MRGAS) have been recovered from many countries worldwide. However, the strain typing information that is available has been insufficient for estimating the total number of macrolide-resistant clones, their geographic distributions, and their evolutionary relationships. In this study, sequence-based strain typing was used to characterize 212 MRGAS isolates from 34 countries. Evaluation of clonal complexes,
emm
type, and resistance gene content [
erm
(A),
erm
(B),
mef
(A), and undefined] indicate that macrolide resistance was acquired by GAS organisms via ≥49 independent genetic events. In contrast to other collections of mostly susceptible GAS, genetic diversification of MRGAS clones has occurred primarily by mutation rather than by recombination. Twenty-two MRGAS clonal complexes were recovered from more than one continent; intercontinental strains represent nearly 80% of the MRGAS isolates under study. The findings suggest that horizontal transfer of macrolide resistance genes to numerous genetic backgrounds and global dissemination of resistant clones and their descendants are both major components of the present-day macrolide resistance problem found within this species.
Generation of a Reporter Cell Line for Detection of Infectious Varicella-Zoster Virus and Its Application to Antiviral Studies
Authors: Wang Guan-Qing , Suzutani Tatsuo , Yamamoto Yumiko , Fukui Yoshiko , Nozawa Naoki , Schmid D. Scott , Kurane Ichiro , Inoue Naoki
Published: August 2006

To simplify the titration of infectious varicella-zoster virus (VZV), we generated a reporter cell line that produced luciferase in a dose-dependent manner upon infection with cell-free VZV. A few VZV-infected cells were detectable by coculturing with the cell line. We demonstrated the usefulness of the cell line for antiviral studies.
Isolates with Low-Level Vancomycin Resistance Associated with Persistent Methicillin-Resistant
Staphylococcus aureus
Bacteremia
Authors: Howden Benjamin P. , Johnson Paul D. R. , Ward Peter B. , Stinear Timothy P. , Davies John K.
Published: August 2006

Low-level vancomycin-resistant
Staphylococcus aureus
(vancomycin-intermediate
S. aureus
[VISA] and heterogenous VISA [hVISA]) is increasingly reported and leads to glycopeptide treatment failure. Various phenotypic features have been reported for these isolates, but the genetic changes leading to hVISA and VISA have yet to be clearly determined. We assessed phenotypic, antibiotic resistance, and genomic changes by using genomic DNA microarray comparison and sequencing of selected loci in five pairs of clinical hVISA/VISA strains and the initial methicillin-resistant
Staphylococcus aureus
(MRSA) isolates obtained prior to vancomycin therapy. The isolates were from adult patients in Australia and New Zealand who had persistent MRSA bacteremia (>7 days) while receiving vancomycin therapy. In all cases, the initial isolates were found to be fully vancomycin-susceptible
Staphylococcus aureus
(VSSA). The hVISA/VISA phenotype was associated with increased cell wall thickness, reduced autolytic activity in four of five hVISA/VISA strains, and a striking reduction in biofilm formation compared to the parent strains in all pairs. All five pairs appeared to be isogenic, and genomic DNA microarray comparison suggested that major genetic changes are not required for the development of the resistant phenotype in these strains. No sequence differences were found in the
agr
locus or the
tcaRA
genes for any pair, but a marked reduction in RNAIII expression was found in four pairs. In summary, hVISA/VISA arises from fully VSSA during persistent infection that fails to respond to glycopeptide therapy and is associated with significant phenotypic changes, including a marked reduction in biofilm-forming ability. These clinically derived pairs of isolates will be a useful resource to elucidate the genetic mechanism of resistance in hVISA/VISA strains.
Plasmid-Mediated Imipenem-Hydrolyzing Enzyme KPC-2 among Multiple Carbapenem-Resistant
Escherichia coli
Clones in Israel
Authors: Navon-Venezia Shiri , Chmelnitsky Inna , Leavitt Azita , Schwaber Mitchell J. , Schwartz David , Carmeli Yehuda
Published: August 2006

Carbapenem resistance in
Escherichia coli
is rare. We report four genetically unrelated carbapenem-resistant
E. coli
isolates cultured from four patients hospitalized in Tel Aviv Medical Center. PCR, sequencing, and Southern blot analysis identified KPC-2 as the imipenem-hydrolyzing enzyme in all four strains, carried on different plasmids with a possible common origin. This is the first discovery of KPC-2 in
E. coli
and the first report of this enzyme originating outside the United States.
In Vitro Activities of Itraconazole, Methiazole, and Nitazoxanide versus
Echinococcus multilocularis
Larvae
Authors: Reuter Stefan , Manfras Burkhard , Merkle Marion , Härter Georg , Kern Peter
Published: August 2006

Albendazole (ABZ) and mebendazole are the only drugs licensed for treatment of human alveolar echinococcosis. In order to augment the armamentarium against this deadly disease, we tested a series of drugs for their efficacy against
Echinococcus multilocularis
larvae.
E. multilocularis
larvae grown intraperitoneally in Mongolian gerbils were transferred into tissue culture. Vesicles budded from the tissue blocks and after 6 weeks, drugs were added, and the effect on the vesicles was observed. We tested the following drugs at various concentrations: ABZ, artemether, caspofungin, itraconazole (ITZ), ivermectin, methiazole (MTZ), miltefosine, nitazoxanide (NTZ), rifampin, and trimethoprim-sulfamethoxazole. ABZ, ITZ, MTZ, and NTZ effectively destroyed parasite vesicles in this in vitro culture system. At high NTZ doses of 10 μg/ml, disintegration of all vesicles was observed after 7 days and was significantly more rapid than with ABZ at equal concentrations (21 days). After drug discontinuation, regrowth of vesicles occurred between 7 and 14 days for all four drugs, indicating a parasitostatic effect. Combination treatment with NTZ-ABZ at concentrations between 1 and 10 μg/ml for either 3 weeks, 3 months, or 6 months yielded no vesicle regrowth during 8 months after drug discontinuation. The treated larval tissue was injected intraperitoneally into gerbils, and no regrowth of larval tissue was observed, suggesting a parasitocidal effect after combined treatment. ITZ, MTZ, and NTZ are potent inhibitors of larval growth, although they proved to be parasitostatic only. The combination of NTZ plus ABZ was parasitocidal in vitro. Animal experiments are warranted for studies of dose, toxicity, and drug interactions.
Rapid Degradation of Oseltamivir Phosphate in Clinical Samples by Plasma Esterases
Authors: Lindegardh Niklas , Davies Geraint R. , Hien Tran Tinh , Farrar Jeremy , Singhasivanon Pratap , Day Nicholas P. J. , White Nicholas J.
Published: August 2006

The anti-influenza drug oseltamivir is an ester prodrug activated by hepatic carboxylesterases. Plasma esterases also convert up to 31.8% of the parent compound to the active metabolite after 4 h ex vivo, with wide interindividual variation. This source of error is removed by adding the esterase inhibitor dichlorvos to blood collection tubes.
In Vitro Activity of Daptomycin against Methicillin-Resistant
Staphylococcus aureus
, Including Heterogeneously Glycopeptide-Resistant Strains
Authors: Diederen Bram M. W. , van Duijn Inge , Willemse Piet , Kluytmans Jan A. J. W.
Published: August 2006

The purpose of the present study was to assess the in vitro activity of daptomycin against a well-defined collection of methicillin-resistant
Staphylococcus aureus
(MRSA) isolates (
n
= 98), including heterogeneously glycopeptide-resistant MRSA (hGISA) strains. Susceptibility testing was performed by using the Etest system. Daptomycin was potent against both glycopeptide-susceptible and hGISA strains.
Mode of Transposition and Expression of 16S rRNA Methyltransferase Gene
rmtC
Accompanied by IS
Ecp1
Authors: Wachino Jun-ichi , Yamane Kunikazu , Kimura Kouji , Shibata Naohiro , Suzuki Satowa , Ike Yasuyoshi , Arakawa Yoshichika
Published: August 2006

A newly identified 16S rRNA methyltransferase gene,
rmtC
, was accompanied by an IS
Ecp1
element at its 5′ end. This IS
Ecp1
element, which contained a transposase gene,
tnpA
, provided a promoter activity for expression of the adjacent
rmtC
; and this structure enabled the
rmtC
gene to be transposed onto another plasmid in
Escherichia coli
.
Escape of
Candida
from Caspofungin Inhibition at Concentrations above the MIC (Paradoxical Effect) Accomplished by Increased Cell Wall Chitin; Evidence for β-1,6-Glucan Synthesis Inhibition by Caspofungin
Authors: Stevens David A. , Ichinomiya Masayuki , Koshi Yukako , Horiuchi Hiroyuki
Published: August 2006

Concentrations above the MIC of caspofungin allow growth of some
Candida
isolates. A strain demonstrating paradoxical growth was grown in the presence and absence of caspofungin, and the cell wall content was analyzed. β-1,3-Glucan declined 81% in the presence of caspofungin, as expected. β-1,6-Glucan declined 73%. Chitin increased 898%, demonstrating a mechanism for paradoxical growth—a rapid shift in the key polymer.
In Vitro Activities of DA-7157 and DA-7218 against
Mycobacterium tuberculosis
and
Nocardia brasiliensis
Authors: Vera-Cabrera Lucio , Gonzalez Eva , Rendon Adrian , Ocampo-Candiani Jorge , Welsh Oliverio , Velazquez-Moreno Victor M. , Hak Choi Sung , Molina-Torres Carmen
Published: August 2006

The in vitro activities of DA-7157, a novel oxazolidinone, against clinical isolates of
Nocardia brasiliensis
and
Mycobacterium tuberculosis
were determined. Equal MIC
50
s and MIC
90
s (0.25 and 0.5 μg/ml, respectively) were found for susceptible and multidrug-resistant isolates of
M. tuberculosis
. The
N. brasiliensis
isolates showed an MIC
90
of 1 μg/ml and an MIC
50
of 1 μg/ml. The DA-7157 prodrug, DA-7218, exhibited similar MICs for
M. tuberculosis
but fivefold-higher MICs for
N. brasiliensis
.
Are Broad-Spectrum Fluoroquinolones More Likely To Cause
Clostridium difficile
-Associated Disease?
Authors: Dhalla Irfan A. , Mamdani Muhammad M. , Simor Andrew E. , Kopp Alex , Rochon Paula A. , Juurlink David N.
Published: August 2006

Limited evidence suggests that broad-spectrum fluoroquinolones such as gatifloxacin and moxifloxacin are more likely to cause
Clostridium difficile
-associated disease than levofloxacin. In a population-based case-control study of outpatients prescribed fluoroquinolones, we found no increased risk of
C. difficile
-associated disease requiring hospitalization among patients prescribed gatifloxacin or moxifloxacin compared to levofloxacin.
Eosin B as a Novel Antimalarial Agent for Drug-Resistant
Plasmodium falciparum
Authors: Massimine Kristen M. , McIntosh Michael T. , Doan Lanxuan T. , Atreya Chloé E. , Gromer Stephan , Sirawaraporn Worachart , Elliott David A. , Joiner Keith A. , Schirmer R. Heiner , Anderson Karen S.
Published: August 2006

4′,5′-Dibromo-2′,7′-dinitrofluorescein, a red dye commonly referred to as eosin B, inhibits
Toxoplasma gondii
in both enzymatic and cell culture studies with a 50% inhibitory concentration (IC
50
) of 180 μM. As a non-active-site inhibitor of the bifunctional
T. gondii
dihydrofolate reductase-thymidylate synthase (DHFR-TS), eosin B offers a novel mechanism for inhibition of the parasitic folate biosynthesis pathway. In the present study, eosin B was further evaluated as a potential antiparasitic compound through in vitro and cell culture testing of its effects on
Plasmodium falciparum
. Our data revealed that eosin B is a highly selective, potent inhibitor of a variety of drug-resistant malarial strains, with an average IC
50
of 124 nM. Furthermore, there is no indication of cross-resistance with other clinically utilized compounds, suggesting that eosin B is acting via a novel mechanism. The antimalarial mode of action appears to be multifaceted and includes extensive damage to membranes, the alteration of intracellular organelles, and enzymatic inhibition not only of DHFR-TS but also of glutathione reductase and thioredoxin reductase. In addition, preliminary studies suggest that eosin B is also acting as a redox cycling compound. Overall, our data suggest that eosin B is an effective lead compound for the development of new, more effective antimalarial drugs.
Mechanism-Based Pharmacodynamic Models of Fluoroquinolone Resistance in
Staphylococcus aureus
Authors: Chung Philip , McNamara Patrick J. , Campion Jeffrey J. , Evans Martin E.
Published: August 2006

Pharmacodynamic modeling from earlier experiments in which two ciprofloxacin-susceptible
Staphylococcus aureus
strains and their corresponding resistant
grlA
mutants were exposed to a series of ciprofloxacin (J. J. Campion, P. J. McNamara, and M. E. Evans, Antimicrob. Agents Chemother. 49:209-219, 2005) and levofloxacin (J. J. Campion et al., Antimicrob. Agents Chemother. 49:2189-2199, 2005) pharmacokinetic profiles in an in vitro system indicated that the subpopulation-specific estimated maximal killing rate constants were similar for both agents, suggesting a common mechanism of action. We propose two novel pharmacodynamic models that assign mechanisms of action to fluoroquinolones (growth inhibition or death stimulation) and compare the abilities of these models and two other maximum effect models (net effect and MIC based) to describe and predict the changes in the population dynamics observed during our previous in vitro system experiments with ciprofloxacin. A high correlation between predicted and observed viable counts was observed for all models, but the best fits, as assessed by diagnostic tests, and the most precise parameter estimates were obtained with the growth inhibition and net effect models. All models, except the death stimulation model, correctly predicted that resistant subpopulations would not emerge when a high-density culture was exposed to a high initial concentration designed to rapidly eradicate low-level-resistant
grlA
mutants. Additional experiments are necessary to elucidate which of the proposed mechanistic models best characterizes the antibacterial effects of fluoroquinolone antimicrobial agents.
Use of Nonlinear Mixed-Effects Analysis for Improved Precision of Early Pharmacodynamic Measures in Tuberculosis Treatment
Authors: Davies Geraint R. , Brindle Richard , Khoo Saye H. , Aarons Leon J.
Published: August 2006

Nonlinear mixed-effects analysis of serial sputum colony-counting data supports the existence of two bacillary subpopulations in sputum, eliminated at different rates. It distinguishes between combination regimens, removes bias, and greatly improves precision, with significant implications for the analysis of surrogate endpoints of “sterilization” in the development of new antituberculosis regimens.
Inhibition of Fungal β-1,3-Glucan Synthase and Cell Growth by HM-1 Killer Toxin Single-Chain Anti-Idiotypic Antibodies
Authors: Selvakumar Dakshnamurthy , Miyamoto Masahiko , Furuichi Yasuhiro , Komiyama Tadazumi
Published: August 2006

Single-chain variable-fragment (scFv) anti-idiotypic antibodies of an HM-1 killer toxin (HM-1) from the yeastWilliopsis saturnusvar.mrakiiIFO 0895 have been produced by recombinant DNA technology from the splenic lymphocytes of mice immunized by idiotypic vaccination with a neutralizing monoclonal antibody (nMAb-KT). The fungicidal activity of scFv anti-idiotypic antibodies against the isolates of fourCandidaspecies was assessed by MIC analysis. scFv antibodies were fungicidal at concentrations of 1.56 to 12.5 μg/ml in vitro against fourCandidaspecies. The scFv antibodies exerted a strong candidacidal activity in vitro, with 50% inhibitory concentration (IC50) values ranging from 7.3 × 10−8to 16.0 × 10−8M, and were neutralized by adsorption with nMAb-KT. Furthermore, all scFv antibodies effectively inhibited fungal β-1,3-glucan synthase activity in vitro, with IC50values ranging from 2.0 × 10−8to 22.7 × 10−8M, values which almost coincide with the values that are inhibitory to the growth of fungal cells. Binding assays showed that the scFv antibodies specifically bind to nMAb-KT, and this binding pattern was confirmed by surface plasmon resonance analysis. The binding ability was further demonstrated by the competition observed between scFv antibodies and HM-1 to bind nMAb-KT. To the best of our knowledge, this is the first study to show that an antifungal anti-idiotypic antibody, in the form of recombinant scFv, potentially inhibits β-1,3-glucan synthase activity.
Metabolic Activation of Pradefovir by CYP3A4 and Its Potential as an Inhibitor or Inducer
Authors: Lin Chin-chung , Fang Che , Benetton Salete , Xu Gui-fen , Yeh Li-Tain
Published: August 2006

Metabolic activation of pradefovir to 9-(2-phosphonylmethoxyethyl)adenine (PMEA) was evaluated by using cDNA-expressed CYP isozymes in portal vein-cannulated rats following oral administration and in human liver microsomes. The enzyme induction potential of pradefovir was evaluated in rats following multiple oral dosing and in primary cultures of human hepatocytes. The results indicated that CYP3A4 is the only cDNA-expressed CYP isozyme catalyzing the conversion of pradefovir to PMEA. Pradefovir was converted to PMEA in human liver microsomes with aKmof 60 μM, a maximum rate of metabolism of 228 pmol/min/mg protein, and an intrinsic clearance of about 359 ml/min. Addition of ketoconazole and monoclonal antibody 3A4 significantly inhibits the conversion of pradefovir to PMEA in human liver microsomes, suggesting the predominant role of CYP3A4 in the metabolic activation of pradefovir. Pradefovir at 0.2, 2, and 20 μM was neither a direct inhibitor nor a mechanism-based inhibitor of CYP3A4, CYP2D6, CYP2C9, CYP2C19, CYP2E1, and CYP1A2 in human liver microsomes. In rats, the liver was the site of metabolic activation of pradefovir, whereas the small intestine did not play a significant role in the metabolic conversion of pradefovir to PMEA. Daily oral dosing (300 mg/kg of body weight) to rats for 8 days showed that pradefovir was not an inducer of P450 enzymes in rats. Furthermore, pradefovir at 10 μg/ml was not an inducer of either CYP1A2 or CYP3A4/5 in primary cultures of human hepatocytes.
In Silico Identification and Biological Evaluation of Antimicrobial Peptides Based on Human Cathelicidin LL-37
Authors: Sigurdardottir Thorgerdur , Andersson Pia , Davoudi Mina , Malmsten Martin , Schmidtchen Artur , Bodelsson Mikael
Published: August 2006

Bacterial lipopolysaccharides (LPS) are important triggers of the widespread inflammatory response, which contributes to the development of multiple organ failure during sepsis. The helical 37-amino-acid-long human antimicrobial peptide LL-37 not only possesses a broad-spectrum antimicrobial activity but also binds and neutralizes LPS. However, the use of LL-37 in sepsis treatment is hampered by the fact that it is also cytotoxic. To find a less toxic analog of LL-37, we used in silico analysis to identify amphipathic helical regions of LL-37. A 21-amino-acid fragment (GKE) was synthesized, the biological actions of which were compared to those of two equally long peptides derived from the N and C termini of LL-37 as well as native LL-37. GKE displayed antimicrobial activity against
Escherichia coli
,
Pseudomonas aeruginosa
,
Staphylococcus aureus
,
Candida albicans
, and
Candida parapsilosis
that was similar to or even stronger than LL-37. GKE, as well as the equally long control peptides, attracted granulocytes in a fashion similar to that of LL-37, while only GKE was as potent as LL-37 in inhibiting LPS-induced vascular nitric oxide production. GKE caused less hemolysis and apoptosis in human cultured smooth muscle cells than LL-37. In summary, we have identified an active domain of LL-37, GKE, which displays antimicrobial activity in vitro and LPS-binding activity similar to those of LL-37 but is less toxic. GKE therefore holds promise as a template for the development of peptide antibiotics for the treatment of sepsis.
Efficacy and Pharmacokinetics of Bacteriophage Therapy in Treatment of Subclinical
Staphylococcus aureus
Mastitis in Lactating Dairy Cattle
Authors: Gill J. J. , Pacan J. C. , Carson M. E. , Leslie K. E. , Griffiths M. W. , Sabour P. M.
Published: August 2006

Bovine mastitis is an inflammation of the udder caused by microbial infection. Mastitis caused by
Staphylococcus aureus
is a major concern to the dairy industry due to its resistance to antibiotic treatment and its propensity to recur chronically. Growing concerns surrounding antibiotic resistance have spurred research into alternative treatment methods. The ability of lytic
S. aureus
bacteriophage K to eliminate bovine
S. aureus
intramammary infection during lactation was evaluated in a placebo-controlled, multisite trial. Twenty-four lactating Holstein cows with preexisting subclinical
S. aureus
mastitis were treated. Treatment consisted of 10-ml intramammary infusions of either 1.25 × 10
11
PFU of phage K or saline, administered once per day for 5 days. The cure rate was established by the assessment of four serial samples collected following treatment. The cure rate was 3 of 18 quarters (16.7%) in the phage-treated group, while none of the 20 saline-treated quarters were cured. This difference was not statistically significant. The effects of phage intramammary infusion on the bovine mammary gland were also studied. In healthy lactating cows, a single infusion of either filter-sterilized broth lysate or a CsCl gradient-purified phage preparation elicited a large increase in the milk somatic cell count. This response was not observed when phage was infused into quarters which were already infected with
S. aureus
. Phage-infused healthy quarters continued to shed viable bacteriophage into the milk for up to 36 h postinfusion. The phage concentration in the milk suggested that there was significant degradation or inactivation of the infused phage within the gland.
New Trisubstituted Imidazolium-Based Room Temperature Ionic Liquids
Authors: Singh Rajendra P. , Meshri Dayal T.
Published: August 2006

Reaction of 1-decyl-2-methylimidazole (1) with linear bromoalkanes 2a, 2b in refluxing acetonitrile leads to the formation of quaternary bromide salts 3a, 3b in excellent isolated yields. Quaternary salts 3a, 3b were metathesized with KPF6 (4a), LiNTf2 (4b), LiBF4 (4c), or KOTf (4d) in water to form the ionic liquids 5a-5h in very good yields. These new ionic liquids are liquid at ambient temperature, immiscible with water, miscible with acetone and chloroform and thermally stable up to 350 °C.
On a New Algorithm for Computing Symmetry of Big Fullerenes
Authors: Ashrafi Ali Reza
Published: August 2006

In this paper, a new algorithm is presented which is useful for computing the automorphism group of chemical graphs. We compare our algorithm with those of Druffel, Schmidt and Wang. It is proved that the running time of the present algorithm is better than the mentioned algorithms. Also, the automorphism group of Euclidean graph of isomers for the fullerenes C180, C240, C260, C320, C500 and C720 are computed.
THE ROLE OF RESONANCES IN PLANETARY SYSTEMS
Authors: DVORAK RUDOLF
Published: August 2006

This paper reviews the important role of resonances in the structure of planetary systems. After a short introduction to the basics of orbital dynamics of motion in resonances we describe the dynamics of our planetary systems and also of extrasolar planetary systems, where up to now more than 100 are known. In our planetary system the planets move in quite regular orbits with small eccentricities although it was found that the motion of the inner planets is "slightly" chaotic on time scales of tenths of millions of years. The quasi regularity (close to so-called quasi-periodic motion on a torus) is not true for the small bodies: the main belt of asteroids between Mars and Jupiter with gaps for special values of semimajor axes on one hand and with families of many small bodies on the other, is sculpted due to the presence of first mean motion resonances with Jupiter and second secular resonances with long-periodic motions of the nodes and perihelia of Jupiter and Saturn. In extrasolar systems the planets — rather surprisingly — are found to move sometimes in very high eccentric orbits when they are at distances comparable to the size of our planets. Because of our still limited observational techniques using indirect methods we have only discovered massive planets comparable to the size of Jupiter. When these planets orbit alone around their host star our research aims at the possibility of additional terrestrial planets moving in such a system. Because of mostly large eccentricities here the resonances are, in contrary to our planets, essential for the stability of orbits, and may protect or destroy an orbit. On the other hand, in multiple planetary systems we concentrate on the stability of their orbits as they are observed: a very interesting new result is that most of these multiple planetary systems with high eccentric orbits move in resonances with a special configuration which protects them from close encounters although these orbits are crossing.
CHAOTIC DYNAMICS OF N-DEGREE OF FREEDOM HAMILTONIAN SYSTEMS
Authors: ANTONOPOULOS CHRIS , BOUNTIS TASSOS , SKOKOS CHARALAMPOS
Published: August 2006

We investigate the connection between local and global dynamics of two N-degree of freedom Hamiltonian systems with different origins describing one-dimensional nonlinear lattices: The Fermi–Pasta–Ulam (FPU) model and a discretized version of the nonlinear Schrödinger equation related to Bose–Einstein Condensation (BEC). We study solutions starting in the vicinity of simple periodic orbits (SPOs) representing in-phase (IPM) and out-of-phase motion (OPM), which are known in closed form and whose linear stability can be analyzed exactly. Our results verify that as the energy E increases for fixed N, beyond the destabilization threshold of these orbits, all positive Lyapunov exponents Li, i = 1,…, N - 1, exhibit a transition between two power laws, Li ∝ EBk, Bk > 0, k = 1, 2, occurring at the same value of E. The destabilization energy Ec per particle goes to zero as N → ∞ following a simple power-law, Ec/N ∝ N-α, with α being 1 or 2 for the cases we studied. However, using SALI, a very efficient indicator we have recently introduced for distinguishing order from chaos, we find that the two Hamiltonians have very different dynamics near their stable SPOs: For example, in the case of the FPU system, as the energy increases for fixed N, the islands of stability around the OPM decrease in size, the orbit destabilizes through period-doubling bifurcation and its eigenvalues move steadily away from -1, while for the BEC model the OPM has islands around it which grow in size before it bifurcates through symmetry breaking, while its real eigenvalues return to +1 at very high energies. Furthermore, the IPM orbit of the BEC Hamiltonian never destabilizes, having finite-size islands around it, even for very high N and E. Still, when calculating Lyapunov spectra, we find for the OPMs of both Hamiltonians that the Lyapunov exponents decrease following an exponential law and yield extensive Kolmogorov–Sinai entropies per particle h KS /N ∝ const., in the thermodynamic limit of fixed energy density E/N with E and N arbitrarily large.
HOW REAL ARE REAL NUMBERS?
Authors: CHAITIN GREGORY
Published: August 2006

We discuss mathematical and physical arguments against continuity and in favor of discreteness, with particular emphasis on the ideas of Emile Borel [1871–1956].
Mechanisms of mitochondrial response to variations in energy demand in eukaryotic cells
Authors: Devin Anne , Rigoulet Michel
Published: August 2006

This review focuses on the different mechanisms involved in the adjustment of mitochondrial ATP production to cellular energy demand. The oxidative phosphorylation steady state at constant mitochondrial enzyme content can vary in response to energy demand. However, such an adaptation is tightly linked to a modification in both oxidative phosphorylation yield and phosphate potential and is obviously very limited in eukaryotic cells. We describe the three main mechanisms involved in mitochondrial response to energy demand. In heart cells, a short-term adjustment can be reached mainly through metabolic signaling via phosphotransfer networks by the compartmentalized energy transfer and signal transmission. In such a complex regulatory mechanism, Ca2+ signaling participates in activation of matricial dehydrogenases as well as mitochondrial ATP synthase. These processes allow a large increase in ATP production rate without an important modification in thermodynamic forces. For a long-term adaptation, two main mechanisms are involved: modulation of the mitochondrial enzyme content as a function of energy demand and/or kinetic regulation by covalent modifications (phosphorylations) of some respiratory chain complex subunits. Regardless of the mechanism involved (kinetic regulation by covalent modification or adjustment of mitochondrial enzyme content), the cAMP signaling pathway plays a major role in molecular signaling, leading to the mitochondrial response. We discuss the energetic advantages of these mechanisms.
Social defeat and footshock increase body mass and adiposity in male Syrian hamsters
Authors: Solomon Matia B. , Foster Michelle T. , Bartness Timothy J. , Huhman Kim L.
Published: August 2006

Obesity is a world-wide epidemic, and many factors, including stress, have been linked to this growing trend. After social stress (i.e., defeat), subordinate laboratory rats and most laboratory mice become hypophagic and, subsequently, lose body mass; the opposite is true of subordinate Syrian hamsters. After social defeat, Syrian hamsters become hyperphagic and gain body mass compared with nonstressed controls. It is unknown whether this increase in body mass and food intake is limited to subordinate hamsters. In experiment 1, we asked, do dominant hamsters increase food intake, body mass, and adiposity after an agonistic encounter? Subordinate hamsters increased food intake and body mass compared with nonstressed controls. Although there was no difference in food intake or absolute body mass between dominant and nonstressed control animals, cumulative body mass gain was significantly higher in dominant than in nonstressed control animals. Total carcass lipid and white adipose tissue (WAT) (i.e., retroperitoneal and epididymal WAT) masses were significantly increased in subordinate, but not dominant, hamsters compared with nonstressed controls. In experiment 2, we asked, does footshock stress increase food intake, body mass, and adiposity. Hamsters exposed to defeat, but not footshock stress, increased food intake relative to nonstressed controls. In animals exposed to defeat or footshock stress, body mass, as well as mesenteric WAT mass, increased compared with nonstressed controls. Collectively, these data demonstrate that social and nonsocial stressors increase body and lipid mass in male hamsters, suggesting that this species may prove useful for studying the physiology of stress-induced obesity in some humans.
Cross-organ interactions between reproductive, gastrointestinal, and urinary tracts: modulation by estrous stage and involvement of the hypogastric nerve
Authors: Winnard Kenneth P. , Dmitrieva Natalia , Berkley Karen J.
Published: August 2006

Central nervous system neurons process information converging from the uterus, colon, and bladder, partly via the hypogastric nerve. This processing is influenced by the estrous cycle, suggesting the existence of an estrous-modifiable central nervous system substrate by which input from one pelvic organ can influence functioning of other pelvic organs. Here, we tested predictions from this hypothesis that acute inflammation of colon, uterine horn, or bladder would produce signs of inflammation in the other uninflamed organs (increase vascular permeability) and that cross-organ effects would vary with estrous and be eliminated by hypogastric neurectomy (HYPX). Under urethane anesthesia, the colon, uterine horn, or bladder of rats in proestrus or metestrus, with or without prior HYPX, was treated with mustard oil or saline. Two hours later, Evans Blue dye extravasation was measured to assess vascular permeability. Extravasation was increased in all inflamed organs, regardless of estrous stage. For rats in proestrus, but not metestrus, either colon or uterine horn inflammation significantly increased extravasation in the uninflamed bladder. Much smaller cross-organ effects were seen in colon and uterine horn. HYPX reduced extravasation in the inflamed colon and inflamed uterine horn, but not the inflamed bladder. HYPX eliminated the colon-to-bladder and uterine horn-to-bladder effects. These results demonstrate that inflaming one pelvic organ can produce estrous-modifiable signs of inflammation in other pelvic organs, particularly bladder, and suggest that the cross-organ effects involve the hypogastric nerve and are at least partly centrally mediated. Such effects could contribute to cooccurrence and cyclicity of distressing pelvic disorders in women.
Burn-induced increase in atrogin-1 and MuRF-1 in skeletal muscle is glucocorticoid independent but downregulated by IGF-I
Authors: Lang Charles H. , Huber Danuta , Frost Robert A.
Published: August 2006

The present study determined whether thermal injury increases the expression of the ubiquitin (Ub) E3 ligases referred to as muscle ring finger (MuRF)-1 and muscle atrophy F-box (MAFbx; aka atrogin-1), which are muscle specific and responsible for the increased protein breakdown observed in other catabolic conditions. After 48 h of burn injury (40% total body surface area full-thickness scald burn) gastrocnemius weight was reduced, and this change was associated with an increased mRNA abundance for atrogin-1 and MuRF-1 (3.1- to 8-fold, respectively). Similarly, burn increased polyUb mRNA content in the gastrocnemius twofold. In contrast, there was no burn-induced atrophy of the soleus and no significant change in atrogin-1, MuRF-1, or polyUb mRNA. Burns also did not alter E3 ligase expression in heart. Four hours after administration of the anabolic agent insulin-like growth factor (IGF)-I to burned rats, the mRNA content of atrogin-1 and polyUb in gastrocnemius had returned to control values and the elevation in MuRF-1 was reduced 50%. In contrast, leucine did not alter E3 ligase expression. In a separate study, in vivo administration of the proteasome inhibitor Velcade prevented burn-induced loss of muscle mass determined at 48 h. Finally, administration of the glucocorticoid receptor antagonist RU-486 did not prevent burn-induced atrophy of the gastrocnemius or the associated elevation in atrogin-1, MuRF-1, or polyUb. In summary, the acute muscle wasting accompanying thermal injury is associated with a glucocorticoid-independent increase in the expression of several Ub E3 ligases that can be downregulated by IGF-I.
Responses of Monkey Vestibular-Only Neurons to Translation and Angular Rotation
Authors: Zhou Wu , Tang Bing Feng , Newlands Shawn D. , King W. M.
Published: August 2006

Single-unit recordings were obtained from central vestibular neurons in three monkeys during passive head movements. Neurons that discharged in relation to head translation or changes in head orientation, but not eye movement (“vestibular-only,” n = 154), were examined in detail. Neuronal discharge rates were analyzed during four stimulus conditions: sinusoidal head translation in the horizontal plane (0.2–4 Hz, 0.2 g peak acceleration), static head tilt in the vertical plane (±20°), oscillatory head tilt (0.5–2 Hz), and sinusoidal angular rotation about an earth-vertical axis (0.5 or 1 Hz). Vestibular-only cells were divided into two groups based on the regularity of their spontaneous discharge rates (CV*). One group (low-sensitivity units) exhibited regular discharge rates (CV* < 0.2), weak discharge modulation during head translation (<25 spikes · s−1· g−1at f = 1 Hz), and persistent discharge rates related to static head tilt (0.68 spikes · s−1· °−1of head tilt). The second group (high sensitivity neurons) exhibited irregular discharge rates (CV* > 0.2), strong discharge modulation during head translation (∼100 spikes · s−1· g−1at f = 1 Hz), and little or no change in discharge rate during static head tilt (0.32 spikes · s−1· °−1). The firing rates of some neurons in both groups were modulated during rotation about an earth-vertical axis (42%), but the modulation was greater for neurons classified as high sensitivity units. Previous reports have described neurons similar to the high sensitivity group; however, the low sensitivity or tilt neurons have not previously been characterized. Significantly, recent theoretical models have predicted neurons with discharge patterns similar to those of low- and high-sensitivity neurons.
Intraspinal Microstimulation Excites Multisegmental Sensory Afferents at Lower Stimulus Levels Than Local α-Motoneuron Responses
Authors: Gaunt R. A. , Prochazka A. , Mushahwar V. K. , Guevremont L. , Ellaway P. H.
Published: August 2006

Microstimulation within the motor regions of the spinal cord is often assumed to activate motoneurons and propriospinal neurons close to the electrode tip. However, previous work has shown that intraspinal microstimulation (ISMS) in the gray matter activates sensory afferent axons as well as α-motoneurons (MNs). Here we report on the recruitment of sensory afferent axons and MNs as ISMS amplitudes increased. Intraspinal microstimulation was applied through microwires implanted in the dorsal horn, intermediate region and ventral horn of the L5–L7 segments of the spinal cord in four acutely decerebrated cats, two of which had been chronically spinalized. Activation of sensory axons was detected with electroneurographic recordings from dorsal roots. Activation of MNs was detected with electromyographic (EMG) recordings from hindlimb muscles. Sensory axons were nearly always activated at lower stimulus levels than MNs irrespective of the stimulating electrode location. EMG response latencies decreased as ISMS stimulus intensities increased, suggesting that MNs were first activated transsynaptically and then directly as intensity increased. ISMS elicited antidromic activity in dorsal root filaments with entry zones up to 17 mm rostral and caudal to the stimulation sites. We posit that action potentials elicited in localized terminal branches of afferents spread antidromically to all terminal branches of the afferents and transsynaptically excite MNs and interneurons far removed from the stimulation site. This may help explain how focal ISMS can activate many MNs of a muscle even though they are distributed in long thin columns.
Pediatric Traumatic Brain Injury: Quo Vadis?
Authors: Kochanek Patrick M.
Published: August 2006

In this review, five questions serve as the framework to discuss the importance of age-related differences in the pathophysiology and therapy of traumatic brain injury (TBI). The following questions are included: (1) Is diffuse cerebral swelling an important feature of pediatric TBI and what is its etiology? (2) Is the developing brain more vulnerable than the adult brain to apoptotic neuronal death after TBI and, if so, what are the clinical implications? (3) If the developing brain has enhanced plasticity versus the adult brain, why are outcomes so poor in infants and young children with severe TBI? (4) What contributes to the poor outcomes in the special case of inflicted childhood neurotrauma and how do we limit it? (5) Should both therapeutic targets and treatments of pediatric TBI be unique? Strong support is presented for the existence of unique biochemical, molecular, cellular and physiological facets of TBI in infants and children versus adults. Unique therapeutic targets and enhanced therapeutic opportunities, both in the acute phase after injury and in rehabilitation and regeneration, are suggested.
Pediatric Traumatic Brain Injury: Past, Present and Future
Authors: Jankowitz Brian T. , Adelson P. David
Published: August 2006

Traumatic brain injury (TBI) is the leading cause of death and disability in children. Evidence-based guidelines for the management of this population are available; however, the data highlight significant deficiencies with few treatment standards or guidelines. Considering the limited availability of resources, it is necessary to define realistic goals. Attention should be given to injury prevention, developing standardized pediatric admission and outcome evaluations, increasing the utility and spectrum of physiological and biochemical testing, and defining the evolving role of imaging in TBI.