bluuebunny/crossref_metadata_2025 huggingface dataset:
Efflux Pump-Mediated Intrinsic Drug Resistance in
Mycobacterium smegmatis
Authors: Li Xian-Zhi , Zhang Li , Nikaido Hiroshi
Published: June 2004

The
Mycobacterium smegmatis
genome contains many genes encoding putative drug efflux pumps. Yet with the exception of
lfrA
, it is not clear whether these genes contribute to the intrinsic drug resistance of this organism. We showed first by reverse transcription (RT)-PCR that several of these genes, including
lfrA
as well as the homologues of
Mycobacterium tuberculosis
Rv1145, Rv1146, Rv1877, Rv2846c (
efpA
), and Rv3065 (
mmr
and
emrE
), were expressed at detectable levels in the strain mc
2
155. Null mutants each carrying an in-frame deletion of these genes were then constructed in
M. smegmatis
. The deletions of the
lfrA
gene or
mmr
homologue rendered the mutant more susceptible to multiple drugs such as fluoroquinolones, ethidium bromide, and acriflavine (two- to eightfold decrease in MICs). The deletion of the
efpA
homologue also produced increased susceptibility to these agents but unexpectedly also resulted in decreased susceptibility to rifamycins, isoniazid, and chloramphenicol (two- to fourfold increase in MICs). Deletion of the Rv1877 homologue produced some increased susceptibility to ethidium bromide, acriflavine, and erythromycin. The upstream region of
lfrA
contained a gene encoding a putative TetR family transcriptional repressor, dubbed LfrR. The deletion of
lfrR
elevated the expression of
lfrA
and produced higher resistance to multiple drugs. Multidrug-resistant single-step mutants, independent of LfrA and attributed to a yet-unidentified drug efflux pump (here called LfrX), were selected in vitro and showed decreased accumulation of norfloxacin, ethidium bromide, and acriflavine in intact cells. Finally, use of isogenic β-lactamase-deficient strains showed the contribution of LfrA and LfrX to resistance to certain β-lactams in
M. smegmatis
.
Model System for High-Throughput Screening of Novel Human Immunodeficiency Virus Protease Inhibitors in
Escherichia coli
Authors: Cheng Ting-Jen , Brik Ashraf , Wong Chi-Huey , Kan Chen-Chen
Published: June 2004

Novel human immunodeficiency virus (HIV) protease inhibitors are urgently needed for combating the drug-resistance problem in the fight against AIDS. To facilitate lead discovery of HIV protease inhibitors, we have developed a safe, convenient, and cost-effective
Escherichia coli
-based assay system. This
E. coli
-based system involves coexpression of an engineered β-galactosidase as an HIV protease substrate and the HIV protease precursor comprising the transframe region and the protease domain. Autoprocessing of the HIV protease precursor releases the mature HIV protease. Subsequently, the HIV protease cleaves β-galactosidase, resulting in a loss of the β-galactosidase activity, which can be detected in high-throughput screens. Using Food and Drug Administration-approved HIV protease inhibitors, this
E. coli
-based system is validated as a surrogate screening system for identifying inhibitors that not only possess inhibitory activity against HIV protease but also have solubility and permeability for in vivo activity. The usefulness of the
E. coli
-based system was demonstrated with the identification of a novel HIV protease inhibitor from a library of compounds that were prepared by an amide-forming reaction with transition-state analog cores. A novel inhibitor with a sulfonamide core of amprenavir, E2, has shown good correlation with the in vitro enzymatic assay and in vivo
E. coli
-based system. This system can also be used to generate drug resistance profiles that could be used to suggest therapeutic uses of HIV protease inhibitors to treat the drug-resistant HIV strains. This simple yet efficient
E. coli
system not only represents a screening platform for high-throughput identification of leads targeting the HIV proteases but also can be adapted to all other classes of proteases.
Oral Efficacy of a Respiratory Syncytial Virus Inhibitor in Rodent Models of Infection
Authors: Cianci Christopher , Genovesi Eugene V. , Lamb Lucinda , Medina Ivette , Yang Zheng , Zadjura Lisa , Yang Hyekyung , D'Arienzo Celia , Sin Ny , Yu Kuo-Long , Combrink Keith , Li Zhufang , Colonno Richard , Meanwell Nicholas , Clark Junius , Krystal Mark
Published: June 2004

BMS-433771 is a potent inhibitor of respiratory syncytial virus (RSV) replication in vitro. Mechanism of action studies have demonstrated that BMS-433771 halts virus entry through inhibition of F protein-mediated membrane fusion. BMS-433771 also exhibited in vivo efficacy following oral administration in a mouse model of RSV infection (C. Cianci, K. Y. Yu, K. Combrink, N. Sin, B. Pearce, A. Wang, R. Civiello, S. Voss, G. Luo, K. Kadow, E. Genovesi, B. Venables, H. Gulgeze, A. Trehan, J. James, L. Lamb, I. Medina, J. Roach, Z. Yang, L. Zadjura, R. Colonno, J. Clark, N. Meanwell, and M. Krystal, Antimicrob. Agents Chemother.48:413-422, 2004). In this report, the in vivo efficacy of BMS-433771 against RSV was further examined in the BALB/c mouse and cotton rat host models of infection. By using the Long strain of RSV, prophylactic efficacy via oral dosing was observed in both animal models. A single oral dose, administered 1 h prior to intranasal RSV inoculation, was as effective against infection as a 4-day b.i.d. dosing regimen in which the first oral dose was given 1 h prior to virus inoculation. Results of dose titration experiments suggested that RSV infection was more sensitive to inhibition by BMS-433771 treatment in the BALB/c mouse host than in the cotton rat. This was reflected by the pharmacokinetic and pharmacodynamic analysis of the efficacy data, where the area under the concentration-time curve required to achieve 50% of the maximum response was ∼7.5-fold less for mice than for cotton rats. Inhibition of RSV by BMS-433771 in the mouse is the result of F1-mediated inhibition, as shown by the fact that a virus selected for resistance to BMS-433771 in vitro and containing a single amino acid change in the F1 region was also refractory to treatment in the mouse host. BMS-433771 efficacy against RSV infection was also demonstrated for mice that were chemically immunosuppressed by cyclophosphamide treatment, indicating that compound inhibition of the virus did not require an active host immune response.
A Small Peptide (CEL-1000) Derived from the β-Chain of the Human Major Histocompatibility Complex Class II Molecule Induces Complete Protection against Malaria in an Antigen-Independent Manner
Authors: Charoenvit Yupin , Brice Gary T. , Bacon David , Majam Victoria , Williams Jackie , Abot Esteban , Ganeshan Harini , Sedegah Martha , Doolan Denise L. , Carucci Daniel J. , Zimmerman Daniel H.
Published: June 2004

CEL-1000 (DGQEEKAGVVSTGLIGGG) is a novel potential preventative and therapeutic agent. We report that CEL-1000 confers a high degree of protection againstPlasmodiumsporozoite challenge in a murine model of malaria, as shown by the total absence of blood stage infection following challenge with 100 sporozoites (100% protection) and by a substantial reduction (400-fold) of liver stage parasite RNA following challenge with 50,000 sporozoites. CEL-1000 protection was demonstrated in A/J (H-2a) and C3H/HeJ (H-2k) mice but not in BALB/c (H-2d) or CAF1 (A/J × BALB/c F1hybrid) mice. In CEL-1000-treated and protected mice, high levels of gamma interferon (IFN-γ) in serum and elevated frequencies of hepatic and splenic CD4+IFN-γ-positive T cells were detected 24 h after administration of an additional dose of CEL-1000. Treatment of A/J mice that received CEL-1000 with antibodies against IFN-γ just prior to challenge abolished the protection, and a similar treatment with antibodies against CD4+T cells partially reduced the level of protection, while treatment with control antibodies or antibodies specific for interleukin-12 (IL-12), CD8+T cells, or NK cells had no effect. Our data establish that the protection induced by CEL-1000 is dependent on IFN-γ and is partially dependent on CD4+T cells but is independent of CD8+T cells, NK cells, and IL-12 at the effector phase and does not induce a detectable antibody response.
Extra Copies of the
Aspergillus fumigatus
Squalene Epoxidase Gene Confer Resistance to Terbinafine: Genetic Approach to Studying Gene Dose-Dependent Resistance to Antifungals in
A. fumigatus
Authors: Liu Wei , May Gregory S. , Lionakis Michail S. , Lewis Russell E. , Kontoyiannis Dimitrios P.
Published: June 2004

With the increasing use of antifungals such as amphotericin B, itraconazole, voriconazole, caspofungin, and terbinafine (TRB) in patients at high risk for invasive aspergillosis, resistance of
Aspergillus fumigatus
to these agents will ultimately emerge. Due to the limited availability of molecular genetics for
A. fumigatus
, few studies have addressed its mechanisms of resistance to antifungals. We transformed
A. fumigatus
protoplasts with a
pyrG
-based
A. fumigatus
genomic DNA library (constructed in the multicopy nonintegrating vector pRG3-AMA1-NotI, which also has the
pyr-4
gene for selection). We obtained one

pyrG
+

transformant that grew in medium containing a fungicidal concentration (0.625 μg/ml) of TRB. To determine whether TRB resistance in that transformant was plasmid dependent, we evicted the plasmid and found concomitant loss of uracil prototrophy and TRB resistance. DNA sequence analysis identified the gene responsible for TRB resistance as the
A. fumigatus
squalene epoxidase gene (
ERG1
), which encodes the target enzyme of TRB. Authentic
A. fumigatus ERG1
, amplified from the genome and cloned into pRG3-AMA1-NotI, also conferred TRB-specific resistance. This molecular approach has the potential to enhance our knowledge of the mechanisms of
A. fumigatus
resistance to modern antifungals.
In Vitro Effects of Resveratrol on the Viability and Infectivity of the Microsporidian
Encephalitozoon cuniculi
Authors: Leiro José , Cano Ernesto , Ubeira Florencio M. , Orallo Francisco , Sanmartín Manuel L.
Published: June 2004

Microsporidians of the genus
Encephalitozoon
are an important cause of disease in immunocompromised patients, and there are currently no completely effective treatments. The present study investigated the viability and infectivity of spores of
Encephalitozoon cuniculi
that had been exposed to resveratrol (RESV), a natural phytoalexin found in grapes and red wine. RESV at 50 μM showed significant sporicidal activity, and at 10 to 50 μM it reduced the capacity of the spores to infect dog kidney epithelial cells of the MDCK line. At 10 μM RESV also significantly inhibited intracellular development of the parasite, without affecting host cell viability. These results suggest that RESV may be useful in the treatment of
Encephalitozoon
infections.
Salmonella
Genomic Island 1 Multidrug Resistance Gene Clusters in
Salmonella enterica
Serovar Agona Isolated in Belgium in 1992 to 2002
Authors: Doublet Benoît , Butaye Patrick , Imberechts Hein , Boyd David , Mulvey Michael R. , Chaslus-Dancla Elisabeth , Cloeckaert Axel
Published: June 2004

Salmonella
genomic island 1 (SGI1) harbors a multidrug resistance (MDR) gene cluster which is a complex class 1 integron. Variant SGI1 MDR gene clusters conferring different MDR profiles have also been identified in several
Salmonella enterica
serovars and classified as SGI1-A to -F. A retrospective study was undertaken to characterize MDR regions from serovar Agona strains harboring SGI1 isolated from poultry in Belgium between 1992 and 2002. A total of 171 serovar Agona strains, displaying resistance to at least one antibiotic, were studied for the presence of SGI1. SGI1 was detected in 94 serovar Agona strains. The most prevalent variant was SGI1-A (85%), which harbors within the SGI1 complex class 1 integron a common region (CR1) containing orf513, a putative transposase gene, adjacent to the
dfrA10
trimethoprim resistance gene. A new variant SGI1 named SGI1-G was identified in two strains. It consisted of the
pse-1
gene cassette, as in SGI1-B, but with additional insertion of the orf513/
dfrA10
region structure. Seven strains displaying the typical SGI1 MDR profile (Ap Cm Ff Sm Sp Su Tc) showed genetic variation at the 3′ end of SGI1. These strains harbored the insertion of the CR1 containing orf513 as in SGI1-A, -D, and -G. However, downstream the right end of CR1, they presented different 7.4- to 8.5-kb deletions of the SGI1 3′ end that extended to the chromosomal genes
yieE
and
yieF
. These results suggest a possible role of CR1 in deletion formation, as has been reported for some insertion sequences. Pulsed-field gel electrophoresis analysis showed that all the serovar Agona SGI1-carrying strains belonged to a single clone. Thus, SGI1 is largely encountered in serovar Agona strains isolated from poultry in Belgium, the most prevalent variant being SGI1-A. SGI1 MDR region undergoes recombinational events resulting in a diversity of MDR gene clusters.
A Chimeric Peptide Composed of a Dermaseptin Derivative and an RNA III-Inhibiting Peptide Prevents Graft-Associated Infections by Antibiotic-Resistant Staphylococci
Authors: Balaban Naomi , Gov Yael , Giacometti Andrea , Cirioni Oscar , Ghiselli Roberto , Mocchegiani Federico , Orlando Fiorenza , D'Amato Giuseppina , Saba Vittorio , Scalise Giorgio , Bernes Sabina , Mor Amram
Published: June 2004

Staphylococcal bacteria are a prevalent cause of infections associated with foreign bodies and indwelling medical devices. Bacteria are capable of escaping antibiotic treatment through encapsulation into biofilms. RNA III-inhibiting peptide (RIP) is a heptapeptide that inhibits staphylococcal biofilm formation by obstructing quorum-sensing mechanisms. K
4
-S4(1-13)
a
is a 13-residue dermaseptin derivative (DD
13
) believed to kill bacteria via membrane disruption. We tested each of these peptides as well as a hybrid construct, DD
13
-RIP, for their ability to inhibit bacterial proliferation and suppress quorum sensing in vitro and for their efficacy in preventing staphylococcal infection in a rat graft infection model with methicillin-resistant
Staphylococcus aureus
(MRSA) or
S. epidermidis
(MRSE). In vitro, proliferation assays demonstrated that RIP had no inhibitory effect, while DD
13
-RIP and DD
13
were equally effective, and that the chimeric peptide but not DD
13
was slightly more effective than RIP in inhibiting RNA III synthesis, a regulatory RNA molecule important for staphylococcal pathogenesis. In vivo, the three peptides reduced graft-associated bacterial load in a dose-dependent manner, but the hybrid peptide was most potent in totally preventing staphylococcal infections at the lowest dose. In addition, each of the peptides acted synergistically with antibiotics. The data indicate that RIP and DD
13
act in synergy by attacking bacteria simultaneously by two different mechanisms. Such a chimeric peptide may be useful for coating medical devices to prevent drug-resistant staphylococcal infections.
Single-Dose Pharmacokinetics and Safety of a Novel Broad-Spectrum Cephalosporin (BAL5788) in Healthy Volunteers
Authors: Schmitt-Hoffmann Anne , Roos Brigitte , Schleimer Michael , Sauer Jill , Man Anthony , Nashed Norman , Brown Thomas , Perez Antonio , Weidekamm Erhard , Kovács Péter
Published: June 2004

BAL5788 is the water-soluble prodrug of BAL9141, a novel broad-spectrum cephalosporin with potent bactericidal activities against methicillin-resistantStaphylococcus aureus(MRSA) and penicillin-resistantStreptococcus pneumoniae. We investigated the safety and pharmacokinetics of BAL5788 in a double-blind, single-ascending-dose study with 40 healthy male subjects. The subjects were randomized to receive placebo (n= 2 subjects per dose) or BAL5788 (n= 6 subjects per dose) as a 200-ml intravenous infusion over 30 min. The BAL5788 doses used were 125, 250, 500, 750, and 1,000 mg (BAL9141 equivalents). All doses were well tolerated, with no severe or serious adverse events (AEs). The most frequent AE was taste disturbance. No electrocardiographic abnormalities and no trends or clinically significant changes in laboratory parameters or vital signs were observed. The maximum concentration of drug in serum and the area under the concentration-time curve for BAL9141 were dose proportional over the dosing range. The elimination half-life of BAL9141 was about 3 h. The volume of distribution at steady state was equal to the volume of the adult extracellular water compartment, and the rate of renal clearance of free drug corresponded to the normal glomerular filtration rate for adults. More than 70% of the administered dose was excreted as BAL9141 in the urine, and almost no prodrug was detected. After the infusion of 750 mg, the mean plasma BAL9141 concentrations exceeded the MIC at which 100% of MRSA isolates are inhibited (4 μg/ml) for approximately 7 h, or 58% of a 12-h dosing interval. These results indicate that infusions of 750 mg twice a day should be adequate for the treatment of infections caused by MRSA.
Real-Time PCR for Dihydrofolate Reductase Gene Single-Nucleotide Polymorphisms inPlasmodium vivaxIsolates
Authors: Brega Sara , de Monbrison Frédérique , Severini Carlo , Udomsangpetch Rachanee , Sutanto Inge , Ruckert Paul , Peyron François , Picot Stéphane
Published: June 2004

Mutations in thedhfrgene ofPlasmodium vivax(pvdhfr) are associated with resistance to the antifolate antimalarial drugs. Polymorphisms in thepvdhfrgene were assessed by hybridization probe technology on the LightCycler instrument with 134P. vivax-infected blood samples from Turkey (n= 24), Azerbaijan (n= 39), Thailand (n= 16), Indonesia (n= 53), and travelers (n= 19). Double mutations (S58R and S117N) or quadruple mutations (F57L/I, S58R, T61M, and S117N) in thepvdhfrgenes were found in all Thai samples (100%).pvdhfrmutant-type alleles were significantly more common in samples from travelers (42%) than in those from patients from Indonesia (5%). Surprisingly, thepvdhfrsingle-mutation allele (S117N) was identified at a high frequency in parasites from Turkey and Azerbaijan (71 and 36%, respectively), where sulfadoxine-pyrimethamine is not recommended for the treatment ofP. vivaxmalaria by the World Health Organization and the Malaria National Programs.
Enzymatic Detachment of
Staphylococcus epidermidis
Biofilms
Authors: Kaplan Jeffrey B. , Ragunath Chandran , Velliyagounder Kabilan , Fine Daniel H. , Ramasubbu Narayanan
Published: June 2004

The gram-positive bacterium
Staphylococcus epidermidis
is the most common cause of infections associated with catheters and other indwelling medical devices.
S. epidermidis
produces an extracellular slime that enables it to form adherent biofilms on plastic surfaces. We found that a biofilm-releasing enzyme produced by the gram-negative periodontal pathogen
Actinobacillus actinomycetemcomitans
rapidly and efficiently removed
S. epidermidis
biofilms from plastic surfaces. The enzyme worked by releasing extracellular slime from
S. epidermidis
cells. Precoating surfaces with the enzyme prevented
S. epidermidis
biofilm formation. Our findings demonstrate that biofilm-releasing enzymes can exhibit broad-spectrum activity and that these enzymes may be useful as antibiofilm agents.
Detection and Susceptibility Testing of Hypermutable
Pseudomonas aeruginosa
Strains with the Etest and Disk Diffusion
Authors: Maciá Maria D. , Borrell Nuria , Pérez José L. , Oliver Antonio
Published: June 2004

Resistance development in
Pseudomonas aeruginosa
from chronically colonized cystic fibrosis (CF) patients has been linked to the presence of a high proportion of mismatch repair-deficient hypermutable strains. The detection of hypermutable strains by microbiology laboratories may be useful for establishing adequate antimicrobial therapies. In this work, we find that the Etest and disk diffusion can be used as simple methods for the detection and susceptibility testing of hypermutable
P. aeruginosa
isolates. Strain PAO1 and its hypermutable derivative strain PAOΔ
mutS
were used to standardize the procedure, which was tested with 35
P. aeruginosa
isolates from 21 CF patients. Mutation frequencies were estimated by standard methods, and 29% of the isolates were found to be hypermutable. MICs and inhibition zone diameters were determined for ceftazidime, imipenem, meropenem, ciprofloxacin, and tobramycin by using Etest strips and conventional disks, respectively. The presence (or absence) of resistant mutant subpopulations, as well as their relative numbers and the highest MICs for them (or smallest inhibition zone diameters), was recorded. The presence of resistant mutant subpopulations within the inhibition zones of three or more antibiotics clearly identified the strains as hypermutable (they were present in 10 of 10 hypermutable strains and 0 of 25 nonhypermutable strains) with both methods. Additionally, these methods allowed us to differentiate between dual effects of hypermutation in antibiotic resistance, namely, that (i) hypermutable isolates were substantially more resistant than nonhypermutable isolates and that (ii) the resistance of hypermutable isolates was dramatically increased by the presence of resistant mutant subpopulations. This differentiation may be relevant for the design of adequate treatments, since the second effect, in contrast to the first, may be overcome by antibiotic combinations.
Constitutive Activation of the
PDR16
Promoter in a
Candida albicans
Azole-Resistant Clinical Isolate Overexpressing
CDR1
and
CDR2
Authors: De Deken Xavier , Raymond Martine
Published: June 2004

Candida albicans
azole-resistant clinical isolates overexpressing the
CDR1
and
CDR2
genes (multidrug transporters) also overexpress the
PDR16
gene (phosphatidylinositol transfer protein). We show here that the
PDR16
promoter displays higher transcriptional activity following integration in an azole-resistant isolate than in the matched azole-susceptible one. Thus, the upregulation of
PDR16
in the resistant strain results from a mutation acting in
trans
.
In Vitro Activities of a Novel Cephalosporin, CB-181963 (CAB-175), against Methicillin-Susceptible or -Resistant
Staphylococcus aureus
and Glycopeptide-Intermediate Susceptible Staphylococci
Authors: Huang Vanthida , Brown William J. , Rybak Michael J.
Published: June 2004

We examined the activity of CB-181963, a novel cephalosporin, against methicillin-resistant
Staphylococcus aureus
(MRSA) (
n
= 200), methicillin-susceptible
S. aureus
(MSSA) (
n
= 50), glycopeptide-intermediate
Staphylococcus
species (GISS) (
n
= 47), and VRSA (
n
= 2) isolates. CB-181963 exhibited MIC profiles similar to those of linezolid against MRSA and GISS; however, activity against MSSA was similar to that of vancomycin. Time-kill study results of investigations of activity against MRSA, MSSA, and GISS at 24 h were as follows: CB-181963 activity = vancomycin activity > linezolid activity (
P
< 0.001); CB-181963 = quinupristin-dalfopristin = vancomycin > linezolid (
P
< 0.05); CB-181963 > linezolid (
P
= 0.003); and CB-181963 = quinupristin-dalfopristin = vancomycin. CB-181963 may provide an alternative treatment for multidrug-resistant staphylococci.
In Vitro Antifungal Susceptibilities of Uncommon Basidiomycetous Yeasts
Authors: Serena Carolina , Pastor Francisco Javier , Ortoneda Montserrat , Capilla Javier , Nolard Nicole , Guarro Josep
Published: June 2004

The in vitro activities of eight antifungal drugs against 50 isolates of basidiomycetous yeasts were determined by a microdilution method. In general fluconazole and micafungin were inactive. Terbinafine was active only against
Sporobolomyces salmonicolor
. The activities of the other antifungals were variable and depended on the species tested. The new triazoles showed the lowest MICs, but amphotericin B and itraconazole were the only drugs active against
Cryptococcus albidus
.
In Vitro Susceptibilities of
Madurella mycetomatis
to Itraconazole and Amphotericin B Assessed by a Modified NCCLS Method and a Viability-Based 2,3-Bis(2-Methoxy-4-Nitro-5- Sulfophenyl)-5-[(Phenylamino)Carbonyl]-2
H
- Tetrazolium Hydroxide (XTT) Assay
Authors: Ahmed Abdalla O. A. , van de Sande Wendy W. J. , van Vianen Wim , van Belkum Alex , Fahal Ahmed H. , Verbrugh Henri A. , Bakker-Woudenberg Irma A. J. M.
Published: June 2004

Susceptibilities of
Madurella mycetomatis
against amphotericin B and itraconazole in vitro were determined by protocols based on NCCLS guidelines (visual reading) and a 2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino) carbonyl]-2
H
-tetrazolium hydroxide (XTT) assay for fungal viability. The XTT assay was reproducible and sensitive for both antifungals. Itraconazole (MIC at which 50% of the isolates tested are inhibited [MIC
50
]) of 0.06 to 0.13 mg/liter) was superior to amphotericin B (MIC
50
of 0.5 to 1.0 mg/liter).
Comparison of Artesunate and Chloroquine Activities against
Plasmodium vivax
Gametocytes
Authors: Nacher Mathieu , Silachamroon Udomsak , Singhasivanon Pratap , Wilairatana Polrat , Phumratanaprapin Weerapong , Fontanet Arnaud , Looareesuwan Sornchai
Published: June 2004

The gametocidal activities of chloroquine and artesunate were compared. The relative risk (RR) of having detectable gametocytes appear after treatment initiation was lower in artesunate-treated patients (
n
= 792) than in chloroquine-treated patients (
n
= 695) (RR = 0.29; 95% CI = 0.2 to 0.40;
P
< 0.0001). The duration and magnitude of gametocyte carriage were also lower for artesunate than chloroquine. By reducing the transmission of
Plasmodium vivax
to the vector, artesunate could therefore reduce the incidence of
P. vivax
malaria.
rpoB
Mutations in
Streptococcus mitis
Clinical Isolates Resistant to Rifampin
Authors: Achour Wafa , Guenni Olfa , Fines Marguerite , Leclercq Roland , Ben Hassen Assia
Published: June 2004

Activity of rifampin against 129
Streptococcus mitis
isolates obtained from patients with hematologic cancer was investigated. One hundred twenty-five strains were susceptible to rifampin, and 4 were resistant (MIC = 32 to 64 μg/ml). Resistance to rifampin was related to mutations in the
rpoB
gene: His
526
Asn in three strains and His
526
Asp in one strain.
Role of dipeptidyl peptidase IV in regulating activity of Na+/H+ exchanger isoform NHE3 in proximal tubule cells
Authors: Girardi Adriana C. C. , Knauf Felix , Demuth Hans-Ulrich , Aronson Peter S.
Published: June 2004

We recently reported that NHE3 exists in multimeric complexes with dipeptidyl peptidase IV (DPPIV) in renal brush-border membranes. To examine the possible role of DPPIV in modulating NHE3 activity, we evaluated whether specific competitive inhibitors that bind to the active site of DPPIV affect NHE3 activity in the OKP line of opossum kidney proximal tubule cells. The DPPIV inhibitors diprotin A and P32/98 significantly reduced NHE3 activity, whereas the inactive isomer P34/98 had no effect. DPPIV inhibitors did not reduce the activity of another brush-border transport process, Na-phosphate cotransport. Effects of DPPIV inhibitors on NHE3 activity were not associated with detectable changes in amount or apparent molecular weight of NHE3 or in NHE3 surface expression. To investigate the signaling mechanisms involved in modulation of NHE3 activity by DPPIV, we used inhibitors of protein kinase pathways known to regulate NHE3. Whereas the PKA inhibitor H-89 failed to block the effect of DPPIV inhibitors, the tyrosine kinase inhibitor genistein alone caused a decrement in NHE3 activity very similar in magnitude to that caused by P32/98. We also found that the effects of genistein and P32/98 on NHE3 activity were not additive. In contrast, forskolin/IBMX and P32/98 had additive inhibitory effects on NHE3 activity. These findings suggested that the effect of DPPIV inhibitors to reduce NHE3 activity results from inhibition of a tyrosine kinase signaling pathway rather than by activation of PKA. We conclude that DPPIV plays an unexpected role in modulating Na+/H+ exchange mediated by NHE3 in proximal tubule cells.
SPI-0211 activates T84 cell chloride transport and recombinant human ClC-2 chloride currents
Authors: Cuppoletti John , Malinowska Danuta H. , Tewari Kirti P. , Li Qiu-ju , Sherry Ann M. , Patchen Myra L. , Ueno Ryuji
Published: June 2004

The purpose of this study was to determine the mechanism of action of SPI-0211 (lubiprostone), a novel bicyclic fatty acid in development for the treatment of bowel dysfunction. Adult rabbit intestine was shown to contain mRNA for ClC-2 using RT-PCR, Northern blot analysis, and in situ hybridization. T84 cells grown to confluence on permeable supports were shown to express ClC-2 channel protein in the apical membrane. SPI-0211 increased electrogenic Cl− transport across the apical membrane of T84 cells, with an EC50 of ∼18 nM measured by short-circuit current ( Isc) after permeabilization of the basolateral membrane with nystatin. SPI-0211 effects on Cl− currents were also measured by whole cell patch clamp using the human embryonic kidney (HEK)-293 cell line stably transfected with either recombinant human ClC-2 or recombinant human cystic fibrosis transmembrane regulator (CFTR). In these studies, SPI-0211 activated ClC-2 Cl− currents in a concentration-dependent manner, with an EC50 of ∼17 nM, and had no effect in nontransfected HEK-293 cells. In contrast, SPI-0211 had no effect on CFTR Cl− channel currents measured in CFTR-transfected HEK-293 cells. Activation of ClC-2 by SPI-0211 was independent of PKA. Together, these studies demonstrate that SPI-0211 is a potent activator of ClC-2 Cl− channels and suggest a physiologically relevant role for ClC-2 Cl− channels in intestinal Cl− transport after SPI-0211 administration.
Downward resetting of the osmotic threshold for thirst in patients with SIADH
Authors: Smith D. , Moore K. , Tormey W. , Baylis P. H. , Thompson C. J.
Published: June 2004

The syndrome of inappropriate antidiuretic hormone (SIADH) is characterized by euvolemic hyponatremia. Patients with SIADH continue to drink normal amounts of fluid, despite plasma osmolalities well below the physiological osmotic threshold for onset of thirst. The regulation of thirst has not been previously studied in SIADH. We studied the characteristics of osmotically stimulated thirst and arginine vasopressin (AVP) secretion in eight subjects with SIADH and eight healthy controls and the nonosmotic suppression of thirst and AVP during drinking in the same subjects. Subjects underwent a 2-h infusion of hypertonic (855 mmol/l) NaCl solution, followed by 30 min of free access to water. Thirst rose significantly in both SIADH (1.5 ± 0.6 to 8.0 ± 1.2 cm, P < 0.0001) and controls (1.8 ± 0.8 to 8.4 ± 1.5 cm, P < 0.0001), but the osmotic threshold for thirst was lower in SIADH (264 ± 5.5 vs. 285.9 ± 2.8 mosmol/kgH2O, P < 0.0001). SIADH subjects drank volumes of water similar to controls after cessation of the infusion (948.8 ± 207.6 vs. 1,091 ± 184 ml, P = 0.23). The act of drinking suppressed thirst in both SIADH and controls but did not suppress plasma AVP concentrations in SIADH compared with controls ( P = 0.007). We conclude that there is downward resetting of the osmotic threshold for thirst in SIADH but that thirst responds to osmotic stimulation and is suppressed by drinking around the lowered set point. In addition, we demonstrated that drinking does not completely suppress plasma AVP in SIADH.
Effect of lowering postprandial hyperglycemia on insulin secretion in older people with impaired glucose tolerance
Authors: Chang Annette M. , Smith Marla J. , Bloem Cathie J. , Galecki Andrzej T. , Halter Jeffrey B.
Published: June 2004

Glucose tolerance declines with age, resulting in a high prevalence of diabetes and impaired glucose tolerance (IGT) in the older population. Hyperglycemia per se can lead to impaired β-cell function (glucose toxicity). We tested the role of glucose toxicity in age-related β-cell dysfunction in older people (65 ± 8 yr) with IGT treated with the α-glucosidase inhibitor acarbose ( n = 14) or placebo ( n = 13) for 6 wk in a randomized, double-blind study. Baseline and posttreatment studies included 1) an oral glucose tolerance test (OGTT), 2) 1-h postprandial glucose monitoring, 3) a frequently sampled intravenous glucose tolerance test (insulin sensitivity, or SI), and 4) glucose ramp clamp (insulin secretion rates, or ISR), in which a variable glucose infusion increases plasma glucose from 5 to 10 mM. The treatment groups had similar baseline body mass index; fasting, 2-h OGTT, and 1-h postprandial glucose levels; and SI. In these carefully matched older people with IGT, both fasting (5.7 ± 0.2 vs. 6.3 ± 0.2 mM, P = 0.002) and 1-h postprandial glucose levels (6.9 ± 0.3 vs. 8.2 ± 0.4 mM, P = 0.02) were significantly lower in the acarbose than in the placebo group. Despite this reduction of chronic hyperglycemia in the acarbose vs. placebo group, measures of insulin secretion (ISR area under the curve: 728 ± 55 vs. 835 ± 81 pmol/kg, P = 0.9) and acute insulin response to intravenous glucose (329 ± 67 vs. 301 ± 54 pM, P = 0.4) remained unchanged and impaired. Thus short-term improvement of chronic hyperglycemia does not reverse β-cell dysfunction in older people with IGT.
Chronic ANG II infusion increases plasma triglyceride level by stimulating hepatic triglyceride production in rats
Authors: Ran Jianmin , Hirano Tsutomu , Adachi Mitsuru
Published: June 2004

We recently observed that ANG II receptor blocker therapy improved the overproduction of triglyceride (TG) in fructose-fed rats and Zucker fatty rats with insulin resistance, which in turn suggests that ANG II may stimulate TG production. Accordingly, we investigated the effects of ANG II on TG production and the association with insulin resistance in normal rats. Male Wistar rats were continuously infused with ANG II (100 ng·min−1·kg body wt−1) via an osmotic minipump for 14 days. ANG II infusion markedly elevated both the systolic and diastolic blood pressure. The plasma TG level increased twofold, but cholesterol was unchanged. ANG II infusion stimulated the TG secretion rate (TGSR) by twofold and increased the hepatic TG content by 31%. Lipogenesis determined by [2-3H]glycerol incorporation into hepatic TG was also significantly increased in ANG II-infused rats. The stimulatory effect of ANG II on TGSR was dose dependent and was not observed until 2 wk after the start of infusion. ANG II infusion significantly reduced insulin sensitivity index (SI) without affecting glucose effectiveness determined by Bergman's minimal model. The plasma TG level was positively correlated with TGSR ( r = 0.88, P < 0.001) and inversely with SI ( r = −0.80, P < 0.005). These results suggest that chronic ANG II infusion stimulates hepatic TG production, which is partly associated with simultaneous development of insulin resistance. Our results may suggest a new mechanism for the intimate association between hypertension and dyslipidemia.
Two modes for concentrating urine in rat inner medulla
Authors: Layton Anita T. , Pannabecker Thomas L. , Dantzler William H. , Layton Harold E.
Published: June 2004

We used a mathematical model of the urine concentrating mechanism of rat inner medulla (IM) to investigate the implications of experimental studies in which immunohistochemical methods were combined with three-dimensional computerized reconstruction of renal tubules. The mathematical model represents a distribution of loops of Henle with loop bends at all levels of the IM, and the vasculature is represented by means of the central core assumption. Based on immunohistochemical evidence, descending limb portions that reach into the papilla are assumed to be only moderately water permeable or to be water impermeable, and only prebend segments and ascending thin limbs are assumed to be NaCl permeable. Model studies indicate that this configuration favors the targeted delivery of NaCl to loop bends, where a favorable gradient, sustained by urea absorption from collecting ducts, promotes NaCl absorption. We identified two model modes that produce a significant axial osmolality gradient. One mode, suggested by preliminary immunohistochemical findings, assumes that aquaporin-1-null portions of loops of Henle that reach into the papilla have very low urea permeability. The other mode, suggested by perfused tubule experiments from the literature, assumes that these same portions of loops of Henle have very high urea permeabilities. Model studies were conducted to determine the sensitivity of these modes to parameter choices. Model results are compared with extant tissue-slice and micropuncture studies.
TP receptors regulate renal hemodynamics during angiotensin II slow pressor response
Authors: Kawada Noritaka , Dennehy Kathryn , Solis Glenn , Modlinger Paul , Hamel Rebecca , Kawada Julie T. , Aslam Shakil , Moriyama Toshiki , Imai Enyu , Welch William J. , Wilcox Christopher S.
Published: June 2004

We investigated the hypothesis that thromboxane A2(TxA2)-prostaglandin H2receptors (TP-Rs) mediate the hemodynamic responses and increase in reactive oxygen species (ROS) to ANG II (400 ng·kg−1·min−1sc for 14 days) using TP-R knockout (TP −/−) and wild-type (+/+) mice. TP −/− had normal basal mean arterial blood pressure (MAP) and glomerular filtration rate but reduced renal blood flow and increased filtration fraction (FF) and renal vascular resistance (RVR) and markers of ROS (thiobarbituric acid-reactive substances and 8-isoprostane PGF2α) and nitric oxide (NOx). Infusion of ANG II into TP +/+ increased ROS and thromboxane B2(TxB2) and increased RVR and FF. ANG II infusion into TP −/− mice reduced ANG I and increased aldosterone but caused a blunted increase in MAP (TP −/−: +6 ± 2 vs. TP +/+: +15 ± 3 mmHg) and failed to increase FF, ROS, or TxB2but increased NOx and paradoxically decreased RVR (−2.1 ± 1.7 vs. +2.6 ± 0.8 mmHg·ml−1·min−1·g−1). Blockade of AT1receptor of TP −/− mice infused with ANG II reduced MAP (−8 mmHg) and aldosterone but did not change the RVR or ROS. In conclusion, during an ANG II slow pressor response, AT1receptors activate TP-Rs that generate ROS and prostaglandins but inhibit NO. TP-Rs mediate all of the increase in RVR and FF, part of the increase in MAP, but are not implicated in the suppression of ANG I or increase in aldosterone. TP −/− mice have a basal increase in RVR and FF associated with ROS.
Resurgent Na Currents in Four Classes of Neurons of the Cerebellum
Authors: Afshari Fatemeh S. , Ptak Krzysztof , Khaliq Zayd M. , Grieco Tina M. , Slater N. Traverse , McCrimmon Donald R. , Raman Indira M.
Published: June 2004

Action potential firing rates are generally limited by the refractory period, which depends on the recovery from inactivation of voltage-gated Na channels. In cerebellar Purkinje neurons, the kinetics of Na channels appear specialized for rapid firing. Upon depolarization, an endogenous open-channel blocker rapidly terminates current flow but prevents binding of the “fast” inactivation gate. Upon repolarization, unbinding of the blocker produces “resurgent” Na current while allowing channels to recover rapidly. Because other cerebellar neurons, including granule cells, unipolar brush cells, and neurons of the cerebellar nuclei, also fire rapidly, we tested whether these cells might also express Na channels with resurgent kinetics. Neurons were acutely isolated from mice and rats, and TTX-sensitive Na currents were recorded under voltage clamp. Unlike Purkinje cells, the other cerebellar neurons produced only tiny resurgent currents in solutions optimized for voltage-clamping Na currents (50 mM Na+; Co2+ substitution for Ca2+). Under more physiological ionic conditions (155 mM Na+; 2 mM Ca2+ with 0.03 mM Cd2+), however, granule cells, unipolar brush cells, and cerebellar nuclear cells all produced robust resurgent currents. The increase in resurgent current, which was greater than predicted by the Goldman-Hodgkin-Katz equation, appeared to result from a combination of knock-off of open-channel blockers by permeating ions as well as relief of divalent block at negative potentials. These results indicate that resurgent current is typical of many cerebellar neurons and suggest that rapid open-channel block and unblock may be a widespread mechanism for restoration of Na channel availability in rapidly firing neurons.
Introduction: The Sociology of Collective Action Reconsidered
Authors: Dubet François , Thaler Henri Lustiger
Published: June 2004

The introductory article argues for a new approach to the sociology of social movements and collective action. It begins with the juxtaposition of reigning theories in the field, criticizing their sectorial nature and overrationalization of actors. In lieu of this, the authors propose an approach that focuses upon social subjectivization and its accompanying matrices of domination. Social movements are therefore more than manifestations of structural conflicts. They participate in the formation of subjects. Central to the views expressed in this article is the subject’s relation to self as a bifurcated process, one that has broken with the reassurances of state and society. This underscores how dominant representations of one’s own deeply human and material resources are constructed, and through which kinds of considerations and experiences actors come to address questions of self.
Oneself as Another: From Social Movement to Experience Movement
Authors: McDonald Kevin
Published: June 2004

Social movements have been largely understood within western civilizational models emphasizing collective identity and a civic conception of action. This article explores two emerging forms of movement, the contemporary anti-globalization movement and the qigong movement that emerged in China over the 1980s. The qigong movement involves forms of embodiment and intensified personhood rather than collective identity. In the anti-globalization movement we encounter a break with representation, grammars of presence/absence rather than ‘we-ness’, and embodied communication. These movements underline singularity and experiences of oneself as another, suggesting a shift from ‘social movement’ to ‘experience movement’.
Social Movements in the Renegotiation of the Bases for Citizenship in West Africa
Authors: Sall Ebrima
Published: June 2004

This article analyses youth movements in the renegotiation of national belonging and citizenship rights in conflict and post-conflict situations, particularly in Côte d’Ivoire, and in rural development initiatives in the Gambia. In one case, an urban-based movement of ‘young patriots’, with rural variants, is contesting peace accords signed in Paris and claiming to defend the ‘constitutional legality’ of their country coming out of a civil war said to have been engineered by ‘foreigners’ who include descendants of immigrants from neighbouring countries. In the second case, youth associations aiming at improving living conditions in rural Gambia are initiating numerous projects and literally running their villages. In both cases, the article argues, there is a struggle for effective citizenship rights as the very bases of true citizenship are being renegotiated, and a quest for meaningful lives among a largely marginalized youth.
The Rift in the Subject: A Late Global Modernist Dilemma
Authors: Thaler Henri Lustiger
Published: June 2004

The article looks at what the author describes as the ‘rift in the subject’. It explains a phenomenon stationed between tradition and modernity, as experienced by young Muslims living in the USA. This experiential standpoint explains their capacities as social actors to engage in forms of collective action that have taken on conflicting global dimensions. The author argues that the experience of living between several geographies of selfhood, (1) defies causal models of cultural continuity and rupture; (2) conflates eastern and western modernities; (3) poses challenges to the western notion of recognition as the most appropriate model for explaining lives claiming radically different forms of cultural difference. In this regard, the young Muslim subject, rather than being a cultural exception, as implied in the ‘clash of civilization thesis’, is a harbinger of how profoundly engrained the problem of difference has become within the western paradigm itself.
Local Actors in Global Politics
Authors: Sassen Saskia
Published: June 2004

Globalization and the new information and communication technologies (ICTs) have enabled a variety of local political actors to enter international arenas once exclusive to national states. Multiple types of claim-making and oppositional politics articulate these developments. Going global has been partly facilitated and conditioned by the infrastructure of the global economy, even as the latter is often the object of those oppositional politics. The article examines these issues through a focus on various political practices and the technologies used, the latter an important part of the analysis partly because they remain understudied and misunderstood in the social sciences. Of particular interest is the possibility that local, often resource-poor organizations and individuals can become part of global networks and struggles. Further, the possibility of global imaginaries has enabled even those who are geographically immobile to become part of global politics. A key question organizing this article concerns the ways in which such localized actors and struggles can be constitutive of new types of global politics and subjectivities. The argument is that local, including geographically immobile and resource-poor, actors can contribute to the formation of global domains or virtual public spheres and thereby to a type of local political subjectivity that needs to be distinguished from what we would usually consider local.
Actors, Conflicts and the Globalization Movement
Authors: Farro Antimo L.
Published: June 2004

Salient features of the globalization movement include: the defence of the subjective specificity of individuals and groups by a plurality of actors; fluid organizational and communication structures; opposition to economic and social domination; resistance to cultural homogenization; construction of social alternative networks; links between local and transnational initiatives that seek alternative modes of development on a global scale; the search for a new democracy. These features imply a specific construction of the movement and, in addition, different significances of its impact on social life. The affirmation of individual and group subjectivities in the construction of the movement implies a new definition of action as no longer collective. The impact of this action on social life resides in: the need to build new institutional mechanisms adequate to regulate global economic fluxes; cultural alternatives expressed through the affirmation of subjective specificity; and the cleavage between the movement’s social networks and ruling actors.
Performance of HS-HR Flexible Foams in Small Open-flame Combustibility Tests
Authors: Hagery Stanley , Skorpenske Richard , Blaszkiewicz Michael , Masciantonio Michael
Published: June 2004

The development of small open-flame tests for measuring or predicting the combustibility characteristics of flexible polyurethane foams continues to be a subject of broad interest and active research. Notable recent activities in the residential furniture area include: (1) efforts by the California Bureau of Home Furnishings and Thermal Insulation to improve CAL TB 117; (2) work towards a national standard by the Consumer Products Safety Commission; and (3) the development and/or evaluation of test methods by the API, PFA, ASTM, and AFMA.

In this paper, we report the results of a systematic study in which several high support, high resilience (HS-HR) flexible polyurethane foams were tested by various small-scale open-flame combustibility tests. These tests include the current CAL TB 117 A Part 1, the February, 2002 draft proposal of the new CAL 117 (Section 3 Options A and B, and Section 5 using a fabric compliant with the current CAL TB 117 E), and a cone calorimeter test. The HS-HR foam variables included level of flame retardant, density, SAN versus PHD solids type and the level of solids. Various performance criteria in the test methods were modeled against each other and against the foam variables. These results highlight the difficulties in correlating performance between different small open-flame tests and provide insights into the factors contributing to passage or failure in these tests. New technology for improving the combustibility performance of HS-HR foams in these tests will be discussed.