bluuebunny/crossref_metadata_2025 huggingface dataset:
T Cell-Independent Rescue of B Lymphocytes from Peripheral Immune Tolerance
Authors: Kouskoff Valerie , Lacaud Georges , Nemazee David
Published: July 2002

Autoimmunity arises when immune tolerance to specific self-antigens is broken. The mechanisms leading to such a failure remain poorly understood. One hypothesis proposes that infectious agents or antigens can break B or T lymphocyte self-tolerance by expressing epitopes that mimic self. Using a transgenic immunoglobulin model, we show that challenge with self-mimicking foreign antigen rescues B cells from peripheral tolerance independent of T cell help, resulting in the accumulation of self-reactive cells in the lymph nodes and secretion of immunoglobulins that bind to a liver-expressed self-antigen. Therefore, our studies reveal a potentially important mechanism by which B lymphocytes can escape self-tolerance.
Homologs of Small Nucleolar RNAs in Archaea
Authors: Omer Arina D. , Lowe Todd M. , Russell Anthony G. , Ebhardt Holger , Eddy Sean R. , Dennis Patrick P.
Published: July 2002

In eukaryotes, dozens of posttranscriptional modifications are directed to specific nucleotides in ribosomal RNAs (rRNAs) by small nucleolar RNAs (snoRNAs). We identified homologs of snoRNA genes in both branches of the Archaea. Eighteen small sno-like RNAs (sRNAs) were cloned from the archaeon
Sulfolobus acidocaldarius
by coimmunoprecipitation with archaeal fibrillarin and NOP56, the homologs of eukaryotic snoRNA-associated proteins. We trained a probabilistic model on these sRNAs to search for more sRNAs in archaeal genomic sequences. Over 200 additional sRNAs were identified in seven archaeal genomes representing both the Crenarchaeota and the Euryarchaeota. snoRNA-based rRNA processing was therefore probably present in the last common ancestor of Archaea and Eukarya, predating the evolution of a morphologically distinct nucleolus.
Chromatin-Independent Nuclear Envelope Assembly Induced by Ran GTPase in
Xenopus
Egg Extracts
Authors: Zhang Chuanmao , Clarke Paul R.
Published: July 2002

The nuclear envelope (NE) forms a controlled boundary between the cytoplasm and the nucleus of eukaryotic cells. To facilitate investigation of mechanisms controlling NE assembly, we developed a cell-free system made from
Xenopus laevis
eggs to study the process in the absence of chromatin. NEs incorporating nuclear pores were assembled around beads coated with the guanosine triphosphatase Ran, forming pseudo-nuclei that actively imported nuclear proteins. NE assembly required the cycling of guanine nucleotides on Ran and was promoted by RCC1, a nucleotide exchange factor recruited to beads by Ran–guanosine diphosphate (Ran-GDP). Thus, concentration of Ran-GDP followed by generation of Ran-GTP is sufficient to induce NE assembly.
Discovery of a Basaltic Asteroid in the Outer Main Belt
Authors: Lazzaro D. , Michtchenko T. , Carvano J. M. , Binzel R. P. , Bus S. J. , Burbine T. H. , Mothé-Diniz T. , Florczak M. , Angeli C. A. , Harris Alan W.
Published: July 2002

Visible and near-infrared spectroscopic observations of the asteroid 1459 Magnya indicate that it has a basaltic surface. Magnya is at 3.15 astronomical units (AU) from the sun and has no known dynamical link to any family, to any nearby large asteroid, or to asteroid 4 Vesta at 2.36 AU, which is the only other known large basaltic asteroid. We show that the region of the belt around Magnya is densely filled by mean-motion resonances, generating slow orbital diffusion processes and providing a potential mechanism for removing other basaltic fragments that may have been created on the same parent body as Magnya. Magnya may represent a rare surviving fragment from a larger, differentiated planetesimal that was disrupted long ago.
Fas Preassociation Required for Apoptosis Signaling and Dominant Inhibition by Pathogenic Mutations
Authors: Siegel Richard M. , Frederiksen John K. , Zacharias David A. , Chan Francis Ka-Ming , Johnson Michele , Lynch David , Tsien Roger Y. , Lenardo Michael J.
Published: July 2002

Heterozygous mutations encoding abnormal forms of the death receptor Fas dominantly interfere with Fas-induced lymphocyte apoptosis in human autoimmune lymphoproliferative syndrome. This effect, rather than depending on ligand-induced receptor oligomerization, was found to stem from ligand- independent interaction of wild-type and mutant Fas receptors through a specific region in the extracellular domain. Preassociated Fas complexes were found in living cells by means of fluorescence resonance energy transfer between variants of green fluorescent protein. These results show that formation of preassociated receptor complexes is necessary for Fas signaling and dominant interference in human disease.
Extension of Life-Span with Superoxide Dismutase/Catalase Mimetics
Authors: Melov Simon , Ravenscroft Joanne , Malik Sarwatt , Gill Matt S. , Walker David W. , Clayton Peter E. , Wallace Douglas C. , Malfroy Bernard , Doctrow Susan R. , Lithgow Gordon J.
Published: July 2002

We tested the theory that reactive oxygen species cause aging. We augmented the natural antioxidant systems of
Caenorhabditis elegans
with small synthetic superoxide dismutase/catalase mimetics. Treatment of wild-type worms increased their mean life-span by a mean of 44 percent, and treatment of prematurely aging worms resulted in normalization of their life-span (a 67 percent increase). It appears that oxidative stress is a major determinant of life-span and that it can be counteracted by pharmacological intervention.
Responses of Vomeronasal Neurons to Natural Stimuli
Authors: Holy Timothy E. , Dulac Catherine , Meister Markus
Published: July 2002

The vomeronasal organ (VNO) of mammals plays an essential role in the detection of pheromones. We obtained simultaneous recordings of action potentials from large subsets of VNO neurons. These cells responded to components of urine by increasing their firing rate. This chemosensory activation required phospholipase C function. Unlike most other sensory neurons, VNO neurons did not adapt under prolonged stimulus exposure. The full time course of the VNO spiking response is captured by a simple quantitative model of ligand binding. Many individual VNO neurons were strongly selective for either male or female mouse urine, with the effective concentrations differing as much as a thousandfold. These results establish a framework for understanding sensory coding in the vomeronasal system.
Anti-inflammatory Activity of IVIG Mediated Through the Inhibitory Fc Receptor
Authors: Samuelsson Astrid , Towers Terri L. , Ravetch Jeffrey V.
Published: July 2002

The molecular basis for the anti-inflammatory property of intravenous gamma globulin (IVIG) was investigated in a murine model of immune thrombocytopenia. Administration of clinically protective doses of intact antibody or monomeric Fc fragments to wild-type or Fcγ receptor–humanized mice prevented platelet consumption triggered by a pathogenic autoantibody. The inhibitory Fc receptor, FcγRIIB, was required for protection, because disruption either by genetic deletion or with a blocking monoclonal antibody reversed the therapeutic effect of IVIG. Protection was associated with the ability of IVIG administration to induce surface expression of FcγRIIB on splenic macrophages. Modulation of inhibitory signaling is thus a potent therapeutic strategy for attenuating autoantibody-triggered inflammatory diseases.
Observation of All-Metal Aromatic Molecules
Authors: Li Xi , Kuznetsov Aleksey E. , Zhang Hai-Feng , Boldyrev Alexander I. , Wang Lai-Sheng
Published: July 2002

Aromaticity is a concept invented to account for the unusual stability of an important class of organic molecules: the aromatic compounds. Here we report experimental and theoretical evidence of aromaticity in all-metal systems. A series of bimetallic clusters with chemical composition MAl
4
–
(M = Li, Na, or Cu), was created and studied with photoelectron spectroscopy and ab initio calculations. All the MAl
4
–
species possess a pyramidal structure containing an M
+
cation interacting with a square Al
4
2–
unit. Ab initio studies indicate that Al
4
2–
exhibits characteristics of aromaticity with two delocalized π electrons (thus following the 4
n
+ 2 electron counting rule) and a square planar structure and maintains its structural and electronic features in all the MAl
4
–
complexes. These findings expand the aromaticity concept into the arena of all-metal species.
Electrochromic Nanocrystal Quantum Dots
Authors: Wang Congjun , Shim Moonsub , Guyot-Sionnest Philippe
Published: July 2002

Incorporating nanocrystals into future electronic or optoelectronic devices will require a means of controlling charge-injection processes and an understanding of how the injected charges affect the properties of nanocrystals. We show that the optical properties of colloidal semiconductor nanocrystal quantum dots can be tuned by an electrochemical potential. The injection of electrons into the quantum-confined states of the nanocrystal leads to an electrochromic response, including a strong, size-tunable, midinfrared absorption corresponding to an intraband transition, a bleach of the visible interband exciton transitions, and a quench of the narrow band-edge photoluminescence.
Conservation Conflicts Across Africa
Authors: Balmford Andrew , Moore Joslin L. , Brooks Thomas , Burgess Neil , Hansen Louis A. , Williams Paul , Rahbek Carsten
Published: July 2002

There is increasing evidence that areas of outstanding conservation importance may coincide with dense human settlement or impact. We tested the generality of these findings using 1°-resolution data for sub-Saharan Africa. We find that human population density is positively correlated with species richness of birds, mammals, snakes, and amphibians. This association holds for widespread, narrowly endemic, and threatened species and looks set to persist in the face of foreseeable population growth. Our results contradict earlier expectations of low conflict based on the idea that species richness decreases and human impact increases with primary productivity. We find that across Africa, both variables instead exhibit unimodal relationships with productivity. Modifying priority-setting to take account of human density shows that, at this scale, conflicts between conservation and development are not easily avoided, because many densely inhabited grid cells contain species found nowhere else.
Quantum Electronic Stability of Atomically Uniform Films
Authors: Luh D.-A. , Miller T. , Paggel J. J. , Chou M. Y. , Chiang T.-C.
Published: July 2002

We have studied the structural stability of thin silver films with thicknesses of
N
= 1 to 15 monolayers, deposited on an Fe(100) substrate. Photoemission spectroscopy results show that films of
N
= 1, 2, and 5 monolayer thicknesses are structurally stable for temperatures above 800 kelvin, whereas films of other thicknesses are unstable and bifurcate into a film with
N
± 1 monolayer thicknesses at temperatures around 400 kelvin. The results are in agreement with theoretical predictions that consider the electronic energy of the quantum well associated with a particular film thickness as a significant contribution to the film stability.
Stages of Polymyxin B Interaction with the
Escherichia coli
Cell Envelope
Authors: Daugelavičius Rimantas , Bakiene˙ Elena , Bamford Dennis H.
Published: July 2002

The effects of polymyxin B (PMB) on the
Escherichia coli
outer (OM) and cytoplasmic membrane (CM) permeabilities were studied by monitoring the fluxes of tetraphenylphosphonium, phenyldicarbaundecaborane, and K
+
and H
+
ions. At concentrations between 2 and 20 μg/ml, PMB increased the OM permeability to lipophilic compounds and induced a leakage of K
+
from the cytosol and an accumulation of lipophilic anions in the cellular membranes but did not cause the depolarization of the CM. At higher concentrations, PMB depolarized the CM, forming ion-permeable pores in the cell envelope. The permeability characteristics of PMB-induced pores mimic those of bacteriophage- and/or bacteriocin-induced channels. However, the bactericidal effect of PMB took place at concentrations below 20 μg/ml, indicating that this effect is not caused by pore formation. Under conditions of increased ionic strength, PMB made the OM permeable to lipophilic compounds and decreased the K
+
gradient but was not able to depolarize the cells. The OM-permeabilizing effect of PMB can be diminished by increasing the concentration of Mg
2+
. The major new findings of this work are as follows: (i) the OM-permeabilizing action of PMB was dissected from its depolarizing effect on the CM, (ii) the PMB-induced ion-permeable pores in bacterial envelope were registered, and (iii) the pore formation and depolarization of the CM are not obligatory for the bactericidal action of PMB and dissipation of the K
+
gradient on the CM.
Linezolid Therapy of
Staphylococcus aureus
Experimental Osteomyelitis
Authors: Patel Robin , Piper Kerryl E. , Rouse Mark S. , Steckelberg James M.
Published: July 2002

The in vivo activity of linezolid or cefazolin against a clinical isolate of methicillin-susceptible
Staphylococcus aureus
(linezolid MIC, 2 μg/ml) was studied in a rat model of experimental osteomyelitis. Sixty rats with experimental
S. aureus
osteomyelitis were treated for 21 days with no antimicrobial, with 25 μg of linezolid per kg of body weight administered intraperitoneally twice or three times a day, or with 50 μg of cefazolin per kg administered intramuscularly three times a day. After treatment, the animals were sacrificed and the infected tibiae were processed for quantitative bacterial cultures. The results of treatment were expressed as log
10
CFU/gram of bone and analyzed by rank sum analysis. The results of linezolid treatment were not significantly different from those of untreated controls, while cefazolin treatment was significantly more active than no treatment or linezolid treatment.
Comparative Antimicrobial Activities of the Newly Synthesized Quinolone WQ-3034, Levofloxacin, Sparfloxacin, and Ciprofloxacin against
Mycobacterium tuberculosis
and
Mycobacterium avium
Complex
Authors: Tomioka Haruaki , Sato Katsumasa , Kajitani Hiroko , Akaki Tatsuya , Shishido Shinji
Published: July 2002

WQ-3034 is a newly synthesized acidic fluoroquinolone. We assessed its in vitro activity against
Mycobacterium tuberculosis
and
M. avium
complex using levofloxacin (LVFX), ciprofloxacin (CPFX), sparfloxacin (SPFX), and KRM-1648 (KRM) as reference drugs. The MICs of these agents were determined by the agar dilution method with 7H11 medium. The MICs at which 50 and 90% of the test strains were inhibited (MIC
50
s, and MIC
90
s, respectively) for the test quinolones for rifampin (RMP)-susceptible
M. tuberculosis
strains were in the order SPFX < LVFX ≦ WQ-3034 ≦ CPFX, while those for RMP-resistant
M. tuberculosis
strains were in the order SPFX ≦ WQ-3034 ≦ LVFX < CPFX. The MICs of KRM for RMP-susceptible
M. tuberculosis
were much lower than those of the test quinolones, while the MIC
90
of KRM for RMP-resistant
M. tuberculosis
strains was higher than those of the quinolones. The MIC
50
s and MIC
90
s of the test drugs for
M. avium
were in the order KRM < SPFX < CPFX ≦ WQ-3034 ≦ LVFX, while those for
M. intracellulare
were in the order KRM < SPFX < WQ-3034 ≒ LVFX ≦ CPFX. Next, we compared the antimicrobial activities of the test drugs against
M. tuberculosis
organisms residing in cells of the Mono Mac 6 macrophage (Mφ)-like cell line (MM6-Mφs) and of the A-549 type II alveolar cell line (A-549 cells). When drugs were added at the concentration that achieves the maximum concentration in blood, progressive killing or inhibition of the
M. tuberculosis
organisms residing in MM6-Mφs and A-549 cells was observed in the order KRM > SPFX ≧ LVFX > WQ-3034 > CPFX. The efficacies of all quinolones against intracellular
M. tuberculosis
organisms were significantly lower in A-549 cells than in MM6-Mφs. WQ-3034 at the MIC caused more marked growth inhibition of intramacrophage
M. tuberculosis
than did LVFX. These findings indicate that the in vitro anti-
M. tuberculosis
activity of WQ-3034 is greater than that of CPFX and is comparable to that of LVFX.
Efficacy of SCH56592 in a Rabbit Model of Invasive Aspergillosis
Authors: Kirkpatrick William R. , McAtee Robert K. , Fothergill Annette W. , Loebenberg David , Rinaldi Michael G. , Patterson Thomas F.
Published: July 2002

SCH56592 (SCH) was evaluated in an immunosuppressed rabbit model of invasive aspergillosis. SCH was more effective than similar doses of itraconazole and as effective as amphotericin B in the clearance of
Aspergillus
spp. from tissues. Compared with controls, SCH regimens reduced mortality, improved survival, and significantly reduced tissue colony counts.
Biochemical-Genetic Characterization and Regulation of Expression of an ACC-1-Like Chromosome-Borne Cephalosporinase from
Hafnia alvei
Authors: Girlich Delphine , Naas Thierry , Bellais Samuel , Poirel Laurent , Karim Amal , Nordmann Patrice
Published: July 2002

A naturally occurring AmpC β-lactamase (cephalosporinase) gene was cloned from the
Hafnia alvei
1 clinical isolate and expressed in
Escherichia coli
. The deduced AmpC β-lactamase (ACC-2) had a pI of 8 and a relative molecular mass of 37 kDa and showed 50 and 47% amino acid identity with the chromosome-encoded AmpCs from
Serratia marcescens
and
Providentia stuartii
, respectively. It had 94% amino acid identity with the recently described plasmid-borne cephalosporinase ACC-1 from
Klebsiella pneumoniae
, suggesting the chromosomal origin of ACC-1. The hydrolysis constants (
k
cat
and

K
m

) showed that ACC-2 was a peculiar cephalosporinase, since it significantly hydrolyzed cefpirome. Once its gene was cloned and expressed in
E. coli
(pDEL-1), ACC-2 conferred resistance to ceftazidime and cefotaxime but also an uncommon reduced susceptibility to cefpirome. A divergently transcribed
ampR
gene with an overlapping promoter compared with
ampC
(
bla
ACC-2
) was identified in
H. alvei
1, encoding an AmpR protein that shared 64% amino acid identity with the closest AmpR protein from
P. stuartii
. β-Lactamase induction experiments showed that the
ampC
gene was repressed in the absence of
ampR
and was activated when cefoxitin or imipenem was added as an inducer. From
H. alvei
1 cultures that expressed an inducible-cephalosporinase phenotype, several ceftazidime- and cefpirome-cross-resistant
H. alvei
1 mutants were obtained upon selection on cefpirome- or ceftazidime-containing plates, and
H. alvei
1 DER, a ceftazidime-resistant mutant, stably overproduced cephalosporinase. Transformation of
H. alvei
1 DER or
E. coli
JRG582 (
ampDE
mutant) harboring
ampC
and
ampR
from
H. alvei
1 with a recombinant plasmid containing
ampD
from
E. coli
resulted in a decrease in the MIC of β-lactam and recovery of an inducible phenotype for
H. alvei
1 DER. Thus, AmpR and AmpD proteins may regulate biosynthesis of the
H. alvei
cephalosporinase similarly to other enterobacterial cephalosporinases.
Transcriptional Analyses of Antifungal Drug Resistance in
Candida albicans
Authors: Lyons Chris N. , White Theodore C.
Published: July 2002

Oral infections with the pathogenic yeast
Candida albicans
are one of the most frequent and earliest opportunistic infections in human immunodeficiency virus-infected patients. The widespread use of azole antifungal drugs has led to the development of drug-resistant isolates. Several molecular mechanisms that contribute to drug resistance have been identified, including increased mRNA levels for two types of efflux pump genes: the ATP binding cassette transporter CDRs (
CDR1
and
CDR2
) and the major facilitator
MDR1
. Using Northern blot analyses, the expression patterns of these genes have been determined during logarithmic and stationary phases of cell growth and during growth in different carbon sources in a set of matched susceptible and fluconazole-resistant isolates that have been characterized previously.
MDR1
,
CDR1
, and
CDR2
are expressed early during logarithmic growth,
CDR4
is expressed late during logarithmic growth, and
CDR1
is preferentially expressed in stationary-phase cells. There is a small decrease in expression of these genes when the cells are grown in carbon sources other than glucose. While increased mRNA levels of efflux pump genes are commonly associated with azole resistance, the causes of increased mRNA levels have not yet been resolved. Southern blot analysis demonstrates that the increased mRNA levels in these isolates are not the result of gene amplification. Nuclear run-on assays show that
MDR1
and
CDR
mRNAs are transcriptionally overexpressed in the resistant isolate, suggesting that the antifungal drug resistance in this series is associated with the promoter and
trans
-acting factors of the
CDR1
,
CDR2
, and
MDR1
genes.
Molecular Characterization of the Plasma Membrane H+-ATPase, an Antifungal Target inCryptococcus neoformans
Authors: Soteropoulos Patricia , Vaz Tanya , Santangelo Rosaria , Paderu Padmaja , Huang David Y. , Tamás Markus J. , Perlin David S.
Published: July 2002

TheCryptococcus neoformans PMA1gene, encoding a plasma membrane H+-ATPase, was isolated from a genomic DNA library of serotype A strain ATCC 6352. An open reading frame of 3,380 nucleotides contains six introns and encodes a predicted protein consisting of 998 amino acids with a molecular mass of approximately 108 kDa. Plasma membranes were isolated, and the H+-ATPase was shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be slightly larger than theS. cerevisiaeH+-ATPase, consistent with its predicted molecular mass. The plasma membrane-bound enzyme exhibited a pH 6.5 optimum for ATP hydrolysis,KmandVmaxvalues of 0.5 mM and 3.1 μmol mg−1min−1, respectively, and an apparentKifor vanadate inhibition of 1.6 μM. ATP hydrolysis in plasma membranes and medium acidification by whole cells were inhibited by ebselen, a nonspecific H+-ATPase antagonist which was also fungicidal. The predictedC. neoformansprotein is 35% identical to proton pumps of both pathogenic and nonpathogenic fungi but exhibits more than 50% identity toPMA1genes from plants. Collectively, this study provides the basis for establishing theCryptococcusH+-ATPase as a viable target for antifungal drug discovery.
Astaxanthin-Rich Algal Meal and Vitamin C Inhibit
Helicobacter pylori
Infection in BALB/cA Mice
Authors: Wang Xin , Willén Roger , Wadström Torkel
Published: July 2002

Helicobacter pylori
infection in humans is associated with chronic type B gastritis, peptic ulcer disease, and gastric carcinoma. A high intake of carotenoids and vitamin C has been proposed to prevent development of gastric malignancies. The aim of this study was to explore if the microalga
Haematococcus pluvialis
rich in the carotenoid astaxanthin and vitamin C can inhibit experimental
H. pylori
infection in a BALB/cA mouse model. Six-week-old BALB/cA mice were infected with the mouse-passaged
H. pylori
strain 119/95. At 2 weeks postinoculation mice were treated orally once daily for 10 days (i) with different doses of algal meal rich in astaxanthin (0.4, 2, and 4 g/kg of body weight, with the astaxanthin content at 10, 50, and 100 mg/kg, respectively), (ii) with a control meal (algal meal without astaxanthin, 4 g/kg), or (iii) with vitamin C (400 mg/kg). Five mice from each group were sacrificed 1 day after the cessation of treatment, and the other five animals were sacrificed 10 days after the cessation of treatment. Culture of
H. pylori
and determination of the inflammation score of the gastric mucosae were used to determine the outcome of the treatment. Mice treated with astaxanthin-rich algal meal or vitamin C showed significantly lower colonization levels and lower inflammation scores than those of untreated or control-meal-treated animals at 1 day and 10 days after the cessation of treatment. Lipid peroxidation was significantly decreased in mice treated with the astaxanthin-rich algal meal and vitamin C compared with that of animals not treated or treated with the control meal. Both astaxanthin-rich algal meal and vitamin C showed an inhibitory effect on
H. pylori
growth in vitro. In conclusion, antioxidants may be a new strategy for treating
H. pylori
infection in humans.
Therapeutic Efficacy of Poly(
dl
-Lactide-Co-Glycolide)-Encapsulated Antitubercular Drugs against
Mycobacterium tuberculosis
Infection Induced in Mice
Authors: Dutt Manisha , Khuller G. K.
Published: July 2002

Poly(
dl
-lactide-co-glycolide) (PLG) microparticles were developed as carriers for isoniazid and rifampin in order to improve compliance of tuberculous chemotherapy. Antitubercular drugs encapsulated in PLG polymers and injected in a single dose subcutaneously resulted in a sustained release (up to 6 weeks) of drugs in various organs of mice. Further,
Mycobacterium tuberculosis
H
37
Rv-infected animals given a single shot of chemotherapy in PLG microparticles exhibited a better or equivalent clearance of CFU in various organs compared to those given a daily administration of free drugs.
Indication of Transposition of a Mobile DNA Element Containing the
vat
(D) and
erm
(B) Genes in
Enterococcus faecium
Authors: Hammerum Anette M. , Flannagan Susan E. , Clewell Don B. , Jensen Lars Bogø
Published: July 2002

The
vat
(D) and
erm
(B) genes encoding streptogramin resistance in
Enterococcus faecium
transferred together, and a direct physical link between
erm
(B) and
vat
(D) was detected. Both the
vat
(D) and
erm
(B) probes hybridized to fragments of different sizes in the donor and transconjugants, which indicated a transposition event.
Action of Deferoxamine against
Pneumocystis carinii
Authors: Clarkson Allen B. , Turkel-Parrella David , Williams Jonathan H. , Chen Lung Chi , Gordon Terry , Merali Salim
Published: July 2002

We found earlier that deferoxamine (DFO), a drug used for treatment of iron overload, is active against a rat model of
Pneumocystis carinii
pneumonia (PCP). We had assumed a mode of action by deprivation of nutritional iron; however, data here show that DFO penetrates
P
.
carinii
, causing irreversible damage, thus indicating a different mode of action. Penetration was demonstrated by showing DFO uptake by high-pressure liquid chromatography analysis. By using calcein-AM as an indicator, exposure to DFO was shown to cause a reduction in
P
.
carinii
cytoplasmic free iron. Exposure to ≥100 μM DFO for ≥8 h in vitro caused growth to cease and cell numbers to decline over several days. This direct and irreversible damage to
P
.
carinii
led to the prediction that infrequent delivery of DFO to the lungs via an aerosol would be an effective treatment in the animal model of PCP. This prediction was confirmed by demonstrating that a once-a-week aerosol treatment of rats was 100% effective both as a prophylactic and as a curative treatment in a rat model of PCP.
Reduction of NO Synthase Expression and Tumor Necrosis Factor Alpha Production in Macrophages by Amphotericin B Lipid Carriers
Authors: Larabi Malika , Legrand Philippe , Appel Martine , Gil Sophie , Lepoivre Michel , Devissaguet Jean-Philippe , Puisieux Francis , Barratt Gillian
Published: July 2002

The present study compared the abilities of different lipid carriers of amphotericin B (AMB) to activate murine peritoneal macrophages, as assessed by their capacities to produce nitric oxide (NO) and tumor necrosis factor alpha (TNF-α). Although AMB alone did not induce NO production, synergy was observed with gamma interferon but not with lipopolysaccharide. This synergy could not be explained by the mobilization of the nuclear activation factor NF-κB by AMB. On the other hand, AMB induced TNF-α production without a costimulator and no synergy was observed. Anti-TNF-α antibodies did not influence NO production, and an inhibitor of NO synthase did not affect TNF-α production, indicating that the production of one of these effector molecules was independent of that of the other. The incorporation of AMB into lipid carriers reduced NO and TNF-α production with all formulations but more so with liposomes than with lipid complexes. NO production was correlated with the induction of NO synthase II, revealed by Western blotting. The extent of association of AMB with macrophages depended on the formulation, especially on the AMB/lipids ratio: the higher the ratio was, the greater the AMB association with macrophages. However, there was no clear correlation between AMB association with macrophages, whether internalized or bound to the membrane, and immunostimulating effects. These results may explain the reduced toxicities of lipid-based formulations of AMB.
Efficacy of Voriconazole in Treatment of Murine Pulmonary Blastomycosis
Authors: Sugar Alan M. , Liu Xiu-Ping
Published: July 2002

We evaluated the efficacy of voriconazole, a new broad-spectrum triazole antifungal compound, in the treatment of murine pulmonary blastomycosis. Since mice metabolize voriconazole rapidly, we took advantage of our previous observation that administration of grapefruit juice to mice resulted in suitable serum voriconazole concentrations so that treatment studies with mice could be done (A. M. Sugar and X.-P. Liu, Med. Mycol. 38:209–121, 2000). Our results show that voriconazole prolonged survival in a dose-dependent fashion and that the fungal burden in the lungs was decreased by voriconazole administered at 40 mg/kg of body weight/day. Voriconazole should be studied in humans with blastomycosis.
IMP-4, a Novel Metallo-β-Lactamase from Nosocomial
Acinetobacter
spp. Collected in Hong Kong between 1994 and 1998
Authors: Chu Yiu-Wai , Afzal-Shah Mariya , Houang Elizabeth T. S. , Palepou Marie-France I. , Lyon Donald J. , Woodford Neil , Livermore David M.
Published: July 2002

Between 1994 and 1998, 97 imipenem-resistant
Acinetobacter
isolates were identified at the Prince of Wales Hospital, Hong Kong, China. A
bla
IMP
PCR product was obtained from 23 of 35 viable cultures; 12 isolates belonged to genomic DNA group 3, 8 belonged to group 2 (
Acinetobacter baumannii
), 2 belonged to group 13TU, and 1 belonged to group 1. The
bla
IMP
homologues were sequenced from two isolates from genomic DNA group 2 and one isolate each from groups 3 and 13TU. The four sequences included an identical 738-bp open reading frame, predicted to encode a polypeptide of 246 amino acids, with 95.6% homology to IMP-1 and 89.3% homology to IMP-2. The new enzyme, designated IMP-4, was partially purified. It had a pI of 8.0 and was strongly active against imipenem and meropenem, with
V
max
values 53 and 8% of that for penicillin G, respectively. Strong activity was also seen against oxyimino-aminothiazolyl cephalosporins but not against aztreonam. Hydrolytic activity was inhibited by EDTA but not by clavulanate or tazobactam. Carbapenem MICs for most
bla
IMP
-positive isolates were 4 to 32 μg/ml, but one isolate with the intact gene was susceptible, with imipenem and meropenem MICs of 0.25 and 0.5 μg/ml, respectively. The latter isolate did not produce the band with a pI of 8.0, and gene expression was inferred to have been lost. None of the isolates studied in detail contained extrachromosomal DNA, and carbapenem resistance was not transmissible to
Escherichia coli
. Nevertheless, the presence of
bla
IMP-4
in different genomic DNA groups implies horizontal transfer, and sequences resembling a GTTRRRY integrase-dependent recombination motif were identified in the flanking regions of
bla
IMP-4
.
Prevalence and Conditions of Selection of E44D/A and V118I Human Immunodeficiency Virus Type 1 Reverse Transcriptase Mutations in Clinical Practice
Authors: Delaugerre Constance , Mouroux Mireille , Yvon-Groussin Anne , Simon Anne , Angleraud Francis , Huraux Jean-Marie , Agut Henri , Katlama Christine , Calvez Vincent
Published: July 2002

Recently, it has been shown that a new mutational pattern (the E44D/A and/or V118I mutation) confers moderate phenotypic lamivudine resistance in the absence of the M184V mutation. The E44D/A and/or the V118I mutation does not exist in drug-naive patients, and the prevalence increases with the number of treatment regimens and lamivudine experience. The mutations can preexist in nucleoside-experienced but lamivudine-naive patients. They are always associated with zidovudine resistance-associated mutations, even in the absence of M184V. These mutations are more stable than the M184V substitution during antiretroviral treatment interruptions.
Potentiation of Inhibition of Wild-Type and Mutant Human Immunodeficiency Virus Type 1 Reverse Transcriptases by Combinations of Nonnucleoside Inhibitors andd- andl-(β)-Dideoxynucleoside Triphosphate Analogs
Authors: Maga Giovanni , Hübscher Ulrich , Pregnolato Massimo , Ubiali Daniela , Gosselin Gilles , Spadari Silvio
Published: July 2002

Combinations of reverse transcriptase (RT) inhibitors are currently used in anti-human immunodeficiency virus therapy in order to prevent or delay the emergence of resistant virus and to improve the efficacy against viral enzymes carrying resistance mutations. Drug-drug interactions can result in either positive (additive or synergistic inhibition) or adverse (antagonistic interaction, synergistic toxicity) effects. Elucidation of the nature of drug interaction would help to rationalize the choice of antiretroviral agents to be used in combination. In this study, different combinations of nucleoside and nonnucleoside inhibitors, includingd- andl-(β)-deoxy- and -dideoxynucleoside triphosphate analogues, have been tested in in vitro RT assays against either recombinant wild-type RT or RT bearing clinically relevant nonnucleoside inhibitor resistance mutations (L100I, K103N, Y181I), and the nature of the interaction (either synergistic or antagonistic) of these associations was evaluated. The results showed that (i) synergy of a combination was not always equally influenced by the individual agents utilized, (ii) a synergistic combination could improve the sensitivity profile of a drug-resistant mutant enzyme to the single agents utilized, (iii)l-(β)-enantiomers of nucleoside RT inhibitors were synergistic when combined with nonnucleoside RT inhibitors, and (iv) inter- and intracombination comparisons of the relative potencies of each drug could be used to highlight the different contributions of each drug to the observed synergy.
Inhibition of Group A Streptococcus Infection by Carboxyfullerene
Authors: Tsao Nina , Luh Tien-Yau , Chou Chen-Kung , Wu Jiunn-Jong , Lin Yee-Shin , Lei Huan-Yao
Published: July 2002

The effect of a water-soluble trimalonic acid derivative of fullerene, carboxyfullerene, againstStreptococcus pyogenesinfection was tested. Pretreatment with carboxyfullerene was able to protect mice fromS. pyogenesinfection in an air pouch model.S. pyogenes-induced death and skin injury were inhibited dose dependently by carboxyfullerene. Administration of carboxyfullerene via the peritoneum and air pouch at 3 h post-S. pyogenesinfection was able to protect 33% of mice from death. Surveys of exudates of the air pouch of carboxyfullerene-treated mice revealed that survival of infiltrating neutrophils was prolonged and that the bacteria were eliminated as a result of enhanced bactericidal activity of the neutrophils. Furthermore, carboxyfullerene was able to directly inhibit in vitro growth ofS. pyogenes. These data suggest that carboxyfullerene can be considered an antimicrobial agent for group A streptococcus infection.
In Vitro Activities of Ertapenem (MK-0826) against Recent Clinical Bacteria Collected in Europe and Australia
Authors: Livermore David M. , Carter Michael W. , Bagel Simone , Wiedemann Bernd , Baquero Fernando , Loza Elena , Endtz Hubert P. , van den Braak Nicole , Fernandes Clarence J. , Fernandes Lorna , Frimodt-Moller Niels , Rasmussen Laura S. , Giamarellou Helen , Giamarellos-Bourboulis Evangelos , Jarlier Vincent , Nguyen Jacqueline , Nord Carl-Erik , Struelens Marc J. , Nonhoff Caire , Turnidge John , Bell Jan , Zbinden Reinhard , Pfister Stefan , Mixson Lori , Shungu Daniel L.
Published: July 2002

Ertapenem (MK-0826, L-749,345) is a 1-β-methyl carbapenem with a long serum half-life. Its in vitro activity was determined by broth microdilution against 3,478 bacteria from 12 centers in Europe and Australia, with imipenem, cefepime, ceftriaxone, and piperacillin-tazobactam used as comparators. Ertapenem was the most active agent tested against members of the family
Enterobacteriaceae
, with MICs at which 90% of isolates are inhibited (MIC
90
s) of ≤1 μg/ml for all species. Ertapenem also was more active than imipenem against fastidious gram-negative bacteria and
Moraxella
spp.; on the other hand, ertapenem was slightly less active than imipenem against streptococci, methicillin-susceptible staphylococci, and anaerobes, but its MIC
90
s for these groups remained ≤0.5 μg/ml.
Acinetobacter
spp. and
Pseudomonas aeruginosa
were also much less susceptible to ertapenem than imipenem, and most
Enterococcus faecalis
strains were resistant. Ertapenem resistance, based on a provisional NCCLS MIC breakpoint of ≥16 μg/ml, was seen in only 3 of 1,611 strains of the family
Enterobacteriaceae
tested, all of them
Enterobacter aerogenes
. Resistance was also seen in 2 of 135 anaerobes, comprising 1
Bacteroides fragilis
strain and 1
Clostridium difficile
strain. Ertapenem breakpoints for streptococci have not been established, but an unofficial susceptibility breakpoint of ≤2 μg/ml was adopted for clinical trials to generate corresponding clinical response data for isolates for which MICs were as high as 2 μg/ml. Of 234
Streptococcus pneumoniae
strains tested, 2 required ertapenem MICs of 2 μg/ml and one required an MIC of 4 μg/ml, among 67 non-
Streptococcus pyogenes
, non-
Streptococcus pneumoniae
streptococci, single isolates required ertapenem MICs of 2 and 16 μg/ml. These streptococci also had diminished susceptibilities to other β-lactams, including imipenem as well as ertapenem. The Etest and disk diffusion gave susceptibility test results in good agreement with those of the broth microdilution method for ertapenem.
gyrA
Mutations Associated with Quinolone Resistance in
Bacteroides fragilis
Group Strains
Authors: Oh Herin , El Amin Nagwa , Davies Todd , Appelbaum Peter C. , Edlund Charlotta
Published: July 2002

Mutations in the
gyrA
gene contribute considerably to quinolone resistance in
Escherichia coli
. Mechanisms for quinolone resistance in anaerobic bacteria are less well studied. The
Bacteroides fragilis
group are the anaerobic organisms most frequently isolated from patients with bacteremia and intraabdominal infections. Forty-four clinafloxacin-resistant and-susceptible fecal and clinical isolates of the
B. fragilis
group (eight
Bacteroides fragilis
, three
Bacteroides ovatus
, five
Bacteroides thetaiotaomicron
, six
Bacteroides uniformis
, and 22
Bacteroides vulgatus
) and six ATCC strains of the
B. fragilis
group were analyzed as follows: (i) determination of susceptibility to ciprofloxacin, levofloxacin, moxifloxacin, and clinafloxacin by the agar dilution method and (ii) sequencing of the
gyrA
quinolone resistance-determining region (QRDR) located between amino acid residues equivalent to Ala-67 through Gln-106 in
E. coli
. Amino acid substitutions were found at hotspots at positions 82 (
n
= 15) and 86 (
n
= 8). Strains with Ser82Leu substitutions (
n
= 13) were highly resistant to all quinolones tested. Mutations in other positions of
gyrA
were also frequently found in quinolone-resistant and -susceptible isolates. Eight clinical strains that lacked mutations in their QRDR were susceptible to at least two of the quinolones tested. Although newer quinolones have good antimicrobial activity against the
B. fragilis
group, quinolone resistance in
B. fragilis
strains can be readily selected in vivo. Mutational events in the QRDR of
gyrA
seem to contribute to quinolone resistance in
Bacteroides
species.
Novel Mutations in
ndh
in Isoniazid-Resistant
Mycobacterium tuberculosis
Isolates
Authors: Lee Ann S. G. , Teo Audrey S. M. , Wong Sin-Yew
Published: July 2002

Novel mutations in NADH dehydrogenase (
ndh
) were detected in 8 of 84 (9.5%) isoniazid (INH)-resistant isolates (T110A [
n
= 1], R268H [
n
= 7]), but not in 22 INH-susceptible isolates of
Mycobacterium tuberculosis
. Significantly, all eight isolates with mutations at
ndh
did not have mutations at
katG, kasA
, or the promoter regions of
inhA
or
ahpC
, except for one isolate. Mutations in
ndh
appear to be an additional molecular mechanism for isoniazid resistance in
M. tuberculosis
.
Molecular Characterization of Chromosomal Class C β-Lactamase and Its Regulatory Gene in
Ochrobactrum anthropi
Authors: Nadjar David , Labia Roger , Cerceau Claude , Bizet Chantal , Philippon Alain , Arlet Guillaume
Published: July 2002

Ochrobactrum anthropi
, formerly known as CDC group Vd, is an oxidase-producing, gram-negative, obligately aerobic, non-lactose-fermenting bacillus of low virulence that occasionally causes human infections. It is highly resistant to all β-lactams except imipenem. A clinical isolate, SLO74, and six reference strains were tested. MICs of penicillins, aztreonam, and most cephalosporins tested, including cefotaxime and ceftazidime, were >128 μg/ml and of cefepime were 64 to >128 μg/ml. Clavulanic acid was ineffective and tazobactam had a weak effect in association with piperacillin. Two genes,
ampR
and
ampC
, were cloned by inserting restriction fragments of genomic DNA from the clinical strain
O. anthropi
SLO74 into pBK-CMV to give the recombinant plasmid pBK-OA1. The pattern of resistance to β-lactams of this clone was similar to that of the parental strain, except for its resistance to cefepime (MIC, 0.5 μg/ml). The deduced amino acid sequence of the AmpC β-lactamase (pI, 8.9) was only 41 to 52% identical to the sequence of other chromosomally encoded and plasmid-encoded class C β-lactamases. The kinetic properties of this β-lactamase were typical for this class of β-lactamases. Upstream from the
ampC
gene, the
ampR
gene encodes a protein with a sequence that is 46 to 62% identical to those of other AmpR proteins and with an amino-terminal DNA-binding domain typical of transcriptional activators of the Lys-R family. The deduced amino acid sequences of the
ampC
genes of the six reference strains were 96 to 99% identical to the sequence of the clinical strain. The β-lactamase characterized from strain SLO74 was named OCH-1 (gene,
bla
OCH-I
).
Mutation in
Serratia marcescens
AmpC β-Lactamase Producing High-Level Resistance to Ceftazidime and Cefpirome
Authors: Raimondi Alessandro , Sisto Francesca , Nikaido Hiroshi
Published: July 2002

Starting from a clinical isolate of
Serratia marcescens
that produced a chromosomally encoded AmpC β-lactamase inducibly, we isolated by stepwise selection two laboratory mutants that showed high levels of resistance to some cephalosporins. The 98R mutant apparently overproduced the unaltered β-lactamase constitutively, but the 520R mutant produced an altered enzyme, also constitutively. Ceftazidime and cefpirome MICs for the 520R mutant were much higher (512 and 64 μg/ml, respectively) than those for the 98R mutant (16 and 16 μg/ml, respectively). Yet the MICs of cephaloridine and piperacillin for the 520R mutant were four- to eightfold lower than those for the 98R mutant. Cloning and sequencing of the
ampC
alleles showed that in the 520R mutant enzyme, the Thr64 residue, about two turns away from the active-site serine, was mutated to isoleucine. This resulted in a >1,000-fold increase in the catalytic efficiency (
k
cat
/
K

m

) of the mutated AmpC enzyme toward ceftazidime, whereas there was a >10-fold decrease in the efficiency of the mutant enzyme toward cefazolin and cephaloridine. The outer membrane permeability of the 520R strain to cephalosporins was also less than in the 98R strain, and the alteration of the kinetic properties of the AmpC enzyme together with this difference in permeability explained quantitatively the resistance levels of both mutant strains to most agents studied.
In Vitro and In Vivo Antibacterial Activities of TAK-083, an Agent for Treatment of
Helicobacter pylori
Infection
Authors: Kanamaru Tsuneo , Nakano Yoshitaka , Toyoda Yukio , Miyagawa Ken-Ichiro , Tada Mayumi , Kaisho Tomoko , Nakao Masafumi
Published: July 2002

The antibacterial activity of TAK-083 was tested against 54 clinical isolates of
Helicobacter pylori
and was compared with those of amoxicillin, clarithromycin, and metronidazole. The growth-inhibitory activity of TAK-083 was more potent than that of amoxicillin, clarithromycin, or metronidazole (the MICs at which 90% of the strains are inhibited were 0.031, 0.125, 64, and 8 μg/ml, respectively). The antibacterial activity of TAK-083 was highly selective against
H. pylori
; there was a >30-fold difference between the concentration of TAK-083 required to inhibit the growth of
H. pylori
and that required to inhibit the growth of common aerobic and anaerobic bacteria. Exposure of
H. pylori
strains to TAK-083 at the MIC or at a greater concentration resulted in an extensive loss of viability. When four
H. pylori
strains were successively subcultured in the medium containing subinhibitory concentrations of TAK-083, no significant change in the MICs of this compound was observed. TAK-083 strongly inhibited the formation of tryptophanyl-tRNA in
H. pylori
while exhibiting little effect on the same system in eukaryotes. TAK-083 was efficacious in the treatment of gastric infection caused by
H. pylori
in Mongolian gerbils. The results presented here indicate that TAK-083 is a promising candidate for the treatment of
H. pylori
infection.
Carrier-Mediated Partitioning of Artemisinin into
Plasmodium falciparum
-Infected Erythrocytes
Authors: Vyas Nehal , Avery Bonnie A. , Avery Mitchell A. , Wyandt Christy M.
Published: July 2002

The purpose of the present study was to characterize the partitioning of artemisinin into both uninfected and
Plasmodium falciparum
-infected red blood cells (RBCs). The partitioning of [
14
C](+)-artemisinin into RBCs was studied at four different hematocrit levels and eight time periods. At the optimum time of 2 h, the partitioning process was investigated with eight different drug concentrations ranging from 0.88 to 3.52 μM at 37 and 4°C. The effect of the presence of unlabeled artemisinin on the partitioning of the same concentration of [
14
C]artemisinin was studied. About 35 to 40% of the drug was seen to partition into uninfected RBCs at a hematocrit of 33%, irrespective of the incubation period or the drug concentration used. In contrast, infected RBCs showed an increase in partitioning of the drug with time until saturation was achieved at 1 h. While the partitioning of artemisinin into parasitized RBCs at 37°C was found to be significantly higher than that in nonparasitized RBCs, at 4°C both parasitized and nonparasitized RBCs showed identical partitioning of the drug. The partitioning of [
14
C]artemisinin into parasitized RBCs was completely inhibited in the presence of the same concentration of unlabeled artemisinin. However, no such effect was observed in nonparasitized cells, and no evidence suggesting that binding of the drug in parasitized RBCs is reversible was found. The partitioning of artemisinin into parasitized RBCs was found to be rapid, saturable, temperature dependent, irreversible, and subject to competitive inhibition with unlabeled artemisinin. The results obtained suggest the involvement of carrier mediation in the partitioning of artemisinin across the parasitized RBC membrane. In contrast, simple passive diffusion of artemisinin was seen in nonparasitized RBCs.
Vancomycin-Resistant Enterococci from Humans and Retail Chickens in Taiwan with Unique VanB Phenotype-
vanA
Genotype Incongruence
Authors: Lauderdale Tsai-Ling , McDonald L. Clifford , Shiau Yih-Ru , Chen Pei-Chen , Wang Hui-Yin , Lai Jui-Fen , Ho Monto
Published: July 2002

Vancomycin resistant enterococci (VRE) with VanB phenotype-
vanA
genotype incongruence were found in all 39 VRE isolated from chicken carcasses and four human VRE isolates in Taiwan. Three identical mutations in the
vanS
gene were found in the VanB phenotype-
vanA
genotype VRE sequenced. This finding indicates possible transmission of glycopeptide resistance among different hosts.