bluuebunny/crossref_metadata_2025 huggingface dataset:
Polarization of Chemoattractant Receptor Signaling During Neutrophil Chemotaxis
Authors: Servant Guy , Weiner Orion D. , Herzmark Paul , Balla Tamás , Sedat John W. , Bourne Henry R.
Published: July 2002

Morphologic polarity is necessary for chemotaxis of mammalian cells. As a probe of intracellular signals responsible for this asymmetry, the pleckstrin homology domain of the AKT protein kinase (or protein kinase B), tagged with the green fluorescent protein (PHAKT-GFP), was expressed in neutrophils. Upon exposure of cells to chemoattractant, PHAKT-GFP is recruited selectively to membrane at the cell's leading edge, indicating an internal signaling gradient that is much steeper than that of the chemoattractant. Translocation of PHAKT-GFP is inhibited by toxin-B from
Clostridium difficile
, indicating that it requires activity of one or more Rho guanosine triphosphatases.
Stem Cells in Epithelial Tissues
Authors: Slack J. M. W.
Published: July 2002

Most, if not all, epithelial tissues contain stem cells. They are responsible for normal tissue renewal or for regeneration following damage. Our present knowledge of their properties is limited and is mainly derived from studies of cell kinetics and from clonal analysis.
Atomic-Scale Structure and Catalytic Reactivity of the RuO2(110) Surface
Authors: Over H. , Kim Y. D. , Seitsonen A. P. , Wendt S. , Lundgren E. , Schmid M. , Varga P. , Morgante A. , Ertl G.
Published: July 2002

The structure of RuO2(110) and the mechanism for catalytic carbon monoxide oxidation on this surface were studied by low-energy electron diffraction, scanning tunneling microscopy, and density-functional calculations. The RuO2(110) surface exposes bridging oxygen atoms and ruthenium atoms not capped by oxygen. The latter act as coordinatively unsaturated sites—a hypothesis introduced long ago to account for the catalytic activity of oxide surfaces—onto which carbon monoxide can chemisorb and from where it can react with neighboring lattice-oxygen to carbon dioxide. Under steady-state conditions, the consumed lattice-oxygen is continuously restored by oxygen uptake from the gas phase. The results provide atomic-scale verification of a general mechanism originally proposed by Mars and van Krevelen in 1954 and are likely to be of general relevance for the mechanism of catalytic reactions at oxide surfaces.
An Ultrasensitive Bacterial Motor Revealed by Monitoring Signaling Proteins in Single Cells
Authors: Cluzel Philippe , Surette Michael , Leibler Stanislas
Published: July 2002

Understanding biology at the single-cell level requires simultaneous measurements of biochemical parameters and behavioral characteristics in individual cells. Here, the output of individual flagellar motors in
Escherichia coli
was measured as a function of the intracellular concentration of the chemotactic signaling protein. The concentration of this molecule, fused to green fluorescent protein, was monitored with fluorescence correlation spectroscopy. Motors from different bacteria exhibited an identical steep input-output relation, suggesting that they actively contribute to signal amplification in chemotaxis. This experimental approach can be extended to quantitative in vivo studies of other biochemical networks.
Contribution of Increasing CO
2
and Climate to Carbon Storage by Ecosystems in the United States
Authors: Schimel David , Melillo Jerry , Tian Hanqin , McGuire A. David , Kicklighter David , Kittel Timothy , Rosenbloom Nan , Running Steven , Thornton Peter , Ojima Dennis , Parton William , Kelly Robin , Sykes Martin , Neilson Ron , Rizzo Brian
Published: July 2002

The effects of increasing carbon dioxide (CO
2
) and climate on net carbon storage in terrestrial ecosystems of the conterminous United States for the period 1895–1993 were modeled with new, detailed historical climate information. For the period 1980–1993, results from an ensemble of three models agree within 25%, simulating a land carbon sink from CO
2
and climate effects of 0.08 gigaton of carbon per year. The best estimates of the total sink from inventory data are about three times larger, suggesting that processes such as regrowth on abandoned agricultural land or in forests harvested before 1980 have effects as large as or larger than the direct effects of CO
2
and climate. The modeled sink varies by about 100% from year to year as a result of climate variability.
Dynamic Variations at the Base of the Solar Convection Zone
Authors: Howe R. , Christensen-Dalsgaard J. , Hill F. , Komm R. W. , Larsen R. M. , Schou J. , Thompson M. J. , Toomre J.
Published: July 2002

We have detected changes in the rotation of the sun near the base of its convective envelope, including a prominent variation with a period of 1.3 years at low latitudes. Such helioseismic probing of the deep solar interior has been enabled by nearly continuous observation of its oscillation modes with two complementary experiments. Inversion of the global-mode frequency splittings reveals that the largest temporal changes in the angular velocity Ω are of the order of 6 nanohertz and occur above and below the tachocline that separates the sun's differentially rotating convection zone (outer 30% by radius) from the nearly uniformly rotating deeper radiative interior beneath. Such changes are most pronounced near the equator and at high latitudes and are a substantial fraction of the average 30-nanohertz difference in Ω with radius across the tachocline at the equator. The results indicate variations of rotation close to the presumed site of the solar dynamo, which may generate the 22-year cycles of magnetic activity.
Direct Targeting of Light Signals to a Promoter Element-Bound Transcription Factor
Authors: Martı́nez-Garcı́a Jaime F. , Huq Enamul , Quail Peter H.
Published: July 2002

Light signals perceived by the phytochrome family of sensory photoreceptors are transduced to photoresponsive genes by an unknown mechanism. Here, we show that the basic helix-loop-helix transcription factor PIF3 binds specifically to a G-box DNA-sequence motif present in various light-regulated gene promoters, and that phytochrome B binds reversibly to G-box–bound PIF3 specifically upon light-triggered conversion of the photoreceptor to its biologically active conformer. We suggest that the phytochromes may function as integral light-switchable components of transcriptional regulator complexes, permitting continuous and immediate sensing of changes in this environmental signal directly at target gene promoters.
Reduction of Tropical Cloudiness by Soot
Authors: Ackerman A. S. , Toon O. B. , Stevens D. E. , Heymsfield A. J. , Ramanathan V. , Welton E. J.
Published: July 2002

Measurements and models show that enhanced aerosol concentrations can augment cloud albedo not only by increasing total droplet cross-sectional area, but also by reducing precipitation and thereby increasing cloud water content and cloud coverage. Aerosol pollution is expected to exert a net cooling influence on the global climate through these conventional mechanisms. Here, we demonstrate an opposite mechanism through which aerosols can reduce cloud cover and thus significantly offset aerosol-induced radiative cooling at the top of the atmosphere on a regional scale. In model simulations, the daytime clearing of trade cumulus is hastened and intensified by solar heating in dark haze (as found over much of the northern Indian Ocean during the northeast monsoon).
Noxa, a BH3-Only Member of the Bcl-2 Family and Candidate Mediator of p53-Induced Apoptosis
Authors: Oda Eri , Ohki Rieko , Murasawa Hideki , Nemoto Jiro , Shibue Tsukasa , Yamashita Toshiharu , Tokino Takashi , Taniguchi Tadatsugu , Tanaka † Nobuyuki
Published: July 2002

A critical function of tumor suppressor p53 is the induction of apoptosis in cells exposed to noxious stresses. We report a previously unidentified pro-apoptotic gene,
Noxa
. Expression of Noxa induction in primary mouse cells exposed to x-ray irradiation was dependent on p53.
Noxa
encodes a Bcl-2 homology 3 (BH3)–only member of the Bcl-2 family of proteins; this member contains the BH3 region but not other BH domains. When ectopically expressed, Noxa underwent BH3 motif–dependent localization to mitochondria and interacted with anti-apoptotic Bcl-2 family members, resulting in the activation of caspase-9. We also demonstrate that blocking the endogenous Noxa induction results in the suppression of apoptosis. Noxa may thus represent a mediator of p53-dependent apoptosis.
An Anti-Apoptotic Role for the p53 Family Member, p73, During Developmental Neuron Death
Authors: Pozniak Christine D. , Radinovic Stevo , Yang Annie , McKeon Frank , Kaplan David R. , Miller Freda D.
Published: July 2002

p53 plays an essential pro-apoptotic role, a function thought to be shared with its family members p73 and p63. Here, we show that p73 is primarily present in developing neurons as a truncated isoform whose levels are dramatically decreased when sympathetic neurons apoptose after nerve growth factor (NGF) withdrawal. Increased expression of truncated p73 rescues these neurons from apoptosis induced by NGF withdrawal or p53 overexpression. In p73–/– mice, all isoforms of p73 are deleted and the apoptosis of developing sympathetic neurons is greatly enhanced. Thus, truncated p73 is an essential anti-apoptotic protein in neurons, serving to counteract the pro-apoptotic function of p53.
Synthesis and Characterization of Helical Multi-Shell Gold Nanowires
Authors: Kondo Yukihito , Takayanagi Kunio
Published: July 2002

Suspended gold nanowires were made in an ultra-high vacuum. The finest of them was 0.6 nanometer in diameter and 6 nanometers in length. By high-resolution electron microscopy, they were shown to have a multi-shell structure composed of coaxial tubes. Each tube consists of helical atom rows coiled round the wire axis. The difference between the numbers of atom rows in outer and inner shells is seven, resulting in magic shell-closing numbers.
Role of Brain Insulin Receptor in Control of Body Weight and Reproduction
Authors: Brüning Jens C. , Gautam Dinesh , Burks Deborah J. , Gillette Jennifer , Schubert Markus , Orban Paul C. , Klein Rüdiger , Krone Wilhelm , Müller-Wieland Dirk , Kahn C. Ronald
Published: July 2002

Insulin receptors (IRs) and insulin signaling proteins are widely distributed throughout the central nervous system (CNS). To study the physiological role of insulin signaling in the brain, we created mice with a neuron-specific disruption of the IR gene (NIRKO mice). Inactivation of the IR had no impact on brain development or neuronal survival. However, female NIRKO mice showed increased food intake, and both male and female mice developed diet-sensitive obesity with increases in body fat and plasma leptin levels, mild insulin resistance, elevated plasma insulin levels, and hypertriglyceridemia. NIRKO mice also exhibited impaired spermatogenesis and ovarian follicle maturation because of hypothalamic dysregulation of luteinizing hormone. Thus, IR signaling in the CNS plays an important role in regulation of energy disposal, fuel metabolism, and reproduction.
Dendritic Computation of Direction Selectivity by Retinal Ganglion Cells
Authors: Taylor W. Rowland , He Shigang , Levick William R. , Vaney David I.
Published: July 2002

Direction-selective ganglion cells (DSGCs) in the retina respond strongly when stimulated by image motion in a preferred direction but are only weakly excited by image motion in the opposite null direction. Such coding represents an early manifestation of complex information processing in the visual system, but the cellular locus and the synaptic mechanisms have yet to be elucidated. We recorded the synaptic activity of DSGCs using strategies to observe the asymmetric inhibitory inputs that underlie the generation of direction selectivity. The critical nonlinear interactions between the excitatory and inhibitory inputs took place postsynaptically within the dendrites of the DSGCs.
The Global Carbon Cycle: A Test of Our Knowledge of Earth as a System
Authors: Falkowski P. , Scholes R. J. , Boyle E. , Canadell J. , Canfield D. , Elser J. , Gruber N. , Hibbard K. , Högberg P. , Linder S. , Mackenzie F. T. , Moore III B. , Pedersen T. , Rosenthal Y. , Seitzinger S. , Smetacek V. , Steffen W.
Published: July 2002

Motivated by the rapid increase in atmospheric CO
2
due to human activities since the Industrial Revolution, several international scientific research programs have analyzed the role of individual components of the Earth system in the global carbon cycle. Our knowledge of the carbon cycle within the oceans, terrestrial ecosystems, and the atmosphere is sufficiently extensive to permit us to conclude that although natural processes can potentially slow the rate of increase in atmospheric CO
2
, there is no natural “savior” waiting to assimilate all the anthropogenically produced CO
2
in the coming century. Our knowledge is insufficient to describe the interactions between the components of the Earth system and the relationship between the carbon cycle and other biogeochemical and climatological processes. Overcoming this limitation requires a systems approach.
Modulation Instability and Pattern Formation in Spatially Incoherent Light Beams
Authors: Kip Detlef , Soljacic Marin , Segev Mordechai , Eugenieva Eugenia , Christodoulides Demetrios N.
Published: July 2002

We report on the experimental observation of modulation instability of partially spatially incoherent light beams in noninstantaneous nonlinear media and show that in such systems patterns can form spontaneously from noise. Incoherent modulation instability occurs above a specific threshold that depends on the coherence properties (correlation distance) of the wave packet and leads to a periodic train of one-dimensional filaments. At a higher value of nonlinearity, the incoherent one-dimensional filaments display a two-dimensional instability and break up into self-ordered arrays of light spots. This discovery of incoherent pattern formation reflects on many other nonlinear systems beyond optics. It implies that patterns can form spontaneously (from noise) in diverse nonlinear many-body systems involving weakly correlated particles, such as atomic gases at (or near) Bose-Einstein condensation temperatures and electrons in semiconductors at the vicinity of the quantum Hall regime.
VirB/D4-Dependent Protein Translocation from
Agrobacterium
into Plant Cells
Authors: Vergunst Annette C. , Schrammeijer Barbara , den Dulk-Ras Amke , de Vlaam Clementine M. T. , Regensburg-Tuı̈nk Tonny J. G. , Hooykaas Paul J. J.
Published: July 2002

The
Agrobacterium
VirB/D4 transport system mediates the transfer of a nucleoprotein T complex into plant cells, leading to crown gall disease. In addition, several Virulence proteins must somehow be transported to fulfill a function in planta. Here, we used fusions between Cre recombinase and VirE2 or VirF to directly demonstrate protein translocation into plant cells. Transport of the proteins was monitored by a Cre-mediated in planta recombination event resulting in a selectable phenotype and depended on the VirB/D4 transport system but did not require transferred DNA.
Hot Plasma and Black Hole Binaries in Starburst Galaxy M82
Authors: Griffiths R. E. , Ptak A. , Feigelson E. D. , Garmire G. , Townsley L. , Brandt W. N. , Sambruna R. , Bregman J. N.
Published: July 2002

High-resolution x-ray observations of the prototype starburst galaxy Messier 82 (M82) obtained with the advanced CCD (charge-coupled device) imaging spectrometer on board the Chandra X-ray Observatory provide a detailed view of hot plasma and energetic processes. Plasma with temperature of about 40,000,000 kelvin fills the inner 1 kiloparsec, which is much hotter than the 1,000,000 to 2,000,000 kelvin interstellar medium component in the Milky Way Galaxy. Produced by many supernova explosions, this central region is overpressurized and drives M82's prominent galactic wind into the intergalactic medium. We also resolved about 20 compact x-ray sources, many of which could be high-mass x-ray binary star systems containing black holes.
From Micro- to Nanofabrication with Soft Materials
Authors: Quake Stephen R. , Scherer Axel
Published: July 2002

Soft materials are finding applications in areas ranging from microfluidic device technology to nanofabrication. We review recent work in these areas, discuss the motivation for device fabrication with soft materials, and describe applications of soft materials. In particular, we discuss active microfluidic devices for cell sorting and biochemical assays, replication-molded optics with subdiffraction limit features, and nanometer-scale resonators and wires formed from single-molecule DNA templates as examples of how the special properties of soft materials address outstanding problems in device fabrication.
Subduction and Slab Detachment in the Mediterranean-Carpathian Region
Authors: Wortel M. J. R. , Spakman W.
Published: July 2002

Seismic tomography models of the three-dimensional upper mantle velocity structure of the Mediterranean-Carpathian region provide a better understanding of the lithospheric processes governing its geodynamical evolution. Slab detachment, in particular lateral migration of this process along the plate boundary, is a key element in the lithospheric dynamics of the region during the last 20 to 30 million years. It strongly affects arc and trench migration, and causes along-strike variations in vertical motions, stress fields, and magmatism. In a terminal-stage subduction zone, involving collision and suturing, slab detachment is the natural last stage in the gravitational settling of subducted lithosphere.
String Tension and Stability of Magic Tip-Suspended Nanowires
Authors: Tosatti E. , Prestipino S. , Kostlmeier S. , Corso A. Dal , Di Tolla F. D.
Published: July 2002

Multishell helical gold nanowires were recently imaged by electron microscopy. We show theoretically that the contact with the gold tips at either end of the wire plays a crucial role and that local minima in the string tension rather than the total wire free energy determine the nanowire stability. Density functional electronic structure calculations of the simplest and thinnest coaxial gold and silver wires of variable radius and chirality were carried out. We found a string tension minimum for a single-tube gold nanowire that is chiral and consists of seven strands, in striking agreement with observation. In contrast, no such minimum was found for silver, where the s-d competition leading to surface reconstruction is lacking.
Once-Daily Dosing in Dogs Optimizes Daptomycin Safety
Authors: Oleson F. B. , Berman C. L. , Kirkpatrick J. B. , Regan K. S. , Lai J.-J. , Tally F. P.
Published: July 2002

Daptomycin is a novel lipopeptide antibiotic with potent bactericidal activity against most clinically important gram-positive bacteria, including resistant strains. Daptomycin has been shown to have an effect on skeletal muscle. To guide the clinical dosing regimen with the potential for the least effect on skeletal muscle, two studies were conducted with dogs to compare the effects of repeated intravenous administration every 24 h versus every 8 h for 20 days. The data suggest that skeletal-muscle effects were more closely related to the dosing interval than to either the maximum concentration of the drug in plasma or the area under the concentration-time curve. Both increases in serum creatine phosphokinase activity and the incidence of myopathy observed at 25 mg/kg of body weight every 8 h were greater than those observed at 75 mg/kg every 24 h despite the lower maximum concentration of drug in plasma. Similarly, the effects observed at 25 mg/kg every 8 h were greater than those observed at 75 mg/kg every 24 h at approximately the same area under the concentration-time curve from 0 to 24 h. Once-daily administration appeared to minimize the potential for daptomycin-related skeletal-muscle effects, possibly by allowing for more time between doses for repair of subclinical effects. Thus, these studies with dogs suggest that once-daily dosing of daptomycin in humans should have the potential to minimize skeletal-muscle effects. In fact, interim results of ongoing clinical trials, which have focused on once-daily dosing, appear to be consistent with this conclusion.
Consequences of Interaction of a Lipophilic Endotoxin Antagonist with Plasma Lipoproteins
Authors: Rose Jeffrey R. , Mullarkey Maureen A. , Christ William J. , Hawkins Lynn D. , Lynn Melvyn , Kishi Yoshito , Wasan Kishor M. , Peteherych Kathy , Rossignol Daniel P.
Published: July 2002

E5531, a novel synthetic lipid A analogue, antagonizes the toxic effects of lipopolysaccharide, making it a potential intravenously administered therapeutic agent for the treatment of sepsis. This report describes the distribution of E5531 in human blood and its activity when it is associated with different lipoprotein subclasses. After in vitro incubation of [
14
C]E5531 with blood, the great majority (>92%) of material was found in the plasma fraction. Analysis by size-exclusion and affinity chromatographies and density gradient centrifugation indicates that [
14
C]E5531 binds to lipoproteins, primarily high-density lipoproteins (HDLs), with distribution into low-density lipoproteins (LDLs) and very low density lipoproteins (VLDLs) being dependent on the plasma LDL or VLDL cholesterol concentration. Similar results were also seen in a limited study of [
14
C]E5531 administration to human volunteers. The potency of E5531 in freshly drawn human blood directly correlates to increasing LDL cholesterol levels. Finally, preincubation of E5531 with plasma or purified lipoproteins indicated that binding to HDL resulted in a time-dependent loss of drug activity. This loss in activity was not observed with drug binding to LDLs or to VLDLs or chylomicrons. Taken together, these results indicate that E5531 binds to plasma lipoproteins, making its long-term antagonistic potency dependent on the plasma lipoprotein composition.
Efficacy of Linezolid in Experimental Otitis Media
Authors: Pelton S. I. , Figueira M. , Albut R. , Stalker D.
Published: July 2002

Therapy for otitis media (OM) due to resistant
Streptococcus pneumoniae
(MIC of penicillin, ≥2.0 μg/ml) is challenging. Linezolid, an oxazolidinone, represent a new class of antimicrobial agents with excellent in vitro activity against penicillin-resistant
S. pneumoniae
; however, in vitro activity against nontypeable
Haemophilus influenzae
(NTHI) is limited. We evaluated its efficacy against experimental acute OM due to a multidrug-resistant
S. pneumoniae
isolate and two isolates of NTHI. The chinchilla model was utilized to evaluate the efficacy of linezolid against experimental infection due to
S. pneumoniae
or NTHI. Serum and middle ear antibiotic concentrations were determined, and sterilization of experimental OM was evaluated. Chinchillas were inoculated directly with
S. pneumoniae
into the superior bulla. Twenty-four hours after inoculation, all animals had positive middle ear and nasopharyngeal cultures. Animals were given linezolid at 25 mg/kg/dose twice a day (b.i.d.) by orogastric feeding tube or amoxicillin at 40 mg/kg/dose b.i.d. intramuscularly for 5 days. By day 5, all animals in the linezolid group had sterile middle ear cultures and eradication of
S. pneumoniae
from the nasopharynx. In the amoxicillin group, all nine animals remained middle ear and nasopharynx positive (
P
< 0.01). In animals inoculated with NTHI, 25 and 37.5 mg/kg b.i.d. failed to sterilize middle ear infection or eradicate colonization. Mean levels in middle ear fluid measured during experimental infection were 12.8 μg/ml at 2 to 6 h and 4.1 μg/ml at 16 to 17 h after orogastric dosing at 25 mg/kg. Linezolid achieved a high concentration in the middle ear during experimental OM. Linezolid eradicated multidrug-resistant
S. pneumoniae
from the middle ear and nasopharynx. Experimental infection and nasopharyngeal colonization due to NTHI persisted despite achievement of concentrations in the middle ear that were above the MIC (for NTHI).
Synergistic Antifungal Activities of Bafilomycin A
1
, Fluconazole, and the Pneumocandin MK-0991/Caspofungin Acetate (L-743,873) with Calcineurin Inhibitors FK506 and L-685,818 against
Cryptococcus neoformans
Authors: Del Poeta Maurizio , Cruz M. Cristina , Cardenas Maria E. , Perfect John R. , Heitman Joseph
Published: July 2002

Cryptococcus neoformans
is an opportunistic fungal pathogen that causes life-threatening infections of the central nervous system. Existing therapies include amphotericin B, fluconazole, and flucytosine, which are limited by toxic side effects and the emergence of drug resistance. We recently demonstrated that the protein phosphatase calcineurin is required for growth at 37°C and virulence of
C. neoformans
. Because calcineurin is the target of potent inhibitors in widespread clinical use, cyclosporine and FK506 (tacrolimus), it is an attractive drug target for novel antifungal agents. Here we have explored the synergistic potential of combining the calcineurin inhibitor FK506 or its nonimmunosuppressive analog, L-685,818, with other antifungal agents and examined the molecular basis of FK506 action by using genetically engineered fungal strains that lack the FK506 target proteins FKBP12 and calcineurin. We demonstrate that FK506 exhibits marked synergistic activity with the H
+
ATPase inhibitor bafilomycin A
1
via a novel action distinct from calcineurin loss of function. FK506 also exhibits synergistic activity with the pneumocandin MK-0991/caspofungin acetate (formerly L-743,873), which targets the essential β-1,3 glucan synthase, and in this case, FK506 action is mediated via FKBP12-dependent inhibition of calcineurin. Finally, we demonstrate that FK506 and fluconazole have synergistic activity that is independent of both FKBP12 and calcineurin and may involve the known ability of FK506 to inhibit multidrug resistance pumps, which are known to export azoles from fungal cells. In summary, our studies illustrate the potential for synergistic activity of a variety of different drug combinations and the power of molecular genetics to define the mechanisms of drug action, as well as identify a novel action of FK506 that could have profound implications for therapeutic or toxic effects in other organisms, including humans.
Characterization of VIM-2, a Carbapenem-Hydrolyzing Metallo-β-Lactamase and Its Plasmid- and Integron-Borne Gene from a
Pseudomonas aeruginosa
Clinical Isolate in France
Authors: Poirel Laurent , Naas Thierry , Nicolas Delphine , Collet Louis , Bellais Samuel , Cavallo Jean-Didier , Nordmann Patrice
Published: July 2002

Pseudomonas aeruginosa
COL-1 was identified in a blood culture of a 39-year-old-woman treated with imipenem in Marseilles, France, in 1996. This strain was resistant to β-lactams, including ureidopenicillins, ticarcillin-clavulanic acid, cefepime, ceftazidime, imipenem, and meropenem, but remained susceptible to the monobactam aztreonam. The carbapenem-hydrolyzing β-lactamase gene of
P. aeruginosa
COL-1 was cloned, sequenced, and expressed in
Escherichia coli
DH10B. The deduced 266-amino-acid protein was an Ambler class B β-lactamase, with amino acid identities of 32% with B-II from
Bacillus cereus
; 31% with IMP-1 from several gram-negative rods in Japan, including
P. aeruginosa
; 27% with CcrA from
Bacteroides fragilis
; 24% with BlaB from
Chryseobacterium meningosepticum
; 24% with IND-1 from
Chryseobacterium indologenes
; 21% with CphA-1 from
Aeromonas hydrophila
; and 11% with L-1 from
Stenotrophomonas maltophilia
. It was most closely related to VIM-1 β-lactamase recently reported from Italian
P. aeruginosa
clinical isolates (90% amino acid identity). Purified VIM-2 β-lactamase had a pI of 5.6, a relative molecular mass of 29.7 kDa, and a broad substrate hydrolysis range, including penicillins, cephalosporins, cephamycins, oxacephamycins, and carbapenems, but not monobactams. As a metallo-β-lactamase, its activity was zinc dependent and inhibited by EDTA (50% inhibitory concentration, 50 μM). VIM-2 conferred a resistance pattern to β-lactams in
E. coli
DH10B that paralleled its in vitro hydrolytic properties, except for susceptibility to ureidopenicillins, carbapenems, and cefepime.
bla
VIM-2
was located on a ca. 45-kb plasmid that in addition conferred resistance to sulfamides and that was not self-transmissible either from
P. aeruginosa
to
E. coli
or from
E. coli
to
E. coli. bla
VIM-2
was the only gene cassette located within the variable region of a novel class 1 integron, In56, that was weakly related to the
bla
VIM-1
-containing integron. VIM-2 is the second carbapenem-hydrolyzing metalloenzyme characterized from a
P. aeruginosa
isolate outside Japan.
Comparison of Nikkomycin Z with Amphotericin B and Itraconazole for Treatment of Histoplasmosis in a Murine Model
Authors: Goldberg Janet , Connolly Patricia , Schnizlein-Bick Carol , Durkin Michelle , Kohler Stephen , Smedema Melinda , Brizendine Edward , Hector Richard , Wheat Joseph
Published: July 2002

Nikkomycin Z was tested both in vitro and in vivo for efficacy againstHistoplasma capsulatum. Twenty clinical isolates were tested for susceptibility to nikkomycin Z in comparison to amphotericin B and itraconazole. The median MIC was 8 μg/ml with a range of 4 to 64 μg/ml for nikkomycin Z, 0.56 μg/ml with a range of 0.5 to 1.0 μg/ml for amphotericin B, and ≤0.019 μg/ml for itraconazole. Primary studies were carried out by using a clinical isolate ofH. capsulatumfor which the MIC of nikkomycin Z was greater than or equal to 64 μg/ml. In survival experiments, mice treated with amphotericin B at 2.0 mg/kg/dose every other day (QOD) itraconazole at 75 mg/kg/dose twice daily (BID), and nikkomycin Z at 100 mg/kg/dose BID survived to day 14, while 70% of mice receiving nikkomycin Z at 20 mg/kg/dose BID and none of the mice receiving nikkomycin Z at 5 mg/kg/dose BID survived to day 14. All vehicle control mice died by day 12. Fungal burden was assessed on survivors. Mice treated with nikkomycin Z at 20 and 100 mg/kg/dose BID had significantly higher CFUs per gram of organ weight in quantitative cultures and higher levels ofHistoplasmaantigen in lung and spleen homogenates than mice treated with amphotericin B at 2.0 mg/kg/dose QOD or itraconazole at 75 mg/kg/dose BID. Studies also were carried out with a clinical isolate for which the MIC of nikkomycin Z was 4 μg/ml. All mice treated with amphotericin B at 2.0 mg/kg/dose QOD; itraconazole at 75 mg/kg/dose BID; and nikkomycin Z at 100, 20, and 5 mg/kg/dose BID survived until the end of the study at day 17 postinfection, while 30% of the untreated vehicle control mice survived. Fungal burden assessed on survivors showed similar levels ofHistoplasmaantigen in lung and spleen homogenates of mice treated with amphotericin B at 2.0 mg/kg/dose QOD; itraconazole at 75 mg/kg/dose BID; and nikkomycin Z at 100, 20, and 5 mg/kg/dose BID. The three surviving vehicle control mice had significantly higher antigen levels in lung and spleen than other groups (P< 0.05). The efficacy of nikkomycin Z at preventing mortality and reducing fungal burden correlates with in vitro susceptibility.
Antibiotic Susceptibility Patterns of
Neisseria meningitidis
Isolates from Patients and Asymptomatic Carriers
Authors: Arreaza L. , de la Fuente L. , Vázquez J. A.
Published: July 2002

The activities of seven antimicrobial agents used for treatment and prophylaxis of meningococcal disease was investigated against 901
Neisseria meningitidis
isolates, 112 of which were recovered from patients and 789 of which were recovered from asymptomatic carriers. The proportions of isolates with decreased susceptibility to penicillin were 55.3 and 39.0%, respectively. Penicillin- and ampicillin-intermediate strains were more common among serogroup C meningococci than among non-serogroup C meningococci from both patients and carriers.
Identification of a Plasmid-Borne Chloramphenicol-Florfenicol Resistance Gene in
Staphylococcus sciuri
Authors: Schwarz Stefan , Werckenthin Christiane , Kehrenberg Corinna
Published: July 2002

The 16.5-kbp plasmid pSCFS1 from
Staphylococcus sciuri
mediated combined resistance to chloramphenicol and florfenicol. The gene responsible for this resistance property,
cfr
, was cloned and sequenced. The amino acid sequence of the Cfr protein revealed no homology to known acetyltransferases or efflux proteins involved in chloramphenicol and/or florfenicol resistance or to other proteins whose functions are known.
Antiviral Efficacy and Pharmacokinetics of Oral Adefovir Dipivoxil in Chronically Woodchuck Hepatitis Virus-Infected Woodchucks
Authors: Cullen John M. , Li Daniel H. , Brown Cynthia , Eisenberg Eugene J. , Cundy Kenneth C. , Wolfe Julie , Toole Jay , Gibbs Craig
Published: July 2002

The antiviral efficacy of orally administered adefovir dipivoxil was evaluated in an 18-week study (12 weeks of treatment and 6 weeks of recovery) conducted with woodchucks chronically infected with woodchuck hepatitis virus (WHV). Adefovir dipivoxil is a prodrug of adefovir designed to enhance its oral bioavailability. Following administration of 15 mg of adefovir dipivoxil per kg of body weight in four WHV-infected animals, the mean maximum concentration of adefovir in serum was 0.462 μg/ml, with an elimination half-life of 10.2 h, and the oral bioavailability of adefovir was estimated to be 22.9% (±11.2%). To study antiviral efficacy, the animals were divided into three groups. There were six animals each in a high-dose group (15 mg/kg/day) and a low-dose group (5 mg/kg/day). A vehicle control group consisted of five animals because WHV DNA was detectable only by PCR at the time of the study in one of the original six animals. Efficacy was evaluated by determining the levels of WHV DNA in serum. The geometric mean WHV DNA level for the high-dose group diminished by >40-fold (>1.6 log10) after 2 weeks of treatment and >300-fold (>2.5 log10) at 12 weeks. There was a >10-fold reduction in five of six low-dose animals by 2 weeks, but levels were unchanged in one animal. By 12 weeks of treatment there was a >45-fold (>1.6 log10) reduction of WHV DNA levels, and serum WHV DNA levels were below the limit of quantification in three of six animals. Viral DNA levels returned to pretreatment levels during the 6-week recovery period. There were no clinically significant changes in body weight, hematology, or serum chemistry values, including bicarbonate or lactate, in any of the treated animals. No histologic evidence of liver injury was apparent in the biopsies. Under the conditions of this study, adefovir dipivoxil was an effective antihepadnaviral agent.
Eradication of Biofilm-Forming
Staphylococcus epidermidis
(RP62A) by a Combination of Sodium Salicylate and Vancomycin
Authors: Polonio Roy E. , Mermel Leonard A. , Paquette Gregory E. , Sperry Jay F.
Published: July 2002

Staphylococcus epidermidis
is a major cause of infections associated with indwelling medical devices. Biofilm production is an important virulence attribute in the pathogenesis of device-related infections. Therefore, elimination of these biofilms is an ideal treatment. Salicylate (5 mM) combined with 1 μg of vancomycin per ml inhibited biofilm formation by
S. epidermidis
(RP62A) by ≥99.9%. When biofilm-coated polystyrene beads were exposed to 5 mM sodium salicylate and 4 μg of vancomycin per ml (one-half the minimum biofilm eradication concentration), there was a >99.9% reduction in viable count.
Papillomavirus Microbicidal Activities of High-Molecular-Weight Cellulose Sulfate, Dextran Sulfate, and Polystyrene Sulfonate
Authors: Christensen Neil D. , Reed Cynthia A. , Culp Tim D. , Hermonat Paul L. , Howett Mary K. , Anderson Robert A. , Zaneveld Lourens J. D.
Published: July 2002

The high-molecular-weight sulfated or sulfonated polysaccharides or polymers cellulose sulfate, dextran sulfate, and polystyrene sulfonate were tested for microbicidal activity against bovine papillomavirus type 1 (BPV-1) and human papillomavirus type 11 (HPV-11) and type 40 (HPV-40). In vitro assays included the BPV-1-induced focus-forming assay and transient infection of human A431 cells with HPVs. The compounds were tested for microbicidal activity directly by preincubation with virus prior to addition to cell cultures and indirectly by addition of virus to compound-treated cells and to virus-coated cells to test inactivation of the virus after virus-cell binding. The data indicated that all three compounds showed direct microbicidal activity with 50% effective concentrations between 10 to 100 μg/ml. These concentrations were nontoxic to cell cultures for both assays. When a clone of C127 cells was tested for microbicidal activity, approximately 10-fold-less compound was required to achieve a 50% reduction in BPV-1-induced foci than for the uncloned parental C127 cells. Pretreatment of cells with compound prior to addition of virus also demonstrated strong microbicidal activity with dextran sulfate and polystyrene sulfonate, but cellulose sulfate required several orders of magnitude more compound for virus inactivation. Polystyrene sulfonate prevented subsequent infection of HPV-11 after virus-cell binding, and this inactivation was observed up to 4 h after addition of virus. These data indicate that the polysulfated and polysulfonated compounds may be useful nontoxic microbicidal compounds that are active against a variety of sexually transmitted disease agents including papillomaviruses.
Clinafloxacin versus Piperacillin-Tazobactam in Treatment of Patients with Severe Skin and Soft Tissue Infections
Authors: Siami G. , Christou N. , Eiseman I. , Tack K. J. ,   the Clinafloxacin Severe Skin And Soft Tissue Infections Study Group
Published: July 2002

Patients (n= 409) with severe skin and soft tissue infections (SSTIs) were randomized to receive clinafloxacin or piperacillin-tazobactam (plus optional vancomycin for methicillin-resistant cocci), administered intravenously, with the option to switch to oral medication. Most patients had cellulitis, wound infections, or diabetic foot infections.Staphylococcus aureus,Enterococcus faecalis, andPseudomonas aeruginosawere the most common baseline pathogens. Fewer baseline pathogens were resistant to clinafloxacin (1.8%) than to piperacillin-tazobactam (6.2%) (P= 0.001). The clinafloxacin and piperacillin-tazobactam groups did not differ significantly in clinical cure rates (68.8 and 65.2%, respectively) or microbiologic eradication rates (61.5 and 57.2%). Clinafloxacin yielded higher eradication rates for all three of the most common pathogenic species, although no differences were statistically significant. Within the power of this study, the overall frequency of adverse events was similar (P= 0.577) in the two treatment groups. Drug-associated adverse events (P= 0.050) and treatment discontinuations (P= 0.052) were marginally more frequent in the clinafloxacin group, primarily due to phototoxicity in outpatients receiving clinafloxacin. Although most cases of phototoxicity were mild to moderate, four cases were reported as severe. In summary, clinafloxacin monotherapy was equivalent in effectiveness to therapy with piperacillin-tazobactam plus optional vancomycin in the treatment of hospitalized patients with severe SSTIs.
Mechanisms of Macrolide Resistance in Clinical Pneumococcal Isolates in France
Authors: Fitoussi Frederic , Doit Catherine , Geslin Pierre , Brahimi Naima , Bingen Edouard
Published: July 2002

The genetic basis of macrolide resistance was investigated in a collection of 48 genotypically unrelated clinical isolates of
Streptococcus pneumoniae
obtained between 1987 and 1997 in France. All strains were resistant to erythromycin, clindamycin, and streptogramin B, exhibiting a macrolide-lincosamide-streptogramin B resistance phenotype, and harbored the
erm
(B) gene. None of the strains carried the
mef
(A) or
erm
(A) subclass
erm
(TR) gene.
Pharmacodynamics of Daptomycin in a Murine Thigh Model of
Staphylococcus aureus
Infection
Authors: Louie Arnold , Kaw Pamela , Liu Weiguo , Jumbe Nelson , Miller Michael H. , Drusano George L.
Published: July 2002

Daptomycin is a lipopeptide antibiotic with activity against gram-positive bacteria, including
Staphylococcus aureus
. We defined the pharmacodynamic parameters that determine the activity of daptomycin for
S. aureus
using in vitro methods and the Craig (W. A. Craig, J. Redington, and S. C. Ebert, J. Antimicrob. Chemother. 27[Suppl. C]:29–40, 1991) neutropenic mouse thigh infection model. In Mueller-Hinton broth, the MICs for three
S. aureus
isolates were 0.1 to 0.2 μg/ml. In mouse serum, the MICs were 1.0 μg/ml. The protein binding of daptomycin was 90 to 92.5% in mouse serum. Single-dose intraperitoneal (i.p.) pharmacokinetic studies with infected mice showed a linear relationship between dose versus the maximum concentration of drug in serum and dose versus the area under the concentration-time curve (AUC). The serum half-life of daptomycin in infected mice was approximately 1.8 h. In single-dose, dose-ranging studies using mice, daptomycin showed a dose-response effect described by an inhibitory sigmoid
E
max
(maximum effect) curve (
r
= 0.974;
P
≪ 0.001). The density of
S. aureus
in untreated controls was 8.26 log
10
CFU/g, and the
E
max
was 3.97 log
10
CFU/g. The 50% effective dose (ED
50
) was 3.7 mg/kg of body weight i.p. and the stasis dose was 7.1 mg/kg. Dose fractionation studies at schedules of Q6h, Q12h, and Q24h, for total 24-h ED
30
, ED
60
, and ED
80
doses of 2.5, 5.6, and 15 mg/kg i.p., showed no difference in effect at each total 24-h dose level by schedule, indicating that the AUC/MIC ratio is the dynamically linked variable.
Plasmid-Encoded Metallo-β-Lactamase (IMP-6) Conferring Resistance to Carbapenems, Especially Meropenem
Authors: Yano Hisakazu , Kuga Akio , Okamoto Ryoichi , Kitasato Hidero , Kobayashi Toshimitsu , Inoue Matsuhisa
Published: July 2002

In 1996,
Serratia marcescens
KU3838 was isolated from the urine of a patient with a urinary tract infection at a hospital in northern Japan and was found to contain the plasmid pKU501. Previously, we determined that pKU501 carries
bla
IMP
and the genes for TEM-1-type β-lactamases as well as producing both types of β-lactamases (H. Yano, A. Kuga, K. Irinoda, R. Okamoto, T. Kobayashi, and M. Inoue, J. Antibiot. 52:1135–1139, 1999). pKU502 is a recombinant plasmid that contains a 1.5-kb DNA fragment, including the metallo-β-lactamase gene, and is obtained by PCR amplification of pKU501. The sequence of the metallo-β-lactamase gene in pKU502 was determined and revealed that this metallo-β-lactamase gene differed from the gene encoding IMP-1 by one point mutation, leading to one amino acid substitution: 640-A in the base sequence of the IMP-1 gene was replaced by G, and Ser-196 was replaced by Gly in the mature enzyme. This enzyme was designated IMP-6. The strains that produced IMP-6 were resistant to carbapenems. The MICs of panipenem and especially meropenem were higher than the MIC of imipenem for these strains. The
k
cat
/

K
m

value of IMP-6 was about sevenfold higher against meropenem than against imipenem, although the MIC of meropenem for KU1917, which produced IMP-1, was lower than that of imipenem, and the MIC of panipenem was equal to that of imipenem. These results support the hypothesis that IMP-6 has extended substrate profiles against carbapenems. However, the activity of IMP-6 was very low against penicillin G and piperacillin. These results suggest that IMP-6 acquired high activity against carbapenems, especially meropenem, via the point mutation but in the process lost activity against penicillins. Although IMP-6 has reduced activity against penicillins due to this point mutation, pKU501 confers resistance to a variety of antimicrobial agents because it also produces TEM-1-type enzyme.
Inhibition of Intramacrophage Growth ofPenicillium marneffeiby 4-Aminoquinolines
Authors: Taramelli Donatella , Tognazioli Clara , Ravagnani F. , Leopardi O. , Giannulis G. , Boelaert J. R.
Published: July 2002

The antimicrobial activities of chloroquine (CQ) and several 4-aminoquinoline drugs were tested againstPenicillium marneffei, an opportunistic fungus that invades and grows inside macrophages and causes disseminated infection in AIDS patients. Human THP1 and mouse J774 macrophages were infected in vitro withP. marneffeiconidia and treated with different doses of drugs for 24 to 48 h followed by cell lysis and the counting ofP. marneffeiCFU. CQ and amodiaquine exerted a dose-dependent inhibition of fungal growth, whereas quinine and artemisinin were fungistatic and not fungicidal. The antifungal activity of CQ was not due to an impairment of fungal iron acquisition in that it was not reversed by the addition of iron nitrilotriacetate, FeCl3, or iron ammonium citrate. Perl's staining indicated that CQ did not alter the ability of J774 cells to acquire iron from the medium. Most likely, CQ's antifungal activity is due to an increase in the intravacuolar pH and a disruption of pH-dependent metabolic processes. Indeed, we demonstrate that (i) bafilomycin A1 and ammonium chloride, two agents known to alkalinize intracellular vesicles by different mechanisms, were inhibitory as well and (ii) a newly synthesized 4-amino-7-chloroquinoline molecule (compound 9), lacking the terminal amino side chain of CQ that assists in drug accumulation, did not inhibitP. marneffeigrowth. These results suggest that CQ has a potential for use in prophylaxis ofP. marneffeiinfections in human immunodeficiency virus-infected patients in countries whereP. marneffeiis endemic.
Improved Efficacy of Ciprofloxacin Administered in Polyethylene Glycol-Coated Liposomes for Treatment ofKlebsiella pneumoniaePneumonia in Rats
Authors: Bakker-Woudenberg Irma A. J. M. , ten Kate Marian T. , Guo Luke , Working Peter , Mouton Johan W.
Published: July 2002

Animal and clinical data show that high ratios of the area under the concentration-time curve and the peak concentration in blood to the MIC of fluoroquinolones for a given pathogen are associated with a favorable outcome. The present study investigated whether improvement of the therapeutic potential of ciprofloxacin could be achieved by encapsulation in polyethylene glycol (PEG)-coated long-circulating sustained-release liposomes. In a rat model of unilateralKlebsiella pneumoniaepneumonia (MIC = 0.1 μg/ml), antibiotic was administered at 12- or 24-h intervals at twofold-increasing doses. A treatment period of 3 days was started 24 h after inoculation of the left lung, when the bacterial count had increased 1,000-fold and some rats had positive blood cultures. The infection was fatal within 5 days in untreated rats. Administration of ciprofloxacin in the liposomal form resulted in delayed ciprofloxacin clearance and increased and prolonged ciprofloxacin concentrations in blood and tissues. The ED50(dosage that results in 50% survival) of liposomal ciprofloxacin was 3.3 mg/kg of body weight/day given once daily, and that of free ciprofloxacin was 18.9 mg/kg/day once daily or 5.1 mg/kg/day twice daily. The ED90of liposomal ciprofloxacin was 15.0 mg/kg/day once daily compared with 36.0 mg/kg/day twice daily for free ciprofloxacin; 90% survival could not be achieved with free ciprofloxacin given once daily. In summary, the therapeutic efficacy of liposomal ciprofloxacin was superior to that of ciprofloxacin in the free form. PEG-coated liposomal ciprofloxacin was well tolerated in relatively high doses, permitting once daily administration with relatively low ciprofloxacin clearance and without compromising therapeutic efficacy.