bluuebunny/crossref_metadata_2025 huggingface dataset:
Small Molecule Inhibitor of Mitotic Spindle Bipolarity Identified in a Phenotype-Based Screen
Authors: Mayer Thomas U. , Kapoor Tarun M. , Haggarty Stephen J. , King Randall W. , Schreiber Stuart L. , Mitchison Timothy J.
Published: July 2002

Small molecules that perturb specific protein functions are valuable tools for dissecting complex processes in mammalian cells. A combination of two phenotype-based screens, one based on a specific posttranslational modification, the other visualizing microtubules and chromatin, was used to identify compounds that affect mitosis. One compound, here named monastrol, arrested mammalian cells in mitosis with monopolar spindles. In vitro, monastrol specifically inhibited the motility of the mitotic kinesin Eg5, a motor protein required for spindle bipolarity. All previously known small molecules that specifically affect the mitotic machinery target tubulin. Monastrol will therefore be a particularly useful tool for studying mitotic mechanisms.
Oligotrophy and Nitrogen Fixation During Eastern Mediterranean Sapropel Events
Authors: Sachs Julian P. , Repeta Daniel J.
Published: July 2002

Nitrogen isotopic measurements in fossil chlorophyll from late Pleistocene organic-rich sediments (sapropels) in the eastern Mediterranean Sea provide geochemical evidence for stratified, nutrient-depleted surface water and extensive nitrogen fixation. This evidence is reconciled with previous indications of high productivity by invoking a model of sapropel formation in which increased river discharge facilitates development of a specialized phytoplankton population whose annual mass sinking provides the organic flux to generate sapropels. This interpretation is consistent with the widespread occurrence of mat-forming diatoms that thrive in stratified water and can harbor diazotrophic bacterial symbionts, but does not support eutrophication of surface waters by enhanced river runoff or a circulation reversal.
Evidence for a Low-Density Universe from the Relative Velocities of Galaxies
Authors: Juszkiewicz R. , Ferreira P. G. , Feldman H. A. , Jaffe A. H. , Davis M.
Published: July 2002

The motions of galaxies can be used to constrain the cosmological density parameter Ω and the clustering amplitude of matter on large scales. The mean relative velocity of galaxy pairs, estimated from the Mark III survey, indicates that Ω = 0.35
−0.25
+0.35
. If the clustering of galaxies is unbiased on large scales, Ω = 0.35 ± 0.15, so that an unbiased Einstein–de Sitter model (Ω = 1) is inconsistent with the data.
Engineering the Provitamin A (β-Carotene) Biosynthetic Pathway into (Carotenoid-Free) Rice Endosperm
Authors: Ye Xudong , Al-Babili Salim , Klöti Andreas , Zhang Jing , Lucca Paola , Beyer Peter , Potrykus Ingo
Published: July 2002

Rice (
Oryza sativa
), a major staple food, is usually milled to remove the oil-rich aleurone layer that turns rancid upon storage, especially in tropical areas. The remaining edible part of rice grains, the endosperm, lacks several essential nutrients, such as provitamin A. Thus, predominant rice consumption promotes vitamin A deficiency, a serious public health problem in at least 26 countries, including highly populated areas of Asia, Africa, and Latin America. Recombinant DNA technology was used to improve its nutritional value in this respect. A combination of transgenes enabled biosynthesis of provitamin A in the endosperm.
Trienoic Fatty Acids and Plant Tolerance of High Temperature
Authors: Murakami Yuuki , Tsuyama Michito , Kobayashi Yoshichika , Kodama Hiroaki , Iba Koh
Published: July 2002

The chloroplast membrane of higher plants contains an unusually high concentration of trienoic fatty acids. Plants grown in colder temperatures have a higher content of trienoic fatty acids. Transgenic tobacco plants in which the gene encoding chloroplast omega-3 fatty acid desaturase, which synthesizes trienoic fatty acids, was silenced contained a lower level of trienoic fatty acids than wild-type plants and were better able to acclimate to higher temperatures.
Resonant Formation of DNA Strand Breaks by Low-Energy (3 to 20 eV) Electrons
Authors: Boudaı̈ffa Badia , Cloutier Pierre , Hunting Darel , Huels Michael A. , Sanche Léon
Published: July 2002

Most of the energy deposited in cells by ionizing radiation is channeled into the production of abundant free secondary electrons with ballistic energies between 1 and 20 electron volts. Here it is shown that reactions of such electrons, even at energies well below ionization thresholds, induce substantial yields of single- and double-strand breaks in DNA, which are caused by rapid decays of transient molecular resonances localized on the DNA's basic components. This finding presents a fundamental challenge to the traditional notion that genotoxic damage by secondary electrons can only occur at energies above the onset of ionization, or upon solvation when they become a slowly reacting chemical species.
Monodisperse FePt Nanoparticles and Ferromagnetic FePt Nanocrystal Superlattices
Authors: Sun Shouheng , Murray C. B. , Weller Dieter , Folks Liesl , Moser Andreas
Published: July 2002

Synthesis of monodisperse iron-platinum (FePt) nanoparticles by reduction of platinum acetylacetonate and decomposition of iron pentacarbonyl in the presence of oleic acid and oleyl amine stabilizers is reported. The FePt particle composition is readily controlled, and the size is tunable from 3- to 10-nanometer diameter with a standard deviation of less than 5%. These nanoparticles self-assemble into three-dimensional superlattices. Thermal annealing converts the internal particle structure from a chemically disordered face-centered cubic phase to the chemically ordered face-centered tetragonal phase and transforms the nanoparticle superlattices into ferromagnetic nanocrystal assemblies. These assemblies are chemically and mechanically robust and can support high-density magnetization reversal transitions.
Resonant Oscillations Between the Solid Earth and the Atmosphere
Authors: Nishida Kiwamu , Kobayashi Naoki , Fukao Yoshio
Published: July 2002

Continuously excited free oscillations of the whole Earth have been found in the ground noise in a frequency band of long-period surface waves. Here we report evidence of an annual variation of this phenomenon, indicating that the excitation source is not within the solid Earth. There is evidence that these seismic free oscillations resonate with acoustic free oscillations of the atmosphere. The observed amplitudes suggest that the excitation source is at or just above Earth's surface.
Atomic Layer Deposition of Oxide Thin Films with Metal Alkoxides as Oxygen Sources
Authors: Ritala Mikko , Kukli Kaupo , Rahtu Antti , Räisänen Petri I. , Leskelä Markku , Sajavaara Timo , Keinonen Juhani
Published: July 2002

A chemical approach to atomic layer deposition (ALD) of oxide thin films is reported here. Instead of using water or other compounds for an oxygen source, oxygen is obtained from a metal alkoxide, which serves as both an oxygen and a metal source when it reacts with another metal compound such as a metal chloride or a metal alkyl. These reactions generally enable deposition of oxides of many metals. With this approach, an alumina film has been deposited on silicon without creating an interfacial silicon oxide layer that otherwise forms easily. This finding adds to the other benefits of the ALD method, especially the atomic-level thickness control and excellent uniformity, and takes a major step toward the scientifically challenging and technologically important task of replacing silica as the gate dielectric in the future generations of metal oxide semiconductor field effect transistors.
Seeing the Herpesvirus Capsid at 8.5 Å
Authors: Zhou Z. Hong , Dougherty Matthew , Jakana Joanita , He Jing , Rixon Frazer J. , Chiu Wah
Published: July 2002

Human herpesviruses are large and structurally complex viruses that cause a variety of diseases. The three-dimensional structure of the herpesvirus capsid has been determined at 8.5 angstrom resolution by electron cryomicroscopy. More than 30 putative α helices were identified in the four proteins that make up the 0.2 billion–dalton shell. Some of these helices are located at domains that undergo conformational changes during capsid assembly and DNA packaging. The unique spatial arrangement of the heterotrimer at the local threefold positions accounts for the asymmetric interactions with adjacent capsid components and the unusual co-dependent folding of its subunits.
A Close-Up Look at Io from Galileo's Near-Infrared Mapping Spectrometer
Authors: Lopes-Gautier Rosaly , Douté S. , Smythe W. D. , Kamp L. W. , Carlson R. W. , Davies A. G. , Leader F. E. , McEwen A. S. , Geissler P. E. , Kieffer S. W. , Keszthelyi L. , Barbinis E. , Mehlman R. , Segura M. , Shirley J. , Soderblom L. A.
Published: July 2002

Infrared spectral images of Jupiter's volcanic moon Io, acquired during the October and November 1999 and February 2000 flybys of the Galileo spacecraft, were used to study the thermal structure and sulfur dioxide distribution of active volcanoes. Loki Patera, the solar system's most powerful known volcano, exhibits large expanses of dark, cooling lava on its caldera floor. Prometheus, the site of long-lived plume activity, has two major areas of thermal emission, which support ideas of plume migration. Sulfur dioxide deposits were mapped at local scales and show a more complex relationship to surface colors than previously thought, indicating the presence of other sulfur compounds.
Discovery of Gaseous S
2
in Io's Pele Plume
Authors: Spencer John R. , Jessup Kandis Lea , McGrath Melissa A. , Ballester Gilda E. , Yelle Roger
Published: July 2002

Spectroscopy of Io's Pele plume against Jupiter by the Hubble Space Telescope in October 1999 revealed absorption due to S
2
gas, with a column density of 1.0 ± 0.2 × 10
16
per square centimeter, and probably also SO
2
gas with a column density of 7 ± 3 × 10
16
per square centimeter. This SO
2
/S
2
ratio (3 to 12) is expected from equilibration with silicate magmas near the quartz-fayalite-magnetite or wüstite-magnetite buffers. Condensed S
3
and S
4
, probable coloring agents in Pele's red plume deposits, may form by polymerization of the S
2
, which is unstable to ultraviolet photolysis. Diffuse red deposits near other Io volcanoes suggest that venting and polymerization of S
2
gas is a widespread feature of Io volcanism.
Field Measurement of Slow Metamorphic Reaction Rates at Temperatures of 500° to 600°C
Authors: Baxter Ethan F. , DePaolo Donald J.
Published: July 2002

High-temperature metamorphic reaction rates were measured using strontium isotopic ratios of garnet and whole rock from a field site near Simplon Pass, Switzerland. For metamorphic conditions of cooling from 612° ± 17°C to 505° ± 15°C at pressures up to 9.1 kilobars, the inferred bulk fluid-rock exchange rate is 1.3
−0.4
+1.1
× 10
−7
grams of solid reacted per gram of solid per year, several orders of magnitude lower than laboratory-based estimates. The inferred reaction rate suggests that mineral chemistry may lag the evolving conditions in Earth's crust during mountain building.
A Metalloprotease Disintegrin That Controls Cell Migration in
Caenorhabditis elegans
Authors: Nishiwaki Kiyoji , Hisamoto Naoki , Matsumoto Kunihiro
Published: July 2002

In
Caenorhabditis elegans
, the gonad acquires two U-shaped arms by the directed migration of its distal tip cells (DTCs) along the body wall basement membranes. Correct migration of DTCs requires the
mig-17
gene, which encodes a member of the metalloprotease-disintegrin protein family. The MIG-17 protein is secreted from muscle cells of the body wall and localizes in the basement membranes of gonad. This localization is dependent on the disintegrin-like domain of MIG-17 and its catalytic activity. These results suggest that the MIG-17 metalloprotease directs migration of DTCs by remodeling the basement membrane.
The Chi-Chi Earthquake Sequence: Active, Out-of-Sequence Thrust Faulting in Taiwan
Authors: Kao Honn , Chen Wang-Ping
Published: July 2002

We combined precise focal depths and fault plane solutions of more than 40 events from the 20 September 1999 Chi-Chi earthquake sequence with a synthesis of subsurface geology to show that the dominant structure for generating earthquakes in central Taiwan is a moderately dipping (20° to 30°) thrust fault away from the deformation front. A second, subparallel seismic zone lies about 15 kilometers below the main thrust. These seismic zones differ from previous models, indicating that both the basal decollement and relic normal faults are aseismic.
Causes of Climate Change Over the Past 1000 Years
Authors: Crowley Thomas J.
Published: July 2002

Recent reconstructions of Northern Hemisphere temperatures and climate forcing over the past 1000 years allow the warming of the 20th century to be placed within a historical context and various mechanisms of climate change to be tested. Comparisons of observations with simulations from an energy balance climate model indicate that as much as 41 to 64% of preanthropogenic (pre-1850) decadal-scale temperature variations was due to changes in solar irradiance and volcanism. Removal of the forced response from reconstructed temperature time series yields residuals that show similar variability to those of control runs of coupled models, thereby lending support to the models' value as estimates of low-frequency variability in the climate system. Removal of all forcing except greenhouse gases from the ∼1000-year time series results in a residual with a very large late-20th-century warming that closely agrees with the response predicted from greenhouse gas forcing. The combination of a unique level of temperature increase in the late 20th century and improved constraints on the role of natural variability provides further evidence that the greenhouse effect has already established itself above the level of natural variability in the climate system. A 21st-century global warming projection far exceeds the natural variability of the past 1000 years and is greater than the best estimate of global temperature change for the last interglacial.
A Neural Basis for General Intelligence
Authors: Duncan John , Seitz Rüdiger J. , Kolodny Jonathan , Bor Daniel , Herzog Hans , Ahmed Ayesha , Newell Fiona N. , Emslie Hazel
Published: July 2002

Universal positive correlations between different cognitive tests motivate the concept of “general intelligence” or Spearman's
g
. Here the neural basis for
g
is investigated by means of positron emission tomography. Spatial, verbal, and perceptuo-motor tasks with high-
g
involvement are compared with matched low-
g
control tasks. In contrast to the common view that
g
reflects a broad sample of major cognitive functions, high-
g
tasks do not show diffuse recruitment of multiple brain regions. Instead they are associated with selective recruitment of lateral frontal cortex in one or both hemispheres. Despite very different task content in the three high-
g
–low-
g
contrasts, lateral frontal recruitment is markedly similar in each case. Many previous experiments have shown these same frontal regions to be recruited by a broad range of different cognitive demands. The results suggest that “general intelligence” derives from a specific frontal system important in the control of diverse forms of behavior.
Primates--A Natural Heritage of Conflict Resolution
Authors: de Waal Frans B. M.
Published: July 2002

The traditional notion of aggression as an antisocial instinct is being replaced by a framework that considers it a tool of competition and negotiation. When survival depends on mutual assistance, the expression of aggression is constrained by the need to maintain beneficial relationships. Moreover, evolution has produced ways of countering its disruptive consequences. For example, chimpanzees kiss and embrace after fights, and other nonhuman primates engage in similar “reconciliations.” Theoretical developments in this field carry implications for human aggression research. From families to high schools, aggressive conflict is subject to the same constraints known of cooperative animal societies. It is only when social relationships are valued that one can expect the full complement of natural checks and balances.
Phosphate Depletion in the Western North Atlantic Ocean
Authors: Wu Jingfeng , Sunda William , Boyle Edward A. , Karl David M.
Published: July 2002

Surface waters of the subtropical Sargasso Sea contain dissolved inorganic phosphate (DIP) concentrations of 0.2 to 1.0 nanomolar, which are sufficiently low to result in phosphorus control of primary production. The DIP concentrations in this area (which receives high inputs of iron-rich dust from arid regions of North Africa) are one to two orders of magnitude lower than surface levels in the North Pacific (where eolian iron inputs are much lower and water column denitrification is much more substantial). These data indicate a severe relative phosphorus depletion in the Atlantic. We hypothesize that nitrogen versus phosphorus limitation of primary production in the present-day ocean may be closely linked to iron supply through control of dinitrogen (N
2
) fixation, an iron-intensive metabolic process. Although the oceanic phosphorus inventory may set the upper limit for the total amount of organic matter produced in the ocean over geological time scales, at any instant in geological time, oceanic primary production may fall below this limit because of a persistent insufficient iron supply. By controlling N
2
fixation, iron may control not only nitrogen versus phosphorus limitation but also carbon fixation and export stoichiometry and hence biological sequestration of atmospheric carbon dioxide.
Magnetic Vortex Core Observation in Circular Dots of Permalloy
Authors: Shinjo T. , Okuno T. , Hassdorf R. , Shigeto † K. , Ono T.
Published: July 2002

Spin structures of nanoscale magnetic dots are the subject of increasing scientific effort, as the confinement of spins imposed by the geometrical restrictions makes these structures comparable to some internal characteristic length scales of the magnet. For a vortex (a ferromagnetic dot with a curling magnetic structure), a spot of perpendicular magnetization has been theoretically predicted to exist at the center of the vortex. Experimental evidence for this magnetization spot is provided by magnetic force microscopy imaging of circular dots of permalloy (Ni
80
Fe
20
) 0.3 to 1 micrometer in diameter and 50 nanometers thick.
A High-Resolution Millennial Record of the South Asian Monsoon from Himalayan Ice Cores
Authors: Thompson L. G. , Yao T. , Mosley-Thompson E. , Davis M. E. , Henderson K. A. , Lin P.-N.
Published: July 2002

A high-resolution ice core record from Dasuopu, Tibet, reveals that this site is sensitive to fluctuations in the intensity of the South Asian Monsoon. Reductions in monsoonal intensity are recorded by dust and chloride concentrations. The deeper, older sections of the Dasuopu cores suggest many other periods of drought in this region, but none have been of greater intensity than the greatest recorded drought, during 1790 to 1796 A.D. of the last millennium. The 20th century increase in anthropogenic activity in India and Nepal, upwind from this site, is recorded by a doubling of chloride concentrations and a fourfold increase in dust. Like other ice cores from the Tibetan Plateau, Dasuopu suggests a large-scale, plateau-wide 20th-century warming trend that appears to be amplified at higher elevations.
Glomalean Fungi from the Ordovician
Authors: Redecker Dirk , Kodner Robin , Graham Linda E.
Published: July 2002

Fossilized fungal hyphae and spores from the Ordovician of Wisconsin (with an age of about 460 million years) strongly resemble modern arbuscular mycorrhizal fungi (Glomales, Zygomycetes). These fossils indicate that Glomales-like fungi were present at a time when the land flora most likely only consisted of plants on the bryophytic level. Thus, these fungi may have played a crucial role in facilitating the colonization of land by plants, and the fossils support molecular estimates of fungal phylogeny that place the origin of the major groups of terrestrial fungi (Ascomycota, Basidiomycota, and Glomales) around 600 million years ago.
The Productive Conformation of Arachidonic Acid Bound to Prostaglandin Synthase
Authors: Malkowski M. G. , Ginell S. L. , Smith W. L. , Garavito R. M.
Published: July 2002

Prostaglandin H synthase-1 and -2 (PGHS-1 and -2) catalyze the committed step in prostaglandin synthesis and are targets for nonsteroidal anti-inflammatory drugs (NSAIDs) like aspirin. We have determined the structure of PGHS-1 at 3 angstrom resolution with arachidonic acid (AA) bound in a chemically productive conformation. The fatty acid adopts an extended L-shaped conformation that positions the 13pro
S
hydrogen of AA for abstraction by tyrosine-385, the likely radical donor. A space also exists for oxygen addition on the antarafacial surface of the carbon in the 11-position (C-11). While this conformation allows endoperoxide formation between C-11 and C-9, it also implies that a subsequent conformational rearrangement must occur to allow formation of the C-8/C-12 bond and to position C-15 for attack by a second molecule of oxygen.
Allosteric Effects of Pit-1 DNA Sites on Long-Term Repression in Cell Type Specification
Authors: Scully Kathleen M. , Jacobson Eric M. , Jepsen Kristen , Lunyak Victoria , Viadiu Hector , Carrière Catherine , Rose David W. , Hooshmand Farideh , Aggarwal Aneel K. , Rosenfeld Michael G.
Published: July 2002

Reciprocal gene activation and restriction during cell type differentiation from a common lineage is a hallmark of mammalian organogenesis. A key question, then, is whether a critical transcriptional activator of cell type–specific gene targets can also restrict expression of the same genes in other cell types. Here, we show that whereas the pituitary-specific POU domain factor Pit-1 activates growth hormone gene expression in one cell type, the somatotrope, it restricts its expression from a second cell type, the lactotrope. This distinction depends on a two–base pair spacing in accommodation of the bipartite POU domains on a conserved growth hormone promoter site. The allosteric effect on Pit-1, in combination with other DNA binding factors, results in the recruitment of a corepressor complex, including nuclear receptor corepressor N-CoR, which, unexpectedly, is required for active long-term repression of the growth hormone gene in lactotropes.
Sediments at the Top of Earth's Core
Authors: Buffett Bruce A. , Garnero Edward J. , Jeanloz Raymond
Published: July 2002

Unusual physical properties at the core-mantle boundary have been inferred from seismic and geodetic observations in recent years. We show how both types of observations can be explained by a layer of silicate sediments, which accumulate at the top of the core as Earth cools. Compaction of the sediments expels most of the liquid iron but leaves behind a small amount of core material, which is entrained in mantle convection and may account for the isotopic signatures of core material in some hot spot plumes. Extraction of light elements from the liquid core also enhances the vigor of convection in the core and may increase the power available to the geodynamo.
Disruption of Signaling by
Yersinia
Effector YopJ, a Ubiquitin-Like Protein Protease
Authors: Orth Kim , Xu Zhaohui , Mudgett Mary Beth , Bao Zhao Qin , Palmer Lance E. , Bliska James B. , Mangel Walter F. , Staskawicz Brian , Dixon Jack E.
Published: July 2002

Homologs of the
Yersinia
virulence effector YopJ are found in both plant and animal bacterial pathogens, as well as plant symbionts. These YopJ family members were shown to act as cysteine proteases. The catalytic triad of the protease was required for inhibition of the mitogen-activated protein kinase (MAPK) and nuclear factor κB (NF-κB) signaling in animal cells and for induction of localized cell death in plants. The substrates for YopJ were shown to be highly conserved ubiquitin-like molecules, which are covalently added to numerous regulatory proteins. YopJ family members exert their pathogenic effect on cells by disrupting this posttranslational modification.
Coding the Location of the Arm by Sight
Authors: Graziano Michael S. A. , Cooke Dylan F. , Taylor Charlotte S. R.
Published: July 2002

Area 5 in the parietal lobe of the primate brain is thought to be involved in monitoring the posture and movement of the body. In this study, neurons in monkey area 5 were found to encode the position of the monkey's arm while it was covered from view. The same neurons also responded to the position of a visible, realistic false arm. The neurons were not sensitive to the sight of unrealistic substitutes for the arm and were able to distinguish a right from a left arm. These neurons appear to combine visual and somatosensory signals in order to monitor the configuration of the limbs. They could form the basis of the complex body schema that we constantly use to adjust posture and guide movement.
Effectiveness of Parks in Protecting Tropical Biodiversity
Authors: Bruner Aaron G. , Gullison Raymond E. , Rice Richard E. , da Fonseca Gustavo A. B.
Published: July 2002

We assessed the impacts of anthropogenic threats on 93 protected areas in 22 tropical countries to test the hypothesis that parks are an effective means to protect tropical biodiversity. We found that the majority of parks are successful at stopping land clearing, and to a lesser degree effective at mitigating logging, hunting, fire, and grazing. Park effectiveness correlates with basic management activities such as enforcement, boundary demarcation, and direct compensation to local communities, suggesting that even modest increases in funding would directly increase the ability of parks to protect tropical biodiversity.
A Three-Dimensional Synthetic Metallic Crystal Composed of Single-Component Molecules
Authors: Tanaka Hisashi , Okano Yoshinori , Kobayashi Hayao , Suzuki Wakako , Kobayashi Akiko
Published: July 2002

Molecular metals normally require charge transfer between two different chemical species. We prepared crystals of [Ni(tmdt)
2
] (tmdt, trimethylenetetrathiafulvalenedithiolate) and carried out crystal structure analyses and resistivity measurements. The analyses and measurements revealed that these single-component molecular crystals are metallic from room temperature down to 0.6 kelvin. Ab initio molecular orbital calculations suggested that π molecular orbitals form conduction bands. The compact molecular arrangement, intermolecular overlap integrals of the highest occupied and lowest unoccupied molecular orbitals, and tight-binding electronic band structure calculation revealed that [Ni(tmdt)
2
] is a three-dimensional synthetic metal composed of planar molecules.
Impact of Polymer Tether Length on Multiple Ligand-Receptor Bond Formation
Authors: Jeppesen Claus , Wong Joyce Y. , Kuhl Tonya L. , Israelachvili Jacob N. , Mullah Nasreen , Zalipsky Samuel , Marques Carlos M.
Published: July 2002

The promoters of cell adhesion are ligands, which are often attached to flexible tethers that bind to surface receptors on adjacent cells. Using a combination of Monte Carlo simulations, diffusion reaction theory, and direct experiments (surface force measurements) of the biotin-streptavidin system, we have quantified polymer chain dynamics and the kinetics and spatial range of tethered ligand-receptor binding. The results show that the efficiency of strong binding does not depend solely on the molecular architecture or binding energy of the receptor-ligand pair, nor on the equilibrium configuration of the polymer tether, but rather on its “rare” extended conformations.
Allergy, Parasites, and the Hygiene Hypothesis
Authors: Yazdanbakhsh Maria , Kremsner Peter G. , van Ree Ronald
Published: July 2002

The increase of allergic diseases in the industrialized world has often been explained by a decline in infections during childhood. The immunological explanation has been put into the context of the functional T cell subsets known as T helper 1 (T
H
1) and T helper 2 (T
H
2) that display polarized cytokine profiles. It has been argued that bacterial and viral infections during early life direct the maturing immune system toward T
H
1, which counterbalance proallergic responses of T
H
2 cells. Thus, a reduction in the overall microbial burden will result in weak T
H
1 imprinting and unrestrained T
H
2 responses that allow an increase in allergy. This notion is contradicted by observations that the prevalence of T
H
1-autoimmune diseases is also increasing and that T
H
2-skewed parasitic worm (helminth) infections are not associated with allergy. More recently, elevations of anti-inflammatory cytokines, such as interleukin-10, that occur during long-term helminth infections have been shown to be inversely correlated with allergy. The induction of a robust anti-inflammatory regulatory network by persistent immune challenge offers a unifying explanation for the observed inverse association of many infections with allergic disorders.
Substrate Specificities of MexAB-OprM, MexCD-OprJ, and MexXY-OprM Efflux Pumps in
Pseudomonas aeruginosa
Authors: Masuda Nobuhisa , Sakagawa Eiko , Ohya Satoshi , Gotoh Naomasa , Tsujimoto Hideto , Nishino Takeshi
Published: July 2002

To find the exact substrate specificities of three species of tripartite efflux systems of
Pseudomonas aeruginosa
, MexAB-OprM, MexCD-OprJ, and MexXY-OprM, we constructed a series of isogenic mutants, each of which constitutively overproduced one of the three efflux systems and lacked the other two, and their isogenic mutants, which lacked all these systems. Comparison of the susceptibilities of the constructed mutants to 52 antimicrobial agents belonging to various groups suggested the following substrate specificities. All of the efflux systems extrude a wide variety of antimicrobial agent groups, i.e., quinolones, macrolides, tetracyclines, lincomycin, chloramphenicol, most penicillins (all but carbenicillin and sulbenicillin), most cephems (all but cefsulodin and ceftazidime), meropenem, and S-4661, but none of them extrude polymyxin B or imipenem. Extrusion of aminoglycosides is specific to MexXY-OprM, and extrusion of a group of the β-lactams, i.e., carbenicillin, sulbenicillin, ceftazidime, moxalactam, and aztreonam, is specific to MexAB-OprM. Moreover, MexAB-OprM and MexCD-OprJ extrude novobiocin, cefsulodin, and flomoxef, while MexXY-OprM does not. These substrate specificities are distinct from those reported previously.
Quinupristin-Dalfopristin Resistance among Gram-Positive Bacteria in Taiwan
Authors: Luh Kwen-Tay , Hsueh Po-Ren , Teng Lee-Jene , Pan Hui-Ju , Chen Yu-Chi , Lu Jang-Jih , Wu Jiunn-Jong , Ho Shen-Wu
Published: July 2002

To understand quinupristin-dalfopristin resistance among clinical isolates of gram-positive bacteria in Taiwan, where this agent is not yet available for clinical use, we evaluated 1,287 nonduplicate isolates recovered from January 1996 to December 1999 for in vitro susceptibility to quinupristin-dalfopristin and other newer antimicrobial agents. All methicillin-susceptible
Staphylococcus aureus
(MSSA) isolates were susceptible to quinupristin-dalfopristin. High rates of nonsusceptibility to quinupristin-dalfopristin (MICs, ≥2 μg/ml) were demonstrated for the following organisms: methicillin-resistant
S. aureus
(MRSA) (31%), coagulase-negative staphylococci (CoNS) (16%),
Streptococcus pneumoniae
(8%), viridans group streptococci (51%), vancomycin-susceptible enterococci (85%), vancomycin-resistant
Enterococcus faecalis
(100%), vancomycin-resistant
Enterococcus faecium
(66%),
Leuconostoc
spp. (100%),
Lactobacillus
spp. (50%), and
Pediococcus
spp. (87%). All isolates of MSSA, MRSA,
S. pneumoniae
, and viridans group streptococci were susceptible to vancomycin and teicoplanin. The rates of nonsusceptibility to vancomycin and teicoplanin were 5 and 7%, respectively, for CoNS, ranging from 12 and 18% for
S. simulans
to 0 and 0% for
S. cohnii
and
S. auricularis
. Moxifloxacin and trovafloxacin had good activities against these isolates except for ciprofloxacin-resistant vancomycin-resistant enterococci and methicillin-resistant staphylococci. In Taiwan, virginiamycin has been used in animal husbandry for more than 20 years, which may contribute to the high rates of quinupristin-dalfopristin resistance.
Syringomycin E Inhibition of
Saccharomyces cerevisiae
: Requirement for Biosynthesis of Sphingolipids with Very-Long-Chain Fatty Acids and Mannose- and Phosphoinositol-Containing Head Groups
Authors: Stock Stephen D. , Hama Hiroko , Radding Jeffrey A. , Young Debra A. , Takemoto Jon Y.
Published: July 2002

Syringomycin E is an antifungal cyclic lipodepsinonapeptide that inhibits the growth of
Saccharomyces cerevisiae
by interaction with the plasma membrane. A screen conducted to find the yeast genes necessary for its fungicidal action identified two novel syringomycin E response genes,
SYR3
and
SYR4
. A
syr3
mutant allele was complemented by
ELO2
and
ELO3
. These genes encode enzymes that catalyze the elongation of sphingolipid very long chain fatty acids. Tetrad analysis showed that
SYR3
was
ELO2
. Strains with deletions of
SYR3/ELO2
and
ELO3
were resistant to syringomycin E, and lipid analyses of both mutants revealed shortened fatty acid chains and lower levels of sphingolipids.
SYR4
was identified by Tn
5
inactivation of genomic library plasmids that complemented a
syr4
mutant allele.
SYR4
was found to be identical to
IPT1
, which encodes the terminal sphingolipid biosynthetic enzyme, mannosyl-diinositolphosphoryl-ceramide synthase. Deletion Δ
syr4/ipt1
strains were viable, were resistant to syringomycin E, did not produce mannosyl-diinositolphosphoryl-ceramide, and accumulated mannosyl-inositolphosphoryl-ceramide. Accumulation of mannosyl-inositolphosphoryl-ceramide was not responsible for resistance since a temperature-sensitive secretory pathway mutant (

sec14-3
ts

) accumulated this sphingolipid and was sensitive to syringomycin E. Finally, Δ
csg1/sur1
and Δ
csg2
strains defective in the transfer of mannose to inositolphosphoryl-ceramide were resistant to syringomycin E. These findings show that syringomycin E growth inhibition of yeast is promoted by the production of sphingolipids with fully elongated fatty acid chains and the mannosyl and terminal phosphorylinositol moieties of the polar head group.
Occurrence of a
Salmonella enterica
Serovar Typhimurium DT104-Like Antibiotic Resistance Gene Cluster Including the
floR
Gene in
S. enterica
Serovar Agona
Authors: Cloeckaert Axel , Sidi Boumedine Karim , Flaujac Geraldine , Imberechts Hein , D'Hooghe Inge , Chaslus-Dancla Elisabeth
Published: July 2002

Recently a chromosomal locus possibly specific for
Salmonella enterica
serovar Typhimurium DT104 has been reported that contains a multiple antibiotic resistance gene cluster. Evidence is provided that
Salmonella enterica
serovar Agona strains isolated from poultry harbor a similar gene cluster including the newly described
floR
gene, conferring cross-resistance to chloramphenicol and florfenicol.
Mild Heating of Amphotericin B-Desoxycholate: Effects on Ultrastructure, In Vitro Activity and Toxicity, and Therapeutic Efficacy in Severe Candidiasis in Leukopenic Mice
Authors: van Etten Els W. M. , van Vianen Wim , Roovers Patty , Frederik Peter
Published: July 2002

Heated (20 min at 70°C) amphotericin B-desoxycholate (hAMB-DOC) was further characterized, as was another formulation obtained after centrifugation (60 min, 3000 ×
g
), hcAMB-DOC. Conventional AMB-DOC consisted of individual micelles (approximately 4 nm in diameter) and threadlike aggregated micelles, as revealed by cryo-transmission electron microscopy. For both hAMB-DOC and hcAMB-DOC, pleiomorphic cobweb structures were observed with a mean particle size of approximately 300 nm as determined by laser diffraction. The potent antifungal activity of AMB-DOC against
Candida albicans
is not reduced by heating. Effective killing of
C. albicans
(>99.9% within 6 h) was obtained at 0.1 mg/liter with each of the AMB formulations. For AMB-DOC, hAMB-DOC, and hcAMB-DOC, cation release (
86
Rb
+
) from
C. albicans
of ≥50% was observed at 0.8, 0.4, and 0.4 mg/liter, respectively. After heating of AMB-DOC, toxicity was reduced 16-fold as determined by red blood cell (RBC) lysis. For AMB-DOC, hAMB-DOC, and hcAMB-DOC, hemolysis of ≥50% was observed at 6.4, 102.4, and 102.4 mg/liter, respectively. In contrast, AMB-DOC and its derivates showed similar toxicities in terms of cation release from RBC. For AMB-DOC, hAMB-DOC, and hcAMB-DOC, cation release (
86
Rb
+
) of ≥50% was observed at 1.6, 0.8, and 0.8 mg/liter, respectively. In persistently leukopenic mice with severe invasive candidiasis, higher dosages of both hAMB-DOC and hcAMB-DOC were tolerated than those of conventional AMB-DOC (3 versus 0.8 mg/kg of body weight, respectively), resulting in significantly improved therapeutic efficacy. In conclusion, this new approach of heating AMB-DOC may be of great value for further optimizing the treatment of severe fungal infections.
Sodium Lauryl Sulfate Increases the Efficacy of a Topical Formulation of Foscarnet against Herpes Simplex Virus Type 1 Cutaneous Lesions in Mice
Authors: Piret Jocelyne , Désormeaux André , Cormier Hélène , Lamontagne Julie , Gourde Pierrette , Juhász Julianna , Bergeron Michel G.
Published: July 2002

The influence of sodium lauryl sulfate (SLS) on the efficacies of topical gel formulations of foscarnet against herpes simplex virus type 1 (HSV-1) cutaneous infection has been evaluated in mice. A single application of the gel formulation containing 3% foscarnet given 24 h postinfection exerted only a modest effect on the development of herpetic skin lesions. Of prime interest, the addition of 5% SLS to this gel formulation markedly reduced the mean lesion score. The improved efficacy of the foscarnet formulation containing SLS could be attributed to an increased penetration of the antiviral agent into the epidermis. In vitro, SLS decreased in a concentration-dependent manner the infectivities of herpesviruses for Vero cells. SLS also inhibited the HSV-1 strain F-induced cytopathic effect. Combinations of foscarnet and SLS resulted in subsynergistic to subantagonistic effects, depending on the concentration used. Foscarnet in phosphate-buffered saline decreased in a dose-dependent manner the viability of cultured human skin fibroblasts. This toxic effect was markedly decreased when foscarnet was incorporated into the polymer matrix. The presence of SLS in the gel formulations did not alter the viabilities of these cells. The use of gel formulations containing foscarnet and SLS could represent an attractive approach to the treatment of herpetic mucocutaneous lesions, especially those caused by acyclovir-resistant strains.
Effects of Amoxicillin, Gentamicin, and Moxifloxacin on the Hemolytic Activity of
Staphylococcus aureus
In Vitro and In Vivo
Authors: Worlitzsch Dieter , Kaygin Hayal , Steinhuber Andrea , Dalhoff Axel , Botzenhart Konrad , Döring Gerd
Published: July 2002

In
Staphylococcus aureus
infection hemolysis caused by the extracellular protein α-toxin encoded by
hla
is thought to contribute significantly to its multifactorial virulence. In vitro, subinhibitory concentrations of β-lactam antibiotics and fluoroquinolones increase the levels of
hla
and α-toxin expression, whereas aminoglycosides decrease the levels of
hla
and α-toxin expression. In the present study we investigated the effects of subinhibitory concentrations of amoxicillin, gentamicin, and moxifloxacin on
hla
and α-toxin expression and total hemolysis of
S. aureus
strain 8325-4, a high-level α-toxin producer, and its α-toxin-negative mutant, DU 1090, in vitro and in a rat model of chronic
S. aureus
infection. The levels of expression of
hla
and α-toxin and total hemolysis did not differ significantly when amoxicillin, gentamicin, or moxifloxacin was added to cultures of
S. aureus
strain 8325-4. In vivo, strain 8325-4 induced a significantly increased level of hemolysis in infected pouches compared to that in uninfected control pouches, but the hemolysis was reduced to control levels by treatment with doses of amoxicillin, gentamicin, or moxifloxacin that reduced bacterial numbers by 2 orders of magnitude. Additionally, the effects of subinhibitory concentrations of the three antibiotics on total hemolysis of four methicillin-resistant
S. aureus
and three methicillin-sensitive
S. aureus
(MSSA) clinical isolates were assessed in vitro. A significant increase in total hemolysis was observed for only one MSSA strain when it was treated with amoxicillin but not when it was treated with moxifloxacin or gentamicin. When purified α-toxin was incubated with purified human neutrophil elastase, α-toxin was cleaved nearly completely. The results suggest that the penicillin-induced increases in
S. aureus
α-toxin expression are strain dependent, that reduction of bacterial numbers in vivo counteracts this phenomenon effectively, and finally, that in localized
S. aureus
infections α-toxin activity is controlled by neutrophil elastase.
Effects of Cytokines and Fluconazole on the Activity of Human Monocytes against
Candida albicans
Authors: Baltch A. L. , Smith R. P. , Franke M. A. , Ritz W. J. , Michelsen P. B. , Bopp L. H.
Published: July 2002

This study evaluates the effects of cytokines, used singly and in combination, on the microbicidal activity of human monocyte-derived macrophages (MDM) against intracellular
Candida albicans
in the presence and absence of fluconazole. In the absence of fluconazole, the addition of tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), gamma interferon (IFN-γ), or IL-4 had no effect on the growth of
C. albicans
. In contrast, the addition of granulocyte-macrophage colony-stimulating factor (GM-CSF) resulted in decreased growth (
P
< 0.05), while the addition of IL-10 resulted in increased growth (
P
< 0.01). In the presence of fluconazole, only the addition of IFN-γ resulted in an increase in the growth of
C. albicans
. In the presence or absence of fluconazole, all cytokine combinations except IFN-γ plus GM-CSF caused significant decreases in growth (
P
< 0.01). IL-10 and IL-4 did not influence the activity of TNF-α or IL-1β. In the absence or presence of
C. albicans
the addition of fluconazole, all of the cytokines studied, and combinations of fluconazole and selected cytokines caused increases in nitric oxide (NO) production (
P
< 0.01). Similar observations were made for superoxide (O
2
−
) only in the presence of
C. albicans
. The greatest concentrations of NO and O
2
−
were produced when
C. albicans
alone was present in the assays. Our results demonstrate that in the presence of low concentrations of fluconazole (0.1 times the MIC), selected cytokines and their combinations significantly increase the microbicidal activity of MDM against intracellular
C. albicans
.
P-113
d
, an Antimicrobial Peptide Active against
Pseudomonas aeruginosa
, Retains Activity in the Presence of Sputum from Cystic Fibrosis Patients
Authors: Sajjan Umadevi S. , Tran Linh T. , Sole Nuria , Rovaldi Christopher , Akiyama Alan , Friden Phillip M. , Forstner Janet F. , Rothstein David M.
Published: July 2002

Antimicrobial peptides are a source of novel agents that could be useful for treatment of the chronic lung infections that afflict cystic fibrosis (CF) patients. Efficacy depends on antimicrobial activity against the major pathogens of CF patients,
Pseudomonas aeruginosa, Staphylococcus aureus
, and
Haemophilus influenzae
, in the environment of the CF patient's airway. We describe the in vitro efficacies of derivatives of histatins, which are histidine-rich peptides produced by the salivary glands of humans and higher primates. P-113, a peptide containing 12 of the 24 amino acid residues of the parent molecule, histatin 5, retained full antibacterial activity and had a good spectrum of activity in vitro against the prominent pathogens of CF patients. However, P-113 was not active in the presence of purulent sputum from CF patients. In contrast, P-113
d
, the mirror-image peptide with the amino acid residues in the
d
configuration, was stable in sputum, was as active as P-113 against pathogens of CF patients in the absence of sputum and retained significant activity in the presence of sputum from CF patients. Recombinant human DNase, which effectively liquefies sputum, enhanced the activity of P-113
d
in undiluted sputum against both exogenous (added) bacteria and endogenous bacteria. Because of its properties, P-113
d
shows potential as an inhalant in chronic suppressive therapy for CF patients.
Inhibition of Herpes Simplex Virus Reactivation by Dipyridamole
Authors: Tenser Richard B. , Gaydos Andrew , Hay Kathleen A.
Published: July 2002

Herpes simplex virus (HSV) reactivation from latency was investigated. Reactivation of thymidine kinase-negative HSV, which is defective for reactivation, was greatly enhanced by thymidine (TdR). The reactivation-enhancing effect of TdR was blocked by dipyridamole (DPM), a known nucleoside transport inhibitor. DPM also inhibited wild-type HSV reactivation, suggesting potential antiviral use.
Spontaneous Mutations That Confer Antibiotic Resistance in
Helicobacter pylori
Authors: Wang Ge , Wilson Trevor J. M. , Jiang Qin , Taylor Diane E.
Published: July 2002

In this study, we systematically examined in vitro frequencies and spectra of the spontaneous mutations in
Helicobacter pylori
that confer resistance to clarithromycin (Cla
r
), metronidazole (Mtz
r
), amoxicillin (Amx
r
), ciprofloxacin (Cip
r
), and rifampin (Rif
r
). The mutation rate of Rif
r
or Cip
r
determined in a fluctuation assay is 1 × 10
−8
to 2 × 10
−8
per cell per division. In contrast, the mutation rates of Cla
r
, Mtz
r
, and Amx
r
are much lower (<10
−9
). However, Mtz
r
mutants could be readily selected in vitro by using the serial passage method, suggesting that the mutagenic effect and selective effect of a sublethal dose of metronidazole contribute to the rapid development of Mtz
r
. Analysis of spontaneous Rif
r
, Cla
r
, and Cip
r
mutants confirmed previous results indicating that mutations within the
rpoB
gene, the 23S rRNA gene, and the
gyrA
gene, respectively, are responsible; also, several new mutant alleles were identified. Mtz
r
mutants resulted most frequently, but not always, from mutations in the
rdxA
gene. DNA fragments containing each mutant allele could readily transform susceptible
H. pylori
strains to resistance, confirming that each mutant allele is responsible for the resistance phenotype.
Comparison of Efficacies of Cysteine Protease Inhibitors against Five Strains of
Plasmodium falciparum
Authors: Singh Ajay , Rosenthal Philip J.
Published: July 2002

Falcipain-2, a cysteine protease and essential hemoglobinase of
Plasmodium falciparum
, is a potential antimalarial drug target. We compared the falcipain-2 sequences and sensitivities to cysteine protease inhibitors of five parasite strains that differ markedly in sensitivity to established antimalarial drugs. The sequence of falcipain-2 was highly conserved, and the sensitivities of all of the strains to falcipain-2 inhibitors were very similar. Thus, cross-resistance between cysteine protease inhibitors and other antimalarial agents is not expected in parasites that are now circulating and falcipain-2 remains a promising chemotherapeutic target.