bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of radiographic techniques (kVp and mAs) on image quality and patient doses in digital subtraction angiography
Authors: Gkanatsios Nikolaos A. , Huda Walter , Peters Keith R.
Published: October 2002

We investigated how varying the x‐ray tube voltage and image receptor input exposure affected image quality and patient radiation doses in interventional neuroradiologic imaging. Digital subtraction angiography (DSA) images were obtained of a phantom with 1 mm diameter vessels containing iodine at concentrations between 4.5 and 50 mg/cc. The detection threshold concentration of iodine was determined by inspecting DSA images obtained at a range of x‐ray tube voltages and input exposure levels. Surface doses were obtained from measured x‐ray tube output data, and corresponding values of energy imparted were determined using the exposure‐area product incident on the phantom. In one series of experiments, the air kerma at the image intensifier was varied between 0.44 μGy per frame and 8.8 μGy per frame at a constant x‐ray tube voltage of 70 kVp. In a second series of experiments, the tube voltage was varied between 50 and 100 kVp, and the mAs adjusted to maintain a constant exposure level at the input of the image intensifier. At a constant x‐ray tube voltage, the surface dose and energy imparted were directly proportional to the input exposure per frame used to acquire the DSA images. On our DSA system operated below 2.2 μGy per frame, the threshold iodine concentration was found to be proportional to which is in reasonable agreement with the theoretical prediction for a quantum noise limited imaging system. Above 2.2 μGy per frame, however, the threshold iodine concentration was proportional to indicating that increasing the input exposure above this value will only achieve modest improvements in image quality. At a constant image intensifier input exposure level, increasing the x‐ray tube voltage from 50 kVp to 100 kVp reduced the surface dose by a factor of 6.1, and the energy imparted by a factor of 3.5. The detection threshold iodine concentration was found to be proportional to where was 2.1 at 1.1 μGy per frame, and 1.6 at 3.9 μGy per frame. For clinical situations that can be modeled by a uniform phantom, reducing the x‐ray tube voltage rather than increasing the exposure level would best achieve improvements on our DSA imaging system performance.
Effects of constant frequency noise in magnetic resonance imaging with nonuniform k‐space sampling
Authors: Du Weiliang , Karczmar Gregory S. , Pan Xiaochuan
Published: October 2002

Magnetic resonance images can be compromised by constant frequency (CF) noise, such as radio frequency (RF) noise. We investigate the effects of CF noise in four imaging methods with nonuniform k‐space sampling: single‐shot echo‐planar imaging (EPI) with sinusoidal readout gradients, phase‐encoded echo‐planar spectroscopic imaging (EPSI) with sinusoidal readout gradients, projection–reconstruction imaging, and single‐shot spiral imaging. The characteristics of the CF artifacts in each imaging method are studied with numerical simulations. CF noise is found to cause artifacts of nonclassic forms in the reconstructed images. Specifically, dashed‐line, streak, and spiral patterns of CF noise appear in EPI/EPSI with sinusoidal readout gradients, projection–reconstruction imaging, and spiral imaging, respectively. The analytical expression for dashed‐line artifacts is found to be a weighted sum of Bessel functions and is verified with in vivo experiments. The CF artifacts can be removed during post‐processing by eliminating the noise spikes in the Fourier domain of the raw data.
The propagation of sound in narrow street canyons
Authors: Iu K. K. , Li K. M.
Published: October 2002

This paper addresses an important problem of predicting sound propagation in narrow street canyons with width less than 10 m, which are commonly found in a built-up urban district. Major noise sources are, for example, air conditioners installed on building facades and powered mechanical equipment for repair and construction work. Interference effects due to multiple reflections from building facades and ground surfaces are important contributions in these complex environments. Although the studies of sound transmission in urban areas can be traced back to as early as the 1960s, the resulting mathematical and numerical models are still unable to predict sound fields accurately in city streets. This is understandable because sound propagation in city streets involves many intriguing phenomena such as reflections and scattering at the building facades, diffusion effects due to recessions and protrusions of building surfaces, geometric spreading, and atmospheric absorption. This paper describes the development of a numerical model for the prediction of sound fields in city streets. To simplify the problem, a typical city street is represented by two parallel reflecting walls and a flat impedance ground. The numerical model is based on a simple ray theory that takes account of multiple reflections from the building facades. The sound fields due to the point source and its images are summed coherently such that mutual interference effects between contributing rays can be included in the analysis. Indoor experiments are conducted in an anechoic chamber. Experimental data are compared with theoretical predictions to establish the validity and usefulness of this simple model. Outdoor experimental measurements have also been conducted to further validate the model.
Inner hair cell loss and steady-state potentials from the inferior colliculus and auditory cortex of the chinchilla
Authors: Arnold Sally , Burkard Robert
Published: October 2002

Steady-state evoked potentials were measured from unanesthetized chinchillas both before and after carboplatin-induced selective inner hair cell loss. Recordings were made from both the inferior colliculus (IC) and the auditory cortex (AC). The steady-state potential was measured in the form of the envelope following response (EFR), obtained by presenting a two-tone stimulus (f1=2000 Hz; f2=2020, 2040, 2080, 2160, or 2320 Hz), and measuring the magnitude of the Fourier coefficient at the f2–f1 difference frequency. From the IC, precarboplatin, EFR amplitude vs difference tone frequency showed a bandpass pattern, with maximum amplitude at either 160 or 80 Hz, depending upon stimulus level. Postcarboplatin, the preferred difference frequency was 80 Hz for all stimulus levels. From the AC, EFR amplitude versus difference tone frequency also showed a bandpass pattern, with the maximum amplitude at 80 Hz both pre- and postcarboplatin. EFR amplitude from the IC was decreased for some conditions postcarboplatin, while the amplitude from the AC showed no significant change.
ATR Homolog Mec1 Promotes Fork Progression, Thus Averting Breaks in Replication Slow Zones
Authors: Cha Rita S. , Kleckner Nancy
Published: October 2002

Budding yeast Mec1, homolog of mammalian ATR, is an essential protein that mediates S-phase checkpoint responses and meiotic recombination. Elimination of Mec1 function leads to genomewide fork stalling followed by chromosome breakage. Breaks do not result from stochastic collapse of stalled forks or other incidental lesions; instead, they occur in specific regions of the genome during a G
2
chromosomal transition. Break regions are found to be genetically encoded replication slow zones (
RSZ
s), a newly discovered yeast chromosomal determinant. Thus, Mec1 has important functions in normal S phase and the genome instability of
mec1
(and, analogously,
ATR
−/−
) mutants stems from defects in these basic roles.
Plant Development: Regulation by Protein Degradation
Authors: Hellmann Hanjo , Estelle Mark
Published: October 2002

Many aspects of eukaryotic development depend on regulated protein degradation by the ubiquitin-proteasome pathway. This highly conserved pathway promotes covalent attachment of ubiquitin to protein substrates through the sequential action of three enzymes called a ubiquitin-activating enzyme (E1), a ubiquitin-conjugating enzyme (E2), and a ubiquitin-protein ligase (E3). Most ubiquitinated proteins are then targeted for degradation by the 26Sproteasome. Recent studies have also shown that the ubiquitin-related protein RUB/Nedd8 and the proteasome-related COP9 signalosome complex cooperate with the ubiquitin-proteasome pathway to promote protein degradation. Most of these components are conserved in all three eukaryotic kingdoms. However, the known targets of the pathway in plants, and the developmental processes they regulate, are specific to the plant kingdom.
C-O Bond Formation by Polyketide Synthases
Authors: Kwon Hyung-Jin , Smith Wyatt C. , Scharon A. Janelle , Hwang Sung Hee , Kurth Mark J. , Shen Ben
Published: October 2002

Polyketide synthases (PKSs) assemble the polyketide carbon backbone by sequential decarboxylative condensation of acyl coenzyme A (CoA) precursors, and the C–C bond-forming step in this process is catalyzed by the β-ketoacyl synthase (KS) domain or subunit. Genetic and biochemical characterization of the nonactin biosynthesis gene cluster from
Streptomyces griseus
revealed two KSs, NonJ and NonK, that are highly homologous to known KSs but catalyze sequential condensation of the acyl CoA substrates by forming C–O rather than C–C bonds. This chemistry can be used in PKS engineering to increase the scope and diversity of polyketide biosynthesis.
Selective and Efficient Platinum(0)-Carbene Complexes As Hydrosilylation Catalysts
Authors: Markó István E. , Stérin Sébastien , Buisine Olivier , Mignani Gérard , Branlard Paul , Tinant Bernard , Declercq Jean-Paul
Published: October 2002

The hydrosilylation reaction enables the production of silicon polymers. Platinum-carbene complexes are reported that catalyze the hydrosilylation reaction of alkenes with remarkable efficiency and exquisite selectivity and avoid the formation of platinum colloids. By-products, typically encountered with previous catalytic systems, are suppressed with these platinum derivatives.
Genetic Loci Affecting Resistance to Human Malaria Parasites in a West African Mosquito Vector Population
Authors: Niaré Oumou , Markianos Kyriacos , Volz Jennifer , Oduol Frederick , Touré Abdoulaye , Bagayoko Magaran , Sangaré Djibril , Traoré Sekou F. , Wang Rui , Blass Claudia , Dolo Guimogo , Bouaré Madama , Kafatos Fotis C. , Kruglyak Leonid , Touré Yeya T. , Vernick Kenneth D.
Published: October 2002

Successful propagation of the malaria parasite
Plasmodium falciparum
within a susceptible mosquito vector is a prerequisite for the transmission of malaria. A field-based genetic analysis of the major human malaria vector,
Anopheles gambiae
, has revealed natural factors that reduce the transmission of
P. falciparum
. Differences in
P. falciparum
oocyst numbers between mosquito isofemale families fed on the same infected blood indicated a large genetic component affecting resistance to the parasite, and genome-wide scanning in pedigrees of wild mosquitoes detected segregating resistance alleles. The apparently high natural frequency of resistance alleles suggests that malaria parasites (or a similar pathogen) exert a significant selective pressure on vector populations.
Predictive Identification of Exonic Splicing Enhancers in Human Genes
Authors: Fairbrother William G. , Yeh Ru-Fang , Sharp Phillip A. , Burge Christopher B.
Published: October 2002

Specific short oligonucleotide sequences that enhance pre-mRNA splicing when present in exons, termed exonic splicing enhancers (ESEs), play important roles in constitutive and alternative splicing. A computational method, RESCUE-ESE, was developed that predicts which sequences have ESE activity by statistical analysis of exon-intron and splice site composition. When large data sets of human gene sequences were used, this method identified 10 predicted ESE motifs. Representatives of all 10 motifs were found to display enhancer activity in vivo, whereas point mutants of these sequences exhibited sharply reduced activity. The motifs identified enable prediction of the splicing phenotypes of exonic mutations in human genes.
Chloroquine Resistance in
Plasmodium falciparum
Malaria Parasites Conferred by
pfcrt
Mutations
Authors: Sidhu Amar Bir Singh , Verdier-Pinard Dominik , Fidock David A.
Published: October 2002

Plasmodium falciparum
chloroquine resistance is a major cause of worldwide increases in malaria mortality and morbidity. Recent laboratory and clinical studies have associated chloroquine resistance with point mutations in the gene
pfcrt
. However, direct proof of a causal relationship has remained elusive and most models have posited a multigenic basis of resistance. Here, we provide conclusive evidence that mutant haplotypes of the
pfcrt
gene product of Asian, African, or South American origin confer chloroquine resistance with characteristic verapamil reversibility and reduced chloroquine accumulation.
pfcrt
mutations increased susceptibility to artemisinin and quinine and minimally affected amodiaquine activity; hence, these antimalarials warrant further investigation as agents to control chloroquine-resistant
falciparum
malaria.
Splay Fault Branching Along the Nankai Subduction Zone
Authors: Park Jin-Oh , Tsuru Tetsuro , Kodaira Shuichi , Cummins Phil R. , Kaneda Yoshiyuki
Published: October 2002

Seismic reflection profiles reveal steeply landward–dipping splay faults in the rupture area of the magnitude (M) 8.1 Tonankai earthquake in the Nankai subduction zone. These splay faults branch upward from the plate-boundary interface (that is, the subduction zone) at a depth of ∼10 kilometers, ∼50 to 55 kilometers landward of the trough axis, breaking through the upper crustal plate. Slip on the active splay fault may be an important mechanism that accommodates the elastic strain caused by relative plate motion.
How Mantle Slabs Drive Plate Tectonics
Authors: Conrad Clinton P. , Lithgow-Bertelloni Carolina
Published: October 2002

The gravitational pull of subducted slabs is thought to drive the motions of Earth's tectonic plates, but the coupling between slabs and plates is not well established. If a slab is mechanically attached to a subducting plate, it can exert a direct pull on the plate. Alternatively, a detached slab may drive a plate by exciting flow in the mantle that exerts a shear traction on the base of the plate. From the geologic history of subduction, we estimated the relative importance of “pull” versus “suction” for the present-day plates. Observed plate motions are best predicted if slabs in the upper mantle are attached to plates and generate slab pull forces that account for about half of the total driving force on plates. Slabs in the lower mantle are supported by viscous mantle forces and drive plates through slab suction.
Rotationally Resolved Infrared Spectrum of the Charge Transfer Complex [Ar-N
2
]
+
Authors: Linnartz H. , Verdes D. , Maier J. P.
Published: October 2002

Difficulties in preparing cluster ions for spectroscopic studies have limited our understanding of intermolecular forces in charged complexes that are typical of many reactive intermediates. Here, the infrared spectrum of the charge transfer complex [Ar–N
2
]
+
, recorded in a supersonic planar plasma with a tunable diode laser spectrometer, is presented. More than 70 adjacent rovibrational transitions were measured near 2272 wave numbers and assigned to the molecular nitrogen stretching fundamental in the
2
Σ
+
ground state of [Ar–N
2
]
+
. The accurate structural parameters that were determined confirm a linear structure and show that the major part of the charge is located at the argon atom. The latter result is surprising and implies a charge switch of the cationic center upon complexation.
Condensation of Semiconductor Microcavity Exciton Polaritons
Authors: Deng Hui , Weihs Gregor , Santori Charles , Bloch Jacqueline , Yamamoto Yoshihisa
Published: October 2002

A phase transition from a classical thermal mixed state to a quantum-mechanical pure state of exciton polaritons is observed in a GaAs multiple quantum-well microcavity from the decrease of the second-order coherence function. Supporting evidence is obtained from the observation of a nonlinear threshold behavior in the pump-intensity dependence of the emission, a polariton-like dispersion relation above threshold, and a decrease of the relaxation time into the lower polariton state. The condensation of microcavity exciton polaritons is confirmed.
Is the Universe a Universal Computer?
Authors: Mitchell Melanie
Published: October 2002

A New Kind of Science
. Stephen Wolfram. Wolfram Media, Champaign, IL, 2002. 1280 pp. $44.95, £40, C$69.95. ISBN 1-57955-008-8.

Wolfram argues that the best way to understand many systems in nature is to think in terms of simple programs instead of mathematical equations.
Dynamics of Hydrogen Bromide Dissolution in the Ground and Excited States
Authors: Hurley S. M. , Dermota T. E. , Hydutsky D. P. , Castleman A. W.
Published: October 2002

The dissolution of acids is one of the most fundamental solvation processes, and an important issue is the nature of the hydration complex resulting in ion pair formation. We used femtosecond pump-probe spectroscopy to show that five water molecules are necessary for complete dissolution of a hydrogen bromide molecule to form the contact ion pair H
+
·Br
–
(H
2
O)

n

in the electronic ground state. In smaller mixed clusters (
n
< 5), the ion pair formation can be photoinduced by electronic excitation.
Excess Polymorphisms in Genes for Membrane Proteins in
Plasmodium falciparum
Authors: Volkman Sarah K. , Hartl Daniel L. , Wirth Dyann F. , Nielsen Kaare M. , Choi Mehee , Batalov Serge , Zhou Yingyao , Plouffe David , Le Roch Karine G. , Abagyan Ruben , Winzeler Elizabeth A.
Published: October 2002

The detection of single-nucleotide polymorphisms in pathogenic microorganisms has normally been carried out by trial and error. Here we show that DNA hybridization with high-density oligonucleotide arrays provides rapid and convenient detection of single-nucleotide polymorphisms in
Plasmodium falciparum
, despite its exceptionally high adenine-thymine (AT) content (82%). A disproportionate number of polymorphisms are found in genes encoding proteins associated with the cell membrane. These genes are targets for only 22% of the oligonucleotide probes but account for 69% of the polymorphisms. Genetic variation is also enriched in subtelomeric regions, which account for 22% of the chromosome but 76% of the polymorphisms.
Large-Scale, Decelerating, Relativistic X-ray Jets from the Microquasar XTE J1550-564
Authors: Corbel S. , Fender R. P. , Tzioumis A. K. , Tomsick J. A. , Orosz J. A. , Miller J. M. , Wijnands R. , Kaaret P.
Published: October 2002

We have detected, at x-ray and radio wavelengths, large-scale moving jets from the microquasar XTE J1550–564. Plasma ejected from near the black hole traveled at relativistic velocities for at least 4 years. We present direct evidence for gradual deceleration in a relativistic jet. The broadband spectrum of the jets is consistent with synchrotron emission from high-energy (up to 10 tera–electron volts) particles that were accelerated in the shock waves formed within the relativistic ejecta or by the interaction of the jets with the interstellar medium. XTE J1550–564 offers a rare opportunity to study the dynamical evolution of relativistic jets on time scales inaccessible for active galactic nuclei jets, with implications for our understanding of relativistic jets from Galactic x-ray binaries and active galactic nuclei.
Particle Accelerators in the Hot Spots of Radio Galaxy 3C 445, Imaged with the VLT
Authors: Prieto M. Almudena , Brunetti Gianfranco , Mack Karl-Heinz
Published: October 2002

Hot spots (HSs) are regions of enhanced radio emission produced by supersonic jets at the tip of the radio lobes of powerful radio sources. Obtained with the Very Large Telescope (VLT), images of the HSs in the radio galaxy 3C 445 show bright knots embedded in diffuse optical emission distributed along the post-shock region created by the impact of the jet into the intergalactic medium. The observations reported here confirm that relativistic electrons are accelerated by Fermi-I acceleration processes in HSs. Furthermore, both the diffuse emission tracing the rims of the front shock and the multiple knots demonstrate the presence of additional continuous re-acceleration processes of electrons (Fermi-II).
G Protein-Coupled Receptors in
Anopheles gambiae
Authors: Hill Catherine A. , Fox A. Nicole , Pitts R. Jason , Kent Lauren B. , Tan Perciliz L. , Chrystal Mathew A. , Cravchik Anibal , Collins Frank H. , Robertson Hugh M. , Zwiebel Laurence J.
Published: October 2002

We used bioinformatic approaches to identify a total of 276 G protein–coupled receptors (GPCRs) from the
Anopheles gambiae
genome. These include GPCRs that are likely to play roles in pathways affecting almost every aspect of the mosquito's life cycle. Seventy-nine candidate odorant receptors were characterized for tissue expression and, along with 76 putative gustatory receptors, for their molecular evolution relative to
Drosophila melanogaster
. Examples of lineage-specific gene expansions were observed as well as a single instance of unusually high sequence conservation.
Evolution of Supergene Families Associated with Insecticide Resistance
Authors: Ranson Hilary , Claudianos Charles , Ortelli Federica , Abgrall Christelle , Hemingway Janet , Sharakhova Maria V. , Unger Maria F. , Collins Frank H. , Feyereisen René
Published: October 2002

The emergence of insecticide resistance in the mosquito poses a serious threat to the efficacy of many malaria control programs. We have searched the
Anopheles gambiae
genome for members of the three major enzyme families— the carboxylesterases, glutathione transferases, and cytochrome P450s—that are primarily responsible for metabolic resistance to insecticides. A comparative genomic analysis with
Drosophila melanogaster
reveals that a considerable expansion of these supergene families has occurred in the mosquito. Low gene orthology and little chromosomal synteny paradoxically contrast the easily identified orthologous groups of genes presumably seeded by common ancestors. In
A. gambiae
, the independent expansion of paralogous genes is mainly a consequence of the formation of clusters among locally duplicated genes. These expansions may reflect the functional diversification of supergene families consistent with major differences in the life history and ecology of these organisms. These data provide a basis for identifying the resistance-associated enzymes within these families. This will enable the resistance status of mosquitoes, flies, and possibly other holometabolous insects to be monitored. The analyses also provide the means for identifying previously unknown molecules involved in fundamental biological processes such as development.
Inversions and Gene Order Shuffling in
Anopheles gambiae
and
A. funestus
Authors: Sharakhov Igor V. , Serazin Andrew C. , Grushko Olga G. , Dana Ali , Lobo Neil , Hillenmeyer Maureen E. , Westerman Richard , Romero-Severson Jeanne , Costantini Carlo , Sagnon N'Fale , Collins Frank H. , Besansky Nora J.
Published: October 2002

In tropical Africa,
Anopheles funestus
is one of the three most important malaria vectors. We physically mapped 157
A. funestus
complementary DNAs (cDNAs) to the polytene chromosomes of this species. Sequences of the cDNAs were mapped in silico to the
A. gambiae
genome as part of a comparative genomic study of synteny, gene order, and sequence conservation between
A. funestus
and
A. gambiae
. These species are in the same subgenus and diverged about as recently as humans and chimpanzees. Despite nearly perfect preservation of synteny, we found substantial shuffling of gene order along corresponding chromosome arms. Since the divergence of these species, at least 70 chromosomal inversions have been fixed, the highest rate of rearrangement of any eukaryote studied to date. The high incidence of paracentric inversions and limited colinearity suggests that locating genes in one anopheline species based on gene order in another may be limited to closely related taxa.
Neuropeptides and Peptide Hormones in
Anopheles gambiae
Authors: Riehle Michael A. , Garczynski Stephen F. , Crim Joe W. , Hill Catherine A. , Brown Mark R.
Published: October 2002

The African malaria mosquito,
Anopheles gambiae
, is specialized for rapid completion of development and reproduction. A vertebrate blood meal is required for egg production, and multiple feedings subsequently allow transmission of malaria parasites,
Plasmodium
spp
.
Regulatory peptides from 35 genes annotated from the
A. gambiae
genome likely coordinate these and other physiological processes.
Plasmodium
parasites may affect actions of newly identified insulin-like peptides, which coordinate growth and reproduction of its vector,
A. gambiae
, as in
Drosophila melanogaster
,
Caenorhabditis elegans
, and mammals. This genomic information provides a basis to expand understanding of hematophagy and pathogen transmission in this mosquito.
Comparative Genome and Proteome Analysis of
Anopheles gambiae
and
Drosophila melanogaster
Authors: Zdobnov Evgeny M. , von Mering Christian , Letunic Ivica , Torrents David , Suyama Mikita , Copley Richard R. , Christophides George K. , Thomasova Dana , Holt Robert A. , Subramanian G. Mani , Mueller Hans-Michael , Dimopoulos George , Law John H. , Wells Michael A. , Birney Ewan , Charlab Rosane , Halpern Aaron L. , Kokoza Elena , Kraft Cheryl L. , Lai Zhongwu , Lewis Suzanna , Louis Christos , Barillas-Mury Carolina , Nusskern Deborah , Rubin Gerald M. , Salzberg Steven L. , Sutton Granger G. , Topalis Pantelis , Wides Ron , Wincker Patrick , Yandell Mark , Collins Frank H. , Ribeiro Jose , Gelbart William M. , Kafatos Fotis C. , Bork Peer
Published: October 2002

Comparison of the genomes and proteomes of the two diptera
Anopheles gambiae
and
Drosophila melanogaster
, which diverged about 250 million years ago, reveals considerable similarities. However, numerous differences are also observed; some of these must reflect the selection and subsequent adaptation associated with different ecologies and life strategies. Almost half of the genes in both genomes are interpreted as orthologs and show an average sequence identity of about 56%, which is slightly lower than that observed between the orthologs of the pufferfish and human (diverged about 450 million years ago). This indicates that these two insects diverged considerably faster than vertebrates. Aligned sequences reveal that orthologous genes have retained only half of their intron/exon structure, indicating that intron gains or losses have occurred at a rate of about one per gene per 125 million years. Chromosomal arms exhibit significant remnants of homology between the two species, although only 34% of the genes colocalize in small “microsyntenic” clusters, and major interarm transfers as well as intra-arm shuffling of gene order are detected.
Immunity-Related Genes and Gene Families in
Anopheles gambiae
Authors: Christophides George K. , Zdobnov Evgeny , Barillas-Mury Carolina , Birney Ewan , Blandin Stephanie , Blass Claudia , Brey Paul T. , Collins Frank H. , Danielli Alberto , Dimopoulos George , Hetru Charles , Hoa Ngo T. , Hoffmann Jules A. , Kanzok Stefan M. , Letunic Ivica , Levashina Elena A. , Loukeris Thanasis G. , Lycett Gareth , Meister Stephan , Michel Kristin , Moita Luis F. , Müller Hans-Michael , Osta Mike A. , Paskewitz Susan M. , Reichhart Jean-Marc , Rzhetsky Andrey , Troxler Laurent , Vernick Kenneth D. , Vlachou Dina , Volz Jennifer , von Mering Christian , Xu Jiannong , Zheng Liangbiao , Bork Peer , Kafatos Fotis C.
Published: October 2002

We have identified 242
Anopheles gambiae
genes from 18 gene families implicated in innate immunity and have detected marked diversification relative to
Drosophila melanogaster
. Immune-related gene families involved in recognition, signal modulation, and effector systems show a marked deficit of orthologs and excessive gene expansions, possibly reflecting selection pressures from different pathogens encountered in these insects' very different life-styles. In contrast, the multifunctional Toll signal transduction pathway is substantially conserved, presumably because of counterselection for developmental stability. Representative expression profiles confirm that sequence diversification is accompanied by specific responses to different immune challenges. Alternative RNA splicing may also contribute to expansion of the immune repertoire.
Explanations for the Birds and the Bees
Authors: Harvey Paul
Published: October 2002

Dr. Tatiana's Sex Advice to All Creation
. Olivia Judson. Chatto and Windus, London, 2002. 317 pp. £16.99. ISBN 0-7011-6925-7. Metropolitan, New York, 2002. 319 pp. $24, C$34.95. ISBN 0-8050-6331-5.

Judson offers a light-hearted but informed and informative survey of sexual practices in the animal kingdom.
A New Global Effort to Control Malaria
Authors: Sachs Jeffrey D.
Published: October 2002

The time has come to resurrect a worldwide effort to control malaria, following decades of neglect during which the disease has resurged in many parts of sub-Saharan Africa and other endemic regions.
The
Anopheles
Genome and Comparative Insect Genomics
Authors: Kaufman Thomas C. , Severson David W. , Robinson Gene E.
Published: October 2002

The
Anopheles gambiae
genome sequence, coupled with the
Drosophila melanogaster
genome sequence, provides a better understanding of the insects, a group that contains our friends, foes, and competitors.
The Mosquito Genome--a Breakthrough for Public Health
Authors: Morel Carlos M. , Touré Yeya T. , Dobrokhotov Boris
Published: October 2002

The
Anopheles gambiae
genome sequence will accelerate identification of new insect vector target genes leading to improved strategies for malaria control.
Malaria--a Shadow over Africa
Authors: Miller Louis H. , Greenwood Brian
Published: October 2002

Reduction in severe disease and death from
falciparum
malaria in Africa requires new, more effective and inexpensive public health measures. The completed genomes of
Plasmodium falciparum
and its vector
Anopheles gambiae
represent a big step toward the discovery of these needed tools.
An Overview of Insecticide Resistance
Authors: Hemingway Janet , Field Linda , Vontas John
Published: October 2002

Insecticide resistance poses a serious threat to current malaria control efforts. The
Anopheles gambiae
genome will enable identification of new resistance genes and will provide new molecular targets for the design of more effective insecticides.
Plasmodium
Chloroquine Resistance and the Search for a Replacement Antimalarial Drug
Authors: Wellems Thomas E.
Published: October 2002

Genetic and biochemical research is providing new information on the mechanism of chloroquine resistance. Drug discovery initiatives are finding new leads that have favorable pharmaceutical properties and efficacy against chloroquine-resistant malaria.
The
Plasmodium falciparum
Genome-- a Blueprint for Erythrocyte Invasion
Authors: Cowman Alan F. , Crabb Brendan S.
Published: October 2002

Erythrocyte invasion by
Plasmodium falciparum
involves multiple ligand-receptor interactions and numerous apparent redundancies. The genome sequence of this parasite reveals new gene families encoding proteins that appear to mediate erythrocyte invasion.
Speciation Within
Anopheles gambiae
-- the Glass Is Half Full
Authors: della Torre A. , Costantini C. , Besansky N. J. , Caccone A. , Petrarca V. , Powell J. R. , Coluzzi M.
Published: October 2002

Restrictions to gene flow among molecular forms of the mosquito
Anopheles gambiae sensu stricto
reveal an ongoing speciation process affecting the epidemiology of malaria in sub-Saharan Africa.
Malaria Control with Genetically Manipulated Insect Vectors
Authors: Alphey Luke , Beard C. Ben , Billingsley Peter , Coetzee Maureen , Crisanti Andrea , Curtis Chris , Eggleston Paul , Godfray Charles , Hemingway Janet , Jacobs-Lorena Marcelo , James Anthony A. , Kafatos Fotis C. , Mukwaya Louis G. , Paton Michael , Powell Jeffrey R. , Schneider William , Scott Thomas W. , Sina Barbara , Sinden Robert , Sinkins Steven , Spielman Andrew , Touré Yeya , Collins Frank H.
Published: October 2002

At a recent workshop, experts discussed the benefits, risks, and research priorities associated with using genetically manipulated insects in the control of vector-borne diseases.
The Ecology of Genetically Modified Mosquitoes
Authors: Scott Thomas W. , Takken Willem , Knols Bart G. J. , Boëte Christophe
Published: October 2002

Ecological and population biology issues constitute serious challenges to the application of genetically modified mosquitos (GMM) for disease control.
Antibiotic Resistance Genes and
Salmonella
Genomic Island 1 in
Salmonella enterica
Serovar Typhimurium Isolated in Italy
Authors: Carattoli Alessandra , Filetici Emma , Villa Laura , Dionisi Anna Maria , Ricci Antonia , Luzzi Ida
Published: October 2002

Fifty-four epidemiologically unrelated multidrug-resistant
Salmonella enterica
serovar Typhimurium isolates, collected between 1992 and 2000 in Italy, were analyzed for the presence of integrons. Strains were also tested for
Salmonella
genomic island 1 (SGI1), carrying antibiotic resistance genes in DT104 strains. A complete SGI1 was found in the majority of the DT104 strains. Two DT104 strains, showing resistance to streptomycin-spectinomycin and sulfonamides, carried a partially deleted SGI1 lacking the

flo
st

,
tetR
, and
tetA
genes, conferring chloramphenicol-florfenicol and tetracycline resistance, and the integron harboring the
pse-1
gene cassette, conferring ampicillin resistance. The presence of SGI1 was also observed in serovar Typhimurium strains belonging to other phage types, suggesting either the potential mobility of this genomic island or changes in the phage-related phenotype of DT104 strains.
Characterization of a Self-Transferable Plasmid from
Salmonella enterica
Serotype Typhimurium Clinical Isolates Carrying Two Integron-Borne Gene Cassettes Together with Virulence and Drug Resistance Genes
Authors: Guerra Beatriz , Soto Sara , Helmuth Reiner , Mendoza M. Carmen
Published: October 2002

An unusual self-transferable virulence-resistance plasmid (pUO-
St
VR2) was found in nine multidrug-resistant (ACSSuT phenotype)
Salmonella enterica
serotype Typhimurium clinical isolates that were assigned to four different phage types and a single and distinctive
Xba
I pulsed-field gel electrophoresis profile. pUO-
St
VR2 is an IncFII plasmid of about 140 kb in length carrying the
spvA
,
spvB
, and
spvC
(
Salmonella
plasmid virulence) and
rck
(resistance to complement killing) genes. It also carries the
oxa1/aadA1a
(ampicillin resistance and streptomycin-spectinomycin resistance) gene cassette configuration located within a class 1 integron with
qacEΔ1/sul1
(ammonium antiseptics resistance and sulfadiazine resistance); the transposon genes
merA
,
tnpA
, and
tnpR
(mercury resistance, transposase, and resolvase of Tn
21
, respectively); and the
catA1
(chloramphenicol resistance) and
tet
(B) (tetracycline resistance) genes. The insertion of resistance genes into a
Salmonella
virulence plasmid constitutes a new and interesting example of plasmid evolution and presents a serious public health problem.
Surveillance for Antiviral-Agent-Resistant Herpes Simplex Virus in the General Population with Recurrent Herpes Labialis
Authors: Bacon Teresa H. , Boon Ron J. , Schultz Margaret , Hodges-Savola Cheryl
Published: October 2002

In a general population survey in the United States, the prevalence of antiviral-agent-resistant herpes simplex virus was very low among more than 1,000 isolates from individuals with an episode of recurrent herpes labialis not treated with topical antiviral agents. Two isolates had borderline resistance to acyclovir (0.2%), and all were susceptible to penciclovir.
Role of
Pseudomonas putida
Indoleacetic Acid in Development of the Host Plant Root System
Authors: Patten Cheryl L. , Glick Bernard R.
Published: October 2002

Many plant-associated bacteria synthesize the phytohormone indoleacetic acid (IAA). While IAA produced by phytopathogenic bacteria, mainly by the indoleacetamide pathway, has been implicated in the induction of plant tumors, it is not clear whether IAA synthesized by beneficial bacteria, usually via the indolepyruvic acid pathway, is involved in plant growth promotion. To determine whether bacterial IAA enhances root development in host plants, the
ipdc
gene that encodes indolepyruvate decarboxylase, a key enzyme in the indolepyruvic acid pathway, was isolated from the plant growth-promoting bacterium
Pseudomonas putida
GR12-2 and an IAA-deficient mutant constructed by insertional mutagenesis. The canola seedling primary roots from seeds treated with wild-type
P. putida
GR12-2 were on average 35 to 50% longer than the roots from seeds treated with the IAA-deficient mutant and the roots from uninoculated seeds. In addition, exposing mung bean cuttings to high levels of IAA by soaking them in a suspension of the wild-type strain stimulated the formation of many, very small, adventitious roots. Formation of fewer roots was stimulated by treatment with the IAA-deficient mutant. These results suggest that bacterial IAA plays a major role in the development of the host plant root system.
Accumulation of Inorganic Polyphosphate in
phoU
Mutants of
Escherichia coli
and
Synechocystis
sp. Strain PCC6803
Authors: Morohoshi Tomohiro , Maruo Tatsuya , Shirai Yoko , Kato Junichi , Ikeda Tsukasa , Takiguchi Noboru , Ohtake Hisao , Kuroda Akio
Published: October 2002

The biological process for phosphate (P
i
) removal is based on the use of bacteria capable of accumulating inorganic polyphosphate (polyP). We obtained
Escherichia coli
mutants which accumulate a large amount of polyP. The polyP accumulation in these mutants was ascribed to a mutation of the
phoU
gene that encodes a negative regulator of the P
i
regulon. Insertional inactivation of the
phoU
gene also elevated the intracellular level of polyP in
Synechocystis
sp. strain PCC6803. The mutant could remove fourfold more P
i
from the medium than the wild-type strain removed.
Acute Septic Arthritis
Authors: Shirtliff Mark E. , Mader Jon T.
Published: October 2002

Acute septic arthritis may develop as a result of hematogenous seeding, direct introduction, or extension from a contiguous focus of infection. The pathogenesis of acute septic arthritis is multifactorial and depends on the interaction of the host immune response and the adherence factors, toxins, and immunoavoidance strategies of the invading pathogen.Neisseria gonorrhoeaeand Staphylococcus aureus are used in discussing the host-pathogen interaction in the pathogenesis of acute septic arthritis. While diagnosis rests on isolation of the bacterial species from synovial fluid samples, patient history, clinical presentation, laboratory findings, and imaging studies are also important. Acute nongonococcal septic arthritis is a medical emergency that can lead to significant morbidity and mortality. Therefore, prompt recognition, rapid and aggressive antimicrobial therapy, and surgical treatment are critical to ensuring a good prognosis. Even with prompt diagnosis and treatment, high mortality and morbidity rates still occur. In contrast, gonococcal arthritis is often successfully treated with antimicrobial therapy alone and demonstrates a very low rate of complications and an excellent prognosis for full return of normal joint function. In the case of prosthetic joint infections, the hardware must be eventually removed by a two-stage revision in order to cure the infection.
Atopic Dermatitis and Fungi
Authors: Faergemann Jan
Published: October 2002

Atopic dermatitis (AD) is a chronic, itching, inflammatory skin disease which is associated with asthma and/or hay fever and a familial occurrence of these conditions. Genetic factors are important in the development of AD, but the exact hereditary pathway is still unknown. Dry skin and the weakened barrier function in patients with AD is very important for the patient's reactions to irritants and other external trigger factors including microorganisms. The standard treatments are topical corticosteroids, topical immunomodulating agents, and emollients. If AD cannot be controlled by this type of treatment, systemic immunomodulating agents may be used. UVB, UVA, or psoralen-UVA may also be used for widespread severe lesions. However, some patients do not respond to these standard treatment, and then it is important to consider the role of microorganisms, house dust mites or food. The role of the Malassezia yeasts in AD, especially AD located to the head and neck region, is now documented in several papers. There are also several papers indicating the role of Candida as an aggravating factor in AD. Patients with AD also develop chronic dermatophyte infections more easily, and patients with AD and chronic dermatophyte infections may show improvement in their AD when treated with antifungal drugs.
Evolutionary and Historical Aspects of the Burden of Malaria
Authors: Carter Richard , Mendis Kamini N.
Published: October 2002

Malaria is among the oldest of diseases. In one form or another, it has infected and affected our ancestors since long before the origin of the human line. During our recent evolution, its influence has probably been greater than that of any other infectious agent. Here we attempt to trace the forms and impacts of malaria from a distant past through historical times to the present. In the last sections, we review the current burdens of malaria across the world and discuss present-day approaches to its management. Only by following, or attempting to follow, malaria throughout its evolution and history can we understand its character and so be better prepared for our future management of this ancient ill.
History of Human Parasitology
Authors: Cox F. E. G.
Published: October 2002

Humans are hosts to nearly 300 species of parasitic worms and over 70 species of protozoa, some derived from our primate ancestors and some acquired from the animals we have domesticated or come in contact with during our relatively short history on Earth. Our knowledge of parasitic infections extends into antiquity, and descriptions of parasites and parasitic infections are found in the earliest writings and have been confirmed by the finding of parasites in archaeological material. The systematic study of parasites began with the rejection of the theory of spontaneous generation and the promulgation of the germ theory. Thereafter, the history of human parasitology proceeded along two lines, the discovery of a parasite and its subsequent association with disease and the recognition of a disease and the subsequent discovery that it was caused by a parasite. This review is concerned with the major helminth and protozoan infections of humans: ascariasis, trichinosis, strongyloidiasis, dracunculiasis, lymphatic filariasis, loasis, onchocerciasis, schistosomiasis, cestodiasis, paragonimiasis, clonorchiasis, opisthorchiasis, amoebiasis, giardiasis, African trypanosomiasis, South American trypanosomiasis, leishmaniasis, malaria, toxoplasmosis, cryptosporidiosis, cyclosporiasis, and microsporidiosis.
What Happened to the Streptococci: Overview of Taxonomic and Nomenclature Changes
Authors: Facklam Richard
Published: October 2002

Since the division of the
Streptococcus genus
into enterococci, lactococci, and streptococci in 1984, many changes in the nomenclature and taxonomy of the
Streptococcus genus
have taken place. The application of genetic comparisons has improved the proper classification of the different species. The Lancefield system of serogrouping the streptococci by the expression of beta-hemolysis on blood agar plates is still very useful for the identification of streptococci for patient management. The Lancefield grouping system cannot be used in itself for accurate identification of specific beta-hemolytic species, but it can be a useful part of the identification procedure. Except for identification of the “
Streptococcus bovis
group” of species and
Streptococcus suis
, Lancefield grouping is of little value in identification of the non-beta-hemolytic streptococci and related genera. In fact, identification of the non-beta-hemolytic species is problematic for conventional as well as commercially available identification procedures. A combination of conventional tests and specific chromogenic tests suggested by several investigators is presented and discussed. Tables are included that suggest tests and procedures to guide investigators attempting to identify all the species.
Tularemia
Authors: Ellis Jill , Oyston Petra C. F. , Green Michael , Titball Richard W.
Published: October 2002

Francisella tularensis is the etiological agent of tularemia, a serious and occasionally fatal disease of humans and animals. In humans, ulceroglandular tularemia is the most common form of the disease and is usually a consequence of a bite from an arthropod vector which has previously fed on an infected animal. The pneumonic form of the disease occurs rarely but is the likely form of the disease should this bacterium be used as a bioterrorism agent. The diagnosis of disease is not straightforward.F. tularensisis difficult to culture, and the handling of this bacterium poses a significant risk of infection to laboratory personnel. Enzyme-linked immunosorbent assay- and PCR-based methods have been used to detect bacteria in clinical samples, but these methods have not been adequately evaluated for the diagnosis of pneumonic tularemia. Little is known about the virulence mechanisms ofF. tularensis, though there is a large body of evidence indicating that it is an intracellular pathogen, surviving mainly in macrophages. An unlicensed live attenuated vaccine is available, which does appear to offer protection against ulceroglandular and pneumonic tularemia. Although an improved vaccine against tularemia is highly desirable, attempts to devise such a vaccine have been limited by the inability to construct defined allelic replacement mutants and by the lack of information on the mechanisms of virulence ofF. tularensis. In the absence of a licensed vaccine, aminoglycoside antibiotics play a key role in the prevention and treatment of tularemia.
Interactions among Strategies Associated with Bacterial Infection: Pathogenicity, Epidemicity, and Antibiotic Resistance
Authors: Martínez José L. , Baquero Fernando
Published: October 2002

Infections have been the major cause of disease throughout the history of human populations. With the introduction of antibiotics, it was thought that this problem should disappear. However, bacteria have been able to evolve to become antibiotic resistant. Nowadays, a proficient pathogen must be virulent, epidemic, and resistant to antibiotics. Analysis of the interplay among these features of bacterial populations is needed to predict the future of infectious diseases. In this regard, we have reviewed the genetic linkage of antibiotic resistance and bacterial virulence in the same genetic determinants as well as the cross talk between antibiotic resistance and virulence regulatory circuits with the aim of understanding the effect of acquisition of resistance on bacterial virulence. We also discuss the possibility that antibiotic resistance and bacterial virulence might prevail as linked phenotypes in the future. The novel situation brought about by the worldwide use of antibiotics is undoubtedly changing bacterial populations. These changes might alter the properties of not only bacterial pathogens, but also the normal host microbiota. The evolutionary consequences of the release of antibiotics into the environment are largely unknown, but most probably restoration of the microbiota from the preantibiotic era is beyond our current abilities.