bluuebunny/crossref_metadata_2025_split huggingface dataset:
Clinical Experience With Headaches in Preadolescent Children
Authors: Pascual Julio , Berciano José 
Published: May 2005

We have reviewed the diagnoses of 654 children aged from 7 to 14 years who attended a neurologist for headache evaluation. Headaches beginning between the age of 7 and 14 represented a higher percentage (18.3%) than the proportion of preadolescent children in our health area (12.9%). Headaches were more common in girls; although cluster, posttraumatic, benign exertional headaches, and the only case of brainstem glioma were restricted to boys. Despite the female predominance, the proportion of males with migraine was significantly higher in the preadolescents than in the over 15 age group. Migraine accounted for the majority of diagnoses (609 ‐ 93% of the total series), while tension‐type headache (27 ‐ 4%), and headache associated with sinus infection (7 ‐ 1%) were the diagnoses which followed in frequency. There were only two headaches (0.3%) associated with intracranial masses.Even though, in terms of frequency, headache is a very common reason for neurology consultation, the present results show that the majority of preadolescents consulting because of headache suffer from benign conditions.
Amphibian Declines in Latin America: Widespread Population Declines, Extinctions, and Impacts1
Authors: Lips Karen R. , Burrowes Patricia A. , Mendelson Joseph R. , Parra‐Olea Gabriela 
Published: May 2005

ABSTRACTAmphibian populations are in decline throughout Latin America; all families of frogs have experienced declines, but the species associated with aquatic habitats in upland areas have been most affected. Declines in Latin America were most common during the 1980s, but new declines continue to be reported. The causes of declines are varied, but they have most often been associated with habitat loss, a pathogenic fungus, and climate change. Scientists are just beginning to grasp the ethical and biological implications of losses of this magnitude. In this Special Section, we provide a general summary of the phenomenon and introduce five contributed papers that provide new data and new insights into Latin American declines.
Predicting the Distribution of the Amphibian Pathogen Batrachochytrium dendrobatidis in the New World1
Authors: Ron Santiago R. 
Published: May 2005

ABSTRACTOne application of ecological niche modeling is predicting suitable areas for the establishment of invasive species. Herein, I model the fundamental niche of the chytrid fungus Batrachochytrium dendrobatidis, a pathogen linked to amphibian declines on several continents. Niche models were generated with the Genetic Algorithm of Rule‐Set Prediction using point distribution data of the pathogen and digital maps of environmental variables integrated in a GIS environment. The distribution of regions suitable for B. dendrobatidis in the New World is extensive and includes significant portions of: (1) Sierra Madre Occidental pine‐oak forest; (2) Sonoran and Sinaloan dry forest; (3) Veracruz moist forest; (4) Central America east from the Isthmus of Tehuantepec; (5) Caribbean Islands; (6) temperate forest in Chile and western Argentina south of latitude 30°S; (7) Andes above 1000 m of altitude in Venezuela, Colombia, and Ecuador; (8) eastern slopes of the Andes in Peru and Bolivia; (9) Brazilian Atlantic forest; (10) Uruguay, Paraguay, and northeastern Argentina; (11) southwestern and Madeira‐Tapajós Amazonian tropical rainforests. The regions with the highest suitability for B. dendrobatidis include habitats that contain the world's most diverse amphibian faunas. Models were built with New World localities, but also showed strong predictability for B. dendrobatidis localities in the Old World. Out of a total of 59 reported Old World localities for B. dendrobatidis, 56 occurred within regions with high predicted suitability. I also present analyses of the environmental envelope of B. dendrobatidis and discuss the implications of the results for the conservation of amphibians in the neotropics.
Amphibian Population Declines in Latin America: A Synthesis1
Authors: Lips Karen R. , Burrowes Patricia A. , Mendelson Joseph R. , Parra‐Olea Gabriela 
Published: May 2005

ABSTRACTThe loss of global amphibian biodiversity has been well documented in recent years. The greatest information from Latin America came from countries such as Costa Rica, Panama, Ecuador, and Puerto Rico. The five papers in this special section illustrate the critical status of Latin American amphibians and further demonstrate certain commonalities of amphibian population declines within the region. These studies provide a framework by which future research and management could proceed in all tropical regions.
Effects of Light Gaps and Litter Removal on the Seedling Performance of Six African Timber Species1
Authors: Makana Jean‐Remy , Thomas Sean C. 
Published: May 2005

ABSTRACTValuable timber tree species frequently show poor regeneration after selective logging in tropical forests. Small size of logging gaps, lack of soil disturbance, and limited seed availability have each been blamed for observed regeneration failures. We investigated seed germination and seedling performance using a split‐plot factorial design involving light availability and litter removal for six Central African timber tree species, hypothesizing that canopy gaps and litter removal would improve seedling establishment, and that less shade‐tolerant species would show stronger responses to both factors. Contrary to our expectations, significantly more germinants established on intact litter than on exposed mineral soil 3 mo after seeding. After 18 mo, seedling survival, height and diameter growth, leaf area, and rooting depth were all much higher in gap plots than in the understory for all species, with the exception of Gilbertiodendron dewevrei, a highly shade‐tolerant species whose survival was higher in the understory. Leaf production was negatively influenced by litter removal in the least shade‐tolerant species, Nauclea diderrichii, with weak or positive effects in other species. G. dewevrei, while displaying a low‐light threshold for growth, exhibited a surprisingly high growth response to increasing light comparable to more shade‐intolerant species, a response that may help explain its local competitive dominance in the region. Due to the rapid closure of small gaps, we suggest that shade‐intolerant species such as N. diderrichii, Khaya anthotheca, and Entandrophragma utile might benefit from more intensive silvicultural practices that create larger canopy gaps.
Artificial Defoliation Induces Trichome Production in the Tropical Shrub Cnidoscolus aconitifolius (Euphorbiaceae)1
Authors: Abdala‐Roberts Luis , Parra‐Tabla Víctor 
Published: May 2005

ABSTRACTInduction of plant defenses and their spatial variability are key subjects in the field of ecology and evolution of defensive traits in plants. Nevertheless, induction has been more commonly studied under controlled environments, ignoring other factors that might influence this process in natural settings. The main goal of this study was to determine if artificial defoliation induces trichome production in three natural populations of the tropical shrub Cnidoscolus aconitifolius. First, we performed trichome counts for each population before imposing artificial defoliation to assess differences in trichome loads between populations. Trichome densities (trichomes/cm2) were quantified for leaf blades, petioles, and flower stalks. To determine if defoliation induced trichome production, three defoliation treatments (0% leaves defoliated or controls, 50% of total leaves defoliated, and 100% defoliation) were applied once at the beginning of the reproductive season. Trichome counts were performed on each structure every ∼20 d during a 3‐mo period after the application of treatments. Trichome counts showed significant differences in trichome densities between populations for all three structures. In turn, artificial defoliation increased trichome density. Significant differences among treatments were found for trichome densities on leaf blades and petioles. In both these structures, the 100 percent defoliation treatment differed significantly from control plants, presenting higher trichome densities. In addition, the treatment × population interaction was not significant for leaf blades and petioles, indicating that induction is a generalized response in this species, at least at the study sites. These results indicate that trichomes in C. aconitifolius are inducible due to defoliation.
Massive Destruction of Symphonia globulifera (Clusiaceae) Flowers by Central American Spider Monkeys (Ateles geoffroyi)1
Authors: Riba‐Hernández Pablo , Stoner Kathryn E. 
Published: May 2005

ABSTRACTAlthough more than 39 primate species have been described as nectar feeders, no studies have documented the negative affect this behavior may have on the reproductive success of the plants they consume. Here we report, for the first time, massive flower destruction of the tropical tree Symphonia globulifera by the frugivorous spider monkey, Ateles geoffroyi, and document the detrimental effect this behavior has on fruit set. Foraging behavior was collected from one troop of A. geoffroyi during 460 contact hours from June 1999 to May 2000 in the tropical humid forest at the Refugio de Vida Silvestre Punta Rio Claro (8°39′N, 83°44′E) in the Osa Peninsula in Southwestern Costa Rica. Detailed phenological data were collected from ten S. globulifera trees that the monkeys fed upon and ten trees that were outside of their home range, but in the Refugio. From July to September 1999 S. globulifera was the most important species consumed, representing from 86 to 100 percent of the total feeding time each month. Monkey foraging on S. globulifera flowers was destructive, detaching the flowers completely from the branches in 80 percent of the foraging bouts, and leaving flowers without petals and with damaged reproductive parts in 20 percent of the bouts. None of the ten trees where the monkeys were foraging set fruit, but seven of ten trees outside of their home range set fruit in November and December 1999. These results suggest that some primates may play an important role in floral herbivory in tropical forests and the subsequent reduction in reproductive success. Future studies should focus on evaluating the long‐term effect this foraging behavior may have on the population structure of this species and evaluate the effect of primate floral herbivory on the reproductive success of other plant species.
Trap Spacing and Transect Design for Dung Beetle Biodiversity Studies1
Authors: Larsen Trond H. , Forsyth Adrian 
Published: May 2005

ABSTRACTStandardized sampling methods are essential for comparing species diversity and abundance patterns across different studies and sites. Although dung beetles are widely used as a focal taxon in biodiversity studies, nothing appears to be known about the effective sampling area of dung‐baited traps. Mark‐recapture experiments using Canthon acutus showed that at least 50 m between traps should minimize trap interference, and that wind affects trap detectability. Consequently, we propose a standardized dung beetle sampling design.
Biosynthetic Pathway of
Pseudomonas aeruginosa
4-Hydroxy-2-Alkylquinolines
Authors: Bredenbruch Florian , Nimtz Manfred , Wray Victor , Morr Michael , Müller Rolf , Häussler Susanne 
Published: May 2005

ABSTRACT

The role of intercellular communication in the regulation of bacterial multicellular behavior has received widespread attention, and a variety of signal molecules involved in bacterial communication have been discovered. In addition to the
N
-acyl-homoserine lactones, 4-hydroxy-2-alkylquinolines (HAQs), including the
Pseudomonas
quinolone signal, have been shown to function as signal molecules in
Pseudomonas aeruginosa
. In this study we unraveled the biosynthetic pathway of HAQs using feeding experiments with isotope-labeled precursors and analysis of extracted HAQs by gas chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy. Our results show that the biosynthesis of various HAQ metabolites is directed via a common metabolic pathway involving a “head-to-head” condensation of anthranilic acid and β-keto fatty acids. Moreover, we provide evidence that the β-keto-(do)decanoic acids, crucial for the biosynthesis of the heptyl and nonyl derivatives of the 4-hydroxyquinolines in
P. aeruginosa
, are at least in part derived from a common pool of β-hydroxy(do)decanoic acids involved in rhamnolipid biosynthesis.
Recycling of the Anhydro-
N
-Acetylmuramic Acid Derived from Cell Wall Murein Involves a Two-Step Conversion to
N
-Acetylglucosamine-Phosphate
Authors: Uehara Tsuyoshi , Suefuji Kyoko , Valbuena Noelia , Meehan Brian , Donegan Michael , Park James T. 
Published: May 2005

ABSTRACT

Escherichia coli
breaks down over 60% of the murein of its side wall and reuses the component amino acids to synthesize about 25% of the cell wall for the next generation. The amino sugars of the murein are also efficiently recycled. Here we show that the 1,6-anhydro-
N
-acetylmuramic acid (anhMurNAc) is returned to the biosynthetic pathway by conversion to
N
-acetylglucosamine-phosphate (GlcNAc-P). The sugar is first phosphorylated by
a
nhydro-

N

-acetyl
m
uramic acid
k
inase (AnmK), yielding MurNAc-P, and this is followed by action of an etherase which cleaves the bond between
d
-lactic acid and the
N
-acetylglucosamine moiety of MurNAc-P, yielding GlcNAc-P. The kinase gene has been identified by a reverse genetics method. The enzyme was overexpressed, purified, and characterized. The cell extract of an
anmK
deletion mutant totally lacked activity on anhMurNAc. Surprisingly, in the
anmK
mutant, anhMurNAc did not accumulate in the cytoplasm but instead was found in the medium, indicating that there was rapid efflux of free anhMurNAc.
16S rRNA Mutations That Confer Tetracycline Resistance inHelicobacter pyloriDecrease Drug Binding inEscherichia coliRibosomes
Authors: Nonaka Lisa , Connell Sean R. , Taylor Diane E. 
Published: May 2005

ABSTRACTTetracycline resistance in clinical isolates ofHelicobacter pylorihas been associated with nucleotide substitutions at positions 965 to 967 in the 16S rRNA. We constructed mutants which had different sequences at 965 to 967 in the 16S rRNA gene present on a multicopy plasmid inEscherichia colistrain TA527, in which all sevenrrngenes were deleted. The MICs for tetracycline of all mutants having single, double, or triple substitutions at the 965 to 967 region that were previously found in highly resistantH. pyloriisolates were higher than that of the mutant exhibiting the wild-type sequence of tetracycline-susceptibleH. pylori. The MIC of the mutant with the 965TTC967 triple substitution was 32 times higher than that of theE. colimutant with the 965AGA967 substitution present in wild-typeH. pylori. The ribosomes extracted from the tetracycline-resistantE. coli965TTC967 variant bound less tetracycline thanE. coliwith the wild-typeH. pylorisequence at this region. The concentration of tetracycline bound to the ribosome was 40% that of the wild type. The results of this study suggest that tetracycline binding to the primary binding site (Tet-1) of the ribosome at positions 965 to 967 is influenced by its sequence patterns, which form the primary binding site for tetracycline.
Regulation of
mtrF
Expression in
Neisseria gonorrhoeae
and Its Role in High-Level Antimicrobial Resistance
Authors: Folster Jason P. , Shafer William M. 
Published: May 2005

ABSTRACT

The obligate human pathogen
Neisseria gonorrhoeae
uses the MtrC-MtrD-MtrE efflux pump to resist structurally diverse hydrophobic antimicrobial agents (HAs), some of which bathe mucosal surfaces that become infected during transmission of gonococci. Constitutive high-level HA resistance occurs by the loss of a repressor (MtrR) that negatively controls transcription of the
mtrCDE
operon. This high-level HA resistance also requires the product of the
mtrF
gene, which is located downstream and transcriptionally divergent from
mtrCDE
. MtrF is a putative inner membrane protein, but its role in HA resistance mediated by the MtrC-MtrD-MtrE efflux pump remains to be determined. High-level HA resistance can also be mediated through an induction process that requires enhanced transcription of
mtrCDE
when gonococci are grown in the presence of a sublethal concentration of Triton X-100. We now report that inactivation of
mtrF
results in a significant reduction in the induction of HA resistance and that the expression of
mtrF
is enhanced when gonococci are grown under inducing conditions. However, no effect was observed on the induction of
mtrCDE
expression in an MtrF-negative strain. The expression of
mtrF
was repressed by MtrR, the major repressor of
mtrCDE
expression. In addition to MtrR, another repressor (MpeR) can downregulate the expression of
mtrF
. Repression of
mtrF
by MtrR and MpeR was additive, demonstrating that the repressive effects mediated by these regulators are independent processes.
Fructose Utilization inLactococcus lactisas a Model for Low-GC Gram-Positive Bacteria: Its Regulator, Signal, and DNA-Binding Site
Authors: Barrière Charlotte , Veiga-da-Cunha Maria , Pons Nicolas , Guédon Eric , van Hijum Sacha A. F. T. , Kok Jan , Kuipers Oscar P. , Ehrlich Dusko S. , Renault Pierre 
Published: May 2005

ABSTRACTIn addition to its role as carbon and energy source, fructose metabolism was reported to affect other cellular processes, such as biofilm formation by streptococci and bacterial pathogenicity in plants. Fructose genes encoding a 1-phosphofructokinase and a phosphotransferase system (PTS) fructose-specific enzyme IIABC component reside commonly in a gene cluster with a DeoR family regulator in various gram-positive bacteria. We present a comprehensive study of fructose metabolism inLactococcus lactis, including a systematic study offrumutants, global messenger analysis, and a molecular characterization of its regulation. Thefruoperon is regulated at the transcriptional level by both FruR and CcpA and at the metabolic level by inducer exclusion. The FruR effector is fructose-1-phosphate (F1P), as shown by combined analysis of transcription and measurements of the intracellular F1P pools in mutants either unable to produce this metabolite or accumulating it. The regulation of thefruoperon by FruR requires four adjacent 10-bp direct repeats. The well-conserved organization of thefrupromoter region in various low-GC gram-positive bacteria, including CRE boxes as well as the newly defined FruR motif, suggests that the regulation scheme defined inL. lactiscould be applied to these bacteria. Transcriptome profiling offruRandfruCmutants revealed that the effect of F1P and FruR regulation is limited to thefruoperon inL. lactis. This result is enforced by the fact that no other targets for FruR were found in the available low-GC gram-positive bacteria genomes, suggesting that additional phenotypical effects due to fructose metabolism do not rely directly on FruR control, but rather on metabolism.
Sulfur Amino Acid Metabolism and Its Control in
Lactococcus lactis
IL1403
Authors: Sperandio Brice , Polard Patrice , Ehrlich Dusko S. , Renault Pierre , Guédon Eric 
Published: May 2005

ABSTRACT

Cysteine and methionine availability influences many processes in the cell. In bacteria, transcription of the specific genes involved in the synthesis of these two amino acids is usually regulated by different mechanisms or regulators. Pathways for the synthesis of cysteine and methionine and their interconversion were experimentally determined for
Lactococcus lactis
, a lactic acid bacterium commonly found in food. A new gene,
yhcE
, was shown to be involved in methionine recycling to cysteine. Surprisingly, 18 genes, representing almost all genes of these pathways, are under the control of a LysR-type activator, FhuR, also named CmbR. DNA microarray experiments showed that FhuR targets are restricted to this set of 18 genes clustered in seven transcriptional units, while cysteine starvation modifies the transcription level of several other genes potentially involved in oxidoreduction processes. Purified FhuR binds a 13-bp box centered 46 to 53 bp upstream of the transcriptional starts from the seven regulated promoters, while a second box with the same consensus is present upstream of the first binding box, separated by 8 to 10 bp.
O
-Acetyl serine increases FhuR binding affinity to its binding boxes. The overall view of sulfur amino acid metabolism and its regulation in
L. lactis
indicates that CysE could be a master enzyme controlling the activity of FhuR by providing its effector, while other controls at the enzymatic level appear to be necessary to compensate the absence of differential regulation of the genes involved in the interconversion of methionine and cysteine and other biosynthesis genes.
Characterization of Methionine Export in
Corynebacterium glutamicum
Authors: Trötschel Christian , Deutenberg Dietrich , Bathe Brigitte , Burkovski Andreas , Krämer Reinhard 
Published: May 2005

ABSTRACT

Corynebacterium glutamicum
is known for its effective excretion of amino acids under particular metabolic conditions. Concomitant activities of uptake and excretion systems would create an energy-wasting futile cycle; amino acid export systems are therefore tightly regulated. We have used a DNA microarray approach to identify genes for membrane proteins which are overexpressed under conditions of elevated cytoplasmic concentrations of methionine. One of these genes was
brnF
, coding for the larger subunit of BrnFE, a previously identified two-component isoleucine export system. By deletion, complementation, and overexpression of the
brnFE
genes in a
C. glutamicum
strain, in which the two uptake systems for methionine were inactivated, we identified BrnFE as being responsible for methionine export. In the presence of both substrates in the cytoplasm, BrnFE was found to transport isoleucine and methionine at similar rates. The expression of the
brnFE
gene cluster depends on an Lrp-type transcription factor and was shown to be strongly induced by increasing cytoplasmic methionine concentration. Methionine was a better inducer than isoleucine, indicating that methionine rather than isoleucine might be the native substrate of BrnFE. When the synthesis of BrnFE was blocked by chloramphenicol, fast methionine export was still observed, but only at greatly increased cytoplasmic levels of this amino acid. This indicates the presence of at least one other methionine export system, presumably with low affinity but high capacity. Under conditions where cytoplasmic methionine does not exceed a concentration of 50 mM, BrnFE is the dominant export system for this amino acid.
Identification of a Turnover Element in Region 2.1 of
Escherichia coli
σ
32
by a Bacterial One-Hybrid Approach
Authors: Obrist Markus , Narberhaus Franz 
Published: May 2005

ABSTRACT

Induction of the heat shock response in
Escherichia coli
requires the alternative sigma factor σ
32
(RpoH). The cellular concentration of σ
32
is controlled by proteolysis involving FtsH, other proteases, and the DnaKJ chaperone system. To identify individual σ
32
residues critical for degradation, we used a recently developed bacterial one-hybrid system and screened for stabilized versions of σ
32
. The five single point mutations that rendered the sigma factor more stable mapped to positions L47, A50, and I54 in region 2.1. Strains expressing the stabilized σ
32
variants exhibited elevated transcriptional activity, as determined by a
groE
-
lacZ
fusion. Structure calculations predicted that the three mutated residues line up on the same face of an α-helix in region 2.1, suggesting that they are positioned to interact with proteins of the degradation machinery.