bluuebunny/crossref_metadata_2025 huggingface dataset:
New bisphosphinites from pamoic acid
Authors: Zhang Qingzhi , Fei Zhaofu , Slawin Alexandra M. Z. , Derek Woollins J.
Published: March 2006

Reaction of PhPCl2 with pamoic acid in a 2:1 molar ratio gives a bisphosphinite 5 as a conformational mixture of 5a and 5b which show different solubility in THF and Et2O. The less soluble biaxial conformer 5a was isolated spectrally pure, while it is very difficult to get pure biequatorial 5b without contamination of 5a. Oxidation of 5a with hydrogen peroxide/elemental sulfur or selenium gave the corresponding chalcogenides. The conformational features of the compounds were revealed by X-ray crystallography. In addition, two examples of complexes of 5a were prepared, the chelate complex [PtCl2{(5a)-P, P′}] and the bis-rhodium bridging complex from [RhCl2Cp*]2 dimer.
Novel aqueous chelating agents for catalytic oxidation of hydrogen sulfide to sulfur by air
Authors: Hua Guoxiong , Zhang Qingzhi , Mcmanus Derek , Slawin Alex M. Z. , Derek Woollins J.
Published: March 2006

Six phosphorus-containing analogues of nitrilotriacetic acid (NTA) or ethylenedinitrilotetraacetic acid (EDTA) form stable Fe(III) complexes which have been tested as catalysts for the oxidation of hydrogen sulfide. Ligand 4, phosphonomethyliminodiacetic acid (NTAP), was found to be comparable with NTA in efficiency of catalytic activity such as the conversion of hydrogen sulfide to sulfur, half-life of ligand, consumption of ligand per kg of sulfur product. A quantitative analytical method of phosphorus-containing ligand in the absorbed solution has been successfully established by applying 31P-{1H} NMR.
Novel chemistry of invasive exotic plants
Authors: Cappuccino Naomi , Arnason J.Thor
Published: March 2006

Of the many exotic plants that have become naturalized in North America, only a small proportion are pests capable of invading and dominating intact natural communities. In the present study, we tested the hypothesis that the most invasive plants are phytochemically unique in their new habitats. A comparison of exotic plant species that are highly invasive in North America with exotics that are widespread, but non-invasive revealed that the invasive plants were more likely to have potent secondary compounds that have not been reported from North American native plants. On average, the compounds found in the invasive plants were reported from fewer species, fewer genera and fewer families than those from non-invasive plants. Many of the unique phytochemicals from invasive plants have been reported to have multiple activities, including antiherbivore, antifungal, antimicrobial and allelopathic (phytotoxic) effects, which may provide the plants with several advantages in their new environments.
Genetic consequences of sex-biased dispersal in a solitary carnivore: Yellowstone cougars
Authors: Biek Roman , Akamine Naomi , Schwartz Michael K , Ruth Toni K , Murphy Kerry M , Poss Mary
Published: March 2006

Male-biased dispersal is a common trait in mammals, including carnivores, but its genetic consequences at the population level have been rarely considered for solitary species. We used long-term genetic data from cougars (
Puma concolor
) in and around Yellowstone National Park to test predictions based on differences in dispersal behaviour among males and females. Consistent with frequent long-distance dispersal of males, we found support for our prediction of less than expected allele sharing in pair-wise comparisons. In contrast, female residents present at the same time and females separated by few generations failed to share more alleles than expected, contrary to our predictions based on limited female dispersal. However, we find that genetic contributions of females with higher reproductive success were still noticeable in subsequent generations, consistent with female offspring showing fidelity to their natal area. These results highlight the importance of male dispersal for inbreeding avoidance, but do not indicate that short-distance dispersal or philopatry in female cougars results in spatial clustering of related individuals.
Mauritian coloured nectar no longer a mystery: a visual signal for lizard pollinators
Authors: Hansen Dennis M , Beer Karin , Müller Christine B
Published: March 2006

Most floral nectars are clear as water, and the enigmatic coloured nectar in three endemic plant species in Mauritius has puzzled scientists studying it. One hypothesis about the possible ecological function of coloured nectar is that it serves as a visual signal for pollinators. Recent studies have shown that at least two of the three Mauritian plant species with coloured nectar are visited and pollinated by endemic
Phelsuma
geckos. We here provide experimental evidence for the visual signal hypothesis by showing that
Phelsuma ornata
geckos prefer coloured over clear nectar in artificial flowers. In flowering plants, coloured nectar could additionally function as an honest signal that allows pollinators to assert the presence and judge the size of a reward prior to flower visitation, and to adjust their behaviour accordingly, leading to increased pollinator efficiency. Our study provides a first step in understanding this rare and intriguing floral trait.
An experimental study into the acousto-mechanical effects of invading the cochlea
Authors: Dong Wei , Cooper Nigel P
Published: March 2006

The active and nonlinear mechanical processing of sound that takes place in the mammalian cochlea is fundamental to our sense of hearing. We have investigated the effects of opening the cochlea in order to make experimental observations of this processing. Using an optically transparent window that permits laser interferometric access to the apical turn of the guinea-pig cochlea, we show that the acousto-mechanical transfer functions of the sealed (i.e. near intact) cochlea are considerably simpler than those of the unsealed cochlea. Comparison of our results with those of others suggests that most previous investigations of apical cochlear mechanics have been made under unsealed conditions, and are therefore likely to have misrepresented the filtering of low-frequency sounds in the cochlea. The mechanical filtering that is apparent in the apical turns of sealed cochleae also differs from the filtering seen in individual auditory nerve fibres with similar characteristic frequencies. As previous studies have shown the neural and mechanical tuning of the basal cochlea to be almost identical, we conclude that the strategies used to process low frequency sounds in the apical turns of the cochlea might differ fundamentally from those used to process high frequency sounds in the basal turns.
Characterization of the Plant-Specific BREVIS RADIX Gene Family Reveals Limited Genetic Redundancy Despite High Sequence Conservation
Authors: Briggs Georgette C. , Mouchel Céline F. , Hardtke Christian S.
Published: March 2006

To date, the function of most genes in the Arabidopsis (Arabidopsis thaliana) genome is unknown. Here we present the first analysis of the novel, plant-specific BRX (BREVIS RADIX) gene family. BRX has been identified as a modulator of root growth through a naturally occurring loss-of-function allele. The biochemical function of BRX is enigmatic, however several domains in BRX are conserved in the proteins encoded by the related BRX-like (BRXL) genes. The similarity between Arabidopsis BRXL proteins within these domains ranges from 84% to 93%. Nevertheless, analysis of brx brx-like multiple mutants indicates that functional redundancy of BRXLs is limited. This results mainly from differences in protein activity, as demonstrated by assaying the propensity of constitutively expressed BRXL cDNAs to rescue the brx phenotype. Among the genes tested, only BRXL1 can replace BRX in this assay. Nevertheless, BRXL1 does not act redundantly with BRX in vivo, presumably because it is expressed at a much lower level than BRX. BRX and BRXL1 similarity is most pronounced in a characteristic tandem repeat domain, which we named BRX domain. One copy of this domain is also present in the PRAF (PH, RCC1, and FYVE)-like family proteins. The BRX domain mediates homotypic and heterotypic interactions within and between the BRX and PRAF protein families in yeast (Saccharomyces cerevisiae), and therefore likely represents a novel protein-protein interaction domain. The importance of this domain for BRX activity in planta is underscored by our finding that expression of the C-terminal fragment of BRX, comprising the two BRX domains, is largely sufficient to rescue the brx phenotype.
Medicago truncatula Mutants Demonstrate the Role of Plant Calcium Oxalate Crystals as an Effective Defense against Chewing Insects
Authors: Korth Kenneth L. , Doege Sarah J. , Park Sang-Hyuck , Goggin Fiona L. , Wang Qin , Gomez S. Karen , Liu Guangjie , Jia Lingling , Nakata Paul A.
Published: March 2006

Calcium oxalate is the most abundant insoluble mineral found in plants and its crystals have been reported in more than 200 plant families. In the barrel medic Medicago truncatula Gaertn., these crystals accumulate predominantly in a sheath surrounding secondary veins of leaves. Mutants of M. truncatula with decreased levels of calcium oxalate crystals were used to assess the defensive role of this mineral against insects. Caterpillar larvae of the beet armyworm Spodoptera exigua Hübner show a clear feeding preference for tissue from calcium oxalate-defective (cod) mutant lines cod5 and cod6 in choice test comparisons with wild-type M. truncatula. Compared to their performance on mutant lines, larvae feeding on wild-type plants with abundant calcium oxalate crystals suffer significantly reduced growth and increased mortality. Induction of wound-responsive genes appears to be normal in cod5 and cod6, indicating that these lines are not deficient in induced insect defenses. Electron micrographs of insect mouthparts indicate that the prismatic crystals in M. truncatula leaves act as physical abrasives during feeding. Food utilization measurements show that, after consumption, calcium oxalate also interferes with the conversion of plant material into insect biomass during digestion. In contrast to their detrimental effects on a chewing insect, calcium oxalate crystals do not negatively affect the performance of the pea aphid Acyrthosiphon pisum Harris, a sap-feeding insect with piercing-sucking mouthparts. The results confirm a long-held hypothesis for the defensive function of these crystals and point to the potential value of genes controlling crystal formation and localization in crop plants.
Interplay between Arabidopsis Activating Factors E2Fb and E2Fa in Cell Cycle Progression and Development
Authors: Sozzani Rosangela , Maggio Caterina , Varotto Serena , Canova Sabrina , Bergounioux Catherine , Albani Diego , Cella Rino
Published: March 2006

Eukaryotic E2Fs are conserved transcription factors playing crucial and antagonistic roles in several pathways related to cell division, DNA repair, and differentiation. In plants, these processes are strictly intermingled at the growing zone to produce postembryonic development in response to internal signals and environmental cues. Of the six AtE2F proteins found in Arabidopsis (Arabidopsis thaliana), only AtE2Fa and AtE2Fb have been clearly indicated as activators of E2F-responsive genes. AtE2Fa activity was shown to induce S phase and endoreduplication, whereas the function of AtE2Fb and the interrelationship between these two transcription factors was unclear. We have investigated the role played by the AtE2Fb gene during cell cycle and development performing in situ RNA hybridization, immunolocalization of the AtE2Fb protein in planta, and analysis of AtE2Fb promoter activity in transgenic plants. Overexpression of AtE2Fb in transgenic Arabidopsis plants led to striking modifications of the morphology of roots, cotyledons, and leaves that can be ascribed to stimulation of cell division. The accumulation of the AtE2Fb protein in these lines was paralleled by an increased expression of E2F-responsive G1/S and G2/M marker genes. These results suggest that AtE2Fa and AtE2Fb have specific expression patterns and play similar but distinct roles during cell cycle progression.
Changes in body mass and hormone levels between wintering and spring staging areas in dark‐bellied brent geese Branta bernicla bernicla
Authors: Poisbleau Maud , Fritz Hervé , Lambrechts Marcel M. , Trouvé Colette , Ebbinge Barwolt S.
Published: March 2006

We document seasonal changes in body mass and plasma hormone levels (testosterone and triiodothyronine) between winter and spring quarters in dark‐bellied brent geese Branta bernicla bernicla. Body mass increased between winter and spring, whereas body size was the same for the birds sampled in winter and those in spring. Adults and males were larger and heavier than juveniles and females. Plasma testosterone levels did not differ significantly between winter and spring, and did not vary with sex, age and morphometry. Plasma triiodothyronine (T3) levels were significantly higher in spring than in winter, and were higher for males than for females. However, T3 levels did not vary significantly with age and body measurements. To explain the findings, we discuss potential impacts of social dominance.
Warm temperatures lead to early onset of incubation, shorter incubation periods and greater hatching asynchrony in tree swallows Tachycineta bicolor at the extremes of their range
Authors: Ardia Daniel R. , Cooper Caren B. , Dhondt André A.
Published: March 2006

The onset of incubation varies in birds, with many species beginning incubation prior to clutch completion. Here we examine whether early onset is more likely to occur during high temperatures, a critical prediction of the egg‐viability hypothesis, which suggest that birds begin incubation prior to clutch completion in order to maintain egg‐viability. We examined onset of incubation in tree swallows Tachycineta bicolor at two locations at the extremes of their breeding range, Alaska and Tennessee. A majority of individuals (68%) began incubation prior to clutch completion. While females in Tennessee were more likely to begin incubation early, there was no difference between sites when differences in temperatures inside nestboxes were controlled in analyses. Rather, early onset of incubation was predicted by the proportion of daily temperatures above physiological zero during laying, a critical prediction of the egg viability hypothesis. Both warm weather and early onset led to shorter incubation periods and increased levels of hatching asynchrony. We found no effect of timing of nesting, female body condition index or clutch size on the probability of beginning incubation prior to clutch completion. Our results are consistent with the egg viability hypothesis, not consistent with a threshold clutch size rule, and do not support the hurry‐up hypothesis, that individuals breeding later in the season would begin incubation early to reduce the time spent nesting. Overall, our results suggest that broad scale geographic differences in incubation behaviour may be explained by individual‐level responses to environmental conditions.
Temperament and character dimensions in patients with atopic dermatitis
Authors: KIM Tae‐Suk , PAE Chi‐Un , JEONG Jeung‐Tae , KIM Sang‐Dong , CHUNG Kyoo‐In , LEE Chul
Published: March 2006

The aim of this study was to assess the personality traits of young male patients with atopic dermatitis (AD), and to examine the correlations between temperament and character dimensions with clinical and other psychological factors. Fifty young adult male AD patients and 83 healthy controls were examined using the temperament and character inventory, the Beck depression inventory and the state‐trait anxiety inventory. The AD patients scored higher on harm avoidance and lower on reward dependence, self‐directedness and cooperativeness than the healthy controls. The illness duration and anxiety correlated negatively with the self‐directedness score, and depression correlated negatively with reward dependence and the persistence scores in AD patients. These results suggest that AD patients have distinctive temperament and character dimensions compared to healthy controls. Moreover, illness duration and anxiety might be associated with some personality problems, and some temperament dimensions (e.g. reward dependence, persistence) may be linked to depressive symptoms in AD patients.
Granulomas induced by subcutaneous injection of leuprorelin acetate
Authors: SAKAMOTO Ryoko , HIGASHI Yuko , MERA Kentaro , KANEKURA Takuro , KANZAKI Tamotsu
Published: March 2006

Leuprorelin acetate, a chemotherapeutic agent used to treat prostate cancer, is a synthetic luteinizing hormone‐releasing hormone (LHRH) agonist. We report a 75‐year‐old man who presented with several large subcutaneous nodules at the site of leuprorelin acetate injections for his prostatic cancer. A biopsy of the nodules disclosed epithelioid granulomatous inflammation and resulted in a diagnosis of drug‐induced granulomatous reaction to leuprorelin acetate.
A case of Sister Mary Joseph's nodule from prostatic cancer
Authors: FUKUDA Hidetsugu , SAITO Ryuzo
Published: March 2006

The metastasis of a visceral malignancy to the umbilicus is known as “Sister Mary Joseph's nodule” (SMJN). We recently encountered an 80‐year‐old man in whom umbilical metastasis of prostatic cancer was revealed during the course of treatment. The lesion was a red, firm, elastic nodule, 2.5 cm in diameter, with a bumpy, irregular surface, but without subjective symptoms. In histopathological examination, atypical cells with intensely stained, small quasi‐circular nuclei and weakly eosinophilic cytoplasm were found in all layers of the dermis. In some parts of these tumor cells, a gland‐like structure was observed. Immunohistochemical investigation of the invading tumor cells disclosed immunoreactivity for prostate specific antigen and prostatic acid phosphatase, supporting a diagnosis of SMJN from prostatic cancer. His general condition gradually deteriorated, and he died 2 months later. Prostate cancer often metastasizes to bones and lymph nodes, but rarely to the skin. Of all the cases of cutaneous metastasis of prostate cancer reported in Japan, only three metastases have occurred to the umbilical region. The present case is therefore an example of a very rare condition.
A case of Papillon–Lefevre syndrome associated with xanthogranulomatous pyelonephritis and hepatitis
Authors: MANSUR A. Tülin , GÖKTAY Fatih , DEMİROK Nüket
Published: March 2006

Papillon–Lefevre syndrome (PLS) is an autosomally recessive palmoplantar keratoderma accompanied by psoriasiform plaques on the extensor surfaces of extremities and leading to premature loss of deciduous and permanent teeth by progressive periodontitis. Patients with PLS may exhibit mental retardation, intracranial ectopic calcifications, nail dystrophies and a tendency to various infectious disorders, in addition to skin and oral findings. Herein, we report a 26‐year‐old man with PLS, who had experienced xanthogranulomatous pyelonephritis and hepatitis during childhood and adolescence. To the best of our knowledge, this is the first report of PLS associated with xanthogranulomatous inflammation.
Can haematological tests predict cardiovascular risk? The 2005 Kettle Lecture*
Authors: Lowe Gordon D. O.
Published: March 2006

The risk of venous or arterial thrombosis is routinely assessed by clinical variables (risk factors) supplemented by measurement of blood lipids and glucose for arterial thrombotic events. Haematological tests that might play a role in risk prediction include haemostatic variables, haematocrit and inflammatory markers (erythrocyte sedimentation rate, plasma viscosity, white cell count). Recent epidemiological studies of these phenotypes and related genotypes are reviewed. For the risk prediction of first venous thrombosis, screening for thrombophilias in ‘high‐risk’ situations does not appear clinically effective or cost‐effective; with the possible exception of women considering oral hormone replacement therapy. General screening after a first venous event to predict recurrence (or risk in asymptomatic relatives) does not appear effective; with the possible exception of d‐dimer, which requires further study. For risk prediction of first arterial thrombosis, screening adds little to prediction by current clinical risk scores. Screening of persons after a first arterial event, or with atrial fibrillation (e.g. with d‐dimer for stroke prediction), requires further study. In conclusion, haematological tests have very limited roles in the prediction of cardiovascular risk, and should only be used according to evidence‐based guidelines. The need for management studies is highlighted.
How are soil use and management reflected by soil organic matter characteristics: a spectroscopic approach
Authors: Gerzabek M. H. , Antil R. S. , Kögel‐Knabner I. , Knicker H. , Kirchmann H. , Haberhauer G.
Published: March 2006

We studied the quantitative and qualitative changes of soil organic matter (SOM) due to different land uses (arable versus grassland) and treatments (organic manure and mineral fertilizer) within an agricultural crop rotation in a long‐term field experiment, conducted since 1956 at Ultuna, Sweden, on a Eutric Cambisol. The organic carbon (OC) content of the grassland plot was 1.8 times greater than that of the similarly fertilized Ca(NO3)2 treated cropped plots. The comparison of two dispersion techniques (a low‐energy sonication and a chemical dispersion which yield inherent soil aggregates) showed that increasing OC contents of the silt‐sized fractions were not matched by a linear increase of silt‐sized aggregates. This indicated saturation of the aggregates with OC and a limited capacity of particles to protect OC physically. Thermogravimetric analyses suggested an increase of free organic matter with increasing OC contents. Transmission FT‐IR spectroscopy showed relative enrichment of carboxylic, aromatic, CH and NH groups in plots with increasing OC contents. The silt‐sized fractions contained the largest SOM pool and, as revealed by 13C NMR spectroscopy, were qualitatively more influenced by the plant residue versus manure input than the clay fractions. Alkyl and O‐alkyl C in the silt‐sized fractions amounted to 57.4% of organic carbon in the animal manure treated plots and 50–53% in the other treatments.
Lignin degradation controls the production of dissolved organic matter in decomposing foliar litter
Authors: Kalbitz K. , Kaiser K. , Bargholz J. , Dardenne P.
Published: March 2006

Lignin is considered to be a crucial component controlling litter decomposition but its role in the production of dissolved organic matter (DOM) from litter is not well understood. Our main objective therefore was to examine the amounts and properties of DOM produced in decomposing litter, with special emphasis on the role of lignin degradation. We exposed litter of five different tree species (Sycamore maple, Mountain ash, European beech, Norway spruce, Scots pine) in litterbags at the soil surface of two neighbouring sites to degradation under field conditions. Litterbags were sampled eight times during 27 months of exposure in the field. We determined mass loss and characterized the lignin fraction by two different methods (van Soest procedure, acid‐detergent lignin: ADL, CuO oxidation). Litter was irrigated in the laboratory and leachates were analysed for dissolved organic carbon (DOC) and characterized by UV and fluorescence spectroscopy. Litter decomposition followed a two‐stage model characterized by initially rapid and then decreasing degradation with time. In the initial phase of litter decomposition, leached amounts of DOM decreased with time and no effects of lignin degradation were found. The contents of ADL in the litter residues and CuO oxidation products suggest larger degradation and oxidation of lignin in beech, spruce and pine litter than in maple and ash litter. The production of DOM from litter with larger lignin degradation increased in the second phase of decomposition, when mass loss exceeded 10–20%. In contrast, DOM produced from litter showing weak lignin degradation (maple, ash) did not increase further in the second phase of decomposition. In the leachates of litter with large lignin degradation (beech, spruce, pine), UV absorbance and fluorescence spectroscopy indicated a larger increase in the contribution of lignin‐derived compounds to DOM with increasing mass loss than for litter species with relatively stable lignin. We conclude that degradation of lignin is an important control on DOM production during the second phase of litter decomposition.
The role of wood density and stem support costs in the growth and mortality of tropical trees
Authors: KING DAVID A. , DAVIES STUART J. , TAN SYLVESTER , NOOR NUR SUPARDI MD.
Published: March 2006

The rapid growth rates of light‐demanding tree species have been attributed in part to their low‐density, low‐cost stems. We evaluated the influence of light and biomass support costs on growth rates of trees 8–25 cm in diameter at breast height (d.b.h.) among 21 species differing in wood density in two aseasonal rain forests.

Measurements of crown width, tree height, d.b.h. and wood density (ρ) were used to estimate the stem biomass (Ms) of a standard‐sized tree (17 m tall and 16 m2in crown area), i.e. the cost in stem biomass of supporting a given sized crown at a given height.

The species showed a three‐fold range in support cost, which was highly correlated with wood density (Ms ∝ ρ0.77,r2 = 0.72 for the log‐transformed relationship). This relationship is due to the high interspecific variation in wood density and the fact that the stem diameter of the standard‐sized tree increased only slightly with decreasing wood density, i.e. light‐wooded species did not compensate for their lighter, weaker wood by substantially increasing stem thickness.

Mean growth rate per species showed a 10‐fold range and increased with the fraction of trees at least partly in gaps (gap fraction), the reciprocal of support cost (1/Ms), and the reciprocal of wood density (1/ρ). The relationship between mean growth rate and 1/Mswas particularly strong when one outlier was excluded (r2 = 0.88) and among the Dipterocarpaceae (r2 = 0.89).

Log(mortality rate), as determined for all trees per species ≥ 1 cm d.b.h., increased linearly with 1/Ms, 1/ρ and gap fraction.

These results suggest an important role for wood density and support costs in the classic tradeoff between rapid growth and increased risks of damage and death.
Ecosystem science and human–environment interactions in the Hawaiian archipelago
Authors: VITOUSEK PETER
Published: March 2006

Tansley's ecosystem concept remains a vital framework for ecological research in part because the approach facilitates interdisciplinary analyses of ecological systems.

Features of the Hawaiian Islands – particularly the nearly orthogonal variation in many of the factors that control variation among ecosystems elsewhere – make the archipelago a useful model system for interdisciplinary research designed to understand fundamental controls on the state and dynamics of ecosystems, and their consequences for human societies.

Analyses of rain forest sites arrayed on a substrate age gradient from c. 300 years to over 4 million years across the Hawaiian archipelago demonstrate that the sources of calcium and other essential cations shift from > 80% rock‐derived in young sites to > 80% derived from marine aerosol on substrates older than 100 000 years. Rock‐derived phosphorus is retained longer within ecosystems, but eventually long‐distance transport of continental dust from Asia becomes the most important source of phosphorus.

A biogeochemical feedback from low nutrient availability to efficient resource use by trees to slow decomposition and nutrient regeneration accentuates the geochemically driven pattern of low phosphorus availability and phosphorus limitation to net primary productivity in the oldest site.

Variations in ecosystem biogeochemistry across the archipelago shaped the development and sustainability of Polynesian agricultural systems in the millennium between their discovery of Hawai’i and contact by Europeans. Irrigated pondfields were largely confined to stream valleys on the older islands, while rain‐fed dryland systems occupied a narrow zone of fertile, well‐watered soils on the younger islands.

The ecosystem approach often represents the most appropriate level of organization for analyses of human influences on ecological systems; it can play a central role in the design and analysis of alternative agricultural, industrial and residential systems that could reduce the human footprint on the Earth.
PerR controls Mn‐dependent resistance to oxidative stress inNeisseria gonorrhoeae
Authors: Wu Hsing‐Ju , Seib Kate L. , Srikhanta Yogitha N. , Kidd Stephen P. , Edwards Jennifer L. , Maguire Tina L. , Grimmond Sean M. , Apicella Michael A. , McEwan Alastair G. , Jennings Michael P.
Published: March 2006

In previous studies it has been established that resistance to superoxide byNeisseria gonorrhoeaeis dependent on the accumulation of Mn(II) ions involving the ABC transporter, MntABC. A mutant strain lacking the periplasmic binding protein component (MntC) of this transport system is hypersensitive to killing by superoxide anion. In this study themntCmutant was found to be more sensitive to H2O2killing than the wild‐type. Analysis of regulation of MntC expression revealed that it was de‐repressed under low Mn(II) conditions. TheN. gonorrhoeae mntABClocus lacks themntRrepressor typically found associated with this locus in other organisms. A search for a candidate regulator ofmntABCexpression revealed a homologue of PerR, a Mn‐dependent peroxide‐responsive regulator found in Gram‐positive organisms. AperRmutant expressed more MntC protein than wild‐type, and expression was independent of Mn(II), consistent with a role for PerR as a repressor ofmntABCexpression. The PerR regulon ofN. gonorrhoeaewas defined by microarray analysis and includes ribosomal proteins, TonB‐dependent receptors and an alcohol dehydrogenase. Both themntCandperRmutants had reduced intracellular survival in a human cervical epithelial cell model.
Characterizing the flagellar filament and the role of motility in bacterial prey‐penetration by Bdellovibrio bacteriovorus
Authors: Lambert Carey , Evans Katy J. , Till Rob , Hobley Laura , Capeness Michael , Rendulic Snjezana , Schuster Stephan C. , Aizawa Shin‐Ichi , Sockett R. Elizabeth
Published: March 2006

The predatory bacterium Bdellovibrio bacteriovorus swims rapidly by rotation of a single, polar flagellum comprised of a helical filament of flagellin monomers, contained within a membrane sheath and powered by a basal motor complex. Bdellovibrio collides with, enters and replicates within bacterial prey, a process previously suggested to firstly require flagellar motility and then flagellar shedding upon prey entry. Here we show that flagella are not always shed upon prey entry and we study the six fliC flagellin genes of B. bacteriovorus, finding them all conserved and expressed in genome strain HD100 and the widely studied lab strain 109J. Individual inactivation of five of the fliC genes gave mutant Bdellovibrio that still made flagella, and which were motile and predatory. Inactivation of the sixth fliC gene abolished normal flagellar synthesis and motility, but a disordered flagellar sheath was still seen. We find that this non‐motile mutant was still able to predate when directly applied to lawns of YFP‐labelled prey bacteria, showing that flagellar motility is not essential for prey entry but important for efficient encounters with prey in liquid environments.
Two aerobic pathways for the formation of unsaturated fatty acids in Pseudomonas aeruginosa
Authors: Zhu Kun , Choi Kyoung‐Hee , Schweizer Herbert P. , Rock Charles O. , Zhang Yong‐Mei
Published: March 2006

The double bond in anaerobic unsaturated fatty acid (UFA) biosynthesis is introduced by the FabA dehydratase/isomerase of the bacterial type II fatty acid biosynthetic pathway. A ΔfabA mutant of Pseudomonas aeruginosa grew aerobically, but required a UFA supplement for anaerobic growth. Wild‐type cells produced 18:1Δ11 as the principal UFA, whereas the ΔfabA strain produced only 16:1Δ9. The double bond in the 16:1Δ9 was introduced after phospholipid formation and was localized in the sn‐2 position. Two predicted membrane proteins, DesA and DesB, possessed the conserved histidine clusters characteristic of fatty acid desaturases. The ΔfabAΔdesA double mutant required exogenous fatty acids for growth but the ΔfabAdesB double mutant did not. Exogenous stearate was converted to 18:1Δ9 and supported the growth of ΔfabAΔdesA double mutant. A ΔfabAΔdesAdesB triple mutant was unable to desaturate exogenous stearate and was an UFA auxotroph. We detected a 2.5‐fold increase in desA expression in ΔfabA mutants, whereas desB expression was derepressed by the deletion of the gene encoding a transcriptional repressor DesT. These data add two aerobic desaturases to the enzymes used for fatty acid metabolism in proteobacteria: DesA, a 2‐position phospholipid Δ9‐desaturase that supplements the anaerobic FabA pathway, and DesB, an inducible acyl‐CoA Δ9‐desaturase whose expression is repressed by DesT.
Bradyrhizobium japonicum senses iron through the status of haem to regulate iron homeostasis and metabolism
Authors: Yang Jianhua , Sangwan Indu , Lindemann Andrea , Hauser Felix , Hennecke Hauke , Fischer Hans‐Martin , O'Brian Mark R.
Published: March 2006

The Irr protein from the bacterium Bradyrhizobium japonicum is expressed under iron limitation to mediate iron control of haem biosynthesis. The regulatory input to Irr is the status of haem and its precursors iron and protoporphyrin at the site of haem synthesis. Here, we show that Irr controls the expression of iron transport genes and many other iron‐regulated genes not directly involved in haem synthesis. Irr is both a positive and negative effector of gene expression, and in at least some cases the control is direct. Loss of normal iron responsiveness of those genes in an irr mutant, as well as a lower total cellular iron content, suggests that Irr is required for the correct perception of the cellular iron status. Degradation of Irr in iron replete cells requires haem. Accordingly, control of Irr‐regulated genes by iron was aberrant in a haem‐defective strain, and iron replete mutant cells behave as if they are iron‐limited. In addition, the haem mutant had an abnormally high cellular iron content. The findings indicate that B. japonicum senses iron via the status of haem biosynthesis in an Irr‐dependent manner to regulate iron homeostasis and metabolism.
Characterization of the Staphylococcus aureus CidR regulon: elucidation of a novel role for acetoin metabolism in cell death and lysis
Authors: Yang Soo‐Jin , Dunman Paul M. , Projan Steven J. , Bayles Kenneth W.
Published: March 2006

The Staphylococcus aureus cid and lrg operons encode a novel regulatory system that affects murein hydrolase activity, stationary‐phase survival and antibiotic tolerance. Expression of the lrgAB operon is positively regulated by a two‐component regulatory system encoded by the lytSR operon located immediately upstream to lrgAB. By comparison, the cidABC operon lies downstream from the cidR gene, encoding a protein homologous to the LysR‐type family of transcriptional regulators. Transcription analysis of a cidR mutant revealed that CidR enhances cidABC expression in the presence of acetic acid generated by the metabolism of excess glucose. Microarray studies identified additional CidR‐regulated operons including the IrgAB and alsSD encoding proteins involved in acetoin production. Surprisingly, Northern blot analyses revealed that cidABC and lrgAB transcription was uninducible in an alsSD mutant grown in the presence of excess glucose, suggesting that the CidR‐mediated upregulation of cidABC and lrgAB transcription is dependent on the presence of intact alsSD genes. Zymographic and quantitative analyses of murein hydrolase activity also revealed that disruption of the alsSD genes results in significantly decreased extracellular murein hydrolase activity compared with that of the parental strain, UAMS‐1. Furthermore, the alsSD mutant displayed decreased stationary‐phase survival relative to UAMS‐1, both in the presence and absence of glucose. The results of this study define the CidR regulon and demonstrate that the generation of acetoin is linked to the control of cell death and lysis in S. aureus.
Cyclic‐diGMP signal transduction systems in Vibrio cholerae: modulation of rugosity and biofilm formation
Authors: Lim Bentley , Beyhan Sinem , Meir James , Yildiz Fitnat H.
Published: March 2006

Cyclic di‐guanylic acid (c‐diGMP) is a second messenger that modulates the cell surface properties of several microorganisms. Concentrations of c‐diGMP in the cell are controlled by the opposing activities of diguanylate cyclases and phosphodiesterases, which are carried out by proteins harbouring GGDEF and EAL domains respectively. In this study, we report that the cellular levels of c‐diGMP are higher in the Vibrio cholerae rugose variant compared with the smooth variant. Modulation of cellular c‐diGMP levels by overexpressing proteins with GGDEF or EAL domains increased or decreased colony rugosity respectively. Several genes encoding proteins with either GGDEF or EAL domains are differentially expressed between the two V. cholerae variants. The generation and characterization of null mutants of these genes (cdgA–E, rocS and mbaA) revealed that rugose colony formation, exopolysaccharide production, motility and biofilm formation are controlled by their action. Furthermore, epistasis analysis suggested that cdgC, rocS and mbaA act in convergent pathways to regulate the phenotypic properties of the rugose and smooth variants, and are part of the VpsR, VpsT and HapR signal transduction pathway.
The enteropathogenic Escherichia coli type III secretion system effector Map binds EBP50/NHERF1: implication for cell signalling and diarrhoea
Authors: Simpson Nandi , Shaw Rob , Crepin Valerie F. , Mundy Rosanna , FitzGerald Anthony J. , Cummings Nicola , Straatman‐Iwanowska Ania , Connerton Ian , Knutton Stuart , Frankel Gad
Published: March 2006

Enteropathogenic Escherichia coli (EPEC) is the single most important contributor to child diarrhoea in developing countries. Nevertheless, the mechanism responsible for EPEC diarrhoea remains elusive. Using the yeast two‐hybrid system to determine the target host cell protein of the EPEC type III secretion system effector Map led to identification of ezrin/radixin/moesin (ERM)‐binding phosphoprotein 50 (EBP50), also known as Na+/H+ exchanger regulatory factor 1 (NHERF1). Protein interaction is mediated by the carboxy‐terminal Thr‐Arg‐Leu (TRL) motif of Map and the PSD‐95/Disk‐large/ZO‐1 domain 1 (PDZ1) of EBP50/NHERF1. Although EBP50/NHERF1 is recruited to site of EPEC adhesion in a Map‐independent mechanism, co‐immunoprecipitation and immunostaining revealed that Map binds to, induces proteolysis of, and colocalizes with EBP50/NHERF1 during infection of cultured epithelial cells. The TRL motif of Map was involved in Map‐induced filopodia formation and brush border elongation on infected HeLa and Caco‐2 cells respectively. As EBP50/NHERF1 regulates ion channels in the intestine we assessed the involvement of Map in diarrhoea using the Citrobacter rodentium mouse model of EPEC. We report significantly greater diarrhoea following infections with wild‐type C. rodentium compared with C. rodentiumΔmap. These results provide new insights into the mechanisms of EPEC diarrhoea.
Influences on gene expression in vivo by a Shine–Dalgarno sequence
Authors: Jin Haining , Zhao Qing , Gonzalez de Valdivia Ernesto I. , Ardell David H. , Stenström Magnus , Isaksson Leif A.
Published: March 2006

The Shine–Dalgarno (SD+: 5′‐AAGGAGG‐3′) sequence anchors the mRNA by base pairing to the 16S rRNA in the small ribosomal subunit during translation initiation. We have here compared how an SD+ sequence influences gene expression, if located upstream or downstream of an initiation codon. The positive effect of an upstream SD+ is confirmed. A downstream SD+ gives decreased gene expression. This effect is also valid for appropriately modified natural Escherichia coli genes. If an SD+ is placed between two potential initiation codons, initiation takes place predominantly at the second start site. The first start site is activated if the distance between this site and the downstream SD+ is enlarged and/or if the second start site is weakened. Upstream initiation is eliminated if a stable stem‐loop structure is placed between this SD+ and the upstream start site. The results suggest that the two start sites compete for ribosomes that bind to an SD+ located between them. A minor positive contribution to upstream initiation resulting from 3′ to 5′ ribosomal diffusion along the mRNA is suggested. Analysis of the E. coli K12 genome suggests that the SD+ or SD‐like sequences are systematically avoided in the early coding region suggesting an evolutionary significance.
Antibody responses and epitope specificities to the Taenia solium cysticercosis vaccines TSOL18 and TSOL45‐1A
Authors: KYNGDON C. T. , GAUCI C. G. , GONZALEZ A. E. , FLISSER A. , ZOLI A. , READ A. J. , MARTÍNEZ‐OCAÑA J. , STRUGNELL R. A. , LIGHTOWLERS M. W.
Published: March 2006

Taenia solium is a cestode parasite that causes cysticercosis in humans and pigs. This study examined the antibody responses in pigs immunized with the TSOL18 and TSOL45‐1A recombinant vaccines against T. solium cysticercosis. Immunization with these proteins induced specific, complement‐fixing antibodies against the recombinant antigens that are believed to be associated with vaccine‐induced protection against T. solium infection. Sera from immunized pigs were used to define the linear B‐cell epitopes of TSOL18 and TSOL45‐1A. Prominent reactivity was revealed to one linear epitope on TSOL18 and two linear epitopes on TSOL45‐1A. These, and oncosphere antigens from other taeniid cestodes, contain a protein sequence motif suggesting that they may show a tertiary structure similar to the fibronectin type III domain (FnIII). Comparison of the location of linear antigenic epitopes in TSOL18 and TSOL45‐1A within the proposed FnIII structure to those within related cestode vaccine antigens reveals conservation in the positioning of the epitopes between oncosphere antigens from different taeniid species.
Evaluation of otoscope cone cleaning and disinfection procedures commonly used in veterinary medical practices: a pilot study
Authors: Newton Heide M. , Rosenkrantz Wayne S. , Muse Russell , Griffin Craig E.
Published: March 2006

The objective of this study was to evaluate the relative efficacy of otoscope cone cleaning and disinfection methods commonly used in veterinary practices. Using sterile technique, 60 new gas‐sterilized 4‐mm otoscope cones were inoculated with a broth culture of 1.5 billionPseudomonas aeruginosabacteria per mL then allowed to dry for 10 min. Six study groups of 10 cones each were created. Group 1 served as positive control and received no cleaning or disinfection. Group 2 cones were wiped with sterile cotton‐tipped applicators and gauze then rinsed with water. Group 3 cones were wiped with 70% isopropyl alcohol. Group 4 cones were scrubbed in a speculum cleaner with Cetylcide II solution (Cetylite Industries, Inc., Pennsauken, NJ). Groups 5 and 6 cones were soaked for 20 min in Cetylcide II and chlorhexidine gluconate 2% solutions, respectively. Using sterile technique and after 10–15 min drying time, the cones were swabbed in a consistent pattern, and samples were submitted for quantitative culture. Culture results showed no growth from cones soaked in Cetylcide II or chlorhexidine solutions. Two of the 10 cones wiped with alcohol, 3/10 cones wiped then rinsed with water, and 3/10 cones scrubbed with the speculum cleaner showed growth ofP. aeruginosa. All (10/10) cones in the control group showed heavy growth ofP. aeruginosa. These results show thatP. aeruginosacan survive on otoscope cones cleaned and disinfected by several commonly used methods. Further study is needed to determine practical and optimal cleaning and disinfection methods for otoscope cones.
Patch testing of experimentally sensitized beagle dogs: development of a model for skin lesions of atopic dermatitis
Authors: Olivry Thierry , Deangelo Kristin B. , Dunston Stanley M. , Clarke Katie B. , Mccall Catherine A.
Published: March 2006

In humans with atopic dermatitis (AD), the epicutaneous application of allergens (atopy patch tests or APT) to which the patients are sensitized often results in the development of inflammation resembling that of spontaneous skin lesions. Dogs are affected with a natural homologue of human AD, but information on the induction of positive patch testing reactions is limited. The objectives of this pilot study were to determine the nature and cellular dynamics of inflammation occurring after APT in dogs hypersensitive to house dust mite and flea allergens. Laboratory Beagles were sensitized experimentally to Dermatophagoides farinae house dust mites (two dogs), Ctenocephalides felis flea saliva (one dog) or both (two dogs). Two other dogs served as nonsensitized controls. Both allergens and saline were applied epicutaneously. Macroscopic evaluations and skin biopsies were performed at 4, 24, 48 and 96 h after starting allergenic challenge. Biopsies were evaluated histologically and immunohistochemically with a panel of monoclonal antibodies specific for canine leucocyte antigens. Positive macroscopic reactions consisted of erythema, oedema and induration, and they occurred between 24 and 96 h after allergen application. Macroscopic and microscopic APT reactions developed only whenever serum IgE was present against tested allergens. Microscopically, positive APT was associated with epidermal hyperplasia, Langerhans’ cell hyperplasia, and eosinophil and lymphocyte epidermotropism. Dermal inflammation was mixed and arranged in a superficial perivascular to interstitial pattern. Numerous IgE+‐CD1+ dendritic cells and gamma‐delta T‐lymphocytes were observed. Macroscopically and microscopically, APT reactions in these experimentally sensitized animals resembled those seen in lesional biopsy specimens of dogs and humans with spontaneous AD. Therefore, APT in hypersensitive dogs provides a relevant experimental model to investigate the pathogenesis and treatment of both canine and human AD skin lesions.
Ciprofloxacin as a representative of disk diffusionin vitrosusceptibility of enrofloxacin for bacterial organisms from the middle‐ear tissue of dogs with end‐stage otitis externa
Authors: Cole Lynette K. , Kwochka Kenneth W. , Hillier Andrew , Kowalski Joseph J. , Smeak Daniel D. , Kelbick Nicole T
Published: March 2006

The purposes of this study were to determine whether ciprofloxacin disk diffusion susceptibility test (DDT) results could be used to assess thein vitrosusceptibility of otic bacterial organisms to enrofloxacin and to determine the effect of concurrent enrofloxacin administration on the DDT results for enrofloxacin and ciprofloxacin. Thirty dogs with end‐stage otitis externa undergoing unilateral total ear canal ablation were enrolled. The dogs were randomized to one of four enrofloxacin‐treatment groups or to the control group. Each dog in the treatment groups received two intravenous doses of enrofloxacin prior to surgical removal of the middle‐ear tissue while the control group did not receive any enrofloxacin. One dog was excluded from the study as no middle‐ear tissue was removed during surgery. Twenty‐four dogs were in the enrofloxacin‐treatment groups and five dogs were in the control group. In 12 of 29 dogs (41.4%), 14 of 82 (17.1%) of bacteria had discrepancies in DDT results for enrofloxacin and ciprofloxacin. Discrepancies between the control group and treatment groups were not significantly different even though the percentage of discrepancies for the combined treatment group was 19.4% compared to 6.7% for the control group. In this study, ciprofloxacin DDT results were not an accurate indicator of thein vitrosusceptibility of enrofloxacin for bacteria isolated from the middle‐ear tissue of dogs with end‐stage otitis.