bluuebunny/crossref_metadata_2025 huggingface dataset:
Defining patch contribution in source‐sink metapopulations: the importance of including dispersal and its relevance to marine systems
Authors: Figueira Will F. , Crowder Larry B.
Published: May 2006

In metapopulations, individual patch contribution (source or sink) is typically calculated as a patch growth rate (the “intrinsic” lambda,λI) dependent only upon local demographics. We demonstrate that when dispersal is explicitly included in the model, the growth rates for all patches calculated in an analogous manner (the “observed” lambda,λO) equilibrate to the overall metapopulation growth rate and thus no longer serve as a useful reflection of the demographic and dispersive characteristics of a given patch. In these situations we suggest an alternative method of estimating patch contribution (the “contribution” lambda,λC) in which a patch is decremented for losses that occur within it and credited for gains that occur anywhere in the metapopulation because of it. We compare values ofλI,λO, andλCfor individual patches in discrete‐time density‐independent metapopulation models of two organisms with very different life histories, mayflies with adult dispersal, and reef fish with larval dispersal. Results confirm that when dispersal is included onlyλCclearly indicates the contribution of a particular patch.λI−λCcomparisons indicate that inclusion of dispersal in the mayfly model was only important if connectivity patterns were random or directional. In the reef fish model, however, results were very different when dispersal was included and there were many cases of patches being misidentified (e.g., as a source when it was really a sink) depending upon the metric used (λIorλC). Our results demonstrate the importance of including dispersal in metapopulation models when considering the contribution of individual patches.
A first assessment of the Ticolichen biodiversity inventory in Costa Rica: the genus Haematomma (Lecanorales: Lecanoraceae)
Authors: NELSEN Matthew P. , LÜCKING Robert , CHAVES José Luis , SIPMAN Harrie J. M. , UMAÑA Loengrin , NAVARRO Enia
Published: May 2006

The genus Haematomma is treated as part of the Ticolichen biodiversity inventory in Costa Rica. Together with literature reports, fourteen taxa are recognized as occurring in the country (plus three species to be expected), and three of them are new to science: Haematomma nicoyense Nelsen, Lücking & Chaves, with a sorediate thallus, russulone and atranorin, and zeorine apothecia with a split between proper excipulum and thalline margin, Haematomma staigeriae Nelsen, Lücking & Umaña, with a sorediate thallus, russulone and lichexanthone, and submuriform ascospores, and Haematomma fluorescens var. longisporum Nelsen, Lücking & Navarro, with russulone and lichexanthone and ascospores up to 120 μ m in length with up to 27 septa. A key is presented for the 17 taxa known or expected from Costa Rica.
Choices and constraints: marriage and inheritance in eighteenth- and early-nineteenth-century Catalonia
Authors: MARFANY JULIE
Published: May 2006

This article looks at marriage in Catalonia during the eighteenth and early nineteenth centuries, a period of rapid economic and social change, using a case study of a proto-industrial community. Differences in age at marriage are related to data on occupations, wealth and age rank in order to consider as many of the factors influencing marriage decisions as possible. Economic factors were one obvious constraint upon marriage, but another was the particular system of impartible inheritance practised in Catalonia. This article shows that, while inheritance continued to affect marriage choices to a considerable extent, the rapid transformation of the economy was breaking down the traditional constraints upon marriage.
Evaluation of Lepto Dri Dot as a rapid test for the diagnosis of leptospirosis
Authors: VIJAYACHARI P. , SUGUNAN A. P. , SEHGAL S. C.
Published: May 2006

Lepto Dri Dot is a new card agglutination test developed by the Dutch Royal Tropical Institute for the rapid diagnosis of leptospirosis. We evaluated the test in field conditions in The Andaman Islands. Patients suspected of leptospirosis who attended three primary health centres were included in the study. The test results were compared with blood culture or microscopic agglutination tests on paired serum samples; 74 of 124 patients were diagnosed as having leptospirosis based on these criteria. Lepto Dri Dot had a sensitivity of 67.6% (50/74) and a specificity of 66.0% (33/50) during week 1. During weeks 2–4 the values increased to 85.5% (47/55) and 80% (40/50) respectively. An IgM ELISA was also performed on the serum samples for comparison and this was marginally less sensitive, but more specific, during the first week of illness. The positivity rates for the Dri Dot test during days 2–3, 4–5 and 6–7 were 53.1% (17/32), 75.0% (18/24) and 83.3% (15/18), respectively. The corresponding values for ELISA were 28.1% (9/32), 54% (13/24) and 77.8% (14/18). Both Dri Dot and ELISA showed good agreement with the standard diagnostic criteria after the first week of illness (κ = 0.65 and 0.74, respectively). The overall concordance of the two tests was 89.5% (κ = 0.79). The test does not require special storage or sophisticated equipment and can be performed by relatively low skilled personnel.
Salmonella and campylobacter contamination of raw retail chickens from different producers: a six year survey
Authors: WILSON I. G.
Published: May 2006

Between 1995 and 2000, a prospective survey was undertaken to investigate the levels of contamination of raw retail chickens (n=1127) with salmonella and campylobacter. The levels of contamination over the 6-year period were 11% (95% CI±6·5%) for salmonella, and 57% (95% CI±9·5%) for campylobacter. S. Bredeney (20%) and S. Enteritidis (18%) were the dominant serovars. Although salmonella contamination was higher than in an earlier survey we conducted (7%), since 1998 it has declined to 6%. Many S. Enteritidis isolates (43%) were associated with one large integrated poultry organization that appears to have successfully managed the contamination, and the serovar has not been isolated since 1998. Contamination ranged from 0 to 44% between different producers. There was no significant difference between producers contributing large and small numbers of samples, although some small producers had much poorer contamination rates than others. S. Bareilly, S. Bredeney, S. Enteritidis and S. Virchow showed associations with particular producers. Campylobacter contamination remains high. Contamination ranged from 47 to 81% between different producers. This study did not show a temporal association between contamination of chickens and human campylobacter infections, indicating that many cases of human campylobacteriosis, particularly during seasonal peaks, do not originate from chickens. Control measures that have reduced salmonella contamination have been largely ineffective against campylobacter and new interventions are needed. Most raw chickens are contaminated with these pathogens, and communicating the importance of minimizing this risk to caterers and the public is vital in reducing human infections.
The occurrence of five major Newcastle disease virus genotypes (II, IV, V, VI and VIIb) in Bulgaria between 1959 and 1996
Authors: CZEGLÉDI A. , HERCZEG J. , HADJIEV G. , DOUMANOVA L. , WEHMANN E. , LOMNICZI B.
Published: May 2006

Partial sequence and restriction enzyme cleavage site analyses of the fusion protein gene were used to genotype 47 Newcastle disease virus strains isolated between 1959 and 1996 in Bulgaria. Viruses belonged to five major genotypes that appeared to be associated with epizootics characterized by temporal and/or geographical restrictions. Genotype IV viruses (responsible for the European branch of the first panzootic) dominated the scene up to the early 1980s, interspersed with sporadic outbreaks caused by genotype II (US strains causing pneumoencephalitis) viruses. Genotype V viruses (transmitted by psittacines from South America) were first shown in 1973 and persisted until the late 1980s. Genotype VI (earliest members from the Middle-East 1968/70 outbreaks) was represented by scattered isolations between 1974 and 1996. A genotype VIIb (recent Middle East epizootic) virus was isolated as early as in 1984. Newcastle disease epizootics in Bulgaria were highlighted by multiple infection with more than one genotype at any one time.
New World origins for haemoparasites infecting United Kingdom grey squirrels (Sciurus carolinensis), as revealed by phylogenetic analysis of bartonella infecting squirrel populations in England and the United States
Authors: BOWN K. J. , ELLIS B. A. , BIRTLES R. J. , DURDEN L. A. , LELLO J. , BEGON M. , BENNETT M.
Published: May 2006

Phylogenetic analyses of bartonella have suggested divergence between bartonellae that infect mammals native to the Old and New Worlds. We characterized bartonella isolated from Eastern grey squirrels (Sciurus carolinensis) in the United States and from grey and red squirrels (Sciurus vulgaris) in the United Kingdom by nucleotide sequence comparison (gltA and groEL). Isolates from grey squirrels in the United States and the United Kingdom were identical, and most similar to Bartonella vinsonii, a species associated with New World rodents. A single and novel bartonella genotype was obtained from all 12 red squirrel isolates. Although grey squirrels were first introduced into the United Kingdom over 125 years ago, they continue to be infected solely by the bartonella associated with grey squirrels native to the United States. These results illustrate that exotic species may be accompanied by the introduction and maintenance, over many generations, of their microparasites.
E. coli O157 phage type 21/28 outbreak in North Cumbria associated with pasteurized milk
Authors: GOH S. , NEWMAN C. , KNOWLES M. , BOLTON F. J. , HOLLYOAK V. , RICHARDS S. , DALEY P. , COUNTER D. , SMITH H. R. , KEPPIE N.
Published: May 2006

In March 1999, a large community outbreak of Escherichia coli O157 infection occurred in North Cumbria. A total of 114 individuals were reported to the Outbreak Control Team (OCT); 88 had laboratory confirmed E. coli O157. Twenty-eight (32%) of the confirmed cases were admitted to hospital, including three children (3·4%) with haemolytic uraemic syndrome. There were no deaths. A case-control study found that illness was strongly associated with drinking pasteurized milk from a local farm (P=<0·0001) on single variable analysis. Microbiological investigations at the farm revealed E. coli O157 phage type (PT) 21/28 VT 2 which was indistinguishable from the human isolates by pulsed field gel electrophoresis. At the time of occurrence this was the largest E. coli O157 outbreak in England and Wales and the first E. coli O157 PT 21/28 VT 2 outbreak associated with pasteurized milk. This outbreak highlights lessons to be learnt regarding on-farm pasteurization.
Characteristics of Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and Staphylococcus aureus isolated from the nasopharynx of healthy children attending day-care centres in the Czech Republic
Authors: ŽEMLIČKOVÁ H. , URBÁšKOVÁ P. , ADÁMKOVÁ V. , MOTLOVÁ J. , LEBEDOVÁ V. , PROCHÁZKA B.
Published: May 2006

Nasopharyngeal carriage of potential pathogens was studied in 425 healthy 3- to 6-year-old children attending 16 day-care centres (DCCs) in nine Czech cities during the winter 2004–2005. The overall carriage of pathogens was 62·8% (Streptococcus pneumoniae, 38·1%; Haemophilus influenzae, 24·9%; Moraxella catarrhalis, 22·1%; Staphylococcus aureus, 16%). An age-related downward trend was observed for colonization with respiratory pathogens in contrast to Staph. aureus whose carriage was significantly higher among older children. The following serotypes of colonizing S. pneumoniae were the most predominant: 23F (20·6%), 6A (15·1%), 6B (12·7%), 18C (7·8%), 15B and 19F (6% each). The majority (94·3%) of H. influenzae isolates were non-typable; among capsulated isolates, serotype b was not found. Decreased susceptibility to penicillin was determined in 3% of pneumococci; 4·6% of H. influenzae strains and 85·1% of M. catarrhalis strains produced β-lactamase. As for non-β-lactam antibiotics, pneumococci resistant to trimethoprim–sulphamethoxazole were the most common (15·7%) among the attendees.
Earthquakes as multiscale dynamic ruptures with heterogeneous fracture surface energy
Authors: Ide Satoshi , Aochi Hideo
Published: May 2006

We propose a model of the wide‐scale growth of dynamic rupture during an earthquake, based on our multiscale simulation of a planar crack in a three‐dimensional homogeneous elastic space. A simple slip‐weakening law governs the fracture/friction processes, and its characteristic parameters, slip‐weakening distance and fracture surface energy, have multiscale heterogeneous distributions. We consider a set of randomly distributed circular patches, whose diameter is proportional to the fracture surface energy. Each patch represents an asperity between irregular fault surfaces, and the size‐number relation of the patches obeys power law statistics. We assess rupture propagation from a small instability using a boundary integral equation method with a renormalization technique. Although most events stop shortly after their initiation, some grow, triggering neighboring patches of similar size. Small and large events show statistically self‐similar properties of rupture growth and stop spontaneously without requiring a special stopping mechanism. The rupture velocity locally exceeds the shear wave speed but globally remains subshear speed due to the increase of the average fracture energy as the rupture grows. The relation between size and frequency of events is a power law, which is explained by the triggering probability between patches. As a consequence of statistically self‐similar random triggering growth, we observe a distinct “main phase” in seismic waves similar to those of natural earthquakes, but we cannot estimate the final size of the event from the initial part of the seismic waves. If this is true for the real earthquakes, predicting the size of a future earthquake would be quite difficult.
Seasonal influence of ENSO on the Atlantic ITCZ and equatorial South America
Authors: Münnich M. , Neelin J. D.
Published: May 2006

In late boreal spring, especially May, a strong relationship exists in observations among precipitation anomalies over equatorial South America and the Atlantic intertropical convergence zone (ITCZ), and eastern equatorial Pacific and central equatorial Atlantic sea surface temperature anomalies (SSTA). A chain of correlations of equatorial Pacific SSTA, western equatorial Atlantic wind stress (WEA), equatorial Atlantic SSTA, sea surface height, and precipitation supports a causal chain in which El Niño/Southern Oscillation (ENSO) induces WEA stress anomalies, which in turn affect Atlantic equatorial ocean dynamics. These correlations show strong seasonality, apparently arising within the atmospheric links of the chain. This pathway and the influence of equatorial Atlantic SSTA on South American rainfall in May appear independent of that of the northern tropical Atlantic. Brazil's Nordeste is affected by the northern tropical Atlantic. The equatorial influence lies further to the north over the eastern Amazon and the Guiana Highlands.
The analysis of the influence of pumice shape on its terminal velocity
Authors: Dellino Pierfrancesco , Mele Daniela , Bonasia Rosanna , Braia Giuseppe , La Volpe Luigi , Sulpizio Roberto
Published: May 2006

Pumice particles represent the basic “ingredient” of many large explosive eruptions and form as a result of magma fragmentation inside the conduit. At the onset of eruption, fragmental pumices are expelled at high velocity from the crater by the overpressure of gas liberated on explosion. The resulting multiphase flow is forced through atmosphere by a variety of transportation mechanisms and pumices eventually decouple from the gas flow, settling down to form pyroclastic deposits. Here we propose new experimental data of terminal velocity together with a quantitative shape analysis of a wide range of pumice particles. The resulting model allows predicting the terminal velocity of pumice by means of easily measured particle characteristics, with an average error of 12%, which compares favourably with previous models.
Dipole strength and variation of the time‐averaged reversing and nonreversing geodynamo based on Thellier analyses of single plagioclase crystals
Authors: Tarduno J. A. , Cottrell R. D.
Published: May 2006

Single plagioclase crystals separated from lavas can contain minute magnetic inclusions that faithfully record the geomagnetic field, while the silicate host limits natural and experimentally induced alteration. Here we use paleointensity analyses of plagioclase crystals to examine three characteristic geodynamo regimes spanning the last 200 Myr: an interval of moderate reversal frequency during the Paleogene, the nonreversing field of the Cretaceous Normal Polarity Superchron, and a period of very high reversal occurrence during the Late Jurassic. An inverse relationship between reversal rate and intensity is supported. Furthermore, the strength of the time‐averaged reversing field is more variable than that of the nonreversing field. These observations are consistent with an active lower mantle, shaping core‐mantle boundary heat flux and efficiency of the geodynamo on timescales of tens of millions of years.
Seasonal variability of aerosols over the Indo‐Gangetic basin
Authors: Jethva Hiren , Satheesh S. K. , Srinivasan J.
Published: May 2006

We examine the spatio‐temporal characteristics of aerosols in the recent years (2000–2003) over the Indian region with special emphasis on the Indo‐Gangetic basin (northern India) using data from Moderate Resolution Imaging Spectroradiometer (MODIS), Aerosol Robotic Network (AERONET) and Total Ozone Mapping Spectroradiometer (TOMS). First, we have compared the MODIS‐derived aerosol optical depth (AOD) and fine‐mode aerosol fraction (FMAF ratio of the fine‐mode AOD to the total mode AOD) with those of AERONET at Kanpur (26.45°N, 80.346°E). It has been found that the MODIS captures the major part of the seasonal variation of aerosols in terms of abundance as well as aerosol type. The absolute errors in AOD were within the predicted uncertainty of Δτ = ±0.05 ± 0.2τ. The monthly mean regional maps of MODIS show high aerosol optical depth (AOD) over the Indo‐Gangetic basin in the range 0.6–1.2 at 550 nm wavelength with significant spatial and temporal variation during the summer (April to June). The associated FMAF was found to be low (<0.4). This indicates that the coarse‐mode particles are dominant in the summer. The spatial distribution of absorbing aerosol index (AAI) derived from TOMS, Ångström exponent (α) and aerosol volume size distribution measured at Kanpur also indicated the presence of absorbing coarse‐mode aerosols during summer. On the other hand, the entire Indo‐Gangetic basin was dominated by the fine‐mode particles during the winter (November to January) with AOD in the range 0.4–0.6. Their spatial and temporal variations, however, were quite low compared to the summer. Results reported in this paper indicate that the Indo‐Gangetic basin has the largest aerosol optical depth in India during both the seasons. The region is dominated by the large absorbing coarse‐mode particles (possibly transported dust from the northwest of India) in the summer and by the probable widespread emission sources of fine‐mode aerosols (primarily of anthropogenic origin) in the winter. The unique topography and weather condition of the region have impact on the observed spatial and temporal distribution of aerosols.
Potential nighttime contamination of CERES clear‐sky fields of view by optically thin cirrus during the CRYSTAL‐FACE campaign
Authors: Lee Yong‐Keun , Yang Ping , Hu Yongxiang , Baum Bryan A. , Loeb Norman G. , Gao Bo‐Cai
Published: May 2006

We investigate the outgoing broadband longwave (LW, 5∼200 μm) and window (WIN, 8∼12 μm) channel radiances at the top of atmosphere (TOA) under clear‐sky conditions, using data acquired by the Cloud and the Earth's Radiant Energy System (CERES) and Moderate‐Resolution Imaging Spectroradiometer (MODIS) instruments on board the NASA Terra satellite platform. In this study, detailed analyses are performed on the CERES Single Scanner Footprint TOA/Surface Fluxes and Clouds product to understand the radiative effect of thin cirrus. The data are acquired over the Florida area during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers – Florida Area Cirrus Experiment (CRYSTAL‐FACE) field program. Of particular interest is the anisotropy associated with the radiation field. Measured CERES broadband radiances are compared to those obtained from rigorous radiative transfer simulations. Analysis of results from this comparison indicates that the simulated radiances tend to be larger than their measured counterparts, with differences ranging from 2.1% to 8.3% for the LW band and from 1.7% to 10.6% for the WIN band. The averaged difference in radiance is approximately 4% for both the LW and WIN channels. A potential cause for the differences could be the presence of thin cirrus (i.e., optically thin ice clouds with visible optical thicknesses smaller than approximately 0.3). The detection and quantitative analysis of these thin cirrus clouds are challenging even with sophisticated multispectral instruments. While large differences in radiance between the CERES observations and the theoretical calculations are found, the corresponding difference in the anisotropic factors is very small (0.2%). Furthermore, sensitivity studies show that the influence due to a ±1 K bias of the surface temperature on the errors of the LW and WIN channel radiances is of the same order as that associated with a ±2% bias of the surface emissivity. The LW and WIN errors associated with a ±5% bias of water vapor amount in the lower atmosphere in conjunction with a ±50% bias of water vapor amount in the upper atmosphere is similar to that of a ±1 K bias of the vertical temperature profile. Even with the uncertainties considered for these various factors, the simulated LW and WIN radiances are still larger than the observed radiances if thin cirrus clouds are excluded.
Estimating forest biomass in the USA using generalized allometric models and MODIS land products
Authors: Zhang Xiaoyang , Kondragunta Shobha
Published: May 2006

Spatially‐distributed forest biomass components are essential to understand carbon cycle and the impact of biomass burning emissions on air quality. We estimated the density of forest biomass components (foliage biomass, branch biomass, and aboveground biomass) at a spatial resolution of 1 km across the Contiguous United States using foliage‐based generalized allometric models and Moderate‐Resolution Imaging Spectroradiometer (MODIS) land data. The foliage biomass for each forest type was calculated from MODIS leaf‐area indices, land cover types, and vegetation continuous fields. The foliage‐based models were developed using available diameter‐based allometric equations and used to estimate branch biomass and aboveground biomass. The resultant aboveground biomass density matches well with the data from Forest Inventory and Analysis program at both state and pixel levels.
Seasonal variability of the permanent thermocline off northern Chile
Authors: Ramos Marcel , Pizarro Oscar , Bravo Luis , Dewitte Boris
Published: May 2006

The seasonal cycle of the depth of several isotherms representative of the main thermocline near the western coast of South America shows important semiannual and annual components. Annual thermocline oscillations are mainly related to wind stress curl changes and, secondarily, to alongshore wind and the annual equatorial Kelvin wave. In contrast, the important semiannual component observed in hydrographic data off Peru and Chile is mainly of equatorial origin. Based on satellite sea level anomalies and Rossby wave theory, we show that the coastal seasonal signal –annual and semiannual– propagates seaward near 21°S in the form of long Rossby waves, which may modulate the thermocline depth several hundreds of kilometers offshore.
Validation of a Tracer Kinetic Model for the Quantification of 5-HT2A Receptors in Human Brain with [11C]MDL 100,907
Authors: Hinz Rainer , Bhagwagar Zubin , Cowen Philip J , Cunningham Vincent J , Grasby Paul M
Published: May 2006

The positron emission tomography (PET) ligand [11C]MDL 100,907 has previously been introduced to image the serotonin 2A (5-HT2A) receptor in human brain. The aim of this work was to contribute to the verification of the tracer kinetic modelling in human studies. Five healthy volunteers were scanned twice after intravenous bolus injection of approximately 370 MBq [11C]MDL 100,907 using dynamic PET. One scan was performed under baseline condition, the other scan commenced 90 mins after a single oral dose of 30 mg of the antidepressant mirtazapine, which binds to the 5-HT2A receptor. There did not appear to be radiolabelled metabolites of [11C]MDL 100,907 in human plasma, which are likely to cross the blood–brain barrier. Total volumes of distribution VD in 11 different brain regions were estimated using a reversible, two tissue, four rate constants compartment model with a variable fractional blood volume term and the metabolite-corrected plasma input function. There were no significant changes of the VD in the cerebellum between the baseline and the blocked scans confirming the cerebellum as a region devoid of displaceable binding. Regional estimates of binding potential were then obtained indirectly using the cerebellar VD and occupancies calculated. The mean occupancy with this clinically effective dose of mirtazapine was 60% without significant regional differences. This study confirmed the use of an arterial input kinetic model for the quantification of 5-HT2A receptor binding with [11C]MDL 100,907 and the use of the cerebellum as a reference region for the free and nonspecific binding.
Quantitative Analysis for Estimating Binding Potential of the Peripheral Benzodiazepine Receptor with [11C]DAA1106
Authors: Ikoma Yoko , Yasuno Fumihiko , Ito Hiroshi , Suhara Tetsuya , Ota Miho , Toyama Hinako , Fujimura Yota , Takano Akihiro , Maeda Jun , Zhang Ming-Rong , Nakao Ryuji , Suzuki Kazutoshi
Published: May 2006

[11C]DAA1106 is a potent and selective ligand for the peripheral benzodiazepine receptor (PBR) with high affinity. It has been reported that the density of PBR is related to brain damage, so a reliable tracer method for the evaluation of PBR would be of use. We evaluated a quantification method of [11C]DAA1106 binding in simulated data and human brain data. In the simulation study, the reliability of parameters estimated from the nonlinear least-squares (NLS) method, graphical analysis (GA), and multilinear analysis (MA) was evaluated. In GA, variation of the estimated distribution volume (DV) was small. However, DV was underestimated as noise increased. In MA, bias was smaller, and variation of the estimated DV was larger than in GA. In NLS, although variation was larger than in GA, it was small enough in regions of interest analysis, and not only DV but also binding potential (BP), determined from the k3/k4without any constraint, could be estimated. The variation of BP estimated with NLS became larger as k3or k4became smaller. In human studies with normal volunteers, regions of interest were drawn on several brain regions, BP was calculated by NLS, and DV was also estimated by NLS, GA, and MA. As a result, DVs estimated with each method were well correlated. However, there was no correlation between BP with NLS and DV with NLS, GA, and MA, because of the variation of K1/k2between individuals. In conclusion, BP is estimated most reliably by NLS with the two-tissue compartment model.
The crystal structure of SdsA1, an alkylsulfatase from
Pseudomonas aeruginosa
, defines a third class of sulfatases
Authors: Hagelueken Gregor , Adams Thorsten M. , Wiehlmann Lutz , Widow Ute , Kolmar Harald , Tümmler Burkhard , Heinz Dirk W. , Schubert Wolf-Dieter
Published: May 2006

Pseudomonas aeruginosa
is both a ubiquitous environmental bacterium and an opportunistic human pathogen. A remarkable metabolic versatility allows it to occupy a multitude of ecological niches, including wastewater treatment plants and such hostile environments as the human respiratory tract.
P. aeruginosa
is able to degrade and metabolize biocidic SDS, the detergent of most commercial personal hygiene products. We identify SdsA1 of
P. aeruginosa
as a secreted SDS hydrolase that allows the bacterium to use primary sulfates such as SDS as a sole carbon or sulfur source. Homologues of SdsA1 are found in many pathogenic and some nonpathogenic bacteria. The crystal structure of SdsA1 reveals three distinct domains. The N-terminal catalytic domain with a binuclear Zn
2+
cluster is a distinct member of the metallo-β-lactamase fold family, the central dimerization domain ensures resistance to high concentrations of SDS, whereas the C-terminal domain provides a hydrophobic groove, presumably to recruit long aliphatic substrates. Crystal structures of apo-SdsA1 and complexes with substrate analog and products indicate an enzymatic mechanism involving a water molecule indirectly activated by the Zn
2+
cluster. The enzyme SdsA1 thus represents a previously undescribed class of sulfatases that allows
P. aeruginosa
to survive and thrive under otherwise bacteriocidal conditions.
Allelic silencing at the tumor-suppressor locus 13q14.3 suggests an epigenetic tumor-suppressor mechanism
Authors: Mertens Daniel , Wolf Stephan , Tschuch Cordula , Mund Cora , Kienle Dirk , Ohl Sibylle , Schroeter Petra , Lyko Frank , Döhner Hartmut , Stilgenbauer Stephan , Lichter Peter
Published: May 2006

Genomic material from chromosome band 13q14.3 distal to the retinoblastoma locus is recurrently lost in a variety of human neoplasms, indicating an as-yet-unidentified tumor-suppressor mechanism. No pathogenic mutations have been found in the minimally deleted region until now. However, in B cell chronic lymphocytic leukemia tumors with loss of one copy of the critical region, respective candidate tumor-suppressor genes are down-regulated by a factor >2, which would be expected by a normal gene-dosage effect. This finding points to an epigenetic pathomechanism. We find that the two copies of the critical region replicate asynchronously, suggesting differential chromatin packaging of the two copies of 13q14.3. Although we also detect monoallelic silencing of genes localized in the critical region, monoallelic expression originates from either the maternal or paternal copy, excluding an imprinting mechanism. DNA methylation analyses revealed one CpG island of the region to be methylated. DNA demethylation of this CpG island and global histone hyperacetylation induced biallelic expression, whereas replication timing was not affected. We propose that differential replication timing represents an early epigenetic mark that distinguishes the two copies of 13q14.3, resulting in differential chromatin packaging and monoallelic expression. Accordingly, deletion of the single active copy of 13q14.3 results in significant down-regulation of the candidate genes and loss of function, providing a model for the interaction of genetic lesions and epigenetic silencing at 13q14.3 in B cell chronic lymphocytic leukemia.
A biochemical rationale for the anticancer effects of Hsp90 inhibitors: Slow, tight binding inhibition by geldanamycin and its analogues
Authors: Gooljarsingh Lata T. , Fernandes Christine , Yan Kang , Zhang Hong , Grooms Michael , Johanson Kyung , Sinnamon Robert H. , Kirkpatrick Robert B. , Kerrigan John , Lewis Tia , Arnone Marc , King Alastair J. , Lai Zhihong , Copeland Robert A. , Tummino Peter J.
Published: May 2006

Heat shock protein (Hsp)90 is emerging as an important therapeutic target for the treatment of cancer. Two analogues of the Hsp90 inhibitor geldanamycin are currently in clinical trials. Geldanamycin (GA) and its analogues have been reported to bind purified Hsp90 with low micromolar potency, in stark contrast to their low nanomolar antiproliferative activity in cell culture and their potent antitumor activity in animal models. Several models have been proposed to account for the ≈100-fold-greater potency in cell culture, including that GA analogues bind with greater affinity to a five-protein Hsp90 complex than to Hsp90 alone. We have determined that GA and the fluorescent analogue BODIPY-GA (BDGA) both demonstrate slow, tight binding to purified Hsp90. BDGA, used to characterize the kinetics of ligand–Hsp90 interactions, was found to bind Hsp90α with
k
off
= 2.5 × 10
−3
min
−1
,
t
1/2
= 4.6 h, and
K
i
* = 10 nM. It was found that BDGA binds to a functional multiprotein Hsp90 complex with kinetics and affinity identical to that of Hsp90 alone. Also, BDGA binds to Hsp90 from multiple cell lysates in a time-dependent manner with similar kinetics. Therefore, our results indicate that the high potency of GA in cell culture and
in vivo
can be accounted for by its time-dependent, tight binding to Hsp90 alone. In the broader context, these studies highlight the essentiality of detailed biochemical characterization of drug–target interactions for the effective translation of
in vitro
pharmacology to cellular and
in vivo
efficacy.
Genetic analysis of Cryptosporidium from 2414 humans with diarrhoea in England between 1985 and 2000
Authors: Leoni F. , Amar C. , Nichols G. , Pedraza-Díaz S. , McLauchlin J.
Published: May 2006

The characterization of Cryptosporidium using DNA extracted from whole faecal samples collected from 2414 humans with diarrhoea in England between 1985 and 2000 where cryptosporidial oocysts were detected using conventional methods is described. Characterization was achieved by PCR/RFLP and DNA sequencing of fragments of the Cryptosporidium oocyst wall protein and the 18S rDNA genes. Cryptosporidium parvum was detected in 56.1 % of cases, Cryptosporidium hominis in 41.7 % and a mixture of C. parvum and C. hominis in 0.9 %. In the remainder of cases, Cryptosporidium meleagridis (0.9 %), Cryptosporidium felis (0.2 %), Cryptosporidium andersoni (0.1 %), Cryptosporidium canis (0.04 %), Cryptosporidium suis (0.04 %) and the Cryptosporidium cervine type (0.04 %) were detected.
Identification of novel cps locus polymorphisms in nontypable group B Streptococcus
Authors: Ramaswamy Srinivas V. , Ferrieri Patricia , Madoff Lawrence C. , Flores Aurea E. , Kumar Nikhil , Tettelin Hervé , Paoletti Lawrence C.
Published: May 2006

Group B Streptococcus (GBS) is an important pathogen responsible for a variety of diseases in newborns and the elderly. A clinical GBS isolate is considered nontypable (NT) when serological methods fail to identify it as one of nine known GBS serotypes. Eight clinical isolates (designated A1–A4, B1–B4) showed PFGE profiles similar to that of a GBS serotype V strain expressing R1, R4 surface proteins. These unique isolates were further characterized by immunologic and genetic methods. Rabbit sera to isolates A1 and A2 reacted weakly with concentrated HCl extracts of A1–A4 isolates, but not with those of B1–B4 isolates. In addition, a type V capsular polysaccharide (CPS) inhibition ELISA revealed that cell wall extracts from isolates A1–A4, but not from B1–B4, expressed low but measurable amounts of type V CPS. Molecular serotyping with PCR analysis showed that all eight isolates contained a type V-specific CPS gene (cpsO) and harboured the gene encoding the surface protein Alp3. Multilocus sequence typing identified isolate A1 as belonging to a new sequence type (ST) designated ST-173, whereas the other seven isolates keyed to ST-1. Sequencing of the 18 genes (17 736 bp) in the cps locus showed that each NT isolate harboured one to three unique polymorphisms, and also identified an IS1381 element in cpsE of the B4 isolate. Collectively, genetic and immunologic analyses revealed that these NT isolates expressing R1, R4 proteins have a genetic profile consistent with that of type V, an emergent, antigenically diverse and increasingly prevalent GBS serotype.
Genotypic identification of presumptive Streptococcus pneumoniae by PCR using four genes highly specific for S. pneumoniae
Authors: Suzuki Nao , Yuyama Mayumi , Maeda Sinsaku , Ogawa Haruhiko , Mashiko Kazuyuki , Kiyoura Yusuke
Published: May 2006

It was previously reported that two oligonucleotide primer sets (spn9802 and spn9828) for discriminatingStreptococcus pneumoniaefrom pneumococcus-like oral streptococcal isolates using PCR had been developed. In this study, PCR amplification of thelytA,ply, spn9802 and spn9828 genes was used to identify presumptiveS. pneumoniae. Two genetic groups were identified by analysing sputum samples from 28 patients with community-acquired pneumonia: thelytA-positive,ply-positive, spn9802-positive and spn9828-negative group, and thelytA-positive,ply-positive, spn9802-positive and spn9828-positive group. Isolates of the former group were resistant to optochin, while those of the latter group showed susceptibility to optochin. ThelytA-positive,ply-positive, spn9802-negative and spn9828-negative isolates, andlytA-positive,ply-positive, spn9802-negative and spn9828-positive isolates, were not detected in sputum from patients with pneumonia. Subsequently, a total of 92 saliva samples from healthy individuals was screened by PCR using these primer sets. ThelytA-positive,ply-positive, spn9802-positive and spn9828-negative group was identified more frequently in saliva from healthy children than in saliva from older healthy individuals and patients with pneumonia. ThelytA-positive,ply-positive, spn9802-positive and spn9828-positive group was found frequently in saliva from healthy children, and in saliva and sputum from patients with pneumonia. This study demonstrates a rapid, optimal screening method for the genotypic identification of presumptiveS. pneumoniaeby PCR using four genes highly specific forS. pneumoniae.
Detection of clinical-stage specific molecular Toxoplasma gondii gene patterns in patients with toxoplasmic lymphadenitis
Authors: Contini Carlo , Giuliodori Margherita , Cultrera Rosario , Seraceni Silva
Published: May 2006

Three cases of symptomatic toxoplasmic lymphadenitis, together with a serologic profile of recent infection, are described, for which quantitative real-time PCR (LightCycler PCR) targeting different parasite genes was designed, in order to quantify Toxoplasma gondii DNA in acute and follow-up blood specimens. Similar parasite gene kinetics and DNA concentrations were observed in the patients studied. However, the profile of each target gene investigated was different. While the level of B1 DNA remained elevated for the entire time of observation, irrespective of clinical and serologic resolution, the SAG-1 gene was detected at the end of acute symptomatic disease, overlapping with a strong anti-T. gondii IgA antibody response, and persisting for over 3 months after infection and clinical recovery. With respect to the two bradyzoite genes investigated (SAG-4 and MAG-1), levels peaked during the symptomatic phase, but did not fall until 2 or 3 months of follow up. The real-time PCR assay with new alternative targets to the B1 gene may have potential for monitoring the clinical outcome of disease and for providing molecular information regarding the actual state of infection.
Identification, subtyping and virulence determination of Listeria monocytogenes, an important foodborne pathogen
Authors: Liu Dongyou
Published: May 2006

Listeria monocytogenesis an opportunistic intracellular pathogen that has become an important cause of human foodborne infections worldwide. Given its close relationship to otherListeriaspecies and its tendency to produce non-specific clinical symptoms, the availability of rapid, sensitive and specific diagnostic tests for the differentiation ofL. monocytogenesfrom otherListeriaspecies is helpful for selecting appropriate treatment regimens. In addition, withL. monocytogenescomprising a diversity of strains of varying pathogenicity, the ability to precisely track the strains involved in listeriosis outbreaks and speedily determine their pathogenic potential is critical for the control and prevention of further occurrences of this deadly disease. Extensive research in recent decades has revealed significant insights regarding the molecular mechanisms ofL. monocytogenesinfection. This in turn has facilitated the development of laboratory procedures for enhanced detection and identification ofL. monocytogenes, and has also contributed to the implementation of improved control and prevention strategies against listeriosis. The purpose of this review is to summarize recent progress in the species-specific identification, subtyping and virulence determination ofL. monocytogenesstrains, and to discuss future research needs pertaining to these important areas of listeriosis.
Human herpesvirus-6 dysregulates monocyte-mediated anticryptococcal defences
Authors: Cermelli Claudio , Cenacchi Valeria , Beretti Francesca , Pezzini Francesco , Luca Dario Di , Blasi Elisabetta
Published: May 2006

In order to investigate the interplay occurring between pathogens in the course of double infections, anin vitromodel was set up in which the monocytic cell line THP-1 was exposed toCryptococcus neoformans(Cn) and human herpesvirus 6 (HHV-6).Cnand HHV-6, both highly neurotropic, can cause serious diseases of the central nervous system and have monocytes, among other cell types, as target cells, causing alteration of their secretion pattern. Here, it was shown that unlike THP-1 cells exposed to cell-free virus inocula, THP-1 exposed to HHV-6-producing lymphocytes exhibited augmented phagocytosis againstCn. The phenomenon occurred after 24 h of monocyte/lymphocyte co-culture and was independent of direct cell-to-cell contact. Moreover, in the presence of HHV-6, THP-1 cells expressed enhanced secretory responses but reduced capability to counteract fungal infection: the enhanced ingestion by monocytes was followed by facilitated fungal survival and replication. These data provide initialin vitroevidence that HHV-6 may dysregulate monocyte-mediated anticryptococcal defences with an overall pro-cryptococcus result.
Sporadic human Yersinia enterocolitica infections caused by bioserotype 4/O : 3 originate mainly from pigs
Authors: Fredriksson-Ahomaa Maria , Stolle Andreas , Siitonen Anja , Korkeala Hannu
Published: May 2006

Yersinia enterocolitica 4/O : 3 is the most frequent cause of sporadic human yersiniosis in Finland and Germany. To investigate the possible link between pigs and humans, 282 human and 534 porcine strains from Finland and Germany were characterized with PFGE using NotI, ApaI and XhoI enzymes. Most of the human strains (>80 %) were indistinguishable from the porcine strains in both countries and most of the genotypes (178/182) were different in Finland and Germany. The indistinguishable genotypes among human and porcine strains together with different genotypes in Finland and Germany indicate that pigs are an important source of sporadic yersiniosis in both countries.
Market for Information and Identity Disclosure in an Experimental Open Limit Order Book
Authors: Perotti Pietro , Rindi Barbara
Published: May 2006

This paper analyses the effects of pre‐trade transparency on market quality in an experimental open limit order book preceded by a market for information. The design of the trading game is akin to the system in use in an increasing number of financial markets. We find that the disclosure of traders’ identities reduces the incentive to acquire information, liquidity and volatility. We also show that a positive relation exists between the proportion of traders buying information and liquidity. The results are consistent with a standard model of price formation where the number of informed traders is endogenous.
Subtoxic concentrations of allergenic haptens induce LC migration and maturation in a human organotypic skin explant culture model: a novel method for identifying potential contact allergens
Authors: Lehé Cynthia L. , Jacobs John J. L. , Hua Chi Mei , Courtellemont P , Elliott Graham R. , Das Pranab K.
Published: May 2006

Abstract:  The accelerated migration of Langerhans cells (LCs) out of the epidermis and up‐regulation of maturation markers, upon treatment with subtoxic concentrations of chemicals, were used as the criteria to determine the potential of allergenic chemicals capable of inducing a hapten‐specific delayed‐type hypersensitivity reaction. Here we report the findings of a study in which seven chemicals, coded and tested in a blind fashion, were classified as contact allergens or non‐allergens using the human organotypic skin explant culture (hOSEC) model. All chemicals that were identified as a contact sensitizer on decoding induced a definite decrease in the number of CD1a and HLA‐DR‐positive epidermal LCs in the epidermis of the skin explants, as determined by both semiquantitative immunohistochemistry and quantitative flow cytometric analysis. A significant increase in the number of CD83+ cells was accompanied by up‐regulation of activation molecules in the epidermis of hOSEC exposed specifically to contact allergens. In contrast, there were only minor alterations in epidermal LC numbers, expression of CD83 and other activation markers by LCs when the biopsies were treated with non‐toxic concentrations of non‐allergenic irritants and vehicles. The data suggest that an increased epidermal LC migration and maturation accompanied by increased expression of activation markers could be used as end‐point determinants to screen allergens in a non‐animal alternative hOSEC model.
Expression of voltage‐gated calcium channel subunit α1C in epidermal keratinocytes and effects of agonist and antagonists of the channel on skin barrier homeostasis
Authors: Denda Mitsuhiro , Fujiwara Shigeyoshi , Hibino Toshihiko
Published: May 2006

Abstract:  Recent studies demonstrated that skin surface electric conditions affect epidermal permeability barrier homeostasis. These results suggest the existence of voltage sensor on the keratinocytes of the epidermis. On the contrary, specific blockers of the voltage‐gated calcium channel (VGCC) also affect epidermal barrier homeostasis, but the existence and function of the channel has not been determined. We demonstrated here immunohistochemically the expression of the main subunit of the L‐type VGCC, α1C, which alone has a calcium channel function, in mouse and human epidermis. Immunostaining, RT–PCR, and Western blotting were carried out to detect the channel protein. Messenger RNA of α1C was also detected in mouse epidermis and human keratinocyte culture by RT–PCR. We also evaluated the function of the channel in the cultured human keratinocytes. Previously, we demonstrated that influx of calcium ion into epidermal keratinocytes delayed the barrier recovery after barrier disruption and topical application of calcium channel blocker accelerated the barrier recovery. In this study, topical application of nifedipine and R‐(+)‐BAY K8644 after tape stripping of hairless mice accelerated the barrier repair rate while application of S‐(–)‐BAY K8644 delayed the barrier recovery. These results suggest that the VGCC exists on epidermal keratinocytes and plays an important role in skin barrier homeostasis.