bluuebunny/crossref_metadata_2025 huggingface dataset:
Trematodes in a Cyathura carinata population from a temperate intertidal estuary: infection patterns and impact on host
Authors: Jensen K. Thomas , Ferreira Susana M. , Pardal Miguel A.
Published: November 2004

A study was initiated to identify trematode patterns in Cyathura from two key sites in the Mondego Estuary: a Zostera-bed and a sand flat. The two subpopulations of Cyathura differ, as the annual recruitment success is much higher and more regular on the sandflat than on the Zostera-bed.

Counting and sizing of trematode cysts inside the body of preserved Cyathura specimens enabled a description of trematode patterns in space and time. Further identification of trematodes was based on DNA studies of unpreserved cysts as well as on identification of parasites in co-occurring mud snails. Two trematode species dominated in Cyathura: Maritrema subdolum (cysts around 190 μm) and a hitherto unknown Levinseniella species (cysts around 340 μm), the latter being the most frequent one. Generally, the prevalence of both species peaked during winter months, when migratory water birds occur in the estuary. Cyathura from the Zostera bed harboured more infections per specimen than those from the sand flat. A much higher density of mud snails ≥52 mm (which can be host to microphallids) and a low abundance of Cyathura are thought to be the main reasons for this pattern. Field data did indicate a host size-dependent maximum number of cysts in Cyathura that could be a result of enhanced mortality at high cyst intensities. Furthermore, parasites were underrepresented among ovigerous Cyathura specimens, suggesting a negative impact on gametogenesis. As a consequence, microphallid trematodes may be a critical factor controlling recruitment strength in Cyathura, especially at the Zostera-site.
Small-scale spatial variation in rates of metacercarial accumulation by a bivalve second intermediate host
Authors: Poulin R. , Mouritsen K.N.
Published: November 2004

In a field experiment, the accumulation of trematode (Echinostomatidae) metacercariae by the New Zealand cockle Austrovenus stutchburyi was compared among treatments with different seabed hydrodynamics and sedimentation rates. There was no significant difference among the treatments in the rate at which cockles accumulated metacercariae, suggesting that infection rates are not influenced by water flow conditions within the normal range experienced in natural habitats. There was, however, substantial spatial variation in infection rates among the experimental plots. This result indicates that metacercarial accumulation varies horizontally as well as vertically within the intertidal zone.
Iron encrustation of the bivalve Montacuta ferruginosa
Authors: Gillan David C. , De Ridder Chantal
Published: November 2004

The epibiotic iron-encrusted biofilms occurring on the shell of the bivalve Montacuta ferruginosa were examined over an annual cycle in order to determine possible variation of the iron-encrustation. Among the 379 examined specimens, well-coated bivalves always predominate. However, it was found that about 50% of the small-sized bivalves were uncoated or weakly coated during the summer months. This result can be explained by the life history of the bivalve and by the physico-chemical conditions in the sediments.
Does light intensity affect embryonic development of squid (Heterololigo bleekeri)?
Authors: Ikeda Yuzuru , Ito Kingo , Matsumoto Gen
Published: November 2004

The effect of light intensity on the course of embryonic development of squid (Heterololigo bleekeri) was examined. Heterololigo bleekeri embryos at an early stage were incubated in the egg cases under six to seven gradients of light intensities which varied from constant darkness to intensive light >1000 lx (12L:12D for all experimental groups except for the constant darkness group). Duration of hatching in every experimental group ranged from seven to 15 days with a peak for ≈30–50% of total number of hatchlings. However, there were no particular relationships between light intensities and duration of embryonic development, duration of hatching, number of hatchlings at hatching peak, and body size of hatchlings. In all groups, body size of hatchlings increased up to seven days post-hatching and thereafter did not change remarkably. Just after hatching, strongly positive photo taxis was observed for H. bleekeri
Lattice location and thermal stability of implanted Fe in ZnO
Authors: Rita E. , Wahl U. , Correia J. G. , Alves E. , Soares J. C. ,   The ISOLDE Collaboration
Published: November 2004

The emission channeling technique was applied to evaluate the lattice location of implanted Fe59 in single-crystalline ZnO. The angular distribution of β− particles emitted by Fe59 was monitored with a position-sensitive electron detector, following 60 keV low dose (2.0×1013cm−2) room-temperature implantation of the precursor isotope Mn59. The emission patterns around the [0001], [1̱102],[1̱101], and [2̱113] directions revealed that following annealing at 800 °C, 95(8)% of the Fe atoms occupy ideal substitutional Zn sites with rms displacements of 0.06-0.09 Å.
Subcellular distribution of enzyme I of the
Escherichia coli
phospho
enol
pyruvate:glycose phosphotransferase system depends on growth conditions
Authors: Patel Himatkumar V. , Vyas Kavita A. , Li Xibing , Savtchenko Regina , Roseman Saul
Published: November 2004

The phospho
enol
pyruvate:glycose phosphotransferase system (PTS) participates in important functions in the bacterial cell, including the phosphorylation/uptake of PTS sugars. Enzyme I (EI), the first protein of the PTS complex, accepts the phosphoryl group from phospho
enol
pyruvate, which is then transferred through a chain of proteins to the sugar. In these studies, a mutant GFP, enhanced yellow fluorescent protein (YFP), was linked to the N terminus of EI, giving Y-EI. Y-EI was active both
in vitro
(≥90% compared with EI) and
in vivo
. Unexpectedly, the subcellular distribution of Y-EI varied significantly. Three types of fluorescence were observed: (
i
) diffuse (dispersed throughout the cell), (
ii
) punctate (concentrated in numerous discrete spots throughout the cell), and (
iii
) polar (at one or both ends of the cell). Cells from dense colonies grown on agar plates with LB broth or synthetic (Neidhardt) medium showed primarily bipolar or punctate fluorescence. In liquid culture, under carefully defined carbon-limiting growth conditions [ribose (non-PTS), mannitol (PTS sugar), or
dl
-lactate], cellular levels of enzymatically active Y-EI remain essentially constant for each carbon source, but fluorescence distribution depends on C source, cell density, growth phase, and apparently on “conditioned medium.” Fluorescence was diffuse during exponential growth on LB or ribose/Neidhardt medium. On ribose they became punctate in the stationary phase, reverting to diffuse when more ribose was added. In LB, both Y-EI and a nonphosphorylatable mutant, H189Q-Y-EI, showed a diffuse fluorescence during growth, but, shortly after the addition of isopropyl β-
d
-thiogalactopyranoside, Y-EI became bipolar; H189Q-Y-EI did not. The functions of EI sequestration remain to be determined.
Physiological function and neuromuscular recruitment in elite South African distance runners
Authors: Noakes Timothy D , Harley Yolande XR , Bosch Andrew N , Marino Frank E , Gibson Alan St Clair , Lambert Michael I
Published: November 2004

Physiological studies of elite and sub-elite black South African runners show that these athletes are typically about 10–12 kg lighter than white athletes and that they are able to sustain higher exercise intensities for longer than white runners. Such superior performance is not a result of higher V O2max values and hence cannot be due to superior oxygen delivery to the active muscles during maximal exercise, as is predicted by the traditional cardiovascular/anaerobic/catastrophic models of exercise physiology. A marginally superior running economy is also unlikely to be a crucial determinant in explaining this apparent superiority. However, black athletes are able to sustain lower rectal and thigh, but higher mean skin, temperatures during exercise. Furthermore, when exercising in the heat, lighter black athletes are able to maintain higher running speeds than are larger white runners matched for running performance in cool environmental conditions. According to the contrasting theory that the body acts as a complex system during exercise, the superiority of black African athletes should be sought in an enhanced capacity to maintain homeostasis in all their inter-dependent biological systems despite running at higher relative exercise intensities and metabolic rates. In this case, any explanation for the success of East African runners will be found in the way in which their innate physiology, training, environment, expectations and genes influence the function of those parts of their subconscious (and conscious) brains that appear to regulate the protection of homeostasis during exercise as part of an integrative, complex biological system.
Responses to fish predation and nutrients by plankton at different levels of taxonomic resolution
Authors: Hansson Lars‐Anders , Gyllström Mikael , Ståhl‐Delbanco Annika , Svensson Marie
Published: November 2004

1. To improve mechanistic understanding of plankton responses to eutrophication, a mesocosm experiment was performed in the shallow littoral zone of a south Swedish lake, in which nutrient and fish gradients were crossed in a fully factorial design.

2. Food chain theory accurately predicted total biomass development of both phyto‐ and zooplankton. However, separating zooplankton and algae into finer taxonomic groups revealed a variety of responses to both nutrient and fish gradients.

3. That both nutrients and fish are important for phytoplankton dynamics was seen more clearly when viewing each algal group separately, than drawing conclusions only from broad system variables such as chlorophyll a concentration or total phytoplankton biovolume.

4. In some taxa, physiological constraints (e.g. sensitivity to high pH and low concentrations of free CO2) and differences in competitive ability may be more important for the biomass development than fish predation, grazing by herbivorous zooplankton, and nutrient availability.

5. We conclude that food chain theory accurately predicted responses in system variables, such as total zooplankton or algal biomass, which are shaped by the dynamics of certain strong interactors (‘keystone species’), such as large cladocerans, cyanobacteria and edible algae (<50 μm), whereas responses at finer taxonomic levels cannot be predicted from current theory.
Effects of fish and nutrient additions on food‐web stability in a charophyte‐dominated lake
Authors: Van De Bund Wouter J. , Van Donk Ellen
Published: November 2004

1. The response of major food‐web constituents to combinations of nutrient addition and zooplanktivorous fish abundance was tested during two subsequent years in the shallow charophyte‐dominated lake Naardermeer in the Netherlands, using in situ enclosures.

2. Treatment effects differed sharply between study years. In 1998, when the summer temperature was low (17–21 °C), high algal biomass only developed at high nutrient levels in the presence of fish, but with no major effect on Chara biomass. In 1999, when the summer temperature was relatively high (20–25 °C), algal blooms occurred at high nutrient levels regardless of fish abundance, and were associated with a drastic decline in Chara biomass.

3. Differences between years in temperature and initial zooplankton composition and biomass were likely to contribute to the varying relative importance of top‐down and bottom‐up effects in these enclosure experiments.

4. The results suggest that when nutrient loads are increased towards levels where the macrophyte‐dominated state is being destabilised, a ‘switch’ is more likely to occur in warm summers.
Continental‐scale patterns of nutrient and fish effects on shallow lakes: introduction to a pan‐European mesocosm experiment
Authors: Stephen D. , Balayla D. M. , Bécares E. , Collings S. E. , Fernández‐Aláez C. , Fernández‐Aláez M. , Ferriol C. , García P. , Gomá J. , Gyllström M. , Hansson L.‐A. , Hietala J. , Kairesalo T. , Miracle M. R. , Romo S. , Rueda J. , Ståhl‐Delbanco A. , Svensson M. , Vakkilainen K. , Valentín M. , Van de Bund W. J. , Van Donk E. , Vicente E. , Villena M. J. , Moss B.
Published: November 2004

1. Shallow lake ecosystems are normally dominated by submerged and emergent plants. Biological stabilising mechanisms help preserve this dominance. The systems may switch to dominance by phytoplankton, however, with loss of submerged plants. This process usually takes place against a background of increasing nutrient loadings but also requires additional switch mechanisms, which damage the plants or interfere with their stabilising mechanisms.

2. The extent to which the details or even major features of this general model may change with geographical location are not clear. Manipulation of the fish community (biomanipulation) has often been used to clear the water of algae and restore the aquatic plants in northerly locations, but it is again not clear whether this is equally appropriate at lower latitudes.

3. Eleven parallel experiments (collectively the International Mesocosm Experiment, IME) were carried out in six lakes in Finland, Sweden, England, the Netherlands and Spain in 1998 and 1999 to investigate the between‐year and large‐scale spatial variation in relationships between nutrient loading and zooplanktivorous fish on submerged plant and plankton communities in shallow lakes.

4. Comparability of experiments in different locations was achieved to a high degree. Cross‐laboratory comparisons of chemical analyses revealed some systematic differences between laboratories. These are unlikely to lead to major misinterpretations.

5. Nutrient addition, overall, had its greatest effect on water chemistry then substantial effects on phytoplankton and zooplankton. Fish addition had its major effect on zooplankton and did not systematically change the water chemistry. There was no trend in the relative importance of fish effects with latitude, but nutrient addition affected more variables with decreasing latitude.

6. The relative importance of top‐down and bottom‐up influences on the plankton differed in different locations and between years at the same location. The outcome of the experiments in different years was more predictable with decreasing latitude and this was attributed to more variable weather at higher latitudes that created more variable starting conditions for the experiments.
Continental‐scale patterns of nutrient and fish effects on shallow lakes: synthesis of a pan‐European mesocosm experiment
Authors: Moss B. , Stephen D. , Balayla D. M. , Bécares E. , Collings S. E. , Fernández‐Aláez C. , Fernández‐Aláez M. , Ferriol C. , García P. , Gomá J. , Gyllström M. , Hansson L.‐A. , Hietala J. , Kairesalo T. , Miracle M. R. , Romo S. , Rueda J. , Russell V. , Ståhl‐Delbanco A. , Svensson M. , Vakkilainen K. , Valentín M. , Van de Bund W.J. , Van Donk E. , Vicente E. , Villena M.J.
Published: November 2004

1. Results are analysed from 11 experiments in which effects of fish addition and nutrient loading on shallow lakes were studied in mesocosms. The experiments, five in 1998, six in 1999, were carried out in six lakes, distributed from Finland to southern Spain, according to a standard protocol.

2. Effects of the treatments on 29 standard chemical, phytoplankton and zooplankton variables are examined to assess the relative importance of bottom‐up (nutrient enrichment) and top‐down (fish predation) effects. For each year, the experiments in different locations are treated as replicates in a meta‐analysis. Results of individual experiments are then compared in terms of the patterns of significant influences of nutrient addition and fish predation with these overall results (the baseline), and between years in the same location.

3. The overall meta‐analysis gave consistent results across the 2 years, with nutrient loading influencing all of the chemical variables, and on average 31% of primary producer and 39% of zooplankton variables. In contrast, fish influenced none of the chemical variables, 11% of the primary producer and 44% of the zooplankton variables. Nutrient effects on the system were thus about three times greater than fish effects, although fish effects were not inconsiderable.

4. The relative importance of nutrients and fish in individual experiments often differed between years at the same location and effects deviated to varying degrees from the baseline. These deviations were treated as measures of consistency (predictability) of conclusions in repeat experiments. Consistency increased southwards and this is interpreted as a consequence of more variable annual weather northwards.

5. The influence of nutrient loading was greater southwards and this was probably manifested through naturally greater annual macrophyte abundance in warmer locations in consequence of the longer plant growing‐season. There was no trend in the relative importance of fish effects with latitude but this may partly be an artefact of the simple fish community used. These findings suggest that nutrient control should be a greater priority than biomanipulation in the restoration of eutrophicated shallow lakes in warm temperate regions.

6. Starting conditions affected the outcome of experiments. High initial concentrations of total phosphorus and planktonic chlorophyll a concentration (created by local conditions prior to the experiment) led to de‐emphasis of the importance of nutrient loading in the experiment.
Late‐ and Post‐Glacial history of the Mustelidae in Europe
Authors: SOMMER ROBERT , BENECKE NORBERT
Published: November 2004

1. Analyses of the subfossil records of mustelid species in Europe indicate specific differences in the pattern of temporal and spatial recolonization of central Europe after the maximum glaciation of the last glacial period.

2. For Meles meles, Martes martes and (with some reservations) Mustela putorius it can be seen that the populations were separated in several glacial refugia during the maximum glaciation of the Weichselian. In contrast, the European population of Lutra lutra was restricted to a single glacial refuge, which had not been clearly localized until now.

3. Besides the known glacial refugia of the Iberian Peninsula, Italian Peninsula and the Balkans, there is evidence of possible additional glacial refugia for mustelids near the Carpathians, in western Moldova and in the northern Pontic region.

4. Gulo gulo, Mustela nivalis, and Mustela erminea show adaptations for survival in Pleistocene conditions, but they were historically also distributed in the warmer areas of southern Europe.

5. Among the more thermophilic mustelid species, Mustela putorius is likely to have been the earliest immigrant following the maximum glaciation. Meles meles has been recorded in comparably early times and also seems to be relatively tolerant of climatic extremes. It is clear that Martes martes had already arrived in central Europe during the Allerød, in connection with the recolonization by birch and pine woods. Lutra lutra, by contrast, seems to have been an absolute Holocene immigrant.
Coat colour variation in the banded palm civet Hemigalus derbyanus and in Owston's civet Chrotogale owstoni
Authors: VERON GÉRALDINE , LAIDLAW RUTH , ROSENTHAL SHELAGH HEARD , STREICHER ULRIKE , ROBERTON SCOTT
Published: November 2004

1. Coat colour variation was studied in two viverrid species belonging to the subfamily Hemigalinae, on the basis of museum specimens and observations of live animals.

2. In both species, polymorphism and ontogenetic colour change occur, and in the Owston's civet, sexual dimorphism in coat colour was identified.
Levamisole can reduce bait monopolization in wild red foxes Vulpes vulpes
Authors: GENTLE MATT , MASSEI GIOVANNA , SAUNDERS GLEN
Published: November 2004

1. Baits are used worldwide to deliver vaccines, contraceptives and poison to wild animal species. In carnivores, multiple bait uptake and bait monopolization by dominant individuals may reduce baiting effectiveness. This study investigated whether a conditioned‐taste‐aversion agent, levamisole, can be used to decrease bait consumption by individual wild foxes Vulpes vulpes.

2. The results indicated that after consuming levamisole‐treated baits, foxes avoided eating treated baits but consumed untreated baits. We concluded that the reduction in bait consumption was achieved through learned aversion to levamisole rather than via conditioned‐taste‐aversion to baits. Adding levamisole to baits could potentially be used to reduce bait monopolization by individual wild foxes.
The Free Economy and the Schizophrenic State: Ideology and the Conservatives
Authors: GARNETT MARK
Published: November 2004

This article focuses on Michael Howard's ideas to illustrate ideological developments within the Conservative party. It recognises that the ideas of a democratic organisation cannot be represented by the thoughts of a single individual, but Howard provides useful insights. He won the leadership unopposed in November 2003 partly because he seemed likely to perform well in debates with Tony Blair, but also because he offered the prospect of policy reform on a range of issues without a radical departure from the Thatcher legacy.

Soon after becoming leader Howard issued an unusually detailed statement of his beliefs. This showed him to be a convinced economic liberal, whose thinking has been heavily influenced by America. The main departure from Thatcherism is that he is even more antipathetic towards the state. This is difficult to reconcile with his support for UK 'sovereignty' within the EU, his hard line on law and order issues, and his insistence that there are no plans to privatise the NHS. It is unlikely to provide a platform for a significant Tory recovery.
Déjà vu? Conservative Problems in Historical Perspective
Authors: SNOWDON PETER , COLLINGS DANIEL
Published: November 2004

Since 2001, the Conservative party has found itself in turbulent times. Yet the party has survived similarly difficult periods in the past, eventually recovering its strength and returning to power. Can it do so again? The problems for today's party exist along four key dimensions: leadership, policy, organisation and political circumstances. How grave are contemporary difficulties in each of these areas in comparison to past experience? To what extent is the party now in uncharted waters? Where are there valid historical parallels? The article offers a brief sketch of the lessons that the party needs to learn to recover its election winning formula ‐ an appetite for power and an impressive ability to adapt to changed circumstances. Today's problems are not insurmountable, but the party still has a huge mountain to climb if it is to return to government.
Something Old, Something New: A Historical Perspective on the Butler Review
Authors: CASE SIMON , HADDON CATHERINE
Published: November 2004

Simon Case and Catherine Haddon demonstrate the value of contemporary history by looking at the recent Butler Report into intelligence on weapons of mass destruction (WMD) in its historical context. Intelligence failures form the most visible activity of the intelligence services, yet from the policy‐maker's perspective it is important that the intelligence process remains undisturbed so that the intelligence product remains useful. The intelligence effort on Iraqi WMD, as with previous changes in intelligence targets, shows the difficulties in establishing good intelligence on a new threat. Increases in demand and the centrality of intelligence put more pressure on the intelligence services. Butler has set a precedent for public awareness and therefore a desire for accountability that must be internalised by government and the intelligence services. The problems experienced over Iraq show the need for continual reappraisal by both producers and users of intelligence products, particularly in light of defence policy changes and the wider machinery of government.
Bank and Nonbank Financial Intermediation
Authors: BOND PHILIP
Published: November 2004

Conglomerates, trade credit arrangements, and banks are all instances of financial intermediation. However, these institutions differ significantly in the extent to which the projects financed absorb aggregate intermediary risk, in whether or not intermediation is carried out by a financial specialist, in the type of projects they fund and in the type of claims they issue to investors. The paper develops a simple unified model that both accounts for the continued coexistence of these different forms of intermediation, and explains why they differ. Specific applications to conglomerate firms, trade credit, and banking are discussed.
The Effect of Banking Relationships on the Firm's IPO Underpricing
Authors: SCHENONE CAROLA
Published: November 2004

This paper investigates the effects of pre‐IPO banking relationships on a firm's IPO. Using a new and unique data set, which compares the firm's pre‐IPO banking relationships to the underwriters managing the firm's new issue, I test whether banking relationships established before the firm's IPO ameliorate asymmetric informa tion problems behind high IPO underpricing. The results show that firms with a pre‐IPO banking relationship with a prospective underwriter face about 17% lower underpricing than firms without such banking relationships. These results are robust to controlling for the firm's endogenous selection of the pre‐IPO banking institution.
Dynamic Mechanical Properties of Agarose Gels Modeled by a Fractional Derivative Model
Authors: Chen Qingshan , Suki Bela , An Kai-Nan
Published: November 2004

The complex modulus E* and elastic modulus E′ of agarose gels (2% to 4%) are measured with a dynamic mechanical analyzer in frequency sweep shear sandwich mode between 0.1 and 20 Hz. The data showed that E* and E′ increase with frequency according to a power law which can be described by a fractional derivative model to characterize the dynamic viscoelasticity of the gel. The functions between the model parameters including storage modulus coefficient H and the power law exponent (β) and the agarose concentration are established. A molecular basis for the application of the fractional derivative model to gel polymers is also discussed. Such an approach can be useful in tissue culture studies employing dynamic pressurization or for validation of magnetic resonance elastography.
Comparison of the Effects of Cyclic Stretching and Compression on Endothelial Cell Morphological Responses
Authors: Wille Jeremiah J. , Ambrosi Christina M. , Yin Frank C-P
Published: November 2004

Recent results demonstrate the exquisite sensitivity of cell orientation responses to the pattern of imposed deformation. Cells undergoing pure in-plane uniaxial stretching orient differently than cells that are simply elongated—likely because the latter stimulus produces simultaneous compression in the unstretched direction. It is not known, however, if cells respond differently to pure stretching than to pure compression. This study was performed to address this issue. Human aortic endothelial cells were seeded on deformable silicone membranes and subjected to various magnitudes and rates of pure stretching or compression. The cell orientation and cytoskeletal stress fiber organization responses were examined. Both stretching and compression resulted in magnitude-dependent but not rate-dependent orientation responses away from the deforming direction. Compression produced a slower temporal response than stretching. However, stress fiber reorganization responses–early disruption followed by reassembly into parallel arrays along the cells’ long axes were similar between the two stimuli. Moreover, the cell orientation and stress fiber responses appeared to be uncoupled since disruption of stress fibers was not required for the cell orientation. Moreover, parallel actin stress fibers were observed at oblique angles to the deforming direction indicating that stress fibers can reassemble when undergoing deformation.
Measurement of the Spatial Redistribution of Water in Rabbit Achilles Tendon in Response to Static Tensile Loading
Authors: Helmer K. G. , Wellen J. , Grigg P. , Sotak C. H.
Published: November 2004

The redistribution of water in response to static tensile loading was investigated in rabbit Achilles tendons in vitro. The distribution of water was measured along a radially oriented line, using a one-dimensional proton-density map created from fits to diffusion-weighted magnetic resonance (MR) data. Water movements were measured during application of tensile loads of 5N (N=7) and 10N (N=6). Water distribution along the line was measured before loading and up to 42 min after load application. Static loading with either 5 or 10N loads caused a steady increase in proton density in the outside edge (rim) of the tendon. The 10N load lowered the proton density in the core of the tendon, but did so in a single step that was observed when the load was applied. The 5N load caused no change in proton density in the core region. The immediate redistribution from the core was statistically significant for the 10N load, but not the 5N load application. Statistically significant within-group proton-density increases were observed in the rim after 42 min postload for all tendons irrespective of load condition. The rate of proton-density postload increase at the rim region did not depend upon load. The rate for the 5N load case was 0.010±0.002 min−1 and 0.007±0.002 min−1 in the 10N case. Thus, while generally consistent with an extrusion model, the data show other features that argue for a more complex model.
NK Cells Contribute to the Control ofTrypanosoma cruziInfection by Killing Free Parasites by Perforin-Independent Mechanisms
Authors: Lieke Thorsten , Graefe Sebastian E. B. , Klauenberg Ulricke , Fleischer Bernhard , Jacobs Thomas
Published: November 2004

The protozoan parasiteTrypanosoma cruzicirculates in the blood as trypomastigotes and invades a variety of cells to multiply intracellularly as amastigotes. The acute phase leads to an immune response that restricts the proliferation of the parasite. However, parasites are able to persist in different tissues, which causes the pathology of Chagas' disease. Natural killer (NK) cells play an important role in innate resistance to a variety of pathogens. In the present study we analyzed whether NK cells participated in the control of experimentalT. cruziinfection. NK cells were depleted from C57BL/6 mice by antiasialo antibodies. This treatment caused an increased parasitemia during the acute phase, but tissue parasite burdens were not significantly altered according to quantitative real-time PCR. Our results demonstrated that NK cells were activated during the initial phase of aT. cruziinfection and exhibited a contact-dependent antiparasitic activity against extracellular parasites that was independent from perforin. Thus, NK cells limit the propagation of the parasite by acting on circulatingT. cruzitrypomastigotes.
Resistance ofMycoplasma pulmonisto Complement Lysis Is Dependent on the Number of Vsa Tandem Repeats: Shield Hypothesis
Authors: Simmons Warren L. , Denison Amy M. , Dybvig Kevin
Published: November 2004

The Vsa proteins are associated with the virulence of the murine respiratory pathogenMycoplasma pulmonis. The antigens consist of a conserved N-terminal region that is combined with one of several different variable C-terminal regions comprised of tandem repeats.M. pulmonisstrains that produce VsaA with about 40 tandem repeats do not adhere to polystyrene or erythrocytes and are highly resistant to complement killing. Strains that produce VsaA with three tandem repeats adhere strongly to polystyrene and erythrocytes and are highly susceptible to complement killing. We report here that the resistance to complement lysis was not due to a lack of activation of the complement cascade. Isolation and analysis ofM. pulmonisstrains that produced Vsa proteins other than VsaA (VsaG and VsaI) with either long or short repeat regions indicated that adherence to polystyrene and resistance to complement were dependent on the length of the repeat region but not on the Vsa type. Furthermore,M. pulmonisVsa variants were susceptible to the polypeptide pore-forming molecule gramicidin D, independent of the Vsa type and length. Collectively, the data indicate the Vsa proteins nonspecifically mediateM. pulmonissurface interactions and function to sterically hinder access of complement to the mycoplasma cell membrane while permitting access of smaller molecules.
Salmonella entericaSerovar Typhimurium Infection Induces Cyclooxygenase 2 Expression in Macrophages: Involvement ofSalmonellaPathogenicity Island 2
Authors: Uchiya Kei-ichi , Nikai Toshiaki
Published: November 2004

Salmonellapathogenicity island 2 (SPI-2) is required for intramacrophage survival and systemic infection in mice. We have recently reported thatSalmonella entericacauses activation of the protein kinase A (PKA) signaling pathway in a manner dependent on SPI-2, resulting in the upregulation of interleukin-10 expression in macrophages (K. Uchiya et al., Infect. Immun. 72:1964-1973, 2004). We show in the present study the involvement of SPI-2 in a signal transduction pathway that induces the expression of cyclooxygenase 2 (COX-2), an inducible enzyme involved in the synthesis of prostanoids. High levels of prostaglandin E2(PGE2) and prostacyclin (PGI2), which are known to activate the PKA signaling pathway via their receptors, were induced in J774 macrophages infected with wild-typeSalmonellacompared to a strain carrying a mutation in thespiCgene, located within SPI-2. The increased production of both prostanoids was dependent on COX-2. COX-2 expression was dose dependently blocked by treatment with a specific inhibitor of the extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway, and the phosphorylation level of ERK1/2 was higher in macrophages infected with wild-typeSalmonellacompared to thespiCmutant. Taken together, these results indicate thatSalmonellacauses an SPI-2-dependent ERK1/2 activation that leads to increased COX-2 expression, resulting in the upregulation of PGE2and PGI2production in macrophages. A COX-2 inhibitor inhibited not onlySalmonella-induced activation of the PKA signaling pathway but also growth of wild-typeSalmonellawithin macrophages, suggesting thatSalmonellautilizes the COX-2 pathway to survive within macrophages and that the mechanism involves activation of the PKA signaling pathway.
Bystander Activation of CD8+T Lymphocytes during Experimental Mycobacterial Infection
Authors: Gilbertson Brad , Germano Susie , Steele Pauline , Turner Steven , de St. Groth Barbara Fazekas , Cheers Christina
Published: November 2004

Infection of C57BL/6 mice withMycobacterium aviumleads to the activation of both CD4+and CD8+gamma interferon (IFN-γ)-producing T cells, although the CD8+cells play no role in protection against infection. Using transfer of different lines of transgenic T cells with T-cell receptors (TCRs) which recognize irrelevant antigens, we show here that transferred CD8+T cells from two of the three lines were activated to the same degree as the host cells, suggesting that the majority of the IFN-γ-producing CD8+T cells of the host represented bystander activation. The third line, specific for the male HY antigen, showed no activation. Activation required the participation of the CD28 coreceptor on T cells and was unaffected by the removal of CD44hi(memory phenotype) T cells. The transferred CD8+T cells proliferated in vivo, although this was not essential for IFN-γ production. Taken together, these data are highly reminiscent of homeostatic proliferation of TCR transgenic T cells upon transfer to lymphopenic hosts, and suggest low-affinity stimulation through the TCR, possibly by self peptides. The findings are discussed in relation to homeostatic proliferation and their significance in the possible induction of autoimmune disease.
Redirecting the Humoral Immune Response againstStreptococcus mutansAntigen P1 with Monoclonal Antibodies
Authors: Oli Monika W. , Rhodin Nikki , McArthur William P. , Brady L. Jeannine
Published: November 2004

The adhesin P1 ofStreptococcus mutanshas been studied as an anticaries vaccine antigen. An anti-P1 monoclonal antibody (MAb) bound toS. mutansprior to mucosal immunization of mice was shown previously to alter the amount, specificity, isotype, and biological activity of anti-P1 antibodies. The present study was undertaken to screen this and four additional anti-P1 MAbs for immunomodulatory activity when complexed withS. mutansand administered by a systemic route and to evaluate sera from immunized mice for the ability to inhibit adherence ofS. mutansto immobilized human salivary agglutinin. All five MAbs tested influenced murine anti-P1 serum antibody responses in terms of subclass distribution and/or specificity. The effects varied depending on which MAb was used and its coating concentration. Two MAbs promoted a more effective, and two others a less effective, adherence inhibition response. An inverse relationship was observed between the ability of the MAbs themselves to inhibit adherence and the ability of antibodies elicited following immunization with immune complexes to inhibit adherence. Statistically significant correlations were demonstrated between the levels of anti-P1 serum immunoglobulin G2a (IgG2a) and IgG2b, but not of IgG1 or IgG3, and the ability of sera from immunized animals to inhibit bacterial adherence. These results indicate that multiple anti-P1 MAbs can mediate changes in the immune response and that certain alterations are potentially more biologically relevant than others. Immunomodulation by anti-P1 MAbs represents a useful strategy to improve the beneficial immune response againstS. mutans.
Long-Term Control ofMycobacterium bovisBCG Infection in the Absence of Toll-Like Receptors (TLRs): Investigation of TLR2-, TLR6-, or TLR2-TLR4-Deficient Mice
Authors: Nicolle Delphine , Fremond Cécile , Pichon Xavier , Bouchot André , Maillet Isabelle , Ryffel Bernhard , Quesniaux Valerie J. F.
Published: November 2004

Live mycobacteria have been reported to signal through both Toll-like receptor 2 (TLR2) and TLR4 in vitro. Here, we investigated the role of TLR2 in the long-term control of the infection by the attenuatedMycobacterium,Mycobacterium bovisBCG, in vivo. We sought to determine whether the reported initial defect of bacterial control (K. A. Heldwein et al., J. Leukoc. Biol. 74:277-286, 2003) resolved in the chronic phase of BCG infection. Here we show that TLR2-deficient mice survived a 6-month infection period withM. bovisBCG and were able to control bacterial growth. Granuloma formation, T-cell and macrophage recruitment, and activation were normal. Furthermore, the TLR2 coreceptor, TLR6, is also not required since TLR6-deficient mice were able to control chronic BCG infection. Finally, TLR2-TLR4-deficient mice infected with BCG survived the 8-month observation period. Interestingly, the adaptive response of TLR2- and/or TLR4-deficient mice seemed essentially normal on day 14 or 56 after infection, since T cells responded normally to soluble BCG antigens. In conclusion, our data demonstrate that TLR2, TLR4, or TLR6 are redundant for the control ofM. bovisBCG mycobacterial infection.
Polymorphisms in the
Chlamydia trachomatis
Cytotoxin Locus Associated with Ocular and Genital Isolates
Authors: Carlson John H. , Hughes Scott , Hogan Daniel , Cieplak Gordon , Sturdevant Daniel E. , McClarty Grant , Caldwell Harlan D. , Belland Robert J.
Published: November 2004

Chlamydia trachomatis
is a strict human pathogen producing infections that cause medically important chronic inflammatory diseases, such as blinding trachoma and tubal factor infertility. Isolates exist as serotypes that fall into distinct biologic and pathological groups corresponding to differences in infection tissue tropism and invasion properties. Paradoxically, genome sequencing of several diverse strains has revealed a remarkable level of genomic synteny, suggesting that minor genetic differences determine the pathogen host- and tissue-specific infection characteristics. To better understand the genetic basis of chlamydial pathobiologic diversity, we performed comparative DNA-DNA microarray genomic hybridizations with all 15
C. trachomatis
serovariants. We found there are few major genetic differences among the 15 serovars. An exception was the cytotoxin locus located in the plasticity zone, a region that exhibited significant polymorphisms among serovars. We therefore sequenced this region from all 15 serovars. The cytotoxin gene was interrupted by extensive mutations and deletions among the different serovars; however, three basic open reading frame motifs were discovered that correlated with noninvasive oculotropic, urogenitotropic, and invasive serovars. Of interest, only noninvasive genitotropic serovars possessed an intact N-terminal portion of the putative toxin gene. This region contains the UDP-glucose binding domain and the glycosyltransferase domain required for enzymatic activity of the clostridial toxin homologs, suggesting a role in urogenital infection or pathogenesis.
A Mutant of
Mycobacterium tuberculosis
H37Rv That Lacks Expression of Antigen 85A Is Attenuated in Mice but Retains Vaccinogenic Potential
Authors: Copenhaver Robert H. , Sepulveda Eliud , Armitige Lisa Y. , Actor Jeffrey K. , Wanger Audrey , Norris Steven J. , Hunter Robert L. , Jagannath Chinnaswamy
Published: November 2004

The
fbpA
and
fbpB
genes encoding the 85A and 85B proteins of
Mycobacterium tuberculosis
H37Rv, respectively, were disrupted, the mutants were examined for their ability to survive, and the strain lacking 85A (Δ
fbpA
) was tested for its ability to immunize mice. The Δ
fbpA
mutant was attenuated in mice after intravenous or aerosol infection, while replication of the Δ
fbpB
mutant was similar to that of the wild type. Complementation of the
fbpA
gene in Δ
fbpA
restored its ability to grow in the lungs of mice. The Δ
fbpA
mutant induced a stronger expression of pulmonary mRNA messages in mice for tumor necrosis factor alpha, interleukin-1 beta (IL-1β), gamma interferon, IL-6, IL-2, and inducible nitric oxide (NO) synthase, which led to its decline, while H37Rv persisted despite strong immune responses. H37Rv and Δ
fbpA
both induced NO in macrophages and were equally susceptible to NO donors, although Δ
fbpA
was more susceptible in vitro to peroxynitrite and its growth was enhanced by NO inhibitors in mice and macrophages. Aerosol-infected mice, which cleared a low-dose Δ
fbpA
infection, resisted a challenge with virulent
M. tuberculosis
. Mice subcutaneously immunized with Δ
fbpA
or
Mycobacterium bovis
BCG and challenged with
M. tuberculosis
also showed similar levels of protection, marked by a reduction in the growth of challenged
M. tuberculosis
. The Δ
fbpA
mutant was thus attenuated, unlike Δ
fbpB
, but was also vaccinogenic against tuberculosis. Attenuation was incomplete, however, since Δ
fbpA
revived in normal mice after 370 days, suggesting that revival was due to immunosenescence but not compensation by the
fbpB
or
fbpC
gene. Antigen 85A thus affects susceptibility to peroxynitrite in
M. tuberculosis
and appears to be necessary for its optimal growth in mice.
Interactions of Pulmonary Collectins with
Bordetella bronchiseptica
and
Bordetella pertussis
Lipopolysaccharide Elucidate the Structural Basis of Their Antimicrobial Activities
Authors: Schaeffer Lyndsay M. , McCormack Francis X. , Wu Huixing , Weiss Alison A.
Published: November 2004

Surfactant proteins A (SP-A) and D (SP-D) play an important role in the innate immune defenses of the respiratory tract. SP-A binds to the lipid A region of lipopolysaccharide (LPS), and SP-D binds to the core oligosaccharide region. Both proteins induce aggregation, act as opsonins for neutrophils and macrophages, and have direct antimicrobial activity.
Bordetella pertussis
LPS has a branched core structure and a nonrepeating terminal trisaccharide.
Bordetella bronchiseptica
LPS has the same structure, but lipid A is palmitoylated and there is a repeating O-antigen polysaccharide. The ability of SP-A and SP-D to agglutinate and permeabilize wild-type and LPS mutants of
B. pertussis
and
B. bronchiseptica
was examined. Previously, wild-type
B. pertussis
was shown to resist the effects of SP-A; however, LPS mutants lacking the terminal trisaccharide were susceptible to SP-A. In this study, SP-A was found to aggregate and permeabilize a
B. bronchiseptica
mutant lacking the terminal trisaccharide, while wild-type
B. bronchiseptica
and mutants lacking only the palmitoyl transferase or O antigen were resistant to SP-A. Wild-type
B. pertussis
and
B. bronchiseptica
were both resistant to SP-D; however, LPS mutants of either strain lacking the terminal trisaccharide were aggregated and permeabilized by SP-D. We conclude that the terminal trisaccharide protects
Bordetella
species from the bactericidal functions of SP-A and SP-D. The O antigen and palmitoylated lipid A of
B. bronchiseptica
play no role in this resistance.
Human Antibody Responses to a Chlamydia-Secreted Protease Factor
Authors: Sharma Jyotika , Bosnic Anthony M. , Piper Jeanna M. , Zhong Guangming
Published: November 2004

We have previously identified a chlamydia-secreted protein (designated chlamydial proteasome/protease-like activity factor, or CPAF) in the cytosol of chlamydia-infected cells. Although CPAF is known to degrade host transcription factors required for major histocompatibility complex antigen expression in cultured cells, it is not clear whether CPAF is produced and maintains similar functions in humans infected with chlamydial organisms. We now report that CPAF does not preexist in chlamydial organisms and that CPAF synthesis requires live organism replication in cultured cells. Mice inoculated with live, but not mice inoculated with dead, chlamydial organisms produced a strong antibody response to CPAF, correlating CPAF-specific antibody production with CPAF synthesis in animals. Sera from women diagnosed withChlamydia trachomatiscervicitis displayed higher levels of antibodies to CPAF than to either chlamydial major outer membrane protein or heat shock protein 60, suggesting that CPAF is both produced and immunogenic during human chlamydial infection.