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Strong Response (strong + response)
Selected AbstractsRefuge-mediated apparent competition in plant,consumer interactionsECOLOGY LETTERS, Issue 1 2010John L. Orrock Abstract At the intersection of consumer behaviour and plant competition is the concept of refuge-mediated apparent competition: an indirect interaction whereby plants provide a refuge for a shared consumer, subsequently increasing consumer pressure on another plant species. Here, we use a simple model and empirical examples to develop and illustrate the concept of refuge-mediated apparent competition. We find that the likelihood that an inferior competitor will succeed via refuge-mediated apparent competition is greater when competitors have similar resource requirements and when consumers exhibit a strong response to the refuge and high attack rates on the superior competitor. Refuge-mediated apparent competition may create an emergent Allee effect, such that a species invades only if it is sufficiently abundant to alter consumer impact on resident species. This indirect interaction may help explain unresolved patterns observed in biological invasion, such as the different physical structure of invasive exotic plants, the lag phase, and the failure of restoration efforts. Given the ubiquity of refuge-seeking behaviour by consumers and the ability of consumers to alter the outcome of direct competition among plants, refuge-mediated apparent competition may be an underappreciated mechanism affecting the composition and diversity of plant communities. Ecology Letters (2010) 13: 11,20 [source] Properties of ecdysteroid receptors from diverse insect species in a heterologous cell culture system , a basis for screening novel insecticidal candidatesFEBS JOURNAL, Issue 11 2009Joshua M. Beatty Insect development is driven by the action of ecdysteroids on morphogenetic processes. The classic ecdysteroid receptor is a protein heterodimer composed of two nuclear receptors, the ecdysone receptor (EcR) and Ultraspiracle (USP), the insect ortholog of retinoid X receptor. The functional properties of EcR and USP vary among insect species, and provide a basis for identifying novel and species-specific insecticidal candidates that disrupt this receptor's normal activity. A heterologous mammalian cell culture assay was used to assess the transcriptional activity of the heterodimeric ecdysteroid receptor from species representing two major insect orders: the fruit fly, Drosophila melanogaster (Diptera), and the Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera). Several nonsteroidal agonists evoked a strong response with the L. decemlineata heterodimer that was consistent with biochemical and in vivo evidence, whereas the D. melanogaster receptor's response was comparatively modest. Conversely, the phytoecdysteroid muristerone A was more potent with the D. melanogaster heterodimer. The additional presence of juvenile hormone III potentiated the inductive activity of muristerone A in the receptors from both species, but juvenile hormone III was unable to potentiate the inductive activity of the diacylhydrazine methoxyfenozide (RH2485) in the receptor of either species. The effects of USP on ecdysteroid-regulated transcriptional activity also varied between the two species. When it was tested with D. melanogaster EcR isoforms, basal activity was lower and ligand-dependent activity was higher with L. decemlineata USP than with D. melanogaster USP. Generally, the species-based differences validate the use of the cell culture assay screen for novel agonists and potentiators as species-targeted insecticidal candidates. [source] Porous Silicon-Based Optical Microsensors for Volatile Organic Analytes: Effect of Surface Chemistry on Stability and SpecificityADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Anne M. Ruminski Abstract Sensing of the volatile organic compounds (VOCs) isopropyl alcohol (IPA) and heptane in air using sub-millimeter porous silicon-based sensor elements is demonstrated in the concentration range 50,800 ppm. The sensor elements are prepared as one-dimensional photonic crystals (rugate filters) by programmed electrochemical etch of p++ silicon, and analyte sensing is achieved by measurement of the wavelength shift of the photonic resonance. The sensors are studied as a function of surface chemistry: ozone oxidation, thermal oxidation, hydrosilylation (1-dodecene), electrochemical methylation, reaction with dicholorodimethylsilane and thermal carbonization with acetylene. The thermally oxidized and the dichlorodimethylsilane-modified materials show the greatest stability under atmospheric conditions. Optical microsensors are prepared by attachment of the porous Si layer to the distal end of optical fibers. The acetylated porous Si microsensor displays a greater response to heptane than to IPA, whereas the other chemical modifications display a greater response to IPA than to heptane. The thermal oxide sensor displays a strong response to water vapor, while the acetylated material shows a relatively weak response. The results suggest that a combination of optical fiber sensors with different surface chemistries can be used to classify VOC analytes. Application of the miniature sensors to the detection of VOC breakthrough in a full-scale activated carbon respirator cartridge simulator is demonstrated. [source] Assessment of European streams with diatoms, macrophytes, macroinvertebrates and fish: a comparative metric-based analysis of organism response to stressFRESHWATER BIOLOGY, Issue 9 2006DANIEL HERING Summary 1. Periphytic diatoms, macrophytes, benthic macroinvertebrates and fish were sampled with standard methods in 185 streams in nine European countries to compare their response to degradation. Streams were classified into two main stream type groups (i.e. lowland, mountain streams); in addition, the lowland streams were grouped into four more specific stream types. 2. Principal components analysis with altogether 43 environmental parameters was used to construct complex stressor gradients for physical,chemical, hydromorphological and land use data. About 30 metrics were calculated for each sample and organism group. Metric responses to different stress types were analysed by Spearman Rank Correlation. 3. All four organism groups showed significant response to eutrophication/organic pollution gradients. Generally, diatom metrics were most strongly correlated to eutrophication gradients (85% and 89% of the diatom metrics tested correlated significantly in mountain and lowland streams, respectively), followed by invertebrate metrics (91% and 59%). 4. Responses of the four organism groups to other gradients were less strong; all organism groups responded to varying degrees to land use changes, hydromorphological degradation on the microhabitat scale and general degradation gradients, while the response to hydromorphological gradients on the reach scale was mainly limited to benthic macroinvertebrates (50% and 44% of the metrics tested correlated significantly in mountain and lowland streams, respectively) and fish (29% and 47%). 5. Fish and macrophyte metrics generally showed a poor response to degradation gradients in mountain streams and a strong response in lowland streams. 6. General recommendations on European bioassessment of streams were derived from the results. [source] The microfood web of grassland soils responds to a moderate increase in atmospheric CO2GLOBAL CHANGE BIOLOGY, Issue 7 2005Ilja Sonnemann Abstract The response of the soil microfood web (microflora, nematodes) to a moderate increase in atmospheric CO2 (+20%) was investigated by means of a free air CO2 enrichment experiment. The study was carried out in a seminatural temperate grassland for a period of 4 consecutive years (1 year before fumigation commenced and 3 years with fumigation). Several soil biological parameters showed no change (microbial biomass, bacterial biomass) or decline (microbial respiration) in the first year of elevated CO2 treatment as compared with controls. Each of these parameters were higher than controls, however, after 3 years of treatment. The relative abundance of predaceous nematodes also decreased in year 1 of the experiment, increased in year 2, but decreased again in year 3. In contrast, the relative abundance of root hair feeding nematodes, at first, increased under elevated CO2 and then returned to the initial level again. Increased microbial biomass indicates enhanced C storage in the labile carbon pool of the active microfood web in subsequent years. According to measurements on the amounts of soil extractable C, changes in resource availability seem to be key to the response of the soil microfood web. We found a strong response of bacteria to elevated CO2, while the fungal biomass remained largely unchanged. This contrasts to findings reported in the literature. We hypothesize that this may be because of contrasting effects of different levels of CO2 enrichment on the microbial community (i.e. stimulation of bacteria at moderate levels and stimulation of fungi at high levels of CO2 enrichment). However, various CO2 effects observed in our study are similar in magnitude to those observed in other studies for a much higher level of atmospheric carbon. These include the particular sensitivity of predaceous nematodes and the long-term increase of microbial respiration. Our findings confirm that the potential of terrestrial ecosystems to accumulate additional carbon might be lower than previously thought. Furthermore, CO2 -induced changes of temperate grassland ecosystems might emerge much earlier than expected. [source] National-scale metacommunity dynamics of carabid beetles in UK farmlandJOURNAL OF ANIMAL ECOLOGY, Issue 2 2008David R. Brooks Summary 1Understanding the wide-scale processes controlling communities across multiple sites is a foremost challenge of modern ecology. Here, data from a nation-wide network of field sites are used to describe the metacommunity dynamics of arable carabid beetles. This is done by modelling how communities are structured at a local level, by changes in the environment of the sampled fields and, at a regional level, by fitting spatial parameters describing latitudinal and longitudinal gradients. 2Local and regional processes demonstrated independent and significant capacities for structuring communities. Within the local environment, crop type was found to be the primary determinant of carabid community composition. The regional component included a strong response to a longitudinal gradient, with significant increases in diversity in an east-to-west direction. 3Carabid metacommunities seem to be structured by a combination of species sorting dynamics, operating at two different, but equally important, spatial scales. At a local scale, species are sorted along a resource gradient determined by crop type. At a wider spatial scale species appear to be sorted along a longitudinal gradient. 4Nation-wide trends in communities coincided with known gradients of increased homogeneity of habitat mosaics and agricultural intensification. However, more work is required to understand fully how communities are controlled by the interaction of crops with changes in landscape structure at different spatial scales. 5We conclude that crop type is a powerful determinant of carabid biodiversity, but that it cannot be considered in isolation from other components of the landscape for optimal conservation policy. [source] Evaluating the enemies hypothesis in a clover-cabbage intercrop: effects of generalist and specialist natural enemies on the turnip root fly (Delia floralis)AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 2 2010Maria Björkman 1The relative importance of the resource concentration hypothesis and the enemies hypothesis was investigated for the turnip root fly Delia floralis in a cabbage,red clover intercropping system compared with a cabbage monoculture. 2Delia floralis egg densities were measured as well as the activity-densities of generalist predators in a field experiment during two growing seasons. In the second year, a study of egg predation with artificially placed eggs was conducted, in addition to a predator exclusion experiment, to estimate total predation during the season. Parasitization rates were estimated from samples of pupae. 3Delia floralis oviposition was greater in the monoculture during both years. The predator activity-densities differed between treatments and study years. The known natural enemies of Delia spp., Bembidion spp. and Aleochara bipustulata showed a strong response to a cultivation system with higher activity-densities in the monoculture. The response, however, appeared to be caused primarily by habitat preferences and not by D. floralis egg densities. 4The reduction in the number of D. floralis pupae in the intercropping may be explained by a disruption in oviposition behaviour caused by the presence of clover because neither predation, nor parasitization rates differed between cultivation systems. [source] Sex pheromone of apple fruit moth Argyresthia conjugella (Lepidoptera: Argyresthiidae)AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 3 2002Gunnhild Jaastad Abstract 1,The apple fruit moth Argyresthia conjugella Zell. (Lepidoptera: Argyresthiidae) is the most important pest of apple in Scandinavia. It invades apple orchards and can destroy an entire crop during years of poor flowering and fruitsetting of its principal host, mountain ash Sorbus aucuparia. We investigated the female sex pheromone of apple fruit moth in order to develop a reliable lure, which can be used to detect migration of apple fruit moth into orchards and thus to avoid preventive insecticide sprays. 2,Pheromonal compounds obtained by solvent extraction of excised A. conjugella female pheromone glands were identified by coupled gas chromatography/electroantennography and gas chromatography/mass spectrometry. Two compounds (Z)-11-hexadecenyl acetate, and the analogous alcohol (Z)-11-hexadecen-1-ol, elicited a strong response from male antennae. (Z)-11-hexadecenyl acetate was highly attractive in field trapping tests, whereas as little as a 1%-addition of (Z)-11-hexadecen-1-ol strongly reduced male attraction. 3,(Z)-13-octadecenyl acetate, a previously reported sex attractant, had no effect on A. conjugella male attraction. [source] Plant species and growth form richness along altitudinal gradients in the southwest Ethiopian highlandsJOURNAL OF VEGETATION SCIENCE, Issue 4 2010Wana Desalegn Abstract Questions: Do growth forms and vascular plant richness follow similar patterns along an altitudinal gradient? What are the driving mechanisms that structure richness patterns at the landscape scale? Location: Southwest Ethiopian highlands. Methods: Floristic and environmental data were collected from 74 plots, each covering 400 m2. The plots were distributed along altitudinal gradients. Boosted regression trees were used to derive the patterns of richness distribution along altitudinal gradients. Results: Total vascular plant richness did not show any strong response to altitude. Contrasting patterns of richness were observed for several growth forms. Woody, graminoid and climber species richness showed a unimodal structure. However, each of these morphological groups had a peak of richness at different altitudes: graminoid species attained maximum importance at a lower elevations, followed by climbers and finally woody species at higher elevations. Fern species richness increased monotonically towards higher altitudes, but herbaceous richness had a dented structure at mid-altitudes. Soil sand fraction, silt, slope and organic matter were found to contribute a considerable amount of the predicted variance of richness for total vascular plants and growth forms. Main Conclusions: Hump-shaped species richness patterns were observed for several growth forms. A mid-altitudinal richness peak was the result of a combination of climate-related water,energy dynamics, species,area relationships and local environmental factors, which have direct effects on plant physiological performance. However, altitude represents the composite gradient of several environmental variables that were interrelated. Thus, considering multiple gradients would provide a better picture of richness and the potential mechanisms responsible for the distribution of biodiversity in high-mountain regions of the tropics. [source] Site-specific mutation of the interferon sensitivity-determining region (ISDR) modulates hepatitis C virus replicationJOURNAL OF VIRAL HEPATITIS, Issue 9 2006T. Kohashi Summary., The number of amino acid substitutions in the interferon sensitivity-determining region (ISDR) in the nonstructural 5A (NS5A) gene of hepatitis C virus (HCV) is closely associated with the interferon (IFN) response and viral load. Several HCV replicon-based studies have reported that ISDR sequences had an influence on viral replication in vitro. However, it is unclear as to how different ISDR sequences affect HCV replication. Various clinically observed ISDR sequences were introduced into HCV replicons and their contribution to viral replication was investigated using a colony formation assay and/or a transient replication assay. A mapping study of the ISDR was performed to identify the amino acid positions that critically affect replication. While no colonies were formed in the colony formation assay using HCV replicons with few mutations (0, 1 and 3) in the ISDR, numerous colonies (>200) appeared when using constructs with six mutations. Introduction of various distinct ISDR sequences with multiple mutations resulted in replication enhancement in transient assays. A mapping study identified several specific sites in the ISDR that critically affected replication, including codon 2209 which, in patients, was closely associated with a strong response to IFN. ISDR sequences associated with a clinical IFN response and viral load modulated the replication of HCV replicons, suggesting the importance of the ISDR sequence in HCV infection. [source] Experimental plant invasion reduces arthropod abundance and richness across multiple trophic levelsOIKOS, Issue 10 2010M. Carolina M. Simao Plant invasions are known to have negative impacts on native plant communities, yet their influence on higher trophic levels has not been well documented. Past studies investigating the effects of invasive plants on herbivores and carnivores have been largely observational in nature and thus lack the ability to tease apart whether differences are a cause or consequence of the invasion. In addition, understanding how plant traits and plant species compositions change in invaded habitats may increase our ability to predict when and where invasive plants will have effects that cascade to animals. To assess effects on arthropods, we experimentally introduced a non-native plant (Microstegium vimineum, Japanese stiltgrass) in a community re-assembly experiment. We also investigated possible mechanisms through which the invader could affect associated arthropods, including changes in native plant species richness, above-ground plant biomass, light availability and vegetation height. In experimentally invaded plots, arthropod abundance was reduced by 39%, and species richness declined by 19%. Carnivores experienced greater reductions in abundance than herbivores (61% vs 31% reduction). Arthropod composition significantly diverged between experimentally invaded and control plots, and particular species belonging to the abundant families Aphididae (aphids), Formicidae (ants) and Phalacridae (shining flower beetles) contributed the most to compositional differences. Among the mechanisms we investigated, only the reduction in native plant species richness caused by invasion was strongly correlated with total arthropod abundance and richness. In sum, our results demonstrate negative impacts of M. vimineum invasion on higher trophic levels and suggest that these effects occur, in part, indirectly through invader-mediated reductions in the richness of the native plant community. The particularly strong response of carnivores suggests that plant invasion could reduce top,down control of herbivorous species for native plants. [source] Edge effects as the principal cause of area effects on birds in fragmented secondary forestOIKOS, Issue 6 2010Cristina Banks-Leite Bird communities in tropical forests are strongly affected by both patch area and habitat edges. The fact that both effects are intrinsically confounded in space raises questions about how these two widely reported ecological patterns interact, and whether they are independent or simply different spatial manifestations of the same phenomenon. Moreover, do small patches of secondary forest, in landscapes where the most sensitive species have gone locally extinct, exhibit similar patterns to those previously observed in fragmented and continuous primary forests? We addressed these questions by testing edge-related differences in vegetation structure and bird community composition at 31 sites in fragmented and continuous landscapes in the imperilled Atlantic forest of Brazil. Over a two-year period, birds were captured with mist nets to a standardized effort of 680 net-hours at each site (,22 000 net-hours resulting in 3381 captures from 114 species). We found that the bird community in patches of secondary forest was degraded in species composition compared to primary continuous forest, but still exhibited a strong response to edge effects. In fragmented secondary forests, edge and area effects also interacted, such that the magnitude of edge to interior differences on bird community composition declined markedly with patch size. The change in bird species composition between forest interiors and edges was similar to the change in community composition between large and small patches (because species had congruent responses to edge and area), but after controlling for edge effects community composition was no longer affected by patch area. Our results show that although secondary forests hold an impoverished bird community, ecological patterns such as area and edge effects are similar to those reported for primary forests. Our data provide further evidence that edge effects are the main drivers of area effects in fragmented landscapes. [source] Japan's Power Shift and Its DPRK PolicyPACIFIC FOCUS, Issue 2 2010Yoshinori Kaseda Many serious issues exist between Japan and North Korea (DPRK), such as nuclear, missile, abduction, and colonial issues. Progress on their resolution has been limited. Consequently, the two countries have remained unfriendly neighbors. Their relations recently deteriorated as a result of the DPRK's satellite launch and its second nuclear test in the first half of 2009, and Japan's strong response to them. In the middle of this period of significant tension, in August 2009, the Democratic Party of Japan (DPJ) won a landslide victory in the lower house elections, ending the dominance of the Liberal Democratic Party (LDP) over the last half a century. This political sea change in Japan has not resulted in major improvements in the Japan,DPRK relations. Yet, the DPJ's stance toward the DPRK's military threat and the Japan,US alliance is different from that of the LDP. So far, the DPJ has opted to avoid following in the LDP's footsteps of strengthening the alliance and expanding Japan's military operations in response to the DPRK's military threat. Instead, it intends to increase Japan's independence from the USA, and reduce US military presence in Japan. Given such intentions, the DPJ seems willing to improve Japan's relations with the DPRK. The question is whether its willingness will be translated into real actions to bring about major improvements. [source] ZnO-based photodetector with internal photocurrent gainPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2010L. A. Kosyachenko Abstract The photoresponsive structures prepared by magnetron sputtering of ZnO on p-Si substrates followed by vacuum evaporation of semitransparent Ni film on ZnO surface are investigated. The obtained Ni/n-ZnO/p-Si structures show high sensitivity that sharply increases with increase in applied voltage. Under a bias voltage of 5,V, the responsivities at ,,=,390,nm and ,,=,850,nm were equal to 210 and 110,A/W, which correspond to quantum efficiencies of 655 and 165, respectively. It is assumed that the observed strong response is attributed to internal gain in the Ni/n-ZnO/p-Si phototransistor structure containing Ni/n-ZnO Schottky contact as the emitter junction and n-ZnO/p-Si heterostructure as the collector junction. The response time of the device is ,10,7,s. Alternative mechanisms of photocurrent multiplication in such structures are also discussed. [source] Growth responses of African savanna trees implicate atmospheric [CO2] as a driver of past and current changes in savanna tree coverAUSTRAL ECOLOGY, Issue 4 2010BARNEY S. KGOPE Abstract Atmospheric CO2 has more than doubled since the last glacial maximum (LGM) and could double again within this century, largely due to anthropogenic activity. It has been suggested that low [CO2] contributed to reduced tree cover in savanna and grassland biomes at LGM, and that increasing [CO2] over the last century promoted increases in woody plants in these ecosystems over the past few decades. Despite the implications of this idea for understanding global carbon cycle dynamics and key global role of the savanna biome, there are still very few experimental studies quantifying the effects of CO2 on tree growth and demography in savannas and grasslands. In this paper we present photosynthetic, growth and carbon allocation responses of African savanna trees (Acacia karroo and Acacia nilotica) and a C4 grass, Themeda triandra, exposed to a gradient of CO2 concentrations from 180 (typical of LGM) to 1000 µmol mol,1 in open-top chambers in a glasshouse as a first empirical test of this idea. Photosynthesis, total stem length, total stem diameter, shoot dry weight and root dry weight of the acacias increased significantly across the CO2 gradient, saturating at higher CO2 concentrations. After clipping to simulate fire, plants showed an even greater response in total stem length, total stem diameter and shoot dry weight, signalling the importance of re-sprouting following disturbances such as fire or herbivory in savanna systems. Root starch (per unit root mass and total root starch per plant) increased steeply along the CO2 gradient, explaining the re-sprouting response. In contrast to the strong response of tree seedlings to the CO2 gradient, grass productivity showed little variation, even at low CO2 concentrations. These results suggest that CO2 has significant direct effects on tree recruitment in grassy ecosystems, influencing the ability of trees to recover from fire damage and herbivory. Fire and herbivore regimes that were effective in controlling tree increases in grassy ecosystems could thus be much less effective in a CO2 -rich world, but field-based tests are needed to confirm this suggestion. [source] Life history traits and foraging behaviour of Cotesia nonagriae (Olliff) (Hymenoptera: Braconidae), a newly recognised member of the Cotesia flavipes complex of stemborer parasitoidsAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 1 2010Kate A Muirhead Abstract Cotesia nonagriae (Olliff) from Australia, a parasitoid of the incidental native pest of sugarcane, Bathytricha truncata (Walker) (Lepidoptera: Noctuidae), was previously thought to be a synonym of Cotesia flavipes Cameron. However, recent studies using DNA sequences, morphology and preliminary biological information show that this parasitoid is clearly a different species than C. flavipes and other members of the species complex. Here we further examine differences in the biology of these species by undertaking a detailed study of the life history traits of C. nonagriae, including adult longevity and the potential and realised fecundity of females. In addition, the influence of learning on microhabitat location and foraging behaviour were investigated. Duration of the larval stages and adult longevity of C. nonagriae were longer than previously recorded for other members of the species complex. The potential fecundity of females was similar to C. flavipes (,200 eggs); however, C. nonagriae oviposited a average of over 100 eggs into each host, almost three times more than for other species in the C. flavipes complex (30,40). The propensity of C. nonagriae to allocate a large number of eggs to each host may be an evolutionary strategy due to the high mortality rate (50,57%) of ovipositing adult wasps. During microhabitat location, both naïve and experienced females demonstrated a strong response towards the plant host complex, with experienced wasps benefiting by having a more rapid response time to host-induced volatiles and cues. [source] Photodynamic therapy with verteporfin in age-related macular degeneration: a systematic review of efficacy, safety, treatment modifications and pharmacoeconomic propertiesACTA OPHTHALMOLOGICA, Issue 2 2009Alan F. Cruess Abstract. Photodynamic therapy (PDT) with verteporfin has been used less comprehensively in the treatment of exudative age-related macular degeneration (AMD), and specifically of choroidal neovascularization (CNV), since the advent of antiangiogenic therapies. Recently, there has been a renewed interest in PDT as an adjunct to these and other agents in the treatment of neovascular AMD. In light of this new development and the European Medicines Evaluation Agency's (EMEA) recent labelling decision to rescind approval for the use of PDT in occult CNV lesions, the present systematic review was undertaken to revisit the evidence supporting its clinical application. Photodynamic therapy provided the first pharmacological treatment for patients suffering from subfoveal CNV, the major cause of severe vision loss in AMD. Key clinical trials evaluating efficacy and safety have examined patients with all lesion subtypes, with the primary labelled indication (i.e. lesions containing a classic component of , 50% ) deriving from the results of the Treatment of Age-related Macular Degeneration with Photodynamic Therapy (TAP) Study. The subsequent TAP Study Group post hoc categorization of lesions as predominantly classic is open to question, however, as it appears that the overall efficacy in this group only may have reflected the especially strong response in 100% classic lesions. Based on a subgroup analysis of the Verteporfin in Photodynamic Therapy Study, the indication for PDT subsequently was expanded in some jurisdictions, including that of the EMEA, to include occult lesions with no classic component. However, the subsequent Visudyne in Occult Study found no benefit in 100% occult lesions, resulting in the EMEA rescinding its approval for this indication. [source] CD3 expression distinguishes two ,,T cell receptor subsets with different phenotype and effector function in tuberculous pleurisyCLINICAL & EXPERIMENTAL IMMUNOLOGY, Issue 3 2009N. Yokobori Summary Tuberculous pleurisy is a naturally occurring site of Mycobacterium tuberculosis (Mtb) infection. Herein, we describe the expression of activation, natural killer (NK) and cell migration markers, as well as effector functions from ,,T cells in peripheral blood (PB) and pleural effusion (PE) from tuberculosis patients (TB). We observed a decreased percentage of circulating ,,T from TB patients and differential expression of NK as well as of chemokine receptors on PB and PE. Two subsets of ,,T cells were differentiated by the CD3/,,T cell receptor (,,TCR) complex. The ,,TCRlow subset had a higher CD3 to TCR ratio and was enriched in V,2+ cells, whereas most V,1+ cells belonged to the ,,TCRhigh subset. In PB from TB, most ,,TCRhigh were CD45RA+CCR7 - and ,,TCRlow were CD45RA+/,CCR7+CXCR3+. In the pleural space the proportion of CD45RA - CCR7+CXCR3+ cells was higher. Neither spontaneous nor Mtb -induced interferon (IFN)-, production was observed in PB-,,T cells from TB; however, PE-,,T cells showed a strong response. Both PB- and PE-,, T cells expressed surface CD107a upon stimulation with Mtb. Notably, PE-,,TCRlow cells were the most potent effector cells. Thus, ,,T cells from PB would acquire a further activated phenotype within the site of Mtb infection and exert full effector functions. As ,,T cells produce IFN-, within the pleural space, they would be expected to play a beneficial role in tuberculous pleurisy by helping to maintain a T helper type 1 profile. [source] The ability to mount multiple immune responses simultaneously varies across the range of the tree swallowECOGRAPHY, Issue 1 2007Daniel R. Ardia Variation in immune responses is an important part of life history variation. When correlations between multiple immune measures are reported, studies report different patterns. I tested whether the correlation between levels of immune response was consistent across a species range. The ability of tree swallows Tachycineta bicolor to simultaneously produce immune responses to both a humoral immune response and T-cell mediated local inflammation to PHA was tested at three sites that span the breeding range. Females in Tennessee maintained stronger PHA responses than did females in either New York or Alaska. In New York and Alaska, individuals that produced strong PHA responses produced low levels of antibodies to a humoral challenge of sheep red blood cells (SRBC). However, in Tennessee, individuals that showed strong local PHA inflammation also mounted strong responses to SRBC. Increasing daily daytime temperatures led to increased PHA response, but there were no differences in the effect of temperature among sites. These results indicate spatial and/or temporal variation occurs in the ability to produce multiple immune responses simultaneously; this pattern suggests important geographic (or temporal) differences in factors driving investment in immune activity. In addition, these results suggest that studies extrapolating results across populations should be careful to consider geographic variation in immune activity. [source] Noise-improved signal detection in cat primary visual cortex via a well-balanced stochastic resonance-like procedureEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2007Klaus Funke Abstract Adding noise to a weak signal can paradoxically improve signal detection, a process called ,stochastic resonance' (SR). In the visual system, noise might be introduced by the image jitter resulting from high-frequency eye movements, like eye microtremor and microsaccades. To test whether this kind of noise might be beneficial or detrimental for cortical signal detection, we performed single-unit recordings from area 17 of anaesthetized cats while jittering the visual stimulus in a frequency and amplitude range resembling the possible range of eye movements. We used weak, sub- and peri-threshold visual stimuli, on top of which we superimposed noise with variable jitter amplitude. In accordance with the typical SR effect, we found that small noise levels actually increased the signal-to-noise ratio (SNR) of previously weak cortical visual responses, while originally strong responses were little affected or even reduced. Above a certain noise level, the SNR dropped a little, but not as a result of increased background activity , as would be proposed by SR theory , but because of a lowered response to signal and noise. Therefore, it seems that the ascending visual pathway optimally utilizes signal detection improvement by a SR-like process, while at the same time preventing spurious noise-induced activity and keeping the SNR sufficiently high. [source] Functional biodiversity of macroinvertebrate assemblages along major ecological gradients of boreal headwater streamsFRESHWATER BIOLOGY, Issue 9 2005JANI HEINOArticle first published online: 3 AUG 200 Summary 1. Biodiversity,environment relationships are increasingly well-understood in the context of species richness and species composition, whereas other aspects of biodiversity, including variability in functional diversity (FD), have received rather little rigorous attention. For streams, most studies to date have examined either taxonomic assemblage patterns or have experimentally addressed the importance of species richness for ecosystem functioning. 2. I examined the relationships of the functional biodiversity of stream macroinvertebrates to major environmental and spatial gradients across 111 boreal headwater streams in Finland. Functional biodiversity encompassed functional richness (FR , the number of functional groups derived from a combination of functional feeding groups and habit trait groups), FD , the number of functional groups and division of individuals among these groups, and functional evenness (FE , the division of individuals among functional groups). Furthermore, functional structure (FS) comprised the composition and abundance of functional groups at each site. 3. FR increased with increasing pH, with additional variation related to moss cover, total nitrogen, water colour and substratum particle size. FD similarly increased with increasing pH and decreased with increasing canopy cover. FE decreased with increasing canopy cover and water colour. Significant variation in FS was attributable to pH, stream width, moss cover, substratum particle size, nitrogen, water colour with the dominant pattern in FS being related to the increase of shredder-sprawlers and the decrease of scraper-swimmers in acidic conditions. 4. In regression analysis and redundancy analysis, variation in functional biodiversity was not only related to local environmental factors, but a considerable proportion of variability was also attributable to spatial patterning of environmental variables and pure spatial gradients. For FR, 23.4% was related to pure environmental effects, 15.0% to shared environmental and spatial effects and 8.0% to spatial trends. For FD, 13.8% was attributable to environmental effects, 15.2% to shared environmental and spatial effects and 5% to spatial trends. For FE, 9.0% was related to environmental variables, 12.7% to shared effects of environmental and spatial variables and 4.5% to spatial variables. For FS, 13.5% was related to environmental effects, 16.9% to shared environmental and spatial effects and 15.4% to spatial trends. 5. Given that functional biodiversity should portray variability in ecosystem functioning, one might expect to find functionally rather differing ecosystems at the opposite ends of major environmental gradients (e.g. acidity, stream size). However, the degree to which variation in the functional biodiversity of stream macroinvertebrates truly portrays variability in ecosystem functioning is difficult to judge because species traits, such as feeding roles and habit traits, are themselves strongly affected by the habitat template. 6. If functional characteristics show strong responses to natural environmental gradients, they also are likely to do so to anthropogenic environmental changes, including changes in habitat structure, organic inputs and acidifying elements. However, given the considerable degree of spatial structure in functional biodiversity, one should not expect that only the local environment and anthropogenic changes therein are responsible for this variability. Rather, the spatial context, as well as natural variability along environmental gradients, should also be explicitly considered in applied research. [source] Differential CD4+ T-cell memory responses induced by two subsets of human monocyte-derived dendritic cellsIMMUNOLOGY, Issue 3 2007Sandra Bajaña Summary Dendritic cells (DC) are powerful inducers of primary T-cell responses, but their role in secondary responses has not been extensively analysed. Here, we address the role of two DC subsets derived from human CD16+ (16+ mDC) or CD16, (16, mDC) monocytes on the reactivation of memory responses. CD4+ CD45RA, memory T cells were obtained from adult blood donors, and central (TCM) and effector (TEM) memory T cells were isolated by fluorescence-activated cell sorting with anti-CCR7 antibodies. The 16+ mDC and 16, mDC were cocultured with autologous lymphocytes, either unpulsed or loaded with purified protein derivatives of Mycobacterium tuberculosis (PPD) or tetanus toxoid (TT), and were analysed for up to 8 days. Over a range of doses, 16+ mDC drove stronger T-cell proliferative responses against both antigens. Overall, antigen-specific memory cells tended to acquire a phenotype of TEM at later time-points in the culture, whereas cells that had completed fewer cycles of division were similar to TCM. The 16+ mDC induced higher rates of proliferation on both TCM and TEM lymphocytes than 16, mDC. This phenomenon was not related to the ability of both DC to induce CD25 expression on T cells, to lower secretion of interleukin-2, or to raise production of interleukin-10 during T-cell/16, mDC cocultures. The induction of TCM effector capacity in terms of interferon-, production was faster and more pronounced with 16+ mDC, whereas both DC had similar abilities with TEM. In conclusion, these data might reveal new potentials in vaccination protocols with 16+ mDC aimed at inducing strong responses on central memory T cells. [source] Hepatitis C virus-specific T-cell immune responses in seronegative injection drug usersJOURNAL OF VIRAL HEPATITIS, Issue 1 2009M. Zeremski Summary., T-cell responses to hepatits C virus (HCV) antigens have been reported in high-risk HCV seronegative persons, suggesting that an effective cellular immune response might be able to clear infection without the development of antibodies. Such findings, however, could be explained by waning antibody or cross-reactivity to other antigens. To address these issues, we evaluated HCV-specific T-cell responses in 26 young (age 18,33 years) aviremic, seronegative injection drug users (IDUs) (median duration of injection, 6 years) by interferon-, enzyme-linked immunospot (ELISpot) assay using 429 overlapping HCV peptides pooled in 21 mixes. Seventeen aviremic, seropositive IDUs (spontaneous resolvers) and 15 healthy people were used as positive and negative controls, respectively. The percentage of patients with HCV-specific cellular immune responses was similar in seronegative and seropositive aviremic IDUs (46%vs 59%, P = 0.4), while these responses were not detected in any of the negative controls. Among the seronegative IDUs, six (23%) had intermediate to very strong responses to 10,20 peptide mixes and another six (23%) had moderately strong responses for two to six mixes. The 12 seronegative IDUs with HCV-specific T-cell responses had higher demographical and behavioural risk profiles than the 14 IDUs without T-cell responses (estimated risk of HCV infection, 0.47 vs 0.26, P < 0.01). In conclusion, HCV-specific T-cell responses are common among high-risk, seronegative IDUs. The responses are broad and are associated with risk factors for HCV exposure, suggesting that they reflect true exposure to HCV in seronegative persons. [source] | |||||||||||||||||||