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Antagonistic
Terms modified by Antagonistic Selected AbstractsSpontaneous Emergence of Homochirality via Coherently Coupled Antagonistic and Reversible Reaction CyclesCHEMPHYSCHEM, Issue 16 2008Michael Mauksch Dr. Abstract Asymmetric synthesis aims at obtaining enantio-enriched products in stereoselective reactions under a chiral influence. We demonstrate both mathematically and numerically that, even under nominally achiral conditions, fully homochiral steady states can be obtained in open reactive systems by spontaneous mirror-symmetry breaking in the homogenous solution phase when the autocatalytic reaction network is closed in the form of coherently coupled antagonistic reversible reaction cycles which, paradoxically, allow for complete recycling of the reactant. We show that the fully reversible Frank mechanism for spontaneous mirror-symmetry breaking is closely related to the Lotka,Volterra system, which models predator,prey relations in ecosystems. Amplification of total enantiomeric excess and the principle of microscopic reversibility are not in conflict for all conceivable reactions. A viable and widely applicable reaction protocol is introduced and discussed, and it permits the theoretical implications to be applied to practical laboratory examples. Implications for the possible origin of biological homochirality on early earth are discussed. [source] Combined effects of two stressors on Kenyan coral reefs are additive or antagonistic, not synergisticCONSERVATION LETTERS, Issue 2 2010Emily S. Darling Abstract A challenge for conservation science is predicting the impacts of co-occurring human activities on ecological systems. Multiple anthropogenic and natural stressors impact ecosystems globally and are expected to jeopardize their ecological functions and the success of conservation and management initiatives. The possibility that two or more stressors interact synergistically is of particular concern, but such nonadditive effects remain largely unidentified in nature. A long-term data set of hard coral cover from Kenyan reefs was used to examine the independent and interactive effects of two stressors: fishing and a temperature anomaly in 1998 that caused mass coral bleaching and mortality. While both stressors decreased coral cover, fishing by 51% and bleaching by 74%, they did not interact synergistically. Instead, their combined effect was antagonistic or weakly additive. The observed nonsynergistic response may be caused by the presence of one dominant stressor, bleaching, and cotolerance of coral taxa to both bleaching and fishing stressors. Consequently, coral bleaching has been the dominant driver of coral loss on Kenyan reefs and while marine reserves offer many benefits to reef ecosystems, they may not provide corals with a refuge from climate change. [source] ,Green alliances' of business and NGOs.CORPORATE SOCIAL RESPONSIBILITY AND ENVIRONMENTAL MANAGEMENT, Issue 1 2002New styles of self-regulation or, dead-end roads'? In recent years, so-called greenalliances between NGOs and business have become popular phenomena, both in practice as well as in academic literature. This is striking, as it concerns collaborative partnerships of agencies whose relationships were quite antagonistic in the past. The question then is how stable and effective these alliances can be, amongst others, in contributing to,or even substituting,environmental policy-making and regulation. To answer this question, the history and (potential) effectiveness of green alliances are analysed from a political modernization and policy arrangement perspective. With that, this paper has a strong theoretical focus. The intention is not to analyse empirical cases thoroughly, but to theorize about the history, strengths and weaknesses of green alliances. Copyright © 2002 John Wiley & Sons, Ltd and ERP Environment [source] Bacteria in oral secretions of an endophytic insect inhibit antagonistic fungiECOLOGICAL ENTOMOLOGY, Issue 6 2006YASMIN J. CARDOZA Abstract 1.,Colonisation of host trees by an endophytic herbivore, the spruce beetle, Dendroctonus rufipennis, is accompanied by invasion of its galleries by a number of fungal species. Four of these associated species were identified as Leptographium abietinum, Aspergillus fumigatus, Aspergillus nomius, and Trichoderma harzianum. 2.,Trichoderma and Aspergillus significantly reduced spruce beetle survival and reproduction in controlled assays. 3.,A previously undescribed behaviour was observed, in which spruce beetle adults exuded oral secretions, especially within fungus-pervaded galleries. 4.,These oral secretions inhibited the growth of fungi except A. nomius, and disrupted the morphology of the latter. Administration of these secretions indicated a dose-dependent inhibitory effect. 5.,Oral secretions cultured on microbiological media yielded substantial bacterial growth. 6.,Filter-sterilised secretions failed to inhibit fungal growth, evidence that the bacteria are responsible for the antifungal activity. 7.,Nine bacterial isolates belonging to the Actinobacteria, Firmicutes, Gammaproteobacteria, and Betaproteobacteria taxa were obtained from the secretions. 8.,Bacterial isolates showed species-specific inhibitory activity against the four fungi antagonistic to spruce beetle. The bacterium with the strongest fungal inhibition activity was the actinomycete Micrococcus luteus. 9.,The production of bark beetle secretions containing bacteria that inhibit fungal growth is a novel finding. This suggests an additional level of complexity to ecological associations among bark beetles, conifers, and microorganisms, and an important adaptation for colonising subcortical tissue. [source] Serfdom and social capital in Bohemia and Russia1ECONOMIC HISTORY REVIEW, Issue 3 2007T. K. DENNISON The ,horizontal' social capital generated by networks and communities is widely regarded as inherently antagonistic to ,vertical' hierarchies such as serfdom. This article examines this view using evidence from pre-Emancipation Bohemia and Russia. It finds that serf communes generated a substantial ,social capital' of shared norms, common information, and collective sanctions. But communal social capital was manipulated by village elites who collaborated with overlords in taxation, land regulation, and demographic control. This benefited communal oligarchies, but harmed ordinary serfs and the wider economy. Horizontal social capital and vertical hierarchies, the article demonstrates, can as easily collude as conflict. [source] Antagonistic interactions among coral-associated bacteriaENVIRONMENTAL MICROBIOLOGY, Issue 1 2010Krystal L. Rypien Summary Reef-building corals are comprised of close associations between the coral animal, symbiotic zooxanthellae, and a diversity of associated microbes (including Bacteria, Archaea and Fungi). Together, these comprise the coral holobiont , a paradigm that emphasizes the potential contributions of each component to the overall function and health of the coral. Little is known about the ecology of the coral-associated microbial community and its hypothesized role in coral health. We explored bacteria,bacteria antagonism among 67 bacterial isolates from the scleractinian coral Montastrea annularis at two temperatures using Burkholder agar diffusion assays. A majority of isolates exhibited inhibitory activity (69.6% of isolates at 25°C, 52.2% at 31°C), with members of the ,-proteobacteria (Vibrionales and Alteromonadales) being especially antagonistic. Elevated temperatures generally reduced levels of antagonism, although the effects were complex. Several potential pathogens were observed in the microbial community of apparently healthy corals, and 11.6% of isolates were able to inhibit the growth of the coral pathogen Vibrio shiloi at 25°C. Overall, this study demonstrates that antagonism could be a structuring force in coral-associated microbial communities and may contribute to pathogenesis as well as disease resistance. [source] Possible role of reactive chlorine in microbial antagonism and organic matter chlorination in terrestrial environmentsENVIRONMENTAL MICROBIOLOGY, Issue 6 2009Per Bengtson Summary Several studies have demonstrated that extensive formation of organically bound chlorine occurs both in soil and in decaying plant material. Previous studies suggest that enzymatic formation of reactive chlorine outside cells is a major source. However, the ecological role of microbial-induced extracellular chlorination processes remains unclear. In the present paper, we assess whether or not the literature supports the hypothesis that extracellular chlorination is involved in direct antagonism against competitors for the same resources. Our review shows that it is by no means rare that biotic processes create conditions that render biocidal concentrations of reactive chlorine compounds, which suggest that extracellular production of reactive chlorine may have an important role in antagonistic microbial interactions. To test the validity, we searched the UniprotPK database for microorganisms that are known to produce haloperoxidases. It appeared that many of the identified haloperoxidases from terrestrial environments are originating from organisms that are associated with living plants or decomposing plant material. The results of the in silico screening were supported by various field and laboratory studies on natural chlorination. Hence, the ability to produce reactive chlorine seems to be especially common in environments that are known for antibiotic-mediated competition for resources (interference competition). Yet, the ability to produce haloperoxidases is also recorded, for example, for plant endosymbionts and parasites, and there is little or no empirical evidence that suggests that these organisms are antagonistic. [source] Pseudomonas community structure and antagonistic potential in the rhizosphere: insights gained by combining phylogenetic and functional gene-based analysesENVIRONMENTAL MICROBIOLOGY, Issue 9 2007Rodrigo Costa Summary The Pseudomonas community structure and antagonistic potential in the rhizospheres of strawberry and oilseed rape (host plants of the fungal phytopathogen Verticillium dahliae) were assessed. The use of a new PCR-DGGE system, designed to target Pseudomonas -specific gacA gene fragments in environmental DNA, circumvented common biases of 16S rRNA gene-based DGGE analyses and proved to be a reliable tool to unravel the diversity of uncultured Pseudomonas in bulk and rhizosphere soils. Pseudomonas -specific gacA fingerprints of total-community (TC) rhizosphere DNA were surprisingly diverse, plant-specific and differed markedly from those of the corresponding bulk soils. By combining multiple culture-dependent and independent surveys, a group of Pseudomonas isolates antagonistic towards V. dahliae was shown to be genotypically conserved, to carry the phlD biosynthetic locus (involved in the biosynthesis of 2,4-diacetylphloroglucinol , 2,4-DAPG), and to correspond to a dominant and highly frequent Pseudomonas population in the rhizosphere of field-grown strawberries planted at three sites in Germany which have different land use histories. This population belongs to the Pseudomonas fluorescens phylogenetic lineage and showed closest relatedness to P. fluorescens strain F113 (97% gacA gene sequence identity in 492-bp sequences), a biocontrol agent and 2,4-DAPG producer. Partial gacA gene sequences derived from isolates, clones of the strawberry rhizosphere and DGGE bands retrieved in this study represent previously undescribed Pseudomonas gacA gene clusters as revealed by phylogenetic analysis. [source] Combined effects of discharge, turbidity, and pesticides on mayfly behavior: Experimental evaluation of spray-drift and runoff scenariosENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2005James M. Dabrowski Abstract The effects of the pyrethroid-insecticide cypermethrin (CYP), increased flow speed (Flow), and increased suspended particles (Part) on drift behavior and activity of mayfly nymphs (Baetis harrisoni) were investigated both individually and in combination in a laboratory stream microcosm. Spray-drift trials were performed by exposing the nymphs to 1 ,g/L of CYP. During runoff trials (CYP × Part), contaminated sediment containing 2,000 ,g/kg of CYP was introduced to the microcosm at a concentration of 500 mg/L. Both trials were carried out under high-flow (CYP × Flow and CYP × Part × Flow) and low-flow (CYP and CYP × Part) conditions, and for all cases, control experiments were performed. Drift rate, drift density (for any treatments with increased flow), and activity were used as behavioral endpoints. Multifactorial analysis of variance shows that CYP exposure significantly increased the drift, whereas Part and Flow trials significantly decreased the drift (p < 0.05). In addition, activity decreased significantly under high-flow conditions. The CYP × Part and CYP × Flow treatments resulted in increased drift rate and drift density, respectively, whereas Part × Flow and CYP × Part × Flow treatments resulted in decreased drift density. The CYP × Part and CYP × Flow trials had a significant antagonistic, interactive effect on drift rate and drift density, respectively, with measured levels being lower than expected levels. The reduction in bioavailability of CYP in the presence of increased flow and sediment levels suggests that mayflies are more likely to be affected by spray-drift exposure (CYP) than by runoff exposure (CYP × Part × Flow). Results indicate that mayflies reacted actively in response to flow conditions and passively in response to pesticide exposure. [source] Pharmacodynamic and Pharmacokinetic Interaction Studies of Loreclezole with Felbamate, Lamotrigine, Topiramate, and Oxcarbazepine in the Mouse Maximal Electroshock Seizure ModelEPILEPSIA, Issue 3 2005Jarogniew J. Luszczki Summary:,Purpose: The study investigated the types of interactions between loreclezole (LCZ) and a variety of newly licensed antiepileptic drugs (AEDs) with different mechanisms of actions [felbamate (FBM), lamotrigine (LTG), topiramate (TPM), and oxcarbazepine (OXC)] by isobolographic analysis. Methods: Anticonvulsant and adverse-effect profiles of combinations of LCZ with other AEDs at fixed ratios of 1:3, 1:1, and 3:1 were investigated in the maximal electroshock (MES)-induced seizures and the chimney test (as a measure of motor impairment) in mice so as to identify optimal combinations. Protective indices (PIs) and benefit indices (BIs) were calculated so that a ranking in relation to advantageous combinations could be established. Results: With isobolography, it was observed that the combination of LCZ and TPM, at the fixed ratios of 1:1 and 3:1, was supraadditive (synergistic; p < 0.05), whereas LCZ with TPM at the fixed ratio of 1:3 and LCZ combined with LTG, FBM, or OXC at the fixed ratios of 1:3, 1:1, and 3:1 were associated with additive interactions. Moreover, the isobolographic analysis in the chimney test revealed that only one combination tested (LCZ and TPM at the fixed ratio of 1:1) was subadditive (antagonistic; p < 0.05), whereas the remaining combinations of LCZ with LTG, FBM, or OXC (at the fixed ratios of 1:3, 1:1, and 3:1) barely displayed additivity. However, these combinations were associated with significant pharmacokinetic interactions, in that LCZ increased brain TPM (94%), OXC (21%), FBM (46%), and LTG (8%) concentrations. In addition, brain LCZ concentrations were decreased by TPM (26%), OXC (37%), LTG (42%), and FBM (19%). None of the examined combinations between LCZ and TPM, OXC, LTG, and FBM altered long-term memory in the step-through passive-avoidance task. Conclusions: LCZ plus TPM appears to be a particularly favorable combination, based on the MES test and the chimney test. LCZ and OXC also is a favorable combination. However, these conclusions are confounded by the fact that LCZ is associated with significant pharmacokinetic interactions. [source] Interactions Between Oxcarbazepine and Conventional Antiepileptic Drugs in the Maximal Electroshock Test in Mice: An Isobolographic AnalysisEPILEPSIA, Issue 4 2003Jarogniew J. Luszczki Summary: ,Purpose: The aim of this study was to determine the types of interactions between oxcarbazepine (OCBZ) and conventional antiepileptic drugs (AEDs) against maximal electroshock-induced seizures (MES test) in mice, by using a method of isobolographic analysis. Methods: Adverse effects of combinations were evaluated in the chimney test (motor performance), also using the isobolographic method, which allowed determination of the median toxic dose (TD50) values for individual combinations; thus the protective indices could be determined. Results: OCBZ and phenytoin (PHT) at the fixed-ratio combination of 1:1 were significantly infraadditive (antagonistic) with respect to the antiseizure protection against MES and simultaneously additive in terms of side effects in the chimney test. Interestingly, combinations between OCBZ and clonazepam (CZP) in the MES test proved antagonistic or synergistic, depending on the proportion of both AEDs in the mixture. Low doses of OCBZ with high doses of CZP exerted antagonism. Conversely, high doses of OCBZ combined with low doses of CZP resulted in a synergistic interaction. Remaining combinations between OCBZ and phenobarbital, valproate, or carbamazepine were purely additive, either as regards the anticonvulsant activity against MES or in terms of motor impairment in the chimney test. Conclusions: The results of this study indicate that interaction of OCBZ and CZP at fixed-ratio combination of 1:1 might be profitable from a clinical point of view. Conversely, combinations of OCBZ with PHT may not be clinically efficient. [source] BIOTIC INTERACTIONS AND MACROEVOLUTION: EXTENSIONS AND MISMATCHES ACROSS SCALES AND LEVELSEVOLUTION, Issue 4 2008David Jablonski Clade dynamics in the fossil record broadly fit expectations from the operation of competition, predation, and mutualism, but data from both modern and ancient systems suggest mismatches across scales and levels. Indirect effects, as when antagonistic or mutualistic interactions restrict geographic range and thereby elevate extinction risk, are probably widespread and may flow in both directions, as when species- or organismic-level factors increase extinction risk or speciation probabilities. Apparent contradictions across scales and levels have been neglected, including (1) the individualistic geographic shifts of species on centennial and millennial timescales versus evidence for fine-tuned coevolutionary relationships; (2) the extensive and dynamic networks of interactions faced by most species versus the evolution of costly enemy-specific defenses and finely attuned mutualisms; and (3) the macroevolutionary lags often seen between the origin and the diversification of a clade or an evolutionary novelty versus the rapid microevolution of advantageous phenotypes and the invasibility of most communities. Resolution of these and other cross-level tensions presumably hinges on how organismic interactions impinge on genetic population structures, geographic ranges, and the persistence of incipient species, but generalizations are not yet possible. Paleontological and neontological data are both incomplete and so the most powerful response to these problems will require novel integrative approaches. Promising research areas include more realistic approaches to modeling and empirical analysis of large-scale diversity dynamics of ostensibly competing clades; spatial and phylogenetic dissections of clades involved in escalatory dynamics (where prey respond evolutionarily to a broad and shifting array of enemies); analyses of the short- versus long-term consequences of mutualistic symbioses; and fuller use of abundant natural experiments on the evolutionary impacts of ecosystem engineers. [source] A CENTENNIAL CELEBRATION FOR QUANTITATIVE GENETICSEVOLUTION, Issue 5 2007Derek A. Roff Quantitative genetics is at or is fast approaching its centennial. In this perspective I consider five current issues pertinent to the application of quantitative genetics to evolutionary theory. First, I discuss the utility of a quantitative genetic perspective in describing genetic variation at two very different levels of resolution, (1) in natural, free-ranging populations and (2) to describe variation at the level of DNA transcription. Whereas quantitative genetics can serve as a very useful descriptor of genetic variation, its greater usefulness is in predicting evolutionary change, particularly when used in the first instance (wild populations). Second, I review the contributions of Quantitative trait loci (QLT) analysis in determining the number of loci and distribution of their genetic effects, the possible importance of identifying specific genes, and the ability of the multivariate breeder's equation to predict the results of bivariate selection experiments. QLT analyses appear to indicate that genetic effects are skewed, that at least 20 loci are generally involved, with an unknown number of alleles, and that a few loci have major effects. However, epistatic effects are common, which means that such loci might not have population-wide major effects: this question waits upon (QTL) analyses conducted on more than a few inbred lines. Third, I examine the importance of research into the action of specific genes on traits. Although great progress has been made in identifying specific genes contributing to trait variation, the high level of gene interactions underlying quantitative traits makes it unlikely that in the near future we will have mechanistic models for such traits, or that these would have greater predictive power than quantitative genetic models. In the fourth section I present evidence that the results of bivariate selection experiments when selection is antagonistic to the genetic covariance are frequently not well predicted by the multivariate breeder's equation. Bivariate experiments that combine both selection and functional analyses are urgently needed. Finally, I discuss the importance of gaining more insight, both theoretical and empirical, on the evolution of the G and P matrices. [source] PERSPECTIVE: SEXUAL CONFLICT AND SEXUAL SELECTION: CHASING AWAY PARADIGM SHIFTSEVOLUTION, Issue 6 2003TOMMASO PIZZARI Abstract., Traditional models of sexual selection propose that partner choice increases both average male and average female fitness in a population. Recent theoretical and empirical work, however, has stressed that sexual conflict may be a potent broker of sexual selection. When the fitness interests of males and females diverge, a reproductive strategy that increases the fitness of one sex may decrease the fitness of the other sex. The chase-away hypothesis proposes that sexual conflict promotes sexually antagonistic, rather than mutualistic, coevolution, whereby manipulative reproductive strategies in one sex are counteracted by the evolution of resistance to such strategies in the other sex. In this paper, we consider the criteria necessary to demonstrate the chase-away hypothesis. Specifically, we review sexual conflict with particular emphasis on the chase-away hypothesis; discuss the problems associated with testing the predictions of the chase-away hypothesis and the extent to which these predictions and the predictions of traditional models of sexual selection are mutually exclusive; discuss misconceptions and mismeasures of sexual conflict; and suggest an alternative approach to demonstrate sexual conflict, measure the intensity of sexually antagonistic selection in a population, and elucidate the coevolutionary trajectories of the sexes. [source] Hauling Down the Double Standard: Feminism, Social Purity and Sexual Science in Late Nineteenth-Century BritainGENDER & HISTORY, Issue 1 2004Lesley Hall Nineteenth-century feminism and the related social purity movement, and the emergent scientific discourse of ,sexology', are usually seen as antagonistic. Both trends, in fact, were in profound opposition to the widespread assumption that the double moral standard was an embodiment of ,natural' transhistorical law. This article suggests that feminist agitation against the Contagious Diseases Acts of the 1860s (and other manifestations of the deleterious legal status of women) overtly attacked unthinking social assumptions about sex and gender, destabilising concepts about the naturalness of the existing sexual system and creating the context for the pioneers of sexology to interrogate even further accepted notions of gender and sexuality. [source] Indication of antagonistic interaction between climate change and erosion on plant species richness and soil properties in semiarid Mediterranean ecosystemsGLOBAL CHANGE BIOLOGY, Issue 2 2009PATRICIO GARCÍA-FAYOS Abstract We analyzed the consequences of climate change and the increase in soil erosion, as well as their interaction on plant and soil properties in semiarid Mediterranean shrublands in Eastern Spain. Current models on drivers of biodiversity change predict an additive or synergistic interaction between drivers that will increase the negative effects of each one. We used a climatic gradient that reproduces the predicted climate changes in temperature and precipitation for the next 40 years of the wettest and coldest end of the gradient; we also compared flat areas with 20° steep hillslopes. We found that plant species richness and plant cover are negatively affected by climate change and soil erosion, which in turn negatively affects soil resistance to erosion, nutrient content and water holding capacity. We also found that plant species diversity correlates weakly with plant cover but strongly with soil properties related to fertility, water holding capacity and resistance to erosion. Conversely, these soil properties correlate weaker with plant species cover. The joint effect of climate change and soil erosion on plant species richness and soil characteristics is antagonistic. That is, the absolute magnitude of change is smaller than the sum of both effects. However, there is no interaction between climate change and soil erosion on plant cover and their effects fit the additive model. The differences in the interaction model between plant cover and species richness supports the view that several soil properties are more linked to the effect that particular plant species have on soil processes than to the quantity and quality of the plant cover and biomass they support. Our findings suggest that plant species richness is a better indicator than plant cover of ecosystems services related with soil development and protection to erosion in semiarid Mediterranean climates. [source] Antagonistic Effects of Hydrogen Peroxide and Glutathione on Acclimation to Excess Excitation Energy in ArabidopsisIUBMB LIFE, Issue 1 2000Barbara Karpinska Abstract The redox status of the quinone B (QB) and plastoquinone (PQ) pools plays a key role in the cellular and systemic signalling processes that control acclimatory responses in plants. In this study, we demonstrate the effects of hydrogen peroxide and glutathione on acclimatory responses controlled by redox events in the proximity of the QB-PQ pools. Our results suggest that the chloroplast is a sink for H2O2 and that, paradoxically, high concentrations of H2O2 in the chloroplast protect the photosynthetic apparatus and the plant cell from photoinhibition and photooxidative damage. Excess glutathione, however, caused an effect antagonistic to that observed for high H2O2. An explanation of this apparent paradox and a hypothetical redox-signalling model are suggested. [source] Synergistic, antagonistic and additive effects of multiple stressors: predation threat, parasitism and pesticide exposure in Daphnia magnaJOURNAL OF APPLIED ECOLOGY, Issue 6 2008Anja Coors Summary 1Predation and parasitism are important factors in the ecology and evolution of natural populations and may, along with other environmental factors, interact with the impact of anthropogenic pollutants. 2Our study aimed at identifying potential interactions between three stressors (predation threat, parasitism and pesticide exposure) and at exploring the predictability of their joint effects by using the model of independent action. We assessed in a full-factorial design the impacts of these stressors on key life-history traits and population growth rate of the water flea Daphnia magna. 3When applied as single stressors, predation threat and parasite challenge induced varying stressor-specific adaptive responses. The pesticide carbaryl was applied at a generally sublethal concentration, which caused low mortality only in first-brood offspring. 4Pesticide exposure interacted synergistically with parasite challenge regarding survival, which suggests immunomodulatory activity of the pesticide. Predation threat by phantom midge larvae showed antagonistic interactions for amount of first-brood offspring with both parasite challenge and carbaryl exposure. All stressors additively affected age and size at maturity, which added up to a considerable delay in the onset of reproduction in the three-stressor combination. The intrinsic rate of natural increase, r, reflected the non-additive and additive effects on single endpoints and showed significant synergistic interactions for all two-stressor combinations. The combination of all stressors resulted in a dramatic reduction of r compared to the stressor-free control. 5The model of independent action proved useful in quantitatively predicting effects of additively acting stressors, and in visualizing the occurrence and magnitude of non-additive effects in accordance with results of analysis of variances. 6Synthesis and applications. Cumulative additive effects and non-additive interactions of natural antagonists and pollutants are shown to result in considerable impacts on ecologically relevant parameters. As a starting point for an environmentally more realistic risk assessment of chemicals, it may be a valuable strategy to screen for non-additive effects among many stress factors simultaneously in simplified experimental designs by using the model of independent action. [source] Suppression of Rhizoctonia solani diseases of sugar beet by antagonistic and plant growth-promoting yeastsJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2004K.A. El-Tarabily Abstract Aims:, Isolates of Candida valida, Rhodotorula glutinis and Trichosporon asahii from the rhizosphere of sugar beet in Egypt were examined for their ability to colonize roots, to promote plant growth and to protect sugar beet from Rhizoctonia solani AG-2-2 diseases, under glasshouse conditions. Methods and Results:, Root colonization abilities of the three yeast species were tested using the root colonization plate assay and the sand-tube method. In the root colonization plate assay, C. valida and T. asahii colonized 95% of roots after 6 days, whilst Rhod. glutinis colonized 90% of roots after 8 days. Root-colonization abilities of the three yeast species tested by the sand-tube method showed that roots and soils attached to roots of sugar beet seedlings were colonized to different degrees. Population densities showed that the three yeast species were found at all depths of the rhizosphere soil adhering to taproots up to 10 cm, but population densities were significantly (P < 0·05) greater in the first 4 cm of the root system compared with other root depths. The three yeast species, applied individually or in combination, significantly (P < 0·05) promoted plant growth and reduced damping off, crown and root rots of sugar beet in glasshouse trials. The combination of the three yeasts (which were not inhibitory to each other) resulted in significantly (P < 0·05) better biocontrol of diseases and plant growth promotion than plants exposed to individual species. Conclusions:, Isolates of C. valida, Rhod. glutinis and T. asahii were capable of colonizing sugar beet roots, promoting growth of sugar beet and protecting the seedlings and mature plants from R. solani diseases. This is the first successful attempt to use yeasts as biocontrol agents against R. solani which causes root diseases. Significance and Impact of the Study:, Yeasts were shown to provide significant protection to sugar beet roots against R. solani, a serious soil-borne root pathogen. Yeasts also have the potential to be used as biological fertilizers. [source] Environmental stresses mediate endophyte,grass interactions in a boreal archipelagoJOURNAL OF ECOLOGY, Issue 2 2010Nora M. Saona Summary 1.,Both evolutionary theory and empirical evidence from agricultural research support the view that asexual, vertically transmitted fungal endophytes are typically plant mutualists that develop high infection frequencies within host grass populations. In contrast, endophyte,grass interactions in natural ecosystems are more variable, spanning the range from mutualism to antagonism and comparatively little is known about their range of response to environmental stress. 2.,We examined patterns in endophyte prevalence and endophyte,grass interactions across nutrient and grazing (from Greylag and Canada geese) gradients in 15 sites with different soil moisture levels in 13 island populations of the widespread grass Festuca rubra in a boreal archipelago in Sweden. 3.,In the field, endophyte prevalence levels were generally low (range = 10,53%) compared with those reported from agricultural systems. Under mesic-moist conditions endophyte prevalence was constantly low (mean prevalence = 15%) and was not affected by grazing pressure or nutrient availability. In contrast, under conditions of drought, endophyte prevalence increased from 10% to 53% with increasing nutrient availability and increasing grazing pressure. 4.,In the field, we measured the production of flowering culms, as a proxy for host fitness, to determine how endophyte-infected plants differed from uninfected plants. At dry sites, endophyte infection did not affect flowering culm production. In contrast, at mesic-moist sites production of flowering culms in endophyte-infected plants increased with the covarying effects of increasing nutrient availability and grazing pressure, indicating that the interaction switched from antagonistic to mutualistic. 5.,A concurrent glasshouse experiment showed that in most situations, the host appears to incur some costs for harbouring endophytes. Uninfected grasses generally outperformed infected grasses (antagonistic interaction), while infected grasses outperformed uninfected grasses (mutualistic interaction) only in dry, nutrient-rich conditions. Nutrient and water addition affected tiller production, leaf number and leaf length differently, suggesting that tillers responded with different strategies. This emphasizes that several response variables are needed to evaluate the interaction. 6.,Synthesis. This study found complex patterns in endophyte prevalence that were not always correlated with culm production. These contrasting patterns suggest that the direction and strength of selection on infected plants is highly variable and depends upon a suite of interacting environmental variables that may fluctuate in the intensity of their impact, during the course of the host life cycle. [source] Assessing the extent of genome-wide intralocus sexual conflict via experimentally enforced gender-limited selectionJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2008E. H. MORROW Abstract Intralocus sexual conflict, which occurs when a trait is selected in opposite directions in the two sexes, is a taxonomically widespread phenomenon. The strongest genetic evidence for a gender load due to intralocus sexual conflict comes from the Drosophila melanogaster laboratory model system, in which a negative genetic correlation between male and female lifetime fitness has been observed. Here, using a D. melanogaster model system, we utilize a novel modification of the ,middle class neighbourhood' design to relax selection in one sex, while maintaining selection in the other. After 26 generations of asymmetrical selection, we observed the expected drop in fitness of the non-selected sex compared to that of the selected sex, consistent with previous studies of intralocus sexual conflict in this species. However, the fitness of the selected sex also dropped compared to the base population. The overall decline in fitness of both the selected and the unselected sex indicates that most new mutations are harmful to both sexes, causing recurrent mutation to build a positive genetic correlation for fitness between the sexes. However, the steeper decay in the fitness of the unselected sex indicates that a substantial number of mutations are gender-limited in expression or sexually antagonistic. Our experiment cannot definitively resolve these two possibilities, but we use recent genomic data and results from previous studies to argue that sexually antagonistic alleles are the more likely explanation. [source] Use of probiotics to control furunculosis in rainbow trout, Oncorhynchus mykiss (Walbaum)JOURNAL OF FISH DISEASES, Issue 6 2002A Irianto Aerobic heterotrophic bacteria were isolated from the intestinal contents of Atlantic salmon, Salmo salar, rainbow trout, Oncorhynchus mykiss, and turbot, Scophthalmus maximus, on tryptone soya agar and De Man Rogosa and Sharpe agar, of which 11 of 177 (6% of the total) of the isolates were antagonistic to Aeromonas salmonicida. Four of these cultures, which were identified tentatively as A. hydrophila, Vibrio fluvialis, Carnobacterium sp. and an unidentified Gram-positive coccus, were beneficial to fish when fed singly or as an equi-mixture. Feed supplemented with the putative probiotics indicated survival of the organisms in the gastrointestinal tract for 7 days. Feeding with the probiotics for 7 and 14 days led to better survival following challenge with A. salmonicida. There was no indication of serum or mucus antibodies to A. salmonicida, but there was an increased number of erythrocytes, macrophages, lymphocytes and leucocytes, and enhanced lysozyme activity in the fish. [source] ACID PH PRODUCED BY LACTIC ACID BACTERIA PREVENT THE GROWTH OF BACILLUS CEREUS IN BOZA, A TRADITIONAL FERMENTED TURKISH BEVERAGEJOURNAL OF FOOD SAFETY, Issue 2 2005KIYMET GÜVEN ABSTRACT The growth and survival of Bacillus cereus, a known pathogen commonly found in cereals, during lactic acid fermentation of boza, a traditional Turkish cereal beverage, was studied. In the boza base inoculated with both the starter culture and B. cereus, the acidity developed to pH 2.6 and 0.8% titratable acidity after 72 h; the growth of B. cereus was reduced from 3.9 log cfu/mL to 1 log cfu/mL within 72 h. The control boza base to which starter was not added had a pH of 3, titratable acidity of 0.8%. The B. cereus in this boza base to which no starter culture was added dropped to 1 log cfu/mL after 72 h. No strains of lactic acid bacteria were found to produce bacteriocins antagonistic to B. cereus. Low pH and acidity were found to be the major factors inhibiting growth of B. cereus in boza. [source] Susceptibility of hepatitis B virus to lamivudine restored by resistance to adefovirJOURNAL OF MEDICAL VIROLOGY, Issue 3 2009H.L. Zaaijer Abstract Serial monotherapy and add-on regimes for treatment of chronic hepatitis B virus (HBV) infection may induce the accumulation of viral resistance mutations in patients, reducing the options for ongoing viral suppression. The induction of antiviral resistance by serial application of polymerase inhibitors does not necessarily imply that the subsequent combined use of the drugs will fail. Some HIV strains resistant to one polymerase inhibitor show increased susceptibility to another polymerase inhibitor. After failure of sequential lamivudine and adefovir monotherapy, two patients with hepatitis B changed to treatment with lamivudine plus adefovir and had renewed suppression of HBV. To study the mutational history of resistant HBV subpopulations in the two patients, a part of the HBV polymerase gene was amplified, cloned, sequenced, and analyzed for the presence of mutations, in sequential plasma samples. In both patients serial monotherapy caused the replacement in all HBV clones of wild-type virus by classical lamivudine resistant mutants (L180M and M204V/I), which were replaced subsequently by adefovir resistant mutants (A181V and N236T). When finally lamivudine was added to adefovir, the A181V adefovir mutation persisted in all clones and lamivudine-related mutations did not reappear. During 18 months of combination therapy, HBV-DNA levels decreased 10,000, respectively, 1,000-fold, despite the earlier resistance to lamivudine and adefovir. Although clinically insufficient, this effect indicates that HBV polymerase resistance mutations may be antagonistic, which is relevant if chronic HBV infection is to be treated by a combination of polymerase inhibitors. J. Med. Virol. 81:413,416, 2009. © 2009 Wiley-Liss, Inc. [source] A cell-biological model of p75NTR signalingJOURNAL OF NEUROCHEMISTRY, Issue 2 2007A. Blöchl Abstract Neurotrophin stimulation of tropomyosin-related kinase (Trk) and p75 receptors influences cellular processes such as proliferation, growth, differentiation, and other cell-specific functions, as well as regeneration. In contrast to Trk receptors, which have a well-defined trophic role, p75 has activities ranging from trophism to apoptosis. Continued neurotrophin stimulation of differentiating neurons transforms the initially trophic character of p75 signaling into negative growth control and overstimulation leads to apoptosis. This function shift reflects the signaling effects of ceramide that is generated upon stimulation of p75. The use of ceramide signaling by p75 may provide a key to understanding the cell-biological role of p75. The review presents arguments that the control of cell shape formation and cell selection can serve as an organizing principle of p75 signaling. Concurrent stimulation by neurotrophins of p75 and Trk receptors constitutes a dual growth control with antagonistic and synergistic elements aimed at optimal morphological and functional integration of cells and cell populations into their context. [source] Pharmacodynamic interaction of recombinant human interleukin-10 and prednisolone using in vitro whole blood lymphocyte proliferationJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 5 2002Abhijit Chakraborty Abstract Prednisolone, a commonly used synthetic corticosteroid, and IL-10, a cytokine under investigation for strong antiinflammatory properties, are being contemplated as a potential joint therapeutic regimen in immune disorders. Their pharmacodynamic interactions were examined in blood from healthy adult male and female volunteers using an in vitro phytohemagglutinin (PHA)-stimulated whole,blood lymphocyte proliferation technique. Isobolograms along with parametric competitive and noncompetitive interaction models were used to determine the nature and intensity of interactions. Single drug effects show prednisolone more efficacious in inhibiting lymphocyte proliferation with an IC50 of 3.3 ng/mL and Imax value of 1, signifying complete suppression. Analogous parameters for IL-10 were 16.2 ng/mL for IC50 and 0.89 for Imax. There were no significant differences in the single drug immunosuppressive effects among genders. Their joint effects showed additive interaction based on isobolographic analysis. Parametric analysis using the competitive interaction model described their interaction as slightly synergistic, while the noncompetitive interaction modeling indicate a small degree of antagonism. Also, the joint effects in females tend to be more antagonistic than males. Concomitant use of prednisolone and IL-10 should thus reflect the net additive responses to concentrations of each agent. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:1334,1342, 2002 [source] Response of MCF-7 human breast cancer cells to some binary mixtures of oestrogenic compounds in-vitroJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 11 2001Takahiro Suzuki The effects of simultaneous administration of some binary mixtures of seven natural and synthetic oestrogenic substances (17,-estradiol, estrone, bisphenol A, butylbenzyl phthalate, endosulfan, methoxychlor and pentachlorophenol) on the cellular proliferation of human breast cancer MCF-7 cells in-vitro (a modified E-screen assay) have been measured. To assess the presence or absence of interactions of the two agents, the data were analysed on the basis of a graphical method in which the types and extents of interactions were described by response-surface diagrams. Of the nine combinations of the agents examined, synergistic interaction was evident for the combination of 17,-estradiol and bisphenol A, whereas the remaining eight combinations were weakly synergistic, additive and/or weakly antagonistic in the dose-range tested. [source] A NEW PARADIGM FOR FRESHWATER FRAGILARIOID DIATOM CLASSIFICATION?JOURNAL OF PHYCOLOGY, Issue 2001A CRITIQUE OF LANGE-BERTALOT'S NEW SYSTEM Morales, E. A.1 & Trainor, F. R.2 1Phycology Section, Patrick Center for Environmental Research, The Academy of Natural Sciences of Philadelphia, PA 19103-1195 USA; 2Department of Ecology & Evolutionary Biology, University of Connecticut, Storrs, CT 06269-3043 USA In a recent study of freshwater diatoms from South America (Rumrich et al. 2000), Lange-Bertalot introduced a new paradigm for the classification of fragilarioid diatoms. This new system is antagonistic to that presented by Williams and Round (1987) because Lange-Bertalot recognizes a marked variability in the characters chosen and a supposed overall continuity of morphological features among the genera created by his English counterparts. Lange-Bertalot then proposes a partitioning of Fragilaria into two genera: Fragilaria and Staurosira mainly based on the presence/absence of rimoportulae and areolate girdle bands. The newly defined Fragilaria includes relatively large phytoplankters such as F. capucina and F. crotonensis. In turn, Staurosira includes, for the most part, small periphytic organisms, and contains several new species that were based on varieties of old Fragilaria taxa. This fragmentation of species and their varieties is based on a supposed morphological discontinuity. As a consequence an apparent increase in species diversity has occurred within the fragilarioid group. The present work analyzes Lange-Bertalot's new paradigm and confronts it with recent LM and SEM evidence. The incorporation of concepts such as plasticity, polymorphism, and parallel evolution in current classification systems is also discussed. It is concluded that Lange-Bertalot's system represents a step backward from that of Williams and Round. Some adjustments in the latter scheme could be sufficient to accommodate the diversity of fragilarioids known at present. [source] AFLP Analysis of Trichoderma spp. from India Compared with Sequence and Morphological-based DiagnosticsJOURNAL OF PHYTOPATHOLOGY, Issue 7-8 2005H. K. Buhariwalla Abstract Trichoderma species offer considerable potential for controlling aflatoxin contamination in groundnut and other crops. Initial classification of 48 Trichoderma isolates, derived from four different groundnut cultivation sites in India was based on alignment of 28S rDNA sequences to GenBank sequences of ex-type strains. This was found to be substantially more reliable than our routine morphological characterization, but did not provide a comprehensive diagnostic solution, as unique single nucleotide polymorphism (SNP) haplotypes could not be identified for all species. However, all the Trichoderma isolates could be readily distinguished by amplified fragment length polymorphism (AFLP) analysis, based on six primer pair combinations, which generated 234 polymorphic bands. In addition, individual AFLP bands were identified which differentiate closely related species. Similarly, AFLP bands were identified that correlated with different types of antagonism to Aspergillus flavus. The implications of these results for the development of simple polymerase chain reaction (PCR)-based diagnostic assays for antagonistic isolates of Trichoderma is discussed. [source] A Narrative-Based View of Coexistence EducationJOURNAL OF SOCIAL ISSUES, Issue 2 2004Gavriel Salomon Collective narratives of groups in conflict,their perceived histories, beliefs, self-image, and those of their adversaries,play a central role in interpreting and fueling the conflict,and, thus, can play an equally central role in facilitating coexistence. One of their main correlates is their implied delegitimization of the "other's" collective narrative, its pains, its sufferings, its history, and its aspirations. It is this deligitimization that ought to be the main target for change if coexistence is to be promoted, including the acknowledgement of one's own contribution to the conflict. Four dilemmas are discussed: coexistence programs for the dominant versus the subordinate groups; possible counterproductive outcomes; resistance against antagonistic, dominant narratives; and the problem of short-term intervention programs. [source] | |||||||||||||||||||||||||||||||||||||