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Potential Importance (potential + importance)
Selected AbstractsPotential importance of alterations in hydrogen sulphide (H2S) bioavailability in diabetesBRITISH JOURNAL OF PHARMACOLOGY, Issue 8 2008D J Lefer British Journal of Pharmacology (2008) 155, 1308; doi:10.1038/bjp.2008.377 [source] Potential importance of alterations in hydrogen sulphide (H2S) bioavailability in diabetesBRITISH JOURNAL OF PHARMACOLOGY, Issue 5 2008D J Lefer Despite its long-standing reputation as a foul smelling and toxic gas that is associated with the decay of biological matter, hydrogen sulphide (H2S) has emerged as an important regulator of cardiovascular homoeostasis. H2S promotes a number of cellular signals that regulate metabolism, cardiac function and cell survival. Endogenous H2S bioavailability is regulated by several enzymes involved in the biosynthesis of cysteine. This study by Brancaleone et al. in the current issue of the British Journal of Pharmacology provides novel insights into the impairment of H2S biosynthesis in the setting of diabetes mellitus. The authors report that enzymic H2S biosynthesis is impaired in a murine model of type 1 diabetes and the attenuation in H2S bioavailability is associated with impaired vascular reactivity. This study has profound implications for the use of pharmacological agents to augment endogenous H2S synthesis or agents that release H2S to augment the levels of this gaseous signalling molecule in cardiovascular disease. British Journal of Pharmacology (2008) 155, 617,619; doi:fn1; published online 22 September 2008 [source] Lactate kinetics in human tissues at rest and during exerciseACTA PHYSIOLOGICA, Issue 4 2010Gerrit Van Hall Abstract Lactate production in skeletal muscle has now been studied for nearly two centuries and still its production and functional role at rest and during exercise is much debated. In the early days skeletal muscle was mainly seen as the site of lactate production during contraction and lactate production associated with a lack of muscle oxygenation and fatigue. Later it was recognized that skeletal muscle not only played an important role in lactate production but also in lactate clearance and this led to a renewed interest, not the least from the Copenhagen School in the 1930s, in the metabolic role of lactate in skeletal muscle. With the introduction of lactate isotopes muscle lactate kinetics and oxidation could be studied and a simultaneous lactate uptake and release was observed, not only in muscle but also in other tissues. Therefore, this review will discuss in vivo human: (1) skeletal muscle lactate metabolism at rest and during exercise and suggestions are put forward to explain the simultaneous lactate uptake and release; and (2) lactate metabolism in the heart, liver, kidneys, brain, adipose tissue and lungs will be discussed and its potential importance in these tissues. [source] Orexins/hypocretins and orexin receptors in apoptosis: a mini-reviewACTA PHYSIOLOGICA, Issue 3 2010M. Laburthe Abstract An unexpected and fascinating aspect of the neuropeptides orexins has recently emerged when it was shown that orexins acting at orexin receptors OX1R or OX2R induce dramatic apoptosis resulting in massive reduction in cell growth in various cancer cell lines. This mini-review will provide the reader with recent findings related to the proapoptotic actions of orexins and the entirely novel mechanism whereby the seven membrane-spanning G-protein-coupled receptor (GPCR) OX1R triggers apoptosis. Recent data show that orexins induce tyrosine phosphorylation of the tyrosine-based motifs , immunoreceptor tyrosine-based inhibitory motif and immunoreceptor tyrosine-based switch motif , in OX1R. These phosphorylations result in the recruitment and activation of the phosphotyrosine phosphatase SHP-2 and subsequent cytochrome c -mediated mitochondrial apoptosis. Finally, this mini-review will also speculate on: (1) the potential importance of tyrosine-based motifs in the large family of GPCRs; (2) the interest of orexin receptors as therapeutic targets in cancer therapy; (3) the possible role of orexin receptor-mediated apoptosis in physiology and pathophysiology in the brain (neurodevelopment, neurodegenerative diseases) and in the periphery. [source] Elevated dominance of extrafloral nectary-bearing plants is associated with increased abundances of an invasive ant and reduced native ant richnessDIVERSITY AND DISTRIBUTIONS, Issue 5 2009Amy M. Savage Abstract Aim, Invasive ants can have substantial and detrimental effects on co-occurring community members, especially other ants. However, the ecological factors that promote both their population growth and their negative influences remain elusive. Opportunistic associations between invasive ants and extrafloral nectary (EFN)-bearing plants are common and may fuel population expansion and subsequent impacts of invasive ants on native communities. We examined three predictions of this hypothesis, compared ant assemblages between invaded and uninvaded sites and assessed the extent of this species in Samoa. Location, The Samoan Archipelago (six islands and 35 sites). Methods, We surveyed abundances of the invasive ant Anoplolepis gracilipes, other ant species and EFN-bearing plants. Results,Anoplolepis gracilipes was significantly more widely distributed in 2006 than in 1962, suggesting that the invasion of A. gracilipes in Samoa has progressed. Furthermore, (non- A. gracilipes) ant assemblages differed significantly between invaded and uninvaded sites. Anoplolepis gracilipes workers were found more frequently at nectaries than other plant parts, suggesting that nectar resources were important to this species. There was a strong, positive relationship between the dominance of EFN-bearing plants in the community and A. gracilipes abundance on plants, a relationship that co-occurring ants did not display. High abundances of A. gracilipes at sites dominated by EFN-bearing plants were associated with low species richness of native plant-visiting ant species. Anoplolepis gracilipes did not display any significant relationships with the diversity of other non-native ants. Main conclusions, Together, these data suggest that EFN-bearing plants may promote negative impacts of A. gracilipes on co-occurring ants across broad spatial scales. This study underscores the potential importance of positive interactions in the dynamics of species invasions. Furthermore, they suggest that conservation managers may benefit from explicit considerations of potential positive interactions in predicting the identities of problematic invaders or the outcomes of species invasions. [source] A review of relationships between interspecific competition and invasions in fruit flies (Diptera: Tephritidae)ECOLOGICAL ENTOMOLOGY, Issue 5 2004Pierre-Francois Duyck Abstract., 1. A number of invasions in the family Tephritidae (fruit flies) have been observed worldwide despite quarantine procedures. In this review, the potential importance of interspecific competition and competitive displacement among different tephritid species is evaluated in the context of recent invasions. 2. Where polyphagous tephritid species have been introduced in areas already occupied by a polyphagous tephritid, interspecific competition has resulted in a decrease in number and niche shift of the pre-established species. No reciprocal invasions have been observed. 3. The data on tephritid invasions seem to support a hierarchical mode of competition; however, complete exclusion usually did not occur. Indeed, tephritid distribution and abundance are markedly structured by various abiotic (mostly climatic) and biotic (host plants) factors. 4. The primary determinant of competitive interactions in near-optimal conditions, such as lowlands with abundant fruit plantations, is probably the life-history strategy. The r,K gradient could be used as a predictor of potential invaders, because K traits (such as large adult size) may favour both exploitation and interference competition. 5. For future research, a better understanding of competition mechanisms seems essential. Different species competing in the same area should be compared with respect to: (i) demographic parameters, (ii) the outcome of experimental co-infestations on the same fruit, and (iii) behavioural and chemical interference mechanisms. [source] Stoichiometric relations in an ant-treehopper mutualismECOLOGY LETTERS, Issue 11 2004Adam D. Kay Abstract Carbon : nitrogen : phosphorus (C : N : P) stoichiometry can underlie physiological and life history characteristics that shape ecological interactions. Despite its potential importance, there is much to learn about the causes and consequences of stoichiometric variation in terrestrial consumers. Here we show that treehoppers (Publilia modesta) tended by ants (Formica obscuripes) contained lower N concentrations than treehoppers on plants from which ants were excluded. Ant presence also affected nutrient concentrations in host plants: on plants with ants, leaves contained uniformly low concentrations of N; on plants without ants, N concentrations were low only in the few leaves fed upon by treehoppers at the time of collection. We suggest treehopper feeding reduces leaf nutrient levels and ants positively affect treehopper abundance, producing a top,down effect on plant quality. Determining the causes of these stoichiometric changes should help elucidate factors guiding the dynamics of conditional mutualisms between ants and homopterans. [source] The metacommunity concept: a framework for multi-scale community ecologyECOLOGY LETTERS, Issue 7 2004M. A. Leibold Abstract The metacommunity concept is an important way to think about linkages between different spatial scales in ecology. Here we review current understanding about this concept. We first investigate issues related to its definition as a set of local communities that are linked by dispersal of multiple potentially interacting species. We then identify four paradigms for metacommunities: the patch-dynamic view, the species-sorting view, the mass effects view and the neutral view, that each emphasizes different processes of potential importance in metacommunities. These have somewhat distinct intellectual histories and we discuss elements related to their potential future synthesis. We then use this framework to discuss why the concept is useful in modifying existing ecological thinking and illustrate this with a number of both theoretical and empirical examples. As ecologists strive to understand increasingly complex mechanisms and strive to work across multiple scales of spatio-temporal organization, concepts like the metacommunity can provide important insights that frequently contrast with those that would be obtained with more conventional approaches based on local communities alone. [source] Widespread occurrence of an intranuclear bacterial parasite in vent and seep bathymodiolin musselsENVIRONMENTAL MICROBIOLOGY, Issue 5 2009Frank U. Zielinski Summary Many parasitic bacteria live in the cytoplasm of multicellular animals, but only a few are known to regularly invade their nuclei. In this study, we describe the novel bacterial parasite "Candidatus Endonucleobacter bathymodioli" that invades the nuclei of deep-sea bathymodiolin mussels from hydrothermal vents and cold seeps. Bathymodiolin mussels are well known for their symbiotic associations with sulfur- and methane-oxidizing bacteria. In contrast, the parasitic bacteria of vent and seep animals have received little attention despite their potential importance for deep-sea ecosystems. We first discovered the intranuclear parasite "Ca. E. bathymodioli" in Bathymodiolus puteoserpentis from the Logatchev hydrothermal vent field on the Mid-Atlantic Ridge. Using primers and probes specific to "Ca. E. bathymodioli" we found this intranuclear parasite in at least six other bathymodiolin species from vents and seeps around the world. Fluorescence in situ hybridization and transmission electron microscopy analyses of the developmental cycle of "Ca. E. bathymodioli" showed that the infection of a nucleus begins with a single rod-shaped bacterium which grows to an unseptated filament of up to 20 ,m length and then divides repeatedly until the nucleus is filled with up to 80 000 bacteria. The greatly swollen nucleus destroys its host cell and the bacteria are released after the nuclear membrane bursts. Intriguingly, the only nuclei that were never infected by "Ca. E. bathymodioli" were those of the gill bacteriocytes. These cells contain the symbiotic sulfur- and methane-oxidizing bacteria, suggesting that the mussel symbionts can protect their host nuclei against the parasite. Phylogenetic analyses showed that the "Ca. E. bathymodioli" belongs to a monophyletic clade of Gammaproteobacteria associated with marine metazoans as diverse as sponges, corals, bivalves, gastropods, echinoderms, ascidians and fish. We hypothesize that many of the sequences from this clade originated from intranuclear bacteria, and that these are widespread in marine invertebrates. [source] Alcohol and mortality: methodological and analytical issues in aggregate analysesADDICTION, Issue 1s1 2001Thor Norström This supplement includes a collection of papers that aim at estimating the relationship between per capita alcohol consumption and various forms of mortality, including mortality from liver cirrhosis, accidents, suicide, homicide, ischaemic heart disease, and total mortality. The papers apply a uniform methodological protocol, and they are all based on time series data covering the post-war period in the present EU countries and Norway. In this paper we discuss various methodological and analytical issues that are common to these papers. We argue that analysis of time series data is the most feasible approach for assessing the aggregate health consequences of changes in population drinking. We further discuss how aggregate data may also be useful for judging the plausibility of individual-level relationships, particularly those prone to be confounded by selection effects. The aggregation of linear and curvilinear risk curves is treated as well as various methods for dealing with the time-lag problem. With regard to estimation techniques we find country specific analyses preferable to pooled cross-sectional/time series models since the latter incorporate the dubious element of geographical co-variation, and conceal potentially interesting variations in alcohol effects. The approach taken in the papers at hand is instead to pool the country specific results into three groups of countries that represent different drinking cultures; traditional wine countries of southern Europe, beer countries of central Europe and the British Isles and spirits countries of northern Europe. The findings of the papers reinforce the central tenet of the public health perspective that overall consumption is an important determinant of alcohol-related harm rates. However, there is a variation across country groups in alcohol effects, particularly those on violent deaths, that indicates the potential importance of drinking patterns. There is no support for the notion that increases in per capita consumption have any cardioprotective effects at the population level. [source] Research perspectives on alcohol craving: an overviewADDICTION, Issue 8s2 2000Cherry Lowman This overview of the Addiction supplement on 'Research Perspectives on Alcohol Craving' has three objectives. The first is to familiarize readers with the variety of theoretical models relevant to craving and the definitions of craving generated by them that are discussed in the supplement. These include phenomenological models, classical and operant conditioning models, the incentive-sensitization theory, a tonic-phasic model of dopamine system regulation, cognitive social learning theory and the cognitive processing theory of craving. The second objective is to provide a brief summary of the methodological articles which focus as a whole more on what can be done than on what has been done in alcohol craving research. The final objective is to emphasize the potential importance of transdisciplinary research-research that integrates components of different theoretical models-for delineating the role of alcohol and drug craving in the complex biobehavioral process known as addiction. It is the hope of the guest editors (the authors of this overview) that the Addiction supplement and this introduction to it will contribute to development of a framework for future transdisciplinary research on alcohol craving. [source] PERSPECTIVE: GENETIC ASSIMILATION AND A POSSIBLE EVOLUTIONARY PARADOX: CAN MACROEVOLUTION SOMETIMES BE SO FAST AS TO PASS US BY?EVOLUTION, Issue 7 2003Massimo Pigliucci Abstract., The idea of genetic assimilation, that environmentally induced phenotypes may become genetically fixed and no longer require the original environmental stimulus, has had varied success through time in evolutionary biology research. Proposed by Waddington in the 1940s, it became an area of active empirical research mostly thanks to the efforts of its inventor and his collaborators. It was then attacked as of minor importance during the "hardening" of the neo-Darwinian synthesis and was relegated to a secondary role for decades. Recently, several papers have appeared, mostly independently of each other, to explore the likelihood of genetic assimilation as a biological phenomenon and its potential importance to our understanding of evolution. In this article we briefly trace the history of the concept and then discuss theoretical models that have newly employed genetic assimilation in a variety of contexts. We propose a typical scenario of evolution of genetic assimilation via an intermediate stage of phenotypic plasticity and present potential examples of the same. We also discuss a conceptual map of current and future lines of research aimed at exploring the actual relevance of genetic assimilation for evolutionary biology. [source] Crystal structure of Fab198, an efficient protector of the acetylcholine receptor against myasthenogenic antibodiesFEBS JOURNAL, Issue 13 2001Konstantinos Poulas The crystal structure of the Fab fragment of the rat monoclonal antibody 198, with protective activity for the main immunogenic region of the human muscle acetylcholine receptor against the destructive action of myasthenic antibodies, has been determined and refined to 2.8 Å resolution by X-ray crystallographic methods. The mouse anti-lysozyme Fab D1.3 was used as a search model in molecular replacement with the amore software. The complementarity determining regions (CDR)-L2, CDR-H1 and CDR-H2 belong to canonical groups. Loops CDR-L3, CDR-H2 and CDR-H3, which seem to make a major contribution to binding, were analyzed and residues of potential importance for antigen-binding are examined. The antigen-binding site was found to be a long crescent-shaped crevice. The structure should serve as a model in the rational design of very high affinity humanized mutants of Fab198, appropriate for therapeutic approaches in the model autoimmune disease myasthenia gravis. [source] Breast cancer risk is not increased in individuals with TWIST1 mutation confirmed Saethre,Chotzen syndrome: An Australian multicenter studyGENES, CHROMOSOMES AND CANCER, Issue 7 2009Paul A. James Saethre-Chotzen syndrome (SCS) is a rare autosomal dominant syndrome involving craniosynostosis, craniofacial abnormalities, and syndactyly. A recent Scandinavian study reported an increased risk of breast cancer in individuals with a clinical diagnosis of SCS. Because of the potential importance of this finding, we organized a multicenter study enrolling people with TWIST1 mutation confirmed SCS to determine if an increased risk of cancer is present. This study did not identify any cases of breast or ovarian cancer in a cohort of equivalent power to that reported previously. These results provide clinical reassurance that at present there is no evidence for breast cancer screening above standard practice for individuals with SCS. © 2009 Wiley-Liss, Inc. [source] A variant of the myosin light chain kinase gene is associated with severe asthma in African AmericansGENETIC EPIDEMIOLOGY, Issue 4 2007Carlos Flores Abstract Asthma is a complex phenotype influenced by environmental and genetic factors for which severe irreversible structural airway alterations are more frequently observed in African Americans. In addition to a multitude of factors contributing to its pathobiology, increased amounts of myosin light chain kinase (MLCK), the central regulator of cellular contraction, have been found in airway smooth muscle from asthmatics. The gene encoding MLCK (MYLK) is located in 3q21.1, a region noted by a number of genome-wide studies to show linkage with asthma and asthma-related phenotypes. We studied 17 MYLK genetic variants in European and African Americans with asthma and severe asthma and identified a single non-synonymous polymorphism (Pro147Ser) that was almost entirely restricted to African populations and which was associated with severe asthma in African Americans. These results remained highly significant after adjusting for proportions of ancestry estimated using 30 unlinked microsatellites (adjusted odds ratio: 1.76 [95% confidence interval, CI: 1.17,2.65], p = 0.005). Since all common HapMap polymorphisms in ,500,kb contiguous regions have low-to-moderate linkage disequilibrium with Pro147Ser, we speculate that this polymorphism is causally related to the severe asthma phenotype in African Americans. The association of this polymorphism, located in the N-terminal region of the non-muscle MLCK isoform, emphasizes the potential importance of the vascular endothelium, a tissue in which MLCK is centrally involved in multiple aspects of the inflammatory response, in the pathogenesis of severe asthma. This finding also offers a possible genetic explanation for some of the more severe asthma phenotype observed in African American asthmatics. Genet Epidemiol 2007. © 2007 Wiley-Liss, Inc. [source] Contrasting effects of repeated summer drought on soil carbon efflux in hydric and mesic heathland soilsGLOBAL CHANGE BIOLOGY, Issue 10 2008ALWYN SOWERBY Abstract Current predictions of climate change include altered rainfall patterns throughout Europe, continental USA and areas such as the Amazon. The effect of this on soil carbon efflux remains unclear although several modelling studies have highlighted the potential importance of drought for carbon storage. To test the importance of drought, and more importantly repeated drought year-on-year, we used automated retractable curtains to exclude rain and produce repeated summer drought in three heathlands at varying moisture conditions. This included a hydric system limited by water-excess (in the UK) and two mesic systems with seasonal water limitation in Denmark (DK) and the Netherlands (NL). The experimental rainfall reductions were set to reflect single year droughts observed in the last decade with exclusion of rain for 2,3 months of the year resulting in a 20,26% reduction in annual rainfall and 23,38% reduction in mean soil moisture during the drought period. Unexpectedly, sustained reduction in soil moisture over winter (between drought periods) was also observed at all three sites, along with a reduction in the maximum water-holding capacity attained. Three hypotheses are discussed which may have contributed to this lack of recovery in soil moisture: hydrophobicity of soil organic matter, increased water use by plants and increased cracking of the soil. The responses of soil respiration to this change in soil moisture varied among the sites: decreased rates were observed at the water-limited NL and DK sites whilst they increased at the UK site. Reduced sensitivity of soil respiration to soil temperature was observed at soil moisture contents above 55% at the UK site and below 20% and 13% at the NL and DK sites, respectively. Soil respiration rates recovered to predrought levels in the NL and DK sites during the winter re-wetting period that indicates any change in soil C storage due to changes in soil C efflux may be short lived in these mesic systems. In contrast, in the hydric UK site after 2 years of drought treatment, the persistent reduction in soil moisture throughout the year resulted in a year-round increase in soil respiration flux, a response that accelerated over time to 40% above control levels. These findings suggest that carbon-rich soils with high organic matter content may act as a significant source of CO2 to the atmosphere following repeated summer drought. Nonrecovery of soil moisture and a persistent increase in soil respiration may be the primary mechanism underlying the reported substantial losses of soil carbon from UK organic soils over the last 20 years. These findings indicate that the water status of an ecosystem will be a critical factor to consider in determining the impact of drought on the soil carbon fluxes and storage. [source] Spatial planning, mobilities and culture,Chinese and New Zealand student preferences for Californian travelINTERNATIONAL JOURNAL OF TOURISM RESEARCH, Issue 3 2007Chris Ryan Abstract Itineraries are under-researched within tourism, which is arguably strange given their potential importance as determinants of visitor expenditure distribution, and how itinerary planning may become a tool of destination management in determining which areas are most affected by visitor flows, whether positively or negatively. This exploratory study required students in New Zealand and the Peoples' Republic of China to draw maps of potential trips to the south-west of the USA in order to assess to what degree differences might exist as to (i) preferred places to visit; (ii) durations of stay; (iii) speeds of dispersion and concentration at the points of embarkation and disembarkation (in this instance Los Angeles); and (iv) total distances travelled. Differences were indeed found, and ethnicity appeared to be the main explanatory variable for the differences. Chinese students were found to travel slightly less, not to become so dispersed overall, but were also found to have higher rates of dispersion and slower rates of concentration at the commencement and at the end of the trip. The itineraries also suggest a further triangular pattern of travel that can be added to the categories identified by Oppermann. Copyright © 2007 John Wiley & Sons, Ltd. [source] Technical Barriers to Trade in the European Union: Importance for Accession CountriesJCMS: JOURNAL OF COMMON MARKET STUDIES, Issue 2 2001Paul Brenton With trade in industrial products between the EU and the countries of central and eastern Europe (CEECs) now essentially free of tariff and non-tariff restrictions, the principal impact of accession to the EU on trade flows will be through access to the single market of the EU. A key element of this will be the removal of technical barriers to trade. In this article we try to highlight the potential importance of technical barriers to trade between the EU and the various CEECs, distinguishing between sectors according to the different approaches to the removal of these barriers in the EU: mutual recognition, detailed harmonization (old approach) and minimum requirements (new approach). We use two sources of information on technical regulations: a sectoral classification from a previous study of the impact of the single market and our own detailed translation of EU product-related directives into the relevant tariff codes. The analysis suggests that the importance of technical barriers varies considerably across the CEECs. The adjustment implications of access to the single market are likely to be greatest for those most advanced in their accession negotiations. [source] Is nurse,patient agreement of importance to cancer nurses' satisfaction with care?JOURNAL OF ADVANCED NURSING, Issue 3 2010Gunilla Mårtensson mårtensson g., carlsson m. & lampic c. (2010) Is nurse,patient agreement of importance to cancer nurses' satisfaction with care? Journal of Advanced Nursing66(3), 573,582. Abstract Aim., This paper is a report of a study of situational (nurse,patient agreement), personal and occupational factors of potential importance to oncology nurses' satisfaction with care provided and general work satisfaction. Background., Nurses have a general tendency to attribute to patients with cancer more problems and suffering than patients themselves report. However, little is known about whether dis/agreement between oncology nurses and patients with cancer concerning perceptions of patients' situation is of importance to nurses' satisfaction with their work. Methods., The study had a comparative and prospective design. Data were collected in 2005 using self-administrated questionnaires with 81 consecutively recruited nurse,patient pairs. Data were analysed with non-parametric tests (for comparison between subgroups) and with multiple regression analyses (for identifying predictors). Results., Initial nurse,patient agreement concerning patients' emotional distress, coping resources and quality of life did not appear to be important to nurses' subsequent satisfaction with the care directed at a specific patient. However, higher satisfaction with care provided as well as general work satisfaction was reported by nurses with more experience of cancer care and with a lower workload. Conclusion., To improve oncology nurses' opportunities to provide high quality cancer care, novice nurses and advanced beginners in particular should receive support and nurses' working conditions must be improved. Further research is needed to examine whether there are other aspects of the nurse,patient relationship that contribute to oncology nurses' satisfaction with the care provided to specific patients. [source] Ecosystem functioning in stream assemblages from different regions: contrasting responses to variation in detritivore richness, evenness and densityJOURNAL OF ANIMAL ECOLOGY, Issue 3 2008B. G. McKie Summary 1The diversity of species traits in a biological assemblage varies not only with species richness, but also with species evenness and organism density, which together influence the concentration of traits within functional guilds. Potential trait diversity at local scales is also constrained by the regional species pool. Implications of such variation for spatio-temporal variability in biodiversity,ecosystem functioning relationships are likely to be complex, but are poorly understood. 2In microcosm experiments conducted at laboratories in Sweden, Ireland and Romania, we investigated effects of species richness, evenness and density of stream-living detritivores on two related processes: detritivore leaf-processing efficiency (LPE) and growth. Assemblage composition varied among laboratories: one taxonomic order (Plecoptera) was studied in Sweden, whereas two orders, encompassing wider trait variation, were studied in Romania (Trichoptera and Plecoptera) and Ireland (Trichoptera and Isopoda). 3Relationships between density and both LPE and growth ranged from negative to positive across the study species, highlighting the potential for density-dependent variation in process rates to alter ecosystem functioning, but indicating that such effects depend on species identity. 4LPE varied with species diversity in the two more heterogeneous assemblages, but whereas LPE in the Romanian study was generally enhanced as richness increased, LPE in the Irish study increased only in less-even polycultures dominated by particular species. Transgressive overyielding was detected in the Irish experiment, indicating complementary resource use and/or facilitation (complementarity). These mechanisms could not be distinguished from the selection effect in the Romanian study. 5Growth was elevated in Romanian species mixtures, reflecting positive complementarity, but lower than expected growth in some Swedish mixtures was associated with negative complementarity, indicating interspecific interference competition. 6Our results emphasize the potential importance of detritivore diversity for stream ecosystem functioning, but both the effects of diversity on the studied processes, and the mechanisms underlying those effects, were specific to each assemblage and process. Such variability highlights challenges in generalizing impacts of diversity change for functional integrity in streams and other ecosystems in which the occurrence of important species traits fluctuates over relatively small spatio-temporal scales. [source] Predicting abundance from occupancy: a test for an aggregated insect assemblageJOURNAL OF ANIMAL ECOLOGY, Issue 3 2003M. Warren Summary 1The ubiquitous, positive abundance-occupancy relationship is of potential value to conservation and pest management because of the possibility of using it to predict species abundance from occupancy measures. 2He & Gaston (2000a) developed a model, and a parameterization method, for the prediction of abundance from occupancy based on the negative binomial distribution. There are to date few empirical tests of either the estimation method or model. Here we conduct such a test in a field-based mesocosm experiment using a Drosophilidae assemblage associated with decaying fruit. 3With individual (and groups of) fruit as minimum mapping units, abundance estimates derived using the parameterization method of the He-Gaston model differed significantly from measured values, and were least accurate for the most abundant species. 4Substitution of k -values corrected for species density in the model did not improve abundance predictions significantly. However, substitution of k -values calculated directly from the negative binomial distribution yielded highly accurate abundance predictions. 5Although the distribution of fly species did not deviate significantly from the negative binomial distribution, and the finest possible minimum mapping units were used (individual fruit), the parameterization method in the He-Gaston model consistently underestimated the abundance of species in the assemblage because individuals were very highly aggregated within fruit. 6Because of its potential importance, this model and parameterization method require further exploration at fine scales, commonly represented by individual habitat units, for highly aggregated species. The incorporation of spatially explicit information may provide a means of improving abundance predictions in this regard. [source] Development of inland lakes as hubs in an invasion networkJOURNAL OF APPLIED ECOLOGY, Issue 1 2005JIM R. MUIRHEAD Summary 1The ability to predict spatially explicit dispersal by non-indigenous species is a difficult but increasingly important undertaking as it allows management efforts to be focused around areas identified as susceptible to invasion. Lakes may serve as useful models for these studies because the habitats are well defined, and vectors of spread may be readily identified and quantified. In this study, we examined patterns of spread of the non-indigenous spiny waterflea Bythotrephes longimanus to inland lakes in Ontario, Canada, to identify lakes for which management efforts to reduce traffic would be most effective. 2We surveyed people using lakes for recreational purposes to quantify movements of trailered boats and other risky activities, to model relative vector traffic from invaded lakes to non-invaded and other invaded lakes. Non-linear functions were developed to describe the cumulative number of invaded and non-invaded destination lakes visited by people leaving five important lakes already invaded by the spiny waterflea (Huron, Simcoe, Muskoka, Panache and Kashagawigamog). The relative difference in these functions was used to identify which lakes will develop into future invasion hubs and will therefore be most important to future dispersal of the species. 3In the recent past, Lake Muskoka has been an important hub from which the spiny waterflea has invaded other lakes. It is unlikely to continue to be a source for waterflea invasion as most outbound traffic is to previously invaded lakes. Conversely, most outbound traffic from Lakes Kashagawigamog and Simcoe is to non-invaded lakes and, therefore, these lakes are likely to develop into hubs in the future. 4Synthesis and applications. These data on zooplankton in lake systems and associated mechanisms of transport indicate patterns not only of intrinsic value to lake management, but also of potential importance in understanding invasions more generally. Frequency distributions of the number of outbound connections to both invaded and non-invaded destinations from invaded sources follow a power function, consistent with scale-free networks. These networks indicate that small proportions of sources function as hubs. Management efforts targeted to remove developing hubs from the invasion network, rather than equal effort applied to outbound vector traffic from all sources, may reduce the predicted rate of new invasions. [source] Employment of stressful conditions during culture production to enhance subsequent cold- and acid-tolerance of bifidobacteriaJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2003J.E. Maus Abstract Aims: This study examined whether exposure of early stationary phase Bifidobacterium longum and B. lactis cells to various combinations of reduced temperature, reduced pH and starvation would enhance the cells' subsequent cold- and/or acid-tolerance. Methods and Results: Survival of B. longum in growth medium at 6°C significantly (P < 0·05) increased as a result of starving cells for 30 or 60 min without any simultaneous decrease in temperature or pH. Acid-tolerance of B. lactis (at pH 3·5 in synthetic gastric fluid) increased significantly when the growth medium pH was decreased from 6·0 to 5·2 and cells experienced 30 or 60 min of starvation. Enhanced B. lactis acid-tolerance persisted through 8,11 weeks of ,80°C storage in the pH 5·2 growth medium. Upon addition to milk during yogurt manufacture, these cells initially had enhanced acid-tolerance relative to untreated cells but untreated cells became equally acid-tolerant during the first 2·5 h of yogurt manufacture. Conclusions: The cold- and acid-tolerance of bifidobacteria vary widely, but may be significantly increased by application of sub-lethal stress to early stationary phase cells during culture production. Significance and Impact of the Study: The enhancement of B. lactis acid-tolerance observed in this study may be of potential importance in the production of effective ready-to-consume probiotic dietary supplements. [source] Gap junctional communication in human osteoclasts in vitro and in vivoJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 6a 2008A. F. Schilling Abstract Bone-forming cells are known to be coupled by gap junctions, formed primarily by connexin43 (Cx43). The role of Cx43 in osteoclasts has so far only been studied in rodents, where Cx43 is important for fusion of mononuclear precursors to osteoclasts. Given the potential importance for human diseases with pathologically altered osteoclasts, we asked whether a similar influence of Cx43 can also be observed in osteoclasts of human origin. For this purpose, Cx43 mRNA expression was studied in a time course experiment of human osteoclast differentiation by RT-PCR. Localization of Cx43 in these cells was determined by immunohistochemistry and confocal microscopy. For the assessment of the effect of gap junction inhibition on cell fusion, gap junctions were blocked with heptanol during differentiation of the cells and the cells were then evaluated for multinuclearity. Paraffin sections of healthy bone and bone from patients with Paget's disease and giant cell tumour of the bone were used to study Cx43 expression in vivo. We found mRNA and protein expression of Cx43 in fully differentiated osteoclasts as well as in precursor cells. This expression decreased in the course of differentiation. Consistently, we found a lower expression of Cx43 in osteoclasts than in bone marrow precursor cells in the histology of healthy human bone. Blockade of gap junctional communication by heptanol led to a dose-dependent decrease in multinuclearity, suggesting that gap junctional communication precedes cell fusion of human osteoclasts. Indeed, we found a particularly strong expression of Cx43 in the giant osteoclasts of patients with Paget's disease and giant cell tumour of the bone. These results show that gap junctional communication is important for fusion of human mononuclear precursor cells to osteoclasts and that gap junctional Cx43 might play a role in the regulation of size and multinuclearity of human osteoclasts in vivo. [source] Deterring illegal downloading: the effects of threat appeals, past behavior, subjective norms, and attributions of harm,JOURNAL OF CONSUMER BEHAVIOUR, Issue 2-3 2007Aron M. Levin The study employs two experiments to examine the effectiveness of various strategies used to dissuade consumers from downloading music illegally. The research investigates two specific strategies that the recording industry has used: (1) fear or threat appeals (e.g., the threat of punishment, such as fines and/or jail time), and (2) attribution of harm (informing consumers of the harm caused by the illegal downloading of music, such as financial loss to either the artist or the recording company). The study also considers whether past illegal downloading behavior reduces the effectiveness of these disincentive strategies. Finally, the impact of subjective norms (i.e., whether subjects think their friends would approve of downloading music) was also investigated. A 3 (level of threat: low, moderate, or high) X 2 (who is harmed by illegal downloading: artist or recording company) experimental design was employed for study one. Undergraduate students (n,=,388) participated in the study. Study two expanded on the design of the first study by adding a variable of subjective norms and by including previous downloading behavior in the model. Undergraduate students (n,=,211) also participated in the second experiment. Findings indicate a significant effect of threat appeal such that stronger threat appeals were found to be more effective than weaker threat appeals in reducing illegal downloading. The first study also showed that prior illegal downloading behavior does not curtail the effects of threat appeals aimed at reducing illegal downloading. In addition, results reveal no differences in downloading behavior in terms of attribution of harm deterrent strategy (harm to either the recording artist or company). The most interesting finding from the second study is that subjective norms appear to equalize low versus high past downloaders, but only under conditions of weak fear. The current manuscript is the first to examine the impact of four different variables (threat appeals, attribution of harm, subjective norms, and previous downloading behavior) on subjects' likelihood to illegally download music in the future. In particular, this research illuminates the potential importance of social norms in discouraging a type of undesirable consumer behavior but shows that this occurs only under a restricted set of conditions: when threat is low and the consumer is not a habitually high downloader. It should be of interest to those in fields where intellectual property can be pirated on the Internet. Copyright © 2007 John Wiley & Sons, Ltd. [source] Temporal dynamics of genotypic diversity reveal strong clonal selection in the aphid Myzus persicaeJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 1 2006C. VORBURGER Abstract Parthenogenetic organisms often harbour substantial genotypic diversity. This diversity may be the result of recurrent formations of new clones, or it may be maintained by environmental heterogeneity acting on ecological differences among clones. In aphids, both processes may be important because obligate and cyclical parthenogens can form mixed populations. Using microsatellites, I analysed the temporal dynamics of clonal diversity in such a population of the aphid Myzus persicae over a 1-year period. The frequency distribution of clonal genotypes was very skewed, with many rare and few common clones. The relative frequencies of common clones underwent strong and rapid changes indicative of intense clonal selection. Differences in their host associations suggest that these shifts may partly be caused by changes in the abundance of annual host plants. Other selective factors of potential importance are also discussed. New, sexually produced genotypes made a minor contribution to clonal diversity, consistent with the observed heterozygote excess characteristic of predominantly asexual populations in M. persicae. [source] Laboratory evaluation of two bioenergetics models applied to yellow perch: identification of a major source of systematic errorJOURNAL OF FISH BIOLOGY, Issue 2 2003P. G. Bajer Laboratory growth and food consumption data for two size classes of age 2 year yellow perch Perca flavescens, each fed on two distinct feeding schedules at 21° C, were used to evaluate the abilities of the Wisconsin (WI) and Karas,Thoresson (KT) bioenergetics models to predict fish growth and cumulative consumption. Neither model exhibited consistently better performance for predicting fish body masses across all four fish size and feeding regime combinations. Results indicated deficiencies in estimates of resting routine metabolism by both models. Both the WI and KT models exhibited errors for predicting growth rates, which were strongly correlated with food consumption rate. Consumption-dependent prediction errors may be common in bioenergetics models and are probably the result of deficiencies in parameter values or assumptions within the models for calculating energy costs of specific dynamic action, feeding activity metabolism or egestion and excretion. Inter-model differences in growth and consumption predictions were primarily the result of differences in egestion and excretion costs calculated by the two models. The results highlighted the potential importance of parameters describing egestion and excretion costs to the accuracy of bioenergetics model predictions, even though bioenergetics models are generally regarded as being insensitive to these parameters. The findings strongly emphasize the utility and necessity of performing laboratory evaluations of all bioenergetics models for assurance of model accuracy and for facilitation of model refinement. [source] Parenting stress in mothers of children with an intellectual disability: the effects of parental cognitions in relation to child characteristics and family supportJOURNAL OF INTELLECTUAL DISABILITY RESEARCH, Issue 6 2005R. Hassall Abstract Background Recent theories of stress and coping in parents of children with intellectual disabilities (ID) emphasize the importance of cognitive appraisals in influencing parents' levels of stress and their adaptations to difficulties presented by the children. This study investigated the relationships between parental cognitions, child characteristics, family support and parenting stress. The aspects of cognitions studied were: parenting self-esteem (including efficacy and satisfaction) and parental locus of control. Methods The group studied consisted of 46 mothers of children with ID. The Vineland Adaptive Behavior Scales and Maladaptive Behavior Domain were administered by interview. Mothers also completed four questionnaires: the Family Support Scale, the Parenting Sense of Competence Scale, a shortened form of the Parental Locus of Control Scale and the Parenting Stress Index (Short Form). Results Data were analysed using Pearson's correlation coefficients, partial correlations and a regression analysis. The results indicated that most of the variance in parenting stress was explained by parental locus of control, parenting satisfaction and child behaviour difficulties. Whilst there was also a strong correlation between family support and parenting stress, this was mediated by parental locus of control. Conclusions The results demonstrate the potential importance of parental cognitions in influencing parental stress levels. It is argued that these results have implications for clinical interventions for promoting parents' coping strategies in managing children with ID and behavioural difficulties. [source] Rho kinase activates ezrin-radixin-moesin (ERM) proteins and mediates their function in cortical neuron growth, morphology and motility in vitroJOURNAL OF NEUROSCIENCE RESEARCH, Issue 1 2007Matilda A. Haas Abstract The ezrin-radixin-moesin (ERM) family of proteins contribute to cytoskeletal processes underlying many vital cellular functions. Their previously elucidated roles in non-neuronal cells are an indication of their potential importance in CNS neurons. The specific mechanisms of their activation are unknown, but are likely to depend on factors such as the cell type and biological context. For ERM proteins to become active they must be phosphorylated at a specific C-terminal threonine residue. In non-neuronal cells, several kinases, including the Rho GTPase family member Rho kinase, have been identified as capable of phosphorylating the C-terminal threonine. In these experiments we have investigated specifically the potential role of Rho kinase mediated ERM activation in cortical neurons, utilizing a new pharmacologic inhibitor of Rho kinase and quantitative analysis of aspects of neuronal functions potentially mediated by ERM proteins. Rho kinase inhibition significantly suppressed aspects of neuronal development including neurite initiation and outgrowth, as well as growth cone morphology, with a concomitant loss of phosphorylated ERM immunolabeling in areas associated with neuronal growth. The ability of the Rho kinase inhibitor to decrease the amount of pERM protein was shown by immunoblotting. Post-injury responses were negatively affected by Rho kinase inhibition, namely by a significant decrease in the number of regenerative neurites. We investigated a novel role for ERM proteins in neuron migration using a post-injury motility assay, where Rho kinase inhibition resulted in significant and drastic reduction in neuron motility and phosphorylated ERM immunolabeling. Thus, Rho kinase is an important activator of ERMs in mediating specific neuronal functions. © 2006 Wiley-Liss, Inc. [source] Areca nut extracts-activated secretion of leukotriene B4, and phosphorylation of p38 mitogen-activated protein kinase and elevated intracellular calcium concentrations in human polymorphonuclear leukocytesJOURNAL OF PERIODONTAL RESEARCH, Issue 5 2007S.-L. Hung Background and Objective:, Polymorphonuclear leukocytes are the major source of leukotriene B4, which is synthesized via the 5-lipoxygenase pathway. Activation of the 5-lipoxygenase pathway is regulated by intracellular calcium and the phosphorylation of p38 mitogen-activated protein kinase (MAPK). The impact of areca nut extracts on the biosynthesis of leukotriene B4 by human polymorphonuclear leukocytes was evaluated, and some of the possible mechanisms underlying the responses were examined. Material and Methods:, Polymorphonuclear leukocytes were treated with various concentrations of areca nut extracts. The concentrations of leukotriene B4 released into the supernatants were evaluated using enzyme immunoassay. The phosphorylation of p38 MAPK was monitored using immunoblotting, and the cytosolic calcium kinetics were assessed fluorometrically using Fura-2. Results:, Exposure of polymorphonuclear leukocytes to areca nut extracts led to a dose-dependent increase in the production of leukotriene B4, with levels peaking at 30 min and decreasing thereafter. Areca nut extracts enhanced the phosphorylation of p38 MAPK, an enzyme known to activate 5-lipoxygenase. Incubation with areca nut extracts also resulted in a rapid elevation of intracellular calcium concentrations in polymorphonuclear leukocytes. The induction of leukotriene B4 by areca nut extracts was suppressed with the p38 MAPK inhibitor, SB203580, or with the intracellular calcium chelator, BAPTA-AM. Conclusion:, The interaction of areca nut extracts with polymorphonuclear leukocytes activated the arachidonic acid metabolic cascade. Incubation of polymorphonuclear leukocytes with areca nut extracts resulted in the activation of intracellular events, such as phosphorylation of p38 MAPK and Ca2+ mobilization, involved in the release of pro-inflammatory lipid mediators. The results of this study emphasize the potential importance of polymorphonuclear leukocytes as a source of leukotriene B4, which may modulate the inflammatory response in areca chewers. [source] | |||||||||||||||||||||||||||||||||||||||||||