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    ABSTRACT: To date, limited research has explicitly examined the antecedents of challenge and threat states proposed by the biopsychosocial model. Thus, the aim of the present study was to examine the influence of perceived required effort and support availability on demand/resource evaluations, challenge and threat states, and motor performance. A 2 (required effort; high, low) x 2 (support availability; available, not available) between-subjects design was used with one hundred and twenty participants randomly assigned to one of four experimental conditions. Participants received instructions designed to manipulate perceptions of required effort and support availability before demand/resource evaluations and cardiovascular responses were assessed. Participants then performed the novel motor task (laparoscopic surgery) while performance was recorded. Participants in the low perceived required effort condition evaluated the task as more of a challenge (i.e., resources outweighed demands), exhibited a cardiovascular response more indicative of a challenge state (i.e., higher cardiac output and lower total peripheral resistance), and performed the task better (i.e., quicker completion time) than those in the high perceived required effort condition. However, perceptions of support availability had no significant impact on participants’ demand/resource evaluations, cardiovascular responses, or performance. Furthermore, there was no significant interaction effect between perceptions of required effort and support availability. The findings suggest that interventions aimed at promoting a challenge state should include instructions that help individuals perceive that the task is not difficult and requires little physical and mental effort to perform effectively.
    International Journal of Psychophysiology. 01/2014;
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    ABSTRACT: This paper examines processes of chute channel formation in four tropical sand-bed meandering rivers; the Strickland and Ok Tedi in Papua New Guinea, the Beni in Bolivia, and the lower Paraguay on the Paraguay/Argentina border. Empirical planform analyses highlight an association between meander bend widening and chute initiation that is consistent with recent physics-based modelling work. GIS analyses indicate that bend widening may be driven by a variety of mechanisms, including scour and cutbank bench formation at sharply-curving bends, point bar erosion due to cutbank impingement against cohesive terrace material, rapid cutbank erosion at rapidly extending bends, and spontaneous mid-channel bar formation. Chute channel initiation is observed to be predominantly associated with two of these widening mechanisms; i) an imbalance between cutbank erosion and point bar deposition associated with rapid bend extension, and ii) bank erosion forced by spontaneous mid-channel bar development. The work extends previous empirical analyses, which highlighted the role of bend extension (elongation) in driving chute initiation, with the observation that the frequency of chute initiation increases once bend extension rates and/or widening ratios exceed a reach-scale threshold. A temporal pattern of increased chute initiation frequency on the Ok Tedi, in response to channel steepening and mid-channel bar development following the addition of mine tailings, mirrors the inter- and intra-reach spatial patterns of chute initiation frequency on the Paraguay, Strickland and Beni Rivers, where increased stream power and sediment load are associated with increased bend extension and chute initiation rates. The process of chute formation is shown to be rate-dependent, and the threshold values of bend extension and widening ratio for chute initiation are shown to scale with measures of river energy, reminiscent of slope–ratio thresholds in river avulsion. Furthermore, Delft3D simulations suggest that chute formation can exert negative feedback on shear stress and bank erosion in the adjacent mainstem bifurcate, such that the process of chute formation may also be rate-limiting. Chute formation is activated iteratively in space and time in response to changes in river energy (and sediment load), predominantly affecting sites of rapid channel elongation, and thereby mediating the river response.
    Sedimentary Geology. 01/2014; 301:93–106.
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    ABSTRACT: Together with carbon monoxide (CO), nitric oxide (̇NO) and hydrogen sulfide (H2S) form a group of physiologically important gaseous transmitters, sometimes referred to as the “gaseous triumvirate”. The three molecules share a wide range of physical and physiological properties: they are small gaseous molecules, able to freely penetrate cellular membranes; they are all produced endogenously in the body and they seem to exert similar biological functions. In the cardiovascular system, for example, they are all vasodilators, promote angiogenesis and protect tissues against damage (e.g. ischemia-reperfusion injury). In addition, they have complex roles in inflammation, with both pro- and anti-inflammatory effects reported. Researchers have focused their efforts in understanding and describing the roles of each of these molecules in different physiological systems, and in the past years attention has also been given to the gases interaction or “cross-talk”. This review will focus on the role of ̇NO and H2S in inflammation and will give an overview of the evidence collected so far suggesting the importance of their cross-talk in inflammatory processes.
    Nitric Oxide. 01/2014;
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    ABSTRACT: Candida albicans demonstrates three main growth morphologies: yeast, pseudohyphal and true hyphal forms. Cell separation is distinct in these morphological forms and the process of separation is closely linked to the completion of mitosis and cytokinesis. In Saccharomyces cerevisiae the small GTPase Tem1 is known to initiate the mitotic exit network, a signalling pathway involved in signalling the end of mitosis and initiating cytokinesis and cell separation. Here we have characterised the role of Tem1 in C. albicans, and demonstrate that it is essential for mitotic exit and cytokinesis, and that this essential function is signalled through the kinase Cdc15. Cells depleted of Tem1 displayed highly polarised growth but ultimately failed to both complete cytokinesis and re-enter the cell cycle following nuclear division. Consistent with its role in activating the mitotic exit network Tem1 localises to spindle pole bodies in a cell cycle-dependent manner. Ultimately, the mitotic exit network in C. albicans appears to co-ordinate the sequential processes of mitotic exit, cytokinesis and cell separation.
    Fungal Genetics and Biology 01/2014;
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    ABSTRACT: The ciliopathies are a group of related inherited diseases characterized by malformations in organ development. The diseases affect multiple organ systems, with kidney, skeleton, and brain malformations frequently observed. Research over the last decade has revealed that these diseases are due to defects in primary cilia, essential sensory organelles found on most cells in the human body. Here we discuss the genetic and cell biological basis of one of the most severe ciliopathies, Meckel-Gruber syndrome, and explain how primary cilia contribute to the development of the affected organ systems.
    Organogenesis 12/2013; 10(1).
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    ABSTRACT: The Arctic Ocean already experiences areas of low pH and high CO2, and it is expected to be most rapidly affected by future ocean acidification (OA). Copepods comprise the dominant Arctic zooplankton; hence, their responses to OA have important implications for Arctic ecosystems, yet there is little data on their current under-ice winter ecology on which to base future monitoring or make predictions about climate-induced change. Here, we report results from Arctic under-ice investigations of copepod natural distributions associated with late-winter carbonate chemistry environmental data and their response to manipulated pCO2 conditions (OA exposures). Our data reveal that species and life stage sensitivities to manipulated OA conditions were correlated with their vertical migration behavior and with their natural exposures to different pCO2 ranges. Vertically migrating adult Calanus spp. crossed a pCO2 range of >140 μatm daily and showed only minor responses to manipulated high CO2. Oithona similis, which remained in the surface waters and experienced a pCO2 range of <75 μatm, showed significantly reduced adult and nauplii survival in high CO2 experiments. These results support the relatively untested hypothesis that the natural range of pCO2 experienced by an organism determines its sensitivity to future OA and highlight that the globally important copepod species, Oithona spp., may be more sensitive to future high pCO2 conditions compared with the more widely studied larger copepods.
    Proceedings of the National Academy of Sciences 12/2013;
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    ABSTRACT: The indiscriminate disposal of plastic to the environment is of concern. Microscopic plastic litter (<5 mm diameter; 'microplastic') is increasing in abundance in the marine environment, originating from the fragmentation of plastic items and from industry and personal-care products [1]. On highly impacted beaches, microplastic concentrations (<1mm) can reach 3% by weight, presenting a global conservation issue [2]. Microplastics are a novel substrate for the adherence of hydrophobic contaminants [1], deposition of eggs [3], and colonization by unique bacterial assemblages [4]. Ingestion by indiscriminate deposit-feeders has been reported, yet physical impacts remain understudied [1]. Here, we show that deposit-feeding marine worms maintained in sediments spiked with microscopic unplasticised polyvinylchloride (UPVC) at concentrations overlapping those in the environment had significantly depleted energy reserves by up to 50% (Figure 1). Our results suggest that depleted energy reserves arise from a combination of reduced feeding activity, longer gut residence times of ingested material and inflammation.
    Current biology: CB 12/2013; 23(23):R1031-3.
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    ABSTRACT: Electroluminescent assays for epitopes on the Complement components C3dg, terminal complement complex (TCC) and factor B/Bb (fB/Bb) have been developed with capture and detection antibodies to produce detection limits C3dg=91±9ng/mL, TCC=3±0.1ng/mL and fB=55.7±0.1ng/mL. The assay performance was assessed against a series of zymosan and heat aggregated IgG (HAIgG) in vitro activations of complement using a calibrated activated complement serum (ACS) as calibration standard. The ACS standard was stable within 20% accuracy over a 6-month period with freeze-thaw cycles as required. Differential activation of the complement cascade was observed for TCC showing a pseudo-first order formation half-life of 3.5hrs after activation with zymosan. The C3dg activation fragment indicates a 10% total activation for both activation agents. The kinetic-epitope analysis for fB indicates the capture epitope is on the fB/Bb protein fragment which can then become covered by the formation of C3bBb or C3bBbP complexes during the time course of the cascade.
    Journal of immunological methods 11/2013;
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    ABSTRACT: The vas::egfp transgenic zebrafish (Danio rerio) could significantly enhance studies on the mechanisms by which environmental estrogens disrupt sexual differentiation since the developing gonad can be visualized during early life via fluorescence detection. However, there are methodological challenges regarding dissecting out the gonads in early-life-stage fish and transgene responses to estrogen exposure have not been tested. We exposed vas::egfp transgenic zebrafish and their wild-type siblings to the model estrogen 17α-ethinylestradiol (EE2 ) (0.62 and 3.33 ng/L measured concentrations) during sexual development (20 to 60 days post hatch) and used the egfp fluorescence to identify and dissect single gonads (at 40 days post hatch) to provide sufficient RNA for individual gene expression analyses, retaining the remaining gonad in the body cavity for histological analyses of sex and stage of development. Genotyping confirmed that all transgenic control fish were phenotypically egfp-positive (showed green fluorescence). Interestingly, however, in a few transgenic fish exposed to EE2 there was no phenotypic egfp signal, most notably for the 3.33 ng/L EE2 exposure, and we subsequently found gonadal vasa expression was reduced by this concentration of EE2 . Hepatic vitellogenin expression demonstrated that the vas::egfp and wild-type lines responded to estrogen with an equivalent sensitivity. We conclude that the vas::egfp zebrafish provides an enhanced and practical system for mechanistic studies on the effects of environmentally relevant concentrations of estrogens on gonad development. Environ Toxicol Chem © 2013 SETAC.
    Environmental Toxicology and Chemistry 11/2013;
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    ABSTRACT: Cold acclimation has been shown to be attenuated by the degradation of the INDUCER OF CBF EXPRESSION1 protein by the E3 ubiquitin ligase HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENES1 (HOS1). However, recent work has suggested that HOS1 may have a wider range of roles in plants than previously appreciated. Here, we show that hos1 mutants are affected in circadian clock function, exhibiting a long-period phenotype in a wide range of temperature and light environments. We demonstrate that hos1 mutants accumulate polyadenylated mRNA in the nucleus and that the circadian defect in hos1 is shared by multiple mutants with aberrant mRNA export, but not in a mutant attenuated in nucleo-cytoplasmic transport of microRNAs. As revealed by RNA sequencing, hos1 exhibits gross changes to the transcriptome with genes in multiple functional categories being affected. In addition, we show that hos1 and other previously described mutants with altered mRNA export affect cold signaling in a similar manner. Our data support a model in which altered mRNA export is important for the manifestation of hos1 circadian clock defects and suggest that HOS1 may indirectly affect cold signaling through disruption of the circadian clock.
    The Plant Cell 11/2013;
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