Phosphoproteomic analysis of platelet signalling cascades by flow cytometry

The activation of blood platelets is a critical haemostatic response that serves to prevent haemorrhage, but unregulated platelet activation is associated with arterial thrombosis. Endothelial-derived inhibitors prostacyclin (PGI₂) and nitric oxide (NO) activate protein kinase-mediated signalling cascades to regulate platelet function and prevent vascular thrombosis. These signalling cascades involve a number of complex protein phosphorylation reactions, which regulate different aspects of platelet function. Dissecting the signalling events that regulate platelet function could facilitate the development of novel antiplatelet agents. Intraplatelet protein phosphorylation is commonly measured by immunoblotting, which is not conducive to whole blood analysis and therefore may not provide an accurate representation of signalling events in a (patho)physiological context. Therefore, the major aim of this thesis was to develop methodologies that could examine platelet signalling events in a more physiological context. In particular, we wanted to develop methodologies that could evaluate the ability of PGI₂ to modulate blood platelet activity. Using whole blood flow cytometry, PGI₂ was found to inhibit platelet fibrinogen binding and P-selectin expression, two independent markers of platelet activation. The inhibition of platelet function by PGI₂ corresponded with increased phosphorylation of proteins known to be targeted by PGI₂-mediated signalling cascades including vasodilator-stimulated phosphoprotein (VASP). In the next series of experiments, we developed an assay to evaluate these signalling events in whole blood. This phosphoflow assay was sensitive enough to accurately and reproducibly detect subtle dose- and time-dependent changes in protein phosphorylation in whole blood that were consistent with immunoblotting protocols with washed platelets. The application of fluorescent barcoding protocols to this assay enabled the simultaneous staining and acquisition of 24-96 samples in a single analysis tube. To exploit the high-throughput nature of the method and demonstrate its value as a drug discovery platform, we screened a library of 70 prostaglandins for their ability to stimulate intraplatelet VASP phosphorylation. The screen revealed three previously uncharacterised molecules that stimulated cAMP formation, induced VASP phosphorylation, and inhibited platelet aggregation. Because whole blood samples could be processed after cold storage, the method could be performed on samples obtained at remote locations such as clinical sites. To this end, we showed that the method could be used to measure signalling events in patients with polycystic ovary syndrome (PCOS), an endocrine disorder associated with platelet dysfunction. We envisage that the method will be useful for basic scientists, clinicians, and pharmacologists seeking novel therapies

Why do participants initiate free recall of short lists of words with the first list item? Toward a general episodic memory explanation.

Participants who are presented with a short list of words for immediate free recall (IFR) show a strong tendency to initiate their recall with the 1st list item and then proceed in forward serial order. We report 2 experiments that examined whether this tendency was underpinned by a short-term memory store, of the type that is argued by some to underpin recency effects in IFR. In Experiment 1, we presented 3 groups of participants with lists of between 2 and 12 words for IFR, delayed free recall, and continuous-distractor free recall. The to-be-remembered words were simultaneously spoken and presented visually, and the distractor task involved silently solving a series of self-paced, visually presented mathematical equations (e.g., 3 + 2 + 4 = ?). The tendency to initiate recall at the start of short lists was greatest in IFR but was also present in the 2 other recall conditions. This finding was replicated in Experiment 2, where the to-be-remembered items were presented visually in silence and the participants spoke aloud their answers to computer-paced mathematical equations. Our results necessitate that a short-term buffer cannot be fully responsible for the tendency to initiate recall from the beginning of a short list; rather, they suggest that the tendency represents a general property of episodic memory that occurs across a range of time scales.This is the accepted manuscript. This article may not exactly replicate the final version published in the APA journal. It is not the copy of record. That's available from APA at http://psycnet.apa.org/journals/xlm/40/6/1551/

Channel Catfish Reproductive Traits in the Lower Platte River, Nebraska, USA

Reproductive traits including fecundity, egg diameter, and condition of freshwater fishes influence offspring survival and abundance and may provide insight regarding timing of reproduction (Winemiller and Rose 1992, Johnston and Leggett 2002). Fish size (i.e., length or weight) may influence the number of eggs produced by an individual female (i.e., fecundity; Michaletz 1998). Larger individuals may, thus, disproportionately contribute to year-classes through increased fecundity if egg and larval survival is similar or greater than those from smaller reproductive females (Gwinn et al. 2015). Likewise, maternal fish size may influence egg diameter and offspring survival, whereby larger egg diameters are associated with greater parental care and increased egg quality (Sargent et al. 1987). Variation in egg diameter within and between individuals in a population may also indicate phenotypic plasticity in reproductive timing. For instance, intra-individual variation in egg diameter may indicate protracted spawning behavior (Pope et al. 1996). Inter-individual variation in egg diameter may indicate differences in sexual maturity and provide insight regarding timing of spawning (Hamel et al. 2015). Understanding relationships between fish size and reproductive traits is important for managing exploited fish populations where relaxed fishing regulations stemming from inaccurate reproductive information may lead to unintended consequences, including over-fishing and reduced population sustainability (Gwinn et al. 2015, Barneche et al. 2018)

Channel Catfish Reproductive Traits in the Lower Platte River, Nebraska, USA

Reproductive traits including fecundity, egg diameter, and condition of freshwater fishes influence offspring survival and abundance and may provide insight regarding timing of reproduction (Winemiller and Rose 1992, Johnston and Leggett 2002). Fish size (i.e., length or weight) may influence the number of eggs produced by an individual female (i.e., fecundity; Michaletz 1998). Larger individuals may, thus, disproportionately contribute to year-classes through increased fecundity if egg and larval survival is similar or greater than those from smaller reproductive females (Gwinn et al. 2015). Likewise, maternal fish size may influence egg diameter and offspring survival, whereby larger egg diameters are associated with greater parental care and increased egg quality (Sargent et al. 1987). Variation in egg diameter within and between individuals in a population may also indicate phenotypic plasticity in reproductive timing. For instance, intra-individual variation in egg diameter may indicate protracted spawning behavior (Pope et al. 1996). Inter-individual variation in egg diameter may indicate differences in sexual maturity and provide insight regarding timing of spawning (Hamel et al. 2015). Understanding relationships between fish size and reproductive traits is important for managing exploited fish populations where relaxed fishing regulations stemming from inaccurate reproductive information may lead to unintended consequences, including over-fishing and reduced population sustainability (Gwinn et al. 2015, Barneche et al. 2018)

Dynamic modelling and visco-elastic parameter identification of a fibre-reinforced soft fluidic elastomer manipulator

A dynamic model of a soft fibre-reinforced fluidic elastomer is presented and experimentally verified, which can be used for model-based controller design. Due to the inherent visco-(hyper)elastic characteristics and nonlinear timedependent behaviour of soft fluidic elastomer robots, analytic dynamic modelling is challenging. The fibre reinforced noninflatable soft fluidic elastomer robot used in this paper can produce both planar and spatial movements. Dynamic equations are developed for both cases. Parameters, related to the viscoelastic behaviour of the robot during elongation and bending motion, are identified experimentally and incorporated into our model. The modified dynamic model is then validated in experiments comparing the time responses of the physical robot with the corresponding outputs of the simulation model. The results validate the accuracy of the proposed dynamic model

Hormesis depends upon the life-stage and duration of exposure: examples for a pesticide and a nanomaterial

Tests to assess toxic effects on the reproduction of adult C. elegans after 72 h exposure for two chemicals, (3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU)), also known as diuron, and silver nanoparticles (Ag NPs) indicated potential, although not significant hormesis. Follow up toxicity tests comparing the potential hormesis concentrations with controls at high replication confirmed that the stimulatory effect was repeatable and also statistically significant within the test. To understand the relevance of the hormesis effects for overall population fitness, full life-cycle toxicity tests were conducted for each chemical. When nematodes were exposed to DCMU over the full life-span, the hormesis effect for reproduction seen in short-term tests was no longer evident. Further at the putative hormesis concentrations, a negative effect of DCMU on time to maturation was also seen. For the Ag NPs, the EC50 for effects on reproduction in the life-cycle exposure was substantially lower than in the short-term test, the EC50s estimated by a three parameter log logistic model being 2.9 mg/L and 0.75 mg/L, respectively. This suggests that the level of toxicity for Ag NPs for C. elegans reproduction is dependant on the life stage exposed and possibly the duration of the exposure. Further, in the longer duration exposures, hormesis effects on reproduction seen in the short-term exposures were no longer apparent. Instead, all concentrations reduced both overall brood size and life-span. These results for both chemicals suggest that the hormesis observed for a single endpoint in short-term exposure may be the result of a temporary reallocation of resources between traits that are not sustained over the full life-time. Such reallocation is consistent with energy budget theories for organisms subject to toxic stres

Can the effects of temporal grouping explain the similarities and differences between free recall and serial recall?

Temporal grouping can provide a principled explanation for changes in the serial position curves and output orders that occur with increasing list length in immediate free recall (IFR) and immediate serial recall (ISR). To test these claims, we examined the effects of temporal grouping on the order of recall in IFR and ISR of lists of between one and 12 words. Consistent with prior research, there were significant effects of temporal grouping in the ISR task with mid-length lists using serial recall scoring, and no overall grouping advantage in the IFR task with longer list lengths using free recall scoring. In all conditions, there was a general tendency to initiate recall with either the first list item or with one of the last four items, and then to recall in a forward serial order. In the grouped IFR conditions, when participants started with one of the last four words, there were particularly heightened tendencies to initiate recall with the first item of the most recent group. Moreover, there was an increased degree of forward-ordered transitions within groups than across groups in IFR. These findings are broadly consistent with Farrell's model, in which lists of items in immediate memory are parsed into distinct groups and participants initiate recall with the first item of a chosen cluster, but also highlight shortcomings of that model. The data support the claim that grouping may offer an important element in the theoretical integration of IFR and ISR.This is the author's accepted manuscript and will be under embargo until the 21st of October 2015. The final publication is available at Springer via http://dx.doi.org/10.3758/s13421-014-0471-5

Aquatic habitat changes within the channelized and impounded Arkansas River, Arkansas, USA

River-wide changes in morphologic character following channelization and impoundment alter the occurrence and distribution of surface water and available habitats for aquatic organisms. Quantifying patterns of creation, redistribution or disappearance of habitats at river-wide and decadal spatiotemporal scales can promote understanding regarding trajectories of different habitat types following alteration and prospects of direct habitat enhancement projects within altered alluvial rivers. Newly available remote-sensing tools and databases may improve detection of river-wide changes in habitat through time. We used a combination of remote-sensing data and generalized linear models to assess changes in surface water coverage from 1984 to 2015 among aquatic habitats of 496 km of the Arkansas River within Arkansas, USA. Changes through time in surface area of permanent and episodically inundated areas — and thus the availability of aquatic habitat — were variable along the river. Overall, the river lost a total 2.1% of permanent and 12.1% of episodic water surface area. The general trend of loss of off-main-channel habitat and increased coverage of permanent water along main-channel habitats may indicate a long-term transition (i.e. ramp-type disturbance) within areas of the Arkansas River where backwaters are transitioning to terrestrial environments, and habitat heterogeneity in the main channel is decreasing. As such, a decadal-scale change of channel form and backwater habitats may be the dominant pattern with limited regeneration of diverse habitat types. Understanding changes to permanent and episodic water availability may aid predictions regarding ecological effects of channelization and impoundments, including both increases and decreases in riverine productivity, biotic diversity and population abundances through space and time. Water resource managers and biologists can use information regarding river-wide changes in habitat availability obtained through remote sensing data to direct river management practices, including dredging and side-channel construction, and to assess ecological responses to such changes