501 research outputs found
Zinc inhibits human CIC-1 muscle chloride channel by interacting with its common gating mechanism
No full textThe definitive version is available at www.blackwell-synergy.comTransition metals block the muscle Cl channel ClC-1, which belongs to a large family of double-barreled Cl channels and transporters. In the Torpedo Cl channel ClC-0, Zn2+ block is closely related to the common gating mechanism that opens and closes both pores of the channel simultaneously, and the mutation C212S, which locks the common gate open, also eliminates the block. In ClC-1, however, previous results suggested that Zn2+ block is independent of gating, and that the cysteine residues involved in Zn2+ binding are in different positions to those that confer Zn2+ sensitivity on ClC-0. In this work, we show that Zn2+ block of ClC-1 is faster at hyperpolarized potentials where the channel is more likely to be in the closed state. Mutation C277S, equivalent to C212S in ClC-0, which locks the common gate in ClC-1 open, virtually eliminates Zn2+ block. A mutation, V321A, which reduces open probability of the common gate, facilitated Zn2+ block. These results demonstrate that Zn2+ block is state dependent, acting on the common gate. The extent of the block, however, is not a simple function of the open probability of the common gate. The Q10 of 13 of the time course of Zn2+ block, which is significantly higher than the Q10 of common gating transitions in WT ClC-1, suggests that Zn2+ binds to a very high temperature-dependent low-probability closed substate of the common gate, which has not yet been characterized in this channel.Michael D. Duffield, Grigori Y. Rychkov, Allan H. Bretag and Michael L. Robert
Identification of unique release kinetics of serotonin from guinea-pig and human enterochromaffin cells
No full textThis is the accepted version of the following article: [Raghupathi, R., Duffield, M. D., Zelkas, L., Meedeniya, A., Brookes, S. J. H., Sia, T. C., Wattchow, D. A., Spencer, N. J. and Keating, D. J. (2013), Identification of unique release kinetics of serotonin from guinea-pig and human enterochromaffin cells. The Journal of Physiology, 591: 5959–5975. doi: 10.1113/jphysiol.2013.259796], which has been published in final form at [http://dx.doi.org/10.1113/jphysiol.2013.259796]. In addition, authors may also transmit, print and share copies with colleagues, provided that there is no systematic distribution of the submitted version, e.g. posting on a listserve, network or automated delivery
The Acquisition of Case in Spanish Pronominal Object Clitics in English-Speaking College-Level L2 Learners
No full textThe Second language acquisition (SLA) of Spanish pronominal object clitics (POCs) has been a topic of research with regards to clitic placement (Houston, 1997; Lee, 1987; LoCoco, 1987; VanPatten, 1984; and VanPatten & Houston 1998), acquiring specific dialectal norms (Geeslin, García-Amaya, Hasler-Barker, Henriksen, & Killam, 2010), and functional usage with datives (Zyzik, 2006). A thorough investigation of how second language (L2) learners acquire Spanish POCs in university-level Spanish classes in the United States including accusative POCs has not yet been carried out. This dissertation extends our knowledge of how these learners acquire Spanish POCs and how instruction impacts the acquisition process.
Zyzik (2006) suggested that L2 learners create a dative POC prototype based on Animacy instead of Case as native speakers do. The first study of this dissertation extends Zyzik’s work by investigating L2 learners’ processing and use of Spanish pronominal object clitics, including the accusative POCs. A total of 121 L2 learners completed sentence-completion and cloze tasks to investigate how Animacy and Case influenced the way they distinguished Spanish POCs. Results from mixed ANOVAs show that lower proficiency L2 learners base POC distinctions on Animacy. However, more advanced learners show indications of shifting toward a Case-based system.
A second study was conducted in order to test whether instruction was effective in preempting (Rutherford, 1989) an Animacy-based system. A second group of 115 L2 learners from different proficiency levels were divided into two groups (instructed and control). These participants completed similar tasks to the first study at three different times (pre-test, post-test, delayed post-test). Between the pre-test and post-test, learners in the instructed group received instruction on Spanish POCs. Results from mixed ANOVAs indicate that instruction was not more effective than exposure to Spanish POCs through the tasks performed. The finding that both participant groups showed evidence of the preemption of an Animacy-based system is taken as evidence that the tasks themselves effectively led learners to change their POC systems. An explanation of this phenomenon is that the tasks provided a type of computer-mediated processing instruction, forcing learners to process the POCs and notice additional possible contexts, effectuating the change
Huntingtin-associated protein 1 regulates exocytosis, vesicle docking, readily releasable pool size and fusion pore stability in mouse chromaffin cells
No full textArticle first published online: 17 FEB 2014Huntingtin-associated protein 1 (HAP1) was initially established as a neuronal binding partner of huntingtin, mutations in which underlie Huntington's disease. Subcellular localization and protein interaction data indicate that HAP1 may be important in vesicle trafficking and cell signalling. In this study, we establish that HAP1 is important in several steps of exocytosis in adrenal chromaffin cells. Using carbon-fibre amperometry, we measured single vesicle exocytosis in chromaffin cells obtained from HAP1(-/-) and HAP1(+/+) littermate mice. Numbers of Ca(2+)-dependent and Ca(2+)-independent full fusion events in HAP1(-/-) cells are significantly decreased compared with those in HAP1(+/+) cells. We observed no change in the frequency of 'kiss-and-run' fusion events or in Ca(2+) entry. Whereas release per full fusion event is unchanged in HAP1(-/-) cells, early fusion pore duration is prolonged, as indicated by the increased duration of pre-spike foot signals. Kiss-and-run events have a shorter duration, indicating opposing roles for HAP1 in the stabilization of the fusion pore during full fusion and transient fusion, respectively. We use electron microscopy to demonstrate a reduction in the number of vesicles docked at the plasma membrane of HAP1(-/-) cells, where membrane capacitance measurements reveal the readily releasable pool of vesicles to be reduced in size. Our study therefore illustrates that HAP1 regulates exocytosis by influencing the morphological docking of vesicles at the plasma membrane, the ability of vesicles to be released rapidly upon stimulation, and the early stages of fusion pore formation.Kimberly D. Mackenzie, Michael D. Duffield, Heshan Peiris, Lucy Phillips, Mark P. Zanin, Ee Hiok Teo, Xin-Fu Zhou and Damien J. Keatin
Living donor liver transplantation - adult donor outcomes: a systematic review
No full textPublished in Liver Transplantation Volume 12, Issue 1, 2006, pp. 24-30 at www.interscience.wiley.comThe objective of this study was to evaluate the safety and efficacy of adult-to-adult living donor liver transplantation, specifically donor outcomes. A systematic review, with searches of the literature up to January 2004, was undertaken. Two hundred and fourteen studies provided information on donor outcomes. The majority of these were case series studies, although there were also studies comparing living donor liver transplantation with deceased donor liver transplantation. Both underreporting and duplicate reporting is likely to have occurred, and so caution is required in interpretation of these results. Overall reported donor mortality was 12 to 13 in about 6,000 procedures (0.2%) (117 studies). Mortality for right lobe donors to adult recipients is estimated to be 2 to 8 out of 3,800 (0.23 to 0.5%). The donor morbidity rate ranged from 0% to 100% with a median of 16% (131 studies). Biliary complications and infections were the most commonly reported donor morbidities. Nearly all donors had returned to normal function by 3 to 6 months (18 studies). In conclusion, there are small, but real, risks for living liver donors. Due to the short history of adult-to-adult living donor liver transplantation, the long-term risks for donors are unknown.Philippa F. Middleton, Michael Duffield, Stephen V. Lynch, Robert T.A. Padbury, Tony House, Peter Stanton, Deborah Verran, Guy Madder
Huntingtin-associated protein-1 is a synapsin I-binding protein regulating synaptic vesicle exocytosis and synapsin I trafficking
No full textHuntingtin-associated protein-1 (HAP1) is involved in intracellular trafficking, vesicle transport, and membrane receptor endocytosis. However, despite such diverse functions, the role of HAP1 in the synaptic vesicle (SV) cycle in nerve terminals remains unclear. Here, we report that HAP1 functions in SV exocytosis, controls total SV turnover and the speed of vesicle fusion in nerve terminals and regulates glutamate release in cortical brain slices. We found that HAP1 interacts with synapsin I, an abundant neuronal phosphoprotein that associates with SVs during neurotransmitter release and regulates synaptic plasticity and neuronal development. The interaction between HAP1 with synapsin I was confirmed by reciprocal co-immunoprecipitation of the endogenous proteins. Furthermore, HAP1 co-localizes with synapsin I in cortical neurons as discrete puncta. Interestingly, we find that synapsin I localization is specifically altered in Hap1(-/-) cortical neurons without an effect on the localization of other SV proteins. This effect on synapsin I localization was not because of changes in the levels of synapsin I or its phosphorylation status in Hap1(-/-) brains. Furthermore, fluorescence recovery after photobleaching in transfected neurons expressing enhanced green fluorescent protein-synapsin Ia demonstrates that loss of HAP1 protein inhibits synapsin I transport. Thus, we demonstrate that HAP1 regulates SV exocytosis and may do so through binding to synapsin I. The Proposed mechanism of synapsin I transport mediated by HAP1 in neurons. HAP1 interacts with synapsin I, regulating the trafficking of synapsin I containing vesicles and/or transport packets, possibly through its engagement of microtubule motors. The absence of HAP1 reduces synapsin I transport and neuronal exocytosis. These findings provide insights into the processes of neuronal trafficking and synaptic signaling.Kimberly D. Mackenzie, Amanda L. Lumsden, Feng Guo, Michael D. Duffield, Timothy Chataway, Yoon Lim, Xin‐Fu Zhou, Damien J. Keatin
BIODIESEL AS A SUBSTITUTE FOR PETROLEUM DIESEL IN A STOCHASTIC ENVIRONMENT
No full textPolicy makers should consider price volatility effects when determining appropriate spending levels for alternative fuel programs.Resource /Energy Economics and Policy,
Geophysical characterization of hydrothermal systems and intrusive bodies, El Chichón volcano (Mexico)
No full text[1] The 1982 explosive eruptions of El Chichón volcano (Chiapas, Mexico) destroyed the inner dome and created a 1-km-wide and 180-m-deep crater within the somma crater. A shallow hydrothermal system was exposed to the surface of the new crater floor and is characterized by an acid crater lake, a geyser-like Cl-rich spring (soap pool), and numerous fumarole fields. Multiple geophysical surveys were performed to define the internal structure of the volcanic edifice and its hydrothermal system. We carried out a high-resolution ground-based geomagnetic survey in the 1982 crater and its surroundings and 38 very low frequency (VLF) transects around the crater lake. A 3-D inversion of the ground-based magnetic data set highlighted three high-susceptibility isosurfaces, interpreted as highly magnetized bodies beneath the 1982 crater floor. Inversion of a digitized regional aeromagnetic map highlighted four major deeply rooted cryptodomes, corresponding to major topographic highs and massive lava dome outcrops outside and on the somma rim. The intracrater magnetic bodies correspond closely to the active hydrothermal vents and their modeled maximum basal depth matches the elevation of the springs on the flanks of the volcano. Position, dip, and vertical extent of active and extinct hydrothermal vents identified by VLF-EM surveys match the magnetic data set. We interpret the shallow lake spring hydrothermal system to be mostly associated with buried remnants of the 550 BP dome, but the Cl-rich soap pool may be connected to a small intrusion emplaced at shallow depth during the 1982 eruption
How and where to restore habitat on farmland to increase the abundance and diversity of moths
No full textModern agriculture has severely impacted the variety of life on earth. Agricultural expansion has cleared > 50% of natural habitats on agriculturally usable land, while agricultural intensification has reduced the abundance and diversity of wildlife in farmed areas. Agri-environment schemes (AESs) offer opportunities to restore habitats for wildlife in farmed landscapes across Europe and elsewhere. This could help to (1) reverse declines in species of conservation concern and (2) provide “ecosystem services”, such as pollination, which contribute to human wellbeing. AES interventions have led to increases in the abundance and diversity of wildlife. However, despite the scale of public investment in AESs, the size and significance of those increases are often unclear. Furthermore, the outcomes of AES interventions vary depending on features of the surrounding landscape, especially semi-natural habitat. Research to date has directed the allocation of AES interventions in a broad sense, for example towards landscapes with < 20% coverage of semi-natural habitat. Still, there is a lack of specific advice about how and where to restore habitat on farmland to maximise benefits for priority insect species. I present ... (continues
Clinical utility of an observation and response chart with human factors design characteristics and a track and trigger system: Study protocol for a two-phase multisite multiple-methods design
No full text©Doug Elliott, Sharon McKinley, Lin Perry, Christine Duffield, Rick Iedema, Robyn Gallagher, Margaret Fry, Michael Roche, Emily Allen. Background: Clinical deterioration of adult patients in acute medical-surgical wards continues to occur, despite a range of systems and processes designed to minimize this risk. In Australia, a standardized template for adult observation charts using human factors design principles and decision-support characteristics was developed to improve the detection of and response to abnormal vital signs. Objective: To describe the study protocol for the clinical testing of these observation and response charts (ORCs). Methods: We propose a two-phase multisite multiple-methods design to test the initial clinical utility of the charts in 10 hospitals of differing types and sizes across state jurisdictions in Australia. Data collection in the first phase includes user surveys, observations and field notes by project officers, handover de-briefs (short interviews with small groups of staff), and an audit of ORC documentation completion compared to the site's existing observation chart. For the second phase, data will be collected using a retrospective audit of observation documentation from the previous hospital observation chart, prospective audit of observation documentation following implementation of the selected ORC, user focus groups, observational field notes, and patient outcome data from routinely collected organizational data sources. Results: Site selection and preparation, project officer training, chart selection and implementation, participant recruitment, and data collection has been completed and the analysis of these results are in progress. Conclusions: This detailed description of these study methods and data collection approaches will enable a comprehensive assessment of the clinical utility of these newly developed track and trigger charts and will be useful for clinicians and researchers when planning and implementing similar studies. Potential methodological limitations are also noted
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