549 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
Prepartum monensin for the reduction of energy associated disease in postpartum dairy cows
No full textA total of 1317 Holstein cows from 45 farms in the Canadian provinces of Quebec, Prince Edward Island (PEI) and Ontario, Canada were enrolled in a randomized trial between 1998 and 1999 to further confirm the efficacy of a monensin controlled release capsule in preventing periparturient disease in lactating dairy cows. Cows were randomized on the farms to receive either a monensin controlled release capsule (CRC) 2 to 4 weeks before expected calving or to serve as negative controls. Health data were collected for 90 d postcalving and were analysed with logistic regression accounting for the intraherd correlation with generalized estimating equations. Monensin CRC significantly reduced the incidence of both clinical ketosis and abomasal displacement postcalving. There was a numerical but nonsignificant decrease in the incidence of retained placenta in cows receiving a monensin CRC. A pooled analysis of two separate but similar studies (conducted between 1995 and 1998) demonstrated a strengthened association between monensin CRC administration precalving and reduced periparturient disease. A 40% reduction in both abomasal displacement and clinical ketosis was observed with precalving administration of a monensin CRC. In addition, the larger dataset highlighted a trend for a 25% reduction in the incidence of retained placenta in monensin-treated cows. Improved energy metabolism as a result of monensin treatment is likely the mechanism for the reduction in incidence of all three of these diseases. Thus, the term energy associated disease was created to assess the combined impact of the precalving monensin treatment on the incidence of retained placenta, displaced abomasum, and clinical ketosis. The monensin controlled release capsule reduced the incidence of energy associated disease by 30%..RN: 17090-79-8; SC: 0A; 0V; 0D; 0I; ZA; VE; CA; BESource type: Electronic(1) http://upei-resolver.asin-risa.ca?sid=SP:CABI&id=pmid:&id=&issn=0022-0302&isbn=&volume=85&issue=2&spage=397&pages=397-405&date=2002&title=Journal%20of%20Dairy%20Science&atitle=Prepartum%20monensin%20for%20the%20reduction%20of%20energy%20associated%20disease%20in%20postpartum%20dairy%20cows.&aulast=Duffield&pid=%3Cauthor%3EDuffield%2c%20T%3bBagg%2c%20R%3bDesCoteaux%2c%20L%3bBouchard%2c%20E%3bBrodeur%2c%20M%3bDuTremblay%2c%20D%3bKeefe%2c%20G%3bLeBlanc%2c%20S%3bDick%2c%20P%3C%2Fauthor%3E%3CAN%3E20023055188%3C%2FAN%3E%3CDT%3EJournal%20article%3C%2FDT%3
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
Defining and diagnosing postpartum clinical endometritis and its impact on reproductive performance in dairy cows
No full textThe objectives of this study were to validate diagnostic criteria for clinical endometritis in postpartum dairy cows and to measure the impact of endometritis on reproductive performance. Data were collected from 1865 cows in 27 herds, including history of dystocia, twins, retained placenta, or metritis. All cows were examined once between 20 and 33 d in milk (DIM) including external inspection, vaginoscopy, and transrectal palpation of the cervix, uterus, and ovaries. All cows were followed for a minimum of 7 mo or until pregnancy or culling. Survival analysis was used to derive a case definition of endometritis based on factors associated with increased time to pregnancy. The significance of clinical findings depended on the interval postpartum when examination took place. The presence of purulent uterine discharge or cervical diameter > 7.5 cm after 20 DIM, or mucopurulent discharge after 26 DIM identified cows with clinical endometritis. Given vaginoscopy, no diagnostic criteria based on palpation of the uterus had predictive value for time to pregnancy. The prevalence of clinical endometritis was 16.9%. Vaginoscopy was required to identify 44% of these cases. Accounting for parity, herd, and ovarian status, cows with clinical endometritis between 20 and 33 DIM had a hazard ratio of 0.73 for pregnancy (took 27% longer to become pregnant), and were 1.7 times more likely to be culled for reproductive failure than cows without endometritis.LR: 20061115; PUBM: Print; JID: 2985126R; ppublishSource type: Electronic(1
- …
