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External Solution (external + solution)
Selected AbstractsCutting to cope , a modern adolescent phenomenonCHILD: CARE, HEALTH AND DEVELOPMENT, Issue 5 2010B. Hall Abstract Background The frequency of young people cutting themselves appears to be increasing, with one review estimating the current prevalence across the UK to be between 1 in 12 and 1 in 15. Aim To identify factors that are associated with self-harm by cutting, and more especially coping strategies that if encouraged might reduce such behaviour. Method Multivariate and exploratory factor analysis were used to analyse the results from a survey of the pupils attending four large comprehensive schools in the North of England where the frequency of cutting behaviour was causing concern. Results Three factors were identified from the analysis , Social & Active Coping, Seeking External Solutions and Non-Productive Coping. The Social & Active Coping was the only factor that significantly correlated with non-cutting behaviour. Conclusions The fostering of the elements that make up Social & Active Coping , namely working successfully and feeling a sense of achievement, together with positive friendship networks and positive diversions, including physical recreation, will help to minimize young people's sense of needing to cope by cutting themselves. [source] Cellular mechanisms of cobalt-induced hippocampal epileptiform dischargesEPILEPSIA, Issue 1 2009Jiwei He Summary Purpose:, To explore the cellular mechanisms of cobalt-induced epileptiform discharges in mouse hippocampal slices. Methods:, Hippocampal slices were prepared from adult mice and briefly exposed to a CoCl2 -containing external solution. Population and single cell activities were examined via extracellular and whole-cell patch recordings. Results:, Brief cobalt exposure induced spontaneous, ictal-like discharges originating from the CA3 area. These discharges were suppressed by anticonvulsants, gap junction blockers, or by raising extracellular Ca2+, but their generation was not associated with overall hyperexcitability or impairment in GABAergic inhibition in the CA3 circuit. Electroencephalographic ictal discharges of similar waveforms were observed in behaving rats following intrahippocampal cobalt infusion. Discussion:, Mechanisms involving activity-dependent facilitation of gap junctional communication may play a major role in cobalt-induced epileptiform discharges. [source] No evidence for calcium electrogenic exchanger in frog semicircular canal hair cellsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2002M. Martini Abstract We investigated the possibility that, in hair cells mechanically isolated from frog semicircular canals, Ca2+ extrusion occurs via a Na+ : Ca2+ (cardiac type) or a Na+ : Ca2+,K+ (retinal type) exchanger. Cells concurrently imaged during whole-cell patch-clamp recordings using the Ca2+ sensitive fluorescent dye Oregon Green 488 BAPTA-1 (100 µm) showed no voltage dependence of Ca2+ clearance dynamics following a Ca2+ load through voltage-gated Ca2+ channels. Reverse exchange was probed in hair cells dialyzed with a Ca2+ - and K+ -free solution, containing a Na+ concentration that saturates the exchanger, after zeroing the contribution to the whole-cell current from Ca2+ and K+ conductances. In these conditions, no reverse exchange current was detected upon switching from a Ca2+ -free external solution to a solution containing concentrations of Ca2+ alone, or Ca2+ + K+ that saturated the exchanger. By contrast, the same experimental protocol elicited peak exchange currents exceeding 100 pA in gecko rod photoreceptors, used as positive controls. In both cell types, we also probed the forward mode of the exchanger by rapidly increasing the intracellular Ca2+ concentration using flash photolysis of two novel caged Ca2+ complexes, calcium 2,2,-{[1-(2-nitrophenyl)ethane-1,2-diyl]bis(oxy)}bis(acetate) and calcium 2,2,-{[1-(4,5-dimethoxy-2-nitrophenyl)ethane-1,2-diyl]bis(oxy)} bis(acetate), in the presence of internal K+ and external Na+. No currents were evoked by UV-triggered Ca2+ jumps in hair cells, whereas exchanger conformational currents up to 400 pA, followed by saturating forward exchange currents up to 40 pA, were recorded in rod photoreceptors subjected to the same experimental conditions. We conclude that no functional electrogenic exchanger is present in this hair cell population, which leaves the abundant plasma membrane Ca2+ -ATPases as the primary contributors to Ca2+ extrusion. [source] Riluzole inhibits the persistent sodium current in mammalian CNS neuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2000Andrea Urbani Abstract The effects of 0.1,100 ,m riluzole, a neuroprotective agent with anticonvulsant properties, were studied on neurons from rat brain cortex. Patch-clamp whole-cell recordings in voltage-clamp mode were performed on thin slices to examine the effects of the drug on a noninactivating (persistent) Na+ current (INa,p). INa,p was selected because it enhances neuronal excitability near firing threshold, which makes it a potential target for anticonvulsant drugs. When added to the external solution, riluzole dose-dependently inhibited INa,p up to a complete blocking of the current (EC50 2 ,m), showing a significant effect at therapeutic drug concentrations. A comparative dose-effect study was carried out in the same cells for the other main known action of riluzole, the inhibitory effect on the fast transient sodium current. This effect was confirmed in our experiments, but we found that it was achieved at levels much higher than putative therapeutic concentrations. Only the effect on INa,p, and not that on fast sodium current, can account for the reduction in neuronal excitability observed in cortical neurons following riluzole treatment at therapeutic concentrations, and this might represent a novel mechanism accounting for the anticonvulsant and neuroprotective properties of riluzole. [source] Oxalate exudation into the root-tip water free space confers protection from aluminum toxicity and allows aluminum accumulation in the symplast in buckwheat (Fagopyrum esculentum)NEW PHYTOLOGIST, Issue 2 2010Benjamin Klug Summary ,A better understanding of aluminum (Al) uptake and transport is expected to contribute to unravel the apparent contradiction between Al exclusion and Al accumulation in buckwheat. ,We studied the effect of Al supply on the root-tip Al and oxalate concentrations of the apoplastic water free space fluid (WFSF) and the symplast as affected by temperature, oxalate supply and the anion-channel blocker phenylglyoxal (PG). ,Aluminum supply rapidly activated the release of oxalate to the WFSF to establish a 1 : 1 Al to oxalate ratio. In the symplast, the Al concentration was 100 times higher than in the external solution, and the Al to oxalate ratio was 1 : 2. Loading and unloading of Al, but not of oxalate, into and from the symplast were reduced at low temperature and are thus under metabolic control. Application of PG reduced the constitutive and the Al-enhanced WFSF oxalate concentrations and enhanced Al-induced root-growth inhibition. Unlike a 1 : 3 Al to oxalate ratio, a 1 : 1 ratio ameliorated only partly Al-induced root-growth inhibition without affecting root-tip Al contents or WFSF Al concentrations. ,We present a hypothesis with an Al oxalate (Ox)+ plasma-membrane transporter in the root cortex and a xylem-loading Al citrate (Cit)n, transporter in the xylem parenchyma cells as key elements of Al accumulation in buckwheat. [source] The properties of the Mn, Ni and Pb transport operating at plasma membranes of cucumber rootsPHYSIOLOGIA PLANTARUM, Issue 3 2007Magdalena Migocka To avoid metal toxicity, plants have developed mechanisms including efflux of metal ions from cells and their sequestration into cellular compartments. In this report, we present evidence for the role of plasma membrane efflux systems in metal tolerance of cucumber roots. We have identified the plasma membrane-transport system participating in Cd, Pb, Mn and Ni efflux from the cytosol. Kinetic characterization of this proton-coupled transport system revealed that it is saturable and has a different affinity for each of the metal ions used (with Km 5, 7.5 and 0.1 mM for Mn, Ni and Pb, respectively). Treatment of cucumber roots with 100 ,M Cd prior to the transport measurements caused a great increase (over 250%) in Cd antiport activity in plasmalemma vesicles. After decreasing the metal concentration to 50 ,M we still observed a large increase (over 150%) of this activity in comparison with the control. Moreover, the addition of 50 ,M Cd to the external solution stimulated not only Cd antiport in the plasmalemma vesicles but also the antiport of other metals used in the experiments. Treatment of cucumber roots with 50 ,M Ni revealed a similar effect: the antiport activity of Cd, Mn, Ni and Pb was stimulated, although to a lesser extent in comparison with stimulation by Cd. The data indicate that the root plasma membrane antiporter system is stimulated by the exogenous presence of heavy metals. [source] A diffusion approach to the electrolyte leakage from plant tissuesPHYSIOLOGIA PLANTARUM, Issue 1 2005Konstantina V. Kocheva The exchange of ions between plant tissues and the external solution in vitro exhibits prominent biphasic kinetics. This is generally ascribed to the different contribution of the two compartments , apoplast and symplast , involved in the process. In this regard, an electro-diffusion model of the leakage is proposed in the paper. On the basis of the balance of fluxes through the plasmalemma and the cell wall, a system of differential equations describing the ion concentration in the outer solution is found. For a wide range of the system's coefficients, its behaviour is well approximated by a previously obtained analytical function. The values of the function's parameters, derived from the fit with experimental data, correlate adequately with the water deficit conditions of the samples. Hence, these parameters may be used to characterize the physiological status of the investigated plants. [source] Glutamate-induced internalization of Cav1.3 L-type Ca2+ channels protects retinal neurons against excitotoxicityTHE JOURNAL OF PHYSIOLOGY, Issue 6 2010Fengxia Mizuno Glutamate-induced rise in the intracellular Ca2+ level is thought to be a major cause of excitotoxic cell death, but the mechanisms that control the Ca2+ overload are poorly understood. Using immunocytochemistry, electrophysiology and Ca2+ imaging, we show that activation of ionotropic glutamate receptors induces a selective internalization of Cav1.3 L-type Ca2+ channels in salamander retinal neurons. The effect of glutamate on Cav1.3 internalization was blocked in Ca2+ -free external solution, or by strong buffering of internal Ca2+ with BAPTA. Downregulation of L-type Ca2+ channel activity in retinal ganglion cells by glutamate was suppressed by inhibitors of dynamin-dependent endocytosis. Stabilization of F-actin by jasplakinolide significantly reduced the ability of glutamate to induce internalization suggesting it is mediated by Ca2+ -dependent reorganization of actin cytoskeleton. We showed that the Cav1.3 is the primary L-type Ca2+ channel contributing to kainate-induced excitotoxic death of amacrine and ganglion cells. Block of Cav1.3 internalization by either dynamin inhibition or F-actin stabilization increased vulnerability of retinal amacrine and ganglion cells to kainate-induced excitotoxicity. Our data show for the first time that Cav1.3 L-type Ca2+ channels are subject to rapid glutamate-induced internalization, which may serve as a negative feedback mechanism protecting retinal neurons against glutamate-induced excitotoxicity. [source] Pore-Forming Properties of Alamethicin F50/5 Inserted in a Biological MembraneCHEMISTRY & BIODIVERSITY, Issue 6 2007Natascia Vedovato Abstract The pore-forming properties of native and synthetic alamethicins were investigated in photoreceptor rod outer segments (OS) isolated from frog retina, and recorded in whole-cell configuration. The peptaibols were applied (and removed) to (from) the OS within less than 50,ms by means of a computer-controlled micro-perfusion system. Once blocked with light, the main OS endogenous conductance, the OS membrane resistance was >1,G,, allowing low-noise and high-resolution recordings. Currents of ca. 700,pA were recorded in symmetric K+ (100,mM) and Ca2+ (1,mM), upon applying 1,,M of alamethicin F50/5 or its [L -Glu(OMe)7,18,19] analogue to the OS membrane (clamped at ,20,mV). In the latter peptide, the Gln residues at positions 7, 18, and 19 were substituted with side-chain esterified Glu residues. For both peptides, the current activated exponentially, with a delay from peptide application, and exponentially returned to zero without any delay, upon removing the peptide from the external solution. The delay as well as the activation (,a) and deactivation (,d) time constants of the current produced by the modified alamethicin were much slower, and the current noise was much larger, with respect to the corresponding values for alamethicin F50/5. Therefore, the above three Gln residues are not a key factor for pore formation, but the [L -Glu(OMe)7,18,19] analogue produces larger pores with a lower probability of formation. [source] Characterization and biodegradability of amphoteric superabsorbent polymersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Dan Wang Abstract Novel amphoteric superabsorbent polymers (SAPs) based on carboxymethyl cellulose, acrylic acid, acrylamide, and [2-(methylacryloyloxy)ethyl]trimethylammonium chloride were prepared by inverse suspension copolymerization. The SAPs were characterized by Fourier transforms infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. The absorbency or swelling behaviors in deionized water, saline solutions, and pH value solutions were investigated. Experimental results indicate that the absorbency in various solutions decreases with an increase of the ion concentration, which was attributed to osmotic pressure of water and ions between the polymeric gel and the external solutions. Biodegradability of the amphoteric SAPs was also reported. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Skills under threat: the case of HIV/AIDS in the mining industry in ZimbabweJOURNAL OF INTERNATIONAL DEVELOPMENT, Issue 5 2006Caroline N. Matangi Abstract The Zimbabwe mining industry is currently battling to arrest further spread of the HIV/AIDS crisis in workplaces, especially its impact on labour productivity. Labour in the closed community of mines has been greatly susceptible to HIV/AIDS infection. The current AIDS incidence in the mine sites is estimated at a weighted average of 15,per,cent amongst miners, with the largest category of workers,the 30,39 years age group,also constituting the worst affected category. Given the current state of the country's economy and consequently its adverse impact on the lifestyle of miners, the pandemic is expected to increase. This paper builds on the work of the ILO (1995) involving a survey of 18 various firms/institutions. The survey was carried out in Zambia in order to assess the impact of HIV/AIDS on the productive labour force. The survey revealed that many of the firms are experiencing irregular work attendance, ,wasted' training as some of the trained workers are constantly ill or die, high medical bills, funeral costs and reduced productivity and profits. An analysis of data on the main causes of death in 1993 shows that at least 61.8,per,cent of deaths could be attributed to causes that are very closely related to HIV/AIDS complications. Based on points highlighted by respondents and analysis of symptoms suffered, it was observed that HIV/AIDS tended to affect most general workers (36.8,per,cent), followed by the lower management (30.9,per,cent) and the middle management (20.6,per,cent). Comparatively, 11.8,per,cent of the deaths in 1993 belonged to the top management. Although it is hard to appreciate the meaning of the figures without knowledge of the number of people in each category, it nevertheless helps to form a clear picture of the impact of HIV/AIDS on industry. This paper seeks to further investigate the impact of HIV/AIDS on the productive labour force, by focusing on one particular industry,mining,using a blend of research methods to collect the data. This paper examines the impact of HIV/AIDS on the productive labour force and management responses. It forms part of the findings of data gathered in 2001 in the mining industry in Zimbabwe, to examine factors affecting management responses to HIV/AIDS in the mine sites. Zimbabwe is a country with a complex historical legacy of mine labour. This phenomenon can largely be attributed to the production oriented nature of the mining industry. Mines focus mainly on mineral extraction and as a result the bulk of mine workers tend to be production workers whose skills have developed over long periods of time. Production workers on mines have a tradition of long-term employment. This phenomenon has meant that labour in the mines is hard to replace as a result of skills, especially tacit knowledge, acquired over many years. Thus while the recent closure of some gold mines, largely due to low commodity prices, has meant that more miners are available in the labour market, this situation has not necessarily eased the process of replacing labour lost to the HIV/AIDS epidemic, as certain skills are firm specific. Production workers are predominantly male with the bulk falling in the 35,39 years age group. Most mine workers reside in mine villages, a colonial legacy that ensured miners were close to the workplace. The village system is a system of housing labourers, which demonstrates capitalistic methods of controlling labour and minimising costs. Of significance in this study's background is how the village system has come to be viewed as a factor in the spread of HIV/AIDS in the mining communities, because of its ,closed' nature. It is against this complex historical backdrop that the paper turns to examine the impact of the HIV/AIDS pandemic on production workers and management responses to the crisis using the Resource Based View of the Firm model (RBV), one of the theories in the Strategic Human Resource Management (SHRM) tradition. RBV was chosen for this study out of many HRM models that exist, because this theory, in particular, explains why it is advantageous for sites to use their ,unique' firm based resources in order to achieve sustainable competitive advantage. Given this rationale it was, therefore, presumed that this theory would best apply in mines battling with the adverse impact of HIV/AIDS on productivity, especially in the light of the harsh national economic climate, which would likely place limitations on response mechanisms. Further, the issue of firm-specific skills was also taken into consideration as an important factor in the mines, limiting their ability to resort to external solutions. Thus, given these factors, RBV was deemed the most appropriate model. The study finds that the pandemic depresses labour productivity through a number of significant ways: increased rate of HIV/AIDS induced absenteeism gradual labour turnover as a result of AIDS induced morbidity; and consequently declining skills availability, particularly firm-specific skills. Maintaining labour productivity in the face of gradually diminishing skills and indisposed labour will be key to softening the adverse economic consequences of the pandemic in the mines. To reduce the threat to labour productivity, mines must find ways of utilising, to the maximum extent practicable, existing skills. Results indicate that a move towards the utilisation of existing miners is the most favoured response mechanism in most mines. Utilising existing miners enables mines from spending financial resources on avoidable recruitment and training and quite often mechanisation, which may not necessarily be compatible with the old infrastructure in certain mines. Copyright © 2006 John Wiley & Sons, Ltd. [source] | |||||||||||||