Variability of the thrombin- and ADP-induced Ca2+ response among human platelets measured using fluo-3 and fluorescent videomicroscopy

AbstractThe intracellular free Ca2+ concentration ([Ca2+]cyt) of individual human platelets localized between siliconized glass cover slips was determined at rest and after stimulation with thrombin and ADP using the Ca2+ indicator fluo-3 (0.97 ± 0.30 mmol/1 cell volume) with fluorescence video microscopy. Resting [Ca2+]cyt in the presence of 2 mM external Ca2+ showed only small inter-platelet variability ([Ca2+]cyt = 86 ± 30 (S.D.) nM). Resting [Ca2+]cyt of individual fluo-3-loaded platelets measured as a function of time had a S.D. of 10 nM or 12% (S.D./mean). Individual platelets showed no affinity for the siliconized support and their [Ca2+]cyt showed no tendency to oscillate in either the resting or in the activated state. When 0.2 U/ml thrombin or 20 μM ADP were added, all platelets showed a characteristic Ca2+ transient whereby [Ca2+]cyt increased to peak values within 8–12 sec and then declined. The Ca2+ transients measured with fluo-3 were in approximate synchrony but peak [Ca2+]cyt values showed large inter-platelet variability. The ensemble average peak [Ca2+]cyt for thrombin and ADP were 672 ± 619 (S.D.) nM and 640 ± 642 (S.D.) nM, respectively. Thus inter-platelet variations (S.D./mean) were 92% or 100% as large as the average measured values. Mathematically-constructed averages of the single platelet experiments agreed reasonably well with platelet-averaged values obtained in parallel experiments with stirred platelet suspensions in a plastic cuvette, measured with a conventional spectrofluorometer. Peak [Ca2+]cyt values reflecting dense tubular Ca2+ release alone (external Ca2+ removed) also showed large interplatelet variation (171 ± 105 (S.D.) nM with thrombin and 183 ± 134 (S.D.) nM with ADP). Dense tubular Ca2+ release induced by cyclopiazonic acid (a dense tubular Ca2+-ATPase inhibitor) gave peak [Ca2+]cyt of 289 ± 170 nM. Thus the size of the dense tubular Ca2+ pool has an inter-platelet variation of 59% (S.D./mean). Variability of the dense tubular pool size accounts for some, but not all, of the large interplatelet variation in peak [Ca2+]cyt seen with thrombin and ADP activation

Can Student Voice be used to develop materials for Secondary School ESL students in the Singaporean context?

This paper discusses the use of Student Voice (SV) as a mechanism for collecting the opinions of ESL secondary students in the Singaporean context. SV is used as a mechanism to collate opinions and to develop negotiated materials which have aims, themes and activities which resonant with these students. SV methodology is employed to act as bridge between white, Anglo-Saxon, middle-aged instructors and Asian teenagers at a private language institute. SV allows a degree of insight that might be unachievable with other methodologies. The paper seeks to assess the viability of producing negotiated materials design using the student voice methodology and seeks to identify potential limitations to this methodology and future research which might be explored

Blood pressure management in ischemic stroke patients undergoing mechanical thrombectomy

The relationship between presenting blood pressure in acute ischemic stroke patients and outcome is complex. Several studies have demonstrated a U-shaped curve with worse outcomes when blood pressure is high or low. The American Heart Association/American Stroke Association guidelines recommend values of blood pressure \u3c 185/110 mmHg in patients treated with intravenous t-PA and permissive hypertension up to 220/120 mmHg in those not treated with intravenous t-PA. The optimal blood pressure target is less clear in patients undergoing mechanical thrombectomy. Before thrombectomy, the guidelines recommend a blood pressure \u3c 185/110 mmHg though patients with even lower systolic blood pressures may have better outcomes. During and after thrombectomy, the guidelines recommend a blood pressure \u3c 180/105 mmHg. However, several studies have suggested that during thrombectomy the primary goal should be to prevent significant low blood pressure (e.g., target systolic blood pressure \u3e 140 mmHg or MAP \u3e 70 mmHg). After thrombectomy, the primary goal should be to prevent high blood pressure (e.g., target systolic blood pressure \u3c 160 mmHg or MAP \u3c 90 mmHg). To make more specific recommendations, large, randomized-control studies are needed that address factors such as the baseline blood pressure, timing and degree of revascularization, status of collaterals, and estimated risk of reperfusion injury

A continuous process for the biological treatment of heavy metal contaminated acid mine water

Alkaline precipitation of heavy metals from acidic water streams is a popular and long standing treatment process. While this process is efficient it requires the continuous addition of an alkaline material, such as lime. In the long term or when treating large volumes of effluent this process becomes expensive, with costs in the mining sector routinely exceeding millions of rands annually. The process described below utilises alkalinity generated by the alga Spirulina sp., in a continuous system to precipitate heavy metals. The design of the system separates the algal component from the metal containing stream to overcome metal toxicity. The primary treatment process consistently removed over 99% of the iron (98.9 mg/l) and between 80 and 95% of the zinc (7.16 mg/l) and lead (2.35 mg/l) over a 14-day period (20 l effluent treated). In addition the pH of the raw effluent was increased from 1.8 to over 7 in the post-treatment stream. Secondary treatment and polishing steps depend on the nature of the effluent treated. In the case of the high sulphate effluent the treated stream was passed into an anaerobic digester at a rate of 4 l/day. The combination of the primary and secondary treatments effected a removal of over 95% of all metals tested for as well as a 90% reduction in the sulphate load. The running cost of such a process would be low as the salinity and nutrient requirements for the algal culture could be provided by using tannery effluent or a combination of saline water and sewage. This would have the additional benefit of treating either a tannery or sewage effluent as part of an integrated process

Effect of Financial Literacy on Voluntary Retirement Planning Among Employees of State Corporations Under the Ministry of Health in Nairobi County, Kenya

Purpose - The study sought to determine the effect of financial literacy on voluntary retirement planning among employees of state corporations under the Ministry of Health in Nairobi County, Kenya. Methodology – This study adopted a descriptive study design and uses primary data collected using a questionnaire with a five point Likert scale on the parameters of each variable. The study applied simple random sampling technique to select respondents to participate in the study. Data is analysed using means, percentages and frequencies. Multiple regression analysis was used to test the relationship between financial literacy and voluntary retirement planning. Findings – Financial literacy was found to influence the level of voluntary retirement planning among the employees since they are able to make key decisions that involve money in such a way that there is minimal risk to them. The study also established that financial literacy has a positive impact on voluntary retirement planning, however the results indicate that other factors such as income levels, age, marital status and level of education are also strongly related to retirement planning. Implications – To boost the voluntary retirement planning process, the eventuality of retirement should be made obvious for all the employees in the Kenyan economy so as to influence peoples’ attitude and receptiveness to the process. There is therefore need to develop financial education programs that focus particularly on important financial planning aspects for employees that will help them strike a balance between consumption and saving. Value – The findings of this study would also be valuable to the Retirement Benefits Authority and the Government of Kenya in development of policies and regulation

Clinical stakeholders' opinions on the use of selective decontamination of the digestive tract in critically ill patients in intensive care units : an international Delphi study

Peer reviewedPublisher PD

Mercury enrichment in anthrosols and adjacent coastal sediments at a Classic Maya site, Marco Gonzalez, Belize

Elevated concentrations of total mercury (THg) are found in the surface soils and flanking wetland sediments at the Classic Maya coastal site of Marco Gonzalez, Belize. Significant concentrations (up to 1.3 µg·g−1 dry mass) of THg occur in leaf litter-rich soils, as well as in the artefact-rich anthrosol spread over the vegetated mound site of structures and occupation debris. The abundance and spatial pattern of major and trace elements measured in the surface soils indicate both site-scale controlling factors of topography, structures and vegetation on soil geochemistry as well as local highs in concentration compared with background, due to human activity. Geochemical stratigraphy of wetland sediment cores shows that a shift from carbonate-reef sediments to mangrove peat in the 13th century AD was attended by an input of allogenic (mineral) elements, including mercury. A THg concentration peak (0.8 μg·g−1) in brackish pool sediment is 210Pb-dated to 1960–1970 AD, but the incorporation of mercury in multiple cores adjacent to the site shows increasing mercury inputs to have occurred before, during Classic-period Maya occupation and following the sites abandonment. Analysis of element values from site-scale soil sampling, combined with results from off-site cores, provides a numerical framework upon which outlier values of THg and other element spatial patterns can be assessed, especially the spatial co-association of elements related to differences in soil–sediment matrices. Geochemical results from active soils developing from occupation deposits (anthrosols) and sediment cores open up questions concerning contemporary and past mercury accumulation at coastal Mayan sites, and the wider interaction of human and natural biogeochemical processes that occur in human-modified soils and coastal wetland sediments

Introduction

Untranslatability has never had a higher profile than at present in popular culture, but translators are always willing to rise to the challenge of at least paraphrasing “untranslatable” material, so does “untranslatable” in practice really mean anything more than “difficult to translate”? The term is in vogue in academic translation studies, too, largely thanks to Barbara Cassin and Emily Apter, whose work has highlighted the importance of translation problems to philosophical enquiry and world literature, respectively. This introductory chapter sets out some of the key terms of the untranslatability debate, and summarises the contributions to follow