Nurses' perceptions of aids and obstacles to the provision of optimal end of life care in ICU

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Twitch-potentiation increases calcium in peripheral more than in central mitochondria of guinea-pig ventricular myocytes

The mitochondrial total calcium content ([Ca]mt) was studied with electron probe microanalysis (EPMA) in isolated guinea-pig ventricular myocytes in order to answer the question of whether electrical stimulation increases [Ca]mt in subsarcolemmal and central mitochondria to a different extent.In unstimulated myocytes subsarcolemmal [Ca]mt was (mean ±s.e.m.) 535 ± 229 μmol (kg dry weight (DW))−1 and central [Ca]mt was 513 ± 162 μmol (kg DW)−1. These values do not differ and correspond to approximately 180 μmol calcium per litre of mitochondria or 180 μM.Contractions were potentiated to an optimum by stimulation with trains of 12 paired stimuli. After potentiation with 12 paired action potentials, cells were shock-frozen 120 ms after the start of the first action potential of the 13th pair. Subsarcolemmal [Ca]mt was 1·3 ± 0·4 mmol (kg DW)−1 (433 μM) and central [Ca]mt was 227 ± 104 μmol (kg DW)−1 (76 μM). The difference was significant.After potentiation with 12 paired voltage-clamp pulses, cells were shock-frozen 120 ms after the start of the first pulse of the 13th pair. Subsarcolemmal [Ca]mt was 2·2 ± 1·0 mmol (kg DW)−1 (733 μM) and central [Ca]mt was 630 ± 180 μmol (kg DW)−1 (210 μM). After removal of extracellular K+, five paired voltage-clamp pulses increased subsarcolemmal [Ca]mt to 2·1 ± 0·8 mmol (kg DW)−1 (700 μM), which was significantly higher than the central [Ca]mt of 389 ± 88 μmol (kg DW) −1 or 130 μM.In unstimulated cells, [Na] and [K] in subsarcolemmal and central mitochondria were not different. In potentiated myocytes, subsarcolemmal [Na]mt was 236 ± 20 mmol (kg DW)−1 or 79 mM, which is significantly higher than the central [Na]mt of 50 ± 5 mmol (kg DW)−1 or 16 mM.The differences in [Ca]mt and [Na]mt are attributed to subsarcolemmal cytosolic microdomains of elevated [Ca2+] and [Na+] generated during contractile potentiation by transmembrane Ca2+ and Na+ fluxes

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© Springer Science+Business Media B.V. 2011.Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEpu

Soziale Ungleichheiten in der Kompetenzentwicklung in der Grundschule und der Sekundarstufe I

Im Zentrum des vorliegenden Beitrags steht die Frage, wie sich die Kompetenzen von Schülerinnen und Schülern unterschiedlicher sozialer Herkunft während der Grundschule und der Sekundarstufe I entwickeln. Dabei ist vor allem von Interesse, inwieweit bereits zu Beginn der Schullaufbahn bestehende Leistungsunterschiede zwischen Schülerinnen und Schülern mit unterschiedlichem sozialem Hintergrund im Laufe der Schulzeit weiter zunehmen, stabil bleiben oder eventuell sogar konvergierende Entwicklungsverläufe zu beobachten sind. Vor diesem Hintergrund werden vorhandene nationale und internationale Längsschnittstudien herangezogen, um ein Bild über empirisch vorzufindende Entwicklungsverläufe zeichnen zu können. Eine Reihe der vorliegenden Befunde deutet auf eine Öffnung der Leistungsschere zwischen Schülerinnen und Schülern unterschiedlicher sozialer Herkunft während der Schulzeit hin, wobei die diesbezügliche Befundlage für die Grundschule konsistenter ausfällt als für die weiterführenden Schulen. Darüber hinaus finden sich auch Hinweise dafür, dass die Schule und die institutionelle Ausgestaltung des Bildungssystems mit zur Öffnung der Leistungsschere beitragen.The article focuses on the question how competencies of students with different social backgrounds develop during elementary and secondary school. In particular, it addresses if achievement disparities which exist before school entrance increase, remain stable, or even diminish during schooling. The article draws on both national and international studies with longitudinal designs examining the achievement development of students of different social backgrounds during primary or secondary school. Although the results are mixed to some extent, a large part indicates that differences in achievement increase during the time of schooling. The evidence seems more consistent for achievement development during elementary school. Additionally, there is some indication that schools and features of the educational system contribute to increasing achievement disparities between students of different social backgrounds