Adenosine, ‘pertussis-sensitive’ G-proteins, and K+ conductance in central mammalian neurones under energy deprivation

There is a striking similarity between the effects of adenosine and of hypoxia or glucose depletion on membrane potential and conductance of hippocampal neurones in tissue slices of rat brain. Both induce a membrane hyperpolarization by an increase in potassium conductance. It seemed likely, therefore, that a rise in extracellular adenosine concentration during energy deprivation may link neuronal metabolism with membrane K+ conductance. To test this hypothesis, we have now investigated the effects of hypoxia/glucose deprivation on hippocampal neurones from pertussis toxin-treated rats. In such slices adenosine had no effect on postsynaptic membrane potential and input resistance. Nevertheless, hypoxia or glucose depletion were as effective as in controls. These data provide evidence against adenosine as the main mediator between cell metabolism and potassium conductance

Cromakalim (BRL 34915) restores in vitro the membrane potential of depolarized human skeletal muscle fibres

The purpose of the present study was to analyze the effects of cromakalim (BRL 34915), a potent drug from a new class of drugs characterized as K+ channel openers, on the electrical activity of human skeletal muscle. Therefore, intracellular recordings were used to measure the effects of cromakalim on the membrane potential and input conductance of fibres from human skeletal muscle biopsies. Cromakalim in a concentration above 1 mol/l induced an increase in membrane K+ conductance. This effect resulted in a membrane hyperpolarization. The magnitude of this polarization depended on the difference between resting and K+ equilibrium potential. The effect had a rapid onset and was quickly reversible after washing. Fibres from two patients with hyperkalaemic periodic paralysis showed an excessive membrane depolarization during and also after exposure to an slightly elevated extracellular K+ concentration. In the latter situation, cromakalim repolarized the fibres to the normal resting potential. Tolbutamide (1 mmol/l) and Ba2+ (3 mmol/l) strongly antagonized the effect of cromakalim. The data show that cromakalim hyperpolarizes depolarized human skeletal muscle fibres maintained in vitro. The underlying mechanism is probably an activation of otherwise silent, ATP-regulated K+ channels. Such an effect may be of therapeutic benefit in a situation in which a membrane depolarization causes muscle paralysis

Nerve damage induced skeletal muscle atrophy is associated with increased accumulation of intramuscular glucose and polyol pathway intermediates

Perturbations in skeletal muscle metabolism have been reported for a variety of neuromuscular diseases. However, the role of metabolism after constriction injury to a nerve and the associated muscle atrophy is unclear. We have analyzed rat tibialis anterior (TA) four weeks after unilateral constriction injury to the sciatic nerve (DMG) and in the contralateral control leg (CTRL) (n = 7) to investigate changes of the metabolome, immunohistochemistry and protein levels. Untargeted metabolomics identified 79 polar metabolites, 27 of which were significantly altered in DMG compared to CTRL. Glucose concentrations were increased 2.6-fold in DMG, while glucose 6-phosphate (G6-P) was unchanged. Intermediates of the polyol pathway were increased in DMG, particularly fructose (1.7-fold). GLUT4 localization was scattered as opposed to clearly at the sarcolemma. Despite the altered localization, we found GLUT4 protein levels to be increased 7.8-fold while GLUT1 was decreased 1.7-fold in nerve damaged TA. PFK1 and GS levels were both decreased 2.1-fold, indicating an inability of glycolysis and glycogen synthesis to process glucose at sufficient rates. In conclusion, chronic nerve constriction causes increased GLUT4 levels in conjunction with decreased glycolytic activity and glycogen storage in skeletal muscle, resulting in accumulation of intramuscular glucose and polyol pathway intermediates

Developments in Australian Buddhism: facets of the diamond

This book examines the adaptation of Buddhism to the Australian socio-cultural context, within the broader context of Buddhism's development in Westernized countries. The book also examines the methodological approaches currently used for studying this process and suggests a synthesis of the approaches used for studying convert and ethnic Buddhist groups. Spuler begins with an example of how Buddhism has adapted to the Australian context, illustrating both seemingly logical adaptations and incongruities. The process that has given rise to this hybridised tradition is examined, and the book provides a history of Buddhism's development. It then focuses on data gathered during field work, on the adaptation of Diamond Sangha Zen Buddhist groups in Australia, and compares this with other Western Buddhist groups, using existing models of cross-cultural acculturation. This book is timely as it provides a much-needed update on Buddhism in Australia. This information is vital for international comparative studies with Buddhism in other countries. It also includes previously unpublished information about the Diamond Sangha Zen Buddhist organisation, one of the largest Zen lineages in the West. Its founding teacher, Robert Aitken, is often cited as a key figure in the history of Western Zen. This book will be of interest to Buddhist practitioners and students and scholars of Buddhist studies, as well as anyone interested in processes of acculturation

A Meta-Analysis of the Relative Effectiveness of Two Cooperative Learning Models in Increasing Mathematics Achievement

The meta-analysis compares two popular cooperative learning models, Student-Teams-Achievement Divisions (STAD) and Teams-Games-Tournaments (TGT), for their relative effectiveness in increasing mathematics achievement of K-12 students. The findings of the available research were integrated to determine both the magnitude and the direction of the effects of the cooperative learning models and effect sizes were calculated. More studies comparing the TGT cooperative learning model with a traditional learning model (81% of the studies) resulted in statistically significant higher gains in mathematics achievement than studies comparing the STAD model with a traditional learning model (51% of the studies). Other measures of relative effectiveness did not clearly support the TGT cooperative learning model as the most effective method for increasing mathematics achievement. Mean effect sizes were compared by goal structure, grade level, length of study, and location. Students who participated in studies comparing the STAD cooperative learning model with a competitive learning model achieved statistically significant higher gains in mathematics achievement than students who participated in studies comparing the TGT cooperative learning model with a competitive learning model. In studies of 13 weeks or longer, students who were included in the TGT cooperative learning method as compared with a traditional learning method achieved higher gains in mathematics than students who were included in the STAD cooperative learning method. In studies of 13 weeks or less, students who were included in the STAD cooperative learning method as compared with a traditional learning method achieved higher gains in mathematics than students who were included in the TGT cooperative learning model. When TGT and STAD studies were compared by grade level, the studies at the elementary level resulted in higher gains in mathematics achievement by students in TGT cooperative learning groups when compared with students in individualized learning models. Yet, when compared with students included in a competitive learning model at the elementary level, students involved in STAD cooperative learning groups garnered higher achievement gains in mathematics. In studies conducted in urban settings, students participating in STAD cooperative learning groups achieved higher gains in mathematics than students participating in TGT cooperative learning groups when compared with traditional learning models

Die Schmetterlinge Europas, Bd. 1-3

Enthält: 1. Allgemeiner Teil - Spezieller Teil, 1908 2. des speziellen Teils., 1910 3. Tafelband, 191