Event-related potentials discriminate familiar and unusual goal outcomes in 5-month-olds and adults

Previous event-related potential (ERP) work has indicated that the neural processing of action sequences develops with age. While adults and 9-month-olds use a semantic processing system, perceiving actions activates attentional processes in 7-month-olds. However, presenting a sequence of action context, action execution and action conclusion could challenge infants' developing working memory capacities. A shortened stimulus presentation of a highly familiar action, presenting only the action conclusion of an eating action, may therefore enable semantic processing in even younger infants. The present study examined neural correlates of the processing of expected and unexpected action conclusions in adults and infants at 5 months of age. We analyzed ERP components reflecting semantic processing (N400), attentional processes (negative central in infants; P1, N2 in adults) and the infant positive slow wave (PSW), a marker of familiarity. In infants, the PSW was enhanced on left frontal channels in response to unexpected as compared to expected outcomes. We did not find differences between conditions in ERP waves reflecting semantic processing or overt attentional mechanisms. In adults, in addition to differences in attentional processes on the P1 and the N2, an N400 occurred only in response to the unexpected action outcome, suggesting semantic processing taking place even without a complete action sequence being present. Results indicate that infants are already sensitive to differences in action outcomes, although the underlying mechanism which is based on familiarity is relatively rudimentary when contrasted with adults. This finding points toward different cognitive mechanisms being involved in action processing during development

Proline at position 14 of alamethicin is essential for hemolytic activity, catecholamine secretion from chromaffin cells and enhanced metabolic activity in endothelial cells

AbstractAlamethicin is known to lyse different biological cells and to induce voltage dependent ion channels in lipid bilayers. A set of analogs with proline shifted from position 14 in the native peptide towards the N- and C-terminus was used to investigate the role of proline in: (i) alamethicin induced hemolysis of human red blood cells, (ii) stimulation of catecholamine secretion from bovine adrenal chromaffin cells and (iii) induction of metabolic activity in bovine aortic endothelial cells. Half maximal hemolytic activity was found at 30μM alamethicin concentration, complete lysis occurred at 100μM. The stimulation of catecholamine secretion in the presence of extracellular Ca2+ was concentration dependent up to 50μM alamethicin. At this high concentration mild secretion was also found in the absence of Ca2+ indicating cell membrane damage. Alamethicin transiently stimulated the metabolic rate of endothelial cells in a concentration dependent mode up to 20μM while the inhibition of metabolism at higher concentrations pointed to a toxic effect. The alamethicin analogs were completely inactive in all the biological assays. The effects correlated with a loss of dye release inducing activities on phosphatidylcholine vesicles and reduction of channel forming properties in lipid bilayers and were associated with modifications of membrane affinity rather than conformational changes of the peptides. The results indicate that proline at position 14 of the native peptide is essential for the interaction with different membrane systems

A model of the Earth's Dole effect

The Earth's Dole effect describes the isotopic [superscript 18]O/[superscript 16]O-enrichment of atmospheric oxygen with respect to ocean water, amounting under today's conditions to 23.5‰. We have developed a model of the Earth's Dole effect by combining the results of three-dimensional models of the oceanic and terrestrial carbon and oxygen cycles with results of atmospheric general circulation models (AGCMs) with built-in water isotope diagnostics. We obtain a range from 22.4‰ to 23.3‰ for the isotopic enrichment of atmospheric oxygen. We estimate a stronger contribution to the global Dole effect by the terrestrial relative to the marine biosphere in contrast to previous studies. This is primarily caused by a modeled high leaf water enrichment of 5–6‰. Leaf water enrichment rises by ∼1‰ to 6–7‰ when we use it to fit the observed 23.5‰ of the global Dole effect. The present model is designed to be utilized in forthcoming paleo studies allowing a quantitative analysis of long-term observations from polar ice cores