Excision of Titin's Cardiac Pevk Spring Element Abolishes PKCα-Induced Increases in Myocardial Stiffness

Protein Kinase C-alpha (PKCalpha) was recently reported to increase myocardial stiffness, an effect that was proposed to be due to phosphorylation of two highly conserved sites (S11878 and S12022) within the proline-gluatamic acid-valine-lysine (PEVK) rich spring element of titin. To test this proposal we investigated the effect of PKCalpha on phosphorylation and passive stiffness in a mouse model lacking the titin exons that contain these two phosphorylation sites, the PEVK knockout (KO). We used skinned, gelsolin-extracted, left ventricular, myocardium from wildtype and PEVK KO mice. Consistent with previous work we found that PKCalpha increased passive stiffness in the WT myocardium by 27 +/-6%. Importantly, this effect was completely abolished in KO myocardium. In addition, increases in the elastic and viscous moduli at a wide range of frequencies (properties important in diastolic filling) following PKCalpha incubation (27 +/-3% and 20 +/-4%, respectively) were also ablated in the KO. Back phosphorylation assays showed that titin phosphorylation following incubation with PKCalpha was significantly reduced by 36+/-12% in skinned PEVK KO myocardial tissues. The remaining phosphorylation in the KO suggests that PKCalpha sites exist in the titin molecule outside the PEVK region; these sites are not involved in increasing passive stiffness. Our results firmly support that the PEVK region of cardiac titin is phosphorylated by PKCalpha and that this increases passive tension. Thus, the PEVK spring element is the critical site of PKCalpha's involvement in passive myocardial stiffness

The Archaeology of Yukon Ice Patches: New Artifacts, Observations, and Insights

Since 1997, more than 207 archaeological objects and 1700 faunal remains have been recovered from 43 melting ice patches in the southern Yukon. The artifacts range in age from a 9000-year-old (calendar) dart shaft to a 19th-century musket ball. This paper provides an update on Yukon ice patch research and summary data on select areas of research conducted since 2003. More than 200 radiocarbon dates have been run on ice patch archaeological and faunal materials, and these data allow us to observe and comment on apparent temporal trends. Analysis undertaken since 2003 has improved our understanding of the development and maintenance of hunting technologies, including dart shaft design, wood selection, and point styles. Of particular interest is the description of three different techniques for the construction of throwing darts and the observation of stability in the hunting technology employed in the study area over seven millennia. Radiocarbon chronologies indicate that this period of stability was followed by an abrupt technological replacement of the throwing dart by the bow and arrow after 1200 BP.Depuis 1997, plus de 350 objets archéologiques et de 1 700 restes fauniques ont été récupérés dans 43 névés en fusion dans le sud du Yukon. L’âge de ces artefacts varie, allant d’une tige de propulseur de 9 000 ans (années civiles) à une balle de mousquet du XIXe siècle. Dans cet article, nous faisons la mise à jour des données sommaires et des travaux de recherche effectués dans les névés de régions choisies du Yukon depuis 2003. Plus de 200 dates au carbone 14 ont été établies pour le matériel faunique et archéologique des névés. Ces données nous permettent d’observer les tendances temporales apparentes et de formuler des commentaires à leur sujet. Les analyses qui ont été effectuées depuis 2003 nous ont permis de mieux comprendre l’évolution et le maintien des techniques de chasse, notamment en matière de conception des tiges de propulseurs, de choix du bois et des types de pointes. La description de trois techniques différentes de fabrication de tirs au propulseur de même que l’observation de la stabilité entourant la technique de chasse employée au cours de la période visée par l’étude, soit plus de sept millénaires, revêtent un intérêt particulier. Les chronologies au carbone 14 indiquent que cette période de stabilité a été suivie d’un remplacement technique abrupt, qui est passé du tir au propulseur aux arcs et aux flèches après 1200 BP

18F-Labelled exendin to image GLP-1 receptor-expressing tissues: from niche to blockbuster?

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Permeation of CO2 and N2 through glassy poly(dimethyl phenylene) oxide under steady- and presteady-state conditions

Glassy polymers are often used for gas separations because of their high selectivity. Although the dual-mode permeation model correctly fits their sorption and permeation isotherms, its physical interpretation is disputed, and it does not describe permeation far from steady state, a condition expected when separations involve intermittent renewable energy sources. To develop a more comprehensive permeation model, we combine experiment, molecular dynamics, and multiscale reaction–diffusion modeling to characterize the time-dependent permeation of N2 and CO2 through a glassy poly(dimethyl phenylene oxide) membrane, a model system. Simulations of experimental time-dependent permeation data for both gases in the presteady-state and steady-state regimes show that both single- and dual-mode reaction–diffusion models reproduce the experimental observations, and that sorbed gas concentrations lag the external pressure rise. The results point to environment-sensitive diffusion coefficients as a vital characteristic of transport in glassy polymers

The cell adhesion protein CAR is a negative regulator of synaptic transmission

The Coxsackievirus and adenovirus receptor (CAR) is essential for normal electrical conductance in the heart, but its role in the postnatal brain is largely unknown. Using brain specific CAR knockout mice (KO), we discovered an unexpected role of CAR in neuronal communication. This includes increased basic synaptic transmission at hippocampal Schaffer collaterals, resistance to fatigue, and enhanced long-term potentiation. Spontaneous neurotransmitter release and speed of endocytosis are increased in KOs, accompanied by increased expression of the exocytosis associated calcium sensor synaptotagmin 2. Using proximity proteomics and binding studies, we link CAR to the exocytosis machinery as it associates with syntenin and synaptobrevin/VAMP2 at the synapse. Increased synaptic function does not cause adverse effects in KO mice, as behavior and learning are unaffected. Thus, unlike the connexin-dependent suppression of atrioventricular conduction in the cardiac knockout, communication in the CAR deficient brain is improved, suggesting a role for CAR in presynaptic processes

Temperature controlled martensitic phase transformations in a model NiAl alloy

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