Endoplasmic Reticulum Remodeling Tunes IP3-Dependent Ca2+ Release Sensitivity

The activation of vertebrate development at fertilization relies on IP3-dependent Ca2+ release, a pathway that is sensitized during oocyte maturation. This sensitization has been shown to correlate with the remodeling of the endoplasmic reticulum into large ER patches, however the mechanisms involved are not clear. Here we show that IP3 receptors within ER patches have a higher sensitivity to IP3 than those in the neighboring reticular ER. The lateral diffusion rate of IP3 receptors in both ER domains is similar, and ER patches dynamically fuse with reticular ER, arguing that IP3 receptors exchange freely between the two ER compartments. These results suggest that increasing the density of IP3 receptors through ER remodeling is sufficient to sensitize IP3-dependent Ca2+ release. Mathematical modeling supports this concept of ‘geometric sensitization’ of IP3 receptors as a population, and argues that it depends on enhanced Ca2+-dependent cooperativity at sub-threshold IP3 concentrations. This represents a novel mechanism of tuning the sensitivity of IP3 receptors through ER remodeling during meiosis

Phonons in Slow Motion: Dispersion Relations in Ultra-Thin Si Membranes

We report the changes in dispersion relations of hypersonic acoustic phonons in free-standing silicon membranes as thin as \sim 8 nm. We observe a reduction of the phase and group velocities of the fundamental flexural mode by more than one order of magnitude compared to bulk values. The modification of the dispersion relation in nanostructures has important consequences for noise control in nano and micro-electromechanical systems (MEMS/NEMS) as well as opto-mechanical devices.Comment: 5 page

Ambient temperature and coronary heart disease mortality in Beijing, China: a time series study

To examine cardiovascular disease (CVD) mortality burden attributable to ambient temperature; to estimate effect modification of this burden by gender, age and education level