RETRACTED ARTICLE: Age-dependent Increase in Desmosterol Restores DRM Formation and Membrane-related Functions in Cholesterol-free DHCR24−/− Mice

Cholesterol is a prominent modulator of the integrity and functional activity of physiological membranes and the most abundant sterol in the mammalian brain. DHCR24-knock-out mice lack cholesterol and accumulate desmosterol with age. Here we demonstrate that brain cholesterol deficiency in 3-week-old DHCR24−/− mice was associated with altered membrane composition including disrupted detergent-resistant membrane domain (DRM) structure. Furthermore, membrane-related functions differed extensively in the brains of these mice, resulting in lower plasmin activity, decreased β-secretase activity and diminished Aβ generation. Age-dependent accumulation and integration of desmosterol in brain membranes of 16-week-old DHCR24−/− mice led to the formation of desmosterol-containing DRMs and rescued the observed membrane-related functional deficits. Our data provide evidence that an alternate sterol, desmosterol, can facilitate processes that are normally cholesterol-dependent including formation of DRMs from mouse brain extracts, membrane receptor ligand binding and activation, and regulation of membrane protein proteolytic activity. These data indicate that desmosterol can replace cholesterol in membrane-related functions in the DHCR24−/− mouse

A methodology to investigate the usage of educational technologies on tablets in schools

This chapter introduces a methodology to study how educational technologies on tablets are being used in schools. Specifically it investigates how different educational technologies influence the organization of the learning environment and the way teachers teach. Educational technologies differ greatly in how they offer educational materials and how they use students’ data (learning analytics). It is important to understand the impact of educational technologies on the way teachers shape educational innovation. We view educational technologies on tablets as an instrument for teachers to support them to improve their teaching. Three models are introduced to investigate how educational technologies impact the organization of the learning environment and teaching practices, namely the class-rotation, the actor-control and the pedagogical decision making model