The Targeting of Plasmalemmal Ceramide to Mitochondria during Apoptosis

Ceramide is a key lipid mediator of cellular processes such as differentiation, proliferation, growth arrest and apoptosis. During apoptosis, ceramide is produced within the plasma membrane. Although recent data suggest that the generation of intracellular ceramide increases mitochondrial permeability, the source of mitochondrial ceramide remains unknown. Here, we determine whether a stress-mediated plasmalemmal pool of ceramide might become available to the mitochondria of apoptotic cells. We have previously established annexin A1—a member of a family of Ca2+ and membrane-binding proteins—to be a marker of ceramide platforms. Using fluorescently tagged annexin A1, we show that, upon its generation within the plasma membrane, ceramide self-associates into platforms that subsequently invaginate and fuse with mitochondria. An accumulation of ceramide within the mitochondria of apoptotic cells was also confirmed using a ceramide-specific antibody. Electron microscopic tomography confirmed that upon the formation of ceramide platforms, the invaginated regions of the plasma membrane extend deep into the cytoplasm forming direct physical contacts with mitochondrial outer membranes. Ceramide might thus be directly transferred from the plasma membrane to the mitochondrial outer membrane. It is conceivable that this “kiss-of-death” increases the permeability of the mitochondrial outer membrane thereby triggering apoptosis

Unravelling receptor and RGD motif dependence of retargeted adenoviral vectors using advanced tumor model systems

Recent advances in engineering adenoviruses are paving the way for new therapeutic gene delivery approaches in cancer. However, there is limited knowledge regarding the impact of adenoviral retargeting on transduction efficiency in more complex tumor architectures, and the role of the RGD loop at the penton base in retargeting is unclear. To address this gap, we used tumor models of increasing complexity to study the role of the receptor and the RGD motif. Employing tumor-fibroblast co-culture models, we demonstrate the importance of the RGD motif for efficient transduction in 2D through the epithelial cell adhesion molecule (EpCAM), but not the epidermal growth factor receptor (EGFR). Via optical clearing of co-culture spheroids, we show that the RGD motif is required for transduction via both receptors in 3D tumor architectures. We subsequently employed a custom-designed microfluidic model containing collagen-embedded tumor spheroids, mimicking the interplay between interstitial flow, extracellular matrix and adenoviral transduction. Image analysis of on-chip cleared spheroids indicated the importance of the RGD motif for on-chip adenoviral transduction. Together, our results show the interrelationship between receptor characteristics, the RGD motif, the 3D tumor architecture and retargeted adenoviral transduction efficiency. The findings are important for the rational design of next-generation therapeutic adenoviruses

High frequency dc/dc power converter with galvanic isolation

There is a steady demand to increase the efficiency and raise the power density of power converters. This trend is desired since it leads to reduced size of the converter. The purpose of this thesis is to investigate materials, topologies, core structure and then build a prototype to demonstrate the result. Two core materials have been compared, Fair-Rite material 68 and Ferroxcube 4F1. The goal was to have 50 V input and 30 V output with 80 % efficiency of the converter. The converter with the Fair-Rite material 68 accomplished a peak efficiency at 11 MHz with 54 % efficiency. The core material Ferroxcube 4F1, reached an efficiency of 52 % at 7 MHz. These results were however with 5 V input and 3 V output. The converter had a low efficiency at 50 V input, which lead to ripple in the circuit. One reason for this behaviour was because the design of the PCB was not optimized for MHz operation. The focus of the PCB was that it should be easy to work with instead of achieving peak performance. Also, from the beginning it was decided that no PCB should be made. The focus was instead on the theory and simulations of the converter so no thoroughly investigation of PCB design was done. The leakage inductance of the transformer core was about 10 % of the primary inductance for both materials. The high leakage inductance is believed to further reduce the efficiency of the converter

Rook- en alcoholspecifieke opvoeding; de huidige stand van zaken op het gebied van onderzoek en preventie

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