Drachtverbetering = samenwerking

Als imker en als KNNV’er en IVN’er, zet bijenteeltleraar Bert Lemmens zich al tientallen jaren in voor dracht- ofwel biodiversiteitsverbetering. Linda Bierings praatte met hem over zijn motieven, aanpak en resultaten

Orchestration of Primary Hemostasis by Platelet and Endothelial Lysosome-Related Organelles

Megakaryocyte-derived platelets and endothelial cells store their hemostatic cargo in α- and δ-granules and Weibel-Palade bodies, respectively. These storage granules belong to the lysosome-related organelles (LROs), a heterogeneous group of organelles that are rapidly released following agonist-induced triggering of intracellular signaling pathways. Following vascular injury, endothelial Weibel-Palade bodies release their content into the vascular lumen and promote the formation of long VWF (von Willebrand factor) strings that form an adhesive platform for platelets. Binding to VWF strings as well as exposed subendothelial collagen activates platelets resulting in the release of α- and δ-granules, which are crucial events in formation of a primary hemostatic plug. Biogenesis and secretion of these LROs are pivotal for the maintenance of proper hemostasis. Several bleeding disorders have been linked to abnormal generation of LROs in megakaryocytes and endothelial cells. Recent reviews have emphasized common pathways in the biogenesis and biological properties of LROs, focusing mainly on melanosomes. Despite many similarities, LROs in platelet and endothelial cells clearly possess distinct properties that allow them to provide a highly coordinated and synergistic contribution to primary hemostasis by sequentially releasing hemostatic cargo. In this brief review, we discuss in depth the known regulators of α- and δ-granules in megakaryocytes/platelets and Weibel-Palade bodies in endothelial cells, starting from transcription factors that have been associated with granule formation to protein complexes that promote granule maturation. In addition, we provide a detailed view on the interplay between platelet and endothelial LROs in controlling hemostasis as well as their dysfunction in LRO related bleeding disorders

Insight into light:The influence of luminance on visual functioning in glaucoma

Glaucoma is a progressive eye disease in which the visual field is permanently damaged but which remains without symptoms until a late stage. Visual field loss in one eye is compensated by the other eye and the brain fills in missing parts. At the ophthalmology outpatient clinic, many glaucoma patients indicated that they experienced difficulty with seeing in extreme (low, high and rapidly changing) luminance conditions – complaints that are not typical for glaucoma. Therefore, the aim of this thesis was to unravel the effect of luminance on the visual function of glaucoma patients. With a questionnaire, we confirmed glaucoma patients had much more difficulty with seeing in extreme luminance conditions, especially in the dark. In a series of experiments we found that glaucoma patients had a standard amount of lower vision in all luminance conditions; from very dark to extremely light. Glaucoma patients did not need longer adaptation times to get used to the dark. With the national citizen science project ‘Insight into light’ we used an app to map the luminance of the Netherlands at night. 6700 measurements of almost 2000 people showed that subjects with an eye disease had more difficulty with walking at night than subjects without an eye disease – an interesting fact given the trend towards fewer streetlights. This thesis confirms that glaucoma patients see less in all luminance conditions and this can be a considerable challenge especially in the dark. Further research is needed to confirm whether these findings can help us to diagnose glaucoma more efficiently in the future