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Rab3a ablation related changes in morphology of secretory vesicles in major endocrine pancreatic cells, pituitary melanotroph cells and adrenal gland chromaffin cells in mice
Saška Lipovšek Delakorda, Franc Janžekovič, Gerd Leitinger, Marjan Rupnik, 2013, original scientific article

Abstract: In this work we have compared the ultrastructural characteristics of major pancreatic endocrine cells, pituitary melanotrophs and adrenal chromaffin cells in the normal mouse strain (wild type, WT) and mice with a known secretory deficit, the Rab3a knockout strain (Rab3a KO). For this purpose, pancreata, pituitary glands and adrenal glands from the Rab3a KO and from the WT mice were analysed, using conventional transmission electron microscopy (TEM). In order to assess the significance of the presence of Rab3a proteins in the relevant cells, we focused primarily on their secretory vesicle morphology and distribution. Our results showed a comparable general morphology in Rab3a KO and WT in all assessed endocrine cell types. In all studied cell types, the distribution of secretory granules along the plasma membrane (number of docked and almost-docked vesicles) was comparable between Rab3a KO and WT mice. Specific differences were found in the diameters of their secretory vesicles, diameters of their electron-dense cores and the presence of autophagic structures in the cells of Rab3A KO mice only. Occasionally, individual electron-dense round vesicles were present inside autophagosome-like structures; these were possibly secretory vesicles or their remnants. The differences found in the diameters of the secretory vesicles confirm the key role of Rab3a proteins in controlling the balance between secretory vesicle biogenesis and degradation, and suggest that the ablation of this protein probably changes the nature of the reservoir of secretory vesicles available for regulated exocytosis.
Keywords: chromaffin cells, melanotrophs, pancreatic endocrine cells
Published in DKUM: 10.07.2015; Views: 1283; Downloads: 87
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Spatial network representation of complex living tissues
Dean Korošak, Marjan Rupnik, 2008, published scientific conference contribution

Abstract: Networks were widely used to describe organizational and functional principles of living organisms across various scales. The topology of such biological complex networks often turned out to be "scale-free", with the power-law distribution of number of links per node, robust and modular with underlying self-similar structure. However, the topology of cytoarchitecture in living tissues has not yet received wide attention from the network perspective. Here we discuss the spatial complex network model of coupled clusters of beta cells in pancreatic islets. Networks of cells in pancreatic islets were constructed from the 2D section images presenting fluorescently labelled intercellular spaces obtained by two-photon laser scanning microscopy of whole pancreas tissue slices, and cells conductances measured electrophysiologically using whole-cell patch-clamp. We find that the heterogeneity of beta cells in intact living islets induces scale-free topology of the tissue network. Furthermore, we show that the islet-like structures visually similar to 2D section images can be obtained using Voronoi diagrams of random points.
Keywords: pancreatic islets, betta cells, complex networks, cytoarchitecture
Published in DKUM: 31.05.2012; Views: 2197; Downloads: 79
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