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- Hoppa, M. B., et al.
(författare)
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Multivesicular exocytosis in rat pancreatic beta cells
- 2012
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Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 1432-0428 .- 0012-186X. ; 55:4, s. 1001-1012
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Tidskriftsartikel (refereegranskat)abstract
- To establish the occurrence, modulation and functional significance of compound exocytosis in insulin-secreting beta cells. Exocytosis was monitored in rat beta cells by electrophysiological, biochemical and optical methods. The functional assays were complemented by three-dimensional reconstruction of confocal imaging, transmission and block face scanning electron microscopy to obtain ultrastructural evidence of compound exocytosis. Compound exocytosis contributed marginally (< 5% of events) to exocytosis elicited by glucose/membrane depolarisation alone. However, in beta cells stimulated by a combination of glucose and the muscarinic agonist carbachol, 15-20% of the release events were due to multivesicular exocytosis, but the frequency of exocytosis was not affected. The optical measurements suggest that carbachol should stimulate insulin secretion by similar to 40%, similar to the observed enhancement of glucose-induced insulin secretion. The effects of carbachol were mimicked by elevating [Ca2+](i) from 0.2 to 2 mu mol/l Ca2+. Two-photon sulforhodamine imaging revealed exocytotic events about fivefold larger than single vesicles and that these structures, once formed, could persist for tens of seconds. Cells exposed to carbachol for 30 s contained long (1-2 mu m) serpentine-like membrane structures adjacent to the plasma membrane. Three-dimensional electron microscopy confirmed the existence of fused multigranular aggregates within the beta cell, the frequency of which increased about fourfold in response to stimulation with carbachol. Although contributing marginally to glucose-induced insulin secretion, compound exocytosis becomes quantitatively significant under conditions associated with global elevation of cytoplasmic calcium. These findings suggest that compound exocytosis is a major contributor to the augmentation of glucose-induced insulin secretion by muscarinic receptor activation.
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| 2. |
- Bimbot, F, et al.
(författare)
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An overwiev of the CAVE project research activities in speaker verification
- 2000
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Ingår i: Speech Communication. - 0167-6393 .- 1872-7182. ; 31:2-3, s. 155-180
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Tidskriftsartikel (refereegranskat)abstract
- This article presents an overview of the research activities carried out in the European CAVE project, which focused on text-dependent speaker verification on the telephone network using whole word Hidden Markov Models. It documents in detail various aspects of the technology and the methodology used within the project. In particular, it addresses the issue of model estimation in the context of limited enrollment data and the problem of a posteriori decision threshold setting. Experiments are carried out on the realistic telephone speech database SESP. State-of-the-art performance levels are obtained, which validates the technical approaches developed and assessed during the project as well as the working infrastructure which facilitated cooperation between the partners.
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| 3. |
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| 4. |
- Heusermann, W, et al.
(författare)
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Exosomes surf on filopodia to enter cells at endocytic hot spots, traffic within endosomes, and are targeted to the ER
- 2016
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Ingår i: The Journal of cell biology. - : Rockefeller University Press. - 1540-8140 .- 0021-9525. ; 213:2, s. 173-184
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Tidskriftsartikel (refereegranskat)abstract
- Exosomes are nanovesicles released by virtually all cells, which act as intercellular messengers by transfer of protein, lipid, and RNA cargo. Their quantitative efficiency, routes of cell uptake, and subcellular fate within recipient cells remain elusive. We quantitatively characterize exosome cell uptake, which saturates with dose and time and reaches near 100% transduction efficiency at picomolar concentrations. Highly reminiscent of pathogenic bacteria and viruses, exosomes are recruited as single vesicles to the cell body by surfing on filopodia as well as filopodia grabbing and pulling motions to reach endocytic hot spots at the filopodial base. After internalization, exosomes shuttle within endocytic vesicles to scan the endoplasmic reticulum before being sorted into the lysosome as their final intracellular destination. Our data quantify and explain the efficiency of exosome internalization by recipient cells, establish a new parallel between exosome and virus host cell interaction, and suggest unanticipated routes of subcellular cargo delivery.
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