| 31. |
- Bokvist, K, et al.
(författare)
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Co-localization of L-type Ca2+ channels and insulin-containing secretory granules and its significance for the initiation of exocytosis in mouse pancreatic B-cells
- 1995
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Ingår i: EMBO Journal. - 1460-2075. ; 14:1, s. 50-57
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Tidskriftsartikel (refereegranskat)abstract
- We have monitored L-type Ca2+ channel activity, local cytoplasmic Ca2+ transients, the distribution of insulin-containing secretory granules and exocytosis in individual mouse pancreatic B-cells. Subsequent to the opening of the Ca2+ channels, exocytosis is initiated with a latency < 100 ms. The entry of Ca2+ that precedes exocytosis is unevenly distributed over the cell and is concentrated to the region with the highest density of secretory granules. In this region, the cytoplasmic Ca2+ concentration is 5- to 10-fold higher than in the remainder of the cell reaching concentrations of several micromolar. Single-channel recordings confirm that the L-type Ca2+ channels are clustered in the part of the cell containing the secretory granules. This arrangement, which is obviously reminiscent of the 'active zones' in nerve terminals, can be envisaged as being favourable to the B-cell as it ensures that the Ca2+ transient is maximal and restricted to the part of the cell where it is required to rapidly initiate exocytosis whilst at the same time minimizing the expenditure of metabolic energy to subsequently restore the resting Ca2+ concentration.
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| 32. |
- Bolmeson, Caroline, et al.
(författare)
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Differences in islet-enriched miRNAs in healthy and glucose intolerant human subjects.
- 2011
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Ingår i: Biochemical and Biophysical Research Communications. - : Elsevier BV. - 1090-2104 .- 0006-291X. ; Dec, s. 16-22
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Tidskriftsartikel (refereegranskat)abstract
- Many microRNAs (miRNAs) are known to be cell-type specific and are implicated in development of diseases. We investigated the global expression pattern of miRNAs in human pancreatic islets compared to liver and skeletal muscle, using bead-based technology and quantitative RT-PCR. In addition to the known islet-specific miR-375, we also found enrichment of miR-127-3p, miR-184, miR-195 and miR-493∗ in the pancreatic islets. The expression of miR-375, miR-127-3p, miR-184 and the liver-enriched miR-122 were positively correlated to insulin biosynthesis, while the expression of miR-127-3p and miR-184 were negatively correlated to glucose-stimulated insulin secretion (GSIS). These correlations were absent in islets of glucose intolerant donors (HbA1c⩾6.1). We suggest the presence of an islet-specific miRNA network, which consists of at least miR-375, miR-127-3p and miR-184, potentially involved in insulin secretion. Our results provide new insight into miRNA-mediated regulation of insulin secretion in healthy and glucose intolerant subjects.
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| 33. |
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| 34. |
- Braun, Matthias, et al.
(författare)
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Regulated Exocytosis of GABA-containing Synaptic-like Microvesicles in Pancreatic {beta}-cells.
- 2004
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Ingår i: Journal of General Physiology. - : Rockefeller University Press. - 0022-1295 .- 1540-7748. ; 123:3, s. 191-204
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Tidskriftsartikel (refereegranskat)abstract
- We have explored whether {gamma}-aminobutyric acid (GABA) is released by regulated exocytosis of GABA-containing synaptic-like microvesicles (SLMVs) in insulin-releasing rat pancreatic ß-cells. To this end, ß-cells were engineered to express GABAA-receptor Cl--channels at high density using adenoviral infection. Electron microscopy indicated that the average diameter of the SLMVs is 90 nm, that every ß-cell contains ~3,500 such vesicles, and that insulin-containing large dense core vesicles exclude GABA. Quantal release of GABA, seen as rapidly activating and deactivating Cl--currents, was observed during membrane depolarizations from -70 mV to voltages beyond -40 mV or when Ca2+ was dialysed into the cell interior. Depolarization-evoked GABA release was suppressed when Ca2+ entry was inhibited using Cd2+. Analysis of the kinetics of GABA release revealed that GABA-containing vesicles can be divided into a readily releasable pool and a reserve pool. Simultaneous measurements of GABA release and cell capacitance indicated that exocytosis of SLMVs contributes ~1% of the capacitance signal. Mathematical analysis of the release events suggests that every SLMV contains 0.36 amol of GABA. We conclude that there are two parallel pathways of exocytosis in pancreatic ß-cells and that release of GABA may accordingly be temporally and spatially separated from insulin secretion. This provides a basis for paracrine GABAergic signaling within the islet.
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| 35. |
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| 36. |
- Börstler, Jürgen, 1960-, et al.
(författare)
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Transitioning to OOP/Java : A never ending story
- 2008
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Ingår i: Reflections on the teaching of programming. - Berlin, Heidelberg : Springer. - 9783540779339 ; , s. 80-97
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Bokkapitel (refereegranskat)
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| 37. |
- Carlquist, Magnus, et al.
(författare)
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Physiological heterogeneities in microbial populations and implications for physical stress tolerance
- 2012
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Ingår i: Microbial Cell Factories. - : Springer Science and Business Media LLC. - 1475-2859. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Background: Traditionally average values of the whole population are considered when analysing microbial cell cultivations. However, a typical microbial population in a bioreactor is heterogeneous in most phenotypes measurable at a single-cell level. There are indications that such heterogeneity may be unfavourable on the one hand (reduces yields and productivities), but also beneficial on the other hand (facilitates quick adaptation to new conditions - i.e. increases the robustness of the fermentation process). Understanding and control of microbial population heterogeneity is thus of major importance for improving microbial cell factory processes. Results: In this work, a dual reporter system was developed and applied to map growth and cell fitness heterogeneities within budding yeast populations during aerobic cultivation in well-mixed bioreactors. The reporter strain, which was based on the expression of green fluorescent protein (GFP) under the control of the ribosomal protein RPL22a promoter, made it possible to distinguish cell growth phases by the level of fluorescence intensity. Furthermore, by exploiting the strong correlation of intracellular GFP level and cell membrane integrity it was possible to distinguish subpopulations with high and low cell membrane robustness and hence ability to withstand freeze-thaw stress. A strong inverse correlation between growth and cell membrane robustness was observed, which further supports the hypothesis that cellular resources are limited and need to be distributed as a trade-off between two functions: growth and robustness. In addition, the trade-off was shown to vary within the population, and the occurrence of two distinct subpopulations shifting between these two antagonistic modes of cell operation could be distinguished. Conclusions: The reporter strain enabled mapping of population heterogeneities in growth and cell membrane robustness towards freeze-thaw stress at different phases of cell cultivation. The described reporter system is a valuable tool for understanding the effect of environmental conditions on population heterogeneity of microbial cells and thereby to understand cell responses during industrial process-like conditions. It may be applied to identify more robust subpopulations, and for developing novel strategies for strain improvement and process design for more effective bioprocessing.
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| 38. |
- Carlsson, Lena, et al.
(författare)
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Association of cystatin C with prostasomes in human seminal plasma
- 2011
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Ingår i: International Journal of Andrology. - : Wiley. - 0105-6263 .- 1365-2605. ; 33:4, s. 363-368
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Tidskriftsartikel (refereegranskat)abstract
- It was recently elucidated that cystatin C, a protein targeted to the classical secretory pathway by its signal peptide sequence, can also be secreted in association with exosomes. Accordingly, we wanted to investigate whether there is a secretory link between cystatin C and prostasomes in human seminal plasma. Cystatin C concentrations in seminal plasma from 50 men including 6 vasectomized men were measured by turbidimetry on an Architect Ci8200. Some of the seminal plasma samples were also analysed utilizing an Epics Profile XL-MCL cytometer. We found high concentrations of cystatin C in seminal plasma. The 2.5-97.5 percentiles, performed by bootstrap estimation, were 25.8 [95% confidence interval (CI): 22.3-29.4] to 77.0 mg/L (95% CI: 71.9-82.1). Cystatin C is present in approximately 50 times higher concentration in seminal plasma compared with blood plasma. There was no clear difference as regards seminal plasma content of cystatin C between vasectomized men and the rest of the group. Immunoblot analysis with chicken anti-cystatin C antibody revealed a firm association of cystatin C with prostasomes. Flow cytometric analysis demonstrated that cystatin C was linked to prostasomes also meaning an at least partial prostasomal membrane surface localization.
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| 39. |
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| 40. |
- Cataldo, Luis Rodrigo, et al.
(författare)
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The human batokine EPDR1 regulates β-cell metabolism and function
- 2022
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Ingår i: Molecular Metabolism. - : Elsevier BV. - 2212-8778. ; 66
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Ependymin-Related Protein 1 (EPDR1) was recently identified as a secreted human batokine regulating mitochondrial respiration linked to thermogenesis in brown fat. Despite that EPDR1 is expressed in human pancreatic β-cells and that glucose-stimulated mitochondrial metabolism is critical for stimulus-secretion coupling in β-cells, the role of EPDR1 in β-cell metabolism and function has not been investigated. Methods: EPDR1 mRNA levels in human pancreatic islets from non-diabetic (ND) and type 2 diabetes (T2D) subjects were assessed. Human islets, EndoC-βH1 and INS1 832/13 cells were transfected with scramble (control) and EPDR1 siRNAs (EPDR1-KD) or treated with human EPDR1 protein, and glucose-stimulated insulin secretion (GSIS) assessed by ELISA. Mitochondrial metabolism was investigated by extracellular flux analyzer, confocal microscopy and mass spectrometry-based metabolomics analysis. Results: EPDR1 mRNA expression was upregulated in human islets from T2D and obese donors and positively correlated to BMI of donors. In T2D donors, EPDR1 mRNA levels negatively correlated with HbA1c and positively correlated with GSIS. EPDR1 silencing in human islets and β-cell lines reduced GSIS whereas treatment with human EPDR1 protein increased GSIS. Epdr1 silencing in INS1 832/13 cells reduced glucose- and pyruvate- but not K+-stimulated insulin secretion. Metabolomics analysis in Epdr1-KD INS1 832/13 cells suggests diversion of glucose-derived pyruvate to lactate production and decreased malate-aspartate shuttle and the tricarboxylic acid (TCA) cycle activity. The glucose-stimulated rise in mitochondrial respiration and ATP/ADP-ratio was impaired in Epdr1-deficient cells. Conclusion: These results suggests that to maintain glucose homeostasis in obese people, upregulation of EPDR1 may improve β-cell function via channelling glycolysis-derived pyruvate to the mitochondrial TCA cycle.
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