1. Physiological levels of adrenaline fail to stop pancreatic beta cell activity at unphysiologically high glucose levelsNastja Sluga, Lidija Križančić Bombek, Jasmina Kerčmar, Srdjan Sarikas, Sandra Postić, Johannes Pfabe, Maša Skelin, Dean Korošak, Andraž Stožer, Marjan Rupnik, 2022, izvirni znanstveni članek Opis: Adrenaline inhibits insulin secretion from pancreatic beta cells to allow an organism to cover immediate energy needs by unlocking internal nutrient reserves. The stimulation of α2-adrenergic receptors on the plasma membrane of beta cells reduces their excitability and insulin secretion mostly through diminished cAMP production and downstream desensitization of late step(s) of exocytotic machinery to cytosolic Ca2+ concentration ([Ca2+]c). In most studies unphysiologically high adrenaline concentrations have been used to evaluate the role of adrenergic stimulation in pancreatic endocrine cells. Here we report the effect of physiological adrenaline levels on [Ca2+]c dynamics in beta cell collectives in mice pancreatic tissue slice preparation. We used confocal microscopy with a high spatial and temporal resolution to evaluate glucose-stimulated [Ca2+]c events and their sensitivity to adrenaline. We investigated glucose concentrations from 8-20 mM to assess the concentration of adrenaline that completely abolishes [Ca2+]c events. We show that 8 mM glucose stimulation of beta cell collectives is readily inhibited by the concentration of adrenaline available under physiological conditions, and that sequent stimulation with 12 mM glucose or forskolin in high nM range overrides this inhibition. Accordingly, 12 mM glucose stimulation required at least an order of magnitude higher adrenaline concentration above the physiological level to inhibit the activity. To conclude, higher glucose concentrations stimulate beta cell activity in a non-linear manner and beyond levels that could be inhibited with physiologically available plasma adrenaline concentration.
Ključne besede: adrenaline, islets, beta cells, cAMP, concentration dependency, [Ca2+]c oscillations, forskolin
Objavljeno v DKUM: 04.07.2024; Ogledov: 155; Prenosov: 10
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2. pH-dependence of glucose- dependent activity of beta cell networks in acute mouse pancreatic tissue sliceSandra Postić, Marko Gosak, Wen-Hao Tsai, Johannes Pfabe, Srdjan Sarikas, Andraž Stožer, Dean Korošak, Shi-Bing Yang, Marjan Rupnik, 2022, izvirni znanstveni članek Opis: Extracellular pH has the potential to affect various aspects of the pancreatic beta cell function. To explain this effect, a number of mechanisms was proposed involving both extracellular and intracellular targets and pathways. Here, we focus on reassessing the influence of extracellular pH on glucose-dependent beta cell activation and collective activity in physiological conditions. To this end we employed mouse pancreatic tissue slices to perform high-temporally resolved functional imaging of cytosolic Ca2+ oscillations. We investigated the effect of either physiological H+ excess or depletion on the activation properties as well as on the collective activity of beta cell in an islet. Our results indicate that lowered pH invokes activation of a subset of beta cells in substimulatory glucose concentrations, enhances the average activity of beta cells, and alters the beta cell network properties in an islet. The enhanced average activity of beta cells was determined indirectly utilizing cytosolic Ca2+ imaging, while direct measuring of insulin secretion confirmed that this enhanced activity is accompanied by a higher insulin release. Furthermore, reduced functional connectivity and higher functional segregation at lower pH, both signs of a reduced intercellular communication, do not necessary result in an impaired insulin release.
Ključne besede: insulin secretion, membrane excitability, potassium channels, beta cell network, collective activity, calcium waves, pancreatic islets, pH-dependence
Objavljeno v DKUM: 01.07.2024; Ogledov: 149; Prenosov: 4
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3. Dinamika enodimenzionalnih sistemovVladimir Grubelnik, Marko Marhl, 2024, univerzitetni, visokošolski ali višješolski učbenik z recenzijo Opis: Učbenik obravnava enodimenzionalne dinamične sisteme z elementarnim pristopom. Cilj je študentom omogočiti boljše razumevanje temeljnih načel dinamike sistemov, kot so določitev stacionarnih stanj, stabilnostna analiza, bifurkacije in dolgoročno obnašanje sistemov. Učbenik je zasnovan predvsem za študente fizike, vendar je uporaben tudi za druge smeri, kjer je matematično modeliranje dinamičnih sistemov del učnega načrta. Vsebinski sklopi učbenika zajemajo osnovne značilnosti dinamičnih sistemov, geometrijski pristop reševanja enodimenzionalnih sistemov, tokove na krožnici, bifurkacije in njihove značilnosti, enodimenzionalne preslikave (mape) ter številne primere enodimenzionalnih sistemov v fiziki, biologiji in kemiji. Primeri so izbrani tako, da študentom pomagajo razvijati intuicijo za dinamiko bolj kompleksnih več dimenzionalnih sistemov, s katerimi se soočajo v vsakdanjem življenju.
Ključne besede: dinamika sistemov, povratne zanke, stabilnostna analiza, bifurkacije, logistična mapa, kaos
Objavljeno v DKUM: 13.02.2024; Ogledov: 368; Prenosov: 40
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5. Collective sensing of ß-cells generates the metabolic codeDean Korošak, Marjan Rupnik, 2018, izvirni znanstveni članek Ključne besede: collective sensing, pancreatic islets, spin glass models, metabolic code, Ca2+ imaging, Ca2+ signaling, correlations, intercellular communication
Objavljeno v DKUM: 25.01.2018; Ogledov: 1646; Prenosov: 129
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6. Quantifying soil complexity using network models of soil porous structureMarko Samec, A. Santiago, J. P. Cardenas, R. M. Benito, A. M. Tarquis, Sacha Jon Mooney, Dean Korošak, 2013, izvirni znanstveni članek Opis: This paper describes an investigation into the properties of spatially embedded complex networks representing the porous architecture of soil systems. We suggest an approach to quantify the complexity of soil pore structure based on the node-node link correlation properties of the networks. We show that the complexity depends on the strength of spatial embedding of the network and that this is related to the transition from a non-compact to compact phase of the network.
Ključne besede: soil complexity, soil pore networks, complex systems
Objavljeno v DKUM: 21.07.2017; Ogledov: 1476; Prenosov: 336
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7. Functional connectivity in islets of Langerhans from mouse pancreas tissue slicesAndraž Stožer, Marko Gosak, Jurij Dolenšek, Matjaž Perc, Marko Marhl, Marjan Rupnik, Dean Korošak, 2013, izvirni znanstveni članek Opis: We propose a network representation of electrically coupled beta cells in islets of Langerhans. Beta cells are functionally connected on the basis of correlations between calcium dynamics of individual cells, obtained by means of confocal laser-scanning calcium imaging in islets from acute mouse pancreastissue slices. Obtained functional networks are analyzed in the light of known structural and physiological properties of islets. Focusing on the temporal evolution of the network under stimulation with glucose, we show thatthe dynamics are more correlated under stimulation than under non-stimulated conditions and that the highest overall correlation, largely independent of Euclidean distances between cells, is observed in the activation and deactivation phases when cells are driven by the external stimulus. Moreover, we find that the range of interactions in networks during activity shows a clear dependence on the Euclidean distance, lending support to previous observations that beta cells are synchronized via calcium waves spreading throughout islets. Most interestingly, the functional connectivity patterns between beta cells exhibit small-world properties, suggesting that beta cells do not form a homogeneous geometric network but are connected in a functionally more efficient way. Presented results provide support for the existing knowledge of beta cell physiology from a network perspective and shedimportant new light on the functional organization of beta cell syncitia whose structural topology is probably not as trivial as believed so far.
Ključne besede: islets of Langerhans, mouse pancreas
Objavljeno v DKUM: 16.06.2017; Ogledov: 1540; Prenosov: 417
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8. Schottkyjeva bariera : moderni pogledi na star problemDean Korošak, Bruno Cvikl, 1998, pregledni znanstveni članek Opis: The description of the metal semiconductor contact in the framework of the general model incorporating the interfacial control layer between the metal and the ordered semiconductor is given. Special attention is given to the iCB Schottky structures for nonzero acceleration voltage featuring the disordered interfacial control layer characterized by the metal atoms incorporated into the semiconductor lattice and the DIGS continuum. The expression for the Schottky barrier height variation in ICB structures is given.
Ključne besede: površine, kovine, polprevodniki, tanke plasti
Objavljeno v DKUM: 10.07.2015; Ogledov: 1318; Prenosov: 50
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9. Schottkyjeva bariera : moderni pogledi na star problemDean Korošak, Bruno Cvikl, 1998, pregledni znanstveni članek Opis: V drugem delu prispevka opisujemo transportne lastnosti stika kovine in polprevodnika. V začetku je podan pregledni opis različnih mehanizmov prenosa naboja v idealni Schottkyjevi diodi. V nadaljevanju je opisan transport naboja v neidealnem stiku z vmesno kontrolno plastjo, ki nastane pri nanašanju z metodo CIS. Dodatni transport naboja v takšnih Schottkyjevih heterostrukturah lahko povzroči kontinuum elektronskih stanj, ki se pojavi na meji med urejenim in neurejenim delom polprevodnika. Opisan je vpliv takšnega transporta naboja na tokovno karakteristiko diode.
Ključne besede: vakuumska tehnika, površine, kovine, polprevodniki, tanke plasti, curek ioniziranih skupkov
Objavljeno v DKUM: 10.07.2015; Ogledov: 1859; Prenosov: 41
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