Dissertationen: „Influx de calcium“

1

Wang, Fang. „DOES CALCIUM INFLUX THROUGH T-TYPE CALCIUM CHANNEL INDUCE CARDIOMYOCYTE PROLIFERATION?“ Diss., Temple University Libraries, 2012. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/214814.

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Physiology
Ph.D.
Cardiovascular disease remains the number one cause or mortally in the western world. Heart failure is the most rapidly growing cardiovascular disease (Hobbs, 2004; Levy, et al., 2002). Heart failure, by definition, is progressive deteriorating function of the heart due to progressive cardiac myocytes loss. Though after decades of endeavor of searching the pathophysiology and treatments for heart failure, it remains highly lethal. Therefore, it is vital to find novel therapies to help treat such chronic disease. Replace the lost cardiomyocyte with new ones could restore cardiac function and reduce mortality. The purpose of this study is to investigate on how TTCCs (T-type calcium channels) affect cardiomyocyte proliferation. In mice after birth, the major TTCC expressed in the heart is Cav3.1/α1G, and therefore we used Cav3.1/α1G transgenic (TG), knockout (-/-) and wild type mice respectively to define the role of TTCC in cardiomyocyte proliferation. In neonatal mouse ventricular myocyte (NMVMs) right after birth, there is almost no TTCC after birth in α1G-/- NMVMs, whereas there are around 35% NMVMs in wild type (WT) show TTCC. On day 7 after birth, there are no T-type calcium currents in both α1G-/- NMVMs and WT NMVMs. Using BrdU, a DNA synthesis marker, we identified plenty of BrdU positive cardiomyocyte during the first seven days after birth. Cardiomyocyte is special due to its double nucleation property. Our cell cycle studies showed that there is significant difference in cell cycle distribution between α1G-/- and WT NMVMs on day seven after birth. Significantly more NMVMs are arrested in G1 phase in α1G-/-, compared to WT NMVMs. Even until 2 month old, there are still significantly more mono-nucleated cardiomyocyte in α1G-/- than in WT. In conclusion, all these evidence showed that blocking T-type calcium channel could partially prevent binucleation from happening and stop cardiomyocytes withdrawal from cell cycle. Mononucleated cardiomyocyte is still able to proliferate. Hence, mononucleated cardiomyocytes in adult still have potential to proliferation because these cardiomyoctes are arrested in their cell-cycle before their terminal differentiation, which could offer a novel approach for cardiac repair.
Temple University--Theses

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2

Yang, Meng. „Calcium influx, celluar signaling and the biology of candida albicans“. Thesis, University of Aberdeen, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499748.

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FIG1 is a gene that encodes a transmembrane protein involved in calcium influx a process that is important for stress responses in pathogens fungi such as Candida albicans. A Cafig1 null mutant took up less calcium ions in mating than control strains confirming its role in Ca²⁺ uptake. Furthermore, C. albicans strains with deletions of FIG1 in other calcium channel mutant backgrounds displayed distinctive phenotypes under vegetative growth conditions, which suggested that Fig1 may be a regulator of other calcium influx systems. Using GFP and LacZ reporter constructs it was shown that in C. albicans FIG1 was induced by mating pheromone and during the interactions of strains of compatible mating type. Localization of Fig1-GFP studied by con-focal imaging showed that the protein had a peri-nuclear distribution and was also found in the plasma membrane at the tips of shmoos. The protein appeared to be located within microdomains and the protein sequence was found to contain a putative site for cysteine palmitoylation that may promote such localization. Because the expression of FIG1 was strongly induced during mating, the induction of FIG1 was used to try to detect where mating took place during experimental infection in mice. Surprisingly FIG1 expression could be observed in the murine gut in control inoculations using C. albicans strains that could not undergo mating. Therefore FIG1 expression is not always strictly mating-dependent. MAP kinases and calcium-calcineurin signalling pathways, in which Fig1 is involved, were studied using bioinformatics approaches. It was shown that these signalling pathways contain conserved signalling components taking part in signal transduction via phosphorelay but they had diverged receptors, sensors, effectors, and phosphorelay regulators across different fungal species.

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3

Pejović, Vojislav. „Glutamate induced potentiation of calcium influx in primary hippocampal culture neurons“. [S.l.] : [s.n.], 2001. http://ArchiMeD.uni-mainz.de/pub/2001/0027/diss.pdf.

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4

McVicker, Clare Geldard. „Calcium influx mechanisms during mediator-induced responses in human airway smooth muscle“. Thesis, King's College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404814.

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5

Makarewich, Catherine Anne. „MICRODOMAIN BASED CALCIUM INFLUX PATHWAYS THAT REGULATE PATHOLOGICAL CARDIAC HYPERTROPHY AND CONTRACTILITY“. Diss., Temple University Libraries, 2014. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/266828.

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Molecular and Cellular Physiology
Ph.D.
Pathological cardiac stressors, including persistent hypertension or damage from ischemic heart disease, induce a chronic demand for enhanced contractile performance of the heart. The cytosolic calcium (Ca2+) transient that regulates myocyte contraction must be persistently increased in disease states in order to maintain cardiac output to sustain the metabolic requirements of the body. Associated with this enhanced intracellular Ca2+ ([Ca2+]i) state is pathological cardiac myocyte hypertrophy, which results in large part from the activation of Ca2+-dependent activation of calcineurin (Cn)-nuclear factor of activated T cells (NFAT) signaling. The puzzling feature of this hypertrophic signaling is that the cytosolic [Ca2+] that controls contractility appears to be separate from the [Ca2+] which activates Cn-NFAT signaling. The overarching theme of this dissertation is to explore the source and spatial constraints of pathological hypertrophic signaling Ca2+ and to investigate how it is possible that sensitive and finely tuned Ca2+-dependent signaling pathways are regulated in the background of massive Ca2+ fluctuations that oscillate between 100nM and upwards of 1-2μM during each cardiac contractile cycle. L-type Ca2+ channels (LTCCs) are a major source of Ca2+ entry in cardiac myocytes and are known to play an integral role in the initiation of myocyte excitation contraction-coupling (EC-coupling). We performed a number of experiments to show that a small population of LTCCs reside outside of EC-coupling domains within caveolin (Cav-3) signaling microdomains where they provide a local source of Ca2+ to activate Cn-NFAT signaling. We designed a Cav-targeted LTCC blocker that could eliminate Cn-NFAT activation but did not reduce myocyte contractility. The activity of Cav-targeted LTCCs could also be upregulated to enhance hypertrophic signaling without affecting contractility. Therefore, we believe that caveolae-localized LTCCs do not participate in EC-coupling, but instead act locally to control the coordinated activation of Cn-NFAT signaling that drives pathological remodeling. Transient Receptor Potential (TRP) channels are also thought to provide a source of Ca2+ for activation of hypertrophic signaling. The canonical family of TRP channels (TRPC) is expressed at low levels in normal adult cardiac tissue, but these channels are upregulated in disease conditions which implicates them as stress response molecules that could potentially provide a platform for hypertrophic Ca2+ signaling. We show evidence that TRPC channel abundance and function increases in cardiac stress conditions, such as myocardial infarction (MI), and that these channels are associated with hypertrophic responses, likely through a Ca2+ microdomain effect. While we found that TRPC channels housed in caveolae membrane microdomains provides a source of [Ca2+] for induction of cardiac hypertrophy, this effect also requires interplay with LTCCs. We also found that TRPC channels have negative effects on cardiac contractility, which we believe are due to local activation of Ca2+/calmodulin-dependent protein kinase (CaMKII) and subsequent modulation of ryanodine receptors (RyRs). Further, we found that inhibiting TRPC channels in a mouse model of MI led to increased basal myocyte contractility and reduced hypertrophy and cardiac structural and functional remodeling, as well as increased survival. Collectively, the data presented in this dissertation provides comprehensive evidence that Ca2+ regulation of Cn-NFAT signaling and resultant pathological hypertrophy can be coordinated by spatially localized and regulated Ca2+ channels. The compartmentalization of LTCCs and TRPC channels in caveolae membrane microdomains along with pathological hypertrophy signaling effectors makes for an attractive explanation for how Ca2+-dependent signaling pathways are regulated under conditions of continual Ca2+ transients that mediate cardiac contraction during each heart beat. Elucidation of additional Ca2+ signaling microdomains in adult cardiac myocytes will be important in more comprehensively resolving how myocytes differentiate between signaling versus contractile Ca2+.
Temple University--Theses

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6

Kortekaas, Phaedra. „Development and function of calcium influx in pyramidal neurons of the hippocampal CA1 region“. [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2000. http://dare.uva.nl/document/55584.

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7

DeJong, Danica. „Calcium Alleviates Symptoms in Hyperkalemic Periodic Paralysis by Reducing the Abnormal Sodium Influx“. Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23487.

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Hyperkalemic periodic paralysis, HyperKPP, is an inherited progressive disorder of the muscles caused by mutations in the voltage gated sodium channel (NaV1.4). The objectives of this thesis were to develop a technique for measurement symptoms in vivo using electromyography (EMG) and to determine the mechanism by which Ca2+ alleviates HyperKPP symptoms, since this is unknown. Increasing extracellular [Ca2+] ([Ca2+]e) from 1.3 to 4 mM did not result in any increases in45Ca2+ influx suggesting no increase in intracellular [Ca2+] ([Ca2+]i) acting on an intracellular signaling pathway or on an ion channel such as the Ca2+sensitive K+ channels. HyperKPP muscles have larger TTX-sensitive22Na+ influx than wild type muscles because of the defective NaV1.4 channels. When [Ca2+] was increased from 1.3 to 4 mM, the abnormal 22Na+ influx was completely abolished. Thus, one mechanism by which Ca2+alleviates HyperKPP symptoms is by reducing the abnormal Na+ influx caused by the mutation in the NaV1.4 channel.

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8

Hoffman, Nicholas. „Mitochondrial Calcium Influx is Determined by Multiple Protein Components Including SLC25A23 and MICU1“. Diss., Temple University Libraries, 2014. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/287159.

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Biochemistry
Ph.D.
Ca2+ control mechanisms employed by the cell at the plasma membrane include receptor operated, voltage-sensitive, and store operated channels for Ca2+ import. Upon entry into the cytosol, Ca2+ is sequestered by Ca2+ binding proteins, the endoplasmic reticulum (ER), or by mitochondria. The largest Ca2+ store in the cell is the ER where Ca2+ levels approach millimolar levels. The ER regulates cytosolic Ca2+ homeostasis by using Ca2+ binding proteins, the SERCA pump, second messenger Ca2+ release upon IP3 receptor activation, and Ca2+-induced Ca2+ release by ryanodine receptors. Basal cytosolic Ca2+ levels are maintained at around 100nM. The mitochondria begins clearing GPRC-depended cytosolic Ca2+elevation after a short time delay during which the cytosolic Ca2+ concentration exceeds 3M. Then, the mitochondria sacrifices a portion of its membrane potential to drive Ca2+ influx across the mitochondrial inner membrane into the matrix. The membrane potential of the mitochondria is created in part by the electron transport, which while transferring electrons, ejects protons from the matrix to the inner membrane space. The rapid mitochondrial Ca2+ uptake decreases mitochondrial membrane potential thus reducing or fully collapsing the mitochondria's ability to generate ATP. This uncoupling of the electron transport chain results in ROS production and decreased cell survival. Mitochondria provide the body with energy that allows a heart to beat, a brain to store memories, and fuels locomotive function. As a stand-alone energy generator, the mitochondria would be interesting, but not dynamic. The dynamic flow of information to the mitochondria through Ca2+ signaling with all the components of symbiotic precision is a true biological phenomenon. In the mitochondria, a complex Ca2+ buffering system of channels, pores, and exchangers directly affects the conversion of chemical potential to ATP. Recent, discoveries of the Ca2+ uniporter (MCU) and other system components have provided the tools to tackle levels of mitochondrion physiologic studies that were not possible only a couple of years ago. There remains a great need for advancement in the understanding of mitochondrial bioenergetics, and undoubtedly, the mitochondria will be viewed as a determinant factor for survival. The mitochondrial inner membrane through its curious construction of 3:1 protein to lipid ratio, carefully regulates the permeability of ions and metabolites. The transport of Ca2+ and other small ions across the inner membrane is an essential signaling pathway for mitochondrial maintenance of metabolic functions, but the mechanisms are still unclear due to a lack of mitochondrial systems biology. For example, the oligomeric MCU with two transmembrane domains is a core component of the major Ca2+ import pathway in mitochondria, and ablation of MCU lowers mitochondrial Ca2+ uptake, however portions such as the highly conserved linker between the two transmembrane was unstudied until recently. Other complex components such as MICU1 and MCUR1, which negatively and positively regulate MCU, are beginning to have their mechanism solved. MICU1 is associated with the mitochondrial inner membrane and has two EF hands, which indicated a possible role in Ca2+ sensing. This role as a Ca2+ sensor proved to be necessary for proper MICU1 inhibition of MCU, but not determinant of MICU1/MCU interaction. MICU1, MCUR1, and MCU are modified in numerous diseases in which a particular component is disproportionately expressed. This is in part due to the classical coupling of gene function to associated transcription factor meaning that because MICU1, MCUR1, and MCU have a Ca2+ flux function, their transcription is also probably controlled by Ca2+ and is altered in chronic inflammation or hypoxic systems such as Ca2+ overload during ischemia/reperfusion. In spite of the low affinity of uniporter, mitochondrial Ca2+ overload occurs due to the close proximity of mitochondria to the ER, however physical tethering of the mitochondria and ER is still not widely accepted. When Ca2+ is physiologically cleared from the cytosol to the mitochondria, it acts as a synchronizing signal to the numerous EF hands present on inner membrane transmembrane proteins and matrix-targeted proteins. . Synchronization of mitochondrial activities is critical for efficiency which has direct implication for both cell growth or damage through the byproduct of inefficiency, mROS (superoxide). Therefore, the EF hands and other Ca2+ response elements enhance the ratio of ATP to superoxide, thus supporting mitogenic function and healthy growth. The inefficient flow of energy leads to dysfunction such as the release of reactive oxygen species (ROS) from the mitochondria. ROS carries its own energy in the chemical form of a radical. This translates into thermodynamically favorable but harmful cellular damage. Sustained import of Ca2+ results in electron transport malfunction followed by loss of membrane potential as seen in ischemia. A common EF hand motif exists on many calcium sensitive proteins. This helix-loop-helix topology recognizes a specific range of calcium concentrations based on the primary and tertiary structure of the domain. Thus, not all EF hands are active at a given physiological Ca2+ concentrations. The Ca2+ is situated in the loop portion by 12 key interactions in a pentagonal bipyramidal geometry. The position of 12th residue supplies two of the interacting oxygen atoms for Ca2+ binding and are conserved as either Glutamate or Aspartate. EF-hand containing proteins do not necessarily transport Ca2+ alone, as many other solutes have also been reported. The EF hand motif can be found on many mitochondrial sensors including LETM-1, MICU1, and non- Ca2+ transporters (Nakayama, Moncrief et al. 1992), suggesting Ca2+ is often the synchronizing signaling molecule but not necessarily transported by the mitochondrial channel of interest. The discovery of the uniporter (MCU) is an exciting event in the field, as many relationships between different transport mechanisms affecting Ca2+ and membrane potential will be elucidated. One such relationship that should be explored is between the uniporter and inorganic phosphate exchange. This relationship may modulate cell death through a critical uptake dynamic between adenine, phosphate and Ca2+ through alternative pathways such as solute carriers. Mitochondrial carriers are crucial for transport across the inner membrane. There are two groups of Ca2+ binding solute carriers in the mitochondria, the aspartate/glutamate carriers (Palmieri, Pardo et al. 2001) and the ATP-magnesium carriers (SCaMC) (Satrustegui, Pardo et al. 2007). Carrier proteins transport molecules by changing shape and therefore can be saturated. Solute carrier activators have been previously reported to include Ca2+, adenosine 3'5'-cyclic monophosphate, protein kinases, and inositol polyphosphates (Dransfield and Aprille 1993). Other previous work has also reported transport of multiple different solutes (Fiermonte, De Leonardis et al. 2004). The higher eukaryote, vertebrate calcium systems, should functionally if not physically interact with conserved lower eukaryote systems such as solute carriers. All known mitochondrial carriers are members of the same family based on three tandem repeats and are predicted to function as oligomers. The human family of these inner mitochondrial membrane proteins is SLC25, and members of the SLC25 family have been identified as the cause of Stanley Syndrome and Amish Microcephaly suggesting the importance of SLC25. SLC25A23 has been proposed to be an ATP-Mg/Pi exchange carrier that allows for both uptake and release of ATP-Mg from mitochondria. As a putative ADP/Pi translocase, it is an interesting component as both ADP and Pi have been shown to play a role in cell survival and cell death. This SLC25A family member is likely to be the critical regulator of these two dynamic molecules. These carriers are stimulated by submicromolar Ca2+ to regulate adenine nucleotide levels in the cytosol and mitochondria. Previous literature has shown SLC25A25 knockout to have little effect on mouse metabolism. SLC25A24 has been shown to be involved in ADP/ATP ratios in the mitochondrial matrix resulting in cytosolic Ca2+ buffering enhancement (21). The functions of SLC25A23 largely remain unknown. It should be pointed out that SLC25A23, SLC25A24, and SLC25A25, Ca2+ induced changes, are not necessarily based on Ca2+ as a channel solute. The ATP/ADP maintained by SLC25 family members may contribute to Ca2+ uptake in the mitochondria and therefore may play a role in cell death through PTP opening. PTP opening is a point of convergence for many cell death pathways. The PTP, which behaves as a voltage-operated channel, can be triggered to open by high mitochondrial Ca2+, ROS, or low membrane potential. In previous studies, SLC25A24 knockdown resulted in increased PTP opening and decreased Ca2+ buffering. Solute carrier family 25 (mitochondrial carrier; phosphate carrier), which includes SLC25A23, SLC25A24, and SLC25A25, transport solutes across the inner membrane, are predicted to form six transmembrane domains sensitive to Ca2+ due to four Ca2+ binding EF hand motifs, and localize to the mitochondria (del Arco and Satrustegui 1998; Iijima, Yamamoto et al. 2001). Based on membrane topology predictions, SLC25 isoforms contain six transmembrane domains with several EF hand motifs. Although the solute carriers in the SCaMC family have been hypothesized to transport adenine, (Aprille 1988) they have never been fully characterized. Mitochondrial solute carriers are found only in eukaryotes (Carafoli and Lehninger 1971; Uribe, Rangel et al. 1992; Palmieri 2004), however Sal1 in yeast has high sequence homology (Kucejova, Li et al. 2008). SLC25A25 knockout was reported to have little effects on mouse metabolism. SLC25A24 has been shown to be involved in ADP/ATP ratios in the mitochondrial matrix resulting in cytosolic Ca2+ buffering enhancement (Traba, Del Arco et al. 2011). The functions of these solute carriers in mitochondrial Ca2+ uptake and mitochondrial ROS are largely unknown.
Temple University--Theses

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9

Torihashi, Shigeko, Toyoshi Fujimoto, Claudia Trost, Shinsuke Nakayama und 茂子鳥橋. „Calcium oscillation linked to pacemaking of interstitial cells of Cajal;Requirement of calcium influx and localisation of TRP4 in caveolae“. The American Society for Biochemistry and Molecular Biology, 2002. http://hdl.handle.net/2237/7447.

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10

Obolensky, Anna. „Pharmacological modulation of calcium influx in freshly isolated rat lymphocytes and lymphoma cell lines“. Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249555.

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11

Perera, Naomi Tessa. „ZnT‐1 expression in the preimplantation mouse embryo and its effect on calcium influx“. Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/13519.

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ZnT-1 expression in the pre-implantation mouse embryo and its effect on calcium influx Pre-implantation embryos develop into 9 stages over the first 5 days post-fertilisation. Calcium influx from the external environment via calcium channels, including the L-type and T-type calcium channels, is critical for embryonic gene activation and cell proliferation. In cardiomyocytes these channels are regulated by the ubiquitously expressed zinc-transporter protein ZnT-1. When plasma membrane bound, ZnT-1 facilitates zinc-efflux. Free cellular zinc regulates ZnT-1 expression, with an increase in zinc inducing transcription. In this study, ZnT-1 mRNA and protein expression were investigated in pre-implantation embryo stages using qPCR and immunofluorescence. Embryos were cultured in vitro in zinc-supplemented media and compared to embryos cultured in the absence of zinc and to in vivo developed embryos. ZnT-1 mRNA was expressed at all stages and the presence of zinc increased mRNA expression a the late 2-cell stage only. There was no difference in expression between in vivo developed and cultured embryos. ZnT-1 protein was expressed from the early 2-cell stage onwards; not affected by zinc culture and localized to the plasma membrane at the late 2-cell stage only. Calcium imaging was performed to examine whether ZnT-1 membrane localization altered calcium influx. Experiments on early and late 2-cell embryos showed that there was no difference in calcium influx when ZnT-1 was localized to the plasma membrane. In summary ZnT-1 transcription was induced by zinc at the late 2-cell stage. Protein expression was not affected by zinc culture but was developmentally regulated, localizing to the plasma-membrane at the late 2-cell stage without effect on calcium influx.

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12

Spasevska, Ivana. „The role of EGR-1 and calcium influx in the antitumor activity of anti-CD20 monoclonal antibodies“. Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1304/document.

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Les anticorps monoclonaux (AcM) anti-CD20 sont essentiels pour le traitement du lymphome non hodgkinien et de la leucémie lymphoïde chronique (LLC). Les AcM agissent soit en activant directement la signalisation apoptotique dans les cellules cibles, soit via le système immunitaire. Dans une étude préclinique, nous avons montré que le traitement avec AcM anti-CD20, rituximab et GA101, induit l'expression de la protéine early growth response 1 (EGR-1) (Dalle et al., 2011). EGR-1 est un facteur de transcription régulé par le calcium (Ca2+) et CD20 est impliqué dans la régulation du flux calcique transmembranaire. Nous avons donc étudié le rôle d'EGR-1 et du flux Ca2+ dans l'activité cytotoxique des AcM anti-CD20. Nous avons montré qu'EGR-1 est rapidement induit suite à l'exposition au rituximab et à GA101. La baisse de l'expression d'EGR-1 par shRNA a supprimé l'effet cytotoxique du GA101 à la fois in vitro et in vivo, indiquant qu'EGR-1 est requis pour la mort cellulaire médiée par CD20. De plus, la surexpression d'EGR-1 augmente la sensibilité au GA101 in vitro et in vivo. En outre, nos résultats indiquent que les AcM anti-CD20 induisent un flux Ca2+. Le blocage du flux Ca2+ par inhibiteurs de canaux calciques (ICC) a aboli l'induction d'EGR-1 ainsi que l'efficacité du GA101 in vivo et ex vivo dans des échantillons de LLC. Plus important, nos données indiquent que les patients recevant des ICC ont une moins bonne réponse au traitement par les AcM anti-CD20. En conclusion, nous avons identifié EGR-1 comme potentiel biomarqueur pour prédire la réponse à la thérapie anti-CD20 et démontré que les ICC ont un impact négatif sur l'efficacité des AcM anti-CD20 chez les patients
Anti-CD20 monoclonal antibodies (mAbs) are an essential component of the treatment of patients with non-Hodgkin's lymphoma and chronic lymphocytic leukemia (CLL). They mediate their antitumor effects by activating the immune system or by direct apoptotic signaling in target cells. In a previous preclinical study, we showed that treatment with anti-CD20 mAbs, rituximab and GA101, resulted in upregulated expression of early growth factor 1 (EGR-1) (Dalle et al. 2011). EGR-1 is a calcium (Ca2+) regulated transcription factor and CD20 is hypothesized to regulate transmembrane Ca2+ flux. Therefore, we aimed to assess the role of EGR-1 and Ca2+ flux in the cytotoxic activity of anti-CD20 mAbs. We have shown that EGR-1 expression is rapidly upregulated in CD20+ cells following rituximab and GA101 exposure. Decreasing EGR-1 expression by shRNA abolishes the direct cytotoxic effect of GA101 both in vitro and in vivo, indicating that EGR-1 is required for CD20-mediated cell death. Additionally, the overexpression of EGR-1 enhances the cytotoxic activity of GA101 both in vitro and in vivo. Furthermore, our results indicate that anti-CD20 mAbs induce calcium influx. Blocking the Ca2+ flux with calcium channel blockers (CCB) abolishes EGR-1 induction and impaires the GA101 efficacy in vivo and ex vivo in CLL blood samples. More importantly, our data indicate that patients receiving CCBs and anti-CD20 therapy have worst progression free survival and overall survival. In conclusion we have identified EGR-1 as a potential biomarker to predict response to anti-CD20 therapy. We demonstrated that co-treatement with CCBs negatively impacts the outcome of patients receiving anti-CD20 mAbs

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13

Cifelli, Carlo. „Impairment of force development in K(ATP) channel deficient skeletal muscle involves calcium ion influx through L-type calcium ion channels“. Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/27342.

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ATP-sensitive potassium (KATP) channels link membrane excitability to metabolism. They are regulated by intracellular nucleotides and other factors, and have been shown to play a role in development of skeletal muscle force, but controversy surrounds their role during fatigue. The aim of this research project was to determine the role of KATP channel under conditions that allow for better assessment of changes in force during fatigue, by virtue of using a smaller whole muscle model less subject to anoxia. Thus, the first objective was to determine the effect of the loss of KATP channel activity on force during fatigue in small FDB muscle bundles. KATP channel deficient fibers had faster and greater decreases in peak tetanic force during fatigue, developed greater resting tension, and had lower force recovery following fatigue compared to control wild type muscles. The second objective was to determine whether the functional impairment in skeletal muscle without KATP channel activity was due to an increase in Ca 2+ influx. When [Ca2+]e was reduced or L-type Ca2+ channels partially blocked, Kir6.2-/- FDB muscle had slower fatigue development, less resting tension, and had an improved force recovery. A novel phenomenon was observed while studying the effect of KATP channel activity in vitro. During a second bout of fatigue the decrease in peak tension was significantly lower than the decrease during the first bout of fatigue. Furthermore, the deleterious effects of the loss of KATP channel activity during an initial fatigue were absent during the second fatigue in FDB exposed to glibenclamide. It is concluded (i) that the KATP channel is important to prevent impairment of function during fatigue, (ii) that this impairment of function is due to an increase in Ca2+ influx through L-type Ca2+ channels, causing Ca2+ overload, and (iii) that fatigue resistance increases while the dependency on the KATP channel to prevent function impairment and fiber damage decreases following one fatigue bout at 37°C; a phenomenon here termed fatigue pre-conditioning.

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Shailes, Sarah. „Regulation of calcium influx and reactive oxygen species production during infection of legumes by rhizobia“. Thesis, University of East Anglia, 2014. https://ueaeprints.uea.ac.uk/48752/.

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Nod factor (NF) can induce two separate calcium responses in legume root hairs. Nuclear-associated calcium spiking is central to the symbiosis signalling (Sym) pathway, which is necessary for the activation of genes required for nodule formation and bacterial infection. In addition NF activates a tip-focused calcium influx, which is less-well studied but is thought to be involved in bacterial infection. NF also activates ROS transient production at the tip of root hair cells. In this thesis I used fluorescent probes (Ca2+-sensitive Cameleons YC2.1 and YC3.6 and the ROS-sensitive CM-H2DCFDA dye) to characterise the NF-induced calcium influx and ROS transient responses in Medicago truncatula. Along with being spatially and temporally co-incident, the responses require similar concentrations of NF to be activated, are inhibited by the NADPH oxidase inhibitor diphenyleneiodonium and are dependent on the NF receptor NFP but independent of the Sym pathway components DMI1 and DMI2. These results suggest the NF-induced calcium influx and ROS transient are part of a common signalling pathway during bacterial infection. ROP signalling is associated with ROS production and calcium influx during developmental root hair elongation. I assessed the role of ROPs during rhizobial infection in M. truncatula and found a ROP-activating protein, MtGAP1, was upregulated in root hairs during bacterial infection and is involved in normal root hair curling and infection thread development. Two pieces of evidence directly link ROP signalling with the NF-induced calcium influx: gap1 mutants were hypersensitive for induction of the calcium influx, and there was a reduction in the number of calcium influx responses in ROP9 RNAi knockdown lines. Drawing parallels between developmental root hair elongation and bacterial infection I propose a model for the regulation of ROP signalling by NF leading to root hair curling, the activation of the calcium influx and ROS transient, and infection thread formation.

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15

Khawaja, Rabia Raheel. „Role of calcium influx through glutamate receptors in white matter brain injury and oligodendrocyte regeneration“. Diss., Temple University Libraries, 2019. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/583654.

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Biomedical Sciences
Ph.D.
Calcium-influx through ionotropic glutamate receptors expressed on non-excitable cells, such as CNS glia, may regulate important cell events via intracellular signaling mechanisms. Oligodendrocytes and oligodendrocyte progenitors (OPCs), two glial populations supporting CNS myelination and myelin repair, express AMPA and NMDA receptors. Although calcium-influx through these receptors is thought to cause glutamate excitotoxicity to oligodendrocytes in CNS injuries, more recent studies suggest that AMPA or NMDA receptor-mediated synaptic transmission between neurons and OPCs plays a positive role in neuronal activity-dependent oligodendrocyte development and regeneration. Given the opposing roles of glutamate receptors in oligodendrocyte death and repair, the clinical relevance of these receptors in white matter injuries remain unclear. Another major challenge for exploring the role of these receptors in white matter injuries is that OPCs and neurons express a similar complement of AMPA and NMDA receptor subunits, which has complicated the interpretation of pharmacological manipulations and global genetic deletion approaches. To define the cell autonomous role of AMPA and NMDA receptor-mediated calcium signaling in oligodendroglia, I abolished the calcium influx through glutamate receptors using two different genetic approaches, and examined their impacts on oligodendrocyte development, injury-induced cell death, and regeneration. First, I employed a new mouse line which allows overexpression of GluA2, the calcium-impermeable AMPA receptor subunit, in a Cre activity-dependent manner. After crossing these mice with OPC- or oligodendrocyte-lineage-specific Cre mice, I applied hypoxic-ischemic injury to these multiple transgenic mice. Surprisingly, even though AMPA receptor-mediated calcium influx was blocked in OPCs, oligodendrogenesis or myelin integrity was not affected. However, GluA2 overexpression significantly promoted oligodendrocyte regeneration and OPC proliferation after injury, while the same manipulation in oligodendrocytes did not protect them from the initial cell loss. Moreover, GluA2 overexpression also stimulated transcriptional activities linked to myelinogenesis, even without injury. Second, I used conditional knockout mice for Grin1, the gene encoding an essential subunit of NMDA receptor complexes. As with GluA2 overexpressing mice, the removal of NMDA receptors from OPCs or all oligodendroglia did not significantly change normal oligodendrocyte development. However, the ablation of NMDA receptor in OPCs exacerbated oligodendrocyte loss by impairing new oligodendrogenesis in hypoxic-ischemic injury. These results suggest that neither AMPA receptors nor NMDA receptors mediate glutamate excitotoxicity in oligodendrocytes in neonatal hypoxic-ischemic injury. Instead, these receptors play distinct roles in post-injury oligodendrocyte development: AMPA receptor-mediated calcium suppresses oligodendrocyte regeneration, and NMDA receptor signaling supports oligodendrocyte regeneration after injury.
Temple University--Theses

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Egunlusi, Ayodeji Olatunde. „Novel norbornane derivatives as potential neuroprotective agents“. University of Western Cape, 2020. http://hdl.handle.net/11394/7339.

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Philosophiae Doctor - PhD
Neurodegenerative disorders are characterised by progressive loss of the brain’s physiological functions as a result of gradual degeneration of neurons in the central nervous system. Even though they are classified as diseases of the elderly, occurrence earlier in life is possible, but that would suggest the influence of genetic and/or environmental factors. Due to the continuous rise in modernisation and industrialisation over the years, there has been an increase in incidence and prevalence of neurodegenerative disorders. With the advances in technology and life expectancy, the rates of the common forms (Alzheimer’s disease and Parkinson’s disease), are expected to increase exponentially by 2050. Unfortunately, there is still no clinically approved treatment or therapy to slow down or halt the degenerative process as most registered drugs only offer symptomatic relief. Confounding this issue is the lack of definite mechanism of neurodegeneration, which is still poorly defined and not completely understood. Nonetheless, the pathology of most neurodegenerative disorders is believed to be a combination of interrelated processes that eventually leads to neuronal cell death. Among the postulated processes, the impact of excitotoxicity mediated by NMDA receptor over-activation is prominent and it is implicated in virtually all neurodegenerative disorders. With this basic insight, it is believed that molecules capable of inhibiting NMDA receptors and associated calcium channels, without affecting the normal physiological functions of the brain, could potentially serve as good neuroprotective drugs. Competitive and uncompetitive blockers (MK-801 and ketamine) have been explored, but none were clinically accepted due to undesirable side effects such as hallucinations, sedation and depression. However, NGP1-01, a polycyclic cage molecule, has been shown to be neuroprotective through modulation of NMDA receptors and voltage gated calcium channels and attenuation of MPP+ -induced toxicity. A similar approach could be useful in the design and development of new neuroprotective drugs. The aim of this study was to synthesise a series of open and rearranged cage-like molecules and explore their neuroprotective potential in neuroblastoma SH-SY5Y cells. The proposed structures, with norbornane scaffolds that contained different moieties, were designed to structurally resemble NGP1-01 and MK-801. Once synthesised, the compounds were purified and characterised, and were evaluated for their biological activities. Compounds were first screened for cytotoxicity at different concentrations. Thereafter, they were evaluated for neuroprotective effects against MPP+ -induced excitotoxicity and for calcium flux modulatory effects on NMDA receptor and voltage gated calcium channels. The norbornane derivatives were synthesised and characterised, and all final products were afforded in sufficient yields. All compounds with the exception of two compounds displayed good cytotoxic profiles towards the SH-SY5Y neuroblastoma cells at 10 µM, 50 µM and 100 µM concentrations as they demonstrated percentage cell viabilities close to 100% (control treated cells). Only two compounds showed percentage cell viability of 51% and 59% at 100 µM. Utilising the same cell line, all compounds, tested at 10 µM, attenuated MPP+ -induced toxicity after 24 hours of exposure to a neurotoxin. This was evident in the 23% to 53% enhancement (significant with p < 0.05) in cell viability when compared to the MPP+ only treated cells. In comparison to known NMDA receptor and/or voltage gated calcium channel blockers (MK-801, NGP1-01 or nimodipine), the synthesised compounds demonstrated mono or dual inhibition of calcium channels as they effectively attenuated calcium influx by blocking NMDA receptors and/or voltage gated calcium channels expressed in neuroblastoma SHSY5Y cells. This group of compounds were found to be more potent NMDA receptor inhibitors, probably due to similarities with MK-801 and memantine, than voltage gated calcium channel inhibitors. All compounds demonstrated moderate to good calcium inhibitory effects at NMDA receptors in the range of 23% to 70% while a selected few displayed very little or no activity at the voltage gated calcium channels. In conclusion, 27 compounds with norbornane scaffolds were successfully synthesised and evaluated for cytotoxicity and neuroprotection. The abilities of the synthesised compounds to protect neurons from the neurotoxin MPP+ and reduce calcium flux into neuronal cells were successfully demonstrated. These characteristics are essential in neuroprotection as they may prove significant in halting or slowing down the disease progression. The compounds showing a good cytotoxicity profile, neuroprotective effects and ability to reduce calcium overload, could potentially act as neuroprotective agents with good safety profiles or contribute as lead structures to the development and design of structurally related molecules that could clinically benefit people with neurodegenerative disorders.

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Bretherton, Nicola. „The effect of cis-5,8,11,14,17-eicosapentaenoic acid upon the contractile mechanisms linked to calcium influx and the mobilisation of intracellular calcium in aortic smooth muscle“. Thesis, Aston University, 1998. http://publications.aston.ac.uk/10988/.

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Epidemiological studies previously identified cis-5,8,11,14,17-eicosapentaenoic acid (EPA) as the biologically active component of fish oil of benefit to the cardiovascular system. Although clinical investigations demonstrated its usefulness in surgical procedures, its mechanism of action still remained unclear. It was shown in this thesis, that EPA partially blocked the contraction of aortic smooth muscle cells to the vasoactive agents KCl and noradrenaline. The latter effect was likely caused by reducing calcium influx through receptor-operated channels, supporting a recent suggestion by Asano et al (1997). Consistently, EPA decreased noradrenaline-induced contractures in aortic tissue, in support of previous reports (Engler, 1992b). The observed effect of EPA on cell contractions to KCl was not simple due to blocking calcium influx through L-type channels, consistent with a previous suggestion by Hallaq et al (1992). Moreover, EPA caused a transient increase in [Ca2+]i in the absence of extracellular calcium. To resolve this it was shown that EPA increased inositol phosphate formation which, it is suggested, caused the release of calcium from an inositol phosphate-dependent internal binding site, possibly that of an intracellular membrane or superficial sarcoplasmic reticulum, producing the transient increase in [Ca2+]i. As it was shown that the cellular contractile filaments were not desensitised to calcium by EPA, it is suggested that the transient increase in [Ca2+]i subsequently blocks further cell contraction to KCl by activating membrane-associated potassium channels. Activation of potassium channels induces the cellular efflux of potassium ions, thereby hyperpolarising the plasma membrane and moving the membrane potential farther from the activation range for calcium channels. This would prevent calcium influx in the longer term and could explain the initial observed effect of EPA to block cell contraction to KCl.

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Ricker, Ellen M. „The inhibitory effects of opioids on voltage-gated calcium influx in neonatal rat carotid body type I cells“. Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1424262410.

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De, Paula Daisy Maria Bentes [UNIFESP]. „Estudo do mecanismo molecular de transfecção mediada por ultrassom“. Universidade Federal de São Paulo (UNIFESP), 2010. http://repositorio.unifesp.br/handle/11600/9564.

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O ultrassom (US) vem sendo amplamente utilizado para melhorar a eficiência de transfecção de vetores não-virais. No entanto, o mecanismo pelo qual o US promove a entrega de DNA nas células ainda é pouco entendido. Este fenômeno é normalmente atribuído a sonoporação. Porém, com base em experimentos anteriores realizados em nosso laboratório, suspeitamos que outro mecanismo esteja envolvido no processo de captação de DNA. Para estudar o mecanismo de entrega, um vetor plasmideal expressando EGFP (pEGFP-N3, 4,7 kb) foi utilizado para transfectar células NIH3T3 com um aparelho de US terapêutico sem a adição de microbolhas. Em condições de insonação de 2 W/cm2, duty cycle de 20% por 30s o US promoveu cerca de 40% de eficiência de transfecção, mas com 1 W/cm2 resultou em níveis muito baixos de transfecção. Fixados esses parâmetros, também foi avaliada a produção de espécies reativas de oxigênio (ROS), o aumento da concentração intracelular de cálcio ([Ca2+]i) e as alterações no potencial de membrana através de microscopia confocal. A produção de ROS foi aumentada durante a insonação, sendo interrompida logo que o US foi desligado. A [Ca2+]i também foi aumentada durante a exposição ao US, mas seus níveis não retornaram ao basal durante os 3 minutos de observação. Porém, 1 W/cm2 não foi suficiente para mobilizar o cálcio durante a insonação, e o influxo de cálcio teve início apenas 12 segundos após o término do US. Quando expostas ao US, as células também apresentaram mudanças no potencial de membrana atingindo um estado de hiperpolarização, retornando ao estado normal logo que o US foi desligado. A alteração desses três parâmetros pelo US sugere que a entrega de DNA plasmideal deva ocorrer por endocitose. Por fim, utilizando DNA plasmideal fluorescente, mostramos que esta molécula entra na célula via endocitose mediada por clatrina.
Ultrasound (US) has been widely used to improve the efficiency of non-viral vector transfection. However, the mechanism that enables the uptake of plasmid DNA in cells by US insonation is poorly understood, but it is typically attributed to sonoporation. Based on our previous results, we hypothesized that other mechanisms, such as endocytosis, are involved in this process. To explore the mechanism of plasmid DNA uptake, a plasmid vector expressing EGFP (pEGFP-N3: 4.7 kb) was used to transfect NIH3T3 cells using a therapeutic US without microbubbles and was monitored in real-time using a confocal microscope. We achieved about 40% transfection efficiency when we applied 2 W/cm2 with 20% of duty-cycle for 30 s, but 1 W/cm2 resulted in a very low level of transfection. In these experiments, the production of reactive oxygen species was augmented during the insonation but was stopped soon after turning off the US. Calcium influx was also augmented during the insonation, but its level did not return to basal levels following the 3-min observation period. However, 1 W/cm2 was not sufficient to mobilize calcium influx during the insonation, and calcium influx began 12 s after turning off the US. US insonation also changed the cell membrane potential to promote a hyperpolarization state, which returned to the normal state soon after turning off the US. The alteration of these parameters by US indicates the uptake of plasmid DNA by endocytosis. Finally, using a fluorescently labeled plasmid, we showed that this molecule enters into cells via clathrin-mediated endocytosis, not via caveolin-1.
TEDE
BV UNIFESP: Teses e dissertações

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Mulligan, Sean Joseph. „Characterization of mitral cell presynaptic calcium influx and synaptic transmission in an in vitro, en bloc frog forebrain preparation“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ37597.pdf.

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Yang, Heng. „TRPM4, a non selective cation-permeable channel regulates Foxp3+ regulatory T cells suppressive function and survival trough modulating calcium influx“. Thesis, Paris 11, 2012. http://www.theses.fr/2012PA114840.

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TRPM4, un canal cationique non-sélective activé par le Ca2+ intracellulaire, est un acteur moléculaire important impliqué de la régulation du signal calcique et l’activation des lymphocytes T conventionnels mais son rôle dans la fonction des lymphocytes T régulateurs (Tregs Foxp3+) reste inconnu. Dans un modèle de souris transgéniques dans lequel le gène Trpm4 a été sélectivement invalidé dans la population des Tregs Foxp3+ (souris Foxp3(YFP)Cre+Trpm4flox/flox), nous avons démontré dans différents modèles in vivo d’inflammation aiguë et chronique que TRPM4 contrôle la fonction suppressive et la mort de ces cellules. Dans le modèle de fibrosarcome induit par le méthylcholanthrène (3-MCA) ou implanté (modèle MCA205), dans lequel le rôle des Tregs est documenté, l’absence de fonction de TRPM4 induit une diminution significative de l’incidence et de la croissance tumorale. Dans l’environnent inflammatoire chronique et hypoxique de ces tumeurs, l’expression de TRPM4 protège les Tregs infiltrant la tumeur de la mort cellulaire induit par l’ATP extracellulaire et stimule ainsi le développent et la progression tumorale. L’absence d’expression de TRPM4 dans les Tregs stimule la réponse anti-tumorale médiée par l’IFNg et induit la régression des tumeurs. En conclusion, en inhibant l’entrée de Ca2+ extracellulaire, TRPM4 régule négativement les fonctions suppressives des Tregs et protège ces cellules de la mort cellulaire induite par l’activation
TRPM4, a Ca2+-activated non-selective cation ion channel is an important regulator of Ca2+ signaling and cell activation in conventional T cells, but its role in Foxp3+ Tregs function remains unknown. Using a model in which Trpm4 gene was selectively invalidated in Foxp3+ Tregs population (Foxp3(YFP)Cre+Trpm4flox/flox mice) we have shown in different in vivo models of acute and chronic inflammation that TRPM4 is an important regulator of Tregs functions and survival. In a model of primary carcinogenesis induced by methylcholantrene (3-MCA) or implanted fibrosarcoma (MCA205 model), in which Tregs role has been documented, lack of TRPM4 expression and function induced significantly decreased incidence and tumor growth. We found that within chronic inflammatory and hypoxic tumor microenvironment, TRPM4 protected Tregs from ATP-induced cell death and therefore promoted tumor initiation and progression. In contrast, TRPM4 deficiency in Tregs favored IFN-g-mediated spontaneous anti-tumor immune response. Thus, through inhibiting Ca2+ influx, TRPM4 acts as a negative modulator of Tregs suppressive functions and protects Tregs from activation-induced cell death

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Zhang, Zehua [Verfasser], Matthias [Akademischer Betreuer] Engel und Peter [Gutachter] Reeh. „The modulatory effects of STW 5 and Menthacarin on cellular calcium ion influx in vitro / Zehua Zhang ; Gutachter: Peter Reeh ; Betreuer: Matthias Engel“. Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2020. http://d-nb.info/1224101979/34.

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Zanatta, Leila. „Mechanism of action of 1(alfa),25-dihydroxyvitamin D3 on cytochrome P-450 aromatase, calcium influx and gamma glutamyl transpeptidase in rat testis“. Florianópolis, SC, 2011. http://repositorio.ufsc.br/xmlui/handle/123456789/95390.

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Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde, Programa de Pós-Graduação em Farmácia, Florianópolis, 2011
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Daziano, Guillaume. „Rôle du propeptide de la sortiline et de ses dérivés dans les mécanismes de survie de la cellule bêta pancréatique“. Electronic Thesis or Diss., Université Côte d'Azur, 2021. http://www.theses.fr/2021COAZ6025.

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En 2019, la Fédération Internationale du Diabète a révélé que près de 500 millions de personnes étaient atteintes de diabète dans le monde. On estime que cette incidence atteindra les 700 millions de personnes en 2045. Outre, l’aspect financier de la prise en charge, le diabète est un véritable enjeu de santé publique. En effet, l’environnement hyperglycémique délétère associé au diabète est à l’origine de graves complications pouvant altérer le fonctionnement de nombreux organes tels que le cœur, le cerveau ou encore le rein. La résistance à l’insuline associée à la détérioration de la sécrétion d’insuline et à la perte de la masse cellulaire bêta pancréatique constituent les principales caractéristiques du diabète de type 2. Ainsi, afin d’améliorer la prise en charge des patients diabétiques, l’identification d’une approche thérapeutique maîtrisée permettant de protéger la masse cellulaire bêta et de favoriser la sécrétion d’insuline uniquement en réponse au glucose et ce, sans effets secondaires, apparaît idéale.Les précédents travaux du laboratoire ont identifié le PE endogène et ses dérivés synthétiques la Spadine et la Mini-Spadine comme des inhibiteurs sélectifs des canaux potassiques TREK-1 au fort potentiel antidépresseur et impliqués dans la sécrétion de sérotonine, la prolifération et la survie neuronale. Au niveau périphérique, la Spadine a été décrite in vitro et in vivo comme un peptide à l’effet incrétine comparable à celui de l’exendine-4, un antidiabétique couramment utilisé en clinique. Ainsi, à la suite de cette étude et par analogie aux effets protecteurs observés sur le neurone, nous avons émis l’hypothèse que le PE et ses dérivés pouvaient avoir un rôle bénéfique dans les mécanismes de survie de la cellule bêta pancréatique.Dans ce manuscrit, nous démontrons que le PE endogène et ses dérivés protègent les cellules bêta de l’apoptose induite par la présence chronique de l’interleukine pro-inflammatoire et diabétogène IL-1β, ainsi que d’un choc toxique aigu induit par la staurosporine. De plus, l’analyse des mécanismes intracellulaires révèle que ces peptides provoquent une augmentation de la concentration en calcium intracellulaire, activent les voies prolifératives et de survie ERK et Akt, et maintiennent l’activité du facteur transcriptionnel CREB dans un environnement délétère via un mécanisme dépendant des calmodulines kinases.Ainsi, ces travaux de thèse montrent que le PE et ses dérivés synthétiques protègent la cellule bêta pancréatique et initient des processus cellulaires vertueux par une voie de signalisation originale indépendante de la PKA, où le potentiel de membrane et le calcium occupent un rôle crucial. Ces données suggèrent le PE endogène et ses dérivés synthétiques comme une nouvelle classe de peptides protecteurs des cellules bêta pancréatiques
In 2019, the International Diabetes Federation revealed that nearly 500 million people have diabetes worldwide. It is estimated that this incidence will reach 700 million people by 2045. In addition to the financial aspect of treatment, diabetes is a real public health issue. Indeed, the deleterious hyperglycemic environment associated with diabetes is could induce serious complications, leading to a functional alteration of many organs such as the heart, the brain or the kidney. Insulin resistance associated with the deterioration of insulin secretion and the loss of pancreatic beta cell mass are the main characteristics of type 2 diabetes. Thus, in order to improve the management of diabetic patients, the identification of a controlled therapeutic approach to protect beta cell mass and promote insulin secretion only in response to glucose and without side effects, appears ideal.The laboratory has identified the endogenous PE and its synthetic derivatives Spadin and Mini-Spadin as selective inhibitors of TREK-1 potassium channels. By this mechanism, the peptides showed also a strong antidepressant potential by modulating serotonin secretion, neuronal proliferation and survival. At the peripheral level, Spadin has been described in vitro and in vivo as a peptide with an incretin effect comparable to that of exendin-4, an antidiabetic commonly used in the clinic. Thus, following this study and by analogy to the protective effects observed on the neuron, we hypothesized that PE and its derivatives may have a beneficial role in the survival mechanisms in the pancreatic beta-cell.In this thesis, we demonstrate that endogenous PE and its derivatives protect beta cells from apoptosis induced by the chronic presence of the pro-inflammatory and diabetogenic interleukin IL-1β, as well as from an acute toxic shock induced by staurosporine. Furthermore, analysis of intracellular mechanisms reveals that these peptides cause an increase in intracellular calcium concentration, activate the ERK and Akt proliferative and survival pathways, and maintain CREB transcriptional factor activity in a deleterious environment via a calmodulin kinase-dependent pathway.Thus, this work shows that PE and its synthetic derivatives protect the pancreatic beta-cell and initiate virtuous cellular processes through an original PKA-independent signaling pathway, where membrane potential and calcium play a crucial role. This suggests the sortilin-derived peptides as a new class of pancreatic beta-cell protective molecules

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Vachel, Laura. „Étude de l'influx calcique des cellules épithéliales bronchiques mucoviscidosiques : implication des canaux TRP“. Thesis, Poitiers, 2014. http://www.theses.fr/2014POIT2303/document.

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Les canaux TRP (Transient Receptor Potential) sont des acteurs clés de l'homéostasie calcique. Plusieurs de ces canaux interviennent dans l'influx calcique des cellules épithéliales bronchiques, notamment TRPC6, qui est impliqué dans un couplage fonctionnel avec le canal Cystic Fibrosis Transmembrane conductance Regulator (CFTR). Les mutations du CFTR (F508del et G551D) sont à l'origine de la mucoviscidose (Cystic Fibrosis (CF)), qui aboutit à l'augmentation de l'influx calcique dans les cellules CF. L'objectif de ce travail a été d'étudier l'implication des canaux TRP dans la dérégulation de l'influx calcique des cellules épithéliales bronchiques CF. Nous avons mis en évidence que CFTR régulait négativement l'activité de TRPC6, tandis que l'influx calcique via TRPC6 permettait de potentialiser l'activité du canal muté CFTR-G551D, activé au préalable par le VX-770. Nous proposons donc une nouvelle stratégie thérapeutique, combinant un potentiateur de CFTR et un activateur spécifique de TRPC6. Nous nous sommes ensuite intéressés au rôle des canaux TRPV, en particulier TRPV5 et TRPV6, dans l'influx calcique des cellules épithéliales bronchiques. Nous avons observé que l'influx Ca2+ constitutif, attribuable à ces deux canaux, était doublé dans les cellules CF, dû à une augmentation de l'activité de TRPV6. En effet, l'expression de la PLC-δ1, une enzyme régulant négativement TRPV6, est dramatiquement réduite dans les cellules CF. La correction de l'adressage du F508del-CFTR a permis de normaliser l'activité de TRPV6 sans restaurer l'expression de la PLC-δ1 dans les cellules CF, suggérant un contrôle plus complexe de TRPV6 dans les cellules épithéliales bronchiques
TRP (Transient Receptor Potential) channels are keys actors of Ca2+ homeostasis. Several of these channels are involved in the Ca2+ influx of bronchial epithelial cells, including TRPC6 which is implicated in a functional coupling with the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) channel. CFTR mutation leads Cystic Fibrosis (CF) disease and causes abnormal Ca2+ homeostasis trought an increased of Ca2+ influx in CF bronchial epithelial cells. Our objective is to investigate the implication of TRP channels in abnormal Ca2+ influx of CF bronchial epithelial cells.We showed that CFTR down regulates TRPC6 activity whereas Ca2+ influx through TRPC6 potentiates G551D-CFTR, activated by VX-770. We propose a new therapeutic strategy that combines a CFTR potentiator and a specific activator of TRPC6. Then, we focused on the role of TRPV channels, particularly TRPV5 and TRPV6, in Ca2+ influx of bronchial epithelial cells. We observed that constitutive Ca2+ influx, related to TRPV5/TRPV6 activity, was twice higher in CF cells due to the increase of TRPV6 activity. The expression of PLC-δ1, an enzyme that negatively regulates TRPV6 activity, is dramatically decreased in CF cells. The correction of F508del-CFTR trafficking allows TRPV6 activity normalization but do not restore PLC-δ1 expression level in CF cells, suggesting a more complex control of TRPV6 in bronchial epithelial cells

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Qu, Mengdi. „Molecular mechanism underlying CaMK1D-dependent function in AgRP neurons“. Electronic Thesis or Diss., Strasbourg, 2024. http://www.theses.fr/2024STRAJ029.

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La perturbation des mécanismes de réponse au stress chez les organismes peut entraîner une dysfonction cellulaire et des maladies telles que le syndrome métabolique. L'équilibre énergétique est principalement régulé par le système nerveux central (SNC), qui intègre des signaux hormonaux, neuronaux et alimentaires provenant de divers tissus. Une dysfonction de ce système est liée à l'obésité et au syndrome métabolique, qui sont tous deux des précurseurs du diabète de type 2 (T2D). Notre laboratoire a découvert que la protéine kinase ID dépendante du calcium/calmoduline (CaMK1D), un gène associé au T2D, favorise la prise alimentaire médiée par la ghréline chez les souris. Cependant, le rôle de la signalisation de CaMK1D dans les neurones NPY/AgRP reste encore à éclaircir. Dans cette étude, nous avons réalisé un séquençage de l'ARN en utilisant la lignée cellulaire hypothalamique GT1-7. Nous avons ainsi découvert que CalHM6 est une cible potentielle en aval de la signalisation de CaMK1D. Les niveaux d'ARNm de CalHM6 sont ainsi significativement augmentés dans les cellules CaMK1D-/- et sont réduits lorsque CaMK1D est ré-exprimé. Cela a également été confirmé in vivo dans l'hypothalamus des souris CaMK1D-/-. CalHM6, probablement un canal calcique dépendant du voltage, a montré des niveaux intracellulaires de Ca2+ augmentés en réponse à la ghréline dans les cellules CaMK1D-/- par rapport aux cellules CaMK1D+/+ en utilisant la méthode jGCamps. En résumé, notre travail a montré que CalHM6 est une nouvelle cible de CaMK1D. Une expression élevée de CaMK1D, entraînant une faible expression de CalHM6, pourrait ainsi favoriser la prise alimentaire et l'obésité en modulant la signalisation dépendante du calcium dans les neurones NPY/AgRP
Disruption of stress response mechanisms in organisms can lead to cellular dysfunction and diseases like metabolic syndrome. Energy balance is mainly regulated by the central nervous system (CNS), which integrates hormonal, neuronal, and dietary signals from various tissues. Dysfunction in this system is linked to obesity and metabolic syndrome, both precursors to type 2 diabetes (T2D). Our laboratory discovered that calcium/calmodulin-dependent protein kinase ID (CaMK1D), a gene associated with T2D, promotes ghrelin-mediated food intake in mice. However, CaMK1D signaling in NPY/AgRP neurons still remains questions. In this work, we proformed RNA sequencing using the GT1-7 hypothalamic cell line. To this end, we found that CalHM6 is a downstream target of CaMK1D signaling. CalHM6 mRNA levels were significantly upregulated in CaMK1D-/- cells and downregulated when CaMK1D was re-expressed. This was confirmed in vivo in the hypothalamus of CaMK1D-/- mice. CalHM6, likely a voltage-gated calcium channel, showed increased intracellular Ca2+ levels in response to ghrelin in CaMK1D-/- cells compared to CaMK1D+/+ cells using jGCamps method. Altogether, our work showed CalHM6 is a novel target of CaMK1D. High CaMK1D, leading to low CalHM6 expression, may enhance food intake and obesity by modulating calcium-dependent signaling in NPY/AgRP neuron

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Sabourin, Jessica. „Influx cationique dépendant des canaux TRPCs dans les cellules musculaires squelettiques : régulation par le complexe dystrophine/alpha1-syntrophine et par la voie PLC : implication dans la dystrophie musculaire de Duchenne“. Poitiers, 2009. http://theses.edel.univ-poitiers.fr/theses/2009/Sabourin-Jessica/2009-Sabourin-Jessica-These.pdf.

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La dystrophine est une protéine du cytosquelette normalement exprimée sous la membrane des cellules musculaires squelettiques. L'absence de cette protéine dans la Dystrophie Musculaire de Duchenne (DMD) entraîne la nécrose des fibres musculaires, résultant entre autres d'une dérégulation des mouvements calciques à travers le sarcolemme et par conséquent d'une augmentation du calcium libre dans le myoplasme. A l'heure actuelle, le lien entre l'absence de dystrophine et l'altération calcique n'est toujours pas établi et l'objectif de ce travail a été de le mettre en évidence. Les expériences ont été principalement réalisées sur les lignées cellulaires SolC1 déficientes en dystrophine et SolD6 exprimant la mini-dystrophine ainsi que sur des cultures primaires de souris normales et de souris mdx, modèle animal de la DMD. Notre étude démontre que, dans les cellules déficientes en dystrophine, les entrées calciques activées par la déplétion en calcium du réticulum sarcoplasmique, sont considérablement augmentées. Par la technique de siRNA, nous avons pu identifier les canaux TRPC1 et TRPC4 par où transitent les influx cationiques dans les myotubes SolD6. Nous avons également décrit pour la première fois un lien moléculaire entre TRPC1/TRPC4 et la dystrophine, l’α1-syntrophine et le domaine PDZ de cette dernière. Ce complexe α1-syntrophine/TRPCs est réduit dans les cellules déficientes en dystrophine car l'expression de l'α1-syntrophine au sarcolemme est diminuée. Nous suggérons qu'une régulation normale des entrées de calcium à travers TRPC1/TRPC4 dépend de l'association entre ces canaux non dépendants du potentiel et l'α1-syntrophine. En effet, la surexpression de l'α1-syntrophine dans les cellules déficientes en dystrophine rétablit l'entrée de calcium. Inversement, des expériences avec des siRNAs dirigés contre l'α1-syntrophine entrainent une augmentation des influx cationiques dans les cellules exprimant la mini-dystrophine à des niveaux proches des influx mesurés dans les cellules déficientes en dystrophine. En plus de son rôle de protéine d'échafaudage, l'α1-syntrophine serait donc cruciale pour réguler l'activité des canaux TRPC1/TRPC4 dans le muscle squelettique. D'autre part, nous avons pu mettre en évidence par des traitements pharmacologiques que l'influx cationique exacerbé des cellules SolC1 déficientes en dystrophine est dépendant de la voie PLC/PKC. Dans ces myotubes, l’absence de la dystrophine et/ou de l'α1-syntrophine entrainent à travers TRPC1 des entrées accrues de calcium, potentialisées par la voie PLC/PKC. Ce travail de thèse a mis clairement en évidence un influx cationique dépendant des canaux TRPCs et régulé par l'α1-syntrophine dans la cellule musculaire squelettique. L'absence de cette dernière au sarcolemme pourrait conférer une nouvelle sensibilité au canal TRPC1 entrainant alors sa suractivation et une entrée incontrôlée de calcium dans le cytoplasme des cellules déficientes en dystrophine
The dystrophin is a cytoskeleton protein normally expressed underneath the sarcolemma of skeletal muscle. The lack of this protein in Duchenne Muscular Dystrophy leads to muscle necrosis and to increased intracellular free calcium in the cytoplasm. Actually, the link between calcium mishandling and the absence of dystrophin is not well established and the aim of my study is to demonstrate it. Our works showed that cationic influx activated by calcium depletion of sarcoplasmic reticulum is strongly increased. We identified TRPC1 and TRPC4 channels supporting cationic influx in myotubes expressing mini-dystrophin. We also described for the first time a molecular link between dystrophin and TRPC1/TRPC4 channels, the alpha1-syntrophin. We suggested that normal regulation of syntrophin overexpression leads to reduction of abnormal cationic influx in dystrophin-deficient myotubes. Conversely, alpha1-syntrophin repression leads to increased cationic entry in myotubes expressing mini-dystrophin. The presence at normal level of this protein appears to be crucial for normal regulation of TRPC1/TRPC4 channels in skeletal muscle. On the other hand, we demonstrated an increased cationic influx supported by TRPC in dystrophin-deficient myotubes, which seems to be potentiated by PLC/PKC pathway

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Rossato, Mateus Fortes. „Eriodictiol: um flavonóide antagonista do receptor trpv1 com atividade antioxidante“. Universidade Federal de Santa Maria, 2010. http://repositorio.ufsm.br/handle/1/11134.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
The transient receptor potential vanilloid 1 (TRPV1) is a calcium permeable channel responsible for the transduction and modulation of acute and chronic pain signaling, being a potential target for treatment of different pain disorders. In spite of that, AMG517, a TRPV1 antagonist, presents several clinical limitations, such as the development of severe hypertermia. The aim of this study was to investigate the possible interaction of the flavonoid eriodictyol with the TRPV1 receptor and its putative antinociceptive and hyperthermic effect. Eriodictyol was able to displace the [3H]-resiniferatoxin binding (IC50 = 47 (21 - 119) nM) and to inhibit the calcium influx mediated by capsaicin (IC50 = 44 (16 125) nM), suggesting that eriodictyol acts as a TRPV1 antagonist. Moreover, eriodictyol induces antinociception in the intraplantar capsaicin test, with maximal effect of 49±10 and 64±4% of inhibition for oral (ED50 = 2 (1-5) mg/kg) and intrathecal (ED50 = 2 (1-3) nmol/site) routes, respectively. Concomitantly, eriodictyol did not induce any alteration on body temperature or locomotor activity. Orally administered eriodictyol (4.5 mg/kg) prevented the nociception induced by intrathecal injection of capsaicin (72±6% of inhibition), the non-protein thiol loss and the 3-nitrotyronise (3-NT) formation induced by capsaicin in spinal cord. Eriodictyol (4.5 mg/kg, p.o.) also reduced the thermal hyperalgesia (100% of inhibition) and mechanical allodynia (62±9% of inhibition) elicited by complete Freund s adjuvant (CFA) paw injection. In conclusion, Eriodictyol acts as an antagonist of TRPV1 receptor and an antioxidant, inducing antinociception without some side effects and limitations expected for TRPV1 antagonists, as hyperthermia.
O receptor de potencial transiente vanilóide 1 (TRPV1) é um canal iônico permeável a cátions ativado por uma série de estímulos nocivos, como calor, acidificação e agentes irritantes como a capsaicina. Este receptor é responsável pela detecção e transmissão da dor aguda e crônica. Devido a isso, substâncias que modulem a atividade deste receptor apresentam um potencial clínico para o tratamento da dor. Assim, este trabalho objetiva a possível interação do flavonóide eriodictiol com o receptor TRPV1. Inicialmente, observamos que o eriodictiol foi capaz de deslocar o radioligante [3H]-resiniferatoxina, em ensaio de união específica, do receptor TRPV1 com uma concentração inibitória 50% (IC50) de 46.9 (20.70 - 118.9) nM. Ao mesmo tempo, o eriodictiol também inibiu o influxo de cálcio estimulado por capsaicina com IC50 de 44,4 (15,6 125,1) nM, sugerindo que este aja como um antagonista do receptor. Além disso, também observamos que o eriodictiol induz antinocicepção no teste da capsaicina intraplantar com efeito máximo de 49,0±10.5 e 63,9±4.0 % de inibição máxima para o tratamento oral e intratecal, respectivamente, e com uma dose efetiva 50% (DE50) de 2,4 (1,0 5,5) mg/kg 2,2 (1,6 2,9) nmol/site, respectivamente. Além disso, não observamos alterações na atividade locomotora ou temperatura corporal dos animais. A administração oral de eriodictiol também foi capaz de prevenir a nocicepção induzida por capsaicina intratecal (71,7±5,7 % de inibição). Ao mesmo tempo, o eriodictiol também aboliu a hiperalgesia térmica e reduziu a alodínia mecânica (62,4±9,2 %) induzidas por adjuvante completo de Freund. Da mesma forma, o eriodictiol também preveniu totalmente a diminuição de tiois não protéicos e formação de 3-nitrotirosina (3-NT) espinhais induzidas por capsaicina, ao passo que apresentou atividade antioxidante direta no texto de neutralização do radical ABTS. Em conclusão, nossos resultados mostram que o eriodictiol age como um antagonista do receptor TRPV1, com atividade antioxidante, induzindo antinocicepção sem os efeitos colaterais e limitações esperados para antagonistas do receptor TRPV1.

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Shoji, Emi. „Early pathogenesis of Duchenne muscular dystrophy modelled in patient-derived human induced pluripotent stem cells“. Kyoto University, 2015. http://hdl.handle.net/2433/200495.

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Sharma, Rajan. „Synthesis & biological evaluation of neuroprotective molecules with polycyclic scaffolds“. University of the Western Cape, 2017. http://hdl.handle.net/11394/6228.

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Doctor Pharmaceuticae - Dpharm
Among neurological disorders, many of the most devastating disorders are neurodegenerative. Modern research associates excitotoxicity to a variety of neuropathological conditions, suggesting that the neurodegenerative diseases with distinct etiologies may have excitotoxicity as a common pathway. Excitotoxicity occurs through over-stimulation of receptors for excitatory neurotransmitters like the N-methyl-D-aspartate (NMDA) receptors. Due to the relevance of NMDA receptors and excitotoxic processes, the antagonism or modulation of NMDA receptors is used as a therapeutic tool against neurodegenerative diseases. NMDA receptor activity can be modulated by S-nitrosylation and this modulation of NMDA receptor activity can be utilised in the development of neuroprotective drugs.

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Djillani, Alaeddine. „Caractérisation des canaux calciques dans les polynucléaires neutrophiles : rôle dans la phagocytose et la production des radicaux libres oxygénés“. Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-01069097.

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Les polynucléaires neutrophiles représentent 50-70% des leucocytes sanguins et possèdent un rôle majeur dans la défense de l'organisme contre les pathogènes. Le Ca2+ est un second messager qui joue un rôle primordial dans le chimiotactisme, la phagocytose, la dégranulation et la production de formes réactives de l'oxygène (FRO) afin de neutraliser l'agent pathogène. Dans ces cellules, l'influx calcique de type SOCE est essentiel pour l'homéostasie calcique. Il est peu étudié en raison du manque d'outils pharmacologiques spécifiques d'où l'importance dans un premier temps de chercher de nouvelles molécules. Les cellules T Jurkat dont le SOCE est largement caractérisé servent de modèle pour la caractérisation initiale de ces molécules. Le 2-APB est parmi les molécules les plus largement utilisées dans la caractérisation du SOCE en raison de sa double activité sur le SOCE avec une potentialisation à [1-10 μM] et une inhibition à [> 20 μM]. En revanche, ce produit manque de spécificité et agit sur d'autres cibles cellulaires comme les récepteurs à l'inositol (1,4,5)-trisphosphate (InsP3Rs). La 1ère étape est de sélectionner à partir d'analogues commerciaux du 2-APB (Methoxy-APB, Dimethoxy-APB, Cyclic-APB, Benzothienyl-APB, Thienyl-APB et MDEB), des composés plus spécifiques et également plus efficaces que la molécule mère. Deux molécules se sont distinguées : le MDEB comme uniquement potentialisant du SOCE et le Benzothienyl-APB comme un puissant inhibiteur. En revanche, tous les analogues du 2-APB inhibent les InsP3Rs à l'exception du MDEB qui semble plus spécifique du SOCE. L'effet du MDEB sur le courant calcique, ICRAC, a été étudié grâce à la technique du patch-clamp. Il augmente d'environ 4 fois l'amplitude de ICRAC par rapport à celle enregistrée dans les cellules contrôle. Par ailleurs, le MDEB ralentie l'inactivation rapide de ICRAC due au Ca2+. Sur le plan physiologique, le MDEB à des concentrations croissantes inhibe la synthèse de l'IL-2 dans les cellules Jurkat stimulées et ceci malgré son effet potentialisant du SOCE. Cette activité est liée à son effet pro-apoptotique dans les cellules Jurkat stimulées. Le MDEB et le Benzothienyl-APB caractérisés dans la 1ère partie nous ont servi d'outils potentiels afin d'étudier le SOCE des cellules PLB-985 différenciées en cellules proches de neutrophiles. Le SOCE a été induit soit par un traitement des cellules avec la thapsigargine (Tg) soit de manière physiologique avec les peptides fMLF et le WKYMVm deux chimioattractants, ligands des récepteurs aux peptides formylés FPR et FPRL1 respectivement. En plus, le SOCE induit par la Tg est modulable par le 2-APB, potentialisé par le MDEB et inhibé par le Benzothienyl-APB. La phagocytose des levures par les cellules PLB-985 différenciées ainsi que la production de FRO intraphagosomales ont été inhibées par le MDEB et le Benzothienyl-APB. Les FRO extracellulaires ont été également inhibées par Benzothienyl-APB en revanche à cause de la forte interférence du MDEB avec la technique de mesure nous n'avons pas pu étudier ses activités. En conclusion, le MDEB et le Benzothienyl-APB sont de nouveaux outils pharmacologiques potentialisant ou inhibant le SOCE des leucocytes, qui nous permettront dans l'avenir une meilleure compréhension de l'entrée calcique et ses rôles dans ces cellules.

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Ampem, Prince Tuffour. „The Transient Receptor Potential Canonical 3 (TRPC3) Channel: Novel Role in Endothelial Cell Apoptosis and its Impact on Atherosclerosis“. University of Toledo Health Science Campus / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=mco1493230041479167.

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Langford, Peter R. „c-Met Initiates Epithelial Scattering through Transient Calcium Influxes and NFAT-Dependent Gene Transcription“. BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/3186.

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Hepatocyte growth factor (HGF) signaling drives epithelial cells to scatter by breaking cell-cell adhesions and migrating as solitary cells, a process that parallels epithelial-mesenchymal transition. HGF binds and activates the c-Met receptor tyrosine kinase, but downstream signaling required for scattering remains poorly defined. This study addresses this shortcoming in a number of ways.A high-throughput in vitro drug screen was employed to identify proteins necessary in this HGF-induced signaling. Cells were tested for reactivity to HGF stimulation in a Boyden chamber assay. This tactic yielded several small molecules that block HGF-induced scattering, including a calcium channel blocker. Patch clamping was used to determine the precise effect of HGF stimulation on Ca2+ signaling in MDCK II cells. Cell-attached patch clamping was employed to detect Ca2+ signaling patterns, and channel blockers were used in various combinations to deduce the identity of Ca2+ channels involved in EMT. The results of these experiments show that HGF stimulation results in sudden and transient increases in calcium channel influxes. These increases occur at predictable intervals and rely on proper tubulin polymerization to appear, as determined through the use of a tubulin polymerization inhibitor. Though multiple channels occur in the membranes of MDCK II cells, noticeably TRPV4 and TrpC6, it is TrpC6 that is specifically required for HGF-induced scattering. These HGF-induced calcium influxes through TrpC6 channels drive a transient increase in NFAT-dependent gene transcription which is required for HGF-induced EMT. This was determined through the use of luciferase-based NFAT reporter assays and confirmed through confocal immunofluorescence. Using a small-molecule inhibitor of WNK kinase, it was determined that loss of WNK kinase function is sufficient to prevent HGF-induced EMT. Furthermore, patch-clamp analysis demonstrated that WNK kinase significantly increases channel opening at the surface of MDCK cells, indicating a possible mechanism of action for c-Met inhibition, but leaving doubt as to whether WNK kinase is in fact normally involved in c-Met signaling, or whether it is simply permissive.

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Barbar, Élie. „Effets de la 4-aminopyridine sur le lymphocyte T Jurkat influx calcique, induction de l'apoptose et perméation d'ions“. Thèse, Université de Sherbrooke, 2004. http://savoirs.usherbrooke.ca/handle/11143/4245.

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La 4-aminopyridine (4-AP) est utilisée dans le traitement expérimental de plusieurs maladies du système nerveux. Son action bénéfique est médiée via le blocage de canaux potassiques, ce qui améliore la transmission de l'influx nerveux ainsi que la force motrice musculaire. Outre sa propriété de bloquer les canaux K + , la 4-AP possède plusieurs autres effets cellulaires qui ne sont pas complètement caractérisés. Par exemple, elle alcalinise le milieu intracellulaire, induit une réponse calcique et peut causer la mort cellulaire. Dans une première étude, nous avons utilisé la lignée de lymphocyte T Jurkat E6.1 comme modèle afin de caractériser la réponse calcique induite par la 4-AP, notamment sa modulation par les protéine kinases et les sérine/thréonine protéines phosphatases. Nos résultats ont montré que la 4-AP induisait une augmentation de la concentration du calcium intracellulaire ([Ca 2+ ] i ), d'une manière qui n'obéissait pas au modèle capacitatif. De plus, l'influx de calcium était sensible à la protéine kinase C, à la phosphatase PP1, et non à la protéine kinase A. Une activation de la PKC et/ou une inhibition de PP1 diminuait considérablement l'influx de calcium induit par la 4-AP, d'une façon additive. Dans une deuxième étude, nos travaux ont ciblé le phénomène de mort cellulaire induit par la 4-AP. Une autre propriété du P2X 7 R est la formation de protubérances membranaires appelées blebs. Nous avons étudié le mécanisme de mort cellulaire induite par la 4-AP chez les cellules T Jurkat. Nos travaux ont montré que la 4-AP induisait la formation de blebs et l'externalisation de la phosphatidylsérine, deux phénomènes précoces de l'apoptose, ainsi que la fragmentation de l'ADN, un phénomène tardif de l'apoptose. Nos résultats ont montré que la 4-AP induisait l'activation des caspase-3, -6 et -9, et non de la caspase-8, ainsi qu'une perte du potentiel membranaire. Ces résultats sont consistants avec l'interprétation que la 4-AP déclenche l'apoptose chez le lymphocyte Jurkat en activant la voie intrinsèque (mitochondriale) de la cascade. Dans une troisième étude, nos travaux se sont adressés à la cible de la 4-AP impliquée dans l'influx de calcium. Cette cible est inconnue mais certains indices obtenus dans notre laboratoire nous ont permis d'établir une cible potentielle de la 4-aminopyridine, soit le récepteur purinergique P2X 7 (P2X 7 R) dont les propriétés liées à la réponse cellulaire coïncident avec celles de la 4-AP. Par exemple, le P2X 7 R permet l'entrée de calcium, et forme un pore membranaire permissif à certains ions de grande taille, comme le cation éthidium (314 Da), et non le cation propidium (414 Da). Nous avons montré cette restriction de perméation de cations chez les cellules Jurkat stimulées à la 4-AP, et aussi chez des cellules CHO tranfectées avec le P2X 7 R de rat, mais pas chez des cellules COS ou HEK transfectées. Ces résultats suggèrent des actions diverses de la 4-AP sur des cibles autres que les canaux potassiques, potentiellement le P2X 7 R, d'une manière spécifique au type cellulaire.

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Waiczies, Sonia. „Modulation of human antigen-specific T-cell response therapeutic implications for multiple sclerosis /“. Doctoral thesis, [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969681844.

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Galdino, Jos? Nildo. „Influ?ncia do teor e granulometria da calcita e da temperatura de sinteriza??o no desenvolvimento de massas cer?micas para revestimento poroso(BIII)“. Universidade Federal do Rio Grande do Norte, 2010. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15903.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
This work aims at studying the influence of the concentration of calcite, its grain size and sintering temperature to obtain porous coating formulations that meet the design specifications. The experiments involved the physical-chemical and mineralogical caracterization of the raw materials, and mechanical tests on specimens dried and sintered, performing a planning mixture and factorial experiment, using the response surface methodology. The ceramic bodies studied were prepared by dry process, characterized, placed in conformity by uniaxial pressing and sintered at temperatures of 940 ? C, 1000?C, 1060?C, 1120?C and 1180?C using a fast-firing cycle. The crystalline phases formed during sintering at temperatures under study, revealed the presence of anorthite and wolastonite, and quartz-phase remaining. These phases were mainly responsible for the physical and mechanical properties of the sintered especimens. The results shown that as increases the participation of carbonate in the composition of ceramic bodies there is an increase of water absorption and a slight reduction in linear shrinkage for all sintering temperatures. As for the mechanical strength it was observed that it tended to decrease for sintering at temperatures between 940 ? C and 1060 ? C and to increase for sintering at temperatures above 1060 ? C occurring with greater intensity for compositions with higher content of calcite. The resistence decreased with increasing participation of quartz in all sintering temperatures. The decrease in grain size of calcite caused a slight increase in water absorption for formulation with the same concentration of carbonate, remaining virtually unchanged the results of linear shrinkage and mechanical strength. In conclusion, porous ceramic coating (BIII) can be obtained using high concentrations of calcite and keeping the properties required in technical standards and that the particle size of calcite can be used as tuning parameter for the properties of ceramic products.
Este trabalho objetiva estudar a influ?ncia da concentra??o de calcita, sua granulometria e temperatura de sinteriza??o na obten??o de formula??es para revestimento poroso que atendam as especifica??es da norma. Os experimentos envolveram a caracteriza??o f?sico qu?mica e mineral?gica das mat?rias-primas, e ensaios mec?nicos nos corpos de prova secos e sinterizados, precedendo-se de um planejamento de experimento de mistura e fatorial, com o uso da metodologia de superf?cie de resposta. As massas cer?micas estudadas foram preparadas pelo processo via seca, caracterizada, conformada por prensagem uniaxial e sinterizadas nas temperaturas de 940?C, 1000?C, 1060?C, 1120?C, e 1180?C utilizando um ciclo de sinteriza??o r?pido. As fases cristalina formadas durante a sinteriza??o nas temperaturas em estudo, revelaram a presen?a de anortita e wolastonita, al?m de quartzo com fase remanescente. Estas fases foram as principais respons?veis pelas propriedades f?sico-mec?nica dos corpos de provas sinterizados. Verificou-se que conforme se aumenta a participa??o do carbonato na composi??o das massas cer?micas ocorre um incremento de absor??o de ?gua e uma pequena redu??o da retra??o linear para todas as temperaturas de sinteriza??o. J? para a resist?ncia mec?nica houve uma tend?ncia de redu??o para sinteriza??o entre 940?C e 1060?C e aumento para sinteriza??o acima da temperatura de 1060?C ocorrendo com maior intensidade para formula??es com maior teor de calcita, e houve diminui??o da resist?ncia com o aumento da participa??o do quartzo em todas as temperaturas de sinteriza??o. A diminui??o da granulometria da calcita provocou um leve aumento na Absor??o de ?gua para formula??o com a mesma concentra??o desse carbonato mantendo praticamente inalterados os resultados de retra??o linear e resist?ncia mec?nica. Conclui-se que produtos cer?micos para revestimento poroso (BIII) podem ser obtidos utilizando altas concentra??es de calcita e mantendo-se as propriedades exigidas em normas t?cnicas e que a granulometria da calcita pode ser usada como par?metro de ajuste para as propriedades dos produtos cer?micos

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Oliveira, Gislaine Alves de. „A ação espasmolítica do óleo essencial de Lippia microphylla Cham. e de seus constituintes majoritários envolve o bloqueio do influxo de cálcio em íleo de cobaia“. Universidade Federal da Paraíba, 2014. http://tede.biblioteca.ufpb.br:8080/handle/tede/6824.

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The essential oil extracted from aerial parts of Lippia microphylla Cham. (Verbenaceae) (LM-OE) presents as major compounds thymol and carvacrol. The aim of this study was to investigate and to characterize oil LM-OE spasmolytic effect on guinea pig ileum, as well to verify if this effect is due its major compunds, thymol and carvacrol. Were performed measures of isometric and isotonic contractions and cytosolic calcium. LM-OE inhibited phasic contractions induced by 10-6 M of histamine or carbachol (CCh) (IC50 = 15.8 ± 2.3 e 24.4 ± 2.9 μg/mL, respectively). In a similar manner, thymol, carvacrol and thymol/carvacrol mixture antagonized histamine- (IC50 = 14.2 ± 1.6; 13.6 ± 1.3 e 13 ± 2.1 μg/mL, respectively) ou CCh- (IC50 = 21.3 ± 3.8; 16 ± 2.6 e 27.9 ± 4.8 μg/mL, respectively) induced phasic contractions. Compared with LM-OE, in neither case was difference. In the same way, LM-OE relaxed pre-contracted organ by 40 mM of KCl, 10-5 M of CCh or 10-6 M of histamine (EC50 = 7.6 ± 0.8; 7.2 ± 1.3 e 6.8 ± 0.6 μg/mL, respectively), being equipotent in the three situations. As CaV are common step on pathway of these three contractile agents, we hypothesized that somehow LM-OE would blocking Ca2+ influx by these channels. Once probably the major compounds are biological markers for this specie, we evaluated their effect upon tonic contraction induced by 40 mM of KCl. We found that thymol, carvacrol and thymol/carvacrol mixture relaxed the ileum in a significant and concentration-dependent manner (EC50 = 5.1 ± 1.1; 11.5 ± 1 e 5.1 ± 1.1 μg/mL, respectively), being carvacrol the least potent among the three, they did not showed statistic difference when compared with LM-OE. To confirm the hypothesis of CaV participation on LM-OE spasmolytic action, were performed cumulative concentration-response curves to CaCl2 in a nominal without Ca2+ depolarizing medium in absence (control) and LM-OE presence, witch one antagonize these contractions besides to relaxes the organ when it was pre-contracted by S-(-)-Bay K 8644 (EC50 = 8.5 ± 1.5 μg/mL), a selective CaV 1, agonist confirming that the CaV subtype involved is CaV 1. The fact of CsCl, a K+ channels nonselective blocker, has not changed the relaxing potency of LM-OE oil on ileum pre-contracted with 10-5 M CCh, discard the hypothesis of positive modulation of these channels, which would lead to an indirect blockade of CaV. In experiments with ileum circular layer, LM-OE antagonized phasic contractions induced by 10-6 M of CCh (IC50 = 30.1 ± 1.5 μg/mL), that suggests a negative modulation of the Ca2+ intracellular signaling by LM-OE oil to exert its spasmolytic effect. Viability of layer longitudinal smooth muscle cells was evaluated in the absence and presence of 81 μg/mL LM-OE oil, and no cell death was verify during 2 h of contact with cells LM-OE oil. In the presence of LM-OE oil, the intensity of fluorescence in intestinal guinea pig myocytes stimulated by histamine was reduced as a result of the reduction of calcium cytosolic concentration ([Ca2+]c). In conclusion, the LM-OE oil act by blocking calcium influx through CaV1, possibly by inhibiting intracellular Ca2+ signaling and reducing [Ca2+]c, to promote its spasmolytic effect in guinea pig ileum
O óleo essencial extraído das partes aéreas de Lippia microphylla Cham. (Verbenaceae) (LM-OE) apresenta como componentes majoritários o timol e o carvacrol. O objetivo deste trabalho foi investigar e caracterizar o efeito espasmolítico do óleo LM-OE em íleo de cobaia, bem como verificar se este efeito era devido aos seus constituintes majoritários. Foram realizadas medidas de contrações isotônicas e isométricas e do cálcio citosólico. O óleo LM-OE inibiu as contrações fásicas induzidas por 10-6 M de histamina ou de carbacol (CCh) (CI50 = 15,8 ± 2,3 e 24,4 ± 2,9 μg/mL, respectivamente). Da mesma forma, o timol, o carvacrol e a mistura timol/carvacrol antagonizaram as contrações fásicas induzidas por histamina (CI50 = 14,2 ± 1,6; 13,6 ± 1,3 e 13,0 ± 2,1 μg/mL, respectivamente) ou por CCh (CI50 = 21,3 ± 3,8; 16,0 ± 2,6 e 27,9 ± 4,8 μg/mL, respectivamente). Quando comparado com o óleo, não houve diferença em nenhum dos casos. Do mesmo modo, o óleo LM-OE relaxou, de maneira equipotente, o órgão pré-contraído com 40 mM de KCl, com 10-5 M de CCh ou com 10-6 M de histamina (CE50 = 7,6 ± 0,8; 7,2 ± 1,3 e 6,8 ± 0,6 μg/mL, respectivamente). Como o passo comum na via de sinalização destes agentes contráteis são os canais de cálcio dependentes de voltagem (CaV), hipotetizou-se que de alguma forma o óleo estaria impedindo o influxo de Ca2+ através destes canais. Visto que provavelmente os componentes majoritários são os marcadores biológicos para esta espécie, avaliou-se o efeito dos mesmos sobre a contração tônica induzida por 40 mM de KCl. Observou-se que o timol, o carvacrol e a mistura timol/carvacrol relaxaram o órgão de maneira significante e dependente de concentração (CE50 = 5,1 ± 1,1; 11,5 ± 1 e 5,1 ± 1,1 μg/mL, respectivamente), sendo o carvacrol o menos potente entre os três, os quais se mostraram equipotentes ao óleo LM-OE. Para confirmar a hipótese da participação dos CaV no mecanismo espasmolítico do óleo LM-OE, foram feitas curvas concentrações-resposta cumulativas ao CaCl2 em meio despolarizante nominalmente sem Ca2+ na ausência (controle) e na presença do óleo LM-OE, o qual antagonizou essas contrações, além de relaxar o órgão pré-contraído com S-(-)-Bay K 8644 (CE50 = 8,5 ± 1,5 μg/mL), agonista seletivo dos CaV1, confirmando assim que o subtipo de CaV envolvido é o CaV1. O fato do CsCl, um bloqueador não seletivo dos canais de K+, não ter alterado a potência relaxante do óleo LM-OE no íleo pré-contraído com 10-5 M de CCh, descarta a hipótese da modulação positiva desses canais, o que levaria a um bloqueio indireto dos CaV. Em experimentos utilizando a camada circular do íleo de cobaia, o óleo antagonizou as contrações fásicas induzidas por 10-6 M de CCh (CI50 = 30,1 ± 1,5 μg/mL), o que sugere uma possível inibição da sinalização intracelular de Ca2+ para exercer seu efeito espasmolítico. A viabilidade das células musculares lisas da camada longitudinal foi avaliada na ausência e na presença de 81 μg/mL do óleo LM-OE, não havendo morte celular no período 2 h de contato das células com o óleo LM-OE. Na presença do óleo LM-OE, a intensidade de fluorescência em miócitos intestinais de cobaia estimulados por histamina foi reduzida em consequência da redução da [Ca2+]c. Em conclusão, o óleo LM-OE age por impedir o influxo de cálcio através dos CaV1, por possivelmente inibir a sinalização intracelular de Ca2+ e redução da concentração citosólica desse íon, para promover seu efeito espasmolítico em íleo isolado de cobaia

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Ferraz, Sandro Aparecido. „Estimativa do influxo de calcio por meio de canais tipo L em miocitos cardiacos isolados de ratos neonatos e adultos“. [s.n.], 2003. http://repositorio.unicamp.br/jspui/handle/REPOSIP/260336.

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Orientadores: Jose Wilson Magalhães Bassani, Rosana Almada Bassani
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Doutorado

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Leite, Jocelmo Cassio de Araujo. „Desenvolvimento embrionário de Ouriços-do-mar da espécie Echinometra lucunter (Linnaeus, 1758) envolve influxo de cálcio através dos canais de cálcio sensíveis à voltagem“. Universidade Federal da Paraíba, 2011. http://tede.biblioteca.ufpb.br:8080/handle/tede/6871.

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Ca2+ is an intracellular messenger that controls a wide range of physiological functions through changes in its cytosolic concentration ([Ca2+]c). The increase in [Ca2+]c is derived of mobilization from intracellular stores or influx through channels, especially voltage-gated (Cav), present on cell surface. According to scientific literature, sea urchins embryogenesis is a process induced exclusively by the release of Ca2+ from the endoplasmic reticulum, and Ca2+ influx is not necessary for this process. However, there are studies in several species of the animal kingdom where Ca2+ influx is crucial for embryogenesis. Therefore, the aim of this study was to evaluate the involvement of Ca2+ influx at fertilization and embryonic development of Echinometra lucunter, a species of sea urchins with wide distribution on Brazilian coast. Thereby, eggs and embryos of E. lucunter were treated with various pharmacological tools and fertilization and embryonic development were monitored. Incubation of gametes in Ca2+ free medium inhibited fertilization and embryo treatment with Ca2+ chelators blocked embryonic development, suggesting that extracellular Ca2+ is essential for both processes. Cav blockers nifedipine, diltiazem and verapamil were also effective in blocking fertilization and embryo development, showing the importance of these channels to embryogenesis of E. lucunter. Inhibitory effect on embryo development is not associated with modulation of ABC superfamily proteins, since embryonic development was not affected, even under inhibition of these proteins. Verapamil inhibitory effect was reversed by prior addition of valinomycin which may be related to a probable increase of [Ca2+]c induced by K+ ionophore. ouabain, a Na+/K+-ATPase blocker that activates the reverse mode of Na+ /Ca2+, also reversed inhibition of development induced by verapamil. The reversal was not observed when compounds were added to embryos after verapamil, suggesting a temporal profile in inhibitory effect of these blockers. Inhibitory effects of verapamil and Ca2+ chelator EGTA were time-dependent, being absent 50 minutes after fertilization, suggesting that Ca2+ influx is seminal only in the first minutes of embryonic development. However, intracellular Ca2+ is essential for embryogenesis, since treatments with BAPTA-AM (chelator of intracellular Ca2+) and chlorpromazine or Trifluoperazine (Ca2+-calmodulin complex blockers) inhibited E. lucunter embryogenesis. Additionally, it was found that the rotundifolone, a plant-derived compound with vasorelaxing activity, attributed to the blockade of Cav, inhibited E. lucunter embryonic development showing an inhibitory profile similar to observed in vascular smooth muscle. Therefore, these results suggest that Ca2+ influx is essential for Echinometra lucunter embryogenesis and certify the embryonic development of this animal as appropriated pharmacological model for the investigation of natural and synthetic products that interferes in Ca2+ cellular dynamics.
O Ca2+ é um mensageiro intracelular que controla uma ampla variedade de funções fisiológicas por meio de alterações na sua concentração citosólica ([Ca2+]c). O aumento na [Ca2+]c é derivado da liberação a partir de estoques intracelulares ou do influxo através dos canais, principalmente os sensíveis à voltagem (Cav), presentes na superfície celular. De acordo com a literatura científica, a embriogênese de ouriços-do-mar é um processo regulado exclusivamente pela liberação de Ca2+ a partir do retículo endoplasmático, sendo o influxo dispensável para esse processo. Entretanto, há relatos em diversas espécies do reino animal onde o influxo de Ca2+ é crucial para a embriogênese. Portanto, o objetivo deste trabalho foi avaliar a participação do influxo de Ca2+ na fertilização e no desenvolvimento embrionário de Echinometra lucunter, uma espécie de ouriço-do-mar com ampla distribuição na costa Brasileira. Dessa forma, óvulos e embriões de E. lucunter foram tratados com diversas ferramentas farmacológicas e a fertilização e o desenvolvimento embrionário monitorados. A incubação dos gametas em meio isento de Ca2+ inibiu a fertilização e o tratamento dos embriões com quelantes de Ca2+ bloqueou o desenvolvimento embrionário, sugerindo que o Ca2+ extracelular é fundamental para ambos os processos. Os bloqueadores de Cav nifedipina, diltiazem e verapamil também foram eficazes no bloqueio da fertilização e do desenvolvimento embrionário, indicando a importância desses canais para a embriogênese de E. lucunter. O efeito inibitório sobre o desenvolvimento embrionário não está associado à modulação de proteínas da superfamília ABC, uma vez que o desenvolvimento embrionário ocorreu de forma normal, mesmo com a inibição dessas proteínas. O efeito inibitório do verapamil foi revertido pela adição prévia de valinomicina e tal fato pode estar relacionado a um provável aumento da [Ca2+]c induzido por este ionóforo de K+. A ouabaína, um bloqueador da Na+/K+-ATPase, capaz de ativar o modo reverso do trocador Na+/Ca2+, também reverteu a inibição do desenvolvimento induzida pelo verapamil. Essa reversão não foi observada quando os compostos foram adicionados aos embriões após o verapamil, sugerindo uma relação temporal no efeito inibitório desses bloqueadores. O efeito inibitório do verapamil e do quelante de Ca2+ EGTA foi dependente de tempo, sendo ausente 50 minutos após a fertilização, sugerindo que o influxo de Ca2+ é um fator determinante apenas nos primeiros minutos do desenvolvimento embrionário. Contudo, o Ca2+ intracelular é indispensável para a embriogênese, uma vez que os tratamentos com o BAPTA-AM, um quelante intracelular de Ca2+, e com trifluoperazina ou clorpromazina, bloqueadores do complexo Ca2+-calmodulina, inibiram a embriogênese de E. lucunter. Adicionalmente, foi verificado que a rotundifolona, um composto de origem vegetal com atividade vaso-relaxante atribuída ao bloqueio dos Cav, inibiu o desenvolvimento embrionário de E. lucunter, obtendo um perfil inibitório similar ao observado em musculatura lisa vascular. Portanto, esses resultados sugerem que o influxo de Ca2+ é essencial para a embriogênese de Echinometra lucunter e legitima o desenvolvimento embrionário desse animal como um excelente modelo farmacológico para a prospecção de produtos naturais e sintéticos bioativos que interferem na dinâmica celular do Ca2+.

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Zanotto, Camila Ziliotto. „Papel da O-glicosilação com N-acetil-glucosamina (O-GlcNAc) no influxo e recaptação de cálcio pelo retículo sarcoplasmático em aorta de ratos: análise funcional“. Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/17/17133/tde-09092013-133940/.

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A O-glicosilação com N-acetil-glucosamina (O-GlcNAc) é uma modificação pós-translacional altamente dinâmica que modula diversas vias de sinalização. O processo de O-GlcNAc é controlado por duas enzimas: a enzima OGT é responsável por catalisar a adição de N-acetil-glucosamina no grupo hidroxila dos resíduos de serina e treonina, enquanto a OGA catalisa a remoção de O-GlcNAc das proteínas modificadas. Proteínas com importante papel na função vascular são alvo de O-GlcNAc e o aumento da expressão de proteínas modificadas por O-GlcNAc promove aumento da reatividade vascular para estímulos contráteis. Um dos mecanismos de extrema importância no controle do tônus vascular está ligado à regulação da concentração de cálcio (Ca2+) intracelular, onde destacamos a participação do sistema STIM1/Orai1. As moléculas de interação estromal (STIM) atuam como sensores dos estoques intracelulares de Ca2+ e as proteínas Orai representam as subunidades que formam os canais de Ca2+ ativados pela liberação de Ca2+ (CRAC). Neste estudo investigamos a hipótese de que o aumento dos níveis vasculares de proteínas glicosiladas aumenta a resposta contrátil em aorta de ratos, por mecanismos relacionados ao controle da concentração intracelular de Ca2+.Em nossos experimentos, utilizamos aortas torácicas de ratos incubadas com PugNAc (inibidor seletivo da OGA, ), por 24h. Utilizando protocolo experimental que permite avaliar contrações induzidas pelo influxo de Ca2+ e liberação de Ca2+ intracelular, demonstramos que a incubação com PugNAc aumentou a resposta contrátil à PE bem como a contração durante o período de influxo de Ca2+, induzida pela reintrodução de solução fisiológica contendo Ca2+ (1,56 mM). O bloqueio dos canais CRAC com 2-APB (100 ) e gadolíneo (Gd3+, 100 ) diminuiu significativamente as contrações induzidas pelo influxo de Ca2+ em aortas incubadas com PugNAc. Além disso, estas aortas apresentaram aumento da expressão protéica de STIM1, o que resultaria em maior influxo de Ca2+. A contração induzida por cafeína (20 mM) e serotonina (10 ), a qual reflete a capacidade funcional do retículo sarcoplasmático (RS) em captar Ca2+, foi maior em aortas incubadas com PugNAc. O papel da Ca2+-ATPase (SERCA) foi avaliado com a utilização de tapsigargina, bloqueador da SERCA. O efeito da tapsigargina foi semelhante em artérias incubadas com PugNAc e veículo, apesar do aumento de expressão proteica da SERCA em aortas incubadas com PugNAc. Como a proteína cinase C (PKC) é ativada por aumentos de Ca2+ intracelular, determinamos se a atividade de proteínas alvo da PKC estavam aumentadas. A incubação com PugNAc aumentou a expressão das formas fosforiladas da CPI-17, MYPT-1 e MLC. Em conjunto, estes resultados sugerem que a ativação de STIM1/Orai1, aumento da liberação de Ca2+ intracelular e ativação da via de sinalização da PKC podem representar mecanismos que modulam as alterações vasculares em resposta ao aumento de proteínas glicosiladas por O-GlcNAc.
Glycosylation with O-linked -N-acetyl-glucosamine (O-GlcNAc) is a highly dynamic post-translational modification. The process of O-GlcNAc is controlled by two enzymes: the OGT enzyme catalyses the addition of N-acetyl-glucosamine to the hydroxyl group of serine and threonine residues of a target protein, while OGA catalyzes the cleavage of O-GlcNAc from post-translationally-modified proteins. Proteins with an important role in vascular function are targets of O-GlcNAc and increased levels of proteins modified by O-GlcNAc increase vascular reactivity to contractile stimuli. The regulation of intracellular calcium (Ca2+) concentration, including the activation of STIM1/Orai1, is key in the control of vascular tone. The stromal interaction molecules (STIM) act as sensors of intracellular Ca2+ stores whereas the Orai proteins represent subunits of the Ca2+ release-activated Ca2+ channels (CRAC). We hypothesized that increased levels of vascular O-GlcNAc proteins augment vascular contractile responses by altering mechanisms that regulate the intracellular Ca2+. Rat thoracic aortas were incubated with PugNAc (OGA selective inhibitor, ) for 24h. Using an experimental protocol that evaluates contractions induced by Ca2+ influx and release, we demonstrated that incubation with PugNAc increases contractile responses to phenylephrine (PE) as well as the contraction induced by Ca2+ influx, after depletion of intracellular Ca2+ stores. The CRAC channel blockers, 2-APB (100 ) and gadolinium (Gd3+, 100 ), significantly reduced the contractions induced by Ca2+ influx in aortas incubated with PugNAc. Furthermore, these aortas showed increased STIM1 protein expression, which could result in increased influx of Ca2+ and, in turn, increase vascular contraction. The contraction induced by the release of intracellular Ca2+ stores, stimulated by caffeine (20 mM) and serotonin (10 ), was increased in aortas incubated with PugNAc. The Ca2+-ATPase (SERCA) inhibitor thapsigargin produced similar effects in arteries incubated with PugNAc or vehicle, despite the increased SERCA protein expression in aortas incubated with PugNAc. Since PKC is activated by increases in intracellular Ca2+ and arteries incubated with PugNAc show activation of PKC, we determined whether the activity of proteins that are targets of PKC was increased in PugNAc-treated aortas. Incubation with PugNAc increased the expression of phosphorylated forms of CPI-17, MYPT-1 and MLC. Together, these results suggest that activation of STIM1/Orai1, increased release of intracellular Ca2+ and PKC activation may represent mechanisms that modulate vascular responses upon increased O-GlcNAc proteins.

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Menasché, Philippe. „Étude expérimentale des solutions cardioplégiques : applications à la chirurgie cardiaque“. Paris 11, 1987. http://www.theses.fr/1987PA112086.

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L'objectif de ce travail a été d'améliorer la protection myocardique au cours des épisodes d'ischémie globale inhérents aux interventions chirurgicales cardiaques. Notre modèle expérimental a été le cœur isolé perfusé de rat, soit travaillant soit isovolumique. Les résultats ont été évalués sur les critères hémodynamiques habituels complétés par les critères biochimiques fournis par RMN du phosphore 31. Dans un premier temps, nous avons cherché à mettre au point une solution cardioplégique ayant pour but principal de limiter la surcharge calcique intracellulaire. A cet effet ont été définis une formulation ionique et un pH appropriés, la qualité de la protection obtenue étant particulièrement démontrée sur une série de cœurs hypertrophiés. En revanche, dans nos conditions d'hypothermie, l'addition de Nifédipine à la cardioplégie s'est révélée sans effet. Une deuxième étape a ensuite consisté à mettre au point une solution destinée à être administrée immédiatement avant la réoxygénation et visant à prévenir les altérations induites par le phénomène de reperfusion Tant expérimentalement que cliniquement, l'usage de cette solution de reperfusion s'est révélé accroître significativement la protection due à la seule solution cardioplégique, validant en cela le bien fondé du concept d'une modification du reperfusat initial, et permettant d'identifier comme facteurs d'efficacité de ce reperfusat, la formule ionique, le pH, la nature des substrats métaboliques et la présence de piégeurs de radicaux libres de l'oxygène

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Rosso, Angela. „Estudo do envolvimento iônico e de proteínas cinases no mecanismo de ação da 1-a,25(OH)2 vitamina D3, no influxo de cálcio em células de Sertoli e em testículos de ratos“. reponame:Repositório Institucional da UFSC, 2012. http://repositorio.ufsc.br/xmlui/handle/123456789/94538.

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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Biológicas, Programa de Pós-graduação em Bioquímica, Florianópolis, 2010
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Tendo em mente que a 1,25D3, produto final do metabolismo da vitamina D3 é essencial para a integridade do sistema reprodutor masculino, e que, a homeostase do Ca+2 desempenha papel chave em muitos processos envolvidos na espermatogênese, avaliamos o efeito em nível membranar da 1,25D3 sobre o metabolismo do Ca+2 em testículo inteiro e célula de Sertoli de ratos imaturos. Foi demonstrado que em após 60 minutos de pré-incubação com o hormônio, não hove variação da captação basal de 45Ca+2 nos tempos de incubação de 30, 60, 150, 300 e 600 segundos. No tempo de incubação de 60 segundos, foi verificado que a 1,25D3 tem a capacidade de aumentar a captação de 45Ca+2 do meio extracelular em diferentes doses em ambos modelos experimentais, sendo este evento independente da ação genômica. Em testículos, observou-se que doses entre 10-15M e 10-9M foram eficazes em aumentar a captação de 45Ca+2, sendo o maior efeito evidenciado da dose de 10-10M (106%). Utilizando esta dose, foi demonstrado que os canais de CCDV do tipo L e T são as principais vias de entrada do íon nas células testiculares, e que há necessidade da manutenção das correntes de K+ e Cl- para que ocorra este evento. Em células de Sertoli também não foi verificada a variação da captação basal de 45Ca+2. Neste sistema, foi verificado que no tempo de 60 segundos de incubação, o hormônio foi capaz de elevar a captação de 45Ca+2 entre as doses de 10-12M e 10-8 M, onde a dose de 10-12 M aumentou em torno de140% a capatação do íon. Já a dose de 10-10 M elevou em 89% o influxo do íon. Desta forma, utilizando a dose de 10-10 M, verificamos que as células de Sertoli comportam- se assim como os testículos: há necessitadade da ativação dos CCDV-L e T para a entrada do Ca+2 assim como das correntes de K+ e Cl-. Também foi verificado que em células de Sertoli há necessidade da ativação das proteínas PKC e p38MAPK para a capatação de Ca+2 estimulada pela 1,25D3. Alé, disso, as proteínas PI3K e ERK1/2 também estão em parte envolvidas neste processo. Por fim, avaliamos que a integridade dos microtúbulos e a atividade dos canais ClC3 faz-se necessária para que ocorra a entrada do íon nas células de Sertoli, sendo esta elevação do íon necessária para que ocorra o processo de secreção celular já demosntrada anteriormente pela 1,25D3.

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Silva, Neto Gilson da. „Estudo de Mat?rias-Primas do Rio Grande do Norte para Uso em Revestimento Poroso: Influ?ncia do teor de dolomita e temperatura de calcina??o nas propriedades f?sico-mec?nicas“. Universidade Federal do Rio Grande do Norte, 2007. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12875.

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The state of Rio Grande do Norte presents a great potentiality for the production of ceramic tiles because of having natural raw material in quantity and quality making its economical exploration possible, beyond the great energetic differential of the state, the natural g?s. This works aims to study the influence of the dolomite and granulometry concentration and calcinations temperature in the obtaining of formulations for porous coverings which have to be coherent to the project,s specifications. The experiments have involved the physical-chemical and mineralogical characterizations of raw materials and mechanical tests in the dry and burnt proof bodies preceding a mixture experiment planning with the use of the response surface methodology, in order to get the best raw materials combinations to produce a ceramic mass with specific properties. The twelve ceramic masses studied in this work were prepared by the via dry process, characterized, shaped by uniaxial pressing and sinterized in the temperatures of 940?C, 1000?C, 1060?C, 1120?C and 1180?C, using a fast burning cycle. The crystalline phases formed during the sintering in the temperatures in study have revealed the presence of anorthite and diopside beyond quartz with a remaining phase. These phases were the main responsible ones by the physical- mechanical properties of the sinterized proof bodies. The proof bodies after the sintering stage have presented water absorption higher than 10% and a good dimensional stability in all studied temperatures. However, the flexural breaking strength results in the temperatures of 940?C, 1000?C and 1060?C, under the temperature zone of the vitrification of ceramic whiteware do not reach the flexural breaking strength specific for the porous wall tile (15 MPa), but in the temperature of 1120?C next to the vitrification temperature zone, some whiteware ceramic (formulations) has reached the specified value for the porous wall tile. The results of this work have showed that the studied raw materials have great importance for used in the production of porous wall tiles (BIII)
Rio Grande do Norte apresenta uma grande potencialidade para produ??o de revestimento cer?mico, haja vista, possuir mat?rias-primas naturais em quantidade e qualidade possibilitando sua explora??o econ?mica, al?m do grande diferencial energ?tico do Estado, que ? o g?s natural. Este trabalho objetiva estudar a influ?ncia da concentra??o de dolomita, sua granulometria e temperatura de sinteriza??o na obten??o de formula??es para revestimento poroso que atendam as especif?ca??es do projeto. Os experimentos envolveram a caracteriza??o f?sico qu?mico e mineral?gica das mat?rias-primas, e ensaios mec?nicos nos corpos de prova secos e queimados, precedendo-se de um planejamento de experimento de mistura, com o uso da metodologia de superf?cie de resposta, a fim de se obter as melhores combina?oes das mat?rias-primas para produzir massa cer?mica com propriedades especif?cas. As doze massas cer?micas estudadas foram preparadas pelo processo via seca, caracterizadas, conformadas por presagem uniaxial e sinterizadas nas temperaturas de 940?C, 1000?C, 1060?C, 1120?C, e 1180?C, utilizando um ciclo de queima r?pido. As fases cristalina formadas durante a sinteriza??o nas temperaturas em estudo, revelaram a presen?a de anortita e diopsita, al?m de quartzo com fase remanescente. Estas fases foram as principais respons?veis pelas propriedades f?sico-mec?nicas dos corpos de provas sinterizados. As fases cristalina formadas durante a sinteriza??o nas temperaturas em estudo, revelaram a presen?a de anortita e diopsita, al?m de quartzo com fase remanescente. Estas fases foram as principais respons?veis pelas propriedades f?sico-mec?nicas dos corpos de provas sinterizados. Os corpos de prova ap?s sinteriza??o apresentaram absor??o de ?gua superior a 10%, e uma boa estabilidade dimensional em todas as temperaturas estudadas, entretanto, os resultados da tens?o de ruptura ? flex?o nas temperaturas ( 940?C, 1000?C,e1060?C) abaixo da faixa de temperatura de gresifica?ao das massas cer?micas, n?o atigiram o valor de TRF especificado para revestimento poroso(15 MPa), por?m, na temperatura de 1120?C pr?xima da faixa da temperatura de gresifica??o, algumas massas cer?micas (formula??es) j? atingiram o valor especificado para revestimento poroso. Os resultados desse trabalho mostraram que, as mat?rias primas estudadas possuem grande potencial para serem utilizadas na fabrica??o de revestimento poroso (BIII)

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44

Kuo-Jung, Lo, und 羅國榮. „Store depletion-induced calcium influx in“. Thesis, 1998. http://ndltd.ncl.edu.tw/handle/35075435790662562236.

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碩士
國防醫學院
生物化學研究所
86
Using the fluorescent Ca2+ indicator fura-2, we found that, in cultured rat cerebellar astrocytes, a sustained increase of cytosolic Ca2+ concentration ([Ca2+]i) was induced by ATP or angiotensin II (AGII) following a transient increase of [Ca2+]i in the presence of extracellular Ca2+, while it was not seen in the absence of extracellular Ca2+, [Ca2+]i being declined to the basal level. Similarly, a slow and sustained [Ca2+]i increase, or a slow but not sustained [Ca2+]i increase was observed after intracellular Ca2+ pump was inhibited by thapsigargin (TG) in the presence or absence of extracellular Ca2+, respectively. These results suggest the existence of store-operated Ca2+ channel (SOC) in rat cerebellar astrocytes. This is further evidenced by the fact that 12 min after TG-induced stores depletion had occurred, [Ca2+]i remained in the sustained phase upon removal of TG, while it rapidly declined to the basal level after extracellular Ca2+ was removed. These results also indicate that activation of SOC was not dependent on its direct interaction with TG. Similar results were observed after Ca2+ stores were depleted by cyclopiazonic acid (CPA). This TG-induced, extracellular Ca2+-sensitive [Ca2+]i increase was highly dependent on the time period of TG exposure. Thus, Ca2+ influx could be detected as early as 2 min after TG exposure, while it was not fully activated until 12 min further suggesting that SOC was not activated until significant degree of Ca2+ stores were depleted. SOC could be detected earlier and TG-induced [Ca2+]i increase was greater in cells bathed in Na+ free buffer than those bathed in normal Na+ containing buffer indicating that SOC is a nonselective cation channel and Ca2+ influx was enhanced in the absence of Na+ since the competetion of Ca2+ with Na+ was no longer existing. However, using the fluorescent Na+ indicator, SBFI, [Na+]i increase was not detected after cells had been exposed to TG. Furthermore, the TG-activated cation channel was not permeable to Sr2+ or Ba2+, either. Using whole cell voltage clamp technique and step-pulse recordings from a holding potential of -70 mV to a test potential of -100 mV, a 60 - 100 pA inward current was activated by TG-induced Ca2+ stores depletion. The current-voltage curve of TG-activated current showed a linear relationship with the reversal poitential ranged from -5 to 0 mV in the presence of high internal Cs+ and external Na+. The amplitude of TG-activated current remained the same in Na+-free external solution, while it was larger at higher concentrations of external Ca2+. Taken together, our results suggest that SOC in rat cerebellar astrocytes is preferentially permeable to Ca2+. Similar SOC activity was seen in human embryonic kidney 293 cells (HEK293 cells) which is nonexcitable cells, while excitable cells, including rat cerebellar granule cells and procine aortic smooth muscle cells, did not display SOC. We next examined whether the activity of SOC was regulated by phosporylation by measuring the fura-2 fluorescence quench induced by Mn2+ influx via SOC. Addition of Mn2+ to the bathing buffer caused a slight but significant fluorescence quench and further fluorescence quench was induced 2 min after coadministration of Mn2+ and TG simultaneously. Pretreatment of cells with staurosporine, a Ser/Thr protein kinase inhibitor, enhanced the TG-induced fluorescence quench, while genistein, a tyrosine kinase inhibitor, had no effect on it indicating that dephosphorylation of Ser/Thr residues of proteins enhanced the SOC activity. This is further supported by the fact that promotion phosphorylation by phorbol 12-myristate 13-acetate or okadaic acid abolished TG-induced fluorescence quench. In conclusion, in rat cerebellar astrocytes, SOC is activated by depletion of Ca2+ store and its activity is regulated by phosporylation and dephosphorylation.

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„Regulation of TRPC3-mediated Ca2+ influx and flow-induced Ca2+ influx“. Thesis, 2006. http://library.cuhk.edu.hk/record=b6074196.

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Kwan Hiu Yee.
"June 2006."
2+ in the title is superscript.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2006.
Includes bibliographical references (p. 131-150).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstracts in English and Chinese.

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E-Fong, Kao, und 高一峰. „Capacitative Calcium Influx in C6 Glioma Cells“. Thesis, 1996. http://ndltd.ncl.edu.tw/handle/01870397043096944408.

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47

Yoo, Andrew. „Role of calcium influx in process extension of oligodendrocytes“. Thesis, 1998. http://hdl.handle.net/2429/8375.

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The effects of phorbol ester, which activates protein kinase C (PKC), and free cytosolic Ca²+ were studied on their role in process extension in cultured murine oligodendrocytes. Previous studies have shown that PKC activation by phorbol esters greatly enhances process formation in cultured oligodendrocytes (OLG), an important step for myelination. Because of the possible involvement of PKC and Ca²+ in process extension in OLGs, we studied the effect of PKC activation on changes in intracellular free Ca²+ concentration ([Ca²+]i). We found that PKC activation by phorbol esters induced a sustained rise in [Ca²+]i of OLGs. This rise was due to transmembrane influx of Ca²+ since omission of extracellular Ca²+ failed to trigger the rise in [Ca²+]i. Changes in [Ca²+]i were also produced by modifying the extracellular [Ca²+] where increasing extracellular [Ca²+] led to a rise in [Ca²+]i. In order to establish the relationship between Ca²+ influx and OLG process formation, OLGs were incubated in media containing various [Ca²+] with or without phorbol ester treatment. After 72 hours, OLGs were immunostained using an antibody against proteolipid protein (PLP). The correlation between the process formation of OLGs and extracellular [Ca²+] was assessed by obtaining the percentage of OLGs with longer processes in the OLG population, the number of primary process per cell body and the area covered by PLP-positive OLG processes. Our results indicate that the degree of OLG process extension is related to the [Ca²+] present in the culture media. We found that increased extracellular [Ca²+] alone, without concurrent phorbol ester application, resulted in increased OLG process extension. When OLGs were treated with phorbol ester, positive correlations between increasing extracellular [Ca²+] and some aspects of OLG process extension were seen, as suggested by the results from analysis of covariance (ANCOVA). In addition, blocking the intracellular Ca²+ signalling by BAPTA as well as inhibiting PKC by RO-31 leads to retraction o f membrane sheath o f OLGs . Our results demonstrate that increasing [Ca²+]i stimulates OLG process outgrowth and suggest that intracellular Ca²+ signalling following either phorbol ester treatment or increasing extracellular [Ca²+] may be an important mediator for OLG process extension.

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48

Shan, Ke, und 單可. „Mitochondrial ROS release triggered by calcium influx activates autophagy“. Thesis, 2019. http://ndltd.ncl.edu.tw/handle/uuc72e.

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碩士
國立臺灣大學
生化科學研究所
107
Autophagy, a self-digestive mechanism, is vital for cellular functions and health. During starvation, autophagosomes form mainly at the endoplasmic reticulum (ER)-mitochondria contact sites. However, how cells timely induce autophagy at these sites are unclear. We aimed to elucidate the roles of ER and mitochondrial calcium-reactive oxygen species (ROS) signaling in autophagosome formation at these sites. We used confocal live-cell imaging to monitor autophagy activity in the absence or presence of calcium and ROS inhibitors. We found that autophagy activity burst at 10-15 minutes of starvation. The autophagy burst was preceded by mitochondrial calcium influx, mitochondrial ROS production and release; the inhibition of these phenomena abolished autophagy burst. Previously, our lab saw Atg4, an LC3 de-conjugating enzyme, was inhibited in the same time frame. Additionally, autophagy induced by plasma membrane damage was also controlled by mitochondrial ROS release. Taken together, we propose that during short-term starvation, mitochondrial calcium influx induces ROS production and release. ROS then facilitate autophagy by local Atg4 inhibition. This calcium-ROS signaling pathway may represent a general autophagy regulatory mechanism in starvation, plasma membrane damage and other autophagy stimuli that involve calcium perturbations.

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49

Hickey, Charlene. „Calcium influx and release controls neuroendocrine cell secretion and excitability“. Thesis, 2009. http://hdl.handle.net/1974/5166.

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Ca2+ dynamics affect many critical cellular processes. In the bag cell neurons of Aplysia californica, intracellular Ca2+ is elevated during a prolonged period of firing known as the afterdischarge. This consists of a fast and slow phase of firing, which triggers peptide secretion and culminates in egg-laying. The present study examines how Ca2+ influx and release shape neurosecretion and membrane activity. Using capacitance tracking as an index of secretion, a 5 Hz, 1 min train, to mimic the fast phase, induced a clear elevation in the membrane surface area of cultured bag cell neurons. The capacitance change was abolished by replacing external Ca2+ with Ba2+ or addition of the Ca2+ channel blocker, Ni2+. Additionally, the response was reduced by either strong buffering of intracellular Ca2+ or pretreatment with N-ethylmaleimide, an alkylating agent that disrupts vesicular transport. Depleting mitochondrial Ca2+ with the protonophore, carbonyl cyanide-p-trifluoromethoxyphenyl-hydrazone (FCCP), also elevated capacitance, while depleting endoplasmic reticulum Ca2+ with the Ca2+-ATPase inhibitor, cyclopiazonic acid, did not. Similarly, FCCP alone depolarized bag cell neurons. In a concentration-dependent manner, FCCP elicited an inward current that was insensitive to Ni2+, associated with an increase in conductance, and a linear current/voltage relationship that reversed around -40 mV. Removal of extracellular Ca2+ reduced the current and left-shifted the reversal, consistent with opening a Ca2+-permeable, voltage-independent, non-selective cation channel. The current was decreased when intracellular Ca2+ was strongly buffered, while fura-imaging demonstrated that FCCP elevated intracellular Ca2+ with a similar time course, suggesting a dependence on intracellular Ca2+. Although both oligomycin A and bafilomycin A, inhibitors of mitochondrial ATP sythetase and V-type H+-ATPase, respectively, gradually increased Ca2+, neither produced a current. The FCCP-induced Ca2+ elevation and the current were also diminished by disabling the mitochondrial permeability transition pore with N-ethylmaleimide. The data suggests that a cation current is preferentially gated by Ca2+ released from the mitochondria, rather than disruption of ATP production. This current could provide depolarizing drive for the afterdischarge. While Ca2+ entry appears to be responsible for initiating neurosecretion, mitochondrial Ca2+ may support prolonged peptide release during and subsequent to the afterdischarge.
Thesis (Master, Physiology) -- Queen's University, 2009-09-18 19:30:32.957

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50

„Role of agonist- and flow-induced caclium influx in vascular tone control“. 2004. http://library.cuhk.edu.hk/record=b6073718.

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"2+" in the title is superscript.
"December 2004."
Thesis (Ph.D.)--Chinese University of Hong Kong, 2004.
Includes bibliographical references (p. 179-204)
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Mode of access: World Wide Web.
Abstracts in English and Chinese.

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