Funke, Frank

[["dc.bibliographiccitation.firstpage","3067"],["dc.bibliographiccitation.issue","6"],["dc.bibliographiccitation.journal","Journal of Neurophysiology"],["dc.bibliographiccitation.lastpage","3079"],["dc.bibliographiccitation.volume","105"],["dc.contributor.author","Kron, Miriam"],["dc.contributor.author","Zimmermann, Jasper L."],["dc.contributor.author","Dutschmann, Mathias"],["dc.contributor.author","Funke, Frank"],["dc.contributor.author","Müller, Michael"],["dc.date.accessioned","2018-09-28T10:28:17Z"],["dc.date.available","2018-09-28T10:28:17Z"],["dc.date.issued","2011"],["dc.description.abstract","Rett syndrome (RTT) patients suffer from respiratory arrhythmias with frequent apneas causing intermittent hypoxia. In a RTT mouse model (methyl-CpG-binding protein 2-deficient mice; Mecp2(-/y)) we recently discovered an enhanced hippocampal susceptibility to hypoxia and hypoxia-induced spreading depression (HSD). In the present study we investigated whether this also applies to infant Mecp2(-/y) brain stem, which could become life-threatening due to failure of cardiorespiratory control. HSD most reliably occurred in the nucleus of the solitary tract (NTS) and the spinal trigeminal nucleus (Sp5). HSD susceptibility of the Mecp2(-/y) NTS and Sp5 was increased on 8 mM K(+)-mediated conditioning. 5-HT(1A) receptor stimulation with 8-hydroxy-2-(di-propylamino)tetralin (8-OH-DPAT) postponed HSD by up to 40%, mediating genotype-independent protection. The deleterious impact of HSD on in vitro respiration became obvious in rhythmically active slices, where HSD propagation into the pre-Bötzinger complex (pre-BötC) immediately arrested the respiratory rhythm. Compared with wild-type, the Mecp2(-/y) pre-BötC was invaded less frequently by HSD, but if so, HSD occurred earlier. On reoxygenation, in vitro rhythms reappeared with increased frequency, which was less pronounced in Mecp2(-/y) slices. 8-OH-DPAT increased respiratory frequency but failed to postpone HSD in the pre-BötC. Repetitive hypoxia facilitated posthypoxic recovery only if HSD occurred. In 57% of Mecp2(-/y) slices, however, HSD spared the pre-BötC. Although this occasionally promoted residual hypoxic respiratory activity (\"gasping\"), it also prolonged the posthypoxic recovery, and thus the absence of central inspiratory drive, which in vivo would lengthen respiratory arrest. In view of the breathing disorders in RTTs, the increased hypoxia susceptibility of MeCP2-deficient brain stem potentially contributes to life-threatening disturbances of cardiorespiratory control."],["dc.identifier.doi","10.1152/jn.00822.2010"],["dc.identifier.pmid","21471397"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/15858"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.relation.eissn","1522-1598"],["dc.title","Altered responses of MeCP2-deficient mouse brain stem to severe hypoxia"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","2590"],["dc.bibliographiccitation.issue","4"],["dc.bibliographiccitation.journal","NeuroImage"],["dc.bibliographiccitation.lastpage","2602"],["dc.bibliographiccitation.volume","54"],["dc.contributor.author","Funke, Frank"],["dc.contributor.author","Gerich, Florian J."],["dc.contributor.author","Müller, Michael"],["dc.date.accessioned","2018-09-28T10:30:44Z"],["dc.date.available","2018-09-28T10:30:44Z"],["dc.date.issued","2011"],["dc.description.abstract","The cellular redox status is determined by various extra- and intracellular factors, and contributes to cytosolic signaling and oxidative stress. Especially mitochondria modulate the cytosolic redox status by oxidizing NADH and FADH(2) and generating reactive oxygen species (ROS). Whereas cellular NADH and FAD levels are reliably detectable as autofluorescence, quantifying cellular ROS production is more demanding, because the various redox-sensitive dyes share major disadvantages including irreversible oxidation, autooxidation and photosensitivity. As an alternative, we took advantage of a genetically engineered redox-sensitive green fluorescent protein (roGFP1), carefully evaluated its response properties, and succeeded to monitor ROS dynamics in cultured rat hippocampal neurons and organotypic slices. The ratiometric properties and reversible oxidation/reduction of roGFP1 enable reliable, semi-quantitative analyses of cytosolic ROS levels and redox status. Cytosolically expressed roGFP1 readily responded to hydrogen peroxide, superoxide and hydroxyl radicals, and was only negligibly affected by intracellular pH or Cl(-) content. Furthermore, roGFP1 was well suited for two-photon excitation, reliably detected changes in endogenous ROS production during impaired mitochondrial respiration or neuronal stimulation, and was even capable of visualizing perimitochondrial ROS microdomains. Modulation of cellular scavenging systems confirmed the functional integration of roGFP1 into the cellular ROS and redox balance. We conclude that roGFP1 is well suited for dynamic, compartment specific, subcellular analyses even in complex neuronal networks. The ability to correlate dynamic changes in cellular ROS levels with mitochondrial metabolism and neuronal network activity is a promising step towards a detailed mechanistic understanding of redox- and ROS-mediated signaling in normal and diseased brain function."],["dc.identifier.doi","10.1016/j.neuroimage.2010.11.031"],["dc.identifier.pmid","21081169"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/6124"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/15859"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","final"],["dc.relation.eissn","1095-9572"],["dc.rights","Goescholar"],["dc.rights.uri","https://goescholar.uni-goettingen.de/licenses"],["dc.title","Dynamic, semi-quantitative imaging of intracellular ROS levels and redox status in rat hippocampal neurons"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","693"],["dc.bibliographiccitation.issue","5"],["dc.bibliographiccitation.journal","Pflügers Archiv : European Journal of Physiology"],["dc.bibliographiccitation.lastpage","708"],["dc.bibliographiccitation.volume","462"],["dc.contributor.author","Keil, Vera C."],["dc.contributor.author","Funke, Frank"],["dc.contributor.author","Zeug, Andre"],["dc.contributor.author","Schild, Detlev"],["dc.contributor.author","Müller, Michael"],["dc.date.accessioned","2018-09-28T10:25:31Z"],["dc.date.available","2018-09-28T10:25:31Z"],["dc.date.issued","2011"],["dc.description.abstract","Using the mitochondrial potential (ΔΨ(m)) marker JC-1 (5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanine iodide) and high-resolution imaging, we functionally analyzed mitochondria in cultured rat hippocampal astrocytes. Ratiometric detection of JC-1 fluorescence identified mitochondria with high and low ΔΨ(m). Mitochondrial density was highest in the perinuclear region, whereas ΔΨ(m) tended to be higher in peripheral mitochondria. Spontaneous ΔΨ(m) fluctuations, representing episodes of increased energization, appeared in individual mitochondria or synchronized in mitochondrial clusters. They continued upon withdrawal of extracellular Ca(2+), but were antagonized by dantrolene or 2-aminoethoxydiphenylborate (2-APB). Fluo-3 imaging revealed local cytosolic Ca(2+) transients with similar kinetics that also were depressed by dantrolene and 2-APB. Massive cellular Ca(2+) load or metabolic impairment abolished ΔΨ(m) fluctuations, occasionally evoking heterogeneous mitochondrial depolarizations. The detected diversity and ΔΨ(m) heterogeneity of mitochondria confirms that even in less structurally polarized cells, such as astrocytes, specialized mitochondrial subpopulations coexist. We conclude that ΔΨ(m) fluctuations are an indication of mitochondrial viability and are triggered by local Ca(2+) release from the endoplasmic reticulum. This spatially confined organelle crosstalk contributes to the functional heterogeneity of mitochondria and may serve to adapt the metabolism of glial cells to the activity and metabolic demand of complex neuronal networks. The established ratiometric JC-1 imaging-especially combined with two-photon microscopy-enables quantitative functional analyses of individual mitochondria as well as the comparison of mitochondrial heterogeneity in different preparations and/or treatment conditions."],["dc.identifier.doi","10.1007/s00424-011-1012-8"],["dc.identifier.pmid","21881871"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/7130"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/15857"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","final"],["dc.relation.eissn","1432-2013"],["dc.rights","Goescholar"],["dc.rights.uri","https://goescholar.uni-goettingen.de/licenses"],["dc.title","Ratiometric high-resolution imaging of JC-1 fluorescence reveals the subcellular heterogeneity of astrocytic mitochondria"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","937"],["dc.bibliographiccitation.issue","5"],["dc.bibliographiccitation.journal","Pflügers Archiv : European Journal of Physiology"],["dc.bibliographiccitation.lastpage","952"],["dc.bibliographiccitation.volume","458"],["dc.contributor.author","Gerich, Florian J."],["dc.contributor.author","Funke, Frank"],["dc.contributor.author","Hildebrandt, Belinda"],["dc.contributor.author","Fasshauer, Martin"],["dc.contributor.author","Müller, Michael"],["dc.date.accessioned","2018-09-28T10:04:34Z"],["dc.date.available","2018-09-28T10:04:34Z"],["dc.date.issued","2009"],["dc.description.abstract","Reactive oxygen species (ROS) released from (dys-)functioning mitochondria contribute to normal and pathophysiological cellular signaling by modulating cytosolic redox state and redox-sensitive proteins. To identify putative redox targets involved in such signaling, we exposed hippocampal neurons to hydrogen peroxide (H(2)O(2)). Redox-sensitive dyes indicated that externally applied H(2)O(2) may oxidize intracellular targets in cell cultures and acute tissue slices. In cultured neurons, H(2)O(2) (EC(50) 118 microM) induced an intracellular Ca(2+) rise which could still be evoked upon Ca(2+) withdrawal and mitochondrial uncoupling. It was, however, antagonized by thapsigargin, dantrolene, 2-aminoethoxydiphenyl borate, and high levels of ryanodine, which identifies the endoplasmic reticulum (ER) as the intracellular Ca(2+) store involved. Intracellular accumulation of endogenously generated H(2)O(2)-provoked by inhibiting glutathione peroxidase-also released Ca(2+) from the ER, as did extracellular generation of superoxide. Phospholipase C (PLC)-mediated metabotropic signaling was depressed in the presence of H(2)O(2), but cytosolic cyclic adenosine-5'-monophosphate (cAMP) levels were not affected. H(2)O(2) (0.2-5 mM) moderately depolarized mitochondria, halted their intracellular trafficking in a Ca(2+)- and cAMP-independent manner, and directly oxidized cellular nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FADH(2)). In part, the mitochondrial depolarization reflects uptake of Ca(2+) previously released from the ER. We conclude that H(2)O(2) releases Ca(2+) from the ER via both ryanodine and inositol trisphosphate receptors. Mitochondrial function is not markedly impaired even by millimolar concentrations of H(2)O(2). Such modulation of Ca(2+) signaling and organelle interaction by ROS affects the efficacy of PLC-mediated metabotropic signaling and may contribute to the adjustment of neuronal function to redox conditions and metabolic supply."],["dc.identifier.doi","10.1007/s00424-009-0672-0"],["dc.identifier.pmid","19430810"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/15851"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.relation.eissn","1432-2013"],["dc.title","H(2)O(2)-mediated modulation of cytosolic signaling and organelle function in rat hippocampus"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]