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Dye Coupling (dye + coupling)
Selected AbstractsElectrophysiological and morphological characterization of dentate astrocytes in the hippocampusDEVELOPMENTAL NEUROBIOLOGY, Issue 2 2005Masako Isokawa Abstract We studied electrophysiological and morphological properties of astrocytes in the dentate gyrus of the rat hippocampus in slices. Intracellular application of Lucifer yellow revealed two types of morphology: one with a long process extruding from the cell body, and the other with numerous short processes surrounding the cell body. Their electrophysiological properties were either passive, that is, no detectable voltage-dependent conductance, or complex, with Na+/K+ currents similar to those reported in the Ammon's horn astrocytes. We did not find any morphological correlate to the types of electrophysiological profile or dye coupling. Chelation of cytoplasmic calcium ([Ca2+]i) by BAPTA increased the incidence of detecting a low Na+ conductance and transient outward K+ currents. However, an inwardly rectifying K+ current (Kir), a hallmark of differentiated CA1/3 astrocytes, was not a representative K+ -current in the complex dentate astrocytes, suggesting that these astrocytes could retain an immature form of K-currents. Dentate astrocytes may possess a distinct current profile that is different from those in CA1/3 Ammon's horn. © 2005 Wiley Periodicals, Inc. J Neurobiol, 2005 [source] Changing patterns of ganglion cell coupling and connexin expression during chick retinal developmentDEVELOPMENTAL NEUROBIOLOGY, Issue 4 2002David L. Becker Abstract We have used dye injection and immunolabeling to investigate the relationship between connexin (Cx) expression and dye coupling between ganglion cells (GCs) and other cells of the embryonic chick retina between embryonic days 5 and 14 (E5,14). At E5, GCs were usually coupled, via soma-somatic or dendro-somatic contacts, to only one or two other cells. Coupling increased with time until E11 when GCs were often coupled to more than a dozen other cells with somata in the ganglion cell layer (GCL) or inner nuclear layer (INL). These coupled clusters occupied large areas of the retina and coupling was via dendro-dendritic contacts. By E14, after the onset of synaptogenesis and at a time of marked cell death, dye coupling was markedly decreased with GCs coupled to three or four partners. At this time, coupling was usually to cells of the same morphology, whereas earlier coupling was heterogeneous. Between E5 and E11, GCs were sometimes coupled to cells of neuroepithelial morphology that spanned the thickness of the retina. The expression of Cx 26, 32, and 43 differed and their distribution changed during the period studied, showing correlation with events such as proliferation, migration, and synaptogenesis. These results suggest specific roles for gap junctions and Cx's during retinal development. © 2002 Wiley Periodicals, Inc. J Neurobiol 52: 280,293, 2002 [source] Olfactory ensheathing cell membrane properties are shaped by connectivityGLIA, Issue 6 2010Lorena Rela Abstract Olfactory ensheathing cells (OECs) have been repeatedly implicated in mediating plasticity, particularly in situ in the olfactory nerve in which they support the extension of olfactory sensory neuron (OSN) axons from the olfactory epithelium to the olfactory bulb (OB). OECs are specialized glia whose processes surround OSN axon fascicles within the olfactory nerve and across the OB surface. Despite their purported importance in promoting axon extension, and following transplants, little is known about either morphology or biophysical properties of OECs in situ. In particular, cell,cell interactions that may influence OEC function are largely unexplored. Here, we studied OEC connectivity and morphology in slice preparations, preserving tissue structure and cell,cell interactions. Our analyses showed that OECs form a matrix of cellular projections surrounding axons, unique among glia, and express high levels of connexin-43. Lucifer Yellow injections revealed selective dye coupling among small subgroups of OECs. Two types of OECs were biophysically distinguished with whole-cell voltage-clamp recordings: (1) with low-input resistance (Ri), linear current profiles, and frequently dye coupled; and (2) with high Ri, nonlinear current profiles, and infrequent dye coupling. Pharmacological blockade of gap junctions changed OEC membrane properties such that linear OECs became nonlinear. Double recordings indicated that the appearance of the nonlinear current profile was associated with the loss of electrical coupling between OECs. We conclude that the diversity of OEC current profiles can be explained by differences in gap-junction connectivity and discuss implications of this diversity for OEC influences on axon growth and excitability. © 2009 Wiley-Liss, Inc. [source] Human and mouse microglia express connexin36, and functional gap junctions are formed between rodent microglia and neuronsJOURNAL OF NEUROSCIENCE RESEARCH, Issue 3 2005K. Dobrenis Abstract Microglia, the tissue macrophages of the central nervous system (CNS), intimately interact with neurons physically and through soluble factors that can affect microglial activation state and neuronal survival and physiology. We report here a new mechanism of interaction between these cells, provided by the formation of gap junctions composed of connexin (Cx) 36. Among eight Cxs tested, expression of Cx36 mRNA and protein was found in microglial cultures prepared from human and mouse, and Cx45 mRNA was found in mouse microglial cultures. Electrophysiological measurements found coupling between one-third of human or mouse microglial pairs that averaged below 30 pico-Siemens and displayed electrical properties consistent with Cx36 gap junctions. Importantly, similar frequency of low-strength electrical coupling was also obtained between microglia and neurons in cocultures prepared from neocortical or hippocampal rodent tissue. Lucifer yellow dye coupling between neurons and microglia was observed in 4% of pairs tested, consistent with the low strength and incidence of electrical coupling. Cx36 expression level and/or the degree of coupling between microglia did not significantly change in the presence of activating agents, including lipopolysaccharide, granulocyte-macrophage colony-stimulating factor, interferon-,, and tumor necrosis factor-,, except for some reduction of Cx36 protein when exposed to the latter two agents. Our findings that intercellular coupling occurs between neuronal and microglial populations through Cx36 gap junctions have potentially important implications for normal neural physiology and microglial responses in neuronopathology in the mammalian CNS. © 2005 Wiley-Liss, Inc. [source] Growth and Differentiation of Osteoblast-Like Cells from Calvaria of Connexin43 Deficient MiceMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 12 2004M. Wiemann Osteoblasten-artige Zellen; Connexin43-defiziente Mäuse; gap junctions; Differenzierung Abstract Extensive cell-cell-coupling via gap junctions has been suspected to play an essential role for osteoblast development. Here, osteoblast-like cells (OBL) from connexin(Cx)43 knock out mice were used to explore the role of Cx43 for osteoblast differentiation. Primary cultures of OBL were derived from calvaria of homozygous (Cx43-/-) and heterozygous (Cx43+/,) knock out mice and also from wild type controls (Cx43+/+). In Cx43-/- OBL Lucifer Yellow dye coupling was largely abolished demonstrating that small molecules could no longer be transferred among neighboring cells. Cx43-/- OBL grew out very slowly from calvarial fragments. Nevertheless their cell density around explants was increased 3-fold vs. controls after 3 weeks. Histochemistry showed that in many Cx43-/- OBL there was an increased alkaline phosphatase activity within the cytoplasm and close to the cell membrane. Mineralization was diminished in Cx43-/- cultures. In heterozygous Cx43+/, OBL all aforementioned effects were less pronounced, pointing to a gene-dosage effect. Data suggest that the loss of Cx43 indirectly impairs the osteoblastic phenotype, e.g. by disturbing cellular functions such as motility and/or secretion. If this holds true, all parameters in the interphase of enosseous implants which lower gap junction expression will also affect bone regeneration. Wachstum und Differenzierung von Osteoblasten-artigen Zellen aus Kalvarien Connexin43-defizienter Mäuse Es wurde oft vermutet, dass die ausgeprägte Zell-Zell-Kopplung von Osteoblasten durch gap junctions eine besondere Rolle für die Differenzierung der gekoppelten Zellen spielt. In dieser Arbeit wurden daher Osteoblasten-artige Zellen (OBL) aus Connexin43 (Cx43) knock out Mäusen benutzt, um die Bedeutung von Cx43-gap-junction-Kanälen für die Differenzierung von Osteoblasten zu untersuchen. Die dafür notwendigen OBL-Primärkulturen wurden aus Calvarienfragmenten von homozygoten (Cx43-/-) und heterozygoten (Cx43+/,) knock out Mäusen sowie aus Wildtyp-Mäusen gewonnen. In Cx43-/- OBL war die Lucifer Yellow-Farbstoffkopplung weitgehend aufgehoben. Dieser Befund zeigt, dass Moleküle ,600 D zwischen Cx43-/- Zellen kaum noch ausgetauscht werden können. Cx43-/- Zellen wuchsen vergleichsweise langsam aus ihren Calvarienfragmenten aus. Dennoch erreichten diese Kulturen nach 3 Wochen eine im Vergleich zur Kontrolle 3fach höhere Zelldichte. Histochemisch zeigte sich, dass in Cx43-/- Zellen die alkalische Phosphatase-Aktivität im Zytoplasma und besonders im Bereich der Zellmembran erhöht war. Die Mineralisierung war hingegen herabgesetzt. In heterozygoten Cx43+/, OBL waren alle genannten Effekte intermediär ausgeprägt, was auf einen Gen-Dosis-Effekt deutet. Insgesamt legen die Befunde nahe, dass der Verlust von Cx43 die Ausprägung des osteoblastären Phänotyps, z.,B. durch eine Behinderung der Zellbeweglichkeit und/oder der Sekretion beeinträchtigt. Daher dürften alle Parameter, die die Expression von Cx43 im Interphase eines enossalen Implantats stören, die Knochenregeneration behindern. [source] Large-scale chromatin remodeling in germinal vesicle bovine oocytes: Interplay with gap junction functionality and developmental competenceMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 6 2007Valentina Lodde Abstract In mammals, oocyte acquires a series of competencies sequentially during folliculogenesis that play critical roles at fertilization and early stages of embryonic development. In mouse, chromatin in germinal vesicle (GV) undergoes dynamic changes during oocyte growth and its progressive condensation has been related to the achievement of developmental potential. Cumulus cells are essential for the acquisition of meiotic competence and play a role in chromatin remodeling during oocyte growth. This study is aimed to characterize the chromatin configuration of growing and fully grown bovine oocytes, the status of communications between oocyte and cumulus cells and oocyte developmental potential. Following nuclear staining, we identified four discrete stages of GV, characterized by an increase of chromatin condensation. GV0 stage represented 82% of growing oocytes and it was absent in fully grown oocytes. GV1, GV2, and GV3 represented, respectively, 24, 31, and 45% of fully grown oocytes. Our data indicated a moderate but significant increase in oocyte diameter between GV0 and GV3 stage. By dye coupling assay the 98% of GV0 oocytes showed fully open communications while the number of oocytes with functionally closed communications with cumulus cells was significantly higher in GV3 group than GV1 and GV2. However, GV0 oocytes were unable to progress through metaphase II while GV2 and GV3 showed the highest developmental capability. We conclude that in bovine, the progressive chromatin condensation is related to the sequential achievement of meiotic and embryonic developmental competencies during oocyte growth and differentiation. Moreover, gap-junction-mediated communications between oocyte and cumulus cells could be implicated in modulating the chromatin remodeling process. Mol. Reprod. Dev. 74: 740,749, 2007. © 2006 Wiley-Liss, Inc. [source] Differential dye coupling reveals lateral giant escape circuit in crayfishTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 1 2003Brian L. Antonsen Abstract The lateral giant (LG) escape circuit of crayfish mediates a coordinated escape triggered by strong attack to the abdomen. The LG circuit is one of the best understood of small systems, but models of the circuit have mostly been limited to simple ball-and-stick representations, which ignore anatomical details of contacts between circuit elements. Many of the these contacts are electrical; here we use differential dye coupling, a technique which could help reveal connection patterns in many neural circuits, to reveal in detail the circuit within the terminal abdominal ganglion. Sensory input from the tailfan forms a somatotopic map on the projecting LG dendrites, which together with interafferent coupling mediates a lateral excitatory network that selectively amplifies strong, phasic, converging input to LG. Mechanosensory interneurons contact LG at sites distinct from the primary afferents and so maximize their summated effect on LG. Motor neurons and premotor interneurons are excited near the initial segments of the LGs and innervate muscles for generating uropod flaring and telson flexion. Previous research has shown that spatial patterns of input are important for signal integration in LG; this map of electrical contact points will help us to understand synaptic processing in this system. J. Comp. Neurol. 466:1,13, 2003. © 2003 Wiley-Liss, Inc. [source] Alterations in connexin expression in the bladder of patients with urge symptomsBJU INTERNATIONAL, Issue 4 2005Jochen Neuhaus OBJECTIVE To compare the formation of gap junctions between detrusor smooth muscle cells in situ and the distribution of connexin (Cx)40, Cx43 and Cx45 expressions in bladder biopsies from a control group (with bladder tumour) and from patients with urge symptoms, as smooth muscle cells of the human detrusor muscle communicate via gap junctions and express several connexin subtypes, alterations of which may be involved in the causes of lower urinary tract symptoms. MATERIALS AND METHODS Connexin expression is prominent in myofibroblast-like cells, supposedly involved in afferent signalling pathways of the bladder. Their strategic position directly beneath the urothelium suggests they are a link between urothelial ATP signalling during bladder filling and afferent A,-fibre stimulation for co-ordination of bladder tonus and initialization of the micturition reflex. Modification of their coupling characteristics may have profound impact on bladder sensation. Bladder tissue probes of patients undergoing cystectomy or transurethral tumour resection for bladder cancer were used as controls. Tissue samples from patients with severe idiopathic urge symptoms were taken for exclusion diagnostics of interstitial cystitis (IC) and carcinoma in situ. The formation of functional syncytia between detrusor smooth muscle cells were examined in dye-coupling experiments by injecting with Lucifer Yellow. The morphology and structure of gap junctions were assessed by transmission electron microscopy and immunogold labelling of Cx43 and Cx45. The expression of connexin subtypes Cx40, Cx43 and Cx45 was compared by indirect immunofluorescence, and confocal laser scanning microscopy used for semiquantitative analysis. RESULTS There was dye coupling between smooth muscle cells of the detrusor in situ. Electron microscopy and immunogold labelling showed very small gap junctional plaques. These findings were confirmed by confocal immunofluorescence. Semiquantitative analyses showed significantly higher Cx43 expression in the detrusor muscle, and a tendency to higher Cx45 expression in the suburothelial layer associated with urge symptoms, whereas Cx40 expression was unaffected. CONCLUSIONS Smooth muscle cells of the human detrusor muscle are coupled by classical gap junctions, forming limited local functional syncytia. Both Cx43 and Cx45 are expressed at low levels in normal detrusor. Up-regulation of Cx43 in patients with urge incontinence supports the possibility of functional changes in the syncytial properties of detrusor smooth muscle cells in this condition. In addition, the observed increase of Cx45 in the myofibroblast cell layer supports the idea that alterations in sensory signalling are also involved. Comparison with previous reports implies that the pathophysiology of urgency is distinct from that of the unstable bladder and other forms of incontinence. [source] | ||||||||||