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  • 1
    Electronic Resource
    Electronic Resource
    Transient decrease in F-actin may be necessary for translocation of proteins into dendritic spines (2005)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 22 (2005), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: It remains poorly understood as to how newly synthesized proteins that are required to act at specific synapses are translocated into only selected subsets of potentiated dendritic spines. Here, we report that F-actin, a major component of the skeletal structure of dendritic spines, may contribute to the regulation of synaptic specificity of protein translocation. We found that the stabilization of F-actin blocked the translocation of GFP-CaMKII and inhibited the diffusion of 3-kDa dextran into spines (in 2–3 weeks cultures). Neuronal activation in hippocampal slices and cultured neurons led to an increase in the activation (decrease in the phosphorylation) of the actin depolymerization factor, cofilin, and a decrease in F-actin. Furthermore, the induction of long-term potentiation by tetanic stimulation induced local transient depolymerization of F-actin both in vivo and in hippocampal slices (8–10 weeks), and this local F-actin depolymerization was blocked by APV, a N-methyl-d-aspartate (NMDA) receptor antagonist. These results suggest that F-actin may play a role in synaptic specificity by allowing protein translocation into only potentiated spines, gated through its depolymerization, which is probably triggered by the activation of NMDA receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.2005.04521.x
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  • 2
    Electronic Resource
    Electronic Resource
    STIM1 is a Ca 2+ sensor that activates CRAC channels and migrates from the Ca 2+ store to the plasma membrane (2005)
    [s.l.] : Nature Publishing Group
    Nature 437 (2005), S. 902-905 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] As the sole Ca2+ entry mechanism in a variety of non-excitable cells, store-operated calcium (SOC) influx is important in Ca2+ signalling and many other cellular processes. A calcium-release-activated calcium (CRAC) channel in T lymphocytes is the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature04147
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  • 3
    Electronic Resource
    Electronic Resource
    The localization of sodium and calcium to Schwann cell paranodal loops at nodes of Ranvier and of calcium to compact myelin (1980)
    Springer
    Journal of neurocytology 9 (1980), S. 185-205 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary High-voltage electron microscopy (HVEM) has been used to determine the distribution of cationic precipitates in myelinated axons resulting from the application of two cytochemical techniques: a direct osmium pyroantimonate treatment for precipitating Na+, Ca2+ and Mg2+; and a 5 mM Ca2+ inclusion procedure (Oschman & Wall) for imparting electron density to Ca2+ binding sites. Electron probe wavelength spectroscopy was then used on semi-thick tissue sections to identify the species of ions present in the following regions: Schwann cell paranodal loops, axoplasm at the node, compact myelin and extracellular matrix. With these combined procedures we were able to localize elevated concentrations of both Na+ and Ca2+ to cytoplasmic compartments of the Schwann cell paranodal loops, as well as to detect the presence of Ca2+ at elevated levels in compact myelin. The involvement of the Schwann cell paranodal loops in providing a source and/or sink for Na+ involved in impulse conduction is suggested by these results, and the significance of such a role is discussed. A role for Ca2+ in the formation and stabilization of myelin lamellae is also suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01205157
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  • 4
    Electronic Resource
    Electronic Resource
    The distribution of orthogonal arrays in the freeze-fractured rat median eminence (1982)
    Springer
    Journal of neurocytology 11 (1982), S. 335-349 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The distribution of orthogonal arrays of particles and their relationships to gap and tight junctions have been studied in the glia of the freeze-fractured rat median eminence (ME). These rectilinear clusters of intramembrane particles are thought to represent trans-membrane channels for ions or metabolites, and were found to be densely packed on the membranous laminations of the pial-glial limitans. Additionally, arrays were found to be present on all of the perivascular glial end-feet examined. Two classes of end-feet were distinguished by their relative densities of orthogonal arrays. End-feet displaying low densities of arrays occurred more frequently in the internal zone, while end-feet displaying high densities occurred more often in the external zone. Similar distinctions based on array density could be made in membranes from other regions of the cell as well. Cross-fractures revealing the cytoplasm underlying these membranes often exposed lipid inclusion bodies, suggesting that membranes containing few arrays belong to tanycytes (or to ‘astrocyte-like tanycytes’). The distribution of arrays appeared to be unrelated to the distribution of gap junctions in the membranes of astrocytes and tanycytes (and ‘astrocyte-like tanycytes’) of the ME, appearing near to and far from gap junctions with approximately equal frequency. Orthogonal arrays were absent from glial membranes near synaptic profiles in the ME. Arrays were also absent from the microvillous membranes of the apical surfaces of ependymal cells, from the cytoplasmic protrusions into the CSF of tanycytes, and from the vicinity of the tight and complex junctions linking the tanycyte and ependymal cell lateral membranes near their apical poles. These results suggest that there is a gradient of array density for most glia of the ME, increasing from the ventricular to the pial surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01258250
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  • 5
    Electronic Resource
    Electronic Resource
    The axoplasmic reticulum within myelinated axons is not transported rapidly (1983)
    Springer
    Journal of neurocytology 12 (1983), S. 393-411 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The axoplasmic reticulum in myelinated axons is an extensive system of branched smooth membranous tubules which is found throughout the length of large axons. To investigate its motility and possible role in fast axonal transport, a focal chilling method was used to arrest transport at two sites separated by a 3 mm wide warm region along the saphenous nerve of mice. The experiments ran for 3–4 h since axoplasmic material travelling faster than 25 mm/day would clear from the central warm region. The nerve was subsequently fixed and processed by a technique that enhances the electron density of the axoplasmic reticulum. Thin and thick sections from several regions along the nerve were then systematically studied using conventional and high voltage electron microscopy. In these studies we found that: 1. the axoplasmic reticulum does not accumulate against the proximal sides of the cold blocks; 2. although often closely associated, there is no evidence of continuity between the axoplasmic reticulum and the discrete membranous compartments that do accumulate proximal to the chilled regions; 3. the axoplasmic reticulum remains in the central 3 mm wide warm region; 4. the axoplasmic reticulum does not accumulate against the distal sides of the cold blocks; 5. retrogradely moving elements that do accumulate distal to the cold blocks do not fuse with the axoplasmic reticulum and are not contained in it; and 6. both retrograde and anterograde vector types are often closely associated with elements of axoplasmic reticulum. These results were supported by quantitative morphometric analysis. We conclude that the axoplasmic reticulum represents a discrete membrane system, separate from either anterogradely or retrogradely moving rapid transport vectors, and that this interconnected cisternal system itself is not rapidly transported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01159382
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  • 6
    Electronic Resource
    Electronic Resource
    The distribution of (Na+ + K+)ATPase is continuous along the axolemma of unensheathed axons from spinal roots of ‘dystrophic’ mice (1987)
    Springer
    Journal of neurocytology 16 (1987), S. 239-248 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary (Na++K+)ATPase-like immunoreactivity along the axolemma of sensory and motor neurons and the plasmalemma of Schwann cells from spinal roots of dystrophic mice (129 ReJ Dy/Dy) was determined using polyclonal antibodies specific for guinea pig renal (Na++K+)ATPase (GP-17), along with polyclonal (439-2) and monoclonal (9A5) antibodies specific for rat renal (Na++K+)ATPase. In normal and dystrophic mice, (Na++K+)ATPase-like immunoreactivity was observed along the axolemma at nodes of Ranvier using GP-17 and 439-2, each of which binds to isozymes of (Na++K+)ATPase composed of the α and α+ forms of the catalytic subunit. Staining was not seen along the nodal axolemma with 9A5, a preparation that binds to the α form of the catalytic subunit. The terminal processes and microvilli of Schwann cells were stained using all three antibody probes. The axolemma of unensheathed axons in dystrophic mice was continuously and uniformly labelled with GP-17 and 439-2, but not 9A5. Concentrations of (Na++K+)ATPase-like immunoreactivity along Schwann cell processes were observed most often in areas adjacent to unensheathed axolemma. At heminodes, staining abruptly decreased along Schwann cell processes in areas that were separated from the unensheathed axolemma by other intervening Schwann cell processes. It was concluded from these data that in dystrophic mice (Na++K+)ATPase is uniformly distributed along unensheathed portions of axons without evidence of detectable focal concentations of the enzyme, and that the catalytic subunit of (Na++K+)ATPase along unensheathed axons is distinct from the α form found in Schwann cells and other organs. In addition, (Na++K+)ATPase is concentrated along the plasmalemma of Schwann cells in regions of close apposition to axolemmal areas associated with large ionic fluxes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01795307
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  • 7
    Electronic Resource
    Electronic Resource
    Clusters of axonal Na+ channels adjacent to remyelinating Schwann cells (1996)
    Springer
    Journal of neurocytology 25 (1996), S. 403-412 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Rat sciatic nerve fibres were demyelinated by injection of lysolecithin and examined at several stages as Schwann cells proliferated, adhered, and initiated remyelination. Immunoperoxidase EM has been used to follow the clustering of Na+ channels that represents an early step in the formation of new nodes of Ranvier. At the peak of demyelination, 1 week postinjection, only isolated sites, suggestive of the original nodes, were labelled. As Schwann cells adhered and extended processes along the axons, regions of axonal Na+ channel immunoreactivity were often found just beyond their leading edges. These channel aggregates were associated only with the axolemma and Na+ channels were not detected on glial membranes. Sites with more than one cluster in close proximity and broadly labelled aggregates between Schwann cells suggested that new nodes of Ranvier formed as neighbouring Na+ channel groups merged. Schwann cells thus seem to play a major role in ion channel distributions in the axolemma. In all of these stages Na+ channel label was found primarily just outside the region of close contact between axon and Schwann cell. This suggests that Schwann cell adherence acts in part to exclude Na+ channels, or that diffusible substances are involved and can act some distance from regions of direct contact.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02284811
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  • 8
    Electronic Resource
    Electronic Resource
    The distribution of orthogonal arrays and their relationship to intercellular junctions in neuroglia of the freeze-fractured hypothalamo-neurohypophysial system (1981)
    Springer
    Cell & tissue research 215 (1981), S. 309-323 
    Details
    ISSN: 1432-0878
    Keywords: Freeze-fracture ; Hypothalamo-neurohypophysial system ; Neuroglia ; Intercellular junctions ; Orthogonal arrays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Using freeze-fracture techniques, we have investigated membrane specializations of the glia associated with the hypothalamo-neurohypophysial system of the rat. In the paraventricular (PVN) and supraoptic (SON) nuclei, astrocytes in areas of high neuronal density (i.e., magnocellular regions) display orthogonal arrays of 6–7 nm particles soley near gap junctions, while astrocytes in areas of lower neuronal density (i.e., parvocellular regions) contain additional arrays in membranes not displaying gap junctions. Arrays are especially numerous on astrocytic perivascular end-feet in both nuclei and in the laminations of the pial-glial limitans ventral to the SON. Ependymal cells near the PVN show arrays both on their lateral surfaces (displaying gap junctions) and on their apical surfaces (facing the CSF). Tight junctions are not noted on astrocytes or ependymal cells, but are noted on both the somas and myelin lamellae of oligodendroglia. Both of these latter membranes occasionally contain gap junctions as well; however, orthogonal arrays are never noted on oligodendroglia. The plasma membranes of pituicytes in the neurohypophysis display gap junctions, complex junctions, and tight junctions. Orthogonal arrays are noted near the first two of these, but not near the last. Arrays in the neural lobe appear most dense on membranes adjacent to subpial or perivascular spaces. Pituicyte membranes containing orthogonal arrays appear infrequently near the neural stalk, increasing towards the distal end of the neural lobe. The distribution of orthogonal arrays in this system, as well as in other systems in which they have been noted, suggests a polarization of membrane activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239117
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  • 9
    Electronic Resource
    Electronic Resource
    Crooked Neck Dwarf (cn) mutant chicken skeletal muscle cells in low density primary cultures fail to express normal α ryanodine receptor and exhibit a partial mutant phenotype (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Developmental Dynamics 197 (1993), S. 189-202 
    Details
    ISSN: 1058-8388
    Keywords: Crooked Neck Dwarf mutation ; Ryanodine receptor isoforms ; Skeletal muscle ; Muscle dysgenesis ; Chicken ; Embryonic development ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The Crooked Neck Dwarf (cn) mutation in chickens causes marked changes in intact embryonic skeletal muscle. We have investigated whether the cn/cn phenotype develops in vitro, and if cultured muscle cells are suitable for studies of this mutation. The properties of cn/cn muscle cells maintained in low density primary cultures (6.25 × 103 cells/cm2) are described in this report. In normal muscle cells, the α ryanodine receptor (RyR) isoform appears prior to, and at greater levels than, the βRyR, and is detected in mononucleated myocytes. The βRyR isoform appears within 24 hr after the initiation of myotube formation, which is earlier than anticipated from studies with intact embryonic muscle. Normal αRyR protein is not detected in cultured cn/cn muscle cells, whereas the βRyR, the α1-subunit of the dihydropyridine receptor, the sarcoplasmic reticulum Ca2+-ATPase, and calsequestrin are expressed at comparable levels in normal and mutant muscle cells. Calcium transients elicited by electrical stimulation, acetylcholine, and caffeine are similar in normal and cn/cn cultured myotubes and are blocked by ryanodine in both cell types. In addition, comparable L- and T-type calcium currents are observed in normal and mutant muscle cells, suggesting that both the α1-subunit of the dihydropyridine receptor and the βRyR in mutant muscle cells are functional. Normal and cn/cn muscle cells proliferate and form myotubes in a similar manner. These latter events do not appear to depend on sarcoplasmic reticulum calcium release, as they also occur in normal muscle cells in which calcium release is prevented by chronic treatment with 100 μM ryanodine. Both cn/cn and ryanodine-treated normal muscle cells exhibit morphological changes similar to those observed in intact cn/cn skeletal muscle. Thus, the mutant phenotype observed in ovo is partially expressed under low density culture conditions, and neither βRyR protein nor its function appear to be capable of preventing the associated changes. © 1993 Wiley-Liss, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001970304
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  • 10
    Electronic Resource
    Electronic Resource
    Failure to make normal α ryanodine receptor is an early event associated with the Crooked Neck Dwarf (cn) mutation in chicken (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Developmental Dynamics 197 (1993), S. 169-188 
    Details
    ISSN: 1058-8388
    Keywords: Crooked Neck Dwarf mutation ; Chicken ; Embryonic development ; Skeletal muscle dysgenesis ; Skeletal muscle dysgenesis ; Skeletal muscle dysfunction ; Ryanodine receptor isoforms ; Skeletal muscle ; Cardiac muscle ; Cerebellum ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We have investigated the molecular basis of the Crooked Neck Dwarf (cn) mutation in embryonic chickens. Using biochemical and pharmacological techniques we are unable to detect normal α ryanodine receptor (RyR) protein in intact cn/cn skeletal muscle. Extremely low levels of αRyR immunoreactivity can be observed in mutant muscles, but the distribution of this staining differs from that in normal muscle and colocalizes with the rough endoplasmic reticulum immunoglobulin binding protein, BiP. This suggests the existence of an abnormal αRyR protein in mutant muscle. In day E12 cn/cn muscle the levels of RyR mRNA are reduced by ∼80%, while the levels of other muscle proteins, including the α1 subunit of the dihydropyridine receptor, the SRCa2+-ATPase, calsequestrin, and glyceraldehyde-3-phosphate dehydrogenase, and their associated mRNAs are essentially normal in cn/cn muscle. There is also a failure to express αRyR in cn/cn cerebellar Purkinje neurons. Expression of the βRyR, a second RyR isoform, is not initiated in normal skeletal muscle until day E18. In cn/cn skeletal muscle significant muscle degeneration has occurred by this time and the βRyR is found at low levels in only a subset of fibers suggesting the reduced levels of this isoform are a secondary consequence of the mutation. The cardiac RyR isoform is found in cn/cn cardiac muscle, which contracts in a vigorous manner. In summary, a failure to make normal αRyR receptor appears to be an event closely associated with the cn mutation and one which may be largely responsible for development of the cn/cn phenotype in embryonic skeletal muscle. © 1993 Wiley-Liss, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001970303
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