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  • 1
    Electronic Resource
    Electronic Resource
    Anatomy of the cochlear nuclear complex of guinea pig (1990)
    Springer
    Anatomy and embryology 182 (1990), S. 123-149 
    Details
    ISSN: 1432-0568
    Keywords: Cochlear nucleus ; Guinea-pig ; Cytoarchitecture ; Auditory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The cyto-and fibre-architecture of the cochlear nuclear complex of the guinea-pig has been studied in serial sections using Nissl, Golgi and combined cellmyelin staining of normal material, and a silver degeneration method after cochlear ablation. The nuclear subdivisions and major cell types can be recognised on the basis of those found in the cat, but there are some differences between the two species in the precise distribution and morphology of the neurons. The rostrodorsal part of the anteroventral cochlear nucleus (AVCN) contains predominantly spherical bushy cells, but these cannot be readily divided into large and small types as in the cat. Globular bushy cells are seen in the caudal region of the AVCN, but the majority occur in the posteroventral cochlear nucleus (PVCN), in an area extending from the nerve root right up to the boundary of the dorsal cochlear nucleus (DCN). The octopus cells constitute a distinct region in the most dorsomedial part of the PVCN underneath the DCN. Giant cells are seen scattered around the nerve root region. Multipolar and small cells are seen throughout the non-granular regions of the ventral cochlear nucleus (VCN) except for the octopus cell area, but occur mainly in the more rostral regions of the PVCN. Small cells occur in greatest abundance in the thin cap area at the dorsal edge of the VCN below a superficial granule cell layer. The latter covers the dorsolateral surface of the VCN, and a lamina of granule cells partially separates the PVCN from the DCN. The DCN can be divided into four layers. The outermost molecular layer (layer 1) is separated from the deeper regions by a prominent layer of granule cells (layer 2) which also contains the pyramidal cells. Molecular layer stellate cells are seen in layer 1 and a staggered row of cartwheel neurons is found at the boundary between layers 1 and 2. Layer 3 contains the basal dendrites of the pyramidal cells and some small (vertical) cells, and is innervated by the descending branches of the cochlear nerve. The deepest layer 4, which contains multipolar cells and giant cells, does not appear to receive this direct cochlear input.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00174013
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  • 2
    Electronic Resource
    Electronic Resource
    Immunocytochemical Evidence that Glutamate is a Neurotransmitter in the Cochlear Nerve: A Quantitative Study in the Guinea-pig Anteroventral Cochlear Nucleus (1996)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 8 (1996), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The large so-called type I afferents of the cochlear nerve carry the majority of the auditory input from the cochlea to the cochlear nuclei in the brainstem. These fibres are excitatory and previous studies have suggested they may use glutamate as their neurotransmitter. In the present investigation therefore, antibodies to glutamate and to the glutamate precursor, glutamine, were applied to resin sections of perfusion-fixed brains and of in vitro brain slices subjected to depolarizing levels of potassium before fixation to study glutamate handling and synaptic release. Ultrathin sections were labelled by the immunogold technique, and the immunoreactivity was quantified by recording the density of gold particles over the various tissue profiles. Non-primary, presumably inhibitory, terminals and glial processes were used as reference structures. The cochlear primary terminals proved to be strongly immunoreactive for glutamate. The density of glutamate labelling was higher in primary terminals than in non-primary ones, and lowest in glial processes. The ratio between the mean glutamate and glutamine labelling densities was also higher in primary terminals than in non-primary ones, and lowest in glial processes in each case. In the primary terminals, the glutamate immunoreactivity was higher over vesicle-containing regions than over vesicle-free regions, whilst glutamine was evenly distributed throughout. The in vitro brain slices showed a potassium-induced, partly calcium-dependent depletion of glutamate from the primary terminals but not from the non-primary ones. These observations strongly support the conclusion that glutamate is a neurotransmitter of type I cochlear afferents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1996.tb01169.x
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  • 3
    Electronic Resource
    Electronic Resource
    Localization of the glutamate–aspartate transporter, GLAST, in rat taste buds (2000)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 12 (2000), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A number of putative neurotransmitter substances have been found in vertebrate taste buds. Amongst these glutamate has been localized in fibres innervating the buds and uptake of glutamate has been shown to occur into receptor cells. It is therefore possible that, in common with other sensory systems, glutamate is a neurotransmitter in taste buds. In the inner ear and retina of mammals, the membranes of supporting cells have been shown to contain the glial glutamate transporter GLAST. In the brain, this protein is involved in glutamate re-uptake into glial cells where the glutamate is converted into glutamine for recycling into glutamatergic terminals. In this study, the presence of GLAST has been investigated in taste buds in the rat vallate papilla and its distribution compared with that of glutamine to determine whether there are cells in this system that play a glia-like role in glutamate handling. Immunofluorescent labelling showed that a subset of cells in the taste bud contains GLAST. Immunogold labelling indicated that it occurs in the plasma membranes of supporting cells, especially on the fine cytoplasmic processes of dark cells towards the basal region of the bud. A protein of molecular mass similar to that of cerebellar GLAST was detected in immunoblots of excised papillae. Double labelling and semiquantitative analysis of glutamine and GLAST immunoreactivity showed that the GLAST-positive cells have a higher level of cytoplasmic glutamine than the adjacent cells. It is proposed that these GLAST-positive cells play a glia-like role in the uptake of glutamate following its release at synapses within the taste bud although the precise location of the latter remains uncertain. The GLAST-positive cells may also be involved in its subsequent conversion to glutamine in a glutamate/glutamine cycle similar to that described in the brain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.2000.00207.x
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  • 4
    Electronic Resource
    Electronic Resource
    Electrically Induced Tentacle Retraction in the Suctorian Protozoon Discophrya collini (Root) (1981)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 28 (1981), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Discophrya collini is a free-living suctorian with retractile tentacles covered by a thick fibrous cortex. The tentacles contain a microtubular central canal surrounded at the base by a fibrous collar. Electrical stimulation induces a reproducible tentacle retraction. With extracellular electrodes, the tentacles nearest the anode respond initially, contracting by up to 75% of their original length. There is an inverse relationship between voltage level and duration of stimulus in producing a threshold response, and at a set voltage, between duration and degree of retraction. With intracellular electrodes, the membrane potential has been measured as -30 mV, and tentacle retraction occurs in response to as little as 1.25 nA when the intracellular electrode is made the cathode of the circuit. SEM studies show that retracted tentacles have a wrinkled cortex, while TEM shows that the microtubular canal bends as it enters the cytoplasm. No consistent changes occur in the microtubule configuration of the canal on retraction, suggesting that the microtubules are not directly involved in the contractile mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1981.tb02823.x
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  • 5
    Electronic Resource
    Electronic Resource
    Immunoreactivity of sensory hair bundles of the guinea-pig cochlea to antibodies against elastin and keratan sulphate (1996)
    Springer
    Cell & tissue research 284 (1996), S. 473-479 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Keratan sulphate ; Elastin ; Extracellular linkages ; Stereocilia ; Hair cell ; Cochlea ; Guinea pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The stereociliary bundles of hair cells contain cross-linking extracellular filaments which have been suggested to play a role in mechanoelectrical transduction. To investigate the composition of these filaments, antibodies to the extracellular matrix molecules elastin and keratan sulphate have been used for light- and electron-microscopic immunocytochemistry of the guinea-pig organ of Corti. With the antibody to elastin, no immunoreactivity was found in hair bundles. This implies either that the epitope recognised by this antibody is not present in the links or that it is obscured. The antibody to keratan sulphate labelled the stereociliary bundles of both inner and outer hair cells but not supporting cells. The tips of the tallest stereocilia, especially on outer hair cells, the tips of the shorter stereocilia where the tip links attach to the stereociliary membrane, and the attachments of the lateral links, were labelled. This suggests that the links contain keratan sulphate proteoglycans, molecules which in other tissues are known to maintain structural integrity and fibrillar spacing, and to influence the microenvironment of the cell surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050608
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  • 6
    Electronic Resource
    Electronic Resource
    Tentacle contraction and ultrastructure inDiscophrya collini: The response to cations (1982)
    Springer
    Protoplasma 112 (1982), S. 92-100 
    Details
    ISSN: 1615-6102
    Keywords: Discophrya ; Tentacle contraction ; Cations ; Calcium ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Discophrya collini is a suctorian protozoan with contractile tentacles containing a microtubule-lined canal and microfilaments. The effects of a range of cations on tentacle contraction and ultrastructure have been determined. Treatment with 80 mM CaCl2 and 95 mM MgCl2 causes contraction to 28% and 57% of the control length respectively. Re-extension takes over 4 hours in the culture medium, but CaCl2-treated tentacles are re-extended after a 5 minutes treatment with 10−2 M EDTA or 5 × 10−3 M EGTA. CuCl2 causes a significant contraction at 10−5 M (to 77%); LaCl3 at 10−4 M (to 65%); ZnCl2 at 10−2 M (to 65%), but BaCl2, CoCl2, MnCl2, NiCl2, and SrCl2 cause significant changes only at 10−1 M. The cytoplasm of CaCl2-treated cells contains two forms of membraneous structures when viewed in TEM; that of MgCl2-treated cells reveals granular areas of medium electron density. None of these features are seen in control cells. The microtubules of the tentacle canal appear to be intact upon its retraction into the cell with no change occurring in the numbers or relative positions of the microtubules. The tentacle cortex is wrinkled. It is suggested from this and previous work that tentacle contraction may be mediated by a microfilament-based mechanism, and that calcium may be involved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01280219
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  • 7
    Electronic Resource
    Electronic Resource
    Organization of microtubules in cochlear hair cells (1990)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 15 (1990), S. 261-279 
    Details
    ISSN: 0741-0581
    Keywords: Cochlea ; Hair cell ; Cytoskeleton ; Immunocytochemistry ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The organization of microtubules in hair cells of the guinea-pig cochlea has been investigated using transmission electron microscopy and correlated with the location of tubulin-associated immunofluorescence in surface preparations of the organ of Corti. Results from both techniques reveal consistent distributions of microtubules in inner and outer hair cells.In the inner hair cells, microtubules are most concentrated in the apex. Reconstruction from serial sections shows three main groups: firstly, in channels through the cuticular plate and in a discontinuous belt around its upper perimeter; secondly, forming a ring inside a rim extending down from the lower perimeter of the plate; and thirdly, in a meshwork underlying the main body of the plate. In the cell body, microtubules line the inner face of the subsurface cistern and extend longitudinally through a tubulo-vesicular track between the apex and base.In outer hair cells, the pattern of microtubules associated with the cuticular plate is similar, although there are fewer present than in inner hair cells. In outer hair cells from the apex of the cochlea, microtubules occur around an infracuticular protrusion of cuticular plate material. In the cell body, many more microtubules occur in the region below the nucleus compared with inner hair cells.The possible functions of microtubules in hair cells are discussed by comparison with those found in other systems. These include morphogenesis and maintenance of cell shape; intracellular transport, e.g., of neurotransmitter vesicles; providing a possible substrate for motility; mechanical support of structures associated with sensory transduction.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060150306
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