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Ribbon synapse

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https://www.readbyqxmd.com/read/28228581/spaceflight-induced-synaptic-modifications-within-hair-cells-of-the-mammalian-utricle
#1
David R Sultemeier, Kristel R Choy, Felix E Schweizer, Larry F Hoffman
Exposure to the microgravity conditions of spaceflight alleviates the load normally imposed by the Earth's gravitational field upon the inner ear utricular epithelia. Previous ultrastructural investigations showed that spaceflight induced an increase in synapse density within hair cells of the rat utricle. However, the utricle exhibits broad physiologic heterogeneity across different epithelial regions, and it is unknown whether capabilities for synaptic plasticity generalize to hair cells across its topography...
February 22, 2017: Journal of Neurophysiology
https://www.readbyqxmd.com/read/28209381/an-easy-fast-and-low-tech-equipment-requiring-alternative-method-to-optimize-immunolabelling-conditions-for-pre-embedding-immunogold-electron-microscopy-and-to-correlate-light-and-electron-microscopical-immunogold-labelling-results
#2
Shweta Suiwal, Gabriele Kiefer, Frank Schmitz, Karin Schwarz
Correlating light microscopic immunolabelling results with electron microscopic data is of great interest in many fields of biomedical research but typically requires very specialized, expensive equipment and complex procedures which are not available in most labs. In this technical study, we describe an easy and "low-tech"-equipment-requiring pre-embedding immunolabelling approach that allows correlation of light microscopical immunolabelling results with electron microscopic (EM) data as demonstrated by the example of immunolabelled synaptic ribbons from retinal rod photoreceptor synapses...
February 13, 2017: Journal of Immunological Methods
https://www.readbyqxmd.com/read/28202712/ribeye-b-domain-binds-to-lipid-components-of-synaptic-vesicles-in-an-nad-h-dependent-redox-sensitive-manner
#3
Karin Schwarz, Frank Schmitz
Synaptic ribbons are needed for fast and continuous exocytosis in ribbon synapses. RIBEYE is a main protein component of synaptic ribbons and necessary to build the synaptic ribbon. RIBEYE consists of a unique A-domain and a carboxyterminal B-domain that binds NAD(H). Within the presynaptic terminal, the synaptic ribbons are in physical contact with large numbers of synaptic vesicles. How this physical contact between ribbons and vesicles is established at a molecular level is not well understood. In the present study, we demonstrate that the RIBEYE(B)-domain can directly interact with lipid components of synaptic vesicles using two different sedimentation assays with liposomes of defined chemical composition...
February 15, 2017: Biochemical Journal
https://www.readbyqxmd.com/read/28193694/different-cav1-3-channel-isoforms-control-distinct-components-of-the-synaptic-vesicle-cycle-in-auditory-inner-hair-cells
#4
Philippe Fy Vincent, Yohan Bouleau, Gilles Charpentier, Alice Emptoz, Saaid Safieddine, Christine Petit, Didier Dulon
The mechanisms orchestrating transient and sustained exocytosis in auditory inner hair cells (IHCs) remain largely unknown. These exocytotic responses are believed to mobilize sequentially a readily releasable pool of vesicles (RRP) underneath the synaptic ribbons and a slowly releasable pool of vesicles (SRP) at farther distance from them. They are both governed by Cav1.3 channels and require otoferlin as Ca(2+) sensor but whether they use the same Cav1.3 isoforms is still unknown. Using whole cell patch clamp recordings in post-hearing mice, we show that only a proportion (∼25 %) of the total Ca(2+) current in IHCs, displaying fast inactivation and resistance to 20 μM nifedipine, a L-type Ca(2+) channel blocker, is sufficient to trigger RRP but not SRP exocytosis...
February 13, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/28183797/ca-2-binding-protein-2-inhibits-ca-2-channel-inactivation-in-mouse-inner-hair-cells
#5
Maria Magdalena Picher, Anna Gehrt, Sandra Meese, Aleksandra Ivanovic, Friederike Predoehl, SangYong Jung, Isabelle Schrauwen, Alberto Giulio Dragonetti, Roberto Colombo, Guy Van Camp, Nicola Strenzke, Tobias Moser
Ca(2+)-binding protein 2 (CaBP2) inhibits the inactivation of heterologously expressed voltage-gated Ca(2+) channels of type 1.3 (CaV1.3) and is defective in human autosomal-recessive deafness 93 (DFNB93). Here, we report a newly identified mutation in CABP2 that causes a moderate hearing impairment likely via nonsense-mediated decay of CABP2-mRNA. To study the mechanism of hearing impairment resulting from CABP2 loss of function, we disrupted Cabp2 in mice (Cabp2(LacZ/LacZ) ). CaBP2 was expressed by cochlear hair cells, preferentially in inner hair cells (IHCs), and was lacking from the postsynaptic spiral ganglion neurons (SGNs)...
February 9, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28160289/melanopsin-expressing-human-retinal-ganglion-cells-subtypes-distribution-and-intraretinal-connectivity
#6
Jens Hannibal, Anders Tolstrup Christensen, Steffen Heegaard, Jan Fahrenkrug, Jens Folke Kiilgaard
Intrinsically photosensitive retinal ganglion cells (ipRGCs) expressing the photopigment melanopsin belong to a heterogenic population of RGCs which regulate the circadian clock, masking behavior, melatonin suppression, the pupillary light reflex and sleep/wake cycles. The different functions seem to be associated to different subtypes of melanopsin cells. In rodents, subtype classification has associated subtypes to function. In primate and human retina such classification has so far, not been applied. In the present study using antibodies against N- and C-terminal parts of human melanopsin, confocal microscopy and 3D reconstruction of melanopsin immunoreactive (-ir) RGCs, we applied the criteria used in mouse on human melanopsin-ir RGCs...
February 3, 2017: Journal of Comparative Neurology
https://www.readbyqxmd.com/read/28154149/the-coupling-between-ca2-channels-and-the-exocytotic-ca2-sensor-at-hair-cell-ribbon-synapses-varies-tonotopically-along-the-mature-cochlea
#7
Stuart L Johnson, Jennifer Olt, Soyoun Cho, Henrique von Gersdorff, Walter Marcotti
: The cochlea processes auditory signals over a wide range of frequencies and intensities. However, the transfer characteristics at hair cell ribbon synapses are still poorly understood at different frequency locations along the cochlea. Using recordings from mature gerbils, we report here a surprisingly strong block of exocytosis by the slow Ca(2+) buffer EGTA (10 mM) in basal hair cells tuned to high frequencies (∼30 kHz). In addition, using recordings from gerbil, mouse and bullfrog auditory organs, we find that the spatial coupling between Ca(2+) influx and exocytosis changes from nanodomain in low-frequency tuned hair cells (<∼2 kHz) to progressively more microdomain in high-frequency cells (>∼2 kHz)...
February 2, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/28089576/conditional-deletion-of-pejvakin-in-adult-outer-hair-cells-causes-progressive-hearing-loss-in-mice
#8
Suzan L Harris, Marcin Kazmierczak, Tina Pangršič, Prahar Shah, Nadiya Chuchvara, Alonso Barrantes-Freer, Tobias Moser, Martin Schwander
Mutations in the Pejvakin (Pjvk) gene cause autosomal recessive hearing loss DFNB59 with audiological features of auditory neuropathy spectrum disorder (ANSD) or cochlear dysfunction. The precise mechanisms underlying the variable clinical phenotypes of DFNB59 remain unclear. Here, we demonstrate that mice with conditional ablation of the Pjvk gene in all sensory hair cells or only in outer hair cells (OHCs) show similar auditory phenotypes with early-onset profound hearing loss. By contrast, loss of Pjvk in adult OHCs causes a slowly progressive hearing loss associated with OHC degeneration and delayed loss of inner hair cells (IHCs), indicating a primary role for pejvakin in regulating OHC function and survival...
March 6, 2017: Neuroscience
https://www.readbyqxmd.com/read/28074469/development-of-cone-photoreceptors-and-their-synapses-in-the-human-and-monkey-fovea
#9
Anita Hendrickson, Chi Zhang
During retinal development, ribbon synapse assembly in the photoreceptors is a crucial step involving numerous molecules. While the developmental sequence of plexiform layers in human retina has been characterized, the molecular steps of synaptogenesis remain largely unknown. In the present study, we focused on the central rod-free region of primate retina, the fovea, to specifically investigate the development of cone photoreceptor ribbon synapses. Immunocytochemistry and electron microscopy were utilized to track the expression of photoreceptor transduction proteins and ribbon and synaptic markers in fetal human and Macaca retina...
January 11, 2017: Journal of Comparative Neurology
https://www.readbyqxmd.com/read/28035673/somatic-and-neuritic-spines-on-tyrosine-hydroxylase-immunopositive-cells-of-rat-retina
#10
Anna Fasoli, James Dang, Aaron H Gouw, Jeffrey S Johnson, Alex Fogli Iseppe, Andrew T Ishida
Dopamine- and tyrosine hydroxylase-immunopositive cells (TH cells) modulate visually driven signals as they flow through retinal photoreceptor, bipolar, and ganglion cells. Previous studies suggested that TH cells release dopamine from varicose axons arborizing in the inner and outer plexiform layers after glutamatergic synapses depolarize TH cell dendrites in the inner plexiform layer and these depolarizations propagate to the varicosities. Although it has been proposed that these excitatory synapses are formed onto appendages resembling dendritic spines, spines have not been found on TH cells of most species examined to date or on TH cell somata which release dopamine when exposed to glutamate receptor agonists...
December 30, 2016: Journal of Comparative Neurology
https://www.readbyqxmd.com/read/28034618/adenosine-receptors-regulate-susceptibility-to-noise-induced-neural-injury-in-the-mouse-cochlea-and-hearing-loss
#11
Srdjan M Vlajkovic, Kaushi Ambepitiya, Meagan Barclay, Detlev Boison, Gary D Housley, Peter R Thorne
Our previous studies have shown that the stimulation of A1 adenosine receptors in the inner ear can mitigate the loss of sensory hair cells and hearing loss caused by exposure to traumatic noise. Here, we focus on the role of adenosine receptors (AR) in the development of noise-induced neural injury in the cochlea using A1AR and A2AAR null mice (A1AR(-/-) and A2AAR(-/-)). Wildtype (WT) and AR deficient mice were exposed to octave band noise (8-16 kHz, 100 dB SPL) for 2 h to induce cochlear injury and hearing loss...
December 26, 2016: Hearing Research
https://www.readbyqxmd.com/read/27833534/on-bipolar-cells-in-macaque-retina-type-specific-synaptic-connectivity-with-special-reference-to-off-counterparts
#12
Yoshihiko Tsukamoto, Naoko Omi
To date, 12 macaque bipolar cell types have been described. This list includes all morphology types first outlined by Polyak (1941) using the Golgi method in the primate retina and subsequently identified by other researchers using electron microscopy (EM) combined with the Golgi method, serial section transmission EM (SSTEM), and immunohistochemical imaging. We used SSTEM for the rod-dense perifoveal area of macaque retina, reconfirmed ON (cone) bipolar cells to be classified as invaginating midget bipolar (IMB), diffuse bipolar (DB)4, DB5, DB6, giant bipolar (GB), and blue bipolar (BB) types, and clarified their type-specific connectivity...
2016: Frontiers in Neuroanatomy
https://www.readbyqxmd.com/read/27822497/lack-of-cabp1-caldendrin-or-cabp2-leads-to-altered-ganglion-cell-responses
#13
Raunak Sinha, Amy Lee, Fred Rieke, Françoise Haeseleer
Calcium-binding proteins (CaBPs) form a subfamily of calmodulin-like proteins that were cloned from the retina. CaBP4 and CaBP5 have been shown to be important for normal visual function. Although CaBP1/caldendrin and CaBP2 have been shown to modulate various targets in vitro, it is not known whether they contribute to the transmission of light responses through the retina. Therefore, we generated mice that lack CaBP2 or CaBP1/caldendrin (Cabp2(-/-) and Cabp1(-/-) ) to test whether these CaBPs are essential for normal retinal function...
September 2016: ENeuro
https://www.readbyqxmd.com/read/27798183/%C3%AE-2%C3%AE-2-controls-the-function-and-trans-synaptic-coupling-of-cav1-3-channels-in-mouse-inner-hair-cells-and-is-essential-for-normal-hearing
#14
Barbara Fell, Stephanie Eckrich, Kerstin Blum, Tobias Eckrich, Dietmar Hecker, Gerald J Obermair, Stefan Münkner, Veit Flockerzi, Bernhard Schick, Jutta Engel
: The auxiliary subunit α2δ2 modulates the abundance and function of voltage-gated calcium channels. Here we show that α2δ2 mRNA is expressed in neonatal and mature hair cells. A functional α2δ2-null mouse, the ducky mouse (du), showed elevated auditory brainstem response click and frequency-dependent hearing thresholds. Otoacoustic emissions were not impaired pointing to normal outer hair cell function. Peak Ca(2+) and Ba(2+) currents of mature du/du inner hair cells (IHCs) were reduced by 30-40%, respectively, and gating properties, such as the voltage of half-maximum activation and voltage sensitivity, were altered, indicating that Cav1...
October 26, 2016: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/27793584/effects-of-long-term-non-traumatic-noise-exposure-on-the-adult-central-auditory-system-hearing-problems-without-hearing-loss
#15
REVIEW
Jos J Eggermont
It is known that hearing loss induces plastic changes in the brain, causing loudness recruitment and hyperacusis, increased spontaneous firing rates and neural synchrony, reorganizations of the cortical tonotopic maps, and tinnitus. Much less in known about the central effects of exposure to sounds that cause a temporary hearing loss, affect the ribbon synapses in the inner hair cells, and cause a loss of high-threshold auditory nerve fibers. In contrast there is a wealth of information about central effects of long-duration sound exposures at levels ≤ 80 dB SPL that do not even cause a temporary hearing loss...
October 25, 2016: Hearing Research
https://www.readbyqxmd.com/read/27635230/new-insights-into-cochlear-sound-encoding
#16
REVIEW
Tobias Moser, Christian Vogl
The inner ear uses specialized synapses to indefatigably transmit sound information from hair cells to spiral ganglion neurons at high rates with submillisecond precision. The emerging view is that hair cell synapses achieve their demanding function by employing an unconventional presynaptic molecular composition. Hair cell active zones hold the synaptic ribbon, an electron-dense projection made primarily of RIBEYE, which tethers a halo of synaptic vesicles and is thought to enable a large readily releasable pool of vesicles and to contribute to its rapid replenishment...
2016: F1000Research
https://www.readbyqxmd.com/read/27581463/selective-vulnerability-of-specific-retinal-ganglion-cell-types-and-synapses-after-transient-ocular-hypertension
#17
Yvonne Ou, Rebecca E Jo, Erik M Ullian, Rachel O L Wong, Luca Della Santina
UNLABELLED: Key issues concerning ganglion cell type-specific loss and synaptic changes in animal models of experimental glaucoma remain highly debated. Importantly, changes in the structure and function of various RGC types that occur early, within 14 d after acute, transient intraocular pressure elevation, have not been previously assessed. Using biolistic transfection of individual RGCs and multielectrode array recordings to measure light responses in mice, we examined the effects of laser-induced ocular hypertension on the structure and function of a subset of RGCs...
August 31, 2016: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/27569111/behavioral-auditory-thresholds-and-loss-of-ribbon-synapses-at-inner-hair-cells-in-aged-gerbils
#18
Otto Gleich, Philipp Semmler, Jürgen Strutz
The potential contribution of auditory synaptopathy to age dependent hearing loss was studied in groups of young and old gerbils. The analysis of the number of inner hair cell ribbon synapses in aged gerbils (37.9±3.3months of age) revealed only a relatively small (11-17%) loss in the basal two thirds of the cochlea, while a more pronounced reduction was identified towards the apex (almost 40%) when compared to a group of young gerbils (9.5±3.2months of age). Mean threshold elevation in the old gerbils was around 25dB at 2 and 10kHz...
November 2016: Experimental Gerontology
https://www.readbyqxmd.com/read/27542193/physical-determinants-of-vesicle-mobility-and-supply-at-a-central-synapse
#19
Jason Seth Rothman, Laszlo Kocsis, Etienne Herzog, Zoltan Nusser, Robin Angus Silver
Encoding continuous sensory variables requires sustained synaptic signalling. At several sensory synapses, rapid vesicle supply is achieved via highly mobile vesicles and specialized ribbon structures, but how this is achieved at central synapses without ribbons is unclear. Here we examine vesicle mobility at excitatory cerebellar mossy fibre synapses which sustain transmission over a broad frequency bandwidth. Fluorescent recovery after photobleaching in slices from VGLUT1(Venus) knock-in mice reveal 75% of VGLUT1-containing vesicles have a high mobility, comparable to that at ribbon synapses...
August 19, 2016: ELife
https://www.readbyqxmd.com/read/27466786/spike-timing-in-auditory-nerve-fibers-during-spontaneous-activity-and-phase-locking
#20
Peter Heil, Adam J Peterson
In vertebrates, all acoustic information transmitted from the inner ear to the central auditory system is relayed by primary auditory afferents (auditory-nerve fibers; ANFs). These neurons are also the most peripheral elements to use action potentials (spikes) to encode the acoustic information. Here, we review what is known about the spiking of ANFs during spontaneous activity, when spike timing might be regarded as largely random, and during stimulation by low-frequency sounds, when spikes are phase locked to the stimulus waveform, a phenomenon generally considered a hallmark of temporal precision and speed in the auditory system...
July 28, 2016: Synapse
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