The Experts below are selected from a list of 1119 Experts worldwide ranked by ideXlab platform

Yu Cao - One of the best experts on this subject based on the ideXlab platform.

  • communication routes within the taste bud by neurotransmitters and neuropeptides
    Chemical Senses, 2005
    Co-Authors: Scott Herness, Fangli Zhao, Namik Kaya, Tiansheng Shen, Yu Cao
    Abstract:

    Taste receptor cells (TRCs) are located throughout the oral cavity, sequestered into morphological structures known as taste buds. These differentiated epithelial cells relay the presence of tastants to the central nervous system via sensory Afferent Nerves. Only a minority of TRCs within the bud synapse with these Nerve Fibers. This anatomical finding has lead to the dichotomization of TRCs into ‘true’ TRCs and supporting cells. However, this original conception—that a single TRC is excited by a tastant molecule and releases neurotransmitter onto its postsynaptic Afferent Nerve Fiber—has been undermined by more recent physiological and molecular findings. For example, a single neurotransmitter, as might be expected from this scheme, has not been observed. Rather, there is evidence for at least five neurotransmitters within the mammalian taste bud: glutamate, serotonin, norepinephrine, acetyl choline and GABA. Additionally, TRCs expressing essential transduction molecules such as gustducin and members of the T2R family are not synaptically connected to the CNS. How then do TRCs equipped to respond to stimuli communicate with the central nervous system? The cloistering of TRCs into the precisely arranged structure of the bud may provide a clue. The bud, a highly conserved morphology of the vertebrate gustatory system, is an obvious substrate for cell to cell communication. Hence, alternative signaling pathways, such as paracrine communication, could explain this paradox. Rather than acting as arbitrarily collected detectors, TRCs within the bud may operate as a unit. Our investigations of neurotransmitters and neuropeptides in rat circumvallate and foliate TRCs have elucidated new pathways of communication among TRCs. Two, serotonin and cholecystokinin, are described here.

David V. Smith - One of the best experts on this subject based on the ideXlab platform.

  • differential expression of carbohydrate blood group antigens on rat taste bud cells relation to the functional marker alpha gustducin
    The Journal of Comparative Neurology, 1999
    Co-Authors: David W. Pumplin, John D. Boughter, Erin Getschman, David V. Smith
    Abstract:

    An Afferent Nerve Fiber supplying a taste bud receives input from several taste receptor cells, yet is predominantly responsive to one of the classic taste qualities (salt, acid, sweet, or bitter). This specificity requires recognition between taste receptor cells and Nerve Fibers that may be mediated by surface markers correlating with function. In an effort to identify potential markers, we used immunofluorescence and confocal microscopy to examine expression of the oligosaccharide blood-group antigens Lewisb, A, and H type 2 in taste buds of the rat oral cavity. We compared the distributions of these antigens with that of α-gustducin, a G-protein subunit implicated in responses to sweet- and bitter-tasting substances. The A and Lewisb antigens were present only on spindle-shaped cells whose apical processes reached the taste pore. These antigens were not present on epithelial cells surrounding taste buds, and Lewisb was not found elsewhere in the digestive tract. Lewisb and A were not removed by lipid extraction, suggesting that they are present on glycoproteins rather than glycolipids. All Lewisb-positive cells expressed α-gustducin, but only a fraction of α-gustducin–positive cells expressed Lewisb. The fraction of taste-bud cells expressing Lewisb decreased in the order: vallate papillae > foliate papillae > nasoincisor duct. The epiglottis had almost no taste-bud cells that expressed Lewisb. The A antigen appeared on taste-bud cells that also expressed α-gustducin in the order: foliate and vallate papillae > nasoincisor duct and epiglottis > fungiform papillae. In addition, the A antigen was present on many cells that lacked α-gustducin in foliate and vallate papillae. In vallate papillae, cells expressed either A or Lewisb, but not both. Lewisb appears to be restricted to differentiated light cells that also express α-gustducin and may be involved in intercellular interactions of these cells. J. Comp. Neurol. 415:230–239, 1999. © 1999 Wiley-Liss, Inc.

Minho Oak - One of the best experts on this subject based on the ideXlab platform.

  • voltage gated k channels contributing to temporal precision at the inner hair cell auditory Afferent Nerve Fiber synapses in the mammalian cochlea
    Archives of Pharmacal Research, 2014
    Co-Authors: Minho Oak
    Abstract:

    To perform auditory tasks such as sound localization in the space, auditory neurons in the brain must distinguish sub-millisecond temporal differences in signals from two ears. Such high temporal resolution is possible when each neuron in the ascending auditory pathway fires brief action potential at very accurate timing. Various pre- and postsynaptic machineries ensuring such high temporal precision of auditory synaptic transmission have been identified. Of particular, in this review, the role of K+ channels in shortening the duration of synaptic potentials will be discussed. First, the contribution of K+ channels to AP firing of general auditory neurons will be discussed. Then, the focus will be moved to the inner hair cell (IHC)-auditory Afferent Nerve Fiber (ANF) synapses, the first synapses of ascending auditory pathway. Molecular and immunohistological techniques have revealed various K+ channels in the cell bodies and their processes of ANFs. Since the development of patch-clamp recordings from the ANF dendrites in 2002, it became possible to monitor the IHC-ANF synaptic transmission in greater detail. As revealed in brain auditory synapses, several different K+ channels appear to participate in reducing the duration of synaptic potentials at the IHC-ANF synapses. In addition, K+ channels at the ANF dendrites might act as potential targets of efferent feedback from the brain. The hypothesis is that, upon loud sound exposure, efferent neurotransmitters released onto the ANF dendrites activate certain K+ channels and prevent excitotoxicity of ANFs. Therefore, K+ channels of the ANF dendrites might provide potential sites of pharmacological actions to prevent noise-induced hearing loss.

Kristien Verhoeven - One of the best experts on this subject based on the ideXlab platform.

  • perilymph pharmacokinetics of marker applied through a cochlear implant in guinea pigs
    PLOS ONE, 2017
    Co-Authors: Alec N Salt, J. J. Hartsock, Ruth M Gill, Daniel Smyth, Jonathon Kirk, Kristien Verhoeven
    Abstract:

    Patients undergoing cochlear implantation could benefit from a simultaneous application of drugs into the ear, helping preserve residual low-frequency hearing and Afferent Nerve Fiber populations. One way to apply drugs is to incorporate a cannula into the implant, through which drug solution is driven. For such an approach, perilymph concentrations achieved and the distribution in the ear over time have not previously been documented. We used FITC-labeled dextran as a marker, delivering it into perilymph of guinea pigs at 10 or 100 nL/min though a cannula incorporated into a cochlear implant with the outlet in the mid basal turn. After injections of varying duration (2 hours, 1 day or 7 days) perilymph was collected from the cochlear apex using a sequential sampling technique, allowing dextran levels and gradients along scala tympani to be quantified. Data were interpreted quantitatively using computer simulations of the experiments. For injections of 2 hours duration, dextran levels were critically influenced by the presence or absence of fluid leakage at the cochleostomy site. When the cochleostomy was fluid-tight, substantially higher perilymph levels were achieved at the injection site, with concentration declining along scala tympani towards the apex. Contrary to expectations, large dextran gradients along scala tympani persisted after 24 hours of sustained injection and were still present in some animals after 7 days injection. Functional changes associated with implantation and dextran delivery, and the histological state of the implant and cannula were also documented. The persistent longitudinal gradients of dextan along the ear were not readily explained by computer simulations of the experiments based on prior pharmacokinetic data. One explanation is that inner ear pharmacokinetics are altered in the period after cochlear implantation, possibly by a permeabilization of the blood-labyrinth barrier as part of the immune response to the implant.

A J Hudspeth - One of the best experts on this subject based on the ideXlab platform.

  • the physics of hearing fluid mechanics and the active process of the inner ear
    arXiv: Neurons and Cognition, 2014
    Co-Authors: Tobias Reichenbach, A J Hudspeth
    Abstract:

    Most sounds of interest consist of complex, time-dependent admixtures of tones of diverse frequencies and variable amplitudes. To detect and process these signals, the ear employs a highly nonlinear, adaptive, real-time spectral analyzer: the cochlea. Sound excites vibration of the eardrum and the three miniscule bones of the middle ear, the last of which acts as a piston to initiate oscillatory pressure changes within the liquid-filled chambers of the cochlea. The basilar membrane, an elastic band spiraling along the cochlea between two of these chambers, responds to these pressures by conducting a largely independent traveling wave for each frequency component of the input. Because the basilar membrane is graded in mass and stiffness along its length, however, each traveling wave grows in magnitude and decreases in wavelength until it peaks at a specific, frequency-dependent position: low frequencies propagate to the cochlear apex, whereas high frequencies culminate at the base. The oscillations of the basilar membrane deflect hair bundles, the mechanically sensitive organelles of the ear's sensory receptors, the hair cells. As mechanically sensitive ion channels open and close, each hair cell responds with an electrical signal that is chemically transmitted to an Afferent Nerve Fiber and thence into the brain. In addition to transducing mechanical inputs, hair cells amplify them [...]

  • the physics of hearing fluid mechanics and the active process of the inner ear
    Reports on Progress in Physics, 2014
    Co-Authors: Tobias Reichenbach, A J Hudspeth
    Abstract:

    Most sounds of interest consist of complex, time-dependent admixtures of tones of diverse frequencies and variable amplitudes. To detect and process these signals, the ear employs a highly nonlinear, adaptive, real-time spectral analyzer: the cochlea. Sound excites vibration of the eardrum and the three miniscule bones of the middle ear, the last of which acts as a piston to initiate oscillatory pressure changes within the liquid-filled chambers of the cochlea. The basilar membrane, an elastic band spiraling along the cochlea between two of these chambers, responds to these pressures by conducting a largely independent traveling wave for each frequency component of the input. Because the basilar membrane is graded in mass and stiffness along its length, however, each traveling wave grows in magnitude and decreases in wavelength until it peaks at a specific, frequency-dependent position: low frequencies propagate to the cochlear apex, whereas high frequencies culminate at the base. The oscillations of the basilar membrane deflect hair bundles, the mechanically sensitive organelles of the ear's sensory receptors, the hair cells. As mechanically sensitive ion channels open and close, each hair cell responds with an electrical signal that is chemically transmitted to an Afferent Nerve Fiber and thence into the brain. In addition to transducing mechanical inputs, hair cells amplify them by two means. Channel gating endows a hair bundle with negative stiffness, an instability that interacts with the motor protein myosin-1c to produce a mechanical amplifier and oscillator. Acting through the piezoelectric membrane protein prestin, electrical responses also cause outer hair cells to elongate and shorten, thus pumping energy into the basilar membrane's movements. The two forms of motility constitute an active process that amplifies mechanical inputs, sharpens frequency discrimination, and confers a compressive nonlinearity on responsiveness. These features arise because the active process operates near a Hopf bifurcation, the generic properties of which explain several key features of hearing. Moreover, when the gain of the active process rises sufficiently in ultraquiet circumstances, the system traverses the bifurcation and even a normal ear actually emits sound. The remarkable properties of hearing thus stem from the propagation of traveling waves on a nonlinear and excitable medium.

  • Review Article The physics of hearing: fluid mechanics and the active process of the inner ear
    2014
    Co-Authors: Tobias Reichenbach, A J Hudspeth
    Abstract:

    Most sounds of interest consist of complex, time-dependent admixtures of tones of diverse frequencies and variable amplitudes. To detect and process these signals, the ear employs a highly nonlinear, adaptive, real-time spectral analyzer: the cochlea. Sound excites vibration of the eardrum and the three miniscule bones of the middle ear, the last of which acts as a piston to initiate oscillatory pressure changes within the liquid-filled chambers of the cochlea. The basilar membrane, an elastic band spiraling along the cochlea between two of these chambers, responds to these pressures by conducting a largely independent traveling wave for each frequency component of the input. Because the basilar membrane is graded in mass and stiffness along its length, however, each traveling wave grows in magnitude and decreases in wavelength until it peaks at a specific, frequency-dependent position: low frequencies propagate to the cochlear apex, whereas high frequencies culminate at the base. The oscillations of the basilar membrane deflect hair bundles, the mechanically sensitive organelles of the ear’s sensory receptors, the hair cells. As mechanically sensitive ion channels open and close, each hair cell responds with an electrical signal that is chemically transmitted to an Afferent Nerve Fiber and thence into the brain. In addition to transducing mechanical inputs, hair cells amplify them by tw