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Piephoff F, Taylor BK, Kehl CE, Mota B, Harley CM. Biomechanics of transduction by mechanosensory cilia for prey detection in aquatic organisms. J Theor Biol 2024; 583:111782. [PMID: 38432503 DOI: 10.1016/j.jtbi.2024.111782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2023] [Revised: 01/14/2024] [Accepted: 02/28/2024] [Indexed: 03/05/2024]
Abstract
Surface-feeding aquatic animals navigate towards the source of water disturbances and must differentiate prey from other environmental stimuli. Medicinal leeches locate prey, in part, using a distribution of mechanosensory hairs along their body that deflect under fluid flow. Leech's behavioral responses to surface wave temporal frequency are well documented. However, a surface wave's temporal frequency depends on many underlying environmental and fluid properties that vary substantially in natural habitats (e.g., water depth, temperature). The impact of these variables on neural response and behavior is unknown. Here, we developed a physics-based leech mechanosensor model to examine the impact of environmental and fluid properties on neural response. Our model used the physical properties of a leech cilium and was verified against existing behavioral and electrophysiological data. The model's peak response occurred with waves where the effects of gravity and surface tension were nearly equal (i.e., the phase velocity minimum). This suggests that preferred stimuli are related to the interaction between fundamental properties of the surrounding medium and the mechanical properties of the sensor. This interaction likely tunes the sensor to detect the nondispersive components of the signal, filtering out irrelevant ambient stimuli, and may be a general property of cilia across the animal kingdom.
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Affiliation(s)
- Faye Piephoff
- Department of Biology, Case Western Reserve University, Cleveland OH, 44106, USA.
| | - Brian K Taylor
- Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland OH, 44106, USA.
| | - Catherine E Kehl
- Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill NC, 27599, USA.
| | - Bruno Mota
- Instituto de Fisica, Universidade Federal do Rio De Janeiro, Rio de Janeiro 21941, Brazil.
| | - Cynthia M Harley
- Department of Natural Sciences, Metropolitan State University, St Paul MN, 55106, USA.
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How to Build a Fast and Highly Sensitive Sound Detector That Remains Robust to Temperature Shifts. J Neurosci 2019; 39:7260-7276. [PMID: 31315946 DOI: 10.1523/jneurosci.2510-18.2019] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 06/13/2019] [Accepted: 07/09/2019] [Indexed: 12/26/2022] Open
Abstract
Frogs must have sharp hearing abilities during the warm summer months to successfully find mating partners. This study aims to understand how frog hair cell ribbon-type synapses preserve both sensitivity and temporal precision during temperature changes. Under room (∼24°C) and high (∼32°C) temperature, we performed in vitro patch-clamp recordings of hair cells and their afferent fibers in amphibian papillae of either male or female bullfrogs. Afferent fibers exhibited a wide heterogeneity in membrane input resistance (Rin) from 100 mΩ to 1000 mΩ, which may contribute to variations in spike threshold and firing frequency. At higher temperatures, most fibers increased their frequency of spike firing due to an increase in spontaneous EPSC frequencies. Hair cell resting membrane potential (Vrest) remained surprisingly stable during temperature increases, because Ca2+ influx and K+ outflux increased simultaneously. This increase in Ca2+ current likely enhanced spontaneous EPSC frequencies. These larger "leak currents" at Vrest also lowered Rin and produced higher electrical resonant frequencies. Lowering Rin will reduce the hair cells receptor potential and presumably moderate the systems sensitivity. Using membrane capacitance measurements, we suggest that hair cells can partially compensate for this reduced sensitivity by increasing exocytosis efficiency and the size of the readily releasable pool of synaptic vesicles. Furthermore, paired recordings of hair cells and their afferent fibers showed that synaptic delays shortened and multivesicular release becomes more synchronous at higher temperatures, which should improve temporal precision. Together, our results explain many previous in vivo observations on the temperature dependence of spikes in auditory nerves.SIGNIFICANCE STATEMENT The vertebrate inner ear detects and transmits auditory information over a broad dynamic range of sound frequency and intensity. It achieves remarkable sensitivity to soft sounds and precise frequency selectivity. How does the ear of cold-blooded vertebrates maintain its performance level as temperature changes? More specifically, how does the hair cell to afferent fiber synapse in bullfrog amphibian papilla adjust to a wide range of physiological temperatures without losing its sensitivity and temporal fidelity to sound signals? This study uses in vitro experiments to reveal the biophysical mechanisms that explain many observations made from in vivo auditory nerve fiber recordings. We find that higher temperature facilitates vesicle exocytosis and electrical tuning to higher sound frequencies, which benefits sensitivity and selectivity.
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Hyde JS. Autobiography of James S. Hyde. APPLIED MAGNETIC RESONANCE 2017; 48:1103-1147. [PMID: 29962662 PMCID: PMC6022859 DOI: 10.1007/s00723-017-0950-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The papers, book chapters, reviews, and patents by James S. Hyde in the bibliography of this document have been separated into EPR and MRI sections, and within each section by topics. Within each topic, publications are listed chronologically. A brief summary is provided for each patent listed. A few publications and patents that do not fit this schema have been omitted. This list of publications is preceded by a scientific autobiography that focuses on selected topics that are judged to have been of most scientific importance. References to many of the publications and patents in the bibliography are made in the autobiography.
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Affiliation(s)
- James S Hyde
- Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plan Road, Milwaukee, WI 53226; 414-955-4000; ; ORCID: 0000-0002-3023-1243
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Willis KL, Carr CE. A circuit for detection of interaural time differences in the nucleus laminaris of turtles. ACTA ACUST UNITED AC 2017; 220:4270-4281. [PMID: 28947499 DOI: 10.1242/jeb.164145] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Accepted: 09/19/2017] [Indexed: 11/20/2022]
Abstract
The physiological hearing range of turtles is approximately 50-1000 Hz, as determined by cochlear microphonics ( Wever and Vernon, 1956a). These low frequencies can constrain sound localization, particularly in red-eared slider turtles, which are freshwater turtles with small heads and isolated middle ears. To determine if these turtles were sensitive to interaural time differences (ITDs), we investigated the connections and physiology of their auditory brainstem nuclei. Tract tracing experiments showed that cranial nerve VIII bifurcated to terminate in the first-order nucleus magnocellularis (NM) and nucleus angularis (NA), and the NM projected bilaterally to the nucleus laminaris (NL). As the NL received inputs from each side, we developed an isolated head preparation to examine responses to binaural auditory stimulation. Magnocellularis and laminaris units responded to frequencies from 100 to 600 Hz, and phase-locked reliably to the auditory stimulus. Responses from the NL were binaural, and sensitive to ITD. Measures of characteristic delay revealed best ITDs around ±200 μs, and NL neurons typically had characteristic phases close to 0, consistent with binaural excitation. Thus, turtles encode ITDs within their physiological range, and their auditory brainstem nuclei have similar connections and cell types to other reptiles.
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Affiliation(s)
- Katie L Willis
- University of Maryland, Department of Biology, Center for Comparative and Evolutionary Biology of Hearing, Neuroscience and Cognitive Science Graduate Program, College Park, MD 20742, USA
| | - Catherine E Carr
- University of Maryland, Department of Biology, Center for Comparative and Evolutionary Biology of Hearing, Neuroscience and Cognitive Science Graduate Program, College Park, MD 20742, USA
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Corbitt C, Farinelli F, Brownell WE, Farrell B. Tonotopic relationships reveal the charge density varies along the lateral wall of outer hair cells. Biophys J 2012; 102:2715-24. [PMID: 22735521 DOI: 10.1016/j.bpj.2012.04.054] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Revised: 04/27/2012] [Accepted: 04/30/2012] [Indexed: 01/12/2023] Open
Abstract
Outer hair cells amplify and improve the frequency selectivity of sound within the mammalian cochlea through a sound-evoked receptor potential that induces an electromechanical response in their lateral wall membrane. We experimentally show that the membrane area and linear membrane capacitance of outer hair cells increases exponentially with the electrically evoked voltage-dependent charge movement (Q(T)) and peak membrane capacitance (C(peak)). We determine the size of the different functional regions (e.g., lateral wall, synaptic basal pole) of the polarized cells from the tonotopic relationships. We then establish that Q(T) and C(peak) increase with the logarithm of the lateral wall area (A(LW)) and determine from the functions that the charge (σ(LW,) pC/μm(2)) and peak (ρ(LW,) pF/μm(2)) densities vary inversely with A(LW) (σ(LW) = 1.3/A(LW) and ρ(LW) = 9/A(LW)). This shows contrary to conventional wisdom that σ(LW) and ρ(LW) are not constant along the length of an individual outer hair cell.
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Affiliation(s)
- Christian Corbitt
- Bobby R. Alford Department of Otolaryngology-Head and Neck Surgery, Baylor College of Medicine, Houston, Texas, USA
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Brownell WE, Qian F, Anvari B. Cell membrane tethers generate mechanical force in response to electrical stimulation. Biophys J 2010; 99:845-52. [PMID: 20682262 PMCID: PMC3297770 DOI: 10.1016/j.bpj.2010.05.025] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Revised: 03/25/2010] [Accepted: 05/10/2010] [Indexed: 11/22/2022] Open
Abstract
Living cells maintain a huge transmembrane electric field across their membranes. This electric field exerts a force on the membrane because the membrane surfaces are highly charged. We have measured electromechanical force generation by cell membranes using optically trapped beads to detach the plasma membrane from the cytoskeleton and form long thin cylinders (tethers). Hyperpolarizing potentials increased and depolarizing potentials decreased the force required to pull a tether. The membrane tether force in response to sinusoidal voltage signals was a function of holding potential, tether diameter, and tether length. Membrane electromechanical force production can occur at speeds exceeding those of ATP-based protein motors. By harnessing the energy in the transmembrane electric field, cell membranes may contribute to processes as diverse as outer hair cell electromotility, ion channel gating, and transport.
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Affiliation(s)
- William E Brownell
- Bobby R. Alford Department of Otolaryngology, Head & Neck Surgery, and Department of Neuroscience, Baylor College of Medicine, Houston, Texas, USA.
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Golowasch J, Thomas G, Taylor AL, Patel A, Pineda A, Khalil C, Nadim F. Membrane capacitance measurements revisited: dependence of capacitance value on measurement method in nonisopotential neurons. J Neurophysiol 2009; 102:2161-75. [PMID: 19571202 DOI: 10.1152/jn.00160.2009] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
During growth or degeneration neuronal surface area can change dramatically. Measurements of membrane protein concentration, as in ion channel or ionic conductance density, are often normalized by membrane capacitance, which is proportional to the surface area, to express changes independently from cell surface variations. Several electrophysiological protocols are used to measure cell capacitance, all based on the assumption of membrane isopotentiality. Yet, most neurons violate this assumption because of their complex anatomical structure, raising the question of which protocol yields measurements that are closest to the actual total membrane capacitance. We measured the capacitance of identified neurons from crab stomatogastric ganglia using three different protocols: the current-clamp step, the voltage-clamp step, and the voltage-clamp ramp protocols. We observed that the current-clamp protocol produced significantly higher capacitance values than those of either voltage-clamp protocol. Computational models of various anatomical complexities suggest that the current-clamp protocol can yield accurate capacitance estimates. In contrast, the voltage-clamp protocol estimates rapidly deteriorate as isopotentiality is reduced. We provide a mathematical description of these results by analyzing a simple two-compartment model neuron to facilitate an intuitive understanding of these methods. Together, the experiments, modeling, and mathematical analysis indicate that accurate total membrane capacitance measurements cannot be obtained with voltage-clamp protocols in nonisopotential neurons. Furthermore, although current-clamp steps can theoretically yield accurate measurements, experimentalists should be aware of limitations imposed by step duration and numerical errors during fitting procedures to obtain the membrane time constant.
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Affiliation(s)
- Jorge Golowasch
- Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, New Jersey 07102, USA.
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Rabbitt RD, Clifford S, Breneman KD, Farrell B, Brownell WE. Power efficiency of outer hair cell somatic electromotility. PLoS Comput Biol 2009; 5:e1000444. [PMID: 19629162 PMCID: PMC2705677 DOI: 10.1371/journal.pcbi.1000444] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2009] [Accepted: 06/23/2009] [Indexed: 11/18/2022] Open
Abstract
Cochlear outer hair cells (OHCs) are fast biological motors that serve to enhance the vibration of the organ of Corti and increase the sensitivity of the inner ear to sound. Exactly how OHCs produce useful mechanical power at auditory frequencies, given their intrinsic biophysical properties, has been a subject of considerable debate. To address this we formulated a mathematical model of the OHC based on first principles and analyzed the power conversion efficiency in the frequency domain. The model includes a mixture-composite constitutive model of the active lateral wall and spatially distributed electro-mechanical fields. The analysis predicts that: 1) the peak power efficiency is likely to be tuned to a specific frequency, dependent upon OHC length, and this tuning may contribute to the place principle and frequency selectivity in the cochlea; 2) the OHC power output can be detuned and attenuated by increasing the basal conductance of the cell, a parameter likely controlled by the brain via the efferent system; and 3) power output efficiency is limited by mechanical properties of the load, thus suggesting that impedance of the organ of Corti may be matched regionally to the OHC. The high power efficiency, tuning, and efferent control of outer hair cells are the direct result of biophysical properties of the cells, thus providing the physical basis for the remarkable sensitivity and selectivity of hearing.
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Affiliation(s)
- Richard D. Rabbitt
- Department of Bioengineering, University of Utah, Salt Lake City, Utah, United States of America
- Marine Biological Laboratory, Woods Hole, Massachusetts, United States of America
| | - Sarah Clifford
- Department of Bioengineering, University of Utah, Salt Lake City, Utah, United States of America
| | - Kathryn D. Breneman
- Department of Bioengineering, University of Utah, Salt Lake City, Utah, United States of America
| | - Brenda Farrell
- Department of Otolaryngology, Head and Neck Surgery, Baylor College of Medicine, Houston, Texas, United States of America
| | - William E. Brownell
- Department of Otolaryngology, Head and Neck Surgery, Baylor College of Medicine, Houston, Texas, United States of America
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Breneman KD, Brownell WE, Rabbitt RD. Hair cell bundles: flexoelectric motors of the inner ear. PLoS One 2009; 4:e5201. [PMID: 19384413 PMCID: PMC2668172 DOI: 10.1371/journal.pone.0005201] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2009] [Accepted: 03/16/2009] [Indexed: 11/18/2022] Open
Abstract
Microvilli (stereocilia) projecting from the apex of hair cells in the inner ear are actively motile structures that feed energy into the vibration of the inner ear and enhance sensitivity to sound. The biophysical mechanism underlying the hair bundle motor is unknown. In this study, we examined a membrane flexoelectric origin for active movements in stereocilia and conclude that it is likely to be an important contributor to mechanical power output by hair bundles. We formulated a realistic biophysical model of stereocilia incorporating stereocilia dimensions, the known flexoelectric coefficient of lipid membranes, mechanical compliance, and fluid drag. Electrical power enters the stereocilia through displacement sensitive ion channels and, due to the small diameter of stereocilia, is converted to useful mechanical power output by flexoelectricity. This motor augments molecular motors associated with the mechanosensitive apparatus itself that have been described previously. The model reveals stereocilia to be highly efficient and fast flexoelectric motors that capture the energy in the extracellular electro-chemical potential of the inner ear to generate mechanical power output. The power analysis provides an explanation for the correlation between stereocilia height and the tonotopic organization of hearing organs. Further, results suggest that flexoelectricity may be essential to the exquisite sensitivity and frequency selectivity of non-mammalian hearing organs at high auditory frequencies, and may contribute to the “cochlear amplifier” in mammals.
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Affiliation(s)
- Kathryn D. Breneman
- Department of Bioengineering, University of Utah, Salt Lake City, Utah, United States of America
| | - William E. Brownell
- Department of Otolaryngology - H&NS, Baylor College of Medicine, Houston, Texas, United States of America
| | - Richard D. Rabbitt
- Department of Bioengineering, University of Utah, Salt Lake City, Utah, United States of America
- Marine Biological Laboratory, Woods Hole, Massachusetts, United States of America
- * E-mail:
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