A technique for protecting delicate specimens during processing

1989 ◽  
Vol 47 ◽  
pp. 982-983
Author(s):  
R.J. Mount ◽  
R.V. Harrison
Keyword(s):  
Basilar Membrane ◽  
Low Cost ◽  
Organ Of Corti ◽  
Region Of Interest ◽  
Sensory Epithelium ◽  
Physical Damage ◽  
Air Drying ◽  
Specimen Handling ◽  
Two Component

The sensory end organ of the ear, the organ of Corti, rests on a thin basilar membrane which lies between the bone of the central modiolus and the bony wall of the cochlea. In vivo, the organ of Corti is protected by the bony wall which totally surrounds it. In order to examine the sensory epithelium by scanning electron microscopy it is necessary to dissect away the protective bone and expose the region of interest (Fig. 1). This leaves the fragile organ of Corti susceptible to physical damage during subsequent handling. In our laboratory cochlear specimens, after dissection, are routinely prepared by the O-T- O-T-O technique, critical point dried and then lightly sputter coated with gold. This processing involves considerable specimen handling including several hours on a rotator during which the organ of Corti is at risk of being physically damaged. The following procedure uses low cost, readily available materials to hold the specimen during processing ,preventing physical damage while allowing an unhindered exchange of fluids.Following fixation, the cochlea is dehydrated to 70% ethanol then dissected under ethanol to prevent air drying. The holder is prepared by punching a hole in the flexible snap cap of a Wheaton vial with a paper hole punch. A small amount of two component epoxy putty is well mixed then pushed through the hole in the cap. The putty on the inner cap is formed into a “cup” to hold the specimen (Fig. 2), the putty on the outside is smoothed into a “button” to give good attachment even when the cap is flexed during handling (Fig. 3). The cap is submerged in the 70% ethanol, the bone at the base of the cochlea is seated into the cup and the sides of the cup squeezed with forceps to grip it (Fig.4). Several types of epoxy putty have been tried, most are either soluble in ethanol to some degree or do not set in ethanol. The only putty we find successful is “DUROtm MASTERMENDtm Epoxy Extra Strength Ribbon” (Loctite Corp., Cleveland, Ohio), this is a blue and yellow ribbon which is kneaded to form a green putty, it is available at many hardware stores.

Stiffness of the Gerbil Basilar Membrane: Radial and Longitudinal Variations

2004 ◽  
Vol 91 (1) ◽  
pp. 474-488 ◽  
Author(s):  
Gulam Emadi ◽  
Claus-Peter Richter ◽  
Peter Dallos
Keyword(s):  
Cross Section ◽  
Basilar Membrane ◽  
Organ Of Corti ◽  
Sound Waves ◽  
Motion Patterns ◽  
Longitudinal Stiffness ◽  
Longitudinal Variations ◽  
Space Constant ◽  
Qualitative Changes

Experimental data on the mechanical properties of the tissues of the mammalian cochlea are essential for understanding the frequency- and location-dependent motion patterns that result in response to incoming sound waves. Within the cochlea, sound-induced vibrations are transduced into neural activity by the organ of Corti, the gross motion of which is dependent on the motion of the underlying basilar membrane. In this study we present data on stiffness of the gerbil basilar membrane measured at multiple positions within a cochlear cross section and at multiple locations along the length of the cochlea. A basic analysis of these data using relatively simple models of cochlear mechanics reveals our most important result: the experimentally measured longitudinal stiffness gradient at the middle of the pectinate zone of the basilar membrane (4.43 dB/mm) can account for changes of best frequency along the length of the cochlea. Furthermore, our results indicate qualitative changes of stiffness-deflection curves as a function of radial position; in particular, there are differences in the rate of stiffness growth with increasing tissue deflection. Longitudinal coupling within the basilar membrane/organ of Corti complex is determined to have a space constant of 21 μm in the middle turn of the cochlea. The bulk of our data was obtained in the hemicochlea preparation, and we include a comparison of this set of data to data obtained in vivo.

scholarly journals Vibration of the organ of Corti within the cochlear apex in mice

2014 ◽  
Vol 112 (5) ◽  
pp. 1192-1204 ◽  
Author(s):  
Simon S. Gao ◽  
Rosalie Wang ◽  
Patrick D. Raphael ◽  
Yalda Moayedi ◽  
Andrew K. Groves ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Phase Difference ◽  
Basilar Membrane ◽  
Organ Of Corti ◽  
Lateral Compartment ◽  
Outer Hair Cells ◽  
Supporting Cells ◽  
Tuning Curves ◽  
Cochlear Amplification

The tonotopic map of the mammalian cochlea is commonly thought to be determined by the passive mechanical properties of the basilar membrane. The other tissues and cells that make up the organ of Corti also have passive mechanical properties; however, their roles are less well understood. In addition, active forces produced by outer hair cells (OHCs) enhance the vibration of the basilar membrane, termed cochlear amplification. Here, we studied how these biomechanical components interact using optical coherence tomography, which permits vibratory measurements within tissue. We measured not only classical basilar membrane tuning curves, but also vibratory responses from the rest of the organ of Corti within the mouse cochlear apex in vivo. As expected, basilar membrane tuning was sharp in live mice and broad in dead mice. Interestingly, the vibratory response of the region lateral to the OHCs, the “lateral compartment,” demonstrated frequency-dependent phase differences relative to the basilar membrane. This was sharply tuned in both live and dead mice. We then measured basilar membrane and lateral compartment vibration in transgenic mice with targeted alterations in cochlear mechanics. Prestin499/499, Prestin−/−, and TectaC1509G/C1509G mice demonstrated no cochlear amplification but maintained the lateral compartment phase difference. In contrast, SfswapTg/Tg mice maintained cochlear amplification but did not demonstrate the lateral compartment phase difference. These data indicate that the organ of Corti has complex micromechanical vibratory characteristics, with passive, yet sharply tuned, vibratory characteristics associated with the supporting cells. These characteristics may tune OHC force generation to produce the sharp frequency selectivity of mammalian hearing.

scholarly journals In vivo optogenetics reveals control of cochlear sensitivity by supporting cells

2021 ◽  
Author(s):  
Victoria Lukashkina ◽  
Snezana Levic ◽  
Patricio Simões ◽  
Zhenhang Xu ◽  
Joseph DiGuiseppi ◽  
...  
Keyword(s):  
Basilar Membrane ◽  
Ex Vivo ◽  
Organ Of Corti ◽  
Outer Hair Cells ◽  
Supporting Cells ◽  
Acoustic Environment ◽  
Cation Conductance ◽  
Fine Control ◽  
Electrical Responses

Abstract Cochlear sensitivity, essential for communication and exploiting the acoustic environment, is due to the sensory-motor outer hair cells (OHCs) that operate in the structural scaffold of supporting cells and extracellular spaces in the cochlear organ of Corti (OoC). It is unclear whether supporting cells (e.g., Deiters cells [DCs] and outer pillar cells [OPCs]) control cochlear sensitivity in vivo. Here we employed optogenetics to measure in vivo sound-induced cochlear mechanical and electrical responses, and ex vivo light-induced DC electrical responses in the OoC of mice that conditionally expressed channelrhodopsins (ChR2) specifically in DCs and OPCs. Illumination activated a nonselective ChR2 cation conductance and depolarized the DCs. This transient action reversibly blocked continuous, normally occurring, minor adjustments of tone-evoked basilar membrane displacements, and OHC voltage responses to tones at and close to their characteristic frequency, and speeded recovery from temporary acoustic desensitization. This is the first direct evidence for the interdependency of the structural, mechanical, and electrochemical arrangement of OHCs and OoC supporting cells which together fine control cochlear sensitivity.

Chlorpromazine Alters Cochlear Mechanics and Amplification: In Vivo Evidence for a Role of Stiffness Modulation in the Organ of Corti

2007 ◽  
Vol 97 (2) ◽  
pp. 994-1004 ◽  
Author(s):  
Jiefu Zheng ◽  
Niranjan Deo ◽  
Yuan Zou ◽  
Karl Grosh ◽  
Alfred L. Nuttall
Keyword(s):  
Outer Hair Cell ◽  
Basilar Membrane ◽  
Organ Of Corti ◽  
Lateral Wall ◽  
Mechanical Force ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Cochlear Amplification

Although prestin-mediated outer hair cell (OHC) electromotility provides mechanical force for sound amplification in the mammalian cochlea, proper OHC stiffness is required to maintain normal electromotility and to transmit mechanical force to the basilar membrane (BM). To investigate the in vivo role of OHC stiffness in cochlear amplification, chlorpromazine (CPZ), an antipsychotic drug that alters OHC lateral wall biophysics, was infused into the cochleae in living guinea pigs. The effects of CPZ on cochlear amplification and OHC electromotility were observed by measuring the acoustically and electrically evoked BM motions. CPZ significantly reduced cochlear amplification as measured by a decline of the acoustically evoked BM motion near the best frequency (BF) accompanied by a loss of nonlinearity and broadened tuning. It also substantially reduced electrically evoked BM vibration near the BF and at frequencies above BF (≤80 kHz). The high-frequency notch (near 50 kHz) in the electrically evoked BM response shifted toward higher frequency in a CPZ concentration-dependent manner with a corresponding phase change. In contrast, salicylate resulted in a shift in this notch toward lower frequency. These results indicate that CPZ reduces OHC-mediated cochlear amplification probably via its effects on the mechanics of the OHC plasma membrane rather than via a direct effect on the OHC motor, prestin. Through modeling, we propose that with a combined OHC somatic and hair bundle forcing, the upward-shift of the ∼50-kHz notch in the electrically-evoked BM motion may indicate stiffness increase of the OHCs that is responsible for the reduced cochlear amplification.

scholarly journals Cochlear amplification and tuning depend on the cellular arrangement within the organ of Corti

2018 ◽  
Vol 115 (22) ◽  
pp. 5762-5767 ◽  
Author(s):  
Hamid Motallebzadeh ◽  
Joris A. M. Soons ◽  
Sunil Puria
Keyword(s):  
Hair Cells ◽  
Outer Hair Cell ◽  
Basilar Membrane ◽  
Measurement Techniques ◽  
Organ Of Corti ◽  
Sensory Epithelium ◽  
Sound Levels ◽  
Cochlear Amplification ◽  
Sound Transduction ◽  
Deiters Cell

The field of cochlear mechanics has been undergoing a revolution due to recent findings made possible by advancements in measurement techniques. While it has long been assumed that basilar-membrane (BM) motion is the most important determinant of sound transduction by the inner hair cells (IHCs), it turns out that other parts of the sensory epithelium closer to the IHCs, such as the reticular lamina (RL), move with significantly greater amplitude for weaker sounds. It has not been established how these findings are related to the complex cytoarchitecture of the organ of Corti between the BM and RL, which is composed of a lattice of asymmetric Y-shaped elements, each consisting of a basally slanted outer hair cell (OHC), an apically slanted phalangeal process (PhP), and a supporting Deiters’ cell (DC). Here, a computational model of the mouse cochlea supports the hypothesis that the OHC micromotors require this Y-shaped geometry for their contribution to the exquisite sensitivity and frequency selectivity of the mammalian cochlea. By varying only the OHC gain parameter, the model can reproduce measurements of BM and RL gain and tuning for a variety of input sound levels. Malformations such as reversing the orientations of the OHCs and PhPs or removing the PhPs altogether greatly reduce the effectiveness of the OHC motors. These results imply that the DCs and PhPs must be properly accounted for in emerging OHC regeneration therapies.

Hair cell changes after cationic stimulation of corti's organ

1989 ◽  
Vol 47 ◽  
pp. 798-799
Author(s):  
Cesar D. Fermin ◽  
Hans-Peter Zenner
Keyword(s):  
Organ Of Corti ◽  
Cross Sectional ◽  
Surface Areas ◽  
High K ◽  
Anatomical Arrangement ◽  
Cell Cytosol ◽  
High Concentrations ◽  
K Concentration ◽  
Cell Changes

Contraction of outer and inner hair cells (OHC&IHC) in the Organ of Corti (OC) of the inner ear is necessary for sound transduction. Getting at HC in vivo preparations is difficult. Thus, isolated HCs have been used to study OHC properties. Even though viability has been shown in isolated (iOHC) preparations by good responses to current and cationic stimulation, the contribution of adjoining cells can not be explained with iOHC preparations. This study was undertaken to examine changes in the OHC after expossure of the OHC to high concentrations of potassium (K) and sodium (Na), by carefully immersing the OC in either artifical endolymph or perilymph. After K and Na exposure, OCs were fixed with 3% glutaraldehyde, post-fixed in osmium, separated into base, middle and apex and embedded in Araldite™. One μm thick sections were prepared for analysis with the light and E.M. Cross sectional areas were measured with Bioquant™ software.Potassium and sodium both cause isolated guinea pig OHC to contract. In vivo high K concentration may cause uncontrolled and sustained contractions that could contribute to Meniere's disease. The behavior of OHC in the vivo setting might be very different from that of iOHC. We show here changes of the cell cytosol and cisterns caused by K and Na to OHC in situs. The table below shows results from cross sectional area measurements of OHC from OC that were exposed to either K or Na. As one would expect, from the anatomical arrangement of the OC, OHC#l that are supported by rigid tissue would probably be displaced (move) less than those OHC located away from the pillar. Surprisingly, cells in the middle turn of the cochlea changed their surface areas more than those at either end of the cochlea. Moreover, changes in surface area do not seem to differ between K and Na treated OCs.

scholarly journals Marker for the pre-clinical development of bone substitute materials

2017 ◽  
Vol 3 (2) ◽  
pp. 711-715
Author(s):  
Michael de Wild ◽  
Simon Zimmermann ◽  
Marcel Obrecht ◽  
Michel Dard
Keyword(s):  
Bone Graft ◽  
Mechanical Stability ◽  
Clinical Performance ◽  
Ex Vivo ◽  
Region Of Interest ◽  
Defect Site ◽  
Novel Approach ◽  
Bone Substitute Materials ◽  
Clinical Experiments

AbstractThin mechanically stable Ti-cages have been developed for the in-vivo application as X-ray and histology markers for the optimized evaluation of pre-clinical performance of bone graft materials. A metallic frame defines the region of interest during histological investigations and supports the identification of the defect site. This standardization of the procedure enhances the quality of pre-clinical experiments. Different models of thin metallic frameworks were designed and produced out of titanium by additive manufacturing (Selective Laser Melting). The productibility, the mechanical stability, the handling and suitability of several frame geometries were tested during surgery in artificial and in ex-vivo bone before a series of cages was preclinically investigated in the female Göttingen minipigs model. With our novel approach, a flexible process was established that can be adapted to the requirements of any specific animal model and bone graft testing.

scholarly journals Optimization of spectral-domain optical coherence tomography with a supercontinuum source for in vivo motion detection of low reflective outer hair cells in guinea pig cochleae

2021 ◽  
Author(s):  
Fumiaki Nin ◽  
Samuel Choi ◽  
Takeru Ota ◽  
Zhang Qi ◽  
Hiroshi Hibino
Keyword(s):  
Optical Coherence Tomography ◽  
High Resolution ◽  
Guinea Pig ◽  
Hair Cells ◽  
Sensory Epithelium ◽  
Outer Hair Cells ◽  
Acquisition Time ◽  
Total Acquisition Time ◽  
Sd Oct

AbstractSound evokes sub-nanoscale vibration within the sensory epithelium. The epithelium contains not only immotile cells but also contractile outer hair cells (OHCs) that actively shrink and elongate synchronously with the sound. However, the in vivo motion of OHCs has remained undetermined. The aim of this work is to perform high-resolution and -accuracy vibrometry in live guinea pigs with an SC-introduced spectral-domain optical coherence tomography system (SD-OCT). In this study, to reveal the effective contribution of SC source in the recording of the low reflective materials with the short total acquisition time, we compare the performances of the SC-introduced SD-OCT (SCSD-OCT) to that of the conventional SD-OCT. As inanimate comparison objects, we record a mirror, a piezo actuator, and glass windows. For the measurements in biological materials, we use in/ex vivo guinea pig cochleae. Our study achieved the optimization of a SD-OCT system for high-resolution in vivo vibrometry in the cochlear sensory epithelium, termed the organ of Corti, in mammalian cochlea. By introducing a supercontinuum (SC) light source and reducing the total acquisition time, we improve the axial resolution and overcome the difficulty in recording the low reflective material in the presence of biological noise. The high power of the SC source enables the system to achieve a spatial resolution of 1.72 ± 0.00 μm on a mirror and reducing the total acquisition time contributes to the high spatial accuracy of sub-nanoscale vibrometry. Our findings reveal the vibrations at the apical/basal region of OHCs and the extracellular matrix, basilar membrane.

scholarly journals In Vivo Usability Test of Vascular Intervention Robotic System Controlled by Two Types of Master Devices

2021 ◽  
Vol 11 (12) ◽  
pp. 5453
Author(s):  
Hwa-Seob Song ◽  
Jae-Hong Woo ◽  
Jong-Yun Won ◽  
Byung-Ju Yi
Keyword(s):  
Radiation Exposure ◽  
Animal Experiments ◽  
X Rays ◽  
Physical Damage ◽  
Vascular Intervention ◽  
Task Load ◽  
Usability Test ◽  
Usability Tests ◽  
System Usability Scale

Conventional vascular intervention (VI) procedures are typically performed manually under exposure to X-rays, whereby several problems are presented that need to be addressed owing to the patients and doctors being exposed to large amounts of radiation. In such cases, employing radiation protection units is not a long-term solution to avoid physical damage. Therefore, to overcome these issues, we propose a robotic VI system in this study. Moreover, we compare the extent of radiation exposure in the case of the conventional manual VI procedure with that in the case of the robotic procedure. The radiation exposure is then analyzed from the perspective of the doctor. Subsequently, the results of usability tests for two proposed master devices are presented in terms of the NASA task load index (NASA-TLX) and the system usability scale (SUS) score. To verify the effectiveness of the robotic VI system, animal experiments are conducted using a pig model. Among the two types of master devices tested with the proposed robotic VI system, the ergonomically designed 2-degree-of-freedom master device is found to be more effective than the joystick-type device in terms of the usability test scores. Hence, the proposed robotic VI procedure is shown to be advantageous in terms of reducing radiation exposure and improving usability.

scholarly journals Organ-specific, multimodal, wireless optoelectronics for high-throughput phenotyping of peripheral neural pathways

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Woo Seok Kim ◽  
Sungcheol Hong ◽  
Milenka Gamero ◽  
Vivekanand Jeevakumar ◽  
Clay M. Smithhart ◽  
...  
Keyword(s):  
High Throughput ◽  
Low Cost ◽  
Optoelectronic Device ◽  
Antenna System ◽  
Neural Pathways ◽  
Organ Specific ◽  
Coil Antenna ◽  
Sensory Fibers

AbstractThe vagus nerve supports diverse autonomic functions and behaviors important for health and survival. To understand how specific components of the vagus contribute to behaviors and long-term physiological effects, it is critical to modulate their activity with anatomical specificity in awake, freely behaving conditions using reliable methods. Here, we introduce an organ-specific scalable, multimodal, wireless optoelectronic device for precise and chronic optogenetic manipulations in vivo. When combined with an advanced, coil-antenna system and a multiplexing strategy for powering 8 individual homecages using a single RF transmitter, the proposed wireless telemetry enables low cost, high-throughput, and precise functional mapping of peripheral neural circuits, including long-term behavioral and physiological measurements. Deployment of these technologies reveals an unexpected role for stomach, non-stretch vagal sensory fibers in suppressing appetite and demonstrates the durability of the miniature wireless device inside harsh gastric conditions.

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