Voltage oscillations and ionic conductances in hair cells isolated from the alligator cochlea

1988 ◽  
Vol 164 (2) ◽  
pp. 151-163 ◽  
Author(s):  
P. A. Fuchs ◽  
M. G. Evans
Keyword(s):  
Hair Cells ◽  
Ionic Conductances

GABAB-mediated modulation of ionic conductances in type I hair cells isolated from guinea-pig semicircular canals

1993 ◽  
Vol 609 (1-2) ◽  
pp. 269-276 ◽  
Author(s):  
Pascale N.M. Lapeyre ◽  
Paul J. Kolston ◽  
Jonathan F. Ashmore
Keyword(s):  
Guinea Pig ◽  
Hair Cells ◽  
Semicircular Canals ◽  
Type I ◽  
Ionic Conductances

Studies of solitary semicircular canal hair cells in the adult pigeon. II. Voltage-dependent ionic conductances

1989 ◽  
Vol 62 (4) ◽  
pp. 935-945 ◽  
Author(s):  
D. G. Lang ◽  
M. J. Correia
Keyword(s):  
Hair Cells ◽  
Semicircular Canal ◽  
Potassium Conductance ◽  
Outward Current ◽  
Resting Membrane Potential ◽  
Calcium Dependent ◽  
Ionic Conductances ◽  
Voltage Dependent ◽  
Steady State Inactivation ◽  
Inward Currents

1. The ionic conductances present in putative type II hair cells enzymatically dissociated from the anterior, posterior, and lateral semicircular canal cristae of the white king pigeon (Columba livia) vestibule were studied under whole cell voltage clamp. 2. Two classes of voltage-dependent potassium conductances were distinguishable on the basis of the time course of activation and inactivation and pharmacologic sensitivity. The rapid potassium conductance, IA, as inhibited by 6 mM 4-aminopyridine (4-AP), whereas the slow potassium conductance, IK, was inhibited by 50 mM tetraethylammonium (TEA). These conductances were not affected by extracellular calcium removal. IA was quite similar to the rapidly-inactivating A-current of molluscan soma, whereas IK was more like the delayed rectifier of molluscan soma. 3. The steady-state inactivation of IA occurred over a potential range from -100 to -40 mV. The threshold for activation of IA occurred between -60 and -50 mV. The slope conductance of the I-V curve over a range of -50 to -20 mV was 13.7 nS when the conditioning pulse was -100 mV, and we estimate it to be approximately 1-2 nS from the resting membrane potential of -56 mV. 4. The steady-state inactivation of IK was approximately 60% at -40 mV and was completely removed at -80 mV. The threshold for activation of IK was between -50 and -40 mV. The slope conductance of the I-V curve over a range of -50 to -20 mV was 10.5 nS when the conditioning pulse was -80 mV, and we estimate it to be approximately 6-7 nS from the resting potential of -56 mV. 5. At -56 mV (the average resting membrane potential of putative type II semicircular canal hair cells), approximately 10-14% of IA channels and approximately 57-70% of IK channels were not inactivated: thus IA and IK can contribute to the outward current during small depolarizations from rest. 6. A small calcium-dependent outward current, IK(Ca), could be elicited during step depolarizations from a holding potential of -40 mV. This calcium-dependent current was active over the range of -20 to +40 mV. 7. Inward currents could not be detected when the cells were exposed to normal physiological solutions. However, when the outward currents were blocked with internal cesium and the external solution contained 20 mM barium, sustained inward currents with rapid activation kinetics could be detected. The threshold for activation of the inward current occurred at -40 mV, and the I-V relationship peaked at -10 mV.(ABSTRACT TRUNCATED AT 400 WORDS)

Voltage-Dependent Conductances in Cephalopod Primary Sensory Hair Cells

1997 ◽  
Vol 78 (6) ◽  
pp. 3125-3132 ◽  
Author(s):  
Abdesslam Chrachri ◽  
Roddy Williamson
Keyword(s):  
Hair Cells ◽  
Outward Current ◽  
Sensory Hair ◽  
Inward Current ◽  
Transient Inward Current ◽  
Outward Currents ◽  
Sensory Hair Cells ◽  
Ionic Conductances ◽  
Voltage Dependent ◽  
Inward Currents

Chrachri, Abdesslam and Roddy Williamson. Voltage-dependent conductances in primary sensory hair cells. J. Neurophysiol. 78: 3125–3132, 1997. Cephalopods, such as sepia, squid, and octopus, show a well-developed and sophisticated control of balance particularly during prey capture and escape behaviors. There are two separate areas of sensory epithelium in cephalopod statocysts, a macula/statolith system, which detects linear accelerations (gravity), and a crista/cupula system, which detects rotational movements. The aim of this study is to characterize the ionic conductances in the basolateral membrane of primary sensory hair cells. These were studied using a whole cell patch-clamp technique, which allowed us to identify five ionic conductances in the isolated primary hair cells; an inward sodium current, an inward calcium current, and three potassium outward currents. These outward currents were distinguishable on the basis of their voltage-dependence and pharmacological sensitivities. First, a transient outward current ( I A) was elicited by depolarizing voltage steps from a holding potential of −60 mV, was inactivated by holding the cell at −40 mV, and was blocked by 4-aminopyridine. A second, voltage-sensitive, outward current with a sustained time course was identified. This current was not blocked by 4-aminopyridine nor inactivated at a holding potential of −40 mV and hence could be separated from I A using these protocols. A third outward current that depended on Ca2+ entry for its activation was detected, this current was identified by its sensitivity to Ca2+ channel blockers such as Co2+ and Cd2+ and by the N-shaped profile of its current-voltage curve. Inward currents were studied using cesium aspartate solution in the pipette to block the outward currents. Two inward currents were observed in the primary sensory hair cells. A fast transient inward current, which is presumably responsible for spike generation. This inward current appeared as a rapidly activating inward current; this was strongly voltage dependent. Three lines of evidence suggest that this fast transient inward current is a Na+ current ( I Na). First, it was blocked by tetrodotoxin (TTX); second, it also was blocked by Na+-free saline; and third, it was inactivated when primary hair cells were held at a potential more than −40 mV. The sustained inward current was not affected by TTX and was increased in amplitude 5 min after equimolar Ba2+ replaced Ca2+ as a charge carrier. This inward current also was blocked after external application of 2 mmol/l Co2+ or Cd2+. Furthermore, this current was reduced significantly in a dose-dependent manner by nifedipine, suggesting that it is an L-type Ca2+ current ( I Ca).

Fluorocitrate Neural Dystrophy of the Guinea Pig Cochlea

1975 ◽  
Vol 33 ◽  
pp. 368-369
Author(s):  
G.J. Spector ◽  
C.D. Carr ◽  
I. Kaufman Arenberg ◽  
R.H. Maisel
Keyword(s):  
Hearing Loss ◽  
Hair Cells ◽  
Sodium Phosphate ◽  
Sensory Cells ◽  
Barium Salt ◽  
Perfusion Medium ◽  
Cochlear Hair Cells ◽  
Neural Degeneration ◽  
Sodium Phosphate Buffer ◽  
Cochlear Neurons

All studies on primary neural degeneration in the cochlea have evaluated the end stages of degeneration or the indiscriminate destruction of both sensory cells and cochlear neurons. We have developed a model which selectively simulates the dystrophic changes denoting cochlear neural degeneration while sparing the cochlear hair cells. Such a model can be used to define more precisely the mechanism of presbycusis or the hearing loss in aging man.Twenty-two pigmented guinea pigs (200-250 gm) were perfused by the perilymphatic route as live preparations using fluorocitrate in various concentrations (15-250 ug/cc) and at different incubation times (5-150 minutes). The barium salt of DL fluorocitrate, (C6H4O7F)2Ba3, was reacted with 1.0N sulfuric acid to precipitate the barium as a sulfate. The perfusion medium was prepared, just prior to use, as follows: sodium phosphate buffer 0.2M, pH 7.4 = 9cc; fluorocitrate = 15-200 mg/cc; and sucrose = 0.2M.

Ultrastructure of superficial neuromasts in the mottled sculpin, Cottus bairdi

1989 ◽  
Vol 47 ◽  
pp. 958-959
Author(s):  
W.R. Jones ◽  
S. Coombs ◽  
J. Janssen
Keyword(s):  
Hair Cells ◽  
Lateral Line System ◽  
Electron Microscopic ◽  
Line System ◽  
Dense Cores ◽  
Sensory Hair Cells ◽  
Cytoplasmic Vesicles ◽  
Cottus Bairdi ◽  
Mottled Sculpin ◽  
Upper Third

The lateral line system of the mottled sculpin, like that of most bony fish, has both canal (CNM) and superficial (SNM) sensory end organs, neuromasts, which are distributed on the head and trunk in discrete, readily identifiable groupings (Fig. 1). CNM and SNM differ grossly in location and in overall size and shape. The former are located in subdermal canals and are larger and asymmetric in shape, The latter are located directly on the surface of the skin and are much smaller and more symmetrical It has been suggested that the two may differ at a more fundamental level in such functionally related parameters as extent of myelination of innervating fibers and the absence of efferent innervation in SNM. The present study addresses the validity of these last two features as distinguishing criteria by examining the structure of those SNM populations indicated in Fig. 1 at both the light and electron microscopic levels.All of the populations of SNM examined conform in general to previously published descriptions, consisting of a neuroepithelium composed of sensory hair cells, support cells and mantle cells, Several significant differences from these accounts have, however, emerged. Firstly, the structural composition of the innervating fibers is heterogeneous with respect to the extent of myelination. All SNM groups, with the possible exception of the TRrs and CFLs, possess both myelinated and unmyelinated fibers within the neuroepithelium proper (Fig. 2), just as do CNM. The extent of myelina- tion is quite variable, with some fibers sheath terminating just before crossing the neuroepithelial basal lamina, some just after and a few retaining their myelination all the way to the base of the hair cells in the upper third of the neuroepithelium. Secondly, all SNMs possess fibers that may, on the basis of ultrastructural criteria, be identified as efferent. Such fibers contained numerous cytoplasmic vesicles, both clear and with dense cores. In regions where such fibers closely apposed hair cells, subsynaptic cisternae were observed in the hair cell (Fig. 3).

Further studies on the ultrastructure of the cochlea

1990 ◽  
Vol 48 (3) ◽  
pp. 440-441
Author(s):  
Zhixian Wang ◽  
Pinjin Zhu ◽  
Jianhe Sun ◽  
Xuezheng Song
Keyword(s):  
Hair Cells ◽  
Military Medicine ◽  
Outer Hair Cells ◽  
Apical Surface ◽  
Epithelial Surface ◽  
Hearing Research ◽  
New Findings ◽  
Fine Structures ◽  
Temporal Bones ◽  
Accurate Observation

Hearing research is important not only for clinical, professional and military medicine, but also for toxicology, gerontology and genetics. Ultrastructure of the cochlea attracts much attention of electron microscopists, (1―3) but the research lags far behind that of the other parts of the organnism. On the basis of careful microdissection, technical improvment and accurate observation, we have got some new findings which have not been reported in the literature.We collected four cochleas from human corpses. Temporal bones dissected 1 h after death and cochleas perfused with fixatives 4 h after death were good enough in terms of preservation of fine structures. SEM:The apical surface of OHCs (Outer hair cells) and DTs (Deiters cells) is narrower than that of IPs (Inner pillar cells). The mosaic configuration of the reticular membrane is not typical. The stereocilia of IHCs (Inner hair cells) are not uniform and some kinocilia could be seen on the OHCs in adults. The epithelial surface of RM (Reissner’s membrane) is not smooth and no mesh could be seen on the mesothelial surface of RM. TEM.

Pengaruh sisplatin dosis tinggi terhadap penurunan fungsi sel rambut luar koklea

2013 ◽  
Vol 40 (2) ◽  
Author(s):  
Asti Kristianti ◽  
Teti Madiadipoera ◽  
Bogi Soeseno
Keyword(s):  
Hair Cells ◽  
Malignant Neoplasm ◽  
Otoacoustic Emission ◽  
Outer Hair Cells ◽  
High Dose ◽  
Distortion Product Otoacoustic Emission ◽  
Inclusion Criteria ◽  
Cochlear Hair Cells ◽  
Distortion Product ◽  
Bilateral Sensorineural Hearing Loss

Background: Chemotherapy is worldwide used nowadays, and its toxicity still remain a problemespecially toxicity to the ear (ototoxicity). Cisplatin (cis-diamminedichloroplatinum) is one of themost commonly used chemotherapy and highly potent in treating epithelial malignancies. Ototoxicitycaused by cisplatin is irreversible, progressive, bilateral, sensorineural hearing loss especially on highfrequency (4-8 KHz) accompanied by tinnitus. Purpose: To observe the cochlear outer hair cells damagein malignancies patients treated with cisplatin. Methods: This study is an observational analytic studywith prospective design to determine the influence of high dose cisplatin on cochlear outer hair cellsfunction. The research was carried out at the ENT-HNS Department, Hasan Sadikin General HospitalBandung, from November 2007 until June 2008. Audiometry, tympanometry, and distortion productotoacoustic emission (DPOAE) examinations were conducted before chemotherapy and DPOAE, andtimpanometry was again measured three days after first and second cycles of cisplatin administration. McNemar test was performed to calculate the effects of high-dose cisplatin to the cochlear outer haircells function. To compare pre and post-cisplatin on alteration of cochlear hair cells function, Wilcoxontest was used. Results: In this study 60 ears from 30 subjects that meet the inclusion criteria, consistedof 25 man (83.3%) and 5 women (16.7%). The prevalence of damaged cochlear outer hair cells were63% at first cycle and 70% at second cycle of cisplatin administration. The decline of cochlear outerhair cells function was significant (p<0.001). Conclusion: High-dose cisplatin decreases cochlear outerhair cells function in patients with malignant neoplasm. Abstrak : Latar belakang: Kemoterapi sekarang rutin digunakan secara klinis di seluruh dunia. Sejalan denganhal tersebut toksisitas kemoterapi, khususnya terhadap telinga saat ini menjadi perhatian. Sisplatin(cis-diamminedichloroplatinum) adalah salah satu obat kemoterapi yang paling banyak digunakandan paling manjur untuk terapi keganasan epitelial. Efek ototoksik sisplatin yaitu terjadi gangguandengar sensorineural yang irreversible, progresif, bilateral pada frekuensi tinggi (4-8 kHz), dan disertaidengan tinitus. Tujuan: Untuk menilai penurunan fungsi sel rambut luar koklea pada penderita tumorganas sesudah pemberian sisplatin dosis tinggi dengan menggunakan DPOAE. Metode: Studi analitikobservasional dengan rancangan prospektif di Bagian IK. THT-KL RS. Hasan Sadikin Bandung mulaibulan November 2007 sampai dengan Juni 2008. Pada penelitian ini dilakukan pemeriksaan audiometrinada murni, timpanometri, dan distortion product otoacoustic emission (DPOAE) prakemoterapi, kemudianDPOAE dan timpanometri diulang tiga hari sesudah siklus pertama dan kedua kemoterapi sisplatin. Datayang diperoleh diuji dengan uji McNemar dan uji Wilcoxon. Hasil: Dari penelitian didapat 60 telingadari 30 subjek penelitian yang memenuhi kriteria inklusi yang terdiri dari 25 laki-laki (83,3%) dan 5perempuan (16,7%). Insidens penurunan fungsi sel rambut luar koklea sebesar 63% (38 kasus) sesudahsiklus pertama dan 70% (42 kasus) sesudah siklus kedua. Hubungan penurunan fungsi sel rambut luarkoklea memberikan nilai yang sangat bermakna sejak pemberian siklus pertama (p<0,001). Kesimpulan:Pemberian sisplatin dosis tinggi pada penderita tumor ganas menyebabkan penurunan fungsi sel rambutluar koklea.Kata kunci: kemoterapi, sisplatin dosis tinggi, sel rambut luar koklea.

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