Electrical filtering in gerbil isolated type I semicircular canal hair cells

1996 ◽  
Vol 75 (5) ◽  
pp. 2117-2123 ◽  
Author(s):  
K. J. Rennie ◽  
A. J. Ricci ◽  
M. J. Correia
Keyword(s):  
Membrane Potential ◽  
Hair Cells ◽  
Semicircular Canal ◽  
Input Resistance ◽  
Constant Current ◽  
Type I ◽  
Type Ii ◽  
Peak Voltage ◽  
Type I Cells ◽  
I Cells

1. Membrane potential responses of dissociated gerbil type I semicircular canal hair cells to current injections in whole cell current-clamp have been measured. The input resistance of type I cells was 21.4 +/- 14.3 (SD) M omega, (n = 25). Around the zero-current potential (Vz = -66.6 +/- 9.3 mV, n = 25), pulsed current injections (from approximately -200 to 750 pA) produced only small-amplitude, pulse-like changes in membrane potential. 2. Injecting constant current to hyperpolarize the membrane to around -100 mV resulted in a approximately 10-fold increase in membrane resistance. Current pulses superimposed on this constant hyperpolarization produced larger and more complex membrane potential changes. Depolarizing currents > or = 200 pA caused a rapid transient peak voltage before a plateau. 3. Membrane voltage was able to faithfully follow sine-wave current injections around Vz over the range 1-1,000 Hz with < 25% attenuation at 1 kHz. A previously described K conductance, IKI, which is active at Vz, produces the low input resistance and frequency response. This was confirmed by pharmacologically blocking IKI. This conductance, present in type I cells but not type II hair cells, would appear to confer on type I cells a lower gain, but a much broader bandwidth at Vz, than seen in type II cells.

Voltage-Gated Calcium Channel Currents in Type I and Type II Hair Cells Isolated From the Rat Crista

2003 ◽  
Vol 90 (1) ◽  
pp. 155-164 ◽  
Author(s):  
Hong Bao ◽  
Weng Hoe Wong ◽  
Jay M. Goldberg ◽  
Ruth Anne Eatock
Keyword(s):  
Hair Cells ◽  
Type I ◽  
Type Ii Cells ◽  
Type Ii ◽  
Α Subunit ◽  
Voltage Gated ◽  
Type I Cells ◽  
Channel Currents ◽  
I Cells

When studied in vitro, type I hair cells in amniote vestibular organs have a large, negatively activating K+ conductance. In type II hair cells, as in nonvestibular hair cells, outwardly rectifying K+ conductances are smaller and more positively activating. As a result, type I cells have more negative resting potentials and smaller input resistances than do type II cells; large inward currents fail to depolarize type I cells above –60 mV. In nonvestibular hair cells, afferent transmission is mediated by voltage-gated Ca2+ channels that activate positive to –60 mV. We investigated whether Ca2+ channels in type I cells activate more negatively so that quantal transmission can occur near the reported resting potentials. We used the perforated patch method to record Ca2+ channel currents from type I and type II hair cells isolated from the rat anterior crista (postnatal days 4–20). The activation range of the Ca2+ currents of type I hair cells differed only slightly from that of type II cells or nonvestibular hair cells. In 5 mM external Ca2+, currents in type I and type II cells were half-maximal at –41.1 ± 0.5 (SE) mV ( n = 10) and –37.2 ± 0.2 mV ( n = 10), respectively. In physiological external Ca2+ (1.3 mM), currents in type I cells were half-maximal at –46 ± 1 mV ( n = 8) and just 1% of maximal at –72 mV. These results lend credence to suggestions that type I cells have more positive resting potentials in vivo, possibly through K+ accumulation in the synaptic cleft or inhibition of the large K+ conductance. Ca2+ channel kinetics were also unremarkable; in both type I and type II cells, the currents activated and deactivated rapidly and inactivated only slowly and modestly even at large depolarizations. The Ca2+ current included an L-type component with relatively low sensitivity to dihydropyridine antagonists, consistent with the α subunit being CaV1.3 (α1D). Rat vestibular epithelia and ganglia were probed for L-type α-subunit expression with the reverse transcription-polymerase chain reaction. The epithelia expressed CaV1.3 and the ganglia expressed CaV1.2 (α1C).

Potassium currents in mammalian and avian isolated type I semicircular canal hair cells

1994 ◽  
Vol 71 (1) ◽  
pp. 317-329 ◽  
Author(s):  
K. J. Rennie ◽  
M. J. Correia
Keyword(s):  
Membrane Potential ◽  
Hair Cells ◽  
Potassium Current ◽  
Columba Livia ◽  
Membrane Properties ◽  
Delayed Rectifier ◽  
Type I ◽  
Type Ii ◽  
Current Clamp ◽  
Whole Cell

1. Type I vestibular hair cells were isolated from the cristae ampullares of the semicircular canals of the Mongolian gerbil (Meriones unguiculatus) and the white king pigeon (Columba livia). Dissociated type I cells were distinguished from type II hair cells by their neck to plate ratio (NPR) and their characteristic amphora shape. 2. The membrane properties of gerbil and pigeon type I hair cells were studied in whole-cell voltage- and current-clamp using the perforated patch technique with amphotericin B as the perforating agent. 3. In whole-cell current-clamp, the average zero-current potential, Vz, measured for pigeon type I hair cells, was -70 +/- 7 (SD) mV (n = 18) and -71 +/- 11 mV (n = 83) for gerbil type I hair cells. 4. At Vz, for both gerbil and pigeon type I hair cells, a potassium current (IKI) was > or = 50% activated. This current deactivated rapidly when the membrane potential was hyperpolarized below -90 mV. 5. IKI was blocked by externally applied 4-aminopyridine (4-AP) (5 mM) and by internally applied 20 mM tetraethylammonium (TEA). It was also reduced when 4 mM barium was present in the external solution. The degree of block by barium increased as the membrane potential became more positive. External cesium (5 mM) blocked the inward component of IKI. When IKI was pharmacologically blocked, Vz depolarized by approximately 40 mV. Therefore IKI appears to be a delayed rectifier and to set the more negative Vz noted for isolated type I hair cells when compared to isolated type II hair cells, which do not have IKI. 6. A second, smaller potassium current was present at membrane potential depolarizations above -40 mV. This current was blocked by 30-50 mM, externally applied TEA, 100 microM quinidine, 100 nM apamin, but not 100 nM charybdotoxin, indicating that this is a calcium-activated potassium current, IK(Ca), different from the maxi-K calcium-activated potassium current found in most other hair cells.

scholarly journals ULTRASTRUCTURE OF THE CAROTID BODY

1966 ◽  
Vol 30 (3) ◽  
pp. 563-578 ◽  
Author(s):  
T. J. Biscoe ◽  
W. E. Stehbens
Keyword(s):  
Blood Vessels ◽  
Schwann Cells ◽  
Carotid Body ◽  
Nerve Fibers ◽  
Nerve Endings ◽  
Type I ◽  
Type Ii Cells ◽  
Type Ii ◽  
Type I Cells ◽  
I Cells

An electron microscope investigation was made of the carotid body in the cat and the rabbit. In thin-walled blood vessels the endothelium was fenestrated. Larger vessels were surrounded by a layer of smooth muscle fibers. Among the numerous blood vessels lay groups of cells of two types covered by basement membranes. Aggregates of Type I cells were invested by Type II cells, though occasionally cytoplasmic extensions were covered by basement membrane only. Type I cells contained many electron-opaque cored vesicles (350 to 1900 A in diameter) resembling those in endocrine secretory cells. Type II cells covered nerve endings terminating on Type I cells and enclosed nerve fibers in much the same manner as Schwann cells. The nerve endings contained numerous microvesicles (∼500 A in diameter), mitochondria, glycogen granules, and a few electron-opaque cored vesicles. Junctions between nerve endings and Type I cells were associated with regions of increased density in both intercellular spaces and the adjoining cytoplasm. Cilia of the 9 + 0 fibril pattern were observed in Type I and Type II cells and pericytes. Nonmyelinated nerve fibers, often containing microvesicles, mitochondria, and a few electron-opaque cored vesicles (650 to 1000 A in diameter) were present in Schwann cells, many of which were situated close to blood vessels Ganglion cells near the periphery of the gland, fibrocytes, and segments of unidentified cells were also seen. It was concluded that, according to present concepts of the structure of nerve endings, those endings related to Type I cells could be efferent or afferent.

Effects of oligohydramnios on lung growth and maturation in the fetal rat

2002 ◽  
Vol 282 (3) ◽  
pp. L431-L439 ◽  
Author(s):  
Joseph A. Kitterman ◽  
Cheryl J. Chapin ◽  
Jeff N. Vanderbilt ◽  
Nicolas F. M. Porta ◽  
Louis M. Scavo ◽  
...  
Keyword(s):  
Fetal Lung ◽  
Alveolar Type ◽  
Type I ◽  
Type Ii Cells ◽  
Type Ii ◽  
Lung Growth ◽  
Type I Cells ◽  
Fetal Lung Development ◽  
Fetal Rat ◽  
I Cells

Oligohydramnios (OH) retards fetal lung growth by producing less lung distension than normal. To examine effects of decreased distension on fetal lung development, we produced OH in rats by puncture of uterus and fetal membranes at 16 days of gestation; fetuses were delivered at 21 or 22 days of gestation. Controls were position-matched littermates in the opposite uterine horn. OH lungs had lower weights and less DNA, protein, and water, but no differences in saturated phosphatidylcholine, surfactant proteins (SP)-A and -B, and mRNA for SP-A, -B, -C, and -D. To evaluate effects on epithelial differentiation, we used RTI40 and RTII70, proteins specific in lung to luminal surfaces of alveolar type I and II cells, respectively. At 22 days of gestation, OH lungs had less RTI40 mRNA ( P < 0.05) and protein ( P < 0.001), but RTII70 did not differ from controls. With OH, type I cells (in proportion to type II cells) covered less distal air space perimeter ( P < 0.01). We conclude that OH, which retards lung growth, has little effect on surfactant and impedes formation of type I cells relative to type II cells.

Freeze-substitution and Postembedding Immunocytochemistry on Rat Taste Buds: G-Proteins, Calcitonin Gene-related Peptide, and Choline Acetyl Transferase

1997 ◽  
Vol 3 (1) ◽  
pp. 53-69 ◽  
Author(s):  
Bert Ph.M. Menco ◽  
Maya P. Yankova ◽  
Sidney A. Simon
Keyword(s):  
Freeze Substitution ◽  
Taste Buds ◽  
Taste Bud ◽  
Type I ◽  
Type Ii ◽  
Choline Acetyl Transferase ◽  
Type I Cells ◽  
Dense Core Granules ◽  
Electron Dense Core ◽  
I Cells

Abstract: We have explored freeze-substitution combined with low-temperature embedding in rat taste buds for postembedding immunocytochemistry. A major difference in taste bud cells that were rapidly frozen without prior chemical fixation and those that were fixed and cryoprotected before freezing was that electron-dense core granules were virtually absent. The antibodies used in these initial studies were directed against calcitonin gene-related peptide (CGRP), a peptide commonly found in nociceptive neurons; the α-subunits of two G-proteins involved in bitter and sweet taste transduction; and choline acetyl transferase (ChAT), an enzyme involved in the synthesis of acetylcholine. Anti-CGRP immunolabeled a subpopulation of unmyelinated perigemmal neurons; anti-Gqα labeled a larger subpopulation of these neurons and the microvilli of cells that were most likely from Type II vallate taste buds. α-Gustducin was found in cytoplasm of Type II and/or III cells and probably in microvilli of Type I cells of vallate taste buds. The best labeling results were obtained with anti-ChAT, which stained microvilli and lateral membranes of some Type II vallate taste bud cells, and the cytoplasm of some other Type II and/or III vallate cells. In addition, anti-ChAT labeled electron-opaque materials inside taste bud pores of vallate papillae, but, under the same conditions, not granules of Type I cells or most of the vesicles in von Ebner's glands. These data suggest that we can not assume a priori that the contents of the electron-dense core granules of Type I cells, or even of those of von Ebner's glands, contain the precursors of the taste bud pore–dense substances.

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