Biomedical subjects

S Komune

Publications and source records attributed to S Komune.

At least 55 records · Page 3Linked to original sources

PubMed1994

Profiles of resting potentials across the stria vascularis in kanamycin-deafened guinea pigs.

The resting potentials of the marginal cells in the stria vascularis of the guinea pig were determined from changes in the combined electrode-tissue resistance of the electrode. The resistance of the electrode was 45.5 +/- 16.0 M omega (n = 20) before penetration of the stria vascularis and 46.7 +/- 17.3 M omega (n = 20) after penetration. The resistance drops across the luminal membrane of the marginal cells were 46.0 +/- 22.6 M omega (n = 12) in kanamycin-deafened guinea pigs and 54.5 +/- 33.1 M omega (n = 9) in normal guinea pigs. The endocochlear potential (EP) and resting potentials in the marginal cells were 90.1 +/- 6.0 mV (n = 14) and 70.4 +/- 11.3 mV (n = 14) in kanamycin-deafened guinea pigs and 84.8 + 5.1 mV (n = 29) and 74.7 +/- 11.7 mV (n = 29) in normal guinea pigs. The resting potentials in the marginal cells decreased gradually and were approximately 0 mV around 20 min after anoxia in both kanamycin-deafened and normal guinea pigs. These changes were comparable to those of EP in kanamycin-deafened guinea pigs during anoxia. The mechanism of the EP in kanamycin-deafened guinea pigs is discussed.

Animals↗

PubMed1994

Potassium circulation in the perilymph of guinea pig cochlea.

To determine whether any differences exist in potassium circulation between the scala vestibuli and scala tympani, we recorded the change in K+ activity in both scalae of the guinea pig cochlea at the basal and third turns, using a double-barrelled, K(+)-sensitive microelectrode after perfusion with artificial perilymph containing 20 mM KCl and 130 mM NaCl. K+ activity increased immediately after the start of perfusion and decreased after its completion. The rates of decrease of K+ activities were approximately 1.0 mEq/l per min in the scala vestibuli of the basal and third turns, also 1.0 mEq/l per min in the scala tympani of the basal turn, and approximately 0.5 mEq/l per min in the scala tympani of the third turn. The rate of decrease of K+ activity in the scala tympani was significantly slower in the third turn than in the basal turn. Blockage of the cochlear aqueduct depressed the rate of decrease of K+ activity in the scala tympani more in the basal turn than in the third turn. These results suggest that there is a difference in potassium circulation between the scala vestibuli and scala tympani, and that the cochlear aqueduct plays an important role in potassium circulation in the perilymph of the scala tympani.

Animals↗

PubMed1994

The effects of ototoxic drugs on mechano-electric transduction channels in chick cochlear hair cells.

The effects of ototoxic drugs on mechano-electrical transduction (MET) currents were investigated in dissociated cochlear hair cells of the chick, using a whole-cell patch-electrode voltage-clamp technique. Dihydrostreptomycin (DHSM) and cisplatin (cis-dichlorodiammine platinum II, CDDP) blocked the MET channel in a dose- and voltage-dependent manner. In contrast, acetyl salicylate did not suppress the MET current. At -50 mV, DHSM and CDDP blocked the MET channel with a Hill coefficient of 0.93 and 2.1, respectively. These findings suggest that a single DHSM molecule or more than one CDDP molecule binds to a single MET channel.

Animals↗

PubMed1994

Voltage-dependent channels in dissociated outer hair cells of the guinea pig.

Voltage-dependent channels in outer hair cells (OHCs) dissociated from the guinea pig cochlea were investigated by the use of a whole-cell patch-clamp technique. Two types of K+ current were recorded from OHCs. One was a slowly inactivating K+ current that was activated at a potential more positive than -30 mV. Another is a K+ current that was already activated at resting membrane potential. After suppressing both K+ currents, depolarizing voltage steps elicited a slowly inactivating inward current that was dependent on external Ca2+ and was indicative of an L-type Ca2+ channel in OHCs. Aminoglycoside antibiotics known to be ototoxic selectively inhibited the Ca2+ current.

Aminoglycosides↗

PubMed1994

Coexistence of MALT-type lymphoma and squamous cell carcinoma of the larynx.

A 66-year-old Japanese man was diagnosed as having a MALT-type lymphoma by histopathological examination. The lesion involved the vocal folds bilaterally, occupying the larynx and extending beyond it, as shown by computed tomography (CT). A course of radiation therapy with moderate doses was given. Six months later, a squamous cell carcinoma was found in the larynx and total laryngectomy was then performed. The patient remained well, without recurrence, 46 months after the operation. thus, MALT-type lymphoma may coexist with a squamous cell carcinoma of the larynx.

Aged↗

PubMed1994

Single channel recordings of calcium currents in chick cochlear hair cells.

Single Ca2+ channel currents were recorded from chick cochlear hair cells by using cell-attached patches. The elementary current was about -2 pA at 70 mV positive to the resting potential (R.P.+ 70 mV); the slope conductance over a 40 mV voltage range was 24 pS. The open time histogram was reasonably well expressed by a single exponential function, while the closed time histogram was expressed by a sum of two exponential functions. The Ca2+ channel was activated around R.P.+ 60 mV and the average ensemble current did not decay during 130 ms depolarization, suggesting that the Ca2+ channel in chick cochlear hair cells is the L-type. The Ca2+ channel has three modes of gating behaviour, expressed as current records with brief openings (mode I), no openings (mode 0), or long-lasting openings and very brief closings (mode 2).

Animals↗

PubMed1993

Cisplatin blocks mechano-electric transducer current in chick cochlear hair cells.

The effects of cisplatin (cis-dichlorodiammine platinum II, CDDP) on the mechano-electrical transduction (MET) current were investigated with a whole-cell patch-electrode voltage clamp technique in dissociated cochlear hair cells of chicks. CDDP blocked the MET channel in a dose- and voltage-dependent manner. At -50 mV, CDDP blocked the MET channel with a Hill coefficient of approximately 2 and a dissociation constant (KD) of 1.5 x 10(-3) M. The kinetics of CDDP blockade consist of a voltage-independent and a voltage-dependent component.

Animals↗

PubMed1993

Mechanism of lack of development of negative endocochlear potential in guinea pigs with hair cell loss.

The endocochlear potential (EP), and the concentration of K+, Na+ and Cl- were measured simultaneously in endolymph of guinea pigs. The EP was 85.6 +/- 0.8 mV in normal guinea pigs, 90.7 +/- 0.8 mV in the kanamycin-treated animals, and 91.6 +/- 1.2 mV in those treated with nitrogen mustard-N-oxide (NMNO). Thirty minutes after the onset of anoxia, the EP (negative EP) was -29.3 +/- 1.0 mV in the normal group, -0.2 +/- 1.0 mV in the kanamycin-treated group, and -1.9 +/- 1.3 mV in the NMNO-treated group. The permeability coefficients of K+ (Pk), Na+ (Pna) and Cl- (Pcl) across the endolymph-perilymph barrier during the period of 20-30 min after the onset of anoxia in the normal group were (341.6 +/- 38.2) x 10(-9) cm3 sec-1, (53.0 +/- 8.1) x 10(-9) cm3 sec-1 and (111.8 +/- 27.2) x 10(-9) cm3 sec-1, respectively. Pk was decreased in the kanamycin- and NMNO-treated groups. Pna did not differ between the normal and treated groups. Pcl was increased in the kanamycin- and NMNO-treated groups. The K+:Na+:Cl- permeability ratio was 1:0.16:0.32 in the normal group, 1:1.12:11.6 in the kanamycin-treated group, and 1:0.44:5.60 in the NMNO-treated group. The results indicate that the lack of development of a negative EP in the kanamycin- and NMNO-treated guinea pigs was attributable to the increased Pcl and the decreased Pk across the endolymph-perilymph barrier, probably the organ of Corti, during anoxia.

Animals↗

PubMed1992

Effects of Ca2+ antagonists and aminoglycoside antibiotics on Ca2+ current in isolated outer hair cells of guinea pig cochlea.

The effects of various Ca2+ antagonists and aminoglycoside antibiotics on the Ca2+ channel in isolated outer hair cells of the guinea pig were investigated using a whole-cell patch-clamp technique. The inhibitory action was in the order of La3+ much greater than Cd2+ much greater than Ni2+ greater than Co2+ for inorganic Ca2+ antagonists, and flunarizine = nicardipine greater than omega-conotoxin greater than methoxyverapamil = diltiazem much greater than amiloride for organic ones. Aminoglycoside antibiotics also had antagonistic effects on the Ca2+ channel.

Aminoglycosides↗

PubMed1992

Interlay method for myringoplasty.

Sixty-nine ears with perforation of the tympanic membrane were reviewed. All had undergone myringoplasty by the interlay method. The average period for complete epithelization was 16.1 days after surgery. Neither blunting of the anterior tympanomeatal angle nor lateralization of the tympanic membrane was observed. The success rate was 94.2% for the initial surgery, when "success" is defined as closure of the perforation and complete epithelization (dry ear). The surgical technique and various advantages of the interlay method of myringoplasty are described.

Adolescent↗

PubMed1992

Importance of atticotomy in chronic otitis media with fixation of ossicles.

Seventy-seven patients with chronic otitis media were reviewed. Of the 77 patients, 42 underwent tympanoplasty with a columella, and 35 underwent myringoplasty and atticotomy. Twenty-five of the latter 35 patients showed less than 10 dB of hearing improvement with a patch test before operation. The ossicular chain was not disconnected in any of the 25 patients, but the mobility was severely restricted. It was interesting that fixation of the malleus was found at surgery in 80% (20/25) of the patients, whereas the stapes was immobilized in only 16% (4/25). Myringoplasty and atticotomy instead of tympanoplasty with a columella was sufficient to achieve hearing improvement in most of such cases. However, conventional atticotomy was not able to achieve improvement in the mobility of the ossicles because the mobility is usually severely restricted at the malleus. Removal of the anterior tympanic spine is the key to recovery of the mobility of the malleus, resulting in hearing improvement. Rate of success was obtained in 24 of 25 ears (96%).

Auditory Threshold↗

PubMed1991

Calcium channel in isolated outer hair cells of guinea pig cochlea.

The physiological and pharmacological properties of the Ca2+ channel in outer hair cells (OHCs) freshly isolated from guinea pig cochlea were investigated using a whole-cell patch-clamp technique. The Ca2+ current (ICa) was activated from a membrane potential of -20 mV and reached peak value around +20 mV in external solution containing 20 mM Ca2+ at a holding potential of -70 mV. The peak amplitude of ICa increased in a hyperbolic manner with increasing extracellular Ca2+ concentration. The ion selectively was Ba2+ much greater than Ca2+ greater than or equal to Sr2+. It was concluded that the Ca2+ channel in OHCs of guinea pig is of the L-type.

Action Potentials↗

PubMed1991

Excitatory amino acid response in isolated spiral ganglion cells of guinea pig cochlea.

1. The physiological and pharmacological properties of excitatory amino acid (EAA)-induced responses were investigated in acutely isolated spiral ganglion cells of guinea pig by a conventional patch-clamp technique combined with a rapid drug application (Y-tube) method. 2. L-glutamate (Glu) and its agonists, quisqualate (QA) and kainate (KA), induced inward currents in a concentration-dependent manner at a holding potential (VH) of -70 mV. The values of half-maximal concentration (EC50) were 4.0 x 10(-4) M for Glu, 2.3 x 10(-5) M for QA, and 1.4 x 10(-4) for KA. The Hill coefficients were 0.96, 1.00, and 1.56 for Glu, QA, and KA, respectively. However, one of Glu agonists, N-methyl-D-aspartate (NMDA), and another excitatory amino acid, L-aspartate (Asp), did not induce any responses even in Mg2(+)-free external solution containing 10(-6) M glycine (Gly). 3. The current-voltage (I-V) relationships for the Glu-, QA-, and KA-induced responses were linear, and these reversal potentials were near 5 mV. 4. Kynurenic acid (Kyn), 6,7-dichloro-3-hydroxy-2-quinoxalinecarboxylic acid (diCl-HQC), and quinoxalinediones such as 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 6,7-dinitro-quinoxaline-2,3-dione (DNQX) suppressed the Glu-, QA-, and KA-induced currents in a concentration-dependent manner. The inhibitory potency was in the order of DNQX = CNQX greater than diCl-HQC greater than Kyn. 5. CNQX antagonized the Glu-, QA-, and KA-induced currents without affecting the maximum responses showing no voltage-dependency, indicating the competitive inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗

PubMed1991

Ototoxic effect of potassium canrenoate on the guinea pig cochlea.

Potassium canrenoate (PC) is a diuretic with antialdosterone action, reducing the reabsorption of sodium in the efferent renal tubules. This drug has been reported to damage only the marginal cells of the stria vascularis in the cochlea. The perilymphatic space of the guinea pig cochlea was perfused with an artificial perilymph containing 5 x 10(-3) M potassium canrenoate. Following the onset of perfusion, the endocochlear dc potential (EP) gradually declined to around 10 mV but did not become negative even when the perfusion was continued. A similar decrease in EP was observed in kanamycin-deafened guinea pigs. When the respirator was turned off and perfusion discontinued, a large negative EP appeared during 5 min of anoxia in normal guinea pigs but not in the kanamycin-deafened guinea pigs. The decreased EP recovered to preanoxic level after resumption of ventilation. The cochlear microphonics (CM) also gradually declined in parallel with the EP. The summating potential (SP) showed only a minor change. The potassium ion activity in the endolymph decreased slightly but the sodium ion activity remained unchanged during perfusion. These findings suggest that the main target of the PC is the cells of the stria vascularis.

Animals↗

PubMed1991

[Neuro-otological study of Laurence-Moon-Biedl syndrome].

Two siblings of Laurence-Moon-Biedl (L-M-B) syndrome with nystagmus and/or sensorineural hearing loss were reported. One sibling had a slight hearing impairment as well as gaze and rebound nystagmus. The auditory brainstem responses (ABR) showed increased latencies of wave V on both ears. The optokinetic nystagmus (OKN) was limited toward the both horizontal sides. Nystagmus was superimposed on the eye tracking movement. Ocular hypermetria was observed, with bilateral weakness of caloric responses and even a failure of visual fixation suppression. Another sibling had a left-beating spontaneous nystagmus. The latencies of wave V of ABR were prolonged in both ears. The leftward OKN was limited and bilateral saccadic pursuits observed on eye tracking test. These results suggest that cerebellar of brain-stem lesions may be involved in L-M-B syndrome.

Adult↗

PubMed1990

Susceptibility of the endocochlear potential to pH and osmolarity changes in the perilymph of the cochlea in the guinea pig.

The effects of artificial perilymph at various pH levels and osmolarities on the endocochlear potential (EP) were investigated in a guinea pig model. In 47 ears, the mean EP was 74.5 +/- 0.5 mV in the second turn of the cochlea before perilymphatic perfusion. The artificial perilymph with a pH ranging from 5 to 9 and tonicity less than 1.25 (osmolarity, 345 mosmol/l) did not alter the EP when testings were recorded for at least 1 h. However, after the start of a perfusion with a pH less than 4, the EP declined gradually but recovered to the pre-perfusion level rapidly when the perfusion was stopped. The artificial perilymph with a pH over 10 decreased the EP considerably but showed no recovery, even after cessation of the perfusion. Tonicity more than 1.35 (osmolarity, 372.6 mosmol/l) also decreased the EP, with this decrease paralleling further increases in the tonicity used. From these data, we have concluded that a perilymph perfusate with a pH from 5 to 9 and an osmolarity less than 350 mosmol/l can be used in animal testing without any noxious effects on the EP.

Animals↗

PubMed1990

ATP-induced current in isolated outer hair cells of guinea pig cochlea.

1. Electrical and pharmacologic properties of ATP-induced current in outer hair cells isolated from guinea pig cochlea were investigated in the whole-cell recording mode by the use of a conventional patch-clamp technique. 2. Under current-clamp conditions, rapid application of ATP depolarized the outer hair cells resulting in an increase in conductance. The ATP-induced response did not show any desensitization during a continuous application. 3. At a holding potential of -70 mV, the ATP-induced inward current increased in a sigmoidal fashion over the concentration range between 3 microM and 1 mM. The half-maximum concentration (EC50) was 12 microM and the Hill coefficient was 0.93. 4. The ATP-induced current had a reversal potential near 6 mV, which was close to the theoretical value (1 mV) calculated from the Goldman-Hodgkin-Katz equation for permeable intra- and extracellular cations. 5. In the current-voltage (I-V) relationship for the ATP response, a slight inward-going rectification was observed at more positive potentials than the reversal potential. 6. The substitution of extracellular Na+ by equimolar choline+ shifted the reversal potential of the ATP-induced current to more negative values. The substitution of Cs+ in the internal solution by N-methyl-D-glucamine+ (NMG+) shifted it in the positive direction. The reversal potential of ATP-induced current was also shifted to positive values with increasing extracellular Ca2+ concentration. A decrease of intracellular Cl- by gluconate- did not affect the reversal potential, thereby indicating that the ATP-induced current is carried through a large cation channel.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗

PubMed1990

[Effect of potassium canrenoate on the EP and Na+, K+ activities in endolymph].

The perilymphatic space was perfused with artificial perilymph containing 5 x 10(-3)M potassium canrenoate. The EP, K+ and Na+ activities in the scala media were measured with double barrelled K+ or Na+ selective microelectrode. Following the onset of the perfusion, the EP gradually declined and was stable after about 20 minutes. K+ activity also declined gradually but Na+ activity was unchanged. When the EP became stable, the artificial ventilation was stopped. The EP dropped to a large negative potential and K+ activity decreased gradually, but Na+ activity increased by degrees. The same results were observed in the untreated animals when the ventilation was stopped. There are no pathological changes both in the TEM view of the stria vascularis and in the SEM view of the hair cell. These results suggest that this drug may affect K+ conductance of the stria vascularis specifically.

Animals↗