Biomedical subjects

S Komune

Publications and source records attributed to S Komune.

79 records · Page 5Linked to original sources

PubMedDate not supplied

Different clinical characteristics of aminoglycoside-induced profound deafness with and without the 1555 A-->G mitochondrial mutation.

Recent genetic studies have shown that hereditary susceptibility to aminoglycoside antibiotics is caused by the 1555 A-->G mitochondrial mutation. We found the 1555 mutation in 4 out of 68 postlingual deaf patients who were candidates for cochlear implantation. All 4 patients developed bilateral profound hearing loss following administration of aminoglycosides. The pedigree of the family shows exclusively maternal transmission of hearing impairment in each case. On comparison with neuro-otological findings from aminoglycoside-induced deaf patients without the 1555 mutation, four distinct characteristics were noted: (1) a progressive nature of hearing loss; (2) better residual pure-tone thresholds; (3) lower thresholds for electrical promontory stimulation, and (4) well-preserved vestibular function. Although other factors such as differing dosages and/or administration routes may also be involved, profound hearing loss associated with the 1555 mutation may be due to a different pathogenic mechanism, i.e., strial dysfunction rather than a direct insult to the hair cells.

Aged↗

PubMedDate not supplied

Correlation between MRI findings and second-Look operation in cholesteatoma surgery.

Two-staged intact canal wall tympanoplasty is a common operation for treatment of middle ear cholesteatoma. MRI provides better tissue differentiation of the middle ear and/or mastoid, which often become occupied with soft density tissue after the first operation. If MRI was able to detect the presence of a recurrent or residual cholesteatoma with sufficient sensitivity and specificity, this may facilitate a decrease in the number of second-look procedures. This study compared MRI findings to surgical findings at second-look surgery and calculated the correlation rates between the two sets of findings. Thirty ears having undergone intact canal wall tympanoplasty for cholesteatoma at the initial operation were examined by MRI prior to the second look. Otoscopic findings of the tympanic membrane were nonsuspect in all cases. The true positive rate was 11/30 (37%) and the true negative rate was 10/30 (33%), leading to a radiosurgical correlation of 70%, whereas the false positive rate was 6/30 (20%) and the false negative rate was 3/30 (10%). This indicates that 30% of the MRI findings were incorrect. Therefore, at the present time, MRI does not appear as a likely replacement for second-look surgery in cases of intact canal wall tympanoplasty.

Adolescent↗

PubMedDate not supplied

Movement of monovalent ions across the membranes of marginal cells of the stria vascularis in the guinea pig cochlea.

The resting potential and monovalent ions in the marginal cells and scala media were measured before and 20 min after the onset of anoxia using ion-sensitive microelectrodes. The resting potential of the marginal cells decreased from 62.7 to -2.4 mV. The K+ activity decreased from 77.7 to 53.2 mEq/l, while the Na+ activity increased from 2.6 to 24.7 mEq/l. The Cl- activity did not change significantly. In the scala media, the endocochlear potential decreased rapidly from 80.9 to -28.0 mV after the onset of anoxia. The K+ activity decreased from 119.0 to 96.5 mEq/l, the Na+ activity increased from 1.3 to 9.5 mEq/l and that of Cl- decreased from 127.0 to 115.1 mEq/l. The electrochemical gradients determined for each ion based on the ionic changes in the scala media and marginal cells, suggested the existence of an Na/K pump and Na-K-2Cl cotransport at the basolateral membrane of the marginal cells, and a rheogenic K pump and Na-K-2Cl transport at the luminal membrane of the marginal cells. The Na+ and K+ must be recycled at the basolateral membrane and luminal membrane of marginal cells, respectively.

Animals↗

PubMedDate not supplied

Bilateral Mondini dysplasia with normal hearing.

A 37-year-old man with both Mondini dysplasia and normal hearing is reported. The patient visited our clinic with a complaint of unsteadiness. Pure-tone audiometry showed a normal hearing level in both ears. Polytomography and computed tomography (CT) revealed enlargement of the vestibules and lateral semicircular canals in both ears but a normal shape of the cochlea and other semicircular canals. The caloric test indicated severe canal paresis (CP) in the left ear and moderate CP in the right ear, whereas the active head rotation test demonstrated that head-eye coordination was preserved at frequencies of 0.33 and 0.67 Hz but slightly deteriorated at 1.0 Hz. The patient's unsteadiness seemed to be attributable to a hypofunction of the bilateral semicircular canals, which may be due to insidious, repeated cerebrospinal fluid otorrhea caused by judo wrestling. Although Mondini dysplasia with normal hearing has been believed to be rare, phylogenetic consideration suggests that more such patients exist than has been assumed.

Adult↗

PubMedDate not supplied

Validity of the two-component theory in the production of endocochlear potential.

To evaluate the mechanism of endocochlear potential (EP) and the validity of the two-component theory in its production, we perfused the endolymphatic space of normal and kanamycin-deafened guinea pigs with artificial endolymph containing 50 mM K+. The K+ activities and EP were simultaneously measured with a double-barreled K+ electrode during and after perfusion. The relationship between the magnitude of the electrogenic potential and K+ active transport was calculated and compared between the two groups of animals. The results showed that the positive component of the EP (positive EP) was mainly dependent on K+ active transport in the stria vascularis but included other electrogenic components not dependent on K+ active transport. The K+ and Na+ conductances (Gk and Gna) between the endolymph and perilymph were also calculated in the normal and kanamycin-deafened guinea pigs. The Gk was much lower in kanamycin-deafened guinea pigs but the Gna did not differ between the two groups of animals. The theoretical EP value during anoxia (negative EP) was consistent with that observed in each group. The difference in the negative EP was approximately 30 mV, but the steady-state EP did not differ between groups. It is concluded that EP is probably not the simple mathematical sum of the positive and negative potentials but involves more complex mechanisms.

Animals↗

PubMedDate not supplied

Pathophysiology of the ototoxicity of cis-diamminedichloroplatinum.

The electrophysiologic and histopathologic changes in the inner ear caused by the administration of cis-diamminedichloroplatinum (CP) were studied in guinea pigs. The endocochlear dc potential (EP) gradually decreased after the intravenous injection of CP and reached approximately 0 mV on the fourth day, but the EP did not become negative. The cochlear microphonics also diminished and could not be recorded on the fourth day. The negative potential of the organ of Corti remained in the normal range during the experiment. A large negative summating potential (SP) was observed one day after injection, but the amplitude of the negative SP became small on the second day. Light microscopic examination demonstrated that the outer hair cells are destroyed in the basal turn of the cochlea and are preserved in the upper turns, while the inner hair cells are almost completely preserved in all turns. The stria vascularis was found to be slightly atrophic. Severe collapse of Reissner's membrane was observed in the basal turn.

Animals↗

PubMedDate not supplied

Ototoxicity of kanamycin sulfate and the barriers in the inner ear.

The effect of kanamycin sulfate administered by three routes on the function of the stria vascularis was monitored electrophysiologically in guinea pigs. The three routes were intramuscular injection, perilymphatic perfusion, or endolymphatic perfusion. Neither systemic administration of 500 mg/kg of body weight per day for 7 to 12 days nor perilymphatic perfusion of 10(-3) M kanamycin affected the endocochlear dc potential (EP). However, with perfusion of kanamycin 10(-3) M in the endolymphatic space, the EP declined severely. Moreover, the decline in the EP was greater with higher concentrations of kanamycin in the endolymphatic perfusate. Furosemide given by each of the three routes produced an approximately equal decrease in the EP. The effects of kanamycin on the cells of the stria vascularis and the evidence for the perilymphatic-endolymphatic and blood-cochlear barriers are discussed.

Animals↗