Hematopoietic stem cells prevent hair cell death after transient cochlear ischemia through paracrine effects.

Transplantation of hematopoietic stem cells (HSCs) is regarded to be a potential approach for promoting repair of damaged organs. Here, we investigated the influence of hematopoietic stem cells on progressive hair cell degeneration after transient cochlear ischemia in gerbils. Transient cochlear ischemia was produced by extracranial occlusion of the bilateral vertebral arteries just before their entry into the transverse foramen of the cervical vertebra. Intrascalar injection of HSCs prevented ischemia-induced hair cell degeneration and ameliorated hearing impairment. We also showed that the protein level of glial cell line-derived neurotrophic factor (GDNF) in the organ of Corti was upregulated after cochlear ischemia and that treatment with HSCs augmented this ischemia-induced upregulation of GDNF. A tracking study revealed that HSCs injected into the cochlea were retained in the perilymphatic space of the cochlea, although they neither transdifferentiated into cochlear cell types nor fused with the injured hair cells after ischemia, suggesting that HSCs had therapeutic potential possibly through paracrine effects. Thus, we propose HSCs as a potential new therapeutic strategy for hearing loss.

Distance dependence of electron transfer across peptides with different secondary structures: the role of Peptide energetics and electronic coupling.

The charge-transfer transition energies and the electronic-coupling matrix element, |H(DA)|, for electron transfer from aminopyridine (ap) to the 4-carbonyl-2,2'-bipyridine (cbpy) in cbpy-(gly)(n)-ap (gly = glycine, n = 0-6) molecules were calculated using the Zerner's INDO/S, together with the Cave and Newton methods. The oligopeptide linkages used were those of the idealized protein secondary structures, the alpha-helix, 3(10)-helix, beta-strand, and polyproline I- and II-helices. The charge-transfer transition energies are influenced by the magnitude and direction of the dipole generated by the peptide secondary structure. The electronic coupling |H(DA)| between (cbpy) and (ap) is also dependent on the nature of the secondary structure of the peptide. A plot of 2.ln|H(DA)| versus the charge-transfer distance (assumed to be the dipole moment change between the ground state and the charge-transfer states) showed that the polyproline II structure is a more efficient bridge for long-distance electron-transfer reactions (beta = 0.7 A(-1)) than the other secondary structures (beta approximately 1.3 A(-1)). Similar calculations on charged dipeptide derivatives, [CH(3)CONHCH(2)CONHCH(3)](+/)(-), showed that peptide-peptide interaction is more dependent on conformation in the cationic than in the anionic dipeptides. The alpha-helix and polyproline II-helix both have large peptide-peptide interactions (|H(DA)| > 800 cm(-1)) which arise from the angular dependence of their pi-orbitals. Such an interaction is much weaker than in the beta-strand peptides. These combined results were found to be consistent with electron-transfer rates experimentally observed across short peptide bridges in polyproline II (n = 1-3). These results can also account for directional electron transfer observed in an alpha-helical structure (different ET rates versus the direction of the molecular dipole).

Adenovirus-mediated overexpression of a gene prevents hearing loss and progressive inner hair cell loss after transient cochlear ischemia in gerbils.

The use of adenoviral vectors has recently provided a novel strategy for direct gene transfer into the cochlea. In this study, we assessed the utility of an adenoviral vector expressing glial-cell-derived neurotrophic factor (GDNF) in ischemia-reperfusion injury of the gerbil cochlea. The vector was injected through the round window 4 days before ischemic insult. The distribution of a reporter transgene was confirmed throughout the cochlea from the basal to the apical turn and Western blot analysis indicated significant upregulation of GDNF protein 11 days following virus inoculation. Hearing ability was assessed by sequentially recording compound action potentials (CAP), and the degree of hair cell loss in the organ of Corti was evaluated in specimens stained with rhodamine-phalloidin and Hoechst 33342. On the seventh day of ischemia, the CAP threshold shift and inner hair cell loss were remarkably suppressed in the Ad-GDNF group compared with the control group. These results suggest that adenovirus-mediated overexpression of GDNF is useful for protection against hair cell damage, which otherwise eventually occurs after transient ischemia of the cochlea.

Effects of lidocaine on basilar membrane vibration in the guinea pig.

The effects of lidocaine on basilar membrane (BM) vibration and compound action potential (CAP) were studied in guinea pigs in order to elucidate the site of lidocaine action in the cochlea. BM vibration was measured with a laser Doppler vibrometer through an opening made in the lateral bony wall of the scala tympani at the basal turn. Ten min after local administration of lidocaine (250 microg) into the scala tympani, the velocity of BM vibration and the CAP amplitude decreased significantly at around the characteristic frequency of the stimulus sound (p < 0.05). The maximum decreases were 4 dB in the velocity of the BM vibration and 40 dB in the CAP amplitude. In contrast, such changes were not observed after i.v. injection of lidocaine (1.5 mg/kg). These results suggest that when lidocaine is administered locally in the cochlea it acts not only on the cochlear nerve but also on the outer hair cells.

Hypothermia reduces glutamate efflux in perilymph following transient cochlear ischemia.

The effect of hypothermia on ischemic injury of the cochlea in gerbils was studied with particular regard to glutamate efflux in the perilymph. Under normothermic conditions interruption of the blood supply to the cochlea for 15 min caused a remarkable elevation of the compound action potential (CAP) threshold, and an increase in perilymphatic glutamate. The CAP threshold recovered to some extent with reperfusion, but not to preischemic levels. CAP thresholds, under hypothermic conditions and with reperfusion, recovered promptly to near pre-ischemic levels, while glutamate concentration did not change. These results, together with electron microscopy studies, suggest that hypothermia prevents hearing loss primarily through reduction of glutamate efflux at the synopses between inner hair cells and primary afferent auditory neurons.

Mouse model of Bell's palsy induced by reactivation of herpes simplex virus type 1.

In order to investigate the mechanism of Bell's palsy, we developed an animal model of facial nerve paralysis induced by the reactivation of herpes simplex virus type 1 (HSV-1). Eight weeks after recovery from facial nerve paralysis caused by inoculation with HSV-1, the mice were treated with auricular skin scratch at the site of the previous inoculation, or with intraperitoneal injection of anti-CD3 monoclonal antibody (mAb), or combination of both procedures. No mice developed facial nerve paralysis when they were treated with either auricular scratch or mAb injection alone. In contrast, 20% of mice developed facial nerve paralysis with the combined treatment. With one exception, no mouse treated with either auricular scratch or mAb injection showed HSV-I DNA in their facial nerve tissue, whereas 4 out of 6 mice receiving both treatments showed HSV-1 DNA on day 10 after treatment. Histopathological findings showed neuronal degeneration in the geniculate ganglion and demyelination of the facial motor nerve in paralyzed mice. These findings suggest that a combination of stimuli, local skin irritation, and general immunosuppression is essential for successfully inducing facial nerve paralysis in mice with latent HSV-1 infection.

Long-term results using a piezoelectric semi-implantable middle ear hearing device: the Rion Device E-type.

The Rion Device E-type (RDE) has been applied to 39 patients with severe mixed deafness that could not be rehabilitated by surgical means or the conventional hearing aid. Careful follow-up studies have been conducted on all of them to assess clinical and audiologic results. The device could function more than 10 years, affording natural quality of hearing without howling and wearing discomforts. Functional principles of the device, indications, and surgical methods of implantation are described. The failures and delayed problems were also presented together with the preventive measures.

Hypothermia prevents hearing loss and progressive hair cell loss after transient cochlear ischemia in gerbils.

The effects of hypothermia on ischemia-reperfusion injury of the cochlea were studied in gerbils. Hearing was assessed by sequentially recording compound action potentials before, during and after the ischemia. The degree of hair cell loss in the organ of Corti was evaluated in specimens stained with rhodamine-phalloidin and the dye Hoechst 33342. Ischemic insult was applied to the animals by occluding the bilateral vertebral arteries for 15 min under normothermic or hypothermic (rectal temperature 32 degrees C) conditions. Interruption of the blood supply to the cochlea caused a tremendous increase in the compound action potential threshold, which usually recovered to some extent with reperfusion. In the ischemia/normothermic group, the threshold did not return to the pre-ischemic level. The average increase in the threshold seven days after ischemia was 20.0 dB. Histologically, the hair cell loss increased gradually until four days after the ischemic insult. On the seventh day, the mean loss of inner and outer hair cells at the basal turn was 31.1 % and 2.4 %, respectively. In the ischemia/hypothermic group, the threshold returned to the pre-ischemic level within 30 min after reperfusion and remained stable thereafter. The mean loss of inner and outer hair cells on the seventh day was 0.1 % and 0.2 %, respectively. These results indicate that hypothermia can prevent inner ear damage, which otherwise occurs after transient ischemia of the cochlea.

Herpes simplex virus in the vestibular ganglion and the geniculate ganglion-role of loose myelin.

This study presents the first direct evidence for herpes simplex virus type 1 (HSV-1) infection in the neurons of the vestibular ganglion. Although many investigators have reported electron microscopic evidence of HSV-1 infection in sensory ganglia, HSV-1 infection in the vestibular ganglion has not been described. Vestibular ganglion neurons have a unique structure, with a loose myelin sheath instead of the satellite cell sheath that is seen in other ganglia. This loose myelin is slightly different from compact myelin which is known as too tight for HSV-1 to penetrate. The role of loose myelin in terms of HSV-1 infection is completely unknown. Therefore, in an attempt to evaluate the role of loose myelin in HSV-1 infection, we looked for HSV-1 particles, or any effects mediated by HSV-1, in the vestibular ganglion as compared with the geniculate ganglion. At the light microscopic level, some neurons with vacuolar changes were observed, mainly in the distal portion of the vestibular ganglion where the communicating branch from the geniculate ganglion enters. At the electron microscopic level, vacuoles, dilated rough endoplasmic reticulum and Golgi vesicles occupied by virus were observed in both ganglia neurons. In contrast, viral infections in Schwann and satellite cells were observed only in the geniculate ganglion, but not in the vestibular ganglion. These results suggest that loose myelin is an important barrier to HSV-1 infection, and it must play an important role in the prevention of viral spread from infected neurons to other cells.

Ossiculoplasty using hydroxyapatite prostheses: long-term results.

The surgical results of ossicular chain reconstruction using a hydroxyapatite prosthesis were evaluated in 106 ears of 101 patients who were followed up for > 5 years. Successful reconstruction was defined as: (1) postoperative air-bone gap of

Ramsay Hunt syndrome in children.

In a retrospective study, 52 children were diagnosed with Ramsay Hunt syndrome. The facial palsy was milder and complete recovery of the function was achieved in 78.6% of patients. Associated cranial neuropathies were less common in children than in adults. The timing of vesicle appearance tended to be delayed in children. In preschool children, Ramsay Hunt syndrome was rare, although the frequency has recently increased. The syndrome is relatively common in older children. This study suggested that vaccination can prevent or reduce the occurrence of Ramsay Hunt syndrome.

Assessment of stapes mobility by use of a newly developed piezoelectric ceramic device. A preliminary experiment in dogs.

A piezoelectric device was developed for assessment of stapes mobility during middle ear surgery. The device comprises a pair of ceramic bimorph elements: one for activation of the stapes and the other to pick up the vibration as an electric output, which varies in accordance with the stapes mobility, ie, the inverse of the cochlear input impedance (Zsc). The device is compact and easily manipulated even in the narrow surgical field of the ear. However, the measuring range is restricted to between 1 and 10 kHz. Measurement of Zsc was conducted with this device in 5 ears of 5 dogs. The mean magnitude of Zsc increased with frequency in the range from 1 to 10 kHz: 0.95 megohm at 1 kHz and 8.8 megohms at 10 kHz. After fixation of the stapes with dental cement, the magnitude increased to more than 10 megohms, except at 1 kHz. The results suggest that the device is useful in detecting decreases in stapes mobility in patients with chronic otitis media.

[Treatment of Bell's palsy with acyclovir and prednisolone].

Many current studies have suggested that herpes simplex virus is a probable cause of Bell's palsy, and that treatment with antiviral agents such as acyclovir might benefit the patients. In the present study, 69 patients with Bell's palsy were treated with oral administration of acyclovir (2000 mg/day) and prednisolone (60-40 mg/day) at Ehime University Hospital between Oct. 1995 and Dec. 1998. Patients enrolled in this study met the following criteria: 1) severe or complete paralysis with a score lower than 20 by the 40-point Japanese grading system, and 2) treatment started within 7 days of onset. The overall recovery rate was 95.7% (66/69). The rate in patients who started this treatment within 3 days after disease onset was 100%, and this early treatment was highly efficacious in the prevention of nerve degeneration and resulted in a significantly better recovery. By comparison, the recovery rate in patients whose treatment was started 4 days or more after onset was only 84.2%. All patients who were given a diagnosis of zoster sine herpete and treated with acyclovir-prednisolone had a good outcome. These results suggest that early treatment, within 3 days after palsy onset, is necessary for effective acyclovir-prednisolone therapy of Bell's palsy.

Hearing loss and glutamate efflux in the perilymph following transient hindbrain ischemia in gerbils.

The mechanism underlying ischemia-induced hearing loss was studied in gerbils with transient hindbrain ischemia. Occlusion of the vertebral arteries caused an increase in the concentration of glutamate in the perilymph and elevated the compound action potential (CAP) threshold to 24.6 dB at 5 minutes. the CAP threshold subsequently recovered on reperfusion, gradually reaching 8.3 dB 120 minutes after reperfusion. Under electron microscopy, afferent dendrites of the cochlear nerve in contact with inner hair cells exhibited abnormal swelling 5 minutes after ischemia/reperfusion. These morphological changes were not observed in cochleas treated with an alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)/kainate-type glutamate receptor antagonist, 6-7-dinitroquinoxaline-2,3-dione (DNQX), before hindbrain ischemia; an N-methyl-D-aspartate (NMDA)-type receptor antagonist, D-2-amino-5-phosphonopentanoate (D-AP5), was ineffective. Moreover, the histopathological alterations noted 5 minutes after reperfusion were spontaneously ameliorated 120 minutes after ischemia/reperfusion. These findings suggest that the ischemia-induced increase in extracellular glutamate concentration with subsequent activation of AMPA/kainate receptors is responsible for neurite degeneration and hearing loss in the early stages following transient hindbrain ischemia.

Two-dimensional analysis of vocal fold vibration in unilaterally atrophied larynges.

OBJECTIVE: Considerable inconsistencies regarding the vibratory pattern of the vocal fold among patients with unilateral vocal fold paralysis (UVFP) have been reported. These differences are derived from differences in the position, stiffness, and atrophy of the paralyzed vocal fold and other factors among patients. The purpose of this study was to assess the effects of unilateral atrophy of the vocal fold on vocal fold vibration. METHODS: Seven excised canine larynges were studied. The unilateral recurrent laryngeal nerve was severed to cause vocal fold atrophy in four of the seven. The lateral and vertical displacements were monitored simultaneously with photoglottography and a laser Doppler vibrometer, respectively. Videostroboscopy of each larynx was also performed before and after the experiment to translate photoglottographic output into absolute lengths. Atrophy of the unilateral vocal fold was confirmed histologically. RESULTS: The lateral amplitude was significantly greater than the vertical amplitude in all larynges. The Lissajous trajectories in the normal larynges were shaped like a reverse crescent. Vibration in the unilaterally atrophied larynges was periodical and symmetrical in phase when the thyroid ala on the atrophied side was pressed medially. The lateral and vertical amplitudes on the atrophied side were significantly greater than those on the normal side. The Lissajous trajectories differed from those of the normal larynges. CONCLUSIONS: In the absence of a prephonatory glottal gap, periodical vibration occurs in unilaterally atrophied larynges and the amplitude of vibrations of the atrophied vocal fold is greater in the lateral and vertical directions than that of the normal fold. This implies that phonosurgical procedures aiming at closure of the prephonatory glottal gap may have a beneficial effect on hoarseness in UVFP patients, although displacements of the vocal folds during vibration are not symmetrical.

Exacerbation of noise-induced hearing loss in mice lacking the glutamate transporter GLAST.

Acoustic overstimulation is one of the major causes of hearing loss. Glutamate is the most likely candidate neurotransmitter for afferent synapses in the peripheral auditory system, so it was proposed that glutamate excitotoxicity may be involved in noise trauma. However, there has been no direct evidence that noise trauma is caused by excessive release of glutamate from the inner hair cells (IHCs) during sound exposure because studies have been hampered by powerful glutamate uptake systems in the cochlea. GLAST is a glutamate transporter highly expressed in the cochlea. Here we show that after acoustic overstimulation, GLAST-deficient mice show increased accumulation of glutamate in perilymphs, resulting in exacerbation of hearing loss. These results suggest that GLAST plays an important role in keeping the concentration of glutamate in the perilymph at a nontoxic level during acoustic overstimulation. These findings also provide further support for the hypothesis that IHCs use glutamate as a neurotransmitter.

Combined rupture of Reissner's membrane and round window: an experimental study in guinea pigs: experimental double-membrane rupture.

OBJECTIVE: Hearing loss caused by combined rupture of Reissner's membrane and the round window (RW) membrane (the double-membrane rupture) may differ depending on the site of the lesion on Reissner's membrane. The purpose of this experimental study was to reveal the relationship between the hearing impairment and the site of the lesion on Reissner's membrane. BACKGROUND: According to experimental studies on perilymphatic fistula (PLF), profound hearing loss is not induced by rupture of RW alone, but by the double-membrane rupture. However, the mechanism responsible for hearing loss in the double-membrane rupture remains unclear. METHODS: Compound action potentials (CAPs) of the cochlear nerve in response to tone pip stimuli (1, 2, 4, and 8 kHz) were recorded before the lesion, 90 minutes after the Reissner's membrane rupture, and 90 minutes after subsequent laceration of the RW. Reissner's membrane was ruptured at one of the four turns for comparison. RESULTS: The double-membrane rupture caused a more severe increase in CAP thresholds than seen with separate ruptures, when the Reissner's membrane was ruptured at the second turn. Such pronounced increase in threshold was not seen in ears with the rupture at other turns. CONCLUSIONS: The double-membrane rupture causes varying degrees of hearing loss depending on the site of the lesion of Reissner's membrane. When the Reissner's membrane was ruptured at the second turn, the most severe hearing loss was detected.