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Kiyofumi Gyo

Publications and source records attributed to Kiyofumi Gyo.

At least 19 recordsLinked to original sources
PubMed2006

Localization of prosaposin in rat cochlea.

Prosaposin, the precursor of the sphingolipid hydrolase activator proteins called saposins A, B, C, and D, is abundant in the nervous system and muscles. Besides its role as the precursor of saposins, prosaposin is reported to function as a neurotrophic factor, initiating neural differentiation and preventing neuronal cell death in vivo and in vitro. In this study, we examined the localization and synthesis of prosaposin in the rat cochlea. Intense prosaposin immunoreactivity was observed in the organ of Corti, stria vascularis, and spiral ganglion. In an immuno-electron microscopic study, prosaposin immunoreactivity was found mainly in lysosomal granules of the cells in these regions. In the lysosome, prosaposin does not always colocalize with cathepsin D, but was localized mainly in the dark area of the lysosome. Prosaposin mRNA was observed in these same regions. Our results suggest that prosaposin plays a role in homeostasis in the peripheral auditory system.

Animals↗
PubMed2006

Storage of the incus in the mastoid bowl for use as a columella in staged tympanoplasty.

OBJECTIVE: To evaluate whether the incus of the cholesteatomatous ear preserved in the mastoid bowl during the first stage of planned two-stage tympanoplasty can tolerate long-term implantation and be used in ossicular reconstruction during the second stage. METHODS: The study group included 24 ears of 23 patients who underwent staged tympanoplasty for the treatment of middle ear cholesteatoma. At the first stage, after removing the incus to eradicate the middle ear disease, it was returned to the mastoid bowl and stored there until use at the second stage. The average interval between the two stages was 8.3 months (range 6-12 months). RESULTS: The incus was identified in all cases at the second stage: 10 incudes were found to be covered with a thin mucosa layer, 12 were buried in fibrous or granulation tissue, and 2 were joined to the surrounding bone. Residual cholesteatoma was found in six ears, either in the attic (three ears) or tympanic sinus (three ears). It never occurred in the mastoid bowl where the incus had been preserved. In 19 cases, the incus was available as a short columella for ossicular reconstruction. The remaining five cases were reconstructed using a hydroxyapatite ossicle as a long columella, since the stapes superstructure was missing at the second stage. In one case, the stored incus underwent remarkable absorption between stages. CONCLUSION: Preservation of the incus in the mastoid bowl is an effective option in planned two-stage tympanoplasty, when the incus is considered useful for ossicular reconstruction at the second stage.

Cholesteatoma, Middle Ear↗
PubMed2006

A new tool for testing ossicular mobility during middle ear surgery: preliminary report of four cases.

OBJECTIVE: We developed an ossicular vibration tester for the objective and quantitative assessment of ossicular mobility, which is one of the most critical factors affecting postoperative hearing after tympanoplasty. METHODS: Our device consists of three components: a probe shaft with a curved tip to be attached to the target ossicle, a vibration exciter to activate the probe, and a piezoelectric sensor to detect vibrations of the probe. These components are encased in a stainless steel holder, allowing easy hand manipulation during ear surgery. The probe is activated with an electric signal at around 1,600 Hz. The system is controlled with a laptop computer, and the results are presented as the ratio of the ossicular resistance (ROR) to a reference value as a percentage. One measurement takes 10 ms. The device was applied in four selected patients during ear surgery. RESULTS: Several measurements in two of the cochlear implantees showed a greater difference in the RORs of the stapes (15-20% in Case 1 and 35-45% in Case 2), whereas the RORs of the malleus and incus were within the same range. This was thought to correspond to the partial cochlear calcification noted in Case 2. In Case 3, who underwent surgery because of otosclerosis, the ROR of the stapes was high, ranging from 70 to 80%. When measured for the malleus-incus fixation anomaly (Case 4), the ROR of the malleus and incus was in the range of 60 to 70%. Owing to the limited surgical view, the ROR of the stapes could not be measured. No problems related to the measurements with this device were noted. CONCLUSION: The design, principles, measuring procedures, and preliminary results of our new tool for testing ossicular mobility are reported. Measuring the ossicular mobility during surgery may provide important information for deciding the surgical procedures.

Adolescent↗
PubMed2005

Neural stem cells suppress the hearing threshold shift caused by cochlear ischemia.

Neural stem cells are multipotent progenitor cells that show self-renewal activity. In this study, we assessed the use of neural stem cells for ameliorating ischemia-reperfusion injury of the gerbil cochlea. Neural stem cells were injected into one inner ear through the round window 1 day after ischemic insult. Immunostaining for nestin showed that the distribution of neural stem cells was concentrated within the organ of Corti. Seven days after ischemia, the injury-induced auditory brainstem response threshold shift and progressive inner hair cell damage were markedly less on the neural stem cell-transplanted side. These results suggest that the transplantation of neural stem cells is therapeutically useful for preventing damage to hair cells that occurs after transient ischemia of the cochlea.

Animals↗
PubMed2005

Ischemic damage increases nitric oxide production via inducible nitric oxide synthase in the cochlea.

The present study was designed to elucidate the dynamic changes of nitric oxide (NO) production in the perilymph and to investigate the immunostaining for inducible nitric oxide synthase (iNOS) in the cochlea for 7 days after transient cochlear ischemia. Moreover, aminoguanidine, which is a selective iNOS inhibitor, was administrated immediately following ischemia and every 24h thereafter for 7 days to investigate whether the production of NO is dependent on the iNOS pathway. Significant increases in the oxidative NO metabolites, nitrite (NO(2)(-)) and nitrate (NO(3)(-)), were measured on day 1 using an in vivo microdialysis and on-line high performance liquid chromatography (HPLC) system. The immunostaining for iNOS was strongly expressed on days 1 and 4 and returned to normal on day 7 after the ischemia. The administration of aminoguanidine reduced the oxidative NO metabolites on day 1 and suppressed the expression of iNOS. These findings suggest that transient ischemia causes a remarkable increase in NO production in the perilymph, which might be attributable to the iNOS pathway.

Animals↗
PubMed2005

Transient cochlear ischemia and its effects on the stria vascularis.

The effects of transient cochlear ischemia on the stria vascularis were studied. Fifteen minutes of ischemia decreased the endocochlear potential by up to 17.5 mV on day 1; it returned to normal on day 7. Immunostaining for Na+,K+-ATPase, a marker for the Na+/K+-pump, and for connexin 26, a marker for gap junctions, was inhibited on days 1 and 4, and returned to normal on day 7. Electron microscopy showed expansion of the intercellular space with abundant vacuolar formation in the stria vascularis. These morphological changes disappeared completely by day 7. The results indicate that transient ischemia causes a reversible functional disorder of the stria vascularis with fine structural changes, which may be owing to dysfunction of Na+/K+-pump or gap junctions.

Animals↗
PubMed2005

Kanamycin ototoxicity in glutamate transporter knockout mice.

Glutamate-aspartate transporter (GLAST), a powerful glutamate uptake system, removes released glutamate from the synaptic cleft and facilitates the re-use of glutamate as a neurotransmitter recycling system. Aminoglycoside-induced hearing loss is mediated via a glutamate excitotoxic process. We investigated the effect of aminoglycoside ototoxicity in GLAST knockout mice using the recorded auditory brainstem response (ABR) and number of hair cells in the cochlea. Kanamycin (100 mg/mL) was injected directly into the posterior semicircular canal of mice. Before the kanamycin treatment, there was no difference in the ABR threshold average between the wild-type and knockout mice. Kanamycin injection aggravated the ABR threshold in the GLAST knockout mice compared with the wild-type mice, and the IHC degeneration was more severe in the GLAST knockout mice. These findings suggest that GLAST plays an important role in preventing the degeneration of inner hair cells in aminoglycoside ototoxicity.

Amino Acid Transport System X-AG↗
PubMed2005

Surgical treatment of retraction pocket with bone pate: scutum plasty for cholesteatoma.

OBJECTIVES: Postoperative attic retraction pocket is a critical issue and may be indicative of disease recurrence after canal-up tympanoplasty for middle ear cholesteatoma. Although scutum plasty is an acceptable procedure that can be used to prevent the pocket formation, how the scutum is reconstructed has remained controversial. The aim of this study was to clarify the value of scutum plasty using bone pate. STUDY DESIGN: Retrospective study. SETTING: Bone pate scutum plasty was performed in 69 ears during first-stage operations. We attempted to reconstruct a smooth attic bony wall. At the time of the second-stage operations, the results of the scutum plasty were examined. RESULTS: The incidence of retraction pocket was statistically reduced from 20.2% to 5.8%. CONCLUSION: Although the reconstructed scutum showed atrophy to some extent, bone pate scutum plasty is effective in preventing postoperative retraction pocket if a smoothly shaped attic wall can be reconstructed.

Adolescent↗
PubMed2005

Role of T-lymphocyte subsets in facial nerve paralysis owing to the reactivation of herpes simplex virus type 1.

CONCLUSION: Although both T-cell subsets are essential for inhibiting HSV-1 reactivation in the GG, CD4 + T cells play a more important role in host defense against virus replication. OBJECTIVE: To elucidate the host immunological factors that participate in herpes simplex virus type 1 (HSV-1) reactivation in the geniculate ganglia (GG) and lead to facial paralysis, we developed a mouse model of facial paralysis that involved the reactivation of HSV-1 following general immune suppression. MATERIAL AND METHODS: Eight weeks after recovery from primary facial paralysis caused by inoculating the auricle with HSV-1 the auricle was scratched and mice (n = 69) were given an i.p. injection of either anti-CD4 (n = 46) or anti-CD8 (n = 23) monoclonal antibody to deplete specific T-lymphocyte subsets. Following this reactivation procedure, the rate of recurrent facial paralysis was compared between the two models. The GG were examined histopathologically and using polymerase chain reaction to detect HSV-1 DNA. RESULTS: Facial paralysis developed in 42% of mice in the anti-CD4 model and in 13% in the anti-CD8 model. HSV-1 DNA was detected in 50% of the mice in both models. Histopathologically, neurons were destroyed in parts of the GG and numerous virus particles were seen in the surviving neurons.

Animals↗
PubMed2004

Characterization of a MAPKK-like protein kinase TOPK.

A MAPKK-like protein kinase TOPK expresses in a wide range of proliferating cells and tissues such as cancer cells and testis. However, details of this kinase are still uncovered. We investigated the intracellular distribution of TOPK and its association with cdk1/cyclin B and microtubules. In interphase cells, TOPK expresses in cytosol and nucleus without any significant association with microtubule networks. During mitosis, TOPK-Thr-9 was phosphorylated by cdk1/cyclin B and TOPK significantly associates with mitotic spindles. When TOPK expression was suppressed, formation of spindle midzone was thinned and dimmed and cytokinesis was disturbed. We propose that TOPK plays a role in the formation of spindle midzone and in cytokinesis.

Animals↗
PubMed2004

Age-related remodeling of the hypopharyngeal constrictor muscle and its subneural apparatuses: a scanning electron microscopical study in rats.

Age-related remodeling of the hypopharyngeal constrictor muscle was studied by comparing the morphological features of the subneural apparatus (SNA) of the thyropharyngeal (TP) and cricopha ryngeal (CP) muscles in young and old rats. Scanning electron microscopy revealed that the TP and CP muscles had both gutter- and depression-type SNAs, although different proportions of the two types of apparatus were found in each muscle. In young-adult rats, the gutter-type SNA was predominant in the TP muscle, whereas in the CP muscle the depression type was predominant. By contrast, in old rats, the depression-type SNA was predominant in the TP muscle, while no such transformation of the dominant SNA was noted in the CP muscle. In addition, the number of type IIb and type I muscle fibers was lower and greater, respectively, in older animals compared with those of younger animals. Furthermore, there were more type IIc fibers in the TP muscle of old rats, but no difference in the CP muscle between young and old animals. These findings suggest that the transformation of SNAs and the muscle fibers of the hypopharyngeal constrictor muscle takes place during aging and that their remodeling processes differ in the TP and CP muscles.

Age Factors↗
PubMed2004

Chondroma of the bony external auditory canal attached to the short process of the malleus.

A chondroma located in the external auditory canal is a rare finding. Here, we report the case of a 12-year-old girl who attended our clinic with complaints of a rustling sound in her left ear. Otoscopic examination revealed a tiny bone-like tumor protruding from the anterior wall of the bony external auditory canal, attached to the short process of the malleus. An audiogram revealed a conductive hearing loss in her left ear, although she did not notice it. After excision of the tumor through the ear canal, her complaints disappeared and her hearing recovered. Histologically, the tumor proved to be a chondroma.

Child↗
PubMed2004

Reconstruction of mastoid cortex defect using bone morphogenetic protein: an experimental study in the guinea pig.

OBJECTIVE: The aim of this experimental study was to examine whether recombinant human bone morphogenetic protein-2 (rhBMP-2) could induce new bone formation in a small hole drilled through the temporal bone near the external auditory canal wall in guinea pigs. MATERIAL AND METHODS: A 4-mm diameter hole was made in the center of the temporal bone and a piece of collagen sheet infiltrated with rhBMP-2 was placed in the hole. New bone formation was confirmed by means of X-ray examination and the bone mineral density was quantified using dual-energy X-ray absorptiometry 1, 2 and 4 weeks after treatment. RESULTS: The bone mineral density in the rhBMP-2-treated group was significantly increased compared to the control group. CONCLUSION: These results suggest that rhBMP-2 induces remarkable new bone formation in the temporal bone and will be useful in clinical ear surgery.

Animals↗
PubMed2004

Restoring vocal fold movement after transection and immediate suturing of the recurrent laryngeal nerve with local application of basic fibroblast growth factor: an experimental study in the rat.

OBJECTIVE: To evaluate the effects of basic fibro-blast growth factor (bFGF) on the recovery of vocal fold movement and the attenuation of laryngeal muscle atrophy after transection of the recurrent laryngeal nerve (RLN). STUDY DESIGN: Quantitative assessment of vocal fold movement using the video cassette recorder (VCR) image-analysis method and histologic examination of the laryngeal muscle. METHODS: Fifty-eight Wistar rats underwent RLN transection and one of the following three procedures: 1) transection of the RLN alone (transection group, n = 18), 2) suture of the nerve stumps followed by local administration of phosphate-buffered saline (PBS) solution using an osmotic pump (PBS group, n =20), or 3) suture of the nerve stumps followed by local administration of bFGF (FGF group, n = 20). Vocal fold movements were recorded with VCR by way of a rigid endoscope, and the VCR images were analyzed on a computer. Histologic changes in the thyroarytenoid (TA) muscle were evaluated by measuring the cross-sectional area of the muscle and average size of muscle fibers. RESULTS: In the transection group, vocal fold movement did not recover, and atrophy of the TA muscle gradually progressed after sectioning the nerve. In contrast, vocal fold movement as assessed by VCR image-analysis recovered in some cases in the immediate suturing groups, more markedly in the FGF group (34.1 +/- 29.1%) than in the PBS group (5.5 +/- 7.9%) (P <.05). Histologically, atrophy of the laryngeal muscle was significantly attenuated by the local administration of bFGF. CONCLUSION: bFGF facilitates regeneration of the transected RLN and attenuation of intrinsic laryngeal muscle atrophy, thereby restoring laryngeal function.

Animals↗
PubMed2003

Free radical scavenger protects against inner hair cell loss after cochlear ischemia.

We investigated the protective effects of edaravone, a free radical scavenger, against ischemic damage of inner hair cells (IHCs) in gerbils. Cochlear ischemia was induced in the animals by occluding the vertebral arteries bilaterally for 15 min. Edaravone (1 mg/kg, i.v.) or saline was administered 1 h after ischemia. Hearing was assessed by auditory brain response (ABR). In animals treated with saline, the ABR threshold shift was 24.1 dB and there was a 26.5% decrease in the number of IHCs. By contrast, in animals treated with edaravone, the threshold shift was 7.5 dB and only 8.8% of IHCs was lost. These results suggest that edaravone protects against damage to the inner ear following transient ischemia.

Analysis of Variance↗
PubMed2003

AMPA/kainate-type glutamate receptor antagonist reduces progressive inner hair cell loss after transient cochlear ischemia.

We investigated the effect of glutamate receptor antagonists on progressive inner hair cell (IHC) loss following transient cochlear ischemia in gerbils. Transient cochlear ischemia was induced by 15-min bilateral vertebral artery occlusion. An alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)/kainate-type glutamate receptor antagonist, 6-7-dinitroquinoxaline-2,3-dione (DNQX), or an N-methyl-D-aspartate (NMDA)-type receptor antagonist, MK-801, was administered 10 min before the ischemic insult. Hearing was assessed by sequentially recording compound action potentials (CAPs) 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 Hoechst 33342. On the seventh day after ischemia, the increases in the CAP threshold and the progressive IHC loss were significantly reduced in cochleae treated with DNQX, while MK-801 was ineffective. These results suggest that the AMPA receptor plays a critical role in the development of the progressive IHC loss induced by ischemia/reperfusion injury in the cochlea.

Acoustic Stimulation↗