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IWASAKI Shinichi

    Graduate School of Medical Sciences Department of Otolaryngology, Head and Neck Surgery　Professor
Last Updated :2024/04/24

Researcher Information

J-Global ID

Research Interests

  • めまい・平衡医学   神経耳科学   耳科学   

Research Areas

  • Life sciences / Otorhinolaryngology

Published Papers

MISC

Research Grants & Projects

  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 2022/04 -2027/03 
    Author : 鵜川 眞也; 岩崎 真一; 柴田 泰宏; 島田 昌一; 熊本 奈都子; 村上 信五; 植田 高史
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 2023/04 -2026/03 
    Author : 蒲谷 嘉代子; 岩崎 真一; 近藤 真前; 浅井 友詞
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 2022/04 -2026/03 
    Author : 的場 拓磨; 岩崎 真一; 川北 大介; 今井 優樹
  • 日本学術振興会：科学研究費助成事業 基盤研究(B)
    Date (from‐to) : 2021/04 -2025/03 
    Author : 藤本 千里; 岩崎 真一; 安部 力; 鴨頭 輝; 森田 啓之
     
    片頭痛に関連するめまい症状を有する患者群に対して、近年、前庭性片頭痛という疾患概念が提唱された。しかしながら、主病変と考えられる前庭障害と前庭性片頭痛の病態との関連は明らかになっていなかった。申請者は、卵形嚢眼反射系の機能を反映する前庭誘発外眼筋電位検査において、前庭性片頭痛確実例の方が前庭性片頭痛疑い例よりも、有意に異常所見を呈することを示し、前庭性片頭痛の病態と卵形嚢眼反射系の機能障害との高い関連性を報告した。本研究課題は、前庭性片頭痛の分子メカニズムにおける最大の謎である「前庭障害と片頭痛の病態のリンク」を解明すること、そして、前庭性片頭痛の新規バイオマーカーを発見し新規治療の開発を目指すことを目的とする。 本年度は、卵形嚢感覚上皮培養細胞UB/UE-1を、冷感疼痛刺激物質イシリンで処理し、Cell Counting Kit-8(CCK-8)による生細胞数測定系、および、トリパンブルー染色による死細胞率測定系を確立した。現在、様々なイシリン濃度・処理時間にて、解析を行っているが、CCK-8を用いたassayでは、ある条件にて生細胞数の軽度の低下を示し、トリパンブルー染色では、ある条件にて死細胞率の軽度の増加が確認されている。 UB/UE-1の生細胞数の低下が示されたイシリン処理条件にて、UB/UE-1細胞のRNAを抽出し、サンプルのquality checkを行い、問題ないことを確認した。現在、RNAシークエンス解析を行っている。また、培養液のエクソソームを抽出し、ナノサイト解析を行い、粒子数が十分であることを確認した。現在、エクソソームの網羅的解析を行っている。
  • 日本学術振興会：科学研究費助成事業 基盤研究(B)
    Date (from‐to) : 2021/04 -2025/03 
    Author : 岩崎 真一; 南方 寿哉; 江崎 伸一; 蒲谷 嘉代子; 藤本 千里
     
    １．突発性難聴、前庭神経炎患者の唾液を用いたウイルス再活性化の解析 突発性難聴、前庭神経炎患者に加えて、急性の顔面神経麻痺であるベル麻痺とハント症候群患者の急性期、慢性期における唾液中のHSV-1, -2,VZV, HHV-6,-7VZV, HHV-6,-7のウイルスDNA量についてのRT-PCR法での解析については、名古屋市立大学医学部の倫理審査委員会の承認を経て、解析をすすめている。現時点までに、約50名の症例の唾液を集め、RT-PCR法で解析を行っている。唾液中にウイルスを認める患者は、慢性期のみならず、急性期でもそれほど多くないことから、ウイルスを有する患者の患者背景についての詳細な検討を行っている段階にある。 ２．ウイルス再活性化によるウイルス性内耳炎モデル動物の作製と病態解析 ウイルス性内耳炎動物モデルでは、まずは、弱毒化した単純ヘルペスウイルス（HF-10)をマウスの中耳に投与することで、一側性の内耳炎を引き起こし、その聴覚障害および前庭障害につき、それぞれ聴性脳幹反応（ABR)とロタロッドで客観的な機能評価を行い、いずれも障害が生じていることを確認した。モデル動物の内耳の組織学的解析について、現在進めているところである。ウイルス再活性化による内耳炎モデルについては、HF-10の耳介から感染させ、再活性化を試みているものの、成功に至っておらず、HF-10の投与量を調節している段階にある。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2020/04 -2024/03 
    Author : 山岨 達也; 岩崎 真一; 木下 淳; 樫尾 明憲; 鴨頭 輝; 近藤 健二; 藤本 千里; 浦田 真次; 松本 有
     
    蝸牛・前庭・半規管の組織を透明化し、三次元的に詳細に観察する技術を構築を試みた。焦点深度の深い顕微鏡の構築はまだ完成しておらず、まずは蝸牛全体では無く、前庭に近い基底回転のみを含めて前庭と半規管を骨胞の透明化により描出する方法を模索し、すべての感覚上皮がコンタミネーションなくきれいに描出できる手法をトライアンドエラーにより確立した。現在ほぼ安定して、前庭の二つの感覚上皮（球形嚢斑、卵形嚢斑）および三つ（前・後・外側）の半規管膨大部を同時に描出することが可能になっている。免疫染色は核染色（DPI）、有毛細胞（ミオシン7a）、細胞骨格（ファロイジン）、神経繊維（NF200）などが可能であり、正常状態における各感覚細胞の細胞カウント、各感覚上皮の三次元的形態、それぞれの感覚上皮の三次元的関係について解析した。細胞カウントについては自動カウントのソフトを導入し、わずかに残るゴミを除去して手動ではない方法でカウントできるようにした。感覚上皮の彎曲や各感覚の三次元的関係については形態の近似値を計算する数式について検討中であり、これが完成すれば投稿予定である。また、障害モデルについてはゲンタシン投与マウスモデルで感覚細胞・シナプス、新鋭の変性および再生過程について経時的に観察を行っている。蝸牛については音響外傷および加齢性難聴での有毛細胞障害後のシナプスの変化、神経変性について、三次元的観察を行い、また血管条の血管形態の変化、マクロファージの分布の変化を検討中である。なお、マウスの音響外傷および老人性難聴にの予備実験として、PQQの予防効果につき、ABRによる機能解析、感覚細胞、シナプス、蝸牛神経、ラセン神経節、血管条を形態学的に調べ、その有効性を確認した。またPQQについては蝸牛有毛細胞株であるHEI-OCIでの酸化ストレス予防効果、ミトコンドリア保護効果などに付き検討し、論文化した。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2018/04 -2021/03 
    Author : Iwasaki Shinichi
     
    Historically, two forms of cell death have been recognized: necrosis as ‘accidental’ and apoptosis as ‘programmed’. Recently, genetically programmed form of necrosis termed ‘necroptosis’ has been reported. We investigated the involvement of necroptosis and apoptosis in gentamicin (GM) ototoxicity to identify potential therapeutic targets. We examined organotypic cultures of P3 ICR mice cochlear explants. We showedd necrotic and apoptotic cells proportion and the levels of typical antibody in hair cells decreased after treating with different concentration of ZVAD (caspase inhibitor) or Nec-1(necrosis inhibitor). Our findings suggest that GM-induced ototoxicity is caused by combination of necrosis, necroptosis, and apoptosis.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
    Date (from‐to) : 2015/06 -2020/03 
    Author : Morita Hironobu
     
    Under the hypothesis that plastic changes in the otolith vestibular system, which is a sensing organ of gravity, are involved in the causes of various medical problems associated with microgravity, we investigated the changes in otolith sensory cells and vestibular nuclei, which are primary neurons, caused by the microgravity environment, and obtained the following results. In addition to previously known functions, the vestibular system is involved in various body function regulation such as feeding, glucose metabolism, body temperature, blood pressure, regulation of muscle mass/bone mass. These functions change when exposed to different gravitational environments with strong plasticity. This plastic change involves changes in gene expression in the saccule and vestibular nuclei. It was suggested that the method of electrically stimulating the vestibular system might be useful as a countermeasure against plastic changes.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research
    Date (from‐to) : 2015/04 -2018/03 
    Author : Iwasaki Shinichi
     
    To evaluate peripheral vestibular function in experimental animals, we have developed a system to record short -latency vestibular evoked potential (VsEP). In this system, we adopted newly developed vibrator and motor to provide linear and angular accelerations, respectively. We could record reliable and repeatable VsEPs in response to linear accelerations of the head in mice. The waveforms of VsEP were different from auditory brainstem responses (ABRs). In mice treated with ototoxic drugs, kanamycin and ethacrynic acids, ABRs were absent, but VsEPs could be recorded. In contrast, in mice whose inner ears were surgically damage, both ABRs and VsEPs were absent. These results suggested that VsEPs evoked by linear acceleration were originated from the vestibular endorgans, probably the otolith organs. On the other hand, we could not record reliable VsEPs in response to angular accelerations, probably due to insufficient power of the rotatory motor that we used to evoke VsEPs.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2014/04 -2018/03 
    Author : SUZUKI Mitsuya
     
    As compared to that in the non-ovariectomized group (control) the ABR threshold in the ovariectomized group was significantly higher at 32 KHz at 1 month after surgery (3-months-old), and at 2, 4, 8, 16, and 32 kHz at 2 months after surgery (4-months-old). 2) The three-layer structure which consists of laminae rarae eterna and interna and lamina densa, could be not identified clearly in the capillary basement membrane in the stria vascularis at both 3-months-old and 4-months-old in both the ovariectomized group and non-ovariectomized group. Distribution of cationic polyethyleneimine (PEI) particles was hardly observed on the capillary basement membranes in the stria vascularis in both the ovariectomized group and control group. 3) No marked difference in expression of ER alpha and ER beta was observed in the cochlea between the control group and the ovariectomized group.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
    Date (from‐to) : 2014/04 -2017/03 
    Author : Yamasoba Tatsuya
     
    When endogenous antioxidant MnSOD was reduced to half, oxidation stress of the cochlea was exacerbated by aging and acoustic trauma aggravated it. When GeO2 was given to mice, cochlear tissue showed marked degeneration with decrease of mitochondrial function. This damage was ameliorated by antioxidant. When gentamycin was injected into the middle ear, hair cell(HC) in semicircular canal showed marked degeneration and showed partial recovery due to regeneration via cell division of the sopporting cells. When TrkB agonist was given, HC showed significant recovery and synapse and afferent fibers were better preserved. When immortalized inner ear cells were exposed to oxidation stress, mitochondria were degenerated, mitochondrial membrane potential decreased, mitochondrial fusion/fission was impaired, and respiratory capacity was affected. We found that the cochlear HC, possess autophagy functoion. When Atg5 was knock out in the cochlear HC, these cells exhibited progressive degeneration.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2013/04 -2017/03 
    Author : Iwasaki Shinichi
     
    To investigate the role of the intracellular proteolysis systems in damages in the inner ear, we analyzed the roles of the ubiquitin-proteasome system and the autophagy-lysosome system. To investigate the role of the autophagy-lysosome system in the inner ear, we generated mice deficient in a gene essential for autophagy (Atg5) in hair cells in the inner ear. Deletion of Atg5 resulted in hair cell degeneration and profound congenital hearing loss. To investigate the role of the ubiquitin-proteasome system in the inner ear, we analyzed the effect of proteasome inhibitor (MG-132) in cultured inner ear cells under oxidative damage. The low concentration of proteasome inhibitor had some protective effect, but it had toxic effect in the higher concentration.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2011/04 -2014/03 
    Author : YAMASOBA TATSUYA; IWASAKI Shin-ichi; KIKKAWA Yayoi; SAKAMOTO Takashi; KASHIO Akinori; YASUI Takuya; PROLLA Tomas A.; SOMEYA Shin-ichi
     
    We investigated the association of oxidative stress and age-related hearing loss (AHL) using several transgenic mice in which the oxidative stress is enhanced or suppressed. We first examined whether reduction in manganese superoxide dismutase (Mn-SOD) accelerated AHL. At 16 months, immunoreactivity of 8-hydroxydeoxyguanosine was significantly greater in Mn-SOD heterozygous knockout (HET) mice compared to WT mice, but that of 4-hydroxynonenal did not differ between them. Age-related ABR threshold shifts and the extent of cochlear degeneration did not differ between WT and HET mice, suggesting that decrease of Mn-SOD by half increases oxidative stress in the cochlea to some extent but does not accelerate AHL. In contrast, glutathion reductase knockout mice exhibited acceleration of ABR threshold shifts at high frequencies, suggesting that oxidization of glutathione is crucial in the development of AHL.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2010 -2012 
    Author : IWASAKI Shinichi
     
    To clarify the origin of ocular vestibular evoked myogenic potential (oVEMP), we performed experiments trying to record oVEMPs from guinea pigs. By inserting an electrode through lower eyelids and contacting it near extraocular muscles, we could record negative potentials with the peak latency of 3 msec. The potential was reduced by destruction of inner ear of the contralateral side, and was abolished by destruction of inner ears of both sides, suggesting that the response was dependent on the inner ears of both sides. Furthermore, by recoding directly from extraocular muscles, we confirmed that the oVEMPs in guinea pigs are originated from both the inferior oblique muscles and the inferior rectus muscles.
  • 日本学術振興会：科学研究費助成事業 挑戦的萌芽研究
    Date (from‐to) : 2009 -2010 
    Author : 山岨 達也; 中島 敏明; 岩崎 真一
     
    高強度トレーニングは、活性酸素の産生を高め、酸化ストレスを亢進することが知られている。低強度加圧筋力トレーニングは、高強度トレーニングに匹敵する筋肥大効果をみとめると報告されており、起立性低血圧の治療に応用した。また加圧トレーニングならびに種々な運動様式の血中酸化ストレス指標に及ぼす影響につき健常人ならびに患者で検討した。各種目において、血中の酸化ストレス指標として活性酸素代謝産物濃度(dROMs test)と抗酸化力指標(BAP test)を測定した。加圧下での低負荷エルゴメーター運動及び筋力トレーニングは、非加圧時に比し、有意なdROMs、BAP上昇を認めた。さらに、健常人では、BAPは、乳酸、WBC、ノルアドレナリン(NOR)と有意な相関をみとめたが、dROMsとは相関は見られなかった。一方、起立性低血圧群では、dROMsは、乳酸、WBC、NORと有意な相関をみとめ、BAPも乳酸、WBCと相関を認めた。このように、加圧トレーニングでは、酸化ストレス・抗酸化力の亢進が見られた。健常人では、運動強度、血流制限に依存して抗酸化力が活性化し、酸化ストレスの上昇を抑制するが、疾患群では、運動強度、血流制限によって依存して酸化ストレスが亢進すると思われ、加圧トレーニングを応用する際には、負荷強度、血流制限の程度などを十分考慮する必要があると思われた。我々は、重篤な起立性低血圧患者においてマシンが使用できない場合は、elastic bandを用いた加圧トレーニング、加圧ウォークなどの負荷の軽い加圧トレーニングも実施している。そこで、高齢者の加圧ウォークの下肢筋力、筋肥大ならびにQOL改善効果についても検討した。加圧ウォークは、高齢者の下肢筋力を改善するとともに、静脈コンプライアンスを改善した。今後、起立性低血圧患者において、加圧トレーニングの効果とともに、安全で効果的なトレーニングメニューの作成につき、酸化ストレス、炎症の面からも研究を継続する予定である。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2007 -2008 
    Author : ITO Ken; IWASAKI Shinichi; SAHARA Yoshinori; SAHARA Yoshinori
     
    ラット前庭神経節細胞の細胞体にその末梢受容器(耳石器・半規管膨大部)を付着した標本を作成し、細胞生理学的実験を行う手法を確立した。培養方法としては、Leibovitz's L-15を使用した短時間(< 5hr)培養が最適であることが分かった。 生理学的実験 : 末梢前庭器-前庭神経細胞体を一体とする標本において、神経のパッチクランプ記録を行うことが可能となった。脱分極刺激(電流注入)による神経発火パターンを記録したところ、主にphasic typeの発火であり、今のところ単離・培養したものと大きな違いが無い結果となっている。同様の標本において前庭神経節細胞をパッチクランプして性質を調べた上でピペット内に予め入れておいたビオチンにより逆向性染色を行う実験は、パッチクランプの成功率が不十分で、また実験中に細胞が死んだりパッチが外れてしまうトラブルが多いことから未だ信頼に足る結果が得られていない。 免疫組織学的・分子生物学的実験 : 末梢前庭器-前庭神経細胞体を一体とする標本において、神経細胞の性質等を検索した後に細胞質を電極内に吸引し、Single Cell RT-PCRを行う実験は成功率が低く、その原因は単離細胞と異なり内容の吸引が難しいことであると分かった。未だ信頼性の高いデータとはなっていない。前庭神経節の興奮性の調節に関与すると分かったイオンチャネルやリガンド受容体の免疫染色については、試薬を購入して実験を開始したばかりの段階である。本研究のここまでの成果を踏まえて、今後も研究を継続する予定である。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2005 -2007 
    Author : IWASAKI Shinichi; ITO Ken
     
    In the present study, we have established the method of culture of primary vestibular ganglions surviving at least 4 days. We have examined the intrinsic firing properties of isolated rat vestibular ganglion cells (VGCs) and explored contributions of K^+ channels to the discharge regularity. Three classes of VGCs were distinguished on the basis of a degree of spike frequency adaptation observed during sustained membrane depolarization: most neurons exhibited a strong adaptation generating just a single spike or short bursts of spikes, and the others showed moderate adaptation or tonic firing. A degree of spike frequency adaptation in a neuron did not correlate with the cell size. Considerable variation in K^+ currents was present in the class of VGCs. In the presence of 4-aminopyridine or α-dendrotoxin (α-DTX), selective blockers of Kvl α subunits, phasic firing turned into sustained firing, indicating that Kvl channel control the firing characteristic of the pahsic VGCs. In tonic VGCs, tetraethylammonium decreased the frequency of discharges at membrane potentials above threshold while α-DTX lowered the threshold for initiation of discharge in response to depolarizing current steps. Blockade of Ca^<2+> activated K^+ channels and H- currents also had some effects on the firing pattern of the tonic VGCs. Our results indicate that VGCs have heterogeneous intrinsic firing properties, and that low-threshold K^+ channels are critical to determining a pattern of spike discharges that optimize the responsiveness of the vestibular neurons, thereby contributing to the timing of VG inputs.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
    Date (from‐to) : 2003 -2006 
    Author : KAGA Kimitaka; YAMASOBA Tatsuya; ITO Ken; IWASAKI Shinichi; KARINO Shotaro; NAKANO Masayuki
     
    In order to illuminate auditory space, sound lateralization tests were performed to compare the magnet coil bone-conduction headphone with the giant magnetostrictive bone-conduction headphone using 18 healthy participants. Although, no significant difference between these bone-conduction headphones was obtained for the interaural time difference and interaural intensity difference, a significant difference was obtained for the time-intensity trade. This revealed that the difference between the headphone is apparent in the integration of the heterogeneous sensations of the time and intensity difference at the cognitive level, but no difference is apparent between the homogeneous sensations of the discrimination of interaural time difference or interoaural intensity difference at the sensory level. It was concluded that the difference of the giant magnetostrictive headphone. However, sound localization test using speakers' method in the aneic room revealed that auditory space of bone conduction is smaller than that of airconductive.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2003 -2005 
    Author : ITO Ken; IWASAKI Shinichi; MATSUI Minoru
     
    This year, we continued our research on the basis of what we have established during the past two years. However, we encountered two troubles at the beginning of the year. First, because of epidemic problems, supply of the knock-out animals was disconnected for about half a year. The stable supply was re-established in November and we resumed the experiments. Secondly, in the meantime, a competing laboratory in the States reported that their mice lacking muscarinic receptors (product independent of our knock-outs) had almost normal hearing and similar susceptibility to ototoxic agents (Maison SF, et al. 2005). However, we made progress in two points. First, we revised the computer software to record OAEs, which was a pending problem from the last year, and enabled recording DPOAEs in animals as well as in humans. Secondly, considering the situation described above, we tried to shift the axis of our research in the inner ear from the auditory system to the vestibular system and finally were able to record action potentials of vestibular ganglion cells in rodents on the whole-cell patch clamp mode. We also revealed the expression of mRNAs for muscarinic receptors in vestibular ganglion cells by means of DNA arrays. Planned studies in the near future : 1) We still continue the experiments on comparative studies on susceptibility to extraordinary noise and to ototoxic drugs using knock-out and wild-type mice. This is because the results may differ from those from the USA group, since the knock-out mice were independently produced. 2) Since the existence of muscarinic receptors on the vestibular ganglion cells in rodents was indicated, we plan first to investigate modulation of excitability of neurons by muscarinic receptors and then to reveal the difference of neuronal firing patterns between knock-out and wild-type mice. Moreover, by investigating the difference in contribution of ionic channels on action potential formation, the contribution of muscarinic receptors to developmental processes of vestibular ganglion cells will be deduced.
  • 日本学術振興会：科学研究費助成事業 若手研究(B)
    Date (from‐to) : 2003 -2004 
    Author : 岩崎 真一
     
    昨年度の研究で、モルモットの単離ダイテルス細胞の膜電流は主にカリウム電流で厚生されており、その大部分は電位依存性カリウムチャンネルのブロッカーであるテトラエチルアンモニウム(TEA)によりブロックされることを明らかにした。 本年度はペアになったダイテルス細胞を使用し、膜容量の測定を行うことで、ギャップジャンクションの薬理学的特性を調べた。ペアになったダイテルス細胞の膜容量はギャップジャンクションのブロッカーである、カルベノキソロンの投与により、約半分に減少した。このことは、ダイテルス細胞間の結合が主にベノキソロン感受性のギャップジャンクションによって結合していることを意味する。別のギャップジャンクションブロッカーであるオクタノールの投与によっても同様の結果が得られた。しかしながら、1回の実験において、ペアになったダイテルス細胞は非常に少数であり、データを効率よく得るのは容易ではなかった。また、ギャップジャンクションに影響を与えることが知られているアミノ配糖体や一酸化窒素の阻害薬の効果も試してはみたが、はっきりとした薬剤の効果をみるには至らなかった。 複数のダイテルス細胞のうち、隣接する2つのダイテルス細胞に対して、それぞれの細胞よりホールセルを記録し、そのコンダクタンスを調べる実験も試みたが、1つの細胞ではホールセル記録を行えるものの、2つの細胞で同時にホールセル記録を行うのは非常に確率が低く、その特性を検討するには至らなかった。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2001 -2004 
    Author : TAKAI Yoshinari; IWASAKI Shin-ichi; USHIO Munetaka; TAKAHIRO Asakage
     
    We performed physiological studies concerning responses of vestibular afferents to short duration extracranial galvanic stimulation in guinea pigs and humans. In guinea pigs, some primary vestibular afferents responded to short duration extracranial galvanic stimulation. In human, short duration extracranial galvanic stimulation caused responses on the sternocleidomastoid mascle. The threshold of this response was 2.5mA and 5Hz was the optimal stimulation rate. Clinical studies suggested that this response is of vstibular origin. And, it was revealed that this response is useful for the differential diagnosis of the nerve lesion from the endrorgan lesion.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2001 -2003 
    Author : SUGASAWA Masashi; ITO Ken; IWASAKI Shinichi; SAKAMOTO Takashi
     
    Recently, Patch clamp techniques have been introduced into hair cell electrophysiological researches. By the way, mechanically and enzymatic ally isolation of hair cells from organ of Corti is necessary for patch clamp of hair cells. To purpose of this study is to clarify factors of cell injuries in the isolation process and to prevent those injuries. Finally rebuilding of normal environment of inner hair cell by double patch is a last purpose. Two indexes of the cell injuries became clear, vacuolation and resting membrane potential. The vacuolation at base occurs in almost all cells after isolation process. The cells without vacuolation showed good behavior during experiment. Other factor was resting membrane potential. The cells whose resting membrane potential was below -6OmV also showed good behavior during experiment. By using these indexes, we tried to prevent cell injures by changing isolation processes but all trials were in vain. It is impossible to reconstruct normal condition of inner hair cells by double patch because of rigidity of upper surface of inner hair cells. We could not make a seal on upper surface of inner hair cells. Another methodology is necessary for keeping inner hair cell condition in experiment.
  • 聴覚・前庭系の細胞生理学、めまい・平衡の臨床研究

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