Seiji Kakehata

Cellular mechanism of acetylcholine-induced response in dissociated outer hair cells of guinea-pig cochlea.

1. The acetylcholine (ACh)‐induced currents (IACh) in dissociated outer hair cells (OHCs) of guinea‐pig cochlea were investigated using the whole‐cell patch‐clamp technique, in both conventional and nystatin perforated‐patch configurations. 2. ACh and carbamylcholine (CCh) induced outward currents at a holding potential (VH) of ‐60 mV in the perforated‐patch configuration. The IACh increased in a sigmoidal fashion over the concentration range between 3 x 10(‐6) and 10(‐3) M. The dissociation constant (KD) was 1.7 x 10(‐5) M and the Hill coefficient (n) was 2.7. The KD and n for CCh were 8.7 x 10(‐5) M and 2.2, respectively. Neither nicotine nor muscarine induced any detectable current up to a concentration of 10(‐3) M. 3. Various muscarinic agonists such as oxotremorine‐M, McN‐A‐343 and oxotremorine could also induce the outward currents, although these current amplitudes were about one‐third that of ACh, indicating that they were partial agonists. 4. The muscarinic antagonists atropine, 4‐DAMP, AF‐DX 116 and pirenzepine inhibited the IACh in a concentration‐dependent manner. The half‐inhibitory concentrations (IC50) for atropine, 4‐DAMP, AF‐DX 116 and pirenzepine were 4.8 x 10(‐6), 6.2 x 10(‐6), 2.1 x 10(‐5) and 2.9 x 10(‐4) M, respectively. 5. When the extracellular Ca2+ concentration ([Ca2+])o) was reduced to lower than 1 mM, the amplitude of IACh, abruptly decreased. In a nominally Ca(2+)‐free external solution ACh did not induce any current. The increase of [Ca2+]o beyond 1 mM did not change the IACh. 6. When OHCs were perfused intracellularly with a pipette solution containing 10 mM BAPTA in the conventional whole‐cell mode, ACh could not induce outward K+ currents. The Ca2+ ionophore A23187 induced an outward current. These results indicate that intracellular Ca2+ is involved in the ACh response. 7. Calmodulin inhibitors such as chlorpromazine, W‐7 and trifluoperazine inhibited the IACh in a concentration‐dependent manner. 8. When OHCs were dialysed with either 100 microM GDP beta S or 1 micrograms/ml pertussis toxin (PTX) through the patch pipette at a VH of ‐60 mV, the IACh diminished within 10 min, whereas the IACh of the control remained steady for over 20 min, suggesting that a PTX‐sensitive G‐protein is involved in the ACh response.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of intratympanic and intravenous dexamethasone treatment on sudden sensorineural hearing loss with diabetes.

Objective: The purpose of this study was to evaluate the efficacy of intratympanic administration of dexamethasone (IT-DEX) treatment on sudden sensorineural hearing loss (SSNHL) patients with diabetes by comparing the results with intravenous administration of dexamethasone (IV-DEX) treatment. Study Design: Comparative study. Setting: University hospital and affiliated hospital. Patients: Ten sequential SSNHL patients with diabetes receiving IT-DEX and 21 sequential SSNHL patients with diabetes receiving IV-DEX. Patients with low tone hearing loss were excluded. Intervention: In the IT-DEX group, two methods were applied to deliver DEX (4 mg/ml): injection through a perforation made by laser-assisted myringotomy or through a tympanostomy tube. IT-DEX administration was performed on 8 sequential days. In the IV-DEX group, DEX was administrated intravenously starting from an amount of 8 mg/d followed by taped doses for 10 days. Main Outcome Measures: Preprocedure and postprocedure hearing levels and complications. Results: In the IT-DEX group, the average hearing level before the treatment was 79 dB. Overall, all 10 patients showed improvement of more than 10 dB in the pure-tone audiogram, with a mean improvement of 41 dB. Seven patients (70%) demonstrated successful results, and four recovered completely. In the IV-DEX group, 14 (67%) of the 21 patients showed improvement of more than 10 dB with a mean improvement of 25 dB. Thirteen patients (62%) demonstrated successful results. Free blood sugar during and after the IT-DEX treatment remained below the pretreatment levels, whereas four patients in the IV-DEX group demonstrated worsening of the hyperglycemia. Conclusion: IT-DEX treatment is at least as effective as IV-DEX treatment for SSNHL patients with diabetes.

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.

Expression of Pendrin Periostin in Allergic Rhinitis Chronic Rhinosinusitis

BACKGROUND Pendrin and periostin are newly identified mediators of the inflammatory process. The expression of these proteins in human sinonasal tissue and their roles in allergic rhinitis and chronic rhinosinusitis remain to be elucidated. This study investigated the expression of pendrin and periostin in sinonasal tissue of patients with allergic rhinitis, chronic rhinosinusitis, and aspirin-induced asthma. Prospective control study conducted at Yamagata University, Japan. METHODS Surgical samples were investigated by means of real-time reverse transcription-polymerase chain reaction to evaluate the expression of pendrin and periostin mRNA. The presence and location of pendrin and periostin were determined by immunohistochemistry and Western blotting. RESULTS Pendrin and periostin production was significantly higher in patients with nasal disorders than in controls. Further significant increases in periostin expression were noted in patients with chronic rhinosinusitis with nasal polyps and in those with aspirin-induced asthma. Immunohistochemistry revealed positive staining for pendrin in epithelial cells and submucosal glands and for periostin in the basement membrane in all three disorders, and additionally for periostin in nasal polyp tissue in chronic rhinosinusitis and aspirin-induced asthma. CONCLUSIONS Production of pendrin and periostin is upregulated in allergic rhinitis, chronic rhinosinusitis with nasal polyps, and aspirin-induced asthma. These findings suggest that pendrin can induce mucus production and that periostin can induce tissue fibrosis and remodeling in the nasal mucosa. Therefore, these mediators may be therapeutic target candidates for allergic rhinitis, chronic rhinosinusitis with nasal polyps, and aspirin-induced asthma.

Developmental Expression of the Outer Hair Cell Motor Prestin in the Mouse

The development of motor protein activity in the lateral membrane of the mouse outer hair cell (OHC) from postnatal day 5 (P5) to P18 was investigated under whole-cell voltage clamp. Voltage-dependent, nonlinear capacitance (Cv), which represents the conformational fluctuations of the motor molecule, progressively increased during development. At P12, the onset of hearing in the mouse, Cv was about 70% of the mature level. Cv saturated at P18 when hearing shows full maturation. On the other hand, Clin, which represents the membrane area of the OHC, showed a relatively small increase with development, reaching steady state at P10. This early maturation of linear capacitance is further supported by morphological estimates of surface area during development. These results, in light of recent prestin knockout experiments and our results with quantitative polymerase chain reaction, suggest that, rather than the incorporation of new motors into the lateral membrane after P10, molecular motors mature to augment nonlinear capacitance. Thus, current estimates of motor protein density based on charge movement may be exaggerated. A corresponding indicator of motor maturation, the motor’s operating voltage midpoint, Vpkcm, tended to shift to depolarized potentials during postnatal development, although it was unstable prior to P10. However, after P14, Vpkcm reached a steady-state level near −67 mV, suggesting that intrinsic membrane tension or intracellular chloride, each of which can modulate Vpkcm, may mature at P14. These developmental data significantly alter our understanding of the cellular mechanisms that control cochlear amplification and provide a foundation for future analysis of genetic modifications of mouse auditory development.

Tuning in to the amazing outer hair cell: Membrane wizardry with a twist and shout

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Endoscopic transtympanic tympanoplasty in the treatment of conductive hearing loss: early results.

Objective: We describe our initial experience with endoscopic transtympanic tympanoplasty and evaluate whether this approach is adequate and minimally invasive in the treatment of conductive hearing loss. Study Design: Prospective trial. Setting: University hospital. Patients: Nine patients underwent endoscopic transtympanic tympanoplasty, with an average follow-up period of 17 months. Presurgical diagnosis was made by transtympanic endoscopy through a perforation made by OtoScan laser-assisted myringotomy in the outpatient clinic. Methods: With clean endoscopic visualization, ossiculoplasty was performed by inserting a trimmed tragal cartilage through the myringotomy perforation made by laser-assisted myringotomy. Two types of ossiculoplasty were performed: columella reconstruction and interposition. The tympanic membrane was covered with a chitin membrane or sealed with a small piece of perichondrium from the tragal cartilage. Main Outcome Measures: Perioperative and postoperative complications and preoperative and postoperative hearing. Results: Endoscopic transtympanic tympanoplasty with columella and endoscopic transtympanic tympanoplasty with interposition were performed in seven and two patients, respectively. Insertion of the cartilage was performed without conversion to a conventional otomicroscopic technique. The average hearing level before the operation was 59 dB. After the endoscopic transtympanic tympanoplasty, the average improved to the level of 27 dB, with an average air-bone gap of 11 dB. The myringotomy perforation was closed within 2 to 3 weeks. Conclusion: As opposed to conventional methods, this procedure does not require surgical exposure such as otosclerosis drilling and skin incision, and avoids the substantial risk of unnecessary injury to the chorda tympani. Endoscopic transtympanic tympanoplasty for a disrupted ossicular chain is an adequate and minimally invasive procedure and should prove to be a useful surgical procedure in future endoscopic tympanoplasty.

Feasibility and Advantages of Transcanal Endoscopic Myringoplasty

Objective When performing transcanal myringoplasty under a microscope, the total circumference of the perforation can be difficult to confirm in patients where the external ear canal is narrow and/or protruded. In such patients, a retroauricular incision approach is usually used. However, we have developed a transcanal endoscopic myringoplasty procedure, and the microscopic and endoscopic views are compared herein for the first time. The feasibility and advantages of transcanal endoscopic myringoplasty were examined. Study Design A prospective case series. Setting Tertiary referral center. Patients Transcanal endoscopic myringoplasty was performed on 25 ears in 21 patients with chronic otitis media between September 2011 and December 2012. Intervention Microscopic and endoscopic views were compared for each patient. The 2 fields of views were both recorded and evaluated to determine the advantages and disadvantages of microscopes and endoscopes. Myringoplasty was performed using an endoscopic technique while comparing views as necessary. Results Endoscopic views revealed the entire tympanic membrane in a single field with clear visualization of the perforation edges even when the ear canal was curved. This clear visualization facilitated reliable refreshing of the perforation edges and grafting. The anterior edge of the perforation was not visible under microscopy in 5 of 25 ears. Under an endoscopic wide view, the tympanic cavity was observable through the perforation, and the orifice of the tube, ossicular chain, and tympanic isthmus were visible especially with large perforations. Transcanal endoscopic myringoplasty was successfully performed with a simple underlay technique or with an intracanal incision in cases of marginal perforation. Conclusion Comparison of microscopic and endoscopic views revealed superior visualization and operability of the endoscopic approach as opposed to transcanal simple underlay myringoplasty. Transcanal endoscopic myringoplasty does not require surgical exposure such as a retroauricular skin incision to get an anterior view. Our results demonstrated that transcanal endoscopic myringoplasty can be performed, regardless of the perforation size and the narrowness and/or protrusion of external ear canal.

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.

Clinical and pathological characteristics of IgG4-related sclerosing sialadenitis†

A new concept of IgG4‐related sclerosing sialadenitis characterized by high serum IgG4 levels and tissue infiltration of IgG4‐expressing plasmacytes has recently been proposed. To determine appropriate serum levels of IgG4 for monitoring disease activity, a total of 36 serum samples and eight tissue samples from patients with IgG4‐related sclerosing sialadenitis were studied.