Akira Minekawa

Postnatal development of the organ of Corti in dominant-negative Gjb2 transgenic mice.

Hereditary hearing loss is one of the most prevalent inherited human birth defects, affecting one in 2000. A strikingly high proportion (50%) of congenital bilateral nonsyndromic sensorineural deafness cases have been linked to mutations in the GJB2 coding for the connexin26. It has been hypothesized that gap junctions in the cochlea, especially connexin26, provide an intercellular passage by which K(+) are transported to maintain high levels of the endocochlear potential essential for sensory hair cell excitation. We previously reported the generation of a mouse model carrying human connexin26 with R75W mutation (R75W+ mice). The present study attempted to evaluate postnatal development of the organ of Corti in the R75W+ mice. R75W+ mice have never shown auditory brainstem response waveforms throughout postnatal development, indicating the disturbance of auditory organ development. Histological observations at postnatal days (P) 5-14 were characterized by i) absence of tunnel of Corti, Nuels space, or spaces surrounding the outer hair cells, ii) significantly small numbers of microtubules in inner pillar cells, iii) shortening of height of the organ of Corti, and iv) increase of the cross-sectional area of the cells of the organ of Corti. Thus, morphological observations confirmed that a dominant-negative Gjb2 mutation showed incomplete development of the cochlear supporting cells. On the other hand, the development of the sensory hair cells, at least from P5 to P12, was not affected. The present study suggests that Gjb2 is indispensable in the postnatal development of the organ of Corti and normal hearing.

Cochlear outer hair cells in a dominant-negative connexin26 mutant mouse preserve non-linear capacitance in spite of impaired distortion product otoacoustic emission

Mutations in the connexin26 gene (GJB2) are the most common genetic cause of congenital bilateral non-syndromic sensorineural hearing loss. Transgenic mice were established carrying human Cx26 with the R75W mutation that was identified in a deaf family with autosomal dominant negative inheritance [Kudo T et al. (2003) Hum Mol Genet 12:995-1004]. A dominant-negative Gjb2 R75W transgenic mouse model shows incomplete development of the cochlear supporting cells, resulting in profound deafness from birth [Inoshita A et al. (2008) Neuroscience 156:1039-1047]. The Cx26 defect in the Gjb2 R75W transgenic mouse is restricted to the supporting cells; it is unclear why the auditory response is severely disturbed in spite of the presence of outer hair cells (OHCs). The present study was designed to evaluate developmental changes in the in vivo and in vitro function of the OHC, and the fine structure of the OHC and adjacent supporting cells in the R75W transgenic mouse. No detectable distortion product otoacoustic emissions were observed at any frequencies in R75W transgenic mice throughout development. A characteristic phenotype observed in these mice was the absence of the tunnel of Corti, Nuels space, and spaces surrounding the OHC; the OHC were compressed and squeezed by the surrounding supporting cells. On the other hand, the OHC developed normally. Structural features of the lateral wall, such as the membrane-bound subsurface cisterna beneath the plasma membrane, were intact. Prestin, the voltage-dependent motor protein, was observed by immunohistochemistry in the OHC basolateral membranes of both transgenic and non-transgenic mice. No significant differences in electromotility of isolated OHCs during development was observed between transgenic and control mice. The present study indicates that normal development of the supporting cells is indispensable for proper cellular function of the OHC.

Bacteriology of recurrent exacerbation of postoperative course in chronic rhinosinusitis in relation to asthma.

OBJECTIVES Co-mobidity of asthma is known to result in a poor prognosis of post-endoscopic sinus surgery (post-ESS). Bacterial infection may play a key role in recurrent pathophysiology of sinusitis in post-ESS. METHODS Forty-two patients with CRS associated with asthma undergoing ESS were enrolled. Bacterial culture was performed from the sinus cavity at the time of acute infectious episodes. Recurrence of sinonasal disease was analyzed in terms of steroid responsiveness and peak expiratory flow (PEF). RESULTS Totally 75 aspirates were obtained during post-ESS; 2 repeat aspirates from 10 patients, 3 from 5 patients, and 4 from 2 patients. Only 6 specimens (8.0%) obtained from 5 patients (11.9%) showed no growth whereas 83 isolates were recovered from 69 specimens. Sixteen patients had at least one episode of a significant decline of PEF. All except one patient complained of symptoms and signs of upper respiratory infections prior to a depression of PEF. Positive culture was obtained in 10 out of 11 patients examined at the time of acute exacerbation of CRS. CONCLUSION Bacterial infection may play a critical role of recurrent polyps and refractory symptoms during post-ESS follow-up. Moreover, worsening of sinusitis accompanies asthma exacerbation.

Clinical effectiveness of ototopical application of mupirocin ointment in methicillin-resistant Staphylococcus aureus otorrhea.

Objective: Methicillin-resistant Staphylococcus aureus (MRSA) otorrhea has become an increasing problem with regard to infection through the tympanic membrane perforation and postsurgical infection. In particular, dry ear, at the preoperative stage, is considered to be a crucial factor in surgery. We evaluated how to control MRSA otorrhea before and after ear surgery. Patients and Methods: Twenty-six patients having MRSA otorrhea were enrolled in the present study and randomly divided into 2 groups, namely, mupirocin ointment therapy for 16 patients and ofloxacin ear drops for 10 patients. Approximately 0.6 mg of mupirocin ointment was administered locally to the tympanic membrane and the promontory around and through the perforation with its adjacent external ear canal 1 to 4 times for 2 or 3 weeks at the clinic. On the other hand, ofloxacin ear drops were administered daily by the patients for 2 or 3 weeks at home. Results: Complete elimination of MRSA from the ear was obtained in all patients of the mupirocin group. This showed a significant improvement (p < 0.001) as compared with the ofloxacin group (improvement + cure rate, 40%). Local application of mupirocin did not aggravate hearing acuity of any patients who were evaluated by pure-tone audiometry before and after treatment. Conclusion: The present findings first indicate that minimally essential application of mupirocin ointment is an extremely useful ototopical agent against MRSA otorrhea without ototoxicity.

Development of distortion product otoacoustic emissions in C57BL/6J mice.

Distortion product otoacoustic emissions (DPOAEs) have been used to examine the development of hearing in the rat and gerbil. However, no reports of DPOAE measurement from the onset of hearing in mice are available. Commercially-available components were assembled and adapted to provide a suitable probe microphone and sound delivery system for measuring DPOAE in developing C57BL/6J mice. Furthermore, DPOAE data were compared with the findings of the auditory brainstem response (ABR). DPOAEs were obtained at 8 kHz from 11 days after birth, 20 kHz from 12 days, and 30 kHz from 13 days. Adult-like patterns of DPOAE were obtained 21 days at 8 and 20 kHz, and 28 days at 30 kHz. On the other hand, the ABR thresholds at 12 to 36 kHz appeared between 11 and 12 days and were saturated at 14 days. Based on these data, the onset of measureable DPOAEs in the mouse were earlier than in the rat and gerbil. The maturation of DPOAE in the mouse begins at a lower frequency in the high frequency range. In addition, the ABR threshold reached maturation earlier than DPOAE.

Surgical Management of Myringosclerosis over an Entire Perforated Tympanic Membrane by Simple Underlay Myringoplasty

The aim of our study is to demonstrate the surgical management of myringosclerosis over a perforated whole tympanic membrane using simple underlay myringoplasty. Simple underlay myringoplasty with fibrin glue was performed in 11 ears with myringosclerosis over the entire tympanic membrane. The patients were one male and ten females and their mean age was 61.8 years (range, 40–73 yr). Surgical success was defined as an intact tympanic membrane 12 months after surgery. Closure of the perforation was successful in 10 (91%) of the 11 patients. Failure of the graft occurred in one patient who then underwent a revision procedure using her stored fascia in the outpatient clinic with a successful outcome. The overall success rate was 100%. Although this study included a small number of cases, removal of myringosclerosis at the edge of a perforation is a beneficial technique for simple underlay myringoplasty in terms of the success rate and postoperative hearing threshold, especially when myringosclerosis extends over the entire tympanic membrane.

Nasal Surgery improvesContinuous Positive AirwayPressure compliance and DaytimeSleepiness in Obstructive SleepApnea Syndrome

Background: The pressure level during nasal continuous positive airway pressure (CPAP) and the compliance may be influenced by the improvement in nasal patency resulting from nasal surgery. Methods: We investigated 12 male OSAS patients, diagnosed by standard polysomnography, nasal airflow resistance, and Epworth sleepiness scale (ESS), who were evaluated before and after nasal surgery under the use of CPAP. Results: The total nasal resistance was reduced after nasal surgery in all OSAS patients. A significant difference was observed in the ESS scores postoperatively. Nasal surgery significantly improved both the CPAP pressure and the compliance in all patients. Conclusion: Nasal continuous positive airway pressure (CPAP) intolerance in obstructive sleep apnea syndrome (OSAS) patients can be adequately improved by nasal surgery. The improvement of CPAP compliance may be brought about by the reduction in applied CPAP pressure after the improvement of nasal patency.

Effectiveness of Glucocorticosteroidfor PostoperativeRecurrence of Nasal Polyps inChronic Rhinosinusitis associatedwith Asthma

Backgrounds: Asthma co-mobidity is known to be associated with a poor prognosis for chronic rhinosinusitis with nasal polyps (CRSwNP). Systemic and topical glucocorticosteroid has been proved to be effective for recurrent nasal polyps after surgery. Methods: We evaluated the steroid responsiveness and bacterial culture in 42 patients with CRSwNP associated with asthma during postoperative follow-up. Results: Seventeen patients controlled by topical glucocorticosteroid therapy did not require systemic glucocorticosteroids (non-users). The remaining 25 patients showed recurrence of nasal polyps in spite of basal medication of topical corticosteroids and required oral corticosteroids. Eight patients were considered to be steroid non-responders. On the other hand, 17 patients responded to a short-term intake of oral corticosteroids (steroid responders). There was a statistically significant difference in the detection rate of pathogens from the sinus during acute exacerbations between steroid responders and non-users of steroids. There was a significant difference in symptomatic scores only between steroid non-responders and non-users of steroids, whereas the other parameters showed no significant differences. Conclusion: Bacterial infection plays a critical role in recurrent polyps and refractory symptoms as well as in the poor response to glucocorticosteroids during postoperative followup. Keywords: Chronic

Bacteriologic Evaluation of Sinus Aspirates Taken by Balloon Catheter Devices in Chronic Rhinosinusitis: Preliminary Study

Purpose: Chronic rhinosinusitis (CRS) is known to be a polymicrobial infection involving both aerobes and Gram-positive and Gram-negative anaerobes. Accurate bacterial evaluation by adequate culture methods can justify subsequent antimicrobial strategies. Methods: Two specimens were obtained from each of 10 patients undergoing catheter-based Balloon Sinuplasty™, one from the middle meatus (endoscopic approach) and the other from the sinus (catheter-based approach). Results: The bacterial culture from the middle meatus was positive in 9 of 10 patients, including 6 different aerobes without anaerobes. The bacterial culture of aspirates from the sinuses were positive in 8 out of 10 patients, with 4 different aerobic bacteria and 4 different anaerobic bacteria. Anaerobes were isolated in 0% of middle meatus samples, which was significantly lower than the 62.5% (5/8) detected in the sinus samples. Conclusions: Bacterial culture of sinus aspirates using a catheter-based technique improves the recovery of bacterial pathogens from CRS patients.

Bacterial contamination of multiple-use atomizers commonly used in Japan.

Before performing transnasal fiberscopy to observe the nasal cavity, pharynx and larynx in outpatient clinics, nasal anesthetics and vasoconstrictive agents are routinely sprayed into the nares in order to improve patients’ comfort. Bacterial contamination of the nozzles of Venturi principle atomizer barrels and their solutions after being used for multiple patients over a long-term period without cleaning is controversial. We evaluated the potential risk of atomizer-associated cross-infection by using atomizers commonly available in Japan that use compressed air to atomize medication. Eighteen of the 23 samples (78.3%) from the external nozzle tips of the atomizers resulted in positive bacterial cultures. These detected bacteria are suggested to be colonized in the nares and to cause bacterial contamination of the atomizer. Of the 25 samples obtained from the spray of the drug solutions, 11 samples showed positive bacterial culture, whereas 16 control samples produced no growth of bacteria. The present study demonstrated that the atomizer widely used in the outpatient ENT clinics in Japan has a potential risk of causing cross-infection of patients.