Robust postmortem survival of murine vestibular and cochlear stem cells

Potential treatment strategies of neurodegenerative and other diseases with stem cells derived from nonembryonic tissues are much less subjected to ethical criticism than embryonic stem cell-based approaches. Here we report the isolation of inner ear stem cells, which may be useful in cell replacement therapies for hearing loss, after protracted postmortem intervals. We found that neonatal murine inner ear tissues, including vestibular and cochlear sensory epithelia, display remarkably robust cellular survival, even 10 days postmortem. Similarly, isolation of sphere-forming stem cells was possible up to 10 days postmortem. We detected no difference in the proliferation and differentiation potential between stem cells isolated directly after death and up to 5 days postmortem. At longer postmortem intervals, we observed that the potency of sphere-derived cells to spontaneously differentiate into mature cell types diminishes prior to the cells losing their potential for self-renewal. Three-week-old mice also displayed sphere-forming stem cells in all inner ear tissues investigated up to 5 days postmortem. In summary, our results demonstrate that postmortem murine inner ear tissue is suited for isolation of stem cells.

Comparison of musical activities of cochlear implant users with different speech-coding strategies

Speech coding might have an impact on music perception of cochlear implant users. This questionnaire study compares the musical activities and perception of postlingually deafened cochlear implant users with three different coding strategies (CIS, ACE, SPEAK) using the Munich Music Questionnaire. Overall, the self-reported perception of music of CIS, SPEAK, and ACE users did not differ by very much.

A Novel Implantable Hearing System with Direct Acoustic Cochlear Stimulation

A new implantable hearing system, the direct acoustic cochlear stimulator (DACS) is presented. This system is based on the principle of a power-driven stapes prosthesis and intended for the treatment of severe mixed hearing loss due to advanced otosclerosis. It consists of an implantable electromagnetic transducer, which transfers acoustic energy directly to the inner ear, and an audio processor worn externally behind the implanted ear. The device is implanted using a specially developed retromeatal microsurgical approach. After removal of the stapes, a conventional stapes prosthesis is attached to the transducer and placed in the oval window to allow direct acoustical coupling to the perilymph of the inner ear. In order to restore the natural sound transmission of the ossicular chain, a second stapes prosthesis is placed in parallel to the first one into the oval window and attached to the patient's own incus, as in a conventional stapedectomy. Four patients were implanted with an investigational DACS device. The hearing threshold of the implanted ears before implantation ranged from 78 to 101 dB (air conduction, pure tone average, 0.5-4 kHz) with air-bone gaps of 33-44 dB in the same frequency range. Postoperatively, substantial improvements in sound field thresholds, speech intelligibility as well as in the subjective assessment of everyday situations were found in all patients. Two years after the implantations, monosyllabic word recognition scores in quiet at 75 dB improved by 45-100 percent points when using the DACS. Furthermore, hearing thresholds were already improved by the second stapes prosthesis alone by 14-28 dB (pure tone average 0.5-4 kHz, DACS switched off). No device-related serious medical complications occurred and all patients have continued to use their device on a daily basis for over 2 years. Copyright (c) 2008 S. Karger AG, Basel.

In vitro expression of the first capsule gene of Streptococcus pneumoniae, cpsA, is associated with serotype-specific colonization prevalence and invasiveness

The polysaccharide capsule protects Streptococcus pneumoniae from phagocytosis during invasive infection, but inhibits adherence. Serotypes vary in their tendency to colonize the nasopharynx or cause invasive infection, and differences in capsule expression may play a role. Expression of the first gene of the capsule operon, cpsA, during in vitro growth of 43 clinical isolates representing 14 common pneumococcal serotypes was compared using quantitative RT-PCR. Serotypes associated with invasive infection (1, 4, 5, 7F, 8 and 14) expressed an average of twofold (P=0.0003) more cpsA than serotypes associated with nasopharyngeal colonization (6A, 6B, 9V, 15, 18C, 19F, 23F and 33). There was no difference in cpsA expression in response to growth under environmental oxygen or anaerobic conditions between the invasive and colonizing transparent strains tested: oxygen concentration did not affect cpsA expression in either the invasive or the colonizing transparent strains. Expression of cpsA at OD(600) 0.6 tended to be greater in strains with a longer lag phase during in vitro growth (P=0.07). Therefore, cpsA expression under ambient oxygen concentrations correlates with serotype-specific invasiveness and is inversely associated with the prevalence of serotype-specific carriage.

Capsule genes of Streptococcus pneumoniae influence growth in vitro

Recently, we showed that the in vitro lag phase correlates with the pneumococcal serotype. This study investigated the role of capsule genes in bacterial growth using strain D39. Deletion of the entire capsule operon induced a significantly prolonged lag phase in Todd Hewitt broth (P=0.0002). However, partial deletions showed a different influence on the lag phase. Supplementation of media with 5% fetal bovine serum restored normal growth, at least partially, in mutants with a prolonged lag phase. Therefore, pneumococcal capsule gene products influence bacterial growth in vitro in strain D39.

A homologue of aliB is found in the capsule region of nonencapsulated Streptococcus pneumoniae

The epidemiology, phylogeny, and biology of nonencapsulated Streptococcus pneumoniae are largely unknown. Increased colonization capacity and transformability are, however, intriguing features of these pneumococci and play an important role. Twenty-seven nonencapsulated pneumococci were identified in a nationwide collection of 1,980 nasopharyngeal samples and 215 blood samples obtained between 1998 and 2002. On the basis of multilocus sequence typing and capsule region analysis we divided the nonencapsulated pneumococci into two groups. Group I was closely related to encapsulated strains. Group II had a clonal population structure, including two geographically widespread clones able to cause epidemic conjunctivitis and invasive diseases. Group II strains also carried a 1,959-bp homologue of aliB (aliB-like ORF 2) in the capsule region, which was highly homologous to a sequence in the capsule region of Streptococcus mitis. In addition, strains of the two major clones in group II had an additional sequence, aliB-like ORF 1 (1,968 to 2,004 bp), upstream of aliB-like ORF 2. Expression of aliB-like ORF 1 was detected by reverse transcription-PCR, and the corresponding RNA was visualized by Northern blotting. A gene fragment homologous to capN of serotypes 33 and 37 suggests that group II strains were derived from encapsulated pneumococci some time ago. Therefore, loss of capsule expression in vivo was found to be associated with the importation of one or two aliB homologues in some nonencapsulated pneumococci.

The tolerance of ambiguity in late cochlear-implanted pre-lingually deaf juveniles

OBJECTIVES: To examine the ambiguity tolerance, i.e. the ability to perceive new, contradictory and complex situations as positive challenges, of pre-lingually deafened adolescents who received a cochlear implant after their eighth birthday and to identify those dimensions of ambiguity tolerance which correlate significantly with specific variables of their oral communication. DESIGN AND SETTING: Clinical survey at an academic tertiary referral center. Participants and main outcome measures: A questionnaire concerning communication and subjectively perceived changes compared to the pre-cochlear implant situation was completed by 13 pre-lingually deafened patients aged between 13 and 23 years, who received their cochlear implants between the ages of 8 and 17 years. The results were correlated with the 'Inventory for Measuring Ambiguity Tolerance'. RESULTS: The patients showed a lower ambiguity tolerance with a total score of 134.5 than the normative group with a score of 143.1. There was a positive correlation between the total score for ambiguity tolerance and the frequency of 'use of oral speech', as well as between the subscale 'ambiguity tolerance towards apparently insoluble problems' and all five areas of oral communication that were investigated. Comparison of two variables of oral communication, which shows a significant difference pre- and postoperatively, yields a positive correlation with the subscale 'ambiguity tolerance towards the parental image'. CONCLUSIONS: Pre-lingually deafened juveniles with cochlear implant who increasingly use oral communication seem to regard the limits of a cochlear implant as an interesting challenge rather than an insoluble problem.

A two-microphone noise reduction system for cochlear implant users with nearby microphones. Part I: Signal processing algorithm design and development

Users of cochlear implant systems, that is, of auditory aids which stimulate the auditory nerve at the cochlea electrically, often complain about poor speech understanding in noisy environments. Despite the proven advantages of multimicrophone directional noise reduction systems for conventional hearing aids, only one major manufacturer has so far implemented such a system in a product, presumably because of the added power consumption and size. We present a physically small (intermicrophone distance 7 mm) and computationally inexpensive adaptive noise reduction system suitable for behind-the-ear cochlear implant speech processors. Supporting algorithms, which allow the adjustment of the opening angle and the maximum noise suppression, are proposed and evaluated. A portable real-time device for test in real acoustic environments is presented.

A two-microphone noise reduction system for cochlear implant users with nearby microphones. Part II: Performance Evaluation

Users of cochlear implants (auditory aids, which stimulate the auditory nerve electrically at the inner ear) often suffer from poor speech understanding in noise. We evaluate a small (intermicrophone distance 7 mm) and computationally inexpensive adaptive noise reduction system suitable for behind-the-ear cochlear implant speech processors. The system is evaluated in simulated and real, anechoic and reverberant environments. Results from simulations show improvements of 3.4 to 9.3 dB in signal to noise ratio for rooms with realistic reverberation and more than 18 dB under anechoic conditions. Speech understanding in noise is measured in 6 adult cochlear implant users in a reverberant room, showing average improvements of 7.9–9.6 dB, when compared to a single omnidirectional microphone or 1.3–5.6 dB, when compared to a simple directional two-microphone device. Subjective evaluation in a cafeteria at lunchtime shows a preference of the cochlear implant users for the evaluated device in terms of speech understanding and sound quality.

Comparison of music perception in bilateral and unilateral cochlear implant users and normal-hearing subjects

Music plays an important role in the daily life of cochlear implant (CI) users, but electrical hearing and speech processing pose challenges for enjoying music. Studies of unilateral CI (UCI) users' music perception have found that these subjects have little difficulty recognizing tempo and rhythm but great difficulty with pitch, interval and melody. The present study is an initial step towards understanding music perception in bilateral CI (BCI) users. The Munich Music Questionnaire was used to investigate music listening habits and enjoyment in 23 BCI users compared to 2 control groups: 23 UCI users and 23 normal-hearing (NH) listeners. Bilateral users appeared to have a number of advantages over unilateral users, though their enjoyment of music did not reach the level of NH listeners.

Cone Beam and Micro-Computed Tomography Validation of Manual Array Insertion for Minimally Invasive Cochlear Implantation

Delivering cochlear implants through a minimally invasive tunnel (1.8 mm in diameter) from the mastoid surface to the inner ear is referred to as direct cochlear access (DCA). Based on cone beam as well as micro-computed tomography imaging, this in vitro study evaluates the feasibility and efficacy of manual cochlear electrode array insertions via DCA. Free-fitting electrode arrays were inserted in 8 temporal bone specimens with previously drilled DCA tunnels. The insertion depth angle, procedural time, tunnel alignment as well as the inserted scala and intracochlear trauma were assessed. Seven of the 8 insertions were full insertions, with insertion depth angles higher than 520°. Three cases of atraumatic scala tympani insertion, 3 cases of probable basilar membrane rupture and 1 case of dislocation into the scala vestibuli were observed (1 specimen was damaged during extraction). Manual electrode array insertion following a DCA procedure seems to be feasible and safe and is a further step toward clinical application of image-guided otological microsurgery.

Internet video telephony allows speech reading by deaf individuals and improves speech perception by cochlear implant users

OBJECTIVE To analyze speech reading through Internet video calls by profoundly hearing-impaired individuals and cochlear implant (CI) users. METHODS Speech reading skills of 14 deaf adults and 21 CI users were assessed using the Hochmair Schulz Moser (HSM) sentence test. We presented video simulations using different video resolutions (1280 × 720, 640 × 480, 320 × 240, 160 × 120 px), frame rates (30, 20, 10, 7, 5 frames per second (fps)), speech velocities (three different speakers), webcameras (Logitech Pro9000, C600 and C500) and image/sound delays (0-500 ms). All video simulations were presented with and without sound and in two screen sizes. Additionally, scores for live Skype™ video connection and live face-to-face communication were assessed. RESULTS Higher frame rate (>7 fps), higher camera resolution (>640 × 480 px) and shorter picture/sound delay (<100 ms) were associated with increased speech perception scores. Scores were strongly dependent on the speaker but were not influenced by physical properties of the camera optics or the full screen mode. There is a significant median gain of +8.5%pts (p = 0.009) in speech perception for all 21 CI-users if visual cues are additionally shown. CI users with poor open set speech perception scores (n = 11) showed the greatest benefit under combined audio-visual presentation (median speech perception +11.8%pts, p = 0.032). CONCLUSION Webcameras have the potential to improve telecommunication of hearing-impaired individuals.