Perchlorate and chlorate reduction by the Crenarchaeon Aeropyrum pernix and two thermophilic Firmicutes

This study reports the ability of one hyperthermophile and two thermophilic microorganisms to grow anaerobically by the reduction of chlorate and perchlorate. Physiological, genomic and proteome analyses suggest that the Crenarchaeon Aeropyrum pernix reduces perchlorate with a periplasmic enzyme related to nitrate reductases, but that it lacks a functional chlorite-disproportionating enzyme (Cld) to complete the pathway. A. pernix, previously described as a strictly aerobic microorganism, seems to rely on the chemical reactivity of reduced sulfur compounds with chlorite, a mechanism previously reported for perchlorate-reducing Archaeoglobus fulgidus. The chemical oxidation of thiosulfate (in excessive amounts present in the medium) and the reduction of chlorite result in the release of sulfate and chloride, which are the products of a biotic-abiotic perchlorate reduction pathway in A. pernix. The apparent absence of Cld in two other perchlorate-reducing microorganisms, Carboxydothermus hydrogenoformans and Moorella glycerini strain NMP, and their dependence on sulfide for perchlorate reduction is consistent with observations made on A. fulgidus. Our findings suggest that microbial perchlorate reduction at high temperature differs notably from the physiology of perchlorate- and chlorate-reducing mesophiles and that it is characterized by the lack of a chlorite dismutase and is enabled by a combination of biotic and abiotic reactions.This research was financially supported by Shell Global Solutions International BV. Research of AJMS is supported by ERC grant (project 323009) and the Gravitation grant (project 024.002.002) of the Netherlands Ministry of Education, Culture and Science and the Netherlands Science Foundation (NWO). Sequencing data for strain NMP have been submitted to the European Nucleotide Archive (ENA) under accession number PRJEB8377. Mass spectrometry proteomics data and database search results have been deposited to the ProteomeXchange Consortium (Vizcaino et al., 2014) via the PRIDE partner repository with the dataset identifier PXD001683 and DOI 0.6019/PXD001683

Ontwikkelingen in direct akoestisch cochleaire stimulatie

Developments in direct acoustic cochlear stimulation:Hearing problems have been associated with poor quality of life, cognitive decline and a source of frustration. Over the past years, an essential progress has been made in hearing aids improving the wearing comfort, speech processing in noise and wireless connectivity. In a subgroup of patients with a combination of an important sensorineural hearing loss and a conductive component, defined as severe to profound mixed hearing loss, hearing rehabilitation was lagging behind. Conventional middle ear surgery and/or hearing aids would not suffice to overcome the degree of hearing loss and often local anatomical issues were complicating the hearing aid use. This subgroup is growing in number because of an increased awareness for hearing with two ears and for communicating. Also because of an aging population, the sensorineural hearing loss component is becoming increasingly important.With the recent development of a new hearing system, a direct acoustic cochlear implant (DACI), the inner ear can be stimulated acoustically at the oval window. In this way, the amplified signal is provided directly to the cochlea and pathological external and middle ear structures are bypassed. This dissertation explores, for the first time, the functioning of direct acoustic cochlear stimulation in several domains. First, as guidance for evidence-based research, a systematic review of the literature on the hearing rehabilitation of mixed hearing loss was carried out. Next, the clinical application and thorough evaluation of DACI compared to the best current alternative are described. Finally, objective electrophysiological measures and new coupling strategies for DACI are developed.In the first study, the clinical outcome and safety of a whole range of acoustic hearing implants in adults with mixed hearing loss was assessed through a systematic review of the literature. It was concluded that acoustic hearing implants and the respective various coupling strategies were beneficial in terms of speech perception in quiet, patient-reported outcome measures and safety regarding residual hearing. Overall, the level of evidence and the quality of the included studies was judged to be moderate to low.The second study consisted of a prospective, multicenter evaluation of nineteen subjects with severe to profound mixed hearing loss due to several etiologies. The DACI treatment was compared to the best-aided preoperative treatment. The mean speech reception threshold (SRT), a measure for speech in noise understanding and representative for real-life communication, improved with 7.9 dB compared to the preoperative aided condition for the study cohort. A mean postoperative aided SRT of 2.6 dB SNR was noted. Patient-reported questionnaires indicated a significant global benefit in hearing ability and in quality of life. The DACI surgery was regarded as a safe and efficient treatment.In the third study, we focused on the development of an objective electrophysiological assessment of the device s coupling and stimulation of the entire auditory pathway. By investigating the feasibility of evoked auditory transient (ABR) and steady-state responses (ASSR), we opened the path for future intra-operative applications. Responses were recorded to click trains in the 40 Hz and 90 Hz range in three DACI subjects. A direct stimulation setup for reliable auditory response recording was developed in a first set of experiments. Next, by comparing amplitude growth function and phase delay in the same stimulus range, validity of the recorded responses was confirmed in DACI subjects. Electrophysiological stimulation thresholds could objectively be determined from the ABRs and ASSRs in all subjects and the relation with behavioral thresholds was made. Estimated latencies were in agreement with electrophysiological auditory pathway studies, with apparent latencies of about 40 and 25 ms for 40 and 90 Hz, respectively. For the first time, auditory evoked potentials could reliably be recorded and analyzed in patients with a digital speech processing DACI.The fourth study aimed to explore the coupling of a DACI transducer to an anatomically easy accessible inner ear site, being the lateral semicircular canal (LC). This could simplify and shorten the surgical procedure. Fresh-frozen human cadaver heads were implanted with the DACI device stimulating the LC in different coupling situations. The LC was kept intact, blue-lined (i.e. thinning but keeping the last shell of bone closed) or opened, respectively, and each condition was compared with standard oval window coupling. As a measure of the performance of the device and its coupling efficiency, the round window velocity was determined using a laser Doppler vibrometry setup. Pairwise comparisons in three frequency ranges showed that round window velocity was significantly lower in case of intact LC stimulation than in the standard oval window coupling condition, confirming the added value of direct inner ear stimulation. Equivalent output calculations showed a modest but significant added value of blue-lining over the intact condition. Opening the canal resulted in a significantly higher round window velocity than in the intact or blue-lined conditions for all frequency ranges, similar to the oval window coupling. Experimentally induced stapes footplate fixation did not impede the DACI performance when stimulating the opened LC.In the different studies in this project important steps have been made towards reliable hearing rehabilitation, even in difficult listening situations, objective electrophysiological measures and easier surgery in the challenging treatment of severe to profound mixed hearing loss.nrpages: 176status: publishe

Outcome of temporal bone carcinomas: a multidisciplinary approach

status: publishe

Research Insights on Neural Effects of Auditory Deprivation and Restoration in Unilateral Hearing Loss: A Systematic Review

Neuroplasticity following bilateral deafness and auditory restoration has been repeatedly investigated. In clinical practice, however, a significant number of patients present a severe-to-profound unilateral hearing loss (UHL). To date, less is known about the neuroplasticity following monaural hearing deprivation and auditory input restoration. This article provides an overview of the current research insights on the impact of UHL on the brain and the effect of auditory input restoration with a cochlear implant (CI). An exhaustive systematic review of the literature was performed selecting 38 studies that apply different neural analyses techniques. The main results show that the hearing ear becomes functionally dominant after monaural deprivation, reshaping the lateralization of the neural network for auditory processing, a process that can be considered to influence auditory restoration. Furthermore, animal models predict that the onset time of UHL impacts auditory restoration. Hence, the results seem to advocate for early restoration of UHL, although further research is required to disambiguate the effects of duration and onset of UHL on auditory restoration and on structural neuroplasticity following UHL deprivation and restoration. Ongoing developments on CI devices compatible with Magnetic Resonance Imaging (MRI) examinations will provide a unique opportunity to investigate structural and functional neuroplasticity following CI restoration more directly.</jats:p

Indications and outcome of subtotal petrosectomy for active middle ear implants

status: publishe

Research Insights on Neural Effects of Auditory Deprivation and Restoration in Unilateral Hearing Loss: A Systematic Review

Neuroplasticity following bilateral deafness and auditory restoration has been repeatedly investigated. In clinical practice, however, a significant number of patients present a severe-to-profound unilateral hearing loss (UHL). To date, less is known about the neuroplasticity following monaural hearing deprivation and auditory input restoration. This article provides an overview of the current research insights on the impact of UHL on the brain and the effect of auditory input restoration with a cochlear implant (CI). An exhaustive systematic review of the literature was performed selecting 38 studies that apply different neural analyses techniques. The main results show that the hearing ear becomes functionally dominant after monaural deprivation, reshaping the lateralization of the neural network for auditory processing, a process that can be considered to influence auditory restoration. Furthermore, animal models predict that the onset time of UHL impacts auditory restoration. Hence, the results seem to advocate for early restoration of UHL, although further research is required to disambiguate the effects of duration and onset of UHL on auditory restoration and on structural neuroplasticity following UHL deprivation and restoration. Ongoing developments on CI devices compatible with Magnetic Resonance Imaging (MRI) examinations will provide a unique opportunity to investigate structural and functional neuroplasticity following CI restoration more directly.status: publishe

Indications and outcome of subtotal petrosectomy for active middle ear implants

The aim of this study was to describe the outcome and possible complications of subtotal petrosectomy (SP) for Vibrant Soundbridge (VSB) device surgery in a tertiary referral center. A secondary objective was the evaluation of hearing results in a subgroup of subjects who received the VSB device. Between 2009 and early 2011, 22 adult subjects with chronic otitis media (COM) underwent a SP, blind sac closure of the external auditory canal and abdominal fat obliteration to facilitate the application of an active middle ear implant (AMEI) in a staged procedure. Indications consisted of mixed hearing loss after previous tympanomastoplasty and failure of hearing rehabilitation with a hearing aid or bone conduction device in COM. Pre- and postoperative pure-tone audiograms were analyzed in respect to deterioration of inner ear function, unaided and aided (hearing aid, bone-anchored hearing aid and VSB) speech audiograms were compared to verify improvements in communications skills and functional gains. Incidence and type of complications were reviewed. No significant change was observed regarding mean bone conduction thresholds after the first stage procedure. Some minor wound healing problems were noted. Speech perception using the VSB (n = 16) showed a mean aided speech discrimination at 65-dB SPL of 75 % [standard deviation (SD) 28.7], at 80-dB SPL of 90 % (SD 25.1). Our results suggest that for selected patients with open mastoid cavities and chronic middle ear disease, SP with abdominal fat obliteration is an effective and safe technique to facilitate safe AMEI placement.status: publishe

Acoustic Hearing Implants for Mixed Hearing Loss: A Systematic Review

A systematic review of literature to determine the clinical outcome and safety of the range of acoustic hearing implants (AHIs) in adults with mixed hearing loss (MHL).status: publishe

Alteration of the relative vibration of the round window membrane after implantation of a direct acoustic cochlear implant

Objective: Subjects implanted with a Direct Acoustic Cochlear Implant (DACI) show improvements in their bone conduction (BC) thresholds after surgery. We hypothesised that a new pathway for BC sound is created via the DACI. The aim of this study was to investigate the contribution of this pathway to the cochlear response via measurements of the promontory and round window membrane (RWM) velocities while stimulating with a conventional bone conductor.Design: This study was a cadaver head study with a repeated measures study design.Study Sample: Eight ears of five fresh-frozen cadaveric whole heads were investigated in this trial.Results: After DACI implantation the promontory and RWM velocities did not change significantly in the frequency range 0.5-2 kHz when the DACI was switched off.Conclusions: No significant changes in the relative vibration magnitude of the RWM after DACI implantation were observed. The improvements in BC thresholds seen in patients implanted with a DACI very likely have their origin in the changed impedance at the oval window after DACI surgery leading to a more efficient contribution from the inner ear components to BC sound.status: Published onlin