Otolaryngology - Research Publications
Now showing items 1-12 of 57
Ring and peg electrodes for minimally-Invasive and long-term sub-scalp EEG recordings
OBJECTIVE: Minimally-invasive approaches are needed for long-term reliable Electroencephalography (EEG) recordings to assist with epilepsy diagnosis, investigation and more naturalistic monitoring. This study compared three methods for long-term implantation of sub-scalp EEG electrodes. METHODS: Three types of electrodes (disk, ring, and peg) were fabricated from biocompatible materials and implanted under the scalp in five ambulatory ewes for 3months. Disk electrodes were inserted into sub-pericranial pockets. Ring electrodes were tunneled under the scalp. Peg electrodes were inserted into the skull, close to the dura. EEG was continuously monitored wirelessly. High resolution CT imaging, histopathology, and impedance measurements were used to assess the status of the electrodes at the end of the study. RESULTS: EEG amplitude was larger in the peg compared with the disk and ring electrodes (p<0.05). Similarly, chewing artifacts were lower in the peg electrodes (p<0.05). Electrode impedance increased after long-term implantation particularly for those within the bone (p<0.01). Micro-CT scans indicated that all electrodes stayed within the sub-scalp layers. All pegs remained within the burr holes as implanted with no evidence of extrusion. Eight of 10 disks partially eroded into the bone by 1.0mm from the surface of the skull. The ring arrays remained within the sub-scalp layers close to implantation site. Histology revealed that the electrodes were encapsulated in a thin fibrous tissue adjacent to the pericranium. Overlying this was a loose connective layer and scalp. Erosion into the bone occurred under the rim of the sub-pericranial disk electrodes. CONCLUSIONS: The results indicate that the peg electrodes provided high quality EEG, mechanical stability, and lower chewing artifact. Whereas, ring electrode arrays tunneled under the scalp enable minimal surgical techniques to be used for implantation and removal.
Organotypic Cocultures of Human Pluripotent Stem Cell Derived-Neurons with Mammalian Inner Ear Hair Cells and Cochlear Nucleus Slices
(Hindawi Limited, 2019-11-20)
Stem cells have been touted as a source of potential replacement neurons for inner ear degeneration for almost two decades now; yet to date, there are few studies describing the use of human pluripotent stem cells (hPSCs) for this purpose. If stem cell therapies are to be used clinically, it is critical to validate the usefulness of hPSC lines in vitro and in vivo. Here, we present the first quantitative evidence that differentiated hPSC-derived neurons that innervate both the inner ear hair cells and cochlear nucleus neurons in coculture, with significantly more new synaptic contacts formed on target cell types. Nascent contacts between stem cells and hair cells were immunopositive for both synapsin I and VGLUT1, closely resembling expression of these puncta in endogenous postnatal auditory neurons and control cocultures. When hPSCs were cocultured with cochlear nucleus brainstem slice, significantly greater numbers of VGLUT1 puncta were observed in comparison to slice alone. New VGLUT1 puncta in cocultures with cochlear nucleus slice were not significantly different in size, only in quantity. This experimentation describes new coculture models for assessing auditory regeneration using well-characterised hPSC-derived neurons and highlights useful methods to quantify the extent of innervation on different cell types in the inner ear and brainstem.
Engineering Biocoatings To Prolong Drug Release from Supraparticles
(American Chemical Society, 2019-09-09)
Supraparticles (SPs) assembled from smaller colloidal nanoparticles can serve as depots of therapeutic compounds and are of interest for long-term, sustained drug release in biomedical applications. However, a key challenge to achieving temporal control of drug release from SPs is the occurrence of an initial rapid release of the loaded drug (i.e., “burst” release) that limits sustained release and potentially causes burst release-associated drug toxicity. Herein, a biocoating strategy is presented for silica-SPs (Si-SPs) to reduce the extent of burst release of the loaded model protein lysozyme. Specifically, Si-SPs were coated with a fibrin film, formed by enzymatic conversion of fibrinogen into fibrin. The fibrin-coated Si-SPs, FSi-SPs, which could be loaded with 7.9 ± 0.9 μg of lysozyme per SP, released >60% of cargo protein over a considerably longer period of time of >20 days when compared with the uncoated Si-SPs that released the same amount of the cargo protein, however, within the first 3 days. Neurotrophins that support the survival and differentiation of neurons could also be loaded at ∼7.3 μg per SP, with fibrin coating also delaying neurotrophin release (only 10% of cargo released over 21 days compared with 60% from Si-SPs). In addition, the effects of incorporating a hydrogel-based system for surgical delivery and the opportunity to control drug release kinetics were investigated—an alginate-based hydrogel scaffold was used to encapsulate FSi-SPs. The introduction of the hydrogel further extended the initial release of the encapsulated lysozyme to ∼40 days (for the same amount of cargo released). The results demonstrate the increasing versatility of the SP drug delivery platform, combining large loading capacity with sustained drug release, that is tailorable using different modes of controlled delivery approaches.
Characterizing Electrocochleography in Cochlear Implant Recipients with Residual Low-Frequency Hearing
(FRONTIERS MEDIA SA, 2017-03-23)
Objective: Lay the groundwork for using electrocochleography (ECochG) as a measure of cochlear health, by characterizing typical patterns of the ECochG response observed across the electrode array in cochlear implant recipients with residual hearing. Methods: ECochG was measured immediately after electrode insertion in 45 cochlear implant recipients with residual hearing. The Cochlear Response Telemetry system was used to record ECochG across the electrode array, in response to 100- or 110-dB SPL pure tones at 0.5-kHz, presented at 14 per second and with alternating polarities. Hair cell activity, as the cochlear microphonic (CM), was estimated by taking the difference (DIF) of the two polarities. Neural activity, as the auditory nerve neurophonic (ANN), was estimated by taking the sum (SUM) of the two polarities. Prior work in humans and animal studies suggested that the expected ECochG pattern in response to a 0.5-kHz pure tone is an apical-peak in CM amplitude and latency. Results: The most prevalent pattern was a peak in the DIF amplitude near the most apical electrode, with a prolongation of latency toward the electrode tip; this was found in 21/39 individuals with successful ECochG recordings. The 21 apical-peak recipients had the best low-frequency hearing. A low amplitude, long-latency DIF response that remained relatively constant across the electrode array was found in 10/39 individuals, in a group with the poorest low- and high-frequency hearing. A third, previously undescribed, pattern occurred in 8/39 participants, with mid-electrode peaks in DIF amplitude. These recipients had the best high-frequency hearing and a progressive prolongation of DIF latency around the mid-electrode peaks consistent with the presence of discrete populations of hair cells. Conclusions: The presence of distinct patterns of the ECochG response with relationships to pre-operative hearing levels supports the notion that ECochG across the electrode array functions as a measure of cochlear health.
Otitis media among high-risk populations: can probiotics inhibit Streptococcus pneumoniae colonisation and the risk of disease?
Otitis media is the second most common infection in children and the leading cause for seeking medical advice. Indigenous populations such as the Inuits, indigenous Australians and American Indians have a very high prevalence of otitis media and are considered to be high-risk populations. Streptococcus pneumoniae, one of the three main bacterial causes of otitis media, colonises the nasopharynx prior to disease development. In high-risk populations, early acquisition of high bacterial loads increases the prevalence of otitis media. In these settings, current treatment strategies are insufficient. Vaccination is effective against invasive pneumococcal infection but has a limited impact on otitis media. Decreasing the bacterial loads of otitis media pathogens and/or colonising the nasopharynx with beneficial bacteria may reduce the prevalence of otitis media. Probiotics are live microorganisms that offer health benefits by modulating the microbial community and enhancing host immunity. The available data suggest that probiotics may be beneficial in otitis media. This review discusses the potential use of probiotics to reduce pathogen colonisation and decrease the prevalence of otitis media, providing justification for further investigation.
Plant perception of beta-aminobutyric acid is mediated by an aspartyl-tRNA synthetase
(NATURE PUBLISHING GROUP, 2014-06-01)
Specific chemicals can prime the plant immune system for augmented defense. β-aminobutyric acid (BABA) is a priming agent that provides broad-spectrum disease protection. However, BABA also suppresses plant growth when applied in high doses, which has hampered its application as a crop defense activator. Here we describe a mutant of Arabidopsis thaliana that is impaired in BABA-induced disease immunity (ibi1) but is hypersensitive to BABA-induced growth repression. IBI1 encodes an aspartyl-tRNA synthetase. Enantiomer-specific binding of the R enantiomer of BABA to IBI1 primed the protein for noncanonical defense signaling in the cytoplasm after pathogen attack. This priming was associated with aspartic acid accumulation and tRNA-induced phosphorylation of translation initiation factor eIF2α. However, mutation of eIF2α-phosphorylating GCN2 kinase did not affect BABA-induced immunity but relieved BABA-induced growth repression. Hence, BABA-activated IBI1 controls plant immunity and growth via separate pathways. Our results open new opportunities to separate broad-spectrum disease resistance from the associated costs on plant growth.
SDHA related tumorigenesis: a new case series and literature review for variant interpretation and pathogenicity
PURPOSE: To evaluate the role of germline SDHA mutation analysis by (1) comprehensive literature review, (2) description of novel germline SDHA mutations and (3) in silico structural prediction analysis of missense substitutions in SDHA. PATIENTS AND METHODS: A systematic literature review and a retrospective review of the molecular and clinical features of patients identified with putative germline variants in UK molecular genetic laboratories was performed. To evaluate the molecular consequences of SDHA missense variants, a novel model of the SDHA/B/C/D complex was generated and the structural effects of missense substitutions identified in the literature, our UK novel cohort and a further 32 "control missense variants" were predicted by the mCSM computational platform. These structural predictions were correlated with the results of tumor studies and other bioinformatic predictions. RESULTS: Literature review revealed reports of 17 different germline SDHA variants in 47 affected individuals from 45 kindreds. A further 10 different variants in 15 previously unreported cases (seven novel variants in eight patients) were added from our UK series. In silico structural prediction studies of 11 candidate missense germline mutations suggested that most (63.7%) would destabilize the SDHA protomer, and that most (78.1%) rare SDHA missense variants present in a control data set (ESP6500) were also associated with impaired protein stability. CONCLUSION: The clinical spectrum of SDHA-associated neoplasia differs from that of germline mutations in other SDH-subunits. The interpretation of the significance of novel SDHA missense substitutions is challenging. We recommend that multiple investigations (e.g. tumor studies, metabolomic profiling) should be performed to aid classification of rare missense variants before genetic testing results are used to influence clinical management.
Gel-Mediated Electrospray Assembly of Silica Supraparticles for Sustained Drug Delivery
(AMER CHEMICAL SOC, 2018-09-19)
Supraparticles (SPs) composed of smaller colloidal particles provide a platform for the long-term, controlled release of therapeutics in biomedical applications. However, current synthesis methods used to achieve high drug loading and those involving biocompatible materials are often tedious and low throughput, thereby limiting the translation of SPs to diverse applications. Herein, we present a simple, effective, and automatable alginate-mediated electrospray technique for the assembly of robust spherical silica SPs (Si-SPs) for long-term (>4 months) drug delivery. The Si-SPs are composed of either porous or nonporous primary Si particles within a decomposable alginate matrix. The size and shape of the Si-SPs can be tailored by controlling the concentrations of alginate and silica primary particles used and key electrospraying parameters, such as flow rate, voltage, and collector distance. Furthermore, the performance (including drug loading kinetics, loading capacity, loading efficiency, and drug release) of the Si-SPs can be tuned by changing the porosity of the primary particles and through the retention or removal (via calcination) of the alginate matrix. The structure and morphology of the Si-SPs were characterized by electron microscopy, dynamic light scattering, N2 adsorption-desorption analysis, and X-ray photoelectron spectroscopy. The cytotoxicity and degradability of the Si-SPs were also examined. Drug loading kinetics and loading capacity for six different types of Si-SPs, using a model protein drug (fluorescently labeled lysozyme), demonstrate that Si-SPs prepared from primary silica particles with large pores can load significant amounts of lysozyme (∼10 μg per SP) and exhibit sustained, long-term release of more than 150 days. Our experiments show that Si-SPs can be produced through a gel-mediated electrospray technique that is robust and automatable (important for clinical translation and commercialization) and that they present a promising platform for long-term drug delivery.
Do experts practice what they profess?
(PUBLIC LIBRARY SCIENCE, 2018-01-05)
We investigated the variation of drilled regions of expert and trainee surgeons performing virtual temporal bone surgery to identify their compliance with standard drilling procedures. To this end, we recruited seven expert and six trainee ENT surgeons, who were asked to perform the surgical preparations for cochlear implantation on a virtual temporal bone. The temporal bone was divided into six regions using a semi-automated approach. The drilled area in each region was compared between groups using a sign test. Similarity within groups was calculated as a ratio of voxels (3D points) drilled by at least 75% of surgeons and at least 25% of surgeons. We observed a significant difference between groups when performing critical tasks such as exposing the facial nerve, opening the facial recess, and finding the round window. In these regions, experts' practice is more similar to each other than that between trainees. Consistent with models of skills development, expertise and expert-performance, the outcome of the analysis shows that experts perform similarly in critical parts of the procedure, and do indeed practice what they profess.
Enriched retinal ganglion cells derived from human embryonic stem cells
(NATURE PUBLISHING GROUP, 2016-08-10)
Optic neuropathies are characterised by a loss of retinal ganglion cells (RGCs) that lead to vision impairment. Development of cell therapy requires a better understanding of the signals that direct stem cells into RGCs. Human embryonic stem cells (hESCs) represent an unlimited cellular source for generation of human RGCs in vitro. In this study, we present a 45-day protocol that utilises magnetic activated cell sorting to generate enriched population of RGCs via stepwise retinal differentiation using hESCs. We performed an extensive characterization of these stem cell-derived RGCs by examining the gene and protein expressions of a panel of neural/RGC markers. Furthermore, whole transcriptome analysis demonstrated similarity of the hESC-derived RGCs to human adult RGCs. The enriched hESC-RGCs possess long axons, functional electrophysiological profiles and axonal transport of mitochondria, suggestive of maturity. In summary, this RGC differentiation protocol can generate an enriched population of functional RGCs from hESCs, allowing future studies on disease modeling of optic neuropathies and development of cell therapies.
Influence of Cochleostomy and Cochlear Implant Insertion on Drug Gradients following Intratympanic Application in Guinea Pigs
Locally applied drugs can protect residual hearing following cochlear implantation. The influence of cochlear implantation on drug levels in the scala tympani (ST) after round window application was investigated in guinea pigs using the marker trimethylphenylammonium (TMPA) measured in real time with TMPA-selective microelectrodes. TMPA concentration in the upper basal turn of the ST rapidly increased during implantation and then declined due to cerebrospinal fluid entering the ST at the cochlear aqueduct and exiting at the cochleostomy. The TMPA increase was found to be caused by the cochleostomy drilling if the burr tip partially entered the ST. TMPA distribution in the second turn was less affected by implantation procedures. These findings show that basal turn drug levels may be changed during implantation and the changes may need to be considered in the interpretation of therapeutic effects of drugs in conjunction with implantation.
Deriving accurate microbiota profiles from human samples with low bacterial content through post-sequencing processing of Illumina MiSeq data
(BIOMED CENTRAL LTD, 2015-05-05)
BACKGROUND: The rapid expansion of 16S rRNA gene sequencing in challenging clinical contexts has resulted in a growing body of literature of variable quality. To a large extent, this is due to a failure to address spurious signal that is characteristic of samples with low levels of bacteria and high levels of non-bacterial DNA. We have developed a workflow based on the paired-end read Illumina MiSeq-based approach, which enables significant improvement in data quality, post-sequencing. We demonstrate the efficacy of this methodology through its application to paediatric upper-respiratory samples from several anatomical sites. RESULTS: A workflow for processing sequence data was developed based on commonly available tools. Data generated from different sample types showed a marked variation in levels of non-bacterial signal and 'contaminant' bacterial reads. Significant differences in the ability of reference databases to accurately assign identity to operational taxonomic units (OTU) were observed. Three OTU-picking strategies were trialled as follows: de novo, open-reference and closed-reference, with open-reference performing substantially better. Relative abundance of OTUs identified as potential reagent contamination showed a strong inverse correlation with amplicon concentration allowing their objective removal. The removal of the spurious signal showed the greatest improvement in sample types typically containing low levels of bacteria and high levels of human DNA. A substantial impact of pre-filtering data and spurious signal removal was demonstrated by principal coordinate and co-occurrence analysis. For example, analysis of taxon co-occurrence in adenoid swab and middle ear fluid samples indicated that failure to remove the spurious signal resulted in the inclusion of six out of eleven bacterial genera that accounted for 80% of similarity between the sample types. CONCLUSIONS: The application of the presented workflow to a set of challenging clinical samples demonstrates its utility in removing the spurious signal from the dataset, allowing clinical insight to be derived from what would otherwise be highly misleading output. While other approaches could potentially achieve similar improvements, the methodology employed here represents an accessible means to exclude the signal from contamination and other artefacts.