Cumulative auditory effects resulting from multiple exposure to intense acoustic stimulation.

Pt. 1. Deafening effects of noise on the cat -- Pt. 2. Histological effects of intense sound on the inner ear.

Mutation in mitochondrial DNA as a cause of presbyacusis

Much of the hearing loss that occurs in old age is likely to be due to the long-term deterioration of the mitochondria in the different structures of the cochlea. The current review surveys some of the basic information on mitochondria and mitochondrial DNA, as a background to their possible involvement in presbyacusis. It is likely that oxygen radicals damage mitochondrial DNA and other components of the mitochondria, such as their proteins and lipids. This further compromises both oxidative phosphorylation and the repair processes in mitochondria, setting up a vicious cycle of degradation. Evidence is presented from inherited point mutations on the possibly most critical sites for mutations in mitochondrial DNA associated with hearing loss. It is suggested that random sorting and clonal expansion of mutations both maintain the integrity of the pool of mitochondrial DNA molecules and give rise to the apoptosis that leads to loss of vulnerable cells, and hence to deafness. It is moreover suggested that apoptosis of the vulnerable cells of the inner ear may to some extent be preventable, or at least delayed. Copyright (C) 2004 S. Karger AG, Basel.

Infrasound initiates directional fast-start escape responses in juvenile roach Rutilus rutilus

Acoustic stimuli within the sonic range are effective triggers of C-type escape behaviours in fish. We have previously shown that fish have an acute sensitivity to infrasound also, with acceleration thresholds in the range of 10(-5) m s(-2). In addition, infrasound at high intensities around 10(-2) m s(-2) elicits strong and sustained avoidance responses in several fish species. In the present study, the possible triggering of C-escapes by infrasonic single-cycle vibrations was examined in juvenile roach Rutilus rutilus. The fish were accelerated in a controlled and quantifiable manner using a swing system. The applied stimuli simulated essential components of the accelerations that a small fish would encounter in the hydrodynamic flow field produced by a predatory fish. Typical C- and S-type escape responses were induced by accelerations within the infrasonic range with a threshold of 0.023 m s(-2) for an initial acceleration at 6.7 Hz. Response trajectories were on average in the same direction as the initial acceleration. Unexpectedly, startle behaviours mainly occurred in the trailing half of the test chamber, in which the fish were subjected to linear acceleration in combination with compression, i.e. the expected stimuli produced by an approaching predator. Very few responses were observed in the leading half of the test chamber, where the fish were subjected to acceleration and rarefaction, i.e. the stimuli expected from a suction type of predator. We conclude that particle acceleration is essential for the directionality of the startle response to infrasound, and that the response is triggered by the synergistic effects of acceleration and compression.

Postnatal developmental expression of the PDZ scaffolds Na+-H+ exchanger regulatory factors 1 and 2 in the rat cochlea

Sensory transduction in the mammalian cochlea requires the maintenance of specialized fluid compartments with distinct ionic compositions. This is achieved by the concerted action of diverse ion channels and transporters, some of which can interact with the PDZ scaffolds, Na+-H+ exchanger regulatory factors 1 and 2 (NHERF-1, NHERF-2). Here, we report that NHERF-1 and NHERF-2 are widely expressed in the rat cochlea, and that their expression is developmentally regulated. Reverse transcription/polymerase chain reaction (RT-PCR) and Western blotting initially confirmed the RNA and protein expression of NHERFs. We then performed immunohistochemistry on cochlea during various stages of postnatal development. Prior to the onset of hearing (P8), NHERF-1 immunolabeling was prominently polarized to the apical membrane of cells lining the endolymphatic compartment, including the stereocilia and cuticular plates of the inner and outer hair cells, marginal cells of the stria vascularis, Reissner's epithelia, and tectorial membrane. With maturation (P21, P70), NHERF-1 immunolabeling was reduced in the above structures, whereas labeling increased in the apical membrane of the interdental cells of the spiral limbus and the inner and outer sulcus cells, Hensen's cells, the inner and outer pillar cells, Deiters cells, the inner border cells, spiral ligament fibrocytes, and spiral ganglion neurons (particularly type II). NHERF-1 expression in strial basal and intermediate cells was persistent. NHERF-2 immunolabeling was similar to that for NHERF-1 during postnatal development, with the exception of expression in the synaptic regions beneath the outer hair cells. NHERF-1 and NHERF-2 co-localized with glial fibrillary acidic protein and vimentin in glia. The cochlear localization of NHERF scaffolds suggests that they play important roles in the developmental regulation of ion transport, homeostasis, and auditory neurotransmission.

Flexible tactile digital feedback for clinical applications

Trauma and damage to the delicate structures of the inner ear frequently occurs during insertion of electrode array into the cochlea. This is strongly related to the excessive manual insertion force of the surgeon without any tool/tissue interaction feedback. The research is examined tool-tissue interaction of large prototype scale (12.5:1) digit embedded with distributive tactile sensor based upon cochlear electrode and large prototype scale (4.5:1) cochlea phantom for simulating the human cochlear which could lead to small scale digit requirements. This flexible digit classified the tactile information from the digit-phantom interaction such as contact status, tip penetration, obstacles, relative shape and location, contact orientation and multiple contacts. The digit, distributive tactile sensors embedded with silicon-substrate is inserted into the cochlea phantom to measure any digit/phantom interaction and position of the digit in order to minimize tissue and trauma damage during the electrode cochlear insertion. The digit is pre-curved in cochlea shape so that the digit better conforms to the shape of the scala tympani to lightly hug the modiolar wall of a scala. The digit have provided information on the characteristics of touch, digit-phantom interaction during the digit insertion. The tests demonstrated that even devices of such a relative simple design with low cost have potential to improve cochlear implants surgery and other lumen mapping applications by providing tactile feedback information by controlling the insertion through sensing and control of the tip of the implant during the insertion. In that approach, the surgeon could minimize the tissue damage and potential damage to the delicate structures within the cochlear caused by current manual electrode insertion of the cochlear implantation. This approach also can be applied diagnosis and path navigation procedures. The digit is a large scale stage and could be miniaturized in future to include more realistic surgical procedures.

Endothelin receptor B and neural crest derived melanocyte development

Neural Crest cells (NCC) constitute a unique embryonic cell population that arises between the prospective epidermis and the dorsal aspect of the neural tube of vertebrates. NCC migrate ventromedially and dorsolaterally throughout the developing embryo giving rise to the peripheral nervous system constituents and melanocytes that ultimately reside in the skin and hair follicles respectively. Mice and humans with mutations in the Endothelin receptor b (Ednrb) gene manifest strikingly similar phenotypes characterized by hypopigmentation, hearing loss and megacolon these are due to absence of melanocytes in the skin and inner ear and lack of enteric ganglia in the distal part of the gut, respectively. Piebald lethal mice and humans with Hirschsprung's disease or Waardenburg syndrome carry different mutations in the Ednrb gene. The major goals of this project were to determine whether the action of Ednrb in NCC is required prior to commitment of these cells to the melanocytic lineage and to investigate its potential participation in the actual process of commitment. In order to achieve these goals transgenic mice that express Ednrb under two different regulatory elements were created. The first, Dct-Ednrb, expresses Ednrb under the control of the DOPAchrome tautomerase (Dct) promoter to direct expression to already committed melanocyte precursors. The second, Nes-Ednrb, expresses Ednrb under the regulation of the human nestin gene second enhancer to direct expression to pre-migratory NCC. Crosses of the Dct-Ednrb mouse with piebald lethal showed that the transgene was capable of rescuing the hypopigmentation phenotype of the later. This result indicates that the action of Ednrb after NCC commit to the melanocytic lineage is sufficient for normal melanocyte development. The Dct-Ednrb was further crossed with two other hypopigmentation mutants that carry mutations in the transcription factors Sox10 and Pax3. The transgene rescued the phenotype of the Sox10 mutant only. This suggests that Ednrb interacts with Sox10 but not with Pax3 during melanocyte development. The Nes-Ednrb mice developed a hypopigmentation phenotype that was augmented when crossed with piebald lethal or lethal spotting (mutation in Edn3, the ligand for Ednrb) mice but was rescued by over expression of Edn3. These results suggest that alterations in Ednrb expression early in development affect melanocyte development. This study provides novel information necessary to better understand the early embryonic development of NCC, clarifies specific interactions between different melanogenic genes and, could eventually help in the implementation of therapies for human pigmentary genetic disorders. ^

Transgenic Expression of Endothelin Receptor-B Rescues the Aganglionosis Phenotype of Piebald Lethal Mice

Neural crest cells (NCC) are a unique population of cells in vertebrates that arise between the presumptive epidermis and the dorsal most region of the neural tube. During neurulation, NCC migrate to many regions of the body to give rise to a wide variety of cell types. NCC that originate from the neural tube at the levels of somite 1-7 colonize the gut and give rise to the enteric ganglia. The endothelin signaling pathway has been shown to be crucial for proper development of some neural crest derivatives. Mice and humans with mutations in the Endothelin receptor b (Ednrb) gene exhibit similar phenotypes characterized by hypopigmentation, hearing loss, and megacolon. Thesephenotypes are due to lack of melanocytes in the skin, inner ear and enteric ganglia in the distal portion of the colon, respectively. It is well established that Ednrb is required early during the embryonic development for normal innervation of the gut. However, it is not clear if Ednrb acts on enteric neuron precursor cells or in pre-committed NC precursors. Additionally, it is controversial whether the action of Ednrb is cell autonomous or non- autonomous. We generated transgenic mice that express Ednrb under the control of the Nestin second intron enhancer (Nes) which drives expression to pre-migrating NCC. These mice were crosses to the spontaneous mouse mutant piebald lethal, which carriers a null mutation in Ednrb and exhibits enteric aganglionosis. The Nes-Ednrb was capable of rescuing the aganglianosis phenotype of piebald lethal mutants demonstrating that expression of Ednrb in pre-committed precursors is sufficient for normal enteric ganglia development. This study provides insight in early embryonic development of NCC and could eventually have potential use in cellular therapies for Hirschsprung's disease.

Ionic composition of endolymph in teleosts: Origin and importance of endolymph alkalinity

Ionic (Na+, K+, Cl-, PO43-, pH), total CO2, total calcium and protein concentrations in the plasma and endolymph of the inner ear were compared in trout Oncorhynchus mykiss and turbot Scophthalmus maximus. In both species, saccular endolymph was characterized by high levels of K+ and total CO2 and in trout by an alkaline pH, The kinetic characteristics of proton secretion across the saccular epithelium of trout were investigated using a titration technique in which isolated saccules were mounted as closed sacs. The rate of proton secretion depends strongly on the pH of the Ringer's solution and secretion stops at a pH below 7.2, Proton secretion is driven by an energy-dependent mechanism involving basolateral ouabain-sensitive Na+/K+ exchangers. Proton secretion was partially inhibited by acetazolamide and completely inhibited in Na+-free Ringer or in the presence of 1 mmol l(-1) amiloride. A cellular model stressing the importance of proton exchange through the saccular epithelium is proposed to explain the regulation of endolymph pH, a crucial factor for the deposition of otolith calcium.

Optical micro-tomography “OPenT” allows the study of large toadfish Halobatrachus didactylus embryos and larvae

Batrachoidids, which include midshipman and toadfish are less known among embryologists, but are common in other fields. They are characteristic for their acoustic communication, and develop hearing and sound production while young juveniles. They lay large benthic eggs (>5mm) with a thick chorion and adhesive disk and slow development, which are particularly challenging for studying embryology. Here we took advantage of a classical tissue clearing technique and the OPenT open-source platform for optical tomography imaging, to image a series of embryos and larvae from 3 to 30mm in length, which allowed detailed 3D anatomical reconstructions non-destructively. We documented some of the developmental stages (early and late in development) and the anatomy of the delicate stato-acoustic organs, swimming bladder and associated sonic muscles. Compared to other techniques accessible to developmental biology labs, OPenT provided advantages in terms of image quality, cost of operation and data throughput, allowing identification and quantitative morphometrics of organs in larvae, earlier and with higher accuracy than is possible with other imaging techniques.

Sources de variation intra-populationelle de la morphologie des otolithes: asymétrie directionnelle et régime alimentaire

Otoliths are calcified structures located in Osteichthyes’ inner ear that are involved in audition and balance. Their morphology is used as an indicator of various ecological processes or properties. This application requires identifying the endogenous and exogenous factors that act simultaneously as sources of shape variation. This thesis aims at detecting and quantifying the relative contributions of directional asymmetry and diet to otolith shape variation at the intra-population level. Directional asymmetry between left and right otoliths was found in flat-fishes, the blind-side otolith being always longer and larger, whereas it was negligible in round-fishes. However, asymmetry amplitude never exceeded 18 %, which suggests evolutionary canalization of otolith shape symmetry. A correlation between global diet and otolith was detected in 4 species studied in situ. Diet composition contributed more than food amount to morphological variation and affected otolith shape both globally and locally. An experimental study on sea bass (Dicentrarchus larbrax) showed that diet composition in terms of essential polyunsaturated fatty acids at larval stage affects otolith morphogenesis during juvenile stage without impacting on individuals’ somatic growth. This result suggests a direct effect of diet on otolith shape and not an indirect one through the somatic-otolith growth relationship. This effect disappeared at later stages, morphogenetic trajectories converging back to a similar shape, which suggests ontogenetic canalization of otolith shape.

Vocal differentiation parallels development of auditory saccular sensitivity in a highly soniferous fish

Vocal differentiation is widely documented in birds and mammals but has been poorly investigated in other vertebrates, including fish, which represent the oldest extant vertebrate group. Neural circuitry controlling vocal behaviour is thought to have evolved from conserved brain areas that originated in fish, making this taxon key to understanding the evolution and development of the vertebrate vocal-auditory systems. This study examines ontogenetic changes in the vocal repertoire and whether vocal differentiation parallels auditory development in the Lusitanian toadfish Halobatrachus didactylus (Batrachoididae). This species exhibits a complex acoustic repertoire and is vocally active during early development. Vocalisations were recorded during social interactions for four size groups (fry: <2 cm; small juveniles: 2-4 cm; large juveniles: 5-7 cm; adults >25 cm, standard length). Auditory sensitivity of juveniles and adults was determined based on evoked potentials recorded from the inner ear saccule in response to pure tones of 75-945 Hz. We show an ontogenetic increment in the vocal repertoire from simple broadband-pulsed 'grunts' that later differentiate into four distinct vocalisations, including low-frequency amplitude-modulated 'boatwhistles'. Whereas fry emitted mostly single grunts, large juveniles exhibited vocalisations similar to the adult vocal repertoire. Saccular sensitivity revealed a three-fold enhancement at most frequencies tested from small to large juveniles; however, large juveniles were similar in sensitivity to adults. We provide the first clear evidence of ontogenetic vocal differentiation in fish, as previously described for higher vertebrates. Our results suggest a parallel development between the vocal motor pathway and the peripheral auditory system for acoustic social communication in fish.

An study on ear detection and its applications to face detection

[EN]OpenCV includes di erent object detectors based on the Viola-Jones framework. Most of them are specialized to deal with the frontal face pattern and its inner elements: eyes, nose, and mouth. In this paper, we focus on the ear pattern detection, particularly when a head pro le or almost pro le view is present in the image. We aim at creating real-time ear detectors based on the general object detection framework provided with OpenCV. After training classi ers to detect left ears, right ears, and ears in general, the performance achieved is valid to be used to feed not only a head pose estimation system but also other applications such as those based on ear biometrics.

Evaluation of capillaries with different inner coatings for DNA analysis using dilute polymer solutions by capillary electrophoresis

In this work three capillary columns, one with uncoated inner wall and two with covalently-bound internal coatings - poly(vinyl alcohol) (PVA) and poly(dimethylacrylamide) (PDMA) - both covalently covered - were used to separate DNA fragments and compared to DNA separation using replaceable polymer solutions. The separations were performed using hydroxyethylcellulose (HEC) (90-105 kDa) in concentrations ranging from 0.00 to 2.00% m/v. The results indicated that the separation efficiency was higher in the PVA capillary than in the PDMA in all evaluated concentrations of HEC. In addition, higher resolution was also observed in PVA-coated capillary since in PDMA the shape of the peaks was not reproducible when subsequent runs were performed. Contrary to what has previously been reported in the literature, no reasonable separation was possible in bare fused silica.

Distortion product otoacoustic emissions in schoolchildren: Effects of ear asymmetry, handedness and gender

The present study examined effects of ear asymmetry, handedness, and gender on distortion-product otoacoustic emissions (DPOAEs) obtained from schoolchildren. A total of 1003 children (528 boys and 475 girls), with a mean age of 6.2 years (SD = 0.4, range = 5.2-7.9 years), were tested in a quiet room at their schools using the GSI-60 DPOAE system. A distortion-product (DP)-gram was obtained for each ear, with f2 varying from 1.1 to 6.0 kHz and the ratio of f2/f1 at 1.21. The signal-to-noise ratios (SNRs) (DPOAE amplitude minus the mean noise floor) at the tested frequencies 1.1, 1.5, 1.9, 2.4, 3.0, 3.8, 4.8, and 6.0 kHz were measured. The results revealed a small but significant difference in SNR between ears, with right ears showing a higher mean SNR than left ears at 1.9, 3.0, 3.8, and 6.0 kHz. At these frequencies, the difference in mean SNR between ears was less than 1 dB. A significant gender effect was also found. Girls exhibited a higher SNR than boys at 3.8, 4.8, and 6.0 kHz. The difference in mean SNR, as a result of the gender effect, was about 1 to 2 dB at these frequencies. There was no significant difference in mean SNR between left-handed and right-handed children for all tested frequencies.

Permeabilization of E-coli K12 inner and outer membranes by bothropstoxin-I, A LYS49 phospholipase A2 from Bothrops jararacussu

Although lacking catalytic activity, the Lys49-PLA(2)s damage artificial membranes by a Ca2+-independent mechanism, and demonstrate a potent bactericidal effect. The relationship between the membrane-damaging activity and bactericidal effect of bothropstoxin-I (BthTx-1), a Lys49-PLA(2) from the venom of Bothrops jararacussu, was evaluated for the wildtype protein and a series of site-directed mutants in the active site and C-terminal regions of the protein. The membrane permeabilization effect against the inner and outer membranes of Escherichia coli K12 was evaluated by fluorescence changes of Sytox Green and N-phenyl-N-naphthylamine, respectively. With the exception of H48Q, all mutants reduced the bactericidal activity, which correlated with a reduction of the permeabilization effect both against the inner bacterial membrane. No significant differences in the permeabilization of the bacterial outer membrane were observed between the native, wild-type recombinant and mutant proteins. These results suggest different permeabilization mechanisms against the inner and outer bacterial membranes. Furthermore, the structural determinants of bacterial inner membrane damage identified in this study correlate with those previously observed for artificial membrane permeabilization, suggesting that a common mechanism of membrane damage underlies the two effects. (C) 2007 Elsevier Ltd. All rights reserved.