Alteration of glycine receptor immunoreactivity in the auditory brainstem of mice following three months of exposure to radiofrequency radiation at SAR 4.0 W/kg.

The increasing use of mobile communication has triggered an interest in its possible effects on the regulation of neurotransmitter signals. Due to the close proximity of mobile phones to hearing-related brain regions during usage, its use may lead to a decrease in the ability to segregate sounds, leading to serious auditory dysfunction caused by the prolonged exposure to radiofrequency (RF) radiation. The interplay among auditory processing, excitation and inhibitory molecule interactions plays a major role in auditory function. In particular, inhibitory molecules, such a glycine, are predominantly localized in the auditory brainstem. However, the effects of exposure to RF radiation on auditory function have not been reported to date. Thus, the aim of the present study was to investigate the effects of exposure to RF radiation on glycine receptor (GlyR) immunoreactivity (IR) in the auditory brainstem region at 835 MHz with a specific absorption rate of 4.0 W/kg for three months using free-floating immunohistochemistry. Compared with the sham control (SC) group, a significant loss of staining intensity of neuropils and cells in the different subdivisions of the auditory brainstem regions was observed in the mice exposed to RF radiation (E4 group). A decrease in the number of GlyR immunoreactive cells was also noted in the cochlear nuclear complex [anteroventral cochlear nucleus (AVCN), 31.09%; dorsal cochlear nucleus (DCN), 14.08%; posteroventral cochlear nucleus (PVCN), 32.79%] and the superior olivary complex (SOC) [lateral superior olivary nucleus (LSO), 36.85%; superior paraolivary nucleus (SPN), 24.33%, medial superior olivary nucleus (MSO), 23.23%; medial nucleus of the trapezoid body (MNTB), 10.15%] of the mice in the E4 group. Auditory brainstem response (ABR) analysis also revealed a significant threshold elevation of in the exposed (E4) group, which may be associated with auditory dysfunction. The present study suggests that the auditory brainstem region is susceptible to chronic exposure to RF radiation, which may affect the function of the central auditory system.

Audiological findings in celiac disease.

OBJECTIVE: Celiac disease (CD) is a gluten-triggered immune enteropathy caused by a genetic predisposition. Recent papers suggest that CD is increasingly recognized by extraintestinal findings. The aim of this study was to investigate the effect of CD on hearing pathway including the olivocochlear efferent system in children. METHODS: Forty-one pediatric CD patients and 31 controls were included in the study. Both groups were evaluated with audiometry, tympanometry, transiently evoked otoacoustic emission (TEOAE), distortion product otoacoustic emission (DPOAE), and contralateral suppression of the TEOAE. RESULTS: The threshold at 250 Hz of the patients with CD was significantly higher (p < 0.05 in CD compared to control group, p < 0.0001). The signal to noise ratio (SNR) amplitudes in DPOAE testing and the SNR amplitudes with and without contralateral acoustic stimulus in TEOAE testing were significantly lower at 1,000 Hz in the CD compared to the control group. There was no significant difference between the CD and the control group regarding contralateral suppression amplitudes. CONCLUSION: CD seems to have an important impact on the auditory system, and results in an elevation of the thresholds at 250 Hz on audiometry and a decrease in the amplitudes of DPOAE and linear TEOAE at 1,000 Hz in children.

[Activation of proto-oncogene c-fos in the auditory tract of rats stimulation with wide-band noise]. / La activación del protooncogén c-fos en la vía auditiva en ratas estimuladas con ruido de banda ancha.

The pattern of expression of the proto-oncogene c-fos was mapped in the auditory pathway of Wistar rats kept in three different experimental conditions: a) a dark, soundproofed room; b) with exposure to usual environmental laboratory noise, and c) with exposure to wide-band noise. Under control conditions (a and b), scattered labeled neurons were found in the ventral periolivary nucleus, lateral lemniscus nuclei, inferior colliculus, medial nucleus of the medial geniculate body, and in three divisions of the temporal auditory cortex. Sound stimulation (c) increased the number of fos-like-immunoreactive (FLI) nuclei in all the auditory pathway structures. FLI nuclei were strong in the dorsal cochlear nucleus, anterior and posterior ventral cochlear nuclei, all the superior olivary complex nuclei, lateral lemniscus nuclei, all areas of the inferior colliculus, medial geniculate body, and the three temporal auditory areas, which showed a barrel pattern. Comparison of these results with the literature indicated that fos activation is not merely a sign of transitory neural activation, but a long-term neural processing pathway that is conditioned by factors such as the frequency, intensity, duration, and direction of the auditory stimulus.

Avian auditory pathways show met-enkephalin-like immunoreactivity.

Pathways associated with a recently defined region of the avian auditory thalamus, the shell of the nucleus ovoidalis (Ov), were examined for met-enkephalin immunoreactivity. The presence of enkephalin-like immunoreactive (ELI) perikarya within the medial margin of the inferior colliculus (ICM), afferent to the Ov shell, implicated ICM as a source of ELI fibers within the Ov shell and tract. The shell also contained ELI perikarya and its targets, including the ventromedial hypothalamus and caudoventral paleostriatal complex, were characterized by ELI fields. These data suggest that enkephalinergic auditory pathways, in parallel with traditionally recognized auditory projections, target regions of the avian basal forebrain.

Immunoelectron microscopic analysis of a novel carbohydrate differentiation antigen (CDA-3C2) in the developing rat olfactory and otic systems.

A carbohydrate differentiation antigen (CDA-3C2) exhibits a highly specific and restricted pattern of expression during rat embryogenesis. In the periphery of the embryo, this antigen is associated transiently with the lateral ectoderm but is retained only in the olfactory and otic epithelium throughout morphogenesis. At the light microscopic level, CDA-3C2 immunoreactivity appears mostly along cell periphery and in the extracellular matrix. The aim of the present study was to determine the specific cellular and subcellular distribution of CDA-3C2 in vivo in order to identify potential sites of cellular and tissue function of the antigen during embryogenesis. There was a strikingly similar subcellular distribution of CDA-3C2 in the developing otic and olfactory systems, found mostly along cell membranes, microvillar projections and acellular secretions of the epithelium. Mature sensory components of the epithelia were not immunoreactive, whereas supportive cells and their secreted structures were densely stained. The highly coincident nature of CDA-3C2 in both sensory epithelia suggests that this carbohydrate epitope, and possibly its carrier macromolecule, participate in a morphogenetic function common to these two sensory epithelia.

Immunocytochemical analysis of a novel carbohydrate differentiation antigen (CDA-3C2) associated with olfactory and otic systems during embryogenesis in the rat.

Carbohydrate differentiation antigens are known to display specific patterns of expression during mammalian development and are thought to participate in significant morphogenetic events. In the present study, two monoclonal antibodies that react with a novel carbohydrate differentiation antigen (CDA-3C2) were used to analyze, by light microscopy, the spatiotemporal distribution of this unique high molecular weight antigen during embryogenesis in the rat. Correlative analysis of the development of peripheral neural structures, in which CDA-3C2 was expressed, was carried out with an anti-neurofilament antibody. Enzymatic digestion, combined with Western blots, reveal that the CDA-3C2 epitope is a carbohydrate which is carried on a high molecular weight glycoprotein with a mass of greater than 1 million Daltons. Characteristic of carbohydrate antigens, immunoreactivity was found in several distinct cellular patterns: only along the apical border of cells, along lateral and basal membranes of cells, and extracellular-like staining in the mesenchyme. During neurulation, CDA-3C2 showed differential staining in the ectoderm, distinguishing lateral from neural regions. Following closure of the neural tube, there was a striking specificity of expression of CDA-3C2 in the periphery, found almost exclusively in olfactory and otic epithelial structures. While CDA-3C2 is found in placode-derived tissues that subserve sensory transduction, it appears to be primarily associated with the supportive cells (and their secretions) in both otic and olfactory regions and less so with the sensory cells. The data suggest that a unique carbohydrate antigen on a large macromolecule may play a role in neurulation and/or morphogenesis of the placode-derived otic and olfactory structures.

Glutamic acid decarboxylase-like immunoreactivity in brainstem auditory nuclei of the rat.

The distribution of GABA-producing neurons in the brainstem auditory nuclei of the rat was investigated immunohistochemically by using an antibody to glutamic acid decarboxylase (GAD). In the cochlear nuclei, GAD immunoreactive neurons are present only in the superficial granular and molecular layers, whereas terminals are found in all subdivisions of the nuclei and are particularly dense surrounding large spherical cells and one type of stellate cell. In the superior olivary complex, GAD immunoreactive neurons are located in the lateral olivary nucleus and throughout the periolivary region. Immunoreactive terminals are distributed along dendrites of principal cells of the medial and lateral olivary nuclei and are clustered around somata of globular neurons of the nucleus of the trapezoid body. An extremely dense band of immunoreactive somata and terminals is present along the ventral edge of the olivary complex. The ventral, intermediate, and dorsal nuclei of the lateral lemniscus contain small fusiform GAD-immunoreactive neurons and a moderately dense plexus of immunoreactive terminals. The inferior colliculus contains a large population of GAD-immunoreactive perikarya and an extremely dense accumulation of immunoreactive terminals in the central, dorsomedial, and external nuclei. These observations indicate that GABA systems are involved in function at all levels of the brainstem auditory pathway.

Calcium binding protein-like immunoreactivity labels the terminal field of nucleus laminaris of the barn owl.

Nucleus laminaris (NL) is the site at which the timing of sounds arriving in the 2 ears is compared in the auditory system of the barn owl. Earlier studies have reported vitamin D-dependent calcium binding protein (CaBP)-like immunoreactivity in the somata of NL. We report here that CaBP-like immunoreactivity stains the terminal field of NL. The specific CaBP immunoreactivity is localized to a dense plexus of fibers that have bouton-like swellings, usually around unstained somata. This type of immunoreactivity is found in a restricted portion of the central nucleus of the inferior colliculus (ICc), in the anterior division of the ventral lateral lemniscal complex (VLVA), and in the superior olivary nucleus (SO), all of which have been shown by anterograde transport of 3H-proline to be innervated by NL. The immunoreactivity is absent from the posterior division of ventral lateral lemniscal complex and from the region that surrounds the portion of ICc innervated by NL. A restricted lesion in NL results in a localized deficit in immunoreactivity in those regions of ICc and VLVA that are known to be innervated by the lesioned area of NL. In adjacent sections processed by the Fink-Heimer method, degenerating axons are present in the region of the deficit in immunoreactivity.

Appearance and development of neuron-specific enolase immunoreactivity in organotypic cultures of mouse embryo otocysts.

The appearance of neuron-specific enolase (NSE) immunoreactivity was studied in sensory and vestibular ganglion cells during the development of mouse embryo otocysts grown in vitro from the 13th gestation day. NSE appeared sequentially in the ganglion and sensory cell populations of the inner ear with a pattern that paralleled their successive maturation. Comparison with NSE immunoreactivity profile during in vivo development shows that NSE appears earlier during organotypic in vitro maturation.