摘要:

Mice homozygous for a defect of the tub (rd5) gene exhibit cochlear and retinal degeneration combined with obesity, and resemble certain human autosomal recessive sensory deficit syndromes. To establish the progressive nature of sensory cell loss associated with the tub gene, and to differentiate tub-related losses from those associated with the C57 background on which tub arose, we evaluated cochleas and retinas from tub/ tub, tub/+, and +/+ mice, aged 2 weeks to 1 year by light and electron microscopy. Cochleas from mice of all three genotypes show progressive inner (IHC) and outer hair cell (OHC) loss. Relative to tub/+ and +/+ animals, however, tub homozygotes show accelerated OHC loss, affecting the extreme cochlear base (hook region) by 1 month, and the apex by 6 months. IHC loss in tub/tub animals is accelerated in the basal half of the cochlea, affecting the hook region by 6 months. Spiral ganglion cell losses were observed only in tub/tub mice, and only in the cochlear base. Retinas of tub/tub mice are abnormal at maturity, exhibiting shortened photoreceptor outer segments by 2 weeks, and progressive photoreceptor loss thereafter. Because the tub mutation causes degeneration of sensory cells in the ear and eye but has no other neurological effects, tubby mice hold unique promise for the study of human syndromic sensory loss.

ISSN:1420-3030    

DOI:10.1159/000259242

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

The compound action potential (CAP) thresholds provide a reliable indicator for cochlear functional integrity during experimentation in birds as well as in mammals. However, if experimental manipulations are necessary in the middle ear/ inner ear spaces, the round window electrodes are often inconvenient. In search for an alternative for CAP recordings, intracranial recordings of acoustically evoked field potentials from the nucleus angularis/magnocellularis were made in pigeons using stereotactically placed electrodes. The responses were compared with those recorded from intracranial surface electrodes placed on the dura mater and compared with CAP responses recorded from the round window. The field potentials recorded from the nucleus angularis/magnocellularis contain a significant contribution from the auditory nerve, as large in amplitude as the CAP recorded at the round window. The recordings from the intracranial surface electrodes were noisier and the contribution from the auditory nerve was too small to be used as a fast monitor of the condition of the inner ear. Threshold curves as a function of frequency could be determined with an automated method from the nucleus angularis/magnocellularis with the same sensitivity and accuracy as from the round window CAP within a few minutes. These results demonstrate that stereotactic recordings of field potentials from the nucleus magnocellularis/angularis region are a suitable alternative to reliably monitor the condition of the inner ear when round window electrodes cannot be used.

ISSN:1420-3030    

DOI:10.1159/000259243

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

The effects of an extract from Ginkgo biloba, EGb 761, on tinnitus were tested using an animal model of tinnitus. Daily oral administration of EGb 761 in doses from 10 to 100 mg/ kg/day began 2 weeks before behavioral procedures and continued until the end of the experiment. Tinnitus was induced by daily administration of 321 mg/kg sodium salicylate s.c. (corresponding to 275 mg/kg/day of salicylate acid) in fourteen groups of pigmented rats, 6 animals/group. The results from salicylate- and EGb-761-treated animals were compared to control groups receiving either salicylate, saline, or EGb 761 only in doses of 100 mg/kg. Administration of EGb 761 resulted in a statistically significant decrease of the behavioral manifestation of tinnitus for doses of 25, 50 and 100 mg/kg/ day.

ISSN:1420-3030    

DOI:10.1159/000259244

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

The topographic arrangement of vestibular nerve fibers innervating semicircular canal cristae of the chinchilla was studied using computer-aided video-microscopy and three-dimensional reconstruction. At the level 20 µm proximal to the base of the crista, bundles consisting of 30-50 nerve fibers each were identified. Nerve fibers in bundles were classified into seven categories depending on the diameter. We confirmed that large nerve fibers were more frequently found in the central bundles and small nerve fibers were more frequently found in the peripheral bundles. The central bundle might function as a physiological unit coding various types of head movements, whereas the peripheral bundle might contribute more to the detection of slow and long-lasting movements giving rise to tonus and posture changes. The canalicular nerve may code rotational acceleration of the head via function- and locus-specific nerve fiber bundles

ISSN:1420-3030    

DOI:10.1159/000259245

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

Thirty-one postlingually deafened adults with 22-channel cochlear implant were evaluated preoperatively using vestibular function tests, the caloric test and stabilometry. The results of caloric response were classified into two diagnostic groups: normo- or hyporeflexia and areflexia. Stabilometric recordings were made using a computerized static posturographic platform. Between the two categories of caloric response, there was a significant difference in consonant recognition, but the recognition of vowels showed no significant difference. The results of the distance of body sway in stabilometry, but not of the area, correlated to the results of consonant recognition in speech perception tests. The degree of residual vestibular function seems to be one of the indicators influencing postoperative speech recognition by cochlear implant patients.

ISSN:1420-3030    

DOI:10.1159/000259246

出版商:S. Karger AG    

年代:1997

数据来源: Karger

ISSN:1420-3030    

DOI:10.1159/000259247

出版商:S. Karger AG    

年代:1997

数据来源: Karger

ISSN:1420-3030    

DOI:10.1159/000259248

出版商:S. Karger AG    

年代:1997

数据来源: Karger