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PubMedDate not supplied

Effect of the acoustic reflex on inner ear damage induced by industrial noise.

Shipyard noise is a variable noise which induces permanent threshold shift (PTS) in exposed workers. In humans, the stapedius reflex has been found to be very stable in this type of exposure. Temporary threshold shift (TTS) in the absence of stapedius reflex has been found to extend downwards through the speech-frequencies instead of showing a high frequency dip as when the stapedius reflex is normal. The features of PTS produced by the same type of noise was investigated in rabbits with and without functioning middle ear muscles. The auditory sensitivity was measured by auditory brain stem response (ABR) and by the stapedius reflex response. Middle ear muscle function was blocked by denervation of the stapedius muscle or by general anesthesia. With normal middle ear reflex very little PTS was found. When the muscles were inactivated during the noise exposure the PTS was very extensive and covered the mid frequency range. On the basis of previous findings in humans and the present animal study it is suggested that the features of the stapedius reflex should be considered both in assessment of individual susceptibility and design of optimal acoustic environments.

Animals↗
PubMed1991

Localization of nerve growth factor receptor in developing inner ear of rats.

NGFR-immunoreactivity was first detected in the epithelia of the otic placode at E 10 and the entire epithelium of the otic vesicles was NGFR-immunoreactive at E 11. At this stage no nerve fibers were present in the epithelia and the immunoreactivity was confined to portions of the otic epithelium where the immunoreactive nerve bundles penetrated. As the development proceeded and the organ of Corti was matured, NGFR-immunoreactivity was localized on the plasma membrane of intraepithelial nerve fibers, that of adjacent epithelial cells apposed to the nerve fibers, and apical microvillous membrane of the supporting cells directly apposed to the hair cells. The occurrence of NGFR-immunoreactivity in the otic epithelial cells from early stages of development suggests that NGFR in the epithelia might provide a means to concentrate NGF on the cells which would become the substratum for growing nerve fibers in development. Furthermore, the specific appearance of NGFR-immunoreactivity in the apical microvillous membrane of the maturing supporting cells implies that NGF secreted into the endolymph from somewhere in the otic epithelia may exert some, yet to be defined effects on the supporting cells in the maturation of the organ of Corti.

Animals↗
PubMed1995

Cochlear blood flow and labyrinthine pressure: effects of glycerol on the inner ear.

Changes in cochlear blood circulation (CoBC) and perilymphatic pressure (Pp) after administration of physiological saline and 50% glycerol (12 ml/kg) were measured simultaneously in guinea pigs to examine the influence of glycerol on CoBC and Pp. The CoBC was measured by the laser-Doppler method. Although neither CoBC nor Pp changed after administration of physiological saline, glycerol produced a marked increase in CoBC and a slight decrease in Pp in 11 of 15 animals. However, the increase in CoBC was transient; CoBC reached a peak as soon as 30 min after glycerol administration and then returned rapidly to its initial value within 1 h after administration, although the Pp was still decreasing. Therefore, the response of CoBC to glycerol does not seem to be directly related to hyperosmolarity due to glycerol administration.

Animals↗
PubMed1995

Cell proliferation in the endolymphatic sac in situ after inner ear immunostimulation.

Cell proliferation in the endolymphatic sac (ES) after immunostimulation was assessed immunohistochemically. Guinea pigs were employed as experimental animals and keyhole limpet hemocyanin was used as the antigen. After i.p. injection of 5-bromo-2'-deoxyuridine (BrdUrd), the BrdUrd+ cells were counted to assess the number of proliferating cells. In the secondary immune reaction of the ES, the IgG+ cell count in the perisaccular region was markedly increased on days 7-14. An increased number of BrdUrd+ cells was detected, peaking on day 3, and the localization of these cells in the ES was similar to that of the IgG+ cells. This suggests that some BrdUrd+ cells may differentiate into IgG- cells within the ES.

Animals↗
PubMed1996

Measles virus in otosclerosis and the specific immune response of the inner ear.

Histologic and immunohistochemical studies of otosclerotic lesions have shown that there is a chronic inflammatory reaction of the otic capsule with bone resorption resulting from vascular invasion accompanied by inflammatory cells. During the active lytic stage of otosclerosis, paramyxoviral structures have been identified by electron microscopy and measles virus antigen expression by immunohistochemistry. Recently, measles virus related sequences have been detected in tissue of otosclerotic lesions. Because the otosclerotic focus has a close relation to the perilymphatic space, the expression of measles virus antigens within it should represent an immunologic challenge to the immune system of the endolymphatic sac. In this study, measles virus specific antibodies were detected in all of the perilymph samples from 19 patients suffering from otosclerosis, and the relative amount of these IgG antibodies was much higher than in serum samples of the same patients or in perilymph of control patients. These findings support the hypothesis that measles viruses play an crucial role in the pathogenesis of otosclerosis.

Antibodies, Viral↗
PubMed1997

Electron probe X-ray microanalysis of otoconia in guinea pig inner ear: a comparison between young and old animals.

Using the electron probe X-ray microanalysis technique, the elemental composition of otoconia was analysed in both young and old normal pigmented guinea pigs. Calcium concentration in both the utricular and the saccular otoconia was lower in the old animals, which indicates that the loss of calcium from otoconia and/or decrease in calcium ion uptake may occur in the old animals. The present study has established that calcium and other elements (P, S, Cl and K) in the otoconia of the young animals are related via a linear function, indicating that P, S, Cl and K are present in the mineral phase of the otoconia. The associations of Ca-P, Ca-K and Ca-S are not maintained in the old animals. It has been suggested that the aging phenomenon may influence the ionic metabolism in the vestibular end organs resulting in the altered mineral composition of otoconia.

Aging↗