Induction of immune-mediated hearing loss in SCID mice by injection of MRL/lpr mouse spleen cells.

Induction of immune-mediated hearing loss in SCID mice by injection of MRL/lpr mouse spleen cells The MRL/lpr mouse, which has a mutation in the Fas gene encoding a cell-surface receptor for apoptosis, shows an accumulation of abnormal immunocompetent cells and SLE-like disease. It has recently been reported that this mouse also manifests sensorineural hearing loss (SHL) with cochlear pathology at 20 weeks of age. We examined the effects of injecting MRL/lpr spleen cells on the development of SHL in severe combined immunodeficient (SCID) mice, which originally develop neither SHL nor cochlear pathology. Immune-mediated SHL and cochlear pathology were, indeed, transferred to the SCID mice by the injection of spleen cells from the MRL/lpr mice. These findings suggest that cell-mediated immunity is involved in the development of SHL and cochlear pathology.

Anionic sites of charge barrier in the guinea pig crista ampullaris.

In present studies we obtained anionic sites in the epithelial and capillary basement membranes in the dark cell area of the crista ampullaris in the guinea pig. The immersion method with cationic tracer polyethyleneimine (PEI) was applied. Electronmicroscopically, the arrangement of PEI particles was observed as two strata along the basement membrane. The number of particles could be counted and compared in each portion. The control test with protamine sulfate showed that the number of PEI particles decreased in both the epithelium and capillaries of the dark cell area. In the experiment using furosemide, the stria vascularis and the dark cells had changed, with pathological findings of interstitial edema and PEI particles reduced in number. It is suggested that the PEI particles reflect different conditions of charge in the basement membrane, which influences the production or absorption of the inner ear fluid.

Menière's disease and autoimmunity: clinical study and survey.

In order to clarify whether autoimmune mechanisms form part of the etiopathogenesis of Meniere's disease, sera and endolymphatic sac tissues from 30 patients with Meniere's disease were analyzed according to the clinical criteria for autoimmune diseases stated by Mackay & Burnet. Several cases showed hyper gamma-globulinemia, antibody elevation to Type II collagen in the serum and endolymph, positive staining to immunoglobulins and C3 or infiltration of immuno-competent cells in the endolymphatic sac, good response to prednisolone and combination with systemic immune disorders. Other examinations showed a significant elevation of OKT 4/8 ratio and a decrease of OKT8-positive cells, and elevated levels of circulating immune complex and antiviral antibody titers. It is suggested that certain cases of Meniere's disease may have an altered immunological background, which may be attributed to an autoimmune mechanism dependent on humoral and/or cellular responses.

Surgical anatomy for infralabyrinthine approach to the internal auditory canal.

Surgical anatomy for infralabyrinthine approach to the internal auditory canal was evaluated using human temporal bone in order to understand advantages and disadvantages of this approach. The procedure is extracranial without any damage of labyrinth. Lateral exposure of the internal auditory canal allows for easy separation of the cochlear and vestibular nerves. There are some potential problems of little importance stemming from anatomical variations, such as high jugular bulb, forward positioned sigmoid sinus and poor pneumatization of the infralabyrinthine space. This approach offers access to the eighth cranial nerve with minimal risk and morbidity.

Alterations of charge barrier in the inner ear following immune reactions.

We investigated electron microscopically the changes of anionic sites of a charge barrier in the capillary basement membrane of the stria vascularis and endolymphatic sac following inner ear immune reactions. Hartley guinea pigs were immunized with bovine type II collagen, keyhole limpet hemocyanin, or horseradish peroxidase, with boosted and challenged antigens through the stylomastoid foramen. Animals were killed painlessly from several days up to 56 days after the antigen challenge. Polyethylenimine was used as a cationic tracer in order to observe the localization of anionic sites of the charge. In the animals immunized with bovine type II collagen or horseradish peroxidase, a significant decrease of anionic charge in the stria and the sac was found in the early stage of immunization. However, the keyhold limpet hemocyanin immunization group did not show any remarkable changes in the charge because of its lesser transfer into the inner ear due to of its high molecular weight and negative surface charge. A decrease of the charge under immunologic conditions may induce a hyperpermeability of vessels and a malabsorption of endolymph, and thus may cause endolymphatic hydrops.

Delayed endolymphatic hydrops and its relationship to Meniére's disease.

Delayed endolymphatic hydrops (EH) can be characterized as having ipsilateral and contralateral types. They are similar in that both have early and late phases of otologic symptoms and that the early phase is a profound hearing loss in one ear. The late phases differ, however, in that the ipsilateral type develops the symptoms of EH (episodic vertigo) in the deaf ear and the contralateral type develops the symptoms of EH (fluctuating hearing loss and/or episodic vertigo) in the hearing ear. In more than half the cases of both types of delayed EH, the profound hearing losses in the early phase are simply discovered to be present in early childhood without a known time of onset. The temporal bones of two patients with contralateral delayed EH show pathologic changes in the deaf ears that are similar to those known to occur in mumps and measles labyrinthitis, whereas the pathologic changes in the hearing ears are similar to those known to occur in Meniere's disease. These observations support the proposition that Meniere's disease may occur as a delayed sequela of inner ear damage sustained during an attack of subclinical viral labyrinthitis occurring in childhood.

Retrograde cochlear neuronal degeneration in human subjects.

The purpose of this study was to identify the structural changes in the organ of Corti that correlate with retrograde cochlear neuronal degeneration. Thirty-eight temporal bones with excellent histological preparation from 23 subjects having hearing losses caused by cochlear disease were selected for study. Cytohistograms were prepared for inner and outer hair cells, inner and outer pillar cells, inner phalangeal cells, and cochlear neurons. The extent of neuronal degeneration was found to be directly related to the extent of injury to inner pillar cells and inner phalangeal cells, but not to loss of inner or outer hair cells. In most cochleas the loss of dendritic nerve fibers exceeded the loss of cell bodies. The findings support the concept that retrograde neuronal degeneration is initiated by injury to the dendritic nerve fibers, secondary to collapse and/or degeneration of the inner pillar cells and inner phalangeal cells.