ABSTRACT
This study assesses several electrocochleographic (ECoG) duration and amplitude measures in a clinically defined Meniere's group and compares the results with those from a normal hearing control group and a hearing loss group (cochlear). The summating potential (SP)/action potential (AP) amplitude ratio was the most efficient diagnostic measure, with 62% of the Meniere's group demonstrating abnormal ratios compared to 4% of the normal control group and 17% of the cochlear group. The SP changes were then studied from three angles: 1. Comparison of SP changes with glycerol test results; 2. Comparison of ECoG results before and after shunt surgery; and 3. Recording of SP's in guinea pig ears in which hydrops had been created by obliterating the endolymphatic duct.
Subject(s)
Evoked Potentials, Auditory , Meniere Disease/physiopathology , Action Potentials , Animals , Audiometry, Evoked Response , Glycerol , Guinea Pigs , Hearing Loss, Sensorineural/physiopathology , Humans , Meniere Disease/diagnosis , Meniere Disease/surgery , Time FactorsABSTRACT
Horseradish peroxidase was injected into the foramen magnum and oval window of guinea pigs to determine perilymphatic communication routes and boundaries. The primary route to the auditory system appeared to be through the cochlear aqueduct. Perineural spaces of the eighth nerve contributed to this communication and provided the principal perilymphatic communication routes to the vestibular system. Light and electron microscopic examination were used to identify membrane permeability and define boundaries in the epithelial lining of the auditory and vestibular endorgans.
Subject(s)
Ear, Inner/anatomy & histology , Labyrinthine Fluids/physiology , Perilymph/physiology , Animals , Basilar Membrane/ultrastructure , Cell Membrane Permeability , Cochlear Aqueduct/ultrastructure , Ear, Inner/physiology , Guinea Pigs , Horseradish Peroxidase , Organ of Corti/cytology , Saccule and Utricle/ultrastructure , Tectorial Membrane/ultrastructure , Vestibulocochlear NerveABSTRACT
Vertebrate lateral line and vestibular systems center their function on highly mechanosensitive hair cells. Each hair cell is equipped with one kinocilium (which resembles a motile cilium) and 50-100 actin-containing stereocilia (which resemble microvilli) at the site of stimulus reception. This report describes electron-microscopic localization of calcium-binding sites on the sensory processes of vertebrate hair cells. Using the Oschman-Wall technique for calcium localization [Oschman, J. L. & Wall, B. J. (1972) J. Cell Biol. 55, 58-73] together with electron-probe x-ray microanalysis of thin sections, we observed: (i) calcium- and iron-containing deposits in the region of the ciliary necklace in goldfish lateral line hair cells, (ii) calcium deposits upon the surface of stereocilia of hair cells of the bullfrog inner ear, and (iii) calcium deposits upon stereocilia of hair cells of the guinea pig vestibular system.
Subject(s)
Calcium/metabolism , Hair Cells, Auditory/metabolism , Animals , Electron Probe Microanalysis , Fishes , Guinea Pigs , Rana catesbeiana , Saccule and Utricle/metabolismABSTRACT
Electronic cochlear prostheses are currently being implanted in the profoundly deaf. Little, however, is known about the biologic effects of electrical stimulation of the auditory system. To study some effects of intracochlear electrical stimulation in monkeys, a totally implantable device that produces a constant current similar to that produced by devices now used in human implantation was designed and miniaturized. This paper reports on the characteristics of the device and a pilot project designed to test it in vivo. The feasibility of primate implantation and behavioral observation, as well as histopathologic study, was also determined. The device was implanted in each of two Macacca nemestrina monkeys, which were then observed. One monkey was killed and the implanted cochlea studied with scanning electron microscopy. Evidence of osteogenesis of the scala tympani was found.
