Perilymphatic potassium changes and potassium homeostasis in isolated semicircular canals of the frog.
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1. Endolymphatic and perilymphatic potassium concentrations were measured with K(+)-sensitive microelectrodes in isolated semicircular canals of the frog. K+ levels were evaluated both at rest and during sinusoidal stimulation (0.05 Hz) of the sensory organ. 2. Mechanical stimulation of hair cells was associated with sinusoidal changes (about 0.2 mM) in the perilymphatic K+ concentration. 3. Perilymphatic K(+)-fluctuations were modified neither by impairment of the synaptic transmission at cyto-neural junctions nor by chronic denervation of the crista ampullaris, thus indicating that K+ ions were actually released by hair cells. 4. Voltage-clamp experiments of the whole sensory organ showed that K+ flows across the crista ampullaris can vary from 3 X 10(11) molecules of K+ s-1 at rest up to about 15 X 10(11) molecules of K+ s-1 during mechanical stimuli. 5. Measurement of intra-ampullar K+ concentration demonstrated that the amount of K+ transported from the perilymph towards the endolymph can be rapidly altered by modifying its perilymphatic levels. This suggests that vestibular organs are endowed with K+ homeostatic mechanisms able to buffer in a very efficient way the concentration of K+ in both the fluids bathing the crista ampullaris. 6. The possible role of K+ homeostatic mechanisms in hair cell adaptation is discussed. (+info)
Perilymphatic fistula of the round window.
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Traumatic fracture of the stapes and perilymph fistula: report of a case.
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We herein report a case of traumatic fracture of the stapes accompanying vestibular window rupture with perilymph fistula, and its diagnosis and surgical procedure were discussed. In the present case, a direct force through the external auditory canal damaged not only the ossicular chain but also the vestibular window. On the exploratory tympanotomy, the complete dislocation and fracture of the stapes with a relatively huge rupture was confirmed. Perilymph fistula was repaired with a connective tissue graft, which was inserted between disrupted vestibular window and the long process of the incus. Vestibular dysfunctions disappeared within 3 days, and a satisfactory audiologic result was obtained one month after surgery. (+info)