Asunto(s)
Tronco Encefálico/fisiología , Núcleo Coclear/fisiología , Sordera/cirugía , Electrodos Implantados , Nervio Vestibulococlear/patología , Adulto , Tronco Encefálico/diagnóstico por imagen , Tronco Encefálico/patología , Núcleo Coclear/diagnóstico por imagen , Núcleo Coclear/patología , Sordera/etiología , Sordera/fisiopatología , Europa (Continente) , Humanos , Neurofibromatosis 2/complicaciones , Neurofibromatosis 2/patología , Neurofibromatosis 2/cirugía , Neuroma Acústico/complicaciones , Neuroma Acústico/patología , Neuroma Acústico/cirugía , Selección de Paciente , Tomografía Computarizada por Rayos X , Estados UnidosRESUMEN
This study, using mice, correlated serum osmotic pressure, experimentally elevated with an intravenous injection of glycerol of varying tonicity (1.3, 2.6 and 5.2 g glycerol/kg body weight) with endolymphatic sac (ES) response. The injection produced a rise in serum osmotic pressure that was measured after 15 min (from 308 +/- 12.9 mosm/kg b.w. to 320 +/- 1.9, 353 +/- 19.3, 427 +/- 9.4 mosm/kg b.w., respectively). Normal levels were noted about 60 min after the injection. The ES was graphically displayed at 0 min, 1, 2 and 4 h using as a basis composite electron micrographs. The ES responded with signs of active secretion and degradation of macromolecular substances which appeared to be related to the rise in serum osmotic pressure. The study showed that the ES responds to glycerol injection with fine structural changes indicative of increased intra-epithelial synthesis of sugar/protein residues which are secreted and degraded within its lumen. The technique used made it possible to characterize the ultrastructural secretory pathways from the epithelial cells into the sac lumen. The results indicate that the ES may sense and respond to dynamic changes of the micro-osmotic environment probably via alterations in inner ear fluid homeostasis.
Asunto(s)
Saco Endolinfático/fisiología , Glicerol/farmacología , Equilibrio Hidroelectrolítico/fisiología , Animales , Saco Endolinfático/efectos de los fármacos , Saco Endolinfático/ultraestructura , Femenino , Homeostasis , Soluciones Hipertónicas/farmacología , Masculino , Ratones , Microscopía Electrónica , Concentración Osmolar , Presión OsmóticaRESUMEN
In observing the fine structure of the human endolymphatic sac (ES) by transmission electron microscopy, we defined the cytologic characteristics of the epithelial lining of the various portions of the sac and identified five types of epithelial cells with presumably somewhat different functions. The morphologic findings may suggest that the human ES is involved in endolymph resorption and phagocytosis. In addition, there are indications that in humans the sac may be involved in pressure regulation in the internal ear. The ES has a possible role in the turnover of macular statoconia.
Asunto(s)
Oído Interno/ultraestructura , Saco Endolinfático/ultraestructura , Capilares/ultraestructura , Citoplasma/ultraestructura , Conducto Endolinfático/anatomía & histología , Saco Endolinfático/anatomía & histología , Saco Endolinfático/irrigación sanguínea , Saco Endolinfático/fisiología , Células Epiteliales , Epitelio/ultraestructura , Humanos , Microvellosidades/ultraestructura , Terminología como AsuntoRESUMEN
Ototoxic drugs of the aminoglycoside type have been shown to accumulate to melanin, suggesting a possible mechanism for their ototoxicity. The present study was undertaken by combining electrophysiologic and morphologic methods to investigate whether the ototoxicity of kanamycin is different in pigmented and albino guinea pigs. In pigmented animals a kanamycin dose of 200 mg per kilogram of body weight per day resulted in hearing loss together with loss of both inner and outer hair cells. The albino animals in the same dose group showed significantly less hearing loss and hair cell degeneration. With daily doses of 20 and 60 mg/kg/day, no difference in ototoxicity was found between the pigmented and albino animals. The results support the hypothesis that affinity of kanamycin to inner ear melanin might be responsible for the difference in ototoxicity between albino and pigmented guinea pigs.