RESUMEN
Obesity-related disorders are closely associated with the development of age-related hearing impairment (ARHI). Adiponectin (APN) exerts protective effects against obesity-related conditions including endothelial dysfunction and atherosclerosis. Here, we investigated the impact of APN on ARHI. APN-knockout (APN-KO) mice developed exacerbation of hearing impairment, particularly in the high frequency range, compared with wild-type (WT) mice. Supplementation with APN prevented the hearing impairment in APN-KO mice. At 2 months of age, the cochlear blood flow and capillary density of the stria vascularis (SV) were significantly reduced in APN-KO mice as compared with WT mice. APN-KO mice also showed a significant increase in terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive apoptotic cells in the organ of Corti in the cochlea at 2 months of age. At the age of 6 months, hair cells were lost at the organ of Corti in APN-KO mice. In cultured auditory HEI-OC1 cells, APN reduced apoptotic activity under hypoxic conditions. Clinically, plasma APN levels were significantly lower in humans with ARHI. Multiple logistic regression analysis identified APN as a significant and independent predictor of ARHI. Our observations indicate that APN has an important role in preventing ARHI.
Asunto(s)
Adiponectina/deficiencia , Envejecimiento/patología , Progresión de la Enfermedad , Pérdida Auditiva/metabolismo , Adiponectina/sangre , Adiponectina/metabolismo , Adiponectina/farmacología , Animales , Apoptosis/efectos de los fármacos , Umbral Auditivo/efectos de los fármacos , Capilares/patología , Línea Celular , Potenciales Evocados Auditivos del Tronco Encefálico/efectos de los fármacos , Células Ciliadas Auditivas/efectos de los fármacos , Células Ciliadas Auditivas/patología , Pérdida Auditiva/sangre , Pérdida Auditiva/patología , Pérdida Auditiva/fisiopatología , Humanos , Masculino , Ratones Noqueados , Persona de Mediana Edad , Órgano Espiral/irrigación sanguínea , Órgano Espiral/efectos de los fármacos , Órgano Espiral/patología , Órgano Espiral/fisiopatología , Flujo Sanguíneo Regional/efectos de los fármacosRESUMEN
Gap junctions (GJs) facilitate communication and promote transfer of signaling molecules or current between adjacent cells in various organs to coordinate cellular activity. In arteries, homocellular GJs are present between adjacent smooth muscle cells (SMCs) and between adjacent endothelial cells (ECs), whilst many arteries also exhibit heterocellular GJs between SMCs and ECs. To test the hypothesis that there is differential cell coupling in guinea pig spiral modiolar arteries (SMA), we used intracellular recording technique to record cellular activities simultaneously in ECs or SMCs in acutely isolated guinea pig SMA preparations. Cell types were identified by injection of a fluorescent dye, propidium iodide (PI), through recording microelectrodes. Stable intracellular recordings were made in 120 cells among which 61 were identified as SMCs and 28 as ECs. Dual intracellular recordings were conducted to detect the coexistence of the two distinct levels of resting potential (RP) and to estimate the intensity of electrical coupling between two cells by a current pulse of up to 0.5-1.5 nA. The electrotonic potential was detected not only in the current-injected cell, but also in the majority of non-injected cells. The electrical coupling ratios (ECRs) of homocellular cells were not significant (P>0.05) (0.084±0.032 (n=6) and 0.069±0.031 (n=7) for EC-EC and SMC-SMC pairs, respectively). By contrast, the ECRs of heterocellular cells were significantly different when a current pulse (1.5 nA, 2s) was injected into EC and SMC respectively (0.072±0.025 for EC; 0.003±0.001 for SMC, n=5, P<0.01). The putative gap junction blocker 18ß-glycyrrhetinic acid significantly attenuated electrical coupling in both homocellular and heterocellular forms. The results suggest that homocellular GJs within SMCs or ECs are well coordinated but myoendothelial couplings between ECs and SMCs are unidirectional.
Asunto(s)
Comunicación Celular , Endotelio Vascular/fisiología , Uniones Comunicantes/fisiología , Músculo Liso Vascular/fisiología , Órgano Espiral/irrigación sanguínea , Animales , Arterias/fisiología , Comunicación Celular/efectos de los fármacos , Estimulación Eléctrica , Endotelio Vascular/efectos de los fármacos , Uniones Comunicantes/efectos de los fármacos , Ácido Glicirretínico/análogos & derivados , Ácido Glicirretínico/farmacología , Cobayas , Potenciales de la Membrana , Microscopía Fluorescente , Músculo Liso Vascular/efectos de los fármacos , Factores de TiempoRESUMEN
The protective benefits of hypoxic preconditioning (HPC) against permanent noise-induced hearing loss (NIHL) were investigated in mice. Hypoxia induced by exposure to 8% O2 for 4 h conferred significant protection against damaging broadband noise delivered 24-48 h later in male and female CBA/J (CBA) and CBA/CaJ mice. No protection was found in C57BL/6 (B6) mice, their B6.CAST-Cdh23(CAST) (B6.CAST) congenics, or in CBAxB6 F1 hybrid mice over the same interval, suggesting that the potential for HPC depends on one or a few autosomal recessive alleles carried by CBA-related strains, and is not influenced by the Cdh23 locus. Protection against NIHL in CBA mice was associated with significant up-regulation of hypoxia-inducible factor-1alpha (HIF-1alpha) within the organ of Corti, not found in B6.CAST. In both CBA and B6.CAST mice, some hypoxia-noise intervals shorter than 24 h were associated with exacerbation of NIHL. Cellular cascades underlying the early exacerbation of NIHL by hypoxia are therefore common to both strains, and not mechanistically linked to later protection. Elucidation of the events that underlie HPC, and how these are impacted by genetics, may lead to pharmacologic approaches to mimic HPC, and may help identify individuals with elevated risk of NIHL.
Asunto(s)
Pérdida Auditiva Provocada por Ruido/genética , Pérdida Auditiva Provocada por Ruido/prevención & control , Precondicionamiento Isquémico/métodos , Animales , Animales Congénicos , Cadherinas/genética , Cóclea/patología , Potenciales Evocados Auditivos del Tronco Encefálico , Femenino , Pérdida Auditiva Provocada por Ruido/patología , Pérdida Auditiva Provocada por Ruido/fisiopatología , Hipoxia/fisiopatología , Subunidad alfa del Factor 1 Inducible por Hipoxia/genética , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos CBA , Órgano Espiral/irrigación sanguínea , Órgano Espiral/fisiopatología , Especificidad de la Especie , Factores de Tiempo , Regulación hacia ArribaRESUMEN
This study was designed to evaluate the effect of recombinant human erythropoietin (rhEPO), insulin-like growth factor-1 (rhIGF-1) and epidermal growth factor (rhEGF) on ischemia-induced hair cell loss in an organotypic cochlea culture. The apical, middle and basal parts of the organs of Corti (newborn rat, postnatal days 3-5) were exposed to ischemia (3.5 h) in glucose-free artificial perilymph (pO2 10-20 mmHg) with or without growth factors. Controls were exposed to normoxia. Twenty-four hours after the onset of ischemia, the cultures were stained using tetramethyl rhodamine isothiocyanate (TRITC) phalloidin (hair cells), propidium iodide (membrane integrity) and apoptosis detection kit (DNA-fragmentation). Ischemia (3.5 h) induced a hair cell loss of 20 and 40% in the middle and basal cochlear parts, respectively, and an increase of the numbers of PI-stained and DNA-fragmented nuclei (controls 0-1, ischemia 4-7 nuclei/100 microm). The basal part was more affected than the apical one. rhEPO and rhIGF-1 significantly attenuated the ischemia-induced hair cell loss by reducing processes involved in apoptosis and necrosis. rhEPO has been in clinical use for more than a decade and found to be well tolerated. Therefore, rhEPO could be an effective drug for the prevention of hearing loss via a hair cell protective mechanism.
Asunto(s)
Factor de Crecimiento Epidérmico/farmacología , Eritropoyetina/farmacología , Células Ciliadas Auditivas/efectos de los fármacos , Células Ciliadas Auditivas/patología , Factor I del Crecimiento Similar a la Insulina/farmacología , Isquemia/patología , Órgano Espiral/irrigación sanguínea , Animales , Animales Recién Nacidos , Apoptosis/efectos de los fármacos , Factor de Crecimiento Epidérmico/genética , Eritropoyetina/genética , Células Ciliadas Auditivas/irrigación sanguínea , Humanos , Técnicas In Vitro , Factor I del Crecimiento Similar a la Insulina/genética , Isquemia/complicaciones , Necrosis/patología , Necrosis/prevención & control , Órgano Espiral/efectos de los fármacos , Órgano Espiral/patología , Ratas , Proteínas Recombinantes/administración & dosificaciónRESUMEN
The relationship between hyperlipidemia and sensorineural hearing loss remains obscure. In this study, we elucidate for the first time the cochlear morphological and auditory alterations and their relationships with hyperlipidemia, atherosclerosis, and endothelial dysfunction in apolipoprotein-E knockout (ApoE-KO) mice. Ten-week-old ApoE-KO mice were fed either atherosclerotic diet (1.25% cholesterol) or normal diet. Wild type mice (C57BL/6J) served as normal controls. Fourteen weeks later, marked hyperlipidemia, atherosclerosis, endothelial dysfunction, and hearing impairment, especially in the high frequencies, had developed in ApoE-KO mice as compared with C57BL/6J mice (P<0.001). A high positive correlation between hearing loss and the extent of atherosclerosis and plasma total cholesterol levels was found. Hearing loss, especially at high frequencies, was detected in all ApoE-KO mice. Hair cell loss mainly at the base turn, thickening of vascular intima, and lumen stenosis of the spiral modiolar artery (SMA) in cochlea were also found; these histological changes were exacerbated by the atherosclerotic diet. Furthermore, endothelial nitric oxide synthase (eNOS) in aortic wall and cochlea was distinctly reduced in ApoE-KO mice. These results demonstrate that hyperlipidemia and atherosclerosis can induce alterations in cochlear morphology and function. The stenosis of SMA, which may cause cochlear ischemia and hypoxia, endothelial dysfunction, and low eNOS activity, may contribute to hearing loss.
Asunto(s)
Apolipoproteínas E/deficiencia , Cóclea/patología , Cóclea/fisiopatología , Acetilcolina/farmacología , Animales , Aorta/efectos de los fármacos , Aorta/fisiopatología , Apolipoproteínas E/genética , Aterosclerosis/complicaciones , Aterosclerosis/genética , Umbral Auditivo , Colesterol/sangre , Endotelio Vascular/efectos de los fármacos , Endotelio Vascular/fisiopatología , Femenino , Células Ciliadas Auditivas/patología , Pérdida Auditiva Sensorineural/etiología , Pérdida Auditiva Sensorineural/patología , Pérdida Auditiva Sensorineural/fisiopatología , Hiperlipidemias/complicaciones , Hiperlipidemias/genética , Técnicas In Vitro , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Óxido Nítrico Sintasa de Tipo II/metabolismo , Óxido Nítrico Sintasa de Tipo III , Órgano Espiral/irrigación sanguínea , Órgano Espiral/patología , Vasodilatación/efectos de los fármacosRESUMEN
To quantitate in absolute terms the prestin mRNA levels in the explant culture of rat cochlea, we used competitive RT-PCR with a synthetic internal cRNA standard. Prestin gene expression was found at levels of 100 fg specific mRNA/microg total RNA on postnatal day 3, which corresponds to about 300 copies per outer hair cell (OHC) and is indicative of an intermediate level of expression. Two days of culturing resulted in an increase of prestin mRNA levels and in the formation of an apical-basal gradient (p<0.001). To elucidate the variations the prestin mRNA levels undergo as a result of damage to the organ of Corti, we exposed the explant cultures to ischemia and hypoxia. While total RNA was observed to remain unchanged, the numbers of OHCs and the prestin mRNA levels were found to decrease by about 20% and 35%, respectively, compared to normoxia. In conclusion, we showed that the prestin mRNA levels during in vitro development increase and form an apical-basal gradient within 2 days in culture, similar to the postnatal in vivo development. Hypoxia and ischemia result in a decrease of the prestin mRNA level in parallel with OHC loss. The prestin mRNA level can therefore be used as marker of damage to or loss of OHCs.
Asunto(s)
Cóclea/metabolismo , Proteínas/metabolismo , ARN Mensajero/metabolismo , Animales , Animales Recién Nacidos , Proteínas de Transporte de Anión , Biomarcadores , Cóclea/irrigación sanguínea , Cóclea/crecimiento & desarrollo , Cóclea/patología , Expresión Génica , Células Ciliadas Auditivas Externas/irrigación sanguínea , Células Ciliadas Auditivas Externas/crecimiento & desarrollo , Células Ciliadas Auditivas Externas/metabolismo , Células Ciliadas Auditivas Externas/patología , Hipoxia/patología , Hipoxia/fisiopatología , Isquemia/patología , Isquemia/fisiopatología , Técnicas de Cultivo de Órganos , Órgano Espiral/irrigación sanguínea , Órgano Espiral/crecimiento & desarrollo , Órgano Espiral/metabolismo , Órgano Espiral/patología , Proteínas/análisis , Proteínas/genética , Ratas , Ratas Wistar , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transportadores de SulfatoRESUMEN
Hypoxia and ischemia are thought to be important pathogenetic factors in bringing about hearing loss. In order to study the effect of these determinants on the loss of inner and outer hair cells (IHCs/OHCs), we used an in vitro hypoxia and ischemia model of the newborn rat cochlea. The specimens of the organ of Corti were exposed either to hypoxia (10-20 mm Hg) or to normoxic glucose deprivation or to both (ischemia) in artificial perilymph for different exposure periods. The number of IHCs and OHCs was counted and the hair cell loss was compared to controls. Normoxic aglycemia did not cause significant hair cell loss as compared to controls. Hypoxia and ischemia led to hair cell loss in a dose-dependent manner, with the loss in the ischemia groups found to be markedly higher than that in the hypoxia groups. Hypoxia resulted in a mean loss of 8% OHC and of 14% IHC after an 8-h exposure. Ischemia increased the loss to 19% OHC and 39% IHC after the same exposure period of 8 h. Our findings suggest that IHCs are more susceptible to hypoxia/ischemia than OHCs.
Asunto(s)
Células Ciliadas Auditivas/patología , Pérdida Auditiva/etiología , Hipoxia/complicaciones , Isquemia/complicaciones , Órgano Espiral/irrigación sanguínea , Análisis de Varianza , Animales , Animales Recién Nacidos , Estudios de Casos y Controles , Modelos Animales de Enfermedad , Susceptibilidad a Enfermedades , Glucosa/química , Células Ciliadas Auditivas/irrigación sanguínea , Técnicas In Vitro , Órgano Espiral/fisiopatología , Oxígeno/química , Ratas , Ratas WistarRESUMEN
To elucidate whether ischemia-reperfusion can cause delayed cell death in the cochlea, the effects of transient cochlear ischemia on hearing and on neuronal structures in the cochlea were studied in Mongolian gerbils. Ischemia was induced by bilaterally occluding the vertebral arteries for 5 minutes in gerbils, which lack posterior cerebral communicating arteries. In gerbils, the labyrinthine arteries are fed solely by the vertebral arteries. Occlusion of the vertebral arteries caused a remarkable increase in the threshold of compound action potentials (CAPs), which recovered over the following day. However, 7 days after the onset of reperfusion, the threshold began to increase again. Morphologic changes in the hair cell stereocilia were revealed by electron microscopy. The number of nuclear collapses was counted in cells stained for DNA and F-actin to evaluate the degree of cell death in the organ of Corti. Changes in spiral ganglion cell (SGC) neuron number were detected, whether or not progressive neuronal death occurred in the SGC. These studies showed that sporadic fusion of hair cells and the disappearance of hair cell stereocilia did not begin until 4 days after ischemia. On subsequent days, the loss of hair cells, especially inner hair cells (IHCs), and the degeneration of SGC neurons became apparent. Ten days after ischemia, the mean percentage cell loss of IHCs was 6.4% in the basal turn, 6.4% in the second turn, and 0.8% in the apical turn, respectively, and the number of SGC neurons had decreased to 89% of preischemic status. These results indicate that transient ischemia causes delayed hearing loss and cell death in the cochlea by day 7 after ischemia.
Asunto(s)
Enfermedades Cocleares/etiología , Pérdida Auditiva Sensorineural/etiología , Órgano Espiral/patología , Órgano Espiral/fisiopatología , Daño por Reperfusión/complicaciones , Potenciales de Acción , Animales , Umbral Auditivo , Muerte Celular , Enfermedades Cocleares/patología , Enfermedades Cocleares/fisiopatología , Modelos Animales de Enfermedad , Progresión de la Enfermedad , Gerbillinae , Células Ciliadas Auditivas Internas/patología , Células Ciliadas Auditivas Internas/ultraestructura , Células Ciliadas Auditivas Externas/patología , Células Ciliadas Auditivas Externas/ultraestructura , Pérdida Auditiva Sensorineural/diagnóstico , Pérdida Auditiva Sensorineural/fisiopatología , Neuronas/patología , Órgano Espiral/irrigación sanguínea , Daño por Reperfusión/patología , Daño por Reperfusión/fisiopatología , Ganglio Espiral de la Cóclea/patología , Arteria Vertebral/fisiopatologíaRESUMEN
A 22-year-old-lady presented with multiple occlusions of the branches of the central retinal artery, accompanied by neuro-encephalic disorders and deafness. This triad is known as SICRET Syndrome (Small Infarction of Cochlear, Retinal and Encephalic Tissue). This rare syndrome, as well referred to as Susac syndrome, affects only the women and the three tissues mentioned above: eye, ear, brain. The course was characterised by a series of partially regressive evolutive steps. A remission had been obtained since two years with immuno-supressor and anti-coagulant therapy. The neuro-encephalic and cochlear disorder regressed in contrast to the severe sequel on the right eye.
Asunto(s)
Infarto Cerebral , Cóclea/irrigación sanguínea , Infarto , Oclusión de la Arteria Retiniana , Adulto , Anticoagulantes/uso terapéutico , Arteriolas/patología , Infarto Cerebral/complicaciones , Infarto Cerebral/tratamiento farmacológico , Sordera/etiología , Diagnóstico Diferencial , Quimioterapia Combinada , Femenino , Cefalea/etiología , Humanos , Inmunosupresores/uso terapéutico , Infarto/complicaciones , Infarto/tratamiento farmacológico , Imagen por Resonancia Magnética , Órgano Espiral/irrigación sanguínea , Prednisolona/uso terapéutico , Oclusión de la Arteria Retiniana/complicaciones , Oclusión de la Arteria Retiniana/tratamiento farmacológico , Ácido Salicílico/uso terapéutico , Síndrome , Vértigo/etiología , Trastornos de la Visión/etiología , Warfarina/uso terapéuticoRESUMEN
The histologic evaluation of the influence of unilateral stimulation and of the ligation of vertebral artery on the hearing organ in guinea pigs were studied. The material consisted of 20 guinea pigs of both sexes, weight 250-300 g. It was proved that the ligation of the unilateral vertebral artery caused hypoxial lesions in the brainstem and subsequently secondary lesions in the spiral ganglion. One side stimulation of above mentioned artery caused the unilateral brainstem lesions as well as the spiral ganglion ones. The more expressed lesions were found in the cochlear nuclei in the ligation group.
Asunto(s)
Isquemia Encefálica/patología , Tronco Encefálico/irrigación sanguínea , Modelos Animales de Enfermedad , Isquemia/patología , Órgano Espiral/irrigación sanguínea , Animales , Isquemia Encefálica/etiología , Tronco Encefálico/ultraestructura , Femenino , Cobayas , Isquemia/etiología , Ligadura , Masculino , Microscopía Electrónica , Órgano Espiral/ultraestructura , Arteria Vertebral/cirugíaRESUMEN
This study has defined the nature and sequence of ultrastructural changes in the organ of Corti following severe, total cochlear ischemia. Afferent nerve endings of IHC became swollen within 15 min and eventually ruptured. Outer hair cells were swollen within 30 min and showed alterations to mitochondria, endoplasmic reticulum and the nucleus whereas IHC remained unchanged for up to 60 min. Both efferent and afferent nerve endings of OHC were unaltered until after 60 min ischemia. Regardless of the type, cells in the base of the cochlea developed abnormalities more rapidly than those in the apical turns. These results imply a differential susceptibility to ischemic damage both among the different cell types and along the organ of Corti.
Asunto(s)
Isquemia/patología , Órgano Espiral/lesiones , Vías Aferentes/ultraestructura , Animales , Vías Eferentes/ultraestructura , Cobayas , Células Ciliadas Auditivas/ultraestructura , Células Ciliadas Auditivas Internas/ultraestructura , Microscopía Electrónica , Terminaciones Nerviosas/ultraestructura , Órgano Espiral/irrigación sanguínea , Órgano Espiral/ultraestructura , Factores de TiempoRESUMEN
The effect of influenza infection on vessels in the stria vascularis of the spiral organ of 60 guinea-pigs infected intranasally or intranasally and intracordially was investigated. The vascular network was examined 1, 3, 7 or 14 days after infection. The animals that were infected intranasally were treated with dimephosphone administered for 7 days intraesophageally. The vessel diameter and blood flow, alkaline phosphatase in the vascular wall, adventitial cells and epithelial cells of the stripe were measured. It was found that the infection produced a strong effect on the vascular network of the stripe, especially 1 day after infection: the caliber of vessels diminished, formed elements accumulated in their lumen, alkaline phosphatase in the vascular wall and adventitial cells decreased. On day 3 alkaline phosphatase activity increased and vessel diameter normalized but congestive changes developed. Dimephosphone given for 7 days had a vasodilatory effect. These observations clarify certain aspects of the origin of hearing disorders accompanying influenza.
Asunto(s)
Cóclea , Órgano Espiral/irrigación sanguínea , Infecciones por Orthomyxoviridae/fisiopatología , Estría Vascular , Animales , Antiinflamatorios no Esteroideos/uso terapéutico , Cobayas , Trastornos de la Audición/etiología , Compuestos Organofosforados/uso terapéutico , Infecciones por Orthomyxoviridae/complicaciones , Factores de TiempoRESUMEN
The blood vessels of the cochlea were studied from birth up to adult age in the gerbil. Even at birth the principal vascular arrangement could be identified in the external wall. However, the early circulatory mainstream appeared even more predominantly radial apico-basal over radiating arterioles-arteriovenous anastomoses-collecting venules than at later stages. At birth, only small sections of capillaries could be observed in the stria vascularis. Stria vascularis achieved its adult vascular appearance rapidly between 8-10 days after birth (DAB). The rapid development of stria vascularis immediately preceded the development of cochlear function and may have been related to the development of the ionic composition of endolymph. At birth the vessel of the basilar membrane showed many large vascular connections with the collecting venules in the scala tympani of the external wall but very few supplying and draining ramifications on the medial side of the vessel. This suggests that the vessel of the basilar membrane originates from the external wall vessels, not from the spiral lamina vessels as has previously been supposed. The peripheral vascular connections degenerated rapidly after birth. The vessel, being very large at birth, degenerated completely by 15 to 20 DAB, ultimately disappearing in the basal turn. The degeneration suggests that its major importance may be during embryonic stages, with great probability for the development of the organ of Corti.
Asunto(s)
Cóclea/irrigación sanguínea , Gerbillinae/crecimiento & desarrollo , Envejecimiento , Animales , Anastomosis Arteriovenosa/anatomía & histología , Membrana Basilar/irrigación sanguínea , Capilares/crecimiento & desarrollo , Acueducto Coclear/irrigación sanguínea , Endolinfa , Técnicas Histológicas , Órgano Espiral/irrigación sanguínea , Especificidad de la Especie , Estría Vascular/irrigación sanguínea , Vestíbulo del Laberinto/irrigación sanguíneaRESUMEN
The capillaries of the spiral limbus in the cochlea of the laboratory rat were investigated under light and electron microscopy. A stereological examination of the capillary volumes of specimens injected with horseradish peroxidase was performed. The volume of capillaries amounted to 2.87%, and, as such, is very high. The ultrastructure of the capillaries showed continuous endothelial cells and basal laminae, discontinuous pericytes and varying relations towards the surrounding tissue. Morphological criteria, such as microvilli and plasmalemmal vesicles, suggest a significant transendothelial transport. The causes for the abundance of vessels in the spiral limbus are discussed: the transport of oxygen to the perilymph and the need of substances for the formation of the tectorial membrane seem to be important factors. The transport processes are obviously controlled by the endothelial cells as well as by the spiral limbus cells.
Asunto(s)
Cóclea/irrigación sanguínea , Lámina Espiral/irrigación sanguínea , Animales , Membrana Basal/ultraestructura , Capilares/ultraestructura , Endotelio/ultraestructura , Microvellosidades/ultraestructura , Órgano Espiral/irrigación sanguínea , RatasRESUMEN
This paper describes a new technique for visualizing the organ of Corti in the living guinea pig. The various cell types and blood supply can be viewed at magnifications up to 625X through a microscope, as seen reflected by a tiny mirror in scala vestibuli. Glass microelectrodes can also be seen as they penetrate the tissues, and can be accurately localized.
Asunto(s)
Microscopía/métodos , Órgano Espiral/citología , Animales , Cobayas , Microelectrodos , Órgano Espiral/irrigación sanguíneaRESUMEN
The vascular pattern of the rat cochlea was demonstrated by the aid of Berlin Blue (Prussian Blue) contrast. The vascular anatomy is similar to other mammals. The infrequent occurrence of the vessel of the basilar membrane under the organ of Corti is interesting in respect to its presumed importance for the oxygen supply to the hair cells. In the place where the vessel of the basilar membrane usually lies when present, a large uninjected channel was often seen throughout the cochlea. In the external wall, radiating arterioles supply and collecting venules drain all capillary areas. The vascular pattern of the external wall is well maintained at the basal end but is more sparse in apical parts of the cochlea as in other mammals. The rat cochlea is somewhat more difficult to manipulate than the cochlea in other mammals due to its small size, but the dissection of different parts of the cochlea was achieved without major problems.
Asunto(s)
Cóclea/anatomía & histología , Cóclea/irrigación sanguínea , Ratas/anatomía & histología , Animales , Membrana Basilar/irrigación sanguínea , Vasos Sanguíneos/anatomía & histología , Órgano Espiral/irrigación sanguínea , Lámina Espiral/irrigación sanguínea , Coloración y Etiquetado , Estría Vascular/irrigación sanguíneaRESUMEN
Intracellular measurements of the resting cell membrane potentials of guinea pig Corti's organ were made in order to determine the sensitivity of this cell potential to anoxic hypoxia (a lowered oxygen state due to lack of respiratory oxygen) and to establish differences according to cell types or morphologic regions of the sensory epithelium. The negative cell potentials measured from successful electrode penetrations were found to be relatively more stable and resistant to change during a 120-s period of anoxia than was the positive endocochlear potential. The intracellular resting potentials were also much slower to recover after resumption of respiration. Data obtained from various cells in two different regions of Corti's organ is receiving oxygen from both the perilymph and the endolymph. An iontophoretic dye-marking technique was used to label some experimental cells for later histologic identification.
Asunto(s)
Hipoxia/fisiopatología , Órgano Espiral/fisiopatología , Potenciales de Acción , Animales , Cobayas , Órgano Espiral/irrigación sanguínea , Órgano Espiral/citología , Coloración y Etiquetado , Factores de TiempoRESUMEN
A detailed study of the feline basilar membrane was performed in 13 cochleae with light microscopy and in six with electron microscopy. The distribution of the mesothelial cells and homogeneous ground substance with the filaments was recorded and plotted as a function of length along the cochlear duct. The width, thickness and number of filaments were also measured. In the lower basal turn the basilar membrane was narrowest and its entire thickness was occupied by filaments. In the apical region the width was maximal and the filaments were fewer. The density of the filaments counted in the bundles showed no significant difference along the cochlear duct or across the width of the basilar membrane, but the number of filaments decreased markedly (approximately a ten-fold difference) from base to apex. The number of mesothelial cells increased towards the apex. These morphological characteristics may be related to the different motion pattern of the basilar membrane along the length of the cochlear duct. A discontinuity of the basement membrane was noted in the apical region in all cochleae studied. These gaps seemed to provide structural evidence for the permeability of the basilar membrane in this area. The vas spiralis was present as a blood vessel in two specimens and only in the apical region. Thus, its function as the sole nutritional source for the organ of Corti is doubtful.
Asunto(s)
Membrana Basilar/ultraestructura , Oído Interno/ultraestructura , Factores de Edad , Animales , Membrana Basal/ultraestructura , Membrana Basilar/fisiología , Gatos , Conducto Coclear/ultraestructura , Citoesqueleto/ultraestructura , Desmosomas/ultraestructura , Epitelio/ultraestructura , Órgano Espiral/irrigación sanguínea , Órgano Espiral/ultraestructuraRESUMEN
Because all stages of melanogenesis (premelanosome, melanosome and melanin granules) were found in intermediate cells of the rat stria vascularis, they can be classified as melanocytes. The marginal and basal cells of these rat specimens contained no pigment. Early in development, the melanocytes or future intermediate cells are located beneath the strial basal lamina. They penetrate this lamina to insert themselves between marginal cells. Both the melanocytes and marginal cells are believed to participate actively in the tissue rearrangements which ultimately bring the two cell types into intimate structural relationship. The ingrowing melanocytes and the mature, pigmented, intermediate cells which they form are frequently associated with blood vessels. Pretreatment with Dopa to enhance the melanin content of early melanocytes did not enable us to identify their route of migration into the stria.
Asunto(s)
Melanocitos/ultraestructura , Órgano Espiral/ultraestructura , Pigmentación , Factores de Edad , Animales , Femenino , Masculino , Monofenol Monooxigenasa/farmacología , Órgano Espiral/irrigación sanguínea , Órgano Espiral/embriología , Ratas , Coloración y EtiquetadoRESUMEN
For the sensory cells of Corti's organ are high susceptible to deficits in O2-supply, all disturbances of blood-flow in the inner ear can deteriorate the hearing function. It is the hypotonic dysregulation of the microcirculation in the stria vascularis, which is much more dangerous for the inner ear auditory receptors than be hypertonic disease. The occurance of acute or progredient hearing loss with symptoms of a sensorineural leason and of tinnitus therefore can be looked as an indication to the beginning of a cardiovascular disease, and necessitates appropriate diagnostic and therapy.