Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cochlear Duct”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 523 records · Page 29Linked to original sources
PubMed1998

Measurement of guinea pig basilar membrane using computer-aided three-dimensional reconstruction system.

Cochleas are known to have the ability to analyze a frequency widely, and this ability seems to be owed mostly to the basilar membrane (BM) configuration. However, the relationship between the cochlear frequency-position map and the BM configuration is not clear. Therefore, in this paper, the internal structures of a guinea pig cochlea, especially the BM configuration, were reconstructed and measured using a computer-aided three-dimensional (3-D) reconstruction system. Then, an attempt was made to examine the influence of the BM configuration on the cochlear frequency-position map. The measurement results indicate that the width of the BM increased and its thickness decreased with an increase in the distance from the basal turn towards the apical turn. Theoretical consideration reveals that the wide frequency-position of the cochlea is achieved by not only the BM configuration change along the length of the cochlea but also the change of the Young's modulus of the BM along the length of the cochlea.

Animals↗
PubMed1998

Longitudinal endolymph movements induced by perilymphatic injections.

Endolymph movements and endocochlear potential (EP) changes were measured during disturbances of perilymphatic pressure. induced by injecting artificial perilymph into scala tympani (ST) or scala vestibuli (SV) of the guinea pig cochlea. Injections were performed either with or without an outlet made in the opposite perilymphatic scala. Injections into ST without an outlet induced large pressure changes but virtually no endolymph movement or EP change. Injection at the same rate into ST with an outlet in SV produced smaller pressure changes which were accompanied by a basally-directed displacement of endolymph and significant EP changes. The magnitude of endolymph displacements and EP changes varied as a function of injection rate. Injections into SV, either with or without an outlet in ST, produced apically-directed endolymph displacement and EP changes. For the SV injections without an outlet, the cochlear aqueduct and round window are likely to provide an outlet and compliance, permitting flow along the perilymphatic scalae to occur even when no ST outlet was provided. We conclude that endolymph movements are not dependent on the absolute pressure of the perilymph, but instead occur when small, sustained pressure gradients are present across the cochlear partition, corresponding to times when perilymph flow is induced. This study demonstrates that in the normal. sealed cochlea, endolymph and EP are insensitive to fluid injections into ST, but are sensitive to fluid injections into SV. Endolymph movements are therefore unlikely to be generated by cerebrospinal fluid pressure fluctuations (such as those produced by respiration, posture changes, coughing, sneezing, etc) which are transmitted to ST by the cochlear aqueduct.

Animals↗
PubMed2000

Endolymphatic hydrops induced by chronic administration of vasopressin.

Recently, many lines of evidence have supported the possibilities that vasopressin (VP) is closely linked to the formation of endolymphatic hydrops in Meniere's disease. In the present study, it was examined whether or not the chronic administration of VP might induce endolymphatic hydrops. For this purpose, histological studies and VP radioimmunoassay were independently performed in 20 and 40 guinea pigs, respectively. The degree of hydrops was quantitatively assessed by the increase ratio (IR) of the scala media area in the mid-modiolar sections of the cochlea. The IR was defined by the following equation: 100x(A-B)/B (A: the cross-sectional area of the bulging scala media; B: the no-bulging scala media, enclosed by an idealized straight Reissner's membrane). VP was administered at the rates of 200 microU/kg/min, 400 microU/kg/min and 1000 microU/kg/min for 1 week via the osmotic mini-pump. The IR of the total of the apical, second, third and basal turns (means+/-S.D.s) were 4.4+/-0.7, 10.4+/-1.8, 17.4+/-7.9 (n=10 ears, each) in respective doses of VP. Comparing with that of the control animals (5.2+/-1.7, n=10 ears), the area increased significantly in the VP dosage of 400 and 1000 microU/kg/min (Bonferroni's method, P<0.05). Plasma VP concentrations produced by the VP administration in these dosages were 2.2+/-0.4, 3.5+/-0.8 and 14.0+/-3.9 (n=10, each) pg/ml. Although 3.5 pg/ml is the upper limit of plasma VP concentration in normal human subjects, 14.0 pg/ml was almost the same concentration as those observed in the acute phase of Meniere's disease (Takeda et al., 1995). Therefore, the formation of endolymphatic hydrops in cases of Meniere's disease might be caused by high concentrations of plasma VP.

Analysis of Variance↗
PubMed1992

Stria vascularis in Ménière's disease: a quantitative histopathological study.

To investigate the role of pathology of the stria vascularis in Ménière's disease, the vascularity and the cross-sectional area of the stria vascularis in a midmodiolar section of the cochlea were examined by histological observation and a computer-aided planimetric, respectively, in eight temporal bones from individuals with Ménière's disease and eight age-matched normal temporal bones. The number of vessels in the stria vascularis was significantly smaller in most of the cochlear turns in ears with Ménière's disease than in control ears, and the cross-sectional area of the stria vascularis in the same sections was significantly smaller in all the cochlear turns in ears with Ménière's disease than in controls. Furthermore, vascularity correlated significantly with the cross-sectional area of the stria vascularis in all the temporal bones examined. From these results it appears that poor vascularity of the stria vascularis is closely related to strial atrophy, and that these pathological findings might be important factors in the pathophysiology of Ménière's disease.

Adult↗
PubMed1984

Effects of glycerol on the inner ear fluid electrolytes of guinea pigs--oral and intravenous administration.

Under sodium pentobarbital anesthesia (25-35 mg/kg), serum, CSF and inner ear fluids from scala tympani perilymph, scala vestibuli perilymph, and scala media endolymph were collected from normal guinea pigs after the oral administration of glycerol (50%, 12 ml/kg) or the intravenous injection of glycerol (1.0 ml/kg). The sodium and potassium concentrations were assessed by microflame photometry. The electrolyte dynamics of the inner ear fluids were compared after these two routes of administration. Serum: There was no significant change in Na or K levels after either route of administration. CSF: The Na concentration increased rapidly after both intravenous and oral administrations of glycerol and remained high until the end of the experiment. The K concentration did not change significantly after intravenous injection. Scala tympani perilymph: The Na concentration increased transiently, after intravenous glycerol, while after oral administration it increased slowly and steadily. The K concentration increased only after oral administration. Scala vestibuli perilymph: The Na level increased slowly and steadily only after oral administration of glycerol, and the K level increased slightly after intravenous injection. Scala media endolymph: No changes in the K level occurred after either route of administration. After oral administration the Na level increased. These experiments show that dehydration persists longer after oral than after intravenous administration of glycerol. In the diagnosis of Meniere's disease, oral administration of glycerol is more effective than intravenous injection.

Administration, Oral↗
PubMed1985

Autoradiographic demonstration of deoxyglucose uptake in guinea pig cochlea.

The 2-deoxyglucose autoradiographic method was applied to whole-body cryosectioning to include the cochlea. The highest levels of 2-deoxyglucose uptake were observed in the vascular stria, spiral ligament and spiral prominence. The cochlear nerve showed the next highest level of uptake, while the organ of Corti and the spiral ganglion showed low levels. The functional significance of the results was briefly discussed.

Animals↗
PubMed1981

Pre-operative bone conduction curves in stapedectomy.

Significant post-stapedectomy cochlear deficit is associated with the following factors in an uncomplicated operation: (1) The age of the patient. (2) A pre-operative bone conduction loss, averaged over 0.25, 0.5, 1.0 and 2.0 KHz, of 20 db or more. (3) A left-to-right sloping bone conduction curve (descending audiometric curve), especially where there is a similar curve in the other ear.

Adult↗
PubMed1989

Spiral prominence epithelium.

Recent studies have shown neuroendocrine-type cells in human spiral prominence epithelium. A light microscopic and ultrastructural study was made on the guinea pig spiral prominence epithelium to try and identify neuroendocrine cells. The study showed that such cells were not present in the guinea pig spiral prominence epithelium. The spiral prominence epithelium was characterized by uniformity of cellular staining with Toluidine blue and the ultrastructural appearance. The morphology of the spiral prominence epithelium was similar to that previously described. The absence of neuroendocrine cells in spiral prominence epithelium in the guinea pig is discussed in relation to species differences.

Animals↗
PubMed2006

Locating the scala media in the fixed human temporal bone for therapeutic access: a preliminary study.

OBJECTIVE: To investigate the location of the scala media in relation to the round window niche in human temporal bones. DESIGN: Ten human temporal bones were investigated by radical mastoidectomy and promontory drill-out. SETTING: Temporal bone laboratory. OUTCOME MEASURES: The distance from the scala media to the anterior edge of the round window niche, measured by Fisch's stapedectomy measuring cylinders. RESULTS: The scala media was identified at the transection point of a vertical line 1.6 to 2.2 mm (mean=1.8 mm; standard deviation=0.2) anterior to the anterior edge of the round window niche and a horizontal line 0.2 mm inferior to the lower border of the oval window. CONCLUSION: This report demonstrates the point of entry into the scala media via the promontory in fixed temporal bone models, which may provide a site of entry for stem cells and gene therapy insertion.

Cochlear Duct↗
PubMed2001

A genetic approach to understanding auditory function.

Little is known of the molecular basis of normal auditory function. In contrast to the visual or olfactory senses, in which reasonable amounts of sensory tissue can be gathered, the auditory system has proven difficult to access through biochemical routes, mainly because such small amounts of tissue are available for analysis. Key molecules, such as the transduction channel, may be present in only a few tens of copies per sensory hair cell, compounding the difficulty. Moreover, fundamental differences in the mechanism of stimulation and, most importantly, the speed of response of audition compared with other senses means that we have no well-understood models to provide good candidate molecules for investigation. For these reasons, a genetic approach is useful for identifying the key components of auditory transduction, as it makes no assumptions about the nature or expression level of molecules essential for hearing. We review here some of the major advances in our understanding of auditory function resulting from the recent rapid progress in identification of genes involved in deafness.

Cochlea↗
PubMed1999

Localization of nontypeable Haemophilus influenzae endotoxin in the middle and inner ear during experimental otitis media.

Nontypeable Haemophilus influenzae (NTHi) lipooligosaccharide, the major component of H. influenzae endotoxin, was localized in the middle and inner ear subsequent to the resolution of experimental otitis media induced by this pathogen. A monoclonal antibody specific for the lipooligosaccharide of this strain was used to probe sections of middle and inner ear tissue and visualized by means of the avidin-biotin peroxidase complex technique. Sixteen to seventeen days post inoculation with either viable or formalin-inactivated NTHi, endotoxin could be localized in both the middle and inner ear at a time when the middle ear was culture negative. Our data demonstrate that endotoxin shed by NTHi during otitis media penetrates the inner ear and binds to both tissue components and inflammatory cells in both the middle and inner ear.

Animals↗
PubMed1986

Pathogenesis of labyrinthitis associated with Haemophilus influenzae type b meningitis in infant rats.

The pathogenesis of labyrinthitis associated with bacterial meningitis was studied by histopathologic examination of inner ears of 114 rats with Haemophilus influenzae type b meningitis produced by ip inoculation of one of 13 clinical isolates. Findings consisted of inflammation of the perilymphatic spaces of the cochlea and semicircular canals with sparing of the endolymphatic space, cochlear nerve fibers, and middle ear. The degree of inflammation peaked at 48 hr after inoculation, then declined by 96 to 144 hr. No interstrain differences in type or degree of pathology were observed. Immunofluorescent staining of cochleae from 15 animals demonstrated that bacteria were present in areas of inflammation and also in the endolymphatic space and organ of Corti. One isolate displayed a tendency to accumulate in the perilymphatic spaces in larger numbers than those seen with three other isolates. These findings suggest that, in this model, inflammation reaches the inner ear by spreading from the subarachnoid space. Bacterial invasion of the organ of Corti may be one mechanism by which deafness occurs in bacterial meningitis.

Animals↗
PubMed1998

Changes in immunostaining of inner ears after antigen challenge into the scala tympani.

To study the mechanisms of immune responses and immune injuries in inner ears, labyrinthitis was induced by inoculation of keyhole limpet hemocyanin (KLH) into the scala tympani of systemically sensitized guinea pigs. Inner ears were then immunostained for KLH, immunoglobulin G (IgG), albumin, connexin26 (Cx26), and sodium-potassium adenosine triphosphate (Na,K-ATPase). Inflammatory cells containing KLH were observed in the scala tympani and in the collecting venule of the spiral modiolar vein (SMV). Spiral ligament, spiral limbus, and blood vessels including the SMV were diffusely positive for IgG and albumin. Immunoreactivity for Cx26 and Na,K-ATPase was decreased compared with the normal ears in the fibrocytes of the spiral ligament. These results suggest that inflammatory cells and blood constituents could extravasate into the cochlea from blood vessels and that fibrocyte damage in the spiral ligament could cause cochlear dysfunction.

Adjuvants, Immunologic↗
PubMed2004

Spiral ligament and stria vascularis changes in cochlear otosclerosis: effect on hearing level.

OBJECTIVE: To investigate the effect of changes within the spiral ligament and stria vascularis on hearing in cochlear otosclerosis, we examined spiral ligament hyalinization, stria vascularis atrophy, and sensory hearing loss in cochlear otosclerosis and described changes in ion transport molecule expression. STUDY DESIGN: Retrospective. SETTING: Tertiary referral center. PATIENTS: Thirty-two cochleae from 24 temporal bone donors with histologic evidence of cochlear otosclerosis, including spiral ligament hyalinization. INTERVENTION: Audiography. MAIN OUTCOME MEASURES: Measurements of spiral ligament width, stria vascularis, and bone-conduction thresholds were compared by the amount of hyalinization. Expression of the ion transport molecules Na,K-ATPase, connexin 26, and carbonic anhydrase II were assessed by immunohistochemical techniques. RESULTS: Hyalinization most often involved the posterior basal turn (88%) and the posterior middle turn (27%). Spiral ligament hyalinization correlated significantly with stria vascularis atrophy in the posterior middle turn of the cochlea (rho = -0.63, p < 0.01). There was a trend toward a significant association in the posterior basal turn (rho = -0.31, p < 0.08). Bone-conduction thresholds at 2,000 and 4,000 Hz were significantly associated with the amount of stria vascularis atrophy (rho = -0.44, -0.40, p < 0.05). In addition, we observed decreased immunostaining for both carbonic anhydrase II with Type I fibrocytes and Na,K-ATPase with stria vascularis and Type II and Type IV fibrocytes of the spiral ligament in cochlear otosclerosis sections compared with normal cochlea. Na,K-ATPase staining within the stria vascularis was further decreased in the presence of spiral ligament hyalinization. No significant differences were seen with connexin 26 immunostaining. However, immunostaining results were somewhat inconsistent. CONCLUSION: These data suggest that spiral ligament structure and function are essential for stria vascularis survival. In addition, dampened expression of ion transport molecules within the spiral ligament and stria vascularis may disrupt potassium ion recycling, resulting in loss of endocochlear potential and sensory hearing loss.

Aged↗
PubMed2004

Effects of hyperbaric therapy on function and morphology of Guinea pig cochlea with endolymphatic hydrops.

OBJECTIVE: The objective of this study was to investigate the effect on experimental endolymphatic hydrops in guinea pigs after hyperbaric therapy. BACKGROUND: The histopathologic character of Ménière's disease is the presence of endolymphatic hydrops. Endolymphatic hypertension could be one of the factors resulting from endolymphatic hydrops. Some treatments of Ménière's disease are aimed toward preventing the endolymphatic hypertension. Exposure to pressure change has risen in recent years. METHODS: Thirty-two guinea pigs were operated on the right ears to induce endolymphatic hydrops by obliterating the endolymphatic sac through an extradural posterior cranial fossa approach. After 5 weeks' survival, 12 guinea pigs were put into a chamber with an absolute atmospheric pressure of 2.2 for 3 weeks (90 minutes once a day 5 times a week). We observed the morphologic and functional changes in guinea pig cochleae of the pressure group, 4-week hydrops group (n = 10), 8-week hydrops group (n = 10), and the normal group (n = 10). We measured the hearing threshold of the auditory brainstem response, the 70-dB SPL action potential (AP) latency, the ratio of 70-dB SPL summating potential magnitude to action potential magnitude (-SP/AP) of the electrocochleogram, and the maximum scala media area (SMA) ratio, respectively. RESULTS: The average 70-dB SPL-SP/AP magnitude of right ears (0.29 +/- 0.09) and the average maximum SMA ratio (2.23 +/- 0.20) in the pressure group were significantly less than that in the 8-week hydrops group (0.69 +/- 0.15 and 4.04 +/- 0.52, respectively) with the same survival time (p < 0.05). The results in the pressure group were almost as similar as that in the 4-week hydrops group (0.29 +/- 0.13 and 2.22 +/- 0.20, respectively) (p > 0.05). The average hearing threshold of ABR of right ears in the pressure group (36.67 +/- 14.30-dB SPL) was lower than that of the 8-week hydrops group (44 +/-1 4.30-dB SPL), but the difference was insignificant (p > 0.05). The average 70-dB SPL AP latency of right ears in the pressure group was not significantly different from those of the 8-week hydrops group, the 4-week hydrops group, or the normal group (p > 0.05). CONCLUSIONS: Our findings suggest hyperbaric therapy can significantly suppress the development of endolymphatic hydrops and improve cochlear function in guinea pigs. This study provided strong evidence for the development of pressure treatment of Ménière's disease without destroying the inner ear.

Animals↗
PubMed2006

Presbycusic neuritic degeneration within the osseous spiral lamina.

OBJECTIVE: To describe a neglected anatomic variant occurring with presbycusis. STUDY DESIGN: Retrospective temporal bone histopathology study. METHODS: Quantitative analysis of peripheral hair cells, neurites, neurons, and the stria vascularis in temporal bones from individuals who had presbycusis. Fifty-three patients aged 65 years or older and with a down-sloping audiogram and clinical diagnosis of presbycusis were reviewed. Nine cases had normal hair and ganglion cell populations but reduced peripheral processes (neuritic presbycusis). These were compared with five normal-hearing controls on measurements of anterior middle and basal turn fiber bundle diameter and the ratio of basal to middle diameters. RESULTS: Thresholds at 4 and 8 kHz were significantly poorer in the neuritic presbycusis group than in the control group (p<or=0.004 and 0.05, respectively), as was speech discrimination score (p<or=0.028). The ratio of basal to middle turn diameters was significantly smaller in the neuritic presbycusis group (p<or=0.003). This effect was quite marked in that there was no overlap in ratios between the groups, with the maximum neuritic presbycusis group ratio smaller than the minimum control group ratio. There was a moderate negative correlation between ratio and threshold at 4 kHz (sigma=-0.49, p<or=0.075). CONCLUSION: Loss of peripheral neurites in the anterior basal cochlear segment is found in conjunction with presbycusis in temporal bones that have no other morphologic abnormalities. These cases can be identified by a gradual down-sloping audiogram in contrast to sensory (hair cell) presbycusis, which is characterized by a precipitous high tone loss.

Aged↗