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PubMed1991

Autoregulation of inner ear blood flow in normal and hydropic guinea pigs.

Inner ear and brainstem blood circulation was measured by three different techniques: the laser Doppler (LD), hydrogen clearance (HC) and oxygen tension (PO2) measurements, while systemic blood pressure (BP) was modulated by norepinephrine infusion or removal of whole blood. Results were as follows: (i) The blood flow (BF) change determined by LD correlated well with that measured by HC and PO2 techniques; (ii) BF in the brainstem was maintained constant in the BP range of 35 to 80 mmHg; however, inner ear BF showed a poor autoregulatory function relative to the change of systemic BP; (iii) although the change of BF was similar for cochlea and semicircular canal the amount of PO2 decrease for lowered BP was significantly less in the cochlea than in the canal; (iv) in guinea pigs with unilaterally obliterated endolymphatic sac and duct, the decrease in cochlear BF was larger on the operated side than on the intact side. This suggests that the autoregulatory function for BF is impaired in the hydropic ear.

Animals↗
PubMed2005

[Distribution of basic fibroblast growth factor in inner ear of guinea pigs injected by different drug-approaches].

OBJECTIVE: To investigate the approach of basic fibroblast growth factor(bFGF) entering inner ear, as well as its the protective mechanism to inner ear and nerve tissue in pathological situation. METHODS: 125I-bFGF was injected into guinea pigs body via the lateral ventricle and muscle under physical situation as well as pathological situation. Then the per minute gamma-radioactive in blood, liver, thyroid gland, brain, cochlear and perilymph fluid was counted, and the distribution and metabolism of bFGF in the inner ear and autoradiography of the cochlea were also observed. RESULTS: Gamma-radioactive cpm of blood and liver increased significantly, while it did not change in brain, cochlea and perilymph after 125I-bFGF intramuscular injections. Gamma-radioactive cpm in blood, liver, brain, perilymph and cochlea had increased and autoradiography granules was found in the cochlea in 30 min after 125I-bFGF injected into CSF. In brain, perilymph and cochlea, a maximal value of gamma-radioactive cpm was obtained between 2 h and 4 h, while that in 8 h decreased significantly. Autoradiography granules still were seen in 8 h. gamma-radioactive cpm in 12 h was still higher than that in control group, but autoradiography granules can't be seen. The result in 24 h was similar to that in control group. The time course of cpm in the blood, cochlea and perilymph always parallel changed. CONCLUSIONS: bFGF has some difficulties in getting across blood-labyrinth barrier (BLB) and blood-brain barrier (BBB) under physical and pathological situation, such as acute anoxia, aminoglycoside-induced deafness. bFGF can reach inner ear, perilymph fluid, brain tissue and blood rapidly when it is injected into CSF and excreted slowly in those tissues. Permeability of BBB and BLB to bFGF is similar and has orientation.

Animals↗
PubMed2005

Inner ear formation during the early larval development of Xenopus laevis.

The formation of the eight independent endorgan compartments (sacculus, utricle, horizontal canal, anterior canal, posterior canal, lagena, amphibian papilla, and basilar papilla) of the Xenopus laevis inner ear is illustrated as the otic vesicle develops into a complex labyrinthine structure. The morphology of transverse sections and whole-mounts of the inner ear was assessed in seven developmental stages (28, 31, 37, 42, 45, 47, 50) using brightfield and laser scanning confocal microscopy. The presence of mechanosensory hair cells in the sensory epithelia was determined by identification of stereociliary bundles in cryosectioned tissue and whole-mounts of the inner ear labeled with the fluorescent F-actin probe Alexa-488 phalloidin. Between stages 28 and 45, the otic vesicle grows in size, stereociliary bundles appear and increase in number, and the pars inferior and pars superior become visible. The initial formation of vestibular compartments with their nascent stereociliary bundles is seen by larval stage 47, and all eight vestibular and auditory compartments with their characteristic sensory fields are present by larval stage 50. Thus, in Xenopus, inner ear compartments are established between stages 45 and 50, a 2-week period during which the ear quadruples in length in the anteroposterior dimension. The anatomical images presented here demonstrate the morphological changes that occur as the otic vesicle forms the auditory and vestibular endorgans of the inner ear. These images provide a resource for investigations of gene expression patterns in Xenopus during inner ear compartmentalization and morphogenesis.

Actins↗
PubMed1977

[Anatomical conditions influencing the therapy of the inner ear (author's transl)].

Morphological factors affecting the course of disturbances of the inner ear are demonstrated. Its important to realise that damaged sensory cells may recover quite a long time after injury. The blood supply and its regulation, possibly by autonomic innervation, are significant in the treatment of the inner ear. The reported findings must be regarded as the combined effort of numerous factors (Biology of the inner ear).

Animals↗
PubMed1987

[Optimization of the immunofluorescence test for antibodies in the serum of patients with inner ear diseases].

Antibodies in the serum of patients with inner ear diseases can be demonstrated immunohistochemically with human kidney tissue. In this study a patient's serum with the typical positive reaction against proximal tubuli (antibodies against microsomes) and a serum with antibodies against mitochondria was tested with different dilutions of the fluorescein marked antiserum (FITC conjugate). For both sera a dilution of 1:160 showed positive reaction. The fluorescence of the control incubation was negligible. Employing the given technical details the immunohistochemical assay of antibodies with human kidney tissue has become a simple and reliable test for the most frequently found antibodies in patients with inner ear diseases.

Autoantibodies↗
PubMed2000

What inner ear diseases cause benign paroxysmal positional vertigo?

Benign paroxysmal positional vertigo (BPPV) originating from the posterior semicircular canal (pSCC) is a common vestibular disorder that is easy to diagnose and usually easy to treat. The majority of patients with BPPV have no known inner ear disease; they have "primary" or "idiopathic" BPPV. However, a minority does have objective evidence of an inner ear disease on the same side as the BPPV and this group has "secondary" or "symptomatic" BPPV. Previous publications differ on the prevalence of secondary BPPV and about the types of inner ear diseases capable of causing it. In order to determine what proportion of patients have secondary as opposed to primary BPPV and which inner ear diseases are capable of causing secondary BPPV, we searched our database for the 10-year period from 1988 to 1997 and found a total of 2847 patients with BPPV. Of these, 81 (3%) had definite pSCC-BPPV secondary to an ipsilateral inner ear disease. Sixteen had Menière's disease, 24 had an acute unilateral peripheral vestibulopathy, 12 had a chronic unilateral peripheral vestibulopathy, 21 had chronic bilateral peripheral vestibulopathy and 8 had unilateral sensorineural hearing loss. It seems that any inner ear disease that detaches otoconia and yet does not totally destroy pSCC function can cause BPPV and that a case can be made for audiometry and caloric testing in all patients with BPPV.

Acute Disease↗
PubMed2006

[An in vitro investigation of the regulation mechanism to the blood-labyrinth barrier permeability of guinea pig inner ear].

OBJECTIVE: To investigate the regulation mechanism of the blood-labyrinth barrier permeability of guinea pig inner ear. METHOD: The cultured endothelial cell was derived from the stria vascularis from guinea pig inner ear. We exposed guinea pig inner ear capillary endothelial cell monolayers to substances known to increase or decrease cyclic AMP and measured their effect on endothelial permeability to albumin and Evan's blue and endothelial cell cyclic AMP and F-actin concentrations. RESULT: Cholera toxin (CT) led to a remarkable increase in cyclic AMP concentration and a marked reduction in F-actin concentration which was associated with remarkable reduction in albumin and Evan's blue transfer across endothelial monolayers; In contrast, katlex led to an obvious reduction in cyclic AMP concentration and a marked increase in F-actin concentration which was associated with obvious increase in albumin and Evan's blue transfer across endothelial monolayers. CONCLUSION: The results indicated that cyclic AMP is an important determinant of the blood-labyrinth barrier in vitro. The barrier function changes are probably associated with apparent endothelial shape changes and qualitative and quantitative changes in F-actin.

Actins↗
PubMed1981

Histochemical study of the efferent nervous system in the guinea pig inner ear.

The efferent nervous system of the guinea pig inner ear is histochemically investigated. Remarkable activity of alkaline phosphatase and acetylcholinesterase is demonstrated by Burstone's (1958) azo dye method and Koelle's (1949) method as modified by Gomori (1952) respectively. The distribution pattern of both enzymes in the efferent nervous system is entirely similar. The intraganglionic spiral bundles, fascicles of the osseous spiral lamina and efferent plexus of the organ of Corti reacted intensely for both enzymes. Afferent nerve fibers give no histochemical reaction for both alkaline phosphatase and acetylcholinesterase. However, spiral and vestibular ganglion cells are rich in both enzymes, though they belong to the afferent nervous system. The significance of both enzymes in the nervous system of the guinea pig inner ear is briefly discussed.

Acetylcholinesterase↗
PubMed2002

[Methods of gene therapy for inner ear diseases].

OBJECTIVE: To study an effective, safety and convenient method for gene transfer and introduction to inner ear. METHOD: Ad GFP were transferred into inner ears of 30 guinea pigs through round window, basal turn of cochlea and cerebrospinal fluid respectively. Auditory brainstem response (ABR)and otoacoustic emission of distortion products (DPOAE) were assayed to these animals preoperatively and postoperatively, then transfection and expression of Ad-GFP in inner ears and structure of cochlear hair cells were observed. RESULT: Transfection and expression of Ad-GFP were found in spiral ganglion of cochlea, stria vascularis and Cortisorgan through all of the three methods. The expression products were in the highest level at the third day after operation. But the operation through round window and basal turn of cochlea could lead to bleeding and coagulum deposited in parietalgyrus, which could result in hair cells injury. Changes of ABR threshold of these animals were not significant. But amplitude of DPOAE decreased significantly in animals through round window and basal turn of cochlea pathways. There was no hair cells injury and changes of DPOAE through cerebrospinal fluid pathway. CONCLUSION: The study suggested the operations through round window and basal turn of cochlea could lead to bleeding in cochleas, which resulted in change of DPOAE amplitude. It is a safe and effective method to transfer through cerebrospinal fluid.

Animals↗
PubMed1996

Inner ear content of glycosaminoglycans as shown by monoclonal antibodies.

Inner ear cells are known to contain combinations of proteins and sugar, which histochemically have been identified to be proteoglycans. To visualize these components in the macula utriculi, crista ampullaris and in the cochlea four different monoclonal antibodies against hyaluronan (HA), keratan sulphate (KS), chondroitin-6-sulphate (C-6-S) and chondroitin-4-sulphate (C-4-S) were used. The results indicate that KS is predominantly present in the lining of the vestibular hair cells, in the otoconial layer and in nerve tissue. C-4-S is present in the sensory hairs as well as in the subepithelial layer but also in the tectorial and basilar membranes of the cochlea. HA is generally present in the surface area of vestibular hair cells, to some extent in the cochlear hair cells and in the stria vascularis. C-6-S is only present to a lesser degree in the inner ear.

Animals↗
PubMed1993

[Functional and pathohistologic changes in an ischemic model of rat inner ear].

We investigated functional and histopathological changes in the inner ear circulatory disorder caused by thrombosis of the anterior inferior cerebellar artery (AICA) in rats. The thrombosis was induced by a photochemical reaction between green light and systemic injection of Rose Bengal. During this experiment, auditory brainstem responses (ABR) were recorded and cochlear blood flow (CBF) was measured by a laser doppler flowmeter. Within 5 weeks after the procedure, histopathological changes were studied by light microscopy following the observation of equilibrium dysfunction and ABR recording. CBF was reduced from the baseline in 30.8 +/- 3.4% (mean +/- SE, n = 25) by occlusion of the AICA, ABR was altered in 96% of animals, and equilibrium dysfunction was observed in 77%. When the AICA was not reopened within a short time, severe histopathological changes were frequently observed. There was no significant correlation between equilibrium dysfunction and histopathological changes in the vestibule. It is concluded that this experimental model may be useful for investigating functional and histopathological changes in the ischemic inner ear.

Animals↗
PubMed2006

Sonic hedgehog promotes mouse inner ear progenitor cell proliferation and hair cell generation in vitro.

Sonic hedgehog (Shh) signaling is essential for auditory cell fate determination and inner ear dorsal/ventral patterning during development. Here, we show that Shh accelerates inner ear progenitor cell proliferation, and the inhibitor of Shh signaling cyclopamine reduces mitotic growth of otocyst cells in vitro. The number of hair cells in cultures of inner ear progenitor cells that were treated with Shh was significantly higher than that in control cultures. When Shh signaling was blocked with cyclopamine, hair cell generation was largely inhibited. Our results suggest that Shh may be a regulator of inner ear progenitor cell growth and hair cell generation.

Animals↗
PubMed1986

Kinetics of gentamicin uptake and release in the rat. Comparison of inner ear tissues and fluids with other organs.

The kinetics of entry and release of gentamicin was investigated in fluids and tissues of the inner ear of the rat, as well as in renal cortex, and in organs that do not share susceptibility to the toxic effects of aminoglycosides. Various modes of administration were used to achieve different patterns of drug plasma concentrations. Electrophysiological and histological examinations were performed to correlate pharmacokinetics and ototoxicity. Results show that: the uptake of the drug by the inner ear tissues is dose dependent and manifests a rapid saturation kinetics with a concentration plateau of about 1 micrograms/mg of protein. The low ratio of the perilymph and endolymph to plasma concentrations argues against the concept of an accumulation of the drug in the inner ear over drug levels in plasma, which has been considered as the basic mechanism of ototoxicity. In renal cortex, the kinetics appears similar to that of the inner ear but the concentrations achieved are 10-fold higher than in cochlear tissues. In other organs (liver, heart, lung, and spleen), no saturation could be demonstrated within the duration of the experiment. Ototoxicity seems to be related to the penetration of the drug into compartment(s) from which the half-life of disappearance is extremely slow. Rapid uptake, early saturation, and long exposure of the tissues to the drug may account for the development of toxicity in inner ear and kidney.

Animals↗
PubMed1984

Retinol and retinyl ester in separated structures of the guinea pig inner ear.

Chemical separation of different vitamin A derivates in inner ear extracts was performed by means of high pressure liquid chromatography (HPLC) with fluorescence and UV detection. For more accurate site identification the membranous cochlea was dissected and the basilar membrane, the spiral ligament and the stria vascularis were isolated for analysis. Retinyl esters were found in the basilar membrane at a concentration of 11.4 +/- 5.9 micrograms/g dry weight, a high concentration compared with that in other tissues of other organs. The spiral ligament contained retinyl esters at a lesser concentration and no retinyl esters were found in the stria vascularis. Retinol was not detected in the spiral ligament or basilar membrane but was found in the stria vascularis at a concentration of 1.2 +/- 0.8 micrograms/g. Retinyl palmitate and retinyl stearate were identified. This investigation shows that vitamin A forms retinyl esters with long-chain fatty acids in the basilar membrane in high concentrations relative to other organs and in greater quantity than in other sites in the inner ear.

Animals↗
PubMed1992

Pseudomonas aeruginosa exotoxin A and Haemophilus influenzae type b endotoxin. Effect on the inner ear and passage through the round window membrane of the chinchilla.

Pseudomonas aeruginosa exotoxin A was applied to the round window membrane of the chinchilla in concentrations ranging from 1 microgram/ml to 1 mg/ml. Haemophilus influenzae type b endotoxin (45,000 endotoxin units/ml) was applied in the same way. Five animals were also subjected to blocking of the Eustachian tube, 3 to 8 months earlier, resulting in serous otitis media and exotoxin A (1 mg/ml) was applied into the round window niche of these animals. Effects on the inner ear was recorded with quantitative morphology (hair cell counting) and electrophysiologically (action potential threshold measurements) 4 weeks after application of exotoxin A. Concentrations of exotoxin A in perilymph was measured with ELISA and concentration of endotoxin in perilymph was measured with Limulus Amoebocyte Lysate and Quantitative Chromogenic Limulus Amebocyte Lysate. Four weeks after application of exotoxin A at a concentration of 10 micrograms/ml severe inner ear damage could be demonstrated. No inner ear damage was demonstrated when lower concentrations were used. Passage into the inner ear could only be demonstrated after exposure of the round window membrane to an exotoxin A concentration of 1 mg/ml. Round window membranes affected by chronic inflammation were shown to be less permeable to exotoxin A, thus indicating that thickening of the round window membrane may have a protective effect on the inner ear. A low passage rate into the inner ear was demonstrated after endotoxin exposure. It may be concluded that small amounts of exotoxin A passing through the round window membrane may cause inner ear damage. The passage rates, however, for both exotoxin A and endotoxins are low.

Animals↗
PubMed1997

[Effect of hyaluronan perfusion through the round window on the function and morphology of the inner ear in guinea pigs].

UNLABELLED: In order to study the effect of the hyaluronan (HA) on the inner ear, twenty-six guinea pigs were divided into experimental and control groups, the experimental group were perfused with 2% HA 0.2 ml through the left round window. Auditory and vestibular function were investigated before and 5, 14, 28 days after perfusion. The threshold of action potential (AP) response to filtered clicks (0.25-10 kHz) were elevated at 5 days and were improved (at 1-4 kHz) at 14 days after perfusion (P < 0.05). At 28 days all AP response thresholds had returned to normal (P > 0.05). The nystagmus duration induced by caloric test (ENG) had no obviously change comparing with that of preoperation (P > 0.05). All guinea pigs were sacrificed 28 days after operation. The histology of inner ear were examined by means of membranous labyrinth mapping and temporal bone section after celloidin embedding. The morphology of Corti's and vestibular organs were not significantly damaged after perfusion. IN CONCLUSION: 1) 2%HA caused reversible and temporary changes in auditory function of inner ear; 2) 2%HA lacked ototoxic adverse effects, whereas exerted considerable osmotic effects and a slow dehydration of inner ears.

Action Potentials↗
PubMed1988

Comparative view of the central organization of afferent and efferent circuitry for the inner ear.

In all vertebrates, eighth nerve fibres from the inner ear distribute to target nuclei situated in the dorsolateral wall of the rhombencephalon. In amniotes, primary auditory and vestibular nuclei are readily delineated in that acoustic nuclei lie dorsal and sometimes rostral to vestibular nuclei. Fishes and aquatic amphibians have, in addition to labyrinthine organs, hair cell receptors in the lateral line system. Eighth nerve and lateral line fibres from these sense organs project to the octavolateralis region of the rhombencephalon. In this region, the primary nuclei cannot be easily divided into functionally distinct units. However, modality-specific zones seem to be present for auditory as well as lateral line projections lie dorsal and sometimes rostral to those from vestibular organs. Projections from the primary auditory and vestibular nuclei to higher order centres follow pathways which are conservative in their architecture among vertebrates. Ascending auditory fibres project either directly or via relay nuclei to a large midbrain center, the torus semicircularis (inferior colliculus) and hence to the forebrain. In fishes and aquatic amphibians, the lateral line system also sends a projection to the midbrain and information from this system may be integrated with auditory input at that level. The organization of vestibulospinal and vestibulo-ocular pathways shows little variation throughout vertebrate phylogeny. The sense organs of the inner ear of all vertebrates and of the lateral line system of anamniotes receive an efferent innervation. In anamniotes and some reptiles, the efferent supply originates from a single nucleus (Octavolateralis Efferent Nucleus) while that of "higher" vertebrates arises from separate auditory and vestibular efferent nuclei. The biological significance of this innervation for all vertebrates is not yet understood. However, an important feature common to all is the association of the efferent system with the motor centres of the hindbrain.

Animals↗
PubMed1998

Distribution of Na,K-ATPase is normal in the inner ear of a mouse with a null mutation of the glucocorticoid receptor.

This study was performed in order to test the hypothesis that the glucocorticoid hormone stimulates the formation of Na,K-ATPase in the inner ear of the mouse. An immunohistochemical study with respect to the presence and distribution of glucocorticoid receptors (GR) and Na,K-ATPase in the vestibular and cochlear regions of the inner ear was performed on a C57BL mouse with a null mutation of the glucocorticoid receptor (GR mutant mouse). The wild type C57BL mouse and the CBA mouse served as normal controls. As expected, the homozygous GR mutant mouse showed no specific staining for GR in the inner ear. The heterozygous GR mutant mouse showed faint staining of GR in the spiral limbus, the spiral ganglion, the organ of Corti and the utricle. This staining was markedly less than in the wild type C57BL mouse. Antibody labelling of Na,K-ATPase in the inner ear showed no significant difference between the homozygous and the heterozygous GR mutant mouse as compared to the control wild type C57BL mouse or the CBA mouse. Although earlier studies have shown a positive correlation between levels of glucocorticoid hormone in serum and the concentration of Na,K-ATPase in the inner ear, the hypothesis that glucocorticoid hormones alone stimulate the formation of Na,K-ATPase in the inner ear could not be confirmed by this study. Thus other regulating substances must be considered.

Adrenal Cortex Hormones↗