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1.
Acta Otolaryngol ; 142(2): 161-167, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-35225159

RESUMO

BACKGROUND: Long-term noise exposure may damage the cochlea and endolymph resorption system, which induces episodic vertigo and/or fluctuating hearing loss in later years. OBJECTIVE: This study adopted clinical symptoms, inner ear test battery, and/or magnetic resonance (MR) imaging to evaluate development of secondary endolymphatic hydrops (EH) in patients with noise-induced hearing loss (NIHL). METHODS: Forty NIHL patients with secondary EH were assigned to Group A. Another 40 age-and sex-matched NIHL patients without EH were assigned to Group B. All patients underwent an inner ear test battery. MR imaging was performed when diagnosis of EH was equivocal via above testing. RESULTS: Group A had significantly higher mean hearing levels (MHLs) than Group B at 1000, 2000, 4000, and 8000 Hz. Both groups displayed a significantly declining sequence of abnormality rates of the inner ear test battery. Under receiver operating characteristic (ROC) curve analysis, the cutoff threshold at 4 kHz for predicting the presence of secondary EH in NIHL patients was 52 dBHL, with a sensitivity of 62% and a specificity of 69%. CONCLUSIONS: NIHL patients revealing a typical 4 kHz dip-type audiogram with dip threshold >52 dBHL may predict development of secondary EH. A longitudinal follow-up coupled with MR imaging is required for confirmation.


Assuntos
Orelha Interna , Hidropisia Endolinfática , Perda Auditiva Provocada por Ruído , Endolinfa , Hidropisia Endolinfática/complicações , Hidropisia Endolinfática/diagnóstico por imagem , Perda Auditiva Provocada por Ruído/complicações , Perda Auditiva Provocada por Ruído/diagnóstico por imagem , Humanos , Imageamento por Ressonância Magnética
2.
Pflugers Arch ; 474(5): 505-515, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35112133

RESUMO

The endolymphatic sac is a small sac-shaped organ at the end of the membranous labyrinth of the inner ear. The endolymphatic sac absorbs the endolymph, in which the ion balance is crucial for inner ear homeostasis. Of the three sections of the endolymphatic sac, the intermediate portion is the center of endolymph absorption, particularly sodium transport, and is thought to be regulated by aldosterone. Disorders of the endolymphatic sac may cause an excess of endolymph (endolymphatic hydrops), a histological observation in Meniere's disease. A low-salt diet is an effective treatment for Meniere's disease, and is based on the assumption that the absorption of endolymph in the endolymphatic sac abates endolymphatic hydrops through a physiological increase in aldosterone level. However, the molecular basis of endolymph absorption in each portion of the endolymphatic sac is largely unknown because of difficulties in gene expression analysis, resulting from its small size and intricate structure. The present study combined reverse transcription-quantitative polymerase chain reaction and laser capture microdissection techniques to analyze the difference of gene expression of the aldosterone-controlled epithelial Na+ channel, thiazide-sensitive Na+-Cl- cotransporter, and Na+, K+-ATPase genes in the three individual portions of the endolymphatic sac in a rat model. A low-salt diet increased the expression of aldosterone-controlled ion transporters, particularly in the intermediate portion of the endolymphatic sac. Our findings will contribute to the understanding of the physiological function of the endolymphatic sac and the pathophysiology of Meniere's disease.


Assuntos
Hidropisia Endolinfática , Saco Endolinfático , Doença de Meniere , Aldosterona/metabolismo , Animais , Dieta Hipossódica , Endolinfa/metabolismo , Hidropisia Endolinfática/metabolismo , Hidropisia Endolinfática/patologia , Saco Endolinfático/metabolismo , Doença de Meniere/metabolismo , RNA Mensageiro/metabolismo , Ratos
3.
Proc Natl Acad Sci U S A ; 119(9)2022 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-35197290

RESUMO

Aminoglycosides (AGs) are commonly used antibiotics that cause deafness through the irreversible loss of cochlear sensory hair cells (HCs). How AGs enter the cochlea and then target HCs remains unresolved. Here, we performed time-lapse multicellular imaging of cochlea in live adult hearing mice via a chemo-mechanical cochleostomy. The in vivo tracking revealed that systemically administered Texas Red-labeled gentamicin (GTTR) enters the cochlea via the stria vascularis and then HCs selectively. GTTR uptake into HCs was completely abolished in transmembrane channel-like protein 1 (TMC1) knockout mice, indicating mechanotransducer channel-dependent AG uptake. Blockage of megalin, the candidate AG transporter in the stria vascularis, by binding competitor cilastatin prevented GTTR accumulation in HCs. Furthermore, cilastatin treatment markedly reduced AG-induced HC degeneration and hearing loss in vivo. Together, our in vivo real-time tracking of megalin-dependent AG transport across the blood-labyrinth barrier identifies new therapeutic targets for preventing AG-induced ototoxicity.


Assuntos
Antibacterianos/metabolismo , Gentamicinas/metabolismo , Proteína-2 Relacionada a Receptor de Lipoproteína de Baixa Densidade/metabolismo , Animais , Antibacterianos/toxicidade , Transporte Biológico , Cilastatina/farmacologia , Endolinfa/metabolismo , Gentamicinas/toxicidade , Células Ciliadas Auditivas/efeitos dos fármacos , Células Ciliadas Auditivas/metabolismo , Audição/efeitos dos fármacos , Proteína-2 Relacionada a Receptor de Lipoproteína de Baixa Densidade/antagonistas & inibidores , Camundongos , Estria Vascular/metabolismo
4.
Sci Total Environ ; 823: 153690, 2022 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-35143791

RESUMO

Over a decade ago, ocean acidification (OA) exposure was reported to induce otolith overgrowth in teleost fish. This phenomenon was subsequently confirmed in multiple species; however, the underlying physiological causes remain unknown. Here, we report that splitnose rockfish (Sebastes diploproa) exposed to ~1600 µatm pCO2(pH ~7.5) were able to fully regulated the pH of both blood and endolymph (the fluid that surrounds the otolith within the inner ear). However, while blood was regulated around pH 7.80, the endolymph was regulated around pH ~8.30. These different pH setpoints result in increased pCO2diffusion into the endolymph, which in turn leads to proportional increases in endolymph [HCO3-] and [CO32-]. Endolymph pH regulation despite the increased pCO2suggests enhanced H+removal. However, a lack of differences in inner ear bulk and cell-specific Na+/K+-ATPase and vacuolar type H+-ATPase protein abundance localization pointed out to activation of preexisting ATPases, non-bicarbonate pH buffering, or both, as the mechanism for endolymph pH-regulation. These results provide the first direct evidence showcasing the acid-base chemistry of the endolymph of OA-exposed fish favors otolith overgrowth, and suggests that this phenomenon will be more pronounced in species that count with more robust blood and endolymph pH regulatory mechanisms.


Assuntos
Membrana dos Otólitos , Água do Mar , Animais , Endolinfa/metabolismo , Peixes , Concentração de Íons de Hidrogênio
5.
Otol Neurotol ; 42(10): 1585-1593, 2021 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-34766952

RESUMO

OBJECTIVE: After 160 years the true underlying cause of Meniere's disease remains enigmatic. The aim of our study is to discuss the possible implication of an obstruction of the ductus reuniens as a cause in Menière's disease. METHODOLOGY: We first conducted an historical study of the description of the ductus reuniens. We then reviewed the literature regarding ductus reuniens obstruction in animal experiments, human post-mortem studies and living ear imaging. We completed its description by modern microCT imaging. Limited knowledge on the fate of dislodged saccular otoconia is summarized. The possible implications for Meniere's attacks are discussed. RESULTS: Victor Hensen was the first to describe the ductus reuniens in 1863. He described its length and width and predicted that saccular otoconia might enter the ductus and the cochlea. On microCT the narrowest width of the human ductus reuniens was 0.14 mm. The literature reports cochlear endolymphatic hydrops occurring after animal experimental obstruction of the duct. Human postmortem studies have confirmed saccular otoconial clumps entering the ductus and the cochlea. A postmortem study has shown sites of endolymphatic obstruction, and imaging speculates on blockages in ears with Meniere's disease. Dislodged utricular otoconia can be in clumps of otolithic membranes. CONCLUSION: Blockages of the ductus reuniens and at other endolymphatic system sites appear to be a feature in Meniere's disease ears. The blockages have been postulated to be saccular otoconia either causing or aggravating hydrops. This could be consistent with observed nystagmus reversals during attacks as the endolymphatic sac attempts to clear the hydrops and the otoconia.


Assuntos
Hidropisia Endolinfática , Saco Endolinfático , Doença de Meniere , Animais , Cóclea , Endolinfa , Hidropisia Endolinfática/complicações , Hidropisia Endolinfática/diagnóstico por imagem , Humanos , Masculino , Doença de Meniere/complicações , Doença de Meniere/diagnóstico por imagem
6.
BMC Med Imaging ; 21(1): 135, 2021 09 25.
Artigo em Inglês | MEDLINE | ID: mdl-34563164

RESUMO

BACKGROUND: Non-contrast FLAIR revealed increased signal within the inner ear in patients with vestibular schwannoma, which is generally assumed to occur in the perilymph; however, the majority of previous studies did not differentiate between the endolymph and perilymph. Therefore, endolymph signal changes have not yet been investigated in detail. The purpose of the present study was three-fold: (1) to assess perilymph signal changes in patients with vestibular schwannoma on heavily T2-weighted (T2W) 3D FLAIR, also termed positive perilymphatic images (PPI), (2) to evaluate signal and morphological changes in the endolymph on PPI, and (3) to establish whether vertigo correlates with the signal intensity ratios (SIR) of the vestibular perilymph or vestibular endolymphatic hydrops. METHODS: Forty-two patients with unilateral vestibular schwannoma were retrospectively recruited. We semi-quantitatively and qualitatively evaluated the perilymph signal intensity on the affected and unaffected sides. We also quantitatively examined the signal intensity of the vestibular perilymph and assessed the relationship between vertigo and the SIR of the vestibular perilymph on the affected side. We semi-quantitatively or qualitatively evaluated the endolymph, and investigated whether vestibular hydrops correlated with vertigo. RESULTS: The perilymph on the affected side showed abnormal signal more frequently (signal intensity grade: overall mean 1.45 vs. 0.02; comparison of signal intensity: overall mean 36 vs. 0 cases) and in more parts (the entire inner ear vs. the basal turn of the cochlea and vestibule) than that on the unaffected side. No significant difference was observed in the SIR of the vestibular perilymph with and without vertigo (5.54 vs. 5.51, p = 0.18). The endolymph of the vestibule and semicircular canals showed the following characteristic features: no visualization (n = 4), signal change (n = 1), or vestibular hydrops (n = 10). A correlation was not observed between vestibular hydrops and vertigo (p = 1.000). CONCLUSIONS: PPI may provide useful information on signal and morphological changes in the endolymph of patients with vestibular schwannoma. Further research is warranted to clarify the relationship between vertigo and the MR features of the inner ear.


Assuntos
Endolinfa/diagnóstico por imagem , Hidropisia Endolinfática/diagnóstico por imagem , Imageamento por Ressonância Magnética , Neuroma Acústico/diagnóstico por imagem , Perilinfa/diagnóstico por imagem , Adulto , Idoso , Idoso de 80 Anos ou mais , Endolinfa/fisiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Neuroma Acústico/patologia , Neuroma Acústico/fisiopatologia , Perilinfa/fisiologia , Estudos Retrospectivos , Vertigem/etiologia
7.
J Physiol ; 599(19): 4497-4516, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34426971

RESUMO

Excitable cochlear hair cells convert the mechanical energy of sounds into the electrical signals necessary for neurotransmission. The key process is cellular depolarization via K+ entry from K+ -enriched endolymph through hair cells' mechanosensitive channels. Positive 80 mV potential in endolymph accelerates the K+ entry, thereby sensitizing hearing. This potential represents positive extracellular potential within the epithelial-like stria vascularis; the latter potential stems from K+ equilibrium potential (EK ) across the strial membrane. Extra- and intracellular [K+ ] determining EK are likely maintained by continuous unidirectional circulation of K+ through a putative K+ transport pathway containing hair cells and stria. Whether and how the non-excitable tissue stria vascularis responds to acoustic stimuli remains unclear. Therefore, we analysed a cochlear portion for the best frequency, 1 kHz, by theoretical and experimental approaches. We have previously developed a computational model that integrates ion channels and transporters in the stria and hair cells into a circuit and described a circulation current composed of K+ . Here, in this model, mimicking of hair cells' K+ flow induced by a 1 kHz sound modulated the circulation current and affected the strial ion transport mechanisms; the latter effect resulted in monotonically decreasing potential and increasing [K+ ] in the extracellular strial compartment. Similar results were obtained when the stria in acoustically stimulated animals was examined using microelectrodes detecting the potential and [K+ ]. Measured potential dynamics mirrored the EK change. Collectively, because stria vascularis is electrically coupled to hair cells by the circulation current in vivo too, the strial electrochemical properties respond to sounds. KEY POINTS: A highly positive potential of +80 mV in K+ -enriched endolymph in the mammalian cochlea accelerates sound-induced K+ entry into excitable sensory hair cells, a process that triggers hearing. This unique endolymphatic potential represents an EK -based battery for a non-excitable epithelial-like tissue, the stria vascularis. To examine whether and how the stria vascularis responds to sounds, we used our computational model, in which strial channels and transporters are serially connected to those hair cells in a closed-loop circuit, and found that mimicking hair cell excitation by acoustic stimuli resulted in increased extracellular [K+ ] and decreased the battery's potential within the stria. This observation was overall verified by electrophysiological experiments using live guinea pigs. The sensitivity of electrochemical properties of the stria to sounds indicates that this tissue is electrically coupled to hair cells by a radial ionic flow called a circulation current.


Assuntos
Potássio , Estria Vascular , Animais , Cóclea , Endolinfa , Cobaias , Células Ciliadas Auditivas
8.
Hear Res ; 409: 108311, 2021 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-34311268

RESUMO

There is now growing evidence that hypercholesterolemia and high serum levels of low-density lipoproteins (LDL) predispose to sensorineural hearing loss. Circulating LDL-cholesterol is delivered to peripheral tissues via LDL receptor (LDLR) -mediated endocytosis. Recently, it has been shown that LDLR gene polymorphisms are associated with higher susceptibility to sudden deafness. These findings suggested that we should investigate the expression of LDLR from the postnatal maturation of the mouse cochlea until adulthood. In the cochlea of newborn mice, we observed that LDLR is mostly expressed in the lateral wall of the cochlea, especially in a band of cells directly facing the cochlear duct. Moreover, LDLR is expressed in the inner and outer hair cells, as well as in the adjacent greater epithelial ridge. In early postnatal stages, LDLR is expressed in the marginal cells of the immature stria vascularis, in the root cells of the spiral ligament, and in the adjacent outer sulcus cells. At the same time, LDLR begins to be expressed in the pillar cells of the immature organ of Corti. From the onset of hearing, LDLR is expressed in the marginal cells of the stria vascularis, in the outer sulcus cells, and in the capillaries of the adjacent spiral ligament. In the organ of Corti, LDLR is expressed in outer pillar cells and Deiters' cells, i.e. in the non-sensory supporting cells that directly surround the outer hair cells. These cells are believed to provide a mechanical coupling with the outer hair cells to modulate electromotility and cochlear amplification. In the stria vascularis of three-month-old mice, LDLR is further expressed in both marginal and intermediate cells. Overall, our results suggest that LDLR is mostly present in cochlear cells that are involved in endolymph homeostasis and cochlear amplification. Further functional studies will be needed to unravel how LDLR regulates extracellular and intracellular levels of cholesterol and lipoproteins in the cochlea, and how it could influence cochlear homeostasis.


Assuntos
Cóclea , Endolinfa , Homeostase , Animais , Camundongos , Receptores de LDL/genética , Estria Vascular
9.
Sci Rep ; 11(1): 11850, 2021 06 04.
Artigo em Inglês | MEDLINE | ID: mdl-34088924

RESUMO

The endolymphatic sac (ES) is the third part of the inner ear, along with the cochlea and vestibular apparatus. A refined sampling technique was developed to analyse the proteomics of ES endolymph. With a tailored solid phase micro-extraction probe, five ES endolymph samples were collected, and six sac tissue biopsies were obtained in patients undergoing trans-labyrinthine surgery for sporadic vestibular schwannoma. The samples were analysed using nano-liquid chromatography-tandem mass spectrometry (nLC-MS/MS) to identify the total number of proteins. Pathway identification regarding molecular function and protein class was presented. A total of 1656 non-redundant proteins were identified, with 1211 proteins detected in the ES endolymph. A total of 110 proteins were unique to the ES endolymph. The results from the study both validate a strategy for in vivo and in situ human sampling during surgery and may also form a platform for further investigations to better understand the function of this intriguing part of the inner ear.


Assuntos
Endolinfa/metabolismo , Saco Endolinfático/metabolismo , Neuroma Acústico/metabolismo , Proteoma/metabolismo , Adulto , Idoso , Animais , Biópsia , Cromatografia Líquida , Cóclea , Orelha Interna/fisiologia , Feminino , Humanos , Masculino , Espectrometria de Massas , Pessoa de Meia-Idade , Espectrometria de Massas em Tandem , Vestíbulo do Labirinto , Microtomografia por Raio-X , Adulto Jovem
10.
Hear Res ; 407: 108282, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34130038

RESUMO

The semicircular canals (SCCs) in the vestibular system can sense angular motion of the head, which performs a crucial role in maintaining the human's sense of balance. The different spatial orientations of the head affect the response of human SCCs to rotational movement. In this study, we combined the numerical model of bilateral human SCCs with vestibulo-ocular reflex experiments, and quantitatively investigated the responses of SCCs to constant angular acceleration when the head was in different left-leaning positions, including the head tilted 0°, 15°, 30°, 45°, 60°, 70°, 80°, and 90° to the left. The results showed that the vertical nystagmus slow-phase velocity (SPV) and the corresponding maximal cupula shear strain at the crista surface rose with an increase in the left-leaning angle of the head, reached a maximum at the position of the head tilted approximately 70° to the left, and then decreased gradually. Both the horizontal nystagmus SPV and the corresponding maximal cupula shear strain at the crista surface were the largest under the position of the head tilted 0° to the left, and decreased gradually as the left-leaning angle of the head increased. The numerical results of cupula shear strain at the crista surface in bilateral SCCs can quantitatively explain the combined effects of each SCC's excitation or inhibition on volunteers' nystagmus SPV under different head positions. In addition, a fluid-structure interaction investigation revealed that different left-leaning head positions changed the endolymphatic pressure gradient distribution in SCCs, which determined the transcupular pressure, cupula shear strain at the crista surface, and nystagmus SPV.


Assuntos
Nistagmo Patológico , Endolinfa , Humanos , Nistagmo Fisiológico , Reflexo Vestíbulo-Ocular , Canais Semicirculares
11.
Sci Rep ; 11(1): 8208, 2021 04 15.
Artigo em Inglês | MEDLINE | ID: mdl-33859270

RESUMO

The vestibular receptor of cupula acts an important role in maintaining body balance. However, the cupula buried in the semicircular canals (SCCs) will be destroyed if it is detached from the relevant environment. The mechanical properties of human cupula still remain ambiguous. In this paper, we explored the cupula responses changing with temperature by experiments and numerical simulation of SCCs model. We obtained 3 volunteers' nystagmus induced by constant angular acceleration when the temperature of volunteers' SCCs was 36 °C and 37 °C respectively. The slow-phase velocity of 3 volunteers decreased by approximately 3°/s when the temperature of SCCs reduced by 1 °C, which corresponded to the reduction of cupula deformation by 0.3-0.8 µm in the numerical model. Furthermore, we investigated the effects of the variation of endolymphatic properties induced by temperature reduction on cupula deformation through numerical simulation. We found that the decrease of cupula deformation was not caused by the change of endolymphatic properties, but probably by the increase of cupula's elastic modulus. With the temperature reducing by 1 °C, the cupula's elastic modulus may increase by 6-20%, suggesting that the stiffness of cupula is enhanced. This exploration of temperature characteristic of human cupula promotes the research of alleviating vestibular diseases.


Assuntos
Fenômenos Biomecânicos/fisiologia , Canais Semicirculares/fisiologia , Temperatura , Aceleração , Adulto , Temperatura Corporal/fisiologia , Endolinfa/fisiologia , Humanos , Masculino , Nistagmo Patológico/fisiopatologia , Reflexo Vestíbulo-Ocular/fisiologia , Rotação , Doenças Vestibulares/etiologia , Doenças Vestibulares/patologia
12.
J Vestib Res ; 31(4): 289-295, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33579885

RESUMO

The mechanisms of ion exchanges and water fluxes underlying the endolymphatic hydrops phenomenon, remain indeterminate so far. This review intends to reposition the physical environment of the endolymphatic compartment within the inner ear, as well as to recall the molecular effectors present in the membranous labyrinth and that could be at the source of the hydrops.


Assuntos
Orelha Interna , Hidropisia Endolinfática , Endolinfa , Humanos
13.
J Vestib Res ; 31(4): 247-249, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33459676

RESUMO

Endolymphatic hydrops is defined as an accumulation of endolymph in the inner ear leading to a buildup of pressure and distortion of intralabyrinthine structures. The pressure variation is neither obvious nor easy to measure and remains not clearly confirmed. The distortion of endolymphatic structures has been the main described phenomenon since Hallpike, Cairns and Yamakawa in 1938. However, some clinical symptoms associated with endolymphatic hydrops are in addition to the typical triad of symptoms of Meniere's disease. This introduction to the state of the art is an analysis of the relationship between hydrops and clinical vestibular disorders, with a focus on the dynamics of endolymphatic hydrops. The distortion of endolabyrinthine structures can be considered as a dynamic process modeled with mechanical elastic behavior.


Assuntos
Orelha Interna , Hidropisia Endolinfática , Doença de Meniere , Doenças Vestibulares , Endolinfa , Humanos , Imageamento por Ressonância Magnética , Doença de Meniere/complicações
14.
Magn Reson Med Sci ; 20(3): 272-279, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32830173

RESUMO

PURPOSE: MRI of endolymphatic hydrops (EH) 4 h after intravenous administration of a single dose of gadolinium-based contrast agent is used for clinical examination in some institutions; however, further improvement in image quality would be valuable for wider clinical utility. Denoising using deep learning reconstruction (Advanced Intelligent Clear-IQ Engine [AiCE]) has been reported for CT and MR. The purpose of this study was to compare the contrast-to-noise ratio of endolymph to perilymph (CNREP) between the improved hybrid of reversed image of the positive endolymph signal and the native image of the perilymph signal multiplied with the heavily T2-weighted MR cisternography (iHYDROPS-Mi2) images, which used AiCE for the three source images (i.e. positive endolymph image [PEI], positive perilymph image [PPI], MR cisternography [MRC]) to those that did not use AiCE. We also examined if there was a difference between iHYDROPS-Mi2 images with and without AiCE for degree of visual grading of EH and in endolymphatic area [EL] ratios. METHODS: Nine patients with suspicion of EH were imaged on a 3T MR scanner. iHYDROPS images were generated by subtraction of PEI images from PPI images. iHYDROPS-Mi2 images were then generated by multiplying MRC with iHYDROPS images. The CNREP and EL ratio were measured on the iHYDROPS-Mi2 images. Degree of radiologist visual grading for EH was evaluated. RESULTS: Mean CNREP ± standard deviation was 1681.8 ± 845.2 without AiCE and 7738.6 ± 5149.2 with AiCE (P = 0.00002). There was no significant difference in EL ratio for images with and without AiCE. Radiologist grading for EH agreed completely between the 2 image types in both the cochlea and vestibule. CONCLUSION: The CNREP of iHYDROPS-Mi2 images with AiCE had more than a fourfold increase compared with that without AiCE. Use of AiCE did not adversely affect radiologist grading of EH.


Assuntos
Aprendizado Profundo , Hidropisia Endolinfática , Meios de Contraste , Endolinfa , Hidropisia Endolinfática/diagnóstico por imagem , Humanos , Imageamento por Ressonância Magnética
15.
Hear Res ; 400: 108113, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33221698

RESUMO

Na+, K+-ATPase (Na,K-ATPase) is an ubiquitous enzyme in the inner ear and a key factor in the maintenance of the osmotic gradient of the endolymph. This study uses Na,K-ATPase α1 subunit immunoreactivity (IR) to identify cellular structures in the normal and disease human cochlea. Formalin-fixed celloidin-embedded (FFCE) human temporal bone sections were immunoreacted with mouse monoclonal antibodies against Na,K-ATPase α1 subunit. Na,K-ATPase α1 IR was examined in the cochlea of 30 patients: four with normal hearing, 5 with Meniere's disease, and 21 with other inner ear diseases: 11 male, 19 female; ages 42 to 96 years-old (yo), average age of 77 yo. Na,K-ATPase α1 IR area was quantified using the ImageJ software program. Na,K-ATPase α1 IR was located in the stria vascularis, and in type I, II and IV fibrocytes of the spiral ligament in the cochlea from patients with normal hearing. Na,K-ATPase α1 IR was seen in Deiters's cells and inner phalangeal cells of the organ of Corti. Na,K-ATPase α1 IR was present in satellite cells that surround the neurons of the spiral ganglia. In the inner ear of pathological specimens, Na,K-ATPase IR area was decreased (compared to the normal) in the stria vascularis, supporting cells in the organ of Corti and satellite cells of the spiral ganglia. These results show that Na,K-ATPase α1 IR is a good marker to identify cellular structures of the human inner ear and may be used to study cellular changes in the cochlea associated with aging and disease. The ubiquitous localization of Na,K-ATPase α1 in the human cochlea is consistent with the Na,K-ATPase role in ionic homeostasis and osmolarity, similar to that seen in animal models.


Assuntos
Orelha Interna , Adulto , Idoso , Idoso de 80 Anos ou mais , Animais , Cóclea/metabolismo , Orelha Interna/metabolismo , Endolinfa/metabolismo , Feminino , Humanos , Masculino , Camundongos , Pessoa de Meia-Idade , ATPase Trocadora de Sódio-Potássio/metabolismo , Estria Vascular/metabolismo
16.
Comput Methods Biomech Biomed Engin ; 24(8): 905-912, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33305605

RESUMO

Vestibular aqueduct is a precise structure embedded in the temporal bone and plays a key role in the physiological function of inner ear by maintaining the endolymphatic circulation and buffering the impact from intracranial pressure. Although the alterations on the morphology or volume of vestibular aqueduct result in variety of diseases, the approaches of evaluating the condition of vestibular aqueduct are still unsatisfing because the pathological sections utilized for the 3D construction model most likely undergoes morphological changes. In this study, the vestibular aqueduct images obtained by CT scanning were processed by finite element method to construct the 3D model. To assess if this numerical model reflects the actual biomechanical properties of vestibular aqueduct, the fluid-solid coupling calculation was applied to simulate the endolymphatic flow in the vestibular aqueduct. By measuring the dynamics of endolymphatic flow, and the pressure and displacement on round membrane under external pressure, we found the numerical 3D model recapitulated the biomechanical characteristics of the real vestibular aqueduct. In summary, our approach of 3D model construction for vestibular aqueduct will provide a powerful method for the research of vestibular aqueduct-related diseases.


Assuntos
Osso Temporal/fisiologia , Osso Temporal/fisiopatologia , Aqueduto Vestibular/fisiologia , Aqueduto Vestibular/fisiopatologia , Fenômenos Biomecânicos , Biofísica , Endolinfa , Análise de Elementos Finitos , Humanos , Imageamento Tridimensional , Pressão Intracraniana , Masculino , Pessoa de Meia-Idade , Pressão , Tomografia Computadorizada por Raios X/métodos
17.
Biol Cybern ; 114(4-5): 421-442, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32889629

RESUMO

The semicircular ducts (SCDs) of the vestibular system play an instrumental role in equilibration and rotation perception of vertebrates. The present paper is a review of quantitative approaches and shows how SCDs function. It consists of three parts. First, the biophysical mechanisms of an SCD system composed of three mutually connected ducts, allowing endolymph to flow from one duct into another one, are analysed. The flow is quantified by solving the continuity equations in conjunction with the equations of motion of the SCD hydrodynamics. This leads to mathematical expressions that are suitable for further analytical and numerical analysis. Second, analytical solutions are derived through four simplifying steps while keeping the essentials of the coupled system intact. Some examples of flow distributions for different rotations are given. Third, the focus is on the transducer function of the SCDs. The complex structure of the mechano-electrical transduction apparatus inside the ampullae is described, and the consequences for sensitivity and frequency response are evaluated. Furthermore, both the contributions of the different terms of the equations of motion and the influence of Brownian motion are analysed. Finally, size limitations, allometry and evolutionary aspects are taken into account.


Assuntos
Endolinfa , Canais Semicirculares , Animais , Movimento (Física) , Ductos Semicirculares , Vertebrados
18.
Toxicol In Vitro ; 67: 104915, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32540163

RESUMO

Despite well-documented neurotoxic and ototoxic properties, styrene remains commonly used in industry. Its effects on the cochlea have been extensively studied in animals, and epidemiological and animal evidence indicates an impact on balance. However, its influence on the peripheral vestibular receptor has yet to be investigated. Here, we assessed the vestibulotoxicity of styrene using an in vitro model, consisting of three-dimensional cultured newborn rat utricles filled with a high­potassium (K+) endolymph-like fluid, called "cysts". K+ entry in the cyst ("influx") and its exit ("efflux") are controlled by secretory cells and hair cells, respectively. The vestibular epithelium's functionality is thus linked to K+ concentration, measured using a microelectrode. Known inhibitors of K+ efflux and influx validated the model. Cysts were subsequently exposed to styrene (0.25; 0.5; 0.75 and 1 mM) for 2 h or 72 h. The decrease in K+ concentration measured after both exposure durations was dose-dependent, and significant from 0.75 mM styrene. Vacuoles were visible in the cytoplasm of epithelial cells from 0.5 mM after 2 h and from 0.25 mM after 72 h. The results presented here are the first evidence that styrene may deregulate K+ homeostasis in the endolymphatic space, thereby altering the functionality of the vestibular receptor.


Assuntos
Endolinfa/efeitos dos fármacos , Potássio/metabolismo , Sáculo e Utrículo/efeitos dos fármacos , Estireno/toxicidade , Animais , Animais Recém-Nascidos , Endolinfa/metabolismo , Feminino , Ratos Long-Evans , Sáculo e Utrículo/metabolismo , Sáculo e Utrículo/patologia
19.
J Neurol ; 267(Suppl 1): 91-103, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32529576

RESUMO

Strong static magnetic fields, as used in magnetic resonance imaging (MRI), stimulate the vestibular inner ear leading to a state of imbalance within the vestibular system that causes nystagmus. This magnetic vestibular stimulation (MVS) also modulates fluctuations of resting-state functional MRI (RS-fMRI) networks. MVS can be explained by a Lorentz force model, indicating that MVS is the result of the interaction of the static magnetic field strength and direction (called "B0 magnetic field" in MRI) with the inner ear's continuous endolymphatic ionic current. However, the high variability between subjects receiving MVS (measured as nystagmus slow-phase velocity and RS-fMRI amplitude modulations) despite matching head position, remains to be explained. Furthermore, within the imaging community, an "easy-to-acquire-and-use" proxy accounting for modulatory MVS effects in RS-fMRI fluctuations is needed. The present study uses MRI data of 60 healthy volunteers to examine the relationship between RS-fMRI fluctuations and the individual orientation of inner-ear anatomy within the static magnetic field of the MRI. The individual inner-ear anatomy and orientation were assessed via high-resolution anatomical CISS images and related to fluctuations of RS-fMRI networks previously associated with MVS. More specifically, we used a subject-specific proxy for MVS (pMVS) that corresponds to the orientation of the individual inner-ear anatomy within the static magnetic field direction (also called "z-direction" in MR imaging). We found that pMVS explained a considerable fraction of the total variance in RS-fMRI fluctuations (for instance, from 11% in the right cerebellum up to 36% in the cerebellar vermis). In addition to pMVS, we examined the angle of Reid's plane, as determined from anatomical imaging as an alternative and found that this angle (with the same sinus transformation as for pMVS) explained considerably less variance, e.g., from 2 to 16%. In our opinion, an excess variability due to MVS should generally be addressed in fMRI research analogous to nuisance regression for movement, pulsation, and respiration effects. We suggest using the pMVS parameter to deal with modulations of RS-fMRI fluctuations due to MVS. MVS-induced variance can easily be accounted by using high-resolution anatomical imaging of the inner ear and including the proposed pMVS parameter in fMRI group-level analysis.


Assuntos
Imageamento por Ressonância Magnética , Vestíbulo do Labirinto , Endolinfa , Substância Cinzenta , Humanos , Campos Magnéticos , Vestíbulo do Labirinto/diagnóstico por imagem
20.
Biomech Model Mechanobiol ; 19(6): 2343-2356, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32440791

RESUMO

The malfunctioning of semicircular canals (SCCs) in the vestibular system results in diseases that disrupt the individual's daily life. Vestibular diseases can be treated more effectively if the functioning of the SCCs is better understood. However, the SCC is difficult to dissect, because it is a complex structure buried deep in the inner ear. To thoroughly understand the function of SCCs and provide better treatment plans for vestibular diseases, we constructed a numerical model of human SCCs and validated it experimentally. Based on the principle of the vestibulo-ocular reflex, the cupula deformation deflects embedded sensory hair cell bundles, transmitting signals to the brain and inducing a slow compensatory eye movement. The slow-phase velocity (SPV) is the characteristic of the slow compensatory eye movement. We investigated the cupula deformation in the numerical model and the SPV under different conditions. The relationship between the cupula deformation and the SPV was quantified for three volunteers. It was observed that the maximal cupula deformation is proportional to the angular acceleration, while the SPV is changing nonlinearly with the angular acceleration. For three volunteers, the relationship between the cupula deformation and the SPV can be expressed by same type function of which the parameters are dependent on individual differences. These results validate the reliability of the numerical model.


Assuntos
Nistagmo Congênito/fisiopatologia , Canais Semicirculares/fisiologia , Aceleração , Endolinfa/fisiologia , Desenho de Equipamento , Movimentos Oculares , Humanos , Modelos Teóricos , Nistagmo Congênito/diagnóstico , Pupila , Reflexo Vestíbulo-Ocular , Reprodutibilidade dos Testes , Rotação , Vertigem/fisiopatologia
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