Netrin 1 is required for semicircular canal formation in the mouse inner ear

Development ◽  
2000 ◽  
Vol 127 (1) ◽  
pp. 13-22 ◽  
Author(s):  
M. Salminen ◽  
B.I. Meyer ◽  
E. Bober ◽  
P. Gruss
Keyword(s):  
Central Nervous System ◽  
Axon Guidance ◽  
Inner Ear ◽  
Semicircular Canal ◽  
Cell Walls ◽  
Semicircular Canals ◽  
Plate Formation ◽  
Multistep Process ◽  
Anterior Semicircular Canal ◽  
The Central Nervous System

The morphogenetic development of the mammalian inner ear is a complex multistep process, the molecular and cellular details of which are only beginning to be unraveled. We show here that mouse netrin 1, known to be involved in axon guidance and cell migration in the central nervous system, also plays a critical morphogenetic role during semicircular canal formation. netrin 1 is expressed at high levels in the otic epithelium, in cells that will come together to form a fusion plate, a prerequisite for the formation of semicircular canals. In netrin 1 mutant mice, fusion plate formation is severely affected resulting in a reduced anterior semicircular canal and the complete lack of the posterior and lateral canals. Our results suggest that netrin 1 facilitates semicircular canal formation through two different mechanisms: (1) it participates in the detachment of the fusion plate epithelia from the basement membrane, and (2) it stimulates proliferation of the periotic mesenchymal cells which then push the epithelial cell walls together to form the fusion plate.

Changes in monkey horizontal semicircular canal afferent responses after spaceflight

1992 ◽  
Vol 73 (2) ◽  
pp. S112-S120 ◽  
Author(s):  
M. J. Correia ◽  
A. A. Perachio ◽  
J. D. Dickman ◽  
I. B. Kozlovskaya ◽  
M. G. Sirota ◽  
...  
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Semicircular Canal ◽  
Semicircular Canals ◽  
Vestibular Stimulation ◽  
Horizontal Semicircular Canal ◽  
Horizontal Canal ◽  
Efferent Connections ◽  
The Central Nervous System ◽  
Afferent Response

Extracellular responses from single horizontal semicircular canal afferents in two rhesus monkeys were studied after recovery from a 14-day biosatellite (COSMOS 2044) orbital spaceflight. On the 1st postflight day, the mean gain for 9 different horizontal canal afferents, tested using one or several different passive yaw rotation waveforms, was nearly twice that for 20 horizontal canal afferents similarly tested during preflight and postflight control studies. Adaptation of the afferent response to passive yaw rotation on the 1st postflight day was also greater. These results suggest that at least one component of the vestibular end organ (the semicircular canals) is transiently modified after exposure to 14 days of microgravity. It is unclear whether the changes are secondary to other effects of microgravity, such as calcium loss, or an adaptive response. If the response is adaptive, then this report is the first evidence that the response of the vestibular end organ may be modified (presumably by the central nervous system via efferent connections) after prolonged unusual vestibular stimulation. If this is the case, the sites of plasticity of vestibular responses may not be exclusively within central nervous system vestibular structures, as previously believed.

Breuer Discovers How the Balance Portion of the Inner Ear Works

2016 ◽  
Author(s):  
Robert W. Baloh
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Inner Ear ◽  
Hair Cells ◽  
Semicircular Canals ◽  
Head Movements ◽  
Nerve Endings ◽  
Basic Premise ◽  
Initial Work ◽  
The Central Nervous System

Josef Breuer presented his initial work on the inner ear to the Imperial Society of Physicians in 1873. His basic premise was that the semicircular canals sense angular movement of the head by movement of the fluid (endolymph) within them. The endolymph moves relative to the walls of the canals because of its inertia. In dissecting the semicircular canals of pigeons, he noted nerve endings contacting cells at the base of the ampulla and microscopic hairs extending from the top of the cells into a gelatinous bulb (the cupula). He hypothesized that movement of the endolymph fluid triggered by angular head movements bent the tiny hairs, activating the nerve endings at the base of the hair cells. The nerves in turn passed on signals reflecting the direction and magnitude of hair deflection to the central nervous system. At approximately the same time, Ernst Mach came to a similar conclusion.

scholarly journals NEUROANATOMÍA DEL SAURÓPODO TITANOSAURIO NARAMBUENATITAN PALOMOI DEL CRETÁCICO SUPERIOR DE PATAGONIA, ARGENTINA.

2020 ◽  
Author(s):  
Ariana Paulina-Carabajal ◽  
Leonardo Filippi ◽  
Fabien Knoll
Keyword(s):  
Semicircular Canal ◽  
Upper Cretaceous ◽  
Semicircular Canals ◽  
Lateral View ◽  
Phylogenetic Position ◽  
Posterior Semicircular Canal ◽  
X Ray ◽  
Anterior Semicircular Canal ◽  
X Ray Computed ◽  
The Brain

this taxon has uncertain phylogenetic relationships within the clade. An X-ray Computed Tomography (CT) scan of the holotypebraincase allowed the first reconstruction of the brain and inner ear of this taxon, making it possible to compare the neuroanatomy with thatof closely related forms. Except for the slightly sigmodal shape of the endocast in lateral view—considered a basal condition—, the brainshows derived titanosaurian traits such as a poorly developed dorsal expansion and a single exit for Cranial Nerve (CN) XII. In contrast, the innerear exhibits slender and long semicircular canals (the anterior semicircular canal is distinctly longer than the posterior semicircular canal), whichis a character present in more basal representatives of the group, such as Sarmientosaurus. We consider, however, the morphology of theinner ear as an unreliable indicator of phylogenetic position. Furthermore, there is a remarkable similarity between the morphology of theendocast of Narambuenatitanand the possible saltasaurid from (FAM 03.064), from the Upper Cretaceous of Fox-Amphoux-Métisson, France,suggesting saltasaurine affinities for the Argentinean taxon.

Ménière Recognizes That Vertigo Can Originate from the Inner Ear

2016 ◽  
Author(s):  
Robert W. Baloh
Keyword(s):  
Hearing Loss ◽  
Inner Ear ◽  
Blood Vessels ◽  
Semicircular Canal ◽  
Semicircular Canals ◽  
Underlying Disease ◽  
The Brain ◽  
Benign Course

Prosper Ménière was the first clinician to conclude that vertigo can result from diseases of the inner ear. The symptom of vertigo originally fell under the rubric of apoplectiform cerebral congestion, a disorder thought to result from overfilling of blood vessels in the brain. Ménière noted that patients with vertigo and hearing loss associated with damage to the inner ear often have a benign course, and aggressive treatments such as bleeding can be more dangerous than the underlying disease. The first hint that the semicircular canals may be related to balance rather than hearing was provided by a Frenchman, Marie Jean Pierre Flourens. He systematically cut each semicircular canal in the pigeon and noted that the animal’s head and body tended to move in the plane of the damaged canal. The gyrations of the animals described by Flourens made Ménière think that vertigo in humans might be a similar phenomenon.

The significance for postoperative hearing of preserving the labyrinth in acoustic neurinoma surgery

1992 ◽  
Vol 77 (5) ◽  
pp. 677-684 ◽  
Author(s):  
Marcos Tatagiba ◽  
Madjid Samii ◽  
Cordula Matthies ◽  
Mowaffak El Azm ◽  
Robert Schonmayr
Keyword(s):  
Hearing Loss ◽  
Inner Ear ◽  
Semicircular Canal ◽  
Semicircular Canals ◽  
Cochlear Nerve ◽  
Acoustic Neurinoma ◽  
Content Type ◽  
Acoustic Neurinomas ◽  
A Prospective Study ◽  
Fine Print

✓ Among 186 patients with preoperative hearing, a total of 189 acoustic neurinomas were removed through a lateral suboccipital approach with anatomical preservation of the cochlear nerve. Functional hearing was preserved in 92 (49%) of these patients; despite anatomical preservation of the cochlear nerve, deafness was the result in 51 % of the series. Many factors have been considered to cause hearing loss in patients whose cochlear nerve was intact after surgery; these include nerve retraction, nerve or cochlear ischemia, overheating and vibration damage to the nerve, and opening of the labyrinth. To evaluate the significance of injury to the labyrinth in postoperative hearing loss, a prospective study was undertaken. High-resolution computerized tomography studies through the inner ear with bone algorithm were performed pre- and postoperatively. The postoperative status of the labyrinth was classified into three patterns: intact, fenestrated, and widely opened. Injury to the labyrinth occurred in 30% of the cases. The most frequently injured labyrinth structures were the crus commune of the posterior and superior semicircular canals (52%), the posterior semicircular canal (23%). the vestibule (21%), and the superior semicircular canal (4%). A statistically significant relationship was found between injury to the labyrinth and deafness, elevated thresholds, and lower discrimination values at pure-tone audiograms and speech audiometry (p < 0.0001). The degree of the injury (comparison between fenestration and wide opening of the labyrinth) was also significantly related to postoperative deafness (p < 0.0001). Disturbance of the inner-ear fluids was considered to be the cause of the hearing loss. In 12 patients labyrinth injury was not associated with deafness. This finding may support the existence of mechanisms of cochlear protection. The homeostatic function of the endolymphatic sac was considered to play an important role in recovery of damaged hearing in these 12 cases.

scholarly journals A New Coordinate System for Magnetic Resonance Imaging of the Vestibular System

2022 ◽  
Vol 12 ◽  
Author(s):  
Weixing Liu ◽  
Gui Chen ◽  
Junyang Xie ◽  
Tianhao Liang ◽  
Chunyi Zhang ◽  
...  
Keyword(s):  
Coordinate System ◽  
Vestibular System ◽  
Semicircular Canal ◽  
Internal Auditory Canal ◽  
Semicircular Canals ◽  
Image Data ◽  
Mean Values ◽  
Medical Software ◽  
Anterior Semicircular Canal ◽  
Imaging Plane

Objectives: To develop and evaluate a new coordinate system for MRI of the vestibular system.Methods: In this study, 53 internal auditory canal MRI and 78 temporal bone CT datasets were analyzed. Mimics Medical software version 21.0 was used to visualize and three-dimensionally reconstruct the image data. We established a new coordinate system, named W–X, based on the center of the bilateral eyeballs and vertex of the bilateral superior semicircular canals. Using the W–X coordinate system and Reid's coordinate system, we measured the orientations of the planes of the anterior semicircular canal (ASCC), the lateral semicircular canal (LSCC), and the posterior semicircular canal (PSCC).Results: No significant differences between the angles measured using CT and MRI were found for any of the semicircular canal planes (p &gt; 0.05). No statistical differences were found between the angles measured using Reid's coordinate system (CT) and the W–X coordinate system (MRI). The mean values of ∠ASCC &amp; LSCC, ∠ASCC &amp; PSCC, and ∠LSCC &amp; PSCC were 84.67 ± 5.76, 94.21 ± 3.81, and 91.79 ± 5.22 degrees, respectively. The angle between the LSCC plane and the horizontal imaging plane was 15.64 ± 3.92 degrees, and the angle between the PSCC plane and the sagittal imaging plane was 48.79 ± 4.46 degrees.Conclusion: A new W–X coordinate system was developed for MRI studies of the vestibular system and can be used to measure the orientations of the semicircular canals.

scholarly journals Commissureless is required both in commissural neurones and midline cells for axon guidance across the midline

Development ◽  
2002 ◽  
Vol 129 (12) ◽  
pp. 2947-2956 ◽  
Author(s):  
Marios Georgiou ◽  
Guy Tear
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Rna Interference ◽  
Protein Expression ◽  
Axon Guidance ◽  
Contralateral Side ◽  
Commissural Axons ◽  
Midline Crossing ◽  
The Central Nervous System ◽  
Midline Cells

In the absence of Commissureless (Comm) function, axons are unable to extend across the central nervous system midline. Comm downregulates levels of Roundabout (Robo), a receptor for the midline repellent Slit, in order to allow axons to cross the midline. comm transcript is expressed at high levels in the midline glia and Comm protein accumulates on axons at the midline. This has led to the hypothesis that Comm moves from the midline glia to the axons, where it can reduce Robo levels. We have found that expression of Comm in the midline cells is unable to rescue the comm phenotype and that tagged versions of Comm are not transferred to axons. A re-examination of Comm protein expression and the use of targeted RNA interference reveal that correct midline crossing requires that Comm is expressed in the commissural axons and midline glia. We suggest that accumulation of Comm protein at the midline spatially limits Comm activity and prevents it from being active on the contralateral side of the central nervous system.

scholarly journals Building Spinal and Brain Commissures: Axon Guidance at the Midline

2013 ◽  
Vol 2013 ◽  
pp. 1-21 ◽  
Author(s):  
Valérie Castellani
Keyword(s):  
Spinal Cord ◽  
Central Nervous System ◽  
Nervous System ◽  
Axon Guidance ◽  
Molecular Mechanisms ◽  
General Role ◽  
Commissural Neurons ◽  
Common Task ◽  
The Central Nervous System ◽  
Brain And Spinal Cord

Commissural circuits are brain and spinal cord connections which interconnect the two sides of the central nervous system (CNS). They play essential roles in brain and spinal cord processing, ensuring left-right coordination and synchronization of information and commands. During the formation of neuronal circuits, all commissural neurons of the central nervous system must accomplish a common task, which is to project their axon onto the other side of the nervous system, across the midline that delineates the two halves of the CNS. How this task is accomplished has been the topic of extensive studies over the last past 20 years and remains one of the best models to investigate axon guidance mechanisms. In the first part of this review, I will introduce the commissural circuits, their general role in the physiology of the nervous system, and their recognized or suspected pathogenic properties in human diseases. In the second part of the review, I will concentrate on two commissural circuits, the spinal commissures and the corpus callosum, to detail the cellular and molecular mechanisms governing their formation, mostly during their navigation at the midline.

scholarly journals Validation of inner ear MRI in patients with Ménière’s disease by comparing endolymphatic hydrops from histopathologic specimens

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Young Sang Cho ◽  
Jong Sei Kim ◽  
Min Bum Kim ◽  
Sung Min Koh ◽  
Chang Hee Lee ◽  
...  
Keyword(s):  
Inner Ear ◽  
Temporal Bone ◽  
Semicircular Canal ◽  
Endolymphatic Hydrops ◽  
Semicircular Canals ◽  
Meniere’S Disease ◽  
Ménière’S Disease ◽  
Affected Side ◽  
Mri Scans ◽  
Temporal Bones

AbstractIntravenous gadolinium-enhanced inner-ear magnetic resonance imaging (IV-Gd inner-ear MRI) has been used to visualize endolymphatic hydrops (EH) in clinical diagnosis of Ménière’s disease (MD). However, lack of histological validation has led to several concerns regarding how best to interpret the resulting images. Here, we compared hydropic changes in temporal bone specimens with the results of IV-Gd inner-ear MRI in patients with MD. Histopathologic images of temporal bones from 37 patients with MD and 10 healthy controls were collected from the National Temporal Bone Bank of the Massachusetts Eye and Ear Infirmary in the United States. The EH ratios in the vestibule and cochlea were calculated from temporal bones using the methods used for IV-Gd inner-ear MRI, and the degree to which the saccular and utricular hydrops contributed to vestibular hydrops was measured. The presence of hydropic change in each semicircular canal was assessed using temporal bone images and compared with IV-Gd inner-ear MRI scans of 74 patients with MD. Based on human temporal bone imagery, the EH ratios in the cochlea and the vestibule on the affected side were 0.314 and 0.757, respectively. In the healthy control group, the ratio was 0.064 for the cochlea and 0.289 for the vestibule; these values were significantly different from those for the affected side of MD patients. The values for the affected ear were similar to the ratios from the IV-Gd inner-ear MRI scans in MD patients. In the vestibule, saccular hydrops were more common than utricular hydrops. The average EH ratios in the saccule and utricle were 0.513 and 0.242, respectively. No significant hydropic change from each of three semicircular canals was evident in temporal bone histopathology. However, herniation of otolithic organs (saccule or utricle) into the lateral semicircular canal was found in 44.4% of the patients, with saccular herniation (24.8%) more common than utricular herniation (16.7%). Although IV-Gd inner-ear MRI might not reflect fully the results of actual histopathology due to the limited resolution of MRI and image-processing techniques, the measured EH ratios from temporal bone specimens and IV-Gd inner-ear MRI scans were similar. Hydropic change in the three semicircular canals was not significant at either the ampullated or nonampullated end. Canal invasion of vestibular hydrops seen on MRI also appeared in temporal bone histopathology, and saccular invasion was dominant.

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