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PubMed2006

Experimental demonstration of subwavelength focusing of electromagnetic waves by labyrinth-based two-dimensional metamaterials.

We studied focusing in a two-dimensional metamaterial that was based on a labyrinth structure. We theoretically showed that the labyrinth-based metamaterial exhibits negative indices of refraction between 6 and 6.4 GHz. We experimentally studied the focusing effect by measuring electric field intensities on the output side of the metamaterial when the source was placed in front of the input side of the metamaterial. Our experimental results showed that it is in fact possible to focus the source field with half-widths as small as wavelength/4 by using the labyrinth-based metamaterial.

Journal Article↗

PubMed1987

A possible role of the glomus cell in controlling vascular tone of the carotid labyrinth of Xenopus laevis.

To clarify the physiological significance of the g-s connection (intimate apposition of the glomus cell to the smooth muscle) in the Xenopus carotid labyrinth, experiments were carried out morphologically and physiologically. Results obtained are as follows. Efferent electrical stimulation of the glossopharyngeal nerve resulted in concentrating dense-cored vesicles on the peripheral region of the glomus cell, and a decrease of vesicles as a whole. In the carotid labyrinth perfused artificially, outflow of the internal and the external carotid arteries decreased with administration of catecholamines (adrenaline, noradrenaline and dopamine). Acetylcholine reduced only the internal outflow. This response was depressed by atropine, hexamethonium and phentolamine, whereas accelerated by propranolol. Sodium cyanide reduced the internal outflow without affecting the external outflow, and its effect is depressed by phentolamine. From these results, a possibility that the glomus cell participates in controlling the blood flow in the labyrinth through the intervention of the g-s connection was discussed.

Acetylcholine↗

PubMed1985

Scanning electron microscope studies of the rat mesenteric lymph node with special reference to high-endothelial venules and hitherto unknown lymphatic labyrinth.

Mesenteric lymph nodes of the rat were studied by scanning electron microscopy after arterial perfusion fixation. Observation was made mainly of the high endothelial venules (HEVs), inner cortex and medulla. The HEVs were distributed not only in the inner cortex, but also in the interfollicular areas in the outer cortex, extending to closely beneath the marginal sinus. Various surface structures of the HEV endothelial cells were recorded, from quite smooth to densely granular. Special attention was paid to endothelial cells with cytoplasmic ridges concentrated at the center of the cell apex. Lymphocytes were numerously attached to the luminal surface of the HEV. Many lymphocytes presumably under and after emigration through the HEV wall could be recognized. Hitherto unknown labyrinths densely filled with lymphocytes were demonstrated in the inner cortex. These tubular and saccular spaces lined by attenuated cells originated from beneath the germinal centers and from around the HEVs to pour into the medullary sinuses. The lymphatic labyrinths were differentiated from the sinuses by their lack of reticular cell trabeculae and by their containing almost exclusively small lymphocytes. It was proposed that lymphocytes in the blood in HEVs massively emigrate to the labyrinth, and via the medullary sinuses, enter the efferent lymphatics of the lymph node. In the medullary sinuses, some lymphocytes in association with a macrophage were found to extend wing-like processes, probably reflecting their activation. Large free cells extending laminar projections, but smooth in surface otherwise, were occasionally found. Their possible identity with the veiled cells (KELLY et al., 1978) was considered.

Animals↗

PubMed1993

Distribution of FMRFamide-immunoreactive nerve fibers in the carotid labyrinth of the bullfrog, Rana catesbeiana in corresponding differential interference-contrast (Nomarski) images.

Immunoreactivities for FMRFamide and substance P (SP) in the carotid labyrinth of the bullfrog were detected using the peroxidase-antiperoxidase method, and the results compared with corresponding differential interference-contrast (Nomarski) images. Colocalization of both peptides was determined by the indirect double immunofluorescence method. Immunoreactivities for FMRFamide and SP were found in nerve fibers distributed in the intervascular stroma of the labyrinth. The FMRFamide-immunoreactive fibers were less numerous than the SP-immunoreactive fibers. In the Nomarski image, FMRFamide-fibers were recognized in relief, with most of them located near the walls of blood vessels. All FMRFamide-fibers coexisted with SP. The results suggest that FMRFamide-immunoreactive fibers are also involved in local vascular regulation of the carotid labyrinth.

Animals↗

PubMed1999

Magnetic resonance imaging virtual endoscopy of the labyrinth.

OBJECTIVE: To explore the feasibility of applying virtual endoscopic (VE) techniques to examine the normal anatomy of the labyrinth using magnetic resonance imaging (MRI) data. STUDY DESIGN: Feasibility study using data from a normal subject. MATERIALS AND METHODS: MRI data was acquired in a single normal subject using a three-dimensional (3D) CISS (Constructive Interference in the Steady State) sequence. Perspective volume rendering (PVR) techniques were used to produce virtual endoscopic visualization of the fluid filled structures of the inner ear. RESULTS: The reconstructive algorithms enabled generation of a "fly-through" simulation of the labyrinth. The cochlea, the oval window, the vestibule, the common crus, and the semicircular canals were successfully visualized. CONCLUSIONS: Virtual endoscopic techniques were successfully applied to MRI data enabling a 3D virtual display of the internal anatomy of the normal labyrinth.

Algorithms↗

PubMed2004

Surgical anatomy of the turbinal wall of the ethmoidal labyrinth.

The upper part of the lateral nasal wall is formed by a common structure or conchal lamina that is attached all along the junction between the ethmoidal roof and the cribriform plate. From this continuous conchal lamina, the different ethmoidal turbinates take their origin. All these structures form a well defined wall that encloses the ethmoidal cells medially and that deserves the name of "turbinal wall of the ethmoidal labyrinth". The objectives of this paper were: 1) to precisely define the anatomical landmarks of the turbinal wall of the ethmoidal labyrinth, and 2) to study, from an anatomical point of view, the consequences of the surgical resection of the middle turbinate. We performed an anatomic study on 12 frozen human heads, cut in a median-sagittal plane, and then photographed with a millimetre scale in order to perform several measurements. The surface of the turbinal wall of the ethmoidal labyrinth can range from 6.1 to 11.3 cm2. The resection of the middle turbinate preserves approximately half of the turbinal wall, this being around 4.3 cm2 (range 2.6 to 6.3 cm2). The conchal lamina appears as the noble sensorial element of the turbinal wall. It can be described as a continuous bone plate, grossly rectangular in shape, measuring approximately 1 cm in height and 3.5 cm in length that forms the lateral wall of the olfactory groove. The anatomic study shows that its dimensions can vary from simple to double in different individuals. It seems to us that instead of considering the difference of height between the cribriform plate and the ethmoidal roof (Keros classification), we should consider the vertical height of the conchal lamina as a potential risk factor in ethmoidal surgery.

Adult↗

PubMed2005

On the vestibular labyrinth of Brachiosaurus brancai.

The extensive remains of large sauropods, excavated in the Upper Jurassic layers of the Tendaguru region of Tanzania, East Africa by Janensch [15], include an intact fossil cast of a vestibular labyrinth and an endocast of the large Brachiosaurus brancai. The approximately 150 million year old labyrinth cast demonstrates clearly a form and organisation congruent in detail to those of extant vertebrate species. Besides the near-orthogonal arrangement of semicircular canals (SCCs), the superior and inferior branches of the vestibulo-acoustic nerve, the endolymphatic duct, the oval and round windows, and the cochlea can be identified. The orientation of the labyrinth in the temporal bone is also equivalent to that of many extant vertebrates. Furthermore, the existence of the twelve cranial nerves can be identified from the endocast. The present study was initiated after the photogrammetric measurement of the skeleton volume of B. brancai [13] yielded a realistic estimate of body mass (74.42 metric tons). Dimensional analysis shows that body mass and average SCC dimensions of B. brancai generally fit with the allometric relationship found in previous studies of extant species. However, the anterior SCC is significantly larger than the allometric relationship would predict. This would indicate greater sensitivity, supporting the idea that the behavioural repertoire must have included much slower pitch movements of the head. These slower movements would most likely have involved flexion of the neck, rather than head pitching about the atlas joint. Pursuing the relationship between body mass and SCC dimensions further, the SCC frequency response is estimated by scaling up from the SCC dimensions of the rhesus monkey; this yields a range between 0.008-26 Hz, approximately one octave lower than for humans.

Animals↗

PubMed1985

Effects of passive flexion of the forepaw on the response gain of limb extensors to sinusoidal stimulation of labyrinth receptors.

The main aim of the present study was to find out whether the dynamic characteristics of responses of limb extensor muscles to labyrinth stimulation were modified by the proprioceptive input elicited by appropriate displacements of the corresponding limb extremity. In cats decerebrated at precollicular or intercollicular level, the multiunit EMG activity of the medial head of the triceps brachii was recorded during roll tilt of the animal at the frequency of 0.15 Hz, +/- 10 degrees leading to selective stimulation of labyrinth receptors. This stimulation was then tested several times at regular intervals of 2 to 6 min for several hours while maintaining the ipsilateral forelimb in the horizontal extended position, i.e. with the plantar surface of the foot lying on the tilting table, or during passive flexion of the forepaw in plantar or dorsal direction. In all the experiments in which the forelimb was in the control position, the multiunit EMG responses of the triceps brachii were characterized by an increased activity during side-down tilt of the animal and a decreased activity during side up tilt. These responses were related to animal position and not to the velocity of animal displacement, thus being attributed to stimulation of macular, utricular receptors. Static displacement of limb extremities following plantar flexion of the forepaw greatly decreased the amplitude of the EMG modulation and thus the gain of the first harmonic component of the multiunit EMG responses of the ipsilateral triceps brachii to animal tilt. This reduced gain was due not only to a reduced number of motor units recruited during labyrinth stimulation, but also to a reduced modulation of firing rate of the active motor units, as shown by recording the activity of individual motor units. On the other hand, displacement of the same extremity in the opposite direction, i.e. following dorsiflexion of the forepaw, enhanced the amplitude of the EMG modulation and thus the gain of the multiunit EMG responses of the ipsilateral triceps brachii to animal tilt. This finding was mainly due to an increased recruitment of motor units during side-down tilt, although an increased modulation of the firing rate of individual motor units could not be excluded. In both instances, no changes in the phase angle to the responses were observed. The changes in response gain described above depended on the amount of passive displacement of the forepaw and persisted unmodified throughout the new maintained position.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1979

The passage of lymphatic leukemia L1210 cells injected into glass bead labyrinth: their flow and retention.

Leukemia L1210 cells and normal lymphocytes were injected into the glass bead packing perfused with a medium containing serum proteins in concentration sufficient to greatly reduce the surface adhesion. The passage of radioactively labeled cells introduced as a concentrated suspension, was studied by the analysis of transit-dilution curves. It was demonstrated that a fraction of cells was retained in the labyrinth; other parameters characterizing the cell flow were similar to those of the medium. The mechanism of the arrest of cells is discussed: it is related to geometrical features of the labyrinth and the hydrodynamic forces influencing the cell surface interactions. Intense washing of the glass bead column results in the release of only a minor fraction of cells which were previously arrested. When the L1210 cells which have passed through the labyrinth without being trapped are reinjected into another glass bead layer, their retention is similar to that observed after the first injection; it appears, therefore, that the L1210 cells are uniform as concerns the properties which are important for surface interactions under flow conditions.

Animals↗

PubMed1984

[Glomus cell in controlling vascular tone of the carotid labyrinth (Xenopus laevis)].

To clarify the physiological significance of g-s connection (intimate apposition of the glomus cell to the smooth muscle), vascular responses of the carotid labyrinth to both catecholamines and chemoreceptor stimulants were investigated using Xenopus laevis. The results obtained were as follows. Density of dense-cored vesicles in the glomus cell was significantly varied in three different parts of the cytoplasm (N, M, P). In the part of the cytoplasm containing the nucleus (N) the density was lowest, and in the processes (P) it was highest. This bias in distribution was intensified by efferent stimulation of the glossopharyngeal nerve. In the artificially perfused labyrinth, the administration of catecholamines (adrenaline, noradrenaline and dopamine) decreased the outflow of the internal carotid artery in many cases. In a few cases it increased the internal outflow. Phentolamine changed the decrease of the outflow to an increase, while propranolol changed the increase to decrease. Acetylcholine strongly reduced the internal outflow. This response was depressed by atropine, hexamethonium and phentolamine, while intensified by propranolol. Sodium cyanide reduced the internal outflow. This effect was depressed by phentolamine. The possibility that the glomus cell participates in controlling the blood flow of the labyrinth as a result of the secretion of catecholamine through the g-s connection is discussed.

Acetylcholine↗

PubMed1982

[Electron microscopic and immunofluorescent microscopic studies on the structure of the bony labyrinth].

The bony labyrinth of the guinea pig is composed of the inner endosteal, the intermediate endochondral and the outer periosteal layer. In addition, the endosteal layer is partially covered by an endosteal cell layer. At the boundary to the spatium perilymphaticum the endosteal layer is covered by an osmiophilic line. Osmiophilic lines also appear as a coating of bone cavities and canaliculi as well as on the periphery of the interglobular spaces in the endochondral layer. Osmiophilic lines were also found at the boundary between the three layers. Within the endochondral and especially the endosteal layer, the collagen fibrils are relatively loose and cover spindle-shaped areas which possess protein-carbohydrate complexes. In the periosteal layer the collagen is arranged in lamellae. Here, it was found that the protein-carbohydrate complexes are not quite as numerous. The high concentration of protein-carbohydrate complexes in all of the three layers is possibly responsible for the exceptional hardness of the otic capsule. Collagen type I is demonstrable in all three of the above layers. Collagen type III was also found to be present in the endosteal and the periosteal layer. The interglobular spaces of the endochondral layer contain only collagen type II and a cartilage-specific proteoglycan. The occurrence of the interglobular spaces, the strand-like formation of the collagen fibres, the areas with the protein-carbohydrate complexes, and the existence of collagen type III support the assumption that the bony labyrinth of the adult guinea pig remains at a low level of development. However, the uniform mineralization, the abundance of osmiophilic lines, and the small amount of the cytoplasm in the osteocytes lead to the conclusion that in the bony labyrinth very little change or transformation actually occurs.

Animals↗

PubMed1996

[Enlarged retro-labyrinthic approach: application to surgery of acoustic neurinoma. Apropos of 55 cases].

The enlarged retro-labyrinthic route described here allows opening of the internal auditory canal, exeresis of tumors localized in the ponto-cerebellous angle and in the internal auditory canal. We used this route for 55 neurinomas of the auditory nerve (7.4% stage I, 23.6% stage II, 45.4% stage III and 23.6% stage IV). Most of the tumors in our series were > 2 cm. There were no post-operative deaths. Risk of fistulization was low, 3.8%. Post-operative meningitis (3.8%) regressed rapidly with treatment. Facial function outcome was equivalent to that obtained with the enlarged trans-labyrinthic route and reported in the literature in series treated via the sub-occipital route (83.6% for grades I and II, 11% for grade III). One patient required hypoglosso-facial anastomosis with a grade IV result at 6 months. Auditive function was preserved at a socially acceptable level in 14.5% of the patients and in 21.8% hearing aids were needed. Selecting a subgroup of 25 patients with good quality hearing prior to surgery (< 30 dB) and a tumor invading less than three-fourths of the internal auditory canal, for all tumor sizes, 28% preserved socially acceptable hearing. To these must be added 20% who had some hearing loss which could be corrected. The modulary mature of the retrolabyrinthic route is easily transposable to the trans-labyrinthic rout. Because of the potential for preserving auditive function this technique should replace the less flexible sub-occipital route.

Audiometry↗

PubMed1985

Pseudomonas labyrinthitis.

Pseudomonas aeruginosa is the gram-negative bacterial rod which is often isolated from chronic aural discharge. This microorganism may also cause necrotizing infection of the external auditory canal in certain patients with impaired host-defense mechanisms. Involvement of the inner ear by this microbe is extremely rare. In this communication, we report a case of pseudomonas labyrinthitis which resulted from traumatic middle ear injury. Infection produced massive granulations and extensive bone destruction of the otic capsule. This case shows that while P.aeruginosa is usually an avirulent opportunistic pathogen, it may also cause a highly destructive labyrinthitis if the inner ear is entered.

Aged↗

PubMed2005

Fine structure histopathology of labyrinthitis ossificans in the gerbil model.

Labyrinthitis ossificans (LO) is the pathological deposition of new bone within the lumen of the cochlea and labyrinth. This process occurs most commonly as a result of infection or inflammation affecting the otic capsule. Trauma and vascular compromise can also lead to neo-ossification within the otic capsule. The mechanism that regulates this process remains unestablished. This study details the end-stage histopathology in high-resolution plastic thin sections. Twenty Mongolian gerbils were infected by intrathecal injection of Streptococcus pneumoniae type 3 followed by subcutaneous penicillin G procaine (8 days) and were painlessly sacrificed 3 months later. The cochleas were serially divided and sectioned for light and electron microscopy. Sixteen of 20 animals (27 of 40 cochleas) demonstrated LO. Cochlear damage was most extensive in the vestibule and basal turn and decreased toward the apex, which often appeared normal. The histopathologic findings consisted of 1) new bone, calcospherites, osteoid, and fibrosis without dense connective tissue or osteoblasts extending from the endosteal wall into the lumen of the vestibule and scala tympani; 2) areas of dense connective tissue and osteoid enclosed by epithelial cells conjoined with the organ of Corti, stria vascularis, spiral ligament, and vestibular (Reissner's) membrane; and 3) partial to complete loss of the organ of Corti, spiral ligament cell bodies, stria vascularis, and spiral ganglion cells. Osteoblastic activity was not demonstrated in end-stage ossification in LO in the gerbil model. Neo-ossification appears to occur by calcospherite deposition along collagen-like fibrils within osteoid. The destruction of the organ of Corti, spiral ganglion cells, stria vascularis, and cells of Reissner's membrane and the spiral ligament occurs even in the absence of ossification of the cochlear duct.

Animals↗

PubMedDate not supplied

Labyrinthitis ossificans.

Three cases with postinflammatory inner ear sequelae are presented to illustrate unusual histopathologic changes. Endolymphatic hydrops without changes in the perilymphatic system was present in one ear following "influenza" meningitis and labyrinthitis ossificans in the contralateral ear. The characteristic histopathological changes of the temporal bones with hematogenic bacterial infection were an extensive labyrinthine ossification associated with a generalized sclerotic change of the whole periotic bone. Bony fixation of the stapedial footplate occurred with the generalized inflammatory process of the otic capsule. Severe and diffuse labyrinthitis ossificans occurred in one case due to tympanogenic inflammation spreading through the round window membrane in the course of suppurative otitis media. A general immunosuppression leading to fatal termination was the apparent factor predisposing to the inner ear complication.

Adult↗

PubMedDate not supplied

Cochlear pathology following experimental ablation of the vestibular labyrinth.

A surgical procedure was performed on 24 cats in which the oval window was entered and the vestibular sense organs were ablated. The operation incited a severe reparative response in the vestibule, characterized by proliferation of fibrous tissue and bone and blockage of the longitudinal flow of endolymph. One inner ear became infected resulting in degeneration of the labyrinth. Of the remaining 23 ears, 20 showed cochlear endolymphatic hydrops (EH) and three did not. All three ears without cochlear EH (as well as two ears with cochlear EH) had fistulae of their endolymphatic systems. The findings are consistent with the concept that fistulization of the membranous labyrinth prior to the blockage of longitudinal flow will prevent the formation of EH. Similarly, fistulization occurring after the onset of EH should arrest its progression. These observations are relevant for surgical procedures designed to control intractable vertigo caused by EH.

Animals↗

PubMed1990

Histopathologic study of the perilymph-suctioned labyrinth.

A small amount of perilymph was suctioned from the scala tympani through the round window membrane of guinea pigs. The animals either were killed immediately after the suctioning or were kept alive for 1 to 3 months. For morphologic study, the conventional celloidin embedding method was employed, and the temporal bones were serially sectioned. Various kinds and degrees of changes in the membranous labyrinth were observed: hydrops, collapse, and rupture. Loss of outer hair cells in the upper turns of the cochlea was noted in the 1- to 3-month recovery specimens. These findings are identical to those found in animals in which artificial perilymph was injected into the subarachnoid space in order to produce experimental perilymphatic fistula. After comparing morphologic changes of the membranous labyrinth following use of each method, we concluded that perilymph suctioning from the round window can be used as an animal model of perilymphatic fistula.

Animals↗

PubMed2005

[Correction of vestibular disorders in patients with otitis media purulenta chronica complicated by labyrinthitis].

A vestibulogic examination was made in 66 patients with otitis media purulenta chronica complicated with labyrinthitis. The patients were divided into two groups: group 1 received surgical treatment in an acute period of labyrinthitis, group 2 was treated conservatively with delayed operation. The patients were examined at admission, 2 weeks, 1, 3, 6 and 12 months after the treatment. It was found that compensation of the vestibular function in group 1 took place 6 months after temporal bone surgery, in group 2-9 months after delayed operation, i.e. 1 years after hospitalization.

Anti-Bacterial Agents↗