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PubMed1981

Relation between cell size and response characteristics of vestibulospinal neurons to labyrinth and neck inputs.

(1) The activity of 136 Deiters' neurons projecting to lumbosacral segments of the spinal cord has been recorded in decerebrate, partially cerebellectomized cats, and their response characteristics to sinusoidal stimulation of labyrinth and neck receptors have been related to cell size inferred from the conduction velocity of the corresponding axons. (2) Vestibulospinal neurons with faster conduction velocity and, by inference, having thicker axons and larger cell bodies differed from those neurons having lower axonal conduction velocity by displaying (i) a relatively irregular interspike interval distribution; (ii) a lower resting discharge rate; (iii) a periodically modulated response to the labyrinth input elicited by sinusoidal tilt around the animal's longitudinal axis (0.026 Hz, 10 degrees) characterized by an increase in firing rate during side-down roll tilt; (iv) an increase in gain (impulses per sec per degree) and phase lag relative to the displacement of the labyrinth response to increasing angular acceleration; (v) a greater gain in labyrinth than neck input, the latter elicited by sinusoidal neck rotation (0.026 Hz, 5 or 10 degrees); and (vi) due to the imbalance of the gains of the separate labyrinth and neck responses and their predictable vectorial summation, a response to both inputs elicited by head rotation resembling that obtained by labyrinth stimulation alone. (3) These findings are discussed in terms of the reciprocal distribution of synaptic contacts of vestibular and neck afferents on vestibulospinal neurons as a function of cell size. The evidence indicates that, in addition to intrinsic neuronal properties related to cell size, the quantitative and qualitative organization of synaptic inputs represents the critical factor controlling the responsiveness of vestibulospinal neurons.

Action Potentials↗
PubMed1995

Peptidergic innervation in the amphibian carotid labyrinth.

The amphibian carotid labyrinth, which corresponds to the mammalian carotid body and carotid sinus, is innervated by nerve fibers containing substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), FMRFamide (FMRF), and somatostatin (SOM). SP, CGRP, VIP, and NPY immunoreactive varicose fibers are more densely distributed in the peripheral portion of the carotid labyrinth than FMRF and SOM fibers. The time of appearance of SP, CGRP, and VIP is different for each. First CGRP fibers, then SP fibers appear at an early stage of larval development, and finally VIP fibres are detected at a later stage of larval development. Most SP fibres show coexistence with CGRP, and some SP fibres which show coexistence with NPY immunoreactivity are assumed to be continuous with those demonstrating VIP immunoreactivity. This indicates the possibility of coexistence of four different peptides in the same nerve fibers within the labyrinth. In various vasculatures of mammals, it has been shown that SP, CGRP, VIP, and NPY have a vasoactive nature in relation to the vascular smooth muscle cells. On this basis, it seems that the target of the peptidergic innervation in the amphibian carotid labyrinth is the smooth muscle cells which are abundantly distributed in the intervascular stroma. Accordingly, the peptidergic innervation may be involved in the vascular regulatory function of the labyrinth, although the possibility that these peptides participate in the chemoreception cannot be ruled out. In addition, the vascular regulatory function of the labyrinth may be modulated by the interaction of multiple neuropeptides.

Amphibians↗
PubMed1994

Magnetic resonance imaging-enhancing lesions of the labyrinth and facial nerve. Clinical correlation.

OBJECTIVE: Gadolinium-enhanced magnetic resonance imaging (MRI) is useful in assessing inflammatory and neoplastic lesions of the labyrinth and facial nerve. The following cases demonstrate the ability of MRI to differentiate neoplastic from inflammatory lesions within the labyrinth. PATIENTS OR OTHER PARTICIPANTS: Nine patients were selected with enhancing lesions of the labyrinth and the facial nerve identified on MRI. INTERVENTION: Acyclovir and prednisone were prescribed for herpes zoster oticus; surgical removal of neoplastic lesions was performed. MAIN OUTCOME MEASURE: The hypothesis was developed in the course of clinical practice. No planned outcome was emphasized, as this article is based on the differential diagnoses of the cases reported. RESULTS: Gadolinium-enhanced MRI is useful in differentiating neoplastic from inflammatory lesions within the labyrinth. Axial and coronal 3-mm sections with gadolinium enhancement were necessary for identifying these lesions and particularly for recognizing the sharp enhancement of the neoplastic margin in contrast to the dull cloudy margins of an inflammatory lesion. CONCLUSIONS: The MRI differentiation of these lesions is helpful in providing appropriate medical and surgical management of neoplastic and inflammatory lesions of the labyrinth.

Adult↗
PubMedDate not supplied

Radiologic diagnosis of labyrinthitis ossificans.

Labyrinthitis ossificans is the pathological ossification of the membranous labyrinthine spaces in response to processes which are destructive of the membranous labyrinth or the endosteum of the otic capsule. It has been primarily a histopathologic diagnosis. Complex motion tomography however, allows a detailed view of the osseous labyrinth and permits the diagnosis in the living state. Radiologic documentation of labyrinthitis ossificans is objective evidence of a process destructive of the membranous labyrinth. It supports the likelihood of an absence of cochlear and vestibular function. It alerts the surgeon to the possible obliteration of key inner ear anatomical landmarks.

Aged↗
PubMed1995

MR imaging of intralabyrinthine schwannoma, labyrinthitis, and other labyrinthine pathology.

This article reviews recent imaging developments in various diseases of the membranous labyrinth. Membranous labyrinth is the initial receptor for acoustic stimuli. Exciting progress has been made in the imaging evaluation of the normal and diseased labyrinth. Structures of the membranous labyrinth, such as the cochlea, vestibule, semicircular canals, and endolymphatic duct and sac can be visualized on routine MR scans. Using high-resolution MR imaging techniques, researches have been able to visualize the cochlear duct, scala tympani, scala vestibuli, and even the otolithic mass. The sensitivity of gadolinium-enhanced MR imaging is such that labyrinthitis or other labyrinthine pathology, including small intralabyrinthine schwannomas, can be diagnosed on routine MR study.

Ear Neoplasms↗
PubMed2001

Preventing labyrinthitis ossificans: the role of steroids.

OBJECTIVE: To identify a possible relationship between the administration of steroids at the time of diagnosis of bacterial meningitis and the development of labyrinthitis ossificans. DESIGN: Retrospective analysis of the charts of 38 children requiring cochlear implantation who presented with bacterial meningitis and then developed bilateral profound deafness. The patients' charts were reviewed for age at diagnosis, the type of antibiotic administered, and the administration, dosage, and duration of steroid (dexamethasone) therapy. Labyrinthitis ossificans was established by preoperative computed tomographic and/or magnetic resonance imaging and by the intraoperative findings as described in the operative report. PATIENTS AND METHODS: Patients were 38 children who received cochlear implantation by a single senior otolaryngologist for bacterial meningitis-related deafness. Ten patients' charts (26%) were available for full review; 9 of these 10 patients had documented pneumococcal meningitis and the other patient had Haemophilus influenzae-type meningitis. RESULTS: One of the 6 patients who received steroid therapy at the time of initial illness had documented evidence of labyrinthitis ossificans either radiographically or at the time of surgery. All 4 patients who failed to receive steroid therapy developed labyrinthitis ossificans. The results achieve statistical significance by chi2 analysis and a t test (P<.01). CONCLUSION: The results of this retrospective study are highly suggestive of a role for steroids in preventing the development of labyrinthitis ossificans in children with pneumococcal meningitis.

Anti-Inflammatory Agents↗
PubMed1999

The role of the labyrinth, proprioception and plantar mechanosensors in the maintenance of an upright posture.

The maintenance of an upright posture in man requires information from vision, the labyrinth, proprioception and plantar mechanosensors. In order to evaluate the role of the labyrinth, proprioception and plantar mechanosensors, stabilometry was performed in subjects with closed eyes. Ten patients with bilateral severe or complete labyrinthine paresis were studied, as well as 9 patients with severe proprioceptive disorders and 10 normal healthy persons whose plantar mechanosensors were anesthetized by hypothermia. Both the area of sway and the total locus length (accumulated shift distance length) were evaluated. On closing eyes, in patients with labyrinthine disorders demonstrated that the area of sway increased more than length. On the other hand, in patients with proprioceptive disorders, length increased more than the area. In plantar anesthetized subjects, similar to the labyrinthine disorder cases, the area of sway increased more than length. These findings suggest that the labyrinth is a main monitor of the area of body sway, while proprioception is a principle monitor of the velocity of body movement of sway (or locus length). The plantar mechanosensor monitors the area of body sway similar to the labyrinth, but works less than the labyrinth. The locus length is the distance per minute and reflects the velocity of body sway. Thus, the length per area is a parameter for the velocity of body sway per area. Since proprioceptive disorders increase both the locus length and the length per area, present findings suggest that if proprioception is damaged, the body begins to move faster. Compensated labyrinthine disorders have a tendency to increase the length per area, indicating that if a labyrinthine disorder is compensated, the body adapts and moves faster to maintain an upright posture.

Achilles Tendon↗
PubMed1991

Labyrinthitis ossificans: histopathologic consideration for cochlear implantation.

Labyrinthitis ossificans may be a hindrance to cochlear implantation by making electrode insertion difficult. We performed a histopathologic study of 24 temporal bones with labyrinthitis ossificans from multiple causes. The organ of Corti was graphically reconstructed and the degree of obstruction was estimated for each millimeter of the cochlea. Correlations were calculated between the degree of new bone formation and the cause, patient's age and sex, and time from the original temporal bone insult. Our results demonstrate that complete cochlear ossification is rare. The scala tympani in the basal turn of the cochlea is the most frequent area of ossification, regardless of the cause of the labyrinthitis ossificans. Meningogenic labyrinthitis, usually a childhood disease, was associated with the greatest amount of ossification. When ossification resulted from tympanogenic labyrinthitis, the scala tympani was completely ossified near the round window niche in all temporal bones. Neo-ossification of the basal turn associated with otosclerosis was limited to the proximal 6 mm of the scala tympani in all cases. Three temporal bones had a patent round window niche and basal turn, but significant apical and middle-turn ossification. Peripheral sensorineural elements were severely degenerated in the region of the ossification in all specimens, and spiral ganglion cell counts were decreased.

Adolescent↗
PubMed2004

[Concomitant labyrinthitis].

The principal pathogenetic mechanism of labyrinthopaty development after traumas and operations lies in autoimmune inflammation of the contralateral ear similar to sympathetic inflammation of the eye. By analogy with sympathetic ophthalmitis, a term < > is proposed. Due to selective permeability of selective membranes, immune system has no connection with < > organs. These organs and tissues are isolated from the key sourse of immunity -- blood. Autotolerance to them is absent and their proteins are autoantigens. In destruction of hemato-labyrinthine barrier these autoantigens can reach lymphoid organs and provoke immune response inducing a cytotoxic action in relation to both the affected and the contralateral labyrinth. Besides pathology of the affected labyrinth, clinical picture of labyrinthopathy is caused by autoimmune labyrinthitis of the contralateral ear whereas in < > labyrinthitis of the affected ear - slow-progressive autoimmune concomitant labyrinthitis. Case reports are presented.

Adult↗
PubMed1990

Comparative studies on the vascular organization of carotid labyrinths of anurans and caudates.

The three-dimensional structures of the carotid labyrinth in five species of anurans representing four families (Rana nigromaculata, Rana catesbeiana, Bufo japonicus, Hyla arborea, and Xenopus laevis), and three species of caudates representing three families (Cynops pyrrhogaster, Hynobius nebulosus, Ambystoma mexicanum) were compared using vascular corrosion castings and scanning electron microscopy (SEM). Anuran carotid labyrinths are spherical in shape and are classified into two groups according to the origin of the external and internal carotid arteries. One group, which included Rana, Hyla, and Bufo, is characterized by the presence of a vascular ring at the proximal end and some vascular routes at the distal end of the labyrinth. The external and internal carotid arteries originate from these structures. The other group, which includes only Xenopus, is characterized by the external carotid artery opening directly from the central chamber or the common carotid artery, and by the internal carotid artery originating from within the vascular maze. The vascular maze is most complex in Xenopus, less so in Rana and Bufo, and simplest in Hyla. The carotid labyrinths in Cynops and Hynobius are oblong in shape. The fundamental organization in salamanders is similar to that in anurans. The vascular maze, however, is much simpler than in Hyla. There is no specialized swelling in Ambystoma mexicanum. The present findings suggest that most amphibian carotid labyrinths have the appropriate architecture for controlling vascular tone.

Animals↗
PubMed1981

Vascular corrosion replicas of chemo-baroreceptors in fish: the carotid labyrinth in Ictaluridae and Clariidae.

Scanning electron microscopy of vascular corrosion replicas and light microscopy revealed a pair of highly vascularized tissues, the carotid labyrinths, in the dorsal head region of the channel catfish, Ictalurus punctatus, the black bullhead, I. melas, and the walking catfish, Clarias batrachus. The labyrinth consists of a myriad of arterioles that arise from the common carotid artery immediately distal to the origin of the common carotid from the efferent branchial (epibranchial) artery of the first gill arch. The arterioles anastomose with each other to form: (1) the internal carotid artery which supplies the brain, and (2) several anteriolateral arteries that extend into the anterior head. In the ictalurids the common carotid artery emerges from the labyrinth intact and continues anteriorly as the large olfactory artery, whereas in Clarias all postlabyrinthine vessels result from arborization of the common carotid and subsequent anastomosis of the arterioles. Similarities between piscine and amphibian carotid labyrinths and the anatomical proximity of the former with the gills suggest that, in Ictaluridae, the labyrinth has a chemo- or baroreceptor function.

Animals↗
PubMed1991

Localization of substance P, CGRP, VIP, neuropeptide Y, and somatostatin immunoreactive nerve fibers in the carotid labyrinths of some amphibian species.

Immunohistochemical localization of substance P (SP), CGRP, VIP, neuropeptide Y (NPY), and somatostatin (SOM) in the carotid labyrinth were compared in some species of amphibians using the peroxidase-antiperoxidase method. Immunoreactivity of SP, CGRP, VIP, and NPY was found in the nerve fibers distributed in the intervascular stroma of the carotid labyrinth. SP, CGRP, and VIP immunoreactive varicose fibers were densely distributed in the peripheral portion of the carotid labyrinth. Some SP-immunoreactive fibers were distributed similarly to CGRP-immunoreactive fibers. The density of NPY and SOM immunoreactive varicose fibers was low. No immunoreactivity of enkephalins was observed in the labyrinth. The intensities of these peptides were varied from species to species. No glomus cells showed immunoreactivity for any of the 7 peptides studied. These results suggest that the vascular regulatory function, which is one of the possible functions of the carotid labyrinth, is controlled by the peptidergic mechanisms in addition to regulation through intimate apposition of glomus and smooth muscle cells (g-s connection).

Ambystoma↗
PubMed1983

Relation between cell size and response characteristics of medullary reticulospinal neurons to labyrinth and neck inputs.

The activity of presumably inhibitory reticulospinal neurons with cell bodies located in the medial aspects of the medullary reticular formation and axons projecting to lumbosacral cord has been recorded in decerebrate cats and their response characteristics to sinusoidal stimulation of labyrinth receptors (134 neurons) and neck receptors (110 neurons) have been related to cell size inferred from the conduction velocity of the corresponding axons. No significant correlation was found between resting discharge and conduction velocity of the axons. Among the recorded reticulospinal neurons, 64/134 (i.e. 47.8%) units responded to roll tilt, while 66/110 (i.e. 60.0%) units responded to neck rotation (0.026 Hz, +/- 10 degrees). A positive correlation was found between gain (imp./s/deg) of the labyrinth and neck responses and conduction velocity of the axons. Thus, due to absence of correlation between resting discharge and conduction velocity of the axons, larger neurons exhibited a greater percentage modulation (sensitivity) to the labyrinth and the neck input than smaller neurons. These findings are attributed to an overall increase in density or efficacy of the synaptic contacts made by the vestibular and neck afferent pathways on reticulospinal neurons of increasing size. Units receiving neck-macular vestibular convergence showed on the average an higher gain of the neck (GN) response with respect to the labyrinth (GL) response (GN/GL: 1.95 +/- 1.49, S.D.; n = 43); however, due to a parallel increase in gain of the reticulospinal neurons to both neck and labyrinth inputs, the relative effectiveness of the two inputs did not vary in different units as a function of cell size. The reticulospinal neurons were mainly excited by the direction of animal orientation and/or neck displacement. In particular, most of these positional sensitive units were excited by side-up animal tilt (37/58, i.e. 63.8%) and by side-down neck rotation (47/60, i.e. 78.3%). These predominant response patterns were particularly found between large size neurons, whereas small size neurons tended to show also other response patterns. The evidence indicates that in addition to intrinsic neuronal properties related to cell size, the quantitative and qualitative organization of synaptic inputs represents the critical factor controlling the responsiveness of reticulospinal neurons to vestibular and neck stimulation.

Afferent Pathways↗
PubMed1985

Placental steroid production by the basal and labyrinth zones during the latter third of gestation in the rat.

Progesterone (P) and testosterone (T) production were investigated in minced rat placental preparations on Days 16, 18, 20, and 22 of pregnancy. Whole placentae were minced or dissected into basal and labyrinth zones and minced prior to a 2-h incubation. Production of P from whole placental minces (pg X mg tissue-1 X 2 h-1) was greatest on Day 16 (P less than 0.05), dropped slightly on Day 18, and fell by nearly 50% on Days 20 and 22. Basal zone P production was greater on Days 16 and 18 (P less than 0.01) than that of the labyrinth zone, but then decreased to become equivalent to that of the labyrinth zone thereafter. Production of T from whole placental minces was greatest on Day 18 (P less than 0.05) and fell to low levels thereafter. The basal zone was almost entirely responsible for T production on all days. Incubation with the 17 alpha-hydroxylase inhibitor Su 10603 [7-chloro-3,4-dihydro-2-(3-pyridyl)-1-(2H)-napthalenone] completely blocked T production concomitant with increased P values. Placental weight increased from Days 16 to 20 because of rapid labyrinth zone growth. Estimated daily P production per placenta was not different among days, although production shifted from the basal to the labyrinth zone as term approached. Production of T per whole placenta reached maximum levels on Day 18 (P less than 0.05) and decreased thereafter. The marked (P less than 0.01) basal zone T production per placenta on Days 16 and 18 fell precipitously on Days 20 and 22.

Animals↗
PubMed2000

Minimal surfaces with self-intersections along straight lines. II. Surfaces forming three-periodic labyrinths.

47 families of minimal surfaces with straight self-intersections have been derived which subdivide R3 into a finite number of congruent three-periodic labyrinths. In most of these cases, namely for 42 families, the number of labyrinths is two. Four congruent labyrinths have been found three times and eight congruent labyrinths twice. Minimal surfaces with three or six labyrinths seem not to exist. Most of these minimal surfaces are non-orientable. The surfaces of three families only are orientable ones.

Journal Article↗
PubMed2004

Prenatal growth and development of the modern human labyrinth.

The modern human bony labyrinth is morphologically distinct from that of all other primates, showing derived features linked with vestibular function and the overall shape of the cranial base. However, little is known of how this unique morphology emerges prenatally. This study examines in detail the developing fetal human labyrinth, both to document this basic aspect of cranial biology, and more specifically, to gain insight into the ontogenetic basis of its phylogenetically derived morphology. Forty-one post-mortem human fetuses, ranging from 9 to 29 weeks gestation, were investigated with high-resolution magnetic resonance imaging. Quantitative analyses of the labyrinthine morphology revealed a number of interesting age-related trends. In addition, our findings show that: (1) the prenatal labyrinth attains an adult equivalent size between 17 and 19 weeks gestation; (2) within the period investigated, shape changes to all or most of the labyrinth cease after the 17-19-week size maturation point or after the otic capsule ossifies; (3) fetal cochlea development correlates with the surrounding petrosal morphology, but not with the midline basicranium; (4) gestational age-related rotations of the ampullae and cochlea relative to the lateral canal, and posterior canal torsion are similar to documented phylogenetic trends whereas other trends remain distinct. Findings are discussed in terms of the ontogenetic processes and mechanisms that most likely led, in part, to the emergence of the phylogenetically derived adult modern human labyrinth.

Cochlea↗
PubMed1976

Asymmetric tonic labyrinth reflexes and their interaction with neck reflexes in the decerebrate cat.

1. Tonic labyrinth and neck reflexes were studied separately and in combination in the decerebrate cat with C1 and C2 spinal roots cut. Reflex effects were observed as changes in length of the isotonically loaded medial head of triceps. 2. The tonic labyrinth reflexes acted asymmetrically on the medial head of triceps. Side-down rotation of the head produced shortening in medial triceps, whereas side-up rotations of the head resulted in a lengthening. 3. The tonic neck reflexes acted asymmetrically on the medial head of triceps. Side-down rotations of the neck produced a lengthening of medial triceps, whereas side-up rotations of the neck resulted in shortening. 4. Labyrinth and neck reflexes produce opposite effects on the same limb extensor muscle so that, if the neck innervation is intact, head tilting produces no change in muscle length. 5. It is suggested that the interaction between the labyrinth and neck reflexes contributes to the stability of the trunk, allowing the head to move freely on the body without affecting this stability. Labyrinth and neck reflexes need therefore to be considered together as a single system.

Animals↗
PubMed2003

Fluid and cellular pathways of rat lymph nodes in relation to lymphatic labyrinths and Aquaporin-1 expression.

The aim of the present study was to examine the organization of lymph fluid and cellular pathways and distribution of the membrane water channel Aquaporin-1 (AQP-1) in rat lymph nodes. Lymph fluid and cellular pathways within lymph nodes were examined by fluorescent protein tracer/confocal microscopy and by scanning electron microscopy (SEM), While the distribution of AQP-1 was studied immunohistochemically. Tracer studies showed the subcapsular sinuses continued directly at the hilum or via the intermediate sinuses to the medullary sinuses, and lymphatic labyrinths originating with blind-ends in the deep cortex drained into medullary sinuses. Afferent lymph tracers were also observed in node cortex interstitium. By SEM, lymphatic labyrinths appeared densely filled with lymphocytes and had few intraluminal sinus reticular cells, while medullary sinuses possessed well-developed networks of sinus reticular cells. The presence of many lymphocytes wedged in the walls of the lymphatic labyrinth suggested that lymphocytes migrate between the node parenchyma and lymphatic labyrinths. AQP-1 was distributed on the membrane of lymphatic endothelium and reticular cells as well as on both luminal and abluminal cell membranes of high endothelial venules (HEVs). Our SEM findings support the concept that lymphocytes migrate from the node parenchyma into lymphatic labyrinths in the deep cortex. The nodal distribution of AQP-1 plus the presence of a polarized distribution of ion pumps and/or ion channels in the HEV endothelium hypothesized in our discussion could explain the mechanism of the reported lymph-to-plasma fluid flux in lymph nodes and also facilitate the entry of afferent lymph antigens into the node cortex interstitium.

Animals↗