PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Labyrinth Supporting Cells”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 181 records · Page 10Linked to original sources
PubMed1988

Possible role of Ca ions in the vestibular system.

The Ca++ messenger system is nearly universally present in the control of cell functions by extracellular messengers. It elicits different kinds of responses: either brief, as in neurotransmission and in skeletal muscle contraction, or sustained, as in smooth muscle contraction and in the regulation of transepithelial transport systems. In this latter function the Ca++ messenger system interacts with other cellular modulation systems such as cAMP production and arachidonic acid cascade. In the vestibular apparatus, the Ca++ messenger system is involved in the transduction processes in that it controls both the release of neurotransmitter at the basal pole of the hair cell and the electrical resonance of the cell. It also figures in the contractile properties of cochlear outer hair cells. The Ca++ messenger system as well as adenylate cyclase and prostaglandins may play an important role in the modulation of endolymph secretion.

Animals↗
PubMed1995

Mechanically induced calcium increases in isolated vestibular hair cells of the guinea pig.

Intracellular Ca2+([Ca2+]i) is elevated by depolarization or mechanical stimulation in some hair cell systems. It is not clear whether both these stimuli promote Ca2+ entry in mammalian vestibular hair cells. We monitored [Ca2+]i with the indicator fluo-3 in isolated type I vestibular hair cells of the guinea pig maintained in Hanks' balanced salt solution (HBSS). Mechanical stimulation by bolus application of HBSS led to an immediate rise of [Ca2+]i. The effect depended upon the presence of extracellular Ca2+([Ca2+]o) and no increase occurred in calcium-free HBSS supplemented with calcium-chelators. When the cells were depolarized by bolus application of KCl (final concentration, 100 mM KCl in modified HBSS), the increase in [Ca2+]i was similar to that elicited by HBSS. In the absence of [Ca2+]o, the application of KCI/HBSS led to a slow sustained increase in the fluorescence of the cells suggesting release of calcium from intracellular stores. Finally, treatment of cells with BAPTA prior to mechanical stimulation prevented the rise in [Ca2+]i indicating the need for intact stereociliary tip-links. The results are consistent with the hypothesis that mechanical stimulation elevates [Ca2+]i in isolated vestibular hair cells via calcium influx through mechanotransduction channels.

Animals↗
PubMed1994

Gap junction systems in the rat vestibular labyrinth: immunohistochemical and ultrastructural analysis.

The distribution of gap junctions within the vestibular labyrinth was investigated using immunohistochemistry and transmission electron microscopy. Connexin26-like immunoreactivity was observed among supporting cells in each vestibular sensory epithelium. Reaction product was also present in the transitional epithelium of each vestibular endorgan and in the planum semilunatum of crista ampullaris. No connexin26-like immunoreactivity was observed among thin wall epithelial cells or among vestibular dark cells. In addition, fibrocytes within vestibular connective tissue were positively immunostained. Reaction product was also detected in the melanocyte area just beneath dark cells. Ultrastructural observations indicated that a gap junction network of vestibular supporting cells extends to the transitional epithelium and planum semilunatum and forms an isolated epithelial cell gap junction system in each vestibular endorgan. In contrast, no gap junctions were found among wall epithelial cells or among dark cells. Fibrocytes and melanocytes were coupled by gap junctions and belong to the connective tissue cell gap junction system, which is continuous throughout the vestibular system and the cochlea. The possible functional significance of these gap junction systems is discussed.

Animals↗
PubMedDate not supplied

Freeze-fracture study of the cell junctions in the utricle and saccule.

The maculae sacculi and utriculi of the chinchilla vestibular labyrinth have been studied by freeze-fracture method. In the replicas extensive zonulae occludentes have been found between sensory and supporting cells at the endolymphatic surface. Gap junctions are located between the supporting cells. Some intramembranous specializations of the synaptic regions are described in both types of the sensory cells.

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↗
PubMedDate not supplied

Organization and density of microtubules in the vestibular sensory cells in the cat.

In the vestibular receptors, the cytoplasmic hair cell microtubules manifest a particular affinity for the membraneous areas juxtaposed to an afferent nerve terminal. Moreover, their number is greater in the type I cells, which possess larger neuro-epithelial surface contacts than either in the type II cells or in the supporting cells. In the discussion, two hypotheses are proposed according to the results; the first concerns the structural role of the cytoskeleton and the second suggests its participation in sensory transduction.

Animals↗
PubMed1983

A morphological study on vestibular sensory epithelia in a strain of the waltzing guinea pig.

The crista ampullaris, the macula utriculi and the macula sacculi in the waltzing guinea pig were investigated with light microscopy, transmission and scanning electron microscopy. The degenerative changes consist of increasing degrees of apical protrusion of the type I hair cell into the endolymphatic space and of sensory hair fusion. The development of an intracellular actin filament rod in the type I hair cell is coupled to the degenerative changes of the apical part of the cell. Progressive hair cell degeneration with actin rod formation and sensory hair fusion as two important findings in the degenerative pattern is observed in type I hair cells of all sensory areas in the vestibular part of the labyrinth in the waltzing guinea pig. Scanning electron microscopy, shows a concentration of the more advanced stages of degenerative changes to the central part of the crista ampullaris and to the striolar area in the macula utriculi and in the macula sacculi. The fact that there is a concentration of sensory cell damage in the central areas of the vestibular end organs in genetically induced inner ear disease as well as in other inner ear damage supports the concept that the central areas have a different function. This paper further supports earlier suggestions that the type I and type II hair cells are genetically different cell types having different functions.

Animals↗
PubMed1984

Neuronal events correlated with long-term adaptation of the horizontal vestibulo-ocular reflex in the primate flocculus.

The activity of flocculus Purkinje cells was examined in Japanese monkeys during sustained vestibular-visual stimulation which caused adaptation of the horizontal vestibulo-ocular reflex (H-VOR). In the floccular area related to the H-VOR by microstimulation. Purkinje cells consistently changed their simple spike responsiveness to head rotation in parallel with the adaptive H-VOR gain change. Similar changes occurred even after the H-VOR had been extinguished by lesioning of the vestibular nuclei. The complex spike discharge, on the other hand, modulated during vestibular-visual stimulation with a reciprocal pattern to the adaptive changes in the simple spike discharge. These results support the hypothesis that the flocculus adaptively modifies the H-VOR through their simple spike activity under the influence of visual climbing fiber signals.

Adaptation, Physiological↗
PubMed1992

Ongoing production of sensory cells in the vestibular epithelium of the chick.

Recent studies have shown that the vestibular and auditory systems of some species of birds have the capacity to generate sensory hair cells postnatally. We used a traditional technique, 3H-thymidine autoradiography, and a newer method, bromodeoxyuridine immunocytochemistry, to determine whether ongoing proliferation of hair cells occurs in the intact chick vestibular epithelium. A ten-day course of 3H-thymidine, bromodeoxyuridine, or both was administered to twelve-day-old chicks. Both autoradiographic and immunocytochemical labeling demonstrated ongoing production of supporting cells and Type II hair cells in all chick vestibular organs. No evidence for production of Type I hair cells was seen in this investigation. New sensory cells were distributed throughout the epithelium; there was no peripheral growth zone analogous to that found in other vertebrates. Labeled Type II hair cells were frequently seen immediately above labeled supporting cells. This observation suggests that supporting cells are precursors for new hair cells. The ongoing, postnatal regeneration of vestibular epithelial cells also suggests that this epithelium may retain the potential for repair after trauma or ototoxic damage.

Animals↗
PubMed1975

Influence of head orientation on visually induced pitch and roll sensation.

Observers viewing rotating scenes in their periphery frequently experience self-motion in the opposite direction. A full field (360 degrees) flight simulator projection system was used to investigate the sensations resulting from pitch, roll, and yaw stimuli at various head orientations. Steady yaw rate (circularvection) and development of a constant roll tilt angle, for the head erect and constant velocity yaw and roll stimuli, confirmed previous reports. Pitch stimuli also were found to produce a sensation of tilting to a steady pitch angle, which was much stronger for pitch forward than backward. Pitch and roll effects were strongly dependent on head position, increasing for the head rolled 90 degrees to the side or inverted, and decreasing for the head pitched 25 degrees forward. These results support a hypothesis that visually induced tilt is limited by conflict with otolith information.

Aerospace Medicine↗
PubMed1986

Crosslinks between stereocilia in hair cells of the human and guinea pig vestibular labyrinth.

The saccules and ampullae of the semicircular canals from human and guinea pig temporal bones were fixed in glutaraldehyde without osmium. Crosslinks were seen between stereocilia of the vestibular hair cells, similar to those previously demonstrated in the guinea pig, although an additional set of crosslinks was displayed: first, horizontal crosslinks were seen between adjacent stereocilia, occupying most of the length of the hair bundle; secondly, a single upward-pointing link ran from the apex of each shorter stereocilium into the shaft of the adjacent taller stereocilium; thirdly, an extensive array of horizontal links were demonstrated between stereocilia close to their insertion into the cuticular plate. We suggest that these basal crosslinks support the long vestibular stereocilia rendering them more rigid, and that the upwind pointing crosslinks are responsible for the initiation of sensory transduction.

Aged↗
PubMed1987

Light microscopic evidence of hair cell regeneration after gentamicin toxicity in chick cochlea.

This study examines the temporal pattern of hair cell loss in the chick basilar papilla following ten days of gentamicin administration in hatchling chicks. Chicks were subsequently killed at ages 11, 18, 25, and 32 days. The basilar papillae were embedded in plastic and serially sectioned for light microscopic analysis. Hair cell counts were obtained at 100-microM intervals throughout the length of the papilla. Significant hair cell loss was documented basally in the 11-day-old chicks, and spread apically over time to maximal loss in the 18-day-old animals. Relative to the control chicks, there was a 36% hair cell loss in these animals. Interestingly, there appears to be a progressive partial recovery of the normal hair cell counts in the 25- and 32-day-old animals.

Animals↗
PubMed1986

The development of the static vestibulo-ocular reflex in the southern clawed toad, Xenopus laevis. II. Animals with acute vestibular lesions.

Acute hemilabyrinthectomized tadpoles of the Southern Clawed Toad (Xenopus laevis), younger than stage 47 (about 6 days old), perform no static vestibulo-ocular reflex (Fig. 1). Older acute lesioned animals respond with compensatory movements of both eyes during static roll. Their threshold roll angle, however, depends on the developmental stage. For lesioned stages 60 to 64, it is 75 degrees while stage 52 to 56 tadpoles respond even during a lateral roll of 15 degrees (Figs. 1 and 2). Selective destruction of single macula and crista organs revealed that the static vestibulo-ocular reflex is evoked by excitation of the macula utriculi (Figs. 3 and 4) even in young tadpoles. The results demonstrate that bilateral projections of the vestibular apparatus must have developed at the time of occurrence of the static VOR, that during the first week of life the excitation of a single labyrinth is subthreshold (Fig. 1). We discuss the possibility whether the loss of the static VOR during the prometamorphic period of life (Fig. 2) is caused by increasing formation of multimodal connections in the vestibular pathway.

Animals↗
PubMed1983

Interaction between signals from vestibular and forelimb receptors in Purkinje cells of the frog vestibulocerebellum.

Activity from vestibulocerebellar Purkinje cells was recorded during roll oscillation (control) and roll oscillation accompanied by passive forelimb movement (test). Control stimulus evoked mossy and climbing fiber responses. In some units, the test evoked a smaller climbing fiber response. This suggests an error-signaling role for the climbing fibers since a larger response was evoked in the absence of appropriate compensatory limb movement.

Afferent Pathways↗
PubMed1983

Spontaneous and impulsively evoked otoacoustic emissions: indicators of cochlear pathology?

The first author's right ear produces a spontaneous otoacoustic emission (SOAE) at 7529 Hz and 16 dB SPL. An external continuous tone is able to suppress the SOAE. The 3 dB iso-suppression curve is broadly tuned and displaced, relative to the SOAE, toward higher frequencies. An audiogram notch exists at frequencies just below that of the SOAE. We explain the occurrence of both spontaneous and impulsively evoked OAEs in terms of disruption of active feedback mechanisms of the OHCs upon basilar membrane vibration. According to this hypothesis, each segment of the organ of Corti feeds back positively upon its segment of basilar membrane and negatively upon adjacent segments. If a patch of OHC loss exists, adjacent segments of the basilar membrane are released from the negative feedback and respond to an impulsive stimulus with exaggerated oscillations at their resonance frequencies, thus producing OAEs. At particularly sharp transitions between normal and abnormal regions of the organ of Corti SOAEs may be generated.

Audiometry↗
PubMed1990

Cell potential and motility of isolated mammalian vestibular sensory cells.

Vestibular hair cells (VHCs) were isolated from the guinea pig inner ear. Using the whole cell variant of the patch clamp recording technique a zero current cell potential of -63.1 +/- 9.9 mV was measured in macular hair cells. Depolarization and repolarization were accompanied by mechanical responses of the solitary VHCs. In addition to the evoked motile events spontaneous shape changes of VHCs were observed. Implications for vestibular micromechanics of the observed evoked force generation in VHCs are discussed.

Animals↗
PubMed1990

Evidence for potassium-induced motility in type I vestibular hair cells in the guinea pig.

In higher vertebrates, vestibular epithelia contain two types of hair cells, type I and type II cells. Physiological properties of single nerve units have been correlated to the corresponding hair cell type and a better knowledge of the hair cell static and dynamic properties should help in understanding transduction and coding in the vestibular system. For the auditory system, isolated outer cochlear hair cells (OHCs) have provided a useful approach for electrophysiological studies and for observations of motile processes involved in the active control of cochlear micromechanics. The present study tests the hypothesis of motile properties in guinea-pig vestibular hair cells, using stimuli known to elicit motile events in OHCs. After exposure to a medium containing a high concentration in potassium (125 mM or 80 mM KCl), 19 of 26 type I hair cells showed an irreversible tilt of the neck region often accompanied by an obvious swelling of the cell body. In contrast, no shape changes were detected in type II cells. In response to extracellular electrical stimulation, no motility was observed in either type I or type II cells.

Animals↗