Biomedical subjects

J C Adams

Publications and source records attributed to J C Adams.

At least 37 records · Page 2Linked to original sources

PubMed1997

Thrombospondin-1.

Thrombospondin-1 is a glycoprotein that is released from platelet alpha-granules in response to thrombin stimulation and that is also a transient component of extracellular matrix in developing and repairing tissues. It is a 420 kDa homotrimer, each subunit of which consists of multiple structural domains. A variety of factors regulate thrombospondin-1 expression and the protein is degraded by both extracellular and intracellular routes. Thrombospondin-1 functions as a cell adhesion molecule and also modulates cell movement, cell proliferation, neurite outgrowth and angiogenesis. The molecular mechanisms underlying these activities are beginning to be examined. Medical interest in thrombospondin-1 centres on its roles in haemostasis and its effects on angiogenesis.

Animals↗

PubMed1997

Cell-adhesive responses to tenascin-C splice variants involve formation of fascin microspikes.

Tenascin-C is an adhesion-modulating matrix glycoprotein that has multiple effects on cell behavior. Tenascin-C transcripts are expressed in motile cells and at sites of tissue modeling during development, and alternative splicing generates variants that encode different numbers of fibronectin type III repeats. We have examined the in vivo expression and cell adhesive properties of two full-length recombinant tenascin-C proteins: TN-190, which contains the eight constant fibronectin type III repeats, and TN-ADC, which contains the additional AD2, AD1, and C repeats. In situ hybridization with probes specific for the AD2, AD1, and C repeats shows that these splice variants are expressed at sites of active tissue modeling and fibronectin expression in the developing avian feather bud and sternum. Transcripts incorporating the AD2, AD1, and C repeats are present in embryonic day 10 wing bud but not in embryonic day 10 lung. By using a panel of nine cell lines in attachment assays, we have found that C2C12, G8, and S27 myoblastic cells undergo concentration-dependent adhesion to both variants, organize actin microspikes that contain the actin-bundling protein fascin, and do not assemble focal contacts. On a molar basis, TN-ADC is more active than TN-190 in promoting cell attachment and irregular cell spreading. The addition of either TN-190 or TN-ADC in solution to C2C12, COS-7, or MG-63 cells adherent on fibronectin decreases cell attachment and results in decreased organization of actin microfilament bundles, with formation of cortical membrane ruffles and retention of residual points of substratum contact that contain filamentous actin and fascin. These data establish a biochemical similarity in the processes of cell adhesion to tenascin-C and thrombospondin-1, also an "antiadhesive" matrix component, and also demonstrate that both the adhesive and adhesion-modulating properties of tenascin-C involve similar biochemical events in the cortical cytoskeleton. In addition to these generic properties, TN-ADC is less active in adhesion modulation than TN-190. The coordinated expression of different tenascin-C transcripts during development may, therefore, provide appropriate microenvironments for regulated changes in cell shape, adhesion, and movement.

Actin Cytoskeleton↗

PubMed1997

Characterization of cell-matrix adhesion requirements for the formation of fascin microspikes.

Cell adhesion to thrombospondin-1 (TSP-1) correlates with assembly of cell-substratum contact structures that contain fascin microspikes. In this analysis, cell-matrix requirements for assembly of fascin microspikes were examined in detail. In six cell lines, cell spreading on a TSP-1 substratum correlated with expression of fascin protein and formation of fascin microspikes. Microspikes were not formed by H9c2 cells adherent on fibronectin, vitronectin, collagen IV, or platelet factor 4. However, both fascin microspikes and focal contacts were assembled by cells adherent on laminin-1. Using mixed substrata containing different proportions of TSP-1, and fibronectin, fascin microspike formation by H9c2 and C2C12 cells was found to be reduced on substrata containing 25% fibronectin and abolished on substrata containing 75% fibronectin. Adhesion to intermediate mixtures of TSP-1 and fibronectin resulted in coassembly of fascin microspikes and focal contacts, colocalization of fascin with actin stress fiber bundles and altered distributions of beta 1 integrins, cortical alpha-actinin, and tropomyosin. In cells adherent on 50% TSP-1:50% fibronectin, GRGDSP peptide treatment decreased focal contact assembly and altered cytoskeletal organization but did not inhibit microspike assembly. Treatment with chondroitin sulfate A or p-nitrophenol beta-D-xylopyranoside decreased microspike formation and modified cytoskeletal organization but did not inhibit focal contact formation. In polarized migratory and postmitotic C2C12 cells, fascin microspikes and ruffles were localized at leading edges and TSP matrix deposition was also concentrated in this region. Depletion of matrix TSP by heparin treatment correlated with decreased microspike formation and cell motility. Thus, the balance of adhesive receptors ligated at the cell surface during initial cell-matrix attachment serves to regulate the type of substratum adhesion contact assembled and subsequent cytoskeletal organization. A role for fascin microspikes in cell motile behavior is indicated.

Actins↗

PubMed1996

Immunolocalization of peptide 19 and other calcium-binding proteins in the guinea pig cochlea.

Calcium ions are known to play critical roles in a variety of cochlear functions. The distributions of a number of calcium binding proteins that regulate calcium ion levels within the cochlea have previously been described. In this report we extend and refine previous reports of the distribution of immunostaining for calmodulin, calbindin, and calretinin and show for the first time the distribution for peptide 19. There were longitudinal and radial gradients of immunostaining for peptide 19 within outer hair cells that appeared to match previously described gradients of efferent innervation of these cells. Gradients of immunostaining for calbindin within outer hair cells were in the opposite directions, which suggests that levels of this protein are correlated with afferent innervation density and perhaps the abundance of subsurface cisternae. No gradients were seen in the distributions of cells stained for calmodulin and calretinin, which included sensory cells and supporting cells respectively. All ganglion cells were stained for calmodulin but the other proteins appeared to be present in limited ganglion cell subpopulations. In addition to staining of sensorineural elements, antisera to all compounds but peptide 19 showed immunostaining of cells within the lateral wall and the spiral limbus. The results suggest that the proteins under study are involved in a wide variety of calcium-regulated functions within the cochlea. Knowledge of the unique distribution of each of the compounds should facilitate further studies of their roles in cochlear function.

Animals↗

PubMed1996

A human temporal bone study of changes in the basilar membrane of the apical turn in endolymphatic hydrops.

We observed that some temporal bones with endolymphatic hydrops (EH) showed varying degrees of basalward displacement (towards the scala tympani) of the basilar membrane (BM) in the apical turn of the cochlea. In some, the BM was adherent to the bony wall of the scala tympani (i.e., the interscalar septum). Such mechanical distortion of the BM could conceivably alter cochlear mechanics and lead to sensorineural hearing loss. The results of a systematic evaluation of 234 temporal bones to characterize, quantify and determine the functional significance of this observation are presented. Four groups of bones were evaluated: normal (N = 78), presbycusis (N = 96), Ménière's disease (N = 23), and EH secondary to labyrinthitis (N = 37). The incidence of extreme displacement of the BM in the apical turn such that it adhered to the interscalar septum was 52% in Ménière's disease, 57% in EH secondary to labyrinthitis, 10% in presbycusis, and 1% in normals. These differences were significant and could not be explained on the basis of age, sex, postmortem time, or artifact of technique or processing. Displacement of the BM was not observed in other turns of the cochlea. Its pathogenesis is not known, but may be related to atrophy of the spiral ligament. It is likely that such BM displacement results in sensorineural hearing loss. However, our data and theoretical analyses both indicate that such a loss will be restricted to frequencies below 100 Hz and that this pathologic change alone is not likely to cause appreciable hearing loss at clinically tested frequencies of 250 HZ and higher. Hence, even though this pathologic finding is common in endolymphatic hydrops, it cannot explain the low-frequency hearing lost observed in Ménière's disease.

Adult↗

PubMed1995

Sound stimulation induces Fos-related antigens in cells with common morphological properties throughout the auditory brainstem.

Cells within the auditory brainstem of cat that respond to sound by producing the transcription factor Fos or related proteins were identified by immunostaining with antisera against Fos and Zif/268. Within the cochlear nucleus, all antisera showed similar staining patterns, however, in the superior olive and inferior colliculus, staining patterns differed between antisera. Immunostained cells were characterized by their size, location, by the presence of perisomatic terminals that immunostained for glutamate decarboxylase or synaptophysin, or by electron microscopy. Most cell classes were not immunopositive. In the ventral cochlear nucleus, roughly 99% of Fos-positive cells had few perisomatic terminals. Within the superior olivary complex (SOC), the majority of immunopositive cells had few perisomatic terminals. Lateral olivocochlear cells were identified as Fos positive by their size, location, lack of perisomatic terminals, and positive costaining for acetylcholinesterase as evidenced by a novel reaction product. This report appears to be the first demonstration of these cells responding to sound stimulation. Within the inferior colliculus, bands of positive cells produced by tonal stimulation extended from the central nucleus throughout the dorsal cortex and the posterior pericentral region, a finding unexpected on the basis of previous electrophysiological recordings and anatomical studies of ascending inputs to the colliculus. Approximately 35% of Fos-positive cells in the inferior colliculus had plentiful perisomatic terminals. Results demonstrate a high degree of specificity of auditory cell types that respond to sound by producing Fos-like proteins and show that previously intractable physiological questions can be addressed by assaying for sound-induced production of these antigens.

Acoustic Stimulation↗

PubMed1995

cDNA cloning, tissue distribution, and chromosomal localization of Ocp2, a gene encoding a putative transcription-associated factor predominantly expressed in the auditory organs.

We report the cloning of the Ocp2 gene encoding OCP-II from a guinea pig organ-of-Corti cDNA library. The predicted open reading frame encodes a protein of 163 amino acids with an estimated molecular mass of 18.6 kDa. A homology search revealed that Ocp2 shares significant sequence similarity with p15, a subunit of transcription factor SIII that regulates the activity of the RNA polymerase II elongation complex. The Ocp2 messenger RNA is expressed abundantly in the cochlea while not significantly in any other tissues examined, including brain, eye, heart, intestine, kidney, liver, lung, thigh muscle, and testis, demonstrating that the expression of this gene may be restricted to auditory organs. A polyclonal antiserum was raised against the N-terminal region of OCP-II. Immunohistochemical staining of paraffin-embedded sections of the cochlea showed that OCP-II is localized abundantly in nonsensory cells in the organ of Corti; in addition, it was also detected, at a lower concentration, in vestibular sensory organs, as well as auditory and vestibular brain stem nuclei. The Ocp2 gene was mapped to mouse chromosome 4 as well as 11. Our results suggest that OCP-II may be involved in transcription regulation for the development or maintenance of specialized functions of the inner ear.

Amino Acid Sequence↗

PubMed1995

Thrombospondin-4 is expressed by early osteogenic tissues in the chick embryo.

The thrombospondins are a family of related glycoproteins found in the embryonic extracellular matrix. To date, five members of this family have been identified. Thrombospondin-1 and thrombospondin-2 have similar primary structure, but are expressed in different tissues at different times during development. Thrombospondins-3, -4, and cartilage oligomeric protein belong to a second thrombospondin subgroup in which the carboxyl-half of each molecule is most similar to thrombospondin-1 and -2. Here we report the cloning and sequencing of a novel probe to avian thrombospondin-4. We have used this probe to determine the origins of thrombospondin-4 in the chick embryo by in situ hybridization. Thrombospondin -4 transcripts first appear in the mesenchyme surrounding bone anlage coinciding with the initial stages of osteogenesis. The expression in osteogenic tissues is transient: thrombospondin-4 mRNAs are not seen in the osteoblasts of bone collars in developing long bones. This pattern is distinct from avian thrombospondin-2 which is expressed in perichondrium and embryonic fibrous connective tissues. Our observations indicate that connective tissues are the principal site of thrombospondin-4 expression in the chick. The diverse origins of different thrombospondin gene family members imply distinctive roles for these proteins related to the growth and differentiation of cartilage, tendons, and bone.

Amino Acid Sequence↗

PubMed1995

Gap junctions in the rat cochlea: immunohistochemical and ultrastructural analysis.

Gap junctions in the rat cochlea were investigated using immunostaining for connexin26 and transmission electron microscopy. Electron microscopy of normal and pre-embedded immunostained material showed that there were gap junctions between and among all cells that light microscopy showed to have immunostained appositions. Light microscopy showed immunostaining between and among cell types that electron microscopy showed to be joined by gap junctions. Immunostaining for connexin26 was therefore taken as providing a reasonable approximation of the locations of gap junctions throughout the cochlea and was used to provide an overview of the extent of those locations. Cells interconnected via gap junctions fell into one of two groups. The first group consists of nonsensory epithelial cells and includes interdental cells of the spiral limbus, inner sulcus cells, organ of Corti supporting cells, outer sulcus cells, and cells within the root processes of the spiral ligament. The second group consists of connective tissue cells and includes various fibrocyte types of the spiral limbus and spiral ligament, basal and intermediate cells of the stria vascularis, and mesenchymal cells which line the scala vestibuli. The present work represents a first attempt towards a description of how serial gap junctions among cochlear cells reflect a level of organization of the tissue. The organization described here, together with a great deal of information from previous investigators, suggest that serially arranged gap junctions of both epithelial and connective tissue cells serve as the structural basis for recycling endolymphatic potassium ions that pass through the sensory cells during the transduction process.

Animals↗

PubMed1995

Osteopontin expression detected in adult cochleae and inner ear fluids.

Localization of protein epitopes and mRNA expression showed that there was a wide-spread distribution of osteopontin (OPN) within the membranous labyrinth of the adult mammalian cochleae. Immunoreaction product and mRNA were found within the stria vascularis, VIIIth cranial nerve, spiral ligament and limbus. Only specific cell types within these regions contained abundant OPN mRNA or protein, the main cell type being fibrocytes that populate the spiral limbus and spiral ligament. Epithelial cells that line the luminal surface of the stria vascularis (marginal cells) and neurons that compose the vestibular and auditory ganglia also showed high opn expression. The pattern of anti-OPN staining within membranous labyrinth was comparable to that observed in tissues such as gall bladder, breast and kidney. In those tissues, luminal epithelial cells, corresponding to the marginal cells of the stria vascularis, may be responsible for manufacturing and secreting OPN into the luminal fluids. consistent with those observations, we detected OPN epitopes in cochlear fluids withdrawn from the scalae media and tympani of the cochlea. We found that the protein species in cochlear fluid differed from those present in cerebrospinal fluid (CSF) suggesting that OPN exists in tissue-specific isoforms that may correspond to particular cellular functions.

Animals↗

PubMed1995

Development of a direct viable count procedure for some gram-positive bacteria.

The direct viable count (DVC) is a procedure for enumerating viable-nonculturable cells. It should be noted, however, that bacteria demonstrating the viable but nonculturable phase have to date included only Gram-negative species, mainly because the DVC procedure does not lend itself to the analysis of Gram-positive bacteria since the DVC procedure is dependent on the bacterium being sensitive to nalidixic acid. The authors report here concerning studies on an analogous procedure for the direct enumeration of viable-nonculturable Gram-positive bacteria. To facilitate a differential DVC for Gram-positive bacteria, ciprofloxacin, enoxacin, norfloxacin or isopropyl cinodine were substituted for nalidixic acid. These antibiotics were chosen because, like nalidixic acid, they are DNA gyrase inhibitors. The concentrations used for each antibiotic were 1000 micrograms ml-1, 100 micrograms ml-1. Pure cultures of Staphylococcus aureus, Enterococcus faecalis, Streptococcus agalactiae, Listeria monocytogenes and Bacillus subtilis were obtained from the culture collection at the University of Wyoming and a faecal streptococcus was isolated from the Laramie wastewater treatment plant. An antibiotic and optimal concentration thereof was found which gave enlarged cells for all the organisms except the faecal streptococcus isolated from the wastewater plant for which no enlarged cells were ever seen. The antibiotic and concentration thereof which gave the optimal percent enlarged cells in the DVC procedure varied between organisms.

Anti-Bacterial Agents↗

PubMed1995

Immunolocalization of aquaporin CHIP in the guinea pig inner ear.

Aquaporin CHIP (AQP-CHIP) is a water channel protein previously identified in red blood cells and water transporting epithelia. The inner ear is an organ of hearing and balance whose normal function depends critically on maintenance of fluid homeostasis. In this study, AQP-CHIP, or a close homologue, was found in specific cells of the inner ear, as assessed by immunocytochemistry with the use of affinity-purified polyclonal antibodies against AQP-CHIP.AQP-CHIP was predominantly found in fibrocytes in close association with bone, including most of the cells lining the bony labyrinth and in fibrocytes lining the endolymphatic duct and sac. AQP-CHIP-positive cells not directly apposing bone include cells under the basilar membrane, some type III fibrocytes of the spiral ligament, fibrocytes of the spiral limbus, and the trabecular perilymphatic tissue extending from the membranous to the bony labyrinth. AQP-CHIP was also found in the periosteum of the middle ear and cranial bones, as well as in chondrocytes of the oval window and stapes. The distribution of AQP-CHIP in the inner ear suggests that AQP-CHIP may have special significance for maintenance of bone and the basilar membrane, and for function of the spiral ligament.

Animals↗

PubMed1995

Formation of stable microspikes containing actin and the 55 kDa actin bundling protein, fascin, is a consequence of cell adhesion to thrombospondin-1: implications for the anti-adhesive activities of thrombospondin-1.

The organisation of the actin cytoskeleton was examined in H9c2 and human intestinal smooth muscle cells adherent on fibronectin or thrombospondin-1. Whereas cells adherent on fibronectin adopted a polygonal shape and rapidly assembled prominent stress fibres and focal contacts, cells adherent on thrombospondin-1 assumed a more irregular morphology with large lamellae containing radial actin microspikes. Focal contacts were not detected in cells adherent on thrombospondin-1, as determined by indirect immunofluorescence staining for vinculin and other focal contact components. Instead, the radial microspikes stained positively for the actin-bundling protein, 55 kDa/fascin, and myosins. In cells adherent on fibronectin, 55 kDa/fascin immunoreactivity was diffuse and tended to be concentrated in the perinuclear region. In long-term adherent cells cultured in serum-containing medium, 55 kDa/fascin was detected in membrane ruffles, in stress fibres and in the perinuclear region. The microspikes formed within 40 minutes of plating cells on thrombospondin-1 and remained present when cells were treated with sodium orthovandate and hydrogen peroxide to increase intracellular phosphotyrosine levels. Indeed, although vanadate-treated cells tended to retract, the microspikes became more prominent and showed an increased intensity of staining for fascin. Under these conditions, a proportion of the microspikes did not appear to be in contact with the substratum: these spikes stained weakly for focal adhesion kinase, talin and vinculin. Cells treated with genistein also spread and formed fascin-containing microspikes which tended to be more slender than those of control cells. In contrast, cells adherent on fibronectin displayed a complex rearrangement of the actin cytoskeleton and a transient enrichment of 55 kDa/fascin-containing structures at the cell surface when treated with sodium orthovanadate and hydrogen peroxide. These observations indicate that cell interactions with fibronectin or thrombospondin-1 send distinct organisational signals to the actin cytoskeleton and may offer a mechanistic framework for further investigations of the anti-adhesive properties of thrombospondin-1.

Actins↗

PubMed1995

Degenerative changes in the organ of Corti and lateral cochlear wall in experimental endolymphatic hydrops and human Menière's disease.

The pathogenesis of sensorineural hearing loss in Menière's disease and experimental endolymphatic hydrops is not fully understood. At the light microscopic level, there is poor correlation between the histopathology and loss of sensitivity and speech discrimination. The results of electron microscopic investigation of histopathology and alterations in immunoreactivity in the organ of Corti and lateral cochlear wall in the hydropic guinea pig are presented. Loss of outer and inner hair cells and spiral ganglion cells, particularly in the apical turn was evident by light microscopy. By electron microscopy, further evidence of degeneration was detected in the cuticular plate of outer hair cells, neural endings of both inner and outer hair cells, myelinated dendritic fibers, spiral ganglion cells, and types I and II fibrocytes of the lateral cochlear wall. There was a marked decrease in immunoreactivity for a variety of enzymes, calcium binding proteins, structural proteins, and integral membrane proteins of gap junctions, particularly among type I and type II fibrocytes of the lateral cochlear wall. The evidence suggests that dysfunction and degeneration of hair cells, afferent neurons and fibrocytes of the lateral cochlear wall are involved in the pathogenesis of hearing loss in endolymphatic hydrops.

Animals↗

PubMed1994

Cell-type specific adhesive interactions of skeletal myoblasts with thrombospondin-1.

Thrombospondin-1 (TSP-1) is an extracellular matrix glycoprotein that may play important roles in the morphogenesis and repair of skeletal muscle. To begin to explore the role of thrombospondin-1 in this tissue, we have examined the interactions of three rodent skeletal muscle cell lines, C2C12, G8, and H9c2, with platelet TSP-1. The cells secrete thrombospondin and incorporate it into the cell layer in a distribution distinct from that of fibronectin. Myoblasts attach and spread on fibronectin- or thrombospondin-coated substrates with similar time and concentration dependencies. Whereas cells adherent on fibronectin organize actin stress fibers, cells adherent on TSP-1 display prominent membrane ruffles and lamellae that contain radial actin microspikes. Attachment to thrombospondin-1 or the 140-kDa tryptic fragment is mediated by interactions with the type 1 repeats and the carboxy-terminal globular domain. Attachment is not inhibited by heparin, GRGDSP peptide, or VTCG peptide but is inhibited by chondroitin sulphate A. Integrins of the beta 1 or alpha V subgroups do not appear to be involved in myoblast attachment to TSP-1; instead, this process depends in part on cell surface chondroitin sulphate proteoglycans. Whereas the central 70-kDa chymotryptic fragment of TSP-1 does not support myoblast attachment, the carboxy-terminal domain of TSP-1 expressed as a fusion protein in the bacterial expression vector, pGEX, supported myoblast attachment to 30% the level of intact TSP-1. Thrombospondin-4 (TSP-4) is also present in skeletal muscle and a fusion protein containing the carboxy-terminal domain of TSP-4 also supported myoblast adhesion, although this protein was less active on a molar basis than the TSP-1 fusion protein. Thus, the carboxyterminal domain of TSP-1 appears to contain a primary attachment site for myoblasts, and this activity is present in a second member of the thrombospondin family.

Actins↗

PubMed1994

Changes in immunostaining of cochleas with experimentally induced endolymphatic hydrops.

Cochleas with experimentally induced endolymphatic hydrops were immunostained for Na+,K(+)-ATPase, intracellular Ca(++)-ATPase, carbonic anhydrase, aldehyde dehydrogenase, calcium-binding proteins, vimentin, and the gap junction protein, connexin 26. No changes in immunostaining of hydropic ears were observed 1 week after blockage of the endolymphatic duct. Two weeks to 1 month after the operation, immunostaining of type I fibrocytes in the spiral ligament, which are positive for all but Na+,K(+)-ATPase, was slightly decreased on the operated side. These changes became more pronounced 3 months after the operation. However, staining for Na+,K(+)-ATPase of the stria vascularis and of type II fibrocytes of the spiral ligament was not reduced until 6 months postoperative. The reduction of enzymes and other cell constituents that may be involved in ion balance of cochlear fluids indicates that cells in the spiral ligament play an important role in cochlear homeostasis and that they merit further study in animal and human otopathology.

Adenosine Triphosphatases↗

PubMed1994

Immunolocalization of Na+, K(+)-ATPase, Ca(++)-ATPase, calcium-binding proteins, and carbonic anhydrase in the guinea pig inner ear.

The distribution of Na+, K(+)-ATPase, Ca(++)-ATPase, carbonic anhydrase, and calcium-binding proteins were investigated immunohistochemically in paraffin sections of guinea pig inner ears. Marginal cells of the stria vascularis, type II fibrocytes of the spiral ligament, and cells in supralimbal and suprastrial regions, were positive for Na+, K(+)-ATPase. Type I fibrocytes of the spiral ligament were positive for Ca(++)-ATPase, carbonic anhydrase, calmodulin and osteopontin. In the vestibular system, dark cells were positive for Na+, K(+)-ATPase. However, these cells and subepithelial fibrocytes were negative for Ca(++)-ATPase, carbonic anhydrase, and the calcium-binding proteins. In the endolymphatic sac, epithelial cells in intermediate and distal portions were positive for Na+, K(+)-ATPase, but the reaction was less than that in the stria. The same endolymphatic sac cells that were positive for Na+, K(+)-ATPase were also positive for Ca(++)-ATPase and calcium-binding proteins, but negative for carbonic anhydrase. The presence of Ca(++)-ATPase and calcium-binding proteins in the type I fibrocytes of the spiral ligament suggests that these cells are involved in mediating Ca++ regulation. Lower levels of Na+, K(+)-ATPase and the co-existence of Ca(++)-ATPase and calcium-binding proteins in the epithelial cells of the endolymphatic sac indicate that these cells have a distinctive role in ion transport that is different from that of the cells of the stria vascularis and vestibular dark cells.

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↗