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D J Lim

Publications and source records attributed to D J Lim.

At least 19 recordsLinked to original sources
PubMed1992

A membrane-based force generation mechanism in auditory sensory cells.

Auditory outer hair cells can elongate and shorten at acoustic frequencies in response to changes of plasma membrane potential. We show that this fast bidirectional contractile activity consists of an electromechanical transduction process that occurs at the lateral plasma membrane and can be activated and analyzed independently in small membrane patches inside a patch electrode. Bidirectional forces are generated by increases and decreases in membrane area in response to hyperpolarization and depolarization, respectively. We suggest that the force generation mechanism is driven by voltage-dependent conformational changes within a dense array of large transmembrane proteins associated with the site of electromechanical transduction.

Animals↗
PubMed1992

Changes in the structure of the cell surface carbohydrates of the chinchilla tubotympanum following Streptococcus pneumoniae-induced otitis media.

Streptococcus pneumoniae (Spn) are among the most frequently isolated pathogens in acute otitis media (AOM) and in otitis media with effusion (OME). Recently, the specific receptor for Spn has been identified as the trisaccharide unit Gal beta 1-4 GlcNAc beta 1-3 Gal beta with GlcNAc beta 1-3 Gal beta as the principal binding site. During the colonization of mucosal surfaces, pneumococci produce a variety of enzymes. This study was conducted to identify any resulting changes in the cell surface carbohydrate structure due to the action of these enzymes during pneumococcal otitis media (OM) in chinchillas. Using a lectin histochemical method with seven different lectins (SNA, LFA, WGA, Succ WGA, BSL II, PNA, ECL), the labeling pattern revealed not only the removal of the terminal sialic acid, but also the exposure of N-acetyl-glucosamine. These results suggested that Spn-produced enzymes uncover part of their own receptor structure and thus may facilitate adherence and subsequent infection.

Acute Disease↗
PubMed1992

Effect of endotoxin on cultured chinchilla middle ear epithelium.

The effect of endotoxin on the growth and morphology of cultured chinchilla middle ear epithelium was examined. Within 24 hours of culture, cells maintained in medium containing endotoxin exhibited dose-dependent morphological changes. The highest concentration of endotoxin (100 mg) resulted in cell death. The growth curve of the cells in culture demonstrated a dose-dependent, significant increase in cell number when endotoxin was added to the medium.

Animals↗
PubMed1992

Expression of sialic acids in the developing murine tubotympanum.

Sialoglycoconjugates in the developing murine tubotympanum were characterized using lectin histochemistry with wheat germ agglutinin (WGA), Limax flavus agglutinin (LFA), Sambucus nigra agglutinin (SNA), Maackia amurensis agglutinin (MAA), peanut agglutinin (PNA), and neuraminidase treatment. WGA, LFA, MAA, and neuraminidase-PNA labeled epithelial goblet cells, glandular mucous cells, and cell surfaces of adult and newborn murine tubotympanum. SNA did not label any secretory components. PNA labeled secretory cells and cell surfaces of the fetal tubotympanum without neuraminidase treatment. After birth, these secretory cells and cell surfaces were labeled with PNA only after neuraminidase treatment. These results revealed that: Sialoglycoconjugates are produced from glandular mucous cells and epithelial goblet cells and are present on cell surfaces and within the mucous blanket; their terminal tri-saccharide linkage appears to be the sequence Neu5Ac(alpha 2-3)Gal(beta 1-3)GalNAc; sialic acids appear before birth and gradually increase; terminal galactose residues are masked by sialic acids after birth.

Aging↗
PubMed1992

Development of the mucociliary system in the eustachian tube and middle ear: murine model.

In order to describe the developmental anatomy of the murine eustachian tube and its related structures, seventy six mice of ages ranging from gestational day 11 to postnatal day 21 were investigated through the light and electron microscopic observations. Development of the ciliated cells was seen concurrently in both the eustachian tube and middle ear on the 16 th gestation day, one day earlier than the epithelial secretory cells appeared in both the eustachian tube and middle ear. The number of ciliated cells and secretory cells increased rapidly after birth. Tubal glands were well identified with evidence of secretory activity around the time of birth. Thus, the findings of this study indicate that the mucociliary defense system starts to develop during the fetal stage and is well established immediately after birth.

Animals↗
PubMed1992

Luminal development of the eustachian tube and middle ear: murine model.

The purpose of this study was to describe the luminal development of the murine eustachian tube and middle ear. Thirty specimens, aging from gestational day 11 to postnatal day 21, were investigated through the light microscopic observations. The present study also used digitizer, computer, and serially sectioned temporal bone specimens for three-dimensional reconstruction to measure the volume of the eustachian tube and middle ear cavity at different gestational and postnatal ages. The first pharyngeal pouch elongated during gestational day 12 to form the tubotympanic recess. Between gestational day 13 and 14 this tubotympanic recess extended to the middle ear area. A rapid increment in the volume of the tubotympanic recess was noted between gestational day 15 and 16. At this age, a definite division of the tubotympanic recess into the eustachian tube and middle ear cavity was observed. During the postnatal period, the maximum change of the middle ear volume was noted on postnatal day 11 when the mesenchymal tissue in the middle ear cavity disappeared completely.

Animals↗
PubMed1991

Primary culture of chinchilla middle ear epithelium.

Chinchilla middle ear epithelium was successfully cultured in medium containing Dulbecco's modified Eagle's medium, Ham's F12 mixture, and fetal bovine serum. After 3 to 5 days, the explants produced outgrowths of primarily flat polygonal and ciliated cells that persisted for up to 10 days in culture. These cells in the outgrowth often formed a "dome" indicating the presence of functional polarization and fluid transportation capability. The ciliated cells were more frequently found near the explant, and were fewer in number in the area distant from the explant. This finding suggests that the ciliated cells in the outgrowth are migrated ciliated cells deriving from the explant. That secretory cells were not identified in the outgrowth indicated that the present culture technique did not support secretory activity. Using the present culture technique, we were able to maintain the explants and primary cultured cells for up to 14 days in a majority of cases; hence, these techniques appear to be applicable to a number of in vitro studies.

Animals↗
PubMed1991

Glycoconjugates in the chinchilla tubotympanum.

Various biotinylated lectins were used to characterize and semiquantitate glycoconjugate residues in the tubotympanum. Epithelial goblet cells were stained predominantly by WGA, LFA, SNA, RCA-I, Con-A, LCA, SBA, PHA-E, and UEA; this finding suggests they contain alpha-neuraminic acid, beta-galactose, alpha-mannose, N-acetyl alpha-galactosamine, and alpha-fucose. Glandular mucous cells were stained predominantly by WGA, LFA, SNA, and RCA-I; this finding suggests that they contain alpha-neuraminic acid and beta-galactose. The glandular serous cells were stained predominantly by Con-A, WGA, and LFA; this finding suggests that they produced alpha-mannose and alpha-neuraminic acid that represented serum-type glycoprotein. The positive staining of epithelial goblet cells and glandular mucous cells with PNA after neuraminidase digestion suggests that they produced mucin-type glycoproteins. The staining of the mucous blanket by WGA, LFA, SNA, RCA-I, LCA, PNA, SBA, PHA-E, and UEA suggests the presence of alpha-neuraminic acid, beta-galactose, N-acetyl alpha-galactosamine, and alpha-fucose. The epithelial cell (nonsecretory) surface was stained largely by WGA, LFA, SNA, RCA-I, Con-A, and LCA; this finding suggests the presence of alpha-neuraminic acid, beta-galactose, and alpha-mannose.

Animals↗
PubMed1991

Serial culture and characterization of the chinchilla middle ear epithelium.

We have successfully cultured a fibroblast-free chinchilla middle ear epithelium up to the 10th passage by using conditioned medium or using irradiated 3T3 cells as feeder cells. The cultured epithelial cells assumed a polygonal shape with a cobblestone appearance, indicating tight junction formation. A small number of the cells began to show abnormal morphology, such as indistinct cell boundaries, fibroid appearance, or giant cell formation, as the passage increased, particularly after the 5th passage. These morphologically transformed cells showed positive labeling with an anticytokeratin antibody, which indicated the epithelial origin of these cells. Neither ciliated nor secretory cells were observed in the serially cultured cells. The rate of cell growth slowed after the 7th passage, and after the 11th passage the cells no longer proliferated. Even with the above limitations, these cultured cells can be used for a number of in vitro experiments.

Animals↗
PubMed1991

Heterogeneity of glycoconjugates in the secretory cells of the chinchilla middle ear and eustachian tubal epithelia: a lectin-gold cytochemical study.

The present study was conducted to characterize and localize the glycoconjugates in the tubotympanum (auditory or eustachian tube and middle ear cavity) of chinchilla on an ultrastructural level, using lectin-gold complexes with six different lectins: BPA, ConA, RCA-1, WGA, LFA, and SNA. A comparison of the affinity of these lectins demonstrated the heterogeneity of secretory cells. The glandular serous cells and epithelial dark granulated cells produced "serum"-type glycoprotein. The glandular mucous cells and goblet cells produced dominantly "mucin"-type glycoprotein in the light granules, but "serum"-type glycoprotein in the dark cores. The labeling of LFA and SNA showed that sialic acids existed mainly in the mucinous granules of secretory cells and ciliated epithelium glycocalyx, and in the mucous blanket. The results also suggested that the dominant linkage of sialic acids of mucin is a Neu5Ac(alpha 2-6)Gal/GalNAc sequence. Furthermore, the data obtained from ConA and BPA suggested that initial O-glycosylation of mucin took place in the cis side of the Golgi apparatus and that initial N-glycosylation of the serum occurred in the rough endoplasmic reticulum.

Animals↗
PubMed1991

Surface active substances in the chinchilla tubotympanum. A biochemical study.

It has been demonstrated that the eustachian tube and middle ear epithelium produce Tubal Surface Active Substances (TSAS), which facilitate the opening of the eustachian tube. In order to characterize the biochemical contents of chinchilla TSAS, the tubal washings were analyzed using 2-D thin layer chromatography. The results indicate that phosphatidylcholine was the predominant phospholipid, followed by sphingomyelin, phosphatidylinositol phosphatidylethanolamine, and phosphatidylserine. In comparison, pulmonary lavage showed phosphatidylcholine to be highest allowed by phosphatidylethanolamine and sphingomyelin. Phosphatidylcholine/phosphatidylethanolanim ratios were 5:1 in the tubal lavage, and 8:1 in the pulmonary lavage. Phosphatidylcholine/sphingomyelin ratios were 2:1 in the tubal lavage, and 67:1 in the pulmonary lavage. It is concluded that the biochemical content of TSAS is similar but not identical to that of pulmonary surfactants.

Animals↗
PubMed1991

[Glycoconjugates in the chinchilla tubotympanum: a lectin histochemical study].

Glycoconjugates are essential for normal functioning of the mucociliary defence system of the tubotympanum. Recently, terminal glycosylation sequences of glycoconjugates have been recognized for their role in mediating biological recognition, such as serving as a receptor for bacterial adherence. In this study, neuraminidase and 6 different lectins: Wheat germ agglutinin (WGA), Limax flavus agglutinin (LFA), Sambucus nigra agglutinin (SNA), Peanut agglutinin (PNA), Ricinus communis agglutinin-I (RCA-I), and Concanavalin A (Con A), were used to characterize histochemically the carbohydrate structures of glycoconjugates of the chinchilla tubotympanum. WGA, LFA, SNA, and RCA-I strongly labeled epithelial goblet cells, glandular mucous cells, cell surfaces, and mucous blanket. PNA weakly labeled only a small number of epithelial goblet cells and glandular mucous cells, and did not label cell surfaces. After neuraminidase treatment, PNA labeled large number of these secretory cells and cell surfaces. Con A predominantly labeled glandular serous cells, epithelial dark granulated cells, and cell surfaces, and also labeled dark cores of mucinous granules. These results revealed that: sialomucin are produced from glandular mucous cells and epithelial goblet cells and are present on cell surfaces and within the mucous blanket; their terminal trisaccharide linkage appears to be the sequence Neu5Ac (alpha 2-6) Gal (beta 1-3) GalNAc and serum type glycoproteins are produced from glandular serous cells and dark cores of mucinous granules.

Animals↗
PubMed1990

An ultrastructural study of the guinea pig tectorial membrane 'type A' protofibril.

Fine structural features of the 'type A' protofibrils in the guinea pig tectorial membrane were examined using negative staining and deep-etching techniques. Negative-stained samples of fragmented tectorial membrane were composed of several fine filamentous subunits showing the clear banding pattern of the type A protofibrils. Deep-etched replicas of the EGTA (ethylene glycol bis-N,N,N',N'-tetraacetic acid)-treated samples showed fine surface structure consisting of several linear arrays of filamentous elements on the extracellular fibrils, which is interpreted to be type A protofibrils.

Animals↗
PubMed1990

Role of middle ear endotoxin in inner ear inflammatory response and hydrops: long-term study.

The permeability of the round window membrane for Salmonella typhimurium-derived endotoxin was examined with use of a total of 33 chinchillas. One milligram of each endotoxin was instilled into the tympanic cavities via the superior bullae. The endotoxin activities in middle ear effusions (MEEs), perilymph, and sera were determined by limulus amebocyte lysate assay. Endotoxin was detected in perilymph on the inoculated side by 12 hours after endotoxin instillation and persisted for up to 3 weeks. Endotoxin level peaked at 24 to 48 hours postinstillation, and it steadily declined afterward. This result suggests that the maximum penetration occurred during the active inflammatory stage. Histologic evidence demonstrated remarkable pathologic changes in the inner ear, including bleeding and inflammatory cell recruitment, mostly in the perilymphatic spaces (eg, scalae tympani, scalae vestibuli, spiral ligament), strial swelling, and sensory cell degeneration. This result suggests that endotoxin present in the middle ear can permeate the round window membrane, causing inner ear tissue damage in this animal model.

Animals↗
PubMed1989

Hazard from weapons impulses: histological and electrophysiological evidence.

Current methods of rating the hazard of weapons impulses for the ear have recently been challenged by electrophysiological data from experiments with animal ears which indicate that the hazard from low-frequency impulses is much lower than the hazard from higher frequency impulses (Dancer et al., 1981; Price, 1986b). To supplement these data, histological data are reported here for 51 cats that were exposed on one occasion to either rifle or howitzer impulses at peak pressures from 145 to 155 dB or 153 to 166 dB, respectively. Histological procedures (scanning electron and light microscopy) were carried out over 2 months after the exposure and after electrophysiological measures had been made. For both types of impulse the losses tended to be in the middle of the cochlea in focused lesions, even though the spectral peaks of the acoustic stimuli had been at about 80 Hz (howitzer) and 1000 Hz (rifle). Outer hair cells were more susceptible than the inner hair cells and interindividual differences in effects were large. Furthermore, the two impulse sources were equally hazardous when the peak pressure of the rifle impulse was lower than the peak pressure of the howitzer impulse by about 9 dB. In terms of A-weighted energy, the exposures were equally hazardous when the rifle exposure contained about 35 times less energy than the howitzer exposure. The histological data are thus consistent with the electrophysiological data, which indicate that present standards for impulse noise exposure may overrate the hazard of low-frequency impulses relative to impulses in the midrange.

Animals↗