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Biomedical subjects

D J Lim

Publications and source records attributed to D J Lim.

At least 91 records · Page 5Linked to original sources
PubMed1988

Current concepts of pathogenesis of otitis media: a review.

A number of important factors singly or in combination contribute to the pathogenesis of otitis media. These are poor tubal function, upper respiratory viral infection, bacterial adherence and nasopharyngeal flora, and immune status of the host. One of the important functions of the tubotympanum is to protect the middle ear from invading microbes. The host has available a number of strategies for this function including mucociliary protection, antibacterial secretory products, and specific immunodefenses. The microbes also possess the capability of escaping host defenses by enhancing their ability to adhere to mucosal surfaces, impairing mucociliary function and evading phagocytosis. Once microbes gain entrance to the middle ear, the microbes must overcome phagocytosis and immunodefense of the host, leading to otitis media. Recent data further indicate that specific qualitative and quantitative deficiencies in the immune system of children may predispose certain children to develop otitis media. These deficiencies appear to be in part due to a lack of maturity of the child's developing immune system as well as functional defects that are attributable to genetic or other unknown factors.

Bacterial Adhesion↗
PubMed1987

Phagocytosis and killing of bacteria by middle ear macrophages.

Because macrophage dysfunction has been suggested as one of the underlying pathogenic mechanisms for otitis media with effusion, we have examined macrophage-bacterial interactions using keyhole limpet hemocyanin-induced middle ear macrophages from chinchillas. Our data indicate that macrophages recruited to the middle ear were functional phagocytes capable of discriminate phagocytosis and intracellular killing of eight species of bacteria associated with otitis media, as determined by a fluorochrome microassay. Streptococcus pneumoniae types 14 and 19F, which are associated with the highest relapse frequency in cases of acute otitis media, were the most resistant to phagocytosis. The two organisms most often involved in chronic otitis media (Staphylococcus epidermidis and nontypable Haemophilus influenzae), however, were among the most readily phagocytized isolates. The relative importance of macrophage function in defense of the middle ear, therefore, may be dependent on the causative agent.

Animals↗
PubMed1987

Effect of preopsonization on phagocytosis of Haemophilus influenzae.

Because bacteria are known to persist in middle ear effusions for extended periods of time despite the presence of increasing titers of specific antibody in both sera and middle ear fluids in humans, we examined the ability of postinfection serum to opsonize Haemophilus influenzae (nontypable and type b) for phagocytosis by middle ear macrophages in chinchillas. Our data indicated that preopsonization of both strains of H influenzae enhanced phagocytosis by macrophages recruited to the middle ear following intrabullar instillation of keyhole limpet hemocyanin. Both the total number of bacteria ingested and the percentage of macrophages phagocytizing were significantly greater in the presence of postinfection serum than preinfection serum for all animals tested.

Animals↗
PubMed1987

Development of the tectorial membrane.

During development, the organization of the stereociliary bundles undergoes drastic changes from the microvilli-like nascent stereocilia to the 'W' formation of the step-like arrangement of the adult form. During this period the developing tectorial membrane (TM) establishes prescribed attachments with various substructures of the developing sensory ciliary bundles and supporting cells. The TM detaches from the supporting cells and inner hair cell stereociliary bundles as Kölliker's organ matures. The inter-connecting linkage system develops postnatally, and the 'tip-linkages' are already found in one-week-old mice, suggesting that the critical organization of the micromechanics of the stereocilia matures rapidly during the postnatal period. The TM develops in stages, and its development parallels that of the organ of Corti. The major TM is initially secreted by the greater epithelial ridge cells, and the minor TM is produced by the lesser epithelial ridge cells. The substructures of the TM are formed by the participation of a number of different supporting cells. During the active stage of production of the substructures by the supporting cells, these cells are intensely Alcian blue-PAS stained, indicating that the glycoconjugates are locally produced by these cells.

Animals↗
PubMed1987

Functional morphology of the tubotympanum related to otitis media: a review.

One of the important functions of the tubotympanum is to protect the middle ear from invading organisms. The host develops a number of strategies for this function (e.g., mucociliary protection, antibacterial secretory products, immunodefense, and phagocytosis). The bacteria also develop their strategy to evade the host protection by enhancing adherence to the mucosal surfaces, impairing mucociliary function, and evading phagocytosis.

Animals↗
PubMed1986

Antibody response in experimental Haemophilus influenzae otitis media.

Because Haemophilus influenzae is one of the most common pathogens in otitis media with effusion, we have investigated the antibody response in the serum and middle ear effusion (MEE) in nontypable H influenzae-induced experimental acute otitis media in the chinchilla, using an enzyme-linked immunosorbent assay. During acute otitis media, a reasonable antibody titer was observed: local antibody titers in the MEEs were equal to or greater than those of the serum samples for four of five MEE samples obtained at one week after inoculation. By two weeks, titers in both serum and MEE samples were increased significantly. However, the bacteria persisted in the middle ear cavity, even in the presence of increasing antibody titers, for up to five weeks after infection. The reason for this persistence of the bacteria in the middle ear is unknown.

Animals↗
PubMed1986

Functional structure of the organ of Corti: a review.

The mammalian auditory organs have a dual sensory system (inner vs. outer hair cells) with distinctly different cellular organizations and innervation patterns. However, the inner (IHCs) and outer (OHCs) hair cells are mechanoreceptors sharing similar general characteristics such as organization of stereocilia (including linkage system) and a gradation of stereociliary height along the length of the cochlea. This gradation of stereociliary height may be the single most important anatomic feature in the tuning capability of the sensory cell. Several lines of evidence suggest that the stereociliary stiffness may be modulated by the sensory cells themselves, most likely via the cuticular plate-rootlet complex. The stereociliary bundles of both types of hair cell are organized in a 'W' formation with a steplike arrangement. In the OHCs, the 'W' formation is sharply angulated and slanted toward the apex, coinciding with the slanted fiber arrangement of the overlying tectorial membrane, which is firmly coupled to the tips of the tallest row of the stereociliary bundles. However, in the IHCs, the 'W' formation is wide and its long axis is linear and arranged at a right angle to the radial axis of the organ of Corti; also, the ciliary bundles are freestanding (with a few exceptions in the basal turn). This arrangement in the IHCs would be best suited for deflection by the radial flow of the endolymph. Present evidence suggests that the subtectorial fluid space exists, is filled with endolymph, and freely communicates with endolymph. Because of the discovery of the phenomenon of 'cochlear emission', the possible motility of the sensory cells, particularly of the OHCs, has drawn intense interest in recent years. Recent investigations with dissociated sensory cells (OHCs) indicate some motile capability under various experimental conditions, although it has not been established that this motility is present in vivo. For this reason, the specialized cellular organization for motility and localization of contractile and cytoskeletal proteins have been investigated. These results support the possibility that the OHCs may have cellular facilities for this function.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

Sero-epidemiological study on hepatitis A and B virus infection among dentists in the Philippines.

Dentists in the Philippines were surveyed for evidence of past hepatitis A and B virus infections. Of the 234 dentists examined, 201 (85.9 per cent) were found to have been infected by HA virus and 137 (58.5 per cent) had been infected by HB virus. The proportion with evidence of past HB virus infection increased as the years in dental practice increased. This increment with age was not found in the general population of the Philippines. It is considered that the incremental pattern could be attributed to the summation of risk during many years of providing dental treatment. Comparing the proportion of dentists with HBV antibodies (anti-HBs/c) in the Philippines, Japan, USA and Denmark, the Philippine dentists were found to be more frequently infected than dentists in the other countries. However, the increment in the proportion positive for HBV as the years in practice advanced was consistent with that found in Japan. The prevalence of post HA virus infection in Philippine dentists was higher than the proportion for dentists in Japan but in both countries it is probable that dentists are infected at the same rate as the general population.

Adult↗
PubMed1985

Developmental morphology of the mouse inner ear. A scanning electron microscopic observation.

The developing inner ears of mice (CBA/CBA), ages ranging from gestational day 12 through postnatal day 21, were examined using scanning electron microscopy following the epoxy-embedding/freeze-fracture technique. This technique provides unique three-dimensional views of surface and fractured structures of the developing inner ear, thus allowing excellent preservation of the relationships between the developing sensory epithelium and the overlying membranes (i.e. the tectorial membrane and cupula) during their development. The tectorial membrane is formed of two distinct parts: the major (medial) and the minor (distal). The major portion is produced by the cells of the greater epithelial ridge prior to the formation of the minor part, which is produced largely by the primordial supporting cells of the lesser epithelial ridge. The developing tectorial membrane has two types of fibers: radial (found mainly in the major part) and slanted (found mainly in the minor part). The slanted fibers become the cover net, which fuses with the marginal band. The marginal zone of the developing tectorial membrane is completely sealed during development by the third row of Deiters' cells. The surfaces of cells that produce the tectorial membrane are characterized by numerous long microvilli which are largely lost when the tectorial membrane completely forms and separates from the supporting cells. The surface of developing auditory sensory cells is initially covered with numerous microvilli, some of which become future stereocilia. Stereocilia form stepped rows in the shape of a "W", with the tallest row located at the periphery of the cell. As the sensory cell matures, the short transitional stereocilia gradually disappear. Kinocilia on hair cells are still seen in the 14-day-old mouse (even though the organ of Corti is morphologically mature) but not in the 21-day-old mouse, indicating that complete maturation of the sensory cells in all turns is attained by 21 days of age. The mouse has upper radial tunnel fibers and basal tunnel fibers. Neural contacts of the upper radial tunnel fibers with the outer hair cells at the apical portions are frequent in the developing organ of Corti. The external sulcus cells undergo drastic changes during development, forming numerous pits that are often covered with mucus-like droplets or grape-like spherical structures of varying sizes. This phenomenon was observed only during postnatal days 6 and 14. The developing cupula starts as a thin amorphous membrane, which later becomes compact and fibrotic-like as the mass increases. By the 6th postnatal day well-developed cupular canals occur.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Applications of scanning electron microscopy and X-ray microanalysis in inner ear pathology.

Surface pathology of inner ear structures so far described in detail concern cochlear and vestibular hair cells and the stria vascularis. In man, surgical intervention into the inner ear is very uncommon and when performed is in general with the primary objective of destroying the diseased peripheral end organs. The vast majority of inner ear tissue available for use with scanning electron microscopy (SEM) is therefore obtained from animals. The present paper reviews the progression of surface pathology caused by aminoglycoside antibiotics, acoustic overstimulation and in a guinea pig strain with genetic inner ear disease. The primary site of onset of surface pathology differs, depending on the underlying cause. Advanced surface pathology shows a similar type of morphological degeneration independent of cause. The combination of SEM and energy dispersive X-ray microanalysis (XRMA) of inner ear pathology has as yet been reported in only three studies, all concerning inner ear fluids or otoconia.

Aminoglycosides↗
PubMed1984

Rheumatoid factor in otitis media with effusion.

Because of the pathologic similarities between rheumatoid arthritis and otitis media with effusion (OME), rheumatoid factor (RF) was measured in 156 human middle ear effusion (MEE) and serum samples from patients with chronic OME. Using a quantitative latex agglutination test, we were able to demonstrate RF in the MEEs of 85% of patients with OME. Demonstrable RF titers were found in only 8% of the patients' serum samples. The titers of mucoid MEE samples were seven times higher than those observed in serous MEE samples. The presence of RF was not related to the age of the patient, the presence of viable bacteria in the MEEs, or history of OME.

Adolescent↗
PubMed1984

Endotoxin in middle-ear effusions from patients with chronic otitis media with effusion.

Endotoxin concentrations were determined in middle-ear effusions (MEEs) from 89 children with chronic otitis media by using the Limulu's amoebocyte lysate assay. Mean concentrations of endotoxin in Haemophilus influenzae-positive and Streptococcus pneumoniae-positive MEEs were 157 and 21.8 ng/ml, respectively, and were significantly different (P less than 0.01). Endotoxin was also found in Gram stain-positive, culture-negative and Gram stain-negative, culture-negative MEEs, but the levels were not significantly different (P greater than 0.05). However, the endotoxin concentrations in both groups of culture-negative MEEs significantly lower than those found in MEEs that grew either H. influenzae or S. pneumoniae (P less than 0.05). These results show that endotoxin is present in a high percentage of human MEEs, including those that are culture negative, and may contribute to the pathogenesis of otitis media with effusion.

Adolescent↗
PubMed1984

Biotypes of serologically nontypable Haemophilus influenzae isolated from the middle ears and nasopharynges of patients with otitis media with effusion.

A biotype analysis was performed on serologically nontypable Haemophilus influenzae isolates from the middle ear effusions and nasopharynges of 33 children with chronic otitis media with effusion (serous otitis media). Over 50% of the H. influenzae isolates from the middle ears belonged to biotype II. The incidence of beta-lactamase production was 17%. The results of this study indicate that future clinical or experimental investigations of chronic otitis media with effusion induced by serologically nontypable H. influenzae should focus on this clinically important biotype.

Child↗
PubMed1984

Functional morphology of the tubotympanum. An overview.

New information concerning the morphology and cell biological aspects of the tubotympanum related to its normal physiology and pathophysiology are reviewed. The tensor veli palatini muscle appears to have two separate insertions, and the possible role of autonomic innervation to the tubotympanum is discussed. Several defense mechanisms are provided in the tubotympanum, such as the mucociliary system, lymphatic system, immune system, and secretory system. The secretory products in the tubotympanum are diverse and complex and serve various important biologic functions. When dysfunction of these elements occurs, the tubotympanum may be subject to otitis media with effusion.

Absorption↗
PubMed1984

Scanning electron microscope specimen preparation technique for dissociated strial marginal cells.

Single strial marginal cells from the cochleas of guinea pigs and chinchillas were successfully isolated in tissue culture medium using the enzyme dissociation technique. Such single cells were successfully preserved for scanning electron microscopic observation in special glass wells following the freeze drying technique. Judging by transmission electron microscopic examination of such cells, the ultrastructural preservation of the dissociated strial marginal cells was excellent.

Animals↗