This study was undertaken to investigate and quantify the morphologic changes in the middle ear mucosa and connective tissue after the inoculation of graded doses (0.001 to 100 micrograms) of endotoxin prepared from Hemophilus influenzae. Histopathologic changes were observed in the middle ear mucosa in all animals. Marked bleeding and new bone formation in the submucosa were prominent at days 4 through 14. These findings indicate that the endotoxin from nontypable H influenzae is capable of inducing inflammation or pathologic changes in the middle ear mucosa and may play an important role in the pathogenesis of otitis media with effusion and its sequelae.

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PubMedDate not supplied

Effect of vitamin A on the growth and differentiation of rat external auditory canal epithelium in organ culture.

Intact rat external ear canal explants were maintained either in retinoid-deficient or retinoid-supplemented medium for 7, 10, 14, and 21 days. The morphology of the external ear canal epidermis was well maintained, including the presence of sebaceous glands even after 21 days in culture with retinoid-deficient medium. However, after culturing in retinoid-supplemented medium, the external ear canal epithelium showed both a loss of keratohyalin granules and the formation of keratin. Extensive microvilli formation occurred, even though the desquamation process continued from the superficial layer after 7, 10, and 14 days in culture with retinoid-enriched medium. After 21 days in culture with retinoid-supplemented medium, the ear canal epithelium contained well-developed Golgi apparatus and secretory granules as well. It was concluded that the ear canal epithelium was transformed into a secretory-like mucosal epithelium by retinoid supplementation.

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PubMedDate not supplied

Developmental anatomy of the eustachian tube and middle ear in mice.

PURPOSE: It is generally accepted that the development of the tubotympanum has significant bearing on the susceptibility to ear infection. A detailed study of the differentiation of ciliated cells in secretory elements will be useful in understanding both the normal physiology and the pathology of the tubotympanum. METHOD: Serially sectioned temporal bones of 76 mice ranging from gestational age day 11 to postnatal day 21 were examined microscopically. RESULTS: During the period of gestation, the tubotympanic recess was formed at the 12th day and began to extend to form the middle ear between the 13th and 14th days. A rapid increase in the volume of the tubotympanic recess was observed between the 15th and 16th days when a definitive division of the tubotympanic recess into the eustachian tube and middle ear cavity was observed. Postnatally the tubotympanum attained an adult form around day 9, and the maximum change of middle ear volume was noted on day 11, when the mesenchymal tissue in the middle ear cavity disappeared completely. Development of the ciliated cells was observed concurrently in both the eustachian tube and middle ear on the 16th gestational day, one day earlier than the appearance of the epithelial secretory cells in both the eustachian tube and middle ear. The number of ciliated cells and secretory cells increased rapidly after birth. Tubal glands were well developed with evidence of secretory activity around the time of birth. CONCLUSIONS: Based on these findings, one can conclude that the mucociliary defense system starts to develop during the fetal stage and is well established immediately after birth.

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