Effect of exogenous surfactant on ventilatory and clearance function of the rat's eustachian tube

Protective effect of pulmonary surfactant on cilia of Eustachian tube in otitis media with effusion

OBJECTIVE

The aim of this study was to evaluate the effect of pulmonary surfactant (PS) on cilia of Eustachian tube (ET) in guinea pigs suffering from otitis media with effusion (OME).

METHODS

A nonviable heat-killed pneumococci (HKP) solution was injected into the tympanum of guinea pig via a transtympanic approach therefore establishing models of OME (effusion in tympanum and hearing loss). After being injected with physiologic saline solution or pulmonary surfactant transtympanically, the response threshold of each guinea pig was taken by ABR. Changes of effusion and ciliary ultrastructure were observed.

RESULTS

Normal group (A), the response threshold is 14.00+/-3.08 dBHL. Abundant and intact cilia were observed, ciliary morphology was normal, cilia regularly arranged in concord, no goblet cells was observed. Model-control group (B0), 5 days following the inoculation of HKP, serous effusion was present in tympanum. The response threshold is 45.00+/-5.67 dBHL. Cilia lost and arranged irregularly, hyperplasia of the goblet cells was observed. Saline group, the previously observed serous effusion of tympanum was increased or unchanged. The response threshold is 65.50+/-6.85 dBHL. Cilia were coalescing and swelling. A lot of cilia lost and arranged disorderly. A number of compound cilia of the bulging type were formed by cytoplasmic protuberances of ciliated cells. Massive mucoid secretions stuck on the surface of the ET. PS group, the previously observed serous effusion of tympanum was reduced in amount or disappeared completely. The response threshold is 23.53+/-6.32 dBHL. Ciliary morphology was generally normal. Cilia comparatively arrange in concord. A mucus deposits was adhering to the tips of cilia.

CONCLUSION

The findings of the study suggest that pulmonary surfactant plays an important role in protecting of cilia of ET of guinea pigs suffering from OME.

Involvement of glycosaminoglycans in the attachment of pneumococci to nasopharyngeal epithelial cells

Streptococcus pneumoniae is a major bacterial pathogen involved in the development of otitis media. The pathogenic mechanisms of this middle ear disease, including the bacterial adherence mechanisms to the mucosal epithelial cells of the host, are poorly understood. In this study, the role of glycosaminoglycans in the adhesion of pneumococci to mucosal epithelial cells is examined. Both nasopharyngeal epithelium from rats and an oral epithelial cell line were used for pneumococcal adherence experiments. Preincubation of pneumococci with heparin, heparan sulfate (HS) and to a lesser extent, chondroitin 4-sulfate (C-4S), was found to inhibit attachment of S. pneumoniae to oral epithelial cells, while dermatan sulfate and hyaluronate did not interfere with pneumococcal binding. Enzymatic removal of HS moieties by heparinase III from nasopharyngeal epithelial cells abolished the attachment of pneumococci to nasopharyngeal epithelium. This study demonstrates that heparin, HS and C-4S are involved in pneumococcal binding to mucosal epithelial cells. This knowledge may contribute to the development of a new prophylactic strategy for otitis media.

Cochlear function in young and adult Fischer 344 rats

Fischer 344 (F344) rats are often used as an animal model for investigation of the mechanisms underlying age-related hearing loss. The aim of this study was to assess cochlear function in young (1-month-old) and adult (6-month-old) F344 rats using recording of otoacoustic emissions and auditory brainstem responses (ABRs). The results were compared with control groups of Long Evans (LE) rats of the same ages. The results demonstrate a significant increase in the hearing threshold in F344 rats in comparison with LE rats, expressed mainly at low frequencies (1-2 kHz). In F344 rats, transient evoked otoacoustic emissions were not measurable and distortion product otoacoustic emissions could be detected within a frequency range of 2.4-6.3 kHz. Tympanometric measurements did not reveal any differences in middle ear parameters between F344 and LE rats. The amplitudes of click-evoked ABRs were significantly lower in 6-month-old F344 rats than in LE rats, but other parameters of the ABRs were almost identical in both rat strains. The results demonstrate a significant deficit in low-frequency hearing and altered otoacoustic emissions in both young and adult F344 rats, suggesting a defect of the inner ear sensory epithelium at the apical part of the cochlea.