Ultracytochemical demonstration of phospholipids in the surface layer of the guinea pig eustachian tube

Ultrastructural and ultracytochemical study of the middle ear epithelium in the chicken, Gallus gallus domesticus

The fine structure of the epithelium lining the tympanic cavity of the chicken was studied by TEM and SEM. In addition, the distribution of nonspecific esterase activity in the epithelium was investigated by TEM. Ultrastructural study revealed the presence of disk-like apical protrusions of the epithelial cells, previously not observed in other cell types. The protrusions contained some cytoplasmic organelles and were characterized by a ring-shaped thickening around their periphery. The ring was made up of a granulo-filamentous material. Our observations clearly indicate the existence of an apocrine secretory mechanism, consisting of a progressive detachment of disk-like protrusions from the apex of the epithelial cells. The ultracytochemical study demonstrated nonspecific esterase activity on the epithelial surface and in the secretory vesicles. We propose that nonspecific esterase is a marker for middle ear surfactant in birds.

Kinetics of the ascension of NTHi from the nasopharynx to the middle ear coincident with adenovirus-induced compromise in the chinchilla

To determine the kinetics of ascension of the eustachian tube (ET) by non-typeable Haemophilus influenzae (NTHi) in situ from the nasopharynx to the middle ear using an experimental model of otitis media (OM), we examined snap-frozen sections of chinchilla ET and middle ear mucosa for adherent bacteria over a 14 day time period. Via fluorescent- and transmission electron-microscopy, we found that NTHi preferentially adhered not to the epithelial cells but to the mucus in the ET and gradually ascended this tubal organ, reaching the middle ear approximately 10 days after intranasal inoculation of adenovirus-infected animals. The number of NTHi adherent to mucus at the pharyngeal portion of the ET increased significantly in the first 4 days after inoculation of the nares whereas the number of adherent bacteria in both the mid and tympanic portions of the ET increased more gradually over time. NTHi were not observed in the middle ear until approximately 7-10 days after inoculation of the nares which was coincident with the onset of clinical signs of OM. These data confirmed our earlier in vitro investigation which suggested that adherence to and growth within stagnant mucus within a ET compromised by adenovirus was a possible mechanism by which NTHi, resident in the nasopharynx, might gain access to the middle ear and induce OM.

Surfactant-producing epithelium in the dorsal part of the cartilaginous eustachian tube of mice. Light, transmission, and scanning electron microscopic observations

The nonciliated area in cartilaginous roof tubothelium of 14 conventional mice was examined histologically and classified as a modified transitional respiratory epithelium. On the free cell surface numerous short microvilli were found. On the lower roof surface in the midcartilaginous portion and especially near the pharyngeal orifice, a convoluted pattern of ridges and pits was observed. These structural peculiarities are interpreted as adaptive features, ensuring survival of the cells in a dynamic tubal environment. On the basis of systematic observations of the multilamellar bodies in the cytoplasm resembling the phospholipid lamellar bodies of pulmonary surfactant, which are discharged in the tubal lumen and to be found in the pits, it is suggested that the nonciliated cells are "specialized" surfactant-producing tubocytes. The synthesis of surfactant-precursors starts in the basal layer. Different phases of the secretory process were observed in the neighboring cells. This finding is related to the cell-cooperation constantly releasing the secretory product, and natural cell-turnover. Unlike the previously reported surfactant-producing cells in the lower tubothelium of other species, roof tubothelial cells of mice are morphologically similar to type II pneumocytes.

The determination of phospholipids in middle ear effusion from experimental otitis media in the chinchilla

Phospholipid types were clarified both in eustachian tube secretion (ETS) and middle ear effusions (MEEs) from chinchilla middle ear. ETS was obtained from normal healthy animals and from animals with experimentally induced purulent otitis media (POM). MEE was obtained from experimentally induced serous and purulent otitis media (SOM and POM). In normal ETS, phosphatidylcholine (36.4%) was predominant followed by phosphatidylethanolamine (30.6%), sphingomyelin (18.0%), phosphatidylinositol (7.2%), phosphatidylglycerol (8.8%) and phosphatidylserine (2.5%). A significant loss of phosphatidylcholine was observed in ETS and MEE from experimentally induced otitis media. These findings suggest that both POM and SOM might be caused by a relative decrease of phospholipids, which is a major component of surfactants. Furthermore, the analysis of phospholipids in MEE may yield baseline information necessary to specify the factors responsible for chronicity or the tendency of recurrence of otitis media.