Mechanical stimulation of the external auditory canal (EAC) in rat, either by scratching or exposure to a stream of air, caused effusion behind an intact ear-drum both in the experimental ear and in the contralateral one. Histologically the pars flaccida appeared oedematous, especially its lamina propria; and was infiltrated by inflammatory cells indicating a vascular leakage. Determination of the histamine level of the content of the middle ear cavity showed elevated levels, not only in the experimental ear but also in the contralateral. This increased level of histamine was recorded as long as 24 hours after stimulation. Though the mechanisms involved are not known, new ideas about the initiation of otitis media with effusion are inferred.

Calcium triggers the secretion of histamine from mast cells after previous exposure to sodium fluoride. The secretory process can be divided into a fluoride-activation step and a calcium-induced secretory step. It was observed that the fluoride-activation step is accompanied by an elevation of cAMP levels within the cells. The attained high levels of cAMP persist during histamine release. It was further found that catecholamines do not markedly alter the fluoride-induced histamine release. It was also confirmed that the second, but not the first, step in sodium fluoride-induced histamine secretion is inhibited by theophylline.

No abstract

Experientia 39 (1983), Birkh~iuser Verlag, CH-4010 Basel/Switzerland 287 mainly in the terminal position occur in morphologically identical cell types. In the case of intracellular staining of galactose residues we do not know whether the latter represent terminal saccharides or incompletely glycosylated glycoconjugates. The distribution of binding sites for DBA (specific for N-acetyl-galactosamine 2~ and BSA I (specific for D-galactopyranosy121) in gastrointestinal cells showed a lack of correlation between PAS reactivity and lectin binding. While surface epithelium and Brunner's gland cells were mainly positive for DBA, PAS positive neck ceils usually failed to stain with DBA-HRP ( fig.), Antra1 gland cells also gave an irregular staining pattern; nonreacting and reacting cells were seen in the same histological preparation. PAS negative parietal cells were positive with DBA; chief cells were almost negative. In the case of BSA I binding, a similar pattern was found. Goblet cells and columnar striated cells exhibited an irregular staining pattern with the 4 lectins used (see table). Generally, the lectins did not bind only to cells with secretory activity but also to glycosylated nonmucus cell products. The heterogeneous lectin binding in histological preparations of normal mucosa suggests qualitative and quantitative differences in the composition of glycoconjugates. This might be due to different functional states and maturation stages; studies including diseased mucosae are needed.1 This study was supported by the Deutsche Forschungsgemeinschaft (Ku 257/5-2 and Ku 257/6-3) Bonn (FRG).Summary. The present study has shown that the pars flaccida of the tympanic membrane of the rat is extremely rich in mast cells. The findings were compared with those from earlier investigations in the rat; the pars flaccida is one of the tissues in this animal in wich mast cells are most abundant.