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Degranulation of mast cells provokes a massive inflammatory reaction in the tympanic membrane.
Umeå University, Faculty of Medicine, Clinical Sciences, Otorhinolaryngology.
Umeå University, Faculty of Medicine, Clinical Sciences, Otorhinolaryngology.
2001 (English)In: The Laryngoscope, ISSN 0023-852X, E-ISSN 1531-4995, Vol. 111, no 7, 1264-1270 p.Article in journal (Refereed) Published
Abstract [en]

OBJECTIVE: The pars flaccida is extremely rich in mast cells. On stimulation the mast cells release preformed and de novo synthesized inflammatory substances. The purpose of this study was to examine how these mast cell substances provoke inflammatory changes in the tympanic membrane. STUDY DESIGN: In vivo, murine model. METHODS: In a rat model, the mast cell secretagogue compound 48/80 was applied locally to the tympanic membrane on 4 consecutive days and the ensuing inflammatory changes were evaluated by otological, light, and electron microscopy 3, 6, 9, 12, 18, 24, 36, and 48 hours and 4, 6, and 8 days later. RESULTS: Degranulation of the mast cells occurred within 3 hours of applying compound 48/80. Release of the mast cell substances coincided with an inflammatory event characterized by a two-stage reaction: an edema stage, peaking 6 hours after application, followed by a massive invasion of inflammatory cells, peaking at 24 and 48 hours. Pars flaccida and pars tensa were both involved, pars flaccida showing the earliest changes. Pars tensa exhibited the same biphasic reaction as pars flaccida, but approximately 6 hours later. CONCLUSIONS: The mast cells of the pars flaccida have the capacity to elicit an intense inflammation of the tympanic membrane. The biphasic reaction pattern resembles that observed in experimental otitis media, suggesting involvement of the mast cells in this inflammatory condition of the middle ear.

Place, publisher, year, edition, pages
2001. Vol. 111, no 7, 1264-1270 p.
Keyword [en]
Tympanic membrane, mast cells, otitis media. inflammation, compound 48/80
National Category
Medical and Health Sciences
URN: urn:nbn:se:umu:diva-3347DOI: 10.1097/00005537-200107000-00023PubMedID: 11568552OAI: diva2:142009
Available from: 2004-01-19 Created: 2004-01-19 Last updated: 2010-04-12Bibliographically approved
In thesis
1. Developing otitis media: experimental studies in particular regarding inflammatory changes in the tympanic membrane
Open this publication in new window or tab >>Developing otitis media: experimental studies in particular regarding inflammatory changes in the tympanic membrane
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Otitis media (OM), one of the commonest of childhood diseases, causes much suffering. OM exists in a variety of forms, two of which are acute otitis media (AOM) and otitis media with effusion (OME). The clinical courses of these conditions differ, AOM usually presenting with earache, fever and/or aural discharge, and the OME usually with hearing impairment. The tympanic membrane (TM) mirrors the events in the middle ear cavity, and pars flaccida (PF) is the initial site of inflammatory changes in the TM. PF is rich in mast cells (MCs), which by releasing various mediators, may trigger TM inflammation.

The aims of the present studies were to investigate early inflammatory changes in the TM in rat models of OM; after mast cell degranulation, in response to AOM, and OME, after myringotomy in AOM and in normal ears. Furthermore, we developed a new rat AOM model, that excludes surgical trauma and resembles the natural route of infection in man.

AOM and OME elicited the first inflammatory response in PF of the TM. The response to OME was discrete, but a slight increase in macrophages was found. During the first 48 hours of AOM, the inflammatory response was intense, following a bimodal pattern. This reaction is similar to that found after MC degranulation. In AOM, macrophages were the predominant cell in PF, while in pars tensa (PT), polymorphonuclear cells (mainly neutrophils) predominated.

When myringotomy was performed in AOM ears, the healing time was shorter than that of myringotomy in normal ears. The highly inflamed lamina propria seemed to promote healing.

During early AOM, as well as following myringotomy, fibrin extravasates into PF and PT. This fibrin deposition may be involved in regulating the inflammatory response.

Repeated nasal challenge with the otitis media pathogen Streptococcus pneumoniae provoked AOM and concomitant TM stimulation reduced the number of AOM cases. This new rat AOM model has the advantage of avoiding trauma in the middle ear cavity, while eliciting an intense inflammatory response in the middle ear cavity (MEC).

56 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 871
Otorhinolaryngology, otitis media with effusion, acute otitis media, myringotomy, tympanic membrane, rat, Streptococcus pneumoniae, compound 48/80, mast cell, Otorhinolaryngologi
National Category
Research subject
urn:nbn:se:umu:diva-180 (URN)91-7305-580-8 (ISBN)
Public defence
2004-02-13, Sal D (grå salen), 1D, Tandläkarhögskolan, Norrlands Universitetssjukhus, Umeå, 09:00 (English)
Available from: 2004-01-19 Created: 2004-01-19 Last updated: 2010-04-12Bibliographically approved

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