Achados otomicroscópicos e histológicos da miringoesclerose induzida em ratos: estudo crítico de um modelo experimental

Conhecimento da anatomia da orelha de cobaias e ratos e sua aplicação na pesquisa otológica básica

O uso de mostras animais é importante na pesquisa otológica e o conhecimento da anatomia de sua orelha permite sua utilização adequada. OBJETIVO: Estudar a anatomia da orelha da cobaia e do rato por microscopia óptica de luz (MOL) e microscopia eletrônica de varredura (MEV) e suas vantagens anatômicas na pesquisa otológica básica. MATERIAL E MÉTODO: Os ossos temporais, as bulas timpânicas e cócleas de três cobaias e ratos albinos foram fotografados e analisados ao MOL e MEV. RESULTADOS: O rato não é tão simples de manipular como a cobaia, e freqüentemente apresenta otite média. O rato apresenta uma junção frágil da bula timpânica, duas e meia espiras na cóclea e a membrana timpânica não veda todo o conduto auditivo externo. A cobaia possui uma bula inteiriça, martelo e bigorna fundidos e três e meia espiras na cóclea. Pela MEV a cobaia e o rato possuem Membrana Tectória, Membrana de Raissner e o Órgão de Corti. As Células de Hensen estão presentes somente na cobaia. CONCLUSÃO: A cobaia foi considerada de fácil manipulação para a microdissecção, pelo tamanho e rigidez do osso temporal, e para experimentos cirúrgicos envolvendo o estribo, janela oval e a membrana timpânica. Pela MEV nota-se semelhança entre cobaia e rato, podendo ambos serem utilizados em estudos da orelha interna.

Understanding the anatomy of ears from guinea pigs and rats and its use in basic otologic research

The use of animal samples is important in otologic research and understanding the anatomy of their ears help make proper use of them in research projects. Aim: to study guinea pig’s and rat’s ears under light microscopy(LM) and scanning electron microscopy(SEM) and understand their anatomical advantages in basic otologic research. Materials and methods: The temporal bones, tympanic bullas and cochleas from three albino guinea pigs and rats were photographed and analyzed under LM and SEM. Results: Rats aren’t as simple to handle as guinea pigs, and often present with otitis media. Rats have a fragile junction of the tympanic bulla, two and half turns in the cochlea, and their tympanic membranes do not seal off the entire external auditory canal. Guinea pigs have full bullas, their incus and malleus are fused and they have three and half cochlear turns. Under SEM, guinea pigs and rats have Tectori Membrane, Raissner’s Membrane and the Organ of Corti. Only guinea pigs have Hensen’s Cells. Conclusion: Guinea pigs were considered easy to handle for microdissection purposes because of the size and robustness of their temporal bones, and for surgical experiments involving the stapes, the oval window and the tympanic membrane. Under SEM there are similarities guinea pigs and rats, and both can be used in inner ear studies.

Histopathological classification of tympanosclerotic plaques

Tympanosclerotic plaques seen in the middle ear and tympanic membrane as a sequelae of otitis media have different characteristics. Tympanosclerotic plaque consistency shows a wide range from soft to hard during surgical excision and can be classified histologically. The aim of this study is to classify surgically excised tympanosclerotic plaques macroscopically and histologically. Seventeen surgically excised tympanosclerotic tissues were examined otomicroscopically and light microscopically. Otomicroscopically, plaques were classified as type I: soft (four cases), type II: moderately hard (six cases) and type III: very hard (seven cases), according to their consistency and surgical detachment feature. Sections prepared from tympanosclerotic tissues were stained with hematoxylin-eosin, Mallory-Azan and von Kossa stains for light microscopic evaluation. In type I tympanosclerotic tissue, fibroblasts and collagen fibers were equally abundant in typical loose connective tissue. A few small calcium crystals were seen. In type II tympanosclerotic tissue, large bundles of collagen fibers, proliferation of fibroblasts and focal calcification points were seen. In type III tympanosclerotic tissue, round shaped condroblast-like cells located in lacunae and intense calcification points were evident. Tympanosclerotic tissues can be classified in respect of their morphological and histological aspects. Histological classification of tympanosclerotic tissue may inform us about the maturation of the tissue, and therefore the grade of the disease. In type I tympanosclerotic disease, even if complete resection of sclerotic tissue is performed, the underlying process may go on and new sclerotic tissue formation can be expected. Type III sclerotic tissue is associated with limited, inactive disease. Progress of the disease and the patient's benefit from surgery can be interpreted according to this classification. However, these results will need to be verified by long-term patient follow-up and comparison of histological classification and clinical audiological symptoms.