Macroscopic description of the external and middle ear of paca (Cuniculus paca Linnaeus, 1766) / Descrição macroscópica da orelha externa e media da paca (Cuniculus paca Linnaeus, 1766)

Paca (Cuniculus paca), one of the largest rodents of the Brazilian fauna, has inherent characteristics of its species which can conribute as a new option for animal experimantation. As there is a growing demand for suitable experimental models in audiologic and otologic surgical research, the gross anatomy and ultrastructural ear of this rodent have been analyzed and described in detail. Fifteen adult pacas from the Wild Animals Sector herd of Faculdade de Ciências Agrárias e Veterinárias, Unesp-Jaboticabal, were used in this study. After anesthesia and euthanasia, we evaluated the entire composition of the external ear, registering and ddescribing the details; the temporal region was often dissected for a better view and detailing of the tympanic bulla which was removed and opened to expose the ear structures analyzed mascroscopically and ultrastructurally. The ear pinna has a triangular and concave shape with irregular ridges and sharp apex. The external auditory canal is winding in its path to the tympanic mebrane. The tympanic bulla is is on the back-bottom of the skull. The middle ear is formed by a cavity region filled with bone and membranous structures bounded by the tympanic membrane and the oval and round windows. The tympanic membrane is flat and seals the ear canal. The anatomy of the paca ear is similar to the guinea pig and from the viewpoint of experimental model has major advantages compared with the mouse ear.(AU)

A paca (Cuniculus paca), um dos maiores roedores da fauna brasileira, possui características inerentes à sua espécie que podem contribuir como uma nova opção de animal experimental; assim, considerando-se que há crescente busca por modelos experimentais apropriados para pesquisas audiológicas e otológica cirúrgicas foram analisados e descritos em detalhes a anatomia macroscópica e ultraestrutural da orelha desse roedor. Para o estudo, utilizaram-se 15 animais adultos provenientes do plantel do Setor de Animais Silvestres da Faculdade de Ciências Agrárias e Veterinárias, Unesp-Jaboticabal, Jaboticabal/SP. Após anestesia e eutanásia, avaliou-se toda a composição da orelha externa, registrando-se e descrevendo-se os detalhes, também se dissecou a região temporal para melhor visibilização e detalhamento da bula timpânica e estas foram removidas e abertas a fim de expor as estruturas da orelha, as quais foram analisadas, macroscopicamente e ultraestruturalmente. O pavilhão auricular apresenta forma triangular e côncava com cristas irregulares e ápice pontiagudo; o conduto auditivo externo é sinuoso em seu trajeto até a membrana timpânica; a bula timpânica encontra-se na parte posterior-inferior do crânio; a orelha média é formada por uma região cavitária preenchida por estruturas ósseas e membranosas. É delimitada pela membrana timpânica e as janelas redonda e oval, sendo a membrana timpânica de forma plana e que veda todo o conduto auditivo. A anatomia da orelha da paca é semelhante à da cobaia e do ponto de vista de modelo experimental apresenta grandes vantagens em comparação com a orelha do rato.(AU)

Macroscopic description of the external and middle ear of paca (Cuniculus paca Linnaeus, 1766) / Descrição macroscópica da orelha externa e media da paca (Cuniculus paca Linnaeus, 1766)

Paca (Cuniculus paca), one of the largest rodents of the Brazilian fauna, has inherent characteristics of its species which can conribute as a new option for animal experimantation. As there is a growing demand for suitable experimental models in audiologic and otologic surgical research, the gross anatomy and ultrastructural ear of this rodent have been analyzed and described in detail. Fifteen adult pacas from the Wild Animals Sector herd of Faculdade de Ciências Agrárias e Veterinárias, Unesp-Jaboticabal, were used in this study. After anesthesia and euthanasia, we evaluated the entire composition of the external ear, registering and ddescribing the details; the temporal region was often dissected for a better view and detailing of the tympanic bulla which was removed and opened to expose the ear structures analyzed mascroscopically and ultrastructurally. The ear pinna has a triangular and concave shape with irregular ridges and sharp apex. The external auditory canal is winding in its path to the tympanic mebrane. The tympanic bulla is is on the back-bottom of the skull. The middle ear is formed by a cavity region filled with bone and membranous structures bounded by the tympanic membrane and the oval and round windows. The tympanic membrane is flat and seals the ear canal. The anatomy of the paca ear is similar to the guinea pig and from the viewpoint of experimental model has major advantages compared with the mouse ear.

A paca (Cuniculus paca), um dos maiores roedores da fauna brasileira, possui características inerentes à sua espécie que podem contribuir como uma nova opção de animal experimental; assim, considerando-se que há crescente busca por modelos experimentais apropriados para pesquisas audiológicas e otológica cirúrgicas foram analisados e descritos em detalhes a anatomia macroscópica e ultraestrutural da orelha desse roedor. Para o estudo, utilizaram-se 15 animais adultos provenientes do plantel do Setor de Animais Silvestres da Faculdade de Ciências Agrárias e Veterinárias, Unesp-Jaboticabal, Jaboticabal/SP. Após anestesia e eutanásia, avaliou-se toda a composição da orelha externa, registrando-se e descrevendo-se os detalhes, também se dissecou a região temporal para melhor visibilização e detalhamento da bula timpânica e estas foram removidas e abertas a fim de expor as estruturas da orelha, as quais foram analisadas, macroscopicamente e ultraestruturalmente. O pavilhão auricular apresenta forma triangular e côncava com cristas irregulares e ápice pontiagudo; o conduto auditivo externo é sinuoso em seu trajeto até a membrana timpânica; a bula timpânica encontra-se na parte posterior-inferior do crânio; a orelha média é formada por uma região cavitária preenchida por estruturas ósseas e membranosas. É delimitada pela membrana timpânica e as janelas redonda e oval, sendo a membrana timpânica de forma plana e que veda todo o conduto auditivo. A anatomia da orelha da paca é semelhante à da cobaia e do ponto de vista de modelo experimental apresenta grandes vantagens em comparação com a orelha do rato.

Histological effects of intratympanic gentamicin on the vestibular organ of guinea pigs.

BACKGROUND: Transtympanic administration of gentamicin may be suitable to achieve unilateral vestibular ablation, in order to control unilateral Ménière's disease. In low doses, gentamicin appears to affect selectively the vestibular system, with relative sparing of the cochlea. An experimental study on guinea pigs was conducted to determine what single dose of gentamicin would produce a unilateral vestibular organ lesion when applied to the middle ear. STUDY DESIGN: Experimental and prospective. METHODS: Four groups of guinea pigs received different gentamicin doses (1, 5, 10 and 25 mg) administered to the middle ear. The animals' vestibular organs were then assessed by scanning electron microscopy, in order to quantify the level of vestibular damage. RESULTS: Study of the utricular macula and the ampullar crista of the lateral semicircular canal revealed vestibular neuroepithelial lesions in all infused ears. CONCLUSIONS: The severity of the vestibular neuroepithelial lesions was dose-dependent. Lower gentamicin doses were observed to damage vestibular structures more than cochlear structures.

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

UNLABELLED: 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.

Conhecimento da anatomia da orelha de cobaias e ratos e sua aplicação na pesquisa otológica básica / Understanding the anatomy of ears from guinea pigs and rats and its use in basic otologic research

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.

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.

Estudio morfológico del oído medio e interno de la Chinchilla laniger / Morphological study of the middle and internal ear of Chinchilla laniger

Introducción: La Chinchilla laniger, roedor originario de la Cordillera de Los Andes, ha sido utilizada como modelo de investigación otológica por más de 40 años. Sin embargo, no existe un estudio anatómico e histológico detallado del oído de este animal. La mayoría de las investigaciones se han desarrollado en neurofisiología de la audición. Objetivos: Describir macroscópica y microscópicamente el oído medio e interno de la Chinchilla laniger. Material y método: Estudio realizado en cinco chinchillas adultas (previa aprobación del Comité de Bioética sobre la Investigación en Animales). Macroscopía: Se realizó una cirugía vía conducto auditivo externo y se estudió también con una tomografía computada de oído s. Microscopía: Disección, fijación e inclusión en parafina. Tinción con hematoxilina-eosina. Resultados: Vía conducto auditivo externo se realiza un colgajo timpanomeatal similar al de estapedectomía. Se accede a la caja timpánica por el cuadrante posterosuperior Se observa que el martillo presenta un delgado mango unido verticalmente al tímpano. Presenta una cabeza con un gran proceso anterior en vez de ligamento timpanomaleolar anterior. Su cabeza se une al yunque, fusionándose. El proceso lenticular del yunque se une a un delgado estribo, en el cual se observa el vestigio de la arteria estapedial, entre las cruras. El promontorio es visible fácilmente dado su tamaño y prominencia. La ventana oval se encuentra levemente más superoanterior que la ventana redonda. La cóclea da 3 y media vueltas sobre el modiolo. El órgano de Corti, sáculo, utrículo y crista ampularis se identificaron en los cortes histológicos. Conclusiones: El estudio morfológico detallado de un modelo de investigación como la chinchilla es imprescindible para el desarrollo de nuevos estudios en audición.

Introduction: Chinchilla laniger is a rodent that has been used as a model of ear research for more than 40 years; nevertheless, a macroscopic and microscopic detailed study of the ear in this animal is lacking. Purposes: Jo describe the anatomy and histology of the middle and inner ear of Chinchilla laniger. Materials and methods: Five adult chinchillas were used in this study. The macroscopic study was made with a computed tomography of the ear and then dissection under a microscope. For the microscopic study ears were dissected, fixed, decalcified, included in paraffin and then sectioned and stained with hematoxylin-eosin. Results: A tympanomeatal flap was made via the external acoustic meatus, similar to a stapedectomy The tympanic cavity was accessed through the posterosuperior quadrant to examine the malleus. A thin manubrium attached vertically to the eardrum could be observed. The malleus head is characterized by a large anterior process, instead of the anterior tympanomallear ligament, and it was fused to the incus. The lenticular process of the latter joined a thin stapedius, in which the vestige of the stapedial artery was observed (between the cruras). The promontory was visible easily because of its size and prominence. The oval window was located more superoanterior than the round window. The cochlea gave 31/2 turns around the modiolus. The organ of Corti, saccule, utricle and ampullary crest were identified in the histological sections. Conclusions: The ear of Chinchilla laniger is similar to the human ear supporting its use as a model in ear research. The study of the ear specially the cochlea, is difficult and needs great dedication in order to obtain good results.

Anatomia microscópica do canal carótico e suas relações com a cóclea e a cavidade timpânica / Microscopic anatomy of the carotid canal and its relations with cochlea and middle ear

As relações entre as diversas estruturas nobres e vitais que se apresentam na intimidade do osso temporal constituem ainda hoje um grande desafio para o cirurgião otológico. Os estudos micro-anatômicos do mesmo se encontram entre as grandes armas na busca deste entendimento. OBJETIVO: Estudar as correlações anatômicas entre o canal carótico e a cóclea, e a ocorrência de deiscências do mesmo junto à cavidade timpânica. MATERIAL E MÉTODO: Estudo microscópico de 122 ossos temporais humanos. RESULTADOS As distâncias médias entre o canal carótico e os giros cocleares foram: no local de menor distância 1,05mm; no giro basal, 2,04mm; no giro médio, 2,32mm; e no giro apical, 5,7mm. A ocorrência de deiscências do canal carótico na cavidade timpânica foi de 35,2 por cento. CONCLUSÃO: A pequena distância entre estruturas cocleares e o canal carótico, e a alta prevalência de deiscências do mesmo na cavidade timpânica nos relembram o desafio com o qual o cirurgião otológico se depara ao atuar sobre o osso temporal.

Microscopic anatomy of the carotid canal and its relations with cochlea and middle ear.

UNLABELLED: The knowledge of the relations between the noble and vital structures of temporal bone is still a great challenge for the otologic surgeon. The microscopic anatomic studies of the temporal bone are one of the greatest help to prevent lesions during surgical intervention. AIM: To study the anatomic correlations between the carotid canal and the cochlea, and the occurrence of dehiscence of the carotid canal in the middle ear tympanic cavity. MATERIAL AND METHODS: Microscopic study of 122 human temporal bones. RESULTS: The average distance between the carotid canal and the cochlea were: the shortest distance, 1.05 mm; basal turn, 2.04 mm; middle turn, 2.32 mm; and apical turn, 5.70 mm. The occurrence of dehiscence of the carotid canal inside the tympanic cavity was 35.2%. CONCLUSION: The small distances between the cochlea and carotid canal, and the high incidence of dehiscence in the tympanic cavity remind us that anatomical knowledge of the temporal bone is required for the best qualification of otologists.