RESUMEN
Otitis media (OM) is one of the most frequent diseases in childhood, and Streptococcus pneumoniae is among the main causative bacterial agents. Since current experimental models used to study the bacterial pathogenesis of OM have several limitations, such as the invasiveness of the experimental procedures, we developed a non-invasive murine OM model. In our model, adapted from a previously developed rat OM model, a pressure cabin is used in which a 40 kPa pressure increase is applied to translocate pneumococci from the nasopharyngeal cavity into both mouse middle ears. Wild-type pneumococci were found to persist in the middle ear cavity for 144 h after infection, with a maximum bacterial load at 96 h. Inflammation was confirmed at 96 and 144 h post-infection by IL-1beta and TNF-alpha cytokine analysis and histopathology. Subsequently, we investigated the contribution of two surface-associated pneumococcal proteins, the streptococcal lipoprotein rotamase A (SlrA) and the putative proteinase maturation protein A (PpmA), to experimental OM in our model. Pneumococci lacking the slrA gene, but not those lacking the ppmA gene, were significantly reduced in virulence in the OM model. Importantly, pneumococci lacking both genes were significantly more attenuated than the DeltaslrA single mutant. This additive effect suggests that SlrA and PpmA exert complementary functions during experimental OM. In conclusion, we have developed a highly reproducible and non-invasive murine infection model for pneumococcal OM using a pressure cabin, which is very suitable to study pneumococcal pathogenesis and virulence in vivo.
Asunto(s)
Otitis Media/etiología , Infecciones Neumocócicas/etiología , Enfermedad Aguda , Animales , Proteínas Bacterianas/genética , Proteínas Bacterianas/fisiología , Secuencia de Bases , Preescolar , Cartilla de ADN/genética , ADN Bacteriano/genética , Modelos Animales de Enfermedad , Oído Medio/microbiología , Femenino , Genes Bacterianos , Humanos , Lactante , Interleucina-1beta/metabolismo , Ratones , Ratones Endogámicos BALB C , Mutación , Nasofaringe/microbiología , Otitis Media/inmunología , Otitis Media/microbiología , Otitis Media/patología , Isomerasa de Peptidilprolil/genética , Isomerasa de Peptidilprolil/fisiología , Infecciones Neumocócicas/inmunología , Infecciones Neumocócicas/microbiología , Infecciones Neumocócicas/patología , Presión , Ratas , Streptococcus pneumoniae/genética , Streptococcus pneumoniae/patogenicidad , Streptococcus pneumoniae/fisiología , Factores de Tiempo , Factor de Necrosis Tumoral alfa/metabolismo , Virulencia/genética , Virulencia/fisiologíaRESUMEN
The purpose of this study was to determine specific characteristics of endolymphatic sac (ES) cells of the developing rat that are considered to be involved in endolymph homeostasis. Because intermediate filament proteins (IFPs) are regarded as markers of cell differentiation and basal lamina proteins (BLPs) are essential in cell<=>matrix interactions, we determined the presence of IFPs [cytokeratins (CKs) and vimentin] and BLPs [collagen IV, heparan sulphate proteoglycan (HSPG) and laminin] at different developmental stages before and after birth. In addition, we studied the expression of two enzymes of oxidative metabolism: cytochrome oxidase and succinate dehydrogenase. The presence of CKs 8, 18 and 19 in all epithelial cells of the ES during the embryonic stage is characteristic of simple (glandular) epithelial cells. Interestingly, a distinct population of these cells shows additional expression of CK 7, which is a feature of secretory cells. These CK 7-positive cells also contain a high concentration of oxidative enzymes and are rich in mitochondria, indicating that they are light cells. It is suggested that light cells possess specific energy-requiring transport capabilities. Loss of CK 19 expression in the distal part and in a large region of the intermediate part of the ES implies that these cells do not differentiate any further and acquire the capacity to proliferate. Furthermore, prominent co-expression of vimentin with the CKs in the distal part of the ES may confer viscoelastic properties on this epithelium. This may facilitate expansion and thus enable cushioning of pressure fluctuations. Finally, the early prominent occurrence of HSPG in the basal lamina of the ES enables transport of ions. In this light our recent observations of early functioning NaK-ATPases in certain ES cells are interesting.
Asunto(s)
Endolinfa/fisiología , Saco Endolinfático/embriología , Homeostasis/fisiología , Animales , Diferenciación Celular/fisiología , División Celular/fisiología , Femenino , Edad Gestacional , Masculino , Embarazo , Ratas , Ratas Wistar , ATPasa Intercambiadora de Sodio-Potasio/fisiologíaRESUMEN
OBJECTIVE: To study the effect of various middle ear effusions on the structure of the lamina propria of the tympanic membrane. METHODS: Sterile and infective middle ear effusions were induced by obstruction of the eustachian tube in specific pathogen-free (SPF) rats and in rats with upper airway infections (URI), respectively. The condition of the tympanic membrane was monitored at regular intervals. After varying survival times, the animals were killed and the tympanic membranes processed for light and electron microscopy. RESULTS: Sterile effusions always resulted in tympanosclerotic lesions. These lesions did not develop in the presence of primary-infected effusions. These effusions had a severe destructive effect on the lamina propria, followed by fibrosis. Generally, secondary infection did not markedly affect preexisting tympanosclerotic lesions. Moreover, calcification disappeared when re-aeration of the middle ear occurred, but the abnormal collagen depositions persisted. CONCLUSIONS: Both sterile and infective effusions result in comprehensive irreversible changes in the lamina propria of the pars tensa. The development of tympanosclerosis is confined to sterile effusions. Mechanical injury and compromised vascularization of the lamina propria are likely to be important etiological factors in the development of tympanosclerosis.
Asunto(s)
Otitis Media con Derrame/patología , Membrana Timpánica/patología , Animales , Membrana Basal/microbiología , Membrana Basal/ultraestructura , Calcinosis/patología , Colágeno/ultraestructura , Modelos Animales de Enfermedad , Enfermedades del Oído/microbiología , Edema/patología , Trompa Auditiva/microbiología , Fibroblastos/patología , Fibrosis , Vida Libre de Gérmenes , Hialina/ultraestructura , Hiperplasia , Macrófagos/patología , Microscopía Electrónica , Neovascularización Patológica/patología , Otitis Media con Derrame/microbiología , Otitis Media con Derrame/terapia , Neumonía por Mycoplasma/patología , Ratas , Infecciones del Sistema Respiratorio/microbiología , Esclerosis , Membrana Timpánica/microbiologíaRESUMEN
The nature of the insertion of the tympanic membrane into the tympanic bone was studied in the rat during the developmental period ranging from 18 days post conception (dpc) to 40 days after birth (dab). Techniques applied were light microscopy, electron microscopy and immunohistochemistry with antibodies to cytoskeletal proteins: vimentin, desmin and alpha-smooth muscle actin (sma) as fibroblast differentiation markers. It was established that the cartilaginous annulus of the pars tensa was connected to the tympanic bone by an interface of specialised connective tissue. Both the fibrocartilage and the interface were derived from the embryonal mesenchyme between the tympanic ring and meatal plate. Electron microscopy showed that the interface was composed of two types of fibroblast. The majority of these cells were myofibroblasts, which were interconnected by junctions and had intimate contact with the collagenous fibres. A small number were identified as genuine fibroblasts. Cytoskeletal characterisation revealed the presence of three types of cell: V cells which expressed vimentin, VA cells which expressed vimentin and alpha-sma and VAD cells which expressed vimentin, alpha-sma and desmin. The myofibroblasts expressed antigens of both smooth muscle cells (alpha-sma, desmin) and connective tissue cells (vimentin). It is suggested that the pars tensa is connected to the tympanic bone by a network of contractile cells and fibres. Contraction will move the membrane in an outward direction and antagonise the inward retraction by the tensor tympani.
Asunto(s)
Hueso Temporal/anatomía & histología , Membrana Timpánica/anatomía & histología , Actinas/metabolismo , Animales , Proteínas del Citoesqueleto/metabolismo , Inmunohistoquímica , Proteínas de Filamentos Intermediarios/metabolismo , Microscopía Electrónica , Ratas , Ratas Wistar , Hueso Temporal/metabolismo , Hueso Temporal/ultraestructura , Membrana Timpánica/ultraestructuraRESUMEN
OBJECTIVE: To investigate the relationship between the anatomical maturation of the middle ear and that of the eustachian tube and paratubal muscles in the rat. DESIGN: Wistar rats ranging from gestational day 12 to postnatal day 40 were used. METHODS: Tissue specimens were examined with routine light microscopy and electron microscopy. Epithelial differentiation was studied immunohistochemically with antibodies to different cytokeratins. RESULTS: The epithelial lining of the tubotympanum showed differentiation-related cytokeratin expression throughout the whole developmental period. The mucociliary epithelium reached mature features around birth. A dorsal extension and its framing cartilage started forming around 5 days after birth. This extension became lined by stratified nonciliated epithelium and attained maturity around 10 days after birth concurrently with the attachment of the dilatory muscles. This process was immediately followed by aeration of the middle ear cavity. CONCLUSIONS: The continuous expression of cytokeratins demonstrates that the epithelial lining of the tubotympanum is only derived from the embryonal endoderm. Furthermore, this study demonstrates that the eustachian tube shows a two-stage postnatal development. First, the mucociliary system matures, providing protection/clearance when the animal starts respiration and swallowing. Subsequently, the dorsal part attains maturity. The features of the epithelial lining of the dorsal part of the eustachian tube and the coincidence of the maturation of this part with the attachment of the dilating muscle fibers and the aeration of the middle ear indicates that this part provides ventilation. These findings support the authors' hypothesis that different parts of the eustachian tube serve different purposes: clearance, protection and ventilation.
Asunto(s)
Oído Medio/anatomía & histología , Trompa Auditiva/anatomía & histología , Animales , Oído Medio/metabolismo , Oído Medio/ultraestructura , Epitelio , Trompa Auditiva/fisiología , Trompa Auditiva/ultraestructura , Edad Gestacional , Inmunohistoquímica , Queratinas/metabolismo , Membrana Mucosa/fisiología , Ratas , Ratas WistarRESUMEN
OBJECTIVE: To evaluate the type of differentiation of keratinocytes of acquired cholesteatoma and its significance for cholesteatoma invasiveness. DESIGN: Forty acquired cholesteatomas and 10 tympanic membranes with persisting perforations were snap frozen and processed for immunohistochemical studies. Cytokeratin antibodies that represented all subgroups and antibodies that were directed against collagen components of the basal lamina were applied. Expression of these constituents was scored by using light microscopy. RESULTS: The phenotype of the matrix was generally characterized by an extension of expression of basal cell cytokeratin 14 and hyperproliferation-associated cytokeratins 6, 16, and 17 into the suprabasal cell layers, while the expression of keratinization marker cytokeratin 10 was down-regulated. These features varied greatly at different sites of the matrix and were most marked at the advancing front of the cholesteatoma. A comparable expression pattern, but less pronounced, was observed at the epidermal front of the mucocutaneous junction of the tympanic membrane perforations. This phenomenon was invariably associated with a mononuclear cell infiltrate in the dermis at both junctions. The basal lamina was always intact. CONCLUSIONS: Acquired cholesteatomas show hyperproliferative features. There is a striking similarity between the pronounced expression of this phenotype and the associated inflammation at the mucocutaneous junctions of cholesteatomas and tympanic membrane perforations and those that are observed after epidermal injury. This indicates that epidermis and middle ear epithelium do not form stable junctions and the front can be considered to be a persisting epidermal defect. This involves the permanent presence of "activated keratinocytes" in the junction area that will lead to proliferation and migration, when additional triggers are present.
Asunto(s)
Colesteatoma del Oído Medio/patología , Queratinocitos/patología , Perforación de la Membrana Timpánica/complicaciones , División Celular , Colesteatoma del Oído Medio/complicaciones , Colesteatoma del Oído Medio/metabolismo , Oído Medio/patología , Epidermis/química , Epidermis/patología , Epitelio/patología , Humanos , Inmunohistoquímica , Queratinocitos/metabolismo , Queratinas/análisis , Membrana Timpánica/química , Membrana Timpánica/patología , Perforación de la Membrana Timpánica/metabolismoRESUMEN
The differentiation of epidermis in the various parts of the human ear canal was documented on the basis of cytokeratin (Ck) expression patterns. Immunohistochemistry was performed on cryostat sections of normal meatal skin using a comprehensive panel of monospecific Ck antibodies representing the main lines of epithelial differentiation. The epidermis of the cartilaginous part showed a Ck profile characteristic of normal skin type differentiation. The deep meatal skin, including the tympanic membrane, showed a peculiar type of differentiation: in addition to epidermal Cks, hyperproliferation-associated Cks 6, 16, and 17 were expressed in the suprabasal cells, while the simple epithelia cell marker Ck 19 was found in the basal cells. The presence of hyperproliferative Cks in the deep meatal skin could only partly be related to areas of proliferative activity. Keratinocytes, which express markers of hyperproliferation, are migratory. Therefore, their presence in the meatal skin is likely to be related to the peculiar pattern of keratinocyte migration, the purpose of which is to keep the meatus free from desquamation products.
Asunto(s)
Conducto Auditivo Externo/citología , Células Epidérmicas , Cartílago/citología , Cartílago/metabolismo , Diferenciación Celular , Conducto Auditivo Externo/metabolismo , Epidermis/metabolismo , Humanos , Inmunohistoquímica , Queratinocitos/citología , Queratinocitos/metabolismo , Queratinas/metabolismo , Valores de Referencia , Membrana Timpánica/citología , Membrana Timpánica/metabolismoRESUMEN
In this developmental study, the distribution and features of melanocytes in the inner ear of pigmented and albino rats was investigated with the use of an antibody, which specifically reacts with a melanocyte differentiation antigen present in the membranes of (pre)melanosomes. Melanocyte precursors could be traced from 13 days post conception onwards and the course was followed to their targets in the inner ear. Melanocytes which settle in the modiolus appeared to reach their target along another pathway than strial and vestibular melanocytes. No difference was observed in the melanocyte distribution between pigmented and albino rats. The integration of melanocytes into the stria vascularis was associated with an increased rate of melanosome production in both strains, but in the albinos far fewer melanosomes were produced. After the stria had reached maturity, melanosome production was arrested and melanosomes were subject to lysosomal digestion. In the stria of the pigmented rats, cells with aggregations of disintegrating melanosomes appeared and persisted into adulthood. In the adult, the majority of the intermediate cells contained only a few scattered melanosomes, while melanosomes could only rarely be detected in the albinos. These observations indicate that there is a close relationship between melanosome production and the process of interdigitation of melanocytes with the marginal cells. It seems unlikely that melanosomes or melanin make any important contribution to the function of the adult stria vascularis. Outside the stria, the features of melanocytes in both strains were similar to skin melanocytes.
Asunto(s)
Cóclea/fisiología , Melanocitos/fisiología , Animales , Cóclea/embriología , Cóclea/crecimiento & desarrollo , Cóclea/ultraestructura , Desarrollo Embrionario y Fetal/fisiología , Inmunohistoquímica , Melanocitos/citología , Melanocitos/ultraestructura , Microscopía Electrónica , Ratas , Ratas Endogámicas BN , Ratas Wistar , Especificidad de la Especie , Estría Vascular/citología , Estría Vascular/ultraestructuraRESUMEN
OBJECTIVE: To determine the behavior of epidermal cells after transplantation in the middle ear. DESIGN: In a rat model, full-thickness meatal skin grafts were transplanted into the middle ear and studied morphologically and immunohistochemically with the use of antibodies directed against different cytokeratin (Ck) polypeptides, which are markers of different types of epithelial cell differentiation. RESULTS: The grafts had either transformed into epithelial cysts or had become integrated into the middle ear epithelium. The epithelium of the integrated grafts showed gradual transition into the epithelium of the middle ear. A clear distinction between epidermal cells and middle ear epithelium could be made only on the basis of their Ck profiles. The Ck profiles of the grafts revealed a decrease in the expression of epidermal Cks, while nonepidermal Cks became expressed. These changes can be ascribed to replacement of the dermal mesenchyma by mesenchyma from the middle ear. In two ears with superimposed infection, the graft epithelium showed expansive growth. CONCLUSIONS: Meatal epidermis is well tolerated in the middle ear, but superimposed infection can induce expansive growth. These findings favor the concept that the progressive growth of cholesteatoma is related to the presence of inflammatory processes.
Asunto(s)
Oído Medio/cirugía , Trasplante de Piel/fisiología , Animales , Anticuerpos Monoclonales , Infecciones Bacterianas/patología , Diferenciación Celular , Tejido Conectivo/patología , Células Dendríticas/patología , Conducto Auditivo Externo/cirugía , Enfermedades del Oído/patología , Quiste Epidérmico/patología , Epidermis/patología , Epitelio/patología , Queratinocitos/patología , Queratinas/análisis , Mesodermo/patología , Ratas , Ratas Wistar , Piel/crecimiento & desarrollo , Piel/patología , Trasplante de Piel/patología , Vimentina/análisisRESUMEN
In the present study the expression of vimentin-type intermediate filament proteins and cytokeratins was studied immunohistochemically in the rat inner ear from 12 days postconception up to 40 days after birth. With the use of a broad spectrum monoclonal antibody, cytokeratin expression was found to be present in the whole epithelial lining except for the sensory cells, throughout all the developmental stages examined. Vimentin was detected in the mesenchymal cells, the mesenchyme-derived tissues and the intermediate cells of the stria vascularis, confirming their origin from melanocyte precursor cells. In addition, the coexpression of vimentin and cytokeratins in the epithelial lining of the membranous inner ear was found to be developmentally regulated. During the final stages of differentiation, vimentin expression disappeared from the majority of the cell types. In the mature cochlea the coexpression of vimentin and cytokeratins was still found in the supporting cells of the organ of Corti, in the cells of Claudius and in external sulcus cells. As far as we could conclude from this study, the sensory cells showed only vimentin expression but not cytokeratin expression. A possible relationship between vimentin expression in adult epithelial cells of the inner ear and a specialised function of these cells is discussed.
Asunto(s)
Cóclea/metabolismo , Oído Interno/metabolismo , Queratinas/biosíntesis , Vimentina/biosíntesis , Animales , Anticuerpos Monoclonales , Diferenciación Celular , Cóclea/ultraestructura , Oído Interno/embriología , Oído Interno/crecimiento & desarrollo , Células Epiteliales , Técnicas para Inmunoenzimas , Órgano Espiral/ultraestructura , Ratas , Ratas Wistar , Vestíbulo del Laberinto/embriología , Vestíbulo del Laberinto/crecimiento & desarrollo , Vestíbulo del Laberinto/metabolismoRESUMEN
The expression of intermediate filament proteins was studied in the mature inner ear of the rat and guinea pig, using a panel of polyclonal and monoclonal antibodies directed against cytokeratins, desmin, neurofilament proteins and glial fibrillary acidic protein (GFAP). The epithelial lining of the endolymphatic space displayed a complex expression pattern of cytokeratin filament proteins, suggesting greater cell diversity than was known sofar from morphological studies. The cytokeratin antibodies when applied to the inner ear tissues revealed the presence of only cytokeratin polypeptides which are typical of simple epithelia (i.e. nos. 7, 8, 18, and 19). Profound differences in cytokeratin expression patterns were, however, found in the various cell types of both the cochlear and vestibular partition. Remarkably, the sensory cells appeared to be devoid of both cytokeratins and neurofilament proteins. Staining with a 200 kDa neurofilament antibody displayed the presence of different populations of ganglion cells in the spiral ganglion and the vestibular ganglion. There was no reaction with antibodies directed against desmin and GFAP. The great resemblance of the intermediate filament protein expression patterns in the inner ear of the rat and guinea pig indicates a close similarity between the different epitopes.
Asunto(s)
Oído Interno/metabolismo , Cobayas/metabolismo , Proteínas de Filamentos Intermediarios/metabolismo , Ratas/metabolismo , Animales , Conducto Coclear/metabolismo , Oído Interno/crecimiento & desarrollo , Inmunohistoquímica/métodos , Órgano Espiral/metabolismo , Ratas Endogámicas , Coloración y Etiquetado , Nervio Vestibular/metabolismo , Vestíbulo del Laberinto/metabolismoRESUMEN
The expression of cytokeratin polypeptides in the different epithelia of the developing inner ear of the rat from 12 days post conception to 20 days after birth was analysed immunohistochemically, using a panel of monoclonal antibodies. Throughout the development of the complex epithelial lining of the inner ear originating from the otocyst epithelium, only cytokeratins which are typical of simple epithelia were expressed. Cytokeratins 8, 18, and 19 were detectable shortly after the formation of the otocyst from the ectoderm (12 dpc), whereas cytokeratin 7 expression was delayed and first appeared in the vestibular portion and subsequently in the developing cochlear duct. During the development of the different types of specialized cells, differentiation-dependent modulation of the cytokeratin expression patterns was observed. In the mature inner ear, the specialized cell types displayed a function-related cytokeratin expression profile, both in the cochlear and vestibular portion. Cytokeratin expression in the flat epithelium of the vestibular portion suggests a more complex composition of this epithelium than has been established from routine morphology. Remarkably, the cochlear sensory cells were apparently devoid of cytokeratins, but no final conclusion could be drawn on the presence of cytokeratins in the sensory cells of the vestibular portion, because of the difficulty to delineate the cell borders between sensory cells and supporting cells.
Asunto(s)
Cóclea/química , Queratinas/análisis , Sáculo y Utrículo/química , Animales , Diferenciación Celular , Cóclea/embriología , Edad Gestacional , Inmunohistoquímica , Órgano Espiral/química , Órgano Espiral/embriología , Ratas , Sáculo y Utrículo/embriologíaRESUMEN
The expression of cytokeratins in the epithelium of the middle ear and external auditory meatus of the rat was studied on cryosections of ethylenediaminetetraacetic acid-decalcified specimens by use of a panel of monoclonal antibodies. The normal middle ear epithelium revealed a complex cytokeratin profile, including regional differences. The induction of sterile middle ear effusions resulted in increased cytokeratin expression. Infective effusions were accompanied by both quantitative and qualitative changes in the cytokeratin expression patterns. The differences observed between the cytokeratin profiles of external meatal skin and those of middle ear epithelium may form a useful tool for research into cholesteatoma development.
Asunto(s)
Oído Medio/citología , Queratinas/análisis , Otitis Media/patología , Animales , Anticuerpos Monoclonales , Células Epiteliales , Hiperplasia , Hipertrofia , Inmunohistoquímica , Masculino , Membrana Mucosa/citología , Ratas , Ratas EndogámicasRESUMEN
Immunohistochemical studies on the epithelium of the adult inner ear are difficult to perform without decalcification of the bony capsule. In this study, we examined the effect of decalcifying agents on the immunoreactivity of various cytokeratin antigens in the cochlear duct epithelium of 2-day-old rats, allowing the comparison of fresh and decalcified specimens. Decalcification of unfixed tissue in a solution containing EDTA or EGTA and polyvinylpyrrolidone, at pH 7.4 and 4 degrees C for a maximum period of 2 days, not only preserved the antigen epitopes but even enhanced the staining intensities in comparison with fresh specimens. This enhancement effect, caused by chelating agents and found to be blocked by prior fixation with acetone, is suggested to be caused by unmasking of the antigenic epitopes.
Asunto(s)
Cóclea/análisis , Conducto Coclear/análisis , Ácido Edético/farmacología , Inmunohistoquímica , Queratinas/análisis , Animales , Ácido Egtácico/farmacología , Epitelio/análisis , Técnicas para Inmunoenzimas , Povidona , Ratas , Ratas EndogámicasRESUMEN
The expression of cytokeratins varies with the type of epithelium, the state of differentiation, and pathological conditions. In this study, the differential expression of cytokeratins in external meatal skin and middle ear epithelium was used for a pathogenetic study of cholesteatoma lesions and infection-induced epidermoid formations in the middle ear of the rat. Immunocytochemistry generally revealed an epidermal-type cytokeratin profile in the cholesteatoma matrix, except for the focal expression of nonepidermal cytokeratins at the invasion front. Comparable observations were made in the middle ear of the rat after an infection-induced invasion of epidermal cells from the meatal skin. An infection-induced-cornifying metaplastic lesion of the middle ear epithelium revealed nonepidermal cytokeratin expression. The results of this combined study suggested that the cholesteatoma specimens studied had an epidermal origin. The expression of nonepidermal cytokeratins was considered to result from a state of hyperproliferation rather than from metaplasia.
Asunto(s)
Colesteatoma/metabolismo , Enfermedades del Oído/metabolismo , Oído Medio/metabolismo , Queratinas/metabolismo , Animales , Colesteatoma/etiología , Enfermedades del Oído/etiología , Epidermis/metabolismo , Epitelio/metabolismo , Trompa Auditiva , Humanos , Técnicas para Inmunoenzimas , Ratas , Ratas EndogámicasRESUMEN
This study deals with an animal model where tympanosclerosis could be evoked with high reproducibility during the course of a sterile otitis media, induced by Eustachian tube obstruction. The histopathological features of this induced lesion were very similar to those reported in human specimens. It was concluded that this process is most probably triggered by a mechanical deformation of the tympanic membrane.
Asunto(s)
Otitis Media con Derrame/patología , Membrana Timpánica/patología , Animales , Vida Libre de Gérmenes , Microscopía Electrónica , Ratas , Ratas Endogámicas , EsclerosisRESUMEN
The middle ear cavity of the rat is lined with ciliated and squamous epithelium. The arrangement of the ciliated cells, interspersed with secretory cells, in distinct tracts and their continuity with the ciliated epithelium of the Eustachian tube, suggests the existence of a mucociliary transport system for cleaning the middle ear cleft. The secretory cells produce either neutral or sulphated glycoproteins, dependent on their location. In addition to these secretions, the epithelium of the lower part of the Eustachian tube is bathed with secretory products of seromucous glands. Also in the areas with squamous epithelium, numerous small secretory cells, the character of which is only identifiable with the electronmicroscope, are present. It is concluded that the middle ear lining can be considered as a locally modified respiratory epithelium. Blockade of the mucociliary transport system, supposedly a crucial aetiological factor in secretory otitis media, by obstruction of the Eustachian tube, induces pathogenic behaviour of microorganisms normally present in the middle ear. This results in either a transient or a longstanding infective middle ear disease, associated with a large variety of changes of the mucosa, especially with respect to the secretory activity. The data obtained indicate that the increased secretory activity encountered in secretory otitis media cannot be attributed to the isolated effect of tubal occlusion, but rather to an infective process.