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vol.15 número1ESTUDIO HISTOLOGICO REGIONAL EN EL EPIDIDIMO DEL PERRO (Canis familiaris, L.)HISTOLOGICAL ASPECTS OF THE STOMACH (PROVENTRICULUS AND GIZZARD) OF THE RED-CAPPED CARDINAL (Paroaria gularis gularis, LINNAEUS, 1766) índice de autoresíndice de materiabúsqueda de artículos
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Revista chilena de anatomía

versión impresa ISSN 0716-9868

Rev. chil. anat. v.15 n.1 Temuco  1997

http://dx.doi.org/10.4067/S0716-98681997000100002 

SCANNING ELECTRON MICROSCOPIC STUDY OF THE HARD PALATINE
MUCOSA OF OPOSSUM (Didelphis albiventris)

ESTUDIO AL MICROSCOPIO ELECTRONICO DE BARRIDO DE LA MUCOSA DEL PALADAR DURO DEL GAMBA (Didelphis albiventris)

* Marcelo Martinez
** Ii-Sei Watanabe
** Francisco Eduardo Martinez
**** Nivalde Antônio Bass
** Osmir Ribeiro
**** Elisa Aparecida Gregório

* Deparment of Health Sciences, Federal University of São Carlos (UFSCAR), Brazil.
** Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo, Brazil.
*** Department of Anatomy, Institute of Biosciences, State University of São Paulo,Brazil.
**** Electron Microscopic Center, State University of São Paulo, Brazil.

This paper was supported by CNPQ and CAPES Grant.

SUMMARY: The three-dimensional characteristics between the epithelium-connective tissue of palatine mucosa of opossum were demonstrated using NaOH method. The tissues were carefully removed and fixed in modified Karnovsky solution for 12 h at 4ºC. Then, the specimens were prepared for scanning electron microscope. The results revealed that the surface of hard palatine mucosa presents stratified squamous keratinized epithelium and several transverse palatine plicae. In the anterior region, some elongated or pointed epithelial protrusions were noted. The lamina propria showed numerous connective tissue papillae disposed in parallel ridges. At high magnification, the thick bundles of collagen fibers were observed.

KEY WORDS: 1.Palatine mucosa; 2. Connective tissue papillae; 3. Opossum; 4.Scanning electron microscopy.

INTRODUCTION

Several investigators have used different methods in order to demonstrated the three-dimensional aspects of epithelial cells and the surface of lamina propria (KLEIN -SZANTO & SCHROEDER, 1977; LOW & MCLUGAGE, 1984: KOBAYASHI, 1990; OHTANI, 1987, 1992). The stereo architecture of buccal mucosa of mammals were published by NAKANO (1991, 1992) in the mouse palate; KOBAYASHI et al. (1989) in the crab-eating lingual papillae; KOBAYSASHI (1992) in the rabbit tongue; WATANABE et al. (1994a) in the Calomys callosus gengival mucosa; AGUNGPRIYONO et al. (1995) in the dorsal papillae of the lesser mouse deer; MARTINEZ et al. (1995a) in the palatine mucosa of armadillo and WATANABE et al. (1995) in the tongue and soft palate mucosa of Macaca fuscata.

The purpose of the present paper is to examine the epithelial cells and the connective tissue papillae of the hard palatine mucosa using a scanning electron microscopic method.

MATERIAL AND METHOD

Hard palatine mucosa of five opossum (Didelphis albiventris) of both sex were used. For light microscopy, the specimens were fixed in Bouin's solution for 24h at room temperature, dehydrated in a graded ethanol and embedded in paraffin routinely. Frontal sections of five micrometers thickness were stained with Masson's thricrome.

For scanning electron microscopy, the specimens were fixed with modified Karnovsky solution containing 2.5% glutaraldehyde, 2.0% paraformaldehyde in 0.1M phosphate buffer (pH 7.2) at 4ºC. The samples were rinsed in distilled water and treated with 10% NaOH solution for 3 to 7 days at room temperature, according to the method reported by OHTANI (1987, 1992).

Then, the tissues were rinsed several times in dis-tilled water and posfixed with 1% osmium tetroxide solution for 2 h at 4ºC. After immersion in 2.0% aqueous solution of tannic acid (MURAKAMI,1974), the samples were dehydrated in a increasing series of ethanol, dried in a critical point Balzers CPD-010, mounted in metal stubs, coated in ion coater Balzers MED-010 and examined in a scanning electron microscope Philips FEM 515 at 15 Kv.

RESULTS

Light microscopy

The histological sections of the hard palatine mucosa of opossum showed a keratinized squamous epithelium constituted by layers of epithelial cells (Fig.1). The lamina propria presents a dense connective tissue layer containing bundles of collagen fibers. In the epithelium-connective tissue interface may be noted numerous connective tissue papillae of different heights and forms (Fig. 1).

Scanning electron microscopy

The scanning electron microscope showed the stratification of the epithelium and the epithelium-connective tissue junctions of the hard palatine mucosa of opossum (Fig. 2). The surface of the epithelium was flat and covered by normal and descamation epithelial cells. It showed many irregular transverse palatine plicae (Fig. 3). In the anterior region, several epithelial protrusions may be noted which were predominantly elongated in shape. Several pointed epithelial projections were also observed (Figs. 3,4).

Epithelial cells were polygonal in shape and showed irregular intercellular borders (Fig.5). At high magnification, microridges of variable forms may be observed (Fig.6).

After the NaOH cell maceration, the epithelial cell layer and the basement membrane were removed to expose the lamina propria. The surface of the lamina propria was characterized by the conspicuous parallel ridges and the presence of the transverse palatine plicae composed by a wall of connective tissue (Fig.7). In the anterior region of the lamina propria, projections which are pointed or elongated in shape may be observed. The surface revealed a meshwork of thick bundles of collagen fibers (Fig.8). The parallel ridges of connective tissue papillae are disposed completely or partially in sagittal direction and showed different wides (Fig.9).

The tip of the parallel ridges is composed by finger-like connective-tissue papillae (Fig.10). At high magnification, the surface of connective tissue revealed bundles of collagen fibers constituting a intricated meshwork (Fig.11).

DISCUSSION

The present data demonstrated the three-dimensional characteristics of epithelial cells and the epithelium- connective tissue interface of the hard palatine mucosa of opossum, Didelphis albiventris.

The masticatory mucosa corresponds to hard and gingiva, lining mucosa include lip, cheek and soft palate, while the lingual dorsum is the specialized mucosa. Some investigators have studied the morphological differences between these mucosae (KOBAYASHI, 1990, 1992; NAKANO, 1991; MORAIS et al. 1991; WATANABE et al. 1994b).

Our findings showed that the hard palate of opossum is lined by stratified squamous keratinized epithelium which were described by transmission electron microscopy by MARTINEZ et al. (1995b). The surface of the mucosa of opossum revealed irregular transverse palatine plicae. These structures are characteristics of species among mammals according to their preying behavior, food habits and mastication ( INQUE & TODA, 1991).

Our data also revealed the presence of epithelial protrusions presenting elongated or pointed shapes in the anterior region of the mucosa. MARTINEZ et al. (1995a) described pointed projections in the anterior region of the hard palate of the armadillo, Dasypus novemcinctus. These structures are related to enlarge the adhesion between epithelium and connective tissues.

At the scanning electron microscopy level, the lamina propria of opossum showed parallel ridges composed by bundles of collagen fibers. Similar observations were made by NAKANO (1992) in the mouse palatine mucosa and WATANABE et al. (1995) in the tongue and soft palate mucosa WATANABE et al. (1995) in the tongue and soft palate mucosa of Macaca fuscata. KLEIN-SZANTO & SCHROEDER (1977) reported the human hard palatine mucosa composed by cylindrical and erect connective papillae. These projections of the lamina propria contains blood vassels and nerves and permit a large anchorage between epithelium-connective tissues (HORSTMANN, 1954). The architecture of the lamina propria of the human hard palate is more consistent than the parallel ridges observed in the mouse (NAKANO, 1992). So, if we compare the food habits pf man (soft diets), we concluded that the architecture of the lamina propria must be genetically defined. Another application on the observation of the lamina propria by scanning electron microscope may be used to investigate the normal and pathological tissues mentioned by WATANABE et al. (1992).

Fig. 1 Light micrograph showing the hard palatine mucosa of opossum. Stratified squamous keratinized epithelium (E), lamina propria (*) and connective tissue papillae are shown (arrow). H.E. X200.
Fig. 2 SEM image showing the surface of the palatine mucosa, squamous epithelium (E) and lamina propria (*). X230.
Fig. 3 SEM image of hard palatine mucosa. Shows transverse palatine plicae (*) and epithelial projections (arrows). X120.
Fig. 4 Shows elongated protrusions on the surface of the palatine mucosa (*). X390.
Fig. 5 SEM image showing polygonal epithelial cells, descamation cells and intercellular border. X200.
Fig. 6 Surface of polygonal epithelial cells showing the microplicae. X3200.

Fig. 7 NaOH treated specimen . General view of the epithelium-connective tissue interface showing transverse palatine plicae (*) and the parallel ridges of connective tissue papillae. X160.
Fig. 8 Shows the meshwork of collagen fibers on the projections of lamina propria (*). X380.
Fig. 9 SEM image showing the parallel ridges of connec-tive tissue papillae of lamina propria. X390.
Fig. 10 At high magnification, shows the tip of connective tissue papillae. X830.
Fig. 11 At high magnification, shows a meshwork of thick bundles of collagen fibers running in several directions. X2120.

RESUMEN: Las características tridimensionales del tejido conectivo epitelial de la mucosa del paladar duro fueron estudiadas usando el método de NaOH. Los tejidos fueron cuidadosamente removidos y fijados en solución de Karnovsky modificado por 12 h a 4ºC. Luego, los especímenes fueron preparados para microscopía electrónica de barrido. Los resultados revelaron que la superficie de la mucosa del paladar duro presenta epitelio escamoso estratificado queratinizado y varios pliegues palatinos transversos. En la región anterior, se observaron algunas protrusiones epiteliales alargadas o punteadas. La lámina propia mostró numerosas papilas de tejido conectivo en froma de elevaciones paralelas. A mayor aumento, se observaron gruesos haces de fibras colágenas.

PALABRAS CLAVE: 1. Mucosa palatina; 2.Papila conectiva; 3.Gambá; 4.Microscopio electrónico de barrido.

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ACKNOWLEDGEMENTS: CAPES/CNPQ

Dirección para correspondencia:
Prof. Dr. Marcelo Martinez
Universidade Estadual Paulista
Campus Botucatu
Instituto de Biociências
Departamento de Anatomía
BOTUCATU, SP - Rubião Junior
CEP 18618-000 - PBX (014) 8212121, r. 2099-2040-2357 - FAX (014) 8213744 - TELEX 0142107
BRASIL

Recibido : 01-12-1996
Aceptado : 03-03-1997

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