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Revista chilena de anatomía

Print version ISSN 0716-9868

Rev. chil. anat. vol.19 n.3 Temuco Dec. 2001

http://dx.doi.org/10.4067/S0716-98682001000300002 

ULTRASTRUCTURE OF ENDOCRINE CELLS OF THE STOMACH
(PROVENTRICULUS AND GIZZARD) OF THE RED-CAPPED CARDINAL
(Paroaria g. gularis, LINNAEUS, 1766)

ULTRAESTRUCTURA DE LAS CÉLULAS ENDOCRINAS DEL ESTÓMAGO (PROVENTRÍCULO
Y MOLLEJA DEL CARDENAL ROJO (Paroaria g. gularis, LINNAEUS, 1766)

 

*M. H. B. Catroxo; **M. A. I. Lima & ***S. Petrella

* Instituto Biológico de São Paulo, São Paulo, Brazil.
** Department of Morphology, Histology, Universidade Federal de São Paulo, São Paulo, Brazil.
*** Instituto Adolfo Lutz, São Paulo, Brazil.

SUMMARY: The endocrine cells of the stomach (proventriculus and gizzard) of the red-capped cardinal (Paroaria g. gularis) were studied by means of the transmission electron microscopy. In the proventriculus these cells are located among the secretory cells of the deep proventricular gland. In the gizzard they are located among the lining cells of the simple tubular gland. Both are elongated and have an oval nucleus, scarce elongated or oval mitochondria with little developing granular endoplasmic reticulum and numerous secretion granules.

KEY WORDS: 1. Birds. 2. Proventriculus 3. Gizzard 4. Endocrine cell 5. Digestive system 6. Ultrastructure.

INTRODUCTION

The red-capped cardinal has two stomachs, the proventriculus (proventriculus), or glandular stomach, which secretes the gastric juice, and the gizzard (ventriculus) or muscular stomach which has a mechanical function (Farner, 1960; Sturkie, 1965; Mc Lelland, 1979). The proventriculus is cranially continuous with esophagus and presents an eliptical shape. The gizzard or ventriculus extends caudally to the proventriculus and is round and flat-shaped with a very thick wall.

The endocrine cells of the avian stomach have been studied by light (Polak et al., 1974;) and electron microscopy (Toner, 1964; Polak et al. and Martinez et al., 1991, 1993).

In the proventriculus these cells are located among the secreting cells of the deep proventricular gland. In the gizzard they are located among the lining cells of the simple tubular glands.

The main purpose of this study is to evaluate the ultrastructure of the endocrine cells of the stomach of the red-capped cardinal and to contribute to the elucidation of their functions.

MATERIAL AND METHOD

Four birds (males, adults) were captured in Peruibe, S.P., Brazil and maintained in individual cages, for 24 hours. They were fed with grains and fruits similar to those found in the capture area and received water "ad libitum". After anesthesia with ether inhalation, the digestive tube was exposed and fragments of proventriculus were immediately fixed in 2.5% glutaraldehyde in 0.1 M, pH7.0 phosphate buffer and post-fixed in 1% osmium tetroxide in the same buffer. After dehydration in ethanol series-propylene oxide (LUFT, 1961), the fragments were embedded in Araldite (CIBA FCY 205).

Ultrathin sections were cut on the LKB ultratome and mounted on copper grids with carbon stabilized supporting film of 0.5% collodium in amyl acetate (González-Santander, 1966). The sections were contrasted with uranyl acetate-lead citrate (Watson, 1958 and Reynolds, 1963) or phospho-tungstic acid (PTA) (Watson, 1958). Phosphotungstic acid (PTA) was used in order to obtain a better contrast of mucopolysaccharides, proteins, basal and plasmic membranes. Observation was made in an Philips EM 300 electron microscope, at 60 kV.

RESULTS

Visualization of ultrathin sections by means of transmission electron microscopy revealed in the proventriculus the presence of elongated cells with endocrine characteristics, located among the secretory cells of the deep proventricular glands (Fig.1). In the gizzard, they were visualized among the lining cells of the simple tubular glands (Fig.4). In both cases, cells are distributed from the basis to the apex of the secretory tubules of the glands. In both chambers of the stomach, proximal to the connective tissue, these cells presented similar characteristics: one ovoid nucleus with an evident nucleolus and disperse chromatin (Figs.1,3,4,5). Cytoplasm of these cells is fulfilled by a great quantity of electrondense granules (Figs.1, 2, 3, 4, 5, 6, 7), some clear others more dark and involved by a membrane (Figs. 2, 3, 5, 6), with a variable diameter, measuring approximately 150-200 nm. In the gizzard, granules are separated from their membranes by a small space of almost 10 mm (Figs. 5, 6). The membrane of these granules presents, sometimes, an irregular surface (Figs. 5, 6). Among these granules, scarce oval or rounded mitochondria are observed (Figs. 1, 2, 3, 4, 5). Some mitochondria present electrondense matrix and hardly any visible crest (3). Endoplasmic granular reticulum represented by flat-shaped vesicles is distributed by the cytoplasm around the nucleus and mitochondria, well developed in the proventriculus (Figs. 1, 2, 3) and rare in the gizzard cells (4). Elements of smooth endoplasmic reticulum or Golgi complex were not visualized.


Fig. 1.  Electron micrography of the endocrine cell in the proventriculus, located among the secretory cells of the deep proventricular gland. Observe: oval nucleus (N) with visible nucleolus ; cytoplasm containing various electrondense granules (big arrow) involved by a membrane, mitochondria (small arrow); granular endoplasmic reticulum (R); gland lumen (L). Stained uranyl acetate and lead citrate. Magnification: 11.000x.


Fig. 2. Detail of the anterior cell in which we can more clearly observe the membrane (arrow) involving the granules (*); mitochondria containing a few crests (M); granular endoplasmic reticulum (R). Stained uranyl acetate and lead citrate. 33.000x.


Fig. 3.  Electron micrography of part of the endocrine cell of the proventriculus in which we observe: oval nucleus (N); nucleolus ; cytoplasm occupied by electrondense granules (* ), involved by a membrane (arrow); mitochondria (M); granular reticulum (R) ; part of the secretory cell (Cs). Stained uranyl acetate and lead citrate. 20.000x.


Fig. 4. Electron micrography of the endocrine cell in the gizzard gland.  Observe: nucleus (N); visible nucleolus ; electrondense granules in the cytoplasm (small arrow), mitochondria (M); granular reticulum (R); capsule of the gland (big arrow). Stained uranyl acetate and lead citrate. 21.400x.


Fig. 5. Electron micrography of part of the endocrine cell of the gizzard, in which we observe: oval nucleus (N); nucleolus ; cytoplasm containing electrondense granules (* ) involved by a membrane (arrow); mitochondria (M) containing a few crests. Stained uranyl acetate and lead citrate. 30.000x.


Fig. 6. Detail of the anterior cell evidencing the cytoplasm, electrondense granules (* ), clearly involved by a membrane (arrow). Stained uranyl acetate and lead citrate. 58.000x.

DISCUSSION

In the present ultrastructural study, cells with endocrine characteristics were observed among the secretory tubules of the deep proventricular glands and close to the connective tissue which involves tubules of the simple tubular gland of the gizzard. Helander (1981) found these cells in the fundic glands of amphibian stomach, in the glands of the proximal portion of the reptile stomach and in the deep proventricular glands of the birds in general. Hill (1971) described the argentaffin cells among the alveolus cells of the deep proventricular glands and among the gizzard cells of the birds, in general. In chicken, Yamanaka et al. (1989) located them in the extension of the gland lobule in the gastrointestinal tract. Within the proventriculus, the endocrine cells appear in close contact with the basal lamina among the mucous and oxynticopeptic cells and they are more abundant deep in the tubular glands and crypts (Martínez et al., 1991). In the proventriculus of the fowl, they are surrounded by the principal cells of the glands but do not reach the lumen.  In the gizzard their bases are often separated from the basement membrane by thin process of chief cell cytoplasm (Toner). Turk (1982) and Klem et al. (1983) reported the presence of argyrophil cells, in the gizzard glands of the birds in general and of the Passer domesticus, respectively.

Our observations on electron microscopy revealed that endocrine cells of both chambers of the stomach presented an elongated shape, being found in the basis of the apex of secretory tubules. In general, these cells in birds may present a phylamentous shape (Hill). In chicken, they are elongated and many times present extensive cytoplasmic processes (Yamanaka et al.; Martínez et al., 1991, 1993) and are likely to be less compact and more elongated in the ventriculus of the fowl (Toner). The endocrine cells in the quail gizzard are round oval and tear drop in shape was located between the glandular epithelium and the basement membrane. Occasionally, cells with elongated cytoplasmic processes were detected in the post-hatching period (Yamaguchi et al., 1987).

The round or oval nucleus and evident nucleolus of endocrine cells were also observed by Martínez et al. (1991) in chicken, by Toner in fowl and by Forssmann et al. in rats. Forssmann et al. reported the presence of a chunky or narrow border of chromatin along the nuclear periphery to surround nucleoli and abundant nuclear pores.

Ultrastructure characteristics reported by us regarding the presence in the endocrine cells of the proventriculus and gizzard, of rounded granules covered by a membrane, occasionally containing some more clear shape, of a variable size and measuring between 150-200 nm were also observed by Toner in fowl and by Martínez et al. (1991) in the type BN endocrine cells of the proventriculus of chicken, classified according to their structure and immunostainning properties. Forssmann et al. described the type 5 endocrine cells found in the rat pylorus, granules clearly surrounded by a membrane, thus variability in the density of the granules, ranging from nearly complete transparency to complete opacity and measuring between 300 and 500 nm. In the gizzard, however, granules are separated from their membranes by a small space of approximately 10 nm. This aspect was also reported by Forssmann et al. in type 3 endocrine cells found in the rat stomach.  Martínez et al. (1991) observed in type NT endocrine cells, granules with 200 nm in diameter, containing an electro-lucent halo which separates the contents from the limiting membrane in the proventriculus of the chicken. The "nibbled-at "appearance of the membrane of the granules described by Forssmann et al. was also observed by us in the secretion granules of the endocrine cells in the gizzard of the red-capped

Additionally, in the cytoplasm of the endocrine cells of both stomachs of the red-capped cardinal, the presence of rare mitochondria presented electrondense matrix and hardly-visible crests. In the endocrine cells, of the chicken proventriculus some mitochondria are present (Martínez et al. (1991)) while in the gastrointestinal tract of the fowl they are numerous and thin and, only one longitudinal-oriented crest is observed in each one of them (Toner). In the endocrine cells of the gastrointestinal tract, it occurs regularly (Forssmann, et al.).

In the cisterns of the granular endoplasmic reticulum, flat-shaped vesicles around the nucleus of mitochondria were observed and distributed by the cytoplasm among the endocrine cells of the proventriculus; in the gizzard it is not much developed. In fowl, the same is diffuse, containing a few cisterns and it is usually dilated (Toner). In chicken, Martínez et al. reported the presence of profiles of granular endoplasmic reticulum. Forsmann et al. described the presence of these organelles only in type 1 and 2 cells although there was no mention regarding its morpho-logy and location.

No smooth endoplasmic reticulum was found by us in these cells, which is in accordance with Forsasmann et al. who did not mention these organelles in any type of endocrine cells described in rats. Toner reported the presence of smooth endo-plasmic reticulum vacuole, better visualized in fowl gizzard.

Golgi complex was also not found, in contrast to Forssmann et al. who identified it in type 1,2 and 4 cells and poorly developed in type 3 cells.

On the other hand, these authors reported that the compact distribution of granules by the cytoplasm, in type 5 cells did not allow to identify almost any type of organelle in the same. In fowl, the Golgi device is small containing dilated sacs and few lamellae (Toner).

In the cytoplasm of the endocrine cells of both stomachs, the presence of many particles of free ribosome which was also observed by Toner (1964) in fowl, by Martínez et al. (1993) in the proventriculus of the chicken and by Forssmann et al. (1969) in the endocrine cells of the gastrointestinal tract of the rat.

Usually, centrioles observed by Martínez et al. (1991, 1993) in the endocrine cells in the proventriculus of the chicken were not observed by us in the endocrine cells of the stomach of the red-capped cardinal.

RESUMEN: Las células endocrinas del estómago (proventrículo y molleja) del cardenal rojo (Paroaria g. gularis), fueron estudiadas a través del microscopio electrónico de transmisión. En el proventrículo, estas células están localizadas entre las células secretoras de la glándula proventricular profunda. En la molleja, están localizadas entre las células de revestimiento tubular simple de la glándula. Los dos tipos de células secretoras y de revestimiento, son alargadas y presentan un núcleo oval, mitocondrias escasamente alargadas u ovales y retículo endoplasmático granular poco desarrollado y numerosos gránulos de secreción.

PALABRAS CLAVE: 1. Birds. 2. Proventriculus 3. Gizzard 4. Endocrine cell 5. Digestive system 6. Ultrastructure.

Dirección para correspondencia:
Dra. Marcia Helena Braga Catroxo
Department of Electron Microscopy
Instituto Biológico
Av. Conselheiro Rodrigues Alves, 1252
CEP: 04010-970
São Paulo - S.P.
BRAZIL

Recibido : 04-06-2001
Aceptado : 01-08-2001

REFERENCES

Farner, D. S. Digestion and digestive system. In: Marshall, A.J.; Biology and Comparative Physiology of birds. New York, Academic Press, 1960. pp411-49.         [ Links ]

Forssmann, W. G.; Orci, L.; Pictet, R.; Renold, A. E. & Rouiller, C. The endocrine cells in the epithelium of the gastrointestinal mucosa of the rat. An electron microscope study. J. Cell. Biol., 40:692-715, 1969.         [ Links ]

González-Santander, R. Técnicas de microscopía electrónica en biología. Madrid, Aguilar, 1969. 666pp.         [ Links ]

Helander, H.F. The cells of the gastric mucosa. Int. Rev. Cit., 70:273-89, 1981.         [ Links ]

Hill, K. J. The structure of the alimentary tract. In: Bell, D.J. & Freeman, B. M. Physiology and Biochemistry of the Domestic Fowl. London Academic Press, 1971. pp 1-23.         [ Links ]

Klem Jr., D.; Finn, S. A.; Nave Jr. & M. J.H. Gross morphology and general histology of the ventriculus, intestinum, caeca and cloaca of the house sparrow (Passer domesticus). Proc. Pa. Acad. Sci., 57:27-32, 1983.         [ Links ]

Luft, J.A. Improvements in an epoxy resin embedding methods. J. Biophys. Biochem. Cytol., 9:409-14, 1961.         [ Links ]

Martínez, A.; López, J. & Barrenechea, M. A. & Sesma, P. Immunocytochemical and ultrastructural characterization of endocrine cells in chicken proventriculus. Cell Tissue Res., 263:541-8, 1991.         [ Links ]

Martínez, A.; López, J. & Sesma, P. Development of the diffuse endocrine system in the chicken proventriculus. Cell Tissue Res., 271:107-13, 1993.         [ Links ]

Mc Lelland, J. Digestive system. In: King, A.S. & Mc Llelland Eds. Form and function in birds. London, Academic Press, 1979. 637p.         [ Links ]

Polak, J. M.; Pearse, A.G.E.; Adams, C. & Garaud, J.C. Immunohistochemical and ultrastructural studies on the endocrine polypeptide (Apud) cells of the avian gastrointestinal tract. Experientia, 30:564-7, 1974.         [ Links ]

Reynolds, E.S. The use of lead citrate at high pH as an electron-opaque stain in electron microscopy. J. Cell. Biol., 17:208-12, 1963.         [ Links ]

Sturkie, P. D. Alimentary Canal: anatomy, prehension, deglutition, appetite, passage of ingesta, motility. In: Farner, D.S. Avian Phisiology. New York, Comstock Publ. Ass. Div. Cornell. Univ. Press., 1965. V.10. pp.272-311.         [ Links ]

Toner, P. G. Fine structure of argyrophil and argentaffin cells in the gastro-intestinal tract of the fowl. Z. Zellforsch., 63:830-39, 1964.         [ Links ]

Turk, D.E. The anatomy of the avian digestive tract as related to feed utilization. Poultry Sci., 61:1225-44, 1982.         [ Links ]

Yamaguchi, S.; Yamada, J.; Kitamura, N. & Yamashita, T. Histological and immunohistochemical study on ontogeny of the endocrine cells in the quail gizzard. Gegenbaurs morphol. Jahrb.Leipzig, 133:71-8, 1987.         [ Links ]

Yamanaka, Y.; Yamada, J.; Kitamura, N. & Yamashita, T. An immunohistochemical study on the distribution of endocrine cells in the chicken gastrointestinal tract. Z. mikrosk. Anat. Forsck. Leipzig, 103:437-46, 1989.         [ Links ]

Watson, M. L. Staining of tissue sections for electron microscopy with heavy metals. J. Biophys. Biochem. Cytol., 4:475-98, 1958.         [ Links ]

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