S. Afr. J. Zoo!. 1990,25(1) 1 Histological and ultrastructural study of the gastric wall of the freshwater bream, Oreochromis mossambicus (Peters) with reference to 'parietal-like' cells
Heleen L. Coetzee*, Maria M. Nel and J.H. Swanepoel Department of Zoology, Rand Afrikaans University, P.O. Box 524, Johannesburg, 2000 Republic of South Africa
Received 5 January 1989; accepted 29 June 1989
The stomach wall of the freshwater bream 0. mossambicus is described and compared with that of other bony fishes and vertebrates. The histology of the stomach layers and fine structure of the various cell types of 0. mossambicus are basically similar to the correspondlngcells of other vertebrates although some differen ces do occur. The mucosa consists of the following. (a) Surface epithelium distinguished by its luminal location and secretory granules. (b) Gastric pit mucous cells identified by their different location, appearance and secretory granules. (c) Gastric gland cells comprising two cell types designated Type I and II. Type I cells, the chief component of the glands, are large cells characterized by tubulovesicles in the apical cytoplasm. Type II cells are identified by the characler of their small dense granules in the cytoplasm. (d) Basally granula- . ted cells were identified. (e) A lamina propria and a muscularis mucosae are also present in the mucosa. A submucosal, muscular and serous coat were distinguished and described. Additionally in the submucosa a prominent stratum compactum and stratum granulosum are present.
Die maagwand van die bloukurper, 0. mossambicus word beskryf en vergelyk met die van ander beenvisse en werweldiere. Die histologie van die lae van die maag en die ultrastruktuur van die verskillende seltipes van O. mossambicus is basies dieselfde as die ooreenstemmende selle van ander vertebrate'alhoewel verskille wei voorkom. Die mukosa bestaan uit die volgende. (a) Oppervlakepiteel wat deur middel van die luminale ligging en sekretoriese granules uitgeken kan word. (b) Slymselle van die gastriese putte wat op grond van ligging, voorkoms en sekretoriese granules onderskeibaar is. (c) Die gastriese klierselle bestaande uit twee seltipes wat as tipe I en II benoem is. Tipe I is <;lie hoofkomponent van die kliere en is groot selle met karakteristieke tubulovesikels wat in die apikale. sitoplasma voorkom. Tipe II-selle word deur die kenmerkende klein digte granules in die sitoplasma identifiseer. (d) Basaal gegranuleerde selle is identifiseer, (e) 'n Lamina propria en muscularis mucosae is ook teenwoordig in die mukosa. 'n Submukosale, muskulere en sereuse I~g word onderskei en beskryf. In die submukosa kom 'n prominente stratum kompaktum en stratum granulosum ook voor.
. )
0 • To whom correspondence should be addressed at: Department of Anatomy, University of Pretoria, P.O. Box 2034, Pretoria, 1
0 0001 Republic of South Africa 2 d e t a One of the earliest studies on the morphology and late summer/early autumn and late ~inter/early spring in d ( the Roodeplaat dam, Transvaal. Stomachs were dissec r histology of the digestive system of bony fish was e
h undertaken by Edinger (1877) who observed that the ted from freshly killed O. mossambieus. Tissue was cut s i l gastric glands of fish differ histologically from those of from the stomach wall immediately after dissection and b u mammals. Subsequent work has confirmed his observa prepared for light and electron microscopy. P Cross sections of the stomach were fixed for light e tions (Dawes 1929; Burnstock 1959; Hale 1965; Weisel h
t microscopy in Bouin's fixative for 12 h, processed,
1973; Huebner & Chee 1978; Sis, Ives, Jones, Lewis & y embedded in paraffin wax and sectioned at 8 ~m. b Haensly 1979).
d Sections were routinely stained with haematoxylin
e Very few ultrastructural investigations have been t (Romeis 1948) and eosin (Humason 1979) and by the n carried out on the stomach wall of teleosts. Ling & Tan a combined Alcian blue-PAS technique (Bancroft & r (1975) studied the fine structure of the gastric epithelium g
Stevens 1982) for collagen. e of the coral fish Chelmon rostratus and Noaillac-Depeyre c Tissue sections of the stomach wall (2 mm by 2 mm) n & Gas (1978) described the ultrastructure of the gastric e 3
c for electron microscopy were fixed in cold 0; 1 mol dm- i
l epithelium of the perch Perea f/uviatilis. The ultrastruc phosphate buffered 4,5% glutaraldehyde for 24 hand r
e tural specialization of the intestinal tract of the intestinal subsequently rinsed in 0,1 mol dm-3 phosphate buffered d air breather Hoplosternum thoraeatum was investigated 3 n 0,2 mol dm- sucrose (Sabatini, Bensch & Barrnett u
by Huebner & Chee (1978). y 1963). Tissues were then transferred to 1% phosphate a The present study was undertaken to determine the buffered osmium tetroxide (Millonig 1961) for 4 h. w e histology and ultrastructural characteristics of the 3 t After fixation the tissues were rinsed in 0,1 mol dm- a various cell types and components constituting the 3
G phosphate buffered 0,2 mol dm- sucrose and dehydra
t stomach wall of O. mossambieus and also to provide a
e ted in ascending concentrations of ethanol (Pease 1964). n morphological basis for future histochemical work on i Thereafter the tissues were rinsed three times in propy b specific cells present in the stomach wall of fishes. a lene oxide for 10 min each and left for 12 h in a 1 : 1 S
y mixture of propylene oxide and Araldite. This was fol b Materials and Methods lowed by immersion into a mixture of 1 : 3 propylene d e
c Freshwater bream O. mossambieus were netted during oxide and Araldite for 2 h. Finally the tissues were u d o r p e R 2 S.-Afr. Tydskr. Diede:. 1990,25(1)
embedded In Araldite (Luft 1961) and polirnerized at for 40 min and lead citrate (Venable & Coggeshall 1965) 650C for 48 h. for 4 min. The sections were studied under a Philips 301$ Thin sections were obtained using a Reichert Ultracut electron microscope. ultramicrotome. For orientation of the tissue 1 $.Lm thick section·s were stained with toluidine blue and observed Rssult8 u·nder the ligbt microscope. For electron microscopy Mucosa gold interference coloured sections were collected and The mucosa consists of the surface epithelial layer, stained with uranyl acetate (Gibbons & Grimstone 1960) gastric glands, lamina propria and muscularis mucosae
. ) 0 1 0 2 d e t a d ( r e h s i l b u P e h t y b d e t n a r g e c n e c i l r e d n u y a w e t Figure oIl A: Histologicallransverse section through the stomach wall. H & E, 8 ~m. 1 = gastric gland; 2 = serosa; 3 = longitudinal a
G muscle layer; 4 = circular muscle layer; 5 == tunica muscularis; 6 '" submucosa; 7 == muscularis mucosae; 8 = mucosa; 9 = gastric t e pit~ 10 = lumen x536. B: Light microscopic transverse section through the surface epithelium and gastric glands. H & E, B ~m. 1 n i = gastric pit; 2 = surface epithelium; 3 = lamina propria; 4 = gastric gland cell nucleus; 5 = gastric gland lumen; 6 = gastric pit b a mucous cell nucleus X \340. C: Micrograph of a transverse section of the basal portion of the mucosa and the submucosa. S
y Toluidine blue, 0,5 ).Lm. 1 = gastric gland base; 2 = lamina propria; 3 = submucosa; 4 = stratum granulosum; 5 = muscularis b
d mucosae; 6 = smooth muscle fibre nucleus X 1340. D: Micrograph of the surface epithelial cells. I 0= muCous granule; 2 = e
O c microviJlus; 3 = mitochondrion; 4 = nucleus; 5 = intercellular space x 2980. u d o r p e R ...... J ~,_"" > ,
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" "<- Cd 7)110 I. ~ • , • . ) 0 1 0 2 d e t a d ( r e h s i l b u • P e h t y b d e t n a r , g e c n e c i l r e d n u y a w e t a G t e n _ ""- -:,._, i ...... b _~.l1II__ •.A-,.. _-,._-.,._-_... ,,,,. . -, _ __,,-.1- • ,= .ZI"-.C! a S w, , • ". y .. - • .-, II• :1- ____. ' , _,,-:,,_ s b . ~ 0-_...... - " .. s _ d ___., . _,_ 'F oR 00;' - 'e' !: •• 1_.) " .,· _._ .... I1 .... h e c , u ..... d o r p e R ...... J ...... , .... 2S('. , , ,. _ .., .,. l.l __ ..lie n .... _ _ ;,h _""->Lbo_ ,_ , ' •• ( F"~ )0). 11:< a LL+ _.,.9J _by ,.1_ ... OIIotlie" boW ...... _ • laWly ,."..., _ ...., .. a _ _ ..,. ... aooI __... :/11.1 ... by L,I ... 1...... ,. __ ,lie ...... , _ _ 6.1 _ ...... ' ~__ 38) ...... ,. b',,_ AsooriaL . ) 0 1 0 2 d e t a d ( r e h s i l b u P e h t y b d e t n a r g e c n e c i l r e d n u y a w e t a G t e n i b a S y b d e c u d o r p e R 8 S.-Afr. Tydskr. Dierk. 1990,25(1) have a homogeneously electron dense core. The from 24,8 nm to 31,0 nm and form a loose network of diameters of the granules vary from 114 nm to 164 nm microfibrils throughout the submucosa. The cellular (Figure 3C). component consists of different cells such as fibroblasts, plasma cells, macrophages and mast cells. Basally granulated cells These cells are located in the mucosa with a number Tunica muscularis accumulating beneath the surface epithelium. Numerous This layer can be subdivided into an inner circular layer granules are situated in the basal portion of the cells. and an outer longitudinal layer according to the The shape of the cells varies, some being triangular in orientation of the smooth muscle fibres (Figure lA). shape and others flask-shaped making contact with the The smooth muscle fibres of the tunica muscularis are gland lumen. The granules are membrane bound with an more robust compared to the fibres of the muscularis electron dense core. The diameter of the granules of the mucosae. The smooth muscle fibres are spindle-shaped different cells varies from approximately 160 nm to 700 with a central oblong nucleus. In the cytoplasm organ nm (Figure 5B). All the cells are in contact with the elles such as myofilaments, dense bodies, mitochondria, gland lumen. Goigi complexes, rough endoplasmic reticulum and glycogen are present (Figure 6B). A large amount of Lamina propria conspicuous dark granules are present between the Light microscopically the lamina propria forms two fairly cristae of the mitochondria (Figure 6B). These granules distinct layers, one layer adjacent to the surface can become so numerous that they displace the cristae. epithelium (Figures 1B & 5C) and the other between the The caveolae of the sarcolemma are grouped in rows, basal ends of the gastric glands and the muscularis two caveolae wide and parallel to the long axis of the mucosae (Figures Ie & 5C). Between the gastric glands fibre. Intervening between the groups of caveolae are the connective tissue of the lamina propria is sparse. dense bands (Figure 6B). Adjacent muscle fibres make Electron microscopically the fibre components of the contact with each other by means of desmosome-like lamina propria consist mainly of collagen microfibrils junctional complexes. A basal lamina surrounds the with diameters of 20 nm to 26 nm. The cellular compo smooth muscle fibres and collagen microfibrils are nents of the lamina propria contain cells such as fibro present between the fibres. blasts, plasma cells and macrophages. Serosa . ) Muscularis mucosae 0 A serosa is present with a single layer of squamous cells 1 The muscularis mucosae consists of a few smooth muscle 0 resting on a prominent sereus connective tissue layer 2 fibres that form a thin circular muscle layer (Figure lA). d (Figure 6C). e Electron microscopically the smooth muscle fibres are t a arranged in two or three layers (Figure 5D). The smooth d Discussion ( muscle fibres are thin and spindle shaped with a centrally r e The fine structure of the surface mucous cells in located nucleus. The cytoplasm contains myofilaments, h s Oreochromis mossambicus differs very little from that i l dense bands, dense bodies and rough endoplasmic reti b described for the perch Perca fluviatilis (Noaillac u culum. The sarcolemma contains numerous caveolae. P Depeyre & Gas 1978), coral fish Chelmon rostratus The smooth muscle fibres are separated from each e (Ling Tan 1975) and other vertebrates (Ito h other by conspicuous amounts of collagen microfibrils & & t y between the individual muscle fibres (Figure 5D). The Winchester 1963; Ito 1967; Stephens & Pheiffer 1968; b Rubin, Ross, Sleisenger & Jeffries 1968; Geuze 1971). d muscle fibres are surrounded by a basal lamina. e t The surface mucous cells of O. mossambicus do not, n a Stratum compactum. A distinct connective tissue layer however, cover the gastric pits as is generally found in r g situated beneath the gastric glands and lamina propria is other vertebrates. Bouhours, Bouhours & Bryon (1981) e c observed with Alcian blue-PAS staining (Figure 5C). distinguish two types of mucus-secreting cells in the n e Electron microscopically the stratum compactum c epithelial cells of the guinea pig stomach. The one type i l seems to be closely packed collagen microfibrils between of mucus-secreting cell has smaller secretory granules r e the smooth muscle fibres of the muscularis mucosae homogeneously electron dense and entirely glycoproteic d n (Figure 5D). in nature. The mucous granules present in the apical u y portion of the surface mucous cells of the bream appear a Stratum granulosum. A conspicuous accumulation of w to be similar to the glycoproteic smaller granule as e t granulated cells adjacent to the stratum compactum in described by Bouhours et al. (1981). The other type of a G the lamina propria and submucosa is observed in O. mucus-secreting cells defined by Bouhours et al. (1981) t e mossambicus (Figure 1C). contains a larger heterogeneous secretory granule. n i b These granules contain a proteinaceous core containing a Submucosa S pepsinogen surrounded by carbohydrates. Similar y The connective tissue forming the submucosa is of a heterogeneous granules have been described by Ito & b d loose type (Figure 6A) with the collagen showing cross Winchester (1963) in the bat Myotis lucifugus lucifugus, e c striations. These collagen microfibrils vary in diameter Ito (1967) in man and Noaillac-Depeyre & Gas (1978) in u d o r p e R S. Afr. J. Zool. 1990,25(1) the perch P. fluviatilis. The gastric pit mucous cells of the noted that multivesicular bodies were particularly bream O. mossambieus contain similar heterogeneous abundant. Although the significance of this is still mucous granules. These granules may be the source of obscure the multi vesicular bodies may be involved in the pepsinogen in the stomach of the bream O. mossambieus activation and deactivation of parietal cell secretions. as no pepsinogenic cells appear to be present. The Winborn & Seelig (1974), however, have attributed the gastric pit mucous cells of O. mossambieus are similar to role of degradation of mitochondria to the multivesicular the mucous neck cells of the perch P. fluviatilis bodies. The remarkably high number and variety of (Noaillac-Depeyre & Gas 1978), the bat M. lucifugus forms of mitochondria in parietal cells are suggestive of a lucifugus (Ito & Winchester 1963), man (Ito 1967; Rubin high oxidative metabolism (Helander 1981), and the et al. 1968), the rat (Wattel, Geuze & de Rooij 1977) and changes in the tubulovesicular compartment could sug the guinea pig (Bouhours et al. 1981), although these gest a role for the multivesicular bodies of membrane cells are located in the gastric pits in contrast to other redistribution or reconstitution. Both these theories seem vertebrates where they are found in the neck region of to be borne out in cell Type I of the gastric gland of O. the gastric gland. mossambicus where multivesicular bodies are found in The gastric glands of O. mossambieus differ from the different stages of formation as noted ultrastructurally. gastric glands that were originally described by Steven & Cells with basally situated granules in the cytoplasm Leblond (1953) for the rat and since then generally used were noted in the mucosa of O. mossambieus. These as the model for gastric glands (Ito & Winchester 1963; cells are possibly endocrine cells and morphologically Ito 1967; Wattel, Geuze & de Rooij, 1977; Fawcett comparable to the argentaffin cells as described by Ito & 1986). This model depicts the gland being divided into an isthmus, neck and base opening into the bottom of a Winchester (1963) in the bat M. lucifugus lucifugus, Ito gastric pit. The uppermost parietal cell marks the (1967) in man, Stephens & Pheiffer (1968) in the ferret, boundary between foveola and isthmus, the uppermost Ling & Tan (1975) in the coral fish Chelmon rostratus mucous neck cell demarcates the boundary between the and Noaillac-Depeyre & Gas (1978) in the perch Perea isthmus and neck and the lowest mucous neck cell the fluviatilis. Further study is currently underway to boundary between the neck and base. In contrast the histochemically determine the nature of these cells. gastric gland of the bream O. mossambieus seems to be far simpler. The gland consists of two cell types, cell References Type I being the main component of the gland. The BANCROFT, J.D. & STEVENS, A. 1982. Theory and . possible equivalent to mucous neck cells in the bream practice of histological techniques. Churchill Livingstone, ) 0 are located in the gastric pits. No cells similar to chief London. 1 0 cells have been observed in the gastric glands of O. BOUHOURS, D., BOUHOURS, J-F. & BRYON, P-A. 2 d mossambieus . 1981. Association of glycoproteins and pepsinogen in the e t It is generally accepted that in the gastric glands of secretory granules of fundic epithelial cells isolated from a d ( bony fish, amphibians, reptiles and birds both hydro guinea pig stomach. Biochem. Biophys. Acta 672: r e chloric acid and pepsinogen are secreted by one cell type 288-296. h s namely the oxynticopeptic cell while the gastric glands of BURNSTOCK, G. 1959. The morphology of the gut of the i l b mammals have separate cells producing hydrochloric brown trout Salmo trutta. Quart. J. micro Sci. 100: u P acid and zymogen (Ito 1967). In O. mossambicus, 183-198. e however, cell Type I of the gastric glands was found to DA WES, B. 1929. The histology of the alimentary tract of h t be similar in ultrastructure to the mammalian parietal the plaice Pleuronectes platessa. Quart. J. micro Sci. 73: y b cell. No zymogen granules appear to be present in the 243-274. d e cytoplasm of these cells. Cell Type I of the gastric gland EDINGER, L. 1877. Ueber die Schleimhaut des t n of the bream, O. mossambieus in contrast to that of other Fischdarmes, nebst Bemerkungen zur Phylogenese der a r g bony fish (Noaillac-Depeyre & Gas 1978; Ling & Tan Drusen des Darmrohres. Arch. f. mikros. Anat. 13: e c 1975), seems to have only a single function i.e. that of 651-692. n e possible hydrochloric acid production. Although cell FAWCETT, D.W. 1986. A text book of histology. W.B. c i l Type I of O. mossambieus appear to be similar to the Saunders Co. r e parietal cell of mammals there are a few differences. Nei GEUZE, J.J. 1971. Light and electron microscope d n ther secretory canaliculi or intracellular canaliculi nor observations on the gastric mucosa of the frog Rana u intercellular canaliculi between the lateral plasmamem esculenta. Z. Zellfrosch. 117: 87-102. y a branes are present in cell Type I of O. mossambicus. GIBBONS, I.R. & GRIMSTONE, A.V. 1960. On the w e t A wide variety of studies have been done on the flagellar structure in certain flagellates. J. biophys. a formation, increase and decrease of tubulovesicles and biochem. Cytol. 7: 679-716. G t e microvilli of parietal cells in a number of different HALE, P.A. 1965. The morphology and histology of the n i animals (Lillibridge 1964; Sedar 1969; Helander & digestive systems of two freshwater teIeosts, Poecilia b a Hirschowitz 1972; Leeson 1973; Ito & Scofield 1974). In reticulata and Gasterosteus aculeatus. J. Zool. 146: S y studies done on the changes that take place in the 132-149. b tubulovesicular compartment of mouse parietal cells HELANDER, H.F. 1981. The cells of the gastric mucosa. d e c during gastric acid secretion, Ito & Schofield (1974) Int. Rev. Cyt. 70: 217-289. u d o r p e R 10 S.-Afr. Tydskr. Dierk. 1990,25(1) HELANDER, H.F. & HIRSCHOWITZ, B.1. 1972. PEASE, D.C. 1964. Histological techniques for electron Quantitative ultrastructural studies on gastric parietal microscopy. Academic Press, New York. cells. Gastroenterol. 63: 951-961. ROMEIS, R. 1948. Mikroskopische Technik. Leibniz HUEBNER, E. & CHEE, G. 1978. Histological and Verlag, Miinchen. ultrastructural specialization of the digestive tract of the RUBIN, W., ROSS, L.L., SLEISENGER, M.H. & intestinal air breather Hoplosternum thoraeatum JEFFRIES, G.H. 1968. The normal human gastric (Teleost). J. Morph. 157: 301-328. epithelia. A fine structural study. Lab. [nv. 19: 598-626. HUMASON, G.L. 1979. Animal tissue techniques. W.H. SABATINI, D.D., BENSCH, K. & BARRNETT, R.L. Freeman and Company, San Francisco. 1963. Cytochemistry and electron microscopy. The ITO, S. 1967. Anatomic structure of the gastric mucosa. In: preservation of cellular ultrastructure and enzymatic activity by aldehyde fixation. J. Cell Bioi. 17: 19-23. Handbook of physiology. (Ed.) Code, C.F., Vol. II, pp. SEDAR, A.W. 1969. Uptake of peroxidase into the smooth 705--741. American Physiology Society, Washington, surfaced tubular system of the gastric acid-secreting cell. D.C. J. Cell Bioi. 43: 179-184. ITO, S. & SCOFIELD, G.C. 1974. Studies on the depletion SIS, R.F., IVES, P.J., JONES, D.M., LEWIS, D.H. & and accumulation of microvilli and changes in the HAENSLY, W.E. 1979. The microscopic anatomy of the tubulovesicular compartment of mouse parietal cells in oesophagus, stomach and intestine of the channel catfish, relation to gastric acid secretion. J. Cell Bioi. 63: Ictalurus punetatus. J. Fish Bioi. 14: 179-186. 364-382. STEPHENS, R.J. & PHEIFFER, C.J. 1968. Ultrastructure ITO, S. & WINCHESTER, R.J. 1963. The fine structure of of the gastric mucosa of normal laboratory ferrets. J. the gastric mucosa in the bat. J. Cell Bioi. 16: 541-577. Ultrastruet. Res. 22: 45--62. LEESON, T.S. 1973. Canaliculi and tubulovesicles of rat STEVENS, C.E. & LEBLOND, C.P. 1953. Renewal of the parietal cells. Am. J. Anat. 136: 541-547. mucosa cells in the gastric mucosa of the rat. Anat. Ree. LILLmRIDGE, C.B. 1964. The fine structure of normal 115: 231-239. human gastric mucosa. Gastroenterol. 47: 269-296. VENABLE, J.H. & COGGESHALL, R. 1965. A simplified LING, E.A. & TAN, C.K. 1975. Fine structure of the lead citrate stain for use in electron microscopy. J. Cell gastric epithelium of the coral fish, Chelmon rostratus Bioi. 25: 407-408. Cuvier. Okajimas Fol. anat. jap. 51: 285--310. WATTEL, W., GEUZE, J.J. & DE ROOU, D.G. 1977. LUFf, J.H. 1961. Improvements in epoxy resin embedding Ultrastructural and carbohydrate histochemical studies on methods. J. biophys. bioehem. Cytol., 9: 409-414. the differentiation and renewal of mucous cells in the rat . ) MILLONIG, G. 1961. Advantages of a phosphate buffer for 0 gastric fundus. Cell Tiss. Res. 176: 445-462. 1 0 osmium tetroxide solution in fixation. J. appl. Physiol. WEISEL, G.F. 1973. Anatomy and histology of the 2 32: 1637-1638. digestive system of the paddlefish Polyodon spathula. J. d e t NOAILLAC-DEPEYRE, J. & GAS, N. 1978. Morph. 140: 243-256. a d Ultrastructural and cytochemical study of the gastric WINBORN, W.B. & SEELIG, L.L. 1974. Pattern of ( r epithelium in a freshwater teleostean fish Perea fluviatilis. osmium' deposition in parietal cells of the stomach. J. Cell e h Tiss. Cell 10: 23-37. Bioi. 63: 99-119. s i l b u P e h t y b d e t n a r g e c n e c i l r e d n u y a w e t a G t e n i b a S y b d e c u d o r p e R