RESUMO
The stomach of the farmed African catfish (Clarias gariepinus, Siluriformes: clariidae) was investigated in this study to establish its basic anatomy, as there is scanty information available on the literature. It produced to baseline data for further investigative research, help fish clinicians in pathology and aid nutritionists in feed management. After cropping from a commercial aquaculture, apparently healthy fish were immobilized and euthanized by using chloroform. The samples were dissected and slices of cardiac, fundic and pyloric stomach processed through routine histological procedures. Grossly, the stomach was J-shape. Cranial to the stomach was the oesophagus but no sphincter was seen separating them. Caudally, a pyloric sphincter separated the stomach from the proximal intestine. The stomach contained three regions cardiac, fundic and pyloric. The entire stomach surface was lined by a simple columnar epithelium containing mucin at the apical cytoplasm. Only the cardiac and fundic regions contained gastric glands in the lamina propria, but the glands were more developed in the fundic region. The tunica muscularis contained smooth muscle cells in an inner circular and outer longitudinal orientation. Mucin histochemistry revealed the presence of only neutral mucin in the stomach. The results obtained in this study suggest that the absence of gastric glands in the pylorus may be an adaptation of this species to reduce the quantity of acid entering the proximal intestine; hence it might help the alkaline medium to maximize pancreatic enzyme actions in the proximal intestine. The presence of only neutral mucin in the stomach will act as a buffer to neutralize the high acidic stomach content. Neutral mucins are also associated with transport of macromolecules.
Se efectuó un estudio de tipo histológico e histoquímico con mucina, en el estómago del bagre africano (Clarias gariepinus, Siluriformes: clariidae) cultivado en granja acuícola, para establecer su anatomía básica, debido a la escasa información disponible en la literatura. La investigación generó datos para ulteriores investigaciones, que contribuirán con los ictiopatólogos y ayudarán a los nutricionistas en el manejo alimentario. Después de su cultivo en una granja acuícola comercial, los peces aparentemente sanos, fueron inmovilizados y sacrificados, usando cloroformo. Se tomaron muestras de las regiones cardial, fúndica y pilórica, y se procesaron histológicamente. En su conjunto, el estómago presentaba una apariencia de J. El esófago estaba situado cranealmente al estómago, pero no se observó un esfínter que los separara. Caudalmente, un esfínter pilórico separaba al estómago del intestino proximal. El estómago contenía tres regiones: cardiaca, fúndica y pilórica. La totalidad de la superficie estomacal se encontraba recubierta por un epitelio cilíndrico, que contenía mucina en el citoplasma apical. Solamente las regiones cardiaca y fúndica tenían glándulas gástricas en la lámina propia, que eran más desarrolladas en la región fúndica. La túnica muscular poseía células musculares lisas con una orientación interna circular y externa longitudinal. La histoquímica mediante la mucina reveló la presencia solo de mucina neutra en el estómago. Los resultados obtenidos en este estudio sugieren que la ausencia de glándulas gástricas en el píloro, pudiera ser el resultado de una adaptación de esta especie para reducir la cantidad de ácido que penetra en el intestino proximal; por tanto, pudiera ayudar al medio alcalino a maximizar las acciones de las enzimas pancreáticas en el intestino proximal. La sola presencia de mucina neutra en el estómago actuaría como amortiguador contra el elevado contenido ácido del estómago. Las mucinas neutras también están asociadas con el transporte de micromoléculas.
RESUMO
The mandibular salivary gland microscopic morphology of the adult African giant pouched rat was investigated. This study was carried out to provide the basic histology of this organ in the giant pouched rat, as there is dearth of information of its microscopic architecture in available literature. This is of the most importance, as the possible use of this species of rodent is considered as a future laboratory animal instead of the Wistar rat because of its bigger size; also, for purposes of domestication and use as a ready source of animal protein. Hence the need to understand the digestive biology to help animal nutritionist in feed formulation. Histology revealed the presence of both serous and mucus secretory acini. Some mucous cells presented serous demilunes. Myoeithelial cells were seen around secretory cells and the intercalated ducts. The serous gland region with more relatively profuse intralobular ducts was larger in size than the mucus gland region. The intralobular ducts of intercalated and striated ducts were lined by simple cuboidal and simple columnar cells respectively. The excretory duct was lined by stratified cuboidal cells. The large serous glandular region reflects the need for more enzymic action in the oral cavity, while the mucus glands will help produce mucin that will lubricate the digestive tract. This study for the first time documents the normal histology of the mandibular salivary gland in this species, hence filling a gap that will help further investigative research, especially the role of myoepithelial cells in secretory glands tumors
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