Secretory Granules in the Columnar Cells of the Cecum and the Great Colon of the Horse

Abstract

Summary The columnar cells of the equine cecum and great colon contain secretory granules between 0.13 and 0.40 μ in diameter. The arrangement of these granules at the apex of the columnar cells presents a peculiarity offering an explanation for the appearance, when viewed through the light microscope, of three zones of cytoplasm at the cell's apex. In contrast, no zonation is observed in the columnar cells of the glandular epithelium, because the entire apex of these cells is filled with secretory granules. Taking into consideration the structure of the granules as well as their electron density and histochemical reactions, it is suggested that they are probably mucous in nature. On the other hand the manner in which they are secreted offers the opinion that it is merocrine. Zusammenfassung Sekretgranula im Säulenepithel des Blinddarms und großen Kolons beim Pferd Die Sekretgranula in den prismatischen Epithelzellen des Blinddarms und grofien Kolons beim Pferd haben einen Durchmesser von 0,13 bis 0,40 μ. Ihre elektronenoptisch sichtbare Anordnung am Apex der Zellen bietet eine Besonderheit dar, die jene 3 Zonen des Zytoplasmas erklärt, die man lichtmikroskopisch beobachtet. Im Gegensatz dazu zeigt das Zytoplasma des Drüsenepithels keinerlei zonale Gliederung, da der gesamte Apex dieser Zellen mit Sekretgranula angefüllt ist. Die Struktur der Granula, ihre Elektronendichte und ihre histochemischen Reaktionen sprechen dafür, daß es sich wahrscheinlich um Schleimgranula handelt. Andererseits weist die Art ihrer Absonderung auf eine merokrine Sekretion hin.

Ultrastructural Features of the Bovine Cecal Mucosa

“…In the rabbit (MARTIN, 1961;SNIPES, 1978), guinea pig (MARTIN, 1961) and horse (KANAKOUDIS, 1973), however, the epithelial lining of the cecal glands contained only a limited number of goblet cells. In the rabbit (MARTIN, 1961;SNIPES, 1978), guinea pig (MARTIN, 1961) and horse (KANAKOUDIS, 1973), however, the epithelial lining of the cecal glands contained only a limited number of goblet cells.…”

“…The surface columnar cells, unlike undifferentiated cells of the glands lacked secretory granules in their apical cytoplasm. Secretion from the surface columnar cells in the horse, therefore, may compensate for the scarcity of goblet cells in the cecum and large colon (KANAKOUDIS, 1973). Similarly, the surface epithelial cells in the horse's cecum and great colon have been observed to contain numerous secretory granules in their apical cytoplasm (KANAKOUDIS, 1973).…”

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The cecal surface epithelium of cattle was lined entirely by columnar cells except near the openings of the glands where a few partially depleted goblet cells were encountered. The work by KANAKOUDIS (1973) in the horse dealt mainly with the secretory, granule-containing surface columnar cells. Surface columnar cells near the openings of the glands contained large cytoplasmic vacuoles and lysosomal-like bodies.

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“…The work by KANAKOUDIS (1973) in the horse dealt mainly with the secretory, granule-containing surface columnar cells. The work by KANAKOUDIS (1973) in the horse dealt mainly with the secretory, granule-containing surface columnar cells.…”