Goblet Cells and Mucus Types in the Digestive Intestine and Respiratory Intestine in Bronze Corydoras (Callichthyidae: Teleostei)

Abstract

The structure and histochemical properties of the intestine in bronze corydoras (Corydoras aeneus), a stomach-containing teleost, are described, with emphasis on goblet cells and mucin types. The proximal intestine displayed a normal structure for teleosts, whereas the distal intestine was wide, translucent, thin-walled, richly vascularized and constantly filled with air, suggesting an important respiratory role. Goblet cells were common throughout the entire intestine and displayed a variable, but mainly faint metachromatic colour after toluidine blue. They were moderately coloured by alcian blue at both pH 2.5 and 0.2 and displayed no colour after periodic acid followed by Schiff's solution (PAS), but a distinct purple-brown colour after high iron diamine followed by alcian blue (pH 2.5). Together, these results suggest that the mucin in the intestine goblet cells consists mainly of sulphated proteoglycans. Further, the results from the present lectin and neuraminidase tests suggest that these mucins contain much N-acetylglucoseamines and some N-acetylgalactosamines and sialic acid, but seem to lack glucose and mannose. They also contain some galactose-N-acetylgalactosamines sequences, normally hidden by sialic acid. The distinct brush border and mucus layer on the epithelial cells in the respiratory intestine may indicate some digestive roles, such as absorption of water, ions and simple carbohydrates. As sulphated proteoglycans are tough and attract much water, this mucus may play important roles in the protection against mechanical and chemical damages and in the defence against micro-organisms throughout the entire intestine, but in the respiratory intestine it may impede significantly the oxygen uptake. However, as this part of the intestine usually contains no digesta, but is completely filled with air, frequently renewed by dry air from the atmosphere, and the main function of the mucus may be to protect the respiratory epithelium against a destroying and dangerous desiccation.

Histochemical and immunohistochemical characterization of rodlet cells in the intestine of two teleosts, Anguilla anguilla and Cyprinus carpio

“…() suggested that BG4 (6% mercuric chloride and 0.1% glutaraldehyde in 1% sodium acetate) is a better fixative for lectin histochemistry. Most studies on lectins (e.g., current study), however, used Bouin's fluid (Diaz, García, & Goldemberg, ; Marchetti et al., ; Neuhaus et al., ,) and/or neutral formaldehyde (Fiertak & Kilarski, ; Leknes, , ; Redondo and Alvarez‐Pellitero, ) as fixatives. It is well known that fixation can create or destroy chemical bonds that alter the normal configuration of carbohydrates and thus alter their reactivity to lectins.…”

Quest for breathing: proliferation of alveolar type 1 cells

“…At the same time, numerous capillary vessels are located between the bodies of the epithelial cells (Jasiński 1973 ; Satora 1998 ; Satora and Winnicki 2000 ). Some GBF can adjust almost 50% of the digestive tract into an additional respiratory organ under hypoxic water conditions (Leknes 2015 ). Also, AT2 cells of varied shape and with numerous lamellar bodies (Fig.…”