Histochemical distribution of enzymes in the small intestine of young milk-fed calves

Rice protein-concentrate meal as a potential dietary ingredient in practical diets for blackspot seabream Pagellus bogaraveo: a histological and enzymatic investigation

Field and laboratory studies were conducted to evaluate the intestinal responses to partial replacement of fish meal with rice protein concentrate (RPC) in practical diets for blackspot seabream Pagellus bogaraveo. Two experimental diets were formulated to be isoproteic and isoenergetic with an increasing level of RPC (20 and 35%, respectively) and were tested against a fish meal-based control diet (RPC0). The diets showed similar features for growth performances and both intestinal histology and digestive enzymes. This study confirmed that RPC does not induce intestinal mucosa alterations in this fish. The dietary RPC supplement caused a significant increase in trypsin activity, whereas lipase activity was reduced.

Filter Function and Immune Complex Trapping in Splenic Ellipsoids

The role of splenic ellipsoids in the trapping of particulate material and immune complexes was investigated in mink (Mustela vison). The ellipsoids were prominent, with typical features such as a permeable endothelium and a discontinuous basement membrane surrounded by a sheath of macrophages and reticular cells. Ellipsoidal trapping of circulating particles was demonstrated 10 min after intracardiac injection of colloidal carbon and fluorescent microspheres. Preformed peroxidase-antiperoxidase immune complexes were detected in ellipsoids 10 min and also 1 h after intracardiac injection. Erythrocytes were frequently observed in the ellipsoidal sheath, and many phagocytized fragments of erythrocytes were found in the ellipsoidal macrophages. It was concluded that mink ellipsoids are effective blood filters with a role in retention of circulating particulate material, and that mammalian splenic ellipsoids also have the ability to trap immune complexes.

Phosphatase activities of rat intestinal enterocytes and their relation to diverse luminal pH, with special references to the possible localization of phytase along the brush border membrane

Phosphatase activities associated with the intestinal brush border membrane (BBM) of the rat were examined histochemically in relation to the characteristic environment of the intestine, where luminal pH fluctuates drastically between alkaline and acid pH ranges. Special attention was given to intestinal alkaline phosphatase (IALP) and phytase on the BBM. Whole body fresh-frozen sections of young rats and their rapidly frozen and freeze-substituted small intestines, embedded in Technovit 7100, were processed for the histochemical demonstration of phosphatase activity at three different pH values (9.2, 7.3, and 5.2), representing the deviation of luminal pH in vivo. Either an azo-dye method or lead-salt method was employed using naphthol AS-MX phosphate and ATP as substrate, respectively. With the azo-dye method, intense phosphatase reactions were demonstrated along the BBM at all three pH ranges. Phosphatase reactions of the BBM at pH 9.2 and 7.3 were abolished by L(+)-phenylalanine, heat pre-treatment, and EDTA chelation although some reaction remained at pH 7.3 after the treatment with EDTA or L(+)-phenylalanine. Phosphatase reactions of the BBM at pH 5.2 were resistant to L(+)-phenylalanine, L(+)-tartrate, PCMB and EDTA chelation, implying that the characteristics of the enzyme responsible for phosphohydrolysis at acid pH values differed from those at higher pH values. The lead-salt method in which ATP was used as substrate revealed intense reactions--which were dependent on Mg++ and stimulated by Ca++ and resistant to L(+)phenylalanine--to be localized along the BBM at alkaline and neutral pH values, but not at acid pH values. In vitro experiments showed progressive hydrolysis of naphthol AS-MX phosphate by purified phytase at pH 5.2, in a dose-dependent manner, and suggested the possible involvement of phytase in the phosphatase reactions of the BBM at acid pH. These data indicate that the phosphatase reactions at alkaline and neutral pH values, associated with the BBM of the rat intestine, represent IALP and Mg++/ Ca++-ATPase, while those at acid pH appear to correspond to phytase activity, something which has not been demonstrated by histochemical methods despite the availability of extensive data based on biochemical analyses.

Potassium-dependent p-nitrophenyl phosphatase and carbonic anhydrase reactivities suggest that lymphoid follicles in the large intestine of lambs are lined with a uniform type of epithelial cell distinct from the absorptive epithelium

The epithelium covering the large intestinal lymphoid follicles in fetal and postnatal lambs was examined for potassium-dependent p-nitrophenyl-phosphatase (K(+)-NPPase), carbonic anhydrase, magnesium-dependent adenosine triphosphatase (Mg(2+)-ATPase) and acid phosphatase. Reactivities for these enzymes indicated a homogenous population of cells in the follicle-associated epithelium (FAE), distinct from the absorptive epithelium. There were essentially no differences in the enzyme reactivities of the large intestinal FAE between fetuses in late gestation and postnatal lambs. The FAE showed a weak reaction for K(+)-NPPase and a variable staining for Mg(2+)-ATPase and acid phosphatase. In contrast, the adjacent absorptive epithelium demonstrated strong reactions for these enzymes. Carbonic anhydrase gave a strong reaction at the luminal and apparent basolateral cell borders of the large intestinal FAE. This distribution of reactivity for carbonic anhydrase resembled that found in the ileal FAE. In absorptive epithelial cells, only the luminal cell border reacted strongly for carbonic anhydrase. Serial sections of large intestinal tissue showed a variation in the basolateral staining of FAE from one section to the next, a finding which suggested that the reaction may be associated with transcytosis. The lymphoid follicles and domes of the large intestine showed a variable granular pattern of carbonic anhydrase staining, which also suggested a dependence on epithelial transcytosis.

An ultrastructural and cytochemical study of the pulmonary lesions and multinucleate giant cells in porcine dermatosis vegetans

The pulmonary lesions and multinucleate giant cell formations in porcine dermatosis vegetans were studied ultrastructurally and cytochemically in seven affected pigs that ranged from one to 120 days of age. At birth, no pulmonary lesions were observed. By seven days of age, there was a moderate infiltration of monocytes/macrophages in the alveoli and interstitium. These changes progressed, and by two weeks of age there was pronounced infiltration of macrophages and lymphocytes in the alveoli. Close apposition of macrophages and lymphocytes was observed, and cellular contact was demonstrated. By three to four weeks of age, small aggregates with epithelioid cells, macrophages, and lymphocytes resembling granulomas were present. In an older pig, aged four months, the inflammatory changes waned. Large macrophages, and large and small multinucleate cells shared common morphological characteristics of cytoplasm endowed with organelles, primary and secondary lysosomes, Golgi profiles, and granular endoplasmic reticulum. Cytochemically, macrophages and MGCs were positive for acid phosphatase. The present study showed that the initial pulmonary changes share morphological characteristics with a granulomatous inflammatory response, and evolve into small granulomas with macrophages, epithelioid cells and lymphocytes. Morphologically, these changes share characteristics with epithelioid cell granulomas. Macrophages and MGCs share common ultrastructural traits, and are positive for acid phosphatase. MGCs seem to evolve in the course of the granulomatous inflammatory response and are probably of monocyte/macrophage origin.

Organization of ruminant Peyer's patches as seen with enzyme histochemical markers of stromal and accessory cells

Five enzyme histochemical reactions were used to characterize calf, goat kid and lamb Peyer's patches. 5'-nucleotidase and acid phosphatase gave a reticular pattern of staining in follicular and interfollicular regions, respectively. Different subpopulations of fibroblastic reticulum cells were suggested for the T cell area, the dome/corona region, and the follicle capsule. The T cell area and the neck portion of the follicle showed a positive reticular reaction with alkaline phosphatase and non-specific esterase. Follicular dendritic cells were positive for Mg2(+)-ATPase in the follicle centre, contrasting with a negative reaction in the periphery. Dendritic cells prevalent in the dome and T cell area showed a Mg2(+)-ATPase reactivity. Macrophages were stained with non-specific esterase and acid phosphatase. No principal differences were found in cell populations between the three species or between fetuses in late gestation and postnatal animals, although the size of the respective compartments varied.

Histochemical distribution of potassium-dependent p-nitrophenylphosphatase in the calf intestine

Potassium-dependent p-nitrophenylphosphatase was demonstrated, using the lead citrate method of Mayahara et al. (1980), in frozen sections of calf intestine fixed in formalin-calcium. The calcium chloride included in the fixative was shown to improve the localization of the reaction markedly. The phosphatase activity observed in the basolateral cell borders of the surface epithelium in the small intestine and colon was reduced by 10 mM ouabain and by substitution of sodium ions for potassium ions, confirming that the reaction was representative for the second step in the Na+/K+-ATPase complex. The intensity of the basolateral enzyme reaction was in the order: colon greater than duodenum, proximal jejunum greater than ileum greater than middle and distal jejunum. The crypts reacted weakly. A reaction in the brush border of the proximal jejunum and duodenum and a granular reaction in the supranuclear cytoplasm of the epithelial cells was not influenced by ouabain. The staining pattern for the potassium-dependent phosphatase differed from that of alkaline phosphatase and Mg2+-dependent ATPase, which gave a reaction that was restricted to the brush border.

Enzyme histochemistry of the small intestinal mucosa in experimental infections of calves with rotavirus and enterotoxigenic Escherichia coli

The effect of rotavirus and enterotoxigenic Escherichia coli, administered in different sequences, on alkaline and acid phosphatase, leucinaminopeptidase, beta-galactosidase, and succinicdehydrogenase of the intestinal mucosa of cesarian-derived, colostrum-deprived calves was investigated. Decrease in enzyme activity was most prominent in dual infections; it also occurred in parts of the small intestine in monoinfected animals. Increases in enzyme activity involved totally either one or all tissue compartments (crypt, basal villus area, villus tips). Increased activity was present in enteric mucosae that were either not affected or were only slightly affected by rotavirus or enterotoxigenic E. coli. We interpret the increase in enzyme activity as an adaptation of the enteric mucosa to maintain the absorptive function.

Is the ileo-caecal Peyer's patch in ruminants a mammalian "bursa-equivalent"?

The ileo-caecal Peyer's patch (IPP) in young ruminants shows prenatal maturation and involution in young age, mainly like the thymus (1, 7, 8). In an examination of three-week-old calves IPP had features compatible with an essentially thymus-independent, primary function, different from that of jejunal patches. Features of IPP included very high lymphoblastic activity despite scarcity of coronal cells and few high endothelial venules in the interfollicular tissue.

Indigestion in young calves. VI. Studies of diarrheic calves fed milk replacers made of normal and heat-treated skim milk and whey powder

Diarrhea occurred in 12 pre-ruminant calves after the introduction of milk replacers. Six of the calves were fed a replacer made of normally treated skim milk and whey powder, while the other 6 got a replacer made of heat-treated powders, although otherwise similar to that of the first group. Abomasal curd formation was deficient in calves fed for 9 or 17 days on the heat-treated replacer (4 of 6 calves). Otherwise, no clear differences between the calves given normally treated and heat-treated replacer occurred, as regards diarrhea, bacteriological, virological, and pathomorphological findings in the intestinal tract. Rotavirus and chlamydial infections were indicated and considered as the major cause of the diarrheic condition, although bacteria, including coliforms and Pseudomonas aeruginosa, may have contributed. The milk replacers may have been involved was provoking factors.

Pathomorphology of the intestinal mucosa in diarrheic calves

The intestinal mucosa was examined in twelve 2–5-week-old calves with a spontaneous intestinal disorder, 8 with diarrhea and 4 convalescents. The calves were fed a defined milk replacer. Light microscopy including morphometry, showed villous atrophy and crypt elongation. Villous epithelial cells had decreased height, and epithelial cells of the posterior small intestine contained an increased amount of fat droplets. Accumulation of neutrophils in crypts was frequent. Scanning electron microscopy revealed blunt villi with increased numbers of necrotic cells in the extrusion zone at the tips of the villi. The convalescents had generally milder changes, particularly in the anterior small intestine. The probable etiological factors included a rotavirus and chlamydial infection, and it is concluded that these agents together with other possible noxious influences were responsible for the increased necrobiosis of apical senescent villous epithelial cells, resulting in villous atrophy and crypt hyperplasia.

An enzyme histochemical investigation of the intestinal mucosa in diarrheic calves

Selected enzymes were examined in the small intestine of twelve 2–5 week-old calves, 8 with diarrhea and 4 convalescents. The diarrheic calves showed a reduction of enzyme reactions mainly in the duodenum and middle small intestine, and the crypt reactions appeared most severely affected. In the duodenum, villous alkaline phosphatase, adenosine triphosphate-(ATP)-splitting enzyme, and β-D-galactosidase were reduced in 3 calves; the reaction in the corresponding crypts was decreased in 6 calves for the ATP-splitting enzyme and in 4 calves for the β-D-galactosidase. Six calves showed decrease of villous brush border acid phosphatase, and 3 of villous non-specific esterase. In the middle jejunum, villous ATP-splitting enzyme was reduced in 3 calves, while 5 showed decrease of the corresponding crypt reaction. Convalescents had no enzyme reduction in the duodenum, whereas 1 showed marked reduction of the ATP-splitting enzyme and aminopeptidase in the middle and posterior jejunum. The decreased enzyme reactions in the present material may be caused by immaturity of epithelial cells associated with regenerative crypt hyperplasia and/or microbial destruction of enzymes.

The epithelium covering Peyer's patches in young milk-fed calves. An ultrastructural and enzyme histochemical investigation

Between the ordinary villi over Peyer’s patches there are small domes or “pseudovilli” caused by bulges in the lymphoid tissue. These “pseudovilli” were studied in 5 healthy milk-fed, about 3-week-old, pre-ruminant calves. Scanning electron microscopy revealed that the “pseudovilli” were covered by a specialized follicle associated epithelium (FAE). The FAE had poorly developed microvilli and often extensive folding of the cell surface close to the cell borders. By transmission electron microscopy the tips of the marginal folds of the FAE seemed to fuse, probably in the process of enfolding bulk material from the lumen. The FAE apical cytoplasm contained numerous thick-walled and bristle-coated invaginations, tubules and vesicles indicative of micropinocytosis. Multivesicular bodies and large vacuoles were frequent. Indications of extracellular unloading of residual bodies were found. Intraepithelial lymphocytes tended to group together, and some were rich in rough endoplasmic reticulum. Enzyme histochemistry showed weak reactions of adenosine triphosphate splitting enzyme and aminopeptidase in the FAE luminal cell border. Cytoplasmic acid phosrphatase showed a marked basal-apical decrease along the “pseudovillus” probably caused by the onset of endocytosis. The results of this study appear compatible with the concept that the FAE takes up macromolecules from the lumen by pinocytosis and sensitizes lymphocytes.