Effect of ayurvedic medicines on beta-glucuronidase activity of Brunner's glands during recovery from cysteamine induced duodenal ulcers in rats

Biochemical and histochemical studies revealed decreased beta-glucuronidase activity in the Brunner's glands of duodenal ulcerated rats. The enzyme activity showed gradual increase during recovery. Rats treated with a mixture of Ayurvedic medicines (Glycyrrhiza glabra, Terminalia chebula, Piper longum and Shanka Bhasma) recovered faster with concomitant increase in beta-glucuronidase activity in the Brunner's glands. It can be concluded that Ayurvedic medicines used do not act as antacid but improve the secretory status of Brunner's glands involved in the protection against duodenal ulcer.     

The trypsin activity in the chyme and parietal layer of the mucus in experimental exclusion of the Brunner's gland section of the duodenum in rats]

The duodenal glands secretion into intestine was excluded by surgical ablation or ligation of Brunner's glands region. The trypsin activity in chyme and adherent mucous layer was reduced following these manipulations. Possible reasons for changes established are discussed.     

Brunner's glands: a structural, histochemical and pathological profile

Brunner's glands are unique to mammalian species and in eutherians are confined primarily to the submucosa of the proximal duodenum. In the majority of species examined, they begin at the gastrointestinal junction and extend for variable distances distally in the wall of the proximal small intestine. Ducts of individual glands empty either directly into the intestinal lumen or unite with overlying intestinal glands (crypts of Lieberkühn) dependent on the species. Secretory units of Brunner's glands consist of epithelial tubules that show frequent distal branchings. The secretory units, with the exception of those found in rabbits and horses, consist primarily of a mucin producing cell type. However, other cell types normally associated with the overlying intestinal epithelium may be encountered scattered within the secretory units reflecting the developmental origin of these glands. Secretion from Brunner's glands contributes to a layer of mucus that forms a slippery, viscoelastic gel that lubricates the mucosal lining of the proximal intestinal tract. The unique capacity of this mucus layer to protect delicate underlying epithelial surfaces is due primarily to the gel-forming properties of its glycoprotein molecules. Mucin glycoproteins produced by Brunner's glands consist primarily but not exclusively of O-linked oligosaccharides attached to the central protein core of the glycoprotein molecule. Human Brunner's glands produce class III mucin glycoproteins and are thought to be the product of mucin gene MUC6 which is assigned to chromosome 11 (11p15-11p15.5 chromosome region). In addition to mucin glycoproteins and a limited amount of bicarbonate, numerous additional factors (epidermal growth factor, trefoil peptides, bactericidal factors, proteinase inhibitors, and surface-active lipids) have been identified within the secretory product of Brunner's glands. These factors, incorporated into the mucus layer, guard against the degradation of this protective barrier and underlying mucosa by gastric acid, pancreatic enzymes, and other surface active agents associated with this region. Yet other factors produced by Brunner's glands function to provide active and passive immunological defense mechanisms, promote cellular proliferation and differentiation, as well as contribute factors that elevate the pH of luminal contents of this region by promoting secretion of the intestinal mucosa, pancreatic secretion and gall bladder contraction. Additional insights concerning the role of Brunner's glands in the mammalian gastrointestinal tract as well as their possible evolution in this class of vertebrates have been gained from a basic understanding of their pathobiology.     

Relationship between digestibility and secondary structure of raw and thermally treated legume proteins: a Fourier transform infrared (FT-IR) spectroscopic study

The secondary structure of proteins in legumes, cereals, milk products and chicken meat was studied by diffuse reflectance infrared spectroscopy in the region of the amide I band. Major secondary structure components ( β-sheets, random coil, α-helix, turns), together with the low- and high-frequency side contributions, were resolved and related to the in vitro digestibility behaviour of the different foods. A strong inverse correlation between the relative spectral weights of the β-sheet structures and in vitro protein digestibility values was measured. Structural modifications in legume proteins induced by autoclaving were monitored by the changes in the amide I spectra. The results indicate that the β-sheet structures of raw legume proteins and the intermolecular β-sheet aggregates, arising upon heating, are primary factors in adversely affecting the digestibility.     

Nutritive value of leaf protein coagulum and cereals mixtures

Experiments were performed to compare the composition and nutritive value of mixtures containing leaf protein coagulum from lucerne with cereals (ground barley, ground wheat and wheat bran), with non-processed cereals alone or with the addition of separately-dried leaf protein. The chemical composition of mixtures and amino acid composition of their proteins were determined by conventional methods. The biological value and true digestibility of cereals and mixture proteins were determined on rats by the Thomas-Mitchell balance method.The biological values of mixture proteins were higher, but their digestibility was lower, than those of cereals alone. Generally, better results were obtained when cereals were mixed with separately-dried leaf protein and with barley rather than wheat.     

The role of Brunner's glands in the mucosal protection of the proximal part of duodenum

In the course of a prospective study authors examined the role of the hyperplasia of Brunner's glands in the mucosal protection of proximal part of duodenum in patients with peptic ulcer, chronic pancreatitis and chronic renal insufficiency. Their method for this study was the histological examination of the endoscopic biopsy specimens. The hyperplasia of Brunner's glands occurs with significant frequency in all the three examined groups of patients, while we found it less frequently in the controls. Hyperplasia of Brunner's glands is one of the protective mechanisms of the organism, which serves the protection of the duodenal mucosa between the pyloric ring and the papilla of Vater, against the damaging effect of the hydrochloric acid.     

Identification of a Low Digestibility δ-Conglutin in Yellow Lupin (Lupinus luteus L.) Seed Meal for Atlantic Salmon (Salmo salar L.) by Coupling 2D-PAGE and Mass Spectrometry

The need of quality protein in the aquaculture sector has forced the incorporation of alternative plant proteins into feeding diets. However, most plant proteins show lower digestibility levels than fish meal proteins, especially in carnivorous fishes. Manipulation of protein content by plant breeding can improve the digestibility rate of plant proteins in fish, but the identification of low digestibility proteins is essential. A reduction of low digestibility proteins will not only increase feed efficiency, but also reduce water pollution. Little is known about specific digestible protein profiles and/or molecular identification of more bioavailable plant proteins in fish diets. In this study, we identified low digestibility L. luteus seed proteins using Atlantic salmon (Salmo salar) crude digestive enzymes in an in vitro assay. Low digestibility proteins were identified by comparing SDS-PAGE banding profiles of digested and non-digested lupin seed proteins. Gel image analysis detected a major 12 kDa protein band in both lupin meal and protein isolate digested products. The 12 kDa was confirmed by 2D-PAGE gels and the extracted protein was analyzed with an ion trap mass spectrometer in tandem mass mode. The MS/MS data showed that the 12 kDa low digestibility protein was a large chain δconglutin, a common seed storage protein of yellow lupin. Comparison of the protein band profiles between lupin meal and protein isolates showed that the isolatation process did not affect the low digestibility of the 12 kDa protein.     

Nutritional study of two Brazilian soybean (Glycine max) cultivars differing in the contents of antinutritional and toxic proteins

The research was conducted with two different recently released Brazilian soybean cultivars (Rio Balsas and Bays) to evaluate whether there is any correlation between the different levels of antinutritional and/or toxic proteins in the cultivars and their nutritive value as sources of protein for monogastric animals (rats). Furthermore, it is discussed, for the first time, the role of the dietary soyatoxin on the performance of rats fed on diets containing soyatoxin-rich (cv. Bays) and soyatoxin-free (cv. Rio Balsas) soybean cultivars. Feeding rats with diets containing raw soybean cultivars showed a lower growth rate, net protein utilization and digestibility, a much higher dry matter and nitrogen excretion and macroscopic alterations in internal organs when compared to rats fed on egg-white protein. The nutritional parameters measured for the diet based on raw Bays cultivar were poorer than those of the diet prepared with Rio Balsas. In the raw soybeans, trypsin inhibitor and lectin, and urease to a lesser extent, significantly affected at different fashion the soybean protein utilization. Heating treatment of the Bays seeds increased the growth rate, NPU, in vivo protein digestibility and practically eliminated or attenuated all the organ alterations observed. This study might be helpful in the choice of safe and nutritious soybean cultivars.     

Effect of 3,4-toluenediamine on output from in situ rat Brunner's glands pouches.

Duodenal and gastric glandular mucosal damage have been observed 24 hr following single subcutaneous doses of 3,4-TDA in fed, unrestrained rats. 3,4-TDA significantly reduced secretion from in situ Brunner's glands pouches in pentobarbital anesthetized rats. The reduction in volume output with a definitely duodenal ulcerogenic dose of this compound was more than twice that observed with a minimally ulcerogenic dose, suggesting a correlation between the duodenal ulcerogenic and duodenal anti-secretory activities of this compound. The animal model described in this communication should facilitate experimentation to establish the inhibitory effect of compounds on the output of protective fluids from the proximal duodenum.     

Nutritional value of proteins from edible seaweed Palmaria palmata (dulse)

Palmaria palmata (Dulse) is a red seaweed that may be a potential protein source in the human diet. Its protein content, amino acid composition, and protein digestibility were studied with algae collected every month over a 1-year period. Significant variations in protein content were observed according to the season: The highest protein content (21.9 +/- 3.5%) was found in the winter-spring period and the lowest (11.9 +/- 2.0%) in the summer-early autumn period. Most of the essential amino acids were present throughout the year. After 6-hour in vitro digestion in a cell dialysis using porcine pepsin and porcine pancreatin, the digestibility of proteins from Palmaria palmata crude powder, represented by dialyzed nitrogen, was estimated at 29.52 +/- 1.47%. Relative digestibility was 56%, using casein hydrolysis as 100% reference digestibility. In vitro digestibility of proteins extracted in water was analyzed by sodium dodecylsulfate polyacrylamide gel electrophoresis using either bovine trypsin, bovine chymotrypsin, pronase from Streptomyces griseus, or human intestinal juice. Dulse proteins were hydrolyzed to a limited extent, which confirmed a rather low digestibility. Hydrolysis rate was higher with trypsin and lower with chymotrypsin compared with the two other enzymatic systems, pronase and intestinal juice, respectively. The association of algal powder and protein extract to casein and bovine serum albumin, respectively, produced a significant decrease in the hydrolysis rate of the standard proteins. In conclusion, the digestibility of Palmaria palmata proteins seems to be limited by the algae non-proteic fraction.     

Immunohistochemical demonstration of alpha1,4-N-acetylglucosaminyltransferase that forms GlcNAcalpha1,4Galbeta residues in human gastrointestinal mucosa.

alpha1,4-N-acetylglucosaminyltransferase (alpha4GnT) is a glycosyltransferase that mediates transfer of GlcNAc to betaGal residues with alpha1,4-linkage, forming GlcNAcalpha1--> 4Galbeta-->R structures. In normal human tissues, glycoproteins having GlcNAcalpha1-->4Galbeta-->R structures at non-reducing terminals are exclusively limited to the mucins secreted from glandular mucous cells of gastric mucosa, Brunner's gland of duodenum, and accessory gland of pancreaticobiliary tract. Recently, we have isolated a cDNA encoding human alpha4GnT by expression cloning. Although alpha4GnT plays a key role in producing this unique glycan in vitro, the actual localization of alpha4GnT was not determined. In this study we examined the localization of alpha4GnT in various human tissues, including gastrointestinal mucosa, using a newly developed antibody against human alpha4GnT. The specificity of the antibody was confirmed by analyses of human gastric adenocarcinoma AGS cells transfected by alpha4GnT cDNA. Expression of alpha4GnT was largely associated with the Golgi region of mucous cells that produce the mucous glycoproteins having GlcNAcalpha1-->4Galbeta-->R, such as the glandular mucous cells of stomach and Brunner's gland. An immunoprecipitation experiment disclosed that two distinct mucin proteins, MUC5AC and MUC6 present in gastric mucin, carried the GlcNAcalpha1-->4Galbeta-->R structures. These results indicate that alpha4GnT is critical to form the mucous glycoproteins having GlcNAcalpha1-->4Galbeta-->R on MUC6 and MUC5AC in vivo.(J Histochem Cytochem 49:587-596, 2001)     

Neural pathways regulating Brunner's gland secretion in guinea pig duodenum in vitro

This study examined the neural pathways innervating Brunner's glands using a novel in vitro model of acinar secretion from Brunner's glands in submucosal preparations from the guinea pig duodenum. Neural pathways were activated by focal electrical stimulation and excitatory agonists, and videomicroscopy was used to monitor dilation of acinar lumen. Electrical stimulation of perivascular nerves evoked large dilations that were blocked by TTX (1 microM) or the muscarinic receptor antagonist 4-diphenylacetoxy-N-(2-chloroethyl)-piperidine hydrochloride (1 microM). The nicotinic agonist 1,1-dimethyl-4-phenylpiperazinium iodide (100 microM) had no effect, and the nerve-evoked responses were not inhibited by hexamethonium (200 microM). Dilations were abolished in preparations from chronically vagotomized animals. Activation of submucosal ganglia significantly dilated submucosal arterioles but not Brunner's glands. Effects of electrical stimulation of perivascular and submucosal nerves were not altered by guanethidine. Capsaicin and substance P also dilated arterioles but had no effect on Brunner's glands. Cholinergic (choline acetyltransferase-immunoreactive) nerve fibers were found in Brunner's glands. These findings demonstrate that Brunner's glands are innervated by cholinergic vagal fibers but not by capsaicin-sensitive or intrinsic enteric nerves.     

Subcellular redistribution of AQP5 by vasoactive intestinal polypeptide in the Brunner's gland of the rat duodenum

Aquaporin (AQP)5, an exocrine-type water channel, was detected in the rat duodenum by Western blot analysis, and was localized by immunohistochemistry in the secretory granule membranes as well as in the apical and lateral aspects of the plasma membrane of Brunner's gland cells. Incubation of duodenal slices with vasoactive intestinal polypeptide (VIP) in vitro significantly increased the amount of AQP5 in the apical membrane fraction in a dose- and time-dependent manner with the amount reaching a plateau at 100 nM VIP and becoming near maximal after a 30-s incubation. Protein kinase inhibitors, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7, 50 muM), and N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H-89; PKA-specific, 1 muM) blocked this increase, but PKC-specific inhibitor calphostin C did not, implying the involvement of PKA but not PKC in this cellular event. Intravenous injection with VIP (40 mug/kg body wt) provoked dilation of the lumen of the Brunner's gland at 2 and 7 min and increased the staining intensity of AQP5 in the apical and lateral membranes. AQP1 (both nonglycosylated and glycosylated forms) was also found to localize in the apical and basolateral membranes of cells of Brunner's gland. VIP, however, did not provoke any significant change in the AQP1 level in the apical membrane, as judged from the results of the above in vitro and in vivo experiments. These results suggest that VIP induced the exocytosis of granule contents and simultaneously caused translocation of AQP5 but not of AQP1 to the apical membrane in Brunner's gland cells.     

Nutritional evaluation of extruded faba bean (Vicia faba L.) as a protein supplement in cereals based diet in rats

The quality of extruded faba bean (EFB) (Vicia faba L.) as a protein supplement in cereals diet was evaluated. Growth rate and protein efficiency ratio was better in 20% EFB blended dietary group of rats than those fed either on cereals alone or at 40% EFB supplementation. Subsequent studies on digestibility co-efficient, biological value, net protein utilization and net protein ratio also confirmed biological utilization of EFB proteins in a better way at low level (20%).     

Effects of caecectomy in the young adult female rat on digestibility of food offered ad libitum and in restricted amounts.

Caecectomized and sham-operated rats were fed a laboratory chow ad libitum and the effects of caecectomy on the digestibility of the food were studied. Compared with sham-operated controls, caecectomized rats showed a decrease in apparent digestibiltiy of organic matter from 77.8 to 73.0%, of crude protein from 83.0 to 79.4%, and of 'carbohydrate' from 74.6 to 69.0%. However, faecal water content increased from 41.6 to 54.8%. 51Cr-labelled EDTA was excreted faster in the faeces after caecectomy. The colon partly adapted to the loss of caecal mucosa by increased length and thus mucosal surface area. In a second concurrent experiment the effect of caecectomy on the apparent digestibility of food during food restriction was studied. Six caecectomized rats, comparable in all respects to those used in the first study, were fed the laboratory chow ad libitum for 3 weeks. They were then fed submaintenance amounts of food to achieve body weight losses of 40--50% and to maintain these low weights for 4 weeks. Finally, they were again fed ad libitum for 3 weeks. During the period of restriction the apparent digestibility of organic matter increased from 72.7 to 75.4%. This was largely due to the increased apparent digestibility of crude protein which rose from 78.4 to 81.9%. Digestibility coefficients returned to control values immediately upon refeeding ad libitum.     

Exocrine secretion of epidermal growth factor from Brunner's glands. Stimulation by VIP and acetylcholine

Brunner's glands of the duodenum are innervated by cholinergic and VIP-ergic nerves, and the glands have been shown to contain epidermal growth factor (EGF). In this study the effect of VIP and acetylcholine (Ach) on secretion of EGF from Brunner's glands was investigated in the rat. Intravenous infusion of VIP stimulated the flow rate of duodenal secretion, an effect which was inhibited by atropine. Ach alone did not significantly increase flow rate, and combined infusion of VIP and Ach induced the same flow as VIP alone. Concentration of EGF in duodenal secretion was increased by infusion of Ach, and this effect was potentiated by VIP. Infusion of VIP alone did not influence EGF concentration. EGF output from Brunner's glands was significantly stimulated by i.v. infusion of VIP and of Ach and combined infusion further increased EGF output. The study has demonstrated exocrine secretion of EGF from Brunner's glands, and it is suggested that stimulation is mediated by interaction of neuronal VIP and Ach.     

Digestibility of extruded proteins and metabolic transit of N ε -carboxymethyllysine in rats

Milk proteins are frequently used as supplements in fortified foods. However, processing produces chemical changes which likely affect the nutritional advantage. This study was intended to explore the possible difference in digestibility between extruded and non-extruded caseins and how the dietary N ^ε -carboxymethyllysine (CML) is metabolised. Normal rats were randomized into either an extruded protein diet (EP) or the same with unextruded proteins (UEP), for two periods of 2 weeks at 7 to 9 and 11 to 13 weeks of age. However, no difference in protein digestibility was detected between the two diets, either in young or in adult animals, despite a 9.4-fold higher level of CML and an 8.5-fold higher level of lysinoalanine in the EP than in the UEP. No diet-related changes were observed in plasma CML, either protein bound or free. Amounts of 38 and 48 % of the orally absorbed CML were excreted in urine and faeces, respectively, in UEP-fed rats. Lower rates of excretion were found in the EP-fed rats (23 and 37 %, respectively). A second animal study using a single oral dose of free CML (400 μg/rat) was set up to measure the systemic concentration of CML every hour from 0 to 4 h. It revealed that protein-bound CML was not affected by the oral dose of CML, and the highest free CML level found in the circulation was 600 ng/mL. Extruded proteins, therefore, appear to be well digested, and CML rapidly eliminated. Since its elimination is, however, incomplete, the question of its biodistribution and metabolism remains open.     

Decreasing Effect of Chitosan on the Apparent Fat Digestibility by Rats Fed on a High-fat Diet

We investigated the effects of various dietary fibers or their likenesses on the apparent fat digestibility by rats fed on a high-fat diet. Each of 23 different fibers was added at 5% (w/w) to a purified diet containing 20% (w/w) corn oil. The rats were fed these diets for 2 weeks, and the feces were collected from each animal during the last 3 days. When compared with cellulose (control), 10 of the tested fibers significantly increased the fecal lipid excretion. Among these fibers, chitosan markedly increased the fecal lipid excretion and reduced the apparent fat digestibility to about a half relative to the control. The apparent protein digestibility was not greatly affected by chitosan. The fatty acid composition of the fecal lipids closely reflected that of the dietary fat. These results suggest that chitosan has potency for interfering with fat digestion and absorption in the intestinal tract, and for facilitating the excretion of dietary fat into the feces.     

mRNA expression of pancreatic enzyme precursors and estimation of protein digestibility in first feeding larvae of the Japanese flounder,Paralichthys olivaceus

An understanding of digestibility in marine fish larvae is required to formulate a diet to replace zooplankton. Using flounder, this study was aimed at determining which digestive enzymes are synthesized in the larval pancreas, and how the proteins are cleaved in the digestive canal. Whole mount in situ hybridization indicated that the mRNA of all digestive enzyme precursors examined, including trypsin, chymotrypsin, elastase, carboxypeptidase A and B, and lipase, was expressed in the pancreas of first feeding larvae at 3 days post-fertilization. In the larvae before differentiation of the stomach, protein digestion in the digestive canal mainly depends on pancreatic proteases. So, to evaluate protein digestibility in the larval digestive canal, the digestion of proteins by pancreatic extract was monitored by gel electrophoresis. It was indicated that thyroglobulin, albumin and lactate dehydrogenase were rapidly cleaved to polypeptide fragments, but ferritin and catalase exerted resistance to proteolysis, suggesting that digestibility in the larval digestive canal differs depending on protein species.     

A novel in vitro model of Brunner's gland secretion in the guinea pig duodenum

A novel in vitro model that combined functional and morphological techniques was employed to directly examine pathways regulating Brunner's gland secretion in isolation from epithelium. In vitro submucosal preparations were dissected from guinea pig duodenum. A videomicroscopy technique was used to measure changes in luminal diameter of glandular acini as an index of activation of secretion. Carbachol elicited concentration-dependent dilations of the lumen (EC(50) = 2 microM) by activating muscarinic receptors on acinar cells. Ultrastructural and histological analyses demonstrated that dilation was accompanied by single and compound exocytosis of mucin-containing granules and the accumulation of mucoid material within the lumen. Inflammatory mediators (histamine, PGE(1), PGE(2)) and intestinal hormones (CCK, gastrin, vasoactive intestinal polypeptide, secretin) also stimulated glandular secretion, whereas activation of submucosal secretomotor neurons by 5-hydroxytryptamine did not. This study directly demonstrates that multiple hormonal, inflammatory, and neurocrine agents activate Brunner's glands, whereas many have dissimilar effects on the epithelium. This suggests that Brunner's glands are regulated by pathways that act both in parallel to and in isolation from those controlling epithelial secretion.