Intestinal Glycoproteins Research Articles

MUC13 negatively regulates tight junction proteins and intestinal epithelial barrier integrity via protein kinase C.

Glycosylated mucin proteins contribute to the essential barrier function of the intestinal epithelium. The transmembrane mucin MUC13 is an abundant intestinal glycoprotein with important functions for mucosal maintenance that are not yet completely understood. We demonstrate that in human intestinal epithelial monolayers, MUC13 localized to both the apical surface and the tight junction (TJ) region on the lateral membrane. MUC13 deletion resulted in increased transepithelial resistance (TEER) and reduced translocation of small solutes. TEER buildup in ΔMUC13 cells could be prevented by addition of MLCK, ROCK or protein kinase C (PKC) inhibitors. The levels of TJ proteins including claudins and occludin were highly increased in membrane fractions of MUC13 knockout cells. Removal of the MUC13 cytoplasmic tail (CT) also altered TJ composition but did not affect TEER. The increased buildup of TJ complexes in ΔMUC13 and MUC13-ΔCT cells was dependent on PKC. The responsible PKC member might be PKCδ (or PRKCD) based on elevated protein levels in the absence of full-length MUC13. Our results demonstrate for the first time that a mucin protein can negatively regulate TJ function and stimulate intestinal barrier permeability.

L-fucose reduces gut inflammation due to T-regulatory response in Muc2 null mice.

Fucose, the terminal glycan of the intestinal glycoprotein Mucin2, was shown to have an anti-inflammatory effect in mouse colitis models and modulate immune response due to macrophage polarization changes. In this study we evaluated the effect of 0.05% L-fucose supplementation of drinking water on immune parameters in the intestine of homozygous mutant Muc2-/-, compared to Muc2+/+ mice. To get into innate and adaptive immunity mechanisms of gut inflammation, we tested PrkdcSCIDMuc2-/- strain, Muc2 knockout on SCID background, that is characterized by lack of lymphocytes, in comparison with PrkdcSCID mice. We evaluated intestinal cytokine profiling, macrophage and eosinophil infiltration, and expression of Nos2 and Arg1 markers of macrophage activation in all strains. Markers of Th1, Treg and Th17 cells (Tbx21, Foxp3, and Rorc expression) were evaluated in Muc2-/- and Muc2+/+ mice. Both Muc2-/- and PrkdcSCIDMuc2-/- mice demonstrated increased numbers of macrophages, eosinophils, elevated levels of TNFa, GM-CSF, and IL-10 cytokines. In Muc2-/- mice we observed a wide range of pro-inflammatory cytokines elevated, such as IFN-gamma, IL-1b, IL-12p70, IL-6, M-CSF, G-CSF, IL-17, MCP-1, RANTES, MIP1b, MIP2. Muc2-/- mice demonstrated increase of Nos2, Tbx21 and Foxp3 genes mRNA, while in PrkdcSCIDMuc2-/- mice Arg1 expression was increased. We found that in Muc2-/- mice L-fucose reduced macrophage infiltration and IL-1a, TNFa, IFNgamma, IL-6, MCP-1, RANTES, MIP1b levels, decreased Nos2 expression, and induced the expression of Treg marker Foxp3 gene. On the contrary, in PrkdcSCIDMuc2-/- mice L-fucose had no effect on macrophage and eosinophil numbers, but increased TNFa, GM-CSF, IL-12p70, IL-6, IL-15, IL-10, MCP1, G-CSF, IL-3 levels and Nos2 gene expression, and decreased Arg1 gene expression. We demonstrated that anti-inflammatory effect of L-fucose observed in Muc2-/- mice is not reproduced in PrkdcSCIDMuc2-/-, which lack lymphocytes. We conclude that activation of Treg cells is a key event that leads to resolution of inflammation upon L-fucose supplementation in Muc2-/- mice.

Disordered Expression of Tight Junction Proteins Is Involved in the Mo-induced Intestinal Microenvironment Dysbiosis in Sheep.

To evaluate the molybdenum (Mo)-induced changes of intestinal morphology and the relationship of intestinal tight junction (TJ) proteins expression and intestinal barrier function, a total of 20 healthy sheep were randomly divided into five groups of four: 0, 5, 10, 20, and 50mg/kg BW/day Na2MoO4·2H2O were administrated in five groups named control group, Mo 5 group, Mo 10 group, Mo 20 group, and Mo 50 group, respectively. After 28days of Mo treatment, the duodenum, the jejunum, and the ileum tissue were collected. The histopathology and the developmental parameters were evaluated by hematoxylin-eosin staining. The intestinal epithelial cell DNA damage was detected by TdT-mediated dUTP nick end labeling assay. The intestinal glycoprotein and the goblet cells were analyzed by Alcian Blue-Periodic Acid-Schiff (AB-PAS) staining and PAS staining, respectively. TJ proteins were determined by immunofluorescence technology. Results showed that excessive Mo significantly decreased the small intestinal villus height (VH), crypt depth (CD), VH/CD, and mucosal thickness (P < 0.05 or P < 0.01) while induced the damage of DNA in small intestinal epithelial cells. Moreover, excessive Mo injured intestinal barrier function by decreasing the percent of glycoprotein distribution area (P < 0.05) and the relative density of intestinal goblet cells (P < 0.05). Mo treatment induced decreased (P < 0.01) expression of Zonula Occludens-1, Occludin, and Claudin-1. In conclusion, excessive Mo interfered with the expression of TJ proteins, inhibited intestinal epithelial development, and further aggravated the intestinal barrier function damage, leading to disturbing the small intestinal microenvironment balance.

Dietary Fucose Affects Macrophage Polarization and Reproductive Performance in Mice

Intestinal mucus protects epithelial and immune cells from the gut resident microorganisms, and provides growth-promoting factors as mucus-derived O-glycans for beneficial bacteria. A lack of intestinal protective mucus results in changes in the commensal microflora composition, mucosal immune system reprogramming, and inflammation. Previous work has shown that fucose, the terminal glycan chain component of the intestinal glycoprotein Mucin2, and fucoidan polysaccharides have an anti-inflammatory effect in some mouse models of colitis. This study evaluates the effect of fucose on reproductive performance in heterozygous mutant Muc2 female mice. We found that even though Muc2+/− females are physiologically indistinguishable from C57Bl/6 mice, they have a significantly reduced reproductive performance upon dietary fucose supplementation. Metagenomic analysis reveals that the otherwise healthy wild-type siblings of Muc2−/− animals have reduced numbers of some of the intestinal commensal bacterial species, compared to C57BL/6 mice. We propose that the changes in beneficial microflora affect the immune status in Muc2+/− mice, which causes implantation impairment. In accordance with this hypothesis, we find that macrophage polarization during pregnancy is impaired in Muc2+/− females upon addition of fucose. Metabolic profiling of peritoneal macrophages from Muc2+/− females reveals their predisposition towards anaerobic glycolysis in favor of oxidative phosphorylation, compared to C57BL/6-derived cells. In vitro experiments on phagocytosis activity and mitochondrial respiration suggest that fucose affects oxidative phosphorylation in a genotype-specific manner, which might interfere with implantation depending on the initial status of macrophages. This hypothesis is further confirmed in BALB/c female mice, where fucose caused pregnancy loss and opposed implantation-associated M2 macrophage polarization. Taken together, these data suggest that intestinal microflora affects host immunity and pregnancy outcome. At the same time, dietary fucose might act as a differential regulator of macrophage polarization during implantation, depending on the immune status of the host.

Lactobacillus fermentum strains of dairy-product origin adhere to mucin and survive digestive juices.

Introduction. There is an ever present need to isolate and characterize indigenous bacterial strains with potential probiotic health benefits for humans.Aim. Lactobacillus fermentum of dairy origin was focused because of its propensity to adhere to the intestinal glycoprotein, mucin.Methodology. The lactobacillus strains were screened for mucin adhesion, resistance to low pH and bile, autoaggregation, hydrophobicity, and survival in an in vitro digestion model. The cholesterol-lowering and oxalate-degrading effects of selected strains were also determined. Safety was assessed for haemolytic, mucinolytic and gelatinase activity, biogenic amine production, antibiotic resistance and phenol resistance. Expression of the 32-mmub adhesion-related gene was also measured following strain exposure to simulated gastrointestinal tract (GIT) digestion.Results. The selected mucin-adhesive strains were tolerant to acid (pH 3.0) and bile (0.25 %) and demonstrated >85 % survival following simulated human digestion in the presence of milk. The digestive treatment did not affect the adhesive potential of PL20, and PL27, regardless of the food matrix. The simulated digestion had less effect on their adhesion than on the type strain and it also did not correlate with the mmub gene expression level as determined by qPCR. The selected strains exhibited cholesterol removal (36-44 %) and degraded oxalate (66-55 %). Neither of these strains exhibited undesirable characteristics.Conclusion. These preliminary findings suggest a functionality in the two strains of L. fermentum with high colonization potential on GIT mucosal membranes and possible health-promoting effects. This prima facie evidence suggests the need for further studies to test these probiotic candidates as live biotherapeutic agents in vivo.

Effect of Fluoride on Small Intestine Morphology and Serum Cytokine Contents in Rats.

This study aimed to determine the effect of excessive fluoride (F) on the morphological characteristics of the small intestine and the contents of serum cytokines in rats. A total of 48 3-week-old healthy female Sprague-Dawley rats were randomly divided into four groups (n = 12). The control group was given deionized distilled water, while the F treatment groups were treated with water containing 25, 50, and 100mgF-/L. After 70days of treatment, the duodenum, the jejunum, and the ileum were collected to measure the developmental parameters and the distribution of intestinal glycoproteins, goblet cells, and mast cells through Pannoramic Viewer, Periodic Acid-Schiff (PAS) staining, Alcian blue and periodic acid-Schiff (AB-PAS) staining, and toluidine blue staining, respectively. The contents of cytokines, namely, interleukin (IL)-1β, IL-2, IL-6, and tumor necrosis factor (TNF)-α, in serum were detected via enzyme-linked immunosorbent assay (ELISA). Results showed that the villus height, crypt depth, villus height to crypt depth ratio, goblet cells, glycoproteins, and mast cells of the small intestine significantly decreased (P < 0.05 or P < 0.01) in the F treatment group. The contents of IL-1β, IL-2, IL-6, and TNF-α were significantly lower in the F treatment group than in the control group (P < 0.05 or P < 0.01). In summary, excessive F intake impaired intestinal development and immune function by decreasing the developmental parameters and the distribution of immune cells, glycoproteins, and cytokines.

Silencing of Intestinal Glycoprotein CD98 by Orally Targeted Nanoparticles Enhances Chemosensitization of Colon Cancer.

Colon cancer is among the most widely occurring cancer types, leading to considerably high mortality rate. The current chemotherapy achieves only limited success, and more effective therapeutic strategies are urgently needed. Human colonic biopsy specimens indicate increased expression of CD98 in patients with colon cancer, suggesting that CD98 might be a potential therapeutic target and/or a receptor for targeted drug delivery in colon cancer treatment. Herein, we coloaded CD98 siRNA (siCD98) and camptothecin (CPT) into CD98 Fab'-functionalized nanoparticles (NPs). The resultant Fab'-siCD98/CPT-NPs showed good monodispersity with an average diameter of approximately 270 nm and a ζ-potential of around -24 mV. These NPs mediated efficient drug delivery to the target cancer cells and tumor tissues, producing much better anticancer and antimigration effects compared to other relevant NPs. Mouse models with orthotopic colon tumors were treated with NP-embedded hydrogel, which revealed that Fab'-siCD98/CPT-NPs exhibited a therapeutic efficacy significantly better than that of single drug-loaded NPs or nonfunctionalized siCD98/CPT-NPs. This study indicates that the Fab'-siCD98/CPT-NP/hydrogel system is able to realize specific release of NPs in the colonic lumen and enable drugs (siCD98 and CPT) to be internalized into target cells, demonstrating a notable potential for clinical applications in colon-cancer-targeted combination therapy.

Importância das vacinas sintéticas contra o carrapato Rhipicephalus microplus

Rhipicephalus microplus, from an economic standpoint, is the most important parasite of cattle herds in Central and South America and Australia, it causes severe direct and indirect losses in animal production. Control of this parasite rests primarily on the use of acaricides drugs that are responsible for the selection of resistant of populations and cause contamination with residues in meat, dairy products and in the environment. This creates a need to the development of alternative, safe and efficient control, which may act in an integrated manner. Advances in molecular biology techniques have driven several lines of research in veterinary parasitology, particularly in vaccine development. Vaccines derived from the intestinal glycoprotein of R. microplus, the Bm86, have broad potential as a non-chemical control of ticks. The synthetic peptide SBm7462®, a synthetic vaccine derivative of the Bm86, has demonstrated its effectiveness in inducing the immune response of animals immunized with it.

The effect of N‐butyl‐deoxynojirimycin on the structure, function and trafficking of intestinal glycoproteins

N‐butyl‐deoxynojirimycin (NB‐DNJ) is a synthetic analogue of D‐glucose which is used for treatment of the Niemann‐Pick Type C and Gaucher diseases. This drug is consumed orally and in most of the cases gives rise to gastrointestinal intolerances similar to congenital carbohydrate intolerance disorders, strongly suggesting that the activities of the disaccharidases in the intestine are affected. We have investigated the role of NB‐DNJ on the major disaccharidases of the intestinal epithelium. Our findings show that an immediate effect of NB‐DNJ is its interference with carbohydrate digestion in the intestinal lumen via reversible inhibition of disaccharidases that cleave α‐glycosidically linked carbohydrates. NB‐DNJ elicits also long term effects on the biosynthesis and processing of intestinal glycoproteins. Thus it reduces the trafficking rates of these proteins, since it interferes with their N‐glycosylation in the ER. These altered glycoforms lose partially their enzymatic function, yet their folding pattern does not grossly change as assessed by the similar proteolytic pattern of the various glycoforms. Therefore a reduction in the activities of brush border enzymes in the apical membrane of intestinal cells occurs due to the combinatorial effects of NB‐DNJ on the trafficking and N‐glycan pattern as well as the immediate inhibition of the enzymes of the brush border membrane.

401 A new Golgi-based signalling cascade involved in tumoural cell invasion

In the rat small intestine, galactosyltransferases are the enzymes implicated in the biosynthesis of glycoproteins of the brush-border membranes and mucins. During postnatal development, the circulating insulin level increased at weaning in parallel with the activities of intestinal galactosyltransferases on O-glycans and N-glycans. This study deals with the role of insulin in the regulation of galactosyltransferase activities during postnatal development. The treatment of immature suckling rats with insulin induced a precocious increase in the activities of the O-glycan and N-glycan galactosyltransferases, partly reproducing the increase in galactosyltransferase activity normally found at weaning, since the O-glycan galactosyltransferase activity increased more quickly than the N-glycan galactosyltransferase activity. The sensitivity of the two galactosyltransferase activities to insulin disappeared after weaning, a period when drastic diet changes occur. In 22-day-old rats submitted to prolonged nursing (high-fat diet), the activities of the O-glycan and N-glycan galactosyltransferases were lower than those found in age-matched normally weaned rats (high-carbohydrate diet), indicating a delay in the maturation of the intestine of prolonged-nursing rats. The circulating insulin level of these animals stayed lower than that of the age-matched weaned rats. When the prolonged-nursing animals were treated with insulin, the 0-glycan and N-glycan galactosyltransferase activities reached levels similar to those of the weaned rats. These observations suggest that insulin is one of the maturation factors for intestinal glycoprotein galactosylation and may be partly responsible for the natural enhancement of intestinal galactosyltransferase activities observed during postnatal development in relation to the dietary changes at weaning.

Biochemical and histochemical study on the intestinal mucosa of the common carp Cyprinus carpio L., with special consideration of mucin glycoproteins

The biochemical and histochemical properties of intestinal mucin glycoproteins of virus and parasite‐free common carp Cyprinus carpio were investigated. The presence of carbohydrates in mucin glycoproteins could be demonstrated by histochemical methods, but generally, no obvious differences in specific staining for mucin glycoproteins were observed in contrast to biochemical techniques. Biochemical staining methods displayed differences in structure and composition of intestinal glycoproteins. Released intestinal glycoproteins contained two types of mucin glycoproteins: type 1 mucins displayed a size of &gt;2000 kDa, and were highly glycosylated, while type 2 mucins ranged between 700 and 70 kDa, and were weakly glycosylated. In epithelial (intracellular) glycoproteins, mainly N‐acetyl‐α‐galactosamine and mannose were found, while in luminal (extracellular) glycoproteins in addition sialic acid was evident. Fucose was not detected. Thus, structure and composition of intestinal glycoproteins of common carp were similar to those found in mammals.

Regulation of the intestinal glycoprotein glycosylation during postnatal development: role of hormonal and nutritional factors

This review focuses on the regulation of the glycoprotein glycosylation process in small intestine and colon during postnatal development. Glycoproteins play a prominent part in intestine as mucins secreted by the goblet cells and as molecules of biological interest largely present in the microvillus membrane of the enterocytes (digestive enzymes, transporters). The age-related changes in the intestinal glycosylation control the quality of glycan chains of glycoproteins. Postnatal maturation is observed at all stages of the glycoprotein glycosylation. But it is essentially characterised in the external glycosylation by a shift from sialylation to fucosylation depending on the transcriptional regulation of the corresponding glycosyltransferases, but also on coordinate changes in the activities of glycosyltransferases and of their regulatory proteins, in nucleotide-sugar bioavailability and in product degradation by oxidases. Many factors have been evoked to trigger these changes, among which are hormonal (glucocorticoids, insulin) and dietary factors. Changes in the structure of the glycoprotein glycans might be important for the transport, the barrier function, the implantation of the immune defences and of the microflora and even probably for the biological activity of some digestive enzymes.

Polyamine participation in the maturation of glycoprotein fucosylation, but not sialylation, in rat small intestine.

The aim of this study was to determine the role of polyamines in the diet-related maturation of the intestinal glycoprotein glycosylation during postnatal development in the rat. The activity of alpha-2,6-sialyltransferase and the sialylated forms of glycoproteins in the intestinal brush-border membranes were found to decrease considerably after weaning, in parallel with the intestinal level of putrescine. By contrast, the activity of alpha-1,2-fucosyltransferases, the mRNA levels for two alpha-1,2-fucosyltransferase genes, FTA and FTB, and the fucosylated forms of glycoproteins all increased after weaning, in parallel with the levels of spermidine and spermine. These results suggest a possible role of polyamines in the evolution of glycosylation. The treatment of suckling rats with spermidine or spermine reproduced the high intestinal levels of these polyamines corresponding to those normally found after weaning. After these treatments, a rise in the activity of the alpha-1,2-fucosyltransferase was observed, associated with a fall in alpha-L-fucosidase activity. The alpha-1,2-fucosyltransferase FTB gene was found to be regulated at the transcriptional level, but not by its inhibitor, fuctinin. The result of these variations was the precocious appearance of several alpha-1,2-fucoproteins, which are normally found in brush-border membranes after weaning. The treatment of suckling rats with putrescine, which induced only a transitory rise in intestinal putrescine, had a similar but weaker effect on the fucosylation process than spermidine or spermine, and treatment with ornithine was ineffective. alpha-2,6-Sialylation was not affected by any of the treatments. Spermidine and spermine turned out to be more effective than putrescine for intestinal glycoprotein fucosylation, but did not affect their sialylation. Spermidine and spermine, whose intestinal levels where found to increase at weaning time, may have been partly responsible for the natural evolution of the intestinal glycoprotein fucosylation that occurred during this period.

Dietary Spermidine and Spermine Participate in the Maturation of Galactosyltransferase Activity and Glycoprotein Galactosylation in Rat Small Intestine

This study considered the role of dietary polyamines in the maturation of intestinal glycoprotein galactosylation during postnatal development. In the rat small intestine, O-glycan: beta-1,3-galactosyltransferase and N-glycan: beta-1,4-galactosyltransferase are, respectively, involved in the glycan chain biosynthesis of mucins and of glycoproteins in the brush border membranes. Their activities increase significantly at weaning, in parallel with a rise in the intestinal content of spermidine and spermine (as determined by high performance liquid chromatography) and in proportion to the polyamine increase in food intake. The oral ingestion of spermidine or spermine (at 0.4 micromol/g body) by immature suckling rats for 4 d reproduced the levels of spermine and spermidine in their intestines at the time of weaning and induced precocious and significant rises in O-glycan: and N-glycan: galactosyltransferase activities to those normally found after weaning. In parallel, more galactose residues (detected in the complex oligosaccharide chains of glycoproteins by specific lectins after electrophoresis and transfer to nitrocellulose membranes) were observed in the brush border membranes of spermidine- and spermine-treated rats. In contrast, the ingestion of putrescine or ornithine had no effect. Diets with different levels of polyamines (milks and commercial diet), when given at weaning, induced variable evolutions of the galactosylation process, partly in relation to the amounts of polyamines ingested. These results indicate that spermidine and spermine are maturation factors that can reproduce, in immature rats, the same increase in intestinal glycoprotein galactosylation that is normally observed during weaning. They also suggest that the maturation of glycoprotein galactosylation may be a multifactorial event in which spermidine and spermine are both involved.

Implication of insulin and nutritional factors in the regulation of intestinal galactosyltransferase activity during postnatal development

In the rat small intestine, galactosyltransferases are the enzymes implicated in the biosynthesis of glycoproteins of the brush-border membranes and mucins. During postnatal development, the circulating insulin level increased at weaning in parallel with the activities of intestinal galactosyltransferases on O-glycans and N-glycans. This study deals with the role of insulin in the regulation of galactosyltransferase activities during postnatal development. The treatment of immature suckling rats with insulin induced a precocious increase in the activities of the O-glycan and N-glycan galactosyltransferases, partly reproducing the increase in galactosyltransferase activity normally found at weaning, since the O-glycan galactosyltransferase activity increased more quickly than the N-glycan galactosyltransferase activity. The sensitivity of the two galactosyltransferase activities to insulin disappeared after weaning, a period when drastic diet changes occur. In 22-day-old rats submitted to prolonged nursing (high-fat diet), the activities of the O-glycan and N-glycan galactosyltransferases were lower than those found in age-matched normally weaned rats (high-carbohydrate diet), indicating a delay in the maturation of the intestine of prolonged-nursing rats. The circulating insulin level of these animals stayed lower than that of the age-matched weaned rats. When the prolonged-nursing animals were treated with insulin, the O-glycan and N-glycan galactosyltransferase activities reached levels similar to those of the weaned rats. These observations suggest that insulin is one of the maturation factors for intestinal glycoprotein galactosylation and may be partly responsible for the natural enhancement of intestinal galactosyltransferase activities observed during postnatal development in relation to the dietary changes at weaning.

Influence of spermine on intestinal maturation of the glycoprotein glycosylation process in neonatal rats

Previous work has shown an inverse evolution of the rat intestinal glycoprotein sialylation that decreases from birth to weaning and of fucosylation that increases markedly after weaning during postnatal development. At weaning time, an increase in the intestinal level of polyamines (and especially that of spermine) was observed, owing partly to the higher level of spermine found in solid food given to rats at this period in comparison with the level found in milk. To study the role of this polyamine as a possible maturation factor of the glycoprotein glycosylation, suckling rats were treated for 4 days with spermine administered orally. This treatment allowed us to mimic the spermine increase that was observed naturally in rat small intestine after weaning because, in intestines of spermine-treated suckling rats, spermine was the only polyamine to be increased and was at a level similar to that of weaned rats. Spermine treatment did not induce appreciable changes in sialyltransferase activity or in sialylation of the brush-border-membrane glycoproteins. On the contrary, this treatment induced a rise in an alpha-1, 2-fucosyltransferase activity that was regulated at the transcriptional level, but not by its inhibitor (fuctinin), and no change in the availability of substrate (GDP-fucose). As a consequence of the increase in alpha-1,2-fucosyltransferase level and of the decrease in alpha-l-fucosidase level after treatment with spermine, several alpha-1,2-fucoproteins, naturally found in brush border membranes after weaning time, appeared precociously in these membranes after the treatment of the immature suckling rats. These results indicate that spermine is a maturation factor for the fucosylation of intestinal brush-border-membrane glycoproteins but not for their sialylation, and that this polyamine might be implicated in the increased fucosylation naturally occurring at weaning time during postnatal development.

Influence of spermine on intestinal maturation of the glycoprotein glycosylation process in neonatal rats

Previous work has shown an inverse evolution of the rat intestinal glycoprotein sialylation that decreases from birth to weaning and of fucosylation that increases markedly after weaning during postnatal development. At weaning time, an increase in the intestinal level of polyamines (and especially that of spermine) was observed, owing partly to the higher level of spermine found in solid food given to rats at this period in comparison with the level found in milk. To study the role of this polyamine as a possible maturation factor of the glycoprotein glycosylation, suckling rats were treated for 4 days with spermine administered orally. This treatment allowed us to mimic the spermine increase that was observed naturally in rat small intestine after weaning because, in intestines of spermine-treated suckling rats, spermine was the only polyamine to be increased and was at a level similar to that of weaned rats. Spermine treatment did not induce appreciable changes in sialyltransferase activity or in sialylation of the brush-border-membrane glycoproteins. On the contrary, this treatment induced a rise in an α-1,2-fucosyltransferase activity that was regulated at the transcriptional level, but not by its inhibitor (fuctinin), and no change in the availability of substrate (GDP-fucose). As a consequence of the increase in α-1,2-fucosyltransferase level and of the decrease in α-L-fucosidase level after treatment with spermine, several α-1,2-fucoproteins, naturally found in brush border membranes after weaning time, appeared precociously in these membranes after the treatment of the immature suckling rats. These results indicate that spermine is a maturation factor for the fucosylation of intestinal brush-border-membrane glycoproteins but not for their sialylation, and that this polyamine might be implicated in the increased fucosylation naturally occurring at weaning time during postnatal development.

The effect of probiotic bacteria on the adhesion of pathogens to human intestinal mucus.

Human intestinal glycoproteins extracted from faeces were used as a model for intestinal mucus to investigate adhesion of pathogenic Escherichia coli and Salmonella strains, and the effect of probiotics on this adhesion. S-fimbriated E. coli expressed relatively high adhesion in the mucus model, but the other tested pathogens adhered less effectively. Probiotic strains Lactobacillus GG and L. rhamnosus LC-705 as well as a L. rhamnosus isolated from human faeces were able to slightly reduce S-fimbria-mediated adhesion. Adhesion of S. typhimurium was significantly inhibited by probiotic L. johnsonii LJ1 and L. casei Shirota. Lactobacillus GG and L. rhamnosus (human isolate) increased the adhesion of S. typhimurium suggesting that the pathogen interacts with the probiotic.

Histochemistry of the development of the digestive system of Siberian sturgeon during early ontogeny

At hatching, the yolk‐sac matrix of Siberian sturgeon Acipenser baeri contained neutral glycoconjugates, glycogen, proteins rich in arginine, lysine, tyrosine, cysteine and cystine, glycoproteins containing mannose (Man) and/or glucose (Glc), N‐acetyl‐D‐galactosamine (GalNAc), L‐fucose (Fuc), sialic acid and/or N‐acetyl‐D‐glucosamine (GlcNAc) residues, as well as neutral and acidic lipids. Buccopharyngeal and anterior oesophageal goblet cellls produced a combination of neutral and acid sialoglycoproteins, while those from the posterior oesophagus secreted only neutral glycoproteins; both types of secretions contained tryptophan and ‐S‐S‐ groups and were unreactive to lectin techniques. Most intestinal goblet cells secreted mainly carboxylated and sulphated sialoglycoproteins with some rests of neutral glycoconjugates, while few of them produced only acid or neutral glycoproteins. Intestinal glycoproteins were rich in GalNAc, GlcNAc and sialic acid residues. Close relationships between digestive enzymes and morphological development of digestive organs were observed. Histochemistry of enzymes revealed that just after hatching, alkaline and acid phosphatase, ATP‐ase and non‐specific esterase activities were detected in the yolk sac. From the onset of exogenous feeding to the juvenile stage (30 days post‐hatch), an enhancement of enzymatic activities was observed, as alkaline and acid phosphatase, ATP‐ase, aminopeptidase M and nonspecific esterase sharply increased. However, lipase activity decreased in the liver and brush border of enterocytes by 13–14 days post‐hatch. Two types of lipase were detected in the alimentary canal, a non‐pancreatic lipase that was secreted in the cardiac stomach by gastric glands, and a pancreatic lipase, which activity was mainly detected in the brush border of the intestinal epithelium.

Interaction of cholera toxin and Escherichia coli heat-labile enterotoxin with glycoconjugates from rabbit intestinal brush border membranes: relationship with ABH blood group determinants.

The capacity of cholera toxin (CT) and type I heat-labile enterotoxin produced by Escherichia coli isolated from human intestine (LTh) to interact with glycoconjugates bearing ABH blood group determinants from rabbit intestinal brush border membranes (BBM) was studied. On the basis of the type of intestinal compounds related to the human ABH blood group antigens, rabbits were classified as AB or H. Toxin binding to the intestinal glycolipids and glycoproteins depends on the blood group determinant borne by the glycoconjugate and on the analyzed toxin. LTh was capable of interacting preferentially with several blood group A- and B-active BBM glycolipids compared to those isolated from animals lacking these antigens (H rabbits). Also, LTh preferably bound to several BBM glycoproteins from AB rabbit intestines compared to those from H ones. One of these glycoproteins, the sucrase-isomaltase complex (EC 3.2.1.48-10) isolated from AB and H rabbits showed the same differential LTh binding. Conversely, CT practically did not recognize either blood group A-, B-, or H-active glycolipids and glycoproteins. These results may be relevant for carrying out in vivo experiments in rabbits in order to disclose the role of ABH active-glycoconjugates in the secretory response induced by LTh in rabbit intestine.