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PubMed1992

Release of mucus glycoconjugates by Pseudomonas aeruginosa rhamnolipid into feline trachea in vivo and human bronchus in vitro.

Pseudomonas aeruginosa colonizes the lower respiratory tracts of patients with severe bronchiectasis, including cystic fibrosis, a condition associated with increased airway mucus output. We have shown that an extract containing chloroform-soluble extracellular products of P. aeruginosa releases glycoconjugates into the cat trachea in vivo. This activity was not related to pyocyanin, a major component of the extract, but was associated with the rhamnolipids. Purified monorhamnolipid (100 micrograms/ml) released radiolabeled and periodic acid-Schiff (PAS)-reactive glycoconjugates (delta 3H = +490 +/- 70%, delta 35S = +170 +/- 40%, delta PAS = +8.6 +/- 1.7 micrograms/min; n = 6, P less than 0.02 for each). Dirhamnolipid (200 micrograms/ml) was also effective (delta 3H = +640 +/- 70%, delta 35S = +130 +/- 20%, delta PAS = +9.3 +/- 1.5 micrograms/min; n = 6, P less than 0.02 for each). Monorhamnolipid (100 micrograms/ml) also released 35S-labeled and PAS-reactive glycoconjugates from human bronchial tissue in vitro (delta 35S = +189 +/- 47%, delta PAS = +26.3 +/- 8.5 micrograms/min; n = 7, P less than 0.001 versus control tissues in which no stimulus was given). The cat tracheal glycoconjugates released by the rhamnolipids differed from those released by pilocarpine 50 microM, in having a higher 3H:35S ratio (P less than 0.001). After gel chromatography on a Sepharose CL-4B column, the void volume fractions of the glycoconjugates also had different profiles in a cesium chloride density gradient. Those released by rhamnolipid banded at 1.62 g/ml, while those released by pilocarpine banded mainly at 1.50 g/ml, with some of the higher density material also present.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Removal of extracellular Mg2+ suppresses sulfation of glycoconjugates secreted from rabbit trachea in culture.

The influences of extracellular Ca2+ and Mg2+ concentrations on the basal secretion of glycoconjugates from rabbit trachea in organ culture were examined. Over 80% of the 35S-labeled and [3H]glucosamine-labeled glycoconjugates secreted by the trachea were digested upon incubation with chondroitinase ABC. The basal secretion did not occur in the medium at 4 degrees C, indicating an energy-dependent process. The basal secretion at 37 degrees C of 35S-labeled glycoconjugates was prominently suppressed in Mg(2+)-free Tyrode solution but not in Ca(2+)-free Tyrode solution containing ethyleneglycol bis(2-aminoethylether)tetraacetic acid (EGTA). In contrast, the basal secretion of [3H]glucosamine-labeled glycoconjugates was not affected by the Mg2+ concentration in the medium. The results suggest that extracellular Mg2+ largely contributes to sulfation of glycoconjugates basally secreted from rabbit trachea.

Animals↗
PubMed1978

Composition of acidic glycoconjugates (glycosaminoglycans and glycoprotein) in myometrium of rabbit uterus under estrogenic condition.

Acidic glycoconjugates (glycosaminoglycans and glycoprotein) were obtained, from myometrium of ovariectomized rabbit under estrogenic condition, by pronase digestion, fractionation with cetylpyridinium chloride and Dowex I column chromatography, in succession. Composition of acidic glycoconjugates was determined enzymatically, employing Streptomyces hyaluronidase, chondroitinase AC II, chondroitinase ABC and crude heparinase. Each glycoconjugate was distributed in 3 approximately 8 fractions obtained by Dowex I column chromatography, indicating its charge and/or molecular heterogeneity. Acidic glycoconjugates consisted of hyaluronic acid (13.4%), chondroitin sulfates A plus C (39.4%), dermatan sulfate (24.6%), heparan sulfate (18.7%) and acidic glycoprotein (most probably sialoglycoprotein) (3.9%). Composition of acidic glycoconjugates in myometrium differed remarkably from that in whole uterus. Myometrium was abundant in chondroitin sulfate isomers (chondroitin sulfates A plus C plus dermatan sulfate), but lacked sulfated glycoprotein. The present results suggested that myometrium and endometrium of uterus may play quite different roles in reproduction.

Animals↗
PubMed1994

Sulfated glycoconjugates as disrupters of Plasmodium falciparum erythrocyte rosettes.

Some strains of Plasmodium falciparum form erythrocyte rosettes that are believed to result from a lectin interaction between malaria-infected and uninfected erythrocytes. The sulfated glycoconjugate heparin and certain heparin derivatives have been observed to disrupt rosettes. To investigate this interaction further, we have studied the effects of four sulfated glycoconjugates on 15 fresh isolates of P. falciparum from Papua New Guinea. A broader range of sulfated glycoconjugates has been tested against a laboratory strain. A concentration of 1,000 micrograms/ml of dextran sulfate (molecular weight [MW] 500,000) was the most potent disrupter of rosettes. Fucoidan, heparin, and dextran sulfate (MW 5,000) were of decreasing effectiveness in 14 of 15 fresh isolates. The same relationship was true for the laboratory strain. Pentosan polysulfate and sulfatide also disrupted rosettes; chondroitin sulfates A, B, and C and keratan sulfate gave either minimal or no rosette disruption. Thus, some sulfated glycoconjugates are potent disrupters of P. falciparum erythrocyte rosettes. Sulfated glycoconjugates that are potent disrupters of P. falciparum rosettes may prove useful in identifying ligands involved in rosette formation.

Animals↗
PubMed1984

Expression of an unusual acidic glycoconjugate in Leishmania donovani.

An acidic glycoconjugate containing mannose, galactose and phosphate in approximately equimolar amounts was extracted from Leishmania donovani promastigotes and partially characterized. The glycoconjugate could be metabolically labeled with either [3H]mannose or [3H]galactose and was extractable from a delipidated residue fraction with water/ethanol/diethyl ether/pyridine/concentrated NH4OH (15:15:5:1:0.017) at 25 degrees C. The radioactively labeled glycoconjugate was found to possess the following characteristics: 1) comprised 45-60% of the total [3H]mannose label incorporated into macromolecules; 2) was soluble in alkaline solvents and 0.5% Triton X-100; 3) migrated as a broad band upon electrophoresis on sodium dodecyl sulfate-polyacrylamide gels with an approximate molecular weight of 15,000-30,000; 4) bound to DE52 cellulose and was eluted with a salt gradient of 0-0.1 M NaCl; 5) was insensitive to Pronase, hyaluronidase, chondroitinase, endo-beta-N-acetylglucosaminidase H, and endo-beta-galactosidase; and 6) possessed hydrophobic properties. An unusual feature of the glycoconjugate was its lability to mild acid hydrolysis (0.02 N HCl, 15 min, 60 degrees C). As determined by alkaline phosphatase and glycosidase digestion and paper chromatographic analysis, the major fragment generated by mild acid hydrolysis was found to be a phosphorylated galactosyl-beta-mannose disaccharide. All of these characteristics suggest that the glycoconjugate may be a polysaccharide and, possibly, may be important in parasite-host cell interactions.

Animals↗
PubMed1980

[Correlation of human cervical ripening and glycoconjugates (glycosaminoglycans and glycoproteins) (author's transl)].

In order to elucidate the role of glycoconjugates on human cervical ripening, glycoconjugates and glycogen obtained from the human non-pregnant cervix uteri in the proliferative phase and secretory phase, and those from the postpartum cervix uteri, were determined chemically. The results were as follows: 1) The water content and the total quantity of glycoconjugates (mg/g dry tissues) of the postpartum cervix uteri were more than those of the non-pregnant cervix uteri. 2) In the fractionations of neutral glycoconjugates, there was a marked decrease of the quantity of glycogen in the postpartum cervix uteri, but in the case of neutral glycopeptides, no difference could be found among the above three tissues. 3) In the fractionations of acidic glycoconjugates, there was a marked increase in the quantities of hyaluronic acid, chondroitin sulfate A and C, heparan sulfate and acidic glycopeptides and a slight decrease of dermatan sulfate in the postpartum cervix uteri. Furthermore, in determining the unsaturated disaccharides in the digestion of chondroitin sulfate A and C in the three tissues by chondroitinase AC-II, the appearance of delta Di-4S was 87--90%, while the rest was delta Di-6S. In other words, most of them were made of chondroitin sulfate A. It was estimated that there was almost nothing unsulfated and oversulfated in these carbohydrate chains, because no delta Di-OS and delta Di-DiS were found. Similarly, as for unsaturated disaccharides of the digestion elements of dermatan sulfate by chondroitinase ABC, delta Di-4S and delta Di-6S appeared to the same degree as the above. It was found that dermatan sulfate was made from a hybrid chain combination. But in the postpartum cervix uteri, there was a slight appearance of delta Di-OS. It was suggested that there was slight amount of unsulfated disaccharide unit in the carbohydrate chain.

Adult↗
PubMed1981

The effects of hydrocortisone on the biosynthesis of sulfated glycoconjugates by human fetal lung.

In order to study the regulation of sulfated glycoconjugate biosynthesis during human fetal lung development, an in vitro organ culture system was utilized. Tissue explants of human fetal lung maintained in organ culture undergo hydrocortisone-potentiated morphological differentiation. Human fetal lung tissue synthesized several classes of sulfated glycoconjugates, including sulfated glycosaminoglycans, sulfated lipids, and a class of glycoproteins containing sulfated oligosaccharide chains. These sulfated oligosaccharides were not released from the polypeptides under alkaline conditions that cleave O-glycosidically linked chains and were not degraded by a variety of chemical and enzymatic treatments which degraded sulfated glycosaminoglycans. Explants maintained in culture during a 6-day period incorporated increasing levels of 35SO4 into glycoconjugates with increases of 7-fold into heparin and heparan sulfate, 3-fold into sulfated glycoproteins, and 2-fold into sulfated lipids. In comparison, incorporation of [3H]mannose into glycoconjugates increased 4-fold, and the incorporation of [3H]thymidine into DNA increased 2- to 3-fold during this culture period. Tissues maintained in culture in the presence of hydrocortisone (10(-7) M) showed an enhanced incorporation of 35SO4 into heparin and heparan sulfate and into sulfated glycoproteins during the culture period compared to cultures maintained in the absence of hydrocortisone. However, the levels of 35SO4 incorporated into lipids, [3H]mannose incorporated into glycoproteins, and [3H]thymidine incorporated into DNA were markedly decreased in cultures maintained in the presence of 10(-7) M hydrocortisone. Only small differences in the synthesis of chondroitin sulfates and dermatan sulfate were observed during the 6-day period that lung tissues were maintained in culture in the presence or absence of hydrocortisone. Thus, the biosynthesis of specific sulfated glycoconjugates by human fetal lung tissues is probably regulated by both developmental events and by circulating steroids.

Cell Differentiation↗
PubMed1990

Glycoconjugate unique to migrating primordial germ cells differs with genera.

Previous cytochemical studies showing that rat primordial germ cells (PGCs) possess a unique surface glycoconjugate containing terminal alpha-N-acetylgalactosamine were extended in this study to determine whether a similar distinctive glycoconjugate coats the surface of PGCs in the mouse. The results showed that mouse PGCs fail to react with peroxidase-conjugated lectins specific for localizing glycoconjugate with terminal N-acetylgalactosamine. All available lectin conjugates with affinity for other terminal sugars or internal sugar linkages also failed to stain mouse PGCs except for the conjugates that bind to alpha-fucose. One fucose-specific lectin conjugate stained only PGCs in the early mouse embryo but stained additional sites in more mature embryos and lost reactivity with PGCs after gestational day 14. Another fucose-specific conjugate stained PGCs until day 15, but with less selectivity, and a third such conjugate bound to several sites, but not to PGCs. The results suggest that the developmental mechanisms mediating cellular interaction, migration, and differentiation may be similar in different genera, but the specific structure of the cell surface glycoconjugate involved in these mechanisms differs.

Animals↗
PubMed1993

Prolactin alters the expression of integumental glycoconjugates in the red-spotted newt, Notophthalmus viridescens.

Prolactin (PRL)-mediated changes in the texture and secretory activity of the skin in adult red-spotted newts may involve alterations in the distribution and/or expression of structural and secretory epidermal glycoconjugates. To explore this possibility, skin samples were obtained from groups of conditioned animals that had received injections of either ovine prolactin or amphibian saline over a 14-day period. Glycoconjugates within the epidermis and cutaneous glands were examined by means of lectin histochemistry using a panel of eight HRP-labelled lectins. PRL increased levels of sialic acid and n-acetylglucosamine in the stratum corneum. In contrast, glycoconjugates containing fucose, galactose, n-acetylgalactosamine, and galactose-(1,3)-n-acetylgalactosamine were decreased by PRL within both glands and epidermis. These results suggest that the integumental effects associated with prolactin in the red-spotted newt are mediated, at least in part, through the alteration of epidermal and glandular glycoconjugates.

Acetylgalactosamine↗
PubMed2002

Expression of specific glycoconjugates in both primary and secondary olfactory pathways in BALB/C mice.

Binding of cell surface carbohydrates to their receptors specifically promotes axon growth and synaptogenesis in select regions of the developing nervous system. In some cases these interactions depend upon cell-cell adhesion mediated by the same glycoconjugates present on the surface of apposing cells or their processes. We have previously shown that the plant lectin Dolichos biflorus agglutinin (DBA) binds to a subpopulation of mouse primary olfactory neurons whose axons selectively fasciculate prior to terminating in the olfactory bulb. In the present study, we investigated whether these glycoconjugates were also expressed by postsynaptic olfactory neurons specifically within the olfactory pathway. We show here for the first time that DBA ligands were expressed both by a subset of primary olfactory neurons as well as by the postsynaptic mitral/tufted cells in BALB/C mice. These glycoconjugates were first detected on mitral/tufted cell axons during the early postnatal period, at a time when there is considerable synaptogenesis and synaptic remodelling in the primary olfactory cortex. This is one of the few examples of the selective expression of molecules in contiguous axon tracts in the mammalian nervous system. These results suggest that glycoconjugates recognized by DBA may have a specific role in the formation and maintenance of neural connections within a select functional pathway in the brain.

Animals↗
PubMed1993

Thrombospondin related anonymous protein (TRAP) of Plasmodium falciparum binds specifically to sulfated glycoconjugates and to HepG2 hepatoma cells suggesting a role for this molecule in sporozoite invasion of hepatocytes.

Thrombospondin related anonymous protein (TRAP) of Plasmodium falciparum contains an amino acid motif based around the sequence WSPCSVTCG which is also found in region II of the circumsporozoite (CS) proteins of different species of Plasmodium. This amino acid motif confers on the CS protein the ability to bind specifically to sulfated glycoconjugates and to hepatocytes. This suggests that the interaction of CS protein with sulfated glycoconjugates on the surface of the hepatocytes may represent the first molecular event of sporozoite invasion of liver cells. Experimental evidence indicates that TRAP is localized both on the micronemes and on the surface of P. falciparum sporozoites implying that TRAP with its putative sulfated glycoconjugate binding motif may also be involved in recognition and/or entry of hepatocytes by the sporozoite. We show here that different TRAP constructs expressed in Escherichia coli bind to sulfogalactosyl-cerebrosides (sulfatides) and to the surface of HepG2 cells. These interactions are dependent on the presence of the conserved amino acid motif WSPCSVTCG within the sequences of the constructs and are completely inhibited by several sulfated glycoconjugates as well as by suramin, a polysulfonated drug with anti-protozoan activity. Moreover, sporozoite invasion of HepG2 cells is inhibited by antisera raised against these different TRAP constructs and by the presence of low concentrations of suramin. We concluded that TRAP may be one of the parasite encoded molecules in the host-parasite interaction that results in sporozoite invasion of hepatocytes.

Amino Acid Sequence↗
PubMed2006

Identification of glycoconjugates in the urine of a patient with congenital disorder of glycosylation by high-resolution mass spectrometry.

More than 150 molecular species were detected in a single glycoconjugate fraction obtained from urine of a congenital disorders of glycosylation (CDG) patient by use of high-resolution FT-ICR MS. With respect to its high-mass accuracy and resolving power, FT-ICR MS represents an ideal tool for analysis of single components in complex glycoconjugate mixtures obtained from body fluids. The presence of overlapping nearly isobaric ionic species in glycoconjugate mixtures obtained from CDG patient's urine was postulated from fragmentation data of several precursor ions obtained by nanoESI Q-TOF CID. Their existence was confirmed by high-resolution/high-mass accuracy FT-ICR MS detection. High-resolution FT-ICR mass spectra can, therefore, be generally considered for glycoscreening of complex mixture samples in a single stage. From the accurate molecular ion mass determinations the composition of glycoconjugate species can be identified. Particular enhancement of identification is offered by computer-assisted calculations in combination with monosaccharide building block analysis, which can be extended by considerations of non-carbohydrate modifications, such as amino acids, phosphates and sulfates. Taking advantage of this strategy, the number of compositions assigned to mass peaks was significantly increased in a fraction obtained from urine by size exclusion and anion exchange chromatography.

Congenital Disorders of Glycosylation↗
PubMed1996

Vasoactive intestinal peptide-stimulated glycoconjugate secretion from conjunctival goblet cells.

We have developed an in vitro and in vivo method to determine if VIP-stimulates conjunctival goblet cell secretion in the rat as nerves which contain vasoactive intestinal peptide (VIP) and are most likely parasympathetic are localized around these cells. For the in vitro method, pieces of rat conjunctiva were incubated for 1 hr with no additions or increasing concentrations of VIP (10(-10)-10(-6)M). Goblet cell secretion was measured by determining the amount of Helix pomatia agglutinin (HPA)-detectable glycoconjugates secreted into the medium. HPA-detectable glycoconjugates were assayed using an enzyme-linked lectin assay. For the in vivo method, drops of buffer containing no additions or varying concentrations of VIP (10(-10)-10(-6) M) were placed on the ocular surface of anesthetized rats for 60 min. The rats were killed, the ocular surface chemically fixed, and a button of conjunctiva removed. Mucin-containing goblet cells were stained by Alcian blue-periodic acid Schiff's reagent and the number of cells per 0.16 mm2 was quantified. A decrease in the number of mucin-containing goblet cells indicated an increase in mucous secretion. By immunofluorescent histochemistry, we found that the lectin HPA was localized predominantly in the secretory granules of rat conjunctival goblet cells with little binding present in the remainder of the conjunctiva. Nerves containing VIP surrounded goblet cells labelled with HPA. In pieces of conjuctiva, in vitro VIP (10(-8)-10(-6) M) stimulated HPA-detectable glycoconjugate secretion in a concentration dependent manner. When applied topically to the ocular surface, in vivo VIP AT 10(-8) M stimulated mucous secretion from conjunctival goblet cells. We conclude that VIP is present in nerves around conjunctival goblet cells and stimulates glycoconjugate secretion from these cells.

Animals↗
PubMed2001

Glycosyl phosphatidylinositol-linked glycoconjugates: structure, biosynthesis and function.

The purpose of this review is to summarize the most recent advances on GPI research. Structural studies on GPI-linked glycoconjugates indicate that there are significant variations in different organisms, although there is a conserved core structure. Furthermore, structural studies suggest that in different cell types, there is an army of glycosyltransferases dedicated to the synthesis of GPI-linked glycoconjugates. Biochemical studies on the synthesis of these GPI-linked glycoconjugates suggest that not only many different enzymes are involved but also that enzymes from different cell types, involving in the conserved core structure can have different substrate specificity. Genetic cloning of the yeast genes involved in synthesizing the core structure suggests that many of these enzymes also have human homologues. However, paroxysmal nocturnal hemogobinuria (PNH) is the only known human disease associated with the synthesis of GPI-linked glycoconjugates. Functional studies suggest that GPI-anchor can act as a signal for protein sorting and localization. Furthermore, GPI-linked receptors play an important role in T-cell activation.

Animals↗
PubMed1993

Cell differentiation of alveolar epithelium in the developing rat lung: ultrahistochemical studies of glycoconjugates on the epithelial cell surface.

Glycoconjugates on the surface of pulmonary epithelial cells were ultrahistochemically examined in the fetal, neonatal and adult rat lung. Lectin and colloidal iron staining procedures were performed in combination with digestion using carbohydrate-degrading enzymes or methylation. The glycoconjugate composition of columnar cells at 16 days gestation was similar to that of cuboidal cells at 19 days gestation. Glycoconjugate differentiation on the cell surface occurred at 20 days gestation, and especially the loss of soybean agglutinin (SBA) binding sites could be detected on type II cells. The contents of Ricinus communis agglutinin-I (RCA-I) and Concanavalin A (Con A) binding sites on type II cells also began to decrease. On the contrary, the content of sulfated saccharides decreased on the surface of type I cells during development. Glycoconjugate differentiation on both type I and II cells was completed with the disappearance of hyaluronic acid and peanut agglutinin (PNA) binding sites; type I and II cells acquired a similar histochemical composition to that on adult type I and II cells at 5 days after birth. Both type I and II cells share a common early precursor cell, that is, the cuboidal epithelial cell at the canalicular stage.

Animals↗
PubMed1990

Oxygen metabolites induced by phorbol myristate acetate increase lateral diffusion of wheat germ agglutinin-labeled glycoconjugates in human polymorphonuclear leukocytes.

To assess the general effects of protein kinase C (PKC) activation on cell membrane receptor mobility in human neutrophilic polymorphonuclear leukocytes (PMNLs), the lateral diffusion of fluoresceinated succinylated wheat germ agglutinin (S-WGA-FITC)-labeled membrane glycoconjugates was measured using fluorescence recovery after photobleaching (FRAP). Activation of PKC was achieved by incubating the PMNLs with different concentrations (5-100 nM) of phorbol myristate acetate (PMA). The membrane effects of dimethyl sulfoxide (DMSO), another possible membrane perturbant, were also studied. We found that PMA treatment (greater than or equal to 10 nM) increased the glycoconjugate diffusion coefficient (D) 2-2.5-fold. The mobile fraction (R) remained constant, around 30%. With DMSO, no effect on the diffusion was seen. The increase in lateral mobility due to cell stimulation with PMA was totally inhibited by catalase (200 units/ml) but only partly with superoxide dismutase (2000 units/ml). Exogenous hydrogen peroxide (0.01-5 mM) had no effect on glycoconjugate mobility in unstimulated cells. We therefore propose that activation of PKC mediates augmented mobility of glycoconjugate receptors in PMNL, a reaction that seems to be critically dependent on formation of reactive oxygen metabolites. The results indicate that endogenous formation of reactive metabolites upon receptor stimulation may have a general effect on receptor mobility.

Catalase↗
PubMed1996

Ontogeny of sulphated glycoconjugate-producing cells in the rat fundic gland.

The ontogeny of sulphated glycoconjugate-producing cells in the rat fundic gland has been studied using high iron diamine (HID), Alcian Blue (AB) at pH 1.0, high iron diamine in combination with Alcian Blue at pH 2.5 (HID-AB), cationic colloidal gold (CCG) at pH 1.0 under light microscopy and CCG (1.0), HID-thiocarbohydrazide (TCH)-silver proteinate (SP)-physical development (PD) under electron microscopy. From day 19.5 of gestation, sulphated glycoconjugate-producing cells were discernible under both light and electron microscopy. The development of such cells can be classified into four stages: (1) a prenatal period from day 19.5 of gestation extending to 0.5 days after birth; (2) 1 day to 2 weeks after birth; (3) 2 to 4 weeks after birth; and (4) the final period from 4 to 8 weeks after birth. Glycoconjugate-producing cells reached maturity by 4 weeks after birth. Our results indicated that glycoconjugate-producing cells were cells along the wall of foveolar lumen, but not those covering the gastric mucosa surface. Our results also suggested that the trans to transmost Golgi apparatus lamellae were the sites of sulphation in the developing rat stomach.

Alcian Blue↗
PubMed2000

The apical membrane of intestinal brush cells possesses a specialised, but species-specific, composition of glycoconjugates--on-section and in vivo lectin labelling in rats, guinea-pigs and mice.

Brush cells are specialised epithelial cells that are assumed to represent chemoreceptors of the digestive tract. They comprise a small population of the epithelial cells lining the intestine, possess a unique ultrastructure and, in many aspects, resemble the receptor cells of taste buds. To characterise glycoconjugates possibly involved in a sensory function, we investigated brush cells in the small intestine of three species using lectin histochemistry in confocal light and thin-section electron microscopy. Brush cells of rats were selectively labelled by the sialic acid-specific lectin Maackia amurensis agglutinin, those of guinea-pigs by the D-galactose-specific lectin Bandeiraea simplicifolia agglutinin, isolectin B4 and those of mice by the L-fucose-specific lectin Ulex europaeus agglutinin lectin I. Lectin binding sites were consistently located in the glycocalyx of the apical membrane and in that of cytoplasmic vesicles. In vivo lectin labelling revealed that the glycoconjugates of the apical membrane are accessible under physiological conditions, that brush cells do not endocytose and that they probably possess a high membrane turnover rate. The results show that specialisations exist in the composition of glycoconjugates forming the glycocalyx of brush cells in all species investigated. The presence of brush cell-specific glycoconjugates would be in accordance with the current hypothesis of a receptive function of brush cells. Differences in the specific glycosylation patterns among rats, guinea-pigs and mice indicate that species-specific adaptations exist.

Animals↗