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PubMed1992

Steroid hormones differentially modulate glycoconjugate synthesis and vectorial secretion by polarized uterine epithelial cells in vitro.

Characterization of glycoconjugates synthesized by polarized immature rabbit uterine epithelial (UE) cells in vitro, their vectorial patterns of secretion, and regulation by ovarian steroid hormones are reported. Large (mol wt, greater than 230 kDa) sialomucoglycoproteins and hyaluronate were primarily (86-96%) secreted from the apical cell surface domain, while heparan sulfate proteoglycans were predominantly secreted from the basal cell surface of the polarized UE cells. The polarized UE cells responded to estrogen and progesterone in vitro and exhibited distinct profiles in their synthesis and secretion of different glycoconjugates. Progesterone and/or estrogen reduced the secretion of the mucosialoglycoproteins; however, progesterone caused a 4- to 5-fold accumulation of mucosialoglycoproteins in the cell-associated fraction, suggesting regulation by the hormone at the level of secretion, rather than synthesis. Estrogen and progesterone both stimulated the synthesis and secretion of hyaluronate by the polarized UE cells. Neither hormone substantially altered the synthesis or secretory pattern of heparan sulfate proteoglycans. Collectively, these studies provide the first comprehensive characterization of the major glycoconjugates synthesized and secreted by rabbit UE cells. Furthermore, these observations demonstrate marked differential direct influences of steroid hormones on the production of distinct classes of UE cell glycoconjugates.

Animals↗
PubMed1997

Cationic colloidal gold staining of acidic glycoconjugates in mouse Paneth cells.

The acidic glycoconjugates of mouse ileum Paneth cells were examined with the aid of light and electron microscopy, using cationic colloidal gold (CCG) as a probe. Specimens of mouse ilea were fixed in half-strength Karnovsky's fixative and embedded in Lowicryl K4M resin. Semithin and ultrathin sections were cut of examination with light and electron microscopy, respectively. Examination of the sections using light microscopy revealed the positive staining of CCG at pH 1.0 and pH 2.5, which was detected at the rim of secretory granules and at the supranuclear regions of the Paneth cells. At pH 4.0, in addition to staining of the secretory granule rim, weak staining was observed in the granule core. At pH 7.2, the cytoplasm other than secretory granules exhibited positive CCG staining. Examination of the sections using electron microscopy, at pH 1.0, the trans lamellae of the Golgi apparatus, the rim of the secretory granules, and lysosomes were labeled selectively by CCG. At pH 2.5, labeling was also discernible over the same structures in the cells. However, at this pH, the labeling intensity was stronger than that at pH 1.0, due to the dual labeling of sulfated and sialylated glycoconjugates in these structures. At pH 4.0, the Golgi apparatus, rims and cores of secretory granules and ribosomes were labeled. Lysosomes and nuclei were also positively stained. At pH 7.2, the rims of secretory granules were not stained. The present results indicate that the CCG method gives good resolution and contrast when applied to staining, and therefore is useful for the specific staining of glycoconjugates such as sulfated, sialylated and phosphated glycoconjugates for light and electron microscopy.

Animals↗
PubMed2005

Glycoconjugate histochemistry of the secretory epithelium lining the seminal vesicles of the miniature pig.

The present study thoroughly examined the localization and characterization of glycoconjugates in the secretory epithelium lining the seminal vesicles of the miniature pig, employing light and electron microscopic histochemical procedures, including lectin methods. The present results showed the epithelial cells and luminal secretions to contain glycoconjugates with abundant neutral saccharides and a small amount of acidic saccharides, containing varying types of terminal sugar residues. At ultrastructural levels, the free surface coat of the plasma membrane was rich in alpha-D-Man, alpha-D-Glc, beta-D-Gal, GlcNAc, and sialic acid. The flocculent contents of the secretory vesicles indicated the localization of alpha-D-Man, alpha-D-Glc, alpha-L-Fuc, beta-D-Gal, GlcNAc, and sialic acid; such sugar residues were also seen in the elements of the Golgi apparatus. The present results have characterized the seminal vesicles of the miniature pig as having a high secretory activity and copiously producing glycoconjugates with various sugar residues. Such glycoconjugates appear to be indispensable substances for porcine reproduction, possibly influencing the fertilizing capacity of spermatozoa within the female genital tract.

Animals↗
PubMed2000

Isolation and characterization of protoporphyrin glycoconjugates from rat harderian gland by HPLC, capillary electrophoresis and HPLC/electrospray ionization MS.

It has been widely reported that the Harderian gland, present in most vertebrates, accumulates high levels of porphyrins, particularly protoporphyrin. The present study describes the extraction, identification and characterization of a group of hitherto unreported protoporphyrin glycoconjugates in the rat Harderian gland using HPLC, capillary electrophoresis, on-line HPLC/electrospray ionization MS and tandem MS. The major glycoconjugate was identified as protoporphyrin-1-O-acyl beta-xyloside with a smaller amount of protoporphyrin-1-O-acyl beta-glucoside also detected. In the Harderian glands studied, 50-70% of the porphyrins present were in the form of protoporphyrin glycoconjugates. This is the first reported occurrence of glycoconjugates of porphyrins in Nature and suggests that previous studies have wrongly identified the major porphyrin in the Harderian gland as the unconjugated protoporphyrin.

Animals↗
PubMed2001

[Sialic acid of glycoconjugates in amniotic fluid].

OBJECTIVES: Sialic acid is a negatively charged monosaccharide attached to non-reducing end of N- and O-linked carbohydrate chains of glycoconjugates. The claimed biological functions of sialic acid include its participation in cell to cell recognition and interaction as well as affecting the function of receptors by providing binding sites for ligand. Increased sialic acid concentration have been observed in several diseases e.g. malignancies, diabetes, inflammatory disorders, rheumatoid arthritis and alcoholism. DESIGN: The aim of the present work was to determine if the amount of sialic acid attached to glycoconjugates of amniotic fluid changes during pregnancy. MATERIALS AND METHODS: The sialic acid content in 47 samples of amniotic fluid derived from pregnant women with gestational age between 13 and 42 was studied by sialic acid specific lectins immunosorbent assay. The patient samples were divided into seven groups. RESULTS: Time dependent changes in the degree of sialylation of glycoconjugates in amniotic fluid during pregnancy, particularly in advanced pregnancy were observed. Moreover, the highest sialic acid content on glycoconjugates in pregnancies complicated by premature rupture of membranes and is prolonged pregnancy were also detected. CONCLUSIONS: Sialic acid content determination in amniotic fluid could be a potentially useful marker of inflammation process of amniochorion during pregnancy.

Adult↗
PubMed2001

[Studies on the glycoconjugates and glycans from Lycium barbarum L in inhibiting low density lipoprotein (LDL) peroxidation].

AIM: To determine the effects of glycoconjugates and their glycans from Lycium barbarum L. on inhibiting low density lipoprotein (LDL) peroxidation. METHODS: Using Cu(2+)-induced oxidation as a model, the oxidative production of thiobarbituric acid-reactive substances (TBARS) and the LDL electrophoresis migration on agarose gel were measured. RESULTS: The effects of glycoconjugates and their glycans from Lycium barbarum L. on inhibiting LDL peroxidation were different, among them, glycoconjugate LbGp5 showed the best effect on inhibiting LDL peroxidation. CONCLUSION: The glycoconjugates can inhibit LDL peroxidatin while their glycans showed no effects on inhibiting LDL peroxidation.

Fruit↗
PubMed1990

Modulation of glycoconjugate biosynthesis by 5-hexyl-2'-deoxyuridine in highly metastatic Lewis lung carcinoma cells.

The mechanism of action of 5-hexyl-2-'deoxyuridine (HUdR), a compound with antitumor activity, has been investigated in the HM cell lines derived from the highly metastatic variant of Lewis lung carcinoma (3LL-HH). It was shown that this pyrimidine analog did not inhibit the biosynthesis of nucleotides but modified the biosynthesis of glycoconjugates. The incorporation of [14C]-glucosamine into cytoplasmic glycoconjugates [glycosaminoglycan (GAG), glycolipid (GL), glycoprotein (GP), neutral polysaccharide (NP)] decreased to a similar level. The [14C]-glucosamine derived radioactivity was reduced to about 60-70% of the untreated controls in the presence of 15 micrograms/ml HUdR, which caused no inhibition of cell proliferation. These results might be explained by the reduced conversion of glucosamine into uridine-5'-diphospho-hexosamine. As more reduction was observed in the glucosamine labeling of glycoconjugates in nuclei and extracellular compartment, it may be conceivable that the intracellular transport of certain glycoconjugates (GAG, GP) is also affected by HUdR. In the extracellular compartment the reduced level of GAG labeling was the most apparent change. However, at a higher concentration of HUdR (75 micrograms/ml) there was a higher radioactivity in the combined GL + GP fraction. Using [35S]-labeling, the GAG fractions also showed a decreased radioactivity but only at the concentration of 75 micrograms/ml HUdR.

Antimetabolites, Antineoplastic↗
PubMed1989

A postembedding staining method of intensifying alcian blue reactions of acidic glycoconjugates with phosphotungstic acid in electron microscopy.

For the effective visualization of acidic glycoconjugates in electron microscopy, a post-embedding staining method has been devised for intensifying their alcian blue (AB) reactions by means of phosphotungstic acid (PTA). Tissue samples were prepared by glutaraldehyde-paraformaldehyde fixation of pieces of the trachea, aorta, and colon from adult rats. LR-White resin-embedded ultrathin sections were stained first with AB (pH = 1.0 or 2.5) and then reacted for PTA. In the tissues examined, the AB reaction of acidic glycoconjugates involved was effectively intensified by subsequent PTA staining in nearly all of the ultrastructures known to contain such carbohydrates. The majority of these ultrastructures failed to show any pronounced densities, if stained singly with PTA under the identical staining conditions. In all the ultrastructures, a series of selective methods such as active methylation and digestion with testicular hyaluronidase or neuraminidase have substantiated the selectivity of the PTA intensified AB reactions for acidic glycoconjugates involved. The present PTA intensified AB method resulted virtually in no contaminations of the backgrounds and can be regarded as a reliable and useful technique for the effective visualization of both intra- and extracellular acidic glycoconjugates in electron microscopy.

Alcian Blue↗
PubMed1994

Bacterial and plant glycoconjugates at the Rhizobium-legume interface.

Many classes of bacterial and plant glycoconjugate have been shown to be involved in establishing the Rhizobium root nodule symbiosis with peas (Pisum sativum). It was demonstrated, using techniques of molecular genetics, that a group of Rhizobium nodulation genes (nod genes) co-operate to synthesize a lipo-oligosaccharide signal molecule that specifically initiates nodule development on legume hosts. An additional gene function, encoded by nodX, has been found to extend the host range of Rhizobium leguminosarum bv. viciae to include nodulation of a pea mutant, cultivar Afghanistan; the nodX gene product specifies the addition of an acetyl group to the terminal N-acetylglucosamine residue at the reducing end of the pentasaccharide core of this signal molecule. Several other classes of bacterial glycoconjugate have also been shown by genetic analysis to be essential for normal nodule development and function: these include a capsular extracellular polysaccharide; lipopolysaccharide in the outer membrane; and cyclic glucans present in the periplasmic space. Potential functions for these glycoconjugates are discussed in the context of tissue and cell invasion by Rhizobium. Some plant components involved in symbiotic interactions have been identified by the analysis of nodule-specific gene expression (early nodulins). Several of the cDNA clones encoding these early nodulins specify proline-rich proteins that presumably correspond to cell wall glycoproteins or membrane arabinogalactan proteins. Other plant glycoconjugates have been identified using monoclonal antibodies as probes. A plant glycoprotein present in intercellular spaces has been identified as a component of the luminal matrix of infection threads. Because it attaches to the surface of bacteria and is itself susceptible to oxidative cross-linking, this glycoprotein may be involved in limiting the progress of microbial infections. Endocytosis of bacteria into the plant cytoplasm is apparently driven by direct interactions between the bacterial surface and the plasma membrane that is exposed within an unwalled infection droplet; glycoprotein and glycolipid components of the plant membrane glycocalyx have been defined using monoclonal antibodies. Differentiation of endosymbiotic bacteroids is preceded by differentiation of the plant-derived peribacteroid membrane which encloses the symbiosome compartment. Using a monoclonal antibody that identifies a group of plant membrane-associated, inositol-containing glycolipids, we have identified a very early marker for the differentiation of peribacteroid membrane from plasma membrane.

Carbohydrate Sequence↗
PubMed1993

[Light and electron microscopic demonstration of acidic glycoconjugates by means of postembedding staining procedures using cationic colloidal gold].

The cytochemical detection of acidic glycoconjugates located in rat gastrointestinal epithelia was performed using tissue sections embedded in Lowicryl K4M and cationic colloidal gold (CCG). CCG was prepared from poly-L-lysine and colloidal gold solution (10 nm). The staining of CCG was amplified after a photochemical silver reaction using silver acetate as an ion donor at the light microscopic level. The staining solutions adjusted to pH 2.5, CCG (2.5) and pH 1.0, CCG (1.0) were used for the characterization of carboxylated and sulfated glycoconjugates. At light microscopic level, CCG (2.5) stained several cell types of mucous cells in the rat gastrointestinal tract, while CCG (1.0) stained selectively mucous cells in gastric pits, glandular pylorus, upper crypts of the proximal colon and entire crypts of the distal colon. At the electron microscopic level, both CCG (2.5) and CCG (1.0) labeled the trans side of the Golgi apparatus and mucous granules in some mucous cells. These results are consistent with previous glycoconjugates histochemistry of the rat gastrointestinal tract at both the light and electron microscopic levels. CCG (2.5) and CCG (1.0) staining methods are useful and reliable postembedding staining procedures for the light and electron microscopic demonstration of intra- and extracellular acidic glycoconjugates.

Animals↗
PubMed1994

Expression of a novel cell surface lipophosphoglycan-like glycoconjugate in Trypanosoma cruzi epimastigotes.

The lipophosphoglycan (LPG)-like glycoconjugate expressed on the cell surface of Trypanosoma cruzi epimastigotes was isolated, purified, and partially characterized. The glycoconjugate migrated as a homogeneous band (42 kDa) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Matrix-assisted laser desorption ionization mass spectral analysis of the native molecule indicated the presence of two major components whose molecular masses were about 18.4 and 22.5 kDa. The LPG could be metabolically labeled with [3H]galactose, [3H]mannose, [14C]glucose, or [3H]palmitic acid. Monosaccharide compositional analysis of the LPG indicated that galactose, glucosamine, and sialic acid predominate over mannose, galactosamine, and inositol. A peptide associated with the LPG molecule contained about 40 amino acid residues per inositol and had threonine as the predominant amino acid. The LPG showed strong binding to Ricinus communis agglutinin-1 and Tritium vulgare wheat germ agglutinin, indicating the presence of terminal beta 1,4-linked galactosyl residue(s) and N-acetylglucosamine, respectively. Lectin binding studies also suggested the presence of a terminal beta-galactose and GlcNAc in the glycan-inositol lipid core of LPG. Virtually all of the sialic acids appeared to be located in the saccharide portion of the molecule. Treatment of the LPG with phosphatidylinositol-specific phospholipase C liberated an alkylacylglycerol. Structural analysis of the alkylacylglycerol and its acidic methanolysis products by gas-liquid chromatography/mass spectrometry indicated that the glycerol substituents were primarily the C16 1-alkyl group and C16 2-acyl group. The ratio of inositol to 1-O-alkyl-2-O-acylglycerol was 1:1. Treatment of the glycoconjugate with nitrous acid released a major phospholipid product that migrated close to the phosphatidylinositol standard on thin layer chromatography. This result implied that phosphatidylinositol was glycosidically linked to the nonacetylated amino sugar. Furthermore, the LPG was found to contain phosphate and was labile to mild acid hydrolysis, strongly suggesting that the intact molecule is related to Leishmania LPG. The most striking and unique feature of T. cruzi LPG is the presence of large amounts of glucosamine and sialic acid as well as galactosamine. These results indicate that the glycoconjugate expressed on the T. cruzi cell surface is a new type of LPG-like molecule anchored on the cell surface via an alkylacylphosphatidylinositol.

Animals↗
PubMed1993

[A histochemical study on the testes from patients with idiopathic male infertility: identification of acidic glycoconjugates in the seminiferous tubular walls].

Acidic glycoconjugates in the seminiferous tubular walls in the testes from patients with idiopathic male infertility was identified light microscopically with the sensitized high iron diamine method in combination with digestions with chondroitinase ABC, chondroitinase B or testicular hyaluronidase. Tissue specimens were obtained by testicular biopsy from 37 patients with idiopathic male infertility and 9 fertile adult males. Chondroitin sulfate A, B and C were identified in the tubular walls of oligozoospermic patients with idiopathic male infertility irrespective of the thickness of the walls. Similar results were obtained in the tubular walls of the testes from normal males. On the other hand, chondroitin sulfate B was a main acidic glycoconjugate in the tubular walls of the testes from azoospermic patients with idiopathic male infertility irrespective of the thickness of the walls. These findings suggest that the etiological factors of the impaired spermatogenesis in patients with idiopathic male infertility are not only the disturbance of nutritional transport across the seminiferous tubular walls due to peritubular thickening but the functional alterations of the tubular walls associated with changes in components of acidic glycoconjugates in the tubular walls. The pathogenesis of oligozoospermia does not seem to be similar to that of azoosspermia since components of acidic glycoconjugates in the peritubular tissues between the two types of disorders are quite different.

Adult↗
PubMed1985

Heterogeneous distribution of glycoconjugates in human kidney tubules.

Paraffin sections of normal human kidney were stained with a battery of ten lectin-horseradish peroxidase conjugates. Staining of proximal tubules revealed a relatively uniform distribution of glycoconjugates having bi- and/or triantennary N-linked sugar chains as well as terminal beta-galactose and alpha-fucose in all cells. In contrast, terminal alpha- and beta-galactose and alpha-fucose were localized in only some cells of the thin limbs, whereas N-linked sugar chains and terminal alpha-N-acetylgalactosamine occurred in all cells. In the ascending thick limbs, terminal alpha-N-acetylgalactosamine was found in some cells and N-linked sugar chains and terminal beta-galactose were present in all cells. The distal convoluted tubules contained N-linked oligosaccharides and terminal beta-galactose in all cells. Terminal alpha-N-acetylgalactosamine was found in some but not all profiles of distal convoluted tubules in a few kidneys. In the initial (connecting) segment of cortical collecting ducts, cells varied in their content of glycogen and glycoconjugates with terminal alpha- and beta-galactose, alpha-fucose and alpha-N-acetylgalactosamine, but cells in this segment evidenced uniform localization of N-linked sugar chains. A similar distribution of sugars occurred in the medullary ray segment of cortical collecting ducts, except for terminal beta-galactose which was present in all cells. In the medullary collecting ducts, there was also considerable cell-to-cell variation in the content and distribution of glycogen and glycoconjugates having N-linked sugar chains, terminal alpha-galactose, alpha-fucose, alpha-N-acetylgalactosamine, and the disaccharide galactose-(beta 1----3)-N-acetylgalactosamine. The content and distribution of glycoconjugates in the nephron varied only slightly between kidneys from different individuals, but individual variability was extensive in the collecting ducts. The reasons for these individual differences have not been determined, however. Cellular heterogeneity of glycosubstances within the different regions of the human kidney correlates with similar findings in other mammals and implies diverse functional roles for the various types of complex carbohydrates in the kidney.

Adolescent↗
PubMed1986

Selective cytochemical demonstration of glycoconjugate-containing terminal N-acetylgalactosamine on some brain neurons.

Paraffin embedded sections of rat, mouse, dog, and human brain were stained with a battery of lectin-horseradish perioxidase conjugates to localize and characterize glycoconjugates. In the rat and mouse cerebral cortex, a subpopulation of nonpyramidal neurons stained selectively with three lectins with specific affinity for terminal N-acetylgalactosamine (GalNAc). These and only these lectins stained the surface of the cell body, dendritic shafts, and proximal parts of the dendritic arborization. Most reactive, nonpyramidal neurons revealed a multipolar dendritic pattern, but some possibly belonged to the bitufted and bipolar types of neuron. The GalNAc-containing neurons appeared widely distributed in layers II-VI with relatively greater abundance in layers IV and V. In the cortex of rats and mice the stained neurons occurred in moderate numbers in the frontal, frontoparietal, striate, retrosplenial, and entorhinal regions, but were less numerous in the hippocampal gyrus, dentate gyrus, and olfactory area. Other neurons in the basal ganglia and brain stem stained weakly for GalNAc. Examination of the frontal cortex of human and canine brains showed a similar distribution of nonpyramidal neurons with affinity for GalNAc-binding lectins. At high magnification, the surface staining of neurons in the cerebral cortex, deep cerebellar nucleus, and other sites appeared periodic rather than continuous. The periodic character of the neuronal surface staining suggested a location for the reactive glycoconjugate in or between the synapses. The GalNAc-containing glycoconjugate occurred in a selected cell type, failed to bind the other lectin conjugates, and differed from biochemically detected glycoconjugates. It is, therefore, considered a newly recognized entity of possible physiologic significance for a population of cortical neurons.

Acetylgalactosamine↗
PubMed1987

Differential effects of retinoic acid on the in vitro growth and cell-surface glycoconjugates of 2 human head and neck squamous-cell carcinomas.

As a part of an assessment of the potential use of retinoids in preventive and adjuvant treatment of HNSCC, we examined the effects of beta-all-trans retinoic acid (RA) on the growth and cell-surface glycoconjugates of 2 HNSCC cell lines. These lines, designated 1483 and 183A, were established from an untreated patient with a well-differentiated SCC of the retromolar trigone and one with a poorly differentiated SCC of the tonsil. Whereas the 1483 cells were sensitive to RA in that their anchorage-dependent growth, their colony growth on solid substratum, and their anchorage-independent growth in semi-solid agarose gel were all inhibited in a dose-dependent fashion by RA concentrations in the range between 1 nM and 10 microM, the 183A cells were not inhibited by RA. Their anchorage-dependent growth and colony formation were stimulated by RA, whereas their anchorage-dependent colony formation was not altered. Cell-surface glycoconjugates were modulated by RA in the sensitive 1483 cells but not in the 183A cells. Treatment of the 1483 cells resulted in a large increase in the cell-surface labelling of high-molecular-weight (Mr greater than 400,000) galactoglycoconjugates and sialoglycoconjugates, as well as an Mr 280,000 sialoglycoconjugate. Glycoconjugates with similar electrophoretic mobilities in polyacrylamide gels were labelled intensely on the surface of the 183A cells even before RA treatment and only minor changes were noticed in their labelling after treatment. These results demonstrate that RA can exert different effects on different HNSCC lines, and suggest that correlations might exist between responsiveness to RA and the stage of differentiation of the HNSCC, and between modulation of cell growth and enhancement of cell-surface glycoconjugate glycosylation by RA.

Carbohydrates↗
PubMed1984

An amphipathic sulphated glycoconjugate of Leishmania: characterization with monoclonal antibodies.

A major glycoconjugate of Leishmania tropica major identified by two monoclonal antibodies was shown to be an externally oriented, amphipathic membrane antigen shed into the culture medium in which the parasites grow. This molecule could be labelled metabolically with [3H]glucose, [3H]galactose, [32P]phosphate and [35S]sulphate. It migrated as a polydisperse band upon electrophoresis in SDS-polyacrylamide gels, spanning the region of the gel corresponding to an apparent mol. wt. of 20 000-67 000 daltons. An apparently identical family of molecules could be labelled on the surface of living promastigotes using galactose oxidase and [3H]-sodium borohydride. This molecule was shown to be released into the supernatant over a period of several hours. Detection of the 3H- or 35S-labelled molecule required several days exposure of autoradiographs, but a novel blotting technique using nitrocellulose coated with monoclonal antibody allowed rapid detection of the molecule in charge shift electrophoresis, Western blotting and dot blotting. The electrophoretic mobility of the glycoconjugate in agarose relative to its mobility in Triton X-100 was increased in the presence of deoxycholate, and decreased in the presence of cetyl trimethyl-ammonium bromide, indicating amphipathic properties consistent with insertion into the lipid bilayer of the membrane. Using the dot-blotting technique the glycoconjugate was detected in all virulent and avirulent clones of LRC-L137 and in two additional isolates of L. tropica major (LRC-L287 and LRC-L251), but not in L. donovani or L. mexicana, consistent with the previously described specificity of the antibodies. However, the general approaches used in this paper showed that L. donovani (LRC-L52) and L. mexicana (LRC-L94) synthesize a similar, but antigenically distinct glycoconjugate.

Animals↗
PubMed1985

The Leishmania receptor for macrophages is a lipid-containing glycoconjugate.

The glycoconjugate of Leishmania major recognized by the monoclonal antibody WIC-79.3 exists in two forms. The cellular form associated with the promastigote is a population of amphipathic molecules consistent with membrane insertion. In contrast, the extracellular form mainly consists of hydrophilic molecules, and probably arises by cleavage of the cellular form by an endogenous phospholipase. The hydrophilic population of extracellular glycoconjugate molecules binds specifically to macrophages but not to T or B lymphoid cells. Binding of the glycoconjugate and also intact promastigotes to macrophages in vitro is specifically inhibited by Fab fragments of WIC-79.3. These data indicate that the L. major glycoconjugate is the parasite receptor for macrophages, and hence the molecule directly involved in the initiation of infection.

Animals↗
PubMed1981

Inhibition of glycoconjugate secretion by colchicine and cytochalasin B. An in vitro study of human airway.

The effects have been analyzed of cytochalasin B and colchicine on the secretion of glycoconjugates by human bronchial explants labeled in vitro with radioactive glucosamine. Both cytochalasin B and colchicine had no effect on baseline 14C-labeled glycoconjugate release but caused a dose-dependent (10(-7)-10(-4) M) inhibition of 14C-glycoconjugate release and discharge of labeled macromolecules from mucous and serous cells induced by 5 X 10(-5) M methacholine. Quantitative autoradiographic analyses showed that neither cytochalasin B nor colchicine inhibited 3H-threonine or 3H-glucosamine incorporation into mucous and serous cells of the submucosal glands or goblet cells of the airway epithelium. Colchicine (10(-5) M) but not cytochalasin B significantly reduced the rate at which labeled macromolecules were transported through mucous, serous and goblet cells but this effect was not observed until 4h after the addition of colchicine. Neither cytochalasin B nor colchicine affected the basal rate of labeled-macromolecule discharge from mucous, serous or goblet cells. At a concentration of 10(-5) M, both agents completely inhibited the increase in labeled-macromolecule discharge induced in mucous and serous cells by methacholine. Our results suggest that in the submucosal gland of human airways microtubules and microfilaments may be important in secretagogue-induced but not in baseline cellular glycoconjugate discharge, implying that the mechanisms of the two processes differ significantly. Furthermore, a role for microtubules is suggested in the transport of secretory granules through mucous, serous and goblet cells.

Aged↗