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Background Glycosaminoglycans are found in human tissues including plasma. They encompass chondroitin sulphates, heparan sulphate/heparin, hyaluronic acid, and keratan sulphate. Glycosaminoglycans, in particular heparan sulphate and heparin, are strongly associated with plasma proteins, so that their purification results quite difficult. Methods In order to study the distribution of glycosaminoglycans in plasma subfractions, we developed a novel method that allows their identification even if they were still associated with proteins or peptides. Plasma was fractionated following the procedure of Cohn–Oncley, and each fraction was treated with proteases. After centrifugation, glycosaminoglycan/protein complexes in the supernatant were analysed using a modified cellulose acetate electrophoresis which allowed identification of glycosaminoglycans in mixtures of glycosaminoglycans/proteins. Results Chondroitin sulphate was recovered in cryoprecipitate and in all Cohn–Oncley fractions. Glycosaminoglycans belonging to the class of heparan sulphate/heparin, however, were recovered in the cryoprecipitate and in fractions I and IV-1, and, in smaller amount, in fraction II + III. Conclusions Since the largest amount of plasma proteins is partitioned in Factions II + III and V, these results demonstrate that heparan sulphate/heparin are not randomly distributed in Cohn–Oncley fractions and are associated with certain plasma proteins. This association might play a role in the physiological function of heparan sulphate/heparin, regulating hemostasis and atherogenesis.

A new and rapid method of nitrous acid treatment for the characterization of N-sulfated glycosaminoglycans is presented. This method permits contemporaneous nitrous acid treatment, elimination of cleavage products, and separation of other glycosaminoglycan components of biological samples during an electrophoretic run on a cellulose acetate plate.

The changes of cell coat and endocellular glycosaminoglycans associated with adhesion of polymorphonuclear leukocytes to tissue culture dishes were studied by electrophoresis on cellulose acetate. Polymorphonuclear leukocytes are coated by chondroitin 4 sulphate, while undersulphated chondroitin 4 sulphate and heparan sulphate are present in the cytoplasm. Upon adhesion polymorphonuclear leukocytes shed into the culture medium chondroitin 4 sulphate and concomitantly hyaluronic acid and heparan sulphate are exposed at the cell surface and shed into the culture medium. The role of these compounds in polymorphonuclear leukocyte physiology is discussed.

SUMMARYCell surface and endocellular polysaccharides of growing and differentiated Dictyostelium discoideum have been isolated and characterized with electrophoretic and chromatographyc procedures.The mould exhibit a very eterogeneous family of sulphated polysaccharides which are externalized during the differentiation.The possible role of cell surface polysaccharides in the differentiation process is discussed.

SUMMARYGlycosaminoglycans (GAGs) of normal, SV-40 and Polyoma virus transformed 3T3 cells were characterized electrophoretically with an improved technique. A variety of compounds were removed from the cell surface with a mild trypsin treatment including hyaluronic acid (HA), chondroitin-4-sulphate {C4S), derma tan sulphate (DS), two heparan sulphate subclasses (HS1 and HS2) and sialosaccharides. Cellular transformation is accompanied by a relative lowering of the amount of heparan sulphate and an increase in hyaluronate. Dermatan sulphate is lowered too while large amounts of chondroitin-4-sulphate appear particularly in polyoma virus transformed cells. The molecular specie of heparan sulphate with the higher degree of iduronate and sulphate (HS2) is lost in transformed cells.

A new rapid, sensitive, and reproducible method is presented which allows the separation of all known animal glycosaminoglycans (including two subclasses of heparan sulfate, chondroitin 4-sulfate, chondroitin 6-sulfate, dermatan sulfate, hyaluronic acid, heparin, and keratan sulfate) in a single monodimensional electrophoresis on cellulose acetate. A very narrow starting band is obtained by formation of a discontinuity in the electric field and all eight compounds are then selectively resolved by combining their migration properties in a barium acetate buffer and their differential sensitivity to precipitation by ethanol.

SUMMARYThe molecular properties of cell surface glycosaminoglycans are considered as well as their interactions with other ‘surface associated’ macromolecules including collagen, actomyosin and fibronectin.Experimental evidences are provided on the role of calcium ions in the modulation of cellular physiology at the cell coat level together with preliminary results suggesting the involvement of cell surface glycosaminoglycans in the maturation and in the neoplastic transformation of bone marrow leukocytes.The possible involvement of cell surface glycosaminoglycans is pellular recognition is postulated and models are presented for a direct or a protein-mediated interaction at the cell surface level.

Interactions of fibronectin and glycosaminoglycans and the involvement of heparan sulphate and hyaluronate in fibronectin-collagen interactions have been studied by affinity chromatography. Partially periodate-oxidized glycosaminoglycans were coupled to adipic acid dihydrazide-substituted agarose. The elution of fibronectin was performed by using increasing concentrations of NaCl. Of the copolymeric glycosaminoglycans, heparin and self-associating heparan sulphates display the highest affinity towards fibronectin while hyaluronic acid and chondroitin 6-sulphate do not bind fibronectin. Competitive release experiments suggest the existence of common binding sites for copolymeric glycosaminoglycans on the fibronectin backbone. Heparan sulphate favours the formation of collagen-fibronectin complexes at low molarity, while hyaluronate is ineffective at low concentrations and prevents the formation of complexes when present at concentrations > 1 mg ml−1. It is suggested that heparan sulphate promotes the formation of complexes which bind with fibronectin thus producing steric changes that increase the affinity for collagen, while hyaluronate prevents the binding of fibronectin to collagen by a steric exclusion mechanism.

Glycosaminoglycans isolated from native non-adhesive surfaces of both endothelial and mesothelial origin and from endothelial cells cultured in vitro were analyzed by electrophoresis and characterized by chemical and enzymatic breakdown. All the surfaces examined expose in vivo chondroitin 6-sulphate as the main glycosaminoglycan. Under in vitro culture, the exposure of chondroitin sulphate is reduced. Paper chromatography of hydrolysis products upon degradation by chondroitinase AC shows equal amounts of both 6- and 4-sulphated disaccharides. At the same time, the surfaces lose their non-adhesiveness to leukocytes. The addition of fibroblast growth factor to endothelial monolayers restores both non-adhesiveness to leukocytes and exposure of chondroitin sulphate. These results seem to indicate that the exposure of chondroitin sulphate is important in preventing cellular adhesion.

The intracellular and extracellular glycosaminoglycans (GAGs) of peripheral leukocytes in normal subjects and leukemic patients were characterised by electrophoresis and enzyme sensitivity. Normal peripheral granulocytes (PMN) are very rich in trypsin removable surface GAGs, while none are present on the surface of leukemic cells in acute myeloid leukemia. The intracellular and extracellular GAGs have also been analysed in the pig and compared to normal pig bone marrow haematopoietic cells. Mesenchymal cells cultured in vitro from marrow matrix and peripheral endothelial cells have also been studied. The results suggest that the exposure of cell surface chondroitin sulphate A is an important step involved in the peripheralisation of PMN.

Fibroblast-like cells were obtained by in vitro cultivation of needle aspirations of human bone-marrow. These cells show a unique composition of coat-associated glycosaminoglycans: 10% chondroitin 4-sulfate, 30% hyaluronic acid and 60% heparan sulfate which were resolved and characterized by electrophoresis, nitrous acid treatment and enzymatic degradation. Chondroitin 4-sulfate is the only glycoaminoglycan detectable on the surface of mature granulocytes, whereas the immature cells do not seem to possess surface glycoaminoglycans. Immature hemopoietic cells can adhere on to marrow-derived fibroblast cells, whereas mature granulocytes cannot. Treatment with mucopolysaccharidases of both mature leukocytes and marrow stromal cells can interfere in these adhesive relationships, suggesting a role of glycoaminoglycans in regulating short-range interactions during hematopoiesis.

Intercellular glycosaminoglycans (GAGs) from various tissues were analyzed by cellulose acetate electrophoresis and enzymatic treatment with specific mucopolysaccharidases. Each tissue exhibits a particular composition of sulfated and unsulfated molecular species. Invariably, malignant human neoplasias and their metastases show striking variations in the electrophoretic pattern typical of the corresponding normal tissue. An absolute or relative increase in surface ChS A/C and HA seems to be a consistent feature of neoplastic transformation. On the other hand, the GAGs composition of benign noninfiltrative tumors does not vary greatly with respect to the original normal tissue.

The binding of the basement-membrane glycoprotein laminin to glycosaminoglycans (aggregating and non-aggregating subsets of heparan sulphates and dermatan sulphates, as well as heparin, chondroitin sulphates and hyaluronic acid) was studied by affinity chromatography. Partially periodate-oxidized chains of glycosaminoglycans were coupled to adipic acid dihydrazide-substituted agarose. Co-polymeric glycosaminoglycans reveal high affinity for laminin, whereas hyaluronic acid does not. Competitive-release experiments indicate that glycosaminoglycans share a common binding site on the laminin molecule.