Biomedical subjects

H B Nader

Publications and source records attributed to H B Nader.

At least 91 records · Page 5Linked to original sources

PubMed1987

N-glycansulfated fibronectin: one of the several sulfated glycoproteins synthesized by endothelial cells in culture.

N-glycanase, an endoglycosidase that cleaves the bond between asparagine and glucosamine, releases oligosaccharides with various degree of sulfation from endothelial cell fibronectin. As shown by analysis by polyacrylamide gel electrophoresis of culture medium conditioned by cells exposed to [35S]sulfate, endothelial cell fibronectin is one of a number of glycoproteins bearing sulfated oligosaccharides, synthesized by this cell type.

Cell Line↗

PubMed1987

Structure and antithrombin-binding properties of heparin isolated from the clams Anomalocardia brasiliana and Tivela mactroides.

Heparin with high anticoagulant activity was isolated from the two marine clam species Anomalocardia brasiliana and Tivela mactroides. A large portion of the polysaccharide chains of both preparations bound with high affinity to immobilized antithrombin. Titrations monitored by tryptophan fluorescence showed that clam polysaccharide chains with Mr approximately 22,500 contained up to three binding sites for antithrombin and that the binding constants for the interaction of these chains with antithrombin were higher than those reported for mammalian heparin of comparable size. Structural analysis of clam heparin fractions and subfractions of clam heparin with differing affinity for immobilized antithrombin revealed the presence of large amounts (up to 25-30% of the total disaccharide units) of the 3-O-sulfated saccharide sequences (-GlcNSO3)-GlcA-GlcNSO3(3-OSO3)- and (-GlcNSO3)-GlcA-GlcNSO3(3,6-di-OSO3)-, previously identified as unique markers for the antithrombin-binding region of heparin. The content of these saccharide sequences was found to increase with increasing affinity of the parent polysaccharide for antithrombin. Structural analysis of the clam heparins also demonstrated the occurrence of a novel saccharide sequence, tentatively identified as (-GlcNSO3)-IdA-GlcNSO3(3,6-di-OSO3)-, that has not previously been found in heparin or related polysaccharides. The contents of this latter sequence, at most 3-4% of the total disaccharide units, showed no correlation with the affinity for antithrombin.

Animals↗

PubMed1987

A relationship between the inhibition of heparan sulfate and chondroitin sulfate synthesis and the inhibition of molting by selenate in the hemipteran Rhodnius prolixus.

The insect Rhodnius prolixus synthesizes heparan sulfate and chondroitin sulfate after a blood meal containing [35S]-inorganic sulfate. A 40 to 80% inhibition of heparan sulfate synthesis was obtained when the meal was supplemented with 10(-5) and 10(-4) M sodium selenate respectively. Likewise an inhibition of the molting in the order of 30 to 60% was observed when the insects were fed with blood containing 10(-5) and 10(-4) M selenate respectively. The insects after a subsequent meal without selenate molted normally. Except for the inhibition of the ecdysis no gross physiological or morphological changes could be observed in the insects. Based on these and other findings the possible role of sulfated glycosaminoglycans in the control of cell growth is discussed.

Animals↗

PubMed1987

Glycosaminoglycan composition of electric organ basement membranes.

The basement membranes of the innervated surface of the electric organ of Discopyge tschudii present a high concentration of mucopolysaccharides as revealed by intense ruthenium red-positive reaction. Glycosaminoglycans (GAGs) were isolated and characterized from these pure basement membranes by using a combination of agarose gel electrophoresis and enzymatic degradation with specific enzymes. The isolated basement membrane showed a high concentration of GAGs (130 mg/g of dry tissue); of this amount 49% was hyaluronic acid, 24% was chondroitin-6-sulfate, 12% was heparan sulfate, and 14% was dermatan sulfate. Controlled digestion with heparinase and heparitinases I and II was used to study the structural features of the heparan sulfate. Four unsaturated disaccharide units were found in the heparan sulfate: disulfated, N-sulfated, N-acetylated, and N-acetylated O-sulfated disaccharides. The disaccharide units of the cholinergic heparan sulfate present a high amount of disulfated disaccharides and a low amount of N-acetylated O-sulfated disaccharides. The N-sulfated disaccharides, in contrast to the N-acetylated ones, were found through all the structure of the cholinergic heparan sulfate. Finally our work shows for the first time the presence of dermatan sulfate in the basal lamina of the electric organ.

Animals↗

PubMed1987

Heparin sequences in the heparan sulfate chains of an endothelial cell proteoglycan.

The structure of the glycosaminoglycan chain of a heparan sulfate proteoglycan isolated from the conditioned medium of an endothelial cell line has been analyzed by using various degradative enzymes (heparitinase I, heparitinase II, heparinase, glycuronidase, sulfatases) from Flavobacterium heparinum. This proteoglycan inhibits the thromboplastin-activated pathway of coagulation; as a consequence, the catalytic conversion of prothrombin to thrombin is arrested. Heparitinase I (EC 4.2.2.8), an enzyme with specificity restricted to the heparan sulfate portion of the polysaccharide, releases fragments with the electrophoretic mobility and the structure of heparin. Conversely, an assessment of the size and distribution of the heparan sulfate regions has been provided by the use of heparinase (EC 4.2.2.7), which, by degrading the heparin sections of the chain, releases two segments that exhibit the structure of heparan sulfate. One of these segments is attached to the protein core. On the basis of these findings, the heparan sulfate chain can be defined as a copolymer containing heparin regions in its structure. The combined use of these enzymes has made it possible to establish the disaccharide sequence of parts of the glycosaminoglycan moiety of this proteoglycan.

Animals↗

PubMed1985

Lack of correlation between "in vitro" and "in vivo" antithrombotic activity of heparin fractions and related compounds. Heparan sulfate as an antithrombotic agent "in vivo".

The anticoagulant (U.S.P., APTT; "in vitro" and "in vivo") antithrombotic (aXa; Yin and Wessler and chromogenic), antilipemic (LPL) activities of heparin, heparin fractions and fragments, heparinoids, heparan sulfate and other sulfated glycosaminoglycans were compared with the activities of these compounds as antithrombotics "in vivo" by four different methods (vena cavae ligature, kaolin, collagen and steel coil). A lack of correlation was observed between the activities "in vitro" and the antithrombotic activity "in vivo". For instance heparan sulfate which shows negligible pharmacological activities "in vitro" is a potent antithrombotic agent "in vivo". Likewise, several heparin fractions and fragments have low aXa activity "in vitro" and high antithrombotic activity "in vivo". It is concluded from these results that the "in vitro" tests used cannot predict the antithrombotic activity "in vivo".

Animals↗

PubMed1985

Isolation and characterization of a heparin with high anticoagulant activity from Anomalocardia brasiliana.

The isolation, some structural features, physicochemical properties and pharmacological activities of a heparin from Anomalocardia brasiliana are reported. It is shown that the mollusc heparin is very similar to those present in mammalian tissues with regard to chemical composition, physicochemical properties, pharmacological activities and susceptibility to heparinase and heparitinase II from Flavobacterium heparinum, as well as to the types of products formed by the action of these enzymes. Three significant quantitative differences were observed for the mollusc heparin when compared with the ones from mammalian origin, namely, a higher degree of binding with antithrombin III (45%), higher molecular weight (27-43 kDa) and higher anticoagulant activity (320 I.U./mg). The possible biological role of heparin is discussed in view of the present findings.

Animals↗

PubMed1985

Structural studies and "in vivo" and "in vitro" pharmacological activities of heparin fractions and fragments prepared by chemical and enzymic depolimerization.

Two heparin families (SM- and FM- heparins) have been fractionated with barium by selective precipitation at different temperatures. Fragments were obtained from these two fractions by enzymic and chemical degradation. Some structural features and pharmacological activities of FM- and SM-heparins as well as the fragments are now reported. The fragments, prepared by ascorbate/H2O2 oxidation (M.W. 4,500) or heparitinase II (M.W. 5,500), are enriched with trisulfated disaccharide units whereas heparin (M.W.12,500) and FM-heparin (M.W. 10,200) contain also N-sulfated and N-acetylated disaccharides. The chemical and enzymic fragments show 1/3 to 1/5 of the anticoagulant activity of heparin by the USP and APTT methods. The LPL releasing activity is also low in the fragments as well as the AXa activity measured by the chromogenic method. On the other hand the AXa activity measured by the Yin and Wessler procedure is two times higher in the fragments when compared to heparin. The fragments resulting from heparin after heparitinase II degradation and ascorbate/H2O2 oxidation were rich in trisulfated disaccharide units whereas heparin and FM-heparin contained also measurable amounts of monosulfated and N-acetylated disaccharide units. The mechanism of ascorbate oxidation and the structural requirements for the pharmacological activities of heparin is discussed in view of these and other findings.

Animals↗

PubMed1985

The effect of sexual hormones on the sulfated glycosaminoglycan pattern of male genital accessory organs.

The absolute and relative amounts of glycosaminoglycans and [35S]sulfate uptake were investigated in several tissues of male guinea pigs and rats under different sexual hormonal conditions (castration, estrogen treatment, or both). The hormonal effects, regarding the pattern of sulfated glycosaminoglycans, were specifically observed in the target organs (vas deferens and seminal vesicles) of both animals. Castration, in both species, decreases the amount of heparan sulfate and chondroitin sulfate, while diethylstilbestrol (DES) treatment causes different effects on rat and guinea pig target organs. In rats the effect of estrogen administration and surgical castration was essentially the same, and in guinea pigs DES increased the content of dermatan sulfate and chondroitin sulfate. The modifications in the specific patterns of the sulfated glycosaminoglycans suggest that these compounds are under sexual hormonal control only in the target organs, and show a specific pattern of distribution according to the tissue layer.

Animals↗

PubMed1985

Sulfated glycosaminoglycan composition of human gastric mucosa: effect of aging, chronic superficial gastritis and adenocarcinoma.

The sulfated glycosaminoglycan (SGAG) composition of gastric mucosa from 24 patients with chronic superficial gastritis, 2 patients with adenocarcinoma and 36 normal subjects is reported. The mucosa was obtained by endoscopic biopsy and after histopathological examination the SGAG were extracted and characterized. Three different SGAG were isolated: chondroitin 4,6-sulfate, dermatan sulfate and heparan sulfate. Their relative concentrations for the different groups were submitted to analysis of variance by Scheffe's method. Different SGAG compositions were observed in two gastric regions (antrum and body), in chronic superficial gastritis, in adenocarcinoma and in two age groups (less than 40 years and greater than 40 years). These and other results suggest that these macromolecules might be involved in the processes of cell division and aging.

Adenocarcinoma↗

PubMed1985

Fractionation and structural features of two heparin families with high antithrombotic, antilipemic and anticoagulant activities.

15 heparin preparations from bovine intestine, pancreas and lung and hog intestine were fractionated in two main components by selective barium precipitation. The ones that precipitated at room temperature with barium (slow moving (SM)-heparins) had a high anticoagulant activity measured by the USP and APTT (activated partial thromboplastin time) assay and low antithrombotic activity by the Yin and Wessler method. The fractions precipitated at 5 degrees C with barium (fast moving (FM)-heparins) had a low anticoagulant action and high antithrombotic activity. The maximum anti-Xa activity (chromogenic method) was present in heparins with molecular weights around 12-15 X 10(3) daltons whereas high APTT and LPL releasing activities were present in SM-heparins with molecular weights of 30-40 X 10(3) and 15-25 X 10(3) daltons, respectively. FM-heparins had a higher anti-Xa activity and lower lipoprotein lipase (LPL)-releasing activity when compared with the SM-heparins with the same molecular weights. Significant structural differences were observed between SM- and FM-heparins by 13C-NMR spectra and enzymatic degradation with heparinase and heparitinase from Flavobacterium heparinum. Also, significant differences were observed for anti-Xa and anticoagulant activities for the two types of heparins depending on the pharmacological assay used.

Animals↗

PubMed1985

High and low anticoagulant activity heparins. Preparation in large scale and degree of complexation with antithrombin III.

Heparin was separated into fractions with high and low anticoagulant activities by selective barium precipitation, gel filtration and ion exchange chromatography methods. Enrichment in the anticoagulant activities were observed in fractions with high molecular weight or high degree of sulfation. The combination of selective barium precipitation and ion exchange chromatography led to the preparation of heparins with very high anticoagulant activities (300 IU/mg). These heparins have a high affinity for antithrombin III (greater than 80%) and were undistinguishable from those prepared by antithrombin III affinity chromatography regarding molecular weight, sulfate/hexosamine ratio, degree of binding to antithrombin III, electrofocusing pattern and anticoagulant activity. These methods allow now the preparation in industrial scale of heparins with high anticoagulant activities for in vivo studies.

Animals↗

PubMed1984

An inverse relationship between heparin content and antibody response in genetically selected mice. Sex effect and evidence of a polygenic control for skin heparin concentration.

The heparin content of genetically selected mice with high and low antibody response to bacterial antigens is reported. An inverse relationship between antibody titres and concentration of heparin was observed for both male and female mice. The lower-antibody-responder line contains twice as much heparin as the higher-responder ones. Furthermore, the female mice also contained twice as much heparin as the male mice. Genetic analysis of the parental and interline hybrids has shown a partial dominance for the character 'heparin content' in favour of the high-heparin phenotype and this character appears to be subjected to polygenic control. The possible biological role of heparin and/or mast cells in the surveillance of the organism against some pathogens is discussed in the light of these and other findings.

Animals↗

PubMed1984

Isolation and structural studies of heparan sulfates and chondroitin sulfates from three species of molluscs.

The isolation and some structural features of heparan sulfates and chondroitin sulfates from three species of molluscs (Pomacea sp., Tagelus gibbus, and Anomalocardia brasiliana) are reported. It is shown that heparan sulfates with structural similarities to the ones found in mammals are present in the three molluscs analyzed. All the heparan sulfates were degraded by heparitinases I and II to four distinct unsaturated disaccharides with the same properties as the ones present in heparan sulfates of mammalian origin. This suggests that these four disaccharide units are maintained through the evolution. Furthermore, the proportion of these units varied in the heparan sulfates according to the species of origin. The chondroitin sulfates, on the other hand, exhibit different structural features according to the species of origin. For instance, by the action of chondroitinase AC, 4- and nonsulfated disaccharides are produced from Pomacea chondroitin, whereas 4- and 6-sulfated disaccharides are formed from Tagelus and Anomalocardia. The possible role of these compounds in cell recognition and/or adhesiveness is discussed in view of the present findings.

Animals↗

PubMed1983

Structural differences of heparan sulfates according to the tissue and species of origin.

Some structural features of thirteen heparan sulfates isolated from different mammalian tissues and species are reported. Two N-acetylated disaccharides, one of then O-sulfated and two N-sulfated disaccharides, one of then 6-sulfated are formed from these compounds by the combined action of heparitinases I and II from Flavobacterium heparinum. The relative proportions of the four disaccharide units vary quite significantly among the thirteen heparan sulfates indicating that the structure of these polymers are tissue and species specific. Based on the frequency of appearance of each one of the disaccharides it was calculated that 10(36) types of heparan sulfates might theoretically be found. The possible role of these polyanions in cell-cell recognition is discussed in view of the present findings.

Animals↗

PubMed1983

Clinical and biochemical changes in a child with type I mucopolysaccharidosis during long-term transfusion of leukocytes.

The effect of two years of periodic transfusions at 2--4 month intervals of mixed leukocytes in a patient with Type I mucopolysaccharidosis is described. There was an increase of urinary chondroitin sulfate B after the first transfusion followed by a progressive decrease to 35% of the initial daily excretion. Chondroitin sulfate AC, which was almost absent prior to the transfusions, was excreted in significant amounts after the 4th transfusion. There was a decrease of hepatosplenomegaly, kyphosis and gibbus and no changes in the other signs of the disease. Regarding stature, mental development and social behavior, the patient is developing thus far as a normal child. The early diagnosis of the disease and the immediate transfusions undoubtedly have been contributing factors to the restoration and/or maintenance of the child in an almost normal condition.

Blood Transfusion↗

PubMed1982

Turnover, change of composition with rate of cell growth and effect of phenylxyloside on synthesis and structure of cell surface sulfated glycosaminoglycans of normal and transformed cells.

The synthesis of sulfated glycosaminoglycans was analysed in mouse fibroblasts during the transition from exponential growth to quiescent monolayers. 'Normal' Swiss 3T3 fibroblasts were compared with SV40 transformed 3T3, C6, ST1 and HeLa cells. p-Nitrophenyl-beta-D-xyloside, an artificial acceptor for glycosaminoglycans synthesis, was used as a probe. Exponentially growing 'normal' 3T3 cells synthesized both dermatan sulfate and chondroitin 4-sulfate, retaining the latter and releasing the former to the medium. Upon reaching quiescence these cells switched to retention of dermatan sulfate and release of chondroitin 4-sulfate. SV3T3 cells synthesized several fold less sulfated glycosaminoglycans than 'normal' 3T3. Even though SV3T3 cells are able to synthesize dermatan sulfate, they only retained chondroitin 4-sulfate, never switching to retention of dermatan sulfate. These results indicated that the transition from rapidly proliferating to resting G0 state in normal cells is accompanied by a switch from chondroitin-sulfate rich to dermatan-sulfate-rich cells. This switching was not observed with transformed cells, which are unable to enter the G0 state. Phenylxyloside caused a several fold increase in glycosaminoglycans released to the medium in both cell types, but it did not interfere with either growth rate or cell morphology. Particularly the phenylxyloside treatment led to an increase of more than 10-fold in production of dermatan and chondroitin sulfate by SV3T3, C6, ST1 and HeLa cells. This demonstrated that transformed cells have a high capacity for glycosaminoglycan synthesis. Analysis of enzymatic degradation products of glycosaminoglycans, synthesized in the presence of phenylxyloside, by normal and transformed cells, led to the finding of 4- and 6-sulfated iduronic and glucuronic acid-containing disaccharides. This result indicated that the xyloside causes the synthesis of a peculiar chondroitin sulfate/dermatan sulfate, in both normal and transformed cells.

Animals↗

PubMed1982

Absence of heparin or heparin-like compounds in mast-cell-free tissues and animals.

Three models were used for the analysis of heparin concentration and the presence of mast cells, namely different fetal and adult bovine tissues, mast-cell-deficient mice and athymic mice. It was observed that heparin and mast cells are present mainly in spleen and liver during fetal development and in skin, lung and ileum in adults. A good correlation between the concentration of heparin and the number of mast cells was observed in all tissues examined. No heparin was detected in animals that did not have mast cells, such as the WBB6Fl W/Wv mice, again suggesting a correlation between mast cells and heparin. No differences in the other sulfated glycosaminoglycans were observed between the mast cell-deficient mice and the normal littermates and breeders. Studies in 'nude' mice have shown that the heparin concentration in different tissues is similar to normal strains.

Age Factors↗