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Biomedical subjects

O Larm

Publications and source records attributed to O Larm.

At least 37 records · Page 2Linked to original sources
PubMed1986

Thrombin inactivation on surfaces with covalently bonded heparin.

About 8000 Daltons porcine mucosa heparin fragments were covalently bonded by end-point attachment to polyethylene. The interaction between the immobilized heparin, added thrombin, and antithrombin III [AT] was investigated. The heparin surface was adsorbed with either albumin, AT dissolved in albumin or Tyrode, or platelet free plasma. Irrespective of the pre-treatment procedure, exposure of the surface to thrombin resulted in the same substantial decrease of thrombin in solution and the same degree of surface-confined thrombin activity. It was concluded that the heparin surface has a large capacity to bind thrombin and that the thrombin inhibitory capacity of high affinity heparin fragments is limited. On exposure of the thrombin-loaded surfaces to defibrinogenated plasma or AT, the surface-confined thrombin was inhibited within 30 seconds. Successive dilutions of plasma or AT decreased the inhibition rate but not the inhibition capacity. It is concluded that inhibition of thrombin adsorbed on the heparin surface occurs as follows: Added AT adheres to high affinity heparin fragments on the surface whereupon adsorbed thrombin migrates in the hydrophilic heparin coating towards the reaction site of AT and becomes inhibited. The inactivated thrombin-AT complex leaves then the surface, thus enabling the process to be repeated.

Antithrombin III↗
PubMed1985

In vivo activation of mouse macrophages with beta-1,3-D-glucan-derivatized plastic beads.

Macrophages obtained from animals treated with beta-1,3-D-glucan-derivatized plastic beads were greatly stimulated, as judged by morphology, esterase release, and cytostatic effect on L-929 tumour cells in vitro. The pretreatment of mice with such beads conferred an apparent absolute local resistance to an otherwise lethal pneumococcal infection but had no effect on the growth of intraperitoneal AA ascites sarcoma. Moreover, peritoneal cells from animals pretreated with glucan beads did not protect the animals in a Winn assay.

Animals↗
PubMed1985

Haemodialysis in dogs with a heparin coated hollow fibre dialyser.

Haemodialysis was performed in non-uraemic dogs with equipment coated with a stable heparin. During a three hour dialysis a constant blood flow of 205 ml/min was easily maintained. There was no increase in whole blood coagulation time and no heparin release from the surface. The platelet count was initially reduced by 15 per cent, but remained constant at this value throughout the dialysis. No increase in FPA concentration was detected. Heparin coating on inherently thrombogenic materials enables haemodialysis in the absence of systemic anticoagulation and without measurable activation of the haemostatic mechanism.

Animals↗
PubMed1984

Stimulatory effect of immobilized glycans on macrophages in vitro.

Mouse macrophages were cultured on chemically modified plastic dishes. On dishes covered with immobilized glycans, the macrophages were stimulated as judged by increased 14C-glucosamine incorporation, increased cytostatic and cytolytic capacities and by morphology as seen by scanning electron microscopy. The corresponding soluble glycans did not have the capacity to stimulate macrophages as measured by these criteria. Plastic surfaces covered with polyethylenimine showed stimulation of the macrophages with regard to some of the parameters measured. These results may indicate that the stimulation is a multistep process and that, contrary to earlier findings, it is not a prerequisite for stimulation that the glycan be intracellular. The results support the idea that a fixed steric arrangement of glycans is necessary for the stimulation of macrophages in vitro.

Amylose↗
PubMed1983

A new non-thrombogenic surface prepared by selective covalent binding of heparin via a modified reducing terminal residue.

A new method for the covalent binding of heparin to artificial surfaces has been developed. The heparinized surface releases insignificant amounts of heparin and can be regarded as stable. The blood contact properties as studied in vitro revealed that the surface was highly thromboresistant in terms of reduced platelet adhesion, surface catalyzed adsorption and inhibition of thrombin and capacity to prevent clotting of nonanticoagulated blood.

Blood Coagulation↗
PubMed1982

Mechanisms of anticoagulant effects of some sulphated polysaccharides.

The anticoagulant activity of a partially reduced sulphated alginic acid, a partially reduced aminated and sulphated alginic acid and sulphated guaran have been studied. The anticoagulant activities in the APTT assay were 28, 39 and 70 IU/mg respectively. None showed any activity in anti-factor Xa assay. Studies on binding to Antithrombin III - Sepharose showed that sulphated guaran and a fraction of the aminated and sulphated alginic acid was bound, whereas no binding occurred with sulphated alginic acid. The inhibition of thrombin activity by these polysaccharides was studied in purified systems with or without added Antithrombin III, using both fibrinogen clotting and chromogenic peptide substrate assays. The two alginic acid preparations showed Antithrombin III-dependent inhibition of thrombin, whereas the sulphated guaran inhibits both by Antithrombin III-dependent and independent mechanisms.

Alginates↗
PubMed1982

Endocytosis of agarose in mouse peritoneal macrophages in vitro.

We have studied the endocytosis of tritium-labelled and of non-radioactive agarose in mouse macrophages in vitro. The endocytosis was greatest and most rapid in syngeneic mouse serum and in human serum, reaching a plateau after 12 h of incubation. Ten per cent serum was the minimum concentration giving optimal ingestion. The endocytosis appeared to be regulated by mechanisms involving complement factors C3 and B. Different pretreatments of sera, inactivating or depleting C3 and B, resulted in 70-80% reduction of endocytosis. Preincubation of agarose in untreated serum increased the endocytosis of agarose in heat-inactivated serum three-fold indicating that the essential factors were bound to agarose. Antibodies against C3 and B reduced endocytosis moderately but significantly.

Animals↗
PubMed1980

Structural studies on the carbohydrate portion of human antithrombin III.

Human antithrombin III has been shown to contain four identical N-glycosidically linked carbohydrate chain per molecule. These carbohydrate chains have been investigated by sugar and methylation analysis before and after removal of N-acetylneuraminic acid residues. The chains have been further investigated by Smith degradation, trifluoroacetolytic degradation, and degradation after chromium trioxide oxidation. As a result of these studies, the following structures is proposed for the carbohydrate chains in human antithrombin III: (formula: see text). NeuNAc, N-acetylneuraminic acid; Galp, galactopyranose; GlcNAcp, 2-acetamido-2-deoxyglucopyranose; Manp, mannopyranose are the abbreviations used in the structure.

Antithrombin III↗
PubMed1979

Identification of N-sulphated disaccharide units in heparin-like polysaccharides.

1. Preparations of heparin and heparan sulphate were degraded with HNO2. The resulting disaccharides were isolated by gel chromatography, reduced with either NaBH4 or NaB3H4 and were then fractionated into non-sulphated, monosulphated and disulphated species by ion-exchange chromatography or by paper electrophoresis. The non-sulphated disaccharides were separated into two, and the monosulphated disaccharides into three, components by paper chromatography. 2. The uronic acid moieties of the various non- and mono-sulphated disaccharides were identified by means of radioactive labels selectively introduced into uronic acid residues (3H and 14C in D-glucuronic acid, 14C only in L-iduronic acid units) during biosynthesis of the polysaccharide starting material. Labelled uronic acids were also identified by paper chromatography, after liberation from disaccharides by acid hydrolysis or by glucuronidase digestion. Similar procedures, applied to disaccharides treated with NaB3H4, indicated 2,5-anhydro-D-mannitol as reducing terminal unit. On the basis of these results, and the known positions and configurations of the glycosidic linkages in heparin, the two non-sulphated disaccharides were identified as 4-O-(beta-D-glucopyranosyluronic acid)-2,5-anhydro-D-mannitol and 4-O-(alpha-L-idopyranosyluronic acid)-2,5-anhydro-D-mannitol. 3. The three monosulphated [1-3H]anhydromannitol-labelled disaccharides were subjected to Smith degradation or to digestion with homogenates of human skin fibroblasts, and the products were analysed by paper electrophoresis. The results, along with the 1H n.m.r. spectra of the corresponding unlabelled disaccharides, permitted the allocation of O-sulphate groups to various positions in the disaccharides. These were thus identified as 4-O-(beta-D-glucopyranosyl-uronic acid)-2,5-anhydro-D-mannitol 6-sulphate, 4-O-(alpha-L-idopyranosyluronic acid)-2,5-anhydro-D-mannitol 6-sulphate and 4-O-(alpha-L-idopyranosyluronic acid 2-sulphate)-2,5-anhydro-D-mannitol. The last-mentioned disaccharide was found to be a poor substrate for the iduronate sulphatase of human skin fibroblasts, as compared with the disulphated species, 4-O-(alpha-L-idopyranosyluronic acid 2-sulphate)-2,5-anhydro-D-mannitol 6-sulphate. 4. The identified [1-3H]anhydromannitol-labelled disaccharides were used as reference standards in a study of the disaccharide composition of heparins and heparan sulphates. Low N-sulphate contents, most pronounced in the heparin sulphates, were associated with high ratios of mono-O-sulphated/di-O-sulphated (N-sulphated) disaccharide units, and in addition, with relatively large amounts of 2-sulphated L-iduronic acid residues bound to C-4 of N-sulpho-D-glucosamine units lacking O-sulphate substituents.

Chemical Phenomena↗
PubMed1976

Bromine oxidation of methyl alpha- and beta-pyranosides of D-galactose, D-glucose, and D-mannose.

Methyl alpha- and beta-pyranosides of D-galactose, D-glucose, and D-mannose have been oxidized with bromine in aqueous solution at various pH values. The resulting keto glycosides were converted into their more-stable O-methyloxime derivatives which were characterized by spectroscopy and chromatography. Oxidation at a ring carbon atom where the hydrogen is axial is hindered by bulky substituents in syn (i.e., a 1,3) diaxial relationship. Thus, the aglycon group in the alpha anomers protects position 3, the axial HO-4 in galactopyranosides protects position 2, and the axial HO-2 in mannopyranosides protects position 4 from oxidation.

Bromine↗