Biomedical subjects

M Jozefowicz

Publications and source records attributed to M Jozefowicz.

At least 37 records · Page 2Linked to original sources

PubMed1992

Insoluble DNA-like phosphorylated polystyrene: specific interactions with anti-DNA antibodies from systemic lupus erythematosus patients.

Systemic lupus erythematosus (SLE) is an autoimmune disease. Antibodies directed mainly against DNA and/or phospholipids are present in the serum of SLE patients. Therefore phosphorylated polystyrene derivatives acting as DNA-like polymers should be able to interact with the SLE anti-DNA antibodies. Such functional polymers were synthesized and subsequently their interactions with the anti-DNA antibodies studied. Adsorption experiments performed with both anti-DNA antibodies and normal immunoglobulins showed high affinity constants of the phosphorylated polymer for anti-DNA antibodies (4 x 10(9) M-1) whereas for normal IgG the affinity was low (2 x 10(5) M-1). Moreover, the interaction was specific involving the idiotypic moiety of the anti-DNA antibodies and an array of phosphoester groups at the surface of this biomaterial.

Adsorption↗

PubMed1991

Interactions of functionalized polystyrene derivatives with the complement system in human serum.

The interactions between blood and insoluble polysaccharidic surfaces result in activation of the immune system of complement. When substituted with carboxymethyl groups, Sephadex loses its capacity to activate complement, whereas Sephadex sulphate has been described as an activator. In order to elucidate the molecular mechanisms of complement activation and inhibition, a simpler polymer model has been chosen: it consists of an insoluble polystyrene backbone on which either isolated hydroxymethyl or sulphonate groups or both are present. The surfaces bearing the isolated groups consume complement but the mechanisms involved are quite different. In contrast, a surface bearing equal proportions of both types of groups is a non-activator. Such model surfaces can be very useful for designing artificial surfaces able to control in situ complement activation.

Biocompatible Materials↗

PubMed1990

Plasmatic antiproteinase activity enhancement by insoluble functionalized polystyrene surfaces.

Antithrombogenic functional polymer surfaces have been obtained by grafting heparin or by substituting insoluble polystyrene with sulphonate and/or amino acid sulphamide groups. Their heparin-like properties have been related to their catalytic effects on the antithrombin III - thrombin complex formation. Amongst these antithrombogenic surfaces, this study demonstrates that some insoluble amino acid sulphamide derivatives of polystyrene strongly potentiate heparin cofactor II, in addition to antithrombin III. In contrast, an insoluble polystyrene sulphonate and, to a lesser extent, an insoluble heparin copolymer, are better catalysts of antithrombin III. It is hypothesized that such different behaviours result from different conformations of the species adsorbed onto the surfaces. The conclusions support the possible use of such amino acid sulphamide groups to prepare antithrombogenic surfaces in contact with blood.

Antithrombin III↗

PubMed1990

Interactions of biospecific functional polymers with blood proteins and cells.

Biospecific functional polymers, i.e. synthetic or artificial polymers substituted with specific chemical functional groups carried by the macromolecular chain are designed to interact with living systems. These polymers are either insoluble or soluble, derived from polystyrene and dextran. Polymers substituted with aryl sulfonate and carboxyl groups specifically interact with antithrombin III and serine-proteases involved in the coagulation of blood. As a consequence, these polymers possess heparin-like activity and are therefore of low thrombogenicity when exposed to flowing blood. Other functional polymers have been prepared in order to interact with various components of the immune system. Soluble and insoluble functional polymers in contact with cells can affect both cell proliferation and metabolism. Some functional polymers have the ability to inhibit or to stimulate cell growth while others can alter cell function without a change in growth characteristics. The functional polymers described have possible applications as plasma expanders, non-thrombogenic catheters, non-complement activating surfaces and other applications in oncology, biotechnology and immunochemistry.

Adsorption↗

PubMed1989

Regulation of the human alternative complement pathway: formation of a ternary complex between factor H, surface-bound C3b and chemical groups on nonactivating surfaces.

Sephadex [alpha(1----6) cross-linked dextran] activates the human alternative pathway of complement. Substitution of hydroxyl groups of Sephadex with carboxymethyl groups (CM) results in a dose-dependent decrease of the activating capacity of the polymer in normal human serum. Sephadex bearing one CM group/glycosyl unit (CM-Seph 0.95) exhibited no activating capacity. CM groups did not interfere with the ability of the polymer to covalently bind C3b in the presence of purified alternative pathway proteins nor with the capacity of bound-C3b to form a C3 convertase in the absence of regulatory proteins. C3b that was bound to CM-Seph 0.95 was more susceptible to inactivation by factors H and I in serum than C3b bound to Sephadex. Binding studies using 125I-labeled H demonstrated that H bound with a similar affinity to the activating particle Sephadex, to Sephadex bearing C3b and to the nonactivating particle CM-Seph 0.95. However, factor H bound with a 5- to 7-fold higher affinity to CM-Seph 0.95 bearing C3b. These results demonstrate a requirement for both CM groups and C3b molecules in order for H to bind with high affinity to C3b on the non-activating surface, and indicate that H formed a ternary complex with surface-bound C3b and CM groups on CM-Seph 0.95. Using a chemically defined model system, the present study provides a molecular basis for the enhanced interaction between surface-bound C3b and factor H on nonactivators of the human alternative pathway.

Complement Activation↗

PubMed1989

Contributions of negatively charged chemical groups to the surface-dependent activation of human plasma by soluble dextran derivatives.

Negatively charged surfaces are known to promote contact activation. The mechanism responsible for increasing affinity for surfaces is not yet quite understood, although the presence of negative charge densities is thought to be a prerequisite. With the availability of soluble dextran derivatives, varyingly substituted with charged methylcarboxylate, methylbenzylamide sulphonate and uncharged methylbenzylamide residues, we were able to discriminate between the contributions of these chemical moieties to contact activation, thus suggesting that the stimulating properties of synthetic negatively charged surfaces should also be described in terms of specific interactions instead of global negative charge density. This could be effected by quantifying the activating capacities as a function of the chemical group composition. A direct correlation linking activating capacities to anticoagulant properties has been observed.

Adsorption↗

PubMed1988

Adsorption of plasma proteins onto anticoagulant polystyrene derivatives: a fluorescence study.

Quenching of fluorescence was used to monitor adsorption of thrombin (T), antithrombin (AT) and their inactive complex (T-AT) onto three anticoagulant biomaterials made of polystyrene beads bearing the functional groups of heparin. An adsorption capacity of 0.12 mumol of T per mg of polymer allowed the formation of a monolayer of protein at the polymer surface. An affinity constant of 3 x 10(7) l.mol-1 between thrombin and polymer was estimated, whatever the polymer used. The affinity of T-AT was similar although weaker. Desorption of proteins from the polymeric interface by means of polycations (polybrene and polylysine) showed that the inactive complex T-AT is more quantitatively and easily released than thrombin.

Adsorption↗

PubMed1988

Heparin-like tubings. III. Kinetics and mechanism of thrombin, antithrombin III and thrombin-antithrombin complex adsorption under controlled-flow conditions.

In previous papers, we described treated tubular materials which exhibit an heparin-like antithrombic activity under dynamic conditions. In order to ascertain the heparin-like mechanism of this activity, we have studied the interactions of thrombin, antithrombin III and thrombin-antithrombin III complex with the inner face of these treated tubings under controlled-flow conditions. Moreover, the kinetics of the adsorption of thrombin were studied at different flow rates to establish the rate-determining step.

Adsorption↗

PubMed1988

Specific antibodies enhance Sephadex-induced activation of the alternative complement pathway in human serum.

Sephadex beads, which resemble cellulose in their basic chemical structure, were used to study the molecular mechanisms by which cellulosic dialysis membranes activate the alternative complement pathway in normal human serum. Sera from different individuals were found to vary in the extent of activation which occurred following incubation with a fixed amount (surface area) of polymer. Preadsorption of serum with an excess of Sephadex at 2 degrees C resulted in loss of activation when the absorbed serum was interacted with fresh Sephadex beads. Acid eluted proteins from absorbed Sephadex restored the capacity of preadsorbed serum to activate complement in the presence of fresh Sephadex. Adsorption of the immunoglobulin G (IgG) fraction and of F(ab')2 fragments from IgG prepared from the plasma of a normal individual with Sephadex, resulted in the specific binding of some IgG and F(ab'2) molecules to the particles. IgG and F(ab')2 coated beads activated complement in Sephadex-adsorbed serum. Thus, specific anti-dextran IgG antibodies trigger activation of the alternative complement pathway by Sephadex in human serum. The effect is independent of the Fc region of IgG. These results suggest that specific antibodies could be important in determining complement activation in vivo in patients undergoing haemodialysis with cellulosic membranes.

Adsorption↗

PubMed1988

Heparin-like tubings. II. Mechanism of the thrombin-antithrombin III reaction at the surface.

In a previous paper we described the surface treatment of tubings made of polystyrene grafted by irradiation onto polyethylene tubular materials. As a result, polystyrene moieties of their inner face were substituted by sulphonate and aspartic acid sulphamide groups. In order to study the mechanism of the thrombin-antithrombin III reaction occurring at the modified surface and to determine the kinetics of the reaction, step by step experiments were set up involving either the protease adsorbed at the surface reacting with the antiprotease circulating in the solution or the opposite. These procedures allowed us to demonstrate the heparin-like catalytic activity of the tubings.

Adsorption↗

PubMed1988

Heparin-like tubings. I. Preparation, characterization and biological in vitro activity assessment.

In order to prepare tubular materials which could be used in blood-circulating medical devices, polystyrene was grafted by irradiation on to polyethylene tubings. A chemical surface treatment was used which resulted in the functionalization of the inner face of the tubing. This procedure is described and the chemical assessment of the constitution of the functionalized polymer has been completed. Tubing, the inner face of which is made of polyethylene-polystyrene copolymer in which polystyrene moieties were substituted with sulphonate and aspartic acid sulphamid groups, was tested for antithrombic properties in a circulating device under controlled transport conditions and by use of purified proteins.

Antithrombin III↗

PubMed1988

The ability of Sephadex to activate human complement is suppressed in specifically substituted functional Sephadex derivatives.

The capacity of Sephadex and of chemically substituted Sephadex derivatives to activate human complement was examined by incubating polymer particles in normal human serum (NHS) under conditions that allow classical and/or alternative pathway activation, and by determining complement consumption or generation of C3a antigen in serum. Sephadex was found to activate complement in NHS, mainly through the alternative pathway. The complement-activating capacity of Sephadex was directly related to the surface area of polymer that could interact with serum. Substitution of hydroxyl groups of Sephadex with carboxymethyl (CM) groups suppressed the complement-activating capacity of the polymer in a dose-dependent fashion so that Sephadex bearing an average of one or more CM groups per saccharidic unit exhibited no complement-activating ability. Blocking of CM groups on CM sephadex with amide bonds did not restore a complement-activating capacity to the polymer, indicating that intact hydroxyl groups of the sugar units are required for complement activation by Sephadex. CM Sephadex was also found to adsorb C3adesArg which bound to the polymer with a calculated affinity of 1 x 10(6) l x M-1. Substitution of Sephadex with carboxymethyl and benzylamide sulphonate groups which confers to the polymer the capacity to catalyse thrombin inactivation on its surface also suppressed the complement-activating capacity of Sephadex. Sephadex derivatives that lack complement-activating properties and adsorb anaphylatoxins may provide useful models for the design of cellulosic membranes and biomaterials with blood compatible properties.

Blood↗

PubMed1988

Absence of effect of heparin on insulin secretion.

Bioartificial pancreatic devices containing isolated islets of Langerhans have been designed, in which the blood of the recipient circulates in contact with an artificial membrane, protecting the islets against immune rejection. This system assumes that heparin, required to prevent blood clotting, does not alter insulin secretion. However, heparin has been reported to inhibit in vitro insulin secretion by rat islets and to suppress in vivo insulin secretion in dogs. Therefore, the following evaluation was made on the effect of different heparin preparations on insulin secretion. (a) Isolated rat islets of Langerhans were perfused or incubated in the absence or presence of 20 micrograms/ml heparin; insulin secretion in response to a stimulation by glucose 20 mM was not altered by the presence of heparin. (b) Insulin secretion by an insulin-secreting cell line (RINm5F) in response to leucine and theophylline was not suppressed by heparin up to 100 micrograms/ml concentration. However, an inhibitory effect was observed at 200 micrograms/ml, which is 100 times higher than the heparin concentration commonly used for therapeutic use. (c) Neither in normal rats nor in dogs did heparin alter portal plasma insulin levels and the increase in plasma insulin following an intravenous injection of glucose. In conclusion, these data do not confirm the formerly observed inhibitory effect of heparin, which can therefore be used for the in vivo evaluation of a bioartificial pancreas.

Animals↗

PubMed1987

Reversible morphological and functional abnormalities of RINm5F cells cultured on polystyrene sulfonate beads.

RINm5F cells (an insulin-secreting cell line) were cultured on PSSO3Na microbeads under static conditions. The cell growth rate was either identical to that of cells grown on plastic wells or slower, depending on the initial cell concentration. With both supports, it was similarly influenced by the fetal calf serum concentration in the culture medium, and protein content per cell was identical. However, no spreading was observed when cells were cultured on microbeads. RINm5F cells cultured on plastic wells responded to arginine + theophylline and to leucine + theophylline by a significant increase in insulin secretion. By contrast, in cells cultured on PSSO3Na microbeads, the increase in this secretion was only slight or nil. All these abnormalities were reversible. Thus, when cells cultured on microbeads were detached and seeded on plastic wells, normal spreading and insulin secretion were observed. Lastly, PSSO3Na beads had an acute suppressive effect on insulin secretion by cells cultured on plastic wells. This study provides an example of cell-biomaterial interaction in which cell growth is possible, but with altered cell function.

Adenoma, Islet Cell↗

PubMed1987

Heparin-like activity of insoluble sulphonated polystyrene resins. Part III: Binding of dicarboxylic amino acids.

It has been demonstrated previously that polystyrene sulphonate possesses anticoagulant properties and that the binding of some amino acids could enhance the heparin-like properties of such resins. These properties depend on the surface density of the active groups, the nature and binding of the group and on the net change borne by the polymer. In this paper, we describe the preparation of copolystyrene (sulphonate-dicarboxylic amino acid sulphamide) resins. By measuring their antithrombotic-surface-activity, we demonstrate that the activity developed by each carboxyl group is at least roughly the same as the activity of one sulphonate group, except in the case of aspartic acid sulphamide resin for which a cooperative effect is shown. The anticoagulant properties of resins bearing phosphonate or monocarboxylic amino acid sulphamides are also examined.

Amino Acids, Dicarboxylic↗

PubMed1985

Heparin-like activity of insoluble sulphonated polystyrene resins. Part I: Influence of the surface density, nature and binding of substituted anionic groups.

It was previously demonstrated that copolystyrene (sulphonate-amino acid sulphamide) resins possessed an anticoagulant heparin-like activity in the presence of blood plasma. Taking into account the variable surfaces of swollen resins developed by these dry resins, it is now shown that the antithrombic activity of crosslinked sulphonated polystyrene is linearly dependent on the surface density of the sulphonate groups. This fact implies that the presence of such isolated groups is sufficient to obtain a catalytic site for increasing the rate of inactivation of thrombin by plasmatic proteins. It is also shown that replacing sulphonate groups either by directly backbone-bonded carboxylate groups or by methionine linked by amide bonds to polystyrene backbone is not sufficient to endow the resulting resins with a significant anticoagulant activity.

Anticoagulants↗

PubMed1984

Adsorption of purified thrombin or antithrombin III for two insoluble anticoagulant polystyrene derivatives: II. Competition with the other plasma proteins.

In the preceding paper, we described results concerning the adsorption of purified thrombin and antithrombin III on two insoluble anticoagulant polystyrene derivatives. We now report similar results obtained in a plasma system. In each case, the purified protein was mixed with fresh platelet poor plasma in order to maintain the same concentrations of all the other plasma proteins. The thrombin molecule was modified by alkyl phosphorylation of the active serine site prior to mixing with plasma. The adsorption of antithrombin was found to be reduced 8 to 9 times when the protein solution was substituted by diluted plasma. In contrast, the thrombin adsorption only depends on the substituents bound on the polymeric chain. These results are supported by those of the study of the competition between purified antithrombin and albumin.

Adsorption↗

PubMed1984

Catalysis of the generation of thrombin-antithrombin complex by insoluble anticoagulant polystyrene derivatives.

The inhibition of thrombin by antithrombin III is known to be accelerated by heparin through the formation of complexes between the muccopolysaccharide and both proteins. In the preceding papers, we reported that polystyrene derivatives absorb thrombin and its inhibitor with a higher affinity for the protease than for the antiprotease. These complexes are responsible for the catalysis of the generation of thrombin-antithrombin complex which was observed either with purified proteins or in plasma. The protease-antiprotease complex has an affinity for the polymer surface which is higher than that of antithrombin but lower than that of thrombin. Therefore, the thrombin-antithrombin complex generated on the insoluble material is desorbed by thrombin and a catalytic anticoagulant effect can be observed with these polymers.

Anticoagulants↗