K. Z. Gumargalieva

Hydrogels in endovascular embolization. II. Clinical use of spherical particles

In this study we report the results of clinical experiments, obtained with spherical particles made from poly(2-hydroxyethyl methacrylate) used in the embolization of arteriovenous anastomoses, in the suppression of pulmonary haemorrhage and haemoptysis and in the occlusion of some other arteries. So far we have used these particles in the treatment of 187 patients. It must be stressed that the advantage of spherical particles consists in the simplicity of their introduction into the blood vessel through a catheter, while in the blood vessel itself the particle swells in blood still more, when compared with the particle size in saline. This results in an immediate and permanent haemostatic effect. No revascularization occurs.

Poly(2-hydroxyethyl methacrylate) beads for the preoperative endovascular occlusion of branches of the hepatic artery in focal alterations of the liver

Spherical particles of porous poly(2-hydroxyethyl methacrylate) have been used in the treatment of patients suffering from focal alterations of the liver, namely haemangioma and hypervascular tumour. The treatment consisted of the preoperative endovascular occlusion of branches of the hepatic artery using these spherical particles, and was followed by an operation. The main merit of the preoperative occlusion of blood vessels is that it substantially reduces blood loss during surgery. In order to determine the optimal time for the operation on the liver, indicators of the coagulation system were examined in successive terms of the postemboilization period. Reaction of the organism to endovascular occlusion is reflected in hypercoagulation changes in the coagulation system.

Hydrogels in endovascular embolization: IV. Effect of radiopaque spherical particles on the living tissue

In this study we report the results of toxicological, histological and haematological experiments on radiopaque spherical particles based on poly(2-hydroxyethyl methacrylate). These particles have been developed for endovascular occlusion of various organs. Radiopacity was attained by two independent methods: the chemical attachment of radiopaque substances to the hydrogel or the precipitation of radiopaque substances in the hydrogel network. The first method yields particles that appear to have uniformly-distributed contrast material, but in the particles prepared by the second procedure the contrast material is predominantly located on the surface. The visibility of such particles by X-rays makes possible controlled embolus introduction and inspection of the polymer for long periods after embolization. Radiopaque contrasting changes the morphology and reduces the porosity of the material but supports quick thrombus formation. Embolic material implanted in rabbits becomes surrounded by a thin fibrous capsule and undergoes partial organization. This and other results of medico-biological investigations have fully demonstrated the biocompatibility of radiopaque spherical emboli, which can now be used clinically.

Hydrogels in endovascular embolization. V: Antitumour agent methotrexate-containing p(HEMA)

The aminohexyl derivative of the copolymer of 2-hydroxyethyl methacrylate and ethylene dimethacrylate (p(HEMA)-Hex) in the form of regular spherical particles was used as a polymeric carrier for chemically sorbed methotrexate (MTX). The effect of the washed p(HEMA)-Hex-MTX carrier on the morphological structure of donor blood, on blood coagulation indicators and on responses of the living tissue surrounding the material which has been in the blood vessel of the rabbit for various periods of time was evaluated. MTX is capable of diffusion for several days from the embolic material.

Haemostatic activity of ethamsylate and aminocaproic acid adsorbed poly(2-hydroxyethyl methacrylate) particles

A haemostatic material suitable for embolization was prepared by the adsorption of haemostatics--ethamsylate and aminocaproic acid in the spherical particles of porous poly(2-hydroxyethyl methacrylate) (p(HEMA)). The degree of purification of ethamsylate-treated particles was tested by an analysis of donor blood in contact with the material. An evaluation of the haemostatic properties of these materials was obtained by the determination of the indicators of blood clotting: activated partial thromboplastin time, thrombin time, and prothrombin time. Ethamsylate or aminocaproic acid-containing p(HEMA) has a distinct haemostatic effect on pathological blood of patients suffering from focal alterations of the liver. These haemostatic emboli materials show promise for the immediate control of various haemorrhages; when introduced into a zone with increased haemorrhage, they may help to correct disturbed haemostasis.

Biodegradation of Polymeric Material and Adhesion Properties of Microorganism Cells

Abstract This paper addresses the possibility of applying IR-spectroscopy with Fourier analysis to the study of the chemical composition of conidia films, defining surface hydrophobia. The possibility was obtained to predict conidium hydrophobia, based on the available data on component ratio. This is the defining factor at microorganism adhesion on solid surfaces and at further processes of biodegradation.

Antioxidant effectiveness in polymer blends

Abstract The connection between the apparent rate constant of chain termination by an antioxidant and the sorption properties of the polymer towards this antioxidant is discussed. Experiments have shown that in oxidation of polyethylene-polypropylene and polyethylene-poly(methylstyrene) blends at 180 °C in the presence of the antioxidant phenyl-β-naphthylamine, the critical antioxidant concentration changes in the direction opposite to the antioxidant concentration in the vapor phase.

Effect of p-toluensulfonic acid on oxidation of polyethylene and polyethylene-poly-p-methylstyrene blends

Abstract p -Toluensulfonic acid retards oxidation of polyethylene and, to a greater extent, of polyethylene-poly- p -methylstyrene blends. The real antioxidant is p -cresol, formed by p -toluensulfonic acid transformation in oxidizing polyethylene and, in blends, through peroxidation and subsequent acid-catalyzed decomposition of hydroperoxides of poly- p -methylstyrene.

Variation of Antioxidant Effectivity with Copolymer Composition

Abstract The variation of inhibited oxidation parameters with the composition of ethylene-propylene and ethylene-vinyl chloride copolymers is studied. In both cases the antioxidant effectivity is minimal in copolymers containing small amounts of the second monomer groups.