Semax prevents learning and memory inhibition by heavy metals.

Separate and joint effect of Semax, ascorbic acid, lead diacetate, and ammonium molybdate on avoidance conditioning in rats was studied. It was established that the heavy metal salts inhibited the avoidance response, and the peptide counteracted this inhibition as strongly as ascorbic acid or to a comparable degree. These findings confirm the antioxidant properties of Semax.

Poly(2-hydroxyethyl methacrylate) particles for preoperative endovascular occlusion of extensive angiodysplasias.

The application of superselective endovascular occlusion in vascular radiology has broadened the scope of possible radical surgery of giant angiodysplasias by reducing considerably the risk of severe haemorrhage during the surgery. Occlusion was performed on 229 patients using spherical and cylindrical particles of porous poly(2-hydroxyethyl methacrylate). The treatment of a patient suffering from angiodysplasia of the pelvis is described as an example. The first day following endovascular occlusion a hypercoagulation reaction developed, with a decrease of both the level of fibrinolysis and of anticoagulant factors. This was mainly due to a decrease of the level of antithrombin III and activation of the factor XIII indicating a strong tendency of intravascular thrombosis. During the third day, the hypercoagulation reaction increased. However, on the fifteenth day, parameters of the haemostasis system were close to normal values. Only the activity of the factor XIII remained high suggesting the stabilization and the organization of fibrin clot in the embolized blood vessel territory.

Hydrogels in endovascular embolization. III. Radiopaque spherical particles, their preparation and properties.

The synthesis and properties of spherical radiopaque hydrogel particles designed for endovascular occlusion are reported. These particles were prepared by the hydroxyl acylation of low crosslinked poly (2-hydroxyethyl methacrylate) beads with a nontoxic radiopaque compound based on triiodobenzoic acid, without affecting their properties which are advantages in medical practice. The effect of the iodine content on the size of dry and swollen particles is discussed. It has been found that an iodine content of about 25-30 wt% is desirable in order to obtain an easily recognizable X-ray image. These particles make the immediate control of embolus application easy and enable periodical inspection of the polymer to check the successful blockage of the vessel. They also open up the method of endovascular occlusion to further improvement.

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.

Effect of infections on the degradation of polyethylene terephthalate implants.

The macrokinetics of degradation of polyethylene terephthalate (PET) protheses removed from patients were investigated. Two types of protheses were analysed in dependance on polymer environment: 15 patients were characterized as normal, with post-operation periods of 1-10 years and 7 patients were operated at different times after implantation having a bacterial environment around the implants. The tensile strengths, surface morphology and molecular mass of these samples were compared. The macrokinetics of the PET degradation have been described. The presence of bacteria characterized by acid pH accelerates the loss of tensile strength and molecular mass in the PET corresponding to the mechanism of the polymer matrix destruction. The protheses not subjected to infection have been degraded on the surface. The experimental values of the rate constant may be used for lifetime prediction of the polymer implants in the human body under different conditions.

Polycaproamide degradation in rabbits and in several model media.

The nets of polycaproamide removed from rabbits after implantation for times up to 400 days showed a significant change in mass and in molecular weight. The degradation of polycaproamide filaments takes place both on the surface (change of mass) and in the bulk of the polymer implant (change in the molecular weight). The role of phosphates and the enzymes in the polymer degradation are discussed.

[X-ray diffraction analysis of disintegration of polyglycolic acid suture material both in vivo and in model media]. / Rentgendifraktsionnoe issledovanie destruktsii shovnykh nitei na osnove poliglikolida v zhivom organizme i v model'nykh sredakh.

Examined were the structural variations of polyglycolic acid surgical suture material by X-ray diffraction methods subsequent to sejour in vivo and in several model mediums. After a long stay in vivo, water and buffer at pH 2 the following structural variations in the polymer were observed: diminution of macroperiod, and certain increase of crystallinity. Rather profound, ten times faster destruction of suture material in alkaline medium at pH 12 did not cause the variation of macroperiod and crystallinity. Even in the case of extensive destruction with mass losses approaching 90% and variation of crystalline structure of the polymer was not observed. These data confirm the theory described previously by the authors on the existence of two possible methods of polymer destruction in aggressive mediums passing through total volume and on the plastic surface only.