Biomedical subjects

J Vacík

Publications and source records attributed to J Vacík.

At least 19 recordsLinked to original sources

PubMed2000

[Surgical treatment of recurrent urethral strictures in males after unsuccessful operations].

BACKGROUND: Subvesical obstructions of any origin represent a frequent and serious disorder occurring predominantly in males. Often it brings incontinence and/or erectility dysfunction, infection of urinary tract. Relapses of the acute pyelonephritis can turn into chronic tubulointersticial one and terminate in the renal insufficiency. To treat strictures, dilation, intermittent catheterization and recently stent introduction were used. Most suitable appears a stent from composite polymers. The aim of our work was to test properties of stents developed in the Institute of Macromolecular Chemistry ASCR. METHODS AND RESULTS: Stents from composite polymers, which are non-toxic, not-irritable can swell in body fluids and have mechanical properties similar to that of silicone rubber. Properties of the material are functionally graded and the casting or repoussé from the material can subsequently change its shape. Ten patients (males, aged 25 to 78 years) with long urethral strictures in its bulbocavernous part (50%) were treated with this method. Strictures were caused by pelvical fractures (4 times), prostate hypertrophy surgery (4 times), prolonged catheterizations (2 times). All patients were followed for 16 to 26 month and had no severities. CONCLUSION: Our results indicate that stent from composite polymers and silicone may have long-acting effects without irritation or crust formation and beneficially effected healing of the spongio-fibrous process.

Adult↗

PubMed2000

Synthetic hydrogel capacity to induce formation of foreign-body giant multinucleate cells differs in vivo and in vitro.

The granulomatous reaction accompanied with MGC formation represents the most striking feature of the non-favourable biological tolerance of implanted devices. We compared MGC formation in the course of the granulomatous reaction in vitro and in vivo employing three types of hydrogels whose biocompatibility had been well studied earlier. The efficiency of the in vitro assay for the granulomatous reaction, including MGC formation, was verified employing the nematode Nippostrongylus brasiliensis, a well-known inductor of MGC formation in vitro. The in vitro results demonstrated a very low level of MGC formation in reaction against all three types of hydrogels without polymer-specific differences in comparison with the nematode experiment characterized by a high extent of MGC formation. On the other hand, the extent of MGC formation was implant type-specific in vivo: pHEMA-co-DMAEMA > pHEMA > pHEMA-co-NaMA. These results indicate that in the in vitro assay it was not possible to discriminate among the types of polymers used in the experiment in comparison with the animal experiment. They also indicate potential differences between granuloma formation induced by parasites and by foreign bodies.

Animals↗

PubMed2000

Development of fixable stent for long-term derivation of lower urinary tract.

The object of the envisaged project is the development of easily fixable non-irritant stent of the lower urinary tract. The project has the aim to remove the obstruction and make passage-way through urethra which, after repeated operations, remains narrowed and requires repeated dilatations or, in the patients who have a chronic epicystostomy due to the non-passable urethra. The prosthesis must be self fixable, non-irritant, easily introduceable and removable by endoscopy, enabling normal urination with urinary continence and, last but not least, at a reasonable price.

Equipment Design↗

PubMed1998

Reactive oxygen species (ROS) generated by xanthine oxidase in the corneal epithelium and their potential participation in the damage of the corneal epithelium after prolonged use of contact lenses in rabbits.

Prolonged use of contact lenses (for 14 days) evoked an imbalance between the activity of xanthine oxidase (an enzyme belonging to reactive oxygen species-generating oxidases) and catalase (an enzyme belonging to reactive oxygen species-scavenging oxidases) in the corneal epithelium of rabbits. The activity of catalase decreased, while xanthine oxidase activity was very high. Of other enzymes studied in the corneal epithelium, the activities of xanthine oxidoreductase, glucoso-6-phosphate dehydrogenase and succinate dehydrogenase were decreased. In contrast, the activities of lactate dehydrogenase and lysosomal hydrolases (acid beta-galactosidase, dipeptidyl peptidase II) were increased and appeared in animals sacrificed immediately after contact lens removal. In rabbits sacrificed later (after 1 h), an additional increase of lactate dehydrogenase and lysosomal hydrolase activities developed in the superficial layers of the corneal epithelium. Catalase supplementation during use of contact lenses prevented both the significant decrease of catalase activity in the corneal epithelium and the development of additional epithelial damage. In contrast, topical treatment with 3-aminotriazole (an inhibitor of catalase) resulted in the nearly complete loss of catalase activity in the corneal epithelium and the appearance of more serious epithelial damage. We conclude that ROS generated by xanthine oxidase induce additional damage of the corneal epithelium related to the use of contact lenses.

Animals↗

PubMed1998

[The histopathologic picture of experimental poisoning with ethylmethacrylates].

Toxic effect of hydroxyethylmethacrylate, acetoxyethylmethacrylate and diethylenglycomethacrylate were studied in rats surviving as long as 1 to 20 days after intramuscular administration. Conspicuous lesion were found only in calf muscles at the site of application. Muscle fibre necroses with inflammatory reaction occurred repeatedly in animals surviving 1-2 days. Newly formed connective tissue replacing impaired muscle fibres was found in rats surviving 5 days. Intoxication related other lesion in rat organs were not identified.

Animals↗

PubMed1997

Anionic polymers for implantation.

The biocompatibility of hydrogels containing carboxylate anions was studied by a panel of tests in vitro and in vivo. In comparison with other types of similar hydrogels, those with COO- anions induced a lower extent of foreign body reaction, and their systemic effect on the immune system also seems lower. The biomimetic effect of carboxylate anions on biocompatibility of synthetic materials could be explained by a similar biomimetic effect of N-acetylneuraminic acid inhibiting the non-self recognition of bacterial cells by non-specific immunity. The encouraging long-term results of clinical trials of intraocular lenses prepared from copolymer of 2-hydroxyethyl methacrylate and sodium methacrylate support this hypothesis.

Animals↗

PubMed1997

Poly (triethylenglycol monomethacrylate) and poly (glycerol monomethacrylate) cross-linked gel as potential viscoelastics for intraoperative use.

BACKGROUND: The highly swelling poly (glycerol monomethacrylate) gel (polyGLYMA) and hydrophilic polymer poly (triethylenglycol monomethacrylate (polyTEGMA) were tested as potential viscoelastics for intraoperative use in anterior segment surgery. METHODS: PolyGLYMA was implanted into the anterior chamber in 5 rabbits, and 40% polyTEGMA in 16 rabbits. The eyes were enucleated 1 week to 3 months after the operation. The corneal endothelium was examined with specular microscopy, and then the whole eye histopathologically. RESULTS: In all eyes of the polyGLYMA group, the clinical findings were characterized by a marked ciliary injection and severe secondary glaucoma, and the histologic ones by a marked inflammatory infiltration and thickening of Descemet's membrane in the anterior chamber angle. Specular microscopy revealed a decrease in the endothelial cell density and polymorphism of the endothelial cells. In the polyTEGMA group, the anterior segment and the fundus were physiologic all the time, and specular microscopy and histologic findings showed no degenerative and/or inflammatory changes. CONCLUSIONS: PolyGLYMA proved unsuitable for intracameral application in rabbits. The new polymer polyTEGMA is characterized by high biologic tolerance after its implantation into the anterior chamber of rabbits. PolyTEGMA 40% might be considered as a potential viscoelastic material in humans.

Animals↗

PubMed1997

Effect of chemical structure of hydrogels on the adhesion and phenotypic characteristics of human monocytes such as expression of galectins and other carbohydrate-binding sites.

The reactivity of diverse immune aspects to the presence of synthetic polymers represents one of the most important aspects of implantable device biocompatibility. In this report, we show the effect of the chemical structure of a synthetic polymer support on monocyte adhesion and selected phenotypic characteristics in vitro as a model for the initial steps of non-self-recognition of an implant. The extent of monocyte adhesion was significantly influenced by the support chemistry. The highest level of monocyte adhesion was observed on a surface copolymer of 2-hydroxyethyl methacrylate with dimethyl aminoethyl methacrylate relative to results of experiments in which poly(2-hydroxyethyl methacrylate) or the copolymer of 2-hydroxyethyl methacrylate with the sodium salt of methacrylic acid was used. Cell adhesion to the polymers tested and to glass was accompanied by enhanced expression of the carbohydrate-binding sites tested for asialoglycoprotein beta-galactosides such as galectins, beta-N-acetylgalactosamine, alpha-mannoside, specific lectin for heparin as well as the lymphokine-macrophage migration inhibitory factor in the monocytes tested. These results suggest the importance of monocyte adhesion to the biomaterial surface for their development into macrophages and further non-self-recognition of the implanted device.

Acetylgalactosamine↗

PubMed1997

[New approaches in clinical ophthalmology: UV absorbers and hindered amines covalently bound to contact lenses. Importance of enzyme histochemistry in studying their effectiveness in vivo].

UV absorbers developed by us are covalently bound in hydrophilic contact lenses. This is great advantage because UV absorbers cannot be diluted from contact lenses. In laboratory investigations and "in vivo" experiments it was found that contact lenses containing UV absorbents prevent the eye against the damaging effect of UV irradiation (UVA, UVB, UVC rays). The second new approach (mentioned in this paper) is the use of Hindered Amine Light Stabilizer (4-methakryloylamino-2,2,6,6-tetramethylpiperidine) covalently bound in the hydrophilic contact or therapeutic lenses--for the healing of the damaged eye. In laboratory measurements the cleavage of hydrogen peroxide (of various concentrations) by hindered amine light stabilizer was confirmed. In "in vivo" experiments it was examined histochemically and morphologically that Hindered Amines Light Stabilizer bound in contact lenses favourable influenced the healing of the damaged anterior eye segment of rabbits. The amount as well as enzyme activation (lysosomal hydrolases) of inflammatory cells was significantly reduced in the anterior eye segment. It is suggested that Hindered Amine Light Stabilizer reacts with reactive oxygen species (oxyradicals and hydrogen peroxide) present in the damaged anterior eye segment (e.g. released from inflammatory cells). During this reaction intermediate products appear and the resulting product is a nitroxide radical. All reaction products as well as resulting product are covalently bound in hydrophilic material. For the development and also evaluation of the efficacy of both new approaches perspective for the use in clinical ophthalmology, biochemical investigations and histochemical methods are employed. Enzyme histochemistry is very important for the evaluation of the efficacy of new therapeutic approaches "in vivo" and therefore the particular attention is devoted to it in this communication.

Acrylates↗

PubMed1996

Influence of intraperitoneal injection of three types of hydrogel beads on expression of carbohydrate-binding sites in spleen macrophages.

The influence of the chemical structure of polymer implants on selected characteristics of macrophages was studied to improve our understanding of the mechanisms of non-self recognition of synthetic materials. Three types of polymers differing in net charge were prepared to compare in vivo responses. Beads from preparation of poly(2-hydroxyethyl methacrylate), a copolymer of 2-hydroxyethyl methacrylate with sodium methacrylate, and a copolymer of 2-hydroxyethyl methacrylate and dimethylaminoethyl methacrylate were injected intraperitoneally into rats and harvested 48 h later. The effects of these polymers on the presence of inflammatory cells in the peritoneal exudate, on the adhesion of macrophages to individual batches of the different types of beads and on distinct molecular aspects of macrophages in the red pulp of spleen were evaluated. Beads from both types of copolymer caused an elevation in the number of macrophages in the exudate, in contrast to the situation in rats treated with poly(2-hydroxyethyl methacrylate) beads and physiological saline solution as control. The molecular design of the implant had no significant influence on the extent of macrophage adhesion to beads or on the expression of selected carbohydrate-binding sites. Since important cellular functions such as cell adhesion and glycoprotein routing depend on the sugar part of glycoconjugates, labelled neoglycoproteins were employed to analyse this aspect of macrophages in the tested animals. The beads of the copolymer of 2-hydroxyethyl methacrylate with dimethylaminoethyl methacrylate clearly led to an elevation of the expression of specific binding sites for beta-galactoside-terminating structures which are presented by asialofetuin, for mannose, fucose, sialic acid and N-acetylgalactosamine, which had been used as the ligand parts of biotinylated neoglycoproteins, in spleen macrophages whereas the levels of sites which recognize mannose-6-phosphate were unaffected. Expression of sites with specificity to N-acetylglucosamine was lessened. The effect of beads from the copolymer of 2-hydroxyethyl methacrylate with sodium methacrylate on the measured glycobiological features in the splenic macrophages was only negligible. These results suggest the possibility of systemic effects of implanted polymers on the distinct recognitive functions of macrophages.

Animals↗

PubMed1996

Cultivation of keratinocytes on poly HEMA and their migration after inversion.

This study demonstrates how the pretreatment of poly HEMA disks with bovine serum influences the adhesion of human keratinocytes in vitro. The ability of these cells to migrate from poly HEMA disks to a polystyrene petri dish surface colonized with irradiated 3T3 cells is also evaluated. The stimulatory effect of 24-h preincubation of the poly HEMA disks with bovine serum on the keratinocyte adhesion and growth was dependent on the concentration of the serum used. The keratinocytes migrated from the poly HEMA disks to polystyrene colonized with irradiated 3T3 cells. The numerous cells which migrated from the poly HEMA were positive for cytokeratin 10 (suprabasal layers) after 3 weeks and for cytokeratin 1 (cornified layer) after 1 month. These results seem to be encouraging for further experiments with respect to clinical application.

Animals↗

PubMed1996

Toxicity of monomers HEMA, DEGMA and AEMA, used in synthesis of hydrogels for medical applications.

Acute toxicity parameters (lethal doses) were evaluated and calculated after i.m. and i.p. administration of 2-hydroxyethyl methacrylate (HEMA), 2-(hydroxyethoxy)ethyl methacrylate (DEGMA) and 2-(acetoxy)ethyl methacrylate (AEMA) to rats. Our previous findings were revisited and corrected. Based on preceding standardization and physiological values study, some clinical chemical and hematological markers of in vivo subacute i.m. toxicity were followed. Hematological parameters revealed to be of low sensitivity to the toxic influence. Clinical chemical tests suggest the prevalent muscle cell injury.

Animals↗

PubMed1996

[Distribution of 3H-labeled acetyl-HEMA monomer in rats].

Original method of tritiation of acetyl-HEMA and its hydrogenated product was developed. Distribution and excretion of both compounds was examined in rat for up to 70 hrs. While the distribution in the tissues examined (liver, spleen, kidney, lung, muscle, heart, and skin) was nearly uniform, the excretion of acetyl-HEMA and its hydrogenated form differed: acetyl-HEMA in the 24. hour is excreted preferably into urine, the hydrogenated form in faeces. In addition to it the later form was absorbed from the application point (muscle) more rapidly. Distinct cumulation of activity (original compound or/and its metabolites) was observed in all tissues.

Acetylation↗

PubMed1995

Mapping of endogenous lectins in macrophages colonizing an implanted polymer surface--effect of polymer structure.

The design of synthetic polymers may affect structural features of inflammatory cells, for example the expression of endogenous sugar receptor molecules like lectins in macrophages and foreign body giant multinucleate cells. This characteristic was studied histochemically by use of biotinylated (neo)glycoproteins. The results demonstrate the influence of polymer structure on the phenotypic expression of molecules recognizing carbohydrates in these cells. Very strong activity was observed for carrier-immobilized beta-galactose in cells colonizing hydrophobic polystyrene implants. Sialic acid moieties were not recognized by cells located on the surface of all types of polymeric implant. This study encourages investigation of the influence of polymer design on the differentiation of macrophages.

Animals↗

PubMed1994

[Use of highly hydrated contact lenses for therapeutic purposes].

The paper deals with the therapeutic use of contact lenses made from a new highly hydrated material developed in the Institute of Macromolecular Chemistry in Prague. Contact lenses made from a meshed copolymer of n-vinyl pyrrolidone with acetoxyethyl meta-acrylate were applied to a group of 83 patients--a total of 87 eyes. A favourable therapeutic effect was achieved in all groups of patients--in simple traumatic erosions, superficial keratopathies, relapsing erosions, bullous keratopathies, corrosion of cornea, for mechanical protection of epithelization and in persisting ulcerations. In 71 eyes (82%) the contact lens was removed after the therapeutic effect was achieved, in 4 (5%) treatment still proceeds. In the remaining patients treatment was discontinued on account of complications, persistence of the pathological finding and frequent losses of contact lenses. In the group there was no case of complicating keratoconjunctivitis. Progressing vascularization was detected in three cases in the group with persisting ulcerations. The authors did not observe development of corneal vascularization in conjunction with application of the lens. Transient corneal oedema was revealed in the group of relapsing erosions in 6 (40%) patients and in the group of persisting superficial keratopathies in 4 (31%). The rare occurrence of inflammatory complications can be explained by the sterile application of contact lenses for the necessary length of time, the local administration of antibiotics while the defect persisted and frequent check-up examinations. Contact lenses made from the described material proved useful for therapeutic application.

Contact Lenses, Hydrophilic↗

PubMed1993

Simulated quantitative and qualitative isotachophoretic indices of 73 amino acids and peptides in the pH range 6.4-10.

Qualitative and quantitative isotachophoretic indices of 73 amino acids, dipeptides and tripeptides were simulated under 24 leading electrolyte conditions covering the pH range 6.4-10. The RE values and time-based zone lengths are tabulated together with the absolute mobility (m0) and pKa values used. The leading electrolyte used was 10 mM HCl and the pH buffers were imidazole, tris(hydroxymethylamino)methane, 2-amino-2-methyl-1,3-propanediol and ethanolamine. The simulated indices will be useful in the assessment of the separability and determination of the listed and related compounds.

Amino Acid Sequence↗

PubMed1992

Determination of limiting ionic mobilities and dissociation constants of some local anaesthetics.

The limiting ionic mobilities and thermodynamic acid dissociation constants were calculated from isotachophoretic experiments for the local anaesthetics procaine, tetracaine, lidocaine, trimecaine, bupivacaine, cinchocaine, diperodone, diocaine, cocaine, psicaine-neu, tropacocaine, amylocaine, beta-eucaine and leucinocaine. The pH values at which the local anaesthetics with very similar limiting ionic mobilities can be isotachophoretically separated were determined from simulated mobility curves. The measuring apparatus employed a high-frequency contactless conductivity detector.

Anesthetics, Local↗

PubMed1992

The surface treatment of polypropylene molds and its effect on the quality of cast contact lenses.

An investigation of the surface by XPS photoelectron spectroscopy has shown that the process of production of cast contact lenses based on poly(2-hydroxyethyl methacrylate-co-diethyleneglycol methacrylate) is accompanied by mass transfer at the lens-mold boundary. This phenomenon, which impairs the compatibility of the lens during its application, can be considerably suppressed by employing a suitable surface modification of polypropylene molds. The surface treatment consisting in the oxidation of the mold surface by an AC corona discharge in the oxygen atmosphere increases hydrophilicity of the material, thus facilitating separation of the lens from the mold. The results of the XPS study were also confirmed microscopically by employing the SEM method.

Contact Lenses, Hydrophilic↗