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Biomedical subjects

M Marek

Publications and source records attributed to M Marek.

At least 55 records · Page 3Linked to original sources
PubMed1986

The use of antibody immobilized on supports coated with polyglycidyl methacrylate in saturation analysis.

A new procedure for separation of free and bound ligand in saturation analysis (e.g., radioimmunoassay, competitive protein binding analysis) is presented. The antibody was immobilized on different carriers (glass rods, aluminium or polyethylene strips) covered with a thin layer of polyglycidyl methacrylate. The surface of the polymer had been activated by reaction with either ethylene diamine and glutaraldehyde or sulfuric acid and sodium periodate. The antibody was immobilized on this activated polymer by a covalent bond. The advantages of the presented separation methods are rapidity, simplicity, and conservation of the free and bound ligand equilibrium. A comparison with other separation techniques is carried out.

Acrylic Resins↗
PubMed1984

Development of a radioimmunoassay for papain.

Various well-tried radioimmunoassay (RIA) techniques were compared for the quantitation of papain. The evaluation of individual assays was performed by logit-log analysis. The most compatible analytical steps were combined in order to obtain the optimal analytical conditions of the assay. The preferred RIA involves papain labelling with lactoperoxidase, a double antibody method as the separation step and a 24 h incubation period at 2 degrees C. It permits the detection of 16 ng of papain per tube. In contrast, a method using immobilized antibody was satisfactory for rapid quantitation of papain with quite acceptable accuracy.

Antibody Affinity↗
PubMed1984

Acceleration of corrosion of dental amalgam by abrasion.

Dental amalgam shows passive behavior, but the protective film can be destroyed by abrasion. In this study, specimens of both low- and high-copper amalgam were abraded, and the effect on the corrosion behavior was examined. The electrochemical measurements showed that the corrosion rate was substantially increased, and that re-passivation was relatively slow.

Copper↗
PubMed1983

In vivo and in vitro studies of the stress-corrosion cracking behavior of surgical implant alloys.

Behavior of implant alloys exposed simultaneously to tensile stresses and corrosion environments has been examined. In the in vivo studies, a stainless steel and a titanium alloy exhibited cracklike features when loaded to the yield stress sigma y and implanted for 16 weeks. A cobalt-chromium alloy stressed beyond sigma y exhibited them in plastically deformed areas. A cobalt-chromium-nickel-molybdenum alloy appeared to be immune. In vitro samples loaded to various stress levels were immersed in Ringer's solution at 37 degrees C. Half of them were subjected to applied anodic potentials; the remaining control group was not. The applied potentials were dc potentials of magnitude similar to those generated by bioelectric effects. No attempt was made to duplicate time dependence or wave forms. Cracklike features were observed in the stainless steel and in the titanium alloy loaded to or beyond sigma y and polarized for 38 weeks. None were observed below sigma y. For the controls, no cracklike features were observed at any stress level after 53 1/2 weeks. Polarization measurements and potential versus time measurements were performed to study possible mechanisms for crack propagation. These investigations suggest that the in vivo corrosion environment is more severe than a 37 degrees C Ringer's solution because of the influence of both bioelectric effects and organic constituents. The implications of these studies for the performance of prosthetic devices is discussed.

Alloys↗
PubMed1983

Corrosion of the eta'(Cu-Sn) phase in dental amalgam.

Previous studies have shown preferential corrosion of the eta'(Cu-Sn) phase in high-copper dental amalgam both in vitro and in vivo, while samples of pure eta' have shown high corrosion resistance. To clarify this contradiction, samples of pure eta' crystals mixed with other phases were prepared and tested. Evaluation of the corrosion resistance was based on the results of coulometry at constant potential and potentiodynamic polarization. The corrosion susceptibility of eta' in the matrix of gamma 1(Ag-Hg) was considerably higher than the susceptibility of isolated eta'. The susceptibility of pure eta' also could be increased by plating it will small amounts of Hg. It was concluded that in dental amalgam, the presence of mercury in the phases surrounding eta' reduces its resistance to corrosion. Although eta' is more resistant to corrosion than gamma 2(Sn-Hg) which appears in low-copper amalgams, it is the least corrosion resistant major phase in high-copper amalgams and can suffer deterioration.

Copper↗
PubMed1983

Proteolytic activity and immunoreactivity of chemically modified papain.

The effect of different chemical modifications of papain on the proteolytic activity and immunoreactivity has been studied. Modification with Dextran T 2000 caused increasing decline in proteolytic activity both with increasing degree of dextran oxidation and amount of bound dextran, whilst the immunoreactivity determined by nephelometry remained unchanged. Modification of papain with glutaraldehyde and formaldehyde causes rapid drops in both activities, even at very low concentrations of agents. Acetylation of papain showed expressive maxima of both proteolytic and immunochemical activities at the same degree of enzyme acetylation. Modification with diazobenzenesulfonic acid caused a high increase in immunoreactivity and a small increase in proteolytic activity.

Acetic Anhydrides↗
PubMed1983

The effect of tensile strain on corrosion of dental amalgam.

In vitro corrosion of two low-copper and three high-copper dental amalgams was examined using stressed and unstressed specimens. Stress was applied in tension; anodic polarization curves and polarization resistance were determined. In stressed condition, the passive current density was higher, and polarization resistance was lower. The changes are attributed mainly to the fracture of passive films by creep strain.

Chemical Phenomena↗
PubMed1980

Corrosion test for dental amalgam.

A corrosion test for dental amalgam, based on controlled potential coulometry, provides an index of corrosion susceptibility. A special cell was designed, and optimum test conditions were determined. The test can be used for the rating of amalgams, and in studies of the effect of variables on the corrosion resistance.

Chemical Phenomena↗
PubMed1978

Corrosion behavior of structural phases in high copper dental amalgam.

The effects of crevice corrosion on the major structural phases of a high copper dental amalgam were studied in vitro. Three kinds of samples were used: (1) amalgam prepared from a high copper, single composition alloy, (2) annealed ingots of the Ag3Sn and Cu3Sn phases, and (3) high copper, single composition alloy tablets electroplated with mercury. Specimens were examined in a scanning electron microscope before and after the exposure to a corrosion environment. The Ag3Sn and Cu3Sn phases were least affected by corrosion. The Ag-Hg-Sn phase (gamma1) slowly deteriorated, but the attack was nonuniform. The Cu6Sn5 phase exhibited good corrosion resistance, better than that of gamma1 phase. Particles of a tin rich phase of uncertain origin were observed on some of the samples after long exposures.

Copper↗
PubMed1978

Spatial structures in a reaction-diffusion system--detailed analysis of the "Brusselator".

Continuous dependence of spatially nonuniform concentration profiles for the 'Brussellator" reaction mechanims on the characteristic length of the system is given both for zero flux and fixed boundary conditions. Branches of solutions arising through primary bifurcation form closed curves. Secondary bifurcations giving rise to spatially asymmetric solutions exist for fixed boundary conditions. Results of a stability analysis of individual solutions are discussed. A method of composing complex spatial profiles for higher lengths from elementary solutions for smaller lenghts is suggested and tested in the case of zero flux boundary conditions. Emergence of subsequently more complex stable patterns in dependence on increasing length of the system suggests many similarities to gradual build up of complex morphogenetic patterns.

Biological Transport↗