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Biomedical subjects

D Jírová

Publications and source records attributed to D Jírová.

9 recordsLinked to original sources
PubMed2005

Hydrophilic polymers--biocompatibility testing in vitro.

Biocompatibility is one of the main prerequisites for safe use of medical devices. Estimation of cytotoxicity is a part of the initial evaluation laid down in ISO standards on biological evaluation of medical devices. Hydrophilic polymers (based on 2-hydroxyethyl methacrylate HEMA) doped by addition of selected additives with antioxidant and/or free radical scavenging potential (vitamin C and hindered amine stabilizer N-(2,2,6,6-tetramethylpiperidin-4-yl)methacrylamide) were tested in different in vitro systems (3T3 Balb/c cell culture and a 3D human skin model) for biocompatibility and suitability for use as wound dressings. The results of the 3T3 NRU cytotoxicity test using both the direct and indirect contact approaches and a 3D skin model modified irritation test (EpiDerm) confirmed high biocompatibility and good skin tolerance of both the basic polymers and those enriched with specific additives up to a balanced level. HEMA polymer showed a beneficial effect against cytotoxicity of an irritant (sodium dodecyl sulfate). The in vitro biocompatibility test results were confirmed by human local skin tolerance testing.

Adult↗
PubMed1996

Immunotoxic effects of carbon tetrachloride--the effect on morphology and function of the immune system in mice.

Carbon tetrachloride (CCL4), a polychlorinated hydrocarbon, is known for its hepatotoxicity, neurotoxicity and skin irritancy. Some epidemiological studies suggest possible carcinogenicity of CCl4. This substance is still present in industrial wastes and in the environment. As the major role of the immune system is immunosurveillance against cancer, we decided to follow the morphological and functional changes of the immune system during acute and subchronic exposures to CCL4 in mice. Mice (A/PhJ) were exposed i.p. to 1.7 mmol CCl4/kg b.w./day administered in olive oil (total volume 0.2 ml), for 2, 7, 14, 23 days. We evaluated: morphology of thymus, spleen and peripheral lymph nodes, immunopathology (thymus and spleen weight, spleen cellularity, number of peripheral blood leukocytes), non-specific immunity (phagocytosis, NK activity), humoral immunity (number of PFC after SRBC immunization, LPS mitogen response), cell-mediated immunity (PHA, ConA mitogen response). Morphological examination showed significant activation of lymphoid tissues in T-cell dependent areas. B-cell areas were also activated, but the formation of active germinal centers in lymphatic follicles has not been observed. The natural immunity was affected in a time dependent manner. A slightly hepatotoxic dose of CCl4 had a significant stimulative effect on phagocytosis and natural killer activity when administered in short-term schedule ("acute exposure"). Subchronic administration of the same dose led to suppression of phagocytosis and Nk activity. Similarly, the lymphocyte response to non-specific mitogens was enhanced during short-term exposure and significantly impaired when CCl4 was administered in long-term schedule. Antigen specific immune response to SRBC was impaired immediately after short-term exposure to CCl4 which suggests that the substance might affect the immunoglobuline proteosynthesis at the cellular level.

Animals↗
PubMed1996

Measurement of cytotoxicity of sulphonated chloroaluminium phthalocyanine on various cell systems.

Phthalocyanines (ClAlPcS) present a new generation of substances for photodynamic treatment of tumors. To find optimal therapeutic doses for i.v. or local application, it is necessary to test the maximal non-toxic concentration on model systems. As a standard testing system (cellular substrate) for definition of the in vitro cytotoxicity, human lymphocytes separated from peripheral human blood and splenocytes obtained from rabbit spleen fragments were chosen. The vitality test on human peripheral lymphocytes proved that the used concentrations in the range 0.1-1.4 mg/ml did not significantly influence vitality of the cellular substrate. The test used for determination of the migration activity did not show any influence on MI in the concentration range 0.1-0.5 mg/ml. The higher concentrations tested (range 0.6-1.4 mg/ml) lead to reduction of the migration activity presented by a decrease in the migration index MI: for c = 0.6 mg/ml, MI = 0.85; for c = 1.4 mg/ml, MI = 0.45 (normal value for MI is in the range 0.9-1.1).

Animals↗
PubMed1993

Effects of orally administered vanadium on the immune system and bone metabolism in experimental animals.

Experiments were carried out to gain more information on the effects of long term exposure to low doses of vanadium administered to mice and rats in drinking water. The selective immunotoxic effects of vanadium were depression of phagocytosis, splenotoxicity, enlargement of spleen, elevation of peripheral blood leucocytes and T and B cell activation. Vanadium accumulates in hard tissues and influences the mineralisation of epiphyseal cartilage. This effect is obviously evident in young animals. Significant differences in vanadium concentration were found between young and adult animals.

Administration, Oral↗
PubMed1987

The toxic effect of dermotrophic substances in tests in vitro.

In the model system of tissue culture, the effect of dermatotrophic substances, such as the tenzides and conservatory substances, was tested. The cytotoxic effect of the substances was evaluated according to the vitality of the cells and the lactate dehydrogenase (LDH) activity in the suspension culture of human lymphocytes and further according to the migration inhibition of cells from the animal spleen fragments (SF). The cells obtained from rabbits, guinea pigs, mice and man were used. The highest correlation between the concentration of the substance in the cultivation medium and its toxic effect in the culture has been proved in the tests of LDH activity from the supernatant of the human peripheral lymphocytes culture and further in the migration inhibition test from rabbit SF. Both the tests are in mutual correlation. The determination of LDH activity represents a sensitive marker of the cell damage, the least sensitive is the estimation of the cell vitality. It has been proved that the system of suspension culture of human peripheral lymphocytes and the migration inhibition test from rabbit SF is suitable for the screening determination of the effect of dermatotrophic substances. The system of tissue culture compared to classical tests of skin irritation performed in vivo secures overall objectivity in evaluating the results and the possibility of making a number of parallels without any ethical limits.

Animals↗
PubMed1983

Adjuvant activity of muramyldipeptide in a guinea pig model of contact allergy to chromium.

New chemical agents encountered increasingly in the human environment underline the urgent need for a routine testing of their sensitizing potential for man and the development of a suitable experimental model appears to be essential for a reliable assessment of this potential. In our present experiment we studied a guinea pig model of contact hypersensitivity to chromium using as immunoadjuvants Freund's complete adjuvant (FCA) and Freund's incomplete adjuvant (FIA) emulsified with muramyldipeptide. The study showed that the use of adjuvants was essential for inducing the state of hypersensitivity in experimental animals. It was also demonstrated that muramyldipeptide was not only a fully potent substitute for FCA, but was even superior to it in all the parameters tested. The optimal time interval for demonstrating the induced hypersensitivity to chromium was the third week after the onset of sensitization. This animal model appears to be well suited for the experimental testing of contact allergen potentials.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMedDate not supplied

In vitro toxicity testing of supramolecular sensitizers for photodynamic therapy.

We report the phototoxicity of meso-tetrakis(4-sulphonatophenyl)porphine (TPPS4) and zinc metallocomplex (ZnTPPS4) sensitizers in the presence or absence of 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD) on G361human melanoma cells. Morphological changes in cell cultures have been evaluated using inversion fluorescent microscope and image analysis. Viability of cells was determined by means of molecular probes for fluorescence microscopy (LIVE/DEAD kit- double staining with Calcein AM and Ethidium Homodimer). The quantitative changes of cell viability in relation to sensitizers concentrations and irradiation doses were proved by fluorometric measurement with fluoroscan Ascent. We found that the most effective sensitizer is ZnTPPS4 bound to HP-beta-CD, since the IC50 value was 12.5 g/ml at the dose of light radiation of 10 J/cm2.

Cell Line, Tumor↗
PubMedDate not supplied

The benefits of the 3T3 NRU test in the safety assessment of cosmetics: long-term experience from pre-marketing testing in the Czech Republic.

We have introduced the 3T3 NRU cytotoxicity test for methodological, economical and ethical reasons as a regular part of tier pre-marketing testing to assess local tolerance of raw materials for cosmetics, household chemicals and final cosmetic products. Using the 3T3 cell line according to the standard INVITTOX protocol No.64 (NRU Assay) the borderline concentration, relevant to the highest tolerated dose, is determined for each material. The toxic effect is reached at different concentration levels specific for individual cosmetics categories, depending on their chemical characteristics. Typical ranges of cytotoxicity for specific categories of cosmetics were established after testing of hundreds of materials. The range lies between 1 microg/ml (anti-dandruff shampoos), up to 2000 microg/ml (toothpastes and mouthwashes). The 3T3 NRU cytotoxicity test is a sensitive tool able to identify more aggressive products, that are also more likely to evoke irritation in human skin. It was even possible to detect protective effects of one natural herbal ingredient. The comparative study of cytotoxicity test results and human patch test results from a group of essential oils is presented. Cytotoxicity tests represent a highly ethical approach for estimation of irritancy. On the basis of in vitro test results suggesting low risk we can proceed to confirmatory tests in human volunteers.

3T3 Cells↗