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Biomedical subjects

M Jirsa

Publications and source records attributed to M Jirsa.

At least 73 records · Page 4Linked to original sources
PubMed1989

Classical bile acids in animals, beta-phocaecholic acid in ducks.

1. Bile samples of different animals were analysed and the percentage content of classical bile acids was determined. 2. Herbivorous birds mostly excreted a large proportion of chenodeoxycholic acid. 3. The anteater (Myrmecophaga tridactyla) excreted deoxycholic acid most probably as a primary bile acid. 4. In the bile of ducks (Anas platyrhynchos) a large amount of (23R)3 alpha, 7 alpha, 23-trihydroxy-5 beta-cholan-24-oic acid (beta-phocaecholic acid) was found.

Animals↗
PubMed1989

[Disruption of biliary calculi in vitro with low amplitude shock waves and verification by chemical dissolution].

In lowering the amplitude of pressure in the point of the shock-wave concentration under MPa (in our equipment by means of lowering discharge tension under 8 kV) macroscopically observable breakdown of stones in vitro after passage of 5 shock-waves will not occur in approximately 1/3 of bile stones. After effect of 5 shock-waves cholesterol elution in model solvents was accelerated. In exposed parts of stones the cholesterol concentration was in the 40th minute in methanol and perchlorethylene solution in 9:1 ratio 2.45 times higher on average. The stones were halved by a diamond knife. Only one half was exposed and the other one was used for comparison. From the study were eliminated such halves of stones that were macroscopically damaged after the shock-wave exposition where acceleration of cholesterol elution is a priori obvious.

Cholelithiasis↗
PubMed1989

[A new model for testing substances affecting the synthesis of heme].

A new model for experimental studies of substances influencing porphyrin metabolism has been created. The model is formed by yeast Saccharomyces cerevisiae (RIBM-75) grown semiaerobically. The main advantages of this model include simple evocation of porphyria (intracellular accumulation of porphyrins in semiaerobic conditions) and direct measurement of experimental values (intracellular and extracellular concentrations of porphyrins). The porphyrinostatic effects of drugs can be assessed on the basis of sum of experimental values. The ratio of experimental criteria enables us to compare the influence of drugs on porphyrin permeation across the cellular membrane. Antimalarials, chloroquine and pyrimethamine, used or tested for therapy of chronic liver porphyria, have been tested on the model. The experiments showed that both chloroquine and pyrimethamine inhibited porphyrin synthesis. This effect can represent the proper therapeutical action of both drugs, which has not been known so far. Chloroquine releases the intracellular porphyrins in yeast similarly as it does in hepatocytes. However, pyrimethamine causes intracellular accumulation of porphyrins booth in yeast and hepatocytes.

Chloroquine↗
PubMed1989

[Inhibition of porphyrin synthesis by isonicotinic acid hydrazide in models simulating porphyria].

Increased activity of haem synthesis key enzyme is a common phenomenon in hepatic porphyrias. Synthase activity of delta-aminolevulinic acid is extensively increased in acute hepatic porphyrias or it can be by means of feedback moderately secondarily increased in their chronic forms. Isonicotinic acid hydrazide (INH) is a competitive inhibitor of delta-aminolevulinic acid synthase as it combines with enzyme co-factor, pyridoxalphosphate (PDX) to form hydrazone. The INH porphyrinstatic effects were verified by testing two experimental models. The yeast model exhibited 5-fold inhibition at 10 mM INH concentration in medium. The chicken germ model after a 10 microM INH dose exhibited 82% inhibition. This inhibition can be eliminated by PDX administration to reach the original porphyrin synthesis at equimolar INH and PDX concentrations. Histological study of transversal chicken liver sections proved that 1 microM INH administration does not result in disturbance of chicken hepatocyte integration. The suggested preparation has the advantage of being commonly manufactured and approved to be used in human medicine.

Animals↗
PubMed1989

[A simple model for verifying the effects of a focused shock wave from our generator on erythrocytes and lymphocytes].

Biological effects of the focused shock wave produced by the generator of our own construction were observed on the erythrocyte and lymphocyte suspension as a model. Erythrocyte haemolysis located into the small volume of the 1.4 ml focus was observed in the dependence on the number of shocks. After 10 shocks it does not exceed 15%. In the previous experiments this particular dosage caused a complete destruction of the bile stone of about 1 cm size. Increase of kalium concentration in correspondence to the degree of haemolysis was discovered in the erythrocyte suspension. Effects of shock wave were observed also in lymphocytes, where no change of blastic transformation in the decrease of the life span approximately by 2% was proved. Regular measurements proved minimum damage of blood cells in given experimental conditions and the results are comparable with biological effects of other sources of the focused shock wave.

Erythrocytes↗
PubMed1988

Porphyrinostatic effect of isonicotinic acid hydrazide on porphyric chick embryo and yeast.

1. The common feature of "inducible" forms of hepatic porphyria is an increased activity of delta-amino-levulinate/ALA/synthase. 2. As a potential therapeutic procedure, isonicotinic acid hydrazide/INH/as inhibitor of this enzyme, was applied and found to show a porphyrinostatic effect, depending on its concentration, both in yeast and porphyric chick embryo models. 3. Moreover, pyridoxalphosphate/PDX/eliminated the porphyrinostatic effect of INH, depending again on its concentration. 4. Histochemical tests did not demonstrate any significant functional or morphological changes in the chick embryo hepatocytes following INH administration.

5-Aminolevulinate Synthetase↗
PubMed1988

Effect of chloroquine on membrane permeability in yeast--release of cellular coproporphyrin.

1. The influx and efflux of labelled substances with and without chloroquine was studied in yeast cells. 2. The uptake of delta-aminolevulinic acid by Saccharomyces cerevisiae is characterized by a KT of 3-4 mM and Jmax of 1.0-1.2 mumol min-1 g dry weight-1. 3. A method for loading yeast with labelled coproporphyrin is suggested. 4. The uptake of sorbitol and coproporphyrin was slightly stimulated, while the uptake of 6-deoxyglucose was slightly, that of 2-aminoisobutyric acid and leucine strongly inhibited by chloroquine. 5. The efflux of coproporphyrin, 2-aminoisobutyric acid and sorbitol was stimulated while that of leucine was not influenced by chloroquine. 6. The result showed that chloroquine influenced directly but nonspecifically the membrane permeability, apparently mainly that of the vacuolar membrane.

Aminoisobutyric Acids↗
PubMed1986

Solid phase extraction and isocratic separation of urinary porphyrins by HPLC.

A method for determining urine porphyrins by HPLC is described. In the preliminary step, porphyrins are purified in high yields and concentrated by low pressure reverse-phase chromatography on C18 (octadecylsilane bonded silica) cartridge. Porphyrins are stable for 10 days after adsorption on C18 cartridge. The separation of porphyrin esters is performed on an aminopropyl-bonded silica column with an eluting system containing n-heptane and ethyl acetate. The system enables rapid isocratic separation of porphyrin methyl esters with high selectivity. The simplicity and reproducibility of the whole procedure allows its application to the routine analysis of urinary porphyrins in the clinical laboratory.

Chromatography, High Pressure Liquid↗
PubMed1986

A model for testing compounds influencing porphyrin synthesis.

The yeast Saccharomyces cerevisiae cultivated semi-anaerobically in a synthetic medium was used as a model to establish (a) total porphyrin synthesis, (b) ratio of intracellular to extracellular porphyrin concentrations. The antimalarials used for the therapy of porphyria cutanea tarda, chloroquine and pyrimethamine, reduced the total synthesis of porphyrins, pyrimethamine being more effective than chloroquine, like in porphyric patients. Both drugs exerted an antagonistic influence on the release of porphyrins from cells. Chloroquine reduced the concentration ratio of porphyrins while pyrimethamine increased it, apparently through inhibition of permeation of porphyrins. Combined treatment with the two compounds may hold promise for the therapy of porphyria cutanea tarda.

Cell Membrane↗