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B Cybulska

Publications and source records attributed to B Cybulska.

At least 37 records · Page 2Linked to original sources
PubMed1986

Structural features determining the haemolytic activity of vacidin A derivatives.

The haemolytic activity of aromatic heptaene antifungal antibiotics (vacidin A and its analogues) can be decreased by chemical modification. It has been shown that the ionic state of the polar head of the antibiotic molecule is essential for this activity. The effect of the net charge of the antibiotic molecule on association constant, K, between polyene and membrane-located cholesterol; and the number, n, of antibiotic molecules per one erythrocyte critical for lysis induction was investigated. In addition, changes in the structure of the polyene-cholesterol complex were monitored by circular dichroism spectroscopy. Zwitterionic native antibiotics (vacidin A and gedamycin), the negatively charged N'-acetyl derivatives and the positively charged methyl esters were used in these studies. The results presented indicate that two different phenomena are responsible for the decrease in the haemolytic activity of the compounds studied: for N'-acetyl derivatives the decrease of activity is mainly a result of lower affinity of negatively charged molecules to the membranes; for methyl esters the drastic decrease of activity is mainly a result of the different structure of the antibiotic-cholesterol complex. The permeabilizing species formed from these complexes are characterized by very low efficiency of ion permeation.

Antifungal Agents↗
PubMed1986

Effect of the polar head structure of polyene macrolide antifungal antibiotics on the mode of permeabilization of ergosterol- and cholesterol-containing lipidic vesicles studied by 31P-NMR.

Natural polyene macrolide antibiotics and their N-acyl and methyl ester derivatives, which differ mainly in their electric net charge, were compared for their ability to increase the ionic permeability of large unilamella vesicles, using the proton-cation exchange method and 31P-NMR spectroscopy. The zwitterionic (amphotericin B, vacidin A) and negatively charged (N-N'-diacetyl vacidin) compounds induced permeability according to an all-or-none process on both cholesterol- and ergosterol-containing membranes. The same mechanism of permeability induction is obtained only on ergosterol-containing vesicles for positively charged antibiotics (perimycin A, vacidin A methyl ester, amphotericin B methyl ester). A different type of action is observed for the latter group of ionophores in cholesterol-containing vesicles. In this case, a progressive proton efflux occurs in which all of the vesicle population is involved. This qualitative difference in the kinetics of ionic fluxes induced by antibiotics without a free carboxyl group in cholesterol-containing as compared to ergosterol-containing membranes was ascribed to differences in polyene-sterol interactions as well as in the life time of the ionic path formed. This difference may provide a basis for the improvement of selective toxicity of this group of antifungal agents by rational modifications.

Antifungal Agents↗
PubMed1983

The influence of electric charge of aromatic heptaene macrolide antibiotics on their activity on biological and lipidic model membranes.

Natural aromatic heptaene macrolide antibiotics and their N-acyl and methyl ester derivatives, which differ mainly in their electric net charge, were compared for their efficiency in inducing yeast growth inhibition, red blood cell lysis, and increase in the ionic permeability of large unilamellar lipidic vesicles. Antifungal activity was found to decrease in the following order: neutral congruent to positively charged greater than negatively charged compounds. Hemolytic activity decreased in the order: neutral greater than negatively charged much greater than positively charged compounds. On lipidic model membranes, themselves either positively or negatively charged, electrostatic interaction was shown to have practically no influence on the efficiency of the differently charged antibiotics. On both biological and model systems, positively charged antibiotics consistently were found to be more active on ergosterol-containing than on cholesterol-containing membranes, and were therefore considered as potentially good candidates for specific antifungal agents.

Antifungal Agents↗
PubMed1982

The effect of short-term and prolonged fructose intake on VLDL-TG and relative properties on apo CIII1 and apo CII in the VLDL fraction in type IV hyperlipoproteinaemia.

Twenty two patients with hyperlipoproteinaemia type IV consumed fructose in a daily dose of 80 g for 28 days. Apart from that they kept their normal diet. We observed the considerable heterogeneity of hyperlipaemic responses of patients under study after 7 days of fructose feeding. However VLDL-TG and the relative ratio apo CIII1/apo CII in VLDL increased in the whole group. The rise in serum VLDL was associated with a fall in LDL-Chol and HDL-Chol. After extention of fructose intake to 28 days a decrease of VLDL-TG with concomitant fall of the relative ratio apo CIII1/apo CII in VLDL was found. LDL-Chol increased. Our observations point to the reversibility of fructose-induced changes in the lipoprotein composition after prolongation of its intake.

Adult↗
PubMed1982

Comparative study of the permeability induced by aromatic and non aromatic heptaenes on small and large lipidic vesicles.

The efficiency in inducing cation permeability of vacidin A, candicidin D and amphotericin B has been compared on small and large lipidic vesicles. Amphotericin B is two times less effective on large than on small vesicles. On the contrary, vacidin A and candicidin D are about ten times more effective on large than on small vesicles. These data are consonant with what is observed on living cells.

Amphotericin B↗
PubMed1981

Cation permeability induced by two aromatic heptaenes, vacidin A and candicidin D on phospholipid unilamellar vesicles.

The cationic permeability induced by two aromatic heptaenes, vacidin A and candicidin D, has been studied on egg yolk L-alpha-phosphatidylcholine single walled vesicles as a function of cholesterol and ergosterol concentration. For comparison amphotericin B and nystatin were also tested. Vacidin A and candicidin D elicit cation permeability in both types of vesicles in the same concentration ranges and exhibit only quantitative differences in cholesterol and ergosterol vesicles. The active concentration range is of the same order of magnitude as the active concentration range of amphotericin B, at variance with what is obtained on biological cells. This difference is interpreted in term of mechanism of action of polyene on both biological and model membranes.

Amphotericin B↗