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A Aszalos

Publications and source records attributed to A Aszalos.

At least 55 records · Page 3Linked to original sources
PubMed1988

Alpha interferon accelerates lateral diffusion of Daudi cell surface differentiation antigens: measurement by fluorescence redistribution after photobleaching.

Lateral diffusion coefficients (D) of two surface differentiation antigens (sIgM and Bp35) were determined on interferon-sensitive (-IFs) or resistant (-IFr) Daudi cells by fluorescence photobleaching, using monospecific FITC-anti-IgM or PE-anti-Leu 16 probes. For untreated Daudi -IFs, mean (D) were 5.8 and 5.3 (x10(-10) cm2/sec). These increased, to 11 and 7.9 x 10(-10) cm2/sec (p less than 0.001) within 30 min after binding of recombinant IFN-a (80 to 800 U/10(6) cells), but decreased by up to 4-fold after Con A Mean (D) of identical surface antigens on Daudi-IFr were 8.2 and 9.4 x 10(-10) cm2/sec; and were not altered by IFN-a. Mean (D) of a lipid analog was up to 40-fold higher than for surface proteins and statistically identical in Daudi-IFs and Daudi-IFr. Rapid acceleration by IFN-a of surface protein lateral diffusion in Daudi-IFs obviously could facilitate anti-proliferative signal transduction; by contrast, a baseline increase of (D) in Daudi-IFr was evidently associated with their refractory state.

Antigens, CD20↗
PubMed1988

Lateral diffusion measurements give evidence for association of the Tac peptide of the IL-2 receptor with the T27 peptide in the plasma membrane of HUT-102-B2 T cells.

Fluorescence photobleaching recovery measurements show that the F1-IgG-labeled Tac peptide of the IL-2R can diffuse in the plane of the membrane of HUT-102-B2 T lymphocytes, with a mean diffusion coefficient of 2 to 3 x 10(-10) cm2s-1. Although only a fraction (mean 37%) of the Tac peptides is mobile on any given cell, lateral diffusion of the Tac peptide can be measured in 94% of cells examined. In contrast, the 95-kDa peptide, T27, is 90 to 100% immobilized in cells labeled with OKT27. Immobilization of T27 also affects the lateral diffusion of the Tac peptide, because the Tac peptide is immobile in more than 30% of cells pretreated with OKT27 and then labeled with anti-Tac IgG. The effect is specific for OKT27 to the extent that pretreatment with an anti-HLA mAb does not immobilize the Tac peptide. It appears, then, that Tac and T27 peptide not only are in proximity on HUT-102-B2 lymphocyte membranes but also interact physically in situ.

Antibodies, Monoclonal↗
PubMed1988

Dynamic analyses of lymphoblast membranes exposed to alpha interferon using flow cytometry and fluorescence recovery after photobleaching.

Interferons represent a major group of the biologic response modifiers which exert multipotent effects upon cell growth, cyto-differentiation and immune functions. Previous experimental studies with alpha interferon (IFN-alpha) have suggested that modulation of transmembrane signaling could be a critical determinant in the bioregulatory diversity. To determine whether any initial changes at the plasma membrane would directly correlate with one or more actions of IFN-alpha, we investigated cultures of Daudi lymphoblasts which are uniquely susceptible to growth inhibition. Complementary biophysical techniques were applied. In one approach, changes in plasma membrane ion flux were measured by flow cytometry, using a fluorescent dye indicator of membrane potential: Cells briefly exposed (5-10 min) to a DNA-recombinant IFN-alpha 2 (100 to 800 U/ml) manifested a consistent plasma membrane hyperpolarization (-60 to -90 mV) which could be blocked by ouabain. In a second approach, changes in diffusion coefficients of plasma membrane-associated macromolecules were determined by measuring the fluorescence redistribution after pulse photobleaching (FRAP): Individual plasma membrane proteins (sIgM, Leu 12 or Leu 16) were labelled with FITC conjugated goat antibodies [F(ab')2 or Fab'] or with phycoerythrin-B conjugated monoclonal mouse antibodies. Statistical comparisons of cells exposed to IFN-alpha 2 for 10 to 30 min showed immediate 27 to 88% increases in mean lateral diffusion rates. Mutant Daudi cells, cloned for resistance to growth inhibition showed no plasma membrane hyperpolarization with IFN-alpha 2 (up to 1000 U/ml), and baseline lateral diffusion coefficients matched those of IFN-alpha 2-treated, non-resistant cells. We conclude that biophysical status and responses of the plasma membrane must be closely linked to the molecular mechanisms of anti-proliferative signal transduction.

Cell Membrane↗
PubMed1987

Early plasma membrane depolarization by alpha interferon: biologic correlation with antiproliferative signal.

Daudi lymphoma cells, of a line sensitive to growth inhibition by alpha interferon, showed dose-dependent plasma membrane depolarization within 10 min after exposure to natural or recombinant alpha interferons (10 to 1000 IU/ml). This biophysical change was detected flow cytometrically by measuring the intensity of fluorescent emission from cells stained with dye indicators of membrane potential. Subclones of Daudi lymphoma cells, resistant to growth inhibition by alpha interferon, showed no membrane depolarization. Parallel results were obtained in initial tests of an isologous pair of T cell and B cell lines which differ in sensitivity to growth inhibition. Thus, decreased membrane potential may herald an interferon signal for antiproliferative action.

Burkitt Lymphoma↗
PubMed1987

Lymphocyte populations with different sensitivity to cyclosporin have different plasma membrane potentials.

Cyclosporin A (CsA), a clinically potent immunosuppressive agent, shows preferential biologic activity against certain lymphocyte subsets. To investigate this activity, we used flow cytometry to separate two distinct lymphocyte populations from unfractionated human peripheral blood lymphocytes, based on their different binding affinity for a biologically active fluorescent, dansylated cyclosporin (dans-CsA) derivative. The separate lymphocyte populations demonstrated different resting plasma membrane potentials. The two lymphocyte populations also had different levels of interleukin-2 (IL-2) receptors and shifted plasma membrane potential differently upon treatment with cyclosporin and lymphokine IL-2. The cell population that bound more dans-CsA contained the cells which possessed IL-2 receptors and responded to CsA and IL-2 with changes in membrane potential. The cell population that did not effectively bind dans-CsA lacked IL-2 receptors and did not respond to CsA or IL-2 with immediate membrane potential changes. Furthermore, stimulation studies of these separated two lymphocyte populations with phytohemagglutinin in the presence and absence of CsA revealed that only the population which binds a low level of dans-CsA shows a marked difference in membrane potential between the cells stimulated in the presence and absence of CsA. We concluded that ion flux changes caused by CsA affect the activation process of naive lymphocytes but not that of already stimulated ones. It can also be postulated that the ion flux changing property of CsA could constitute its primary or main mode of action.

Cell Membrane↗
PubMed1986

Depolymerization of microtubules alters membrane potential and affects the motional freedom of membrane proteins.

Two independent lines of evidence were obtained indicating that microtubule depolymerization affects the functions and the physical state of membranes in intact Chinese hamster ovary cells. The first type of evidence was obtained by using the dye dihexyloxacarbocyanine iodide to measure membrane potential before and after treatment with several microtubule active agents. Microtubule depolymerization resulted in a decrease in cell fluorescence, whereas stabilization of microtubules with taxol resulted in an increase in cell fluorescence. These effects of the drugs were due to their interactions with microtubules and not to direct effects of the drugs on the plasma membranes for the following reasons: effects were time dependent and required entry into the cells as indicated by the lack of fluorescence change in a multi-drug-resistant mutant that does not accumulate antimicrotubule drugs and a colcemid-resistant tubulin mutant did not show these effects on cell fluorescence. Evidence for altered motional freedom of membrane proteins in the plasma membrane was obtained by using electron spin resonance analysis of maleimide spin probe labeled cells. This study showed that depolymerization of microtubules results in increased motional freedom of maleimide-labeled sulfhydryl group containing proteins. Taken together, these data argue that microtubules function in mammalian cells to regulate the physical state of membranes and modulate membrane potential generated across cell membranes.

Animals↗
PubMed1986

Cytoplasmic membrane potential of mouse lymphocytes is decreased by cyclosporins.

Membrane potential of mouse lymphocytes was investigated in the presence and absence of cyclosporin A (CsA) and cyclosporin G (CsG) by flow cytometry and fluorescence spectroscopy. A carbocyanine dye, dihexyloxacarbocyanine iodide [DIOC6(3)], was applied as a membrane potential probe. A dose-dependent decrease in the membrane potential of T and B lymphocytes was observed in the presence of CsA and CsG. However, pretreatment of lymphocytes with insulin reduced the effect of the cyclosporins. Mobile ionophores, such as valinomycin, ionomycin and A23187 were less effective in changing the membrane potential of lymphocytes in the presence of CsA. The channel forming ionophore, gramicidin or high extra-cellular potassium concentration (160 mM) strongly reduced the membrane potential regardless of the absence or presence the CsA. These observations suggest incorporation of CsA into the cytoplasmic membrane causing changes in ion fluxes. Other reported biochemical effects of CsA may be secondary to the observed membrane potential changes. The membrane potential change induced by CsA may have selective biological consequences in a certain subpopulation of lymphocytes.

Animals↗
PubMed1986

Comparison of biophysical parameters of primary low and high metastatic Lewis lung tumor cells.

Lewis lung tumor cells from tumors of both high and low metastatic potential were isolated from the leg muscle of C57-B1 mice and were purified by density gradient centrifugation. The purified cells retained most of their tumor-forming capacity; however, the difference in the metastatic capacity of the 2 cell lines increased with the purification process. The purified and viable cells were subjected to different biophysical studies. Electron spin resonance studies showed that the motional freedom of lipid and protein molecules of the cellular membrane is higher in the low metastatic cell population. Both cell types reduce penetrating and non-penetrating free radicals, but the reducing ability of the low metastatic cell population is 4 times greater than that of the high metastatic cell line. These findings argue for increased membrane dynamics in the low metastatic cell population.

Animals↗
PubMed1985

Depolymerization of microtubules increases the motional freedom of molecular probes in cellular plasma membranes.

Depolymerization of microtubules resulted in an increase in the motional freedom of molecular probes in the plasma membranes of Chinese hamster ovary cells expressed by the order parameter, S, measured with two different lipid-soluble spin label probes, 5-doxyl stearic acid and 16-doxyl methylstearate. Treatment with a variety of microtubule-depolymerizing agents, including Colcemid, colchicine, vinblastine, podophyllotoxin, and griseofulvin, all had similar effects on motional freedom of the probes whereas beta-lumicolchicine was inactive. Several independent lines of evidence suggest that these changes in motional freedom of the probes were not the direct result of the interaction of these relatively hydrophobic drugs with the plasma membrane: the effects of the drugs were not immediate; the dose response of the Colcemid effect was the same as the dose response for depolymerization of microtubules; taxol, which stabilizes microtubules but does not affect motional freedom in the membranes, blocked the effect of Colcemid on motional freedom; a mutant cell line which is resistant to colchicine because of reduced uptake of the drug showed no effects of colchicine on probe motional freedom; and a Colcemid-resistant mutant cell line with an altered beta-tubulin showed no effect of Colcemid on motional freedom in the membrane. These results support the hypothesis that microtubules might affect, directly or indirectly, plasma membrane functions.

Animals↗
PubMed1985

Physico-chemical and microbiological comparison of nystatin, amphotericin A and amphotericin B, and structure of amphotericin A.

Two polyene antibiotics, nystatin and amphotericin A, were compared by physico-chemical and microbiological methods. The two antibiotics were found to have the same molecular weight, 926, by plasma desorption and electron-impact MS. However, 13C NMR spectrometry and HPLC studies indicated that the two molecules are different. The 200 MHz NMR studies indicated a chemical environment of 24 carbons of amphotericin A identical with that of the carbons of amphotericin B and nystatin. The structure of amphotericin A is identical with that of amphotericin B, except that there is a single bond between carbons 28 and 29 instead of a double bond, as shown by two-dimensional NMR studies.

Amphotericin B↗
PubMed1984

Studies on the action of nystatin on cultured rat myocardial cells and cell membranes, isolated rat hearts, and intact rats.

The action of nystatin, a polyene antibiotic, was studied in rat myocardial cells, isolated rat hearts, and intact rats. Myocardial cells responded to 10 and 25 micrograms nystatin/ml with arrhythmias that could be minimized by elevated concentrations of K+ and Mg2+ or reversed by washing the cells. Similarly, the isolated heart responded to 100 micrograms nystatin/ml with arrhythmias that could be tempered by addition of elevated concentrations of K+ and Mg2+. The i.v. injection of the drug caused heart failure in intact animals at the 4-mg/kg dose level. At the subcellular level, nystatin made the myocardial cell membranes more rigid, as measured by electron spin resonance spectrometry. These findings indicate a parallel between physiocochemical changes caused by nystatin in the myocardial cell membrane and the biological changes caused by this drug in myocardial cells, isolated heart, and heart of the intact animal.

Animals↗
PubMed1984

Quantitation of amphotericins by reverse-phase high-performance liquid chromatography.

A reverse-phase high-performance liquid chromatographic (HPLC) method was developed for simultaneous potency determination of amphotericin A and amphotericin B in bulk amphotericin B preparations. This single, rapid, specific, and simple method can be used for qualitative and quantitative analyses and is proposed to replace a combination of cumbersome official tests presently in use. This new HPLC method employs an isocratic acidic phosphate bufhotericin A and amphotericin B in bulk amphotericin B preparations. This single, rapid, specific, and simple method can be used for qualitative and quantitative analyses and is proposed to replace a combination of cumbersome official tests presently in use. This new HPLC method employs an isocratic acidic phosphate buffer-methanol mixture in a reverse mode on an octade-cylsilane-bonded silica column at ambient temperature, using UV detection at 313 nm. Results obtained by HPLC compare favorably with the official assay results. During these studies, an apparent heptaenic component, not previously described, was detected in commercial amphotericin B preparations at concentrations ranging from approximately 6 to 14%.

Amphotericin B↗
PubMed1981

High-performance liquid chromatographic determination of components of bleomycin preparations.

A fast and sensitive method was developed for the quantitative determination of at least 10 components of pharmaceutical bleomycin sulfate preparations. The method is based on the reversed-phase high-performance liquid chromatographic (HPLC) separation of the components on a muBondapak C18 column with a mobile phase having a linear gradient of 10--40% methanol in aqueous 0.005 M 1-pentanesulfonic acid at pH 4.3. With this assay, the average standard deviations for components A2 and B2 are 0.92 and 0.87, respectively, for a 7.5--22.5 x 10(-3)-mg sample. Regulatory agencies presently use the official Code of Federal Regulations (CFR) method, which is based on CM-Sephadex column chromatography. It was demonstrated that this CFR method does not separate the bleomycin A2 component from some other minor bleomycin components. After elution from the CM-Sephadex column, the "A2 component" was separated into five components by the HPLC method. Bleomycin A2 is stable under these HPLC conditions.

Bleomycin↗
PubMed1981

Quantitation of daunorubicin, doxorubicin, and their aglycones by ion-pair reversed-phase chromatography.

A fast and sensitive high-pressure liquid chromatographic method was developed for the quantitation of doxorubicin, daunorubicin, and their aglycones in pharmaceutical preparations. Because its higher pH extends column life while permitting determination of impurities, this system represents an improvement over previously published methods. It utilizes a C18 bonded silica gel column and a solvent system consisting of methanol-0.01 M monobasic ammonium phosphate aqueous solution (65:35) at pH 4.0 and 1600 psi of pressure. The accuracy of the doxorubicin and daunorubicin determinations, expressed as the coefficient of variation, is 1.65 and 1.27% respectively. The aglycones can be determined with a precision of less than 1.3%.

Chromatography, High Pressure Liquid↗
PubMed1980

Macrophage cytostasis and T and B cell blastogenic transformation in mice treated with nystatin.

Treatment of normal BALB/c mice with nystatin, an amphoteric polyene, activated macrophages to become tumoricidal for MBL-2 lymphoblastic leukemia target cells while augmenting the in vitro blastogenic response of splenic lymphocytes to B and T cell mitogens. These responses were both shown to be highly dose dependent and occurred 6 days following the intraperitoneal injection of nystatin into normal mice. Macrophages from untreated mice did not show similar activity. The significance of these observations and the potential use of nystatin as a pharmacologic agent is discussed.

Animals↗