Search PubMed⌕ Search

Biomedical subjects

B Somogyi

Publications and source records attributed to B Somogyi.

At least 55 records · Page 3Linked to original sources
PubMed1981

Characterization of living normal and leukemic mouse lymphocytes by fluorescein diacetate.

The esterases activity of normal and acute leukemic mouse lymphocytes and that of their homogenates was investigated using fluorescein diacetate (FDA) as a fluorogenic substrate. The activity proved to be the same for the two cell populations as well as for the homogenates prepared from them. In cell suspensions, having different osmolalities, the rate of FDA hydrolysis decreased significantly with the increasing osmolality only in the case of intact leukemic lymphocytes. changes in the membrane and cytoplasmic viscosity caused by increased or decreased environmental osmolality of cell suspensions occurred in the same direction and to the same extent for both normal and leukemic cells. Fluorescein, the fluorescent product of the hydrolysis, accumulates in leukemic lymphocytes, whereas it easily effluxes form normal lymphocytes. A flow microfluorimetry analysis of the cell population revealed that the fluorescein content of large leukemic lymphocytes was three times higher than that of small, normal ones. The observed differences specific for leukemic lymphocytes might be useful in detecting leukemic transformation in an early stage of acute lymphoid leukemia.

Animals↗
PubMed1980

Correlation between activity and dynamics of the protein matrix of phosphorylase b.

Quenching of the tryptophan fluorescence of phosphorylase b was studied by using iodide and acrylamide. Steady-state measurements indicated that all indole side chains were accessible to the nonionic quencher, although only 3 out of the total of 12 residues could be quenched by I-. From Stern--Volmer plots and the fluorescence lifetime data, it was concluded that the quenching was mainly of dynamic character. The value of the collisional quenching rate constant was found to be an order of magnitude less than that obtained in the case of fully exposed tryptophans. The relatively high activation energy, 30.9 kJ/mol, of the diffusion-controlled process and the value of the activation entropy suggest that the diffusion takes place in a fluctuating, structured medium. In spite of the application of sensitive fluorescent techniques, no gross conformational changes were found in the presence of acrylamide. However, the catalytic rate of the glycogen synthesis was decreased with the residual activity of the enzyme, proportional to the concentration of the probe. Binding of activator (AMP) and substrates (glucose 1-phosphate and glycogen) was found to be unaffected by acrylamide in concentrations applied (0--0.8 M). In a similar manner, activation enthalpy did not change in the presence of the quencher either. The complete reversibility of both activity inhibition and fluorescence quenching ruled out the irreversible denaturation of the enzyme or the covalent modification of any of the functional groups. We concluded that a model, suggesting the cross-correlation of activity and fluctuation, was consistent with the experimental findings.

Acrylamides↗
PubMed1980

Fluorescence energy transfer studies on normal and leukemic mouse lymphocytes.

Control and acute leukemic cells of AKR:Lac C3H mg:Lac/F1 hybride mice were labeled either with ethidium bromide or ethidium bromide plus fluorescamine. Theoretical and experimental evidence shows that the ethidium bromide binding ability of cells and the average efficiency of Förster-type fluorescence energy transfer between fluorescamine and ethidium bromide inside the cells depend on both the cell and dye concentrations. It is shown further that fluorescamine treatment enhances the uptake of ethidium bromide by both normal and leukemic cells. A sevenfold difference was found in ethidium bromide binding ability between normal and leukemic cells at optimal dye concentration.

Animals↗
PubMed1980

Changes in the intramembrane viscosity of sheep erythrocytes in the presence of membrane bound proteins.

Some dynamic properties of protein- and antibody-treated cell membranes were investigated. The membrane viscosity of sheep erythrocytes increased upon binding various proteins as determined from the fluorescence emission anisotropy of 1,6-diphenyl 1,3,5-hexatriene dissolved in the membranes. However, specific, IgM type immunoglobulins produced against the erythrocytes decreased the intramembrane viscosity of cells. The applicability of the above dye to follow the binding of specific and non-specific proteins to erythrocytes is also discussed.

Animals↗
PubMed1979

A fluorescence energy transfer system for studying the functional properties of chromatin.

3YI-B-1 rat embryo fibroblasts were used for double fluorescent labeling. The labeling was carried out with fluorescamine and ethidium bromide as an energy donor-acceptor pair. The fluorimetric measurements proved the existence of an energy transfer process. The parameters of this transfer depended on both cell and dye concentrations. It is this character that makes this labeling technique promising as a means of distinction between cells with different structures.

Animals↗