Search PubMed⌕ Search

Biomedical subjects

M Shinitzky

Publications and source records attributed to M Shinitzky.

At least 127 records · Page 7Linked to original sources
PubMed1976

Membrane changes in malignant cells--modulation of receptors and antigens by lipids.

The dynamic characteristics of lipid regions in biological membranes can be expressed in terms of microviscosity parameters. These parameters not only determine the lateral and rotational movements of specific membrane sites but also their degree of exposure to the outer surrounding. Changes in microviscosity can thus reversibly displace the vertical position of antigens or receptor sites and modulate their active expression. The lipid mediated modulation of antigens and receptors may play an active role in the various physiological manifestations of malignant cells.

Antibody Formation↗
PubMed1975

Elevated microviscosity in membranes of erythrocytes affected by hereditary spherocytosis.

Erythrocytes affected by hereditary spherocytosis (HS), obtained from several splenectomized patients, showed a varying degree of elevated osmotic fragility. In order to evaluate a possible role of the erythrocyte membrane lipids in HS, microviscosity of the membrane lipid core was measured by a fluorescence-polarization technique. Intact HS-affected red cells, as well as their ghost membranes and liposomes prepared from their lipid extract, all showed a distinctly higher micro-viscosity than the respective normal control. The increased microviscosity correlated with the severity of HS. The data support the proposition that the defect in HS-affected red cells is associated, at least in part, with alterations in the membrane lipids.

Cell Membrane↗
PubMed1974

Cholesterol as a bioregulator in the development and inhibition of leukemia.

Leukemia in mice and humans is accompanied by a marked deficiency of unesterified cholesterol in the surface membrane of leukemic cells as compared to normal leukocytes. This deficiency induces a significant reduction in their membrane microviscosity. Since cholesterol in the cell surface membrane is exchangeable with cholesterol in the serum lipoproteins, concomitant to the cellular deficiency of cholesterol, the average level of cholesterol in the blood serum of leukemic patients is substantially below the average normal level. Based on these observations and the effect of membrane microviscosity on biological functions, a working hypothesis that describes the role of cholesterol in the development and inhibition of leukemia is suggested. This hypothesis can also account for the effect of cholesterol and membrane microviscosity on various other cellular activities of leukocytes.

Cell Membrane↗
PubMed1974

Increase of cholesterol level in the surface membrane of lymphoma cells and its inhibitory effect on ascites tumor development.

An ascites form of malignant transformed lymphoma cells were treated in vitro with liposomes of 1:1 lecithin-cholesterol in order to increase the cholesterol level of the cell-surface membranes and thereby to increase the rigidity of the lipid layer. This treatment was found to inhibit the rate of killing by ascites tumor after intraperitoneal inoculation into adult mice of 10(4) and 10(5) treated cells per animal. With 10(3) treated cells per animal, full survival was observed up to 90 days after inoculation, whereas with the same number of untreated cells all infected mice died within 30 days after inoculation. An analogous treatment of the malignant lymphoma cells with liposomes of pure lecithin did not result in any appreciable inhibitory effect on the ascites tumor development in vivo, as initiated by inoculation of 10(5), 10(4), or 10(3) cells per animal.

Animals↗
PubMed1972

Purification by affinity chromatography of the molecular forms of acetylcholinesterase present in fresh electric-organ tissue of electric eel.

An acetylcholinesterase inhibitor-Sepharose conjugate was prepared by coupling a derivative of the powerful acetylcholinesterase inhibitor, N-methylacridinium, to CNBr-activated Sepharose. Use of this conjugate permitted direct purification, by affinity chromatography, of the two molecular forms of acetylcholinesterase, 14 and 18 S, present in fresh electric organ tissue. The purified 14S and 18S acetylcholinesterases retained the capacity to aggregate at low ionic strength displayed by crude extracts of the enzyme. The major polypeptide components of the 14S and 18S enzymes, as revealed by acrylamide gel electrophoresis, closely resemble those observed in the 11S form of acetylcholinesterase, previously purified after tryptic digestion of electric-organ tissue.

Acetylcholinesterase↗
PubMed1970

Failure of Energy Transfer between Identical Aromatic Molecules on Excitation at the Long Wave Edge of the Absorption Spectrum.

Electronic energy transfer among identical molecules has been followed by the depolarization of the fluorescence in concentrated solutions as well as in dimers, polymers, and micelle systems. In the many aromatic fluorophores examined, unlike a few nonaromatic ones, transfer is much decreased or altogether undetectable on excitation at the red edge of the absorption spectrum. The phenomenon is not due to the transfer taking place during a small fraction of the total fluorescence lifetime, nor is it explainable by a decrease in overlap of absorption and emission upon edge excitation.

Journal Article↗