Search PubMed⌕ Search

Biomedical subjects

A Livne

Publications and source records attributed to A Livne.

At least 73 records · Page 4Linked to original sources
PubMed1982

Interaction between vaccinia virus and human blood platelets.

The objective of the present study was to characterize the interaction between human platelets and vaccinia virus and to examine possible impairment of platelet functions. The vaccinia virus was selected for our model system because it lacks detectable neuraminidase activity. Platelets were incubated with purified viral particles labeled with 3H-thymidine and binding parameters were analyzed. Binding reached saturation with an average of 5 particles/platelet. It was not affected by the plasma but was sensitive to temperature and to metabolic inhibitors. 3H-thymidine-labeled vaccinia virus and formaldehyde-fixed platelets were used to measure viral adsorption. The adsorption was temperature-independent but was affected by ionic strength, indicating electrostatic interactions. Treatment of the fixed platelets with neuraminidase or with alkaline phosphatase reduced viral adsorption, indicating that sialate and phosphate residues on the platelet surface may be involved in the adsorption. Platelet activities were markedly affected by vaccinia virus. The virus caused a dramatic 14C-serotonin release with no added inducer. The release was inhibited by aspirin, a known inhibitor of serotonin release related to prostaglandin synthesis. Furthermore, the virus inhibited platelet aggregation, induced by either ADP, collagen, or thrombin. This study demonstrates that although vaccinia virus lacks neuraminidase activity, it does bind to platelets and affects their function.

Adsorption↗
PubMed1980

Membrane dynamic alterations associated with activation of human platelets by thrombin.

Two fluorescent probes, N-carboxymethylisatoic anhydride, which binds to membrane proteins, and 1,6-diphenyl-1,3,5-hexatriene, a lipophilic label, have been used to follow membrane microenvironmental changes. Activation of human platelets by thrombin resulted in a simultaneous increase in values of fluorescence polarization (P) of both probes during the stages of shape change and secretion, which further increased during platelet aggregation. The similar pattern of changes in P for both probes indicates the interdependence of lipids and proteins in the activated platelet membrane.

Blood Platelets↗
PubMed1980

Effect of oxidant agents on normal and G6PD-deficient erythrocytes.

The effects of several oxidant agents on metabolic and membrane parameters of glucose-6-phosphate dehydrogenase deficient erythrocytes (Mediterranean type) were examined in order to explore a possible common mechanism for their action on the deficient cells. The increase in methemoglobin and the decrease in GSH levels elicited by e oxidants were more pronounced in the deficient cells, provided glucose was present during the incubation of the cells with the drugs. However, glucose did not differentially modify other parameters: ATP level, filterability and osmotic fragility. There was no correlation between the effects produced by the oxidants on various parameters in either normal or deficient cells. It is concluded that in terms of the parameters studied more than one mechanism for the effects of the oxidants on cells should be assumed.

Aminophenols↗
PubMed1979

Membrane microenvironmental changes during activation of human blood platelets by thrombin. A study with a fluorescent probe.

Membrane microenvironmental changes associated with thrombin-induced platelet activation were followed by fluorescence intensity and polarization studies of 1,6-diphenyl-1,3,5-hexatriene (DPH)-labeled human platelets. The labeling of washed platelets with DPH did not alter platelet intactness and morphology. In response to thrombin, DPH-labeled platelets exhibited reduced serotonin release, yet aggregation was barely inhibited. Shape change induced by thrombin or ADP was indistinguishable in control and in DPH-labeled platelets. During platelet aggregation induced by thrombin, fluorescence intensity increased by about 14%, which may indicate a more hydrophobic exposure of the probe. However, no change in fluorescence was detected during platelet shape change, induced either by thrombin in presence of EDTA or by ADP. Thrombin-activated platelets exhibited an increase in values of fluorescence polarization (P) during the stages of shape change and secretion, which further increased during aggregation. A similar pattern of increase in P values characterized platelet shape changes, caused either by thrombin in the presence of EDTA or by ADP. Changes in individual platelets are discernible from the alterations of the aggregating cells. These results may indicate that platelet activation is accompanied by an increase in rigidity of the membrane lipids. Functionally, the elevated "microviscosity" may reflect a primary role of membrane lipids in modulating the process of platelet activation or secondary transitions in lipids due to membrane events mediated by proteins.

Adenosine Diphosphate↗
PubMed1977

The erythrocyte membrane site for the effect of temperature on osmotic fragility.

The osmotic fragility of human erythrocytes is well known to decrease as the temperature is elevated. The cellular site for the temperature effect was studied by assessing possible roles of hemoglobin and of membrane lipids and by taking advantage of the unique response of camel erythrocytes to temperature. It is concluded that the erythrocyte membrane is the site for the temperature effect on osmotic fragility. The human erythrocyte is likely to rupture in protein--lipid boundary regions in the membrane, from which cholesterol is apparently excluded.

Animals↗
PubMed1977

Plasma constituent (s) inhibiting platelet adhesiveness.

Adhesiveness in citrated whole blood is critically pH dependent at hydrogenion concentrations close to the physiological range. While platelets in platelet-rich plasma (PRP) adhere poorly in glass-bead columns, washed platelets and particularly gel-filtered platelets (GFP), prepared from PRP, are adhesive, Separation of PRP on a Sepharose 2B column revealed the presence of an inhibitor of adhesiveness of GFP. The inhibitory compound is thermostable and nondialyzable. It is inactivated completely by pronase digestion and partally by trypsin digestion. It is distinct from any one of the known platelet factors. Washed erythrocytes and erythrocyte membranes attenuate the potency of the inhibitor. Following separation by isoelectric focusing, the inhibitory activity is limited primarily to a single fraction with an isoelectric point of 5.1 containing equal amounts of proteins and lipids. Two protein bands are revealed by sodium dodecyl sulfate-gel electrophoresis of the purified fraction. It is concluded that PRP contains a compound, apparently a lipoprotein, which inhibits platelet adhesiveness.

Adult↗
PubMed1976

Impairment of ADP-induced platelet aggregation by hashish components.

ADP-induced aggregation of washed human platelets is inhibited by the hashish components delta1-tetrahydrocannabinol (THC) and cannabidiol (CBD). The inhibition is counteracted by added ADP. When the cannabinoids are present at concentrations higher than 10(-5)M, the platelets aggregate non-reversibly, independently of an added inducer, apparently due to lysis and release of endogenous inducers. THC is clearly more potent than CBD in exhibiting the biphasic effect. Collagen- and thrombin-induced aggregation of washed platelets are hardly affected by the cannabinoids. THC and CBD also curtail ADP-induced reversible aggregation in platelet-rich plasma, while serotonin release and irreversible aggregation, caused by either ADP, collagen or thrombin, are not affected by the cannabinoids in platelet-rich plasma. The data point to associated sites for ADP and the cannabinoids on the platelet membrane.

Adenosine Diphosphate↗
PubMed1976

Unique properties of the camel erythrocyte membrane, II. Organization of membrane proteins.

Camel erythrocyte membranes are distinguished by some unique properties of stability and composition. Notable is their abundance in proteins (protein:lipid ratio of 3:1). Membrane proteins of camel erythrocytes were compared with those of human eruthrocytes, which have been intensively investigated. Proteins were extracted with various aqueous media (EDTA, alkaline or high ionic strength) and with ionic and non-ionic detergents and were analyzed by gel electrophoresis. In membranes of camel erythrocytes, the peripheral proteins constitute, proportionally, a much smaller fraction of total proteins than in the human erythrocyte, while their distribution is identical per unit of surface area. The camel erythrocyte membrane is particularly rich in integral proteins and in intramembranous particles. The proteins in this membrane are more closely organized than in the human system, as revealed by crosslinking and freeze-etching studies. It is proposed that protein-protein interaction of integral proteins, presumably constituting an "integral skeleton", is a dominant structural feature stabilizing the camel erythrocyte membrane.

Animals↗
PubMed1976

Sensitivity of erythrocyte acethylcholinesterase to inhibition by linolenoyl sorbitol. Dependence on a transmembrane potential.

Acetylcholinesterase activity of human erythrocytes is known to be inhibited by linolenoyl sorbitol, the inhibition being critically dependent on cell membrane intactness. The extent of enzyme inhibition by the added lipid is correlated with the magnitude of Cl- gradient across the erythrocyte membrane, indicating that enzyme sensitivity is associated with a transmembrane potential. If linolenoyl sorbitol is allowed to interact with the erythrocytes while a Cl- gradient exists, enzyme sensitivity can subsequently be demonstrated not only in the absence of a gradient but even when the cells are lyzed. It is consluded that the transmembrane potential determines the accessibility of a membrane component to the added lipid.

Acetylcholinesterase↗
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↗