Zbigniew A. Figaszewski

Characterization of the Cell Membrane During Cancer Transformation

The electric properties of the plasma membrane is an indicator of cell condition. The simple, and highly effective, normal-phase (NP) and reversed-phase (RP) high-performance liquid chromatography (HPLC) methods assess phospholipid and free unsaturated fatty acid content, respectively. Herein we focus on changes in phospholipid content (phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylethanoloamine (PE), phosphatidylcholine (PC)) and free unsaturated fatty acid content (arachidonic acid (AA), linoleic acid (LA), α-linolenic acid (ALA), palmitoleic acid (PA)) in the plasma membranes of non-metastatic colorectal cancer cells (pT3 stage, G2 grade). Surface charge density of normal and tumor large intestine tissue was measured by electrophoresis. The surface charge density as a function of pH, acidic (C TA ) and basic (C TB- ) functional group concentrations and their average association constants with hydrogen (K AH ) or hydroxyl (K BOH- ) ions were evaluated. Cancer transformation was accompanied by an increase in total phospholipids as well as and increase in C TA , C TB and K BOH whereas the content of free fatty acids and K AH decreased compared with unchanged tumor cells.

Changes in physico-chemical properties of human large intestine tumour cells membrane.

Tumour cells produce and excrete to blood many substances which are present in the cell itself in trace amounts only. Our work has been aimed at the determination of changes in electric charge and in phospholipid composition of large intestine normal mucosa and colorectal cancer cells.Surface charge density of tumour unaffected mucosa and of tissue sections from tumours, was measured by electrophoresis. The measurements were carried out at various pH of solution. Membrane isoelectric point was determined by measuring its electric charge in function of pH as well as total positive charge at low pH and total negative charge at high pH. Qualitative and quantitative composition of phospholipids in the membrane was determined by HPLC. Four phospholipid classes were identified: PI, PS, PE and PC and their surface concentrations were determined.The electric charge calculated from phospholipid concentrations is by three orders of magnitude higher than that determined electrophoretically. It indicates that the groups present in the membrane surface are involved in equilibria in which the charge is neutralized.The electric charge calculated from phospholipid concentrations is by three orders of magnitude higher than that determined electrophoretically. It indicates that the groups present in the membrane surface are involved in equilibria in which the charge is neutralized.Tumour changes provoke an increase in surface charge density of large intestine membrane, whereas the content of individual phospholipids increased or decreased depending on a patient.

Interfacial tension of bilayer lipid membrane formed from phosphatidylethanolamine.

The dependence of the interfacial tension of a lipid membrane on the pH of the aqueous solution has been studied. Interfacial tension measurements of phosphatidylethanolamine (PE) were carried out. A theoretical equation is derived to describe this dependence in the whole pH range. A maximum corresponding to the isoelectric point appears both in the theoretical equation and in the experimental data.

The Equilibria of Phosphatidylethanolamine-Cholesterol and Phosphatidylcholine–Phosphatidylethanolamine in Monolayers at the Air/Water Interface

Monolayers of phosphatidylethanolamine (PE), cholesterol (Ch), phosphatidylcholine (PC), and binary mixtures (PC-PE or PE-Ch) were investigated at the air/water interface. The surface tension values of pure and mixed monolayers were used to calculate π -A isotherms. The surface tension measurements were carried out at 20°C using an improved Teflon trough and a Nima 9000 tensiometer. The Teflon trough was filled with a subphase of triple-distilled water. Known amounts of lipid dissolved in 1-chloropropane were placed at the surface using a syringe. The interactions between phosphatidylethanolamine and cholesterol as well as phosphatidylcholine and phosphatidylethanolamine result in significant deviations from the additivity rule. An equilibrium theory to describe the behavior of monolayer components at the air/water interface was developed in order to obtain the stability constants of PC-PE and PE-Ch complexes. We considered the equilibrium between the individual components and the complex and established that phosphatidylethanolamine and cholesterol as well as phosphatidylcholine and phosphatidylethanolamine formed highly stable 1:1 complexes.

The interfacial tension of the lipid membrane formed from lipid-cholesterol and lipid-lipid systems

Interfacial tension has been determined for phosphatidylcholine-cholesterol, phosphatidylcholine-phosphatidylethanolamine, and phosphatidylethanolamine-cholesterol membranes. Phosphatidylcholine (PC), phosphatidylethanolamine (PE), and cholesterol (Ch) were to be investigated, because of their presence in biological membranes. Interfacial tension values of pure components are 0.81×10−3 N/m, 1.67×10−3 N/m, and 2.36×10−3 N/m, respectively. The 1∶1 complexes were formed during formation of the PC-Ch, PC-PE, and PE-Ch lipid membranes. The following parameters describing the complexes were determined: A3−1, the surface concentrations of the lipid membranes formed from these complexes; γ3, the interfacial tensions of such membranes and K, the stability constants of these complexes.

Influence of green tea on surface charge density and phospholipids composition of erythrocytes membrane in ethanol intoxicated rats.

Ethanol is oxidized to acetaldehyde and then to acetic acid and these processes are acompanied by free radical generation. This paper reports the effect of green tea on electric charge and phospholipids composition of erythrocytes membrane from rats intoxicated with ethanol. Electrophoresis technique and HPLC have been applied to above-menthioned studies. Ethanol administration caused increase in erythrocyte membrane surface charge density and phospholipid composition. Ingestion of green tea with ethanol partially prevented changes in structure and function of membrane caused by chronic ethanol intoxication.

Analytical applications of electrode sensitive to labetalol in pharmaceuticals

The analytical properties of an ion-selective electrode sensitive to labetalol with a liquid membrane, based on ion-pair complexes with sodium tetraphenylborate (TPB-Na+) are described. The studied electrode can be used for the determination of labetalol hydrochloride as a protonated form of labetalol in pharmaceuticals. The calibration curve, e.g. EMF=f(pCLabHCl) is linear in the range from 10−5 to 10−2 mol L−1 with a correlation coefficient of 0.9992 and slope of 61.13 mV/decade, which is close to the Nernstian slope. The detection limit of the examined electrode is 7.20×10−6 mol L−1. The influence of pH of the tested solutions on the formulation of the electrode is not as considerable since the electrode works correctly in the pH range 3.0–8.0. The main attributes of the developed electrode are: stability, good reproducibility of EMF and short response time, close to 30 seconds depending on labetalol concentration in the solution. The electrode shows good selectivity for many inorganic ions. The selectivity for drug cations is weaker due to the structural similarity of the interfering cations to labetalol. The results of labetalol determination using direct potentiometry in drugs such as Pressocard (Polpharma) and Trandate (GlaxoWellcome) were compatible with the quantity of labetalol declared by the manufacturer, and with parallel UV spectrophotometric and HPLC determinations.

Investigation of interaction of human platelet membrane components with anticoagulant drugs Abciximab and Eptifibatide.

Abciximab (Abci) and eptifibatide (Epti) are antiaggregate drugs which may reduce thrombotic complications in acute coronary syndromes. The aim of this work was the investigation of the interaction between the phospholipid-GPIIb/IIIa glycoprotein complex and Abci or Epti, and the influence of these drugs on the phospholipid ratio in the platelet membrane. The interaction between the phospholipid-GPIIb/IIIa glycoprotein complex and antiaggregate drugs were investigated using the Surface Plasmon Resonance Imaging technique (SPRI). Phospholipids phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylethanolamine (PE), phosphatidylcholine (PC) and sphingomyelin (SM) were first immobilized onto the gold chip surface. The phospholipid ratio in the platelet membrane was determined by the HPLC. Only PI, PS, PE and PC were determined. Human platelets treated in vitro with Abci or Epti exhibit changes in the phospholipid ratio in the platelet membrane. The ratio of PS decreases and PC rises. The SPRI distinctly shows interactions between phospholipids and glycoprotein GPIIb/IIIa, and between the phospholipid-glycoprotein GPIIb/IIIa complex and Abci or Epti. The interaction between phospholipids and glycoprotein GPIIb/IIIa is growing in the sequence: PI<<SM<PE<PC<PS. The interaction between phospholipid-glycoprotein GPIIb/IIIa complex and Abci/Epti is growing in the sequence: PS<PI<PC<PE<SM. SPRI was proved to be excellent tool for observation of such interactions.

In Vitro Interaction of Lithium on Phospholipids in Human Erythrocytes

ABSTRACT Lithium salts are used in the treatment of mania and as prophylaxis against manic depressive disorder. The aim of these studies was the in vitro investigation of the effect of lithium on phospholipids of human erythrocyte membranes. Erythrocytes were treated with lithium for 1 h. Phospholipids phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylethanolamine (PE), and phosphatidylocholine (PC) were separated from erythrocyte ghosts and determined by HPLC. Blood samples from healthy adults were investigated. A very strong decrease in PC content in erythrocyte membranes due to lithium in vitro treatment was found, as well as a statistically significant increase in PI content.

Binding of trivalent metal ions (Al3+, In3+, La3+) with phosphatidylcholine liposomal membranes investigated by microelectrophoresis

Abstract.Interactions between trivalent metal ions (Al3+, In3+, La3+) and phosphatidylcholine (PC) liposomes are studied by microelectrophoresis. The dependence of the PC membrane surface charge density and zeta potential on