Hypertension is one of the most common cardiovascular diseases in the world and is associated with oxidative stress. The aim of this study was to examine the effect of the chronic administration of the fatty-acid amide hydrolase inhibitor (URB597-[3-(3-carbamoylphenyl)phenyl]N-cyclohexylcarbamate) to rats with primary (SHRs - spontaneously hypertensive rats) and secondary (DOCA-salt - 11-desoxycorticosterone acetate-salt-induced hypertension) hypertension on the composition and physicochemical properties of erythrocytes membrane. Because changes in membrane composition lead to modifications of electrical charge what may affect cell functions, the levels of following components were determined: four classes of membrane phospholipids (by HPLC - high-performance liquid chromatograph), sialic acid (by resorcinol method), lipid peroxidation product - malondialdehyde (by GCMS - gas chromatography-mass spectrometry). The reduced levels of phospholipids and sialic acid, as well as the increased levels of malonodialdehyde observed in the erythrocyte membrane of rats with primary and secondary hypertension led to a decrease in the negative electrical charge of the membrane. Long-term administration of URB597 to SHRs and DOCA-salt-treated rats partially prevented changes caused by hypertension. Using theoretical equations and the dependence of cell surface charge density as a function of pH, total surface concentrations of acid and base groups and their association constants have been determined. Considering the changes in physicochemical parameters of erythrocyte membranes, URB597 can be considered a potential protective factor for erythrocytes in situations of metabolic changes associated with oxidative stress.

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 [Formula: see text] ([Formula: see text] range from 2 to 10) of the aqueous metal chloride solutions is determined. The obtained results indicate the adsorption of Al3+, In3+ and La3+ ions on phosphatidylcholine model membranes, leading to changes in the electrical properties of the membranes. The theoretical considerations on equilibria occurring between phosphatidylcholine liposomal membrane and trivalent metal ions are presented. A mathematical model describing the interactions in a quantitative way is proposed.

Hypertension is a civilization disease leading to remodeling and damage of blood vessels, impaired renal function and premature death. The aim of this study was to compare the effect of chronic administration of URB597, the FAAH (fatty acid amide hydrolase) inhibitor, to rats with primary (SHRs) and secondary (DOCA-salt hypertensive rats) hypertension on electrical and physicochemical properties of kidney cells membranes. Changes in the electrical charge of the membrane may affect the cell functions. The electrical properties of the kidney cells (surface charge density, zeta potential) were measured by electrophoresis. Qualitative and quantitative composition of the membrane (phospholipids and proteins) was determined by HPLC and lipid peroxidation product (4-hydroxy-2E-hexenal; 4-HHE) level was examined by GCMSMS, while the sialic acid content was measured by resorcinol method. In rats with primary hypertension (SHR) and secondary hypertension (DOCA-salt), changes in electrical properties (increase of electric charge and zeta potential) and membrane composition (increase in sialic acid and protein concentration and decrease in phospholipid level) of kidney cells are observed in comparison to control animals. Greater changes were observed in DOCA-salt hypertensive rats. Changes in membrane properties caused by URB597 depend on the type of hypertension. The administration of URB597 to rats with primary hypertension partially prevents changes in the electrical properties (electrical charge, zeta potential) of the membrane caused by hypertension as well as in the sialic acid and proteins content. However, there is no reduction in oxidative stress, assessed by the level of 4-HHE, which may affect the metabolic function of the kidneys. URB597 administered to rats with DOCA salt does not prevent, but rather intensifies, changes caused by hypertension in the kidney. In conclusion, URB597 given to individuals with hypertension, particularly with secondary hypertension, enhancing some disturbances in electric and physicochemical properties of kidney cells observed in hypertension what may lead to additional kidney disorders. Therefore, further researches are necessary.

Human skin provides the body's first line of defense against physical and environmental assaults. This study sought to determine how rutin affects the membrane electrical properties, sialic acid content, and lipid peroxidation levels of fibroblast membranes after disruption by ultraviolet (UV) radiation. Changes in cell function may affect the basal electrical surface properties of cell membranes, and changes can be detected by electrokinetic measurements. The charge density of the fibroblast membrane surface was measured as a function of pH. A four-component equilibrium model was used to describe the interaction between ions in solution and ions on the membrane surface. Agreement was found between experimental and theoretical charge variation curves of fibroblast cells between pH 2.5 and 8. Sialic acid content was determined by Svennerholm's resorcinol method, and lipid peroxidation was estimated by measuring the malondialdehyde level. Compared to untreated cells, ultraviolet A (UVA)- or ultraviolet B (UVB)-treated skin cell membranes exhibited higher concentrations of acidic functional groups and higher average association constants with hydroxyl ions, but lower average association constants with hydrogen ions. Moreover, our results showed that UVA and UVB radiation is associated with increased levels of sialic acid and lipid peroxidation products in fibroblasts. Rutin protected cells from some deleterious UV-associated membrane changes, including changes in electrical properties, oxidative state, and biological functions.

Interactions of alkali metal cations (Li+, Na+, K+, Cs+) with phosphatidylcholine (PC) liposomal membranes were investigated through experimental studies and theoretical considerations. Using a microelectrophoresis technique, charge densities of experimental membrane surfaces were measured as a function of the pH of electrolyte solutions. Equilibria between the PC liposomal membranes and monovalent ions were mathematically analyzed and described quantitatively through a previously proposed theoretical model. Association constants between functional groups of PC and the studied ions were determined and used to define theoretical curves of membrane surface charge density versus pH. Theoretical and experimental data were compared to verify the model. The PC membrane was found to have the highest affinity for lithium ions, among the ions tested.

In this paper, we examined the effect of adsorbed monovalent ions on the surface charge of liposomal membranes formed from neutral (sphingomyelin), anionic (phosphatidylinositol) lipids mixed in various ratios. The surface charge density of the membrane was determined from electrophoretic mobility measurements at various pHs of solution. A four-quilibria model describing adsorption of ions on the sphingomyelin (SM) membrane and a two-equilibria model describing adsorption of ions on the phosphatidylinositol (PI) membrane was presented. We proposed a mathematical model for characterizing these equilibria. Using these models, together with experimental data of the membrane surface charge density, we determined association constants characterizing the equilibria. The correctness of the proposed model was proven by comparing the theoretical charge variation curves for SM and PI membranes with the experimental date.

The skin is the largest human organ, providing the first line of defense to protect the body from physical and environmental effects. The aim of this study was to determine the influence of short-wave ultraviolet (UVB) radiation on the membrane electrical properties, phospholipid content, and lipid peroxidation levels of fibroblasts and keratinocytes. Changes in cell function may affect the basal electrical surface properties of cell membranes. These changes can be detected using electrokinetic measurements. In this study, the surface charge densities of fibroblasts and keratinocytes were measured as a function of pH. A four-component equilibrium model was used to describe the interaction between the ions in solution and on cell membrane surfaces. Agreement was found between the experimental and theoretical charge variation curves of leukemia cells from pH 2.5 to pH 9. Phospholipid composition was determined qualitatively and quantitatively by HPLC, and lipid peroxidation was estimated by measuring the level of malondialdehyde. The acidic functional group concentrations and average association constants with hydroxyl ions were higher, and the average association constants with hydrogen ions were smaller in UVB-treated skin cell membranes compared to those in untreated cells. Moreover, our results showed that UVB radiation is associated with increased levels of phospholipids and lipid peroxidation products in fibroblasts and keratinocytes.

Equilibria between the membranes of erythrocytes as well as thrombocytes and solution ions in fatal accidental hypothermia were analyzed using a theoretical four-equilibria model. The model was developed to determinate parameters characterizing cell membrane-surrounding ion interactions: the total surface concentrations of both acidic and basic groups C (A), C (B), and association constants K (AH), K (BOH). Knowledge of these parameters was necessary to calculate the theoretical values of surface charge density. The model was validated by curve-fitting the experimental data points to simulated data generated by the model. The experimental and theoretical surface charge density values agree at pH 2-8, at higher pH the deviation was observed.

The effect of fatal carbon monoxide poisoning on equilibria between cell membranes and surrounding ions was described using a theoretical four-equilibria model. The model was developed to obtain parameters characterizing the interactions between solution ions and erythrocyte or thrombocyte membrane surface. The parameters are the total surface concentrations of both acidic and basic groups C A, C B and their association constants with solution ions K AH, K BOH. These parameters were used to calculate the theoretical values of surface charge density. The model was validated by comparison of these values to experimental data, which were determined from the electrophoretic mobility measurements of the blood cells. The experimental and theoretical surface charge density values agree at pH 2-8, and at higher pH, the deviation was observed.

Phenomena associated with changes in cell membranes are thought to play an important role in the cancer transformation. We hypothesized that the electrical charge of tumor cells can indirectly represent membrane-based changes that have occurred during cell transformation and may indicate tumor cell status. Here, we describe work showing that phospholipids, proteins content, and electric charge, are all altered in the cell membranes of pT2 stage/grade G3 bladder cancer. Qualitative and quantitative phospholipid composition and the presence of integral membrane proteins were identified using high-performance liquid chromatography. Protein composition was determined using selective hydrolysis of isolated bladder cell membrane proteins and peptide resolution. The surface charge density of human bladder cell membranes was determined using electrophoresis. Our results show that cancer transformation is associated with increased phospholipid levels and a decreased level of integral proteins. Moreover, the process of cancer transformation significantly enhanced changes in the surface charge density of the human bladder cell membrane. In conclusion, this study demonstrates that cell membrane structure and function are modified in bladder cancer cells and that further work in this area is warranted.

Kidney tissue is particularly susceptible to reactive oxygen species attack which leads to development of cancer. During oxidative stress, membrane lipids and proteins are major targets of re-active oxygen species (ROS). This work is focused on changes of phospholipids, proteins content and electric charge that occur in cell membranes of kidney cancer of pT3 stage, grade G3 and with metastasis. Qualitative and quantitative phospholipid composition and the presence of integral membrane proteins were determined by high-performance liquid chromatography. Electrophoresis was used to determine the surface charge density of the human kidney cell membrane. It was shown that the process of cancer transformation was accompanied by an increase phospholipid levels and altered the level of integral proteins as determined by decrease phenylalanine, tyrosine, cysteine and arginine. Moreover, the process of cancer transformation significantly enhanced changes in the surface charge density of the human kidney cell membrane. Cell membrane structure and function are modified by neoplasm lesion.

The aim of this study was to determine the influence of cisplatin and novel dinuclear platinum(II) complexes on the membrane electrical properties and lipid peroxidation levels of the Molt-4 human leukemia cell line. Changes in cell function may affect the basal electrical surface properties of cell membranes. These changes can be detected using electrokinetic measurements. Surface charge densities of Molt-4 cells were measured as a function of pH. A four-component equilibrium model was used to describe the interaction between the ions in solution and on cell membrane surfaces. Agreement was found between the experimental and theoretical charge variation curves of the leukemia cells at pH 2.5–9. Lipid peroxidation was estimated by measuring levels of 8-iso-prostaglandine F2α [isoprostanes]. Acid and base functional group concentrations and average association constants with hydroxyl ions were smaller in cisplatin- or dinuclear platinum(II) complex-treated leukemia cell membranes compared to those in untreated cancer cells, and the average association constants with hydrogen ions were higher. Levels of lipid peroxidation products in cisplatin- or dinuclear platinum(II) complex-treated leukemia cell were higher than those found in untreated cancer cells.

In this paper, we characterized the interactions between two-component liposomal membranes and monovalent electrolyte ions. Liposomes were formed from neutral (phosphatidylcholine) and anionic (phosphatidylglycerol) lipids mixed in various ratios. Microelectrophoresis was used to determine the dependence of the membrane surface charge density on the p H of the electrolyte solution. Changes in the membrane electric charge caused by the adsorption of Na(+), Cl(-), H(+), and OH(-) ions were observed, and the equilibria among these ions and the phosphatidylcholine-phosphatidylglycerol membrane surface were quantified. We proposed a mathematical model for characterizing these equilibria. Using this model, together with experimental data of the membrane surface charge density, we determined association constants characterizing the equilibria. Knowledge of these parameters was necessary to calculate the theoretical curves of the model. We validated the model by curve-fitting the experimental data points to simulated data generated by the model.

The effect of monovalent ion (Li⁺, Na⁺, Cs⁺) interaction with monolayers of phosphatidylcholine (lecithin, PC) was investigated at the air/water interface. We present surface tension measurements of lipid monolayers obtained using a Langmuir method as a function of monovalent ion concentration. Measurements were carried out at 22 °C using a Teflon trough and a Nima 9000 tensiometer. Interactions between lecithin and monovalent ions 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 and area occupied by one molecule of PC-monovalent ion complexes (PC⁻Me⁺).

The objective of this investigation was to evaluate postmortem changes of electric charge of human erythrocytes and thrombocytes after fatal carbon monoxide (CO) poisoning. The surface charge density values were determined on the basis of the electrophoretic mobility measurements of the cells carried out at various pH values of electrolyte solution. The surface charge of erythrocyte membranes after fatal CO poisoning as well as after sudden unexpected death increased compared to the control group in the whole range of experimental pH values. Also, a slight shift of the isoelectric point of erythrocyte membranes to high pH values was observed. The surface charge of thrombocyte membranes after fatal CO poisoning decreased at low pH compared to the control group. However, at high pH, the values increased compared to the control group. The isoelectric point of thrombocyte membranes after fatal CO poisoning was considerably shifted toward low pH values compared to the control group. The observed changes are probably connected with the destruction of blood cell structure.

This paper discusses the application of chronopotentiometry to study of membrane electroporation. The experiments were performed on bilayer lipid membranes formed using the painting technique. Phosphatidylcholine and cholesterol were chosen for the study because they fulfill essentials functions in living organisms. The studies have been carried out at various forming solution compositions and at various potassium ion concentrations in the electrolyte solution. Based on chronopotentiometric curves and mathematical equations, the membrane capacitance, resistance, and breakdown voltage as well as pore conductance and diameter were calculated. (C) 2013 The Electrochemical Society. [DOI: 10.1149/2.051303jes] All rights reserved.

Studies of the electrical surface properties of biological cells have provided fundamental knowledge about the cell surface. The change in biological functions of cells may affect the surface properties and can be detected by electrokinetic measurements. The surface density of fibroblasts and breast cancer cells (MDA-MB-231 and MCF-7) as a function of pH was measured by electrophoresis. The interaction between solution ions and the breast cancer cell or fibroblast surface was described by a four-component equilibrium model. The agreement between the experimental and theoretical charge variation curves of the breast cancer cells and fibroblasts was good at pH 2.5–9. The extent of fibroblast and breast cancer cell lipid peroxidation was estimated by HPLC measurement of the malondialdehyde level. The acid ( C TA ) and basic ( C TB ) functional group concentrations and the average association constant with hydroxyl ( K BOH ) ions values of the breast cancer cell membranes were higher than in normal cells, while the average association constant with hydrogen ( K AH ) value was smaller. The level of lipid peroxidation products was higher in breast cancer cells than in normal cells.

Phospholipids are ubiquitous in nature and are essential for the lipid bilayer of cell membranes. Their structural and functional properties are pivotal for the survival of the cell. In this study the phospholipids of healthy and cancerous human renal tissues from the same patients are compared with special reference to the electric charge of the membrane. A simple and highly effective normal-phase method is described for analyzing phospholipids content. This work is focused on changes of phospholipids content (PtdIns, phosphatidylinositol; PtdSer, phosphatidylserine; PtdEtn, phosphatidylethanoloamine; PtdCho, phosphatidylcholine) in cell membranes of renal cancer of pT1 stage, G2 grade, without metastasis. Surface charge density of healthy and cancerous human renal tissues was measured by electrophoresis. The measurements were carried out at various pH of solution. Depending on 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. The process of cancer transformation was accompanied by an increase in total amount of phospholipids as well as an increase in C(TA) and K(BOH), whereas K(AH) and C(TB) were decreased compared with unchanged tumor cells.

The effect of Ca(2+) ion interaction with monolayers of phosphatidylcholine (lecithin, L) was investigated at the air/water interface. We present surface tension measurements of lecithin monolayers obtained using a Langmuir method as a function of Ca(2+) ion concentration. The measurements were carried out at 22 degrees C using a Teflon trough and a Nima 9000 tensiometer. The interactions between lecithin and Ca(2+) ions 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 and area occupied by one molecule of LCa(+) and L(2)Ca complexes. The stability constants, K(1) = 1.92 x 10(3) m(2) mol(-1) and K(2) = 5.35 x 10(5) m(2) mol(-1) were calculated by inserting the experimental data. The value of area occupied by one LCa(+) complex is 65 A(2) molecule(-1), while the area occupied by an L(2)Ca complex is 117 A(2) molecule(-1).