The effect of cationic electrolytes on the electrostatic behavior of cellular surfaces with ionizable groups

Based on the assumption that the electrostatic charges on the surface of sheep leukocytes arise from the dissociation of ionogenic groups, together with the presence of divalent cation (or trivalent cation) in the suspending medium of low ionic strength (or high ionic strength), the non-linear Poisson-Boltzmann equation for cell interaction with a solid surface with constant potential (or constant charge) is numerically solved in this paper. The cellular surface potential and the repulsive (or attractive) force is expressed as the function of separation distance. Because of shrinking the thickness of the electrostatic double layer at high ionic strength, the presence of cationic electrolyte has a less influential role on both the cellular surface potential and interaction force than at low ionic strength. However, due to the continuous equilibration of the ionogenic groups on the cellular surface as separation distance decreases, the presence of cationic electrolyte will not always reduce the interaction force during the whole adhesion period. The distance at which the cationic electrolyte changes its effect from positive to negative is termed the critical separation distance in this paper.     

The effect of membrane-fluidizing agents on the adhesion of CHO cells

Treatment of CHO cells with drugs which are known to increase membrane lipid fluidity reduced the cells' ability to adhere to protein coated substrates, The concentrations of local anesthetics, nonionic detergents or aliphatic alcohols required to reduce CHO cell adhesion by 50% were similar to those reported to block nerve conduction, indicating that these drugs can affect the membrane at physiologically significant concentrations. Nonionic detergents and aliphatic alcohols, but not local anesthetics, caused increases in the fluidity of CHO plasma membranes (measured by fluorescence polarization) at concentrations which inhibited cell adhesion. The adhesion versus temperature profile had a sigmoidal shape, suggesting that a temperature dependent cooperative process such as a lipid phase transition, might be involved. However, the temperature profile for CHO membrane fluidity manifested no discontinuities, indicating the absence of any discrete phase transitions of the lipid matrix. This observation, coupled with the result that the inhibition of CHO cell adhesion produced by low temperatures was not relieved by drugs which can increase membrane fluidity, suggests that the reduced adhesion seen at low temperature is probably not due to reduced lipid fluidity.     

The effect of the cationic proteins of human blood cells on the growth of Escherichia coli

The antibacterial effect of cationic proteins (CP) on donor leukocytes and thrombocytes with respect to the growth of E. coli has been demonstrated in vitro, the maximum recorded inhibition being caused by the action of leukocytic CP. Differences in the inhibitory action may be linked with the presence of anomalies in the amino acid composition of leukocytic CP and thrombocytic CP, manifested by the deterioration of the basic properties of the latter, as well as by the fractional composition whose characteristic features for thrombocytic CP are the appearance of high-molecular components and a decrease in the proportion of low-molecular fractions. In patients with different forms of leukosis (chronic myeloleukemia, chronic lympholeukemia, acute myelomonoblastic leukosis) leukocytic CP retain their antibacterial activity. Under the action of blood cell CP changes in the outer and cytoplasmic membranes have been noted.     

The effect of electrolytes on the contractile elements of muscle

The effects of changes in electrolyte concentration on muscles which had been preserved in 50 per cent glycerol or washed in water were studied. The psoas preparation of Szent-Györgyi was generally used, but smooth and cardiac muscle gave the same results. If the preparations are immersed in 0.16 molar NaCl or KCl and if the electrolyte subsequently is washed out with distilled water, tension rises. This effect is not obtained if solutions of CaCl₂ or MgCl₂ are used, but it is restored by brief immersion in NaCl or KCl solutions. Changes in pH have no effect. It is concluded that divalent cations are bound more firmly than monovalent ions, but that divalent exchange with monovalent ions. After the application of ATP washing out electrolytes produces a much larger and more rapid rise in tension. This effect persists after ATP has been washed out and seems to be due to the removal of a substance which diminishes the dissociation of bound cations. Washing out electrolytes also causes a large increase in transparency and swelling. These effects are also enhanced by previous application of ATP and are abolished or diminished by divalent cations. The rise in tension and the swelling are explained as the result of an increase in the charge of the polar groups of the proteins. Because this mechanism produces only a small degree of shortening, it does not explain normal contraction, but it may be a part of this process. The significance of the phenomena described in relation to recent theories of the mechanism of muscular contraction is discussed. The observations show that increase in the charge of the contractile proteins causes contraction, not relaxation, as has been commonly assumed.     

The effect of sub-lethal ALA-PDT on the cytoskeleton and adhesion of cultured human cancer cells

5-Aminolevulinic acid (ALA), a precursor of the endogenous photosensitizer protoporphyrin IX, is used in the photodynamic therapy (PDT) of cancer. Sub-lethal ALA-PDT (1-min irradiation with 370-450 nm blue light, 0.6 mW/cm(2) after 2-h incubation with 1 mM ALA) has been earlier shown to change cell morphology and to inhibit both trypsin-induced detachment of cultured cancer cells from the plastic substrata and cell attachment to the bottom of the plastic well plates. In the present study, we found that such treatment of human adenocarcinoma WiDr cells grown in dense colonies stimulated the formation of actin cortex between cells in the colonies and increased the number of actin stress fibres in some, but not in all, cells. However, ALA-PDT did not change the microtubular cytoskeleton in these cells. A similar treatment of glioblastoma D54Mg cells, which grow separately and communicate by protrusions, caused loss of fibrillar actin structures in growth cones, retraction of protrusions, and surface blebbing in some cells. The application of the cytoskeleton inhibitors cytochalasin D, colchicine or taxol showed that the inhibition of trypsin-induced detachment of photosensitized WiDr cells was related to ALA-PDT-induced changes in actin and microtubular cytoskeleton. Some signal transduction processes are suggested to be involved in ALA-PDT-induced changes in cytoskeleton, cell shape, and adhesion.     

The effect of ions on the adhesion and internalization of Chlamydia trachomatis by HeLa cells

The adhesion and internalization of Chlamydia trachomatis by HeLa cells was unaffected by removal of K+, Mg2+, or glucose from the incubation medium, slightly reduced by removal of Na+, and significantly reduced by omission of Ca2+, Sr2+, Mg2+, and Mn2+ could replace Ca2+ in the adhesion but only Sr2+ supported internalization, and La3+, Co2+, Fe3+, Ba2+, and Zn2+ all reduced internalization more than adhesion. During initial infection there was no measurable difference in the uptake or release of 45Ca2+ or 86Rb+ between infected and noninfected HeLa monolayers. Infection was not prevented by pretreatment of the monolayers with the calcium channel blockers, verapamil, D600, and nitrendipine, or the calmodulin inhibitors, TMB-8 or trifluperazine. The results suggest that divalent cations are not essential for chlamydial infection but that the process of internalization is facilitated by the presence of cations, particularly Na+ and Ca2+.     

The effect of cationic surface-active agents on the Escherichia coli ATPase

The authors studied the effect of cationic surfactants (CS), such as alkyl(C8H17-C18H37)dimethylbenzylammonium (I), alkyl(C8H17-C16H33)benzyltrimethylammonium (II), alkyl(C8H17-C16H33)di-beta-hydroxyethylbenzylammonium (III) chlorides and chlorhydrate of glycine decyl ester (IV) on the ATPase activity of E. coli 1257 cell, spheroplasts, and isolated membranes. Changes in the ATPase activity of the E. coli cells and spheroplasts were found to depends on the concentration and the structure of the cationic surfactants. The removal of the cell wall increased the destroying effect of CS on the cytoplasmic membranes and enhanced the ATPase inhibition. The compounds with 16 and 18 carbon atom radical had the highest inhibitory effect. The action of cationic surfactants on the membrane is accompanied by changes in the protein and phospholipid composition and by significant solubilization of ATPase with pronounced inactivation of the enzyme. The kinetics of inhibition of E. coli membrane ATPase was studied to the presence of the homological series I and IV. The cationic surfactants under study inhibited the ATP hydrolysis catalysed by E. coli ATPase by a mixed type mechanism. Ki = 58.21.10(-4) M for IC10H21; 10.67.10(-4) M for IC12H25; 0.58.10(-4) M for IC16H33; 0.16.10(-4) M for IC18H37, and 5.93.10(-4) M for IV.     

The differential effect of normal cells and their neoplastic transformants on embryonic cell adhesion

The adhesion of 7 day old embryonic chick neural retina cells was reduced by adult calf serum whereas foetal calf serum diminished adhesion to a lesser extent. Conditioned media from normal cells either increased the adhesion of neural retina cells or had no effect. Media from malignant cells reduced the adhesion of the retina cells. The results are discussed in relation to malignant invasion.     

Analysis of the effect of disturbed flow on monocytic adhesion to endothelial cells

The preferential adhesion of monocytes to vascular endothelial cells (ECs) at regions near branches and curvatures of the arterial tree, where flow is disturbed, suggests that hemodynamic conditions play significant roles in monocyte adhesion. The present study aims to elucidate the effects of disturbed flow on monocyte adhesion to ECs and the adhesive properties of ECs. We applied, for the first time, the micron-resolution particle image velocimetry (μPIV) technique to analyze the characteristics of the disturbed flow produced in our vertical-step flow (VSF) chamber. The results demonstrated the existence of a higher near-wall concentration and a longer residence time of the monocytic analog THP-1 cells near the step and the reattachment point. THP-1 cells showed prominent adhesion to ECs pretreated with TNF in the regions near the step and the reattachment point, but they showed virtually no adhesion to un-stimulated ECs. Pre-incubation of the TNF-treated ECs with antibodies against intercellular adhesion molecule-1 (ICAM-1), vascular adhesion molecule-1 (VCAM-1), and E-selectin inhibited the THP-1 adhesion; the maximal inhibition was observed with a combination of these antibodies. Pre-exposure of ECs to disturbed flow in VSF for 24 h led to significant increases in their surface expressions of ICAM-1 and E-selectin, but not VCAM-1, and in the adhesion of THP-1 cells. Our findings demonstrate the importance of complex flow environment in modulating the adhesive properties of vascular endothelium and consequently monocyte adhesion in regions of prevalence of atherosclerotic lesions.     

Structural and functional analysis of the effect of cationic surfactants on Escherichia cells and spheroplasts

The character of the growth of Escherichia culture after treatment with alkyl dimethylbenzyl ammonium chloride (a cation surface-active substance) has been studied. The action of the preparation at bacteriostatic concentrations is reversible and manifested only by the increased duration of the lag phase. The complete restoration of the processes ensuring the growth and mitosis of the cells usually occurs. The preparation causes disturbances in the permeability barrier of the cell membranes, appearing immediately on contact with cation surface-active substances. This compound affects the cytoplasmic membranes of Escherichia cells at extremely low concentrations (0.0001-0.0002%); as a result, the leakage of low-molecular substances from the cells occurs. These disturbances in permeability are not accompanied by the disappearance of nucleic acids from the cells. The preparation used at bactericidal and subbactericidal concentrations denatures high-molecular cell components to a variable degree. The study of the ultrastructure of cells and spheroblasts shows that alkyl dimethyl-benzyl ammonium chloride destroys the structure of the outer and cytoplasmic membranes, as well as the ribosomal apparatus of Escherichia cells.     

Potential effect of cationic liposomes on interactions with oral bacterial cells and biofilms

Context: Although oral infectious diseases have been attributed to bacteria, drug treatments remain ineffective because bacteria and their products exist as biofilms. Cationic liposomes have been suggested to electrostatically interact with the negative charge on the bacterial surface, thereby improving the effects of conventional drug therapies. However, the electrostatic interaction between oral bacteria and cationic liposomes has not yet been examined in detail.

Objective: The aim of the present study was to examine the behavior of cationic liposomes and Streptococcus mutans in planktonic cells and biofilms.

Materials and methods: Liposomes with or without cationic lipid were prepared using a reverse-phase evaporation method. The zeta potentials of conventional liposomes (without cationic lipid) and cationic liposomes were ?13 and 8?mV, respectively, and both had a mean particle size of approximately 180?nm. We first assessed the interaction between liposomes and planktonic bacterial cells with a flow cytometer. We then used a surface plasmon resonance method to examine the binding of liposomes to biofilms. We confirmed the binding behavior of liposomes with biofilms using confocal laser scanning microscopy.

Results: The interactions between cationic liposomes and S. mutans cells and biofilms were stronger than those of conventional liposomes. Microscopic observations revealed that many cationic liposomes interacted with the bacterial mass and penetrated the deep layers of biofilms.

Discussion and conclusion: In this study, we demonstrated that cationic liposomes had higher affinity not only to oral bacterial cells, but also biofilms than conventional liposomes. This electrostatic interaction may be useful as a potential drug delivery system to biofilms.     

A note on the diffusion of electrolytes in cells

A somewhat simpler solution is given to the problem previously discussed by R. R. Williamson relating to the diffusion of a metabolized electrolyte whose ions have different mobilities.     

The effect of the dimeric and multimeric forms of fibronectin on the adhesion and growth of primary glomerular cells

Primary glomerular cells placed in a chemically defined medium containing Waymouth's medium MB 752/1 supplemented with insulin, transferrin, fibroblast growth factor, nonessential amino acids, sodium pyruvate, and antibiotics showed rapid outgrowth of cells which morphologically resembled well differentiated visceral epithelial cells followed by outgrowth of poorly differentiated cells; morphologic evidence suggests these latter cells are precursor cells of the epithelial cell lineage. Whereas the well differentiated glomerular epithelial cells were never observed to divide by sequential phase microscopic observations, a chemically defined medium was developed for optimal growth of the poorly differentiated cell type. This serum-free medium contained Waymouth's medium MB 752/1 supplemented with insulin, transferrin, selenium, and fibronectin (plus non-essential amino acids, sodium pyruvate, and antibiotics). Using this chemically defined medium, we have compared the effects of dimeric and multimeric fibronectin (high molecular weight disulfide-bonded fibronectin produced by incubation of dimeric fibronectin with 3 M guanidine followed by dialysis against 0.05 M cyclohexylaminopropane sulfonic acid (CAPS) buffer, pH 11) on the adhesion and growth of the poorly differentiated primary glomerular cell type. Dimeric fibronectin (FN) was twice as effective as multimeric FN in promoting glomerular cell adhesion, although both forms of FN promoted cell adhesion better than an uncoated substratum. In contrast, cell growth studies demonstrated that multimeric FN was a more potent growth stimulant than dimeric FN. The differential effects of dimeric and multimeric forms of FN in vitro suggests that these molecules may have different functions in vivo.     

The effect of solution electrolytes on the uptake of photosensitizers by liposomal membranes: a salting-out effect

In this study we investigated, spectroscopically, the effect of electrolytes on the partitioning of hematoporphyrin IX (HP) and hypericin (Hy) into non-charged lipid vesicles. Our aim was to assess the salting-out effect of electrolytes on membrane-partitioning. We titrated aqueous solutions of HP and Hy with lecithin liposomes, at different concentrations of several monovalent and divalent electrolytes in the suspension. The partitioning constant of HP to lecithin liposomes increased from 3.3 (mL/mg) in water containing only 5mM buffer to 8.7 (mL/mg) at 0.36M KCl. KF had a similar effect. NaCl caused a 3-fold increase in the partitioning of Hy to liposomes. MgSO(4) and MgCl(2) also increased the partitioning of HP, by a factor of more than 4 and this occurred already at 0.03M concentration. We analyze the comparative effects of the electrolytes in relation to the Hofmeister series. The salting-out effect could be utilized to enhance the uptake of HP and Hy, and possibly other photosensitizers as well, by artificial and natural membranes.