Influence of stearic acid monolayers upon the procaine adsorption from underlying alkaline aqueous solutions.

Adsorption of procaine at the air/water interface and its penetration into stearic acid monolayers from aqueous subphase of pH 8 are studied by measuring surface tension of aqueous procaine solutions and by recording surface pressure vs. mean molecular area curves for stearic acid monolayers spread onto procaine solutions of different concentrations. The amount of procaine in the interface is derived by means of Gibbs' equation. Results are compared to those obtained earlier at pH 2 and on unbuffered subphases. With increasing pH an increasing procaine adsorption and procaine penetration is observed. This phenomenon is interpreted in terms of protolytic equilibria in which participate both surfactants procaine and stearic acid.

Nuclear magnetic resonance investigation of human erythrocytes in the presence of manganese ions. Evidence for a thermal transition.

Water proton transverse relaxation was investigated in whole blood and washed erythrocytes samples, respectively, at various temperatures and manganese concentrations. Water diffusional exchange controls proton relaxation in whole blood samples at higher Mn2+ concentrations (20-30 mM) or in washed erythrocyte samples at low Mn2+ content (1-5 mM). Mn2+ uptake is significant in washed normal erythrocyte samples when its concentration is about 18 mM or higher in the medium, at temperatures below about 26 degrees C. The thermal transition as revealed by the NMR doping method represents a switch from a water exchange process, mainly seen in the higher temperature range, to a paramagnetic ion controlled water proton relaxation in the lower temperature range.

Comparison of human and rat liver microsomes by spin label and biochemical analyses.

Detailed lipid analyses of human and rat liver microsomes revealed interesting differences. It was found that human liver microsomes contain twice as much lipid as those from the rat. This increased lipid content is not associated with an increase in content of a particular lipid class; human liver microsomes contain higher amounts of each of the lipid classes. Human and rat liver microsomes differ especially in the essential fatty acid composition of total lipids and phospholipids: human liver microsomes contain more linoleic acid and less arachidonic acid than those of the rat. Such a pattern of distribution of fatty acids is similar to that previously reported for human liver mitochondria and has not been reported for other species. Although the previously reported for human liver mitochondria and has not been reported for other species. Although the unsaturation of lipids is lower in human than in rat liver microsomes, spin label studies revealed a higher fluidity in human membranes. It is suggested that this might arise from a lesser immobilization of lipids by proteins in human liver subcellular membranes.

NMR investigation of the influence of procaine and its metabolites on the water exchange through human erythrocyte membranes.

The effect of procaine hydrochloride and its metabolites on the diffusional water exchange through erythrocyte membranes was investigated at 37 degrees C and at concentrations ranging between 5 X 10(-5) M and 5 X 10(-1) M by using the NMR manganese doping method. Procaine hydrochloride and 2-diethylaminoethanol have a moderate stimulating effect on the water exchange, of up to 20% at concentrations ranging between 10(-3) and 10(-2) M, while an increasing inhibitory effect was found at higher concentrations. The p-aminobenzoic acid has no effect on the water exchange up to 10(-2) M and, at higher concentrations, and apparent decreasing inhibition was noticed which is thought to be an artefact due to the uptake of Mn2+ by the cells. The temperature dependence studies suggest that procaine HCl enhances the uptake of Mn2+ by the cells. An opposite effect was found for rigid erythrocytes. The p-aminobenzoic acid and 2-diethylaminoethanol appeared to be more effective than procaine hydrochloride in increasing the uptake of Mn2+.

The uptake of manganese ions and the apparent thermal transition of the erythrocyte membranes.

The nuclear magnetic resonance manganese doping technique is currently used for the determination of the water diffusional exchange time through human erythrocyte membranes. An apparent thermal transition at 26 degrees C was noticed at 18-30 mM manganese doping in the suspending solution. An analysis in terms of a two-phase nuclear spin exchanging system revealed that apparent thermal transitions are expected to occur in the upper and lower temperature regions. They represent a shift from intermediate exchange rates where water diffusion through the membrane is dominant to either fast or slow exchange rates where proton relaxation is the controlling process. The lower temperature apparent transition may be altered by the intracellular manganese concentration; the lower the Mn2+ concentration the lower the transition. Also according to this interpretation only a fraction of the erythrocytes are significantly permeated by Mn2+. The upper transition depends on the Mn2+ concentration in the extracellular volume; it decreases with decreasing Mn2+ concentration.

Fourier analysis of potential oscillations of a liquid membrane for the discrimination of taste substances.

Electrical potential oscillations were obtained across a liquid membrane composed of nitrobenzene/picric acid placed between two aqueous phases in the presence of various taste (i.e. salty, sweet and bitter) substances. The influence of these compounds on electrical oscillations was studied using Fourier analysis to establish a "fingerprint" of the substance that can be correlated with its taste index. Various concentrations of each substance were tested to obtain a Fourier spectrum with discrete peaks which can be further processed. The electrical oscillations consisted of a number of weak damped oscillators, and the Fourier spectra of these signals were found to have a number of discrete peaks of decreasing amplitude at low frequencies (0-0.5 Hz). A correlation of the frequency of the first peak of the Fourier spectrum with the taste index was found for bitter substances, whereas for salty substances the amplitude of the first two peaks of the spectrum was correlated with the taste index.

A non-archimedean theory of interaction of chemical compounds with membranes.

The permeability of procaine across axon membranes and the effect of formaldehyde (FA), crotonic aldehyde (CA) and glutaraldehyde (GA) on the compound action potential of frog sciatic nerve was studied by utilizing a non-archimedean (NA) model of the relaxation process. Such models allow a characterization of biosystems exhibiting more than one time scale. Expansions using Laguerre polynomials have been obtained for relaxation functions. The new approach is tested by fitting the model to the experimental data of other authors, and then applying to extract molecular level information from macroscopic data.

Characteristics of ionic transport processes in fish intestinal epithelial cells.

A general mathematical version of the cell model of a leaky epithelium for the NaCl absorption is presented, analysed and integrated numerically. The model consists in the adequate differential equations that describe the rate of change of the intracellular ion concentrations and are expressed in strict accordance with the law of mass conservation. The model includes many state variables representing ion concentrations, the cell volume, and membrane potentials. Ion movements are described by the Michaelis-Menten kinetics or by the constant field flux equation (Goldman-Hodgkin-Katz). In this paper, we model the intracellular ion concentrations, change in the cell volume, the transmembrane flux and membrane potentials of intestinal epithelium of both fresh water and sea water fish, and generate several simulations (in both the steady state and the transient state analysis) that appear to accord with prior experimental data in this area. For the ion movements of the sea water fish intestine, there were included a Na+/K+ pump, a K(+)-Cl- symport system, the K+ and Cl- channels in the basolateral membrane, whereas a Na(+)-K(+)-2Cl- cotransporter for NaCl absorption and K+ channels are located in the apical membrane. In the fresh water fish intestinal cells, the NaCl absorption is performed by two coupled antiporters Na+/H+ and Cl-/HCO3- presumably responsible for the intracellular pH regulation. In this type of cells, Na+ and K+ channels are located within the apical membrane, whereas Cl- channels are located within the basolateral membrane. The osmotically induced water transport across the apical and basolateral membranes has been taken into account as well. The simulations plot the steady state values for membrane potential difference, short-circuit current and intracellular ionic concentrations using the magnitude of the transmembrane flux through the Na+/K+ pump and Na(+)-K(+)-2Cl- cotransporter, or the basolateral Cl- permeability as dependent variables. The model behaves appropriately with regard to several experimental studies regarding the hyperpolarization (sea water fish intestine) and depolarization (fresh water fish intestine) of the apical membrane potential and inhibition of the short-circuit flux with reduced NaCl absorption. The model is also used to make several analytical predictions regarding the response of the membrane potential and ionic concentrations to variations in the basolateral Cl- flux. Furthermore, maintaining conservation of both mass and electroneutrality and taking into account the osmolar forces is an important advantage, because it allows a rigorous analysis of the relationship between membrane potential difference, volume and flux. The model can be used in the analysis and planning of the experiments and is capable of predicting the instantaneous values of ionic fluxes and intracellular concentrations and of cell volume.

Procaine effect on the active and passive ionic transport through isolated epithelia.

A study on the influence of procaine on both active and passive transport properties of isolated frog skin, at temperatures ranging between 15 and 25 degrees C and at increasing concentrations up to 2%, was carried out. The active transport of sodium as expressed by the short-circuit current, is inhibited when procaine is added to the solution bathing the inside of the skin, the inhibition being steeper at higher concentrations. No apparent effect of procaine with temperature was noticed. The Na and K ionic flows were measured by flam-photometric dosimetry allowing a 10(-5) Kg. m-2 s-1 sensitivity. The diffusional potassium flow through frog skin was stimulated, while the diffusional sodium flow was inhibited by procaine. The stimulation of potassium diffusion was more evident at lower procaine concentrations, whereas the inhibition of sodium diffusion was more evident at higher procaine concentrations.

Increased autophagocytosis induced by colchicine in rat sympathetic neurons.

The effect of colchicine was followed up in the superior cervical ganglion of rats. An increase was observed in the number of autophagocytosis vacuoles in the neurons, especially three and four hours after the intraperitoneal injection of colchicine (0.05 mg/100 g.b.w.). These vacuoles presented very various ultrastructural characters due to their different content and stage of degradation. Their high number is explained by the action of colchicine upon cytoplasmic microtubules, the secondary inhibition of the intracellular movement, and the blockage or reduction of the fusion of primary lysosomes with the autophagic vacuoles, which are continuously formed in the neuron cytoplasms, as well as in other cells.

The action of Cu2+ on the frog epithelium.

The mechanism of action of Cu2+ when applied to the external side of the frog skin preparation was investigated. Cu2+ acts most probably on the external barrier of this preparation, since it increases the transport pool of Na proportionally to the increase in the short-circuit current (I(sc)). Cu2+ does not open new routes for the Na+ entry since the stimulated I(sc) is still completely abolished by amiloride. The I(sc) dependence of Na concentration in the external medium is modified by cooper, since the Ksm value increases in addition to changes in I(sc).

Evaluation of the stimulatory capacity of procaine on Na transport through frog skin.

Procaine has different effects on various ionic conductive pathways through the frog skin. We investigated the season and temperature dependence of the stimulation by mucosal procaine, of the Na-conductive pathway. For this stimulation, we found higher half-maximal saturation constants (KNa) in winter animals (6.38 +/- 0.8 mmol/l), than in summer ones (4.03 +/- 0.7 mmol/l). Summer frogs kept for 2 weeks at 4 degrees C, reacted like winter frogs (6.24 +/- 0.8 mmol/l). However, the maximal sodium currents (INa max) did not depend on temperature adaptation. Procaine-induced increased of KNa is associated with an increase of INa. The effects of procaine associated with BIG (benzoylimidazole-2-guanidine) were non-additive, while with vasopressin they were additive. A biphasic, dose-dependent response was recorded after procaine application to the inner surface. Vasopressin counteracted the serosal procaine-induced inhibition of the Na-transport.

Evidence for various degrees of motional freedom of the "boundary" lipid in cytochrome oxidase.

The cytochrome oxidase-lipid complex from beef heart mitochondria after various degrees of lipid extraction has been studied by electron spin resonance spectroscopy using spin labelled fatty acids and phospholipids. With cytochrome oxidase at the lowest lipid content (below 0.2 mg/mg of protein) i.e. at the level sometimes referred to as the "boundary" lipid, with spin labelled fatty acids an immobilized spectrum is observed. However, when spin labelled phospholipids are used under the same conditions, a mobile component is also observed. A quantitative estimation of the spectral components by computer analysis has been performed. The difference in behaviour of the spin labelled fatty acids and phospholipids suggest that the part of the residual lipid of the complex, which in some conditions is apparently immobilised, may exhibit in other conditons a considerably high degree of mobility.

Self-organization and competition in the immune response to cancer invasion: a phase-orientated computational model of oncogenesis.

MOTIVATION: Recent studies indicate that fractal dimensions can uncover aspects of cellular dynamics prior to pathological manifestation. In this respect we are interested in building a computational model of oncogenesis able to generate patterns with the same fractal dimension spectrum as the in vivo tumor. RESULTS: A new theoretical model incorporating a systemic view of oncogenesis in a computational model was proposed. The tumor growth is viewed as competition for resources between the two self-organizing subsystems: the neoplastic and the immune. Numerical simulations revealed that tumor escape can be uncovered in some earlier stage of the immune-system-tumor interaction using multifractal measures. The described computational model is able to simulate also the case of immune, surgical, chemical and radiotherapeutical treatment, as well as their effects. AVAILABILITY: T The software used is available on request from the authors. CONTACT: Sorinel Oprisan, University of New Orleans, Department of Psychology, Ne w Orleans, LA 70148, USA. soprisan@uno.edu

Interactions of some local anesthetics and alcohols with membranes.

A review of the results obtained by our group in the last decade regarding the interactions of procaine, lidocaine, dibucaine and tetracaine with membranes is presented in the context of the literature data. The action upon membranes, in first approximation monomolecular film of stearic acid spread at the air/water interface used as a membrane model, the modification of biomembrane structure and function using diffraction methods, lipid phase transition, fluidity of lipids and proteins, membrane expansion and platelet aggregation were studied. The thermodynamic knowledge of membrane-alcohol interactions improved by using highly sensitive calorimetric techniques are briefly reported. One of the main conclusions is that the physical state of a monolayer model membrane was the result of competitive interactions between film-film and film-substrate interactions. It was taken into account that local anesthetics, such as lidocaine, carbisocaine, mesocaine, showed changes in the bilayer structure, reflected in macroscopic mechanical properties. This restructuring of the lipid bilayer has a significant influence on the operation of functional subunits, e.g. ionic channels formed by gramicidin. The results support the concept of non-specific interactions of local anesthetics with lipid bilayers. The theoretical modeling of the interactions of local anesthetics is closely compared with experimental data. Our new theory of relaxation for these interactions is using a non-archimedean formalism based on a process resulting from superpositions of different component processes which take place at different scales of time.

Procaine effects on the sodium transport in frog skin.

A study on the influence of procaine on the sodium transport properties in frog skin was carried out. The application of procaine hydrochloride on either the mucosal or the serosal sides of the isolated frog skin has opposite effects. When added to the mucosal compartment, the procaine (as well as two procaine based drugs: Gerovital H3 and Aslavital) biphasically increase the short-circuit current (Isc) with a noticeable "recline" phenomenon, and decrease the slope resistance, as given by the I-V curves. When applied in the serosal compartment, Isc is decreased and the slope resistance of the epithelium is increased. The procaine effect on the apical membranes shows a pronounced dependence on the external sodium concentration. The shift of the E2 inflection point (which indicates the critical intensity of the electric field at which the epithelial conductance changes), with respect to the transepithelial open-circuit potential, shows a rapid and quasi-exponential increase following the application of 25 mM procaine in addition to the different mucosal Na concentrations.

Temperature dependence of the effects of tertiary amines on osmotic hemolysis.

The effects of four tertiary amines (procaine, lidocaine, tetracaine and dibucaine) on the osmotic fragility and the rate of hemolysis of human erythrocytes were investigated in the range between 22-42 degrees C. The temperature dependence of the relative hemolysis indicates the existence of certain critical points in the antihemolytic effect of these substances. The relative rate of hemolysis, which is well known to be a parameter accounting for the fluidity of erythrocyte membrane, decreases with increasing drug concentration, indicating a decrease in membrane fluidity. The amount of drugs actually bound to the erythrocytes increases linearly with the external concentration, as shown by UV-absorption.

Procaine has opposite effects on passive Na and K permeabilities in frog skin.

Procaine has opposite effects on the active transport of Na+ when applied on the mucosal side of the frog skin [where it produces a stimulation of the short-circuit current (Isc)] or when added on the serosal side (where it produces an inhibition of Isc). In an attempt to reveal and localize the primary effect of procaine on either the apical or latero-basal membranes of the epithelial cells, we have tried to "chemically dissect" both membrane functions with inhibitors and ionophores. When applied on the apical side of the latero-basally depolarized epithelium, 25 mmol/l procaine increases Isc and Voc (transepithelial open-circuit potential), while decreasing the transepithelial resistance. The E1-E2 linearity domain of the I-V curves is narrowed. On the serosal side of the depolarized epithelium, the same concentration of procaine does not affect Isc and Voc (which are already inhibited) but it produces an increase in the transepithelial resistance (Rt). Procaine influence on the passive K+ permeability was studied by using the ionophore nystatin, which is assumed to form channels permeable to K+, when applied on the amiloride blocked apical membrane. In nystatin-treated epithelia, 25 mmol/l procaine on the apical side decreased Isc, Voc and Rt. In parallel experiments during Cl- substitution by SO2-(4), the procaine effects on Isc and Voc are no longer maintained, but transient.(ABSTRACT TRUNCATED AT 250 WORDS)