Search PubMed⌕ Search

Biomedical subjects

A B Kaulin

Publications and source records attributed to A B Kaulin.

At least 19 recordsLinked to original sources
PubMed1991

[Changes in the membrane potential, the cytoplasmic Ca2+ concentration and in the transport of fluorescein anions across the macrophage plasma membrane under the influence of O2(-) and H2O2 in small concentrations].

It has been shown that under the influence of superoxide anion (300 nM) and hydrogen peroxide (100 nM) on murine peritoneal macrophages, the depolarization of membrane takes place, and a change in the rate of fluorescein anion efflux from the cells occurs. Hydrogen peroxide (but not superoxide anions) causes a transient increase in the cytoplasmic Ca2+ concentration. These changes are regarded as early signs of macrophage activation. It is assumed that macrophage activation with reactive oxygen intermediates at such a low concentration might be interpreted as follows: a small portion of stimulated phagocytes activates the whole population with the aid of the products of their own oxidative burst.

Animals↗
PubMed1991

[The measurement of the macrophage membrane potential by using an oxonol fluorescent probe].

Technical questions of macrophage (MP) membrane potential measuring with a probe bis(1,3-dibutyl barbiturate) trimethineoxonol (diBA-C4 (3)) have been elaborated. Measurements were made of single adherent cells. It was shown that at a high concentration of probe in the medium (900 nM) the fluorescent signal well traces the depolarization of membrane, whereas at a low concentration of probe (110 nM) the hyperpolarization is detected more effectively. To find out the reasons for this difference, measurements were made of dye distribution between the cell and the medium measured as well as of the kinetics of probe efflux from MP in the dye-free medium. The gradient of dye concentration on the cell-medium interface appeared to depend on the concentration of diBA-C4 (3) in the medium. Using gramicidin D and Na- and Cl-free solutions, the calibration of fluorescent signal was done; the value of K+ equilibrium potential of MP was -66 - -71 mV. The effect of quinidine and the binding of intracellular calcium result in a significant depolarization of MP membrane; a conclusion is made of the significant contribution of Ca(+)-dependent K(+)-channels to the maintenance of the MP resting potential.

Animals↗
PubMed1991

[Macrophage activation by synthetic peptides. III. Changes in the membrane potential, Ca2+ content and the regulatory decrease of macrophage volume under the action of tuftsin and its antagonist].

With the use of oxonol voltage-sensitive fluorescent dye it has been shown that the stimulation of macrophages (MP) with tuftsin results in a two-phase change in membrane potential: depolarization followed by hyperpolarization of plasma membrane. The pattern of changes in membrane potential depends on Na+ concentration in the medium and is disturbed with binding of cytoplasmic Ca2+. Fluorescent signal obtained from MP loaded with Ca(2+)-activated photoprotein obelin points to a significant increase in the concentration of cytoplasmic Ca2+ under the influence of tuftsin on cells: the source for Ca2+ being the medium. The rate of regulatory voltage decrease in MP increases under the influence of tuftsin: the effect of this peptide being similar to that of calcium ionophore. All these findings taken together enable us to suggest a phenomenological scheme of transmembrane ion signals arising during stimulation of MP with tuftsin: the receptor-mediated calcium channel provides a rise in cytoplasmic Ca2+ which opens non-selective cation channels for Na+ ions to activate eventually Ca(2+)-dependent K(+)-transport.

Animals↗
PubMed1989

[Macrophage activation by synthetic peptides. II. The effect of oxidative burst products on the fluorescence kinetics of macrophages stained with fluorescein diacetate].

Our previous study has shown that the intensity of macrophages in a medium containing fluorescein diacetate (FDA) retains a certain constant level ready to fall upon the addition of stimulants. The decrease in fluorescence was attempted to explain by secretion of oxygen metabolites during the activation process. The decrease in fluorescence is much smaller in the medium containing catalase and superoxide dismutase. Hydrogen peroxide (50 nM and higher) causes a reversible decrease in the fluorescent intensity of resting macrophages. These experiments suggest that the oxidative burst products may serve as regulators of the feedback control during macrophage activation.

Animals↗
PubMed1989

[Macrophage activation by synthetic peptides. I. Kinetic changes in the transport of fluorescein anions across the plasma membrane of macrophages].

As shown by cytofluorimetric technique, fluorescein anions formed in macrophages due to hydrolysis of fluorescein diacetate (FDA) release into the extracellular medium through the probenecid-inhibitable transport system of organic acids. Technical procedures have been elaborated to record separately the process of FDA hydrolysis characterising the activity of intracellular esterases, and the fluorescein anion transport representing secretion of organic acids by macrophages. It has been established that the tetrapeptide tuftsin stimulates the cell esterase activity without affecting the rate of fluorescein efflux. The peptide KPR (Lys-Pro-Arg) decreases both the esterase activity and the fluorescein anion efflux.

Amino Acid Sequence↗
PubMed1988

[Use of fluorescein diacetate for research on macrophage activation].

Kinetic of changes in the fluorescence intensity of macrophages in a medium containing fluorescein diacetate (FDA) has been analysed. It is shown that under certain conditions the intensity of macrophages retains a constant level for rather a long time. The addition of stimulants such as lipopolysaccharide or tuftsin to the incubation medium leads to characteristic changes in the cell fluorescence level related to the increase in the activity of FDA intracellular hydrolyses and fluorescein efflux from macrophages. It is concluded that the kinetic of changes in the macrophages fluorescence intensity in a medium with FDA may serves as a test for detecting early functional changes upon macrophage activation.

Animals↗
PubMed1988

[Intravital research on hydrophobic interactions in protein fibrils using a fluorescence polarization method].

Fluorescent probe of acridine orange (AO) is known to be bound exclusively by materials of thick protofibril muscle fibres. The dependence of fluorescence anisotropy of AO in frog muscle fibres on the temperature has been studied. It has been found that the fluorophore orientation decreases with temperature, i.e. here the adsorbent cold denaturation takes place. This phenomenon was demonstrated for living, skinned and glycerinated muscle fibres. It shows that hydrophobic interactions contribute much to stabilization of the myosin structure. After contraction of glycerinated muscle fibres at the action of ATP, the AO fluorescence anisotropy grows independently of the temperature which is indicative of structural rearrangements in materials of thick protofibrils upon contraction.

Acridine Orange↗
PubMed1987

[Intravital study of the hydrophobic interactions in protein fibrils by a polarization-fluorescence method. I. Collagen fibrils].

It has been shown earlier that anisotropy of extrinsic fluorescence (AEF) of ordered structures in living cell may serve as a measure of the free structure energy. The experimental study of AEF changes of myelin at varying temperatures (0-30 degrees C) revealed cold denaturation. This phenomenon occurs only in cases when the structure in question is stabilized through hydrophobic interactions. The purpose of this work was to show that not only membranes but also some native ordered protein structures might be analysed by fluorescence polarization to detect hydrophobic interactions. The fluorescence anisotropy of primulin adsorbed by collagen fibrils from rat tail has been investigated. The fluorophore orientation decreases with temperature, i.e. here the phenomenon of cold denaturation is observed. When the medium humidity falls down to 80%, no cold denaturation occurs. AEF of collagen fibrils depends to a considerable extent on organic substances (ethanol, ethylene glycol) added in small concentrations to the incubation medium. It is concluded that the dependence of the whole collagen molecular structure in fibrils on the content and structure of the solvent shell is of critical nature.

Animals↗
PubMed1985

[Structural changes in the myelin sheath membranes exposed to anisotonic media. A fluorescence polarization study].

Extrinsic fluorescence polarization (P parallel and P perpendicular) of intact myelinated nerve fibres in anisotonic media has been investigated. Fluorescent probes of Acridine orange and Perylen were used for the experiment. Changes in fluorescent polarization of nerve fibres, associated with osmotic movement of water, arise immediately after the incubation of fibres in hypo- or hypertonic solutions. During exosmotic and endosmotic movement of water P parallel and P perpendicular and in quite a different manner. This fact demonstrates an asymmetry of structural membrane alterations. The results obtained are explained by asymmetry of swelling and shrinking of carbohydrate gel between two adjacent extracellular membrane surfaces of the myelin sheath.

Animals↗
PubMed1984

[Structural changes in the myelin sheath membranes detectable by using the nonpolar probe perylene. A fluorescence polarization study].

Perylene as a fluorescent probe has been used to investigate membranes of the myelin sheath of surviving nerve fibres. Fluorescence polarization (P) of perylene was measured in stained nerve fibres, and their dependence on the angle (AD) between the geometrical axis of the fibre and electrical vector of exciting light was studied. The dependence of AD on the temperature showed that P (90 degrees) decreased gradually when the temperature increased at heating within the range of 0-32 degrees. A model of the prove movement in the lipid matrix is described. This model considers the rotation around the axis perpendicular to the plane of the perylene molecule only. Comparison of the results of model calculations and the experimental data allows to estimate the value of energy of viscosity activation. It proved to be 20-25 kcal/mol. Possible causes of such a high value of the kinetic barrier are discussed.

Animals↗
PubMed1981

[Fluorescence anisotropy and myelin structure. IV. An analysis of the effect of temperature changes on the membrane structure].

The temperature dependence of birefringence and fluorescent polarization of stained nerve fibers has been studied. Theoretical aspects of the determination of the orientation of chromophores from polarized emission experiments are aslo considered. The experiments with changing temperature permits a conclusion that the organization of polar groups of the membrane becomes random with the decline of temperature from 20 degrees to 0 degree C, while the order of organization of hydrophobic groups increases.

Animals↗
PubMed1981

[Diffusion of fluorescein molecules in muscle fiber. I. The determination of the coefficient of diffusion].

Two methods for measuring the diffusion coefficient of fluorescein molecules (molecular weight 376 D) micropipetted to frog muscle fibre are discussed. The first (photoelectric) method implies that the fluorescein intensity is determined at a known distance from the site of injection using a photometric probe. The time dependence of this intensity has a maximum. If to apply the equation of heat conductance in a cylinder with impermeable walls on supply of point heat impulse, a simple formula is obtained for calculating the diffusion coefficient. The second method consists in photographing a stained portion of the fibre in fluorescence light. After densitometry of the film, the diffusion coefficient is calculated from the Gaussian equation. As demonstrated by the measurements, the diffusion coefficient values for fluorescein are three-fold lower than for water.

Animals↗
PubMed1981

[Diffusion of fluorescein molecules in muscle fiber. II. The ratio of the coefficient of diffusion to the fiber diameter].

The diffusion of sodium fluorescein was studied upon alteration of the medium tonicity and the fibre stretching. In the former case, coefficients of both translational (Dt) and of rotational (Dr) diffusion changed, but not equally. With a decrease of the fibre diameter on hypertonia, Dt is reduced more drastically than Dr, which means that the diffusion anisotropy (see formula in text) is diminished. On stretching muscle fibres, provided their volumes are constant, the diffusion rate is not changed. It is concluded that the surface-ordered water in muscle fibre capillaries, in which dye molecules are diffusing, becomes desorganized in the process of hypertonic contraction due to the increase of ionic concentration (potassium, for the most time).

Animals↗
PubMed1978

[Fluorescence anisotropy and myelin structure. II. Azimuth characteristic of surviving nerve fibers].

The dependence of fluorescence polarization of stained nerve fibres on the angle between the fibre axis and electrical vector of exciting light (azimuth characteristics) has been considered. Evidence is provided that the azimuth characteristics of stained nerve fibres depends on dye molecules adsorbed on the myelin sheath membranes. From the previous calculations it may be concluded that part of the dye molecules are oriented at a small angle to the geometrical axis of the nerve fibre.

Animals↗
PubMed1978

[Fluorescence anisotropy and myelin structure. III. Effect of temperature changes on the orientation of dye molecules in nerve fibers].

The temperature dependence of fluorescence polarization of stained nerve fibres has been studied. As has been previously demonstrated by the authors, the dependence of fluorescence polarization on the angle between the electrical vector of exciting light and the fibre axis (azimuth characteristics) is associated with the molecular orientation of dyes adsorbed on the membranes of the myelin sheath. This permits an indirect conclusion to be made about the structure and structural changes of an adsorbent. The experiments with changing temperature show that the molecular orientation of dyes decreases with decline of temperature from the room temperature to the freezing point of the Ringer solution. The structure of myelin membranes is suggested to be stabilized through hydrophobic interaction.

Acridines↗
PubMed1977

[Properties of cell water].

An attempt was made to analyse and summarize findings concerning water properties of animal and plant cells. From the physical evidence of surface influence on the structure of vicinal water layers, a conclusion is drawn that the structure and properties of cell water are likely to be affected by intracellular interfaces.

Animals↗