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Biomedical subjects

V A Kabanov

Publications and source records attributed to V A Kabanov.

At least 19 recordsLinked to original sources
PubMed2006

[Therapeutic algorithm in stenosis of the larynx and cervical trachea of various etiology].

An algorithm of the treatment of laryngo- tracheal stenosis (LTS) is proposed to raise efficacy of surgical treatment of LTS and to reduce the number of postoperative complications. The algorithm comprises adequate preoperative preparation of the patients including pharmacological prophylaxis of inflammation in the operative zone; effective use of laryngotracheoplasty; prophylaxis of postoperative scarring including reconstruction of created laryngotracheal passage and administration of medicines influencing general and local immunity, tissue metabolism, repair in the region of postoperative inflammation. The efficacy of the algorithm was followed up un 54 (33.7%) patients with laryngostenosis and 106 (66.3%) patients with laryngo-tracheal stenosis. The algorithm application help rehabilitate all the patients with laryngeal stenosis and 92 (86.8%) patients with laryngo-tracheal stenosis.

Algorithms↗
PubMed2003

Effect of polylysine on transformations and permeability of negative vesicular membranes.

Small (40-60 nm in diameter) and large (300-350 nm) negative vesicles were complexed with a cationic polypeptide, poly-L-lysine (PL). Laser microelectrophoresis experiments showed that in small vesicles rendered anionic with the addition of cardiolipin (CL(2-)), only the CL(2-) in the outer leaflet is involved in the complexation with PL. Calorimetric and other data demonstrate that the binding of PL to the membrane surface causes domains ("rafts") of CL(2-) to form in the outer leaflet, and it is these domains that electrostatically bind the polymer. The kinetics of transmembrane permeation of doxorubicin (Dox, a fluorescent anti-tumor drug) was monitored with and without PL binding to the outer surface of the vesicles. It was found that PL mediates the permeation of Dox into the vesicle interior. In the absence of PL, the Dox molecule (possessing an amino group of pK(a)=8.6) binds to the anionic vesicles in the protonated form and, consequently, suffers an impaired mobility through the membrane. On the other hand, when the PL covers the vesicle surface, Dox passes though the membrane with greater ease. The effects of salt and polyanion on the stability of PL-vesicle complexes and the PL-mediated Dox permeation are also discussed.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2002

Reversibility of structural rearrangements in the negative vesicular membrane upon electrostatic adsorption/desorption of the polycation.

Interaction of small unilamellar vesicles (SUVs), composed of negative diphosphatidylglycerol (cardiolipin, CL(2-)) and neutral dipalmitoylphosphatidylcholine (DPPC), with poly(N-ethyl-4-vinylpyridinium bromide) (PEVP) was studied in water solution above and below the vesicular membrane melting point by means of differential scanning calorimetry, photon correlation spectroscopy, microelectrophoresis, conductometry, and fluorescence techniques. It has been found that CL(2-) species are homogeneously distributed within DPPC-CL(2-) SUV membrane leaflets and between them. Interaction of PEVP with DPPC-CL(2-) SUVs led to drastic structural rearrangements in the membrane if it was in the fluid state (liquid SUVs). Negative CL(2-) molecules migrated from the inner to the outer membrane leaflet and segregated in the vicinity of adsorbed PEVP chains. In addition, PEVP adsorption terminated completely the exchange of lipid molecules between the SUVs. At the same time, the integrity of liquid SUVs contacting PEVP remained unchanged. Since the interaction of PEVP with liquid SUVs was predominantly electrostatic in nature, the polycation could be completely removed from the vesicular membrane by addition of an excess of polyacrylic acid (PAA) polyanions forming a more stable electrostatic complex with PEVP. Removal of PEVP resulted in complete resumption of the original distribution of lipids in lateral and transmembrane directions as well as intervesicular lipid exchange. In contrast, PEVP interacting with DPPC-CL(2-) SUVs formed defects in the vesicular membrane if it was in the gel state (solid SUVs). Such interaction was contributed not only by electrostatic but most likely by hydrophobic interactions involving the defected membrane sites. PEVP kept contacting solid SUVs in the presence of an abundant amount of PAA. The established phenomena may be important for understanding the biological effects of polycations.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2002

What happens to negatively charged lipid vesicles upon interacting with polycation species?

Complexation of synthetic polycations with negative lipid vesicles as cell-mimetic species was studied. It was found that such interaction could be accompanied by lateral lipid segregation, highly accelerated transmembrane migration of lipid molecules (polycation-induced flip-flop), incorporation of adsorbed polycations into vesicular membrane as well as aggregation and disruption of vesicles. A polycation adsorbed on the surface of liquid vesicles due to electrostatic attraction could be completely removed from the membrane by increase in simple salt concentration or by recomplexation with polyanions. In contrast, adsorption of a polycation carrying pendant hydrophobic groups was irreversible apparently due to incorporation of these groups into the hydrophobic part of the vesicular membrane. The above mentioned phenomena were examined depending on the polycation structure, fraction of charged lipids in the membrane, vesicle phase state and ionic strength of solution.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2001

Conventional and gemini surfactants embedded within bilayer membranes: contrasting behavior.

Laser microelectrophoresis (coupled with conductance, fluorescence, and dynamic light scattering) is shown to be a highly instructive tool in comparing the dynamics of conventional and gemini surfactants embedded within vesicle bilayers. The following can be listed among the more important observations and conclusions: a) Cationic conventional surfactant, added to a "solid" (gel) lipid vesicle containing an anionic phospholipid, charge-neutralizes only half the anionic charge. With a "liquid" (liquid crystalline) vesicle, however, the entire negative charge is neutralized. Thus, the cationic conventional surfactant can "flip-flop" readily only in the liquid membrane. b) A cationic gemini surfactant charge-neutralizes only the anionic lipid in the outer membrane leaflet of either solid or liquid membranes, thus indicating an inability to flip-flop regardless of the phase-state of the bilayer. c) Mixed population experiments show that surfactants can hop from one vesicle to another in liquid but not solid membranes. d) In liquid, but not solid, bilayers, a surface-adsorbed cationic polymer can electrostatically "drag" anionic surfactant from the inner leaflet to the outer leaflet where the polymer resides. e) Peripheral fluorescence quenching experiments show that a cationic polymer, adhered to anionic vesicles, can be forced to dissociate in the presence of high concentrations of salt or an anionic polymer. f) Adsorbed polymer, of opposite charge to that imparted to vesicles by a gemini surfactant, is unable to dislocate surfactant even in a liquid membrane. g) In our systems, ionic polymers will not bind to neutral vesicles made solely of zwitterionic phospholipid. On the other hand, ionic polymers bind to neutral vesicles if charge neutrality is obtained by virtue of the membrane containing equimolar amounts of cationic and anionic surfactant. This is attributable to surfactant segregation within the bilayer. h) Experiments prove that polymer migration can occur among a population of neutral ternary vesicles.

Lipid Bilayers↗
PubMed2001

Interaction of a cationic polymer with negatively charged proteoliposomes.

Proteoliposomes were prepared by making bilayer vesicles from neutral egg yolk lecithin and negatively charged alpha-chymotrypsin that had been previously stearoylated. Interaction of these proteoliposomes with a cationic polymer, poly-(N-ethyl-4-vinylpryidinium bromide) (PEVP) was examined. For comparison purposes, interaction of PEVP with egg lecithin vesicles containing an anionic phospholipid, cardiolipin, was also examined. Binding of PEVP to both types of vesicles was electrostatic in nature with the polymer manifesting a higher affinity to the cardiolipin relative to the enzyme. PEVP had no effect on the permeability of the bilayer membranes to sodium chloride. On the other hand, PEVP increased the transmembrane permeability of the nonionic anti-tumor drug, doxorubicin. The greater the negatively charged component in the membrane, the greater the PEVP effect. Polycation binding to the vesicles was accompanied by clustering of the stearoylated chymotrypsin (sCT) molecules within the membrane. This protein clustering is most likely responsible for the increase in the doxorubicin permeation. Enzymatic activity of the membrane-associated sCT remained unchanged upon PEVP binding. These findings seem relevant to the effects of polyelectrolytes on cellular membranes.

Cations↗
PubMed1999

Catalytic properties and conformation of hydrophobized alpha-chymotrypsin incorporated into a bilayer lipid membrane.

A set of artificially hydrophobized alpha-chymotrypsin derivatives, carrying 2-11 stearoyl residues per enzyme molecule, were synthesized and their catalytic parameters and conformation in water solution and in the liposome-bound state were investigated. Hydrophobization of alpha-chymotrypsin and its further incorporation into phosphatidylcholine (PC) liposomes have no effect on the rate constant of the N-acetyl-L-tyrosine ethyl ester (ATEE) ester bond hydrolysis (k(cat)). At the same time, an increase in the number of stearoyl residues attached to the enzyme results in a drastic decrease of ATEE binding to the active center (K(M) increase). Incorporation of the hydrophobized enzyme into the PC liposome membrane results in K(M) recovery to nearly that of native alpha-chymotrypsin. The above changes are accompanied by partial unfolding of the enzyme molecules observed by fluorescence measurements. The obtained results are of interest to mimic the contribution of surface hydrophobic sites in the functioning of membrane proteins.

Animals↗
PubMed1997

Reversibility of structural rearrangements in lipid membranes induced by adsorption-desorption of a polycation.

Interaction of poly(N-ethyl-4-vinylpyridinium bromide) with mixed cardiolipin/phosphatidyl-choline (1/9) liposomes was studied by differential scanning calorimetry and photon correlation spectroscopy. It was found that the adsorption of polycation on the surface of liquid liposomes was accompanied by transmembrane migration of negatively charged cardiolipin molecules from the inner to outer membrane leaflet and lateral lipid segregation. At the same time, the liposome integrity was retained, and the adsorbed polycation can be displaced from the membrane by recomplexation with polyanions. As a result, the initial transmembrane and lateral lipid distribution in the membrane was restored.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1996

DNA affinity to biological membranes is enhanced due to complexation with hydrophobized polycation.

The interaction of negatively charged liquid phosphatidylcholine/cardiolipin liposomes with water-soluble negatively charged DNA/cetylpyridinium bromide and DNA/poly(N-alkyl-4-vinylpyridinium bromide) complexes was studied. It is shown that the DNA/cetylpyridinium bromide complex while interacting with the liposomes is destroyed, so that the cetylpyridinium cation is incorporated into the liposomal membrane and DNA remains in the solution. The DNA/poly-(N-ethyl-4-vinylpyridinium bromide) complex does not interact at all with the liposomes. On the contrary, the complex of DNA with the poly(vinylpyridinium) cation carrying a small amount of N-cetyl groups is adsorbed on the membrane as a whole. The data obtained indicate that complexation of DNA with hydrophobized polycations can be used for enhancing DNA affinity to biological membranes.

Cardiolipins↗
PubMed1994

A polycation causes migration of negatively charged phospholipids from the inner to outer leaflet of the liposomal membrane.

Aggregation of the negatively charged liposomes caused by the addition of the linear polycation, poly-N-ethyl-4-vinylpyridine bromide, was studied. At the point of maximal size and zero electrophoretic mobility of aggregates, the concentration of positive charges brought in by the adsorbed polycation was found to be equal to the total concentration of negative charges both on the outer and inner surface of the lipid bilayer. Since polycation saturation of the liposomal negative charges was found to occur without disruption of the membrane, it was concluded that the polycation induced migration of negatively charged phospholipid molecules from the inner to outer leaflet of the bilayer.

Binding Sites↗
PubMed1992

Pluronic micelles as a tool for low-molecular compound vector delivery into a cell: effect of Staphylococcus aureus enterotoxin B on cell loading with micelle incorporated fluorescent dye.

Micelles of pluronic P85 (poly(oxyethylene)-poly(oxypropylene) block copolymer) are used as microcontainers for in vitro delivery of fluorescein into Jurkat and MDCK cells. In order to target the fluorescein containing micelles into the cell, Staphylococcus aureus enterotoxin B (SEB) is covalently conjugated with a pluronic molecule and the conjugate is incorporated into the micelle content. The incorporation of SEB capable of receptor-mediated endocytosis results in a drastic enhancement of the efficiency of cell loading with the fluorescent dye. This effect is not observed under the conditions (4 degrees C) when endocytosis is abolished.

Animals↗
PubMed1991

DNA interpolyelectrolyte complexes as a tool for efficient cell transformation.

A tool was developed for enhancement of plasmid penetration into an intact cell, based on increasing DNA hydrophobicity via inclusion into a soluble interpolyelectrolyte complex (IPC) with polycations. The characteristics of formation of DNA IPC with synthetic polycations [poly(N-ethyl-4-vinylpyridinium)bromide (PVP) and PVP modified with 3% of N-cetyl-4-vinylpyridinium units (PVP-C)] were studied using ultracentrifugation and polyacrylamide gel electrophoresis methods. The conditions were established under which the mixing of DNA and polycation aqueous solutions results in the self-assembly of soluble IPC species. Incorporation of DNA into IPC results in the enhancement of DNA binding with isolated Bacillus subtilis membranes. A considerable increase in the efficiency of transformation of B. subtilis cells with pBC16 plasmid resulted from incorporation of the plasmid into the IPC with PVP and CVP.

Bacillus subtilis↗
PubMed1990

Recognition of target colloid species by conjugates of a linear polyelectrolyte with a vector protein.

Redistribution reaction of quaternized poly-4-vinylpyridine polycations and their conjugates with alpha-chymotrypsin by oppositely charged latex particles is disclosed. The polycations are strongly adsorbed on the latex surface. Nevertheless, they are able to migrate between the latex species via occasional interparticle contacts. In the case of a homogeneous latex such interchange results in uniform distribution of polycations by latex particles. The distribution drastically changes, when alpha-chymotrypsin-polycation conjugates interact with a mixture of two latexes: one chemically modified by bovine serum albumin and the other one by specific protein inhibitor of alpha-chymotrypsin. In this case the interchanging polycations are finally fixed on the latex particles carrying the centres of specific binding of the enzyme vector, i.e. recognize them in the latex mixture. The obtained results are considered to mimic physico-chemical interaction and recognition of target supermolecular bio-objects by large macromolecules carrying relatively small molecular vectors.

Adsorption↗
PubMed1990

Respecrins--a new type of compound with targeted action.

A new technique for the creation of compounds with targeted action is described. In such compounds, termed respecrins (receptor-specific, screened toxin), a physiologically active component carries an epitope-containing fragment of the target antigen and is screened or masked by antibody specific to this antigen. Interaction of the respecrin with the target cell results in dissociation of this immunocomplex, and thereby activation of the physiologically active component. The kinetics of dissociation of a respecrin during interaction with a cell were investigated by flow cytometry. Possible applications of the principle are illustrated by investigation on the antigen-dependent activation of the mitogenic activity of staphylococcal enterotoxin A.

Allosteric Regulation↗
PubMed1987

[Plastic surgery using cutaneo-fascial flaps in the treatment of burns].

Results of 67 plasties with fasciocutaneous flaps in 59 patients operated upon for burns and their sequellae are described. The correlation of length and width of the flaps was from 1.5:1 and 3:1. Good results were obtained in 90% of the patients. Causes of unfavorable outcomes are analyzed. The method is recommended for the introduction into practice of treatment of burns and their sequellae.

Adolescent↗
PubMed1985

Enzymes in polyelectrolyte complexes. The effect of phase transition on thermal stability.

Penicillin amidase, alpha-chymotrypsin and urease have been immobilized in water-soluble nonstoichiometric polyelectrolyte complexes (N-PEC). N-PEC are formed by modified poly(N-ethyl-4-vinyl-pyridinium bromide) (polycation) and excess poly(methylacrylic acid) (polyanion). N-PEC are a new class of polymers capable, characteristically, of phase transitions solution in equilibrium precipitate induced by slight change in pH or ionic strength. Neither the chemical structure of the carrier nor the number of cross-linkages between an enzyme and a carrier change on phase transition. That gives an unique opportunity to elucidate the difference between enzymes immobilized on water-soluble and water-insoluble supports. A detailed study of the phase transition effect on thermal stability of the enzymes and protein-protein interactions has been carried out. The following effects were found. Pronounced thermal stabilization of penicillin amidase and urease may be achieved on two conditions: the enzyme is in the precipitate; (b) the enzyme is linked to the N-PEC nucleus. Then the thermal stability of N-PEC-bound penicillin amidase increases 7-fold at pH 5.7, 60 degrees C, and 300-fold at pH 3.1, 25 degrees C, compared to the native enzyme. For urease, the thermal stabilization increases 20-fold at pH 5.0, 70 degrees C. The localization of enzyme on N-PEC has been established by titration of alpha-chymotrypsin bound to a polycation or polyanion with basic pancreatic trypsin inhibitor. Both in solution (pH 6.1) and in N-PEC precipitate (pH 5.7), an alpha-chymotrypsin molecule bound to a polyanion is fully exposed to the solution. If the enzyme is bound to a polycation, only 20% of alpha-chymotrypsin molecules in the precipitate and 40% in solution retain their ability for protein-protein interactions. This means that a polycation-bound enzyme is localized in the hydrophobic nucleus of the complex, whereas the polyanion-bound enzyme sits on the hydrophilic shell of the complex. On pH-induced phase transition (pH decreases from 6.1 to 5.7), there occurs a stepwise decrease in penicillin amidase activity which is due to a 9.8-fold increase in the Km for 2-nitro-4-phenylacetamidobenzoic acid. Change of the catalytic activity and thermal stability of N-PEC-bound penicillin amidase is fully reversible and reproducible. Such soluble-insoluble immobilized enzymes with controllable thermal stability and activity may be used for simulating events in vivo and in biotechnology.

Chymotrypsin↗