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Biomedical subjects

V K Lishko

Publications and source records attributed to V K Lishko.

At least 73 records · Page 4Linked to original sources
PubMedDate not supplied

[Interaction of the Latrodectus tredecimguttatus spider venom with liposomes].

It is established that interaction of Latrodectus tredecimguttatus venom with bilayer phospholipid membranes of liposomes results in formation of ion channels. Liposome permeability variations are estimated by input and output of 86Rb+ and 45Ca2+ isotopes. It is shown that LaCl3 in 0.5 mM concentration decreases considerably both input and output of Rb+ in proteoliposomes and it may be used as an inhibitor of latrotoxin channels in experiments with phospholipid vesicles. When studying electrophoretic spectrum of proteins bound with liposomes it is shown that latrotoxin (a polypeptide) with molecular mass 130 kDa predominates in proteoliposomes.

Animals↗
PubMedDate not supplied

[Relation between the functional characteristics of fast sodium channels and lipid composition of neuroblastoma C1300 cells].

The paper deals with functional characteristics of fast sodium channels modified by liposomes of differentiated neuroblastoma cells. Cells with a 60% increased total cholesterol content were used. The cells were found to contain lysolecithin. In lecithin the amount of polyunsaturated fatty acids was enhanced. It is established that veratrin added to the culture medium of cholesterol-enriched cells increased the rate of 86Rb release to a greater extent than in the control cells. When studying the temperature dependence of veratrin-activated transport of Rb+ in the intact and lecithin-cholesterol-lyposomes-modified cells it was shown that the veratrin-activated Rb+ release is more sensitive to temperature fluctuations than nonactivated one. In this case it is higher in lecithin-cholesterol-lyposomes-modified cells than in intact ones.

Cell Line↗
PubMedDate not supplied

[Study of channel-forming properties of latrotoxin in liposomes].

Interaction of latrotoxin with phospholipid vesicles and bilayer lipid membranes is shown to proceed differently. Latrotoxin when interacting with liposomes is sorbed on the membrane surface forming no ionic channels in this case. Only latrotoxin fragments obtained due to the toxin hydrolysis by pronase or trypsin are able to form channels. These fragments being inserted into liposomes are coupled strongly with the membrane and are not subjected to the further splitting by proteinases. The electrophoretic spectrum of peptides bound with liposomes is presented by protein components with a molecular weight of 116, 100, 92, 67, 52 and 45 kDa, while zone typical of latrotoxin is absent in this spectrum. The method of small-angle X-rays scattering has shown that tryptic fragments of latrotoxin penetrate into the phospholipid bilayer of liposomes.

Arthropod Venoms↗
PubMedDate not supplied

[Calcium permeability of synaptosomes induced by alpha-latrotoxin].

The paper deals with characteristics of ionic alpha-latrotoxin-induced permeability of rat brain synaptosomes. It has been shown that the addition of alpha-latrotoxin to synaptosomes in the Ca2+-containing media resulted in an extensive and rapid uptake of 45Ca2+ in synaptosomes. alpha -Latrotoxin was not able to enhance the 22Na+ and 86Rb+ uptake or efflux in the Ca2+-containing and Ca2+- and Mg2+-free media. The dye di-O-C3 was used to monitor the membrane potential changes as a consequence of alpha-latrotoxin treatment of synaptosomes. It has been found that alpha-latrotoxin increased synaptosomal fluorescence in the Ca2+-containing media, but failed to induce any increase of fluorescence in Ca2+- and Mg2+-free media. It has been also shown that the calcium uptake induced by alpha-latrotoxin depends on free calcium concentration in synaptosomes. Toxin-induced calcium flows are shown to be of the vector character.

Animals↗
PubMedDate not supplied

[Interaction of alpha-latrotoxin with synaptosomes; metabolic control of the induction of calcium channels].

The aim of the present study is to elucidate the possible significance of metabolic control of the calcium permeability of synaptosomes induced by alpha-latrotoxin. The alpha-latrotoxin influence of processes of GABA release and reuptake is shown to depend on synaptosomal metabolism. It has been found that incubation by the synaptosomes during one hour at 37 degrees C or their treatment by 10(-3) M monoiodacetate during 10 min at 10 degrees C or at room temperature completely abolished or at least strongly decreased the ability of alpha-latrotoxin to induce the calcium influx. Under the same conditions the ability of alpha-latrotoxin to activate the GABA release and inhibit the GABA reuptake do not change. It is concluded that only formation of calcium channels by alpha-latrotoxin is strictly controlled by the level of synaptosomal metabolism.

Animals↗
PubMedDate not supplied

[Modification of latrotoxin channels under the effect of pronase and antibodies to latrotoxin].

The action of pronase and latrotoxin antibodies on alpha-latrotoxin channels in lipid bilayers has been investigated. Proteolysis of the protruding portions of the inserted channels changed slightly its conductivity and selectivity. Latrotoxin antibodies added to either side of the membrane decreased channel conductivity. The effect depends on the membrane potential. It is suggested that the channel conformation depends on the transmembrane potential and selective centre localized in the inner region of a bilayer is insensitive to proteolysis of protruding segments.

Antibodies↗
PubMedDate not supplied

[Binding of latrotoxin to synaptosomes and synaptic membranes of the rat brain].

The binding of [125I] alpha-latrotoxin to synaptosomes from the rat brain is studied. It is shown that the constant rate of toxin association with the synaptosome receptor at 37 degrees C is equal to 8.2 +/- 1.3 x 10(7) M-1.s-1, while that of synaptosomal membrane -7.6 +/- 2.7 x 10(6) M-1 s-1. Depolarization of the synaptosome membrane induced by 55 mM KCl decreases the binding rate of toxin to the receptor, the rate constant being equal to 3.9 +/- 1.5 x 10(7) m-1 s-1. The pattern of the dissociation process of the toxin-receptor complex of synaptosomes and of synaptosomal membrane is different. In the first case dissociation follows two stages with the rate constants 3.6 x 10(-3) s-1 and 1.2/10(-4) s-1, in the second case it follows one stage with the constant equalled 2.0 x 10(-5) s-1. The quantity of the toxin binding sites on synaptosomes may vary under the action of agents modifying the activity of calcium fluxes which are induced by alpha-latrotoxin. It is supposed that a decrease in the ATP level in synaptosomes as well as deenergy of the surface membrane leads to a change in the state of the alpha-latrotoxin receptor.

Animals↗
PubMedDate not supplied

[The effect of muramyl dipeptide analog, GMPD, incorporated into liposomes of various composition on the functional activity of macrophages].

Liposomes of different composition and N-acetylglucosaminyl-N-acetylmuramyl-L-alanyl-D-isoglutamine (GMPD) encapsulated in them are studied for their effect on the functional activity of macrophages by means of determining the 5'-nucleotidase and adenosine deaminase activity in the in vivo experiments. It is shown that both liposomes and GMDP encapsulated in them increase the activity of adenoside deaminase and decrease that of 5'-nucleotidase. This evidences for a change in the adenosine metabolism in the alveolar and peritoneal macrophages and an increase in the functional activity of cells which resulted from that rise. The manifestation of the process depends both on the lipid composition of liposomes and their charge. The observed increase in the functional activity of the alveolar macrophages under the effect of liposomes and GMDP encapsulated in them correlates with inhibition of the lung metastases development in mice.

5'-Nucleotidase↗
PubMedDate not supplied

[Hypoglycemic effect of insulin incorporated into liposomes after oral administration to animals with different types of experimental diabetes].

Different doses of insulin incorporated into liposomes were administered to normal animals and to those with certain forms of experimental diabetes. Lecithin-cholesterol liposomes in the molar ratio 9:1 were used. They were formed by the supersound treatment of the lipid suspension with the crystalline insulin in the buffer containing 140 mM NaCl and 10 mM tris-HCl (pH 7.4). Incorporation of insulin into liposomes was 16.2% in determination by [125I] insulin and 9.7% in determination of immunoreactive insulin after destruction of liposomes. Dynamics of glycemia and insulinemia was studied in these animals. It is established that insulin from liposomes being per os administered to animals evokes an expressed hypoglycemic effect and hyperinsulinemia. Effective sugar-lowering doses of liposomal insulin for animals with the experimental diabetes were from 6 ME/kg and for normal animals--from 30 ME/kg.

Administration, Oral↗
PubMedDate not supplied

[Stability and absorption of liposomes with incorporated insulin in the small intestine].

Lecithin-cholesterol liposomes with the incorporated insulin were studied in vitro for their stability to the action of some factors of gastrointestinal tract--hydrochloric acid, gastric juice, pepsin, trypsin, bile. A considerable destructive action of bile on liposomes is established. Modification of the lipid composition of liposomes makes it possible to increase their stability to the bile action. Suction of liposomes from the isolated sites of rat small intestine is studied. Insulin from liposomes is established to be sucked most intensive from the initial parts of small intestine. In this case it penetrates into the blood bed not in a free state but in the composition of liposomes.

Animals↗
PubMedDate not supplied

[Resistance of liposomes with different physico-chemical characteristics to the effect of plasma].

The chemical composition, liquid content sign and value of charge as well as structure and size of lipid vesicles are studied for the effect they exert on the liposome permeability for 22Na+ in the presence of human blood plasma. The rate of the isotope outlet from the electroneutral lecithin liposomes is determined by the size of vesicles and the quantity of phospholipid bilayers in their membrane. The presence either of a negative or a positive charge on the surface of the liposome membrane has no essential effect on the outlet rate of the radioactive marker. Introduction of different amounts of cholesterol or sphingomyelin into the liposome composition decreases considerably the lipid vesicle permeability and an increase in the liquid content of their membranes due to the temperature elevation is accompanied by a sharp rise in the isotope outlet rate. A conclusion is drawn on the possibility to control the outlet rate of the liposome content in the presence of blood plasma.

Chemical Phenomena↗
PubMedDate not supplied

[Effect of blood components on the stability of liposomes].

The human blood plasma is studied for its effect on the outlet of different substances from lecithin liposomes. It is shown that in the presence of the whole blood the permeability of liposomal membrane for the low-molecular weight compounds increases sharply. Blood plasma proteins play a key role in this process but the influence of albumin, gamma-globulins, fibrinogen as well as of serum lipases is rather insignificant. An increase in the rate of outlet of substances in the presence of blood plasma depends on their molecular weight and may be explained by the formation of dynamic defects or pores of definite size in the liposomal membrane. The formation of these defects (pores) is supposed to proceed due to insertion of blood plasma proteins into the phospholipid matrix of liposomes.

Blood Proteins↗
PubMedDate not supplied

[Channel-forming properties of Steatoda paykulliana spider venom].

While studying Steatoda paykulliana spider venom interaction with bilayer lipid membranes (BLM) it was shown that venom formed ionic channels permeable for bi- and monovalent cations. The selectivity of these channels was determined. It was found that their living time in open state depended on the membrane potential. It was stated that cadmium ions were the effective blockers of investigated channels. The properties of these channels could be compared with those produced by latrotoxin in BLM.

Arthropod Venoms↗