PubMed Health⌕ Search

Biomedical subjects

A S Kaprel'iants

Publications and source records attributed to A S Kaprel'iants.

At least 19 recordsLinked to original sources
PubMed2002

[Eradication of Helicobacter pylori in patients with duodenal ulcer following the short course of treatment with azitromycin and amoxycillin].

The efficacy of short-term treatment with azithromycin in 17 patients with acute doudenal ulcer associated with H. pylori was evaluated. Bioptats of the gastric mucosa taken at the beginning and after one month of treatment were investigated for H. pylori presence by histological, bacteriological methods, by urease test and by PCR. All the patients with positive H. pylori test were treated with Gastrozol (omeperazole, ICN Pharmaceutical) 40 mg per day for 1 week followed by 20 mg per day for 3 weeks, Sumamed (azithromycin, peira) 0.5 g once daily for 3 days and amoxycillin 0.5 mg four times a day for 10 days. Bioptats analysis before treatment revealed H. pylori in 100% for PCR methods, in 94.1% for urease test, in 88.2% for histological test. After the treatment H. pylori was revealed in 12.5% for urease and histological test, in 18.8% for bacteriological test and in 25% for PCR test. Thus the treatment efficacy was 75%. Side effects for short-term azithromycin therapy were shown in 5.9% cases.

Adult↗
PubMed2001

[Methods of Helicobacter pylori detection].

There is the HP diagnostic methods review. The classification of main methods is presented. Diagnostic significance and defects of all these methods were demonstrated. There are own data of HP and its strains revealing in the patients with duodenal peptic ulcer.

Duodenal Ulcer↗
PubMed1999

[The possibility of Helicobacter pylori being present in the resting state in the gastric mucosa of peptic acid patients after treatment].

AIM: To develop experimental approaches to detection of inactive forms of Helicobacter pylori (HP) in patients treated for gastroduodenal ulcer, to try the role of such HP forms in emergence of ulcer recurrences. MATERIALS AND METHODS: Examination for HP was made using a fast CLO test, polymerase chain reaction (PCR), histologically. A simple quantitative spectrophotometric test for urease activity in biopsies of gastric mucosa is proposed. RESULTS: Antibacterial and other treatments led to a significant decline in urease activity dependent on the amount of the agents in the biopsies. PCR found HP in 48% of patients after the treatment. In these cases HP may be in dormancy. This state is not safe because of possible HP activation eventuating in ulcer recurrence. CONCLUSION: PCR can be used for prediction of ulcer recurrence as it is sensitive to HP when wide-spread urease test gives negative results.

Biopsy↗
PubMed1996

[Participation of 2-C-methyl-D-erythritol-2,4-cyclopyrophosphate in reactions of bacteria on oxidative stress and their persistence in macrophages].

In aerated medium, Corynebacterium ammoniagenes cells accumulate 2-C-methyl-D-erythritol-2,4-cyclopyrophosphate (MEC) during heat shock and in the presence of O2--generating compounds or ozone. The ability to accumulate MEC was genetically transformed from C. ammoniagenes to E. coli XL-1; transformed E. coli (2-31 clone) accumulates MEC in the presence of glucose and glucose oxidase (generation of H2O2) or benzylviologen (generation of O2-); the viability of transformed bacteria inside the murine peritoneal macrophages also significantly increases. However, model conditions of phagosomes of warm-blooded animals (NO + H2O2 + O2-) did not cause MEC accumulation by C. ammoniagenes but increased the formation of polyphosphate which can be due to selective oxidative aberration of biosynthetic processes. Growth rate of Acanthamoeba castellanii on solid medium with bacterial lawn was not significantly different in C. ammoniagenes, C. ammoniagenes with preaccumulated MEC, E. coli XL-1, and E. coli 2-31 and did not depend on the accumulation of MEC by bacteria. Unlike the recipient E. coli strain, the transformed 2-31 clone synthesizes two nonpolar lipids (Rf = = 0.85 and 0.75; TCL on Silufol in hexane) and carotinoid pigments; this can be due to changes in metabolic pathways of isopentenylpyrophosphate that can be a precursor of MEC biosynthesis. Thus, MEC is involved in bacterial responses to certain components of oxidative stress and in bacterial persistence inside the macrophages.

Animals↗
PubMed1988

[Dynamic spatial organization of enzymes in the cell and the regulation of metabolism].

The proteins in membranes and cytosol are often distributed unevenly in space and form the dynamic aggregates and functional assemblies. This property is important for functioning of multienzyme systems. The experimental results indicate the existence of a special type of regulation and integration of cellular metabolism based on the change of mutual rearrangement of enzymes in the cell and formation of transient protein assemblies.

Animals↗
PubMed1983

[Dynamic organization of the electron transport chain in bacterial membrane by radiation inactivation].

A complete cross-linking of proteins in isolated Micrococcus lysodeikticus membranes under effect of glutaric aldehyde causes 50% inhibition of the NADH-oxidase activity. Using the irradiation inactivation procedure, it was demonstrated that the size of the irradiation target for NADH-oxidase coincides with that for NADH-dehydrogenase and makes up to about 50 KD. In glutaric aldehyde-treated membranes the target size for NADH-oxidase is 3 times more than that, i.e. 150 KD. It is assumed that the effective electron transfer is mediated by a carrier assembly united into a supramolecular complex with a terminal life-time. Different assemblies exchange their components due to lateral diffusion of proteins in the membrane, which can account for the small size of the irradiation target for the oxidase activity.

Cell Membrane↗
PubMed1983

[Interrelation between the available boundary lipids in the bacterial membrane and the respiratory chain function].

In order to establish a possible correlation between the expression of the boundary lipid and the NADH-oxidase activity, the temperature dependences of the membranes of bacteria grown at 14 and 38 degrees C were investigated. The Tmelt. for the boundary lipid determined by comparing the excimerization parameters of the fluorescent probe pyrene in the vicinity of the proteins and in the total lipid phase was directly correlated with Tgrowth. A similar temperature dependence was observed with the NADH-oxidase activity, i. e. inhibition of activity at T greater than Tmelt. coincided with the disappearance of the boundary lipid. Incorporation of a cis-unsaturated fatty acid (linoleic acid) into the membranes markedly decreased the structural heterogeneity of membrane lipids and caused a simultaneous inhibition of the NADH-oxidase activity. No structural-functional changes were observed in the case of saturated fatty acids (stearic acid). It was assumed that the presence of boundary lipids in the membrane is essential for the normal functioning of the multienzyme system of the respiratory chain. Presumably, the state of the immediate lipid environment controls the function of the micrococcal respiratory chain at the level of interaction between the carriers in the membrane.

Electron Transport↗
PubMed1982

[Existence of boundary lipids in reconstituted hydrophobic protein-lipid system].

A fraction of hydrophobic proteins (9, 14, 18 kD) soluble in a chloroform-methanol mixture (2:1) has been isolated from Micrococcus lysodeikticus bacterial membranes. The proteins obtained were introduced into proteoliposomes at a protein/lipid weight ratio ranging from 0.1 to 0.25 in combination with the fluorescent probe pyrene or the spin probe 2-(14-carboxytetradecyl)-2-ethyl-4.4-dimethyl-3-oxasolidinyloxyl. The excimertization of pyrene upon direct excitation of its molecules (gamma excit.=338nm) and under conditions of energy transfer from the excited protein chromophores to pyrene (gamma excit.=286nm) and the spin-spin exchange between the spin probe molecules was investigated. The experimental results suggest that the hydrophobic protein molecules are surrounded by a structurally heterogenous lipid area containing up to 3.3 mg of lipid per l mg of protein. The maximal expression of structural heterogeneity was observed at the minimal content of protein in the proteoliposomes. Treatment with the membranotropic antibiotic gramicidin S resulted in disappearance of lateral heterogeneity of lipids in the constituted system and in lipid aggregation in bacterial membranes. It is assumed that the aggregability of membrane proteins depends on the structural rearrangement of some part of lipid bilayer around them.

Bacterial Proteins↗
PubMed1982

[Dynamic protein assemblies in biological membranes].

The peculiarities of structural organization and functioning of enzymes in biological membranes are reviewed. Based on experimental data it is suggested that these peculiarities are due to the ability of many proteins to form intramembrane aggregates and assemblies differing in life-time and consisting of related and functionally different enzymes, which determines the structural and functional heterogeneity of biological membranes. The importance of formation of dynamical essembl es for the functioning of multienzyme systems is illustrated by the hormone--receptor--adenylate cyclase and redox carrier chains. The general principles of functioning of these systems (e. g. lateral diffusion of constituent components, formation of protein-protein aggregates with terminal life-time, etc.) are discussed. On the whole the biological membranes appear as microheterogenous dynamical structures, whose functioning strongly depends on aggregation-deaggregation of membrane proteins. These processes are affected (i. e. accelerated or decelerated) by a number of factors, such as, for instance, multienzyme system functioning, which also stabilize the molecular assemblies formed. It is assumed that changes in reciprocal intramembrane arrangement of the enzymes and formation of protein-protein complexes may control the local activity of membrane-dependent processes in the cell.

Adenylyl Cyclases↗
PubMed1981

[Changes in the structural state of boundary lipids in bacterial membrane under effect of the membranotropic antibiotic gramicidin S].

Using data from measurements of excimerization at different wave-lengths of fluorescence excitation of the fluorescent probe pyrene in isolated M. lysodeikticus membranes and using the phenomenon of energy transfer in the protein tryptophanyl-pyrene system, a method for monitoring the probe population localized in the immediate proximity to protein structures, has been developed. This method allows to detect the existence within the physiological temperature range of a specific lipid population or a boundary lipid vicinal to the membrane proteins. The changes in this region under membrane treatment with the cyclodecapeptide antibiotic gramicidin S were studied. Incubation of membranes with the antibiotic increases the efficiency of quenching of membrane protein fluorescence by the quenchers localized in the membrane phase, i.e. 2-(14-carboxytetradecyl)-2-ethyl-4,4-dimethyl-3-oxasolidinyloxyl, cetylpyridinium chloride and pyrene, and changes the protein chromophore accessibility for J-. The lateral mobility of pyrene during gramicidin S adsorption on the lipid and protein-lipid membranes is decreased. The results obtained are interpreted in favour of partial disturbance in the interaction of the boundary lipid and membrane proteins under effects of gramicidin S.

Cell Membrane↗
PubMed1981

[Functional and structural changes of E. coli membranes induced by low temperature freezing].

Low temperature freezing of E. coli cells causes a fall in endogenous respiration and stimulation of respiration by the non-penetrant substrate NADH. This decrease is not due to disturbances in the function of electron transport chain, since the dehydrogenase and oxidase activities and cytochrome content in the membranes of intact and frozen cells are practically the same. Frozen E. coli cells are incapable of ATP synthesis by artificial proton motive force, although the ATPase activity of isolated membranes is not changed. The disturbances in the penetrability barrier of protons after freezing can be revealed from changes in pH of cell suspensions after rapid acidification. It is assumed that the cell penetrability barrier undergoes alterations causing a loss of respiration substrates and, probably, oxidative phosphorylation uncoupling. A correlation between constant damages of the membrane penetrability barrier and cell survival was established. Using spin labelling of different localization, the changes in the state of membrane surface at the intact hydrophobic lipid zone were demonstrated. It was found that freezing does not induce lipid peroxidation.

Adenosine Triphosphatases↗
PubMed1981

[Structure of the Micrococcus lysodeikticus respiratory chain using low concentrations of Triton X-100 and glutaric aldehyde].

Using low (0.0025 -- 0.025%) concentrations of Triton X-100, the correlation between the decrease of NADN- and malate oxidase activities and NADH- and malate dehydrogenase release in large fragments of Micrococcus lysodeikticus membranes was established. This was accompanied by membrane suspension clearance and a decrease of microviscosity of the membrane lipid component. Using NADH-dehydrogenase, it was shown that the attachment of NADH-dehydrogenase to the membrane treated with glutaric aldehyde occurs in two steps, this being indicative of different environment of this enzyme in the membrane. The data obtained are discussed in terms of laterally heterogenous structure of the bacterial membrane with respect to the electron transport enzymes, in particular in favour of an existence of individual sites of the membrane containing dehydrogenases rather than other respiratory chain components.

Alcohol Oxidoreductases↗
PubMed1979

[Lateral heterogeneity of bacterial membranes].

Isolated membranes of M. lysodeikticus were rapidly frozen and disrupted in a Hughes press. After disruption the fragments were centrifuged at 144000 g for 1 hour and part of the supernatant just above the pellet was subjected to isopycnic centrifugation in a continuous sucrose density gradient. It was found that the material tested was a mixture of fragments differing in their buoyant densities. These fragments also differed in their protein/lipid ratios, cytochrome content and dehydrogenase activities calculated per protein and lipid as well as in proportion of the respiratory chain enzymes. The results obtained are indicative of lateral heterogeneity of the bacterial membrane and the existence of areas in the membrane having high concentration of the respiratory chain enzymes. The latter may suggest that the system of substrate oxidation is segregated in the membrane. It is assumed that there exists in the membrane an exchange of components between different electron-transporting chains operated due to their lateral diffusion.

Cell Membrane↗
PubMed1979

[Compartmentation of gramicidin 5 in membranes of sensitive bacteria and protein-lipid interactions].

Gramicidin S is sorbed on the isolated membranes of granicidin-sensitive Micrococcus lysodeikticus strain. The antibiotic inhibits the membrane malate dehydrogenase within the temperature range of 9--42 degrees C, i.e. under conditions of gel and liquid-crystalline lipid state; however its effect at 10 degrees C is 10 times as low as is observed at 42 degrees C. The inhibitory effect of gramicidin S on malate dehydrogenase can be eliminated and the antibiotic can be removed from the membrane by an excess of different phospholipids. No transfer of the membrane components on exogenous phospholipids is observed. A prolonged (about 2 hrs, 30 degrees C) incubation of the membranes with gramicidin S results in irreversible inactivation of malate dehydrogenase, although the antibiotic can be still eliminated by an addition of phospholipid emulsions. It is suggested that gramicidin S forms complexes with phospholipids, in which the antibiotic is oriented to water. These complexes disturb the lipid-protein interactions, resulting in relaxation of the binding between the boundary phospholipids and proteins, in the loosening of near-protein lipid zones and simultaneous condensation of acid phospholipids in the whole membrane. Destruction of the lipid zone is accompanied by changes in the enzyme activity, by separation of lipid and protein regions and by transphase enzyme transitions (expulsion or immersion). A slow formation of secondary protein-protein associates may be irreversible.

Cell Membrane↗
PubMed1977

[Effect of deep freezing on isolated rat liver lysosomes].

The level of the non--sedimentating activity of acid hydrolases (deoxyribonuclease, phosphatase, cathepsins) and electron microscopy of lysosomes has been studied after freezing to --30 degrees, --70 degrees, --140 degrees and --196 degrees. It has been found that enzyme solubilistion and lysosome ultrastructure distortion are mostly marked in the temperature range between 0 degrees and --30 degrees C. Additional membrane damage is observed in the temperature range from --140 degrees to --196 degrees C. It is suggested that not only physico-chemical changes during phase transitions of free water in the freezing medium but also recrystallization processes and the freezing-out of water structurally bound with membranes may contribute to mechanism of lysosome cryoinjury.

Animals↗
PubMed1977

[Membranes of bacteria and mechanism of action of the antibiotic gramicidin S].

The cyclopeptide antibiotic gramicidin S taken at a concentration of 100--200 mkg/mg membrane protein rapidly increases the permeability of M. lysodeikticus protoplast membranes for substrates of respiratory chain and exogenous cytochromes c. Prolonged incubation of gramicidin S with protoplasts results in their lysis which is more fast at low temperatures. In contrast to natural gramicidin, a derivative of gramicidin S with acetylated amino groups does not inhibit either the micrococcus membrane dehydrogenase or the whole of respiratory chain and does not affect the osmotic barrier of protoplasts. Aliphatic diamines (at concentrations up to 0.1 M) and Ca2+ ions (10(-2) M) do not affect the functioning of the respiratory chain in isolated micrococcus membranes. Another derivative of the antibiotic with an increased distance of loaded amino groups from the cyclopeptide framework (diglycyl gramicidin S) affects the membrane in a way similar to that of natural gramicidin. Washing of gramicidin-treated membranes with NaCl enhances the inhibitory effect of the antibiotic on membrane enzymes. The data obtained suggest that in addition to ionic interactions some hydrophobic interactions also occur during gramicidin S binding to the bacterial membrane, probably at the expense of a hydrophobic peptide ring. It is assumed that gramicidin S, similar to Ca2+ and some other membranotropic agents provides for phase separation of negatively charged phospholipids from other groups of phospholipids, manifesting itself in an appearance of "frozen" sites on the membrane which destroys its barrier properties. This is due to the formation of ionic bonds of negatively charged phospholipids. Simultaneously, unlike Ca2+, gramicidin S, when interacting with membrane proteins, prevents their redistribution in more liquid parts of the membrane, which results in a situation when the respiratory enzymes become surrounded by alkyl chains with restricted motion.

Bacteriolysis↗