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A A Deev

Publications and source records attributed to A A Deev.

At least 19 recordsLinked to original sources
PubMed2005

Three-dimensional reconstruction of synapses and dendritic spines in the rat and ground squirrel hippocampus: new structural-functional paradigms for synaptic function.

Published data are reviewed along with our own data on synaptic plasticity and rearrangements of synaptic organelles in the central nervous system. Contemporary laser scanning and confocal microscopy techniques are discussed, along with the use of serial ultrathin sections for in vivo and in vitro studies of dendritic spines, including those addressing relationships between morphological changes and the efficiency of synaptic transmission, especially in conditions of the long-term potentiation model. Different categories of dendritic spines and postsynaptic densities are analyzed, as are the roles of filopodia in originating spines. The role of serial ultrathin sections for unbiased quantitative stereological analysis and three-dimensional reconstruction is assessed. The authors' data on the formation of more than two synapses on single mushroom spines on neurons in hippocampal field CA1 are discussed. Analysis of these data provides evidence for new paradigms in both the organization and functioning of synapses.

Animals↗
PubMed1999

Proximal transcribed regions of bacterial promoters have a non-random distribution of A/T tracts.

Promoter sequences of Escherichia coli were compiled and their transcribed regions characterized by site-specific cluster analysis. Here we report that transcribed regions contain a non-random distribution of A/T tracts with strongly preferred positions at 6 +/- 3, 23 +/- 3, 40 +/- 2 and 56 +/- 2. The maxima of this distribution follow an unusual periodicity (approximately 17 bp) and are in phase with important promoter elements involved in interaction with RNA polymerase, while the value of periodicity numerically fits the spacer length between the canonical -35 and -10 elements. The possible functional significance of this newly described feature is discussed in the context of promoter clearance and transcription pausing.

Adenine↗
PubMed1999

DNA bendability--a novel feature in E. coli promoter recognition.

The distribution of deformable base-pair steps in the structure of bacterial promoters is analyzed with respect to their possible structural and functional role. A regular positioning of TA and TG stacks is detected with the best fit period 5.6 bp. This value is interpreted as a half of the sequence period 11.2 bp, somewhat higher than the structural helical repeat of B-DNA (10.55 bp). The difference, +0.65 bp, suggests a sequence-dependent helical writhe of the promoter DNA--a right-handed superhelix. Apparently, to favour rotational setting of DNA on the surface of RNA polymerase the flexible steps deformable largely towards the grooves, follow the half-period spacing. Such rotational setting is consistent with the DNase I footprinting data. Periodical distribution of deformable base-pair stacks shows negative correlation with the presence of -35 canonical hexamer, suggesting the functional significance of this novel element for promoter recognition. The RNA polymerase--DNA recognition is discussed as interaction of distributional type that involves many elements of different nature which are in partially compensatory relations.

Computer Simulation↗
PubMed1998

Structural organization and phase behavior of DNA-calcium-dipalmitoylphosphatidylcholine complex.

Freeze-fracture study of ultrastructure of DNA--calcium--dipalmitoylphosphatidylcholine (DPPC) complex was carried out at different temperatures. For high-speed cryofixation from controllable initial temperatures, a special thermostatic chamber was designed. The fracture surface of the complex was found to be considerably different from the initial DPPC liposomes: 1) the period of ripple phase was 25 nm in contrast to 15 nm for control samples; 2) the ripple phase was observed at temperatures ranging from 6 degreesC to lipid melting temperature; 3) at temperature above the lipid melting unordered worm-like folds were formed on the fracture surface. Their length was correlated with the length of DNA fragments used in the experiment. We suppose that DNA molecules adsorbed on the membrane surface were segregated to clusters, resulting in formation of a new phase with specific structure and properties.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1997

Non-canonical sequence elements in the promoter structure. Cluster analysis of promoters recognized by Escherichia coli RNA polymerase.

Nucleotide sequences of 441 promoters recognized by Escherichia coli RNA polymerase were subjected to a site-specific cluster analysis based on the hierarchical method of classification. Five regions permitting promoter subgrouping were identified. They are located at -54 +/- 4, -44 +/- 3, -35 +/- 3 (-35 element), -29 +/- 2 and -11 +/-4 (-10 element). Promoters were independently subgrouped on the basis of their sequence homology in each of these regions and typical sequence elements were determined. The putative functional significance of the revealed elements is discussed on the basis of available biochemical data. Those promoters that have a high degree of homology with the revealed sequence elements were selected as representatives of corresponding promoter groups and the presence of other sequence motifs in their structure was examined. Both positive and negative correlations in the presence of particular sequence motifs were observed; however, the degree of these interdependencies was not high in all cases, probably indicating that different combinations of the signal elements may create a promoter. The list of promoter sequences with the presence of different sequence elements is available on request by Email: ozoline@venus.iteb. serpukhov.su.

Base Sequence↗
PubMed1996

DNA initiates polymorphic structural transitions in lecithin.

The inverted micellar phase, obtained by treating lecithin and Ca(2+)-DNA complex with chloroform, was used as an intermediate step in the preparation of DNA-Ca(2+)-lecithin complex. DSC analysis demonstrated the involvement of a large fraction of lipid in the interaction with DNA. Freeze-fracture electron microscopy revealed (i) rod-like structures on the hydrophobic fracture surface of membranes and (ii) regular bundles of fibrils with a repeat distance of about 6 nm, which were located free in solution. Similar regular bundles of fibrils were also revealed by staining the samples with uranyl acetate. According to the suggested model, the observed structures are hexagonally packed inverted lipid tubes, with DNA located in their central cores. The possible biological relevance of the capability of Ca(2+)-DNA to initiate polymorphic phase transitions of lecithin is discussed.

Animals↗
PubMed1992

The structural and functional organization of the baseplate distal part of T4 bacteriophage.

The structural organization of the baseplate distal part of bacteriophage T4 has been studied. The investigations resulted in revealing the functional role of gene products '11' and '12' in the course of baseplate reorganization and DNA injection. A new model of 'arrangement' of gp12 in the intact particle is suggested. A functional interrelationship between long fibers of the phage and the protein complex of baseplate distal part has been established.

Bacteriophage T4↗
PubMed1990

Results of a three-year trial of arterial hypertension prevention in a population of children aged 11-15 years by overweight control.

As part of a study of prevention of atherosclerosis precursors mass examinations were performed in two districts of Moscow. In the intervention district, the sample included 1123 pupils aged 11-12 years (544 boys, 579 girls), in the control district 1963 pupils (963 boys, 1000 girls) were examined. Repeat checks were performed one, 2 and 3 years after initial examination (blood pressure, body mass and height, skinfold thickness above m. triceps and below the scapula). The prevention programme addressed the whole population, with special emphasis on obese children (instruction about diet and correct feeding habits, body mass control) and their social microenvironment. Favourable results were registered, in terms of blood pressure and skinfold thickness reduction, during the first 2 years in boys; in girls diastolic BP dropped in the 1st year only, skinfold thickness was reduced in the first 2 years. Multiple regression analysis confirmed that the observed changes could be ascribed to the effect of the preventive programme.

Arteriosclerosis↗