[Biophysical basis of medical thermovision].

Characteristics of the thermal relief of the human body are reviewed. It is shown that the usage of thermovision in medical diagnostics requires the simultaneous and compatible consideration in the research process of three components: the contribution of the object itself, the influence of the medium through which the infrared radiation passes and the instrumental parameters of the infrared imager registering this radiation.

[A model for the development of stable competitive interrelations in the self-organization of biosystems].

A model is proposed that allows one to reveal specific features of the biosystem dynamics based on competitive processes of binary interaction. The model assumes a two-level hierarchy of system organization. Objects at the lower level of a system being investigated interact in a random way. The upper level determines the modulation of the development of a random process at the lower level. The application of the results of modeling to processes such as oxygen transport by proteins, adaptation of living organisms to varying environment, muscle contraction, and adaptation to stresses is discussed.

Gains and unexpected lessons from genome-scale promoter mapping.

Potential promoters in the genome of Escherichia coli were searched by pattern recognition software PlatProm and classified on the basis of positions relative to gene borders. Beside the expected promoters located in front of the coding sequences we found a considerable amount of intragenic promoter-like signals with a putative ability to drive either antisense or alternative transcription and revealed unusual genomic regions with extremely high density of predicted transcription start points (promoter 'islands'), some of which are located in coding sequences. PlatProm scores converted into probability of RNA polymerase binding demonstrated certain correlation with the enzyme retention registered by ChIP-on-chip technique; however, in 'dense' regions the value of correlation coefficient is lower than throughout the entire genome. Experimental verification confirmed the ability of RNA polymerase to interact and form multiple open complexes within promoter 'island' associated with appY, yet transcription efficiency was lower than might be expected. Analysis of expression data revealed the same tendency for other promoter 'islands', thus assuming functional relevance of non-productive RNA polymerase binding. Our data indicate that genomic DNA of E. coli is enriched by numerous unusual promoter-like sites with biological role yet to be understood.

[Clock synchronization in various modes of regulation].

In this study, which is dedicated to the participants of I. M. Gelfand's scientific seminar, the regulation mechanisms for the clock synchronization in an isolated biological community are analyzed. A comparison has been carried out of the time consumed and the work done taking into account the specific error value for three modes of regulation: centralized regulation, centralized hierarchy regulation, and self-organization based on paired interaction. The results of the study may have different biophysical applications.

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.

[Specificiety of DNA-protein interactions within transcription complexes of Escherichia coli]. / Osobennosti DNK-belkovykh vzaimodeistvii v transkriptsionnykh kompleksakh Escherichia coli.

Current requirement for description of each new promoter assumes identification of all DNA-protein and protein-protein contacts important for transcription complex formation. Experimental approaches allow estimating which one of seven alternative sigma-subunits is employed for RNA synthesis and verifying transcription dependence on known regulatory proteins. Promoter sequence by itself also contains this information. That is why, the type of promoter as well as potential regulatory proteins with high probability may be proposed, if the transcription start point has been determined. Transcription activity of the promoter is usually less predictive. It depends on the specific contacts formed by sigma-subunits with correspondent conservative elements and on many other non-specific factors that are hardly taken into account. Interaction with RNA polymerase alpha-subunits seems does not require any particular functional group of nucleotides thus exemplifying non-sequence-specific binding within binary polymerase-promoter complexes. The role of this interaction in the transcription complex formation is the main subject of this survey that summarizes our own experimental results and the data of other authors. Attempts have been made to compare nucleotide sequences of the promoters recognized by different sigma-factors within putative contact regions with alpha-subunits and to discuss regulatory propensity of free alpha-subunits.

[Three-dimensional reconstruction of synapse and dendritic spines in the hippocampus of rats and ground squirrels: new paradigms of the structure and function of a synapse]. / Trekhmernye rekonstruktsii sinapsov i dendritnykh shipikov v gippokampe krys i suslikov: novye strukturno-funktsional'nye paradigmy raboty sinapsa.

The article reviews the literature data and results obtained by the authors concerning synaptic plasticity and remodeling of synaptic organelles in the central nervous system. Modern techniques of laser scanning confocal microscopy and serial thin sectioning for in vivo and in vitro studies of dendritic spines including a correlation between morphological changes and synaptic transmission efficiency are discussed, particularly, in relation to long-term potentiation. Organization of different types of dendritic spines and involvement of filopodia in spine genesis are examined. Significance of serial ultrathin sections for unbiased quantitative stereological analysis and three-dimensional reconstructions is discussed. The contact of one dendritic spine with two presynaptic boutons (multiple synapses) on both CA1 mushroom dendritic spines is discussed. The analyzed findings suggest new ideas for organization and functioning of synapses.

[Levels in the structural organization of Escherichia coli promoter DNA]. / Urovni strukturnoi organizatsii promotornoi DNK.

A number of additional structural elements were identified by statistic analysis of nucleotide sequences in promoters recognized by Escherichia coli RNA polymerase. Together with canonical hexanucleotides, these elements characterize different levels in the structural organization of promoter DNA. Sequence motifs exhibiting the highest statistical significance, which dominate in the contact regions with RNA polymerase alpha and sigma subunits, are considered as targets for specific interaction with RNA polymerase. A typical feature of these elements is the presence of easily deformable dinucleotides (TG, CA and TA) or tracts containing only A/T base pairs. Thus, we noticed that the frequency of occurrence of TA in the promoter DNA is essentially higher than the average value for the genome. Besides the regions of specific interaction with RNA polymerase, these dinucleotides are often located in the number of other sites periodically distributed along the promoter DNA. This preferred disposition suggests that deformable elements participate in the adaptive conformational transitions of the promoter DNA favoring optimal configuration of the transcription complex. Probably, the most important feature of promoter DNA revealed by statistic analysis is the presence of A/T-tracts regularly distributed in the wide range from -160 up to +75 relative to the transcription start point. Both of these spatially distributed elements (TA dinucleotides and A/T-tracts) are linked with canonical regions and, therefore, may contribute to the conformational or dynamic features of the transcription machinery. Having high statistic significance, these elements might be considered as additional factors discriminating the promoter DNA on the background of other nucleotide sequences in the genome.

[Distribution and functional significance of A/T tracts in promotor sequences of Escherichia coli]. / A/T-treki v strukture promotorov Escherichia coli: kharakter raspredeleniia i funktsional'noe znachenie.

Distribution of the A/T tracts described in earlier publications in the region extending from nucleotide -250 to +150 relative to the transcription initiation site of gene transcribed regions adjacent to promoter was studied. Upstream of the -35 region a succession of A/T tracts was discovered distributed at a shorter distance one from another than in analogous elements of the transcribed region (1 and 1.5 helix turns, respectively). Such a positional dependence suggests different functional manifestation of A/T tracts at different transcription steps. Single initiation using the T7D promoter mutant derivatives devoid of A/T tracts in two critical positions, +41 and , yielded shortened products of the corresponding length. One might speculate that such elements adjacent to promoter region play a significant role in transcription complex functioning.

[Quantitative analysis of variability of electrocardiograms typical for polymorphic arrhythmias]. / Kolichestvennyi analiz variabel'nosti élektrokardiogramm, tipichnykh dlia polimorfnykh aritmii.

A new approach to the analysis of variability of electrocardiograms (ECGs) typical of polymorphic arrhythmias is developed. In these ECGs, separate QRS complexes can be often hardly identified. As a result, the mathematical methods that have been elaborated hitherto are not suitable for such arrhythmias. The approach presented here is based on the quantitative estimation of the variability of neighboring parts of the ECG. In this case, the necessity of the identification of separate QRS complexes ceases to be significant. Based on this approach, the analysis of normalized ECG variability is developed in the framework of which two indices that characterize the oscillation variability and its changes in time are related to a part of the ECG and/or the ECG as a whole. Variations of these indices allow both the polymorphism of a separate ECG to be estimated and different ECGs to be compared with each other. The method presented may be useful in studies of the mechanisms and in the diagnosis of polymorphic arrhythmias.

[How does environment modify the spatial structure of Dictyostelium discoideum population]. / Kak vneshniia sreda izmeniaet prostranstvennuiu strukturu populiatsii Dictyostelium discoideum.

The transformation of the spatial structure of a Dictyostelium discoideum population in response to environmental changes induced by this population was investigated. A comparative analysis of the spatial and temporal characteristics of the D. discoideum colony is given for two cases: (a) when the colony is cultivated on a bacterial lawn, i.e. under conditions close to natural, and (b) in the absence of the bacterial lawn when the colony grows on the nutrient substrate enriched with folic acid. It is shown that the environmental changes induced by cell metabolism modify the spatial structure of the D. discoideum population first, the rate of population propagation falls drastically, which correlates with a decrease in the substrate pH; second, the spatial redistribution of the D. discoideum cell density correlates with the redistribution of folic acid in the substrate. The mechanism of the environment impact on the D. discoideum colony transformation is discussed.

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.