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Biomedical subjects

V B Strelets

Publications and source records attributed to V B Strelets.

At least 19 recordsLinked to original sources
PubMed2006

Relationship between EEG power and rhythm synchronization in health and cognitive pathology.

We report here studies of comparative measures of spectral density and cortical interactions in EEG rhythms in health and schizophrenia. In healthy subjects, all rhythms were symmetrical and synchronous. In "acute" schizophrenia, unlike the situation in health, there was asymmetry (predominantly right-sided) in the distribution of the spectral power of EEG rhythms. In chronic patients, asymmetry was less marked, though the power of most EEG rhythms was significantly lower than in the other two study groups. "Acute" patients showed a lack of interhemisphere interactions for all rhythms apart from the alpha rhythm, while the number of cortical interactions in chronic patients was rather lower than that in the "acute" patients, though there were significantly fewer than in healthy subjects. In addition, the gamma range showed only one interhemisphere association in the posterior areas. These neurophysiological characteristics may underlie a number of the impairments of mental activity in patients with schizophrenia. These data may also indicate that the linkage between power characteristics and synchronization of EEG rhythms is a necessary condition for normal perceptive and cognitive activity and the organization of behavior.

Acute Disease↗
PubMed2002

Cortical connectivity in high frequency beta-rhythm in schizophrenics with positive and negative symptoms.

During the last decade the role of high frequency EEG activity in the 'binding phenomenon' was discovered. It was supposed that this phenomenon provided the integration between different brain structures underlying higher nervous functions and possibly even consciousness [Proc. Natl. Acad. Sci. 90 (1993) 2078; Annu. Rev. Neurosci. 18 (1995) 555; J. Neurosci. V 16 (1996) 4240; Am. Physiol. Soc. (1998) 1567; Induced Rhythms in the Brain (1992) 425; NeuroReport 8 (1997) 531; Proc. Natl. Acad. Sci. USA 94 (1997) 12198]. Schizophrenia is considered as a disorder of the integration between different brain regions [Review of Psychiatry 18 (1999a) 29; Conceptual Advances in Russian Neuroscience: Complex Brain Functions (1999) 151; Brain Res. Rev. 31 (2000) 301], and in the present work we have studied cortical connectivity, focusing on those connections which are maintained by high frequency EEG-rhythm (20-40 Hz). The results showed a high degree of biopotential synchronisation between definite cortical areas during cognitive processes in normal subjects and have evidenced significant functional connectivity disturbances in schizophrenia in this EEG frequency domain.

Adult↗
PubMed1995

Ancient splice junction shadows with relation to blocks in protein structure.

Splice junction shadows (ancient exon-exon junctions) presumably reflect the existence of amino acid primary blocks which were used in the course of evolution for the construction of new proteins. The lengths of such blocks (i.e. regions between splice junctions), as the lengths of corresponding inserted or duplicated ancient exons, should be divisible by three in order to store the preexisting coding frame in the course of evolution. In this paper, we will test the hypothesis of intron-mediated recombination in a model of block molecular evolution (exon shuffling) by revealing corresponding blocks in existing database-contained coding sequences. For this purpose, we use a weight matrix prediction of ancient splice junction shadows in coding regions of the nucleotide sequences in current databases. The usage of splice junction shadows allows us to test the block evolution hypothesis in better detail in comparison with previous methods which were based only on currently existing recent exons. Our result of block length distribution at the nucleotide level shows a clear tendency to be divisible by three. At the protein level, several unexpected favorable block lengths, which are six, nine, 12 and 15 amino acids in length, were observed. Further refinements in our method for revealing splice junction shadows (structural block boundaries) might reveal peptides which probably maintain stable folds in different structures. The latter can in turn be used for protein structure prediction.

Biological Evolution↗
PubMed1995

Compression of protein sequence databases.

We have created an algorithm for compressing a PIR database to assist individual researchers and software developers who utilize sequence database information but may not have huge storage space. The resulting compact databank contains compressed PIR information and an interface written in C which allows fast direct access to the stored information without extensive decompression of corresponding files. The databank files as well as the interface C-file can be used on both PC-compatibles and UNIX-based computers without any modifications. The interface supports all standard PIR Request Network queries (i.e. gets databank SEQ number by entry; for a defined databank SEQ number, gets specified information like: name, organism(s), keyword(s), sequence, sequence features with coordinates, etc.). In contrast with PIR Request Network, our package allows us to call PIR-contained information directly from the C programs, even on a personal computer not on a network. Our PIR-derived databank, SAGITTARIUS PIR, was implemented in the form of separate file sets. Each file set contains database information of independent types (i.e. sequences, entry indexes, organisms, etc.). On a particular computer, the available configuration of the PIR information (and storage space) can be easily changed as needed by the user without affecting retrievals of other types of stored information. Due to an original alignment-based algorithm, in the compression of protein sequences themselves, our package out-performs the well-known ZIP file compressor. For PC-compatibles, a dialogue shell is available which supports all standard PIR Request Network queries plus homology searches, alignments, etc.

Algorithms↗
PubMed1995

[The topographic EEG mapping of patients with an organic brain lesion].

Brain mapping was carried out in 50 patients with organic brain lesions (tumors, disturbances of vascular circulation, multiple sclerosis, consequences of brain trauma ets.) The parallelism between the severity of the organic brain lesion and the degree of bioelectrical activity disturbances has been discovered. In patients with brain tumors, consequences of the stroke, severe trauma and multiple sclerosis the focuses of pathological activity corresponded to location of the brain lesion.

Adolescent↗
PubMed1994

Analysis of peptides from known proteins: clusterization in sequence space.

A combinatorial sequence space (CSS) model was introduced to represent sequences as a set of overlapping k-tuples of some fixed length which correspond to points in the CSS. The aim was to analyze clusterization of protein sequences in the CSS and to test various hypotheses about the possible evolutionary basis of this clusterization. The authors developed an easy-to-use technique which can reveal and analyze such a clusterization in a multidimensional CSS. Application of the technique led to an unexpectedly high clusterization of points in the CSS corresponding to k-tuples from known proteins. The clusterization could not be inferred from nonuniform amino acid frequencies or be explained by the influence of homologous data. None of the tested possible evolutionary and structural factors could explain the clusterization observed either. It looked as if certain protein sequence variations occurred and were fixed in the early course of evolution. Subsequent evolution (predominantly neutral) allowed only a limited number of changes and permitted new variants which led to preservation of certain k-tuples during the course of evolution. This was consistent with the theory of exon shuffling and protein block structure evolution. Possible applications of sequence space features found were also discussed.

Biological Evolution↗
PubMed1994

Data bank homology search algorithm with linear computation complexity.

A new algorithm for data bank homology search is proposed. The principal advantages of the new algorithm are: (i) linear computation complexity; (ii) low memory requirements; and (iii) high sensitivity to the presence of local region homology. The algorithm first calculates indicative matrices of k-tuple 'realization' in the query sequence and then searches for an appropriate number of matching k-tuples within a narrow range in database sequences. It does not require k-tuple coordinates tabulation and in-memory placement for database sequences. The algorithm is implemented in a program for execution on PC-compatible computers and tested on PIR and GenBank databases with good results. A few modifications designed to improve the selectivity are also discussed. As an application example, the search for homology of the mouse homeotic protein HOX 3.1 is given.

Algorithms↗
PubMed1994

[A comparison of the results of topographic EEG mapping with the data from a neurological examination and computed tomography of the brain].

The data of topographic EEG brain mapping were compared to neurological evidence and CT data in 6 patients with organic lesions (sequelae of vertebrobasilar ischemic stroke, brain atrophy, brain tumor). Cortical activity typical for these nosological entities appeared on the EEG maps. In 5 out of 6 patients foci of alpha- and delta-activity indicated the location of the lesion. The authors suggest that EEG brain mapping of the large number of patients with neural and mental diseases will provide insight into pathogenetic mechanisms of these diseases. The authors also think it necessary for patients undergoing EEG brain mapping to be examined neurologically.

Adult↗
PubMed1984

[Effect of vasopressin on long-term memory (psychophysiological and clinical aspects)].

In chronic alcoholic patients with reduced ability for memorizing, lysin-vasopressin (LVP) exerts an obvious positive effect upon the involuntary long-term memory. The effect is more obvious in tests demanding a semantic processing of information rather than the automatic memorizing. Under the LVP effect, an enhancement of the alpha-rhythm synchronization occurs in the EEG. The maximal "inhibitory" effect of the LVP occurs against background of desynchronization with an initial increased level of unspecific ascending influences. The LVP rises the upper limit of the response in the form of the EEG rhythms rearrangement, i. e. it increases the lability of cerebral structures. In conditioning therapy of chronic alcoholism the LVP increases the negative reflex to ethanol formed on the basis of apomorphine. The data obtained reveal an essential acceleration and increased durability of conditioning to ethanol as the result of the LVP use.

Adult↗
PubMed1982

[Evoked negative cortical wave as a reflection of selective attention].

The study is devoted to the negative wave which sets in the cerebral cortex in response to a significant stimulus. Such negativity may be detected by way of subtracting from the amplitude of the EP to the significant stimulus of the amplitude of the EP to a less significant one. It was found that the negativity consists of two components: the first one, with a peak latency of 140 ms, is most pronounced in the analyser projection zone; it may be recorded during both voluntary and involuntary attention and is apparently due to selective activation of the cortex by the ascending thalamocortical system. The second peak, with a latency of 200 ms, is diffusely spread over the cortex and is recorded only during voluntary attention; it may be caused by activation of the cortex by the mesencephalic reticular formation.

Attention↗
PubMed1978

[Brain potentials evoked by stimuli of different intensities in normal subjects and in hysterical psychopathy].

The author studied evoked potentials of 5 different intensitities to electroskin stimula in normals and psychopathic personalities of a hysterical type. It was established that different in their genesis the components of evoked potentials change differently in a change of the stimula intensity. The highest intensity of the stimula is reflected in the early sensory component of evoked potentials, the amplitude of which in normals in an increase of intensity successionaly rises. In hysterical personalities the amplitude of early sensorial components of evoked potentials in an increase of stimula intensity increases only to a certain limit, after which it begins to drop. This phenomenon called "reducing" indicates to a weakness of the sensory systems and relative prevalence of nonspecific brain systems in hysterical psycopathy.

Antisocial Personality Disorder↗