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A V Markov

Publications and source records attributed to A V Markov.

At least 19 recordsLinked to original sources
PubMed2006

[Large and small rearrangements in the evolution of prokaryotic genomes].

Relative frequencies of large and small genome rearrangements (inversions and transpositions) in the evolution of prokaryotic genomes can be evaluated using the ratio between the index S (the ratio of the number of identical pairs of neighboring genes in two genomes to the total number of genes in the sample of interest) and 1 - 6 x L/n, where L is the mean difference in intergenic distances and n is the number of genes in the sample. The S value uniformly decreases with the fixation of genome rearrangements, while the decrease rate of I - 6 x L/n is determined by the rearrangement size. Specifically, large inversions and transpositions lead to a dramatic decrease in the index value, while small rearrangements result in an insignificant decrease. The ratio between these indices was computed for twenty pairs of closely related species belonging to different groups of bacteria and archaea. The pairs examined strongly differed in the relative frequency of large and small rearrangements. However, computer simulation showed that the total variation can be reproduced with the same input parameters of the model. This means that the differences observed can be stochastic and can be interpreted without assuming different mechanisms and factors of genome rearrangements for different groups of prokaryotes. Relative frequencies of large and small rearrangements displayed no noticeable correlations with taxonomic position, total rate of rearrangement fixation, habitation conditions, and the abundance of transposons and repetitive sequences. It is suggested that, in some cases, phage activity increases the frequency of large genome rearrangements.

Bacteria↗
PubMed2005

New effective method for analysis of the component composition of enzyme complexes from Trichoderma reesei.

A method for analysis of the component composition of multienzyme complexes secreted by the filamentous fungus Trichoderma reesei was developed. The method is based on chromatofocusing followed by further identification of protein fractions according to their substrate specificity and molecular characteristics of the proteins. The method allows identifying practically all known cellulases and hemicellulases of T. reesei: endoglucanase I (EG I), EG II, EG III, cellobiohydrolase I (CBH I), CBH II, xylanase I (XYL I), XYL II, beta-xylosidase, alpha-L-arabinofuranosidase, acetyl xylan esterase, mannanase, alpha-galactosidase, xyloglucanase, polygalacturonase, and exo-beta-1,3-glucosidase. The component composition of several laboratory and commercial T. reesei preparations was studied and the content of the individual enzymes in these preparations was quantified. The influence of fermentation conditions on the component composition of secreted enzyme complexes was revealed. The characteristic features of enzyme preparations obtained in "cellulase" and "xylanase" fermentation conditions are shown.

Binding Sites↗
PubMed2005

[Choice of the extent and the terms of sanifying procedures after vascular reconstructive surgeries in patients with stage IV chronic arterial lower limb insufficiency].

Results of vascular reconstructions with the following sanifying procedures performed in 82 patients with stage IV chronic arterial lower limb insufficiency are analyzed. Based on complex evaluation of microcirculation three types of tissues ischemic lesion are revealed: irreversible, severe and mild. Patients with irreversible lesion of the tissues of a distal part of the lower extremity require vascular reconstruction with simultaneous amputation at the upper third of the shank. In a severe reversible ischemic lesion of the tissues radical sanifying surgery with preservation of limb support function is better to perform not earlier than one month after vascular reconstruction. Mild ischemia of tissues permits performing minimal sanifying procedure with primary closure of the wound simultaneously with vascular surgery.

Chronic Disease↗
PubMed2005

[Gene orders in genomes of alpha-proteobacteria: similarity and evolution].

The gene orders in the genomes of nine alpha-proteobacteria were compared using quantitative indices S (the relative number of common pairs of adjacent genes) and L (the mean difference between intergenic distances). A sample of 200 homologous genes, occurring in all 11 strains, was studied. In all of the genomes examined, 20 conserved, "uninterrupted" regions, including in total 63 out of 200 genes, were found. The rate of evolutionary change in the gene order widely varied in different evolutionary lineages. The highest rate (40 to 60 genome rearrangements per 100 Myr) was characteristic of the intercellular parasite Wolbachia (Rickettsiales). Computer simulation has showed that the S to L ratio observed in the sample testified that the probability of large genome rearrangements was somewhat lower than that of small ones.

Bacteria↗
PubMed2003

[Localization of cohesin complexes of polytene chromosomes of Drosophila melanogaster located on interbands].

The distribution of cohesin complex in polytene chromosomes of Drosophila melanogaster was studied. Cohesin is a complicated protein complex which is regulated by the DRAD21 subunit. Using immunostaining for DRAD21p, the cohesins were shown to be preferentially located in the interband regions. This specificity was not characteristic for puffs, where uniform staining was observed. The presence of a few brightly fluorescent regions (five to ten per chromosome arm) enriched with cohesin complexes was shown. Some of these regions had permanent location, and the others, variable location. No antibody binding was detected in the chromocenter. Immunostaining of interphase nuclei of neuroblasts revealed large cohesin formations. On the polytene chromosomes of D. melanogaster, the Drad21 gene was mapped to the chromocentric region (81) of the L arm of chromosome 3.

Animals↗
PubMed2002

Viscometric method for assaying of total endodepolymerase activity of pectinases.

An improved method for assaying of the total endodepolymerase activity of pectinases has been developed. The method is based on the determination of the viscosity of a citrus pectin solution in the presence of the enzyme using an Ostwald viscometer. The depolymerizing activity of different pectinases can be detected including polygalacturonase, polymethylgalacturonase, pectin lyase, and pectate lyase. One unit of the endodepolymerase activity corresponds to the activity resulting in 50% decrease in the relative viscosity of 0.5% citrus pectin solution for 5 min at 40 degrees C and the appropriate pH. Depending on the pH-optima of the enzymes, two modifications of the method are described: 1) for acid pectinases at pH 5.0, and 2) for neutral (mildly alkaline) pectinases at pH 8.0. The modifications differed in the control and in the calculation of the activity. Six enzyme preparations were used to demonstrate the applicability of the method. The parameter used for the calculation of the enzymatic activity was directly proportional to the enzyme concentration (the dependence was linear in the range of at least 10-fold change in the enzyme concentration). The relative error of the method did not exceed 10%.

Aspergillus↗
PubMed2001

Study of protein adsorption on indigo particles confirms the existence of enzyme--indigo interaction sites in cellulase molecules.

Adsorption of several crude and purified cellulases (from Trichoderma reesei, Penicillium verruculosum and Chrysosporium lucknowense) on indigo particles and Avicel cellulose was studied. Much higher amounts of protein were bound to indigo than to cellulose under similar conditions. For different purified enzymes, the quantity of bound protein per mg of adsorbent (indigo or cellulose) varied in the range of 57-111 and 0-62 microg x mg(-1), respectively. However, in general, the enzyme adsorption on indigo was less specific than the adsorption on cellulose. Three endoglucanases, having the highest indigo-binding ability, demonstrated the best washing performance in the process of enzymatic denim treatment. These data confirmed our previous findings that certain cellulases, which have indigo-binding sites (clusters of closely located aromatic and other non-polar residues) on the surface of their molecules, may remove indigo from the denim fabric better than cellulases with lower content of hydrophobic residues exposed to solvent.

Adsorption↗
PubMed2000

Electrochemical assay of endo-depolymerase activity of cellulases.

A method for determination of endo-1,4-beta-D-glucanase activity of cellulase samples based on the indirect measurement of decrease in viscosity of a carboxymethylcellulose solution in an electrochemical cell in the presence of an electron carrier was developed. A rotating disk electrode is used as the working electrode. When two reactions (enzymatic and electrochemical) proceeded in the cell simultaneously, the limiting diffusion current at a constant applied potential increases as the viscosity of the solution decreases. Conditions where the initial rate of change of diffusion current (dI/dt) is proportional to the enzyme concentration were found. A good correlation between the new method and a previously known viscometric method for determination of endoglucanase activity was observed.

Carboxymethylcellulose Sodium↗
PubMedDate not supplied

[The return of the Red Queen, or the law of the growth in the mean duration of the existence of genera during evolution].

Phanerozoic marine genera apparently do not become less extinction-prone with age. Higher extinction probability in "young" cohorts of genera is better explained by initially different levels of extinction-tolerance of genera in the cohort. This fact agrees with one of the two basic statements of the "Red Queen" hypothesis (Van Valen, 1973). In the second statement (the idea that the increase in fitness lowers extinction probability) the term "fitness" should be changed to "adaptability". The increase of extinction-tolerance, that can be interpreted as the increase of adaptability to unpredictable changes of environment, is found in succession of "generations" of genera that replace one another through time. This increase reveals itself, firstly, in the growth of mean duration of genera, as well as in the decrease of extinction/origination rates, gradual accumulation of long-lived genera and origination of genera with higher duration. The increase of adaptability may be caused by selective extinction of stenotopic, ecologically specialized forms; Cope's law; evolution of ecosystems that involves development of more effective mechanisms of sustaining homeostasis which may stimulate the recovery of a genus after partial extinction.

Aging↗
PubMedDate not supplied

[A new approach to modeling the diversity dynamics of Phanerozoic marine biota].

Modeling of fossil diversity dynamics is usually done with the help of the models borrowed from the population dynamics theory. However there are principal differences between organisms and taxa, reproduction and divergence, mortality and extinction that make this approach doubtful. Another model is presented here, in which absolute origination rate does not depend on diversity, the ability of new genera to sustain unpredictable environmental changes increases three times abruptly at Cambrian/Ordovician, Permian/Triassic and Cretaceous/Tertiary boundaries. In this model the diversity increases due to accumulation of long-lived genera. The computer simulation showed that the model agrees with empirical data by 15 major criteria. The laws of community evolution apparently can explain the general pattern of punctuated equilibrium in the evolution of marine biota.

Fossils↗
PubMedDate not supplied

[Combined therapy of voiding irritative disorders after surgical treatment of benign prostatic hyperplasia with Andro-Gin].

The results of operative and rehabilitative treatment of benign prostatic hyperplasia (BPH) was analysed for 69 BPH patients with postoperative irritative disorders of voiding. The patients were divided into four groups by rehabilitative therapy: group 1 received antibacterial therapy; group 2--antibacterial therapy+alpha-adrenoblockers; group 3--antibacterial therapy+transrectal laser and magnetic physiotherapy; group 4--antibacterial therapy+alpha-adrenoblockers+transrectal laser and magnetic physiotherapy. The worst result was obtained in group 1, the best one in groups 3 and 4 (the response was compatible). Thus, the addition of physiotherapy to the complex of postoperative rehabilitation of patients operated for BPH is justified and provides treatment improvement.

Aged↗
PubMedDate not supplied

[Genetic characterization of pathogenic Borrelia, group A14S, isolated in Ukraine].

Borrelia Ir-5215, isolated from ticks Ixodes ricinus in Ukraine (the Crimean autonomous region), was identified by the method of the polymorphism of the fragment length of the restriction amplicon of rRNA spacer region 5S-23S. Its Msel-restriction profile was relatively similar to that of B. afzelii. The sequencing of spacer region rrf (5S)-rrl (23S) and 16S rRNA gene, as well as the analysis of the similarity of nucleotide sequences, obtained in the course of these study, revealed the differences between Borrelia sp, lr-5215 and six European species of Borrelia burgdorferi sensu lato and a high level of similarity (more than 95.1% for 5S-23S rRNA and 99.4% for 16S rRNA gene) to three known representatives of genome group A14S (Borrelia spp. A14S, I-77 and PC-Rq17). This suggests that isolated Borrelia lr-5215 is a new representative of pathogenic B. burgdorferi sensu lato genome group A14S, which is spread, together with Central Europe, also in southern Ukraine.

Animals↗
PubMedDate not supplied

[Sexual reproduction of insects is regulated by cytoplasmic bacteria].

The effects have been considered that the intracellular symbiotic alpha-proteobacteria Wolbachia pipientis induces in its hosts, such as insects and other arthropods: cytoplasmic incompatibility upon mating, feminization, parthenogenesis, and androcide. Specific features of the bacterium genome and possible mechanisms of its action on hosts are discussed.

Animals↗
PubMedDate not supplied

[Homologous protein domains in superkingdoms Archaea, Bacteria, and Eukaryota and the problem of the origin of eukaryotes].

The distribution of protein domains was analyzed in superkingdoms Archaea, Bacteria, and Eukaryota. About a half of eukaryotic domains have prokaryotic origin. Many domains related to information processing in the nucleocytoplasm were inherited from archaea. Sets of domains associated with metabolism and regulatory and signaling systems were inherited from bacteria. Many signaling and regulatory domains common for bacteria and eukaryotes were responsible for the cellular interaction of bacteria with other components of the microbial community but were involved in coordination of the activity of eukaryotic organelles and cells in multicellular organisms. Many eukaryotic domains of bacterial origin could not originate from ancestral mitochondria and plastids but rather were adopted from other bacteria. An archaeon with the induced incorporation of alien genetic material could be the ancestor of the eukaryotic nucleocytoplasm.

Animals↗
PubMedDate not supplied

[The hypothesis of immune testing of partners--coordinated adaptations and changes in mating preferences].

Reproductive isolation plays the key role in speciation. According to the prevailing ideas, the main speciation mechanism is gradual accumulation of genetic differences in isolated populations (allopatric phase of speciation) based on mutations, selection, and genetic drift. In this case, reproductive isolation emerges as an occasional byproduct of adaptation to different conditions (ecological speciation) or accumulation of random changes in the gene pool resulting from long-term isolation. Pure sympatric speciation assumes isolation as a direct product of selection (divergent or disruptive selection) that favors individuals selectively mating with their likes. A third possibility is substantiated below. We believe that isolation can be a regular and determined product rather than occasional byproduct of divergence. It can rely on the friend/foe discrimination mechanisms, some of which can be "immune-based" and compare the partner's and own properties (signaling molecules, pheromones, and other antigens in a broad sense). Antigens of the major histocompatibility complex (MHC) can play a substantial role in such testing of potential mates.

Adaptation, Psychological↗
PubMedDate not supplied

[Genetic heterogeneity of Borrelia afzelii in the natural focus of the Middle Urals].

As shown by sequencing the spacer rrf (5S)--rrl (23S) in 72 isolates of B. afzelii (one of the causative agents of Ixodes tick borne Borrelia infections) and the chromosomal gene coding protein P66 in 22 isolates, that in the natural focus located in the Middle Urals two different genetic subgroups (VS461 and NT28) of this genospecies simultaneously circulate. These subgroups are represented by 5 gene variants (rrf) 5S--(rrl) 23S and 5 allelic variants in gene p66. The latter, similarly to spacer gene variants, are not linked with a definite host and occur in different rrf--rrl variants of the infective agent. At the same time the definite species of vectors and carriers may be the host of several different B. afzelii variants, both in the spacer and in the gene coding protein P66, which maintains the genetic heterogeneity of B. afzelii population in the natural focus.

Alleles↗