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Biomedical subjects

V A Potapov

Publications and source records attributed to V A Potapov.

At least 37 records · Page 2Linked to original sources
PubMed1983

[Ultrastructural changes in tissues in postburn cicatricial esophageal stenosis during bougienage and prolonged intubation].

The ultrastructure of tissues in postburn esophageal strictures was studied in 24 patients varying in ages from 23 to 70 years with the postburn period ranging from 1 1/2 months to 36 years. Biopsy samples for the study were collected during fibroesophagoscopies before treatment, after bougienage and longterm intubation with the Tkachenko tube. Before treatment, pathologically altered granulation tissue forming the surface of ulcerated esophageal strictures was found to contain such mature forms of fibroblasts as collagenoblasts with moderate collagen-producing activity, myofibroblasts, and fibrocytes. Mechanical effects of bougienage and intubation of the esophagus stimulated formation of young granulation tissue in the area of ulcerated strictures, intubation of the strictures stimulating both biosynthesis and catabolism of collagen. Mature forms of fibroblasts of young granulation tissue formed in bougienage were represented by collagenoblasts with intensive collagen-producing activity, myofibroblasts, fibrocytes, and after long-term esophageal intubation also by fibroclasts.

Adult↗
PubMed1982

[Morphology of postburn cicatricial stenosis of the esophagus: examination of specimens obtained at spot biopsy].

The authors examined 352 biopsy specimens taken at fibroesophagoscopy in 71 patients with postburn cicatricial esophagostenoses varying in ages from 18 to 70 years. The time after the organ burn ranged from 1 1/2 months to 52 years. Formation of a young granulation tissue was found in treatment of ulcerated structures by bougieurage which is believed to be associated with mechanical effects of the manipulations. In epithelization of cicatricial structures of the esophagus, correlating interactions of the epithelium and connective tissues similar to those observed in healing of skin wounds were recorded. Epithelization of the structures was found to require the elimination of traumatizing effects by food masses. As a rule, languid chronic esophagitis and signs of parakeratosis and hyperkeratosis were found in the area of suprastenotic esophagectasias.

Adolescent↗
PubMed1976

[Modification of the method of extracting DNA-polymerase from E. coli].

Described earlier method of isolation of E. coli DNA-polymerase is modified. In order to decrease the possible effect of proteases on DNA-polymerase, the time of autolysis was shortened. An additional stage of precipitation by ammonium sulfate of 65-80% of saturation was introduced. Chromatography on DEAE-Sephadex A-25 revealed 4 fractions exhibiting DNA-polymerase activity. It is established that combination of certain DNA-polymerase fractions, belonging to different peaks, significantly intensifies the enzyme activity. It may be due to the formation of enzymic complexes.

Chromatography, Ion Exchange↗
PubMedDate not supplied

[Features of the structure and evolution of complex tandemly organized Bsp-repeats in the fox genome. II. Tissue-specific and recombinant BamHI-dimer sites].

The complex structure of the clustered Bsp-repeats in fox genome seems to have evolved throughout a long period of time as a result of multiplication, recombination and divergence events. The sequence of the subrepeat (SR) approximately 245 b.p long is the basic substructure for the hierarchically arranged Bam HI-repeat 1468 b.p. long. The monomer consists of 3 SRs with a 43-59% homology. A dimer is composed of 2 monomers with a 93% homology. Amplification of the Bsp-repeats during evolution seems to have occurred at least twice: first--on the SR ancestral form level, second--on the monomer level. Despite profound divergence, there are still conservative regions in SRs with sequences homologous to known functional sites in eukaryotes. However qualitative and quantitative composition of most functional motifs is stringently individual in every SR. The performed analysis revealed that throughout evolution SRs acquired significant amount of motifs homologous to promoter and enhancer regions in tissue-specific genes and virus regulatory regions. Functional motifs in separate SRs are being differently grouped. Most inducible motifs are located in the III and II subrepeats, putative promoters--in the II one; elements participating both in transcriptional and replicational processes--mainly in the I subrepeat. A few ensembles of functional motifs remotely resemble extended regulatory regions of some tissue-specific genes. The monomers are potentially capable of ensuring diverse aspects of transcriptional regulation. As a whole, motifs of the 3 SRs are potentially capable of regulating the RNA synthesis periodicity with respect to the cellular cycle, activation and repression of genetical material in response to signals from the environment (AP-1, AP-2, AP-4, T-antigen, etc) and temporal ("octamers") etc. Apart from the BamHI-dimer, a few homologues fragments were isolated from fox genome and sequenced. Some of them were rearranged with respect to the BamHI-dimer. Inversion locally alters the composition of motifs and the sequence acquires new functional potential. Thus, the analysis of the emergence and development of Bsp-repeat structural variations allows us to consider repetitive DNA sequences as an ideal material in constructing multiprofile regulatory sequences.

Animals↗
PubMedDate not supplied

[Features of the structure and evolution of complex, tandemly organized Bsp-repeats in the fox genome. I. Structure and internal organization of the BamHI-dimer].

A 1468 b.p. DNA BamHI-fragment homologous to the Bsp-repeat was isolated from the fox genome and sequenced. This fragment is an hierarchically arranged dimer. Its 734 b.p.-monomers consist of three subrepeats (SR), each 245 b.p. long, abundant with overlapping imperfect tandem repeats which in turn are rich in short direct related repeats (each 4-7 b.p. in size). The latters are mainly composed of AG, TG dinucleotides and their complements CT, CA. All subrepeats in the BamHI-dimer are flanked by motifs homologous to Jeffreys' sites. At certain points the sites are doubled. The above data allow to assume that the Bsp-repeat complex structure is likely to have developed throughout long multi-step evolution of relatively simple DNA sequences which had emerged de novo. Single substitutions, small inserts and deletions, multiple duplication and recombination events seem to have most contributed to the evolution of the Bsp-repeats. Single substitutions in SRs with respect to the consensus are not equally distributed along their length. A wave-like pattern of this distribution is the evidence for non-random character of mutations accumulation. A correspondence was noted between conservative regions in SR and the presence therein of functional motifs homologous to the binding sites of already known regulatory proteins.

Animals↗
PubMedDate not supplied

[Reverse transcription of heterologous RNA by RNA-dependent DNA polymerase from Escherichia coli].

The appropriate conditions for the reverse transcription of rabbit globin mRNA by E. coli RNA-dependent DNA polymerase has been studied. By reducing the ionic strength, increasing the incubation temperature from 37 to 43 degrees and predenaturing the template it was possible to increase the cDNA size. The molar ratio of Mn2+ and dNTP optimal for cDNA synthesis is approximately 1.5-1.7:1. The increase of dNTP concentration from 0.05 to 0.4 mM each, under conditions of Mn2+ deficiency, results in the decrease of the cDNA size to 4S, obviously, the inhibitory effect of dNTP is not complexed with Mn2+. The synthesis of cDNA is inhibited also by the excess of Mn2+. Hybridization of cDNA with globin mRNA protects the former from S1-nuclease. Optimization of the conditions for reverse transcription of heterologous RNa by E. coli RNA-dependent DNA polymerase led to the increase of the cDNA length up to approximately 550 nucleotides which is about 70% of the RNA template length.

Animals↗
PubMedDate not supplied

[Separation of the enzyme catalyzing polymerization of deoxyribonucleoside diphosphates from preparations of E. coli DNA-polymerase I].

The enzyme which catalyses template independent synthesis of polydeoxynucleotides from deoxynucleoside diphosphates was separated from E. coli DNA polymerase I by DEAE-cellulose chromatography followed by ultrafiltration through the M-50 Amicon filter. The ultrafiltration data indicate that the molecular weight of the enzyme is not higher than 50,000. The enzyme is not able to use deoxynucleoside triphosphates, ribonucleoside di- or triphosphates as substrates for the polymerization. The reaction of template independent polymerization proceeds with a lag period varying from 2 to 20 hours (for different preparations of enzyme) and is activated by Mg2+ (the optimal concentration 1-2 . 10(-3) M). The pH optimum of the reaction is at 8.5. The optimal concentration of deoxyribonucleoside diphosphates is 10(-3) M, and its increase strongly inhibits polymerization. The enzyme was supposed to be called deoxynucleoside diphosphate: olygonucleotide deoxynucleotidyltransferase (catalyzing polymerization without template). The presence of the enzyme in the preparations of E. coli DNA-polymerase I can explain the ability of the latter to catalyze the untemplated synthesis of poly dG : poly dC.

DNA Polymerase I↗