Biomedical subjects
V Vlassov
Publications and source records attributed to V Vlassov.
The role of alcohol and social stress in Russia's mortality rate.
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Soviet pilot-physician program.
The program for training pilot-physicians was started in 1952. It was the first and the only one in the history of the USSR/Russia. Young military physicians from different military forces and graduates of the Saratov Military Medical Faculty were invited to participate in the program. Selected military physicians were sent for 2 yr of flight training. Six graduates from Omsk School became bomber pilots, while eight graduates from Chuguev School were appointed instructor pilots. Special positions and regulations for pilot-physicians were not created. Some pilot-physicians continued their aviation career, and some returned to medicine. For a short time a limited number of pilot-physician positions existed in the research institute in Moscow. Two graduates from this program were appointed to these positions. One of the pilot-physicians became a cosmonaut; and at least six obtained scientific degrees in medicine and made significant contributions to the development of aerospace medicine.
Structural flexibility of a DNA hairpin located in the long terminal repeat of the Drosophila 1731 retrotransposon.
The structure of the DNA binding site of the Nuclear single-stranded Binding Factor (NssBF), located in the long terminal repeat of the Drosophila 1731 retrotransposon, was investigated by melting temperature experiments, chemical probing and fluorescence measurements using a macrocyclic bis-acridine. The most probable structure of this element, named Bc, mainly involves two hairpins in equilibrium at pH 6.0 at low concentration. The hairpins differ in their apical loop size; 4 and 8 nt. The structural flexibility of Bc probably derives from the three consecutive CATA repeats complementary to the GTAT nucleotides of the palindrome. In contrast, the Bc complementary strand adopts a single hairpin. Since Bc is implicated in repression of transcription via binding of two specific factors, its structural flexibility could be associated with this process.
Pulmonary function in space.
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Sequence-specific cleavage of yeast tRNA(Phe) with oligonucleotides conjugated to a diimidazole construct.
Oligonucleotide derivatives conjugated to a chemical construction with two histamine residues imitating the catalytic center of ribonuclease A have been synthesized. In experiments with the conjugates complementary to the 3'-end and to the variable loop and the T loop of yeast tRNA(Phe), it was shown that the compounds can accomplish sequence-specific cleavage of the target RNA in physiologic conditions.
Triplex-forming oligonucleotides trigger conformation changes of a target hairpin sequence.
We used a DNA duplex formed between the 5' end of a 69mer (69T) and an 11mer (OL7) as a substrate for BamHI. The former oligonucleotide folds into a hairpin structure, the stem of which contains a stretch of pyrimidines in one strand and consequently a stretch of purines in the other strand. The oligomer 69T was used as a target for complementary oligodeoxypyrimidines made of 10 nt (OL1), 16 nt (OL5) or 26 nt (OL2) which can engage the same 10 pyrimidine-purine-pyrimidine triplets with the 69T hairpin stem. Although the binding site of OL7 did not overlap that of OL1, OL2 or OL5, the BamHI activity on 69T-OL7 complexes was drastically modified in the presence of these triplex-forming oligomers: OL1 abolished the cleavage by BamHI whereas OL5 and OL2 strongly increased it. Using footprinting assays and point-mutated oligonucleotides we demonstrated that these variations were due to different conformations of the 69T-OL7 complex induced by the binding of oligomers OL1, OL2 or OL5. Therefore, oligonucleotides can act as structural switchers, offering one additional mode for modulating gene expression.
Experimenting on the vulnerable.
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Oligodeoxynucleotides interact with recombinant CD4 at multiple sites.
Phosphodiester oligodeoxynucleotides bearing the 5'-alkylating moiety 4-(N-2-chloroethyl-N-methyl)aminobenzylamine specifically modify recombinant soluble CD4 (rsCD4) in solution. This reaction is saturable with respect to the alkylating oligonucleotide reagent. The existence of at least two binding sites, with different affinities, on the rsCD4 molecule, were demonstrated. The values of apparent Kd for the sites are approximately 0.1 and 1 microM. The existence of two sites was confirmed by electrophoretic analysis of the modified protein, in which two distinct gel bands were seen. The modification is inhibited by excess non-alkylating oligonucleotide, as well as by phosphorothioate oligonucleotides. Quantitative estimates of the competition constants (Kc), for the binding of these competitors of the binding of the alkylating oligonucleotide reagent with rsCD4, have been made. By use of this method, several anionic dyes as well as potential anti-HIV therapeutic agents were also demonstrated to interact with rsCD4. Phosphorothioate oligonucleotides also inhibit binding of rsCD4 with the monoclonal antibody L71.1.1 This monoclonal antibody recognizes the CDR3-like loop (D1 domain) of the rsCD4 molecule. Thus, oligonucleotide binding sites exist on two remote regions (i.e. both the CDR2- and CDR3-like loops) of the D1 domain of CD4.
Effect of magnesium ions and low pH on interaction of pyrimidine oligonucleotides with dsDNA: affinity modification study.
Pyrimidine oligonucleotides bearing 2-chloroethylamino groups bind to corresponding sequences in dsDNA in highly specific way and efficiently alkylate target guanosine residues in purine DNA strand. At acidic pH in the presence of magnesium ions, the oligonucleotides can form nonperfect complexes with partially complementary nucleotide sequences in which some nucleotide units of the oligonucleotides are looped out. Introduction of guanosine residues in pyrimidine oligonucleotides aimed to tolerating thymidines in the purine DNA strand causes a considerable local distortions of the complex structure.
Sequence specific alkylation of dsDNA by 2-chloroethylamine derivatives of purine oligonucleotides.
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Specificity of HIV inhibition by modified antisense oligonucleotides.
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Interaction of oligonucleotides with cellular receptors.
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Interaction of complementary oligonucleotides with the 3'-end of yeast tRNA(Phe).
Interaction of yeast tRNA(Phe) with oligodeoxyribonucleotides (ONs), complementary to the nucleotides 62-76 was investigated. Results of gel-mobility shift assay and RNase A probing evidence that the ONs containing the sequence complementary to the tRNA ACCA end can easily invade the hairpin structure under physiological conditions. The limiting step of association process is the tRNA unfolding.
Mechanism and specificity of RNA cleavage by chemical ribonucleases.
Cleaving of model RNA substrates by chemical ribonucleases constructed by conjugation of 1,4 diazabicyclo[2,2,2]octane with histamine and histidine was investigated. Similarly to RNase A, the chemical RNases produce fragments with 5' hydroxy-group and 3'-cyclophosphate. The cleavage occurs as the catalytic reaction: more than 150 phosphodiester bonds in RNA can be cleaved by one molecule of RNase mimic.
Activation of spleen lymphocytes by plasmid DNA.
It was shown that plasmid pUC19 DNA stimulates in vitro proliferation of CBA mouse splenocytes in a dose-dependent manner. Stimulation effect of the plasmid DNA is additive with COn A or LPS, synergistic with PMA and is inhibited by nonimmunogenic phosphodiester oligonucleotides and Fab fragments of antimouse Ig antibodies. These data and the data of affinity labelling of ODN-binding proteins indicate that immunoglobulin receptors are involved in DNA-induced lymphocyte activation.
Uptake of oligonucleotides by keratinocytes.
Oligonucleotides (ODNs) conjugated to rhodamin (Rh) and 4-[(N-2-chloroethyl-N-methyl)amino] benzylamine were used to investigate ODNs transport into keratinocytes. Affinity labeling of two proteins, 63 and 35 kDa, and the inhibition of the affinity labeling and ODNs uptake by the cells in the presence of nucleic acids, polyanions and trypsin suggest, that the proteins are involved in transport of nucleic acids in keratinocytes.