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Biomedical subjects

A V Ivanov

Publications and source records attributed to A V Ivanov.

At least 19 recordsLinked to original sources
PubMed2006

Nontrapping arrest of Langmuir wave damping near the threshold amplitude.

Evolution of a Langmuir wave is studied numerically for finite amplitudes slightly above the threshold which separates damping from nondamping cases. Arrest of linear damping is found to be a second-order effect due to ballistic evolution of perturbations, resonant power transfer between field and particles, and organization of phase space into a positive slope for the average distribution function f(av) around the resonant wave phase speed nu(ph). Near the threshold trapping in the wave potential does not arrest damping or saturate the subsequent growth phase.

Journal Article↗
PubMed2006

Hepatitis C virus RNA-dependent RNA polymerase: study on the inhibition mechanism by pyrogallol derivatives.

Pyrogallol reversibly and noncompetitively inhibits the activity of the hepatitis C RNA-dependent RNA polymerase. Based on molecular modeling of the inhibitor binding in the active site of the enzyme, the inhibition was suggested to be realized via chelation of two magnesium cations involved in the catalysis at the stage of the phosphoryl residue transfer. The proposed model allowed us to purposefully synthesize new derivatives with higher inhibitory capacity.

Aminobutyrates↗
PubMed2006

Epizootic situation and fox rabies prophylaxis in the territory of Tatarstan.

Data on the epizootic situation of rabies in the Republic of Tatarstan from 1970-2003 were obtained from epizootological and immunological monitoring. The districts in Tatarstan were divided into four groups according to the intensity of indices and a map of epizootics was developed. A three- to five-year cyclic recurrence of rabies, with peaks in the spring-winter-autumn seasons of the year was established. Foxes are the basic source and spreader of rabid infection in the Republic amounting to 96.5 % of rabies cases among wild animals. The present study gives the results of epizootological analysis of the efficacy of oral immunization of foxes in the republic since 1996.

Animals↗
PubMed2005

Criticality in a Vlasov-Poisson system: a fermioniclike universality class.

A model Vlasov-Poisson system is simulated close to the point of marginal stability, thus assuming only the wave-particle resonant interactions are responsible for saturation, and shown to obey the power-law scaling of a second-order phase transition. The set of critical exponents analogous to those of the Ising universality class is calculated and shown to obey the Widom and Rushbrooke scaling and Josephson's hyperscaling relations at the formal dimensionality d=5 below the critical point at nonzero order parameter. However, the two-point correlation function does not correspond to the propagator of Euclidean quantum field theory, which is the Gaussian model for the Ising universality class. Instead, it corresponds to the propagator for the fermionic vector field and to the upper critical dimensionality d(c) = 2. This suggests criticality of collisionless Vlasov-Poisson systems corresponds to a universality class analogous to that of critical phenomena of a fermionic quantum field description.

Journal Article↗
PubMed2005

Virus-based reporter systems for monitoring transcriptional activity of hypoxia-inducible factor 1.

Being key regulator of oxygen homeostasis hypoxia-inducible factor 1 (HIF-1) plays significant roles in cancer progression as well as in cardiovascular diseases. The modulation of HIF-1alpha activity in vivo may represent a valuable therapeutic approach to these disorders. In order to monitor HIF-1 transcriptional activity, we have developed HIF-1alpha-responsive reporter constructs, in which lacZ gene expression is driven by minimal Hsp70 gene promoter or minimal immediate early promoter of cytomegalovirus (CMV) and a combination of hypoxia response elements from regulatory regions of PGK1, ENO1 and LDHA genes. For the efficient delivery to a wide variety of cell types we chose retroviral and lentiviral vectors as carriers of the reporter cassette. We demonstrate that the obtained reporter system i) has a high inducibility in response to treatments leading to HIF-1alpha activation, ii) shows upregulation in response to HIF-1 activation and downregulation following inhibition of HIF-1alpha expression by small interfering RNA, iii) follows the dynamics of endogenous HIF-1 target gene expression. The retrovirus- and lentivirus-based reporters can be used for high-throughput screening of HIF-1alpha modulators and for the study of crosstalk between HIF-1 and different related signal transduction pathways. Potential applications for the reporters are discussed.

Animals↗
PubMed2005

Structural-functional relationships between terminal deoxynucleotidyltransferase and 5'-triphosphates of nucleoside analogs.

Substrate properties of nucleoside 5'-triphosphate (NTP) analogs, namely, 5'-triphosphates of L- and D-arabinonucleosides (D-FIAUTP, D-FMAUTP, and L-FMAUTP), D- and L-enantiomers of ddCTP analogs (D-ddCTP, L-ddCTP, D-FOddCTP, L-OddCTP, and L-SddCTP), and acyclic guanosine analogs (acyclovir and penciclovir) towards terminal deoxynucleotidyltransferase (TdT, EC 2.7.7.31) were studied. TdT can polymerize 5'-triphosphates of arabinonucleoside analogs (D-FIAUTP and D-FMAUTP). In contrast, L-FMAUTP is not recognized by TdT as a substrate. Kinetic parameters of D- and L-enantiomers of ddCTP analogs and 5'-triphosphates of acyclic nucleosides were evaluated. It is shown that stereospecificity of dNTP analogs and structure of the furanose residue play crucial roles in the interaction with TdT:L-enantiomers are much less potent as substrates compared to their D-counterparts. 5'-Triphosphates of acyclovir (ACVTP) and penciclovir (PCVTP) are about two orders of magnitude less effective as substrates than nucleosides bearing furanose residues, with PCVTP being a better substrate than ACVTP. It can be assumed that the hydroxyl group of PCVTP mimics the 3'-hydroxyl group of the ribose residue and plays an important role in the interaction with TdT.

Catalysis↗
PubMed2004

New non-nucleoside inhibitors of hepatitis C virus RNA-dependent RNA polymerase.

Recombinant RNA-dependent RNA polymerase of hepatitis C virus was purified using a bacterial expression system (Escherichia coli). The system for enzyme activity detection was optimized. The maximum activity was achieved when the reaction was carried out at 30 degrees C in the presence of 3 mM Mg2+ or 0.75 mM Mn2+. Among alpha- and beta-pyrogallaldehydes, effective inhibitors were found. It was shown that they acted at the primer elongation stage, and their binding to the protein is reversible.

Enzyme Inhibitors↗
PubMed2004

[Prophylaxis and treatment of phlebothrombosis of deep veins of the lower extremities].

Prophylactic measures carried out in 32,400 patients permitted to decrease significantly the rate of thrombosis of lower extremities deep veins (to 2.2%). Use of standard and low-molecular heparin led to a similar rate of thrombus formation (2.4 and 2.0%), but the number of hemorrhagic complications in use of the later decreased (3.8 and 0.6%, respectively). Among 902 inpatients with thrombosis, lesion of distal segment of the lower extremities venous bed was revealed in 25.5%, femoral-popliteal - in 43.3%, ileofemoral - in 31.2% patients. Floppy emboli-dangerous thromboses were diagnosed in 19.1% cases. Cava-filter was implanted when floppy thrombus was in proximal part of iliac vein or in infrarenal segment of inferior cava vein only. When embologenous thrombus was lower to inguinal fold thrombectomy was performed with subsequent plication of superficial femoral vein. 3 years after cava-filter implantation chronic venous insufficiency in both less of II degree was seen in 45.2% patients, III degree - in 24.1%, thrombosis of inferior cava vein - in 1.3% patients. In plication of superficial femoral vein chronic venous insufficiency of II degree was revealed in 9.2% patients, III degree - in 1.7 cases. It is recommended to perform thrombectomy with plication of superficial femoral vein when floppy thrombus is located in ileo-femoral segment to prevent pulmonary artery thromboembolism.

Age Factors↗
PubMed2004

[Instability of plasmid DNA integrated into mammalian somatic cell genome].

The phenomenon of loosing exogenic DNA from the mammalian somatic cell genome is under investigation. It is found that foreign DNA incorporated into cell genome as a result of transfection by electrophoretion may be lost with the frequency from 1/100 up to 1/100 000 per cell division during cultivation. This effect is not dependent of the nature of cell line and vector DNA. It is actual for different cell lines: A23, human fibroblasts AG 11395, murine embryonic line F9, and for different plasmid vectors: p16, p.39, pATR4 and pcDNA3.1-Higr (WRN). Integration of pDNA into genome and the following loosing of this DNA is registered by selection markers G418 and hygromycin B resistance and gancyclovir sensibility. The presence of foreign DNA in the genome was controlled by PCR. It is found that true foreign DNA deletion from the genome takes place rather than gene expression changes. For closely linked plasmid genes deletion of both genes at once as well as loosing any one gene separately is shown. Thus, the phenomenon of selective deletion of exogenic DNA from genome has been demonstrated for different mammalian cells.

Animals↗
PubMed2003

Activation of molecular oxygen by infrared laser radiation in pigment-free aerobic systems.

With the goal of mimicking the mechanisms of the biological effects of low energy laser irradiation, we have shown that infrared low intensity laser radiation causes oxygenation of the chemical traps of singlet oxygen dissolved in organic media and water saturated by air at normal atmospheric pressure. The photooxygenation rate was directly proportional to the oxygen concentration and strongly inhibited by the singlet oxygen quenchers. The maximum of the photooxygenation action spectrum coincided with the maximum of the oxygen absorption band at 1270 nm. The data provide unambiguous evidence that photooxygenation is determined by the reactive singlet (1)Delta(g )state formed as a result of direct laser excitation of molecular oxygen. Hence, activation of oxygen caused by its direct photoexcitation may occur in natural systems.

Aerobiosis↗
PubMed2003

[Surgical treatment of a patient over 90 years of age with abdominal aortic aneurysm].

Presented herein is a case of successful surgical treatment of infrarenal aortic aneurysm in a 95-year-old patient with coexistent pathology. The patient underwent replacement of the abdominal aorta with implantation of the inferior mesenteric artery. After treatment of complications which occurred in the postoperative period, the patient was discharged home in a satisfactory condition. The success of surgical treatment of infrarenal aortic aneurysm in elderly patients depends on the anesthesiological control and postoperative care of patients.

Aged↗
PubMed2002

Thermal-field propagation in an exocontact zone of a magmatic body and its impact on radiogenic isotope concentrations in minerals.

In application of radioactive isotope systems (K-Ar, Rb-Sr etc.) during the last decades, experience was gained not only on their geochronometrical uses, but also on estimations of some important parameters of geological processes, especially temperatures and durations of superimposed thermal events. In this paper, the formation of an exocontact thermal field of a magmatic intrusion is considered as a spreading of a thermal source delta-function. Appropriate solutions of the heat-transfer equation are deduced and correlated with diffusion parameters of the radiogenic argon, coupling radioactive, thermal and kinetic parameters in an exocontant zone of a magmatic body. These solutions were used for quantitative reinterpretations of data taken from Hart's classical paper [The petrology and isotopic mineral age relations of a contact zone in the Front Range, Colorado. J. Geol., 1964, v. 72, pp. 493-525]. Theoretic and measured radiogenic argon and strontium concentrations within exocontact aureoles are found to be in good concordance.

Geological Phenomena↗
PubMed2001

Photodynamic effect of deuteroporphyrin IX and hematoporphyrin derivatives on single neuron.

The photodynamic effects of 6 new deuteroporphyrin IX derivatives with different amphiphilicity and lipophilicity, as well as effects of known hematoporphyrin derivatives Photofrin II and Photoheme on isolated crayfish mechanoreceptor neurons were studied. After 30 min photosensitization, neurons were irradiated with He-Ne laser (632.8 nm, 0.3 W/cm(2)), and changes in their firing frequency were recorded. Neuron firing was shown to be very sensitive to photodynamic effect of the studied deuteroporphyrin IX derivatives causing irreversible firing abolition at pikomolar concentrations while Photoheme and Photofrin II were effective in the nanomolar range. The most effective sensitizers were 4-(1-methyl-3-hydroxybutyl)- and 4-(1-methyl-2-acetyl-3-oxobutyl)-deuteroporphyrins. Extinction and amphiphilicity were shown to be the most important properties determining photodynamic efficiency of the studied photosensitizers.

Action Potentials↗
PubMed2001

High constitutive level of NF-kappaB is crucial for viability of adenocarcinoma cells.

Most of cells exhibit low nuclear level of NF-kappaB. However, in some cell lines and tissues aberrantly activated NF-kappaB is playing an important role in cell motility, growth control and survival. Here we describe the result of decrease of constitutive NF-kappaB level in different adenocarcinoma cell lines. Treatment of mouse adenocarcinoma cell line CSML-100 with both synthetic (TPCK or PDTC) or natural (I(kappaB)-alpha) NF-kappaB inhibitors caused apoptotic death. Low doses of TPCK were harmless for CSML100 cells but sensitized them to TNF-induced apoptosis. Death of CSML100 cells in the presence of high concentration TPCK was not accompanied with significant changes in c-myc activity but strongly correlated with rapid decrease in p53 level. Thus, mutual behavior p53 and NF-kappaB represented a unique feature of TPCK-induced apoptosis in CSML-100 adenocarcinoma cells.

Adenocarcinoma↗
PubMed2001

Laser radiation control in photodynamic therapy of tumors.

This article presents the ideology and basic principles of designing diagnostic and therapeutic medical systems for treating malignant tumors by means of photosensitizers. The designed system is based on optoelectronic devices, which realize selective laser tumor destruction during photodynamic therapy. A distinguishing feature of this system is that laser-beam formation is performed in real time. This enables one to follow changes in the tumor shape during the treatment. As a result of this study, a photodynamic technique for selective phototreatment was developed and tested. Moreover, we detemined light doses for such treatment.

Algorithms↗