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Biomedical subjects

S V Kuznetsov

Publications and source records attributed to S V Kuznetsov.

At least 19 recordsLinked to original sources
PubMed2002

[Clinical significance of erythrocyte ferritin in refractory anemia and chronic myeloid leukemia].

AIM: To find out if the RBC ferritin elevation can serve as an additional criterion of inefficient erythropoiesis during progression of chronic myeloid leukemia (CML) and in various types of refractory anemia. MATERIAL AND METHODS: The study group consisted of 56 MDS patients and 73 patients at various stages of CML. 20 healthy donors and 105 patients with verified inefficient erythropoiesis (20--with B12 deficiency before and after the treatment, 85--with beta-thalassemia) were the controls. A ferritin level was measured by radioimmunoassay in RBC hemolysates. RESULTS: The RBC ferritin level in all types of refractory anemia was elevated throughout the disease course, increasing with the development of transfusion dependency. The CML progression was also accompanied by RBC ferritin level elevation associated with abnormal erythroid cell accumulation and elevation of intracellular PAS-positive substance (p < 0.05). CONCLUSION: RBC ferritin level elevation can be considered as an additional biochemical criterion of inefficient erythropoiesis that may be useful in differentiation of anemias, adequate therapy selection and follow-up of erythropoiesis.

Adult↗
PubMed2001

Characterization of thermal stability of the Escherichia coli Fapy-DNA glycosylase.

Thermal stability of Escherichia coli Fpg protein was studied using far-UV circular dichroism and intrinsic fluorescence. Experimental data indicate that Fpg irreversibly aggregates under heating above 35 degrees C. Heat aggregation is preceded by tertiary conformational changes of Fpg. However, the secondary structure of the fraction that does not aggregate remains unchanged up to approximately 60 degrees C. The kinetics of heat aggregation occurs with an activation enthalpy of approximately 21 kcal/mol. The fraction of monomers forming aggregates decreases with increasing urea concentration, with essentially no aggregation observed above approximately 3 M urea, suggesting that heat aggregation results from hydrophobic association of partially unfolded proteins. With increasing urea concentration, Fpg unfolds in a two-state reversible transition, with a stability of approximately 3.6 kcal/mol at 25 degrees C. An excellent correlation is observed between the unfolded fraction and loss of activity of Fpg. A simple kinetic scheme that describes both the rates and the extent of aggregation at each temperature is presented.

Circular Dichroism↗
PubMed2001

Configurational diffusion down a folding funnel describes the dynamics of DNA hairpins.

Elucidating the mechanism of folding of polynucleotides depends on accurate estimates of free energy surfaces and a quantitative description of the kinetics of structure formation. Here, the kinetics of hairpin formation in single-stranded DNA are measured after a laser temperature jump. The kinetics are modeled as configurational diffusion on a free energy surface obtained from a statistical mechanical description of equilibrium melting profiles. The effective diffusion coefficient is found to be strongly temperature-dependent in the nucleation step as a result of formation of misfolded loops that do not lead to subsequent zipping. This simple system exhibits many of the features predicted from theoretical studies of protein folding, including a funnel-like energy surface with many folding pathways, trapping in misfolded conformations, and non-Arrhenius folding rates.

DNA↗
PubMed2001

A semiflexible polymer model applied to loop formation in DNA hairpins.

A statistical mechanical "zipper" model is applied to describe the equilibrium melting of short DNA hairpins with poly(dT) loops ranging from 4 to 12 bases in the loop. The free energy of loop formation is expressed in terms of the persistence length of the chain. This method provides a new measurement of the persistence length of single-stranded DNA, which is found to be approximately 1.4 nm for poly(dT) strands in 100 mM NaCl. The free energy of the hairpin relative to the random coil state is found to scale with the loop size with an apparent exponent of > or = 7, much larger than the exponent of approximately 1.5-1.8 expected from considerations of loop entropy alone. This result indicates a strong dependence of the excess stability of the hairpins, from stacking interactions of the bases within the loop, on the size of the loop. We interpret this excess stability as arising from favorable hydrophobic interactions among the bases in tight loops and which diminish as the loops get larger. Free energy profiles along a generalized reaction coordinate are calculated from the equilibrium zipper model. The transition state for hairpin formation is identified as an ensemble of looped conformations with one basepair closing the loop, and with a lower enthalpy than the random coil state. The equilibrium model predicts apparent activation energy of approximately -11 kcal/mol for the hairpin closing step, in remarkable agreement with the value obtained from kinetics measurements.

Base Composition↗
PubMed2001

[Experience in the use and comparative assessment of the effectiveness of crystalloid and blood cardioplegia].

Due to an increasing attention to questions of adequate protection of the myocardium and widely spread use of the method of blood cardioplegia the authors have made a comparative analysis of effectiveness of using 2 methods of cardioplegia--pharmacocrystalloid and cool blood antegrade cardioplegia: 34 patients were operated upon under conditions of extracorporeal blood circulation for aortic and mitral valve replacement. A comparison was made of 17 patients with intermittent antegrade cool crystalloid cardioplegia (group 1) and 17 patients with intermittent antegrade cold blood cardioplegia (group II). The results have shown that intermittent antegrade cool blood cardioplegia is a safe and effective method for myocardial protection during cardiopulmonary bypass.

Adolescent↗
PubMed1999

Ultraviolet-B-induced damage to Escherichia coli Fpg protein.

We investigated the effect of UVB light (290 < or = lambda < or = 320 nm) on the structure and enzymatic activities of Escherichia coli Fpg protein (2,6-diamino-4-hydroxy-5N-methylformamidopyrimidine-DNA glycosylase), a DNA repair enzyme containing a zinc finger motif and five chromophoric Trp residues. Irradiation with UVB light of air-saturated pH 7.4 buffered aqueous solutions of Fpg induces the formation of polymers as shown by sodium dodecyl sulfate polyacrylamide gel electrophoretic analysis. In argon-saturated solutions, polymer formation produces a precipitate. The polymerization quantum yield is 0.07 +/- 0.01 and 0.15 +/- 0.02 in air- and argon-saturated solutions, respectively. In the polymerized Fpg protein, second-derivative absorption spectroscopy indicates that three and one Trp residues are destroyed in air- and argon-saturated solutions, respectively. Polymers are devoid of all three activities of the Fpg protein, whereas the unpolymerized protein retains full activities. Matrix-assisted laser desorption/ionization experiments demonstrate that polymer formation is accompanied by the formation of short polypeptides containing the first 32 or 33 residues of the N-terminal domain. Theses polypeptides are most probably formed by the photolytic cleavage of Fpg protein induced by light absorption by the adjacent Trp-34 residue.

Amino Acid Sequence↗
PubMed1999

[Interferon alfa-2b treatment of adult patients during early chronic phase of Ph1-positive chronic myeloid leukemia (initial report on a cooperative study, protocol CML-MIG-97)].

AIM: Evaluation of clinical effectiveness of two regimens of induction therapy of an early chronic stage of Ph'-positive chronic myeloid leukemia including interferon-alpha 2b (intron-A, "Schering Plough") in a cooperative randomised trial on the protocol CML MIG-97. MATERIALS AND METHODS: 42 patients with chronic myeloid leukemia were treated either with intron-A in standard doses (5 IU/m2/day) alone or in combination with monthly 10-day courses of low-dose cytosine-arabinoside (10 mg/m2/twice a day). The effect was assessed by the international criteria of a complete and partial hematologic remission and the cytogenetic response. RESULTS: Intron-A therapy in standard doses produced a pronounced cytogenetic response in 28.6% of the patients. In low-dose interferon-alpha-2b (reaferon and intron-A, 1-3 IU/m2/day) in combination with various regimens of chemotherapy only minimal cytogenetic response was achieved. CONCLUSION: A pronounced cytogenetic response in early chronic stage of CML to standard doses of intron A holds promise in prolongation of CML patients survival and design of new effective therapy programs.

Adjuvants, Immunologic↗
PubMed1998

Effect of single mutations on the structural dynamics of a DNA repair enzyme, the Escherichia coli formamidopyrimidine-DNA glycosylase--a fluorescence study using tryptophan residues as reporter groups.

The effects on the structure dynamics of the Escherichia coli wild-type formamidopyrimidine-DNA glycosylase (Fpg) protein of the single mutations Lys57-->Gly (FpgK57G), Pro2-->Gly (FpgP2G) and Pro2-->Glu (FpgP2E) were studied by fluorescence techniques, namely: lifetime measurements and acrylamide quenching of the fluorescence of Trp residues. The fluorescence decays of Fpg and its mutant forms were analysed by the maximum-entropy method and lifetime distributions in the range 200 ps to 9 ns were obtained. The lifetime distribution profiles of FpgK57G, FpgP2G and FpgP2E are different from that of wild-type Fpg. Both dynamic and static quenching by acrylamide were observed for all the proteins. At 20 degrees C, the bimolecular collisional quenching rate constant of the FpgP2E fluorescence by acrylamide was only 0.8 M(-1) s(-1) as compared to about 1.4 M(-1) s(-1) for the three other proteins. At 6 degrees C, all the spectroscopic properties of these four proteins are about the same. The analysis of experimental data demonstrates that all three mutations induce a structural reorganization of the Fpg protein. However, only the P2E mutation lead to a reduced accessibility of some Trp residues to acrylamide quenching. It is concluded that the single P2E replacement induces a conformational change leading to a more rigid globular structure as opposed to the wild type and K57G and P2G mutations. The influence of the single mutations on the enzyme activities of the Fpg protein is discussed.

Acrylamide↗
PubMed1998

[An evaluation of the prognostic significance of antigen CD95(Fas/APO-1) expression on the cells of patients with a myelodysplastic syndrome, acute myeloid leukemia and chronic myeloleukemia].

AIM: The expression of CD95(Fas/APO-1) antigen was studied on bone marrow cells of 19 MDS patients, peripheral blood blast cells of 15 acute myeloid leukemia (AML) patients, blast cells and granulocytes of 68 patients with chronic myeloid leukemia (CML)--24 in chronic, 9 in accelerated phase and 35 in blastic crisis (BC)--by indirect surface immunofluorescence assay using flow cytometry (FACScan, Becton Dickinson, USA). RESULTS: CD95(Fas/APO-1) antigen was revealed on bone marrow cells of 8 out of 19 (36.8%) MDS patients; the percentage of antigen-positive cells was 38.1 +/- 19.2%; on 45.5 +/- 22.8% of cells in 6(45%) of 15 AML patients. Fas/APO-1 antigen was totally absent in CML chronic stage; its expression was found in 34% (12 of 35) of our patients with CML BC on peripheral blood blasts and in 56% (5 of 9) on peripheral blast cells of CML patients in acceleration phase. CONCLUSION: The data on overall survival of CD95-positive MDS patients suggest that the presence of Fas antigen is a favorable prognostic sign for patients with MDS. The patients from CD95-negative group represent a risk group both for survival and AML transformation. In CML BC group the survival does not depend upon Fas-antigen expression.

Acute Disease↗
PubMed1997

[The role of the Cell Saver autologous transfusion method in preventing the pulmonary distress syndrome during open-heart operations on children].

Complex estimation of the state of the lungs at the postperfusion and early postoperative periods based on roentgenological, clinical data, investigations of the parameters of oxygenation and mechanics of respiration was carried out in 32 children with septal defects of the heart, operated upon under conditions of artificial blood circulation with different kinds of the transfusion maintenance including the apparatus "Cell Saver 5" (CS) for the reinfusion of autoerythrocytes. The dynamics of endotoxicosis, hematological parameters during and after operation and requirements in transfusion media were studied. Differences in these indicators were established between the patients operated upon with the use of donor hemocomponents and those who were operated upon with CS. It allowed a conclusion about the role of the method of intraoperative reinfusion of erythrocytes in substantially less frequency and severity of the postperfusional pulmonary complications in this category of patients.

Blood Transfusion, Autologous↗
PubMed1994

[The specialization and advancement of military physicians in radiodiagnosis].

The article deals with the questions of post-graduate training of army diagnostic radiologists. The authors make a detailed description of all stages of basic and enhanced training of radiologists and ultrasound diagnostic specialists. The article emphasizes the necessity to endorse the candidates for further specialized training depending on duration of their professional time-in-service period. Each stage of enhancing training is also described from the point of view of new professional skills acquired in the process of training.

Diagnostic Imaging↗
PubMed1993

[The causes of death in animals with hydrogen peroxide poisoning].

Hydrogen peroxide (HP) was administered to experimental rats at the level of LD100. The indices of external breathing, blood pressure, ECG, heart thrust were determined. It was found that the increasing tonus of the vagus nucleus was an essential feature of the pathogenesis of HP poisoning, inducing a series of pathological changes in animals. A certain role was played by extensive gas embolism. About 80% of the experimental animals survived after administration of atropine or lobeline.

Acute Disease↗
PubMed1991

[Plasmapheresis in the treatment of patients with hypertension].

The authors discuss the results of the use of plasmapheresis in multimodality treatment of patients with stage II essential hypertension. At present the prevalence, ever increasing accessibility and relative simplicity of plasmapheresis make it possible to use it for the treatment of essential hypertension. Analysis of the data obtained shows the high efficacy of plasmapheresis in essential hypertension. Since plasmapheresis turned out effective in combination with drug therapy and alone as well, it is concluded that plasmapheresis is not only an approach to overcoming resistance to hypotensive therapy but also an independent treatment modality that exerts a considerable effect on the immunologic and hemorheologic blood properties. The above-indicated allows recommending plasmapheresis for the treatment of patients suffering from essential hypertension, since it may lead to a long-term decrease of arterial pressure, to the enhancement of the sensitivity to hypotensive drugs, to the diminution of drug requirements, thereby ameliorating the course and prognosis of the disease in patients suffering from essential hypertension.

Antihypertensive Agents↗