[Changes in the cell differentiation rate of a megakaryocytic line after cytotoxic exposure].
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Animals↗
Biomedical subjects
V A Selivanov
Publications and source records attributed to V A Selivanov.
[Mathematical model study of megakaryocytopoiesis. 1. The simulation model, cell steady-state distribution and the number of divisions in a proliferating population].
A method of simulation has been proposed for studying megakaryocytopoiesis. A model has been developed which takes into account the age structure of cell population, the stochasticity of their maturation, and the principles of megakaryocytopoiesis regulation (known from the experiments). The mean number of divisions in a proliferating pool has been determined, as well as the duration of development of the cells with a positive acetylcholine esterase reaction.
Blood Platelets↗
[Megakaryocytopoiesis studied in a mathematical model. 2. Regulation of cell differentiation following damage to part of the proliferating bone marrow pool by hydroxyurea].
Analysis of the earlier obtained data on the effect of hydroxyurea on megakaryocytopoiesis by a simulation model has shown that differentiation of proliferating precursors of the megakaryocytes depends on their amount in bone marrow; the time of their involvement in the proliferating pool increases if the number of proliferating cells decreases. Within 24 h after the treatment with hydroxyurea (900 mg/kg), the transit time for the mouse megakaryocytes is reduced by about 14 h due to acceleration of the latest developmental stages. A hypothesis is put forward which accounts for correlation between the duration of proliferative period and the volume and maturation time of megakaryocytes.
Animals↗
[Megakaryocytopoiesis studied in a mathematical model. 3. Regulation of cell differentiation in immune thrombocytopenia].
Simulation experiments have shown that just after antiplatelet serum of rabbit blood is introduced into mice the transit time of early proliferating precursors of the megakaryocytes is reduced by about 17 h, the transit time for megakaryoblasts increases, and within 24 h after the treatment the transit time for mature megakaryocytes is reduced b about 17 h. The data obtained confirmed our earlier hypothesis on correlation between the duration of proliferative period and the mean size of megakaryocytes.
Animals↗
[Megakaryocytopoiesis studied in a mathematical model. 4. Regulation of cell flow in a transit population].
The role of cells capable of formation of megakaryocytic colonies (CFUm) in regulation of thrombocytopoiesis was studied using a simulation model of megakaryocytopoiesis. The CFUm were shown to be the least differentiated cells involved in regulation of megakaryocytopoiesis in mice upon immune thrombocytopenia and after intravenous injection of hydroxyurea. A correlation was found between the CFUm population productivity and the number of cells in a transit population of the megakaryocytic line which makes it possible to reproduce experimental kinetics in the model. The duration of cell development from CFUm to megakaryocytes is about 3 days.
Animals↗
[Quantitative evaluation of radiation damage to thrombocytopoiesis].
From the comparison of the results of model and experimental kinetics of thrombocytopoiesis the following parameters have been quantitatively estimated: (1) the percentage of cells killed during the interphase (interphase death) and (2) the duration of the mitosis delay and the abortive rise. There was a 1.3-1.5-fold and 2-3-fold nonspecific and postirradiation, respectively, decrease in the megacaryocyte maturation time. The transit time of the committed megacaryocyte precursors was reduced due to death of premature precursors and survival of mature forms.
Animals↗
[Mechanism of low intensity ultrasound effect on mitochondria].
Ultrasound of 0,2 Wt/cm2 intensity affects the ionic transport across the mitochondrial membrane in vitro. In the presence of 1 mM EGTA in the incubation medium ultrasound slows down K+ exit into the external medium after the addition of an uncoupling agent (2,4-dinitrophenol). With the addition of 100 divided by 400 mM Ca2+ to the starting medium ultrasound makes the amount of Ca2+ absorbed by mitochondrial decrease and the rate of Ca2+/H+ electroneutral exchange increase. Without Ca2+ ultrasound does not influence the rate of coupled and 2,4-dinitrophenol uncoupled respiration and oxidative phosphorylation, i.e. does not produce strong functional changes.
2,4-Dinitrophenol↗
[Light-induced changes in pH and buffer capacity in reaction center preparations of Rhodopseudomonas spheroides].
In experiments with reaction centers (RC) preparations of Rps. sphaeroides, strain 1760-1, pH of the suspension medium was found to change under continuous light excitation. The concentration of hydrogen ions starts to decrease fastly (t1/2 = 2--4 s) after the light is on, whereupon it increases slowly, to a steady-state level, within t1/2 = 5--7 min. During the fast phase 0.3 microM H+/1 microM of RC are absorbed and 7--8 microM H+/1 microM of RC are released under the slow phase. The fast phase is suppressed by ortho-phenantroline (10 mM)--an inhibitor of electron transfer from the primary (Fe-quinone complex) to the secondary (quinone) electron acceptors. Glutaraldehyde which is known to modify a protein structure of the RC inhibits the slow phase. The obtained data suggest that fast light-induced pH changes are due to a H+ uptake by the secondary quinoid anion-radical products; slow pH changes are ascribed to structural changes within the RC complex, which lead to a pK shift and/or changes in the amount of dissociating groups on the protein interfacial surface. The conclusion was supported by an observation of light-induced changes in buffer capacity of an RC suspension and by a light-induced increase in the amount of SH-groups titrated by 5.5-dithio-bis(2 nitro)-benzoic acid. The role of conformational dynamics of photoactive pigment--protein complexes in the functions of the RC is discussed.
Bacterial Proteins↗
[Analysis and interaction of myosin active centers during a mechanochemical cycle].
A model of myosin complex with two active sites is considered. Each of the sites is supposed to pass through four states during a cycle of ATP hydrolysis. The model describes the distribution of the complex between states and the ATP hydrolysis rate as dependent on ATP concentration and reaction constants. Some of the constants were determined experimentally [6], but these values reproduce experimental curves [5] only with the assumption of cooperativity. If the first site is bind to actin, the rate of binding for the second one is shown to increase tenfold. If one of the sites is bind to actin by a "pulling" bridge, and the second site is in "rigor" state, then the ATP binding for the second site is about ten times faster. The transition into the rigor state proceeds much faster if both sites form pulling bridges. The rate of binding to actin is the same for one and for two sites.
Actins↗