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1.
M. Dubničková E. A. Kuzmina V. N. Chausov I. Ravnachka A. V. Boreyko E. A. Krasavin 《Physics of Particles and Nuclei Letters》2016,13(2):274-278
The modulatory effects of lipid A (diphosphoryl lipid A (DLA) and monophosphoryl lipid A (MLA)) on apoptosis induction and DNA structure damage (single and double-strand breaks (SSBs and DSBs, respectively)) in peripheral human blood lymphocytes are studied for 60Co gamma-irradiation. It is shown that in the presence of these agents the amount of apoptotic cells increases compared with the irradiated control samples. The effect is most strongly pronounced for DLA. In its presence, a significant increase is observed in the number of radiation-induced DNA SSBs and DSBs. Possible mechanisms are discussed of the modifying influence of the used agents on radiation-induced cell reactions 相似文献
2.
The heavy ion accelerators of the Joint Institute for Nuclear Research were used to study the regularities and mechanisms
of formation of different types of mutations in prokaryote cells. The induction of direct (lac−, ton B−, col B) mutations for Esherichia coli cells and reverse his− → His+ mutations of Salmonella typhimurium, Bacillus subtilis cells under the action of radiation in a wide range of linear energy
transfer (LET) was studied. The regularities of formation of gene and structural (tonB trp-) mutations for Esherichia coli
bacteria under the action of accelerated heavy ions were studied. It was demonstrated that the rate of gene mutations as a
function of the dose under the action of Γ rays and accelerated heavy ions is described by linear-quadratic functions. For
structural mutations, linear “dose-effect” dependences are typical. The quadratic character of mutagenesis dose curves is
determined by the “interaction” of two independent “hitting” events in the course of SOS repair of genetic structures. The
conclusion made was that gene mutations under the action of accelerated heavy ions are induced by δ electron regions of charged
particle tracks. The methods of SOS chromotest, SOS lux test, and λ prophage induction were used to study the regularities
of SOS response of cells under the action of radiations in a wide LET range. The following proposition was substantiated:
the molecular basis for formation of gene mutations are cluster single-strand DNA breaks, and that for structural mutations,
double-strand DNA breaks. It was found out that the LET dependence of the relative biological efficiency of accelerated ions
is described by curves with a local maximum. It was demonstrated that the biological efficiency of ionizing radiations with
different physical characteristics on cells with different genotype, estimated by the lethal action, induction of gene and
deletion mutations, precision excision of transposons, is determined by the specific features of energy transfer of the radiations
that affect the character of induced DNA damage, and the efficiency inducible and constitutive cell repair systems. The growth
of relative biological efficiency of heavy charged particles is determined by the growth of the damage yield of the DNA participating
in the formation of radiation-induced effects, and higher efficiency of inducible repair systems. It was established that
the LET value (L
max) for which the maximum (according to the applied irradiation criteria) coefficients of relative biological efficiency are
observed varies depending on the character of the registered radiation induced effect. It was demonstrated that for gene mutations
and induction of precision excision of mobile elements the values of L
max are realized in a LET range of ≈20 keV/μm. For lethal effects of irradiation and induction of deletion mutations the value
of L
max is ≈ 100 and 50 keV/μm, respectively. The differences in the L
max for the studied radiation gene effectis are determined by the different type of DNA damage participating in the mutation
process. A molecular model of the formation of gene mutations in Escherichia coli cells under the action of ionizing radiation
was proposed. Basic DNA radiation damage and main repair ways were considered in the framework of this model. The basis is
the idea of the decisive role of mutagenic, error-prone, branch of SOS repair in fixing premutation DNA damage into point
mutations. It was demonstrated that the central mechanism in this process is the formation of an inducible multi-enzymatic
complex including the DNA polymerase V (Umu C), RecA-protease, SSB proteins, subunits of DNA polymerase III, performing erroneous
DNA synthesis on the damaged matrix. A mathematical model of induction of gene mutations under ultraviolet cell irradiation
was developed based on the molecular model. 相似文献
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5.
Simple Zeros of the Riemann Zeta-Function 总被引:1,自引:0,他引:1
Assuming the Riemann Hypothesis, Montgomery showed by meansof his pair correlation method that at least two-thirds of thezeros of Riemann's zeta-function are simple. Later he and Taylorimproved this to 67.25 percent and, more recently, Cheer andGoldston increased the percentage to 67.2753. Here we proveby a new method that if the Riemann and Generalized LindelöofHypotheses hold, then at least 70.3704 percent of the zerosare simple and at least 84.5679 percent are distinct. Our methoduses mean value estimates for various functions defined by Dirichletseries sampled at the zeros of the Riemann zeta-function. 1991Mathematics Subject Classification: 11M26. 相似文献
6.
This paper concerns a Markov operator T on a space L1, and aMarkov process P which defines a Markov operator on a spaceM of finite signed measures. For T, the paper presents necessaryand sufficient conditions for:
- a the existence of invariant probabilitydensities (IPDs)
- b the existence of strictly positive IPDs,and
- c the existence and uniqueness of IPDs.
- b the existence of strictly positive IPDs,and
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8.
A. P. Kozlov E. A. Krasavin A. V. Boreyko A. P. Chernyaev P. Yu. Alekseeva U. A. Bliznyuk 《Physics of Particles and Nuclei Letters》2008,5(2):127-130
Human erythrocyte membrane damage under the impact of γ radiation on blood suspension is studied in a wide dose range (2–1000 Gy, irradiation dose rate 2.75 Gy/min). It is shown that the irradiation in the absorbed dose range from 600 Gy and higher results in hemolysis of erythrocytes immediately (or within several hours) after irradiation, and the value of the hemolysis rate constant increases with increasing absorbed dose. For finding hidden membrane damage occurring several hours after irradiation with smaller doses, the suspension was affected by a high voltage pulsed electric field (PEF). It is shown that, for an absorbed dose range from 2 to ~350 Gy, no noticeable increase in the erythrocyte hemolysis rate was observed after the action of PEF on the suspension, as compared to the nonirradiated suspension. This testifies that, in this dose range, the degree of membrane damage is small and practically independent of absorbed dose value. For doses from 400 to ~550 Gy, a noticeable increase in the hemolysis rate after the action of PEF growing with increasing absorbed dose was observed. 相似文献
9.
T. S. Bulanova M. G. Zadneprianetc L. Ježková E. A. Kruglyakova E. V. Smirnova A. V. Boreyko 《Physics of Particles and Nuclei Letters》2018,15(1):121-126
The induction and repair of DNA double-strand breaks are studied using the immunohistochemical staining procedure of paraffin-embedded rat cerebellum tissues after exposure to γ-rays of 60Co. The dose dependence of radiation-induced colocalized γH2AX/53BP1 foci is studied and its linear character is established. It is shown that these foci are efficiently eliminated 24 h after irradiation. 相似文献
10.
应用新发展的单一轨迹积分方法求解库仑加线性位的基态量子波函数,得到基态能量和波函数的一般解析表达式,并讨论了解的收敛性.应用此方法讨论了重夸克偶素系统. 相似文献