The changing of cell-free DNA properties of peripheral blood and TCR-mutant cell frequency in individuals exposed to ionizing radiation

Some properties of the cell-free DNA (cfDNA) of peripheral blood plasma were assessed in 153 employees of atomic industry enterprises. The contents of ribosomal repeat (rDNA) and its concentration in plasma increased in cfDNA of the group of persons in comparison with non-irradiated individuals. The contents of satellite III in cfDNA of donors and of irradiated persons do not differ and less than in DNA nucleus. The correlation between cumulative dose of radiation, contents of rDNA in cfDNA and the frequency of lymphocytes bearing mutations at T-cell receptor (TCR) locus was obtained. The definition of three indications in irradiated persons: the contents of ribosomal genes in cfDNA, TCR-mutant cell frequency and concentration of ribosomal genes in blood plasma--may be useful for revealing individuals in organism of which an intensive cell apoptosis takes place and there is an increased probability of carcinogenesis and of progress of disease of immune system.     

The analytical review of the schemes of the acute radiation disease treatment used in experiment and in clinic

The analysis of the original sources showed that there are some differences in approaches to radiation injuries treatment used mainly by Russian and foreign researches in their experiments. In Russian radiobiology the main way was the single usage of high molecular substances of different chemical structure and of natural origin soon after radiation exposure. These substances were designated then as cytokine inductors. Foreign researchers investigated in the beginning analogous substances too, but then--recombinant cytokines exclusively. In native radiobiology the urgent (in limits of 2 h) and early (in limits of 6-24 h) pathogenic therapy develops already for a long time. There are preparations, betaleukine (recombinant human interleukine 1 beta) and dezoksinat (degraded DNA), as results of developing the directions. Both have licenses on the administration at radiation accidents. But the issues of various medicaments optimal combinations in a common scheme of early (in first 24 h) medical help remain undefined accurately. The consensus protocol of radiation injuries treatment in clinic consists of the supportive therapy (aseptic conditions, wide antimicrobic antibiotics, thrombocytes and erythrocytes transfusions) and the myelostimulation therapy by cytokine combinations. The hemopoietic stem cells transplantation in cases of severe radiation damages treatment remains under question in the reason of immunological conflict between a host and a graft.     

Differences in activation of the motoneurone inhibitory receptors in a frog Rana ridibunda by GABA and glycine and their interaction

The membrane potential responses evoked by GABA and glycine bath applications were studied intracellularly in the motoneurons of the isolated frog spinal cord. The amplitude of glycine-evoked responses was 1.5-2.0 larger than that of GABA-evoked response at the same concentration. EC50 were 0.75 mM and 1.57 mM for glycine and GABA, respectively. The amplitude of responses induced by the simultaneous applications of both agonists were 79.1 +/- 2.4% (n = 19) of the sum of individual responses and 130.1 +/- 1.5% (n = 19) of individual glycine-induced responses (partial occlusion). GABA-evoked responses were decreased by 85.3 +/- 0.2% (n = 10) as a result of glycine preliminary application while preapplication of GABA reduced glycine-evoked responses only by 52.9 +/- 0.3% (n = 11). Glycine- and GABA-evoked responses were selectively suppressed by strychnine and bicuculline, respectively. These results suggest that amphibian spinal motoneurones express (less specifically than those of mammals) both glycine (predominantly) and GABAA receptors, with asymmetric cross-inhibition possibly taking place in them.     

The influence of potassium humate on 137Cs accumulation by barley growing on soil with different fertility

The changes studied in 137Cs uptake by plants and its distribution between vegetative and generative organs of barley cultivated with the application of potassium humate. A relationship has been found between 137Cs accumulation size in barley at various ontogenesis stages and way of potassium humate application (treatment of seeds or plants), as well as availability of mineral nutrients in the soil. Changes in K+ and NH4+ concentrations in soil solution are shown to be of prevailing importance in regulating 137Cs uptake by plants compared with potassium humate effects.     

The effect of X-rays and artificial hypotermia on lipids in rat neocortex

Lipid content of tissue and of fraction of microsomes in neocortex of Wistar rats was studies under artificial hypothermia, after X-ray irradiation in dose 8 Gy under conditions of normothermia and artificial hypothermia in 48 h. The condition of artificial hypothermia get by cooling of rats to 15-18 degrees C. It was shown, that in fraction of microsomes of hypothermia rats the content of phosphatidylinositol was decreased, and in 48 h after cooling of rats the amount of protein, total and individual phospholipids was increased. The lipid content in tissue and in fraction of microsomes of rats, which were irradiated in normotermia, had no changes after 48 h. In fraction of microsomes of rats, which were irradiated after hypothermia, the amount of protein, total phospholipids, sphingomyelin, phosphatidylcholine and phosphatidylserine is increased trustworthy. Thus, we think, that radioprotective effect of hypotermia may be connected with the accumulation of proteins and of phospholipids in the endoplasmic reticulum membranes of neocortex.     

The mechanisms of 232Th and of Ce (III) toxic action on Chlorella vulgaris Beijer. Estimation of 232Th radiation impact contribution into toxic effect induced

232Th and Ce (III) toxic effects and its modifications with caffeine and D,L-buthionine-(S,R)-sulphoximine on Chlorella vulgaris Beijer were studied using an optical density measure after 24 hours growth. Concentrations of 232Th or of Ce--toxic effect relationship were shown to be nonlinear. In the first (nontoxic) concentration range (for Ce 0.036-1.642 micromol/L and for 232Th 0.001-1.551 micromol/L) algae biomass production registered by optical density do not significantly differ from the control one. In the second (toxic) concentration range dose-effect relationship for 232Th is characterized with quadratic dependence and in the case of Ce--with exponential dependence. 232Th radiation component contribution into effect observed is appeared as induction of DNA damages additional to spontaneous at the radionuclide concentration (equal to 0.345 micromol/L) that is three times lower than in case of the non-radioactive chemical analog Ce (1.071 micromol/L).     

Repolarization of canine ventricular myocardium under the supraventricular rhythm

The ventricular myocardium is characterized by heterogeneity of activation-recovery interval durations. The transmural ARI gradients are present in the right ventricular apex (ARIs monotonically decreased as one moved from the endocardium to the epicardium), and in the left ventricular base (repolarization in the subepicardial layers was significantly shorter than that in the midmyo cardial layers whereas subendocardial ARIs did not differ from the others). The repolarization pattern of these myocardial regions is governed by the distribution of ARIs. In the apical left ventricular and basal right ventricular areas, no significant transmural differences in the repolarization durations were found. The repolarization pattern of these myocardial regions is governed by the activation sequence. In the right ventricle, ARIs were significantly longer at the base and shorter at the apex. In contrast, in the left ventricle, the apical ARIs were prolonged whereas the basal ARIs were abbreviated. The apex-to-base sequence of myocardial repolarization seems to depend on apex-to-base gradient of activation-recovery intervals durations.     

Methylene substitution at the alpha-beta bridging position within the phosphate chain of dUDP profoundly perturbs ligand accommodation into the dUTPase active site

dUTP pyrophosphatase, a preventive DNA repair enzyme, contributes to maintain the appropriate cellular dUTP/dTTP ratio by catalyzing dUTP hydrolysis. dUTPase is essential for viability in bacteria and eukaryotes alike. Identification of species-specific antagonists of bacterial dUTPases is expected to contribute to the development of novel antimicrobial agents. As a first general step, design of dUTPase inhibitors should be based on modifications of the substrate dUTP phosphate chain, as modifications in either base or sugar moieties strongly impair ligand binding. Based on structural differences between bacterial and human dUTPases, derivatization of dUTP-analogous compounds will be required as a second step to invoke species-specific character. Studies performed with dUTP analogues also offer insights into substrate binding characteristics of this important and structurally peculiar enzyme. In this study, alpha,beta-methylene-dUDP was synthesized and its complex with dUTPase was characterized. Enzymatic phosphorylation of this substrate analogue by pyruvate kinase was not possible in contrast to the successful enzymatic phosphorylation of alpha,beta-imino-dUDP. One explanation for this finding is that the different bond angles and the presence of the methylene group may preclude formation of a catalytically competent complex with the kinase. Crystal structure of E. coli dUTPase:alpha,beta-methylene-dUDP and E. coli dUTPase:dUDP:Mn complexes were determined and analyzed in comparison with previous data. Results show that the "trans" alpha-phosphate conformation of alpha,beta-methylene-dUDP differs from the catalytically competent "gauche" alpha-phosphate conformation of the imino analogue and the oxo substrate, manifested in the shifted position of the alpha-phosphorus by more than 3 A. The three-dimensional structures determined in this work show that the binding of the methylene analogue with the alpha-phosphorus in the "gauche" conformation would result in steric clash of the methylene group with the protein atoms. In addition, the metal ion cofactor was not bound in the crystal of the complex with the methylene analogue while it was clearly visible as coordinated to dUDP, arguing that the altered phosphate chain conformation also perturbs metal ion complexation. Isothermal calorimetry titrations indicate that the binding affinity of alpha,beta-methylene-dUDP toward dUTPase is drastically decreased when compared with that of dUDP. In conclusion, the present data suggest that while alpha,beta-methylene-dUDP seems to be practically nonhydrolyzable, it is not a strong binding inhibitor of dUTPase probably due to the altered binding mode of the phosphate chain. Results indicate that in some cases methylene analogues may not faithfully reflect the competent substrate ligand properties, especially if the methylene hydrogens are in steric conflict with the protein.     

Myosin phosphatase interacts with and dephosphorylates the retinoblastoma protein in THP-1 leukemic cells: its inhibition is involved in the attenuation of daunorubicin-induced cell death by calyculin-A

Reversible phosphorylation of the retinoblastoma protein (pRb) is an important regulatory mechanism in cell cycle progression. The role of protein phosphatases is less understood in this process, especially concerning the regulatory/targeting subunits involved. It is shown that pretreatment of THP-1 leukemic cells with calyculin-A (CL-A), a cell-permeable phosphatase inhibitor, attenuated daunorubicin (DNR)-induced cell death and resulted in increased pRb phosphorylation and protection against proteolytic degradation. Protein phosphatase-1 catalytic subunits (PP1c) dephosphorylated the phosphorylated C-terminal fragment of pRb (pRb-C) slightly, whereas when PP1c was complexed to myosin phosphatase target subunit-1 (MYPT1) in myosin phosphatase (MP) holoenzyme dephosphorylation was stimulated. The pRb-C phosphatase activity of MP was partially inhibited by anti-MYPT1(1-296) implicating MYPT1 in targeting PP1c to pRb. MYPT1 became phosphorylated on both inhibitory sites (Thr695 and Thr850) upon CL-A treatment of THP-1 cells resulting in the inhibition of MP activity. MYPT1 and pRb coprecipitated from cell lysates by immunoprecipitation with either anti-MYPT1 or anti-pRb antibodies implying that pRb-MYPT1 interaction occurred at cellular levels. Surface plasmon resonance-based experiments confirmed binding of pRb-C to both PP1c and MYPT1. In control and DNR-treated cells, MYPT1 and pRb were predominantly localized in the nucleus exhibiting partial colocalization as revealed by immunofluorescence using confocal microscopy. Upon CL-A treatment, nucleo-cytoplasmic shuttling of both MYPT1 and pRb, but not PP1c, was observed. The above data imply that MP, with the targeting role of MYPT1, may regulate the phosphorylation level of pRb, thereby it may be involved in the control of cell cycle progression and in the mediation of chemoresistance of leukemic cells.     

The effects of inbreeding and low temperature on the pattern of chromosome synapsis in the ovarian nurse nuclei of Drosophila melanogaster strains

The effects of inbreeding and low temperature on the pattern of homologous chromosome synapsis in ovarian nurse cell nuclei of Drosophila melanogaster strains were studied. Exposure to decreased temperature (16 degrees C) caused a noticeable increase in the rate of asynapses of homologous chromosomes, whereas this effect was insignificant for F30 inbreeding generation. Long-term inbreeding has a substantial effect on the relative positions of chromosomes in the nurse cell nuclei. This is visually evident only in the interstrain hybrids between highly inbred strains LA (F923) and HA (F923) or between either strain and laboratory strain Canton S or the flies from the natural population, where abnormalities in homologous chromosome synapsis are observed in virtually all nuclei.