Formation of ECR Plasma in a Dielectric Plasma Guide under Self-Excitation of a Standing Ion-Acoustic Wave

The formation of a spatially localized plasma with a high brightness has been experimentally observed in a dielectric plasma guide under the electron cyclotron resonance discharge at the excitation of a standing ion-acoustic wave. The results obtained show the possibility of designing compact high-intensity radiation sources with a spectrum determined by the working gas or gas mixture type, high-intensity chemically active particle flow sources, and plasma thrusters for correcting orbits of light spacecraft.     

Dose-effect and time-effect characteristics in process of tumorigenesis under combined action of ionizing radiation and chemical carcinogen

Studying of dose and time dependences of frequency of adenomas appearing under the combined effect of radiation and urethane ingressed during different terms after irradiation has show that the frequency of tumours is determined both by radiation dose, and the time interval between irradiation and ingressing of cancerogenic substance. The data obtained show the period of preservation of the induced damages and non-linearity of the process of tumour-formation under the combined effect of radiation and toxic factors on the organism. The latter is necessary to be taken into account when forecasting the radiation risk under the real ecological conditions.     

Induction of DNA strand breaks by laser irradiation in a visible range

A possibility of formation of breaks in DNA chains under the influence of visible laser radiation (lambda = 532 nm) on DNA--dye-intercalator complexes has been demonstrated theoretically and corraborated experimentally. The most probable mechanisms of the induction of breaks in DNA chains are discussed. Theoretical estimates and the experiments have been performed on complexes of DNA of lambda-phage with acridine orange dye (AO) under irradiation of these complexes by picosecond (tau p = 30 ps) pulses of second harmonic YAG:Nd laser. A strong effect of the formation of double-strand breaks is observed at light intensity of some GW/sm2 and dose of several hundred pulses.     

Axillary bud proliferation and ethylene production as controlled by radiation of different spectral composition and exogenous phytohormones

The effect of radiation of different spectral composition on axillary proliferation of lavandin (Lavandula officinalis Chaix ×Lavandula latifolia Villars cv. Grosso) was studied in combination with application of exogenous benzyladenine (BA) and putrescine (Put) and endogenous ethylene production. The effect of BA was predominant over the radiation. Continuous far-red showed a fluence rate-dependent promotion of shoot proliferation in the presence of BA. On BA-free medium, shoot number was enhanced under blue, white, and red radiation, at low photon fluence rates. BA, however, could reduce the inhibiting effect of blue and ultraviolet radiation, at high photon fluence rates. Exogenous Put stimulated axillary bud proliferation under some radiation treatments in the presence of BA. Moreover, Put, analogously to BA, could overcome the detrimental effect of ultraviolet radiation. A positive correlation between biotic ethylene production and shoot formation was evidenced under far-red at high photon fluence rate in the presence of BA, and under white, red and blue radiation at low photon fluence rate in the BA-free medium. However, when abiotic ethylene (released from the agarized medium) was stimulated by UV, no improvement of shoot formation was observed.     

Oxygen levels do not determine radiation survival of breast cancer stem cells

For more than a century oxygen has been known to be one of the most powerful radiosensitizers. However, despite decades of preclinical and clinical research aimed at overcoming tumor hypoxia, little clinical progress has been made so far. Ionizing radiation damages DNA through generation of free radicals. In the presence of oxygen these lesions are chemically modified, and thus harder to repair while hypoxia protects cells from radiation (Oxygen enhancement ratio (OER)). Breast cancer stem cells (BSCSs) are protected from radiation by high levels of free radical scavengers even in the presence of oxygen. This led us to hypothesize that BCSCs exhibit an OER of 1. Using four established breast cancer cell lines (MCF-7, T47D, MDA-MB-231, SUM159PT) and primary breast cancer samples, we determined the number of BCSCs using cancer stem cell markers (ALDH1, low proteasome activity), compared radiation clonogenic survival and mammosphere formation under normoxic and hypoxic conditions, and correlated these results to the expression levels of key members of the free radical scavenging systems. The number of BCSCs increased with increased aggressiveness of the cancer. This correlated with increased radioresistance (SF(8Gy)), and decreasing OERs. When cultured as mammospheres, breast cancer cell lines and primary samples were highly radioresistant and not further protected by hypoxia (OER～1).We conclude that because BCSCs are protected from radiation through high expression levels of free radical scavengers, hypoxia does not lead to additional radioprotection of BCSCs.     

The development and structure of the optic nerve in normal embryos and fetuses of the white rat and after x-ray irradiation]

With the aim to reveal the ionising radiation effect to formation and structure of the optic nerve (ON), 55 white rat intact embryos and fetuses and 77 experimental embryos and fetuses, subjected to x-ray irradiation on the 10th-14th day of development, have been studied. The main regularities in formation of the ON have been stated under normal conditions. Certain disturbances in formation of the ON and in the internal membrane of the optic vesicle (future retina) under effect of x-rays in the dose of 2.24 Gy have been detected during the intrauterine period of development--folds, rosellas of retina, retardation in differentiation of the retina nervous layer, aberration of the ON growth with a subsequent reduction, the ON hypo- and aplasia, retardation in formation of neural sheaths, absence of intraspace between the sheaths.     

Content of cyclic nucleotides and lipid peroxidation products in the brain of irradiated mice

The effect of radiation on the cyclic nucleotide content of mouse brain has been studied. High radiation doses have been found to increase cGMP and to decrease cAMP content of the brain. These alterations correlate with the processes of lipid peroxidation and formation of diene conjugates and malonic dialdehyde.     

Membrane and intracellular modes of sugar-dependent increments in red cell stability

Sugar-dependent increments in red cell stability under osmotic stress can be ascribed to changes either in the membrane or in the intracellular matrix. These two possible modes of action have been tested and characterized.Rheological investigation of membrane-free haemoglobin solutions has shown that D-glucose, but not D-fructose, promotes the formation of a visco-plastic gel structure. gel strength is a function of glucose concentration, haemoglobin concentration and temperature. The ability of various sugars to promote gel formation correlates with their solution properties. The existence of gel structure reduces K⁺ and haemoglobin leak from red cells whose membranes were partially destroyed by γ- radiation. Reduced osmotic swelling in the presence of glucose is also due to gel formation since the glucose effect is lost in resealed red cell ghost.D-Fructose does not protect red cells against radiation damage; its mode of action in increasing red cell stability under osmotic stress is a membrane effect. Cell sizing using the Coulter Counter has shown that fructose, but not glucose, can increase the maximal volume at lysis. At 50 mM., D-fructose expands the red cell ghost voloume by 11.2%; this represents a 7.2% increase in membrane area. Ghost expansion by fructose is fructose concentration dependent (0–100 mM) and is insensitive to temperature variation (0–37 °C).     

Sporulation of Botrytis cinerea as affected by photoselective polyethylene sheets and filters

Sporulation of Botrytis cinerea was studied in vitro under various filters and polyethylene co-polymer (PE) sheets. It was found that continuous darkness blocked sporulation completely. Sporulation was inhibited by reduced ultraviolet (u.v.) radiation. Almost total inhibition of sporulation was also found when cultures were grown under a blue filter. The reduction of spore formation was negatively related to the ratio of transmitted blue/u.v. light. The possibility of using this effect to control the incidence of Botrytis cinerea in greenhouses is discussed. A brief report has been published (Reuveni, Raviv, Allingham & Bar, 1988).     

Purification of factor Ts: studies on the formation and stability of nucleotide complexes containing transfer factor Tu

Transfer factor Ts has been purified to near homogeneity from E. coli. Its molecular weight and amino acid composition have been determined, and it has been used in studies on the ionic requirements for Tu-nucleotide interaction. Mg²⁺ has been shown to have a stabilizing effect on the Tu-GDP and Tu-GTP complexes. Mg²⁺ has also been shown to be an absolute requirement for the formation of Tu-GDP from the Tu-Ts complex and for the formation of AA-tRNA-Tu-GTP from Tu-GTP and AA-tRNA. NH₄⁺ does not appear to appreciably influence the formation of Tu-[³H] GDP or Tu-[³H] GTP from Tu or Tu-GDP in the presence of Ts. NH₄⁺ also does not affect the formation of AA-tRNA-Tu-GTP from AA-tRNA and Tu-GTP, but appears to stimulate the formation of the ternary complex under conditions where ternary complex formation is dependent on Ts.     

Detection of nitrite and nitrosocompounds in chemical systems and biological liquids by the calorimetric method

The capacity of nitrite, S-nitrosothiols (RS-NO), dinitrosyl iron complexes (DNICs) with thiolcontaining ligands, and nitrosoamines to inhibit catalase has been used for the selective determination of these compounds in purely chemical systems and biological liquids: cow milk and colostrum. The limiting sensitivity of the method is 50 nM. A comparison of the results of the determinations of RS-NO, DNIC, and nitrite by the catalase method and the Griess method conventionally used for nitrite detection showed that, firstly, Griess reagents decompose DNIC and RS-NO to form nitrite. Therefore, the Griess method cannot be used for nitrite determination in solutions of these substances. Secondly, Griess reagents interact with complexes of mercury ions with RS-NO, inducing the release of nitrosonium ions from the complex followed by the hydrolysis of nitrosonium to nitrite. Thus, the proposition about the spontaneous decay of the complexes of mercury ions with RS-NO is incorrect. Keeping in mind a high sensitivity of the method, the use of catalase as an enzyme detector of nitrosocompounds allows one to detect these compounds in neutral medium without prior purification of the object, thereby preventing artificial effects due to noncontrolled modifications of the compounds under study.     

The effect of the biochemical adaptations in the Manchu alder (Duschecia fruticosa (Rupr)) to an elevated natural radiation background on the survivability of seedlings and on the radiosensitivity of its seeds

Seeds and sprouts of bushy alder existing for long under the condition of the enhances natural radiation background (ENRB; from 1.4 to 72.0 mCu/(kg.s)) have been examined to determine biochemical adaptations to permanent low-level irradiation. To achieve this goal a combined cytological and biochemical technique for the assessment of the activity of genome of the sprout root meristem in response to translation, replication and reparation has been applied. The activity of antioxidant systems has been studied. The data obtained allow us to reveal mechanisms of alder bush biochemical adaptations to various ENRB rates and their effect upon seeds radiosensitivity and sprouts survival. It is determined that the increase in sprout vitality and high radioresistance of seeds ripened under the conditions of low-level natural radiation is due to the content of low molecular antioxidants and activation of systems of genome reparation.     

Membrane and intracellular modes of sugar-dependent increments in red cell stability.

Sugar-dependent increments in red cell stability under osmotic stress can be ascribed to changes either in the membrane or in the intracellular matrix. These two possible modes of action have been tested and characterized. Rheological investigation of membrane-free haemoglobin solutions has shown that D-glucose, but not D-fructose, promotes the formation of a visco-plastic gel structure. Gel strength is a function of glucose concentration, haemoglobin concentration and temperature. The ability of various sugars to promote gel formation correlates with their solution properties. The existence of gel structure reduces K+ and haemoglobin leak from red cells whose membranes were partially destroyed by gamma-radiation. Reduced osmotic swelling in the presence of glucose is also due to gel formation since the glucose effect is lost in resealed red cell ghosts. D-Fructose does not protect red cells against radiation damage; its mode of action in increasing red cell stability under osmotic stress is a membrane effect. Cell sizing using the Coulter Counter has shown that fructose, but not glucose, can increase the maximal volume at lysis. At 50 mM, D-fructose expands the red cell ghost volume by 11.2%; this represents a 7.2% increase in membrane area. Ghost expansion by fructose is fructose concentration dependent (0-100 mM) and is insensitive to temperature variation (0-37 degrees C).     

Risk to preimplantation mouse embryos of combinations of heavy metals and radiation

The influence of arsenic, cadmium, lead or mercury on radiation risk to preimplantation mouse embryos in vitro was studied under various conditions. Morphological development, cell proliferation, and formation of micronuclei were used for assessment of risk after combined exposure to these metals and X-rays. No conditions were found under which arsenic altered radiation risk; the effects were merely additive. Cadmium acted similarly, though a few results indicated that morphological development might be impaired more strongly after combined exposure than expected from the addition of the single effects. Lead enhanced radiation risk with regard to micronucleus formation, but had an additive effect only in the case of morphological development and cell proliferation. Of all four metals, mercury had the greatest potential for enhancement of radiation risk, when morphological development and cell proliferation were studied. The observed combination effects exceeded even those effects which were calculated by taking into account the shape of the dose-effect curves (isobologram analysis, envelope of additivity). Mercury neither induced micronuclei nor enhanced their formation in combination experiments.     

Some radiobiological effects in higher plants growing on the territory of the East Ural Radioactive Trace

The spontaneous level of cytogenetic damage in three plant species (Achyrophorus maculatus (Scop.) L.; Plantago lanceolata L.; and Plantago media L.) growing on the territory of the East Ural Radioactive Trace is studied. The radiation resistance of plants from radioactive and control nonpolluted sites is determined. The effects of additional fractionated irradiation at different doses and the role of antioxidant systems in the formation of the radioprotector effect are examined. It is shown that the level of the mutation process in the plant population growing at the radiation polluted sites is increased compared to the control populations from nonpolluted territories. Additional acute γ irradiation of seeds collected from polluted and nonpolluted territories demonstrates improved radiation resistance of the plants from the polluted territory. In the control population of A. maculatus in the versions with a one-hour interval between fractions, the radiation effect follows the additivity principle; at the same time, at a one-day interval between fractions, a highly significant radioprotective effect is manifested clearly in the experimental population. For higher plants, the enhanced effectiveness of the functioning of the antioxidant systems in plants growing on territories contaminated with radiation is shown for the first time. Thus, the radioprotector mechanisms of low-dose chronic and preliminary irradiation are similar and one of these mechanisms is activation of the antioxidant systems in plants growing under conditions of chronic low-intensity irradiation for long periods of time.     

The mechanisms of lymphoid regulation and the radiosensitivity of the hematopoietic system]

On the basis of the authors' own data and the literature it has been inferred that the key principles of the haemopoietic system regulation are similar to those of the immune system. The cells of a lymphoid origin are found, which implement helper and suppressor functions with respect to early haemopoiesis precursors; the influence of lymphokines on this compartment under the effect of radiation is described. Disturbances in the haemopoiesis system regulation, that result from various damaging effects, might be corrected by T-lymphocytes and lymphokines. The data obtained suggest that the formation of splenic colonies is the result of the interaction of some cell populations. That is why many radiobiological characteristics of CFUs may be attributed to partner cells (for instance, T-lymphocytes).     

Biological effect of 9 GeV protons and the radioprotective effect of ATP and AMP on epithelial cells of the mouse cornea

The cytogenetic and cytological effects induced in mouse cornea epithelium cells by 9 GeV protons and "standard" radiation have been studied. The RBE coefficients are different at different times of observation. ATP and AMP are shown to produce a protective effect on the frequency of formation of aberrant mitoses. DMF values for protons determined 24 and 72 h following irradiation are 1.8 +/- 0.2 and 1.7 +/- 0.2, respectively.     

Infrared method of studying the action of vasoactive substances on cerebral circulation

A method for the investigation of cerebral blood flow changes under the influence of vasoactive drugs has been suggested. The method is based on continuous infrared radiation and registration of the reflection from the local brain region through the cerebral cranium. The experiments were conducted on anesthetized cats. The dependence of Pa CO2 on the recorded parameters is shown. The changes in the cerebral blood flow (in conventional units) determined by the alterations of the infrared radiation reflection are shown upon the injection of 1.2 microgram/kg, 2.5 micrograms/kg and 5 micrograms/kg of noradrenaline.     

Effect of ionizing radiation on the structure of human serum albumin. Effect of irradiation on the content of free amino groups and on the ability of HSA to be digested by proteinases

The effect of gamma-quanta on human serum albumin (HSA) solutions (1.6 mg/ml, borate buffer pH 7.45) in the air has been investigated. Using 2,4,6-trinitro-benzene-sulfonic acid it has been shown that 2-22 kGy radiation reduces the free amino groups content of HSA and increases its resistance to the hydrolytic effect of trypsin and pronase which is not influenced by the postirradiation exposure to heat. It is concluded that epsilon-NH2-groups of lysine residues are modified and firm cross-links are formed in HSA under the effect of radiation.     

Effect of pH on low-density lipoprotein oxidation by O2-./HO2. free radicals produced by gamma radiolysis.

This study aimed to analyze quantitatively the initiation and the consequences of low-density lipoprotein (LDL) peroxidation by O2-./HO2. free radicals produced by gamma radiolysis. The action of increasing radiation doses on aqueous LDL solutions has been monitored simultaneously by several parameters: a decrease in endogenous vitamin E, the formation of thiobarbituric acid-reactive substances (TBARS) and conjugated dienes, the appearance of a differential fluorescence (excitation wavelength = 360 nm), and an increase of the relative electrophoretic mobility. Initial radiation yields (decrease in vitamin E, formation of TBARS) have been determined at pH 7 and pH 5.7 as a function of LDL concentration (from 0.75 to 9 g liter-1). From the comparison of these yields with those of O2-. radicals produced by water radiolysis, we have deduced reaction mechanisms for LDL peroxidation initiated by O2-./HO2. free radicals.