Modification of Combined Effect of Radiation and Sodium Chloride on Microorganisms by Chemical Agents during Irradiation

Effects of various chemical agents on the synergistic action of NaCl to the radiation inactivation of bacteria and yeast were studied. The remarkable modification of the radiation lethal effect by some reagents is considered to be a strong evidence for an indirect nature of NaCl synergistic action during irradiation. Most of these modification effects were restricted to the actions during irradiation, supporting the free radical hypothesis in which the short-life active species formed by radiation were considered to attack bacterial cells. Furthermore, pre-irradiation effects under various conditions suggest that the enhancement of radiation lethal effect by NaCl may involve the intracellular events.     

Effect of microwave radiation on a dusty plasma

The effect of microwave radiation on a complex plasma produced by an external ionizer is studied using numerical simulations. It is shown that, as the radiation intensity increases, the scattering of the incident radiation by charged metal grains is enhanced and radiation at the second harmonic of the incident radiation appears in the scattered spectrum. This effect is associated with the grain charge oscillations caused by the nonlinear action of the microwave field. It is found that, under the action of strong microwave radiation, the grain charge can increase by one order of magnitude. It is shown that, when the microwave intensity is high enough, the distribution of the electric field near a dust grain is shown to change so radically that the field component normal to the grain surface can even change its sign.     

Effect of irradiation and chemical differentiation inducers on the survival of thymus lymphocytes in mice

Chemical inductors of differentiation were shown to produce a cytotoxic effect on thymus cells. The protein synthesis inhibitors prevented this effect. The toxic action of the inductors was more pronounced in a most radiosensitive thymocyte fraction. A combination of differentiation inductors and ionizing radiation did not produce the additive effect. This was observed after the effect of radiation and substances being not the differentiation inductors but toxic for cells.     

Effects of Alkali Halides and Other Inorganic Salts on Radiation Inactivation of Taka-amylase in Aqueous System

Effects of alkali halides on radiation inactivation of Taka-amylase A were investigated in connection with their synergistic action to the radiation inactivation of microorganisms. Effective concentrations of these halides in protection against irradiation inactivation of this enzyme were well corresponded to that observed in the synergistic action to microorganisms. Removal of dissolved oxygen from halide solutions decreased their protective effect. Irradiated alkali halide solutions of relatively higher concentrations exhibited the inactivating action to this enzyme, and various types of addition effects of halogens and halogenoxyacids were observed with or without irradiation. Sodium nitrite showed effective protection even with higher radiation doses, and the heavy metal cations, Cu⁺⁺ and Fe⁺⁺⁺, also gave a protective action in low concentrations. From these observations, the possible interpretation on the mode of protection of alkali halides was attempted.     

Ultra-violet radiation and 8-methoxypsoralen have actions similar to those of known inhibitors of thromboxane A2 synthesis in rat mesenteric blood vessels

In the rat mesenteric vascular bed three structurally different agents (imidazole, benzydamine and N-0164) which have been reported to be inhibitors of thromboxane (TX) A2 synthesis at certain concentrations, all have a characteristic spectrum of action. They inhibit pressor responses to nor-adrenaline and angiotensin with equal potency and the inhibition can be reversed by exogenous PGE2: they do not inhibit responses to potassium. Ultra-violet (UV) radiation has a similar spectrum of action. The main difference between the action of imidazole and that of UV radiation is that the former is rapidly reversible while the latter is not. However irradiation administered to preparations inhibited by imidazole has no irreversible effect provided that the radiation is switched off before the imidazole is removed. The imidazole protects against radiation damage suggesting that the drug may stabilize the site affected by UV light. 8-methoxypsoralen, a light sensitizing agent used in treatment of psoriasis also inhibited noradrenaline and angiotensin but not potassium responses and seemed to make the preparation more sensitive to radiation damage. It is possible that UV radiation and 8-methoxypsoralen may inhibit TXA2 synthesis but this requires confirmation by direct methods.     

Structural and metabolic analysis of the reaction of the central nervous system to the combined action of microwave and ionizing radiations

Structural and functional changes in the central nervous system were shown to be the same with both microwave and ionizing radiation having different mechanism of action. When the two types of radiation were delivered in a combination the sequence of delivery was of a significant importance. Antagonism of the effects was noted when microwave radiation was delivered prior to gamma-radiation. The effect was synergistic when the exposure to microwaves followed gamma-irradiation.     

Combined Effects of Radiation and Inorganic Reagents during Irradiation on Radiosensitivity of Bacterial Cells

The combined effects of inorganic reagents and radiation on the inactivation of E. coli in the resting state were studied. Among these reagents halides such as NaCI, KCI, KBr and KI were found to have a considerable synergistic action to radiation. Temperature effect on the halide action during irradiation was not observed, but removal of oxygen from halide solutions increased the radiosensitivity of cells. Combined effects of radiation and some other inorganic reagents were also investigated. Heavy metal salts and hydrogen peroxide were synergistic, nitrates and sulfates having no influence or a slightly protective action. Barium chloride and calcium chloride were protective in lower concentrations and synergistic in higher concentrations. These synergistic actions of inorganic reagents except ferric salts were observed during irradiation, but not after the irradiation.     

Influence of an alternating magnetic field on the bactericidal effect of ionizing radiation

A study was made of the effect of alternating magnetic field (AMF) and ionizing radiation delivered separately or in a combination on the microorganisms differing in radio-resistance. AMF (240 and 750 E) had no pronounced bactericidal action. A synergistic increase in the sterilizing effect of ionizing radiation was demonstrated after incubation of irradiated bacteria in AMF. The radiation-magnetic technique is proposed for sterilization of preparations and articles made of non-thermoresistant materials which permits to decrease by 1.5 times the bactericidal dose of ionizing radiation.     

Mechanisms of the synergistic action of ionizing radiation and hydrogen peroxide on the viability of bacteria

The combined effect of ionizing radiation and minor concentrations of hydrogen peroxide (0.1-0.01 M) has been studied on bacteria differing in the cell wall structure (Gy+, Gy-), radioresistance, and activity of DNA repair system. The H2O2 concentrations applied, which have a slight antibacterial action, enhance significantly the bactericidal effect of ionizing radiation producing a synergistic effect due to the decreased effectiveness of repair of DNA single-strand breaks.     

Spectral Requirements for Flower Initiation in Two Longday Plants, Rape (Brassica campestris cv. Ceres), and Spring Wheat (Triticum×aestivum)

Action spectra for the promotion of flowering by long periods of irradiation in the red and far-red regions of the spectrum have been determined by the use of interference filters. The percentage floral initiation was greatest at 710–720 um for both wheat and rape (about 1 k erg · cm^?2· s^?1). Lowering the temperature from 35 to 15°C did not shift the most effective wavelength, suggesting that the effect of high levels of radiation at 710 nm was not related to a balance between photoactivation of phytochrome and its destruction. In both wheat and rape, an increase in temperature promoted the flower-initiating action of broad-band far-red and 710 nm radiation more than the action of broadband red or 660 nm radiation. The flower-promoting effect of broad-band red and 600 nm radiation was particularly depressed by temperatures above 25°C. It is concluded that the promotion of flowering by long periods of high energy at 710 nm is caused by the activity of a high-energy pigment, rather than through a special effect of phytochrome.     

Postradiation changes in the systems of active ion transport in the CNS. Potassium ion reaccumulation by surviving brain slices

The data are reported concerning the effects of ionizing radiation (0.155 C/kg, 0.206 C/kg, and 0.31 C/kg), A2 phospholipase and short-chain fatty acids that are indicative of an essential contribution of a membrane lipid component to the effect of radiation on Na-K pump of the neuron and the universality of the mechanisms of action of ionizing radiation on organisms differing in radiosensitivity.     

The effect of electromagnetic radiation with extremely high frequency and low intensity on cytotoxic activity of human natural killer cells]

EHF electromagnetic radiation under short-time action suppresses the cytotoxical activity of the natural killer cells from granulocyte fraction and peripheral blood of healthy volunteers; the observed effect is non-linear. Under the long-time irradiation of the natural killer cells from the mononuclear fraction of blood, the suppressing effect gets a practically linear character after the 20-30 minutes action. Under the long-time irradiation of peripheral blood the insignificant stimulation of natural killers was observed. It is assumed that the radiation applied can suppress the cytotoxic activity of the natural killers, breaking the normal metabolic pathway of phosphatidylinositphosphate.     

The action of helium-neon laser radiation on the growth of Mycobacterium tuberculosis

The growth properties of M. tuberculosis subjected to the action of helium-neon laser radiation was studied. Laser radiation was shown to change the quantitative and qualitative composition of mycobacterial population. Disturbances in the viability of mycobacteria appear as a consequence of changes in the morphological structure of mycobacterial cells. The maximum effect of helium-neon laser radiation was achieved after the irradiation of M. tuberculosis culture on days 2-3 after inoculation. These results made it possible to suggest that the effect of helium-neon laser radiation was most pronounced in cells at the stage of mitosis (the logarithmic stage of growth) with the highest degree of metabolism.     

Increase in the discharge duration under the action of ion-cyclotron plasma heating in the T-11M tokamak

Results are presented from experimental and theoretical studies of the heating of a hydrogen plasma with a lithium admixture at the fundamental ion-cyclotron frequency of hydrogen in the T-11M tokamak. It is found experimentally that the action of RF radiation on a hydrogen plasma containing a small amount (less than 4%) of lithium increases the duration of the discharge current pulse. The effect of the increase in the discharge current pulse under the action of RF radiation is simulated numerically.     

Effect of vitamins A and E on the structural-functional state of retinal lysosomes

Vitamins A and E (alpha-tocopheryl-acetate and retinol-palmitate) are studied for their effect on structural and functional state of retina lysosomes. These vitamins are shown to exert a pronounced membrane-tropic effect on lysosomes. Vitamin E in chosen concentrations stabilizes membranes of retina lysosomes both in the in vitro and in vivo experiments. Vitamin A acts on them as a labilizing agent. The mentioned effect of vitamins may be corrected by low-energy radiation of the monochromatic coherent light (lambda = 632.8 nm). It is substantiated experimentally that the stabilizing effect of vitamin E may be intensified in case of the action combined with laser radiation on lysosomes. The labilizing effect of vitamin A on membranes of organelles under study may be weakened by application of laser radiation of low intensities.     

Effect of the gaseous hypoxic mixture GHM-10 on the radiosensitivity of the fetus and the development of offspring

A gas hypoxic mixture containing 10 percent of O2 and 90 percent of N2 was shown to exert a radioprotective action on pregnant rats and young rats of the first generation if animals were exposed to ionizing radiation during the periods of preimplantation, organogenesis and fetus development. The effect depended on the radiation dose and the period of the intrauterine development of fetus.     

Time effects in molecular radiation Biology

Summary Radiation action occurs over a broad timescale which extends from the very early physical processes associated with energy absorption to the very late biological effects, such as carcinogenesis which may not become apparent until many years later. The various temporal stages of radiation action are classified and their interrelationships described. Experimental projects in cellular radiation chemistry, including pulse radiolysis, are discussed, together with some applications of the techniques in this general area.The paper also deals with some aspects of the oxygen effect in radiobiology and the mechanisms of its action. Various studies employing fast response techniques have been useful in verifying the role of fast free radical reactions in the oxygen effects and examples are given of some applications. Investigations with other hypoxic cell sensitizers, the electron affinic agents, are also briefly discussed, with an account of how studies of the timescale of radiation sensitization can be valuable in understanding mechanisms. Possible mechanisms of action of radiation sensitization by oxygen and other agents, including radical fixation and direct action processes, are considered in the light of evidence from some model systems.Invited paper, presented at the 14th Annual Meeting of European Society of Radiation Biology, Jülich, Germany, October 8–14, 1978     

Effect of temperature on the modification of spectral properties of tryptophan aqueous solutions induced by water previously treated with laser radiation

It was shown that preliminary exposure of a solvent (water) to low-intensity laser radiation reduces the tryptophan fluorescence intensity, and this fluorescence quenching effect is retained throughout the temperature range explored (from 8 up to 50 degrees C). The effects found are interpreted as resulting from changes in solvent properties induced by the action of electromagnetic radiation on interaction of water molecules with solute.     

The indirect effect of radiation reduces the repair fidelity of NHEJ as verified in repair deficient CHO cell lines exposed to different radiation qualities and potassium bromate

The complexity of DNA lesions induced by ionizing radiation is mainly dependent on radiation quality, where the indirect action of radiation may contribute to different extent depending on the type of radiation under study. The effect of indirect action of radiation can be investigated by using agents that induce oxidative DNA damage or by applying free radical scavengers. The aim of this study was to investigate the role of the indirect effect of radiation for the repair fidelity of non-homologous end-joining (NHEJ), homologous recombination repair (HRR) and base excision repair (BER) when DNA damage of different complexity was induced by gamma radiation, alpha particles or from base damages (8-oxo-dG) induced by potassium bromate (KBrO(3)). CHO cells lines deficient in XRCC3 (HRR) irs1SF, XRCC7 (NHEJ) V3-3 and XRCC1 (BER) EM9 were irradiated in the absence or presence of the free radical scavenger dimethyl sulfoxide (DMSO). The endpoints investigated included rate of cell proliferation by the DRAG assay, clonogenic cell survival and the level of primary DNA damage by the comet assay. The results revealed that the indirect effect of low-LET radiation significantly reduced the repair fidelity of both NHEJ and HRR pathways. For high-LET radiation the indirect effect of radiation also significantly reduced the repair fidelity for the repair deficient cell lines. The results suggest further that the repair fidelity of the error prone NHEJ repair pathway is more impaired by the indirect effect of high-LET radiation relative to the other repair pathways studied. The response to bromate observed for the two DSB repair deficient cell lines strongly support earlier studies that bromate induces complex DNA damages. The significantly reduced repair fidelity of irs1SF and V3-3 suggests that NHEJ as well as HRR are needed for the repair, and that complex DSBs are formed after bromate exposure.