Removal of Nonvolatile Hydrophobic Compounds from Artificially and Naturally Contaminated Soils by Column Flotation

Removal of a nonvolatile paraffin oil from spiked soils using column flotation with countercurrent bubbles was explored at both ambient and elevated temperatures. Up to 80% of the contaminant was separated from the coarse fraction (250 to 800?µm) by flotation at 45°C using aqueous solutions of anionic and nonionic surfactants or alkali salt as collectors. With the 75 to 800?µm fraction, removal efficiencies of up to 65% was achieved. Sodium dodecyl-sulfate and Triton 100X at 50?ppm concentrations as well as sodium carbonate at pH 10 were found to yield similar removal efficiencies. Same surfactants were tested in soil washing experiments at similar and higher dosages. Removal efficiency by flotation was higher than those obtained by soil washing in all cases. In addition, as high surfactant dosage are not used in flotation, unlike in the case of soil washing, the problem of formation of stable emulsions was absent. Experiments with soil polluted by hydrocarbons from a contaminated site demonstrated the feasibility of the flotation process for decontamination of coarse (250 to 830?µm) fractions. A 70% reduction of petroleum hydrocarbon in soil was achieved as a result of flotation at 45°C using the above surfactants.     

Effects of Ionizing Radiation on Bacterial DNA-membrane Complexes

THE model proposed by Alper¹ for lethal radiation damage to cells is based on inferential evidence that there are two important sites of damage by ionizing radiation. At one site, damage referred to as type “N” is associated with a low oxygen enhancement ratio (OER) and is probably to nucleic acid, while at the other site, type “O” damage is associated with a considerably higher oxygen enhancement value and is to a non-nucleic acid target. The model demands that the two values of OER are respectively less and greater than that observed for the overall lethal effect. More recently² Alper reviewed further inferential evidence³ that cell membranes are the site of type O damage, though there may be subsequent interaction with the lesions following energy deposition in DNA⁴.     

Effects of Actinomycin D and Ultraviolet and Ionizing Radiation on Pichinde Virus

Actinomycin D (0.05 μg/ml) suppresses the synthesis of ribosomal RNA of baby hamster kidney (BHK21) cells. The production of infectious Pichinde virus was enhanced in the presence of actinomycin D, although the production of virus particles was not substantially different from cultures inoculated in the absence of the drug. By prelabeling BHK21 cells with ³H-uridine and then allowing the virus to replicate in the presence of actinomycin D, it was possible to show that ribosomal RNA synthesized prior to infection was incorporated into the virion. A single-hit kinetics of inactivation of Pichinde virus was observed with ultraviolet light, suggesting that the virus contains only a single copy of genome per virion. Comparison of the inactivation kinetics by gamma irradiation of Pichinde virus with Sindbis and rubella virus indicated that the radiosensitive genome of Pichinde virus was about 6 × 10⁶ to 8 × 10⁶ daltons. This value is greater than the 3.2 × 10⁶ daltons which was estimated by biochemical analysis. One possible explanation considered is that the ribosomal RNA of host cell origin is functional and accounts for the differences in genome size estimated by the two methods.     

Effect of Ionizing Radiation on Immunity

Ionizing radiation has a deleterious effect on the immunity mechanism, particularly when large but sublethal doses are applied over a short period of time. The hematopoietic system is extremely sensitive, and a fall in the lymphocytes is one of the most characteristic manifestations. The normal balance of the microflora of the intestinal and respiratory tracts is disturbed, which results in a bacteremia and may lead to death of the host. Active immunity is seriously interfered with if the irradiation occurs shortly before the injection of an antigen. There is also reduced resistance to pathogenic micro-organisms, which may lead to fatal infections. Prolonged irradiation at low levels does not seem to affect immunity adversely. Active immunization should be carried out well in advance of exposure to radiation, and supportive treatment commenced immediately after exposure to large doses.     

Ionizing Radiation and the Physician

The increasing awareness of the medical profession and the general public of the dangers associated with ionizing radiation necessitates a thorough understanding by the physician of the uses and dangers of this hazard. In addition to their application in the fields of diagnosis and therapeutic radiology, x-rays and radioisotopes are increasingly used in research laboratories and in various industries. The effects of low levels of ionizing radiation are still uncertain and it is possible that there is a “threshold” dose at which cellular damage is evident. With the increased number of atmospheric nuclear tests the concentrations of strontium-90, cesium-137, and the shorter lived isotopes such as iodine-131 in food will increase. The present levels of these isotopes do not merit concern and their early efficient removal will assure continued low fallout levels in our major food supplies.     

Effects of Dimeric Bisbenzimidazoles and Ionizing Radiation on MCF-7 Breast Cancer Stem Cells

Biophysics - Abstract—This study aimed to determine how to eliminate and/or increase the radiosensitivity of a population of cancer stem cells that are responsible for radioresistance in...     

Effects of Ionizing Radiation on Synchronous Cultures of Escherichia coli B/r

The sensitivity of Escherichia coli B/r to X-irradiation is correlated with the replication cycle of deoxyribonucleic acid (DNA). The sensitivity to X-irradiation in the wild type can be attributed to the presence of nuclear targets plus DNA repair mechanisms. The effects of nuclear targets are observed in the recombination-deficient (rec−) mutant B/r, but the sensitivity reflected by changes in the slope of killing curves is absent. A study of different growth conditions indicates that maximal resistance to X rays occurs toward the middle of the division cycle. Evidence is offered that branched chromosomes respond as one-hit targets to X-irradiation. The killing effects of heavy-ion bombardment on E. coli are due primarily to ionizing radiation.     

The Study of Ionizing Radiation Effects on Escherichia coli by Density Gradient Sedimentation

Density gradient sedimentation of bacterial cells in cesium chloride has been used to separate cells which have been irradiated with ⁶⁰Co gamma rays and have lost an appreciable amount of their DNA by subsequent degradation. Irradiated cells are found to band mainly at two characteristic densities, one corresponding to normal unirradiated cells and the other at a considerably lower density. The region corresponding to normal density cells is the only one that contains cells which will form colonies. Cells capable of synthesizing DNA following irradiation are found mainly at the region of normal density cells with some spreading into the lower density region. Cells in the lower density region contain less DNA than normal density cells. From an analysis of the relative numbers of cells in the two regions, it is suggested that the process of DNA degradation either takes place to a considerable extent in the genome or not at all. Analysis of the data in terms of numbers of cells having intact DNA and those having degraded DNA indicates a strong correlation between DNA degradation and cell death in this strain, JG151, and suggests that DNA degradation is a major but not the only cause of cell death.     

The Inhibitory Effects of Low-Dose Ionizing Radiation in IgE-Mediated Allergic Responses

Ionizing radiation has different biological effects according to dose and dose rate. In particular, the biological effect of low-dose radiation is unclear. Low-dose whole-body gamma irradiation activates immune responses in several ways. However, the effects and mechanism of low-dose radiation on allergic responses remain poorly understood. Previously, we reported that low-dose ionizing radiation inhibits mediator release in IgE-mediated RBL-2H3 mast cell activation. In this study, to have any physiological relevance, we investigated whether low-dose radiation inhibits allergic responses in activated human mast cells (HMC-1(5C6) and LAD2 cells), mouse models of passive cutaneous anaphylaxis and the late-phase cutaneous response. High-dose radiation induced cell death, but low-dose ionizing radiation of <0.5 Gy did not induce mast cell death. Low-dose ionizing radiation that did not induce cell death significantly suppressed mediator release from human mast cells (HMC-1(5C6) and LAD2 cells) that were activated by antigen-antibody reaction. To determine the inhibitory mechanism of mediator released by low-dose ionizing radiation, we examined the phosphorylation of intracellular signaling molecules such as Lyn, Syk, phospholipase Cγ, and protein kinase C, as well as the intracellular free Ca²⁺ concentration ([Ca²⁺]_i). The phosphorylation of signaling molecules and [Ca²⁺]_i following stimulation of FcεRI receptors was inhibited by low dose ionizing radiation. In agreement with its in vitro effect, ionizing radiation also significantly inhibited inflammatory cells infiltration, cytokine mRNA expression (TNF-α, IL-4, IL-13), and symptoms of passive cutaneous anaphylaxis reaction and the late-phase cutaneous response in anti-dinitrophenyl IgE-sensitized mice. These results indicate that ionizing radiation inhibits both mast cell-mediated immediate- and delayed-type allergic reactions in vivo and in vitro.     

The Acute Effects of Ionizing Radiation on DNA Synthesis and the Development of Antibody-Producing Cells

Ionizing radiation inhibited the development of specific haemolysin-producing cells (PFC) and depressed the incorporation of (³H) thymidine by rabbit spleen explants responding to SRC in the culture medium. In contrast to these effects, the rates of incorporation of precursors for protein and RNA synthesis were much less affected. The depression of (³H) thymidine incorporation was found to result from a quantitative reduction of new DNA synthesis, without any change in the proportion of labelled cells, at any time after irradiation. The DNA synthesis occurring in these cells preparing to develop antibody-producing capacity was thus radio-sensitive, but the exact nature of the defect resulting from exposure to radiation requires further study.     

The Robustness of Naturally and Artificially Selected Nucleic Acid Secondary Structures

Thermodynamic stability and mutational robustness of secondary structure are critical to the function and evolutionary longevity of RNA molecules. We hypothesize that natural and artificial selection for functional molecules favors the formation of structures that are stable to both thermal and mutational perturbation. There is little direct evidence, however, that functional RNA molecules have been selected for their stability. Here we use thermodynamic secondary structure prediction algorithms to compare the thermal and mutational robustness of over 1000 naturally and artificially evolved molecules. Although we find evidence for the evolution of both types of stability in both sets of molecules, the naturally evolved functional RNA molecules were significantly more stable than those selected in vitro, and artificially evolved catalysts (ribozymes) were more stable than artificially evolved binding species (aptamers). The thermostability of RNA molecules bred in the laboratory is probably not constrained by a lack of suitable variation in the sequence pool but, rather, by intrinsic biases in the selection process.     

Persistence of Caliciviruses in Artificially Contaminated Oysters during Depuration

The fate of calicivirus in oysters in a 10-day depuration was assessed. The norovirus gene was persistently detected from artificially contaminated oysters during the depuration, whereas feline calicivirus in oysters was promptly eliminated. The prolonged observation of norovirus in oysters implies the existence of a selective retention mechanism for norovirus within oysters.     

Some Short-Term Cell Kinetic Effects of Ionizing Radiation On Mouse Bladder Urothelium

Abstract. Early morphological changes and the pattern of reactive proliferation of the hairless mouse urinary bladder urothelium after irradiation are reported. Groups of female hairless mice were anaesthetized with sodium pentobarbital and irradiated over the bladder region with 0, 10, 20 and 30 Gy. Control groups were sham-treated. Short-term cell kinetic changes were monitored using incorporation of tritiated thymidine and flow cytometry. Only minor radiation-induced alterations in the cell kinetic pattern were recorded, and no significant histomorphological changes were seen. However, a marked increase in the thymidine incorporation was seen in the control animals on the first day after anaesthesia. Radiation proctitis induced early deaths in the 30 Gy irradiated animals. the present results are in accordance with commonly accepted radiobiological theories, but not in agreement with results previously published by others     

电离辐射诱导基因的研究进展

电离辐射诱导基因是一类受电离辐射调控表达的基因,其表达随辐射条件和所处生理环境的不同呈现复杂多变的特征。电离辐射诱导基因参与细胞内各种代谢途径,在细胞周期调控、细胞生长调节、细胞凋亡、DNA损伤修复中发挥着重要的作用。介绍了电离辐射诱导基因的种类、功能,及其引起的生物效应的分子机制及应用。