Fragmentation of extracellular DNA by long-term exposure to radiation from uranium in aquatic environments

Persistent harmful scenarios associated with disposal of radioactive waste, high-background radiation areas and severe nuclear accidents are of great concern regarding consequences to both human health and the environment. Of particular concern is the extracellular DNA in aquatic environments contaminated by radiological substances. Strand breaks induced by radiation promote decrease in the transformation efficiency for extracellular DNA. The focus of this study is the quantification of DNA damage following long-term exposure (over one year) to low doses of natural uranium (an alpha particle emitter) to simulate natural conditions, since nothing is known about alpha radiation induced damage to extracellular DNA. A high-resolution Atomic Force Microscope was used to evaluate DNA fragments. Double-stranded plasmid pBS as a model for extracellular DNA was exposed to different amounts of natural uranium. It was demonstrated that low concentrations of U in water (50 to 150 ppm) produce appreciable numbers of double strand breaks, scaling with the square of the average doses. The importance of these findings for environment monitoring of radiological pollution is addressed.Brazilian agency FAPESPFAPESP Brazilian agencyCNPq Brazilian agencyBrazilian agency CNP

Study of biophysical effects induced by the combination of exposure to Ionizing Radiation and Magnetic Fields

Campos Magnéticos de moderadas intensidades eficientemente provocam alterações em sistemas biológicos. Resultados obtidos neste Laboratório com células expostas a gamas e a Campos Elétricos Estáticos (CEE), indicaram ser este um eficiente radiossensitizador. Um CEE de 200V provocou drástica redução no ombro de reparo da D. radiodurans. Questões não respondidas, referentes à ação de Campos Magnéticos Estáticos (CME): (1) indução de efeitos biofísicos em células íntegras, e (2) interferência na viabilidade de células irradiadas. D. radiodurans, a espécie mais resistente à radiação ionizante, foi irradiada com gamas entre 0.5 e 13 kGy, no Instituto de Pesquisas Nucleares (IPEN), e imediatamente submetida aos CMEs de 0,08 T e 0,8 T. E. coli foi utilizada como controle negativo. Principais conclusões: (a) a exposição de células de D. radiodurans a altas doses de radiação e em seguida a CMEs, aumenta sua viabilidade; (b) a recuperação das células irradiadas é proporcional à intensidade do CME; (c) o processo de recuperação celular (aumento da viabilidade) é estocástico.Moderate intensities Magnetic Fields induce changes in biologic systems. Results from this Laboratory with cells exposed to both gammas and Static Electric Fields (SEF), indicates this agent as an efficient radiosensitizer. A 200V SEF caused accentuated depletion of D. radiodurans repair shoulder. Unanswered questions related to the role of Static Magnetic Fields (SMF) are: (1) induction of biophysical effects in whole cells, and (2) interference effects in irradiated cells viability. D. radiodurans, a resistant species to ionizing radiation, was exposed to gammas between 0.5 and 13 kGy, at the Nuclear Research Institute (IPEN), and immediately after exposed to SMFs of 0.08 T and 0.8 T. E. coli was employed as negative control. Mainly conclusions are: (a) exposure of D. radiodurans cells to both high doses of radiation and SMF increases its viability; (b) the viability recuperation of irradiated cells is proportional to the SMF intensity; (c) the cell recuperation process (viability increase) is stochastic

Evaluation of Uranium in Organs of Residents from an Uranium-Rich Region using Teeth as Bioindicators

The Uranium extraction and processing plant of INB (Brazilian Nuclear Industries) is in Caetité, a city located in a region hosting the largest Uranium reserve of the country. The degree of Uranium contamination in the Caetité population was investigated before using teeth as bioindicator, where a quite high Uranium concentration was measured in this region, about 160 times higher than the world-wide average. Radiobiological risks are here evaluated from Uranium burdens in organs as skeleton, kidneys, liver, tissues and blood, which were estimated from transfer coefficients and effective internal doses. This was accomplished by means of calculations with the use of the STATFLUX/ICRP approach, plus a set of Uranium transfer rate parameters as function of individual’s age assuming an uninterrupted exposure over a period of 60 years. It was found that U ingestion rates by residents of Caetité are three orders of magnitude higher than worldwide average, indicating that food and water would exhibit high levels of contamination. Calculated effective internal doses range from a minimum of one to a maximum of three orders of magnitude higher than background doses, for blood and bones respectively. The likelihood that this circumstance could lead to serious health problems as e.g. neoplasia is addressed. The methodology presented in this work offers subsidies for further studies on environmental pollution by radionuclides

Taylor's power law for ecological communities: an explanation on nonextensive/nonlinear statistical grounds

A new idea on how to conceptually interpret the so-called Taylor’s power law for ecological communities is presented. The core of our approach is based on nonextensive/nonlinear statistical concepts, which are shown to be at the genesis of all power laws, particularly when a system is constituted by long-range interacting elements. In this context, the ubiquity of the Taylor’s power law is discussed and addressed by showing that long-range interactions are at the heart of the internal dynamics of populations.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

DNA fragmentation by gamma radiation and electron beams using atomic force microscopy

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Double-stranded pBS plasmid DNA was irradiated with gamma rays at doses ranging from 1 to 12 kGy and electron beams from 1 to 10 kGy. Fragment-size distributions were determined by direct visualization, using atomic force microscopy with nanometer-resolution operating in non-tapping mode, combined with an improved methodology. The fragment distributions from irradiation with gamma rays revealed discrete-like patterns at all doses, suggesting that these patterns are modulated by the base pair composition of the plasmid. Irradiation with electron beams, at very high dose rates, generated continuous distributions of highly shattered DNA fragments, similar to results at much lower dose rates found in the literature. Altogether, these results indicate that AFM could supplement traditional methods for high-resolution measurements of radiation damage to DNA, while providing new and relevant information.383531542Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

DNA fragmentation by gamma radiation and electron beams using atomic force microscopy

Double-stranded pBS plasmid DNA was irradiated with gamma rays at doses ranging from 1 to 12 kGy and electron beams from 1 to 10 kGy. Fragment-size distributions were determined by direct visualization, using atomic force microscopy with nanometer-resolution operating in non-tapping mode, combined with an improved methodology. The fragment distributions from irradiation with gamma rays revealed discrete-like patterns at all doses, suggesting that these patterns are modulated by the base pair composition of the plasmid. Irradiation with electron beams, at very high dose rates, generated continuous distributions of highly shattered DNA fragments, similar to results at much lower dose rates found in the literature. Altogether, these results indicate that AFM could supplement traditional methods for high-resolution measurements of radiation damage to DNA, while providing new and relevant information.FAPESPCNP