Efecte biològic dels raigs X de baixa energia, utilitzats en mamografies

Actualment s'assumeix que tots els raigs X, independentment de la seva energia, tenen el mateix efecte. Tot i així, hi ha estudis científics que ho qüestionen, i indiquen que els raigs X de baixa energia (com els que s'utilitzen en les mamografies) podrien tenir un efecte superior a l'assumit fins ara. Investigadors del grup de recerca d'"Estudis citogenètics i moleculars dels efectes de les radiacions ionitzants i del càncer" de la UAB han avaluat el dany produït pels raigs X de 30 kVp i els seus resultats semblen indicar que és superior al produït per raigs X d'energies més elevades.Actualmente se asume que todos los rayos X, independientemente de su energía, tienen el mismo efecto. Sin embargo, hay estudios científicos que lo cuestionan e indican que los rayos X de baja energía (como los que se utilizan en las mamografías) podrían tener unefecto superior que el asumido hasta ahora. Investigadores del grupo de investigación "Estudios citogenéticos y moleculares de los efectos de las radiaciones ionizantes y del cáncer"de la UAB han evaluado el daño producido por rayos X de 30 kVp y sus resultados parecen indicar que es superior al producido por rayos X de energías más elevadas

A New Model of Biodosimetry to Integrate Low and High Doses

Biological dosimetry, that is the estimation of the dose of an exposure to ionizing radiation by a biological parameter, is a very important tool in cases of radiation accidents. The score of dicentric chromosomes, considered to be the most accurate method for biological dosimetry, for low LET radiation and up to 5 Gy, fits very well to a linear-quadratic model of dose-effect curve assuming the Poisson distribution. The accuracy of this estimation raises difficulties for doses over 5 Gy,the highest dose of the majority of dose-effect curves used in biological dosimetry. At doses over 5 Gy most cells show difficulties in reaching mitosis and cannot be used to score dicentric chromosomes. In the present study with the treatment of lymphocyte cultures with caffeine and the standardization of the culture time, metaphases for doses up to 25 Gy have been analyzed. Here we present a new model for biological dosimetry, which includes a Gompertz-type function as the dose response, and also takes into account the underdispersion of aberrationamong-cell distribution. The new model allows the estimation of doses of exposures to ionizing radiation of up to 25 Gy. Moreover, the model is more effective in estimating whole and partial body exposures than the classical method based on linear and linear-quadratic functions, suggesting their effectiveness and great potential to be used after high dose exposures of radiation

Cell to Cell Variability of Radiation-Induced Foci : relation between Observed Damage and Energy Deposition

Most studies that aim to understand the interactions between different types of photon radiation and cellular DNA assume homogeneous cell irradiation, with all cells receiving the same amount of energy. The level of DNA damage is therefore generally determined by averaging it over the entire population of exposed cells. However, evaluating the molecular consequences of a stochastic phenomenon such as energy deposition of ionizing radiation by measuring only an average effect may not be sufficient for understanding some aspects of the cellular response to this radiation. The variance among the cells associated with this average effect may also be important for the behaviour of irradiated tissue. In this study, we accurately estimated the distribution of the number of radiation-induced γH2AX foci (RIF) per cell nucleus in a large population of endothelial cells exposed to 3 macroscopic doses of gamma rays from 60Co. The number of RIF varied significantly and reproducibly from cell to cell, with its relative standard deviation ranging from 36% to 18% depending on the macroscopic dose delivered. Interestingly, this relative cell-to-cell variability increased as the dose decreased, contrary to the mean RIF count per cell. This result shows that the dose effect, in terms of the number of DNA lesions indicated by RIF is not as simple as a purely proportional relation in which relative SD is constant with dose. To analyse the origins of this observed variability, we calculated the spread of the specific energy distribution for the different target volumes and subvolumes in which RIF can be generated. Variances, standard deviations and relative standard deviations all changed similarly from dose to dose for biological and calculated microdosimetric values. This similarity is an important argument that supports the hypothesis of the conservation of the association between the number of RIF per nucleus and the specific energy per DNA molecule. This comparison allowed us to calculate a volume of 1.6 μm3 for which the spread of the specific energy distribution could explain the entire variability of RIF counts per cell in an exposed cell population. The definition of this volume may allow to use a microdosimetric quantity to predict heterogeneity in DNA damage. Moreover, this value is consistent with the order of magnitude of the volume occupied by the hydrated sugar-phosphate backbone of the DNA molecule, which is the part of the DNA molecule responsible for strand breaks

A Natural Human Retrovirus Efficiently Complements Vectors Based on Murine Leukemia Virus

Background: Murine Leukemia Virus (MLV) is a rodent gammaretrovirus that serves as the backbone for common gene delivery tools designed for experimental and therapeutic applications. Recently, an infectious gammaretrovirus designated XMRV has been identified in prostate cancer patients. The similarity between the MLV and XMRV genomes suggests a possibility that the two viruses may interact when present in the same cell. Methodology/Principal Findings: We tested the ability of XMRV to complement replication-deficient MLV vectors upon coinfection of cultured human cells. We observed that XMRV can facilitate the spread of these vectors from infected to uninfected cells. This functional complementation occurred without any gross rearrangements in the vector structure, and the co-infected cells produced as many as 10 4 infectious vector particles per milliliter of culture medium. Conclusions/Significance: The possibility of encountering a helper virus when delivering MLV-based vectors to human cells in vitro and in vivo needs to be considered to ensure the safety of such procedures

Concentration-Dependent Protection by Ethanol Extract ofPropolis against γ-Ray-Induced Chromosome Damage in HumanBlood Lymphocytes

[EN] Radioprotection with natural products may be relevant to the mitigation of ionizing radiation-induced damage in mammalian systems; in this sense, propolis extracts have shown effects such as antioxidant, antitumoral, anti-inflammatory, and immunostimulant. We report for the first time a cytogenetic study to evaluate the radioprotective effect, in vitro, of propolis against radiation-induced chromosomal damage. Lymphocytes were cultured with increasing concentrations of ethanol extract of propolis (EEP), including 20, 40, 120, 250, 500, 750, 1000, and 2000 ¿g mL-1 and then exposed to 2 Gy ¿-rays. A significant and concentration-dependent decrease is observed in the frequency of chromosome aberrations in samples treated with EEP. The protection against the formation of dicentrics was concentration-dependent, with a maximum protection at 120 ¿g mL-1 of EEP. The observed frequency of dicentrics is described as negative exponential function, indicating that the maximum protectible fraction of dicentrics is approximately 44. Free radical scavenging and antioxidant activities are the mechanisms that these substances use to protect cells from ionizing radiation. Copyright © 2011 A. Montoro et al.This research was supported in part by the Company Dieteticos Intersa S.A., U.P.V., and Hospital Universitario La Fe of Valencia and Consejo de Seguridad Nuclear (2696/SRO). The authors express their appreciation to Dr. Pepe Perez (Hospital Universitario La Fe) and Dr. Alberto Yuste (U.P.V.).Montoro, A.; Barquinero, J.; Almonacid, M.; Montoro, A.; Sebastià, N.; Verdú Martín, GJ.; Sahuquillo, V.... (2011). Concentration-Dependent Protection by Ethanol Extract ofPropolis against γ-Ray-Induced Chromosome Damage in HumanBlood Lymphocytes. Evidence-based Complementary and Alternative Medicine. 1-7. doi:10.1155/2011/174853S1

Módulos MMIC multifunción para aplicaciones espaciales

This paper presents the design of multifunction monolithic microwave integrated circuits (MMIC) to be used in transmit/receive modules for onboard satellite applications. Two chips have been developed: one for frequency generation including a negatron VCO, a frequency tripler and a digital frequency divider, and a second for signal amplification and conversion including AGC amplifiers and mixers. The goal of the work is to reduce the number and size (and consequently the cost) of the circuitry actually in use, without sacrificing system performance, through the use of a mature GaAs PHEMT technology. Issues such as suitable circuit topologies, dc power consumption, circuit area minimization and optimization are all important factors addressed during the project

Review of retrospective dosimetry techniques for external ionising radiation exposures

The current focus on networking and mutual assistance in the management of radiation accidents or incidents has demonstrated the importance of a joined-up approach in physical and biological dosimetry. To this end, the European Radiation Dosimetry Working Group 10 on 'Retrospective Dosimetry' has been set up by individuals from a wide range of disciplines across Europe. Here, established and emerging dosimetry methods are reviewed, which can be used immediately and retrospectively following external ionising radiation exposure. Endpoints and assays include dicentrics, translocations, premature chromosome condensation, micronuclei, somatic mutations, gene expression, electron paramagnetic resonance, thermoluminescence, optically stimulated luminescence, neutron activation, haematology, protein biomarkers and analytical dose reconstruction. Individual characteristics of these techniques, their limitations and potential for further development are reviewed, and their usefulness in specific exposure scenarios is discussed. Whilst no single technique fulfils the criteria of an ideal dosemeter, an integrated approach using multiple techniques tailored to the exposure scenario can cover most requirements. © The Author 2010. Published by Oxford University Press. All rights reserved

Polymorphisms in MDM2 and TP53 genes and risk of developing therapy-related myeloid neoplasms

One of the most severe complications after successful cancer therapy is the development of therapy-related myeloid neoplasms (t-MN). Constitutional genetic variation is likely to impact on t-MN risk. We aimed to evaluate if polymorphisms in the p53 pathway can be useful for predicting t-MN susceptibility. First, an association study revealed that the Pro variant of the TP53 Arg72Pro polymorphism and the G allele of the MDM2 SNP309 were associated with t-MN risk. The Arg variant of TP53 is more efficient at inducing apoptosis, whereas the Pro variant is a more potent inductor of cell cycle arrest and DNA repair. As regards MDM2 SNP309, the G allele is associated with attenuation of the p53 apoptotic response. Second, to evaluate the biological effect of the TP53 polymorphism, we established Jurkat isogenic cell lines expressing p53Arg or p53Pro. Jurkat p53Arg cells presented higher DNA damage and higher apoptotic potential than p53Pro cells, after treatment with chemotherapy agents. Only p53Pro cells presented t(15;17) translocation and del(5q). We suggest that failure to repair DNA lesions in p53Arg cells would lead them to apoptosis, whereas some p53Pro cells, prone to cell cycle arrest and DNA repair, could undergo misrepair, generating chromosomal abnormalities typical of t-MN