Sophisticated security verification on routing repaired balanced cell-based dual-rail logic against side channel analysis

Conventional dual-rail precharge logic suffers from difficult implementations of dual-rail structure for obtaining strict compensation between the counterpart rails. As a light-weight and high-speed dual-rail style, balanced cell-based dual-rail logic (BCDL) uses synchronised compound gates with global precharge signal to provide high resistance against differential power or electromagnetic analyses. BCDL can be realised from generic field programmable gate array (FPGA) design flows with constraints. However, routings still exist as concerns because of the deficient flexibility on routing control, which unfavourably results in bias between complementary nets in security-sensitive parts. In this article, based on a routing repair technique, novel verifications towards routing effect are presented. An 8 bit simplified advanced encryption processing (AES)-co-processor is executed that is constructed on block random access memory (RAM)-based BCDL in Xilinx Virtex-5 FPGAs. Since imbalanced routing are major defects in BCDL, the authors can rule out other influences and fairly quantify the security variants. A series of asymptotic correlation electromagnetic (EM) analyses are launched towards a group of circuits with consecutive routing schemes to be able to verify routing impact on side channel analyses. After repairing the non-identical routings, Mutual information analyses are executed to further validate the concrete security increase obtained from identical routing pairs in BCDL.

Análisis de la eficiencia de los sistemas de colonias de hormigas para problemas de accesibilidad

A pesar de los avances en materia de predicción, los desastres naturales siguen teniendo consecuencias devastadoras. Entre los principales problemas a los que se enfrentan los equipos de ayuda y rescate después de un desastre natural o provocado por el hombre se encuentra la planificación de las tareas de reparación de carreteras para conseguir la máxima ventaja de los limitados recursos económicos y humanos. En la presente Tesis Fin de Máster se intenta dar solución al problema de la accesibilidad, es decir, maximizar el número de supervivientes que consiguen alcanzar el centro regional más cercano en un tiempo mínimo mediante la planificación de qué carreteras rurales deberían ser reparadas dados unos recursos económicos y humanos limitados. Como se puede observar, es un problema combinatorio ya que el número de planes de reparación y conexiones entre las ciudades y los centros regionales crece de forma exponencial con el tamaño del problema. Para la resolución del problema se comienza analizando una adaptación básica de los sistemas de colonias de hormigas propuesta por otro autor y se proponen múltiples mejoras sobre la misma. Posteriormente, se propone una nueva adaptación más avanzada de los sistemas de colonias de hormiga al problema, el ACS con doble hormiga. Este sistema hace uso de dos tipos distintos de hormigas, la exploradora y la trabajadora, para resolver simultáneamente el problema de encontrar los caminos más rápidos desde cada ciudad a su centro regional más cercano (exploradora), y el de obtener el plan óptimo de reparación que maximice la accesibilidad de la red (trabajadora). El algoritmo propuesto se ilustra por medio de un ejemplo de gran tamaño que simula el desastre natural ocurrido en Haití, y su rendimiento es comparado con la combinación de dos metaheurísticas, GRASP y VNS.---ABSTRACT---In spite of the advances in forecasting, natural disaster continue to ocasionate devastating consequences. One of the main problems relief teams face after a natural or man-made disaster is how to plan rural road repair work to take maximum advantage of the limited available financial and human resources. In this Master´s Final Project we account for the accesability issue, that is, to maximize the number of survivors that reach the nearest regional center in a minimum time by planning whic rural roads should be repaired given the limited financial and human resources. This is a combinatorial problem since the number of possible repairing solutions and connections between cities and regional centers grows exponentially with the size of the problem. In order to solve the problem, we analyze the basic ant colony system adaptation proposed by another author and point out multiple improvements on it. Then, we propose a novel and more advance adaptation of the ant colony systems to the problem, the double- ant ACS. This system makes use of two diferent type of ants, the explorer and the worker, to simultaneously solve the problem of finding the shorthest paths from each city to their nearest regional center (explorer), and the problem of identifying the optimal repairing plan that maximize the network accesability (worker). The proposed algorithm is illustrated by means of a big size example that simulates the natural disaster occurred in Haiti, and its performance is compared with a combination of two metaheuristics, GRASP and VNS.

Sistemas de ayuda al diagnóstico y a la terapia funcional en enfermedades neurodegenerativas

El incremento de la esperanza de vida en los países desarrollados (más de 80 años en 2013), está suponiendo un crecimiento considerable en la incidencia y prevalencia de enfermedades discapacitantes, que si bien pueden aparecer a edades tempranas, son más frecuentes en la tercera edad, o en sus inmediaciones. Enfermedades neuro-degenerativas que suponen un gran hándicap funcional, pues algunas de ellas están asociadas a movimientos involuntarios de determinadas partes del cuerpo, sobre todo de las extremidades. Tareas cotidianas como la ingesta de alimento, vestirse, escribir, interactuar con el ordenador, etc… pueden llegar a ser grandes retos para las personas que las padecen. El diagnóstico precoz y certero resulta fundamental para la prescripción de la terapia o tratamiento óptimo. Teniendo en cuenta incluso que en muchos casos, por desgracia la mayoría, sólo se puede actuar para mitigar los síntomas, y no para sanarlos, al menos de momento. Aun así, acertar de manera temprana en el diagnóstico supone proporcionar al enfermo una mayor calidad de vida durante mucho más tiempo, por lo cual el esfuerzo merece, y mucho, la pena. Los enfermos de Párkinson y de temblor esencial suponen un porcentaje importante de la casuística clínica en los trastornos del movimiento que impiden llevar una vida normal, que producen una discapacidad física y una no menos importante exclusión social. Las vías de tratamiento son dispares de ahí que sea crítico acertar en el diagnóstico lo antes posible. Hasta la actualidad, los profesionales y expertos en medicina, utilizan unas escalas cualitativas para diferenciar la patología y su grado de afectación. Dichas escalas también se utilizan para efectuar un seguimiento clínico y registrar la historia del paciente. En esta tesis se propone una serie de métodos de análisis y de identificación/clasificación de los tipos de temblor asociados a la enfermedad de Párkinson y el temblor esencial. Empleando técnicas de inteligencia artificial basadas en clasificadores inteligentes: redes neuronales (MLP y LVQ) y máquinas de soporte vectorial (SVM), a partir del desarrollo e implantación de un sistema para la medida y análisis objetiva del temblor: DIMETER. Dicho sistema además de ser una herramienta eficaz para la ayuda al diagnóstico, presenta también las capacidades necesarias para proporcionar un seguimiento riguroso y fiable de la evolución de cada paciente. ABSTRACT The increase in life expectancy in developed countries in more than 80 years (data belongs to 2013), is assuming considerable growth in the incidence and prevalence of disabling diseases. Although they may appear at an early age, they are more common in the elderly ages or in its vicinity. Nuero-degenerative diseases that are a major functional handicap, as some of them are associated with involuntary movements of certain body parts, especially of the limbs. Everyday tasks such as food intake, dressing, writing, interact with the computer, etc ... can become large debris for people who suffer. Early and accurate diagnosis is crucial for prescribing optimal therapy or treatment. Even taking into account that in many cases, unfortunately the majority, can only act to mitigate the symptoms, not to cure them, at least for now. Nevertheless, early diagnosis may provide the patient a better quality of life for much longer time, so the effort is worth, and much, grief. Sufferers of Parkinson's and essential tremor represent a significant percentage of clinical casuistry in movement disorders that prevent a normal life, leading to physical disability and not least social exclusion. There are various treatment methods, which makes it necessary the immediate diagnosis. Up to date, professionals and medical experts, use a qualitative scale to differentiate the disease and degree of involvement. Therefore, those scales are used in clinical follow-up. In this thesis, several methods of analysis and identification / classification of types of tremor associated with Parkinson's disease and essential tremor are proposed. Using artificial intelligence techniques based on intelligent classification: neural networks (MLP and LVQ) and support vector machines (SVM), starting from the development and implementation of a system for measuring and objective analysis of the tremor: DIMETER. This system besides being an effective tool to aid diagnosis, it also has the necessary capabilities to provide a rigorous and reliable monitoring of the evolution of each patient.

Desarrollo sostenible de la construcción naval: dinámica evolutiva y eco-innovación en el sector de reparaciones europeo

El impacto ambiental directo de la construcción naval, que se refiere a la construcción, mantenimiento y reparación de buques, no es de ninguna manera pequeño. La construcción de buques depende de un gran número de procesos que por sí mismos constituyen un riesgo significativo de daño medio ambiental en el entorno de los astilleros y que conducen a emisiones significativas de gases de efecto invernadero. Además, la construcción naval utiliza algunos materiales que no sólo puede llevar a graves consecuencias para el daño ambiental durante su producción y su uso en el proceso de construcción de la nave, sino también posteriormente durante la reparación de buques, el funcionamiento y las actividades de reciclaje. (OECD 2010) El impacto ambiental directo de la construcción naval constituye de por sí, un desafío importante para la industria. Pero este impacto no queda limitado a su entorno inmediato, aunque la Construcción Naval no es directamente responsable de la repercusión en el medio ambiente de la operación y el reciclaje de buques comerciales, si es una parte integral de estas actividades. (OECD 2010) En esta tesis se sugiere que el sector de la construcción naval puede y debe aceptar sus responsabilidades ambientales no solo en el entorno del astillero; también en la operación de los buques, sus productos; tomando conciencia, a través de un enfoque de ciclo de vida, del desempeño ambiental de la industria en su conjunto. Es necesario intensificar esfuerzos a medida que el impacto ambiental de la industria es cada vez más visible en el dominio público, en pro de un crecimiento verde que permita aumentar la capacidad de actividad o producción económica al tiempo que reduce o elimina, los impactos ambientales. Este será un imperativo para cualquier futura actividad industrial y exigirá naturalmente conocimiento ambiental intrincado perteneciente a todos los procesos asociados. Esta tesis - aprovechando como valiosa fuente de información los desarrollos y resultados del proyecto europeo: “Eco_REFITEC”. FP7-CP-266268, coordinado por el autor de esta Tesis, en nombre de la Fundación Centro Tecnológico SOERMAR - tiene como primer objetivo Investigar la interpretación del concepto de Construcción Naval y Transporte Marítimo sostenible así como las oportunidades y dificultades de aplicación en el sector de la Construcción y reparación Naval. Ello para crear o aumentar el entendimiento de la interpretación del concepto de transporte marítimo sostenible y la experiencia de su aplicación en particular en los astilleros de nuevas construcciones y reparación. Pretende también contribuir a una mejor comprensión de la industria Marítima y su impacto en relación con el cambio climático, y ayudar en la identificación de áreas para la mejora del desempeño ambiental más allá de las operaciones propias de los astilleros; arrojando luz sobre cómo puede contribuir la construcción naval en la mejora de la eficiencia y en la reducción de emisiones de CO2 en el transporte marítimo. Se espera con este enfoque ayudar a que la Industria de Construcción Naval vaya abandonando su perspectiva tradicional de solo mirar a sus propias actividades para adoptar una visión más amplia tomando conciencia en cuanto a cómo sus decisiones pueden afectar posteriormente las actividades aguas abajo, y sus impactos en el medio ambiente, el cambio climático y el crecimiento verde. Si bien cada capítulo de la tesis posee su temática propia y una sistemática específica, a su vez retoma desde una nueva perspectiva cuestiones importantes abordadas en otros capítulos. Esto ocurre especialmente con algunos ejes que atraviesan toda la tesis. Por ejemplo: la íntima relación entre el transporte marítimo y el sector de construcción naval, la responsabilidad de la política internacional y local, la invitación a buscar nuevos modos de construir el futuro del sector a través de la consideración de los impactos ambientales, económicos y sociales a lo largo de ciclo de vida completo de productos y servicios. La necesidad de una responsabilidad social corporativa. Estos temas no se cierran ni terminan, sino que son constantemente replanteados tratando de enriquecerlos. ABSTRACT The direct environmental impact of shipbuilding, which refers to construction, maintenance and repair of vessels, is by no means small. Shipbuilding depends on a large number of processes which by themselves constitute significant risks of damage to the shipyards‘ surrounding environment and which lead to significant emissions of greenhouse gases. In addition, shipbuilding uses some materials which not only may carry serious implications for environmental harm during their production and usage in the ship construction process, but also subsequently during ship repairing, operation, and recycling activities. (OECD 2010) The direct environmental impact of shipbuilding constitutes a major challenge for the industry. But this impact is not limited on their immediate surroundings, but while not being directly responsible for the impact on the environment from the operation and final recycling of commercial ships, shipbuilding is an integral part of these activities. (OECD 2010) With this in mind, this thesis is suggested that the shipbuilding industry can and must take up their environmental responsibilities not only on their immediate surroundings, also on the ships operation, becoming aware through a “life cycle” approach to ships, the environmental performance of the industry as a whole. As the environmental impact of the industry is becoming increasingly visible in the public domain much more effort is required for the sake of “green growth” which implies the ability to increase economic activity or output while lowering, or eliminating, environmental impacts. This will be an imperative for any future industrial activity and will naturally demand intricate environmental knowledge pertaining to all associated processes. This thesis making use as a valuable source of information of the developments and results of an European FP7-collaborative project called "Eco_REFITEC, coordinated by the author of this thesis on behalf of the Foundation Center Technology SOERMAR, has as its primary objective to investigate the interpretation of a sustainable Shipbuilding and Maritime Transport concept and the challenges and opportunities involved in applying for the Shipbuilding and ship repair Sector. It is done to improve the current understanding regarding sustainable shipping and to show the application experience in shipbuilding and ship repair shipyards. Assuming that sustainability is more than just an act but a process, this academic work it also aims to contribute to a much better understanding of the maritime industry and its impact with respect to climate change, and help in identifying areas for better environmental performance beyond the shipyard's own operations; shedding light on how shipbuilding can contribute in improving efficiency and reducing CO2 emissions in shipping. It is my hope that this thesis can help the Shipbuilding Industry to abandon its traditional perspective where each simply looks at its own activities to take a broader view becoming aware as to how their decisions may further affect downstream activities and their impacts on the environment, climate change and green growth. Although each chapter will have its own subject and specific approach, it will also take up and re-examine important questions previously dealt with. This is particularly the case with a number of themes which will reappear as the thesis unfolds. As example I will point to the intimate relationship between the shipping and shipbuilding industry, the responsibility of international and local policy, the call to seek other ways of building the future of the sector through the consideration of the environmental, economic and social impacts over the full life cycle of the products and services, the need for a corporate social responsibility. These questions will not be dealt with once and for all, but reframed and enriched again and again.

Adult brain retains the potential to generate oligodendroglial progenitors with extensive myelination capacity

Remyelination of focal areas of the central nervous system (CNS) in animals can be achieved by transplantation of glial cells, yet the source of these cells in humans to similarly treat myelin disorders is limited at present to fetal tissue. Multipotent precursor cells are present in the CNS of adult as well as embryonic and neonatal animals and can differentiate into lineage-restricted progenitors such as oligodendroglial progenitors (OPs). The OPs present in adults have a different phenotype from those seen in earlier life, and their potential role in CNS repair remains unknown. To gain insights into the potential to manipulate the myelinating capacity of these precursor and/or progenitor cells, we generated a homogenous culture of OPs from neural precursor cells isolated from adult rat subependymal tissues. Phenotypic characterization indicated that these OPs resembled neonatal rather than adult OPs and produced robust myelin after transplantation. The ability to generate such cells from the adult brain therefore opens an avenue to explore the potential of these cells for repairing myelin disorders in adulthood.

DNA double-strand break repair proteins are required to cap the ends of mammalian chromosomes

Recent findings intriguingly place DNA double-strand break repair proteins at chromosome ends in yeast, where they help maintain normal telomere length and structure. In the present study, an essential telomere function, the ability to cap and thereby protect chromosomes from end-to-end fusions, was assessed in repair-deficient mouse cell lines. By using fluorescence in situ hybridization with a probe to telomeric DNA, spontaneously occurring chromosome aberrations were examined for telomere signal at the points of fusion, a clear indication of impaired end-capping. Telomeric fusions were not observed in any of the repair-proficient controls and occurred only rarely in a p53 null mutant. In striking contrast, chromosomal end fusions that retained telomeric sequence were observed in nontransformed DNA-PKcs-deficient cells, where they were a major source of chromosomal instability. Metacentric chromosomes created by telomeric fusion became even more abundant in these cells after spontaneous immortalization. Restoration of repair proficiency through transfection with a functional cDNA copy of the human DNA-PKcs gene reduced the number of fusions compared with a negative transfection control. Virally transformed cells derived from Ku70 and Ku80 knockout mice also displayed end-to-end fusions. These studies demonstrate that DNA double-strand break repair genes play a dual role in maintaining chromosomal stability in mammalian cells, the known role in repairing incidental DNA damage, as well as a new protective role in telomeric end-capping.

Induction of wild-type p53 activity in human cancer cells by ribozymes that repair mutant p53 transcripts

Several groups have attempted to develop gene therapy strategies to treat cancer via introduction of the wild-type (wt) p53 cDNA into cancer cells. Unfortunately, these approaches do not result in regulated expression of the p53 gene and do not reduce expression of the mutant p53 that is overexpressed in cancerous cells. These shortcomings may greatly limit the utility of this gene replacement approach. We describe an alternative strategy with trans-splicing ribozymes that can simultaneously reduce mutant p53 expression and restore wt p53 activity in various human cancers. The ribozyme accomplished such conversion by repairing defective p53 mRNAs with high fidelity and specificity. The corrected transcripts were translated to produce functional p53 that can transactivate p53-responsive promoters and down-modulate expression of the multidrug resistance (MDR1) gene promoter. The level of wt p53 activity generated was significant, resulting in a 23-fold induction of a p53-responsive promoter and a 3-fold reduction in MDR1 promoter expression in transfected cancer cells. Once efficient delivery systems are developed, this strategy should prove useful for making human cancers more responsive to p53 activity and more sensitive to chemotherapeutic agents.

Stimulation of human 8-oxoguanine-DNA glycosylase by AP-endonuclease: potential coordination of the initial steps in base excision repair

8-Oxoguanine-DNA glycosylase 1 (OGG1), with intrinsic AP lyase activity, is the major enzyme for repairing 7,8-dihydro-8-oxoguanine (8-oxoG), a critical mutagenic DNA lesion induced by reactive oxygen species. Human OGG1 excised the damaged base from an 8-oxoG·C-containing duplex oligo with a very low apparent kcat of 0.1 min–1 at 37°C and cleaved abasic (AP) sites at half the rate, thus leaving abasic sites as the major product. Excision of 8-oxoG by OGG1 alone did not follow Michaelis–Menten kinetics. However, in the presence of a comparable amount of human AP endonuclease (APE1) the specific activity of OGG1 was increased ∼5-fold and Michaelis–Menten kinetics were observed. Inactive APE1, at a higher molar ratio, and a bacterial APE (Nfo) similarly enhanced OGG1 activity. The affinity of OGG1 for its product AP·C pair (Kd ∼ 2.8 nM) was substantially higher than for its substrate 8-oxoG·C pair (Kd ∼ 23.4 nM) and the affinity for its final β-elimination product was much lower (Kd ∼ 233 nM). These data, as well as single burst kinetics studies, indicate that the enzyme remains tightly bound to its AP product following base excision and that APE1 prevents its reassociation with its product, thus enhancing OGG1 turnover. These results suggest coordinated functions of OGG1 and APE1, and possibly other enzymes, in the DNA base excision repair pathway.

Detection and determination of oligonucleotide triplex formation-mediated transcription-coupled DNA repair in HeLa nuclear extracts

Transcription-coupled repair (TCR) plays an important role in removing DNA damage from actively transcribed genes. It has been speculated that TCR is the most important mechanism for repairing DNA damage in non-dividing cells such as neurons. Therefore, abnormal TCR may contribute to the development of many age-related and neurodegenerative diseases. However, the molecular mechanism of TCR is not well understood. Oligonucleotide DNA triplex formation provides an ideal system to dissect the molecular mechanism of TCR since triplexes can be formed in a sequence-specific manner to inhibit transcription of target genes. We have recently studied the molecular mechanism of triplex-forming oligonucleotide (TFO)-mediated TCR in HeLa nuclear extracts. Using plasmid constructs we demonstrate that the level of TFO-mediated DNA repair activity is directly correlated with the level of transcription of the plasmid in HeLa nuclear extracts. TFO-mediated DNA repair activity was further linked with transcription since the presence of rNTPs in the reaction was essential for AG30-mediated DNA repair activity in HeLa nuclear extracts. The involvement of individual components, including TFIID, TFIIH, RNA polymerase II and xeroderma pigmentosum group A (XPA), in the triplex-mediated TCR process was demonstrated in HeLa nuclear extracts using immunodepletion assays. Importantly, our studies also demonstrated that XPC, a component involved in global genome DNA repair, is involved in the AG30-mediated DNA repair process. The results obtained in this study provide an important new understanding of the molecular mechanisms involved in the TCR process in mammalian cells.

Significance analysis of microarrays applied to the ionizing radiation response

Microarrays can measure the expression of thousands of genes to identify changes in expression between different biological states. Methods are needed to determine the significance of these changes while accounting for the enormous number of genes. We describe a method, Significance Analysis of Microarrays (SAM), that assigns a score to each gene on the basis of change in gene expression relative to the standard deviation of repeated measurements. For genes with scores greater than an adjustable threshold, SAM uses permutations of the repeated measurements to estimate the percentage of genes identified by chance, the false discovery rate (FDR). When the transcriptional response of human cells to ionizing radiation was measured by microarrays, SAM identified 34 genes that changed at least 1.5-fold with an estimated FDR of 12%, compared with FDRs of 60 and 84% by using conventional methods of analysis. Of the 34 genes, 19 were involved in cell cycle regulation and 3 in apoptosis. Surprisingly, four nucleotide excision repair genes were induced, suggesting that this repair pathway for UV-damaged DNA might play a previously unrecognized role in repairing DNA damaged by ionizing radiation.

High efficiency mutagenesis, repair, and engineering of chromosomal DNA using single-stranded oligonucleotides

Homologous DNA recombination is a fundamental, regenerative process within living organisms. However, in most organisms, homologous recombination is a rare event, requiring a complex set of reactions and extensive homology. We demonstrate in this paper that Beta protein of phage λ generates recombinants in chromosomal DNA by using synthetic single-stranded DNAs (ssDNA) as short as 30 bases long. This ssDNA recombination can be used to mutagenize or repair the chromosome with efficiencies that generate up to 6% recombinants among treated cells. Mechanistically, it appears that Beta protein, a Rad52-like protein, binds and anneals the ssDNA donor to a complementary single-strand near the DNA replication fork to generate the recombinant. This type of homologous recombination with ssDNA provides new avenues for studying and modifying genomes ranging from bacterial pathogens to eukaryotes. Beta protein and ssDNA may prove generally applicable for repairing DNA in many organisms.

Rad52 forms DNA repair and recombination centers during S phase

Maintenance of genomic integrity and stable transmission of genetic information depend on a number of DNA repair processes. Failure to faithfully perform these processes can result in genetic alterations and subsequent development of cancer and other genetic diseases. In the eukaryote Saccharomyces cerevisiae, homologous recombination is the major pathway for repairing DNA double-strand breaks. The key role played by Rad52 in this pathway has been attributed to its ability to seek out and mediate annealing of homologous DNA strands. In this study, we find that S. cerevisiae Rad52 fused to green fluorescent protein (GFP) is fully functional in DNA repair and recombination. After induction of DNA double-strand breaks by γ-irradiation, meiosis, or the HO endonuclease, Rad52-GFP relocalizes from a diffuse nuclear distribution to distinct foci. Interestingly, Rad52 foci are formed almost exclusively during the S phase of mitotic cells, consistent with coordination between recombinational repair and DNA replication. This notion is further strengthened by the dramatic increase in the frequency of Rad52 focus formation observed in a pol12-100 replication mutant and a mec1 DNA damage checkpoint mutant. Furthermore, our data indicate that each Rad52 focus represents a center of recombinational repair capable of processing multiple DNA lesions.

Assembly of RecA-like recombinases: Distinct roles for mediator proteins in mitosis and meiosis

Members of the RecA family of recombinases from bacteriophage T4, Escherichia coli, yeast, and higher eukaryotes function in recombination as higher-order oligomers assembled on tracts of single-strand DNA (ssDNA). Biochemical studies have shown that assembly of recombinase involves accessory factors. These studies have identified a class of proteins, called recombination mediator proteins, that act by promoting assembly of recombinase on ssDNA tracts that are bound by ssDNA-binding protein (ssb). In the absence of mediators, ssb inhibits recombination reactions by competing with recombinase for DNA-binding sites. Here we briefly review mediated recombinase assembly and present results of new in vivo experiments. Immuno-double-staining experiments in Saccharomyces cerevisiae suggest that Rad51, the eukaryotic recombinase, can assemble at or near sites containing ssb (replication protein A, RPA) during the response to DNA damage, consistent with a need for mediator activity. Correspondingly, mediator gene mutants display defects in Rad51 assembly after DNA damage and during meiosis, although the requirements for assembly are distinct in the two cases. In meiosis, both Rad52 and Rad55/57 are required, whereas either Rad52 or Rad55/57 is sufficient to promote assembly of Rad51 in irradiated mitotic cells. Rad52 promotes normal amounts of Rad51 assembly in the absence of Rad55 at 30°C but not 20°C, accounting for the cold sensitivity of rad55 null mutants. Finally, we show that assembly of Rad51 is induced by radiation during S phase but not during G1, consistent with the role of Rad51 in repairing the spontaneous damage that occurs during DNA replication.

RecA protein stimulates homologous recombination in plants.

A number of RecA-like proteins have been found in eukaryotic organisms. We demonstrate that the prokaryotic recombination protein RecA itself is capable of interacting with genomic homologous DNA in somatic plant cells. Resistance to the DNA crosslinking agent mitomycin C requires homologous recombination as well as excision repair activity. Tobacco protoplasts expressing a nucleus-targeted RecA protein were at least three times as efficient as wild-type cells in repairing mitomycin C-induced damage. Moreover, homologous recombination at a defined locus carrying an endogenous nuclear marker gene was stimulated at least 10-fold in transgenic plant cells expressing nucleus-targeted RecA. The increase in resistance to mitomycin C and the stimulation of intrachromosomal recombination demonstrate that Escherichia coli RecA protein is functional in genomic homologous recombination in plants, especially when targeted to the plant nucleus.

Ensaio clínico randomizado do uso do curativo gel de clorexidina para a prevenção da colonização do cateter venoso central em pacientes adultos críticos

Os acessos venosos são indispensáveis para assistência do paciente em situação crítica. O cateter venoso central (CVC) é um acesso que viabiliza a terapêutica dessa clientela, mas o seu uso pode levar à infecções. Estas infecções ocasionam maior permanência hospitalar, elevam os custos totais das instituições e aumentam a morbidade e a mortalidade do paciente. O uso de curativos como cobertura do sítio de saída do CVC é eficaz na prevenção das infecções relacionadas a estes cateteres, em particular, o uso de curativos impregnados com antissépticos como o curativo gel de clorexidina. Este estudo teve como objetivo comparar a efetividade do curativo gel de clorexidina com a do filme transparente de poliuretano na prevenção da colonização do cateter venoso central em pacientes adultos críticos. Trata-se de estudo experimental, do tipo ensaio clínico randomizado, com tratamentos em paralelo, prospectivo e monocêntrico, realizado de acordo com as recomendações do Consolidated Standards of Reporting Trials (CONSORT). O estudo foi realizado na Unidade de Terapia Intensiva e na Unidade Coronariana de um hospital de ensino do interior do Estado de São Paulo. Participaram do estudo 102 indivíduos hospitalizados nestes locais, divididos aleatoriamente em dois grupos: grupo intervenção, no qual o tipo de cobertura utilizada foi o curativo de gel de clorexidina e grupo controle, que utilizou como cobertura o filme transparente de poliuretano. O desfecho primário mensurado foi a colonização do cateter e os desfechos secundários foram a infecção clínica do sítio de saída, a infecção microbiológica do sítio de saída e a infecção da corrente sanguínea relacionada ao cateter. Para a coleta de dados foi elaborado um instrumento, e este validado quanto ao seu conteúdo e forma por 13 enfermeiros pertencentes aos locais do estudo. Estes profissionais foram treinados para a realização dos curativos e coleta das pontas dos cateteres centrais, swabs dos sítios de saída e hemoculturas. Análises descritivas foram usadas para todas as variáveis do estudo. O teste Exato de Fisher foi utilizado para comparar as proporções de cada desfecho nos grupos de intervenção e controle, e a regressão logística para explorar se a colonização no CVC poderia ser associada com o tempo de uso do cateter e com o Acute Physiology and Chronic Health Evaluation II (APACHE II) dos pacientes do estudo. De acordo com os resultados não houve diferença estatisticamente significante entre a colonização nos dois grupos (p valor = 1.00), para a infecção microbiológica do sítio de saída (p valor = 0.08), para a infecção clínica do sítio de saída (p valor = 0.77) e para as infecções da corrente sanguínea relacionadas ao cateter (p valor = 1,00). Conclui-se que o presente estudo pode contribuir para que as unidades de saúde tenham subsídios para realizar a escolha do tipo de curativo baseado em suas necessidades institucionais e no desenvolvimento de protocolos relacionados à medidas de inserção e manutenção do cateter, bem como medidas educativas permanentes