Viruses in Astrobiology

Viruses are the most abundant biological entities on Earth, and yet, they have not received enough consideration in astrobiology. Viruses are also extraordinarily diverse, which is evident in the types of relationships they establish with their host, their strategies to store and replicate their genetic information and the enormous diversity of genes they contain. A viral population, especially if it corresponds to a virus with an RNA genome, can contain an array of sequence variants that greatly exceeds what is present in most cell populations. The fact that viruses always need cellular resources to multiply means that they establish very close interactions with cells. Although in the short term these relationships may appear to be negative for life, it is evident that they can be beneficial in the long term. Viruses are one of the most powerful selective pressures that exist, accelerating the evolution of defense mechanisms in the cellular world. They can also exchange genetic material with the host during the infection process, providing organisms with capacities that favor the colonization of new ecological niches or confer an advantage over competitors, just to cite a few examples. In addition, viruses have a relevant participation in the biogeochemical cycles of our planet, contributing to the recycling of the matter necessary for the maintenance of life. Therefore, although viruses have traditionally been excluded from the tree of life, the structure of this tree is largely the result of the interactions that have been established throughout the intertwined history of the cellular and the viral worlds. We do not know how other possible biospheres outside our planet could be, but it is clear that viruses play an essential role in the terrestrial one. Therefore, they must be taken into account both to improve our understanding of life that we know, and to understand other possible lives that might exist in the cosmos

Phenotypic effect of mutations in evolving populations of RNA molecules

Abstract Background The secondary structure of folded RNA sequences is a good model to map phenotype onto genotype, as represented by the RNA sequence. Computational studies of the evolution of ensembles of RNA molecules towards target secondary structures yield valuable clues to the mechanisms behind adaptation of complex populations. The relationship between the space of sequences and structures, the organization of RNA ensembles at mutation-selection equilibrium, the time of adaptation as a function of the population parameters, the presence of collective effects in quasispecies, or the optimal mutation rates to promote adaptation all are issues that can be explored within this framework. Results We investigate the effect of microscopic mutations on the phenotype of RNA molecules during their in silico evolution and adaptation. We calculate the distribution of the effects of mutations on fitness, the relative fractions of beneficial and deleterious mutations and the corresponding selection coefficients for populations evolving under different mutation rates. Three different situations are explored: the mutation-selection equilibrium (optimized population) in three different fitness landscapes, the dynamics during adaptation towards a goal structure (adapting population), and the behavior under periodic population bottlenecks (perturbed population). Conclusions The ratio between the number of beneficial and deleterious mutations experienced by a population of RNA sequences increases with the value of the mutation rate μ at which evolution proceeds. In contrast, the selective value of mutations remains almost constant, independent of μ, indicating that adaptation occurs through an increase in the amount of beneficial mutations, with little variations in the average effect they have on fitness. Statistical analyses of the distribution of fitness effects reveal that small effects, either beneficial or deleterious, are well described by a Pareto distribution. These results are robust under changes in the fitness landscape, remarkably when, in addition to selecting a target secondary structure, specific subsequences or low-energy folds are required. A population perturbed by bottlenecks behaves similarly to an adapting population, struggling to return to the optimized state. Whether it can survive in the long run or whether it goes extinct depends critically on the length of the time interval between bottlenecks.Support from the Spanish MICINN through research project FIS2008-05273 is gratefully acknowledged.Peer Reviewe

DESAFÍOS DE UNA ENFERMEDAD

En 1995 se identificó la existencia del síndrome pulmo nar por hantavirus en la región surandina argentina y a su agente causal, el virus Andes. Este artículo relata los principales sucesos e investigaciones que contribuyeron a revelar las características de las infecciones por este virus y las peculiaridades que lo distinguen del resto de los miembros de su género

La Responsabilidad Social Corporativa: el papel de la Inversión Socialmente Responsable

Las alarmas han saltado tras la última cumbre de las naciones unidas: nos encontramos en el tiempo de descuento para salvar nuestro planeta y todos debemos ser partícipes de ello.Desde hace varios años, más concretamente desde el final de la última guerra mundial, se han ido incorporando criterios de responsabilidad en las empresas e instituciones para intentar mitigar los daños realizados en estos años de guerras y, procurar cambiar la visión de desarrollo hasta entonces establecida.Estos cambios no solo se están viendo en el mundo de la empresa tradicional, sino también en las finanzas ya que, como veremos más adelante, son pieza clave en esta transición.En este trabajo voy a analizar el papel de las Finanzas Sostenibles, centrándome, concretamente, en el papel de la Inversión Socialmente Responsable y los Fondos de Inversión Sostenible.<br /

Tunable dual-band filters based on capacitive-loaded stepped-impedance resonators

This paper proposes the design of tunable dual-band filters for multi-band multi-standard systems. The main objective is to provide frequency tunability in the second band while maintaining the first band fixed. To this end, the capacitive-loaded stepped-impedance resonator is used. The work is divided into two main parts. In the first part, a deep analysis of the capacitive-loaded stepped-impedance resonator structure is done, which provides analytical closed-form design equations which eases their design in front of the several approaches available in the literature up to now. The analysis is also particularized for the case of the capacitive-loaded uniform resonator. In the second part, resonators are integrated in two dual-band tunable filters.Postprint (published version

Qualidade da água de consumo doméstico proveniente dos poços proximos das latrinas: Quality of domestic drinking water from wells near latrines

O sistema de abastecimento de água em Angola é extremamente débil. É notável que a maior parte das localidades do país não tem sistemas de abastecimento do líquido adequado. Nas regiões onde existe sistema de abastecimento é muito frágil no seu conjunto, embora em algumas áreas apresente algumas normalidades, com o esfoço que o governo vem fazendo para melhoria. Embora se considere Angola com umas das maiores redes hidrográficas da Africa Austral e até mesmo do mundo, comparando com muitos países em certas áreas do país a água consumida não tem qualidade aceitável para o consumo humano, porém as populações recorrem a alternativas para o obter o liquido, sobretudo ao recurso dos Poços, onde adquirem direitamente o líquido e o consomem sem o devido tratamento. O trabalho teve como objectivo avaliara a qualidade de água consumida pelas populações nas em algumas áreas da cidade do Huambo, mormente nos bairros da vila da Graça. Usou-se a metodologia de constatação in loco, entrevistas com as populações e coleta de amostras de água que foi analisada em laboratório de referência de acordo exigências da OMS sobre qualidade de água para o consumo humano analises físico-químico e biológico. Os resultados biológicos indicaram presença de variedades de coliformes fecais o que representam perigo para saúde humana. Já os resultados físico-químicos estiveram próximo dos parâmetros exigidos pela OMS. Concluiu-se a população da Vila da Graça corre um perigo de saúde pública e que o governo deve melhorar as condições de abastecimento nesta localidade e outras que usam o mesmo sistema

The balance between fitness advantages and costs drives adaptation of bacteriophage Qβ to changes in host density at different temperatures

IntroductionHost density is one of the main factors affecting the infective capacity of viruses. When host density is low, it is more difficult for the virus to find a susceptible cell, which increases its probability of being damaged by the physicochemical agents of the environment. Nevertheless, viruses can adapt to variations in host density through different strategies that depend on the particular characteristics of the life cycle of each virus. In a previous work, using the bacteriophage Qβ as an experimental model, we found that when bacterial density was lower than optimal the virus increased its capacity to penetrate into the bacteria through a mutation in the minor capsid protein (A1) that is not described to interact with the cell receptor.ResultsHere we show that the adaptive pathway followed by Qβ in the face of similar variations in host density depends on environmental temperature. When the value for this parameter is lower than optimal (30°C), the mutation selected is the same as at the optimal temperature (37°C). However, when temperature increases to 43°C, the mutation selected is located in a different protein (A2), which is involved both in the interaction with the cell receptor and in the process of viral progeny release. The new mutation increases the entry of the phage into the bacteria at the three temperatures assayed. However, it also considerably increases the latent period at 30 and 37°C, which is probably the reason why it is not selected at these temperatures.ConclusionThe conclusion is that the adaptive strategies followed by bacteriophage Qβ, and probably other viruses, in the face of variations in host density depend not only on their advantages at this selective pressure, but also on the fitness costs that particular mutations may present in function of the rest of environmental parameters that influence viral replication and stability

Allele-Specific Expression of APC in Adenomatous Polyposis Families

BACKGROUND & AIMS: Germline mutations in the APC gene cause of most cases of familial adenomatous polyposis (FAP) and a lesser proportion of attenuated FAP (AFAP). Systematic analysis of APC at the RNA level could provide insight into the pathogenicity of identified mutations and the molecular basis of FAP/AFAP in families without identifiable mutations. Here, we analyzed the prevalence of imbalances in the allelic expression of APC in polyposis families with germline mutations in the gene and without detectable mutations in APC and/or MUTYH. METHODS: Allele-specific expression (ASE) was determined by single nucleotide primer extension using an exon 11 polymorphism as an allele-specific marker. In total, 52 APC-mutation-positive (36 families) and 24 APC/MUTYH-mutation-negative (23 families) informative patients were analyzed. Seventy-six controls also were included. RESULTS: Of the APC-mutation-positive families, most of those in whom the mutation was located before the last exon of the gene (12 of 14) had ASE imbalance, which is consistent with a mechanism of nonsense-mediated decay. Of the APC/MUTYH-mutation-negative Families, 2 (9%) had ASE imbalance, which might cause the disease. Normal allele expression was restored shortly after lymphocytes were cultured with puromycin, supporting a 'nonsense-mediated' hypothesis. CONCLUSIONS: ASE analysis might be used to determine the pathogenesis of some cases of FAP and AFAP in which APC mutations are not found. ASE also might be used to prioritize the order in which different areas of APC are tested. RNA-level studies are important for the molecular diagnosis of FAP

Errores, actitud y desempeño matemático del ingresante universitario

Para conocer los errores matemáticos típicos más frecuentes del ingresante universitario y analizar su vinculación con la actitud afectiva hacia la matemática y su rendimiento, se administró una prueba diagnóstica a 405 alumnos de Ciencias de la Salud que cursan la asignatura matemática en el primer año de la Universidad de Buenos Aires. Los alumnos tienen dificultades para: representar números racionales en la recta real (pero no para comparar fracciones); especializar una función; aplicar propiedades de la potenciación; plantear matemáticamente enunciados de problemas; y en menor medida, para resolver ecuaciones lineales. Se observó además que existe correlación entre el desempeño en el primer parcial de la asignatura y el desempeño en la prueba diagnóstica, la opinión del nivel matemático de la escuela, y la representación que tiene de la matemática

¿Se vacunaría con Janssen o AstraZeneca? Ocho expertos tienen clara la respuesta

La aparición de raros cuadros de trombos con plaquetas bajas en personas vacunadas contra la covid-19 con las soluciones de Janssen y AstraZeneca ha provocado que varios gobiernos hayan pausado las campañas o restringido los rangos de edad, lo que ha creado desconcierto y temor entre la población. Muchas personas ya han recibido la primera dosis y no saben cuándo van a recibir la segunda. Otras rechazan ponerse alguna de estas vacunas. Hemos sondeado a varios de los principales especialistas en epidemiología, inmunología, vacunología, virología y salud pública para preguntarles directamente qué harían ellos: ¿se vacunarían con las de Janssen y AstraZeneca