Amyloid plaques and normal ageing have differential effects on microglial Ca2+ activity in the mouse brain.

In microglia, changes in intracellular calcium concentration ([Ca2+]i) may regulate process motility, inflammasome activation, and phagocytosis. However, while neurons and astrocytes exhibit frequent spontaneous Ca2+ activity, microglial Ca2+ signals are much rarer and poorly understood. Here, we studied [Ca2+]i changes of microglia in acute brain slices using Fluo-4-loaded cells and mice expressing GCaMP5g in microglia. Spontaneous Ca2+ transients occurred ~ 5 times more frequently in individual microglial processes than in their somata. We assessed whether microglial Ca2+ responses change in Alzheimer's disease (AD) using AppNL-G-F knock-in mice. Proximity to Aß plaques strongly affected microglial Ca2+ activity. Although spontaneous Ca2+ transients were unaffected in microglial processes, they were fivefold more frequent in microglial somata near Aß plaques than in wild-type microglia. Microglia away from Aß plaques in AD mice showed intermediate properties for morphology and Ca2+ responses, partly resembling those of wild-type microglia. By contrast, somatic Ca2+ responses evoked by tissue damage were less intense in microglia near Aß plaques than in wild-type microglia, suggesting different mechanisms underlying spontaneous vs. damage-evoked Ca2+ signals. Finally, as similar processes occur in neurodegeneration and old age, we studied whether ageing affected microglial [Ca2+]i. Somatic damage-evoked Ca2+ responses were greatly reduced in microglia from old mice, as in the AD mice. In contrast to AD, however, old age did not alter the occurrence of spontaneous Ca2+ signals in microglial somata but reduced the rate of events in processes. Thus, we demonstrate distinct compartmentalised Ca2+ activity in microglia from healthy, aged and AD-like brains.

Head-to-head comparison of six warning scores to predict mortality and clinical impairment in COVID-19 patients in emergency department.

The aim was to evaluate the ability of six risk scores (4C, CURB65, SEIMC, mCHOSEN, QuickCSI, and NEWS2) to predict the outcome of patients with COVID-19 during the sixth pandemic wave in Spain. A retrospective observational study was performed to review the electronic medical records in patients ≥ 18 years of age who consulted consecutively in an emergency department with COVID-19 diagnosis throughout 2 months during the sixth pandemic wave. Clinical-epidemiological variables, comorbidities, and their respective outcomes, such as 30-day in-hospital mortality and clinical deterioration risk (a combined outcome considering: mechanical ventilation, intensive care unit admission, and/or 30-day in-hospital mortality), were calculated. The area under the curve for each risk score was calculated, and the resulting curves were compared by the Delong test, concluding with a decision curve analysis. A total of 626 patients (median age 79 years; 49.8% female) fulfilled the inclusion criteria. Two hundred and ninety-three patients (46.8%) had two or more comorbidities. Clinical deterioration risk criteria were present in 10.1% (63 cases), with a 30-day in-hospital mortality rate of 6.2% (39 cases). Comparison of the results showed that score 4C presented the best results for both outcome variables, with areas under the curve for mortality and clinical deterioration risk of 0.931 (95% CI 0.904-0.957) and 0.871 (95% CI 0.833-0.910) (both p < 0.001). The 4C Mortality Score proved to be the best score for predicting mortality or clinical deterioration risk among patients with COVID-19 attended in the emergency department in the following 30 days.

Actividad antibacteriana de actinomicetos frente a Escherichia coli y Staphylococcus aureus multirresistentes de origen hospitalario / Antibacterial activity of actimycetes against multiresistant Escherichia coli and Staphylococcus aureus isolated from a hospital

Introducción: La resistencia a los antimicrobianos (RAM) es un problema de salud pública que manifiesta la disminuida eficacia de estos agentes en la prevención y tratamiento de una proporción cada vez más amplia de patologías. Los actinomicetos son un grupo bacteriano importante de productores de metabolitos activos contra patógenos. Objetivo: Aislar actinomicetos del bosque tropical de Nariño, con potencial producción de metabolitos inhibitorios contra bacterias multidrogo-resistentes. Materiales y métodos: Se tomaron muestras de suelo de Bosque Tropical Húmedo de la Reserva Natural del Río Ñambí, se analizaron microbiológica y molecularmente. Se estimuló la producción in vitro de metabolitos secundarios y evaluó el efecto inhibitorio de estos extractos contra las bacterias multidrogo-resistentes Escherichia coli y Staphylococcus aureus. Resultados: Se obtuvieron 11 aislados presuntivos, se confirmó que cuatro de ellos correspondieron al género Streptomyces sp. Las pruebas de inhibición contra bacterias multidrogo-resistentes E. coli y S. aureus, permitieron verificar que el aislado P3772 fue el más eficiente en la inhibición de los patógenos. Conclusiones: Todos los actinomicetos evaluados presentan actividad antibacteriana contra al menos una de las bacterias patógenas estudiadas; destacando el aislado P3772, que inhibe a E. coli y S. aureus. Se espera caracterizar los compuestos vinculados a la actividad antibacteriana.

Introduction: Antimicrobial resistance (AR) is a public health problem that reveals the diminished efficacy of these agents in the prevention and treatment of an increasingly larger number of pathologies. Actinomycetes are an important bacterial producer group of metabolites that are active against pathogens. Objective: To isolate actinomycetes from the tropical forest of Nariño (Colombia), which have the potential to produce inhibitory metabolites against multi-drug resistant bacteria. Materials and methods: Soil samples were taken from the Humid Tropical Forest of the Río Ńambí Natural Reserve and analyzed through microbiological and molecular assays. In vitro production of secondary metabolites was first stimulated, followed by the assessment of the inhibitory effect of these extracts against multi-drug resistant Escherichia coli and Staphylococcus aureus. Results: 11 presumptive isolates were obtained, confirming that four of them corresponded to the Streptomyces sp. genus. The bacterial isolate P3772 was identified as the one with the highest inhibitory effect against multi-drug resistant E. coli and S. aureus. Conclusions: All the actinomycetes evaluated presented antibacterial activity. The isolate P3772 stands out, which inhibited both E. coli and S. aureus. The compounds associated with this antibacterial activity will be characterized in future studies.

Synapse development is regulated by microglial THIK-1 K+ channels.

Microglia are the resident immune cells of the central nervous system. They constantly survey the brain parenchyma for redundant synapses, debris, or dying cells, which they remove through phagocytosis. Microglial ramification, motility, and cytokine release are regulated by tonically active THIK-1 K+ channels on the microglial plasma membrane. Here, we examined whether these channels also play a role in phagocytosis. Using pharmacological blockers and THIK-1 knockout (KO) mice, we found that a lack of THIK-1 activity approximately halved both microglial phagocytosis and marker levels for the lysosomes that degrade phagocytically removed material. These changes may reflect a decrease of intracellular [Ca2+]i activity, which was observed when THIK-1 activity was reduced, since buffering [Ca2+]i reduced phagocytosis. Less phagocytosis is expected to result in impaired pruning of synapses. In the hippocampus, mice lacking THIK-1 expression had an increased number of anatomically and electrophysiologically defined glutamatergic synapses during development. This resulted from an increased number of presynaptic terminals, caused by impaired removal by THIK-1 KO microglia. The dependence of synapse number on THIK-1 K+ channels, which control microglial surveillance and phagocytic ability, implies that changes in the THIK-1 expression level in disease states may contribute to altering neural circuit function.

Monitoring phagocytic uptake of amyloid ß into glial cell lysosomes in real time.

Phagocytosis by glial cells is essential to regulate brain function during health and disease. Therapies for Alzheimer's disease (AD) have primarily focused on targeting antibodies to amyloid ß (Aß) or inhibitng enzymes that make it, and while removal of Aß by phagocytosis is protective early in AD it remains poorly understood. Impaired phagocytic function of glial cells during later stages of AD likely contributes to worsened disease outcome, but the underlying mechanisms of how this occurs remain unknown. We have developed a human Aß1-42 analogue (AßpH) that exhibits green fluorescence upon internalization into the acidic organelles of cells but is non-fluorescent at physiological pH. This allowed us to image, for the first time, glial uptake of AßpH in real time in live animals. We find that microglia phagocytose more AßpH than astrocytes in culture, in brain slices and in vivo. AßpH can be used to investigate the phagocytic mechanisms responsible for removing Aß from the extracellular space, and thus could become a useful tool to study Aß clearance at different stages of AD.

GABAAR isoform and subunit structural motifs determine synaptic and extrasynaptic receptor localisation.

GABAA receptors (GABAARs) are the principal inhibitory neurotransmitter receptors in the central nervous system. They control neuronal excitability by synaptic and tonic forms of inhibition mostly mediated by different receptor subtypes located in specific cell membrane subdomains. A consensus suggests that α1-3ßγ comprise synaptic GABAARs, whilst extrasynaptic α4ßδ, α5ßγ and αß isoforms largely underlie tonic inhibition. Although some structural features that enable the spatial segregation of receptors are known, the mobility of key synaptic and extrasynaptic GABAARs are less understood, and yet this is a key determinant of the efficacy of GABA inhibition. To address this aspect, we have incorporated functionally silent α-bungarotoxin binding sites (BBS) into prominent hippocampal GABAAR subunits which mediate synaptic and tonic inhibition. Using single particle tracking with quantum dots we demonstrate that GABAARs that are traditionally considered to mediate synaptic or tonic inhibition are all able to access inhibitory synapses. These isoforms have variable diffusion rates and are differentially retained upon entering the synaptic membrane subdomain. Interestingly, α2 and α4 subunits reside longer at synapses compared to α5 and δ subunits. Furthermore, a high proportion of extrasynaptic δ-containing receptors exhibited slower diffusion compared to δ subunits at synapses. A chimera formed from δ-subunits, with the intracellular domain of γ2L, reversed this behaviour. In addition, we observed that receptor activation affected the diffusion of extrasynaptic, but not of synaptic GABAARs. Overall, we conclude that the differential mobility profiles of key synaptic and extrasynaptic GABAARs are determined by receptor subunit composition and intracellular structural motifs. This article is part of the special issue entitled 'Mobility and trafficking of neuronal membrane proteins'.

Amyloid ß oligomers constrict human capillaries in Alzheimer's disease via signaling to pericytes.

Cerebral blood flow is reduced early in the onset of Alzheimer's disease (AD). Because most of the vascular resistance within the brain is in capillaries, this could reflect dysfunction of contractile pericytes on capillary walls. We used live and rapidly fixed biopsied human tissue to establish disease relevance, and rodent experiments to define mechanism. We found that in humans with cognitive decline, amyloid ß (Aß) constricts brain capillaries at pericyte locations. This was caused by Aß generating reactive oxygen species, which evoked the release of endothelin-1 (ET) that activated pericyte ETA receptors. Capillary, but not arteriole, constriction also occurred in vivo in a mouse model of AD. Thus, inhibiting the capillary constriction caused by Aß could potentially reduce energy lack and neurodegeneration in AD.

Ion Channels and Receptors as Determinants of Microglial Function.

Microglia provide immune surveillance of the CNS. They display diverse behaviors, including nondirectional and directed motility of their processes, phagocytosis of targets such as dying neurons or superfluous synapses, and generation of reactive oxygen species (ROS) and cytokines. Many of these functions are mediated by ion channels and cell surface receptors, the expression of which varies with the many morphological and functional states that microglial cells can adopt. Recent progress in understanding microglial function has been facilitated by applying classical cell physiological techniques in situ, such as patch-clamping and live imaging, and cell-specific transcriptomic analyses. Here, we review the contribution of microglial ion channels and receptors to microglial and brain function.

Dynamics and Embedded Internet of Things Input Shaping Control for Overhead Cranes Transporting Multibody Payloads.

Input shaping is an Optimal Control feedforward strategy whose ability to define how and when a flexible dynamical system defined by Ordinary Differential Equations (ODEs) and computer controlled would move into its operative space, without command induced unwanted dynamics, has been exhaustively demonstrated. This work examines the issue of Embedded Internet of Things (IoT) Input Shaping with regard to real time control of multibody oscillatory systems whose dynamics are better described by differential algebraic equations (DAEs). An overhead crane hanging a double link multibody payload has been appointed as a benchmark case; it is a multibody, multimode system. This might be worst scenario to implement Input Shaping. The reasons can be found in the wide array of constraints that arise. Firstly, the reliability of the multibody model was tested on a Functional Mock-Up Interface (FMI) with the two link payload suspended from the trolley by comparing the experimental video tapping signals in time domain faced with the signals extracted from the multibody model. The FFTs of the simulated and the experimental signal contain the same frequency harmonics only with somewhat different power due to the real world light damping in the joints. The application of this approach may be extended to other cases i.e., the usefulness of mobile hydraulic cranes is limited because the payload is supported by an overhead cable under tension that allows oscillation to occur during crane motion. If the payload size is not negligible small when compared with the cable length may introduce an additional oscillatory mode that creates a multibody double pendulum. To give the insight into the double pendulum dynamics by Lagrangian methods two slender rods as payloads are analyzed dealing with the overhead crane and a composite revolute-revolute joint is proposed to model the cable of the hydraulic crane, both assumptions facilitates an affordable analysis. This allows developing a general study of this type of multibody payloads dynamics including its normal modes, modes ratios plus ranges of frequencies expected. Input Shapers were calculated for those multimodes of vibration by convolving Specified Insensitivity (SI) shapers for each mode plus a novel Direct SI-SI shaper well suited to reduce the computational requirements, i.e., the number of the shaper taps, to carry out the convolution sum in real time by the IoT device based on a single microcontroller working as the command generator. Several comparisons are presented for the shaped and unshaped responses using both the multibody model, the experimental FMI set-up and finally a real world hydraulic crane under slewing motion commanded by an analog Joystick connected by two RF modules 802.15.4 to the IoT device that carry out the convolution sum in real time. Input Shaping improves the performances for all the cases.

Polyhydroxyalkanoate biosynthesis by oxalotrophic bacteria from high Andean soil / Biosíntesis de polihidrxialcanoato por bacterias oxalotróficas de suelos altoandinos / Biossínteses de polihidroxialcanoato por bactérias oxalotróficas de solos andinos

Abstract Oxalate is a highly oxidized organic acid anion used as a carbon and energy source by oxalotrophic bacteria. Oxalogenic plants convert atmospheric CO2 into oxalic acid and oxalic salts. Oxalate-salt formation acts as a carbon sink in terrestrial ecosystems via the oxalate-carbonate pathway (OCP). Oxalotrophic bacteria might be implicated in other carbon-storage processes, including the synthesis of polyhydroxyalkanoates (PHAs). More recently, a variety of bacteria from the Andean region of Colombia in Narino have been reported for their PHA-producing abilities. These species can degrade oxalate and participate in the oxalate-carbonate pathway. The aim of this study was to isolate and characterize oxalotrophic bacteria with the capacity to accumulate PHA biopolymers. Plants of the genus Oxalis were collected and bacteria were isolated from the soil adhering to the roots. The isolated bacterial strains were characterized using biochemical and molecular biological methods. The consumption of oxalate in culture was quantified, and PHA production was monitored in batch fermentation. The polymeric composition was characterized using gas chromatography. Finally, a biosynthetic pathway based on our findings and on those from published sources is proposed. Strains of Bacillus spp. and Serratia sp. were found to metabolize calcium oxalate and synthesize PHA.

Resumen El oxalato es un anión de ácido orgánico altamente oxidado usado como fuente carbono y energía por bacterias oxalotróficas. Las plantas oxalogénicas convierten CO2 atmosférico en ácido oxálico y sales oxálicas. La formación de sales de oxalato actúa como un sumidero de carbono en ecosistemas terrestres via oxalato-carbonato (OCP). Las bacterias oxalotróficas podrían estar implicadas en otros procesos de almacenamiento de carbono, incluyendo la síntesis de polihidroxialcanoatos (PHAs). Recientemente, una variedad de bacterias de la región andina colombiana en Nariño ha sido reportada por su habilidad para producir PHAs. Estas especies pueden degradar oxalato y participar en la vía del oxalato-carbonato. El objetivo de este estudio fue aislar y caracterizar bacterias oxalotróficas con capacidad de acumular biopolímeros PHA. Se colectaron plantas del genero Oxalis y se aislaron bacterias del suelo adheridas a las raíces. Las cepas bacterianas aisladas se caracterizaron usando métodos bioquímicos y de biología molecular. Se cuantificó el consumo de oxalato en cultivo, y se monitoreó la producción de PHA en fermentación por lotes. La composición polimérica se caracterizó usando cromatografía de gases. Finalmente, se propone una via biosintética basada en nuestros hallazgos y en los de otras fuentes publicadas. Se encontró que las cepas de Bacillus spp. y Serratia sp. metabolizan oxalato de calcio y sintetizan PHA.

Resumo O oxalato é um ânion de ácido orgânico altamente oxidado utilizado como fonte de carbono e nergía por bactérias oxalotróficas. As plantas oxalogênicas convertem CO2 atmosférico em ácido oxálico e sais oxálicos. A formação de sais de oxalato atua como um sumidouro de carbono em ecossistemas terrestres via oxalato-carbono (OCP). As bactérias oxalotróficas poderiam estar envolvidas em outros processos de armazenamento de carbono, incluindo a sínteses de polihidroxialcanoatos (PHAs). Recentemente, uma variedade de bactérias da região Andina colombiana no Departamento de Nariño foi reportada devido a sua habilidade para produzir PHAs. Estas espécies podem degradar oxalato e participar na via oxalato-carbono. O objetivo de esse estudo foi isolar e caracterizar bactérias oxalotróficas com capacidade de acumular biopolímeros PHA. Plantas do género Oxalis foram coletadas e se isolaram bactérias do solo aderido a suas raízes. As cepas bacterianas isoladas se caracterizaram utilizando métodos bioquímicos e de biologia molecular. O consumo de oxalato em cultivo foi quantificado, e a produção de PHA foi monitorada em fermentação por lotes. A composição polimérica se caracterizou utilizando Cromatografia de Gases. Finalmente, se propõe uma via biossintética baseada em nossos resultados juntamente com resultados da literatura. Se encontrou que as cepas de Bacillus spp. e Serratia sp. metabolizam oxalato de cálcio e sintetizam PHA.

Improving Mouse Models for Dementia. Are All the Effects in Tau Mouse Models Due to Overexpression?

Mouse models of Alzheimer's disease have commonly used transgenic overexpression of genes involved in production of amyloid ß (APP and/or PSEN1/2) or Tau (MAPT) with mutations that result in familial forms of dementia. We discuss possible improvements that may create full models while avoiding the problems of overexpression and report synaptic results in APPKI models. We stress use of inappropriate controls without overexpression of the normal human protein and the mismatch between the learning deficits reported in mice with plaques but no tangles and the human condition. We focus on Tau overexpression, including new data that support previous reports of the grossly nonlinear relationship between Tau overexpression and neurofibrillary tangle load, with a twofold increase in Tau protein, resulting in a 100-fold increase in tangle density. These data also support the hypothesis that a high concentration of soluble Tau, in overexpression models, plays an important direct role in neurodegeneration, rather than only via aggregation. Finally, we hypothesize that there is an optimal concentration range over which Tau can bind to microtubules and a threshold beyond which much of the overexpressed protein is unable to bind. The excess thus causes toxicity in ways not necessarily related to the process in human dementias.

Human Induced Pluripotent Stem Cells and the Modelling of Alzheimer's Disease: The Human Brain Outside the Dish.

BACKGROUND: Neurodegenerative diseases like Alzheimer's Disease (AD) are a global health issue primarily in the elderly. Although AD has been investigated using primary cultures, animal models and post-mortem human brain tissues, there are currently no effective treatments. SUMMARY: With the advent of induced pluripotent stem cells (iPSCs) reprogrammed from fully differentiated adult cells such as skin fibroblasts, newer opportunities have arisen to study the pathophysiology of many diseases in more depth. It is envisioned that iPSCs could be used as a powerful tool for neurodegenerative disease modelling and eventually be an unlimited source for cell replacement therapy. This paper provides an overview of; the contribution of iPSCs towards modeling and understanding AD pathogenesis, the novel human/mouse chimeric models in elucidating current AD pathogenesis hypotheses, the possible use of iPSCs in drug screening, and perspectives on possible future directions. KEY MESSAGES: Human/mouse chimeric models using iPSCs to study AD offer much promise in better replicating AD pathology and can be further exploited to elucidate disease pathogenesis with regards to the neuroinflammation hypothesis of AD.

Eficiencia en la reducción de Cromo por una bacteria silvestre en un tratamiento tipo Batch utilizando como sustrato agua residual del municipio de Pasto, Colombia / Efficiency in the reduction of chromium by a wild bacterium in a Batch treatment type using residual water substrate from the municipality of Pasto, Colombia

Resumen Objetivo: Evaluar la eficiencia en la reducción de Cromo en un tratamiento tipo Batch, utilizando como sustrato agua residual municipal inoculada con una bacteria silvestre. Materiales y métodos: Se verificó a escala de laboratorio el porcentaje de reducción de Cromo hexavalente de tres bacterias silvestres previamente aisladas de agua residual del Río Pasto (Bacillus thuringiensis, Bacillus amyloliquefaciens y Paenibacillus sp.); se seleccionó el aislado que presentó mayor porcentaje de reducción de Cr y fue sometido a diferentes tratamientos. El análisis de los resultados se hizo mediante estadística descriptiva. Resultados: B. thuringiensis, B. amyloliquefaciens, y Paenibacillus sp., presentaron porcentajes de reducción de Cr (VI) de 82,01%; 80,85% y 79,27%, respectivamente. Se determinó que el tercer tratamiento (agua sin esterilizar del Río Pasto con B. thuringiensis) presentó diferencias significativas respecto a los demás (p = 0,0001 α = 0,05), concluyendo que B. thuringiensis reduce en mayor proporción el Cr (VI), los resultados encontrados en esta investigación son promisorios en el campo de la biorremediación de efluentes contaminados con Cromo ya que pueden ser tomados como base para implementar estrategias de biorremediación a gran escala. Conclusión: La bacteria B. thuringiensis presentó alta eficiencia en la reducción de Cromo hexavalente (99,42%), cuando fue implementada en un tratamiento a escala de laboratorio de agua residual sin esterilizar.

Abstract Objective: To evaluate the efficiency in the reduction of chromium in a Batch treatment type, using municipal residual water substrate inoculated with a wild bacterium. Materials and methods: The reduction percentage of hexavalent chromium of three wild bacteria previously isolated from residual water from the Pasto River was verified at laboratory scale (Bacillus thuringiensis, Bacillus amyloliquefaciens and Paenibacillus sp.); the isolated that showed the highest percentage of reduction of Cr was selected and was subjected to different treatments. The analysis of results was done using descriptive statistics. Results: B. thuringiensis, B. amyloliquefaciens, and Paenibacillus sp., presented percentages of reduction of Cr (VI) of 82,01%; 80,85% and 79,27%, respectively. It was determined that the third treatment (nonsterile water from the Pasto River with B. thuringiensis) presented significant differences with regard to the other (p = 0.0001 α = 0.05), concluding that B. thuringiensis reduces in greater proportion the Cr (VI). The results found in this research are promising in the field of bioremediation of contaminated effluents with Chrome since they may be taken as the basis for implementing strategies of bioremediation on a large scale. Conclusion: The bacteria B. thuringiensis presented high efficiency in the reduction of hexavalent chromium (99.42%) when implemented in a treatment at laboratory scale of residual nonsterile water.

Diseño instruccional para argumentación científica en línea / Instructional design for scientific argumentation on line

El propósito de la investigación realizada fue evaluar la efectividad de la enseñanza de procesos estructurados de argumentación en el desarrollo de la argumentación científica de estudiantes inscritos en un curso virtual de Biotecnología. Con un diseño experimental se compararon dos grupos de estudiantes, solo uno recibió orientación sobre procesos de argumentación. Ambos grupos participaron en un foro de trabajo colaborativo en línea. En ambos grupos la evaluación de la competencia argumentativa se realizó aplicando el instrumento de evaluación para argumentación dialógica en línea, propuesta por Clark y Sampson (2008); este modelo consta de tres categorías: estructura argumentativa, calidad de la argumentación y nivel de oposición al que llega el grupo. Para realizar el experimento se construyó un diseño instruccional basado en la argumentación dialógica. El primer componente del diseño corresponde a la enseñanza del modelo argumentativo. El segundo elemento es el contexto de aprendizaje a partir del cual se desarrolla la interacción y el tercero corresponde a las mediaciones tecnológicas. El diseño instruccional se incorporó en el curso virtual de Biotecnología alojado en la plataforma tecnológica de la Universidad, la cual utiliza Moddle 2X. Los resultados indicaron que el 60% de los estudiantes del grupo experimental utilizó todas las categorías argumentativas de Toulmin; al contrario, ningún estudiante del grupo control obtuvo un nivel de estructuración con todas las categorías. Asimismo, la enseñanza explícita de procesos estructurados de argumentación provoca mejor desempeño en el foro de trabajo colaborativo en aspectos como nivel de calidad de los argumentos y nivel de oposición.

Teaching argumentation is a strategy of great interest within the community involve in the study of didactic in science since there are numerous studies showing the relationship between the development of scientific thought and the argumentation structured processes (Khun, 2008), however in virtual learning environments teaching argumentation is a relatively new issue and therefore constitutes a challenge for the instructional designer of the virtual course. Collaborative learning in virtual environments is a strategy implemented in recent years in such contexts under the assumption that computer-mediated and asynchronously communication facilitates the maintenance of dialogue (Schwarz & Glassner, 2003). However, studies indicate that these students' dialogues in virtual forums can be weak and based on beliefs not justified instead of using reasons articulated between theory and evidence, otherwise can be characterized because students within the group accept explanations without paying enough attention on the relationship between a statement and the available evidence and therefore readily accepted arguments without making opposition. This condition can be explained because in the context of collaborative internet the problems increase due to issues like complexity of interfaces, decreasing communication channels regarding classroom situations, or the ease of students to mask his inactivity within collaborative groups (Peñaloza, García & Espinoza, 2011). Although most researchers agree that the dialogic argumentation promotes the acquisition of scientific concepts, also they say it is difficult to integrate the teaching of argumentation structured processes into a virtual course of experimental science as well as evaluating appropriation of concepts through arguments. In this paper the results of an investigation conducted to evaluate the effectiveness of an instructional design based on structured argument process in the development of the argumentative capacity of higher education students enrolled in an online course biotechnology is presented. The population under investigation corresponds to higher education students of both sexes who are enrolled in a Biotechnology online course offered by a distance university in Colombia. Instructional design incorporated three elements: the first is the teaching of Toulmin argumentative model, the second element incorporated was the situated learning context from which the interaction is developed and for this study corresponds to a Biotechnology theme and the third component included the design and development of techno-didactic mediations to promote educational interactivity where virtual learning objects, guide activities and assessment rubrics were included. These elements were incorporated into the virtual course within the Moodle 2.1 platform. Moreover, learning strategy based on dialogic argument was developed in four stages: (a) scientific research, (b) argumentative paper development, (c) counter argument, and (d) scientific consensus. To evaluate the effectiveness of instructional design and online learning strategy based on dialogic argumentation an experimental design was conducted with a control group and post-test. The assessment of the argumentative capacity was performed by applying the online assessment tool for dialogic argumentation proposed by Clark and Sampson (2008). This model evaluates the argumentative process in the virtual forum both individually and group. Data were analyzed with non -parametric statistical tests. The research results indicated significant differences in the level of argumentative competence in the experimental group compared with the control group. The experimental group had higher ratings on their ability to structure texts, support arguments within the group and make reasoned opposition to reach consensus. Also, results of this research support the design and learning strategy based on the argument for virtual environments and shown it can be effective to increase the academic performance of students participating in collaboration online forums. Students in the control group did not performed opposition, and, most students in the experimental group achieved level three opposition on the scale of Clark and Sampson (2008), this aspect indicates the need to develop strategies to increase the level of opposition.

Degradación de oxalato por bacterias oxalotróficas asociadas a plantas del género Oxalis sp en regiones Andinas del departamento de Nariño, Colombia / Oxalate degradation by oxalotrophic bacteria associated with plants of the genus Oxalis sp in the Andean region of the department of Nariño, Colombia

Introducción: El ácido oxálico (H2C2O4) y las sales de oxalato son sustancias altamente oxidadas y consideradas tóxicas para algunos sistemas biológicos, incluido el humano, no obstante, pueden ser utilizadas como fuente de carbono y energía por algunas comunidades bacterianas, denominadas oxalotróficas, las cuales por su capacidad metabólica forman parte de la ruta biogeoquímica oxalato-carbonato (OCP, oxalate-carbonate pathway). Objetivo: Aislar y caracterizar bacterias oxalotróficas a partir de plantas del género Oxalis sp., de zonas alto-andina de Nariño- Colombia. Materiales y métodos: Se recolectaron muestras de suelo rizosférico de plantas oxalogénicas que fueron analizadas con parámetros fisicoquímicos y se utilizó un medio selectivo Schlegel para el aislamiento de bacterias oxalotróficas. Resultados: Las bacterias aisladas en medio selectivo Schlegel fueron caracterizadas bioquímicamente como: (Serratia fonticola, Bacillus amyloliquefaciens, Bacillus subtilis, Bacillus vallismortis y Bacillus cereus). Estas especies fueron capaces de degradar oxalato e incrementar el pH producto de la degradación. Conclusión: Este tipo de bacterias pueden ser estudiadas en trabajos complementarios para evaluar su potencial como biofertilizantes y/o alternativas de bioremediación en suelos ácidos. El estudio a pesar de ser indicativo a nivel biológico, puede en un futuro y con base en mayores soportes en investigación, tornarse en una promisoria aplicación para reducir el oxalato de calcio en los alimentos de consumo diario que presentan un renglón de importancia agrícola en la región, potencialmente dañinos para la función renal.

Introduction: Oxalic acid (H2C2O4) and oxalate salts are highly oxidized substances, which are considered as toxic for some biological systems, including the human being; however, they can be used as a source of carbon and energy for some bacterial communities called oxalotrophic which are part of the so called oxalate-carbonate geochemistry pathway (OCP) due to its metabolic capacity. Objective: The aim of this research was to isolate and characterize oxalotrophic bacteria from plants of the genus Oxalis sp. in the high-andean zone of the department of Nariño, Colombia. Materials and methods: Samples of rhizosphere soil from oxalogenic plants were analyzed with physicochemical parameters and a Schlegel selective medium was used to isolate oxalotrophic bacteria. Results: The isolated bacteria through Schlegel selective medium were identified biochemically as: (Serratia fonticola, Bacillus amyloliquefaciens, Bacillus subtilis, Bacillus vallismortis and Bacillus cereus). The identified species play an important role in the rhizosphere soil, principally for the capacity to increase the pH during oxalate consumption. Conclusion: This type of bacteria can be studied in additional studies to evaluate their potential as bio-fertilizers and/or bioremediation alternatives in acid soils. Despite that the study is indicative at a biological level, it can become a promising application, in the future and with greater support in research, to reduce the calcium oxalate in food of daily consumption which represent an agricultural important line in the region and are potentially harmful to kidney finction.

Unidades de soporte vital avanzado en España 2008. Mapa de situación / Advanced life support units in Spain: the situation in 2008

Objetivo: Determinar el número de unidades de soporte vital avanzado (USVA) dedicadas a emergencias que operan en España, su distribución y su relación con la población, la densidad de población y la extensión de las comunidades autónomas. Método: Estudio descriptivo a 1 de enero de 2009. Para el número y localización de las USVA se han utilizado fuentes públicas de información, y se completó con los datos obtenidos de personal de esos servicios y de los centros de coordinación. Se ha definido el concepto de USVA y se ha delimitado el estudio a las dedicadas a servicios primarios. Los datos de población y extensión se han tomado del último Censo Oficial del Instituto Nacional de Estadística (Diciembre 2008).Resultados: Se han identificado un total de 362 USVA: 327 terrestres y 35 helicópteros medicalizados. Existe una USVA por cada 127.308 habitantes (0,78 USVA/100.000hab.), con variaciones desde una cada 63.000 (1,58 USVA/100.000 hab.) hasta una porcada 232.000 (0,43 USVA/100.000 hab.). En el aspecto geográfico, hay un promedio de una unidad de SVA por cada 1.400 Km2 (7,2 USVA/10.000 Km2), con extremos de 1USVA por cada 129 Km2 (77,2 USVA/10.000 Km2) y una USVA cada 5.200 Km2 (1,9 USVA/10.000 Km2). Por cuanto se refiere a la distribución por densidad de población, tenemos un promedio de 12 habitantes por Km2 y unidad, con extremos entre 1 y 31habitantes.Conclusiones: Hay una notable disparidad entre las comunidades autónomas en cuanto a los índices relativos de USVA sobre su extensión, población y densidad de población. Las variaciones entre índices encontrados no guardan relación con la población, extensión y densidad de población de cada comunidad. Las diferencias citadas pueden atribuirse a disparidad de criterios en la planificación y a factores, geográficos, climatológicos, de vías de comunicación, o de otro tipo no estudiadas aquí (AU)

Objective: To determine the number of emergency advanced life support teams currently operating in Spain, their locations, the proportion of the population served, the population density, and the territorial extension covered in the different autonomous communities. Method: Descriptive study of the Spanish situation as of January 1, 2009. Public information sources were used to identify the number and locations of advanced life support teams. The data gathered were complemented with information obtained by interviewing the staff of hospital emergency departments and dispatch centers. The concept of advanced life support team was defined and the study was limited to teams providing initial care. Population and territorial extension data were taken from the latest official census published by the Spanish National Institute of Statistics in December 2008.Results: We identified 362 teams meeting the defined criteria; 327 use road transport ambulances and 35 use helicopter ambulances. We found advanced life support teams operating at a ratio of 1 to 127 308 inhabitants (0.78/100 000 population), with ratios varying from 1 to 63 000 (1.58/100 000 population) to 1 to 232 000 (0.43/100 000 population). Geographically, we found 1 team for every 1400 km2 (7.2/10 000 km2) on the average, with a range of 1 unit for every 129 km2 (77.2/10 000 km2) to 1 unit for every 5200 km2 (1.9/10 000 km2). Density averaged 12 persons per square kilometer attended by a unit, with a range in density of 1 to 31 per square kilometer attended Conclusions: 1) There is considerable disparity between different Spanish autonomous communities with regard to use of advanced life support units, the territorial extension covered, populations served, and density. 2) The differences in coverage by life support units are unrelated to population, territory, or population density. 3) The differences can be attributed to disparity in criteria applied when planning and to factors related to geography and climate, communication infrastructure or other unstudied variables(AU)

The biomed caged-ball cardiac valve prosthesis. A study of 120 implants

The purpose of this study was to report our experience with 120 prosthetic valves implanted in 105 patient over an 8 year period. Their preoperative status was compared at an average follow-up period of 4 years (range 1 to 6 years) with the posoperative results. We conclude that the Mexican-made valvels (Biomed) meet the highest international quality standards: they are well tolerated by the patients; their performance is excellent and no postoperative dysfunction of the valves was ever detected. the few complications observed were no different from those reported for foreing ball caged valves. Finally, most of our patients showed a marked improvement postoperatively

Reemplazo valvular con prótesis mecánica de bola de fabricación nacional / Valve replacement with cage ball valve manufactured in Mexico

Este informe preliminar documenta la experiencia clínica con el uso de una prótesis mecánica de bola de fabricación nacional mexicana. Entre mayo de 1985 y marzo de 1986, se efectuaron en forma consecutiva 25 reemplazos valvulares en 23 pacientes: 14 en posición aórtica, 9 mitrales y 2 mitro aórtios. La edad promedio fue de 32 años. La etiología fue reumática en el 95% de los casos. La clase funcional pre-operatorio fué: clase II en 6 pacientes, clase III en 15 pacientes y clase IV en 2 casos. La mortalidad operatoria fue de un caso (4.5%). Se efectuó seguimiento en todos los sobrevivientes con promedio de 5 meses. No se han observado muertes tardías ni complicaciones relacionadas con la prótesis, la curva de sobrevida actuarial a 10 meses es de 96.0%. La mayor parte de los pacientes pasaron a clase funcional I (80%) y II (20%). Nuestro estudio sugiere que la prótesis mecánica de bola Biomed tiene buen funcionamiento y que los resultados clínicos justifican hasta ahora continuar con el uso de ella