Análisis espacial y ambiental de lecherías infectadas con Mycobacterium avium subsp. paratuberculosis en Antioquia (Colombia)

The present study aimed to describe the spatial distribution of Mycobacterium avium subsp. paratuberculosis (MAP) in dairy herds, and to detail environmental variables taken as reference of the physical background of the study area, specifically those related to MAP-qPCR positive herds located in six municipalities of the Northern region of the Province of Antioquia (Colombia), based on environmental sampling and qPCR analysis. The study herds (n = 386) were located in 63 different districts from six municipalities. Participant herds were visited once between June and October (2016) to collect an environmental sample, and identification of MAP was achieved using a duplex quantitative real-time PCR method. Rainfall trends, day and nighttime surface temperature, and vegetation cover index were taken as environmental references of the physical background of the study area. In addition, distribution maps of MAP-qPCR positive and negative herds, as well as maps of temperature variations and vegetation cover, were constructed. As results, there was an increase in MAP-positive herds in the North-West, South, and Southeast of the study area. An overall high rainfall regime was found and day- and nighttime surface temperatures showed important variations during sampling months. No evidence of management of the vegetation cover was found, in both pastures and areas with native vegetation, except for a conservancy area. In conclusion, the general environmental conditions, where the detection of MAP-positive herds is most likely to happen, were reported herein, considering approaches using the same (or a very approximate) sample collection and handling, and molecular detection method.El presente estudio tuvo como objetivo describir la distribución espacial de Mycobacterium avium subsp paratuberculosis (MAP) en hatos lecheros, y detallar variables ambientales tomadas como referencia de los antecedentes físicos del área de estudio, específicamente aquellas relacionadas con los hatos positivos por MAP-qPCR, ubicados en seis municipios de la región norte de la Provincia de Antioquia (Colombia), de acuerdo con el muestreo ambiental y análisis por qPCR. Los hatos del estudio (n = 386) se ubicaron en 63 distritos diferentes de seis municipios. Los hatos participantes fueron visitados una vez entre junio y octubre (2016) para recolectar una muestra ambiental, y la identificación de MAP se logró utilizando un método de PCR cuantitativa dúplex en tiempo real. Las tendencias de lluvia, la temperatura de la superficie diurna y nocturna, y el índice de cobertura vegetal se tomaron como referencias ambientales del entorno físico del área de estudio. Además, se construyeron mapas de distribución de hatos positivos y negativos a MAP-qPCR, así como mapas de variaciones de temperatura y cobertura vegetal. Como resultado, hubo un aumento en los hatos positivos para MAP en el noroeste, sur y sudeste del área de estudio. Se encontró un régimen general de alta precipitación y las temperaturas superficiales diurnas y nocturnas mostraron variaciones importantes durante los meses de muestreo. No se encontró evidencia de manejo de la cubierta vegetal, tanto en pastizales como en áreas con vegetación nativa, excepto en un área de conservación. En conclusión, se reportan las condiciones Recibido: mmmm_AAAA / Aceptado: mmmm_AAAA 11ambientales generales, donde es más probable que ocurra la detección de hatos positivospara MAP, considerando enfoques que utilizan el mismo método de recolección (o uno muyaproximado), el manejo de muestras y el método de detección molecular

Spatial and environmental analysis of Mycobacterium avium infected dairies in Antioquía (Colombia)

The present study aimed to describe the spatial distribution of Mycobacterium avium subsp. paratuberculosis (MAP) in dairy herds, and to detail environmental variables taken as refer- ence of the physical background of the study area, specifically those related to MAP-qPCR positive herds located in six municipalities of the northern region of the Province of Antioquia (Colombia), based on environmental sampling and qPCR analysis. The study herds (n = 386) were located in 63 different districts from six municipalities. Participant herds were visited once between June and October (2016) to collect an environmental sample, and iden- tification of MAP was achieved using a duplex quantitative real-time PCR method. Rainfall trends, day and nighttime surface temperature, and vegetation cover index were taken as environmental references of the physical background of the study area. In addition, distribution maps of MAP-qPCR positive and negative herds, as well as maps of temperature variations and vegetation cover, were constructed. As a result, there was an increase in MAP-positive herds in the North-West, South, and Southeast of the study area. An overall high rainfall regime was found and day- and nighttime surface temperatures showed important variations during sampling months. No evidence of management of the vegetation cover was found, in both pastures and areas with native vegetation, except for a conservancy area. In conclusion, the general environmental conditions, where the detection of MAP-positive herds is most likely to happen, were reported herein, considering approaches using the same (or a very ap- proximate) sample collection and handling, and molecular detection method

Xanthomonas axonopodis pv. eucalyptorum pv. nov. causing bacterial leaf blight on eucalypt in Brazil.

Bacterial leaf blight is a major disease of eucalypt, especially under nursery conditions. Different bacterial species have been associated with the disease in several countries, and despite its importance worldwide, it is not clear to date whether similar disease symptoms are caused by the same or by different etiological agents. In this study, 43 bacterial strains were isolated from blighted eucalypt leaves collected in different geographic areas of Brazil and inoculated onto a susceptible eucalypt clone. Polyphasic taxonomy, including morphological, physiological, biochemical, molecular, and pathogenicity tests showed that only certain strains of Xanthomonas axonopodis caused symptoms of the disease. Strains varied in their aggressiveness, but no correlation with geographic origin was observed. MLSA-based phylogenetic analysis using concatenated dnaK, fyuA, gyrB and rpoD gene sequences allocated the strains in a well-defined clade, corresponding to Rademarker?s group RG 9.6. Inoculation of nineteen plant species belonging to seven botanical families with representative strain LPF 602 showed it to be pathogenic only on Eucalyptus spp, and Corymbia spp. Based on distinct biochemical and pathogenic characteristics that differentiate the eucalypt strains from other pathovars of the X. axonopodis species, here we propose their allocation into the new pathovar X. axonopodis pv. eucalyptorum pv. nov

An Investigation of the Ionic Conductivity and Species Crossover of Lithiated Nafion 117 in Nonaqueous Electrolytes

Nonaqueous redox flow batteries are a fast-growing area of research and development motivated by the need to develop low-cost energy storage systems. The identification of a highly conductive, yet selective membrane, is of paramount importance to enabling such a technology. Herein, we report the swelling behavior, ionic conductivity, and species crossover of lithiated Nafion 117 membranes immersed in three nonaqueous electrolytes (PC, PC : EC, and DMSO). Our results show that solvent volume fraction within the membrane has the greatest effect on both conductivity and crossover. An approximate linear relationship between diffusive crossover of neutral redox species (ferrocene) and the ionic conductivity of membrane was observed. As a secondary effect, the charge on redox species modifies crossover rates in accordance with Donnan exclusion. The selectivity of membrane is derived mathematically and compared to experimental results reported here. The relatively low selectivity for lithiated Nafion 117 in nonaqueous conditions suggests that new membranes are required for competitive nonaqueous redox flow batteries to be realized. Potential design rules are suggested for the future membrane engineering work.United States. Dept. of Energy. Office of Basic Energy Sciences. Joint Center for Energy Storage Researc

Photosynthesis, leaf hydraulic conductance and embolism dynamics in the resurrection plant Barbacenia purpurea

The main parameters determining photosynthesis are stomatal and mesophyll conductance and electron transport rate, and for hydraulic dynamics they are leaf hydraulic conductance and the spread of embolism. These parameters have scarcely been studied in desiccation-tolerant (resurrection) plants exposed to drought. Here, we characterized photosynthesis and hydraulics during desiccation and rehydration in a poikilochlorophyllous resurrection plant, Barbacenia purpurea (Velloziaceae). Gas exchange, chlorophyll fluorescence, and leaf water status were monitored along the whole dehydration-rehydration cycle. Simultaneously, embolism formation and hydraulic functioning recovery were measured at leaf level using micro-computed tomography imaging. Photosynthesis and leaf hydraulic conductance ceased at relatively high water potential (?1.28 and ?1.54?MPa, respectively), whereas the onset of leaf embolism occurred after stomatal closure and photosynthesis cessation (<?1.61?MPa). This sequence of physiological processes during water stress may be associated with the need to delay dehydration, to prepare the molecular changes required in the desiccated state. Complete rehydration occurred rapidly in the mesophyll, whereas partial xylem refilling, and subsequent recovery of photosynthesis, occurred at later stages after rewatering. These results highlight the importance of stomata as safety valves to protect the vascular system from embolism, even in a plant able to fully recover after complete embolism.Este trabajo fue apoyado por el proyecto PGC2018-093824-B-C41 del Ministerio de Ciencia, Innovación y Universidades (España), el Fondo Europeo de Desarrollo Regional (FEDER), y La Région Auvergne-Rhône-Alpes "Pack Ambition International 2020" a través del proyecto "ThirsTree" 20-006175-01, 20-006175-02. MN recibió el apoyo de la beca predoctoral BES-2015-072578, financiada por el Ministerio de Economía y Competitividad (MINECO) y el Fondo Social Europeo; y las becas postdoctorales Juan de la Cierva-Formación (FJC2020-043902-I y FJC2020-042856-I), financiadas por MCIN/AEI/10.13039/501100011033 (España) y la Unión Europea ("NextGenerationEU/PRTR").Barbacenia purpureaPublishe

Representation of Dynamical Stimuli in Populations of Threshold Neurons

Many sensory or cognitive events are associated with dynamic current modulations in cortical neurons. This raises an urgent demand for tractable model approaches addressing the merits and limits of potential encoding strategies. Yet, current theoretical approaches addressing the response to mean- and variance-encoded stimuli rarely provide complete response functions for both modes of encoding in the presence of correlated noise. Here, we investigate the neuronal population response to dynamical modifications of the mean or variance of the synaptic bombardment using an alternative threshold model framework. In the variance and mean channel, we provide explicit expressions for the linear and non-linear frequency response functions in the presence of correlated noise and use them to derive population rate response to step-like stimuli. For mean-encoded signals, we find that the complete response function depends only on the temporal width of the input correlation function, but not on other functional specifics. Furthermore, we show that both mean- and variance-encoded signals can relay high-frequency inputs, and in both schemes step-like changes can be detected instantaneously. Finally, we obtain the pairwise spike correlation function and the spike triggered average from the linear mean-evoked response function. These results provide a maximally tractable limiting case that complements and extends previous results obtained in the integrate and fire framework

From Spiking Neuron Models to Linear-Nonlinear Models

Neurons transform time-varying inputs into action potentials emitted stochastically at a time dependent rate. The mapping from current input to output firing rate is often represented with the help of phenomenological models such as the linear-nonlinear (LN) cascade, in which the output firing rate is estimated by applying to the input successively a linear temporal filter and a static non-linear transformation. These simplified models leave out the biophysical details of action potential generation. It is not a priori clear to which extent the input-output mapping of biophysically more realistic, spiking neuron models can be reduced to a simple linear-nonlinear cascade. Here we investigate this question for the leaky integrate-and-fire (LIF), exponential integrate-and-fire (EIF) and conductance-based Wang-Buzsáki models in presence of background synaptic activity. We exploit available analytic results for these models to determine the corresponding linear filter and static non-linearity in a parameter-free form. We show that the obtained functions are identical to the linear filter and static non-linearity determined using standard reverse correlation analysis. We then quantitatively compare the output of the corresponding linear-nonlinear cascade with numerical simulations of spiking neurons, systematically varying the parameters of input signal and background noise. We find that the LN cascade provides accurate estimates of the firing rates of spiking neurons in most of parameter space. For the EIF and Wang-Buzsáki models, we show that the LN cascade can be reduced to a firing rate model, the timescale of which we determine analytically. Finally we introduce an adaptive timescale rate model in which the timescale of the linear filter depends on the instantaneous firing rate. This model leads to highly accurate estimates of instantaneous firing rates

Combined assessment of DYRK1A, BDNF and homocysteine levels as diagnostic marker for Alzheimer’s disease

Early identification of Alzheimer’s disease (AD) risk factors would aid development of interventions to delay the onset of dementia, but current biomarkers are invasive and/or costly to assess. Validated plasma biomarkers would circumvent these challenges. We previously identified the kinase DYRK1A in plasma. To validate DYRK1A as a biomarker for AD diagnosis, we assessed the levels of DYRK1A and the related markers brain-derived neurotrophic factor (BDNF) and homocysteine in two unrelated AD patient cohorts with age-matched controls. Receiver-operating characteristic curves and logistic regression analyses showed that combined assessment of DYRK1A, BDNF and homocysteine has a sensitivity of 0.952, a specificity of 0.889 and an accuracy of 0.933 in testing for AD. The blood levels of these markers provide a diagnosis assessment profile. Combined assessment of these three markers outperforms most of the previous markers and could become a useful substitute to the current panel of AD biomarkers. These results associate a decreased level of DYRK1A with AD and challenge the use of DYRK1A inhibitors in peripheral tissues as treatment. These measures will be useful for diagnosis purposes.This work was supported by the FEANS. We acknowledge the platform accommodation and animal testing of the animal facility at the Institute Jacques-Monod (University Paris Diderot) and the FlexStation3 facility of the Functional and Adaptive Biology (BFA) LaboratoryPeer reviewe

Effective Stimuli for Constructing Reliable Neuron Models

The rich dynamical nature of neurons poses major conceptual and technical challenges for unraveling their nonlinear membrane properties. Traditionally, various current waveforms have been injected at the soma to probe neuron dynamics, but the rationale for selecting specific stimuli has never been rigorously justified. The present experimental and theoretical study proposes a novel framework, inspired by learning theory, for objectively selecting the stimuli that best unravel the neuron's dynamics. The efficacy of stimuli is assessed in terms of their ability to constrain the parameter space of biophysically detailed conductance-based models that faithfully replicate the neuron's dynamics as attested by their ability to generalize well to the neuron's response to novel experimental stimuli. We used this framework to evaluate a variety of stimuli in different types of cortical neurons, ages and animals. Despite their simplicity, a set of stimuli consisting of step and ramp current pulses outperforms synaptic-like noisy stimuli in revealing the dynamics of these neurons. The general framework that we propose paves a new way for defining, evaluating and standardizing effective electrical probing of neurons and will thus lay the foundation for a much deeper understanding of the electrical nature of these highly sophisticated and non-linear devices and of the neuronal networks that they compose