Mesopelagic N-2 fixation related to organic matter composition in the Solomon and Bismarck Seas (Southwest Pacific)

Dinitrogen (N-2) fixation was investigated together with organic matter composition in the mesopelagic zone of the Bismarck (Transect 1) and Solomon (Transect 2) Seas (Southwest Pacific). Transparent exopolymer particles (TEP) and the presence of compounds sharing molecular formulae with saturated fatty acids and sugars, as well as dissolved organic matter (DOM) compounds containing nitrogen (N) and phosphorus (P) were higher on Transect 1 than on Transect 2, while oxygen concentrations showed an opposite pattern. N-2 fixation rates (up to similar to 1 nmol N L-1 d(-1)) were higher in Transect 1 than in Transect 2, and correlated positively with TEP, suggesting a dependence of diazotroph activity on organic matter. The scores of the multivariate ordination of DOM molecular formulae and their relative abundance correlated negatively with bacterial abundances and positively with N-2 fixation rates, suggesting an active bacterial exploitation of DOM and its use to sustain diazotrophic activity. Sequences of the nifH gene clustered with Alpha-, Beta-, Gamma- and Deltaproteobacteria, and included representatives from Clusters I, III and IV. A third of the clone library included sequences close to the potentially anaerobic Cluster III, suggesting that N-2 fixation was partially supported by presumably particle-attached diazotrophs. Quantitative polymerase chain reaction (qPCR) primer-probe sets were designed for three phylotypes and showed low abundances, with a phylotype within Cluster III at up to 10(3) nifH gene copies L-1. These results provide new insights into the ecology of non-cyanobacterial diazotrophs and suggest that organic matter sustains their activity in the mesopelagic ocean

Species richness influences the spatial distribution of trees in European forests

The functioning of plant communities is strongly influenced by the number of species in the community and their spatial arrangement. This is because plants interact with their nearest neighbors and this interaction is expected to be stronger when the interacting individuals are ecologically similar in terms of resource use. Recent evidence shows that species richness alters the balance of intra- versus interspecific competition, but the effect of species richness, and phylogenetic and functional diversity on the spatial pattern of the plant communities remain less studied. Even far, how forest stand structure derived from past management practices can influence the relationship between species richness and spatial pattern is still unknown. Here, we evaluate the spatial distribution of woody individuals (DBH >7.5 cm) in 209 forest stands (i.e. plots) with an increasing level of species richness (from 1 up to 10 species) in six forest types along a latitudinal gradient in Europe. We used completely mapped plots to investigate the spatial pattern in each forest stand with point pattern techniques. We fitted linear models to analyze the effect of species richness (positively correlated with phylogenetic diversity) and functional diversity on tree spatial arrangements. We also controled this relationship by forest type and stand structure as a proxy of the management legacy. Our results showed a generalized positive effect of species richness and functional diversity on the degree of spatial clustering of trees, and on the spatial independence of tree sizes regardless of the forest type. Moreover, current tree spatial arrangements were still conditioned by its history of management; however its effect was independent of the number of species in the community. Our study showed that species richness and functional diversity are relevant attributes of forests influencing the spatial pattern of plant communities, and consequently forest functioning. © 2019 Nordic Society Oikos. Published by John Wiley & Sons LtdThis research was supported by the FunDivEUROPE project, receiving funding from the European Union Seventh Framework Programme (FP7/2007–2013) under grant agreement no.265171, the Spanish‐funded project REMEDINAL TE‐CM S2018/EMT‐4338 and COMEDIAS FEDER/Ministerio de Ciencia, Innovación y Universidades – Agencia Estatal de Investigación/_Proyecto CGL2017‐83170‐R. RB was funded by a Marie Skłodowska‐Curie Intra‐European fellowship (grant agreement no. 302445)

Efecto del uso de fluazurón para control de Rhipicephalus (Boophilus) microplus en bovinos

Objective. To demonstrate the effect on the tick population of the use of fluazuron in grazing cattle. Materials and methods. Case study performed in Fusagasuga (Cundinamarca, Colombia); three groups of 25 heifers each were formed, G1= two applications of Fluazuron separated 60 days, G2= fluazuron applied only on study day 0 and G3= treated with a spray of chlorpyriphos. Periodically tick count was done in five animals of each group and the degree of contamination of pastures with tick larvae was determined by dragging. Results. Infestation levels between the groups were not homogeneous, and the paddocks also showed different levels of larval infestation. The compound was useful for protecting animals from tick infestation for more than eight weeks. Given the soil temperature in the region, the adult larva period is fulfilled between 50 and 65 days. Conclusion. The effect of treatment of cattle with fluazuron on larval contamination of pastures will only be reflected almost two months after treatment. Strategic design schemes must consider this component, of the soil temperature.Objetivo. Demostrar el efecto poblacional sobre la garrapata del uso de fluazurón en ganado en pastoreo. Materiales y métodos. Estudio de caso realizado en Fusagasugá (Cundinamarca, Colombia); se conformaron tres grupos de 25 novillas cada uno, G1= dos aplicaciones de Fluazurón separadas 60 días, G2= fluazurón sólo el día 0 del estudio y G3= tratado por aspersión con Clorpirifos. Se hizo periódicamente recuento de teleoginas en cinco bovinos de cada grupo y se determinó el grado de contaminación de praderas con larvas de garrapata, mediante rastreo. Resultados. Los niveles de infestación entre los grupos no fueron homogéneos, y los potreros también demostraron diversos niveles de infestación larvaria. El compuesto fue útil para proteger a los animales de la infestación por garrapatas por más de ocho semanas. Dada la temperatura del suelo en la región, el período adulto larva se cumple entre 50 y 65 días. Conclusión. El efecto del tratamiento del ganado con fluazurón sobre la contaminación larvaria de las praderas, sólo se reflejará casi dos meses después del tratamiento. El diseño de esquemas estratégicos debe considerar este componente, de la temperatura del suelo

Efecto del uso de fluazurón para control de Rhipicephalus (Boophilus) microplus en bovinos

Objective. To demonstrate the effect on the tick population of the use of fluazuron in grazing cattle. Materials and methods. Case study performed in Fusagasuga (Cundinamarca, Colombia); three groups of 25 heifers each were formed, G1= two applications of Fluazuron separated 60 days, G2= fluazuron applied only on study day 0 and G3= treated with a spray of chlorpyriphos. Periodically tick count was done in five animals of each group and the degree of contamination of pastures with tick larvae was determined by dragging. Results. Infestation levels between the groups were not homogeneous, and the paddocks also showed different levels of larval infestation. The compound was useful for protecting animals from tick infestation for more than eight weeks. Given the soil temperature in the region, the adult larva period is fulfilled between 50 and 65 days. Conclusion. The effect of treatment of cattle with fluazuron on larval contamination of pastures will only be reflected almost two months after treatment. Strategic design schemes must consider this component, of the soil temperature.Objetivo. Demostrar el efecto poblacional sobre la garrapata del uso de fluazurón en ganado en pastoreo. Materiales y métodos. Estudio de caso realizado en Fusagasugá (Cundinamarca, Colombia); se conformaron tres grupos de 25 novillas cada uno, G1= dos aplicaciones de Fluazurón separadas 60 días, G2= fluazurón sólo el día 0 del estudio y G3= tratado por aspersión con Clorpirifos. Se hizo periódicamente recuento de teleoginas en cinco bovinos de cada grupo y se determinó el grado de contaminación de praderas con larvas de garrapata, mediante rastreo. Resultados. Los niveles de infestación entre los grupos no fueron homogéneos, y los potreros también demostraron diversos niveles de infestación larvaria. El compuesto fue útil para proteger a los animales de la infestación por garrapatas por más de ocho semanas. Dada la temperatura del suelo en la región, el período adulto larva se cumple entre 50 y 65 días. Conclusión. El efecto del tratamiento del ganado con fluazurón sobre la contaminación larvaria de las praderas, sólo se reflejará casi dos meses después del tratamiento. El diseño de esquemas estratégicos debe considerar este componente, de la temperatura del suelo

Comparative Analysis of Different Definitions of Amyloid-beta Positivity to Detect Early Downstream Pathophysiological Alterations in Preclinical Alzheimer

Amyloid-β (Aβ) positivity is defined using different biomarkers and different criteria. Criteria used in symptomatic patients may conceal meaningful early Aβ pathology in preclinical Alzheimer. Therefore, the description of sensitive cutoffs to study the pathophysiological changes in early stages of the Alzheimer’s continuum is critical. Here, we compare different Aβ classification approaches and we show their performance in detecting pathophysiological changes downstream Aβ pathology. We studied 368 cognitively unimpaired individuals of the ALFA+ study, many of whom in the preclinical stage of the Alzheimer’s continuum. Participants underwent Aβ PET and CSF biomarkers assessment. We classified participants as Aβ -positive using five approaches: (1) CSF Aβ42 12; (4) Aβ PET Centiloid > 30 or (5) Aβ PET Positive visual read. We assessed the correlations between Aβ biomarkers and compared the prevalence of Aβ positivity. We determined which approach significantly detected associations between Aβ pathology and tau/neurodegeneration CSF biomarkers. We found that CSF-based approaches result in a higher Aβ-positive prevalence than PET-based ones. There was a higher number of discordant participants classified as CSF Aβ-positive but PET Aβ-negative than CSF Aβ-negative but PET Aβ-positive. The CSF Aβ 42/40 approach allowed optimal detection of significant associations with CSF p-tau and t-tau in the Aβ-positive group. Altogether, we highlight the need for sensitive Aβ -classifications to study the preclinical Alzheimer’s continuum. Approaches that define Aβ positivity based on optimal discrimination of symptomatic Alzheimer’s disease patients may be suboptimal for the detection of early pathophysiological alterations in preclinical Alzheimer

Control of intestinal stem cell function and proliferation by mitochondrial pyruvate metabolism.

Most differentiated cells convert glucose to pyruvate in the cytosol through glycolysis, followed by pyruvate oxidation in the mitochondria. These processes are linked by the mitochondrial pyruvate carrier (MPC), which is required for efficient mitochondrial pyruvate uptake. In contrast, proliferative cells, including many cancer and stem cells, perform glycolysis robustly but limit fractional mitochondrial pyruvate oxidation. We sought to understand the role this transition from glycolysis to pyruvate oxidation plays in stem cell maintenance and differentiation. Loss of the MPC in Lgr5-EGFP-positive stem cells, or treatment of intestinal organoids with an MPC inhibitor, increases proliferation and expands the stem cell compartment. Similarly, genetic deletion of the MPC in Drosophila intestinal stem cells also increases proliferation, whereas MPC overexpression suppresses stem cell proliferation. These data demonstrate that limiting mitochondrial pyruvate metabolism is necessary and sufficient to maintain the proliferation of intestinal stem cells