Different composition of plant residues as a driver of microbial community structure and soil organic matter composition: a microcosm study.

Soil organic matter (SOM) is the main pathway of carbon (C) input to the soil with the decomposition of shoot residues, roots and their exudates. The objective was to evaluate the contribution of different vegetal composition and plant parts of Caatinga species and the effects of introducing a grass in the soil microbial community structure and biochemical composition of SOM. A trial was conducted under controlled conditions (120 days) using, separately, the shoot and roots residues of native species from the herbaceous (HERB) and shrub-arboreal (ARB) strata and a grass (GRASS). Megathyrsus maximum, which is native from Africa, but well adapted to the semi-arid conditions of Brazil, was used. Combinations of these species in different proportions were also evaluated: (i) 55 % shrub and trees + 45 % grass (MIX1) and (ii) 75 % shrub and trees + 25 % grass (MIX2). At the end of incubation, soil samples were collected to evaluate the microbial community structure through the phospholipid fatty acids (PLFA). Physical fractioning of SOM into particulate organic matter (POM) and mineralassociated organic matter (MAOM) was also performed, followed by biochemical characterization of these fractions by thermochemolysis analysis. The ARB shoot residue resulted in a 181.5 % increase (p < 0.05) in total PLFA biomass in the soil. A significant increase (p < 0.05) in the abundance of fungi and bacteria was observed with the incorporation of shoot residues. MAOM was characterized by a higher abundance of aliphatic (31.6 ± 5.0 %) and nitrogen-bearing compounds (21.0 ± 2.0 %), while higher lignin derivatives were observed in POM (18.0 ± 0.6 %). The ground cover provided a diversity of compounds in the SOM, thus regulating the structure of the microbial community. These results highlight the importance of conserving biodiversity, both in natural ecosystems and in agroecosystems in the semi-arid environment

Volatilização de amônia proveniente da uréia adicionada de zeolita natural.

Para aumentar a eficiência do uso de N-fertilizante novas tecnologias devem ser desenvolvidas a fim de reduzir as perdas desse nutriente. Zeolitas naturais podem reduzir perdas de amônia por volatilização, porém aditivos ligantes e tamanho do granulo podem afetar esse efeito. Implantou-se um experimento em casa de vegetação, onde cinco formulações de uréia adicionada de zeolitas e ligante orgânico, em três classes granulométricas, 4mm, mais sulfato de amônio e uréia recoberta com inibidor de urease NBPT foram aplicados na superfície de Planossolo Háplico, em dose equivalente a 100 kg N ha-1. Foram avaliadas as perdas por volatilização de amônia durante 13 dias, através de coletor semi-aberto. A adição de zeolitas naturais recobrindo ou em todo grânulo da uréia diminuiu as perdas por volatilização 20%, em média, com destaque para NZ2 (recobrimento da uréia granulometria > 4 mm) que diminui as perdas em 64%, equivalente à uréia recoberta com NBPT

Quantification of damage in DNA recovered from highly degraded samples – a case study on DNA in faeces

BACKGROUND: Poorly preserved biological tissues have become an important source of DNA for a wide range of zoological studies. Measuring the quality of DNA obtained from these samples is often desired; however, there are no widely used techniques available for quantifying damage in highly degraded DNA samples. We present a general method that can be used to determine the frequency of polymerase blocking DNA damage in specific gene-regions in such samples. The approach uses quantitative PCR to measure the amount of DNA present at several fragment sizes within a sample. According to a model of random degradation the amount of available template will decline exponentially with increasing fragment size in damaged samples, and the frequency of DNA damage (λ) can be estimated by determining the rate of decline. RESULTS: The method is illustrated through the analysis of DNA extracted from sea lion faecal samples. Faeces contain a complex mixture of DNA from several sources and different components are expected to be differentially degraded. We estimated the frequency of DNA damage in both predator and prey DNA within individual faecal samples. The distribution of fragment lengths for each target fit well with the assumption of a random degradation process and, in keeping with our expectations, the estimated frequency of damage was always less in predator DNA than in prey DNA within the same sample (mean λ(predator )= 0.0106 per nucleotide; mean λ(prey )= 0.0176 per nucleotide). This study is the first to explicitly define the amount of template damage in any DNA extracted from faeces and the first to quantify the amount of predator and prey DNA present within individual faecal samples. CONCLUSION: We present an approach for characterizing mixed, highly degraded PCR templates such as those often encountered in ecological studies using non-invasive samples as a source of DNA, wildlife forensics investigations and ancient DNA research. This method will allow researchers to measure template quality in order to evaluate alternate sources of DNA, different methods of sample preservation and different DNA extraction protocols. The technique could also be applied to study the process of DNA decay

Data collection and analysis strategies for phMRI

Although functional MRI traditionally has been applied mainly to study changes in task-induced brain function, evolving acquisition methodologies and improved knowledge of signal mechanisms have increased the utility of this method for studying responses to pharmacological stimuli, a technique often dubbed “phMRI”. The proliferation of higher magnetic field strengths and the use of exogenous contrast agent have boosted detection power, a critical factor for successful phMRI due to the restricted ability to average multiple stimuli within subjects. Receptor-based models of neurovascular coupling, including explicit pharmacological models incorporating receptor densities and affinities and data-driven models that incorporate weak biophysical constraints, have demonstrated compelling descriptions of phMRI signal induced by dopaminergic stimuli. This report describes phMRI acquisition and analysis methodologies, with an emphasis on data-driven analyses. As an example application, statistically efficient datadriven regressors were used to describe the biphasic response to the mu-opioid agonist remifentanil, and antagonism using dopaminergic and GABAergic ligands revealed modulation of the mesolimbic pathway. Results illustrate the power of phMRI as well as our incomplete understanding of mechanisms underlying the signal. Future directions are discussed for phMRI acquisitions in human studies, for evolving analysis methodologies, and for interpretative studies using the new generation of simultaneous PET/MRI scanners.status: publishe

Desenvolvimento e avaliação agronômica de novos fertilizantes organominerais como fonte de potássio para a produção orgânica.

A utilização de fertilizantes com alta eficiência agronômica no sistema de produção orgânico é muito limitado. O desenvolvimento de novas tecnologias na área é muito importante, visto a necessidade que esse setor possui. Foram desenvolvidos novos fertilizantes organominerais para servir como fonte de K2O para esse sistema. Esses produtos foram avaliados quanto à aplicação e eficiência no suprimento de potássio, usando como cultura teste o Rabanete. A matéria orgânica presente no composto influenciou no acumulo de matéria seca. Os fertilizantes organominerais obtiveram melhores resultados no acúmulo de matéria seca e de potássio aos fertilizantes minerais

Cortical depth-specific microvascular dilation underlies laminar differences in blood oxygenation level-dependent functional MRI signal

Changes in neuronal activity are accompanied by the release of vasoactive mediators that cause microscopic dilation and constriction of the cerebral microvasculature and are manifested in macroscopic blood oxygenation level-dependent (BOLD) functional MRI (fMRI) signals. We used two-photon microscopy to measure the diameters of single arterioles and capillaries at different depths within the rat primary somatosensory cortex. These measurements were compared with cortical depth-resolved fMRI signal changes. Our microscopic results demonstrate a spatial gradient of dilation onset and peak times consistent with “upstream” propagation of vasodilation toward the cortical surface along the diving arterioles and “downstream” propagation into local capillary beds. The observed BOLD response exhibited the fastest onset in deep layers, and the “initial dip” was most pronounced in layer I. The present results indicate that both the onset of the BOLD response and the initial dip depend on cortical depth and can be explained, at least in part, by the spatial gradient of delays in microvascular dilation, the fastest response being in the deep layers and the most delayed response in the capillary bed of layer I