A stable Leifsonia xyli subsp. xyli GFP‐tagged strain reveals a new colonization niche in sugarcane tissues

Ratoon stunting disease (RSD), caused by the bacterium Leifsonia xyli subsp. xyli (Lxx), is one of the most economically important diseases of sugarcane worldwide. Because knowledge on the interaction of Lxx with its host at the microscopic level is limited, the development of tools to monitor Lxx during the colonization process could shed new light on the processes that control disease development. In this investigation, a transformation protocol was optimized and a mutant Lxx strain engineered that stably expressed the gfp gene in sugarcane tissues. In vitro, the growth of the mutant did not differ from that of the wild type. Also, plants inoculated with both strains showed comparable growth and development when analysed 180 days after inoculation (dai). Fluorescence microscopy of roots, stalks, meristems and leaf tissues of Lxx‐GFP‐inoculated plants was performed at 180 dai. In the leaves, Lxx‐tagged cells were observed within the xylem vessels as has been described before but, in addition, they were found in a new niche within the host tissues, in the mesophyll and in the bundle sheath cells surrounding the vascular system. This finding indicates that Lxx is able to move from the xylem to the parenchyma of the leaf cells. This first report of an Lxx mutant expressing a heterologous gene revealed that colonization of sugarcane by this pathogen is not limited to the xylem vessels as commonly reported.     

Morphological comparison of wild,farmed and hybrid specimens of two South American silversides,Odontesthes bonariensis and Odontesthes hatcheri

In this study, body shape of hybrid and presumptive introgressed South American silversides was studied. Body shape of O. bonariensis and O. hatcheri from wild populations and farmed stocks was compared to provide basic information on the effects of fish farming on morphometric parameters. Subsequently, wild presumptive introgressed individuals and artificially hybridized farmed individuals were morphologically analysed to assess the effects of hybridization on the same parameters. Most farmed purebred individuals were shorter and higher than their wild counterparts, which is probably due to the favourable growth conditions compared to the wild habitat. However, the results evidenced that purebred individuals were more slender than both hybrid (farmed) fish and introgressed (wild) fish. Further studies on the growth performance of hybrid Odontesthes will be required in order to assess whether the combination of hybridization and sterilization could produce, under farming conditions, growth performances which satisfy the requirements of aquaculture.     

Daily rhythm of salivary and serum urea concentration in sheep

Background  

In domestic animals many biochemical and physiological processes exhibit daily rhythmicity. The aim of the present study was to investigate the rhythmic pattern of salivary and serum urea concentrations in sheep.     

The use of Kohonen neural networks for runoff–erosion modeling

Purpose

We investigated the application of Kohonen Neural Networks (KNNs) in order to estimate sediment yield based on runoff and climatological data in a semiarid region of Brazil. Accurate estimations of sediment yield are essential to improve the management of soil erosion in semiarid areas, where large quantities of sediments tend to be produced only periodically.

Materials and methods

The case study is an erosion plot within the São João do Cariri Experimental Basin, which is located in the semiarid portion of Paraíba State, Brazil. KNNs are unsupervised neural networks capable of reducing a multidimensional data set to a bidimensional matrix of features, which can be used for analysis and prediction purposes. A total of 60 rainfall events, which occurred between 1999 and 2002, were used to calibrate and test the model. The application of a multivariate linear regression (MLR) model was also carried out.

Results and discussion

Statistical indexes were used as criteria for evaluating the performance of the KNN and MLR models for the test data set. The correlation and relative bias of the KNN model estimations with those from observed data were 0.90 and ?4.39 %, respectively. A correlation of 0.70 and a relative bias of 15.63 % were found from the comparison of sediment yields obtained by the MLR model with those of the observed data. Analysis of the outcomes indicates that the KNN model, which is capable of detecting and extracting nonlinear trends, produced more reliable results than the regression model.

Conclusions

The KNN model results appear to be superior to those generated by the MLR model and suggest that the developed methodology may be applied to similar case studies.     

Prior and concomitant dehydroepiandrosterone treatment affects immunologic response of cultured macrophages infected with Trypanosoma cruzi in vitro?

DHEA, a steroid hormone synthesized from cholesterol by cells of the adrenal cortex, plays an essential role in enhancing the host's resistance to different experimental infections. Receptors for this hormone can be found in distinct immune cells (especially macrophages) that are known to be the first line defense against Trypanosoma cruzi infection. These cells operate through an indirect pathway releasing nitric oxide (NO) and cytokines such TNF-α and IL-12 which in turn trigger an enhancement of natural killer cells and lymphocytes which finally secrete pro and anti-inflammatory cytokines. The effects of pre- and post-infection DHEA treatment on production of IL-12, TNFα and NO were evaluated. T. cruzi infected macrophages post treated with DHEA displayed enhanced concentrations of TNF-α, IL-12 and NO. Probably, the mechanisms that induced the production of cytokines by infected cells are more efficient when the immune system has been stimulated first by parasite invasion, suggesting that the protective role of DHEA is greater when administered post infection.     

Meta-analysis of the effects of endoparasites on pig performance

A meta-analysis was carried out in order to study the effects of endoparasites on the performance of growing pigs. Criteria that should be considered for the publication selection were: (1) the health challenge caused by parasites; (2) pig in growing phase; (3) presentation of the nutritional composition of the diets and (4) animal performance. Meta-analysis followed three sequential analysis: graphical, correlation and variance-covariance. The group that were infected with parasites had an average daily feed intake 5% lower than that the control group (2044 vs. 2147 g d(-1); P<0.001), their average daily weight gain was also 31% lower (665 vs. 987 g d(-1); P<0.001) and their feed conversion ratio was 17% superior than that of the control group (3.07 vs. 2.62; P<0.001). The variance decomposition demonstrated that 59% of the reduction in weight gain was explained by the reduction in their feed intake, as well as a 6% reduction being due to parasites.     

Synthesis of a combinatorial library of amides and its evaluation against the fall armyworm, Spodoptera frugiperda

The fall armyworm Spodoptera frugiperda is a polyphagous pest that causes important damage in different regions of America and mainly affects corn crops in both tropical and subtropical areas. Currently, control relies on both transgenic plants and/or chemical pesticides. In this work we describe the preparation of an indexed combinatorial library of amides and its toxic effect by contact against S. frugiperda . (E)-1-(1-Piperidinyl)-3-[4-(trifluoromethoxy)phenyl]-2-propen-1-one was the most active compound with an LD(50) = 0.793 μg mg(-1) of larva. This amide was also evaluated by ingestion and at the lowest concentration (1 mg kg(-1)) achieved 83.3% mortality.