Regressões lineares em geocronologia: isócronas, errócronas e pseudoisócronas

Several methods of linear regression reported in the literature for use in geochonology are discussed in order to guide geochronologists in the selection of an adequate model and also to distinguish among isochrons, errorchrons and pseudoisochrons. For Rb/Sr isochron methods, at least 6 models or statistical treatments are available, each one with its peculiarities. Based in two examples, we show that for cases when the experimental data points scatter within limits determined by the experimental errors, and using or not the weighted regression treatment, the resultant parameters are essentially concordant. The estimates of associated error, however especially for initial ratios, show variations by up to a factor of 7, depending upon the statistical procedure. In view of this fact and on the basis of simulated test data, we propose not only more adequate models, but also general criteria that must be observed in the selection of samples in order to obtain an isochron. If the data to be regressed show a scatter in excess of experimental error for geological reasons (open system), four regression models are available to treat the parameters defined in these cases as errorchrons. These models are briefly discussed in terms of their applications. In the Pb/U methods, in which the usual regression treatment is applied to obtain the best-fit line, some additional peculiarities are pointed outDiversos métodos de regressão linear propostos na literatura, para fins geocronológicos, são discutidos de modo a orientar os geocronólogos na escolha de modelos adequados e também distinguir entre isócronas, errócronas ou pseudoisócronas. No caso do método isocrôni co Rb/Sr, são disponíveis pelo menos 6 modelos ou abordagens estatísticas, cada qual com peculiaridades específicas. Exemplifica-se o caso em que os pontos se alinham dentro dos erros experimentais e utilizando modelos, adequados ou não, que empregam a técnica de pondera ção dos pontos, os parâmetros resultantes são praticamente concordantes, porém os erros podem variar até por um fator tão alto quanto 7, conforme a formulação estatística proposta. Em vista deste fato, propõem-se, com base também em exemplos, os modelos mais adequados e também critérios gerais que devem ser observados até na seleção de amostras para a obtenção de isócronas. Nos casos em que os pontos não se alinham dentro dos erros experimentais, por causas geológicas (sistema aberto), são abordados 4 dos modelos sugeridos e é feita também uma discussão em que casos seriam aplicáveis. No método da concórdia Pb/U, em que as regressões usuais também são aplicáveis para determinar a melhor reta, algumas particularidades adicionais são discutida

BALB/c Mice Infected with Antimony Treatment Refractory Isolate of Leishmania braziliensis Present Severe Lesions due to IL-4 Production

Leishmaniasis is a neglected disease that affects more than 12 million people worldwide. In Brazil, the cutaneous disease is more prevalent with about 28,000 new cases reported each year, and L. braziliensis is the main causative agent. The interesting data about the infection with this parasite is the wide variety of clinical manifestations that ranges from single ulcerated lesions to mucocutaneous and disseminated disease. However, experimental models to study the infection with this parasite are difficult to develop due to high resistance of most mouse strains to the infection, and the mechanisms underlying the distinct manifestations remain poorly understood. Here, the authors use a mouse experimental model of infection with different L. braziliensis isolates, known to induce diseases with distinct severity in the human hosts, to elucidate immune mechanisms that may be involved in the different manifestations. They showed that distinct parasite isolates may modulate host response, and increased IL-4 production and Arg I expression was related to more severe disease, resulting in longer length of disease with larger lesions and reduced parasite clearance. These findings may be useful in the identification of immunological targets to control L. braziliensis infection and potential clinical markers of disease progression

Characterization of the macrophage transcriptome in glomerulonephritis-susceptible and -resistant rat strains

Crescentic glomerulonephritis (CRGN) is a major cause of rapidly progressive renal failure for which the underlying genetic basis is unknown. WKY rats show marked susceptibility to CRGN, while Lewis rats are resistant. Glomerular injury and crescent formation are macrophage-dependent and mainly explained by seven quantitative trait loci (Crgn1-7). Here, we used microarray analysis in basal and lipopolysaccharide (LPS)-stimulated macrophages to identify genes that reside on pathways predisposing WKY rats to CRGN. We detected 97 novel positional candidates for the uncharacterised Crgn3-7. We identified 10 additional secondary effector genes with profound differences in expression between the two strains (>5-fold change, <1% False Discovery Rate) for basal and LPS-stimulated macrophages. Moreover, we identified 8 genes with differentially expressed alternatively spliced isoforms, by using an in depth analysis at probe-level that allowed us to discard false positives due to polymorphisms between the two rat strains. Pathway analysis identified several common linked pathways, enriched for differentially expressed genes, which affect macrophage activation. In summary, our results identify distinct macrophage transcriptome profiles between two rat strains that differ in susceptibility to glomerulonephritis, provide novel positional candidates for Crgn3-7, and define groups of genes that play a significant role in differential regulation of macrophage activity

Physical and chemical characterization of biochars derived from different agricultural residues

Biochar is widely recognized as an efficient tool for carbon sequestration and soil fertility. The understanding of its chemical and physical properties, which are strongly related to the type of the initial material used and pyrolysis conditions, is crucial to identify the most suitable application of biochar in soil. A selection of organic wastes with different characteristics (e.g., rice husk (RH), rice straw (RS), wood chips of apple tree (Malus pumila) (AB), and oak tree (Quercus serrata) (OB)) were pyrolyzed at different temperatures (400, 500, 600, 700, and 800 °C) in order to optimize the physicochemical properties of biochar as a soil amendment. Low-temperature pyrolysis produced high biochar yields; in contrast, high-temperature pyrolysis led to biochars with a high C content, large surface area, and high adsorption characteristics. Biochar obtained at 600 °C leads to a high recalcitrant character, whereas that obtained at 400 °C retains volatile and easily labile compounds. The biochar obtained from rice materials (RH and RS) showed a high yield and unique chemical properties because of the incorporation of silica elements into its chemical structure. The biochar obtained from wood materials (AB and OB) showed high carbon content and a high absorption character.This work was partly supported by the bilateral project of the Japan Society for the Promotion of Science (JSPS) and the Spanish National Research Council (CSIC).Peer reviewe

Serum total cholesterol concentration and 10-year mortality in an 85-year-old population

Yutaka Takata,1 Toshihiro Ansai,2 Inho Soh,2 Shuji Awano,2 Ikuo Nakamichi,1 Sumio Akifusa,3 Kenichi Goto,1 Akihiro Yoshida,2 Hiroki Fujii,1 Ritsuko Fujisawa,1 Kazuo Sonoki3 1Division of General Internal Medicine, 2Division of Community Oral Health Development, 3Department of Oral Health and Environment, School of Oral Health Science, Kyushu Dental College, Kitakyushu, Japan Abstract: Little is known about the association between total cholesterol (TC) and all-cause mortality in the elderly (especially the very elderly). Here we examined the association between TC and all-cause mortality in 207 very elderly (85-year-old) participants. In 2003, we performed a baseline laboratory blood examination, and blood pressure (BP) and body mass index (BMI) measurements, and lifestyle questionnaires were completed by the participants. The participants were followed for the subsequent 10 years. As of 2013, of the 207 participants in 2003, 70 participants had survived, 120 individuals had died, and 17 were lost to follow up. The TC values were divided into high-TC (&ge;209 mg/dL), intermediate-TC (176&ndash;208 mg/dL), and low-TC (&le;175 mg/dL) categories. With the Kaplan&ndash;Meier method, we found that both the high-TC and intermediate-TC participants survived longer than the low-TC participants. The men with high TC survived longer than those with low TC, but no corresponding difference was found for the women. A multivariate Cox proportional hazards regression model, with adjustment for gender, smoking, alcohol intake, history of stroke or heart disease, serum albumin concentration, BMI, and systolic BP, revealed that the total mortality in the low-TC group was 1.7-fold higher than that in the high-TC group. Mortality, adjusted for the same factors, decreased 0.9% with each 1 mg/dL increase in the serum TC concentration and decreased 0.8% with each 1 mg/dL increase in the serum (low-density lipoprotein) LDL-cholesterol (LDL-C) concentration. Our results indicate an association between lower serum TC concentrations and increased all-cause mortality in a community-dwelling, very elderly population. Mortality decreased with the increases in both TC and LDL-C concentrations, after adjustment for various confounding factors. These findings suggest that low TC and low LDL-C may be independent predictors of high mortality in the very elderly. Keyword: community-dwelling, very elderly, LDL-cholesterol, gender difference, prospective cohor