Method validation of nanoparticle tracking analysis to measure pulmonary nanoparticle content: the size distribution in exhaled breath condensate depends on occupational exposure

A particle exposure assessment based on the dose deposited in the lungs would be the gold standard for the evaluation of any resulting health effects. Measuring particles in exhaled breath condensate (EBC)-a matrix containing water and airway lining fluid-could help to evaluate particle retention in the lungs. This study aimed to (1) validate a nanoparticle tracking analysis (NTA) method for determining the particle number concentration and their hydrodynamic size distribution in EBC, and (2) apply this method to EBC collected from workers exposed to soapstone (n = 55) or quartz dust (n = 12) and controls (n = 11). A standard latex bead solution was used to determine the linear range, limit of detection (LOD), repeatability (coefficient of variation, CV), and bias in spiked EBC. An LM10 NanoSight instrument with NTA version 3.1 software was used for measurement. RTubes(®) were used for field collection of EBC. The repeatability obtained for a D50 size distribution in EBC showed less than 8% variability, with a bias <7%. The particle concentration was linear in the range ≤2.5 × 10(8) particles ml(-1) with a LOD of 4 × 10(6) particles ml(-1). A recovery of 117 ± 20% at 6.2 × 10(7) particles ml(-1) was obtained with a CV <10% and a bias <20%. EBC from workers exposed to quartz, who experienced the largest exposure to silica particles, consistently exhibited a statistically significant (p < 0.01) higher concentration of particles in their EBC, with a size distribution shift towards larger values than the other groups. Results showed that the NTA technique performed well for characterizing the size distribution and concentrations of particles in EBC. The technique needs to be corroborated with a larger population of workers

Evidência de infecção por Leishmania (Leishmania) infantum em cães de Juiz de Fora, Minas Gerais, Brasil, detectada pelo teste imunocromatográfico rápido DPP e PCR

In Brazil, domestic dogs are branded as the primary reservoir for zoonotic visceral leishmaniasis, due to the clear positive correlation observed between human and canine infection rates. This study aimed to carry out a serological survey of canine visceral leishmaniasis (CVL) in dogs housed at a public kennel in the municipality of Juiz de Fora, Minas Gerais State, Brazil, using the immunochromatographic TR DPP® CVL rapid test. Additionally, conventional and/or real time PCR assay was used to detect and confirm L. infantum infection in the DPP positive dogs only. Of the 400 dogs studied, most did not present clinical signs for CVL (p ; 0.05). Both conventional and real time PCR tests confirmed L. infantum infection in nine (75.0%) of the twelve DPP seropositive dogs that remained alive during the follow-up period. This study is the first seroepidemiologic survey of CVL held in the city of Juiz de Fora, and the results reinforce the idea that this disease is currently in a process of expansion and urbanization in Brazil. Furthermore, this study highlights the use of the DPP test as an alternative for diagnosing CVL in large and mid-sized cities, due to its ease of implementation.No Brasil, cães domésticos são considerados como os principais reservatórios da leishmaniose visceral zoonótica, devido à clara correlação positiva existente entre as curvas de infecção humana e canina. Este estudo objetivou a realização de um inquérito sorológico da leishmaniose visceral canina (LVC) em cães abrigados em um canil público de Juiz de Fora, Minas Gerais, Brasil, através do teste rápido imunocromatográfico TR DPP®. Adicionalmente, a PCR convencional e/ou em tempo real foi usada para detectar/confirmar a infecção por L. infantum apenas nos animais DPP positivos. Dos 400 cães estudados, a maioria não apresentou sinais clínicos para a LVC (p ; 0,05). PCR convencional e em tempo real confirmaram a infecção por L. infantum em nove (75,0%) dos doze animais DPP positivos que permaneceram vivos durante o estudo. Este é o primeiro estudo soroepidemiológico sobre LVC realizado no município de Juiz de Fora, e os resultados reforçam a idéia de que esta doença está em processo de expansão e urbanização no Brasil. Além disto, este estudo destaca o uso do DPP como uma alternativa para o diagnóstico da LVC em cidades de médio e grande porte, devido à facilidade de execução

Adsorption of Cd, Cu, Ni and Zn in tropical soils under competitive and non-competitive systems

The adsorption of heavy metals in soils affects their behavior in the environment and their bioavailability to plants. The knowledge of the adsorption mechanisms in competitive systems allows a more realistic evaluation of the metals' behavior in the soil than the single metal adsorption. The objectives of this study were (i) to evaluate Cd, Cu, Ni, and Zn adsorption in 14 surface samples (0-0.2 m) of representative soils of the Brazilian humid-tropical region, in competitive and non-competitive systems, and (ii) to establish metal affinity sequences for each soil, based in the maximum adsorption capacity (MAC) estimated by the Langmuir model. The Rhodic Eutrudox, the Kandiudalf Eutrudox, the Arenic Hapludalf, the Arenic Hapludult and the Typic Argiudoll had the highest metals' adsorption capacity, whereas the Typic Quartzipsamment and the sandy-textured Arenic Hapludult had the lowest values. In general, the MAC values for metals were lower in the competitive than in the non-competitive system. In the non-competitive system, the most common affinity sequence was Cu > Zn > Ni > Cd, whereas the most common sequence was Cu > Cd > Zn > Ni in the competitive system. In general, the Langmuir model fitted well the adsorption data of metals on the studied soils.A adsorção de metais pesados em solos afeta seu comportamento e biodisponibilidade às plantas. O conhecimento dos mecanismos de adsorção em sistemas competitivos permite uma avaliação mais realista do comportamento dos metais no solo do que estudos com adsorção de cada metal, isoladamente. Os objetivos desse trabalho foram: (i) avaliar a adsorção de Cd, Cu, Ni e Zn em amostras superficiais (0-0,2 m) de 14 solos representativos da região tropical úmida, em sistema competitivo e não-competitivo, e (ii) estabelecer sequências de afinidade metálica para cada solo, com base nos valores de capacidade máxima de adsorção (CMA) dos metais estimados por meio do modelo de Langmuir. O Rhodic Eutrudox, o Kandiudalfic Eutrudox, o Arenic Hapludalf (Alf2), o Arenic Hapludult (Ult2) e o Typic Argiudoll apresentaram elevadas capacidades de adsorção dos metais, ocorrendo o inverso para o Typic Quartzipsamment e para o Arenic Hapludult textura arenosa. No geral, a CMA dos metais aos solos foi menor no sistema competitivo. A sequência de afinidade mais comumente encontrada no sistema não-competitivo foi Cu > Zn > Ni > Cd. No sistema competitivo, a sequência foi Cu > Cd > Zn > Ni. Em geral, o modelo de Langmuir simulou de maneira satisfatória a adsorção dos metais nas amostras de solo

Seasonal drought limits tree species across the Neotropics

Within the tropics, the species richness of tree communities is strongly and positively associated with precipitation. Previous research has suggested that this macroecological pattern is driven by the negative effect of water-stress on the physiological processes of most tree species. This process implies that the range limits of taxa are defined by their ability to occur under dry conditions, and thus in terms of species distributions it predicts a nested pattern of taxa distribution from wet to dry areas. However, this ‘dry-tolerance’ hypothesis has yet to be adequately tested at large spatial and taxonomic scales. Here, using a dataset of 531 inventory plots of closed canopy forest distributed across the Western Neotropics we investigated how precipitation, evaluated both as mean annual precipitation and as the maximum climatological water deficit, influences the distribution of tropical tree species, genera and families. We find that the distributions of tree taxa are indeed nested along precipitation gradients in the western Neotropics. Taxa tolerant to seasonal drought are disproportionally widespread across the precipitation gradient, with most reaching even the wettest climates sampled; however, most taxa analysed are restricted to wet areas. Our results suggest that the ‘dry tolerance’ hypothesis has broad applicability in the world's most species-rich forests. In addition, the large number of species restricted to wetter conditions strongly indicates that an increased frequency of drought could severely threaten biodiversity in this region. Overall, this study establishes a baseline for exploring how tropical forest tree composition may change in response to current and future environmental changes in this region