A retrospective study was conducted to evaluate lung retention of particles containing cerium in subjects with and without previous occupational exposure to mineral dusts. Analytical transmission electron microscopy was performed on 459 samples of bronchoalveolar lavage (BAL) fluid and 75 samples of lung tissue. Study of the distribution of mineralogical species in human samples showed that particles containing cerium were encountered in less than 10% of subjects. The proportion of subjects with particles containing cerium in their biological samples was not different between controls and subjects with previous occupational exposure to fibrous or nonfibrous mineral dusts. This was considered as the background level of lung retention of cerium in the general population. By contrast, determination of the absolute concentration of particles containing cerium in BAL fluid and lung tissue samples showed that 1 2% (from BAL fluid) and 15% (from lung tissue) of subjects with previous exposure to mineral particles had high lung retention of particles containing cerium. This study is believed to be the first one in which lung retention of cerium was estimated in the general population.
For diagnostic purposes, mineralogical analysis was performed in bronchoalveolar lavage fluid and lung tissue from a 58-year-old patient previously exposed to asbestos and rare earth dusts. No significant retention of asbestos was demonstrated in lung tissue by light microscopy (asbestos bodies) or transmission electron microscopy analysis (uncoated fibers). Particles containing rare earth (cerium, lanthanum) and phosphorus were identified in alveolar macrophages in bronchoalveolar lavage fluid, and cerium-containing particles accounted for 70% of particles observed in the lung tissue. Ultrastructural analysis of lung tissue revealed the presence of particles containing cerium and phosphorus in interstitial macrophages and elastic fibers. These results suggest that rare earth is metabolized and should be considered as biopersistent in the human respiratory tract, since occupational inquiries revealed that exposure to cerium oxide abrasive powder had ceased at least 15 years earlier.
The Medium Solimões River region in the Brazilian Amazon Basin is an area utilized for reproduction and nesting by a variety of species of migratory aquatic birds such as Black Skimmers (Rynchops niger). These migratory birds form mixed-species reproductive colonies with high population densities and exhibit a large range of migration routes. This study aimed to describe the prevalence and diversity of the avian malaria parasites Plasmodium and Haemoproteus in Black Skimmers, on the basis of the association between microscopic observation of blood smears and amplification of the mitochondrial cytochrome b gene (mtDNA cyt-b). The overall prevalence rates of the parasites for juvenile and adult bird specimens were 16% (5/31) and 22% (15/68), respectively. Sequencing the mtDNA cyt-b marker revealed two Plasmodium lineages, which had been previously described in different regions of the American continent, including a Neotropical region in Southeast Brazil, and one Haemoproteus lineage. The fact that avian malarial parasites have been found infecting the Black Skimmers in the Brazilian Amazon ecosystem, which exhibits considerable diversity, highlights the importance of these migratory birds as a potential source of infection and dispersion of pathogens to other susceptible birds of the Nearctic and Neotropical regions.
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