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Background Hemocyanins are respiratory proteins with multiple functions. In diverse crustaceans hemocyanins can release histidine-rich antimicrobial peptides in response to microbial challenge. In penaeid shrimp, strictly antifungal peptides are released from the C-terminus of hemocyanins. Methods The three-dimensional structure of the antifungal peptide PvHCt from Litopenaeus vannamei was determined by NMR. Its mechanism of action against the shrimp pathogen Fusarium oxysporum was investigated using immunochemistry, fluorescence and transmission electron microscopy. Results PvHCt folded into an amphipathic α-helix in membrane-mimicking media and displayed a random conformation in aqueous environment. In contact with F. oxysporum , PvHCt bound massively to the surface of fungal hyphae without being imported into the cytoplasm. At minimal inhibitory concentrations, PvHCt made the fungal membrane permeable to SYTOX-green and fluorescent dextran beads of 4 kDa. Higher size beads could not enter the cytoplasm. Therefore, PvHCt likely creates local damages to the fungal membrane. While the fungal cell wall appeared preserved, gradual degeneration of the cytoplasm most often resulting in cell lysis was observed in fungal spores and hyphae. In the remaining fungal cells, PvHCt induced a protective response by the formation of daughter hyphae. Conclusion The massive accumulation of PvHCt at the surface of fungal hyphae and subsequent insertion into the plasma membrane disrupt its integrity as a permeability barrier, leading to disruption of internal homeostasis and fungal death. General significance The histidine-rich antimicrobial peptide PvHCt derived from shrimp hemocyanin is a strictly antifungal peptide, which adopts an amphipathic α-helical structure, and selectively binds to and permeabilizes fungal cells.

In order to establish how long after the first application of the latex of Euphorbia milii it remains with activity on the metabolic pathways of molluscs host, this study aimed to screen the effects of latex exposure from 24 hours until 35 days after exposure to the latex solution to check how long the solution exhibits harmful effects on the carbohydrate metabolism and on the nitrogen excretion products of molluscs. Snails exposed to the solution presented a reduction of the glycogen levels in the tissues analyzed and changes in the ways of excreting nitrogen and the concentration of total proteins in the hemolymph, an effect that was strongest in the groups exposed up to 14 days after preparation of the solution. In both cases, the glycogen concentrations and the nitrogen excretions products in the treated groups only returned near the levels in the control groups from the 21 days onwards, but there were still statistically significant differences. These results contribute to the optimization of the use of this product as a molluscicide of natural origin and the development of protocols for control of schistosomiasis.

Este trabalho tem por objetivo apresentar a influência da representação ambiental e da formação de biólogos e médicos no controle da esquistossomose mansônica no Brasil. Este questionamento está pautado na teoria sistêmica e nos conceitos de educação ambiental para saúde. O trabalho apresenta uma visão histórico-ecológica do controle da esquistossomose, enfocando a representação do meio ambiente e o entendimento da relação parasito-hospedeiro de forma ampla pelos profissionais envolvidos nas ações de controle. São relatadas pesquisas que abordam uma postura diferenciada do sujeito na construção do conhecimento, permitindo discutir novas metodologias para o controle da esquistossomose, que promoverão a curto, médio e longo prazo, ações preventivas para melhorar a qualidade de vida e a promoção da saúde.

Experiments were performed on coral species containing clade A (Stylophora pistillata, Montipora aequituberculata) or clade C (Acropora sp., Pavona cactus) zooxanthellae. The photosynthetic efficiency (F(v)/F(m)) of the corals was first assessed during a short-term increase in temperature (from 27 degrees C to 29 degrees C, 32 degrees C, and 34 degrees C) and acute exposure to UV radiation (20.5 W m(-2) UVA and 1.2 W m(-2) UVB) alone or in combination. Increasing temperature to 34 degrees C significantly decreased the F(v)/F(m) in S. pistillata and M. aequituberculata. Increased UV radiation alone significantly decreased the F(v)/F(m) of all coral species, even at 27 degrees C. There was a combined effect of temperature and UV radiation, which reduced F(v)/F(m) in all corals by 25% to 40%. During a long-term exposure to UV radiation (17 days) the F(v)/F(m) was significantly reduced after 3 days' exposure in all species, which did not recover their initial values, even after 17 days. By this time, all corals had synthesized mycosporine-like amino acids (MAAs). The concentration and diversity of MAAs differed among species, being higher for corals containing clade A zooxanthellae. Prolonged exposure to UV radiation at the nonstressful temperature of 27 degrees C conferred protection against independent, thermally induced photoinhibition in all four species.

The sex ratio of adult worms has been observed biased towards males in Schistosoma mansoni under natural conditions. The origin of this bias is unknown. This paper determines whether males are more infective than females under controlled experimental bisexual conditions, and hence if the sex ratio is male-biased as a consequence of this. The male and female cercarial infectivities in uni- and bisexual vertebrate host infections using a range of controlled cercarial sex ratios were studied. The results showed that, in experimental unisexual infections, male cercariae were more infective than females, and that in experimental bisexual infections, male cercarial infectivity was similar to that of female, irrespective of cercarial sex ratio. Furthermore, cumulative male and female cercarial infectivity was maximal when sex ratio was equilibrated. The unbiased sex ratios obtained in our experimental bisexual infections are discussed in terms of behavioural and/or biochemical male–female interaction. Alternative explanations of the natural biased sex ratio are proposed.