Silver nanoparticles are lethal to the ciliate model Tetrahymena and safe to the pike silverside Chirostoma estor.

Ciliate ectoparasites are one of the most important groups of pathogens in fish culture, and the traditional treatments are sometimes harmful to the fish and the environment. Thus, the search for novel compounds that are effective at low concentrations and safe for fish are necessary to optimise treatments in aquaculture. The antiprotozoal capacity of silver nanoparticles (AgNPs) against the ciliate Tetrahymena has been documented; however, their toxicity may vary with the synthesis methodology and nanoparticle size. The objectives of this study were a) to evaluate the acute toxicity in vitro of two AgNPs (Argovit™ and UTSA) on Tetrahymena sp., a biological model for ciliated ectoparasites of fish and b) to test the safety of lethal and higher doses of UTSA AgNPs for ciliates on the fish C. estor. Light microscopy and scanning electron microscopy (SEM) were used to determine whether AgNPs affected the structure of the cell surface of Tetrahymena. The mortality, histopathological alterations and metagenomics of the fish were used to determine the major effects of UTSA AgNPs. In Tetrahymena, the median lethal concentration (LC50) for Argovit™ was 2501 ± 1717 ng/L at 15 min and 796 ± 510 ng/L at 60 min, while the LC50 for UTSA AgNPs was 4 ± 2 and 1 ± 0.6 ng/L at 15 min and 60 min, respectively. A concentration of 3300 ng/L Argovit™ and 10.6 ng/L UTSA AgNPs for 15 and 60 min, respectively, was 100% effective against Tetrahymena. After 60 min of exposure to 0.25 and 0.50 ng/L UTSA AgNPs, the number of cilia significantly reduced, there were small holes on the cell surface, and the cellular membrane was ruptured. In fish exposed to lethal (10.6 ng/L) and higher (31.8 and 95.4 ng/L) doses of UTSA, the AgNPs did not affect fish survival after 96 h, and there were no signs of histopathological damage or gut microbial changes. This study is the first report on microscopic and ultrastructural changes in Tetrahymena after exposure to significantly low concentrations of UTSA AgNPs with antiprotozoal efficacy without evidence of harmful effects on fish. These results provide the basis for further studies of both pet aquarium and commercial fish that may validate these findings at a larger experimental scale, taking into account AgNPs bioaccumulation, safety for human consumption and environmental impact.

Parasitic fauna of eight species of ornamental freshwater fish species from the middle Negro River in the Brazilian Amazon Region / Fauna parasitária de oito espécies de peixes ornamentais de água doce do médio Rio Negro na Amazônia brasileira

Para estudos parasitológicos, 27 espécimes de cardinal Paracheirodon axelrodi, 33 rosa-céu Hyphessobrycon copelandi (Characidae), 28 peixes borboleta Carnegiella strigata e 26 Carnegiella martae (Gasteropelecidae), 27 bodó ou cascudo Ancistrus hoplogenys (Loricariidae), 31 peixes-lápis Nannostomus eques e 38 Nannostomus unifasciatus (Lebiasinidae) e 13 acará-bandeira Pterophyllum scalare (Cichlidae) foram coletados no médio Rio Negro, estado do Amazonas, Brasil. Em um total de 223 peixes examinados, 143 (64,1%) estavam parasitados por pelo menos uma espécie de parasito. A maior taxa de prevalência foi de Monogenea (36,7%), seguida de Ichthyophthirius multifiliis (Ciliophora) (20,6%), Trichodina spp. (Ciliophora) (4,0%), Piscinoodinium pillulare (Dinoflagellida) (1,3%), Tetrahymena sp. (Ciliophora) (0,89%) e Procamallanus sp. (Nematoda) (0,4%). Todas as oito espécies de peixes mostraram Monogenea (Gyrodactylidae and Dactylogyridae) nas brânquias, mas a maior prevalência ocorreu em P. scalare e menor em P. axelrodi e C. strigata. Porém, maior intensidade média de Monogenea foi encontrada em P. scalare e A. hoplogenys. O protozoário I. multifiliis ocorreu nas seis espécies de peixes ornamentais examinadas, porém C. strigata e C. martae tiveram a maior prevalência e intensidade média. Trichodina spp. foram encontradas somente nas brânquias de C. strigata, C. martae e N. eques, mas a maior intensidade média foi em C. strigata. Por outro lado, o protozoário P. pilullare foi encontrado somente nas brânquias de C. martae. No Brasil, este é o primeiro relato de Tetrahymena sp. e ocorreu nas brânquias de C. strigata.(AU)

Twenty-seven specimens of cardinal tetra Paracheirodon axelrodi, 33 rosy tetra Hyphessobrycon copelandi (Characidae), 28 marbled hatchetfish Carnegiella strigata, 26 blackwing hatchetfish Carnegiella martae (Gasteropelecidae), 27 bodó Ancistrus hoplogenys (Loricariidae), 31 brown pencilfish Nannostomus eques, 38 oneline pencilfish Nannostomus unifasciatus (Lebiasinidae) and 13 angelfish Pterophyllum scalare (Cichlidae) were collected from the middle Negro River, State of Amazonas, Brazil, for parasitological studies. Out of the total of 223 fish examined, 143 (64.1%) were parasitized by at least one parasite species. The highest prevalence rate was for Monogenea (36.7%), followed by Ichthyophthirius multifiliis (Ciliophora) (20.6%), Trichodina spp. (Ciliophora) (4.0%), Piscinoodinium pillulare (Dinoflagellida) (1.3%), Tetrahymena sp. (Ciliophora) (0.89%), and Procamallanus sp. (Nematoda) (0.4%). All eight fish species had Monogenea (Gyrodactylidae and Dactylogyridae) in the gills, but the highest prevalence occurred in P. scalare and the lowest in P. axelrodi and C. strigata. However, the highest mean intensity of Monogenea was found in P. scalare and A. hoplogenys. The protozoan I. multifiliis occurred in the six ornamental fish species examined, but C. strigata and C. martae had higher prevalence and mean intensity. Trichodina spp. were found only in the gills of C. strigata, C. martae and N. eques, and with higher mean intensity in C. strigata. On the other hand, the protozoan P. pilullare was found only in the gills of C. martae. This is the first report of Tetrahymena sp. in Brazil, and it occurred in the gills of C. strigata.(AU)

A bioreactor model system specifically designed for Tetrahymena growth and cholesterol removal from milk.

This work describes the configuration and operation of a bioreactor system especially designed for Tetrahymena cultivation and its use for milk improvement, particularly cholesterol elimination by the action of this cell. An advantage of the proposed method is the re-use of the growth medium; thus, the medium is used twice to provide two batches of Tetrahymena biomass without the need of further inoculation. This makes the procedure of producing the cell biomass faster and more economical. Cells are concentrated in the culture vessels by sedimentation at room temperature and then transferred to milk suspensions, where they can further grow for at least one generation with the benefit of reducing steeply cholesterol level. Milk treated according to this process is separated from the biomass by centrifugation. Under these conditions, less than 5% of the cells remain in the milk, and cholesterol elimination amounts to 75 +/- 10% of that initially present. No changes in sensorial properties of the milk, such as clotting or butyric odor, were observed as a result of this treatment. In addition, the bioreactor allows the aseptic recovery of the spent growth medium, which contains diverse enzymes of interest, and the cell pellets, to exploit particular lipids like phosphonolipids, abundant poly-unsaturated fatty acids and co-enzyme Q(8).

Tetrahymenidae infection in mosquito populations in a malaria-endemic region of the Amazon.

In a field survey performed in a malaria-endemic region of Northern Amazon, Brazil, we encountered ciliate protozoa of the family Tetrahymenidae infecting adults and larvae of the following mosquito species: Culex sp., Anopheles albitarsis l.s., Anopheles strodei, Anopheles mattogrossensis, Anopheles darlingi, and Anopheles oswaldoi l.s. Based on morphological features and life style, we have tentatively identified the parasite as Lambornella sp. The association appears pathogenic for the mosquito. Prevalence of infection in both larvae and adults was higher in the dry season.

Opioid activity of beta-endorphin-like proteins from Tetrahymena.

Morphine and other opioids have been reported to modulate phagocytosis in the ciliate Tetrahymena. However, the endogenous signaling molecule responsible for these effects remains uncharacterized. In this work we present evidence for the presence of beta-endorphin-like protein(s) in Tetrahymena thermophila. Subcellular extracts and cell-free culture supernatants were fractionated by hydrophobic chromatography on Sep Pack C18 columns and by affinity chromatography on polyclonal anti-beta-endorphin columns. Both preparations exhibited opioid-like effects in two different systems: 1) they inhibited phagocytosis in murine peritoneal macrophages, and 2) they blocked the response to mechanical stimuli in the ciliate Stentor. Both of these effects were reversed by naloxone, consistent with an opioid receptor-mediated mechanism. Chromatographic (HPLC) fractionation of the subcellular extracts resolved a component with beta-endorphin-like immunoreactivity, whose retention time was similar to that of the human beta-endorphin standard. Fractions were also analyzed by immunoblots using a monoclonal antibody that recognizes the N-terminus of human beta-endorphin. This antibody detected two antigenic components (corresponding to Mr 9,000 and Mr 12,000 polypeptides) in subcellular extracts, but only a single antigen (corresponding to a Mr 7,000 polypeptide) in culture supernatants. These results indicate that Tetrahymena produces one or more proteins that share some properties with beta-endorphin and that these may form part of an opioid mechanism that originated early in evolution.

Lysosomal glycerophosphocholine phosphodiesterase in Tetrahymena.

The purification and characterization of a novel phosphodiesterase (PDE) is presented. The activity was detected in the extracellular medium of Tetrahymena thermophila cultures, by the release of p-nitrophenol from p-nitrophenylphosphocholine (PNPPC) with an acidic pH optimum. In cell homogenates, it is sedimentable, shows a latency similar to that of acid phosphatase and is co-secreted with this enzyme, indicating that it is a lysosomal hydrolase. PNPPC-PDE was purified to homogeneity from the extracellular medium, yielding a single band of 58 kD on SDS polyacrylamide gel electrophoresis. It catalyzed the release of glycerol from glycerophosphocholine (GPC) and GPC competitively inhibits degradation of PNPPC. We present further evidence indicating that the natural substrate for PNPPC-PDE is GPC. Thus, Tetrahymena becomes the first eukaryote in which a lysosomal GPC-PDE is observed. This finding provides a new pathway for the complete breakdown of phosphatidylcholine in a lysosomal medium.