241Am-Be(α,n) CHARACTERIZATION FOR A NEW LABORATORY FACILITY IN BRAZIL.

The Laboratório de Ciências Radiológicas is developing an irradiator for neutron survey meters calibration. Part of this work is related to the characterization of the neutron source that will be used in the irradiator. Therefore, a source of 241Am-Be(α,n) was characterized according to the following attributes: neutron energy distribution, anisotropy and emission rate. In order to make these values into high-level metrological references traceable by the Bureau International des Poids et Mesures, these measurements were taken at the Neutron Laboratory part of the Laboratório Nacional de Metrologia das Radiações Ionizantes. Results obtained for the source spectrum have strong adherence to the reference spectrum established by ISO 8529-1. The new laboratory for neutron calibration will allow calibration in an approximate ambient dose equivalent ranging 20-4500 µSv/h.

Assessment of the impact of changes in temperature in Biomphalaria glabrata (Say, 1818) melanic and albino variants infected with Schistosoma mansoni (Sambon, 1907) / Avaliação de impacto de alterações na temperatura em Biomphalaria glabrata variantes melânica e albina infectadas com Schistosoma mansoni

Abstract Fluctuations in population density of planorbid hosts of S. mansoni are influenced by climatic factors. The knowledge about interference from changes in water temperature in these populations is an important aspect of the epidemiology of schistosomiasis. In this experiment, it is explored the influence of different temperatures on the development of Schistosoma mansoni in Biomphalaria glabrata melanic and albino variants. The results indicated an intrinsic relationship between temperature and development of the parasite in the intramollusc phase, independent of the pigmentation of the mantle of the molluscs. The higher the temperature, the shorter the period necessary for the development of the parasite was while the higher the mortality of infected mollusks. It is concluded that, in the presence of climate change, the increasement of temperature in cold and flooded regions may encourage the establishment of new foci of transmission of schistosomiasis by changing the geographic extent and extending the epidemiological transmission potential. In warm climates, higher temperatures, however, could compromise the transmission of the disease because of biological stress suffered by parasite and host. Under these conditions, it can result in the death of the parasite or a change in their ability to infect new host species of molluscs in new areas. Mantle pigmentation patterns in molluscs have not shown significant interference in the development of the parasite.

Resumo Flutuações na densidade populacional de planorbídeos hospedeiros do S. mansoni são influenciadas por fatores climáticos. O conhecimento sobre a interferência de alterações na temperatura da água nestas populações é um aspecto importante da epidemiologia da esquistossomose. Neste experimento avaliou-se a influência de diferentes temperaturas no desenvolvimento de Schistosoma mansoni em Biomphalaria glabrata variantes melânica e albina. Os resultados indicaram uma relação intrínseca entre temperatura e desenvolvimento do parasito na fase intramolusco, independente da pigmentação do manto dos moluscos. Quanto mais elevada a temperatura, menor o período necessário para desenvolvimento do parasito e maior mortalidade dos moluscos infectados. Conclui-se que, na presença de alterações climáticas, o aumento da temperatura em regiões frias e alagadas poderá favorecer o estabelecimento de novos focos de transmissão da esquistossomose alterando a extensão geográfica e ampliando o potencial epidemiológico da transmissão. Em regiões de clima quente, o aumento da temperatura, por sua vez, poderá comprometer a transmissão da doença em virtude do estresse biológico sofrido por parasito e hospedeiro. Nestas condições, poderá ocorrer a morte do parasito ou uma alteração na sua habilidade de infectar novas espécies de moluscos hospedeiros em novas áreas. Padrões de pigmentação do manto nos moluscos não demonstraram interferência significativa no desenvolvimento do parasita.

Susceptibility of Biomphalaria glabrata submitted to concomitant infection with Angiostrongylus costaricensis and Schistosoma mansoni / Suscetibilidade de Biomphalaria glabrata submetida à infecção concomitante com Angiostrongylus costaricensis e Schistosoma mansoni

Abstract The easy adaptation of Angiostrongylus costaricensis, nematode responsible for abdominal angiostrongyliasis to several species of terrestrial and freshwater molluscs and the differences observed in the interactions of trematodes with their intermediate hosts have induced us to study the concomitant infection of Biomphalaria glabrata with Schistosoma mansoni and A. costaricensis. Prior exposure of B. glabrata to A. costaricensis (with an interval of 48 hours), favored the development of S. mansoni, observing higher infection rate, increased release of cercariae and increased survival of molluscs, when compared to molluscs exposed only to S. mansoni. Prior exposure of B. glabrata to A. costaricensis and then to S. mansoni also enabled the development of A. costaricensis since in the ninth week of infection, higher amount of A. costaricensis L3 larvae was recovered (12 larvae / mollusc) while for molluscs exposed only to A. costaricensis, the number of larvae recovered was lower (8 larvae / mollusc). However, pre-exposure of B. glabrata to S. mansoni (with an interval of 24 hours), and subsequently exposure to A. costaricensis proved to be very harmful to B. glabrata, causing extensive mortality of molluscs, reduced pre-patent period to release cercariae and greater recovery of L3 A. costaricensis larvae.

Resumo A facilidade de adaptação do Angiostrongylus costaricensis, nematódeo responsável pela angiostrongiliase abdominal, a diversas espécies de moluscos terrestres e dulciaquícolas e as divergências observadas nas interações dos trematódeos com seus hospedeiros intermediários nos induziu a estudar a infecção concomitante de Biomphalaria glabrata com Schistosoma mansoni e A. costaricensis. A exposição prévia de B. glabrata ao A. costaricensis (com intervalo de 48 horas), favoreceu o desenvolvimento do S. mansoni observando-se elevação da taxa de infecção, maior liberação de cercárias e maior sobrevivência dos moluscos, quando comparado com os moluscos expostos somente ao S. mansoni. A exposição de B. glabrata previamente ao A. costaricensis e posteriormente ao S. mansoni também facilitou o desenvolvimento do A. costaricensis uma vez que na nona semana de infecção foi recuperada maior quantidade de larvas L3 de A. costaricensis, enquanto nos moluscos expostos somente ao A. costaricensis, o número de larvas recuperadas foi menor . Entretanto a pré-exposição de B. glabrata ao S. mansoni (com intervalo de 24 horas), e posteriormente a exposição ao A. costaricensis mostrou-se muito prejudicial à B. glabrata provocando grande mortalidade dos moluscos, redução do período pré-patente para liberação de cercárias e maior recuperação de larvas L3 de A. costaricensis.

Host-parasite relationship between Biomphalaria amazonica (Paraense, 1966) and Schistosoma mansoni (Sambon, 1907) / Relação parasito-hospedeiro entre Biomphalaria amazonica e Schistosoma mansoni

Abstract Biomphalaria amazonica is a planorbid species considered a potential host of Schistosoma mansoni. It is widely distributed in the Neotropical zone, particularly in the North and Centre-West of Brazil and in the North of Bolivia. The aim of the present study was to determine the host-parasite relationship between B. amazonica and S. mansoni (BH and SJ strains). Specimens of B. amazonica and their snail-conditioned water were examined in terms of their ability to attract miracidia. The infectivity of the mollusks was determined by exposing them to 20 miracidia of both strains. Sporocyst development and amebocyte reactions were studied after each mollusk specimen was exposed to 100 miracidia. Although no cercariae were eliminated, specimens of B. amazonica proved capable of attracting 77% of the miracidia they were exposed to. Viable sporocysts with no amebocyte reaction were found 96 hours after the exposure to miracidia. These results indicate the susceptibility of B. amazonica to the BH and SJ strains of S. mansoni, and therefore demonstrate the importance of this planorbid species as a potential vector of the trematode in the areas where it occurs.

Resumo Biomphalaria amazonica é uma espécie de planorbídeo considerada vetora potencial do Schistosoma mansoni. É amplamente distribuída na zona neotropical, especialmente no Norte e Centro-Oeste do Brasil e Norte da Bolívia. O presente trabalho teve por objetivo estudar a relação parasito-hospedeiro entre B. amazonica e S. mansoni (linhagens BH e SJ). Espécimes de B. amazonica e sua água de condicionamento foram examinados em relação à sua capacidade de atração miraxonal. A infectividade dos moluscos foi testada expondo-os a 20 miracídios de ambas as linhagens. A viabilidade dos esporocistos e o desenvolvimento de reações amebocitárias foram estudados após cada molusco ser exposto a 100 miracídios. Apesar de não eliminarem cercárias, B. amazonica provou ser capaz de atrair 77% dos miracídios a que foram expostos. Esporocistos viáveis sem reação amebócitaria foram encontrados 96 horas após a exposição aos miracídios. Esses resultados indicam a suscetibilidade de B. amazonica às linhagens BH e SJ de S. mansoni e, portanto, demonstram a importância desta espécie de planorbídeo como um vetor potencial do trematodeo na área onde ele ocorre.

Host-parasite relationship between Biomphalaria amazonica (Paraense, 1966) and Schistosoma mansoni (Sambon, 1907).

Biomphalaria amazonica is a planorbid species considered a potential host of Schistosoma mansoni. It is widely distributed in the Neotropical zone, particularly in the North and Centre-West of Brazil and in the North of Bolivia. The aim of the present study was to determine the host-parasite relationship between B. amazonica and S. mansoni (BH and SJ strains). Specimens of B. amazonica and their snail-conditioned water were examined in terms of their ability to attract miracidia. The infectivity of the mollusks was determined by exposing them to 20 miracidia of both strains. Sporocyst development and amebocyte reactions were studied after each mollusk specimen was exposed to 100 miracidia. Although no cercariae were eliminated, specimens of B. amazonica proved capable of attracting 77% of the miracidia they were exposed to. Viable sporocysts with no amebocyte reaction were found 96 hours after the exposure to miracidia. These results indicate the susceptibility of B. amazonica to the BH and SJ strains of S. mansoni, and therefore demonstrate the importance of this planorbid species as a potential vector of the trematode in the areas where it occurs.

Susceptibility of Biomphalaria glabrata submitted to concomitant infection with Angiostrongylus costaricensis and Schistosoma mansoni.

The easy adaptation of Angiostrongylus costaricensis, nematode responsible for abdominal angiostrongyliasis to several species of terrestrial and freshwater molluscs and the differences observed in the interactions of trematodes with their intermediate hosts have induced us to study the concomitant infection of Biomphalaria glabrata with Schistosoma mansoni and A. costaricensis. Prior exposure of B. glabrata to A. costaricensis (with an interval of 48 hours), favored the development of S. mansoni, observing higher infection rate, increased release of cercariae and increased survival of molluscs, when compared to molluscs exposed only to S. mansoni. Prior exposure of B. glabrata to A. costaricensis and then to S. mansoni also enabled the development of A. costaricensis since in the ninth week of infection, higher amount of A. costaricensis L3 larvae was recovered (12 larvae / mollusc) while for molluscs exposed only to A. costaricensis, the number of larvae recovered was lower (8 larvae / mollusc). However, pre-exposure of B. glabrata to S. mansoni (with an interval of 24 hours), and subsequently exposure to A. costaricensis proved to be very harmful to B. glabrata, causing extensive mortality of molluscs, reduced pre-patent period to release cercariae and greater recovery of L3 A. costaricensis larvae.

Assessment of the impact of changes in temperature in Biomphalaria glabrata (Say, 1818) melanic and albino variants infected with Schistosoma mansoni (Sambon, 1907).

Fluctuations in population density of planorbid hosts of S. mansoni are influenced by climatic factors. The knowledge about interference from changes in water temperature in these populations is an important aspect of the epidemiology of schistosomiasis. In this experiment, it is explored the influence of different temperatures on the development of Schistosoma mansoni in Biomphalaria glabrata melanic and albino variants. The results indicated an intrinsic relationship between temperature and development of the parasite in the intramollusc phase, independent of the pigmentation of the mantle of the molluscs. The higher the temperature, the shorter the period necessary for the development of the parasite was while the higher the mortality of infected mollusks. It is concluded that, in the presence of climate change, the increasement of temperature in cold and flooded regions may encourage the establishment of new foci of transmission of schistosomiasis by changing the geographic extent and extending the epidemiological transmission potential. In warm climates, higher temperatures, however, could compromise the transmission of the disease because of biological stress suffered by parasite and host. Under these conditions, it can result in the death of the parasite or a change in their ability to infect new host species of molluscs in new areas. Mantle pigmentation patterns in molluscs have not shown significant interference in the development of the parasite.

Nucleotide excision repair pathway assessment in DNA exposed to low-intensity red and infrared lasers.

Low-intensity lasers are used for prevention and management of oral mucositis induced by anticancer therapy, but the effectiveness of treatment depends on the genetic characteristics of affected cells. This study evaluated the survival and induction of filamentation of Escherichia coli cells deficient in the nucleotide excision repair pathway, and the action of T4endonuclease V on plasmid DNA exposed to low-intensity red and near-infrared laser light. Cultures of wild-type (strain AB1157) E. coli and strain AB1886 (deficient in uvrA protein) were exposed to red (660 nm) and infrared (808 nm) lasers at various fluences, powers and emission modes to study bacterial survival and filamentation. Also, plasmid DNA was exposed to laser light to study DNA lesions produced in vitro by T4endonuclease V. Low-intensity lasers:i) had no effect on survival of wild-type E. coli but decreased the survival of uvrA protein-deficient cells,ii) induced bacterial filamentation, iii) did not alter the electrophoretic profile of plasmids in agarose gels, andiv) did not alter the electrophoretic profile of plasmids incubated with T4 endonuclease V. These results increase our understanding of the effects of laser light on cells with various genetic characteristics, such as xeroderma pigmentosum cells deficient in nucleotide excision pathway activity in patients with mucositis treated by low-intensity lasers.

Low-intensity red and infrared laser effects at high fluences on Escherichia coli cultures.

Semiconductor laser devices are readily available and practical radiation sources providing wavelength tenability and high monochromaticity. Low-intensity red and near-infrared lasers are considered safe for use in clinical applications. However, adverse effects can occur via free radical generation, and the biological effects of these lasers from unusually high fluences or high doses have not yet been evaluated. Here, we evaluated the survival, filamentation induction and morphology of Escherichia coli cells deficient in repair of oxidative DNA lesions when exposed to low-intensity red and infrared lasers at unusually high fluences. Cultures of wild-type (AB1157), endonuclease III-deficient (JW1625-1), and endonuclease IV-deficient (JW2146-1) E. coli, in exponential and stationary growth phases, were exposed to red and infrared lasers (0, 250, 500, and 1000 J/cm2) to evaluate their survival rates, filamentation phenotype induction and cell morphologies. The results showed that low-intensity red and infrared lasers at high fluences are lethal, induce a filamentation phenotype, and alter the morphology of the E. coli cells. Low-intensity red and infrared lasers have potential to induce adverse effects on cells, whether used at unusually high fluences, or at high doses. Hence, there is a need to reinforce the importance of accurate dosimetry in therapeutic protocols.

Nucleotide excision repair pathway assessment in DNA exposed to low-intensity red and infrared lasers

Low-intensity lasers are used for prevention and management of oral mucositis induced by anticancer therapy, but the effectiveness of treatment depends on the genetic characteristics of affected cells. This study evaluated the survival and induction of filamentation of Escherichia coli cells deficient in the nucleotide excision repair pathway, and the action of T4endonuclease V on plasmid DNA exposed to low-intensity red and near-infrared laser light. Cultures of wild-type (strain AB1157) E. coli and strain AB1886 (deficient in uvrA protein) were exposed to red (660 nm) and infrared (808 nm) lasers at various fluences, powers and emission modes to study bacterial survival and filamentation. Also, plasmid DNA was exposed to laser light to study DNA lesions produced in vitro by T4endonuclease V. Low-intensity lasers:i) had no effect on survival of wild-type E. coli but decreased the survival of uvrA protein-deficient cells,ii) induced bacterial filamentation, iii) did not alter the electrophoretic profile of plasmids in agarose gels, andiv) did not alter the electrophoretic profile of plasmids incubated with T4 endonuclease V. These results increase our understanding of the effects of laser light on cells with various genetic characteristics, such as xeroderma pigmentosum cells deficient in nucleotide excision pathway activity in patients with mucositis treated by low-intensity lasers.

Low-intensity red and infrared laser effects at high fluences on Escherichia coli cultures

Semiconductor laser devices are readily available and practical radiation sources providing wavelength tenability and high monochromaticity. Low-intensity red and near-infrared lasers are considered safe for use in clinical applications. However, adverse effects can occur via free radical generation, and the biological effects of these lasers from unusually high fluences or high doses have not yet been evaluated. Here, we evaluated the survival, filamentation induction and morphology of Escherichia coli cells deficient in repair of oxidative DNA lesions when exposed to low-intensity red and infrared lasers at unusually high fluences. Cultures of wild-type (AB1157), endonuclease III-deficient (JW1625-1), and endonuclease IV-deficient (JW2146-1) E. coli, in exponential and stationary growth phases, were exposed to red and infrared lasers (0, 250, 500, and 1000 J/cm2) to evaluate their survival rates, filamentation phenotype induction and cell morphologies. The results showed that low-intensity red and infrared lasers at high fluences are lethal, induce a filamentation phenotype, and alter the morphology of the E. coli cells. Low-intensity red and infrared lasers have potential to induce adverse effects on cells, whether used at unusually high fluences, or at high doses. Hence, there is a need to reinforce the importance of accurate dosimetry in therapeutic protocols.

Compatibility characteristics of five radiographic films utilised in Brazilian diagnostic radiology.

To evaluate the quality of the radiographic films in Brazil, according to the recommendations of ISO 9236-1, a radiographic images simulator was used. A study of the control of the quality in radiographic films was implemented. With regard to this study, the results of five films of different manufacturers are presented. The characteristic curves for the ISO qualities of 55, 70, 90 and 120 kV are presented. The PTW REX simulator was used to determine the image quality parameters. Film 2 presents problems due to high sensitivity. Film 1 has a higher energy dependence than the other films. Film 5 yields the best results for almost all the sensitometric parameters. In conclusion, existing films in the Brazilian market vary considerably with relation to image quality.

Unravelling remote sensing signatures of plants contaminated with gasoline and diesel: an approach using the red edge spectral feature.

Pipeline systems used to transport petroleum products represent a potential source of soil pollution worldwide. The design of new techniques that may improve current monitoring of pipeline leakage is imperative. This paper assesses the remote detection of small leakages of liquid hydrocarbons indirectly, through the analysis of spectral features of contaminated plants. Leaf and canopy spectra of healthy plants were compared to spectra of plants contaminated with diesel and gasoline, at increasing rates of soil contamination. Contamination effects were observed both visually in the field and thorough changes in the spectral reflectance patterns of vegetation. Results indicate that the remote detection of small volumes of gasoline and diesel contaminations is feasible based on the red edge analysis of leaf and canopy spectra of plants. Brachiaria grass ranks as a favourable choice to be used as an indicator of HCs leakages along pipelines.

Evaluation of radiographic image quality parameters obtained with the REX simulator.

The PTW REX phantom was used to study the radiographic image quality parameters in X-ray devices in the X-ray Diagnostics Department, as well as the system of film processing at the University Hospital of Rio de Janeiro State. X-ray devices were evaluated by performing tests on 11 screen-film combinations from X-ray devices in 3 rooms. The results showed that six film-screen combinations exhibited poor performances. For determination of air kerma output in the X-ray field, two devices presented significant variation >2 %. The grid attenuation factor in three devices had been approved, while two films were within the limits of sensitometric specifications. The modulation transfer function, which evaluates the level of image degradation, revealed that five film-screen combinations exhibited bad performance. The tests with the REX phantom revealed that the X-ray equipment and the system of processing at the University Hospital presented discrepancies in relation to the expected values, contributing to loss of quality of the radiographs.

Differences in the number of hemocytes in the snail host Biomphalaria tenagophila, resistant and susceptible to Schistosoma mansoni infection.

The relationships between schistosomiasis and its intermediate host, mollusks of the genus Biomphalaria, have been a concern for decades. It is known that the vector mollusk shows different susceptibility against parasite infection, whose occurrence depends on the interaction between the forms of trematode larvae and the host defense cells. These cells are called amebocytes or hemocytes and are responsible for the recognition of foreign bodies and for phagocytosis and cytotoxic reactions. The defense cells mediate the modulation of the resistant and susceptible phenotypes of the mollusk. Two main types of hemocytes are found in the Biomphalaria hemolymph: the granulocytes and the hyalinocytes. We studied the variation in the number (kinetics) of hemocytes for 24 h after exposing the parasite to genetically selected and non-selected strains of Biomphalaria tenagophila, susceptible or not to infection by Schistosoma mansoni. The differences were analyzed referred to the variations in the number of hemocytes in mollusks susceptible or not to infection by S. mansoni. The hemolymph of the selected and non-selected snails was collected, and hemocytes were counted using a Neubauer chamber at six designated periods: 0 h (control, non-exposed individuals), 2 h, 6 h, 12 h, 18 h and, 24 h after parasite exposure. Samples of hemolymph of five selected mollusks and five non-selected mollusks were separately used at each counting time. There was a significant variation in the number of hemocytes between the strains, which indicates that defense cells have different behaviors in resistant and susceptible mollusks.

Genetic differences between strains of Biomphalaria glabrata (Planorbidae) that are susceptible and unsusceptible to schistosomiasis.

Despite the implementation control programs, schistosomiasis continues to spread throughout the world. Among modern control strategies, vector control is currently being emphasized. Within this context, analysis of the genetic variability of intermediate host snails (Biomphalaria spp) is important because it allows identification of specific sequences of the genome of this mollusk related to susceptibility/resistance to Schistosoma mansoni infection. We investigated Brazilian albino (non-pigmented) and pigmented (wild type) strains of Biomphalaria glabrata; these strains differ in their susceptibility to S. mansoni infection. Genetic variability was studied by RAPD-PCR using different random primers. The electrophoretic patterns resulting from amplification showed specific polymorphic markers for the albino and pigmented strains of B. glabrata. This information will help in the identification and isolation of genes specifically related to susceptibility, demonstrating that RAPD-PCR is an appropriate and efficient methodological approach for analysis of the genetic variability of schistosomiasis vectors.

Attraction of Schistosoma mansoni Sambon, 1907 miracidia to Biomphalaria glabrata (Say, 1818) in the presence of Angiostrongylus costaricensis Morera and Céspedes, 1971 infection.

The attraction exerted by Biomphalaria glabrata infected with Angiostrongylus costaricensis on Schistosoma mansoni miracidia of the BH strain was tested, using a glass apparatus composed by two circular chambers connected to a channel. One mollusk or a sample of a snail conditioning water (SCW) was placed in one of the chambers, randomly selected, and the remaining of the apparatus was filled with chlorine-free water. Ten miracidia were placed in the centre of the channel and their behaviour was observed for 15 minutes. Ten replicates were made for each treatment (snail or SCW), using different specimens of mollusks or different samples of SCW. Mollusks infected with A. costaricensis attracted significantly less S. mansoni miracidia than non-infected B. glabrata. In addition, miracidia were also significantly more attracted to SCW from mollusks infected with A. costaricensis.

Behaviour of albino and melanic variants of Biomphalaria glabrata Say, 1818 (Mollusca: Planorbidae) following infection by Schistosoma mansoni Sambon, 1907.

The behaviour of the albino and melanic variants of Biomphalaria glabrata of Belo Horizonte (MG. Brazil) was studied comparatively, in terms of their respective susceptibilities to infection by Schistosoma mansoni of the same origin, through observation of the elimination of cercariae for a three-month period and the calculation of mortality and infection rates, in control and in infected snails. The number of amoebocytes, granulocytes and hyalinocytes in the circulating hemolymph during different periods of infection was analyzed. The evolution of the infection in the tissues was observed by means of histological cross-sections. The melanic variant showed greater susceptibility to infection and a higher mortality rate. The albino variant showed a higher number of circulating amoebocytes, both granulocytes and hyalinocytes. A higher number of degenerated sporocysts were seen in the histological cross-sections of the albino variant. The results suggest that the melanic variant of B. glabrata was more susceptible to infection by S. mansoni than was the albino variant.

Behaviour of albino and melanic variants of Biomphalaria glabrata Say, 1818 (Mollusca: Planorbidae) following infection by Schistosoma mansoni Sambon, 1907 / Comportamento de Biomphalaria glabrata variantes albina e melânica frente à infecção pelo Schistosoma mansoni

The behaviour of the albino and melanic variants of Biomphalaria glabrata of Belo Horizonte (MG. Brazil) was studied comparatively, in terms of their respective susceptibilities to infection by Schistosoma mansoni of the same origin, through observation of the elimination of cercariae for a three-month period and the calculation of mortality and infection rates, in control and in infected snails. The number of amoebocytes, granulocytes and hyalinocytes in the circulating hemolymph during different periods of infection was analyzed. The evolution of the infection in the tissues was observed by means of histological cross-sections. The melanic variant showed greater susceptibility to infection and a higher mortality rate. The albino variant showed a higher number of circulating amoebocytes, both granulocytes and hyalinocytes. A higher number of degenerated sporocysts were seen in the histological cross-sections of the albino variant. The results suggest that the melanic variant of B. glabrata was more susceptible to infection by S. mansoni than was the albino variant.

Foi estudado comparativamente o comportamento das variantes albina e melânica de Biomphalaria glabrata de Belo Horizonte (MG. Brasil), em relação à susceptibilidade à infecção pelo Schistosoma mansoni de mesma origem, através da observação da eliminação de cercárias por um período de três meses e a verificação das taxas de mortalidade e infecção nos moluscos controles e infectados. Analisou-se também, o número de amebócitos granulócitos e hialinócitos na hemolinfa circulante em diferentes períodos de infecção. A evolução da infecção nos tecidos foi observada através de cortes histológicos. A variante melânica apresentou maior susceptibilidade à infecção e maior taxa de mortalidade. A variante albina apresentou maior número de amebócitos circulantes, tanto granulócitos quanto hialinócitos. Nos cortes histológicos foi verificado maior número de esporocistos degenerados na variedade albina. Por estes resultados sugere-se que nas populações estudadas a variante melânica de B. glabrata, foi mais susceptível à infecção pelo S. mansoni.

Schistosoma mansoni: evaluation of an RNAi-based treatment targeting HGPRTase gene.

Hypoxanthine-guanine phosphoribosyltransferase (HGPRTase) is an essential gene of the parasite Schistosoma mansoni and it is well conserved in its hosts (mouse and human) at the protein but not at the RNA level. This feature prompted us to assess RNA interference (RNAi) to combat schistosomiasis. Small interfering RNAs (siRNAs) were produced against HGPRTase, injected in infected mice and the number of worms was counted six days after injection. The total number of parasites was reduced by approximately 27% after treatment. RT-PCR analyzes showed a significant reduction in parasite target mRNA but not in host's homologue. The use of low doses of molecules did not oversaturate si- or miRNA pathways as mice survival rates were not affected by siRNAs. This is the first successful in vivo demonstration of a RNAi-based treatment against schistosomiasis. We believe that improvements in molecule delivery and an increase on siRNA dose could rapidly eliminate parasite.