Chronic aerobic exercise associated to low-dose L-NAME improves contractility without changing calcium handling in rat cardiomyocytes

Nitric oxide (NO) inhibition by high-dose NG-nitro-L-arginine methyl ester (L-NAME) is associated with several detrimental effects on the cardiovascular system. However, low-dose L-NAME increases NO synthesis, which in turn induces physiological cardiovascular benefits, probably by activating a protective negative feedback mechanism. Aerobic exercise, likewise, improves several cardiovascular functions in healthy hearts, but its effects are not known when chronically associated with low-dose L-NAME. Thus, we tested whether the association between low-dose L-NAME administration and chronic aerobic exercise promotes beneficial effects to the cardiovascular system, evaluating the cardiac remodeling process. Male Wistar rats were randomly assigned to control (C), L-NAME (L), chronic aerobic exercise (Ex), and chronic aerobic exercise associated to L-NAME (ExL). Aerobic training was performed with progressive intensity for 12 weeks; L-NAME (1.5 mg·kg-1·day-1) was administered by orogastric gavage. Low-dose L-NAME alone did not change systolic blood pressure (SBP), but ExL significantly increased SBP at week 8 with normalization after 12 weeks. Furthermore, ExL promoted the elevation of left ventricle (LV) end-diastolic pressure without the presence of cardiac hypertrophy and fibrosis. Time to 50% shortening and relaxation were reduced in ExL, suggesting a cardiomyocyte contractile improvement. In addition, the time to 50% Ca2+ peak was increased without alterations in Ca2+ amplitude and time to 50% Ca2+ decay. In conclusion, the association of chronic aerobic exercise and low-dose L-NAME prevented cardiac pathological remodeling and induced cardiomyocyte contractile function improvement; however, it did not alter myocyte affinity and sensitivity to intracellular Ca2+ handling.

Differential lectin labelling of circulating hemocytes from Biomphalaria glabrata and Biomphalaria tenagophila resistant or susceptible to Schistosoma mansoni infection

Lectins/carbohydrate binding can be involved in the Schistosoma mansoni recognition and activation of the Biomphalaria hemocytes. Therefore, expression of lectin ligands on Biomphalaria hemocytes would be associated with snail resistance against S. mansoni infection. To test this hypothesis, circulating hemocytes were isolated from B. glabrata BH (snail strain highy susceptible to S. mansoni), B. tenagophila Cabo Frio (moderate susceptibility), and B. tenagophila Taim (completely resistant strains), labelled with FITC conjugated lectins (ConA, PNA, SBA, and WGA) and analyzed under fluorescence microscopy. The results demonstrated that although lectin-labelled hemocytes were detected in hemolymph of all snail species tested, circulating hemocytes from both strains of B. tenagophila showed a larger number of lectin-labelled cells than B. glabrata. Moreover, most of circulating hemocytes of B. tenagophila were intensively labelled by lectins PNA-FITC and WGA-FITC, while in B. glabrata small hemocytes were labeled mainly by ConA. Upon S. mansoni infection, lectin-labelled hemocytes almost disappeared from the hemolymph of Taim and accumulated in B. glabrata BH. The role of lectins/carbohydrate binding in resistance of B. tengophila infection to S. mansoni is still not fully understood, but the data suggest that there may be a correlation to its presence with susceptibility or resistance to the parasite.

Activity of praziquantel on in vitro transformed Schistosoma mansoni sporocysts

Praziquantel (PZQ) is effective against all the evolutive phases of Schistosoma mansoni. Infected Biomphalaria glabrata snails have their cercarial shedding interrupted when exposed to PZQ. Using primary in vitro transformed sporocysts, labeled with the probe Hoechst 33258 (indicator of membrane integrity), and lectin of Glycine max (specific for carbohydrate of N-acetylgalactosamine membrane), we evaluated the presence of lysosomes at this evolutive phase of S. mansoni, as well as the influence of PZQ on these acidic organelles and on the tegument of the sporocyst. Although the sporocyst remained alive, it was observed that there was a marked contraction of its musculature, and there occurred a change in the parasite's structure. Also, the acidic vesicles found in the sporocysts showed a larger delimited area after contact of the parasites with PZQ. Damages to the tegument was also observed, as show a well-marked labeling either with Hoechst 33258 or with lectin of Glycine max after contact of sporocysts with the drug. These results could partially explain the interruption/reduction mechanism of cercarial shedding in snails exposed to PZQ.

Comparison between morphological and staining characteristics of live and dead eggs of Schistosoma mansoni

Schistosoma mansoni eggs are classified, according to morphological characteristics, as follows: viable mature and immature eggs; dead mature and immature eggs, shells and granulomas. The scope of this study was to compare the staining characteristics of different morphological types of eggs in the presence of fluorescent labels and vital dyes, aiming at differentiating live and dead eggs. The eggs were obtained from the intestines of infected mice, and put into saline 0.85 percent. The fluorescent labels were Hoechst 33258 and Acridine Orange + Ethidium Bromide and vital dyes (Trypan Blue 0.4 percent and Neutral Red 1 percent). When labelled with the probe Hoechst 33258, some immature eggs, morphologically considered viable, presented fluorescence (a staining characteristic detected only in dead eggs); mature eggs did not present fluorescence, and the other types of dead eggs, morphologically defined, showed fluorescence. As far as Acridine Orange + Ethidium Bromide are concerned, either the eggs considered to be live, or the dead ones, presented staining with green color, and only the hatched and motionless miracidium was stained with an orange color. Trypan Blue was not able to stain the eggs, considered to be dead but only dead miracidia which had emerged out of the shell. Neutral Red stained both live and dead eggs. Only the fluorescent Hoechst 33258 can be considered a useful tool for differentiation between dead and live eggs.

The effects of drugs, ions, and poly-l-lysine on the excretory system of Schistosoma mansoni

We have been able to label the excretory system of cercariae and all forms of schistosomula, immature and adult worms with the highly fluorescent dye resorufin. We have shown that the accumulation of the resorufin into the excretory tubules and collecting ducts of the male adult worm depends on the presence of extracellular calcium and phosphate ions. In the adult male worms, praziquantel (PZQ) prevents this accumulation in RPMI medium and disperses resorufin from tubules which have been prelabelled. Female worms and all other developmental stages are much less affected either by the presence of calcium and phosphate ions, or the disruption caused by PZQ. The male can inhibit the excretory system in paired female. Fluorescent PZQ localises in the posterior gut (intestine) region of the male adult worm, but not in the excretory system, except for the anionic carboxy fluorescein derivative of PZQ, which may be excreted by this route. All stages of the parasite can recover from damage by PZQ treatment in vitro. The excretory system is highly sensitive to damage to the surface membrane and may be involved in vesicle movement and damage repair processes. In vivo the adult parasite does not recover from PZQ treatment, but what is inhibiting recovery is unknown, but likely to be related to immune effector molecules.

Cross-immunoreactivity between anti-potato apyrase antibodies and mammalian ATP diphosphohydrolases: potential use of the vegetal protein in experimental schistosomiasis

We have previously showed that Schistosoma mansoni ATP-diphosphohydrolase and Solanum tuberosum potato apyrase share epitopes and the vegetable protein has immunostimulatory properties. Here, it was verified the in situ cross-immunoreactivity between mice NTPDases and anti-potato apyrase antibodies produced in rabbits, using confocal microscopy. Liver samples were taken from Swiss Webster mouse 8 weeks after infection with S. mansoni cercariae, and anti-potato apyrase and TRITC-conjugated anti-rabbit IgG antibody were tested on cryostat sections. The results showed that S. mansoni egg ATP diphosphohydrolase isoforms, developed by anti-potato apyrase, are expressed in miracidial and egg structures, and not in granulomatous cells and hepatic structures (hepatocytes, bile ducts, and blood vessels). Therefore, purified potato apyrase when inoculated in rabbit generates polyclonal sera containing anti-apyrase antibodies that are capable of recognizing specifically S. mansoni ATP diphosphohydrolase epitopes, but not proteins from mammalian tissues, suggesting that autoantibodies are not induced during potato apyrase immunization. A phylogenetic tree obtained for the NTPDase family showed that potato apyrase had lower homology with mammalian NTPDases 1-4, 7, and 8. Further analysis of potato apyrase epitopes could implement their potential use in schistosomiasis experimental models.

Primary culture of the region of the amebocyte-producing organ of the snail Biomphalaria glabrata, the intermediate host of Schistosoma mansoni

Biomphalaria glabrata snails are major hosts for the digenetic trematoda Schistosoma mansoni, the causative agent of human schistosomiasis. The success or failure of the infection will be dependent on the mobilization of the molluskan internal defense system, where a major role will be played by circulating hemocytes produced by the APO (amebocyte-producing organ) of the snail. In this report, the primary culture of the APO region of B. glabrata was obtained for the first time, as well as a control culture of the ovotestis. Three different cell populations migrated easily from the explants in culture, with no need of any dispersion agent. The cells grew in suspension at an incubation temperature of 15°C and the cultures were maintained viable for up to two weeks. Two of these cell populations obtained resembled cell types known to be present in the hemolymph of Biomphalaria. The availability of APO cells in culture may contribute to a better understanding of the internal defense in mollusks, in general, as well as the specific response of B. glabrata to S. mansoni infection.

Biomphalaria tenagophila/Schistosoma mansoni interaction: premises for a new approach to biological control of schistosomiasis

Biomphalaria tenagophila is very important for schistosomiasis transmission in Brazil. However its mechanisms of interaction with Schistosoma mansoni are still scantly studied. Since this snail displays strains highly susceptible or completely resistant to the parasite infection, the knowledge of that would be a useful tool to understand the mechanism of snail resistance. Particularly, the Taim strain consistently shows absolute resistance against the trematode, and this resistance is a dominant character. A multidisciplinary research group was created aiming at studying B. tenagophila/S. mansoni interaction. The possibility for applying the knowledge acquired to obtain a biological model for the control of S. mansoni transmission in endemic areas is discussed.

The use and misuse of the "impact factor" as a parameter for evaluation of scientific publication quality: a proposal to rationalize its application

We present a critical analysis of the generalized use of the "impact factor". By means of the Kruskal-Wallis test, it was shown that it is not possible to compare distinct disciplines using the impact factor without adjustments. After assigning the median journal the value of one (1.000), the impact factor value for each journal was calculated by the rule of three. The adjusted values were homogeneous, thus permitting comparison among distinct disciplines.

Hepatic regeneration after partial hepatectomy in mice infected with Schistosoma mansoni, at the acute and chronic phases of the disease

Outbred male albino mice normal or infected with 30 cercariae of Schistosoma mansoni (LE strain) were submitted to 65 percent hepatectomy during the acute (70 days) and chronic phase (160 days) phases of the disease. A group of the infected animals was treated with 400 mg/kg of oxamniquine during the acute phase before hepatectomy. Non-infected, infected and treated but not hepatectomized animals were kept as controls. Hepatic regeneration was evaluated by incorporation of tritiated thymidine, intraperitoneally injected into non-hepatectomized and hepatectomized animals, 24 hours after surgery. The results showed that removal of 65 percent of the hepatic parenchyma, during the acute phase, led to a statistically significant increase of thymidine incorporation, when compared with the uninfected hepatectomized controls. This phenomenon was not observed at the chronic phase. Treatment with oxamniquine administered during the acute phase led to a decrease in thymidine incorporation rate 160 days after infection (90 days after treatment) and 24 hours after hepatectomy. The data suggest that infection with S. mansoni represents a considerable stimulus for the regenerative capacity of the liver during the acute, but not the chronic phase of disease

Influence of Schistosoma mansoni infection on the reproductive capacity of albino mice

This paper reports reduction on the reproductive capacity of female mice infected with Schistosoma mansoni, either in the acute phase or in the chronic one of the disease. This decrease in the reproductive capacity was highly significant (93.3% and 86.7%, for the acute and chronic phases, respectively).

Este trabalho trata de redução na capacidade reprodutiva de camundongos fêmeas infectados com Schistosoma mansoni, tanto na fase aguda como na fase crônica da doença. Esta diminuição da capacidade reprodutiva foi altamente significativa, com índices de 93,3% e 86,7% nas fases aguda e crônica, respectivamente.

Quantification of the population and phagocytary activity of hemocytes of resistant and susceptible strains of Biomphalaria glabrata and Biomphalaria tenagophila infected with Schistosoma mansoni

Entre os fatores determinantes na resistencia e suscetibilidade da Biomphalaria ao Schistosoma mansoni, os hemocitos desempenharam importante papel. Com o objetivo de estudar as interacoes S. mansoni/Biomphalaria relativas aos hemocitos o primeiro passo e certamente relacionado a padronizacao desta populacao de celulas em Biomphalaria nao infectada. Desta forma a quantificacao desta populacao de celulas na hemolinfa bem como sua capacidade fagocitaria foi determinada pela primeira vez. Alem disso, usando cepas de B. glabrata e B. tenagophila suscetiveis e resistentes, o hemocitograma e a capacidade fagocitaria dos hemocitos, apos infeccao com S. mansoni, foram tambem determinados. Cepas de B. glabrata (BA e BH respectivamente) resistentes e suscetiveis bem como cepas de B. tenagophila (TAIM e CF respectivamente) foram infectadas com 10 miracidios das cepas LE e SJ de S. mansoni, respectivamente. Estes caramujos infectados e respectivos controles nao infectados foram avaliados em relacao ao numero de hemocitos circulantes e alteracao da capacidade fagocitaria, usando Zimozan e MTT...

Resistance to oxamnique of a Schistosoma mansoni strain isolated from patient submitted to repeated treatments

Uma cepa de Schistosoma mansoni (R) foi isolada de paciente previamente submetido a quatro tratamentos com o oxamniquine e a um outro praziquantel. Os resultados obtidos com o teste quimioterapeutico, usando oxcamniquine em camundongos infectados com as cepas R1 e Le (padrao) mostraram resistencia evidente a droga em vermes de cepa R1. Assim, com a dose de 250 mg/kg de oxamniquine, todos os camundongos (17) dos 17 camundongos infectados com a cepa R1 apresentaram vermes sobreviventes...

The effect of chronic ingestion of ethanol on modulation of granulomatous inflammation in experimental schistosomiasis in mice

We studied the role of ethanol on the modulation of liver granulomata around Schistosoma mansoni eggs in mice. Albino mice, receiving 7 ethanol as the sole drinking liquid, at 60 and 90 days post-infection, presented smaller granulomata than controls did, when sacrificed at 120 days post-infection. No differences in diameters could be observed, when ethanol was given 4 months before up to 120 days after infection. The results suggested that modulation of schistosome granulomata by ethanol ingestion varies with time and duration of drug consumption.

Aspectos epidemiológicos da esquistossomose mansoni em bovinos / Epidemiological aspects of Schistosomiasis mansoni in bovine

Com o objetivo de avaliar a inserçäo da espécie bovina no processo de transmissäo da esquistossomose mansoni, realizaram-se exames de fezes e raspagem de mucosa retal em 894 bezerros, provenientes de 20 fazendas de bovinocultura de leite e 10 de aptidäo mista, selecionadas segundo critérios bioecológicos relativos à transmissäo da parasitose. Detectaram-se ovos viáveis de Schistosoma mansoni nas fezes de nove bezerros, obtendo-se uma prevalência de 1 por cento. Foi impossível infectar B. glabrata criadas em laboratório, a partir das fezes de um bezerro, que num período de observaçäo de seis meses, eliminou ovos viáveis. Concluiu-se que a participaçäo de bovinos enquanto hospedeiros e transmissores do S. mansoni, é determinado, além de critérios biológicos pela forma de organizaçäo da produçäo agropecuária

Schistosoma mansoni: acquired immunity in mice after the use of oxamniquine at the evolutive skin and pulmonary phases

Camundongos infectados com 350 cercarias de Schistosoma mansoni (cepa LE) foram tratados com oxamniquina, em dose unica de 400 mg/kg, 24, 48, 72 e 96 horas apos a infeccao. Quarenta dias apos o tratamento, os animais foram submetidos a uma infeccao desafio com 80 cercarias, atraves da pele abdominal e da orelha. O numero de vermes imaturos nos grupos de animais tratados 24 e 96 horas apos a primeira infeccao foi menor do que no grupo controle, evidenciando que a morte de esquistossomulos por quimioterapia, durante as fases da pele e do pulmao, causa um estado de resistencia adquirida.

Schistosoma mansoni: preclinical studies with 9-acridanone-hydrazones in Cebus monkeys experimentally infected

Derivados de acridina (9-acridanona-hidrazonas) foram testados em macacos Cebus experimentalmente infectados com Schistosoma mansoni, nas doses de 50, 25 e 12,5 mg/kg, em dose unica, via oral. Quatro compostos, pelo menos, mostraram-se muito promissores, causando alteracoes no oograma e reduzindo drasticamente a carga de vermes, mesmo quando a dose mais baixa (12,5 mg/kg) foi usada. Efeitos colaterais nao foram detectados apos administracao da droga.

ELISA detection of specific circulating antibodies against Schistosoma mansoni in mice after treatment with oxamniquine

Mice infected with 80 cercariae of Schistosoma mansoni treated with a single oral dose of oxamnique (400 mg/kg) 65 days after infection. Groups of 8-12 animals were sacrificed approximately 2 weeks after treatment and then at montly intervals. The sera obtained were evaluated for S. mansoni antibodies by enzyme-linked immunosorbeent assay (ELISA) at 1:200 dilution. Worms could not be recovered on days 14, 28, 58, 90, 119, 154 and 180 after treatment, indicating the efficacy of the chemotherapy. When performed with different antigens obtained from several stages in the life cycle of S. mansoni, i.e., soluble egg antigen, adult worm tegument, cercaria antigen, schistosomule tegument and adult worm (10 *g antigen/ml), the ELISA showed a decrease in specific antibody levels as a function of time after treatment starting on day 58, reaching levels close to control (noninfected untreated) in most animals 120 days after treatment. Purified antigens from the adult worm and the schistosomule tegument appear to be promising for use in clinical studies evaluating schistosomiasis after drug treatment