Adhesion to the yeast cell surface as a mechanism for trapping pathogenic bacteria by Saccharomyces probiotics.

Recently, much attention has been given to the use of probiotics as an adjuvant for the prevention or treatment of gastrointestinal pathology. The great advantage of therapy with probiotics is that they have few side effects such as selection of resistant bacteria or disturbance of the intestinal microbiota, which occur when antibiotics are used. Adhesion of pathogenic bacteria onto the surface of probiotics instead of onto intestinal receptors could explain part of the probiotic effect. Thus, this study evaluated the adhesion of pathogenic bacteria onto the cell wall of Saccharomyces boulardii and Saccharomyces cerevisiae strains UFMG 905, W303 and BY4741. To understand the mechanism of adhesion of pathogens to yeast, cell-wall mutants of the parental strain of Saccharomyces cerevisiae BY4741 were used because of the difficulty of mutating polyploid yeast, as is the case for Saccharomyces cerevisiae and Saccharomyces boulardii. The tests of adhesion showed that, among 11 enteropathogenic bacteria tested, only Escherichia coli, Salmonella Typhimurium and Salmonella Typhi adhered to the surface of Saccharomyces boulardii, Saccharomyces cerevisiae UFMG 905 and Saccharomyces cerevisiae BY4741. The presence of mannose, and to some extent bile salts, inhibited this adhesion, which was not dependent on yeast viability. Among 44 cell-wall mutants of Saccharomyces cerevisiae BY4741, five lost the ability to fix the bacteria. Electron microscopy showed that the phenomenon of yeast-bacteria adhesion occurred both in vitro and in vivo (in the digestive tract of dixenic mice). In conclusion, some pathogenic bacteria were captured on the surface of Saccharomyces boulardii, Saccharomyces cerevisiae UFMG 905 and Saccharomyces cerevisiae BY4741, thus preventing their adhesion to specific receptors on the intestinal epithelium and their subsequent invasion of the host.

Morphological aspect of the midgut of anopheles aquasalis (Curry, 1932) Insecta: Diptera / Aspecto morfológico del intestino medio de anopheles aquasalis (Curry, 1932) Insecta: Diptera

The midgut of adult female Anopheles aquasalis presents a narrow anterior or thoracic region and a distensible posterior or abdominal region constituted by the epithelium formed by a cell layer whose apical portion presents microvilli and the basal portion, a basal labyrinth. The thoracic region revealed heterogeneous cellular staining affinity mainly by the presence of acidic components. The ultrastructural aspect showed columnar cells with the presence of the vesicle, mitochondria, endoplasmic reticulum and secreting cells. The abdominal region of the midgut revealed an irregular epithelium whose cells presented a basophilic cytoplasm and acidophil granules. It was also found secreting and/or basal cells with narrow cytoplasm. The ultrastructural observation of this region demonstrated cells with evident nucleus, endoplasmic reticulum and mitochondria. Larger vesicles and small granules were found distributed throughout the cytoplasm. The basal lamina that supports the epithelium presented a generally irregular aspect and the muscle fibers have longitudinal and circular organization and were found separating the epithelium from the haemocel. This study will contribute to analyses on the vector mosquito-parasite interaction mechanism in this specimen.

La seccion media del intestino de la hembra de Anopheles aquasalis presenta una estrecha region anterior o toráxica y una region posterior o abdominal constituida por el epitelio formado por una camada de células cuya porcion apical presenta microvilosidades y la porcion basal presenta un laberinto basal. La region toráxica reveló afinidad de tintura celular principalmente para componentes acídicos. El aspecto ultra estructural mostró células columnares con la presencia de la vesícula, mitocondrias, retículo endoplasmático y células secretoras. La region abdominal del intestino medio reveló un epitelio irregular con células con citoplasma basófilo y granulos acidófilos. También se encontraron células secretoras y/o básales con citoplasma estrecho. La observacion ultra estructural de la region mostró células con núcleos, retículo endoplasmático y mitocondrias evidentes. Vesículas largas y granulos pequeños fueron encontrados distribuidos por todo el citoplasma. La lámina basal que apoya el epitelio presentó un aspecto irregular y las fibras musculares tienen organizacion longitudinal y circular y separan el epitelio del hemocele. Este estudio contribuirá al análisis del mecanismo de interaccion entre el mosquito y el parásito en este espécimen.

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.

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.