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PubMed1988

Effect of prolonged administration of sublethal concentrations of aridanin isolated from Tetrapleura tetraptera and bayluscide on the glycogen and protein content of Biomphalaria glabrata.

The effect of chronic application of sublethal concentrations of aridanin isolated from Tetrapleura tetraptera (0.25-0.125 ppm) and of bayluscide (0.05-0.025 ppm) on the glycogen and protein content of Biomphalaria glabrata was determined. Aridanin and bayluscide produced significant reductions in the glycogen content of B. glabrata, but a significant decrease in the protein content of the snails was not apparent until after 4 weeks of continuous exposure. The results indicate that the molluscicides may exert their primary molluscicidal action on the carbohydrate metabolism of the snail.

Animals↗
PubMed1991

Subchronic exposure of Biomphalaria glabrata eggs to aridanin and niclosamide.

Treatment of 3-day-old Biomphalaria glabrata eggs with aridanin caused a knock-down effect on the prehatch snails, making this group the most susceptible. The development and hatching of 0- to 1-day-old eggs could not be prevented but was prolonged by continuous exposure to aridanin (0.5-10 mg/l). Prehatch snails were less susceptible than juvenile and adult snails. Niclosamide (0.625-0.35 mg/l) arrested the development of B. glabrata. The results predict a poor action of aridanin as an ovicidal agent in the control of snail intermediate hosts of schistosomiasis.

Animals↗
PubMed1996

The effects of extracts from Tetrapleura tetraptera (Taub.) and Bayluscide on cells and tissue structures of Biomphalaria glabrata (Say).

Subchronic experiments were conducted with low concentrations of saponins from Tetrapleura tetraptera and Bayluscide to study the ultrastructural effects of these molluscicides on Biomphalaria glabrata. The ratio of the digestive cells to the crypt cells was inverted in molluscicide treated snails which showed an increase in the number of secretory cells and a decrease in the number of digestive cells. In the snail foot connective tissues, dose-dependent autolytic areas were observed. The major ultrastructural effects were seen in the digestive gland with dose-dependent autolysis of the membranous structures such as the golgi apparatus, mitochondria and endoplasmic reticulum. The results show that the molluscicides produced non-specific effects on the membranous structures.

Animals↗
PubMed1992

Studies on carbohydrates extracted from native and chemically treated Biomphalaria alexandrina snails.

1. Carbohydrates were extracted from total tissue extracts of Biomphalaria alexandrina snails and were analyzed to their monosaccharides using GLC. 2. The snails were chemically treated with thioxanthone derivatives (compounds I, II, III) and the change in the monosaccharide constituents of their carbohydrates was investigated. 3. The isolated monosaccharides from native and chemically pretreated snails were injected into mice and their protective effects were examined after infection of mice with cercariae of Schistosoma mansoni. 4. The results showed that the main monosaccharides in carbohydrates of snails were galactose, glucose, fucose and mannose and that chemical treatment caused a drop in the galactose content. 5. Moreover, monosaccharide fractions from snails treated with compound III were the most effective in inducing protection against Schistosoma infection in mice.

Animals↗
PubMed1994

Interleukin 1 activity in haemolymph from strains of the snail Biomphalaria glabrata varying in susceptibility to the human blood fluke, Schistosoma mansoni: presence, differential expression, and biological function.

Cytokines control many of the steps in the complex pathways of immune and inflammatory responses in mammals. Recent reports also indicate that some invertebrates may produce cytokines such as interleukin 1 (IL-1). Certain strains of the snail, Biomphalaria glabrata (intermediate host for the human blood fluke, Schistosoma mansoni), possess a soluble plasma factor that stimulates the haemocyte-mediated killing of larval schistosomes, making them resistant to infection. In this study, we have sought to determine whether these snails possessed IL-1 in their plasma, and whether this cytokine was associated with resistance of B. glabrata to S. mansoni. Plasma from susceptible (M-line) and resistant (10-R2, 13-16-R1) strains of B. glabrata that had been unexposed or exposed to S. mansoni were tested for the presence of IL-1-like activity. Experiments employing both a bioassay and an immunoassay indicated that an IL-1-like molecule was present, in varying quantities, among the snail strains. Further, plasma IL-1 levels were significantly affected by exposure to S. mansoni, with levels dropping in M-line and 10-R2 snails, but increasing in the 13-16-R1 strain. However, both resistant strains maintained significantly higher IL-1 levels than M-line snails. Recombinant, human IL-1 (rhIL-1) was shown to prime haemocytes from both resistant snail strains for superoxide production, but had no effect on haemocytes from susceptible B. glabrata. Moreover, the addition of an IL-1 receptor antagonist protein (IRAP) eliminated this priming effect. Priming with rhIL-1 and/or IRAP had no effect on phagocytosis rates in any of the snail strains tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2006

Compatibility in the Biomphalaria glabrata/Echinostoma caproni model: Potential involvement of proteins from hemocytes revealed by a proteomic approach.

As an approach to investigate the suspected involvement of cellular factors in Biomphalaria glabrata resistance/susceptibility to Echinostoma caproni, we compared protein patterns from hemocytes collected from susceptible and resistant snails. This proteomic approach revealed that twelve hemocytic proteins exhibited significant differences in their apparent abundance. The genes corresponding to five of them were characterized by a combination of mass spectrometry and molecular cloning. They encode an aldolase, an intermediate filament protein, a cytidine deaminase, the ribosomal protein P1 and the histone H4. Furthermore, we investigated their expression in parasite-exposed or -unexposed snails. These last experiments revealed changes in transcript levels corresponding to intermediate filament and histone H4 proteins post-infection.

Amino Acid Sequence↗
PubMed2006

The lethality of Euphorbia conspicua to adults of Biomphalaria glabrata, cercaria of Schistosoma mansoni and larvae of Artemia salina.

Leaf extracts of Euphorbia conspicua (Euphorbiaceae), together with the latex and fractions derived therefrom, were evaluated for their molluscicidal and cercaricidal activities and their toxicities to brine shrimps. Whilst the leaf extracts were inactive against Biomphalaria glabrata, the latex, its triterpenic fraction and irritant fractions I and II exhibited high activities against adult snails with LC90 values of 4.87, 10.55, 0.64 and 0.10 microg/mL, respectively. The latex and its derived fractions were considered lethal to the cercaria of Schistosoma mansoni at concentrations of 100 microg/mL. The toxicities of the latex and the irritant fractions, but not of the triterpenic fraction, against Artemia salina were high with LC50 values < 10 microg/mL. The possible application of the latex of E. conspicua as an alternative natural molluscicide is considered.

Animals↗
PubMed2006

Thin layer chromatographic analysis of glucose and maltose in estivated Biomphalaria glabrata snails and those infected with Schistosoma mansoni.

Thin layer chromatography was used to analyze the glucose and maltose concentrations of the digestive gland-gonad complex (DGG) of uninfected-estivated Biomphalaria glabrata snails and estivated B. glabrata patently infected with Schistosoma mansoni. All snails were estivated in a most chamber at a relative humidity of 98+/-1% and a temperature of 23+/-1 degrees C for 14 days. Carbohydrates were extracted from the DGG with 70% aqueous ethanol, and extracts were analyzed on silica gel preadsorbent plates using ethyl acetate-glacial acetic acid-methanol-water (60:15:15:10) mobile phase, alpha-naphthol-sulfuric acid detection reagent, and quantification by densitometry. The concentrations of glucose and maltose were significantly reduced in both uninfected-estivated snails and infected-estivated snails.

Animals↗
PubMed2004

Use of individual polymorphism to validate potential functional markers: case of a candidate lectin (BgSel) differentially expressed in susceptible and resistant strains of Biomphalaria glabrata.

BgSel has been identified in Biomphalaria glabrata as a candidate adhesion molecule exhibiting both an Ig-like domain and a carbohydrate recognition domain showing similarities with the l domain of C-type lectins. As susceptibility or resistance of B. glabrata to the trematode Echinostoma caproni correlates with a differential hemocytic adhesive behavior, we investigated the expression of BgSel in snails selected for their susceptibility or resistance. Semi-quantitative RT-PCR analysis of BgSel expression revealed that (i) BgSel expression level was high in susceptible snails and almost undetectable in resistant snails, and that (ii) exposure to the parasite did not affect the expression level of BgSel in either strain. In order to validate this apparent association between low levels of BgSel expression and resistance, we used Real-Time PCR to characterize the relative expression of BgSel in individual snails segregating for susceptibility/resistance. Results established that differential expression of BgSel represents a functional strain marker, but is not a marker of resistance/susceptibility. It is suggested that this correlative approach may be a rapid and efficient alternative to complete functional analyses, and may facilitate the validation of candidate transcripts potentially identified through the numerous differential analyses of animal transcriptomes.

Animals↗
PubMed2004

Free radical scavengers in susceptible/resistant Biomphalaria alexandrina snails before and after infection.

The activities of catalase (Cat), superoxide dismutase (SOD), glutathione peroxidase (GSHPx), glutathione transferase (GST), glucose-6-phosphate dehydrogenase (G6PD) and glyceraldehyde3-phosphate dehydrogenase (G3PD) were studied in tissue and hemolymph of susceptible (S) (EgBS(2)) and resistant (R) (EgBR(2)) Biomphalaria alexandrina snails. The results showed that CAT and GST were higher in the hemolymph of snails susceptible to Schistosoma mansoni than in that of snails resistant to infestation, while SOD and G3PD were lower in the susceptible snails. The role of these enzymes as free radical scavengers was traced 1 and 24 h after infection of the two snail lines with S. mansoni. Moreover, the activities of SOD and G3PD were also measured 2 and 4 weeks post infection. The results revealed that the overall enzymatic activities were higher in susceptible than in resistant snail tissues. After 1 h of infection, all enzymes were increased in R and S snails except GST and G6PD which decreased in S snails. After 24 h of infection, GST increased in S snails and G3PD decreased in both S and R snails while other enzymes reached normal levels.

Animals↗
PubMed2005

Differential expression of FREP genes in two strains of Biomphalaria glabrata following exposure to the digenetic trematodes Schistosoma mansoni and Echinostoma paraensei.

Fibrinogen-related proteins (FREPs) are hypothesized to function in non-self-recognition in the snail Biomphalaria glabrata. To investigate this assumption, the expression of four members of the FREP gene family was studied using quantitative PCR at 0.5-16 days following exposure of M line and BS-90 strain B. glabrata to Echinostoma paraensei and Schistosoma mansoni. Both strains react to, but fail to eliminate E. paraensei. Only the BS-90 strain is immunologically resistant to S. mansoni. Both snail strains responded to E. paraensei with significantly elevated expression of FREP 2 and 4. Following exposure to S. mansoni, resistant BS-90 snails showed an increase in expression of FREP 2 and 4 (57-fold and 4.5-fold increase, respectively), susceptible M line snails did not display a FREP response. Expression of FREP 3 and 7 was not significantly elevated in any snail/trematode combination. These expression profiles support the hypothesis that some FREPs play a role in the anti-trematode responses in B. glabrata.

Animals↗
PubMed2004

Gene discovery and expression analysis of immune-relevant genes from Biomphalaria glabrata hemocytes.

The immune effector cells (hemocytes) of the snail host Biomphalaria glabrata are known to play a key role in recognition and elimination of larval helminths such as the human blood fluke Schistosoma mansoni. To identify novel immune-relevant genes, we undertook an expressed sequence tag program. A hemocyte cDNA library was constructed using snails that were not exposed to a particular pathogen or parasite but maintained in non-axenic conditions. Putative function could be assigned to 53% of the 1613 high quality cDNAs analysed. Based on sequence similarities, we identified 31 immune-relevant genes corresponding either to cellular defence effectors, proteases and protease inhibitors, pattern recognition receptors, cell adhesion molecules or immune regulators. In order to further investigate the potential involvement of these genes in snail-trematode immunobiological interactions, we analysed their expression in unchallenged and parasite-challenged snails, using the immunosuppressive trematode Echinostoma caproni and snail strains selected for resistance or susceptibility to this parasite. Real-time PCR analysis of expression ratios at 7 time-points post-exposure revealed both (i) genes displaying constitutive expression differences between the two strains; and (ii) genes differentially modulated after parasite exposure.

Animals↗
PubMed2006

In vivo and in vitro knockdown of FREP2 gene expression in the snail Biomphalaria glabrata using RNA interference.

RNA interference (RNAi) is reported here for the first time for Biomphalaria glabrata, the snail intermediate host for the human parasite Schistosoma mansoni. The fibrinogen-related protein 2 (FREP2) gene, normally expressed at increased levels following exposure to digenetic trematode parasites, such as S. mansoni or Echinostoma paraensei, was targeted for knockdown. Double-stranded RNA (dsRNA) corresponding to specific regions of the FREP2 gene was introduced into snails by direct injection into the hemolymph, 2 days prior to exposure to trematodes, or added to co-cultures of B. glabrata embryonic (Bge) cells and E. paraensei sporocysts. After introduction of FREP2 dsRNA, expression levels of FREP2 were significantly reduced, to 20-30% of control values. In addition, we were able to disrupt expression of the house-keeping myoglobin gene, further confirming the feasibility of RNAi for B. glabrata. Cross-reactivity in RNAi has not been observed either among four FREP gene subfamilies or between FREP2 and myoglobin. Establishment of RNAi techniques in B. glabrata provides an important tool for clarifying the function of genes believed to play a role in host-parasite interactions, specifically between B. glabrata and its trematode parasites, including S. mansoni.

Animals↗
PubMed2006

Identification and expression of gene transcripts generated during an anti-parasitic response in Biomphalaria glabrata.

In order to gain further insights into the molecular basis of gastropod anti-parasite immune responses, we investigated transcripts of Biomphalaria glabrata regulated during hemocytic encapsulation. Using a snail strain that is resistant to the parasite Echinostoma caproni, we performed suppression subtractive hybridization (SSH) to construct cDNA libraries of transcripts more abundantly expressed in unexposed or parasite-exposed snails. After sequence analysis and quantitative PCR analysis of expression, we identified 10 candidates of particular interest. They belonged to various functional groups such as detoxification enzymes (GST, SOD), antimicrobial proteins (LBI/BPI), protease inhibitors (cystatins), calcium-binding proteins, or C-type lectins. In situ hybridization (ISH) analysis revealed that one overexpressed cystatin-like candidate is specifically expressed in hemocytes participating in parasite encapsulation or aggregating at the site of infection. Two other candidates (C-type lectin and a LBP/BPI) were expressed in the albumen gland, further supporting the role of this organ in immunity and/or host-parasite interaction.

Animals↗
PubMed2006

Biomphalaria glabrata transcriptome: identification of cell-signalling, transcriptional control and immune-related genes from open reading frame expressed sequence tags (ORESTES).

Biomphalaria glabrata is the major intermediate snail host for Schistosoma mansoni, one of the important schistosomes infecting man. Much remains to be discovered concerning specific molecules mediating the defence events in these intermediate hosts, triggered by invading schistosomes. An expressed sequence tag (EST) gene discovery strategy known as ORESTES has been employed to identify transcripts that might be involved in snail-schistosome interactions in order to examine gene expression patterns in infected B. glabrata. Over 3930 ESTs were sequenced from cDNA libraries made from both schistosome-exposed and unexposed snails using different tissue types, producing a database of 1843 non-redundant clones. The non-redundant set has been assessed for gene ontology and KEGG pathway assignments. This approach has revealed a number of signalling, antioxidant and immune-related gene homologues that, based on current understanding of molluscan and other comparative systems, might play an important role in the molluscan defence response towards infection.

Animals↗
PubMed2003

Schistosoma mansoni miracidia transformed by particle bombardment infect Biomphalaria glabrata snails and develop into transgenic sporocysts.

Miracidia (and adults) of Schistosoma mansoni which had been subjected to particle bombardment with a plasmid DNA encoding enhanced green fluorescent protein (EGFP) under control of the S. mansoni heat shock protein 70 (HSP70) promoter and termination elements were shown to express the reporter gene. Bombarded miracidia were able to penetrate and establish in Biomphalaria glabrata the intermediate host snail. Gold particles could be detected in the germ balls of parasites in paraffin-sections of snail tissue. The bombarded miracidia were able to develop normally and to transform into mother sporocysts. Reporter gene activity could be determined at 10 days post-infection by RT-PCR in snail tissues, but not by microscopy or Western blot which probably reflected sub-optimal expression levels of constructs. Our findings indicated that it is feasible to return transgenic miracidia to the life cycle, a crucial step for the establishment of a transgenesis system for schistosomes.

Animals↗
PubMedDate not supplied

Schistosoma mansoni: resistant specific infection-induced gene expression in Biomphalaria glabrata identified by fluorescent-based differential display.

The freshwater tropical snail Biomphalaria glabrata is an intermediate host for Schistosoma mansoni, the causative agent of human intestinal schistosomiasis, and strains differ in their susceptibility to parasite infection. Changes in gene expression in response to parasite infection have been simultaneously examined in a susceptible strain (NHM1742) and a resistant strain (NHM1981) using a newly developed fluorescent-based differential display method. Such RNA profiling techniques allow the examination of changes in gene expression in response to parasite infection, without requiring previous sequence knowledge, or selecting candidate genes that may be involved in the complex neuroendocrine or defence systems of the snail. Thus, novel genes may be identified. Ten transcripts were initially identified, present only in the profiles derived from snails of the resistant strain when exposed to infection. The differential expression of five of these genes, including HSP70 and several novel transcripts with one containing at least two globin-like domains, has been confirmed by semi-quantitative RT-PCR.

Amino Acid Sequence↗
PubMed2005

Energy allocation patterns in Biomphalaria alexandrina snails in response to cadmium exposure and Schistosoma mansoni infection.

This study was aimed to investigate the effects of both parasitism and environmental stress on the growth, reproduction, and survival of Biomphalaria alexandrina snails. Resource allocation strategies may be influenced by both biotic and abiotic factors. Using the planorbid snail B. alexandrina and Schistosoma mansoni, this hypothesis was examined by raising snails fed the same diet under two stressors (infection and Cd exposure). The snails divided into four groups, uninfected, infected, Cd-exposed uninfected, and Cd-exposed infected snails. Egg production, growth, and survival of the snails were monitored over a 9-week period postinfection. Inhibition of snail reproductive activity by parasitism results in increased snail growth in the first week postinfection, termed gigantism, during which the snail is hypothesized to allocate excess energy normally used for reproduction to somatic growth. Infection status and Cd exposure had significant effects on snail growth and reproduction. The infected and Cd-exposed infected snails exhibiting reduced survival relative to snails of other treatments. It was found that parasite development influenced by Cd exposure. Results of this study suggest that energy allocation patterns are context-dependent in B. alexandrina snails, influenced by infection and Cd exposure.

Animals↗